Astronomie en Astrofisika
Ons fokus op die koppeling van fundamentele fisika met astronomiese waarnemings om die fundamentele wette van die heelal te verstaan, en om die aard van donker materie en donker energie te ontrafel.
In die besonder sluit ons aktiewe navorsingsrigtings die tydperk van reionisasie, ekstragalaktiese sterrekunde, die vroeë heelal, indirekte opsporing van donker materie, neutronsterre en swart gate in.
Ons is betrokke by Suid-Afrika se MeerKAT, Square Kilometre Array (SKA), Hydrogen Epoch of Reionization Array (HERA) teleskope, LSST (Vera C. Rubin Observatory), FAST teleskoop en CMB Stage-4, en gebruik ook data van die Atacama Cosmology Telescope, South Pool Telescope, ESO se Kilo-Degree Survey (KiDS), en Dark Energy Survey Instrument (DESI).
Navorsing
Navorsingsfokusareas
- Radio-astronomie: Epok van Reionisasie, Donker Materie-soektog in radiogolflengte, Pulsar-tydsberekeningsskikking, 21-cm Intensiteitskartering
- Ekstragalaktiese Sterrekunde: sterrestelsel-eienaardige snelheidsveld, termiese en kinetiese Sunyaev-Zel’dovich-effek, dinamika van plaaslike groepe, nabye-veld-kosmologie
- Teoretiese Kosmologie: die kosmiese mikrogolfagtergrondstraling, waarnemingstoetse van inflasie, swaartekragteorieë
Huidige projekte
- Hydrogen Epoch Reionization Array (HERA): Kalibrasie en kragspektra-analises
- Square Kilometer Array (SKA) team: EoR, HI, Kosmologie Wetenskap werksgroepe
- Rubin Observatory (LSST) wetenskaplike span
- CMB Stage-4 Opname
Institusionele samewerking
The Kapetyn Astronomical Institute, University of Groningen, Netherlands
Samewerkers
- 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
Navorsingsgroep
Media gallery
Ons is betrokke by die VSA-SA samewerkingsprojek "Hydrogen Epoch Reionization Array" (HERA) wat die hoë-rooiverskuiwing 21-cm sein met radio-interferometrie tegniek meet.
Die kosmiese evolusie van 13.7 miljard jaar is die hoofnavorsingsdoelwit van ons navorsing.
Ons gebruik die Kosmiese mikrogolfagtergrondstraling (KMB) van Planck en KMB-S4 om die aanvanklike toestand van die heelal te verstaan.
Ons is betrokke by die MeerKAT en Square Kilometer Array (SKA) projek.
Intreeredes
Prof Yin-Zhe Ma
Mediadekking
CGTN onderhoud met prof Yin-Zhe Ma, 183de Nobel Symposium Outreach Talk, Universiteit van die Wes-Kaap, Oktober 2022
"Searching for Axion Dark Matter" —NITheCS seminaar
“Echoes of the Skies”, SKA projek
NItheCS seminaar - dr. Anslyn John
Onlangse navorsingshoogtepunte
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.
Met erkenning
Loopbaan- en studiemoontlikhede
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])