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ERC

EGGS Report Summary

Project ID: 278202
Funded under: FP7-IDEAS-ERC
Country: Denmark

Mid-Term Report Summary - EGGS (The first Galaxies)

The astrophysics of galaxy formation is deeply fascinating. From tiny density fluctuations of quantum mechanical nature, structure slowly formed through gravitational collapse. This process is strongly dependent on the nature of the dominant, but unknown form of matter – the dark matter. In EGGS (Emission-line Galaxies and Gamma-ray burstS) I study the epoch of first galaxy formation and the subsequent few billion years of galaxy evolution. The project has three sub-projects, described in more detail below. This reflects my overarching approach to the study of galaxy formation and evolution. The subject is so rich and multifaceted that it would be haphazard to focus on only one perspective/technique. The Indian story of blind monks examining an elephant is a very suitable analogy.

In the first sub-project I study the afterglows of Gamma-ray Bursts (GRBs). GRBs are caused by exploding very massive stars. We can use them both pinpoint the locations of very distant galaxies (hence probing very early galaxies in the Universe) and to measure the properties of the interstellar media of such early galaxies by recording the absorption imprint of this material on the light of the afterglows. In particular, I am interested in using this approach to measure chemical abundances of very early galaxies. Except hydrogen and helium all the elements are formed in supernovae inside galaxies and using GRBs we can measure how this build up the elements has proceeded. What we can see in the data is that this build-up is not homogeneous. Rather there is a very large variance in the abundances of elements inside galaxies at all redshifts. We are also interested in using the most distant GRBs, those at redshifts beyond z=6, to probe the re-ionzation of the Universe. This is the last major transitional phase in the intergalactic medium at which the gas went from being neutral to being ionized due to the production of ionizing radiation by the first luminous sources formed after the Big Bang. We had a workshop in Granada in March 2014 to thoroughly discuss the next major activity in the collaboration namely to write up of sample papers. We suspect the first sample papers will be submitted in early 2015.

In the second sub-project I am co-PI of the UltraVISTA project where we try to build up an ultra-deep image of the so-called COSMOS field in the constellation of Sextans. I lead the part of UltraVISTA that uses custom made narrow band filters to detect emission line galaxies in the COSMOS field. Emission line galaxies are gas rich galaxies with active star-formation. This approach will be sensitive to a range of star-forming galaxies, mainly H-alpha emitters at redshifts of 0.9, Oxygen emitters at redshifts of 1.4 and 2.2 and finally potentially Lyman-alpha emitters at a very high redshift of 8.8. The first years were hampered by slow progress caused by technical problems with the mirror of the telescope, but now the project is progressing steadily and well. We have published a thorough on-sky characterization of the narrow-band filters and the first papers on emission line galaxies are in preparation. A number of interesting publications using the broad band filter data in UltraVISTA to study z=7 galaxies as well as a very interesting gravitationally lensed galaxy at z=2.4.

In the third sub-project I study galaxies in absorption. the approach here is to study the gaseous parts of galaxies that happen to lie along the line-of-sight to background quasars. These objects are known as Damped Lyman-alpha Absorbers. Here I am leading a project that has lead to what it is fair to describe as a break-through, namely a project that characterizes the emission counterparts (the "galaxies") causing the DLAs in quasar spectra. Finding these galaxies (in emission) has been extremely difficult and has seen little progress in the latest 2-3 decades. Thanks to the project I lead in X-shooter (also involving data from the Hubble Space Telescope), the number of such systems detected in emission has more than doubled. A spin-off of this project is a search for red quasars. Here we search for quasars that have been reddened due to dust in foreground DLAs. We have found two such systems, but in addition to this a very large number of quasars that seem to be reddened by dust in their host galaxies. This project is ongoing and I try to involve students in it as part of a course I give on observational astrophysics.

All in all I feel that all sub-projects of EGGs are on a good track and I expect many interesting publications to come out also in the 2nd half of the project.

Contact

Ivan Kristoffersen, (Head of Department)
Tel.: +45 35322626
Fax: +45 35324612
E-mail
Record Number: 180049 / Last updated on: 2016-04-19
Information source: SESAM