Resolve the origin of mid-infrared AGN-selection false positives

Determine whether mid-infrared color-selected active galactic nuclei in dwarf galaxies are genuine accreting black holes or contaminants produced by young stellar populations, high-mass X-ray binaries, and ultraluminous X-ray sources.

Background

The paper explains that dust heating associated with high-mass X-ray binaries and ultraluminous X-ray sources can generate mid-infrared temperatures similar to those expected from active galactic nuclei. Consequently, the reliability of WISE color selections—especially in star-forming dwarf galaxies—remains unresolved and affects estimates of the black-hole occupation fraction.

References

As dust heating near HMXBs and ULXs can match temperatures near AGN, the question of false positives challenges our limited understanding the frequency and distribution of stellar-mass compact objects vs. intermediate- and higher-mass BHs.

— A Comprehensive AGN Inventory for the Dwarf-Dominated RESOLVE and ECO Surveys: Mass-Dependent AGN Types and Occupation Fractions  (2610.22115 - Polimera et al., 15 Oct 2026) in Section 3, AGN Detection using Mid-IR WISE Colors

While the current data do not allow us to draw a firm conclusion, this diagnostic again leaves open the possibility that U13151 might be a composite system with, perhaps, a weak AGN contribution. Overall, deeper, higher-resolution UV spectroscopy will be crucial to finally identify the dominant source of ionization in this peculiar system and to assess whether U13151 could host an accreting intermediate-mass black hole (IMBH).

— PRISMS/U13151. A Glimpse into the Earliest Phases of Galaxy Formation through an Ultra-Faint System $\approx$ 500 Myr after the Big Bang  (2610.26560 - Rinaldi et al., 19 Oct 2026) in Section 3.2.8, subsection “Does U13151 host an AGN?”; reiterated in Section 5