J/MNRAS/454/593 Young moving groups in solar neighbourhood (Bell+, 2015)
A self-consistent, absolute isochronal age scale for young moving groups in
the solar neighbourhood.
Bell C.P.M., Mamajek E.E., Naylor T.
<Mon. Not. R. Astron. Soc., 454, 593-614 (2015)>
=2015MNRAS.454..593B 2015MNRAS.454..593B (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; Stars, nearby ; Photometry ;
Stars, distances
Keywords: techniques: photometric - stars: evolution -
Hertzsprung-Russell and colour-magnitude diagrams -
stars: pre-main-sequence - open clusters and associations: general -
solar neighbourhood
Abstract:
We present a self-consistent, absolute isochronal age scale for young
(≲200Myr), nearby (≲100pc) moving groups in the solar neighbourhood
based on homogeneous fitting of semi-empirical pre-main-sequence model
isochrones using the τ2 maximum-likelihood fitting statistic of
Naylor & Jeffries (2006MNRAS.373.1251N 2006MNRAS.373.1251N) in the MV, V-J
colour-magnitude diagram. The final adopted ages for the groups are as
follows: 149+51-19Myr for the AB Dor moving group, 24±3Myr for
the β Pic moving group (BPMG), 45+11-7Myr for the Carina
association, 42+6-4Myr for the Columba association, 11±3Myr for
the η Cha cluster, 45±4Myr for the Tucana-Horologium moving
group (Tuc-Hor), 10±3Myr for the TW Hya association and
22+4-3Myr for the 32 Ori group. At this stage we are uncomfortable
assigning a final, unambiguous age to the Argus association as our
membership list for the association appears to suffer from a high
level of contamination, and therefore it remains unclear whether these
stars represent a single population of coeval stars. Our isochronal
ages for both the BPMG and Tuc-Hor are consistent with recent lithium
depletion boundary (LDB) ages, which unlike isochronal ages, are
relatively insensitive to the choice of low-mass evolutionary models.
This consistency between the isochronal and LDB ages instils
confidence that our self-consistent, absolute age scale for young,
nearby moving groups is robust, and hence we suggest that these ages
be adopted for future studies of these groups. Software implementing
the methods described in this study is available from
http://www.astro.ex.ac.uk/people/timn/tau-squared/.
Description:
We focus on the following young (≲200Myr), nearby (≲100pc) moving
groups: the AB Dor moving group, Argus association, BPMG, Carina
association, Columba association, η Cha cluster, Tuc-Hor, TWA, and
32 Ori group. Assigning members to young moving groups is typically
based on a combination of kinematic diagnostics (e.g. proper motions,
radial velocities, etc.) in conjunction with youth indicators such
as Hα and X-ray emission, and Li absorption. Having established
a list of members and high-probability candidate members (hereafter
simply referred to together as 'members') for each group, we then
compile broadband photometric measurements and assign distances to
these stars so that we can then place them in a CMD before fitting
with model isochrones.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 128 526 VJ photometry, spectral types and distances for
member stars in our sample of young moving groups
refs.dat 161 79 References
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- Star Star name
25 A1 --- n_Star [*] Note on Star (1)
27- 28 A2 --- Group Group (2)
34- 44 A11 --- SpType MK spectral type
46- 50 A5 --- r_SpType Reference fop SpType in refs.dat file
52- 57 F6.3 mag Vmag V magnitude
61- 65 F5.3 mag e_Vmag rms uncertainty on Vmag
69- 70 I2 --- r_Vmag Reference for Vmag in refs.dat file
73- 78 F6.3 mag V-J V-J colour index, J-band photometry from
2MASS PSC unless otherwise stated
79 A1 --- n_V-J [bc] Note on V-J (3)
82- 86 F5.3 mag e_V-J rms uncertainty on V-J
90- 95 F6.3 pc Dist Distance
96 A1 --- n_Dist [d] Note on Dist (3)
98-103 F6.3 pc e_Dist rms uncertainty on Dist
107-108 I2 --- r_Dist Reference for Dist in refs.dat file
111-116 F6.3 mag VMAG Absolute V magnitude
120-124 F5.3 mag e_VMAG rms uncertainty on VMAG
128 A1 --- Memb [Y/N-] Membership flag (4)
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Note (1): * denotes double or multiple star with unresolved spectral type.
Note (2): Groups as follows:
AB = AB Dor moving group
Ar = Argus
BP = BPMG
Ca = Carina
Co = Columba
EC = eta Cha cluster
TH = Tuc-Hor
TW = TWA
32 = 32 Ori
Note (3): Notes on V-J and Dist as follows:
b = V-J colour estimated from the B-V colour due to poor 2MASS PSC
photometry (see Section 2.2)
c = V-J colour estimated from the V-Ks colour due to poor J-band 2MASS PSC
photometry (see Section 2.2)
d = Distance based on the weighted average of stars within the group with
trigonometric distances (see Section 2.3)
Note (4): indicates whether the given star has a position in CMD space which is
commensurate with group membership based on the best-fitting model as
calculated using the tau2 fitting statistic (see Section 4.2 for details).
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference number
4- 23 A20 --- BibCode BibCode
24- 42 A19 --- Aut Author's name
44-161 A118 --- Com Comments
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 24-Jun-2016