Astronomers using the NASA / ESA Hubble Space Telescope have observed an unexpected thin disk of material surrounding a super effective dungeon in the heart of the spiral galaxy NGC 3147, located 130 million light-years away.
The presence of the black hole disk in an active galaxy of low luminosity surprises astronomers. Black holes in certain types of galaxies such as NGC 3147 are considered hungry since there is not enough gravitationally captured material to feed them regularly. Therefore, it is puzzling that there is a thin disk surrounding a hungry black hole that imitates the much larger discs found in extremely active galaxies.
Of particular interest, this disk of material surrounding the black hole offers a unique opportunity to test Albert Einstein's theories of relativity. The disc is so deeply embedded in the intense gravitational field of the black hole that the light of the gas disk is altered, according to these theories, giving astronomers a unique look at the dynamic processes near a black hole.
"We have never seen the effects of general and special relativity in visible light so clearly," said team member Marco Chiaberge of AURA for ESA, STScI and Johns Hopkins University.
Hubble measured that the disk material rotated around the black hole at more than 10% of the speed of light. At such extreme speeds, the gas seems to shine as it travels toward the Earth on the one hand, and attenuates as it moves away from our planet on the other. This effect is known as relativistic emission. The Hubble observations also show that the gas is embedded so deeply in a gravitational well that the light is struggling to escape, and therefore seems stretched at redder wavelengths. The mass of the black hole is about 250 million times that of the Sun.
"This is an intriguing look at a disk very close to a black hole, so close that the velocities and intensity of the gravitational force affect the way we see photons of light," explained the study's first author, Stefano Bianchi, of Università. degli Studi Roma Tre in Italy.
The artistic impression of the peculiar and thin disc of material that surrounds a super massive black hole in the heart of the spiral galaxy NGC 3147, located 130 million light-years away. Credit: ESA / Hubble, M. Kornmesser
To study the swirling matter deep within this disc, the researchers used the Hubble Space Telescope's (STIS) Space Imaging Spectrograph instrument. This diagnostic tool divides the light of an object into its many individual wavelengths to determine the speed, temperature and other characteristics of the object with very high precision. STIS was essential to effectively observe the region of low luminosity around the black hole, blocking the bright light of the galaxy.
Astronomers initially selected this galaxy to validate accepted models of low-luminosity active galaxies: those with malnourished black holes. These models predict that discs of material must form when a large amount of gas is trapped by the strong gravitational pull of a black hole, which then emits a lot of light and produces a bright light called quasar.
Top-down view of an artist's impression of the peculiar, thin disk of material that surrounds a supermassive black hole in the heart of the spiral galaxy NGC 3147, located 130 million light-years away. Credit: ESA / Hubble, M. Kornmesser
"The type of disc we see is a small quasar that we did not expect to exist," Bianchi explained. "It's the same kind of disk we see in objects that are 1000 or even 100 000 times brighter." The predictions of current models for very weak active galaxies clearly failed. "
The team hopes to use Hubble to search for other very compact discs around low-luminosity black holes in similar active galaxies.
Publication: Stefano Bianchi, et al., "HST reveals a compact and relatively relativistic broad-line region in the true candidate type 2 NGC 3147", MNRAS, 2019; doi: 10.1093 / mnrasl / slz080