Three Spectacular HII-buried-AGN Galaxies from SDSS

TL;DR

This study analyzes three SDSS galaxies with hidden AGN features within HII regions, revealing their transitional phase from starburst to active galactic nucleus activity through spectral analysis.

Contribution

It identifies a new class of galaxies with buried AGN signatures in HII regions and characterizes their properties indicating a transitional evolutionary stage.

Findings

Galaxies exhibit HII-region emission lines but Seyfert-like features after stellar emission removal.

All three galaxies have high Eddington ratios, small black holes, and low star formation rates.

They are likely in a transition from starburst-dominated to AGN-dominated phases.

Abstract

We present our analysis of the three HII-buried-AGN: SDSS J091053+333008, SDSS J121837+091324, and SDSS J153002-020415, by studying their optical spectra extracted from SDSS. The location in the BPT diagnostic diagrams of the three galaxies indicates that the narrow emission lines are mainly exited from HII regions. However, after the removal of the host galaxy's stellar emission, the emission lines display the typical feature of Narrow-line Seyfert 1-like. All of the three objects have large Eddington ratio, small black hole mass, and low star formation rate. We propose that the three galaxies are at the transit stage from the starburst-dominated phase to AGN-dominated phase.