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Title: A Massive, Dusty, Hi Absorption–Selected Galaxy at z ≈ 2.46 Identified in a CO Emission Survey
Abstract We report a NOrthern Extended Millimeter Array (NOEMA) and Atacama Large Millimeter/submillimeter Array search for redshifted CO emission from the galaxies associated with seven high-metallicity ([M/H] ≥ −1.03) damped Ly α absorbers (DLAs) at z ≈ 1.64–2.51. Our observations yielded one new detection of CO(3–2) emission from a galaxy at z = 2.4604 using NOEMA, associated with the z = 2.4628 DLA toward QSO B0201+365. Including previous searches, our search results in detection rates of CO emission of ≈ 56 − 24 + 38 % and ≈ 11 − 9 + 26 %, respectively, in the fields of DLAs with [M/H] > −0.3 and [M/H] < −0.3. Further, the H i –selected galaxies associated with five DLAs with [M/H] > −0.3 all have high molecular gas masses, ≳5 × 10 10 M ⊙ . This indicates that the highest-metallicity DLAs at z ≈ 2 are associated with the most massive galaxies. The newly identified z ≈ 2.4604 H i –selected galaxy, DLA0201+365g, has an impact parameter of ≈7 kpc to the QSO sightline, and an implied molecular gas mass of (5.04 ± 0.78) × 10 10 × ( α CO /4.36) × ( r 31 /0.55) M ⊙ . Archival Hubble Space Telescope Wide Field and Planetary Camera 2 imaging covering the rest-frame near-ultraviolet (NUV) and far-ultraviolet (FUV) emission from this galaxy yield nondetections of rest-frame NUV and FUV emission, and a 5 σ upper limit of 2.3 M ⊙ yr −1 on the unobscured star formation rate (SFR). The low NUV-based SFR estimate, despite the very high molecular gas mass, indicates that DLA0201+365g either is a very dusty galaxy, or has a molecular gas depletion time that is around 2 orders of magnitude larger than that of star-forming galaxies at similar redshifts.  more » « less
Award ID(s):
2107989 2107990 2107991
PAR ID:
10345117
Author(s) / Creator(s):
; ; ; ; ; ;
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
934
Issue:
1
ISSN:
0004-637X
Page Range / eLocation ID:
87
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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