Seminar - Abhijeet Anand (MPI for Astrophysics)


Monday, December 13, 2021, 11:00am to 11:30pm



" The cool CGM in absorption with large spectroscopic surveys"

The gas flows in the circumgalactic medium (CGM) play a pivotal role in several key processes regulating galaxy formation, implying that our understanding of galaxy formation is limited by our current understanding of the CGM. In this talk, I will present the recent constraints that we obtained on the properties of the CGM of passive and star-forming galaxies using absorption line studies with large spectroscopic surveys. Towards this aim, I’ll discuss the details of an automated pipeline that we develop to estimate the optical continuum of quasars and detect intervening metal absorption line systems. We process ~ 1 million quasars in the latest Data Release 16 (DR16) of SDSS and compile a large sample of ~ 160,000 MgII absorbers, together with ~ 70,000 FeII systems, in the redshift range 0.35 < z_abs < 2.3. Combining these with the SDSS DR16 spectroscopy of ~ 1.1 million luminous red galaxies (LRGs) and ~ 200,000 emission-line galaxies (ELGs), we investigate the nature of cold gas absorption at 0.5 < z < 1. These large samples allow us to characterize the scale dependence of MgII in their CGM. We also see a sudden transition between the regime where the CGM is regulated by galactic outflows and the regime where the CGM is in thermal balance with the dark matter halo. I will also present how the properties of MgII absorbers correlate with galaxy properties that help to understand the complex nature and origin of MgII absorbers in their halos. Our analysis implies that cool circumgalactic gas has a different physical origin for star-forming versus quiescent galaxies.

Additionally, I will also summarize the latest constraints on the properties of cool gas (T ~ 10,000 K, traced by MgII absorbers) in the intracluster medium (ICM), followed by a discussion on the clues to the origin of MgII absorbers in ICM and their relations to the properties of cluster and its member galaxies.

See also: Seminars, 2021-22