OPTICALLY SELECTED BL LACERTAE CANDIDATES FROM THE SLOAN DIGITAL SKY SURVEY DATA RELEASE SEVEN
- Department of Astronomy, University of Washington, P.O. Box 351580, Seattle, WA 98195 (United States)
- Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)
- Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
- Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, ON M3J 1P3 (Canada)
- Physics Department, Rochester Institute of Technology, Rochester, NY 14623 (United States)
- Department of Physics, University of North Texas, Denton, TX 76203 (United States)
- Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, Postfach 1312, D-85741 Garching (Germany)
- University of Chicago and the Fermi Institute, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)
- Princeton University Observatory, Peyton Hall, Ivy Lane, Princeton, NJ 08544 (United States)
- Apache Point Observatory, Sunspot, NM 88349 (United States)
We present a sample of 723 optically selected BL Lac candidates from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) spectroscopic database encompassing 8250 deg{sup 2} of sky; our sample constitutes one of the largest uniform BL Lac samples yet derived. Each BL Lac candidate has a high-quality SDSS spectrum from which we determine spectroscopic redshifts for {approx}60% of the objects. Redshift lower limits are estimated for the remaining objects utilizing the lack of host galaxy flux contamination in their optical spectra; we find that objects lacking spectroscopic redshifts are likely at systematically higher redshifts. Approximately 80% of our BL Lac candidates match to a radio source in FIRST/NVSS, and {approx}40% match to a ROSAT X-ray source. The homogeneous multiwavelength coverage allows subdivision of the sample into 637 radio-loud BL Lac candidates and 86 weak-featured radio-quiet objects. The radio-loud objects broadly support the standard paradigm unifying BL Lac objects with beamed radio galaxies. We propose that the majority of the radio-quiet objects may be lower-redshift (z < 2.2) analogs to high-redshift weak line quasars (i.e., active galactic nucleus with unusually anemic broad emission line regions). These would constitute the largest sample of such objects, being of similar size and complementary in redshift to the samples of high-redshift weak line quasars previously discovered by the SDSS. However, some fraction of the weak-featured radio-quiet objects may instead populate a rare and extreme radio-weak tail of the much larger radio-loud BL Lac population. Serendipitous discoveries of unusual white dwarfs, high-redshift weak line quasars, and broad absorption line quasars with extreme continuum dropoffs blueward of rest-frame 2800 A are also briefly described.
- OSTI ID:
- 21301376
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 139, Issue 2; Other Information: DOI: 10.1088/0004-6256/139/2/390; Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
Similar Records
X-RAY AND MULTIWAVELENGTH INSIGHTS INTO THE NATURE OF WEAK EMISSION-LINE QUASARS AT LOW REDSHIFT
Radio-loud Active Galaxies in the Northern {ital ROSAT} All-Sky Survey. III. New Spectroscopic Identifications from the RASS{endash}Green Bank BL Lacertae Survey