J/ApJ/725/2485 X-rays from the star-forming complex W40 (Kuhn+, 2010)
A Chandra observation of the obscured star-forming complex W40.
Kuhn M.A., Getman K.V., Feigelson E.D., Reipurth B., Rodney S.A.,
Garmire G.P.
<Astrophys. J., 725, 2485-2506 (2010)>
=2010ApJ...725.2485K 2010ApJ...725.2485K
ADC_Keywords: Clusters, open ; H II regions ; X-ray sources ;
Cross identifications ; Photometry, infrared ; YSOs
Keywords: ISM: individual objects (W40) - X-rays: stars -
open clusters and associations: individual (W40) -
protoplanetary disks - stars: formation - stars: pre-main sequence
Abstract:
The young stellar cluster illuminating the W40 HII region, one of the
nearest massive star-forming regions, has been observed with the ACIS
detector on board the Chandra X-ray Observatory. Due to its high
obscuration, this is a poorly studied stellar cluster with only a
handful of bright stars visible in the optical band, including three
OB stars identified as primary excitation sources. We detect 225 X-ray
sources, of which 85% are confidently identified as young stellar
members of the region. Two potential distances of the cluster, 260pc
and 600pc, are used in the paper.
Description:
The Chandra X-ray Observatory (CXO) observed W40 for ∼38ks during
2007 August using the ACIS camera. The observation has a nominal
pointing of RA=18:31:23.8 and DEC=-2:05:59 (J2000), the approximate
center of the W40 cluster, and a roll angle of 251°. Data from the
imaging array (ACIS-I) are analyzed.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 98 225 Basic source properties
table2.dat 132 225 IR and radio counterparts to Chandra sources
table3.dat 73 39 Additional non X-ray cluster members
table4.dat 127 225 X-ray spectroscopy
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2012)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/AJ/140/968 : A cluster of compact radio sources in W40 (Rodriguez+, 2010)
J/ApJS/163/306 : Chandra study of the Cep B star-forming region (Getman+, 2006)
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 X-ray catalog sequence number; RA sorted
5- 22 A18 --- CXOW40 IAU designation (HHMMSS.ss+DDMMSS.s; J2000)
24- 33 F10.6 deg RAdeg Right ascension in decimal degrees (J2000)
35- 43 F9.6 deg DEdeg Declination in decimal degrees (J2000)
45- 47 F3.1 arcsec ePos [0/1.5] Positional error (1)
49- 52 F4.1 arcmin theta Off-axis angle θ
54- 59 F6.1 ct NCt Extracted net counts in full band (0.5-8keV)
61- 64 F4.1 ct e_NCt Average 1σ error in NCt
66- 69 F4.1 ct BCt Background counts in the extraction region
71- 75 F5.1 ct HCt Extracted net counts in hard band (2-8keV)
77- 80 F4.2 --- PSF PSF fraction enclosed within extraction
region (2)
82- 85 F4.1 --- Signi Source significance (3)
87 I1 --- Anom [0/1] Source anomalies (4)
89 I1 --- Var [1/4] Variability characterization (5)
91- 94 F4.1 ks Exp Effective exposure (6)
96- 98 F3.1 keV Emed Median energy of net counts in full
(0.5-8keV) band
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Note (1): Estimated standard deviation of the random component of the position
error, (σx2+σy2)0.5. The single-axis
position errors, σx and σy, are estimated from the
single-axis standard deviations of the PSF inside the extraction
region and the number of counts extracted.
Note (2): A reduced PSF fraction (significantly below 90%) may indicate that
the source is in a crowded region.
Note (3): Computed as net counts divided by the upper error on net counts.
Note (4):
1 = fractional time that source was on a detector (FRACEXPO from mkarf)
is <0.9.
Note (5): Based on K-S statistic (full band) as follows:
2 = no evidence for variability (0.05<PKS);
3 = possibly variable (0.005<PKS<0.05);
4 = definitely variable (PKS<0.005).
1 = source has with fewer than four counts or is located in a chip gap or
on a field edge.
Note (6): Approximate time the source would have to be observed at the aimpoint
of the ACIS-I detector in Cycle 8 to obtain the reported number of
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 X-ray catalog sequence number
5- 22 A18 --- CXOW40 IAU designation (HHMMSS.ss+DDMMSS.s)
24- 39 A16 --- 2MASS 2MASS source designation ("9999999999999999"
when no information)
41- 45 F5.1 arcsec Offset [0/2.6]?=-99 Chandra-2MASS positional offset
47- 52 F6.2 mag Jmag ?=-99 2MASS J-band magnitude
54- 59 F6.2 mag e_Jmag ?=-99 Error on Jmag
61- 66 F6.2 mag Hmag ?=-99 2MASS H-band magnitude
68- 73 F6.2 mag e_Hmag ?=-99 Error on Hmag
75- 80 F6.2 mag Ksmag ?=-99 2MASS KS-band magnitude
82- 87 F6.2 mag e_Ksmag ?=-99 Error on Ksmag
89- 94 A6 --- qual 2MASS photometry quality and confusion flag
("999999" when no information)
96-103 A8 --- Mm Membership class (G1)
105-110 F6.2 mag Av ?=-99 Visual absorption from J vs. J-H diagram
113-118 F6.2 Msun Mass ?=-99 Stellar mass from J vs. J-H diagram
120-125 F6.2 Msun e_Mass ?=-99 Error on mass from J vs. J-H diagram
128 I1 --- U [0/3] UKIRT counterparts (7)
130-132 I3 --- VLA [1/20]?=-99 VLA source (Rodriguez et al. 2010,
Cat. J/AJ/140/968, <[RRR2010] W40-VLA NN> in
Simbad)
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Note (7): UKIRT flag as follows:
0 = no source;
1 = single source present;
2 = outside Field of View;
3 = double source present.
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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- 16 A16 --- Name 2MASS name (HHMMSSss+DDMMSSs) or OS 3a
18- 22 F5.2 mag Jmag 2MASS J-band magnitude
24- 27 F4.2 mag e_Jmag Jmag uncertainty
29- 33 F5.2 mag Hmag 2MASS H-band magnitude
35- 38 F4.2 mag e_Hmag Hmag uncertainty
40- 44 F5.2 mag Ksmag 2MASS Ks-band magnitude
46- 49 F4.2 mag e_Ksmag Ksmag uncertainty
51- 56 A6 --- qual 2MASS photometry quality and confusion flag
58- 62 F5.2 mag Av Visual absorption (1)
64- 68 F5.2 Msun Mass Stellar mass (1)
70- 73 F4.2 Msun e_Mass Mass uncertainty
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Note (1): Visual absorption and stellar mass derived from the color-magnitude
J vs J-H diagram assuming distance of 600pc and age of 1Myr.
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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 X-ray catalog sequence number; RA sorted
5- 22 A18 --- CXOW40 IAU designation
24- 30 F7.2 ct NCt Extracted net counts in full band
32- 35 F4.2 keV Emed Median energy of net counts in full band
37- 44 A8 --- Mm Membership class (G1)
46- 50 F5.2 [10-7W] Lh1 ?=99 Apparent hard-band (2-8keV) luminosity
from XSPEC fit
52- 57 F6.2 [10-7W] Lt1 ?=-99 Apparent full-band (0.5-8keV) luminosity
from XSPEC fit
59- 64 F6.2 keV kT1 ?=-99 Plasma temperature inferred
from XSPEC fit
66- 71 F6.2 [cm-2] NH1 ?=-99 Column density inferred
from XSPEC fit
73- 78 F6.2 [10-7W] Lhc1 ?=-99 Intrinsic hard-band (2-8keV) luminosity
from XSPEC fit
80- 85 F6.2 [10-7W] Ltc1 ?=-99 Intrinsic full-band (0.5-8keV) luminosity
from XSPEC fit
87- 92 F6.2 [cm-2] NH2 ?=-99 H2 column density obtained from XPHOT
94- 99 F6.2 [cm-2] e_NH2 ?=-99 Error on NH2
101-106 F6.2 [10-7W] Lhc2 ?=-99 Intrinsic hard-band (2-8keV) luminosity
from XPHOT
108-113 F6.2 [10-7W] e_Lhc2 ?=-99 Error on Lhc2
115-120 F6.2 [10-7W] Ltc2 ?=-99 Intrinsic full-band (0.5-8keV) luminosity
from XPHOT
122-127 F6.2 [10-7W] e_Ltc2 ?=-99 Error on Ltc2
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Global note:
Note (G1): Membership class as follows:
W40-noKs = W40 stars without Ks-excess;
W40-Ks = W40 stars with Ks-excess;
W40 = W40 stars with no Ks-excess classification;
FRG = foreground stars;
EG = Extragalactic sources.
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Nomenclature note:
For tables 1, 2 and 4, sources are <[KGF2010] NNN> =
<CXOW40 JHHMMSS.ss+DDMMSS.s> for Simbad.
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 13-Aug-2012