Supermassive black holes control star formation in large galaxies

January 1, 2018, University of California - Santa Cruz
This artist's concept depicts a supermassive black hole at the center of a galaxy. The blue color here represents radiation pouring out from material very close to the black hole. The grayish structure surrounding the black hole, called a torus, is made up of gas and dust. Credit: NASA/JPL-Caltech

Young galaxies blaze with bright new stars forming at a rapid rate, but star formation eventually shuts down as a galaxy evolves. A new study, published January 1, 2018, in Nature, shows that the mass of the black hole in the center of the galaxy determines how soon this "quenching" of star formation occurs.

Every has a central supermassive black hole, more than a million times more massive than the sun, revealing its presence through its gravitational effects on the galaxy's and sometimes powering the energetic radiation from an active galactic nucleus (AGN). The energy pouring into a galaxy from an is thought to turn off by heating and dispelling the gas that would otherwise condense into stars as it cooled.

This idea has been around for decades, and astrophysicists have found that simulations of galaxy evolution must incorporate feedback from the black hole in order to reproduce the observed properties of galaxies. But observational evidence of a connection between and star formation has been lacking, until now.

"We've been dialing in the feedback to make the simulations work out, without really knowing how it happens," said Jean Brodie, professor of astronomy and astrophysics at UC Santa Cruz and a coauthor of the paper. "This is the first direct observational evidence where we can see the effect of the black hole on the star formation history of the galaxy."

The new results reveal a continuous interplay between black hole activity and star formation throughout a galaxy's life, affecting every generation of stars formed as the galaxy evolves.

Led by first author Ignacio Martín-Navarro, a postdoctoral researcher at UC Santa Cruz, the study focused on massive galaxies for which the mass of the central black hole had been measured in previous studies by analyzing the motions of stars near the center of the galaxy. To determine the star formation histories of the galaxies, Martín-Navarro analyzed detailed spectra of their light obtained by the Hobby-Eberly Telescope Massive Galaxy Survey.

Spectroscopy enables astronomers to separate and measure the different wavelengths of light from an object. Martín-Navarro used computational techniques to analyze the spectrum of each galaxy and recover its star formation history by finding the best combination of stellar populations to fit the spectroscopic data. "It tells you how much light is coming from stellar populations of different ages," he said.

When he compared the star formation histories of galaxies with black holes of different masses, he found striking differences. These differences only correlated with black hole mass and not with galactic morphology, size, or other properties.

"For galaxies with the same mass of stars but different black hole mass in the center, those galaxies with bigger black holes were quenched earlier and faster than those with smaller black holes. So star formation lasted longer in those with smaller central black holes," Martín-Navarro said.

Other researchers have looked for correlations between star formation and the luminosity of active galactic nuclei, without success. Martín-Navarro said that may be because the time scales are so different, with star formation occurring over hundreds of millions of years, while outbursts from active galactic nuclei occur over shorter periods of time.

A supermassive black hole is only luminous when it is actively gobbling up matter from its host galaxy's inner regions. Active galactic nuclei are highly variable and their properties depend on the size of the black hole, the rate of accretion of new material falling onto the black hole, and other factors.

"We used black hole mass as a proxy for the energy put into the galaxy by the AGN, because accretion onto more massive leads to more energetic feedback from , which would quench star formation faster," Martín-Navarro explained.

The precise nature of the feedback from the black hole that quenches star formation remains uncertain, according to coauthor Aaron Romanowsky, an astronomer at San Jose State University and UC Observatories.

"There are different ways a black hole can put energy out into the galaxy, and theorists have all kinds of ideas about how quenching happens, but there's more work to be done to fit these new observations into the models," Romanowsky said.

Explore further: Expanding super bubble of gas detected around massive black holes in the early universe

More information: Ignacio Martín-Navarro et al, Black-hole-regulated star formation in massive galaxies, Nature (2017). DOI: 10.1038/nature24999

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reid barnes
2.3 / 5 (3) Jan 01, 2018
We can just skip the Black Hole. From the article: "We used black hole mass as a proxy for the energy put into the galaxy by the AGN, … active galactic nuclei,
which would quench star formation faster," Martín-Navarro explained.
mackita
1 / 5 (3) Jan 01, 2018
The energy pouring into a galaxy from an active galactic nucleus is thought to turn off star formation by heating and dispelling the gas that would otherwise condense into stars as it cooled
Well, this is already known quite notoriously. But most of mature galaxies (including the Milky Way) have quite large and yellow galactic bulge which indicates the presence of mature lazy stars which don't evolve anymore - but their black holes don't affect their neighborhood significantly. And this is where the actual questions begin: what prohibits the stars in their development there?
mackita
1 / 5 (1) Jan 01, 2018
shows that the mass of the black hole in the center of the galaxy determines how soon this "quenching" of star formation occurs
BTW Many small dwarf galaxies have also unusually high hydrogen content, which would imply that their formation was interrupted very soon, so that they should have large black holes in their center - but it just seems, they're lacking them completely = another paradox.
Tuxford
2.3 / 5 (6) Jan 01, 2018
BTW Many small dwarf galaxies have also unusually high hydrogen content, which would imply that their formation was interrupted very soon, so that they should have large black holes in their center - but it just seems, they're lacking them completely = another paradox.

Another committed merger maniac grasping at cherished assumptions, already countered.

https://phys.org/...ack.html

Poring through data from a large sky survey, astronomers have found more than 100 small, dwarf galaxies with characteristics indicating that they harbor massive black holes feeding on surrounding gas. The discovery confounds a common assumption that only much larger galaxies hold such monsters and may help resolve the question of how such black holes originated and grew in the early universe.

Tuxford
2 / 5 (4) Jan 01, 2018
Smaller galaxies have smaller core stars, being therefore less active and less frequently visible.
Chris_Reeve
Jan 02, 2018
This comment has been removed by a moderator.
Tuxford
2 / 5 (4) Jan 02, 2018
When he compared the star formation histories of galaxies with black holes of different masses, he found striking differences. These differences only correlated with black hole mass and not with galactic morphology, size, or other properties.
"For galaxies with the same mass of stars but different black hole mass in the center, those galaxies with bigger black holes were quenched earlier and faster than those with smaller black holes. So star formation lasted longer in those galaxies with smaller central black holes," Martín-Navarro said.

Larger cores are more actively ejecting more massive winds of newly formed matter therefrom, dispersing the central region of the quiescent conditions needed for conventional star formation. Yes, the cores control star formation rate, not the merger mania preferred opposite.

Feedback. LOL. Maniacs grasping to explain the obvious. Feedback starts at the sub-atomic level, being at the heart of new matter creation. Study LaViolette's SQK!
milnik
1 / 5 (2) Jan 04, 2018
All these arbitrary stories were due to the ignorance of the structure of the universe and the chain of the formation of celestial bodies. It is interesting that there is no knowledge of how and from which the first celestial bodies are formed in this chain of processes. The universe with its logic and the unwavering power of forming all the material-energetic, formed from the substance Aether that fills the infinite universe, is not as stupid as my patent, and it does not know how it all worked out and why. Large black holes "swallow" more stars, and small, smaller ones. But science does not know how to form a black hole and what its purpose is, and in particular, it is unknown the sequence of the formation of matter and celestial bodies.
Tuxford
1 / 5 (2) Jan 04, 2018
Further recall that core growth outpaces galactic growth, being a quadratic function. This would imply that the core grows in an increasing accelerated manner as it grows more massive, exactly per LaViolette's Continuous Creation model.

https://phys.org/...tml#nRlv

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