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CORDIS - Résultats de la recherche de l’UE

The first Galaxies

Final Report Summary - EGGS (The first Galaxies)

The EGGs project focused on gaining new insights into the properties of the first galaxies that formed and evolved during the first about 3 billion years after the so-called Big Bang. In the project I have worked along three different lines or sub-projects. The first subproject is the UltraVISTA project, which is a deep, public (meaning that the data are immediately accessible) survey of a special field referred to as the COSMOS field. By gathering several 1000 hrs of observing time at the ESO VISTA telescope the UltraVISTA team, which also includes members in the UK, France and the Netherlands, have build the deepest image of degree-scale size of the distant Universe at near-infrared wavelengths. This has given new insight especially about the high-mass end of the early galaxy population: there appears to be more high-mass galaxies in the early Universe than anticipated. The second subproject in EGGs uses powerful cosmic explosions known as gamma-ray bursts (GRBs) to probe the interiors of distant galaxies. By doing spectroscopy of so-called afterglows of the GRBs we have been able to collect information otherwise inaccessible especially about the content of chemical elements and molecules in galaxies at look-back times of 8-13 billion years. The last subproject has had a similar aim, but rather than using GRBs we here have used background very luminous objects known as quasars. Ny analysing the light from the quasars using spectrographs we have again been able to study the chemical content of galaxies lying in front of the quasars. In so doing we found that there was a bias such that quasars with foreground galaxies with a high content of chemical elements would tend to disappear from the samples due to dust-reddening. Because of this we have developed a new selection technique for reddened quasars and used this technique to build a new survey for quasars (known as the HAQ survey). This survey has also resulted in the discovery of foreground galaxies with a very high content of chemical elements. This work shows that we have underestimated the amount of chemical elements formed in stars using existing quasar absorption line samples.