Conveners
Science: Galaxies
- K. Kesebonye
Science: Galaxy Clusters
- Sinenhlanhla Precious Sikhosana (University Of Kwazulu-Natal)
Science: Transients, Compact Objects
- Bret Yotti (University of Cape Town)
Science: Stars, star formation
- Wilice Obonyo (Technical University of Kenya)
Science: ML & Techniques
- Daniel Egbo (UCT/SAAO)
Science: Instruments
- Zara Randriamanakoto (SAAO/University of Antananarivo)
Science: Galaxies
- Mirjana Povic (Space Science and Geospatial Institute (SSGI))
Science: Science - Others
- Portia Legodi (University of South Africs)
Science: Cosmology
- Catherine Cress (UNISA)
Galaxies within a group or a cluster have their radial velocities and positions known to a high degree of accuracy. This information is sufficient to estimate the group mass from the observed deviations from the external Hubble field of velocities by making critical assumptions on eccentricities and equipartition. For a full understanding of the evolution of a galaxy group, we require accurate...
Many, if not all, galaxies are believed to host a supermassive black hole (SMBH) which is thought to form an integral ingredient in the evolution of the host galaxies through feedback mechanisms. In this scenario, the host and SMBH is expected to grow symbiotically and one of the favoured scenarios comes from major mergers of galaxies where the SMBHs are expected to merge. To this date, very...
Low surface brightness galaxies (LSBGs) being considered to account for a significant fraction of the total number density of galaxies play a crucial role in galaxy evolution. However, their connection to their local environment remains poorly understood, despite the well-established influence of the environment on the evolution of galaxies. In this talk, I will primarily present our recent...
The presence of an accretion disk (AD) in active galactic nuclei (AGN) has limited and indirect observational support. In order to evaluate the extent to which the AD is a source of the broad Balmer lines and high ionization UV lines in radio-loud (RL) AGN, we focused on an extremely jetted RL quasar 3C 47 at z = 0.425, that shows a double-peaked profile. The work presents its new optical...
The SC2RG survey aims to constrain the star formation history (SFH) of collisional ring galaxies (CRGs) by investigating bound stellar clusters and large-scale star-forming clumps in their field. CRGs are the result of a drop-through collision between the rotation axis of larger spiral disk galaxy and a nearby small companion. They represent a special class of interacting galaxies...
Measurements of galaxy cluster kinematics have the potential to provide constraints in dark modeling and a unique constraint on baryon density in an intercluster medium. This work uses a 1-point statistical detection of the kSZ signal in ACTPol DR4 maps. To obtain the kSZ signal, we perform aperture photometry on BOSS NORTH and Deep 56 regions of ACTPol DR4 using galaxy cluster positions from...
The Shapley Superlcuster is the most massive gravitationally bound structure in the nearby Universe, consisting of many galaxy clusters and groups at various evolutionary stages of merger activity. Using various SKA pathfinders, we study this prime example of large scale structure formation at unprecedented sensitivities. In particular, we present the findings in our multiwavelendgth study of...
The Fornax cluster provides an interesting environment to study galaxy evolution. It is still actively assembling mass, with the infalling group Fornax A on the outskirts and an overdense region around the brightest cluster galaxy at the center. The study of this cluster’s environment and the physical processes that govern the transition from blue to red galaxies is crucial for understanding...
The diffuse intragroup light (IGL) is a pervasive feature of galaxy groups consisting of an extended low-surface-brightness component that permeates the intergalactic medium of these galaxy associations. It is believed to form from stars removed from the outermost regions of the galaxies, or that have formed in situ due to the numerous close interactions during the initial phases of galaxy...
Detected on the 9th of October in 2022, the brightest of all time (BOAT) gamma-ray burst GRB 221009A has been estimated to occur once per 10,000 years by extrapolating gamma-ray fluence distribution of known GRBs to the fluence of GRB 221009A. It would be a large coincidence if such a GRB occurred in the approximately 50 years that humanity has had the ability to detect such bursts. Here we...
Mauve is a satellite equipped with a 13-cm telescope and a UV-Visible spectrometer (with an
operative wavelength range of 200-700 nm) conceived to measure the stellar magnetic activity and
variability. The science program will be delivered via a multi-year collaborative survey program,
with thousands of hours each year available for long baseline observations of hundreds of...
MAXI J1535-571 outburst evolution is driven by physical mechanisms that mediate the accretion flow dynamical behavior/characteristics. In this study, MAXI J1535-571 data observed by MAXI/GSC, NuSTAR, and SWIFT/BAT, were analyzed using HEASoft v6.2 and its software packages. Spectral fitting/modelling was done in XSPEC v12.10.1f using phenomenological and physical models. MAXI J1535-571 X-ray...
Magnetic active stars, manifest in chromospheric and coronal emissions and offer insights into stellar evolution, magnetic dynamo mechanisms, and their interaction with surrounding environments. Using the SARAO MeerKAT Galactic Plane Survey (SMGPS), an $L$-band survey centred at 1.3 GHz, we investigated chromospheric and coronal activity in stars in the Galactic Plane. Coronal active stars...
Black widow and redback compact binaries are collectively known as ‘spider’ binary systems in which a millisecond pulsar heats and ablates its low-mass companion via its intense pulsar wind. They are an important type of pulsar system differentiated by their companion’s mass and nature. These systems manifest a rich empirical phenomenology, including radio eclipses, optical light curves from a...
Many newly discovered near-Earth asteroids (NEAs) are small ($<$100 m), yet they still pose significant risks if they impact Earth. Therefore, continued research and observation are crucial for the small NEA population, where characterisation significantly lags behind discovery rates. Our program at the South African Astronomical Observatory (SAAO) utilises the robotic capabilities of the...
Over the past decade, we have picked up additional pieces of the puzzle of the formation of massive stars from high-resolution millimeter observations and high cadence maser monitoring observations. Filaments, fibre, pre-stellar core (still fair elusive but more have been detected), cold and hot cores, accretions bursts are among the pieces of the puzzle with which to reconstruct the...
From a survey of 24 star-forming regions made using the Green Bank 100m telescope with the C-band receiver in full Stokes mode, we have discovered two sources of 4.765 GHz exOH masers that display circular polarisation. Linear polarisation has previously been found in flaring 4.765 GHz exOH masers in Mon R2 IRS 3, but this is the first time that circular polarisation has been found in these...
The 4.765 GHz OH masers in Mon R2 IRS 3 region are the only 4.7 GHz OH masers to exhibit linear polarisation. Linear polarisation is not expected for this maser transition and its origin is unclear. Recent flaring of the OH masers has been monitored using both the HartRAO and Green Bank single-dish radio telescopes and imaged using the e-MERLIN array. Observations show a first detection of...
Massive stars release vast amounts of energy into the interstellar medium through their lifetime processes and supernova explosions, compressing nearby regions and triggering star formation. While triggering mechanisms have been studied on smaller scales, comprehensive analysis on a larger MilkyWay scale has been hindered by the lack of high-quality radio imaging and the limited angular...
The study of protoplanetary disks provides invaluable insights into the processes governing planetary formation and the chemistry of the early solar systems. This talk will present new data on the detection of COMs in the disk around V883 Ori. Using high-resolution spectroscopy of Atacama Large Millimeter/submillimeter Array (ALMA) Band 7 observations, we explored the spatial distribution and...
The next generation of telescopes such as the SKA and the Vera C. Rubin Observatory will produce enormous data sets, far too large for traditional analysis techniques. Machine learning has proven invaluable in handling massive data volumes and automating many tasks traditionally done by human scientists. In this talk, I will explore the use of machine learning for automating the discovery and...
Compton-thick AGN (CT AGN) are characterised by extreme dust obscuration, and limited visibility in X-ray wavelengths due to the X-ray radiation from the corona being reprocessed into near infrared wavelengths by dust and gas in the torus. New JWST surveys permit investigation of the properties of AGN and host galaxy populations in rest-frame optical between $0.5 < z < 4$; this spans the...
We investigate star formation activities in galaxy clusters by leveraging radio continuum data from the red-sequence Matched-filter Probabilistic Percolation (redMaPPer) catalogs, which encompass a redshift range of 0.06 to 0.55. These clusters serve as a robust dataset for studying the interplay between galaxy evolution and cluster environments. To achieve this, we employ a stacking analysis...
The next generation of radio telescopes, such as the Square Kilometre Array, set to become the largest radio telescope in the world, will conduct surveys generating catalogues of millions of radio galaxies. Analysing and maximising the scientific return from these enormous astronomical datasets will require the development of innovative techniques.
The 21 cm neutral hydrogen (HI) emission...
I will provide an overview of the telescopes owned, operated and hosted by the South African Astronomical Observatory, a national facility of the National Research Foundation of South Africa, at the observing site near Sutherland in the Northern Cape of South Africa. This includes the Southern African Large Telescope (SALT), 3 SAAO 1-m class telescopes and a number of international hosted...
SALT is a 10-m class optical telescope located in Sutherland, South Africa, owned by an international consortium and operated in fully queue-scheduled mode by the South African Astronomical Observatory.
In this paper we present an update on all observatory performance metrics since the start of full science operations in late 2011, including science time, weather and technical downtime, and...
The Intelligent Observatory (IO) program represents a transformative step forward in the field of astronomical research and operations, led by the South African Astronomical Observatory (SAAO). This initiative integrates advanced automation, artificial intelligence (AI), and data science into observatory operations to enhance the efficiency, accessibility, and scientific output of telescopes...
Flash is a new telescope being commissioned at the University of Cape Town to later be permanently installed at the South African Astronomical Observatory’s site in Sutherland, Northern Cape. This telescope will have two running modes, both utilizing CMOS technology to image at 1-second cadences. Survey mode will scan the full sky using SDSS filters going as deep as 17.7 magnitudes and...
The Robotic Optical Transient Search Experiment (ROTSE, http://www.rotse.net/) was a network of 4 robotic telescopes, designed to respond to alerts of transient events, particular fast transients like gamma-ray bursts. I will discuss the project to refurbish the ROTSE IIIc facility, situated at the HESS site in Namibia, which was de-commissioned in 2013. Of the 3 other ROTSE III systems, in...
Radio emission from radio loud galaxies is dominated by synchrotron radiation from their powerful radio jets. Their radio quiet counterparts lack these powerful jets hence their source of radio emission is still unclear hence several options have been proposed including; AGN winds, corona, jets and star formation. In this work, we use NGC 1068 as a representative candidate of a radio quiet...
Most (if not all) galaxies host a supermassive black hole (SMBH) in their center. These SMBHs accrete cold gas, and the viscous drag on the accretion disks produces a highly luminous source we identify as an active galactic nuclei (AGN). AGNs are some of the most luminous sources of electromagnetic radiation in the universe, as such they play an important role in the study of galaxy evolution...
Context. Active galactic nuclei (AGN) are some of the brightest sources in the Universe, emitting light at all wavelengths due to their complex structure. Deep multiwavelength extragalactic surveys are therefore important for understanding the full physics of AGN and their role in the formation and evolution of galaxies. The Lockman-SpReSO survey is one of the deepest multiwavelength...
Astrophysics traditionally deals with phenomena and objects in which quantum effects are not expected to be important or even significant – too large, too massive, too hot. Therefore, does it make sense to speak about “quantum astrophysics” as a separate discipline, and what would its key features and ideology be?
We consider a general relativistic model of a self-interacting complex scalar...
The cosmic web is the largest geometric structure in our universe, consisting of an intricate network of voids, walls, filaments, and dense nodes. $\Lambda$CDM predicts that dark matter halos, which trace this multiscale structure, form hierarchically and host smaller substructures known as subhalos. Understanding how the abundance and internal kinematics of subhalos vary across different...
We present in this study a recent analysis of the challenges surrounding the preservation of night sky quality in astronomical observatories, focusing particularly on the Oukaimeden Observatory in Morocco's Atlas Mountains. This work draws on recent research into light pollution, its impacts on astronomical observations, and mitigation strategies.
Findings reveal that increasing...
In recent decades, flux-transport-dynamo models have emerged as a promising and crucial framework for understanding the dynamics of the Sun's magnetic field and solar cycle (Choudhuri et al. (1995); Dikpati et al. (2009); Wang et al. (1991)). Their importance lies in their ability to reproduce key features of the solar cycle and provide valuable insights into the Sun's magnetic field...
This study focuses on geological mapping of young (< 20 Ma) Martian craters that are considered to be possible sources of Martian meteorites. The objective is to examine differences and similarities, taking advantage of the fresh morphologies, not affected by a long-history of post-impact processes.
Here we report preliminary results related to the geological mapping of five craters; Mojave,...
The detection of exoplanets, particularly Earth-like ones, requires achieving unparalleled contrast levels to separate faint planetary signals from the overwhelming glare of host stars. Coronagraphy remains a cornerstone of high-contrast imaging, with its performance closely tied to advancements in apodization techniques.
In this study, we focus on Interferometric Apodization by Homothety...
Neutrinos, while often considered Majorana fermions, can also behave effectively as Dirac fermions, making them candidates for pseudo-Dirac particles. This concept introduces the possibility of oscillations between active and sterile neutrinos, driven by a small mass-squared difference. This phenomenon differs from the standard oscillation scenario involving only the three active neutrino...
This study investigates the time delays (∆t) in the arrival times of photons with different frequencies from multiple Gamma-Ray Burst (GRB) events, using a novel Linear Frequency Dependent Speed of Light (LFDSL) model developed from Maxwell’s equations, dispersion effects and plasma physics. The delays are hypothesized to arise from the interaction between photons and the electrons in a...
Since the accidental discovery of the Cosmic Microwave Background (CMB) in 1964-65, detailed studies of it have allowed us to measure many of the most important properties of the Universe. Cosmic Inflation, first proposed by Alan Guth in 1980, argues that between about $10^{-36}$ and $10^{-32}~{\rm s}$ after the Big Bang the Universe underwent a period of very rapid expansion, increasing its...
In the talk I discuss a novel approach to leverage the anisotropy of the HI 21-cm signal, traditionally used to study the astrophysics of the reionization era, as a powerful diagnostic for post-reionization dark energy. These findings demonstrate that the anisotropy probe achieves a signal-to-noise ratio (SNR) of approximately 10, measurable in both auto-correlation and cross-correlation with...
Most galaxies do not evolve in isolation. Their properties are impacted by their environment. Galaxy clusters are the most massive, densest, gravitationally bound structures in the universe comprised of thousands of galaxies contained within a region of a few cubic megaparsecs. In this environment, galaxies have frequent, high-speed interactions that disrupt their outer disks. Further, as they...
Historically, radio telescopes have been used follow-up observations of transients identified in other wavelengths, such as supernovae, X-ray binaries, novae, and gamma-ray bursts. These events have traditionally been first detected in the X-ray or optical regimes before their radio counterparts were studied. However, with the advent of next-generation radio telescopes such as MeerKAT, the...