The Embedded Super-Star Cluster of SBS 0335-052

Abstract

We analyze the infrared (6-100 µm) spectral energy distribution of the blue compact dwarf and metal-poor (Z=Z ⊙ /41) galaxy SBS 0335-052. With the help of DUSTY (Ivezić et al. 1999), a program that solves the radiation transfer equations in a spherical environment, we evaluate that the infrared (IR) emission of SBS 0335-052 is produced by an embedded super-star cluster (SSC) hidden under 10 5 M ⊙ of dust, causing 30 mag of visual extinction. This implies that one cannot detect any stellar emission from the 2×10 6 M ⊙ stellar cluster even at nearinfrared (NIR) wavelengths. The derived grain size distribution departs markedly from the widely accepted size distribution inferred for dust in our galaxy (the so-called MRN distribution, Mathis et al. (1977)), but resembles what is seen around AGNs, namely an absence of PAH and smaller grains, and grains that grow to larger sizes (around 1 µm). The fact that a significant amount of dust is present in such a low-metallicity galaxy, hiding from UV and optical view most of the star formation activity in the galaxy, and that the dust size distribution cannot be reproduced by a standard galactic law, should be borne in mind when interpreting the spectrum of primeval galaxies.