Seminars and Colloquia at ESO Santiago

A large fraction of the material that accretes onto the supermassive black hole in an active galactic nucleus (AGN) on parsec scales does not fall into the black hole, but is instead launched outwards by radiation-driven outflows, primarily in the form of ionised gas. However, accurately determining the strength and structure of these outflows remains a challenge, and many open questions regarding AGN outflows still remain.

In this talk I will present the results of my 3-month internship at ESO, of which the aim has been to characterise the ionised outflows of the Seyfert Type II AGN in the Circinus galaxy. Being one of the AGNs closest to us, it is a great laboratory for improving our understanding of their physics. Using long-slit spectroscopic data of the [S IV] 10.51 μm and [Ne II] 12.81 μm coronal lines from VLT/VISIR, we created a pseudo-IFU and used it to measure emission line properties along the slits, most importantly the velocities. We then fitted a model consisting of a biconical outflow and a rotating disk to these velocities to determine the orientation and geometry of the ionised outflows of the Circinus AGN. I will lay down the results of both steps of this procedure, discuss how these results compare to the literature and lay down the next steps in improving our understanding of AGN outflows.

Instrumental polarization has long been a concern in optical interferometry, as different optical paths affect the incoming light differently, potentially reducing fringe contrast. But what if we went a step further by characterizing the polarization introduced by the VLTI telescopes and offering a polarimetric observing mode to the community? 

Such a mode would combine the high spatial resolution of the VLTI instruments with accurate polarimetric capabilities, enabling the study of dusty environments. To achieve this, I will present the development and calibration of a model designed to retrieve the intrinsic polarization state of the incoming light, by correcting for instrumental effects. This model is intended to be applied to the observed visibilities of on-sky data, providing access to the polarized signal information.

Warm gas giants are valuable targets for understanding how planetary systems form and evolve, as their transits and radial velocities provide key clues about structure and dynamics. In this talk, I will present part of my PhD work on the detection and characterisation of these planets, using transit photometry, radial velocities, and transit timing variations.
I will focus on TOI-4504, where we detected transits from a planet that was not transiting a few years ago and has since begun transiting due to dynamical interactions in the system. This enabled a much better characterisation of the system. I will also discuss five planetary systems with close-in gas giants and long-period companions identified through extended radial velocity monitoring. Together, these systems expand the sample of giant planet architectures and help place warm gas giants in a broader dynamical context.

I will present my ERC advanced grant project, StarDance. This is based on the knowledge gaps in the study of star clusters, such as the existence of multiple stellar populations in globular clusters, with different chemistry, and of exotic stellar populations, that are thought to be byproducts of stellar interaction. Given the mounting problems faced by the most favored scenarios to explain multiple populations, it is now time to revisit the foundations of our current thinking. New results show that: (i) the peculiarities in the chemistry of multiple populations are not limited to the oldest globular clusters; (ii) they can be transient in the evolution of individual cluster stars; and most importantly (iii) binary interactions and fast stellar rotation cannot be neglected in the study of star clusters and do have the capability to produce the observed chemistry. The ERC StarDance hypothesis assumes that multiple stellar populations and non-canonical stellar populations (extreme horizontal branch stars and hot sub-dwarfs; extended main sequence turn-offs; red stragglers and sub-subgiants; lithium-rich stars; and blue stragglers) are caused by the interplay between stellar rotation and binary interactions, that are greatly enhanced in the special environment of star cluster, with spectacular results. I will also briefly describe the ERC funding scheme. 

To be announced

The elusive cosmological redshift drift — predicted by General Relativity as a direct and model-independent signature of the Universe's accelerated expansion — remains one of the most ambitious goals in observational cosmology. In this work, we take the first steps toward detecting this effect using the Lyman-α forest of bright quasars as tracers of the expanding Universe. Focusing on the most luminous quasar in the southern sky, J052915.80−435152.0, we present results from three high-resolution, high signal-to-noise spectral epochs obtained with ESO's ESPRESSO instrument over a two-year baseline. By comparing the positions of the Lyman-α absorption features across epochs, we constrain the cosmological acceleration at the level of 3.6 m/s/yr, currently the tightest high-redshift constraint to date. We also investigate the dominant observational systematics — including wavelength calibration stability and precision — that will ultimately limit the detection of the cosmological signal, expected to be of order 0.5 cm/s/yr in a ΛCDM Universe. Finally, we show that a joint long-term VLT/ESPRESSO + ELT/ANDES programme targeting the seven super-bright quasars identified by the QUBRICS survey could achieve a significant detection of the redshift drift by the 2080s.

To be announced

To be announced

Mapping cold molecular gas and dust at sub-kiloparsec (kpc) scales in galaxies is essential for understanding the physical processes driving star formation in the ISM, particularly during the peak epoch of cosmic star formation (z~2-3; cosmic noon). At these redshifts, near-IR IFU and rest-frame UV/optical observations with JWST and HST reveal turbulent rotating disks, dominated by compact and bright stellar clumps. However, the origin and role of these stellar clumps in galaxy assembly remain debated. Addressing this requires resolving their parent giant molecular clouds (GMCs) with sub-kpc CO observations tracing the cold molecular gas. Detecting GMCs at z>1, however, is extremely challenging due to the required sensitivity and resolution. Strong gravitational lensing can overcome these limits when combined with the high capabilities of ALMA. I will present high-resolution ALMA Band-3 and JWST/NIRCam observations of J0658, a 20x-magnified main-sequence star-forming galaxy at z=2.78. Using a new JWST-based strong lensing model, we performed a detailed characterization of the star-forming clumps and tested the Kennicutt--Schmidt (KS) relation at sub-kpc scales. We found a breakdown of the KS relation driven by the resolution of individual evolutionary stages of the star formation cycle in J0658, as well as evidence for a lensed galaxy pair at z~2.78 thanks to new ALMA Band-4 observations. Finally, I will highlight ongoing and upcoming projects targeting various highly magnified sources, aimed at extending these analyses to a broader population of high-z galaxies.

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