New abundance measurements in UKS 1927–177, a very metal-poor galaxy in the Local Group^*

¹ European Southern Observatory, Casilla 19001, Santiago 19, Chile
² Osservatorio Astronomico di Padova, vicolo dell'Osservatorio 5, 35122 Padova, Italy e-mail: (rizzi, held)@pd.astro.it
³ Dipartimento di Astronomia, Università di Padova, vicolo dell'Osservatorio 2, 35122 Padova, Italy e-mail: momany@pd.astro.it
⁴ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 e-mail: bresolin@ifa.hawaii.edu

Corresponding author: I. Saviane, isaviane@eso.org

Received: 26 February 2002
Accepted: 15 May 2002

Abstract

We present new results from optical spectroscopy of the brightest Hii region in the dwarf irregular galaxy in Sagittarius (SagDIG). From high signal-to-noise spectra, reddening-corrected line flux ratios have been measured with typical uncertainties of a few percent, from which the oxygen abundance is rediscussed, and new abundance estimates are derived for N and Ne. The O abundance in SagDIG, estimated with the empirical abundance indicator and other methods, is in the range to . The fact that SagDIG is 10 times closer than I Zw 18 makes it an ideal target to test the hypothesis of the existence of young galaxies in the present-day universe. Indeed, stellar photometry suggests that this galaxy may harbor a stellar population older than a few Gyr, and possibly an old stellar component as well. The case of SagDIG therefore supports the view that very low chemical abundances can be maintained throughout the life of a dwarf stellar system, even in the presence of multiple star formation episodes.