Astronomy and Astrophysics
We focus on connecting fundamental physics with astronomical observations to understand the fundamental laws of the Universe, and to unravel the nature of dark matter and dark energy. In particular, our active research directions include the epoch of reionization, extragalactic astronomy, the early Universe, dark matter indirect detection, neutron stars and black holes. We heavily involve in South Africa’s MeerKAT, Square Kilometre Array (SKA), Hydrogen Epoch of Reionization Array (HERA) telescopes, LSST (Vera C. Rubin Observatory), FAST telescope and CMB Stage-4, and also use data from Atacama Cosmology Telescope, South Pole Telescope, ESO’s Kilo-Degree Survey (KiDS), and Dark Energy Survey Instrument (DESI).
Research
Research Interests
- Radio Astronomy: Epoch of Reionization, Dark Matter search in radio wavelength, Pulsar Timing Array, 21-cm Intensity Mapping
- Extragalactic Astronomy: galaxy peculiar velocity field, thermal and kinetic Sunyaev-Zel’dovich effect, dynamics of local group, near-field cosmology
- Theoretical Cosmology: the cosmic microwave background radiation, observational tests of inflation, gravity theories
Current Collaboration Projects
- Hydrogen Epoch Reionization Array (HERA): Calibration and power spectra analysis
- Square Kilometer Array (SKA) team: EoR, HI, Cosmology Science working groups
- Rubin Observatory (LSST) science team
- CMB Stage-4 Survey
Institutional Collaboration
The Kapetyn Astronomical Institute, University of Groningen, Netherlands
Collaborators
- Prof Rene Breton, The University of Manchester
- Prof Xuelei Chen, National Astronomical Observatory, China
- Prof Clive Dickinson, The University of Manchester
- Prof Yu Gao, Institute of High Energy Physics
- Prof Hongjian He, Shanghai JiaoTong University
- Prof Di Li, National Astronomical Observatory, China
- Prof Douglas Scott, University of British Columbia
- Prof Aaron Parsons, University of California at Berkeley
- Prof Denis Tramonte, Xian-JiaoTong Liverpool University
- Prof Ludovic Van Waerbeke, University of British Columbia
- Prof Amanda Weltman, University of Cape Town
- Prof Qiang Yuan, Purple Mountain Observatory
Research group
Media gallery
We are involved in the US-SA collaboration project “Hydrogen Epoch Reionization Array” (HERA) which measures the high-redshift 21-cm signal with radio interferometry technique.
The cosmic evolution of 13.7 billion years is the major research objective of our research.
We utilise the Cosmic microwave background radiation (CMB) from Planck and CMB-S4 to understand the initial condition of the Universe.
We are involved in the MeerKAT and Square Kilometre Array (SKA) project.
Inaugural lectures
Media coverage
CGTN interview of Prof Yin-Zhe Ma at the 183rd Nobel Symposium Outreach Talk in the University of the Western Cape in October 2022.
Searching for Axion Dark Matter —NITheCS Seminar.
Documentary movie “Echoes of the Skies” for South Africa’s SKA project
NItheCS Seminar on viscous dark matter by Dr. Anslyn John
Recent research highlights
Examination of cosmic-ray electrons with solar gamma rays
TeV-range cosmic ray electrons and positrons (CREs) have been directly observed in quests to uncover new physics or unidentified astrophysical origins. These CREs possess the capability to elevate solar photons’ energies into gamma ray ranges through inverse-Compton scattering. In Yang et al. (2023), we investigate the prospective augmentation of the inverse Compton emission spectrum due to a potential surplus of CREs. The diagram illustrates the plausible signal (depicted by residual black lines) within the solar gamma ray spectrum incorporating the CRE surplus. This surplus signal can be examined through extensive observations utilizing water Cherenkov telescopes.
Detection of the Integrated Sachs-Wolfe effect (ISW) and thermal Sunyaev-Zeldovich effect cross-correlations
The Integrated Sachs-Wolfe (ISW) effect refers to the redshift or blueshift experienced by cosmic microwave background photons due to the evolving gravitational potential, which, in principle, is correlated with thermal gas on large scales. In Ibitoye et al. (2024), we successfully detected this phenomenon using Planck data with a confidence level of 3.6 sigma. The left panel illustrates the real SZ-ISW correlated power spectrum alongside 100 simulations represented by colored curves, while the right panel displays the signal-to-noise ratio of the genuine SZ-ISW correlation compared to the 100 simulations. Additionally, we employed the cross-correlation power spectrum, as well as tSZ and ISW auto-spectra, to constrain cosmological parameters, yielding intriguing results concerning parameters such as H_0 and S_8. For further elaboration, interested readers are encouraged to consult Ibitoye et al. (2024).
Cosmic web’s contribution to FRB’s dispersion measure (DM)
In Walker et al. (2024), we utilized the cosmological simulation “IllustrisTNG” to investigate the dispersion measures (DMs) of fast radio bursts (FRBs) accumulated as they traverse various types of large-scale structure (LSS). Along randomly selected sightlines, we pinpointed halos, filaments, voids, and collapsed structures and computed their respective contributions to DM. As depicted in the right panel, our analysis revealed that filamentary structures predominantly contribute to DM, increasing from approximately 71% to about 80% on average for FRBs for redshift range [0.1, 5]. Conversely, the contribution from halos decreases, while the contribution from voids remains relatively constant, fluctuating within approximately 1%. The primary source of DM variability among sightlines stems from halo and filamentary environments, suggesting that sightlines traversing voids exclusively could serve as more accurate probes for cosmological parameters.
Acknowledgements
Career and study opportunities
One Postdoctoral Fellow For 2025-2027
Astrophysics Research Group, Stellenbosch University
DEADLINE: 30th April 2025
The Astrophysics Research Group within the Department of Physics at Stellenbosch University invites applications for a postdoctoral fellowship, commencing in June 2025 or shortly thereafter. Established in 2023, the group comprises approximately 20 full-time researchers and is engaged in cutting-edge investigations across astrophysics and cosmology. Key research areas include the epoch of reionization, cosmic microwave background (CMB) studies, galaxy surveys and large-scale structures, neutron stars and black holes, and the indirect detection of dark matter.
The group plays a central role in South Africa’s MeerKAT telescope, the MeerKAT Extended Array, and the Hydrogen Epoch of Reionization Array (HERA). It also maintains formal collaborations with international projects such as the LSST (Vera C. Rubin Observatory), the SKA Science Working Groups, FAST, and the CMB Stage-4 survey in the United States. Additionally, the group has established a strategic partnership with the Kapteyn Astronomical Institute at Groningen University, with seven jointly supervised PhD students starting in 2025. Further collaborations extend to Stellenbosch University’s Faculty of Engineering and the School for Data Science, leveraging expertise in radio antenna technology and advanced big-data analytics. More details are available at: https://www.su.ac.za/en/faculties/science/department/physics/astro
Given the group’s involvement in these experiments, preference for this fellowship will be given to candidates with experience in any of the following areas: low-frequency radio data analysis, pulsar-timing arrays, CMB data analysis, galaxy surveys, or weak gravitational lensing.
BURSARY VALUES and DURATION: The fellowship is ZAR 320 000 (tax-free) per annum for two year (24 months), supplemented with a once-off relocation coverage, a once-off equipment grant and a limited travel allowance.
MINIMUM REQUIREMENTS: Ph.D. in astronomy, physics, or a related field (graduated within the last 5 years). Significant computational and data analysis skills are preferred.
APPLICATIONS: Please send a single PDF document to Professor Yin-Zhe Ma ([email protected]) by the closing date containing the:
- Your CV and Publication List.
- Degree Certificates
- A 3-page statement describing the previous/current research and future plan
- Names and Email addresses for 2-3 referees.
Applicants should also arrange for the 2 or 3 reference letters to be sent directly to Prof. Ma by the same closing date. An incomplete application will not be accepted.
Postdoctoral fellows are not appointed as employees and as their fellowships are awarded tax-free, they are not eligible for employee benefits. Stellenbosch University reserves the right NOT to make an appointment if suitable candidates do not apply.
INQUIRIES: Please contact Professor Yin-Zhe Ma ([email protected])