J/AJ/158/235 Candidate X-ray sources in IRAS 09002-4732 region (Getman+, 2019)
IRAS 09002-4732: a laboratory for the formation of rich stellar clusters.
Getman K.V., Feigelson E.D., Kuhn M.A., Broos P.S., Garmire G.P.
<Astron. J., 158, 235 (2019)>
=2019AJ....158..235G 2019AJ....158..235G (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Star Forming Region ; X-ray sources ;
Stars, pre-main sequence ; Photometry, infrared ; Stars, ages
Keywords: Dense interstellar clouds - Collapsing clouds -
Interstellar filaments - Compact H II region - Protostars -
Infrared excess - Single X-ray stars - Young star clusters -
Star-forming regions - Pre-main sequence
Abstract:
IRAS 09002-4732 is a poorly studied embedded cluster of stars in the
Vela Molecular Ridge at a distance of 1.7 kpc. Deep observations with
the Chandra X-ray Observatory, combined with existing optical and infrared
surveys, produce a catalog of 441 probable pre-main-sequence members of
the region. The stellar spatial distribution has two components: most stars
reside in a rich, compact, elliptical cluster, but a minority reside within
a molecular filament several parsecs long that straddles the cluster. The
filament has active distributed star formation with dozens of unclustered
protostars. The cluster pre-main-sequence population is =<0.8 Myr old
and deeply embedded; its most massive member is extremely young, producing
an ultracompact H II region. The cluster total population deduced from
the X-ray luminosity function is surprisingly rich, twice that of the
Orion Nebula Cluster. The cluster core is remarkably dense where strong
N-body interactions should be occurring; its initial mass function may be
deficient in massive stars. We infer that IRAS 09002-4732 is a rare case
where a rich cluster is forming today in a molecular filament, consistent
with astrophysical models of cluster formation in clouds that involve
the hierarchical formation and merging of groups in molecular filaments.
Description:
Three observations of IRAS 09002-4732 were obtained during Chandra
X-ray Observatory Cycle 18 using the Advanced CCD Imaging Spectrometer
imaging array (ACIS-I; Garmire et al. 2003SPIE.4851...28G 2003SPIE.4851...28G). The 17'x17'
image from four contiguous CCD chips was centered at
(α, δ)J2000=(09:01:55.00, -47:43:46.8) and the total
exposure was close to 100 ks. The instrument was operated in Very Faint
Timed Exposure mode.
Objects:
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RA (ICRS) DE Designation(s)
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09 01 54.3 -47 43 59 IRAS 09002-4732 = GAL 268.4-00.9
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 87 1034 Candidate X-ray sources
table3.dat 277 386 X-ray PMS members of IRAS 09002-4732
table4.dat 139 55 MIRES sources from Povich et al. (2013,
J/ApJS/209/31) undetected in X-rays
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
IX/57 : The Chandra Source Catalog (CSC), Release 2.0 (Evans+, 2019)
J/A+A/434/987 : Near-IR sources around IRAS 09002-4732 (Apai+, 2005)
J/ApJS/209/31 : The MYStIX IR-Excess Source catalog (MIRES) (Povich+, 2013)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- CXOU Chandra X-ray Observatory Unidentified source
(HHMMSS.ss+DDMMSS.s)
20- 29 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
31- 40 F10.6 deg DEdeg Declination in decimal degrees (J2000)
42- 45 F4.2 arcsec ePos [0.03/2.33] Position error (63%)
47- 50 F4.1 arcmin OffAxis [0.4/11.6] Off-axis angle on detector
52- 56 F5.1 ct NetCt [1.1/287.8] Net counts
58- 61 F4.1 ct e_NetCt [1.5/17.1] Error on NetCt
63- 66 F4.1 ct BkCt [0.1/20.6] Background counts
68- 71 F4.2 --- fPSF [0.39/0.91] Point Spread Function fraction
73- 76 F4.1 [-] ProbB [-5/-0.7] Log probability of source existence
(1)
78- 79 A2 --- Anom Anomaly flag (2)
81- 82 A2 --- Var Variability flag (3)
84- 87 F4.2 keV MedE [0.5/7.6] Median photon energy of net counts
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Note (1): ProbB is the logarithm of the probability of source existence;
specifically, the probability that the observed total number of extracted
counts will occur in a single trial of the Poisson distribution given the
observed local background counts BkCt. A value of -5.0 indicates probability
<0.00001.
Note (2): Anomaly flag as follows:
NA = Indicates no detector anomaly; `
a = Reports that photometry and spectrum may contain more than 10% cosmic ray
afterglow events in the detector;
g = Reports that the source spent more than 10% of the observation on dead
regions of the detector (principally chip gaps) and its count rate may be
underestimated.
Note (3): Variability flag based on the Kolmogorov-Smirnov test:
NA = Indicates no evidence of variability;
1 = Indicates possible (0.005<PKS<0.05) variability;
2 = Indicates definite variability (PKS<0.005).
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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 [1/386] IRAS 09002-4732 probable member
sequence number
5- 22 A18 --- CXOU Chandra X-ray Observatory Unidentified
source (HHMMSS.ss+DDMMSS.s)
24- 28 F5.2 [10-7W] logLX [29.75/32.13]? Log X-ray luminosity,
absorption-corrected, 0.5-8 keV (in erg/s)
32- 35 F4.2 [10-7W] e_logLX [0.08/0.7]? Error of logLX (in erg/s)
40- 44 F5.2 [cm-2] logNH [20.95/24]? Log hydrogen column density
inferred from X-ray median energy
48- 51 F4.2 [cm-2] e_logNH [0.08/0.96]? Error of logNH
56- 71 A16 --- 2MASS 2MASS catalog identifier (HHMMSSss+DDMMSSs)
73- 77 F5.2 mag Jmag [10.54/18.44]? 2MASS J band magnitude
81- 84 F4.2 mag e_Jmag [0.02/0.25]? Error of Jmag
89- 93 F5.2 mag Hmag [9.71/16.95]? 2MASS H band magnitude
97-100 F4.2 mag e_Hmag [0.02/0.35]? Error of Hmag
105-109 F5.2 mag Ksmag [9.14/16.25]? 2MASS Ks band magnitude
113-116 F4.2 mag e_Ksmag [0.02/0.25]? Error of Ksmag
121-126 A6 --- Qflg Quality flag of 2MASS photometry (1)
129-133 F5.2 mag IRX [-2.59/1.96]? Infrared excess from 2MASS
photometry
137-139 F3.1 Myr AgeJX [0.1/2.6]? Stellar age from 2MASS and Chandra
photometry
145-149 F5.2 mag 3.6mag [7.85/14.98]? Spitzer/IRAC 3.6µm
(Channel 1) magnitude
153-156 F4.2 mag e_3.6mag [0.03/0.21]? Error of 3.6mag
161-165 F5.2 mag 4.5mag [7.34/14.29]? Spitzer/IRAC 4.5µm
(Channel 2) magnitude
169-172 F4.2 mag e_4.5mag [0.03/0.31]? Error of 4.5mag
177-181 F5.2 mag 5.6mag [6.69/13.16]? Spitzer/IRAC 5.6µm
(Channel 3) magnitude
185-188 F4.2 mag e_5.6mag [0.02/0.35]? Error of 5.6mag
193-197 F5.2 mag 8.0mag [5.66/12.94]? Spitzer/IRAC 8.0µm
(Channel 4) magnitude
201-204 F4.2 mag e_8.0mag [0.03/0.34]? Error of 8.0mag
209-213 F5.2 --- SpIndex [-3.54/5.48]? Spectral index from 2MASS and
Spitzer photometry
217-221 F5.2 mag rmag [12.31/22.68]? VPHAS r band magnitude
225-228 F4.2 mag e_rmag [0/0.28]? Error of rmag
233-237 F5.2 mag imag [12.35/22.01]? VPHAS i band magnitude
241-244 F4.2 mag e_imag [0/0.24]? Error of imag
249-251 F3.1 mag AV(JHK) [0/8.1]? Visual band absorption from 2MASS
photometry
257-259 F3.1 Myr Age(ri) [0.1/7]? Stellar age from VPHAS photometry
264-269 F6.3 mas Plx [-1.943/5.99]? Gaia parallax
272-277 F6.3 mas e_Plx [0.019/1.846]? Error of Plx
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Note (1): Adopted from the 2MASS catalog (see Cat. II/246 for details).
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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 [387/441] IRAS 09002-4732 probable member
sequence number
5- 21 A17 --- IRAC Spitzer/IRAC designation (Galactic coordinates;
GLLL.llll+BB.bbbb)
23- 30 F8.4 deg RAdeg Approximate Right Ascension in decimal degrees
(J2000)
32- 39 F8.4 deg DEdeg Approximate Declination in decimal degrees
(J2000)
41- 45 F5.2 mag Jmag [14.13/17.03]? UKIDSS J band magnitude
47- 50 F4.2 mag e_Jmag [0.05/0.21]? Error of J band magnitude
52- 56 F5.2 mag Hmag [12.73/16.34]? UKIDSS H band magnitude
59- 62 F4.2 mag e_Hmag [0.05/0.22]? Error of H band magnitude
64- 68 F5.2 mag Kmag [11.61/15.3]? UKIDSS K band magnitude
71- 74 F4.2 mag e_Kmag [0.05/0.18]? Error of K band magnitude
76- 80 F5.2 mag 3.6mag [8.23/14.64] Spitzer/IRAC Channel 1 magnitude
83- 86 F4.2 mag e_3.6mag [0.05/0.17] Error or 3.6mag
88- 92 F5.2 mag 4.5mag [6.92/13.98] Spitzer/IRAC Channel 2 magnitude
95- 98 F4.2 mag e_4.5mag [0.05/0.16] Error of 4.5mag
100-104 F5.2 mag 5.6mag [5.93/13.16]? Spitzer/IRAC Channel 3 magnitude
107-110 F4.2 mag e_5.6mag [0.1/0.32]? Error of 5.6mag
112-116 F5.2 mag 8.0mag [5.1/12.32]? Spitzer/IRAC Channel 4 magnitude
118-121 F4.2 mag e_8.0mag [0.1/0.3]? Error of 8.0mag
123-127 F5.2 --- alpha [-1.8/2.02] Infrared Spectral Energy Distribution
slope
130-133 F4.2 --- e_alpha [0.12/0.47] Error of SED slope
135-136 I2 --- Nalpha [2/4] Number of photometric points in SED slope
138-139 I2 --- Stage [-1/2] Estimated evolutionary stage (1)
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Note (1): Evolutionary stage as follows:
1 = Corresponds to Class 0/I protostar;
2 = Corresponds to Class II/III pre-main sequence star;
-1 = Corresponds to an ambiguous status.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 27-Jan-2020