J/ApJS/209/10 UGSs. V. kernel approach (Massaro+, 2013)
Unveiling the nature of the unidentified gamma-ray sources.
V. Analysis of the radio candidates with the kernel density estimation.
Massaro F., D'Abrusco R., Paggi A., Masetti N., Giroletti M., Tosti G.,
Smith H.A., Funk S.
<Astrophys. J. Suppl. Ser., 209, 10 (2013)>
=2013ApJS..209...10M 2013ApJS..209...10M
ADC_Keywords: Gamma rays ; Radio sources ; Photometry, infrared ;
Photometry, VRI ; Cross identifications
Keywords: BL Lacertae objects: general - galaxies: active -
radiation mechanisms: non-thermal
Abstract:
Nearly one-third of the γ-ray sources detected by Fermi are
still unidentified, despite significant recent progress in this area.
However, all of the γ-ray extragalactic sources associated in
the second Fermi-LAT catalog have a radio counterpart. Motivated by
this observational evidence, we investigate all the radio sources of
the major radio surveys that lie within the positional uncertainty
region of the unidentified γ-ray sources (UGSs) at a 95% level
of confidence. First, we search for their infrared counterparts in the
all-sky survey performed by the Wide-field Infrared Survey Explorer
(WISE) and then we analyze their IR colors in comparison with those of
the known γ-ray blazars. We propose a new approach, on the basis
of a two-dimensional kernel density estimation technique in the single
[3.4]-[4.6]-[12]µm WISE color-color plot, replacing the constraint
imposed in our previous investigations on the detection at 22µm of
each potential IR counterpart of the UGSs with associated radio
emission. The main goal of this analysis is to find distant
γ-ray blazar candidates that, being too faint at 22µm, are
not detected by WISE and thus are not selected by our purely IR-based
methods. We find 55 UGSs that likely correspond to radio sources with
blazar-like IR signatures. An additional 11 UGSs that have blazar-like
IR colors have been found within the sample of sources found with deep
recent Australia Telescope Compact Array observations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 115 55 Unidentified gamma-ray sources in the Northern
and Southern samples
table3.dat 109 11 Unidentified gamma-ray sources in the Southern
Deep ATCA (SDA) sample
table4.dat 54 60 Optical magnitudes for the WISE counterparts
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See also:
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
I/284 : The USNO-B1.0 Catalog (Monet+ 2003)
J/ApJS/199/31 : Fermi LAT second source catalog (2FGL) (Nolan+, 2012)
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/ApJ/748/68 : WISE IR colors of gamma-ray blazars (D'Abrusco+, 2012)
J/ApJ/742/66 : New Fermi/LAT extragalactic sources (Teng+, 2011)
J/ApJ/741/30 : Radio/γ-ray correlation in AGN (Ackermann+, 2011)
J/ApJ/726/16 : γ-ray loud blazars (Linford+, 2011)
J/ApJ/718/587 : The Fermi-AT20G catalog (Mahony+, 2010)
J/ApJ/707/L56 : VLBI and bright Fermi/LAT sources (Kovalev, 2009)
J/ApJ/706/L7 : The Fermi LAT sky as seen by INTEGRAL/IBIS (Ubertini+, 2009)
J/ApJS/135/155 : Radio identification of 3EG EGRET sources (Mattox+, 2001)
Byte-by-byte Description of file: table2.dat table3.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Set Southern, Northern UGS sample ("SU", "NU") or
SDA sample ("SDA") (1)
5- 8 A4 --- --- [2FGL]
9- 21 A13 --- 2FGL 2FGL designation (JHHMM.m+DDMMc)
23- 41 A19 --- WISE WISE designation (JHHMMSS.ss+DDMMSS.s)
43- 61 A19 --- RName Radio name (NVSS, SUMSS or MRSS in table 2;
IAU name in table 3)
63- 66 F4.2 mag [3.4/4.6] [0.48/1.33] WISE [3.4]-[4.6] color index
68- 71 F4.2 mag e_[3.4/4.6] [0.03/0.2] [3.4/4.6] 1σ uncertainty
73- 76 F4.2 mag [4.6/12] [1.81/3.08] WISE [4.6]-[12] color index
78- 81 F4.2 mag e_[4.6/12] [0.03/0.5] [4.6/12] 1σ uncertainty
83- 86 F4.1 --- CL [9.5/97.2] Estimate level of confidence
derived from the KDE analysis (πkde)
88- 98 A11 --- Notes Note(s) (2)
100-104 F5.3 --- z [0.05/0.2]? Redshift from literature
106 A1 --- u_z [?] Uncertainty flag on z or unknown
108-115 A8 --- Comp Comparison with previous analyses (3)
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Note (1): The unidentified gamma-ray sources (UGSs) sample considered is
the one constituted by all the Fermi sources listed in the 2FGL with
no assigned counterpart at low energies and without any γ-ray
analysis flag listing 299 sources (Nolan et al. 2012, J/ApJS/199/31).
We further divided this sample in two subsamples: the northern UGS
(NU) sample comprising only sources with declination δ>-40°,
and the southern UGS (SU) sample comprising sources with declination
δ←30°. Last, we also considered the list of all the radio
sources recently found by Petrov et al. (2013MNRAS.432.1294P 2013MNRAS.432.1294P) using
deep ATCA observations for the UGSs in the southern hemisphere. This
sample is labeled as "southern deep ATCA" (SDA) sample.
See section 2 for further explanations.
Note (2): Notes as follows:
N = NVSS (Condon et al. 1998, Cat. VIII/65),
F = FIRST (Becker et al. 1995ApJ...450..559B 1995ApJ...450..559B; White et al. 1997;
Cat. VIII/90),
M = 2MASS (Skrutskie et al. 2006, Cat. VII/233),
s = SDSS dr9 (Adelman-McCarthy et al., 2012, Cat. V/139)
6 = 6dFG (Jones et al. 2004MNRAS.355..747J 2004MNRAS.355..747J, 2009, Cat. VII/259);
X = ROSAT (Voges et al. 1999, Cat. IX/10);
QSO = quasar,
BL = BL Lac;
v = variable in WISE bands (var_flag>5 in at least one band;
see Cutri et al. 2012, Cat. II/311, for additional details);
rv = variable in the radio bands at 1.4 GHz.
Note (3): Results of the comparison with previous analyses as follows:
1 = UGS analyzed in Massaro et al. (Pap. III, 2013, Cat. J/ApJS/207/4),
2 = UGS analyzed in Massaro et al. (Pap. II, 2013, Cat. J/ApJS/206/13),
3 = UGS analyzed in Paggi et al. (Pap. IV, 2013, Cat. J/ApJS/209/9).
Exclamation mark "!" indicates that the γ-ray blazar candidate
is the same IR source found in the previous investigation.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- WISE WISE designation (JHHMMSS.ss+DDMMSS.s)
21- 25 F5.2 mag B1mag [16.9/20.9]? USNO-B first B-band magnitude
27- 31 F5.2 mag R1mag [15.7/20.5]? USNO-B first R-band magnitude
33- 37 F5.2 mag B2mag [15.8/21.5]? USNO-B 2nd B-band magnitude
39- 43 F5.2 mag R2mag [15.5/21.3]? USNO-B 2nd R-band magnitude
45- 49 F5.2 mag Imag [15.5/19.3]? USNO-B I-band magnitude
51- 54 F4.2 arcsec Theta [0.04/2.7] Separation between WISE and
optical counterpart
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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 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
(End) Emmanuelle Perret [CDS] 20-Nov-2013