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Astron. Astrophys. 357, 101-110 (2000)

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HS 0822+3542 - a new nearby extremely metal-poor galaxy

A.Y. Kniazev 1, S.A. Pustilnik 1, J. Masegosa 2, I. Márquez 2, A.V. Ugryumov 1, J.-M. Martin 3, Y.I. Izotov 4, D. Engels 5, N. Brosch 6, U. Hopp 7, S. Merlino 2 and V.A. Lipovetsky *  1

1 Special Astrophysical Observatory, Nizhnij Arkhyz, Karachai-Circessia, 369167, Russia
2 Instituto de Astrofisica de Andalucia, CSIC, Aptdo. 3004, 18080 Granada, Spain
3 Observatoire de Paris-Meudon, 92195 Meudon, France
4 Main Astronomical Observatory, Goloseevo, Kiev-127, 03680, Ukraine
5 Hamburger Sternwarte, Gojenbergswerg 112, 21029 Hamburg, Germany
6 Wise Observatory, Tel-Aviv University, 69978 Tel-Aviv, Israel
7 Universitätssternwarte München, 81679 München, Germany

Received 11 January 1999 / Accepted 7 March 2000


We present the results of spectrophotometry and BVR CCD photometry, as well as integrated HI radio measurements of a new blue compact galaxy (BCG) HS 0822+3542 with extremely low oxygen abundance: 12 + log(O/H) = 7.35, or 1/36 of solar value. The galaxy is the third most metal-deficient BCG after I Zw 18 and SBS 0335-052. Its very high mass fraction of gas ([FORMULA] 95% of all visible mass) and blue colours of underlying nebulosity are also similar to those of SBS 0335-052. This suggests that HS 0822+3542 is one of the nearest and dimmest galaxies experiencing a recently-started first star formation (SF) episode. Its properties imply that for such galaxies there is a linear scaling of the main parameters, at least for the baryon mass range (0.3-20)[FORMULA]108 [FORMULA]. The total mass estimate indicates that the galaxy is dynamically dominated by a dark matter (DM) halo, which itself is one of the least massive for galaxies.

Key words: galaxies: abundances – galaxies: fundamental parameters – galaxies: individual: HS 0822+3542 – galaxies: starburst – galaxies: photometry

* Deceased 1996 September 22

Send offprint requests to: A. Kniazev (akn@sao.ru)

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© European Southern Observatory (ESO) 2000

Online publication: May 3, 2000