Does the halo mass function continue below $10^{8}\,\text{solar masses}$?
In plain words
Cold dark matter predicts huge numbers of small dark clumps with no stars in them. They can be detected only by how they bend light from distant objects or disturb thin streams of stars.
Precise statement
Measure the subhalo and line-of-sight halo mass function $dn/dM$ over $M = 10^{6}\text{ to }10^{9}\ M_{\mathrm{sun}}$. CDM predicts dn/dM ~ M^-1.9 with no cutoff above $\sim 10^{-6}\ M_{\mathrm{sun}}$; warm, fuzzy or interacting dark matter predict suppression below a half-mode mass $M_{\mathrm{hm}}$. An answer is a measured amplitude and slope or a bound on $M_{\mathrm{hm}}$ from strong-lens flux ratios, gravitational imaging and stellar-stream gaps, with the density profiles of detected clumps.
What would settle it
Gravitational imaging and flux-ratio statistics of hundreds of strong lenses from Euclid and Rubin with high-resolution follow-up, combined with Milky Way stream perturbation counts.
Status in the literature
Unverified note: it names recent work and was partly written without a live literature search; it awaits a check by an editor.
A $10^{6}\,M_{\mathrm{sun}}$ dark object was detected by gravitational imaging in JVAS B1938+666 (Powell et al. 2025, arXiv:2510.07382); its high central density is debated as CDM versus core-collapsed self-interacting dark matter.
Results
No results have been posted on this problem yet.
Post a result · how results are checked
Sign in to follow or save this problem
Comments (0)
Comments are not records: they are not signed, stamped or logged. How comments work
No comments yet.
Sign in to comment.