Seminars and Colloquia at ESO Garching and on the campus
December 2016
Abstract
In the core accretion scenario for planet formation (the best candidate to explain Earth-like planets), the micron-sized dust particles found in the interstellar medium have to grow by at least 12 orders of magnitude in size in order to form the planetary cores. Modeling the grain growth process is extremely difficult as it involves very different regimes and scales.
Measurements of the spatial distribution of dust grain sizes in protoplanetary disks is a major missing input for theoretical models of planet formation. Sub-mm and radio observations from modern radio interferometers like ALMA and the VLA now allow us to probe the bulk of the dust mass residing in protoplanetary disks with an unprecedented sharp view, resolving the spatial scales where planet formation occurs.
Marco will show the power of the multi-wavelength analysis that he has developed which allows him to constrain simultaneously the dust grain size spatial distribution and the disk structure. He will show that in some disks the analysis provided evidence of a connection between grain growth and the chemical environment.
Finally, Marco will present how we are getting prepared for the first systematic study of grain growth in a large sample of spatially resolved disks.
Abstract
Mixing in the radiative zones of stars is one of the least well understood components of stellar evolution, and yet can, in many instances, play a crucial role. In recent years, however, much progress has been made in quantifying mixing by a variety of hydrodynamic instabilities, thanks to numerical experiments that have strongly benefited from advances in supercomputing. I will review the state of the field, and present perspectives on what can and should be done next by the stellar evolution community, and by the astrophysical fluid dynamics community.
Video
Abstract
The interstellar medium (ISM) of galaxies drives galaxy evolution. However, it???s multi-phase structure is typically unresolved in cosmological galaxy formation simulations. I present recent progress on high-resolution numerical simulations (the SILCC project) investigating the differential impact of major physical processes setting the chemical and thermal multi-phase structure of the ISM including OB stellar winds, radiation and supernova explosions. We find evidence that stellar winds and radiation from massive stars primarily regulate star formation, while supernova explosions set the properties of the outflow driving hot gas. I also discuss the potential impact of non-thermal ISM components - magnetic fields and cosmic rays - on galactic outflows. With these simulations we also make first attempts towards more accurate predictions of important emission lines which are a major observables for galaxy formations studies at all cosmic epochs.
Video
Abstract
Accretion onto neutron stars and black holes powers the most luminous phenomena in the Universe. Associated to it is the existence of outflows, in the form of uncollimated winds or highly collimated relativistic jets. The origin of outflows and their feedback to the environment is one of the most debated topics in astrophysics today. In this talk I will review the current understanding of winds in X-ray binaries, their launching mechanism and their relation to specific accretion states. I will also discuss the potential interplay between the appearance/disappearance of winds and jets and the insight gained with ongoing observational programmes focused on the variability of such phenomena.
Video
Abstract
The discovery of high energy extraterrestrial neutrinos by IceCube has opened a new era for the neutrino astronomy. Their observations are compatible with cosmic neutrinos undergoing three flavor oscillations and the topologies of the events have been used to probe ordinary and exotic physics. However many important questions are still unresolved: what is the source and the mechanism of production of high energy neutrinos? Are the neutrinos extragalactic or there is also a galactic population? Andrea will present the status.
November 2016
Abstract
Galactic outflows are poorly understood although they are essential to feedback processes that quench star formation and limit the total mass of large galaxies. Thus, insufficient understanding of feedback associated with them -- in particular of the molecular phase -- is one of the greatest shortcomings in our knowledge of galaxy evolution. Multiphase outflows associated with galactic winds have been well-studied at a range of wavelengths, but detailed observations of the molecular phase are only now feasible with new instruments such as ALMA and NOEMA. We present ALMA observations and kinematic models of the molecular outflows in Circinus galaxy and NGC 253. Using these data, we constrain the molecular mass of the winds and mass outflow rates - both crucial to future star formation. We explore the possibility of gas leaving the galaxies entirely, consider additional molecular gas tracers of physical conditions, and explore optical depth effects. We compare the AGN-driven molecular wind in Circinus to the starburst-driven wind in NGC 253 and note key differences in the ways each type of wind impacts star formation. We also consider how Circinus and NGC 253 adhere to current trends involving molecular outflows.
Abstract
The evolution with cosmic time of the star formation rate density (SFRD) and of the main-sequence star formation rate-stellar mass relations are two well-established observational facts. The implications of these two relations combined will be analytically explored, showing that quenching of star formation must start already at very early cosmic times and the quenched fraction then dominates ever since over the star-forming one. Thus, a simple picture of the cosmic evolution of the global SFRD is derived, in terms of the interplay between star formation and its quenching.
Abstract
Most star clusters are collisional systems, i.e. their two-body relaxation timescale is shorter than their lifetime. This simple fact has strong implications: intense dynamical processes occur during the entire evolution of a star cluster, shaping both its structural properties and its stellar content. Mass segregation and Spitzer instability imprint their features already in the early stages of star cluster evolution, leading to repeated collisions of massive stars. This process might lead to the formation of very massive stars (>150 Msun) and even intermediate-mass black holes (IMBHs, 100-1000 Msun), depending on star cluster metallicity. Moreover, binary systems undergo frequent three-body encounters and even dynamical exchanges, which lead to dynamical ejections and/or the formation of more and more massive binaries. These aspects are crucial for the demography of massive double black hole binaries, which are important sources of gravitational waves for both ground-based and space-borne detectors. Finally, one of the most important (but less studied) ingredients of star cluster dynamics is the role of gas during star cluster formation. I show that torques in the parent molecular cloud imprint a substantial amount of rotation to embedded star clusters, potentially affecting their further evolution.
Video
Abstract
Two of the basic questions in galaxy evolution are how galaxies get progressively enriched in heavy elements, and how the dust content of galaxies evolves. A primary challenge in observing distant galaxies is that the light emitted by them is often too faint to allow detailed studies. Absorption lines in quasar spectra can be used to probe interstellar gas in galaxies at various stages of evolution, and thus provide powerful probes of the history of star formation and chemical enrichment in galaxies. Using this technique, we found that the gas-rich damped Lyman-alpha (DLA) absorbers are on average metal-poor even at low redshifts. On the other hand, the less gas-rich sub-DLAs are more metal-rich on average, including some that reached several times the Sun's metallicity 7-10 billion years ago. We are now pushing the limits of this technique to reach galaxies in the first ~1 billion years after the Big Bang. We will discuss recent results for a sub-DLA at redshift z=5.0 which shows some unusual element abundances. We are also using the absorption-line technique to trace the evolution of cosmic dust with time. We have detected silicate dust in many quasar absorbers at redshifts z < 1.4. The dust in these galaxies appears to be different (e.g., more silicate-rich) compared to the dust in the Milky Way and the Magellanic Clouds. Furthermore, the silicate dust in some distant galaxies could be crystalline, unlike the interstellar dust in the Milky Way.
Abstract
The Advanced LIGO (aLIGO) gravitational-wave detector this year reported the discovery of the first direct detection of gravitational waves confirming Einstein's Theory of General Relativity in its extreme limit. All sources of these gravitational waves detected so far were caused by the merging of two massive stellar-mass black holes. In this talk I will first summarize the main aLIGO results and then discuss in detail the three main channels that have been proposed to explain their origin, involving (1) dynamical formation, (2) common-envelope evolution, and (3) chemical homogeneous evolution (CHE), and how it may be possible to distinguish among these models. I will then focus on the CHE formation model, showing recent results from our own work, including cosmological simulations and their implications for the future detection of intermediate-mass black-hole mergers, gamma-ray bursts, pair-instability supernovae and neutron-star/black-hole mergers. The model also has application to ultra-luminous X-ray sources, in particular the most luminous ones.
Video
Abstract
CARMENES stands for Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs) is a next-generation instrument built for the 3.5 m telescope at the Calar Alto Observatory by a consortium of German and Spanish institutions. It consists of two separated spectrographs covering the wavelength ranges from 0.52 to 0.96 µm and from 0.96 to 1.71 µm with spectral resolutions R = 80,000-100,000, each of which performs high-accuracy radial-velocity measurements (∼1 m s-1) with long-term stability. The fundamental science objective of CARMENES is to carry out a survey of ∼300 late-type main-sequence stars with the goal of detecting low-mass planets in their habitable zones. The science survey of Guaranteed Time Observations started on 01 Jan 2016 and will last for at least three years. I will briefly describe the homonymous instrument, consortium and science project, present preliminary results from our survey, and show our prospects for the future.
Abstract
Being one of the largest stellar nurseries in the Galaxy, the Carina Nebula Complex plays an important role in understanding the star formation processes in regions with a high level of massive star feedback. Housing a significant population of high mass stars (~70 O-type stars) at a moderate distance of 2.3 kpc, it allows detailed studies at high spatial resolutions. In this talk, I will present extinction maps of the complex based on the NICEST technique, which uses the reddening of background stars due to intervening dust in the line of sight to determine the extinction. I will discuss global properties like the total cloud mass and estimate the young stellar content of this region. Also, the column density PDF will be shown and discussed.
Abstract
The Excellence Cluster Universe organizes the Research Area F Science Day. Experimental as well as theoretical Cluster scientists and students who are active in the field "What processes drive the building of the visible structures in the Universe?" come together to present current research results and developments.
Abstract
We have been using intensive time-sampling/monitoring in spectropolarimetric studies and are applying activity filtering techniques to map their surfaces and simultaneously beat down the activity jitter in T Tauri stars. This has led to the discovery of one of the youngest RV planets known to date and a potential detection around another T Tauri star. In this discussion I will outline how these techniques work focussing on their application to weak-line T Tauri stars. I will summarise what our results might imply about the incidence and survival of hot Jupiters by comparing our findings for T Tauri stars to their more evolved main sequence counterparts.
Abstract
A 2-3 million year old 60Fe-signal was detected in Pacific deep-sea geological archives and in lunar samples. This long-lived isotope is not produced on Earth, however, it is generated in massive stars and ejected during supernova explosions. We have found that this signal is extended in time and is present in marine reservoirs around the globe. A second 6.5-8.7 Myr old signature was revealed in a manganese crust. The recent injection of 60Fe into the solar system coincides with the formation of the Local Bubble, a large cavity in the interstellar medium produced by multiple supernovae, which surrounds our solar system. The most likely sources are stellar explosions within a moving group that passed the solar vicinity, and whose surviving members are now in the Scorpius-Centaurus stellar association. With analytical and numerical models generating the Local Bubble, we explain the younger 60Fe-signature and link the recent evolution of the solar neighborhood to the terrestrial anomalies.
Video
Abstract
Quasars, the accreting supermassive black holes at the centers of galaxies, are the most luminous objects in the universe and in principle ideal for use as so-called "standard candles." Despite possessing a number of spectral features long known to correlate with luminosity, quasars have failed to live up to their potential this way. We have employed statistical techniques to identify quasars with virtually identical spectra, which we call doppelgangers, in order to understand the limits of determining luminosity from spectral features alone. While the majority of doppelgangers have very similar luminosity, there exists a surprisingly large scatter. We offer some possible physical explanations for this large variance and their implications for cosmological application.
Abstract
The variation of the Sun's rotation with latitude and depth plays a key role in dynamo theories. Differential rotation is thought to result from the transport of angular momentum by turbulent stresses that arise from rotating convection. Unfortunately these turbulent stresses cannot be computed from first principles, they can only be approximated using simple models or numerical simulations. Helioseismology offers the possibility of measuring fluctuating velocities near the top of the solar convection zone. I will present HMI/SDO measurements of horizontal Reynolds stresses at different latitudes and at different spatial scales. The observations indicate that a transition in the nature of turbulence occurs between the deep convection zone where convection is strongly constrained by rotation and the near surface layers where it is not.
October 2016
Abstract
The very first comparison project undertaken in computational cosmology was initiated by Carlos Frenk in Santa Barbara in 1994. It led to a seminal paper published in 1999 (Frenk et al. 1999) where several codes for performing (non-cooling) hydrodynamical simulations were compared against each other with a special focus on the radial profile of a galaxy cluster. Over the past two decades there have been huge advances in both computational techniques and resources available and thus a comparison of 10 of the latest hydrodynamical codes has been undertaken. The nIFTy Cluster Comparison project was initiated in Madrid in 2014 and there have been two follow up workshops in Perth and Cape Town. I will present a brief overview of the main results from the Cluster Comparison project and mention some of the challenges faced as well as discuss the way forward and future projects.
Abstract
ESA's Planck mission has recently delivered on its promise to obtain ~few percent level constraints on the fundamental parameters of the standard model of cosmology, the LambdaCDM model. In spite of commonly-made claims that "all is well", detailed comparisons to other datasets are beginning to reveal some interesting tensions. Some measurements of local large-scale structure (LSS) in particular appear at odds with the CMB results. A few recent studies have proposed massive neutrinos as a way to reconcile the CMB and LSS measurements. However, before arriving at such a strong conclusion (or adopting any other modification of the standard model) we must be certain that we have properly dealt with all important sources of systematic error. Precisely modelling large-scale structure is challenging in particular, due to the non-negligible effects of feedback processes associated with galaxy formation. Here I present the first results from a new large hydrodynamical simulation campaign (BAHAMAS - BAryons and HAloes of MAssive Systems) designed specifically for LSS cosmology purposes and that realistically captures the effects of feedback on LSS. A number of the simulations include a massive neutrino component. Using virtual observations of the simulations, I re-assess the evidence for tensions between the CMB and various LSS probes, including cosmic shear, CMB lensing, galaxy clustering, the Sunyaev-Zel'dovich effect and so on. I then show the effects of massive neutrinos on these various LSS tests and discuss the current evidence for and against their cosmological importance.
Video
Abstract
What is the star-formation history of the Milky Way? How old are Galactic halo and thick disk stars? Traditional age-dating of stars relies on clusters, which only offer a limited view of these stellar populations. I will show that white dwarf stars offer a way forward. Specifically, I will show how optical and near-IR photometry, Gaia astrometry, and a Bayesian modeling approach allows us to determine precision ages for individual white dwarfs and derive population ages.
Abstract
The supply and lifetime of gas and dust in circumstellar disks are among the primary determinants of the properties of young planetary systems. Most of the information on disk evolution has so far come from infrared surveys, which have established that hot dust in primordial disks dissipates in approximately 5-10 Myr. ALMA is now playing a central role in these studies by probing colder gas and dust in disks. In this talk, I present recent results from an ALMA survey of 106 disks in the Upper Sco OB association. At an age of 5 Myr, Upper Sco is a benchmark region to establish the properties of disks at the end state of their evolution. By comparing Upper Sco with disk properties in young regions, we can assess how the gas and dust in disks evolve on timescales of 5 Myr.
Abstract
In 1916, Albert Einstein predicted the existence of gravitational waves but considered them to be too weak to be ever detected. Nonetheless, 100 years after their prediction, and after 50 years of effort, scientists and engineers have succeeded in this challenge, building multi-kilometer laser interferometers capable of measuring length changes close to the Heisenberg uncertainty limit. The first detections of gravitational waves allow us to listen to the ripples of space-time and witness the merging of black holes more than a billion years ago. Gravitational-wave astronomy has started and, together with electromagnetic and neutrino observations, is expected to shed new light on energetic astrophysical events.
Video
Abstract
The Excellence Cluster Universe organizes the Research Area G Science Day. Experimental as well as theoretical Cluster scientists and students who are active in the field "Origin of the cosmic chemical elements and the compositional evolution of the universe" come together to present current research results and developments.
Abstract
The importance of cold gas in the picture of galaxy evolution is well known, as is its role as a probe of recent environmental effects on galaxies. However, sensitivity limitations mean the extent to which environment impacts the gas-star formation cycle of galaxies remains unclear. With this talk I will show how we take full advantage of the powerful HI spectral stacking technique to overcome this obstacle and quantify the gas content for the entire gas-poor to -rich regime. This was accomplished using an the largest sample of HI and multi-wavelength information available (28,000 galaxies), selected according to stellar mass (M*>109 Msol) and redshift (0.02 <= z <= 0.05). I will present HI scaling relations with key structural, star formation and environmental metrics, using stacking to provide strong observational evidence of significant and systematic environment driven gas suppression across the group regime, well before galaxies enter the cluster. Furthermore, I will show that gas depletion is more closely associated to halo mass than local density and cannot be reproduced by starvation of the gas supply alone, invoking systematic ram-pressure stripping of the cold gas to explain this. Finally, I will show preliminary results highlighting the role of HI in regulating the correlation between stellar mass, star formation and gas-phase metal abundance known as the “fundamental" mass-metallicity relation.
Abstract
Stefan Hilbert, Junior Research Group Leader at the Excellence Cluster Universe, organizes a Universe Workshop entitled "Towards Accurate Lightcones for Cosmology".
Dates: 18-20 Oct 2016
Venue: MIAPP building, Garching
Abstract
Hierarchical structure formation in a LambdaCDM cosmology gives rise to virialized dark matter halos that contain a wealth of subtructure. Dark matter subhalos are believed to host satellite galaxies, and their demographics is therefore directly linked to the small-scale clustering of galaxies. Frank will demonstrate a crisis in our understanding of this small scale clustering, and argue that it arises from numerical issues in cosmological simulations that are used to model subhalo demographics. He will present a detailed discussion of both physical and numerical effects that lead to subhalo disruption, and show that current simulations are unable to accurately resolve the dynamical evolution of dark matter substructure. Frank will end with a discussion of implications for our ability to do precision cosmology using clustering data on small, non-linear scales.
Abstract
The Clusters Around Radio-Loud AGN project used Spitzer 3.6 and 4.5 micron imaging to select z>1.3 targets around a sample of 200 type I and 200 type II AGN. We confirm that 80% of the fields are indeed overdense. This represents the largest statistical high-z cluster sample to date, and allows new science, e.g. the determination of the cluster luminosity function. In my talk, I will introduce the project and the main results. In a future talk, Gaël Noirot will present the spectroscopic confirmation of the 20 most promising proto-cluster candidates using HST grism spectroscopy.
Abstract
While primordial universe was extremely uniform, it is now deeply structured with huge density contrasts from galaxy clusters to planets. This implies that intense episodes of accretion are taken place recursively at all spatial scales. How does it exactly happen and what role are these accretion events playing ? During the talk I will focus on three particular types of objects, namely the molecular clouds, the proto-stellar clusters and the late proto-planetary discs. For each of these three cases, I will describe how accretion proceeds and how it contributes, together with other physical processes, to drive the evolution of the system.
Video
Abstract
The Excellence Cluster Universe organizes the Research Area B Science Day. Experimental as well as theoretical Cluster scientists and students who are active in the field of symmetries in the early Universe come together to present current research results and developments.
Abstract
I will talk about how resolved stellar populations can and have been used to study the fossil record of star formation in nearby Local Group galaxies. This requires accurate colours, variability, chemistry and kinematic measurements of large samples of individual stars from deep imaging and spectroscopy. These studies provide a detailed picture of galaxy evolution going back to the earliest times, providing insights into the initial star forming properties of the early Universe, and how these have changed over time.
Abstract
Starting with two of the greatest empirical discoveries in galactic dynamics which are in most cases not even mentioned in modern-day textbooks, namely the baryonic Tully-Fisher relation and the mass-discrepancy-acceleration correlation, augmented by observations such as Renzo's rule, I will discuss an underlying symmetry in the equations of motions. This space-time scale invariance leads to Milgromian dynamics, the origin of which needs to be understood and may perhaps be related to quantum mechanical processes in the vacuum.
Abstract
Circumstellar disks around young stellar objects are sites of planet formation, the so-called protoplanetary disks. These disks exhibit Keplerian rotation and typically have radii of a few hundred AU. Understanding the formation mechanism of Keplerian disks is one of the key issues in present astrophysics because it is the starting point to form planetary systems. Conventionally, Keplerian disks are expected to form and grow as the consequence of angular momentum conservation. Theoretical studies incorporating magnetic field show that disk formation and growth can be suppressed by magnetic braking which removes angular momentum. The efficiency of magnetic braking in protostellar sources remains unknown, and it is still unclear as to how Keplerian disks form and grow from less than 10 AU to more than 100 AU in size. In this presentation, I will introduce our observational results of Keplerian disks around young protostars and gas kinematics in protostellar sources from 10,000 AU to inner 100 AU scale obtained with single-dish telescopes, SMA, and ALMA, and discuss their implication in the context of disk formation and growth.
September 2016
Abstract
SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research in Europe) is a second-generation instrument for the ESO Very Large Telescope (VLT) dedicated to the direct detection and spectral characterization of giant extra-solar planets, which is one of the most exciting but also one of the most challenging areas in modern astronomy due to the very large contrast between the host star and the planet at very small angular separations. SPHERE combines an extreme adaptive optics system, various coronagraphic devices and a suite of focal instruments providing imaging, integral field spectroscopy and polarimetry capabilities in the visible and near-infrared spectral ranges. After almost 10 years of development, SPHERE has been successfully commissioned at the VLT in 2014 and is now offered to the community since April 2015. I will give an overview of the science objectives and main instrument features, review the achieved performances and present a summary of the main results obtained during the first year of operations.
Abstract
The Excellence Cluster PhD Meeting is a traditional event that aims to gather the Excellence Cluster PhD students in a two-days socializing event. The 2016 event will be organized in two days: the first day will be dedicated to meet up, to present current/past work to each other through talks, and to attend talks given by senior scientists. On the second day we plan to go hiking in the Bavarian Alps and visit the Wendelstein Observatory.
The meeting intends to be informal to foster lively discussions and to create a productive atmosphere to share our results and experiences.
Abstract
My talk will focus on the centers of nearby galaxies and the effects of central supermassive black holes (SMBHs) on the surrounding environment. There has been increasing evidence that most, if not all, galaxies host SMBHs at their centers and correlations of the SMBH mass to host galaxy properties show that the growth of both are tied together. SMBHs are additionally known to span more than 5 orders of magnitude in mass and can be extremely quiescent or the dominant energy source within a galaxy. I will first discuss preliminary results from a survey of nearby LINER (low ionization nuclear emission line region) galaxies. This class of active galaxies is common in the local universe, with ~1/3 of galaxies within 40 Mpc hosting LINERs, but their physical nature is not well understood. The goal of the survey is to constrain the excitation mechanisms of near-infrared emission lines from singly ionized iron and molecular hydrogen using integral field spectroscopic observations at high spatial resolutions. This survey is being conducted with the OSIRIS integral field spectrograph at the Keck Observatory, which we have recently upgraded with a new detector to roughly double the instrument’s sensitivity. I will finally discuss the recent results of improved constraints on the mass and distance of our own Milky Way SMBH (Sgr A*).
Abstract
Dr. Ben Gripaios is a Lecturer in Theoretical Physics in the Cavendish High Energy Theory Group at the University of Cambridge. He received his D. Phil. from Oxford University in 2004 and previously held post-doctoral positions at the European Laboratory for Particle Physics (CERN), the Swiss Federal Institute of Technology (EPF Lausanne), and Oxford University. He is also a Fellow of King's College, Cambridge.
Ben is a Cluster guest (host: Prof. Dr. Martin Beneke, TUM Physics Dep.) and will present the lectures in three parts on 13th, 14th and 15th September, 11am.
Abstract: Ben will discuss the quantization of a perfect fluid. This differs from textbook quantum field theory, because of the presence of vortex modes, which correspond to an infinite collection of quantum mechanical free particles rather than harmonic oscillators. As a result, the theory is plagued by infra-red divergences. He will show that there exists, nevertheless, a consistent effective field theory description, valid at large distances and times.
Abstract
Dr. Ben Gripaios is a Lecturer in Theoretical Physics in the Cavendish High Energy Theory Group at the University of Cambridge. He received his D. Phil. from Oxford University in 2004 and previously held post-doctoral positions at the European Laboratory for Particle Physics (CERN), the Swiss Federal Institute of Technology (EPF Lausanne), and Oxford University. He is also a Fellow of King's College, Cambridge.
Ben is a Cluster guest (host: Prof. Dr. Martin Beneke, TUM Physics Dep.) and will present the lectures in three parts on 13th, 14th and 15th September, 11am.
Abstract: Ben will discuss the quantization of a perfect fluid. This differs from textbook quantum field theory, because of the presence of vortex modes, which correspond to an infinite collection of quantum mechanical free particles rather than harmonic oscillators. As a result, the theory is plagued by infra-red divergences. He will show that there exists, nevertheless, a consistent effective field theory description, valid at large distances and times.
Abstract
The stellar populations properties of galaxies and their gradients have received many attention in the last fifty years since they start to become crucial ingredients to test the predictions of the simulations describing the formation of galaxies. In the talk I will present our investigation on the stellar populations and their gradients of the bulge dominated regions focusing, in particular, on the isolated galaxies.
Abstract
Dr. Ben Gripaios is a Lecturer in Theoretical Physics in the Cavendish High Energy Theory Group at the University of Cambridge. He received his D. Phil. from Oxford University in 2004 and previously held post-doctoral positions at the European Laboratory for Particle Physics (CERN), the Swiss Federal Institute of Technology (EPF Lausanne), and Oxford University. He is also a Fellow of King's College, Cambridge.
Ben is a Cluster guest (host: Prof. Dr. Martin Beneke, TUM Physics Dep.) and will present the lectures in three parts on 13th, 14th and 15th September, 11am.
Abstract: Ben will discuss the quantization of a perfect fluid. This differs from textbook quantum field theory, because of the presence of vortex modes, which correspond to an infinite collection of quantum mechanical free particles rather than harmonic oscillators. As a result, the theory is plagued by infra-red divergences. He will show that there exists, nevertheless, a consistent effective field theory description, valid at large distances and times.
Abstract
We use Herschel spectroscopy of BHR71, an embedded Class 0 protostar, to provide unprecedented constraints on its physical properties. We model the structure of the envelope using the dust radiative transfer code, Hyperion, to fit the spectral energy distribution (SED). Our model incorporates rotational collapse and an outer static envelope as well as an outflow cavity and disk, and shows that the evolution of a rotating collapsing envelope can be constrained by the Herschel SED along with the azimuthally-averaged radial intensity profile and that the structure of the outflow cavity plays a critical role at shorter wavelengths. Emission at 20-40 um requires a cavity with a constant-density inner region and a power-law density outer region. The corresponding mass infall rate in the envelope is about the same as the derived mass accretion rate onto the star, while the mass loss rate estimated from the CO outflow is 20 % of the mass accretion rate onto the star.
Abstract
In the last 15 years, studies of velocity shifts between metal transitions observed in high-resolution quasar spectra with the largest optical telescopes identified possible evidence for variation in the fine-structure constant, α. Recent ‘supercalibration’ techniques have shown that these spectra likely have significant systematic distortions in their wavelength scales that undermine the α measurements.
We have selected the brightest southern quasar HE 0515-4414 at z_abs > 1 to obtain the highest S/N spectrum available, achieve the smallest statistical error on Δα/α to date and, most importantly, to allow systematic effects to be tracked and corrected with high fidelity. For this purpose we have combined HE 0515-4414 spectra observed with UVES/VLT over 10 years, producing an extremely high signal-to-noise ratio spectrum (peaking at ~250 pix^-1). This provides the most precise measurement of ∆α/α from a single absorption system to date, ∆α/α = −1.42 ± 0.55_stat ± 0.65_sys parts per million (ppm). This has a similar precision to previous measurements from large samples of ~150 absorption systems. This measurement is corrected for the largest systematic effect present in all (except one) previous measurements, the long-range wavelength distortions, which would add 10 ppm to the systematic error budget. We also discuss how our methods for correcting the spectra, in this case, can be applied to future spectra, in particular from the upcoming ESPRESSO spectrograph. Our spectrum also offers a preview of the data quality available from the next generation of telescopes, but also the problems that must be overcome to access the full photon-limited precision.
Abstract
AstroSat, India’s first space observatory, was launched on Sept 28th, 2015 into a circular, near-Earth, and nearly equatorial orbit by the Indian Space Research Organization. The satellite was built by a consortium of institutes and is equipped with several co-aligned instruments capable of observing simultaneously in one of the widest X-ray bands and in near-UV, far-UV and optical bands. Several observations have been carried out since its launch and verification phase that lasted until March 31, 2016, mainly by the instrument teams for their guaranteed time that will end in early Oct, 2016. The results obtained so far from observing all kinds of cosmic objects ranging from Blazars, Seyfert galaxies, clusters of galaxies, magnetic cataclysmic variables, supernova remnants and stars, would be presented.
August 2016
Abstract
On July 20, 2015 at the Royal Society in London, Yuri Milner and Stephen Hawking announced a set of privately funded global initiatives to answer the fundamental science questions surrounding the origin, extent and nature of life in the universe. These include a Search for Extra Terrestrial Intelligence (SETI) called ‘Breakthrough Listen’ and a prize contest to devise potential messages in response to a SETI detection, entitled ‘Breakthrough Message’. The Initiatives are managed by the Breakthrough Prize Foundation and are funded at the $100M level.
On April 12, 2016 atop the One World Observatory in New York, Yuri Milner and Stephen Hawking announced ‘Breakthrough StarShot’. An initiative to develop and launch the Earth’s first interstellar probe to our nearest star within a generation. Facebook’s Mark Zuckerberg joined Milner and Hawking to oversee the initiative – initially funded at $100M.
July 2016
Abstract
Weak gravitational lensing analysis is a powerful tool to explore the properties of galaxy clusters. However different sources of systematic uncertainties can affect the final result. In this talk Nathalia will briefly introduce the CODEX (COnstrain Dark Energy with X-ray clusters) survey and discuss the stacked weak lensing analysis performed for a subsample of the CODEX galaxy clusters at z~0.5. We paid particular attention to two different sources of systematics: the contamination of the background sample by cluster members and the off-centring effect. She will explore the effects of these uncertainties over the constraints on mass and concentration and the adopted approach to circumvent these.
Abstract
The radio galaxy and merger remnant NGC 1316 is one of the most interesting galaxies in the nearby universe. Its population structure, its nucleus, its gas content, its dust content, its dynamics challenge attempts of conventional interpretations. I shall draw a general portrait of NGC 1316 with emphasis on recent MUSE data and their potential for providing a deeper understanding.
Abstract
Astronomical research has been historically neglected in Southeast Asia, but in recent years it has been experiencing a significant progress. In particular, the National Astronomical Research Institute of Thailand has assembled a core group of experienced researchers and several postdocs, and has developed modern facilities which include the largest telescope in the region, a 2.4-m equipped with imagers and spectrographs, and several smaller telescopes spread around the globe. Also a high-performance computing centre and a large radiotelescope are under development. I will present a brief review of the status, some scientific highlights and the collaboration opportunities concerning astronomical research in the region and in Thailand in particular. I will then focus on EVA, the Evryscope for the Arctic and Antarctic, a joint project between NARIT, the University of North Carolina at Chapel Hill and the University of Toronto. EVA follows in the footprints of the first Evryscope already operated at Cerro Tololo by UNC, which consists of 27 commercial lenses and large format detectors assembled on a single mount to cover about 8,000 sq degrees simultaneously each 2 minutes. The first EVA is planned to be deployed in the high Canadian Arctic in 2017/18, and targets a number of scientific cases ranging from transits of exoplanets to asteroseismology to stellar variability to transients and supernovae. A second EVA in the Antarctic is under consideration.
Abstract
Spectacular measurements of the Cosmic Microwave Background (CMB) provide an understanding of the initial conditions that are at the origin of the cosmic structures we see today. We now know the basic constituents of the present Universe, but only a minority of the baryons can be probed by observations of starlight from galaxies. Celine will review results form recent studies about the remaining 90% of the baryons, as traced by the intergalactic gas. The overall goal is to reach a complete understanding of the physical processes by which gas travels into, through, and out of galaxies; the so-called cosmic baryon cycle.
Celine will present the lectures in three parts:
1) assessing the gas reservoir for star formation
2) using kinematics information to disentangle inflows from outflows and
3) characterising the metallicity and other physical properties of the circumgalactic medium. Such studies are essential to reach a complete understanding of the formation of galaxies and the growth of structure in the Universe.
Abstract
Spectacular measurements of the Cosmic Microwave Background (CMB) provide an understanding of the initial conditions that are at the origin of the cosmic structures we see today. We now know the basic constituents of the present Universe, but only a minority of the baryons can be probed by observations of starlight from galaxies. Celine will review results form recent studies about the remaining 90% of the baryons, as traced by the intergalactic gas. The overall goal is to reach a complete understanding of the physical processes by which gas travels into, through, and out of galaxies; the so-called cosmic baryon cycle.
Celine will present the lectures in three parts:
1) assessing the gas reservoir for star formation
2) using kinematics information to disentangle inflows from outflows and
3) characterising the metallicity and other physical properties of the circumgalactic medium. Such studies are essential to reach a complete understanding of the formation of galaxies and the growth of structure in the Universe.
Abstract
Spectacular measurements of the Cosmic Microwave Background (CMB) provide an understanding of the initial conditions that are at the origin of the cosmic structures we see today. We now know the basic constituents of the present Universe, but only a minority of the baryons can be probed by observations of starlight from galaxies. Celine will review results form recent studies about the remaining 90% of the baryons, as traced by the intergalactic gas. The overall goal is to reach a complete understanding of the physical processes by which gas travels into, through, and out of galaxies; the so-called cosmic baryon cycle.
Celine will present the lectures in three parts:
1) assessing the gas reservoir for star formation
2) using kinematics information to disentangle inflows from outflows and
3) characterising the metallicity and other physical properties of the circumgalactic medium. Such studies are essential to reach a complete understanding of the formation of galaxies and the growth of structure in the Universe.
Abstract
Abstract
Protostars drive energetic jets that entrain surrounding gas in the form of outflows, simultaneously injecting momentum in the surrounding gas. Hence, outflows are a bridge for feedback from individual protostars to their nascent cluster environment. The outflow morphology and efficiency of momentum transfer between jet-outflow-cluster likely determines the extent to which outflows provide significant feedback to regulate ongoing star formation. This is especially relevant in clusters, which are the most common environments for star formation. Comprehensive observing campaigns of outflow feedback in clusters should incorporate single dish and interferometer observations that are sensitive to emission on cluster (few parsecs) to core (hundreds of AU) scales, respectively. Here we present such observations and analysis of the protostellar cluster Serpens South, which is experiencing an early and active phase of star formation. Following the combination of IRAM+CARMA (single dish + interferometer) maps of Serpens South, recent ALMA observations feature several cases of complex outflow morphologies near the central ``hub'' region that we mapped. Our suite of observations probe scales ranging from 400 AU to 0.8 pc. High-resolution observations clearly link outflows with their driving sources, and in this case they reveal an episodic accretion and launch mechanism. Highly-collimated, episodic outflows likely provide efficient momentum transfer for driving turbulence. This study provides constraints for simulations of protostellar outflows in clusters that (should) include episodic accretion and outflow-driven turbulence.
Abstract
The aim of this Joint international conference is to explore the importance of stellar and gaseous discs in a variety of galaxies from high redshift to the Milky Way in the context of exciting new observations and numerical simulations.
Rationale:
Understanding how the internal structures of galaxies form and evolve is key to understanding the origin of the Hubble sequence. This is a timely topic given the current investment in high resolution instrumentation which probes the resolved properties of distant galaxies and the increased detail in our understanding of stars and gas in nearby galaxies. Stellar and gaseous discs represent the most important structural component in normal galaxies and interpreting their early formation and destruction via observations and numerical simulations indicates the key processes that shape the eventual Hubble sequence. Observations of discs in high redshift star-forming and quiescent galaxies are complemented by an increasing detailed understanding of the kinematics and chemistry of stars in the Milky Way. The conference will synthesize these different aspects of disc evolution at an important time when exciting new results are arriving from resolved studies of distant galaxies as well from numerous Galactic surveys.
Key questions the meeting will address include:
- What can the kinematic and chemical structure of the Milky Way and nearby galaxies tell us about their earlier evolution? What is the consensus on the nature and origin of the proposed `thick disc’? How did the physically-extensive local HI discs form and become chemically-enriched?
- What processes given the duty cycle of self-regulated star formation and can these explain the exponential profile of stellar discs? Have we clearly understood why recent models claim to match local disc scaling relations? What explains the `disc-halo’ conspiracy proposed to explain flat rotation curves and what is the origin of turbulence in galactic discs?
- Can we reconcile the evolving mass-metallicity relations in the context of models for gas inflow and outflow? What are the prospects for observing and interpreting metal gradients in high redshift galaxies? How did the first disc galaxies form and what transformations occurred in the history of elliptical and lenticular galaxies? Can we understand the declining baryonic fraction with cosmic time?
The workshop will take place at the ESO Headquarters in Garching (Germany) from July 11 - 15, 2016.
This workshop is jointly supported and coordinated by ESO, MPA, MPE, the Excellence Cluster Universe, LMU and TUM
Abstract
Planets form in gaseous protoplanetary disks surrounding newborn stars. As such, the best way to directly learn how they form from observations, is to watch them forming in disks. By doing so, we can directly address the three most fundamental questions in planet formation: when, where, and how do planets form. In the past, due to the difficulties in directly detecting planets in gas disks, planet formation was largely a subject of theoretical astrophysics. Now, thanks to a fleet of new instruments with unprecedented resolving power, such as VLT/SPHERE and ALMA, that have come online in the past few years, we have just started to be able to directly resolve structures in protoplanetary disks that are mostly likely associated with embedded (unseen) planets, such as gaps, spiral arms, and lopsided disks. By comparing observations with theoretical models of planet-disk interactions, the locations and properties of these still forming planets can be constrained. This is the onset of a new field — observational planet formation. I will review some recent progresses in this field, in particular the current status of hydrodynamic and radiative transfer modeling of observational signatures of planet-induced structures in disks, and the comparisons between models and observations.
Abstract
Circumgalactic medium (CGM), the interface between interstellar medium and intergalactic medium (IGM), provides a suitable site to study the IGM accretion and galactic outflows. QSO absorption line systems are amongst the best places to study the physical properties of the CGM. We have recently built a unique sample of 9 Damped Lyman-alpha (DLA) absorbers at z~0.6 from HST/ACS from which we identified 7 new DLA-galaxies at small impact parameters (<30 kpc) using VLT/X-Shooter. We estimate the metallicity of the CGM (0.05-0.6 Z_solar) and also the emission metallicity (0.2-0.9 Z_solar) and star formation rate of the host galaxies of DLAs. We further discover two quiescent galaxies that host huge neutral hydrogen reservoirs at impact parameters < 15 kpc. Here we demonstrate how a comparison between the properties of the host galaxies and the absorbing gas can be used to constrain the nature of the CGM.
Abstract
Physics data taking with GERDA Phase II started in December 2015. The first data set covering the period until beginning of June was unblinded and an updated half-life for neutrinoless double beta decay of 76Ge extracted. The performance of the experiment and the result will be presented by Matteo Agostini at the Neutrino 2016 conference next week.
June 2016
Abstract
Throughout the history of the universe, shocks and large-scale gas flows have moulded the arms of spiral galaxies, formed the bulges of the most massive galaxies in the universe, fed supermassive black holes in the centers of galaxies, fueled generation upon generation of new stars, and enriched the intergalactic medium with metals. For local galaxies, we use multi-object integral field spectroscopy to build the largest sample of galaxies with wide 3-dimensional imaging spectroscopy. We combine these results with insights into the early universe probed through gravitational lensing and near-infrared integral field spectroscopy. I will present the latest results from our large local and high-z 3D surveys to understand the relationship between gas inflows, galactic-scale outflows, star-formation, and active galactic nuclei in galaxies as a function of environment and redshift. I will finish by discussing how this field will be transformed with JWST and in the ELT era.
Video
Abstract
Active Galactic Nuclei (AGN) are being discovered in ever-larger numbers over the whole electromagnetic spectrum. Different bands employ different methods to identify these sources but, most importantly, provide different windows on AGN physics. The infrared band is mostly sensitive to obscuring material and dust, the optical/UV band is related to emission from the accretion disk, while the X-ray band traces the emission of a (putative) corona. γ-ray and (high flux density) radio samples, on the other hand, preferentially select AGN emitting strong non-thermal radiation. This has led to a proliferation of classes, which outsiders (but insiders as well!) find mesmerizing. The main goal of the Workshop is to paint the AGN “big picture”, which comes out of these multi-wavelength surveys, and understand the truly intrinsic and fundamental properties of AGN and the physics behind them. This will be done by discussing primarily these topics:
- the different types of AGN selected in the various bands
- the similarities/differences they display
- the impact of selection effects on the interpretation of the results
- the physical mechanism(s) behind emission in a given band
- the effective range of black hole mass and Eddington ratio probed by a given selection method
- the possible limitations of current observations and/or facilities
- the "big picture" of AGN
All of the above will be achieved by having a truly multi-wavelength Workshop consisting of review and contributed talks distributed over six sessions: radio, infrared, optical, X-ray, γ-ray, and variability.
Review speakers: Vernesa Smolcic, Roberto Assef, Gordon Richards, Dave Alexander, Paolo Giommi, Barbara De Marco, and Phil Hopkins.
Abstract
Unlike Athena, who sprang full grown from the forehead of Zeus, the Hubble Space Telescope had a long and difficult gestation. It was one of the original goals in building Earth orbiting satellites, but finally came under serious consideration only in 1971. The next two decades first saw battles to gain support from astronomers and financial support from the US and European governments. The next phase saw the challenges of designing and building something that had never been done before—a long duration observatory in space. I’ll then close out with an explanation of the problems with the primary mirror, how these were corrected, and a brief report on the observatory’s condition.
Abstract
Progress in our understanding of galaxy formation, improved numerical algorithms, and increased computing power have recently lead to a number of impressive large-scale hydrodynamical simulations, which are able to reproduce key observables of the local and higher redshift Universe. These simulations allow us, for the first time, to study the interplay between large-scale structure and galaxy formation in detail. I will present recent results of these efforts and discuss some successes and failures of them.
Video
Abstract
In this talk we will present results that come out from a partial exploitation of the VMC database, focussed on star clusters located in both Magellanic Clouds. Through a quick journey over our previous recent work, we will show the capability of the VMC database in reaching the main sequence turnoff of intermediate-age clusters, in uncovering the connection history of the SMC and the Bridge, in highlighting the spatial variation of the cluster formation history in the central regions of the LMC, in discovering new star cluster candidates in the densest part of the SMC, among others. Besides, we will describe some procedures developed for homogeneously analysing the VMC database.
Abstract
The mass of protoplanetary discs in gas is a quantity of great interest
for assessing their planet formation potential. However, disc gas masses
are traditionally inferred from measured dust masses by applying an
assumed standard gas to dust ratio of 100.
Here we present the results of applying a new modelling technique to the
Herbig Ae star HD 163296: We combine SED modelling with fits to the CO
snowline location and C18O J=2-1 line emission from ALMA and find that
all of the modelling steps are crucial to break degeneracies in the
parameter space.
We find that use of all these constraints favours a solution with a
notably low gas to dust ratio (g/d<20). We propose that the technique
can be applied to a range of discs and opens up the prospect of being
able to measure disc dust and gas budgets without making assumptions
about the gas to dust ratio.
Abstract
Radiative feedback is thought to play a crucial role in the formation of massive stars and the star clusters in which they form. I will review the physical problems and large body of work that has addressed these basic questions before turning to our own contributions. For massive star formation, we have developed a new hybrid radiative transfer code that operates in a 3D, adaptive mesh code (FLASH) that can, for the first time, follow the heating and momentum transfer by both discrete stellar sources as well as by diffuse radiative background in complex geometries. We simulate the gravitational collapse of massive dense gaseous "cores" of 30 to 200 solar masses. We find several major differences with respect to previous works including radiatively driven bubbles that don't cool and fragment, as well as a suppression of fragmentation of the massive disks into multiple stars. Our results compare favourably to recent observations of massive disks around massive stars.
I will also present our new work on radiative feedback simulations of the formation of young clusters
in turbulent Giant Molecular Clouds and on how cloud structure affects this process. In particular, we find that the star formation efficiency in such clouds and the masses of star clusters are strongly influenced by how gravitationally bound the cloud are initially - an effect that is more important than radiative feedback. These results are compared with observations.
Abstract
I will present new results from the first deep ALMA continuum image of the Hubble Ultra Deep Field (HUDF), designed to better connect our UV/optical and FIR/mm views of the high-redshift Universe. From a mosaic of 45 ALMA pointings we have constructed a 1.3mm image covering the full 4.5 sq arcmin of the HUDF as previous imaged with WFC3/IR and ACS on Hubble. This new image reaches an rms depth of 35 micro-Jy at a resolution of of 0.7 arcsec. I will describe the design and implementation of this project, and the analysis of the final data product both for source discovery and stacking in the galaxy mass/redshift plane. After presenting our results I will discuss the implications of our findings for our understanding of the 1.3mm background, the mass dependence of star formation and dust obscuration, and the history of cosmic star-formation density. I will close by discussing the prospects for future progress.
Abstract
The next generation of large sky photometric surveys will be finally able to use strong lensing by clusters as a cosmological probe. In his talk Carlo will present in particular how arc counts and strong lensing properties by clusters are sensitive to the variation of two cosmological parameters: the total matter density parameter (Omega_M)and the normalisation of the primordial power spectrum (sigma_8). He will introduce a pseudo-analytical code MOKA to generate high resolution convergence maps of galaxy clusters, using recent results from numerical simulations, and discuss how strong lensing phenomenologies are sensitive to cluster structural properties. Finally Carlo will talk about how sensible is the distribution of the Einstein radii on the cosmological parameters Omega_M – sigma_8 finding that cosmologies with higher Omega_M and sigma_8 possess a large sample of strong lensing clusters.
Abstract
In this talk, I will address how the state of the art chemo-dynamical simulations, combined with the results of recent ESO/Large programs dedicated to chemical abundances of hundreds of individual stars, have improved our understanding of the formation and evolution of dwarf spheroidal galaxies (dSphs). Indeed, those new stellar abundances provide us with important constraints that must be fulfilled by numerical models. Thanks to a large sample of simulations performed with our Tree/SPH chemo-dynamical code GEAR that treats the complex physics of baryons I will show how the large variety in the dSph properties can now be understood. In addition, I will discuss some tensions existing between dSph models and LCDM predictions.
Abstract
Neutron stars offer a unique environment in which to develop and test theories of the strong force. Densities in neutron star cores can reach up to ten times the density of a normal atomic nucleus, and the stabilising effect of gravitational confinement permits long-timescale weak interactions. This generates matter that is neutron-rich, and opens up the possibility of stable states of strange matter, something that can only exist in neutron stars. Strong force physics is encoded in the Equation of State (EOS), the pressure-density relation, which links to macroscopic observables such as mass M and radius R via the stellar structure equations. By measuring and inverting the M-R relation we can recover the EOS and diagnose the underlying dense matter physics.
One very promising technique for simultaneous measurement of M and R exploits hotspots (burst oscillations) that form on the neutron star surface when material accreted from a companion star undergoes a thermonuclear explosion (a Type I X-ray burst). As the star rotates, the hotspot gives rise to a pulsation. Relativistic effects then encode information about M and R into the pulso profile. However the mechanism that generates burst oscillations remains unknown, 20 years after their discovery. Ignition conditions, flame spread, and the magnetohydrodynamics of the star's ocean all play a role. I will review the progress that we are making towards cracking this long-standing problem, and establishing burst oscillations as a tool par excellence for measuring M and R. This is a major goal for future large-area hard X-ray telescope concepts such as eXTP and LOFT.
Abstract
No matter how you ended up in science, sooner or later you will face a situation in which you will be confronted with hard reality and the borders traced by your limits. The fire that burned so bright may lose its strength and the dreams of revolutionizing physics will probably become weaker and weaker. You may also start asking yourself about the usefulness of what you are doing and whether it really made sense to invest your best years and energies in pursuing very abstract questions. Questions that often remain unanswered.
In my talk I will try to address these points going through my personal experience, exposing its bright and dark sides, sharing with you perplexities and hopes.
Abstract
By comparing 3 constituents of Orion A (gas, protostars, and pre-main-sequence stars), both morphologically and kinematically, we show the following. Essentially all of Orion A’s Integral Shaped Filament (ISF) protostars lie superposed on the ISF, while almost all pre-main-sequence (Class II) stars do not. Combined with the fact that protostars move < 1 km/s relative to the filament, while stars move several times faster, this implies that a slingshot mechanism may eject protostars from the dense filamentary cradle, thereby cutting off their accretion of new gas. The ISF/ONC is the 3rd in a series of star bursts that are progressively moving south through Orion A, with separations of ~ 2 Myr in time and ~ 3 pc in space. This, combined with the ISF's observed undulations (spatial and velocity), suggest that repeated propagation of transverse waves thru the filament is progressively digesting the gas that formerly connected Orion A and B into stars in approximately discrete episodes. The presence of transverse waves implies the action of a buoyant restoring force acting against gravity. Combined with previous observations of magnetic field geometry and strength in the ISF, this suggests that the ISF transverse waves are magnetically induced. The presence of straight filaments in low mass regions (e.g., Taurus and L1641) as well as in turbulence simulations indicates that Taurus-like filaments are a direct reflection of initial conditions. In contrast, the observed undulations of the ISF, the fact that the ISF is the only nearby cluster in formation, the fact that it has survived repeated burst of intense star formation, and the equality between the inferred gravitational potential energy and magnetic energy on ~ 1 pc scales near the filament ridge, together lead to the following conclusion: the key physical difference in the ISF is that it is massive enough to have survived the initial star formation episode, allowing it to undergo internal evolution leading to concentration of B-fields confined by a deep gravitational potential well.
Abstract
Soon after the formulation of Special Relativity in 1905 Einstein started to think about the problem of how gravity would fit into this new concept of a unified space-time structure. Whereas Special Relativity was perfectly tailored to fit Maxwell's electrodynamics, it was totally unclear how the only other fundamental interaction known by then, gravity, cold be reconciled with the requirements of Special Relativity. After some failed attempts Einstein came quite soon to the conclusion that gravity was irreconcilable with Special Relativity and proposed to subsume gravity, inertia, and space-time geometry into a single mathematical representation. It might seem like a miracle that Einstein succeeded to actually perform this almost freely floating construction. In my talk I will try to elucidate in a pedagogical fashion the physical, mathematical, philosophical, and epistemological guiding principles that served Einstein over the ten years 1905-1915 of "hiking in path-less terrain" to find what is now one of the most successful theories in all of physics: General Relativity.
May 2016
Abstract
The structure in our Universe is thought to have formed in a hierarchical fashion. As such, galaxies, and the dark matter halos in which they are embedded, grow through accretion, and through interactions and mergers with other galaxies. In the concordance (Lambda cold dark matter) cosmological model these interactions of galaxies and their halos are expected to be relevant on all scales, from large galaxy clusters to tiny dwarf galaxies. Moreover, within the LCDM framework small dark matter halos are ubiquitous, and many may not have been able to form stars. These small, star-less, halos are possibly indirectly detectable through their gravitational effects on luminous matter. Insights from these gravitational effects are perhaps promising for unveiling the presence of the hitherto missing satellites, and may provide novel clues to the nature of the dark matter.I will present a suite of simulations studying the effects of infalling dark satellites on dwarf galaxies. We find that these interactions can lead to the formation of irregular, starbursting, and spheroidal dwarf galaxies. Furthermore, we characterize the effects of small dark matter halos quantitatively through morphological and kinematical indicators to aid their observational identification. A significant fraction of the dwarf galaxies at the present day can be expected to have recently experienced such an interaction. Studying these interactions can shed light on dark influences on crucial episodes in the evolution of dwarf galaxies. Interactions with smaller dark matter halos may well contribute to the diversity of the dwarf galaxy population.
Abstract
I will present the Galactic Cold Cores project where Planck and Herschel satellite data are used to investigate interstellar clouds and star formation. I will concentrate on recent results from Herschel studies of interstellar dust. I will also discuss the parallel work done on the extinction mapping of interstellar medium and will conclude with a description of our ongoing work and future plans.
Abstract
We also find a much higher space density of very luminous Lyman-alpha emitters at z~2-7 than previously assumed, which we confirm spectroscopically with Keck and the VLT. At z~7 our sources (e.g. CR7) show signatures of PopIII-like stellar populations and/or direct collapse black holes. Our results are extremely important for our understanding of re-ionisation, showing that the steep drop in the Lya luminosity function into the epoch of re-ionisation happens only for the faint Lya emitters, while the bright ones likely ionise their own bubbles very early on, and thus are visible at the earliest cosmic times.
Abstract
A fundamental goal in observational cosmology is to understand the link between the luminous properties of galaxies and the dark matter halos in which they reside. A precise understanding of the key mechanisms that determine the growth, evolution, and global properties of galaxies has eluded astronomers for more than half a century. Dark matter is thought to play a key role in setting the conditions that determine galaxy properties but the exact details of how dark matter influences galaxy formation remains a topic of active debate. Weak lensing, which relies simply on the laws of gravity, is a unique method that can be used to directly probe the dark matter components of galaxies. While previous weak lensing surveys have been modest, reaching at most a few hundred square degrees, the state-of-the art in this field is changing dramatically with surveys such as the Hyper Suprime Cam (HSC) survey, an ambitious multi-wavelength (g,r,i,z,y) weak-lensing program to map out 1500 square degrees of the sky with the 8.2m Subaru Telescope to i???26 mag. Euclid, WFIRST and LSST will follow in less than a decade. In this talk, I will discuss new frontiers that are opening up with these expanded data-sets. New programs that will soon be within reach include detailed studies of the interconnected assembly histories of massive galaxies and dark matter, lensing-based constraints on the inner profiles of dark matter halos and possibly also of the stellar Initial Mass Function (IMF), and direct measurements of the halo masses of dwarf galaxies.
Abstract
Superb Hubble Space Telescope imaging and extensive Very Large Telescope spectroscopy, along with fundamental developments in the strong lensing modelling phase, have allowed us to measure with unprecedented precision the mass distribution of massive galaxy clusters acting as gravitational lenses. I will show how strong lensing models have been employed to reproduce the observed multiple-image positions of distant galaxies substantially better than thought possible even just a few years ago, to predict accurately position, magnification and time delay of a lensed supernova (SN ‘Refsdal’) before it became visible, to probe the structure and substructure properties of galaxy clusters, and to estimate the values of the cosmological parameters defining the global structure of the Universe. I will conclude by outlining the roadmap towards possible extensions beyond the current frontiers of strong lensing studies in galaxy clusters and their implications for cosmology.
Abstract
I will describe recent results from the Palomar Cosmic Web Imager (PCWI). These include the discovery of filamentary Lyman alpha emission and a giant (>120 kpc) protogalactic disk around a QSO, filamentary emission and a large gas proto-disk with possible spiral inflow near a second QSO, and filamentary emission around and kinematics in a Lyman Alpha Blob consistent with a large rotating gas disk. The discovery of filamentary and disk-like structures is evidence for cold accretion inflows with significant angular momentum. I will also describe future instrumentation exploring IGM emission on the ground and in space.
Video
Abstract
Be stars account for 1-2% of all naked-eye stars, and in the local Universe ~5% of all SNe may have Be stars as their progenitors. They possess self-ejected Keplerian disks, from which the emission lines arise that add the attribute “e” to the spectral type. Be stars rotate very rapidly but typically only reach 70% of critical rotation. The missing energy is believed to be contributed by nonradial pulsation while viscosity redistributes angular moment in the ejecta such that the disks are rotationally supported. Be disks are the closest and angularly largest disks in the family that ranges from accretion disks in young stars via mass-exchanging binaries to AGN.
I will describe the big leap forward in the understanding of the role of nonradial pulsation that has been enabled by space-precision photometry with micro- and nanosatellites. The combination with long series of echelle spectra is vital for the distinction between stellar and circumstellar variations and has led to the development of a model describing the coupling of the star, the disk, and the transition region.
April 2016
Abstract
A theory of logical inference should be all-encompassing, applying to any subject about which inferences are to be made. This includes problems ranging from the early applications of games of chance, to modern applications involving astronomy, biology, chemistry, geology, jurisprudence, physics, signal processing, sociology, and even quantum mechanics. This talk focuses on how the theory of inference has evolved in recent history: expanding in scope, solidifying its foundations, deepening its insights, and growing in calculational power.
Abstract
Understanding how star clusters form and evolve has crucial implications for many areas of astrophysics, from star and planet formation, to the history of the Galactic thin disc field star population.
The coming few years will witness a revolution in this research area.
The Gaia mission will indeed soon provide exquisite proper motions and parallaxes for several nearby star clusters, allowing us to test different proposed scenarios.
In a parallel effort, in the last 4-5 years a number of spectroscopic
surveys have been started, providing complementary information to Gaia astrometry. In this context, I will show how Gaia-ESO, a large public spectroscopic survey carried out with FLAMES on the VLT, is already making a significant contribution to the field.
Specifically, I will focus on some of the recent findings from the survey, which shed new light on our current understanding of cluster formation and early evolution, and suggest that the dynamical properties of nearby young clusters are more complex than previously thought.
Abstract
Physics is traditionally conceived of as a set of laws that universally governs the behavior of physical systems. These laws, however they are decreed, are believed to govern the behavior of not only everything in the universe, but the form of the universe itself.
However, this traditional concept of physics as an universal governance is at odds with our modern theories of quantum mechanics and relativity, which place the observer and information in a central role.
In this talk, Kevin aims to rethink the foundations and attempts to build physics from the bottom up based on the very simple foundational idea that all one can possibly know is that there exist things that influence one another.
This is called Influence Theory. He will demonstrate that a great deal of physics can be derived in this context from symmetries and consistent quantification. For example, one can show that there is a unique consistent quantified description of a network of influence events, which is given by the mathematics of relativistic space-time.
Moreover, from this theory, one can derive that our description of space-time can only be 1+1 or 3+1 dimensional. In addition, making inferences about influence events leads to the relativistic quantum mechanics of fermions. As a result, many ‘fundamental’ concepts in physics and their relationships to one another can be derived from a more fundamental picture based on influence.
Abstract
I will report on progress on the new 2MTF survey to study cosmic flows in the nearby Universe and attempts to unveil extragalactic structure hidden behind the southern Milky Way using blind 21 cm surveys. I will also touch on future cosmology optical and radio surveys planned for TAIPAN and ASKAP.
Abstract
The dynamics of dark matter provides the backbone of studies of cosmic structure formation. Despite our ignorance about the particle physics nature of the elusive dark matter, its microscopic properties leave a distinct imprint on its macroscopic dynamics which can be studied in computer simulations. Such N-body simulations have driven most of our theoretical knowledge about the distribution of matter in the Universe which in turn reflects properties of the dark matter particle. I will review the theoretical assumptions underlying such simulations and how they are used to study the nature of dark matter through its dynamics. I will particularly focus on recent attempts to model dark matter in the continuum limit. I will demonstrate how such new methods can be used to overcome known problems of N-body simulations, but also help to gain completely new insights into dark matter dynamics. Finally, I will report on recent results on the formation and evolution of the very first haloes in cold dark matter cosmologies.
Video
Abstract
The discovery of close correlations between supermassive BHs and their host-galaxy properties has sparked a flood of observational studies pertaining both to the local Universe and cosmic history over the last decade. Nevertheless, a clear understanding of their origin still eludes us. Uncertainty remains as to the fundamental driver of these relations, whether purely local and baryonic or global and dark matter dominated. While studying the evolution of these relations with cosmic time provides valuable clues, a definitive resolution of this conundrum relies on understanding slope and scatter of local relations for AGNs. We discuss results from a unique three-fold approach. (i) From a sample of ~100 AGNs in the local Universe, we build a robust baseline of the BH mass scaling relations (MBH-sigma, MBH-L, MBH-M), combining spatially-resolved Keck spectroscopy with SDSS imaging. (ii) We study the evolution of the MBH-sigma and MBH-L relations out to a look-back time of 4-6 Gyrs using Keck spectra and HST images. (iii) We extend this study out to the pivotal cosmic time between the peak of AGN activity and the establishment of the present-day Hubble sequence, a look-back time of 8-10 Gyrs. We measure spheroid stellar masses using deep multi-color HST images from GOODS and determine the MBH-M relation. The results (i) indicate that AGNs follow the same scaling relations as inactive galaxies. From (ii-iii) we conclude that BH growth precedes bulge assembly. Combining results from (i-iii) allows us to test the hypothesis that evolution is driven by disks being transformed into bulges.
Abstract
The Large Area Telescope on the Fermi satellite sees gamma-ray pulsations from over two hundred pulsars: the largest class of GeV sources in the Milky Way. Their diverse properties -- radio loud versus quiet, young versus old, luminosity versus spindown power, and so on -- constrain emission models.
A simple population model helps to better understand their contributions to Galactic ecology. I will describe the current gamma-ray pulsar sample, highlighting some recent discoveries and some ongoing debates.
Abstract
ALMA Cycle 4 deadline is on April 21. For the first time, solar observations and mmVLBI including ALMA will be offered. In this talk I will give a whistle-stop tour round the galaxy to highlight exciting results for ALMA Galactic Science, and to give ideas for your ALMA proposals!
Abstract
The discovery of extrasolar planets has revealed an unexpected diversity among planetary systems.
Our Solar System appears to be a "minority case", given that about 75% of the stars seem to have planets with characteristics that are absent in our own system.
Understanding the origin of such a diversity is a major goal in planet formation and evolution models.
Video
Abstract
Oleg will briefly review the string picture of quark interactions. His topics are the string models of mesons and baryons as well as those of tetraquarks, pentaquarks, and other exotic configurations of quarks and gluons.
Abstract
The LISA Technology Package (LTP) is a space-borne physics laboratory that aims to demonstrate the technical feasibility of a Gravitational Waves (GW) Observatory in space, the evolved Laser Interferometer Space Antenna (eLISA). Space-born observatories shall extend the frequency and sensitivity range of GW measurements beyond the small windows accessible by Earth bound observatories, like advanced LIGO in the US, which directly detected the signature of gravitational waves in September 2015. Advanced LIGO exploits the same technique now being explored in space with LTP. Some partners are the same in both projects.
Airbus DS was chosen by ESA as prime contractor for the gravitational wave observatory demonstrator, which was eventually launched into space on 3 December 2015. It has already undergone commissioning and has just entered into the exciting science operations phase. The presentation gives an overview over the Pathfinder mission, shows how technologies were developed to measure distances with pico-meter accuracy and accelerations as small as 10^{-15} m/s2 to detect gravitational waves with gains as tiny as 10^{-21}.
Abstract
After more than 10 years of autonomous travel the Rosetta Mission arrived at the comet Churyumov-Gerasimenko on 6 August 2014. On its way to the comet, Rosetta completed a complex trajectory that included four gravity assist manoeuvres (3 × Earth, 1 × Mars) and several months of hibernation. Since then, the spacecraft has been orbiting the comet and is performing scientific observation in the close vicinity of the comet. After deploying the lander Philae on the comet surface, Rosetta concluded the initial scientific program. Rosetta will accompany the comet on its journey around the Sun. Its scientific program enter the final stage in September 2016 with the landing of the Rosetta probe itself on the comet.
The talk will provide a view on the challenges of building the Rosetta probe , on its journey to the comet, and on the surprising landing of Philae on the comet. Few highlights of the huge scientific harvest will be presented. The speaker, Dr. Rüdiger Gerndt, was part of the Rosetta Mission Prime Contractor’s Team of Airbus DS (former Dornier) and was in charge of the coordination of scientific payloads, including the lander Philae.
Abstract
The satellite galaxies of the Milky Way and of the Andromeda galaxy preferentially co-orbit within narrow planes, and there is increasing evidence that satellite planes are also present around more distant hosts. Detailed comparisons show that similarly anisotropic phase-space distributions of sub-halos are extremely rare in cosmological simulations. This makes the satellite planes one of the most-serious small-scale problem for ΛCDM. In contrast to other small-scale problems, the satellite planes issue is not strongly affected by baryonic processes because the distribution of sub-halos on scales of hundreds of kpc is dominated by gravitational effects. While scenarios explaining the coherence of satellite positions and orbits exist, they all are currently unable to satisfactorily resolve the issue. Consequently, the current debate on this topic is highly controversial. Claims range from rejecting that there is significant evidence for the existence of satellite planes, over them being natural in cosmological simulations (despite not having been predicted), to them being catastrophic failures of ΛCDM cosmology itself. To understand the existence and origin of the satellite planes, we will have to move beyond a descriptive to a deductive use of the observed satellite correlations, and also consider additional, potentially related features and dwarf galaxy alignments in the Local Group.
March 2016
Abstract
An enormous amount of what we know about the universe and our own place on Earth depends on our understanding of stars. Yet, even for the most familiar stars, there are still major unsolved questions related to rotation, magnetic activity, and mass loss. I will discuss an emerging self-consistent picture that links all of these processes together and to the overall evolution of Sun-like and low-mass stars. This progress is due to large and diverse new datasets, advances in physical models for the loss of angular momentum (which itself depends upon magnetism and mass loss), and the incorporation of these models into long-term stellar evolution calculations.
Video
Abstract
Understanding the distribution of gas in galaxies and its interaction with the CGM is crucial in order to complete the picture of galaxy evolution. At all redshifts, absorption features seen in QSO spectra serve as a unique probe of the gaseous content of foreground galaxies and the CGM, extending out to ~200 kpc. Studies show that star formation history is intimately related to the co-evolution of galaxies and the CGM. In order to study the environments traced by absorption systems and the role of inflows and outflows, it is critical to measure the emission properties of host galaxies and their halos. However, the success rate for detecting host galaxies still incredibly low (in some cases, less than 30%). In recent years, great strides have been made towards overcoming the deficit of confirmed host galaxies compared to the number of observed absorption systems. New techniques and instrumentation have allowed us to overcome the challenge of detecting absorption host galaxies with the use of SDSS and the MUSE integral field spectrograph on VLT. SDSS provides the wide coverage at low redshift necessary to probe configurations of galaxies and QSOs in imaging, while MUSE's large field of view and sensitivity to emission lines has allowed a never-before seen match between the number density of absorbers along QSO sightlines and the number density of emission line galaxies within 200 kpc of the QSO. These galaxies represent a sample for which previously elusive connections can be made between mass, metallicity, SFR, and absorption properties.
Abstract
Standard solar models (SSMs) provide a reference framework across a number of research fields: solar and stellar models, solar neutrinos, particle physics the most conspicuous among them. The accuracy of the physical description of the global properties of the Sun that SSMs provide has been challenged in the last decade by a number of developments in stellar spectroscopic techniques. Over the same period of time, solar neutrino experiments, and Borexino in particular, have measured the four solar neutrino fluxes from the pp-chains that are associated with 99% of the nuclear energy generated in the Sun. Borexino has also set the most stringent limit on CNO energy generation, only ? 40% larger than predicted by SSMs. More recently, and for the first time, radiative opacity experiments have been performed at conditions that closely resemble those at the base of the solar convective envelope. In this talk, Aldo will review these developments and discuss the current status of SSMs, including its intrinsic limitations.
Abstract
There is observational evidence that the environment of star forming regions can significantly affect the evolution of protostellar and protoplanetary discs (PPDs). In particular, the energetic (FUV) radiation permeating young associations can drive photoevaporative winds from the discs' outer regions. Hitherto, such mechanism has been considered to be significant in quite extreme environments only, as in the Orion Nebula Cluster. However, I will show that when grain growth in the disc is taken into account, new hydrodynamical models indicate that the mass loss rates in these photoevaporative flows are high enough to affect the global evolution of PPDs even in moderate environments. In particular, such thermal winds might drive the dispersal of the outer disc of the majority of PPDs, which needs to be dispersed on a short timescale to match observational constraints. I will also highlight how these winds are now potentially detectable with ALMA at the outer edge of protoplanetary discs.
Abstract
Stars and star clusters form by gravitational collapse in regions of high density in the complex multi-phase interstellar medium. The process of stellar birth is controlled by the intricate interplay between the self-gravity of the star-forming gas and various opposing agents, such as supersonic turbulence, magnetic fields, radiation pressure, and gas pressure. Turbulence plays a dual role. On global scales it provides support, while at the same time it can promote local collapse. This process is modified by the thermodynamic response of the gas, which is determined by the balance between various heating and cooling processes, which in turn depend on the chemical composition of the material. I discuss examples of recent progress and controversy. I address some puzzles and uncertainties in deriving galactic-scale star formation relations and argue that there may be a large reservoir of CO-dark H2 gas in disk galaxies such as our Milky Way. Also, I report of recent attempts to quantify the amount of diffuse CO emission in the Galaxy.
Abstract
On December 15th 2015 both the ATLAS and the CMS experiments reported of an excess found in the gamma-gamma spectrum around 750 GeV in the proton-proton collision data recorded at sqrt(s) = 13 TeV. The results of these analyses will be discussed with a focus on the analysis techniques and the signal models taken into consideration.
Abstract
Star formation in galaxies is observed to occur in molecular clouds.
However, the origins and evolution of these clouds remains unclear,
impeding the construction of a predictive theory of star formation.
Indeed, the necessity of molecules for star formation has come into
question, as it becomes clear that their formation may just be a side
effect of star formation, correlated with gravitational collapse but
not causing it. This seems consistent with the structuring of
star-forming galaxies by gravitational instabilities that drive the
formation of spirals and bars. In this talk I present kiloparsec-scale,
well-resolved, MHD simulations of the stratified, supernova-driven,
interstellar medium performed with the Flash code. I use the
results of these simulations to argue that gravitational collapse
rather than any sort of turbulent equilibrium determines the dynamics
of molecular clouds, with a focus on the relationships between size,
velocity dispersion, and surface density of the clouds.
Abstract
In this talk I would like to present the extended redshift distribution of the South Pole Telescope (SPT) selected Dusty Star-Forming Galaxies (DSFGs).
We used ALMA to perform spectral scans between 84-114 GHz for 15 galaxies to obtain redshifts and to target an additional eight sources at 1mm to confirm redshifts for these sources. With APEX/FLASH and APEX/SEPIA we obtained [CII] and CO mid-J observations for five sources for which only a single line was detected in spectral-scan data from ALMA Cycle 0 or Cycle 1. We combine the new observations with previously published and new mm/submm line and photometric data of the SPT-selected DSFGs to study their redshift distribution. We find a median redshift of z=3.9 with the highest-redshift source at z=5.8. I will in the talk discuss how the selection of our sources affects the redshift distribution, focusing on source brightness, selection wavelength, and strong gravitational lensing. The talk will also include a preliminary sneak peak of our newly received ALMA spectral scans.
Abstract
The DEAP-3600 experiment uses a 3.6 tonne liquid argon target for a direct dark matter search with a projected sensitivity to the spin-independent WIMP-nucleon cross-section of 10^-46 cm^2 at 100 GeV WIMP mass after a three-year background-free exposure.
DEAP is operated as a single-phase detector. The liquid argon volume is viewed by 255 high efficiency photo multiplier tubes, which record the scintillation light emitted when particles interact there. The resulting pulse shapes allow very efficient rejection of the overwhelming electromagnetic backgrounds from the dark matter signal region using pulse shape discrimination.
To meet the detector’s extremely stringent background targets, remaining backgrounds are suppressed through several layers of active and passive shielding - including 6000 m.w.e of rock overburden, through material screening, through the use of clean construction techniques, through careful detector design, and in offline analysis through fiducialization.
The DEAP detector was built between the years of 2011 and 2016 at the SNOLAB facility, 2 km underground, and is currently taking commissioning data. We will present the status of the experiment and results from analysis of the first commissioning data on behalf of the DEAP-3600 collaboration.
Abstract
Using new very deep Chandra and XMM-Newton X-ray observations of nearby galaxy clusters we are obtaining an unprecedented view of the intracluster medium in the cores of these objects. Rather than purely symmetric hydrostatic atmospheres, we see dynamic places where multiple physical processes are important, including AGN feedback, gas sloshing, mergers, sound waves, turbulence, enrichment and plasma instabilities. I will review some interesting results from the launch of these satellites and show some recent results from deep observations of the Centaurus, Coma and Perseus galaxy clusters.
Video
Abstract
Low-mass galaxies at high redshift play a key role in galaxy formation and evolution as
building blocks of more massive galaxies seen at later epochs. I will talk about star formation
properties and their diversity of Ly-alpha Emitters (LAEs) at z ≃ 2.2, a commonly seen
low-mass galaxy population. First, by stacking deep Spitzer/MIPS and Herschel/PACS
images for 213 LAEs in the GOODS-South, we find for the first time that LAEs typically
have very low IR luminosities less than L^{3sigma}_{TIR} = 1.1 x 10^{10} L⊙
(3 sigma upper limit) and that their attenuation curve is consistent not with the Calzetti curve
but with the SMC curve (Kusakabe et al. 2015, ApJ, 800, L29). Second, we divide 604 LAEs
in the SXDS field into sub-samples based on the distribution of four UV physical parameters:
M_{UV}, beta, L_{Ly-alpha}, and EW_{Ly-alpha,r}.
Then, we calculate the halo mass and stellar population parameters for each sub-sample
from clustering analysis and SED fitting with SMC curve, respectively.
While two thirds of the entire sample are on the SFMS with stellar masses of ~10 9 M⊙,
the remaining one third, which are the lowest-mass objects in our sample, are forming
stars burstly with stellar masses of ~10 7 M⊙ with SFRs exceeding the baryon accretion
rates of their hosting halos. These low-stellar mass LAEs may be in initial forming phases
at cosmic noon (Kusakabe et al. in prep).
Abstract
The search for organic material and biosignatures on Mars is a highly complex endeavor and scientists are at odds when it comes to evaluate the chances for detecting life on Mars. Past conditions of Mars may have allowed life to develop. In particular, the earliest liquid-water rich era would present the most habitable conditions. For life to develop, chemical raw materials are necessary, hence space missions that investigate the composition of comets and asteroids and in particular their organic content provide major opportunities to determine the prebiotic reservoirs available to the early Earth and Mars. Endogenous production of organic material on Mars may have proceeded through similar mechanisms as suggested for the early Earth. Life on Earth originated approximately 3.5 billion years ago and has adapted to nearly every explored environment. Today, the Martian surface is cold, dry and hostile. A combination of solar ultraviolet radiation and oxidation processes in the soil are destructive to organic material and life on and close to the surface. However, the progress and the revolutionary quality and quantity of data on "extreme life" on Earth have transformed our view of habitability beyond Earth. Mars is still the central object of interest for habitability studies and life detection beyond Earth and can be visited frequently by robotic spacecrafts, paving the way for returned samples and human exploration. Extensive science activities in support of Mars exploration are performed worldwide in the laboratory, in the field and through simulation studies. This lecture will highlight data from past and current Mars missions and discuss the science and technology that supports robotic efforts investigating habitability and biosignatures on Mars.
Abstract
The quest for identifying the bulk chemical composition of extrasolar planets and robust observational evidence that between 25% and 50% of all Milky Way white dwarfs host currently dynamically-active planetary systems motivate investigations that link their formation and fate. Here I provide a review of our current knowledge of these systems, including the groundbreaking recent discovery of multiple co-orbital disintegrating planetesimals around white dwarf WD 1145+017. I show how this field incorporates several facets of astrophysics and planetary science, including orbital dynamics, stellar evolution, astrochemistry, atmospheric science and surface processes. I outline the fundamental outstanding questions which remain about the origin and evolution of these fascinating systems.
February 2016
Abstract
Gravitational lensing provides powerful means to study dark energy and dark matter in the Universe. In particular, strong lens systems with measured time delays between the multiple images can be used to determine the "time-delay distance" to the lens, which is primarily sensitive to the Hubble constant, whose measurement is crucial for inferring properties of dark energy. I will describe the ingredients and newly developed techniques for measuring accurately time-delay distances with a realistic account of systematic uncertainties. A program initiated to measure the Hubble constant to < 4% in precision from gravitational lens time delays is in progress, and I will present the first results and their implications. Current and upcoming imaging surveys will contain thousands of new time-delay lenses, and I will describe ongoing efforts to find these objects. An exciting discovery is the first strongly lensed supernova, which has offered a rare opportunity to perform a true blind test of model predictions. I will describe the bright prospects of using gravitational lens time delays as an independent and competitive cosmological probe.
Abstract
The recent development of sensitive near-infrared detectors has opened up a new window for the study of high-redshift galaxies. Using the new near-infrared capabilities of the MOSFIRE and LRIS instruments at the Keck observatory, we have undertaken a spectroscopic survey of about 100 quiescent galaxies in the redshift range 1 < z < 2.5. Our deep spectra reveal the rest-frame optical absorption lines, which are the most effective probe of the physical nature of quiescent galaxies, and allow us to measure velocity dispersions and stellar ages. In particular, we are able to overcome the issue of connecting galaxy populations at different redshifts, which is the most challenging aspect of observational studies. I will discuss our main results, including the comparison of dynamical and stellar masses, and a solution for the puzzling size growth of quiescent galaxies.
Abstract
Dark matter makes up roughly 80% of the matter in the universe, yet the details of its particle nature remain unknown. Many particle dark matter candidates can pair annihilate to produce Standard Model particles, including gamma-ray photons, charged particles, and neutrinos, providing a means of indirectly detecting this elusive component of the universe. In recent years an excess of gamma rays from the Inner Galaxy in the Fermi LAT data has been identified. This emission has been interpreted as a possible signature of the annihilation of dark matter particles. I will review these recent results, and discuss possible ways to confirm a dark matter signal, including the potential of multi-wavelength searches.
Abstract
BRIght Target Explorer (BRITE) is the first scientific mission using nano-satellites for making observations from space. It is aimed at precise photometry of the brightest stars in the sky. Equipped with either blue or red filter, BRITE satellites provide up to six-month long observations of selected stars. This allows for a detection of multimode pulsations with sub-mmag amplitudes as well as many other types of variability. Most of about 300 up-to-date observed targets are massive hot main-sequence stars. I will summarize the objectives of the mission and show a few examples of the first scientific results based on BRITE data.
Abstract
I will discuss the predictions of the theory of quantum origin of the universe structure and their experimental verification.
Abstract
The star formation process is intimately linked to dense molecular gas. Extragalactic studies reveal that the luminosity of the dense gas is well correlated with the star formation rate in a system, though recent results point out that there are multiple parameters in this relationship. At smaller physical scales in our own Galaxy, we study the foundation of these broad trends by linking the structure of dense gas to actual process of star formation occurring in cores and clumps. In this talk, I will outline the unique properties of ammonia as a dense gas tracer and summarize several studies that leverage these properties. In particular, I will emphasize new results from the GBT Ammonia Survey (GAS) that highlight the ubiquity of quiescent cores and probe the connection of between cores and clouds. I will then connect those results to follow-up studies in the Galactic plane that illustrate how we can bootstrap our knowledge up to larger scales.
Abstract
I will present recent efforts to understand early cluster formation phases in the distant Universe, when the first giant dark matter halos were growing, and baryons falling into their deep potential wells took part to prodigiously vigorous activity of galaxy and black hole assembly. These phases are expected to be crucial to understand the processes leading to the formation of dominant elliptical population and well relaxed hot gas atmospheres, as observed in local massive galaxy clusters. New observations with ALMA, NOEMA, Herschel, HST and Keck of two dense structures at z=2 and 2.5 provide new insights into these problematics. Euclid, Athena, ALMA, SKA, JWST, Keck CWI (a bluer MUSE!), and the ELT(s) hold the promise to revolutionise this field in the coming decades.
Video
Abstract
Studying the emergent properties of hot and dense nuclear matter is one of the main goals of relativistic heavy-ion collision experiments. At the highest energies a Quark-Gluon Plasma (QGP) phase arises with partonic degrees of freedom. Due to the extremely short life time of the QGP, only probes which are created during the collision can be used to study its properties. Alexander will discuss recent developments at STAR for two of the most important probes from soft and hard physics, namely elliptic flow and jets. He will furthermore give an overview of the Beam Energy Scan program (BES) at RHIC, which was carried out to find signatures of a QCD critical point and a first order phase transition. At the end he will give an outlook of BES phase II, which is anticipated for the years 2018-2019.
Abstract
The SAMI Galaxy Survey is a pioneering multiplexed optical integral field spectroscopic survey that upon completion will comprise 3400 galaxies. Such a large sample of spatially resolved galaxies will allow us to tackle the fundamental questions of galaxy evolution that remain elusive in smaller samples. This talk will present some of the key science results produced by the SAMI team thus far and how this relates to my own PhD work on a distinct sample of luminous local AGN.
January 2016
Abstract
In August 2014 Rosetta arrived at comet 67P/Churyumov-Gerasimenko after a more than 10 years journey through the inner planetary system. Since then, the spacecraft explores the comet and its immediate neighbourhood with its instruments, and on 12 November 2014 it deployed the Philae lander to the nuclear surface. In September 2016 the mission will end with the soft landing of the orbiter on a comet. The Rosetta and Philae investigations focus on the nucleus surface and its interior, the composition of the cometary ice and dust, the physical processes in the cometary environment, and the cometary activity and how it works. The overall connecting science goal is the message, comets can provide on the origin of the solar and planetary system and whether and how comets are linked to water and life on Earth. More than half way through the mission, results on several scientific objectives are available providing new insights in planetary science with comets.
Abstract
Time is one of the 7 basic physics quantities. However, a dispute is ongoing in contemporary philosophy, with physicists involved on both sides, whether the notions “past, presence, future” are objective notions and make sense in considerations of physics (or more generally speaking of natural science) or whether they are purely subjective notions of human consciousness. The perspective of the past, presence and future plays an essential role for human activities (and is intimately connected with the free will, another central notion for practical philosophy). As a matter of fact, these notions do not appear in any physics law. However, physics laws are meant to describe reality. So the question is whether past, present and future play a role in objective descriptions of real processes. Particular attention is paid to real reference systems for space and time which are needed to objectively describe real processes.
Abstract
The advent of ALMA makes it possible either detections of far-infrared (FIR)
metal and molecular cooling lines arising from single galaxies that formed at the
end of the Reionization Epoch (EoR), and blind surveys that aim at following
the global evolution of cold gas across cosmic time. In the first part of this talk
I will focus on the cold neutral gas. I will present a theoretical model that,
coupled with high resolution radiative transfer cosmological simulations, allows
to predict the luminosity of [CII] 158 µm line arising from the neutral diffuse gas
and from dense Photodissociation Regions. I will show that the model has been
successfully used to interpret ALMA [CII] detections in galaxies at the end of
EoR, and how we can use the [CII] line to put constraints the relative abundance
of different gas phases composing the ISM of the first galaxies. In the second
part, I will focus on the cosmic evolution of the molecular gas mass fraction.
I will discuss how a proper decomposition of the FIR luminosity function can
be exploited to derive the evolution of the CO luminosity function for different
galaxy classes and in particular of the AGN.
Abstract
Large galaxy surveys have been a driving force in developing our understanding of galaxy evolution for more than two decades. Their role is to systematically characterise galaxies as a function of key parameters and to disentangle the complex interplay between dark matter, stars, gas, dust and AGN. While much of the action in galaxy evolution happens at redshifts > 1, the value of low-redshift surveys lies in the comprehensiveness and statistical power with which they are able to describe the end product of galaxy evolution. In this talk I will review a selection of results from the recently completed Galaxy And Mass Assembly survey. GAMA combines an extensive spectroscopic survey with imaging data from seven ground-based facilities and four space missions in order to construct a unique multi-wavelength data set covering all major galaxy constituents. I will present results concerning the galaxy stellar mass function, the halo masses and mass-to-light ratios of galaxies and groups, the star formation rate and the build-up of stellar mass through mergers.
Abstract
Electromagnetic radiation is the ideal probe to study the formation of hot and dense matter in heavy ion collisions. Real and virtual photons are produced in all the stages of the collision, allowing to study the whole system evolution. Moreover, electromagnetic radiation is transparent to the medium bringing information unaffected by final state interactions. By detecting photons and dileptons one can study the system temperature, via the extraction of thermal radiation, and the chiral symmetry restoration that is expected to happen in the deconfined phase via the modification of the spectral funcions of vector mesons. We review the experimental dielectron studies in Heavy Ion Collisions, from RHIC to the LHC, with particular focus on the expectations from the recently collected data from Pb-Pb collisions at centre-of-mass energies per nucleon pair of 5 TeV by the ALICE experiment.
Abstract
While the star formation density over cosmic time is well studied, very little is known about neutral hydrogen, the fuel for star formation, over the same epoch. I'll give an overview of current observations, look ahead to upcoming surveys in the era of the SKA, and motivate why these efforts are essential for a complete picture of galaxy formation and evolution.
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