Edge-on HI-bearing ultra diffuse galaxy candidates in the 40% ALFALFA
  catalog
  Ultra-diffuse galaxies (UDGs) are objects which have very extended morphology
and faint central surface brightness. Most UDGs are discovered in galaxy
clusters and groups, but also some are found in low density environments. The
diffuse morphology and faint surface brightness make them difficult to
distinguish from the sky background. Several previous works have suggested that
at least some UDGs are consistent with exponential surface brightness profiles
(S\'{e}rsic n ~ 1). The surface brightness of exponential disks is enhanced in
edge-on systems, so searching for edge-on systems may be an efficient way to
select UDGs. In this paper, we focus on searching for edge-on HI-bearing
ultra-diffuse sources (HUDS) from the 40% ALFALFA catalog, based on SDSS g- and
r-band images. After correcting the observed central surface brightness to a
face-on perspective, we discover 11 edge-on HUDS candidates. All these newly
discovered HUDS candidates are blue and HI-bearing, similar to other HUDS in
70% ALFALFA catalog, and different from UDGs in clusters.
