Seminars and Colloquia at ESO Garching and on the campus

Despite most supermassive black hole (SMBH) growth occurring via merger-free processes, the underlying mechanisms driving this secular evolution are poorly understood. I will present my work highlighting the role that both strong and weak large-scale galactic bars play in mediating this growth, by analysing the active galactic nucleus (AGN) presence. Strongly barred galaxies have a higher fraction of AGN than weakly barred galaxies, which in turn have a higher fraction than unbarred galaxies. Thus, while bars are not required in order to grow an SMBH in a disc galaxy, large-scale galactic bars appear to facilitate AGN fuelling, and the presence of a strong bar makes a disc galaxy more than twice as likely to host an AGN than an unbarred galaxy at all galaxy stellar masses and colours. I will then present more recent work that separates the contribution of the bar and the contribution of the galactic bulge to AGN presence.

Sub-Saturns, which are planets with radii between 4 and 8 Earth radii, are key to understanding the transition from ice giants to gas giants. Their distribution is shaped by the Neptunian desert (a scarcity of Neptune-sized planets on short orbits), the Neptunian ridge (an overdensity at orbital periods of 3–6 days), and the Neptunian savanna (a slight underdensity at longer periods). These features reflect the complex interplay of atmospheric escape, migration, and formation. In this talk, I will present our recent study using the GASTLI interior structure model to derive the envelope mass fractions (fenv) of 26 warm sub-Saturns. By comparing our results to a formation model, we find that sub-Saturns require significantly metal-enriched atmospheres to match the synthetic planets. Additionally, we find a bimodal distribution of fenv, with a notable gap that aligns with theoretical predictions for the onset of runaway gas accretion.

Faint blazars are often difficult to identify, as their recognition typically requires cross-matching positional counterparts across radio, optical, and X-ray catalogs. To support high-energy studies for the Cherenkov Telescope Array Observatory (CTAO), we adopted an alternative approach. Starting from the Fermi-LAT 4FGL-DR4 catalog (5,062 γ-ray sources at galactic latitude |b| > 10°), we searched for blazar counterparts using Firmamento*, a web-based platform developed within the Open Universe initiative of UNOOSA. Firmamento integrates multi-frequency data and high-level analysis tools for spectral energy distribution (SED) studies.
By combining automated algorithms with visual inspection and validation by experts, high-school, and undergraduate students — given the large size of the sample — we discovered 421 new blazar associations, reducing the fraction of unassociated Fermi-LAT sources from 25% to 17%. The resulting catalog, 1FLAT, has been published in the Astrophysical Journal Supplement Series.
This talk presents both the scientific results and the educational framework behind this collaborative effort.

 

* https://firmamento.nyuad.nyu.edu/data_access