Maximum likelihood membership analysis of OB associations with Gaia
Leiden U, Leiden, NL
The OB associations in the Gould's Belt play a key role in the large
scale propagation of star formation in the solar vicinity, and in the
shaping and evolution of the interstellar medium (ISM). Ionizing
radiation, stellar winds and supernova explosions of massive stars
accelerate, sweep-up, and compress the ISM in an episodic fashion, to
form shells that may cool, collapse, fragment, and eventually give birth
to a new generation of stars.
To exactly quantify the impact of OB associations to the star formation processes, an accurate knowledge of their stellar membership, distances and kinematics is required, complemented by the astrophysical information obtained from photometric and spectroscopic data. With Gaia's highly accurate parallaxes and proper motions, we expect to make real breakthroughs in the study of OB associations, and Orion will be the region where most of the new discoveries will be made. Indeed, even though Orion is the best studied region of star formation in our Galaxy, the 3D structure of its stellar population is largely uncertain. Moreover, the likely presence of a foreground population suggests a more complex star formation scenario than previously thought.
In this contribution, we present the results of a maximum likelihood procedure that we used to carry on a membership estimation of a simulated young moving group of stars. With this method we will be able to determine the membership probability of the individual group stars to the moving group, and to estimate the space velocity and the internal velocity dispersion of the moving group itself. We plan to apply the method to the new data in Orion, with the aim to accurately characterize the distribution of young stellar populations toward this region. Moreover, thanks to its generality and versatility, the method can be applied to many other star forming regions.
C. Manara, ESTEC, NL
A. Brown, Leiden U, NL
J. de Bruijne, ESTEC, NL