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On the Relationship between Optical and X-Ray Luminosity of Quasars
F. la Franca, A. Franceschini, S. Cristiani +1
The issue of the X-ray to optical luminosity relationship () is addressed for both optically and X-ray selected quasar samples. We have applied a generalized regression al…
The Space Distribution of the Lyman Alpha Clouds in the Line of Sight to the Z=3.66 QSO 0055-269
S. Cristiani, S. D'Odorico, A. Fontana +2
The spectrum of the quasar Q0055-269 () has been observed at the resolution of 14 km s in the wavelength interval 4750--6300 Å. We give a list of Lyman lines and…
The Homogeneous Bright Quasar Survey and the Quasar Evolution in the Optical, X and Radio Bands
S. Cristiani, F. La Franca
The present status of the ESO key-programme ``A Homogeneous Bright QSO Survey'' is described together with the first results concerning the QSO counts and the optical luminosity fu…
Sky Subtraction with Fiber-Spectrographs
C. Lissandrini, S. Cristiani, F. La Franca
The sky subtraction performances of multi-fiber spectrographs are discussed, analysing in detail the case of the OPTOPUS system at the 3.6 meter ESO telescope at La Silla. A standa…
The Gunn-Peterson Effect in the Spectrum of the Z=4.7 QSO 1202-0725: The Intergalactic Medium at Very High Redshift
E. Giallongo, S. D'Odorico, A. Fontana +5
A measure of the average depression between Lyman absorption lines in the spectrum of the faint quasar BR1202-0725 () is presented. The relatively high resolution of…