Astronomy & Astrophysics

Free access article

Issue		A&A Volume 397, Number 2, January II 2003
Page(s)		463 - 472
Section		Galactic structure and dynamics
DOI		10.1051/0004-6361:20021450

A&A 397, 463-472 (2003)
DOI: 10.1051/0004-6361:20021450

The Hamburg/SAO Survey for low metallicity blue compact H II galaxies (HSS-LM)

I. The first list of 46 strong-lined galaxies

A. V. Ugryumov^{1, 2}, D. Engels³, S. A. Pustilnik^{1, 2}, A. Y. Kniazev^{1, 4, 2}, A. G. Pramskij^{1, 2} and H.-J. Hagen³

¹ Special Astrophysical Observatory RAS, Nizhnij Arkhyz, Karachai-Circassia 369167, Russia
² Isaac Newton Institute of Chile, SAO Branch
³ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
⁴ Max Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

(Received 28 January 2002 / Accepted 10 September 2002 )

Abstract
We present the description and the first results of a new project devoted to the search for extremely metal-deficient blue compact/H II-galaxies (BCGs) and to the creation of a well selected large BCG sample with strong emission lines. Such galaxies should be suitable for reliable determination of their oxygen abundance through the measurement of the faint [ $\ion{O}{iii}$ ] $\lambda$ 4363 Å line. The goals of the project are two-fold: a) to discover a significant number of new extremely metal-poor galaxies ( $Z \lesssim$ 1/20 Z $_{\odot}$ ), and b) to study the metallicity distribution of local BCGs. Selection of candidates for follow-up slit spectroscopy is performed on the database of objective prism spectra of the Hamburg Quasar Survey. The sky region is limited by $\delta \geq 0$ ° and $b^{\rm II} \leq -30$ °. In this paper we present the results of the follow-up spectroscopy conducted with the Russian 6 m telescope. The list of observed candidates contained 52 objects, of which 46 were confirmed as strong-lined BCGs ( EW([ $\ion{O}{iii}$ ] $\lambda$ 5007) $\ge$ 100 Å). The remaining five lower excitation ELGs include three BCGs, and two galaxies classified as SBN (Starburst Nucleus) and DANS (Dwarf Amorphous Nucleus Starburst). One object is identified as a quasar with a strong Ly $\alpha$ emission line near $\lambda$ 5000 Å ( $z\sim 3$ ). We provide a list with coordinates, measured radial velocities, B-magnitudes, equivalent widths EW([ $\ion{O}{iii}$ ] $\lambda$ 5007) and EW(H $\beta$ ) and for the 46 strong-lined BCGs the derived oxygen abundances 12+ $\log$ (O/H). The abundances range between 7.42 and 8.4 (corresponding to metallicities between 1/30 and 1/3 Z $_{\odot}$ ). The sample contains four galaxies with $Z \lesssim$ 1/20 Z $_{\odot}$ , of which three are new discoveries. This demonstrates the high efficiency of the new project to find extremely metal-deficient galaxies. The radial velocities of the strong-lined ELGs range between 500 and 19 000 km s ^-1 with a median value of ~6400 km s ^-1. The typical B-magnitudes of the galaxies presented are $17\fm0{-}18\fm0$ .

Key words: galaxies: dwarf -- galaxies: abundances -- galaxies: distances and redshifts -- surveys

Offprint request: A. V. Ugryumov, and@sao.ru

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