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Deep observations of CO line emission from star-forming galaxies in a cluster candidate at z = 1.5

Aravena, M. and Carilli, C. L. and Salvato, M. and Tanaka, M. and Lentati, L. and Schinnerer, E. and Walter, F. and Riechers, D. and Smolčić, V. and Capak, P. and Aussel, H. and Bertoldi, F. and Chapman, S. C. and Farrah, D. and Finoguenov, A. and Le Floc'h, E. and Lutz, D. and Magdis, G. and Oliver, S, and Riguccini, L. and Berta, S. and Magnelli, B. and Pozzi, F. (2012) Deep observations of CO line emission from star-forming galaxies in a cluster candidate at z = 1.5. Monthly Notices of the Royal Astronomical Society, 426 (1). pp. 258-275. ISSN 0035-8711. http://resolver.caltech.edu/CaltechAUTHORS:20121112-163050209

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Abstract

We report results from a deep Jansky Very Large Array (JVLA) search for ^(12)CO J = 1–0 line emission from galaxies in a candidate galaxy cluster at z ∼ 1.55 in the COSMOS field. We target four galaxies with optical spectroscopic redshifts in the range z = 1.47–1.59, consistent with the likely redshift for the candidate galaxy cluster. Two of these four galaxies, ID 51613 and ID 51813, are nominally detected in CO 1–0 line emission at the 3–4σ level. We find CO luminosities of (2.42 ± 0.58) × 10^(10) K km s^(−1) pc^2 and (1.26 ± 0.38) × 10^(10) K km s^(−1) pc^2, respectively. Taking advantage from the clustering and expanded 2-GHz bandwidth of the JVLA, we perform a search for emission lines in the proximity of optical sources within the field of view of our observations (60 arcsec). We limit our search to galaxies with K_S < 23.5 (AB) and z_phot = 1.2–1.8. We find two bright optical galaxies, ID 51207 and ID 51380, to be associated with significant emission line peaks (>4σ) in the data cube, which we identify with the CO 1–0 line emission. To test the reliability of the line peaks found, we performed a parallel search for line peaks using a Bayesian inference method. Both CO line emitting candidates are identified with probabilities of 13 per cent and 72 per cent that there are line emitting sources in each case, respectively. Monte Carlo simulations show that such associations are statistically significant, with probabilities of chance association of 3.5 per cent and 10.7 per cent for ID 51207 and ID 51380, respectively. Modelling of their optical/IR spectral energy distributions indicates that the CO detected galaxies and candidates have stellar masses and star formation rates in the range (0.3–1.1) × 10^(11) M_⊙ and 60–160 M_⊙ yr^(−1), with star formation efficiencies comparable to that found in other star-forming galaxies at similar redshifts. By comparing the space density of CO emitters derived from our observations with the space density derived from previous CO detections at z ∼ 1.5, and with semi-analytic predictions for the CO luminosity function, we suggest that the latter tend to underestimate the number of CO galaxies detected at high redshift. Finally, we argue about the benefits of future searches for molecular gas line emission in clustered fields with upcoming submillimetre/radio facilities.


Item Type:Article
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URLURL TypeDescription
http://dx.doi.org/10.1111/j.1365-2966.2012.21697.xDOIUNSPECIFIED
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2966.2012.21697.x/abstractPublisherUNSPECIFIED
Additional Information:© 2012 The Authors. Monthly Notices of the Royal Astronomical Society. © 2012 RAS. Accepted 2012 July 10. Received 2012 May 30; in original form 2012 April 8. We thank the anonymous referee for the comments and suggestions that helped to improve this manuscript. MA and this work were co-funded under the Marie Curie Actions of the European Commission (FP7-COFUND). CC thanks the Kavli Institute for Cosmology for their hospitality. Based on observations obtained, within the COSMOS Legacy Survey, the National Radio Astronomy Observatory JVLA, CFHT, Subaru, KPNO, Cerro Tololo Inter-American Observatory (CTIO), and ESO Observatories. The National Radio Astronomy Observatory is a facility of the National Science Foundation (NSF), operated under cooperative agreement by Associated Universities Inc.
Group:COSMOS
Funders:
Funding AgencyGrant Number
Marie Curie Actions of the European Commission (FP7-COFUND)UNSPECIFIED
Subject Keywords:galaxies: clusters: general; galaxies: high-redshift; galaxies: ISM
Record Number:CaltechAUTHORS:20121112-163050209
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20121112-163050209
Official Citation:Aravena, M., Carilli, C. L., Salvato, M., Tanaka, M., Lentati, L., Schinnerer, E., Walter, F., Riechers, D., Smǒlcić, V., Capak, P., Aussel, H., Bertoldi, F., Chapman, S. C., Farrah, D., Finoguenov, A., Le Floc'h, E., Lutz, D., Magdis, G., Oliver, S., Riguccini, L., Berta, S., Magnelli, B. and Pozzi, F. (2012), Deep observations of CO line emission from star-forming galaxies in a cluster candidate at z=1.5. Monthly Notices of the Royal Astronomical Society, 426: 258–275. doi: 10.1111/j.1365-2966.2012.21697.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35418
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:13 Nov 2012 19:36
Last Modified:23 Aug 2016 00:16

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