The angular momentum of cosmological coronae and the inside-out growth
  of spiral galaxies
  Massive and diffuse haloes of hot gas (coronae) are important intermediaries
between cosmology and galaxy evolution, storing mass and angular momentum
acquired from the cosmic web until eventual accretion on to star-forming discs.
We introduce a method to reconstruct the rotation of a galactic corona, based
on its angular momentum distribution (AMD). This allows us to investigate in
what conditions the angular momentum acquired from tidal torques can be
transferred to star forming discs and explain observed galaxy-scale processes,
such as inside-out growth and the build-up of abundance gradients. We find that
a simple model of an isothermal corona with a temperature slightly smaller than
virial and a cosmologically motivated AMD is in good agreement with galaxy
evolution requirements, supporting hot-mode accretion as a viable driver for
the evolution of spiral galaxies in a cosmological context. We predict
moderately sub-centrifugal rotation close to the disc and slow rotation close
to the virial radius. Motivated by the observation that the Milky Way has a
relatively hot corona (T ~ 2 x 10^6 K), we also explore models with a
temperature larger than virial. To be able to drive inside-out growth, these
models must be significantly affected by feedback, either mechanical (ejection
of low angular momentum material) or thermal (heating of the central regions).
However, the agreement with galaxy evolution constraints becomes, in these
cases, only marginal, suggesting that our first and simpler model may apply to
a larger fraction of galaxy evolution history.
