H_2 molecular gas absorption-selected systems trace CO molecular gas-rich galaxy overdensities

Abstract

Absorption-selected galaxies offer an effective way to study low-mass galaxies at high redshift. However, the physical properties of the underlying galaxy population remains uncertain. In particular, the multiphase circum-galactic medium is thought to hold key information on gas flows into and out of galaxies that are vital for galaxy evolution models. Here we present ALMA observations of CO molecular gas in host galaxies of H_2-bearing absorbers. In our sample of six absorbers we detect molecular gas-rich galaxies in five absorber fields although we did not target high-metallicity (>50 per cent solar) systems for which previous studies reported the highest detection rate. Surprisingly, we find that the majority of the absorbers are associated with multiple galaxies rather than single haloes. Together with the large impact parameters these results suggest that the H_2-bearing gas seen in absorption is not part of an extended disk, but resides in dense gas pockets in the circum-galactic and intra-group medium.

arXiv commentAccepted for publication in MNRAS; 8 pages, 7 figures

References in corpus (40)

• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Global Schmidt Law in Star Forming Galaxies
• The CO-to-H2 Conversion Factor
• Cool Gas in High Redshift Galaxies
• Damped Lyman alpha Systems
• The COS-Halos Survey: Physical Conditions and Baryonic Mass in the Low-Redshift Circumgalactic Medium
• Gaseous Galaxy Halos
• Damped Lyman Alpha Systems at z<1.65: The Expanded SDSS HST Sample
• The COS-Halos Survey: An Empirical Description of the Metal-Line Absorption in the Low-Redshift Circumgalactic Medium
• The Cosmic Baryon and Metal Cycles
• Field Galaxy Evolution Since Z~1 from a Sample of QSO Absorption-Selected Galaxies
• The origin of fast molecular outflows in quasars: molecule formation in AGN-driven galactic winds
• Molecular Hydrogen in High-Velocity Clouds
• Multi-phase Circum-Galactic Medium probed with MUSE and ALMA
• Nature of the Absorbing Gas associated with a Galaxy Group at z~0.4
• MUSE Analysis of Gas around Galaxies (MAGG) -- I: Survey design and the environment of a near pristine gas cloud at z~3.5
• Evidence for diffuse molecular gas and dust in the hearts of gamma-ray burst host galaxies
• Probing the intra-group medium of a z = 0.28 galaxy group
• Hubble Space Telescope Observations of Sub-Damped Lyman-alpha Absorbers at z < 0.5, and Implications for Galaxy Chemical Evolution
• Detection of molecular hydrogen at z=1.15 toward HE 0515-4414
• MUSE-ALMA Halos V: Physical properties and environment of z < 1.4 HI quasar absorbers
• Molecular Emission from a Galaxy Associated with a z~2.2 Damped Lyman-alpha Absorber
• An HST/COS survey of molecular hydrogen in DLAs & sub-DLAs at z < 1: Molecular fraction and excitation temperature
• First Connection between Cold Gas in Emission and Absorption: CO Emission from a Galaxy-Quasar Pair
• ALMACAL III: A combined ALMA and MUSE Survey for Neutral, Molecular, and Ionised Gas in an HI-Absorption-Selected System
• The cosmic abundance of cold gas in the local Universe
• ALMA + VLT observations of a Damped Lyman-α absorbing galaxy: Massive, wide CO emission, gas-rich but with very low SFR
• Massive, Absorption-selected Galaxies at Intermediate Redshifts
• Molecular Hydrogen Absorption from the Halo of a z ~ 0.4 Galaxy
• MusE GAs Flow and Wind (MEGAFLOW) VI. A study of CIV and MgII absorbing gas surrounding [OII] emitting galaxies
• Stellar masses, metallicity gradients and suppressed star formation revealed in a new sample of absorption selected galaxies
• ALMA observations of a metal-rich damped Lyα absorber at z = 2.5832: evidence for strong galactic winds in a galaxy group
• HE 0515-4414 - an unusual sub-damped Ly alpha system revisited
• ALMACAL V: Absorption-selected galaxies with evidence for excited ISMs
• A high molecular fraction in a sub-damped absorber at z=0.56
• High Molecular Gas Masses in Absorption-selected Galaxies at $z\approx 2$
• HST/COS Detection of Deuterated Molecular Hydrogen in a DLA at z = 0.18
• MUSE-ALMA Halos VI: Coupling Atomic, Ionised & Molecular Gas Kinematics of Galaxies
• The Cosmic Ultraviolet Baryon Survey (CUBS) II: Discovery of an H${}_2$-Bearing DLA in the Vicinity of an Early-Type Galaxy at z = 0.576

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• MUSE-ALMA Haloes VII: Survey Science Goals & Design, Data Processing and Final Catalogues
• Towards ultra metal-poor DLAs: linking the chemistry of the most metal-poor DLA to the first stars
• The variation of the gas content of galaxy groups and pairs compared to isolated galaxies
• ALMACAL X: Constraints on molecular gas in the low-redshift circumgalactic medium
• MUSE-ALMA Haloes XIII. Molecular gas in $z\sim 0.5$ HI-selected galaxies
• MUSE-ALMA Haloes XIV: The ALMA Large Programme Data Release