TK-GRB-10

Probing the early Universe with GRB afterglows

 Partecipanti

Mappa

 Word cloud

Esplora la "nuvola delle parole (Word Cloud) per avere un'idea di massima del progetto.

 Obiettivo del progetto (Objective)

'Gamma-ray bursts (GRBs) are cosmic, stellar explosions, that emit a typical amount of energy of 10^51 erg in gamma-rays on short time scales of 0.1 to 100 seconds. The prompt emission in gamma-rays is followed by a longer-lasting afterglow, which can be detected in all wavelength ranges from radio, optical, to X- and gamma-rays up to several days after the explosion. The large energy release and high luminosity of GRBs and their afterglows make them ideal probes for studying the early Universe and the cosmic evolution. Furthermore, GRBs are linked to the death of massive stars, and hence to star formation in the very early evolution of the Universe. GRBs light up distant galaxies undergoing a process of star formation, which would remain undetected otherwise. The main aim of this proposal is to provide training for the applicant via cutting edge research in one of the most exciting and active fields in astronomy at a world leading institute, the Dark Cosmology Centre at the Niels Bohr Institute, University of Copenhagen. The proposal is based on three training and research aims. One of the major science aspects is to work and be trained on optical afterglow spectroscopy with the newly commissioned X-shooter instrument at the VLT. An X-shooter spectrum of a GRB afterglow is a powerful diagnostic of the chemical conditions in the local environment and the interstellar material of the host galaxies of GRBs. The second aspect is based on multi-wavelength studies of GRB afterglows using ground- and space-based observatories. The aim is to constrain the dust content and the total metal column density along the line of sight towards the burst. The third aspect are investigations about the population of GRB host galaxies. The proposed project can constrain properties of low-mass, star-forming galaxies in the early Universe, which are the most common galaxies but difficult to find with different strategies; a GRB pinpoints their location.'

Introduzione (Teaser)

EU-funded astronomers worked with the brilliant afterglows of gamma-ray bursts (GRBs) to probe distant galaxies. By analysing the light spectrum emitted, they gleaned insights into stellar nurseries.

Descrizione progetto (Article)

One of the greatest challenges of modern astrophysics has been the quest to identify the first generations of stars that formed in the Universe. Long-duration GRBs are explosions that occur when massive stars run out of fuel for nuclear fusion in their cores. The explosion (GRB) and its aftermath (GRB afterglow) are so bright that they can be observed across the entire visible universe, back to the time of the first stars. They are therefore used to understand how and where stars are formed at all times in the history of the universe.

Stars form in vast clouds of molecular gas and dust, and there was an expectation that the afterglows of GRBs should show signs of this material in their spectra. However, contrary to expectation, most GRB afterglows were found to be free of molecular gas and dust until the project 'Probing the early Universe with GRB afterglows' (TK-GRB-10).

The TK-GRB-10 scientists helped solve this mystery by examining heavily dust-obscured afterglows and the host galaxies of GRB afterglows that were completely missed because of obscuration by dust. They used spectral absorption lines to measure how many heavy elements (those heavier than helium, that is) were present in the host galaxy, and showed that GRBs did not only explode in galaxies that were young and poor in these heavy elements, but that many GRB afterglows were missed because they occurred in galaxies where dust was more likely to form. This means that GRBs can be used to examine the formation and evolution of massive stars not only in rare situations free from molecular gas and dust.

At the time the GRB-progenitor star died, it was building the elements the Universe needed to evolve. Together with numerous other GRBs included in the catalogue populated during the TK-GRB-10 project, it has helped astronomers better understand the huge Universe we live in. Their findings are described in a series of 22 papers published in international peer-reviewed journals.