Modelling of the spectral energy distribution of Fornax A: leptonic and hadronic production of high-energy emission from the radio lobes

作者：McKinley B^*; Yang R; Lopez Caniego M; Briggs F; Hurley Walker N; Wayth R B; Offringa A R; Crocker R; Bernardi G; Procopio P; Gaensler B M; Tingay S J; Johnston Hollitt M; McDonald M; Bell M; Bhat N D R; Bowman J D; Cappallo R J; Corey B E; Deshpande A A; Emrich D; Ewall Wice A; Feng L; Goeke R; Greenhill L J; Hazelton B J; Hewitt J N; Hindson L; Jacobs D; Kaplan D L; Kasper J C; Kratzenberg E; Kudryavtseva N

来源：Monthly Notices of the Royal Astronomical Society, 2015, 446(4): 3478-3491.

DOI：10.1093/mnras/stu2310

• galaxies: active
• galaxies: individual: NGC1316
• radio continuum: galaxies

We present new low-frequency observations of the nearby radio galaxy Fornax A at 154 MHz with the Murchison Widefield Array, microwave flux-density measurements obtained from WMAP and Planck data, and gamma-ray flux densities obtained from Fermi data. We also compile a comprehensive list of previously published images and flux-density measurements at radio, microwave and X-ray energies. A detailed analysis of the spectrum of Fornax A between 154 and 1510 MHz reveals that both radio lobes have a similar spatially averaged spectral index, and that there exists a steep-spectrum bridge of diffuse emission between the lobes. Taking the spectral index of both lobes to be the same, we model the spectral energy distribution of Fornax A across an energy range spanning 18 orders of magnitude, to investigate the origin of the X-ray and gamma-ray emission. A standard leptonic model for the production of both the X-rays and gamma-rays by inverse-Compton scattering does not fit the multiwavelength observations. Our results best support a scenario where the X-rays are produced by inverse-Compton scattering and the gamma-rays are produced primarily by hadronic processes confined to the filamentary structures of the Fornax A lobes.

• 出版日期2015-2
• 单位MIT; CSIRO