the magnetic field of the Galaxy, from optical starlight polarization.
What makes our Galaxy’s ecosystem so fascinating is the
complex interactions between its components: stars, gas, dust,
magnetic fields, and cosmic rays. Of these components, the
Galactic magnetic field may well be the most enigmatic.
Only partially observable through indirect means, its study
relies heavily on modeling, almost exclusively using
line-of-sight integrated radio-polarimetric data. Although much
has been learned, many questions are still unanswered especially
about the turbulent, small-scale field component and
The innovations in the ERC project MAGALOPS are large
independent data sets with 3D (distance) information – which can
only be provided by stars polarized due to differential
absorption by interstellar dust, with known distances – and more
advanced Bayesian statistics which allows including prior
knowledge and enables quantitative model comparison.
MAGALOPS consists of three sub-projects:
Optical polarimetric surveys: two new polarization
surveys in the V (visual) band will result in polarimetry of
millions of stars across the southern sky. With distance
information provided by the GAIA satellite, this improves the
current data situation by 3 orders of magnitude.
Modeling the Galactic magnetic field using bayesian
methods and statistics: this will make use of IMAGINE, a
Bayesian inference software package which we are
developing. Our optical polarimetric data will be included as a
new tracer; the first tracer in a 3D grid instead of a 2D projection.
Interstellar dust: In order to include optical polarimetry, we need to produce
a 3D all-sky (out to absorption limits) dust distribution consistent
with both UV/optical/near IR absorption and optical
We expect that MAGALOPS will result in a next-generation
Galactic magnetic field model that includes heterogeneous observational tracers and can
use informative priors. It will allow mapping out interstellar
magnetized turbulence in the Galaxy, instead of providing
averaged parameters only, and understanding the interplay
between the local magnetic field, gas and dust. Its legacy is a 1000x
increased stellar polarization catalog, an all-sky 3D dust
model, a bayesian sampler for Galactic magnetic field models,
and a superior Galactic magnetic field model for use in cosmic ray modeling or foreground subtraction.