New Delhi: Actively feeding supermassive black holes consume gas and dust from the surrounding galaxies voraciously. The tortured infalling material glows brightly, at times outshining all the stars in the surrounding galaxy, known as Active Galactic Nuclei (AGN). AGN can heat up and expel gas, forming winds that dissipate molecular clouds, preventing the formation of new stars in a galaxy, known as AGN feedback. To understand how the winds from AGN affect star formation in galaxies, different gas phases have to be observed simultaneously, allowing scientists to track the interactions of the wind with the gas, and how much material they heat up or drag away.
Astronomers have used a number of ground-based telescopes to study obscured quasars, or AGN which are obscured by dust, allowing scientists to better study the gas and stellar properties in the host galaxies. The researchers found winds reaching velocities of up to nine million kmph in the warn ionised, and hot ionised gas phases in six quasars. The observations indicate both gas phases are tracing the same wind. The scientists were surprised when they did not find warm molecular winds in any of the quasars, which require a large reservoir of molecular gas in the quasars to show outflows, without which they remain undetected. The researchers intend to examine a larger sample of quasars, and other, less luminous active galaxies to better understand the behaviour of warm molecular gas in AGNs.
Black Holes feed in episodes
A paper describing the research has been published in Astronomy and Astrophysics. Lead author of the study, Pedro Henrique Cezar says, “AGN have episodic winds, associated with periods of high accretion onto the central supermassive black hole. What we found is that the winds in the warm ionised and hot ionised phases have similar velocities and spatial extents across the galaxy, suggesting that they are tracing the same wind event. The difference is that the warm ionised wind carries, on average, six times more mass than the hot ionised wind.”