J/ApJ/802/60 Structure of young stellar clusters. II. (Kuhn+, 2015)
The spatial structure of young stellar clusters.
II. Total young stellar populations.
Kuhn M.A., Getman K.V., Feigelson E.D.
<Astrophys. J., 802, 60 (2015)>
=2015ApJ...802...60K 2015ApJ...802...60K
ADC_Keywords: YSOs ; Associations, stellar ; Molecular clouds ; H II regions
Keywords: infrared: stars; ISM: structure;
open clusters and associations: general; stars: formation
stars: pre-main sequence; X-rays: stars
Abstract:
We investigate the intrinsic stellar populations (estimated total
numbers of OB and pre-main-sequence stars down to 0.1M☉) that
are present in 17 massive star-forming regions (MSFRs) surveyed by the
MYStIX project. The study is based on the catalog of >31000 MYStIX
Probable Complex Members with both disk-bearing and disk-free
populations, compensating for extinction, nebulosity, and crowding
effects. Correction for observational sensitivities is made using the
X-ray luminosity function and the near-infrared initial mass function
--a correction that is often not made by infrared surveys of young
stars. The resulting maps of the projected structure of the young
stellar populations, in units of intrinsic stellar surface density,
allow direct comparison between different regions. Several regions
have multiple dense clumps, similar in size and density to the Orion
Nebula Cluster. The highest projected density of ∼34000 stars/pc2 is
found in the core of the RCW 38 cluster. Histograms of surface density
show different ranges of values in different regions, supporting the
conclusion of Bressert et al. (B10; 2010MNRAS.409L..54B 2010MNRAS.409L..54B) that no
universal surface-density threshold can distinguish between clustered
and distributed star formation. However, a large component of the
young stellar population of MSFRs resides in dense environments of
200-10000 stars/pc2 (including within the nearby Orion molecular
clouds), and we find that there is no evidence for the B10 conclusion
that such dense regions form an extreme "tail" of the distribution.
Tables of intrinsic populations for these regions are used in our
companion study of young cluster properties and evolution.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 74 142 Intrinsic population estimates from the X-ray
luminosity function (XLF) and
initial mass function (IMF)
fits.dat 77 17 Massive star-forming regions (MSFRs) FITS images
summary
fits/* . 2 Figures 3 and 5 of MSFRs FITS files
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See also:
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/other/JApA/34.393 : X-rays obs. in 8 young open star clusters (Bhatt+, 2013)
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/ApJ/768/99 : X-ray survey of YSOs in Orion A (Pillitteri+, 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/A+A/539/A74 : NGC1893 Chandra X-ray catalog (Caramazza+, 2012)
J/A+A/533/A121 : Missing low-mass stars in S254-S258 (Mucciarelli+, 2011)
J/ApJS/194/14 : A Pan-Carina YSO catalog (Povich+, 2011)
J/ApJS/194/12 : Trumpler 16 in the CCCP (Wolk+, 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/716/474 : The Rosette star-forming complex. III. (Wang+, 2010)
J/ApJ/713/871 : Star-forming region Cyg-OB2 sources from X-ray (Wright+, 2010)
J/ApJS/186/259 : Taurus Spitzer survey: new candidate members (Rebull+, 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/AJ/138/227 : Stellar clusters in NGC 6334 complex (Feigelson+, 2009)
J/ApJ/696/47 : Rosette star-forming complex with Chandra. II. (Wang+, 2009)
J/ApJ/677/401 : Xray properties of protostars in ONC (Prisinzano+, 2008)
J/ApJS/169/353 : Chandra sources in M17 (Broos+, 2007)
J/ApJS/168/100 : X-ray study of star-forming region NGC 6357 (Wang+, 2007)
J/ApJS/160/353 : Membership of the Orion nebula population (Getman+, 2005)
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 designation as
in Paper I (Kuhn+, 2014, J/ApJ/787/107)
12- 22 F11.7 deg RAdeg Right ascension in decimal degrees (J2000) (1)
24- 34 F11.7 deg DEdeg Declination in decimal degrees (J2000) (1)
36- 40 F5.2 arcmin amaj [0.07/61] Semimajor axis of subcluster;
4x core ellipse
42- 46 F5.2 arcmin bmin [0.07/13.1] Semiminor axis of subcluster;
4x core ellipse
48- 50 I3 deg PA Position angle of the subcluster;
East from North
52- 56 F5.2 [-] Nxlf [0.9/3.7]?=-9.99 Log intrinsic number of stars
inferred via XLF (2)
58- 62 F5.2 [-] e_Nxlf ?=-9.99 Uncertainty on Nxlf (3)
64- 68 F5.2 [-] Nimf [0.5/3.6]?=-9.99 Log intrinsic number of stars
inferred via initial mass function (IMF) (2)
70- 74 F5.2 [-] e_Nimf ?=-9.99 Uncertainty on Nimf (3)
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Note (1): Of subcluster center.
Note (2): Entries with values of -9.99 indicate missing data because the
subcluster has too few stars with good JH photometry to estimate a
mass-completeness limit and/or the IMF scaling.
XLF is the probability distribution of the total, absorption corrected
0.5-8.0keV X-ray luminosity (see section 2.1).
Note (3): Estimates of uncertainty include the N0.5 Poisson uncertainty, but
do not include the multiple sources of systematic error in the XLF
and IMF analysis.
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Byte-by-byte Description of file: fits.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- HDU [1/17] HDU "IMAGE" extension number
4- 10 A7 --- Name MYStIX region name
12- 14 I3 --- Nx [512] Number of pixels along X-axis (RA)
15 A1 --- --- [x]
16- 18 I3 --- Ny [362/815] Number of pixels along Y-axis (DE)
20- 28 F9.5 deg RAdeg Right ascension of center (J2000)
29- 37 F9.5 deg DEdeg Declination of center (J2000)
39- 43 F5.3 arcsec/pix Scale [0.9/7.5] Scale of the image
45- 60 A16 --- FileName1 FITS file of Fig.3 in subdirectory fits (1)
62- 77 A16 --- FileName2 FITS file of Fig.5 in subdirectory fits (2)
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Note (1): Figure 3 is the inferred fractional completeness of the MYStIX
Probable Complex Members (MPCM) catalogs in various regions. The
fraction of young stellar members that we expect to include in our
MPCM list at any point is indicated by the shading of the maps, with
dark shades indicating low detection fractions and light shades
indicating high detection fractions.
Note (2): Figure 5 shows intrinsic stellar surface density for the 17 MSFRs
regions. Observed surface densities for X-ray selected MPCMs are
calculated following the Ogata et al. (2003, Appl. Stat., 52, 499),
Ogata (2004, JGR, 109, 2004), adaptive-smoothing method and then
corrected to the intrinsic populations by dividing the observed
surface densities by the detection fraction maps. These maps can thus
be directly compared with each other.
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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 III. 2015ApJ...812..131K 2015ApJ...812..131K
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 23-Jul-2015