An enormous black hole located at the heart of a massive elliptical galaxy is leaving an imprint on its surroundings, with a single letter seemingly carved in the X-ray glow around it. The latest X-ray map of the scorching gas around Messier 84 (M84) reveals an “H”-shaped structure.
As gas is drawn in by the black hole's gravitational pull, a portion of it plunges into the abyss, never to be seen again. However, some of the gas escapes this fate and is instead ejected from the black hole as jets of particles. These jets can create voids in the hot gas enveloping the black hole.
Due to the orientation of the jets relative to Earth and the hot gas profile, the cavities in M84 resemble the letter “H.” The H-shaped formation is an instance of pareidolia, where people perceive familiar patterns or shapes in random data. Pareidolia can arise in a variety of contexts, including clouds, rocks, and astronomical images.
To produce a map of the hot gas (pink) in and around M84, which extends to within approximately 100 light-years of the black hole at the galaxy's center, astronomers employed NASA's Chandra X-ray Observatory. This gas emits X-rays primarily due to its temperatures, which reach tens of millions of degrees.
The “H” shape in the X-ray glow around the black hole at the center of Messier 84 (M84) is approximately 40,000 light-years tall, which is about half the Milky Way's width. A radio image from the National Science Foundation's Karl G. Jansky Very Large Array (VLA) (blue) reveals the jets emanating from the black hole, while the Sloan Digital Sky Survey's optical data (white) shows M84 and its neighboring galaxies. The black hole's position and the letter “H” are labeled. A close-up of the area within the square is presented in an additional graphic, with separate optical and radio labels for the galaxy and jets, respectively.
Researchers have used Chandra and the VLA to investigate M84 and discovered that the jets may exert more influence on the hot gas flow towards the black hole than the black hole's gravitational pull. For instance, the team estimates that matter falls towards the black hole from the north, the direction of the radio wave-emitting jet, at a rate of approximately 500 times the Earth's mass per year. This rate is only a quarter of the rate at which matter falls in from directions without the jet, such as to the east and west. It is plausible that the cavities lift gas along the jet's direction, slowing the rate of gas falling into the black hole.
The researchers tested a theoretical model called Bondi accretion, which posits that all matter within a particular distance from a black hole, essentially within a sphere, is close enough to be impacted by the black hole's gravity and start falling inwards at an equal rate from all directions. The dashed circle in the close-up image marks the black hole's center and indicates the approximate distance from which gas should begin falling inwards. These findings indicate that Bondi accretion is not taking place in M84 since matter does not fall evenly towards the black hole from all directions.
M84, a massive elliptical galaxy at the center of the Virgo Cluster, is a relative of Messier 87 (M87) – the galaxy that contains the first-ever black hole image captured by the Event Horizon Telescope network. Similar to M87, M84 also hosts a supermassive black hole that generates jets of particles. However, the X-ray emission from material close to the black hole in M84 is over ten times fainter than in M87, enabling more detailed study of gas falling towards the black hole that is farther out. Chandra observations of M84 provide valuable insights into how the black hole affects its surroundings, and these findings are set to be published in The Monthly Notices of the Royal Astronomical Society. A preprint is also available on arXiv.