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

Astronomy & Astrophysics, Main Journal 357, 101

A.Y. Kniazev [1], S.A. Pustilnik [1], J. Masegosa [2], I. Marquez [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], V.A. Lipovetsky [1]

  1. Special Astrophysical Observatory, Nizhnij Arkhyz, Karachai-Circessia, 357147, Russia
  2. Instituto de Astrofisica de Andalucia, CSIC, Aptdo. 3004, 18080, Granada, Spain
  3. Departement de Radioastronomie ARPEGES, Observatoire de Paris, F-92195 Meudon Cedex, France
  4. Main Astronomical Observatory, Goloseevo, Kiev-127, 03680, Ukraine
  5. Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany
  6. Wise Observatory, Tel-Aviv University, Tel-Aviv 69978, Israel
  7. Universitätssternwarte München, Scheiner Str. 1, D-81679 München, Germany


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 (~ 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) * 10e8 Msun. 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: starburst - galaxies: abundances - galaxies: photometry - galaxies: individual (HS 0822+3542)

Contact: Alexei Kniazev.

Preprint (compressed PS-File, 137 Kb)