SPIDER - X. Environmental effects in central and satellite early-type galaxies through the stellar fossil record

La Barbera, F.; Pasquali, A.; Ferreras, I.; Gallazzi, A.; de Carvalho, R. R.; de la Rosa, I. G.
Bibliographical reference

Monthly Notices of the Royal Astronomical Society, Volume 445, Issue 2, p.1977-1996

Advertised on:
12
2014
Number of authors
6
IAC number of authors
1
Citations
43
Refereed citations
41
Description
A detailed analysis of how environment affects the star formation history of early-type galaxies (ETGs) is undertaken via high signal-to-noise ratio stacked spectra obtained from a sample of 20 977 ETGs (morphologically selected) from the Sloan Digital Sky Survey-based SPIDER survey. Two major parameters are considered for the study: the central velocity dispersion (σ), which relates to local drivers of star formation, and the mass of the host halo, which relates to environment-related effects. In addition, we separate the sample between centrals (the most massive galaxy in a halo) and satellites. We derive trends of age, metallicity, and [α/Fe] enhancement, with σ. We confirm that the major driver of stellar population properties in ETGs is velocity dispersion, with a second-order effect associated with the central/satellite nature of the galaxy. No environmental dependence is detected for satellite ETGs, except at low σ - where satellites in groups or in the outskirts of clusters tend to be younger than those in the central regions of clusters. In contrast, the trends for centrals show a significant dependence on halo mass. Central ETGs in groups (i.e. with a halo mass >1012.5 M⊙) have younger ages, lower [α/Fe], and higher internal reddening, than `isolated' systems (i.e. centrals residing in low-mass, <1012.5 M⊙, haloes). Our findings imply that central ETGs in groups formed their stellar component over longer time scales than `isolated' centrals, mainly because of gas-rich interactions with their companion galaxies.
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Traces of Galaxy Formation: Stellar populations, Dynamics and Morphology
We are a large, diverse, and very active research group aiming to provide a comprehensive picture for the formation of galaxies in the Universe. Rooted in detailed stellar population analysis, we are constantly exploring and developing new tools and ideas to understand how galaxies came to be what we now observe.
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