cosmology seminar: Yuanyuan Su, University of Alabama

Title: X-ray observations of hot gas in early-type galaxies and fossil groups Abstract: In the hierarchical Universe, groups are made up of galaxies and are regarded as the building blocks of clusters of galaxies. Metals are synthesized in early-type galaxies and eventually enrich the intracluster/group medium of groups and clusters. In the first part of my talk, I will discuss the heavy metal content of the hot ISM of early-type galaxies. The measured emission-weighted metal abundance of the hot gas in early-type galaxies has been known to be lower than theoretical expectations for 20 years. In addition, both X-ray luminosity and metal abundance vary significantly among galaxies of similar optical luminosities. This suggests some missing factors in the galaxy evolution process, especially the metal enrichment process. I will describe our investigation of the potential dilution of the hot ISM via the accretion of surrounding pristine gas in the enrichment processes with Chandra and XMM X-ray observatories. In the second part of my talk, I will focus on "fossil" groups of galaxies. Fossil galaxy groups, each dominated by a relatively isolated giant elliptical galaxy, have many properties intermediate between regular groups and clusters of galaxies. I will show our study of the X-ray brightest fossil group ESO3060170 out to the virial radius with the Suzaku X-ray Observatory to better elucidate the relation between fossil groups, normal groups, and clusters. We find that the entropy and pressure profiles in the outer regions are flatter than simulated, which may indicate the gas is clumpy, as found in some massive clusters, and/or the gas has been redistributed.