scholarly journals Can We Detect the Anisotropic Shapes of Quasar HiiRegions during Reionization through the Small‐Scale Redshifted 21 cm Power Spectrum?

2008 ◽  
Vol 673 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Shiv Sethi ◽  
Zoltan Haiman
Keyword(s):  
Power Spectrum ◽  
Small Scale

Small-Scale Power Spectrum and Correlations in Lambda + Cold Dark Matter Models

1996 ◽  
Vol 466 ◽  
pp. 13 ◽  
Author(s):  
Anatoly Klypin ◽  
Joel Primack ◽  
Jon Holtzman
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Cold Dark Matter ◽  
Small Scale

scholarly journals Small-scale Substructure in Dark Matter Haloes: Where Does Galaxy Formation Come to an End?

2004 ◽  
Vol 220 ◽  
pp. 91-98 ◽  
Author(s):  
J. E. Taylor ◽  
J. Silk ◽  
A. Babul
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Structure Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Small Scale ◽  
Analytic Model ◽  
Model Predictions ◽  
Low Mass

Models of structure formation based on cold dark matter predict that most of the small dark matter haloes that first formed at high redshift would have merged into larger systems by the present epoch. Substructure in present-day haloes preserves the remains of these ancient systems, providing the only direct information we may ever have about the low-mass end of the power spectrum. We describe some recent attempts to model halo substructure down to very small masses, using a semi-analytic model of halo formation. We make a preliminary comparison between the model predictions, observations of substructure in lensed systems, and the properties of local satellite galaxies.

scholarly journals Interferometric observations of the small-scale structure of Galactic neutral hydrogen

1985 ◽  
Vol 106 ◽  
pp. 321-322
Author(s):  
J. Crovisier ◽  
J. M. Dickey
Keyword(s):  
Power Spectrum ◽  
Dynamic Range ◽  
Neutral Hydrogen ◽  
Scale Structure ◽  
Small Scale ◽  
Turbulence Spectrum ◽  
Small Scale Structure ◽  
Image Position ◽  
Spatial Power Spectrum

The small-scale structure of galactic neutral hydrogen may be statistically described by the spatial power spectrum of the 21-cm line. This latter may be readily observed by interferometer arrays since it is the squared modulus of the visibility function. We have observed the , region with the Westerbork Synthesis Radio Telescope (Crovisier and Dickey, 1983). Brightness fluctuations of the 21-cm line were detected in this region on scales as small as 1.7 arcmin (corresponding to less than 5 pc). The Westerbork observations, combined with single-dish observations made at Nançay and Arecibo, allow determination of the spatial power spectrum over a dynamic range of about 106 in intensity. The spectrum follows roughly a power law with indices ~ −3 to −2. An interpretation in terms of the turbulence spectrum is proposed by Dickey (1985).

scholarly journals The halo mass function in alternative dark matter models

2020 ◽  
Vol 493 (1) ◽  
pp. L11-L15 ◽  
Author(s):  
M R Lovell
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Particle Physics ◽  
Mass Function ◽  
Small Scale ◽  
Acoustic Oscillations ◽  
Sterile Neutrinos ◽  
Matter Power Spectrum ◽  
Alternative Approach ◽  
Good Agreement

ABSTRACT The claimed detection of large amounts of substructure in lensing flux anomalies, and in Milky Way stellar stream gap statistics, has led to a step change in constraints on simple warm dark matter models. In this study, we compute predictions for the halo mass function both for these simple models and for comprehensive particle physics models of sterile neutrinos and dark acoustic oscillations. We show that the mass function fit of Lovell et al. underestimates the number of haloes less massive than the half-mode mass, $M_\mathrm {hm}$, by a factor of 2, relative to the extended Press–Schechter (EPS) method. The alternative approach of applying EPS to the Viel et al. matter power spectrum fit instead suggests good agreement at $M_\mathrm {hm}$ relative to the comprehensive model matter power spectrum results, although the number of haloes with mass $\rm{\lt} M_\mathrm {hm}$ is still suppressed due to the absence of small-scale power in the fitting function. Overall, we find that the number of dark matter haloes with masses $\rm{\lt} 10^{8}{\, \rm M_\odot }$ predicted by competitive particle physics models is underestimated by a factor of ∼2 when applying popular fitting functions, although careful studies that follow the stripping and destruction of subhaloes will be required in order to draw robust conclusions.

scholarly journals H I Emission and Absorption in the Southern Galactic Plane Survey

2001 ◽  
Vol 18 (1) ◽  
pp. 84-90 ◽  
Author(s):  
N. M. McClure-Griffiths ◽  
John M. Dickey ◽  
B. M. Gaensler ◽  
A. J. Green ◽  
R. F. Haynes ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Radio Telescope ◽  
Large Scale ◽  
Galactic Plane ◽  
Pilot Project ◽  
Small Scale ◽  
Preliminary Results ◽  
Test Region ◽  
Scale Structures ◽  
Spatial Power Spectrum

AbstractWe present preliminary results from the Southern Galactic Plane Survey (SGPS) Test Region and Parkes data. As part of the pilot project for the Southern Galactic Plane Survey, observations of a Test Region (325·5° ≤l ≤ 333·5°; −0·5° ≤ b ≤ 3·5°) were completed in December 1998. Single-dish observations of the full survey region (253° ≤ l ≤ 358 ° |b| ≤ 1°) with the Parkes Radio Telescope were completed in March 2000. We present a sample of SGPS H I data, with particular attention to the smallest-and largest-scale structures seen in absorption and emission, respectively. On the large scale, we detect many prominent H I shells. On the small scale, we note extremely compact, cold clouds seen in H I self-absorption. We explore how these two classes of objects probe opposite ends of the H I spatial power spectrum.

scholarly journals Power spectrum for the small-scale Universe

2009 ◽  
Vol 397 (3) ◽  
pp. 1275-1285 ◽  
Author(s):  
Lawrence M. Widrow ◽  
Pascal J. Elahi ◽  
Robert J. Thacker ◽  
Mark Richardson ◽  
Evan Scannapieco
Keyword(s):  
Power Spectrum ◽  
Small Scale

scholarly journals Magnetic power spectrum in the undisturbed solar photosphere

2020 ◽  
Vol 1 (1) ◽  
pp. 1-5
Author(s):  
Valentina Abramenko ◽  
Olga Kutsenko
Keyword(s):  
Power Spectrum ◽  
Power Spectra ◽  
Active Regions ◽  
Reliable Estimate ◽  
Small Scale ◽  
Solar Photosphere ◽  
Dynamo Action ◽  
Quiet Sun ◽  
Turbulent Dynamo ◽  
Wide Range

Using the magnetic field data obtained with the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO), an investigation of magnetic power spectra in the undisturbed solar photosphere was performed. The results are as follows. 1) To get a reliable estimate of a magnetic power spectrum from the uniformly distributed quiet-sun magnetic flux, a sample pattern of no less than 300 pixels length should be adopted. With smaller patterns, energy on all observable scales might be overestimated. 2) For patterns of different magnetic intensity (e.g., a coronal hole, a quiet-sun area, an area of supergranulation), the magnetic power spectra in a range of (2.5-10) Mm exhibit very close spectral indices of about -1. The observed spectrum is more shallow than the Kolmogorov-type spectrum (with a slope of -5/3) and it differs from steep spectra of active regions. Such a shallow spectrum cannot be explained by the only direct Kolmogorov’s cascade, but it can imply a small-scale turbulent dynamo action in a wide range of scales: from tens of megameters down to at least 2.5 Mm. On smaller scales, the HMI/SDO data do not allow us to reliably derive the shape of the spectrum. 3) Data make it possible to conclude that a uniform mechanism of the small-scale turbulent dynamo is at work all over the solar surface outside active regions.

scholarly journals A multiscale approach for precipitation verification applied to the FORALPS case studies

2008 ◽  
Vol 16 ◽  
pp. 3-9 ◽  
Author(s):  
A. Lanciani ◽  
S. Mariani ◽  
M. Casaioli ◽  
C. Accadia ◽  
N. Tartaglione
Keyword(s):  
Power Spectrum ◽  
Prediction Models ◽  
Weather Prediction ◽  
Power Spectra ◽  
Multiscale Methods ◽  
Precipitation Forecast ◽  
Diagnostic Tools ◽  
Small Scale ◽  
Multiscale Approach ◽  
Skill Scores

Abstract. Multiscale methods, such as the power spectrum, are suitable diagnostic tools for studying the second order statistics of a gridded field. For instance, in the case of Numerical Weather Prediction models, a drop in the power spectrum for a given scale indicates the inability of the model to reproduce the variance of the phenomenon below the correspondent spatial scale. Hence, these statistics provide an insight into the real resolution of a gridded field and must be accurately known for interpolation and downscaling purposes. In this work, belonging to the EU INTERREG IIIB Alpine Space FORALPS project, the power spectra of the precipitation fields for two intense rain events, which occurred over the north-eastern alpine region, have been studied in detail. A drop in the power spectrum at the shortest scales (about 30 km) has been found, as well as a strong matching between the precipitation spectrum and the spectrum of the orography. Furthermore, it has also been shown how the spectra help understand the behavior of the skill scores traditionally used in Quantitative Precipitation Forecast verification, as these are sensitive to the amount of small scale detail present in the fields.

scholarly journals Quantifying the power spectrum of small-scale structure in semi-analytic galaxies

2019 ◽  
Vol 488 (4) ◽  
pp. 5085-5092 ◽  
Author(s):  
Sean Brennan ◽  
Andrew J Benson ◽  
Francis-Yan Cyr-Racine ◽  
Charles R Keeton ◽  
Leonidas A Moustakas ◽  
...  
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Gravitational Lensing ◽  
Cold Dark Matter ◽  
Scale Structure ◽  
Small Scale ◽  
Small Scale Structure ◽  
Mass Distributions ◽  
Theoretical Predictions ◽  
Spectrum Distribution

Abstract In the cold dark matter (CDM) picture of structure formation, galaxy mass distributions are predicted to have a considerable amount of structure on small scales. Strong gravitational lensing has proven to be a useful tool for studying this small-scale structure. Much of the attention has been given to detecting individual dark matter subhaloes through lens modelling, but recent work has suggested that the full population of subhaloes could be probed using a power spectrum analysis. In this paper, we quantify the power spectrum of small-scale structure in simulated galaxies, with the goal of understanding theoretical predictions and setting the stage for using measurements of the power spectrum to test dark matter models. We use a sample of simulated galaxies generated from the galacticus semi-analytic model to determine the power spectrum distribution first in the CDM paradigm and then in a warm dark matter scenario. We find that a measurement of the slope and amplitude of the power spectrum on galaxy strong lensing scales (k ∼ 1 kpc−1) could be used to distinguish between CDM and alternate dark matter models, especially if the most massive subhaloes can be directly detected via gravitational imaging.

Sign in / Sign up

Export Citation Format

Share Document