A Free-Form Lensing Grid Solution for A1689 with New Mutiple Images

Hubble Space Telescope imaging of the galaxy cluster Abell 1689 has revealed an exceptional number of strongly lensed multiply-imaged galaxies, including high-redshift candidates. Previous studies have used this data to obtain the most detailed dark matter reconstructions of any galaxy cluster to date, resolving substructures ~25 kpc across. We examine Abell 1689 (hereafter, A1689) non-parametrically, combining strongly lensed images and weak distortions from wider field Subaru imaging, and we incorporate member galaxies to improve the lens solution. Strongly lensed galaxies are often locally affected by member galaxies, however, these perturbations cannot be recovered in grid based reconstructions because the lensing information is too sparse to resolve member galaxies. By adding luminosity-scaled member galaxy deflections to our smooth grid we can derive meaningful solutions with sufficient accuracy to permit the identification of our own strongly lensed images, so our model becomes self consistent. We identify 11 new multiply lensed system candidates and clarify previously ambiguous cases, in the deepest optical and NIR data to date from Hubble and Subaru. Our improved spatial resolution brings up new features not seen when the weak and strong lensing effects are used separately, including clumps and filamentary dark matter around the main halo. Our treatment means we can obtain an objective mass ratio between the cluster and galaxy components, for examining the extent of tidal stripping of the luminous member galaxies. We find a typical mass-to-light ratios of M/L_B = 21 inside the r<1 arcminute region that drops to M/L_B = 17 inside the r<40 arcsecond region. Our model independence means we can objectively evaluate the competitiveness of stacking cluster lenses for defining the geometric lensing-distance-redshift relation in a model independent way.Comment: 23 pages with 25 figures Replced with MNRAS submitted version. Some figures have been corrected and minor text edit

On Gravitational Waves in Spacetimes with a Nonvanishing Cosmological Constant

We study the effect of a cosmological constant $\Lambda$ on the propagation and detection of gravitational waves. To this purpose we investigate the linearised Einstein's equations with terms up to linear order in $\Lambda$ in a de Sitter and an anti-de Sitter background spacetime. In this framework the cosmological term does not induce changes in the polarization states of the waves, whereas the amplitude gets modified with terms depending on $\Lambda$. Moreover, if a source emits a periodic waveform, its periodicity as measured by a distant observer gets modified. These effects are, however, extremely tiny and thus well below the detectability by some twenty orders of magnitude within present gravitational wave detectors such as LIGO or future planned ones such as LISA.Comment: 8 pages, 4 figures, accepted for publication in Physical Review

Solar and stellar system tests of the cosmological constant

Some tests of gravity theories - periastron shift, geodetic precession, change in mean motion and gravitational redshift - are applied in solar and stellar systems to constrain the cosmological constant. We thus consider a length scale range from 10^8 to 10^{15} km. Best bounds from the solar system come from perihelion advance and change in mean motion of Earth and Mars, Lambda < 10^{-36} km^{-2}. Such a limit falls very short to estimates from observational cosmology analyses but a future experiment performing radio ranging observations of outer planets could improve it by four orders of magnitude. Beyond the solar system, together with future measurements of periastron advance in wide binary pulsars, gravitational redshift of white dwarfs can provide bounds competitive with Mars data.Comment: 4 pages; this is a preprint of an article accepted for publication in Physical Review

Gravitational lensing in metric theories of gravity

Gravitational lensing in metric theories of gravity is discussed. I introduce a generalized approximate metric element, inclusive of both post-post-Newtonian (ppN) contributions and gravito-magnetic field. Following Fermat's principle and standard hyphoteses, I derive the time delay function and deflection angle caused by an isolated mass distribution. Several astrophysical systems are considered. In most of the cases, the gravito-magnetic correction offers the best perspectives for an observational detection. Actual measurements distinguish only marginally different metric theories one from another.Comment: 15 pages; to appear in Phys. Rev.

Estimativa da habilidade materna em éguas da raça pantaneira através do tempo de mamada.

Este trabalho teve como objetivo estimar a habilidade materna em éguas da raça Pantaneira através do tempo de mamada. Utilizaram-se 30 éguas com potro ao pé com idade média de 7 ,2::t 1,92 ano. Nove observadores foram distribuídos em turnos de 6h/dia, anotando-se o tempo da mamada, horário, clima, égua, sexo do potro, interrupção da mamada realizada pelo potro/égua. Não houve associação entre o tempo de mamada e o horário (manhã ou tarde), bem como horário e interrupção da mamada, independente do potro ou a égua interromper a mamada. Observou-se tempo médio de mamada (n=746) de 1,14 :t 0,59 minutos com coeficiente de variação de 42%. Houve associação (X2, P=O,OOl) entre ordem do parto e tempo da mamada, evidenciando que a habilidade materna das éguas primíparas é inferior as demais éguas com idade superior a 4,5 anos ou mais de duas crias, decrescendo após os sete anos ou mais de cinco partos

Transient perceptual neglect: visual working memory load affects conscious object processing

Visual working memory (VWM) is a capacity-limited cognitive resource that plays an important role in complex cognitive behaviors. Recent studies indicate that regions subserving VWM may play a role in the perception and recognition of visual objects, suggesting that conscious object perception may depend on the same cognitive and neural architecture that supports the maintenance of visual object information. In the present study, we examined this question by testing object processing under a concurrent VWM load. Under a high VWM load, recognition was impaired for objects presented in the left visual field, in particular when two objects were presented simultaneously. Multivariate fMRI revealed that two independent but partially overlapping networks of brain regions contribute to object recognition. The first network consisted of regions involved in VWM encoding and maintenance. Importantly, these regions were also sensitive to object load. The second network comprised regions of the ventral temporal lobes traditionally associated with object recognition. Importantly, activation in both networks predicted object recognition performance. These results indicate that information processing in regions that mediate VWM may be critical to conscious visual perception. Moreover, the observation of a hemifield asymmetry in object recognition performance has important theoretical and clinical significance for the study of visual neglect

Measuring the Three-Dimensional Structure of Galaxy Clusters. II. Are clusters of galaxies oblate or prolate?

The intrinsic shape of galaxy clusters can be obtained through a combination of X-ray and Sunyaev-Zeldovich effect observations once cosmological parameters are assumed to be known. In this paper we discuss the feasibility of modelling galaxy clusters as either prolate or oblate ellipsoids. We analyze the intra-cluster medium distribution for a sample of 25 X-ray selected clusters, with measured Sunyaev-Zeldovich temperature decrements. A mixed population of prolate and oblate ellipsoids of revolution fits the data well, with prolate shapes preferred on a 60-76% basis. We observe an excess of clusters nearly aligned along the line of sight, with respect to what is expected from a randomly oriented cluster population, which might imply the presence of a selection bias in our sample. We also find signs that a more general triaxial morphology might better describe the morphology of galaxy clusters. Additional constraints from gravitational lensing could disentangle the degeneracy between an ellipsoidal and a triaxial morphology, and could also allow an unbiased determination of the Hubble constant.Comment: 9 pages, 8 figures, accepted for publication in Astrophys.