Galaxy Cluster Masses at Moderate Redshifts

The masses of galaxy clusters are dominated by dark matter, and a robust determination of their masses has the potential of indicating how much dark matter exists on large scales in the universe, and the cosmological parameter Omega. X-ray observations of galaxy clusters provide a direct measure of both the gas mass in the intra-cluster medium, and also the total gravitating mass of the cluster. We used new and archival ROSAT observations to measure these quantities for a sample of intermediate redshift clusters which have also been subject to intensive dynamical studies, in order to compare the mass estimates from different methods. A direct comparison of dynamical mass estimates yielded surprisingly good results

Red Sequence Cluster Finding in the Millennium Simulation

We investigate halo mass selection properties of red-sequence cluster finders using galaxy populations of the Millennium Simulation (MS). A clear red sequence exists for MS galaxies in massive halos at redshifts z < 1, and we use this knowledge to inform a cluster-finding algorithm applied to 500 Mpc/h projections of the simulated volume. At low redshift (z=0.4), we find that 90% of the clusters found have galaxy membership dominated by a single, real-space halo, and that 10% are blended systems for which no single halo contributes a majority of a cluster's membership. At z=1, the fraction of blends increases to 22%, as weaker redshift evolution in observed color extends the comoving length probed by a fixed range of color. Other factors contributing to the increased blending at high-z include broadening of the red sequence and confusion from a larger number of intermediate mass halos hosting bright red galaxies of magnitude similar to those in higher mass halos. Our method produces catalogs of cluster candidates whose halo mass selection function, p(M|\Ngal,z), is characterized by a bimodal log-normal model with a dominant component that reproduces well the real-space distribution, and a redshift-dependent tail that is broader and displaced by a factor ~2 lower in mass. We discuss implications for X-ray properties of optically selected clusters and offer ideas for improving both mock catalogs and cluster-finding in future surveys.Comment: final version to appear in MNRAS. Appendix added on purity and completeness, small shift in red sequence due to correcting an error in finding i

Dynamical Masses of RCS Galaxy Clusters

A multi-object spectroscopy follow-up survey of galaxy clusters selected from the Red-sequence Cluster Survey (RCS) is being completed. About forty clusters were chosen with redshifts from 0.15 to 0.6, and in a wide range of richnesses. One of the main science drivers of this survey is a study of internal dynamics of clusters. We present some preliminary results for a subset of the clusters, including the correlation of optical richness with mass, and the mass-to-light ratio as a function of cluster mass.Comment: 5 pages, 5 figures, to appear in the Proceedings of IAU Colloquium 195: "Outskirts of Galaxy Clusters: intense life in the suburbs", Torino Italy, March 200

BENEFITS OF CONTROLLING SALINE WATER IN COLORADO

The Arkansas River in Colorado is confronted with a salinity issue; the majority of this salinity problem is due to agricultural runoff caused by irrigation. Reducing applications of irrigation water through adoption of more technically efficient irrigation systems is one means of improving water quality in the Arkansas River basin. This research uses positive mathematical programming to model the cropping practices of the farms along the Arkansas River. It examines the affect of acreage and profit levels of these farms given the choice of changing their irrigation technologies.Environmental Economics and Policy,

Development of a Multicriteria Decision Model for Prioritizing Air Force Environmental Restoration Program Projects

Cleaning up hazardous and toxic wastes left from past activities has become one of the major goals of the Department of Defense. Within the Air Force, individual major commands (MAJCOMs) annually review numerous projects submitted under the Defense Environmental Restoration Program (DERP) and forward these projects to HQ USAF/CEVR for funding. Until recently, adequate resources have been available to fully fund all projects. However, within the last two years, funding shortfalls have been experienced, and projects have received only partial funding. The Air Force needs a decision support system that will assist in determining funding priorities for these projects. This thesis presents two possible methodologies and resulting multicriteria decision models for determining funding priorities within the constraints of a limited budget. The first method utilizes a Delphi procedure to elicit pertinent criteria, weights, and utilities from DERP experts. The second method utilizes multiattribute utility theory to determine the preference structure of a single decision maker. Each method results in a working model which can be used to prioritize DERP projects. Both models resulted in risk being the primary decision criterion. Additionally the Delphi model also utilized cost, community acceptance, technical feasibility, mission impact, and socioeconomic impact

Phospholipid reactivation of plasmalogen metabolism

This report is concerned mainly with the properties of an enzyme from rat liver microsomes which hydrolyzes the alkenyl ether bond of 1‐(1′‐alk‐1′‐enyl)‐glycero‐3‐phosphoryl‐choline (alkenyl‐GPC hydrolase).Destruction of the normal environment of the microsomes by treatment with phospholipases A or C caused inactivation of the alkenyl‐GPC hydrolase, which was then partially reactivated by the addition of exogenous phospholipids. Both sphingomyelin and diacyl‐GPC were efficient in restoring activity; diacyl‐GPE was less effective; and monoacyl‐GPC and monoacyl‐GPE were ineffective. The presence of two long hydrocarbon chains in the lipid activator is apparently required for reactivation, suggesting that interaction of hydrophobic areas of the enzyme with the phospholipid is necessary for maximal activity. High concentrations of sucrose mimicked the effect of phospholipids, and because the sucrose and diacyl‐GPC did not show an additive effect, they may reactivate the enzyme in a similar manner.Disrupting the enzyme’s environment by freezing and thawing the preparation also resulted in a loss of enzymatic activity, which was restored by added exogenous phospholipids.The alkenyl‐GPC hydrolase was inhibited by imidazole and some of its derivatives. Histidine and N‐acetyl histidine did not inhibit the enzyme, presumably due to the presence of a negative charge on the carboxyl group rather than the steric bulk of that group, since histidine methyl ester did inhibit the enzyme. Kinetic evidence showed imidazole to be a competitive inhibitor. The enzymatic activity of imidazole‐treated microsomes also increased following addition of exogenous phospholipids. Imidazole inhibition differed from the phospholipase A‐inactivation in that it was partially reversed by KCl, but not by sucrose. Imidazole did not inhibit other microsomal enzymes tested, indicating that it is not a general inhibitor of membrane‐associated enzymes.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141883/1/lipd0111.pd