• Active Galactic Nuclei. III. Accretion Flow in an Externally Supplied Cluster of Black Holes

      Pacholczyk, A. G.; Stepinski, T. F.; Stoeger, W. R.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1988-10)
      This third paper in the series modeling QSOs and AGN as clusters of accreting black holes studies the accretion flow within an externally supplied cluster. Significant radiation will be emitted by the cluster core, but the black holes in the outer halo, where the flow is considered spherically symmetric, will not contribute much to the overall luminosity of the source because of their large velocities relative to the infalling gas, and therefore their small accretion radii. As a result the scenario discussed in Paper I will refer to the cluster cores, rather than to entire clusters. This will steepen the high frequency region of the spectrum unless inverse Compton scattering is effective. In many cases accretion flow in the central part of the cluster will be optically thick to electron scattering resulting in a spectrum featuring optically thick radiative component in addition to power -law regimes. The fitting of these spectra to QSO and AGN observations is discussed, and application to 3C 273 is worked out as an example.
    • Activity of the Nuclei of Seyfret Galaxies in the Visual and Infrared : Proceedings of the 44th IAU Symposium

      Pacholczyk, A. G.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1970-07)
    • Are All Blue Stragglers Binaries?

      Hintzen, P. M. N. O.; Scott, J. S.; Whelan, J. A. J.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1974)
      Radial velocity studies for five bright blue stragglers are reported and cluster membership is confirmed for four of them. Two of the stars show no significant radial velocity variations on a timescale of about 75 days and two others show no significant variation on timescales of 15 and 30 days respectively. The star for which cluster membership is uncertain may be a velocity variable. The data do not support the theory of blue straggler production involving mass transfer in a close binary. A spread in formation time of the stars in a cluster is shown to be a plausible explanation of the blue stragglers studied.
    • Axions and SN1987A

      Burrows, A.; Turner, M. S.; Brinkmann, R. P.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1988-10)
      We consider the effect of free -streaming axion emission on numerical models for the cooling of the newly born neutron star associated with SN1987A. We find that for an axion mass of greater than -10-3 eV, axion emission shortens the duration of the expected neutrino burst so significantly that it would be inconsistent with the neutrino observations made by the Kamiokande II (KII) and Irvine -Michigan- Brookhaven (IMB) detectors. However, we have not investigated the possibility that axion trapping (which should occur for masses 20.02 eV) sufficiently reduces axion emission so that axion masses greater than -2 eV would be consistent with the neutrino observations.
    • The Bowen Fluorescence Mechanism in Planetary Nebulae and Seyfert Galaxy Nuclei

      Weymann, R. J.; Williams, R. E.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1969-01)
      The efficiency of the Bowen fluorescence mechanism in models of planetary nebulae and Seyfert galaxy nuclei has been calculated by solving the equation of transfer for He II Ly -o( and the Bowen lines using the Feautrier method. The calculated efficiencies, which do not show significant differences between planetary nebulae and Seyfert galaxies, range from about 40% to 50% for realistic models. These values are somewhat higher than recent empirical determinations of Bowen conversion in planetary nebulae. Certain discrepancies between theoretical and observed line ratios are noted, however, which make the comparison with observation ambiguous. The efficiencies are shown to be rather insensitive to changes in various parameters. It is also noted that observations do not necessarily show that the Bowen lines are systematically weaker in Seyfert galaxy nuclei than in planetary nebulae.
    • CCD/Transit Instrument (CTI) Blue Object Survey

      Kirkpatrick, J. D.; McGraw, J. T.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1989)
    • The Color Structure and the Distribution of Neutral Hydrogen Within Messier 51

      Worden, S. P.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1973)
    • The Comparison of the Seeing Between orado and La Silla

      Irwin, J. B.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1967-12)
    • A Comparison of Variable and Non-Variable Stars in the Cepheid Strip

      Schmidt, E. G.; Rosendhal, J. D.; Jewsbury, C. P.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1974)
      Spectra of three Cepheids (RX Aur, X Cyg and T Mon) and 11 non -variable supergiants are analyzed. Additional evidence is presented for the presence of non -variables within the Cepheid strip. Temperatures determined from Ha line profiles and broad band photometry were used together with model atmospheres and line strengths from the spectra to determine the gravities, turbulent velocities and element abundances. The gravities of the Cepheids appear to be lower than for the non -variables at the same luminosity while the turbulent velocities are higher. No differences of significance are found in the element abundances. The gravity differences can be explained either in terms of mass loss in the Cepheids or very low helium abundance in the non -variables. The former interpretation fails to explain why some Cepheid strip stars do not vary while the latter raises problems in connection with the origin of the elements. If we assume that pulsation causes some mass loss a more consistent picture emerges in which only moderate helium deficiencies are required in the non-variables.
    • Conditions for Carbon Monoxide Vibration-Rotation LTE in Late Stars

      Thompson, R. I.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1973)
      Collisional vibration and rotation transition rates are found for carbon monoxide due to H, H2, He and electrons. These rates are compared to the radiative rates of transition in carbon monoxide to establish temperature -pressure regions in which Vibration -Rotation LTE is a good approximation and those regions in which possible non -LTE effects may occur. Comparison of these data with current late star model atmospheres indicates that possible vibrational non -LTE effects may occur in supergiants, but in all late star computed atmospheres rotational LTE should be a good approximation. The further question of total molecular LTE is examined and rate equations set up. Rough order of magnitude estimates are made on the conditions for total LTE in CO.
    • Continuum Radiative Transfer in a Hot Plasma, with Application to Scorpius X-1

      Felten, J. E.; Rees, M. J.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1971-06-07)
    • THE CORRELATION OF OPTICAL ABNORMALITIES AND SMALL RADIO SOURCES IN GALAXY NUCLEI

      Tifft, William G.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1970-06)
      Radio emission from small sources in galaxy nuclei is shown to be correlated with the optical photometric properties. Within the limitations of the small sample available, the following observations are made: (1) no galaxy with a photometrically normal nuclear region contains a small radio source, although it may contain a large source; (2) when a small radio source is present the galaxy nuclei are abnormally red or blue. The opposite is not true, however, since (3) not all photometrically blue or red nuclei contain small radio sources. Finally, (4+) the sources in red nuclei are apparently smaller than in blue nuclei and are the ones showing abnormal radio spectra. A close similarity between the abnormal nuclei and QSS phenomena is noted and it is proposed that the phenomena is either (1) a small scale QSS phenomena or (2) pre and /or post QSS stages.
    • The Correlation of Redshift with Magnitude and Morphology in the Coma Cluster

      Tifft, W. G.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1971-09)
      Redshifts and magnitudes for 93 faint galaxies in the core of the Coma Cluster are now available. The sample is nearly complete to seventeenth nuclear region magnitude (central 4.8 arc second spot). Nuclear region magnitudes show a good correlation with redshift in the sense that galaxies fall in bands sloping fainter with increasing redshift. A magnitude decrease of 0.6 magnitudes per 1000 km /sec redshift increase is observed. The deviation from the expected random correlation of nuclear region magnitude and redshift is significant at a probability less than 10 -3 by x2 testing. It is further observed that nearly all of the higher redshift galaxies in the Coma Cluster are nonelliptical. This is not expected from a normal dynamical model and is remarkably similar to the pattern in the Virgo Cluster where the spiral galaxies show a distinctly greater redshift that the ellipticals. The observed redshift -magnitude pattern reality is further tested by comparison with two outlying concentrations of galaxies in the Coma Cluster which show nearly identical patterns slightly shifted in redshift. The pattern is also used to predict the m -logz diagram for field galaxies. Observed field galaxies are shown to fit the predicted pattern and to deviate from the normal velocity dispersion model. After allowance for magnitude and redshift uncertainties it is shown that a residual true Doppler velocity dispersion in the Coma Cluster cannot exceed about 140 km /sec, and the cluster is not dynamically unstable. In the presence of an intrinsic unexplained redshift which produced the observed pattern, the mean redshift of a group of galaxies need not be the same as the Hubble velocity of the cluster. Systematic trends in the deviation of the Hubble velocity from the mean redshift are possible due to selection with distance and may explain the local apparent anisotropy in the Hubble law.
    • The Correlation of Redshift with Magnitude and Morphology in the Coma Cluster

      Tifft, W. G.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1972-03)
      Redshifts and magnitudes for nearly 100 galaxies in the core of the Coma Cluster are now available. The sample is nearly complete to seven- teenth nuclear region magnitude (central 4.8 arc second spot). Nearly all the higher redshift galaxies in the Coma Cluster are nonellipticals. The separation of the ellipticals from the nonellipticals is significant in both the redshift and magnitude coordinates and is shown to be a maximum in a linear combination of redshift and magnitude along a direction sloping close to 0.6 magnitude fainter per 1000 km /sec increase in redshift. The morphological separation is in the same sense as the pattern in the Virgo Cluster. When the redshift magnitude diagram is examined in the direction of the maximum morphological separation it is shown to have a strongly banded structure which is not present in any other direction. The observed redshift -magnitude pattern is compared with an outlying distinct group of galaxies in the Coma Cluster which shows a nearly identical pattern slightly shifted in redshift. The pattern is also used to predict the m -logz diagram for field galaxies. Observed field galaxies are shown to fit the predicted pattern and to deviate from the normal velocity dispersion model. After allowance for magnitude and redshift uncertainties it is shown that residual true Doppler velocity dispersion in the Coma Cluster cannot exceed about 220 km /sec, and the cluster is not dynamically unstable. In the presence of an intrinsic unexplained redshift which produced the observed pattern, the mean redshift of a group of galaxies need not be the same as the Hubble velocity of the cluster. Systematic trends in the deviation of the Hubble velocity from the mean redshift are possible due to selection with distance and may explain the local apparent dependence of the Hubble constant on distance.
    • Cosmic Radiation Bubbles|Cosmic Structure from Radiation-Blown Bubbles

      Hogan, C. J.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1988-12)
    • The Cosmic X-Ray Background

      Weymann, R. J.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1967-09)
    • The Definition, Visibility, and Significance of Redshift-Magnitude Bands

      Tifft, W. G.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1973-06)
      Redshift- magnitude bands as they occur in the Coma cluster are formally defined and the original bands as observed in 1972 are shown to have a likelihood of random occurance of only 0.005 independent of their direction. The properties of the Coma bands are transformed to m_p magnitudes and used to show that an independent sample of outlying Coma galaxies shows strong band related characteristics. The proper- ties of the Coma bands are then used to predict band properties for the A2199 cluster. The resultant power spectrum test of a preliminary A2199 sample shows agreement which has a random likelihood of occurance of only 0.001. The A2199 cluster also shows a band related morphological separation as in Coma.
    • Detectability of Distant Galaxies During a Hypothetical Bright Phase and the Associated Ionization of Intergalactic Matter

      Weymann, R. J.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1966-11)
      Simple models for bright, helium producing phases in the lives of massive galaxies are used to investigate the distance out to which they could be seen as individual objects. Roughly speaking, objects radiating at effective temperatures of ..;40,000 o could be detected out to redshifts as large as 8 -+12. Such redshifts correspond to densities at which we might reasonably have expected galaxy condensation to occur, except possibly for the lowest part of the probable range of go-values. Such Objects ought to be bluer than ordinary "nearby" galaxies, and for open cosmological models would be expected to be much more numerous than ordinary galaxies; for closed models the numbers of bright and ordinary galaxies should be comparable. The feasibility of detecting such objects by ground -based measures of their integrated skybrightness in the L and M windows is discussed, and it appears that such a technique would be feasible and superior to direct photographic detection only for relatively low effective temperatures in the 20,000 to 1+0,000 range. The possibility of explaining the lack of general Ljy -c4 absorption in distant WO as due to a high degree of ionization brought about by W radiation from these bright galaxies is investigated. The conclusion is that this mechanism will not usually be adequate -- and when it is adequate, the objects causing the ionization should be detectable -- unless the current mean density of uncondensed gas is very low, of the order of 10 -7 particles /cm3 or less.
    • Detection of Earth Orbiting Objects by IRAS

      Dow, K. L.; Sykes, M. V.; Low, F. J.; Vilas, F.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1989-10)
      A systematic examination of 1836 images of the sky constructed from scans made by the Infrared Astronomical Satellite has resulted in the detection of 466 objects which are shown to be in Earth orbit. Analysis of the spatial and size distribution and thermal properties of these objects, which may include payloads, rocket bodies and debris particles, is being conducted as one step in a feasibility study for space -based debris detection technologies.