J/MNRAS/508/1033 Stars groups in CMa OB 1 with Gaia DR2 (Santos-Silva+, 2021)
Canis Major OB1 stellar group contents revealed by Gaia.
Santos-Silva T., Perottoni H.D., Almeida-Fernandes F., Gregorio-Hetem J.,
Jatenco-Pereira V., Mendes De Oliveira C., Montmerle T., Bica E.,
Bonatto C., Monteiro H., Dias W.S., Barbosa C.E., Fernandes B.,
Galli P.A.B., Borges Fernandes M., Kanaan A., Ribeiro T., Schoenell W.
<Mon. Not. R. Astron. Soc. 508, 1033-1055, (2021)>
=2021MNRAS.508.1033S 2021MNRAS.508.1033S (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Associations, stellar ; Star Forming Region ;
Astrometric data ; Stars, distances ; Optical ; Extinction ;
Space velocities
Keywords: star: early-type - stars: formation - stars: pre-main-sequence -
open clusters and associations: general
Abstract:
Canis Major OB1 (CMa OB1) is a Galactic stellar association with a
very intriguing star-formation scenario. There are more than two dozen
known star clusters in its line of sight, but it is not clear which
ones are physically associated with CMa OB1. We use a clustering code
that employs five-dimensional data from the Gaia DR2 catalogue to
identify physical groups and obtain their astrometric parameters and,
in addition, we use two different isochrone-fitting methods to
estimate the ages of these groups. We find 15 stellar groups with
distances between 570 and 1650 pc, including 10 previously known and
five new open cluster candidates. Four groups, precisely the youngest
ones (<20Myr), CMa05, CMa06, CMa07, and CMa08, are confirmed to be
part of CMa OB1. We find that CMa08, a new cluster candidate, may be
the progenitor cluster of runaway stars. CMa06 coincides with the
well-studied CMa R1 star-forming region. While CMa06 is still forming
stars, due to the remaining material of the molecular cloud associated
with the Sh 2-262 nebula, CMa05, CMa07, and CMa08 seem to be in more
evolved stages of evolution, with no recent star-forming activity. The
properties of these CMa OB1 physical groups fit well in a monolithic
scenario of star formation, with a common formation mechanism, and
having suffered multiple episodes of star formation. This suggests
that the hierarchical model alone, which explains the populations of
other parts of the same association, is not sufficient to explain its
whole formation history.
Description:
Aiming at clarifying the complex star-forming history of CMa OB1 and
confirming its cluster membership, we conduct a multidimensional study
of stellar groups in the region, taking into account the positions,
proper motions, and parallax from the Gaia DR2 catalogue (Gaia
Collaboration et al. 2018A&A...616A...1G 2018A&A...616A...1G, Cat. I/345).
This stars catalogue allows us to apply a list of criteria selections
within a search radius of 4.1 degrees centred on the coordinates
covering the entire CMa OB1 association. (i.e section 2.1 Sample
selection). After applying all of these criteria, our final sample
contains 249522 stars.
Hereafter, we proceed to a substructure search (see section 3).
Clustering methods constitute the most commonly used technique of
unsupervised learning and are a powerful tool for data analysis. There
are several clustering algorithms, but one shown to be powerful and
efficient in different astronomy fields is Hierarchical Density-Based
Spatial Clustering of Applications with Noise (HDBSCAN), which has
been used to search for stellar clusters (Castro-Ginard et al.
2020A&A...635A..45C 2020A&A...635A..45C, Cat. J/A+A/635/A45). Thus, we use this algorithm
in the 5D space of astrometric parameters (pmRA, pmDE, Plx, RAdeg,
DEdeg) which giving birth to 29 stellars groups.
To validate the clusters identified by HDBSCAN and estimate the
membership probability of each star belonging to a specific group, we
have computed 400 bootstrap repetitions, taking into account the
uncertainties of the astrometric parameters of the stars. We attribute
a membership probability P of each star belonging to a specific
cluster according to the percentage of assignment to it. We considered
that a star is a cluster member if it is assigned to a specific
cluster in at least 50 per cent of the realizations (P≥50 per cent).
Results are available in the table cma00.dat to cma28.dat. This method
is similar to that one described by Limberg et al.
(2021ApJ...907...10L 2021ApJ...907...10L, Cat. J/ApJ/907/10), (i.e please refer to
sections 3.1 Searching for groups and 3.2 Validation).
More, we further apply a second memebership validation test (explained
in the section 3.2.2 Bayesian method) on our results based on
comparison with a recent study of the young population related to our
groups.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
cma00.dat 95 152 Astrometric parameters and membership
probability of the CMa00 member stars
cma01.dat 95 66 Astrometric parameters and membership
probability of the CMa01 member stars
cma02.dat 95 71 Astrometric parameters and membership
probability of the CMa02 member stars
cma03.dat 95 103 Astrometric parameters and membership
probability of the CMa03 member stars
cma04.dat 95 132 Astrometric parameters and membership
probability of the CMa04 member stars
cma05.dat 95 31 Astrometric parameters and membership
probability of the CMa05 member stars
cma06.dat 95 404 Astrometric parameters and membership
probability of the CMa06 member stars
cma07.dat 95 34 Astrometric parameters and membership
probability of the CMa07 member stars
cma08.dat 95 76 Astrometric parameters and membership
probability of the CMa08 member stars
cma09.dat 95 180 Astrometric parameters and membership
probability of the CMa09 member stars
cma10.dat 95 37 Astrometric parameters and membership
probability of the CMa10 member stars
cma11.dat 95 31 Astrometric parameters and membership
probability of the CMa11 member stars
cma12.dat 95 38 Astrometric parameters and membership
probability of the CMa12 member stars
cma13.dat 95 80 Astrometric parameters and membership
probability of the CMa13 member stars
cma14.dat 95 104 Astrometric parameters and membership
probability of the CMa14 member stars
cma15.dat 95 384 Astrometric parameters and membership
probability of the CMa15 member stars
cma16.dat 95 93 Astrometric parameters and membership
probability of the CMa16 member stars
cma17.dat 95 1096 Astrometric parameters and membership
probability of the CMa17 member stars
cma18.dat 95 227 Astrometric parameters and membership
probability of the CMa18 member stars
cma19.dat 95 245 Astrometric parameters and membership
probability of the CMa19 member stars
cma20.dat 95 258 Astrometric parameters and membership
probability of the CMa20 member stars
cma21.dat 95 35 Astrometric parameters and membership
probability of the CMa21 member stars
cma22.dat 95 117 Astrometric parameters and membership
probability of the CMa22 member stars
cma23.dat 95 239 Astrometric parameters and membership
probability of the CMa23 member stars
cma24.dat 95 46 Astrometric parameters and membership
probability of the CMa24 member stars
cma25.dat 95 96 Astrometric parameters and membership
probability of the CMa25 member stars
cma26.dat 95 70 Astrometric parameters and membership
probability of the CMa26 member stars
cma27.dat 95 49 Astrometric parameters and membership
probability of the CMa27 member stars
cma28.dat 95 33 Astrometric parameters and membership
probability of the CMa28 member stars
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/347 : Distances to 1.33 billion stars in Gaia DR2
(Bailer-Jones+, 2018)
J/A+A/635/A45 : 570 new open clusters in the Galactic disc
(Castro-Ginard+, 2020)
J/ApJ/907/10 : Initial vs final sample of the VMP HK/HES stars (Limberg+,2021)
Byte-by-byte Description of file: cma??.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR2 Gaia DR2 identifier (ID_GAIA)
21- 23 I3 --- Pmemb Membership probability (P)
25- 30 F6.2 deg RAdeg Barycentric right ascension (ICRS)
at Ep = 2015.5 (RA)
32- 35 F4.2 deg e_RAdeg Standard right ascension error (e_RA)
37- 42 F6.2 deg DEdeg Barycentric declination (ICRS)
at Ep = 2015.5 (DE)
44- 47 F4.2 deg e_DEdeg Standard declination error (e_DE)
49- 53 F5.2 mas/yr pmRA Proper motion in right ascension
direction (pmRA*cosDE)
55- 58 F4.2 mas/yr e_pmRA Standard error of proper motion in right
ascension direction (e_pmRA*cosDE)
60- 64 F5.2 mas/yr pmDE Proper motion in declination direction (pmDE)
66- 69 F4.2 mas/yr e_pmDE Standard error of pmDE (e_pmDE)
71- 74 F4.2 mas Plx Absolute stellar parallax (Plx)
76- 79 F4.2 mas e_Plx Standard error of parallax (e_Plx)
81- 84 I4 pc D Astrometric distance (DA) (1)
86- 89 F4.2 mag Av Visual extinction (AV) (2)
91- 95 F5.2 km/s Vt Tangential velocity (Vt)
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Note (1): For consistency, in this work we also used astrometric distances
(DA) estimated by Bailer-Jones et al. (2018AJ....156...58B 2018AJ....156...58B,
Cat. I/347) using Gaia DR2 (Gaia Collaboration 2018A&A...616A...1G 2018A&A...616A...1G,
Cat. I/345) data for all stars selected.
Note (2): The association is located in a region of high extinction, and
therefore the visual extinction values (AV) can vary significantly
with distance. In order to take this into account, we use the
astrometric distance of each star to obtain its AV from the
three-dimensional dust map of BAYESTAR19 (Green et al.
2019ApJ...887...93G 2019ApJ...887...93G). To consider the probabilistic nature of
BAYESTAR19, we used it with mode = mean. Furthermore, we applied the
corrections from Schlafly & Finkbeiner (2011ApJ...737..103S 2011ApJ...737..103S) to the
AV values.
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 26-Jul-2024