Tag Archives: star formation

Hubble spots black hole “giving birth” to new star

Black holes are the most massive objects in the universe. Their gravitational pull is so strong that nothing can escape it — not even light. But according to a new NASA study, black holes may play a more complex role in galactic ‘ecosystems’. Specifically, a black hole was found to be contributing to the formation of a new star in its vicinity, offering tantalizing clues about how massive black holes develop in the first place.

A pullout of the central region of dwarf starburst galaxy Henize 2-10 traces an outflow, or bridge of hot gas 230 light-years long, connecting the galaxy’s massive black hole and a star-forming region. Hubble data on the velocity of the outflow from the black hole, as well as the age of the young stars, indicates a causal relationship between the two. Image credits: NASA, ESA, Zachary Schutte (XGI), Amy Reines (XGI); Image Processing: Alyssa Pagan (STScI).

A stellar nursery

Some ten years ago, Amy Reines, then a graduate student, discovered a black hole in a galaxy about 30 million light-years away from Earth, in the southern constellation Pyxis. She knew something was off right away, but it wasn’t until recently that new Hubble observations shed light on the situation.

“At only 30 million light-years away, Henize 2-10 is close enough that Hubble was able to capture both images and spectroscopic evidence of a black hole outflow very clearly. The additional surprise was that, rather than suppressing star formation, the outflow was triggering the birth of new stars,” said Zachary Schutte, Reines’ graduate student and lead author of the new study.

The galaxy, called Henize 2-10, is a so-called “starburst” galaxy — a galaxy where stars are being formed at a much higher rate than normal, around 1,000 times faster. The galaxy is also relatively small — a so-called dwarf galaxy — and has a black hole at its center, much like the Milky Way.

Researchers were already aware of an unusual cocoon of gas in the area, but Hubble managed to also image an outflow linked to the central black hole. Although the process is not fully understood, astronomers do believe that black holes (or at least some black holes) do have an outflow despite their massive gravity. In Henize 2-10, this outflow moves at about a million miles per hour, slamming into the gas cocoon — and as it turns out, newborn stars follow the path of the outflow.

Image credits: Schutte and Reines (2022).

In large galaxies, the opposite happens: material falling towards the black hole forms jets of plasma that don’t allow the formation of stars. But apparently, in the less-massive Henize 2-10, the outflow has just the right characteristics to precipitate new star formation. Previously, studies mostly focused on larger galaxies, where there is more observational evidence. Dwarf galaxies are still understudied, and it’s only thanks to Hubble that researchers were able to study this.

“Hubble’s amazing resolution clearly shows a corkscrew-like pattern in the velocities of the gas, which we can fit to the model of a precessing, or wobbling, outflow from a black hole. A supernova remnant would not have that pattern, and so it is effectively our smoking-gun proof that this is a black hole,” Reines said.

The role that black holes play in the universe is one of the biggest puzzles in astronomy, and the more data comes in, the more it’s starting to look like this is not a straightforward role, but rather a complex one. For instance, it was just recently demonstrated that researchers realized that most (if not all) galaxies have a black hole at their center. The more massive the galaxy, the more massive the central black hole — or possibly, the other way around, and the mass of the black hole is affecting the galaxy.

But we don’t really know how these central black holes (often called supermassive black holes) formed. Some researchers suspect they formed like “regular” black holes and somehow accumulated more and more mass; others believe they could only have formed in special conditions in the early stages of the universe; a further competing theory claims that the “seeds” of these black holes come from dense star clusters that collapse gravitationally. The black hole in Henize 2-10 could offer clues about these theories.

The black hole in the galaxy remained relatively small over cosmic time and did not accumulate a lot of material. This would suggest that it’s relatively unchanged since its formation, essentially offering a window into the early days of the universe.

“The era of the first black holes is not something that we have been able to see, so it really has become the big question: where did they come from? Dwarf galaxies may retain some memory of the black hole seeding scenario that has otherwise been lost to time and space,” Reines concludes.

Galactic neighbourhoods have an influence on stellar nurseries

Astronomers have completed the first in-depth census of molecular clouds in the nearby Universe. The study has revealed that these star-forming regions not only look different but also behave differently. This finding runs in opposition to previous scientific consensus, which considered these clouds of dust and gas to be fairly uniform.

Using the Atacama Large Millimeter/submillimeter Array (ALMA) scientists conducted a census of nearly 100 galaxies in the nearby Universe. (ALMA (ESO/NAOJ/NRAO)/S. Dagnello (NRAO))

The project–Physics at High Angular Resolution in Nearby GalaxieS (PHANGS)–consisted of a systematic survey of 100,000 molecular clouds in 90 galaxies in the local Universe. The primary aim of the PHANGS was to get an idea of how these star-forming regions are influenced by their parent galaxies.

The census was conducted with the use of the Atacama Large Millimeter/ submillimeter Array (ALMA) located on the Chajnantor plateau, in the Atacama Desert of northern Chile. Whilst not marking the first time stellar nurseries have been studied with ALMA, this is the first census of its kind to observe globular clusters across more than either one galaxy or a small region of a single galaxy.

“We have carried out the first real ‘census’ of these stellar nurseries, and it provided us with details about their masses, locations, and other properties,” Adam Leroy, Associate Professor of Astronomy at Ohio State University (OSU) tells ZME Science. “Some people thought that all stellar nurseries across every galaxy look more or less the same, and it took having a really big, sensitive, and high-resolution survey of many galaxies with a telescope such as ALMA to see that this is not the case. This survey allows us to see how the stellar nurseries change across different galaxies. “

As a result, this is the first time that astronomers have been granted a look at the ‘big picture’ when it comes to these star-forming regions. Erik Rosolowsky, Associate Professor of Physics at the University of Alberta, and a co-author of the research points out that what ALMA has allowed the team of astronomers to create is essentially a new form of ‘cosmic cartography’ consisting of 90 maps of unparalleled detail detailing the regions of space where the next generation of stars will be born.

“By doing this we will combine what we are learning from ALMA about the clouds that form stars with pictures of newly formed stars from these other telescopes. This promises to give us the best view ever of the full life cycle of these stellar nurseries, and our most complete picture ever of the full cycle of star birth and death.”

Left: NGC 2903 galaxy on GALEX sky survey Right: CO(2–1) emission measured by PHANGS–ALMA for NGC 2903 The high-resolution view shows clumpy structures corresponding to individual massive molecular clouds. (Leroy. A., Schinnerer. E., Hughes. A., et al, [2021])

“Our survey is the first one to capture the demographics of these stellar nurseries across a large number of the galaxies near the Milky Way,” adds Leroy, the lead author of a paper presenting the PHANGS ALMA survey. “We used these measurements to measure the characteristics of these nurseries, their lifetimes, and the ability of these objects to form new stars.”

How Galactic Neighborhoods Influence Star-Forming Clouds

The variety displayed by the molecular clouds surveyed in the PHANGS project was visible due to ALMA’s ability to take millimeter-wave images with the same sharpness and quality as images taken in the visible spectrum.

“While optical pictures show us light from stars, these ground-breaking new images show us the molecular clouds that form those stars,” says Leroy. “That helped us to see that stellar nurseries actually change from place to place.”

Left: Colour composite image of the spiral galaxy M 66 (or NGC 3627) obtained with the FORS1 and FORS2 multi-mode instruments (ESO) Right: emission measured by PHANGS–ALMA for NGC 2903 The high-resolution view shows clumpy structures corresponding to individual massive molecular clouds. (Leroy. A., Schinnerer. E., Hughes. A., et al, [2021])

The team compared the changes displayed by molecular clouds from galaxy to galaxy to changes in houses, neighbourhoods and cities from region to region here on Earth.

“How stellar nurseries relate to their parent galaxies has been a big question for a long time. We’re able to answer this because our survey expands the amount of data on stellar nurseries by a factor of almost 100,” says Leroy. “Before this, it was very common to study a few hundred nurseries in one galaxy. So it was kind of like trying to learn about houses in general by looking only at neighbourhoods in Columbus, Ohio.

“You will learn some things about houses, but you miss the big picture and a lot of the variation, complexity, and commonality With this survey we looked at houses in many cities across many countries.”

Adam Leroy, Ohio State University

Leroy continues by explaining that stellar nurseries ‘know’ about their neighbourhood, meaning that molecular clouds are different depending on what galaxy they live in or where in that galaxy they are located. “So the stellar nurseries that we see in the Milky Way won’t be the same as those in a different galaxy, and the stellar nurseries in the outer part of a galaxy–where we live–aren’t the same as those near the galaxy centre.”

The team found clouds in the dense central regions of galaxies tend to be more massive, denser, and more turbulent than those located on the outskirts of a galaxy. In addition to this, the census revealed the lifecycle of clouds also depends on their environment. Annie Hughes, an astronomer at L’Institut de Recherche en Astrophysique et Planétologie (IRAP) explains that this means that both the rate at which a cloud forms stars and the processes that ultimately destroy clouds both seem to depend on where the cloud lives.

How Differences in Globular Clusters Influence the Birth of Stars

Because all stars are formed in molecular clouds, understanding the differences in these clouds of gas and dust and how they are caused by the conditions in which they exist is key to better understanding the processes that are driving the birth of stars like our own Sun.

These molecular clouds are so vast that they can birth anywhere from thousands to hundreds of thousands of stars before being exhausted of raw materials. These new observations have shown astronomers that each cosmic neighbourhood can have an effect on where stars are born and how many stars are spawned.

“Every star in the sky, in fact, every star in every galaxy, including our Sun, was born in one of these stellar nurseries. These are really the engines that build galaxies and make planets, and they’re just an essential part of the story of how we got here.”

Adam Leroy, Ohio State University
Preperations are underway for the launch of the JWST which Leroy says will likely contribute to the further investigation of stellar nurseries (JWST)

The next step for the astronomers will be to combine the data provided by ALMA with surveys conducted by other telescopes including the Hubble space telescope, and the Very Large Telescope (VLT) also located in the Atacama desert, Chile. Leroy hopes that this along with observations made with the James Webb Space Telescope (JWST), will help astronomers answer the question of how the diversity of molecular structures affects the stars which form within them. He explains: “By doing this we will combine what we are learning from ALMA about the clouds that form stars with pictures of newly formed stars from these other telescopes.

This promises to give us the best view ever of the full life cycle of these stellar nurseries, and our most complete picture ever of the full cycle of star birth and death.”

Adam Leroy, Ohio State University

Leroy concludes by pointing out why the study of these star-forming regions is so important. “This is the first time we have gotten a clear view of the population of these stellar nurseries across the whole nearby universe,” the researcher says. “It’s a big step towards understanding where we come from.”

Scientists find a new way to make virtual stars

Simulations are great tools for astrophysics, we can model everything from our (cosmic) backyard to things outside the Milky Way galaxy — and the universe itself. Now we have a new example of simulated star formation. 

In a new computer simulation called STARFORGE (pictured), an enormous cloud of gas collapses into a collection of new stars. Image credits: Northwestern University / University of Texas at Austin.

A group of scientists from several American universities developed a numerical simulation called STARFORGE (STAR FORmation in Gaseous Environments). STARFORGE is a 3D simulation of star formation, it is the first to provide the visual of an entire gas cloud. It’s also the first simulation to include complex physical parameters into its code.

Producing stars is complicated (both in the real life, and in simulations), and in order to create more accurate reproductions, STARFORCE considers a long list of physical phenomena, not just gravity but also thermodynamics and stellar dynamics. Perhaps the most important physical input to the simulation is magnetohydrodynamics — which describes how an extremely hot ionized gas, a star in this case, behaves.

The best example of what STARFORGE can do is the massive giant molecular cloud named ‘The Anvil of Creation’ by the team. In the video you can see the time evolution in Mega years of the stars forming in the middle of the gas. As the stars appear, you will notice the white marbles popping in the screen, some emit massive yellow jets, those jets emanating from them. The stunning detail of the simulation is great to look at even without knowing exactly what’s going on.

The “Anvil of Creation”, the first STARFORGE simulation to combine jet, wind, radiation, and supernova feedback in concert. Mock stellar point-spread functions thanks to Fresco (Rieder & Pelupessy 2019).

It is also possible to simulate supernovae with the algorithm. The team assumes every star with 8 times the mass of the Sun can go supernova, and STARFORGE will help them explore the phenomenon and how it is affected by various parameters. The simulation can be carried out until it reaches the supernova remnant stage.

To get an idea of how important this study is, consider the Hubble Space Telescope observed the supernova in NGC 2525 for an entire year (from February 2018 to February 2019) just to get a timelapse of the dim phenomenon — and observation tools like Hubble are limited. With simulations like STARFORGE, scientists can study the evolution of stars and supernovae remnants in less time and with much better resolution.  

Credits: ESA/Hubble & NASA, M. Kornmesser, M. Zamani, A. Riess and the SH0ES team.

With STARFORGE, the team also observed an interesting effect in star formation. According to other studies, every time the star forms ejecting jets it is expected that stars lose lots of material that could make up for their total mass. Reasonable, right? The simulation had seen this happening very clearly, and also concluded that this doesn’t change much the global gas where the stars form. A great result for STARFORGE, proving it is a reliable tool for astrophysics.

The study was published in the Monthly Notices of the Royal Astronomical Society journal.

Astronomers witness the ‘death’ of a galaxy

The process that causes the end of star formation in galaxies, their transition to an inactive phase and thus their figurative ‘death’ has been a puzzle for astronomers and astrophysicist for some time. Many researchers believe that ‘galactic death’ begins with the ejection of a massive quantity of gas, but thus far, researchers have failed to capture evidence of the escape of this star-forming fuel in such volumes. Thus the confirmation of how this transition to galactic quintessence occurs has also proved elusive.

Now an international team of astronomers have used the  Atacama Large Millimeter/submillimeter Array (ALMA) located in the desert region of Chile to spot a distant galaxy in which such a massive ejection of gas is progressing.

“Using ALMA we have discovered a distant galaxy, ID2299, which is ejecting about half of its cold gas reservoir out of the galaxy,” Annagrazia Puglisi, Centre for Extragalactic Astronomy, Durham University, lead researcher on the study, tells ZME Science. “This is the first time we have observed a typical massive star-forming galaxy in the distant Universe about to ‘die’ because of a massive cold gas ejection.”

This artist’s impression of ID2299 shows the galaxy, the product of a galactic collision, and some of its gas being ejected by a “tidal tail” as a result of the merger. New observations made with ALMA, in which ESO is a partner, have captured the earliest stages of this ejection, before the gas reached the very large scales depicted in this artist’s impression. (ESO/M. Kornmesser)
This artist’s impression of ID2299 shows the galaxy, the product of a galactic collision, and some of its gas being ejected by a “tidal tail” as a result of the merger. New observations made with ALMA, in which ESO is a partner, have captured the earliest stages of this ejection before the gas reached the very large scales depicted in this artist’s impression. (ESO/M. Kornmesser)

ID2299 is so distant that the light it emits takes 9 billion years to reach Earth, which means the team were able to observe it at a time when the universe was just 4.5 billion years old.

The rate of gas ejection that ID2299–a galaxy with a similar mass to the Milky way– is experiencing is equivalent to 10,000 Suns per year, removing an extraordinary 48% of its total cold gas content. In addition to this, the galaxy is still forming stars at a rapid rate, hundreds of times faster than the star formation rate of our own galaxy.

Puglisi explains that the gas ejection, together with a large amount of star formation in the nuclear regions of the galaxy, will eventually deprive the galaxy of the fuel need to make new stars.

“This would stop star formation in the object, effectively halting the galaxy’s development.”

Annagrazia Puglisi, Centre for Extragalactic Astronomy, Durham University

The team’s research, published in the latest edition of the journal Nature Astronomy, is significant because it represents three ‘firsts’ for astronomy. “This is the first time we observe a typical massive star-forming galaxy in the distant Universe about to ‘die’ because of a massive cold gas ejection,” explains Puglisi. “Also, for the first time, we were able to tell that massive gas ejection might be frequent enough to cause the cessation of star formation in a large number of massive distant galaxies. Finally, we were able to study the physical properties of the ejected gas in a distant galaxy.”

The researcher goes on to explain that these factors are important in the understanding of the triggering mechanism of the ejection– the galaxy’s distinct tidal tail.

Galactic Collisions and Tidal Tails

The research team that discovered ID2299 believe that it was created during a collision between two galaxies and their eventual merger. Ironically this process seems to have triggered the rapid gas loss that will eventually cause it to become inactive.

Another stunning example of a tidal tail is the ‘Tadpole’s Tail’ emerging from the galaxy Arp 188. This tail stretches a stunning 280 thousand light years and was caused by a gravitational interaction with another galaxy. (Hubble Legacy Archive/ NASA/ ESA)

“ID2299 is a galaxy with a large mass in stars and is forming new stars at a rate 300 times faster than our Galaxy– a result of the collision between two galaxies,” co-author Chiara Circosta, Department of Physics & Astronomy, University College London, tells ZME.

The main clue that points towards ID2299’s creation by collision is the fact its ejected gas has taken the form of a tidal tail. These elongated streams of stars and gas that reach into interstellar space are often too faint to see and are theorised to be the result of galactic mergers.

“Collisions between galaxies are very powerful and spectacular phenomena. During the interaction, tidal forces develop and can trigger ejection of gas through tidal tails,” says Circosta. “Our study suggests that these ejections could be frequent enough to stop the formation of new stars in a large number of massive galaxies in the distant Universe.

“Our research shows that these interactions can have an important role in the life-cycles of galaxies.

Chiara Circosta, Department of Physics & Astronomy, University College London

What makes the team’s findings even more impressive is the fact that it’s a discovery that occurred predominantly through good fortune.

Serendipity and a Series of Firsts

Because tidal tails of gas such as the one that the team observed being ejected from ID2299 are extremely faint and thus, difficult for astronomers to observe. In fact, the team weren’t looking for a galaxy like ID2299 at all.

“The discovery of this object was serendipitous. I was inspecting the spectra of 100 star-forming galaxies from the ALMA telescope,” says Puglisi, who goes on to explain that the spectrum of galaxy ID2299 immediately caught her attention as it displayed an excess of emission near the very prominent emission line from the galaxy. “I was very surprised when I measured the flux of this excess emission because it indicated that the galaxy was expelling a large amount of gas.

 “I was thrilled to discover such an exceptional galaxy! I was eager to learn more about this weird object because I was convinced that there was some important lesson to be learned about how distant galaxies evolve.

Annagrazia Puglisi, Centre for Extragalactic Astronomy, Durham University

The discovery of ID2299 sparked a discussion within the team about the mechanism that is causing the gas ejection of gas at such a rapid rate. They concluded that alternative mechanisms simply couldn’t account for ejection in such large amounts.

“We discussed a lot to understand what could have been the possible cause of this phenomenon. Broad components are fairly common in the spectra of distant galaxies and are typically associated with galactic winds,” says Puglisi. “Nor the active black hole nor the strong star formation hosted in ID2299 were powerful enough to produce this ejection.

“The numbers didn’t just add up.”

The ALMA antennas at the Llano Chajnantor–above them, the bright Milky Way is visible–played a vital role in the discovery of ID2299 and will now assist in the further investigation of gas movements in the galaxy (ESO/Y. Beletsky)

The next steps for the team are to use ALMA to make high-resolution observations of ID2299 and the motion of gas within it in order to better understand the gas ejection occurring there. Looking beyond this galaxy, Puglisi says she will also look for similar occurrences in other galaxies.

“I personally find quite fascinating the study of galaxy interactions and mergers. These phenomena are visually spectacular,” the researcher adds. “I find quite poetic that galaxies can get close to each other and influence their life and evolution so dramatically.”

The research the team presents could either overturn current theories that suggest star-forming material is actually ejected by the activity of supermassive black holes at the centre of galaxies or could provide another mechanism by which this can occur. Either way, the discovery represents a significant step forward in our understanding of how galaxies develop.

“I see galaxy evolution as a complex puzzle that researchers are trying to complete through their studies,” Circosta concludes. “A crucial part of the puzzle is about the mechanisms that halt the formation of new stars and ‘kill’ galaxies.

“Witnessing such a massive disruption event allowed us to shed new light on one of the possible culprits responsible for the death of distant galaxies. This adds an important piece to the puzzle of galaxy evolution!”

Chiara Circosta, Department of Physics & Astronomy, University College London

Original research:

Puglisi. A., Daddi. E., Brusa. M., et al, ‘A titanic interstellar medium ejection from a massive starburst galaxy at z=1.4,’ Nature Astronomy, [2021], [DOI: 10.1038/s41550-020-01268-x].

NGC1569 is a star-forming galaxy. Galaxies such as this could see their star formation rates affected by strong winds emanating from a central black hole. (HST/NASA/ESA)

Black Holes could stunt the growth of dwarf galaxies

NGC1569 is a star-forming galaxy. Galaxies such as this could see their star formation rates affected by strong winds emanating from a central black hole. (HST/NASA/ESA)
NGC1569 is a star-forming galaxy. Galaxies such as this could see their star formation rates affected by strong winds emanating from a central black hole. (HST/NASA/ESA)

Black holes at the centre of small dwarf galaxies could slow or even halt the formation of stars via the powerful winds they produce, researchers from University of California, Riverside, have discovered. This suppression of star-formation could have a marked influence on the evolution of such galaxies.

The result seems to confirm the long-held suspicion that supermassive black holes at the centre of galaxies can influence that galaxy’s evolution — including how they grow and the way that they age. But, the research also delivers a surprise; the winds that the astronomers measured coming from the black hole were more powerful than the team reckoned for. This means that models of star formation in dwarf galaxies may require a rethink.

“We expected we would need observations with much higher resolution and sensitivity, and we had planned on obtaining these as a follow-up to our initial observations,” said Gabriela Canalizo, a professor of physics and astronomy at UC Riverside who led the research team. “But we could see the signs strongly and clearly in the initial observations.

“The winds were stronger than we had anticipated.”

Gabriela Canalizo

Thus meaning that black holes don’t just influence the development of larger galaxies, but also play a role in the evolution of smaller dwarf galaxies — galaxies containing anywhere from a few thousand to a few billion stars.

Canalizo continues: “Our findings now indicate that their effect can be just as dramatic, if not more dramatic, in dwarf galaxies in the universe.”

The study — the results of which are discussed in the Astrophysical Journal — used data collected in the Sloan Digital Sky Survey (SDSS), a project which maps 35% of the sky above Earth. In doing so, the survey has been able to identify 50 dwarf galaxies — 29 of which demonstrated clear characteristics of possessing black holes at their centres. A further six of these showed evidence of high-velocity outflows of ionised gas — the powerful winds in question.

The next step for the researchers was to use the Keck telescopes — based in Hawaii — to both detect and measure the properties of these winds, marking the first time this has been achieved.

Discussing what her team found, Canalizo adds: “We found some evidence that these winds may be changing the rate at which the galaxies are able to form stars.”

Studying dwarf galaxies could be the key to understanding how galaxies in general evolve

The study of these smaller galaxies could help scientists answer lingering about galactic evolution in general.

“Larger galaxies often form when dwarf galaxies merge together,” explains Christina Manzano-King, a doctoral student in Canalizo’s lab and the first author of the paper. As a consequence of this, she continues, dwarf galaxies are particularly useful in understanding how galaxies evolve.

Dwarf galaxies hosting active galactic nuclei that have spatially extended outflows. (SDSS)
Dwarf galaxies hosting active galactic nuclei that have spatially extended outflows. (SDSS)

“Dwarf galaxies are small because after they formed, they somehow avoided merging with other galaxies,” she adds. “Thus, they serve as fossils by revealing what the environment of the early universe was like.

“Dwarf galaxies are the smallest galaxies in which we are directly seeing winds — gas flows up to 1,000 kilometres per second — for the first time.”

Christina Manzano-King

Explaining what causes these powerful winds, Manzano-KIng points to material being fed into the black hole. This material — usually gas and dust — forms an accretion disc around the black hole. In this disc — which gradually feeds the black hole — conditions are so violent that friction and tremendous tidal forces heats the material. This releases radiative energy which shoves gas out of the galaxy’s centre and into intergalactic space.

This negatively affects the amount of gas available for star formation.

Manzano-King continues: “What’s interesting is that these winds are being pushed out by active black holes in the six dwarf galaxies rather than by stellar processes such as supernovae.

“Typically, winds driven by stellar processes are common in dwarf galaxies and constitute the dominant process for regulating the amount of gas available in dwarf galaxies for forming stars.”

Astronomers believe that winds emanating from black holes can compress gas and thus aid the gravitational collapse of gas clouds, kick-starting star-formation. But, if the wind is too strong and thus expels gas from the galaxy’s centre, rather than aiding the star formation process, gas becomes unavailable and hinders the process.

This is exactly what appears to be happening in the six galaxies that the team’s research highlighted. In these cases, the wind has had a clear detrimental impact on star formation rates.

Rethinking the relationship between black holes and star formation rates

This research may result in a rethinking of models of star formation and the evolution of galaxies. Current models do not take into account the impact of black holes in dwarf galaxies.

From left to right: Laura Sales, Christina Manzano-King, and Gabriela Canalizo. The team’s research could force a rethinking of star formation rates in dwarf galaxies ( Stan Lim, UC Riverside)
From left to right: Laura Sales, Christina Manzano-King, and Gabriela Canalizo. The team’s research could force a rethinking of star formation rates in dwarf galaxies ( Stan Lim, UC Riverside)

“Our findings show that galaxy formation models must include black holes as important, if not dominant, regulators of star formation in dwarf galaxies,” points out Laura V. Sales, assistant professor of physics and astronomy at UC Riverside.

As for the future of this research, the team next plans to investigate characteristics of gas outflows such as mass and momentum.

“This would better inform theorists who rely on such data to build models,” concludes Manzano-King. “These models, in turn, teach observational astronomers just how the winds affect dwarf galaxies.

“We also plan to do a systematic search in a larger sample of the Sloan Digital Sky Survey to identify dwarf galaxies with outflows originating in active black holes.”

Original research: ‘AGN-Driven Outflows in Dwarf Galaxies’ Christina M. Manzano-King, Gabriela Canalizo, and Laura V. Sales.

Ancient galaxies from the study are visible to ALMA (right) but not to Hubble (left). Credit: © 2019 Wang et al.

‘Hidden’ ancient galaxies discovery may redefine our understanding of the Universe

The discovery of 39 ‘hidden’ ancient galaxies urges scientists to rethink their theories of fundamental aspects of the Universe — including supermassive black holes, star formation rates, and the ever-elusive, dark matter.

Ancient galaxies from the study are visible to ALMA (right) but not to Hubble (left). Credit: © 2019 Wang et al.

In an unprecedented discovery of astronomers, researchers have utilised the combined power of a multitude of observatories across the globe to discover a vast array of 39 previously hidden galaxies.

The finding — described by the researchers from the University of Tokyo as a ‘treasure trove’ — is the first multiple discoveries of this kind. But the finding is significant for more than its size alone.

In addition to containing a wealth of newly discovered ancient galaxies, an abundance of this particular type of galaxy suggests that scientists may have to refine current models of the universe.

This is because our current understanding of the universe and how it formed is built upon observations of galaxies in ultraviolet light. But observations in these wavelengths under-represent the most massive galaxies — those with high dust content and crucially, the most ancient.

This means that a discovery of such galaxies — such as the one just made — must force us to reconsider the rates of star formation in the early universe. The study explains that the population of stars discovered may mean that star formation rates were actually ten times greater in early epochs than previous estimates held.

There are also particular ramifications for our understanding of both supermassive black holes and their distribution, and for the concept of dark matter — the elusive substance which makes up 80% of the matter in the universe.

Despite the wealth of astronomical data that has become available to scientists since the launch of the Hubble Space Telescope, researchers at the Institute of Astronomy in Toyko were aware there were things that Hubble simply couldn’t show us. It was these things — fundamental pieces of the cosmic puzzle — that they wanted to investigate.

They achieved this by unifying different observatories, using them to look more deeply in the Universe than Hubble alone could do. This is what led them to this huge collection of galaxies.

Researcher Tao Wang describes the uniqueness and magnitude of the team’s discovery: “This is the first time that such a large population of massive galaxies was confirmed during the first two billion years of the 13.7-billion-year life of the universe.

“These were previously invisible to us.”

Wang continues: “This finding contravenes current models for that period of cosmic evolution and will help to add some details, which have been missing until now.”

A different view of the universe

Wang explains that if we could see these galaxies and the light they shed, our view from the Milky way would be significantly different: “For one thing, the night sky would appear far more majestic. The greater density of stars means there would be many more stars close by appearing larger and brighter.

“But conversely, the large amount of dust means farther-away stars would be far less visible, so the background to these bright close stars might be a vast dark void.”

The galaxies have been difficult to see from Earth due to how faint they are. Were we able to see these stars, their density would make the night sky majestic, Wang says.

The light from these galaxies also has to battle extinction — the absorption of light) by intervening interstellar dust clouds. The light from the galaxies also has to travel great distances meaning the wavelength is redshifted by the expansion of the universe making it even less visible.

Professor Kotaro Kohno. Credit: © 2019 Rohan Mehra — Division of Strategic Public Relations

Professor Kotaro Kohno explains that this phenomenon is how the galaxies escaped Hubble’s gaze: “The light from these galaxies is very faint with long wavelengths invisible to our eyes and undetectable by Hubble.

“So we turned to the Atacama Large Millimeter/submillimeter Array (ALMA), which is ideal for viewing these kinds of things. I have a long history with that facility and so knew it would deliver good results.”

This redshift due to cosmic expansion does have its advantages, however. It allows astronomers to estimate not just the distances to the galaxies in question, but it also allows them to calculate just how long ago the light was emitted.

The hidden implications of these hidden galaxies

The team’s finding is so controversial and poses such a radical rethink that they found their fellow astronomers were initially reluctant to believe they had found what they claimed.

A few of the 66 radio telescope antennas that make up ALMA. Credit: © 2019 Kohno et al.

Wang explains: “It was tough to convince our peers these galaxies were as old as we suspected them to be. Our initial suspicions about their existence came from the Spitzer Space Telescope’s infrared data.

“But ALMA has sharp eyes and revealed details at submillimeter wavelengths, the best wavelength to peer through dust present in the early universe. Even so, it took further data from the imaginatively named Very Large Telescope in Chile to really prove we were seeing ancient massive galaxies where none had been seen before.”

The discovery has the potential to reshape our ideas of the supermassive black holes that scientists currently believe nestle at the centre of most galaxies.

Kohno elaborates: “The more massive a galaxy, the more massive the supermassive black hole at its heart.

“So the study of these galaxies and their evolution will tell us more about the evolution of supermassive black holes, too.”

Kohno also explains that some ideas regarding dark matter may have to be revised, too: “Massive galaxies are also intimately connected with the distribution of invisible dark matter. This plays a role in shaping the structure and distribution of galaxies. Theoretical researchers will need to update their theories now.”

In addition to the potential shake up the team believes that their findings may already present, they expect more surprises to come.

Wang concludes: These gargantuan galaxies are invisible in optical wavelengths so it’s extremely hard to do spectroscopy, a way to investigate stellar populations and chemical composition of galaxies. ALMA is not good at this and we need something more.

“I’m eager for upcoming observatories like the space-based James Webb Space Telescope to show us what these primordial beasts are really made of.”

Original research: T. Wang, C. Schreiber, D. Elbaz, Y. Yoshimura, K. Kohno, X. Shu, Y. Yamaguchi, M. Pannella, M. Franco, J. Huang, C.F. Lim & W.H. Wang. A dominant population of optically invisible massive galaxies in the early Universe. Nature. DOI: 10.1038/s41586–019–1452–4

Supermassive black holes eventually stop star formation

Researchers analyzed the correlation between the mass of supermassive black hole and the history of star formation in its galaxy. They found that the bigger the black hole is, the harder it is for the galaxy to generate new stars.

Scientists have been debating this theory for a while, but until now, they lacked enough observational data to prove or disprove it.

Via Pixabay/12019

Researchers from the University of Santa Cruz, California used data from previous studies measuring supermassive black hole mass. They then used spectroscopy to determine how stars formed in galaxies featuring such gargantuan black holes and correlate the two.

Spectroscopy is a technique that relies on measuring the wavelength of light emerging from objects — stars, in this case. The paper’s lead author Ignacio Martín-Navarro used computational analysis to determine how the black holes affected star formation — in a way, he tried to solve a light puzzle.

“It tells you how much light is coming from stellar populations of different ages,” he said in a press release.

Via Pixabay / imonedesign.

Next, the research team plotted the size of supermassive black holes and compared them to a history of star formation in that galaxy. They found that as the black holes grew more and more, star formation was significantly slowed down. Other characteristics of the galaxies, such as shape or size, were found irrelevant to the study.

“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.

Star gas from Carina Nebula, source: Pixabay/skeeze

Scientists still trying to determine why this happens. One theory suggests that the lack of cold gas is the main culprit for reduced star formation. The supermassive black holes suck in the nearby gas, creating high-energy jets in the process. These jets ultimately expel cold gas from the galaxy. Without enough cold gas, there is no new star formation, so the galaxy becomes practically sterile.

In the press release, co-author Aaron Romanowsky concluded:

“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.”

The paper was published in Nature on the 1st of January 2018.

An artist’s rendering of the quasar 3C 279 (credit: European Southern Observatory)

First stars formed 750 million years after the Big Bang

An artist’s rendering of the quasar 3C 279 (credit: European Southern Observatory)

An artist’s rendering of the quasar 3C 279 (credit: European Southern Observatory)

Determining when stars first started to form through out the early Universe is a matter of great importance for astronomers and astrophysicists looking to understand how the cosmos evolved from its incipient point of origin. Recently, researchers at MIT who have been studying the most distant quasar observed so far found  no discernible trace of heavy elements, such as carbon and oxygen. Their findings suggest that stars had yet to be born 750 million years after the Big Bang.

The elements are only formed by stars –  essentially we all come from stars. If these basic building blocks aren’t visible then  the quasar dates to an era nearing that of the universe’s first stars.

After the Big Bang massive amounts of matter and energy were flung, leading to the expansion of the early Universe. In the minutes following the explosion, protons and neutrons collided in nuclear fusion reactions to form hydrogen and helium. Once the Universe cooled, fusion ceased along with the generation of  these primordial elements. It would be until the first stars appeared that heavy elements such as oxygen or carbon could be synthesized.

Lack of these elements in observations suggests that stars hadn’t been formed during that phase of the Universe. So far, the farthest astronomers have gone to study the light of distant objects was 11 billion years – the Universe is 13.7 billion years old, and each time heavy elements were found. Last year scientists discovered  the earliest quasar found so far, which provided a snapshot of our universe during its infancy, a mere 750 million years after the initial explosion that created the universe.

“The first stars will form in different spots in the universe … it’s not like they flashed on at the same time,” says Robert Simcoe, an associate professor of physics at MIT. “But this is the time that it starts getting interesting.”

“[The astrophysics community] sort of hit this wall,” says Simcoe, an astrophysicist at MIT’s Kavli Institute for Astrophysics and Space Research. “When this [quasar] was discovered, we could sort of leapfrog further back in time and make a measurement that was substantially earlier.”

Before stars shone bright

An artist’s rendering of how the most distant quasar found to date would have appeared just 770 million years after the Big Bang (credit: European Southern Observatory/M. Kornmesser)

An artist’s rendering of how the most distant quasar found to date would have appeared just 770 million years after the Big Bang (credit: European Southern Observatory/M. Kornmesser)

Recently MIT astronomers pointed the Magellan Telescope, a massive ground-based telescope in Chile, which they fitted with a carefully designed spectrometer, towards the quasar to study its light spectrum. Each element gives of a pattern, based on how it characteristically absorbs light. Based on this, the scientists found evidence of hydrogen, but no oxygen, silicon, iron or magnesium in the light data.

“[The birth of the first stars] is one of these important moments in the history of the universe,” Simcoe says. “It went from looking like the early universe, which was just gas and dark matter, to looking like it does today, where there are stars and galaxies … it’s the point when the universe started to resemble what it looks like today. And it’s sort of amazing how early that happens. It didn’t take long.”

Other scientists, like John O’Meara, an associate professor of physics at St. Michael’s College in Vermont, believe that more observations of distant quasars is needed in order to confirm the findings.

“Prior to this result, we have not seen regions of the universe this old and devoid of heavy elements, so there was a missing link in our understanding of how the elemental content of the universe has evolved with time,” O’Meara adds. “[This] discovery possibly provides such a rare environment where the universe had yet to form stars.”

Results were published in the journal Nature.

source: MIT

Diagram above show how star production has decreased over billions of years. The new re­sults in­di­cate that, meas­ured by mass, the pro­duc­tion rate of stars has dropped by 97 per­cent since its peak 11 bil­lion years ago. (c) D. Sobral

The Universe will stop making new stars very soon – no more than 5% more stars will be born

A startling study, which looked at data 10 times more comprehensive compared to previous similar efforts, found that half of all the stars that have ever existed were created between 9 and 11 billion years ago, with the other half created in the years since. What this means is an exponential fall in new stars being born, to the point that no more than 5 per­cent more stars will form over the re­main­ing his­to­ry of the cos­mos, even if we wait for­ev­er.

For years, scientists were confused by the disparity between the number of stars we can observe and the number of stars we know should have been created by the universe. Numerous studies have each looked at specific periods in our Universe’s history in order to assess star formation, however since multiple methods were used, it was fairly difficult to aggregate and establish a comparative conclusion.

Diagram above show how star production has decreased over billions of years.  The new re­sults in­di­cate that, meas­ured by mass, the pro­duc­tion rate of stars has dropped by 97 per­cent since its peak 11 bil­lion years ago. (c) D. Sobral

Diagram above show how star production has decreased over billions of years. The new re­sults in­di­cate that, meas­ured by mass, the pro­duc­tion rate of stars has dropped by 97 per­cent since its peak 11 bil­lion years ago. (c) D. Sobral

A team of international researchers decided to run a complete survey from the very dawn of the first stars using three telescopes — the UK Infrared Telescope and the Subaru Telescope, both in Hawaii, and Chile’s Very Large Telescope. Snapshots were taken of the look of the Universe at various instances in time when it was 2, 4, 6 and 9 billion years old  –  that’s 10 times as large as any previous similar study. The as­tro­no­mers con­clud­ed that the rate of forma­t­ion of new stars in the Uni­verse is now only 1/30th of its peak.

“You might say that the uni­verse has been suf­fer­ing from a long, se­ri­ous ‘cri­sis:’ cos­mic GDP out­put is now only 3 per­cent of what it used to be at the peak in star pro­duc­tion!” said Da­vid So­bral of the Uni­vers­ity of Lei­den in the Neth­er­lands.

“If the meas­ured de­cline con­tin­ues, then no more than 5 per­cent more stars will form over the re­main­ing his­to­ry of the cos­mos, even if we wait for­ev­er. The re­search sug­gests that we live in a uni­verse dom­i­nat­ed by old stars.”

According to the current accepted models of the Universe’s evolution, stars first began to form some 13.4 billion years ago, or 300 million years after the Big Bang. Now, these ancient stars were nothing like those commonly found through out the cosmos. These were like titans with respect to Olympus’ gods – standing at hundreds of times more massive than our sun. Alas, the giants’ life would’ve been short lived, quickly exhausting their fuel, they had only one million years or so worth of time. Lighter stars, like our own, in contrast can shine long and bright for billions of years.

It’s from these huge, first stars that other smaller, more long-lived stars form as the cosmic dust was recycled. Our Sun, for ex­am­ple, is thought to be a third genera­t­ion star, and has a typ­i­cal mass, or weight, by to­day’s stan­dards. To identify star formations, the astronomers searched for alpha particles emitted by Hydrogen atoms, appearing as a bright red light.

“Half of these were born in the ‘boom’ that took place be­tween 11 and 9 bil­lion years ago and it took more than five times as long to pro­duce the rest,” So­bral said. “The fu­ture may seem rath­er dark, but we’re ac­tu­ally quite lucky to be liv­ing in a healthy, star-form­ing gal­axy which is go­ing to be a strong con­trib­u­tor to the new stars that will form.

“Moreo­ver, while these mea­sure­ments pro­vide a sharp pic­ture of the de­cline of star-forma­t­ion in the Uni­verse, they al­so pro­vide ide­al sam­ples to un­veil an even more fun­da­men­tal mys­tery which is yet to be solved: why?”

Results were published in the Monthly Notices of the Royal Astronomical Society.

Gigantic storms are sweeping entire galaxies clean

If you think that the recent outbreak of tornadoes are bad, boy are you in for a shocker. An international team of researchers from the Max Planck Institute for Extraterrestrial Physics has found that enormous storms of molecular gas are sweeping entire galaxies, destroying everything they come across until they wipe the galaxy clean.

Galactic events

Some of these galactic storms have speeds of up to 1000 kilometres per second, which is a thousand times more than what hurricanes have on Earth. Observations show that the more active galaxies have faster winds which basically blow away the entire gas reservoir in a galaxy, thus inhibiting the formation of new stars and the growing of the central black hole. This is the first information researchers have had about galactic winds, which play a very important role in the evolution of galaxies.

The distant and therefore yourger part of the universe, most galaxies are way more active than the Milky Way; it is commonly accepted that gas-rich galaxies merge, thus triggering stellar formation in what is called a starburst galaxy. This is also associated with the growth of the supermassive black hole at the center of the galaxy.

However, this process often seemed to just shut down, for no apparent reason. Astrophysicsts scrambled trying to find what could cause such an unbelievable stop of growth in such a short timespan, but there seemed to be no result.

Blowing in the wind

galactic storm

The answer to the riddle came rather unexpectedly, in the form of the powerful winds I was telling you about, which blow gas outwards from the center of the galaxy; it does seem kind of counterintuitive for the winds to blow from the center, but they are powered up by newly formed stars or shocks from stellar explosions, and they have enough energy to remove virtually all the gas supply from the galaxy, putting a stop to the very processes that created them, in an ultimate self-destruction act.

“Outflows are key features in models of galactic formation and evolution, but prior to our work no decisive evidence of their active role in such processes had been gathered,” explains Eckhard Sturm from the Max Planck Institute for Extraterrestrial Physics (MPE).

Sturm has been leading studies that estimate the outflow of these gigantic winds, and even estimated the quantity that is eliminated.

“By detecting outflows in cold molecular gas from which stars are born, we can finally witness their direct impact on star formation,” Sturm adds. “Star formation stalls as the gas supply is blown out of the centres of the galaxies with a rate of up to a thousand solar masses per year.”

Even though this study is not definitive, it definitely pins down some suspects regarding the driving force behind these outflows. From this point of view, galaxies seem to fall into two categories:

  • starburst-dominated objects, which lose material of up to a few hundred solar masses per year – a number similar to their formation rate; with velocities of a few hundred kilometres per second these outflows are probably driven by radiation pressure from starbursts or supernovae explosions
  • galaxies dominated by the activity of the black hole in their centre lose material at much higher rates, up to a thousand solar masses per year or more; with velocities around 1000 kilometres per second these outflows are probably powered mostly by radiation pressure from the active galactic nucleus
  • However, in order to confirm these theories, researchers will have to analyze a much bigger set of data, but due to Herschel incredible sensitivity, that is not really a big problem.

    A star is born [great pics]

    The nebula you are looking at is known as the North American nebula, and the pictures were taken with the Spitzer telescope, using an infrared vision; researchers still have some unanswered questions about the group of massive stars thought to be dominating the nebula. The lower left of this first image shows the “baby” stars in the complex, no older than a million years.

    Scientists have calculated that the North American nebula is some 1.800 light years away, in the Cygnus constellation, which makes it a fave for (amateur and professional) astronomers, because it’s in a rich and interesting region, it’s not so far away, and can be observed for most of the year from the Northern hemisphere. But the whole region looks very differently when viewed through Spitzer.

    Stellar formation starts with the gravitational collapse of a molecular cloud; gravity collapses the cloud (or a part of it), with the collapse itself creating heat energy. This piece then condenses due to the heat and pressure and forms what is called a protostar.

    This is a turning point for the protostar. If it doesn’t gather enough mass, it will eventually cool off and become a brown dwarf.

    Pictures via NASA.

    Ancient Galaxies Really Sucked (Gas, That Is)

    When early galaxies formed, there was a surprisingly high rate of new stars being formed, which was explained by major galactic collisions; however, recent evidence suggests that in fact the answer is much simpler, and not nearly as violent.

    An artist's representation of a galaxy sucking surrounding gas. Credit: ESO/L. Calçada

    Astronomers using the European Southern Observatory’s Very Large Telescope in Chile have observed three ancient galaxies with “patches of star formation” towards their center; they found that these galaxies were literally sucking hydrogen and helium from the space between galaxies and using it as fuel.

    “It solves the problem of providing to the galaxies fuel to form their stars in a continuous way, without having to invoke violent mergers and galaxy interactions,” said study researcher Giovanni Cresci of Italy’s OsservatorioAstrofisico di Arcetri. “Those certainly exist, but these new findings show that they are not the main driver of star formation in the early universe.”

    Theoretical models developed so far suggest that the earliest galaxies formed about a billion years after the Big Bang, but they were quite small, way smaller than the Milky Way, for example. But somehow they grew in stars and accumulated more and more stars, and so galactic collisions seemed to be a reasonable explanation.

    However, recent evidence suggests that such a violent star formation would fade within a few million years, and the studied galaxies showed stars that lasted billions of years. Also, some galaxies showed absolutely no sign of such a collision, so a new solution had to be found.

    Cresci and his colleagues concluded that early galaxies have sucked the hydrogen and helium that surrounded them and thus drove new star formation for billions of years. Their study of non-merging galaxies seems to back up their claim.

    “This is the link between the large-scale structures dominated by dark matter and the local Hubble-type galaxies such as our own,” he said. “We are trying to understand how our home in the universe, the Milky Way, was built.”

    Via Space.com