Internal motions in OB-associations with Gaia DR2

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 sigma_v =4.5 km s-1. The median virial and stellar masses of OB-associations are M_vir=8.9 x 10^5 and M_st=8.1 x 10^3 Ms, respectively. The median star-formation efficiency in parent giant molecular clouds appears to be epsilon=1.2 per cent. 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 +\- 1.7 km s-1.

14 pages, 7 figures, accepted for publication in MNRAS

References in corpus (10)

• The Gaia mission
• Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes
• A comprehensive set of simulations studying the influence of gas expulsion on star cluster evolution
• Gaia Data Release 1: Catalogue validation
• The Global Evolution of Giant Molecular Clouds. I: Model Formulation and Quasi-Equilibrium Behavior
• The Tycho-Gaia astrometric solution. How to get 2.5 million parallaxes with less than one year of Gaia data
• Filamentary Accretion Flows in the Infrared Dark Cloud G14.225-0.506 Revealed by ALMA
• Not all stars form in clusters - measuring the kinematics of OB associations with $Gaia$
• Kinematics of OB-associations in Gaia epoch
• Galactic resonance rings. Modelling of motions in the wide solar neighborhood

Cited by in corpus (21)

• OB associations and their origins
• A Census of the Stellar Populations in the Sco-Cen Complex
• The Formation of a Stellar Association in the NGC 7000/IC 5070 Complex: Results from Kinematic Analysis of Stars and Gas
• The Age of the Carina Young Association and Potential Membership of HD 95086
• The formation of clusters and OB associations in different density spiral arm environments
• Canis Major OB1 stellar groups contents revealed by Gaia
• Mapping the distribution of OB stars and associations in Auriga
• The Great Dimming of the hypergiant star RW Cephei: CHARA Array images and spectral analysis
• Distance scale for high-luminosity stars in OB associations and in field with Gaia DR2. Spurious systematic motions
• Search for OB associations in {\sl Gaia} early Data Release 3
• The origin of the high-mass X-ray binary 4U 2206+54/BD +53 2790
• Investigating the metallicity dependence of the mass-loss rate relation of red supergiants
• Extreme mass ratios and fast rotation in three massive binaries
• HD 60431, the CP2 star with the shortest rotational period -- Physical parameters and period analysis
• The $\text{Gaia}$ view of the Cepheus OB2 association
• The extended population associated with W40
• Peculiarities of Open Star Clusters with High Vertical Velocities from the Region of the Sco-Cen OB Association
• Magnetic fields and young stellar objects in cometary cloud LDN 1616
• Painting a Family Portrait of the Yellow Super- and Hypergiants in the Milky Way I. Constraining the Distances and Luminosities
• The stellar population in the SARAO MeerKAT Galactic Plane Survey
• Spatial distribution and clustering properties of the young stellar populations in the Carina Nebula complex and Car OB1