Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 476, Issue 1, Pages 133-150Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/sty065
Keywords
gravitational lensing: strong; galaxies: elliptical and lenticular, cD; galaxies: evolution; galaxies: kinematics and dynamics; galaxies: structure
Categories
Funding
- Science and Technology Facilities Council (STFC)
- Ernest Rutherford Fellowship
- NASA [NAS 5-26555]
- W. M. Keck Foundation
- [GO 13661]
- STFC [ST/K004182/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/K004182/1] Funding Source: researchfish
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We present models for the dark and luminous mass structure of 12 strong lensing early-type galaxies. We combine pixel-based modelling of multiband Hubble Space Telescope imaging with Jeans modelling of kinematics obtained from Keck/ESI spectra to disentangle the dark and luminous contributions to the mass. Assuming a generalised NFW (gNFW) profile for the dark matter halo and a spatially constant stellar-mass-to-light ratio Gamma(star) for the baryonic mass, we infer distributions for Gamma(star) consistent with initial mass functions (IMFs) that are heavier than the Milky Way's (with a global mean mismatch parameter relative to a Chabrier IMF mu(alpha c) = 1.80 +/- 0.14) and halo inner density slopes that span a large range but are generally cuspier than the dark-matter-only prediction (mu(gamma)' = 2.01(-0.22)(+0.19)). We investigate possible reasons for overestimating the halo slope, including the neglect of spatially varying stellar-mass-to-light ratios and/or stellar orbital anisotropy, and find that a quarter of the systems prefer radially declining stellar-mass-to-light ratio gradients, but that the overall effect on our inference on the halo slope is small. We suggest a coherent explanation of these results in the context of inside-out galaxy growth, and that the relative importance of different baryonic processes in shaping the dark halo may depend on halo environment.
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