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Published April 10, 2013 | Published + Submitted
Journal Article Open

ALMA Redshifts of Millimeter-selected Galaxies from the SPT Survey: The Redshift Distribution of Dusty Star-forming Galaxies


Using the Atacama Large Millimeter/submillimeter Array, we have conducted a blind redshift survey in the 3 mm atmospheric transmission window for 26 strongly lensed dusty star-forming galaxies (DSFGs) selected with the South Pole Telescope. The sources were selected to have S_(1.4mm) > 20 mJy and a dust-like spectrum and, to remove low-z sources, not have bright radio (S_843MHz) < 6 mJy) or far-infrared counterparts (S_(100μm) < 1 Jy, S_(60μm) < 200 mJy). We robustly detect 44 line features in our survey, which we identify as redshifted emission lines of ^(12)CO, ^(13)CO, C I, H_2O, and H_2O^+. We find one or more spectral features in 23 sources yielding a ~90% detection rate for this survey; in 12 of these sources we detect multiple lines, while in 11 sources we detect only a single line. For the sources with only one detected line, we break the redshift degeneracy with additional spectroscopic observations if available, or infer the most likely line identification based on photometric data. This yields secure redshifts for ~70% of the sample. The three sources with no lines detected are tentatively placed in the redshift desert between 1.7 < z < 2.0. The resulting mean redshift of our sample is z = 3.5. This finding is in contrast to the redshift distribution of radio-identified DSFGs, which have a significantly lower mean redshift of z = 2.3 and for which only 10%-15% of the population is expected to be at z > 3. We discuss the effect of gravitational lensing on the redshift distribution and compare our measured redshift distribution to that of models in the literature.

Additional Information

© 2013 American Astronomical Society. Received 2012 October 31; accepted 2013 February 15; published 2013 March 28. The authors thank A. Blain and N. Scoville for many useful discussions related to this work, and A. Benson, C. Baugh, C. Hayward, and C. Lacey for providing us with the predicted redshift distributions from their models and useful discussions regarding their implications. This paper makes use of the following ALMA data:ADS/JAO.ALMA#2011.0.00957.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. Based on observations taken with European Southern Observatory Very Large Telescope, Paranal, Chile, with program ID 088.A-0902(C), and with the Atacama Pathfinder Experiment under program IDs 086.A-0793(A), 086.A-1002(A), 087.A-0815(A) and 087.A-0968(A). APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The SPT is supported by the National Science Foundation through grant ANT-0638937, with partial support through PHY-1125897, the Kavli Foundation and the Gordon and Betty Moore Foundation. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Partial support for this work was provided by NASA through grant HST-GO-12659 from the Space Telescope Science Institute. This work is based in part on observations made with Herschel, a European Space Agency Cornerstone Mission with significant participation by NASA, and supported through an award issued by JPL/Caltech for OT2_jvieira_5. T.R.G. gratefully acknowledges support from a STFC Advanced Fellowship.

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Published - 0004-637X_767_1_88.pdf

Submitted - 1303.2726v1.pdf


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