23 research outputs found
Halo Shapes, Dynamics and Environment
In the hierarchical structure formation model cosmic halos are supposed to
form by accretion of smaller units along anisotropic direction, defined by
large-scale filamentary structures. After the epoch of primary mass aggregation
(which depend on the cosmological model), violent relaxation processes will
tend to alter the halo phase-space configuration producing quasi-spherical
halos with a relatively smooth density profiles.
Here we attempt to investigate the relation between halos shapes, their
environment and their dynamical state. To this end we have run a large ( Mpc, particles) N-body simulation of a flat low-density
cold dark matter model with a matter density , Hubble constant km s
Mpc and a normalization parameter of . The particle mass
is comparable to the mass of
one single galaxy. The halos are defined using a friends-of-friend algorithm
with a linking length given by where is the mean
density. This linking length corresponds to an overdensity at the present epoch () and the total number of halos
with more than 130 particles () is 57524.Comment: To be published in "Groups Of Galaxies In The Nearby Universe", held
in Chile, December 2005, edited by I.Saviane, V.Ivanov and J.Borissova.
Springer-Verlag series "ESO Astrophysics Symposia
The Equity Impacts of Municipal Tax Incentives: Leveling or Tilting the Playing Field?
The widespread use over the past two decades of Michigan's PA 198 Industrial Tax Abatement program provides an opportunity to assess the inter-urban equity impacts of this economic development tool. Not only has PA 198 been used relatively more often by suburban municipalities, local governments at the metropolitan periphery are more likely to use abatements to attract new plants and new jobs. The older central cities primarily use the program to retain existing jobs, albeit at high cost of lost tax revenues. On balance, it appears that PA 198 has done little to alter the location decisions of participating firms. Copyright 2006 by The Policy Studies Organization.