---
license: other
license_name: vizier-scientific-use
license_link: https://cds.unistra.fr/vizier-org/licences_vizier.html
pretty_name: "Sydney University Molonglo Sky Survey (SUMSS)"
language:
  - en
description: "SUMSS catalog of 211,050 radio sources at 843 MHz from the Molonglo Observatory Synthesis Telescope."
task_categories:
  - tabular-classification
  - tabular-regression
tags:
  - space
  - radio
  - sumss
  - molonglo
  - 843mhz
  - astronomy
  - open-data
size_categories:
  - 100K<n<1M
---

# Sydney University Molonglo Sky Survey (SUMSS)

The Sydney University Molonglo Sky Survey (SUMSS) at 843 MHz, the southern-sky complement to
NVSS. Observed with the Molonglo Observatory Synthesis Telescope (MOST), covering declinations
south of -30 deg. Contains **211,050** discrete radio sources.

## Dataset description

SUMSS is a deep radio survey at 843 MHz covering 8,100 square degrees of the southern sky
(declination < -30 deg) with 45 x 45 cosec|dec| arcsecond resolution. It fills the gap left
by northern-hemisphere surveys like NVSS and FIRST, providing a matched-sensitivity southern
radio catalog essential for all-sky studies.

## Schema

| Column | Type | Description |
|--------|------|-------------|
| `ra_deg` | float64 | Right ascension J2000 (degrees) |
| `dec_deg` | float64 | Declination J2000 (degrees) |
| `peak_flux_mjy` | float64 | Peak flux density (mJy/beam) |
| `integrated_flux_mjy` | float64 | Integrated flux density (mJy) |
| `e_integrated_flux_mjy` | float64 | Error on integrated flux (mJy) |
| `major_axis_arcsec` | float64 | Fitted major axis FWHM (arcsec) |
| `minor_axis_arcsec` | float64 | Fitted minor axis FWHM (arcsec) |
| `position_angle_deg` | float64 | Position angle (degrees) |
| `deconv_major_arcsec` | float64 | Deconvolved major axis (arcsec) |
| `deconv_minor_arcsec` | float64 | Deconvolved minor axis (arcsec) |
| `deconv_pa_deg` | float64 | Deconvolved position angle (degrees) |
| `mosaic_name` | string | Mosaic image name |
| `is_resolved` | bool | True if deconvolved major axis > 0 |

## Quick stats

- **211,050** radio sources at 843 MHz
- **0** resolved sources (0.0%)
- Median peak flux: 18.90 mJy/beam
- Sky coverage: RA 0.0--360.0 deg, Dec -89.9---26.0 deg

## Usage

```python
from datasets import load_dataset

ds = load_dataset("juliensimon/sumss-radio-catalog", split="train")
df = ds.to_pandas()

# Flux distribution
import matplotlib.pyplot as plt
df["peak_flux_mjy"].clip(upper=500).hist(bins=200, log=True)
plt.xlabel("Peak flux at 843 MHz (mJy/beam)")
plt.ylabel("Count")
plt.title("SUMSS Source Flux Distribution")
plt.show()

# Sky coverage (southern sky)
plt.scatter(df["ra_deg"], df["dec_deg"], s=0.01, alpha=0.1)
plt.xlabel("RA (deg)")
plt.ylabel("Dec (deg)")
plt.title("SUMSS Sky Coverage (843 MHz, Dec < -30)")
plt.show()

# Resolved vs unresolved
print(f"Resolved: {df['is_resolved'].sum():,}")
print(f"Unresolved: {(~df['is_resolved']).sum():,}")
```

## Data source

Mauch, T., Murphy, T., Buttery, H.J., Curran, J., Hunstead, R.W., Piestrzynski, B.,
Robertson, J.G., and Sadler, E.M. (2003),
*SUMSS: A wide-field radio imaging survey of the southern sky. II. The source catalogue.*
Monthly Notices of the Royal Astronomical Society, 342, 1117.
Via [VizieR](https://vizier.cds.unistra.fr/) CDS Strasbourg (VIII/81B).

## Pipeline

Source code: [juliensimon/space-datasets](https://github.com/juliensimon/space-datasets)

## Citation

```bibtex
@dataset{sumss_radio_catalog,
  author = {Simon, Julien},
  title = {Sydney University Molonglo Sky Survey (SUMSS)},
  year = {2026},
  publisher = {Hugging Face},
  url = {https://huggingface.co/datasets/juliensimon/sumss-radio-catalog},
  note = {Based on Mauch et al. (2003) via VizieR CDS Strasbourg}
}
```

## License


[VizieR Scientific-Use Terms](https://cds.unistra.fr/vizier-org/licences_vizier.html)