README.md

---
license: other
license_name: vizier-scientific-use
license_link: https://cds.unistra.fr/vizier-org/licences_vizier.html
pretty_name: "Veron-Cetty AGN/Quasar Catalog (13th edition)"
language:
  - en
description: "The Veron-Cetty & Veron Quasars and Active Nuclei catalog, 13th edition (VizieR VII/258) — the canonical reference compilation of 168,940 quasars and active galactic nuclei published through 2010, cov"
task_categories:
  - tabular-classification
tags:
  - space
  - astronomy
  - agn
  - quasars
  - active-galactic-nuclei
  - seyfert
  - blazars
  - bl-lac
  - vizier
  - open-data
  - tabular-data
  - parquet
size_categories:
  - 100K<n<1M
configs:
  - config_name: default
    data_files:
      - split: train
        path: data/veron_agn_catalog.parquet
    default: true
---

# Veron-Cetty AGN/Quasar Catalog (13th edition)


<div align="center">
  <img src="banner.jpg" alt="Artist concept of a supermassive black hole with a relativistic jet — AGN engine" width="400">
  <p><em>Credit: NASA/JPL-Caltech</em></p>
</div>


*Part of a [dataset collection](https://huggingface.co/collections/juliensimon/galaxies-and-cosmology-69c792b117242a3b236df55d) on Hugging Face.*

## Dataset description

The Veron-Cetty & Veron Quasars and Active Nuclei catalog, 13th edition (VizieR VII/258) — the canonical reference compilation of 168,940 quasars and active galactic nuclei published through 2010, covering optical/UV-selected quasars, X-ray-selected AGN, radio galaxies, and BL Lac objects.

The catalog merges every published QSO and AGN identification with a homogeneous position, spectroscopic redshift, optical photometry, B-V and U-B colors, absolute magnitude, and (where available) radio fluxes at 6 cm and 20 cm. It remains the standard look-up source for cross-matching unidentified sources against the established AGN population, for selecting training/test samples by spectral subclass (Seyfert 1, Seyfert 2, LINER, BL Lac), and for population statistics in redshift, luminosity, and color spaces.

Object class column conventions: 'Q' marks quasars (M_V <= -23, brighter than the historical QSO/AGN boundary), 'A' marks lower-luminosity AGN (M_V > -23), and 'B' marks BL Lac objects. The spectral classification column captures Seyfert sub-type and special spectral phenomena. Use this dataset alongside juliensimon/milliquas (the more recent Million Quasars Catalog that supersedes Veron for survey-era discoveries), juliensimon/gaia-dr3-qso-candidates (Gaia-selected QSOs), juliensimon/black-hole-catalog, juliensimon/4xmm-dr14-xray-sources, and juliensimon/icrf3-reference-frame for AGN cross-mission analysis.

This dataset is suitable for **tabular classification** tasks.

## Schema

| Column | Type | Description | Sample | Null % |
|--------|------|-------------|--------|--------|
| `object_class` | str | Object classification: 'Q' = quasar (M_abs <= -23, brighter than -23), 'A' = AGN (M_abs > -23, fainter), 'B' = BL Lac object | Q | 0.0% |
| `radio_flag` | str | Radio-detection flag: '*' = detected at radio frequencies, blank = not detected (or no radio coverage) | * | 11.3% |
| `name` | str | Primary designation (catalog and survey ID), typically 'SDSS Jhhmm+ddmm', '4C+nn.nn', 'PG hhmm+ddd', etc. | SDSS J03003+0009 | 0.0% |
| `position_origin` | str | Origin code for the J2000 coordinates: 'O' = optical position, 'R' = radio position, 'X' = X-ray, etc. | O | 2.5% |
| `ra` | float64 | Right ascension (degrees, J2000) | 45.07541666666666 | 0.0% |
| `dec` | float64 | Declination (degrees, J2000) | 0.1524999999999999 | 0.0% |
| `flux_20cm_mjy` | float64 | Radio flux density at 20 cm (1.4 GHz) in mJy where detected | 0.0 | 89.2% |
| `flux_20cm_reference` | float64 | Bibliographic reference code for the 20 cm flux measurement | 2068.0 | 64.6% |
| `redshift` | float64 | Spectroscopic or photometric redshift z (dimensionless); range ~0 to ~7 in this compilation | 2.23 | 0.4% |
| `spectral_classification` | str | Spectral subclass code: 'S1' = Seyfert 1, 'S2' = Seyfert 2, 'S1.5'/'S1.9' = intermediate types, 'NLAGN' = narrow-line AGN, 'HP' = high polarization, 'LINER' = LINER, blank = standard QSO | S2 | 82.7% |
| `magnitude_band` | str | Photometric system letter for the magnitude: 'V' = Johnson V, 'B' = blue, 'R' = red, 'g' = SDSS g, etc. | * | 81.4% |
| `apparent_magnitude` | float64 | Apparent magnitude in the band identified by magnitude_band; brighter sources have smaller values | 20.45 | 0.4% |
| `color_bv` | float64 | Johnson B-V color index (mag); positive values indicate redder colors | 0.28 | 22.1% |
| `color_ub` | float64 | Johnson U-B color index (mag); the 'UV excess' (negative U-B) is the historical AGN selection signature | -0.18 | 9.7% |
| `absolute_magnitude` | float64 | Absolute V magnitude M_V (mag); the Q/A class boundary is M_V = -23. Computed assuming H_0 = 71, Omega_M = 0.27, Omega_lambda = 0.73 | -24.4 | 0.7% |
| `finding_chart_reference` | float64 | Bibliographic reference code for a published finding chart of the source | 529.0 | 93.5% |
| `magnitude_reference` | float64 | Bibliographic reference code for the magnitude measurement | 2068.0 | 9.1% |
| `redshift_reference` | float64 | Bibliographic reference code for the redshift | 2068.0 | 0.0% |

## Quick stats

- **168,940** quasars + AGN + BL Lac objects in the canonical compilation
- **133,335** quasars (M_V <= -23) + **34,231** lower-luminosity AGN + **1,374** BL Lac objects
- **149,874** sources with detected radio counterparts (6cm or 20cm)
- Redshift range: **0.00** to **6.43** (median 1.35)
- Absolute magnitude (M_V): **-31.5** (most luminous) to **-7.8** (faintest)

## Usage

```python
from datasets import load_dataset

ds = load_dataset("juliensimon/veron-agn-quasar-catalog", split="train")
df = ds.to_pandas()
```

```python
from datasets import load_dataset
import matplotlib.pyplot as plt
import numpy as np

df = load_dataset("juliensimon/veron-agn-quasar-catalog", split="train").to_pandas()

# Hubble diagram: absolute magnitude vs redshift, colored by class
mask = df["redshift"].notna() & df["absolute_magnitude"].notna()
fig, ax = plt.subplots(figsize=(10, 6))
for cls, color in zip(["Q", "A", "B"], ["blue", "orange", "red"]):
    sub = df[mask & (df["object_class"] == cls)]
    ax.scatter(sub["redshift"], sub["absolute_magnitude"], s=2, alpha=0.3, color=color, label=cls)
ax.axhline(-23, color="grey", linestyle="--", label="QSO/AGN boundary")
ax.invert_yaxis()  # brighter = up
ax.set_xscale("log")
ax.set_xlabel("Redshift z")
ax.set_ylabel("Absolute V magnitude")
ax.legend()
plt.tight_layout()
plt.show()

# Seyfert sub-type breakdown
print(df["spectral_classification"].value_counts().head(15))
```

## Data source

https://cdsarc.cds.unistra.fr/viz-bin/cat/VII/258

## Related datasets

- [juliensimon/milliquas](https://huggingface.co/datasets/juliensimon/milliquas)

- [juliensimon/gaia-dr3-qso-candidates](https://huggingface.co/datasets/juliensimon/gaia-dr3-qso-candidates)

- [juliensimon/black-hole-catalog](https://huggingface.co/datasets/juliensimon/black-hole-catalog)

- [juliensimon/4xmm-dr14-xray-sources](https://huggingface.co/datasets/juliensimon/4xmm-dr14-xray-sources)

- [juliensimon/icrf3-reference-frame](https://huggingface.co/datasets/juliensimon/icrf3-reference-frame)

- [juliensimon/roma-bzcat-blazars](https://huggingface.co/datasets/juliensimon/roma-bzcat-blazars)

> If you find this dataset useful, please consider [giving it a like](https://huggingface.co/datasets/juliensimon/veron-agn-quasar-catalog) on Hugging Face. It helps others discover it.

## About the author

Created by [Julien Simon](https://julien.org) — AI Operating Partner at Fortino Capital. Part of the [Space Datasets](https://julien.org/datasets) collection.

## Citation

```bibtex
@dataset{veron_agn_quasar_catalog,
  title = {Veron-Cetty AGN/Quasar Catalog (13th edition)},
  author = {juliensimon},
  year = {2026},
  url = {https://huggingface.co/datasets/juliensimon/veron-agn-quasar-catalog},
  publisher = {Hugging Face}
}
```

## License


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