Dust reddened quasars in first and UKIDSS: Beyond the tip of the iceberg
- Department of Physics, Middlebury College, Middlebury, VT 05753 (United States)
- Leibniz Institut fr Astrophysik, An der Sternwarte 16, D-14482 Potsdam (Germany)
- National Radio Astronomy Observatory, Charlottesville, VA (United States)
- California Institute of Technology, Pasadena, CA 91125 (United States)
- Department of Physics and Yale Center for Astronomy and Astrophysics, Yale University, P.O. Box 208121, New Haven, CT 06520-8121 (United States)
- Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006 (Australia)
- Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)
- Astronomy Department, University of Florida, 211 Bryant Space Science Center, P.O. Box 112055, Gainesville, FL 32611 (United States)
We present the results of a pilot survey to find dust-reddened quasars by matching the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) radio catalog to the UKIDSS near-infrared survey and using optical data from Sloan Digital Sky Survey to select objects with very red colors. The deep K-band limit provided by UKIDSS allows for finding more heavily reddened quasars at higher redshifts as compared with previous work using FIRST and Two Micron All Sky Survey (2MASS). We selected 87 candidates with K ≤ 17.0 from the UKIDSS Large Area Survey (LAS) First Data Release (DR1), which covers 190 deg{sup 2}. These candidates reach up to ∼1.5 mag below the 2MASS limit and obey the color criteria developed to identify dust-reddened quasars. We have obtained 61 spectroscopic observations in the optical and/or near-infrared, as well as classifications in the literature, and have identified 14 reddened quasars with E(B – V) > 0.1, including 3 at z > 2. We study the infrared properties of the sample using photometry from the Wide-Field Infrared Survey Explorer and find that infrared colors improve the efficiency of red quasar selection, removing many contaminants in an infrared-to-optical color-selected sample alone. The highest-redshift quasars (z ≳ 2) are only moderately reddened, with E(B – V) ∼ 0.2-0.3. We find that the surface density of red quasars rises sharply with faintness, comprising up to 17% of blue quasars at the same apparent K-band flux limit. We estimate that to reach more heavily reddened quasars (i.e., E(B – V) ≳ 0.5) at z > 2 and a depth of K = 17, we would need to survey at least ∼2.5 times more area.
- OSTI ID:
- 22341919
- Journal Information:
- Astrophysical Journal, Vol. 778, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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