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Suppressing star formation in quiescent galaxies with supermassive black hole winds

Astronomy News - 26 May 2016 - 9:28am

Suppressing star formation in quiescent galaxies with supermassive black hole winds

Nature 533, 7604 (2016). doi:10.1038/nature18006

Authors: Edmond Cheung, Kevin Bundy, Michele Cappellari, Sébastien Peirani, Wiphu Rujopakarn, Kyle Westfall, Renbin Yan, Matthew Bershady, Jenny E. Greene, Timothy M. Heckman, Niv Drory, David R. Law, Karen L. Masters, Daniel Thomas, David A. Wake, Anne-Marie Weijmans, Kate Rubin, Francesco Belfiore, Benedetta Vulcani, Yan-mei Chen, Kai Zhang, Joseph D. Gelfand, Dmitry Bizyaev, A. Roman-Lopes & Donald P. Schneider

Quiescent galaxies with little or no ongoing star formation dominate the population of galaxies with masses above 2 × 1010 times that of the Sun; the number of quiescent galaxies has increased by a factor of about 25 over the past ten billion years (refs 1, 2, 3, 4). Once star formation has been shut down, perhaps during the quasar phase of rapid accretion onto a supermassive black hole, an unknown mechanism must remove or heat the gas that is subsequently accreted from either stellar mass loss or mergers and that would otherwise cool to form stars. Energy output from a black hole accreting at a low rate has been proposed, but observational evidence for this in the form of expanding hot gas shells is indirect and limited to radio galaxies at the centres of clusters, which are too rare to explain the vast majority of the quiescent population. Here we report bisymmetric emission features co-aligned with strong ionized-gas velocity gradients from which we infer the presence of centrally driven winds in typical quiescent galaxies that host low-luminosity active nuclei. These galaxies are surprisingly common, accounting for as much as ten per cent of the quiescent population with masses around 2 × 1010 times that of the Sun. In a prototypical example, we calculate that the energy input from the galaxy’s low-level active supermassive black hole is capable of driving the observed wind, which contains sufficient mechanical energy to heat ambient, cooler gas (also detected) and thereby suppress star formation.

Astrophysics: How black holes restrain old galaxies

Astronomy News - 26 May 2016 - 9:27am

Astrophysics: How black holes restrain old galaxies

Nature 533, 7604 (2016). doi:10.1038/533473a

Authors: Marc Sarzi

Supermassive black holes are thought to keep star formation under control by ejecting or stirring gas in galaxies. Observations of an old galaxy reveal a potential mechanism for how this process occurs. See Letter p.504

Physics: Invest in neutrino astronomy

Astronomy News - 26 May 2016 - 9:26am

Physics: Invest in neutrino astronomy

Nature 533, 7604 (2016). doi:10.1038/533462a

Author: Spencer Klein

Spencer Klein calls for bigger telescope arrays to catch particles from the most energetic places in the Universe.

VIDEO: Hunting universe's strangest particles

Astronomy News - 26 May 2016 - 9:13am

Deep underground, beneath Daya Bay in the south of China, scientists are hunting for the oddest particles in the cosmos - neutrinos.

Contract to construct giant telescope

Astronomy News - 26 May 2016 - 9:12am

The contract is signed that will lead to the construction of one of this century's key astronomical facilities - the European Extremely Large Telescope.

Students taste life as a space scientist in Cassini competition

Astronomy News - 25 May 2016 - 9:36am

Over the past 12 years, the NASA/ESA/ASI Cassini-Huygens mission has made numerous exciting discoveries and returned many stunning images of the Saturnian system. Saturn, its moons, and rings provide the inspiration behind the 'Cassini scientist for a day' competition that is designed to give school students a taste of life as a space scientist. More than 900 students from across Europe participated in the 2015–2016 competition and the winners have now been selected.

Hubble finds clues to the birth of supermassive black holes [heic1610]

Astronomy News - 25 May 2016 - 9:36am

Astrophysicists have taken a major step forward in understanding how supermassive black holes formed. Using data from Hubble and two other space telescopes, Italian researchers have found the best evidence yet for the seeds that ultimately grow into these cosmic giants.

NASA Telescopes Find Clues For How Giant Black Holes Formed So Quickly

Astronomy News - 25 May 2016 - 9:35am
Using data from NASA’s Great Observatories, astronomers have found the best evidence yet for cosmic seeds in the early universe that should grow into supermassive black holes.

Cranky young sun could have kickstarted life on Earth

Astronomy News - 24 May 2016 - 9:28am

Giant solar storms may have turned early Earth's atmosphere into a cosy blanket and also helped life get going

Incoming asteroids could crumble harmlessly before they hit us

Astronomy News - 23 May 2016 - 3:54pm

Stand down, Bruce Willis. Space rocks are much more brittle than Earth rocks, suggesting that asteroids on a collision course are more likely to burn up as fireballs in the sky

Are mystery Mars plumes caused by space weather?

Astronomy News - 23 May 2016 - 3:53pm

Mysterious high-rise clouds seen appearing suddenly in the martian atmosphere on a handful of occasions may be linked to space weather, say Mars Express scientists.

VIDEO: Building a new dish

Astronomy News - 23 May 2016 - 3:44pm

BBC science correspondent Rebecca Morelle travels to China to take a close up tour of the Five-hundred-metre Aperture Spherical Telescope - or Fast for short.

Close-up of the Red Planet [heic1609]

Astronomy News - 20 May 2016 - 9:22am

During May 2016 the Earth and Mars get closer to each other than at any time in the last ten years. The NASA/ESA Hubble Space Telescope has exploited this special configuration to catch a new image of our red neighbour, showing some of its famous surface features. This image supplements previous Hubble observations of Mars and allows astronomers to study large-scale changes on its surface.

Hubble Takes Mars Portrait Near Close Approach

Astronomy News - 20 May 2016 - 9:22am

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On May 12, 2016, astronomers using NASA's Hubble Space Telescope captured this striking image of Mars, when the planet was 50 million miles from Earth. The photo reveals details as small as 20 miles to 30 miles across. This observation was made just a few days before Mars opposition on May 22, when the sun and Mars will be on exact opposite sides of Earth. Mars also will be 47.4 million miles from Earth. On May 30, Mars will be the closest it has been to Earth in 11 years, at a distance of 46.8 million miles. Mars is especially photogenic during opposition because it can be seen fully illuminated by the sun as viewed from Earth.

Mars was once devastated by giant 50-metre tsunamis

Astronomy News - 20 May 2016 - 9:21am

Massive waves once crashed over the shores of the Red Planet, which could explain why we struggle to see its coastlines today

Tadpole galaxy spawns stars after eating invisible gas cloud

Astronomy News - 20 May 2016 - 9:20am

New Hubble observations suggest a nearby tadpole galaxy collided with a gas cloud and started to grow – the same thing may have happened to the Milky Way

First evidence of icy comets orbiting a sun-like star

Astronomy News - 20 May 2016 - 9:19am

An international team of astronomers have found evidence of ice and comets orbiting a nearby sun-like star, which could give a glimpse into how our own solar system developed.

Using data from the Atacama Large Millimeter Array (ALMA), the researchers, led by the University of Cambridge, detected very low levels of carbon monoxide gas around the star, in amounts that are consistent with the comets in our own solar system.

The results, which will be presented today at the ‘Resolving Planet Formation in the era of ALMA and extreme AO’ conference in Santiago, Chile, are a first step in establishing the properties of comet clouds around sun-like stars just after the time of their birth.

Comets are essentially ‘dirty snowballs’ of ice and rock, sometimes with a tail of dust and evaporating ice trailing behind them, and are formed early in the development of stellar systems. They are typically found in the outer reaches of our solar system, but become most clearly visible when they visit the inner regions. For example, Halley’s Comet visits the inner solar system every 75 years, some take as long as 100,000 years between visits, and others only visit once before being thrown out into interstellar space.

It’s believed that when our solar system was first formed, the Earth was a rocky wasteland, similar to how Mars is today, and that as comets collided with the young planet, they brought many elements and compounds, including water, along with them.

The star in this study, HD 181327, has a mass about 30% greater than the sun and is located 160 light years away in the Painter constellation. The system is about 23 million years old, whereas our solar system is 4.6 billion years old.

“Young systems such as this one are very active, with comets and asteroids slamming into each other and into planets,” said Sebastián Marino, a PhD student from Cambridge’s Institute of Astronomy and the paper’s lead author. “The system has a similar ice composition to our own, so it’s a good one to study in order to learn what our solar system looked like early in its existence.”

Using ALMA, the astronomers observed the star, which is surrounded by a ring of dust caused by the collisions of comets, asteroids and other bodies. It’s likely that this star has planets in orbit around it, but they are impossible to detect using current telescopes.

“Assuming there are planets orbiting this star, they would likely have already formed, but the only way to see them would be through direct imaging, which at the moment can only be used for very large planets like Jupiter,” said co-author Luca Matrà, also a PhD student at Cambridge’s Institute of Astronomy.

In order to detect the possible presence of comets, the researchers used ALMA to search for signatures of gas, since the same collisions which caused the dust ring to form should also cause the release of gas. Until now, such gas has only been detected around a few stars, all substantially more massive than the sun. Using simulations to model the composition of the system, they were able to increase the signal to noise ratio in the ALMA data, and detect very low levels of carbon monoxide gas.

“This is the lowest gas concentration ever detected in a belt of asteroids and comets – we’re really pushing ALMA to its limits,” said Marino.

“The amount of gas we detected is analogous to a 200 kilometre diameter ice ball, which is impressive considering how far away the star is,” said Matrà. “It’s amazing that we can do this with exoplanetary systems now.”

The results have been accepted for publication in the Monthly Notices of the Royal Astronomical Society.

S. Marino et al. ‘Exocometary gas in the HD 181327 debris ring.’ Paper presented to the Resolving Planet Formation in the era of ALMA and extreme AO conference, Santiago, May 16-20, 2016.

Inset image: ALMA image of the ring of comets around HD 181327 (colours have been changed). The white contours represent the size of the Kuiper Belt in the Solar System. Credit: Amanda Smith, University of Cambridge.

Astronomers have found the first evidence of comets around a star similar to the sun, providing an opportunity to study what our solar system was like as a ‘baby’.

The system has a similar ice composition to our own, so it’s a good one to study in order to learn what our solar system looked like early in its existence.Sebastián MarinoAmanda Smith, University of CambridgeIllustration of the dust ring surrounding HD 181327

The text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.


Evidence of ancient tsunamis on Mars

Astronomy News - 20 May 2016 - 9:10am

Scientists suggest that at least two huge tsunamis once swept across the Red Planet, triggered by large impacts.

A Beautiful Instance of Stellar Ornamentation

Astronomy News - 19 May 2016 - 9:15am
In this image from ESO’s Very Large Telescope (VLT), light from blazing blue stars energises the gas left over from the stars’ recent formation. The result is a strikingly colourful emission nebula, called LHA 120-N55, in which the stars are adorned with a mantle of glowing gas. Astronomers study these beautiful displays to learn about the conditions in places where new stars develop.

Astrophysics: Illuminating brown dwarfs

Astronomy News - 19 May 2016 - 9:12am

Astrophysics: Illuminating brown dwarfs

Nature 533, 7603 (2016). doi:10.1038/533330a

Authors: Adam P. Showman

Objects known as brown dwarfs are midway between stars and planets in mass. Observations of a hot brown dwarf irradiated by a nearby star will help to fill a gap in our knowledge of the atmospheres of fluid planetary objects. See Letter p.366