arXiv subjects

George F. Smoot

Publications and source records attributed to George F. Smoot.

83 records · Page 5Linked to original sources

arXiv1997

The Cosmic Microwave Background Spectrum

This paper given at the Strasbourg NATO school on the CMB and cosmology reports the contents of four hours of lectures on the CMB spectrum, potential distortions, and implications. It was followed by 6 hours of lectures on CMB anisotropy. This paper reviews the observations and theoretical implications for the CMB frequency spectrum - both for the monopole (essentially total power) and the dipole and higher order anisotropies including the Sunyaev-Zeldovich effect.

astro-ph↗

arXiv1997

The Cosmic Microwave Background Anisotropy Experiments

This paper reports a summary of the contents contents of six hours of lectures on the CMB anisotropy experiments given at the Strasbourg NATO school on the CMB and cosmology. (Its companion paper, astro-ph/9705101 reports the lectures on the CMB spectrum.) A context is set as a bridge from the theoretical CMB anisotropy lectures and the experimental situation. The COBE DMR results are reveiwed in detail and as pioneer for future space missions. Current and planned experiments are discussed in preference to reviewing already completed observations. The NASA MidEX mission MAP is discussed in some detail including figures. The ESA M3 mission Max Planck Surveyor is also reviewed in some detail though its final configuration is not yet fully settled. The recent history and current versions are presented. Tables and references for experiments are included.

astro-ph↗

arXiv1997

Constraining topology with the CMB

We present a new data analysis method to study rectangular T^3 ``small universes" with one or two of its dimensions significantly smaller than the present horizon (which we refer to as T^1- and T^2-models, respectively). We find that the 4 year COBE/DMR data set a lower limit on the smallest cell size for T^1- and T^2-models of 3000h^{-1} Mpc, at 95% confidence, for a scale invariant power spectrum (n=1).

astro-ph↗

arXiv1997

Constraints on the topology of the universe from the 2-yr COBE data

The cosmic microwave background (CMB) is a unique probe of cosmological parameters and conditions. There is a connection between anisotropy in the CMB and the topology of the Universe. Adopting a universe with the topology of a 3-Torus, or a universe where only harmonics of the fundamental mode are allowed, and using 2-years of COBE/DMR data, we obtain constraints on the topology of the Universe. Previous work constrained the topology using the slope information and the correlation function of the CMB. We obtain more accurate results by using all multipole moments, avoiding approximations by computing their full covariance matrix. We obtain the best fit for a cubic toroidal universe of scale 7200h^{-1} Mpc for n=1. The data set a lower limit on the cell size of 4320h^{-1} Mpc at 95% confidence and 5880h^{-1} Mpc at 68% confidence. These results show that the most probable cell size would be around 1.2 times larger than the horizon scale, implying that the 3-Torus topology is no longer an interesting cosmological model.

astro-ph↗

arXiv1997

Can the lack of symmetry in the COBE/DMR maps constrain the topology of the universe?

Although the cubic T^3 "small universe" has been ruled out by COBE/DMR results as an interesting cosmological model, we still have the possibility of living in a universe with a more anisotropic topology such as a rectangular T^3 "small universe" with one or two of its dimensions significantly smaller than the present horizon (which we refer to as T^1- and T^2-models, respectively). In order to rule out these anisotropic topologies as well, we apply a new data analysis method that searches for the specific kind of symmetries that these models should produce. We find that the 4 year COBE/DMR data set a lower limit on the smallest cell size for T^1- and T^2-models of 3000h^{-1} Mpc, at 95% confidence, for a scale invariant power spectrum (n=1). These results imply that ALL toroidal universes (cubes and rectangles) are ruled out as interesting cosmological models.

astro-ph↗

arXiv1997

CMB Experiment Baseline Determination by Minimizing Pixel Observations Dispersion

This paper discusses a couple of approaches to removing instrument gain and baseline variation from observations of the CMB anisotropy. These techniques were tested on the COBE DMR data, a balloon experiment, and by monte carlo simulations. This work, though considered technical, is made available because CMB anisotropy mapping data processing is currently very active and a significant number of groups are working on this issue. Specifically, time-ordered estimates of the gain and baseline via fitting to limited sections of data or to the full or a large section of data are considered and compared. An expression is given for the correlation between pixels introduced by the residual baseline and removal technique.

astro-ph↗

arXiv1997

Introduction & Overview: CMB Sessions

This is a very exciting time for the CMB field. It is widely recognized that precision measurements of the CMB can provide a definitive test of cosmological models and determine their parameters accurately. At present observations give us the first rough results but ongoing experiments promise new and improved results soon and eventually satellite missions (MAP and COBRAS/SAMBA now named Planck) are expected to provide the requisite precision measurements. Other areas such as observations of the spectrum and Sunyaev-Zeldovich effect are also making significant progress. There has long been anticipation that cosmic microwave background (CMB) radiation would provide significant information about the early Universe due to its early central role and its general lack of interaction in the later epochs. Though there have been many observations of the CMB since its discovery by Penzias and Wilson in 1964, the Cosmic Background Explorer satellite, COBE, provided two watershed observations: (1) the CMB is extremely well described by a black-body spectrum and (2) the discovery of a spectrum of CMB anisotropies.

astro-ph↗

arXiv1997

Contribution of Extragalactic Infrared Sources to CMB Foreground Anisotropy

We estimate the level of confusion to Cosmic Microwave Background anisotropy measurements caused by extragalactic infrared sources. CMB anisotropy observations at high resolution and high frequencies are especially sensitive to this foreground. We use data from the COBE satellite to generate a Galactic emission spectrum covering mm and sub-mm wavelengths. Using this spectrum as a template, we predict the microwave emission of the 5319 brightest infrared galaxies seen by IRAS. We simulate skymaps over the relevant range of frequencies (30-900 GHz) and instrument resolutions (10'-10 degrees Full Width Half Max). Analysis of the temperature anisotropy of these skymaps shows that a reasonable observational window is available for CMB anisotropy measurements.

astro-ph↗

arXiv1995

The Cosmic Background Radiation, Snowmass Workshop

Observations of the Cosmic Microwave background have provided many of the most powerful constraints we have on cosmology and events in the early universe. The spectrum and isotropy of CBR have long been a pillar of Big Bang models. The discovery of low levels on anisotropy has provided new information and tools for our understanding of the early universe. Further observations promise to enhance greatly our knowledge of processes in the early universe and cosmological parameters. We can anticipate rapid advance in this field up to and through the year 2000 which will dramatically focus our efforts in cosmology during the next millenium. This paper outlines the primary science likely to be discovered and defined by a vigorous airborne and ground-based program which should be strongly supported. If successfully excuted, we an anticipate a measurement of the CBR anisotropy spectrum to within a factor of two of the confidence level unavoidably set by cosmic variance. Even so, observations of the CBR are the best and often the only way to obtain information on many critical parameters so that an ambitious satellite experiment that maps the full-sky to the delta T/T ~ 10^{-6} level is well justified. Draft CBR description and recommendations from the Snowmass Workshop comments to smoot@cosmos.lbl.gov

astro-ph↗

arXiv1995

LONG WAVELENGTH OBSERVATIONS OF HIGH GALACTIC LATITUDE DUST

The properties of high latitude dust are of great interest to extragalactic astronomers and cosmologists. It is proposed here that essentially all high Galactic latitude interstellar dust is at a typical temperature of about 20~K (i.e. it is warm dust) and that if any cold high latitude interstellar dust exists, its emission at mm-wavelengths is less than 5\%\ of that from the primary component of warm dust observed by IRAS. Thus the IRAS maps reveal the high latitude dust of import. The crucial issue is how the emissivity of the dust scales with wavelength. The mm-wavelength emission in this warm dust only model is consistent with roughly a wavelength%, $λ$, dependent emissivity $ε(λ) \propto λ^{-1.5}$. Such a dependence has been observed in the infrared previously. What is new here is the proposal that this extends to the mm-wavelength region. Proceedings of Workshop on Molecules, Dust, & Backgrounds to be published in Planetary & Space Sciences

astro-ph↗

arXiv1992

Gravity's rainbow

Could COBE DMR be detecting the imprint from a spectrum of gravitational waves generated during inflation? The conventional inflationary prediction had been that the cosmic microwave anisotropy is dominated by energy density fluctuations generated during inflation and that the gravitational waves contribute negligibly. In this paper, we report on recent work (in collaboration with R. Davis, H. Hodges, and M. Turner) that has shown that the conventional wisdom may be wrong; specifically, gravitational waves may dominate the anisotropy in inflationary models where the spectrum of perturbations deviates significantly from scale invariance (e.g., extended and power-law inflation models and extreme versions of chaotic inflation). If gravitational waves do dominate at the large-angular scales measured by COBE DMR, the expectation and interpretation of anisotropies on small-angular scales is profoundly altered. Invited Paper for Proceedings of the Journees Relativistes, Amsterdam, May 14-16, 1992

astro-ph↗