Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2011-09-16
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
13 pages, 16 figures. Submitted to ApJ
Scientific paper
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.
Aguirre Anthony
Guedes Javiera
Madau Piero
Mayer Lucio
Shen Sijing
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