High Gas Fraction in a CO-detected Main-sequence Galaxy at z > 3

Gowardhan, A.; Riechers, D.; Pavesi, R.; Daddi, E.; Dannerbauer, H.; Neri, R.
Referencia bibliográfica

The Astrophysical Journal, Volume 875, Issue 1, article id. 6, 6 pp. (2019).

Fecha de publicación:
4
2019
Número de autores
6
Número de autores del IAC
1
Número de citas
29
Número de citas referidas
28
Descripción
We report NOrthern Extended Millimetre Array (NOEMA) observations of warm molecular gas traced by CO(5 ‑ 4) in a z∼ 3.2 gas-rich main-sequence (MS) galaxy, initially serendipitously detected in CO(3 ‑ 2) emission in “blind” deep NOEMA observations. Our target shows a gas excitation consistent with that seen in z∼ 1.5 MS galaxies ({L}CO(5-4)}{\prime }/{L}CO (3-2)}{\prime }=0.41+/- 0.14), albeit toward the low end, as well as a similar star formation efficiency based on the CO(3 ‑ 2) line luminosity and the {L}IR}. However, it shows a high molecular gas fraction ({f}gas}=0.9+/- 0.2) as compared to z∼ 1.5 MS galaxies ({f}gas}∼ 0.42), consistent with a cosmologically increasing gas fraction beyond z≳ 3 and our current understanding of scaling relations between z, {f}gas}, the stellar mass M *, and the specific star formation rate. Our results are consistent with recent findings by the COLDz and ASPECS molecular line scan surveys, and suggest that deep searches for CO emission are a powerful means to identify gas-rich, star-forming galaxies at high redshift.
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