Chemical Abundances in AGNs based on the HOMERUN Code

• Grant number: 25/09778-1
• Support Opportunities: Scholarships abroad - Research
• Start date: January 08, 2026
• End date: February 09, 2026
• Field of knowledge: Physical Sciences and Mathematics - Astronomy - Extragalactic Astrophysics
• Principal Investigator: Oli Luiz Dors Junior
• Grantee: Oli Luiz Dors Junior
• Host Investigator: Giovanni Cresci
• Host Institution: Instituto de Pesquisa e Desenvolvimento (IP&D). Universidade do Vale do Paraíba (UNIVAP). São José dos Campos , SP, Brazil
• Institution abroad: Osservatorio Astrofisico di Arcetri, Italy

Abstract

The present project consists of a technical visit (from 01/08/2026 to 02/08/2026) to the Arcetri Observatory (https://www.arcetri.inaf.it/) in Italy, to be carried out in January 2026 under the supervision of Prof. Giovanni Cresci (https://www.arcetri.inaf.it/giovanni.cresci/). This marks the beginning of a collaboration between the groups, which justifies the short duration of the visit.Funding is being requested from FAPESP to cover travel expenses, specifically airfare and daily allowances for a period of 30 days. The main objective of the project is to investigate metallicity (Z) determinations and the ionization degree (measured by the ionization parameter, U) in narrow-line regions (NLRs) of Active Galactic Nuclei (AGNs). These determinations have been carried out by the extragalactic astrophysics group at UNIVAP over the past 10 years using two methods: the direct method (or Te-method) and strong-line methods.Both methods require the use of photoionization models. These models, typically built using the Cloudy code (www.nublado.org), are subject to various uncertainties, especially when they assume the usual approximation of a single cloud with constant Z, U, and electron density (Ne) along the nebular radius, as done by the UNIVAP group. Comparisons of these models with optical spectroscopic data from NLRs reveal, as also occurs in H II regions, the inability to reproduce auroral lines such as [O III]¿4363. This limitation is reflected in the well-known discrepancy between Z estimates derived from models and those obtained using the Te-method. Additionally, U estimates based on ultraviolet and optical lines show inconsistencies with each other. These remain open problems in astrophysics.Recently, the use of the HOMERUN code - based on the Cloudy code - has demonstrated that combining multiple clouds with different physical properties (Z, U, Ne) in photoionization models is capable, for the first time, of reproducing auroral lines in H II regions. Motivated by this promising result, we propose to apply the HOMERUN code to the study of AGN NLRs, with the aim of investigating the effects of using multiple clouds on the estimation of nebular parameters in this class of objects. (AU)