VLA Observations of NGC 253: Supernova Remnants and H II Regions at 1 Parsec Resolution

摘要: The edge-on starburst galaxy NGC 253 has been imaged with the VLA at wavelengths ranging from 1.3 to 20 cm, resolutions between 1 and 15 pc. These images reveal a large number of compact radio sources embedded within diffuse structure in inner 200 pc galaxy. We have identified approximately 64 individual Of strongest 17 sources, for which flux densities are high enough measure spectral indices moderately low errors, about half flat spectra steep spectra; this indicates that perhaps dominated by thermal emission H II regions. Over an 8 yr timescale, few, if any, varied density, limits 1%-2% yr-1 on rate decrease. At highest resolution pc, beginning be resolved, least different can innermost Individual explored more detail. source, 5.79-39.0 (TH2), assumed nucleus galaxy, brightness temperature greater than 20,000 K 22 GHz 40,000 GHz. It is unresolved may either active galactic or very (nonvariable) supernova remnant. A resolved flat-spectrum 5.72-40.1 (TH6), located ~20 southwest. apparent size 2.4 × 1.2 appears region similar part 30 Doradus, containing 105 M☉ stars, as well ~600 ionized gas. Source counts, lack variability, new imply no 0.3 yr-1, consistent estimates made other wave bands.