juliensimon/galaxy-clusters

Planck PSZ2 Galaxy Cluster Catalog

Part of the Astronomy Datasets collection on Hugging Face.

Complete catalog of galaxy clusters detected by the Planck satellite via the Sunyaev-Zel'dovich (SZ) effect, sourced via NASA HEASARC. Currently 1,655 clusters.

Dataset description

Galaxy clusters are the largest gravitationally bound structures in the universe. The Planck satellite detected them through the thermal Sunyaev-Zel'dovich effect: hot intracluster gas distorts the cosmic microwave background spectrum. The PSZ2 catalog is the second and final Planck SZ source catalog, based on the full mission data.

This dataset includes positions, redshifts, SZ-derived mass proxies, integrated SZ signal, signal-to-noise ratio, and detection pipeline information.

Galaxy clusters occupy a unique position in cosmology: they sit at the intersection of structure formation theory and observational cosmology. As the most massive virialized objects in the universe, their abundance as a function of mass and redshift is exquisitely sensitive to the matter density parameter, the amplitude of density fluctuations (sigma_8), and the dark energy equation of state. Counting clusters at different epochs therefore provides independent constraints on cosmological parameters complementary to those from the CMB power spectrum, baryon acoustic oscillations, and Type Ia supernovae.

The thermal Sunyaev-Zel'dovich effect exploited by Planck arises when CMB photons inverse-Compton scatter off the hot electrons in the intracluster medium, which can reach temperatures of 10^7 to 10^8 K. This produces a characteristic spectral distortion -- a decrement below ~217 GHz and an increment above -- that is independent of redshift, making SZ surveys uniquely capable of detecting massive clusters at any distance. The integrated SZ signal (Y_5R500) is tightly correlated with total cluster mass, providing a nearly mass-limited sample that is essential for cluster cosmology.

The PSZ2 catalog has served as the definitive SZ-selected cluster sample for nearly a decade, anchoring studies of cluster scaling relations, gas physics, and the calibration of weak-lensing mass estimates. It also provides the reference sample for follow-up observations with X-ray telescopes (Chandra, XMM-Newton) and optical/infrared surveys that measure galaxy populations, velocity dispersions, and strong-lensing features within these massive structures.

Schema

Column	Type	Description
name	string	Planck cluster name (e.g. "PSZ2 G000.13+78.04")
ra	float	Right ascension (degrees)
dec	float	Declination (degrees)
lii	float	Galactic longitude (degrees)
bii	float	Galactic latitude (degrees)
redshift	float	Cluster redshift
redshift_source_name	string	Source of redshift measurement
mass_sz	float	SZ mass proxy M_SZ (10^14 solar masses)
mass_sz_pos_err	float	Mass proxy positive uncertainty
mass_sz_neg_err	float	Mass proxy negative uncertainty
y5r500	float	Integrated SZ signal Y_5R500 (arcmin^2)
y5r500_error	float	SZ signal uncertainty
snr	float	Detection signal-to-noise ratio
det_pipeline_codes	string	Detection pipeline code(s) used

Quick stats

• 1,655 galaxy clusters
• 1,094 with measured redshift (median z = 0.224, max z = 0.972)
• Median detection SNR: 5.6

Usage

from datasets import load_dataset

ds = load_dataset("juliensimon/galaxy-clusters", split="train")
df = ds.to_pandas()

# Redshift distribution
z = df["redshift"].dropna()
print(f"{len(z):,} clusters with redshift, median z = {z.median():.3f}")

# Most massive clusters
top = df.nlargest(10, "mass_sz")[["name", "redshift", "mass_sz", "snr"]]

# Sky map in Galactic coordinates
import matplotlib.pyplot as plt
plt.scatter(df["lii"], df["bii"], c=df["snr"], s=3, cmap="viridis")
plt.colorbar(label="SNR")
plt.xlabel("Galactic longitude (deg)")
plt.ylabel("Galactic latitude (deg)")
plt.title("Planck PSZ2 Galaxy Clusters")

Data source

All data comes from the Planck PSZ2 Catalog hosted by NASA's High Energy Astrophysics Science Archive Research Center (HEASARC), accessed via the TAP protocol.

Original reference: Planck Collaboration, 2016, A&A, 594, A27.

Update schedule

Quarterly (1st Monday of January, April, July, October at 19:30 UTC) via GitHub Actions.

Related datasets

• supernova-remnants — Green's SNR Catalog
• gamma-ray-bursts — Fermi GBM GRB Catalog
• exoplanets — NASA Exoplanet Archive

Pipeline

Source code: juliensimon/space-datasets

Support

If you find this dataset useful, please give it a ❤️ on the dataset page and share feedback in the Community tab! Also consider giving a ⭐️ to the space-datasets repo.

Citation

@dataset{galaxy_clusters,
  author = {Simon, Julien},
  title = {Planck PSZ2 Galaxy Cluster Catalog},
  year = {2026},
  publisher = {Hugging Face},
  url = {https://huggingface.co/datasets/juliensimon/galaxy-clusters},
  note = {Based on Planck PSZ2 Catalog via NASA HEASARC}
}

License

CC-BY-4.0