VLA–ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (VLASPECS): Total Cold Gas Masses and CO Line Ratios for z = 2–3 Main-sequence Galaxies

Riechers, Dominik A.; Boogaard, Leindert A.; Decarli, Roberto; González-López, Jorge; Smail, Ian; Walter, Fabian; Aravena, Manuel; Carilli, Christopher L.; Cortes, Paulo C.; Cox, Pierre; Díaz-Santos, Tanio; Hodge, Jacqueline A.; Inami, Hanae; Ivison, Rob J.; Kaasinen, Melanie; Wagg, Jeff; Weiß, Axel; van der Werf, Paul

doi:10.3847/2041-8213/ab9595

VLA–ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (VLASPECS): Total Cold Gas Masses and CO Line Ratios for z = 2–3 Main-sequence Galaxies

Riechers, Dominik A.; Boogaard, Leindert A.; Decarli, Roberto; González-López, Jorge; Smail, Ian; Walter, Fabian; Aravena, Manuel; Carilli, Christopher L.; Cortes, Paulo C.; Cox, Pierre; Díaz-Santos, Tanio; Hodge, Jacqueline A.; Inami, Hanae; Ivison, Rob J.; Kaasinen, Melanie; Wagg, Jeff; Weiß, Axel; van der Werf, Paul

Authors

Dominik A. Riechers

Leindert A. Boogaard

Roberto Decarli

Jorge González-López

Professor Ian Smail ian.smail@durham.ac.uk
Emeritus Professor

Fabian Walter

Manuel Aravena

Christopher L. Carilli

Paulo C. Cortes

Pierre Cox

Tanio Díaz-Santos

Jacqueline A. Hodge

Hanae Inami

Rob J. Ivison

Melanie Kaasinen

Jeff Wagg

Axel Weiß

Paul van der Werf

Abstract

Using the NSF's Karl G. Jansky Very Large Array (VLA), we report six detections of CO(J = 1 → 0) emission and one upper limit in z = 2–3 galaxies originally detected in higher-J CO emission in the Atacama Large Millimeter/submillimeter Array Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS). From the CO(J = 1 → 0) line strengths, we measure total cold molecular gas masses of M gas = (2.4–11.6) × 1010 (α CO/3.6)M ⊙. We also measure a median CO(J = 3 → 2) to CO(J = 1 → 0) line brightness temperature ratio of r 31 = 0.84 ± 0.26, and a CO(J = 7 → 6) to CO(J = 1 → 0) ratio range of r 71 < 0.05 to r 71 = 0.17. These results suggest that CO(J = 3 → 2) selected galaxies may have a higher CO line excitation on average than CO(J = 1 → 0) selected galaxies, based on the limited, currently available samples from the ASPECS and VLA CO Luminosity Density at High Redshift (COLDz) surveys. This implies that previous estimates of the cosmic density of cold gas in galaxies based on CO(J = 3 → 2) measurements should be revised down by a factor of sime2 on average based on assumptions regarding CO excitation alone. This correction further improves the agreement between the best currently existing constraints on the cold gas density evolution across cosmic history from line scan surveys, and the implied characteristic gas depletion times.

Citation

Riechers, D. A., Boogaard, L. A., Decarli, R., González-López, J., Smail, I., Walter, F., …van der Werf, P. (2020). VLA–ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (VLASPECS): Total Cold Gas Masses and CO Line Ratios for z = 2–3 Main-sequence Galaxies. Astrophysical Journal Letters, 896(2), Article L21. https://doi.org/10.3847/2041-8213/ab9595

Journal Article Type	Article
Acceptance Date	May 19, 2020
Online Publication Date	Jun 15, 2020
Publication Date	Jun 20, 2020
Deposit Date	Jul 8, 2020
Publicly Available Date	Jul 9, 2020
Journal	Astrophysical Journal
Print ISSN	2041-8205
Publisher	American Astronomical Society
Peer Reviewed	Peer Reviewed
Volume	896
Issue	2
Article Number	L21
DOI	https://doi.org/10.3847/2041-8213/ab9595