Properties of spherical galaxies and clusters with an NFW density profile

Using the standard dynamical theory of spherical systems, we calculate the properties of spherical galaxies and clusters whose density profiles obey the universal form first obtained in high resolution cosmological N-body simulations by Navarro, Frenk & White. We adopt three models for the internal kinematics: isotropic velocities, constant anisotropy and increasingly radial Osipkov-Merritt anisotropy. Analytical solutions are found for the radial dependence of the mass, gravitational potential, velocity dispersion, energy and virial ratio and we test their variability with the concentration parameter describing the density profile and amount of velocity anisotropy. We also compute structural parameters, such as half-mass radius, effective radius and various measures of concentration. Finally, we derive projected quantities, the surface mass density and line-of-sight as well as aperture velocity dispersion, all of which can be directly applied in observational tests of current scenarios of structure formation. On the mass scales of galaxies, if constant mass-to-light is assumed, the NFW surface density profile is found to fit well Hubble-Reynolds laws. It is also well fitted by Sersic R^(1/m) laws, for m ~ 3, but in a much narrower range of m and with much larger effective radii than are observed. Assuming in turn reasonable values of the effective radius, the mass density profiles imply a mass-to-light ratio that increases outwards at all radii.Comment: 13 pages, 13 figures, uses mn.sty and epsf.tex, revised version accepted by MNRAS (results for anisotropic models added, comparison with observations extended

Aging, Retirement and Human Resources Management: A Strategic Approach

This chapter introduces the organizational view of retirement by exploring the relationship between organizational strategy and human resource management decisions regarding retirement. The authors begin with an overview of organizational strategy and discuss two methods used to plan for an aging and retiring workforce. Several key human resource decisions related to retirement are then addressed. In the pre-retirement phase, the role of HR In helping employees to prepare for retirement Is discussed, focusing primarily on financial planning and other retirement-related benefits. Next, human resource decisions pertaining to managing a retirement-ready workforce are discussed, addressing specifically the issues of knowledge transfer and motivating performance. Finally, interactions with individuals after retirement are discussed by looking at recruitment and bridge employment

Recruiting Older Workers: Realities and Needs of the Future Workforce

This chapter examines literature pertaining to the recruitment of older workers. It begins by addressing the question of relevance and why older worker recruitment matters. It then examines what is known about older workers, including their attitudes, motivations, and behaviors. Next the chapter addresses what employers are looking for in older workers and, more specifically, discusses the continuum of employers’ practices from those that aggressively try to attract and retain older workers and apply a conservation model of older worker management to those that apply a depreciation model and focus primarily on retrenchment and downsizing older employees. Finally, it addresses how employers can recruit older workers through changes in organizational policies and practices

Putting off Tomorrow to Do What You Want Today: Planning for Retirement

In this article we note that in the coming years, a larger number of people will be experiencing retirement for a longer period of time than ever before and that despite this fact, many will find themselves unprepared for this stage of their lives. We review the literature on retirement preparation, structuring our review around the key questions that need to be addressed when planning for retirement: (a) What will I do? (b) How will I afford it? (c) Where will I live? and (d) Who will I share it with? We make a number of suggestions for research and practice. We conclude that although psychology has begun to play a role in understanding and addressing retirement preparation, there are considerable opportunities for psychologists to engage with this issue in their research and applied work

Fourlined Plant Bug (Hemiptera: Miridae), a Reappraisal: Life History, Host Plants, and Plant Response to Feeding

Phenology of the fourlined plant bug, Poecilocapsus lineatus, is presented for southcen- tral Pennsylvania; life history and habits are re-examined. Although breeding was previously thought to occur only on woody plants, we found that nymphs develop on numerous herbs. An extensive list of hosts, more than 250 species in 57 families, is compiled from the literature and the authors\u27 observations; preferences are noted for plants in the Labiatae, Solanaceae, and Compositae. Damage consists of lesions on foliage, the size and shape of the spots varying with leaf texture, pubescence, and venation. Plant response to feeding is immediately visible, the lesions seeming to appear simultaneously with insertion of the bug\u27s stylets. Histolysis of plant tissues, the most rapid response to mind feeding yet reported, is attributed to a potent lipid enzyme whose active constituents are under investigation

Investigation of Metal and Organic Contaminant Distributions and Sedimentation Rates in Backwater Lakes along the Illinois River

Systematic sub-sampling of sediment cores in sections of uniform thickness is necessary in order to evaluate historic changes in sediment quality, to determine the vertical extent of contamination, and to measure sedimentation rates. With these objectives in mind, fourteen sediment cores were collected during March 2002 using the Illinois State Water Survey vibracorer. Concentrations of metals and total organic carbon were measured using standard techniques. Concentrations of chlorinated pesticides, phenolic compounds, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) were measured by gas chromatography/mass spectrometry (GC-MS). The concentrations of chlorinated pesticides, phenolic compounds and polychlorinated biphenyls (PCBs) were below the method detection limit in all sediment samples analyzed. However, there was a wide range in concentrations of polycyclic aromatic hydrocarbons (PAHs) which were detected in all sediment samples. Also, a wide range of metal concentrations was noted in the sediments evaluated. Lower concentrations of metals were found in the upper 0.5 m of sediment but concentrations were elevated at depths ranging from 1.0 m to 1.5 m. Sedimentation rates were estimated using cesium-137 radiometric dating on 14 vibracores. Sedimentation rates range from < 0.1 to 1.9 cm/yr, with an average of 0.9 cm/yr. These rates are comparable to those reported in previous studies.Illinois Sustainable Technology Centerpublished or submitted for publicationis peer reviewe

Fiber pulling apparatus modification

A reduced gravity fiber pulling apparatus (FPA) was constructed in order to study the effects of gravity on glass fiber formation. The apparatus was specifically designed and built for use on NASA's KC-135 aircraft. Four flights have been completed to date during which E-glass fiber was successfully produced in simulated zero, high, and lunar gravity environments. In addition simulated lunar soil samples were tested for their fiber producing properties using the FPA

Breaking the mass / anisotropy degeneracy in the Coma cluster

We provide the first direct lifting of the mass/anisotropy degeneracy for a cluster of galaxies, by jointly fitting the line of sight velocity dispersion and kurtosis profiles of the Coma cluster, assuming an NFW tracer density profile, a generalized-NFW dark matter profile and a constant anisotropy profile. We find that the orbits in Coma must be quasi-isotropic, and find a mass consistent with previous analyses, but a concentration parameter 50% higher than expected in cosmological N-body simulations. We then test the accuracy of our method on realistic non-spherical systems with substructure and streaming motions, by applying it to the ten most massive structures in a cosmological N-body simulation. We find that our method yields fairly accurate results on average (within 20%), although with a wide variation (factor 1.7 at 1 sigma) for the concentration parameter, with decreased accuracy and efficiency when the projected mean velocity is not constant with radius.Comment: 5 pages, oral presentation at IAU Colloquium 195, Outskirts of Galaxy Clusters: intense life in the suburbs, ed. A. Diaferi

Dark matter distribution in the Draco dwarf from velocity moments

We study the distribution of dark matter in the Draco dwarf spheroidal galaxy by modelling the moments of the line-of-sight velocity distribution of stars obtained from new velocity data of Wilkinson et al. The luminosity distribution is approximated by a Sersic profile fitted to the data by Odenkirchen et al. We assume that the dark matter density profile is given by a formula with an inner cusp and an outer exponential cut-off, as recently proposed by Kazantzidis et al. as a result of simulations of tidal stripping of dwarfs by the potential of the Milky Way. The dark matter distribution is characterized by the total dark mass and the cut-off radius. The models have arbitrary velocity anisotropy parameter assumed to be constant with radius. We estimate the three parameters by fitting both the line-of-sight velocity dispersion and kurtosis profiles, which allows us to break the degeneracy between the mass distribution and velocity anisotropy. The results of the fitting procedure turn out to be very different depending on the stellar sample considered, that is on our choice of stars with discrepant velocities to be discarded as interlopers. For our most reliable sample, the model parameters remain weakly constrained, but the robust result is the preference for weakly tangential stellar orbits and high mass-to-light ratios. The best-fitting total mass is then 7 10^7 M_sun, much lower than recent estimates, while the mass-to-light ratio is M/L_V = 300 and almost constant with radius. If the binary fraction in the stellar population of Draco turns out to be significant, the kurtosis of the global velocity distribution will be smaller and the orbits inferred will be more tangential, while the resulting mass estimate lower.Comment: 11 pages, 8 figures, accepted for publication in MNRA