Carbon abundances and radial gradients in NGC300 and other nearby spiral galaxies

Abstract: We present preliminary results of deep echelle spectrophotometry of a sample of HII regions along the disk of the Scd galaxy NGC300 obtained with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the Very Large Telescope (VLT) with the aim of detect and measure very faint OII and CII permitted lines. We focus this study on the C and O abundances obtained from faint optical recombination lines (ORLs) instead of the most commonly used collisionally excited lines (CELs). We have derived the ionic abundances of C++ from the CII 4267 angstrom RL and O++ from the multiplet 1 of OII around 4649 angstrom in several objects. Finally, we have computed the radial gradients of C/H, O/H and C/O ratios in NGC300 from RLs, which has allowed the comparison with similar data obtained by our group in other nearby spiral galaxies.