Talk abstract details
Planetary nebulae in NGC300: their chemical abundances and the abundance gradient in this galaxy
Abstract
A spectrophotometric analysis of a significant sample of PNe and compact HII regions in two zones (center and outskirts) of NGC300 is presented. Data were obtained with FORS2 at the VLT-ESO. A wide wavelength coverage allows us to obtain several temperature and density sensitive diagnostic ratios. Abundances of He, N, O, Ar and S were derived for 18 PNe and 9 compact HII regions were the [OIII] electron temperature was measured.
Results: HII regions and PNe show similar O/H abundance range, although some PNe, mainly in the center, present low O abundance. PNe are N-richer than HII regions and three of them are Type I. Our PNe are located in a range of galactocentric distances allowing us to analyze the O, Ne, and Ar abundance gradients in the disk in comparison with the gradients derived from HII regions. The PNe gradients are flatter than the HII gradients and show larger dispersion.. Some phenomena like ON-cycle, hot- bottom burning and stellar migration, that could be causing these flatter gradients are discussed. An additional result, derived from HII regions, show that N/O is much lower in the external zone of NGC300 (possible the disk is less evolved in the periphery). Also a less-steep gradient is observed for the Ar/O abundance ratio.
Results: HII regions and PNe show similar O/H abundance range, although some PNe, mainly in the center, present low O abundance. PNe are N-richer than HII regions and three of them are Type I. Our PNe are located in a range of galactocentric distances allowing us to analyze the O, Ne, and Ar abundance gradients in the disk in comparison with the gradients derived from HII regions. The PNe gradients are flatter than the HII gradients and show larger dispersion.. Some phenomena like ON-cycle, hot- bottom burning and stellar migration, that could be causing these flatter gradients are discussed. An additional result, derived from HII regions, show that N/O is much lower in the external zone of NGC300 (possible the disk is less evolved in the periphery). Also a less-steep gradient is observed for the Ar/O abundance ratio.