http://arxiv.org/abs/1908.06983
The free-streaming length of dark matter depends on fundamental dark matter physics, and determines the abundance and central densities of dark matter halos on sub-galactic scales. Using the image positions and flux-ratios from eight quadruply-imaged quasars, we constrain the free-streaming length of dark matter, the amplitude of the subhalo mass function (SHMF), and the logarithmic slope of the SHMF. We model both main deflector subhalos and halos along the line of sight, and account for warm dark matter (WDM) free-streaming effects on both the mass function and the mass-concentration relation. By calibrating the evolution of the SHMF with host halo mass and redshift using a suite of simulated halos, we infer a global normalization for the SHMF. Our analysis accounts for finite-size background sources, and marginalizes over the mass profile of the main deflector. Parameterizing dark matter free-streaming through the half-mode mass $m_{\rm{hm}}$, we constrain dark matter warmth and the corresponding thermal relic particle mass $m_{\rm{DM}}$. At $2 \sigma$: $m_{\rm{hm}} < 10^{7.8} M_{\odot}$ ($m_{DM} > 5.2 \ \rm{keV}$). Assuming CDM, we simultaneously constrain the projected mass in substructure between $10^6 – 10^{9} M_{\odot}$ near lensed images and the logarithmic slope of the SHMF. At $2 \sigma$, we infer $1.3 – 6.6 \times 10^{7} M_{\odot} \rm{kpc^{-2}}$, corresponding to mean projected mass fractions of $\bar{f}{\rm{sub}} = 0.034{-0.022}^{+0.024}$, respectively. At $1 \sigma$, we constrain the logarithmic slope of the SHMF $\alpha = -1.896_{-0.014}^{+0.010}$. These results are in excellent agreement with the predictions of cold dark matter.
D. Gilman, S. Birrer, A. Nierenberg, et. al.
Wed, 21 Aug 19
42/78
Comments: submitted to MNRAS, 27 pages, 13 figures, comments welcome
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