Astrometric weak lensing of quasars could detect 10^{-6} solar mass dark matter microhalos
The arXiv preprint outlines a novel astrometric probe of substellar dark matter halos using multiply imaged quasars. It forecasts sensitivity to microhalos via relative image accelerations in decade-long campaigns. Positive signals would tighten dark matter particle mass limits by orders of magnitude; robust nulls would constrain halo survival.
The method exploits time-domain astrometric weak lensing on systems like B1422+231 and SDSS J1029+2623. Each macro-image path crosses numerous microhalos, producing measurable relative angular accelerations when halo crossing times exceed a ten-year survey with 300 epochs. Forecasts assume 0.1-1 microarcsecond per-epoch precision and half the projected mass in microhalos, yielding variance signal-to-noise of order ten for the galaxy lens. This extends lensing sensitivity twelve to fourteen orders of magnitude below current limits on structures in Lambda CDM. A detection would raise fermion dark matter mass bounds to at least 400 keV and boson bounds to 10^{-12} eV while constraining kinetic decoupling above 10 MeV. The approach also tests the running of the primordial spectral tilt at the 0.01 level over 15-20 e-folds. Null results would instead limit microhalo survival fractions or indicate deviations from standard cold dark matter.
Van Tilburg: No peer-reviewed confirmation of microhalo detection via this channel before 2032 with current 0.1 microarcsecond facilities.
Sources (2)
- [1]Primary Source(https://arxiv.org/abs/2608.27557)
- [2]Supporting Source(https://arxiv.org/abs/astro-ph/0501589)