Supermassive black holes, these cosmic giants lurking at the heart of galaxies, continue to intrigue scientists. A recent study, combining data from NASA's IRAS and NuSTAR telescopes, reveals that more than a third of these cosmic monsters are hidden behind thick layers of gas and dust, a figure much higher than previous estimates.
This discovery, published in
The Astrophysical Journal, suggests that 35% of supermassive black holes are heavily obscured, a percentage that challenges current models of galaxy growth. The researchers used IRAS's infrared archives, a telescope from the 1980s, to identify these hidden objects, then used NuSTAR to confirm their presence through X-ray observations.
Artist's concept of a supermassive black hole surrounded by a dust torus, seen through different wavelengths.
Credit: NASA/JPL-Caltech The study highlights the importance of astronomical archives and combining observations at different wavelengths to uncover the secrets of the Universe. Supermassive black holes, though invisible directly, profoundly influence the structure and evolution of the galaxies that host them.
The researchers also discovered that these hidden black holes play a crucial role in regulating star formation. By absorbing or ejecting matter, they can alter the dynamics of galaxies, a process still poorly understood but essential for determining cosmic evolution.
This study opens new perspectives on understanding supermassive black holes and their impact on the Universe. It also underscores the importance of space missions like NuSTAR, which allow us to observe the Universe in wavelengths inaccessible from Earth.
Finally, the researchers hope that these discoveries will encourage further studies to refine cosmological models and better understand the mechanisms governing the growth of galaxies and the supermassive black holes they host.
How do supermassive black holes influence galaxies?
Supermassive black holes, located at the center of galaxies, play a crucial role in the evolution of galaxies. By absorbing matter, they can generate jets of particles and powerful winds that redistribute gas and dust. This process can stimulate or inhibit the formation of new stars, thereby influencing the structure and dynamics of the host galaxy.
The interactions between supermassive black holes and their host galaxies are an active area of research. Scientists are trying to understand how these interactions vary depending on the mass of the black hole, the amount of matter available for accretion, and the properties of the galaxy itself.
Why are some supermassive black holes hidden?
Some supermassive black holes are surrounded by a thick torus of gas and dust, which can make them invisible at certain wavelengths. This phenomenon is due to the orientation of the torus relative to our line of sight: if the torus is viewed edge-on, it blocks the light emitted by the accretion disk around the black hole.
This obscuration can vary depending on the activity of the black hole and the amount of matter available to form the torus. Active supermassive black holes, which accrete large amounts of matter, are more likely to be surrounded by a thick torus.
Observations in infrared and X-rays allow us to pierce this obscuration. Infrared can reveal the heat emitted by the torus, while high-energy X-rays can penetrate the torus and reach detectors, offering a glimpse into the innermost regions around the black hole.