Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session C9: Cosmology/Structure Formation |
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Sponsoring Units: DAP Chair: Rachel Bean, Princeton University Room: Marriott Tampa Waterside Room 5 |
Saturday, April 16, 2005 1:30PM - 1:42PM |
C9.00001: Deconvolution Map-Making for Cosmic Microwave Background Observations Charmaine Armitage, Benjamin Wandelt We describe a new map-making code for cosmic microwave background (CMB) observations from scanning telescopes which removes artifacts due to beam asymmetries and far sidelobes. The deconvolution map-making method implements the fast algorithms for convolution and transpose convolution of two functions on the sphere [B.~Wandelt and K.~G\'{o}rski, Phys.~Rev.~D $\bf{63}$, 123003 (2001)]. Our approach is a generalization of existing CMB map-making techniques to solve the maximum likelihood map-making problem for arbitrary beam shapes. We test our algorithm on simulated time-ordered data for three beam models and two scanning patterns, including a coarsened version of the WMAP strategy. We quantitatively compare our results with a standard map-making method and demonstrate that the true sky is recovered with high accuracy via the deconvolution method. Deconvolution map-making recovers features of the CMB sky on the smallest scale of the beam, thereby achieving a form of super-resolution imaging. [Preview Abstract] |
Saturday, April 16, 2005 1:42PM - 1:54PM |
C9.00002: Detailed study of the hot and cold spots in the CMB David Larson, Benjamin Wandelt We perform a detailed statistical analysis of the one and two-point properties of the local extrema in the WMAP (Wilkinson Microwave Anisotropy Probe) data. For the one-point functions, our previous work found that the simple white noise model indicated a 95\% detection of non-Gaussianity in the mean temperature of the hot and cold spots: the hot and cold spots are not hot and cold enough. We will discuss the relevance this result and our new findings in light of other studies of non-Gaussianity in the literature. We will also discuss how the results of the white and correlated noise differ at varying resolutions. [Preview Abstract] |
Saturday, April 16, 2005 1:54PM - 2:06PM |
C9.00003: The Diffuse Neutrino Background and the Cosmological Star Formation Rate Louis Strigari The cosmological star formation rate provides a unique window for studying galaxy formation and evolution. The limit on the diffuse neutrino background, produced from the core collapse of the most massive stars, provides the strongest limit on models for the star formation rate. Recent determinations of the star formation rate, in particular from the UV luminosity density evolution, indicate that the neutrino background is in fact near the current flux limit, predicting the milestone first discovery of a cosmological source of neutrinos. Based on recent work with John Beacom, Manoj Kaplinghat, Gary Steigman, Terry Walker, and Pengjie Zhang, I will discuss the implications of this discovery, and the utility of the neutrino background as a measurement of the cosmological star formation rate. [Preview Abstract] |
Saturday, April 16, 2005 2:06PM - 2:18PM |
C9.00004: The Evolution of Dark Matter Halos through the Mergers of Comparable Mass Galaxies Jonathon Van Schelt, Susan Lamb, Nathan Hearn, Irina Marinova Galactic dark matter halos are affected greatly in collisions and mergers of galaxies. In order to follow this adequately in numerical simulations, much higher resolution is required than is generally available in large-scale structure simulations. It is very important to investigate the results of collisions and mergers on individual pairs of galactic dark matter halos. We have initiated an investigation of the results of collisions between comparable mass galaxies by simulating collisions and mergers of galaxies using N-body techniques, employing between 250,000 and a million particles using the code of Hearn (2002, Ph.D Thesis, UIUC). The luminous matter will also have an effect on the eventual density distribution of the various galactic components and we include a representation of the disk and bulge. In our initial studies we simulate the merger of galaxies approaching at near escape velocity with small impact parameters that lead to slightly off-center collisions. Results show that by a time of 1.75 Gyr a central high-density region has formed in the dark matter halo with a radius of approximately 80 kpc, scaling our results to the Milky Way. Most of the dark matter remains in the region occupied by luminous matter throughout the simulation, but a small amount is spread to very large radii and would be lost to the overall potential in a cluster. [Preview Abstract] |
Saturday, April 16, 2005 2:18PM - 2:30PM |
C9.00005: Numerical simulations of collisions of disk galaxies: the formation of tidal tails and tidal dwarf galaxies I.S. Marinova, S.A. Lamb, N.C. Hearn, J. Van Schelt Evidence suggests that galaxies are formed hierarchically; however, this picture may be complicated by the generation of dwarf galaxies from collisions involving disk galaxies. Observations of so-called `tidal dwarfs' (eg. Duc {\&} Mirabel,1998; Duc et al., 2000) indicate that they are associated with the tidal tails often formed in such collisions. It is of interest to investigate numerically under what conditions dwarf galaxies might be formed in galactic collisions. We have performed numerical studies of the formation of tidal features in colliding disk galaxies for several collision geometries and have explored the possible associations of these features with `tidal dwarfs.' The simulations were performed using the N- body/SPH code of Hearn (2002, Ph.D Thesis, UIUC) with galaxy models that consist of a stellar disk and bulge, a gaseous disk, and a roughly spherical halo. We explore collisions that take place along directions parallel to a disk spin axis for several relative disk orientations, and run the simulations for periods that correspond to several Gyrs for real systems. Extensive tidal features are a common result of these collisions and, once formed, they persist to the end of our simulations. The tails often extend to very large distances beyond the galactic cores. However, the presence of long-term self-gravity in these features remains open to further investigation. [Preview Abstract] |
Saturday, April 16, 2005 2:30PM - 2:42PM |
C9.00006: Metallicity of Galactic Bulge RR0 Lyrae Andrea Kunder, Brian Chaboyer, Piotr Popowski, Sergei Nikolaev, Kem Cook We present metallicities of 3092 RR0 Lyrae stars towards the Galactic bulge from the MACHO Survey bulge fields. These [Fe/H] metallicities are based upon a empirically calibrated relationship between the Fourier coefficients of the light curve and [Fe/H]. We find that the 333 RR0 stars from the MACHO bulge fields associated with Sagittarius dwarf galaxy have a lower average metallicity than the RR0 Lyrae stars associated with the Galactic bulge. We investigate the dispersion of the metallicity in the bulge RR0 Lyrae stars and the correlation between metallicity and the location of the stars within the bulge. [Preview Abstract] |
Saturday, April 16, 2005 2:42PM - 2:54PM |
C9.00007: Planetary System Occultation from Lunar Halo Orbit (PSOLHO) Thomas Clarke The author has suggested that planetary systems including terrestrial planets may be rare because they are the result of the injection of radionuclides from a supernova nearby in space and time to the condensation of the system nebula. Absent such a supernova, the norm would be a planetary system where the inner system comprises an asteroid belt formed from material, unmelted by radiogenic heat, which failed to condense into terrestrial planets. To test this theory, observations of the statistics of planetary systems that include terrestrial planets are required. Direct or even indirect detection of terrestrial planets is currently impossible and likely to remain difficult with current techniques. This paper discusses a Discovery mission concept that would utilize occultations by the Moon to enable detection of terrestrial planets. Earth orbiting spacecraft utilizing lunar occulations for observations such as planet detection have been proposed; but sky coverage from Earth orbit is limited and there are problems with Earthshine on the Moon. A low altitude lunar orbit would produce occultations by the farside of the moon over much of the sky, but they would be too rapid for optimum detection of faint objects. A better spacecraft location is a halo orbit around the Earth-Moon L2 point, which can be referred to as PSOLHO (Planetary System Occultation from Lunar Halo Orbit.) The portion of the Moon that impinges on the telescope field will be largely un-Earth-lit and occultations will occur at rate determined by lunar sidereal period. [Preview Abstract] |
Saturday, April 16, 2005 2:54PM - 3:06PM |
C9.00008: Plasma Redshift and the Cosmological Redshift Ari Brynjolfsson The newly discovered plasma redshift of photons has profound effect on many cosmological phenomena. It explains the high plasma temperatures in the solar corona, the galactic corona and in the intergalactic space, and it explains the solar redshift, the magnitude-redshift relation for supernovae Ia, the cosmological redshift, and the variations in the Hubble constant. It predicts that Quasars and many other objects have intrinsic redshifts. The hot intergalactic plasma, which is a consequence of the plasma redshift, explains the cosmic microwave background (CMB), which is emitted by the hot intergalactic plasma. Plasma redshift is based on basic conventional physics and is relatively simple to deduce. We will pinpoint and elucidate the improvements that were made to the equations commonly used in the literature; and we will make clear how the approximations that were conventionally used prevented the deduction of the plasma redshift. [Preview Abstract] |
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