THE FERMI BUBBLES. I. POSSIBLE EVIDENCE FOR RECENT AGN JET ACTIVITY IN THE GALAXY

By Fulai Guo, W. Mathews. 2011

159 citations recorded by the source corpus.

The Fermi Gamma-ray Space Telescope reveals two large gamma-ray bubbles in the Galaxy, which extend about 50° (∼10 kpc) above and below the Galactic center (GC) and are symmetric about the Galactic plane. Using axisymmetric hydrodynamic simulations with a self-consistent treatment of the dynamical cosmic ray (CR)–gas interaction, we show that the bubbles can be created with a recent active galactic nucleus (AGN) jet activity about 1–3 Myr ago, which was active for a duration of ∼0.1–0.5 Myr. The bipolar jets were ejected into the Galactic halo along the rotation axis of the Galaxy. Near the GC, the jets must be moderately light with a typical density contrast 0.001 ≲ η ≲ 0.1 relative to the ambient hot gas. The jets are energetically dominated by kinetic energy, and overpressured with either CR or thermal pressure which induces lateral jet expansion, creating fat CR bubbles as observed. The sharp edges of the bubbles imply that CR diffusion across the bubble surface is strongly suppressed. The jet activity induces a strong shock, which heats and compresses the ambient gas in the Galactic halo, potentially explaining the ROSAT X-ray shell features surrounding the bubbles. The Fermi bubbles provide plausible evidence for a recent powerful AGN jet activity in our Galaxy, providing new insights into the origin of the halo CR population and the channel through which massive black holes in disk galaxies release feedback energy during their growth.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/877fe782ccab1bfc4f0044c96467c92f3ee73479

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Citations in the corpus

Hot Accretion Flows Around Black Holes (2014, background): “The two Fermi bubbles detected above and below the Galactic center (Su et al. 2010) are also thought to be inflated by a jet or wind from Sgr A* during a period of activity in the last few million years (Zubovas et al. 2011, Guo & Mathews 2012).”
THE STRUCTURE OF THE MILKY WAY'S HOT GAS HALO (2013, background): “Guo & Mathews (2012) and Yang et al. (2012) modeled the Fermi bubbles, assuming an ambient medium similar to our determined halo model, to recreate the bubbles’ observed structure and found an average density in the plane of ∼10−3 cm−3.”
THE SPECTRUM AND MORPHOLOGY OF THE FERMI BUBBLES (2014, background): “The formation of the bubbles can be modeled by emission of a jet from the black hole (Guo & Mathews 2012; Guo et al. 2012; Yang et al. 2012), a spherical outflow from the black hole (Zubovas et al. 2011), a wind from supernova explosions (Crocker & Aharonian 2011), or a sequence of shocks from…”
Cool outflows in galaxies and their implications (2020, background): “few Myr ago) rather than a starburst event as the energy source for the Fermi Bubbles and related structures (e.g. Zubovas et al. 2011; Guo and Mathews 2012; Yang et al. 2012; Bland-Hawthorn et al. 2013; Mou et al. 2014; Ruszkowski et al. 2014; Miller and Bregman 2016; Bland-Hawthorn et al. 2019).”