Until recently, one out of every eight channels in an MWA observation were considered unreliable due to a quirk of the critically sampled polyphase filter bank.
The regular spacing of these channels has obscured large regions of the 21cm power spectrum, limiting the EoR experiment.
Recent upgrades to receiver and correlator hardware have enabled oversampling, which offers a much...
Radio surveys of the Galactic Plane are essential for understanding how the Milky Way evolves, what it is composed of, and what emission processes take place. Low radio frequencies are particularly useful for constraining the distribution of cosmic rays and magnetic fields, as well as studying the spectral properties of pulsars and the diffuse emission of supernova remnants.
The GLEAM-X...
Traditional pulsar surveys have primarily employed time-domain periodicity searches. However, these methods are susceptible to effects like scattering, eclipses and orbital motion. At lower radio frequencies ($\lesssim$ 300\,MHz), factors such as dispersion measure and pulse broadening become more prominent, reducing the detection sensitivity. On the other hand, image domain searches for...
Thanks to MWA observations of the entire southern sky, through the GLEAM Survey, it has been possible to create a legacy compilation of the brightest radio-sources (S$_{\mathrm{151\,MHz}}$ > 4 Jy) in preparation for the SKA: the GLEAM 4-Jy (G4Jy) Sample (White et al. 2020a, 2020b). In this talk I will present the results of widely-awaited multiwavelength analysis, which includes the...
The Galactic and Extragalactic All-sky MWA (GLEAM) survey covers the sky up to declination ~+30 across most of the frequencies MWA observes at, covering multiple telescope configurations. This talk will cover some uses of these archival datasets, namely the previously unreleased GLEAM 300 MHz survey (GLEAM-300) and strategies to combine phase I and phase II GLEAM data for imaging projects...
In an rapidly approaching SKA era, the need to characterise radio sources and their host galaxies accurately has emerged as a non-trivial problem, especially for undetected host galaxies. For this population without clear hosts, overlapping with infrared-faint radio sources (IFRSs), the bottleneck in obtaining redshifts lies in dedicated follow-up at sub-mm or infrared wavelengths using...
Recent radio surveys have demonstrated that the radio sky is far more dynamic and variable than previously thought, with a host of new transient discoveries rapidly following wide-area surveys conducted with SKA precursors such as LOFAR, ASKAP, and the MWA. In particular, the long-period radio transients (LPTs) have motivated searches of the time domain between seconds to hours, a timescale...
The MWA archive is creaking; data is being deleted.
All of that data represents valuable observing time, yet some of that data has never been examined.
Both of these problems relate to the size of the file; when the processing takes too long the data never gets imaged, particularly if one starts to consider division by frequency or time.
However, if we could reduce the sizes of the files...
In this presentation I will introduce the BLINK pipeline, now publicly available, a novel high time resolution imaging software for low-frequency Fast Radio Bursts (FRBs) searches within MWA VCS observations.
Detection of FRBs at low frequencies is computationally challenging due to the high time and frequency resolution requirements imposed by the nature of FRBs, coupled with the large...
The 21 cm hydrogen line is a unique tool that allows scientists to study the vast space between galaxies, known as the intergalactic medium (IGM) and to track how it changed over time as the universe evolved. By measuring tiny fluctuations in this signal, researchers can learn about the temperature and ionisation state of the early universe.
In this talk, we present the deepest limits ever...
In Nunhokee et al (2025), the MWA EoR Collaboration published the deepest limits on the brightness temperature of the 21cm signal from 800 million years after the Big Bang. This work used all of the observed data from the EoR0 field, and our high-band at 167-197MHz, culminating in 267 hours of clean data. That work reached a limit of 30.2 mK in brightness temperature fluctuation on scales of...
Exploration of the 21cm signal from the Cosmic Dawn and the Epoch of Reionisation (EoR) can unravel the mysteries of the early Universe when the first stars and galaxies were born and reionised the intergalactic medium. However, the 21cm signal is exceptionally weak; thus, detecting amidst the bright foregrounds is extremely challenging. The Murchison Widefield Array (MWA) aims to measure the...
The redshifted 21 cm line is a powerful tool for studying the state of the intergalactic medium (IGM) before the epoch of reionization. The MWA’s ultra-low-frequency band, spanning 75 MHz to 100 MHz, covers the 21 cm line from redshift of 15. This redshift corresponds to the epoch when the first stars formed and the IGM was heated by X-ray radiation. However, observations at these frequencies...
Spherical harmonic functions are a natural set of basis functions for describing the brightness distribution of the celestial sphere. As the Earth rotates, the fringes projected on the sky by a zenith phased interferometer sample the celestial sphere. The resulting visibilities measured by a single baseline are therefore periodic over a sidereal day, and are Fourier conjugate with the...
Radio surveys are unique tracers of black holes in the distant Universe. Only the most massive black holes ($10^8-10^9\,$M$_\odot$) can produce the synchrotron jets which are luminous enough to appear in relatively shallow all sky radio surveys. After stagnating for a decade or so, we have seen a renaissance in this field over recent years with the discovery of numerous radio-loud AGN in the...
Over the past decade, pulsar and fast transient science with the MWA has critically relied on the voltage capture system (VCS) and associated software sub-systems and processing pipelines. Notwithstanding numerous data management/processing challenges and inevitable software development/support needed for science extraction, this unique capability has been exploited for a range of science in...
Millisecond pulsars (MSPs) are the most precise natural clocks in the known Universe and have proven to be powerful tools for advancing fundamental physics. Observations of MSPs at low radio frequencies (below 300 MHz) play an important role in characterising both their emission properties and the effects of the ionised interstellar medium on the received signals; both of which are critically...
The Southern-Sky MWA Rapid Two-Metre (SMART) pulsar survey is an ongoing project to search the whole southern sky for pulsars and fast transients with the Murchison Widefield Array (MWA) telescope. The observing campaign for SMART has been completed, with 71 80-minute observations taken with the Voltage Capture System (VCS) covering the whole southern sky below 30deg declination. The second...
Our work proposes an optimized pulsar search pipeline that utilizes deep learning to sift ``snapshot'' candidates generated by folding de-dispersed time series data. This approach significantly accelerates the search process. We also developed a script to generate simulated pulsar signals, optimizing the training set and improving model performance. The benchmark uses the globular cluster NGC...
The SMART Pulsar survey has generated petabytes of raw data, of which only a small fraction has undergone coarse processing for pulsar searches using PRESTO, a toolkit that supports basic thread- and node-level parallelism. To search a larger portion of the dataset and enable more refined searches within reasonable timeframes, software improvements are necessary. The bulk of computation in...
Pulsars, nature's most precise cosmic clocks, have proven to be invaluable tools for a wide range of applications, including space weather studies. Extending these studies to low radio frequencies presents exciting opportunities to deepen our understanding of space weather dynamics.
Low-frequency pulsar observations are especially sensitive to dispersive and scattering effects induced by...
Over the past decade the MWA has established itself as the leading instrument for high fidelity and dynamic range spectroscopic high time resolution images at low radio frequencies. These unprecedented images have enabled a wide variety of solar science, especially for detailed studies of the brightest and faintest active emissions. More recently the MWA solar group has been developing...
Spectroscopic snapshot solar imaging at radio wavelengths can yield detailed understanding of the emission processes responsible for solar radio bursts associated with massive eruptive events like flares and coronal mass ejections (CMEs). Cutting-edge radio interferometers, e.g. Murchison Widefield Array (MWA), are exceptionally well-suited for this purpose. However, spatially resolved...
Modern low-frequency instruments, such as the Murchison Widefield Array (MWA), coupled with the technique of interplanetary scintillation (IPS), have made key advances in the field of solar and space science. IPS is a fantastic space weather tool as it is able to measure the solar wind density along any line of sight an arbitrary distance from the Sun, and with the MWA’s huge field of view,...
Type-II solar radio bursts are plasma emissions generated by collisionless shocks in the corona and interplanetary space, typically driven by energetic solar eruptions such as flares and coronal mass ejections (CMEs). Their close association with such large-scale eruptionsmakes them relevant for space weather studies as well. The geoeffectiveness of a CME largely depends on the properties of...
Accurate calibration of instrumental polarization is essential for extracting magnetic field information from polarized radio emissions in astrophysical, heliospheric, and geospace environments. At meter wavelengths, this task becomes complicated due to the lack of bright polarized calibrators, a consequence of strong Faraday depolarization. We present a new calibration framework tailored for...
For nearly five decades, it has been widely assumed that linear polarization from the Sun at low radio frequencies would be entirely depolarized by strong Faraday rotation in the solar corona. As a result, most solar radio studies at these wavelengths either ignored linear polarization measurements or treated them as zero during calibration.
Here, we will present the first robust evidence...
Construction of SKA-Low is well underway, with four full stations already operational in the current Array Assembly (AA0.5), and at least another twelve stations expected to be integrated into the array by the end of this year. SKA-Low AA0.5 is already being used to progress a comprehensive suite of Science Commissioning activities. Through our first tests of SKA-Low’s interferometric and...
