A&A 378, 345360 (2001)
DOI: 10.1051/00046361:20011240
Kinematics of the local universe
IX. The PerseusPisces supercluster and the TolmanBondi model
M. O. Hanski^{1}, G. Theureau^{2, 3}, T. Ekholm^{4, 1} and P. Teerikorpi^{1}^{1} Tuorla Observatory, 21500 Piikkiö, Finland
^{2} Observatoire de Meudon, 92195 Meudon Cedex, France
email: gilles.theureau@obspm.fr
^{3} Osservatorio di Capodimonte, Via Moiariello 16, 80131 Naples, Italy
^{4} Observatoire de Lyon, 69561 SaintGenis Laval Cedex, France
(Received 24 June 1999 / Accepted 5 September 2001)
Abstract
The matter distribution around the PerseusPisces (PP) supercluster is studied by comparing
peculiar velocities given by the Kinematics of the local universe (KLUN) galaxy sample to those predicted by TolmanBondi
(TB) models. To restrict the TB solutions we first solve the mass of the densest part of PP. This part is identified as a
sphere at
,
Mpc having a radius of
15 h^{1} Mpc. This sphere surrounds the main part of the PP ridge and four most prominent clusters of the region. Using viriallike
mass estimators we calculate the cluster masses and obtain the upper and lower limits for the mass inside the
15 h^{1} Mpc sphere:

. This corresponds to a mass overdensity
, or

. Mass to light ratios of the clusters are M/L = 200 600
, giving mass density ratio
0.3, if the value of M/L is assumed to be representative elsewhere in the universe.
We estimate a radial density distribution around the PP core using two toy models and a smoothed density distribution observed
for IRAS galaxies. The cosmological density parameters
and the PP mass are free parameters in the TB calculations. The KLUN velocities, obtained by TullyFisher relation and the
normalized distance method, are adjusted by the Local Group (LG) infall velocity towards PP. Comparison of the TB velocities
to KLUN data points indicates that the infall velocity
km s^{1}. Allowing
to vary within the limits given above we get constraints for the value of ;
0.4 are prefered to the more extreme values,
or 1. A choice of either
or 0 do not cause any significant changes in the results.
The validity of the TB model in complex environments is studied with an Nbody simulation. There we see that the radially averaged velocity fields around simulated clusters are compatible with the
corresponding TB velocities. This confirms the applicability of the TB model around large galaxy concentrations, providing
that smoothed density and radially averaged velocity fields are used.
Key words: galaxies: clusters: general  galaxies: clusters: PersPisc supercluster  cosmology: theory  largescale structure of the universe
Offprint request: M. Hanski, mihanski@astro.utu.fi
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