THE WISE GAMMA-RAY STRIP PARAMETERIZATION: THE NATURE OF THE GAMMA-RAY ACTIVE GALACTIC NUCLEI OF UNCERTAIN TYPE
- SLAC National Laboratory and Kavli Institute for Particle Astrophysics and Cosmology, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)
- Harvard-Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)
- Dipartimento di Fisica, Universita degli Studi di Perugia, 06123 Perugia (Italy)
- ASI Science Data Center, ESRIN, I-00044 Frascati (Italy)
Despite the large number of discoveries made recently by Fermi, the origins of the so-called unidentified {gamma}-ray sources remain unknown. The large number of these sources suggests that there could be a population among them that significantly contributes to the isotropic gamma-ray background and it is therefore crucial to understand their nature. The first step toward a complete comprehension of the unidentified {gamma}-ray source population is to identify those that can be associated with blazars, the most numerous class of extragalactic sources in the {gamma}-ray sky. Recently, we discovered that blazars can be recognized and separated from other extragalactic sources using the infrared (IR) WISE satellite colors. The blazar population delineates a remarkable and distinctive region of the IR color-color space, the WISE blazar strip. In particular, the subregion delineated by the {gamma}-ray emitting blazars is even narrower and we named it the WISE Gamma-ray Strip (WGS). In this paper, we parameterize the WGS on the basis of a single parameter s that we then use to determine if {gamma}-ray active galactic nuclei of the uncertain type (AGUs) detected by Fermi are consistent with the WGS and can be considered blazar candidates. We find that 54 AGUs out of a set of 60 analyzed have IR colors consistent with the WGS; only 6 AGUs are outliers. This result implies that a very high percentage (i.e., in this sample about 90%) of the AGUs detected by Fermi are indeed blazar candidates.
- OSTI ID:
- 22034461
- Journal Information:
- Astrophysical Journal, Vol. 750, 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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