Probabilistic learning for pulsar classification

In this work, we explore the possibility of using probabilistic learning to identify pulsar candidates. We make use of Deep Gaussian Process (DGP) and Deep Kernel Learning (DKL). Trained on a balanced training set in order to avoid the effect of class imbalance, the performance of the models, achieving relatively high probability of differentiating the …

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A void in the Hubble tension? The end of the line for the Hubble bubble

The Universe may feature large-scale inhomogeneities beyond the standard paradigm, implying that statistical homogeneity and isotropy may be reached only on much larger scales than the usually assumed ∼100 Mpc. This means that we are not necessarily typical observers and that the Copernican principle could be recovered only on super-Hubble scales. Here, we do not assume …

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CRC MSc AND PhD BURSARIES FOR 2023 

DEADLINE:  6 June 2022 The Centre for Radio Cosmology (CRC) at UWC is internationally recognised for its research in cosmology and galaxy evolution with MeerKAT, the Square Kilometre Array (SKA) and other telescopes (see astro.uwc.ac.za for further details). In  2022, the CRC research team includes 21 PhD/ MSc students and 11postdoctoral fellows. Postgraduate students at the CRC work in a friendly and highly active …

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A measurement of the Integrated Sachs-Wolfe Effect with the Rapid ASKAP Continuum Survey

The evolution of the gravitational potentials on large scales due to the accelerated expansion of the Universe is an important and independent probe of dark energy, known as the integrated Sachs-Wolfe (ISW) effect. We measure this ISW effect through cross-correlating the cosmic microwave background maps from the \textit{Planck} satellite with a radio continuum galaxy distribution …

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Wavelet Moments for Cosmological Parameter Estimation

Extracting non-Gaussian information from the non-linear regime of structure formation is key to fully exploiting the rich data from upcoming cosmological surveys probing the large-scale structure of the universe. However, due to theoretical and computational complexities, this remains one of the main challenges in analyzing observational data. We present a set of summary statistics for …

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The MeerTime Pulsar Timing Array — A Census of Emission Properties and Timing Potential

MeerTime is a five-year Large Survey Project to time pulsars with MeerKAT, the 64-dish South African precursor to the Square Kilometre Array. The science goals for the programme include timing millisecond pulsars (MSPs) to high precision (< 1 μs) to study the Galactic MSP population and to contribute to global efforts to detect nanohertz gravitational waves …

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Direct Optimal Mapping for 21cm Cosmology: A Demonstration with the Hydrogen Epoch of Reionization Array

Motivated by the desire for wide-field images with well-defined statistical properties for 21cm cosmology, we implement an optimal mapping pipeline that computes a maximum likelihood estimator for the sky using the interferometric measurement equation. We demonstrate this direct optimal mapping with data from the Hydrogen Epoch of Reionization (HERA) Phase I observations. After validating the …

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MIGHTEE-HI: The relation between the HI gas in galaxies and the cosmic web

We study the 3D axis of rotation (3D spin) of 77 HI galaxies from the MIGHTEE-HI Early Science observations, and its relation to the filaments of the cosmic web. For this HI-selected sample, the alignment between the spin axis and the closest filament (|cosψ|) is higher for galaxies closer to the filaments, with ⟨|cosψ|⟩=0.66±0.04 for galaxies <5Mpc from …

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Megamaser “Nkalakatha” discovered by astronomers using MeerKAT

Using the MeerKAT radio telescope, a team of researchers from the University of the Western Cape, the University of Cape Town, Rhodes University, the South African Radio Astronomy Observatory and the South African Astronomical Observatory together with colleagues from twelve other countries have discovered a powerful megamaser – a radio-wavelength laser indicative of colliding galaxies. …

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