Title: Efficient cold outflows driven by cosmic rays in high redshift galaxies and their global effects on the IGM,
Abstract: We present semi-analytical models of galactic outflows in high redshift
galaxies driven by both hot thermal gas and non-thermal cosmic rays. Thermal
pressure alone may not sustain a large scale outflow in low mass galaxies (i.e
$M\sim 10^8$~M$_\odot$), in the presence of supernovae (SNe) feedback with
large mass loading. We show that inclusion of cosmic ray pressure allows
outflow solutions even in these galaxies. In massive galaxies for the same
energy efficiency, cosmic ray driven winds can propagate to larger distances
compared to pure thermally driven winds. On an average gas in the cosmic ray
driven winds has a lower temperature which could aid detecting it through
absorption lines in the spectra of background sources. Using our constrained
semi-analytical models of galaxy formation (that explains the observed UV
luminosity functions of galaxies) we study the influence of cosmic ray driven
winds on the properties of the intergalactic medium (IGM) at different
redshifts. In particular, we study the volume filling factor, average
metallicity, cosmic ray and magnetic field energy densities for models invoking
atomic cooled and molecular cooled halos. We show that the cosmic rays in the
IGM could have enough energy that can be transferred to the thermal gas in
presence of magnetic fields to influence the thermal history of the
intergalactic medium. The significant volume filling and resulting strength of
IGM magnetic fields can also account for recent $\gamma$-ray observations of
blazars.