| Issue |
A&A
Volume 397, Number 2, January II 2003
|
|
|---|---|---|
| Page(s) | 463 - 472 | |
| Section | Extragalactic astronomy | |
| DOI | https://doi.org/10.1051/0004-6361:20021450 | |
| 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
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
Corresponding author: A. V. Ugryumov, and@sao.ru
Received:
28
January
2002
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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