J/A+A/567/A52 Membership in stellar kinematic groups (Klutsch+, 2014)
Reliable probabilistic determination of membership in stellar kinematic groups
in the young disk.
Klutsch A., Freire Ferrero R., Guillout P., Frasca A., Marilli E.,
Montes D.
<Astron. Astrophys., 567, A52-52 (2014)>
=2014A&A...567A..52K 2014A&A...567A..52K
ADC_Keywords: Associations, stellar ; Space velocities
Keywords: stars: kinematics and dynamics - methods: data analysis -
stars: low-mass
Abstract:
Over the last century, the overdensities in the velocity distributions
of nearby stars were attributed to stellar kinematic groups or moving
groups. Although their reality was initially questioned, their
existence is now supported by a confluence of evidence.
To pursue investigations, quantitative methods should be clearly
defined to identify new stars belonging to these groups. Here, we
present two probabilistic methods to determine the likelihood of
kinematic membership for possible candidates in five of the known
young stellar kinematic groups - namely, Pleiades, IC2391, Castor,
Ursa Major, and Hyades - in which all are younger than 650Myr.
We tried different methods to handle kinematic data of their known
members. We succeeded in developing two independent procedures able to
identify new candidates of these five stellar stream. We tested the
robustness of our two approaches by means of extensive Monte Carlo
simulations.
Our methods are consistent with one another in more than 90% of cases
and for almost all the stellar kinematic groups under scrutiny. The
IC2391 supercluster is an exception. Applying our statistical methods
to a large sample of young low-mass stars, we confirmed almost all the
likely members and good candidates of these stellar streams. We also
proposed 39 additional candidates based on the agreement and the high
likelihood of age and kinematic membership.
These probabilistic methods are very powerful to reliably identify new
candidate members of young stellar kinematic groups. However, the
kinematic criteria alone are not sufficient to distinguish between
coeval stars that are evaporated from open clusters and other field
stars trapped by dynamical processes generated by galactic
perturbations. The identification of stars belonging to the remnant of
a past star-forming event can be possible with the help of additional
information, such as indicators of chromospheric activity, age proxies
(lithium abundance), and chemical composition.
Description:
The search for new members of close young associations and SKGs was
done earlier by using mainly qualitative methods, such as the
Eggen's criteria (Eggen 1958MNRAS.118...65E 1958MNRAS.118...65E, 1995AJ....110.2862E 1995AJ....110.2862E). To
gain in objectivity, we determine the membership by means of
probabilistic procedures using the kinematic properties of known SKG
members (Klutsch 2008, Ph.D. thesis, Observatoire de Strasbourg,
France; Klutsch et al. in Highlights of Spanish Astrophysics VI, eds.
M.R. Zapatero Osorio, J. Gorgas, J. Maiz Apellaniz, J. R. Pardo, &
A. Gil de Paz, p. 534). We tried different methods to handle kinematic
data, and we succeeded to develop two independent procedures (CES and
M2M) to be able to identify new candidates of five young MGs. We
widely used n-dimensional normal Gaussian distributions to determine
the kinematic membership probabilities of each stellar candidate
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 150 162 Kinematic properties of young low-mass stars and
their likelihood of membership in stellar
kinematic groups (SKG)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 27 A27 --- Name Source name
29 A1 --- n_Name [c] Young star without association (1)
31- 32 I2 h RAh Right ascension (J2000)
34- 35 I2 min RAm Right ascension (J2000)
37- 41 F5.2 s RAs Right ascension (J2000)
43 A1 --- DE- Declination sign (J2000)
44- 45 I2 deg DEd Declination (J2000)
47- 48 I2 arcmin DEm Declination (J2000)
50- 53 F4.1 arcsec DEs Declination (J2000)
55- 60 F6.2 km/s Uvel U space velocity
62- 67 F6.2 km/s Vvel V space velocity
69- 74 F6.2 km/s Wvel W space velocity
76- 77 I2 % PS12 ?=- Probability of kinematic match from S12
(Shkolnik et al., 2012ApJ...758...56S 2012ApJ...758...56S,
Cat. J/ApJ/758/56)
79- 80 I2 % P2D [0/99]?=- Probability of 2D kinematic match
82- 85 F4.1 % P3D [0/99]?=- Probability of 3D kinematic match
88- 95 A8 --- S12 Best kinematic group match from S12 criteria
97-104 A8 --- M2M Best kinematic group match from M2M method (2)
106-113 A8 --- CES Best kinematic group match from CES method (2)
115-122 A8 --- Egg Best kinematic group match from Eggen's criteria
124-126 A3 ---- Q1 [AB-] Match 3-criteria quality from S12 (A=best)
128-129 A2 ---- Q2 Match quality from our index (3)
131-132 A2 --- l_Age [∼ =>] Limit flag on Age
133-136 I4 Myr Age ?=- Stellar age or lower value if interval
from Shkolnik et al. (2009ApJ...699..649S 2009ApJ...699..649S,
Cat. J/ApJ/699/649)
137 A1 --- --- [-] indicates an age interval
138-141 I4 Myr Age2 ?=- Upper value of stellar age if interval
143-150 A8 --- SKG Likely SKG members/candidates (4)
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Note (1): c: Source younger than 300Myr that are located in the locus of the
young-disk population, but are associated to none of moving groups or
associations.
Note (2): Method used:
CES = continuous ellipsoidal shape
M2M = member-to-member
Note (3): Our membership index consists of two letters:
First letter = M2M membership category (as defined in Table 2):
G=Good; P=Possible; U=Unlikely
Second letter = CES membership: Y=yes, N=no
"--" flag = source classified as non-member by both our methods
Note (4): This denotes every source for which both likelihoods of membership
are larger than 10% and the age estimate is consistent with that of the best
kinematic (SKG) match. The 14 moving groups are: AB Dor, beta Pic, Carina,
Castor, ChaNear, Columba, Her-Lyr, Hyades, IC 2391, LA/IC, Pleiades, TWA,
Tuc-Hor, and UMa.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 22-Sep-2014