Marc-Antoine Miville-Deschenes

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Research Summary

Marc-Antoine Miville-Deschenes' primary research interests are related to the physics of the diffuse interstellar medium. In particular his work concerns the study of interstellar turbulence, using simulations and 21 cm interferometric observations of the local HI gas. Miville-Deschenes also works on the evolution of dust in the diffuse ISM and its relation with the gas properties. This includes the impact of turbulent motion on dust evolution (coagulation, fragmentation) and the relation between dust properties and gas phase evolution (chemistry, thermodynamics). Finally Miville-Deschenes is involved in the component separation effort of several projects where the description of diffuse Galactic emission is mandatory for the study of extra-galactic and cosmological signals.

Research Projects:
(September 2002 - August 2003)

Study of interstellar turbulence using spectro-imagery observations of HI clouds

In collaboration with F. Levrier and E. Falgarone (ENS, France), Marc-Antoine Miville-Deschenes used fractional Brownian motion (fBm) simulations to study how the statistical properties of 3D density and velocity fields can be retrieved from spectro-imagery observations of an optically thin tracer. Miville-Deschenes showed that for typical turbulent power spectra, the centroid velocity field of spectro-imagery data allows one to retrieve the power spectrum of the 3D velocity field and therefore determine directly the energy spectrum of interstellar turbulence. With G. Joncas (Laval), F. Boulanger (IAS, France) and E. Falgarone (ENS, France), Marc-Antoine Miville-Deschenes used 21 cm interferometric observations to determine the power spectrum of the 3D density and velocity field in a local HI cloud (the Ursa Major cirrus), over 3 orders of magnitude in scale. This work shows that interstellar turbulence has a similar power spectrum than incompressible turbulence (Kolmogorov). This result puts important constraints on the impact of compressibility and magnetic field in MHD turbulent fluids. In collaboration with A. Daigle and G. Joncas (Laval), Marc-Antoine Miville-Deschenes works on the use of neural network to detect HI expanding shells in 21 cm spectro-imagery observations. Using fBm simulations they showed that turbulence does not produce significant spurious detections.

Dust evolution in the ISM

Marc-Antoine Miville-Deschenes conducted several projects on dust evolution in the ISM using Infrared Space Observatory (ISO) data, including work with the ISOGAL team that published catalogs of points sources and diffuse images of Galactic plane regions observed with ISO, but also a study of the PAH properties in a star-forming core in the Trifid Nebula, in collaboration with B. Lefloch (Grenoble) and J. Cernicharo (Madrid). Miville-Deschenes also participated in the discovery in L134N of one of the coldest core found in molecular clouds (dust temperature ~ 7.6K). This work, done in collaboration with L. Pagani (Paris), brings very interesting insights on dust evolution scenari (formation of fractal aggregates) and really challenges dust theory. Miville-Deschenes also used dust models and radiative transfer code to characterize dust properties in diffuse interstellar clouds using infrared observations. With M. Sc. student F. Fressin he showed that the smallest dust grains (PAH-like) coagulate on bigger grains very rapidly in the gas condensation process. This has an impact on our understanding of the thermodynamical and chemical scenario of the formation of long-lived molecular structures.

Component separation

Because of his interest in diffuse interstellar clouds, Marc-Antoine Miville-Deschenes also worked on component separation which is essential for the detection and characterization of extra-galactic and cosmological signals. In particular he made the first detection of the cosmic infrared background fluctuations at 60 and 100 micron using IRAS data, in collaboration with G. Lagache and J.-L. Puget (IAS, France). Miville-Deschenes is involved in several projects devoted to the observation of very low column density HI clouds, to characterize their gas and dust properties and to evaluate the possibility of using 21 cm observations to remove foreground emissions. These observations are done with the DRAO (Penticton, Canada) and GBT (Virginia, USA) radio-telescopes, and with SIRTF. This work is done in collaboration with P. Martin (CITA), J. Lockman (NRAO) and the IAS team (France).

Planck mission

As part of the Canadian contribution to Planck (an European Space Agency satellite devoted to the study of the CMB in the sub-millimeter), CITA is developing the Quick Look Analysis (QLA) software that will be used for the visualization and analysis of ground calibration and in-flight data. Marc-Antoine Miville-Deschenes, a Canadian Planck scientific associate, continued work on the design and development of the QLA, making the link between the instrumental and data processing teams in Europe and the developers at CITA, and assuring that the developments at CITA follow the needs.

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