Flux Ratios as a Probe of Dark Substructures in Quadruple-Image Gravitational Lenses

By R. Metcalf, HongSheng Zhao. 2001

166 citations recorded by the source corpus.

We demonstrate that the flux ratios of quadruple-image lensed quasars provide a powerful means of probing the small-scale structure of dark matter halos. A family of smooth lens models can precisely predict certain combinations of flux ratios using only the positions of the images and the lens as inputs. Using five observed lens systems, we show that real galaxies cannot be described by smooth singular isothermal ellipsoids, nor by the more general elliptical power-law potentials. Large-scale distortions from the elliptical models cannot yet be ruled out. Nevertheless, we find by comparing with simulations that the data can be accounted for by a significant (≳5%) amount of dark substructures within a projected distance of several kiloparsecs from the center of the lenses. This interpretation favors the cold dark matter model over the warm or self-interacting dark matter models.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/8e8efee37a707d64799aa01163f79b2cbf0078f8

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Citations in the corpus

Gravitational lensing (2010, background): “In [337] it was estimated that 5% of the lensing halo mass must be contained in substructures and it was argued that elliptically deformed power-law models embedded into external shear are insufficient for most lenses.”
ΛCDM-based Models for the Milky Way and M31. I. Dynamical Models (2001, background): “…known radio/optical lenses show significant variance of image flux ratios from that of smooth lens models, which has been suggested by several groups to be evidence for dark/faint clumps in the line of sight (Chiba 2002; Metcalf & Zhao 2002; Dalal & Kochanek 2002; Keeton 2002; Bradač et al. 2002).”
Dark Matter Substructure and Gamma-Ray Annihilation in the Milky Way Halo (2006, background): “Mass Fractions in Substructure and Gravitational Lensing Standard smooth gravitational lens models have difficulties in explaining the relative fluxes of multiply imaged quasars (Mao & Schneider 1998; Metcalf & Zhao 2002).”
Inference of the cold dark matter substructure mass function at z = 0.2 using strong gravitational lenses (2014, background): “Indeed, Metcalf & Madau (2001), Chiba (2002), Dalal & Kochanek (2002), Metcalf & Zhao (2002), Keeton et al. (2003) and Nierenberg et al. (2014) showed that mass substructure could be responsible for a violation of the magnification relations.”
Bayesian strong gravitational-lens modelling on adaptive grids: objective detection of mass substructure in Galaxies (2008, background): “…can be related to the presence of (dark matter) substructure around the lensing galaxy on scales smaller than the image separation (Bradačet al. 2002; Chiba 2002; Dalal & Kochanek 2002; Metcalf & Zhao 2002; Keeton et al. 2003; Kochanek & Dalal 2004; Bradač et al. 2004; Keeton et al. 2005).”
HerMES: CANDIDATE GRAVITATIONALLY LENSED GALAXIES AND LENSING STATISTICS AT SUBMILLIMETER WAVELENGTHS (2012, background): “In combination with dynamical studies, lensing mass reconstruction allows one to obtain the density profile of the dark matter in individual lensing galaxies down to ∼ 10 kpc scales (e.g. Miralda-Escude 1995; Dalal & Kochanek 2002; Metcalf & Zhao 2002; Rusin & Kochanek 2005; Treu & Koopmans 2004).”
Tests for Substructure in Gravitational Lenses (2003, background): “Previous studies of the effects of changes in the macro model show that changes in the radial structure from the standard SIEs with external shear do not provide a solution (Metcalf & Zhao 2002; Keeton et al. 2003).”
Quasar Microlensing at High Magnification and the Role of Dark Matter: Enhanced Fluctuations and Suppressed Saddle Points (2002, background): “On fairly general grounds (e.g., Gaudi & Petters 2002), these pairs of images are expected to be roughly equal in brightness, with model-dependent uncertainties on the order of 10% (Metcalf & Zhao 2002).”
Detection of a dark substructure through gravitational imaging (2009, unknown): “2002; Chiba 2002; Dalal & Kochanek 2002; Metcalf & Zhao 2002; Keeton et al. 2003; Kochanek & Dalal 2004; Bradač et al. 2004; Keeton et al. 2005; McKean et al. 2007; Chen et al. 2007; More et al. 2009).”
CLUMPY STREAMS FROM CLUMPY HALOS: DETECTING MISSING SATELLITES WITH COLD STELLAR STRUCTURES (2010, unknown): “Gravitational lensing has been suggested to be a useful tool to probe the presence of subhalos (Chiba 2002; Metcalf & Zhao 2002; Chen et al. 2003; Moustakas & Metcalf 2003; Metcalf et al. 2004; Keeton & Moustakas 2009; Riehm et al. 2009; Xu et al. 2009).”
Direct Detection of Cold Dark Matter Substructure (2001, methodology): “While we analyzed the lenses using singular isothermal ellipsoids in an external shear for the macro model, Metcalf & Zhao (2002) have shown that the flux ratios cannot be explained by a broad range of macro models.”
Luminosity function and radial distribution of Milky Way satellites in a ΛCDM Universe (2009, background): “One possibility is that they could be detected via gravitational lensing (e.g. Metcalf & Zhao 2002) since those small subhaloes will act as perturbers of the lensing signal coming from the main halo.”
Gravitational Imaging of CDM Substructure (2005, background): “Flux-ratio anomalies have already hinted at its existence, either dark or luminous (e.g. Mao & Schneider 1998; Metcalf & Madau 2001; Chiba 2002; Metcalf & Zhao 2002; Dalal & Kochanek 2002; Bradač et al. 2002; Keeton 2003).”