VLA H53α Observations of the Central Region of the Super Star Cluster Galaxy NGC 5253

Abstract

We present observations in the H53α line and radio continuum at 43 GHz carried out with the VLA in the D configuration (2" angular resolution) toward the starburst galaxy NGC 5253. VLA archival data have been reprocessed to produce a uniform set of 2, 1.3, and 0.7 cm high angular (0.2^''×0.1^'') radio continuum images. The radio recombination line (RRL) H53α, a previously reported measurement of the H92α RRL flux density, and the reprocessed high angular resolution radio continuum flux densities have been modeled using a collection of H II regions. Based on the models, the ionized gas in the nuclear source has an electron density of ~6×10⁴ cm^-3 and a volume filling factor of 0.05. A Lyman continuum photon production rate of 2×10⁵² s^-1 is necessary to sustain the ionization in the nuclear region. The number of required O7 stars in the central 1.5 pc of the supernebula is ~2000. The H53α velocity gradient (10 km s^-1 arcsec^-1) implies a dynamical mass of ~3×10⁵ M_solar this mass suggests that the supernebula is confined by gravity.