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Session: Extragalactic Astronomy and Astrophysics

Name: Mr. Evangelos-Dimitrios Paspaliaris (NOA & AUTh)
Coauthors: No coauthors were included.
Type: Oral
Title: Star-forming early-type galaxies and quiescent late-type galaxies in the local Universe.
Abstract:

There is a general consensus that late-type galaxies undergo intense star-formation activity while early-type galaxies are mostly inactive. We question this general conception and investigate the existence of star-forming early-type galaxies and quiescent late-type galaxies in the local Universe. Our sample consists of 2,209 morphologically classified galaxies in the GAMA survey. The separation into star-forming and quiescent galaxies is based on the dominant ionising process, making use of established criteria based on the WHα width and the [NII/Hα] ratio. Performing a spectral energy distribution fitting analysis we derived the physical properties of these galaxies, such as the stellar mass, dust mass, star-formation rate, and we also estimated the unattenuated and the dust-absorbed stellar emission, for both the young (≤ 200 Myr) and old (> 200 Myr) stellar populations. In order to explore the differences from their “typical” counterparts, we compared their average spectral energy distributions, their physical and structural properties, as well as the density of their local environment. We found that about 47% of E/S0 galaxies in our sample show ongoing star-formation activity and 8% of late-type galaxies are quiescent. Moreover, the unattenuated shape of the average SED of the star-forming galaxies and the scaling relations of their physical properties are very similar, for all morphological types. Concerning their structural parameters, quiescent galaxies tend to show larger values of the Sérsic index and larger effective radii (compared to star-forming galaxies). Finally, we find that star-forming galaxies preferably reside in lower density environments compared to the quiescent ones, which exhibit a higher percentage of sources being members of groups.