Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published June 20, 2012 | Published
Journal Article Open

CO J = 2-1 Line Emission in Cluster Galaxies at z ~ 1: Fueling Star Formation in Dense Environments


We present observations of CO J = 2–1 line emission in infrared-luminous cluster galaxies at z ∼ 1 using the IRAM Plateau de Bure Interferometer. Our two primary targets are optically faint, dust-obscured galaxies (DOGs) found to lie within 2Mpc of the centers of two massive (>10^(14)M_☉) galaxy clusters. CO line emission is not detected in either DOG. We calculate 3σ upper limits to the CO J = 2–1 line luminosities, L_(CO) < 6.08×10^9 and <6.63×10^9 K km s^(−1) pc^2. Assuming a CO-to-H_2 conversion factor derived for ultraluminous infrared galaxies in the local universe, this translates to limits on the cold molecular gas mass of M_(H2) < 4.86×10^9 M_☉ and M_(H2) < 5.30×10^9 M_☉. 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_(IR) < 7.4×10^(11)L_☉, 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'_(CO)= (1.94 ± 0.35)× 10^(10) K km s^(−1) pc^2, which leads to an estimated cold molecular gas mass M_(H2)= (1.55 ± 0.28) × 10^(10)M_☉ . A significant reservoir of molecular gas in a z ∼ 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.

Additional Information

© 2012 The American Astronomical Society. Received 2012 February 3; accepted 2012 April 12; published 2012 May 30. We thank Jan-Martin Winters, Melanie Krips, and Roberto Neri for their helpful advice and guidance with the data analysis. For their contributions to this survey, we thank Anthony Gonzalez and Thomas Soifer, as well as Adam Stanford for the LRIS spectrum. This work was co-funded under the Marie Curie Actions of the European Commission (FP7-COFUND). Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Part of this work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Attached Files

Published - Wagg2012p18925Astrophys_J.pdf


Files (633.0 kB)
Name Size Download all
633.0 kB Preview Download

Additional details

August 22, 2023
October 18, 2023