J/ApJ/481/95 Radio identification of EGRET sources (Mattox+ 1997)
The identification of EGRET sources with flat-spectrum radio sources.
Mattox J.R., Schachter J., Molnar L., Hartman R.C., Patnaik A.R.
<Astrophys. J. 481, 95 (1997)>
=1997ApJ...481...95M 1997ApJ...481...95M (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Radio sources ; Gamma rays ;
Cross identifications
Mission_Name: CGRO
Keywords: galaxies: active - gamma rays: observations - quasars: general
Abstract:
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.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 141 154 Potential radio identifications of sources in
the second EGRET catalog
table2.dat 139 60 Potential radio identifications of EGRET sources
in the supplement to the second EGRET catalog
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See also:
J/ApJS/101/259 : The second EGRET catalog (Thompson+ 1995)
J/ApJS/107/227 : Supplement to Second EGRET Catalog (Thompson+ 1996)
Byte-by-byte Description of file: table1.dat table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- 2EG J2000 position name of the EGRET source
11 A1 --- n_2EG [cfj] Note (1)
13- 18 F6.2 deg GLON Galactic longitude
20- 25 F6.2 deg GLAT Galactic latitude
26 A1 --- n_GLAT [km] Note on GLAT (2)
27- 31 F5.2 --- VI ? Variability index (3)
33- 40 A8 --- ID ? EGRET catalogue identification
(OtherName in EGRET catalog description)
41 A1 --- u_ID [?] ?: lower confidence level,
else high-confidence level
43- 54 A12 --- RadioID Possible radio counterpart (4)
55 A1 --- n_RadioID [abdginxy] Note (5)
57- 68 A12 ---- Names Other name of counterpart
69 A1 --- n_Names [hlew] Note (6)
70- 74 I5 mJy S5GHz ? Density flux at 4.85GHz
76- 79 F4.1 --- SI ? Radio spectral index
81- 86 F6.1 arcmin r0 ? Characteristic angle between confusing
sources that are at least as bright and
flat as this radio source
88- 95 F8.6 --- eta ? a priori probability η = p(id) that the
source is a γ-ray source
97-101 F5.1 arcmin r ? Angle between the EGRET position estimate
and the radio position
103-107 F5.1 arcmin r95 ? Radius of the 95% confidence contour in
the direction of the radio source
109-115 F7.3 % Contour ? Position contour at the radio position
117-131 E15.3 --- LR ? Likelihood ratio indicating the strength of
the indication for the determination
133-140 E8.3 --- p(id/r) ? a posteriori probability that the
identification is correct
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Note (1): c: Verbunt et al. (1996A&A...311L...9V 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.
Note (2): k: Using the position of Hunter et al. (1994ApJ...436..216H 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', φ=8°)
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.
Note (3): Variability index, -logP, where P is the probability that the source
is invariant based on a χ2 test of flux for all available
viewing periods. A grater variability index corresponds to a higher
probability that the source is variable
Note (4): B1950 position are used for Green Bank sources and original
J2000 position names are used for PMN sources
Note (5): a: Planetary nebula.
b: Shows OVV behavior.
d: A gamma-ray hare was reported by Lundgren et al.
(1995IAUC.6258....1L 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 1995ApJ...445..189M) and Nolan et al. (1996ApJ...459..100N 1996ApJ...459..100N).
i: Dingus et al. (1996ApJ...467..589D 1996ApJ...467..589D) note this possible
identification.
n: Fich (1993ApJS...86..475F 1993ApJS...86..475F) identified this extended radio source
with an H II region. Therefore, it is unlikely to be the EGRET
source.
x: A γ-flare of this source (NRAO 190) was observed by
McGlynn et al., 1997ApJ...481..625M 1997ApJ...481..625M
y: This potential identification noted by Thompson et al.
(1996ApJS..107..227T 1996ApJS..107..227T , their table2)
Note (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 1996ApJ...472L...9B).
l: Classified as a galaxy by Stickel & Kuhr
(1994, Cat. J/A+AS/105/211)
w: 0219+428 = 3C 66
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History: Prepared via OCR at CDS.
References:
Fichtel et al., The first EGRET catalog 1994ApJ....94..551F 1994ApJ....94..551F
(End) James Marcout, Patricia Bauer [CDS] 07-Oct-1997