H{alpha} photometry in NGC 7020

Inside and around the hexagonal structure, H{alpha} emission is also present at the inner disk. To characterize the population of the HII regions, as well as their ionizing clusters, we imaged NGC7020 with narrowband H{alpha} and nearby continuum filters attached to GMOS-S installed on the Gemini South telescope.

We found 202 HII regions or complexes of HII regions evenly distributed between the outer ring and the central disk The nucleus and ansae also present H{alpha} emission. The equivalent width of the H{alpha} line (WH{alpha}) is systematically greater at the regions of the outer ring relative to those of the inner disk. We discuss the influence of the metallicity gradient of the disk and the upper limit of the masses of the initial mass function on WH{alpha}, and we conclude that the data are still consistent with the occurrence of a younger burst of HII region formation in the outer ring.