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  • 1
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    Niobium in R And (S6, 6e) and HR 1105 (S5, 3) (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Lines of the first multiplet of niobium are strong in R And and HR 1105. These lines are also present in other S stars: HR 8714, R Cam, V Cnc, R CMi, and T Sgr. They are also visible in the M stars, Beta-Peg and Mu-UMa. An approximation to the abundance ratio, Nb/Fe, has been deduced from pairs of lines having nearly equal intensity. In R And, the ratio is about 200 times the solar value. It is hoped that good plates will soon be obtained for the near infrared region, so that the significant Nb/Rb abundance ratio may be determined.
    Keywords: ASTROPHYSICS
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  • 2
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    The evolution of large-scale structure in a universe dominated by cold dark matter (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The results of numerical simulations of nonlinear gravitational clustering in universes dominated by weakly interacting, 'cold' dark matter are presented. The numerical methods used and the way in which initial conditions were generated are described, and the simulations performed are catalogued. The evolution of the fundamental statistical properties of the models is described and their comparability with observation is discussed. Graphical comparisons of these open models with the observed galaxy distribution in a large redshift survey are made. It is concluded that a model with a cosmological density parameter omega equal to one is quite unacceptable if galaxies trace the mass distribution, and that models with omega of roughly two, while better, still do not provide a fully acceptable match with observation. Finally, a situation in which galaxy formation is suppressed except in sufficiently dense regions is modelled which leads to models which can agree with observation quite well even for omega equal to one.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 292; 371-394
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  • 3
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    Numerical techniques for large cosmological N-body simulations (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Techniques for carrying out large N-body simulations of the gravitational evolution of clustering in the fundamental cube of an infinite periodic universe are described and compared. The accuracy of the forces derived from several commonly used particle mesh schemes is examined, showing how submesh resolution can be achieved by including short-range forces between particles by direct summation techniques. The time integration of the equations of motion is discussed, and the accuracy of the codes for various choices of 'time' variable and time step is tested by considering energy conservation as well as by direct analysis of particle trajectories. Methods for generating initial particle positions and velocities corresponding to a growing mode representation of a specified power spectrum of linear density fluctuations are described. The effects of force resolution are studied and different simulation schemes are compared. An algorithm is implemented for generating initial conditions by varying the number of particles, the initial amplitude of density fluctuations, and the initial peculiar velocity field.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 57; 241-260
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  • 4
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    Massive superclusters as a probe of the nature and amplitude of primordial density fluctuations (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: It is pointed out that correlation studies of galaxy positions have been widely used in the search for information about the large-scale matter distribution. The study of rare condensations on large scales provides an approach to extend the existing knowledge of large-scale structure into the weakly clustered regime. Shane (1975) provides a description of several apparent massive condensations within the Shane-Wirtanen catalog, taking into account the Serpens-Virgo cloud and the Corona cloud. In the present study, a description is given of a model for estimating the frequency of condensations which evolve from initially Gaussian fluctuations. This model is applied to the Corona cloud to estimate its 'rareness' and thereby estimate the rms density contrast on this mass scale. An attempt is made to find a conflict between the density fluctuations derived from the Corona cloud and independent constraints. A comparison is conducted of the estimate and the density fluctuations predicted to arise in a universe dominated by cold dark matter.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 297; 365-370
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  • 5
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    Interstellar absorption features toward the compact infrared source W33A (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A high-resolution (lambda/Delta lambda of approximately 2000) broad-bandwidth (3.3-5.0 microns) spectrum of the compact infrared source W33A is presented. Four absorption features are associated with compositionally distinct components in the interstellar medium: solid-phase C3, CN, or CH3OH at 4.9 microns, solid-phase CO and either solid or gaseous CH3NC near 4.6 microns and the well-known dirty ice feature near 3 microns. The analysis of this spectrum supports chemically complex models of grain mantle evolution in cold, quiescent molecular clouds.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 299; 873-880
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