CO J = 2-1 LINE EMISSION IN CLUSTER GALAXIES AT z {approx} 1: FUELING STAR FORMATION IN DENSE ENVIRONMENTS

Journal Article · Wed Jun 20 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/752/2/91· OSTI ID:22037048

Wagg, Jeff ^[1]; Pope, Alexandra; Alberts, Stacey ^[2]; Armus, Lee; Desai, Vandana ^[3]; Brodwin, Mark ^[4]; Bussmann, Robert S ^[5]; Dey, Arjun; Jannuzi, Buell ^[6]; Le Floc'h, Emeric ^[7]; Melbourne, Jason ^[8]; Stern, Daniel ^[9]

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1. European Southern Observatory, Casilla 19001, Santiago (Chile)
2. Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)
3. Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA 91125 (United States)
4. Department of Physics, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States)
5. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
6. National Optical Astronomy Observatory, Tucson, AZ 85726-6732 (United States)
7. AIM, CNRS, Universite Paris Diderot, Bat. 709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex (France)
8. California Institute of Technology, Pasadena, CA 91125 (United States)
9. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

We present observations of CO J = 2-1 line emission in infrared-luminous cluster galaxies at z {approx} 1 using the IRAM Plateau de Bure Interferometer. Our two primary targets are optically faint, dust-obscured galaxies (DOGs) found to lie within 2 Mpc of the centers of two massive (>10{sup 14} M{sub Sun }) galaxy clusters. CO line emission is not detected in either DOG. We calculate 3{sigma} upper limits to the CO J = 2-1 line luminosities, L'{sub CO} < 6.08 Multiplication-Sign 10{sup 9} and <6.63 Multiplication-Sign 10{sup 9} K km s{sup -1} pc{sup 2}. Assuming a CO-to-H{sub 2} conversion factor derived for ultraluminous infrared galaxies in the local universe, this translates to limits on the cold molecular gas mass of M{sub H{sub 2}}< 4.86 Multiplication-Sign 10{sup 9} M{sub Sun} and M{sub H{sub 2}}< 5.30 Multiplication-Sign 10{sup 9} M{sub Sun }. Both DOGs exhibit mid-infrared continuum emission that follows a power law, suggesting that an active galactic nucleus (AGN) contributes to the dust heating. As such, estimates of the star formation efficiencies in these DOGs are uncertain. A third cluster member with an infrared luminosity, L{sub IR} < 7.4 Multiplication-Sign 10{sup 11} L{sub Sun }, is serendipitously detected in CO J = 2-1 line emission in the field of one of the DOGs located roughly two virial radii away from the cluster center. The optical spectrum of this object suggests that it is likely an obscured AGN, and the measured CO line luminosity is L'{sub CO} = (1.94 {+-} 0.35) Multiplication-Sign 10{sup 10} K km s{sup -1} pc{sup 2}, which leads to an estimated cold molecular gas mass M{sub H{sub 2}}= (1.55{+-}0.28) Multiplication-Sign 10{sup 10} M{sub Sun }. A significant reservoir of molecular gas in a z {approx} 1 galaxy located away from the cluster center demonstrates that the fuel can exist to drive an increase in star formation and AGN activity at the outskirts of high-redshift clusters.

• OSTI ID: 22037048
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 752; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
CARBON MONOXIDE
COSMIC DUST
EMISSION SPECTRA
GALACTIC EVOLUTION
GALAXIES
GALAXY CLUSTERS
HYDROGEN
INFRARED RADIATION
INTERFEROMETERS
LUMINOSITY
MASS
MOLECULES
PHOTON EMISSION
RED SHIFT
STARS
UNIVERSE