Kinematics in Young Star Clusters and Associations with Gaia DR2

By M. Kuhn, L. Hillenbrand, A. Sills, Eric D. Feigelson, Konstantin Getman. Astrophysical Journal, 2018

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The Gaia mission has opened a new window into the internal kinematics of young star clusters at the sub-km s−1 level, with implications for our understanding of how star clusters form and evolve. We use a sample of 28 clusters and associations with ages from ∼1–5 Myr, where lists of members are available from previous X-ray, optical, and infrared studies. Proper motions from Gaia DR2 reveal that at least 75% of these systems are expanding; however, rotation is only detected in one system. Typical expansion velocities are on the order of ∼0.5 km s−1, and in several systems, there is a positive radial gradient in expansion velocity. Systems that are still embedded in molecular clouds are less likely to be expanding than those that are partially or fully revealed. One-dimensional velocity dispersions, which range from to 3 km s−1, imply that most of the stellar systems in our sample are supervirial and that some are unbound. In star-forming regions that contain multiple clusters or subclusters, we find no evidence that these groups are coalescing, implying that hierarchical cluster assembly, if it occurs, must happen rapidly during the embedded stage.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/ff109c949dcad75685b2176bdfdd84abe250a33c

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In Astronomy and Astrophysics

Citations in the corpus

Clusters and mirages: cataloguing stellar aggregates in the Milky Way (2019, background): “Photometric and astrometric studies of young clusters reveal clues about stellar formation processes (Jensen & Haugbølle 2018; Kuhn et al. 2019), while old objects hold fossil information about the past of our Galaxy (e.g. Phelps et al. 1994; Bragaglia & Tosi 2006; Sestito et al. 2008; Hayes et al.…”
Global hierarchical collapse in molecular clouds. Towards a comprehensive scenario (2019, background): “Then they quote Ward & Kruijssen (2018), Kuhn et al. (2019), and Kounkel et al. (2018) as examples that Gaia shows no such radial motions in Orion and other complexes, again concluding that the observations contradict the GHC scenario.”