J/ApJ/743/166 X-ray and infra-red study of RCW 38 (Winston+, 2011)
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 2011ApJ...743..166W
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Photometry, infrared ;
X-ray sources
Keywords: infrared: stars - stars: formation - stars: massive -
stars: pre-main sequence - X-rays: stars
Abstract:
We present 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 (3-8um) is
combined with Two Micron All Sky Survey 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. We identify
624 YSOs: 23 class 0/I and 90 flat spectrum protostars, 437 class II
stars, and 74 class III stars. We 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. We find
strong evidence of subclustering in the region.
Description:
We have obtained observations of the RCW 38 region with the Spitzer
IRAC in 4 wavelength bands: 3.6, 4.5, 5.8, and 8.0um at different
epochs as part of PID 20127 (2006 June 5 and 2007 February 21).
This photometry was supplemented by J-, H-, and K-band photometry from
the Two Micron All Sky Survey (2MASS) point-source catalog (Skrutskie
et al., 2006, Cat. VII/233).
We observed the RCW 38 cluster on two occasions with the Multiband
Imaging Photometer for Spitzer. The observations were taken as part of
PID 20127. Epochs are 2006 March 3 and 2006 June 18).
This paper utilizes the previous Chandra observations of RCW 38, first
presented in Wolk et al. (2006, Cat. J/AJ/132/1100) and now available
on the ANCHORS archive (AN archive of Chandra Observations of Regions
of Star formation, http://cxc.harvard.edu/ANCHORS/).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 89 536 RCW 38: Chandra X-ray source photometry
table3.dat 38 624 Astrometry in RCW 38
table4.dat 116 624 Photometry in RCW 38
table5.dat 106 178 Photometry of the candidate YSOs in RCW 38
(with [3.6] versus [3.6-5.8])
table6.dat 139 24 Astrometry and photometry of candidate
variable YSOs in RCW 38
table7.dat 135 29 Astrometry and photometry of candidate
O-type stars in RCW 38
table8.dat 135 3 Astrometry and photometry of stars associated
with 24um emission in RCW 38
--------------------------------------------------------------------------------
See also:
J/AJ/132/1100 : X-ray and IR sources in RCW 38 (Wolk+, 2006)
J/AJ/138/33 : VLT JHKs imaging of RCW 38 (Derose+, 2009)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- IDX [1/536] Chandra identification number
5 I1 h RAh Hour of Right Ascension (J2000)
7- 8 I2 min RAm Minute of Right Ascension (J2000)
10- 14 F5.2 s RAs Second of Right Ascension (J2000)
16 A1 --- DE- Sign of the Declination (J2000)
17- 18 I2 deg DEd Degree of Declination (J2000)
20- 21 I2 arcmin DEm Arcminute of Declination (J2000)
23- 27 F5.2 arcsec DEs Arcsecond of Declination (J2000)
29- 34 F6.1 ct/s RCts Raw counts
36- 41 F6.1 ct/s NCts Net counts (1)
43- 48 F6.2 10+22/cm2 NH ? HI column density
50- 54 F5.2 10+22/cm2 e_NH ? Uncertainty in NH
56- 60 F5.2 keV kT ? Energy
62- 66 F5.2 keV e_kT ? Uncertainty in kT
68- 75 E8.6 mW/m2 Fabs ? Absorbed flux; in erg/cm2/s
77- 84 E8.6 mW/m2 Ftot ? Total unabsorbed flux; in erg/cm2/s
86- 89 F4.2 --- chi2 ? Model χ2
--------------------------------------------------------------------------------
Note (1): Background subtracted and aperture corrected from raw counts.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Class YSO class (G1)
5- 7 I3 --- ID [1/814] Spitzer identifier
9 I1 --- Ep [1/4] Epoch identifier
11 I1 h RAh Hour of Right Ascension (J2000)
13- 14 I2 min RAm Minute of Right Ascension (J2000)
16- 20 F5.2 s RAs Second of Right Ascension (J2000)
22 A1 --- DE- Sign of the Declination (J2000)
23- 24 I2 deg DEd Degree of Declination (J2000)
26- 27 I2 arcmin DEm Arcminute of Declination (J2000)
29- 33 F5.2 arcsec DEs Arcsecond of Declination (J2000)
35- 38 A4 --- Note X-ray and/or variable source (2)
--------------------------------------------------------------------------------
Note (2): X-ray and/or variable source flag as follows:
x = Chandra X-ray detection
v = Candidate variable
o = An O-star candidate
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- Type YSO type
20- 22 I3 --- ID [1/814] Spitzer identifier
24 I1 --- Ep [1/4] Epoch identifier
27- 31 F5.2 mag Jmag ? 2MASS J band magnitude
33- 36 F4.2 mag e_Jmag ? Uncertainty in Jmag
38- 42 F5.2 mag Hmag ? 2MASS H band magnitude
44- 47 F4.2 mag e_Hmag ? Uncertainty in Hmag
49- 53 F5.2 mag Kmag ? 2MASS Ks band magnitude
55- 58 F4.2 mag e_Kmag ? Uncertainty in Kmag
60- 64 F5.2 mag [3.6] ? Spitzer/IRAC 3.6 micron band magnitude
66- 69 F4.2 mag e_[3.6] ? Uncertainty in [3.6]
71- 75 F5.2 mag [4.5] ? Spitzer/IRAC 4.5 micron band magnitude
77- 80 F4.2 mag e_[4.5] ? Uncertainty in [4.5]
82- 86 F5.2 mag [5.8] ? Spitzer/IRAC 5.8 micron band magnitude
88- 91 F4.2 mag e_[5.8] ? Uncertainty in [5.8]
93- 99 F7.2 mag [8.0] ? Spitzer/IRAC 8.0 micron band magnitude
101-105 F5.2 mag e_[8.0] ? Uncertainty in [8.0]
107-111 F5.2 --- alpha ? Spectral index of the IRAC band data
113-116 F4.2 mag AK ? The Ks band extinction
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [605/802] Spitzer identifier
5 I1 --- Ep [1/4] Epoch identifier
7 I1 h RAh Right ascension (J2000)
9- 10 I2 min RAm Right ascension (J2000)
12- 16 F5.2 s RAs Right ascension (J2000)
18 A1 --- DE- Declination sign (J2000)
19- 20 I2 deg DEd Declination (J2000)
22- 23 I2 arcmin DEm Declination (J2000)
25- 29 F5.2 arcsec DEs Declination (J2000)
31- 35 F5.2 mag Jmag ?=- 2MASS J magnitude
37- 40 F4.2 mag e_Jmag ?=- rms uncertainty on Jmag
42- 46 F5.2 mag Hmag ?=- 2MASS H magnitude
48- 51 F4.2 mag e_Hmag ?=- rms uncertainty on Hmag
53- 57 F5.2 mag Kmag ?=- 2MASS Ks magnitude
59- 62 F4.2 mag e_Kmag ?=- rms uncertainty on Kmag
64- 68 F5.2 mag [3.6] ?=- Spitzer/IRAC 3.6um magnitude
70- 73 F4.2 mag e_[3.6] ?=- rms uncertainty on [3.6]
75- 79 F5.2 mag [4.5] ?=- Spitzer/IRAC 4.5um magnitude
81- 84 F4.2 mag e_[4.5] ?=- rms uncertainty on [4.5]
86- 90 F5.2 mag [5.8] ?=- Spitzer/IRAC 5.8um magnitude
92- 95 F4.2 mag e_[5.8] ?=- rms uncertainty on [5.8]
97-101 F5.2 mag [8.0] ?=- Spitzer/IRAC 8.0um magnitude
103-106 F4.2 mag e_[8.0] ?=- rms uncertainty on [8.0]
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat table7.dat table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Spitzer identifier (1)
10 I1 --- Ep [1/4] Epoch identifier
12 I1 h RAh Right ascension (J2000)
14- 15 I2 min RAm Right ascension (J2000)
17- 22 F6.3 s RAs Right ascension (J2000)
23 A1 --- DE- Declination sign (J2000)
24- 25 I2 deg DEd Declination (J2000)
27- 28 I2 arcmin DEm Declination (J2000)
30- 33 F4.1 arcsec DEs Declination (J2000)
35- 40 F6.3 mag Jmag ?=- 2MASS J magnitude
42- 47 F6.4 mag e_Jmag ?=- rms uncertainty on Jmag
49- 54 F6.3 mag Hmag ?=- 2MASS H magnitude
56- 60 F5.3 mag e_Hmag ?=- rms uncertainty on Hmag
62- 68 F7.4 mag Kmag ?=- 2MASS Ks magnitude
70- 74 F5.3 mag e_Kmag ?=- rms uncertainty on Kmag
76- 82 F7.4 mag [3.6] ?=- Spitzer/IRAC 3.6um magnitude
84- 89 F6.4 mag e_[3.6] ?=- rms uncertainty on [3.6]
91- 96 F6.3 mag [4.5] ?=- Spitzer/IRAC 4.5um magnitude
98-102 F5.3 mag e_[4.5] ?=- rms uncertainty on [4.5]
104-109 F6.3 mag [5.8] ?=- Spitzer/IRAC 5.8um magnitude
111-116 F6.4 mag e_[5.8] ?=- rms uncertainty on [5.8]
118-123 F6.3 mag [8.0] ?=- Spitzer/IRAC 8.0um magnitude
125-129 F5.3 mag e_[8.0] ?=- rms uncertainty on [8.0]
130 A1 --- Flag [v]
132-135 F4.2 mag AK ?=- The Ks band extinction
137-139 A3 --- Class YSO Class (only for table6) (G1)
--------------------------------------------------------------------------------
Note (1): Names as:
table6: vNN, ocNN-Vnn for sources also in table7
table7: ocNN, ocNN-Vnn for sources also in table6,
NNN for sources also in table3
table8: eN
--------------------------------------------------------------------------------
Global notes:
Note (G1):
0/I = Class 0/I YSO;
FS = Flat Spectrum YSO;
II = Class II YSO;
III = Class III YSO.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 21-Mar-2013