Carbon Abundances in Starburst Galaxies of the Local Universe

TL;DR

This study investigates the origin of carbon in starburst galaxies by measuring C/O and O/H ratios, revealing insights into stellar contributions to carbon production at various metallicities.

Contribution

It provides new measurements of carbon and oxygen abundances in local starburst galaxies using spectral analysis and MCMC, enhancing understanding of carbon's cosmological origin.

Findings

C/O vs. O/H slope is steeper than in other samples

Massive stars contribute more to carbon production at higher metallicities

Different object types occupy specific regions in the [C/O] vs. [O/H] diagram

Abstract

The cosmological origin of carbon, the fourth most abundant element in the Universe, is not well known and matter of heavy debate. We investigate the behavior of C/O to O/H in order to constrain the production mechanism of carbon. We measured emission-line intensities in a spectral range from 1600 to 10000 \AA\ on Space Telescope Imaging Spectrograph (STIS) long-slit spectra of 18 starburst galaxies in the local Universe. We determined chemical abundances through traditional nebular analysis and we used a Markov Chain Monte Carlo (MCMC) method to determine where our carbon and oxygen abundances lie in the parameter space. We conclude that our C and O abundance measurements are sensible. We analyzed the behavior of our sample in the [C/O] vs. [O/H] diagram with respect to other objects such as DLAs, neutral ISM measurements, and disk and halo stars, finding that each type of object seems to be located in a specific region of the diagram. Our sample shows a steeper C/O vs. O/H slope with respect to other samples, suggesting that massive stars contribute more to the production of C than N at higher metallicities, only for objects where massive stars are numerous; otherwise intermediate-mass stars dominate the C and N production.