J/ApJ/673/331 X-ray observations of CG 12 (Getman+, 2008)
The stellar population and origin of the mysterious high-latitude star-forming
cloud CG 12.
Getman K.V., Feigelson E.D., Lawson W.A., Broos P.S., Garmire G.P.
<Astrophys. J., 673, 331-353 (2008)>
=2008ApJ...673..331G 2008ApJ...673..331G
ADC_Keywords: Clusters, open ; Globules ; X-ray sources ; Proper motions
Keywords: H II regions - ISM: globules -
open clusters and associations: individual (CG 12) -
stars: formation - stars: pre-main sequence - X-rays: stars
Abstract:
The mysterious high Galactic latitude cometary globule CG 12 has
been observed with the ACIS detector on board the Chandra X-Ray
Observatory. We detect 128 X-ray sources, of which half are likely
young stars formed within the globule's head. This new population of
≳50 T Tauri stars and one new embedded protostar is far larger than
the previously reported few intermediate-mass and two protostellar
members of the cloud.
Description:
The observations were obtained with the ACIS camera on board Chandra.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 111 128 Basic source properties
table3.dat 107 45 X-ray spectroscopy for photometrically selected
sources: thermal plasma fits
table4.dat 153 128 Optical and NIR counterparts
--------------------------------------------------------------------------------
See also:
B/chandra : The Chandra Archive Log (CXC, 1999-)
J/MNRAS/355/1272 : BVIJHKs photometry around CG 12 (Maheswar+, 2004)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Fld Chandra ACIS-I fields surveyed in the CG 12
region (G1)
5- 6 I2 --- Src X-ray source number within the field,
[GFL2008] "Field" "Source" in Simbad
8- 25 A18 --- CXOU CXOUJ designation (HHMMSS.dd+DDMMSS.s)
27- 36 F10.6 deg RAdeg Right ascension in decimal degrees (J2000)
38- 47 F10.6 deg DEdeg Declination in decimal degrees (J2000)
49- 52 F4.2 arcsec e_Pos Positional uncertainty
54- 58 F5.2 arcmin Theta Off-axis angle
60- 64 F5.1 ct Fnet Estimated net counts from extracted area in
total energy band 0.5-8.0keV
66- 69 F4.1 ct e_Fnet rms uncertainty on ctNetF
71- 74 F4.1 ct Fbg Estimated background counts from extracted
area in total energy band
76- 80 F5.1 ct Hnet Estimated net counts from extracted area in
hard energy band 2-8keV
82- 85 F4.2 --- Frac Fraction of the PSF at the fiducial energy of
1.497keV enclosed within the extracted
area (2)
87- 90 F4.1 --- Signi Source significance in σ
92- 93 A2 --- Anom [ge ] Source anomalies (3)
95 A1 --- Var [abc] Variability characterization based on
K-S statistics (4)
97-100 F4.1 ks Texp Source effective exposure
102-105 F4.2 keV Emed Background-corrected median photon energy in
the total 0.5-8keV energy band
107-111 F5.2 [-] logPB Logarithm of K-S probability that background
and source spectra are drawn from the same
distribution (5)
--------------------------------------------------------------------------------
Note (2): Note that a reduced PSF fraction (significantly below 90%) may
indicate that the source is in a crowded region or on the edge of the
field.
Note (3): Source anomalies flags as follows:
g = fractional time that source was on a detector (FRACEXPO from mkarf)
is <0.9
e = source on field edge
p = source piled up
s = source on readout streak
Note (4): Source variability flags as follows:
a = no evidence for variability
b = possibly variable
c = definitely variable.
blank = No test is performed for sources with fewer than 4 total full-band
counts. No value is reported for sources in chip gaps
or on field edges.
Note (5): The value of logPB has been truncated at -4.0 for sources with
significantly different background and source spectra.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Fld Chandra ACIS-I fields surveyed in the CG 12
region (G1)
5- 6 I2 --- Src X-ray source number within the field
8- 25 A18 --- CXOU CXOUJ designation (HHMMSS.dd+DDMMSS.s)
27- 31 F5.1 ct Fnet Estimated net counts from extracted area in
total energy band 0.5-8.0keV
33- 36 F4.2 keV Emed Background-corrected median photon energy in
the total 0.5-8keV energy band
38- 41 F4.1 [cm-2] logNH Best-fit value or the column density (1)
43- 45 F3.1 [cm-2] E_logNH ? Error on logNH (upper limit)
47- 49 F3.1 [cm-2] e_logNH ? Error on logNH (lower limit)
51- 55 F5.2 keV kT Best-fit value for plasma temperature (1)
56- 58 F3.1 keV E_kT ? Error on kT (upper limit)
60- 63 F4.1 keV e_kT ? Error on kT (lower limit)
65- 69 F5.2 [10-7W] logLh Hard band (2-8keV) X-ray luminosity (2)
71- 74 F4.2 [10-7W] e_logLh rms uncertainty on logLh
76- 80 F5.2 [10-7W] logLhc Hard band (2-8keV) absorption-corrected
X-ray luminosity (2)
82- 85 F4.2 [10-7W] e_logLhc rms uncertainty on logLhc
87- 91 F5.2 [10-7W] logLt Total band (-0.5-8keV) X-ray luminosity (2)
93- 96 F4.2 [10-7W] e_logLt rms uncertainty on logLt
98-102 F5.2 [10-7W] logLtc Total band (-0.5-8keV) absorption-corrected
X-ray luminosity (2)
104-107 F4.2 [10-7W] e_logLtc rms uncertainty on logLtc
--------------------------------------------------------------------------------
Note (1): All fits used the "wabs(apec)" model in XSPEC and assumed
0.3Z☉ abundances. Uncertainties represent 90% confidence
intervals. More significant digits are used for uncertainties <0.1 in
order to avoid large rounding errors; for consistency, the same number
of significant digits is used for both lower and upper uncertainties.
Uncertainties are missing when XSPEC was unable to compute them or
when their values were so large that the parameter is effectively
unconstrained. Fitted values with logNH<20.0cm-2 are truncated at
20.0 because ACIS-I spectra are insensitive to differences in very
low column densities. Fitted values with kT>15keV are truncated at
15keV because the data often cannot discriminate between very high
temperature values.
Note (2): X-ray luminosities are calculated assuming a distance of 550pc
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Fld Chandra ACIS-I fields surveyed in the CG 12
region (G1)
5- 6 I2 --- Src X-ray source number within the field
8- 25 A18 --- CXOU CXOUJ designation (HHMMSS.dd+DDMMSS.s)
27- 38 A12 --- NOMAD NOMAD identifier (NNNN-NNNNNNN)
40- 42 F3.1 arcsec Sep1 ? Chandra-NOMAD positional offset
44- 48 A5 --- [MMB2004b] Source identifier from Maheswar et al.
(2004, Cat. J/MNRAS/355/1272)
50- 54 F5.2 mag Vmag ? V magnitude (1)
56- 59 F4.2 mag e_Vmag ? rms uncertainty on Vmag
61- 65 F5.2 mag Rmag ? R magnitude (1)
67- 70 F4.2 mag e_Rmag ? rms uncertainty on Rmag
72- 76 F5.1 mas/yr pmRA ? Best proper motion along RA
(pmRA*cosDE) (2)
78- 81 F4.1 mas/yr e_pmRA ? rms uncertainty on pmRA
83- 87 F5.1 mas/yr pmDE ? Best proper motion along DE (2)
89- 92 F4.1 mas/yr e_pmDE ? rms uncertainty on pmDE
94-109 A16 --- 2MASS 2MASS designation (HHMMSSss+DDMMSSs)
111-113 F3.1 arcsec Sep2 ? Chandra-2MASS positional offset
115-119 F5.2 mag Jmag ? 2MASS J magnitude
121-124 F4.2 mag e_Jmag ? rms uncertainty on Jmag
126-130 F5.2 mag Hmag ? 2MASS H magnitude
132-135 F4.2 mag e_Hmag ? rms uncertainty on Hmag
137-141 F5.2 mag Ksmag ? 2MASS Ks magnitude
143-146 F4.2 mag e_Ksmag ? rms uncertainty on Ksmag
148-153 A6 --- Flags 2MASS photometry quality and
confusion-contamination flag
--------------------------------------------------------------------------------
Note (1): When formal statistical errors are given, V and R magnitudes are
from Maheswar et al. (2004, Cat. J/MNRAS/355/1272). V magnitudes for
three B-type stars, I 57, I 58, and I 74, are from Williams et al.
(1977MNRAS.180..709W 1977MNRAS.180..709W). Otherwise, V and R magnitudes are from the
NOMAD catalog, in which case all V magnitudes except for the Chandra
source I 81 are from the YB6 (=USNO unpublished) catalog, and all R
magnitudes except for the Chandra source I 57 are from the USNO-B1.0
catalog (R magnitudes from USNO-B1.0 are second red magnitudes R2,
except for the Chandra sources I 70 and II 9, for which it is a first
red magnitude R1). For the Chandra source I 81 V magnitude is from
the Tycho-2 catalog, and for the Chandra source I 57 R magnitude is
from the UCAC2 catalog.
Note (2): "Best" proper motions and their mean errors from catalogs
compiled in NOMAD (Cat. I/297)
--------------------------------------------------------------------------------
Global notes:
Note (G1): I-primary pointing; II, III, and IV-secondary pointings.
Table1 : CG 12 Observations
-------------------------------------------------------------------------------
Field ObsID Start Time Exp RA (J2000.0) DE Roll Angle
(UT) (ks) (deg)
-------------------------------------------------------------------------------
I 6423 2006/04/15 16:19:17 30.8 13 57 44.52 -39 58 48.31 11.5
II 6424 2006/06/02 07:25:09 3.1 13 57 42.87 -39 43 01.76 285.0
III 6425 2006/04/13 08:44:08 3.1 13 56 19.40 -39 42 47.94 14.7
IV 6426 2006/04/15 12:54:20 3.1 13 56 19.40 -39 58 48.09 11.1
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 08-Apr-2010