J/ApJ/481/95 J/ApJ/481/95 Radio identification of EGRET sources J R Mattox J Schachter L Molnar R C Hartman A R Patnaik Astrophys. J. 481 95 1997 1997ApJ...481...95M J/ApJS/101/259 : The second EGRET catalog (Thompson+ 1995) J/ApJS/107/227 : Supplement to Second EGRET Catalog (Thompson+ 1996) Fichtel et al., The first EGRET catalog 1994ApJ....94..551F Active gal. nuclei Cross identifications Gamma rays Radio sources galaxies: active gamma rays: observations quasars: general We present a method to assess the reliability of the identification of EGRET sources with extragalactic radio sources. We verify that EGRET is detecting the blazar class of active galactic nuclei (AGNs). However many published identifications are found to be questionable. We provide a table of 42 blazars that we expect to be robust identifications of EGRET sources. This includes one previously unidentified EGRET source, the lensed AGN PKS 1830-210, near the direction of the Galactic center. We provide the best available positions for 16 more radio sources that are also potential identifications for previously unidentified EGRET sources. All high Galactic latitude EGRET sources (|b|>3) that demonstrate significant variability can be identified with flat-spectrum radio sources. This suggests that EGRET is not detecting any type of AGN other than blazars. This identification method has been used to establish with 99.998% confidence that the peak gamma-ray flux of a blazar is correlated with its average 5GHz radio flux. An even better correlation is seen between gamma-ray flux and the 2.29GHz flux density measured with VLBI at the base of the radio jet. Also, using high-confidence identifications, we find that the radio sources identified with EGRET sources have greater correlated VLBI flux densities than the parent population of flat radio spectrum sources.

CGRO

2EG J2000 position name of the EGRET source --- n_2EG Note number=1 c: Verbunt et al. (1996A&A...311L...9V) identify this source with millisecond pulsar J0218+4232. f: Identification analysis not performed, radio survey source confused j: Not (completely) in GB or PMN survey. --- GLON Galactic longitude deg GLAT Galactic latitude deg n_GLAT Note on GLAT number=2 k: Using the position of Hunter et al. (1994ApJ...436..216H), which differs significantly from that of Thompson et al. (1995, Cat. <J/ApJS/101/259>) because of the use of a different Galactic diffuse model. m: Position estimate (and error ellipse a=35', b=20', {phi}=8{deg}) obtained from VP7.2 with E>1000Mev data, the analysis used for the identification of Thompson et al. (1995, Cat. <J/ApJS/101/259>) with 2022-077. --- VI Variability index number=3 Variability index, -logP, where P is the probability that the source is invariant based on a {chi}^2^ test of flux for all available viewing periods. A grater variability index corresponds to a higher probability that the source is variable --- ID EGRET catalogue identification (OtherName in EGRET catalog description) --- u_ID ?: lower confidence level, else high-confidence level --- RadioID Possible radio counterpart number=4 B1950 position are used for Green Bank sources and original J2000 position names are used for PMN sources --- n_RadioID Note number=5 a: Planetary nebula. b: Shows OVV behavior. d: A gamma-ray hare was reported by Lundgren et al. (1995IAUC.6258....1L) during the 1995 August 8-22 EGRET exposure. An optical spectrum (S. Lundgren 1997, private communication) found only a BL Lac-type continuum spectrum. g: This potential identification indicated by Mukherjee et al. (1995ApJ...445..189M) and Nolan et al. (1996ApJ...459..100N). i: Dingus et al. (1996ApJ...467..589D) note this possible identification. n: Fich (1993ApJS...86..475F) identified this extended radio source with an H II region. Therefore, it is unlikely to be the EGRET source. x: A {gamma}-flare of this source (NRAO 190) was observed by McGlynn et al., 1997ApJ...481..625M y: This potential identification noted by Thompson et al. (1996ApJS..107..227T , their table2) --- Names Other name of counterpart ---- n_Names Note number=6 e: Classified as a galaxy by Stickel & Kuhr 1994. However, S. Wagner (1996, private communication) finds optical variability on a ~ 1week timescale. h: This source is very likely to be the EGRET source because it is detected at TeV energies (Buckley et al., 1996ApJ...472L...9B). l: Classified as a galaxy by Stickel & Kuhr (1994, Cat. <J/A+AS/105/211>) w: 0219+428 = 3C 66 --- S5GHz Density flux at 4.85GHz mJy SI Radio spectral index --- r0 Characteristic angle between confusing sources that are at least as bright and flat as this radio source arcmin eta a priori probability {eta} = p(id) that the source is a {gamma}-ray source --- r Angle between the EGRET position estimate and the radio position arcmin r95 Radius of the 95% confidence contour in the direction of the radio source arcmin Contour Position contour at the radio position % LR Likelihood ratio indicating the strength of the indication for the determination --- p(id/r) a posteriori probability that the identification is correct --- James Marcout, Patricia Bauer CDS 1997Oct07 UNKNOWN UNKNOWN Prepared via OCR at CDS. J_ApJ_481_95.xml