Cosmological simulations 
of number counts

Abstract In this paper we present for the first time the angular power spectra C ℓ(z,z') for number counts from relativistic N-body simulations. We use the relativistic N-body code gevolution with its exact integration of lightlike geodesics which include all relativistic scalar contributions to the number counts. We compare our non-perturbative numerical results with the results from class using the hmcode approximation for the non-linear matter power spectrum. We find that this simple description is excellent for both, the density and the convergence. On the other hand, the current implementation of redshift-space distortions in Boltzmann codes is not accurate. We also find that the largest contribution to the unequal-redshift power spectra is the cross-correlation of the density and the lensing contribution to the number counts, especially for redshift bins that are far apart. Correlating the number counts with the convergence map we find that the signal is dominated by the lensing-lensing term when the convergence field redshift is not higher than the number counts one, while it is dominated by the density-lensing term in the opposite case. In the present study, the issue of galaxy bias is deliberately left aside by considering only unbiased samples of matter particles from the simulations.

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Developing a unified pipeline for large-scale structure data analysis with angular power spectra – I. The importance of redshift-space distortions for galaxy number counts

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2366 ◽

2019 ◽

Vol 489 (3) ◽

pp. 3385-3402 ◽

Cited By ~ 9

Author(s):

Konstantinos Tanidis ◽

Stefano Camera

Keyword(s):

Parameter Estimation ◽

Large Scale ◽

Power Spectra ◽

Computation Time ◽

Large Scale Structure ◽

Scale Structure ◽

Cosmological Parameter ◽

Wide Range ◽

Galaxy Bias ◽

Number Counts

ABSTRACT We develop a cosmological parameter estimation code for (tomographic) angular power spectra analyses of galaxy number counts, for which we include, for the first time, redshift-space distortions (RSDs) in the Limber approximation. This allows for a speed-up in computation time, and we emphasize that only angular scales where the Limber approximation is valid are included in our analysis. Our main result shows that a correct modelling of RSD is crucial not to bias cosmological parameter estimation. This happens not only for spectroscopy-detected galaxies, but even in the case of galaxy surveys with photometric redshift estimates. Moreover, a correct implementation of RSD is especially valuable in alleviating the degeneracy between the amplitude of the underlying matter power spectrum and the galaxy bias. We argue that our findings are particularly relevant for present and planned observational campaigns, such as the Euclid satellite or the Square Kilometre Array, which aim at studying the cosmic large-scale structure and trace its growth over a wide range of redshifts and scales.

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The Matter Power Spectrum

Symposium - International Astronomical Union ◽

10.1017/s0074180900216215 ◽

2005 ◽

Vol 201 ◽

pp. 145-157

Author(s):

J. A. Peacock

Keyword(s):

Large Scale ◽

Cold Dark Matter ◽

Power Spectra ◽

Scale Invariant ◽

Close Match ◽

Matter Power Spectrum ◽

Cold Dark Matter Model ◽

Galaxy Bias ◽

Dark Matter Model ◽

Cluster Abundance

The main tools describing the formation of large-scale structure are reviewed. Detailed emphasis is given to the Cold Dark Matter model, since this appears to be a close match to observation. A consistent normalization that satisfies both CMB constraints and the cluster abundance requires Ωm ⋍ 0.35 for a flat universe and scale-invariant fluctuations. Discrepancies between observed galaxy power spectra and CDM predictions are discussed; a heuristic model for galaxy bias is proposed that potentially allows such scale-dependent bias to be understood.

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Recent behaviour of Glaciar Upsala, a fast-flowing calving glacier in Lago Argentino, southern Patagonia

Annals of Glaciology ◽

10.3189/172756403781816202 ◽

2003 ◽

Vol 36 ◽

pp. 184-188 ◽

Cited By ~ 45

Author(s):

Pedro Skvarca ◽

Bruce Raup ◽

Hernan de Angelis

Keyword(s):

Cross Correlation ◽

High Spatial Resolution ◽

Winter Period ◽

Optical Images ◽

Southern Patagonia ◽

Glacier Front ◽

Calving Rate ◽

Depth Relationship ◽

Surface Ice ◽

First Time

AbstractSequential optical images of high spatial resolution were used for the first time to derive surface ice velocities of Glaciar Upsala, a fast-moving fresh-water calving glacier in southern Patagonia. Cross-correlation methods applied to four Landsat ETM+ images acquired in 2000–01 yielded average velocities of around 1600 m a−1, similar to values measured in the field in November 1993. The derived velocities show almost no seasonal variation for the analyzed calving termini. During the period of satellite coverage, clear readvances were detected in the autumn–winter period, followed by recessions during summers. Between 24 April 1999 and 14 October 2001, the glacier front has been fluctuating seasonally within about 400 m, in contrast to the previous dramatic recession. During the last 2.5 years, Glaciar Upsala west terminus had a net advance of around 300 m. In addition, the available satellite images allowed us to determine recent calving speeds and confirm the improved calving-rate/water-depth relationship, recently proposed by incorporating new data from Patagonian glaciers.

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Searching for cross-correlation between stochastic gravitational-wave background and galaxy number counts

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3159 ◽

2020 ◽

Vol 500 (2) ◽

pp. 1666-1672

Author(s):

Kate Z Yang ◽

Vuk Mandic ◽

Claudia Scarlata ◽

Sharan Banagiri

Keyword(s):

Gravitational Wave ◽

Cross Correlation ◽

Sloan Digital Sky Survey ◽

Number Count ◽

Frequency Bands ◽

Galaxy Count ◽

Harmonic Decomposition ◽

Number Counts ◽

Gravitational Wave Background ◽

The Universe

ABSTRACT Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo have recently published the upper limit measurement of persistent directional stochastic gravitational-wave background (SGWB) based on data from their first and second observing runs. In this paper, we investigate whether a correlation exists between this maximal likelihood SGWB map and the electromagnetic (EM) tracers of matter structure in the Universe, such as galaxy number counts. The method we develop will improve the sensitivity of future searches for anisotropy in the SGWB and expand the use of SGWB anisotropy to probe the formation of structure in the Universe. In order to compute the cross-correlation, we used the spherical harmonic decomposition of SGWB in multiple frequency bands and converted them into pixel-based sky maps in healpix basis. For the EM part, we use the Sloan Digital Sky Survey alaxy catalogue and form healpix sky maps of galaxy number counts at the same angular resolution as the SGWB maps. We compute the pixel-based coherence between these SGWB and galaxy count maps. After evaluating our results in different SGWB frequency bands and in different galaxy redshift bins, we conclude that the coherence between the SGWB and galaxy number count maps is dominated by the null measurement noise in the SGWB maps, and therefore not statistically significant. We expect the results of this analysis to be significantly improved by using the more sensitive upcoming SGWB measurements based on the third observing run of Advanced LIGO and Advanced Virgo.

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Determination of the complex frequencies for the normal modes below 1mHz after the 2010 Maule and 2011 Tohoku earthquakes

Annals of Geophysics ◽

10.4401/ag-6400 ◽

2014 ◽

Vol 56 (5) ◽

Author(s):

Hao Ding ◽

Wen-Bin Shen

Keyword(s):

Time Series ◽

Normal Modes ◽

Power Spectra ◽

Tohoku Earthquake ◽

Superconducting Gravimeter ◽

Width Ratio ◽

Maule Earthquake ◽

Attenuation Models ◽

First Time

Based upon SG (superconducting gravimeter) records, the autoregressive method proposed by Chao and Gilbert [1980] is used to determine the frequencies of the singlets of seven spheroidal modes (0S2, 2S1, 0S3, 0S4, 1S2, 0S0, and 3S1) and the degenerate frequencies of three toroidal modes (0T2, 0T3, and 0T4) below 1 mHz after two recent huge earthquakes, the 2010 Mw8.8 Maule earthquake and the 2011 Mw9.1 Tohoku earthquake. The corresponding quality factor Qs are also determined for those modes, of which the Qs of the five singlets of 1S2 and the five singlets (m=0, m=±2, and m=±3) of 0S4 are estimated for the first time using the SG observations. The singlet m=0 of 3S1 is clearly observed from the power spectra of the SG time series without using other special spectral analysis methods or special time series from pole station records. In addition, the splitting width ratio R of 3S1 is 0.99, and consequently we conclude that 3S1 is normally split. The frequencies and Qs of the modes below 1mHz may contribute to refining the 3D density and attenuation models of the Earth.

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Xspect / Xpol : CMB angular power spectra estimator using cross-correlation

10.22323/1.027.0063 ◽

2007 ◽

Author(s):

Matthieu Tristram

Keyword(s):

Cross Correlation ◽

Power Spectra

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Mobile Radar Observations of the Evolving Debris Field Compared with a Damage Survey of the Shawnee, Oklahoma, Tornado of 19 May 2013

Monthly Weather Review ◽

10.1175/mwr-d-19-0215.1 ◽

2020 ◽

Vol 148 (5) ◽

pp. 1779-1803 ◽

Cited By ~ 1

Author(s):

Roger M. Wakimoto ◽

Zachary Wienhoff ◽

Howard B. Bluestein ◽

David J. Bodine ◽

James M. Kurdzo

Keyword(s):

Cross Correlation ◽

Vertical Structure ◽

Leading Edge ◽

Radar Data ◽

Radar Reflectivity ◽

Vertical Profiles ◽

Damage Survey ◽

X Band ◽

First Time ◽

Rapid Scanning

Abstract A detailed damage survey is combined with high-resolution mobile, rapid-scanning X-band polarimetric radar data collected on the Shawnee, Oklahoma, tornado of 19 May 2013. The focus of this study is the radar data collected during a period when the tornado was producing damage rated EF3. Vertical profiles of mobile radar data, centered on the tornado, revealed that the radar reflectivity was approximately uniform with height and increased in magnitude as more debris was lofted. There was a large decrease in both the cross-correlation coefficient (ρhv) and differential radar reflectivity (ZDR) immediately after the tornado exited the damaged area rated EF3. Low ρhv and ZDR occurred near the surface where debris loading was the greatest. The 10th percentile of ρhv decreased markedly after large amounts of debris were lofted after the tornado leveled a number of structures. Subsequently, ρhv quickly recovered to higher values. This recovery suggests that the largest debris had been centrifuged or fallen out whereas light debris remained or continued to be lofted. Range–height profiles of the dual-Doppler analyses that were azimuthally averaged around the tornado revealed a zone of maximum radial convergence at a smaller radius relative to the leading edge of lofted debris. Low-level inflow into the tornado encountering a positive bias in the tornado-relative radial velocities could explain the existence of the zone. The vertical structure of the convergence zone was shown for the first time.

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Force spectroscopy-based simultaneous topographical and mechanical characterization to study polymer-to-polymer interactions in coated alginate microspheres

Scientific Reports ◽

10.1038/s41598-019-56547-z ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 3

Author(s):

Maria Virumbrales-Muñoz ◽

Edorta Santos-Vizcaino ◽

Laura Paz ◽

Amparo Maria Gallardo-Moreno ◽

Gorka Orive ◽

...

Keyword(s):

Cross Correlation ◽

Mechanical Characterization ◽

Force Spectroscopy ◽

Covalent Bonding ◽

Design Rationale ◽

Polymer Interactions ◽

First Time ◽

Hydrogel Microspheres

AbstractCell-laden hydrogel microspheres have shown encouraging outcomes in the fields of drug delivery, tissue engineering or regenerative medicine. Beyond the classical single coating with polycations, many other different coating designs have been reported with the aim of improving mechanical properties and in vivo performance of the microspheres. Among the most common strategies are the inclusion of additional polycation coatings and the covalent bonding of the semi-permeable membranes with biocompatible crosslinkers such as genipin. However, it remains challenging to characterize the effects of the interactions between the polycations and the hydrogel microspheres over time in vitro. Here we use a force spectroscopy-based simultaneous topographical and mechanical characterization to study polymer-to-polymer interactions in alginate microspheres with different coating designs, maintaining the hydrogels in liquid. In addition to classical topography parameters, we explored, for the first time, the evolution of peak/valley features along the z axis via thresholding analysis and the cross-correlation between topography and stiffness profiles with resolution down to tens of nanometers. Thus, we demonstrated the importance of genipin crosslinking to avoid membrane detachment in alginate microspheres with double polycation coatings. Overall, this methodology could improve hydrogel design rationale and expedite in vitro characterization, therefore facilitating clinical translation of hydrogel-based technologies.

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Measurements of solar internal rotation obtained with the Mt. Wilson 60-foot solar tower

Symposium - International Astronomical Union ◽

10.1017/s0074180900157699 ◽

1988 ◽

Vol 123 ◽

pp. 41-44

Author(s):

Edward J. Rhodes ◽

Alessandro Cacciani ◽

Martin Woodard ◽

Steven Tomczyk ◽

Sylvain Korzennik ◽

...

Keyword(s):

Time Series ◽

Cross Correlation ◽

Rotational Velocity ◽

Optical Filter ◽

Power Spectra ◽

Mean Value ◽

Current Limit ◽

Surface Rotation ◽

Cross Correlation Analysis ◽

Full Disk

We have obtained estimates of the solar internal rotational velocity from measurements of the frequency splittings of p-mode oscillations. Specifically, we have analyzed a 10-day time series of full-disk Dopplergrams obtained during July and August 1984 at the 60-Foot Tower Telescope of the Mt. Wilson Observatory. The Dopplergrams were obtained with a Na magneto-optical filter and a 244 × 248-pixel CID camera. From the time series we computed power spectra for all of the prograde and retrograde sectoral p-modes from ℓ = 0 to 200 and for all of the tessaral harmonics up to ℓ = 89. We then applied a cross-correlation analysis to the resulting sectoral power spectra to obtain estimates of the frequency splittings. From ℓ = 4 to ℓ = 30 we obtained a mean value of the frequency spitting of roughly 450 nHz (sidereal) in close agreement with most previously published results, while from ℓ = 40 to ℓ = 140 we obtained a mean value of about 470 nHz. We believe that the latter value is slightly higher than the surface rotational splitting of 461 nHz because of possible confusion due to the temporal sidelobes introduced by the day/night observing cycle. Confirmation of this possibility will have to await our computation of tesseral power spectra for degrees greater than our current limit of 89. Finally, for degrees between 140 and 200, the frequency splittings are indistinguishable from the surface rotation rate.

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EUVE J0825-16.3 and EUVE J1501-43.6: Two dMe Double–Lined Spectroscopic Binaries

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307006369 ◽

2006 ◽

Vol 2 (S240) ◽

pp. 690-696

Author(s):

D. Montes ◽

I. Crespo-Chacón ◽

M.C. Gálvez ◽

M.J. Fernández-Figueroa

Keyword(s):

High Resolution ◽

Orbital Period ◽

Binary Systems ◽

Cross Correlation ◽

Rotational Velocity ◽

Spectroscopic Binaries ◽

Balmer Lines ◽

First Time ◽

Orbital Solution ◽

Similar Intensity

AbstractHigh-resolution echelle spectroscopic observations taken with the FEROS spectrograph at the ESO 2.2-m telescope confirm the binary nature of the dMe stars EUVE J0825−16.3 and EUVE J1501−43.6, previously reported by Christian & Mathioudakis (2002). In these binary systems, emission of similar intensity from both components is detected in the Na i D1 & D2, He i D3, Ca II H&K, Ca II IRT and Balmer lines. We have determined precise radial velocities by cross-correlation with radial velocity standard stars, which have allowed us to obtain for the first time the orbital solution of these systems. Both binaries consist of two nearly equal M0V components with an orbital period shorter than 3.5 days. We have analyzed the behaviour of the chromospheric activity indicators (variability and possible flares). In addition, we have determined its rotational velocity and kinematics.

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