Speaker
Dr
Sijing Shen
(University of California, Santa Cruz)
Description
I will present results on the kinematics, thermal and ionization state and spatial distribution of metal-enriched gas in the circumgalactic medium (CGM) of galaxies of different mass scales, using two suites of very high resolution cosmological hydrodynamic “zoom-in” simulations from Milky Way-like scales to (“Eris”) down to dwarf galaxies. The runs adopt a blastwave scheme for supernova feedback that produces large-scale galactic outflows, a star formation recipe based on a high gas density threshold, metal-dependent radiative cooling, and a model for the diffusion of metals and thermal energy. The effect of the local UV radiation field is added in post-processing. The star formation and feedback models are able to produce simulated galaxies with various properties consistent with observations.
At redshift 2-3, the CGM of Eris contains multiple phases having a wide range of physical conditions, and the synthetic spectra produce interstellar absorption line strengths of Lyα, CII, CIV, SiII, and SiIV as a function of galactocentric impact parameter that are in broad agreement with those observed at high-redshift. The fraction of sightlines within one virial radius that intercept optically thick material is 27%, in agreement with recent observations by Rudie et al. 2012. Such optically thick absorption is shown to trace inflowing "cold" streams that penetrate deep inside the virial radius. The streams, enriched to metallicities above 0.01 solar by previous episodes of star formation in the main host and in nearby dwarfs, give origin to strong CII absorption with a covering factor of 22% within the virial radius. In the simulation of dwarf galaxies, the field dwarfs appear to have very large mass loading factors (several tens to hundred) and eject about 90% of their metals by redshift 0. Metals propagates into the underdense intergalactic medium, reaching ~ 15 times the virial radius of the host, with little of them recycled back onto the halo. I will briefly discuss how the observed CGM properties depend on radiative cooling, mixing of metals and the stellar UV radiation.
