J/ApJ/752/61 Blazars in unidentified γ-ray sources (Massaro+, 2012)
Unidentified γ-ray sources: hunting γ-ray blazars.
Massaro F., D'Abrusco R., Tosti G., Ajello M., Paggi A., Gasparrini D.
<Astrophys. J., 752, 61 (2012)>
=2012ApJ...752...61M 2012ApJ...752...61M
ADC_Keywords: Gamma rays ; Photometry, infrared ; QSOs ; BL Lac objects
Keywords: BL Lacertae objects: general; galaxies: active; gamma rays: galaxies;
radiation mechanisms: non-thermal
Abstract:
One of the main scientific objectives of the ongoing Fermi mission is
unveiling the nature of unidentified γ-ray sources (UGSs).
Despite the major improvements of Fermi in the localization of
γ-ray sources with respect to the past γ-ray missions,
about one-third of the Fermi-detected objects are still not associated
with low-energy counterparts. Recently, using the Wide-field Infrared
Survey Explorer survey, we discovered that blazars, the rarest class
of active galactic nuclei and the largest population of γ-ray
sources, can be recognized and separated from other extragalactic
sources on the basis of their infrared (IR) colors. Based on this
result, we designed an association method for the γ-ray sources
to recognize if there is a blazar candidate within the positional
uncertainty region of a generic γ-ray source. With this new IR
diagnostic tool, we searched for γ-ray blazar candidates
associated with the UGS sample of the second Fermi γ-ray LAT
catalog (2FGL). We found that our method associates at least one
γ-ray blazar candidate as a counterpart to each of 156 out of
313 UGSs analyzed. These new low-energy candidates have the same IR
properties as the blazars associated with γ-ray sources in the
2FGL catalog.
Description:
To build our association procedure, we considered a sample of blazars
selected from the combination of ROMA-BZCAT (Massaro et al. 2009, Cat.
J/A+A/495/691; 2010arXiv1006.0922M 2010arXiv1006.0922M) and 2FGL (Nolan et al. 2012, Cat.
J/ApJS/199/31), as described and used in Paper II (Cat. J/ApJ/748/68)
and used in Paper III (2012ApJ...750..138M 2012ApJ...750..138M) to parameterize the WGS
(WISE γ-ray blazar Strip (Paper II, Cat. J/ApJ/748/68)), denoted
by the 2FB sample. It contains 284 γ-ray blazars (135 BZBs and
149 BZQs) that have optical and radio counterparts as reported in the
ROMA-BZCAT and also have a WISE counterpart within 2.4" radius (see
Papers I (2011ApJ...740L..48M 2011ApJ...740L..48M) and III).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 95 301 Unidentified gamma-ray sources (UGS) associations
for 156 2FGL
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See also:
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
J/ApJS/209/10 : UGSs. V. kernel approach (Massaro+, 2013)
J/ApJS/209/9 : Unidentified gamma-ray sources. IV. X-ray (Paggi+, 2013)
J/ApJS/207/4 : Unidentified γ-ray sources. III. Radio (Massaro+, 2013)
J/ApJS/206/17 : New gamma-ray blazar candidates in the 3PBC (Maselli+, 2013)
J/ApJS/206/13 : Blazars with γ-ray counterparts. II. (Massaro+, 2013)
J/ApJS/206/12 : Blazars with γ-ray counterparts. I. (D'Abrusco+, 2013)
J/other/RAA/13.259 : gamma-ray Doppler factor for Fermi blazars (Fan+, 2013)
J/ApJ/748/68 : WISE IR colors of gamma-ray blazars (D'Abrusco+, 2012)
J/ApJS/199/31 : Fermi LAT second source catalog (2FGL) (Nolan+, 2012)
J/A+A/541/A160 : X & gamma-ray observations of selected blazars (Giommi+, 2012)
J/ApJ/743/171 : The 2LAC catalog (Ackermann+, 2011)
J/ApJ/732/116 : IR spectra of γ-ray bright blazars (Malmrose+, 2011)
J/ApJ/722/520 : Gamma-ray light curves of Fermi blazars (Abdo+, 2010)
J/ApJ/709/1407 : SED of the Fermi blazars (Li+, 2010)
J/ApJ/700/597 : FERMI LAT detected blazars (Abdo+, 2009)
J/A+A/495/691 : Multifrequency cat. of blazars, Roma-BZCAT (Massaro+, 2009)
J/ApJ/626/95 : Gamma-ray blazar candidates (Sowards-Emmerd+, 2005)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [2FGL]
6- 17 A12 --- 2FGL Unidentified γ-ray source (UGS) identifier
(JHHMM.m+DDMM)
19- 37 A19 --- WISE The γ-ray blazar candidate identifier
(JHHMMSS.ss+DDMMSS.s)
39- 45 F7.2 arcsec Sep [13/2081] Distance of WISE candidate from UGS
47- 50 F4.2 mag c1-2 [0.4/1.4] WISE (3.4-4.6) micron band color index
52- 55 F4.2 mag e_c1-2 The 1σ error in c1-2
57- 60 F4.2 mag c2-3 [1.7/3.5] WISE (4.6-12) micron band color index
62- 65 F4.2 mag e_c2-3 The 1σ error in c2-3
67- 70 F4.2 mag c3-4 [1.2/3] WISE (12-22) micron band color index
72- 75 F4.2 mag e_c3-4 The 1σ error in c3-4
77- 80 F4.2 --- sb The sb parameter (1)
82- 85 F4.2 --- sq The sq parameter (1)
87 A1 --- Cl [A-C] WISE source classification (2)
89- 95 A7 --- pi Association confidence π (3)
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Note (1): The s parameter represents an estimate of the distance, in the IR
colors' parameter space and weighted with the errors on each axes,
between the WGS (WISE gamma-ray strip; see D'Abrusco et al. 2012,
Paper II, Cat. J/ApJ/748/68) and a generic WISE source, that could
potentially belong to it; this s parameter is different from zero
only in the case in which all color error bars of a WISE source are
consistent with the WGS. To test if a generic WISE source has IR
colors consistent with the BZBs (BL Lacs) or with the BZQs (flat
spectrum radio quasars) subregion of the WGS, the total strip
parameters are referred to as sb and sq, respectively. See
section 2.4 and 2.5 of Paper III (Massaro et al. 2012ApJ...750..138M 2012ApJ...750..138M)
for further explanations.
Note (2): Classification as follows:
A = WISE sources with 0.24<sb<1.00 and 0.38<sq<1.00; these objects
are the most probable blazar counterparts of the UGSs.
B = WISE sources with 0.24<sb<1.00 or 0.38<sq<1.00;
C = WISE sources with 0.10<sb<0.24 and 0.14<sq<0.38.
See section 3.2 for further explanations.
Note (3): That here is the ratio between the number of WISE sources of the same
class and the total number of WISE sources that lie in the region of
comparison (see Section 3.3).
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History:
From electronic version of the journal
References:
Blazar identifications:
Massaro et al. Paper I. 2011ApJ...740L..48M 2011ApJ...740L..48M
D'Abrusco et al. Paper II. 2012ApJ...748...68D 2012ApJ...748...68D Cat. J/ApJ/748/68
Massaro et al. Paper III. 2012ApJ...750..138M 2012ApJ...750..138M
UGSs series:
D'Abrusco et al. Paper I. 2013ApJS..206...12D 2013ApJS..206...12D Cat. J/ApJS/206/12
Massaro et al. Paper II. 2013ApJS..206...13M 2013ApJS..206...13M Cat. J/ApJS/206/13
Massaro et al. Paper III. 2013ApJS..207....4M 2013ApJS..207....4M Cat. J/ApJS/207/4
Paggi et al. Paper IV. 2013ApJS..209....9P 2013ApJS..209....9P Cat. J/ApJS/209/9
Massaro et al. Paper V. 2013ApJS..209...10M 2013ApJS..209...10M Cat. J/ApJS/209/10
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 04-Feb-2014