Can the unresolved X-ray background be explained by the emission from the optically-detected faint galaxies of the GOODS project?

The emission from individual X-ray sources in the Chandra Deep Fields and XMM – Newton Lockman Hole shows that almost half of the hard X-ray background above 6 keV is unresolved and implies the existence of a missing population of heavily obscured active galactic nuclei (AGN). We have stacked the 0.5–8 keV X-ray emission from optical sources in the Great Observatories Origins Deep Survey (GOODS; which covers the Chandra Deep Fields) to determine whether these galaxies, which are individually undetected in X-rays, are hosting the hypothesized missing AGN. In the 0.5–6 keV energy range, the stacked-source emission corresponds to the remaining 10–20 per cent of the total background – the fraction that has not been resolved by Chandra . The spectrum of the stacked emission is consistent with starburst activity or weak AGN emission. In the 6–8 keV band, we find that upper limits to the stacked X-ray intensity from the GOODS galaxies are consistent with the ∼40 per cent of the total background that remains unresolved, but further selection refinement is required to identify the X-ray sources and confirm their contribution.     

Large-scale solar magnetic field: Latitudinal dependence

Large-scale solar magnetic fields in the latitude range 50° S–50° N are analyzed in detail for a long time interval (1915–1990). We are primarily concerned with the two types of large-scale fields forming the two-and four-sector patterns on the Sun. The rotation parameters of these structures are obtained for all latitudes considered. The contribution of the two-sector structure grows and that of the four-sector structure decreases toward high latitudes. The magnetic field is activated simultaneously over a wide latitude range. Since both magnetic-field systems exhibit quasi-rigid rotation, their current systems must either be concentrated in a narrow latitude range or be situated beneath the convection zone, where rotation is only weakly differential. A period of about three years is manifest in the difference between the rotation periods for the two types of magnetic field. Physically, this may imply that these oscillations are external with respect to any level, and there is some phase delay due to their propagation from one level to another. We can conclude with a fair degree of certainty that as the activity level rises, the rotation speed decreases, and vice versa.     

Spatial correlation of unidentified gamma-ray sources with flaring and Wolf-Rayet stars

The spatial positions of unidentified gamma-ray sources ( E>100 MeV) were analyzed. This analysis shows that gamma-ray sources with fluxes >5×10^?7 cm^?2 s^?1 correlate with Wolf-Rayet stars, while gamma-ray sources with fluxes <5×10^?7 cm^?2 s^?1 may be associated with flaring stars.     

The evolution of regional development concepts: some new trends

This paper traces the theoretical development of the regional concept and the use of regionalization techniques in Soviet geography and seeks to compare this history with comparable trends in Western geography. It is severely critical of the major and rapid paradigm shifts noticed in post-war Western geographical science and relates these to shifts in the approach to global development issues.     

LRS Bianchi type-I models with constant deceleration parameter in?creation field cosmology

We have studied Locally Rotationally Symmetric (LRS) Bianchi type-I space-time having constant deceleration parameter and filled with perfect fluid in the Hoyle-Narlikar C-field cosmology. Here, the creation field C is a function of time t only. The geometrical and physical aspects for the models are also studied.     

An in situ investigation of the preservation and alteration of presolar silicates in the Miller Range 07687 chondrite

Dust grains that formed around ancient stars and in stellar explosions seeded the early solar protoplanetary disk. While most of such presolar grains were destroyed during solar system formation, a fraction of such grains were preserved in primitive materials such as meteorites. These grains can provide constraints on stellar origins and secondary processing such as aqueous alteration and thermal metamorphism on their parent asteroids. Here, we report on the nature of aqueous alteration in the Miller Range (MIL) 07687 chondrite through the analysis of four presolar silicates and their surrounding material. The grains occur in the Fe-rich and Fe-poor lithologies, reflecting relatively altered and unaltered material, respectively. The O-isotopic compositions of two grains, one each from the Fe-rich and Fe-poor matrix, are consistent with formation in the circumstellar envelopes of low-mass Asymptotic Giant Branch (AGB)/Red Giant Branch (RGB) stars. The other two grains, also one each from the Fe-rich and Fe-poor matrix, have O-isotopic compositions consistent with formation in the ejecta of type-II supernovae (SNe). The grains derived from AGB/RGB stars include two polycrystalline pyroxene grains that contain Fe-rich rims. The SNe grains include a polycrystalline Ca-bearing pyroxene and a polycrystalline assemblage consistent with a mixture of olivine and pyroxene. Ferrihydrite is observed in all focused ion beam sections, consistent with parent-body aqueous alteration of the fine-grained matrix under oxidizing conditions. The Fe-rich rims around presolar silicates in this study are consistent with Fe-diffusion into the grains resulting from early-stage hydrothermal alteration, but such alteration was not extensive enough to lead to isotopic equilibration with the surrounding matrix.     

PROBLEMS IN CONSTRUCTING A BATHYMETRIC BASE MAP FOR THE GULF OF FINLAND

The various steps required for compilation of a bathymetric chart of the Gulf of Finland are outlined, taking into account the specific conditions characteristic of that water body. The use of available initial source materials and special survey work required for supplementing these sources is discussed. Translated by Edward Torrey, Alexandria, VA 22308 from: Geodeziya i kartografiya, 1988, No. 8, pp. 40-42.