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2006 ASP Annual Award Recipients

Robert J. Trumpler Award
Steven Furlanetto
Harvard University, USA

As the Universe expanded and cooled after the Big Bang, it underwent several transitions, marked by eras during which it created first baryons, then atoms, stars and finally galaxies as we see them today. The period between the recombination of electrons and protons to make the first neutral atoms at about 380,000 years after creation and the subsequent reionization of these atoms when the first generation of stars or quasars turned on is now referred to as the "Dark Ages." The Dark Ages ended several hundred million years after recombination in the so-called Epoch of Reionization, a time of great interest to astrophysicists today. That is in part because studies of the Epoch of Reionization (EoR) will tell us so much about the first luminous objects to form in the Universe, and in part because several planned, low frequency, radio arrays may soon detect and characterize the EoR (through the redshifted 21 cm line of hydrogen, which is strong in the pre-reionization Universe but disappears as the gas is ionized).

We honor Steven Furlanetto, the 2006 winner of the Trumpler Award, for his contributions to our understanding of the Epoch of Reionization. His thesis and the subsequent research derived from it have provided important guidance to astronomers planning redshifted 21 cm observations of the EoR. These include groups planning the Square Kilometer Array and some of its smaller predecessors such as the Mileura Wide Field Array (of which he is a team member). Furlanetto extended earlier work by Chris Carilli of the National Radio Astronomy Observatory to model the distribution of sizes and optical depths of the observable features imprinted during the EoR. These calculations are serving to guide the design of the experiments to characterize the EoR and the sources of "first light" in the Universe.

Furlanetto’s Harvard thesis produced five other novel and important astrophysical results, all coauthored with his advisor, Abraham Loeb. One of these explores a new mechanism for the generation of magnetic fields in the intergalactic medium, an open and intriguing question in astrophysics. The Furlanetto and Loeb paper argues that magnetic field originating in the accretion disk around a central Black Hole in a galaxy can be spread by outflows from the AGN. We see once again the close link between the properties of galaxies and of their resident, central Black Holes. Another of the papers derived from Furlanetto’s thesis treats the 511 keV annihilation line from positrons produced by relativistic jets from active Galactic nuclei. In addition to its wide range, his thesis is praised for its mathematical sophistication, originality and attention to detail. The papers derived from it are already having a substantial impact on cosmology and extragalactic astronomy generally, and the ASP is proud to highlight the excellence of Steven Furlanetto’s thesis by presenting him the Trumpler Award for 2006.