Dartmouth Events

Abstract: Active galactic nuclei are the extremely bright regions at the centers of galaxies created by the emission of material falling into the galaxy’s central black hole. Unraveling the relationship between active galactic nuclei accretion – also framed in terms of the Eddington ratio – and host galaxy evolution is a key question of modern astronomy. These relationships are often unclear across large populations of AGN because of the diversity of the AGN population and unreliable in individual AGN given the stochastic nature of their accretion across long and short time-scales. We will use a Chandra deep X-ray AGN catalog spanning mid-to-high mass and low-redshift galaxies to trace AGN evolution in our local environment by investigating the distribution of AGN Eddington ratios across detected AGN. Given the local environment and moderate x-ray luminosities of the sources in our more local environment, this survey probes a relatively characteristic AGN population. We model a full population to correct for the flux-limited Eddington Ratio cut-off of our observations. We use Markov Chain Monte Carlo simulations to match our detected AGN populations against model Eddington ratio distributions governed by a Schechter function. We recover the results that the power-law slope of the distribution is constant across redshift bins. Further, we find that the absolute likelihood of detecting an AGN in a given redshift bin decreases from redshift of z=1.1 to z=0.3. This effect in particular would point to the  higher availability of cold gas at higher red-shift that may increase the luminosity of black hole accretion. Recovering these results in another population of AGN emphasizes that these results are insensitive to the stochastic nature of AGN accretion and reveal a more intrinsic tie between AGN fueling and galaxy evolution.

Advisor: Professor Ryan Hickox

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https://dartmouth.zoom.us/j/91835088479?pwd=T2oxMGthOTNkSXIvckdyMG9yWUljQT09

Meeting ID: 918 3508 8479
Passcode: Burrows