QORG Catalog: 501,756 All-Sky Optical Objects Associated with Radio/X-Ray Sources

501,756 optical objects are associated with radio or X-ray detections, representing 99.4% sky coverage from APM and USNO-A surveys. The Quasars.org (QORG) Catalog overlays multiple X-ray and radio survey data onto optical catalogs to calculate probabilities for each object being a quasar, galaxy, star, or erroneous association. This master catalog was created by the HEASARC in November 2004 based on CDS data and is maintained by NASA.

Use Cases

• Classifying astronomical objects as quasars, galaxies, or stars based on calculated probability scores.
• Cross-matching optical objects with radio/X-ray detections from surveys like NVSS, FIRST, SUMSS, and ROSAT.
• Identifying candidate double-lobe radio sources from the 21,498 entries.
• Analyzing the correlation between optical magnitudes and radio/X-ray fluxes for associated objects.

Strengths

• Covers 501,756 objects, including 48,285 catalogued quasars.
• Provides 99.4% sky coverage by combining APM and USNO-A optical surveys.
• Integrates data from six major radio and X-ray catalogs released between 2001 and 2003.
• Includes calculated probability scores for object classification.

Limitations

• Column-level documentation is absent; field semantics must be inferred after download.
• Data is based on surveys from the early 2000s; newer observations are not included.
• Row count for specific subset catalogs is unknown.

Provenance

Source

National Aeronautics and Space Administration (NASA), HEASARC, based on CDS Catalog J/A+A/427/387.

Collection Method

Alignment and overlay of multiple X-ray, radio, and optical survey catalogs onto APM and USNO-A optical data.

Time Range

Based on survey data releases from 2001-2003.

Freshness

Last updated 2026-03-13 18:28:37.055776; freshness should be verified.

Geography

All-sky (99.4% coverage).