The bimodal spiral galaxy surface brightness distribution |
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Authors: | Eric F Bell † W J G de Blok ‡ |
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Institution: | Department of Physics, University of Durham, Science Laboratories, South Road, Durham DH1 3LE; Astrophysics Group, School of Physics, University of Melbourne, Parkville, VIC 3052, Australia |
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Abstract: | We have assessed the significance of Tully and Verheijen's bimodal Ursa Major Cluster spiral galaxy near-infrared surface brightness distribution, focusing on whether this bimodality is simply an artefact of small number statistics. A Kolmogorov–Smirnov style of significance test shows that the total distribution is fairly represented by a single-peaked distribution, but that their isolated galaxy subsample (with no significant neighbours within a projected distance of ∼80 kpc) is bimodal at the 96 per cent level. We have also investigated the assumptions underlying the isolated galaxy surface brightness distribution, finding that the (often large) inclination corrections used in the construction of this distribution reduce the significance of the bimodality. We conclude that the Ursa Major Cluster data set is insufficient to establish the presence of a bimodal near-infrared surface brightness distribution: an independent sample of ∼100 isolated, low-inclination galaxies is required to establish bimodality at the 99 per cent level. |
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Keywords: | galaxies: clusters: individual: Ursa Major galaxies: evolution galaxies: general galaxies: photometry galaxies: spiral galaxies: statistics |
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