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).

Personnel

Professor Yin-Zhe Ma (PhD: University of Cambridge (2011))

Position: Full Professor and Head of Astrophysics
Interests: Theoretical Astrophysics, Cosmology and Radio Astronomy
Tel: +27 21 808 3372
Office: 1018 Merensky Building
ORCID: ORCID ID
Google ScholarProfile 

Dr. Anslyn John (PhD: University of KwaZulu-Natal (2012))

Position: Lecturer
Interests: General Relativity, Theoretical cosmology, Relativistic Astrophysics
Tel: +27 21 808 3371
Office: 1028 Merensky Building
Google ScholarProfile

Dr. Michael Sarkis (PhD: University of Witwatersrand (2023))

Position: Postdoctoral Fellow
Interests: Dark Matter, Pulsar Timing Array

Dr. Sheean Jolicoeur (PhD: University of the Western Cape (2019))

Position: Postdoctoral Fellow
Interests: Theoretical and computational Cosmology, Forecasting algorithms (Fisher and MCMC)

Dr. Guo-Jian Wang (PhD: Beijing Normal University (2020))

Position: Postdoctoral Fellow
Interests: Machine Learning, 21-cm Cosmology

Mr. Clinton Stevens

PhD Student
Interests: 21-cm Cosmology, Epoch of Reionization 

Mr. Phillip Badenhorst

PhD Student
Interests: Dark Matter, Neutron Stars

Mr. Jaymie Van der Merwe

MSc Student
Interest:
theoretical cosmology

Ms Victoria Nakafingo

MSc Student
Interests: 21-cm Cosmology, Large-Scale Structure

Mr. John Powell

Intern
Interests:
Big-Bang Nucleosynthesis, Early Universe

If you wish to contact us, please use this contact form and we will get back to you.

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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:

 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

Media

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

We heavily involve 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 heavily involve in the MeerKAT and Square Kilometre Array (SKA) project.

Recent Research Highlight

1. 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.

2. 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).

3. 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.

Publication

2024

12. Hydrogen Epoch of Reionization Array (HERA) Phase II Deployment and Commissioning. Lindsay M. Berkhout et al. (including Yin-Zhe Ma), 2024, Publications of the Astronomical Society of the Pacific, 136, 045002, arXiv: 2401.04304 https://doi.org/10.1088/1538-3873/ad3122 

11. Constraining primordial non-Gaussianity using Neural Networks. Chandan G. Nagarajappa, & Yin-Zhe Ma, 2024, Monthly Notices of the Royal Astronomical Society, 529, 3289-3300, arXiv: 2403.02115 https://doi.org/10.1093/mnras/stae679 

10. Cross-correlation of cosmic voids with thermal Sunyaev-Zel’dovich data. Gang Li, Yin-Zhe Ma, Denis Tramonte, Guo-Liang Li, 2024, Monthly Notices of the Royal Astronomical Society, 27, 2663-2671, arXiv: 2311.00826 https://doi.org/10.1093/mnras/stad3396

9. Cross-correlation between the thermal Sunyaev-Zeldovich effect and the Integrated Sachs- Wolfe effect. Ayodeji Ibitoye, Wei-Ming Dai, Yin-Zhe Ma, Patricio Vielva, Denis Tramonte, Amare Abebe, Aroonkumar Beesham, Xuelei Chen, 2024, The Astrophysical Journal Supplement Series (ApJS), 270, 16, arXiv: 2310.18478 https://doi.org/10.3847/1538-4365/ad08c5

8. The Dispersion Measure Contributions of the Cosmic Web. Charles R. H. Walker, Laura G. Spitler, Yin-Zhe Ma, Cheng Cheng, M. Celeste Artale, Cameron Hummels, 2024, Astronomy and Astrophysics, 683, A71, arXiv: 2309.08268 https://doi.org/10.1051/0004-6361/202347139 

7. HI content of selected mid-infrared bright, starburst blue compact dwarf galaxies. Yogesh Chandola, Di Li, Chao-Wei Tsai, Guodong Li, Yingjie Peng, Pei Zuo, Travis McIntyre, Yin-Zhe Ma, Daniel Stern, Roger Griffith, Thomas Jarrett, Peter Eisenhardt, Chantal Balkowski, 2024, Monthly Notices of the Royal Astronomical Society, 527, 603-619, arXiv: 2310.02202 https://doi.org/10.1093/mnras/stad3018

2023

6. Solar gamma ray probe of local cosmic ray electrons. Hong-Gang Yang, Yu Gao, Yin-Zhe Ma, Roland M. Crocker, 2023, Physical Review D (Letter) 108, L061304 https://journals.aps.org/prd/pdf/10.1103/PhysRevD.108.L061304

5. Implications for primordial black holes from cosmological constraints on scalar-induced gravitational wave. Junsong Cang, Yin-Zhe Ma, Yu Gao, 2023, The Astrophysical Journal, 949, 64 (6 pages), arXiv: 2210.03476 https://iopscience.iop.org/article/10.3847/1538-4357/acc949/pdf

4. Constraints on dark matter annihilation from the FAST observation of the Coma Berenices dwarf galaxy. Wen-Qing Guo, Yichao Li, Xiaoyuan Huang, Yin-Zhe Ma, Geoff Beck, Yogesh Chandola, Feng Huang, 2023, Physical Review D, 107, 103011, arXiv: 2209.15590 https://journals.aps.org/prd/pdf/10.1103/PhysRevD.107.103011

3. GMRT HI mapping of mid-infrared bright Blue Compact Dwarf Galaxies W1016+3754 & W2326+0608. Yogesh Chandola, Chao-Wei Tsai, Di Li, Chandreyee Sengupta, Yin-Zhe Ma, Pei Zuo, 2023, Monthly Notices of the Royal Astronomical Society, 523, 3848-3862 https://doi.org/10.1093/mnras/stad1618

2. CoLFI: Cosmological Likelihood-free Inference with Neural Density Estimators. Guo-Jian Wang, Cheng Cheng, Yin-Zhe Ma, Jun-Qing Xia, Amare Abebe, and Aroonkumar Beesham, 2023, The Astrophysical Journal Supplement Series, 268, 7 https://doi.org/10.3847/1538-4365/ace113

1. Cross-Correlation Forecast of CSST Spectroscopic Galaxy and MeerKAT Neutral Hydrogen Intensity Mapping Surveys. Yu’er Jiang, Yan Gong, Meng Zhang, Qi Xiong, Xingchen Zhou, Furen Deng, Xuelei Chen, Yin-Zhe Ma, and Bin Yue, 2023, Research in Astronomy and Astrophysics, 23, 075003 (12 pages) https://iopscience.iop.org/article/10.1088/1674-4527/accdc0/pdf

 

Acknowledgement