Early science with the Large Millimeter Telescope: a 1.1 mm AzTEC survey of red-Herschel dusty star-forming galaxies

We present Large Millimeter Telescope (LMT)/AzTEC 1.1mm observations of similar to 100 luminous high-redshift dusty star-forming galaxy candidates from the similar to 600 sq.deg Herschel-ATLAS survey, selected on the basis of their SPIRE red far-infrared colours and with S-500 mu m = 35 - 80 mJy. With an effective theta(FWHM) approximate to 9.5 arcsec angular resolution, our observations reveal that at least 9 per cent of the targets break into multiple systems with signal-to-noise ratio >= 4 members. The fraction of multiple systems increases to similar to 23 per cent (or more) if some non-detected targets are considered multiples, as suggested by the data. Combining the new AzTEC and deblended Herschel photometry, we derive photometric redshifts, infrared luminosities, and star formation rates. While the median redshifts of the multiple and single systems are similar (z(med) approximate to 3.6), the redshift distribution of the latter is skewed towards higher redshifts. Of the AzTEC sources, similar to 85 per cent lie at z(phot) > 3 while similar to 33 per cent are at z(phot) > 4. This corresponds to a lower limit on the space density of ultrared sources at 4 < z< 6 of similar to 3 x 10(-7) Mpc(-3) with a contribution to the obscured star formation of greater than or similar to 8 x 10(-4)M(circle dot) yr(-1) Mpc(-3). Some of the multiple systems have members with photometric redshifts consistent among them suggesting possible physical associations. Given their angular separations, these systems are most likely galaxy over-densities and/or early-stage pre-coalescence mergers. Finally, we present 3mm LMT/RSR spectroscopic redshifts of six red-Herschel galaxies at z(spec) = 3.85-6.03, two of them (at z similar to 4.7) representing new redshift confirmations. Here, we release the AzTEC and deblended Herschel photometry as well as catalogues of the most promising interacting systems and z > 4 galaxies.

Automated summary

The study presents observations of high-redshift dusty star-forming galaxy candidates using Large Millimeter Telescope (LMT)/AzTEC, revealing the presence of multiple systems within the targets, some of which show possible physical associations. Photometric redshifts, infrared luminosities, and star formation rates are derived from AzTEC and deblended Herschel photometry, providing insights into the spatial density of high-redshift ultrared sources and their contribution to obscured star formation.