The Intrinsic Shapes of Low Surface Brightness Galaxies: a Discriminant
  of LSBG Formation Mechanisms
  We use the low surface brightness galaxy (LSBG) samples created from the
Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP, 781 galaxies), the Dark
Energy Survey (DES, 20977 galaxies), and the Legacy Survey (selected via HI
detection in the Arecibo Legacy Fast ALFA Survey, 188 galaxies) to infer the
intrinsic shape distribution of the low surface brightness galaxy population.
To take into account the effect of the surface brightness cuts employed when
constructing LSBG samples, we simultaneously model both the projected
ellipticity and the apparent surface brightness in our shape inference. We find
that the LSBG samples are well-characterized by oblate spheroids, with no
significant difference between red and blue LSBGs. This inferred shape
distribution is in good agreement with similar inferences made for
ultra-diffuse cluster galaxy samples, indicating that environment does not play
a key role in determining the intrinsic shape of low surface brightness
galaxies. We also find some evidence that LSBGs are more thickened than
similarly massive high surface brightness dwarfs. We compare our results to
intrinsic shape measures from contemporary cosmological simulations, and find
that the observed LSBG intrinsic shapes place considerable constraints on the
formation path of such galaxies. In particular, LSBG production via the
migration of star formation to large radii produces intrinsic shapes in good
agreement with our observational findings.
