The Galaxy-Circumgalactic Medium Ecosystem in Cosmological Simulations
Sijing Shen (UC Santa Cruz) - December 9, 2013 at 12:10 pm
How gas is accreted into galactic halos from the intergalactic medium, processed in galaxies and ejected back to the environment are crucial questions in understanding galaxy formation and evolution. Studies of the spacial distribution, chemical composition, kinematics and ionization states of the gas within several hundreds kpc -- the circumgalactic medium (CGM) -- provide clues to understanding the cycle of baryons. In this talk, I will present a study of the co-evolution of the galaxy-CGM ecosystem using two suites of cosmological, hydrodynamic simulations from Milky Way-like scale to dwarf galaxies. The simulations adopt a blastwave scheme for supernova feedback that produce large-scale galactic outflows, metal-dependent radiative cooling, and a model for the turbulent mixing of metals. I will discuss the complex origins of the enriched CGM around massive galaxies at z ~ 3, and identify the relative contributions from the central galaxy and its accreting satellites. I will then present a detailed comparison with absorption-line studies on the distribution, kinematics and evolution of neutral hydrogen (H I) and various metal ions (Si II, Si IV, C II, C IV, Mg II and O VI) in the CGM around galaxies. We find that the CGM around massive galaxies exhibits highly multi-phase structures with kinematically aligned high and low-ionization metal absorbers. The absorption strength as a function of the the impact parameter is in good agreement with observations for all ions. The cold accretion flows probed by Lyman-limit systems (LLSs) can be enriched substantially from dwarf satellites and re-accreted outflows, making them detectable using low ionization metal species (such as MgII). If time permits, I will also discuss how these observed CGM properties depend on stellar feedback, radiative cooling and the mixing of metals.
The seminar will be held in B-1 Hearst Field Annex.
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