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Dust is Hiding how Powerful Quasars Really are

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In the 1970s, astronomers discovered a persistent radio source at the center of our galaxy. supermassive black hole (SMBH).Today, this gravitational giant is known as Sagittarius A* It has about 4 million times the mass of the Sun. Since then, investigations have shown that SMBHs are present at the centers of most massive galaxies and play an important role. star formation When galaxy evolutionAdditionally, the way these black holes consume gas and dust causes each galaxy to emit vast amounts of radiation from its galactic center.

These are what astronomers call active galactic nucleus (AGN), or quasars, become so bright that they temporarily outshine all stars in the disk. In fact, AGN is the most powerful compact and stable energy source in the universe. That’s why astronomers are always looking to take a closer look at AGN. for example, new research Scientists led by the University of California, Santa Cruz (UCSC) noted that they were unaware of how much the AGN’s light could be dimmed by dust, thus greatly underestimating the amount of energy emitted by the AGN. is showing.

Artist’s impression of a powerful young quasar.Credit: ESO/M. Kornmesser Credit: ESO/M. Kornmesser

The research was led by Dr. Martin Gaskell, Research Fellow and Lecturer in the Department of Astronomy and Astrophysics, UCSC. He was joined by a team of engineers, mathematicians, astronomers, and astrophysicists from Harvey His Mad His College, Princeton University, and the University of California, Berkeley. For their study, the team looked at NGC 5548, a Type I Seyfert galaxy about 244.6 million light-years away. The galaxy has a bright AGN attributed to a central SMBH of approximately 65 million solar masses.

The amount of dust is measured by the way the light from the AGN shifts towards the red end of the spectrum. This effect is known as “reddening”, and the amount of reddening corresponds directly to the amount of dimming. Scientists have long recognized that dust can dim the light from her AGN, but the amount was widely thought to be negligible. The problem arose from the fact that astronomers predicted the amount of reddening based on theories about the inherent unreddened colors that astronomers should see.

The results of this latest study show that the amount of obscuring dust, as well as the AGN’s overall brightness, may have been underestimated. The team reached this conclusion by studying the dust reddening effect of the best-studied AGN (NGC 5548) using seven different indices. These included the mean AGN reddening curve, the Milky Way standard reddening curve, and the Small Magellanic Cloud (SMC) curve. In all cases, the reddening of NGC 5548 was found to be about 14 times greater than that observed near the Sun due to the small amount of dust.

As Dr. Gaskell explained to the Royal Astronomical Society, Press release:

“A small particle intervening in our line of sight makes things behind it appear darker. You can see this at sunset on a clear day when the sun is faint. Good between different indicators of redness.” The coincidence was a pleasant surprise, and strongly supports a simple theory of emission from active galactic nuclei, without the need for exotic explanations of color, making life simpler for researchers. , accelerating our understanding of what happens when a black hole engulfs matter.”

Credits: ESA/Hubble, ESO, M. Kornmesser
Artist’s impression of a supermassive black hole and an accretion disk. Credits: ESA/Hubble, ESO, M. Kornmesse

These results indicate that at ultraviolet wavelengths, where most of the energy is emitted, typical AGNs emit orders of magnitude more energy than previously thought. Another point is that AGNs are very similar, and what was thought to be a fundamental difference in brightness and energy output is actually the result of different amounts of dust. This could have dramatic implications for our understanding of the role her SMBH plays in galaxy formation, evolution, and both.

References: Royal Astronomical Society, MNRAS

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