VLA H53alpha observations of the central region of the Super Star Cluster Galaxy NGC 5253

TL;DR

This study uses VLA observations of radio recombination lines and continuum to analyze the ionized gas and dynamics of the super star cluster in NGC 5253, revealing high-density ionized gas, star formation rates, and gravitational confinement.

Contribution

First detailed modeling of ionized gas and dynamics in NGC 5253's super star cluster using H53alpha line and radio continuum data.

Findings

Ionized gas density ~6 x 10^4 cm^-3

Approximately 2000 O7 stars needed for ionization

Supernebula mass ~3 x 10^5 solar masses

Abstract

We present observations in the H53alpha line and radio continuum at 43 GHz carried out with the VLA in the D array (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 X 0.''1) radio continuum images. The RRL H53alpha, a previously reported measurement of the H92alpha RRL flux density and the reprocessed high angular resolution radio continuum flux densities have been modeled using a collection of HII regions. Based on the models, the ionized gas in the nuclear source has an electron density of ~6 X 10^4 cm^-3 and an volume filling factor of 0.05. A Lyman continuum photon production rate of 2 X 10^52 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 H53alpha velocity gradient 10 km s^-1 arcsec^-1) implies a dynamical mass of ~3X10^5 Msun; this mass suggests the supernebula is confined by gravity.