Evolution of the Ionizing Background at High Redshifts

We use a Maximum-Likelihood analysis to constrain the value and evolution of the ionizing background for 2<z<4.5, taking account of possible systematic errors. (The paper has a more detailed abstract)Comment: 12 figures (9 of those double plots), 17 pages. Accepted by MNRA

CONSTRAINTS ON REIONIZATION FROM THE THERMAL HISTORY OF THE INTERGALACTIC MEDIUM 1,2

ABSTRACT The temperature of the diffuse, photoheated intergalactic medium (IGM) depends on its reionization history because the thermal timescales are long. The widths of the hydrogen Lya absorption lines seen in the spectra of distant quasars that arise in the IGM can be used to determine its temperature. We use a wavelet analysis of the Lya forest region of quasar spectra to demonstrate that there is a relatively sudden increase in the line widths between redshifts and 3.0, which we associate with entropy injection resulting from the reionization of z ≈ 3.5 He ii. The subsequent falloff in temperature after is consistent with a thermal evolution dominated by z ≈ 3.5 adiabatic expansion. If, as expected, the temperature also drops rapidly after hydrogen reionization, then the high temperatures inferred from the line widths before He ii reionization imply that hydrogen reionization occurred below redshift . z p

Reviews

The following publications have been reviewed by the mentioned authors;Design Assignments for GCSE and Standard Grade by Jeff Nocholls, reviewed by Bob BoothDesign and Communication for Foundation Courses by Peter Gowers, reviewed by Peter ToftThe Celtic Art Source Book by Courtney Davis, reviewed by Rosemary BoothThe World of Plastics by the British Plastics Federation, reviewed by George RaperIllumination: A Source Book for Modern Calligraphers by Christopher Jarman, reviewed by John LancasterCraft, Design and Technology. Materials: Investigation and Choice. A database for pupil use by David Barles, Simon Powell, Sheila Nelmes and Adrienne Jones, reviewed by David BarlexDesign in Context by Penny Sparke, reviewed by John H. CarswellDesignwise 2 by N. McLean, reviewed by H. G. DentonAirbrushing the Human Form by Andy Charlesworth, reviewed by S. W. GarnerDouglas Scott by Johnathan Glancey, reviewed by K. J. McAule

Gravity and light - Gravitational lenses and black holes (PVC-R Visiting Professor Lecture Series)

We explore how light behaves near massive objects, and show that for gravitational lenses, gravitational redshifts and black holes, the main concepts can be understood in general terms from Einstein's oft-quoted equation, E=mc^2. Light paths are changed as they pass close to the sun and to massive galaxies, so giving us the idea of gravitational lenses which can change the appearance of distant galaxies and quasars. Some examples of multiply imaged quasars and lensed galaxies are given. Gravitational redshifts of light from compact stars have been measured. In the extreme case of very compact objects - black holes - no light can escape at all. There are compelling reasons for believing that massive black holes reside near the centers of many galaxies, and particularly the center of the Milky Way. Professor Carswell was invited to Swinburne under the Board of Research Visiting Professor Grant Scheme, and this lecture was presented as part of the PVC(R) Visiting Professor Lecture Series

Exchanging emissions for biodiversity: In pursuit of an integrated solution in New Zealand

With New Zealand's recent ratification of the Kyoto Protocol (December 2002) we ask whether it might be possible to design a programme that reduces corporate New Zealand's greenhouse gas (GHG) emissions while also benefitting New Zealand's biodiversity in the many cases where emissions cannot be entirely eliminated. This article describes progress since 2001 in formulating and implementing a trial of such an integrated solution. We provide a description of the framework applied to date for integrating efforts by businesses and communities in both emissions reduction and biodiversity restoration, incorporating lessons that may help us refine our model