Bulge–disc decompositions and structural bimodality of Ursa Major cluster spiral galaxies |
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Authors: | Michael McDonald † Stéphane Courteau R Brent Tully |
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Institution: | Department of Physics, Engineering Physics and Astronomy, Queen's University, Kingston, ON, Canada;Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI, USA |
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Abstract: | We present bulge and disc (B/D) decompositions of existing K ' surface brightness profiles for 65 Ursa Major (UMa) cluster spiral galaxies. This improves upon the disc-only fits of Tully et al. The 1996 disc fits were used by Tully & Verheijen for their discovery of the bimodality of structural parameters in the UMa cluster galaxies. It is shown that our new one-dimensional B/D decompositions yield disc structural parameters that differ only slightly from the basic fits of Tully et al. and evidence for structural bimodality of UMa galaxies is maintained. Our B/D software for the decomposition of one-dimensional surface brightness profiles of galaxies uses a non-linear minimization scheme to recover the best-fitting Sérsic bulge and the exponential disc while accounting for the possible presence of a compact nucleus and spiral arms and for the effects of seeing and disc truncations. In agreement with Tully & Verheijen, we find that the distribution of near-infrared disc central surface brightnesses is bimodal with an F-test confidence of 80 per cent. There is also strong evidence for a local minimum in the luminosity function at . A connection between the brightness bimodality and a dynamical bimodality, based on new H i linewidths, is identified. The B/D parameters are presented in Table 1 . |
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Keywords: | galaxies: clusters: general galaxies: evolution galaxies: formation galaxies: luminosity function mass function galaxies: statistics galaxies: structure |
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