--- title: "Galactic chemical evolution" description: "Follow gas and net yields, calculate delayed enrichment, and connect stellar birth populations to conditional observations." canonical_url: "https://sandboxphysics.com/stories/galactic-chemical-evolution/" language: "en" page_type: "story" alternate_languages: zh-CN: "https://sandboxphysics.com/zh/stories/galactic-chemical-evolution/" last_modified: "2026-11-05" --- Galactic chemical evolution # Galactic chemical evolution Sandbox Physics · 2026-11-05 Stars inherit the composition of their birth gas. Follow where that material goes, why sources arrive on different schedules, and how a chemical track becomes a measured stellar population. 1. L1 ## [Why magnesium and iron remember star formation](https://sandboxphysics.com/stories/galactic-chemical-evolution/why-magnesium-and-iron-remember-star-formation/) Stars retain clues to when their gas was enriched. Learn why magnesium and iron respond differently, and why their ratio is not a unique clock. 2. L1 ## [Follow the gas and the newly made elements](https://sandboxphysics.com/stories/galactic-chemical-evolution/follow-the-gas-and-new-elements/) Build a one-zone mass budget, distinguish recycled material from net yields, and derive why a well-mixed wind need not lower abundance at fixed time. 3. L2 ## [Calculate a delayed enrichment track](https://sandboxphysics.com/stories/galactic-chemical-evolution/calculate-a-delayed-enrichment-track/) Derive a closed-box control, normalize a delay-time distribution, and calculate how past star formation supplies present magnesium and iron. 4. L3 ## [From a gas track to a stellar abundance population](https://sandboxphysics.com/stories/galactic-chemical-evolution/from-gas-tracks-to-stellar-abundances/) Weight a chemical track by stellar birth mass, propagate shared iron errors, and build a normalized conditional density for measured abundances. 5. L3 ## [Recompute a fixed Sculptor abundance sample](https://sandboxphysics.com/stories/galactic-chemical-evolution/recompute-a-fixed-sculptor-sample/) Run an independent one-zone calculation, validate birth-mixture integration, and locally extract a fixed 99-star source with 96 usable abundance pairs. 6. L4 ## [Delayed sources and imperfect mixing](https://sandboxphysics.com/stories/galactic-chemical-evolution/delayed-sources-and-imperfect-mixing/) Read a fixed 2026 dwarf-galaxy study through its figures: Ia delay, r-process source degeneracies, yield sensitivity and failures of a mixed one-zone model. ## Standalone scientific materials [Download the scientific ZIP](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/chemical-evolution-science-v1.zip) · [Read setup and calculation scope](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/README.md) The offline calculation needs Python, NumPy and SciPy. It solves four histories and compares saved synthetic measurements. Optional fixed Hill extraction runs locally with pdftotext; the ZIP has no original observations, paper or browser Engine. Individual scripts, sizes and SHA-256 - [README.md](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/README.md) (5754 B) `5a638f0c540b5d489ab149d2af7b8713a376a85a66f6a1a241a57052fee5ea1a` - [LICENSE.txt](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/LICENSE.txt) (1271 B) `c8d56106a2c4041b440e94509790c6403bbad8908db7efdbf09bbfe4c893ce82` - [requirements.txt](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/requirements.txt) (27 B) `39b93fa1b8397265839a510ca7601608248a7f3524067b61667e977bf4351475` - [source-identities.json](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/source-identities.json) (1618 B) `f7d7dc4c91ee350ab7f809a2c4c54c7f2e6c650a87e3b4b7476cdaa1c59ed127` - [fixed-inputs.json](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/fixed-inputs.json) (533 B) `98aaf54949a88e6ee5e4697b5ff25050bfff5790faa17d6d6ee5b7b02f9f1ac2` - [model-family.json](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/model-family.json) (537 B) `58dac14f9a01ed44a43c4d45dc88e12aa76c9a26c5fd977940099811242751a4` - [own-observations.json](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/own-observations.json) (10029 B) `3c2f318702cf26a370d4d298b8e4ed37da26e19c5052d51ef9a0daee06dba2f0` - [compare.py](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/compare.py) (3237 B) `785b41dd356c57e90165197b70ec11adf6271daafe85e096e793f237bcc2c860` - [evolution.py](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/evolution.py) (4572 B) `4deabefc6e7087e882bf44fe43b582762ba461d08c634d7e5237615760fcf108` - [extract\_hill.py](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/extract_hill.py) (2549 B) `59aa4cd821574c65110549c41e513fe7161210789c319eeb9342b26d659598d3` - [fetch\_hill.py](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/fetch_hill.py) (1705 B) `d31ccb38d10b8cd8a90194ba6a6d5b3e97af81b41c3dbef903c48ecc9b413696` - [io\_helpers.py](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/io_helpers.py) (1894 B) `2a07f3ab2f0792f19d5575e5fbb38a6d1370df6e01c20c1cde0a3e2fa072a959` - [make\_observations.py](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/make_observations.py) (1327 B) `5498e13a03606dc0adf97488f0f1d1bef92f04ed275aa16f7fe111a0d5683e79` - [make\_records.py](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/make_records.py) (1461 B) `3f25e9ee127836c6e2ade3f922de38941ca941bf26ebd9c85bf21538655b611a` - [make\_reference.py](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/make_reference.py) (4034 B) `cb0b779f168fe6e8ec93614da0eae1de7f82c37d61a632f05b5e987fe4e14f69` - [observation\_quadrature.py](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/observation_quadrature.py) (1662 B) `5b1ad8917ef50bff8a63248c883e5b56f72875eaa49470b41d98db44ca21186a` - [plot.py](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/plot.py) (3976 B) `55f9242160e7bd86321117136b5fc12a735c39cb1d5ae2ccd57481f76fb2ec6d` - [validate.py](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/validate.py) (7153 B) `1e089465eae28b0bcbf8bf9e696c3ccd7e07a645bcf7173cb536c72e878e5c00` - [verify\_package.py](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/verify_package.py) (926 B) `16d0c1b6185e7107b33fd33639456aa4806f3984269ca671f9b1b70bf487cd3d` - [SHA256SUMS.json](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/SHA256SUMS.json) (3112 B) `28a1797407ef24a767fde830473a49ca5d8ddb675f13ce03135ba1a2fe4b567a` - [chemical-evolution-science-v1.zip](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/chemical-evolution-science-v1.zip) (26888 B) `63dc82bb31bcd276c9abc76191e3201804d13d068811c5ff27bd244b17dcc06d` ## Sources and calculation scope 1. [Weinberg, Andrews & Freudenburg, Equilibrium and Non-Equilibrium Aspects of Galactic Chemical Evolution, arXiv:1604.07435v1](https://arxiv.org/abs/1604.07435v1) Complete fixed 30-page paper read again, including both appendices. Net yields, recycled material and analytic controls follow sections 2–3; delay approximations and birth weighting follow section 5. Its oxygen and exponential-delay examples are not silently relabeled as our fixed magnesium and finite power-law kernel. Its gas-linked formation law differs from our prescribed histories. 2. [Hill et al., VLT/FLAMES high-resolution chemical abundances in Sculptor, arXiv:1812.01486v2](https://arxiv.org/abs/1812.01486v2) Main sections 1–7 and appendices A/B read again; Table C5 extracted in two text modes with exact agreement on 99 rows and 96 finite Mg/Fe pairs. Methods specify the 25-arcminute-diameter field and upper-RGB selection; conclusions use inconsistent radius wording. Full per-star covariance and a numerical model-solar harmonization are not established here. Original observations, PDF and measured-derived figures remain local. 3. [VICE v1.3.1 fixed effective yields and solar reference](https://github.com/giganano/VICE/tree/v1.3.1) Previously frozen native defaults: Kroupa convention, effective net core-collapse and Type Ia magnesium/iron yields, Asplund 2009 reference and the declared hydrogen conversion. Public materials contain scalar values and identities, not a new yield grid or VICE executable. The independent Python does not execute VICE. 4. [Henderson, Kirby, de los Reyes & Surman, Constraints on the r-process Delay Time from Dwarf Spheroidal Galaxies, arXiv:2610.15946v1](https://arxiv.org/abs/2610.15946v1) Full fixed 24-page preprint, both appendices, Figures 1–12 and Tables 1–4 read; source figures and tables visually inspected. Posted 11 October 2026, internal draft 14 October. Actual PDF SHA-256 is 25e460e527705c40f64feaf0bc06e0a840f8967b67fed681c3acec5ad71ebcdc; server ETag differs and is not treated as a content signature. This is a primary-paper guide, not a rerun of its multi-element sampling or an identification of r-process sites. Original PDF and figures are not redistributed. 5. [Independent one-zone chemical-evolution Python materials](https://sandboxphysics.com/stories/galactic-chemical-evolution/materials/chemical-evolution-science-v1.zip) Original continuous convolution/DOP853 producers, saved fourteen-field inventories and birth populations, finite refinement, normalized conditional mixtures and mathematical limits. Public inputs and figures are original synthetic data. Default is offline; optional fixed Hill source is fetched and analyzed on the reader’s computer. No App/Engine, original paper, observed rows or measured-derived plot is included.