2013-B, 128T

The MWA long-term radio sky monitor

Authors: Dr. Martin Bell (Sydney/CAASTRO), Dr. Tara Murphy (Sydney/CAASTRO), Prof. David Kaplan (UW‐Milwaukee), Dr. Nadia Kudryavtseva (Curtin), Lu Feng (MIT), Dr. Randall Wayth (Curtin), Dr. Paul Hancock (Sydney/CAASTRO), Prof. Bryan Gaensler (Sydney/CAASTRO), Dr. Natasha Hurley‐Walker (Curtin), Dr. Keith Bannister (CSIRO/CAASTRO), Dr. Steve Croft (UC Berkeley), Dr. Cath Trott (Curtin), Dr. J-P Marquart (Curtin), Dr. Davide Burlon (Sydney/CAASTRO) and the MWA transients collaboration.

Abstract: We propose a wide-field, long-term survey to search for, and monitor, low frequency transient and variable radio sources in the southern sky. This survey would target relatively long duration transient and variable activity (> one month) over almost the entire southern hemisphere. We request 60 hours of night time observing with a cadence of one observation per month. Using drift scan observations of three different declination strips at 150 MHz only, we plan to gradually re-visit different overlapping regions of the sky over the observing semester. These regions will be searched with the Variables and Slow Transients (VAST) detection pipeline. The motivation for this survey is as follows: (i) To obtain temporal data on an extremely large and robust sample of low frequency sources to probe, explore and quantify both intrinsic and extrinsic variability. (ii) To search and find new classes of low frequency radio transients that previously remained undetected and obscured from multi-wavelength discovery. (iii) To place rigorous statistics on the occurrence of both transients and variables prior to the Australian SKA era.

Authors: Iver Cairns, Divya Oberoi, Tim Bastian, Leo Benkevitch, Judd Bowman, Alina Donea, Owen Giersch, Bernie Jackson, Gaetan Le Chat, Leon Golub, Justin Kasper, John Kennewell, Colin Lonsdale, Vasili Lobzin, Lynn Matthews, John Morgan, Janardhan Padmanabhan, Prasad Subramanian, R. Ramesh, John Raymond, Kathy Reeves, Alan Rogers, Steven Tingay, Steven Tremblay, Durgesh Tripathi, David Webb, Stephen White

Abstract: Thirty hours of daytime observing is desired with an unbiased observing pattern over one solar rotation (1 specific hour per day for 30 consecutive days). Three sets of related science goals will be addressed: (A) Solar Radio Bursts, focusing on their imaging, polarization, and spectral properties and their correlation with solar activity like coronal mass ejections (CMEs) and flares, searching for radio “nanoflares” and investigating their role in coronal heating, and observations in conjunction with NuSTAR; (B) Calibration of MWA and solar phenomena via comparisons with the galactic background radiation and EDGES, Learmonth, and Culgoora observations; and (C) Quiet Sun science, including variability of the intrinsic flux and spectral index of background emission and comparing the observed solar scattering disk with expected scattering from density turbulence. A relatively long and unbiased observing pattern will allow us to explore the new phase space opened up by MWA free of any pre-conceived notions.

Authors: Dr. Paul Hancock (SIfA/CAASTRO Sydney University), Prof. David Kaplan (UWMilwaukee), Dr. James Miller-Jones (Curtin University), Dr. Martin Bell (SIfA/CAASTRO Sydney University), Prof. Bryan Gaensler (SIfA/CAASTRO Sydney University), Dr. Natasha Hurley-Walker (Curtin University), Dr. Jean Pierre Macquart (Curtin University), Dr John Morgan (Curtin University), Dr. Tara Murphy (SIfA/CAASTRO Sydney University), Dr. Randall Wayth (Curtin University), and the MWA transients collaboration.

Abstract: We propose to use the MWA to carry out a search for low frequency, scintillation induced variability of extragalactic radio sources. At frequencies 300MHz the variability is likely to be dominated by (strong) refractive interstellar scintillation (RISS). The degree and timescale of variability of compact radio sources is related to variations in gas density along the line of sight, and as such can be used to probe the turbulent structure of the intervening gas. Probing many lines of sight through the Milky Way and Magellanic clouds therefore provides a measure of turbulence in the ISM. The work of Slee & Siegman (1988) used sources that sparsely covered the southern sky, and found a high incidence of variability which was in part attributed to scintillation. Their analysis also showed a weak increase in variability at low galactic latitudes. With a denser coverage of the Galactic plane it is possible to look for correlations in the RISS properties between closely spaced sources that could demonstrate the spatial structure of the ISM. By including fields outside of the Galactic plane we can also measure the correlation between the strength and incidence of scintillation with Galactic latitude. Such a project has not yet been carried out due to the large amount of observing time required to conduct a blind survey of extragalactic point sources, and then monitor a large population of them long enough to see monthly and yearly variations. With the large field of view of the MWA and the relatively short amount of time required to reach the confusion limit, this project is ideally suited to the MWA.

Authors: Prof. David Kaplan (UWM); Dr. James Miller-Jones (Curtin); Dr. Megan DeCesar (UWM); Dr. Martin Bell (University of Sydney), Dr. Tara Murphy (Sydney), Dr. Randall Wayth (Curtin), Dr. Paul Hancock (Sydney), Prof. Bryan Gaensler (Sydney), Dr. Natasha Hurley-Walker (Curtin), Dr. Keith Bannister (CSIRO), Lu Feng (MIT), Dr. Nadia Kudryavtseva (Curtin), Dr. Peter Williams (Harvard/Smithsonion CfA), Dr. Cath Trott (Curtin) and the MWA Transients collaboration

Abstract: We propose weekly MWA monitoring of the Galactic Plane, including the Galactic Center. We aim to monitor the periastron passage of the gas cloud G2 as it orbits Sgr A constrain the nature of the mysterious bursting source GCRT J1745-3009, and provide high-cadence radio light curves of X-ray binary outbursts. At the same time, the extremely wide field-of-view afforded by the MWA means that the specific targets listed below will be joined by many serendipitous targets spread throughout the Galaxy. Using the transients pipeline, we will also monitor other classes of radio transient, including magnetar giant outbursts, flare stars and active binaries.

Authors: Dr. Nadia Kudryavtseva (Curtin), Lu Feng (MIT), Prof. David Kaplan (UW – Milwaukee), Dr. Martin Bell (Sydney, CAASTRO), Dr. Tara Murphy (Sydney), Dr. Daniel Mitchell (Melbourne, CAASTRO), Dr. Randall Wayth (Curtin, CAASTRO), Dr. Natasha HurleyWalker (Curtin), Dr. Steven Tingay (Curtin), Dr. Paul Hancock (Sydney, CAASTRO), Dr. Keith Bannister (CSIRO, CAASTRO), Prof. Bryan Gaensler (Sydney, CAASTRO), Dr. Jean-Pierre Macquart (Curtin), Dr. Cathryn Trott (Curtin, CAASTRO), Dr. Davide Burlon (Sydney), Dr. James Miller-Jones (Curtin), Dr. Roberto Soria (Curtin), Dr. John Morgan (Curtin), Dr. Hayley Bignall (Curtin), Dr. Rachel Webster (Melbourne), Prof. Jacqueline Hewitt (MIT), Prof. Edo Berger (Harvard), Dr. Peter Williams (Harvard) and the MWA transients collaboration.

Abstract: Many types of variable and transient sources are predicted and observed at low frequencies. For example, flares from low-mass stars and brown dwarfs, magnetars, and flares associated with state transitions in accreting stellar-mass and intermediate-mass black holes. In addition, possible nonrepeating transient sources, such as merging black holes, and tidal disruption events are expected to emit at MWA frequencies. However, the low-frequency radio sky is not well explored. Observations with the MWA are extremely well-suited for blind transient surveys due to its large instantaneous field of view and high sensitivity. We propose a survey of transient and variable sources in the EOR (Epoch of Reionisation) fields. This is a commensal observation, sharing data with the EOR collaboration. This proposal targets transient events on time scales from 8 seconds to weeks and covers 1830 square degrees of the sky over 370 hours of observations. This will allow us to study the variable and transient nature of multiple types of sources.

Authors:A. R. Offringa (ANU, CAASTRO), F. H. Briggs (ANU), L. Hindson (Wellington)

Abstract: We intend to study the detailed spectra of extragalactic continuum radio sources with highest achievable level of calibration. The study will make use of the extensive MWA data sets taken in the course of fulfilling other high-priority MWA programs. The results will complement and enhance other key MWA projects by building confidence in our understanding of the instrument’s behaviour and reliability in the calibration. The project will result in low-frequency high-resolution spectral energy distributions (SEDs) for hundreds of extragalactic point-like sources. Using these SEDs, we will verify whether low-frequency source spectra are smooth. This is a key assumption that is required for extracting the redshifted 21-cm emission of the Epoch of Reionisation (EoR) from lowfrequency measurements, but one that has never been extensively tested. This project does not require additional observing time, as we will only use data sets already taken for the EoR project.

Authors: G. Rowell, S. Balenderan, F. Brun, P. Chadwick, W. Domainko, J. Hawkes, J. Hinton, L. McComb, P. O'Brien, D. Parsons, G. Puehlhofer, E. de Ona Wilhelmi, J-P. Lenain for the H.E.S.S. Collaboration

Abstract: This proposal aims to explore the technical aspects of linking the H.E.S.S. and MWA telescopes in gamma-ray and radio studies of transient sources. We will investigate two aspects (1) MWA triggers for H.E.S.S. follow-up observations and (2) H.E.S.S. triggers for MWA follow-up or re-pointing. We request access to a sample of MWA trigger data from the 2013-B period in order to configure data pipelines to/from H.E.S.S. and to investigate transient alert filtering and follow-up policies. A companion proposal to support this activity has recently been submitted to H.E.S.S.

Authors: Prof Lister Staveley-Smith (ICRAR/UWA), Dr Natasha Hurley-Walker, Dr K. S. Dwarakanath (RRI), Prof Bryan Gaensler (U. Sydney), Dr D. Anish Roshi (NRAO), Dr Randall Wayth (ICRAR/Curtin), Dr Takuya Akahori (U. Sydney), Mr Craig Anderson (U.Sydney), Dr Edo Berger (CfA), Dr Gianni Bernardi (SKA-SA), Dr Judd Bowman (ASU), Dr Robert Braun (CSIRO), Dr Davide Burlon (U. Sydney), Mr Joe Callingham (U.Sydney), Dr Ettore Carretti (CSIRO), Dr Roland Crocker (ANU), Prof John Dickey (U. Tasmania), Dr Jamie Farnes (U. Sydney), Dr Sean Farrell (U.Sydney), Dr Ilana Feain (CSIRO), Dr Bi-Qing For (ICRAR/UWA), Ms Niloofar Gheissari (U. Sydney), Prof Anne Green (U. Sydney), Dr Lisa Harvey-Smith (CSIRO), Dr Luke Hindson (VUW), Dr Alex Hill (CSIRO), Dr Carole Jackson (CSIRO), Dr Daniel Jacobs (ASU), Dr Melanie Johnston-­‐Hollitt (VUW), Ms Jane Kaczmarek (U. Sydney), Dr Slava Kitaeff (ICRAR/UWA), Dr Nadia Kudryavtseva (ICRAR/Curtin), Dr Emil Lenc (U. Sydney), Mr George Lijo (RRI), Dr Naomi McClure-­‐Griffiths (U. Sydney), Mr Ben McKinley (ANU), Dr Daniel Mitchell (U.Melbourne), Dr Miguel Morales (U. Washington), Dr John Morgan (ICRAR/Curtin), Dr Paul Nulsen (Harvard/CfA), Dr Divya Oberoi (MIT/Haystack), Dr Andre Offringa (ANU), Dr Steven Ord (ICRAR/Curtin), Dr Shane O'Sullivan (U. Sydney), Dr Cormac Purcell (U. Sydney), Prof. Peter Quinn (ICRAR/UWA), Prof Elaine Sadler (U.Sydney), Dr. Lakshmi Saripalli (RRI), Dr Nick Seymour (CSIRO), Ms Sara Shakouri (VUW), Dr Pat Slane (CfA), Mr Raghav Srinivasa (VUW), Ms Kim Steele (ICRAR/Curtin), Dr Xiaohui Sun (U. Sydney), Dr Ravi Subrahmanyan (RRI), Prof Steven Tingay (ICRAR/Curtin), Dr. N. Udaya Shankar (RRI), Dr Andrew Walsh (ICRAR/Curtin), Dr. Peter Williams (CfA), Dr Alex Zauderer (CfA), Dr Cathie Zheng (VUW), Dr Maria Cunningham (UNSW), Dr George Heald (ASTRON), Dr Paul Jones (UNSW), Dr Ruta Kale (U.Bologna & INAF), Dr Gavin Rowell (U.Adelaide)

Abstract: We propose a GaLactic and Extragalactic All-sky MWA (GLEAM) survey at the full range of MWA frequencies (80-230 MHz) in order to study phenomena ranging in scale from pulsar wind nebulae to the Cosmic Web. Commensurate with the low frequency and high surface brightness sensitivity of the MWA, our science aims are dominated by the study of non-thermal processes in diffuse objects. For example, detection of new giant radio galaxies will allow us to probe intergalactic pressure in a wider range of environments than currently available; stacking of emission from the cosmic web will allow us to better constrain the amplification of primordial magnetic fields; and a study of clusters will allow us to discriminate between viable cosmic ray acceleration processes in the largest virialised objects in the Universe. Studies of nearby galaxies will allow de-blending of the non-thermal and thermal components of radio emission, an examination of the non-thermal radio/FIR relation, and its dependence on spatial scale. Within our own Galaxy, the proposed frequency coverage will give excellent spectral coverage for rotation measure studies of the Galactic magnetic field and its threedimensional configuration. It will also be a valuable resource for the discovery of the Galaxy’s "missing" supernova remnants. The GLEAM survey will provide valuable knowledge on foreground subtraction techniques for the proposed EOR project, will provide an important sky template for the study of transient radio sources, and will provide a list of polarisation-selected pulsar candidates for further study. Furthermore, the GLEAM survey overlaps and complements the ongoing LOFAR MSSS survey, and will provide a valuable low-frequency reference for the ASKAP EMU survey. Finally, the science aims are related to at least two of the key SKA science goals, provide a low-risk, high-return range of science and will be a valuable all-sky legacy for the astronomy community.

Authors: Adam Beardsley (Washington), Dr Gianni Bernardi (CfA), Prof Judd Bowman (Arizona State), Prof Frank Briggs (ANU), Josh Dillon (MIT), Aaron Ewall-Wice (MIT), Lu Feng (MIT), Prof Steve Furlanetto (UCLA), Prof Bryan Gaensler (Sydney), Robert Goeke (MIT), Dr Lincoln Greenhill (CfA), Dr Bryna Hazelton, (Washington), Prof Lars Herquist (Harvard), Prof Jackie Hewitt (MIT), Dr Daniel Jacobs (Arizona State), Dr Emil Lenc (Sydney), Dr Al Levine (MIT), Dr Adrian Liu (UC Berkeley), Prof Avi Loeb (Harvard), Dr Colin Lonsdale (Haystack MIT), Ben McKinley(ANU), Dr Daniel Mitchell (Melbourne), Prof Miguel Morales (Washington), Dr Ed Morgan (MIT), Abraham Neben (MIT), Dr André Offringa (ANU), Sourabh Paul (RRI), Dr Bart Pindor (Melbourne), Dr Pietro Procopio (Melbourne), Dr Ron Remillard (MIT), Jenny Riding (Melbourne), Dr Shiv Sethi (RRI), Prof Udaya Shankar (RRI), Prof Ravi Subrahmanyan (RRI), Dr Ian Sullivan (Washington), Prof Max Tegmark (MIT), Prof Steven Tingay (Curtin), Dr Cath Trott (Curtin), Dr Randall Wayth (Curtin), Prof Rachel Webster (Melbourne), Dr Chris Williams (MIT), Prof Stuart Wyithe (Melbourne)

Abstract: The Murchison Widefield Array is designed to measure the fluctuations in the 21cm emission from neutral hydrogen during the Epoch of Reionisation. The built telescope with 128 tiles has the sensitivity to detect the theoretical signal, with sufficient observing time. The real challenge will be to understand and remove the foreground signals from the galaxy and extragalactic sources. We have demonstrated a pipeline that successfully removes the foregrounds from a few hours of data obtained on the MWA 32-tile test array. This proposal requests 400 hours of observing time in semester 2013-B to (1) acquire an adequately sensitive dataset to probe and understand the limitations of the array design for foreground removal, (2) obtain the first dataset required to meet the estimated sensitivity requirements for a detection of the Epoch of Reionisation, (3) establish the optimal observing strategy for such a detection, and (4) explore the large N-small d design parameter space to advise the design of SKA-low as those options are being narrowed down over the next 12 months. We note that the MWA Statement of Collaboration specifies that priority will be given to the EoR and SHI collaborations during early science operations.

Constraining Xray and Dark Matter heating Before the Epoch of Reionization (EoR): Preliminary Observations at Low Frequency with the MWA

Authors:. Aaron Ewall-Wice (MIT), Pierre Christian (CfA), Abraham Neben (MIT), Josh Dillon (MIT), Jackie Hewitt (MIT), Andrei Mesinger (SNS), Avi Loeb (CfA), Frank Briggs (ANU), Max Tegmark (MIT)

Abstract: The MWA 128T is designed to detect the power spectrum of 21cm fluctuations in the high redshift intergalactic medium (IGM) during the Epoch of Reionization (EoR). During the late stages of reionization (6< ~z < ~10), these fluctuations are dominated by the ionization structures sourced by the first generations of luminous galaxies. Prior to reionization, many models predict that the X-ray heating, from high mass X-ray binaries, miniquasars, and dark matter (DM) annihilation, raised the temperature of the IGM to bring it into emission against the Cosmic Microwave Background (CMB). At low redshift, when the gas is already heated, the 21cm brightness temperature is expected to depend little on the spin temperature, so power spectrum fluctuations are dominated by ionization. At higher redshifts, before the completion of heating, (z > ~10) large fluctuations in the spin temperature can increase the amplitude of the power spectrum above the MWA’s expected thermal noise. A detection or non-detection of these spin temperature fluctuations would constrain the thermal history of the IGM, complementing a low redshift power spectrum detection that would constrain the reionization history. Encoded in this thermal history is the abundance of early astrophysical sources of X-rays, as well as cosmological information such as the warm dark matter (WDM) particle mass and the cold dark matter (CMD) annihilation cross-section.

Beyond the thermal noise, foreground removal, terrestrial radio-frequency interference (RFI; particularly the FM band), and ionosphere propagation effects are severe challenges at low frequencies. Also, the increased size of the field of view will likely present an additional calibration challenge. This proposal requests 24 hours of observing time in semester 2013-B to determine whether thermal sensitivity limited measurements within the EoR window are possible in the presence of low frequency systematics.