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%R 1993ApJ...415...50C %A Cavaliere, A.; Colafrancesco, S.; Menci, N. %J Astrophysical Journal, Part 1, vol.415, no. 1, p. 50-57. %D 09/1993 %L 57 %T Distant clusters of galaxies detected by X-rays %K Cosmic Plasma, Dark Matter, Galactic Clusters, X-ray Astronomy, Baryons, Luminosity, Redshift %B The dynamical masses of groups and clusters of galaxies decrease on average with increasing redshift, after the hierarchical cosmogonies dominated by direct collapses of dark matter overdensities. We show that the masses of intracluster plasma emitting in the X-ray band are to decrease more rapidly. We also show that consideration of the intrinsic spread in the dynamical formation times leads us to predict more numerous faint sources at given dynamical mass. The model we compute yields steeper luminosity functions in the X-ray band with a specific change in lookback time: the bright end shifts back. Such negative evolution is fast even at modest redshifts z less than about 0.5 if the external gas infalling into groups of clusters was preheated and has cooled down after z of about 1.5-2. If so, the evolution is considerably faster in the X-ray than in the optical band, comparing interestingly with data from the existing surveys. %Z Abell, Ci. 0. 1958, ApJS, 3, 211 Barcons, X., Fabian, A. C., & Rees, M. J. 1991, Nature, 350, 685 Bardeen, J. M., Bond, J. R., Kaiser, N., & Szalay, A. 5. 1986, ApJ, 403, 15 Blumenthal, Ci., Faber, S. M., Primack, J. R., & Rees, M. J. 1984, Nature, 311, 517 Bohringer, H., et al. 1991, in Proc. NATO ASI "Clusters and Superclusters of Galaxies," ed. A. C. Fabian (Dordrecht: Kluwer), 71 Burg, R., Cavaliere, A., & Menci, N. 1993, ApJ, 404, L55 Cavaliere, A., Gursky, H., & Tucker, W. H. 1971, Nature, 231, 437 Cavaliere, A., & Colafrancesco, 5. 1988, ApJ, 331, 660 ---. 1990, in Clusters of Galaxies (Cambridge: Cambridge Univ. Press), 43 Cavaliere, A., Burg, R., & Giacconi, R. 1991, ApJ, 366, L61 %R 1993ApJ...415L..51F %A Furton, Douglas G.; Witt, Adolf N. %J Astrophysical Journal, Part 2 - Letters, vol. 415, no. 1, p. L51-L54. %D 09/1993 %L 54 %T Activation of extended red emission photoluminescence in carbon solids by exposure to atomic hydrogen and UV radiation %K Carbon, Hydrogen Atoms, Interstellar Matter, Photoluminescence, Ultraviolet Radiation, Cosmic Dust, Interstellar Extinction %B We report on new laboratory results which relate directly to the observation of strongly enhanced extended red emission (ERE) by interstellar dust in H2 photodissociation zones. The ERE has been attributed to photoluminescence by hydrogenated amorphous carbon (HAC). We are demonstrating that exposure to thermally dissociated atomic hydrogen will restore the photoluminescence efficiency of previously annealed HAC. Also, pure amorphous carbon (AC), not previously photoluminescent, can be induced to photoluminesce by exposure to atomic hydrogen. This conversion of AC into HAC is greatly enhanced by the presence of UV irradiation. The presence of dense, warm atomic hydrogen and a strong UV radiation field are characteristic environmental properties of H2 dissociation zones. Our results lend strong support to the HAC photoluminescence explanation for ERE. %R 1993ApJ...415...33D %A de Vaucouleurs, G. %J Astrophysical Journal, Part 1, vol. 415, no. 1, p. 33-39. %D 09/1993 %L 39 %T Specific frequencies of globular clusters in elliptical galaxies - A new test of the extragalactic distance scale %K Elliptical Galaxies, Galactic Structure, Globular Clusters, Hubble Constant, Distance, Lenticular Bodies, Scaling %B The specific frequency, S, values of globular clusters in elliptical galaxies (S is the ratio between total (extrapolated) number, N(t), and absolute luminosity of the galaxy) depend on the adopted distance scale. If the distance is derived form the redshift with an assumed value of the Hubble ratio, h = H/100, then the optimum value of h may be derived for a sample of normal E galaxies covering a sufficient range of distances by finding the value of h which minimizes the dispersion. In this paper, the best consistency between the specific frequencies of globular clusters among nine normal E galaxies is reached for H = 85 +/- 4, where the error is evidently an internal error only. H = 85 is also the value that minimizes the mean specific frequency itself. %R 1993ApJ...415....1S %A Sandage, Allan; Tammann, G. A. %J Astrophysical Journal, Part 1, vol. 415, no. 1, p. 1-9. %D 09/1993 %L 9 %T The Hubble diagram in V for supernovae of Type Ia and the value of H(0) therefrom %K Cepheid Variables, Galactic Structure, Hubble Space Telescope, Supernovae, Astronomical Photometry, Calibrating %B The Hubble diagram for Type I supernovae is derived in V and is summarized from the literature in B and in m(pg). The ridge line equation of the diagram in V and the calibration of the absolute magnitudes at maximum are presented. The intrinsic (B - V) color at B maximum light is 0.09 +/- 0.04 mag. The Virgo Cluster distance is derived and found to be 23.9 +/- 2.4 Mpc. This Virgo distance gives the cosmic value of the Hubble constant to be H(0) = 47 +/- 5 km/sec per Mpc. %R 1995ldef.symp...37R %A Reitz, G. %T Dosimetric results on EURECA %J In NASA. Langley Research Center, LDEF: 69 Months in Space. Third Post-Retrieval Symposium, Part 1 p.37-42 %D 02/1995 %L 42 %B Detector packages were exposed on the European Retrievable Carrier (EURECA) as part of the Biostack experiment inside the Exobiology and Radiation Assembly (ERA) and at several locations around EURECA. The packages consist of different plastic nuclear track detectors, nuclear emulsions and thermoluminescence dosimeters (TLD's). Evaluation of these detectors yields data on absorbed dose and particle and LET spectra. Preliminary results of absorbed dose measurements in the EURECA dosimeter packages are reported and compared to results of the LDEF experiments. The highest dose rate measured on EURECA is 63.3 plus or minus 0.4 mGy d(exp -1) behind a shielding thickness of 0.09 g cm(exp -2) in front of the detector package.
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