Geophysics

Contains reports on four research projects

Geophysics

Contains reports on four research projects.United States Air Force (Contract AF19(628)-500)Lincoln Laboratory (Purchase Order DDL BB-107

The Santa Fe Light Cone Simulation Project: II. The Prospects for Direct Detection of the WHIM with SZE Surveys

Detection of the Warm-Hot Intergalactic Medium (WHIM) using Sunyaev-Zeldovich effect (SZE) surveys is an intriguing possibility, and one that may allow observers to quantify the amount of "missing baryons" in the WHIM phase. We estimate the necessary sensitivity for detecting low density WHIM gas with the South Pole Telescope (SPT) and Planck Surveyor for a synthetic 100 square degree sky survey. This survey is generated from a very large, high dynamic range adaptive mesh refinement cosmological simulation performed with the Enzo code. We find that for a modest increase in the SPT survey sensitivity (a factor of 2-4), the WHIM gas makes a detectable contribution to the integrated sky signal. For a Planck-like satellite, similar detections are possible with a more significant increase in sensitivity (a factor of 8-10). We point out that for the WHIM gas, the kinematic SZE signal can sometimes dominate the thermal SZE where the thermal SZE decrement is maximal (150 GHz), and that using the combination of the two increases the chance of WHIM detection using SZE surveys. However, we find no evidence of unique features in the thermal SZE angular power spectrum that may aid in its detection. Interestingly, there are differences in the power spectrum of the kinematic SZE, which may not allow us to detect the WHIM directly, but could be an important contaminant in cosmological analyses of the kSZE-derived velocity field. Corrections derived from numerical simulations may be necessary to account for this contamination.Comment: 9 pages, submitted to Astrophysical Journa

Galaxy clusters discovered with a Sunyaev-Zel'dovich effect survey

The South Pole Telescope (SPT) is conducting a Sunyaev-Zel'dovich (SZ) effect survey over large areas of the southern sky, searching for massive galaxy clusters to high redshift. In this preliminary study, we focus on a 40 square-degree area targeted by the Blanco Cosmology Survey (BCS), which is centered roughly at right ascension 5h30m, declination -53 degrees. Over two seasons of observations, this entire region has been mapped by the SPT at 95 GHz, 150 GHz, and 225 GHz. We report the four most significant SPT detections of SZ clusters in this field, three of which were previously unknown and, therefore, represent the first galaxy clusters discovered with an SZ survey. The SZ clusters are detected as decrements with greater than 5-sigma significance in the high-sensitivity 150 GHz SPT map. The SZ spectrum of these sources is confirmed by detections of decrements at the corresponding locations in the 95 GHz SPT map and non-detections at those locations in the 225 GHz SPT map. Multiband optical images from the BCS survey demonstrate significant concentrations of similarly colored galaxies at the positions of the SZ detections. Photometric redshift estimates from the BCS data indicate that two of the clusters lie at moderate redshift (z ~ 0.4) and two at high redshift (z >~ 0.8). One of the SZ detections was previously identified as a galaxy cluster using X-ray data from the ROSAT All-Sky Survey (RASS). Potential RASS counterparts (not previously identified as clusters) are also found for two of the new discoveries. These first four galaxy clusters are the most significant SZ detections from a subset of the ongoing SPT survey. As such, they serve as a demonstration that SZ surveys, and the SPT in particular, can be an effective means for finding galaxy clusters.Comment: 11 pages, 3 figures, revised to match published version, uses emulateap

Some characteristics of three exact solutions of Einstein equations minimally coupled to a Quintessence field

We show some characteristics of three exact solutions to the Einstein's gravity minimally coupled to a Quintessence field. Besides eternal inflation, several other interesting inflationary processes, such as transitory inflation, are attained in these solutions. Singularity is avoided in some special cases.Comment: 6 pages, 3 figures. Submitted to Chinese Physics

Scalar field-perfect fluid correspondence and nonlinear perturbation equations

The properties of dynamical Dark Energy (DE) and, in particular, the possibility that it can form or contribute to stable inhomogeneities, have been widely debated in recent literature, also in association to a possible coupling between DE and Dark Matter (DM). In order to clarify this issue, in this paper we present a general framework for the study of the nonlinear phases of structure formation, showing the equivalence between two possible descriptions of DE: a scalar field \phi self-interacting through a potential V(\phi) and a perfect fluid with an assigned negative equation of state w(a). This enables us to show that, in the presence of coupling, the mass of DE quanta may increase where large DM condensations are present, so that also DE may partake to the clustering process.Comment: 16 pages, accepted for publication in JCA

Cosmological limit on the neutrino mass

We have performed a careful analysis of constraints on the neutrino mass from current cosmological data. Combining data from the cosmic microwave background and the 2dF galaxy survey yields an upper limit on the sum of the three neutrino mass eigenstates of \sum m_nu < 3 eV (95% conf.), without including additional priors. Including data from SNIa observations, Big Bang nucleosynthesis, and HST Hubble key project data on H_0 tightens the limit to \sum m_nu < 2.5 eV (95% conf.). We also perform a Fisher matrix analysis which illustrates the cosmological parameter degeneracies affecting the determination of \sum m_nu.Comment: 6 pages, 2 figures, uses Revtex

Scientific optimization of a ground-based CMB polarization experiment

We investigate the science goals achievable with the upcoming generation of ground-based Cosmic Microwave Background polarization experiments and calculate the optimal sky coverage for such an experiment including the effects of foregrounds. We find that with current technology an E-mode measurement will be sample-limited, while a B-mode measurement will be detector-noise-limited. We conclude that a 300 sq deg survey is an optimal compromise for a two-year experiment to measure both E and B-modes, and that ground-based polarization experiments can make an important contribution to B-mode surveys. Focusing on one particular experiment, QUaD, a proposed bolometric polarimeter operating from the South Pole, we find that a ground-based experiment can make a high significance measurement of the acoustic peaks in the E-mode spectrum, and will be able to detect the gravitational lensing signal in the B-mode spectrum. Such an experiment could also directly detect the gravitational wave component of the B-mode spectrum if the amplitude of the signal is close to current upper limits. We also investigate how a ground-based experiment can improve constraints on the cosmological parameters. We estimate that by combining two years of QUaD data with the four-year WMAP data, an optimized ground-based polarization experiment can improve constraints on cosmological parameters by a factor of two. If the foreground contamination can be reduced, the measurement of the tensor-to-scalar ratio can be improved by up to a factor of six over that obtainable from WMAP alone.Comment: 17 pages, 11 figures replaced with version accepted by MNRA

The blocks of the partition algebra in positive characteristic

In this paper we describe the blocks of the partition algebra over a field of positive characteristic