README.md

metadata

license: cc-by-4.0
pretty_name: GSWLC-2 Galaxy Properties
language:
  - en
description: >-
  659K galaxies with stellar masses, star formation rates, and dust attenuation
  from UV+optical+IR SED fitting of GALEX, SDSS, and WISE photometry.
task_categories:
  - tabular-classification
  - tabular-regression
tags:
  - space
  - galaxies
  - stellar-mass
  - star-formation
  - sdss
  - galex
  - wise
  - astronomy
  - open-data
  - tabular-data
size_categories:
  - 100K<n<1M
configs:
  - config_name: default
    data_files:
      - split: train
        path: data/gswlc_galaxy_properties.parquet
    default: true

GSWLC-2 Galaxy Properties

Part of the Astronomy Datasets collection on Hugging Face.

659,229 galaxies with physical properties derived from UV-to-infrared spectral energy distribution (SED) fitting. GSWLC-2 (GALEX-SDSS-WISE Legacy Catalog 2) combines ultraviolet photometry from GALEX, optical photometry from SDSS, and mid-infrared photometry from WISE to estimate stellar masses, star formation rates, and dust attenuation for galaxies at redshifts 0.01 < z < 0.30.

Dataset description

The GSWLC is the definitive catalog for physical properties of low-redshift galaxies, covering ~90% of the SDSS spectroscopic footprint. Version 2 (Salim et al. 2018) incorporates WISE mid-IR photometry to better constrain dust-obscured star formation. The "X" variant (GSWLC-X2) is the master catalog that selects the deepest available UV observation for each galaxy from the A (shallow), M (medium), and D (deep) sub-catalogs.

Physical properties are derived using the CIGALE SED fitting code with Bayesian estimation of stellar mass, star formation rate, and dust attenuation.

Quick stats

• 659,229 galaxies in the catalog
• 650,599 with valid stellar mass estimates
• 650,599 with valid SFR estimates
• 340,258 classified as star-forming (log sSFR > -11)
• 310,341 classified as quiescent
• Median stellar mass: 10^{10.81} solar masses
• Median redshift: 0.1039

Schema

Column	Type	Description
objid	int64	SDSS photometric object ID
glxid	int64	GALEX photometric ID (null if no UV match)
plate	int64	SDSS spectroscopic plate number
mjd	int64	SDSS spectroscopic plate date (MJD)
fiber_id	int64	SDSS spectroscopic fiber ID
ra	float64	Right Ascension (J2000, degrees)
dec	float64	Declination (J2000, degrees)
redshift	float64	Spectroscopic redshift from SDSS
chi2_r	float64	Reduced chi-squared of SED fit
log_mstar	float64	Log stellar mass (solar masses)
log_mstar_err	float64	Error on log stellar mass
log_sfr_sed	float64	Log UV/optical SFR (solar masses/yr)
log_sfr_sed_err	float64	Error on log SFR
a_fuv	float64	Dust attenuation in rest-frame FUV (mag)
a_fuv_err	float64	Error on A_FUV
a_b	float64	Dust attenuation in rest-frame B band (mag)
a_b_err	float64	Error on A_B
a_v	float64	Dust attenuation in rest-frame V band (mag)
a_v_err	float64	Error on A_V
flag_sed	int64	SED fitting flag (0=OK, 1=broad-line, 2=chi2>30, 5=missing photometry)
uv_survey	int64	UV survey depth (1=shallow/A, 2=medium/M, 3=deep/D)
flag_uv	int64	UV detection flag (0=none, 1=FUV only, 2=NUV only, 3=both)
flag_midir	int64	Mid-IR flag (0=none, 1=12um, 2=22um, 5=AGN-corrected)
flag_mgs	int64	SDSS Main Galaxy Sample flag (0=no, 1=yes)
log_ssfr	float64	Derived: log specific SFR (log SFR - log M*, yr^-1)
is_star_forming	bool	Derived: log sSFR > -11
uv_survey_name	string	Derived: human-readable UV survey name

Usage

from datasets import load_dataset

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

# Star-forming galaxies
sf = df[df["is_star_forming"]]

# Massive quiescent galaxies
massive_quiescent = df[(df["log_mstar"] > 11) & (~df["is_star_forming"])]

# Star formation main sequence
import matplotlib.pyplot as plt
valid = df[df["log_sfr_sed"].notna() & df["log_mstar"].notna()]
plt.hexbin(valid["log_mstar"], valid["log_sfr_sed"], gridsize=100, mincnt=1)
plt.xlabel("log M* (Msun)")
plt.ylabel("log SFR (Msun/yr)")
plt.title("Star Formation Main Sequence")

# Dusty galaxies (high FUV attenuation)
dusty = df[df["a_fuv"] > 3.0]

# Cross-match with SDSS using objid

Data source

GSWLC-2 — Salim et al. (2016, 2018).

• Salim et al. (2016), "GALEX-SDSS-WISE Legacy Catalog (GSWLC): Star Formation Rates, Stellar Masses, and Dust Attenuations of 700,000 Low-Redshift Galaxies", ApJS, 227, 2. arXiv:1610.00712
• Salim et al. (2018), "Dust Attenuation Curves in the Local Universe: Demographics and New Laws for Star-forming Galaxies and High-redshift Analogs", ApJ, 859, 11. arXiv:1804.05850

Related datasets

• galaxy-zoo-2-morphology — Galaxy Zoo 2 visual morphological classifications
• open-ngc — NGC/IC galaxy and nebula catalog

Pipeline

Source code: juliensimon/space-datasets

Citation

@dataset{gswlc_galaxy_properties,
  author = {Simon, Julien},
  title = {GSWLC-2 Galaxy Properties},
  year = {2026},
  publisher = {Hugging Face},
  url = {https://huggingface.co/datasets/juliensimon/gswlc-galaxy-properties},
  note = {Based on GSWLC-2 data (Salim et al. 2016, ApJS 227, 2; Salim et al. 2018, ApJ 859, 11)}
}

License

CC-BY-4.0