rays in ENZO)
Large Scale Shocks are responsible for the heating of the ICM and
be important sources of Cosmic Rays (CR) in the Universe.
In a first article, we presented an original implementation to
model at run-time the
injection, advection and dynamical feedback of CR in
cosmological simulations (also using AMR) working on the public
release of ENZO. This implementation is mostly based
on "pioneristic" works proposed by several people >10 years ago
(T.Jones, H.Kang, F.Miniati...), which we tried
to merge within ENZO and using adaptive mesh refinement in
Read the full article here (Vazza, Bruggen, Gheller & Brunetti
Also the violent energy release which is supposed to operate
during feedback from Active Galactic Nuclei onto
the intra cluster medium can enrich galaxy clusters with CRs.
In a second work, we studied this topic by implementing basic
recipes of AGN feedback in ENZO simulations, modelling
several "flavors" of feedback: kinetic energy input from jets,
theral energy input from "quasars", and buoyant
rise of evacuated bubbles. We studied the way each of these
mechanisms should inject CRs in the ICM, and we
evolved galaxy clusters also following radiative cooling and
energy losses of CRs. We produced forecasts of X-ray, gamma-ray
emission and turbulent features connected to each feedback model,
which are almost within reach of existing telescopes, and can
set upper-limits on the energetics and duty cycle of AGN feedback
withi clusters when complemented with the
information provided by CRs.
Read the full article here (Vazza, Bruggen, Gheller
We tested our procedure against shock-tubes tests and 1-D
collapse test, finding very good performances.
Our code allows us to test the various "blocks" of CR physics
advection, injection, reduced thermalization, pressure feedback)
separately. Also the efficiency of acceleration with M can be
We investigated the distribution of CR in large scale structures,
both fixed grid runs (dx=200kpc/h) and runs with adaptive mesh
The most important findings are:
A MOVIE SHOWING THE RUN-TIME INJECTION OF CR, AND THEIR
STARTING FROM Z=1 IN A
- The level of CR energy inside cosmic structures is found to
small, Pcr/Pg < 0.1, with a peak at the over-density
outer accretion regions. We report that only the distribution
outside of cosmic structures is strongly dependent on the
involved in the acceleration in the early cosmic epochs (and
the most rarefied environments) while the distributions
stable for the innermost regions of clusters.
- In massive galaxy clusters, the dynamical role of
energy is always quite small, and plays a
significant dynamical role only close to ∼ R200. In the centre
clusters instead the pressure of CRs is small, Pcr/Pg ∼ 0.02 −
0.05. These values are presently consistent with the
provided from γ-ray observations.
- The effects of CRs on the overall evolution of clusters have
small and systematic effects on the 3–D distribution of the
baryonic gas. In all re-simulated clusters in the innermost
density, temperature and entropy are reduced by a few percent,
while they are enhanced on average by the same amount at R200.
comes from the fact that CRs first modify the
compressibility of outer accretion regions during the
structures, leading to an enhanced post-shock compression and
a slightly faster expansion of the outer cluster layers
- This produces also a corresponding decrease of X-ray
of the thermal SZ signal from the inner cluster
region, and an enhancement of a factor ∼ 0.4−4 close to R200,
depending of the dynamical state of the clusters.
- These systematic trends in galaxy clusters are at
with SPH simulations, where rather opposite trends are
COSMOLOGICAL RUN USING AMR (the movie is embedded in Youtube)
IS A MOVIE SHOWING THE EVOLUTION OF GAS PRESSURE AND CR PRESSURE
IN TWO RESIMULATIONS
OF THE SAME CLUSTERS, USING PURE COOLING OR FEEDBACK BY JETS
(the movie is embedded in Youtube)
slices of Mach number (measured at run-time), injected CR
in the post-shock, and gas energy for a cluster simulated
with AMR and
our sciENZO modules.
Merger sequence for a cluster simulated with AMR.
Top row: gas
energy for a slice of 50 kpc/h. Middle row: CR energy
within the same
slice. Bottom row: ratio of the two for the same regions.