• MALIN: A Quiescent Disk Galaxy|MALIN 1: A Quiescent Disk Galaxy

      Impey, C. D.; Bothun, G. D.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1988-11)
      We present new optical and radio spectroscopic observations of the remarkable galaxy Malin 1. This galaxy has unique features that include an extremely low surface brightness disk with an enormous mass of neutral hydrogen, and a low luminosity Seyfert nucleus. Malin 1 is exceptional in its values of MHO, LB, and MHI /Ln, and modest in its surface mass density of gas and stars. Spirals with large Min /LB tend to have low mean column densities of HI, and are close to the threshold for star formation due to instabilities in a rotating gas disk. In these terms, Malin 1 has a disk with extremely inefficient star formation. The bulge spectrum is dominated by the absorption features of an old, metal rich stellar population, although there is some evidence for hot (young) stars. The emission line excitations and widths in the nucleus are typical of a Seyfert galaxy; but Malin 1 is in the lowest 5% of the luminosity function of Seyferts, despite a copious fuel supply. Malin 1 is in a low density region of the universe. We propose it as an unevolving disk galaxy, where the surface mass density is so low that the chemical composition and mass fraction in gas change very slowly over a Hubble time. Its properties are similar to those of the damped Lyman -a absorption systems seen in the spectra of high redshift quasars. We emphasize that there are strong observational selection effects against finding gas -rich galaxies that are both massive and diffuse. Finally, we suggest that large and massive HI disks may have formed as early as z - 2, and remained quiescent to the present day. Subject headings : individual (Malin 1) - galaxies : photometry - galaxies : Seyfert - galaxies : stellar content - radio sources : 21 cm radiation - stars : formation
    • MALIN: A Quiescent Disk Galaxy|MALIN 1: A Quiescent Disk Galaxy

      Impey, C. D.; Bothun, G. D.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1988-11)
      A study of the Galactic Center stellar population is continuing with a sensitive 2μm CCD camera. Using a 64 x 64 detector array, background limited images are recorded with modest amounts of observing time (tob, 20 sec to reach K =13). Magnitudes have been extracted using DAOPHOT from repeated imaging of the central 5' x 5' to search among approximately 1500 stars for long period variables (LPV's, P > 200d), particularily Miras. Miras have a well defined period - luminosity relationship as well as one in period -mass. This program investigates the nature of highly luminous stars at the Galactic Center. Presently 12 variables have been found and have several characteristics consistant with Miras. They have a maximum bolometric luminosity of -4.4 mag which supports the case that high luminosity stars in the central 6 pc are young supergiants.
    • Microturbulence vs Metal Abundance: An Observational Test

      Barry, D. C.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1967-01)
    • NGC 2818, An Open Cluster containing a Planetary Nebulae

      Tifft, W. G.; Connolly, L. P.; Webb, D. F.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1971-12)
      Three color UBV photometry of the cluster NGC 2818 shows it to lie at a distance of 3.2 kpc. The cluster has a color excess E_(B-V)= 0.22 and an ultraviolet excess of 0.09. The evolutionary turnoff from the main sequence occurs in mid A. The faint main sequence in the cluster shows a distinct bend or discontinuity. Preliminary velocity measurements indicate that the high excitation planetary nebula NGC 2818 is probably associated with the cluster.
    • OB Stars Near the Supernova Remnant RCW 86

      Westerlund, B. E.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1969-05)
      The filamentary nebula RCW 86, identical with the non - thermal radio source MSH 14 - 63, is part of a supernova remnant. A group of OB stars is found near the radio source. The distance of the group is 2500 pc; this agrees well with the radio distance of the remnant. It is suggested that the remnant was formed by the explosion of a member of the group; the explosion occurred probably in 185 A. D.
    • Observable Signatures of Young Galaxies

      White, S. D. M.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1989-10)
      I review theoretical expectations for the probable appearance of galaxies during their formation phase, placing particular emphasis on the uncertainties in these ideas. Recent models suggest that formation may occur relatively recently, but that young galaxies are less spectacular than previously supposed. They may be analogous to recently discovered high red - shift radio galaxies, and indeed they may have been observed directly in faint galaxy counts. I summarise several other lines of evidence which suggest that galaxy formation may have been a recent process. Finally I give preliminary results from a detailed analytic study of the observable properties of young galaxies in a Cold Dark Matter universe. Predictions are given for faint galaxy counts and redshift distributions, and for the galaxy luminosity function.
    • Observational Evidence for Galactic Spiral Structure

      Bok, B. J.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1970-08)
    • Photoelectric Photometry of Some Galaxies in the Region of the Virgo Cluster

      Tifft, W. G.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1973-01)
      Four color photometry of 26 galaxies, mostly in the region of the Virgo Cluster, is presented.
    • Photometric Standards for the Southern Hemisphere

      Bok, B. J.; Bok, P. F.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1969-08)
    • Polarization and Structure of the Crab Nebula : Proceedings of the 23rd IAU Colloquium

      Felten, J. E.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1973-04-03)
      Present knowledge of the optical, radio and X -ray polarization of the Crab is reviewed and discussed as it bears on the structure of the magnetic field, time scales in the nebula, and relations between nebula and pulsar. Not as much high -resolution polarimetry has been done on the Crab as might have been expected. Loops of field and a large -scale structure can be recognized, but it is not known whether the fields generally are smooth or chaotic on a small scale. Field lines tend to curl around the filaments. The large angular size of the X -ray source poses a difficulty to conventional theory. The form of the nebula does not single out the pulsar as its source, and the exact relation between pulsar and nebula is uncertain. The wave -field or "synchro- Compton" interpretation of the continuum emission is erroneous but has led to interesting observations of circular polarization. Circular polarization of the ordinary synchrotron radiation might be observable in the radio band. Magnetic flux may have been generated in the nebula by winding of lines around the rotating pulsar. Polaroid photographs then suggest that the pulsar rotation axis is roughly NW -SE, but confirmation is lacking.
    • Polarization of Radio Sources. I. Transfer of synchrotron Radition through an Extended Radio Source with Faraday Rotation|Polarization of Radio Sources. I. Homogeneous Source of Arbitrary Optical Thickness

      Pacholczyk, A. G.; Swihart, T. L.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1966-11)
      The problem of transfer of radiation in a medium with polarized emission, polarized absorption and Faraday rotation of the plane of polarization is formulated. Solutions are obtained for the case of a homogeneous source. In the range of frequencies for which a medium is optically thick the degree of polarization of synchrotron radiation depends on the type of absorption process and is different for synchrotron absorption and for thermal absorption. It is therefore suggested that the low frequency polarization measurements of radio sources with curved spectra may determine whether synchrotron self -absorption or thermal absorption or another process is responsible for the low frequency curvature in spectra of certain radio sources.
    • Polarization of Radio Sources. II. Faraday Effect in the Case of Quasitransverse Propagation

      Pacholczyk, A. G.; Swihart, T. L.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1970)
      Under the conditions of quasitransverse propagation of electromagnetic waves in a magnetoionic plasma, the effect analogous to Faraday rotation in the quasilongítudinal case (which we will call Faraday pulsation) can produce a large elliptical polarization of originally linearly polarized radiation. Therefore, the presence of elliptical polarization in the radiation cannot serve as a means for distinguishing between a synchrotron mechanism with high energy electrons and any other type of emission process in radio sources in which conditions suggesting quasi - transverse propagation (large magnetic fields) may take place. The Faraday pulsation has a wavelength dependence through which it can be identified.
    • A Possible Rotation Chain of Galaxies|Possible Systematic Redshifts in a Chain of Galaxies

      Gregory, S. A.; Connolly, L. P.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1972-11)
      Redshifts are reported for two groups of galaxies. Although these two groups have previously been assigned to the same cluster, their redshifts indicate that they are not associated. A systematic variation of redshifts is found across the chain of one of these groups, Abell 2247, and three possible interpretations are discussed. It is concluded that rotation of the chain is the most likely explanation of the systematic motions.
    • Possible Thermal Histories of Intergalactic Gas

      Weymann, R. J. (Steward Observatory, The University of Arizona (Tucson, Arizona), 1967-07)
    • Pulsation Constants and Densities for Double Mode Variables in the Cepheid Instability Strip

      Fitch, W. S.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1970)
      Pulsation constants and period ratios are given for the first six radial pulsation modes of a set of seven polytropes with indices ranging from n = 2.25 to n = 4.00. The polytrope results are combined with published theoretical data from stellar model pulsation calculations and observational data on thirteen double mode variables in the Cepheid instability strip to obtain four interpolation formulae relating fundamental periods Po, pulsation constants Qo, and period ratios P1 /P0 and P2 /P1. The derived relations are used to obtain accurate densities for the thirteen observed variables, which include six dwarf Cepheids or AI Vel stars, one S Sct star, one RR Lyr star, and five Cepheids. Approximate masses and luminosities are obtained for some of these stars. The probable connection between mass- luminosity ratios and the existence of double mode variables is discussed.
    • Radiative Acceleration of Material

      Weymann, R. J.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1973)
    • Rapid Evolution of Galactic Nuclei : Proceedings of the 44th IAU Symposium

      Tifft, W. G.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1970-08)
    • Redshift Magnitude Bands and Quasi Stellar Absorption Line Multiple Redshifts

      Tifft, W. G.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1972)
      Quasi stellar absorption line redshifts are shown to be consistent with the redshift- magnitude band pattern concept. The redshifts in multiple redshift objects tend to concentrate at band crossings corresponding to the magnitude of each object.
    • Redshift Quantization in the Lyman-alpha Forest and the Measurement of qo

      Cocke, W. J.; Tifft, W. G.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1988-12)
      We present evidence for redshift quantization in the Lyman -a forest of several QSOs. The Ly -a data are at redshifts z from 1.89 to 3.74, and the theory of redshift quantization proposed by Cocke (1983, 1085) is used to scale the quantization interval (24.15 km s -') to these high redshift. The sealing depends on the deceleration parameter qo, and the quantization is present at a statistical significance of greater than 99% for qo = 1/2. This may be taken as confirming the inflationary model of the early history of the universe. The significance of the quantization is highest at go rs 0.48, and the width of the peak is about 0.03 . The result can also be seen as providing confirmatory evidence for both the theory of the redshift quantization and the above value of qo, but at a significance of only 03 %. The scenario proposed for the relativistic generalization of the theory is that of fermion wavefunctione and quantum operators in a background Riemannian spacetime satisfying Einstein's field equations.
    • Redshift-Magnitude Bands, Quasi Stellar Sources, and Systems of Redshift

      Tifft, W. G.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1972-08)
      The visibility and character of redshift- magnitude bands in a diagram of general field galaxies compared to specific clusters depends upon the cosmological model. In the normal expanding universe model where galaxies have lives comparable to the age of the universe, no band structure should be visible outside of clusters. Band structure is, however, shown to exist among quasi stellar sources and to show the identical slope and band spacing characteristics as do the galaxies in the Coma cluster. At least 14 bands can be identified forming a convergent band series among QSS emission line objects. The validity of the band phenomenon is tested by power spectrum analysis and shown to be highly significant. The distribution of points about the band structure is Gaussian. Cross projections of the band system are shown to give rise to harmonic periodicities which can explain some or all of the periodicities observed in the z distribution of QSS objects. The Coma galaxy band system is shown to be a scaled version of the QSS band system. Galaxies appear to occupy a separate band system which is convergent to the start of the QSS system as its series limit. QSS absorption line objects are further shown to apparently form a third independent band system beginning at the high redshift limit of the QSS emission line system. The band phenomenon is briefly discussed in terms of a model invoking multiple states of matter, rapid galaxy evolution, and possible time evolution of matter observed as a function of lookback time in a singular origin Universe.