J/ApJ/914/42 Radio follow-up to 4FGL-DR2 unassociated sources (Bruzewski+, 2021)
Radio counterpart candidates to unassociated 4FGL-DR2 sources.
Bruzewski S., Schinzel F.K., Taylor G.B., Petrov L.
<Astrophys. J., 914, 42 (2021)>
=2021ApJ...914...42B 2021ApJ...914...42B
ADC_Keywords: Gamma rays; Radio continuum; Cross identifications
Keywords: High energy astrophysics ; Surveys ; Radio source catalogs ;
Spectral index ; Radio astronomy ; Active galaxies ;
Gamma-ray astronomy ; Radio continuum emission
Abstract:
For the duration of the Fermi Gamma-Ray Space Telescope's mission,
approximately one-third of the point sources detected have been noted
as "unassociated," meaning that they seem to have no known counterpart
at any other wavelength/frequency. This mysterious part of the
gamma-ray sky is perhaps one of the largest unknowns in current
astronomical pursuits and as such has been probed extensively by
various techniques at various frequencies. Radio frequencies have been
perhaps one of the most fruitful, producing a large fraction of the
identified and associated active galactic nuclei and pulsars noted in
each update of the point-source catalogs. Here we present a catalog of
7432 radio counterpart candidates for unassociated gamma-ray fields in
the Second Data Release of the Fourth Fermi Point Source Catalog
(4FGL-DR2). A description of the catalog and source types is provided
followed by a discussion that demonstrates how the results of this
work will aid new associations and identifications. As part of this
work, we also present a first catalog derived from "quicklook" images
of the Very Large Array Sky Survey.
Description:
This work combines our previous VLA observations targeting
unassociated Fermi/Large Area Telescope detected objects reported in
the Fermi Large Area Telescope second (2FGL) and third (3FGL) source
catalogs with new dedicated observations of newly discovered
unassociated γ-ray objects reported in the fourth source catalog
(4FGL), including data release 2 (4FGL-DR2).
The conducted VLA observations totaled 57 hours, including overheads,
and 2456 pointings, corresponding to a covered sky area of
approximately 43deg2 at 6.0GHz. The observations (projects S5272,
S7104 and 15A-466) between 2012 and 2015 were discussed in the context
of 2FGL and 3FGL by Schinzel+ (2015, J/ApJS/217/4 and
2017, J/ApJ/838/139). The two other projects are 18A-098 and SB072 (in
2019). See Section 2.1 for further details.
The Karl G. Jansky Very Large Array Sky Survey (VLASS; see
Lacy+ 2020PASP..132c5001L 2020PASP..132c5001L) is an ongoing effort to survey the entire
northern sky (δ>-40°) at 3.5GHz, separated into three epochs.
See the Appendix.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 350 7432 F357 catalog (Fermi γ-ray sources with 3GHz,
5GHZ and 7GHz radio frequencies)
table5.dat 201 2232726 *VLASS (Karl G. Jansky Very Large Array Sky Survey)
catalog; see the Appendix
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Note on table5.dat: We note that an alternative VLA sky survey quicklook
catalog has been made available while our work was in preparation
(Gordon+ 2020RNAAS...4..175G 2020RNAAS...4..175G). The major difference between this
catalog and the one we present here is that it did not apply
astrometric source position corrections as described in the Appendix.
We similarly did not correct for the apparent slight underestimation
of flux densities of the order of ∼10%.
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See also:
II/328 : AllWISE Data Release (Cutri+ 2013)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
IX/57 : The Chandra Source Catalog (CSC), Release 2.0 (Evans+, 2019)
VII/284 : A Catalogue of Galactic Supernova Remnants (Green, 2019)
IX/58 : 2SXPS Swift X-ray telescope point source catalogue (Evans+, 2020)
IX/67 : Incremental Fermi LAT 4th source cat. DR3 (Fermi-LAT col., 2022)
J/MNRAS/432/1294 : Fermi unassociated sources ATCA observations (Petrov+, 2013)
J/ApJS/217/4 : 2FGL sources observed between 5-9GHz (Schinzel+, 2015)
J/A+A/588/A103 : 2nd ROSAT all-sky survey (2RXS) source cat. (Boller+, 2016)
J/ApJ/820/8 : 3FGL sources statistical classif. (Saz Parkinson+, 2016)
J/A+A/598/A78 : The GMRT 150MHz all-sky radio survey (Intema+, 2017)
J/ApJ/838/139 : 3FGL unassociated sources with radio obs. (Schinzel+, 2017)
J/ApJS/247/33 : Fermi LAT fourth source catalog (4FGL) (Abdollahi+, 2020)
J/ApJ/892/105 : 4th cat. of Fermi LAT-detected AGNs (4LAC) (Ajello+, 2020)
J/ApJ/904/49 : 4FGLJ0407.7-5702 opt. spectroscopy & LC (Miller+, 2020)
J/MNRAS/501/1116 : GAIA pulsars and where to find them (Antoniadis, 2021)
http://library.nrao.edu/vlass.shtml : VLASS memos
http://www.cv.nrao.edu/F357/ : F357 NRAO data
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [F357]
6- 24 A19 --- Name F357 generated source name
(JHHMMSS.ss+DDMMSS.s)
26- 33 F8.4 deg RAdeg Right ascension (J2000) (RA)
35- 43 E9.4 deg e_RAdeg [2.7e-7/0.0003] RAdeg uncertainty (RAErr)
45- 53 F9.5 deg DEdeg Declination (J2000) (Dec)
55- 63 E9.4 deg e_DEdeg [1.9e-7/0.0003] DEdeg uncertainty (DecErr)
65- 72 F8.3 mJy/beam Fpk3GHz [0.5/1280]? Peak flux density of VLASS
(3.0GHz) source (PeakFlux_VLASS)
74- 79 F6.4 mJy/beam e_Fpk3GHz [0.07/4]? Fpk3GHz uncertainty
(PeakFluxErr_VLASS)
81- 88 F8.3 mJy S3GHz [0.3/2110]? Integrated flux density of
VLASS (3.0 GHz) source (IntFlux_VLASS)
90- 95 F6.3 mJy e_S3GHz [0.1/65]? S3GHz uncertainty
(IntFluxErr_VLASS)
97- 102 F6.3 mJy/beam Fpk5GHz [0.18/47.1]? Peak flux density of D5GHZ
(5.0GHz) source (PeakFlux_D5GHZ)
104- 109 F6.4 mJy/beam e_Fpk5GHz [0.01/1.1]? Fpk5GHz uncertainty
(PeakFluxErr_D5GHZ)
111- 116 F6.3 mJy S5GHz [0.14/50.1]? Integrated flux density of
D5GHZ (5.0 GHz) source (IntFlux_D5GHZ)
118- 123 F6.4 mJy e_S5GHz [0.02/2.2]? 5GHz uncertainty
(IntFluxErr_D5GHZ)
125 I1 --- Lim5GHz [0/1] Given flux values may be treated as
lower limits (IsLowerLim_D5GHZ)
127- 132 F6.3 mJy/beam Fpk7GHz [0.16/62]? Peak flux density of D7GHZ (7.0
GHz) source (PeakFlux_D7GHZ)
134- 139 F6.4 mJy/beam e_Fpk7GHz [0.03/1.1]? Fpk7GHz uncertainty
(PeakFluxErr_D7GHZ)
141- 146 F6.3 mJy S7GHZ [0.14/57]? Integrated flux density of
D7GHZ (7.0 GHz) source (IntFlux_D7GHZ)
148- 153 F6.4 mJy e_S7GHZ [0.04/2]? S7GHZ uncertainty
(IntFluxErr_D7GHZ)
155 I1 --- Lim7GHZ [0/1] Given flux values may be treated as
lower limits (IsLowerLim_D7GHZ)
157- 165 F9.5 --- alpha [-11.3/3.1]? Calculated of fit spectral
index
167- 173 F7.5 --- e_alpha [0.0008/2.5]? alpha uncertainty (AlphaErr)
175- 178 A4 --- --- [4FGL]
180- 192 A13 --- 4FGL Name of encompassing Fermi source
(JHHMM.m+DDMMa) (FermiName)
194- 212 I19 --- Gaia ? Gaia DR2 cross-match (1" cutoff)
(MatchGAIA)
214- 220 F7.5 arcsec SepGaia [0.002/1]? Distance to Gaia source
(DistGAIA)
222- 240 A19 --- WISEA AllWISE cross-match (1" cutoff)
(JHHMMSS.ss+DDMMSS.s) (MatchAllWISE)
242- 248 F7.5 arcsec SepWISEA [0.005/1]? Distance to AllWISE source
(DistAllWISE)
250- 253 A4 --- --- [2RXS]
255- 270 A16 --- 2RXS 2RXS cross-match (11" cutoff)
(JHHMMSS.s+DDMMSS) (Match2RXS)
272- 278 F7.5 arcsec Sep2RXS [0/10]? Distance to 2RXS source (Dist2RXS)
280- 284 A5 --- --- [2SXPS]
286- 301 A16 --- 2SXPS 2SXPS cross-match (13" cutoff)
(JHHMMSS.s+DDMMSS) (Match2SXPS)
303- 310 F8.5 arcsec Sep2SXPS [0.1/10.2]? Distance to 2SXPS source
(Dist2SXPS)
312- 315 A4 --- --- [2CXO]
317- 332 A16 --- 2CXO CSCR2 (IX/57) cross-match (9" cutoff)
(JHHMMSS.s+DDMMSS) (MatchCSCR2)
334- 340 F7.5 arcsec SepCSCR2 [0.08/7.2]? Distance to CSCR2 source
(DistCSCR2)
342 I1 --- Res [0/1] Indicates resolved graph structure
(IsResolved)
344- 346 A3 --- Type Type codes (PyBDSF) for VLASS, D5GHZ, and
D7GHZ (TypeCode) (1)
348- 350 A3 --- Class Spectral classification of source (2)
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Note (1): This qualitatively describes the morphology of the source at
each frequency. The relevant "S-Codes" generated by PyBDSF
(Mohan & Rafferty 2015ascl.soft02007M), combined as a single string
with three characters ("S", "C", or "M" from PyBDSF, or "-" when no
source was identified at that frequency). For example, a TypeCode of
"SM-" represents a source with unresolved emission at 3GHz (singular),
some type of resolved emission at 5GHz, and a nondetection at 7GHz.
The exact nature of these S-Codes is related to the Gaussian fitting
process used during source extraction, and it is recommended those
interested view the PyBDSF documentation for full descriptions.
See Section 3 and 4.4.
Note (2): Class as follows:
EXT = Extended source; see Section 4.4 (178 occurrences)
STP = Steep-spectrum source; see Section 4.1 (80 occurrences)
PCL = Peculiar source; see section 4.3 (65 occurrences)
FLT = Flat-spectrum source; see Section 4.2 (79 occurrences)
IFR = "Inferred Steep Spectrum"; see Section 4.1 (11 occurrences)
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [V1Q]
4- 23 A20 --- Name VLASS Epoch 1 name of the source
(JHHMMSS.ss+DDMMSS.s)
25- 35 F11.7 deg RAdeg Right ascension (J2000) (RA)
37- 48 E12.7 deg e_RAdeg [3e-7/0.06]? RAdeg uncertainty (RAErr)
50- 60 F11.7 deg DEdeg [-40.02/89.83] Declination (J2000) (Dec)
62- 73 E12.7 deg e_DEdeg [1.2e-6/0.9]? DEdeg uncertainty (DecErr)
75- 86 E12.7 Jy Flux [3.34e-8/9.31] Integrated flux (IntFlux)
88- 99 E12.7 Jy e_Flux [5.83e-9/0.24] Flux uncertainty (IntFluxErr)
101- 112 E12.7 Jy/beam Fpk [0/3.92] Peak flux of VLASS source (PeakFlux)
114- 125 E12.7 Jy/beam e_Fpk [2.8e-8/0.04] Fpk uncertainty (PeakFluxErr)
127 A1 --- Type [SCM] Source morphology code from PyBDSF
(Mohan & Rafferty 2015ascl.soft02007M)
(TypeCode)
129- 172 A44 --- Pointing Pointing/image information for source
174- 183 A10 "Y/M/D" Obs.date Date of observation
184 A1 --- --- [T]
185- 186 I2 h Obs.h Hour of observation
187 A1 --- --- [:]
188- 189 I2 min Obs.m Minute of observation
190 A1 --- --- [:]
191- 199 F9.6 s Obs.s Second of observation
201 I1 --- Flag [0/2] Flag (0=Alone,1=Useful,2=Redundant)
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 06-Dec-2022