Galaxies Close to the Line of Sight to two z=1 Quasars — Implications for Galactic Halos and Gravitational Lensing

1995 ◽  
pp. 287-288
Author(s):  
Josef W. Fried
Keyword(s):  
Gravitational Lensing ◽  
Line Of Sight ◽  
Galactic Halos

scholarly journals Mapping dark matter and finding filaments: calibration of lensing analysis techniques on simulated data

2020 ◽  
Vol 496 (3) ◽  
pp. 3973-3990
Author(s):  
Sut-Ieng Tam ◽  
Richard Massey ◽  
Mathilde Jauzac ◽  
Andrew Robertson
Keyword(s):  
Gravitational Lensing ◽  
Simulated Data ◽  
Line Of Sight ◽  
Radial Density ◽  
Density Profiles ◽  
Analysis Techniques ◽  
Scientific Goal ◽  
Mass Mapping ◽  
Mapping Techniques ◽  
Suppress Noise

ABSTRACT We quantify the performance of mass mapping techniques on mock imaging and gravitational lensing data of galaxy clusters. The optimum method depends upon the scientific goal. We assess measurements of clusters’ radial density profiles, departures from sphericity, and their filamentary attachment to the cosmic web. We find that mass maps produced by direct (KS93) inversion of shear measurements are unbiased, and that their noise can be suppressed via filtering with mrlens. Forward-fitting techniques, such as lenstool, suppress noise further, but at a cost of biased ellipticity in the cluster core and overestimation of mass at large radii. Interestingly, current searches for filaments are noise-limited by the intrinsic shapes of weakly lensed galaxies, rather than by the projection of line-of-sight structures. Therefore, space-based or balloon-based imaging surveys that resolve a high density of lensed galaxies could soon detect one or two filaments around most clusters.

scholarly journals MACS J0416.1–2403: Impact of line-of-sight structures on strong gravitational lensing modelling of galaxy clusters

2018 ◽  
Vol 614 ◽  
pp. A8 ◽  
Author(s):  
G. Chirivì ◽  
S. H. Suyu ◽  
C. Grillo ◽  
A. Halkola ◽  
I. Balestra ◽  
...  
Keyword(s):  
Galaxy Clusters ◽  
Gravitational Lensing ◽  
Line Of Sight ◽  
Mass Distributions ◽  
Strong Gravitational Lensing ◽  
Cluster Mass ◽  
Critical Curves ◽  
Single Lens ◽  
Best Fitting ◽  
Modelling Techniques

Exploiting the powerful tool of strong gravitational lensing by galaxy clusters to study the highest-redshift Universe and cluster mass distributions relies on precise lens mass modelling. In this work, we aim to present the first attempt at modelling line-of-sight (LOS) mass distribution in addition to that of the cluster, extending previous modelling techniques that assume mass distributions to be on a single lens plane. We have focussed on the Hubble Frontier Field cluster MACS J0416.1–2403, and our multi-plane model reproduces the observed image positions with a rms offset of ~0.′′53. Starting from this best-fitting model, we simulated a mock cluster that resembles MACS J0416.1–2403 in order to explore the effects of LOS structures on cluster mass modelling. By systematically analysing the mock cluster under different model assumptions, we find that neglecting the lensing environment has a significant impact on the reconstruction of image positions (rms ~0.′′3); accounting for LOS galaxies as if they were at the cluster redshift can partially reduce this offset. Moreover, foreground galaxies are more important to include into the model than the background ones. While the magnification factor of the lensed multiple images are recovered within ~10% for ~95% of them, those ~5% that lie near critical curves can be significantly affected by the exclusion of the lensing environment in the models. In addition, LOS galaxies cannot explain the apparent discrepancy in the properties of massive sub-halos between MACS J0416.1–2403 and N-body simulated clusters. Since our model of MACS J0416.1–2403 with LOS galaxies only reduced modestly the rms offset in the image positions, we conclude that additional complexities would be needed in future models of MACS J0416.1–2403.

scholarly journals Testing Gravity using Void Profiles

2014 ◽  
Vol 11 (S308) ◽  
pp. 555-560 ◽  
Author(s):  
Yan-Chuan Cai ◽  
Nelson Padilla ◽  
Baojiu Li
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Modified Gravity ◽  
Large Scale ◽  
Line Of Sight ◽  
Number Density ◽  
Density Profiles ◽  
Photometric Redshift ◽  
Redshift Survey ◽  
Near Future

AbstractWe investigate void properties inf(R)models using N-body simulations, focusing on their differences from General Relativity (GR) and their detectability. In the Hu-Sawickif(R)modified gravity (MG) models, the halo number density profiles of voids are not distinguishable from GR. In contrast, the samef(R)voids are more empty of dark matter, and their profiles are steeper. This can in principle be observed by weak gravitational lensing of voids, for which the combination of a spectroscopic redshift and a lensing photometric redshift survey over the same sky is required. Neglecting the lensing shape noise, thef(R)model parameter amplitudesfR0=10-5and 10-4may be distinguished from GR using the lensing tangential shear signal around voids by 4 and 8 σ for a volume of 1 (Gpc/h)3. The line-of-sight projection of large-scale structure is the main systematics that limits the significance of this signal for the near future wide angle and deep lensing surveys. For this reason, it is challenging to distinguishfR0=10-6from GR. We expect that this can be overcome with larger volume. The halo void abundance being smaller and the steepening of dark matter void profiles inf(R)models are unique features that can be combined to break the degeneracy betweenfR0and σ8.

scholarly journals Modeling pulse profiles in X-Ray pulsars with accretion column

2021 ◽  
Author(s):  
I. D. Markozov ◽  
Keyword(s):  
Neutron Star ◽  
Gravitational Lensing ◽  
Rotation Axis ◽  
Magnetic Axis ◽  
Line Of Sight ◽  
Schwarzschild Metric ◽  
X Ray

The pulse profiles of the radiation coming from X-ray pulsars with an accretion column were modeled. Gravitational lensing and redshift in the Schwarzschild metric, as well as the reflection of X-Ray photons from the surface of a neutron star, were taken into account. On the basis of the obtained pulse profiles an analysis of possible errors in the measurements of the luminosities of X-ray pulsars associated with the inability of the observer to correctly take into account the anisotropy in the radiation emerging from the neutron star, as well as the angles between the pulsar’s rotation axis, the magnetic axis and the line of sight, was carried out.

scholarly journals Constraints on the Dark Matter

1987 ◽  
Vol 117 ◽  
pp. 410-410
Author(s):  
B. J. Carr
Keyword(s):  
Black Holes ◽  
Dark Matter ◽  
Neutron Stars ◽  
Gravitational Lensing ◽  
White Dwarfs ◽  
Big Bang ◽  
Galactic Halos ◽  
M Dwarfs ◽  
Population Iii Stars ◽  
Population Iii

There is evidence for four types of dark matter: (1) the local d.m. in the galactic disc; (2) the d.m. associated with galactic halos; (3) the d.m. in clusters; and (4) a background closure density of d.m. required if the Universe undergoes an inflationary phase. There are three types of explanation: (1) remnants of a first generation of Population III stars, including black holes (SMOs, VMOs or MOs), neutron stars, white dwarfs, or LMOs (M-dwarfs and Jupiters); (2) elementary particle relicts of the Big Bang (inos), usefully classified - according to their mass - as hot, warm, or cold, since this determines the scale on which they can cluster; and (3) primordial black holes, formed from density perturbations or phase transitions in the early Universe. Various constraints on the d.m. candidates are indicated by the shaded regions in the Figure below. The conventional model of cosmological nucleosynthesis precludes Population III remnants providing the closure and perhaps cluster d.m., while stellar nucleosynthesis constraints preclude neutron stars from explaining anything and allow white dwarfs to provide only the local d.m. Source counts exclude M-dwarfs from providing the local or halo d.m., while gravitational lensing effects exclude SMOs larger than 108M⊙ from explaining anything and LMOs or VMOs from having the closure density. Dynamical considerations imply M<2M⊙ for the local d.m., M<106M⊙ for the halo d.m., and M<109M⊙ for the cluster d.m.; they also imply that the local d.m. cannot be inos and that the halo d.m. cannot be a hot ino. The table suggests the following conclusions: (1) no single candidate can explain all four d.m. problems; (2) the best candidate for the closure d.m. is an ino; (3) the best candidates for the local d.m. are white dwarfs or Jupiters; (4) the halo (and possibly cluster) d.m. could plausibly be black holes or Jupiters.

scholarly journals PROBING COLD DARK MATTER CUSPS BY GRAVITATIONAL LENSING

2006 ◽  
Vol 15 (12) ◽  
pp. 2059-2073 ◽  
Author(s):  
V. K. ONEMLI
Keyword(s):  
Dark Matter ◽  
Density Profile ◽  
Gravitational Lensing ◽  
Time Scale ◽  
Cold Dark Matter ◽  
Weakly Interacting Massive Particles ◽  
Indirect Detection ◽  
Galactic Halos ◽  
Ring Model ◽  
Density Perturbations

I elaborate on my prediction that an indirect detection of cold dark matter (CDM) may be possible by observing the gravitational lensing effects of the CDM cusp caustics at cosmological distances. Cusps in the distribution of CDM are plentiful once density perturbations enter the nonlinear regime. Caustic Ring Model of galactic halos provides a well-defined density profile and a geometry near the cusps of the caustic rings. I calculate the lensing effects in this model. As a point-like background source passes behind a cusp of a cosmological foreground halo, the magnification in its image may be detected by present instruments. Depending on the strength of detected effect and the time scale of brightness change, it may even be possible to discriminate between the CDM candidates: axions and weakly interacting massive particles.

scholarly journals Gravitational Lensing by Elliptical Galaxies

2005 ◽  
Vol 201 ◽  
pp. 490-491
Author(s):  
Daniel J. Mortlock ◽  
Rachel L. Webster
Keyword(s):  
Cross Section ◽  
Gravitational Lensing ◽  
Velocity Dispersion ◽  
High Redshift ◽  
Elliptical Galaxies ◽  
Line Of Sight ◽  
Density Parameter ◽  
Core Radius ◽  
The Core ◽  
Weakly Dependent

The probability that high-redshift quasars are gravitationally-lensed by intervening galaxies increases rapidly with the cosmological constant, ΩΛ0 (whilst being only weakly dependent on the density parameter, Ωm0), and the low number of lenses observed implies that ΩΛ0 ≲ 0.7 (e.g. Kochanek 1996). One of many uncertainties has been the (small) core radii of elliptical galaxies, which, at least naively, reduce their lensing cross-section. However, if ellipticals are normalised relative to their observed line-of-sight velocity dispersion, σ||, then increasing the core radius must result in an increased mass normalisation (specified by the assymptotic velocity dispersion, σ∞).

scholarly journals Line of sight depth of the Large and Small Magellanic Clouds

2008 ◽  
Vol 4 (S256) ◽  
pp. 63-68
Author(s):  
Annapurni Subramaniam ◽  
Smitha Subramaniam
Keyword(s):  
Gravitational Lensing ◽  
Magellanic Clouds ◽  
Optical Center ◽  
Line Of Sight ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Colour Distribution ◽  
Red Clump ◽  
Minor Mergers ◽  
Lyrae Stars

AbstractWe used the red clump stars from the Optical Gravitational Lensing Experiment (OGLE II) survey and the Magellanic Cloud Photometric Survey (MCPS), to estimate the line-of-sight depth. The observed dispersion in the magnitude and colour distribution of red clump stars is used to estimate the line-of-sight depth, after correcting for the contribution due to other effects. This dispersion due to depth, has a range from minimum dispersion that can be estimated, to 0.46 mag (a depth of 500 pc to 10.44 kpc), in the LMC. In the case of the SMC, the dispersion ranges from minimum dispersion to 0.35 magnitude (a depth of 665 pc to 9.53 kpc). The thickness profile of the LMC bar indicates that it is flared. The average depth in the bar region is 4.0 ± 1.4 kpc. The halo of the LMC (using RR Lyrae stars) is found to have larger depth compared to the disk/bar, which supports the presence of an inner halo for the LMC. The large depth estimated for the LMC bar and the disk suggests that the LMC might have had minor mergers. In the case of the SMC, the bar depth (4.90 ± 1.23 kpc) and the disk depth (4.23 ± 1.48 kpc) are found to be within the standard deviations. We find evidence for an increase in depth near the optical center (up to 9 kpc). On the other hand, the estimated depth for the halo (RR Lyrae stars) and disk (RC stars) for the bar region of the SMC is found to be similar. Thus, increased depth and enhanced stellar as well as H i density near the optical center suggests that the SMC may have a bulge.

scholarly journals Gravitational microlensing I: A unique astrophysical tool

2015 ◽  
Vol 24 (07) ◽  
pp. 1530020 ◽  
Author(s):  
Sohrab Rahvar
Keyword(s):  
Gravitational Lensing ◽  
Galactic Halo ◽  
Mass Function ◽  
Line Of Sight ◽  
High Magnification ◽  
Gravitational Microlensing ◽  
Single Lens ◽  
History Of ◽  
Degeneracy Problem ◽  
Remnant Mass

In this paper, we review the astrophysical application of gravitational microlensing. After introducing the history of gravitational lensing, we present the key equations and concept of microlensing. The most frequent microlensing events are single-lens events and historically it has been used for searching dark matter in the form of compact astrophysical halo objects in the Galactic halo. We discuss about the degeneracy problem in the parameters of lens and perturbation effects that can partially break the degeneracy between the lens parameters. The rest of paper is about the astrophysical applications of microlensing. One of the important applications is in the stellar physics by probing the surface of source stars in the high magnification microlensing events. The astrometric and polarimetric observations will be complimentary for probing the atmosphere and stellar spots on the surface of source stars. Finally we discuss about the future projects as space-based telescopes for parallax and astrometry observations of microlensing events. With this project, we would expect to produce a complete stellar and remnant mass function and study the structure of Galaxy in term of distribution of stars along our line of sight towards the center of galaxy.

scholarly journals Line-of-sight effects in strong gravitational lensing

2021 ◽  
Vol 2021 (08) ◽  
pp. 024
Author(s):  
Pierre Fleury ◽  
Julien Larena ◽  
Jean-Philippe Uzan
Keyword(s):  
Gravitational Lensing ◽  
Line Of Sight ◽  
Strong Gravitational Lensing
Sign in / Sign up

Export Citation Format

Share Document