@article{b9156e90687a4d9b980fbca02d37e3b2,
title = "Extremely red quasars from SDSS, BOSS and WISE: Classification of optical spectra",
abstract = "Quasars with extremely red infrared-to-optical colours are an interesting population that can test ideas about quasar evolution as well as orientation, obscuration and geometric effects in the so-called AGN unified model. To identify such a population, we match the quasar catalogues of the Sloan Digital Sky Survey (SDSS), the Baryon Oscillation Spectroscopic Survey (BOSS) to the Wide-Field Infrared Survey Explorer (WISE) to identify quasars with extremely high infrared-to-optical ratios. We identify 65 objects with rAB - W4Vega > 14 mag (i.e. Fν(22 μm)/Fν (r) ≳ 1000). This sample spans a redshift range of 0.28 < z < 4.36 and has a bimodal distribution, with peaks at z ~ 0.8 and z ~ 2.5. It includes three z > 2.6 objects that are detected in the W4 band but not W1 or W2 (i.e. 'W1W2 dropouts'). The SDSS/BOSS spectra show that the majority of the objects are reddened type 1 quasars, type 2 quasars (both at low and high redshift) or objects with deep low-ionization broad absorption lines (BALs) that suppress the observed r-band flux. In addition, we identify a class of type 1 permitted broad emission-line objects at z ≃ 2-3 which are characterized by emission line rest-frame equivalent widths (REWs) of ≳150 {\AA}, much larger than those of typical quasars. In particular, 55 per cent (45 per cent) of the non-BAL type 1s with measurable CIV in our sample have REW(C IV) > 100 (150) {\AA}, compared to only 5.8 per cent (1.3 per cent) for non-BAL quasars in BOSS. These objects often also have unusual line ratios, such as very high NV/Ly α ratios. These large REWs might be caused by suppressed continuum emission analogous to type 2 quasars; however, there is no obvious mechanism in standard unified models to suppress the continuum without also obscuring the broad emission lines.",
keywords = "Galaxies: evolution, Infrared: galaxies, Quasars: general, Surveys",
author = "Ross, {Nicholas P.} and Fred Hamann and Zakamska, {Nadia L.} and Richards, {Gordon T.} and Carolin Villforth and Strauss, {Michael A.} and Greene, {Jenny E.} and Rachael Alexandroff and Brandt, {W. Niel} and Guilin Liu and Myers, {Adam D.} and Isabelle P{\^a}ris and Schneider, {Donald P.}",
note = "Funding Information: We thank R. M. Cutri and the IPAC team for the Explanatory Supplement to the WISE All-Sky and AllWISE Data Release Products resource. Peregrine McGehee and the IRSA HelpDesk were also very useful. NPR thanks Nathan Bourne for useful discussions on IR-to-radio flux ratios. AllWISE makes use of data from WISE, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, and NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology. WISE and NEOWISE are funded by the National Aeronautics and Space Administration. NPR acknowledges that funding for part of this projectwas supplied by NASA and the Hubble grant number: HST-GO-13014.06. FH acknowledges support from the USA National Science Foundation grant AST-1009628. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy. The SDSS-III web site is http://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 Astrofisica 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. Facilities: SDSS, WISE Funding Information: We thank R. M. Cutri and the IPAC team for the Explanatory Supplement to the WISE All-Sky and AllWISE Data Release Products resource. Peregrine McGehee and the IRSA HelpDesk were also very useful. NPR thanks Nathan Bourne for useful discussions on IR-to-radio flux ratios. AllWISE makes use of data from WISE, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, and NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology. WISE and NEOWISE are funded by the National Aeronautics and Space Administration. NPR acknowledges that funding for part of this project was supplied by NASA and the Hubble grant number: HST-GO-13014.06. FH acknowledges support from the USA National Science Foundation grant AST-1009628. Funding Information: Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy. The SDSS-III web site is http://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 Astrofisica 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. Facilities: SDSS, WISE Publisher Copyright: {\textcopyright} 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.",
year = "2015",
month = nov,
day = "11",
doi = "10.1093/mnras/stv1710",
language = "English (US)",
volume = "453",
pages = "3932--3952",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "4",
}