J/ApJ/853/151 Oxygen abundances for giant HII regions in NGC 2403 (Mao+, 2018)
Internal variations in empirical oxygen abundances for giant HII regions in the
galaxy NGC 2403.
Mao Y.-W., Lin L., Kong Xu
<Astrophys. J., 853, 151 (2018)>
=2018ApJ...853..151M 2018ApJ...853..151M
ADC_Keywords: Galaxies, nearby; H II regions; Abundances; Spectra, optical;
Interstellar medium
Keywords: galaxies: abundances; galaxies: individual (NGC 2403); galaxies: ISM;
H II regions; ISM: lines and bands
Abstract:
This paper presents a spectroscopic investigation of 11 HII regions in
the nearby galaxy NGC 2403. The HII regions are observed with a
long-slit spectrograph mounted on the 2.16m telescope at XingLong
station of National Astronomical Observatories of China. For each of
the HII regions, spectra are extracted at different nebular radii
along the slit-coverage. Oxygen abundances are empirically estimated
from the strong-line indices R23, N2O2, O3N2, and N2 for each
spectrophotometric unit, with both observation- and model-based
calibrations adopted into the derivation. Radial profiles of these
diversely estimated abundances are drawn for each nebula. In the
results, the oxygen abundances separately estimated with the
prescriptions on the basis of observations and models, albeit from the
same spectral index, systematically deviate from each other; at the
same time, the spectral indices R23 and N2O2 are distributed with flat
profiles, whereas N2 and O3N2 exhibit apparent gradients with the
nebular radius. Because our study naturally samples various ionization
levels, which inherently decline at larger radii within individual HII
regions, the radial distributions indicate not only the robustness of
R23 and N2O2 against ionization variations but also the sensitivity of
N2 and O3N2 to the ionization parameter. The results in this paper
provide observational corroboration of the theoretical prediction
about the deviation in the empirical abundance diagnostics. Our future
work is planned to investigate metal-poor HII regions with measurable
Te, in an attempt to recalibrate the strong-line indices and
consequently disclose the cause of the discrepancies between the
empirical oxygen abundances.
Description:
We selected 11 HII regions, bright and large enough for spatially
resolved studies, inside NGC 2403 from the catalog of Sivan+
1990A&A...237...23S 1990A&A...237...23S as the sample.
Spectroscopic observations were taken during seven nights in the years
2007 and 2008, with the 2.16m telescope mounted at XingLong station of
National Astronomical Observatories of China, as part of a
spectroscopic survey of HII regions in nearby galaxies (Kong+
2014ChA&A..38..427K 2014ChA&A..38..427K ; Lin et al. 2017, in preparation). The OMR
(Opto-Mechanics Research Inc.) long-slit spectrograph was used to
obtain spectra with a wavelength range of 3500-8000Å and a spectral
resolution of 500-550 at 5000Å.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 79 12 Basic properties for the HII regions and
information about the observations
table2.dat 81 101 Observed emission-line fluxes for the
spectrophotometric units
table3.dat 82 101 Attenuation-corrected emission-line fluxes for the
spectrophotometric units
table4.dat 76 12 Empirical oxygen abundances (12+log(O/H)) for
the HII regions with integrated measurements
table5.dat 76 12 Empirical oxygen abundances (12+log(O/H)) for
the centers of the HII regions
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See also:
J/AJ/116/2805 : H II regions in spiral galaxies (Van Zee+, 1998)
J/ApJ/510/104 : Ionizing Stars of Extragalactic H II Regions (Bresolin+ 1999)
J/ApJ/513/168 : HST observations of carbon in spiral galaxies (Garnett+, 1999)
J/ApJS/190/233 : Spectroscopy & abundances of SINGS galaxies (Moustakas+, 2010)
J/AJ/139/1066 : X-ray view of NGC 2403 central region (Yukita+, 2010)
J/ApJ/755/40 : HII reg. in Magellanic clouds from MCELS (Pellegrini+, 2012)
J/ApJS/208/10 : κ-distribution effects in HII regions (Dopita+, 2013)
J/A+A/569/A68 : Green Bank Telescope observations of NGC 2403 (de Blok+, 2014)
J/ApJ/789/76 : UV and IR properties for galaxies (Mao+, 2014)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Reg HII region identifier (1)
6- 7 I2 h RAh Hour of right ascension (J2000) (2)
9- 10 I2 min RAm Minute of right ascension (J2000)
12- 15 F4.1 s RAs Second of right ascension (J2000)
17 A1 --- DE- Sign of declination (J2000) (2)
18- 19 I2 deg DEd Degree of declination (J2000) (2)
21- 22 I2 arcmin DEm Arcminute of declination (J2000)
24- 25 I2 arcsec DEs Arcsecond of declination (J2000)
27- 32 F6.3 10-16W/m2 FHa [0.3/30.1] Hα flux
in 10-13erg/s/cm2 units (1)
34 A1 --- f_FHa [a] Flag on FHa for HII region no. 351 (3)
36- 46 A11 "Y/M/D" Date Observation date (UT)
48- 51 I4 s Exp Exposure time
53 A1 --- --- [x]
55 I1 --- Nexp Number of exposure
57- 66 A10 --- Std Standard star selected from the IRS catalog
(Corbin & Warren 1991, I/172)
68- 72 F5.1 deg Slit [-78/63] Rotation angle of the spectrographic
slit (4)
74- 79 F6.4 --- Airmass [1.1/1.2] Airmass at each slit position
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Note (1): Data are obtained from Sivan et al. (1990A&A...237...23S 1990A&A...237...23S).
We observed the No. 044 HII region twice with two different position
angles of the slit. The two observations are identified as 044a and
044b, respectively.
Note added by CDS: in Table 1 of the paper, "244" is very likely
a misprint for "224" (see Hα flux in Sivan et al.).
Note (2): Data are obtained from astrometry information in the
continuum-subtracted Hα narrowband image of NGC 2403, taken with
the 2.1m telescope at Kitt Peak National Observatory.
Note (3):
a = The F(Hα) for No. 351 HII region in this table is in reality a
sum of fluxes for the HII regions Nos. 348, 351, and 352, since the
three HII regions are unable to be resolved in our observations.
Note (4): The orientation from north to east is defined to be positive, and
that from north to west is defined to be negative.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Reg HII region identifier
5 A1 --- --- [_]
6- 8 A3 --- ID Source identifier within Reg
10- 15 F6.2 10-18W/m2 Hb [0.3/289.2] Hβ line flux;
in 1e-15erg/s/cm2 units
17- 20 F4.2 10-18W/m2 e_Hb [0.1/2.2] Uncertainty in Hb
22- 26 F5.2 --- OII-3727 [1.2/21.1] The [OII]3727Å line flux (1)
28- 31 F4.2 --- e_OII-3727 [0.02/5.8] Uncertainty in OII-3727
33- 36 F4.2 --- Hg [0.3/1.4] The Hγ line flux (1)
38- 41 F4.2 --- e_Hg [0/0.7]? Uncertainty in Hg
43- 46 F4.2 --- OIII-4959 [0.2/1.5] The [OIII]4959Å line flux (1)
48- 51 F4.2 --- e_OIII-4959 [0/0.7] Uncertainty in OIII-4959
53- 56 F4.2 --- OIII-5007 [0.6/4.5] The [OIII]5007Å line flux (1)
58- 61 F4.2 --- e_OIII-5007 [0.01/1.1] Uncertainty in OIII-5007
63- 66 F4.2 --- Ha [1.7/4.3] Hα line flux (1)
68- 71 F4.2 --- e_Ha [0.01/1.1] Uncertainty in Ha
73- 76 F4.2 --- NII-6583 [0.09/0.9]? The [NII]6583Å line flux (1)
78- 81 F4.2 --- e_NII-6583 [0/1.6]? Uncertainty in NII-6583
--------------------------------------------------------------------------------
Note (1): Relative to Hb. All the fluxes are NOT corrected for internal
dust attenuation.
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Reg HII region identifier
5 A1 --- --- [_]
6- 8 A3 --- ID Source identifier within Reg
10- 15 F6.2 10-18W/m2 Hb [0.4/347.3] Hβ line flux;
in 1e-15erg/s/cm2 units
17- 20 F4.2 10-18W/m2 e_Hb [0.1/9.7] Uncertainty in Hb
22- 26 F5.2 --- OII-3727 [1.2/21.7] The [OII]3727Å line flux (1)
28- 32 F5.2 --- e_OII-3727 [0.03/29.7] Uncertainty in OII-3727
34- 37 F4.2 --- Hg [0.3/1.4] The Hγ line flux (1)
39- 42 F4.2 --- e_Hg [0.01/1.3]? Uncertainty in Hg
44- 47 F4.2 --- OIII-4959 [0.2/1.5] The [OIII]4959Å line flux (1)
49- 52 F4.2 --- e_OIII-4959 [0.01/0.7] Uncertainty in OIII-4959
54- 57 F4.2 --- OIII-5007 [0.6/4.5] The [OIII]5007Å line flux (1)
59- 62 F4.2 --- e_OIII-5007 [0.01/2] Uncertainty in OIII-5007
64- 67 F4.2 --- Ha [1.7/2.9] Hα line flux (1)
69- 72 F4.2 --- e_Ha [0.02/3] Uncertainty in Ha
74- 77 F4.2 --- NII-6583 [0.08/0.8]? The [NII]6583Å line flux (1)
79- 82 F4.2 --- e_NII-6583 [0/1.7]? Uncertainty in NII-6583
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Note (1): Relative to Hb.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Reg HII region identifier
6- 10 F5.3 --- R23K99i [8.4/8.9] R23 calibration addressed in
Kobulnicky+ (1999ApJ...514..544K 1999ApJ...514..544K);
integrated measurements
12- 16 F5.3 --- e_R23K99i [0.008/0.08] R23K99i uncertainty
18- 22 F5.3 --- N2O2K02i [8.2/8.9]? N2O2 calibration addressed in
Kewley & Dopita (2002ApJS..142...35K 2002ApJS..142...35K);
integrated measurements
24- 28 F5.3 --- e_N2O2K02i [0.006/0.07]? N2O2K02i uncertainty
30- 34 F5.3 --- R23P05i [7.9/8.6] R23 calibration addressed in
Pilyugin & Thuan (2005ApJ...631..231P 2005ApJ...631..231P);
integrated measurements
36- 40 F5.3 --- e_R23P05i [0.009/0.09] R23P05i uncertainty
42- 46 F5.3 --- N2O2B07i [7.9/8.5]? N2O2 calibration addressed in
Bresolin (2007ApJ...656..186B 2007ApJ...656..186B);
integrated measurements
48- 52 F5.3 --- e_N2O2B07i [0.006/0.06]? N2O2B07i uncertainty
54- 58 F5.3 --- O3N2P04i [8/8.5]? O3N2 calibration addressed in
Pettini & Pagel (2004MNRAS.348L..59P 2004MNRAS.348L..59P);
integrated measurements
60- 64 F5.3 --- e_O3N2P04i [0.003/0.03]? O3N2P04i uncertainty
66- 70 F5.3 --- N2P04i [8/8.4]? N2 calibration addressed in
Pettini & Pagel (2004MNRAS.348L..59P 2004MNRAS.348L..59P);
integrated measurements
72- 76 F5.3 --- e_N2P04i [0.004/0.03]? N2P04i uncertainty
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Reg HII region identifier
6- 10 F5.3 --- R23K99 [8.5/8.9] R23 calibration addressed in
Kobulnicky+ (1999ApJ...514..544K 1999ApJ...514..544K); HII center
12- 16 F5.3 --- e_R23K99 [0.004/0.08] R23K99 uncertainty
18- 22 F5.3 --- N2O2K02 [8.2/9]? N2O2 calibration addressed in
Kewley & Dopita (2002ApJS..142...35K 2002ApJS..142...35K); HII center
24- 28 F5.3 --- e_N2O2K02 [0.005/0.07]? N2O2K02 uncertainty
30- 34 F5.3 --- R23P05 [8.1/8.7] R23 calibration addressed in
Pilyugin & Thuan (2005ApJ...631..231P 2005ApJ...631..231P);
HII center
36- 40 F5.3 --- e_R23P05 [0.004/0.09] R23P05 uncertainty
42- 46 F5.3 --- N2O2B07 [7.9/8.5]? N2O2 calibration addressed in
Bresolin (2007ApJ...656..186B 2007ApJ...656..186B); HII center
48- 52 F5.3 --- e_N2O2B07 [0.004/0.07]? N2O2B07 uncertainty
54- 58 F5.3 --- O3N2P04 [8/8.5]? O3N2 calibration addressed in
Pettini & Pagel (2004MNRAS.348L..59P 2004MNRAS.348L..59P); HII center
60- 64 F5.3 --- e_O3N2P04 [0.002/0.03]? O3N2P04 uncertainty
66- 70 F5.3 --- N2P04 [8/8.4]? N2 calibration addressed in
Pettini & Pagel (2004MNRAS.348L..59P 2004MNRAS.348L..59P); HII center
72- 76 F5.3 --- e_N2P04 [0.003/0.04]? N2P04 uncertainty
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 31-Oct-2018