English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The Fermi satellite discovery of the gamma-ray emitting bubbles extending 50deg (10 kpc) from the Galactic Centre has revitalized earlier claims that ourGalaxy has undergone an explosive episode in the recent past. We now explore anew constraint on such activity. The Magellanic Stream is a clumpy gaseousstructure passing over the South Galactic Pole (SGP) at a distance of at least50-100 kpc. Patchy H-alpha emission discovered along the Magellanic Stream overthe SGP is a factor of 5 too bright to have been produced by the Galacticstellar population. Time-dependent models of Stream clouds exposed to a flarein ionising photon flux show that the ionised gas must recombine and cool for atime interval 0.6 - 2.9 Myr for the emitted H-alpha surface brightness to dropto the observed level. A nuclear starburst is ruled out. Sgr A* is a morelikely candidate because it is two orders of magnitude more efficient atconverting gas to UV radiation. The central black hole (4 x 10^6 Msun) cansupply the required ionising luminosity with a fraction of the Eddingtonaccretion rate (3-30%). In support of nuclear activity, the H-alpha emissionalong the Stream has a polar angle dependence peaking close to the SGP.Moreover, it is now generally accepted that the Stream over the SGP must befurther than the Magellanic Clouds. At the lower halo gas densities, shocksbecome too ineffective and are unlikely to give rise to a polar angledependence in the H-alpha emission. Thus it is likely that the Stream emissionarose from a `Seyfert flare' that was active 1-3 Myr ago, consistent with thecosmic ray lifetime in the Fermi bubbles. Sgr A* activity today is greatlysuppressed (70-80 dB) relative to the Seyfert outburst...

Fossil imprint of a powerful flare at the Galactic Centre along the Magellanic Stream