Deep optical images of Malin 1 reveal new features
  We present Megacam deep optical images (g and r) of Malin 1 obtained with the
6.5m Magellan/Clay telescope, detecting structures down to ~ 28 B mag arcsec-2.
In order to enhance galaxy features buried in the noise, we use a noise
reduction filter based on the total generalized variation regularizator. This
method allows us to detect and resolve very faint morphological features,
including spiral arms, with a high visual contrast. For the first time, we can
appreciate an optical image of Malin 1 and its morphology in full view. The
images provide unprecedented detail, compared to those obtained in the past
with photographic plates and CCD, including HST imaging. We detect two peculiar
features in the disk/spiral arms. The analysis suggests that the first one is
possibly a background galaxy, and the second is an apparent stream without a
clear nature, but could be related to the claimed past interaction between
Malin 1 and the galaxy SDSSJ123708.91 + 142253.2. Malin 1 exhibits features
suggesting the presence of stellar associations, and clumps of molecular gas,
not seen before with such a clarity. Using these images, we obtain a diameter
for Malin 1 of 160 kpc, ~ 50 kpc larger than previous estimates. A simple
analysis shows that the observed spiral arms reach very low luminosity and mass
surface densities, to levels much lower than the corresponding values for the
Milky Way.
