Riechers, Dominik A. and Carilli, Christopher L. and Walter, Fabian and Weiss, Axel and Wagg, Jeff and Bertoldi, Frank and Downes, Dennis and Henkel, Christian and Hodge, Jacqueline (2011) Imaging the Molecular Gas Properties of a Major Merger Driving the Evolution of a z = 2.5 Submillimeter Galaxy. Astrophysical Journal Letters, 733 (1). Art. No. L11. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20110902-094604243
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We report the detection of spatially extended CO(J = 1→0) and CO(J = 5→4) emission in the z = 2.49 submillimeter galaxy (SMG) J123707+6214, using the Expanded Very Large Array and the Plateau de Bure Interferometer. The large molecular gas reservoir is spatially resolved into two CO(J = 1→0) components (northeast and southwest; previously identified in CO J = 3→2 emission) with respective gas masses of 4.3 and 3.5×10^(10) (α_(CO)/0.8) M_☉. We thus find that the optically invisible northeast component slightly dominates the gas mass in this system. The total molecular gas mass derived from the CO(J = 1→0) observations is ≳2.5× larger than estimated from CO(J = 3→2). The two components are at approximately the same redshift, but separated by ~20 kpc in projection. The morphology is consistent with that of an early-stage merger. The total amount of molecular gas is sufficient to maintain the intense 500 M_☉ yr^(–1) starburst in this system for at least ~160 Myr. We derive line brightness temperature ratios of r_(31) = 0.39 ± 0.09 and 0.37 ± 0.10, and r_(51) = 0.26 ± 0.07 and 0.25 ± 0.08 in the two components, respectively, suggesting that the J ≥ 3 lines are substantially subthermally excited. This also suggests comparable conditions for star formation in both components. Given the similar gas masses of both components, this is consistent with the comparable starburst strengths observed in the radio continuum emission. Our findings are consistent with other recent studies that find evidence for lower CO excitation in SMGs than in high-z quasar host galaxies with comparable gas masses. This may provide supporting evidence that both populations correspond to different evolutionary stages in the formation of massive galaxies.
|Additional Information:||© 2011 The American Astronomical Society. Received 2010 September 7; accepted 2011 April 12; published 2011 May 2. We thank the referee for a critical reading of the manuscript and for a helpful report. D.R. acknowledges support from NASA through Hubble Fellowship grant HST-HF-51235.01 awarded by STScI, operated by AURA for NASA, under contract NAS 5-26555. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.|
|Subject Keywords:||cosmology: observations; galaxies: active; galaxies: formation; galaxies: high-redshift; galaxies: starburst; radio lines: galaxies|
|Classification Code:||PACS: 98.54.Ep; 98.62.Ai; 98.62.Bj; 98.62.Py; 95.85.Bh|
|Official Citation:||Imaging the Molecular Gas Properties of a Major Merger Driving the Evolution of a z = 2.5 Submillimeter Galaxy Dominik A. Riechers et al. 2011 ApJ 733 L11|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||02 Sep 2011 19:19|
|Last Modified:||26 Dec 2012 13:39|
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