Stellar populations of cluster E and S0 galaxies

Spectral line indices for a sample of 290 nearby E and S0 galaxies are used to investigate the stellar populations of these galaxies. Relations are established between the line indices (Mg2, , Hbeta) and the velocity dispersions, the masses of the galaxies, the M/L ratios and the cluster environment. The difference between the slope of the Mg2-sigma relation and the slope of the -sigma relation indicates that the abundance ratio [Mg/Fe] increases with the velocity dispersion. The index is stronger correlated with the projected cluster surface density, than with the galaxy mass or the velocity dispersion. Also the Mg2 index depends on the cluster environment. The dependence on the environment implies that [Mg/Fe] decreases with increasing density. The M/L ratios are strongly correlated with the Mg2 and Hbeta, while is only weakly correlated with the M/L ratio. Based on current stellar population models it is not yet possible to derive unique physical parameters (mean age, mean abundances, mean IMF, and fraction of dark matter) from the observables (line indices, velocity dispersion, mass, M/L ratio).Comment: 29 pages, 14 figures and 10 tables included, LaTeX MN style. Accepted for publication in MNRA

Yersinia ruckeri challenge on rainbow trout fed different diet types

A challenge for sustainable rainbow trout production is an increasing use of plant sources in fish feed due to shortage of marine protein and oil sources. Diets with high plant content are known to cause enteritis and injury to the intestine, which will affect the absorption of nutrients, affecting the overall health status and welfare of the fish. The result is a higher risk of disease following exposure to pathogenic microorganisms. The aim of this study was to elucidate how different feed types with varying amounts of marine versus organic plant protein and oil sources affected the survival of rainbow trout in connection with an infection. Enteric redmouth disease caused by Yersinia ruckeri is an economically important disease which causes problems in rainbow trout. Experimental infections (intraperitoneal injection of 150-200 g fish fed the different diets over a two month period) were done and mortalities in the different diet groups were recorded. Two weeks post challenge the mortalities in the different groups were between 50 and 89 %. The mortalities were lowest in the group fed the diet where half of the fish oil was replaced by organic plant oil. Unfortunately, the results were blurred due to a natural infection with Y. ruckeri that had occurred in the diet groups two months prior to the experimental infection (mortalities between 2 and 9 % in the different groups), and the half fish oil half plant oil group had had the highest cumulative mortality percentage in connection with this natural infection

Aphid acceptance of Hordeum genotypes is affected by plant volatile exposure and is correlated with aphid growth

Nineteen genotypes of Hordeum vulgare were characterized as partially resistant or susceptible regarding growth of the bird cherry - oat aphid (Rhopalosiphum padi L.). These genotypes were treated with volatiles from undamaged plants of barley cultivar Alva. Aphid host acceptance (AHA) was significantly affected in seven genotypes, and the magnitude of the effect was positively correlated with aphid growth (AG) in a resistance screening test. Changes in AHA induced by volatiles from the same genotype were also positively correlated with AG. All genotypes were tested as inducers with cultivar Kara as the receiver of volatiles. Five genotypes induced significant reductions in AHA of Kara. The results show that aphids are able to detect changes in responding plants induced by volatiles from another cultivar. Plant volatile interactions may thus be a component of induced resistance to aphids. These interactions could influence the results of experiments used to select for insect-resistant plants in plant breeding programmes

The Fundamental Plane at z=0.18

We present preliminary results regarding the Fundamental Plane (FP) for galaxies in the two rich clusters Abell 665 and Abell 2218. Both clusters have a redshift of 0.18. We have compared the FP for A665 and A2218, and for the cluster CL0024+16 at z=0.39, with the FP for the Coma cluster. The scatter around the FP is similar for all four clusters. There may be indications that the slope of the FP is more shallow for the intermediate redshift clusters than for the Coma cluster. More complete samples of galaxies in intermediate redshift clusters are needed to map in detail the possible change of the slope as function of redshift. The mass-to-light (M/L) ratio as measured by the FP changes with redshift. At z=0.18 the M/L ratio (in Gunn r) is 16+-9% smaller than for the Coma cluster. Together with earlier results reported for CL0024+16 this implies that the M/L ratio changes with redshift as Delta log M/L_r ~ -0.4 Delta z. The results presented here are in agreement with passive evolution of a stellar population, which formed at a redshift larger than one. However, the possible presence of more recent bursts of star formation complicates the interpretation of the data.Comment: 10 pages, 5 figures included, LaTeX style lamuphys.sty To appear in the proceedings of the 3rd ESO-VLT Workshop Galaxy Scaling Relations, eds. da Costa et al., Springe

Stellar populations and evolution of early-type cluster galaxies: Constraints from optical imaging and spectroscopy of z=0.5-0.9 galaxy clusters

We present an analysis of stellar populations and evolutionary history of galaxies in three similarly rich galaxy clusters MS0451.6-0305 (z=0.54), RXJ0152.7-1357 (z=0.83), and RXJ1226.9+3332 (z=0.89); based on high S/N ground-based optical spectroscopy and HST imaging for 17-34 members in each cluster. We find no indication of evolution of sizes or velocity dispersions with redshift at a given dynamical galaxy mass. We establish the Fundamental Plane (FP) and scaling relations between absorption line indices and velocity dispersions. We confirm the steeper FP at z=0.86 compared to the low redshift FP, indicating (under the assumption of passive evolution) the formation redshift, z_form, depends on the galaxy velocity dispersion (or mass). z_form varies from z_form=1.24+-0.05 at velocity dispersion of 125 km/s to 1.95+-0.25 at 225 km/s. The three clusters and the low redshift sample follow similar scaling relations between absorption line indices and velocity dispersions. The strength of the higher order Balmer lines Hdelta and Hgamma implies z_form>2.8. From the line strengths we find that [M/H] for MS0451.6-0305 is about 0.2 dex below that of the other clusters, and confirm our previous result that [alpha/Fe] for RXJ0152.7-1357 is about 0.3 dex higher than that of the other clusters. These differences between the high-redshift clusters and the low redshift sample are inconsistent with a passive evolution scenario for early-type cluster galaxies over the redshift interval studied. (abridged)Comment: Accepted for publication in Astronomical Journal, 77 pages, uses emulateapj.cls, 36 figures. High resolution color figures available by e-mail request to the first autho

Optimal resource allocation in General Cournot-competitive equilibrium

Conventional economic theory stipulates that output in Cournot competition is too low relative to that which is attained in perfect competition. We revisit this result in a General Cournot-competitive Equilibrium model with two industries that differ only in terms of productivity. We show that in general equilibrium, the more efficient industry produces too little and the less efficient industry produces too much compared to an optimal scenario with perfect competition

Asymptotic analytical methods in fluid mechanics related to drag prediction

Some recent theoretical work of a purely analytical nature is described which promises to provide engineering predictions for the important drag-related phenomena of flow in the stall regime. This analytical work deals with rigorous asymptotic studies of the complete Navier-Stokes equations that govern the viscous flow around any aerodynamic body under conditions where boundary layer separation takes place from the body surface