Upload GALAH DR4: 917,588 stars, 30 elements

README.md

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+---
+license: cc-by-4.0
+pretty_name: "GALAH DR4 — Stellar Abundances for 917k Stars"
+language:
+  - en
+description: "The fourth data release of the Galactic Archaeology with HERMES survey — radial velocities, stellar parameters, and up to 31 elemental abundances for 917,588 stars."
+task_categories:
+  - tabular-classification
+  - tabular-regression
+tags:
+  - space
+  - stars
+  - spectroscopy
+  - galah
+  - abundances
+  - astronomy
+  - open-data
+  - tabular-data
+size_categories:
+  - 100K<n<1M
+configs:
+  - config_name: default
+    data_files:
+      - split: train
+        path: data/galah_dr4_allstar.parquet
+    default: true
+---
+
+# GALAH DR4 — Stellar Abundances for 917k Stars
+
+*Part of the [Astronomy Datasets](https://huggingface.co/collections/juliensimon/astronomy-datasets-69c24caf2f17e36128946743) collection on Hugging Face.*
+
+The fourth data release of the GALactic Archaeology with HERMES (GALAH) survey,
+providing radial velocities, stellar parameters, and up to 31 elemental abundances
+for **917,588** stars observed with the HERMES spectrograph on the
+Anglo-Australian Telescope.
+
+## Dataset description
+
+GALAH DR4 is one of the largest stellar spectroscopic surveys, designed to unravel
+the formation and evolution of the Milky Way through chemical tagging. Each star has
+high-resolution spectra decomposed into fundamental stellar parameters and individual
+elemental abundances spanning light elements, alpha-elements, iron-peak elements,
+and neutron-capture elements.
+
+Key properties:
+- **906,689** stars with radial velocity measurements
+- **906,432** stars with at least one elemental abundance
+- **30** elemental abundance columns ([X/Fe])
+- Median **24** abundances per star
+- Median SNR: **48.1** per pixel
+
+## Schema
+
+| Column | Type | Description |
+|--------|------|-------------|
+| `sobject_id` | string | GALAH observation identifier |
+| `star_id` | string | GALAH unique star identifier |
+| `tmass_id` | string | 2MASS identifier |
+| `gaiadr3_source_id` | string | Gaia DR3 source identifier |
+| `ra` | float64 | Right Ascension J2000 (degrees) |
+| `dec` | float64 | Declination J2000 (degrees) |
+| `teff_k` | float64 | Effective temperature (K) |
+| `logg` | float64 | Surface gravity (log cm/s^2) |
+| `fe_h_dex` | float64 | Iron abundance [Fe/H] (dex) |
+| `vmic` | float64 | Microturbulence velocity (km/s) |
+| `vsini` | float64 | Projected rotational velocity (km/s) |
+| `radial_velocity_kms` | float64 | Barycentric radial velocity (km/s) |
+| `radial_velocity_comp2_kms` | float64 | Binary companion RV (km/s) |
+| `snr_px_ccd1`..`snr_px_ccd4` | float64 | Signal-to-noise per pixel (4 CCDs) |
+| `snr_mean` | float64 | Mean SNR across all 4 CCDs |
+| `flag_sp` | Int64 | Spectroscopic quality flag (0 = best) |
+| `flag_red` | Int64 | Reduction pipeline quality flag |
+| `li_fe`..`eu_fe` | float64 | Elemental abundances [X/Fe] (dex) — 31 elements |
+| `n_abundances` | Int64 | Count of non-null abundance measurements |
+
+### Abundance columns
+
+Light: `li_fe`, `c_fe`, `n_fe`, `o_fe` ·
+Odd-Z: `na_fe`, `al_fe`, `k_fe` ·
+Alpha: `mg_fe`, `si_fe`, `ca_fe`, `ti_fe` ·
+Iron-peak: `sc_fe`, `v_fe`, `cr_fe`, `mn_fe`, `co_fe`, `ni_fe`, `cu_fe`, `zn_fe` ·
+s-process: `rb_fe`, `sr_fe`, `y_fe`, `zr_fe`, `mo_fe`, `ba_fe`, `la_fe`, `ce_fe`, `nd_fe` ·
+r-process: `ru_fe`, `sm_fe`, `eu_fe`
+
+## Usage
+
+```python
+from datasets import load_dataset
+
+ds = load_dataset("juliensimon/galah-dr4-stellar-abundances", split="train")
+df = ds.to_pandas()
+
+# High-quality stars with best spectroscopic flags
+best = df[df["flag_sp"] == 0]
+
+# Metal-poor stars
+metal_poor = df[df["fe_h_dex"] < -1.0]
+
+# Stars rich in europium (r-process)
+eu_rich = df[df["eu_fe"] > 0.5]
+
+# Stars with the most measured abundances
+well_measured = df.sort_values("n_abundances", ascending=False).head(1000)
+
+# Kiel diagram (logg vs Teff)
+import matplotlib.pyplot as plt
+sample = df[df["flag_sp"] == 0].sample(50000)
+plt.scatter(sample["teff_k"], sample["logg"], c=sample["fe_h_dex"],
+            s=0.1, cmap="coolwarm", vmin=-1.5, vmax=0.5)
+plt.gca().invert_xaxis()
+plt.gca().invert_yaxis()
+plt.xlabel("Teff (K)")
+plt.ylabel("log g")
+plt.colorbar(label="[Fe/H]")
+```
+
+## Data source
+
+[GALAH Survey DR4](https://www.galah-survey.org/dr4/) (Buder et al. 2024).
+Observed with the HERMES spectrograph (R ≈ 28,000) on the 3.9m Anglo-Australian
+Telescope at Siding Spring Observatory.
+
+## Update schedule
+
+Static dataset — uploaded once from the DR4 release catalog.
+
+## Related datasets
+
+- [gaia-dr3-astrophysical-parameters](https://huggingface.co/datasets/juliensimon/gaia-dr3-astrophysical-parameters) — Gaia DR3 stellar parameters
+- [exoplanet-catalog](https://huggingface.co/datasets/juliensimon/exoplanet-catalog) — Confirmed exoplanets
+- [pulsar-catalog](https://huggingface.co/datasets/juliensimon/pulsar-catalog) — Pulsar catalog
+
+## Pipeline
+
+Source code: [juliensimon/space-datasets](https://github.com/juliensimon/space-datasets)
+
+## Citation
+
+```bibtex
+@article{buder2024galah,
+  author = {Buder, Sven and others},
+  title = {The GALAH Survey: Data Release 4},
+  year = {2024},
+  journal = {arXiv preprint arXiv:2409.19858},
+}
+```
+
+## License
+
+[CC-BY-4.0](https://creativecommons.org/licenses/by/4.0/)

data/galah_dr4_allstar.parquet

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