J/ApJ/787/107 Spatial structure of young stellar clusters. I. (Kuhn+, 2014)
The spatial structure of young stellar clusters.
I. Subclusters.
Kuhn M.A., Feigelson E.D., Getman K.V., Baddeley A.J., Broos P.S.,
Sills A., Bate M.R., Povich M.S., Luhman K.L., Busk H.A., Naylor T.,
King R.R.
<Astrophys. J., 787, 107 (2014)>
=2014ApJ...787..107K 2014ApJ...787..107K
ADC_Keywords: Associations, stellar ; H II regions ; Molecular clouds ;
Infrared sources ; X-ray sources
Keywords: H II regions; ISM: structure; methods: statistical;
open clusters and associations: general; stars: formation;
stars: pre-main sequence
Abstract:
The clusters of young stars in massive star-forming regions show a
wide range of sizes, morphologies, and numbers of stars. Their highly
subclustered structures are revealed by the MYStIX project's sample of
31754 young stars in nearby sites of star formation (regions at
distances <3.6kpc that contain at least one O-type star.) In 17 of the
regions surveyed by MYStIX, we identify subclusters of young stars
using finite mixture models --collections of isothermal ellipsoids
that model individual subclusters. Maximum likelihood estimation is
used to estimate the model parameters, and the Akaike Information
Criterion is used to determine the number of subclusters. This
procedure often successfully finds famous subclusters, such as the
BN/KL complex behind the Orion Nebula Cluster and the KW-object
complex in M17. A catalog of 142 subclusters is presented, with 1-20
subclusters per region. The subcluster core radius distribution for
this sample is peaked at 0.17pc with a standard deviation of 0.43dex,
and subcluster core radius is negatively correlated with gas/dust
absorption of the stars --a possible age effect. Based on the
morphological arrangements of subclusters, we identify four classes of
spatial structure: long chains of subclusters, clumpy structures,
isolated clusters with a core-halo structure, and isolated clusters
well fit by a single isothermal ellipsoid.
Description:
The regions included in this study, listed in Table 1, are nearby
sites of high-mass star formation that are included in the MYStIX
sample (Feigelson et al. 2013ApJS..209...26F 2013ApJS..209...26F).
These regions are covered in the near-IR by the UKIRT Infrared Deep
Sky Survey (King et al. 2013, J/ApJS/209/28) or Two-Micron All Sky
Survey (Skrutskie et al. 2006, VII/233), in the mid-IR by Spitzer IRAC
observations (Kuhn et al. 2013, J/ApJS/209/29), and in the X-ray by
the ACIS-I array on the Chandra X-Ray Observatory in the 0.5-8.0keV
band (Kuhn et al. 2013, J/ApJS/209/27; Townsley et al. 2014,
J/ApJS/213/1). Other sources to produce multiwavelength catalogs are
described in section 2. The multiwavelength point-source catalogs are
combined with a list of spectroscopic OB stars from the literature,
and sources are classified probabilistically to obtain a list of
MYStIX Probable Complex Members (MPCMs) (Broos et al. 2013,
J/ApJS/209/32).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 55 17 *MYStIX targets for subcluster analysis
table2.dat 64 142 MYStIX subcluster properties
table3.dat 77 27647 Membership of MYStIX subclusters
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Note on table1.dat: Properties of star-forming regions and statistics of the
MYStIX Probable Complex Member (MPCM) sample used here. See Broos et al.
(2013, J/ApJS/209/32) and associated MYStIX technical papers for details on
the sample definitions and selection.
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See also:
J/ApJ/802/60 : Structure or young stellar clusters. II. (Kuhn+, 2015)
J/ApJS/213/1 : The MSFRs Omnibus X-ray Catalog (MOXC) (Townsley+, 2014)
J/ApJS/209/32 : Probable young stars in the MYStIX project (Broos+, 2013)
J/ApJS/209/31 : The MYStIX IR-Excess Source catalog (MIRES) (Povich+, 2013)
J/ApJS/209/30 : MYStIX project: Bayesian matching (Naylor+, 2013)
J/ApJS/209/29 : MYStIX: Mid-IR observations and catalogs (Kuhn+, 2013)
J/ApJS/209/28 : MYStIX Wide-Field NIR data: crowded fields (King+, 2013)
J/ApJS/209/27 : MYStIX: the Chandra X-ray sources (Kuhn+, 2013)
J/AJ/144/192 : Spitzer survey of Orion A & B. I. YSO catalog (Megeath+, 2012)
J/MNRAS/426/2917 : X-rays sources in Trumpler 37 (Getman+, 2012)
J/ApJS/194/14 : A Pan-Carina YSO catalog (Povich+, 2011)
J/ApJS/194/11 : Chandra study of Trumpler 15 in Carina (Wang+, 2011)
J/ApJS/194/9 : X-ray star clusters in the Carina complex (Feigelson+, 2011)
J/ApJS/194/2 : Chandra Carina Complex Project (CCCP) catalog (Broos+, 2011)
J/ApJ/725/2485 : X-rays from the star-forming complex W40 (Kuhn+, 2010)
J/ApJ/708/1760 : Flux estimations of faint X-ray sources (Getman+, 2010)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/ApJ/699/1454 : YSOs around Cepheus B (Getman+, 2009)
J/AJ/138/227 : Stellar clusters in NGC 6334 complex (Feigelson+, 2009)
J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)
J/ApJ/676/1109 : Velocities of stars in ONC (Furesz+, 2008)
J/ApJ/675/464 : Chandra observations of NGC 2244 (Wang+, 2008)
J/A+A/476/199 : Trumpler 14 JHKL' photometry (Ascenso+, 2007)
J/A+A/468/353 : XMM-Newton Extended Survey of Taurus (Guedel+, 2007)
J/ApJ/641/389 : Millimetric observations of IRDC cores (Rathborne+, 2006)
J/ApJS/160/319 : COUP: observations and source lists (Getman+, 2005)
J/AJ/128/1254 : VLT 3.8µm Trapezium catalog (Lada+, 2004)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Reg Massive star-forming region (MSFR) name
15- 19 F5.3 kpc Dist [0.4/3.6] Distance to region used in MYStIX
analysis (Feigelson et al. 2013ApJS..209...26F 2013ApJS..209...26F)
21- 25 F5.2 ph/s/cm2 logFX [-6.8/-5.9] Apparent 0.5-8.0keV X-ray photon flux
limit imposed for spatial uniformity
27- 30 I4 --- Ns [246/2790] Total number of stars used in analysis
32- 33 I2 % Nsp [38/96] Percentage of all MPCMs
35- 38 I4 --- Nx [174/2043] Number of X-ray stars
40- 42 I3 --- Nir [49/815] Number of MYStIX InfraRed Excess (MIRES)
stars
44- 46 I3 --- Nob [1/134] Number of OB stars
48- 55 A8 --- MSFR MYStIX region name as in tables 2 and 3;
column added by CDS
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- MSFR MYStIX region name
10 A1 --- m_MSFR Subcluster assignment (G1)
12- 13 I2 h RAh Hour of right ascension (J2000) (1)
15- 16 I2 min RAm Minute of right ascension (J2000)
18- 21 F4.1 s RAs Second of right ascension (J2000)
23 A1 --- DE- Sign of declination (J2000) (1)
24- 25 I2 deg DEd Degree of declination (J2000) (1)
27- 28 I2 arcmin DEm Arcminute of declination (J2000)
30- 31 I2 arcsec DEs Arcsecond of declination (J2000)
33- 37 F5.2 pc amaj [0.01/10.2] Semimajor axis of the ellipsoid
core region
39- 42 F4.2 pc bmin [0.01/2.1] Semiminor axis of the ellipsoid
core region
44- 47 F4.2 --- ell [0/0.9] Ellipticity
49- 51 I3 deg PA [0/248] Orientation angle of the ellipse;
east from north
53- 55 I3 --- Ns [2/834] Number of stars (2)
57- 60 F4.2 mag J-H [0.6/3] J-H color index as measure of
absorption
62- 64 F3.1 keV Emed [1/4.4] Median X-ray median energy as a
measure of absorption
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Note (1): Celestial coordinates (J2000) for the ellipsoid center.
Note (2): Number of stars estimated by integrating the model component out
to four times the size of the core.
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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- 18 A18 --- MCPM MYStIX source name (HHMMSS.ss+DDMMSS.s; J2000) (1)
20- 30 F11.7 deg RAdeg Right Ascension in decimal degrees (J2000)
32- 42 F11.7 deg DEdeg Declination in decimal degrees (J2000)
44 I1 --- X [0/1] X-ray selection? (2)
46 I1 --- IR [0/1] IR-excess selected? (2)
48 I1 --- OB [0/1] OB star? (2)
50- 54 F5.2 keV ME [0.5/7.6]?=-9.99 Median 0.5-8.0keV band X-ray
energy
56- 60 F5.2 mag J-H [-2.1/7.5]?=-9.99 J-H color index
62- 66 F5.2 [10-7W] LXtc [27.4/33.6]?=-9.99 The 0.5-8.0kev band X-ray
luminosity (erg/s)
68- 75 A8 --- MSFR MYStIX region name
77 A1 --- m_MSFR Subcluster assignment (G1)
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Note (1): MYStIX Probable Complex Member (MPCM) designation
(Broos et al. 2013, J/ApJS/209/32).
Note (2):
1 = the source meets this criteria for inclusion in the "flattened"
MPCM sample;
0 = the source does not meet this criteria for inclusion in the
"flattened" MPCM sample.
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Global notes:
Note (G1): Subcluster assignment:
* Letters "A"-"T" give the subcluster assignments for particular
MYStIX Probable Complex Members (MPCMs). Component name are labeled
from east to west.
* The letter "U" indicates that this MPCM is part of the unclustered
population, while the letter "X" indicates that assignment is
uncertain for this object.
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History:
From electronic version of the journal
References:
Kuhn et al. Paper II. 2015ApJ...802...60K 2015ApJ...802...60K Cat. J/ApJ/802/60
Kuhn et al. Paper III. 2015ApJ...812..131K 2015ApJ...812..131K
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 23-Jul-2015