| Description |
Nitrogen is the fifth most abundant element in the local Universe. It
is essential component of molecules associated to Earth-type
life. Yet, the reservoir of nitrogen in the dense ISM, where stars,
and ultimately planets, form, is not known. This is for good
reasons. The main reservoir of gas-phase nitrogen are expected to be N
or N2, and it is likely that most of the nitrogen be indeed frozen-out
on dust grains in the form of ammonia ices. However, N and N2 are not
observable in the shielded environments characterizing the embryos of
star-forming regions. Hence, all what is know about nitrogen must rely
on indirect observations of N-bearing molecules, the lightest (and
thus among the easiest to form) of which are hardly detectable from
the ground. To date, and despite longstanding efforts, our
comprehension of the chemistry of nitrogen remains elusive. The
HSO/HIFI instrument is opening new avenues in this respect, allowing
astronomers to readily detect nitrogen hydrides and several key
species of the nitrogen chemistry. This is the aim of this
proposal. We propose the observation of key species that are
observable only with Herschel. Those include NH, NH2 and NH3 (in their
ortho and para forms), as well as their deuterated isotopologues, and
other pivotal species like CH and CH2. This corpus of observations in
order will allow to assess our understanding of the chemistry of
nitrogen in dark cloud conditions, and answer the fundamental and open
question, whether dust processes are necessary catalysts in this
chemistry. |
