J/MNRAS/400/518 Velocity and proper motion of OB associations (Melnik+, 2009)
Kinematics of OB associations and new reduction of the Hipparcos data.
Melnik A.M., Dambis A.K.
<Mon. Not. R. Astron. Soc. 400, 518 (2009)>
=2009MNRAS.400..518M 2009MNRAS.400..518M
ADC_Keywords: Clusters, open ; Associations, stellar ; Radial velocities ;
Proper motions
Keywords: Galaxy: kinematics and dynamics -
Galaxy: open clusters and associations
Abstract:
The proper motions of OB-associations computed using the old (1997,
Cat. I/239) and new (2008, Cat. I/311) reductions of the Hipparcos
data are in a good agreement with each other. The Galactic rotation
curve derived from the analysis of line-of-sight velocities and proper
motions of OB-associations is almost flat in the 3-kpc neighborhood of
the Sun. The angular rotation velocity at the solar distance is
Omega0=31(±1)km/s/kpc. The standard deviation of the velocities of
OB-associations from the rotation curve is sigma=7.2km/s. The distance
scale for OB associations by Blaha and Humpreys (1989AJ.....98.1598B 1989AJ.....98.1598B)
should be shortened by 10-20%. The residual velocities of
OB-associations calculated for the new and old reductions differ, on
average, by 3.5km/s. The mean residual velocities of OB-associations
in the stellar-gas complexes depend slightly on the data reduction
employed.
Description:
For every OB-association from the list by Blaha and Humphreys
(1989AJ.....98.1598B 1989AJ.....98.1598B) we give the mean galactic coordinates l and b,
the mean heliocentric distance r, median line-of-sight velocity Vr,
the dispersion of line-of-sight velocities dvr, and number of stars
with known line-of-sight velocity nvr. The line-of-sight velocities
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 10km/s which corresponds to the quality
estimations A, B, and C. We also present median proper motions of
OB-associations along l- and b- coordinates, mul and mub. The data
obtained for the old reduction (1997, Cat. I/239) are denoted by
the subscript 1, whereas those based on the reduction by van Leewen
(2008, Cat. I/311) are marked by the subscript 2. For each OB
association we represent the dispersions of proper motions, dml and
dmb, as well as a number of stars nmu with known proper motion. The
last column shows the total number of stars with known photometric
measurements, Nt, used for determination of the distances for
OB-associations. The distances r correspond to the short distance
scale for classical Cepheids. They are equal to the distances from the
catalog by Blaha and Humphreys (1989AJ.....98.1598B 1989AJ.....98.1598B), rBH,
multiplied by a factor of 0.8, r=0.8*rBH.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 85 91 Kinematic parameters for 91 OB-associations
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See also:
I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)
I/311 : Hipparcos, the New Reduction (van Leeuwen, 2007)
J/AJ/117/354 : OB associations from Hipparcos (de Zeeuw+, 1999)
J/PAZh/21/13 : New list of OB associations (Melnik+, 1995)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Names of OB-associations from BH list,
Blaha & Humpreys, 1989AJ.....98.1598B 1989AJ.....98.1598B
11- 15 F5.1 deg GLon Mean galactic longitude of the association
17- 21 F5.1 deg GLat Mean galactic latitude of the association
23- 25 F3.1 kpc r Mean heliocentric distance of the association
27- 31 F5.1 km/s RV ? Median line-of-sight velocity
33- 36 F4.1 km/s dRV ? Dispersion of line-of-sight velocities
38- 39 I2 --- o_RV Number of stars with known line-of-sight
velocity
41- 45 F5.1 mas/yr pmGLon1 ? Median proper motion along l-direction,
old reduction
47- 49 F3.1 mas/yr dpmGLon1 ? Dispersion of pmGLon1
51- 54 F4.1 mas/yr pmGLat1 ? Median proper motion along b-direction,
old reduction
56- 58 F3.1 mas/yr dpmGLat1 ? Dispersion of pmGLat1
60- 64 F5.1 mas/yr pmGLon2 ? Median proper motion along l-direction,
new reduction
66- 68 F3.1 mas/yr dpmGLon2 ? Dispersion of pmGLon2
70- 74 F5.1 mas/yr pmGLat2 ? Median proper motion along b-direction,
new reduction
76- 78 F3.1 mas/yr dpmGLat2 ? Dispersion of pmGLat2
80- 81 I2 --- o_pm Number of stars with known proper motions
83- 85 I3 --- Nt Number of stars with known photometry
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Acknowledgements:
Anna Melnik, anna(at)sai.msu.ru
(End) Anna Melnik [SAI, Russia], Patricia Vannier [CDS] 19-Nov-2009