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Articles 1 - 14 of 14
Full-Text Articles in Cosmology, Relativity, and Gravity
Weak Gravitational Lensing Analysis In Two Superclusters Of Galaxies, Sarah B. Rice
Weak Gravitational Lensing Analysis In Two Superclusters Of Galaxies, Sarah B. Rice
Electronic Theses and Dissertations
Observations of the Universe on very large scales have shown it to be filled with galaxy clusters and superclusters connected by walls and filaments of galaxies, with vast areas mostly devoid of luminous matter separating them. It is widely accepted that the amount of luminous matter does not provide the mass needed to hold galaxies and galaxy clusters together, and the nature of the missing "dark matter" is one of the most prominent astrophysical mysteries today. Since dark matter interacts with luminous matter gravitationally, it stands to reason that dark matter might organize itself in a similar manner to luminous …
First Steps In The Small-Scale Structure Formation In The Universe: The Emergence Of Galaxies, Da Bi
First Steps In The Small-Scale Structure Formation In The Universe: The Emergence Of Galaxies, Da Bi
Theses and Dissertations--Physics and Astronomy
Galactic morphology in the contemporary universe results from the convergence of a long list of physical processes, not all of them yet fully understood and quantified. The universe exhibits a hierarchical structure: galaxies grow being immersed in dark matter (DM) halos, which in turn are fed by diffuse and filamentary accretion. I use a suite of very high-resolution zoom-in cosmological simulations of galaxies in order to study the assembly of galaxies at high redshifts, z ≥ 2, to quantify the role of environment and of the parent DM halos in this procss. My models have been chosen to lie within …
Precise Mass Determination Of Spt-Cl J2106-5844, The Most Massive Cluster At Z > 1, Jinhyub Kim, M. James Jee, Saul Perlmutter, Brian Hayden, David Rubin, Xiaosheng Huang, Greg Aldering, Jongwan Ko
Precise Mass Determination Of Spt-Cl J2106-5844, The Most Massive Cluster At Z > 1, Jinhyub Kim, M. James Jee, Saul Perlmutter, Brian Hayden, David Rubin, Xiaosheng Huang, Greg Aldering, Jongwan Ko
Physics and Astronomy
We present a detailed high-resolution weak-lensing study of SPT-CL J2106-5844 at z = 1.132, claimed to be the most massive system discovered at z > 1 in the South Pole Telescope Sunyaev–Zel'dovich survey. Based on the deep imaging data from the Advanced Camera for Surveys and Wide Field Camera 3 on board the Hubble Space Telescope, we find that the cluster mass distribution is asymmetric, composed of a main clump and a subclump ~640 kpc west thereof. The central clump is further resolved into two smaller northwestern and southeastern substructures separated by ~150 kpc. We show that this rather complex …
Alpha Radiation Studies And Related Backgrounds In The Darkside-50 Detector, Alissa Monte
Alpha Radiation Studies And Related Backgrounds In The Darkside-50 Detector, Alissa Monte
Doctoral Dissertations
DarkSide-50 is the current phase of the DarkSide direct dark matter search program, operating underground at the Laboratori Nazionali del Gran Sasso in Italy. The detector is a dual-phase argon Time Projection Chamber (TPC), designed for direct detection of Weakly Interacting Massive Particles (WIMPs), and housed within a veto system of liquid scintillator and water Cherenkov detectors. Since switching to a target of low radioactivity argon extracted from underground sources in April 2015, the background is no longer dominated by naturally occurring 39Ar. However, alpha backgrounds from radon and its daughters remain, both from the liquid argon bulk and internal …
Probing Dark Matter-Neutrino Connection Via Indirect Detection Experiments, Bradley Knockel
Probing Dark Matter-Neutrino Connection Via Indirect Detection Experiments, Bradley Knockel
Physics & Astronomy ETDs
Various evidence reveals that dark matter is a primary component of this universe. The amount of dark matter is known, but its identity is a mystery. To determine its properties, efforts to detect and produce dark matter are underway. Dark matter annihilations throughout the galaxy may produce photons, neutrinos, and cosmic rays. Neutrino and photon detectors may then indirectly detect dark matter by detecting these annihilation products. The annihilation rate, dark matter mass, and dark matter scattering rate off of matter affect the signals received at Earth. These signals can therefore probe the identity of dark matter, especially if dark …
Logarithmic Spiral Arm Pitch Angle Of Spiral Galaxies: Measurement And Relationship To Galactic Structure And Nuclear Supermassive Black Hole Mass, Benjamin Lee Davis
Logarithmic Spiral Arm Pitch Angle Of Spiral Galaxies: Measurement And Relationship To Galactic Structure And Nuclear Supermassive Black Hole Mass, Benjamin Lee Davis
Graduate Theses and Dissertations
In this dissertation, I explore the geometric structure of spiral galaxies and how the visible structure can provide information about the central mass of a galaxy, the density of its galactic disk, and the hidden mass of the supermassive black hole in its nucleus. In order to quantitatively measure the logarithmic spiral pitch angle (a measurement of tightness of the winding) of galactic spiral arms, I led an effort in our research group (the Arkansas Galaxy Evolution Survey) to modify existing two-dimensional fast Fourier transform software to increase its efficacy and accuracy. Using this software, I was able to lead …
Lensed Type Ia Supernovae As Probes Of Cluster Mass Models, J Nordin, David Rubin, J Richard, E Rykoff, Greg Aldering, R Amanullah, H Atek, K Barbary, S Deustua, H K. Fakhouri, A S. Fruchter, A Goobar, I Hook, E Y. Hsiao, Xiaosheng Huang, J P. Kneib, C Lidman, J Meyers, S Perlmutter, C Saunders, A L. Spadafora, N Suzuki
Lensed Type Ia Supernovae As Probes Of Cluster Mass Models, J Nordin, David Rubin, J Richard, E Rykoff, Greg Aldering, R Amanullah, H Atek, K Barbary, S Deustua, H K. Fakhouri, A S. Fruchter, A Goobar, I Hook, E Y. Hsiao, Xiaosheng Huang, J P. Kneib, C Lidman, J Meyers, S Perlmutter, C Saunders, A L. Spadafora, N Suzuki
Physics and Astronomy
Using three magnified Type Ia supernovae (SNe Ia) detected behind CLASH (Cluster Lensing and Supernovae with Hubble) clusters, we perform a first pilot study to see whether standardizable candles can be used to calibrate cluster mass maps created from strong lensing observations. Such calibrations will be crucial when next-generation Hubble Space Telescope cluster surveys (e.g. Frontier) provide magnification maps that will, in turn, form the basis for the exploration of the high-redshift Universe. We classify SNe using combined photometric and spectroscopic observations, finding two of the three to be clearly of Type Ia and the third probable. The SNe exhibit …
Elvis: Exploring The Local Volume In Simulations, Shea Garrison-Kimmel, Michael Boylan-Kolchin, James S. Bullock, Kyle Lee
Elvis: Exploring The Local Volume In Simulations, Shea Garrison-Kimmel, Michael Boylan-Kolchin, James S. Bullock, Kyle Lee
Mathematics, Physics, and Computer Science Faculty Articles and Research
We introduce a set of high-resolution dissipationless simulations that model the Local Group (LG) in a cosmological context: Exploring the Local Volume in Simulations (ELVIS). The suite contains 48 Galaxy-size haloes, each within high-resolution volumes that span 2-5 Mpc in size, and each resolving thousands of systems with masses below the atomic cooling limit. Half of the ELVIS galaxy haloes are in paired configurations similar to the Milky Way (MW) and M31; the other half are isolated, mass-matched analogues. We find no difference in the abundance or kinematics of substructure within the virial radii of isolated versus paired hosts. On …
A Lagrangian Which Mathematically Models Lambda Cdm Cosmology And Explains The Null Results Of Dark Astroparticle Searches., Hontas Farmer
A Lagrangian Which Mathematically Models Lambda Cdm Cosmology And Explains The Null Results Of Dark Astroparticle Searches., Hontas Farmer
Hontas F Farmer
Background: The Lambda CDM model or is the standard model of modern cosmology. It is named for dark energy and cold dark matter. This model contains a number of separate components with different mathematical formulations. Strong observational evidence for dark matter has been found by astronomy. At the same time astroparticle physics observations have not found solid evidence of dark matter. Purpose: The purpose of this paper is to reconcile observations of dark matter effects on the galactic and cosmological scales with the null results of astroparticle physics observations such as CDMS and ANTARES. This paper will also provide a …
Dark Matter Scaling Relations And The Assembly Epoch Of Coma Early-Type Galaxies, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J Magorrian, E. M. Corsini, G. Wegner
Dark Matter Scaling Relations And The Assembly Epoch Of Coma Early-Type Galaxies, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J Magorrian, E. M. Corsini, G. Wegner
Dartmouth Scholarship
Axisymmetric, orbit-based dynamical models are used to derive dark matter scaling relations for Coma early-type galaxies. From faint to bright galaxies, halo core radii and asymptotic circular velocities increase. Compared to spirals of the same brightness, the majority of Coma early-type galaxies—those with old stellar populations—have similar halo core radii but more than two times larger asymptotic halo velocities. The average dark matter density inside 2 r eff decreases with increasing luminosity and is 6.8 times larger than in disk galaxies of the same B-band luminosity. Compared at the same stellar mass, dark matter densities in ellipticals are 13.5 …
Erasing Dark Matter Cusps In Cosmological Galactic Halos With Baryons, Emilio Romano-Diaz, Isaac Shlosman, Yehuda Hoffman, Clayton Heller
Erasing Dark Matter Cusps In Cosmological Galactic Halos With Baryons, Emilio Romano-Diaz, Isaac Shlosman, Yehuda Hoffman, Clayton Heller
Department of Physics and Astronomy Faculty Publications
We study the central dark matter (DM) cusp evolution in cosmologically grown galactic halos. Numerical models with and without baryons (baryons+DM, hereafter BDM model, and pure DM, PDM model, respectively) are advanced from identical initial conditions, obtained using the Constrained Realization method. The DM cusp properties are contrasted by a direct comparison of pure DM and baryonic models. We find a divergent evolution between the PDM and BDM models within the inner few × 10 kpc region. The PDM model forms an R−1 cusp as expected, while the DM in the BDM model forms a larger isothermal cusp R …
Large-Scale Power Spectrum And Structures From The Enear Galaxy Peculiar Velocity Catalogue, S. Zaroubi, M. Bernardi, L. N. Da Costa, Y. Hoffman, M. V. Alonso, G. Wegner
Large-Scale Power Spectrum And Structures From The Enear Galaxy Peculiar Velocity Catalogue, S. Zaroubi, M. Bernardi, L. N. Da Costa, Y. Hoffman, M. V. Alonso, G. Wegner
Dartmouth Scholarship
We estimate the mass density fluctuations power spectrum (PS) on large scales by applying a maximum likelihood technique to the peculiar velocity data of the recently completed redshift—distance survey of early-type galaxies (hereafter ENEAR). Parametric cold dark matter (CDM)-like models for the PS are assumed, and the best-fitting parameters are determined by maximizing the probability of the model given the measured peculiar velocities of the galaxies, their distances and estimated errors. The method has been applied to CDM models with and without COBE normalization. The general results are in agreement with the high-amplitude power spectra found from similar analyses of …
Comparison Of The Enear Peculiar Velocities With The Pscz Gravity Field, A Nusser, L. N. Da Costa, E Branchini, M. Bernardi, M V. Alonso, G Wegner
Comparison Of The Enear Peculiar Velocities With The Pscz Gravity Field, A Nusser, L. N. Da Costa, E Branchini, M. Bernardi, M V. Alonso, G Wegner
Dartmouth Scholarship
We present a comparison between the peculiar velocity field measured from the ENEAR all-sky Dn−σ catalogue and that derived from the galaxy distribution of the IRAS Point Source Catalog Redshift Survey (PSCz). The analysis is based on a modal expansion of these data in redshift space by means of spherical harmonics and Bessel functions. The effective smoothing scale of the expansion is almost linear with redshift reaching 1500kms−1 at 3000kms−1. The general flow patterns in the filtered ENEAR and PSCz velocity fields agree well within 6000kms−1, assuming a linear biasing relation between the mass and …
Comparison Of The Sfi Peculiar Velocities With The Iras 1.2-Jy Gravity Field, L. N. Da Costa, A. Nusser, W. Freudling, R. Giovanelli, M. P. Haynes, J J. Salzer, G. Wegner
Comparison Of The Sfi Peculiar Velocities With The Iras 1.2-Jy Gravity Field, L. N. Da Costa, A. Nusser, W. Freudling, R. Giovanelli, M. P. Haynes, J J. Salzer, G. Wegner
Dartmouth Scholarship
We present a comparison between the peculiar velocity fields measured from a recently completed I-band Tully-Fisher survey of field spirals (SFI) and that derived from the IRAS 1.2-Jy redshift survey galaxy distribution. The analysis is based on the expansion of these data in redshift space using smooth orthonormal functions, and is performed using low- and high-resolution expansions, with an effective smoothing scale which increases almost linearly with redshift. The effective smoothing scales at 3000 km s−1 are 1500 and 1000 km s−1 for the low- and high-resolution filters. The agreement between the high- and low-resolution SFI velocity …