J/ApJS/206/13 Blazars with γ-ray counterparts. II. (Massaro+, 2013)
Unveiling the nature of unidentified gamma-ray sources.
II. Radio, infrared, and optical counterparts of the gamma-ray blazar
candidates.
Massaro F., D'Abrusco R., Paggi A., Masetti N., Giroletti M., Tosti G.,
Smith H.A., Funk S.
<Astrophys. J. Suppl. Ser., 206, 13 (2013)>
=2013ApJS..206...13M 2013ApJS..206...13M (SIMBAD/NED BibCode)
ADC_Keywords: BL Lac objects ; Photometry, infrared ; QSOs ; Gamma rays ;
Cross identifications ; Active gal. nuclei ; Redshifts
Keywords: BL Lacertae objects: general - galaxies: active -
radiation mechanisms: non-thermal
Abstract:
A significant fraction (∼30%) of the high-energy gamma-ray sources
listed in the second Fermi Large Area Telescope catalog (2FGL) are
still of unknown origin, being not yet associated with counterparts at
low energies. We recently developed a new association method to
identify if there is a γ-ray blazar candidate within the
positional uncertainty region of a generic 2FGL source. This method is
entirely based on the discovery that blazars have distinct infrared
colors with respect to other extragalactic sources found, thanks to
the Wide-field Infrared Survey Explorer (WISE) all-sky observations.
Several improvements have also been performed to increase the
efficiency of our method in recognizing γ-ray blazar candidates.
In this paper we applied our method to two different samples, the
first constituted by unidentified γ-ray sources (UGSs), and the
second by active galaxies of uncertain type, both listed in the 2FGL.
We present a catalog of IR counterparts for ∼20% of the UGSs
investigated. Then, we also compare our results for the associated
sources with those present in the literature. In addition, we
illustrate the extensive archival research carried out to identify the
radio, infrared, optical, and X-ray counterparts of the WISE-selected,
γ-ray blazar candidates. Finally, we discuss the future
developments of our method based on ground-based follow-up
observations.
Description:
Our primary sample of unidentified γ-ray sources (UGSs) consists
of all the sources for which no counterpart was assigned at low
energies in the 2FGL or in the 2LAC (Nolan et al. 2012, Cat.
J/ApJS/199/31; Ackermann et al. 2011, Cat. J/ApJ/743/171,
respectively), for a total of 590 γ-ray objects. We considered
and analyzed independently two subsamples of UGSs, distinguishing the
299 Fermi sources without any γ-ray analysis flags from the
other 291 objects that have a warning in their γ-ray detection.
The complete description of our association procedure together with
the estimates of its efficiency and its completeness can be found in
D'Abrusco et al. (Paper I, 2013, Cat. J/ApJS/206,12).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 122 75 Unidentified γ-ray sources (UGSs) without
γ-ray analysis flags
table4.dat 122 71 Unidentified γ-ray sources (UGSs) with
γ-ray analysis flags
table5.dat 124 78 Active galaxies of uncertain type (AGUs) (00-12hr)
table6.dat 124 47 Active galaxies of uncertain type (AGUs) (12-24hr)
table7.dat 16 114 UGSs without associated γ-ray blazar
candidates
table8.dat 63 69 Optical magnitudes of the USNO B1 catalog for
the UGSs without γ-ray analysis flags
table9.dat 63 32 Optical magnitudes of the USNO B1 catalog for
the UGSs with γ-ray analysis flags
table10.dat 63 73 Optical magnitudes of the USNO B1 catalog for
the AGUs (00hr-12hr)
table11.dat 63 40 Optical magnitudes of the USNO B1 catalog for
the AGUs (12hr-24hr)
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See also:
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
I/284 : The USNO-B1.0 Catalog (Monet+ 2003)
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
J/A+A/495/691 : Multifrequency catalog of blazars, Roma-BZCAT (Massaro+, 2009)
J/ApJS/206/13 : New gamma-ray blazar candidates in the 3PBC (Maselli+, 2013)
J/ApJS/206/12 : Paper I. (D'Abrusco+, 2013)
J/ApJS/199/31 : Fermi LAT second source catalog (2FGL) (Nolan+, 2012)
J/ApJ/743/171 : The 2LAC catalog (Ackermann+, 2011)
J/ApJ/718/587 : The Fermi-AT20G catalog (Mahony+, 2010)
J/ApJS/175/97 : CGRaBS: survey of γ-ray blazar candidates (Healey+, 2008)
J/ApJ/609/564 : Blazar counterparts for 3EG sources (Sowards-Emmerd+, 2004)
J/ApJ/537/101 : Optical Study for blazars. I. (Fan+, 2000)
J/A+AS/128/315 : BVRI photometry of blazars (Jia Guibin+ 1998)
Byte-by-byte Description of file: table3.dat table4.dat table5.dat table6.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- 2FGL 2FGL name (JHHMM.m+DDMMc)
15- 33 A19 --- WISE WISE name (JHHMMSS.ss+DDMMSS.s)
35- 59 A25 --- OName Other name (Roma-BZCAT, NVSS, SDSS, AT20G,
or NED)
61- 64 F4.2 mag [3.4/4.6] WISE 3.4-4.6 um color index corrected for
Galactic extinction
66- 69 F4.2 mag e_[3.4/4.6] 3.4-4.6um color index 1σ uncertainty
71- 74 F4.2 mag [4.6/12] WISE 4.6-12 um color index corrected for
Galactic extinction
76- 79 F4.2 mag e_[4.6/12] 4.6-12um color index 1σ uncertainty
81- 84 F4.2 mag [12/22] WISE 12-22 um color index corrected for
Galactic extinction
86- 89 F4.2 mag e_[12/22] 12-22um color index 1σ uncertainty
91- 93 A3 --- Type Object type (BZB=BL Lac object,
BZQ=Flat Spectrum Radio Quasar)
95 A1 --- Cl [ABC] Class of the candidate blazar
according to our method (1)
97-114 A18 --- Note Notes about associations and classes (2)
116-121 F6.4 --- z ? Redshift
122 A1 --- u_z [?] Uncertainty flag on z (3)
124 A1 --- Flag [y/n] Reassociation flag (tables 5,6) (4)
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Note (1): We define three classes (i.e., A = most probable candidates,
B, and C) of reliability for the γ-ray blazar candidates. A
generic source is assigned to class A, class B, or class C when its
score is higher than the threshold values defined by the 90th, 60th,
and 30th percentiles of the score distributions of all the γ-ray
blazars that constitute the locus, respectively. See section 3.
Note (2): Note as follows:
N = NVSS (Cat. VIII/65),
F = FIRST (Cat. VIII/90),
S = SUMSS (Cat. VIII/81),
A = AT20G (Cat. J/MNRAS/402/2403),
M = 2MASS (Cat. II/246),
s = SDSS dr9 (Cat. V/139),
6 = 6dFGS (Cat. VII/259),
x = XMM-Newton (B/xmm) or Chandra (B/chandra),
X = ROSAT (Cat. IX/10);
QSO = quasar,
Sy = Seyfert,
LNR = LINER,
BL = BL Lac objects,
XB = X-ray-bright optically inactive galaxies,
v = variability in WISE (var_flag >5 in at least one band)
Note (3): If redshift blank "?" = unknown else "?" = uncertain.
Note (4): Reassociation flag: "y" if the association of our method corresponds
to the one provided in the 2FGL; "n" otherwise.
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Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [2FGL]
5- 16 A12 --- 2FGL 2FGL name (JHHMM.m+DDMM)
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Byte-by-byte Description of file: table8.dat table9.dat table10.dat table11.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- 2FGL 2FGL name (JHHMM.m+DDMMc)
15- 33 A19 --- WISE WISE name (JHHMMSS.ss+DDMMSS.s)
35- 39 F5.2 mag B1mag ? USNO-B1 B1 band magnitude
41- 45 F5.2 mag R1mag ? USNO-B1 R1 band magnitude
47- 51 F5.2 mag B2mag ? USNO-B1 B2 band magnitude
53- 57 F5.2 mag R2mag ? USNO-B1 R2 band magnitude
59- 63 F5.2 mag Imag ? USNO-B1 I band magnitude
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History:
From electronic version of the journal
References:
D'Abrusco et al. Paper I. 2013ApJS..206...12D 2013ApJS..206...12D Cat. J/ApJS/206/12
Massaro et al. Paper III. 2013ApJS..207....4M 2013ApJS..207....4M Cat. J/ApJS/207/4
(End) Emmanuelle Perret [CDS] 26-Jun-2013