J/A+A/661/A118 628 new open clusters found with OCfinder (Castro-Ginard+, 2022)
Hunting for open clusters in Gaia EDR3:
628 new open clusters found with OCfinder.
Castro-Ginard A., Jordi C., Luri X., Cantat-Gaudin T., Carrasco, J.M.,
Casamiquela L., Anders F., Balaguer-Nunez L., Badia R.M.
<Astron. Astrophys. 661, A118 (2022)>
=2022A&A...661A.118C 2022A&A...661A.118C (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Clusters, open ; Parallaxes, trigonometric ;
Proper motions ; Radial velocities
Keywords: Galaxy: disc - open clusters and associations: general - astrometry -
methods: data analysis
Abstract:
The improvements in the precision of the published data in Gaia EDR3
with respect to Gaia DR2, particularly for parallaxes and proper
motions, offer the opportunity to increase the number of known open
clusters in the Milky Way by detecting farther and fainter objects
that have so far go unnoticed. Our aim is to keep completing the open
cluster census in the Milky Way with the detection of new stellar
groups in the Galactic disc.
We use Gaia EDR3 up to magnitude G=18mag, increasing in one unit the
magnitude limit and therefore the search volume explored in our previous
studies.
We use the OCfinder method to search for new open clusters in Gaia EDR3
using a Big Data environment. As a first step, OCfinder identifies stellar
statistical overdensities in the five dimensional astrometric space
(position, parallax and proper motions) using the DBSCAN clustering
algorithm. Then, these overdensities are classified into random statistical
overdensities or real physical open clusters using a deep artificial neural
network trained on well-characterised G, GBP-GRP colour-magnitude
diagrams.
We report the discovery of 628 new open clusters within the Galactic
disc, most of them located beyond 1 kpc from the Sun. From the
estimation of ages, distances and line-of-sight extinctions of these
open clusters, we see that young clusters align following the Galactic
spiral arms while older ones are dispersed in the Galactic disc.
Furthermore, we find that most open clusters are located at low
Galactic altitudes with the exception of a few groups older than 1Gyr.
We show the success of the OCfinder method leading to the discovery of
a total of 1310 open clusters (joining the discoveries here with the
previous ones based on Gaia DR2), which represents almost 50% of the
know population. Our ability to perform big data searches on a large
volume of the Galactic disc, together with the higher precision in
Gaia EDR3, enable us to keep completing the census with the discovery
of new open clusters.
Description:
The methodology developed to search for new OCs in Gaia data,
OCfinder, is described in detail in Paper I (Castro-Ginard et al.,
2018A&A...618A..59C 2018A&A...618A..59C, Cat. J/A+A/618/A59. It was successfully applied
to detect 23 new nearby OCs (Castro-Ginard et al.,2018A&A...618A..59C 2018A&A...618A..59C,
Cat. J/A+A/618/A59) in the TGAS data set of Gaia DR1. It was also
applied to Gaia DR2 where 53 new OCs were detected in a direction near
the Galactic anticentre (Castro-Ginard et al. 2019) and hundreds of
new OCs in a big data search on the whole Galactic disc (Castro-Ginard
et al., 2020A&A...635A..45C 2020A&A...635A..45C, Cat. J/A+A/635/A45).
Table 1 contains mean astrometric parameters for the detected
clusters.
Table 2 contains the member stars found for the new UBC open clusters
reported in the paper. The columns are for astrometric parameters for
the member stars, i.e. positions, parallax, proper motions and radial
velocity when available, as well as the photometric information in the
G, GBP and GRP bands. It also includes the Gaia source_id to allow
the cross-match with other catalogues.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 133 628 Mean parameters for the reported UBC clusters
table2.dat 244 25466 Members for the reported UBC clusters
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/627/A35 : New open clusters in Galactic anti-centre (Castro-Ginard+ 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [0/627] cluster sequential number
5- 11 A7 --- Cluster Cluster name (UBCNNN)
13- 18 F6.2 deg RAdeg Right Ascension mean (ICRS) at Ep=2015.5
20- 25 F6.2 deg s_RAdeg Right Ascension standard deviation
27- 32 F6.2 deg DEdeg Declination mean (ICRS) at Ep=2015.5
34- 37 F4.2 deg s_DEdeg Declination standard deviation
39- 44 F6.2 deg GLON Galactic longitude mean
46- 49 F4.2 deg s_GLON Galactic longitude standard deviation
51- 56 F6.2 deg GLAT Galactic latitude mean
58- 61 F4.2 deg s_GLAT Galactic latitude standard deviation
63- 66 F4.2 mas plx Parallax mean
68- 71 F4.2 mas s_plx Parallax standard deviation
73- 77 F5.2 mas/yr pmRA Proper motion in right ascension mean,
pmRA*cosDE
79- 82 F4.2 mas/yr s_pmRA Proper motion in right ascension standard
deviation
84- 88 F5.2 mas/yr pmDE Proper motion in declination mean
90- 93 F4.2 mas/yr s_pmDE Proper motion in declination standard
deviation
95-100 F6.2 km/s RV ? Radial velocity mean
102-106 F5.2 km/s s_RV ? Radial velocity standard deviation
108-110 I3 --- Nmemb Number of cluster members
112 I1 --- NmembRV Number of cluster members with
radial velocity measurements
114 A1 --- Flag [a] Note (1)
116-120 F5.3 [yr] logAge Logarithm of the cluster age
122-127 F6.1 pc Dist Distance to the cluster
129-133 F5.3 --- AV Line-of-sight extinction
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Note (1): Note as follows:
a = positional coincidence with Kharchenko et al. (2013A&A...558A..53K 2013A&A...558A..53K,
Cat. J/A+A/558/A53)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Seq [0/25465] Star sequential number
7- 13 A7 --- Cluster Cluster name (UBCNNNN)
15- 33 I19 --- GaiaEDR3 Gaia EDR3 source_id
35- 54 F20.16 deg RAdeg Right Ascension (ICRS) at Ep=2015.5
56- 75 F20.16 deg DEdeg Declination (ICRS) at Ep=2015.5
77- 96 F20.16 deg GLON Galactic longitude
98-116 E19.16 deg GLAT Galactic latitude
118-137 F20.16 mas plx Parallax
139-159 E21.16 mas/yr pmRA Proper motion in right ascension, pmRA*cosDE
161-182 E22.17 mas/yr pmDE Proper motion in declination
184-203 F20.16 km/s RV ? Radial velocity
205-222 F18.15 mag Gmag Gaia G magnitude
224-244 F21.18 mag BP-RP ? Gaia BP-RP colour
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Acknowledgements:
Alfred Castro-Ginard, acastro(at)strw.leidenuniv.nl
(End) Alfred Castro-Ginard [Leiden Obs.], Patricia Vannier [CDS] 11-Apr-2022