J/MNRAS/513/3818 MAVERIC radio continuum sources from 26 GCs (Tudor+, 2022)
The MAVERIC survey: a catalogue of radio sources in southern globular clusters
from the Australia Telescope Compact Array.
Tudor V., Miller-Jones J.C.A., Strader J., Bahramian A., Shishkovsky L.,
Plotkin R.M., Chomiuk L., Heinke C.O., Maccarone T.J., Sivakoff G.R.,
Tremou E., Anderson G.E., Russell T.D., Tzioumis A.K.
<Mon. Not. R. Astron. Soc. 513, 3818-3835 (2022)>
=2022MNRAS.513.3818T 2022MNRAS.513.3818T (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Radio continuum ; Radio sources ;
Photometry ; Positional data ; Stars, distances
Keywords: globular clusters: general - pulsars: general -
radio continuum: general - surveys - X-rays: binaries
Abstract:
Radio continuum observations offer a new window on compact objects in
globular clusters compared to typical X-ray or optical studies. As
part of the MAVERIC survey, we have used the Australia Telescope
Compact Array to carry out a deep (median central noise level ~= 4 mJy
beam-1) radio continuum survey of 26 southern globular clusters at
central frequencies of 5.5 and 9.0 GHz. This paper presents a
catalogue of 1285 radio continuum sources in the fields of these 26
clusters. Considering the surface density of background sources, we
find significant evidence for a population of radio sources in seven
of the 26 clusters, and also identify at least 11 previously known
compact objects (six pulsars and five X-ray binaries). While the
overall density of radio continuum sources with 7.25-GHz flux
densities ~> 20 mJy in typical globular clusters is relatively low,
the survey has already led to the discovery of several exciting
compact binaries, including a candidate ultracompact black hole X-ray
binary in 47 Tuc. Many of the unclassified radio sources near the
centres of the clusters are likely to be true cluster sources, and
multiwavelength follow-up will be necessary to classify these objects
and better understand the demographics of accreting compact binaries
in globular clusters.
Description:
In this paper, we catalogue radio continuum sources in deep
observations of 26 southern Galactic globular clusters, taken with the
Australia Telescope Compact Array (ATCA). We select the MAVERIC survey
designed to sample massive clusters with those limits chosen for
sensitivity to quiescent radio emission from accreting black holes,
and a restriction to the more massive clusters most likely to host
them. We also included a few other more distant, massive globular
clusters which may contain intermediate-mass black holes, and others
with high interaction rates or bright quiescent X-ray sources, (i.e
see section 2.1 Sample selection).
Sources and data extractions methods are summarized in the sections
2.3 Data reduction and 3.1 Source finding. Specifically, we extract
radio sources from 5.5-, 9.0-, and the (stacked) 7.25-GHz images via
source extraction software. After cross-matching between the three
producted catalogues, we only keep those sources with SNR => 5 in at
least one band, to ensure the catalogue is reliable, (see more details
in the section 3 Methods).
Next, as presented in the section Results, we detected a total of 1285
sources across our 26 globular cluster fields where positions,
relative distances, radio fluxes and spectral indices are regrouped in
the table4.dat for all the 1285 sources.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
cluster.dat 10 26 Globular clusters in our sample
table4.dat 128 1285 Radio continuum sources sample across our 26
globular cluster fields
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See also:
J/ApJ/903/73 : MAVERIC survey: deep VLA imaging of 25 GCs
(Shishkovsky+, 2020)
J/ApJ/766/136 : Stellar encounter rates in Galactic GCs (Bahramian+, 2013)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/MNRAS/478/1520 : Milky Way globular clusters data (Baumgardt+, 2018)
Byte-by-byte Description of file: cluster.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Cluster Cluster name (Cluster)
9- 10 I2 --- Nbr Number of ATCA radio sources in the cluster
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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- 7 A7 --- Cluster Cluster name (Cluster)
9- 14 A6 --- ID Realtive source ATCAXX name (ID)
16- 26 F11.7 deg RAdeg Right Ascension (J2000) (RA)
28- 38 F11.7 deg DEdeg Declination (J2000) (DEC)
40- 43 F4.2 arcsec e_RAdeg Positional uncertainty of RAdeg (DeltaRA) (1)
45- 48 F4.2 arcsec e_DEdeg Positional uncertainty of DEdeg (DeltaDEC) (1)
50 A1 --- l_S5.5 Upper limit flag for S5.5
52- 58 F7.1 uJy S5.5 Flux density at 5.5 GHz (S5.5)
60- 65 F6.1 uJy e_S5.5 ? Uncertainty 1σ in S5.5 (DeltaS5.5)
67 A1 --- l_S7.25 Limit flag for S7.25
69- 76 F8.1 uJy S7.25 ? Flux density at 7.25 GHz (S7.25)
78- 83 F6.1 uJy e_S7.25 ? Uncertainty 1σ in S7.25 (DeltaS7.25)
85 A1 --- l_S9 Limit flag for S9
87- 94 F8.1 uJy S9 ? Flux density at 9.0 GHz (S9)
96-101 F6.1 uJy e_S9 ? Uncertainty 1σ in S9 (DeltaS9)
103 A1 --- l_alpha Limit flag for alpha
105-109 F5.2 --- alpha ? Spectral index of source (2)
111-115 F5.2 --- e_alpha ? Uncertainty 1σ in alpha (Deltaalpha)
117-122 F6.2 --- Rc Distance from center in units of cluster core
radius (Rc)
124-128 F5.2 --- Rh Distance from center in units of cluster
half-light radius (Rh)
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Note (1): The quoted errors in astrometry are statistical only. An additional
systematic error of order 1/10th of the beam size might be expected
(see discussion in Shishkovsky et al. 2020ApJ...903...73S 2020ApJ...903...73S,
Cat. J/ApJ/903/73).
Note (2): Spectral indices α, Sν ∝ να, where
Sν is the flux density at frequency ν and the specrtal index
as α = log(S5.5/S9)/log(5.5/9).
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 09-Jan-2025