Agenda

24/02
10:30 hrs
Sala F-210

Peter L. Biermann
University of Bonn
University Karlsruhe
University of Alabama at Tuscaloosa
University of Alabama at Huntsville

The first stars ever in the Universe

The paradox of Olbers basically states, that the sky would be infinitely bright in any wavelength of electromagnetic light, in neutrinos, or any other non-absorbed particle flux, if space were homogeneous, and non-evolving.  It is not, and so we know the universe evolves.  There must have been the first stars, and today we know, they existed around 13 billion years ago.  Stars form in galaxies, and galaxies are dominated by dark matter: dark matter is the key to understanding the first stars: We can go back to galaxy data to derive the key properties of the dark matter particle: Abundant work clearly points to a keV particle.  A right-handed neutrino is a candidate to be this particle: This particle has the advantage to allow star formation very early, near redshift 80, and so also allows the formation of supermassive black holes near redshift 50, possibly formed out of agglomerating massive stars in the gravitational potential of dark matter clumps.  Black holes in turn also merge, and so may explain the supermassive black hole mass function as the result of mergers between black holes.  Our conclusion is that a right-handed neutrino of a mass of a few keV is the most interesting candidate to constitute dark matter.  The detection at very high redshift of massive star formation, stellar evolution and the formation of the first super-massive black holes would constitute the most  striking and a beautifully testable prediction of this dark matter particle proposal.  Both the super-massive stars as well as the ensuing first super-massive black holes can be expected to accrete at their accretion limit, and so might be  detectable in sensitive surveys. These first stars could begin the cycle of explosions, black hole formation, enrichment, magnetic fields, cosmic rays, dust formation and life in the universe just 20 million years after the big bang.