Issue |
A&A
Volume 384, Number 2, MarchIII 2002
|
|
---|---|---|
Page(s) | 393 - 402 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20020047 | |
Published online | 15 March 2002 |
The Sagittarius dwarf irregular galaxy: Metallicity and stellar populations*
1
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
2
Dipartimento di Astronomia, Università di Padova, vicolo dell'Osservatorio 2, 35122 Padova, Italy
3
Osservatorio Astronomico di Padova, vicolo dell'Osservatorio 5, 35122 Padova, Italy e-mail: held, rizzi@pd.astro.it
4
European Southern Observatory, Casilla 19001, Santiago 19, Chile e-mail: isaviane@eso.org
Corresponding author: Y. Momany, momany@pd.astro.it
Received:
1
August
2001
Accepted:
2
January
2002
We present deep BVI observations of the dwarf
irregular galaxy UKS 1927-177 in Sagittarius (SagDIG). Statistically
cleaned V, color-magnitude diagrams
clearly display the key evolutionary features in this galaxy.
Previously detected C stars are located in the color-magnitude
diagrams and shown to be variable, thus confirming the presence of a
significant upper-AGB intermediate age population. A group of likely
red supergiants is also identified, whose magnitude and
color is consistent with a 30 Myr old burst of star formation.
The observed colors of both blue and red stars in SagDIG are best
explained by introducing a differential reddening scenario in which
internal dust extinction affects the star forming regions.
Adopting a low reddening for the red giants,
,
gives [ Fe/H
for the mean stellar metallicity,
a value consistent with the [O/H] abundance measured in the
regions. This revised metallicity, which is in accord with the trend of
metallicity against luminosity for dwarf irregular galaxies, is indicative
of a “normal”, although metal-poor, dIrr galaxy.
A quantitative description is given of the spatial distribution of
stars in different age intervals, in comparison with the distribution
of the neutral hydrogen. We find that the youngest stars are located
near the major peaks of emission on the shell, whereas the red
giants and intermediate-age C stars define an extended halo or disk
with scale length comparable to the size of the hydrogen cloud. The
relationship between the distribution of ISM and star formation is
briefly discussed.
Key words: galaxies: fundamental parameters / galaxies: individual: UKS 1927-177 / galaxies: dwarf / galaxies: local group / Galaxy: stellar content
© ESO, 2002
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.