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Determining broad-band spectra of radio galaxies with the EVLA

Determining broad-band spectra of radio galaxies with the EVLA. Jeremy Harwood YERAC 2011. Background Image courtesy of NASA/CXC/CfA/R.Kraft et al.; MPIfR/ESO/APEX/A. Weiss et al.; ESO/WFI. What are radio galaxies?. Type of active galaxy Fanaroff and Riley class I

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Determining broad-band spectra of radio galaxies with the EVLA

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  1. Determining broad-band spectra of radio galaxies with the EVLA Jeremy HarwoodYERAC 2011 Background Image courtesy of NASA/CXC/CfA/R.Kraft et al.; MPIfR/ESO/APEX/A. Weiss et al.; ESO/WFI

  2. What are radio galaxies? • Type of active galaxy • Fanaroff and Riley class I • Fanaroff and Riley class II • Quasars (in unified models) • Definition of galaxy class is subjective • Predominantly found in massive ellipticals • Radio features are non-thermal sources • The shape of their SED’s can often give key insights into the underlying physics of the source

  3. Previous generation of radio telescopes • Poor sampling in frequency space, a few GHz frequencies at best • Narrow band observations (50 MHz with the VLA) • Producing detailed SED’s previously required large amounts of observing time J1548–3216 (Machalskiet al. 2010)

  4. The next generation of radio telescopes • EVLA once fully upgraded will not suffer these problems • 128 MHz bandwidth currently; 8 GHz when fully upgraded • Develop methods of analysis using this new capability • Determine the importance of spectral ageing in FR-II galaxies Image courtesy of NRAO/AUI and NRAO

  5. Spectral ageing in the radio lobes of FR-II galaxies • What is spectral ageing? • Preferential cooling of higher energy particles - • Break frequency dependant on time and magnetic field - • Can be used to determine the age of a region • Previously unable to produce detailed SED’s to directly test its importance • Indirect arguments using colour-colour diagrams needed • Katz-Stone et al. 1993 Hughes 1991 “Beams and Jets in Astrophysics”

  6. Latest results • Emission intensity maps • High resolution spectral mapping • Full map spectral profiling • Detailed spectra of specific emission regions

  7. Latest Results

  8. What’s next? • Fitting of spectral ageing models • Colour-colour plots for direct comparison to previous works e-Merlin • Extragalactic jets legacy project • Jet dynamics • 3 dimensional structure of powerful jets • Magnetic field configuration • Particle acceleration in jets and hotspots LOFAR • Low energy observations of powerful radio galaxies • Comparison to inverse-Compton observations

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