Untitled - Laboratoire d'Astrophysique de l'Observatoire de Grenoble

Chapter 3
Results
3.1 Overview
In this chapter we will briefly describe the activity of Astromol, enlightening the major results achieved during
the period 2002-2005. This chapter is structured into three sections. The first section describes the results
relative to the “Star Formation” activity, while the second section reports the results relative to the “Molecular
Physics” studies. A third section will describe in detail the research about the “Proto-planetary Disks”, which
is a “meeting point” of the Astromol and FOST teams. This is treated as a separate section to emphasize the
synergy between the two LAOG teams on such an important and hot field of research.
Before giving a brief description of the overall activities, we report here the three most important results
achieved by the Astromol team in the last four years. They are:
i) The study of the molecular deuteration in the regions of low mass star formation: Astromol, in collaboration
with WAGOS, had and keeps having an important role in this field of research, with the discovery of
doubly and triply deuterated molecules with D/H ratios enhanced by up to 13 orders of magnitudes with
respect to the D/H elemental abundance ratio (e.g. Parise et al. 2004). We are proud to say that our
first results on the subject, starting from 1998 (Ceccarelli et al. A&A 338, L43), have given a new élan to
this field, and triggered a flurry of new observations and new theories about the molecular deuteration in
cold and dense gas. It is important to emphasize that the new observational and theoretical framework of
molecular deuteration has lead to recognize not only the role of the grain surface and gas phase chemistry
during the pre-collapse phase, but also to identify the only way we have to probe the innermost regions of
the pre-stellar cores and the midplane of proto-planetary disks : the H2D + and HD + 2
ground transitions
in the submillimeter (Caselli et al. 2003; Ceccarelli et al. 2004). They not only give us the information
about the dynamics in those regions, but also, and not least, the measure of the gas degree of ionization,
a key quantity in both classes of objects (Ceccarelli & Dominik 2005. Our leading role in these studies
is testified by the several invitations to international congresses to review the subject (for a list of our
articles on this subject see §3.2.2).
ii) The chemical composition of the envelopes of the youngest low mass protostars, and the discovery of the
hot corinos, warm and dense regions where complex organic molecules are abundantly formed (Cazaux et
al. 2003). Astromol, in collaboration with WAGOS, had and keeps having a leading role on this field,
as testified by the several invitations to international congresses to give reviews on the subject. We were
the first to predict the existence of warm and dense regions around low mass protostars (Ceccarelli et al.
2000, A&A 357, L9), and to prove it with several observations. The most important findings is that these
regions have sizes comparable to those of our Solar System (few tens of AUs; Maret et al. 2004), and that
complex organic molecules are formed there, against the first theoretical expectations. We were also the
first to obtain the resolved images of the first discovered hot corino (around IRAS16293-2422: Bottinelli
et al. 2004b) with the PdB interferometer in two complex organic molecules.
iii) Considerable progress has been achieved in the accurate determination of intermolecular interactions with
the combination of explicitely correlated ab-initio approaches and multi-dimensional investigations. In
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