Flattened structures of dwarf satellites around massive host galaxies in
  the MATLAS low-to-moderate density fields
  It was first observed in the 1970s that the dwarf galaxies surrounding our
Milky Way, so-called satellites, appear to be arranged in a thin, vast plane.
Similar discoveries have been made around additional galaxies in the local
Universe such as Andromeda, Centaurus A, and potentially M83. In the specific
cases with available kinematic data, the dwarf satellites also appear to
preferentially co-orbit their massive host galaxy. Planes of satellites are
rare in the lambda cold dark matter ($\Lambda$CDM) paradigm, although they may
be a natural consequence of projection effects. Such a phase-space correlation,
however, remains difficult to explain. In this work we analyzed the 2D spatial
distribution of 2210 dwarf galaxies around early-type galaxies (ETGs) in the
low-to-medium density fields of the "Mass Assembly of early-Type GaLAxies with
their fine Structures" (MATLAS) survey. Under the assumption that the dwarfs
are satellite members of the central massive ETG, we identified flattened
structures using both a variation in the Hough transform and total least square
(TLS) fitting. In 119 satellite systems, we find 31 statistically significant
flattened dwarf structures using a combination of both methods with subsequent
Monte Carlo (MC) simulations with random data. The vast majority of these dwarf
structures lie within the estimated virial radii of the massive host. The major
axes of these systems are aligned better than 30{\deg} with the estimated
orientation of the large-scale structure in nine (50%) cases. Additional
distance measurements and future kinematic studies will be required to confirm
the planar nature of these structures and to determine if they are corotating
systems.
