Transient surveys play a crucial role in understanding the dynamic Universe, with radio transients serving as indicators of explosive and energetic astrophysical events. Despite their importance, conducting commensal radio imaging surveys for transients often demands extensive computational resources, data storage, and processing time. The MeerKAT radio telescope, with its high sensitivity and...
Short gamma-ray bursts (SGRBs) and magnetar giant flares (MGFs) are short gamma-ray transients (SGRTs) with similar temporal profiles but distinct progenitors—SGRBs arise from compact binary mergers, while MGFs originate from magnetars in nearby galaxies. When MGFs are observed at large distances, their characteristic fading pulses may be undetectable, making them difficult to distinguish from...
Recently the KM3NeT neutrino telescope detected the most-energetic neutrino event ever, dubbed KM3-230213A, at an estimated energy of 220 PeV. Given its near horizontal direction and exceptionally high energy, the most likely explanation is that the muon resulted from interaction of a muon neutrino of cosmic origin. In this talk I will explore an astrophysical source origin, both transients...
Neutral hydrogen (HI) intensity mapping (IM) experiments
probe the large-scale structure of the universe through the integrated
redshifted 21-cm line emission from unresolved sources of neutral
hydrogen. Optical surveys also probe the large-scale structure of the
universe with much higher precision and depth by mapping the galaxy
distribution. In this article, we study the...
The Kepler KL4040 sCMOS camera by Finger Lakes Instruments was evaluated for its suitability as an affordable alternative to older CCD sensors for optical photometry at the Boyden Observatory. Due to the sensor architecture where each pixel has its own electron to voltage converter, a thorough characterisation and calibration study was conducted to identify key performance factors and...
Among the active galactic nuclei (AGNi), blazars are the brightest emitters of high- (HE, $E \ge 100\,\mathrm{MeV}$) to very-high-energy (VHE, $E \geq 100\,\mathrm{GeV}$) $\gamma$-rays from their jets. Radio galaxies, being the misaligned parent population of the blazar class, were historically not observed at these frequencies. However, there is a growing number of radio galaxies detected in...
The latest DESI results, suggesting a dynamical dark energy equation of state, have reinvigorated interest in modified teleparallel theories, such as $f(T)$ gravity, as viable alternatives to the standard cosmological model. In this talk, I present a systematic investigation of several popular and novel $f(T)$ models, examining their viability in light of current observational data. By...
Various empirical correlations between observable and derived parameters have been proposed to use Gamma-Ray Bursts (GRBs) as standard candles similar to Type Ia supernovae (SNe Ia) for measuring cosmological distances. The Yonetoku relation, which connects the intrinsic peak energy to the isotropic peak luminosity, stands out as a promising tool. In this work, we present results from machine...
We study an FLRW cosmological model in $f(R,\mathcal{G}, T)$ gravity by assuming a specific form of the deceleration parameter. A Markov Chain Monte Carlo (MCMC) analysis is performed using the Cosmic Chronometer and Pantheon datasets to determine the parameters of the model. A viable model is obtained which exhibits a transition from deceleration to acceleration and which satisfies...
Modern radio interferometers, with their exceptional sensitivity and angular resolution, are uniquely suited to detect the faint signatures predicted from Weakly Interacting Massive Particles (WIMPs). Among the most powerful instruments in the southern hemisphere is MeerKAT, a precursor to the Square Kilometre Array (SKA), which provides unparalleled capabilities for exploring dark matter...
The Affordable Multiple-Aperture Spectroscopy Explorer Prototype (AMASE-P) is an innovative project aimed at improving high-resolution integral field spectroscopy for investigating ionised gas in the Milky Way and nearby galaxies. A critical component of AMASE-P is the fibre instrument cable (FIC), designed to efficiently transmit light from the telescope to the spectrographs. Compact fibre...
Galaxies are gravitationally bound systems composed of stars, gas, dust, and dark matter. Various galaxy properties—such as luminosity, stellar mass, and star formation rate—are significantly correlated with their local environment, such as whether they reside in dense clusters or more isolated regions. Understanding these environmental correlations is crucial for studying galaxy evolution...
The joint detection of gravitational waves (GW170817) by LIGO and Virgo, together with the short gamma-ray burst (sGRBs) GRB 170817A observed by Fermi and INTEGRAL, has confirmed that at least some sGRBs originate
from the merger of two neutron stars (NS-NS). Despite this breakthrough, the evolutionary pathways that lead to such
mergers remain uncertain.
In this project, we study the...
MeerKAT's combination of high-sensitivity and angular resolution makes it a particularly well suited radio interferometer for detecting faint cosmic radio emissions that would otherwise remain inaccessible by other instruments.
This capability is especially important in identifying weak, diffuse radio signals that could be associated with dark matter interactions.
Our research focuses on...
Gamma-Ray Burst (GRB) afterglows arise from the interaction of relativistic ejecta with the circumburst medium and are observed across the electromagnetic spectrum. Polarisation is expected during the early and late phases of the afterglow depending on the presence of reverse shocks and the viewing geometry of the jet. Polarimetric observations of GRB afterglows serve as a unique diagnostic...
Giant radio galaxies (GRGs) are peculiar astrophysical objects because of their exceptionally large linear sizes (>0.7 Mpc). The cause for their huge sizes remains a mystery.
We investigate the spectral behaviour of a small sample of seven (7) GRGs detected from the MeerKAT Galaxy Cluster Legacy Survey (MGCLS). These sources have a minimum linear size of 0.723 Mpc to a maximum linear size of...
Active Galactic Nuclei (AGN) play a critical role in regulating and shaping galaxy evolution through various influential processes or mechanisms that impact the surrounding interstellar and intergalactic medium. In dense environments such as galaxy clusters, this interplay becomes even more complex due to environmental effects like ram pressure stripping, tidal interactions, and strangulation....
Blazars, a subclass of active galactic nuclei, have emerged as candidates for the sources of very-high-energy astrophysical neutrinos observed by the IceCube Neutrino Observatory. Notable temporal and spatial coincidences, particularly the event IceCube-170922A coinciding with a flare from TXS 0506+056, have sparked interest in the connection between these objects and neutrino production. In...
In this talk, I will show recent results from the deep optical imaging and spectroscopic study of the spectacular nearby galaxy NGC2865.
NGC2865 is well-known for its system of relatively bright stellar shells in the galaxy's outskirts believed to be remnants of a recent merger event. I will, however, unveil a remarkable but hidden stellar feature at the centre of this galaxy which is...
Dark Matter (DM) makes up a significant portion of the universe's mass-energy content, yet its fundamental nature remains elusive. Neutrinos are nearly massless particles that interact weakly with ordinary matter and may provide evidence of subtle interactions with DM. One possibility is that dense DM spikes, which form around supermassive black holes, can weaken the high-energy neutrino flux...
We present an analysis of the X-ray bright galaxy cluster ZwCl 3146 (redshift z = 0.291) using archival 90 ks Chandra observations, along with our 1.4 GHz GMRT observations. Beta model subtracted residual and unsharp X-ray images reveal spiral-like features within the central 230 kpc, indicative of gas sloshing in the intracluster medium (ICM). We also detect an offset of about 11 kpc between...
With the WIMP parameter space slowly being ruled out by experiments on all fronts, axions have become a highly studied alternative dark matter candidate. In this talk we present a particle physics model where the pion states of a dark copy of QCD have both axion and dilaton phenomenologies. This model allows for the formation of dilute axion stars over a far larger parameter space than allowed...
Fast Radio Bursts (FRBs) are millisecond-duration radio emissions originating from cosmological distances, as indicated by their large dispersion measures. While numerous FRBs have now been localised to their host galaxies, a distinct class of compact electromagnetic counterpart, the Persistent Radio Source (PRS), has also been identified in some cases. These PRSs, have so far only been found...
Enrico Fermi first proposed the stochastic acceleration of protons due to interactions with parsec-scale interstellar magnetic fields as a method of cosmic ray acceleration around the time of the 1950s. Since then, the theoretical framework of stochastic acceleration in magnetohydrodynamic (MHD) turbulence has undergone significant refinement with recent numerical simulations incorporating...
In this work, we study the dynamics of the universe using Thawing Dark Energy (TDE) model with a minimally coupled scalar field that evolves away from the dominance of potential energy. As the equation of state parameter 𝑤(𝑎) evolves, this offers a dynamic framework where the impact of dark energy may change over time. The structure formation of the universe will be highlighted in TDE using...
The Atacama Cosmology Telescope (ACT) conducted an arcmin resolution survey of the southern sky at millimetre wavelengths from 2008-2022. In this talk I will present an update on the ACT search for galaxy clusters using the redshift independent Sunyaev-Zel'dovich (SZ) effect, using data from the full ACT survey, covering 15,000 square degrees. The final ACT Data Release 6 (DR6) cluster catalog...
Pinpointing the true source of radio emission in galaxies is a rather complex task that requires detailed modelling of radio spectral energy distributions. With the recent availability of catalogues of radio sources detected with interferometers such as MeerKAT, uGMRT, and LOFAR, we are able to push down the detectable flux range to the point where we can detect the faintest radio emission in...
The Mesosphere and Lower Thermosphere (MLT) region of the upper atmosphere is an essential atmospheric layer that significantly influences energy exchange, atmospheric dynamics, and space weather interactions. Comprehending the temperature of the MLT is essential, as this region acts as a critical interface between Earth's atmosphere and outer space, with its temperature directly affecting...
The trend worldwide is to preserve astronomical photographic plates by digitisation, with some plates dating back to over a century. Indeed, South Africa should be no exception and has a long tradition of observing the night sky of the Southern Hemisphere, initially to produce star charts for improved navigation by seafaring ships. This gave way to observatories for mapping star positions...
