{"artifact_id":"L1-912","layer":"L1","title":"Dark Matter — Galactic Rotation & Halo Profile","domain":"Astrophysics","sub_domain":"Dark Matter Halos","physics_fingerprint":{"intro":"Galaxies rotate as if far more mass is present than we see. Either dark matter exists, or gravity is modified. Fitting halo profiles (NFW) to rotation curves — and recovering halo parameters across many galaxies — discriminates the hypotheses.","title":"Dark Matter — Galactic Rotation & Halo Profile","domain":"Astrophysics","chapter":"Ch.11 Physics & Cosmology","why_hard":"Baryonic uncertainties, beam smearing, and degeneracies between halo profiles and modified-gravity laws make inference ambiguous; conclusions must hold across diverse galaxies.","agent_idea":"An agent that fits halos across a galaxy catalog and quantifies the evidence for dark matter vs modified gravity.","approaches":["Bayesian / simulation-based inference of halo parameters from rotation curves","Joint baryon+halo modeling to break degeneracies","Population-level tests of NFW vs MOND"],"sub_domain":"Dark Matter Halos","forward_model":"Circular velocity v(r)=√(G·M(r)/r) with an NFW halo ρ(r)=ρ_s/[(r/r_s)(1+r/r_s)²]; infer halo parameters from rotation curves.","benchmark_goal":"Recover the dark-matter halo profile from HI/Hα rotation curves (reduced χ² ≲ 1.2; M200 within ~0.1 dex).","challenge_blurb":"Pin down the dark-matter halo from how galaxies rotate — distinguish particle dark matter from modified gravity.","challenge_group":"physics","challenge_short":"Dark Matter","grand_challenge":true,"governing_equation":"v(r) = √(G·M(r)/r);  ρ_NFW(r) = ρ_s / [(r/r_s)(1+r/r_s)²]"},"observable_profile":{"unit":"reduced χ² of rotation-curve fit (lower better)","floor":1.5,"metric":"rotcurve_chi2","sota_reference":"SPARC rotation-curve NFW/MOND fits"},"size_tiers":{"galaxies":[50,175,1000],"radial_bins":[10,30,100]},"hardness_fn":{"type":"grand_challenge","metric":"rotcurve_chi2","baseline":"Single-NFW least-squares","delta_tier":50},"initiator_dataset":[{"name":"SPARC galaxy rotation-curve database","weight":0.6,"ipfs_cid":null,"license_hash":null},{"name":"THINGS HI velocity fields","weight":0.4,"ipfs_cid":null,"license_hash":null}],"status":"testnet","staked_pwm":5000.0,"chain_hash":null,"chain_tx_hash":null,"chain_block":null,"wp":{},"plain_intro":"Dark Matter — Galactic Rotation & Halo Profile (Dark Matter Halos) is a problem in Astrophysics. The forward model maps the hidden the unknown quantity to a measurement. The inverse goal is to recover the the unknown quantity from the observed data."}