paper

HST observations of the blue compact dwarf SBS 0335-052: a probable young galaxy

arXiv:astro-ph/9607121 · doi:10.1086/303737

Abstract

We present HST WFPC2 V and I images and GHRS UV spectrophotometry of the spectral regions around Ly and OI 1302 of the extremely metal-deficient (Z~Zsun/41) blue compact dwarf (BCD) galaxy SBS 0335-052. All the star formation in the BCD occurs in six super-star clusters (SSC) with ages =< 3-4 Myr. Dust is clearly present and mixed spatially with the SSCs. There is a supershell of radius ~380 pc, delineating a large supernova cavity. The instantaneous star formation rate is ~0.4 Msun yr^-1. Strong narrow Ly emission is not observed. Rather there is low intensity broad (FWZI = 20 A) Ly emission superposed on even broader Ly absorption by the HI envelope. This broad low-intensity emission is probably caused by resonant scattering of Ly photons. The BCD appears to be a young galaxy, undergoing its very first burst of star formation. This conclusion is based on the following evidence: 1) the underlying extended low-surface-brightness component is very irregular and filamentary, suggesting that a significant part of the emission comes from ionized gas; 2) it has very blue colors (-0.34 =< (V-I) =< 0.16), consistent with gaseous emission colors; 3) the OI 1302 line is not detected in absorption in the GHRS spectrum, setting an upper limit for N(O)/N(H) in the HI envelope of the BCD of more than 3000 times smaller than the value in Orion.

20 pages and 6 Postscript figures. Submitted to Astrophysical Journal

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