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  • 1
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    The dust and gas surrounding LkH-alpha 101 (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The linear polarization of the reflection nebula NGC 1579 and the CO (1 to 0) emission from the associated molecular gas have been mapped for several minutes of arc around the exciting star LkH-alpha 101. These maps show conclusively that LkH-alpha 101 is the sole significant source of illumination in the region. The dust in the reflection nebula appears to be uniform over the illuminated region and is uniformly illuminated by LkH-alpha 101. Despite the patchy obscuration, the dark cloud which obscures LkH-alpha 101 does not surround the star. LkH-alpha 101 may have formed out of a placental cloud whose remnants now include four molecular cloud fragments, two in front of and two behind the reflection nebula, as well as an H I cloud previously detected in the region.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 303; 300-310
    Format: text
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  • 2
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    Some astrophysical consequences of the existence of a heavy stable neutral lepton (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: It is suggested that a stable, massive, neutral lepton may dominate the present mass density in the universe. To investigate this assumption, attention is given to an analysis of extended gauge theories as they apply to a lepton with a mass of a few GeV/sq cm. A critical factor in the accuracy of the hypothesis is the actual mass of the lepton, and it is noted that the more massive the individual particle, the smaller the particle's aggregate contribution to the universal mass density. High energy accelerators could prove a useful tool in an empirical determination of the lepton's mass. It is further suggested that the lepton considered might provide the material in galactic halos, or supply the mass necessary to bind galactic clusters. A study of intergalactic annihilation radiation is expected to yield more data pertaining to the lepton's existence.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 223
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  • 3
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    CCD photometry of Abell clusters. I - Magnitudes and redshifts for 84 brightest cluster galaxies (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The way in which the luminosity of brightest cluster galaxy varies with cluster parameters is investigated in a sample of 84 Abell clusters of moderate redshift and of richness classes in the zero-to-5 range. A photometric system is used which is well matched with the low noise CCD detector employed, as well as to the arrangement of galaxies with different redshifts on a standard system. The data, together with measurements from earlier work which forms a low redshift sample of the 199 brightest cluster galaxies, confirm that the luminosity dispersion in first-rank cluster galaxies is about 0.34 mag. The colors of giant ellipticals have not changed since redshifts of 0.25, and the richness correction is well established at 0.10 mag/Abell richness class. Application of these corrections reduces the luminosity dispersion to 0.29 mag.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 264
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  • 4
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    Q0957+561 - Detailed models of the gravitational lens effect (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The galaxy responsible for causing multiple gravitational lens images of QSO Q0957+561 has been reobserved spectroscopically and a more accurate redshift of 0.36 was obtained. In addition, detailed models of the gravitational lens effect were computed. These models, which can explain all optical and radio data for the system, predict delays of up to five years between variations in the A and B images (with A preceding B). It is suggested that the third image is rather faint and located close to the center of the lens galaxy; it is possible that this third image contributes to the observed galaxy core. The possibility that this system can be used to measure the Hubble constant is discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 5
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    The double quasar Q0957 + 561 A, B - A gravitational lens image formed by a galaxy at z = 0.39 (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Deep CCD pictures show a rich cluster of galaxies around the double quasar Q0957 + 561 as well as faint extended wings on the image of the southern quasar. Calculations of gravitational imaging by King model mass distributions show that the cluster and the brightest galaxy together, acting as a gravitational lens on the light from a single, more distant QSO, can easily reproduce all of the present observations. It is concluded that the double quasar is almost certainly the multiple image of a single object produced by a gravitational lens.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 6
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    Evolution of the cluster X-ray luminosity function slope (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The results of an X-ray survey of 58 clusters of galaxies at moderate and high redshifts are reported. Using a luminosity-limited subsample of 25 objects, it is found that to a redshift of 0.5 the slope of the luminosity function of distant clusters is independent of redshift and consistent with that of nearby clusters. The time scale for change in the slope must be greater than 9 billion years. The implications of the data for theoretical models are discussed. In particular, Perrenod's models (1980) with high Omega are excluded by the present data.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 262
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  • 7
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    Spectrophotometry of faint cluster galaxies and the Hubble diagram - An approach to cosmology (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: New spectrophotometric data are presented for large-redshift galaxies in clusters. A new approach to aperture corrections and the analysis of the Hubble diagram is outlined, including the explicit incorporation of evolutionary effects. The importance of selection effects on the usual methods of analysis are in principle overcome in the analysis, although the heterogeneity of the sample still makes conclusions about cosmology slightly suspect. Formal values of the deceleration parameter are derived under several sets of assumptions, yielding results between +0.33 and -1.27 with formal standard deviations of order 0.7.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 195; Jan. 15
    Format: text
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  • 8
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    Further observations of BL Lacertae (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Spectrophotometric observations of BL Lac have been obtained under conditions of fair to excellent seeing with BL Lac near the zenith. The nucleus was faint for all observations. Four absorption features identified as the Mg I and MgH band, the 4410-A band, the G-band, and H and K of Ca II, are observed. The redshift is approximately 0.070, in agreement with results in a previous paper. When the effects of the radiation from the central bright source are removed as well as possible, the residual spectral energy distribution is found to be very similar to that of a standard giant elliptical galaxy redshifted by 0.070 and reddened by a factor corresponding to a color excess of 0.28 to 0.40. The absolute visual magnitude of the underlying galaxy is -22.6 if the Hubble constant is 60 km/s per Mpc and the color excess is 0.28.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 201; Oct. 1
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  • 9
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    The evolution of galaxies (1982)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The recent observational evidence on the evolution of galaxies is reviewed and related to the framework of current ideas for galaxy formation from primordial density fluctuations. Recent strong evidence for the evolution of the stellar population in ellipticals is presented, as well as evidence that not all ellipticals behave as predicted by any simple theory. The status of counts of faint galaxies and the implications for the evolution of spirals is discussed, together with a discussion of recent work on the redshift distribution of galaxies at faint magnitudes and a spectroscopic investigation of the Butcher-Oemler blue cluster galaxies. Finally a new picture for the formation and evolution of disk galaxies which may explain most of the features of the Hubble sequence is outlined.
    Keywords: ASTROPHYSICS
    Type: Astrophysical cosmology; Sep 28, 1981 - Oct 02, 1981; Vatican City State
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  • 10
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    Infrared emission and mass loss from evolved stars in elliptical galaxies (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Small aperture 10.2-micron measurements of normal elliptical galaxies show that for almost all of these galaxies the 12-micron emission seen by IRAS is extended on the scale of the galaxy. NGC 1052 and NGC 3998 are exceptions to this; much of their 10-12-micron emission comes from the inner regions of the galaxies and may be associated with their active nuclei, as is the case for many radio galaxies. The distribution of the IR light and the IR colors of elliptical galaxies suggest that the most plausible source of the 12-micron emission is photospheric and circumstellear emission from cool evolved red giant stars. The 12-micron emission is well in excess of that expected from photospheric emission alone; about 40 percent of it probably comes from circumstellar dust.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 399; 1; p. 76-93.
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