scholarly journals Shape noise and dispersion in precision weak lensing

2021 ◽  
Vol 502 (4) ◽  
pp. 5612-5621
Author(s):  
Pol Gurri ◽  
Edward N Taylor ◽  
Christopher J Fluke
Keyword(s):  
Measurement Errors ◽  
Low Noise ◽  
Weak Lensing ◽  
High Dispersion ◽  
Mass Relation ◽  
Underlying Assumption ◽  
Two Factors ◽  
Velocity Information ◽  
Current Sample ◽  
Average Dispersion

ABSTRACT We analyse the first measurements from precision weak lensing (PWL): a new methodology for measuring individual galaxy–galaxy weak lensing through velocity information. Our goal is to understand the observed shear distribution from PWL, which is broader than can be explained by the statistical measurement errors. We identify two possible sources of scatter to explain the observed distribution: a shape noise term associated with the underlying assumption of circular stable rotation, and an astrophysical signal consistent with a lognormal dispersion around the stellar-to-halo mass relation (SHMR). We have modelled the observed distribution as the combination of these two factors and quantified their most likely values given our data. For the current sample, we measure an effective shape noise of σγ = 0.024 ± 0.007, highlighting the low noise impact of the method and positioning PWL as ∼10 times more precise than conventional weak lensing. We also measure an average dispersion in shears of $\xi _\gamma = 0.53^{+0.26}_{-0.28}$ dex over the range of 8.5 < log M⋆ < 11. This measurement is higher than expected, which is suggestive of a relatively high dispersion in halo mass and/or profile.

scholarly journals The weak lensing radial acceleration relation: Constraining modified gravity and cold dark matter theories with KiDS-1000

2021 ◽  
Vol 650 ◽  
pp. A113
Author(s):  
Margot M. Brouwer ◽  
Kyle A. Oman ◽  
Edwin A. Valentijn ◽  
Maciej Bilicki ◽  
Catherine Heymans ◽  
...  
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Modified Gravity ◽  
Cold Dark Matter ◽  
Weak Lensing ◽  
Mass Relation ◽  
Gravitational Acceleration ◽  
Radial Acceleration ◽  
The Galaxy ◽  
The Difference

We present measurements of the radial gravitational acceleration around isolated galaxies, comparing the expected gravitational acceleration given the baryonic matter (gbar) with the observed gravitational acceleration (gobs), using weak lensing measurements from the fourth data release of the Kilo-Degree Survey (KiDS-1000). These measurements extend the radial acceleration relation (RAR), traditionally measured using galaxy rotation curves, by 2 decades in gobs into the low-acceleration regime beyond the outskirts of the observable galaxy. We compare our RAR measurements to the predictions of two modified gravity (MG) theories: modified Newtonian dynamics and Verlinde’s emergent gravity (EG). We find that the measured relation between gobs and gbar agrees well with the MG predictions. In addition, we find a difference of at least 6σ between the RARs of early- and late-type galaxies (split by Sérsic index and u − r colour) with the same stellar mass. Current MG theories involve a gravity modification that is independent of other galaxy properties, which would be unable to explain this behaviour, although the EG theory is still limited to spherically symmetric static mass models. The difference might be explained if only the early-type galaxies have significant (Mgas ≈ M⋆) circumgalactic gaseous haloes. The observed behaviour is also expected in Λ-cold dark matter (ΛCDM) models where the galaxy-to-halo mass relation depends on the galaxy formation history. We find that MICE, a ΛCDM simulation with hybrid halo occupation distribution modelling and abundance matching, reproduces the observed RAR but significantly differs from BAHAMAS, a hydrodynamical cosmological galaxy formation simulation. Our results are sensitive to the amount of circumgalactic gas; current observational constraints indicate that the resulting corrections are likely moderate. Measurements of the lensing RAR with future cosmological surveys (such as Euclid) will be able to further distinguish between MG and ΛCDM models if systematic uncertainties in the baryonic mass distribution around galaxies are reduced.

scholarly journals The stellar-to-halo mass relation of GAMA galaxies from 100 deg2of KiDS weak lensing data

2016 ◽  
Vol 459 (3) ◽  
pp. 3251-3270 ◽  
Author(s):  
Edo van Uitert ◽  
Marcello Cacciato ◽  
Henk Hoekstra ◽  
Margot Brouwer ◽  
Cristóbal Sifón ◽  
...  
Keyword(s):  
Weak Lensing ◽  
Mass Relation

scholarly journals Keck HIRES spectroscopy of SkyMapper commissioning survey candidate extremely metal-poor stars

2019 ◽  
Vol 485 (4) ◽  
pp. 5153-5167 ◽  
Author(s):  
A F Marino ◽  
G S Da Costa ◽  
A R Casey ◽  
M Asplund ◽  
M S Bessell ◽  
...  
Keyword(s):  
High Resolution ◽  
Galactic Halo ◽  
High Dispersion ◽  
Chemical Abundances ◽  
Data Survey ◽  
Current Sample

Abstract We present results from the analysis of high-resolution spectra obtained with the Keck HIRES spectrograph for a sample of 17 candidate extremely metal-poor (EMP) stars originally selected from commissioning data obtained with the SkyMapper telescope. Fourteen of the stars have not been observed previously at high dispersion. Three have [Fe/H] ≤ −3.0, while the remainder, with two more metal-rich exceptions, have −3.0 ≤ [Fe/H] ≤ −2.0 dex. Apart from Fe, we also derive abundances for the elements C, N, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, and Zn, and for n-capture elements Sr, Ba, and Eu. None of the current sample of stars is found to be carbon-rich. In general, our chemical abundances follow previous trends found in the literature, although we note that two of the most metal-poor stars show very low [Ba/Fe] (∼−1.7) coupled with low [Sr/Ba] (∼−0.3). Such stars are relatively rare in the Galactic halo. One further star, and possibly two others, meet the criteria for classification as a r-I star. This study, together with that of Jacobson et al. (2015), completes the outcomes of the SkyMapper commissioning data survey for EMP stars.

scholarly journals Cluster–galaxy weak lensing

2020 ◽  
Vol 28 (1) ◽  
Author(s):  
Keiichi Umetsu
Keyword(s):  
Galaxy Clusters ◽  
Gravitational Lensing ◽  
First Principles ◽  
Weak Lensing ◽  
Mass Relation ◽  
Matter Distribution ◽  
Cluster Galaxy ◽  
Weak Gravitational Lensing ◽  
Mass Calibration ◽  
Theoretical Foundations

AbstractWeak gravitational lensing of background galaxies provides a direct probe of the projected matter distribution in and around galaxy clusters. Here, we present a self-contained pedagogical review of cluster–galaxy weak lensing, covering a range of topics relevant to its cosmological and astrophysical applications. We begin by reviewing the theoretical foundations of gravitational lensing from first principles, with a special attention to the basics and advanced techniques of weak gravitational lensing. We summarize and discuss key findings from recent cluster–galaxy weak-lensing studies on both observational and theoretical grounds, with a focus on cluster mass profiles, the concentration–mass relation, the splashback radius, and implications from extensive mass-calibration efforts for cluster cosmology.

scholarly journals Sample Size Effects on Measuring Grade and Dollar Value of Farmers' Stock Peanuts1

1992 ◽  
Vol 19 (2) ◽  
pp. 121-126 ◽  
Author(s):  
F. E. Dowell
Keyword(s):  
Sample Size ◽  
Size Effects ◽  
Measurement Errors ◽  
Human Error ◽  
Total Error ◽  
Foreign Material ◽  
Human Errors ◽  
Sample Variances ◽  
Current Sample ◽  
Multiple Samples

Abstract Multiple samples of two sizes from 40 trailers of farmers' stock peanuts were inspected to determine sample size effects on measuring grade factors and dollar value. Grade factors and dollar value were measured using the current sample size (IX) and in a sample double the current size (2X). The 2X sample variances for determining sound mature kernels, sound splits, other kernels, damaged kernels, foreign material, loose shelled kernels, and load value were significantly lower than the IX sample variances in only 8 or less of the 40 trailers. Average dollar values indicate measurement errors caused by equipment and human errors when cleaning samples, determining kernel size, and determining damaged kernels may be increasing as sample size increases. At least 24% of the total error can be attributed to equipment and human error. The grade factors with the smallest percentage of total error attributable to equipment and human error will benefit most by increasing sample size. Thus, dollar value, sound mature kernel, foreign material and damaged kernel measurements will benefit most by increasing sample size; whereas, loose shelled kernels, sound split and other kernel measurements will benefit most by improving equipment and procedures.

scholarly journals Abundant proteins contribute strongly to noise in the growth rate of optimally growing bacteria

2020 ◽  
Author(s):  
L.H.J. Krah ◽  
R. Hermsen
Keyword(s):  
Growth Rate ◽  
Low Noise ◽  
Cellular Growth ◽  
Bacterial Cells ◽  
Noise Levels ◽  
Physiological Variables ◽  
Stochastic Fluctuations ◽  
Two Factors ◽  
The Mean ◽  
Related Proteins

AbstractIn bacterial cells, protein expression is a highly stochastic process. At the same time, physiological variables such as the cellular growth rate also fluctuate significantly. A common intuition is that, due to their relatively high noise amplitudes, proteins with a low mean expression level are the most important causes of these fluctuations on a larger, physiological scale. Noise in highly expressed proteins, whose stochastic fluctuations are relatively small, is often ignored. In this work, we challenge this intuition by developing a theory that predicts the contribution of a protein’s expression noise to the noise in the instantaneous, cellular growth rate. Using mathematical analysis, we decomposed the contribution of each protein into two factors: the noise amplitude of the protein, and the sensitivity of the growth rate to fluctuations in that protein’s concentration. Next, we incorporated evolution, which has shaped the mean abundances of growth-related proteins to optimise the growth rate, causing protein abundances, but also cellular sensitivities to be non-random. We show that in cells that grow optimally fast, the growth rate is most sensitive to fluctuations in highly abundant proteins. This causes such proteins to overall contribute strongly to the noise in the growth-rate, despite their low noise levels. The results are confirmed in a stochastic toy model of cellular growth.

scholarly journals Weak lensing reveals a tight connection between dark matter halo mass and the distribution of stellar mass in massive galaxies

2019 ◽  
Vol 492 (3) ◽  
pp. 3685-3707 ◽  
Author(s):  
Song Huang ◽  
Alexie Leauthaud ◽  
Andrew Hearin ◽  
Peter Behroozi ◽  
Christopher Bradshaw ◽  
...  
Keyword(s):  
Dark Matter ◽  
Stellar Mass ◽  
Ex Situ ◽  
Dark Matter Halo ◽  
High Mass ◽  
Weak Lensing ◽  
Mass Relation ◽  
Massive Galaxies ◽  
Mass Distributions ◽  
Tight Connection

ABSTRACT Using deep images from the Hyper Suprime-Cam (HSC) survey and taking advantage of its unprecedented weak lensing capabilities, we reveal a remarkably tight connection between the stellar mass distribution of massive central galaxies and their host dark matter halo mass. Massive galaxies with more extended stellar mass distributions tend to live in more massive dark matter haloes. We explain this connection with a phenomenological model that assumes, (1) a tight relation between the halo mass and the total stellar content in the halo, (2) that the fraction of in situ and ex situ mass at r <10 kpc depends on halo mass. This model provides an excellent description of the stellar mass functions (SMFs) of total stellar mass ($M_{\star }^{\mathrm{max}}$) and stellar mass within inner 10 kpc ($M_{\star }^{10}$) and also reproduces the HSC weak lensing signals of massive galaxies with different stellar mass distributions. The best-fitting model shows that halo mass varies significantly at fixed total stellar mass (as much as 0.4 dex) with a clear dependence on $M_{\star }^{10}$. Our two-parameter $M_{\star }^{\mathrm{max}}$–$M_{\star }^{10}$ description provides a more accurate picture of the galaxy–halo connection at the high-mass end than the simple stellar–halo mass relation (SHMR) and opens a new window to connect the assembly history of haloes with those of central galaxies. The model also predicts that the ex situ component dominates the mass profiles of galaxies at r < 10 kpc for log M⋆ ≥ 11.7. The code used for this paper is available online https://github.com/dr-guangtou/asap

A Psychometric Analysis of the Epworth Sleepiness Scale

2007 ◽  
Vol 15 (3) ◽  
pp. 177-188 ◽  
Author(s):  
Karen Heaton ◽  
Debra Anderson
Keyword(s):  
Factor Analysis ◽  
Epworth Sleepiness Scale ◽  
Sleep Problems ◽  
Cost Effective ◽  
Time Cost ◽  
Cronbach’S Alpha ◽  
Cronbach's Alpha ◽  
Two Factors ◽  
Effective Instrument ◽  
Current Sample

Psychometric performance of the Epworth Sleepiness Scale (ESS) has not been evaluated in groups of workers. This study evaluated its use in a sample of 843 long-haul truckers. Interitem correlations and Cronbach’s alpha were conducted. Correlation of the ESS with the sleep problems subscale of the Trucker Strain Monitor (TSM) was performed. Dimensionality was evaluated using factor analysis. Cronbach’s alpha (.79) was strong. Interitem correlations were significant. A weak but significant correlation between the ESS and TSM sleep problems subscale (r = .18, p = < .001) was shown. Factor analysis yielded two factors that explained 56.2% of scale variance. The ESS performed well in the current sample. It is an inexpensive, time/cost-effective instrument. It should be considered for use in studies of workers in naturalistic settings.

scholarly journals KiDS+GAMA: The weak lensing calibrated stellar-to-halo mass relation of central and satellite galaxies

2020 ◽  
Vol 642 ◽  
pp. A83 ◽  
Author(s):  
Andrej Dvornik ◽  
Henk Hoekstra ◽  
Konrad Kuijken ◽  
Angus H. Wright ◽  
Marika Asgari ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Stellar Mass ◽  
Weak Lensing ◽  
Mass Relation ◽  
Overlapping Data ◽  
The Galaxy ◽  
Galaxy Halo ◽  
Satellite Galaxies ◽  
Mass Assembly ◽  
Halo Masses

We simultaneously present constraints on the stellar-to-halo mass relation for central and satellite galaxies through a weak lensing analysis of spectroscopically classified galaxies. Using overlapping data from the fourth data release of the Kilo-Degree Survey (KiDS), and the Galaxy And Mass Assembly survey (GAMA), we find that satellite galaxies are hosted by halo masses that are 0.53 ± 0.39 dex (68% confidence, 3σ detection) smaller than those of central galaxies of the same stellar mass (for a stellar mass of log(M⋆/M⊙) = 10.6). This is consistent with galaxy formation models, whereby infalling satellite galaxies are preferentially stripped of their dark matter. We find consistent results with similar uncertainties when comparing constraints from a standard azimuthally averaged galaxy-galaxy lensing analysis and a two-dimensional likelihood analysis of the full shear field. As the latter approach is somewhat biased due to the lens incompleteness and as it does not provide any improvement to the precision when applied to actual data, we conclude that stacked tangential shear measurements are best-suited for studies of the galaxy-halo connection.

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