SpringerLink
Forum Springer Astron. Astrophys.
Forum Whats New Search Orders


Astron. Astrophys. 352, 363-370 (1999)

Previous Section Next Section Title Page Table of Contents

7. Conclusions

We have presented V and I CCD photometry of [FORMULA] stars in the Local Group dIrr galaxy SagDIG. The colour-magnitude diagram shows a well defined red giant branch, and a sequence of blue stars. Based on the I magnitude of the TRGB we have derived the distance modulus of SagDIG to be [FORMULA] for an adopted extinction of [FORMULA]. From the mean colour of the RGB [FORMULA], a mean metallicity [Fe/H] [FORMULA] is obtained. With this low Fe abundance, SagDIG could be the lowest metallicity star forming dIrr known.

The absolute total magnitude, the total colour, and the central surface brightness of SagDIG are derived to be [FORMULA], [FORMULA] and [FORMULA] mag arcsec-2. The radial star density distribution is fitted by an exponential law of scale length [FORMULA], corresponding to 140 pc.

The star formation history of SagDIG has been estimated from the number of blue and red stars in the colour-magnitude diagram and using a synthetic CMD as reference. The star formation rate has been evaluated for the intervals of time 0.2-15 Gyr, 0.05-0.2 Gyr and 0-0.05 Gyr, for which has been obtained [FORMULA] [FORMULA] yr-1, [FORMULA] [FORMULA] yr-1, and [FORMULA] [FORMULA] yr-1, respectively (see a summary in Table 1). The current

strong enhancement of the observed star formation rate is a common feature of galaxies classified as dIrrs.

Previous Section Next Section Title Page Table of Contents

© European Southern Observatory (ESO) 1999

Online publication: December 2, 1999
helpdesk.link@springer.de