The nature of ionized gas in early-type galaxies

TL;DR

This study investigates ionized gas in 65 nearby early-type galaxies, revealing widespread emission, predominantly LINERs, with ionization mechanisms varying with galacto-centric distance.

Contribution

It provides a detailed analysis of ionized gas properties and ionization mechanisms in early-type galaxies using optical spectra, highlighting spatial variations.

Findings

89% of galaxies show emission lines

Most galaxies classified as LINERs

Ionization mechanisms vary with distance from galaxy center

Abstract

We present a study of the ionized gas in a sample of 65 nearby early-type galaxies, for which we have acquired optical intermediate-resolution spectra. Emission lines are detected in ~89 % of the sample. The incidence of emission appears independent from the E or S0 morphological classes. According to classical diagnostic diagrams, the majority of the galaxies are LINERs. However, the galaxies tend to move toward the "Composites" region (at lower [NII]/Halpha values) as the emission lines are measured at larger galacto-centric distances. This suggests that different ionization mechanisms may be at work in LINERs.