We have made deep VLA maps of NGC 253 which show that it has at least 35 compact radio sources similar to those in the prototypical infrared starburst galaxy M82. NGC 253 is a twin of M82 in infrared spectrum and luminosity as well as distance. The sources in M82, at least some of which are rapidly expanding and fading, have been identified as extremely young supernova remnants. They appear to provide spectacular evidence for the starburst model, as well as yielding information on a key model parameter, the supernova rate. Most of the sources we detect in NGC 253 are unresolved or only marginally resolved, with typical diameters no greater than 2-5 pc. Assuming that they are young supernova remnants expanding at 12,000 km s^-1^, the source ages are no more than 160-400 yr. This requires a supernova rate of 0.1 yr^-1^. This estimate is very much a lower limit because of the high detection threshold in the confused central region. If the nucleus were in a steady state, the luminosity of the progenitor stellar population would exceed the observed bolometric luminosity of the nucleus. Therefore if the compact radio sources are in fact young supernova remnants, star formation must have ceased shortly after the progenitors of the current supernovae were produced. Our sources are distributed amorphously over ~600 pc, in contrast to the ~120 pc line of sources discovered by Turner and Ho; we discuss the relationship of their sources to the new ones reported in this Letter.
No takes yet. Share an insight, caveat, or question.
Antonucci et al. (1988) studied this question.