juliensimon/galah-dr4-stellar-abundances
GALAH DR4 — Stellar Abundances for 917k Stars Credit: NASA/ESA/Hubble Part of a dataset collection on Hugging Face. Dataset description 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. GALAH DR4 is one of the largest stellar spectroscopic surveys… See the full description on the dataset page: https://huggingface.co/datasets/juliensimon/galah-dr4-stellar-abundances.
GALAH DR4 — Stellar Abundances for 917k Stars
<div align="center"> <img src="banner.jpg" alt="A youthful globular star cluster observed by the Hubble Space Telescope" width="400"> <p><em>Credit: NASA/ESA/Hubble</em></p> </div>
Part of a [dataset collection](https://huggingface.co/collections/juliensimon/astronomy-datasets-69c24caf2f17e36128946743) on Hugging Face.
Dataset description
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.
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.
GALAH was specifically designed for chemical tagging — the idea that stars born in the same molecular cloud retain a unique multi-dimensional chemical fingerprint that persists long after the birth cluster has dispersed. The HERMES spectrograph delivers four non-contiguous optical wavelength channels at R ~ 28,000, capturing lines of light elements (Li, C, N, O), alpha-elements (Mg, Si, Ca, Ti), iron-peak elements (Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), and neutron-capture elements (Rb, Sr, Y, Zr, Mo, Ba, La, Ce, Nd, Ru, Sm, Eu) — up to 31 distinct abundance dimensions per star.
DR4 represents a major advance over DR3, incorporating improved spectral analysis techniques, better treatment of non-LTE effects for critical elements, and cross-matching with Gaia DR3 for precise astrometric information. The inclusion of both s-process elements (Ba, La, Ce from AGB nucleosynthesis) and r-process elements (Eu from neutron star mergers) makes GALAH uniquely powerful for constraining the sites and timescales of heavy element production in the Milky Way.
Schema
Quick stats
- 917,588 stars observed with HERMES spectrograph
- 906,689 stars with radial velocity measurements
- 906,432 stars with at least one elemental abundance (99%)
- 30 elemental abundance columns ([X/Fe]), median 24 per star
- 663,075 stars with clean spectroscopic flags (flag_sp == 0)
- Median SNR across 4 HERMES CCDs: 48.1 per pixel
Usage
from datasets import load_dataset
import matplotlib.pyplot as plt
ds = load_dataset("juliensimon/galah-dr4-stellar-abundances", split="train")
df = ds.to_pandas()
# Kiel diagram (Teff vs logg) coloured by [Fe/H] — shows stellar populations
best = df[(df["flag_sp"] == 0) & df["teff_k"].notna() & df["logg"].notna()]
sample = best.sample(min(50_000, len(best)), random_state=42)
sc = plt.scatter(sample["teff_k"], sample["logg"],
c=sample["fe_h_dex"], s=0.1, cmap="coolwarm",
vmin=-1.5, vmax=0.5, alpha=0.6)
plt.gca().invert_xaxis()
plt.gca().invert_yaxis()
plt.xlabel("Effective Temperature (K)")
plt.ylabel("log g (dex)")
plt.title("GALAH DR4 Kiel Diagram")
plt.colorbar(sc, label="[Fe/H] (dex)")
plt.tight_layout()
plt.show()
# Abundance pattern: alpha-element enhancement vs metallicity
alpha_cols = ["mg_fe", "si_fe", "ca_fe", "ti_fe"]
best["alpha_fe"] = best[alpha_cols].mean(axis=1)
sub = best.dropna(subset=["fe_h_dex", "alpha_fe"]).sample(30_000, random_state=0)
plt.figure()
plt.scatter(sub["fe_h_dex"], sub["alpha_fe"], s=0.1, alpha=0.3, c="steelblue")
plt.axhline(0, color="gray", lw=0.5, ls="--")
plt.xlabel("[Fe/H] (dex)")
plt.ylabel("[alpha/Fe] (dex)")
plt.title("Alpha-element Enhancement vs Metallicity")
plt.tight_layout()
plt.show()Data source
https://www.galah-survey.org/dr4/
Update schedule
Static dataset — uploaded once from the DR4 release catalog
Related datasets
Citation
@dataset{galah_dr4_stellar_abundances,
title = {GALAH DR4 — Stellar Abundances for 917k Stars},
author = {Simon, Julien},
year = {2026},
url = {https://huggingface.co/datasets/juliensimon/galah-dr4-stellar-abundances},
publisher = {Hugging Face},
note = {Derived from GALAH Survey, https://www.galah-survey.org/dr4/}
}