Nonthermal X-Rays from the Galactic Ridge: a Tracer of Low Energy Cosmic Rays ?

A distinct low energy cosmic-ray component has been proposed to explain the essentially constant Be/Fe ratio at low metallicities. Atomic collisions of such low energy ions produce characteristic nonthermal X-ray emission. In this paper, we study the possible contribution of such X-rays to the Galactic ridge emission. We show that they would account for < 10% of the 10-60 keV luminosity of the thin Galactic disk component detected with RXTE. They could make a more significant contribution in the 0.5-10 keV energy range, provided that the nonthermal ion population extends down to about 1 MeV/nucleon and delivers about 10$^{42}$ erg s$^{-1}$ to the interstellar medium, comparable to the total power suplied by the Galactic supernovae. But since the nonthermal X-rays in this energy range are essentially produced below the thresholds of the Be-producing cross sections, their detection does not necessarily imply a low energy cosmic-ray origin for the spallogenic light elements. A significant contribution of nonthermal X-rays could alleviate the problem of the origin of the hard component observed with ASCA in the Scutum arm region.Comment: latex 9 pages, uses paspconf.sty, 4 figures. To appear in "LiBeB, Cosmic Rays and Gamma-Ray Line Astronomy", ASP Conference Series, eds. R. Ramaty, E. Vangioni-Flam, M. Casse and K. Oliv

Science with the Constellation-X Observatory

The Constellation X-ray Mission is a high throughput X-ray facility emphasizing observations at high spectral resolution (E/\Delta E \sim 300-3000), and broad energy bandpass (0.25-40 keV). Constellation-X will provide a factor of nearly 100 increase in sensitivity over current high resolution X-ray spectroscopy missions. It is the X-ray astronomy equivalent of large ground-based optical telescopes such as the Keck Observatory and the ESO Very Large Telescope. When observations commence toward the end of next decade, Constellation-X will address many fundamental astrophysics questions such as: the formation and evolution of clusters of galaxies; constraining the baryon content of the Universe; determining the spin and mass of supermassive black holes in AGN; and probing strong gravity in the vicinity of black holes.Comment: to appear in "After the Dark Ages: When Galaxies Were Young", eds. S.S. Holt and E.P. Smith, 4 pages, 1 figur

Systematic spectral analysis of GX 339-4: influence of Galactic background and reflection models

Black hole X-ray binaries display large outbursts, during which their properties are strongly variable. We develop a systematic spectral analysis of the 3-40 keV RXTE/PCA data in order to study the evolution of these systems and apply it to GX 339-4. Using the low count rate observations, we provide a precise model of the Galactic background at GX 339-4's location and discuss its possible impact on the source spectral parameters. At higher fluxes, the use of a Gaussian line to model the reflection component can lead to the detection of a high-temperature disk, in particular in the high-hard state. We demonstrate that this component is an artifact arising from an incomplete modeling of the reflection spectrum.Comment: 6 pages, 3 figures, Proceeding of the XMM-Newton 2015 Science Workshop 'The Extremes of Black Hole Accretion', Accepted for publication in Astronomical Note

The Use of Remote Sensing Data for Advancing America's Energy Policy

After briefly reviewing America's Energy Policy laid out by the Obama Administration, we outline how a Global Carbon Observing System designed to monitor Carbon from space can provide the necessary data and tools to equip decision makers with the knowledge necessary to formulate effective energy use and practices policy. To stabilize greenhouse gas emissions in the atmosphere in a manner that it does not interfere with the Earth's climate system (which is one of the goals of United Nations Framework for Convention on Climate Change) requires vastly improved prediction of the atmospheric carbon dioxide (CO2) concentrations. This in torn requires a robust understanding of the carbon exchange mechanisms between atmosphere, land, and oceans and a clear understanding of the sources and sinks (i.e. uptake and storage) of CO2. We discuss how the Carbon Observing System from space aids in better understanding of the connection between the carbon cycle and climate change and provides more accurate predictions of atmospheric CO2 concentration. It also enables implementation of greenhouse gas (GHG) mitigation policies such as cap and trade programs, international climate treaties, as well as formulation of effective energy use policies

RXTE Hard X-ray Observation of A754: Constraining the Hottest Temperature Component and the Intracluster Magnetic Field

Abell 754, a cluster undergoing merging, was observed in hard X-rays with the Rossi X-ray Timing Explorer (RXTE) in order to constrain its hottest temperature component and search for evidence of nonthermal emission. Simultaneous modeling of RXTE data and those taken with previous missions yields an average intracluster temperature of $\sim 9$ keV in the 1-50 keV energy band. A multi-temperature component model derived from numerical simulations of the evolution of a cluster undergoing a merger produces similar quality of fit, indicating that the emission measure from the very hot gas component is sufficiently small that it renders the two models indistinguishable. No significant nonthermal emission was detected. However, our observations set an upper limit of $7.1 \times 10^{-14} ergs/(cm^2 s keV)$ (90% confidence limit) to the nonthermal emission flux at 20 keV. Combining this result with the radio synchrotron emission flux we find a lower limit of 0.2 $\mu$G for the intracluster magnetic field. We discuss the implications of our results for the theories of magnetic field amplifications in cluster mergers.Comment: Accepted for Publication in the Astrophysical Journal, 22 pages, 5 figure

NASA Laser Remote Sensing Technology Needs for Earth Science in the Next Decade and Beyond

In late 2005 the NASA Earth Science Technology Office convened a working group to review decadal-term technology needs for Earth science active optical remote sensing objectives. The outcome from this effort is intended to guide future NASA investments in laser remote sensing technologies. This paper summarizes the working group findings and places them in context with the conclusions of the National Research Council assessment of Earth science needs, completed in 2007

Credible targets for environmental management

In the year 2000, countries of the European Union agreed to harmonise water management by implementing the European Water Framework Directive (WFD). The WFD uses good ecological status as the overall goal, which is defined as minor deviation from an undisturbed state. Reference conditions provide the means of estimating water status and ecological integrity, which are the focal point of decision-making processes. When determining reference conditions, the WFD prescribes the use of all available knowledge so as to reduce the predictive uncertainties. While the goal of achieving conditions similar to an undisturbed state can be desirable, the use of reference conditions as a target creates inherent complexity on multiple levels. This thesis focuses on evaluating the implications of different interpretations and implementations of WFD reference conditions for status assessment of Swedish surface waters. Specifically, the objectives were to: (I) define the implications of different reference condition criteria and understand the diversity of ways in which the term is used, (II) compare independent estimates of reference conditions estimated using historical fish archives and biogeochemical modelling for acidification assessment, (III) evaluate recovery from acidification of acid sensitive Swedish lakes and analyse potential confounding factors influencing future management, (IV) develop empirical models to estimate historical and present temporal trends in lake total organic carbon concentrations. Together and individually these studies have developed methods and models in which predictive uncertainties associated with reference conditions have been reduced. This thesis show how multiple methods can be used to reduce the uncertainties in surface water reference condition estimates as well as presenting approaches to the use of all available information as prescribed by the WFD. Furthermore, this thesis highlight the multiple competing, but equally valid, approaches to estimate reference conditions based on knowledge from different sources. In this thesis, it is argued that representations of the undisturbed state are a moving target and greater acceptance for multiple reference conditions based on all available knowledge is needed

EU-Water Framework Directive, reference conditions & public participation : a comprehensive directive with antagonistic poles or a harmonious monopole?

The European Union accepted and approved the European Water Framework Directive (WFD) in 2000 through the European Parliament (WFD 2000/60/EC). It was seen as a joint decision to improve the water quality within the Union’s borders. The overall goal for water management is given as ‘good ecological status’ (GES) 15 years after implementation of the WFD. Two different scientific disciplines and often contradicting epistemologies lie at the heart of the WFD. Firstly, the classification of ecological status is with respect to a reference condition (RC), and RC is thought of as being the same as it was prior to significant human activity or disturbance, referred to as an “undisturbed state”. Secondly, public participation (PP), where it is explicitly argued that the success of the directive rested much on the outcome of PP. Information sharing from the decision makers seem to be the foremost important task when it comes to use of PP in the WFD. This study examined the relationship between RC and PP in the WFD through estimations of RC for 20 Swedish lakes with different input data, and a lake specific case-study in which perceptions of stakeholders in relation to what they believed was important for “their” lake. Furthermore, this study has explored the origin of the phrase ‘undisturbed state’ in relation to water bodies and explored the relationship between science and policy in the WFD. The results indicate that there is no direct relationship between PP and RC when considering the public’s perception. This study shows that the local people posses a great knowledge on specific events that they have visually experienced. The link between RC and PP in the WFD is clearer when the uncertainties for science are too large and classification of a lake cannot be made. Then local knowledge bought out through public participation could help in the classification of a lake and the establishment of the RC. This study supports the difficulties and uncertainties of determining RC for Swedish surface water, however, the basic values people hold about clean and unpolluted water corresponds well with the overall goal of GES for Swedish lakes. This raises the questions, should we keep our focus mainly on RC or use more of the basic values and local knowledge to focus on human benefits