J/ApJ/715/671 X-ray and IR emission from YSOs (Wolk+, 2010)
X-ray and infrared emission from young stellar objects near LkHα 101.
Wolk S.J., Winston E., Bourke T.L., Gutermuth R., Megeath S.T.,
Spitzbart B.D., Osten R.
<Astrophys. J., 715, 671-695 (2010)>
=2010ApJ...715..671W 2010ApJ...715..671W
ADC_Keywords: X-ray sources ; Stars, pre-main sequence ; YSOs ;
Photometry, infrared ; Spectral types ; Equivalent widths
Keywords: infrared: stars - stars: distances - stars: protostars - X-rays: stars
stars: individual (LkHα101) - stars: pre-main sequence
Abstract:
We report on a multiwavelength study of a partially embedded region of
star formation centered on the Herbig Be star LkHα 101. Using
two 40ks Chandra observations, we detect 213 X-ray sources in the
∼17'x17' ACIS-I field. We combine the X-ray data with Two Micron All
Sky Survey near-IR observations and Spitzer IRAC and MIPS 24um
observations to obtain a complete picture of the cluster. A total of
158 of the X-ray sources have infrared counterparts. Of these, we find
nine protostars, 48 Class II objects, five transition objects, and 72
Class III objects. From the Spitzer data we identify an additional 10
protostars, 53 Class II objects, and four transition disk candidates
which are not detected by Chandra. We obtained optical spectra of a
sample of both X-ray-detected and non-X-ray-detected objects.
Combining the X-ray, Spitzer, and spectral data, we obtain independent
estimates of cluster distance and the total cluster size -excluding
protostars. We obtain consistent distance estimates of
510+100-40pc and a total cluster size of 255+50-25 stars. We
find the Class II:III ratio is about 5:7 with some evidence that the
Class III sources are spatially more dispersed. The cluster appears
very young with three sites of active star formation and a median age
of about 1Myr.
Description:
The original goal of this program was the simultaneous Chandra and VLA
observation of active stars (Osten & Wolk 2009ApJ...691.1128O 2009ApJ...691.1128O).
The field was observed by Chandra on 2005 March 6 starting at 17:16 UT
for 40.2ks of total time and 39.6ks of the so-called good time
(ObsID 5429). It was observed again on 2005 March 8 starting at 17:43
UT for essentially the same duration (ObsID 5428).
The region near LkHα 101 was observed with the Infrared Array
Camera (IRAC) and the Multiband Imaging Photometer for Spitzer (MIPS)
on board the Spitzer Space Telescope as a part of a GTO program (PID 6
- Structure and Incidence of Young Embedded Clusters; Gutermuth et al.
2009, Cat. J/ApJS/184/18). IRAC observations were made on 2005 May 13.
MIPS data were obtained from 24um observations on 2005 October 9.
Spectroscopy in the far-red was carried out using the Hectospec
multi-object moderate dispersion spectrograph on the converted 6.5m
MMT on Mt. Hopkins, Arizona, in 2005 October, 2006 March, and 2006
November. The spectral range covered was 3000-9000Å, with a
resolution of ∼6Å.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 41 213 X-ray sources detected in the LkHα 101 field
table2.dat 51 140 2MASS photometry of X-ray sources
table3.dat 89 158 Spitzer photometry of X-ray sources
table4.dat 57 87 LkHα 101 cluster spectral classification
table7.dat 64 88 Spectral fits to X-ray sources
table8.dat 63 30 Spectral fits to X-ray sources (lower quality)
table10.dat 55 69 PMS stars detected by Spitzer but not detected in
X-rays (2MASS colors)
table11.dat 81 69 PMS stars not detected in X-rays (Spitzer)
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2012)
B/mk : Catalogue of Stellar Spectral Classifications (Skiff, 2012)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/AJ/128/1233 : LkHa 101 and the young cluster in NGC 1579 (Herbig+, 2004)
J/AJ/126/1916 : JHK photometry of young clusters near the Sun (Porras+, 2003)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [2/231] Running source number (skips indicate
the spurious detections)
5- 22 A18 --- ID Source identification; (HHMMSS.ss+DDMMSS.s;
<LkHa101CXO JHHMMSS.ss+DDMMSS.s> in Simbad)
24- 29 F6.1 arcsec Off Offset from axis
31- 34 I4 ct RCts Raw counts
36- 41 F6.1 ct NCts Net counts
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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- 3 I3 --- Seq [2/231] Source index number
5- 8 F4.2 arcsec X/2M X-ray/2MASS positional offset
10- 14 F5.1 arcsec Off2M Offset from axis
16- 20 F5.2 mag Jmag 2MASS J band magnitude
22- 25 F4.2 mag e_Jmag ? Uncertainty in Jmag
27- 31 F5.2 mag Hmag 2MASS H band magnitude
33- 36 F4.2 mag e_Hmag ? Uncertainty in Hmag
38- 42 F5.2 mag Kmag 2MASS K band magnitude
44- 47 F4.2 mag e_Kmag ? Uncertainty in Kmag
49- 51 A3 --- Qual 2MASS photometry quality codes
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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- 3 I3 --- Seq [2/231] Source index number (1)
5- 8 F4.2 arcsec X/Sptz X-ray/Spitzer positional offset
10- 14 F5.1 arcsec Off Offset from axis
16- 20 F5.2 mag [3.6] ? Spitzer/IRAC 3.6 micron band magnitude
22- 26 F5.2 mag [4.5] ? Spitzer/IRAC 4.5 micron band magnitude
28- 32 F5.2 mag [5.8] ? Spitzer/IRAC 5.8 micron band magnitude
34- 38 F5.2 mag [8.0] ? Spitzer/IRAC 8.0 micron band magnitude
40- 43 F4.2 mag [24] ? Spitzer/MIPS 24 micron band magnitude
45- 48 F4.2 mag e_[3.6] ? Uncertainty in [3.6]
50- 53 F4.2 mag e_[4.5] ? Uncertainty in [4.5]
55- 58 F4.2 mag e_[5.8] ? Uncertainty in [5.8]
60- 63 F4.2 mag e_[8.0] ? Uncertainty in [8.0]
65- 68 F4.2 mag e_[24] ? Uncertainty in [24]
70- 73 F4.2 mag AK The K band extinction
75- 88 A14 --- Class Source classification (1, 2, III, T(transition),
gal (background galaxy), or LkHα 101)
89 A1 --- f_Class [b] b: star within 90" of LkHα 101 (2)
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Note (1): In addition to their IAU approved Names:
<LkHa101CXO JHHMMSS.ss+DDMMSS.s> given in Table 1, these sources are
equally identified as: <LkHa101SST JHHMMSS.ss+DDMMSS.s>.
Note (2): Stars with a notation "b" are within 90 arcsec of LkHα 101.
Their proximity, led to the conclusion that they were cluster
members, despite missing some IRAC data. For these stars 2MASS data
played an enhanced role in determining Class identification.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [2/231]? Chandra identification number
5- 22 A18 --- ID LkHaSST identification (HHMMSS.ss+DDMMSS.s;
<LkHa101SST JHHMMSS.ss+DDMMSS.s> in Simbad)
24- 27 A4 --- SpT MK spectral type
29- 31 F3.1 --- e_SpT SpT uncertainty
33- 37 I5 K Teff Effective temperature
39- 44 F6.3 [-] logL Overall luminosity log(Lbol/L0)
46- 53 F8.2 0.1nm EWHa Hα (6563Å) equivalent width
55- 57 F3.1 0.1nm EWLi ? LiI (6707Å) equivalent width
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Byte-by-byte Description of file: table7.dat table8.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [2/231] Source index number
5- 10 F6.1 ct NCts Net counts
12- 16 F5.2 10+22/cm2 NH Hydrogen column density
18- 21 F4.2 10+22/cm2 e_NH ? The 1σ uncertainty in NH
23 A1 --- l_kT Limit flag on kT
25- 30 F6.2 keV kT Effective temperature
32- 35 F4.2 keV e_kT ? The 1σ uncertainty in kT
37- 42 F6.2 [mW/m2] logF.A Log of Absorbed flux; erg/s/cm2
44- 49 F6.2 [mW/m2] logF.U Log of Unabsorbed flux; erg/s/cm2
51- 54 F4.2 --- chi2 The reduced χ2 of the fit (1)
56- 64 A9 --- Model Model used in fit (2)
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Note (1): Included for "cstat" models for completeness. One model was
calculated with C statistics, it is unclear how this relates to
goodness of fit. The formal errors are unbiased however.
Note (2): The model used for the fit is coded in two parts. The left hand side
indicates the type of model used. The right hand side indicates the
data set. The overall model is written: LHS_RHS.
LHS as follows:
cstat = C-statistics used for the fit with an initial guess of kT=1keV and
NH=1021cm-2.
crs = c-stat used for initial guess with those input parameters and then
refit using Raymond-Smith plasma for final fit.
Mekal = again c-stat used for initial guess and then Mekal for final fit,
APEC = cstat used for initial guess and then APEC for final fit.
RHS as follows:
29 = only data from first observation (Obsid = 5429) used in fit,
28 = only data from second observation (Obsid = 5428) used in fit,
all = data from both observations used in fit.
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Byte-by-byte Description of file: table10.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- ID Source identification; (HHMMSS.ss+DDMMSS.s;
<LkHa101SST JHHMMSS.ss+DDMMSS.s> in Simbad) (1)
20- 24 F5.2 mag Jmag ? 2MASS J band magnitude
26- 29 F4.2 mag e_Jmag ? Uncertainty in Jmag
31- 35 F5.2 mag Hmag ? 2MASS H band magnitude
37- 40 F4.2 mag e_Hmag ? Uncertainty in Hmag
42- 46 F5.2 mag Ksmag ? 2MASS Ks band magnitude
48- 51 F4.2 mag e_Ksmag ? Uncertainty in Kmag
53- 55 A3 --- Qual 2MASS photometry quality codes
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Note (1): Source 042955.68+352021.2 has been modified at CDS into
042955.68+352021.0 as in table 11 and 2MASS catalog.
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Byte-by-byte Description of file: table11.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- ID Source identification; (HHMMSS.ss+DDMMSS.s;
<LkHa101SST JHHMMSS.ss+DDMMSS.s> in Simbad)
20 A1 --- f_ID [*] outside Chandra field of view (1)
22- 26 F5.2 mag [3.6] Spitzer/IRAC 3.6 micron band magnitude
28- 31 F4.2 mag e_[3.6] Uncertainty in [3.6]
33- 37 F5.2 mag [4.5] ? Spitzer/IRAC 4.5 micron band magnitude
39- 42 F4.2 mag e_[4.5] ? Uncertainty in [4.5]
44- 48 F5.2 mag [5.6] ? Spitzer/IRAC 5.6 micron band magnitude
50- 53 F4.2 mag e_[5.6] ? Uncertainty in [5.6]
55- 59 F5.2 mag [8.0] ? Spitzer/IRAC 8.0 micron band magnitude
61- 64 F4.2 mag e_[8.0] ? Uncertainty in [8.0]
66- 69 F4.2 mag [24] ? Spitzer/MIPS 24 micron band magnitude
71- 74 F4.2 mag e_[24] ? Uncertainty in [24]
76- 79 F4.2 mag AK The K band extinction
81 A1 --- Cl [012T] Classification (Class 0, I, II or
T=possible transition objects)
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Note (1):
* = These Spitzer identified PMS stars are off the Chandra field of view.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 21-May-2012