ALMA Observations of Gas-rich Galaxies in z ∼ 1.6 Galaxy Clusters: Evidence for Higher Gas Fractions in High-density Environments
- Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)
- Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, ON MJ3 1P3 (Canada)
- Departamento de Ciencias Físicas, Universidad Andres Bello, Fernandez Concha 700, Las Condes 7591538, Santiago, Región Metropolitana (Chile)
- The University of Kansas, Department of Physics and Astronomy, 1251 Wescoe Hall Drive, Lawrence, KS 66045 (United States)
- European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München (Germany)
- Department of Physics, McGill University, 3600 rue University, Montréal, QC H3A 2T8 (Canada)
- Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States)
- Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada)
- Department of Physics, University of California Berkeley, 366 LeConte Hall, MC 7300, Berkeley, CA 94720-7300 (United States)
- Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States)
- Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción, Región del Biobío (Chile)
We present ALMA CO (2–1) detections in 11 gas-rich cluster galaxies at z ∼ 1.6, constituting the largest sample of molecular gas measurements in z > 1.5 clusters to date. The observations span three galaxy clusters, derived from the Spitzer Adaptation of the Red-sequence Cluster Survey. We augment the >5 σ detections of the CO (2–1) fluxes with multi-band photometry, yielding stellar masses and infrared-derived star formation rates, to place some of the first constraints on molecular gas properties in z ∼ 1.6 cluster environments. We measure sizable gas reservoirs of 0.5–2 × 10{sup 11} M {sub ☉} in these objects, with high gas fractions ( f {sub gas}) and long depletion timescales ( τ ), averaging 62% and 1.4 Gyr, respectively. We compare our cluster galaxies to the scaling relations of the coeval field, in the context of how gas fractions and depletion timescales vary with respect to the star-forming main sequence. We find that our cluster galaxies lie systematically off the field scaling relations at z = 1.6 toward enhanced gas fractions, at a level of ∼4 σ , but have consistent depletion timescales. Exploiting CO detections in lower-redshift clusters from the literature, we investigate the evolution of the gas fraction in cluster galaxies, finding it to mimic the strong rise with redshift in the field. We emphasize the utility of detecting abundant gas-rich galaxies in high-redshift clusters, deeming them as crucial laboratories for future statistical studies.
- OSTI ID:
- 22654452
- Journal Information:
- Astrophysical Journal Letters, Vol. 842, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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