Oral Presentation Astronomical Society of Australia Annual Scientific Meeting including HWWS 2013

The giant lobes of Centaurus A observed with the Murchison Widefield Array (#15)

Benjamin McKinley 1 , Frank Briggs 1 , Bryan Gaensler 2 , Ilana Feain 3 , MWA Builders List
  1. Australian National University, Canberra, ACT, Australia
  2. University of Sydney, Sydney, Australia
  3. CSIRO, Sydney, Australia

Due to our fortuitous position in space, we have access to an ideal laboratory to study one particular radio galaxy in great detail: Centaurus A. Since its discovery in 19481 as the discrete radio source associated with the nearby (3.8 Mpc) elliptical galaxy NGC5128, it has been intensely studied across a wide range of wavelengths and physical scales. The most striking features of Centaurus A are the giant radio lobes, which, due to the galaxy’s close proximity, have an unusually large angular extent of approximately 8 by 4 degrees on the sky, presenting a practical challenge to radio astronomers. Feain et al3 have produced the first high-resolution images of the giant lobes to date, achieving 50 arcsec (600 pc) resolution at 1.4 GHz with the Australia Telescope Compact Array and unveiling a complex morphological structure. The spatially-resolved spectral properties of the lobes at low radio frequencies are interesting as they provide clues as to the particle acceleration history of the lobes and the physical processes which caused their current morphology. However, low-frequency spectral-index maps have so far been hampered by the low spatial resolution of the images below 1.4 GHz2 or small frequency ranges5. The Murchison Widefield Array (MWA4,6), with a spatial resolution of several arcmins and observing frequencies between 80 and 300 MHz, is ideally suited to providing the low-frequency maps needed to examine the spectra of the giant lobes of Centaurus A in detail. I will summarise the initial low-frequency studies conducted with the MWA 32-tile prototypeand present the latest observations of Centaurus A conducted during the recent science commissioning of the full 128-tile instrument.

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  3. Feain, I. J., Ekers, R. D., Murphy, T., et al, 2009, ApJ, 707, 114
  4. Lonsdale, C. J., Cappallo, R. J., Morales, M. F., et al, 2009, in Proc. IEEE, 97, 8
  5. Stefan, I. I., Carilli, C. L., Green, D. A., et al, 2012, arXiv:1212.1624
  6. Tingay, S. J., Goeke, R., Bowman, J. D., et al, 2013, PASA, 30, 7
  7. McKinley et al, in prep