scholarly journals Interpreting large-scale redshift-space distortion measurements

2012 ◽  
Vol 420 (3) ◽  
pp. 2102-2119 ◽  
Author(s):  
L. Samushia ◽  
W. J. Percival ◽  
A. Raccanelli
Keyword(s):  
Large Scale ◽  
Space Distortion

scholarly journals Joint growth-rate measurements from redshift-space distortions and peculiar velocities in the 6dF Galaxy Survey

2020 ◽  
Vol 494 (3) ◽  
pp. 3275-3293 ◽  
Author(s):  
Caitlin Adams ◽  
Chris Blake
Keyword(s):  
Growth Rate ◽  
Large Scale ◽  
Likelihood Method ◽  
Distortion Parameter ◽  
Peculiar Velocities ◽  
Cross Covariance ◽  
Space Distortion ◽  
Standard Cosmological Model ◽  
Parameter Constraints ◽  
Field Galaxy

ABSTRACT We present a new model for the cross-covariance between galaxy redshift-space distortions and peculiar velocities. We combine this with the autocovariance models of both probes in a fully self-consistent, maximum-likelihood method, allowing us to extract enhanced cosmological parameter constraints. When applying our method to the 6-degree Field Galaxy Survey (6dFGS), our constraint on the growth rate of structure is $f\sigma _8 = 0.384 \pm 0.052 \rm {(stat)} \pm 0.061 \rm {(sys)}$ and our constraint for the redshift-space distortion parameter is $\beta = 0.289^{+0.044}_{-0.043} \rm {(stat)} \pm 0.049 \rm {(sys)}$. We find that the statistical uncertainty for the growth rate of structure is reduced by 64 per cent when using the complete covariance model compared to the redshift-space distortion autocovariance model and 50 per cent when compared to using the peculiar-velocity autocovariance model. Our constraints are consistent with those from the literature on combining multiple tracers of large-scale structure, as well as those from other 6dFGS analyses. Our measurement is also consistent with the standard cosmological model.

scholarly journals Determining Ω0 and λ0 from Cosmological Redshift Distortion of Galaxies and Quasars

1999 ◽  
Vol 183 ◽  
pp. 235-240
Author(s):  
Yasushi Suto
Keyword(s):  
Large Scale ◽  
Collaborative Work ◽  
Cosmological Parameters ◽  
Three Dimensional ◽  
Density Parameter ◽  
Cosmological Redshift ◽  
Peculiar Velocity ◽  
Dimensional Distribution ◽  
Space Distortion ◽  
The Universe

The three-dimensional distribution of galaxies in the redshift surveys differ from the true one since the distance to each galaxy cannot be determined by its redshift z only; for z ≪ 1 the peculiar velocity of galaxies, typically ∼ (100–1000)km/sec, contaminates the true recession velocity of the Hubble flow, while the true distance for objects at z ≳ 1 sensitively depends on the (unknown and thus assumed) cosmological parameters. This hampers the effort to understand the true distribution of large-scale structure of the universe. Nevertheless such redshift-space distortion effects are quite useful since through the detailed theoretical modeling, one can derive the peculiar velocity dispersions of galaxies as a function of separation, and also can infer the cosmological density parameter Ω0, the dimensionless cosmological constant λ0, and the spatial biasing factor b of galaxies and/or quasars, for instance. In this talk, I discuss the importance of such redshift distortion induced by the geometry of the universe, which summarizes the recent results of my collaborative work in this topic (Matsubara & Suto 1996; Nakamura, Matsubara, & Suto 1998; Magira, Matsubara, Jing, & Suto 1998).

scholarly journals The impact of Lyman-α radiative transfer on large-scale clustering in the Illustris simulation

2018 ◽  
Vol 614 ◽  
pp. A31 ◽  
Author(s):  
C. Behrens ◽  
C. Byrohl ◽  
S. Saito ◽  
J. C. Niemeyer
Keyword(s):  
Radiative Transfer ◽  
Selection Bias ◽  
Large Scale ◽  
High Redshift ◽  
Formation Rate ◽  
Acoustic Oscillation ◽  
Density Region ◽  
Space Distortion ◽  
High Density Region ◽  
The Impact

Context. Lyman-α emitters (LAEs) are a promising probe of the large-scale structure at high redshift, z ≳ 2. In particular, the Hobby-Eberly Telescope Dark Energy Experiment aims at observing LAEs at 1.9 < z < 3.5 to measure the baryon acoustic oscillation (BAO) scale and the redshift-space distortion (RSD). However, it has been pointed out that the complicated radiative transfer (RT) of the resonant Lyman-α emission line generates an anisotropic selection bias in the LAE clustering on large scales, s ≳ 10 Mpc. This effect could potentially induce a systematic error in the BAO and RSD measurements. Also, there exists a recent claim to have observational evidence of the effect in the Lyman-α intensity map, albeit statistically insignificant. Aims. We aim at quantifying the impact of the Lyman-α RT on the large-scale galaxy clustering in detail. For this purpose, we study the correlations between the large-scale environment and the ratio of an apparent Lyman-α luminosity to an intrinsic one, which we call the “observed fraction”, at 2 < z < 6. Methods. We apply our Lyman-α RT code by post-processing the full Illustris simulations. We simply assume that the intrinsic luminosity of the Lyman-α emission is proportional to the star formation rate of galaxies in Illustris, yielding a sufficiently large sample of LAEs to measure the anisotropic selection bias. Results. We find little correlation between large-scale environment and the observed fraction induced by the RT, and hence a smaller anisotropic selection bias than has previously been claimed. We argue that the anisotropy was overestimated in previous work due to insufficient spatial resolution; it is important to keep the resolution such that it resolves the high-density region down to the scale of the interstellar medium, that is, ~1 physical kpc. We also find that the correlation can be further enhanced by assumptions in modeling intrinsic Lyman-α emission.

scholarly journals Measuring the cosmic bulk flow with 6dFGSv

2014 ◽  
Vol 11 (S308) ◽  
pp. 336-339 ◽  
Author(s):  
Christina Magoulas ◽  
Christopher Springob ◽  
Matthew Colless ◽  
Jeremy Mould ◽  
John Lucey ◽  
...  
Keyword(s):  
Velocity Field ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Distortion Parameter ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
Redshift Surveys ◽  
Luminous Matter ◽  
The Galaxy ◽  
Space Distortion

AbstractWhile recent years have seen rapid growth in the number of galaxy peculiar velocity measurements, disagreements remain about the extent to which the peculiar velocity field - a tracer of the large-scale distribution of mass - agrees with both ΛCDM expectations and with velocity field models derived from redshift surveys. The 6dF Galaxy Survey includes peculiar velocities for nearly 9 000 early-type galaxies (6dFGSv), making it the largest and most homogeneous galaxy peculiar velocity sample to date. We have used the 6dFGS velocity field to determine the amplitude and scale of large-scale cosmic flows in the local universe and test standard cosmological models. We also compare the galaxy density and peculiar velocity fields to establish the distribution of dark and luminous matter and better constrain key cosmological parameters such as the redshift-space distortion parameter.

Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1

1999 ◽  
Vol 173 ◽  
pp. 243-248
Author(s):  
D. Kubáček ◽  
A. Galád ◽  
A. Pravda
Keyword(s):  
Image Processing ◽  
Large Scale ◽  
Harvard College ◽  
Oak Ridge ◽  
Large Scale Structures ◽  
Short Period Comet ◽  
Short Period ◽  
Scale Structures ◽  
Harvard College Observatory ◽  
Period Comet

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

Large-scale Motion of Solar Filaments

2000 ◽  
Vol 179 ◽  
pp. 205-208
Author(s):  
Pavel Ambrož ◽  
Alfred Schroll
Keyword(s):  
Magnetic Flux ◽  
Proper Motion ◽  
Time Scale ◽  
Large Scale ◽  
Accuracy Of Measurements ◽  
Solar Filaments ◽  
General Movement ◽  
Scale Motion ◽  
Velocity Scatter

AbstractPrecise measurements of heliographic position of solar filaments were used for determination of the proper motion of solar filaments on the time-scale of days. The filaments have a tendency to make a shaking or waving of the external structure and to make a general movement of whole filament body, coinciding with the transport of the magnetic flux in the photosphere. The velocity scatter of individual measured points is about one order higher than the accuracy of measurements.

Some applications of electron beam microanalysis techniques in VLSI process evaluation

1983 ◽  
Vol 41 ◽  
pp. 160-161
Author(s):  
Simon Thomas
Keyword(s):  
Integrated Circuits ◽  
Process Evaluation ◽  
Large Scale ◽  
Technology Development ◽  
Analytical Techniques ◽  
Successful Implementation ◽  
Analysis Of Failures ◽  
Characterization Of Materials ◽  
Circuits Vlsi

Trends in the technology development of very large scale integrated circuits (VLSI) have been in the direction of higher density of components with smaller dimensions. The scaling down of device dimensions has been not only laterally but also in depth. Such efforts in miniaturization bring with them new developments in materials and processing. Successful implementation of these efforts is, to a large extent, dependent on the proper understanding of the material properties, process technologies and reliability issues, through adequate analytical studies. The analytical instrumentation technology has, fortunately, kept pace with the basic requirements of devices with lateral dimensions in the micron/ submicron range and depths of the order of nonometers. Often, newer analytical techniques have emerged or the more conventional techniques have been adapted to meet the more stringent requirements. As such, a variety of analytical techniques are available today to aid an analyst in the efforts of VLSI process evaluation. Generally such analytical efforts are divided into the characterization of materials, evaluation of processing steps and the analysis of failures.

Electron microscopy study of reactively sputter-deposited Ti/N films on silicon

1992 ◽  
Vol 50 (2) ◽  
pp. 1362-1363
Author(s):  
V. C. Kannan ◽  
A. K. Singh ◽  
R. B. Irwin ◽  
S. Chittipeddi ◽  
F. D. Nkansah ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Large Scale ◽  
Hexagonal Phase ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Process Conditions ◽  
Tin Films ◽  
Wide Range ◽  
Fcc Phase ◽  
Circuits Vlsi

Titanium nitride (TiN) films have historically been used as diffusion barrier between silicon and aluminum, as an adhesion layer for tungsten deposition and as an interconnect material etc. Recently, the role of TiN films as contact barriers in very large scale silicon integrated circuits (VLSI) has been extensively studied. TiN films have resistivities on the order of 20μ Ω-cm which is much lower than that of titanium (nearly 66μ Ω-cm). Deposited TiN films show resistivities which vary from 20 to 100μ Ω-cm depending upon the type of deposition and process conditions. TiNx is known to have a NaCl type crystal structure for a wide range of compositions. Change in color from metallic luster to gold reflects the stabilization of the TiNx (FCC) phase over the close packed Ti(N) hexagonal phase. It was found that TiN (1:1) ideal composition with the FCC (NaCl-type) structure gives the best electrical property.

Evolution of the microstructure of Cu(Ti)/SiO2 layers annealed in NH3

1995 ◽  
Vol 53 ◽  
pp. 452-453
Author(s):  
J. Liu ◽  
N. D. Theodore ◽  
D. Adams ◽  
S. Russell ◽  
T. L. Alford ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Titanium Nitride ◽  
Large Scale ◽  
Standard Procedure ◽  
Alloy Film ◽  
Electron Beam Evaporation ◽  
Copper Metallization ◽  
Nominal Composition ◽  
Ti Alloy ◽  
Thermally Grown

Copper-based metallization has recently attracted extensive research because of its potential application in ultra-large-scale integration (ULSI) of semiconductor devices. The feasibility of copper metallization is, however, limited due to its thermal stability issues. In order to utilize copper in metallization systems diffusion barriers such as titanium nitride and other refractory materials, have been employed to enhance the thermal stability of copper. Titanium nitride layers can be formed by annealing Cu(Ti) alloy film evaporated on thermally grown SiO2 substrates in an ammonia ambient. We report here the microstructural evolution of Cu(Ti)/SiO2 layers during annealing in NH3 flowing ambient.The Cu(Ti) films used in this experiment were prepared by electron beam evaporation onto thermally grown SiO2 substrates. The nominal composition of the Cu(Ti) alloy was Cu73Ti27. Thermal treatments were conducted in NH3 flowing ambient for 30 minutes at temperatures ranging from 450°C to 650°C. Cross-section TEM specimens were prepared by the standard procedure.

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