Welcome to the homepage of

Dr. Roger


Postdoctoral fellow

Instituto de Astrofísica de Andalucía - CSIC, Granada, Spain.

This is my homepage where I share my research in Astronomy, with topics related to the interstellar medium, nearby galaxies, star formation, galaxy clusters, programming tips, Linux.


I obtained my Ph.D. in Astronomy in June 2014, at the University of Cape Town, under the general guidance of Prof. W. J. G. de Blok. The thesis title was "Interstellar medium properties and star formation in nearby galaxies". My thesis received an A rating from all three external examiners. My subsequent peer-reviewed papers have been valuable for theoretical models that assess the role and origin of turbulence in the interstellar medium. The thesis made use of high-resolution interferometric observations of neutral atomic hydrogen (HI) gas in nearby galaxies to measure with high precision fundamental parameters, relevant for star formation studies. I achieved this robust measurement by reducing the effects of noise using a spectral-line stacking technique.

The University of Cape Town, South Africa.
Max Planck Institute for Astronomy, Heidelberg, Germany.

After my Ph.D., I worked as a postdoctoral fellow at the University of South Africa. There I continued my research on HI observations of nearby galaxies, focusing on the morphological and the radial dependence of the HI line widths. Together with international collaborators, I also worked on similar research topics, involving a comparative study of HI versus carbon-monoxide (CO) line widths. The resulting papers have also received a number of citations, especially from studies of the physics of star formation. After receiving funding from the Alexander von Humboldt Foundation, I went to Germany for a two-year postdoctoral fellowship at the Max Planck Institute for Astronomy (MPIA). This gave me the opportunity to work with a vibrant research group led by Dr. Fabian Walter. Through this fellowship, I focused on two main projects. One is analyzing how possible systematic effects during image reconstruction process affect the shapes of the resulting HI velocity profiles. The second one is to develop a new stacking technique to detect faint HI emissions at the outer disks of nearby galaxies.

After spending time at MPIA, I went back to South Africa as a postdoctoral fellow at the Centre for Radio Astronomy Techniques and Technologies (RATT), Rhodes University, working with a group led by Prof. Oleg Smirnov. I have since been heavily involved in HI science with MeerKAT. I have so far led two successful MeerkAT proposals. One is titled "A Search For Diffuse HI Emission In The Nearby Dwarf Irregular Galaxy WLM and IC 1613". At the time of observations, the dwarf galaxy IC 1613 was too close to the sun and was not observed. The aim was to make detailed 3D modeling of the HI morphologies and kinematics of the galaxy to search for signs of gas accretion. The second successful MeerKAT project which I led was titled "Mapping the starburst galaxy NGC 4945 with MeerKAT-64". The aim of this project is to map the extended HI disk and radio continuum emission in NGC 4945. The scientific goal is to study the interplay between gas and star formation in a chaotic environment such as the interstellar medium of NGC 4945.

Rhodes University, Grahamstown, South Africa.

Now, I am a postdoctoral fellow at the Instituto de Astrofísica de Andalucía - CSIC, Granada, Spain, part of a team led by Dr. Lourdes Verdes-Montenegro. I am involved in a research on the lifecycle of gas in galaxy groups. Particularly, I am analysing recently obtained MeerKAT HI data of the Hickson Compact Groups. I aim to investigate the link between star formation and gas removal in Hickson Compact Groups. In addition by means of kinematic modelling, I aim to separate intra-group gas from galaxy gas.

Instituto de Astrofísica de Andalucía - CSIC, Granada, Spain.

The interstellar medium of nearby galaxies

Since my PhD, I have been studying the resolved properties of the interstellar medium of nearby galaxies. I have used data from major surveys such as THINGS, HALOGAS, HERACLES, which mapped the neutral atomic hydrogen (H I) and the carbon monoxide (CO) gas in a number of nearby galaxies. Recently, I have used the MeerKAT radio telescopes to study the kinematics and the morphologies of the H I gas in two nearby galaxies, WLM and NGC 4945.

Galaxy clusters

I am interested in how galaxies get transformed by the environment of the intracluster medium. Galaxies can lose their gas, change morphologies, and eventually quench their star formation through various mechanisms as they fall into the cluster cores. The imprints of these can be studied by observing the H I content of galaxy clusters. I have recently began to work on a MeerKAT data to study the H I content of a number of galaxy clusters. This allows us to investigate the effects of environment on the morphologies and star formation properties of galaxies.

Software development

During my three months research visit at the Max Planck Institute for Astronomy in Germany, I worked together with Dr. Fabian WALTER to develop a python package to do spectral line stacking of nearby galaxies. The aim of this was to detect faint H I emission at the outer disk of nearby galaxies that would otherwise be missed by conventional method such as moment analyses. This visit has allowed me to acquire software development skills and helped foster my interests in this area. I would like to thank the Alexander von Humboldt foundation for making this visit possible.

research experience

Education and Experience


University of Cape Town

PhD in Astronomy

Thesis title: Interstellar medium properties and star formation in nearby galaxies.


University of Cape Town

M.Sc. in Astrophysics and Space Science

Coursework and dissertation, thesis title: The shapes of the H I velocity profiles of The H I Nearby Galaxy Survey (THINGS) galaxies.


University of Cape Town

Honours in Astrophysics and Space Science

Coursework and dissertation, thesis title: Asymptotic Giant Branch Variables (AGB) in the Fornax dwarf spheroidal galaxy.


University of Antananarivo

Honours in Physics

By coursework.

2019 Humboldt Alumni Award for Innovative Networking Initiatives

I received the 2019 Humboldt Alumni Award for Innovative Networking Initiatives. With this award, I aim to promote STEM subjects in Madagascar, with a particular emphasis on Astronomy.

Photo taken during the conferrement of the award. The award was handed over to the awardees by chancellor Angela Merkel.

Malagasy Astronomy And Space Science Association (MASS)

I am a member of the Malagasy Astronomy and Space Science Association (MASS). MASS is a not for profite association, aimed at promoting Astronomy in Madagascar. For more information on MASS, visit https://malagasyastro.wixsite.com/mass.

International Astronomical Union (IAU)

I am a junior member of the International Astronomical Union. The IAU is a nongovernmental organisation to advance Astronomy and use it as a tool for sustainable development. https://www.iau.org/administration/membership/individual/19966/.




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