A Long Stream of Metal-Poor Cool Gas around a Massive Starburst Galaxy at z = 2.67. (arXiv:2101.06273v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Fu_H/0/1/0/all/0/1">Hai Fu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Xue_R/0/1/0/all/0/1">Rui Xue</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Prochaska_J/0/1/0/all/0/1">J. Xavier Prochaska</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stockton_A/0/1/0/all/0/1">Alan Stockton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ponnada_S/0/1/0/all/0/1">Sam Ponnada</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lau_M/0/1/0/all/0/1">Marie Wingyee Lau</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cooray_A/0/1/0/all/0/1">Asantha Cooray</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Narayanan_D/0/1/0/all/0/1">Desika Narayanan</a>
We present the first detailed dissection of the circumgalactic medium (CGM)
of massive starburst galaxies at z > 2. Our target is a submillimeter galaxy
(SMG) at z = 2.674 that has a star formation rate of 1200 $M_odot$/yr and a
molecular gas reservoir of $1.3times10^{11} M_odot$. We characterize its CGM
with two background QSOs at impact parameters of 93 kpc and 176 kpc. We detect
strong HI and metal-line absorption near the redshift of the SMG towards both
QSOs, each consisting of three main subsystems spanning over 1500 km/s. The
absorbers show remarkable kinematic and metallicity coherence across a
separation of 86 kpc. In particular, the cool gas in the CGM of the SMG
exhibits high HI column densities ($log N_{rm HI}/{rm cm}^{-2} = 20.2,
18.6$), low metallicities ([M/H] $approx$ -2.0), and similar radial velocities
($approx$ -300 km/s). While the HI column densities match previous results on
the CGM around QSOs at z > 2, the metallicities are lower by more than an order
of magnitude, making it an outlier in the line width$-$metallicity relation of
damped Ly$alpha$ absorbers. The large physical extent, the velocity coherence,
the high surface density, and the low metallicity are all consistent with the
cool, inflowing, and near-pristine gas streams predicted to penetrate hot
massive halos at z > 1.5. We estimate a total gas accretion rate of ~100
$M_odot$/yr from three such streams, which falls short of the star formation
rate but is consistent with simulations. At this rate, it takes about a
gigayear to acquire the molecular gas reservoir of the central starburst.
We present the first detailed dissection of the circumgalactic medium (CGM)
of massive starburst galaxies at z > 2. Our target is a submillimeter galaxy
(SMG) at z = 2.674 that has a star formation rate of 1200 $M_odot$/yr and a
molecular gas reservoir of $1.3times10^{11} M_odot$. We characterize its CGM
with two background QSOs at impact parameters of 93 kpc and 176 kpc. We detect
strong HI and metal-line absorption near the redshift of the SMG towards both
QSOs, each consisting of three main subsystems spanning over 1500 km/s. The
absorbers show remarkable kinematic and metallicity coherence across a
separation of 86 kpc. In particular, the cool gas in the CGM of the SMG
exhibits high HI column densities ($log N_{rm HI}/{rm cm}^{-2} = 20.2,
18.6$), low metallicities ([M/H] $approx$ -2.0), and similar radial velocities
($approx$ -300 km/s). While the HI column densities match previous results on
the CGM around QSOs at z > 2, the metallicities are lower by more than an order
of magnitude, making it an outlier in the line width$-$metallicity relation of
damped Ly$alpha$ absorbers. The large physical extent, the velocity coherence,
the high surface density, and the low metallicity are all consistent with the
cool, inflowing, and near-pristine gas streams predicted to penetrate hot
massive halos at z > 1.5. We estimate a total gas accretion rate of ~100
$M_odot$/yr from three such streams, which falls short of the star formation
rate but is consistent with simulations. At this rate, it takes about a
gigayear to acquire the molecular gas reservoir of the central starburst.
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