R. G. Cruddace

The ROSAT-ESO Flux-Limited X-ray (REFLEX) Galaxy Cluster Survey. IV. The X-ray luminosity function

The X-ray galaxy cluster sample from the REFLEX Cluster Survey, which covers the X-ray brightest galaxy clusters detected in the ROSAT All-Sky Survey in the southern sky, is used to construct the X-ray luminosity function of clusters in the local universe. With 452 clusters detected above an X-ray flux limit of 3 × 10-12 ergs s-1 cm-2 in 4.24 sr of the sky, this sample is the most comprehensive X-ray cluster sample with a well-documented selection function, providing the best current census of the local X-ray galaxy cluster population. In this paper we discuss the construction of the luminosity function and the effects of flux measurement errors and of variations with sample region, and we compare the results with those from previous surveys.

Multilayer-coated blazed grating performance in the soft x-ray region.

Useful grating efficiences for a variety of new spectrometer types have been attained. These results are discussed.

The COSMOS/UKST Catalog of the Southern Sky

We have prepared an ‘object’ catalog of the Southern sky south of + 2.5 degrees Declination from COSMOS scans of the IIIa-J and Short Red surveys taken with the UK Schmidt Telescope. The catalog consists of upwards of 500 million objects down to the limit of the plates. A version of the catalog in compact form is available for distribution, and a database management system has been produced which allows rapid access to any part of the catalog. We also describe the creation of a catalog of clusters of galaxies derived from the galaxies appearing in the object catalog. The cluster catalog contains some 70 000 candidate clusters in the Southern hemisphere and forms the basis for further major programs of follow-up study.

An X-ray survey of clusters of galaxies. IV - A survey of southern clusters and a compilation of upper limits for both Abell and southern clusters

The results of the HEAO 1 A-1 X-ray survey of galaxy clusters are reported. X-ray error boxes and intensities are presented for all clusters in the Abell catalog and for the catalog of southern clusters and groups compiled by Duus and Newell (1977). A correlation is derived on the basis of the X-ray luminosity function for 2-6 keV which may be used to calculate the contribution of clusters to the diffuse X-ray background at different energies. The cluster X-ray is estimated to be 9.3 percent (+ 1.9 or - 1.5 percent). Correlations between X-ray luminosity and other cluster properties are exmained, and it is found that the distribution of upper limits may be applied to obtaining a more precise estimate of the average X-ray luminosity of clusters. The Abell richness class and southern cluster concentrations were strongly correlated with X-ray luminosity. Correlations between optical x-ray luminosity and optical radius velocity dispersion, spiral fraction, and radio power are analyzed. The evidence for all these correlations was considered to be weak because of poor scatter in the data.

Multilayer-coated laminar grating with 16% normal-incidence efficiency in the 150-Å wavelength region

We characterized a laminar grating with a Mo/Si multilayer coating by using synchrotron radiation and atomic force microscopy. The grating substrate had 2400 grooves/mm, 40-A groove depth, and 2080-A groove width. The microroughness of the grating substrate was 5 A rms. The multilayer coating was optimized to have peak normal-incidence reflectance at a wavelength near 150 A. For an angle of incidence of 10 degrees the peak grating efficiency was 16.3% in the +1 order and 15.0% in the -1 order. The efficiency in the zero order was lower by a factor of 40 owing to the excellent matching of the groove depth and groove width to the wavelength of the incident radiation. By dividing the grating efficiencies by the measured reflectance of the multilayer coating, we obtained inferred groove efficiencies of 34% and 32% in the +1 and -1 orders, respectively.

Measurements of the normal-incidence X-ray reflectance of a molybdenum-silicon multilayer deposited on a 2000 l/mm grating

Normal-incidence grating optics coated with appropriate multilayers show great promise as a means of achieving high spectral resolution at x-ray wavelengths. Multilayer-coated mirrors have been made and tested successfully, but comparatively little work on such multilayer-coated gratings has been reported. We describe the results of reflectance meansurements made on a superpolished flat mirror and a Ferranti-Astron ion-etched 2000 l/mm laminar grating, which were coated simultaneously at the Lawrence Livermore National Laboratory with a 25-period Mo-Si multilayer. The multilayer was designed so that at normal incidence the mirror would have a maximum reflectance of 31% at a wavelength of 176 A. The measurements were performed using a reflectometer and monochromator installed on the Naval Research Laboratory X24C beamline at the Brookhaven National Synchrotron Light Source.

Performance of a tungsten/carbon multilayer-coated, blazed grating from 150 to 1700 eV

The advantages of multilayer coated blazed gratings are discussed, and multilayer/grating matching conditions are considered. Measurements of a W/C multilayer-coated, 2000 g/mm 3.8° blaze angle ion-etched grating and superpolished flat are reported. These include reflectometer measurements as well as operational performance of the pair as multilayer-multilayer grating diffraction elements in a two-crystal type monochromator. The results are promising for a variety of new spectrometer types.

X-ray observations of the Galactic center by Spartan 1

The results of Spartan 1 X-ray observations of the region within 1.25 deg of the Galactic center are presented. Four strong, hard X-ray point sources were detected: A1742-294, 1E 1740.7-2942, IE 1743.1-2843, and a new source SP 1744.2-2959 about 0.5 deg southeast of A1742-294. The new source had an intensity about 20 percent of that of A1742-294 and was relatively hard, having spectral parameters close to those of the diffuse source and of the Galactic bulge source GX 3+1. The Galactic nucleus X-ray source appears to have been a factor of four fainter during the 1985 Spartan 1 observations than during the 1979 Einstein observations. Hard, diffuse X-ray emission centered near the Galactic center, about 1 deg in extent, aligned to within 20 deg of the Galactic equator, and having a maximum 2-10 keV brightness of 1.5 x 10 to the -6th ergs/sq cm/s/sr was detected, as were two weaker point sources about 0.1 deg northeast and southeast of the Galactic nucleus, embedded in the diffuse emission. 34 references.

Long-term stability of a Mo/Si multilayer structure

The normal-incidence reflectance of a Mo/Si multilayer mirror, with peak reflectance near 130 A, was measured over a period of 20 months by using synchrotron radiation. The measured reflectances were unchanged over this period of time, and this indicates that the material layers and interfaces were stable.

Optimization of layered synthetic microstructures for broadband reflectivity at soft x-ray and EUV wavelengths.

A technique is described which allows the thickness of each layer in a layered synthetic microstructure to yield a useful constant efficiency over a broad band of wavelengths, several hundred angstroms wide, in the soft x-ray and EUV wave bands.