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J/ApJ/675/1213      Abundances in M33 HII regions            (Rosolowsky+, 2008)

The M33 metallicity project: resolving the abundance gradient discrepancies in M33. Rosolowsky E., Simon J.D. <Astrophys. J., 675, 1213-1222 (2008)> =2008ApJ...675.1213R
ADC_Keywords: Galaxies, nearby ; H II regions ; Abundances Keywords: galaxies: abundances - galaxies: individual (M33) - galaxies: spiral - H II regions - ISM: abundances - ISM: evolution Abstract: We present a new determination of the metallicity gradient in M33, based on Keck LRIS measurements of oxygen abundances using the temperature-sensitive emission line [OIII] λ4363 in 61 HII regions. These data approximately triple the sample of direct oxygen abundances in M33. We find a central abundance of 12+log(O/H)=8.36±0.04 and a slope of -0.027±0.012dex/kpc, in agreement with infrared measurements of the neon abundance gradient but much shallower than most previous oxygen gradient measurements. There is substantial intrinsic scatter of 0.11dex in the metallicity at any given radius in M33, which imposes a fundamental limit on the accuracy of gradient measurements that rely on small samples of objects. We also show that the ionization state of neon does not follow the ionization state of oxygen as is commonly assumed, suggesting that neon abundance measurements from optical emission lines require careful treatment of the ionization corrections. Description: The M33 Metallicity Project is a long-term program in which we plan to obtain deep spectroscopy of ∼1000 HII regions in M33 drawn from the unified catalog of Hodge et al. (2002, An Atlas of Local Group Galaxies (Dordrecht: Kluwer)). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 126 63 HII region line fluxes table2.dat 99 63 Balmer series line ratios and derived properties
See also: J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006) J/PASP/111/685 : HII regions of M33. II. (Hodge+, 1999) J/A+A/512/A63 : Abundances of M33 HII regions (Magrini+, 2010) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Seq [1/61] Sequential number 3 A1 --- n_Seq [d] Same object observed on multiple slit masks 5- 6 I2 h RAh Right ascension (J2000.0) (1) 8- 9 I2 min RAm Right ascension (J2000.0) (1) 11- 14 F4.1 s RAs Right ascension (J2000.0) (1) 16 A1 --- DE- Declination sign (J2000.0) (1) 17- 18 I2 deg DEd Declination (J2000.0) (1) 20- 21 I2 arcmin DEm Declination (J2000.0) (1) 23- 24 I2 arcsec DEs Declination (J2000.0) (1) 26- 31 A6 --- Name Cross-identifications (2) 33- 36 F4.2 kpc Rgal Galactocentric distance 38- 42 F5.3 --- F[OII] Flux of [OII]λ3727 line (3) 44- 48 F5.3 --- e_F[OII] rms uncertainty on F[OII] 50- 55 F6.4 --- F[NeIII] Flux of [NeIII]λ3869 line (3) 57- 62 F6.4 --- e_F[NeIII] rms uncertainty on F[NeIII] 64- 70 F7.5 --- F[OIII]1 Flux of [OIII]λ 4363 (3) 72- 77 F6.4 --- e_F[OIII]1 rms uncertainty on F[OIII] 79- 84 F6.4 --- F[OIII]2 Flux of [OIII]λ 4959 (3) 86- 91 F6.4 --- e_F[OIII]2 rms uncertainty on F[OIII] 93- 98 F6.4 --- F[OIII]3 Flux of [OIII]λ 5007 (3) 99-104 F6.4 --- e_F[OIII]3 rms uncertainty on F[OIII] 105-109 I5 K Te([OIII]) Electron temperature, from [OIII] lines 111-114 I4 K e_Te([OIII]) rms uncertainty on Te([OIII]) 116-120 F5.3 --- eps(O) Oxygen abundance{epsilson}(O)=12+log(O/H) 122-126 F5.3 --- e_eps(O) rms uncertainty on oxygen abundance
Note (1): Actual position observed based on targets identified in the Local Group Survey images of Massey et al. (2006, Cat. J/AJ/131/2478). Note (2): Closest matching cataloged HII region for observed coordinates. Catalog abbreviations are: MA = Mayall & Aller (1942ApJ....95....5M), [MA42] NNa in Simbad S = Searle (1971ApJ...168..327S), [S71] M 33 NN in Simbad B = Boulesteix et al. (1974A&A....37...33B), BCLMP NNNNA in Simbad C = Courtes et al. (1987A&A...174...28C), CPSDP NNNA in Simbad Full designations of substructure within individual HII regions (indicated by the letters at the end of the catalog names) are taken from Hodge et al. (2002, An Atlas of Local Group Galaxies (Dordrecht: Kluwer)). Note (3): Extinction-corrected line fluxes relative to Hβ=1.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Seq [1/61] Running identification number 4 A1 --- f_EWHb [b] b when equivalent width was poorly defined 6- 12 F7.2 0.1nm EWHb ? Hβ emission line equivalent width 14- 19 F6.2 0.1nm e_EWHb ? Uncertainty in EWHb 21- 25 F5.3 --- cHb Hβ reddening correction 27- 31 F5.3 --- e_cHb Uncertainty in cHb 33- 37 F5.2 0.1nm EW* Stellar absorption equivalent width 39- 43 F5.2 0.1nm e_EW* Uncertainty in EW* 45- 50 F6.4 --- OHg Observed Hγ relative to Hβ 52- 57 F6.4 --- OHd Observed Hδ relative to Hβ 59- 65 F7.4 --- OH7 Observed H7 relative to Hβ 67- 74 F8.5 --- OH9 Observed H9 relative to Hβ 76- 80 F5.3 --- Hgc Extinction/Absorption corrected Hγ 82- 86 F5.3 --- Hdc Extinction/Absorption corrected Hδ 88- 92 F5.3 --- H7c Extinction/Absorption corrected H7 94- 99 F6.4 --- H9c Extinction/Absorption corrected H9
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 10-Jul-2010
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