A new catalog of HI supershell candidates in the outer part of the
  Galaxy
  The main goal of this work is to a have a new neutral hydrogen HI supershell
candidates catalog to analyze their spatial distribution in the Galaxy and to
carry out a statistical study of their main properties.}{This catalog was
carried out making use of the Leiden-Argentine-Bonn (LAB) survey. The
supershell candidates were identified using a combination of two techniques: a
visual inspection plus an automatic searching algorithm. Our automatic
algorithm is able to detect both closed and open structures. A total of 566
supershell candidates were identified. Most of them (347) are located in the
second Galactic quadrant, while 219 were found in the third one. About $98 \,
\%$ of a subset of 190 structures (used to derive the statistical properties of
the supershell candidates) are elliptical with a mean weighted eccentricity of
$0.8 \pm 0.1$, and $\sim 70 \,\%$ have their major axes parallel to the
Galactic plane. The weighted mean value of the effective radius of the
structures is $\sim$ 160 pc. Owing to the ability of our automatic algorithm to
detect open structures, we have also identified some "galactic chimney"
candidates. We find an asymmetry between the second and third Galactic
quadrants in the sense that in the second one we detect structures as far as 32
kpc, while for the 3rd one the farthest structure is detected at 17 kpc. The
supershell surface density in the solar neighborhood is $\sim$ 8 kpc$^{-2}$,
and decreases as we move farther away form the Galactic center. We have also
compared our catalog with those by other authors.
