Axion core - halo mass and the black hole - halo mass relation: constraints on a few parsec scales

Understand

If the dark matter is made of ultra-light axions, stable solitonic cores form at the centers of virialized halos.

• In some range for the mass $m$ of the axion particle, these cores are sufficiently compact and can mimic supermassive black holes (SMBH) residing at galactic nuclei.
• We use the solitonic core--halo mass relation, validated in numerical simulations, to constrain a new range of allowed axion mass from measurements of the SMBH mass in (pseudo)bulge and bulgeless galaxies.
• These limits are based on observations of galactic nuclei on scales smaller than 10 pc.