This one-day meeting on "Active Galactic Nuclei (AGN) Science" is to celebrate the career of Prof. Prajval Shastri on her superannuation at IIA. The meeting will cover various frontier areas of AGN science, with invited participation from leading researchers in the field from within the country and abroad. The meeting will be open to all IIA academic staff and students.
All massive galaxies in the Universe possess a supermassive black hole in their centre. Active Galactic Nuclei (AGN) are a fraction of these galaxies that have actively accreting supermassive black holes. Accretion results in luminous galactic nuclei that can outshine the light from the entire galaxy and, in many cases, produces bipolar outflows that can span intergalactic scales. These outflows in turn can modulate the star-formation in their host galaxies through shocks, creating a close symbiotic link between the host galaxy and its active nucleus.
The last few decades have seen dramatic increases in both observing and computational power, with several new path-breaking telescopes including the Chandra, Fermi, NuSTAR, Astrosat, Jansky VLA, uGMRT, eMERLIN, Event Horizon Telescope, and several more like the Square Kilometre Array (SKA) on the horizon. The complex inner structure and the important role played by AGN in galaxy evolution has come to light with these observatories. With the current computational power, AGN have become a test bed for general relativistic magneto hydrodynamics (GRMHD). As AGN are the past and/or future sites of coalescing supermassive black holes, they are one of the primary science drivers of the future gravitational wave
While we now know a lot about AGN and the important role they play in the Universe, several nagging questions remain. We do not know why only 10% of AGN produce large 100-kpc-scale radio outflows, while 90% produce small or no jets that stay confined to their host galaxies. We do not know how important the black hole mass or spin is in producing the observed morphologies of radio jets. For instance, are the black holes spinning slower in low luminosity AGN (LLAGN) like Seyferts and LINER galaxies as suggested by the "spin paradigm" of Sikoraet al. 2007? This is however contradictory to the suggestion of maximally spinning black holes in Seyfert galaxies in studies carried out with the gravitationally-redshifted Fe K-alpha line. The role played by stellar winds and accretion disk winds is also unclear in the case of LLAGN. Another intriguing mystery is the extremely low numbers (really only a handful) of candidate supermassive black hole binaries, when galaxy hierarchical models predict them in large numbers. Several such puzzling topics will be the focus of this one-day meeting.
A significant amount of research on AGN has also been achieved using the Indian facilities such as the GMRT and the Himalayan Chandra Telescope (HCT), as well as from the new Indian space instruments UVIT and SXT onboard ASTROSAT. Both dedicated timing observations of AGN using X-ray, Gamma-ray and optical observations have been explored and high resolution imaging/spectroscopy of AGN using radio, optical, X-ray observations have been done from India in the past two decades. Leading researchers from the country will summarise some of these achievements and present new directions in the broad area of AGN research. This meeting also will serve as a forum to encourage discussion and collaboration for the growing number of students working in the area of AGN science.