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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
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)
    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) 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), rBH,
    multiplied by a factor of 0.8, r=0.8*rBH.

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table1.dat        85       91   Kinematic parameters for 91 OB-associations


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

   Bytes Format Units   Label     Explanations

   1-  9  A9    ---     Name      Names of OB-associations from BH list,
                                   Blaha & Humpreys, 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


Acknowledgements:
    Anna Melnik, anna(at)sai.msu.ru
(End)           Anna Melnik [SAI, Russia], Patricia Vannier [CDS]    19-Nov-2009