Can we use Weak Lensing to Measure Total Mass Profiles of Galaxies on 20 kiloparsec Scales?

Abstract

Current constraints on dark matter density profiles from weak lensing are typically limited to radial scales greater than 50-100 kpc. In this paper, we explore the possibility of probing the very inner regions of galaxy/halo density profiles by measuring stacked weak lensing on scales of only a few tens of kpc. Our forecasts focus on scales smaller than the equality radius (Req) where the stellar component and the dark matter component contribute equally to the lensing signal. We compute the evolution of Req as a function of lens stellar mass and redshift and show that Req=7-34 kpc for galaxies with the stellar mass of 10^{9.5}-10^{11.5} solar masses. Unbiased shear measurements will be challenging on these scales. We introduce a simple metric to quantify how many source galaxies overlap with their neighbours and for which shear measurements will be challenging. Rejecting source galaxies with close-by companions results in about a 20 per cent decrease in the overall source density. Despite this decrease, we show that Euclid and WFIRST will be able to constrain galaxy/halo density profiles at Req with signal-to-noise ratio >20 for the stellar mass of >10^{10} solar masses. Weak lensing measurements at Req, in combination with stellar kinematics on smaller scales, will be a powerful means by which to constrain both the inner slope of the dark matter density profile as well as the mass and redshift dependence of the stellar initial mass function.

19 pages, 14 figures, 3 tables, submitted to MNRAS, included the referee comments

References in corpus (15)

• The Cosmic Evolution Survey (COSMOS) -- Overview
• The propagation of uncertainties in stellar population synthesis modeling I: The relevance of uncertain aspects of stellar evolution and the IMF to the derived physical properties of galaxies
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Data Processing, Sky Maps, and Basic Results
• COSMOS Photometric Redshifts with 30-bands for 2-deg2
• zCOSMOS: A Large VLT/VIMOS redshift survey covering 0 < z < 3 in the COSMOS field
• Concentration, Spin and Shape of Dark Matter Haloes as a Function of the Cosmological Model: WMAP1, WMAP3 and WMAP5 results
• A systematic variation of the stellar initial mass function in early-type galaxies
• PRIMUS: Constraints on Star Formation Quenching and Galaxy Merging, and the Evolution of the Stellar Mass Function From z=0-1
• Weak Gravitational Lensing with COSMOS: Galaxy Selection and Shape Measurements
• Cosmological puzzle resolved by stellar feedback in high redshift galaxies
• COSMOS: 3D weak lensing and the growth of structure
• Bayesian Galaxy Shape Measurement for Weak Lensing Surveys -I. Methodology and a Fast Fitting Algorithm
• Density profiles of galaxy groups and clusters from SDSS galaxy-galaxy weak lensing
• The Stability of the Point Spread Function of the Advanced Camera for Surveys on the Hubble Space Telescope and Implications for Weak Gravitational Lensing
• The Baryon Fractions and Mass-to-Light Ratios of Early-Type Galaxies

Cited by in corpus (6)

• Dark matter halo properties of GAMA galaxy groups from 100 square degrees of KiDS weak lensing data
• The Weak Lensing Signal and the Clustering of BOSS Galaxies II: Astrophysical and Cosmological Constraints
• Strong lensing by fermionic dark matter in galaxies
• The eROSITA Final Equatorial-Depth Survey (eFEDS) -- Splashback radius of X-ray galaxy clusters using galaxies from HSC survey
• The Subaru HSC weak lensing mass-observable scaling relations of spectroscopic galaxy groups from the GAMA survey
• Splashback radius and the mass accretion rate of RASS MCMF galaxy clusters