Quasars are the most luminous subset of the Active Galactic Nuclei (AGN) population and represent the most rapid phase of supermassive black hole (SMBH) growth. Strong observational evidence supports a connection between SMBH accretion and the evolution of their host galaxies, where obscured quasars are expected to play a key role. However, this role has not yet been fully understood since large quasar samples have biases, typically against obscured AGN, low-luminosity AGNs, etc. In this talk, I will present results from a complete and unbiased sample of high-luminosity mid-infrared quasars at z=1−3. By combining multiwavelength data from X-rays to radio wavelengths, including ALMA submillimeter observations, we probe the physical properties of both the AGN and their host galaxies, revealing fundamental differences in the radio and star-formation properties between obscured and unobscured populations. I will discuss how these findings challenge the standard AGN orientation model and point toward possible evolutionary links among quasar populations. With the objective of pushing forward obscured quasar research, I will then introduce and show the first results of the 4MOST IR AGN survey, the first large-scale optical spectroscopic survey targeting obscured IR AGN. I will finish my talk by discussing how upcoming multiwavelength large-scale surveys will allow us to improve our understanding of the relationship between different AGN populations and galaxies.

Location: ASU Spořilov 101

online připojení https://us02web.zoom.us/j/3464248686

Understanding the co-evolution of active galactic nuclei (AGN) and their host galaxies requires the robust decomposition of their respective emission to reliable constrain the AGN and host galaxy physical properties. Leveraging the unique NIR capabilities of Euclid’s Quick Data Release (Q1), I performed spectral energy distribution (SED) fitting to simultaneously constrain the properties of AGN and their hosts. Moreover, I present a new method to assess and improve the reliability of the measurements, based on simulated SEDs built from combined quasar and galaxy observations. I quantify how AGN emission impacts physical property estimations and demonstrate that SED fitting serves as a powerful diagnostic for AGN identification, achieving 85% purity and completeness. Furthermore, a comparative analysis of AGN selected via different methods reveals that these techniques probe partially distinct populations, highlighting the importance of multi-wavelength, multi-method approaches to mitigate selection biases in studies of galaxy evolution. Finally, we investigate the X-ray to mid-infrared luminosity relation and the evolution of the stellar mass–bolometric luminosity correlation across cosmic time. These results validate the utility of Euclid for constructing large, homogeneous AGN samples, providing a crucial foundation for mapping the co-evolution of supermassive black holes and their hosts over a wide range of redshifts. I will conclude my talk by showcasing how the community can leverage this catalogue for future AGN studies.

Location: ASU Sporilov, 101

online připojení https://us02web.zoom.us/j/3464248686

Location: Seminar room, Prague

X-ray binaries hosting compact objects exhibit often characteristic variability patterns in their lightcurves, attributed to thermoviscous instabilities within their accretion disks. In particular, the short-term limit-cycle oscillations are believed to arise from radiation pressure induced (RPI) instabilities, operating in the inner regions of the disk, where radiation pressure is dominant. A model investigating such RPIs in accretion disks was developed by Janiuk et al. (2002) and has since been applied to several black hole X-ray binaries. In the talk, I plan to elaborate on our efforts to study how irradiation from the central source affects the evolution of an unstable disk around a black-hole, within the framework of the disk-instability model. In recent years, irradiation has been recognized as an important factor in the disk evolution e.g. by Dubus et al (1999). The central compact region can be a hot corona in case of black hole accretors, or a hot boundary layer, between the disk and the stellar surface, in case of accreting neutron stars. For our study, we employ the code GLADIS, which computes a 1D, vertically averaged, global hydrodynamical model of the disk. We include the extra flux in our energy balance equation, whose net contribution to the cells depends strongly on the geometry of the system. We then explore different types of oscillations an irradiated, unstable disk can produce, and use them to model the “heartbeat” oscillations observed in the X-ray binary 4U 1630-47 by Fan et al. (2025). I’ll attempt to briefly present our results, showing how irradiation significantly changes the evolution of the disk and what more physics can we include in our models.

Location: ASU-Praha, Spořilov