scholarly journals Cluster assembly times as a cosmological test

2021 ◽  
Author(s):  
Yuba Amoura ◽  
Nicole E Drakos ◽  
Anael Berrouet ◽  
James E Taylor
Keyword(s):  
Cosmological Parameters ◽  
Cluster Assembly ◽  
Relative Importance ◽  
Subsequent Growth ◽  
Two Factors ◽  
Fluctuation Amplitude ◽  
Number Counts ◽  
Parameter Constraints ◽  
Structural Probes ◽  
Cluster Age

Abstract The abundance of galaxy clusters in the low-redshift universe provides an important cosmological test, constraining a product of the initial amplitude of fluctuations and the amount by which they have grown since early times. The degeneracy of the test with respect to these two factors remains a limitation of abundance studies. Clusters will have different mean assembly times, however, depending on the relative importance of initial fluctuation amplitude and subsequent growth. Thus, structural probes of cluster age such as concentration, shape or substructure may provide a new cosmological test that breaks the main degeneracy in number counts. We review analytic predictions for how mean assembly time should depend on cosmological parameters, and test these predictions using cosmological simulations. Given the overall sensitivity expected, we estimate the cosmological parameter constraints that could be derived from the cluster catalogues of forthcoming surveys such as Euclid, the Nancy Grace Roman Space Telescope, eROSITA, or CMB-S4. We show that by considering the structural properties of their cluster samples, such surveys could easily achieve errors of Δσ8 = 0.01 or better.

scholarly journals Using quasar X-ray and UV flux measurements to constrain cosmological model parameters

2020 ◽  
Vol 497 (1) ◽  
pp. 263-278 ◽  
Author(s):  
Narayan Khadka ◽  
Bharat Ratra
Keyword(s):  
Cosmological Parameters ◽  
Hubble Constant ◽  
Acoustic Oscillation ◽  
Joint Analysis ◽  
Model Parameters ◽  
Density Parameter ◽  
Current Standard ◽  
X Ray ◽  
Flux Measurements ◽  
Parameter Constraints

ABSTRACT Risaliti and Lusso have compiled X-ray and UV flux measurements of 1598 quasars (QSOs) in the redshift range 0.036 ≤ z ≤ 5.1003, part of which, z ∼ 2.4 − 5.1, is largely cosmologically unprobed. In this paper we use these QSO measurements, alone and in conjunction with baryon acoustic oscillation (BAO) and Hubble parameter [H(z)] measurements, to constrain cosmological parameters in six different cosmological models, each with two different Hubble constant priors. In most of these models, given the larger uncertainties, the QSO cosmological parameter constraints are mostly consistent with those from the BAO + H(z) data. A somewhat significant exception is the non-relativistic matter density parameter Ωm0 where QSO data favour Ωm0 ∼ 0.5 − 0.6 in most models. As a result, in joint analyses of QSO data with H(z) + BAO data the 1D Ωm0 distributions shift slightly towards larger values. A joint analysis of the QSO + BAO + H(z) data is consistent with the current standard model, spatially-flat ΛCDM, but mildly favours closed spatial hypersurfaces and dynamical dark energy. Since the higher Ωm0 values favoured by QSO data appear to be associated with the z ∼ 2 − 5 part of these data, and conflict somewhat with strong indications for Ωm0 ∼ 0.3 from most z < 2.5 data as well as from the cosmic microwave background anisotropy data at z ∼ 1100, in most models, the larger QSO data Ωm0 is possibly more indicative of an issue with the z ∼ 2 − 5 QSO data than of an inadequacy of the standard flat ΛCDM model.

I. On the physiology of the embryonic heart (preliminary communication)

1893 ◽  
Vol 52 (315-320) ◽  
pp. 461-467 ◽  
Keyword(s):  
Embryonic Heart ◽  
Relative Importance ◽  
Two Factors ◽  
Preliminary Communication ◽  
Contractile Tissue

The object of the following experiments has been to study the effect of varying conditions on the heart previous to the development of a nervous mechanism, and thus to throw some light on the discussion as to the relative importance of the two factors in the heart’s action, viz., the contractile tissue and the nervous elements. The heart I have used is that of the chick at a period of incubation of seventy-two hours at a temperature of 38°C.

scholarly journals Cosmological constraints from galaxy–lensing cross-correlations using BOSS galaxies with SDSS and CMB lensing

2019 ◽  
Vol 491 (1) ◽  
pp. 51-68 ◽  
Author(s):  
Sukhdeep Singh ◽  
Rachel Mandelbaum ◽  
Uroš Seljak ◽  
Sergio Rodríguez-Torres ◽  
Anže Slosar
Keyword(s):  
Cosmological Parameters ◽  
Small Scale ◽  
The Galaxy ◽  
Scale Modelling ◽  
Modelling Uncertainties ◽  
Cent Level ◽  
Cross Correlations ◽  
Galaxy Bias ◽  
The Impact ◽  
Parameter Constraints

ABSTRACT We present cosmological parameter constraints based on a joint modelling of galaxy–lensing cross-correlations and galaxy clustering measurements in the SDSS, marginalizing over small-scale modelling uncertainties using mock galaxy catalogues, without explicit modelling of galaxy bias. We show that our modelling method is robust to the impact of different choices for how galaxies occupy dark matter haloes and to the impact of baryonic physics (at the $\sim 2{{\ \rm per\ cent}}$ level in cosmological parameters) and test for the impact of covariance on the likelihood analysis and of the survey window function on the theory computations. Applying our results to the measurements using galaxy samples from BOSS and lensing measurements using shear from SDSS galaxies and CMB lensing from Planck, with conservative scale cuts, we obtain $S_8\equiv \left(\frac{\sigma _8}{0.8228}\right)^{0.8}\left(\frac{\Omega _\mathrm{ m}}{0.307}\right)^{0.6}=0.85\pm 0.05$ (stat.) using LOWZ × SDSS galaxy lensing, and S8 = 0.91 ± 0.1 (stat.) using combination of LOWZ and CMASS × Planck CMB lensing. We estimate the systematic uncertainty in the galaxy–galaxy lensing measurements to be $\sim 6{{\ \rm per\ cent}}$ (dominated by photometric redshift uncertainties) and in the galaxy–CMB lensing measurements to be $\sim 3{{\ \rm per\ cent}}$, from small-scale modelling uncertainties including baryonic physics.

Can pay gaps between gay men and lesbians shed light on male–female pay gaps?

2019 ◽  
Vol 40 (2) ◽  
pp. 178-189
Author(s):  
Jing Wang ◽  
Morley Gunderson
Keyword(s):  
Gay Men ◽  
Gender Discrimination ◽  
Comparison Group ◽  
Wage Gap ◽  
Relative Importance ◽  
Lesbian Women ◽  
Pay Gap ◽  
Content Type ◽  
Two Factors ◽  
Shed Light

Purpose The purpose of this paper is to estimate the relative importance of gender discrimination and differences in household responsibilities as determinants of the male–female pay gap. Design/methodology/approach It parses out the relative importance of those two factors by using the pay between gay men vs lesbian women as a comparison group that should reflect only gender discrimination. Subtracting the pay gap between gay men and lesbians (reflecting only gender discrimination) from the male–female pay gap for their heterosexual counterparts (reflecting both gender discrimination and household responsibilities) provides evidence of the relative importance of gender discrimination and household responsibilities in explaining the male–female pay gap. Findings The results show that essentially all of the male–female pay gap is attributed to differences in household responsibilities. Originality/value This paper advances the literature of gender wage gap by using a novel comparison group – gay men vs lesbian women – to estimate the relative importance of gender discrimination and differences in household responsibilities as determinants of the male–female pay gap.

scholarly journals The influence of chitin structure on its enzymatic deacetylation

2016 ◽  
Vol 37 (2) ◽  
pp. 261-267 ◽  
Author(s):  
Malgorzata M. Jaworska ◽  
George A.F. Roberts
Keyword(s):  
Chain Conformation ◽  
Relative Importance ◽  
Main Obstacle ◽  
High Crystallinity ◽  
Satisfactory Method ◽  
Two Factors ◽  
The Subject

Abstract The possibility of producing chitosan by enzymatic deacetylation of chitin has been the subject of numerous investigations over the last twenty years, but to date no satisfactory method has been developed. In this paper the influence of chitin chain conformation and chitin particle crystallinity on the enzymatic deacetylation of chitin is investigated to determine the relative importance of these two factors on the process. It is shown that the high crystallinity of chitin is the main obstacle to converting chitin to chitosan by enzymatic deacetylation.

scholarly journals The roles of standing genetic variation and evolutionary history in determining the evolvability of anti-predator strategies

2014 ◽  
Author(s):  
Jordan Fish ◽  
Daniel R O'Donnell ◽  
Abhijna Parigi ◽  
Ian Dworkin ◽  
Aaron P Wagner
Keyword(s):  
Genetic Variation ◽  
Evolutionary History ◽  
Relative Importance ◽  
Digital Evolution ◽  
Relative Ease ◽  
Evolutionary Response ◽  
Two Factors ◽  
The Face ◽  
Evolutionary Trajectories ◽  
Different Levels

Standing genetic variation and the historical environment in which that variation arises (evolutionary history) are both potentially significant determinants of a population’s capacity for evolutionary response to a changing environment. We evaluated the relative importance of these two factors in influencing the evolutionary trajectories in the face of sudden environmental change. We used the open-ended digital evolution software Avida to examine how historic exposure to predation pressures, different levels of genetic variation, and combinations of the two, impact anti-predator strategies and competitive abilities evolved in the face of threats from new, invasive, predator populations. We show that while standing genetic variation plays some role in determining evolutionary responses, evolutionary history has the greater influence on a population’s capacity to evolve effective anti-predator traits. This adaptability likely reflects the relative ease of repurposing existing, relevant genes and traits, and the broader potential value of the generation and maintenance of adaptively flexible traits in evolving populations.

scholarly journals Constraining the astrophysics and cosmology from 21 cm tomography using deep learning with the SKA

2020 ◽  
Vol 494 (4) ◽  
pp. 5761-5774 ◽  
Author(s):  
Sultan Hassan ◽  
Sambatra Andrianomena ◽  
Caitlin Doughty
Keyword(s):  
Thermal Noise ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Great Accuracy ◽  
Machine Learning Techniques ◽  
Data Sets ◽  
Density Parameter ◽  
Huge Data ◽  
Learning Techniques ◽  
Fluctuation Amplitude

ABSTRACT Future Square Kilometre Array (SKA) surveys are expected to generate huge data sets of 21 cm maps on cosmological scales from the Epoch of Reionization. We assess the viability of exploiting machine learning techniques, namely, convolutional neural networks (CNNs), to simultaneously estimate the astrophysical and cosmological parameters from 21 cm maps from seminumerical simulations. We further convert the simulated 21 cm maps into SKA-like mock maps using the detailed SKA antennae distribution, thermal noise, and a recipe for foreground cleaning. We successfully design two CNN architectures (VGGNet-like and ResNet-like) that are both efficiently able to extract simultaneously three astrophysical parameters, namely the photon escape fraction (fesc), the ionizing emissivity power dependence on halo mass (Cion), and the ionizing emissivity redshift evolution index (Dion), and three cosmological parameters, namely the matter density parameter (Ωm), the dimensionless Hubble constant (h), and the matter fluctuation amplitude (σ8), from 21 cm maps at several redshifts. With the presence of noise from SKA, our designed CNNs are still able to recover these astrophysical and cosmological parameters with great accuracy ($R^{2} \gt 92{{\ \rm per\ cent}}$), improving to $R^{2} \gt 99{{\ \rm per\ cent}}$ towards low-redshift and low neutral fraction values. Our results show that future 21 cm observations can play a key role to break degeneracy between models and tightly constrain the astrophysical and cosmological parameters, using only few frequency channels.

Low resolution STEM imaging

1978 ◽  
Vol 36 (1) ◽  
pp. 350-351
Author(s):  
R. Hutchings ◽  
I.P. Jones ◽  
M.H. Loretto
Keyword(s):  
Structure Factor ◽  
Copper Alloy ◽  
Relative Importance ◽  
Low Resolution ◽  
Two Factors ◽  
Contrast Mechanism ◽  
Factor Type ◽  
Complex Copper ◽  
Effect Limit

IntroductionIn recent papers (Fraser and Jones 1975, Fraser, Jones and Loretto 1977) it has been shown that STEM does not offer an increase in penetration of metallurgical specimens over that available in CTEM. It was argued that two factors, lack of intensity and a top/bottom effect, limit penetration in both CTEM and STEM and the relative importance of these factors is expected to differ for different experimental requirements. The present paper examines an experiment with requirements such that the intensity limit in STEM may be overcome by using a large probe of about 40nm diameter.ExperimentalSpecimens of a complex copper alloy (Long 1977) containing particles of Cr (∼10nm in diameter) and particles of SiO2 (∼0.5 μm in diameter) have been examined at 100kV in STEM and CTEM using a Philips EM40O fitted with a conventional tungsten hairpin filament. In addition micrographs have also been obtained at 1MV in an AEI EM7. The contrast mechanism was of structure factor type.

The Functions of the Corpus Allatum in Rhodnius Prolixus (Hemiptera)

1948 ◽  
Vol 25 (1) ◽  
pp. 1-15
Author(s):  
V. B. WIGGLESWORTH
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Juvenile Hormone ◽  
Adult Female ◽  
Corpus Allatum ◽  
Relative Importance ◽  
Egg Development ◽  
Mature Adult ◽  
Two Factors ◽  
The Central Nervous System

Two factors are involved in the control of metamorphosis in Rhodnius: (a) The corpus allatum of the 5th-stage nymph no longer secretes the juvenile hormone (inhibitory hormone). The latent imaginal characters can thus be realized. (b) The corpus allatum in the 5th-stage nymph, particularly in the later stages of moulting, actively favours the production of imaginal characters. The evidence suggests that this activity (b) consists, not in the secretion of a metamorphosis promoting hormone favouring adult differentiation in the tissues directly, but in the elimination of the small quantities of juvenile hormone persisting in the blood and tissues. If we suppose that these two factors differ in relative importance in different insects we may perhaps have the basis for a theory of metamorphosis applicable to all groups of insects. The corpus allatum of the mature adult Rhodnius again begins to secrete the juvenile hormone; and the juvenile hormone of the 4th-stage nymph will induce egg development in the adult female. It is probable that the yolk-forming hormone and the juvenile hormone are identical. The sequence in the secretory activities of the corpus allatum, and so the number of instars, is controlled by some other centre, perhaps in the central nervous system.

scholarly journals A framework for measuring weak-lensing magnification using the Fundamental Plane

2020 ◽  
Vol 496 (3) ◽  
pp. 2998-3014
Author(s):  
Jenna K C Freudenburg ◽  
Eric M Huff ◽  
Christopher M Hirata
Keyword(s):  
Surface Brightness ◽  
Cosmological Parameters ◽  
Elliptical Galaxies ◽  
Weak Lensing ◽  
Selection Function ◽  
Source Population ◽  
Fundamental Plane ◽  
Background Population ◽  
Number Counts ◽  
Better Than

ABSTRACT Galaxy–galaxy lensing is an essential tool for probing dark matter haloes and constraining cosmological parameters. While galaxy–galaxy lensing measurements usually rely on shear, weak-lensing magnification contains additional constraining information. Using the Fundamental Plane (FP) of elliptical galaxies to anchor the size distribution of a background population is one method that has been proposed for performing a magnification measurement. We present a formalism for using the FP residuals of elliptical galaxies to jointly estimate the foreground mass and background redshift errors for a stacked lens scenario. The FP residuals include information about weak-lensing magnification κ, and therefore foreground mass, since to first order, non-zero κ affects galaxy size but not other FP properties. We also present a modular, extensible code that implements the formalism using emulated galaxy catalogues of a photometric galaxy survey. We find that combining FP information with observed number counts of the source galaxies constrains mass and photo-z error parameters significantly better than an estimator that includes number counts only. In particular, the constraint on the mass is 17.0 per cent if FP residuals are included, as opposed to 27.7 per cent when only number counts are included. The effective size noise for a foreground lens of mass $M_\mathrm{ H}=10^{14}\, \mathrm{M}_\odot$, with a conservative selection function in size and surface brightness applied to the source population, is σκ, eff = 0.250. We discuss the improvements to our FP model necessary to make this formalism a practical companion to shear analyses in weak-lensing surveys.

Sign in / Sign up

Export Citation Format

Share Document