Accurate Measurement of the Lensing Magnification by BOSS CMASS Galaxies and Its Implications for Cosmology and Dark Matter

Abstract

Magnification serves as an independent and complementary gravitational lensing measurement to shear. We develop a novel method to achieve an accurate and robust magnification measurement around BOSS CMASS galaxies across physical scales of 0.016 h ^−1 Mpc 70 h ^−1 kpc, our magnification measurements are in good agreement with both WMAP and Planck cosmologies, resulting in an estimation of the matter fluctuation amplitude of S _8 = 0.816 ± 0.024. However, at r _p < 70 h ^−1 kpc, we observe an excess magnification signal, which is higher than the DMO model in Planck cosmology at 2.8 σ and would be exacerbated if significant baryon feedback is included. Implications of the potential small scale discrepancy for the nature of dark matter and for the processes governing galaxy formation are discussed.

Keywords

• Gravitational lensing
• Dark matter
• Observational cosmology
• Intergalactic dust clouds