UCSC: New Insights into the Quenching of Star Formation in Galaxies

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UCSC: New Insights into the Quenching of Star Formation in Galaxies

Post by bystander » Sat Jul 18, 2020 3:28 pm

How Galaxies Die: New Insights into the
Quenching of Star Formation in Galaxies

University of California, Santa Cruz | 2020 Jul 16

A simple model explains a wide range of observations by describing a contest between galaxy halos and their central black holes that eventually turns off star formation

Image
A new theory explains how black holes grow as a function of galaxy mass and
eventually quench star formation in their host galaxies. The graph shows how the
evolution of small, dense galaxies differs from that of larger, more diffuse galaxies.
(Credit: Sandra Faber/Sofia Quiros/SDSS)

Astronomers studying galaxy evolution have long struggled to understand what causes star formation to shut down in massive galaxies. Although many theories have been proposed to explain this process, known as “quenching,” there is still no consensus on a satisfactory model.

Now, an international team ... has proposed a new model that successfully explains a wide range of observations about galaxy structure, supermassive black holes, and the quenching of star formation.

The model supports one of the leading ideas about quenching which attributes it to black hole “feedback,” the energy released into a galaxy and its surroundings from a central supermassive black hole as matter falls into the black hole and feeds its growth. This energetic feedback heats, ejects, or otherwise disrupts the galaxy’s gas supply, preventing the infall of gas from the galaxy’s halo to feed star formation. ...

Based on this model, the researchers concluded that quenching begins when the total energy emitted from the black hole is approximately four times the gravitational binding energy of the gas in the galactic halo. The binding energy refers to the gravitational force that holds the gas within the halo of dark matter enveloping the galaxy. Quenching is complete when the total energy emitted from the black hole is twenty times the binding energy of the gas in the galactic halo. ...

Quenching as a Contest between Galaxy Halos and Their Central Black Holes ~ Zhu Chen et al
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