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The Formation of a Stellar Association in the NGC 7000/IC 5070 Complex: Results from Kinematic Analysis of Stars and Gas

Kuhn, Michael A. and Hillenbrand, Lynne A. and Carpenter, John M. and Avelar Menendez, Angel Rodrigo (2020) The Formation of a Stellar Association in the NGC 7000/IC 5070 Complex: Results from Kinematic Analysis of Stars and Gas. Astrophysical Journal, 899 (2). Art. No. 128. ISSN 1538-4357. https://resolver.caltech.edu/CaltechAUTHORS:20200624-072323808

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Abstract

We examine the clustering and kinematics of young stellar objects (YSOs) in the North America/Pelican Nebulae, as revealed by Gaia astrometry, in relation to the structure and motions of the molecular gas, as indicated in molecular-line maps. The Gaia parallaxes and proper motions allow us to significantly refine previously published lists of YSOs, demonstrating that many of the objects previously thought to form a distributed population turn out to be nonmembers. The members are subdivided into at least six spatio-kinematic groups, each of which is associated with its own molecular cloud component or components. Three of the groups are expanding, with velocity gradients of 0.3–0.5 km s⁻¹ pc⁻¹, up to maximum velocities of ~8 km s⁻¹ away from the groups' centers. The two known O-type stars associated with the region, 2MASS J20555125+4352246 and HD 199579, are rapidly escaping one of these groups, following the same position–velocity relation as the low-mass stars. We calculate that a combination of gas expulsion and tidal forces from the clumpy distribution of molecular gas could impart the observed velocity gradients within the groups. However, on a global scale, the relative motions of the groups do not appear either divergent or convergent. The velocity dispersion of the whole system is consistent with the kinetic energy gained due to gravitational collapse of the complex. Most of the stellar population has ages similar to the freefall timescales for the natal clouds. Thus, we suggest the nearly freefall collapse of a turbulent molecular cloud as the most likely scenario for star formation in this complex.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/aba19aDOIArticle
https://arxiv.org/abs/2006.08622arXivDiscussion Paper
ORCID:
AuthorORCID
Kuhn, Michael A.0000-0002-0631-7514
Carpenter, John M.0000-0003-2251-0602
Additional Information:© 2020 The American Astronomical Society. Received 2020 May 6; revised 2020 June 15; accepted 2020 June 24; published 2020 August 20. We thank Min Fang for expert advice about the NAP region, Kevin Fogarty and Michael Grudić for helpful discussions, and the anonymous referee for useful comments. Development of YSO Corral was supported by NASA Award NNX17AF41G. A.R.A.M. was supported by Caltech's Freshman Summer Research Institute (FSRI). Facilities: FCRAO - Five College Radio Astronomy Observatory's Telescope, Gaia - , Keck:I (HIRES) - . Software: astropy (Astropy Collaboration et al. 2013, 2018), BUGS (Lunn et al. 2009), class (Venables & Ripley 2002), JAGS (Plummer 2017), mclust (Scrucca et al. 2016), numpy (van der Walt et al. 2011), pandas (McKinney 2010; Pandas Development Team 2020), postgres (PostgreSQL development team 2020), R (R Core Team 2018), rjags (Plummer 2019), SAOImage DS9 (Joye & Mandel 2003), scipy (Virtanen et al. 2020), scikit-learn (Pedregosa et al. 2012), TOPCAT (Taylor 2005).
Group:Astronomy Department
Funders:
Funding AgencyGrant Number
NASANNX17AF41G
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Subject Keywords:Star formation ; Star forming regions ; Stellar associations ; Stellar kinematics ; Space astrometry ; Young stellar objects ; T Tauri stars ; Giant molecular clouds ; Millimeter astronomy ; OB stars
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Star formation (1569); Star forming regions (1565); Stellar associations (1582); Stellar kinematics (1608); Space astrometry (1541); Young stellar objects (1834); T Tauri stars (1681); Giant molecular clouds (653)
Record Number:CaltechAUTHORS:20200624-072323808
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200624-072323808
Official Citation:Michael A. Kuhn et al 2020 ApJ 899 128
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103977
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:24 Jun 2020 14:35
Last Modified:24 Aug 2020 16:44

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