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

TL;DR

This study measures faint optical recombination lines in NGC300 to determine carbon and oxygen abundances and their radial gradients, providing insights into chemical composition variations in spiral galaxy disks.

Contribution

It introduces a method focusing on faint ORLs for abundance measurements, offering a new perspective compared to traditional CEL-based analyses.

Findings

Derived C++ and O++ abundances from faint lines in NGC300.

Computed radial gradients of C/H, O/H, and C/O ratios in NGC300.

Compared these gradients with those in 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.