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Test Results of IsoDen Method

Figure 4 shows results obtained using IsoDen for Model 3, using both statistical and evaporative methods to reject spurious halos. In this particular case all of the halos found by IsoDen turn out to be real, in terms of their internal velocities (when examined individually). This is the case for both methods of noise suppression. Also, IsoDen distinguishes halos even in the high density central region of the cluster -- the single large central halo found by FOF is split into 9 smaller halos by IsoDen (or 10 halos using the evaporative test). All halos found by FOF using tex2html_wrap_inline2032 or evaporative testing are also found by IsoDen. The only difference between the IsoDen results using the two noise suppression tests is that the evaporative method identifies three extra halos which did not pass the significance test with n=3.

Figure: Results of the IsoDen method for Model 3, using the same format as Figure 1. The panels on the left show results using the statistical noise suppression test; those on the right use the evaporative test. For each halo only those particles with densities between tex2html_wrap_inline2120, the halo peak (central) density, and tex2html_wrap_inline2124, the density of the first overlap of that halo, are shown.

John Salmon
Sat Sep 27 18:44:36 PDT 1997