Galaxy Zoo: 3D -- Crowd-sourced Bar, Spiral and Foreground Star Masks
  for MaNGA Target Galaxies
  The challenge of consistent identification of internal structure in galaxies
- in particular disc galaxy components like spiral arms, bars, and bulges - has
hindered our ability to study the physical impact of such structure across
large samples. In this paper we present Galaxy Zoo: 3D (GZ: 3D) a crowdsourcing
project built on the Zooniverse platform which we used to create spatial pixel
(spaxel) maps that identify galaxy centres, foreground stars, galactic bars and
spiral arms for 29831 galaxies which were potential targets of the MaNGA survey
(Mapping Nearby Galaxies at Apache Point Observatory, part of the fourth phase
of the Sloan Digital Sky Surveys or SDSS-IV), including nearly all of the
10,010 galaxies ultimately observed. Our crowd-sourced visual identification of
asymmetric, internal structures provides valuable insight on the evolutionary
role of non-axisymmetric processes that is otherwise lost when MaNGA data cubes
are azimuthally averaged. We present the publicly available GZ:3D catalog
alongside validation tests and example use cases. These data may in the future
provide a useful training set for automated identification of spiral arm
features. As an illustration, we use the spiral masks in a sample of 825
galaxies to measure the enhancement of star formation spatially linked to
spiral arms, which we measure to be a factor of three over the background disc,
and how this enhancement increases with radius.
