J/ApJ/870/32 Kinematics in young star clusters & associations (Kuhn+, 2019)
Kinematics in young star clusters and associations with Gaia DR2.
Kuhn M.A., Hillenbrand L.A., Sills A., Feigelson E.D., Getman K.V.
<Astrophys. J., 870, 32 (2019)>
=2019ApJ...870...32K 2019ApJ...870...32K
ADC_Keywords: Clusters, open; Associations, stellar; H II regions;
Proper motions; Velocity dispersion; Radial velocities;
Parallaxes, trigonometric
Keywords: astrometry; open clusters and associations: general; stars: formation;
stars: kinematics and dynamics
Abstract:
The Gaia mission has opened a new window into the internal kinematics
of young star clusters at the sub-km/s 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 ∼1-5Myr, 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
∼0.5km/s, 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 σ1D=1 to 3km/s, 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.
Description:
This Gaia study is based on samples of YSOs, with typical ages of
1-5Myr, from the Massive Young Star-forming Complex Study in Infrared
and X-ray survey (MYStIX; Broos+ 2013, J/ApJS/209/32 and
Feigelson+ 2013ApJS..209...26F 2013ApJS..209...26F the Star Formation in Nearby Clouds
study (SFiNCs; Getman+ 2017, J/ApJS/229/28), and a similar study of
NGC 6231 (Kuhn+ 2017, J/AJ/154/87).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 97 33 Cluster/association sample
table3.dat 73 19 Velocity dispersions in select clusters
table5.dat 54 26 Radial velocities of clusters
fig16.dat 32 28 Data behind Figure 16
refs.dat 55 15 References
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See also:
B/ocl : Optically visible open clusters and Candidates (Dias+ 2002-2015)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
VII/50 : CO Radial Velocities Toward Galactic H II Regions (Blitz+ 1982)
J/A+A/171/261 : RRLs of Southern HII Regions (Caswell+ 1987)
J/MNRAS/341/805 : UBVI CCD photometry of Cep OB3b (Pozzo+, 2003)
J/PASJ/56/313 : 13CO survey of Mon & CMa molecular clouds (Kim+, 2004)
J/A+A/437/467 : VLT-FLAMES survey of massive stars (Evans+, 2005)
J/A+A/438/1163 : Catalogue of Open Cluster Data (COCD) (Kharchenko+, 2005)
J/ApJ/648/1090 : Radial velocities of NGC 2264 stars (Furesz+, 2006)
J/AJ/131/2114 : Radial velocities in Fornax dSph (Walker+, 2006)
J/ApJ/676/1109 : Vel. of stars in the Orion Nebula Cluster (Furesz+, 2008)
J/ApJ/697/1103 : Kinematics of Orion Nebula Cluster (Tobin+, 2009)
J/ApJS/209/27 : the Chandra X-ray sources (Kuhn et al., 2013)
J/ApJS/209/28 : Wide-Field near-IR data in crowded fields (King et al., 2013)
J/ApJS/209/29 : Mid-IR observations and catalogs (Kuhn et al., 2013)
J/ApJS/209/30 : MYStIX project: Bayesian matching (Naylor+, 2013)
J/ApJS/209/31 : The MYStIX IR-Excess Source catalog (MIRES) (Povich+, 2013)
J/ApJS/209/32 : Probable young stars in the MYStIX project (Broos+, 2013)
J/ApJ/787/107 : Spatial structure of young stellar clusters. I. (Kuhn+, 2014)
J/ApJ/787/108 : Ages for massive SFR stellar populations (Getman+, 2014)
J/ApJ/807/27 : IN-SYNC. III. RVs of IC348 stars (Cottaar+, 2015)
J/ApJ/799/136 : IN-SYNC. II. Cand. young stars in NGC 1333 (Foster+, 2015)
J/ApJ/812/131 : Spatial structure of stellar clusters. III. (Kuhn+, 2015)
J/ApJ/802/60 : Structure of young stellar clusters. II. (Kuhn+, 2015)
J/A+A/596/A82 : X-ray study of the young cluster NGC6231 (Damiani+, 2016)
J/ApJ/821/8 : Spectroscopic binary pop. of ONC and NGC2264 (Kounkel+, 2016)
J/MNRAS/461/794 : Scorpius-Centaurus K-Type Stars (Pecaut+, 2016)
J/MNRAS/460/2593 : Cygnus OB2 DANCe: Proper motion study (Wright+, 2016)
J/ApJS/229/28 : SFiNCs: X-ray, IR and membership catalogs (Getman+, 2017)
J/ApJ/834/142 : Gould's Belt Distances Survey. II. OMC (Kounkel+, 2017)
J/AJ/154/87 : Stellar pop. of the young star cluster NGC 6231 (Kuhn+, 2017)
J/A+A/616/A12 : Gaia DR2 sources in GC and dSph (Gaia Collaboration+, 2018)
J/MNRAS/477/L50 : Structure of the Upper Scorpius association (Galli+, 2018)
J/AJ/156/84 : APOGEE-2 survey of Orion Complex. II. (Kounkel+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Complex Large star-forming complex including several
regions
10- 23 A14 --- Reg Region name
25- 26 I2 h RAh System center hour of right ascension (J2000)
28- 29 I2 min RAm System center minute of right ascension (J2000)
31- 35 F5.2 s RAs System center second of right ascension (J2000)
37 A1 --- DE- System center sign of declination (J2000)
38- 39 I2 deg DEd System center degree of declination (J2000)
41- 42 I2 arcmin DEm System center arcminute of declination (J2000)
44- 47 F4.1 arcsec DEs System center arcsecond of declination (J2000)
49- 52 I4 --- Ns [29/1285] Number of stars used in
the analysis for this system
54- 58 F5.2 mas/yr pmRA [-7/7.3] Proper motion of the system
center in RA
60- 63 F4.2 mas/yr e_pmRA [0.07/0.3] pmRA uncertainty
65- 69 F5.2 mas/yr pmDE [-9.7/3] Proper motion of the system
center in DE
71- 74 F4.2 mas/yr e_pmDE [0.07/0.5] pmDE uncertainty
76- 79 F4.2 mas Plx [0.2/3.4] Parallax of the system center
81- 84 F4.2 mas e_Plx [0.04/0.06] Plx uncertainty
86- 89 I4 pc Dist [296/3790] Distance
91- 93 I3 pc e_Dist [5/510] Negative error on Dist
95- 97 I3 pc E_Dist [5/700] Positive error on Dist
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Reg System name
16- 18 I3 --- Ns [11/278] Number of stars used to calculate
velocity dispersions
20- 22 F3.1 km/s Sig1D [0.8/2.8] Characteristic one-dimensional
velocity dispersion
24- 26 F3.1 km/s e_Sig1D [0.1/0.5] Sig1D uncertainty
28- 30 F3.1 km/s Sigpc1 [0.9/3.4] Velocity dispersion in the first
principal component for the two-dimensional
velocity model
32- 34 F3.1 km/s e_Sigpc1 [0.1/0.7] Sigpc1 uncertainty
36- 38 F3.1 km/s Sigpc2 [0.7/2.2] Velocity dispersion in the second
principal component for the two-dimensional
velocity model
40- 42 F3.1 km/s e_Sigpc2 [0.1/0.7] Sigpc2 uncertainty
44- 46 F3.1 --- Spc1/pc2 [1/2] Ratio of velocity dispersions in the
first and second velocity principal
components (a measure of overall velocity
anisotropy)
48- 50 F3.1 --- e_Spc1/pc2 [0.1/0.9] Spc1/pc2 uncertainty
52- 54 I3 deg PA [5/179] Position angle (east from north) of
the semimajor axis of the velocity dispersion
56- 57 I2 % Nout [9/23]? Fraction of stars belonging to
the second component of the mixture model (1)
58 A1 --- u_Nout Uncertainty flag on Nout
60- 61 I2 % e_Nout [4/17]? Nout uncertainty
63- 66 F4.1 km/s Sigout [2/13]? Velocity dispersion for the second
component of the mixture model (1)
68- 73 F6.1 --- DelBIC [-106/5.4]? Change in the Bayesian Information
Criterion (BIC) when the second component
was added (1)
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Note (1): These three columns were only used when a multiple component velocity
model was required.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Reg Region name
15 A1 --- n_Reg Flag on Reg (1)
17- 18 I2 --- Set [0/12] Number of members with Gaia
RV measurements
20- 25 F6.2 km/s RVgaia [-28.7/35.6]? Median RV (barycentric)
26 A1 --- u_RVgaia Uncertainty flag on RVgaia
28- 32 F5.2 km/s e_RVgaia [0.9/10]? RVgaia uncertainty
34- 54 A21 km/s RVlit RV measurements from the literature
(barycentric) (2)
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Note (1): Flag as follows:
a = Orion A cloud
c = Carina
Note (2): Measurements for cloud gas are marked with an asterisk.
See refs.dat file for the references.
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Byte-by-byte Description of file: fig16.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Reg Designation of the stellar system
16- 19 F4.2 [Msun] Mass [2.1/4.2] Log of mass of the stellar system
21- 24 F4.2 [Myr] Age [5.8/6.6] Log of median age of the stellar system
26- 30 F5.2 [pc] Rad [-0.5/0.6] Log of half-mass radius of
the stellar system
32 A1 --- Emb Flag indicating whether a stellar system
is embedded, partially embedded, or revealed (1)
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Note (1): Flag as follows:
E = The stellar system is embedded in its natal molecular cloud;
P = The stellar system is partially embedded in its molecular cloud;
R = The system is revealed.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1 A1 --- Ref Reference code
3- 21 A19 --- BibCode Bibcode of the reference
23- 39 A17 --- Aut First author's name(s)
41- 55 A15 --- Comm VizieR catalog reference
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Feb-2020