Nature and Evolution of Gas in Galaxy Groups and Elliptical Galaxies

University Of California-Santa Cruz, Santa Cruz CA

Investigators

Abstract

AST 0098351 Matthews This project lies at the intersection of two emerging revolutions in astronomy: the scientific maturation of our understanding of galaxy evolution and cosmology and the exploitation of the riches of X-ray observations of violently heated regions of the universe. The origin and heating of X-ray luminous hot gas around massive elliptical galaxies are both internal and external. Deep inside the stellar galaxy, most of the hot gas originates from mass loss from normally evolving stars; further out, gas has accumulated by intergalactic accretion. When cosmic gas falls onto the dark matter halos surrounding giant elliptical galaxies, its kinetic energy is converted into heat, reaching temperatures as hot as the center of the sun! This gas is heated even further -- and enriched in heavy elements -- by supernovae explosions from young massive stars. Understanding this latter type of heating is a central problem in modern cosmology -- the "feedback" problem -- and this is one of the key problems addressed in this project. Elliptical galaxies are perhaps the most dramatic manifestations of these ancient heating activity. The theoretical calculations in this project are aimed at understanding the complex interplay of gas ejection from young star-forming galaxies and the subsequent evolution of this gas into the enormous X-ray clouds typically observed around elliptical galaxies. The calculations begin with initial concentrations of dark matter in an expanding universe, and after 13 billion years the computed radial variation of gas density, temperature and iron enrichment all agree with X-ray observations of large elliptical galaxies. This project will build on these results to study the heating of diffuse gas in groups of galaxies, the way collective supernova-driven galactic winds can produce the abundances of elements typically observed in the richest clusters of galaxies, the physics of the gas cooling process in clusters of galaxies, and the way X-ray emission lines in from the cores of cooling flows is absorbed by partially cooled gas. In addition, the project will study a variety of additional problems relevant to recent XMM and Chandra (x-ray satellite) observations. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC). ***