Garrelt MellemaHead of the department
About me
I am a professor at Stockholm University working at the department of Astronomy and the Oskar Klein Centre. I am currently the head of the deparment of astronomy. I am further a member of Royal Swedish Academy of Sciences. This profile page provides an overview of my various work-related activities.
Teaching
Undergraduate education
Over the years I have taught a range of different courses. These are
- Cosmology (AS7009, now AS5003) - a third year bachelor programme course on basic cosmology
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Astrophysical Gas Dynamics (AS7002) - a master level course on the behaviour of astrophysical gases.
- Galaxy Formation and Evolution (AS8001) - a master level course on the (astro)physicaö processes behind the formation and evolution of galaxies.
And was also one of the teachers on
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AS7011: Early and Late Stages of Stellar Evolution - a master level course on stellar evolution; I focused on the later stages in the evolution of low mass stars. This course is no longer being given.
I regularly supervise students in their degree projects, both at the Bachelor and Master level.
I have also worked at the managerial level as director of studies for the department of astronomy. I had the overall responsibility for the courses taught at the first and second level, which means our Bachelor courses, Master courses and our introductory courses.
Postgraduate education
For several years I was in charge of the PhD programme in astronomy as director of (post)graduate studies. I have also been the main supervisor of nine PhD students at Stockholm University.
PhD students can take this numerical assignment which I designed:
Research
My main research focus is on the period in the history of the Universe when the first stars and galaxies formed, several 100s of millions of years after the Big Bang, or 13 billion years ago. We do not know much about this period as even the largest existing telescopes are barely powerful enough to detect the galaxies from this time.
However, efforts are underway to detect and map the distribution of matter during this era by using a new generation of radio telescopes. These radio telescopes operate at low frequencies (below 200 MHz) and can pick the signal produced by the neutral hydrogen in the Universe. The distribution of neutral hydrogen will teach us much about the state of the Universe in this watershed period when the first stars and galaxies formed.
The two radio telescope project I am involved in are LOFAR (Low Frequency Array), a European collaboration involving Sweden together with the Netherlands, Germany, Great Britain, France, Poland and Ireland, and SKA (Square Kilometre Array), a global project also involving Sweden. LOFAR is currently collecting data and the SKA will start construction soon and operations are expected to commence towards the end of the 2020s.
My contributions to these projects consist of detailed numerical simulations of what the signal from neutral hydrogen will look like and how we can use it to extract detailed information about the first stars and galaxies. These numerical simulations are among the most advanced in the world and are performed using the largest supercomputers in the world. Courtesy of the National Academic Infrastructure for Supercomputing in Sweden I make for example use of the dardel supercomputer at the PDC Center for High Performance Computing at the KTH Royal Institute of Technology. I have also used European supercomputers through PRACE (Partnership for Advanced Computing in Europe)
Previously I have also worked on other areas of astronomy. I started my career by developing computer simulations of perhaps the most beautiful objects in astronomy, Planetary Nebulae. These objects form when stars such as the Sun reach the end of their lives and start ejecting larges amounts of material as well as producing enormous amounts of ionizing radiation.
During the early 2000s I was also active in the field of planet formation, developing numerical simulations of the interaction of young planets with the circumstellar disk in which they were born.
