Nebular Abundances of Nearby Southern Dwarf Galaxies

Astrophysics, abstract
astro-ph/0301492

From: Henry Lee <lee@mpia-hd.mpg.de>

Date: Fri, 24 Jan 2003 10:30:49 GMT   (233kb)

Authors:
Henry Lee (1,2),
Eva K. Grebel (1),
Paul Hodge (3) ((1) Max-Planck-Institute for Astronomy, Heidelberg, Germany; (2) York University, Toronto, Canada; (3) University of Washington, Seattle, USA)

Comments: Accepted, A&A; 22 pages incl. 7 eps figures (A&A v5.2 LaTeX2e)

The results of optical spectroscopy of H II regions in a sample of southern
dwarf irregulars consisting of five dwarf galaxies in the Centaurus A group,
four dwarfs in the Sculptor group, and eight additional dwarf galaxies are
presented. Oxygen abundances are derived using the direct method where [O
III]4363 is detected; otherwise, abundances are derived with the bright-line
method using the McGaugh and the Pilyugin calibrations. ESO358-G060 has the
lowest oxygen abundance (12+log(O/H) = 7.32), which is comparable to the value
for the second most metal-poor galaxy known (SBS0335-052). In all, new oxygen
abundances are reported for nine dwarf galaxies; updated values are presented
for the remaining galaxies. Derived oxygen abundances are in the range from 3%
to 26% of the solar value. Oxygen abundances for dwarfs in the southern sample
are consistent with the metallicity-luminosity relationship defined by a
control sample of dwarf irregulars with [O III]4363 abundances and
well-measured distances. However, NGC5264 appears to have an (upper branch)
oxygen abundance approximately two to three times higher than other dwarfs at
similar luminosities. Nitrogen-to-oxygen and neon-to-oxygen abundance ratios
are also reported; in particular, IC1613 and IC5152 show elevated
nitrogen-to-oxygen ratios for their oxygen abundances.

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