Properties of ultralight bosons from heavy quasar spins via superradiance

Caner Unal, Fabio Pacucci, Abraham Loeb

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


The mass and the spin of accreting and jetted black holes, at the center of Active Galactic Nuclei (AGNs), can be probed by analyzing their electromagnetic spectra. For this purpose, we use the Spin-Modified Fundamental Plane of black hole activity, which non-linearly connects the following four variables (in the source frame): radio luminosity, X-ray or optical luminosity (via the [OIII] emission line), black hole mass and spin. Taking into account the uncertainties in luminosity measurements, conversion factors, relativistic beaming and physical properties of the AGN system, we derive lower bounds on the spins of a group of heavy, jetted AGNs. Using these results, we study the direct implications on the mass spectrum of the ultra-light particles of scalar (axion-like), vector (dark photon) and tensor types (additional spin-2 particles). We close unexplored gap in the parameter space 10-20-10-19eV. We obtain upper bounds on the axion decay constant (equivalently lower bounds on the self-interaction strength) considering self-interactions could prevent the axion particles entering the instability, and be the reason for non-observation of superradiance. Assuming axion is described by mass and decay constant, we obtain upper limits on what fraction of dark matter can be formed by ultra-light particles and find that single spieces axion-like light particle can constitute at most 10% of the dark matter in the mass range: 10-21 < μ (eV) < 10-17.

Original languageEnglish
Article number007
JournalJournal of Cosmology and Astroparticle Physics
Issue number5
StatePublished - 1 May 2021

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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