Plasma Physics

Contains research objectives and reports on three research projects.United States Atomic Energy Commission AT(30-1)-1842

Galaxy Properties from the Ultra-violet to the Far-Infrared: Lambda-CDM models confront observations

We combine a semi-analytic model of galaxy formation with simple analytic recipes describing the absorption and re-emission of starlight by dust in the interstellar medium of galaxies. We use the resulting models to predict galaxy counts and luminosity functions from the far-ultraviolet to the sub-mm, from redshift five to the present, and compare with an extensive compilation of observations. We find that in order to reproduce the rest-UV and optical luminosity functions at high redshift, we must assume an evolving normalization in the dust-to-metal ratio, implying that galaxies of a given bolometric luminosity (or metal column density) must be less extinguished than their local counterparts. In our best-fit model, we find remarkably good agreement with observations from rest-frame 1500 Angstroms to 250 microns. At longer wavelengths, most dramatically in the sub-mm, our models underpredict the number of bright galaxies by a large factor. The models reproduce the observed total IR luminosity function fairly well. We show the results of varying several ingredients of the models, including various aspects of the dust attenuation recipe, the dust emission templates, and the cosmology. We use our models to predict the integrated Extragalactic Background Light (EBL), and compare with an observationally-motivated EBL model and with other available observational constraints.Comment: 27 pages, 17 figures, 1 table, accepted to MNRAS, this version matches accepted manuscrip

On the origin of M81 group extended dust emission

Galactic cirrus emission at far-infrared wavelengths affects many extragalactic observations. Separating this emission from that associated with extragalactic objects is both important and difficult. In this paper we discuss a particular case, the M81 group, and the identification of diffuse structures prominent in the infrared, but also detected at optical wavelengths. The origin of these structures has previously been controversial, ranging from them being the result of a past interaction between M81 and M82 or due to more local Galactic emission. We show that over an order of a few arcmin scales, the far-infrared (Herschel 250 mu m) emission correlates spatially very well with a particular narrow-velocity (2-3 km s(-1)) component of the Galactic HI. We find no evidence that any of the far-infrared emission associated with these features actually originates in the M81 group. Thus we infer that the associated diffuse optical emission must be due to galactic light-back scattered off dust in our galaxy. Ultraviolet observations pick out young stellar associations around M81, but no detectable far-infrared emission. We consider in detail one of the Galactic cirrus features, finding that the far-infrared HI relation breaks down below arcmin scales and that at smaller scales there can be quite large dust-temperature variation

EXIT-chart aided hybrid multiuser detector design for frequency-domain-spread chip-interleaved MC-CDMA

With the advent of EXtrinsic Information Transfer (EXIT) charts, we are capable of analyzing, predicting and visually comparing the convergence behaviours of different turbo Multi-User Detectector (MUD)s. The different MUDs have diverse EXIT characteristics and hence their superposition allows us to create a combined EXIT curve, which closely matches that of the channel decoder. Hence a near-capacity operation is facilitated by combining the benifits of different MUDs and therefore to create a superior MUD. Thus in this contribution, we propose a novel hybrid MUD combining scheme, which combines the advantages of a high performance and low complexity in form of an advanced hybrid MUD solution. The transmitted bits are unknown at the receiver, hence it is not feasible to directly evaluate the mutual information gain of the iterative MUD in consecutive iterations, hence we propose a realistic algorithm for estimating this mutual information gain, which is then used for activating the most appropriate constituent MUD as and when it is necessary. The constituent MUDs are the Matched Filter (MF) based Soft Interference Cancellation (SoIC) and the optimum Bayesian MUDs, which are invoked in the scenario of Frequency-Domain-Spread Chip-Interleaved (FDSCI) Multiple Carrier Code Division Multiple Access (MC-CDMA). The resultant hybrid MUD is capable of outperforming both the MF-SoIC and Bayesian turbo MUDs in the terms of the attainable complexity and Bit-Error-Rate (BER) performance

SPIRE imaging of M82: cool dust in the wind and tidal streams

M82 is a unique representative of a whole class of galaxies, starbursts with superwinds, in the Very Nearby Galaxy Survey with Herschel. In addition, its interaction with the M81 group has stripped a significant portion of its interstellar medium from its disk. SPIRE maps now afford better characterization of the far-infrared emission from cool dust outside the disk, and sketch a far more complete picture of its mass distribution and energetics than previously possible. They show emission coincident in projection with the starburst wind and in a large halo, much more extended than the PAH band emission seen with Spitzer. Some complex substructures coincide with the brightest PAH filaments, and others with tidal streams seen in atomic hydrogen. We subtract the far-infrared emission of the starburst and underlying disk from the maps, and derive spatially-resolved far-infrared colors for the wind and halo. We interpret the results in terms of dust mass, dust temperature, and global physical conditions. In particular, we examine variations in the dust physical properties as a function of distance from the center and the wind polar axis, and conclude that more than two thirds of the extraplanar dust has been removed by tidal interaction, and not entrained by the starburst wind.Comment: accepted in A&A Herschel special issu

Clinical Outcomes by Race and Ethnicity in the Systolic Blood Pressure Intervention Trial (SPRINT): A Randomized Clinical Trial

BACKGROUND: The Systolic Blood Pressure Intervention Trial (SPRINT) showed that targeting a systolic blood pressure (SBP) of ≤ 120 mm Hg (intensive treatment) reduced cardiovascular disease (CVD) events compared to SBP of ≤ 140 mm Hg (standard treatment); however, it is unclear if this effect is similar in all racial/ethnic groups. METHODS: We analyzed SPRINT data within non-Hispanic White (NHW), non-Hispanic Black (NHB), and Hispanic subgroups to address this question. High-risk nondiabetic hypertensive patients (N = 9,361; 30% NHB; 11% Hispanic) 50 years and older were randomly assigned to intensive or standard treatment. Primary outcome was a composite of the first occurrence of a myocardial infarction, acute coronary syndrome, stroke, decompensated heart failure, or CVD death. RESULTS: Average postbaseline SBP was similar among NHW, NHB, and Hispanics in both treatment arms. Hazard ratios (HRs) (95% confidence interval) (intensive vs. standard treatment groups) for primary outcome were 0.70 (0.57–0.86), 0.71 (0.51–0.98), 0.62 (0.33–1.15) (interaction P value = 0.85) in NHW, NHB, and Hispanics. CVD mortality HRs were 0.49 (0.29–0.81), 0.77 (0.37–1.57), and 0.17 (0.01–1.08). All-cause mortality HRs were 0.61 (0.47–0.80), 0.92 (0.63–1.35), and 1.58 (0.73–3.62), respectively. A test for differences among racial/ethnic groups in the effect of treatment assignment on all-cause mortality was not significant (Hommel-adjusted P value = 0.062) after adjustment for multiple comparisons. CONCLUSION: Targeting a SBP goal of ≤ 120 mm Hg compared to ≤ 140 mm Hg led to similar SBP control and was associated with similar benefits and risks among all racial ethnic groups, though NHBs required an average of ~0.3 more medications

The Herschel Multi-tiered Extragalactic Survey: HerMES

The Herschel Multi-tiered Extragalactic Survey, HerMES, is a legacy program designed to map a set of nested fields totalling ~380 deg^2. Fields range in size from 0.01 to ~20 deg^2, using Herschel-SPIRE (at 250, 350 and 500 \mu m), and Herschel-PACS (at 100 and 160 \mu m), with an additional wider component of 270 deg^2 with SPIRE alone. These bands cover the peak of the redshifted thermal spectral energy distribution from interstellar dust and thus capture the re-processed optical and ultra-violet radiation from star formation that has been absorbed by dust, and are critical for forming a complete multi-wavelength understanding of galaxy formation and evolution. The survey will detect of order 100,000 galaxies at 5\sigma in some of the best studied fields in the sky. Additionally, HerMES is closely coordinated with the PACS Evolutionary Probe survey. Making maximum use of the full spectrum of ancillary data, from radio to X-ray wavelengths, it is designed to: facilitate redshift determination; rapidly identify unusual objects; and understand the relationships between thermal emission from dust and other processes. Scientific questions HerMES will be used to answer include: the total infrared emission of galaxies; the evolution of the luminosity function; the clustering properties of dusty galaxies; and the properties of populations of galaxies which lie below the confusion limit through lensing and statistical techniques. This paper defines the survey observations and data products, outlines the primary scientific goals of the HerMES team, and reviews some of the early results.Comment: 23 pages, 17 figures, 9 Tables, MNRAS accepte

Status of CMB Polarization Measurements from DASI and Other Experiments

We review the current status and future plans for polarization measurements of the cosmic microwave background radiation, as well as the cosmology these measurements will address. After a long period of increasingly sensitive upper limits, the DASI experiment has detected the E-mode polarization and both the DASI and WMAP experiments have detected the TE correlation. These detections provide confirmation of the standard model of adiabatic primordial density fluctuations consistent with inflationary models. The WMAP TE correlation on large angular scales provides direct evidence of significant reionization at higher redshifts than had previously been supposed. These detections mark the beginning of a new era in CMB measurements and the rich cosmology that can be gleaned from them.Comment: 22 pages, 9 figures; To be published in the proceedings of "The Cosmic Microwave Background and its Polarization", New Astronomy Reviews, (eds. S. Hanany and K.A. Olive