Volume 397, Number 2, January II 2003
|Page(s)||463 - 472|
|Published online||17 December 2002|
The Hamburg/SAO Survey for low metallicity blue compact H II galaxies (HSS–LM)*
I. The first list of 46 strong-lined galaxies
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
Corresponding author: A. V. Ugryumov, email@example.com
Accepted: 10 September 2002
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  λ 4363 Å line. The goals of the project are two-fold: a) to discover a significant number of new extremely metal-poor galaxies ( 1/20 Z ), 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 ° and °. 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( λ 5007) ≥ 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 Lyα emission line near λ 5000 Å (). We provide a list with coordinates, measured radial velocities, B-magnitudes, equivalent widths EW( λ 5007) and EW(Hβ) and for the 46 strong-lined BCGs the derived oxygen abundances 12+(O/H). The abundances range between 7.42 and 8.4 (corresponding to metallicities between 1/30 and 1/3 Z ). The sample contains four galaxies with 1/20 Z , 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 .
Key words: galaxies: dwarf / galaxies: abundances / galaxies: distances and redshifts / surveys
© ESO, 2003
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