J/A+A/605/A85 NGC 3293 Chandra X-ray observation (Preibisch+, 2017)
Chandra X-ray observation of the young stellar cluster NGC 3293 in the
Carina Nebula Complex.
Preibisch T., Flaischlen S., Gaczkowski B., Townsley L., Broos P.
<Astron. Astrophys. 605, A85 (2017)>
=2017A&A...605A..85P 2017A&A...605A..85P (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; X-ray sources ; Infrared sources
Keywords: X-ray: stars - stars: pre-main sequence - stars: formation
Abstract:
NGC 3293 is a young stellar cluster at the northwestern periphery of
the Carina Nebula Complex that remained poorly explored until now.
We want to characterize the stellar population of NGC 3293 in order to
evaluate key parameters of the cluster population like the age and the
mass function, and to test claims of an abnormal IMF and a deficit of
M≤2.5M☉ stars.
WWe performed a deep (70 ksec) X-ray observation of NGC 3293 with
Chandra and detected 1026 individual X-ray point sources. These X-ray
data directly probe the low-mass (M≤2M☉) stellar population
by means of the strong X-ray emission of young low-mass stars. We
identify counterparts for 74% of the X-ray sources in our deep
near-infrared images.
Our data clearly show that NGC 3293 hosts a large population of
∼solar-mass stars, refuting claims of a lack of M≤2.5M☉
stars. The analysis of the color-magnitude diagram suggests an age of
∼8-10Myr for the low-mass population of the cluster. There are at
least 511 X-ray detected stars with color-magnitude positions that are
consistent with young stellar members within 7 arcmin from the cluster
center.
The number ratio of X-ray detected stars in the [1-2]M☉ range
versus the M≤5M☉ stars (known from optical spectroscopy) is
well consistent with the expectation from a normal field initial mass
function.
Most of the early B-type stars and ∼20% of the later B-type stars are
detected as X-ray sources.
Our data shows that NGC 3293 is one of the most populous stellar
clusters in the entire Carina Nebula Complex (only excelled by Tr 14,
and very similar to Tr 16 and Tr 15). The cluster has probably
harbored several O-type stars, the supernova explosions of which may
have had an important impact on the early evolution of the Carina
Nebula Complex.
Description:
We used the Chandra X-ray observatory to perform a deep pointing of
the cluster NGC 3293 with the Imaging Array of the Chandra Advanced
CCD Imaging Spectrometer (ACIS-I). The observation was performed as an
open time project with ObsID 16648 (PI: T. Preibisch) during Chandra
Observing Cycle 15 in October 2015 (start date: 2015-10-07T10:14:23,
end date: 2015-10-08T06:43:28). The imaging array ACIS-I provides a
field of view of 17'x17' on the sky (which corresponds to
11.3x11.3pc at the distance of 2.3kpc), and has a pixel size of
0.492".
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 101 1026 Primary Chandra Catalog: Basic Source Properties
table2.dat 97 719 VISTA and VST source identification for the
X-ray sources in NGC 3293
table3.dat 83 54 X-ray luminosities of B-type stars in NGC 3293
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See also:
II/341 : VPHAS+ DR2 survey (Drew+, 2016)
J/A+A/437/467 : VLT-FLAMES survey of massive stars (Evans+, 2005)
J/A+A/572/A116 : The VISTA Carina Nebula Survey (Preibisch+, 2014)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq X-ray catalog sequence number, sorted by RA
6- 23 A18 --- CXName IAU designation of the X-ray source
(HHMMSS.ss+DDMMSS.s,
CXONGC3293 JHHMMSS.ss+DDMMSS.s)
25- 34 F10.6 deg RAdeg Right ascension (J2000)
36- 45 F10.6 deg DEdeg Declination (J2000)
47- 49 F3.1 arcsec e_Pos Position error
51- 54 F4.1 arcmin Theta Off-axis angle
56- 60 F5.1 ct CtTnet Net counts in the total energy band (0.5-8keV)
62- 65 F4.1 ct e_CtTnet 1-sigma errors on net counts
67- 71 F5.1 ct Bct Background counts expected in the source
extraction region
73- 77 F5.1 ct CtHnet Net counts in the hard energy band (2-8keV)
79- 82 F4.2 --- PSFfrac Fraction of the PSF (at 1.497keV) enclosed
within the extraction region
84- 87 F4.1 --- Signi Photometric significance
89 A1 --- l_logPB Limit flag on logPB
90- 93 F4.1 --- logPB Logarithmic probability that extracted counts
are solely from background
95 A1 --- Anom [ag] Source anomalies (1)
97 A1 --- Var [abc] Variability characterization based on
K-S statistic (2)
99-101 F3.1 keV Emed Background-corrected median photon energy
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Note (1): Source anomalies flag as follows:
g = fractional time that source was on a detector is <0.9
p = source piled up
s = source on readout streak
a = photometry and spectrum contain >10% afterglow events
Note (2): Variability flag as follows:
a = no evidence for variability (0.05<PKS)
b = possibly variable (0.005<PKS<0.05)
c = definitely variable (PKS<0.005)
No value is reported for sources with fewer than four counts or for sources
in chip gaps or on field edges
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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- 5 I5 --- Seq Chandra X-ray catalog sequence number (1)
8- 25 A18 --- CXName Chandra X-ray catalog source name (1)
29- 52 A24 --- VCNS Identifier in the VISTA VCNS source catalog
or 2MASS name (2)
57- 64 A8 --- --- [VPHASDR2]
66- 83 A18 --- VPHAS Identifier in the VST VPHAS-DR2
source catalog (3)
85- 97 A13 --- sourceID SourceID in the VST VPHAS-DR2 source
catalog (3)
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Note (1): as in Table 1
Note (2): see Preibisch et al., 2014, Cat. J/A+A/572/A116
Note (3): see Drew et al., VPHAS+ DR2 survey, Cat. II/341
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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- 5 A5 --- ESL NGC 3293 ESL Number (based on Evans et al.
2005, Cat. J/A+A/437/467,
Cl* NGC 3293 ESL NNN in Simbad)
8- 19 A12 --- Name Name of the star (as listed in SIMBAD, if
available)
24- 27 I4 --- Seq ? X-ray catalog sequence number
31- 43 A13 --- SpType Spectral type
46- 53 E8.3 10-7W LX ? X-ray luminosity for stars with X-ray
detection (1)
57- 64 E8.3 10-7W ulLX ? Upper limit to the X-ray luminosity for
stars without X-ray detection
69- 73 F5.2 [-] logLX/Lb ? Logarithm of the X-ray to bolometric
luminosity ratio (1)
79- 83 F5.2 [-] ullogLX/Lb ? Logarithm of the upper limit to the X-ray
to bolometric luminosity ratio
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Note (1): all luminosities are calculated for a distance of 2.3kpc.
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Acknowledgements:
Thomas Preibisch, preibisch(at)usm.uni-muenchen.de
(End) T. Preibisch [Univ.-Sternwarte Muenchen], P. Vannier [CDS] 19-Jul-2017