Housing Tenure in Ireland

This paper investigates the sources of the extremely high level of owner occupation in Ireland. After using census data to explore the evolution of this phenomenon, the paper makes a cross-country comparison of owner occupation within the EU-15. Explanations are found for the high level of owner occupation that go beyond fiscal privilege to include wider microeconomic factors, as well as historical factors. Within the EU-15, the Irish housing stock is exceptional not just in the high incidence of owner occupation, but also in the small number of dwellings relative to population.

Changes in Relative Consumer Prices and the Substitution Bias of the Laspeyres Price Index - Ireland, 1985-2001

This paper shows that Irish relative consumer prices have changed significantly, 1985- 2001, at the ten commodity-group level. A “true” cost-of-living index is derived from Madden’s (1993) parameter estimates for an Almost Ideal Demand System. Despite relative price changes, the substitution bias of a computed Laspeyres index is small, and the official Consumer Price Index tracks the computed index closely. Superlative indices are also constructed, but are not satisfactory cost-of-living indices in this context. Cost-of-living indices are computed for different income groups, and the impact of inflation in recent years is found to be negatively correlated with income.

Understanding contextualised rational action - author's response

Understanding contextualised rational action - author's respons

Probing Galaxy Formation with TeV Gamma Ray Absorption

We present here the extragalactic background light (EBL) predicted by semi-analytic models of galaxy formation, and show how measurements of the absorption of gamma rays of $\sim$ TeV energies via pair production on the EBL can probe cosmology and the formation of galaxies. Semi-analytic models permit a physical treatment of the key processes of galaxy formation -- including gravitational collapse and merging of dark matter halos, gas cooling and dissipation, star formation, supernova feedback and metal production -- and have been shown to reproduce key observations at low and high redshift. Using this approach, we investigate the consequences of variations in input assumptions such as the stellar initial mass function and the underlying cosmology. We conclude that observational studies of the absorption of $\sim 10^{-2}-10^{2}$ TeV gamma rays will help to constrain the star formation history of the universe, and the nature and extent of the extinction of starlight due to dust and reradiation of the absorbed energy at infrared wavelengths.Comment: 17 pages, 8 figures, presented at the VERITAS Workshop on TeV Astrophysics of Extragalactic Sources, eds. M. Catanese and T. Weekes, to be published in Astroparticle Physic

Objective Classification of Galaxy Spectra using the Information Bottleneck Method

A new method for classification of galaxy spectra is presented, based on a recently introduced information theoretical principle, the `Information Bottleneck'. For any desired number of classes, galaxies are classified such that the information content about the spectra is maximally preserved. The result is classes of galaxies with similar spectra, where the similarity is determined via a measure of information. We apply our method to approximately 6000 galaxy spectra from the ongoing 2dF redshift survey, and a mock-2dF catalogue produced by a Cold Dark Matter-based semi-analytic model of galaxy formation. We find a good match between the mean spectra of the classes found in the data and in the models. For the mock catalogue, we find that the classes produced by our algorithm form an intuitively sensible sequence in terms of physical properties such as colour, star formation activity, morphology, and internal velocity dispersion. We also show the correlation of the classes with the projections resulting from a Principal Component Analysis.Comment: submitted to MNRAS, 17 pages, Latex, with 14 figures embedde

Extragalactic Background Light and Gamma-Ray Attenuation

Data from (non-) attenuation of gamma rays from active galactic nuclei (AGN) and gamma ray bursts (GRBs) give upper limits on the extragalactic background light (EBL) from the UV to the mid-IR that are only a little above the lower limits from observed galaxies. These upper limits now rule out some EBL models and purported observations, with improved data likely to provide even stronger constraints. We present EBL calculations both based on multiwavelength observations of thousands of galaxies and also based on semi-analytic models, and show that they are consistent with these lower limits from observed galaxies and with the gamma-ray upper limit constraints. Such comparisons "close the loop" on cosmological galaxy formation models, since they account for all the light, including that from galaxies too faint to see. We compare our results with those of other recent works, and discuss the implications of these new EBL calculations for gamma ray attenuation. Catching a few GRBs with groundbased atmospheric Cherenkov Telescope (ACT) arrays or water Cherenkov detectors could provide important new constraints on the high-redshift star formation history of the universe.Comment: 12 pages, 8 multi-panel figures, Invited talk at the 25th Texas Symposium on Relativistic Astrophysics, Heidelberg December 6-10, 201