NGC 5044 as seen by XMM-Newton. Astronomers say they are able to see hot gas moving in this galaxy because of an interaction with another galaxy millions of years ago. Credit: E. O’Sullivan & ESA
So galaxy group NGC 5044 was just sitting quietly by itself a few million years ago when galaxy NGC 5054 decided to pass right through it. That close encounter finished long ago, but the ricochet is still visible in telescopes as astronomers spotted hot gas rippling through the host galaxy.
“Galaxies are social beasts that are mostly found in groups or clusters – large assemblies of galaxies that are permeated by even larger amounts of diffuse gas. With temperatures of 10 million degrees or more, the gas in galaxy groups and clusters is hot enough to shine brightly in X-rays and be detected by ESA’s XMM-Newton X-ray observatory,” the European Space Agency stated.
“As galaxies speed through these gigantic cauldrons, they occasionally jumble the gas and forge it into lop-sided shapes. An example is revealed in this composite image of the galaxy group NGC 5044, the brightest group in X-rays in the entire sky.”
Fresh observations from XMM-Newton (in blue) are visible in this composite image with other pictures from the Wide-field Infrared Survey Explorer, the Digitized Sky Survey (optical) and Galex (near-ultraviolet).
Publication of this research was accepted in MNRAS and is currently available on prepublishing site Arxiv. The lead author is Ewan O’Sullivan, a visiting scientist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
Galaxy z8_GND_5296 (seen in the inset) is the earliest galaxy that astronomers have measured the distance to accurately. It formed approximately 700 million years after the Big Bang, and is forming stars at an incredibly rapid rate. [Credit: V. Tilvi (Texas A&M), S. Finkelstein (UT Austin), the CANDELS team, and HST/NASA]
“The farthest galaxy yet seen!” Haven’t we heard that one before? (See here and here, for example.) While it’s true that astronomers keep pushing farther back in time with better instruments, there are fundamental challenges both in observing and measuring the distances to the earliest galaxies in the cosmos.
That’s why this new observation of a galaxy that formed about 700 million years after the Big Bang is significant. While scores of galaxies have been identified that formed in that era, astronomers have only measured accurate distances for five of them. This galaxy marks the sixth, and it is the farthest of the bunch. Perhaps even more important than the distance measurement, researchers determined that this galaxy gave birth to new stars at more than 100 times the rate the Milky Way does today. That indicates early galaxies may have been more aggressive with star-formation than previously believed. Continue reading “Taking Measure: A ‘New’ Most Distant Galaxy”
A picture of the object J1000+0221, which demonstrates the most distant gravitational lens ever discovered. This Hubble picture shows a normal galaxy's center region (the glow in the picture), but the object is also aligned with a younger, star-creating galaxy that is in behind. The object in the foreground pulls light from the background galaxy with gravity -- making rings of pictures. Credit: NASA/ESA/A. van der Wel
Here’s a picture of what deflected light looks like from 9.4 billion years away. This is the most faraway “gravitational lens” that we know of, and a demonstration of how a galaxy can bend the light of an object behind it. The phenomenon was first predicted by Einstein, and is a handy way of measuring mass (including the mass of mysterious dark matter.)
“The discovery was completely by chance,” stated Arjen van der Wel, who is with the Max Planck Institute for Astronomy in Heidelberg, Germany.
“I had been reviewing observations from an earlier project when I noticed a galaxy that was decidedly odd. It looked like an extremely young galaxy, but it seemed to be at a much larger distance than expected. It shouldn’t even have been part of our observing program.”
The alignment between object J1000+0221 and the object in behind is so perfect that you can see rings of light being formed in the image. Scientists previously believed this kind of lens would happen very rarely. This leaves two possibilities: that the astronomy team was lucky, or there are way more young galaxies than previously thought.
This schematic image represents how light from a distant galaxy is distorted by the gravitational effects of a nearer foreground galaxy, which acts like a lens and makes the distant source appear distorted, but brighter, forming characteristic rings of light, known as Einstein rings. An analysis of the distortion has revealed that some of the distant star-forming galaxies are as bright as 40 trillion Suns, and have been magnified by the gravitational lens by up to 22 times. Credit: ALMA (ESO/NRAO/NAOJ), L. Calçada (ESO), Y. Hezaveh et al.
“Gravitational lenses are the result of a chance alignment. In this case, the alignment is very precise,” a press release on the discovery stated.
“To make matters worse, the magnified object is a starbursting dwarf galaxy: a comparatively light galaxy … but extremely young (about 10-40 million years old) and producing new stars at an enormous rate. The chances that such a peculiar galaxy would be gravitationally lensed is very small. Yet this is the second starbursting dwarf galaxy that has been found to be lensed.”
“This has been a weird and interesting discovery,” added van der Wel. “It was a completely serendipitous find, but it has the potential to start a new chapter in our description of galaxy evolution in the early universe.”
The research will be available soon in the Astrophysical Journal; in the meantime, check out a preprint version on Arxiv.
This detailed view shows the central parts of the nearby active galaxy NGC 1433. The dim blue background image, showing the central dust lanes of this galaxy, comes from the NASA/ESA Hubble Space Telescope. The coloured structures near the centre are from recent ALMA observations that have revealed a spiral shape, as well as an unexpected outflow, for the first time. Credit: ALMA (ESO/NAOJ/NRAO)/NASA/ESA/F. Combes
Did you ever wonder what it would be like to observe what happens to a galaxy near a black hole? For all of us who remember that wonderful Disney movie, it would be a remarkable – if not hypnotic – experience. Now, thanks to the powerful observational tools of the Atacama Large Millimeter/submillimeter Array (ALMA), two international astronomy teams have had the opportunity to study the jets of black holes near their galactic cores and see just how they impact their neighborhood. The researchers have captured the best view so far of a molecular gas cloud surrounding a nearby, quiescent black hole and were gifted with a surprise look at the base of a massive jet near a distant one.
These aren’t lightweights. The black holes the astronomers are studying weigh in a several billion solar masses and make their homes at the center of nearly all the galaxies in the Universe – including the Milky Way. Once upon a time, these enigmatic galactic phenomena were busy creatures. They absorbed huge amounts of matter from their surroundings, shining like bright beacons. These early black holes thrust small amounts of the matter they took in through highly powerful jets, but their current counterparts aren’t quite as active. While things may have changed a bit with time, the correlation of black hole jets and their surroundings still play a crucial role in how galaxies evolve. In the very latest of studies, both published today in the journal Astronomy & Astrophysics, astronomers employed ALMA to investigate black hole jets at very different scales: a nearby and relatively quiet black hole in the galaxy NGC 1433 and a very distant and active object called PKS 1830-211.
“ALMA has revealed a surprising spiral structure in the molecular gas close to the center of NGC 1433,” says Françoise Combes (Observatoire de Paris, France), who is the lead author of the first paper. “This explains how the material is flowing in to fuel the black hole. With the sharp new observations from ALMA, we have discovered a jet of material flowing away from the black hole, extending for only 150 light-years. This is the smallest such molecular outflow ever observed in an external galaxy.”
Need feedback? Well, that’s exactly what this process is called. “Feedback” may enlighten us to the relationship between black hole mass and the mass of the surrounding galactic bulge. The black hole consumes gas and becomes active, but then it creates jets which purge gas from its proximity. This halts star formation and controls the growth of the central bulge. In PKS 1830-211, Ivan Marti-Vidal (Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden) and his team witnessed a supermassive black hole with a jet, “but a much brighter and more active one in the early universe. It is unusual because its brilliant light passes a massive intervening galaxy on its way to Earth, and is split into two images by gravitational lensing.”
Are supermassive black holes messy eaters? You bet. There have been occasions when a supermassive black hole will unexpectedly consume a staggering amount of mass which, in turn, turbo-charges the power of the jets and lights up the radiation output to the very pinnacle of energy output. This energy is emitted as gamma rays, the shortest wavelength and highest energy form of electromagnetic radiation. And now ALMA has, by chance, caught one of these events as it happened in PKS 1830-211.
“The ALMA observation of this case of black hole indigestion has been completely serendipitous. We were observing PKS 1830-211 for another purpose, and then we spotted subtle changes of color and intensity among the images of the gravitational lens. A very careful look at this unexpected behavior led us to the conclusion that we were observing, just by a very lucky chance, right at the time when fresh new matter entered into the jet base of the black hole,” says Sebastien Muller, a co-author of the second paper.
The main image, showing the nearby active galaxy NGC 1433, comes from the NASA/ESA Hubble Space Telescope. The coloured structures near the centre shown in the insert are from recent ALMA observations that have revealed a spiral shape, as well as an unexpected outflow, for the first time. Credit: ALMA (ESO/NAOJ/NRAO)/NASA/ESA/F. CombesAs with all astronomical observations, the key to discovery is confirmation. Did the ALMA findings show up on other telescopic observations? The answer is yes. Thanks to monitoring observations with NASA’s Fermi Gamma-ray Space Telescope, there was a definite gamma ray signature exactly where it should be. Whatever was responsible for the scaling up of radiation at ALMA’s long wavelengths was also responsible for making the light of the black hole jet flare impressively.
“This is the first time that such a clear connection between gamma rays and submillimeter radio waves has been established as coming from the real base of a black hole’s jet,” adds Sebastien Muller.
It isn’t the end of the story, however. It’s just the beginning. ALMA will continue to probe into the mysterious workings of supermassive black hole jets – both near and far. Combes and her investigative team are already observing close active galaxies with ALMA, and even a unique object cataloged as PKS 1830-211. The research will continue, and with it we may one day have answers to many questions.
“There is still a lot to be learned about how black holes can create these huge energetic jets of matter and radiation,” concludes Ivan Marti-Vidal. “But the new results, obtained even before ALMA was completed, show that it is a uniquely powerful tool for probing these jets — and the discoveries are just beginning!”
Artist's conception of a star being born, within a protective shroud of gas and dust. New research shows that magnetic winds aid the growth of both protostars and SMBHs. Credit: NASA
Stars are born in private. Hidden in dust and gas clouds, these bright beacons in the universe slowly coalesce. All that debris makes it hard to spot the stars, but mapping out the pockets of starbirth is a good start to understanding what is going on inside.
A new survey tracked down 6,000 of these areas in our galaxy (the Milky Way), with the aim of understanding more about what happens when stars are just starting to come together. Most surveys, the team says, focus more on the “protostar” stage, when these objects are starting to look recognizably like stars.
“Starless clumps have only been detected in small numbers to date,” stated Yancy Shirley, an astronomer with the University of Arizona’s Steward Observatory who led the research. “Now, for the first time, we have seen this earliest phase of star formation, before a cluster actually forms, in large numbers in an unbiased way.”
Artist’s conception of the Milky Way galaxy. Credit: Nick Risinger
These areas are difficult to peer through in visible light, but radio works just fine. The astronomers used the Sub-Millimeter Telescope at the Arizona Radio Observatory to conduct the survey, which looks at “all parts of the galactic plane visible from the northern hemisphere”, the team says.
It’s the first survey to show the environments where different stages of starbirth take place. While the team did not immediately disclose their plans for a follow-up in a press release, they state that one aim of mapping these areas is to “better understand how the properties of these regions change as star formation progresses.”
PGC 6240, a petal-like galaxy that probably was altered by a galactic merger. Credit: ESA/Hubble & NASA with acknowledgement to Judy Schmidt
Across the universe, some 350 million light-years away, lies a galaxy that looks like it has white rose petals. Don’t let the tranquil appearance of PGC 6240 fool you as to its past, however. This galaxy in Hydrus (The Water Snake) likely was dramatically altered by a galactic merger.
There’s a bunch of evidence pointing to this. There are “star shells” of globular clusters around the galaxy, but they’re distributed unevenly — some are close in, some are way out in the distant suburbs. Also, “several wisps of material have been thrown so far that they appear to be almost detached from the galaxy altogether,” stated the Hubble European Space Agency Information Centre.
“The most likely explanation for both the galaxy’s stacked shell structure and the unexpectedly young star clusters is that PGC 6240 merged with another galaxy at some point in the recent past,” the agency added.
“Such a merger would send ripples through the galaxy and disrupt its structure, forming the concentric shells of material seen here. It would also ignite a strong burst of star formation in the galaxy, which would then trigger similar activity in nearby space — leading to the creation of new, younger globular clusters around PGC 6240.”
Image of a galaxy with rendering showing a stream of inflowing gas, as rendered in a supercomputer. Credit: MPIA (G. Stinson / A.V. Maccio)
“Primordial hydrogen” sounds like a great name for a band. It’s also a great thing to find when you’re looking at a galaxy. This ancient gas is a leftover of the Big Bang, and astronomers discovered it in a faraway star-forming galaxy that was created when the universe was young.
A continuous stream of gas was likely responsible for a cornucopia of star formation that took place about 10 billion years ago, when galaxies were churning out starbirths at a furious rate.
The astronomers spotted the gas by using a quasar that lit up the fuel from behind. Quasars a handy tool to use if you want to illuminate something, because even though quasars don’t live for very long in cosmic terms — they occur when matter falls into a ginormous black hole — they are extremely bright. Since the gas absorbs the light at certain frequencies, the absorption lines that show up in spectrometers reveal information about the composition, temperature and density of the gas.
“This is not the first time astronomers have found a galaxy with nearby gas, revealed by a quasar. But it is the first time that everything fits together,” stated Neil Crighton, who is with the Max Planck Institute for Astronomy and Swinburne University and led the research. His team found the galaxy using the Keck I telescope in Hawaii.
“The galaxy is vigorously forming stars,” added Crighton, “and the gas properties clearly show that this is pristine material, left over from the early universe shortly after the Big Bang.”
Q1442-MD50 (as the galaxy is called) is 11 billion light years away from us — pretty close to the start of the universe about 13.8 billion years ago. The quasar that lit it up is called QSO J1444535+291905.
“Since this discovery is the result of a systematic search, we can now deduce that such cold flows are quite common,” stated Joseph Hennawi, the leader of the ENIGMA research group at the Max Planck Institute for Astronomy. “We only had to search 12 quasar-galaxy pairs to discover this example. This rate is in rough agreement with the predictions of supercomputer simulations, which provides a vote of confidence for our current theories of how galaxies formed.”
You can read more details in the article (which is in Astrophysical Letters) or in this preprint version on Arxiv.
Galaxy M60-UCD1 is an ultra-compact dwarf galaxy, and is packed with an extraordinary number of stars. Credit: X-ray: NASA/CXC/MSU/J.Strader et al, Optical: NASA/STScI
Meet galaxy M60-UCD1. This is not your average, every day, ordinary galaxy. First of all, it’s what is known as an ‘ultra-compact dwarf galaxy,’ which – as the name implies — are unusually dense and small galaxies. Additionally, it is the most luminous known galaxy of its type and one of the most massive, weighing 200 million times more than our Sun. But M60-UCD1 is jam-packed with an extraordinary number of stars, making it the densest galaxy in the nearby Universe that we know of. Stars in M60-UCD1 are thought to be 25 times closer together than the stars in our galaxy.
Quick and easy access to neighboring star systems (if you lived there) might be your first thought. But remember, space is big, no matter where you are.
“Traveling from one star to another would be a lot easier in M60-UCD1 than it is in our galaxy,” said Jay Strader of Michigan State University in Lansing, first author of a paper describing these results. “But it would still take hundreds of years using present technology.”
Ultra-compact dwarf galaxies were discovered about a decade ago. They are typically about only 100 light years across compared to the 1,000 light years or more than other dwarf galaxies. Our Milky Way galaxy is 120,000 light-years across.
This graph shows where M60-UCD1 fits in as far as luminosity and size. Credit: Strader et al.
Strader said that what makes M60-UCD1 so remarkable is that about half of its mass is found within a radius of only about 80 light years. This would make the density of stars about 15,000 times greater than found in Earth’s neighborhood in the Milky Way.
“Our discovery of M60-UCD1 lends support to the idea that ultra-compact dwarfs could be stripped-down version of more massive galaxies,” Strader wrote in a post on the Chandra blog. “The first reason is its mass: we estimate that it contains about 400 million stars, far more than observed for even massive star clusters, and much closer to the galaxy regime. We also observe that M60-UCD1 has two “parts”: an inner, even denser core embedded in a more diffuse field of stars. This structure is not expected for a star cluster, but it’s a natural outcome of the tidal stripping process that could produce an ultra-compact dwarf.”
And so, this UCD is providing astronomers with clues to how these types of galaxies fit into the galactic evolutionary chain.
Additionally, this galaxy appears to have a central black hole, as Chandra X-ray Observatory reveal the presence of an X-ray source sitting right at the center.
While supermassive black holes are known to be common in the most massive galaxies, it is unknown whether they occur in less massive galaxies like M60-UCD1, Strader said.
“Further observations of M60-UCD1 and other ultra-compact dwarfs could confirm a new, significant population of massive black holes,” Strader said. “These masses of these black holes would be notable: while most central black holes in galaxies have only a fraction of a percent of the mass of their host galaxies, in ultra-compact dwarfs the black holes could be a full 10% of the mass of the dwarf. This is because so many of the dwarf’s outer stars have been stripped away, essentially boosting the contribution of the unaffected central black hole to the total mass of the galaxy.”
M60-UCD1 is located near a massive elliptical galaxy NGC 4649, also called M60, about 60 million light years from Earth. The galaxy was discovered with NASA’s Hubble Space Telescope and follow-up observations were done with NASA’s Chandra X-ray Observatory, the Keck Observatory in Hawaii, and the Multiple Mirror Telescope in Arizona.
Radio telescope image of the galaxy 4C12.50, nearly 1.5 billion light-years from Earth. Inset shows detail of location at end of superfast jet of particles, where a massive gas cloud (yellow-orange) is being pushed by the jet.
(Credit: Morganti et al., NRAO/AUI/NSF)
It’s long been a mystery for astronomers: why aren’t galaxies bigger? What regulates their rates of star formation and keeps them from just becoming even more chock-full-of-stars than they already are? Now, using a worldwide network of radio telescopes, researchers have observed one of the processes that was on the short list of suspects: one supermassive black hole’s jets are plowing huge amounts of potential star-stuff clear out of its galaxy.
Astronomers have theorized that many galaxies should be more massive and have more stars than is actually the case. Scientists proposed two major mechanisms that would slow or halt the process of mass growth and star formation — violent stellar winds from bursts of star formation and pushback from the jets powered by the galaxy’s central, supermassive black hole.
“With the finely-detailed images provided by an intercontinental combination of radio telescopes, we have been able to see massive clumps of cold gas being pushed away from the galaxy’s center by the black-hole-powered jets,” said Raffaella Morganti, of the Netherlands Institute for Radio Astronomy and the University of Groningen.
The scientists studied a galaxy called 4C12.50, nearly 1.5 billion light-years from Earth. They chose this galaxy because it is at a stage where the black-hole “engine” that produces the jets is just turning on. As the black hole, a concentration of mass so dense that not even light can escape, pulls material toward it, the material forms a swirling disk surrounding the black hole. Processes in the disk tap the tremendous gravitational energy of the black hole to propel material outward from the poles of the disk.
NGC 253, aka the Sculptor Galaxy, is also blowing out gas but as the result of star formation (Image: T.A. Rector/University of Alaska Anchorage, T. Abbott and NOAO/AURA/NSF)
At the ends of both jets, the researchers found clumps of hydrogen gas moving outward from the galaxy at 1,000 kilometers per second. One of the clouds has much as 16,000 times the mass of the Sun, while the other contains 140,000 times the mass of the Sun.
The larger cloud, the scientists said, is roughly 160 by 190 light-years in size.
“This is the most definitive evidence yet for an interaction between the swift-moving jet of such a galaxy and a dense interstellar gas cloud,” Morganti said. “We believe we are seeing in action the process by which an active, central engine can remove gas — the raw material for star formation — from a young galaxy,” she added.
The researchers published their findings in the September 6 issue of the journal Science.
This image shows "slices" of the Universe at different times throughout its history (present day, and at 4 and 11 billion years ago). Each slice goes further back in time, showing how galaxies of each type appear. The shape is that of the Hubble tuning fork diagram, which describes and separates galaxies according to their morphology. Credit: NASA, ESA, M. Kornmesser
What we’re gonna’ do here is go back. Way back into time. Back to when the only thing that existed was… galaxies? When astronomers employed the power of Hubble’s CANDELS survey to observe different galaxy types from the distant past, they expected to see a variety of spiral, elliptical, lenticular and peculiar structures, but what they didn’t expect was that things were a whole lot more “peculiar” a long time ago!
Known as the Hubble Sequence, astronomers use this classified system for listing galaxy sizes, shapes and colors. It also arranges galaxies according to their morphology and star-forming activity. Up to the present, the Hubble Sequence covered about 80% of the Universe’s history, but the latest information shows that the sequence was valid as much as 11 billion years ago! Out of what we currently know, there are two dominant galaxy types – spiral and elliptical – with the lenticular structure as a median. Of course, this is constrained to the regions of space which we can readily observe, but how true did the sequence hold back when the Universe theoretically began?
“This is a key question: when and over what timescale did the Hubble Sequence form?” says BoMee Lee of the University of Massachusetts, USA, lead author of a new paper exploring the sequence. “To do this you need to peer at distant galaxies and compare them to their closer relatives, to see if they too can be described in the same way.”
Using the Hubble Space Telescope, astronomers took on the sequence challenge to peer back 11 billion years in time to study galaxy structure. Up until now, researchers could confirm the sequence was valid as long ago as 8 billion years, but these new studies pushed CANDELS, the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, to the outer limits. It is simply the largest project ever, and soaked up 902 assigned orbits of observing time. Using the WFC3 and ACS cameras, the team examined structures that existed less than one billion years after the Big Bang. While earlier studies had aimed for lower-mass galaxies in this era, no study had really taken on serious observation of mature structures – ones similar to our own galaxy. Now the new CANDELS observations show us that all galaxies, regardless of size, fit into a totally different classification!
“This is the only comprehensive study to date of the visual appearance of the large, massive galaxies that existed so far back in time,” says co-author Arjen van der Wel of the Max Planck Institute for Astronomy in Heidelberg, Germany. “The galaxies look remarkably mature, which is not predicted by galaxy formation models to be the case that early on in the history of the Universe.”
Just what did this study see that’s so different? Just the power of two. Galaxies were either complex, with blue star forming regions and irregular structures, or they were like our nearby neighbors: massive red galaxies that exhibit no new star-formation. In the early Universe, galaxies like the Milky Way were uncommon. With so little to study, it was nearly impossible to get a large enough sample to sufficiently catalog their characteristics. Early research could only peer back in visible light, a format which emphasized star formation and revealed the red-shifted ultraviolet emission of the galaxies. This information was inconclusive because galaxy structure appeared disrupted and unlike the formations we see near to us. Through the use of infra-red, astronomers could observe the now red-shifted massive galaxies in their visible rest frame. Thanks to CANDELS lighting the way, astronomers were able to thoroughly sample a significantly larger amount of mature galaxies in detail.
“The huge CANDELS dataset was a great resource for us to use in order to consistently study ancient galaxies in the early Universe,” concludes Lee. “And the resolution and sensitivity of Hubble’s WFC3 is second to none in the infrared wavelengths needed to carry out this study. The Hubble Sequence underpins a lot of what we know about how galaxies form and evolve — finding it to be in place this far back is a significant discovery.”
