193 research outputs found
AGN feedback from Jet-ISM/IGM interactions
We study the propagation of relativistic jets originating from AGNs within
the Interstellar/Intergalactic Medium of their host galaxies, and use it to
build a model for the suppression of stellar formation within the expanding
cocoon.Comment: 2 pages, 3 figures. Poster presented at IAU Symp. no. 245 ("Formation
and Evolution of Galaxy Bulges"), Oxford, July 16-20, 200
The String Tension in Two Dimensional Gauge Theories
We review and elaborate on properties of the string tension in
two-dimensional gauge theories. The first model we consider is massive QED in
the limit. We evaluate the leading string tension both in the
fermionic and bosonized descriptions. We discuss the next to leading
corrections in . The next-to-leading terms in the long distance behavior
of the quark-antiquark potential, are evaluated in a certain region of external
versus dynamical charges. The finite temperature behavior is also determined.
In we review the results for the string tension of quarks in cases with
dynamical quarks in the fundamental, adjoint, symmetric and antisymmetric
representations. The screening nature of is re-derived.Comment: 25 pages, Latex. v2: several changes, mainly in section
On the Dynamical Origin of Bias in Clusters of Galaxies
We study the effect of the dynamical friction induced by the presence of
substructure on the statistics of the collapse of density peaks. Applying the
results of a former paper we show that within high density environments, like
rich clusters of galaxies, the collapse of smaller peaks is strongly delayed
until very late epochs. A bias of dynamical nature thus naturally arises
because high density peaks preferentially collapse For a standard CDM model we
find that this dynamical bias can account for a substantial part of the total
bias required by observations on cluster scales.Comment: 14 pages, postscript, 3 postscript figures available by anonymous ftp
on convex.ct.astro.it in /nbody/fig#.ps. Submitted to Astrophysical Journal
Letter
Substructure recovery by 3D Discrete Wavelet Transforms
We present and discuss a method to identify substructures in combined
angular-redshift samples of galaxies within Clusters. The method relies on the
use of Discrete Wavelet Transform (hereafter DWT) and has already been applied
to the analysis of the Coma cluster (Gambera et al. 1997). The main new
ingredient of our method with respect to previous studies lies in the fact that
we make use of a 3D data set rather than a 2D. We test the method on mock
cluster catalogs with spatially localized substructures and on a N-body
simulation. Our main conclusion is that our method is able to identify the
existing substructures provided that: a) the subclumps are detached in part or
all of the phase space, b) one has a statistically significant number of
redshifts, increasing as the distance decreases due to redshift distortions; c)
one knows {\it a priori} the scale on which substructures are to be expected.
We have found that to allow an accurate recovery we must have both a
significant number of galaxies ( for clusters at z or
about 800 at z 0.4) and a limiting magnitude for completeness .
The only true limitation to our method seems to be the necessity of knowing
{\it a priori} the scale on which the substructure is to be found. This is an
intrinsic drawback of the method and no improvement in numerical codes based on
this technique could make up for it.Comment: Accepted for publication in MNRAS. 7 pages, 2 figure
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