# ⚛  L1 Principle — Galaxy SED Fitting

**ID:** `L1-377` · **Status:** ⊙ Testnet (genesis catalog)

> **🌐 Domain:** Astrophysics — *Galaxy properties*
> **🎯 Problem class:** parameter estimation · **🧮 Solution space:** galaxy parameter vector
> **📡 Carrier:** photon · **🌫 Noise:** observation gaussian
> **⚖ Difficulty (δ):** 3 · **⛓ Block:** 41555178

---

## 🧠 1. Introduction

**Galaxy SED Fitting** is a **parameter-estimation problem** whose unknown lives in **galaxy parameter vector** space, within the **Galaxy properties** sub-domain of **Astrophysics**.

Measurements consist of photons collected by an optical detector via a **broadband photometric sed** sensing mechanism.

The forward operator applies, in order: operator inherits structure from a graph (mesh, network); S · dust · attenuation calzetti operator; O · chi2 · photometric operator.

Observations are corrupted by observation gaussian. Existence of the recovered galaxy_parameter_vector is guaranteed within the declared Omega bounds. Uniqueness holds on the measurement-supported subspace; out-of-support modes are controlled by declared priors. Stability is conditionally stable (kappa_eff ~= 80); AGN_contamination dominates the stability cliff; the remaining mismatch parameters contribute higher-order bias terms. Observation gaussian sets the irreducible data-fidelity floor.

## ⚙ 2. Forward Model

Physical chain: **x** → Structured graph operator → S · dust · attenuation calzetti → O · chi2 · photometric → **y** (detector).

```
y = `O.chi2.photometric` `S.dust.attenuation_calzetti` G x
```

**Measurement DAG:**

| Primitive | What it does |
|---|---|
| `G.structured` | Operator inherits structure from a graph (mesh, network) |
| `S.dust.attenuation_calzetti` | S · dust · attenuation calzetti operator |
| `O.chi2.photometric` | O · chi2 · photometric operator |

## 🔬 3. Physics Fingerprint

| Property | Value |
|---|---|
| Domain | Astrophysics |
| Sub domain | Galaxy properties |
| Carrier | photon |
| Problem class | parameter_estimation |
| Solution space | galaxy_parameter_vector |
| Noise model | observation_gaussian |
| Integration axis | spectral_energy_distribution |
| Difficulty delta | 3 |
| L dag | 3 |

## 📡 4. Measurement Model

Existence of the recovered galaxy_parameter_vector is guaranteed within the declared Omega bounds. Uniqueness holds on the measurement-supported subspace; out-of-support modes are controlled by declared priors. Stability is conditionally stable (kappa_eff ~= 80); AGN_contamination dominates the stability cliff; the remaining mismatch parameters contribute higher-order bias terms. Observation gaussian sets the irreducible data-fidelity floor.

| Metric | Value |
|---|---|
| Metric | SFR_log_RMSE |
| Secondary | stellar_mass_log_RMSE |

## 📏 5. Operating Range (Ω)

**Center problem class:** `parameter_estimation` · **Forward operator:** `broadband_photometric_sed`

**Center point:**

| Parameter | Unit | Value |
|---|---|---|
| A v mag | — | 0.5 |
| N filters | — | 10 |
| Redshift z | — | 0.5 |
| Snr per band | — | 10 |

**Allowed bounds:**

| Parameter | Unit | Range |
|---|---|---|
| A v mag | — | 0.0 – 3.0 |
| N filters | — | 3 – 30 |
| Redshift z | — | 0.0 – 6.0 |
| Snr per band | — | 3 – 100 |

## 🎯 6. Tolerance (ε)

**Center tolerance:** 0.25 SFR_log_RMSE

| Metric | Range |
|---|---|
| Sfr log rmse | 0.05 – 0.8 |

## ⚖ 7. Hardness Function

Hardness scales as **`epsilon_fn`** on **SFR_log_RMSE**, with κ = `2000` and δ = `3`.

## 💾 8. Reference Dataset

- **primary** · weight 1.0 · IPFS _(not pinned yet)_

## 9. On-chain Registration

- **Chain hash:** `0xf8e3e00e1cc0411d28bd55c61d6adb81a9a8ea4f0115d558874f4c077531f6bb`
- **Chain tx hash:** `0x824b97c247312d5ca6d0c13ccc8c2b6db28f86ef8b339727234aea29c549a239`
- **Chain block:** `41555178`

---

## File Mapping

This bundle consists of: `L1-377.md`, `L1-377.json`.

| File | Role | How to regenerate |
|------|------|-------------------|
| `L1-377.md` | Source of truth — edit this | Human or LLM |
| `L1-377.json` | Structured metadata for the registry | LLM regenerates from the sections above |

**Prompt for your LLM after editing this Markdown:**

> Read the attached Markdown. Regenerate the sibling `.json` so every field matches.
> Preserve the schema documented in the rows above.
> Output each file in its own fenced code block tagged with the filename.
> Output only the JSON object.

_This Markdown was auto-synthesized from the catalog row for `L1-377`._
_Edit it, regenerate the JSON, and submit at [/submit](/submit) to claim the artifact._