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  • 1
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    Paired quasars near NGC 2639 - Evidence for quasars in superclusters (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Arp (1979, 1980) has found quasars with similar redshifts which appear to be paired across low-redshift galaxies. Arp concludes that the pairings provide evidence for an association between high-redshift quasars and a small, low-redshift galaxy. Oort et al. (1981) suggested an alternative hypothesis to explain the close redshift pairs. They proposed that the two closest pairs are in superclusters at the cosmological distances implied by the quasars' redshifts. The low-redshift quasar pair U7/U10 (0.303/0.305) is close enough to allow detection of any associated clusters of galaxies on deep red photographs. The present investigation had originally the objective to test the supercluster hypothesis by searching for faint clusters which might comprise a supercluster at z approximately 0.3. Unfortunately, the disappearance of the pairs makes it impossible to test the hypothesis in this field. The search for a supercluster at z = 0.30 revealed a faint rich cluster of galaxies near the quasar U10 (z = 0.305). It was found that U10 is not associated with the cluster.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 266
    Format: text
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  • 2
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    Observed dynamics of superclusters (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Radial velocity measurements of two large, rich superclusters show evidence of a gravitational slowing of the Hubble flow within the superclusters. Models assuming spherically symmetric, noncrossing mass shells yield mass density estimates for the clusters ranging from less than one to several times the critical density, and preliminary counts of galaxies and Abell clusters indicate a density enhancement within the superclusters of 10-71 times the field mass density. The combination of these two results is found to favor an open universe, assuming a standard Friedmann cosmology. It is noted that all forms of mass that are clumped on the scale of superclusters, or smaller, will be detected by these measurements, including neutrinos sufficiently massive to significantly contribute to the cosmological density parameter.
    Keywords: ASTROPHYSICS
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  • 3
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    Cluster redshifts in five suspected superclusters (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Redshift surveys for rich superclusters were carried out in five regions of the sky containing surface-density enhancements of Abell clusters. While several superclusters are identified, projection effects dominate each field, and no system contains more than five rich clusters. Two systems are found to be especially interesting. The first, field 0136 10, is shown to contain a superposition of at least four distinct superclusters, with the richest system possessing a small velocity dispersion. The second system, 2206 - 22, though a region of exceedingly high Abell cluster surface density, appears to be a remarkable superposition of 23 rich clusters almost uniformly distributed in redshift space between 0.08 and 0.24. The new redshifts significantly increase the three-dimensional information available for the distance class 5 and 6 Abell clusters and allow the spatial correlation function around rich superclusters to be estimated.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 293; 69-74
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  • 4
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    Redshifts of groups and clusters in the rich superclusters 1451+22 and 1615+43 (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Redshift measurements and finding charts are presented for galaxy clusters in the field of two rich, distant superclusters. Both systems are shown to have morphological and dynamical properties similar to the nearby superclusters, including small internal velocity dispersions and high density contrasts in redshift space. This data is consistent with two interpretations: either both superclusters are highly flattened systems with major axes close to the plane of the sky, or the observed velocity dispersions do not arise from unperturbed Hubble flow. If the latter explanation is correct, these radial velocity data are a powerful probe of the large scale matter density in the universe.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 273; 24-35
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  • 5
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    The Lyman edge test of the quasar emission mechanism (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The Lyman edge region in the spectra of 11 high-redshift quasars is studied using data designed to detect broadened Lyman edge absorption predicted by thermal models of the 'big blue bump' continuum component, especially thin accretion disks. Three objects have broadened, partial edges near the systemic redshifts, as expected for thermal models. In two cases, however, narrow Lyamn lines with the edge absorption, ruling out the disk interpretation. Thus, the data are negative for thermal models, at least for opaque thin accretion disks.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 342; 64-82
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  • 6
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    FOS spectroscopy of resolved structure in the nucleus of NGC 1068 (1991)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The results of FOS spectroscopy of the continuum peak of NGC 1068 in the wavelength range 2200-7000 A are reported. Detailed analysis reveals the emission lines to be complex in shape and to consist of a number of different velocity components. Both the Balmer lines and the strong forbidden lines have a contribution from a component with full width at half-maximum on the order of 2200 km/s. However, the broad H-beta emission observed in polarized light is not detected. This implies that the continuum peak is not the mirror which reflects light from the hidden Seyfert I nucleus. It could possibly contribute some of the reflected light, but the equivalent width of the H-beta BLR line, if present at all, is much weaker than expected from the ground-based nuclear polarized-flux spectrum.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 377; L9-L12
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  • 7
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    Maximum entropy deconvolution of the optical jet of 3C 273 (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The technique of maximum entropy image restoration is applied to the problem of deconvolving the point spread function from a deep, high-quality V band image of the optical jet of 3C 273. The resulting maximum entropy image has an approximate spatial resolution of 0.6 arcsec and has been used to study the morphology of the optical jet. Four regularly-spaced optical knots are clearly evident in the data, together with an optical 'extension' at each end of the optical jet. The jet oscillates around its center of gravity, and the spatial scale of the oscillations is very similar to the spacing between the optical knots. The jet is marginally resolved in the transverse direction and has an asymmetric profile perpendicular to the jet axis. The distribution of V band flux along the length of the jet, and accurate astrometry of the optical knot positions are presented.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 347; 68-73
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