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Kinematics in Young Star Clusters and Associations with Gaia DR2

Kuhn, Michael A. and Hillenbrand, Lynne A. and Sills, Alison and Feigelson, Eric D. and Getman, Konstantin V. (2019) Kinematics in Young Star Clusters and Associations with Gaia DR2. Astrophysical Journal, 870 (1). Art. No. 32. ISSN 1538-4357. doi:10.3847/1538-4357/aaef8c.

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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 σ_(1D) = 1 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Kuhn, Michael A.0000-0002-0631-7514
Sills, Alison0000-0003-3551-5090
Feigelson, Eric D.0000-0002-5077-6734
Getman, Konstantin V.0000-0002-6137-8280
Additional Information:© 2019. The American Astronomical Society. Received 2018 July 5; revised 2018 November 4; accepted 2018 November 5; published 2019 January 2. We thank Alberto Krone-Martins and Lennart Lindegren for expert advice on Gaia, Floor van Leeuwen for advice about astrometry, and Fred Adams, Michael Grudić, and Anushree Sengupta for useful feedback on the article. We would also like to thank the referee for helpful comments. E.D.F. and K.V.G. are supported by NASA grant NNX15AF42G and Chandra grants AR7-18002X, GO7-18001X, and G06-17015x, and the Chandra ACIS Team contract SV474018 (G. Garmire & L. Townsley, principal investigators) issued by the Chandra X-ray Center under contract NAS8-03060. Facility: Gaia. - Software: astro (Kelvin 2014), celestial (Robotham 2016), MVN (Korkmaz et al. 2014), R (R Core Team 2018), relaimpo (Grömping 2006), spatstat (Baddeley & Turner 2005), TOPCAT (Taylor 2005).
Group:Astronomy Department
Funding AgencyGrant Number
Subject Keywords:astrometry; open clusters and associations: general; stars: formation; stars: kinematics and dynamics
Issue or Number:1
Record Number:CaltechAUTHORS:20190102-155136487
Persistent URL:
Official Citation:Michael A. Kuhn et al 2019 ApJ 870 32
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92000
Deposited By: George Porter
Deposited On:03 Jan 2019 16:14
Last Modified:16 Nov 2021 03:46

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