1999ApJ...511..639I


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.05CET17:47:12

1999ApJ...511..639I - Astrophys. J., 511, 639-659 (1999/February-1)

Heavy-element abundances in blue compact galaxies.

IZOTOV Y.I. and THUAN T.X.

Abstract (from CDS):

We present high-quality ground-based spectroscopic observations of 54 supergiant H II regions in 50 low-metallicity blue compact galaxies with oxygen abundances 12+logO/H between 7.1 and 8.3. We use the data to determine abundances for the elements N, O, Ne, S, Ar, and Fe. We also analyze Hubble Space Telescope (HST) Faint Object Spectrograph archival spectra of 10 supergiant H II regions to derive C and Si abundances in a subsample of seven BCGs. The main result of the present study is that none of the heavy element-to-oxygen abundance ratios studied here (C/O, N/O, Ne/O, Si/O, S/O, Ar/O, Fe/O) depend on oxygen abundance for BCGs with 12+logO/H≤7.6 (Z≤Z/20). This constancy implies that all of these heavy elements have a primary origin and are produced by the same massive (M≥10 M) stars responsible for O production. The dispersion of the ratios C/O and N/O in these galaxies is found to be remarkably small, being only ±0.03 and ±0.02 dex, respectively. This very small dispersion is strong evidence against any time-delayed production of C and primary N in the lowest metallicity BCGs (secondary N production is negligible at these low metallicities). The absence of a time-delayed production of C and N is consistent with the scenario that galaxies with 12+logO/H≤7.6 are now undergoing their first burst of star formation, and that they are therefore young, with ages not exceeding 40 Myr. If very low metallicity BCGs are indeed young, this would argue against the commonly held belief that C and N are produced by intermediate-mass (3 M≤M≤9 M) stars at very low metallicities, as these stars would not have yet completed their evolution in these lowest metallicity galaxies. In higher metallicity BCGs (7.6<12+logO/H<8.2), the abundance ratios Ne/O, Si/O, S/O, Ar/O, and Fe/O retain the same constant value they had at lower metallicities. By contrast, there is an increase of C/O and N/O along with their dispersions at a given O. We interpret this increase as due to the additional contribution of C and primary N production in intermediate-mass stars, on top of that by high-mass stars. The above results lead to the following timeline for galaxy evolution: (1) all objects with 12+logO/H≤7.6 began to form stars less than 40 Myr ago; (2) after 40 Myr, all galaxies have evolved so that 12+logO/H>7.6; (3) by the time intermediate-mass stars have evolved and released their nucleosynthetic products (100-500 Myr), all galaxies have become enriched to 7.6<12+logO/H<8.2. The delayed release of primary N at these metallicities greatly increases the scatter in N/O; (4) later, when galaxies get enriched to 12+logO/H>8.2, secondary N production becomes important. BCGs show the same O/Fe overabundance with respect to the Sun (∼0.4 dex) as Galactic halo stars, suggesting the same chemical enrichment history. We compare heavy elements yields derived from the observed abundance ratios with theoretical yields for massive stars and find general good agreement. However, the theoretical models are unable to reproduce the observed N/O and Fe/O. Further theoretical developments are necessary, in particular to solve the problem of primary nitrogen production in low-metallicity massive stars. We discuss the apparent discrepancy between abundance ratios N/O measured in BCGs and those in high-redshift damped Lyα galaxies, which are up to 1 order of magnitude smaller. We argue that this large discrepancy may arise from the unknown physical conditions of the gas responsible for the metallic absorption lines in high-redshift damped Lyα systems. While it is widely assumed that the absorbing gas is neutral, we propose that it could be ionized. In this case, ionization correction factors can boost N/O in damped Lyα galaxies into the range of those measured in BCGs.

Abstract Copyright:

Journal keyword(s): Galaxies: Abundances - Galaxies: Compact - Galaxies: ISM

VizieR on-line data: <Available at CDS (J/ApJ/511/639): table1.dat>

CDS comments: T.1 : 0907+527 not identified

Simbad objects: 56

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Number of rows : 56

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NGC 450 H2G 01 15 30.470 -00 51 38.98   13.4   13.3 13.2 ~ 207 0
2 IRAS F02183+0019 AGN 02 20 54.530 +00 33 24.46   16.50       ~ 56 1
3 Mrk 600 G 02 51 04.57 +04 27 13.9 14.76 15.07 14.70 14.50 14.29 ~ 117 0
4 SBSG 0335-052 bCG 03 37 44.04 -05 02 38.5     16.65     ~ 438 1
5 NGC 1741 IG 05 01 38.3 -04 15 25   13.7   13.02 13.6 ~ 252 0
6 Mrk 5 H2G 06 42 15.9 +75 37 40   17.0       ~ 109 0
7 SBSG 0723+692B G 07 28 +69.1           ~ 7 0
8 SBSG 0723+692A G 07 28.0 +69 06           ~ 8 0
9 NGC 2363A HII 07 28 42.8 +69 11 21           ~ 543 3
10 NGC 2366 H2G 07 28 51.85 +69 12 31.1 12.25 11.86 11.39 11.33   ~ 711 0
11 Mrk 1409 G 07 45 29.7 +53 25 37   17.0       ~ 18 0
12 LEDA 2800845 G 07 53 41.6 +56 41 52   18.0       ~ 23 0
13 SBSG 0749+582 G 07 53 54.00 +58 08 00.0   19       ~ 20 0
14 UGC 4483 GiG 08 37 03.29 +69 46 29.2 15.70 15.46 14.98 14.89   ~ 272 0
15 Mrk 1416 G 09 20 56.0 +52 34 07   17.0       ~ 55 0
16 LEDA 26955 G 09 30 09.041 +60 28 05.37           ~ 44 0
17 Mrk 116 PaG 09 34 02.1 +55 14 25           ~ 1015 1
18 SBSG 0940+544N G 09 44 16.70 +54 11 33.0           ~ 26 0
19 SBSG 0943+560 G 09 46 47.3 +55 51 47   19       ~ 6 0
20 Mrk 22 Sy1 09 49 30.3096198376 +55 34 46.971972356   15.7       ~ 67 0
21 LEDA 28398 EmG 09 51 31.7633448632 +52 59 36.023024415   18       ~ 44 0
22 Mrk 1434 SBG 10 34 10.155 +58 03 49.13   16.5   16.54   ~ 65 0
23 Mrk 1271 EmG 10 56 09.1156462299 +06 10 22.394369445   14.8       ~ 51 0
24 MCG+06-24-038 G 10 57 47.0058448322 +36 15 38.809066318   15.5 16     ~ 39 1
25 Mrk 36 SBG 11 04 58.298 +29 08 16.54   15.50 15.29     ~ 215 0
26 Mrk 162 GiG 11 05 08.163 +44 44 48.93   14.6       ~ 46 0
27 LEDA 34646 G 11 19 24.8 +58 03 51   19.5       ~ 21 0
28 UGC 6456 bCG 11 28 00.43 +78 59 38.4   14.50       ~ 312 1
29 LEDA 35516 EmG 11 31 16.361 +57 03 58.81   18.5       ~ 33 0
30 Mrk 1450 H2G 11 38 35.6604109660 +57 52 26.730510064   15.5       ~ 108 1
31 Mrk 1304 IG 11 42 12.253 +00 20 03.68   14.16 13.67 13.41 13.03 ~ 160 0
32 Mrk 750 H2G 11 50 02.739 +15 01 23.71   15.4       ~ 69 0
33 LEDA 37102 Sy1 11 51 33.3534243441 -02 22 21.893770899   17       ~ 149 0
34 Mrk 1307 Sy1 11 52 37.19 -02 28 09.9   14.79   14.09 14.9 ~ 160 0
35 Mrk 193 G 11 55 28.5 +57 39 44   16.5       ~ 57 0
36 LEDA 2815986 G 12 02 02.493 +54 15 51.05   18.0       ~ 67 0
37 LEDA 2500941 Sy2 12 08 04.6677594513 +55 24 27.546138667   17.08 16.47     ~ 11 0
38 LEDA 39055 EmG 12 14 02.479 +53 45 17.35   18       ~ 73 0
39 2MASX J12250543+6109097 G 12 25 05.438 +61 09 09.72   17.0       ~ 42 0
40 Mrk 209 bCG 12 26 16.02 +48 29 36.6   15.3       ~ 310 0
41 LEDA 2790846 EmG 12 51 52.4 +49 03 25   18.0       ~ 49 0
42 Mrk 59 AGN 12 59 00.288 +34 50 42.45           ~ 309 2
43 NGC 4861 H2G 12 59 02.340 +34 51 33.98   12.90 12.32     ~ 358 2
44 LEDA 2816050 G 13 21 22.6 +57 41 29   18.5       ~ 26 0
45 2MASX J13212499+5741501 GiP 13 21 24.045 +57 41 40.13   18.5       ~ 27 0
46 SBSG 1331+493N G 13 33 +49.0           ~ 7 0
47 MCG+08-25-018 G 13 33 23.308 +49 06 12.95   15.11 14.78     ~ 46 0
48 Mrk 1486 H2G 13 59 50.9093088961 +57 26 22.936953937   17.0       ~ 51 0
49 MCG+07-29-060 QSO 14 17 01.716 +43 30 13.52   15.6       ~ 155 0
50 LEDA 2816094 G 14 22 38.8397551662 +54 14 09.196345495   18.5       ~ 29 0
51 Mrk 475 EmG 14 39 05.4770066664 +36 48 21.868544960   17.0       ~ 98 0
52 CASG 1258 EmG 14 44 00.146 +29 15 56.62   17.13 16.71     ~ 22 0
53 NVSS J153412+571655 rG 15 34 13.3860337334 +57 17 07.294760490   15.8       ~ 69 1
54 SBSG 1533+574B GiP 15 34 14.10 +57 17 04.0   16.6       ~ 26 1
55 Mrk 487 bCG 15 37 04.237 +55 15 47.60   15.2       ~ 127 0
56 Mrk 930 AGN 23 31 58.630 +28 56 50.51 14.27 15.04 14.63 14.56 14.46 ~ 125 0

    Equat.    Gal    SGal    Ecl

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2021.03.05-17:47:12

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