DESI Stellar Gas Distribution Prior

Date: 2026-05-09

Status: PRIOR_BRIDGE_HOLD_FIT

Decision: ADMIT_PRIOR_BRIDGE_HOLD_FIT

Claim boundary: DESI large-scale structure can supply an environment prior for stellar-gas distribution. A coarse DESI/MaNGA cell join exists; object-level crossmatch remains HOLD. This is not a direct gas map, not a cosmology fit, and not a local shock model.

Core Idea

DESI does not directly measure stellar gas. It measures a huge galaxy/quasar redshift tracer field. That is still useful because gas is not randomly placed: it follows halos, filaments, nodes, voids, star-formation history, feedback, and selection effects.

So the safe inference is:

DESI tracer density
  -> matter / environment prior
  -> probable stellar-gas distribution
  -> local update from MaNGA line ratios
  -> residual map where the prior fails

Inference Ladder

L0: delta_g(x,z) = (n_g(x,z) - mean(n_g(z))) / mean(n_g(z))
L1: delta_m(x,z) ~= delta_g(x,z) / b_g(type,z)
L2: P(env | x,z) = softmax([void, sheet, filament, node]; delta_m, grad(delta_m), Hessian(Phi))
L3: rho_gas_prior(x,z) proportional_to f_b * rho_m(x,z) * G(env,z) * S(selection)
L4: P(gas_state | DESI_env, MaNGA_lines) proportional_to P(MaNGA_lines | gas_state) * P(gas_state | DESI_env)

The important step is L4. DESI supplies the wide-field environment prior; MaNGA supplies local emission-line evidence.

What This Gives Us Now

A principled way to turn large-scale topology into a gas-distribution prior.
A join target for MaNGA line-ratio diagnostics.
A residual surface: places where cosmic-web environment predicts gas state poorly become high-value FAMM/scar targets.
A clean SMN interpretation: DESI environment classes and MaNGA diagnostic classes are high semantic-load objects, but still not proof.

What Remains HOLD

direct stellar gas map             HOLD
cosmology fit                      HOLD
dark-energy evolution claim        HOLD
shock transfer claim               HOLD
object-level DESI/MaNGA crossmatch HOLD
coarse DESI/MaNGA cell join        EXISTS

Next Tool Step

Use the existing coarse DESI/MaNGA cell join as the population prior, then keep the object-level crossmatch path explicitly held until a cone and redshift window receipt exists:

match if angular_sep < theta_max and |z_DESI - z_MaNGA| < dz_max

After that, fit environment bins against MaNGA line-ratio classes and keep the negative controls visible.

Receipt

shared-data/data/stack_solidification/desi_stellar_gas_distribution_prior_receipt.json

Receipt Backlinks

Coarse cell join receipt: shared-data/data/stellar_gas_observation/desi_epoviz_manga_population_cell_join_receipt.json
Tiddler: 6-Documentation/tiddlywiki-local/wiki/tiddlers/DESI Stellar Gas Distribution Prior.tid

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