juliensimon/desi-dr1-redshifts

DESI DR1 Bright Galaxy Survey Redshifts

Part of the Astronomy Datasets collection on Hugging Face.

Spectroscopic redshifts from the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 — the largest spectroscopic survey ever conducted. This dataset contains the Bright Galaxy Survey (BGS) subset: 5,000,000 sources with reliable redshift measurements (zwarn=0, main_primary=true).

Dataset description

DESI is a robotic fiber-fed spectrograph on the Mayall 4-meter telescope at Kitt Peak National Observatory, capable of measuring 5,000 spectra simultaneously. DR1 contains 28.4 million unique spectroscopic redshifts from 14,600+ square degrees.

The Bright Galaxy Survey targets galaxies with r < 19.5 magnitude during bright lunar conditions. This curated subset includes only the main survey observations with reliable redshift fits (zero warning flags) and primary measurements (no duplicates).

Breakdown by spectral type:

• 3,519,828 galaxies (70.4%)
• 1,439,945 stars (28.8%)
• 40,227 QSOs (0.8%)

Schema

Column	Type	Description
targetid	int64	Unique DESI target identifier
ra	float64	Right ascension — fiber position (degrees)
dec	float64	Declination — fiber position (degrees)
redshift	float64	Best-fit spectroscopic redshift
redshift_err	float64	Redshift uncertainty
spectype	string	Spectral classification: GALAXY, STAR, or QSO
subtype	string	Spectral subtype (e.g., stellar type K, G, F)
deltachi2	float64	Chi-squared difference between best and second-best fit
chi2	float64	Best-fit chi-squared
coadd_numexp	int16	Number of coadded exposures
coadd_numnight	int16	Number of observation nights
coadd_numtile	int16	Number of observed tiles
coadd_exptime	float32	Total coadded exposure time (seconds)

Quick stats

• 5,000,000 sources with reliable redshifts
• Median redshift: 0.1658
• Mean redshift: 0.1712
• 3,519,828 galaxies, 1,439,945 stars, 40,227 QSOs
• Sky coverage: ~14,600 square degrees

Usage

from datasets import load_dataset

ds = load_dataset("juliensimon/desi-dr1-redshifts", split="train")
df = ds.to_pandas()

# Galaxy redshift distribution
galaxies = df[df["spectype"] == "GALAXY"]
print(f"{len(galaxies):,} galaxies, median z = {galaxies['redshift'].median():.4f}")

# Redshift histogram
import matplotlib.pyplot as plt
galaxies["redshift"].hist(bins=200, range=(0, 0.6))
plt.xlabel("Redshift")
plt.ylabel("Count")
plt.title("DESI BGS Galaxy Redshift Distribution")

# Sky coverage plot
plt.figure(figsize=(12, 6))
plt.scatter(df["ra"], df["dec"], s=0.01, alpha=0.1)
plt.xlabel("RA (deg)")
plt.ylabel("Dec (deg)")
plt.title("DESI DR1 BGS Sky Coverage")

Data source

All data comes from the DESI Data Release 1 via the NOIRLab Astro Data Lab TAP service.

DESI Collaboration (2025). "The DESI Data Release 1." arXiv:2503.14745.

Related datasets

• sdss-dr18-spectra — SDSS DR18 optical spectroscopy
• exoplanet-archive — NASA Exoplanet Archive

Pipeline

Source code: juliensimon/space-datasets

Citation

@dataset{desi_dr1_redshifts,
  author = {Simon, Julien},
  title = {DESI DR1 Bright Galaxy Survey Redshifts},
  year = {2026},
  publisher = {Hugging Face},
  url = {https://huggingface.co/datasets/juliensimon/desi-dr1-redshifts},
  note = {Based on DESI DR1 (DESI Collaboration 2025) via NOIRLab Astro Data Lab}
}

License

CC-BY-4.0