The Mass Function of an X-Ray Flux-Limited Sample of Galaxy Clusters

A new X-ray selected and X-ray flux-limited galaxy cluster sample is presented. Based on the ROSAT All-Sky Survey the 63 brightest clusters with galactic latitude |bII| >= 20 deg and flux fx(0.1-2.4 keV) >= 2 * 10^{-11} ergs/s/cm^2 have been compiled. Gravitational masses have been determined utilizing intracluster gas density profiles, derived mainly from ROSAT PSPC pointed observations, and gas temperatures, as published mainly from ASCA observations, assuming hydrostatic equilibrium. This sample and an extended sample of 106 galaxy clusters is used to establish the X-ray luminosity--gravitational mass relation. From the complete sample the galaxy cluster mass function is determined and used to constrain the mean cosmic matter density and the amplitude of mass fluctuations. Comparison to Press--Schechter type model mass functions in the framework of Cold Dark Matter cosmological models and a Harrison--Zeldovich initial density fluctuation spectrum yields the constraints OmegaM = 0.12^{+0.06}_{-0.04} and sigma8 = 0.96^{+0.15}_{-0.12} (90% c.l.). Various possible systematic uncertainties are quantified. Adding all identified systematic uncertainties to the statistical uncertainty in a worst case fashion results in an upper limit OmegaM < 0.31. For comparison to previous results a relation sigma8 = 0.43 OmegaM^{-0.38} is derived. The mass function is integrated to show that the contribution of mass bound within virialized cluster regions to the total matter density is small, i.e., OmegaCluster = 0.012^{+0.003}_{-0.004} for cluster masses larger than 6.4^{+0.7}_{-0.6} * 10^{13} h_{50}^{-1} Msun.Comment: 35 pages; accepted for publication in The Astrophysical Journal; this and related papers, supplementary information, as well as electronic files of the tables given in this paper are available at http://www.astro.virginia.edu/~thr4f

Electronic invoicing for small businesses

Masteroppgave i informasjons- og kommunikasjonsteknologi IKT590 2011 – Universitetet i Agder, GrimstadThe Norwegian government has released an act suggesting that all invoices sent to the public sector should be sent electronically by the year 2012. In addition more and more large companies demand their suppliers to send invoices electronically. Such demands may exclude less resourceful participants from taking part in trade with a section of the market. Hence, this project is set out to find a solution for sending electronic invoices aimed at the less resourceful small businesses and sole proprietors. The study has identified user habits with issues involved, and carried out a market analysis including research of existing infrastructure and related systems. The findings of the made studies have been transferred to a solution design, prepared for release within Norway and possibly for use within the Pan-European Public Procurement On Line, PEPPOL consortium. Morover, certain aspects of the solution design have been implemented in a prototype. It is believed that the proposed solution will ensure that less resourceful participants can still take part in trade with all of the market. The documented design specification, in combination with the prototype, provides a solid foundation for full-scale implementation

Jupiter atmospheric entry mission study. Volume 1 - Management summary Final report

Management summary and technical requirements for Jupiter atmospheric entry mission in 1978 using TOPS or Pioneer F/G spacecraf

Lunar contour mapping system /lucom/ final report, 5 aug. 1964 - 18 mar. 1965

Radar sensor system for acquisition of lunar surface data - Lunar contour mapping syste

The large-scale structure of the Universe; environmental effects and relativistic corrections

Over the cosmic age gravity has formed the structures in the universe where galaxies are part of. We study here the effect of the environmet on the formation of dark-matter haloes and find that the growth can be quenched. Moreover we study relativistic corrections on the observed large-scale structure of galaxies, as upcomming surveys will be able to observe correlation on larger scale

The structure and content of the galaxy and galactic gamma rays

Papers are presented dealing with galactic structure drawing on all branches of galactic astronomy with emphasis on the implications of the new gamma ray observations. Topics discussed include: (1) results from the COS-B gamma ray satellite; (2) results from SAS-2 on gamma ray pulsar, Cygnus X-3, and maps of the galactic diffuse flux; (3) recent data from CO surveys of the galaxy; (4) high resolution radio surveys of external galaxies; (5) results on the galactic distribution of pulsars; and (6) theoretical work on galactic gamma ray emission