Compound Gravitational Lensing as a Probe of Dark Matter Substructure within Galaxy Halos

By R. Metcalf, P. Madau. 2001

292 citations recorded by the source corpus.

We show how observations of multiply imaged quasars at high redshift can be used as a probe of dark matter clumps (subhalos with masses ≲109 M☉) within the virialized extent of more massive lensing halos. A large abundance of such satellites is predicted by numerical simulations of galaxy formation in cold dark matter (CDM) cosmologies. Small-scale structure within galaxy halos affects the flux ratios of the images without appreciably changing their positions. We use numerical simulations to quantify the effect of dark matter substructure on the distribution of magnifications and find that the magnification ratio of a typical image pair will deviate significantly from the value predicted by a smooth lensing potential if, near the Einstein radius, only a few percent of the lens surface density is contained in subhalos. The angular size of the continuum source dictates the range of subclump masses that can have a detectable effect: to avoid confusion with gravitational microlensing caused by stars in the lens galaxy, the background source must be larger than the optical-continuum-emitting region of a QSO. We also find that substructure will cause distortions to images on milliarcsecond scales and bias the distribution of QSO magnification ratios—two other possible methods of detection.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/1430fcfd36507d807130b417262cf8c36a1dfba0

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Citations in the corpus

Halo Substructure and the Power Spectrum (2002, background): “Of particular interest for obtaining measurements in distant galaxies are studies that aim to detect substructure via flux ratio anomalies in strong gravitational lenses (Moore et al. 1999a; Metcalf & Madau 2001; Metcalf & Zhao 2002; Bradač et al. 2002).”
Dark matter annihilation in the halo of the Milky Way (2003, result): “They are consistent with the findings of other authors (Klypin et al. 1999; Moore et al. 1999; Font et al. 2001; Metcalf & Madau 2001; Helmi, White & Springel 2002), although the range of published values (1.75 to 1.9) suggests that the close agreement C© 2003 RAS, MNRAS 345, 1313–1322 Downloaded…”
Tests for Substructure in Gravitational Lenses (2003, background): “…make the flux statistics of the brightest saddle point (as predicted by smooth potentials) different from those of either the brightest minimum (A) or the two fainter images (the minimum B and the saddle point C; Metcalf & Madau 2001; Keeton 2003; Schechter & Wambsganss 2002; Bradac et al. 2002).”
Orbital parameters of infalling dark matter substructures (2004, result): “Observational tests for its presence, though not yet conclusive, are in good agreement with the theoretical expectations (Metcalf & Madau 2001; Chiba 2002; Dalal & Kochanek 2002).”
Gravitational Lens Time Delays: A Statistical Assessment of Lens Model Dependences and Implications for the Global Hubble Constant (2006, methodology): “Anomalous flux ratios observed in many gravitational lens systems indicate that substructures are indeed present (Metcalf & Madau 2001; Chiba 2002; Dalal & Kochanek 2002; Bradač et al. 2002; Keeton et al. 2005; Kochanek & Dalal 2004; Metcalf et al. 2004; Chiba et al. 2005).”
Flux Ratios as a Probe of Dark Substructures in Quadruple-Image Gravitational Lenses (2001, methodology): “Metcalf & Madau (2001) showed that if the CDM model is correct and these substructures exist within the strong gravitational lenses responsible for multiply imaged quasars, they will have a dramatic effect on the image magnifications—compound gravitational lensing.”
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.”
Galaxy Masses: A Review (2013, result): “The first lensing studies of this topic, based on the so-called flux-ratio anomalies Mao & Schneider (1998); Metcalf & Madau (2001) of radio-loud lenses quasars from the CLASS survey (Dalal & Kochanek 2002) indicated a level of substructure broadly consistent with the expectations of CDM cosmology.”
Time delay cosmography (2016, background): “This effort seems well motivated, not only by the ultimate goal of improving our understanding of the fundamental constituents of the universe, but also by the opportunity to use lensed quasars to learn about the astrophysics of dark matter (Metcalf and Madau 2001; Dalal and Kochanek 2002; Metcalf 2”
Probing Dark Matter Substructure in Lens Galaxies (2001, background): “…lens model is complicated by basically an infinite number 1Since this paper being submitted, a new investigation has also appeared in astro-ph (Metcalf & Madau 2001) which explores similar issues and reaches compatible conclusions. of degeneracies, where different models yield different image…”
DETECTION OF LENSING SUBSTRUCTURE USING ALMA OBSERVATIONS OF THE DUSTY GALAXY SDP.81 (2016, background): “…gravitational lensing is sensitive to galactic substructure, even if that substructure is completely devoid of baryons (e.g., Mao & Schneider 1998; Metcalf & Madau 2001; Dalal & Kochanek 2002; Moustakas & Metcalf 2003; Kochanek & Dalal 2004; Koopmans 2005; Keeton et al. 2006; Vegetti & Koopmans…”
Disruption of Dark Matter Substructure: Fact or Fiction? (2017, methodology): “…different dark matter models are gravitational lensing, either by using timedelays (e.g., Keeton & Moustakas 2009), flux-ratio anomalies (e.g., Metcalf & Madau 2001; Bradač et al. 2002; Dalal & Kochanek 2002), or perturbations of the surface brightness distribution of lensed arcs and Einstein…”
A Determination of H0 with the CLASS Gravitational Lens B1608+656. III. A Significant Improvement in the Precision of the Time Delay Measurements (2002, background): “Recently, several papers have suggested that the substructure is due to the small dark matter satellite halos expected from CDM structure-formation models (e.g., Metcalf & Madau 2001; Chiba 2002; Dalal &Kochanek 2002).”
Quasar Microlensing at High Magnification and the Role of Dark Matter: Enhanced Fluctuations and Suppressed Saddle Points (2002, background): “Millilensing andMini-Halos The present work is fundamentally similar to (although on the surface quite different from) that of Metcalf & Madau (2001), Chiba (2002), and Dalal & Kochanek (2002) who argue that the brightness ratio anomalies observed in quadruple systems are due to the presence of…”