The elliptical galaxy NGC 5044: Stellar population and ionized gas

• Published in: Astronomy and astrophysics (Berlin) 2004-05, Vol.419 (2), p.449-458
• Main Authors: Rickes, M. G., Pastoriza, M. G., Bonatto, Ch
• Format: Article
• Language: English
• Subjects: galaxies: elliptical and lenticular; galaxies: fundamental parameters; galaxies: individual: NGC 5044
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361:20034302

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 α elements, particularly towards the central region. The stellar population synthesis showed that the component with $[Z/Z_\odot]\sim0.0$ dominates the $\lambda5870$ 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 $[Z/Z_\odot]\sim-0.4$ contributes with ~$32\%$ in the central region, and ~$55\%$ in the external regions. The component with $[Z/Z_\odot]\sim-1.1$ 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 $\frac{\ion{[N}{ii]}}{\rm H\alpha}$ 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.