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Issue A&A
Volume 397, Number 2, January II 2003
Page(s) 463 - 472
Section Galactic structure and dynamics
DOI http://dx.doi.org/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. Ugryumov1, 2, D. Engels3, S. A. Pustilnik1, 2, A. Y. Kniazev1, 4, 2, A. G. Pramskij1, 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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