J/MNRAS/493/2339 Internal motions in OB-associations (Melnik+, 2020)
Internal motions in OB-associations with Gaia DR2.
Melnik A.M., Dambis A.K.
<Mon. Not. R. Astron. Soc. 493, 2339 (2020)>
=2020MNRAS.493.2339M 2020MNRAS.493.2339M (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Associations, stellar ; Stars, OB ; Proper motions ;
Radial velocities ; Photometry
Keywords: Galaxy: open clusters and associations: general -
kinematics and dynamics - stars: formation
Abstract:
We study the motions inside 28 OB-associations with the use of Gaia
DR2 proper motions. The average velocity dispersion calculated for 28
OB-associations including more than 20 stars with Gaia DR2 proper
motion is sigmav=4.5km/s. The median virial and stellar masses of
OB-associations are 8.9x105 and 8.1x103M☉, respectively. The
median star-formation efficiency in parent giant molecular clouds
appears to be epsilon=1.2%. Gaia DR2 proper motions confirm the
expansion in the Per OB1, Car OB1 and Sgr OB1 associations found
earlier with Gaia DR1 data. We also detect the expansion in Gem OB1,
Ori OB1 and Sco OB1 associations which became possible for the first
time now when analyzed with Gaia DR2 proper motions. The analysis of
the distribution of OB-stars in the Per OB1 association shows the
presence of a shell-like structure with the radius of 40 pc. Probably,
the expansion of the Per OB1 association started with the velocity
greater than the present-day expansion velocity equal to
5.0±1.7km/s.
Description:
Table 1 lists 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
(1989AJ.....98.1598B 1989AJ.....98.1598B), 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. It also gives the
heliocentric distance to the OB-association by Blaha and Humphreys
(1989AJ.....98.1598B 1989AJ.....98.1598B), rBH, reduced to the short distance
scale, r=0.8 rBH. Table 1 also lists Gaia DR2 data (2018, Cat.
I/345/gaia2) (2018A&A...616A...1G 2018A&A...616A...1G): the equatorial coordinates of the
star, its Galactic coordinates, the G-band magnitude, the parallax,
proper motions along the l- and b-directions and their errors. It also
presents the number of visibility periods, Nvis of the star, (Arenou
et al. 2018A&A...616A..17A 2018A&A...616A..17A), and the re-normalised unit weight error
(RUWE), which measures how well the Gaia observations agree with the
five-parameter single-star model and whose large value (RUWE>1.4)
could indicate an astrometric binary (Lindegren 2018, Gaia technical
note GAIA-C3-TN-LU-LL-124). We also added to Table 1 the stellar
line-of-sight velocities, Vr, and their errors, e_Vr, taken from the
catalog Barbier-Brossat and Figon (1999, Cat. III/213), which are
available for 52% of stars of OB-associations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 208 2209 Kinematic data for stars in OB-associations
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See also:
I/345 : Gaia DR2 (Gaia, 2018)
III/213 : General Catalog of mean radial velocities (Barbier-Brossat+, 2000)
J/MNRAS/472/3887 : Kinematic data for stars in OB-associations (Melnik+, 2017)
Byte-by-byte Description of file: table1.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 the OB-association
35- 38 A4 --- SpType Spectral type of the star
41- 42 I2 --- LClass Code of the luminosity class (1)
45- 49 F5.2 mag Vmag Apparent V-band magnitude of the star
53- 56 F4.2 kpc r Heliocentric distance of the OB-association
59- 75 F17.13 deg RAdeg ? Barycentric right ascension (ICRS)
at Ep=2015.5 (ra) (Gaia DR2)
78- 94 F17.13 deg DEdeg ? Barycentric declination (ICRS)
at Ep=2015.5 (dec) (Gaia DR2)
98-103 F6.3 mag Gmag ? G-band mean magnitude of the star (Gaia DR2)
106-114 F9.5 deg GLON ? Galactic Longitude of the star
117-125 F9.5 deg GLAT ? Galactic Latitude of the star
128-135 F8.4 mas Plx ? Absolute stellar parallax (Gaia DR2)
138-143 F6.4 mas e_Plx ? Standard error of parallax (Gaia DR2)
148-154 F7.3 mas/yr pmGLON ? Proper motion along Galactic Longitide
158-162 F5.3 mas/yr e_pmGLON ? Error of pmGLON
167-173 F7.3 mas/yr pmGLAT ? Proper motion along Galactic Latitide
177-181 F5.3 mas/yr e_pmGLAT ? Error of pmGLAT
184-189 F6.1 km/s HVR ? Heliocentric radial velocity of the star
192-195 F4.1 km/s e_HVR ? Error of HVR
199-200 I2 --- Nvis ? Number of visibility periods
202-208 F7.3 --- RUWE ? Re-normalised unit weight error
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Note (1): Code of the luminosity class:
2 = Ia
4 = Iab
6 = Ib
8 = II
10 = III
12 = IV
14 = V
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Acknowledgements:
Anna Melnik, anna(at)sai.msu.ru
(End) Anna Melnik [SAI, Russia], Patricia Vannier [CDS] 25-Mar-2020