juliensimon/erosita-erass1-xray

---
license: cc-by-4.0
pretty_name: "eROSITA eRASS1 X-Ray Source Catalog"
language:
- en
description: "The largest X-ray source catalog ever compiled — 930,203 sources from the first eROSITA All-Sky Survey (eRASS1), released January 2024."
task_categories:
- tabular-classification
- tabular-regression
tags:
- space
- x-ray
- erosita
- erass1
- astronomy
- mpe
- open-data
size_categories:
- 100K<n<1M
---

# eROSITA eRASS1 X-Ray Source Catalog


The largest X-ray source catalog ever compiled: **930,203** sources from the
first eROSITA All-Sky Survey (eRASS1).

## Dataset description

The extended ROentgen Survey with an Imaging Telescope Array (eROSITA) aboard
the Spectrum-Roentgen-Gamma (SRG) satellite performed its first All-Sky Survey
(eRASS1) in the 0.2--2.3 keV band, detecting approximately 900,000 X-ray
sources across the Western Galactic hemisphere. This is the largest X-ray
source catalog ever produced, comprising active galactic nuclei, galaxy clusters,
stars, X-ray binaries, and other X-ray-emitting objects.

Released in January 2024, the eRASS1 catalog represents a four-fold increase
over the total number of X-ray sources known before eROSITA.

## Schema

| Column | Type | Description |
|--------|------|-------------|
| `source_name` | string | eROSITA IAU source designation |
| `ra_deg` | float64 | Right Ascension (degrees, ICRS) |
| `dec_deg` | float64 | Declination (degrees, ICRS) |
| `glon_deg` | float64 | Galactic longitude (degrees) |
| `glat_deg` | float64 | Galactic latitude (degrees) |
| `extent_arcsec` | float64 | Source extent (arcsec, 0 = point-like) |
| `position_error_arcsec` | float64 | Positional uncertainty (arcsec) |
| `mjd` | float64 | Modified Julian Date of observation |
| `is_extended` | bool | Extended source flag (extent > 0) |

## Quick stats

- **930,203** X-ray sources
- **26,682** extended sources (galaxy clusters, etc.)
- **903,521** point-like sources (AGN, stars, etc.)

## Usage

```python
from datasets import load_dataset

ds = load_dataset("juliensimon/erosita-erass1-xray", split="train")
df = ds.to_pandas()

# Extended sources (galaxy clusters)
clusters = df[df["is_extended"] == True]

# Sky map
import matplotlib.pyplot as plt
fig, ax = plt.subplots(figsize=(12, 6))
ax.scatter(df["ra_deg"], df["dec_deg"], s=0.01, alpha=0.1)
ax.set_xlabel("RA (deg)")
ax.set_ylabel("Dec (deg)")
ax.invert_xaxis()
```

## Data source

Merloni et al. (2024), *The SRG/eROSITA All-Sky Survey: The first X-ray
catalogue (eRASS1)*. A&A 682, A34. Data retrieved via
[VizieR CDS](https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/A+A/682/A34).

## Update schedule

Semi-annual (June 1) via [GitHub Actions](https://github.com/juliensimon/space-datasets).

## Related datasets

- [fermi-4fgl-dr4](https://huggingface.co/datasets/juliensimon/fermi-4fgl-dr4) -- Fermi gamma-ray source catalog
- [pulsar-catalog](https://huggingface.co/datasets/juliensimon/pulsar-catalog) -- Pulsar catalog
- [galaxy-cluster-catalog](https://huggingface.co/datasets/juliensimon/galaxy-cluster-catalog) -- Galaxy cluster catalog

## Pipeline

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

## Citation

```bibtex
@dataset{erosita_erass1,
author = {Simon, Julien},
title = {eROSITA eRASS1 X-Ray Source Catalog},
year = {2026},
publisher = {Hugging Face},
url = {https://huggingface.co/datasets/juliensimon/erosita-erass1-xray},
note = {Based on eROSITA eRASS1 catalog (Merloni et al. 2024) via VizieR CDS}
}
```

## License

[CC-BY-4.0](https://creativecommons.org/licenses/by/4.0/)