scholarly journals Scale dependence of galaxy biasing investigated by weak gravitational lensing: An assessment using semi-analytic galaxies and simulated lensing data

2018 ◽  
Vol 613 ◽  
pp. A15 ◽  
Author(s):  
Patrick Simon ◽  
Stefan Hilbert
Keyword(s):  
Gravitational Lensing ◽  
Spatial Scales ◽  
Scale Dependence ◽  
Reconstruction Technique ◽  
Weak Gravitational Lensing ◽  
Physical Scale ◽  
The Galaxy ◽  
Galaxy Bias ◽  
The Impact ◽  
Lens Galaxies

Galaxies are biased tracers of the matter density on cosmological scales. For future tests of galaxy models, we refine and assess a method to measure galaxy biasing as a function of physical scalekwith weak gravitational lensing. This method enables us to reconstruct the galaxy bias factorb(k) as well as the galaxy-matter correlationr(k) on spatial scales between 0.01hMpc−1≲k≲ 10hMpc−1for redshift-binned lens galaxies below redshiftz≲ 0.6. In the refinement, we account for an intrinsic alignment of source ellipticities, and we correct for the magnification bias of the lens galaxies, relevant for the galaxy-galaxy lensing signal, to improve the accuracy of the reconstructedr(k). For simulated data, the reconstructions achieve an accuracy of 3–7% (68% confidence level) over the abovek-range for a survey area and a typical depth of contemporary ground-based surveys. Realistically the accuracy is, however, probably reduced to about 10–15%, mainly by systematic uncertainties in the assumed intrinsic source alignment, the fiducial cosmology, and the redshift distributions of lens and source galaxies (in that order). Furthermore, our reconstruction technique employs physical templates forb(k) andr(k) that elucidate the impact of central galaxies and the halo-occupation statistics of satellite galaxies on the scale-dependence of galaxy bias, which we discuss in the paper. In a first demonstration, we apply this method to previous measurements in the Garching-Bonn Deep Survey and give a physical interpretation of the lens population.

scholarly journals The impact of AGN feedback on galaxy intrinsic alignments in the Horizon simulations

2020 ◽  
Vol 492 (3) ◽  
pp. 4268-4282 ◽  
Author(s):  
Adam Soussana ◽  
Nora Elisa Chisari ◽  
Sandrine Codis ◽  
Ricarda S Beckmann ◽  
Yohan Dubois ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Gravitational Lensing ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Three Dimensions ◽  
High Mass ◽  
Angular Momenta ◽  
The Galaxy ◽  
The Impact ◽  
The Universe

ABSTRACT The intrinsic correlations of galaxy shapes and orientations across the large-scale structure of the Universe are a known contaminant to weak gravitational lensing. They are known to be dependent on galaxy properties, such as their mass and morphologies. The complex interplay between alignments and the physical processes that drive galaxy evolution remains vastly unexplored. We assess the sensitivity of intrinsic alignments (shapes and angular momenta) to active galactic nuclei (AGN) feedback by comparing galaxy alignment in twin runs of the cosmological hydrodynamical Horizon simulation, which do and do not include AGN feedback, respectively. We measure intrinsic alignments in three dimensions and in projection at $z$ = 0 and $z$ = 1. We find that the projected alignment signal of all galaxies with resolved shapes with respect to the density field in the simulation is robust to AGN feedback, thus giving similar predictions for contamination to weak lensing. The relative alignment of galaxy shapes around galaxy positions is however significantly impacted, especially when considering high-mass ellipsoids. Using a sample of galaxy ‘twins’ across simulations, we determine that AGN changes both the galaxy selection and their actual alignments. Finally, we measure the alignments of angular momenta of galaxies with their nearest filament. Overall, these are more significant in the presence of AGN as a result of the higher abundance of massive pressure-supported galaxies.

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.

scholarly journals Substructure and halo population of Double Cluster h and χ Persei

2019 ◽  
Vol 624 ◽  
pp. A34 ◽  
Author(s):  
Jing Zhong ◽  
Li Chen ◽  
M. B. N. Kouwenhoven ◽  
Lu Li ◽  
Zhengyi Shao ◽  
...  
Keyword(s):  
Parameter Space ◽  
Spatial Scales ◽  
Open Clusters ◽  
Halo Structure ◽  
Internal Motions ◽  
Halo Stars ◽  
Physical Scale ◽  
Cluster Cores ◽  
The Impact ◽  
Double Cluster

Context. Gaia DR2 provides an ideal dataset to study the stellar populations of open clusters at larger spatial scales because the cluster member stars can be well identified by their location in the multidimensional observational parameter space with high precision parameter measurements. Aims. In order to study the stellar population and possible substructures in the outskirts of Double Cluster h and χ Persei, we use Gaia DR2 data in a sky area of about 7.5° in radius around the Double Cluster cores. Methods. We identified member stars using various criteria, including their kinematics (namely, proper motion), individual parallaxes, and photometric properties. A total of 2186 member stars in the parameter space were identified as members. Results. Based on the spatial distribution of the member stars, we find an extended halo structure of h and χ Persei about six to eight times larger than their core radii. We report the discovery of filamentary substructures extending to about 200 pc away from the Double Cluster. The tangential velocities of these distant substructures suggest that they are more likely to be remnants of primordial structures, instead of a tidally disrupted stream from the cluster cores. Moreover, internal kinematic analysis indicates that halo stars seem to experience a dynamic stretching in the RA direction, while the impact of the core components is relatively negligible. This work also suggests that the physical scale and internal motions of young massive star clusters may be more complex than previously thought.

Weak Lensing By Individual Galaxies

1996 ◽  
Vol 173 ◽  
pp. 183-188
Author(s):  
Tereasa G. Brainerd ◽  
Roger D. Blandford ◽  
Ian Smail
Keyword(s):  
Gravitational Lensing ◽  
Angular Separation ◽  
Weak Lensing ◽  
Bright Galaxy ◽  
Weak Gravitational Lensing ◽  
Circular Velocity ◽  
Angular Extent ◽  
Individual Galaxies ◽  
Lens Galaxies

In this paper we report on an investigation of statistical weak gravitational lensing of cosmologically distant faint galaxies by foreground galaxies. The signal we seek is a distortion of the images of faint galaxies resulting in a weakly preferred tangential alignment of faint galaxies around brighter galaxies. That is, if the faint galaxies have been gravitationally lensed by the brighter systems, the major axes of their images will tend to lie perpendicular to the radius vectors joining the centroids of the faint and bright galaxies (Fig. 1). Modeling a lens galaxy as a singular isothermal sphere with circular velocity Vc, an ellipticity of ∼ 2πVc2 /c2θ is induced in the image of a source galaxy at an angular separation θ from the lens. This is of order a few percent for faint–bright galaxy pairs with separations θ ∼ 30″ where the lens is a typical bright spiral. Over 1000 pairs must be measured in order to detect such a signal in the presence of the noise associated with the intrinsic galaxy shapes. Given a sufficiently large number of pairs, it may be possible to use the variation of the induced ellipticity with θ to study the angular extent of the halos of the lens galaxies.

scholarly journals Microlensing and photon bunching: the impact of decoherence

2019 ◽  
Vol 491 (4) ◽  
pp. 5789-5792
Author(s):  
Geraint F Lewis ◽  
Peter Tuthill
Keyword(s):  
Time Delay ◽  
Gravitational Lensing ◽  
Resolving Power ◽  
Extended Source ◽  
Arrival Times ◽  
The Galaxy ◽  
Multiple Paths ◽  
Spatially Extended ◽  
Stellar Sources ◽  
The Impact

ABSTRACT Gravitational microlensing within the Galaxy offers the prospect of probing the details of distant stellar sources, as well as revealing the distribution of compact (and potentially non-luminous) masses along the line of sight. Recently, it has been suggested that additional constraints on the lensing properties can be determined through the measurement of the time delay between images through the correlation of the bunching of photon arrival times; an application of the Hanbury–Brown Twiss effect. In this paper, we revisit this analysis, examining the impact of decoherence of the radiation from a spatially extended source along the multiple paths to an observer. The result is that, for physically reasonable situations, such decoherence completely erases any correlation that could otherwise be used to measure the gravitational lensing time delay. Indeed, the divergent light paths traverse extremely long effective baselines at the lens plane, corresponding to extremes of angular resolving power well beyond those attainable with any terrestrial technologies; the drawback being that few conceivable celestial objects would be sufficiently compact with high enough surface brightness to yield usable signals.

scholarly journals Weak Gravitational Lensing by Horndeski Theory Using the Gauss-Bonnet Theorem

2020 ◽  
Author(s):  
Wajiha Javed ◽  
Jameela Abbas ◽  
Yashmitha Kumaran ◽  
Ali Övgün
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Field Approximation ◽  
Weak Field ◽  
Plasma Medium ◽  
Weak Gravitational Lensing ◽  
The Deflection Angle ◽  
Bonnet Theorem ◽  
The Impact

The main goal of this paper is to study the weak gravitational lensing by Horndeski black hole in weak field approximation. In order to do so, we exploit the Gibbons-Werner method to the optical geometry of Horndeski black hole and implement the Gauss-Bonnet theorem to accomplish the deflection angle of light in weak field region. Furthermore, we have endeavored to extend the scale of our work by comprising the impact of plasma medium on the deflection angle as properly. Later, the graphical influence of the deflection angle of photon on Horndeski black hole in plasma and non-plasma medium is examined.

scholarly journals Effect of the Hair on Deflection Angle by Asymptotically Flat Black Holes in Einstein-Maxwell-Dilaton Theory

2019 ◽  
Author(s):  
Wajiha Javed ◽  
Jameela Abbas ◽  
Ali Övgün
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Maxwell Theory ◽  
Weak Gravitational Lensing ◽  
Asymptotically Flat ◽  
The Deflection Angle ◽  
The Impact ◽  
Hairy Black Hole

In this paper, we are interested in a model of exact asymptotically flat charged hairy black holes in the background of dilaton potential. We study the weak gravitational lensing in the spacetime of hairy black hole in Einstein-Maxwell theory with a non-minimally coupled dilaton and its non-trivial potential. In doing so, we use the optical geometry of the flat charged hairy black hole for some range of parameter $\gamma$. For this purpose, by using Gauss-Bonnet theorem, we obtain the deflection angle of photon in a spherically symmetric and asymptotically flat spacetime. Moreover, we also investigate the impact of plasma medium on weak gravitational lensing by asymptotically flat charged hairy black hole with a  dilaton potential. Our analytically analyses show the effect of the hair on the deflection angle in weak field limits.

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