Speaker: Benjamin Rosenwasser, University of Wisconsin - Madison
Abstract: Over the past decade the Cosmic Origins Spectrograph (COS) has obtained high S/N FUV spectra of hundreds of distant QSOs, illuminating the gaseous structures that lie within the cosmic web at redshift < 1. Besides Lyman alpha forest absorption, the next most common type of absorber are low column density OVI absorbers, often appearing as apparent single components with one or two associated HI lines. Many studies have shown that the absorbers with large column densities are in the inner regions of galaxy halos, while the much more numerous single component OVI absorbers have not been the subject of much scrutiny. We have been studying a large sample of 600 OVI absorbers, and I will focus on our effort to characterize the galaxy environments of the common single component systems. We show that some appear to trace halos, but many are clearly isolated, and sometimes embedded within filamentary structure traced by nearby galaxies on Mpc scales. We discuss the possible origins and physical properties of the gas in this intra-filament medium.