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Large gas reservoirs and free–free emission in two lensed star-forming galaxies at z = 2.7

Aravena, M. and Vieira, J. D. (2013) Large gas reservoirs and free–free emission in two lensed star-forming galaxies at z = 2.7. Monthly Notices of the Royal Astronomical Society, 433 (1). pp. 498-505. ISSN 0035-8711.

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We report the detection of CO(1–0) line emission in the bright, lensed star-forming galaxies SPT-S 233227−5358.5 (z = 2.73) and SPT-S 053816−5030.8 (z = 2.78), using the Australia Telescope Compact Array. Both galaxies were discovered in a large-area millimetre survey with the South Pole Telescope (SPT) and found to be gravitationally lensed by intervening structures. The measured CO intensities imply galaxies with molecular gas masses of (3.2 ± 0.5) × 10^10(μ/15)^(−1)(X_CO/0.8) and (1.7 ± 0.3) × 10^10(μ/20)^(−1)(XCO/0.8) M_⊙, and gas depletion time-scales of 4.9 × 107(X_CO/0.8) and 2.6 × 10^7(X_CO/0.8) yr, respectively, where μ corresponds to the lens magnification and X_CO is the CO luminosity to gas mass conversion factor. In the case of SPT-S 053816−5030.8, we also obtained significant detections of the rest-frame 115.7 and 132.4 GHz radio continuum. Based on the radio-to-infrared spectral energy distribution and an assumed synchrotron spectral index, we find that 42 ± 10 and 55 ± 13 per cent of the flux at rest-frame 115.7 and 132.4 GHz arises from free–free emission. We find a radio-derived intrinsic star formation rate of 470 ± 170 M_⊙ yr^(−1), consistent within the uncertainties with the infrared estimate. Based on the morphology of this object in the source plane, the derived gas mass and the possible flattening of the radio spectral index towards low frequencies, we argue that SPT-S 053816−5030.8 exhibits properties compatible with a scaled-up local ultraluminous infrared galaxy.

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URLURL TypeDescription Paper
Aravena, M.0000-0002-6290-3198
Additional Information:© 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2013 April 26. Received 2013 April 5; in original form 2013 February 13. First published online: May 21, 2013. We thank Andy Biggs for useful discussions. MA and this work was co-funded under the Marie Curie Actions of the European Commission (FP7-COFUND). The Australia Telescope is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. The SPT is supported by the National
Funding AgencyGrant Number
European Commission Marie Curie ActionsFP7-COFUND
Commonwealth of AustraliaUNSPECIFIED
Kavli FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:galaxies: evolution; galaxies: formation; galaxies: high-redshift; galaxies: starburst; cosmology: observations
Issue or Number:1
Record Number:CaltechAUTHORS:20130918-113141597
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41385
Deposited By: Jason Perez
Deposited On:18 Sep 2013 21:51
Last Modified:09 Mar 2020 13:18

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