Dr. Francesco Fontani, U. Bologna

"A search for high-mass pre-stellar cores"

Abstract:
The initial conditions of the high-mass star formation process are still
poorly understood. I will present a work in which
we have measured deuterium fractionation and CO depletion factor (the
ratio between expected and observed CO abundance) in a sample of
high-massprotostellar candidates, in order to understand whether the
earliest evolutionary stages of massive stars have chemical
characteristics similar to those of low-mass ones. We have detected N2D+
emission in 7 of the 10 sources of our sample, and found values of
deuterium fractionation nearly 3 orders of magnitude larger than the
cosmic D/H abundance, but lower than those found in low-mass pre-stellar
cores. Given the low angular resolution of the data, the cold gas that
generates the N2D+ emission in principle can be distibuted in the
extended envelope of the massive protostellar object, or concentrated into
one (or more) pre-stellar cores located close to it. Higher angular
resolution observations will be very helpful in deciding which solution is
correct. I will also show some recent SMA observations performed towards
IRAS05345+3157, one of the sources of the initial sample that stands
out from the rest for its interesting characteristics.