J/ApJ/812/131 Spatial structure of young stellar clusters. III. (Kuhn+, 2015)
The spatial structure of young stellar clusters.
III. Physical properties and evolutionary states.
Kuhn M.A., Feigelson E.D., Getman K.V., Sills A., Bate M.R., Borissova J.
<Astrophys. J., 812, 131 (2015)>
=2015ApJ...812..131K 2015ApJ...812..131K (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; Clusters, open ; H II regions
Keywords: infrared: stars - ISM: structure - methods: statistical -
open clusters and associations: general - stars: formation -
stars: pre-main sequence - X-rays: stars
Abstract:
We analyze the physical properties of stellar clusters that are
detected in massive star-forming regions in the MYStIX project
- a comparative, multiwavelength study of young stellar clusters within
3.6 kpc that contain at least one O-type star. Tabulated properties of
subclusters in these regions include physical sizes and shapes,
intrinsic numbers of stars, absorptions by the molecular clouds, and
median subcluster ages. Physical signs of dynamical evolution are
present in the relations of these properties, including statistically
significant correlations between subcluster size, central density, and
age, which are likely the result of cluster expansion after gas
removal. We argue that many of the subclusters identified in Paper I
(Kuhn et al. 2014, J/ApJ/787/107) are gravitationally bound because
their radii are significantly less than what would be expected from
freely expanding clumps of stars with a typical initial stellar
velocity dispersion of ∼3 km/s for star-forming regions. We explore a
model for cluster formation in which structurally simpler clusters are
built up hierarchically through the mergers of subclusters - subcluster
mergers are indicated by an inverse relation between the numbers of
stars in a subcluster and their central densities (also seen as a
density versus radius relation that is less steep than would be
expected from pure expansion). We discuss implications of these
effects for the dynamical relaxation of young stellar clusters.
Description:
This paper uses the Paper I (Kuhn et al. 2014, J/ApJ/787/107) catalog
of 142 subclusters of young stars in 17 MYStIX star-forming regions.
These subclusters were found and characterized using the stars in the
MYStIX Probable Complex Member (MPCM) catalogs from Broos et al.
(2013, J/ApJS/209/32). The multiwavelength data analysis efforts that
went into this catalog are described by Feigelson et al. (2013,
J/ApJS/209/26), King et al. (2013, J/ApJS/209/28), Kuhn et al. (2013,
J/ApJS/209/27; 2013, J/ApJS/209/29), Naylor et al. (2013, J/ApJS/209/30),
Povich et al. (2013, J/ApJS/209/31), and Townsley et al. (2014,
J/ApJS/213/1), which provided uniform data coverage across the
17 star-forming regions investigated here, including the most
comprehensive and reliable lists of young stars in many of the nearest
MSFRs.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
sources.dat 60 17 MYStIX targets for subcluster analysis
(from J/ApJ/787/107)
table1.dat 67 141 Intrinsic Subcluster Properties
table6.dat 53 142 Dynamical Subcluster Properties
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See also:
J/AJ/138/227 : Stellar clusters in NGC 6334 complex (Feigelson+, 2009)
J/ApJ/725/2485 : X-rays from the star-forming complex W40 (Kuhn+, 2010)
J/ApJS/194/2 : Chandra Carina Complex Project (CCCP) catalog (Broos+, 2011)
J/ApJS/194/9 : X-ray star clusters in the Carina complex (Feigelson+, 2011)
J/AJ/144/192 : Spitzer survey of Orion A & B. I. YSO catalog (Megeath+, 2012)
J/ApJ/787/107 : Spatial structure of young stellar clusters. I. (Kuhn+, 2014)
J/ApJS/213/1 : The MSFRs Omnibus X-ray Catalog (MOXC) (Townsley+, 2014)
J/ApJS/209/27 : MYStIX: the Chandra X-ray sources (Kuhn+, 2013)
J/ApJS/209/28 : MYStIX Wide-Field NIR data: crowded fields (King+, 2013)
J/ApJS/209/29 : MYStIX: Mid-IR observations and catalogs (Kuhn+, 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/802/60 : Structure of young stellar clusters. II. (Kuhn+, 2015)
Byte-by-byte Description of file: sources.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Reg Massive star-forming region (MSFR) name
17- 21 F5.3 kpc Dist [0.4/3.6] Distance to region used in MYStIX
analysis (Feigelson et al. 2013ApJS..209...26F 2013ApJS..209...26F)
23- 27 F5.2 ph/s/cm2 logFX [-6.8/-5.9] Apparent 0.5-8.0keV X-ray photon flux
limit imposed for spatial uniformity
29- 32 I4 --- Ns [246/2790] Total number of stars used in analysis
34- 35 I2 % Nsp [38/96] Percentage of all MPCMs
37- 40 I4 --- Nx [174/2043] Number of X-ray stars
42- 44 I3 --- Nir [49/815] Number of MYStIX InfraRed Excess (MIRES)
stars
46- 48 I3 --- Nob [1/134] Number of OB stars
50- 57 A8 --- MSFR MYStIX region name as in tables 1 and 6;
column added by CDS
59- 60 I2 --- N [1/20] Number of subcluster(s) in this region
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Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- MSFR MYStIX region name
10 A1 --- m_MSFR Subcluster designation as in Paper I
(Kuhn+, 2014, J/ApJ/787/107) (G1)
12- 17 A6 --- Class Morphological classification
19- 23 F5.2 [pc] logr4 Log of fiducial subcluster radius (=4rc)
25 A1 --- l_logN4 [>] Limit flag on logN4
26- 29 F4.2 --- logN4 ? Log of number of stars within four core radii
30 A1 --- u_logN4 [:] Uncertainty flag on logN4
31 A1 --- n_logN4 [+] Note on logN4 (1)
33 A1 --- l_logEps0 [>] Limit flag on logEps0
34- 37 F4.2 [pc-2] logEps0 ? Log of central surface density (stars/pc2)
38 A1 --- u_logEps0 [:] Uncertainty flag on logEps0
39 A1 --- n_logEps0 [+] Note on logEps0
41 A1 --- l_logrho0 [>] Limit flag on logrho0
42- 45 F4.2 [pc-3] logrho0 ? Log of estimated central volumetric density
(stars/pc3)
46 A1 --- u_logrho0 [:] Uncertainty flag on logrho0
47 A1 --- n_logrho0 [+] Note on logrho0
49- 52 F4.2 --- Ell Subcluster ellipticity
54- 57 F4.2 mag J-H J-H NIR absorption index
59- 62 F4.2 keV ME X-ray median energy absorption indicator
64- 67 F4.2 [yr] logAge ? Log of median age
--------------------------------------------------------------------------------
Note (1): Note as follows:
+ = Not explained in this paper.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- MSFR MYStIX region name
10 A1 --- m_MSFR Subcluster designation as in Paper I
(Kuhn+, 2014, J/ApJ/787/107) (G1)
12- 15 F4.2 [yr] logtff ? Log of free-fall time for the subcluster
(stellar mass only)
17- 21 F5.2 [km/s] logsig ? Log of mean velocity dispersion for stars
within four core radii assuming that the
subcluster is virialized
23- 26 F4.2 [yr] logtcr1 Log of subcluster crossing time assuming
a velocity dispersion of 3.0 km/s
28- 31 F4.2 [yr] logtcr2 ? Log of subcluster crossing time assuming
a virial velocity dispersion
33- 36 F4.2 [yr] logtrel1 ? Log of dynamical relaxation time assuming
a velocity dispersion of 3.0 km/s
38- 41 F4.2 [yr] logtrel2 ? Log of dynamical relaxation time assuming
a virial velocity dispersion
43- 47 F5.2 [yr] logNrel1 ? Log of subcluster dynamical age in relaxation
time
49- 53 F5.2 [yr] logNrel2 ? Log of subcluster dynamical age in relaxation
time
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Global notes:
Note (G1): Letters "A"-"T" give the subcluster assignments for particular MYStIX
Probable Complex Members (MPCMs). Component name are labeled from
east to west.
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History:
From electronic version of the journal
References:
Kuhn et al. Paper I 2014ApJ...787..107K 2014ApJ...787..107K, Cat. J/ApJ/787/107
Kuhn et al. Paper II 2015ApJ...802...60K 2015ApJ...802...60K, Cat. J/ApJ/802/60
(End) Prepared by Tiphaine Pouvreau [CDS] 05-Oct-2017