  We perform spherically-symmetric general-relativistic simulations of core
collapse and the postbounce preexplosion phase in 32 presupernova stellar
models of solar metallicity with zero-age-main-sequence masses of 12 M_{sun} to
120 M_{sun}. Using energy-dependent three-species neutrino transport in the
two-moment approximation with an analytic closure, we show that the emitted
neutrino luminosities and spectra follow very systematic trends that are
correlated with the compactness (~M/R) of the progenitor star's inner regions
via the accretion rate in the preexplosion phase. We find that these
qualitative trends depend only weakly on the nuclear equation of state, but
quantitative observational statements will require independent constraints on
the equation of state and the rotation rate of the core as well as a more
complete understanding of neutrino oscillations. We investigate the simulated
response of water Cherenkov detectors to the electron antineutrino fluxes from
our models and find that the large statistics of a galactic core collapse event
may allow robust conclusions on the inner structure of the progenitor star.
