26,078 research outputs found
Weak Lensing Determination of the Mass in Galaxy Halos
We detect the weak gravitational lensing distortion of 450,000 background
galaxies (20<R<23) by 790 foreground galaxies (R<18) selected from the Las
Campanas Redshift Survey (LCRS). This is the first detection of weak lensing by
field galaxies of known redshift, and as such permits us to reconstruct the
shear profile of the typical field galaxy halo in absolute physical units
(modulo H_0), and to investigate the dependence of halo mass upon galaxy
luminosity. This is also the first galaxy-galaxy lensing study for which the
calibration errors are negligible. Within a projected radius of 200 \hkpc, the
shear profile is consistent with an isothermal profile with circular velocity
164+-20 km/s for an L* galaxy, consistent with typical disk rotation at this
luminosity. This halo mass normalization, combined with the halo profile
derived by Fischer et al (2000) from lensing analysis SDSS data, places a lower
limit of (2.7+-0.6) x 10^{12}h^{-1} solar masses on the mass of an L* galaxy
halo, in good agreement with satellite galaxy studies. Given the known
luminosity function of LCRS galaxies, and the assumption that for galaxies, we determine that the mass within 260\hkpc of normal
galaxies contributes to the density of the Universe (for
) or for . These lensing data suggest
that (95% CL), only marginally in agreement with the usual
Faber-Jackson or Tully-Fisher scaling. This is the most
complete direct inventory of the matter content of the Universe to date.Comment: 18 pages, incl. 3 figures. Submitted to ApJ 6/7/00, still no response
from the referee after four months
Factors shaping attitudes towards UK bank brands: An exploratory analysis of social media data
Social media provides a huge amount of data and rich market insight, and has changed the way customers interact with brands. This interaction is of great concern for any organisation as it transfers the power to shape brand image from advertisers to consumers. In light of the global financial crisis and the ensuing negative attitudes towards bank brands, this study has extracted 1176 comments on bank advertisements from the verified Facebook pages of 10 UK banks. These comments have been thematically analysed to identify seven key factors that shape customer attitudes to bank brands. The study presents the power of social media as a platform for brands and customers to engage and build relationships, especially bank–customer relationships in the UK, providing managers with important insights that can guide the development and execution of their brand-relationship campaigns. The fact that this study is based on real-life advertisements and real-life responses from social media network users can be considered as one of its strengths, as it does not suffer from various issues relating to experimental studies. Nonetheless, the study’s limitations and suggestions for future research directions are provided
A Generalized Diffusion Tensor for Fully Anisotropic Diffusion of Energetic Particles in the Heliospheric Magnetic Field
The spatial diffusion of cosmic rays in turbulent magnetic fields can, in the
most general case, be fully anisotropic, i.e. one has to distinguish three
diffusion axes in a local, field-aligned frame. We reexamine the transformation
for the diffusion tensor from this local to a global frame, in which the Parker
transport equation for energetic particles is usually formulated and solved.
Particularly, we generalize the transformation formulas to allow for an
explicit choice of two principal local perpendicular diffusion axes. This
generalization includes the 'traditional' diffusion tensor in the special case
of isotropic perpendicular diffusion. For the local frame, we motivate the
choice of the Frenet-Serret trihedron which is related to the intrinsic
magnetic field geometry. We directly compare the old and the new tensor
elements for two heliospheric magnetic field configurations, namely the hybrid
Fisk and the Parker field. Subsequently, we examine the significance of the
different formulations for the diffusion tensor in a standard 3D model for the
modulation of galactic protons. For this we utilize a numerical code to
evaluate a system of stochastic differential equations equivalent to the Parker
transport equation and present the resulting modulated spectra. The computed
differential fluxes based on the new tensor formulation deviate from those
obtained with the 'traditional' one (only valid for isotropic perpendicular
diffusion) by up to 60% for energies below a few hundred MeV depending on
heliocentric distance.Comment: 8 pages, 6 figures, accepted in Ap
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