SBS 0335−052, A Probable Nearby Young Dwarf Galaxy: Evidence Pro and Con
Author(s) -
Y. I. Izotov,
V. A. Lipovetsky,
Frederic H. Chaffee,
Craig B. Foltz,
N. G. Guseva,
A. Y. Kniazev
Publication year - 1997
Publication title -
the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.1086/303664
Subject(s) - astrophysics , physics , metallicity , galaxy , abundance (ecology) , dwarf galaxy , doubly ionized oxygen , abundance of the chemical elements , analytical chemistry (journal) , emission spectrum , astronomy , spectral line , chemistry , biology , fishery , chromatography
The results of Multiple Mirror Telescope spectrophotometry of the extremelylow-metallicity blue compact galaxy (BCG) SBS 0335-052 are presented. Theoxygen 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 closeto those derived in other BCGs, suggesting that heavy element enrichment in theHII region is due to massive star evolution. We detect auroral [OIII] 4363emission in the inner part of HII region with a diameter of 3.6 kpc and findthat the HII region inside this diameter is hot, T_e~20000K. The oxygenabundance 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 discussthe origin of blue underlying extended low-intensity emission detected in SBS0335-052. The (V-I) and (R-I) color distributions suggest that a significantcontribution to the extended envelope is due to ionized gas emission. However,the observed equivalent width of Hbeta emission in the extended envelope is 2-3times lower than the value expected in the case of pure gaseous emission. Thesefindings suggest that, along with the blue young (~10^7yr) stellar clusters, anolder stellar population with age ~10^8yr may be present in the extendedenvelope of SBS 0335-052, having a total mass conclude that SBS 0335-052 is ayoung nearby dwarf galaxy with age ~10^8 yr.Comment: 27 pages and 8 Postscript figures, uses aaspp4.sty. Submitted to Astrophysical Journa
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