The Diagnostics and Possible Evolution in Active Galactic Nuclei Associated With Starburst Galaxies

TL;DR

This study analyzes the properties of various active galactic nuclei and starburst galaxies, using optical spectral diagnostics to distinguish their types and explore potential evolutionary pathways among them.

Contribution

It introduces new diagnostic equations and statistical methods to classify AGNs and starburst galaxies, suggesting possible evolutionary links.

Findings

HBLR Sy2s may be the edge-on counterparts of Sy1s

Distinct emission-line ratios effectively separate galaxy types

Starburst galaxies may evolve into different AGN subclasses

Abstract

We present a large sample which contains 45 Seyfert 1 galaxies (Sy1s), 46 hidden broad-line region (HBLR) Seyfert 2 galaxies (Sy2s), 57 non-HBLR Sy2s, and 22 starburst galaxies to distinguish their properties and to seek the possible evolution of active galactic nuclei (AGNs) and starburst galaxies. We show that (1) using a plot of [O III] {\l}5007/H/alpha versus [N II] {\l}6584/H/alpha of standard optical spectral diagnostic diagrams, we find that a equation can separate well non-HBLR Sy2s and HBLR Sy2s; (2) the emission-line ratios and both the combination of the ratios and polycyclic aromatic hydrocarbon (PAH) strength are utilized effectively to separate starburst galaxies and Seyfert galaxies; (3) we compare a number of quantities from the data and confirm well the separations with statistics; (4) on the basis of statistics, we suggest that HBLR Sy2s may be the counterparts of Sy1s at edge-on orientation. In addition, we discuss the possibility of starburst galaxies evolving to non-HBLR Sy2s and HBLR Sy2s and then evolving to Sy1s based on the statistical analysis.