منابع مشابه
Objective transmission gratings for large schmidt telescopes.
Several lamellar gratings of 18-in. aperture, with 300 diffraction elements per inch, have been made for determining stellar spectra with wide angle telescopes. Central orders are missing at lambda4800, and weak at adjacent wavelengths. The two, equal first orders are about l(m) weaker than spectra by a prism or echelette grating. Dispersion is linear. The procedure of manufacture is adaptable ...
متن کاملFaint Quasar Surveys
Faint quasar surveys are necessary complements to bright quasar surveys to remove the degeneracy between redshift and luminosity inherent in any single magnitude-limited sample. I discuss two ongoing surveys for faint quasars at 3.3 < z < 5 and 5 < z < 6 using imaging data from the Big Throughput Camera on the CTIO 4-m. I also discuss a sample of faint spectroscopically selected AGN with z < 4....
متن کاملSurveys of ultraviolet-excess quasar candidates in large fields
We describe the results of a survey for moderately bright quasars performed in a 20.6-square-degree field around the galaxy NGC 450. The quasar candidates were selected on the basis of their ultraviolet excess: by comparative visual inspection of the double image of each single object on a U/B dual-exposure Schmidt photographic plate, 95 primary and 45 secondary quasar candidates were selected ...
متن کاملThe obscured quasar population from optical, mid-infrared, and X-ray surveys
Over the last few years, optical, mid-infrared and X-ray surveys have brought to light a significant number of candidate obscured AGN and, among them, many Type 2 quasars, the long-sought after “big cousins” of local Seyfert 2 galaxies. However, despite the large amount of multi-wavelength data currently available, a proper census and a panchromatic view of the obscured AGN/quasar population ar...
متن کاملSelection of quasar candidates from combined radio and optical surveys using neural networks
The application of supervised artificial neural networks (ANNs) for quasar selection from combined radio and optical surveys with photometric and morphological data is investigated, using the list of candidates and their classification from the work of White et al. Seven input parameters and one output, evaluated to 1 for quasars and 0 for non-quasars during the training, were used, with archit...
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ژورنال
عنوان ژورنال: International Astronomical Union Colloquium
سال: 1995
ISSN: 0252-9211
DOI: 10.1017/s0252921100022375