PhD thesis defense by Peter Laursen

Peter Laursen will defend his PhD thesis Monday 23 August 2010 at 15:15 in the Rockefeller Auditorium.

Title: Interpreting Lyman Alpha radiation from young, dusty galaxies.

Abstract:
The significance of the Ly emission line as a probe of the high-redshift Universe has long been established. Originating mainly in the vicinity of young, massive stars and in association with accretion of large bulks of matter, it is ideal for detecting young galaxies, the fundamental building blocks of our Universe. Since many different processes shape the spectrum and the spatial distribution of the Lyphotons in various ways, a multitude of physical properties of galaxies can be unveiled.

However, this also makes the interpretation of Ly observations a notoriously difficult. Because Ly is a resonant line, it scatters on neutral hydrogen, having its path length from the source to our telescopes vastly increased, and taking it through regions of unknown physical conditions.

In this work, a numerical code capable of calculating realistically the radiative transfer of Ly is presented. The code is capable of performing the radiative transfer in an arbitrary and adaptively refined distribution of Ly source emission, temperature and velocity field of the interstellar and intergalactic medium, as well as density of neutral and ionized hydrogen, and, particularly important, dust.

Accordingly, it is applied to galaxies simulated at high resolution, yielding a number of novel and interesting results, most notably the escape fractions of Ly photons, the effect of dust, and the impact of the transfer through the intergalactic medium.

Furthermore, the remarkable detection of Ly emission from a so-called "damped Lyabsorber" - a special type of objects thought to be the progenitor of presentday's galaxies - is presented, and the potential of the code for interpreting observations is demon-strated.

You can download his thesis here >>