Volume 588, April 2016
|Number of page(s)||22|
|Published online||22 March 2016|
Isolated elliptical galaxies in the local Universe
1 Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Av. V. Mackenna 4860, Santiago, Chile
2 Centro de Astro-Ingeniería, Pontificia Universidad Católica de Chile, Av. V. Mackenna 4860, Santiago, Chile
3 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
4 Instituto de Astronomía, Universidad Nacional Autónoma de México, A.P. 70-264, 04510 México D. F., Mexico
5 Instituto de Astrofísica de Andalucía IAA – CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
Received: 26 November 2015
Accepted: 6 January 2016
Context. We have studied a sample of 89 very isolated, elliptical galaxies at z < 0.08 and compared their properties with elliptical galaxies located in a high-density environment such as the Coma supercluster.
Aims. Our aim is to probe the role of environment on the morphological transformation and quenching of elliptical galaxies as a function of mass. In addition, we elucidate the nature of a particular set of blue and star-forming isolated ellipticals identified here.
Methods. We studied physical properties of ellipticals, such as color, specific star formation rate, galaxy size, and stellar age, as a function of stellar mass and environment based on SDSS data. We analyzed the blue and star-forming isolated ellipticals in more detail, through photometric characterization using GALFIT, and infer their star formation history using STARLIGHT.
Results. Among the isolated ellipticals ≈20% are blue, ≲8% are star forming, and ≈10% are recently quenched, while among the Coma ellipticals ≈8% are blue and just ≲1% are star forming or recently quenched. There are four isolated galaxies (≈4.5%) that are blue and star forming at the same time. These galaxies, with masses between 7 × 109 and 2 × 1010 h-2 M⊙, are also the youngest galaxies with light-weighted stellar ages ≲1 Gyr and exhibit bluer colors toward the galaxy center. Around 30–60% of their present-day luminosity, but only <5% of their present-day mass, is due to star formation in the last 1 Gyr.
Conclusions. The processes of morphological transformation and quenching seem to be in general independent of environment since most of elliptical galaxies are “red and dead”, although the transition to the red sequence should be faster for isolated ellipticals. In some cases, the isolated environment seems to propitiate the rejuvenation of ellipticals by recent (<1 Gyr) cold gas accretion.
Key words: galaxies: elliptical and lenticular, cD / galaxies: formation / galaxies: fundamental parameters / galaxies: photometry / galaxies: structure / galaxies: star formation
© ESO, 2016
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