Interstellar magnetic cannon targeting the Galactic halo

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.

OB Associations and their origins

“…Krause et al (2018) verify this by using a 3D hydrodynamic simulation to show that the observed massive star population could reproduce the size and morphology of the observed superbubbles. The presence of soft X-ray emission from the US bubble coupled with the detection of 26 Al confirms that there has been at least one relatively recent ( 1 Myr) supernova from within this subgroup (Robitaille et al 2018;Krause et al 2018).…”

“…The interstellar medium surrounding Sco-Cen shows numerous large, loop-like structures and shells that suggest significant interaction between the association and the surrounding medium. They are most clearly seen in Hi observations (e.g., Weaver et al 1977;de Geus 1992;Robitaille et al 2018), with small bubbles centred around US and LCC and a larger bubble encasing the entire association and approximately centred on UCL (de Geus 1992). The total Hi mass of these bubbles has been estimated to be ∼ 5 × 10 5 M and suggested to be composed of gas swept up by stellar winds and supernovae from the progenitor giant molecular cloud that Sco-Cen formed from, as well as the ambient ISM (de Geus 1992).…”

“…Super-bubbles surrounding the nearby OB associations are well known and have been studied in some detail. These include the Orion-Eridanus super-bubble surrounding Orion OB1 (Reynolds & Ogden 1979), the IRAS Vela shell surrounding Vela OB2 (Sahu 1992), the Cygnus super-bubble surrounding Cyg OB2 (Cash et al 1980), and the multiple bubbles surrounding Sco-Cen (Weaver et al 1977;de Geus 1992;Robitaille et al 2018). See Figure 21 for examples of these bub- The positions of Vel OB5, Velorum cluster, Vel OB2, Tr 10, and NGC 2547 are indicated.…”

Through thick or thin: multiple components of the magneto-ionic medium towards the nearby H ii region Sharpless 2–27 revealed by Faraday tomography

“…Gaensler et al 2001). At 2.3 GHz in the S-band Polarization All Sky Survey (S-PASS, Carretti et al 2019) Sh2-27 has been identified as a Faraday screen, modulating the polarization angle but not producing polarized emission itself (Robitaille et al 2017(Robitaille et al , 2018Iacobelli et al 2014). In polarization observations at 1.4 GHz, such as GMIMS-HBN, Sh2-27 can be identified as a depolarizing region.…”

A JWST Preview: Adaptive-Optics Images of H$_2$, Br-$γ$, and K-continuum in Carina's Western Wall

“…Radiative feedback and winds from newly-formed stars into the nascent cloud material also drive structures on scales of tens or even hundreds of pc, and create sequential episodes of star formation (e.g. Venuti et al 2018) and clear out chimneys and bubbles perpendicular to the galactic plane (Robitaille et al 2018). On smaller scales, how massive stars form remains a topic of intense theoretical work, as models must include the effects of strong radiation pressure and photoevaporation from massive protostars that both limit the available timescale for accretion and may widen existing outflow cavities (Tanaka et al 2017;Rosen et al 2016).…”