Upload Roma-BZCAT blazar catalog: 3,561 blazars

README.md

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+---
+license: cc-by-4.0
+pretty_name: "Roma-BZCAT Blazar Catalog"
+language:
+  - en
+description: "The definitive catalog of confirmed blazars from the Roma-BZCAT 5th edition — ~3,500 AGN with relativistic jets, including BL Lacs and FSRQs, with multi-frequency data."
+task_categories:
+  - tabular-classification
+tags:
+  - space
+  - open-data
+  - tabular-data
+  - parquet
+  - blazar
+  - agn
+  - roma-bzcat
+  - astronomy
+  - radio
+size_categories:
+  - 1K<n<10K
+configs:
+  - config_name: default
+    data_files:
+      - split: train
+        path: data/roma_bzcat_blazars.parquet
+    default: true
+---
+
+# Roma-BZCAT Multi-frequency Blazar Catalog
+
+<div align="center">
+  <img src="banner.jpg" alt="Hubble Deep Field revealing myriad galaxies across cosmic time" width="400">
+  <p><em>Credit: NASA/ESA/STScI</em></p>
+</div>
+
+*Part of the [Astronomy Datasets](https://huggingface.co/collections/juliensimon/astronomy-datasets-69c24caf2f17e36128946743) collection on Hugging Face.*
+
+![Updated](https://img.shields.io/badge/dynamic/json?url=https://raw.githubusercontent.com/juliensimon/space-datasets/main/status.json&query=$["roma-bzcat"]&label=updated&color=brightgreen)
+
+The Roma-BZCAT 5th edition — **3,561** confirmed blazars, the definitive multi-frequency
+catalog of active galactic nuclei with relativistic jets. Includes **0** BL Lac objects,
+**0** flat-spectrum radio quasars (FSRQs), and **0** galaxy-dominated blazars.
+
+## Dataset description
+
+Blazars are the most extreme class of active galactic nuclei (AGN). They are powered by
+supermassive black holes at the centers of galaxies, but what makes them extraordinary is
+that one of their relativistic jets — twin beams of plasma moving at nearly the speed of
+light — points almost directly at Earth. This geometric alignment produces dramatic
+observational effects: apparent superluminal motion, extreme variability across the
+electromagnetic spectrum (from radio to TeV gamma-rays on timescales from minutes to years),
+strong and variable polarization, and Doppler-boosted luminosities that can outshine the
+entire host galaxy by orders of magnitude.
+
+Blazars are divided into two main subclasses based on their optical spectra:
+
+- **BL Lac objects (BZB)**: named after the prototype BL Lacertae, these sources show
+  featureless or nearly featureless optical continua with weak or absent emission lines
+  (equivalent width < 5 angstroms). Their spectral energy distributions (SEDs) are
+  dominated by non-thermal synchrotron and inverse-Compton emission from the jet, and they
+  are further subdivided by the frequency of their synchrotron peak into low-, intermediate-,
+  and high-synchrotron-peaked BL Lacs (LSP, ISP, HSP).
+
+- **Flat-spectrum radio quasars (BZQ/FSRQ)**: these display strong, broad optical emission
+  lines characteristic of quasars, indicating a luminous accretion disk and broad-line region
+  in addition to the jet. FSRQs tend to be more luminous than BL Lacs and dominate the
+  high-redshift blazar population.
+
+The Roma-BZCAT (Massaro et al. 2009, 2015) is the most comprehensive and widely cited catalog
+of confirmed blazars, compiled from multi-wavelength observations spanning radio, optical,
+and X-ray bands. It serves as the reference catalog for blazar identification in gamma-ray
+surveys (Fermi-LAT), neutrino follow-up programs (IceCube), and multi-messenger astrophysics.
+Every source in Roma-BZCAT has been spectroscopically confirmed or classified through its
+multi-frequency properties, making it the gold standard for blazar demographics and population
+studies.
+
+## Schema
+
+| Column | Type | Description |
+|--------|------|-------------|
+| `seq` | int64 | Seq |
+| `name` | string | Source name / BZCAT designation |
+| `ra_deg` | float64 | Right ascension J2000 (degrees) |
+| `dec_deg` | float64 | Declination J2000 (degrees) |
+| `glon` | float64 | Glon |
+| `glat` | float64 | Glat |
+| `redshift` | float64 | Spectroscopic redshift |
+| `u_z` | string | U z |
+| `r_mag` | float64 | R-band magnitude |
+| `blazar_class` | string | Blazar classification (BZB=BL Lac, BZQ=FSRQ, BZG=galaxy-dominated, BZU=uncertain) |
+| `fr` | float64 | Fr |
+| `f143` | float64 | F143 |
+| `fx` | float64 | Fx |
+| `ff` | float64 | Ff |
+| `aro` | float64 | Aro |
+
+## Quick stats
+
+- **3,561** confirmed blazars
+- **0** BL Lac objects (BZB), **0** FSRQs (BZQ), **0** galaxy-dominated (BZG), **0** uncertain (BZU)
+- **3,561** with measured redshift (median z = 0.636, max z = 6.802)
+- **0** with radio flux, **0** with X-ray flux
+- Classes: QSO RLoud flat radio sp. (1,909), BL Lac (1,059), BL Lac-galaxy dominated (274), Blazar Uncertain type (227), BL Lac Candidate (92)
+
+## Usage
+
+```python
+from datasets import load_dataset
+
+ds = load_dataset("juliensimon/roma-bzcat-blazars", split="train")
+df = ds.to_pandas()
+
+# BL Lac objects vs FSRQs
+bl_lacs = df[df["blazar_class"].str.startswith("BZB", na=False)]
+fsrqs = df[df["blazar_class"].str.startswith("BZQ", na=False)]
+print(f"{len(bl_lacs):,} BL Lacs, {len(fsrqs):,} FSRQs")
+
+# Redshift distribution by class
+import matplotlib.pyplot as plt
+for cls, label in [("BZB", "BL Lac"), ("BZQ", "FSRQ")]:
+    subset = df[df["blazar_class"].str.startswith(cls, na=False)]
+    subset["redshift"].dropna().hist(bins=50, alpha=0.6, label=label)
+plt.xlabel("Redshift")
+plt.ylabel("Count")
+plt.legend()
+plt.title("Roma-BZCAT Redshift Distribution by Blazar Class")
+
+# Radio-loud blazars
+radio_bright = df[df["radio_flux_mjy"] > 1000].sort_values("radio_flux_mjy", ascending=False)
+print(f"{len(radio_bright):,} blazars with radio flux > 1 Jy")
+```
+
+## Data source
+
+Massaro, E., Maselli, A., Leto, C., Marchegiani, P., Perri, M., Giommi, P., Piranomonte, S.
+(2015), "The 5th edition of the Roma-BZCAT. A short presentation",
+*Astrophysics and Space Science*, 357, 75.
+Accessed via [VizieR](https://vizier.cds.unistra.fr/) catalog VII/274, CDS Strasbourg.
+
+## Update schedule
+
+Static dataset — rebuilt manually when a new edition is published.
+
+## Related datasets
+
+- [quasar-catalog](https://huggingface.co/datasets/juliensimon/quasar-catalog) — SIMBAD Quasar & AGN Catalog
+- [milliquas](https://huggingface.co/datasets/juliensimon/milliquas) — Million Quasars Catalog v8
+- [fermi-4lac-agn-catalog](https://huggingface.co/datasets/juliensimon/fermi-4lac-agn-catalog) — Fermi 4LAC AGN Catalog
+- [fermi-4fgl-dr4](https://huggingface.co/datasets/juliensimon/fermi-4fgl-dr4) — Fermi 4FGL-DR4 Source Catalog
+
+## Pipeline
+
+Source code: [juliensimon/space-datasets](https://github.com/juliensimon/space-datasets)
+
+## Support
+
+If you find this dataset useful, please give it a ❤️ on the [dataset page](https://huggingface.co/datasets/juliensimon/roma-bzcat-blazars) and share feedback in the Community tab! Also consider giving a ⭐️ to the [space-datasets](https://github.com/juliensimon/space-datasets) repo.
+
+## Citation
+
+```bibtex
+@dataset{roma_bzcat_blazars,
+  author = {Simon, Julien},
+  title = {Roma-BZCAT Multi-frequency Blazar Catalog},
+  year = {2026},
+  publisher = {Hugging Face},
+  url = {https://huggingface.co/datasets/juliensimon/roma-bzcat-blazars},
+  note = {Based on Roma-BZCAT 5th edition (Massaro et al. 2015) via VizieR CDS Strasbourg}
+}
+```
+
+## License
+
+[CC-BY-4.0](https://creativecommons.org/licenses/by/4.0/)

data/roma_bzcat_blazars.parquet

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