Abstract
We present a detailed study of the metal-enriched circum-galactic medium of a
massive galaxy at redshift 3 using results from the "Eris" suite of new
cosmological hydrodynamic "zoom-in" simulations in which a close analog of a
Milky Way disk galaxy arises at the present epoch. The reference run adopts a
blastwave scheme for supernova feedback that generates galactic outflows
without explicit wind particles, a star formation recipe based on a high gas
density threshold, and metal-dependent radiative cooling. Eris main progenitor
at redshift 3 resembles a "Lyman break" galaxy of total mass M_vir=2.4e11 solar
masses, virial radius R_vir=48 kpc, and star formation rate 18 Msun/yr, and its
metal-enriched CGM extends as far as 200 (physical) kpc from its center.
Approximately 41, 9, and 50 percent of all gas-phase metals at z=3 are locked
in a hot (T> 3e5 K), warm (3e5 >T> 3e4 K), and cold (T< 3e4 K) medium,
respectively. We identify three sources of heavy elements: 1) the main host,
responsible for 60% of all the metals found within 3R_vir; 2) its satellite
progenitors, which shed their metals before and during infall, and are
responsible for 28% of all the metals within 3R_vir, and for only 5% of those
beyond 3R_vir; and its satellite dwarf companions, which give origin to 12% of
all the metals within $3R_vir and 95% of those beyond 3R_vir. Late (z<5)
galactic "superwinds" account for only 9% of all the metals observed beyond
2R_vir, the bulk having been released at redshifts 5< z < 8 by early star
formation and outflows. In the IGM, lower overdensities are typically enriched
by `older', colder metals. Heavy elements are accreted onto Eris along
filaments via low-metallicity cold inflows, and are ejected hot via galactic
outflows at a few hundred km/s. The outflow mass-loading factor as a function
of redshift ranges between 0.1 and 1.2, and shows no correlation with the mass
of the host.
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