J/ApJS/213/23 Deep Chandra obs. of the giant HII region N11 in LMC (Naze+, 2014)
A deep Chandra observation of the giant H II region N11.
I. X-ray sources in the field.
Naze Y., Wang Q.D., Chu Y.-H., Gruendl R., Oskinova L.
<Astrophys. J. Suppl. Ser., 213, 23 (2014)>
=2014ApJS..213...23N 2014ApJS..213...23N
ADC_Keywords: X-ray sources ; H II regions ; Magellanic Clouds ;
Cross identifications ; Infrared sources
Keywords: galaxies: star clusters: general;
ISM: individual: LMC N11; Magellanic Clouds; X-rays: stars
Abstract:
A very sensitive X-ray investigation of the giant H II region N11 in
the Large Megallanic Cloud was performed using the Chandra X-ray
Observatory. The 300ks observation reveals X-ray sources with
luminosities down to 1032erg/s, increasing the number of known point
sources in the field by more than a factor of five. Among these
detections are 13 massive stars (3 compact groups of massive stars, 9
O stars, and one early B star) with log (LX/LBOL)~-6.5 to -7,
which may suggest that they are highly magnetic or colliding-wind
systems. On the other hand, the stacked signal for regions
corresponding to undetected O stars yields log (LX/LBOL)~-7.3,
i.e., an emission level comparable to similar Galactic stars despite
the lower metallicity. Other point sources coincide with 11 foreground
stars, 6 late-B/A stars in N11, and many background objects. This
observation also uncovers the extent and detailed spatial properties
of the soft, diffuse emission regions, but the presence of some hotter
plasma in their spectra suggests contamination by the unresolved
stellar population.
Description:
The Chandra ACIS-I observations of N11 were made in six separate
segments (ObsID 8210, 8469, 8468, 8467, 8470 and 8211) within two
months (June-July) in 2007.
We found 165 sources in N11: 43 of them were detected with the highest
confidence or smallest P value in the S band (soft 0.5-2keV), 5 in the
H band (hard 2-8keV), and 117 in the T band (total 0.5-8keV).
We further used Hα, [OIII], and [SII] images taken with the
MOSAIC camera on the Blanco 4m Telescope at the Cerro Tololo
Inter-American Observatory. The [OIII]λ5007 observations and
the [SII]6716,6731 observations consist of four dithered 450s
exposures for each location; these images were obtained on 2011
October 31. We have also used infrared observations made with the
Spitzer Space Telescope from Gruendl & Chu (2009, Cat. J/ApJS/184/172).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 80 165 Chandra source list
table3.dat 128 71 Counterparts to the X-ray sources within 1"
table4.dat 106 84 Counterparts to X-ray sources found within 1" of
our dedicated data (optical [SII] image, 3.6+8.0um
Spitzer data) and suggested nature of the sources
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
II/288 : IRSF Magellanic Clouds Point Source Catalog (Kato+ 2007)
II/228 : DENIS Catalogue toward Magellanic Clouds (DCMC) (Cioni+ 2000)
J/A+A/555/A83 : X-ray properties of HM1 and IC2944/2948 (Naze+, 2013)
J/ApJ/747/107 : QSO Candidates in the MACHO LMC database (Kim+, 2012)
J/ApJS/194/7 : X-ray properties of O and B stars in Carina (Naze+, 2011)
J/A+A/506/1055 : Hot stars emitting in X-ray. I. (Naze, 2009)
J/ApJS/184/172 : High- and intermediate-mass YSOs in the LMC (Gruendl+, 2009)
J/AJ/136/18 : LMC SAGE. New candidate YSOs (Whitney+, 2008)
J/AJ/132/2653 : JHKs photometry of N11 young stellar objects (Hatano+, 2006)
J/ApJS/160/319 : COUP: observations and source lists (Getman+, 2005)
J/A+A/418/841 : XMM-Newton observations of N11 in the LMC (Naze+, 2004)
J/AJ/128/1606 : Magellanic Clouds Photometric Survey: LMC (Zaritsky+, 2004)
J/AJ/125/1940 : JHKs photometry in LMC HII region N11B (Barba+, 2003)
J/AJ/118/1684 : UBV photometry of 4 LMC compact OB groups (Walborn+, 1999)
J/AJ/103/1205 : Stellar Content of LH 9 and 10 in the LMC (Parker+ 1992)
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 [1/165] Running source number
5- 23 A19 --- CXOU Chandra identifier (JHHMMSS.ss+DDMMSS.s) (1)
25- 27 F3.1 arcsec ePos [0.2/4.6] The 1σ position uncertainty (2)
29- 32 F4.2 ct/ks CR [0.04/7.5] On-axis source total count rate (3)
34- 37 F4.2 ct/ks e_CR Uncertainty in CR
39- 43 F5.2 --- HR1 [-1/1]? First hardness ratio (4)
45- 48 F4.2 --- e_HR1 ? Uncertainty in HR1
50- 54 F5.2 --- HR2 [-1/1]? Second hardness ratio (5)
56- 59 F4.2 --- e_HR2 ? Uncertainty in HR2
61- 64 F4.1 arcmin theta [0.2/11.4] Off-axis angle
66- 69 I4 ct Cts [5/1000] Raw counts
71- 74 F4.1 ct bgCt Background counts
76- 78 I3 ks Exp Effective exposures in the detection aperture
80 A1 --- Det [TSH] Detection flag (6)
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Note (1): Following the Chandra naming convention and the IAU
Recommendation for Nomenclature.
Note (2): Calculated from the maximum likelihood centroiding and an approximate
off-axis angle (r) dependent systematic error 0.2"+1.4"(r/8')2
(an approximation to Fig. 4 of Feigelson et al. (2002,
Cat. J/ApJ/574/258)), which are added in quadrature. Note that they
may be overestimated, see Getman et al. (2005, Cat. J/ApJS/160/319,
in particular Fig.9).
Note (3): The sum of the exposure-corrected count rates in the 4 narrow bands.
Note (4): HR1=(H-S2)/(H+S2) where H=2.0-8.0keV band and
S2=1.0-2.0keV band. Listed only for values with uncertainties
less than 0.2.
Note (5): HR2=(S2-S1)/S where S=0.5-2.0keV band, S2=1.0-2.0keV band,
and S1=0.5-1.0keV band. Listed only for values with
uncertainties less than 0.2.
Note (6): The label "T", "S", or "H" mark the band in which a source is
detected with the most accurate position that is adopted in column 2.
H is the hard band, 2.0-8.0keV, S is the soft band, 0.5-2.0keV,
and T is the total band, 0.5-8.0keV.
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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 [1/165] Running source number
4 A1 --- f_Seq [*] Flag on Seq (1)
6- 9 F4.2 arcsec Off2M [0.09/0.9]? 2MASS position offset
11- 26 A16 --- 2MASS 2MASS counterpart ID (J2000; Cat. II/246)
28- 31 F4.2 arcsec OffDC [0.1/0.8]? DCMC position offset
33- 51 A19 --- DCMC DCMC counterpart identifier (Cat. II/228)
53- 56 F4.2 arcsec OffGSC [0.09/1]? GSC position offset
58- 67 A10 --- GSC2.3 GSC-II counterpart identifier (Cat. I/305)
69- 72 F4.2 arcsec OffH6 [0.1/0.7]? Hatano et al. 2006,
Cat. J/AJ/132/2653 position offset
74- 83 A10 --- [HKN2006] Hatano et al. counterpart identifier (2)
85- 88 F4.2 arcsec OffIR [0.1/1]? IRSF position offset
90-105 A16 --- IRSF IRSF counterpart ID (J2000; Cat. II/288) (3)
107-110 F4.2 arcsec OffMC [0.04/1]? MCPS position offset (4)
112-115 F4.2 arcsec OffU [0.1/1]? USNO position offset
117-128 A12 --- USNO USNO-B1.0 counterpart identifier (Cat. I/284)
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Note (1): An "*" indicates a source associated with a massive
star (see Table 6).
Note (2): The type suggested by Hatano et al. (2006, Cat. J/AJ/132/2653) is
given between the parentheses.
Note (3): For IRSF, there are additional components within 1" for
Num 24, 36, 38, 77, 106, 123, 164. Only the closest source is
mentioned above.
Note (4): Magellanic Clouds Photometric Survey (MCPS; Zaritsky et al. 2004,
Cat. J/AJ/128/1606).
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/165] Running source number
5 A1 --- SII? [y ] Emission from [SII] detected?
7 A1 --- 3.6? [y ] Spitzer 3.6µm emission detected? (1)
9 A1 --- 8.0? [y ] Spitzer 8.0µm emission detected? (1)
11- 14 F4.2 arcsec Offset [0.09/1]? Spitzer position offset
16- 33 A18 --- Name Spitzer identifier (HHMMSS.ss+DDMMSS.s) (1)
35- 73 A39 --- Comm Comment
75-106 A32 --- Nature Suggested nature of source
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Note (1): Detections in only two Spitzer channels are noted, but a few named
sources have detections only in the other channels. Some sources are
quoted with a visual detection ("y" in the third and/or fourth
columns) without a name listed for the Spitzer counterpart: this
happens because the automated detection misses some sources,
especially faint ones in high background regions.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 05-Sep-2014