TY - JOUR
T1 - Neutral CGM as damped Ly α absorbers at high redshift
AU - Stern, Jonathan
AU - Sternberg, Amiel
AU - Faucher-Giguère, Claude André
AU - Hafen, Zachary
AU - Fielding, Drummond
AU - Quataert, Eliot
AU - Wetzel, Andrew
AU - Anglés-Alcázar, Daniel
AU - El-Badry, Kareem
AU - Kereš, Dušan
AU - Hopkins, Philip F.
N1 - Publisher Copyright:
© 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
PY - 2021/10/1
Y1 - 2021/10/1
N2 - Recent searches for the hosts of z ∼4 damped Ly α absorbers (DLAs) have detected bright galaxies at distances of tens of kpc from the DLA. Using the FIRE-2 cosmological zoom simulations, we argue that these relatively large distances are due to a predominantly cool and neutral inner circumgalactic medium (CGM) surrounding high-redshift galaxies. The inner CGM is cool because of the short cooling time of hot gas in ≤ 1012, M\odot haloes, which implies that accretion and feedback energy are radiated quickly, while it is neutral due to high volume densities and column densities at high redshift that shield cool gas from photoionization. Our analysis predicts large DLA covering factors (≥ 50 per cent) out to impact parameters ∼0.3[(1 + z)/5]3/2Rvir from the central galaxies at z ≥ 1, equivalent to a proper distance of ∼21, M121/3 (1+z)/5)1/2\, kpc (Rvir and M12 are the halo virial radius and mass in units of 1012, M, respectively). This implies that DLA covering factors at z ∼4 may be comparable to unity out to a distance ∼10 times larger than stellar half-mass radii. A predominantly neutral inner CGM in the early universe suggests that its mass and metallicity can be directly constrained by absorption surveys, without resorting to the large ionization corrections as required for ionized CGM.
AB - Recent searches for the hosts of z ∼4 damped Ly α absorbers (DLAs) have detected bright galaxies at distances of tens of kpc from the DLA. Using the FIRE-2 cosmological zoom simulations, we argue that these relatively large distances are due to a predominantly cool and neutral inner circumgalactic medium (CGM) surrounding high-redshift galaxies. The inner CGM is cool because of the short cooling time of hot gas in ≤ 1012, M\odot haloes, which implies that accretion and feedback energy are radiated quickly, while it is neutral due to high volume densities and column densities at high redshift that shield cool gas from photoionization. Our analysis predicts large DLA covering factors (≥ 50 per cent) out to impact parameters ∼0.3[(1 + z)/5]3/2Rvir from the central galaxies at z ≥ 1, equivalent to a proper distance of ∼21, M121/3 (1+z)/5)1/2\, kpc (Rvir and M12 are the halo virial radius and mass in units of 1012, M, respectively). This implies that DLA covering factors at z ∼4 may be comparable to unity out to a distance ∼10 times larger than stellar half-mass radii. A predominantly neutral inner CGM in the early universe suggests that its mass and metallicity can be directly constrained by absorption surveys, without resorting to the large ionization corrections as required for ionized CGM.
KW - galaxies: evolution
KW - galaxies: high-redshift
KW - quasars: absorption lines
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U2 - 10.1093/mnras/stab2240
DO - 10.1093/mnras/stab2240
M3 - Article
AN - SCOPUS:85116534775
SN - 0035-8711
VL - 507
SP - 2869
EP - 2884
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -