Identification of 1.4 Million AGNs in the Mid-Infrared using WISE Data

TL;DR

This paper presents an all-sky catalog of approximately 1.4 million AGNs identified through infrared color selection using WISE data, with high completeness and minimal star contamination, greatly expanding known AGN samples.

Contribution

The study introduces a new all-sky AGN catalog based on infrared photometry, achieving high completeness and low star contamination, and includes a large number of previously uncatalogued AGNs.

Findings

Mean AGN density of ~38 per square degree

Completeness of >84% for AGNs brighter than R<19

Less than 0.041% contamination from optically-identified stars

Abstract

We present an all-sky sample of ~ 1.4 million AGNs meeting a two color infrared photometric selection criteria for AGNs as applied to sources from the Wide-Field Infrared Survey Explorer final catalog release (AllWISE). We assess the spatial distribution and optical properties of our sample and find that the results are consistent with expectations for AGNs. These sources have a mean density of ~ 38 AGNs per square degree on the sky, and their apparent magnitude distribution peaks at g ~ 20, extending to objects as faint as g ~ 26. We test the AGN selection criteria against a large sample of optically-identified stars and determine the "leakage" (that is, the probability that a star detected in an optical survey will be misidentified as a QSO in our sample) rate to be < 4.0 x 10^-5. We conclude that our sample contains almost no optically-identified stars (< 0.041%), making this sample highly promising for future celestial reference frame work by significantly increasing the number of all-sky, compact extragalactic objects. We further compare our sample to catalogs of known AGNs/QSOs and find a completeness value of > 84% (that is, the probability of correctly identifying a known AGN/QSO is at least 84%) for AGNs brighter than a limiting magnitude of R < 19. Our sample includes approximately 1.1 million previously uncatalogued AGNs.