Giant HII regions BOND abundances

We present the Bayesian oxygen and nitrogen abundance determinations (bond) method. bond is a Bayesian code (available at: bond.ufsc.br) to simultaneously derive oxygen and nitrogen abundances in giant HII regions. It compares observed emission lines to a grid of photoionization models without assuming any relation between O/H and N/O. Our grid spans a wide range in O/H, N/O and ionization parameter U, and covers different starburst ages and nebular geometries.

Varying starburst ages accounts for variations in the ionizing radiation field hardness, which arise due to the ageing of HII regions or the stochastic sampling of the initial mass function. All previous approaches assume a strict relation between the ionizing field and metallicity. The other novelty is extracting information on the nebular physics from semistrong emission lines.