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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
    Details
    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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    A lower limit on the magnitude of the companion to HDE 226868 /Cygnus X-1/ (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: High-precision digital spectra of the HDE 226868/Cygnus X-1 system have been obtained at a variety of orbital phases, using a Digicon photon counting array at the coude focus of the Lick Shane reflector. The spectra have been cross-correlated to search for evidence for the existence of a luminous stellar companion to HDE 226868, as has been suggested by several models where the secondary star is not a black hole. We find no evidence for such a star and place a lower limit on the difference between HDE 226868 and its companion of 4 magnitudes. This limit rules out all of the models for the Cygnus X-1 system calculated by Avni and Bahcall which include main-sequence stars as secondaries rather than black holes. A merit function generally useful for cross-correlation of digital spectra is described.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 5
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    The spectrum of OH 471 /0642+44/ (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Results of image-tube and Digicon spectroscopy of OH 471 (0642+44) are reported. Wavelengths of 89 stronger absorption features in the range 4000-6000 A are given, and a number of absorption redshift systems are suggested. The lack of radiation shortward of 4000 A is attributed to Lyman continuum absorption in the gas giving rise to the various absorption-line systems.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 195; Jan. 15
    Format: text
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  • 6
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    Discovery of a magnetic DA white dwarf (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The spectrum of the white dwarf suspect, GD 90, is shown to contain broad Balmer lines with resolved Zeeman structure. All the observed features correspond to the calculated spectrum of hydrogen at 5 plus or minus 0.5 MG. A region of approximately 20% of the observed stellar disk must be subject to a reasonably uniform field of this strength. The sigma components of the Zeeman patterns in H beta and H gamma are found to be circularly polarized, indicating that the field has a component directed along the line of sight. There is evidence for an additional stronger and less homogeneous field, as would be expected if the dominant 5 -MG region were at the equator of a dipolar field.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 194; Nov. 15
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  • 7
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    Redshifts of groups and clusters in the rich superclusters 1451+22 and 1615+43 (1983)
    In:  Other Sources
    Details
    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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