Research Specialisation: Space Physics

Title: Investigation of GICs over the African low-latitude region during varying geomagnetic storms

Abstract:

Geomagnetically induced currents (GICs) represent a significant space weather issue for power grid and pipeline infrastructure, particularly during severe geomagnetic storms. The impacts of GICs on critical infrastructure are severe in high-latitude regions due to the fact that the Earth’s magnetic field configuration is open at the poles. Thus, multiple studies have been conducted and despite understandable limitations in providing accurate warnings, research centres are in a position to offer near real-time forecasts of impacts of GICs on vulnerable infrastructures. However, not much studies has been conducted on the low-latitude regions that can be turned into early warning operational purposes to the said infrastructure, particularly in the African low-latitude regions. Ground-based magnetometer station data will be primarily used in order to investigate the severity of GICs during varying geomagnetic storms in the African low-latitude regions. Moreover, multiple solar and geomagnetic indices will also be used to supplement the investigation. Therefore, the student will employ different techniques using multiple data sources to analyse the cascading mechanisms during geomagnetic storms of varying magnitudes leading to the disturbance in magnitudes of the equatorial electro-jets (EEJ) which in turn results to GICs over African low-latitude region. It is also mandatory that the candidates have background in using Python or R programming languages.

Research Specialisation: Cosmology

Title: Evolution and day-to-day variability of night-time equatorial ionospheric plasma density irregularities

Abstract:

Post-sunset ionospheric plasma density irregularities in low latitudinal and equatorial regions are generally known as equatorial spread F (ESF). It is a post-sunset phenomena in which the F-region of the ionosphere becomes unstable as a result of Rayleigh-Taylor instability. As a result of this instability, large scale plasma bubbles develop at the bottom of F-region and arise to more than 1000 km altitudes. Although it has been studied more than eight decades since the discovery of ionospheric plasma irregularities by Booker and Wells (1938), the basic physical mechanism of how these irregularities form and their day-to-day variability remain a challenging issue. Understanding its short time characteristics and forecasting its occurrence is very important because of its impact on radio communications that degrade ground and satellite-based communications and navigation systems. In this study we will utilize data from multiple ground – based instruments including GPS and magnetometers and also satellite based measurements to study magnetically quiet and disturbed time characteristics of plasma irregularities. The study also includes developing empirical representation of ESF over the African longitudinal sector.

Contact Person: Dr Nigussie Mezgebe
Assistant Professor of Space Science at the Department of Space Science and Applications Research & Development, Ethiopian Space Science and Technology Institute (ESSTI), Ethiopia Department of Space Science and Applications Research & Development
Entoto Observatory Research Center (EORC)
Ethiopian Space Science and Technology Institute (ESSTI)
Tele: (+251) 118961050
Mobile: (+251) 944242039
P.O. Box 33679
Addis Ababa,
Ethiopia
Dr Ephrem Beshir, Associate Researcher of Space Science at the Department of Space Science and Applications Research & Development, Ethiopian Space Science and Technology Institute (ESSTI), Ethiopia

Research Specialisation: Astrophysics, AGN, Data Analysis Techniques

Title: Spectral energy distribution of bright phases of Blazar PKS 1424-418

Abstract:

The bright gamma-ray blazar PKS 1424-418 is an Active Galactic Nucleus with jet that is oriented along our line of sight. This source has shown unusual flaring activity through the whole electromagnetic spectrum in recent years. The Fermi-Large Area Telescope, a space-based gammaray detector, has detected multiple outbursts and also followed up by the Hartebeesthoek Radio Astronomy Observatory. In this project, a student will use specialized tools to analyze Fermi-Large Area Telescope data of PKS 1424-418 during its outbursts and interpret results using scientific models. Studies of the flaring pattern and variability of this source can explain the physics of the gamma-ray production and the particles in the jet that are radiating.

Requirements:

The student should be familiar with or willing to learn computer software and programming language. A background in Astrophysical object data analysis will be a plus.

Contact Person: Feraol F. Dirirsa (PhD)
Telephone: (+251) 900 645 373
Email: :ffdirirsa@gmail.com or :fana@aims-senegal.org
Addis Ababa University
College of Natural Sciences
Department of Physics
Addis Ababa,
Ethiopia

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Research Specialisation: Cosmology

Title: Effect cosmological dark matter and dark energy components at the current epoch

Abstract:

The recent observation evident that the expansion of the Universe appears to be accelerating, which has astonished cosmologists. There exist many reasonable realizations of a “dark energy” component that explain the Universe’s expansion at an accelerating rate. In the standard model of cosmology, dark energy representing more than 70% of the total energy of the Universe. There are also deep theoretical issues with most dark energy models. One such issue is the coincidence problem; among the many surprising things about the unreasonable smallness of the dark energy density in magnitude that we happen to live in the very short epoch during which the dark energy density is comparable in magnitude to the matter density. The purpose of this project is to understand the effect of dark matter and dark energy at the current epoch and its evolution during the expansion of the Universe. A student will analyze a modified Einstein equation of the Friedmann-Lemaitre-Robertson-Walker equations. Then type Ia supernovae and Quasars updated data set will be used to constrain the dark matter and dark energy parameters and investigate their effect at the current epoch.

Host Contact: Feraol F. Dirirsa (PhD)
Telephone: (+251) 900 645 373
Email: :ffdirirsa@gmail.com or :fana@aims-senegal.org
Addis Ababa University
College of Natural Sciences
Department of Physics
Addis Ababa,
Ethiopia

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Research Specialisation: Earth Observation, Atmospheric sciences

Title: Studying the equatorial ionospheric irregularities

Abstract:

Ionized particles that inhabit the Earth’s upper atmosphere vary in space and time. The spatio-temporal variations of ionospheric ion density are a threat for trans-ionospheric propagation radio wave dependent applications like navigation, positioning, and so on. The effect of equatorial ionospheric ion density irregularities after sunset is found to be the most intense and most frequent compared to high and middle latitude regions ionospheric irregularities. As observed recently using Low Earth Orbiting (LEO) Satellite in-situ data, the African equatorial ionosphere exhibited the highest and frequency occurrence of equatorial ion density irregularities which is called equatorial plasma bubble (EPB). However, the triggering mechanisms for the day-to-day and longitudinal variations of EPB are not yet fully understood. To tackle this research problem multiple ground and space-based data will be used; for example COSMIC II is a constellation of six LEO satellites launched on June 25, 2019 into low degree inclination. It is equipped with different atmospheric and ionospheric sensors. From those sensors ionospheric and atmospheric parameters such as GNSS TEC, RO electron density profiles, amplitude and phase scintillation, in-situ ion density, plasma drift velocity, neutral temperature and wind speed are being obtained; and these measurements are available for public use. In addition, GNSS observations available for public use all over the globe are useful to drive conditions of the equatorial ionosphere. These and similar observations can be used to quantify equatorial ionospheric irregularity and associated driving parameters like vertical drift velocity. Moreover, it is suggested that atmospheric gravity waves seed the occurrence of equatorial ionospheric irregularity even though its role on the day-to-day and longitudinal variations EPB is not yet well understood. Therefore, the role of atmospheric gravity waves on the occurrence EPB will be investigated using atmospheric parameters such as neutral temperature profile and wind speed observed by SABER/TIMED and COSMIC II satellites. In addition to space observations different empirical and physical model data can be used to investigate this problem. Therefore, a student in this study will investigate comprehensively the playing factors in the occurrence of low-latitude postsunset ionospheric irregularities and their evolution, under varying space weather conditions, using multiple data sources and the underlying fundamental physics.

Contact person: Nigussie Mezgebe Giday, PhD
Department of Space Science and Applications Research & Development
Entoto Observatory Research Center (EORC)
Ethiopian Space Science and Technology Institute (ESSTI)
Tele: (+251) 118961050
Mobile: (+251) 944242039
Addis Ababa, Ethiopia
P.O. Box 33679

Research Specialisation: Earth Observation, Atmospheric sciences

Title: Equatorial plasma drift velocity modeling

Abstract:

The equatorial ionosphere exhibits very complex variability that adversely affects trans-ionospheric propagation radio wave dependent applications. The equatorial ionospheric electrodynamics is believed to be the main role player for the occurrence of equatorial ionospheric irregularities. Especially, the post-sunset equatorial ionospheric irregularity which is commonly called equatorial spread F (ESF) is mainly controlled by the Pre-reversal Enhancement (PRE) vertical plasma drift velocity. Theoretical investigations have shown that the post-sunset F region zonal neutral wind speed, through ionospheric dynamo, produces PRE zonal electric field that is directly related to PRE vertical plasma drift. Other variables like the geomagnetic field strength and ionospheric conductivity affect the vertical plasma drift. To enrich our understanding about the role of the electrodynamics on the occurrence of ionospheric irregularity, plasma drift models have been developed by different studies. However, the empirical models that have been developed so far did not consider main drivers like zonal neutral wind speed as the model driver and as a result those empirical models are not able to mimic the diurnal and longitudinal variations vertical drift velocity. Therefore, the aim of this project is to develop a model that can describe the longitudinal and diurnal variations of the equatorial ionosphere plasma drift velocity using multi-data sources. Different ionospheric and thermospheric parameters such as neutral wind speed, vertical plasma drift, ionospheric conductivity, geomagnetic field strength, and deviations between solar terminator and geomagnetic field line will be used in this model development. Therefore, a candidate must have an excellent background in modeling physical processes and processing Low Earth orbiting satellite and ground based ionospheric and thermospheric data using Python or R programming language.

Contact person: Nigussie Mezgebe Giday, PhD Department of Space Science and Applications Research & Development
Entoto Observatory Research Center (EORC)
Ethiopian Space Science and Technology Institute (ESSTI)
Tele: (+251) 118961050
Mobile: (+251) 944242039
Addis Ababa, Ethiopia
P.O. Box 33679

Research Specialisation: Astrophysics, Cosmology, GRB, Data Analysis Techniques

Title: Fermi Gamma-ray Space Telescope modeling of Short Gamma-Ray Bursts

Abstract:

Gamma-ray burst is one of the most powerful astronomical events emitting a large amount of energy in gamma-ray photons within a short period of time and is related to the binary merger of compact objects. This can be produced by the accretion disk around the inner engine but the nature of the central engine and the composition of the jet are still unanswered questions. Fermi gamma-ray space telescope is a NASA satellite, surveys the sky and detects gamma rays from a variety of sources, including gamma-ray bursts. By detecting gamma-ray bursts researchers can know about the physics and astrophysics of these power sources, such as source environment, emission mechanism, and cosmology of a short gamma-ray burst. In this project, a student will use specialized science tools to analyze gamma-ray data from Fermi and interpret results using spectral models of gammaray bursts. Besides, the project will consist of modeling the synchrotron and synchrotron self-Compton emission in a multi‐wavelengths and multi‐messengers approach from optical to high-energy emission.

Requirements:

The student should be familiar with or willing to learn computer software and programming language. A background in Astrophysical object data analysis will be a plus.

Host Contact: Feraol F. Dirirsa (PhD)
Telephone: (+251) 900 645 373
Email: :ffdirirsa@gmail.com or :fana@aims-senegal.org
Addis Ababa University
College of Natural Sciences
Department of Physics
Addis Ababa,
Ethiopia

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Research Specialisation: Cosmology

Title: A Comparative Analysis of Galaxy Number Count and Cosmic Magnification as Cosmological Probes

Abstract:

As we enter the era of precision cosmology, where surveys will have unprecedented measurement ability, observational data will hold unmatched power for testing theoretical ideas. This presents a strong opportunity for innovative work. For example, it will be possible to develop a novel framework to answer the crucial question: Which is a better cosmological probe: galaxy number count or cosmic magnification? It is important to answer thi question since, in order to realise the full potential of the forthcoming precise observational data, we need to employ only the right, most effective and/or efficient analytical tools (the cosmological observables). The galaxy number count has been widely used in cosmology to hunt down the signatures of dark energy and modified gravity in the large-scale structure. However, most of the theoretical models appear degenerate by this approach. A recent work suggest that the cosmic magnification holds the potential to distinguish, specifically, models of interacting dark energy. This needs to be investigated further. In this work we will build on this effort and extend it to standard, non-interacting dark energy theories and alternative theories of gravity.

We will compare the results with a corresponding rigorous analysis using the galaxy number counts. We will provide a comprehensive investigation of the effectiveness of both the galaxy number count and the cosmic magnification as cosmological probes of models of the late-time cosmic accelerated expansion. Method: This project will involve mainly analytical calculations and computer programming in python. Given the allowed duration for this project (6 months), the potential student is expected to have good background in cosmology or astrophysics, and a substantial experience with python. The candidate needs to be hardworking. Potential output: A minimum of one research publication in an international journal is expected from this project.

Contact Person: Dr. Adams Duniya
duniyaa@biust.ac.bw
Department of physics and Astronomy
Botswana International University of Science and Technology (BIUST)
Private Mail Bag 16, Palapye
BOTSWANA

Research Specialisation: Planetary Science and astrobiology

Title: The astrobiological potential of the Makgadikgadi pans (Botswana)

Abstract:

The Makgadikgadi, Botswana, is the largest inland evaporitic basin in the world covering 16,000 km2. The basin comprises myriads of small evaporitic lakes and three larger pans, Ntwetwe, Sua and Nxai. Water and brines within the pans provide broad spectra of compositions have varying compositions: from Ca, Na and K dominated brines. The surface of the pan is dry for 8 months, from April to November, and is characterized by precipitation of layers of authigenic clays and evaporites such as gypsum, halite and potash. The halophilic environment harbours thriving microbial communities of extremophiles and fungi and includes unique niches ideal for testing new hypothesis on the resilience of life that can lead to breakthroughs in exobiological studies. Understanding functional metagenomics of the saltpans will potentially provide valuable information on the molecular adaptation and resistance to extreme environmental conditions.

The huge surface area provides environments that vary from playa lakes with ephemeral springs to the fossil dunes fields with direct analogies to Mars morphologies. The Makgadikgadi is fed by surface runoff and by groundwater upwelling that give rise to flood channels, ephemeral springs and layered morphologies. These peculiar layered morphologies are easily identified from remote sensing and are comparable to those observed in the equatorial region of Mars. The cyclical seasonal rise of water table leads to the formation of evaporite deposits comparable with the playa deposits found in Meridiani Planum and other regions on Mars with chloride and sulphate deposits. The Makgadikgadi pans represent an unparalleled example of the overlap of groundwater and wind activity paving the way for experiment aimed at testing existing hypothesis of Martian hydrogeology of Mars. The main goals of this project would be to: i) perform a microstratigraphic study of the pan sediments to provide a geological and sedimentological framework to further studies; ii) perform radiocarbon dating measures to further constraint the age of the pan deposits; iii) study the presence of organominerals and the extent of the interactions between the extremophiles living in the pan and the authigenic minerals formed at the pan surface and in the subsurface. This project will include a strong field work component and analytical phase including Raman spectroscopy, SEM-EDX and cathodoluminescence.

Contact Person: Dr. Fulvio Franchi
franchif@biust.ac.bw
Department of Earth and Environmental Sciences
Botswana International University of Science and Technology (BIUST)
Private Mail Bag 16, Palapye
BOTSWANA

Research Specialisation: Remote sensing and earth observation

Title: Dynamics of Surface Water Quality Derived from Satellite Remote Sensing: Insights from water quality contrasts of Lake Tana in Ethiopia and Okavango Delta in Botswana

Abstract:

Water quality refers to the chemical, physical, biological, and radiological characteristics of water. Surface Water quality indexes include physical, chemical, and biological properties These indexes are conventionally ascertained by in-situ measurements. For large area of water body, in-situ measurements are a labour intensive and time-consuming process. Moreover, the accuracy and precision of in-situ data can be questionable due to both asynoptic field sampling and laboratory errors. As a result, it is not viable to provide a simultaneous surface water quality fluctuation database on a regional scale that represent point estimations of the surface water conditions in time and space. Obtaining spatial and temporal variations of quality indices in large water body sampling is almost impossible under these conditions. Therefore, these difficulties of successive and integrated sampling become a significant obstacle to the monitoring and management of the dynamics of surface water quality.

However, with advent of space borne remote sensing techniques, it has become possible to monitor and identify large scale regions and water bodies that suffer from water quality problems in a more effective and efficient manner. Using remote sensing, water bodies can be monitored using the interaction of its optically active constituents with light and the change in reflected energy spectrum. Other properties of water which is optically inactive include acidity, and pathogens, which have no directly detectable signals, but may be interpretable and inferable from those detectable water quality parameters with which strong correlations can be found. Many researchers frequently use the visible and near infrared bands of the solar spectrum (mostly from blue to near infrared region) in their investigations to obtain robust correlations between water column reflection and physical and biogeochemical constituents, such as transparency, chlorophyll concentration (phytoplankton), organic matters and mineral suspended sediments in different water bodies.

Lake Tana is located outside the Rift Valley on the north-western plateau of Ethiopia and it is the largest water bodies in Ethiopia. In the Lake Tana watershed, four major rivers contribute about 93% of the stream flow into the lake. Among the largest tributary river, Gilgel Abay contributes 50% of the streamflow followed by Gumara 32%, Ribb 12%, and Megech 6%. The local and regional ground water in flows contribute only 3% and 7%, respectively. The lake is geologically dammed by quaternary and tertiary basalts in the south and western part where the out flowing Blue Nile River drains out. The damming has cut off any oozing out flow which simplifies modeling of the lake stage. Lake Tana has rich natural resources and great potential for the development of irrigation, hydroelectric power, high value crops, aquatic products, livestock products, and ecological tourism. But currently the lake is endangered by heavy sediment loads, eutrophication, invasive weed (e.g., water hyacinth) and heavy metals thereby degrading its surface water. Moreover, the water quality and quantity have been deteriorating due to rapid population growth, soil erosion, sedimentation and eutrophication by organic and inorganic fertilizers from agriculture. The quick loss of vegetative cover and land use change due to recent agricultural intensification could have also attributed to recent increases in sedimentation and biodiversity degradation in the lake.

In contrast, the Okavango Delta is believed to be pristine until recent past. The delta is known for its shallow valleys, meandering channels, oxbow lakes and grassy floodplains that sustain a fragile and complex ecosystem. The annual water inflow in the basin is in the range from 3120 Mm3, during the dry season, to 10,900 Mm3, during wet season. Approximately 95% of the water inflow into the basin is from the Angolan (upper) catchment. In the Delta, about 98% of all water is lost by evapotranspiration. The effects of climate changes and human activities on the water quantity and quality of the Okavango Delta are still poorly understood and there is, to date, no comprehensive report on the resilience of the system to hydroclimatic extremes.

This study aims to provide comprehensive and robust relationship between environmental factors and some of the major water quality indicators such as chlorophyll-a (chl-a), colored dissolved organic matters (CDOM), Secchi disk depth (SDD), turbidity, total suspended sediments (TSS), and total phosphorus (TP) for the two contrasting water bodies based on analysis of satellite imageries that cover longer period in order to determine (i) change in the land cover/land use around the two water bodies; (ii) water quality dynamics over a period of 18 years (2002-2019); and (iii) obtain insights from similarities and contrasts in the dynamics of water quality that might be useful for intervention measures and policies.

Research Specialisation: Observational astrophysics and instrumentation – site selection

Title: Survey and characterisation of potential observatory sites in Zambia

Abstract:

Zambia is centrally located and has great potential to complement sky surveys that, at present, are mostly done in the southern and northern parts of the continent. This is largely because there are no telescopes installed in Zambia in particular and Central Africa in general and that potential sites to host any such telescopes have not been sited save for the SKA site in Kasempa and the AVN site in Mwembeshi. This project aims to survey potential sites for hosting future telescope projects and carry out preliminary site characterisation for areas that will show potential for both optical and radio telescope observatories. The project will involve travelling to different places across Zambia, including mostly the remote places.

Contact Person: Prospery Simpemba
pcs200800@gmail.com
Copperbelt University
Department of Physics
School of Mathematics and Natural Sciences
P.O Box 21692
Kitwe, Zambia

Phone: +260 21 2290945
Mobile: +260977704168 (WhatsApp)
Skype ID: simpemba

Research Specialisation: Theoretical Astrophysics

Title: Investigation into the Origins of the Titius-Bode Law Using Exoplanetary Data

Abstract

The Titius-Bode Law (TBL) is an empirical relation giving the placement of a planet from its host-star. In the advent of exoplanets, this relation has been tested by a number of authors and found to work. The shortcoming however is that there are two free parameters which are specific to the system under consideration and in-order to know what these parameters are, one has to first measure them. What this means is that the TBL is not only grossly limited but handicapped insofar as its predictive power is concerned. The reason for this is that the origins of the TBL are not known hence the free-parameters. In our recent works which are not yet published, it has been shown that these gap in the free-parameters can be closed. What is needed is to carry out field-wide study of explanets from the currently available data whereby a rigous statistical analysis is carried out in-order to strengthen the preliminary results that we have.

Contact Person: Dr. Golden Gadzirai Nyambuya
gadzirai@gmail.com Copperbelt University
Department of Physics
School of Mathematics and Natural Sciences
P.O Box 21692
Kitwe, Zambia

Phone: +260 21 2290945
Email: gadzirai@gmail.com
Mobile: +260 969269213 (WhatsApp)
Research Specialisation : Cosmology Title: Investigation into the Mass of the Photon Using Gamma-Ray Burst Time Delays Abstract: Abstract Gamma-Ray Burst (GRB) events are one of the most energetic events in the Universe. In these events, it has been observed that photons of different frequencies emanating from these events arrive at the Earth based telescope at different times. This has given rise to the phenomenon known as “Time Delays in the Arrival Times of GRB Photons of Different Frequency”. The mundane assumption in prevalent and contemporary physics is that these time delays are a result of the Photon being endowed with a non-zero mass. In this project, while the Photon is assumed to be massive, the time delay is not attributed to the mass-effect but to the cosmic medium being a rarefield plasma and this plasma has a dispersive effect on the propagating Photon. This view we have arrived at from preliminary results on 9 GRBs which have given an excellent picture that this may very well be the case that the . In this project, the student is expected to make a wide survey of the GRB database and search for this signature of a rarefied cosmic plasma. Contact person Dr. Golden Gadzirai Nyambuya Copperbelt University Department of Physics School of Mathematics and Natural Sciences P.O Box 21692 Kitwe, Zambia Phone: +260 21 2290945 Email: gadzirai@gmail.com Mobile: +260 969269213 (WhatsApp)

Research Specialization: Astrophysics, Pulsars

Title: Pulsar glitch activity parameter and its effect on magnitude of neutron star inner crust

Abstract

Spinning neutron stars, known as pulsars, provide specimens where matter exists in extraordinary conditions not found here on earth. Understanding the dynamics of their interior is of utmost importance to scientists as it presents a picture of how matter in degenerate state interacts. The interior of neutron star is mostly enriched with degenerate neutrons in form of superfluid. Based on current understanding of neutron star structure, this superfluid is located in the inner crust and the core of the neutron star. An impulsive dynamic anomaly in the spin evolution of neutron stars known as pulsar glitch is considered as the most striking manifestation of the existence of a neutron superfluid in the inner crust that rotates independently. However, due to a trigger mechanism that is yet to be well understood, this independently rotating superfluid can suddenly transfer angular momentum to the rest of the neutron star components resulting in the sudden spin-up of the crust – the glitch. Glitch behaviors in pulsar are mainly studied through the glitch sizes and the inter-glitch time intervals. The behavior can be very different from pulsar to pulsar and from event to event. Pulsar researchers rely on the glitch behavior to extract some information about the structure of neutron star. One of such behaviors of interest is the pulsar glitch phenomenon. Pulsar glitch activity parameter, which is the mean fractional change in pulsar spin frequency per year due to glitch, is being used to constrain the magnitude of the neutron star inner crust. The usual way to calculate the glitch activity parameter is a linear regression of the cumulative glitch sizes with respect to the cumulative inter-glitch time intervals. This approach certainly underestimates the errors on the activity parameter. This is largely because this approach assumes a linear dependence of glitch sizes on the inter-glitch time intervals, as well as equal variance in the fit residuals. In reality, both assumptions are not in line with glitch data. When the glitch activity parameter obtained in this approach is used to constrain the magnitude of the inner crust, results which are in conflict with theoretical predictions are usually obtained.

In this project, the usual ways of calculating the glitch activity parameter is to be reviewed, a model for proper quantification of the errors involved shall be developed. In addition, Equations-of-State governing the neutron star structure is to be constrained by the improved glitch activity results.

Contact Person: Augustine Chukwude (Ph.D)
augustine.chukwude@unn.edu.ng
Department of Physics and Astronomy
University of Nigeria Nsukka
Enugu State
Nigeria

Research Specialization: Astrophysics, Star formation

Title: Star formation and AGN activities in nearby star-forming HII galaxies

Abstract

Galaxy formation and evolution involves complex physical processes and understanding how galaxies evolve through cosmic time remains a fundamental question in astrophysical research. Star-formation (SF), one of the most important processes is fundamental to the formation and evolution of galaxies. A measure of the rate of star formation, along with other properties of a galaxy such as the stellar mass, are obtained through fitting SED (spectral energy distribution) models to multi-wavelength spectrophotometric observational data of the galaxy. This allows for SFR calibrations of luminosities at various wavelengths. The Hα emission line stands out as the best tracer of SF coming from HII regions ionised by massive stars. However such line can also arise from these same massive stars heated by Active Galactic Nuclei (AGN), hence SFR calibrations based on Hα line can be overestimated by the presence of an AGN if the AGN’s contribution is not taken into account. In this project, our goal is to study the effect of AGN on the SFR of it’s host galaxy. We will use the python-based code, CIGALE (Code Investigating GALaxy Emission), a state-of-the-art galaxy SED-fitting model relying on energy balance, to compute the contribution of an AGN in a self consistent manner in estimating the SFR of a statistical significant sample of nearby star forming galaxies. This will be followed by a comparative analysis of the AGN contributions obtained from other independent methods such as line ratio diagnostic diagrams as well as that obtained with other SED-fitting models. Correlations between the AGN Xray luminosity and SFR will be searched for. The analytical component of the project will also involve some level of computing/modelling.

Contact Person: Dr. Iyke A. Obi
tonykassidy_z@yahoo.com
NASRDA-Centre for Basic Space Sciences
University of Nigeria Nsukka
Enugu State
Nigeria

Research Specialization: Astrophysics, Observational, Instrumentation

Title: A Portable Pulsar Detection Radio Telescope operating at 608 – 611 MHz: Design, Construction and Performance

Abstract

Pulsar signals are relatively weak and detected with a very sensitive receiver, at least when compared to that used to detect other radio sources. The first pulsar PSR J1919+21 was discovered by Jocelyn Bell in 1967 with a 16,000 m 2 array of 2000 dipoles tuned to 81.5 M Hz. With the recent introduction of the Software Defined Receivers (SDR) and availability of high performance PCs, this same observation can be carried out today with a relatively small antenna of no more than 2m2 and consisting of no more than 35 dipole elements, However, the detection of pulsar will NOT be in real time as done in professional radio telescopes but the approach is to record the signal and use modern specialised techniques of digital signal processing to increase the Signal-to-Noise Ratio (SNR) and be able to detect the pulses. This project will basically involve the design and construction of a small portable radio telescope (along with its frontends and backends) with processing software capable of collecting sufficient data over a 4 to 6 hour time-frame to detect the brightest pulsars in the northern and southern hemispheres, PSR B0329+54 and PSR B0833-45, in the frequency band 608-611 M Hz.

Briefly, the front-end system will comprise a 2.5 m long 17-element Yagi which will be designed (using the YagiCAD software) and constructed by the student, a 5-element interdigital mechanical filter that will be also designed and constructed, ultra-low noise amplifiers, power dividers and bias tees that will be acquired from reputable radio astronomy equipments manufacturers. For the back-end components, a number of SDRs with at least a bandwidth of 2 MHz and precise internal clocks will be used as the receiver, a PC running Linux will be used for data acquisition and analysis.

Data acquisition softwares will be based on the GNU Radio Consortium while data analysis and validation will be done using PRESTO (PulsaR Exploration and Search TOolkit), a C and python based analysis software primarily designed to efficiently search for binary millisecond pulsars from long observations. This project will serve as a basis for subsequent ones which will be aim at detecting less brighter pulsars by improving the overall system temperature.

Contact Person: Dr. Iyke A. Obi
tonykassidy_z@yahoo.com
NASRDA-Centre for Basic Space Sciences
University of Nigeria Nsukka
Enugu State
Nigeria

Research Specialization: High Energy Astrophysics

Title: A Study of the Mechanism for the X-rays Emission from Symbiotic Stars

Abstract

Symbiotic stars (SySts) are particularly interesting as they are a possible progenitors of Type Ia supernovae, which are themselves used as ‘standard candles’ for cosmological studies. Despite this use, the class themselves cover a broad range of systems, typically identified in the optical, where they are often bright. The X-ray emission is often quite soft (i.e. low energy), and many systems may be undetected due to absorption of the X-rays by the Galactic interstellar medium. In the case of a white dwarfs as a primary, the secondary can be either a red giant or an asymptotic giant branch (AGB) star, and they are categorized as white dwarf (WD) symbiotic, whereas in the case of a neutron star as a primary, the secondary can be either a giant, AGB star, or a supergiant, and they are categorized as symbiotic X-ray binaries. Efforts are currently ongoing to unravel the uncertainty associated with the origin of the X-ray emission from Symbiotic Stars (SySts), a broad class composed of interacting, binary systems formed from a red giant or a supergiant, which transfers matter to a much hotter companion, either a white dwarf (WD) or neutron star. A century ago Merril 1919, identified the first such system in the odd variable star, R Aqr, which appeared to have an optical spectrum typical of an M dwarf but with bright [O III] lines, a higher ionization state expected from a cool star. Decades later SySts were detected in X-rays, but this has not simplified the situation. Researchers have divergent views on the origin of the X-rays emission, resulting in classifications of X-ray emitting SySts as follows: (a) the supersoft X-ray sources with energies ≤0.4 KeV, likely emitted directly from the white dwarf α-type, (b) soft X-ray objects that exhibit a peak at 0.8 keV and maximum energies up to 2.4 KeV, likely originating from a hot, shocked gas where the stellar winds collide β-type, (c) objects with a non-thermal emission and energies higher than 2.4 KeV γ-type,due to the accretion of mass onto a neutron star, and (d) those with very hard X-ray emission (>10 KeV) the δ-type, assumed to be emitted from the boundary layer of the accretion disk and the accreting hot companion. In many cases, however, the precise mechanism and physics responsible for the production of X-ray emission remains uncertain, in part because their distances are poorly estimated or not available. We propose to use newly-available data on the distances of X-ray emitting SySts from ESA’s Gaia mission combined with archival X-ray data from the Chandra, XMM-Newton, and Swift satellites to determine the true X-ray luminosities and spectra of SySts. We will then correlate this data with the different proposed types to search for a better understanding of the physics and origin of these unusual systems.

The main objective of this project is re-analyze all of the existing Chandra, XMM-Newton, and Swift X-ray observations of SySts with known Gaia distances to search for correlations between the different types SySts, with intention of getting a clearer understanding of the mechanism for the X-rays emission from these perculiar sources. Specifically, the research will focus on answering such questions like: (i) how does the hot component accrete matter from the secondary star? (ii) what is the physical nature of the accretion flow in SySts? and (iii) how are the X-rays (soft and hard) produced? A major component of this project is the re-analysis of all of the existing Chandra, XMM-Newton, and Swift X-ray observations of SySts with known Gaia distances using the latest Chandra CIAO and software from the other missions.

Contact Person: Prof. Romanus Eze
romanus.eze@unn.edu.ng
Department of Physics and Astronomy
University of Nigeria Nsukka
Enugu State
Nigeria

Title: Multi-wavelength Study of Active Galactic Nuclei across Cosmic Time

Abstract

Galaxies are the fundamental building blocks of the universe and massive galaxies are known to be active due to intense accretion of matter onto a supermassive blackhole at the centre of the galaxy. It is widely believed that the energetic output of radio-loud active galactic nuclei (AGN), which launch powerful relativistic jets of material, plays a significant role in controlling star formation in their surrounding galaxies. This PhD project is designed to address some of the existing gaps in our knowledge of the physical processes that drive radio-loud AGN activity and how these physical processes evolve across cosmic time. This research will be possible through the vast samples of radio-loud AGN being generated in various surveys at radio, optical, X-ray and γ-ray frequencies. The research will focus on developing some theoretical framework for modelling and statistical interpretation of the observed data for both high- and low-redshift AGN.

Specifically, the project will employ multi-wavelength data that are readily available in public archives to investigate the accretion/emission properties of AGN over a wide range of redshift. Special attention will be paid to similarities and/or systematic differences in the data, which could be interpreted in the context of the evolutionary scenario.

Contact Person: Dr Finbarr C Odo
finbarr.odo@unn.edu.ng
Department of Physics and Astronomy
University of Nigeria Nsukka
Enugu State
Nigeria

Title: Estimating Groundwater Storage Changes in the Western Cape using satellite data and machine learning

Abstract

Access to sufficient quantities of clean water for drinking, farming and sanitation is a fundamental human need. As the largest continental landmass straddling the Equator, Africa is predicted to be most at risk from climate change driven by increasing temperatures. This vulnerability is exacerbated by high poverty levels and a strong dependence not only on subsistence farming, but also rapid urbanisation (that will see Lagos, Nigeria becoming the largest city in the world by 2100) and growth of informal settlements lacking basic infrastructure. It is clear that groundwater resources will play an increasingly important role in Africa’s future. In South Africa in 2018, the Western Cape had experienced 3 years of drought and South Africa’s 3rd largest city Cape Town was on the brink of a complete water shutdown (“Day Zero”), despite stringent mitigation measures. Catastrophe was averted by good rains later in 2018; however, the neighbouring Eastern Province is now in the grip of a similar situation. In times of drought, groundwater can provide a much needed alternative; however, more research is needed to understand groundwater storage changes within the country.

One way in which storage changes can be quantified is through satellite data. The GRACE (Gravity Recovery and Climate Experiment) mission was launched in 2002 by NASA and DLR of German as part of the international Earth Observing System of satellites. The mission was made up of 2 identical satellites that mapped the Earth’s gravity field until 2017.

Because the GRACE satellites recorded from 2002 to 2017, it is possible to investigate changes in the Earth’s gravity field over time, such as changes due to groundwater variation. This project will use GRACE satellite gravity data in conjunction with machine learning to understand this change in groundwater storage over time in the Western Cape. This will be compared with ground measurements. Machine learning will also be used to investigate the impact climate change will have on storage changes going forward.

In this project, the near surface that hosts aquifers will be characterised using ESA’s Swarm (magnetic) and SMOS (soil moisture and ocean salinity) satellite data. The Swarm satellites were launched in 2013 by the European Space Agency and will continue until 2021. The 3 satellites host a variety of instruments, including magnetometers to map lithospheric magnetic sources. While the SMOS mission launched in 2009 and also continuing until 2021, has mapped variation in soil moisture levels using microwave L-band measurements, which have been used to create of climate change models.

The ultimate aim of this project will be to influence policy making around climate change and sustainable development in South Africa.

Requirements: Experience in geophysics and programming. Additional background in hydrogeology is beneficial.

Contact Person: Stephanie Enslin
stephanie.scheiber@wits.ac.za
School of Geoscience,
University of the Witwatersrand
South Africa

Title: Charactering antenna configuration performance in the transition from MeerKAT to the Square Kilometre Array

Abstract

One of the great advantages of building a radio interferometer is that once a small sub-set of the total number of antennas have been built, astronomical observations can begin in parallel with the continued construction of the full array. This was the case with MeerKAT, with first science observations beginning with just 16 of the final 64 antennas. The same will be true of MeerKAT’s transition into the expanded MeerKAT+ array, which will see 20 SKA1-mid 15-metre antennas added to the existing 13.5-metre MeerKAT antennas in the first half of this decade. In the second half of the decade, the array will be expanded to a total of 197 antennas to make up the SKA mid-frequency array. Decisions on the optimal deployment and commissioning of antennas will have practical, financial, and scientific optimisation constraints. This PhD project will explore aspects of those tradeoffs using sophisticated interferometric simulation software. The software will produce synthetic data products that closely mimic those achievable with a suite of possible sub-sets of antennas in the transition from MeerKAT to MeerKAT+ to SKA1-mid. The supervisors of this group played an instrumental part in the optimisation of the MeerKAT+ antenna configuration and final design selection. The software and methodology they developed to do so will be used and enhanced in this PhD project in order to make informed, optimal decisions of the array expansion, including array performance metrics such as imaging fidelity and dynamic range using realistic sky models and instrument models (e.g. primary beams, polarisation leakage). The simulations will also include enhancements possible with prospective African VLBI stations, and explore performance metrics of sub-array of the MeerKAT, MeerKAT+ and SKA1-mid in this regard.

Contact Person: Prof Roger Deane
roger.deane@wits.ac.za
Wits Centre for Astrophysics
University of the Witwatersrand
Johannesburg
South Africa

Project 3

Title: Modelling the detection of hadronic acceleration in starburst/Seyfert galaxies with next-generation multi-messenger observatories

Abstract

Cosmic-ray, neutrino, and gravitational wave detectors have ushered in the golden age of multi-messenger astrophysics. Both ultra-high energy cosmic ray (UHECR) detectors and neutrino detectors have begun to detect significant anisotropies in their angular distribution. In the case of the Pierre Auger cosmic ray observatory and the IceCube neutrino observatory, the highest significance positions in the northern sky, while below the threshold for being considered a detection, are coincident with galaxies that display both starburst (high star formation) and AGN-driven (Seyferts, evidence for jets) activity; NGC 4945 in the case of Auger, and NGC 1068 in the case of IceCube. Both UHECRs and neutrinos can be considered evidence of acceleration of protons, which can occur through both starburst and AGN-driven processes.

Wits is a member of both the next generation very high-energy gamma-ray telescope, the Cherenkov Telescope Array (CTA) consortium, and a next-generation neutrino observatory, KM3NeT. Taking advantage of the accumulated experience in multiwavelength and multi-messenger astrophysics and access to CTA and KM3Net development, this PhD project will be to develop models of hadronic emission in starburst/Seyfert galaxies to determine a) whether they can explain the UHECR and neutrino observations and b) whether they will produce detectable emission in next-generation instruments, including CTA and KM3NeT.

Contact Person: Prof Andrew Chen
andrew.chen@wits.ac.za
Abstract

The Astronomical Plate Archive of the South African Sky, comprising dozens of historically important photographic plates taken at the Johannesburg Observatory dating back to 1909, is now based in the School of Physics at Wits. In order to maximise the potential of this invaluable data archive for scientific research, the contents of the plates must be digitised and rendered into a modern, open data format accessible to scientists worldwide.

Wits has begun the process of producing calibrated digital photographs of the plates and digitising the contents of the associated log books. What is needed is an automated process that can transform the digitised contents of the plates and log books into data formatted with astronomically relevant metadata and images compatible with resources such as the Virtual Observatory and other scientific open access databases. This MSc project will be to research the appropriate data format and algorithms and to develop and deploy the automated proces that will transform the raw data of the digitised plate archive into a valuable and globally accessible resource for astronomical research.

Contact Person: Prof Andrew Chen
andrew.chen@wits.ac.za
Wits Centre for Astrophysics
University of the Witwatersrand
Johannesburg
South Africa