(Sub)millimetre interferometric imaging of a sample of COSMOS/AzTEC submillimetre galaxies

Abstract

We used the Plateau de Bure Interferometer (PdBI) to map a sample of 15 submillimetre galaxies (SMGs) in the COSMOS field at the wavelength of 1.3 mm. The target SMGs were originally discovered in the James Clerk Maxwell Telescope (JCMT)/AzTEC 1.1 mm continuum survey at S/N 1.1 mm = 4−4.5. This paper presents, for the first time, interferometric millimetre-wavelength observations of these sources. The angular resolution of our observations, ∼1. 8, allowed us to accurately determine the positions of the target SMGs. Using a detection threshold of S/N 1.3 mm > 4.5 regardless of multiwavelength counterpart association, and 4 < S/N 1.3 mm ≤ 4.5 if a multiwavelength counterpart within 1. 5 is also present, the total number of detections in our survey is 22. The most significant PdBI detection of S/N 1.3 mm = 10.3 is towards AzTEC19. Three of our detected SMGs (AzTEC21, 27, and 28; which corresponds to 20%) are marginally resolved at our angular resolution, and these sources are found to have elongated or clumpy morphologies and/or multiple components. Using optical to near-infrared photometric redshifts, available spectroscopic redshifts, and redshifts estimated from the radio-to-submm spectral index we infer a median redshift ofz = 3.20 ± 0.25 for our sample. To study the overall multiplicity and redshift distribution of flux-limited samples of SMGs we combined these sources with the 15 brightest JCMT/AzTEC SMGs detected at 1.1 mm, AzTEC1−15, and studied previously. This constitutes a complete, flux-and S/N-limited 1.1-mm selected sample. We find that the median redshift for the 15 brightest JCMT/AzTEC SMGs (z = 3.05 ± 0.44) is consistent with that for AzTEC16−30. This conforms to recent observational findings that SMGs do not exhibit any significant trend between the redshift and (sub)mm flux density. For the combined AzTEC1−30 sample we derive a median redshift ofz = 3.17 ± 0.27, consistent with previous results based on mm-selected samples. We further infer that within the combined AzTEC1−30 sample ∼25 ± 9% of sources separate into multiple components.

HerMES: ALMA IMAGING OFHERSCHEL-SELECTED DUSTY STAR-FORMING GALAXIES

“…We explore two intrinsic number counts that are intended to bracket the plausible range of values for DSFGs based on two interferometric surveys. One is the number counts measured in ALESS , and the other is from interferometric follow-up of the first AzTEC survey in COSMOS (Scott et al 2008) using the SMA (Younger et al 2007(Younger et al , 2009) and PdBI (Miettinen et al 2015). These interferometric observations have shown that all of the sources in their surveys are either unlensed or lensed by magnification factors 2 < (a similar result is found based on ALMA imaging of 52 DSFGs in the Ultra Deep Survey; Simpson et al 2015).…”

“…4. Intrinsic number counts for DSFGs with a form that matches observations in COSMOS (Miettinen et al 2015) underpredict the number of lensed sources with apparent S 10 mJy 870 > . Number counts based on ALESS observations provide a better match to our magnification measurements.…”

“…The Figure 8. Left: observed number counts from interferometer follow-up of millimeter sources in COSMOS (black circles; Younger et al 2007Younger et al , 2009Miettinen et al 2015) and from ALESS (pink diamonds; Karim et al 2013). The magneta and blue lines represent the range of plausible intrinsic number counts for DSFGs given these two datasets.…”

A Spectroscopic Follow-up Program of Very Massive Galaxies at 3 < z < 4: Confirmation of Spectroscopic Redshifts, and a High Fraction of Powerful AGNs

“…The spectroscopic program targeted two additional galaxies, C1-2127 and C1-19764, consistent with being at z 3  but not originally included in the sample presented in Marchesini et al (2010) because they did not strictly satisfy the completeness limit in stellar mass (though both massive with log (M M 11.2 11.3 * ) -). Table 1 also lists C1-21316 from the sample of Marchesini et al (2010) but not targeted by our spectroscopic follow-up program, since it has a previously confirmed spectroscopic redshift of z 3.971 spec = Smolčić et al 2012; but see also Miettinen et al 2015). Table 1 Ground-based Spectroscopic Observations Notes.…”

The VLA-COSMOS 3 GHz Large Project: Continuum data and source catalog release

“…), 6 GHz VLA (Myers et al, in prep. ), and the deep multiwavelength X-ray to mm photometry (Scoville et al 2007;Koekemoer et al 2007;Hasinger et al 2007;Capak et al 2007;Sanders et al 2007;Bertoldi et al 2007;Elvis et al 2009;Ilbert et al 2013;McCracken et al 2012;Scott et al 2008;Aretxaga et al 2011;Smolčić et al 2012;Miettinen et al 2015;Civano et al 2016;Laigle et al 2016, Capak et al, in prep. ) and more than 97 000 optical spectroscopic redshifts (Salvato et al, in prep.…”