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

in the midplane of young disks surrounding solar type protostars and their dust to gas ratio, two key
parameters in the theories of disk evolution and planet formation. This is a very recent result, and we
certainly plan to fully exploit this new line of research, by carrying out systematic surveys, both with
single dish telescopes and modeling. So far CSO, SMA (since spring 2005) and APEX (since October 2005)
permit these observations, but in a not too far future the ortho-H2D + line used for these studies will be
accessible with ALMA. In addition, the para-H2D + , as well as both ortho and para lines of HD + 2
will also
be accessible with the advent of Herschel HIFI and SOFIA. ii) The detection of deuterated water by our
group has also open a new way to probe the history of the dust grains, and specifically the fate of their icy
mantles during the proto-planetary phase. Again, this is a field just started and that clearly deserves a full
exploitation. One by-product is the prediction of the observability of water vapor in proto-planetary disks
with Herschel, observations which will become available in the incoming four years. iii) More in general,
we plan to expand our observational and modeling capabilities on the chemistry of proto-planetary disks,
by applying, exporting and expanding what we have learned so far in the studies of the previous phases.
Notable examples are the chemistry of sulfur, oxygen and carbon in proto-planetary disks, which haven’t
been exploited so far, and on which we have a good expertise.
4. The interaction of the forming star with the surroundings: outflows and X-rays Our group is currently
investing stronger efforts in the studies on protostellar outflows. The emphasis is put on both the observational
and theoretical sides. Observationally, the goal is to determine the physical conditions (velocity,
density, temperature) in the entrained gas and in the shock regions, based on the H2 line emission, accessible
in the mid- and near-IR, and the emission of the high-excitation line of molecular tracers in the
mm/submm windows. Theroretically, it is necessary to improve the existing models to a) reach a multidimensional
(2D/3D) description, required to provide a realistic treatment of the leading bow in outflows,
b) make predictions not only on the (velocity-integrated) line flux but on the line profiles. These aspects
are undertaken in collaboration with colleagues at LERMA in Paris (G. Pineau des Forets, S. Cabrit)
and at DAMIR in Madrid (J. Cernicharo, J. Martin-Pintado). A large-scale survey of the CO emission
in TMC 1 has been undertaken, in collaboration with IRAM colleagues (K. Schuster, C. Thum) to search
in an unbiased way for molecular outflows and their protostars, down to the smallest scale size, comparable
to the cooling lengthscale in MHD shocks (10 16 cm), and investigate their impact on the global star
formation in the cloud.
5. X-rays: from astronomy to the laboratory
• Among the unsolved questions is the problem of the X-ray emission from the youngest protostars (socalled
Class 0, still in a state of gravitational collapse). Up to now, and in spite of extensive searches on
∼ 20 low-mass star-forming regions, no Class 0 protostar has been detected in X-rays (Montmerle et al.,
in preparation). This is most likely due to the fact that the extinction of their dense envelopes is very high
(AV > 500). With a careful summing of existing XMM and Chandra observations, it is however hoped to
at least set stringent upper limits to the intrinsic X-ray luminosity. Another way to attack the problem
is, here also, to look for indirect evidence in the mm range, in the form of specific radicals (like HCO +
or DCO + ) that could be the signature of internal X-ray irradiation. Except perhaps in one case, IRAS
16293 (see Ceccarelli et al. 2002b), no evidence was found so far and more observations are planned. Here
again, the ultimate goal is to measure the ionization fraction of the envelope and the resulting coupling
between the material and magnetic fields.
Similar observations will be conducted in and around more evolved sources, from evolved protostars (Class
I) to T Tauri stars still embedded in molecular clouds, for which the X-ray luminosity is measured and
can be compared with chemical tracers of irradiation.
• Another approach is to do laboratory experiments. Several years ago, T. Montmerle co-supervised a
PhD thesis (S. Gougeon, 1998) which featured X-ray irradiation experiments on model interstellar dust
grains (PAHs, coals, etc.) using the ESRF facility in Grenoble, to compare with ISO data in star-forming
regions. The laboratory IR spectra from irradiated grains proved to be complex and difficult to interpret,
but revealed many interesting features (like spectral lines associated with certain bonds like C-C, C-H,
etc.), some evolving with the irradiation dose, others not. On the other hand, the X-ray energies at ESRF
(nearly 10 keV) tend to be high with respect to typical stellar energies (a few keV), precluding a direct
comparison with astronomical data. It is envisaged in the current prospective period (2007-2010), to set
up follow-up experiments at the SOLEIL facility, which offers softer X-rays, and compare the resulting IR
spectra with modern, more sensitive astronomical IR spectra such as obtained by Spitzer.
Along the same lines, a fruitful collaboration with French meteoriticists and experimentalists (e.g., M.
Gounelle from Orsay, M. Chaussidon from Nancy, H. Leroux from Lille, possibly also E. Quirico from
LPG) has been established, with the aim of federating experiments in various related fields of astrophysical
interest nationwide (approved proposal to PNPS).
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