J/A+A/618/A59 Gaia DR2 confirmed new nearby open clusters (Castro-Ginard+, 2018)
A new method for unveiling open clusters in Gaia.
New nearby open clusters confirmed by DR2.
Castro-Ginard A., Jordi C., Luri X., Julbe F., Morvan M., Balaguer-Nunez L.,
Cantat-Gaudin T.
<Astron. Astrophys., 618, A59 (2018)>
=2018A&A...618A..59C 2018A&A...618A..59C (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Galactic center ; Clusters, open
Keywords: surveys - open clusters and associations: general - astrometry -
methods: data analysis
Abstract:
The publication of the Gaia Data Release 2 (Gaia DR2) opens a new era
in astronomy. It includes precise astrometric data (positions, proper
motions, and parallaxes) for more than 1.3 billion sources, mostly
stars. To analyse such a vast amount of new data, the use of
data-mining techniques and machine-learning algorithms is mandatory.
A great example of the application of such techniques and algorithms
is the search for open clusters (OCs), groups of stars that were born
and move together, located in the disc. Our aim is to develop a method
to automatically explore the data space, requiring minimal manual
intervention.
We explore the performance of a density-based clustering algorithm,
DBSCAN, to find clusters in the data together with a supervised
learning method such as an artificial neural network (ANN) to
automatically distinguish between real OCs and statistical clusters.
The development and implementation of this method in a
five-dimensional space (l, b, p, µα*, µδ) with
the Tycho-Gaia Astrometric Solution (TGAS) data, and a posterior
validation using Gaia DR2 data, lead to the proposal of a set of new
nearby OCs.
We have developed a method to find OCs in astrometric data, designed
to be applied to the full Gaia DR2 archive.
Description:
We have designed, implemented, and tested an automated datamining
system for the detection of OCs using astrometric data. The method is
based on i) DBSCAN, an unsupervised learning algorithm to find groups
of stars in a N-dimensional space (our implementation uses five
parameters l, b, varpi, pmRA*, pmDE) and ii) an ANN trained to
distinguish between real OCs and spurious statistical clusters by
analysis of CMDs. This system is designed to work with minimal manual
intervention for its application to large datasets, and in particular
to the Gaia second data release, Gaia DR2.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
centers.dat 230 23 Mean parameters for the reported UBC clusters
(table2 of the paper)
members.dat 191 1318 Members for the reported UBC clusters
--------------------------------------------------------------------------------
See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: centers.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Cluster Cluster name (UBCNN_a) (UBC1-UBC32)
9- 27 F19.15 deg GLON Galactic longitude mean
29- 47 F19.17 deg e_GLON Galactic longitude standard deviation
49- 68 F20.16 deg GLAT Galactic latitude mean
70- 88 F19.17 deg e_GLAT Galactic latitude standard deviation
90-107 F18.16 mas Plx Parallax mean
109-128 F20.18 mas e_Plx Parallax standard deviation
130-149 F20.17 mas/yr pmRA* Proper motion in right ascension mean
(pmRA*cosDE)
151-169 F19.17 mas/yr e_pmRA* Proper motion in right ascension
standard deviation
171-190 F20.17 mas/yr pmDE Proper motion in declination mean
192-210 F19.17 mas/yr e_pmDE Proper motion in declination
standard deviation
212-217 F6.2 km/s RV ?=- Radial velocity
219-223 F5.2 km/s e_RV ?=- rms uncertainty on RV
225-227 I3 --- N Number of members found
229-230 I2 --- NRV Number of members used to compute
mean radial velocity
--------------------------------------------------------------------------------
Byte-by-byte Description of file: members.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Cluster Cluster name (UBCNN_a)
9- 27 I19 --- Source Gaia DR2 source_id
29- 47 F19.15 deg GLON Galactic longitude mean
49- 68 F20.16 deg GLAT Galactic latitude mean
70- 87 F18.16 mas Plx Parallax mean
89-111 F23.19 mas/yr pmRA* Proper motion in right ascension (pmRA*cosDE)
113-133 F21.18 mas/yr pmDE Proper motion in declination
135-153 F19.16 mag Gmag Gaia G magnitude magnitude
155-172 E18.13 mag BPmag ?=- Gaia BP magnitude
174-191 E18.13 mag RPmag ?=- Gaia RP magnitude
--------------------------------------------------------------------------------
Acknowledgements:
Alfred Castro-Ginard, acastro(at)fqa.ub.edu
(End) Alfred Castro-Ginard [Univ. Barcelona], Patricia Vannier [CDS] 06-Jun-2019