J/ApJ/954/206 A GCs search in M31 with Gaia, PS1, LAMOST, PAndAS (Wang+, 2023)
Searching for new globular clusters in M31 with Gaia EDR3.
Wang Y., Yuan H., Chen B., Chen X., Wu H., Niu Z., Huang S., Liu J.
<Astrophys. J., 954, 206 (2023)>
=2023ApJ...954..206W 2023ApJ...954..206W
ADC_Keywords: Clusters, globular; Galaxies, nearby; Colors; Photometry, ugriz;
Spectra, optical
Keywords: Globular star clusters ; Star clusters ; Random Forests ;
Observational astronomy
Abstract:
We have found 50 new globular cluster (GC) candidates around M31 with
Gaia Early Data Release 3 (EDR3), with the help of Pan-STARRS1 DR1
magnitudes and Pan-Andromeda Archaeological Survey (PAndAS) images.
Based on the latest Revised Bologna Catalog and simbad, we trained two
random forest (RF) classifiers, the first one to distinguish extended
sources from point sources and the second one to further select GCs
from extended sources. From 1.85 million sources of 16m<g<19.5m
and within a large area of ∼392deg2 around M31, we selected
20,658 extended sources and 1934 initial GC candidates. After visual
inspection of the PAndAS images, to eliminate the contamination from
noncluster sources, particularly galaxies, we finally got
50 candidates. These candidates are divided into three types (a, b,
and c), according to their projected distance D to the center of M31
and their probability of being a true GC, PGC, which is calculated
by our second RF classifier. Among these candidates, 14 are found to
be associated (in projection) with the large-scale structures within
the halo of M31. We also provide several simple parameter criteria for
selecting extended sources effectively from Gaia EDR3, which can reach
a completeness of 92.1% with a contamination fraction lower than 10%.
Description:
The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS),
located at Hawaii, conducted a stacked 3π Steradian Survey in the
five broad bands grizyp1. We used the PSF magnitude of grizyp1 and
the colors (g-r, r-i, i-y, and y-z). See Section 2.1.
We used the classification data in the Low-Resolution Spectroscopic
(LRS) Survey of the Large Sky Area Multi-Object Fiber Spectroscopic
Telescope (LAMOST) DR8 as auxiliary data in Sections 3.1 and 4.2.
LAMOST, also called the Guo Shou Jing Telescope, is a specially
designed Schmidt telescope with both a large aperture (an effective
aperture of 3.6-4.9m) and a wide field of view (5°). It is capable
of observing thousands of targets using 4000 fibers in a single
observation. The spectrum wavelength coverage is from 370 to 900nm,
with a resolving power of ∼1800. We used a subsample of LAMOST DR8 LRS
that had a signal-to-noise ratio (S/N) larger than 20. To avoid
contamination from M31, we excluded the sources in a 3.5°x3.5°
area centered at M31. see Section 2.3.
Our visual inspection relies on the optical images of the PAndAS
survey, which were obtained around M31 and M33 by the
Canada-France-Hawaii Telescope, with average seeings of 0.6" and 0.67"
in the i and g bands, respectively. See Section 2.4.
Objects:
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RA (ICRS) DE Designation(s)
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00 42 44.33 +41 16 07.5 M31 = NAME Andromeda Galaxy
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table8.dat 82 20658 Catalog of the 20,658 extended sources classified by
Clf1 (see Section 3.2)
table10.dat 65 50 Catalog of the visually checked globular cluster
(GC) candidates
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See also:
V/143 : Revised Bologna Catalog of M31 clusters, V.5 (Galleti+ 2012)
V/156 : LAMOST DR7 catalogs (Luo+, 2019)
VII/285 : Gaia DR2 quasar & galaxy classification (Bailer-Jones+, 2019)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
II/389 : The Pan-STARRS release 1 (PS1) Survey - DR2 (Magnier+, 2025)
J/A+A/416/917 : Revised Bologna Cat. of M31 globular clusters (Galleti+, 2004)
J/AJ/134/706 : New globular clusters in M 31 (Kim+, 2007)
J/PASP/119/7 : HST WFPC2 star clusters in M31 (Krienke+, 2007)
J/ApJS/177/174 : Star clusters in M31 (Narbutis+, 2008)
J/MNRAS/402/803 : M31 globular cluster system (Peacock+, 2010)
J/AJ/142/139 : A new catalog of HII regions in M31 (Azimlu+, 2011)
J/ApJ/752/95 : PHAT stellar cluster survey. I. Year 1 (Johnson+, 2012)
J/ApJS/199/37 : GALEX catalog of star clusters in M31 (Kang+, 2012)
J/ApJ/802/127 : PHAT stellar cluster survey. II. AP catalog (Johnson+, 2015)
J/ApJ/833/167 : PAndAS view of Andromeda satellites. II. (Martin+, 2016)
J/ApJ/868/55 : Large-scale structure of M31. II. PAndAS (McConnachie+, 2018)
J/A+A/623/A65 : Multiphot. of M31 outer halo globular clusters (Wang+, 2019)
J/ApJ/899/140 : 632 Gaia Ultracompact Dwarf galaxy candidates (Voggel+, 2020)
J/A+A/649/A3 : Gaia EDR3 photometric passbands (Riello+, 2021)
J/A+A/658/A51 : New M31 star cluster candidates (Wang+, 2022)
J/ApJ/947/34 : New velocity measurements of NGC 5128 GCs (Hughes+, 2023)
Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- Gaia Gaia EDR3 identifier
21- 29 F9.6 deg RAdeg [0/22.7] Right Ascension (J2000)
31- 39 F9.6 deg DEdeg [29.2/53.3] Declination (J2000)
41- 46 F6.3 mag Gmag [15.7/22.4] Gaia EDR3 G band magnitude
48- 53 F6.3 mag gmag [15.1/19.5] Pan-STARRs g band AB magnitude
55- 59 F5.3 mag g-r [0.001/2.2] Pan-STARRs (g-r) color
61- 65 F5.3 [-] E(BP/RP) [0.04/2.5] Log of Gaia EDR3 bprpexcess
parameter; Section 2.2
67- 72 F6.3 mag Gp-G [-4.92/0.6] Difference between predicted and
observed Gaia G magnitudes
74- 77 F4.2 --- Pext [0.5/1] Likelihood source is extended (G1)
79- 82 F4.2 --- PGC [0/1] Likelihood source is a globular
cluster (G1)
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Byte-by-byte Description of file: table10.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq [1/50] Identifier; same as in Figure 14
4- 12 F9.6 deg RAdeg [0.6/22.6] Right Ascension (J2000)
14- 22 F9.6 deg DEdeg [33.4/49.2] Declination (J2000)
24- 29 F6.3 mag Gmag [18.3/22] Gaia EDR3 G band magnitude
31- 36 F6.3 mag gmag [16.7/19.5] Pan-STARRs g band AB magnitude
38- 42 F5.3 mag g-r [0.002/1.2] Pan-STARRs (g-r) color
44- 48 F5.3 [-] E(BP/RP) [0.4/1.5] Log of Gaia EDR3 bprpexcess
parameter; Section 2.2
50- 55 F6.3 mag Gp-G [-3.2/-0.7] Difference between predicted and
observed Gaia G magnitudes
57- 60 F4.2 --- Pext [0.6/1] Likelihood source is extended (G1)
62- 65 F4.2 --- PGC [0.27/0.97] Likelihood source is a globular
cluster (G1)
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Global notes:
Note (G1): For detail about these 2 probability, please refer to
Sections 3.2 and 3.3.
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History:
From electronic version of the journal
Licences: cc-by
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 14-Oct-2025