J/ApJ/905/173 Galactic center compact radio sources from JVLA obs. (Zhao+, 2020)
A population of compact radio variables and transients in the radio-bright zone
at the Galactic Center observed with the Jansky Very Large Array.
Zhao J.-H., Morris M.R., Goss W.M.
<Astrophys. J., 905, 173 (2020)>
=2020ApJ...905..173Z 2020ApJ...905..173Z
ADC_Keywords: Radio sources; Galactic center; X-ray sources
Keywords: Galactic center ; Black holes ; Radio pulsars ;
Millisecond pulsars ; Neutron stars ; White dwarf stars ;
Discrete radio sources ; Radio transient sources ;
Interstellar medium ; Radio continuum emission ; Radio interferometry
Abstract:
Using Jansky Very Large Array data obtained from high-resolution
observations at 5.5GHz at multiple epochs in 2014 and 2019, we have
detected a population of radio variables and transients in the
radio-bright zone at the Galactic center. With observations covering a
sky area of 180arcmin2 at an angular resolution of 0.4, we report
new detections of 110 Galactic center compact radio (GCCR) sources
with a size of <1". The flux densities of GCCR sources exceed
70µJy, with at least 10σ significance. Among these sources,
82 are variable or transient and 28 are nonvariable. About 10% of them
are expected to be extragalactic background sources. We discuss the
possible astrophysical nature of the detected sources. As compared to
the Galactic disk (GD) population of normal pulsars (NPs) and
millisecond pulsars (MSPs), a majority (80%) of the GCCR sources
appear to fall within the high flux density tail of the pulsar
distribution, as extrapolated from a sample of NPs in the GD. However,
MSPs extrapolated from the GD population are too weak to have
contributed significantly to the GCCR population that has been
detected. We also cross-correlated the GCCR sources with X-ray sources
in Chandra X-ray catalogs and found that 42 GCCR sources have
candidate X-ray counterparts. Most of the GCCR sources having X-ray
counterparts are likely to be associated with unresolved or slightly
resolved radio jets launched from X-ray binaries with a compact
object, either a black hole or a neutron star.
Description:
New Jansky Very Large Array (JVLA) observations in the A array were
carried out on 2019-September-8 at 5.5GHz (PID: 19A-289). Along with
two previous A-array observations at epochs 2014-May-26 (PID: 14A-346)
and 2014-May-17 (PID: 14A-346), we have a total of three A-array data
sets at 5.5GHz. These observations were all carried out with an
identical VLA standard correlator setup for wideband continuum
covering 2GHz bandwidth, with a single field pointing at a position
near the geometrical center of the Sgr A East radio shell.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 121 110 A catalog of compact radio sources at 5.5GHz
notes.dat 120 74 Source sizes (from Note in Table 2)
table3.dat 51 42 Identifications of candidate X-ray counterparts
of Galactic center compact radio (GCCR) sources
(See Section 4)
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
B/psr : ATNF Pulsar Catalogue (Manchester+, 2005)
VII/156 : Catalog of 558 Pulsars (Taylor+ 1993)
VII/189 : Catalog of Pulsars (Taylor+ 1995)
J/MNRAS/273/411 : Multifrequency fluxes of 280 pulsars (Lorimer+ 1995)
J/ApJ/589/225 : Chandra X-ray sources toward Galactic Center (Muno+, 2003)
J/ApJS/165/173 : Chandra sources in Galaxy central 150pc (Muno+, 2006)
J/ApJS/181/110 : Galactic center X-ray sources (Muno+, 2009)
J/A+A/570/A2 : Spectra and RVs of nuclear stars (Feldmeier+, 2014)
J/A+A/566/A47 : MW nuclear star cluster extinction map (Schoedel+, 2014)
J/ApJS/223/15 : 8yr INTEGRAL/IBIS soft gamma-ray source obs. (Bird+, 2016)
J/ApJ/825/132 : NuSTAR hard X-ray survey of the GC. II. (Hong+, 2016)
J/AJ/154/252 : A VLA survey of magnetic CVs. I. The data (Barrett+, 2017)
J/ApJS/230/7 : Spectral flux densities from 50MHz to 50GHz (Perley+, 2017)
J/MNRAS/474/4629 : Polarimetry of pulsars from 1.4GHz obs. (Johnston+, 2018)
J/ApJS/235/4 : 105-month Swift-BAT all-sky hard X-ray survey (Oh+, 2018)
J/ApJS/235/26 : Ultradeep cat. of X-ray point sources in the GC (Zhu+, 2018)
J/ApJ/875/80 : Faint radio sources in GOODSN & -S. I. VLA 5GHz (Gim+, 2019)
J/A+A/641/A102 : MW nuclear star cluster HKs photometry (Schoedel+, 2020)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Type Object type (1)
5- 8 A4 --- --- [GCCR]
9- 11 I03 --- GCCR [1/110] GCCR number;
<[ZMG2020] GCCRNNN> in Simbad
13- 14 I2 h RAh [17] Hour of Right Ascension (J2000)
16- 17 I2 min RAm [45/46] Minute of Right Ascension (J2000)
19- 24 F6.3 s RAs Second of Right Ascension (J2000)
26 A1 --- DE- [-] Sign of the Declination (J2000)
27- 28 I2 deg DEd [28/29] Degree of Declination (J2000)
30- 31 I2 arcmin DEm Arcminute of Declination (J2000)
33- 37 F5.2 arcsec DEs Arcsecond of Declination (J2000)
39- 43 F5.1 arcsec rTheta [6.9/455] Angular distance of source
to phase center
45- 50 F6.1 arcsec DelRA [-313/401] Right Ascension offset with
respect to Sgr A*
52- 57 F6.1 arcsec DelDE [-297/417] Declination offset with
respect to Sgr A*
59- 62 F4.1 --- FPB [1/45] Primary beam correction factor
64- 68 F5.3 --- FPB1 [0.003/7.1] Fractional uncertainty in FPB
70 A1 --- l_S1 Limit flag on S1
71- 75 F5.2 mJy S1 [0.07/17.2] 5.5GHz flux density on 2019-09-08
77- 80 F4.2 mJy e_S1 [0.01/0.9]? Uncertainty in S1
82 A1 --- l_S2 Limit flag on S2
83- 87 F5.2 mJy S2 [0.02/8.08] 5.5GHz flux density on 2014-05-26
89- 92 F4.2 mJy e_S2 [0.01/0.3]? Uncertainty in S2
94 A1 --- l_S3 Limit flag on S3
95- 99 F5.2 mJy S3 [0.02/8.4] 5.5GHz flux density on 2014-05-17
101-104 F4.2 mJy e_S3 [0.01/0.2]? Uncertainty in S3
106-108 I3 uJy/beam sigma [5/300] RMS in regions near source
110-115 A6 --- Class GCCR source classification (2)
117-118 I2 --- Note [1/74]? Note (see notes.dat file)
120-121 A2 --- FlX X-ray identification? (3)
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Note (1): Object type as follows:
VaT = Variables and transients (82 occurrences);
NV = Non-variables (28 occurrences).
Note (2): GCCR source classification as follows:
u-core = unresolved compact source (36 occurrences);
c-core = compact source with a size determined from 2D Gaussian fitting
(44 occurrences);
l-core = compact source associated with a linear feature (16 occurrences);
t-core = compact source having a tail (12 occurrences);
d-core = double compact source (2 occurrences).
Note (3): Code as follows:
y = identified with X-ray counterparts with a positional offset between
X-ray and radio less than 1 arcsec (ΔX-R<1") or located in
the inner region of an X-ray halo;
y? = a possible X-ray counterpart is present near the GCCR or
ΔX-R=1" to 2" for the offsets between the GCCR and
X-ray candidate;
n = no X-ray counterpart has been identified for the GCCR
with ΔX-R>2".
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Byte-by-byte Description of file: notes.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Note [1/74] Code number of the note
4- 7 F4.2 arcsec amaj [0.2/0.98]? Major axis (θMajor)
9- 12 F4.2 arcsec e_amaj [0.02/0.25]? amaj uncertainty
14- 17 F4.2 arcsec bmin [0.04/0.51]? Minor axis (θMinor)
19- 22 F4.2 arcsec e_bmin [0.01/0.2]? bmin uncertainty
24- 26 I3 deg PA [-4/176]? Position angle
28- 29 I2 deg e_PA [3/30]? PA uncertainty
31- 120 A90 --- Comm Comment
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [GCCR]
5- 7 I3 --- GCCR GCCR number
9- 24 A16 --- XID CXOGC or Galactic identifier
26- 29 I4 --- Z18 [185/3042]? Sequential number from
Zhu et al. 2018, J/ApJS/235/26
31- 33 F3.1 arcsec Sep [0.2/2]? Positional offset between
X-ray and radio (ΔθX-R)
35- 40 F6.2 10-7ph/cm2/s S2-8keV [1.12/190] 2-8keV flux, or lower range
42- 47 F6.2 10-7ph/cm2/s S2-8keVup [1.2/186]? upper range of 2-8keV flux
49- 51 A3 --- Ref Reference (1)
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Note (1): Reference as follows:
a = Muno et al. (2009, J/ApJS/181/110 ; in Simbad);
b = Zhu et al. (2018, J/ApJS/235/26);
c = Muno et al. (2008ApJ...673..251M 2008ApJ...673..251M ; <[MBB2008] GLLL.lll+B.bbb> in Simbad);
d = Park et al. (2005ApJ...631..964P 2005ApJ...631..964P)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 28-Jul-2022