J/ApJ/923/78 HII regions in the northern half of M33 (Sawant+, 2021)
Limits to ionization-parameter mapping as a diagnostic of HII region optical
depth.
Sawant A.N., Pellegrini E.W., Oey M.S., Lopez-Hernandez J., Micheva G.
<Astrophys. J., 923, 78-78 (2021)>
=2021ApJ...923...78S 2021ApJ...923...78S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, optical; H II regions; Abundances
Keywords: Disk galaxies; Irregular galaxies; Starburst galaxies
Emission line galaxies; Interstellar line emission; Nebulae
Direct imaging; Radiative transfer; Young massive clusters
Star formation; Astrostatistics distributions
Abstract:
We employ ionization-parameter mapping (IPM) to infer the optical
depth of HII regions in the northern half of M33. We construct
[OIII]λ5007/[OII]λ3727 and
[OIII]λ5007/[SII]λ6724 ratio maps from narrowband images
continuum-subtracted in this way, from which we classify the
HII regions by optical depth to ionizing radiation, based on their
ionization structure. This method works relatively well in the
low-metallicity regime, 12+log(O/H)≤8.4, where
[OIII]λλ4959,5007 is strong. However, at higher
metallicities, the method breaks down due to the strong dependence of
the [OIII]λλ4959,5007 emission lines on the nebular
temperature. Thus, although O++ may be present in metal-rich
HII regions, these commonly used emission lines do not serve as a
useful indicator of its presence, and hence the O ionization state. In
addition, IPM as a diagnostic of optical depth is limited by spatial
resolution. We also report a region of highly excited [OIII] extending
over an area ∼1kpc across and [OIII]λ5007 luminosity of
4.9±1.5x1038erg/s, which is several times higher than the ionizing
budget of any potential sources in this portion of the galaxy.
Finally, this work introduces a new method for continuum subtraction
of narrowband images based on the dispersion of pixels around the mode
of the diffuse-light flux distribution. In addition to M33, we
demonstrate the method on CIII]λ1909 imaging of Haro 11,
ESO338-IG004, and Mrk 71.
Description:
The north half of M33 was observed with the MOSAIC-1.1 imaging camera
at the Mayall 4m telescope, Kitt Peak National Observatory, on
2011 October 28-29. We used the narrowband filters for
[OII]λ3727 ("O2" FWHM 50Å), [OIII]λ5007 ("O3," FWHM
50Å), and [SII]λ6724 ("ha16," FWHM 81Å) for line imaging.
For the continuum, we used broadband filters BATC454 (∼4320-4700Å)
and BATC705 (∼6950-7920Å) for continuum subtraction of [OII] and
[OIII], and of Hα and [SII], respectively. We also used archive
Hα observations obtained in 2001.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 122 108 HII regions in northern M33
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See also:
J/A+A/426/11 : XMM-Newton survey of M33 (Pietsch+, 2004)
J/A+A/462/535 : Low-metallicity HII regions and galaxies (Yin+, 2007)
J/AJ/134/2474 : Ha emission-line stars in 7 dwarfs galaxies (Massey+, 2007)
J/ApJ/733/123 : The Wolf-Rayet content of M33 (NGC 598) (Neugent+, 2011)
J/ApJ/755/40 : HII reg. in Magellanic clouds from MCELS (Pellegrini+, 2012)
J/A+A/559/A114 : Updated O3N2 and N2 abundance indicators (Marino+, 2013)
J/ApJ/842/97 : Spectroscopic obs. of 413 HII regions in M33 (Lin+, 2017)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Object Identifier
13 I1 h RAh [1] Hour of Right Ascension (J2000)
15- 16 I2 min RAm [32/35] Minute of Right Ascension (J2000)
18- 22 F5.2 s RAs Second of Right Ascension (J2000)
24 A1 --- DE- [+] Sign of Declination (J2000)
25- 26 I2 deg DEd [30/31] Degree of Declination (J2000)
28- 29 I2 arcmin DEm Arcminute of Declination (J2000)
31- 34 F4.1 arcsec DEs Arcsecond of Declination (J2000)
36- 40 F5.3 [-] 12+log(O/H) [8/8.7] Metallicity (12+log(O/H)) (1)
42- 46 F5.3 [-] e_12+log(O/H) [0.003/0.03] Lower error of 12+log(O/H) (1)
48- 52 F5.3 [-] E_12+log(O/H) [0.003/0.03] Upper error of 12+log(O/H) (1)
54 I1 --- Opac [1/5] Opacity classification (2)
56- 63 E8.2 10+29W LHa [4.6/4710] H-alpha luminosity of the
object, 10+36erg/s
65- 71 E7.1 10+29W e_LHa [0.01/63] Error in LHa
73- 80 E8.2 10+29W LOII [2/1750] OII luminosity of the object,
10+36erg/s
82- 88 E7.1 10+29W e_LOII [0.01/61] Error in LOII
90- 97 E8.2 10+29W LOIII [0.1/2030] OIII luminosity of the object,
10+36erg/s
99- 105 E7.1 10+29W e_LOIII [0.03/29] Error in LOIII
107- 114 E8.2 10+29W LSII [0.9/802] SII luminosity of the object,
10+36erg/s
116- 122 E7.1 10+29W e_LSII [0.02/40] Error in LSII
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Note (1): Oxygen Abundances taken from Lin+ (2017, J/ApJ/842/97)
Spectroscopic Observation and Analysis of HII Regions in M33 with MMT:
Temperatures and Oxygen Abundances
Note (2): Opacity classification numbered as follows:
1 = optically thick (74 occurrences)
2 = blister (12 occurrences)
3 = optically thin (7 occurrences)
4 = shocked (8 occurrences)
5 = indeterminate (2 occurrences)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-May-2023