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RCW38YSO - RCW 38 Young Stellar Objects Catalog

HEASARC
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Overview

This table contains some of the results from a study of the structure of the high-mass star-forming region RCW 38 and the spatial distribution of its young stellar population. Spitzer Infrared Array Camera (IRAC) photometry (3-8 micron) is combined with Two Micron All Sky Survey (2MASS) near-IR data to identify young stellar objects (YSOs) by IR-excess emission from their circumstellar material. Chandra X-ray data are used to identify class III pre-main-sequence stars lacking circumstellar material. The authors identify 624 YSOs: 23 class 0/I and 90 flat spectrum (FS) protostars, 437 class II stars, and 74 class III stars. They also identify 29 (27 new) O star candidates over the IRAC field. Seventy-two stars exhibit IR-variability, including 7 class 0/I and 12 flat spectrum YSOs. A further 177 tentative candidates are identified by their location in the IRAC [3.6] versus [3.6]-[5.8] color-magnitude diagram. The authors find strong evidence of subclustering in the region. Three subclusters were identified surrounding the central cluster, with massive and variable stars in each subcluster. The central region shows evidence of distinct spatial distributions of the protostars and pre-main-sequence stars. A previously detected IR cluster, DB2001_Obj36, has been established as a subcluster of RCW 38. This suggests that star formation in RCW 38 occurs over a more extended area than previously thought. The gas-to-dust ratio is examined using the X-ray derived hydrogen column density, NH and the K-band extinction, and found to be consistent with the diffuse interstellar medium, in contrast with Serpens and NGC 1333. The authors posit that the high photoionizing flux of massive stars in RCW 38 affects the agglomeration of the dust grains.

This table contains the list of 624 young stellar objects (given in Tables 3 and 4 of the reference paper) found among the Spitzer sources in the field of RCW 38 using the two selection techniques described in Section 3 of the reference paper: (1) selection of stars with IR excesses in IR color-color diagrams, and (2) identification of X-ray luminous YSOs by comparing X-ray sources with IR detections. The latter technique was used to identify Type III YSOs lacking emission from a dusty disk. This table does NOT contain (i) the 177 candidate YSOs listed in Table 5 of the reference paper which were identified using the [3.6] versus [3.6] - [5.8] color-magnitude diagram, since contamination removal methods could not be utilized for these objects, (ii) the 24 candidate variable YSOs listed in Table 6 of the reference paper, nor (iii) 21 of the 29 candidate O-star cluster members which were listed in table 7 of the reference paper.


Catalog Bibcode

2011ApJ...743..166W

References

The Structure of the Star-forming Cluster RCW 38
    Winston E., Wolk S.J., Bourke T.L., Megeath S.T., Gutermuth R.,
    Spitzbart B.
   <Astrophys. J., 743, 166 (2011)>
   =2011ApJ...743..166W

Provenance

This table was created by the HEASARC in January 2012 based on an electronic version of Tables 3 and 4 from the reference paper which were obtained from the ApJ web site.

Parameters

Spitzer_Source_Number
A unique sequential identification number for each Spitzer source.

Name
The name for the young stellar object. This was created by the HEASARC using the '[WWB2011]' prefix (for Winston, Wolk, Bourke 2011) and the source number value, in the style recommended by the Dictionary of Nomenclature of Celestial Objects, e.g., '[WWB2011] 72'.

RA
The Right Ascension of the young stellar object in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.01 seconds of time in the original reference.

Dec
The Declination of the young stellar object in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.01 arcseconds in the original reference.

LII
The Galactic Longitude of the young stellar object.

BII
The Galactic Latitude of the young stellar object.

Epoch_ID
The Spitzer IRAC observation epoch identifier, as described in Table 1 of the reference paper, reproduced below:

  Epoch ID   Date           Int. Time      R.A.(J2000) Dec.(J2000)   Coverage
                                (s)                                   (arcmin)

    1   2006.06.05 05:53:33     12         8:58:59.7    -47:26:37.6   ~30 x 30
    2   2006.06.05 06:58:53      2         8:59:25.9    -47:32:34.8   ~15 x 15
    3   2007.02.21 19:42:03     12         8:59:05.7    -47:30:43.6   ~30 x 30
    4   2007.02.21 20:45:35      2         8:59:05.9    -47:30:38.7   ~15 x 15
  

Yso_Type
The YSO classification using the standard scheme:

  YSO Type   Meaning

  0/I        Class 0/I YSO (protostar)
  FS         Flat spectrum YSO
  II         Class II YSO (classic T Tauri star with dusty disk)
  III        Class III YSO (weak-lined T Tauri star lacking dusty disk)
  

Source_Flags
This parameter flags various source properties, as follows:

  Flag       Meaning

  X          X-Ray source
  v          Variable source
  o          O star candidate
  

Jmag
The 2MASS J-band magnitude of the young stellar object.

Jmag_Error
The uncertainty in the 2MASS J-band magnitude of the YSO.

Hmag
The 2MASS H-band magnitude of the young stellar object.

Hmag_Error
The uncertainty in the 2MASS H-band magnitude of the YSO.

Kmag
The 2MASS Ks-band magnitude of the young stellar object.

Kmag_Error
The uncertainty in the 2MASS Ks-band magnitude of the YSO.

IRAC_3p6_um_Mag
The Spitzer/IRAC 3.6-micron band magnitude of the YSO.

IRAC_3p6_um_Mag_Error
The uncertainty in the Spitzer/IRAC 3.6-micron band magnitude of the YSO.

IRAC_4p5_um_Mag
The Spitzer/IRAC 4.5-micron Band Magnitude of the YSO.

IRAC_4p5_um_Mag_Error
The uncertainty in the Spitzer/IRAC 4.5-micron band magnitude of the YSO.

IRAC_5p8_um_Mag
The Spitzer/IRAC 5.8-micron Band Magnitude of the YSO.

IRAC_5p8_um_Mag_Error
The uncertainty in the Spitzer/IRAC 5.8-micron band magnitude of the YSO.

IRAC_8p0_um_Mag
The Spitzer/IRAC 8.0-micron Band Magnitude of the YSO.

IRAC_8p0_um_Mag_Error
The uncertainty in the Spitzer/IRAC 8.0-micron band magnitude of the YSO.

IRAC_Spectral_Index
The spectral index of the IRAC data for the YSO, alphaIRAC = d[log(lambda*Flambda)]/d[log(lambda)]. The conversion from magnitudes to fluxes in W cm-2 s-1 used the following zero fluxes for the J, H, K_s, [3.6], [4.5], [5.8], and [8.0] bands, respectively: 3.13 x 10-13, 1.13 x 10-13, 4.28 x 10-14, 6.57 x 10-15, 2.65 x 10-15, 1.03 x 10-15, 3.02 x 10-16. The slope was calculated by a least-squares fit over the available IRAC bands.

Kmag_Extinction
The Ks band extinction of the YSO, in magnitudes.

Class
The HEASARC Browse object classification of the YSO, based on the value of the yso_type parameter.


Contact Person

Questions regarding the RCW38YSO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 10-Jan-2012