<i>JWST</i> lensed quasar dark matter survey – II. Strongest gravitational lensing limit on the dark matter free streaming length to date
Ryan E. Keeley, Anna Nierenberg, Daniel Gilman, Charles Gannon, Simon Birrer, Tommaso Treu, Andrew Benson, Xiaolong Du, Kevork N. Abazajian, T. Anguita, Vardha N. Bennert, S. G. Djorgovski, K. K. Gupta, S. Hoenig, Alexander Kusenko, Cameron Lemon, M. Malkan, V. Motta, Leonidas A. Moustakas, Maverick S. H. Oh, Dominique Sluse, Daniel Stern, Risa H. Wechsler
Abstract
ABSTRACT This is the second in a series of papers in which we use JWST Mid Infrared Instrument multiband imaging to measure the warm dust emission in a sample of 31 multiply imaged quasars, to be used as a probe of the particle nature of dark matter. We present measurements of the relative magnifications of the strongly lensed warm dust emission in a sample of nine systems. The warm dust region is compact and sensitive to perturbations by populations of haloes down to masses $\sim 10^6$ M$_{\odot }$. Using these warm dust flux-ratio measurements in combination with five previous narrow-line flux-ratio measurements, we constrain the halo mass function. In our model, we allow for complex deflector macromodels with flexible third- and fourth-order multipole deviations from ellipticity, and we introduce an improved model of the tidal evolution of subhaloes. We constrain a WDM model and find an upper limit on the half-mode mass of $10^{7.6}\, {\rm M}_\odot$ at posterior odds of 10:1. This corresponds to a lower limit on a thermally produced dark matter particle mass of 6.1 keV. This is the strongest gravitational lensing constraint to date, and comparable to those from independent probes such as the Ly $\alpha$ forest and Milky Way satellite galaxies.