# Browsing by Subject "probe wmap observations"

Now showing 1 - 8 of 8

- Results Per Page
1 5 10 20 40 60 80 100

- Sort Options
Ascending Descending

Item Bayesian Analysis Of An Anisotropic Universe Model: Systematics And Polarization(2010-10) Groeneboom, Nicolaas E.; Ackerman, Lotty; Wehus, Ingunn K.; Eriksen, Hans Kristian; Ackerman, LottyShow more We revisit the anisotropic universe model previously developed by Ackerman, Carroll, and Wise (ACW), and generalize both the theoretical and computational framework to include polarization and various forms of systematic effects. We apply our new tools to simulated Wilkinson Microwave Anisotropy Probe (WMAP) data in order to understand the potential impact of asymmetric beams, noise misestimation, and potential zodiacal light emission. We find that neither has any significant impact on the results. We next show that the previously reported ACW signal is also present in the one-year WMAP temperature sky map presented by Liu & Li, where data cuts are more aggressive. Finally, we re-analyze the five-year WMAP data taking into account a previously neglected (-i)(l-l')-term in the signal covariance matrix. We still find a strong detection of a preferred direction in the temperature map. Including multipoles up to l = 400, the anisotropy amplitude for the W band is found to be g = 0.29 +/- 0.031, nonzero at 9 sigma. However, the corresponding preferred direction is also shifted very close to the ecliptic poles at (l, b) = (96, 30), in agreement with the analysis of Hanson & Lewis, indicating that the signal is aligned along the plane of the solar system. This strongly suggests that the signal is not of cosmological origin, but most likely is a product of an unknown systematic effect. Determining the nature of the systematic effect is of vital importance, as it might affect other cosmological conclusions from the WMAP experiment. Finally, we provide a forecast for the Planck experiment including polarization.Show more Item The Cosmic Near Infrared Background. III. Fluctuations, Reionization, And The Effects Of Minimum Mass And Self-Regulation(2012-05) Fernandez, Elizabeth R.; Iliev, Illian T.; Komatsu, Eiichiro; Shapiro, Paul R.; Komatsu, Eiichiro; Shapiro, Paul R.Show more Current observations suggest that the universe was reionized sometime before z similar to 6. One way to observe this epoch of the universe is through the Near Infrared Background (NIRB), which contains information about galaxies which may be too faint to be observed individually. We calculate the angular power spectrum (C-l) of the NIRB fluctuations caused by the distribution of these galaxies. Assuming a complete subtraction of any post-reionization component, C-l will be dominated by galaxies responsible for completing reionization (e.g., z similar to 6). The shape of C-l at high l is sensitive to the amount of nonlinear bias of dark matter halos hosting galaxies. As the nonlinear bias depends on the mass of these halos, we can use the shape of C-l to infer typical masses of dark matter halos responsible for completing reionization. We extend our previous study by using a higher-resolution N-body simulation, which can resolve halos down to 10(8) M-circle dot. We also include improved radiative transfer, which allows for the suppression of star formation in small-mass halos due to photoionization heating. As the nonlinear bias enhances the dark matter halo power spectrum on small scales, we find that C-l is steeper for the case with a complete suppression of small sources or partial suppression of star formation in small halos (the minimum galaxy mass is M-min = 10(9)M(circle dot) in ionized regions and M-min = 10(8)M(circle dot) in neutral regions) than for the case in which these small halos were unsuppressed. In all cases, we do not see a turnover toward high l in the shape of l(2)C(l).Show more Item The Cosmic Near-Infrared Background. II. Fluctuations(2010-02) Fernandez, Elizabeth R.; Komatsu, Eiichiro; Iliev, Illian T.; Shapiro, Paul R.; Komatsu, Eiichiro; Shapiro, Paul R.Show more The near-infrared background (NIRB) is one of a few methods that can be used to observe the redshifted light from early stars at a redshift of 6 and above, and thus it is imperative to understand the significance of any detection or nondetection of the NIRB. Fluctuations of the NIRB can provide information on the first structures, such as halos and their surrounding ionized regions in the intergalactic medium (IGM). We combine, for the first time, N-body simulations, radiative transfer code, and analytic calculations of luminosity of early structures to predict the angular power spectrum (C(l)) of fluctuations in the NIRB. We study in detail the effects of various assumptions about the stellar mass, the initial mass spectrum of stars, the metallicity, the star formation efficiency (f(*)), the escape fraction of ionizing photons (f(esc)), and the star formation timescale (t(SF)), on the amplitude as well as the shape of C(l). The power spectrum of NIRB fluctuations is maximized when f(*) is the largest (as C(l) proportional to f(*)(2))and f(esc) is the smallest (as more nebular emission is produced within halos). A significant uncertainty in the predicted amplitude of C(l) exists due to our lack of knowledge of t(SF) of these early populations of galaxies, which is equivalent to our lack of knowledge of the mass-to-light ratio of these sources. We do not see a turnover in the NIRB angular power spectrum of the halo contribution, which was claimed to exist in the literature, and explain this as the effect of high levels of nonlinear bias that was ignored in the previous calculations. This is partly due to our choice of the minimum mass of halos contributing to NIRB (similar to 2 x 10(9) M(circle dot)), and a smaller minimum mass, which has a smaller nonlinear bias, may still exhibit a turnover. Therefore, our results suggest that both the amplitude and shape of the NIRB power spectrum provide important information regarding the nature of sources contributing to the cosmic reionization. The angular power spectrum of the IGM, in most cases, is much smaller than the halo angular power spectrum, except when f(esc) is close to unity, t(SF) is longer, or the minimum redshift at which the star formation is occurring is high. In addition, low levels of the observed mean background intensity tend to rule out high values of f(*) greater than or similar to 0.2.Show more Item Fast Estimator Of Primordial Non-Gaussianity From Temperature And Polarization Anisotropies In The Cosmic Microwave Background. II. Partial Sky Coverage And Inhomogeneous Noise(2008-05) Yadav, Amit P. S.; Komatsu, Eiichiro; Wandelt, Benjamin D.; Liguori, Michele; Hansen, Frode K.; Matarrese, Sabino; Komatsu, EiichiroShow more In the recent paper by Yadav and coworkers we described a fast cubic (bispectrum) estimator of the amplitude of primordial non-Gaussianity of local type, f(NL), from a combined analysis of the cosmic microwave background (CMB) temperature and E-polarization observations. In this paper we generalize the estimator to deal with a partial sky coverage as well as inhomogeneous noise. Our generalized estimator is still computationally efficient, scaling as O(N-pix(3/2)) compared to the O(N-pix(5/2)) scaling of the brute- force bispectrum calculation for sky maps with Npix pixels. Upcoming CMB experiments are expected to yield high- sensitivity temperature and E- polarization data. Our generalized estimator will allow us to optimally utilize the combined CMB temperature and E- polarization information from these realistic experiments and to constrain primordial non- Gaussianity.Show more Item Inverting Color-Magnitude Diagrams To Access Precise Star Cluster Parameters: A New White Dwarf Age For The Hyades(2009-05) Degennaro, Steven; von Hippel, Ted; Jefferys, William H.; Stein, Nathan; van Dyk, David; Jeffery, Elizabeth; Degennaro, Steven; von Hippel, Ted; Jefferys, William H.; Stein, Nathan; Jeffery, ElizabethShow more We have extended our Bayesian modeling of stellar clusters-which uses main-sequence stellar evolution models, a mapping between initial masses and white dwarf (WD) masses, WD cooling models, and WD atmospheres-to include binary stars, field stars, and two additional main-sequence stellar evolution models. As a critical test of our Bayesian modeling technique, we apply it to Hyades UBV photometry, with membership priors based on proper motions and radial velocities, where available. Under the assumption of a particular set of WD cooling models and atmosphere models, we estimate the age of the Hyades based on cooling WDs to be 648 +/- 45 Myr, consistent with the best prior analysis of the cluster main-sequence turnoff (MSTO) age by Perryman et al. Since the faintest WDs have most likely evaporated from the Hyades, prior work provided only a lower limit to the cluster's WD age. Our result demonstrates the power of the bright WD technique for deriving ages and further demonstrates complete age consistency between WD cooling and MSTO ages for seven out of seven clusters analyzed to date, ranging from 150 Myr to 4 Gyr.Show more Item Perturbation Theory Reloaded. II. Nonlinear Bias, Baryon Acoustic Oscillations, And Millennium Simulation In Real Space(2009-01) Jeong, Donghui; Komatsu, Eiichiro; Jeong, Donghui; Komatsu, EiichiroShow more We calculate the nonlinear galaxy power spectrum in real space, including nonlinear distortion of the baryon acoustic oscillations, using the standard third-order perturbation theory (PT). The calculation is based upon the assumption that the number density of galaxies is a local function of the underlying, nonlinear density field. The galaxy bias is allowed to be both nonlinear and stochastic. We show that the PT calculation agrees with the galaxy power spectrum estimated from the Millennium Simulation, in the weakly nonlinear regime (defined by the matter power spectrum) at high redshifts, 1 <= z <= 6. We also show that, once three free parameters characterizing galaxy bias are marginalized over, the PT power spectrum fit to the Millennium Simulation data yields unbiased estimates of the distance scale, D, to within the statistical error. This distance scale corresponds to the angular diameter distance, D(A)(z), and the expansion rate, H(z), in real galaxy surveys. Our results presented in this paper are still restricted to real space. The future work should include the effects of nonlinear redshift space distortion. Nevertheless, our results indicate that nonlinear galaxy bias in the weakly nonlinear regime at high redshifts is reasonably under control.Show more Item Simple Foreground Cleaning Algorithm For Detecting Primordial B-Mode Polarization Of The Cosmic Microwave Background(2011-08) Katayama, Nobuhiko; Komatsu, Eiichiro; Komatsu, EiichiroShow more We reconsider the pixel-based, "template" polarized foreground removal method within the context of a next-generation, low-noise, low-resolution (0 degrees.5 FWHM) space-borne experiment measuring the cosmological B-mode polarization signal in the cosmic microwave background (CMB). This method was first applied to polarized data by the Wilkinson Microwave Anisotropy Probe (WMAP) team and further studied by Efstathiou et al. We need at least three frequency channels: one is used for extracting the CMB signal, whereas the other two are used to estimate the spatial distribution of the polarized dust and synchrotron emission. No extra data from non-CMB experiments or models are used. We extract the tensor-to-scalar ratio (r) from simulated sky maps outside the standard polarization mask (P06) of WMAP consisting of CMB, noise (2 mu K arcmin), and a foreground model, and find that, even for the simplest three-frequency configuration with 60, 100, and 240 GHz, the residual bias in r is as small as Delta r approximate to 0.002. This bias is dominated by the residual synchrotron emission due to spatial variations of the synchrotron spectral index. With an extended mask with f(sky) = 0.5, the bias is reduced further down to <0.001.Show more Item What Does Cosmology Tell Us About Particle Physics Beyond The Standard Model?(2012-03) Komatsu, E.; Komatsu, EiichiroShow more Cosmology demands particle physics beyond the Standard Model: we need to explain the nature of dark matter and dark energy, and the physics of cosmic inflation. Cosmology also provides the tightest upper bound on the sum of neutrino masses, and it seems only a matter of time before we measure the absolute mass of neutrinos, unveiling the neutrino mass hierarchy. It also provides a measurement of the number of relativistic species at the photon decoupling epoch (at which the temperature of the universe is 3000 K). Astronomy and Astrophysics Decadal Survey conducted by USA's National Academy of Sciences has identified these four topics (dark matter, dark energy, inflation and neutrinos) as the most important subjects to study in cosmology over the next decade. In this contribution, we review the current status on these topics, in light of the recent cosmological constraints.Show more