Metal content in the central region of galaxies

M.V. CARDACI; G.F. HÄGELE; A.I. DÍAZ

Campos do Jordao

Workshop; Chemical Abundances in Gaseous Nebulae; 2016

UNIVAPVAP

Accurate abundance determinations for the central regions of a great amount of galaxies would be necessary to improve the calibration of abundances in the over solar regime. Circumnuclear Star Forming Re- gions (CNSFRs) in early type galaxies, being close to the galactic nuclei, are expected to be of high metal content and in fact empirical abundance indicators constructed with strong optical emission lines point to over- solar abundances up to 3 times solar. Due to the difficulty in deriving abundances directly the calibrations have to be provided by theoretical photoionization models which require several assumptions to be made. Different models/assumptions provide different calibrations. The optical observational analysis of the warm ionized gas of CNSFRs yields oxygen abundances lower than expected from empirical abundance indicators. These findings point to a deficiency of light alpha elements (O, Ne) in the central regions of M 82. If this is common among regions dominated by recent star formation, the estimated oxygen abundances might not be representative of the true metal content of these regions. This could have a profound effect on abundance calibrations leading to fundamental relations like the Mass-Metallicity and Luminosity-Metallicity relations. X-ray emission analysis can provide abundances for the hot gas phase. This hot plasma is thought to be mainly heated by the supernovae explo- sions so that the X-ray gas should trace the current abundances of the galaxies. These alternative estimations of the metal content of the central region of galaxies would provide new observational constrains for models of chemical evolution.