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Astron. Astrophys. 333, 795-802 (1998)

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1. Introduction

Binggeli & Jerjen (1998) conclude that the shape of a dwarf-elliptical galaxy's surface-brightness profile (as quantified by the curvature parameter n from Sérsic's (1968) [FORMULA] law) is not a useful distance indicator. Their conclusion is based on their finding that the scatter on the relevant correlations `can be reduced...never below [FORMULA] mag., at least for the Virgo cluster.'

Should the intrinsic scatter on the relevant correlations be as large as 0.7 mag., the profile-shape indicator would indeed be of only limited value, and there would be strong grounds for believing that Virgo dwarf ellipticals define a single cluster of galaxies of small depth. Should however, the intrinsic scatter be about 0.5 mag. or lower, profile shape would be a valuable indicator of distance and there would be strong grounds for believing that the Virgo Cluster's depth is significant. Note however, that the latter interpretation does not require the existence of a `prolate structure' as presumed by Binggeli & Jerjen. There are of course alternative models, notably the substructure model we favoured in Young & Currie (1995) (hereunder YC95). The central issue in this debate is therefore whether Binggeli & Jerjen have demonstrated that the intrinsic scatter in the scaling relationships is, as they claim, of the order of 0.7 [FORMULA] mag., or whether or not they have at least put forward strong circumstantial evidence in support of their case.

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© European Southern Observatory (ESO) 1998

Online publication: April 28, 1998

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