1801.01883
Evidence for radial variations in the stellar mass-to-light ratio of massive galaxies from weak and strong lensing
Sonnenfeld, Leauthaud, et al
The IMF for massive galaxies can be constrained by combining stellar dynamics with strong gravitational lensing. However, this method is limited by degeneracies between the density profile of DM and the stellar mass-to-light ratio. In this work, reduce this degeneracy by combining WL together with SL and stellar kinematics. The analysis is based on two galaxy samples: 45 SL from the SLACS survey and 1700 massive quiescent galaxies from the SDSS main spectroscopic sample with WL measurements from the HSC survey. Use a Bayesian hierarchical approach to jointly model all 3 observables. Fit the data with models of varying complexity and show that model with a radial gradient in the stellar mass-to-light ratio is required to simultaneously describe both galaxy samples. Models with no gradient result in too small dark matter masses when fitted to the SL sample, at odds with WL constraints. The measurements are unable to determine whether M*/L gradients are due to variations in stellar population parameters at fixed IMF, or to gradients in the IMF itself. The inclusion of M*/L gradients decreases dramatically the inferred IMF normalization, compared to previous lensing-based studies. The main effect of strong lensing selection is to shift the stellar mass distribution towards the high mass end, while the halo mass and stellar IMF distribution at fixed stellar mass are not significantly affected.
1801.01886
Weak lensing peaks in simulated light-cones: Investigating the coupling between dark matter and dark energy
Giocoli, et al
In this paper, study the statistical properties of WL peaks in light-cones generated from numerical simulations. Focus on interacting DE cosmological models, characterized by a coupling term between DE and DM which allows studies of how such an interaction affects a particular second-order WL statistics. Cosmological models characterized by a a larger population of massive clusters tend to also have more numerous high signal-to-noise peaks; however structural properties like e.g. the halo concentration play an important role: models characterized by the same number of haloes possess more WL peaks if their haloes are more concentrated. The various cosmological models exhibit large differences in peaks for high values of the S/N ratio, due to intervening massive haloes along the LoS, demonstrating a clear connection between peaks in the convergence field and galaxy clusters with M200>=1e14 Msun/h. The most extreme model under investigation shows a difference of about 20% with respect to the reference LCDM model and a clearly different behavior with respect to the LCDM model with the same power spectrum normalization, proving that different expansion histories and growth rates produce a clear signature on peak properties. The analysis underscores the point that WL peak statistics represent an important tool for disentangling DE models by accurately tracing the structure formation processes as a function of the comic time. Stress its complementary to cosmic shear measurements.
Evidence for radial variations in the stellar mass-to-light ratio of massive galaxies from weak and strong lensing
Sonnenfeld, Leauthaud, et al
The IMF for massive galaxies can be constrained by combining stellar dynamics with strong gravitational lensing. However, this method is limited by degeneracies between the density profile of DM and the stellar mass-to-light ratio. In this work, reduce this degeneracy by combining WL together with SL and stellar kinematics. The analysis is based on two galaxy samples: 45 SL from the SLACS survey and 1700 massive quiescent galaxies from the SDSS main spectroscopic sample with WL measurements from the HSC survey. Use a Bayesian hierarchical approach to jointly model all 3 observables. Fit the data with models of varying complexity and show that model with a radial gradient in the stellar mass-to-light ratio is required to simultaneously describe both galaxy samples. Models with no gradient result in too small dark matter masses when fitted to the SL sample, at odds with WL constraints. The measurements are unable to determine whether M*/L gradients are due to variations in stellar population parameters at fixed IMF, or to gradients in the IMF itself. The inclusion of M*/L gradients decreases dramatically the inferred IMF normalization, compared to previous lensing-based studies. The main effect of strong lensing selection is to shift the stellar mass distribution towards the high mass end, while the halo mass and stellar IMF distribution at fixed stellar mass are not significantly affected.
1801.01886
Weak lensing peaks in simulated light-cones: Investigating the coupling between dark matter and dark energy
Giocoli, et al
In this paper, study the statistical properties of WL peaks in light-cones generated from numerical simulations. Focus on interacting DE cosmological models, characterized by a coupling term between DE and DM which allows studies of how such an interaction affects a particular second-order WL statistics. Cosmological models characterized by a a larger population of massive clusters tend to also have more numerous high signal-to-noise peaks; however structural properties like e.g. the halo concentration play an important role: models characterized by the same number of haloes possess more WL peaks if their haloes are more concentrated. The various cosmological models exhibit large differences in peaks for high values of the S/N ratio, due to intervening massive haloes along the LoS, demonstrating a clear connection between peaks in the convergence field and galaxy clusters with M200>=1e14 Msun/h. The most extreme model under investigation shows a difference of about 20% with respect to the reference LCDM model and a clearly different behavior with respect to the LCDM model with the same power spectrum normalization, proving that different expansion histories and growth rates produce a clear signature on peak properties. The analysis underscores the point that WL peak statistics represent an important tool for disentangling DE models by accurately tracing the structure formation processes as a function of the comic time. Stress its complementary to cosmic shear measurements.
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