J/ApJ/903/73 MAVERIC survey: deep VLA imaging of 25 GCs (Shishkovsky+, 2020)
The MAVERIC survey: radio catalogs and source counts from deep Very Large Array
imaging of 25 Galactic globular clusters.
Shishkovsky L., Strader J., Chomiuk L., Tremou E., Tudor V.,
Miller-Jones J.C.A., Bahramian A., Heinke C.O., Maccarone T.J.,
Sivakoff G.R.
<Astrophys. J., 903, 73 (2020)>
=2020ApJ...903...73S 2020ApJ...903...73S
ADC_Keywords: Clusters, globular; Radio sources; Surveys
Keywords: Globular star clusters ; Radio source counts ; Surveys ; X-ray
binary stars ; Radio pulsars ; Radio sources
Abstract:
The MAVERIC survey is the first deep radio continuum imaging survey of
Milky Way globular clusters, with a central goal of finding and
classifying accreting compact binaries, including stellar-mass black
holes. Here we present radio source catalogs for 25 clusters with
ultra-deep Karl G. Jansky Very Large Array observations. The median
observing time was 10 hr per cluster, resulting in typical rms
sensitivities of 2.3 and 2.1µJy per beam at central frequencies of
5.0 and 7.2GHz, respectively. We detect nearly 1300 sources in our
survey at 5σ, and while many of these are likely to be
background sources, we also find strong evidence for an excess of
radio sources in some clusters. The radio spectral index distribution
of sources in the cluster cores differs from the background, and shows
a bimodal distribution. We tentatively classify the steep-spectrum
sources (those much brighter at 5.0GHz) as millisecond pulsars and the
flat-spectrum sources as compact or other kinds of binaries. These
provisional classifications will be solidified with the future
addition of X-ray and optical data. The outer regions of our images
represent a deep, relatively wide-field (∼0.4deg2) and
high-resolution C band background survey, and we present source counts
calculated for this area. We also release radio continuum images for
these 25 clusters to the community.
Description:
Pilot observations for the survey were made as part of National Radio
Astronomy Observatory (NRAO) programs VLA/10C-109 (P.I. Chomiuk) in
2011 and VLA/12B-073 (P.I. Strader) in 2012. The main survey was
approved as an NRAO Large Program (project codes VLA/13B-014 and
VLA/15A-100), with observations made in 2014 and 2015, respectively.
For all clusters we observed with the C band receiver, including full
polarization products. Data taken in 2014 or earlier used an 8 bit
setup with two 1GHz basebands centered at 5.0 and 7.4GHz, while the
2015 data used 3 bit receivers with two 2GHz basebands centered at
5.0 and 7.0GHz. However, the final central wavelengths depend on the
details of the flagging of radio frequency interference, which varies
among the sample (see Table 2).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 30 108 Epochs of VLA data
table2.dat 90 25 Information for our cluster sample and images
table3.dat 112 1267 Radio continuum sources
--------------------------------------------------------------------------------
See also:
J/A+AS/58/1 : 1412MHz catalog of Westerbork survey. I. (Windhorst+, 1984)
J/ApJ/405/498 : Counts and spectral indices at 8.44GHz (Windhorst+, 1993)
J/AJ/129/348 : Radio compact HII regions in the Milky Way (Giveon+, 2005)
J/AJ/135/2470 : Radio observations of the HDFS region. IV. (Huynh+, 2008)
J/ApJS/205/1 : CORNISH project. II. Source catalog (Purcell+, 2013)
J/MNRAS/454/952 : Chandra Deep Field-South ATLAS 5.5GHz DR2 (Huynh+, 2015)
J/A+A/602/A1 : VLA-COSMOS 3 GHz Large Project (Smolcic+, 2017)
J/MNRAS/472/3706 : Globular cluster 47 Tuc with Chandra (Bhattacharya+, 2017)
J/MNRAS/478/1520 : Milky Way globular clusters data (Baumgardt+, 2018)
J/A+A/621/A139 : VLA-COSMOS 3GHz sources average radio SED (Tisanic+, 2019)
J/ApJ/901/57 : MAVERIC survey: Chandra sources in 38 GCs (Bahramian+, 2020)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- ID Globular cluster identifier
7- 17 A11 "Y/M/D" Date Observation date (UT)
19- 22 F4.2 h Exp [1/5] Observation time
24- 30 A7 --- PID Project code
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- ID Globular cluster identifier
7- 8 I2 h RAh [13/21] Hour of Right Ascension (J2000) (1)
10- 11 I2 min RAm Minute of Right Ascension (J2000) (1)
13- 17 F5.2 s RAs Second of Right Ascension (J2000) (1)
19- 19 A1 --- DE- Sign of the Declination (J2000) (1)
20- 21 I2 deg DEd Degree of Declination (J2000) (1)
23- 24 I2 arcmin DEm Arcminute of Declination (J2000) (1)
26- 30 F5.2 arcsec DEs Arcsecond of Declination (J2000) (1)
32- 35 F4.1 kpc Dist [1.8/24] Distance (1)
37- 41 F5.1 arcsec CRad [1.8/108] Core radius (1)
43- 47 F5.1 arcsec HLRad [28.8/260] Half-light radius (1)
49- 50 I2 h Exp [5/12] Total integration time
52- 54 F3.1 h ExpOS [3.2/9] On-source exposure time
56- 58 F3.1 GHz nulow [4.9/5.3] ν low
60- 63 F4.2 arcsec beamlowa [0.35/1.54] Beam, ν-low, major axis length
65- 68 F4.2 arcsec beamlowb [0.36/1.16] Beam, ν-low, minor axis length
70- 72 F3.1 uJy/beam rmslow [1.7/3.8] Noise, ν-low
74- 76 F3.1 GHz nuhi [6.8/7.4] ν high
78- 81 F4.2 arcsec beamhia [0.3/1.14] Beam, ν high, major axis length
83- 86 F4.2 arcsec beamhib [0.26/0.72] Beam, ν high, minor axis length
88- 90 F3.1 uJy/beam rmshi [1.6/4] Noise, ν high
--------------------------------------------------------------------------------
Note (1): Sources for the photometric centers, distances, and structural
parameters are as in Tremou et al. (2018ApJ...862...16T 2018ApJ...862...16T)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- ID Globular cluster identifier
6 A1 --- --- [-]
7- 11 A5 --- VLA Identifier within Cluster (VLANN;
<[SSC2020] {ID}-VLANN> in Simbad)
13- 14 I2 h RAh [13/21] Hour of Right Ascension (ICRS)
16- 17 I2 min RAm Minute of Right Ascension (ICRS)
19- 24 F6.3 s RAs Second of Right Ascension (ICRS)
26- 26 A1 --- DE- Sign of the Declination (ICRS)
27- 28 I2 deg DEd Degree of Declination (ICRS)
30- 31 I2 arcmin DEm Arcminute of Declination (ICRS)
33- 37 F5.2 arcsec DEs Arcsecond of Declination (ICRS)
39- 42 F4.2 arcsec eRA [0.03/0.14]? Positional uncertainty on RA
44- 47 F4.2 arcsec eDE [0.03/0.13]? Positional uncertainty on DEC
49- 49 A1 --- l_S5GHz Limit flag for S5GHz (1)
51- 57 F7.1 uJy S5GHz [5/19014] Flux density in the lower subband (1)
59- 62 F4.1 uJy e_S5GHz [-8/14.5] Uncertainty in S5GHz (1)
64- 64 A1 --- l_S7GHz Limit flag for S7GHz (1)
66- 72 F7.1 uJy S7GHz [4/12724] Flux density in the higher subband (1)
74- 78 F5.1 uJy e_S7GHz [-12/17] Uncertainty in S7GHz (1)
80- 84 A5 --- Note Source note (2)
86- 89 F4.2 arcmin Rad [0.04/3.8] Projected radius from the cluster
center
91- 94 A4 --- loc Source is within core (rc) or
half-light (rh) radius
96- 96 A1 --- l_alpha Limit flag for α
98-102 F5.2 --- alpha [-3.41/1.5]? Spectral index α of source,
for S~να
104-107 F4.2 --- e_alpha [0.01/1.3]? Lower uncertainty in α
109-112 F4.2 --- E_alpha [0.01/1.2]? Upper uncertainty in α
--------------------------------------------------------------------------------
Note (1): When a 3σ upper limit (l_S5 or l_S7) is given the error column
for S5 and/or S7 reports the exact flux density at the corresponding pixel
at the location of the detection at the other frequency. In some cases this
"error" may be negative.
Note (2): Source notes -- Whether the source is extended (ext) or a possible
imaging artifact (art).
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 06-Jan-2022