Peculiar early-type galaxies in the Sloan Digital Sky Survey Stripe82
Abstract
We explore the properties of `peculiar' early-type galaxies (ETGs) in the local Universe that show (faint) morphological signatures of recent interactions such as tidal tails, shells and dust lanes. Standard-depth (~51-s exposure) multicolour galaxy images from the Sloan Digital Sky Survey (SDSS) are combined with the significantly (~2 mag) deeper monochromatic images from the public SDSS Stripe82 to extract, through careful visual inspection, a robust sample of nearby (z < 0.05), luminous (Mr < -20.5) ETGs, including a subset of ~70 peculiar systems. ~18 per cent of ETGs exhibit signs of disturbed morphologies (e.g. shells), while ~7 per cent show evidence of dust lanes and patches. An analysis of optical emission-line ratios indicates that the fraction of peculiar ETGs that are Seyferts or LINERs (19.4 per cent) is twice the corresponding values in their relaxed counterparts (10.1 per cent). LINER-like emission is the dominant type of nebular activity in all ETG classes, plausibly driven by stellar photoionization associated with recent star formation. An analysis of ultraviolet-optical colours indicates that, regardless of the luminosity range being considered, the fraction of peculiar ETGs that have experienced star formation in the last Gyr is a factor of ~1.5 higher than that in their relaxed counterparts. The spectrophotometric results strongly suggest that the interactions that produce the morphological peculiarities also induce low-level recent star formation which, based on the recent literature, are likely to contribute a few per cent of the stellar mass over the last ~1Gyr. Peculiar ETGs preferentially inhabit low-density environments (outskirts of clusters, groups or the field), either due to high peculiar velocities in clusters making merging unlikely or because shell systems are disrupted through frequent interactions within a cluster crossing time. The catalogue of galaxies that forms the basis of this paper can be obtained at http://www.mssl.ucl.ac.uk/~ska/stripe82/skaviraj_stripe82.dat or on request from the author.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- July 2010
- DOI:
- 10.1111/j.1365-2966.2010.16714.x
- arXiv:
- arXiv:1004.3775
- Bibcode:
- 2010MNRAS.406..382K
- Keywords:
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- galaxies: elliptical and lenticular;
- cD;
- galaxies: evolution;
- galaxies: formation;
- galaxies: interactions;
- galaxies: peculiar;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- MNRAS in press