J/ApJ/905/78 Chandra obs. of IRDCs G034.43+00.24 and G035.39-00.33 (Yu+, 2020)
An X-ray view of two infrared dark clouds G034.43+00.24 and G035.39-00.33.
Yu H., Wang J., Tan J.C.
<Astrophys. J., 905, 78 (2020)>
=2020ApJ...905...78Y 2020ApJ...905...78Y
ADC_Keywords: X-ray sources; Molecular clouds; Photometry, infrared; YSOs
Keywords: Star formation ; Infrared dark clouds ; X-ray stars
Abstract:
We present a high spatial resolution Chandra X-ray study of two
infrared dark clouds (IRDCs), G034.43+00.24 and G035.39-00.33, which
are expected to be in the early phases of star cluster formation. We
detect 112 and 209 valid X-ray point sources toward G034.43+00.24 and
G035.39-00.33, respectively. We cross-match the X-ray point sources
with the Two Micron All Sky Survey (2MASS), Galactic Legacy Infrared
Midplane Survey Extraordinaire (GLIMPSE), and Wide-field Infrared
Survey Explorer (WISE) catalogs and find 53% and 59% of the X-ray
sources in G034.43+00.24 and in G035.39-00.33 have corresponding
infrared counterparts, respectively. These sources are probable
members of young massive clusters in formation, and using stellar
isochrones we estimate that a population of 1-2Myr old, intermediate-
to high-mass young stellar objects (YSOs) exist in both IRDCs. Two and
10 Class II counterparts to X-ray sources were identified in
G034.43+00.24 and in G035.39-00.33, respectively, which are located in
or near dark filaments. The X-ray luminosity function (XLF) of
G035.39-00.33 implies that the total mass consists of up to
∼1700M☉ of stars, using the XLF of the well-studied Orion Nebula
Cluster as a calibrator. This corresponds to a star formation
efficiency of at most 5%, indicating the system is still very much gas
dominated and in an early stage of the star formation process. The
population of G034.43+00.24 is less well determined due to the lower
sensitivity of its observations.
Description:
The two infrared dark clouds (IRDCs), G034.43+00.24 (G34.4) and
G035.39-00.33 (G35.4), were observed (PI: Tan) in 2013 and 2017,
respectively, with the Imaging Array of ACIS (ACIS-I) on board
Chandra. The field of view of ACIS-I is 17'x17' in a single pointing.
Total exposure time is 63ks for G34.4 and 182ks for G35.4.
As the exposure time and roll angle were different in the different
subobservations of the same target, basic information of these
observations is listed in Table 1.
Objects:
----------------------------------------------------------------
RA (ICRS) DE Designation(s)
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18 53 18.9 +01 26 39 G034.43+00.24 = MSXDC G034.43+0.24
18 57 09.0 +02 07 46 G035.39-00.33 = MSXDC G035.39-0.33
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 70 7 Log of Chandra observations of
IRDCs G034.43+0.2 (G34.4) and G035.39-0.33 (G35.4)
table2.dat 110 112 Basic source information of G34.4
table3.dat 110 209 Basic source information of G35.4
table5.dat 104 43 X-ray spectroscopy for selected sources of G34.4:
thermal plasma fits
table6.dat 104 121 X-ray spectroscopy for selected Sources of G35.4:
thermal plasma fits
table7.dat 163 112 Stellar counterparts of G34.4
table8.dat 163 209 Stellar counterparts of G35.4
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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)
II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
J/AJ/111/1964 : JHK photometry of NGC1333 (Lada+, 1996)
J/ApJ/574/258 : X-ray-emitting young stars in Orion nebula (Feigelson+, 2002)
J/ApJ/573/366 : Infrared photometry of Trapezium cluster (Muench+, 2002)
J/ApJS/160/353 : Membership of the Orion nebula population (Getman+, 2005)
J/ApJS/163/306 : Chandra study of the Cep B star-forming region (Getman+, 2006)
J/ApJ/641/389 : Millimetric observations of IRDC cores (Rathborne+, 2006)
J/ApJ/639/227 : MSX IRDC candidate catalog (Simon+, 2006)
J/ApJ/653/1325 : Galactic distribution of infrared dark clouds (Simon+, 2006)
J/ApJS/169/353 : Chandra sources in M17 (Broos+, 2007)
J/A+A/468/353 : XMM-Newton Extended Survey of Taurus (Guedel+, 2007)
J/ApJS/168/100 : X-ray study of star-forming region NGC 6357 (Wang+, 2007)
J/ApJ/688/418 : X-ray flares in Orion young stars. I. (Getman+, 2008)
J/ApJ/675/464 : Chandra observations of NGC 2244 (Wang+, 2008)
J/A+A/505/405 : A catalogue of Spitzer dark clouds (Peretto+, 2009)
J/ApJ/714/L285 : YSO candidates in M17 SWex (Povich+, 2010)
J/ApJS/194/11 : Chandra study of Trumpler 15 in Carina (Wang+, 2011)
J/AJ/144/101 : Multiwavelength data of IRAS 20050+2720 (Guenther+, 2012)
J/ApJS/209/32 : Probable young stars in the MYStIX project (Broos+, 2013)
J/ApJS/209/27 : MYStIX: the Chandra X-ray sources (Kuhn+, 2013)
J/ApJS/209/31 : The MYStIX IR-Excess Source catalog (MIRES) (Povich+, 2013)
J/A+A/606/A133 : IRDC G035.39-00.33 NH3 and CCS data cubes (Sokolov+, 2017)
J/ApJS/235/43 : The 2nd MSFRs Omnibus X-ray Catalog (MOXC2) (Townsley+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Name IRDC target
13- 18 A6 --- Target Other name of the IRDC target
20- 24 I5 --- ObsID [14541/20103] Chandra observation identifier
26- 36 A11 "Y/M/D" Obs.date Observation date, start (UT)
38- 45 A8 "h:m:s" Obs.time Obervation time, start (UT)
47- 51 I5 s Exp [17115/56074] Exposure time
53- 58 F6.2 deg RAdeg [283.32/284.3] Right ascension aim point (J2000)
60- 63 F4.2 deg DEdeg [1.4/2.13] Declination aim point (J2000)
65- 70 F6.2 deg Roll [146.9/239.21] Roll angle
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Byte-by-byte Description of file: table[23].dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/209] X-ray catalog sequence number
5- 22 A18 --- CXOU IAU designation (HHMMSS.ss+DDMMSS.s; J2000)
24- 33 F10.6 deg RAdeg [283.19/284.5] Right ascension (J2000)
35- 42 F8.6 deg DEdeg [1.2/2.4] Declination (J2000)
44- 46 F3.1 arcsec Err [0/1.5] Estimated random component
of position error
48- 51 F4.1 arcmin Theta [0.3/11.8] Offaxis angle
53- 57 F5.1 ct Net-F [2/893] Estimated net counts extracted in
total energy band (0.5-8keV)
59- 62 F4.1 ct delNet-F [1.5/31] Average of upper and lower errors
on Net-F
64- 69 F6.1 ct Bk-F [100/1997] Background counts extracted
71- 75 F5.1 ct Net-H [-0.5/541] Estimated net counts extracted
in hard band (2-8keV)
77- 79 F3.1 --- fPSF [0.4/0.9] Fraction of PSF enclosed within
extraction region
81- 84 F4.1 --- Sig [1.1/29.1] Photometric significance
86 A1 --- l_logPB Limit flag on logPB
87- 90 F4.1 --- logPB [-5/-2.3] Log probability (1)
92- 92 A1 --- Anom Source anomalies (2)
94- 94 A1 --- Var Variability characterization based
on K-S statistics (3)
96-100 F5.1 ks Exp [28.1/180] Effective Exposure time
102-104 F3.1 keV Emed [0.8/7] Background-corrected median
photon energy
106-110 F5.2 --- HR [-1/1] Hardness ratio, (H-S)/(H+S), with
hard-band: 2-8keV and soft-band: 0.5-1.2keV
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Note (1): That extracted counts (total band) are solely from background.
Note (2): Source anomalies as follows:
g = fractional time that the 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 (3): Variability characterization based on K-S statistic (total band)
as follows:
a = no evidence for variability (0.05<PK-S);
b = possibly variable (0.005<PK-S<0.05);
c = definitely variable (PK-S<0.005).
No value is reported for sources with fewer than 4 counts or for
sources in chip gaps or on field edges.
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Byte-by-byte Description of file: table[56].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/209] X-ray source number
5- 22 A18 --- CXOU IAU designation (HHMMSS.ss+DDMMSS.s; J2000)
24- 27 F4.1 ct NetCts [10/99] Estimated net counts extracted
in total band
29- 31 F3.1 --- Sig [2.2/9.1] Photometric significance
33- 36 F4.1 [cm-2] logNH [20.2/23.5] Estimated column density
38- 40 F3.1 [cm-2] E_logNH [0.1/2.6]? Upper uncertainty in logNH
42- 44 F3.1 [cm-2] e_logNH [0.1/0.9]? Lower uncertainty in logNH
46- 49 F4.1 keV kT [0.2/10] Estimated plasma energy
51- 53 F3.1 keV e_kT [0.2/5.5]? Lower uncertainty in kT
55- 57 F3.1 keV E_kT [0.5/10]? Upper uncertainty in kT
59- 62 F4.1 [cm-3] logEM [51.7/57.8] Estimated plasma emission measure
64- 66 F3.1 [cm-3] e_logEM [0.1/9.4] Lower uncertainty in logEM
68- 70 F3.1 [cm-3] E_logEM [0.1/3.3]? Upper uncertainty in logEM
72- 75 F4.1 [10-7W] logLs [25.2/31.3] Observed soft band (0.5-1.2keV)
X-ray luminosity, in erg/s
77- 80 F4.1 [10-7W] logLh [27.8/32.2] Observed hard band (2-7keV)
X-ray luminosity, in erg/s
82- 85 F4.1 [10-7W] logLhc [27.9/32.7] Absorption corrected hard band
X-ray luminosity, in erg/s
87- 90 F4.1 [10-7W] logLt [29.7/32.2] Observed total band X-ray luminosity
in erg/s units
92- 95 F4.1 [10-7W] logLtc [30/35.7] Absorption corrected total band
X-ray luminosity, in erg/s
97-104 A8 --- Note Additional notes
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Byte-by-byte Description of file: table[78].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/209] X-ray catalog sequence number
5- 22 A18 --- CXOU IAU designation (HHMMSS.ss+DDMMSS.s; J2000)
24- 39 A16 --- 2MASS NIR identification (HHMMSSss+DDMMSSs; J2000)
41- 46 F6.3 mag Jmag [8.6/18.6]? J band apparent magnitude
48- 53 F6.3 mag Hmag [8.3/16.7]? H band apparent magnitude
55- 60 F6.3 mag Kmag [8.1/15.7]? K band apparent magnitude
62- 80 A19 --- WISE WISE source name (JHHMMSS.ss+DDMMSS.s)
82- 87 F6.3 mag W1mag [7.5/13.3]? W1 band apparent magnitude
89- 94 F6.3 mag W2mag [7/13.7]? W2 band apparent magnitude
96-101 F6.3 mag W3mag [3.5/11.3]? W3 band apparent magnitude
103-108 F6.3 mag W4mag [-0.92/8.7]? W4 band apparent magnitude
110-126 A17 --- GLIMPSE MIR identification (GLLL.llll+BB.bbbb)
128-133 F6.3 mag 3.6mag [7.4/15.6]? IRAC 3.6um band apparent magnitude
135-140 F6.3 mag 4.5mag [7.4/14.2]? IRAC 4.5um band apparent magnitude
142-147 F6.3 mag 5.8mag [6.9/12.7]? IRAC 5.8um band apparent magnitude
149-154 F6.3 mag 8.0mag [5.8/12.1]? IRAC 8.0um band apparent magnitude
156-163 A8 --- Note Additional notes
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Acknowledgements:
Junfeng Wang [jfwang at xmu.edu.cn]
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 26-Jul-2022