Paige Ramsden, Sean L. McGee, and Matt Nicholl, researchers from the University of Edinburgh’s School of Physics and Astronomy, have uncovered an unexpected population of galaxies that could have implications for our understanding of how galaxies evolve and how supermassive black holes (SMBHs) influence their host galaxies. Their findings were recently published in the journal Nature Astronomy.
The team studied tidal disruption events (TDEs), which occur when a star passes too close to a SMBH and is torn apart by the black hole’s gravitational forces. These events provide a unique opportunity to study otherwise hidden SMBHs at the lower end of the mass spectrum. By analyzing the light emitted by 42 TDE host galaxies, the researchers were able to estimate the stellar masses, specific star formation rates, and SMBH masses of these galaxies.
The researchers first confirmed a well-established result: quenched galaxies, which are galaxies that have stopped forming stars, tend to host more massive SMBHs than star-forming galaxies of the same stellar mass. This result is widely interpreted as evidence that SMBH growth drives the transition of galaxies from the blue (star-forming) sequence to the red (quenched) sequence.
However, when the researchers examined the TDE sample in isolation, they uncovered a surprising trend at lower masses. They found a population of low-mass, quenched galaxies hosting SMBHs that are systematically less massive than those in star-forming galaxies of comparable stellar mass. This suggests that the quenching mechanism in these TDE hosts is different from that in more massive galaxies.
The researchers ruled out potential biases in their analysis and concluded that this trend reflects a physical difference in the quenching mechanism. They suggest that this difference could be driven by environmental processes, such as interactions with other galaxies or the hot gas in galaxy clusters, which can end star formation and hinder SMBH growth. They also note that the quenched and post-starburst population within the TDE sample is likely under-represented due to selection biases, suggesting that the true fraction could be even higher than observed.
This research has important implications for the energy sector, particularly for understanding the role of SMBHs in galaxy evolution and the potential impact of environmental processes on star formation and SMBH growth. As we continue to develop new technologies for exploring the universe, such as the James Webb Space Telescope, we can expect to learn even more about these fascinating objects and their role in shaping the galaxies we see today.
This article is based on research available at arXiv.