SBS 0335−052, A Probable Nearby Young Dwarf Galaxy: Evidence Pro and Con
| Autor: | Yuri I. Izotov, Valentin A. Lipovetsky, Frederic H. Chaffee, Craig B. Foltz, Natalia G. Guseva, Alexei Y. Kniazev |
|---|---|
| Rok vydání: | 1997 |
| Předmět: | |
| Zdroj: | The Astrophysical Journal. 476:698-711 |
| ISSN: | 1538-4357 0004-637X |
| DOI: | 10.1086/303664 |
| Popis: | The results of Multiple Mirror Telescope spectrophotometry of the extremely low-metallicity blue compact galaxy (BCG) SBS 0335-052 are presented. The oxygen abundance in central brightest part of the galaxy is found to be 12 + log(O/H) = 7.33+-0.01. The N/O, Ne/O, S/O and Ar/O abundance ratios are close to those derived in other BCGs, suggesting that heavy element enrichment in the HII region is due to massive star evolution. We detect auroral [OIII] 4363 emission in the inner part of HII region with a diameter of 3.6 kpc and find that the HII region inside this diameter is hot, T_e~20000K. The oxygen abundance in this region is nearly constant (12 + log(O/H) = 7.1 - 7.3), implying effective mixing of ionized gas on short time-scales. We also discuss the origin of blue underlying extended low-intensity emission detected in SBS 0335-052. The (V-I) and (R-I) color distributions suggest that a significant contribution to the extended envelope is due to ionized gas emission. However, the observed equivalent width of Hbeta emission in the extended envelope is 2-3 times lower than the value expected in the case of pure gaseous emission. These findings suggest that, along with the blue young (~10^7yr) stellar clusters, an older stellar population with age ~10^8yr may be present in the extended envelope of SBS 0335-052, having a total mass conclude that SBS 0335-052 is a young nearby dwarf galaxy with age ~10^8 yr. Comment: 27 pages and 8 Postscript figures, uses aaspp4.sty. Submitted to Astrophysical Journal |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|