By Professor Carolina Ödman
Using early science data for the MIGHTEE project on the MeerKAT radio telescope, a researcher at the University of the Western Cape – with collaborators from eight countries, including four other South African institutions – has analysed over 2 000 galaxies, growing our understanding of the evolution of galaxies over cosmic time.
Dr Fangxia An - a postdoctoral researcher at IDIA and a member of the UWC Astrophysics group - and her collaborators used early science data collected over nearly 20 hours by the South African MeerKAT radio telescope to analyse the galaxies thoroughly.
To do so, the team needed more than radio astronomy data. Indeed, different astrophysical phenomena lead to the emission of light in different wavelengths, including radio, visible light, infra-red, ultra-violet and x-rays. And it is therefore important to be able to combine different observations.
The part of the sky that was observed for this study is called the COSMOS field and is one area very well studied using many telescopes. The team combined radio astronomy data from the MeerKAT with observations from the VLA radio telescope in the US and the GMRT radio telescope in India. In addition, they used astronomy data science products such as catalogues of galaxies generated with other observations, in particular infra-red.
The work of combining observations is not straightforward and the team had to analyse many aspects of the selection of 2094 galaxies.
“The new observations using MeerKAT help us better understand the nature of these galaxies, and furthermore, the formation and evolution of galaxies in general, including our home galaxy, the Milky Way,” said Dr An, who led the analysis.
She forms part of the The MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) project, which seeks to observe the extragalactic sky to explore the cosmic evolution of galaxies. It is one of the MeerKAT Large Survey Projects prioritised by the South African Radio Astronomy Observatory (SARAO).
The complex work was carried out using both the Centre for High Performance Computing in Cape Town, and the scientific cloud computing facility of the Inter-University Institute for Data Intensive Astronomy (IDIA). This facility, called ilifu, enables South African researchers and their collaborators to process and analyse the very large amounts of data from the MeerKAT telescope, ensuring South African leadership in radio astronomy in the age of the Square Kilometre Array (SKA).
“Cloud computing technologies such as these are essential to manage the deluge of data soon to be obtained with the SKA and will allow South African astronomers to play a key role in their scientific exploitation.” said Professor Mattia Vaccari, UWC eResearch director and a co-author on the paper.
The findings of the team following this analysis demonstrates that in order for us to gain a deep understanding of all the happenings in galaxies, like the formation of new stars, magnetic fields capturing electrons and other charged particles, and more, any observation is improved with additional data. At different frequencies, or wavelengths of light, different processes dominate.
Observations in the radio range of 1.3 to 3GHz, where the MeerKAT radio telescope is very sensitive, are dominated by a type of radiation called synchrotron radiation. This is light emitted when charged particles are travelling across bent trajectories, for example in a magnetic field.
The strength of the signal at different frequencies forms the spectrum. In these observations, each galaxy has parts of its spectrum analysed. The spectra show different features depending on how many stars are being formed in the galaxy in question.
This is checked in two different ways in the published analysis and shows that further studies in the low-frequency part of the radio spectrum are needed to better understand the correlation between infra-red and radio light coming from galaxies with a lot of star formation going on.
The research was published in the Monthly Notices of the Royal Astronomical Society, a leading scientific journal in Astronomy. This paper is the first UWC-led paper from the MIGHTEE project on the MeerKAT radio telescope.
* Professor Carolina Ödman is the Associate Director of Development and Outreach at IDIA. Trained in physics at EPFL in Switzerland, she holds a PhD in cosmology from Cambridge University, UK. After a Marie Curie research fellowship in Italy, she became the first international project manager of Universe Awareness.