M/L and Color Evolution for A Deep Sample of M* Cluster Galaxies at z~1: The Formation Epoch and the Tilt of the Fundamental Plane

We have measured velocity dispersions for a sample of 36 galaxies with J < 21.2 or Mr < -20.6 mag in MS1054-03, a massive cluster of galaxies at z = 0.83. Our data are of uniformly high quality down to our selection limit, our 16-hour exposures typically yielding errors of only \delta(dispersion)~10% for L* and fainter galaxies. By combining our measurements with data from the literature, we have 53 cluster galaxies with measured dispersions, and HST/ACS-derived sizes, colors and surface brightnesses. This sample is complete for the typical L* galaxy at z~1, unlike most previous z~1 cluster samples which are complete only for the massive cluster members (>1e11 M_sun). We find no evidence for a change in the tilt of the fundamental plane (FP). Nor do we find evidence for evolution in the slope of the color-dispersion relation and M/L_B-dispersion relations; measuring evolution at a fixed dispersion should minimize the impact of size evolution found in other work. The M/L_B at fixed dispersion evolves by \Delta log10 M/L_B=-0.50 +/- 0.03 between z=0.83 and z=0.02 or d(log10 M/L_B)=-0.60 +/- 0.04 dz, and we find \Delta (U-V)_z=-0.24 +/- 0.02 mag at fixed dispersion in the rest-frame, matching the expected evolution in M/L_B within 2.25 standard deviations. The implied formation redshift from both the color and M/L_B evolution is z*=2.0 +/- 0.2 +/- 0.3 (sys), during the epoch in which the cosmic star-formation activity peaked, with the systematic uncertainty showing the dependence of z* on the assumptions we make about the stellar populations. The lack of evolution in either the tilt of the FP or in the M/L- and color-dispersion relations imply that the formation epoch depends weakly on mass, ranging from z*=2.3 +1.3 -0.3 at 300 km/s to z*=1.7 +0.3 -0.2 at 160 km/s and implies that the IMF similarly varies slowly with galaxy mass.Comment: revised; typos corrected, references updated, and other cosmetic changes to meet ApJ format ApJ accepted, 22 pages in emulate ApJ format, 8 color figures, 1 b/w figur

Phase space geometry in scalar-tensor cosmology

We study the phase space of spatially homogeneous and isotropic cosmology in general scalar-tensor theories. A reduction to a two-dimensional phase space is performed when possible-in these situations the phase space is usually a two-dimensional curved surface embedded in a three-dimensional space and composed of two sheets attached to each other, possibly with complicated topology. The results obtained are independent of the choice of the coupling function of the theory and, in certain situations, also of the potential.Comment: 18 pages, 9 figures, latex, to appear in Ann. Phys. (NY

The neonicotinoid insecticide Imidacloprid repels pollinating flies and beetles at field-realistic concentrations

Neonicotinoids are widely used systemic insecticides which, when applied to flowering crops, are translocated to the nectar and pollen where they may impact upon pollinators. Given global concerns over pollinator declines, this potential impact has recently received much attention. Field exposure of pollinators to neonicotinoids depends on the concentrations present in flowering crops and the degree to which pollinators choose to feed upon them. Here we describe a simple experiment using paired yellow pan traps with or without insecticide to assess whether the commonly used neonicotinoid imidacloprid repels or attracts flying insects. Both Diptera and Coleoptera exhibited marked avoidance of traps containing imidacloprid at a field-realistic dose of 1 μg L-1, with Diptera avoiding concentrations as low as 0.01 μg L-1. This is to our knowledge the first evidence for any biological activity at such low concentrations, which are below the limits of laboratory detection using most commonly available techniques. Catch of spiders in pan traps was also slightly reduced by the highest concentrations of imidacloprid used (1 μg L-1), but catch was increased by lower concentrations. It remains to be seen if the repellent effect on insects occurs when neonicotinoids are present in real flowers, but if so then this could have implications for exposure of pollinators to neonicotinoids and for crop pollination. © 2013 Easton, Goulson

Cosmological Scaling Solutions with Tachyon:Modified Gravity Model

Modifying the Einstein's gravity at large distance scales is one of the interesting proposals to explain the late time acceleration of the universe. In this paper, we analyse scaling solutions in modified gravity models where the universe is sourced by a background matter fluid together with a tachyon type scalar field. We describe a general prescription to calculate the scaling potential in such models. Later on, we consider specific examples of modifications and apply our method to calculate the scaling potential and the scale factor. Our method can be applied to any modified gravity model, in presence of a tachyon field.Comment: 6 pages, latex style, modified version, two new figures included, new refernces added, Accepted for publication in Physics Letters

Self-similar cosmological solutions with a non-minimally coupled scalar field

We present self-similar cosmological solutions for a barotropic fluid plus scalar field with Brans-Dicke-type coupling to the spacetime curvature and an arbitrary power-law potential energy. We identify all the fixed points in the autonomous phase-plane, including a scaling solution where the fluid density scales with the scalar field's kinetic and potential energy. This is related by a conformal transformation to a scaling solution for a scalar field with exponential potential minimally coupled to the spacetime curvature, but non-minimally coupled to the barotropic fluid. Radiation is automatically decoupled from the scalar field, but energy transfer between the field and non-relativistic dark matter can lead to a change to an accelerated expansion at late times in the Einstein frame. The scalar field density can mimic a cosmological constant even for steep potentials in the strong coupling limit.Comment: 10 pages, 1 figure, revtex version to appear in Phys Rev D, references adde

Cosmic Microwave Background Temperature and Polarization Anisotropy in Brans-Dicke Cosmology

We develop a formalism for calculating cosmic microwave background (CMB) temperature and polarization anisotropies in cosmological models with Brans-Dicke gravity. We then modify publicly available Boltzmann codes to calculate numerically the temperature and polarization power spectra. Results are illustrated with a few representative models. Comparing with the general-relativistic model with the same cosmological parameters, both the amplitude and the width of the acoustic peaks are different in the Brans-Dicke models. We use a covariance-matrix calculation to investigate whether the effects of Brans-Dicke gravity are degenerate with those of variation in other cosmological parameters and to simultaneously determine whether forthcoming CMB maps might be able to distinguish Brans-Dicke and general-relativistic cosmology. Although the predicted power spectra for plausible Brans-Dicke models differ from those in general relativity only slightly, we find that MAP and/or the Planck Surveyor may in principle provide a test of Brans-Dicke theory that is competitive to solar-system tests. For example, if all other parameters except for the CMB normalization are fixed, a value of the Brans-Dicke parameter omega as large as 500 could be identified with MAP, and for Planck, values as large as omega \simeq3000 could be identified; these sensitivities are decreased roughly by a factor of 3 if we marginalize over the baryon density, Hubble constant, spectral index, and reionization optical depth. In more general scalar-tensor theories, omega may evolve with time, and in this case, the CMB probe would be complementary to that from solar-system tests.Comment: 27 pages, 10 figures, typeset using RevTe

Understanding value creation and word-of-mouth behaviour at cultural events

Cultural value is a highly contested concept, despite its undoubted importance to practitioners and policy makers. Reseach into cultural value has, meanwhile, tended to employ a unidimensional value framework. This has hamprered the understanding of behaviour related to the word-of-mouth (WOM) communication behaviour of cultural values. This paper presents a cultural value segmentation based on a multidimensional value framework, allowing a profile of WOM behaviour (both online and offline) of each segment to be developed. The segmentation has four distinct segments of cultural consumer, each with different combinations of cultural values and WOM communication preferences. In this way, the study challenges current understandings of value creation and transfer in cultural settings. By way of practical recommendations, the study favours the use of market segmentation based on multi-dimensional value ‘constellations’, which can not only achieve better audience development but also to encourage wider WOM communication of the values in question

Data and 2D scaling relations for galaxies in Abell 1689: a hint of size evolution at z~0.2

{abridged} We present imaging and spectroscopy of Abell 1689 (z=0.183) from GEMINI/GMOS-N and HST/ACS. We measure integrated photometry from the GMOS g' and r' images (for 531 galaxies) and surface photometry from the HST F625W image (for 43 galaxies) as well as velocities and velocity dispersions from the GMOS spectra (for 71 galaxies). We construct the Kormendy relation (KR), Faber-Jackson relation (FJR) and colour-magnitude relation (CMR) for early-type galaxies in Abell 1689 using this data and compare them to those of the Coma cluster. We measure the intrinsic scatter of the CMR in Abell 1689 to be 0.054 \pm 0.004 mag which places degenerate constraints on the ratio of the assembly timescale to the time available (beta) and the age of the population. Making the assumption that galaxies in Abell 1689 will evolve into those of Coma over an interval of 2.26 Gyr breaks this degeneracy and limits beta to be > 0.6 and the age of the red sequence to be > 5.5 Gyr (formed at z > 0.55). Without corrections for size evolution but accounting for magnitude cuts and selection effects, the KR & FJR are inconsistent and disagree at the 2 sigma level regarding the amount of luminosity evolution in the last 2.26 Gyr. However, after correcting for size evolution the KR & FJR show similar changes in luminosity (0.22 \pm 0.11 mag) that are consistent with the passive evolution of the stellar populations from a single burst of star formation 10.2 \pm 3.3 Gyr ago (z = 1.8+inf-0.9). Thus the changes in the KR, FJR & CMR of Abell 1689 relative to Coma all agree and suggest old galaxy populations with little or no synchronisation in the star formation histories. Furthermore, the weak evidence for size evolution in the cluster environment in the last 2.26 Gyr places interesting constraints on the possible mechanisms at work, favouring harassment or secular processes over merger scenarios.Comment: Accepted for publication in MNRA

Solution generating in scalar-tensor theories with a massless scalar field and stiff perfect fluid as a source

We present a method for generating solutions in some scalar-tensor theories with a minimally coupled massless scalar field or irrotational stiff perfect fluid as a source. The method is based on the group of symmetries of the dilaton-matter sector in the Einstein frame. In the case of Barker's theory the dilaton-matter sector possesses SU(2) group of symmetries. In the case of Brans-Dicke and the theory with "conformal coupling", the dilaton- matter sector has $SL(2,R)$ as a group of symmetries. We describe an explicit algorithm for generating exact scalar-tensor solutions from solutions of Einstein-minimally-coupled-scalar-field equations by employing the nonlinear action of the symmetry group of the dilaton-matter sector. In the general case, when the Einstein frame dilaton-matter sector may not possess nontrivial symmetries we also present a solution generating technique which allows us to construct exact scalar-tensor solutions starting with the solutions of Einstein-minimally-coupled-scalar-field equations. As an illustration of the general techniques, examples of explicit exact solutions are constructed. In particular, we construct inhomogeneous cosmological scalar-tensor solutions whose curvature invariants are everywhere regular in space-time. A generalization of the method for scalar-tensor-Maxwell gravity is outlined.Comment: 10 pages,Revtex; v2 extended version, new parts added and some parts rewritten, results presented more concisely, some simple examples of homogeneous solutions replaced with new regular inhomogeneous solutions, typos corrected, references and acknowledgements added, accepted for publication in Phys.Rev.

Qualitative properties of scalar-tensor theories of Gravity

The qualitative properties of spatially homogeneous stiff perfect fluid and minimally coupled massless scalar field models within general relativity are discussed. Consequently, by exploiting the formal equivalence under conformal transformations and field redefinitions of certain classes of theories of gravity, the asymptotic properties of spatially homogeneous models in a class of scalar-tensor theories of gravity that includes the Brans-Dicke theory can be determined. For example, exact solutions are presented, which are analogues of the general relativistic Jacobs stiff perfect fluid solutions and vacuum plane wave solutions, which act as past and future attractors in the class of spatially homogeneous models in Brans-Dicke theory.Comment: 19 page