Black holes may grow quietly alongside galaxies even without violent mergers

Astronomers have discovered that massive black holes can grow within galaxies that lack a central bulge, challenging the belief that mergers are necessary for black hole growth. By analyzing data from the Dark Energy Spectroscopic Instrument (DESI), researchers identified 546 bulgeless galaxies among 2,435 disk galaxies hosting actively feeding black holes.

The study, published in Monthly Notices of the Royal Astronomical Society, suggests that black holes can grow through secular processes like gas inflows along spiral arms and bars, rather than merging with other galaxies. The findings, led by Sophie M. Jewell of the University of Oxford, indicate that bulgeless galaxies still exhibit a black hole-to-stellar mass relation consistent with galaxies that have bulges, implying merger-free growth can produce normal co-evolution.

However, the discrepancy between observed black hole masses and those predicted by cosmological simulations hints at limitations in the simulations, potentially underrepresenting a large population of SMBHs.