J/AJ/156/121 A catalog of 518 likely open cluster NGC 6405 members (Gao, 2018)
Memberships of the open cluster NGC 6405 based on a combined method: Gaussian
mixture model and random forest.
Gao X.
<Astron. J., 156, 121 (2018)>
=2018AJ....156..121G 2018AJ....156..121G (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Models ; Populations, stellar
Keywords: methods: data analysis - methods: statistical -
open clusters and associations: individual (NGC 6405) - parallaxes -
proper motions
Abstract:
This paper presents a combined method of Gaussian mixture model and
random forest to compute membership probabilities of stars by using large,
high-dimensional data sets. A significant advantage of this method is
that it allows us to easily identify likely cluster members in large data
sets starting from small training samples. As a benchmark, we select
40318 stars in the field of the open cluster NGC 6405 from the Gaia Data
Release 2 (Gaia-DR2, Cat. I/345) by means of all five astrometric
(positions, proper motions, and parallax) and photometric parameters.
We use this combined method to determine likely cluster members in an
eleven-dimensional parameter space. A total number of 518 high-probability
(≥0.6) memberships are obtained, and the mean parallax and proper motion
of the cluster are determined to be 2.171±0.005 mas (461±1 pc) and
(<µαcosδ>, <µδ>)=(-1.357±0.023,
-5.823±0.020) mas/yr, respectively. In addition, we quantitatively
evaluate the relative importance of the parameters for membership
determination and find that colors and magnitudes cannot be ignored in
membership determination when using the RF method. Our results show that
this combined method exhibits good performance in handling arbitrary
high-dimensional and large data sets, such as Gaia-DR2, and it can also
be used to investigate other open clusters.
Description:
In this paper, we investigate a method based on the combination of the
Gaussian Mixture Model (GMM) and Random Forest (RF) to compute membership
probabilities for stars in the field of NGC 6405. We make use of the
astrometric and photometric data of the Gaia-DR2 catalog (Cat. I/345).
After selecting likely cluster members in a multi-dimensional parameter
space, we also measure the distance and absolute proper motion of this
cluster.
To reject a large number of field stars, we select sample stars in the
field of this cluster based on the following three criteria: (1) the stars
must lie within a radius of 25' from the cluster center, (2) the stars
must lie within the proper motion range of |µαcosδ|=<20
and |µδ|=<20 mas/yr, and (3) the stars must have five
astrometric parameters (positions, parallax, and proper motions) and three
photometric parameters (G-band magnitude, BP-band magnitude, and RP-band
magnitude). Based on these criteria, we obtain 40318 sample stars from
the Gaia-DR2 catalog.
Objects:
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RA (ICRS) DE Designation(s)
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17 40 20 -32 15.2 NGC 6405 = NAME Butterfly Cluster
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 57 518 A catalog of fundamental information for 518 likely
cluster members with PRF≥0.6
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/446/949 : Open clusters proper motions based on UCAC2 (Dias+, 2006)
J/A+A/454/171 : CCD Δa-photometry of 8 open clusters (Paunzen+, 2006)
J/PAZh/38/571 : Astrophysical parameters for 593 open clusters
(Gozha+, 2012)
J/A+A/585/A101 : Milky Way global survey of star clusters. V.
(Kharchenko+, 2016)
J/AJ/151/49 : M6 open cluster: star members properties (Kilicoglu+, 2016)
J/MNRAS/470/3937 : 1876 open clusters multimembership catalog (Sampedro+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- Source Gaia DR2 identifier
21- 35 F15.11 deg RAdeg Gaia DR2 Right Ascension (ICRS) at Ep=2015.5
37- 51 F15.11 deg DEdeg Gaia DR2 Declination (ICRS) at Ep=2015.5
53- 57 F5.3 --- PRF [0.603/1] Random Forest (RF) membership probability
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 01-Mar-2019