The elliptical galaxy NGC 5044: Stellar population and ionized gas

Abstract

In this work we investigate the stellar population, metallicity distribution and ionized gas in the elliptical galaxy NGC 5044, using long-slit spectroscopy and a stellar population synthesis method. We found differences in the slope of metal-line profiles along the galaxy which suggests an enhancement of a elements, particularly towards the central region. The stellar population synthesis showed that the component with [Z/Z⊙] ∼ 0.0 dominates the λ5870 Å flux in the central region of NGC 5044, contributing with ∼42% of the total flux, while in the external regions the contribution decreases to ∼8.0%. The component with [Z/Z⊙] ∼ -0.4 contributes with ∼32% in the central region, and ∼55% in the external regions. The component with [Z/Z⊙] ∼ -1.1 contributes with ∼26% in the central region, and ∼37% in the external regions. The three components have ∼1010 years. The presence of a non-thermal ionization source, such as a low-luminosity AGN and/or shock ionization, is implied by the large values of the ratio [NII]/H α observed in all sampled regions. However, the emission lines observed in the external regions indicate the presence of an additional ionization source, probably hot, post-AGB stars.