Nothing evokes a spiral of existential perspectives more than looking at a picture of the galaxy. At first glance, these sublime buildings may seem rather serene. In reality, however, the centers of many galaxies are turbulent environments containing actively feeding supermassive black holes. These incredibly dense objects feed the black holes, the gases and dust that emit abundant energy across the electromagnetic spectrum, from high-energy gamma rays and X-rays to visible light, infrared, and radio waves. It orbits around a swirling accretion disk. By studying accretion disks, astronomers can improve our understanding of the evolution of black holes and their host galaxies. However, most accretion disks cannot be imaged directly due to their great distance and relatively small size. Instead, astronomers use the spectrum of light emitted from the disk’s interior to characterize its size and behavior.
Using this approach, astronomers using the Gemini North Telescope, half of the International Gemini Observatory operated by NSF’s NOIRLab, have discovered for the first time two near-infrared emission lines in the accretion disk of galaxy III Zw 002. and broke new ground in space. The size of this magnificent building. To understand these observations, let us first lay the groundwork by discussing what emission lines are and what they tell us about the region around a supermassive black hole. Emission lines are formed when atoms in an excited state fall to a lower energy level, emitting light in the process. Because each atom has a unique energy level, the emitted light has a distinct wavelength that acts like a fingerprint, identifying the atom’s origin. Emission lines often appear as narrow, sharp peaks in the spectrum.
However, in the accretion disk vortex, the excited gas is moving at speeds of thousands of kilometers per second under the gravitational influence of the supermassive black hole, and the emission line spreads to a flatter apex. The region of the accretion disk where these lines originate is called the broadline region. As mentioned earlier, it is very difficult to image the accretion disk directly, as only two sources were imaged thanks to the high angular resolution of the Event Horizon Telescope. Unless we have access to a worldwide network of radio telescopes, how can astronomers know when a supermassive black hole is surrounded by a disk? It turned out to be found in a specific pattern of broad emission lines, called .
As the disc rotates, gas on one side moves away from the observer and gas on the other side moves toward the observer. These relative movements stretch the emission lines to longer and shorter wavelengths, respectively. The result is a broad line with two distinct peaks, one on each side of the rapidly spinning disc. These double peak profiles are a rare phenomenon as their occurrence is restricted to sources observable near the front. In some sources where this was observed, double peaks were found in his H-alpha and H-beta rays, two emission lines in her from hydrogen atoms appearing in the visible wavelength range. These lines come from inside the broad line region near the supermassive black hole and do not indicate the overall size of the accretion disk. However, recent near-infrared observations have revealed the existence of a previously unseen region outside the broadline. Dr. Denimara Díaz dos Santos, a student at the National Institute of Pesquizas in Brazil and the lead author of the study, is Alberto Rodríguez Ardila, a researcher at the Brazilian National Institute of Astronomy, Swayamutrupta In collaboration with Panda and Murillo Marinero, they made the first unambiguous discovery of two nearby objects. Infrared double peak profile in the broadline region of -III Zw 002.
The Paschen alpha (hydrogen) line originates from the interior of the broadline region, and the OI (neutral oxygen) line originates from the edge of the broadline region, a previously unobserved region. These are the first double-peak profiles discovered in the near-infrared region and unexpectedly appeared during observations with the Gemini Near-Infrared Spectrometer (GNIRS). Visible observations of III Zw 002 in 2003 showed evidence of an accretion disk, and a 2012 study found similar results. In 2021, Rodriguez Ardila and his team set out to complement these discoveries with near-infrared observations using GNIRS, which can see the entire near-infrared spectrum (800-2500 nanometers) at once. Other instruments require switching between multiple filters to cover the same area. This takes time and can introduce uncertainties as atmospheric conditions and calibrations change from observation to observation. Because GNIRS can observe across multiple optical bands simultaneously, the team was able to collect a single clean, consistently calibrated spectrum that revealed multiple double-peak profiles. “We didn’t know that III Zw 002 had this double-peak profile before, but when we zoomed in on the data, we could see it very clearly,” he said Rodriguez-Ardila. I’m here. “In fact, I’ve reduced the data several times, wondering if it’s an error, and each time I get the same interesting results.”
These observations not only confirm the theoretical existence of an accretion disk, but also advance astronomers’ understanding of the broadline region. “For the first time, the detection of such a double-peak profile imposes hard constraints on the geometry of the region that would otherwise be unsolvable,” said Rodriguez-Ardila. “And now we have clear evidence of feeding processes and internal structures in active galaxies.” By comparing these observations with existing disk models, the research team was able to extract parameters that more clearly indicate the supermassive black hole and broad line region of III Zw 002. The model predicts that Paschen alpha rays occur at a radius of 16.77 light-days (the one-day travel distance of light on Earth as measured from a supermassive black hole), and O I rays are produced at a radius of 18.86 light-days. is showing. The outer radius of the broadline region is also predicted to be 52.43 light days. The model also suggests that the broadline region of III Zw 002 is tilted 18 degrees to observers on Earth, and that the supermassive black hole at its center is 400-900 million times the mass of the Sun. It also shows
Source: The Astrophysical Journal Letters (2023). DOI: 10.3847/2041-8213/ace974