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Articles 1 - 18 of 18
Full-Text Articles in Physical Sciences and Mathematics
Hubble Tension And Gravitational Self-Interaction, Corey Sargent, William Clark, Alexander Deur, Balša Terzić
Hubble Tension And Gravitational Self-Interaction, Corey Sargent, William Clark, Alexander Deur, Balša Terzić
Physics Faculty Publications
One of the most important problems vexing the ΛCDM cosmological model is the Hubble tension. It arises from the fact that measurements of the present value of the Hubble parameter performed with low-redshift quantities, e.g. the Type IA supernova, tend to yield larger values than measurements from quantities originating at high-redshift, e.g. fits of cosmic microwave background radiation. It is becoming likely that the discrepancy, currently standing at 5σ, is not due to systematic errors in the measurements. Here we explore whether the self-interaction of gravitational fields in General Relativity, which are traditionally neglected when studying the evolution …
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 …
Updated Analysis Of An Unexpected Correlation Between Dark Matter And Galactic Ellipticity, D. M. Winters, Alexandre Deur, X. Zheng
Updated Analysis Of An Unexpected Correlation Between Dark Matter And Galactic Ellipticity, D. M. Winters, Alexandre Deur, X. Zheng
Physics Faculty Publications
We investigate a correlation between the dark matter content of elliptical galaxies and their ellipticity ϵ that was initially reported in 2014. We use new determinations of dark matter and ellipticities that are posterior to that time. Our data set consists of 237 elliptical galaxies passing a strict set of criteria that selects a homogeneous sample of typical elliptical galaxies. We find a relation between the mass-to-light ratio and ellipticity ϵ that is well fitted by M/L = (14.1 ± 5.4)ϵ, which agrees with the result reported in 2014. Our analysis includes 135 galaxies that were not in …
Significance Of Gravitational Nonlinearities On The Dynamics Of Disk Galaxies, Alexandre Deur, Corey Sargent, Balša Terzić
Significance Of Gravitational Nonlinearities On The Dynamics Of Disk Galaxies, Alexandre Deur, Corey Sargent, Balša Terzić
Physics Faculty Publications
The discrepancy between the visible mass in galaxies or galaxy clusters and that inferred from their dynamics is well known. The prevailing solution to this problem is dark matter. Here we show that a different approach, one that conforms to both the current standard model of particle physics and general relativity (GR), explains the recently observed tight correlation between the galactic baryonic mass and the measured accelerations in the galaxy. Using direct calculations based on GR's Lagrangian and parameter-free galactic models, we show that the nonlinear effects of GR make baryonic matter alone sufficient to explain this observation. Our approach …
Dark Matter And No Dark Matter: On The Halo Mass Of Ngc 1052, Duncan Forbes, Adebusola Alabi, Jean Brodie, Aaron Romanowsky
Dark Matter And No Dark Matter: On The Halo Mass Of Ngc 1052, Duncan Forbes, Adebusola Alabi, Jean Brodie, Aaron Romanowsky
Faculty Publications
The NGC 1052 group, and in particular the discovery of two ultra-diffuse galaxies with very low internal velocity dispersions, has been the subject of much attention recently. Here we present radial velocities for a sample of 77 globular clusters associated with NGC 1052 obtained on the Keck telescope. Their mean velocity and velocity dispersion are consistent with that of the host galaxy. Using a simple tracer mass estimator, we infer the enclosed dynamical mass and dark matter fraction of NGC 1052. Extrapolating our measurements with a Navarro–Frenk–White (NFW) mass profile we infer a total halo mass of 6.2(±0.2) × 1012 …
The Role Of Angular Momentum In The Interplay Between Disk Galaxies And Their Host Dark Matter Halos: Corollaries For The Hubble Fork Diagram, Angela Collier
The Role Of Angular Momentum In The Interplay Between Disk Galaxies And Their Host Dark Matter Halos: Corollaries For The Hubble Fork Diagram, Angela Collier
Theses and Dissertations--Physics and Astronomy
A majority of disk galaxies host stellar bars that regulate and amplify the flow of angular momentum, J, between disks and their parent dark matter (DM) halos. These bars constitute the prime factor driving internal galaxy evolution. Yet, a non-negligible fraction of disks lack this morphological feature, which led to adoption of the Hubble Fork Diagram. The complex evolution of barred galaxies has been studied by means of numerical simulations, complemented by observations. Despite prolonged efforts, many fundamental questions remain, in part because cosmological simulations still lack the necessary resolution to account for resonant interactions and simulations of isolated …
The Sluggs Survey: Dark Matter Fractions At Large Radii And Assembly Epochs Of Early-Type Galaxies From Globular Cluster Kinematics, Adebusola Alabi, Duncan Forbes, Aaron Romanowsky, Jean Brodie, Jay Strader, Joachim Janz, Christopher Usher, Lee Spitler, Sabine Bellstedt, Anna Ferré-Mateu
The Sluggs Survey: Dark Matter Fractions At Large Radii And Assembly Epochs Of Early-Type Galaxies From Globular Cluster Kinematics, Adebusola Alabi, Duncan Forbes, Aaron Romanowsky, Jean Brodie, Jay Strader, Joachim Janz, Christopher Usher, Lee Spitler, Sabine Bellstedt, Anna Ferré-Mateu
Faculty Publications
We use globular cluster kinematics data, primarily from the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey, to measure the dark matter fraction (fDM) and the average dark matter density (〈ρDM〉) within the inner 5 effective radii (Re) for 32 nearby early-type galaxies (ETGs) with stellar mass log (M*/M⊙) ranging from 10.1 to 11.8. We compare our results with a simple galaxy model based on scaling relations as well as with cosmological hydrodynamical simulations where the dark matter profile has been modified through various physical processes. We find a high fDM (≥0.6) within 5 Re in most of our sample, …
The Mass Discrepancy Acceleration Relation In Early-Type Galaxies: Extended Mass Profiles And The Phantom Menace To Mond, Joachim Janz, Michele Cappellari, Aaron Romanowsky, Luca Ciotti, Adebusola Alabi, Duncan Forbes
The Mass Discrepancy Acceleration Relation In Early-Type Galaxies: Extended Mass Profiles And The Phantom Menace To Mond, Joachim Janz, Michele Cappellari, Aaron Romanowsky, Luca Ciotti, Adebusola Alabi, Duncan Forbes
Faculty Publications
The dark matter (DM) haloes around spiral galaxies appear to conspire with their baryonic content: empirically, significant amounts of DM are inferred only below a universal characteristic acceleration scale. Moreover, the discrepancy between the baryonic and dynamical mass, which is usually interpreted as the presence of DM, follows a very tight mass discrepancy acceleration (MDA) relation. Its universality, and its tightness in spiral galaxies, poses a challenge for the DM interpretation and was used to argue in favour of MOdified Newtonian Dynamics (MOND). Here, we test whether or not this applies to early-type galaxies. We use the dynamical models of …
First Results From The Madcash Survey: A Faint Dwarf Galaxy Companion To The Low-Mass Spiral Galaxy Ngc 2403 At 3.2 Mpc*, Jeffrey Carlin, David Sand, Paul Price, Beth Willman, Ananthan Karunakaran, Kristine Spekkens, Eric Bell, Jean Brodie, Denija Crnojević, Duncan Forbes, Jonathan Hargis, Evan Kirby, Robert Lupton, Annika Peter, Aaron Romanowsky, Jay Strader
First Results From The Madcash Survey: A Faint Dwarf Galaxy Companion To The Low-Mass Spiral Galaxy Ngc 2403 At 3.2 Mpc*, Jeffrey Carlin, David Sand, Paul Price, Beth Willman, Ananthan Karunakaran, Kristine Spekkens, Eric Bell, Jean Brodie, Denija Crnojević, Duncan Forbes, Jonathan Hargis, Evan Kirby, Robert Lupton, Annika Peter, Aaron Romanowsky, Jay Strader
Faculty Publications
No abstract provided.
Dark Matter Halo Concentration And The Evolution Of Spiral Structure In N-Body, Barred Spiral Galaxies, Jazmin Esmeralda Berlanga Medina
Dark Matter Halo Concentration And The Evolution Of Spiral Structure In N-Body, Barred Spiral Galaxies, Jazmin Esmeralda Berlanga Medina
Graduate Theses and Dissertations
Motivated by the evidence of relationships between pitch angle (the tightness of spiral arm structure in the disk), P, and various indicators of central mass concentration, as well as the theoretical relationship between halo mass concentration and the density of visible matter in the central part of the galaxy, we look at a possible relationship between P and cvir (the virial concentration of the dark matter halo) in N-body simulations of barred, spiral galaxies. We also look at the evolution of pitch angle over time in higher temporal resolution than any data currently available in the literature. We find that …
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 …
Dynamical Models Of Elliptical Galaxies – I. Simple Methods, A. Angello, N. Evans, Aaron Romanowsky
Dynamical Models Of Elliptical Galaxies – I. Simple Methods, A. Angello, N. Evans, Aaron Romanowsky
Faculty Publications
We study dynamical models for elliptical galaxies, deriving the projected kinematic profiles in a form that is valid for general surface-brightness profiles and (spherical) total mass profiles, without the need for any explicit deprojection. We then show that an almost flat rotation curve, combined with modest velocity anisotropy, is already sufficient to recover the kinematic profiles of nearby ellipticals. As an application, we provide two different sets of mass estimators for elliptical galaxies, based on either the velocity dispersion at a specific location near the effective radius, or the aperture-averaged velocity dispersion. In the large aperture (virial) limit, mass estimators …
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 …
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 …
Structure Formation Inside Triaxial Dark Matter Halos: Galactic Disks, Bulges, And Bars, Clayton Heller, Isaac Shlosman, Evangelie Athanassoula
Structure Formation Inside Triaxial Dark Matter Halos: Galactic Disks, Bulges, And Bars, Clayton Heller, Isaac Shlosman, Evangelie Athanassoula
Department of Physics and Astronomy Faculty Publications
We investigate formation and evolution of galactic disks immersed in assembling live DM halos. Models have been evolved from cosmological initial conditions and represent the collapse of an isolated density perturbation. The baryons include gas participating in star formation (SF) and stars with the energy feedback onto the ISM. We find that (1) the triaxial halo figure tumbling is insignificant and the angular momentum (J) is channeled into the internal circulation, while the baryonic collapse is stopped by the centrifugal barrier; (2) density response of the (disk) baryons is out of phase with DM, thus washing out the …
Dynamical Modelling Of Luminous And Dark Matter In 17 Coma Early-Type Galaxies, J. Thomas, R. O. Saglia, R. Bender, D. Thomas, J K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner
Dynamical Modelling Of Luminous And Dark Matter In 17 Coma Early-Type Galaxies, J. Thomas, R. O. Saglia, R. Bender, D. Thomas, J K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner
Dartmouth Scholarship
Dynamical models for 17 early‐type galaxies in the Coma cluster are presented. The galaxy sample consists of flattened, rotating as well as non‐rotating early‐types including cD and S0 galaxies with luminosities between MB=−18.79 and −22.56. Kinematical long‐slit observations cover at least the major‐axis and minor‐axis and extend to 1–4reff. Axisymmetric Schwarzschild models are used to derive stellar mass‐to‐light ratios and dark halo parameters. In every galaxy, the best fit with dark matter matches the data better than the best fit without. The statistical significance is over 95 per cent for eight galaxies, around 90 per …
The Oxford-Dartmouth Thirty Degree Survey - Ii. Clustering Of Bright Lyman Break Galaxies: Strong Luminosity-Dependent Bias At Z = 4, Paul D. Allen, Leonidas A. Moustakas, Gavin Dalton, Emily Macdonald, Chris Blake, Lee Clewley, Catherine Heymans, Gary Wegner
The Oxford-Dartmouth Thirty Degree Survey - Ii. Clustering Of Bright Lyman Break Galaxies: Strong Luminosity-Dependent Bias At Z = 4, Paul D. Allen, Leonidas A. Moustakas, Gavin Dalton, Emily Macdonald, Chris Blake, Lee Clewley, Catherine Heymans, Gary Wegner
Dartmouth Scholarship
We present measurements of the clustering properties of bright (L > L*) z~4 Lyman break galaxies (LBGs) selected from the Oxford-Dartmouth Thirty Degree Survey (ODT). We describe techniques used to select and evaluate our candidates and calculate the angular correlation function, which we find best fitted by a power law, ω(θ) =Awθ−β with Aw= 15.4 (with θ in arcsec), using a constrained slope of β= 0.8. Using a redshift distribution consistent with photometric models, we deproject this correlation function and find a comoving Mpc in a Ωm= 0.3 flat λ cosmology for iAB≤ 24.5. This corresponds to a linear bias value …
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 …