Galactic H I supershells: kinetic energies and possible origin★
Instituto de Astronomía y Física del Espacio (CONICET-UBA), Ciudad Universitaria, C.A.B.A, Argentina
2 Instituto Argentino de Radioastronomía (CCT-La Plata, CONICET; CICPBA), C.C. No. 5, 1894 Villa Elisa, Argentina
3 Facultad de Ingeniería, Universidad de Buenos Aires (FIUBA), C.A.B.A, Argentina
4 Tensor Learning Unit - RIKEN Center for Advanced Intelligence Project, 1-4-1 Nihonbashi, Chuo-ku, 103-0027 Tokyo, Japan
5 Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, La Plata, Argentina
Accepted: 17 January 2019
Context. The Milky Way, when viewed in the neutral hydrogen line emission, presents large structures called Galactic supershells (GSs). The origin of these structures is still a subject of debate. The most common scenario invoked is the combined action of strong winds from massive stars and their subsequent explosion as supernova.
Aims. The aim of this work is to determine the origin of 490 GSs that belong to the catalogue of H I supershell candidates in the outer part of the Galaxy.
Methods. To know the physical processes that took place to create these expanding structures, it is necessary to determine their kinetic energies. To obtain all the GS masses, we developed and used an automatic algorithm, which was tested on 95 GSs whose masses were also estimated by hand.
Results. The estimated kinetic energies of the GSs vary from 1 × 1047 to 3.4 × 1051 erg. Considering an efficiency of 20% for the conversion of mechanical stellar wind energy into the kinetic energy of the GSs, the estimated values of the GS energies could be reached by stellar OB associations. For the GSs located at high Galactic latitudes, the possible mechanism for their creation could be attributed to collision with high velocity clouds (HVC). We have also analysed the distribution of GSs in the Galaxy, showing that at low Galactic latitudes, |b| < 2°, most of the structures in the third Galactic quadrant seem to be projected onto the Perseus Arm. The detection of GSs at very high distances from the Galactic centre may be attributed to diffuse gas associated with the circumgalactic medium of M31 and to intra-group gas in the Local Group filament.
Key words: ISM: structure / methods: data analysis / techniques: image processing / radio lines: ISM
Tables 3 and 4 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (22.214.171.124) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A43
© ESO 2019