Páll Jakobsson, Professor, Centre for Astrophysics and Cosmology, University of Iceland


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Research

I used to do work on gravitational lensing and did my M.Sc. studies on that subject at the Niels Bohr Institute (1999-2002). I did my Ph.D. studies on gamma-ray bursts (GRBs) at the same place (2002-2005) and then joined the Dark Cosmology Centre as a postdoc before moving to the UK for a couple of years as a Marie Curie Fellow (2006-2008): Centre for Astrophysics Research at the University of Hertfordshire.

Currently my main research interests are GRBs and galaxy evolution and formation. Basically, GRBs are the most luminous electromagnetic events occurring in the Universe since the Big Bang. They are flashes of gamma rays emanating from seemingly random places in deep space at random times. The duration of a GRB is typically a few seconds, but can range from a few milliseconds to several minutes, and the initial burst is usually followed by a longer-lived "afterglow" emitting at longer wavelengths (X-ray, ultraviolet, optical, infrared and radio). GRBs are detected by orbiting satellites about 2-3 times per week. Most observed GRBs appear to be collimated emissions caused by the collapse of the core of a rapidly rotating, high-mass star into a black hole (see this illustration). More info on GRBs and their host galaxies can be found at the Centre for Astrophysics and Cosmology at the University of Iceland.

To be more specific, the goals of our group and closest collaborators are aimed at better understanding the reionization of the Universe and the star formation history over cosmic time. GRBs, the brightest explosions in the Universe, offer a direct means of answering these questions via observations of their afterglows and host galaxies. The Swift satellite and its ability to rapidly and accurately locate 100 GRBs/year now makes this feasible. We complement this with wide-ranging follow-up programmes on numerous telescopes, e.g. the Nordic Optical Telescope, the Very Large Telescope and the Hubble Space Telescope. The main objectives are:

  1. Systematic search for and study of GRBs and their afterglows at very high redshifts, corresponding to an epoch when the Universe was less than 1 billion years old. These bursts will be used to probe the early star formation, including the collapse of the first stars, and the ionization state of the Universe at that time.
  2. Building up a complete sample of GRBs with measured redshifts and model their distribution. This is crucial in order to investigate their energetics, application as "standard candles" and their link to the star formation history of the Universe.
  3. Characterize GRB host galaxies from a carefully defined sub-sample, e.g. determine the luminosity function and the effect of reddening.