Ben-Gurion University of the NegevAstrophysics and Cosmology GroupAstrophysics, Relativity, Cosmology, and Space Physics |
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Speaker: Christoph Pfrommer (Heidelberg ITS) May 20, 2015 Cosmic ray feedback in galaxies and cool core clusters Abstract: Understanding
the physics of galaxy formation is arguably among the greatest problems
in modern astrophysics. Recent cosmological simulations have
demonstrated that "feedback" by star formation, supernovae and active
galactic nuclei appears to be critical in obtaining realistic disk
galaxies, to slow down star formation to the small observed rates, to
move gas and metals out of galaxies into the intergalactic medium, and
to balance radiative cooling of the low-entropy gas at the centers of
galaxy clusters. However the particular physical processes underlying
this "feedback" still remain elusive. In particular, these simulations
neglected cosmic rays and magnetic fields, which provide a comparable
pressure support in comparison to turbulence in our Galaxy, and are
known to couple dynamically and thermally to the gas. Using
hydrodynamic simulations of galaxy formation, I will show how cosmic
rays are able to drive powerful galactic winds in low-mass galaxies.
This reduces the available amount of gas for star formation and implies
a shallower slope of the faint-end of the galaxy luminosity function as
required by observations. In the second part of the talk I demonstrate
that cosmic-ray heating can balance radiative cooling of the
low-entropy gas at the centers of galaxy clusters and helps in
mitigating the star formation of the brightest cluster galaxies. New
data on the low-frequency radio and gamma-ray emission of M87, the
closest active galaxy interacting with the cooling cluster plasma,
enable us to put forward a comprehensive, physics-based model of
feedback by active galactic nuclei.
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Last updated
by Uri Keshet,
2013 |