HII-CHI-Mistry-IR for AGN. Abundances

While studies of the chemical composition of the ISM based on optical observations have been widely spread over decades for SFG and, more recently, for AGN, similar studies need to be performed using IR data. This regime can be especially useful in the case of AGN given that it is less affected by temperature and dust extinction, traces higher ionic species and can also provide robust estimations of the chemical abundance ratio N/O. We present a new tool based on a bayesian-like methodology (HII-CHI-Mistry-IR) to estimate chemical abundances from IR emission lines in AGN.

We use a sample of 58 AGN with IR spectroscopic data retrieved from the literature, composed by 43 Seyferts, 8 ULIRGs, 4 LIRGs and 3 LINERs, to probe the validity of our method. The estimations of the chemical abundances based on IR lines in our sample are later compared with the corresponding abundances derived from the optical emission lines in the same objects. HII-CHI-Mistry-IR takes advantage of photoionization models, characterized by the chemical abundance ratios O/H and N/O and the ionization parameter U, to compare their predicted emission- line fluxes with a set of observed values.