THE CIRCUMGALACTIC MEDIUM OF MASSIVE GALAXIES ATz∼ 3: A TEST FOR STELLAR FEEDBACK, GALACTIC OUTFLOWS, AND COLD STREAMS
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abstract
We present new results on the kinematics, thermal and ionization state, and
spatial distribution of metal-enriched gas in the circumgalactic medium (CGM)
of massive galaxies at redshift 3, using the "Eris" suite of cosmological
"zoom-in" simulations. The reference run adopts a blastwave scheme for
supernova feedback that produces 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. Synthetic spectra through
the multiphase CGM produce interstellar absorption line strengths of Lya, CII,
CIV, SiII, and SiIV as a function of galactocentric impact parameter (scaled to
the virial radius) that are in broad agreement with those observed at
high-redshift by Steidel et al. (2010). Only about one third of all the gas
within R_vir is outflowing. 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, give origin to strong
(log N > 13) CII absorption with a covering factor of 22% within R_vir and 10%
within 2 R_vir. Galactic outflows do not cause any substantial suppression of
the cold accretion mode. The central galaxy is surrounded by a large OVI halo,
with a typical column density log N>14 and a near unity covering factor
maintained all the way out to 150 kpc. This matches the trends recently
observed in star-forming galaxies at low redshift by Tumlinson et al. (2011).
Our zoom-in simulations of this single system appear to reproduce
quantitatively the complex baryonic processes that determine the exchange of
matter, energy, and metals between galaxies and their surroundings. (Abridged)
