Speaker
Description
The chemical abundance of active galaxies, which host active galactic nuclei (AGN) at their centre, remains poorly studied due to the difficulty of removing the effect of AGN in metallicity measurements. In particular, the chemical abundance of active galaxies in different environments, including clusters and groups, is still unknown. We use a novel HCm code (HII-CHI-mistry) adapted to measure the chemical abundance of type-2 AGN. We measure the oxygen abundance (12 + log(O/H)), nitrogen abundance (log(N/O)), and the ionisation parameter (logU) for ~12,000 type-2 AGN selected from the SDSS survey. We analyse the metallicity properties of type-2 AGNs in relation to other properties of AGN host galaxies, such as morphology, stellar mass, and star formation rate (SFR). For galaxies in groups and clusters, we study the metallicity properties in relation to their properties (e.g., cluster-centric distance and the number of galaxies in the group/cluster). We do not observe a clear mass-metallicity relation; however, we find that in groups and clusters, 12 + log(O/H) abundance is higher in galaxies with higher stellar mass. The abundance decreases with increasing SFR in all environments. We do not find a fundamental plane of type-2 AGN, suggesting complex interactions among stellar mass, SFR, and metallicity when AGN are present compared to pure star-forming galaxies. Type-2 AGN hosts, both early- and late-type, show on average higher 12 + log(O/H) abundances in groups and clusters compared to field galaxies, independent of redshift. Our results indicate that type-2 AGN in groups and clusters have higher metallicities for a given stellar mass, and neither group or cluster membership nor cosmic-centric distance seems to drive this effect. Finally, this work provides the largest catalogue of chemical abundances of type-2 AGN to date.
| Stream | Science or Engineering |
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