Recent James Webb Space Telescope (JWST) observations have unveiled a surprising dearth of active black holes at the centers of galaxies, challenging prior expectations. This revelation, submitted in a paper to arXiv.org on August 22, has ignited inquiries into the growth of supermassive black holes and their influence on host galaxies.
Typically, large black holes residing at galaxy cores remain relatively quiescent. However, they can undergo activation, emitting copious light across all wavelengths when they consume interstellar material, frequently following galaxy collisions, resulting in what astronomers call active galactic nuclei (AGN). These AGN can outshine their host galaxies and rank among the universe's brightest light sources.
Astronomers had anticipated that JWST's infrared capabilities, more sensitive than prior space-based infrared telescopes, would identify numerous active black holes. Yet, when JWST scrutinized a well-studied sky region where the Spitzer Space Telescope had previously detected AGN signatures in nearly one-third of 19 galaxies, it found active galactic nuclei in only 6 percent of nearly 500 surveyed galaxies.
This revelation implies that astronomers are now exploring a fresh galaxy population distinct from prior studies. These galaxies, situated in the universe's distant realms, may contain rapidly growing black holes concealed within interstellar dust, making them challenging to discern due to current technical limitations.
If the number of swiftly growing black holes is indeed lower than anticipated, it could disrupt prevailing theories about black hole and galaxy formation. Supermassive black holes, some weighing as much as several billion suns, are believed to amass mass during their AGN phase. However, if not all galaxies experience this active phase, some black holes might require an initial substantial mass rather than evolving from smaller entities.
Moreover, active black holes can significantly affect their host galaxies by raising their temperature, inhibiting star formation, and propelling powerful winds that disrupt the formation of life-sustaining planets. If numerous black holes bypass the AGN phase, their influence on host galaxies could be limited.
Alternatively, the perceived scarcity of active black holes in JWST's data may be due to their fleeting, sporadic bursts of activity, making their detection a formidable challenge.
Further insights may emerge from forthcoming JWST observations, as astronomers intend to expand their search to thousands of galaxies in forthcoming research endeavors.