Non-isothermal X-ray Emitting Gas in Clusters of Galaxies

We have analyzed X-ray spectra from six galaxy clusters which contain cooling flows: A85, A478, A1795, A2142, A2147, & A2199. The X-ray spectra were taken with the HEAO1-A2 Medium and High Energy Detectors and the Einstein Solid State Spectrometer. For each cluster, we simultaneously fit the spectra from these three detectors with models incorporating one or more emission components comprised of either thermal or cooling flow models. Five of the clusters (all but A2142) are better fit by a multi-component model (a cooling flow plus one or two thermal components or a two thermal component model) than by isothermal models. In four of the clusters (A85, A1795, A2147, & A2199), we find evidence for cool gas outside of the canonical cooling flow region. These latter four clusters can be characterized by three temperature components: a temperature inversion in the central region, a hotter region with an emission-weighted temperature which is higher than that of an isothermal model fit to the entire cluster, and a cooler region with an emission-weighted temperature of ~1 keV. The cool component outside the cooling flow region has a large minimum emission measure which we attribute, in part, to diffuse cool gas in the outer cluster atmosphere. If at least some of the cool exterior gas is virialized, this would imply a radially decreasing temperature profile. Together with the density profiles we have found, this leads to a baryon fraction in gas which increases with radius and is larger than that for an isothermal cluster atmosphere. Consequently, if clusters of galaxies trace the mass distribution in the Universe, the gas mass fraction we have calculated for an isothermal gas (which is ~15%) together with the nominal galaxy contribution (~5%) gives a baryon fraction of ~20%. Using the upper limit to the baryon density derived from BigComment: gzipped tar file of 26 PostScript pages, including 2 figures, 7 tables. Also available at http://www.astr.ua.edu/preprints/white/INDEX_READ_ME_1st.htm

Angry expressions strengthen the encoding and maintenance of face identity representations in visual working memory

This work was funded by a BBSRC grant (BB/G021538/2) to all authors.Peer reviewedPreprin

Static magnetic field models consistent with nearly isotropic plasma pressure

Using the empirical magnetospheric magnetic field models of Tsyganenko and Usmanov (TU), we have determined the self-consistent plasma pressure gradients and anisotropies along the midnight meridian in the near-Earth magnetosphere. By “inverting” the magnetic field, we determine what distributions of an anisotropic plasma, confined within the specified magnetic field configuration, are consistent with the magnetohydrostatic equilibrium condition, J × B = ∇ · P. The TU model, parameterized for different levels of geomagnetic activity by the Kp index, provided the magnetic field values from which J × B was numerically evaluated. A best fit solution was found that minimized the average difference between J × B and ∇ · P along an entire flux tube. Unlike previous semi-empirical models, the TU models contain magnetic stresses that can be balanced by a nearly isotropic plasma pressure with a reasonable radial gradient at the equator

Coordinated IUE, Einstein and optical observations of accreting degenerate dwarfs

Three binary systems believed to be composed of a white dwarf and a late type star, AM Her, SS Cyg, and U Gem were observed simultaneously in the IV X-ray and optical wavelengths. The system AM Her was in its customary high state at the time of the observations, while SS Cyg and U Gem were in a low state. In all three cases, a significant UV black body component with KT approximately greater than 10 eV was found. The flux in this component is in excess of the amount predicted by current scenarios of gravitational energy release

Magnetospheric plasma pressures in the midnight meridian: Observations from 2.5 to 35 RE

Plasma pressure data from the ISEE 2 fast plasma experiment (FPE) were statistically analyzed to determine the plasma sheet pressure versus distance in the midnight local time sector of the near-earth (12–35 RE) magnetotail plasma sheet. The observed plasma pressure, assumed isotropic, was mapped along model magnetic field flux tubes (obtained from the Tsyganenko and Usmanov [1982] model) to the magnetic equator, sorted according to magnetic activity, and binned according to the mapped equatorial location. In regions (L ≳ 12 RE) where the bulk of the plasma pressure was contributed by particles in the energy range of the FPE (70 eV to 40 keV for ions), the statistically determined peak plasma pressures vary with distance similarly to previously determined lobe magnetic pressures (i.e., in a time-averaged sense, pressure balance normal to the magnetotail magnetic equator in the midnight meridian is maintained between lobe magnetic and plasma sheet plasma pressures). Additional plasma pressure data obtained in the inner magnetosphere (2.5 \u3c L \u3c 7) by the Explorer 45, ATS 5, and AMPTE CCE spacecraft supplement the ISEE 2 data. Estimates of plasma pressures in the “transition” region (7–12 RE), where the magnetic field topology changes rapidly from a dipolar to a tail-like configuration, are compared with the observed pressure profiles. The quiet time “transition” region pressure estimates, obtained previously from inversions of empirical magnetic field models, bridge observations both interior to and exterior to the “transition” region in a reasonable manner. Quiet time observations and estimates are combined to provide profiles of the equatorial plasma pressure along the midnight meridian between 2.5 and 35 RE

Yucca Mountain Saturated Zone Carbon-14

This Scientific Investigation Plan (SIP) provides an overview of the work described in “Yucca Mountain Saturated Zone Carbon-14”, a proposal funded by the U.S. Department of Energy’s (DOE) Office of Repository Development under the UCCSN/YMP Co-op in support of the Science and Technology Initiatives. The objective of this work is to provide improved estimates of the time required for ground water to travel from the site of the proposed high-level radioactive waste repository at Yucca Mountain, Nevada, to the accessible environment

A Leafhopper Pest of Plants in the Mint Family, Eupteryx decemnotata Rey (Hemiptera: Auchenorrhyncha: Cicadellidae), Ligurian Leafhopper, New to North America

The Ligurian leafhoppter, Eupteryx decemnotata Rey (Hemiptera: Auchenorrhyncha: Cicadellidae), is reported for the first time in North America (USA: Florida and California). Diagnostic characters for species identification, summary of hosts and damage, and U.S. known distribution are given