@article{10902/4115,
year = {2013},
month = {4},
url = {http://hdl.handle.net/10902/4115},
abstract = {The Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) provides an unprecedented opportunity to search for blazars at sub-mm wavelengths. We cross-matched the Faint Images of the Radio Sky at Twenty-cm (FIRST) radio source catalogue with the 11 655 sources brighter than 35 mJy at 500 μm in the ∼135 deg2 of the sky covered by the H-ATLAS equatorial fields at 9h and 15h, plus half of the field at 12h. We found that 379 of the H-ATLAS sources have a FIRST counterpart within 10 arcsec, including eight catalogued blazars (plus one known blazar that was found at the edge of one of the H-ATLAS maps). To search for additional blazar candidates we have devised new diagnostic diagrams and found that known blazars occupy a region of the log (S500 μm/S350 μm) versus log (S500 μm/S1.4 GHz) plane separated from that of sub-mm sources with radio emission powered by star formation, but shared with radio galaxies and steep-spectrum radio quasars. Using this diagnostic we have selected 12 further possible candidates that turn out to be scattered in the (r − z) versus (u − r) plane or in the Wide-Field Infrared Survey Explorer colour–colour diagram, where known blazars are concentrated in well defined strips. This suggests that the majority of them are not blazars. Based on an inspection of all the available photometric data, including unpublished VISTA Kilo-degree Infrared Galaxy survey photometry and new radio observations, we found that the spectral energy distributions (SEDs) of only one out of the 12 newly selected sources are compatible with being synchrotron dominated at least up to 500 μm, i.e. with being a blazar. Another object may consist of a faint blazar nucleus inside a bright star-forming galaxy. The possibility that some blazar hosts are endowed with active star formation is supported by our analysis of the SEDs of Planck Early Release Compact Source Catalogue blazars detected at both 545 and 857 GHz. The estimated rest-frame synchrotron peak frequencies of H-ATLAS blazars are in the range 11.5 ≤ log (νpeak, Hz) ≤ 13.7, implying that these objects are low synchrotron peak. Six of them also show evidence of an ultraviolet excess that can be attributed to emission from the accretion disc. Allowing for the possibility of misidentifications and of contamination of the 500 μm flux density by the dusty torus or by the host galaxy, we estimate that there are seven or eight pure synchrotron sources brighter than S500 μm = 35 mJy over the studied area, a result that sets important constraints on blazar evolutionary models.},
organization = {The authors would like to thank an anonymous referee for useful comments and suggestions. Partial financial support to this work was provided by the Spanish Ministerio de Economía y Competitividad projects AYA2010-21490-C02-01, AYA2010-21766-C03- 01 and CSD2010-00064, by ASI/INAF Agreement I/072/09/0 for the Planck LFI activity of Phase E2, by MIUR PRIN 2009 and by INAF through the PRIN 2009 ‘New light on the early Universe with sub-mm spectroscopy’. ML-C thanks the Spanish Ministerio de Economía y Competitividad for a Juan de la Cierva fellowship. JG-N thanks the Spanish CSIC for a JAE DOC fellowship. This research has made use of the NASA/IPAC Extragalactic Database (NED), of SDSS DR8 data and of data products from the Wide-field Infrared Survey Explorer (WISE). The NED is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. WISE is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation and the US Department of Energy Office of Science. The SDSS-III web site is www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, University of Cambridge, University of Florida, the French Participation Group, the German Participation Group, the Instituto de Astrofísica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington and Yale University.},
publisher = {Royal Astronomical Society},
publisher = {Monthly Notices of the royal astronomical Society, 2013, 430(3), 1566-1577},
title = {Mining the Herschel-Astrophysical Terahertz Large Area Survey: submillimetre-selected blazars in equatorial fields},
author = {López-Caniego Alcarria, Marcos and González-Nuevo, Joaquín and Massardi, Marcella and Bonavera, Laura and Herranz Muñoz, Diego and Negrello, Mattia and De Zotti, Gianfranco and Carrera Troyano, Francisco Jesús and Danese, Luigi and Fleuren, Simone and Hardcastle, Martin J. and Jarvis, Matt J. and Klöckner, Hans Rainer and Mauch, Tom and Procopio, Pietro and Righini, Simona and Sutherland, William J. and Auld, Robbie, R. and Baes, Maarten and Buttiglione, Sara and Clark, Christopher and Cooray, Asantha Roshan and Dariush, Ali A. and Dunne, Loretta and Dye, Simon and Eales, Steve A. and Hopwood, Ros H. B. and Hoyos, Carlos and Ibar, Edo and Ivison, Rob J. and Maddox, Steve J. and Valiante, Elisabetta},
}