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  • Other Sources  (9)
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  • 1
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    Enriched gas in clusters and the dynamics of galaxies and clusters Implications for theories of galaxy formation (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Recent observations of the rotation of elliptical galaxies and of X-ray clusters are cited in developing a simple model for the formation of elliptical and spiral galaxies; the model provides for continuous galaxy formation from redshift values of about 100 onwards. In particular, it is argued that a fundamental alteration in the manner in which cosmic material fragmented to form stellar objects took place at a redshift value of approximately five. This change of regime may be employed to explain the formation of Population I disks, the origin of hot intracluster gas, the galaxy luminosity function, and the mass-to-light ratio stratification of galaxies.
    Keywords: ASTROPHYSICS
    Type: Comments on Modern Physics; vol. 7
    Format: text
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  • 2
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    X-ray emission from M87 - A pressure confined cooling atmosphere surrounding a low mass galaxy (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A conventional model for the mass of the galaxy M87 (500-billion solar masses) is used to show that a radiative cooling flow agrees well with spectroscopically derived mass flow rates (10 solar masses per year) and surface brightness profiles of X-ray emission around the galaxy. A temperature of 100-million K, and a density of a few x 10 to the -4th/cu cm are obtained without the use of a massive halo. The atmosphere contains 1-trillion solar masses of gas, with a temperature profile increasing outward and gas acting as a reservoir for the flow. The present models indicate that thermal conductivity in M87 is less than 0.002 of its classical value, and does not significantly affect properties of the surrounding gas.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 247
    Format: text
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  • 3
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    The radius-dependence of velocity dispersion in elliptical galaxies (1980)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The equations of stellar hydrodynamics are used to derive the radial variation of velocity dispersion in galaxies whose mass-to-light ratios are constant and whose brightness profiles obey the r to the 1/4 law. It is found that the projected central velocity dispersion in such a system should be about 40 percent lower than the peak velocity dispersion. The observability and physical interpretation of this phenomenon is discussed. There is some evidence that a similar effect has been observed in the structure of rich clusters of galaxies.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 190
    Format: text
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  • 4
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    Tidal interactions in the expanding universe - The formation of prolate systems (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The study estimates the magnitude of the anisotropy that can be tidally induced in neighboring initially spherical protostructures, be they protogalaxies, protoclusters, or even uncollapsed density enhancements in the large-scale structure of the universe. It is shown that the linear analysis of tidal interactions developed by Peebles (1969) predicts that the anisotropy energy of a perturbation grows to first order in a small dimensionless parameter, whereas the net angular momentum acquired is of second order. A simple model is presented for the growth of anisotropy by tidal interactions during the nonlinear stage of the development of perturbations. A possible observational test is described of the alignment predicted by the model between the orientations of large-scale perturbations and the positions of neighboring density enhancements.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 188
    Format: text
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  • 5
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    Radiative regulation of gas flow within clusters of galaxies - A model for cluster X-ray sources (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 215
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  • 6
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    Twisted and warped disks as consequences of heavy halos (1978)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Observationally testable consequences of the hypothesis that galactic disks are confined less by their self-gravity than that of some hot stellar component are sought. Theoretical and observational studies are reviewed which suggest that elliptical galaxies are typically triaxial in form. It is argued that any hot stellar component is likely to be similarly spherical. The motion of a galactic disk about such a population is calculated. Within the plane the flow is to first order along similar concentric ellipses and without of the plane, provided that certain conditions on the background field are met, an oscillation may be excited which can cause isolated galaxies to become warped. The circular motion of matter in such disks will manifest itself in the misalignment of the apparent minor axis and the H I zero-velocity contour. Such an effect may be present in a number of recent H I surveys, although the data presently available do not allow definite conclusions. Alternative explanations of galactic warps are reviewed and their relation to the present proposal discussed.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 183
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  • 7
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    On the rotation of elliptical galaxies (1978)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The tensor virial theorem is applied to models of early-type galaxies. First the theorem is applied to rotating elliptical galaxies whose constant-density surfaces are similar ellipsoids. A relationship is obtained between the observed rotations and the forms of generally triaxial galaxies. By applying the results of Robert (1962) to the evaluation of the components of the Chandrasekhar tensor which occurs in this relationship, it is found that the form of a galaxy that lacks global velocity anisotropy uniquely determines the ratio of its rotational and random kinetic energies independently of the radial density profile of that galaxy. A distribution of three-dimensional prolate spheroids is derived which accounts for the observed distribution of ellipticities reported by Sandage, Freeman, and Stokes (1970). This is then used to derive curves giving the expected frequency of occurrence of galaxies of given rotational velocities for each of a number of different apparent elongations on the sky. It is found that if elliptical galaxies are prolate, there should be little correlation between apparent ellipticity and rotation velocity.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 183
    Format: text
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  • 8
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    The effect of galaxy triaxiality on globular clusters (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Evidence of triaxiality and central mass concentration in the Galaxy and in M31 and M87 is examined. It is proposed that globular clusters on box orbits in the inner parts of these systems pass close enough to the center to be destroyed by tidal shocks. Remaining clusters will preferentially populate tube orbits with relatively high angular momentum. The process is used to explain the cluster distribution in M87 reported by Lauer and Kormendy (1986). Models are presented for cluster destruction by massive black holes in M87's dark halo. Consideration is given to techniques for testing the suggestion that clusters form only on box orbits.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 241; 849-871
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  • 9
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    Velocity mapping and models of the elliptical galaxies NGC 720, NGC 1052, and NGC 4697 (1990)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: CCD surface photometry and extensive long-slit spectroscopy are used to construct detailed models of the flattened ellipticals NGC 720, 1052, and 4697. The models are combined with the Jeans equations to yield predicted fields of line-of-sight velocity dispersion and streaming velocity. By comparing these fields with observed velocities, it is concluded that none of these systems can have isotropic velocity dispersion tensors, and diminishing the assumed inclination of any given galaxy tends to decrease the line-of-sight velocity dispersion and, counterintuitively, to increase the line-of-sight rotation speeds. The ratio of the line-of-sight velocity dispersion along the minor axis to that along the major axis is found to be a sensitive diagnostic of the importance of a third integral for the galaxy's structure.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 361; 78-97
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