A new catalog of HI supershell candidates in the outer part of the Galaxy

SUAD, L.A.; CAIAFA,C.; ARNAL, E.M.; CICHOWOLSKI, S.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2014 vol. 564 p. 116 - 129

0004-6361

Aims. The main goal of this work is to a have a new neutral hydrogen (Hi) supershell candidate catalog to analyze their spatialdistribution in the Galaxy and to carry out a statistical study of their main properties.Methods. This catalog was carried out making use of the Leiden-Argentine-Bonn (LAB) survey. The supershell candidates wereidentified using a combination of two techniques: a visual inspection plus an automatic searching algorithm. Our automatic algorithmis able to detect both closed and open structures.Results. A total of 566 supershell candidates were identified. Most of them (347) are located in the second Galactic quadrant, while219 were found in the third one. About 98% of a subset of 190 structures (used to derive the statistical properties of the supershellcandidates) are elliptical with a mean weighted eccentricity of 0.8 ± 0.1, and ∼70% have their major axes parallel to the Galacticplane. The weighted mean value of the effective radius of the structures is ∼160 pc. Owing to the ability of our automatic algorithmto detect open structures, we have also identified some ?galactic chimney? candidates. We find an asymmetry between the second andthird Galactic quadrants in the sense that in the second one we detect structures as far as 32 kpc, while for the 3rd one the fartheststructure is detected at 17 kpc. The supershell surface density in the solar neighborhood is ∼8 kpc−2, and decreases as we move fartheraway form the Galactic center. We have also compared our catalog with those by other authors.