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

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10. Conclusions

The findings presented in YC95 were based on the assumption that the relatively small scatters observed in two scaling relationships found for Fornax and Local Group dwarfs, are also applicable to Virgo dwarfs. Although, we still consider this assumption to be a most reasonable one, we concede that we should have stated it explicitly in YC95. Unlike Binggeli & Jerjen, we (YC95 & this work) did not make any prior assumption as to the actual depth of Virgo when making our case. Also, contrary to the impression given by Binggeli & Jerjen, our case is not undermined by any dependence between the scaling laws-which merely means that we slightly under-estimated our internal errors in YC95. In this paper, we have also presented further statistical evidence to support our case based on Binggeli & Jerjen's own dataset.

Binggeli & Jerjen claim to have presented evidence both that (1) profile shape is not a useful distance indicator because scaling laws based on it have large intrinsic scatters and that (2) the spatial depth of the Virgo Cluster must be small. However, all that they have in fact achieved in their paper, is merely to point out that if one first assumes that the depth of the cluster is small enough, then there must be large intrinsic scatters in the scaling laws in question for Virgo galaxies. In order to explain away the smaller intrinsic scatters found in Fornax and Local Group samples of galaxies, they suggest [in the absence of any supporting evidence] that either there is a dichotomy between Virgo and non-Virgo dwarfs or that our samples of non-Virgo dwarfs are not representative. They therefore cannot legitimately claim to have presented evidence for both (1) and (2) simultaneously; or to have presented evidence for (1) or (2) without first assuming (2) or (1) respectively.

The Virgo Cluster is not a suitable target for investigating the reliability of the curvature-based indicators. Reliable photometry of galaxies in other clusters and groups, where there is no controversy concerning line-of-sight depth, are required for this purpose.

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© European Southern Observatory (ESO) 1998

Online publication: April 28, 1998