arXiv subjects

Lindsay King

Publications and source records attributed to Lindsay King.

22 records · Page 2Linked to original sources

arXiv2001

Weak-Lensing Halo Numbers and Dark-Matter Profiles

Integral measures of weak gravitational lensing by dark-matter haloes, like the aperture mass, are sensitive to different physical halo properties dependent on the halo mass density profile. For isothermal profiles, the relation between aperture mass and virial mass is steeper than for haloes with the universal NFW profile. Consequently, the halo mass range probed by the aperture mass is much wider for NFW than for isothermal haloes. We use recent modifications to the Press-Schechter mass function in CDM models normalised to the local abundance of rich clusters, to predict the properties of the halo sample expected to be accessible with the aperture mass technique. While ~10 haloes should be detected per square degree if the haloes have NFW profiles, their number density is lower by approximately an order of magnitude if they have isothermal profiles. These results depend only very mildly on the cosmological background model. We conclude that counts of haloes with a significant weak-lensing signal are a powerful discriminator between different dark-matter profiles.

astro-ph↗

arXiv2000

Cluster Mass Profiles from Weak Lensing II

In Schneider, King & Erben (2000) we developed likelihood techniques to compare the constraints on cluster mass profiles that can be obtained using the shear and magnification information. This work considered circularly symmetric power-law models for clusters at fairly low redshifts where the redshift distribution of source galaxies could be neglected. Here this treatment is extended to encompass NFW profiles which are a good description of clusters from cosmological N-body simulations, and NFW clusters at higher redshifts where the influence of various scenarios for the knowledge of the redshift distribution are examined. Since in reality the overwhelming majority of clusters have ellipsoidal rather than spherical profiles, the singular isothermal ellipsoid (SIE) is investigated. We also briefly consider the impact of substructure on such a likelihood analysis. In general, we find that the shear information provides a better constraint on the NFW profile under consideration, so this becomes the focus of what follows. The ability to differentiate between the NFW and power-law profiles strongly depends on the size of the data field, and on the number density of galaxies for which an ellipticity can be measured. For higher redshift NFW profiles, there is very little reduction (~1.5%) in the dispersion of parameter estimates when spectroscopic redshifts, as opposed to photometric redshift estimates, are available for the galaxies used in the lensing analysis.

astro-ph↗

arXiv1999

Cluster mass profiles from weak lensing: shear vs. magnification information

A massive foreground cluster lens changes the shapes (shear effect) and number density (magnification effect) of the faint background galaxy population. In this paper we investigate how the shear, magnification and combined information can be used to constrain cluster mass profiles in the weak lensing regime. We develop maximum likelihood techniques to make quantitative predictions for each of the methods. Our analytic results are checked against Monte Carlo simulations. In general, we find that the shear method is superior to the magnification method. However, the magnification information complements the shear information if the former has accurate external calibration. For the magnification method, we discuss the effects of random and systematic uncertainties in the background galaxy counts.

astro-ph↗

arXiv1995

Spectroscopic Evidence That the Extreme Properties of IRAS F10214+4724 are due to Gravitational Lensing

The extreme bolometric luminosity of IRAS F10214+4724, and in particular the huge mass in molecular gas inferred from the CO line fluxes have led to suggestions that this is a giant galaxy in the process of formation. An arc-like structure and the closeness of a second object suggest, however, that gravitational lensing may be responsible for its anomalously high luminosity and mass. In this paper, we use an optical spectrum taken in conditions of 0.7-arcsec seeing to provide further evidence that F10214+4724 is a gravitationally lensed system. We measure tentative redshifts of 0.896 and 0.899 for galaxies projected $\approx 1$ and $\approx 3$ arcsec from IRAS F10214+4724 respectively. Identifying the former as the lensing galaxy we obtain a mass:light ratio consistent with those derived for other lenses, and find that its luminosity is consistent with the velocity dispersion deduced from the radius of the Einstein ring. If lensed, our models suggest magnification by a factor $\sim 10$, and hence an intrinsic bolometric luminosity for F10214+4724 similar to local ULIRGs.

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