J/A+A/694/A176 Multiwavelength ctp of Fermi gamma-ray sources (Ulgiati+, 2025)
Search for the multiwavelength counterparts to extragalactic unassociated
Fermi gamma-ray sources.
Ulgiati A., Paiano S., Pintore F., Russell T.D.., Sbarufatti B., Pinto C.,
Ambrosi E., D'Ai A., Cusumano G., Del Santo M.
<Astron. Astrophys. 694, A176 (2025)>
=2025A&A...694A.176U 2025A&A...694A.176U (SIMBAD/NED BibCode)
ADC_Keywords: Gamma rays ; Active gal. nuclei ; X-ray sources ; Radio sources
Keywords: galaxies: active - BL Lacertae objects: general -
quasars: supermassive black holes - gamma rays: galaxies -
radio line: galaxies - X-rays: galaxies
Abstract:
In this paper, we searched for multi-wavelength (X-ray, optical and
radio) counterparts to the unassociated gamma-ray sources
(UGS) of the Fermi 4FGL-DR4 catalog. The main goal is to identify new
blazars and/or new active galactic nuclei (AGNs) emitting at GeV
energies [like (Narrow Line) Seyfert-1 and radio galaxies].
We focus on sky regions observed by the Swift satellite that overlap
with the reported positions of the UGSs. Since our primary interest
lies in extra-galactic sources, we focus on UGSs located outside the
Galactic plane (|b|>10°). Due to the large number of sources
(about 1800 UGS), we developed a pipeline to automatised the search for
counterparts and significantly reduce the computational time for the
analysis. Our association process begins by identifying potential
X-ray counterparts for each UGS; if one is found, we further look for
corresponding radio and optical counterparts in the X-ray counterpart
error box, thus minimizing ambiguities.
Out of the 1284 UGSs in the 4FGL-DR4 catalog, 714 were observed at
east once by Swift/XRT. We detected, with a significance of
≥3σ, at least one X-ray source within the Fermi error box for
274 of these gamma-ray emitters. Among these, 193 UGSs have a single
potential X-ray counterpart (referred to as UGS1), while 81 have
multiple potential X-ray counterparts within the Fermi error box
(referred to as UGS2). Of the UGS2, 54 have two X-ray counterparts, 11
have three, and the remaining 16 have more than three. Each UGS1 has
an optical counterpart, and 113 also could be associated to a radio
counterpart. We performed a comparison of the possible counterpart
properties with those of the gamma-ray emitters identified by Fermi,
with the aim to assess the goodness of our associations.
Description:
Among the 714 UGSs with Swift/XRT observation, we find that 274
objects have at least one X-ray detection with a SNR ≥3 inside the
Fermi error box. For 193 of them, only one possible counterpart in the
Fermi error box was found (hereafter UGS1), while 81 have more than
one potential X-ray counterparts (hereafter UGS2). Details about the
Swift/XRT observations and all X-ray detections related to UGS1 and
UGS2 are in Tables 1 and 2, respectively. For each X-ray detection, we
performed X-ray spectral data analysis (see Sec. 5) and in Tables 3
and 4, we report the results of the XRT spectral fitting for UGS1 and
UGS2. The spectral analysis allows us to estimate the source absorbed
flux and to give a first, rough indication on the spectral slope.
Using the position of each X-ray detection, we the list the potential
optical and radio counterparts for UGS1 and UGS2 in Tables 5 and 6,
providing the optical coordinates, the magnitude in the g and r bands,
the optical and the radio flux.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 81 193 Information about the Swift/XRT detections within
the 3σ Fermi error box of UGS1 sample
(UGS with a single potential X-ray counterpart)
table2.dat 81 238 Information about the Swift/XRT detections within
the 3σ Fermi error box of UGS2 sample
(UGS with more than one potential X-ray
table3.dat 128 193 Results of the X-ray spectral fitting for UGS1
sample
table4.dat 128 238 Results of the X-ray spectral fitting for UGS2
sample
table5.dat 156 193 MWL counterparts of UGS1 sample
table6.dat 156 237 MWL counterparts of UGS2 sample
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See also:
IX/67 : Incremental Fermi LAT 4th source cat. (4FGL-DR3) (Fermi-LAT col., 2022)
Byte-by-byte Description of file: table1.dat table2.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- UGS 4FGL name
19- 22 F4.1 --- Siggamma gamma-ray detection, in sigma unit
24- 28 F5.1 ks Texp Swift exposure time
30- 52 A23 --- XRT Swift/XRT source name
54- 61 F8.4 deg RAdeg Right Ascension (J2000)
63- 70 F8.4 deg DEdeg Declination (J2000)
73- 75 F3.1 arcsec ePos Positional error
78- 81 F4.1 --- SigXRT X-ray detection significance, in sigma unit
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Byte-by-byte Description of file: table3.dat table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- UGS 4FGL name
19- 41 A23 --- XRT Swift/XRT source
43- 48 F6.2 10-3ct/s Crate Count rate
50 A1 --- --- [-]
51- 54 F4.2 10-3ct/s e_Crate Lower limit count rate
56- 60 F5.2 10-3ct/s E_Crate Upper limit count rate
62- 65 F4.1 10+20cm-2 nH Equivalent hydrogen column density
67- 70 F4.1 --- GAMMA Power-law index
72 A1 --- --- [-]
73- 75 F3.1 --- e_GAMMA ? Lower limit power-law index
77- 80 F4.1 --- E_GAMMA ? Upper limit power-law index
82- 87 F6.2 ph/keV/cm2/s Norm Normalization factor
88 A1 --- --- [-]
89- 93 F5.2 ph/keV/cm2/s e_Norm Lower limit normalization factor
94- 99 F6.2 ph/keV/cm2/s E_Norm Upper limit normalization factor
100-105 F6.1 mW/m2 Fabs Absorbed flux in the range 0.3-10keV
107 A1 --- --- [-]
108-112 F5.1 mW/m2 e_Fabs Lower limit absorbed flux in the
range 0.3-10keV
113-119 F7.1 mW/m2 E_Fabs Upper limit absorbed flux in the
range 0.3-10 keV
121-124 F4.2 --- chi2n ?=- chi2n value
126-128 I3 --- dof ? Relative degrees of freedom
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Byte-by-byte Description of file: table5.dat table6.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- UGS 4FGL name
20- 42 A23 --- XRT Swift/XRT source
43 A1 --- n_XRT [*] * for sources with proper motion
46- 76 A31 --- Rad Radio source
79-102 A24 --- Opt Optical source
104-111 F8.4 deg RAdeg ?=- Right Ascension of optical counterpart
(J2000)
113-120 F8.4 deg DEdeg ?=- Declination of optical counterpart
(J2000)
122-125 F4.1 mag gmag ?=- g magnitude of the optical source
127-130 F4.1 mag rmag ?=- r magnitude of the optical source
132-142 F11.1 mW/m2/Hz Fopt ?=- Optical density flux
144 A1 --- l_Frad limit flag on Frad
145-149 F5.1 mJy Frad ? Radio density flux
151 A1 --- l_R Limit flag n R
152-156 I5 --- R ?=- Radio-loudness parameter
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Acknowledgements:
Alberto Ulgiati, alberto.ulgiati(at)inaf.it
(End) Patricia Vannier [CDS] 30-Dec-2024