Fuelling, evolution, and diversity of active galactic nuclei in dwarf galaxies: Insights from star formation and black hole scaling relations

We investigated the star formation activity and black hole scaling relations in a sample of 1, 451 active galactic nuclei (AGNs) hosted by dwarf galaxies (łog (M_⋆/M_⊙) 4). We note that black hole masses have been estimated from narrow-line diagnostics, which introduce significant scatter and can carry substantial uncertainties for individual sources, though they remain useful for identifying statistical trends. Our key findings are: (i) All AGN populations show suppressed star formation at low AGN luminosities, with SFR_ norm rising above unity at different luminosity thresholds depending on AGN type. (ii) LINERs show flat SFR_ norm trends with M_ BH remaining broadly consistent with unity. Seyferts display a mild increase with M_ BH while IR AGNs show a more pronounced positive trend. (iii) LINERs have older stellar populations than Seyferts. (iv) At fixed stellar mass, Seyferts host more massive black holes than LINERs, with IR AGNs falling in between. (v) The M_ BH /M_⋆ ratio is elevated relative to local scaling relations and remains approximately constant with redshift over 0. 5 < z < 0. 9, in agreement with high-z AGN measurements. (vi) The ratio decreases with stellar mass up to łog (M_⋆/M_⊙) ∼ 11, beyond which it flattens towards values consistent with those of local, inactive galaxies; this trend is clearest for Seyferts and IR AGNs, while LINERs show no clear dependence. These results suggest that AGNs in dwarf galaxies follow diverse evolutionary pathways, shaped by gas availability, feedback, and selection effects.