EDP Sciences
Free access
Issue
A&A
Volume 421, Number 2, July II 2004
Page(s) 519 - 528
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20035949


A&A 421, 519-528 (2004)
DOI: 10.1051/0004-6361:20035949

Pox 186: An ultracompact galaxy with dominant ionized gas emission

N. G. Guseva1, P. Papaderos2, Y. I. Izotov1, K. G. Noeske2, 3 and K. J. Fricke2

1  Main Astronomical Observatory, Ukrainian National Academy of Sciences, Zabolotnoho 27, Kyiv 03680, Ukraine
2  Universitäts-Sternwarte, Geismarlandstraße 11, 37083 Göttingen, Germany
3  University of California, 1156 High St., Santa Cruz, CA 95064, USA

(Received 26 December 2003 / Accepted 23 March 2004)

Abstract
We present a ground-based optical spectroscopic and HST  U, V, I photometric study of the blue compact dwarf (BCD) galaxy Pox 186. It is found that the emission of the low-surface brightness (LSB) component in Pox 186 at radii  $\la$3´´ ( $\la$270 pc in linear scale) is mainly gaseous in origin. We detect H $\alpha$ emission out to radii as large as 6´´. At radii  $\ga$3´´ the light of the LSB component is contaminated by the emission of background galaxies complicating the study of the outermost regions. The surface brightness distribution in the LSB component can be approximated by an exponential law with a scale length  $\alpha \la 120$ pc. This places Pox 186 among the most compact dwarf galaxies known. The derived  $\alpha$ is likely to be an upper limit to the scale length of the LSB component because of the strong contribution of the gaseous emission. The oxygen abundance in the bright H II region derived from the 4.5 m Multiple Mirror Telescope (MMT) and 3.6 m ESO telescope spectra are $12 + \log\,{\rm (O/H)} = 7.76 \pm 0.02$ and  $7.74 \pm 0.01$ (~ $Z_\odot$/15), respectively, in accordance with previous determinations. The helium mass fractions found in this region are $Y = 0.248 \pm 0.009$ (MMT) and  $Y = 0.248 \pm 0.004$ (3.6 m) suggesting a high primordial helium abundance.


Key words: ISM: abundances -- galaxies: dwarf -- galaxies: ISM -- galaxies: irregular

Offprint request: N. G. Guseva, guseva@mao.kiev.ua

SIMBAD Objects



© ESO 2004

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access.

An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account.
    In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.