̽��ֱ�� of Cambridge - Francesco D’Eugenio

Astronomers detect black hole ‘starving’ its host galaxy to death

sc604 — Thu, 12 Sep 2024 11:36:56 +0000

̽��ֱ��international team, co-led by the ̽��ֱ�� of Cambridge, used Webb to observe a galaxy roughly the size of the Milky Way in the early universe, about two billion years after the Big Bang. Like most large galaxies, it has a supermassive black hole at its centre. However, this galaxy is essentially ‘dead’: it has mostly stopped forming new stars.

“Based on earlier observations, we knew this galaxy was in a quenched state: it’s not forming many stars given its size, and we expect there is a link between the black hole and the end of star formation,” said co-lead author Dr Francesco D’Eugenio from Cambridge’s Kavli Institute for Cosmology. “However, until Webb, we haven’t been able to study this galaxy in enough detail to confirm that link, and we haven’t known whether this quenched state is temporary or permanent.”

This galaxy, officially named GS-10578 but nicknamed ‘Pablo’s Galaxy’ after the colleague who decided to observe it in detail, is massive for such an early period in the universe: its total mass is about 200 billion times the mass of our Sun, and most of its stars formed between 12.5 and 11.5 billion years ago.

“In the early universe, most galaxies are forming lots of stars, so it’s interesting to see such a massive dead galaxy at this period in time,” said co-author Professor Roberto Maiolino, also from the Kavli Institute for Cosmology. “If it had enough time to get to this massive size, whatever process that stopped star formation likely happened relatively quickly.”

Using Webb, the researchers detected that this galaxy is expelling large amounts of gas at speeds of about 1,000 kilometres per second, which is fast enough to escape the galaxy’s gravitational pull. These fast-moving winds are being ‘pushed’ out of the galaxy by the black hole.

Like other galaxies with accreting black holes, ‘Pablo’s Galaxy’ has fast outflowing winds of hot gas, but these gas clouds are tenuous and have little mass. Webb detected the presence of a new wind component, which could not be seen with earlier telescopes. This gas is colder, which means it’s denser and – crucially – does not emit any light. Webb, with its superior sensitivity, can see these dark gas clouds because they block some of the light from the galaxy behind them.

̽��ֱ��mass of gas being ejected from the galaxy is greater than what the galaxy would require to keep forming new stars. In essence, the black hole is starving the galaxy to death. ̽��ֱ��results are reported in the journal Nature Astronomy.

“We found the culprit,” said D’Eugenio. “ ̽��ֱ��black hole is killing this galaxy and keeping it dormant, by cutting off the source of ‘food’ the galaxy needs to form new stars.”

Although earlier theoretical models had predicted that black holes had this effect on galaxies, before Webb, it had not been possible to detect this effect directly.

Earlier models had predicted that the end of star formation has a violent, turbulent effect on galaxies, destroying their shape in the process. But the stars in this disc-shaped galaxy are still moving in an orderly way, suggesting that this is not always the case.

“We knew that black holes have a massive impact on galaxies, and perhaps it’s common that they stop star formation, but until Webb, we weren’t able to directly confirm this,” said Maiolino. “It’s yet another way that Webb is such a giant leap forward in terms of our ability to study the early universe and how it evolved.”

New observations with the Atacama Large Millimeter-Submillimiter Array (ALMA), targeting the coldest, darkest gas components of the galaxy, will tell us more about if and where any fuel for star formation is still hidden in this galaxy, and what is the effect of the supermassive black hole in the region surrounding the galaxy.

̽��ֱ��research was supported in part by the Royal Society, the European Union, the European Research Council, and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Reference:
Francesco D’Eugenio, Pablo G. Pérez-González et al. ‘A fast-rotator post-starburst galaxy quenched by supermassive black-hole feedback at z=3.’ Nature Astronomy (2024). DOI: 10.1038/s41550-024-02345-1

Astronomers have used the NASA/ESA James Webb Space Telescope to confirm that supermassive black holes can starve their host galaxies of the fuel they need to form new stars.

JADES Collaboration

'Pablo's Galaxy'

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Earliest detection of metal challenges what we know about the first galaxies

sc604 — Thu, 06 Jun 2024 14:52:26 +0000

Using the James Webb Space Telescope (JWST), an international team of astronomers led by the ̽��ֱ�� of Cambridge observed a very young galaxy in the early universe and found that it contained surprising amounts of carbon, one of the seeds of life as we know it.

In astronomy, elements heavier than hydrogen or helium are classed as metals. ̽��ֱ��very early universe was almost entirely made up of hydrogen, the simplest of the elements, with small amounts of helium and tiny amounts of lithium.

Every other element that makes up the universe we observe today was formed inside a star. When stars explode as supernovas, the elements they produce are circulated throughout their host galaxy, seeding the next generation of stars. With every new generation of stars and ‘stardust’, more metals are formed, and after billions of years, the universe evolves to a point where it can support rocky planets like Earth and life like us.

̽��ֱ��ability to trace the origin and evolution of metals will help us understand how we went from a universe made almost entirely of just two chemical elements, to the incredible complexity we see today.

“ ̽��ֱ��very first stars are the holy grail of chemical evolution,” said lead author Dr Francesco D’Eugenio, from the Kavli Institute for Cosmology at Cambridge. “Since they are made only of primordial elements, they behave very differently to modern stars. By studying how and when the first metals formed inside stars, we can set a time frame for the earliest steps on the path that led to the formation of life.”

Carbon is a fundamental element in the evolution of the universe, since it can form into grains of dust that clump together, eventually forming into the first planetesimals and the earliest planets. Carbon is also key for the formation of life on Earth.

“Earlier research suggested that carbon started to form in large quantities relatively late – about one billion years after the Big Bang,” said co-author Professor Roberto Maiolino, also from the Kavli Institute. “But we’ve found that carbon formed much earlier – it might even be the oldest metal of all.”

̽��ֱ��team used the JWST to observe a very distant galaxy – one of the most distant galaxies yet observed – just 350 million years after the Big Bang, more than 13 billion years ago. This galaxy is compact and low mass – about 100,000 times less massive than the Milky Way.

“It’s just an embryo of a galaxy when we observe it, but it could evolve into something quite big, about the size of the Milky Way,” said D’Eugenio. “But for such a young galaxy, it’s fairly massive.”

̽��ֱ��researchers used Webb’s Near Infrared Spectrograph (NIRSpec) to break down the light coming from the young galaxy into a spectrum of colours. Different elements leave different chemical fingerprints in the galaxy’s spectrum, allowing the team to determine its chemical composition. Analysis of this spectrum showed a confident detection of carbon, and tentative detections of oxygen and neon, although further observations will be required to confirm the presence of these other elements.

“We were surprised to see carbon so early in the universe, since it was thought that the earliest stars produced much more oxygen than carbon,” said Maiolino. “We had thought that carbon was enriched much later, through entirely different processes, but the fact that it appears so early tells us that the very first stars may have operated very differently.”

According to some models, when the earliest stars exploded as supernovas, they may have released less energy than initially expected. In this case, carbon, which was in the stars’ outer shell and was less gravitationally bound than oxygen, could have escaped more easily and spread throughout the galaxy, while a large amount of oxygen fell back and collapsed into a black hole.

“These observations tell us that carbon can be enriched quickly in the early universe,” said D’Eugenio. “And because carbon is fundamental to life as we know it, it’s not necessarily true that life must have evolved much later in the universe. Perhaps life emerged much earlier – although if there’s life elsewhere in the universe, it might have evolved very differently than it did here on Earth.”

̽��ֱ��results have been accepted for publication in the journal Astronomy & Astrophysics and are based on data obtained within the JWST Advanced Deep Extragalactic Survey (JADES).

̽��ֱ��research was supported in part by the European Research Council, the Royal Society, and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Reference:
Francesco D’Eugenio et al. ‘JADES: Carbon enrichment 350 Myr after the Big Bang.’ Astronomy & Astrophysics (in press). DOI: 10.48550/arXiv.2311.09908

Astronomers have detected carbon in a galaxy just 350 million years after the Big Bang, the earliest detection of any element in the universe other than hydrogen.

NASA, ESA, CSA, STScI, Brant Robertson (UC Santa Cruz), Ben Johnson (CfA), Sandro Tacchella (Cambridge), Phill Cargile (CfA)

Deep field image from JWST

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Earliest, most distant galaxy discovered with James Webb Space Telescope

Anonymous — Thu, 30 May 2024 11:04:20 +0000

Found in a region near the Hubble Ultra Deep Field by the JWST Advanced Deep Extragalactic Survey (JADES) team, these galaxies mark a major milestone in the study of the early Universe.

“These galaxies join a small but growing population of galaxies from the first half billion years of cosmic history where we can really probe the stellar populations and the distinctive patterns of chemical elements within them,” said Dr Francesco D’Eugenio of the Kavli Institute for Cosmology at the ̽��ֱ�� of Cambridge, one of the team behind the discovery.

Because of the expansion of the Universe, the light from distant galaxies stretches to longer wavelength as it travels, an effect known as redshift. In these galaxies, the effect is extreme, stretching by a factor of 15, and moving even the ultraviolet light of the galaxies to infrared wavelengths where only JWST has the capability to see it.

Modern theory holds that galaxies develop in special regions where gravity has concentrated the cosmic gas and dark matter into dense lumps known as ‘halos’. These halos evolved quickly in the early Universe, rapidly merging into more and more massive collections of matter. This fast development is why astronomers are so eager to find yet earlier galaxies: each small increment moves our eyes to a less developed period, where luminous galaxies are even more distinctive and unusual.

̽��ֱ��two newly discovered galaxies have been confirmed spectroscopically. In keeping with the collaboration’s standard naming practice, the galaxies are now known as JADES-GS-z14-0 and JADES-GS-z14-1, the former being the more distant of the two.

In addition to being the new distance record holder, JADES-GS-z14-0 is remarkable for how big and bright it is. JWST measures the galaxy at over 1,600 light-years in diameter. Many of the most luminous galaxies produce the bulk of their light via gas falling into a supermassive black hole, producing a quasar, but at this size JADES-GS-z14-0 cannot be this. Instead, the researchers believe the light is being produced by young stars.

̽��ֱ��combination of the high luminosity and the stellar origin makes JADES-GS-z14-0 the most distinctive evidence yet found for the rapid formation of large, massive galaxies in the early Universe. This trend runs counter to the pre-JWST expectations of theories of galaxy formation. Evidence for surprisingly vigorous early galaxies appeared even in the first JWST images and has been mounting in the first two years of the mission.

“JADES-GS-z14-0 now becomes the archetype of this phenomenon,” said Dr Stefano Carniani of the Scuola Normale Superiore in Pisa, lead author on the discovery paper. “It is stunning that the Universe can make such a galaxy in only 300 million years.”

Despite its luminosity, JADES-GS-z14-0 was a puzzle for the JADES team when they first spotted it over a year ago, as it appears close enough on the sky to a foreground galaxy that the team couldn’t be sure that the two weren’t neighbours. But in October 2023, the JADES team conducted even deeper imaging—five full days with the JWST Near-Infrared Camera on just one field—to form the “JADES Origins Field.” With the use of filters designed to better isolate the earliest galaxies, confidence grew that JADES-GS-z14-0 was indeed very distant.

“We just couldn’t see any plausible way to explain this galaxy as being merely a neighbour of the more nearby galaxy,” said Dr Kevin Hainline, research professor at the ̽��ֱ�� of Arizona.

Fortunately, the galaxy happened to fall in a region where the team had conducted ultra-deep imaging with the JWST Mid-Infrared Instrument. ̽��ֱ��galaxy was bright enough to be detected in 7.7 micron light, with a higher intensity than extrapolation from lower wavelengths would predict.

“We are seeing extra emission from hydrogen and possibly even oxygen atoms, as is common in star-forming galaxies, but here shifted out to an unprecedented wavelength,” said Jakob Helton, graduate student at the ̽��ֱ�� of Arizona and lead author of a second paper on this finding.

These combined imaging results convinced the team to include the galaxy in what was planned to be the capstone observation of JADES, a 75-hour campaign to conduct spectroscopy on faint early galaxies. ̽��ֱ��spectroscopy confirmed their hopes that JADES-GS-z14-0 was indeed a record-breaking galaxy and that the fainter candidate, JADES-GS-z14-1, was nearly as far away.

Beyond the confirmation of distance, the spectroscopy allows further insight into the properties of the two galaxies. Being comparatively bright, JADES-GS-z14-0 will permit detailed study.

“We could have detected this galaxy even if it were 10 times fainter, which means that we could see other examples yet earlier in the Universe—probably into the first 200 million years,” says Brant Robertson, professor of astronomy and astrophysics at the ̽��ֱ�� of California-Santa Cruz, and lead author of a third paper on the team’s study of the evolution of this early population of galaxies. “ ̽��ֱ��early Universe has so much more to offer.”

Reference
Carniani, S et al. A shining cosmic dawn: spectroscopic confirmation of two luminous galaxies at z∼14. arXiv:2405.18485 [astro-ph.GA]

̽��ֱ��two earliest and most distant galaxies yet confirmed, dating back to only 300 million years after the Big Bang, have been discovered using NASA’s James Webb Space Telescope (JWST), an international team of astronomers today announced.

These galaxies join a small but growing population of galaxies from the first half billion years of cosmic history where we can really probe the stellar populations and the distinctive patterns of chemical elements within them

Francesco D’Eugenio

NASA, ESA, CSA, STScI, Brant Robertson (UC Santa Cruz), Ben Johnson (CfA), Sandro Tacchella (Cambridge), Phill Cargile (CfA)

Infrared image showing JADES-GS-z14-0 galaxy

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Astronomers spot oldest ‘dead’ galaxy yet observed

sc604 — Wed, 06 Mar 2024 16:00:10 +0000

Using the James Webb Space Telescope, an international team of astronomers led by the ̽��ֱ�� of Cambridge have spotted a ‘dead’ galaxy when the universe was just 700 million years old, the oldest such galaxy ever observed.

This galaxy appears to have lived fast and died young: star formation happened quickly and stopped almost as quickly, which is unexpected for so early in the universe’s evolution. However, it is unclear whether this galaxy’s ‘quenched’ state is temporary or permanent, and what caused it to stop forming new stars.

̽��ֱ��results, reported in the journal Nature, could be important to help astronomers understand how and why galaxies stop forming new stars, and whether the factors affecting star formation have changed over billions of years.

“ ̽��ֱ��first few hundred million years of the universe was a very active phase, with lots of gas clouds collapsing to form new stars,” said Tobias Looser from the Kavli Institute for Cosmology, the paper’s first author. “Galaxies need a rich supply of gas to form new stars, and the early universe was like an all-you-can-eat buffet.”

“It’s only later in the universe that we start to see galaxies stop forming stars, whether that’s due to a black hole or something else,” said co-author Dr Francesco D’Eugenio, also from the Kavli Institute for Cosmology.

Astronomers believe that star formation can be slowed or stopped by different factors, all of which will starve a galaxy of the gas it needs to form new stars. Internal factors, such as a supermassive black hole or feedback from star formation, can push gas out of the galaxy, causing star formation to stop rapidly. Alternatively, gas can be consumed very quickly by star formation, without being promptly replenished by fresh gas from the surroundings of the galaxy, resulting in galaxy starvation.

“We’re not sure if any of those scenarios can explain what we’ve now seen with Webb,” said co-author Professor Roberto Maiolino. “Until now, to understand the early universe, we’ve used models based on the modern universe. But now that we can see so much further back in time, and observe that the star formation was quenched so rapidly in this galaxy, models based on the modern universe may need to be revisited.”

Using data from JADES (JWST Advanced Deep Extragalactic Survey), the astronomers determined that this galaxy experienced a short and intense period of star formation over a period between 30 and 90 million years. But between 10 and 20 million years before the point in time where it was observed with Webb, star formation suddenly stopped.

“Everything seems to happen faster and more dramatically in the early universe, and that might include galaxies moving from a star-forming phase to dormant or quenched,” said Looser.

Astronomers have previously observed dead galaxies in the early universe, but this galaxy is the oldest yet – just 700 million years after the big bang, more than 13 billion years ago. This observation is one of the deepest yet made with Webb.

In addition to the oldest, this galaxy is also relatively low mass – about the same as the Small Magellanic Cloud (SMC), a dwarf galaxy near the Milky Way, although the SMC is still forming new stars. Other quenched galaxies in the early universe have been far more massive, but Webb’s improved sensitivity allows smaller and fainter galaxies to be observed and analysed.

̽��ֱ��astronomers say that although it appears dead at the time of observation, it’s possible that in the roughly 13 billion years since, this galaxy may have come back to life and started forming new stars again.

“We’re looking for other galaxies like this one in the early universe, which will help us place some constraints on how and why galaxies stop forming new stars,” said D’Eugenio. “It could be the case that galaxies in the early universe ‘die’ and then burst back to life – we’ll need more observations to help us figure that out.”

Reference:
Tobias J Looser et al. ‘A recently quenched galaxy 700 million years after the Big Bang.’ Nature (2024). DOI: 10.1038/s41586-024-07227-0

A galaxy that suddenly stopped forming new stars more than 13 billion years ago has been observed by astronomers.

JADES Collaboration

False-colour JWST image of a small fraction of the GOODS South field, with JADES-GS-z7-01-QU highlighted

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