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Home / Science / Black holes slow down the growth of dwarf galaxies – astronomers are surprised by 2,000,000 mph of wind

Black holes slow down the growth of dwarf galaxies – astronomers are surprised by 2,000,000 mph of wind



  NGC1569 Star formation galaxy

NGC1569 is a star formation galaxy. Credit: HST / NASA / ESA

UC Riverside astronomers note that large winds associated with active black holes in small galaxies suppress star formation. Black holes in the centers of dwarf galaxies have a significant impact on their evolution Galaxies by suppressing star formation.

Dwarf galaxies are small galaxies that contain between 1

00 million and several billion stars. In contrast, the Milky Way has 200-400 billion stars. Dwarf galaxies are the most abundant galaxy types in the universe and often orbit larger galaxies.

The team of three astronomers was surprised by the strength of the detected winds.

Sensitivity, and we had planned to receive it as a result of our initial observations, "said Gabriela Canalizo, professor of physics and astronomy at UC Riverside, who led the research team. "But we clearly and clearly saw the signs in the first observations. The winds were stronger than expected. "

  Dwarf galaxies

Dwarf galaxies with active galactic nuclei showing spatially extensive outflows. Credit: SDSS

Canalizo explained that in recent decades astronomers have suggested that supermassive black holes in the centers of large galaxies can have profound effects on the growth and age of large galaxies.

"Our results suggest that their effect on dwarf galaxies in the universe may be as dramatic, if not more dramatic," she said.

Study results appear in the Astrophysical Journal.

The researchers, including Laura V. Sales, assistant professor of physics and astronomy; and Christina M. Manzano-King, a graduate student in Canalizo's laboratory, used some of the data from the Sloan Digital Sky Survey, which maps more than 35% of the sky, to identify 50 dwarf galaxies, 29 of which have black holes in them their centers are associated. Six of these 29 galaxies showed signs of winds – especially outflow of ionized high-velocity gas – from their active black holes.

"With the Keck telescopes in Hawaii, we were not only able to capture certain properties, but also measure this wind, as well as its kinematics, distribution and energy source – the first time this has been done," said Canalizo. "We have found evidence that these winds alter the speed at which galaxies can form stars."

  Laura Sales, Christina Manzano-King and Gabriela Canalizo

The photo shows the researchers. From left to right: Laura Sales, Christina Manzano-King and Gabriela Canalizo. Credit: Stan Lim, UC Riverside

Manzano-King, the first author of the research paper, explained that many unanswered questions about galaxy evolution can be resolved by studying dwarf galaxies.

"Larger galaxies are common when dwarf galaxies merge together," she said. "Dwarf galaxies are therefore useful for understanding how galaxies develop. Dwarf galaxies are small because after their formation they have avoided merging with other galaxies. So they serve as fossils, revealing what the environment of the early Universe was like. Dwarf galaxies are the smallest galaxies in which we see winds for the first time – gas flows up to 1,000 km / s -. "(1,000 km / s equals 3,600,000 km / h)

Manzano-king explained that material, when it falls into a black hole heats up and releases radiant energy due to friction and strong gravitational fields , This energy pushes ambient gas from the center of the galaxy into the intergalactic space.

"Interestingly, these winds are more likely to be ejected from active black holes in the six dwarf galaxies than from star processes such as supernovae," she said. "Normally, winds driven by star processes are common in dwarf galaxies and are the predominant process of regulating the amount of gas available in dwarf galaxies to form stars."

Astronomers suspect that when wind emanates from a black hole, it compresses the gas from the wind, which can increase star formation. However, when all the wind is expelled from the center of the galaxy, gas is no longer available and star formation may decrease. The latter seems to occur in the six dwarf galaxies identified by the researchers.

"In these six cases, the wind has a negative effect on star formation," Sales said. "Theoretical models for the formation and evolution of galaxies have not taken into account the influence of black holes in dwarf galaxies. However, we see evidence of suppression of star formation in these galaxies. Our results indicate that galaxy formation models must include black holes as important if not dominant regulators of star formation in dwarf galaxies.

Next, the researchers plan to study the mass and momentum of gas outflows in dwarf galaxies.

] "This would better inform theoreticians who rely on such data to build models," said Manzano-King. "These models in turn teach observing astronomers how the winds affect dwarf galaxies. We also plan a systematic search in a larger sample of the Sloan Digital Sky Survey to identify dwarf galaxies with black-hole effluents.

The research was funded by the National Science Foundation, NASA and the Hellman Foundation. The data was collected at the W. M. Keck Observatory and made possible through financial support from the W. M. Keck Foundation.


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