2009ApJ...700..309B

Query : 2009ApJ...700..309B

2009ApJ...700..309B - Astrophys. J., 700, 309-330 (2009/July-3)

Extragalactic chemical abundances: do H II regions and young stars tell the same story? the case of the spiral galaxy NGC 300.

BRESOLIN F., GIEREN W., KUDRITZKI R.-P., PIETRZYNSKI G., URBANEJA M.A. and CARRARO G.

Abstract (from CDS):

We have obtained new spectrophotometric data for 28 H II regions in the spiral galaxy NGC 300, a member of the nearby Sculptor Group. The detection of several auroral lines, including [O III] λ4363, [S III] λ6312, and [N II] λ5755, has allowed us to measure electron temperatures and direct chemical abundances for the whole sample. We determine for the first time in this galaxy a radial gas-phase oxygen abundance gradient based solely on auroral lines, and obtain the following least-square solution: 12 + log(O/H) = 8.57(±0.02) - 0.41(±0.03)R/R25, where the galactocentric distance is expressed in terms of the isophotal radius R25. The characteristic oxygen abundance, measured at 0.4xR25, is 12 + log(O/H) = 8.41. The gradient corresponds to -0.077±0.006 dex/kpc, and agrees very well with the galactocentric trend in metallicity obtained for 29 B and A supergiants in the same galaxy, -0.081±0.011 dex/kpc. The intercept of the regression for the nebular data virtually coincides with the intercept obtained from the stellar data, which is 8.59(±0.05). This allows little room for depletion of nebular oxygen onto dust grains, although in this kind of comparison we are somewhat limited by systematic uncertainties, such as those related to the atomic parameters used to derive the chemical compositions. We discuss the implications of our result with regard to strong-line abundance indicators commonly used to estimate the chemical compositions of star-forming galaxies, such as R23. By applying a few popular calibrations of these indices based on grids of photoionization models on the NGC 300 H II region fluxes, we find metallicities that are higher by 0.3 dex (a factor of 2) or more relative to our nebular (Tebased) and stellar ones. We detect Wolf-Rayet stellar emission features in ∼1/3 of our H II region spectra, and find that in one of the nebulae hosting these hot stars the ionizing field has a particularly hard spectrum, as gauged by the "softness" parameter η = (O+/O++)/(S+/S++). We suggest that this is related to the presence of an early WN star. By considering a larger sample of extragalactic H II regions we confirm, using direct abundance measurements, previous findings of a metallicity dependence of η, in the sense that softer stellar continua are found at high metallicity.

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Journal keyword(s): galaxies: abundances - galaxies: individual: NGC 300 - galaxies: ISM

Nomenclature: Fig. 1, Table 2: [BGK2009] NN (Nos 1-28).

Simbad objects: 76

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Number of rows : 76
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 M 31 AGN 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 13622 1
2 WG 2 WD* 00 50 03.6496829856 -52 08 15.516264516 13.354 14.157 14.206 14.31 14.428 DA2.7 92 0
3 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 12317 1
4 [DCL88] 5 HII 00 54 16.19 -37 34 32.4           ~ 8 0
5 [DCL88] 6 HII 00 54 16.39 -37 34 52.5     18.66     ~ 12 2
6 PEB NGC 300 7 HII 00 54 16.64 -37 35 23.5           ~ 7 1
7 [BGK2009] 3 HII 00 54 17.98 -37 35 33.2           ~ 3 0
8 [DCL88] 12 HII 00 54 22.87 -37 34 23.0           ~ 6 0
9 [BL97] N300-H3 HII 00 54 28.75 -37 41 32.7     18.05     ~ 13 0
10 [DCL88] 25 HII 00 54 28.77 -37 38 36.6           ~ 6 0
11 STWR 8 WR* 00 54 31.4 -37 37 59           WNe 3 0
12 [BL97] N300-H4 HII 00 54 31.71 -37 37 58.4           ~ 9 0
13 [BL97] N300-H5 HII 00 54 32.18 -37 38 34.6           ~ 8 0
14 [BGK2009] 9 HII 00 54 35.48 -37 39 38.4           ~ 11 0
15 XMMU J005438.1-374144 HII 00 54 38.42 -37 41 43.7           ~ 14 0
16 [BGK2009] 12 HII 00 54 40.46 -37 40 55.1     16.85     ~ 17 0
17 [DCL88] 46 HII 00 54 40.56 -37 43 00.5           ~ 7 0
18 STWR 10 WR* 00 54 42.1 -37 43 06           ~ 4 0
19 [DCL88] 50 HII 00 54 42.34 -37 38 53.6           ~ 6 0
20 [BL97] N300-S11 SNR 00 54 42.61 -37 43 13.7           ~ 16 2
21 [DCL88] 53C HII 00 54 42.77 -37 42 54.9     17.09     ~ 9 0
22 [SCA2003] 4 WR* 00 54 42.78 -37 43 01.8           WN 2 0
23 [DCL88] 53A SNR 00 54 43.41 -37 43 07.5     18.09     ~ 18 2
24 [BGK2009] 15 HII 00 54 44.21 -37 40 26.6           ~ 12 0
25 [BGK2009] 16 HII 00 54 44.62 -37 40 00.8           ~ 6 0
26 [SCA2003] 7 WR* 00 54 45.22 -37 38 48.0           ~ 2 0
27 XMMU J005445.3-373847 HII 00 54 45.27 -37 38 45.9           ~ 14 0
28 [SCA2003] 8 WR* 00 54 45.28 -37 38 47.0           WNL 3 0
29 [BGK2009] 18 HII 00 54 45.50 -37 37 55.2           ~ 8 0
30 STWR 9 WR* 00 54 49.9 -37 38 21   19.4       WCwn+ 5 0
31 [BAT97] I 2 WR* 00 54 50.2 -37 38 23   21.4       WNE 4 0
32 [S66b] 39 HII 00 54 50.34 -37 38 22.6     17.24     ~ 16 2
33 [SCA2003] 18 WR* 00 54 51.65 -37 39 39.2     18.79     ~ 2 0
34 XMMU J005451.7-373939 HII 00 54 51.96 -37 39 38.5 17.168 19.517 19.073     ~ 19 0
35 NGC 300 GiG 00 54 53.4465638304 -37 41 03.168402396 8.83 8.69 8.13 7.46   ~ 1614 2
36 [BGK2009] 21 HII 00 54 57.02 -37 41 12.4           ~ 3 0
37 PEB NGC 300 2 HII 00 55 00.59 -37 40 36.6     18.21     ~ 12 0
38 [BL97] N300-H18 SNR 00 55 03.50 -37 42 46.0     17.44     ~ 22 2
39 [SCA2003] 35 WR* 00 55 03.55 -37 42 49.4     18.82     ~ 2 0
40 [SCA2003] 36 WR* 00 55 03.64 -37 43 20.0     17.97     ~ 2 0
41 [DCL88] 119A SNR 00 55 03.74 -37 43 18.3     16.70     ~ 19 2
42 [MKW2020] 118-WR1 WR* 00 55 03.780 -37 42 51.80     18.56     WC 3 0
43 [DCL88] 128 HII 00 55 08.57 -37 41 39.4           ~ 5 0
44 STWR 4 WR* 00 55 12.63 -37 41 39.4   19.0       WN3/6 5 0
45 [SCA2003] 50 WR* 00 55 12.65 -37 41 38.5     19.73     ~ 2 0
46 [SCA2003] 51 WR* 00 55 12.72 -37 41 44.6     20.38     ~ 2 0
47 [DRW83] NGC 300 14 HII 00 55 12.79 -37 41 37.0     16.84     ~ 20 2
48 [BGK2002] A10 V* 00 55 31.961 -37 41 38.33   19.05 18.98     A2 8 0
49 [S66b] 80 SR? 00 55 33.83 -37 43 12.9           ~ 14 1
50 [DCL88] 161 HII 00 55 36.50 -37 41 46.0           ~ 8 0
51 NAME Scl Group GrG 01 00 06 -33 44.2           ~ 526 0
52 IC 1613 GiC 01 04 48.4071 +02 07 10.185   10.42 10.01 9.77   ~ 1316 2
53 M 33 GiG 01 33 50.8965749232 +30 39 36.630403128 6.17 6.27 5.72     ~ 6226 1
54 NGC 604 HII 01 34 32.1 +30 47 01           ~ 608 0
55 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 7988 0
56 CPD-69 177 WD* 03 10 31.0195960176 -68 36 03.380768388 10.757 11.413 11.394 11.47 11.558 DA3.0 299 0
57 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 19090 0
58 NAME Ori Trapezium OpC 05 35 16.5 -05 23 14           ~ 1708 1
59 M 42 HII 05 35 16.8 -05 23 15           ~ 4411 0
60 NAME 30 Dor Region reg 05 38.0 -69 06           ~ 261 0
61 NGC 3109 AG? 10 03 06.877 -26 09 34.46 11.10 10.42 10.04 9.91   ~ 825 2
62 [CPB2015] NGC5194-4.3+63.3 HII 13 29 52.300 +47 12 46.34           ~ 11 0
63 M 51 Sy2 13 29 52.698 +47 11 42.93   9.26 8.36 8.40   ~ 4565 4
64 M 101 GiP 14 03 12.583 +54 20 55.50   8.46 7.86 7.76   ~ 3138 2
65 NGC 5471 EmG 14 04 28.627 +54 23 52.84           ~ 250 1
66 CXOU J140429.1+542353 SNR 14 04 29.1 +54 23 53           ~ 37 0
67 NGC 5471A HII 14 04 29.50 +54 23 47.1           ~ 22 0
68 CD-38 10980 WD* 16 23 33.8380498896 -39 13 46.161043572 9.916 10.885 11.029 10.936 10.841 DA2 526 0
69 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 16269 0
70 M 8 OpC 18 03 37 -24 23.2           ~ 644 1
71 NGC 6618 OpC 18 20 47 -16 10.3           ~ 1700 0
72 NGC 6822 G 19 44 56.199 -14 47 51.29   18 8.1     ~ 1661 0
73 LAWD 87 WD* 21 32 16.2327040616 +00 15 14.399267982 13.717 14.634 14.674 14.675 14.676 DB4 195 1
74 NGC 7293 PN 22 29 38.5454047152 -20 50 13.747242408 11.894 13.158 13.524 13.689 13.898 DAO.5 983 1
75 NGC 5471D HII ~ ~           ~ 16 0
76 NAME Local Group GrG ~ ~           ~ 9325 0

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