J/ApJ/755/40 HII regions in the Magellanic clouds from MCELS (Pellegrini+, 2012)
The optical depth of H II regions in the Magellanic Clouds.
Pellegrini E.W., Oey M.S., Winkler P.F., Points S.D., Smith R.C.,
Jaskot A.E., Zastrow J.
<Astrophys. J., 755, 40 (2012)>
=2012ApJ...755...40P 2012ApJ...755...40P
ADC_Keywords: H II regions ; Magellanic Clouds
Keywords: catalogs; H II regions; ISM: structure; Magellanic Clouds
radiative transfer; stars: massive
Abstract:
We exploit ionization-parameter mapping (IPM) as a powerful tool to
measure the optical depth of star-forming H II regions. Our
simulations using the photoionization code CLOUDY and our new,
SURFBRIGHT surface-brightness simulator demonstrate that this
technique can directly diagnose most density-bounded, optically thin
nebulae using spatially resolved emission-line data. We apply this
method to the Large and Small Magellanic Clouds (LMC and SMC), using
the data from the Magellanic Clouds Emission Line Survey. We generate
new H II region catalogs based on photoionization criteria set by the
observed ionization structure in the [S II]/[O III] ratio and Hα
surface brightness. The luminosity functions from these catalogs
generally agree with those from Hα-only surveys. We then use IPM
to crudely classify all the nebulae into optically thick versus
optically thin categories, yielding fundamental new insights into
Lyman-continuum (LyC) radiation transfer.
Description:
We apply our technique of ionization-parameter mapping (IPM) to the
LMC and SMC, which have been mapped with narrowband emission-line
imaging by the Magellanic Clouds Emission Line Survey (MCELS; Smith
et al. 1998PASA...15..163S 1998PASA...15..163S, 2005AAS...207.2507S 2005AAS...207.2507S; Points et al.
2005AAS...20713211P 2005AAS...20713211P; Winkler et al. 2005AAS...20713203W 2005AAS...20713203W). This is
a spatially complete, flux-limited survey carried out at the Cerro
Tololo Inter-American Observatory (CTIO) with the University of
Michigan's Curtis 0.6/0.9m Schmidt telescope. Over the course of five
years, the LMC and SMC were imaged in [SII]λλ6717, 6731,
[OIII]5007, and Hα, with respective filter widths of 50, 40, and
30Å. The final product, mosaics in both low- and high-ionization
line emission, and in the Hα recombination line, traces the
ionized ISM at both large and small scales. The process of mosaicking
the images resulted in a binned pixel scale of 3.0 and 2.0"/pixel for
the LMC and SMC, respectively. These correspond to a spatial scale of
0.7pc and 0.6pc for distances of 49kpc and 61kpc, respectively, with
an effective resolution of ∼5".
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 64 401 Magellanic Clouds Emission Line Survey (MCELS)
LMC HII region catalog (from erratum:
2013, ApJ, 766, 138)
table6.dat 64 214 Magellanic Clouds Emission Line Survey (MCELS)
SMC HII region catalog (from erratum:
2013, ApJ, 766, 138)
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See also:
VII/232 : Nebulae in the Magellanic Clouds (Davies+ 1976)
J/A+A/509/A11 : SMC clusters Hα emission-line objects (Martayan+, 2010)
J/ApJS/184/1 : Molecular clouds in the LMC by NANTEN. II. (Kawamura+, 2009)
J/ApJ/566/880 : ISO-SWS observations of H II regions (Giveon+, 2002)
J/MNRAS/311/741 : SMC emission-line objects (Murphy+, 2000)
J/AJ/117/238 : LMC extended catalog (Bica+, 1999)
J/A+A/280/365 : H-alpha Survey of SMC (Le Coarer+ 1993)
Byte-by-byte Description of file: table[56].dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- --- [MCELS-]
7- 10 A4 --- MCELS Object identifier (LNNN for LMC or SNNN)
12- 25 A14 --- OName Other identifier (1)
27 A1 --- f_OName [cd] More identifier flag (2)
29- 30 I2 h RAh Hour of Right Ascension (J2000)
32- 33 I2 min RAm Minute of Right Ascension (J2000)
35- 38 F4.1 s RAs Second of Right Ascension (J2000)
40 A1 --- DE- Sign of the Declination (J2000)
41- 42 I2 deg DEd Degree of Declination (J2000)
44- 45 I2 arcmin DEm Arcminute of Declination (J2000)
47- 48 I2 arcsec DEs Arcsecond of Declination (J2000)
50 I1 --- Type ? Region type (3)
52- 56 F5.2 10+21/cm2 NHI [0/14] Column density of H I
58- 62 F5.2 [10-7W] logL [33/40] Log Hα luminosity; erg/s
64 A1 --- f_logL [ef] Flag on logL (4)
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Note (1): Identifiers are from:
DEM = Davies et al. (1976, Cat. VII/232;
or in Simbad),
BSDL = Bica et al. (1999, Cat. J/AJ/117/238; in Simbad),
N = Henize (1956ApJS....2..315H 1956ApJS....2..315H; for LMC or
in Simbad for SMC).
Note (2): Flag as follows:
c = Object identified in Ye et al. (1995MNRAS.275.1218Y 1995MNRAS.275.1218Y).
d = Object identified in Ye et al. (1991MNRAS.249..722Y 1991MNRAS.249..722Y).
Note (3): Object type as follows:
0 = indeterminate;
1 = optically thick;
2 = blister;
3 = optically thin;
4 = shocked nebulae.
Note (4): Flag as follows:
e = Object includes separately catalogued substructure in the line of sight.
Photometry for the substructure is not included in the photometry of
the larger region.
f = Local Hα backgrounds could not be unambiguously determined for
luminosity measurements of these objects due to a high DIG luminosity,
even though structure is seen in [SII]/[OIII]. Therefore the background
was set to the surface brightness of the outermost area of the LMC
observed by the MCELS survey, as discussed in the text.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 10-Mar-2014