Colloquium: Benjamin Rossenwasser

October 29, 2021

03:15 PM - 12:00 PM



The Physical Properties and Environments of Common Low-z OVI Absorbers
Abstract: The connection between galaxies, the circumgalactic medium (CGM) and the intergalactic medium (IGM) within the large scale structure of the universe remains a topic of great interest. Direct observational insight into CGM and IGM structure at low redshift comes from quasar absorption lines, primarily in the form of either HI and OVI lines. In particular, there are still many open questions about the nature of the OVI absorption, two of them being the origin of its ionization and its location in the IGM vs. CGM. Statistical studies have long hinted that much of the OVI lies beyond the virial radius of galaxies and thus in the IGM, but due to relatively small sample sizes and incomplete galaxy surveys the question remains open. Moreover, the origin of the ionization of OVI is still a mystery, since it can be produced both by both photoionization and collisional ionization. In this talk, we present results on a study of OVI using a new large sample from the Cosmic Origins Spectrograph (COS) archive of FUV quasar spectra. We focus on the most abundant type of OVI absorption, those with single-component profiles, and discuss their physical properties and galaxy environments. 

Chris Churchill