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Published June 2012 | Published
Journal Article Open

The source counts of submillimetre galaxies detected at λ= 1.1 mm


The source counts of galaxies discovered at submillimetre and millimetre wavelengths provide important information on the evolution of infrared-bright galaxies. We combine the data from six blank-field surveys carried out at 1.1 mm with AzTEC, totalling 1.6 deg^2 in area with root-mean-square depths ranging from 0.4 to 1.7 mJy, and derive the strongest constraints to date on the 1.1 mm source counts at flux densities S_1100= 1–12 mJy. Using additional data from the AzTEC Cluster Environment Survey to extend the counts to S1100∼ 20 mJy, we see tentative evidence for an enhancement relative to the exponential drop in the counts at S_1100∼ 13 mJy and a smooth connection to the bright source counts at >20 mJy measured by the South Pole Telescope; this excess may be due to strong-lensing effects. We compare these counts to predictions from several semi-analytical and phenomenological models and find that for most the agreement is quite good at flux densities ≳ 4 mJy; however, we find significant discrepancies (≳ 3σ) between the models and the observed 1.1-mm counts at lower flux densities, and none of them is consistent with the observed turnover in the Euclidean-normalized counts at S_1100≲ 2 mJy. Our new results therefore may require modifications to existing evolutionary models for low-luminosity galaxies. Alternatively, the discrepancy between the measured counts at the faint end and predictions from phenomenological models could arise from limited knowledge of the spectral energy distributions of faint galaxies in the local Universe.

Additional Information

© 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS. Accepted 2012 March 10. Received 2012 February 15; in original form 2011 November 28. Article first published online: 17 Apr. 2012. We thank Chris Pearson and Alberto Franceschini for providing us with predictions of the 1.1 mm source counts from their galaxy evolution models. KSS is supported by the National Radio Astronomy Observatory, which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. IA and DHH acknowledge support from CONACyT projects #39953-F. BH is supported by a Research Fellowship for Young Scientists from the Japan Society of the Promotion of Science. JSD acknowledges the support of the Royal Society via a Wolfson Research Merit award, and also the support of the European Research Council via the award of an Advanced Grant. This work is supported in part by grants #0907952 and #0838222 from the National Science Foundation. This work is supported in part by the MEXT Grant-in-Aid for Specially Promoted Research (#20001003) and Scientific Research on Priority Areas (#15071202). The ASTE project is driven by the Nobeyama Radio Observatory, a branch of the NAOJ, in collaboration with the University of Chile and Japanese institutes including the University of Tokyo, Nagoya University, Osaka Prefecture University, Ibaraki University and Hokkaido University. The James Clerk Maxwell Telescope is operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the United Kingdom, the Netherlands Organization for Scientific Research, and the National Research Council of Canada.

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August 22, 2023
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