2,114 research outputs found
Where do "red and dead" early-type void galaxies come from?
Void regions of the Universe offer a special environment for studying
cosmology and galaxy formation, which may expose weaknesses in our
understanding of these phenomena. Although galaxies in voids are observed to be
predominately gas rich, star forming and blue, a sub-population of bright red
void galaxies can also be found, whose star formation was shut down long ago.
Are the same processes that quench star formation in denser regions of the
Universe also at work in voids?
We compare the luminosity function of void galaxies in the 2dF Galaxy
Redshift Survey, to those from a galaxy formation model built on the Millennium
Simulation. We show that a global star formation suppression mechanism in the
form of low luminosity "radio mode" AGN heating is sufficient to reproduce the
observed population of void early-types. Radio mode heating is environment
independent other than its dependence on dark matter halo mass, where, above a
critical mass threshold of approximately M_vir~10^12.5 M_sun, gas cooling onto
the galaxy is suppressed and star formation subsequently fades. In the
Millennium Simulation, the void halo mass function is shifted with respect to
denser environments, but still maintains a high mass tail above this critical
threshold. In such void halos, radio mode heating remains efficient and red
galaxies are found; collectively these galaxies match the observed space
density without any modification to the model. Consequently, galaxies living in
vastly different large-scale environments but hosted by halos of similar mass
are predicted to have similar properties, consistent with observations.Comment: 6 pages, 3 figures, accepted MNRA
Corporate Social Responsibility Strategy and its Influence over Consumer Purchasing Decisions in Financial Institutions
The aim of this research is how CSR activities can influence the purchasing behaviour of consumers when it comes to financial institutions. Whilst there have been significant amounts of literature written on CSR there is still a gap in understanding how CSR activities influence consumers perception. This gap is particularly evident in the financial services sector given they are the largest contributors to CSR in Australia (ACCSR, 2011). In addressing the research problem, the study focusses on understanding the most influential CSR initiatives, understanding how the influence of CSR initiatives can change depending on situational context and then delves further to understand how demographic attributes can alter perception. Bhattacharya and Sen’s (2004) framework was used to frame the questionnaire that was answered by 1014 respondents, showing to be sufficiently representative of the Australian population. The outcomes of this research were used to develop a comprehensive framework for Australian Financial Institutions to use when developing their CSR strategy. It was clear that across all investment types and situational contexts, Community Support was the most influential form of CSR across the sample. Whilst this was the case, the level of influence differed across demographic groups and changed to varying degrees based on situational context dependent on the respondent. Community Support’s influence as a CSR initiative was clearly ahead of others presented to the respondents followed by Employee Support and Environment Support dependent on the investment method and the situational context
Cosmological Constraints from Galaxy Clustering and the Mass-to-Number Ratio of Galaxy Clusters
We place constraints on the average density (Omega_m) and clustering
amplitude (sigma_8) of matter using a combination of two measurements from the
Sloan Digital Sky Survey: the galaxy two-point correlation function, w_p, and
the mass-to-galaxy-number ratio within galaxy clusters, M/N, analogous to
cluster M/L ratios. Our w_p measurements are obtained from DR7 while the sample
of clusters is the maxBCG sample, with cluster masses derived from weak
gravitational lensing. We construct non-linear galaxy bias models using the
Halo Occupation Distribution (HOD) to fit both w_p and M/N for different
cosmological parameters. HOD models that match the same two-point clustering
predict different numbers of galaxies in massive halos when Omega_m or sigma_8
is varied, thereby breaking the degeneracy between cosmology and bias. We
demonstrate that this technique yields constraints that are consistent and
competitive with current results from cluster abundance studies, even though
this technique does not use abundance information. Using w_p and M/N alone, we
find Omega_m^0.5*sigma_8=0.465+/-0.026, with individual constraints of
Omega_m=0.29+/-0.03 and sigma_8=0.85+/-0.06. Combined with current CMB data,
these constraints are Omega_m=0.290+/-0.016 and sigma_8=0.826+/-0.020. All
errors are 1-sigma. The systematic uncertainties that the M/N technique are
most sensitive to are the amplitude of the bias function of dark matter halos
and the possibility of redshift evolution between the SDSS Main sample and the
maxBCG sample. Our derived constraints are insensitive to the current level of
uncertainties in the halo mass function and in the mass-richness relation of
clusters and its scatter, making the M/N technique complementary to cluster
abundances as a method for constraining cosmology with future galaxy surveys.Comment: 23 pages, submitted to Ap
Topology Synthesis of Structures Using Parameter Relaxation and Geometric Refinement
Typically, structural topology optimization problems undergo relaxation of certain design parameters to allow the existence of intermediate variable optimum topologies. Relaxation permits the use of a variety of gradient-based search techniques and has been shown to guarantee the existence of optimal solutions and eliminate mesh dependencies. This Technical Publication (TP) will demonstrate the application of relaxation to a control point discretization of the design workspace for the structural topology optimization process. The control point parameterization with subdivision has been offered as an alternative to the traditional method of discretized finite element design domain. The principle of relaxation demonstrates the increased utility of the control point parameterization. One of the significant results of the relaxation process offered in this TP is that direct manufacturability of the optimized design will be maintained without the need for designer intervention or translation. In addition, it will be shown that relaxation of certain parameters may extend the range of problems that can be addressed; e.g., in permitting limited out-of-plane motion to be included in a path generation problem
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