J/MNRAS/472/3887 Kinematic data for stars in OB-associations (Melnik+, 2017)
Kinematics of OB-associations in Gaia epoch.
Melnik A.M., Dambis A.K.
<Mon. Not. R. Astron. Soc. 472, 3887 (2017)>
=2017MNRAS.472.3887M 2017MNRAS.472.3887M (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Associations, stellar ; Stars, OB ; Proper motions ;
Radial velocities ; Photometry
Keywords: Galaxy: kinematics and dynamics -
open clusters and associations: general -
open clusters and associations: individual: Per OB1, Car OB1 -
stars: formation
Abstract:
We use stellar proper motions from the catalog TGAS (2016, Cat. I/337)
to study the kinematics of OB-associations identified by Blaha and
Humphreys (1989AJ.....98.1598B 1989AJ.....98.1598B). The TGAS proper motions of
OB-associations generally agree well with the Hipparcos proper
motions. The parameters of the Galactic rotation curve obtained with
TGAS and Hipparcos proper motions agree within the errors. The average
internal velocity dispersion calculated for 18 OB-associations with
more than 10 TGAS stars is sigmav=3.9km/s, which is considerably
smaller, by a factor of 0.4, than the velocity dispersions derived
from Hipparcos data. The effective contribution from binary OB-stars
into the velocity dispersion sigma_v inside OB-associations is
sigmab=1.2km/s. The median virial and stellar masses of
OB-associations are equal to 7.1x105 and 9.0x103M☉,
respectively. Thus OB-associations must be unbound objects provided
they do not include a lot of dense gas. The median star-formation
efficiency is epsilon=2.1%. Nearly one third of stars of
OB-associations must lie outside their tidal radius. We found that the
Per OB1 and Car OB1 associations are expanding with the expansion
started in a small region of 11-27pc 7-10Myr ago. The average
expansion velocity is 6.3km/s.
Description:
Table 1 gives the coordinates and kinematic parameters for
OB-associations from the list by Blaha and Humphreys
(1989AJ.....98.1598B 1989AJ.....98.1598B). It presents the average Galactic coordinates l
and b, the average heliocentric distance r, the total number of stars
with known photometric measurements, Nt, used for determination of the
distance for an OB-association. The distance r is equal to the
distance from the catalog by Blaha and Humphreys, rBH, multiplied by
a factor of 0.8, r=0.8*rBH. Table 1 also lists the median
line-of-sight velocities Vr of OB-associations, the dispersions of
line-of-sight velocities, sigma_vr, and the number of stars with known
line-of-sight velocity nvr in an OB-association. The line-of-sight
velocities of individual stars were taken from the catalog by
Barbier-Brossat and Figon (1999, Cat. III/213). We used only the
velocities measured with errors of less than 10 km/s which corresponds
to the quality estimations A, B, C and D. We also present the median
proper motions of OB-associations along l- and b-coordinates, mul and
mub, derived from stellar proper motions taken from the catalog TGAS
(2016, Cat. I/337), the dispersions of proper motions, sigma_mul and
sigma_mub, as well as a number of stars, nmu, with known TGAS proper
motions.
Table 2 gives the spectral, photometric and kinematic data for stars
in OB-associations. It presents the name of a star, the name of the
OB-association to which it is assigned by Blaha and Humphreys (1989),
spectral type of the star, code of its luminosity class cL:
2 - Ia, 4 - Iab, 6 - Ib, 8 - II, 10 - III, 12 - IV, 14 - V, where the
corresponding odd numbers (1, 3,..., 13) reflect the uncertainty in
its determination. Table 2 also shows the Galactic coordinates l and b
of a star, the heliocentric distance r to its assigned OB-association,
the line-of-sight velocity of the star Vr, if available, and its error
evr taken from the catalog Barbier-Brossat and Figon (1999, Cat.
III/213). Table 2 gives the Hipparcos number HIP (1997, Cat. I/239) of
the star, TGAS proper motions, mul and mub, if available, and their
errors (2016, Cat. I/337). If a Hipparcos star is absent in the TGAS
catalog, then we give its Hipparcos proper motions and their errors
(1997, Cat. I/239); flag F indicates the source of proper motions: 'G'
means TGAS and 'H' - Hipparcos. Table 2 also presents color indexes
B-V and U-B, apparent and absolute magnitudes, mv and Mv, and the
V-band extinction, Av, adopted from the catalog by Blaha and Humphreys
(1989AJ.....98.1598B 1989AJ.....98.1598B).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 96 91 Kinematic parameters for 91 OB-associations
table2.dat 162 2227 Kinematic data for stars in OB-associations
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See also:
I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Ass Name of OB-associations from the list by BH
12- 17 F6.2 deg GLON Average Galactic Longitude
20- 25 F6.2 deg GLAT Average Galactic Latitude
29- 32 F4.2 kpc r Average Heliocentric distance
35- 37 I3 --- Nt Number of stars with known photometry
41- 45 F5.1 km/s HVR ? Median heliocentric Radial velocity
49- 52 F4.1 km/s s_HVR ? Dispersion of HVR
56- 57 I2 --- nvr Number of stars with known HVR
62- 66 F5.2 mas/yr pmGLON ? Median proper motion along Galactic Longitude
71- 74 F4.2 mas/yr s_pmGLON ? Dispersion of pmGLON
79- 83 F5.2 mas/yr pmGLAT ? Median proper motion along Galactic Latitude
88- 91 F4.2 mas/yr s_pmGLAT ? Dispersion of pmGLAT
95- 96 I2 --- nmu Number of stars with known TGAS proper motions
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 21 A21 --- Name Star name
24- 32 A9 --- Ass Name of OB-association
35- 38 A4 --- sp Spectral type of the star
41- 42 I2 --- cL Code of the luminosity class (1)
45- 49 F5.2 mag Vmag Apparent V magnitude of the star
52- 57 F6.2 deg GLON Galactic Longitude of the star, or of
the association
60- 65 F6.2 deg GLAT Galactic Latitude of the star, or of
the association
68- 71 F4.2 kpc r Heliocentric distance of the OB-association
74- 79 F6.1 km/s HVR ? Heliocentric radial velocity of the star
82- 85 F4.1 km/s e_HVR ? Error of HVR
89- 94 I6 --- HIP ? Hipparcos catalog number
98-104 F7.3 mas/yr pmGLON ? Proper motion along Galactic Longitide
106-111 F6.3 mas/yr e_pmGLON ? Error of pmGLON
115-121 F7.3 mas/yr pmGLAT ? Proper motion along Galactic Latitide
123-128 F6.3 mas/yr e_pmGLAT ? Error of pmGLAT
131 A1 --- F Source of proper motions (2)
135-139 F5.2 mag B-V Color index B-V of the star
143-147 F5.2 mag U-B ? Color index U-B of the star
151-155 F5.2 mag VMAG Absolute V magnitude of the star
159-162 F4.2 mag AV V-band extinction
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Note (1): Code of the luminosity class as follows:
2 = Ia
4 = Iab
6 = Ib
8 = II
10 = III
12 = IV
14 = V
Note (2): Source of proper motions as follows:
G = TGAS catalog
H = Hipparcos catalog
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Acknowledgements:
Anna Melnik, anna(at)sai.msu.ru
(End) Anna Melnik [SAI, Russia], Patricia Vannier [CDS] 12-Oct-2017