CRC

MeerKAT discovers mystery clouds

An international team led by astronomers Gyula Józsa, Michelle Cluver, and Thomas Jarrett has utilized the South African MeerKAT telescope to discover a mysterious chain of hydrogen gas clouds the size of a massive galaxy. Indeed, the accumulation of so much elemental hydrogen without associated stellar components is the largest yet discovered. Appearing at the …

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Large MeerKAT data release reveals beautiful new cosmic puzzles

An international team led by a young South African researcher has just announced a comprehensive overview paper for the MeerKAT Galaxy Cluster Legacy Survey (MGCLS). The paper to be published in the Astronomy & Astrophysicsjournal presents some exciting, novel results, and is accompanied by the public release of a huge trove of curated data now available …

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HERA Phase I Limits on the Cosmic 21-cm Signal: Constraints on Astrophysics and Cosmology During the Epoch of Reionization

Recently, the Hydrogen Epoch of Reionization Array (HERA) collaboration has produced the experiment’s first upper limits on the power spectrum of 21-cm fluctuations at z~8 and 10. Here, we use several independent theoretical models to infer constraints on the intergalactic medium (IGM) and galaxies during the epoch of reionization (EoR) from these limits. We find …

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Quenching and the UVJ diagram in the SIMBA cosmological simulation

Over the past decade, rest-frame color-color diagrams have become popular tools for selecting quiescent galaxies at high redshift, breaking the color degeneracy between quiescent and dust-reddened star-forming galaxies. In this work, we study one such color-color selection tool — the rest-frame U−V vs. V−J diagram — by employing mock observations of cosmological galaxy formation simulations. In particular, we conduct …

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Gaussian Process Regression for foreground removal in HI intensity mapping experiments

We apply for the first time Gaussian Process Regression (GPR) as a foreground removal technique in the context of single-dish, low redshift HI intensity mapping, and present an open-source python toolkit for doing so. We use MeerKAT and SKA1-MID-like simulations of 21cm foregrounds (including polarisation leakage), HI cosmological signal and instrumental noise. We find that …

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Young scientist has her eyes firmly fixed on the stars

Astrophysics student Nicole Thomas, who is completing her PhD at the University of the Western Cape’s Department of Physics and Astronomy, was selected to attend the 69th Nobel Laureate Meeting in Lindau, Germany, in 2019. Nicole, one of our students, is interviewed in UWC’s latest 360º Perspectives Magazine (p.24-25) – a big issue packed with retrospectives and …

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On the road to percent accuracy V: the non-linear power spectrum beyond ΛCDM with massive neutrinos and baryonic feedback

In the context of forthcoming galaxy surveys, to ensure unbiased constraints on cosmology and gravity when using non-linear structure information, percent-level accuracy is required when modelling the power spectrum. This calls for frameworks that can accurately capture the relevant physical effects, while allowing for deviations from ΛCDM. Massive neutrino and baryonic physics are two of the …

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First HETDEX Spectroscopic Determinations of Lyα and UV Luminosity Functions at z=2−3: Bridging a Gap Between Faint AGN and Bright Galaxies

We present Lyα and ultraviolet-continuum (UV) luminosity functions (LFs) of galaxies and active galactic nuclei (AGN) at z=2.0−3.5 determined by the un-targetted optical spectroscopic survey of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We combine deep Subaru imaging with HETDEX spectra resulting in 11.4 deg2 of fiber-spectra sky coverage, obtaining 18320 galaxies spectroscopically identified with Lyα emission, 2126 of which host type 1 AGN showing broad …

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