Mon. Not. R. Astron. Soc., 406, 382-394 (2010/July-3)
Peculiar early-type galaxies in the Sloan Digital Sky Survey Stripe82.
Abstract (from CDS):
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.
© 2010 The Author. Journal compilation © 2010 RAS
galaxies: elliptical and lenticular, cD - galaxies: evolution - galaxies: formation - galaxies: interactions - galaxies: peculiar
VizieR on-line data:
<Available at CDS (J/MNRAS/406/382): catalog.dat>
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