Mathematics – Logic
Scientific paper
Mar 1982
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1982phdt........26p&link_type=abstract
Thesis (PH.D.)--UNIVERSITY OF FLORIDA, 1982.Source: Dissertation Abstracts International, Volume: 43-09, Section: B, page: 2935
Mathematics
Logic
3
Scientific paper
Photometric data for nearly 250 quasars, BL Lacertids, and active galaxies have been obtained at the Rosemary Hill Observatory during a continuous 13-year monitoring program. Long-term optical records for 130 of these sources are employed in an effort to assess the physical and cosmological properties of quasi-stellar objects. Photographic P and B magnitudes were obtained with the 76- and 46-cm telescopes at Rosemary Hill. Corrections for galactic absorption, emission lines, and the K-term are applied to the raw data yielding monochromatic flux densities at a standard emitted wavelength of 2500 (ANGSTROM). Long -term light curves are compiled for all objects and 3 levels of activity are determined for each individual source. The MEAN, BASE, and MAX brightness levels are then used to study QSOs in their average, quiescent, and active phases, respectively. Absolute intrinsic luminosities of all sources in the sample are computed from the monochromatic flux densities based on relativistic cosmological models. Radio -emitting quasars, radio-quiet QSOs, and active galaxies fall into 3 distinct groups and are examined separately. The cosmological properties of QSOs are studied by plotting apparent magnitude vs. redshift, the so-called Hubble diagram. Scatter in the diagram due to variability is substantially reduced by plotting log z vs. the MEAN, BASE, and MAX flux densities. The brightest QSOs at each redshift are then chosen as "standard candles" in an effort to determine if quasars obey Hubble's law for expanding universe. It is found that they fit the Hubble relation quite well if certain selection effects are accounted for. Other evidence for the cosmological origin of QSOs is briefly discussed. Variability provides a test as to whether individual quasars are essentially multiple in nature (the "Christmas Tree" model), or are single coherent sources (such as a massive black hole). The amplitude of variability vs. absolute luminosity relation is used to discriminate between the two models. Although the degree of optical variability is found to decrease with increasing luminosity, the magnitude of this inverse correlation is insufficient to substantiate the multiple subunit model. Instead, results favor a black hole model in which discrete events are superimposed on a continuously accreting disk of material. Information pertaining to the radio properties of QSOs has been compiled and 5 GHz spectral indices have been calculated for the radio sources. Cross-correlation analyses between various optical and radio parameters yield negative results. The lack of correlation indicates that optical and radio emissions are probably independent of one another and generally originate from different regions within the QSO.
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