We present a detailed study of the metal-enriched circumgalactic medium (CGM) of a massive galaxy at z = 3 using results from "ErisMC," a new cosmological hydrodynamic "zoom-in" simulation of a disk galaxy with mass comparable to the Milky Way. The reference run adopts a blast wave scheme for supernova feedback that generates galactic outflows without explicit wind particles, a star formation recipe based on a high gas density threshold and high-temperature metal cooling. ErisMC's main progenitor at z = 3 resembles a "Lyman break" galaxy of total mass M vir = 2.4 × 1011 M·, virial radius R vir = 48 kpc, and star formation rate 18 M· yr-1, and its metal-enriched CGM extends as far as 200 (physical) kpc from its center. Approximately 41%, 9%, and 50% of all gas-phase metals at z = 3 are locked in a hot (T > 3 × 105 K), warm (3 × 105 K > T > 3 × 104 K), and cold (T < 3 × 104 K) medium, respectively. We identify three sources of heavy elements: (1) the main host, responsible for 60% of all the metals found within 3 R vir; (2) its satellite progenitors, which shed their metals before and during infall, and are responsible for 28% of all the metals within 3 R vir, and for only 5% of those beyond 3 R vir; and (3) nearby dwarfs, which give origin to 12% of all the metals within 3 R vir and 95% of those beyond 3 R vir. Late (z < 5) galactic "superwinds" - the result of recent star formation in ErisMC - account for only 9% of all the metals observed beyond 2 R vir, the bulk having been released at redshifts 5 ≲ z ≲ 8 by early star formation and outflows. In the CGM, lower overdensities are typically enriched by "older," colder metals. Heavy elements are accreted onto ErisMC along filaments via low-metallicity cold inflows and are ejected hot via galactic outflows at a few hundred km s -1. The outflow mass-loading factor is of order unity for the main halo, but can exceed a value of 10 for nearby dwarfs. We stress that our "zoom-in" simulation focuses on the CGM of a single massive system and cannot describe the enrichment history of the intergalactic medium as a whole by a population of galaxies with different masses and star formation histories.
Shen, S., Madau, P., Aguirre, A., Guedes, J., Mayer, L., Wadsley, J. (2012). The origin of metals in the circumgalactic medium of massive galaxies at z = 3. THE ASTROPHYSICAL JOURNAL, 760(1) [10.1088/0004-637x/760/1/50].
The origin of metals in the circumgalactic medium of massive galaxies at z = 3
Madau P.;
2012
Abstract
We present a detailed study of the metal-enriched circumgalactic medium (CGM) of a massive galaxy at z = 3 using results from "ErisMC," a new cosmological hydrodynamic "zoom-in" simulation of a disk galaxy with mass comparable to the Milky Way. The reference run adopts a blast wave scheme for supernova feedback that generates galactic outflows without explicit wind particles, a star formation recipe based on a high gas density threshold and high-temperature metal cooling. ErisMC's main progenitor at z = 3 resembles a "Lyman break" galaxy of total mass M vir = 2.4 × 1011 M·, virial radius R vir = 48 kpc, and star formation rate 18 M· yr-1, and its metal-enriched CGM extends as far as 200 (physical) kpc from its center. Approximately 41%, 9%, and 50% of all gas-phase metals at z = 3 are locked in a hot (T > 3 × 105 K), warm (3 × 105 K > T > 3 × 104 K), and cold (T < 3 × 104 K) medium, respectively. We identify three sources of heavy elements: (1) the main host, responsible for 60% of all the metals found within 3 R vir; (2) its satellite progenitors, which shed their metals before and during infall, and are responsible for 28% of all the metals within 3 R vir, and for only 5% of those beyond 3 R vir; and (3) nearby dwarfs, which give origin to 12% of all the metals within 3 R vir and 95% of those beyond 3 R vir. Late (z < 5) galactic "superwinds" - the result of recent star formation in ErisMC - account for only 9% of all the metals observed beyond 2 R vir, the bulk having been released at redshifts 5 ≲ z ≲ 8 by early star formation and outflows. In the CGM, lower overdensities are typically enriched by "older," colder metals. Heavy elements are accreted onto ErisMC along filaments via low-metallicity cold inflows and are ejected hot via galactic outflows at a few hundred km s -1. The outflow mass-loading factor is of order unity for the main halo, but can exceed a value of 10 for nearby dwarfs. We stress that our "zoom-in" simulation focuses on the CGM of a single massive system and cannot describe the enrichment history of the intergalactic medium as a whole by a population of galaxies with different masses and star formation histories.
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