TY - JOUR
T1 - Hydrogen and metal line absorption around low-redshift galaxies in cosmological hydrodynamic simulations
AU - Ford, Amanda Brady
AU - Oppenheimer, Benjamin D.
AU - Davé, Romeel
AU - Katz, Neal
AU - Kollmeier, Juna A.
AU - Weinberg, David H.
PY - 2013/4/17
Y1 - 2013/4/17
N2 - We study the physical conditions of the circumgalactic medium (CGM)
around z = 0.25 galaxies as traced by H I and metal line absorption,
using cosmological hydrodynamic simulations that include galactic
outflows. Using lines of sight targeted at impact parameters from 10 kpc
to 1 Mpc around galaxies with halo masses from
1011-1013 M⊙, we study the physical
conditions and their variation with impact parameter b and line-of-sight
velocity Δv in the CGM as traced by H I, Mg II, Si IV, C IV, O VI
and Ne VIII absorbers. All ions show a strong excess of absorption near
galaxies compared to random lines of sight. The excess continues beyond
1 Mpc, reflecting the correlation of metal absorption with large-scale
structure. Absorption is particularly enhanced within about Δv
<300 km s-1 and roughly 300 kpc of galaxies (with
distances somewhat larger for the highest ion), approximately
delineating the CGM; this range contains the majority of global metal
absorption. Low ions like Mg II and Si IV predominantly arise in denser
gas closer to galaxies and drop more rapidly with b, while high ions O
VI and Ne VIII trace more diffusely distributed gas with a comparatively
flat radial profile; C IV is intermediate. All ions predominantly trace
T ˜ 104-4.5 K photoionized gas at all b, but when hot
CGM gas is present (mostly in larger haloes), we see strong
collisionally ionized O VI and Ne VIII at b ≤ 100 kpc. Larger halo
masses generally produce more absorption, though overall the trends are
not as strong as that with impact parameter. These findings arise using
our favoured outflow scalings as expected for momentum-driven winds;
with no winds, the CGM gas remains mostly unenriched, while our outflow
model with a constant velocity and mass loading factor produce hotter,
more widely dispersed metals.
AB - We study the physical conditions of the circumgalactic medium (CGM)
around z = 0.25 galaxies as traced by H I and metal line absorption,
using cosmological hydrodynamic simulations that include galactic
outflows. Using lines of sight targeted at impact parameters from 10 kpc
to 1 Mpc around galaxies with halo masses from
1011-1013 M⊙, we study the physical
conditions and their variation with impact parameter b and line-of-sight
velocity Δv in the CGM as traced by H I, Mg II, Si IV, C IV, O VI
and Ne VIII absorbers. All ions show a strong excess of absorption near
galaxies compared to random lines of sight. The excess continues beyond
1 Mpc, reflecting the correlation of metal absorption with large-scale
structure. Absorption is particularly enhanced within about Δv
<300 km s-1 and roughly 300 kpc of galaxies (with
distances somewhat larger for the highest ion), approximately
delineating the CGM; this range contains the majority of global metal
absorption. Low ions like Mg II and Si IV predominantly arise in denser
gas closer to galaxies and drop more rapidly with b, while high ions O
VI and Ne VIII trace more diffusely distributed gas with a comparatively
flat radial profile; C IV is intermediate. All ions predominantly trace
T ˜ 104-4.5 K photoionized gas at all b, but when hot
CGM gas is present (mostly in larger haloes), we see strong
collisionally ionized O VI and Ne VIII at b ≤ 100 kpc. Larger halo
masses generally produce more absorption, though overall the trends are
not as strong as that with impact parameter. These findings arise using
our favoured outflow scalings as expected for momentum-driven winds;
with no winds, the CGM gas remains mostly unenriched, while our outflow
model with a constant velocity and mass loading factor produce hotter,
more widely dispersed metals.
KW - methods: numerical
KW - galaxies: evolution
KW - galaxies: formation
KW - intergalactic medium
KW - quasars: absorption lines
KW - cosmology: theory
U2 - 10.1093/mnras/stt393
DO - 10.1093/mnras/stt393
M3 - Article
VL - 432
SP - 89
EP - 112
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 1
ER -