Spectral Energy Distribution Mapping of Two Elliptical Galaxies on sub-kpc scales

TL;DR

This study maps the spectral energy distribution of two elliptical galaxies at sub-kiloparsec scales, revealing their dust and stellar content, and identifying a recent starburst and metallicity gradients.

Contribution

It provides high-resolution SED maps of elliptical galaxies, linking dust distribution to young star fractions and metallicity gradients, using Herschel-PACS and multi-wavelength data.

Findings

Elliptical galaxies have significant dust not aligned with stellar content.

A recent starburst (~0.5 Gyr) is identified in both galaxies.

Metallicity decreases steeply with radius.

Abstract

We use high-resolution Herschel-PACS data of 2 nearby elliptical galaxies, IC1459 & NGC2768 to characterize their dust and stellar content. IC1459 & NGC2768 have an unusually large amount of dust for elliptical galaxies (1-3 x 10^5 Msun), this dust is also not distributed along the stellar content. Using data from GALEX (ultraviolet) to PACS (far-infrared), we analyze the spectral energy distribution (SED) of these galaxies with CIGALEMC as a function of the projected position, binning images in 7.2" pixels. From this analysis, we derive maps of SED parameters, such as the metallicity, the stellar mass, the fraction of young star and the dust mass. The larger amount of dust in FIR maps seems related in our model to a larger fraction of young stars which can reach up to 4% in the dustier area. The young stellar population is fitted as a recent (~ 0.5 Gyr) short burst of star formation for both galaxies. The metallicities, which are fairly large at the center of both galaxies, decrease with the radial distance with fairly steep gradient for elliptical galaxies.