| Issue |
A&A
Volume 367, Number 2, February IV 2001
|
|
|---|---|---|
| Page(s) | 388 - 404 | |
| Section | Cosmology (including clusters of galaxies) | |
| DOI | https://doi.org/10.1051/0004-6361:20010063 | |
| Published online | 15 February 2001 | |
The chemical abundances in a sample of dwarf irregular galaxies*,**
I. Small scale variations within NGC 6822?
1
Astronomiska observatoriet, Box 515, 751 20 Uppsala, Sweden e-mail: kjell.olofsson@astro.uu.se
2
Instituto de Astrofísica de Andalucía, CSIC, Apdo. 3004, 18080 Granada, Spain e-mail: pepa@iaa.es
Corresponding author: A. M. Hidalgo-Gámez, anamaria@astro.uu.se
Received:
9
November
1999
Accepted:
18
October
2000
Deep groundbased spectra of Hubble V and Hubble X, the two
largest and
brightest H ii regions in the Local Group dwarf galaxy,
NGC 6822, are presented.
The extinction, excitation and ionization are studied
on scales as small as 4 pc.
The chemical composition of some elements within the regions
as well as possible small scale variations in the
abundances of helium, nitrogen, oxygen and neon over the face of the
two regions are investigated.
The detection of the emission lines
OI
and ClIII are probably related to shock-heating
from gas
ejected from supernova explosions and planetary nebula
ejections, respectively, although the
contribution to the total ionization is very small.
No significant differences in chemical composition was found
between Hubble V and Hubble X.
However, some small scale variations in the abundances of oxygen,
and possibly nitrogen and helium, over the face
of both H ii regions were noted, although different physical
conditions could apply within the regions, such as local fluctuations in the temperature.
Key words: galaxies: evolution / galaxies: irregular / galaxies: stellar content / ISM: H ii regions
© ESO, 2001
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