Misc,
The Aspen--Amsterdam Void Finder Comparison Project
(2008)cite arxiv:0803.0918 Comment: 14 pages, version accepted by MNRAS.
Abstract
Despite a history that dates back at least a quarter of a century studies of
voids in the large--scale structure of the Universe are bedevilled by a major
problem: there exist a large number of quite different void--finding
algorithms, a fact that has so far got in the way of groups comparing their
results without worrying about whether such a comparison in fact makes sense.
Because of the recent increased interest in voids, both in very large galaxy
surveys and in detailed simulations of cosmic structure formation, this
situation is very unfortunate. We here present the first systematic comparison
study of thirteen different void finders constructed using particles, haloes,
and semi--analytical model galaxies extracted from a subvolume of the
Millennium simulation. The study includes many groups that have studied voids
over the past decade. We show their results and discuss their differences and
agreements. As it turns out, the basic results of the various methods agree
very well with each other in that they all locate a major void near the centre
of our volume. Voids have very underdense centres, reaching below 10 percent of
the mean cosmic density. In addition, those void finders that allow for void
galaxies show that those galaxies follow similar trends. For example, the
overdensity of void galaxies brighter than $m_B = -20 $ is found to be smaller
than about -0.8 by all our void finding algorithms.
