Galaxy surface photometry

We describe galaxy surface photometry based on fitting ellipses to the isophotes of the galaxies. Example galaxies with different isophotal shapes are used to illustrate the process, including how the deviations from elliptical isophotes are quantified using Fourier expansions. We show how the definitions of the Fourier coefficients employed by different authors are linked. As examples of applications of surface photometry we discuss the determination of the relative disk luminosities and the inclinations for E and S0 galaxies. We also describe the color-magnitude and color-color relations. When using both near-infrared and optical photometry, the age-metallicity degeneracy may be broken. Finally we discuss the Fundamental Plane where surface photometry is combined with spectroscopy. It is shown how the FP can be used as a sensitive tool to study galaxy evolution.Comment: 40 pages. Lectures given at the Nordic-Baltic Research Course in Applied Astrophysical Photometry, held September 1999 at the Moletai Observatory, Lithuania. Baltic Astronomy, 8, 535 (1999), in press. Note the year. The paper with Fig. 2, 14 and 15 in original (high) resolution is available at http://www.astro.ku.dk/~milvang/papers/BA_MJ_J.ps.gz or http://www.gemini.edu/documentation/preprints/pre58.htm

Population ageing, public debt and sustainable fiscal policy

Due to rising life expectancy and declining fertility, the world’s population is ageing rapidly. Not only does the number of elderly relative to the number of working-age people increase, so does the proportion of the very old in the general population of the aged. In consequence, government spending on pensions, health care and other services provided for the aged is increasing and has been projected to rise on an even larger scale after the turn of the century. How can the old-age social expenditures be accommodated into a sustainable path for the general government budget?2 In most European countries, public outlays allocated to the elderly are financed on a pay-as-you-go (PAYG) basis, i.e. benefits paid to retired people are directly financed by contemporaneous taxes levied on workers. In periods with dramatic swings in the age structure, the tax rate is likely to swing as well. For example, when the population is ageing, the ratio of the number of persons of drawing age to that of those of contributing age increases, and PAYG financing implies an increase in the transfers from young to old. Does that cause generational conflicts, and will the PAYG scheme eventually be undermined?

Probing the truncation of galaxy dark matter halos in high density environments from hydrodynamical N-body simulations

We analyze high resolution, N-body hydrodynamical simulations of fiducial galaxy clusters to probe tidal stripping of the dark matter subhalos. These simulations include a prescription for star formation allowing us to track the fate of the stellar component as well. We investigate the effect of tidal stripping on cluster galaxies hosted in these dark matter subhalos as a function of cluster-centric radius. To quantify the extent of the dark matter halos of cluster galaxies, we introduce the half mass radius r_half as a diagnostic, and study its evolution with projected cluster-centric distance R as a function of redshift. We find a well defined trend for (r_half,R): the closer the galaxies are to the center of the cluster, the smaller the half mass radius. Interestingly, this trend is inferred in all redshift frames examined in this work ranging from z=0 to z=0.7. At z=0, galaxy halos in the central regions of clusters are found to be highly truncated, with the most compact half mass radius of 10 kpc. We also find that r_half depends on luminosity and we present scaling relations of r_half with galaxy luminosity. The corresponding total mass of the cluster galaxies is also found to increase with projected cluster-centric distance and luminosity, but with more scatter than the (r_half,R) trend. Comparing the distribution of stellar mass to total mass for cluster galaxies, we find that the dark matter component is preferentially stripped, whereas the stellar component remains protected by the halo and is much less affected by tidal forces. We compare these results with galaxy-galaxy lensing probes of r_half and find qualitative agreement. (Abridged)Comment: Accepted for publication in Ap

Authenticity and Fraud Information to Consumers regarding Control of Quality and Safety in Organic Production Chains

This leaflet provides a practical overview for consumers of what is done to secure the authenticity and integrity of 7 types of organically produced foods, where improvements are possible and what the consumers can do to support efforts that meet their demands. Other leaflets for consumers cover taste, freshness and nutrients or safety and contamination, and separate leaflets aim at retailers or at production of specific commodities