# Browsing by Subject "dark matter"

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Item The Central Dark Matter Distribution Of NGC 2976(2012-01) Adams, Joshua J.; Gebhardt, Karl; Blanc, Guillermo A.; Fabricius, Maximilian H.; Hill, Gary J.; Murphy, Jeremy D.; van den Bosch, Remco C. E.; van de Ven, Glenn; Hill, Gary J.; van den Bosch, Remco C. E.Show more We study the mass distribution in the late-type dwarf galaxy NGC 2976 through stellar kinematics obtained with the Visible Integral Field ReplicableUnit Spectrograph Prototype and anisotropic Jeans models as a test of cosmological simulations and baryonic processes that putatively alter small-scale structure. Previous measurements of the Ha emission-line kinematics have determined that the dark matter halo of NGC 2976 is most consistent with a cored density profile. We find that the stellar kinematics are best fit with a cuspy halo. Cored dark matter halo fits are only consistent with the stellar kinematics if the stellar mass-to-light ratio is significantly larger than that derived from stellar population synthesis, while the best-fitting cuspy model has no such conflict. The inferred mass distribution from a harmonic decomposition of the gaseous kinematics is inconsistent with that of the stellar kinematics. This difference is likely due to the gas disk not meeting the assumptions that underlie the analysis such as no pressure support, a constant kinematic axis, and planar orbits. By relaxing some of these assumptions, in particular the form of the kinematic axis with radius, the gas-derived solution can be made consistent with the stellar kinematic models. A strong kinematic twist in the gas of NGC 2976' s center suggests caution, and we advance the mass model based on the stellar kinematics as more reliable. The analysis of this first galaxy shows promising evidence that dark matter halos in late-type dwarfs may in fact be more consistent with cuspy dark matter distributions than earlier work has claimed.Show more Item The Dark Matter Density Profile Of The Fornax Dwarf(2012-02) Jardel, John R.; Gebhardt, Karl; Jardel, John R.; Gebhardt, KarlShow more We construct axisymmetric Schwarzschild models to measure the mass profile of the Local Group dwarf galaxy Fornax. These models require no assumptions to be made about the orbital anisotropy of the stars, as is the case for commonly used Jeans models. We test a variety of parameterizations of dark matter density profiles and find cored models with uniform density rho c = (1.6 +/- 0.1) x 10(-2) M-circle dot pc(-3) fit significantly better than the cuspy halos predicted by cold dark matter simulations. We also construct models with an intermediate-mass black hole, but are unable to make a detection. We place a 1 sigma upper limit on the mass of a potential intermediate-mass black hole at M. <= 3.2 x 10(4) M-circle dot.Show more Item Dark Matter Scaling Relations And The Assembly Epoch Of Coma Early-Type Galaxies(2009-01) Thomas, Jens; Saglia, R. P.; Bender, Ralf; Thomas, D.; Gebhardt, Karl; Magorrian, John; Corsini, E. M.; Wegner, G.; Gebhardt, KarlShow more 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 2r(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 times higher than in spirals. Different baryon concentrations in ellipticals and spirals cannot explain the higher dark matter density in ellipticals. Instead, the assembly redshift (1 + z) of Coma early-type halos is likely about two times larger than of comparably bright spirals. Assuming that local spirals typically assemble at a redshift of one, the majority of bright Coma early-type galaxy halos must have formed around z approximate to 2-3. For about half of our Coma galaxies, the assembly redshifts match with constraints derived from stellar populations. We find dark matter densities and estimated assembly redshifts of our observed Coma galaxies in reasonable agreement with recent semi-analytic galaxy formation models.Show more Item Detecting Dark Matter In The MSSM With Non-Universal Higgs Masses(2009-02) Sandick, P.; Sandick, PearlShow more We discuss the direct detection prospects for neutralino dark matter via elastic scattering in variations of the MSSM with non-universal supersymmetry-breaking contributions to the Higgs masses Taking as our starting point the CMSSM, in which supersymmetry-breaking contributions to all scalar masses are universal, we examine scenarios in which both Higgs scalar masses are non-universal by the same amount (NUHM1) and scenarios in which the Higgs scalar masses are independently non-universal (NUHM2)Show more Item Dwarf Galaxy Dark Matter Density Profiles Inferred From Stellar And Gas Kinematics(2014-07) Adams, Joshua J.; Simon, Joshua D.; Fabricius, Maximilian H.; van den Bosch, Remco C. E.; Barentine, John C.; Bender, Ralf; Gebhardt, Karl; Hill, Gary J.; Murphy, Jeremy D.; Swaters, R. A.; Thomas, Jens; van de Ven, Glenn; Barentine, John C.; Gebhardt, Karl; Hill, Gary J.Show more We present new constraints on the density profiles of dark matter (DM) halos in seven nearby dwarf galaxies from measurements of their integrated stellar light and gas kinematics. The gas kinematics of low-mass galaxies frequently suggest that they contain constant density DM cores, while N-body simulations instead predict a cuspy profile. We present a data set of high-resolution integral-field spectroscopy on seven galaxies and measure the stellar and gas kinematics simultaneously. Using Jeans modeling on our full sample, we examine whether gas kinematics in general produce shallower density profiles than are derived from the stars. Although two of the seven galaxies show some localized differences in their rotation curves between the two tracers, estimates of the central logarithmic slope of the DM density profile, gamma, are generally robust. The mean and standard deviation of the logarithmic slope for the population are gamma = 0.67 +/- 0.10 when measured in the stars and gamma = 0.58 +/- 0.24 when measured in the gas. We also find that the halos are not under-concentrated at the radii of half their maximum velocities. Finally, we search for correlations of the DM density profile with stellar velocity anisotropy and other baryonic properties. Two popular mechanisms to explain cored DM halos are an exotic DM component or feedback models that strongly couple the energy of supernovae into repeatedly driving out gas and dynamically heating the DM halos. While such models do not yet have falsifiable predictions that we can measure, we investigate correlations that may eventually be used to test models. We do not find a secondary parameter that strongly correlates with the central DM density slope, but we do find some weak correlations. The central DM density slope weakly correlates with the abundance of a elements in the stellar population, anti-correlates with Hi fraction, and anti-correlates with vertical orbital anisotropy. We expect, if anything, the opposite of these three trends for feedback models. Determining the importance of these correlations will require further model developments and larger observational samples.Show more Item Five-Year Wilkinson Microwave Anisotropy Probe Observations: Cosmological interpretation(2009-02) Komatsu, Eiichiro; Dunkley, J.; Nolta, M. R.; Bennett, C. L.; Gold, B.; Hinshaw, G.; Jarosik, N.; Larson, D.; Limon, M.; Page, L.; Spergel, D. N.; Halpern, M.; Hill, R. S.; Kogut, A.; Meyer, S. S.; Tucker, G. S.; Weiland, J. L.; Wollack, E.; Wright, E. L.; Komatsu, EiichiroShow more The Wilkinson Microwave Anisotropy Probe (WMAP) 5-year data provide stringent limits on deviations from the minimal, six-parameter. cold dark matter model. We report these limits and use them to constrain the physics of cosmic inflation via Gaussianity, adiabaticity, the power spectrum of primordial fluctuations, gravitational waves, and spatial curvature. We also constrain models of dark energy via its equation of state, parity-violating interaction, and neutrino properties, such as mass and the number of species. We detect no convincing deviations from the minimal model. The six parameters and the corresponding 68% uncertainties, derived from the WMAP data combined with the distance measurements from the Type Ia supernovae (SN) and the Baryon Acoustic Oscillations (BAO) in the distribution of galaxies, are: Omega(b)h(2) = 0.02267(-0.00059)(+0.00058), Omega(c)h(2) = 0.1131 +/- 0.0034, Omega(Lambda) = 0.726 +/- 0.015, n(s) = 0.960 +/- 0.013, tau = 0.084 +/- 0.016, and Delta(2)(R) = (2.445 +/- 0.096) x 10(-9) at k = 0.002 Mpc(-1). From these, we derive sigma(8) = 0.812 +/- 0.026, H-0 = 70.5 +/- 1.3 kms(-1) Mpc(-1), Omega(b) = 0.0456 +/- 0.0015, Omega(c) = 0.228 +/- 0.013, Omega(m)h(2) = 0.1358(-0.0036)(+0.0037), z(reion) = 10.9 +/- 1.4, and t(0) = 13.72 +/- 0.12 Gyr. With the WMAP data combined with BAO and SN, we find the limit on the tensor-to-scalar ratio of r < 0.22 (95% CL), and that n(s) > 1 is disfavored even when gravitational waves are included, which constrains the models of inflation that can produce significant gravitational waves, such as chaotic or power-law inflation models, or a blue spectrum, such as hybrid inflation models. We obtain tight, simultaneous limits on the (constant) equation of state of dark energy and the spatial curvature of the universe: -0.14 < 1 + w(0) < 0.12 (95% CL) and -0.0179 < Omega(k) < 0.0081 (95% CL). We provide a set of "WMAP distance priors," to test a variety of dark energy models with spatial curvature. We test a time-dependent w with a present value constrained as -0.33 < 1 + w(0) < 0.21 (95% CL). Temperature and dark matter fluctuations are found to obey the adiabatic relation to within 8.9% and 2.1% for the axion-type and curvaton-type dark matter, respectively. The power spectra of TB and EB correlations constrain a parity-violating interaction, which rotates the polarization angle and converts E to B. The polarization angle could not be rotated more than -5 degrees.9 < Delta alpha < 2 degrees.4 (95% CL) between the decoupling and the present epoch. We find the limit on the total mass of massive neutrinos of Sigma m(v) < 0.67 eV (95% CL), which is free from the uncertainty in the normalization of the large-scale structure data. The number of relativistic degrees of freedom (dof), expressed in units of the effective number of neutrino species, is constrained as N-eff = 4.4 +/- 1.5 (68%), consistent with the standard value of 3.04. Finally, quantitative limits on physically-motivated primordial non-Gaussianity parameters are -9 < f(NL)(local) < 111 (95% CL) and -151 < f(NL)(equil) < 253 (95% CL) for the local and equilateral models, respectively.Show more Item Five-Year Wilkinson Microwave Anisotropy Probe Observations: Data Processing, Sky Maps, and Basic Results(2009-02) Hinshaw, G.; Weiland, J. L.; Hill, R. S.; Odegard, N.; Larson, D.; Bennett, C. L.; Dunkley, J.; Gold, B.; Greason, M. R.; Jarosik, N.; Komatsu, Eiichiro; Nolta, M. R.; Page, L.; Spergel, D. N.; Wollack, E.; Halpern, M.; Kogut, A.; Limon, M.; Meyer, S. S.; Tucker, G. S.; Wright, E. L.; Komatsu, EiichiroShow more We present new full-sky temperature and polarization maps in five frequency bands from 23 to 94 GHz, based on data from the first five years of the Wilkinson Microwave Anisotropy Probe (WMAP) sky survey. The new maps are consistent with previous maps and are more sensitive. The five-year maps incorporate several improvements in data processing made possible by the additional years of data and by a more complete analysis of the instrument calibration and in-flight beam response. We present several new tests for systematic errors in the polarization data and conclude that W-band polarization data is not yet suitable for cosmological studies, but we suggest directions for further study. We do find that Ka-band data is suitable for use; in conjunction with the additional years of data, the addition of Ka band to the previously used Q- and V-band channels significantly reduces the uncertainty in the optical depth parameter, tau. Further scientific results from the five-year data analysis are presented in six companion papers and are summarized in Section 7 of this paper. With the five-year WMAP data, we detect no convincing deviations from the minimal six-parameter Lambda CDM model: a flat universe dominated by a cosmological constant, with adiabatic and nearly scale-invariant Gaussian fluctuations. Using WMAP data combined with measurements of Type Ia supernovae and Baryon Acoustic Oscillations in the galaxy distribution, we find (68% CL uncertainties): Omega(b)h(2) = 0.02267(-0.00059)(+0.00058), Omega(c)h(2) = 0.1131 +/- 0.0034, Omega(Lambda) = 0.726 +/- 0.015, n(s) = 0.960 +/- 0.013, tau = 0.084 +/- 0.016, and Delta(2)(R) = (2.445 +/- 0.096) x 10(-9) at k = 0.002 Mpc(-1). From these we derive sigma(8) = 0.812 +/- 0.026, H(0) = 70.5 +/- 1.3 km s(-1) Mpc(-1), Omega(b) = 0.0456 +/- 0.0015, Omega(c) = 0.228 +/- 0.013, Omega(m)h(2) = 0.1358(-0.0036)(+0.0037), z(reion) = 10.9 +/- 1.4, and t(0) = 13.72 +/- 0.12 Gyr. The new limit on the tensor-to-scalar ratio is r < 0.22 (95% CL), while the evidence for a running spectral index is insignificant, dn(s)/d ln k = - 0.028 +/- 0.020 (68% CL). We obtain tight, simultaneous limits on the (constant) dark energy equation of state and the spatial curvature of the universe: - 0.14 < 1 + w < 0.12 (95% CL) and -0.0179 < Omega(k) < 0.0081 (95% CL). The number of relativistic degrees of freedom, expressed in units of the effective number of neutrino species, is found to be N(eff) = 4.4 +/- 1.5 (68% CL), consistent with the standard value of 3.04. Models with N(eff) = 0 are disfavored at >99.5% confidence. Finally, new limits on physically motivated primordial non-Gaussianity parameters are -9 < f(NL)(local) < 111 (95% CL) and -151 < f(NL)(equil) < 253 (95% CL) for the local and equilateral models, respectively.Show more Item Galaxy Kinematics With Virus-P: The Dark Matter Halo Of M87(2011-03) Murphy, Jeremy D.; Gebhardt, Karl; Adams, Joshua J.; Murphy, Jeremy D.; Gebhardt, Karl; Adams, Joshua J.Show more We present two-dimensional stellar kinematics of M87 out to R = 238 '' taken with the integral field spectrograph VIRUS-P. We run a large set of axisymmetric, orbit-based dynamical models and find clear evidence for a massive dark matter halo. While a logarithmic parameterization for the dark matter halo is preferred, we do not constrain the dark matter scale radius for a Navarro-Frenk-White (NFW) profile and therefore cannot rule it out. Our best-fit logarithmic models return an enclosed dark matter fraction of 17.2(-5.0)(+5.0)% within one effective radius (R-e congruent to 100 ''), rising to 49.4(-8.8)(+7.2)% within 2 R-e. Existing SAURON data (R <= 13 ''), and globular cluster (GC) kinematic data covering 145 '' <= R <= 554 '' complete the kinematic coverage to R = 47 kpc (similar to 5R(e)). At this radial distance, the logarithmic dark halo comprises 85.3(-2.4)(+2.5)% of the total enclosed mass of 5.7(-0.9)(+1.3) x 10(12) M-circle dot making M87 one of the most massive galaxies in the local universe. Our best-fit logarithmic dynamical models return a stellar mass-to-light ratio (M/L) of 9.1(-0.2)(+0.2) (V band), a dark halo circular velocity of 800(-25)(+75) km s(-1), and a dark halo scale radius of 36(-3)(+7) kpc. The stellar M/L, assuming an NFW dark halo, is well constrained to 8.20(-0.10)(+0.05) (V band). The stars in M87 are found to be radially anisotropic out to R congruent to 0.5 R-e, then isotropic or slightly tangentially anisotropic to our last stellar data point at R = 2.4 R-e where the anisotropy of the stars and GCs are in excellent agreement. The GCs then become radially anisotropic in the last two modeling bins at R = 3.4 R-e and R = 4.8 R-e. As one of the most massive galaxies in the local universe, constraints on both the mass distribution of M87 and anisotropy of its kinematic components strongly inform our theories of early-type galaxy formation and evolution in dense environments.Show more Item Hobby-Eberly Telescope Observations Of The Dark Halo In NGC 821(2010-06) Forestell, Amy D.; Gebhardt, Karl; Forestell, Amy D.; Gebhardt, KarlShow more We present stellar line-of-sight velocity distributions (LOSVDs) of elliptical galaxy NGC 821 obtained to approximately 100 '' (over two effective radii) with long-slit spectroscopy from the Hobby-Eberly Telescope. Our measured stellar LOSVDs are larger than the planetary nebulae measurements at similar radii. We fit axisymmetric orbit-superposition models with a range of dark halo density profiles, including two-dimensional kinematics at smaller radii from SAURON data. Within our assumptions, the best-fitted model gives a total enclosed mass of 2.0 x 10(11) M(circle dot) within 100 '', with an accuracy of 2%; this mass is equally divided between halo and stars. At 1 R(e), the best-fitted dark matter halo accounts for 13% of the total mass in the galaxy. This dark halo is inconsistent with previous claims of little to no dark matter halo in this galaxy from planetary nebula measurements. We find that a power-law dark halo with a slope 0.1 is the best-fitted model; both the no dark halo and Navarro-Frenk-White models are worse fits at a greater than 99% confidence level. NGC 821 does not appear to have the expected dark halo density profile. The internal moments of the stellar velocity distribution show that the model with no dark halo is radially anisotropic at small radii and tangentially isotropic at large radii, while the best-fitted halo models are slightly radially anisotropic at all radii. We test the potential effects of model smoothing and find that there are no effects on our results within the errors. Finally, we run models using the planetary nebula kinematics and assuming our best-fitted halos and find that the planetary nebulae require radial orbits throughout the galaxy.Show more Item The impact of x-rays on primordial minihalos(2014-05) Oliveri, Anthony; Bromm, VolkerShow more One of the current problems in cosmology is to understand how the first gravitationally- bound objects, or dark matter minihalos, evolved to form chemically rich, star-forming galaxies. The first stars to exist are believed to have formed in the center of minihalos that have cooled and collapsed enough to fragment into stellar-sized gas clouds. However, to reach such low temperatures, minihalos needed a more effective coolant than atomic hydrogen, namely molecular hydrogen (H2). The formation of H2 could be catalyzed by an x-ray background, which is expected to originate primarily from high-mass x-ray binaries (HMXBs). By simulating the collapse of a minihalo in the presence of x-ray backgrounds of varying strengths, we ascertain the resulting properties of a minihalo and compare to the case of no x-ray background. For sufficiently weak backgrounds (energy density uXR < 10−16J/m3), a minihalo can cool to lower temperatures than without an x- ray background, leading to the formation of lower mass stars. The mass of these primitive stars affected the abundance of heavy chemical elements that formed during their deaths as supernovae, which in turn influenced how the earliest galaxies formed.Show more Item The Massive Satellite Population Of Milky-Way-Sized Galaxies(2013-08) Rodriguez-Puebla, Aldo; Avila-Reese, Vladimir; Drory, Niv; Drory, NivShow more Several occupational distributions for satellite galaxies more massive than m(*) approximate to 4 x 10(7) M-circle dot around Milky-Way (MW)-sized hosts are presented and used to predict the internal dynamics of these satellites as a function of m(*). For the analysis, a large galaxy group mock catalog is constructed on the basis of (sub) halo-to-stellar mass relations fully constrained with currently available observations, namely the galaxy stellar mass function decomposed into centrals and satellites, and the two-point correlation functions at different masses. We find that 6.6% of MW-sized galaxies host two satellites in the mass range of the Small and Large Magellanic Clouds (SMC and LMC, respectively). The probabilities of the MW-sized galaxies having one satellite equal to or larger than the LMC, two satellites equal to or larger than the SMC, or three satellites equal to or larger than Sagittarius (Sgr) are approximate to 0.26, 0.14, and 0.14, respectively. The cumulative satellite mass function of the MW, N-s(>= m(*)), down to the mass of the Fornax dwarf is within the 1 sigma distribution of all the MW-sized galaxies. We find that MW-sized hosts with three satellites more massive than Sgr (as the MW) are among the most common cases. However, the most and second most massive satellites in these systems are smaller than the LMC and SMC by roughly 0.7 and 0.8 dex, respectively. We conclude that the distribution N-s(>= m(*)) for MW-sized galaxies is quite broad, the particular case of the MW being of low frequency but not an outlier. The halo mass of MW-sized galaxies correlates only weakly with N-s(>= m(*)). Then, it is not possible to accurately determine the MW halo mass by means of its N-s(>= m(*)); from our catalog, we constrain a lower limit of 1.38 x 10(12) M-circle dot at the 1 sigma level. Our analysis strongly suggests that the abundance of massive subhalos should agree with the abundance of massive satellites in all MW-sized hosts, i.e., there is not a missing (massive) satellite problem for the Lambda CDM cosmology. However, we confirm that the maximum circular velocity, v(max), of the subhalos of satellites smaller than m(*) similar to 10(8) M-circle dot is systematically larger than the v(max) inferred from current observational studies of the MW bright dwarf satellites; different from previous works, this conclusion is based on an analysis of the overall population of MW-sized galaxies. Some pieces of evidence suggest that the issue could refer only to satellite dwarfs but not to central dwarfs, then environmental processes associated with dwarfs inside host halos combined with supernova-driven core expansion should be on the basis of the lowering of v(max).Show more Item Measuring Dark Matter Profiles Non-Parametrically In Dwarf Spheroidals: An Application To Draco(2013-02) Jardel, John R.; Gebhardt, Karl; Fabricius, Maximilian H.; Drory, Niv; Williams, M. J.; Jardel, John R.; Gebhardt, KarlShow more We introduce a novel implementation of orbit-based (or Schwarzschild) modeling that allows dark matter density profiles to be calculated non-parametrically in nearby galaxies. Our models require no assumptions to be made about velocity anisotropy or the dark matter profile. The technique can be applied to any dispersion-supported stellar system, and we demonstrate its use by studying the Local Group dwarf spheroidal galaxy (dSph) Draco. We use existing kinematic data at larger radii and also present 12 new radial velocities within the central 13 pc obtained with the VIRUS-W integral field spectrograph on the 2.7 m telescope at McDonald Observatory. Our non-parametric Schwarzschild models find strong evidence that the dark matter profile in Draco is cuspy for 20 <= r <= 700 pc. The profile for r >= 20 pc is well fit by a power law with slope alpha = -1.0 +/- 0.2, consistent with predictions from cold dark matter simulations. Our models confirm that, despite its low baryon content relative to other dSphs, Draco lives in a massive halo.Show more Item Neutralino Dark Matter In MSSM Models With Non-Universal Higgs Masses(2010-06) Sandick, P.; Sandick, PearlShow more We consider the Minimal Supersymmetric Standard Model (MSSM) with varying amounts of non-universality in the soft supersymmetry-breaking contributions to the Higgs scalar masses. In addition to the constrained MSSM (CMSSM) in which these are universal with the soft supersymmetry-breaking contributions to the squark and slepton masses at the input GUT scale, we consider scenarios in which both the Higgs masses are non-universal by the same amount (NUHM1), and scenarios in which they are independently non-universal (NUHM2). As the lightest neutralino is a dark matter candidate, we demand that the relic density of neutralinos not be in conflict with measurements by WMAP and others, and examine the viable regions of parameter space. Prospects for direct detection of neutralino dark matter via elastic scattering in these scenarios are discussed.Show more Item Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results(2013-10) Hinshaw, G.; Larson, D.; Komatsu, Eiichiro; Spergel, D. N.; Bennett, C. L.; Dunkley, J.; Nolta, M. R.; Halpern, M.; Hill, R. S.; Odegard, N.; Page, L.; Smith, K. M.; Weiland, J. L.; Gold, B.; Jarosik, N.; Kogut, A.; Limon, M.; Meyer, S. S.; Tucker, G. S.; Wollack, E.; Wright, E. L.; Komatsu, EiichiroShow more We present cosmological parameter constraints based on the final nine-year Wilkinson Microwave Anisotropy Probe (WMAP) data, in conjunction with a number of additional cosmological data sets. The WMAP data alone, and in combination, continue to be remarkably well fit by a six-parameter Delta CDM model. When WMAP data are combined with measurements of the high-l cosmic microwave background anisotropy, the baryon acoustic oscillation scale, and the Hubble constant, the matter and energy densities, Omega(b)h(2), Omega(c)h(2), and Omega(Lambda), are each determined to a precision of similar to 1.5%. The amplitude of the primordial spectrum is measured to within 3%, and there is now evidence for a tilt in the primordial spectrum at the 5 sigma level, confirming the first detection of tilt based on the five-year WMAP data. At the end of the WMAP mission, the nine-year data decrease the allowable volume of the six-dimensional Delta CDM parameter space by a factor of 68,000 relative to pre-WMAP measurements. We investigate a number of data combinations and show that their Delta CDM parameter fits are consistent. New limits on deviations from the six-parameter model are presented, for example: the fractional contribution of tensor modes is limited to r < 0.13 (95% CL); the spatial curvature parameter is limited to Omega(k) = -0.0027(-0.0038)(+0.0039); the summed mass of neutrinos is limited to Sigma m(nu) < 0.44 eV (95% CL); and the number of relativistic species is found to lie within N-eff = 3.84 +/- 0.40, when the full data are analyzed. The joint constraint on N-eff and the primordial helium abundance, Y-He, agrees with the prediction of standard big bang nucleosynthesis. We compare recent Planck measurements of the Sunyaev-Zel'dovich effect with our seven-year measurements, and show their mutual agreement. Our analysis of the polarization pattern around temperature extrema is updated. This confirms a fundamental prediction of the standard cosmological model and provides a striking illustration of acoustic oscillations and adiabatic initial conditions in the early universe.Show more Item Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results(2013-10) Bennett, C. L.; Larson, D.; Weiland, J. L.; Jarosik, N.; Hinshaw, G.; Odegard, N.; Smith, K. M.; Hill, R. S.; Gold, B.; Halpern, M.; Komatsu, Eiichiro; Nolta, M. R.; Page, L.; Spergel, D. N.; Wollack, E.; Dunkley, J.; Kogut, A.; Limon, M.; Meyer, S. S.; Tucker, G. S.; Wright, E. L.; Komatsu, EiichiroShow more We present the final nine-year maps and basic results from the Wilkinson Microwave Anisotropy Probe (WMAP) mission. The full nine-year analysis of the time-ordered data provides updated characterizations and calibrations of the experiment. We also provide new nine-year full sky temperature maps that were processed to reduce the asymmetry of the effective beams. Temperature and polarization sky maps are examined to separate cosmic microwave background (CMB) anisotropy from foreground emission, and both types of signals are analyzed in detail. We provide new point source catalogs as well as new diffuse and point source foreground masks. An updated template-removal process is used for cosmological analysis; new foreground fits are performed, and new foreground reduced CMB maps are presented. We now implement an optimal C-1 weighting to compute the temperature angular power spectrum. The WMAP mission has resulted in a highly constrained Delta CDM cosmological model with precise and accurate parameters in agreement with a host of other cosmological measurements. When WMAP data are combined with finer scale CMB, baryon acoustic oscillation, and Hubble constant measurements, we find that big bang nucleosynthesis is well supported and there is no compelling evidence for a non-standard number of neutrino species (N-eff = 3.84 +/- 0.40). The model fit also implies that the age of the universe is t(0) = 13.772 +/- 0.059 Gyr, and the fit Hubble constant is H-0 = 69.32 +/- 0.80 km s(-1) Mpc(-1). Inflation is also supported: the fluctuations are adiabatic, with Gaussian random phases; the detection of a deviation of the scalar spectral index from unity, reported earlier by the WMAP team, now has high statistical significance (n(s) = 0.9608 +/- 0.0080); and the universe is close to flat/Euclidean (Omega(k) = -0.0027(-0.0038)(+0.0039)). Overall, the WMAP mission has resulted in a reduction of the cosmological parameter volume by a factor of 68,000 for the standard six-parameter Delta CDM model, based on CMB data alone. For a model including tensors, the allowed seven-parameter volume has been reduced by a factor 117,000. Other cosmological observations are in accord with the CMB predictions, and the combined data reduces the cosmological parameter volume even further. With no significant anomalies and an adequate goodness of fit, the inflationary flat Delta CDM model and its precise and accurate parameters rooted in WMAP data stands as the standard model of cosmology.Show more Item Numerical Boltzmann Equation Solutions for Secretly Asymmetric Dark Matter Scenarios(2017-05) Dessert, Christopher; Kilic, CanShow more The Standard Model (SM) of particle physics was completed as we know it today in 1967, but experimental confirmation had to wait until 2012 when the Large Hadron Collider (LHC) announced the discovery of the Higgs boson. In the meantime many particle theorists have been searching for physics Beyond the Standard Model (BSM), one part of which is the search for a particle physics explanation of dark matter. One potential explanation is asymmetric dark matter (ADM), in which the initial amount of dark matter and antidark matter in the universe is unequal. What makes our model, one of several ADM models, special is that there are three flavors, or types, of dark matter and even though the initial amounts are unequal in each flavor, the total amount of dark matter is equal to that of antidark matter. The three flavors interact in various ways. These interactions serve to change the flavor of the dark matter particles or annihilate them altogether. One important interaction is the decay of the heavier flavors into lighter flavors, and after a long time only the light flavor will remain. In this case there will appear to only be one flavor of dark matter with equal amounts of dark matter and antidark matter. For this reason, the model is named "Secretly Asymmetric Dark Matter (SADM)." The results presented in this thesis are a direct followup to this work. We would like to understand if the model could be a realistic theory for dark matter. To do so, we use the interactions to write down a set of equations, known as Boltzmann equations, that model the density of the dark matter in the early universe as it expands and see if the results match experimental measurements today. The interactions are complicated and the resulting equations are impossible to solve by hand. I have written a program in Mathematica 11 that will solve them numerically.Show more Item The Rising Stellar Velocity Dispersion Of M87 From Integrated Starlight(2014-04) Murphy, Jeremy D.; Gebhardt, Karl; Cradit, Mason; Gebhardt, KarlShow more We have measured the line-of-sight velocity distribution from integrated stellar light at two points in the outer halo of M87 (NGC 4486), the second-rank galaxy in the Virgo Cluster. The data were taken at R = 480 '' (similar to 41.5 kpc) and R = 526 '' (similar to 45.5 kpc) along the SE major axis. The second moment for a non-parametric estimate of the full velocity distribution is 420 +/- 23 km s(-1) and 577 +/- 35 km s(-1), respectively. There is intriguing evidence in the velocity profiles for two kinematically distinct stellar components at the position of our pointing. Under this assumption, we employ a two-Gaussian decomposition and find the primary Gaussian having rest velocities equal to M87 (consistent with zero rotation) and second moments of 383 +/- 32 km s(-1) and 446 +/- 43 km s(-1), respectively. The asymmetry seen in the velocity profiles suggests that the stellar halo of M87 is not in a relaxed Stateand confuses a clean dynamical interpretation. That said, either measurement (full or two component model) shows a rising velocity dispersion at large radii, consistent with previous integrated light measurements, yet significantly higher than globular cluster measurements at comparable radial positions. These integrated light measurements at large radii, and the stark contrast they make to the measurements of other kinematic tracers, highlight the rich kinematic complexity of environments like the center of the Virgo Cluster and the need for caution when interpreting kinematic measurements from various dynamical tracers.Show more Item A Second-Order Bias Model For The Logarithmic Halo Mass Density(2012-07) Jee, Inh; Park, Changbom; Kim, Juhan; Choi, Yun-Yong; Kim, Sungsoo S.; Jee, InhShow more We present an analytic model for the local bias of dark matter halos in a Lambda CDM universe. The model uses the halo mass density instead of the halo number density and is searched for various halo mass cuts, smoothing lengths, and redshift epochs. We find that, when the logarithmic density is used, the second-order polynomial can fit the numerical relation between the halo mass distribution and the underlying matter distribution extremely well. In this model, the logarithm of the dark matter density is expanded in terms of log halo mass density to the second order. The model remains excellent for all halo mass cuts (from M-cut = 3 x 10(11) to 3 x 10(12) h (1) M-circle dot), smoothing scales (from R = 5 h(-1) Mpc to 50h(-1) Mpc), and redshift ranges (from z = 0 to 1.0) considered in this study. The stochastic term in the relation is found to be not entirely random, but a part of the term can be determined by the magnitude of the shear tensor.Show more Item Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: are there Cosmic Microwave Background Anomalies?(2011-02) Bennett, C. L.; Hill, R. S.; Hinshaw, G.; Larson, D.; Smith, K. M.; Dunkley, J.; Gold, B.; Halpern, M.; Jarosik, N.; Kogut, A.; Komatsu, Eiichiro; Limon, M.; Meyer, S. S.; Nolta, M. R.; Odegard, N.; Page, L.; Spergel, D. N.; Tucker, G. S.; Weiland, J. L.; Wollack, E.; Wright, E. L.; Komatsu, EiichiroShow more A simple six-parameter Lambda CDM model provides a successful fit to WMAP data. This holds both when the WMAP data are analyzed alone or in combination with other cosmological data. Even so, it is appropriate to examine the data carefully to search for hints of deviations from the now standard model of cosmology, which includes inflation, dark energy, dark matter, baryons, and neutrinos. The cosmological community has subjected the WMAP data to extensive and varied analyses. While there is widespread agreement as to the overall success of the six-parameter Lambda CDM model, various "anomalies" have been reported relative to that model. In this paper we examine potential anomalies and present analyses and assessments of their significance. In most cases we find that claimed anomalies depend on posterior selection of some aspect or subset of the data. Compared with sky simulations based on the best-fit model, one can select for low probability features of the WMAP data. Low probability features are expected, but it is not usually straightforward to determine whether any particular low probability feature is the result of the a posteriori selection or non-standard cosmology. Hypothesis testing could, of course, always reveal an alternative model that is statistically favored, but there is currently no model that is more compelling. We find that two cold spots in the map are statistically consistent with random cosmic microwave background (CMB) fluctuations. We also find that the amplitude of the quadrupole is well within the expected 95% confidence range and therefore is not anomalously low. We find no significant anomaly with a lack of large angular scale CMB power for the best-fit Lambda CDM model. We examine in detail the properties of the power spectrum data with respect to the Lambda CDM model and find no significant anomalies. The quadrupole and octupole components of the CMB sky are remarkably aligned, but we find that this is not due to any single map feature; it results from the statistical combination of the full-sky anisotropy fluctuations. It may be due, in part, to chance alignments between the primary and secondary anisotropy, but this only shifts the coincidence from within the last scattering surface to between it and the local matter density distribution. While this alignment appears to be remarkable, there was no model that predicted it, nor has there been a model that provides a compelling retrodiction. We examine claims of a hemispherical or dipole power asymmetry across the sky and find that the evidence for these claims is not statistically significant. We confirm the claim of a strong quadrupolar power asymmetry effect, but there is considerable evidence that the effect is not cosmological. The likely explanation is an insufficient handling of beam asymmetries. We conclude that there is no compelling evidence for deviations from the Lambda CDM model, which is generally an acceptable statistical fit to WMAP and other cosmological data.Show more Item Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological interpretation(2011-02) Komatsu, Eiichiro; Smith, K. M.; Dunkley, J.; Bennett, C. L.; Gold, B.; Hinshaw, G.; Jarosik, N.; Larson, D.; Nolta, M. R.; Page, L.; Spergel, D. N.; Halpern, M.; Hill, R. S.; Kogut, A.; Limon, M.; Meyer, S. S.; Odegard, N.; Tucker, G. S.; Weiland, J. L.; Wollack, E.; Wright, E. L.; Komatsu, EiichiroShow more The combination of seven-year data from WMAP and improved astrophysical data rigorously tests the standard cosmological model and places new constraints on its basic parameters and extensions. By combining the WMAP data with the latest distance measurements from the baryon acoustic oscillations (BAO) in the distribution of galaxies and the Hubble constant (H-0) measurement, we determine the parameters of the simplest six-parameter Lambda CDM model. The power-law index of the primordial power spectrum is n(s) = 0.968 +/- 0.012 (68% CL) for this data combination, a measurement that excludes the Harrison-Zel'dovich-Peebles spectrum by 99.5% CL. The other parameters, including those beyond the minimal set, are also consistent with, and improved from, the five-year results. We find no convincing deviations from the minimal model. The seven-year temperature power spectrum gives a better determination of the third acoustic peak, which results in a better determination of the redshift of the matter-radiation equality epoch. Notable examples of improved parameters are the total mass of neutrinos, Sigma m(nu) < 0.58 eV (95% CL), and the effective number of neutrino species, N-eff = 4.34(-0.88)(+0.86) (68% CL), which benefit from better determinations of the third peak and H-0. The limit on a constant dark energy equation of state parameter from WMAP+BAO+H-0, without high-redshift Type Ia supernovae, is w = -1.10 +/- 0.14 (68% CL). We detect the effect of primordial helium on the temperature power spectrum and provide a new test of big bang nucleosynthesis by measuring Y-p = 0.326 +/- 0.075 (68% CL). We detect, and show on the map for the first time, the tangential and radial polarization patterns around hot and cold spots of temperature fluctuations, an important test of physical processes at z = 1090 and the dominance of adiabatic scalar fluctuations. The seven-year polarization data have significantly improved: we now detect the temperature-E-mode polarization cross power spectrum at 21 sigma, compared with 13 sigma from the five-year data. With the seven-year temperature-B-mode cross power spectrum, the limit on a rotation of the polarization plane due to potential parity-violating effects has improved by 38% to Delta a = -1 degrees.1 +/- 1 degrees.4(statistical) +/- 1 degrees.5(systematic) (68% CL). We report significant detections of the Sunyaev-Zel'dovich (SZ) effect at the locations of known clusters of galaxies. The measured SZ signal agrees well with the expected signal from the X-ray data on a cluster-by-cluster basis. However, it is a factor of 0.5-0.7 times the predictions from "universal profile" of Arnaud et al., analytical models, and hydrodynamical simulations. We find, for the first time in the SZ effect, a significant difference between the cooling-flow and non-cooling-flow clusters (or relaxed and non-relaxed clusters), which can explain some of the discrepancy. This lower amplitude is consistent with the lower-than-theoretically expected SZ power spectrum recently measured by the South Pole Telescope Collaboration.Show more