Gaia and the Galactic Interstellar Medium
The interstellar medium (ISM) is a fascinating place!
The more we look at it, the more its complexity is revealed.
The evolution of matter in a galaxy is indeed guided by complex physics,
including magneto-hydrodynamics turbulence, gravity and stellar feedback.
The result is a multi-phase medium, with extreme contrasts in temperature and density,
out of which stars form. Our understanding of the star formation process
has progressed immensely in the last decades thanks to exquiste
hyperspectral data, extinction measurements, and continuum data
including polarization, combined with enlightning numerical simulations.
One inherent difficulty of this research field is the fact that the
multidimensional cycle of interstellar matter through its various
phases is usually interpreted from its projection onto the 2D sky.
This calls for specific data inversion techniques, comparison of
observational data with synthetic observations from numerical simulations,
and the combination of multiple observational probes.
The new Gaia catalog (to be released in April 2018) is about
to add a totally new dimension to ISM physics : the third one!
ESA’s Gaia mission was launched in 2013 with the aim of providing
unprecedented positional measurements for about one billion stars
in the Milky Way and the Local Group. It will provide global astrometry,
absolute parallaxes and proper motions, with the addition of all-sky
homogeneous multi-colour photometry and spectroscopy. These unique
capabilities go well beyond, but are complementary to, the science cases
being addressed by ground based surveys such as RAVE, SDSS, Pan-Starrs,
APOGEE, LSST, etc. On practically all aspects of Galactic evolution,
the exploitation of the Gaia data is expected to lead to scientific
breakthroughs: measurement of the rotation curve, the gravitational
potential, the structure of our Galaxy, its mass growth, etc. With the
new Gaia catalog we can now gain insight on the kinematics,
temperature, density structure and magnetic field properties of the
different ISM phases by combining it with data from various observational
tracers (21 cm, synchrotron, H-alpha, molecular lines, dust).
This program is about using the new Gaia data to infer three-dimensional
information of the distribution of matter in 6D phase-space. It will bring
together experts of the Gaia data release and data analysis, and experts on
both the stellar and interstellar physics, theoreticians and observers alike.
The goal is to foster collaborations and create new analysis tools benefiting
from the new Gaia data.