Interstellar magnetic cannon targeting the Galactic halo

A young bubble at the origin of the Ophiuchus and Lupus molecular complexes

¹ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
e-mail: jean-francois.robitaille@univ-grenoble-alpes.fr
² Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
³ INAF Istituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy
⁴ Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands
⁵ Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT, Australia
⁶ CSIRO Astronomy and Space Science, PO Box 76, Epping, NSW 1710, Australia
⁷ International Centre for Radio Astronomy Research, M468, University of Western Australia, Crawley, WA 6009, Australia
⁸ ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO), M468, University of Western Australia, Crawley, WA 6009, Australia

Received: 4 May 2018
Accepted: 27 June 2018

Abstract

We report the detection of a new Galactic bubble at the interface between the halo and the Galactic disc. We suggest that the nearby Lupus complex and parts of the Ophiuchus complex constitute the denser parts of the structure. This young bubble, ≲3 Myr old, could be the remnant of a supernova and it expands inside a larger HI loop that has been created by the outflows of the Upper Scorpius OB association. An HI cavity filled with hot X-ray gas is associated with the structure, which is consistent with the Galactic chimney scenario. The X-ray emission extends beyond the west and north-west edges of the bubble, suggesting that hot gas outflows are breaching the cavity, possibly through the fragmented Lupus complex. Analyses of the polarised radio synchrotron and of the polarised dust emission of the region suggest the connection of the Galactic centre spur with the young Galactic bubble. A distribution of HI clumps that spatially corresponds well to the cavity boundaries was found at V_LSR ≃−100 km s⁻¹. Some of these HI clumps are forming jets, which may arise from the fragmented part of the bubble. We suggest that these clumps might be “dripping” cold clouds from the shell walls inside the cavity that is filled with hot ionised gas. It is possible that some of these clumps are magnetised and were then accelerated by the compressed magnetic field at the edge of the cavity. Such a mechanism would challenge the Galactic accretion and fountain model, where high-velocity clouds are considered to be formed at high Galactic latitude from hot gas flows from the Galactic plane.