Astrophysics and Astronomy Commons^™

Extending The Reach Of Directional Dark Matter Experiments Through Novel Detector Technologies, Nguyen S. Phan

Physics & Astronomy ETDs

Dark matter is believed to comprise over 80% of the matter in the Universe. Its composition could be in the form of weakly interacting massive particles (WIMPs), which are predicted by extensions of the Standard Model, namely supersymmetric theories. Even though hints of its existence were detected in astronomical observations over eighty years ago, its detection through means other than the gravitational influence on observable luminous matter still eludes us.

Currently, there are many ongoing direct detection experiments, that aim to measure the signals left by the elastic scattering of WIMPs with nuclei in the detector target material. The detection …

Mond Prediction For The Velocity Dispersion Of The "Feeble Giant" Crater Ii, Stacy S. Mcgaugh

Faculty Scholarship

Crater II is an unusual object among the dwarf satellite galaxies of the Local Group in that it has a very large size for its small luminosity. This provides a strong test of MOND, as Crater II should be in the deep MOND regime (g in ≈ 34 km2 s-2 kpc-1 ≪ a 0 = 3700 km2 s-2 kpc-1). Despite its great distance (≈120 kpc) from the Milky Way, the external field of the host (g ex ≈ 282 km2 s-2 kpc-1) comfortably exceeds the internal field. Consequently, Crater II should be subject to the external field effect, a feature …

Sparc: Mass Models For 175 Disk Galaxies With Spitzer Photometry And Accurate Rotation Curves, Federico Lelli, Stacy S. Mcgaugh

Faculty Scholarship

We introduce SPARC (Spitzer Photometry and Accurate Rotation Curves): a sample of 175 nearby galaxies with new surface photometry at 3.6 μm and high-quality rotation curves from previous H I/Hα studies. SPARC spans a broad range of morphologies (S0 to Irr), luminosities (∼5 dex), and surface brightnesses (∼4 dex). We derive [3.6] surface photometry and study structural relations of stellar and gas disks. We find that both the stellar mass-H I mass relation and the stellar radius-H i radius relation have significant intrinsic scatter, while the H I mass-radius relation is extremely tight. We build detailed mass models and quantify …

Radial Acceleration Relation In Rotationally Supported Galaxies, Stacy S. Mcgaugh, Federico Lelli

Faculty Scholarship

We report a correlation between the radial acceleration traced by rotation curves and that predicted by the observed distribution of baryons. The same relation is followed by 2693 points in 153 galaxies with very different morphologies, masses, sizes, and gas fractions. The correlation persists even when dark matter dominates. Consequently, the dark matter contribution is fully specified by that of the baryons. The observed scatter is small and largely dominated by observational uncertainties. This radial acceleration relation is tantamount to a natural law for rotating galaxies.

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 …

Dependence Of Gama Galaxy Halo Masses On The Cosmic Web Environment From 100 Deg2 Of Kids Weak Lensing Data., Margot M. Brouwer, Marcello Cacciato, Andrej Dvornik, Lizzie Eardley, Catherine Heymans, Henk Hoekstra, Konrad Kuijken, Tamsyn Mcnaught-Roberts, Cristobal Sifon, Massimo Viola, Mehmet Alpaslan, Maciej Bilicki, Joss Bland-Hawthorn, Sarah Brough, Ami Choi, Simon P. Driver, Thomas Erben, Aniello Grado, Hendrik Hildebrandt, Benne W. Holwerda, Andrew M. Hopkins, Jelte T. A. De Jong, Jochen Liske, John Mcfarland, Reiko Nakajima, Nicola R. Napolitano, Peder Norberg, John A. Peacock, Mario Radovich, Aaron S. G. Robotham, Peter Schneider, Gert Sikkema, Edo Van Uitert, Gijs Verdoes Kleijn, Edwin A. Valentijn

Faculty and Staff Scholarship

Galaxies and their dark matter haloes are part of a complex network of mass structures, collectively called the cosmic web. Using the tidal tensor prescription these structures can be classified into four cosmic environments: voids, sheets, filaments and knots. As the cosmic web may influence the formation and evolution of dark matter haloes and the galaxies they host, we aim to study the effect of these cosmic environments on the average mass of galactic haloes. To this end we measure the galaxy–galaxy lensing profile of 91 195 galaxies, within 0.039 < z < 0.263, from the spectroscopic Galaxy And Mass Assembly survey, using ∼100deg2" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; border: 0px; font-variant: inherit; font-stretch: inherit; line-height: normal; font-family: inherit; vertical-align: baseline; display: inline-table; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; position: relative;">∼100deg2∼100deg2

of overlapping data from the Kilo-Degree Survey. In …

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 …

The Relation Between Stellar And Dynamical Surface Densities In The Central Regions Of Disk Galaxies, Federico Lelli, Stacy S. Mcgaugh, Marcel S. Pawlowski

Faculty Scholarship

We use the Spitzer Photometry and Accurate Rotation Curves (SPARC) database to study the relation between the central surface density of stars and dynamical mass in 135 disk galaxies (S0 to dIrr). We find that correlates tightly with over 4 dex. This central density relation can be described by a double power law. High surface brightness galaxies are consistent with a 1:1 relation, suggesting that they are self-gravitating and baryon dominated in the inner parts. Low surface brightness (LSB) galaxies systematically deviate from the 1:1 line, indicating that the dark matter contribution progressively increases but remains tightly coupled to the …

The Small Scatter Of The Baryonic Tully-Fisher Relation, Federico Lelli, Stacy S. Mcgaugh

Faculty Scholarship

In a Γ cold dark matter (ΓCDM) cosmology, the baryonic TullyFisher relation (BTFR) is expected to show significant intrinsic scatter resulting from the massconcentration relation of dark matter halos and the baryonic-tohalo mass ratio. We study the BTFR using a sample of 118 disk galaxies (spirals and irregulars) with data of the highest quality: extended H I rotation curves (tracing the outer velocity) and Spitzer photometry at 3.6 μm (tracing the stellar mass). Assuming that the stellar mass-to-light ratio (Υ∗) is nearly constant at 3.6 μm, we find that the scatter, slope, and normalization of the BTFR systematically vary with …

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.

Gas Dynamics In Tidal Dwarf Galaxies: Disc Formation At Z = 0, Federico Lelli, Stacy Mcgaugh

Faculty Scholarship

Tidal dwarf galaxies (TDGs) are recycled objects that form within the collisional debris of interacting and merging galaxies. They are expected to be devoid of non-baryonic dark matter, since they can only form from dissipative material ejected from the discs of the progenitor galaxies. We investigate the gas dynamics in a sample of six bona fide TDGs around three interacting and post-interacting systems: NGC 4694, NGC 5291, and NGC 7252 ("Atoms for Peace"). For NGC 4694 and NGC 5291, we analyse existing HI data from the Very Large Array (VLA),while for NGC 7252 we present new HI observations from the …

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

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 …

The Third Law Of Galactic Rotation, Stacy S. Mcgaugh

Faculty Scholarship

I review the connection between dynamics and the baryonic mass distribution in rotationally-supported galaxies. The enclosed dynamical mass-to-light ratio increases with decreasing galaxy luminosity and surface brightness. The correlation with surface brightness appears to be the more fundamental, with the dependence on luminosity following simply from the weaker correlation between luminosity and surface brightness. In addition to this global relation, there is also a local relation between the amplitude of the mass discrepancy and the acceleration predicted by the observed distribution of baryons. I provide an empirical calibration of this mass discrepancy-acceleration relation. The data are consistent with the operation …

Model-Independent Plotting Of The Cosmological Scale Factor As A Function Of Lookback Time, H. I. Ringermacher, L. R. Mead

Faculty Publications

In this work we describe a model-independent method of developing a plot of scale factor a(t) versus lookback time t_L from the usual Hubble diagram of modulus data against redshift. This is the first plot of this type. We follow the model-independent methodology of Daly & Djorgovski used for their radio-galaxy data. Once the a(t)data plot is completed, any model can be applied and will display as described in the standard literature. We then compile an extensive data set to z = 1.8 by combining Type Ia supernovae (SNe Ia) data from SNLS3 …

Co-Orbiting Planes Of Sub-Halos Are Similarly Unlikely Around Paired And Isolated Hosts, Marcel S. Pawlowski, Stacy S. Mcgaugh

Faculty Scholarship

Sub-halos in dark-matter-based cosmological simulations tend to be distributed approximately isotropically around their host. The existence of highly flattened, co-orbiting planes of satellite galaxies has therefore been identified as a possible problem for these cosmological models, but so far studies have not considered the hosts' environments. That satellite planes are now known around both major galaxies in the Local Group raises the question whether they are more likely to be found around paired hosts. In a first attempt to investigate this possibility, we focus on the flattening and orbital coherence of the 11 brightest satellite galaxies of the vast polar …

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 …

Secular Damping Of Stellar Bars In Spinning Dark Matter Halos, Stacy Long, Isaac Shlosman, Clayton Heller

Physics and Astronomy Faculty Publications

We demonstrate using numerical simulations of isolated galaxies that growth of stellar bars in spinning dark matter halos is heavily suppressed in the secular phase of evolution. In a representative set of models, we show that for values of the cosmological spin parameter λ ≳ 0.03, bar growth (in strength and size) becomes increasingly quenched. Furthermore, the slowdown of the bar pattern speed weakens considerably with increasing λ until it ceases completely. The terminal structure of the bars is affected as well, including extent and shape of their boxy/peanut bulges. The essence of this effect lies in the modified angular …

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

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 …

Andromeda Dwarfs In Light Of Mond. Ii. Testing Prior Predictions, Stacy S. Mcgaugh

Faculty Scholarship

We employ recently published measurements of the velocity dispersions in the newly discovered dwarf satellite galaxies of Andromeda to test our previously published predictions of this quantity. The data are in good agreement with our specific predictions for each dwarf made a priori with modified Newtonian dynamics (MOND), with reasonable stellar mass-to-light ratios, and no dark matter, while Newtonian dynamics point to quite large mass discrepancies in these systems. MOND distinguishes between regimes where the internal field of the dwarf, or the external field of the host, dominates. The data appear to recognize this distinction, which is a unique feature …

Andromeda Dwarfs In Light Of Modified Newtonian Dynamics, Stacy S. Mcgaugh

Faculty Scholarship

We compare the recently published velocity dispersions for 17 Andromeda dwarf spheroidals with estimates of the modified Newtonian dynamics predictions, based on the luminosities of these dwarfs, with reasonable stellar mass-to-light values and no dark matter. We find that the two are consistent within the uncertainties. We further predict the velocity dispersions of another 10 dwarfs for which only photometric data are currently available. © 2013. The American Astronomical Society. All rights reserved..

Constraints On Cosmic Rays, Magnetic Fields, And Dark Matter From Gamma-Ray Observations Of The Coma Cluster Of Galaxies With Veritas And Fermi, P. T. Reynolds, Et. Al.

Physical Sciences Publications

Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated and, on account of weak energy losses, can accumulate, suggesting that clusters may also be sources of very high energy (VHE; E > 100 GeV) gamma-ray emission. We report here on VHE gamma-ray observations of the Coma galaxy cluster with the VERITAS array of imaging Cerenkov telescopes, with complementing Fermi Large Area Telescope observations at GeV energies. No significant gamma-ray emission from the Coma Cluster was detected. Integral flux upper limits at the 99% confidence level were measured to be on the order …

Modified Newtonian Dynamics (Mond): Observational Phenomenology And Relativistic Extensions, Stacy S. Mcgaugh

Faculty Scholarship

A wealth of astronomical data indicate the presence of mass discrepancies in the Universe. The motions observed in a variety of classes of extragalactic systems exceed what can be explained by the mass visible in stars and gas. Either (i) there is a vast amount of unseen mass in some novel form - dark matter - or (ii) the data indicate a breakdown of our understanding of dynamics on the relevant scales, or (iii) both. Here, we first review a few outstanding challenges for the dark matter interpretation of mass discrepancies in galaxies, purely based on observations and independently of …

The Dark Side Of The Universe: Dark Matter In The Galaxy And Cosmos, Shane L. Larson

Public Talks

No abstract provided.

Scaling Relations And Overabundance Of Massive Clusters At Z ≳ 1 From Weak-Lensing Studies With The Hubble Space Telescope, M J. Jee, Ks Dawson, H Hoekstra, S Perlmutter, P Rosati, M Brodwin, N Sukuzi, B Koester, M Postman, L Lubin, J Meyers, Sa Stanford, K Barbary, F Barrientos, P Eisenhardt, Hc Ford, Dg Gibank, Md Gladders, A Gonzalez, Dw Harris, Xiaosheng Huang, C Lidman, Es Rykoff, D Rubin, Al Spadafora

Physics and Astronomy

We present weak gravitational lensing analysis of 22 high-redshift (z 1) clusters based on Hubble Space Telescope images. Most clusters in our sample provide significant lensing signals and are well detected in their reconstructed two-dimensional mass maps. Combining the current results and our previous weak-lensing studies of five other high-z clusters, we compare gravitational lensing masses of these clusters with other observables. We revisit the question whether the presence of the most massive clusters in our sample is in tension with the current ΛCDM structure formation paradigm. We find that the lensing masses are tightly correlated with the …

Local Group Dwarf Spheroidals: Correlated Deviations From The Baryonic Tully-Fisher Relation, Stacy S. Mcgaugh

Faculty Scholarship

Local Group dwarf spheroidal satellite galaxies are the faintest extragalactic stellar systems known. We examine recent data for these objects in the plane of the Baryonic Tully-Fisher Relation (BTFR). While some dwarf spheroidals adhere to the BTFR, others deviate substantially. We examine the residuals from the BTFR and find that they are not random. The residuals correlate with luminosity, size, metallicity, ellipticity, and susceptibility of the dwarfs to tidal disruption in the sense that fainter, more elliptical, and tidally more susceptible dwarfs deviate farther from the BTFR. These correlations disfavor stochastic processes and suggest a role for tidal effects. We …

Veritas Search For Vhe Gamma-Ray Emission From Dwarf Spheroidal Galaxies, P. T. Reynolds, Et. Al.

Physical Sciences Publications

Indirect dark matter searches with ground-based gamma-ray observatories provide an alternative for identifying the particle nature of dark matter that is complementary to that of direct search or accelerator production experiments. We present the results of observations of the dwarf spheroidal galaxies Draco, Ursa Minor, Boötes 1, and Willman 1 conducted by the Very Energetic Radiation Imaging Telescope Array System (VERITAS). These galaxies are nearby dark matter dominated objects located at a typical distance of several tens of kiloparsecs for which there are good measurements of the dark matter density profile from stellar velocity measurements. Since the conventional astrophysical background …

In Search Of Empty Places: Voids In The Distribution Of Galaxies, Brian K. Bucklein

Theses and Dissertations

We investigate several techniques to identify voids in the galaxy distribution of matter in the universe. We utilize galaxy number counts as a function of apparent magnitude and Wolf plots to search a two- or three-dimensional data set in a pencil-beam fashion to locate voids within the field of view. The technique is able to distinguish between voids that represent simply a decrease in density as well as those that show a build up of galaxies on the front or back side of the void. This method turns out to be primarily useable only at relatively short range (out to …

Comparing The Dark Matter Halos Of Spiral, Low Surface Brightness, And Dwarf Spheroidal Galaxies, Stacy S. Mcgaugh

Faculty Scholarship

We consider dark masses measured from kinematic tracers at discrete radii in galaxies for which baryonic contributions to overall potentials are either subtracted or negligible. Recent work indicates that rotation curves due to dark matter (DM) halos at intermediate radii in spiral galaxies are remarkably similar, with a mean rotation curve given by log10(V c,DM/(km s-1)) = 1.47+0.15-0.19 + 0.5log10(r/kpc). Independent studies show that while estimates of the dark mass of a given dwarf spheroidal (dSph) galaxy are robust only near the half-light radius, data from the Milky Way's (MW's) dSph satellites are consistent with a narrow range of mass …