The Galactic Centre - A Laboratory for Starburst Galaxies (?)
arXiv:1112.6249 · doi:10.1017/S1743921312009441
Abstract
The Galactic centre - as the closest galactic nucleus - holds both intrinsic interest and possibly represents a useful analogue to star-burst nuclei which we can observe with orders of magnitude finer detail than these external systems. The environmental conditions in the GC - here taken to mean the inner 200 pc in diameter of the Milky Way - are extreme with respect to those typically encountered in the Galactic disk. The energy densities of the various GC ISM components are typically ~two orders of magnitude larger than those found locally and the star-formation rate density ~three orders of magnitude larger. Unusually within the Galaxy, the Galactic centre exhibits hard-spectrum, diffuse TeV (=10^12 eV) gamma-ray emission spatially coincident with the region's molecular gas. Recently the nuclei of local star-burst galaxies NGC 253 and M82 have also been detected in gamma-rays of such energies. We have embarked on an extended campaign of modelling the broadband (radio continuum to TeV gamma-ray), non- thermal signals received from the inner 200 pc of the Galaxy. On the basis of this modelling we find that star-formation and associated supernova activity is the ultimate driver of the region's non-thermal activity. This activity drives a large-scale wind of hot plasma and cosmic rays out of the GC. The wind advects the locally-accelerated cosmic rays quickly, before they can lose much energy in situ or penetrate into the densest molecular gas cores where star-formation occurs. The cosmic rays can, however, heat/ionize the lower density/warm H2 phase enveloping the cores. On very large scales (~10 kpc) the non-thermal signature of the escaping GC cosmic rays has probably been detected recently as the spectacular 'Fermi bubbles' and corresponding 'WMAP haze'.
Invited talk to appear in Proceedings of IAU Symposium No. 284, 2011 (R.J. Tuffs & C.C. Popescu, eds.) `The Spectral Energy Distribution of Galaxies'
References in corpus (13)
- Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
- The Fermi Bubbles: Giant, Multi-Billion-Year-Old Reservoirs of Galactic Center Cosmic Rays
- Discrete sources as the origin of the Galactic X-ray ridge emission
- Extended Anomalous Foreground Emission in the WMAP 3-Year Data
- A cosmic-ray dominated ISM in Ultra Luminous Infrared Galaxies: new initial conditions for star formation
- The Starburst Contribution to the Extra-Galactic Gamma-Ray Background
- Evidence for a Long-Standing Top-Heavy IMF in the Central Parsec of the Galaxy
- Wild at Heart:-The Particle Astrophysics of the Galactic Centre
- Galactic center at very high-energies
- Origin of the Fermi Bubble
- Fermi gamma-ray `bubbles' from stochastic acceleration of electrons
- Absorption Line Survey of H3+ toward the Galactic Center Sources II. Eight Infrared Sources within 30 pc of the Galactic Center
- Gamma-Rays and the Far-Infrared-Radio Continuum Correlation Reveal a Powerful Galactic Centre Wind