Wednesday Colloquium


"Constraining the Cosmology with Quasars"

Raj Prince (Center for Theoretical Physics, Polish Academy of Sciences, Warsaw, Poland)

Quantifying the accelerated expansion of the Universe is one of the key issues of cosmology. Various probes are used for this purpose, like observations of the Cosmic Microwave Background, Supernovae Ia, Baryon Acoustic Oscillations, gravitational lensing, and gamma-ray bursts. Quasars, or more generally, Active Galactic Nuclei (AGN) also joined the class of sources with cosmological applications, and several specific methods to use these objects were proposed: continuum time delays and emission-line time delays. Several recent measurements based on different methods imply the tension between the Hubble constant H0 determination based on the early Universe and the value coming from the relatively local measurements-SNIa has posed many serious questions on the standard cosmological model. I will talk about one of the local measurements using the quasars and how we can use them as a cosmological tool. While addressing the quasars, I will also discuss the issues that we should be careful about in their application to cosmology.


"Coevolution of Supermassive Black Holes and Host Galaxies on cosmological time scales"

Peter Berczik (Main Astronomical Observatory, National Academy of Sciences of Ukraine)

Supermassive black holes are unique objects: the physical description, the origin and evolution of which (i.e., the so-called “life cycle”) and is one of the biggest problems in modern astrophysics. Determining the masses and sizes of black holes at different redshifts, as well as finding double AGNs, are extremely important. Such binary systems are one of the most high-energy dynamic objects in the centers of galaxies. Simulations of a dusty torus for the different initial conditions taking into account the effects which are present in the AGNs central regions will allow to explain a number of observations in the different wave bands. On a base the machine learning algorithms the complex link between spectroscopic and photometric data of modern surveys will been establish. The obtained regularities will allow to create the most complete catalogue of extragalactic sources and to carry out the classification and to obtain additional information from the largest modern surveys of the sky.

Seminar in hybrid version.


"On halo and galaxy connection with the cosmic web"

Wojciech Hellwing (Center for Theoretical Physics, Warsaw)

The Cosmic Web -- an intricate network of clusters, filaments, walls, and walls -- can have many aspects. Most of the features of the Web and the associated impact they induce on the formation and evolution of haloes and galaxies are subject to ongoing debate. The differences are mostly driven by a specific choice among many existing-working definitions of the Cosmic Web. Nonetheless, it is clear that different segments of this net establish different intimate environments and ecosystems for the local halo and galaxy formation. In this talk, I will demonstrate, using the NEXUS+ definition for the Cosmic Web identification, how indeed the disparate environments affect the local formation histories and hence properties of dark matter clumps and galaxies living within. I will focus on internal kinematics and morphological features and distribution of satellite systems. Our findings indicate a fundamental role that the local cosmic environment plays in shaping galaxy and halo formation histories, which in turn have profound implications for their intrinsic properties.



(Research Associate, Cardiff University)

Research Associate, Cardiff University

"AGN fueling and feedback: role of molecular tori"

Francoise Combes (College de France and Observatoire de Paris)

Gas inflows directly fueling AGN are now traceable with current high-resolution observations with ALMA and NOEMA. Dynamical mechanisms are essential to exchange angular momentum and drive the gas to the super-massive black hole. While at 100pc scale, the gas is sometimes stalled in nuclear rings, recent observations reaching ~10pc scale (or 50mas), inside the sphere of influence of the black hole, may bring smoking gun evidence of fueling, within a randomly oriented nuclear molecular disk. AGN feedback as molecular outflows are also observed at high resolution helping to identify the responsible mechanisms, either radiative of kinetic AGN mode, or starburst.