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

in relation with planet formation. Currently unsolved problems involve the exact nature of gravitational
collapse: what is the leading factor, magnetic fields or turbulence ? The physico-chemistry of protostellar
envelopes and young protoplanetary disks, with a whole array of spectral diagnostics down to the innermost
regions (< 1 AU), will give us precious indications about the velocity field and extent of the accretionejection
phenomenon, the density and temperature conditions, the existence and abundance of possible
prebiotic molecules, etc. The advent of Herschel (to be launched in early 2008) will allow LAOG to
attack these questions with sophisticated chemistry and radiative transfer models to identify and interpret
thousands of spectral lines. ALMA will later expand the result at high spectral resolution; however the
spectral line diagnostic will be unable to include the lines that are undetectable from the ground. Currently,
ALMA is not expected to be operational before 2012, so within the current prospective a major effort will
be devoted by the Astromol team to the interpretation of Herschel data, while increasing the involvement
in existing facilities like the IRAM telescopes (single-dish 30m and PdBI interferometer), JCMT and
CSO in Hawaii, APEX in Chile (a precursor to ALMA antennae). A complementary view, mainly for
comparison with the early solar system, will be offered by the laboratory study of irradiation effects by
high-energy photons and particles emitted by the central protostar.
At later stages, other issues related to global star formation emerge, also on the FOST side: e.g., why is it
that star formation occurs in cluster mode and in isolated mode; more generally in so many different modes
(including starbursts in galaxies for instance); what is the origin of brown dwarfs, and in particular of the
“free-floating” low-mass objects far from star-forming regions ? To what extent is the IMF universal ?
The FOST teams attacks some of these problems with modern tools like N-body simulations and extended
surveys at CFHT like CFH12K and WIRCAM KP surveys of young open clusters, or extended nearby
star-forming regions like Taurus.
• Disk evolution and planet formation. One of the most exciting challenges of modern astronomy,
with many deep implications like the universality of life, is to know whether the solar system is typical or
exceptional among all planetary systems. Two different approaches can be considered.
(i) On the one hand, to understand whether and how planets (especially terrestrial planets) form as the
ultimate phase of evolution of circumstellar disks around young, solar-type stars. This requires an indepth
study of the evolution of disks, from their young stages dominated by accretion and correlated jets,
to later stages where dynamical interactions (instabilities, companions, etc.) deeply affect the growth of
dust grains into planetesimals and planets, over timescales of ∼ 10-100 Myr. While LAOG currently is
not directly involved in the study of planet formation per se, it is certainly in an enviable place to obtain
constraints on prevailing physical conditions, and on the history of disk structure evolution (gaps, rings,
spirals, etc.) from observations and models.
(ii) The other approach is to consider already formed exoplanetary systems. With a sufficiently large
sample (hundreds ?) of planetary systems down to the lowest possible planetary masses (Earthlike,
ideally), one can start to apprehend the rules and the exceptions, in comparison with our solar system.
The current arsenal of exoplanetary search consists of a majority of radial-velocity (stellar reflex motion)
detection (30 of them have a LAOG member as co-discoverer), and of a handful of transits in front of
the host star. Apart from the only confirmed (so far) recent detection of a planetary mass object around
a brown dwarf (a situation hardly comparable to the solar system), no direct imaging of exoplanets is
currently available. The development of instruments able to bridge this gap will open an entirely new
era –if only because systems with orientations at large angles to the line of sight will become detectable,
significantly enriching the parameter space for exoplanetary systems and putting new constraints on their
origin.
With the Astromol and FOST teams, LAOG has the expertise to have these two ends meet and study
how well (or how badly) these two approaches may converge, in particular with the new instrumental
projects (see below) it is leading. In short, at the horizon 2010 LAOG hopes to make radical advances in
our current understanding of star and planet formation, with the ultimate goal to pin down the connection
(or lack thereof) between exoplanetary systems and our solar system.
• The close environment of accreting objects, from black holes to young stars. As its core activity,
over the term of the present prospective (2010) the SHERPA team will focus on the physical processes that
take place in the close environment of Black Holes. This includes the analysis of the gross phenomenon
combining MHD and gravitation, to high energy radiation and astroparticle physics, via the turbulent
transport theory and the kinetic theory of relativistic plasmas and particle acceleration. These theoretical
developments will be applied to various physical environments: the Blazar phenomenon (stratified models,
variability); micro-quasars (“two-flow” paradigm, modelization of the changes of state); signatures of the
Kerr metric in the phenomenology of AGNs and micro-quasars; instabilities and turbulent transport in jets
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