2018-A, Extended

Authors: C. Sobey (ICRAR, CSIRO), S. Johnston (CSIRO), M. Xue (ICRAR, CAASTRO), N.D.R. Bhat (ICRAR, CAASTRO), S.E. Tremblay (ICRAR, CAASTRO), S.J. McSweeney (ICRAR, CAASTRO), B.W. Meyers (ICRAR, CSIRO, CAASTRO), S.M. Ord (CSIRO)

Abstract: We propose to observe several polarised pulsars at three centre frequencies between 105 and 230 MHz using the MWA. We will study the properties and evolution of the pulse profiles at low frequencies, with complementary information already available from the Parkes telescope at higher frequencies. This will provide further insights into the radio emission mechanism behaviour from pulsar magnetospheres with extremely high magnetic field strengths (~10^12 G), which is currently not well understood.

Authors: S. W. Duchesne (Victoria U. of Wellington & Peripety Scientific Ltd.), Dr. M. Johnston-Hollitt (CEO, Peripety Scientific Ltd.), Dr. Q. Zheng (Victoria U. of Wellington & Peripety Scientific Ltd.), Dr. G. Bernardi (IRA-INAF & Rhodes University), S.R. Keel (Victoria U. of Wellington & Peripety Scientific Ltd.)

Abstract: After performing surveys on non-biased samples of galaxy clusters we have compiled a new catalogue of diffuse, non-thermal radio sources associated with galaxy clusters (haloes and relics) with the Galactic and Extragalactic All-sky MWA survey and the Epoch of Reionization 0-hour field. These catalogues are hindered by the low resolution of the Phase I MWA and follow-up observations with the extended configuration MWA Phase II are required to confirm the nature of the emission. We propose 8 target fields comprised of a number of clusters to be observed in 5 frequencies for moderate integration times in the extended configuration. These observations will allow the confirmation of the objects as well as a description of their spectral energy distributions, further confirming their nature. Confirming these haloes and relics will allow them to be added to the currently small (<70 of each) global samples of such emission, allowing better insight into the dynamical nature of clusters leading to constraints on cosmological parameters, indirectly probing the evolution of cosmic magnetism.

Authors: G. Bernardi (IRA-INAF & Rhodes University)

Abstract: The presence of Mpc-scale diffuse synchrotron emission (radio halos) in galaxy clusters is currently explained through the turbulent (re)acceleration of particles following cluster mergers. Although this scenario has received increasing observational support, its key predictions can only be tested through observations of statistically significant cluster samples. Such a sample was recently observed with KAT-7 (Bernardi et al. 2016). We propose to observe the KAT-7 sample with the MWA in order to characterize its low frequency radio properties and provide the first stringent test of the turbulent (re)acceleration model in mass-selected, low-redshift clusters.

Authors: T. Venturi (IRA-INAF)

Abstract: The Shapley Concentration is a galaxy supercluster (few tens of degrees) in the Local Universe (z < 0.048) which is currently undergoing cluster mergers and group accretion. It is a diversified environment, with cluster complexes in advanced evolutionary stage, groups of clusters in the very early stages of merger, fairly massive clusters with ongoing accretion activity, and smaller groups located in filaments. These features makes it an ideal place to observe the signatures of the formation of large-scale structures in the Universe. We propose to observe the Shapley Concentration at 150 and 216 MHz in order to detect diffuse synchrotron emission on Mpc scales and, therefore, directly probing its large-scale dynamical and mass assembly processes.

Authors: Dr. C. Lynch (U. Sydney, CAASTRO), Dr. G. Anderson (Curtin), Dr. T. Murphy (U. Sydney, CAASTRO), Dr. D. Kaplan (UW-Milwaukee), Dr. K. Bannister (CSIRO), Dr. A. Williams (Curtin), A. Zic (U. Sydney, CAASTRO)

Abstract: We propose a Directors Discretionary Time project to test the capabilities of the MWA to provide efficient radio follow up to extreme X-ray stellar flares that trigger the Swift Burst Alert Telescope (BAT). Flaring activity is a common characteristic of magnetically active stars. These events produce emission throughout the electromagnetic spectrum, implying a range of physical processes, yet the details connecting energetics at different wavelengths are still unclear. Fender et al. (2015) discovered GHz radio emission associated with a X-ray superflare detected by Swift-BAT, with radio activity lasting up to 48 hours after the initial event. Whether low-frequency radio emission is associated with X-ray superflares is unknown. The purpose of the proposed observations is to determine whether the magnetic events that lead to these X-ray superflares also result in bright low-frequency radio bursts. By doing this we can characterize the physical processes that occur during the most extreme stellar flare events.