Seminars and Colloquia at ESO Santiago

After my retirement from ALMA, I did not return to my home country, for various reasons. Staying in the Chilean campo, about 120 Km NW from Santiago, I became more aware of the education system, in particular in the more remote regions. I decided to start a small observatory for the young population. That is Observatorio Ocoa, a settlement in the community Hijuelas, ruta-5 Km 100, in the fifth region. To be more effective in astronomy and science teaching, it was soon clear that one also would need a planetarium. However, there are no funds for such an education tool. With the strict isolation required by the COVID-pandemia, no travel, I decided to design and construct one myself. A small, simple one, at low cost that I could build mostly myself. This resulted in a 6-meter diameter planetarium that can host to about 40 students. The impact of the planetarium shows on the students was staggering. So next step…more planetariums.

Have gotten the experience by building one, I changed the design; it is now completely prefabricated. The most challenging part is the operation. I will explain the approach to get well functioning planetariums. And more about the status of the project: “Planetarios Educativos para Chile”.

Supermassive black holes (SMBHs) exist in almost all massive galaxies, and accretion of material onto these SMBHs is known to power active galactic nuclei (AGN). In this talk, I will present the results obtained by analysing ALMA data of a diverse sample of 35 nearby galaxies to study the link between circumnuclear (≤100pc) molecular gas reservoirs and AGN fuelling to better understand the powering mechanism. We find that the cold molecular gas mass within the nuclear regions does not correlate with any measure of AGN activity. This suggests that the AGN fuelling is not a ubiquitous process, even when cold gas is present. I will then discuss the origin of the nuclear mm emission in these sources. We find a strong relation between the nuclear mm emission from our galaxies and the SMBH mass, and an even tighter correlation is observed if the 2-10 keV X-ray emission is included. We find this can naturally arise from advection-dominated accretion flows (ADAFs). This result suggests that radiatively-inefficient processes are ongoing in our sources (spanning a wide range of AGN types), and provides a new method to indirectly measure SMBH masses.

Binarity is ubiquitous among OB-type stars. Among these, classical Be stars hold unique clues to binary evolution in general and to the physics of binary mass transfer specifically. Be stars form self-ejected Keplerian disks as a means to shed excess angular momentum, which was in many cases acquired in a past binary mass transfer episode. Post-mass-transfer Be stars typically have stripped helium-burning companions of the subdwarf OB-type (sdOB), which can further evolve into white dwarfs (WD) or if massive enough into neutron stars, for the binary systems to become high-mass Be X-ray binaries. Although sdOB and WD companions are expected to be common, they are very hard to detect due to their low masses and luminosities compared to the Be star primaries. Only about two dozen hot sdO companions have been confirmed so far, with cooler sdB as well as WD companions being even more elusive. In an interferometric program on the binarity of Be stars with the CHARA Array and the VLTI, we detected and mapped the astrometric orbits of almost a dozen sdO companions, as well as of a few bloated pre-subdwarf companions, which are caught in a short-lived unstable phase immediately following the mass transfer. We also confirmed the first sdB companion with temperature similar to that of the Be star, suggesting a hidden population of cooler stripped companions. Complementing interferometry with (far-UV) spectroscopy, we were able to obtain 3D orbital solutions and determine dynamical masses for eight post-mass-transfer Be binaries, providing new insights into the properties of the past mass transfer, such as its unexpectedly high efficiency. We were also able to shed light on the hotly debated Be stars with gamma-Cas-like X-rays, with observational evidence mounting that they have accreting WD companions, forming a special class of Be X-ray binaries. The new interferometry together with SED data also enable studying the effects that binarity has on the structure of Be star disks, such as the presence of large circumbinary structures, whih are also predicted by recent state-of-the-art hydrodynamic simulations.

The possibilities for the future and the eventual paths to take, is always a constant thought on a young scientist’s mind. In this talk I will talk about how to best prepare for job applications in academia and the industry, how to prepare your CV for such occasions and what type of applicants the recruiters are looking for. We will discuss some strategies for presenting yourself in the best possible light and to ensure your application stands out among a sea of other applications. We will try to consider cover letters, CVs, applications and recommendation letters. The format will be more of a discussion rather than a lecture.

TBD

Streamers and accretion shocks are predicted by theoretical models, however, only few protostars show evidence of these physical processes at the disk-envelope interface. Infalling streamers can replenish the disk with fresh material from the envelope and accretion shocks are able to sublimate molecules to the gas-phase that, otherwise, will remain looked into dust grains.

tbd

tbd

tbd

tbd

tbd

TBD

TBD

tbd

The weakness of the hyperfine 21cm line, the main tracer of the atomic gas content of galaxies, has meant that we know little about the HI mass of high-redshift galaxies and its evolution. This has long been one of the biggest lacunae in our understanding of galaxy evolution. ``Stacking'' of the 21cm emission signals from a large sample of high-redshift galaxies, with known optical positions and redshifs and observed simultaneously with a radio interferometer, can allow one to determine the atomic gas properties of the galaxy population. The advent of new or upgraded radio interferometers, with wideband spectral capabilities and modern correlators, has recently yielded dramatic progress in this field. In this talk, I will describe the state of the art in such 21cm stacking experiments from deep studies with the Giant Metrewave Radio Telescope that have yielded the first measurements of the atomic gas properties of star-forming galaxies during the era of cosmic noon.

tbd

tbd

TBD

tbd

Gamma-ray bursts fascinate astronomers both for their astounding power and for their effectiveness as cosmological probes. Spectroscopy of their bright optical counterparts allows to dissect the interstellar and circumgalactic medium of high-redshift star-forming galaxies, testing their gas, metals, dust, and molecular content. At the same time, also thanks to a new suite of instruments, we have been discovering a richer diversity of progenitor systems - with the two main players being collapsing massive stars and binary compact object mergers. I will highlight the recent progress and surprises in the field achieved via the "Stargate" program at the VLT.

tbd

TBD