Back to the Beginning: Probing the First Galaxies with Webb

A spectacular firestorm of star birth suddenly lit up the heavens and populated the first galaxies when the universe was less than five percent of its current age. This fiery flurry—possibly the cosmos' busiest star-forming period—occurred just a few hundred million years after the big bang. Soon, through the power of NASA's James Webb Space Telescope (JWST), astronomers will look back to that raucous, early period in a deep-sky survey to trace the formation and evolution of the first galaxies.

This is a Hubble Space Telescope view of a portion of GOODS-South, the southern field of a large deep-sky study by several observatories to trace the formation and evolution of galaxies. The image shows a rich tapestry of 7,500 galaxies stretching back through most of the universe's history. The farthest galaxies, a few of the very faint red specks, are seen as they appeared more than 13 billion years ago, or roughly 650 million years after the Big Bang. Soon, the James Webb Space Telescope will peer back even farther into this field to trace the formation and evolution of the very first galaxies. Credits: NASA, ESA, R. Windhorst, S. Cohen, M. Mechtley, and M. Rutkowski (Arizona State University, Tempe), R. O'Connell (University of Virginia), P. McCarthy (Carnegie Observatories), N. Hathi (University of California, Riverside), R. Ryan (University of California, Davis), H. Yan (Ohio State University), and A. Koekemoer (Space Telescope Science Institute). Hi-res image

Called JADES—the JWST Advanced Deep Extragalactic Survey—this large, ambitious survey totals nearly 800 hours of observing time. The survey takes advantage of Webb's sensitivity to infrared light, which has longer wavelengths than visible light and is invisible to the human eye.

"Galaxies, we think, begin building up in the first billion years after the big bang, and sort of reach adolescence at 1 to 2 billion years. We're trying to investigate those early periods," explained JADES teammate Daniel Eisenstein, a professor of astronomy at Harvard University.   "We must do this with an infrared-optimized telescope because the expansion of the universe causes light to increase in wavelength as it traverses the vast distance to reach us. So even though the stars are emitting light primarily in optical and ultraviolet wavelengths, that light is shifted quite relentlessly out into the infrared. Only Webb can get to the depth and sensitivity that's needed to study these early galaxies."

Joining Forces

The JADES survey is a collaboration of two Webb instrument teams granted Guaranteed Time Observations: the Near Infrared Camera (NIRCam) and the Near Infrared Spectrograph (NIRSpec) teams. The program combines the imaging of NIRCam and the spectroscopic capabilities of NIRSpec with Webb's Mid-Infrared Instrument (MIRI), which boasts both a camera and a spectrograph. Through the use of coordinated, parallel observations, the JADES team will get the best out of all three instruments. 

Scientists will then combine Webb's results with the deepest data from NASA's Hubble Space Telescope, NASA's Chandra X-ray Observatory, and the ground-based Atacama Large Millimeter/submillimeter Array and Jansky Very Large Array radio telescopes to produce an unprecedented view of the universe's very earliest galaxies. By studying galaxies across all these wavelengths, scientists will get a complete picture, allowing them to analyze the light of the galaxies' stars, the dust and the interstellar medium, and the supermassive black holes that are thought to reside within these galaxies. 

Galaxies Through Time 

Discover how telescopes make it possible to look back in time and study the history of the universe, and how NASA’s James Webb Space Telescope will fill in new details on galaxy evolution over time. The earliest pages of cosmic history are blank, but Webb will allow us to look back farther in time than ever before, helping to fill in the lost pages of the universe’s story.  Credits: NASA, ESA, CSA, and L. Hustak and D. Player (STScI).

 

More than 13 billion years ago, during the Era of Reionization, the universe was a very different place. The gas between galaxies was largely opaque to energetic light, making it difficult to observe young galaxies. What allowed the universe to become completely ionized, or transparent, eventually leading to the "clear" conditions detected in much of the universe today? The James Webb Space Telescope will peer deep into space to gather more information about objects that existed during the Era of Reionization to help us understand this major transition in the history of the universe. Credits: NASA, ESA, and J. Kang (STScI). Hi-res image

Studying Familiar Fields

The team chose two, previously well-studied fields from the Great Observatories Origins Deep Survey (GOODS) for their observations. GOODS united extremely deep observations from NASA's Spitzer, Hubble, and Chandra, as well as ESA's Herschel and XMM-Newton space telescopes, and from the most powerful ground-based facilities to survey the faintest light then detectable in the distant universe across the electromagnetic spectrum. The survey covered two large fields, GOODS-North and GOODS-South, which are located in the northern constellation Ursa Major and the southern constellation Fornax, respectively. GOODS-South also contains the Hubble Ultra Deep Field, which is to this day the deepest, most sensitive image of the sky ever taken with Hubble. Now, looking at the same areas, Webb will go even deeper.

"We chose these fields because they have such a great wealth of supporting information. They've been studied at many other wavelengths, so they were the logical ones to do," said Marcia Rieke, who co-leads the JADES Team with Pierre Ferruit of the European Space Agency (ESA). Rieke is also the principal investigator on Webb's NIRCam instrument and a professor of astronomy at the University of Arizona.

The team is also observing the two widely separated fields to study the differences between the number of galaxies at different distances in one field, as compared with the other.

Seeing the Formation of Galaxies, Stars and Black Holes

How rapidly galaxies form and assemble, and how quickly and where they form their stars are still open questions. Several ambitious goals of the JADES program include understanding the distribution of stellar mass in infant galaxies, as well as stellar luminosity, star-formation rates, and stellar age, size and composition. JADES will also analyze galaxies' nuclear activity, determine galaxy structure, and map gas movement over a wide range of distances.

Another goal of the program is understanding the properties of the first generation of black holes. Scientists have measured a tight relationship between the mass of a galaxy's central black hole and the mass of that galaxy's bulge, but how that occurs is currently only the stuff of models and speculation. The JADES team hopes to illuminate the nature of this relationship.

Scientists know these supermassive black holes were already in place with billions of solar masses less than 1 billion years after the big bang, which is less than 10 percent of the universe’s current age. But how such enormous black holes came about so early in the universe is very difficult to understand. 

"We hope to detect the primeval seeds of these monster black holes, the smaller black holes that formed soon after the big bang, and to understand what were their masses, how they were accreting mass, and where they were located," explained JADES teammate Roberto Maiolino, a member of ESA's NIRSpec Instrument Science Team and a professor of experimental astrophysics at the University of Cambridge in the United Kingdom. "For a long time, Webb will be the only facility to possibly detect and understand the processes that later on resulted in these monsters that were already created in the early universe."

Seeking the First Stars

Another mystery involves the gas between the galaxies, which astronomers know today is highly ionized and transparent. But in the first million years, it was not ionized—it was neutral gas that was opaque. How the transition from neutral to ionized gas—from opaque to transparent—occurred is something that scientists have been trying to understand for a long time.

"This transition is a fundamental phase change in the nature of the universe," said JADES teammate Andrew Bunker, another member of the ESA NIRSpec Instrument Science Team and a professor of astrophysics at the University of Oxford in the United Kingdom. "We want to understand what caused it. It could be that it's the light from very early galaxies and the first burst of star formation." 

The JADES team hopes to discover this first population of extremely massive, luminous and hot stars to form after the big bang. "That’s kind of one of the Holy Grails, to find the so-called Population III stars that formed from the hydrogen and helium of the big bang," explained Bunker. "People have been trying to do this for many decades and results have been inconclusive so far." 

Why Webb?

The extremely distant targets of the JADES team appear very small and faint, and their light is often completely shifted beyond optical wavelengths. For these reasons, these objects can only be observed with superlative infrared capability of a large, cold telescope. Webb was built specifically for this purpose; this was one of the major science cases driving its design. 

Because of Webb's sheer size, it will have spatial resolution in the infrared similar to what astronomers have enjoyed with Hubble. Webb will give them a much clearer view at long wavelengths than they have ever had before. 

Webb's ability to get simultaneous spectra of multiple objects at infrared wavelengths is another critical aspect of the JADES program. NIRSpec will be able to target more than 100 galaxies at one time, taking a spectrum of each.

Webb's much larger collecting area, its ability to observe fainter galaxies, and its capacity to simultaneously study multiple objects in a way that scientists have not been able to do before make ambitious, large surveys such as JADES possible for the first time.

"We tend to talk about projects like this in the context of theories and models that we have right now," said Rieke. "But I'm hoping that with Webb we'll find something that we haven't suspected at all—that there will be some new surprise—and that will be great fun!"

The James Webb Space Telescope will be the world's premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

For more information about Webb, visit www.nasa.gov/webb.

Ann Jenkins / Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland
410-338-4488 / 410-338-4366
jenkins@stsci.edu / cpulliam@stsci.edu

Editor: Lynn Jenner

Source:  NASA/Solar System and Beyond

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Researchers Rewind the Clock to Calculate Age and Site of Supernova Blast

Supernova Remnant 1E 0102.2-7219
Credits:NASA, ESA, STScI, and J. Banovetz and D. Milisavljevic (Purdue University) 

Release images  - Release videos

Astronomers are winding back the clock on the expanding remains of a nearby, exploded star. By using NASA's Hubble Space Telescope, they retraced the speedy shrapnel from the blast to calculate a more accurate estimate of the location and time of the stellar detonation.

The victim is a star that exploded long ago in the Small Magellanic Cloud, a satellite galaxy to our Milky Way. The doomed star left behind an expanding, gaseous corpse, a supernova remnant named 1E 0102.2-7219, which NASA's Einstein Observatory first discovered in X-rays. Like detectives, researchers sifted through archival images taken by Hubble, analyzing visible-light observations made 10 years apart.

The research team, led by John Banovetz and Danny Milisavljevic of Purdue University in West Lafayette, Indiana, measured the velocities of 45 tadpole-shaped, oxygen-rich clumps of ejecta flung by the supernova blast. Ionized oxygen is an excellent tracer because it glows brightest in visible light.

To calculate an accurate explosion age, the astronomers picked the 22 fastest moving ejecta clumps, or knots. The researchers determined that these targets were the least likely to have been slowed down by passage through interstellar material. They then traced the knots' motion backward until the ejecta coalesced at one point, identifying the explosion site. Once that was known, they could calculate how long it took the speedy knots to travel from the explosion center to their current location.

According to their estimate, light from the blast arrived at Earth 1,700 years ago, during the decline of the Roman Empire. However, the supernova would only have been visible to inhabitants of Earth's southern hemisphere. Unfortunately, there are no known records of this titanic event.

The researchers' results differ from previous observations of the supernova's blast site and age. Earlier studies, for example, arrived at explosion ages of 2,000 and 1,000 years ago. However, Banovetz and Milisavljevic say their analysis is more robust.

"A prior study compared images taken years apart with two different cameras on Hubble, the Wide Field Planetary Camera 2 and the Advanced Camera for Surveys (ACS)," Milisavljevic said. "But our study compares data taken with the same camera, the ACS, making the comparison much more robust; the knots were much easier to track using the same instrument. It's a testament to the longevity of Hubble that we could do such a clean comparison of images taken 10 years apart."

The astronomers also took advantage of the sharp ACS images in selecting which ejecta clumps to analyze. In prior studies, researchers averaged the speed of all of the gaseous debris to calculate an explosion age. However, the ACS data revealed regions where the ejecta slowed down because it was slamming into denser material shed by the star before it exploded as a supernova. Researchers didn't include those knots in the sample. They needed the ejecta that best reflected their original velocities from the explosion, using them to determine an accurate age estimate of the supernova blast.

Hubble also clocked the speed of a suspected neutron star—the crushed core of the doomed star—that was ejected from the blast. Based on their estimates, the neutron star must be moving at more than 2 million miles per hour from the center of the explosion to have arrived at its current position. The suspected neutron star was identified in observations with the European Southern Observatory's Very Large Telescope in Chile, in combination with data from NASA's Chandra X-ray Observatory.

"That is pretty fast and at the extreme end of how fast we think a neutron star can be moving, even if it got a kick from the supernova explosion," Banovetz said. "More recent investigations call into question whether the object is actually the surviving neutron star of the supernova explosion. It is potentially just a compact clump of supernova ejecta that has been lit up, and our results generally support this conclusion."

So the hunt may still be on for the neutron star. "Our study doesn't solve the mystery, but it gives an estimate of the velocity for the candidate neutron star," Banovetz said. 

Banovetz will present the team's findings Jan. 14 at the American Astronomical Society's winter meeting.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

Contacts

Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4493 / 410-338-4514
dweaver@stsci.edu / villard@stsci.edu

John Banovetz / Danny Milisavljevic
Purdue University, West Lafayette, Indiana
jbanovet@purdue.edu / dmilisav@purdue.edu

Source:HubbleSite/News

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Magnetic ‘Highway’ Channels Material Out of Cigar Galaxy

Magnetic fields in Messier 82, or the Cigar galaxy, are shown as lines over a visible light and infrared composite image of the galaxy from the Hubble Space Telescope and the Spitzer Space Telescope. Stellar winds streaming from hot new stars form a galactic super wind that is blasting out plumes of hot gas (red) and a huge halo of smoky dust (yellow/orange) perpendicular to the narrow galaxy (white). Researchers used the Stratospheric Observatory for Infrared Astronomy magnetic field data and tools that have been used extensively to study the physics around the Sun to extrapolate the magnetic field’s strength 20,000 lights-years around the galaxy. They appear to extend indefinitely into intergalactic space, like the Sun’s solar wind, and may help explain how the gas and dust have traveled so far away from the galaxy.  Credits: NASA, SOFIA, L. Proudfit; NASA, ESA, Hubble Heritage Team; NASA, JPL-Caltech, C. Engelbracht. Hi-res image

 

What’s fueling the massive ejection of gas and dust out of the Cigar galaxy, otherwise known as Messier 82?

We know that thousands of stars bursting into existence are driving a powerful super-wind that’s blowing matter into intergalactic space. New research shows that magnetic fields are also contributing to the expulsion of material from Messier 82, a well-known example of a starburst galaxy with a distinctive, elongated shape.

The findings from NASA’s Stratospheric Observatory for Infrared Astronomy, or SOFIA, help explain how dust and gas can move from inside galaxies into intergalactic space, offering clues to how galaxies formed. This material is enriched with elements like carbon and oxygen that support life and are the building blocks for future galaxies and stars. The research was presented at the meeting of the American Astronomical Society.

SOFIA, a joint project of NASA and the German Aerospace Center, DLR, previously studied the direction of magnetic fields close to the core of Messier 82, as the Cigar galaxy is officially known. This time the team applied tools that have been used extensively to study the physics around the Sun, known as heliophysics, to understand the magnetic field’s strength surrounding the galaxy at a distance 10 times larger than before.

“This is old physics for studying the Sun, but new for galaxies,” said Joan Schmelz, an associate director at the Universities Space Research Association based at NASA’s Ames Research Center in Silicon Valley, and co-author of the upcoming paper about this research. “It’s helping us understand how the space between stars and galaxies became so rich with matter for future cosmic generations.”

Located 12 million light-years from Earth in the constellation Ursa Major, the Cigar galaxy is undergoing an exceptionally high rate of star formation called a starburst. The star formation is so intense that it creates a “super wind” that blows material out of the galaxy. As SOFIA previously found using the instrumented called the High-Resolution Airborne Wideband Camera, or HAWC+, the wind drags the magnetic field near the galaxy’s core so that it’s perpendicular to the plane of the galaxy across 2,000 light-years.

Researchers wanted to learn if the magnetic field lines would extend indefinitely into intergalactic space like the magnetic environment in the solar wind, or turn over to form structures similar coronal loops that are found in active regions of the Sun. They calculate that the galaxy’s magnetic fields extend out like the solar wind, allowing the material blown by the super wind to escape into intergalactic space.

These extended magnetic fields may help explain how gas and dust spotted by space telescopes have traveled so far away from the galaxy. NASA’s Spitzer Space Telescope detected dusty material 20,000 lightyears beyond the galaxy, but it was unclear why it had spread so far away from the stars in both directions instead of in a cone-shaped jet.

“The magnetic fields may be acting like a highway, creating lanes for galactic material to spread far and wide into intergalactic space,” said Jordan Guerra Aguilera, a postdoctoral researcher at Villanova University in Pennsylvania and co-author on the upcoming paper.

With rare exceptions, the magnetic field in the solar corona cannot be measured directly. So, about 50 years ago, scientists developed methods to accurately extrapolate magnetic fields from the Sun’s surface into interplanetary space, known in heliophysics as the potential field extrapolation. Using SOFIA’s existing observations of central magnetic fields, the research team modified this method to estimate the magnetic field about 25,000 light-years around the Cigar galaxy.

“We can’t easily measure the magnetic fields at scales this large, but we can extrapolate it with these tools from heliophysics,” said Enrique Lopez-Rodriguez, a Universities Space Research Association scientist for SOFIA based at Ames and lead author on the study. “This new, interdisciplinary method gives us the larger perspective that we need to understand starburst galaxies.”

SOFIA is a joint project of NASA and the German Aerospace Center. NASA’s Ames Research Center in California’s Silicon Valley manages the SOFIA program, science, and mission operations in cooperation with the Universities Space Research Association, headquartered in Columbia, Maryland, and the German SOFIA Institute at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California. The High-Resolution Airborne Wideband Camera instrument was developed and delivered to NASA by a multi-institution team led by NASA’s Jet Propulsion Laboratory.

Media Contact: 

Elizabeth Landau 
NASA Headquarters, Washington 
202-358-0845 
elizabeth.r.landau@nasa.gov 

Alison Hawkes 
NASA Ames Research Center, Silicon Valley, Calif. 
650-604-4789 
alison.hawkes@nasa.gov 

Editor: Kassandra Bell

Source: NASA/Galaxies

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Rose of star formation around distant supermassive black hole

NGC 1097

Credit: ESO/TIMER survey

Captured with the MUSE instrument on ESO’s Very Large Telescope (VLT), this image of the distant spiral galaxy NGC 1097 shows a textbook example of a star-bursting nuclear ring. Located 45 million light-years away from Earth, in the constellation of Fornax, this ring lies at the very centre of its galaxy. It spans only 5,000 light years across, being dwarfed by the full size of its host galaxy, which extends some tens of thousands of light-years beyond its centre.

The darker lanes seen in this MUSE image show dust, gas and debris from the galaxy (or possibly from a satellite galaxy), which are being funnelled into the supermassive black hole at its centre. This process heats up the surrounding matter forming an accretion disc around the black hole and launching huge amounts of energy into the surrounding area. Nearby dust is heated up and star formation accelerates in the area around the supermassive black hole, forming the star-bursting nuclear ring shown in pink and purple tones in the image.

MUSE, which stands for Multi Unit Spectroscopic Explorer, is attached to Yepun, one of the four, 8.2-metre telescopes that make up the VLT at ESO’s Paranal Observatory. Its unique design has allowed researchers to map complex mechanisms within many galaxies and analyse the formation of stars and star clusters.

Source: ESO/potw

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Magnetic Chaos Hidden Within the Whirlpool Galaxy

Magnetic field streamlines detected by SOFIA are shown over an image of the Whirlpool galaxy, M51, from NASA’s Hubble Space Telescope. For the first time, SOFIA’s infrared view shows that the magnetic fields in the outer arms do not follow the galaxy's spiral shape and are instead distorted. The intense star formation activity in these regions, shown in red, may be causing the chaos, along with the forces from the yellow neighboring galaxy, NGC 5195, tugging on one of the spiral arms. Credits: NASA, the SOFIA science team, A. Borlaff; NASA, ESA, S. Beckwith (STScI) and the Hubble Heritage Team (STScI/AURA). Hi-res image

Not all appears as it would seem in the Whirlpool galaxy. One of the best-studied spiral galaxies and a delight to amateur astronomers, Messier 51, as it’s officially named, is influenced by powerful, invisible forces.  

Located 31 million light-years away in the constellation Canes Venatici, the galaxy’s arms are strikingly visible as they reach out along the central spine structure, displaying swirling clouds of gas and dust that are massive star-making factories. But new observations by NASA’s Stratospheric Observatory for Infrared Astronomy, or SOFIA, presented at this week’s 237th meeting of the American Astronomical Society, shows  a more complicated picture.  

Radio telescopes previously detected neatly-drawn magnetic fields throughout the length of the galaxy’s massive arms. But under SOFIA’s infrared gaze for the first time those lines give way to a chaotic scene in the outer spiral arms. Using a far-infrared camera and imaging polarimeter instrument called the High-Resolution Airborne Wideband Camera, or HAWC+, researchers found that the magnetic fields in the outskirts of the galaxy no longer follow the spiral structure and are instead distorted. 

What’s causing all this magnetic pandemonium? The intense star formation in these areas creates chaos that can only be seen with infrared flight. A nearby, yellowish galaxy called NGC 5195 tugging at the outermost tip of one of the arms adds to the turmoil, possibly strengthening the magnetic fields. The research builds on SOFIA’s previous findings that show magnetic fields are important in shaping spiral galaxies and helps unravel the complex role magnetic fields play in the evolution of galaxies. 

Media Contact: 

Elizabeth Landau 
NASA Headquarters, Washington 
202-358-0845 
elizabeth.r.landau@nasa.gov 

Alison Hawkes 
NASA Ames Research Center, Silicon Valley, Calif. 
650-604-4789 
alison.hawkes@nasa.gov 

Editor: Kassandra Bell

 

Source: NASA/Galaxies

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Mistaken identity: A presumed supernova is actually something much rarer

Screenshot of the NASA-produced animation showing a giant star being slowly devoured as it orbits the galaxy’s central black hole. Image is courtesy of NASA’s Goddard Space Flight Center.

Pasadena, CA—In a case of comic mistaken identity, an international team of astronomers revealed that what they once thought was a supernova is actually periodic flaring from a galaxy where a supermassive black hole gives off bursts of energy every 114 days as it tears off chunks of an orbiting star.

Six years after its initial discovery—reported in The Astronomer’s Telegram by Carnegie’s Thomas Holoien—the researchers, led by Anna Payne of University of Hawai’i at Mānoa, can now say that the phenomenon they observed, called ASASSN-14ko, is a periodically recurring flare from the center of a galaxy more than 570 million light-years away in the southern constellation Pictor.

Their findings—based on 20 instances of regular outbursts—will be published in The Astrophysical Journal and presented by Payne at the American Astronomical Society’s annual meeting.

Active galaxies, such as the host of ASASSN-14ko, have unusually bright and variable centers. These objects produce much more energy than the combined contribution of all their stars. Astrophysicists think this is due to gravitational and frictional forces heating up a swirling disk of gas and dust that accumulates around the central supermassive black hole. The black hole slowly consumes the material, which creates low-level, random changes in the light emitted by the disk.

This is the first unambiguous example of such clockwork behavior from an active galaxy. Periodically recurring flares, such as those from ASASSN-14ko, could be evidence of observationally elusive cosmic phenomena that have been previously predicted by theorists.

“Knowing the schedule of this extragalactic Old Faithful allows us to coordinate and study it in more detail,” Payne said.

ASASSN-14ko was first detected by the All-Sky Automated Survey for Supernovae (ASAS-SN), a global network of 20 robotic telescopes headquartered at The Ohio State University (OSU) in Columbus. When Payne examined all the ASAS-SN data on the phenomenon, she noticed a series of 17 regularly spaced flares.

Based on this discovery, the astronomers predicted that the galaxy would experience another burst on May 17 of last year and coordinated ground- and space-based facilities to make observations. They have since successfully predicted and witnessed flares on September 7 and December 26.

“ASAS-SN is designed to probe the physics of our universe by looking for transient and variable events.” Holoien said. “It’s exciting that the luminous object we originally thought was a violent supernova explosion—which would be interesting in its own right, but more commonplace—turned out to be a long-sought-after cosmic event.”

Swift, TESS Catch Eruptions From an Active Galaxy

So, what causes the repeated flares? The team considered several possible explanations, but think the most likely is what’s called a partial tidal disruption event.

Tidal disruption events, or TDEs, occur when a star gets too close to a supermassive black hole, which tears it to shreds. Some of its material gets flung out into space and the rest falls back onto the black hole, forming a disk of hot, bright gas as it is consumed.

In this instance, instead of a star being obliterated by interaction with the black hole, it would be slowly stripped during each orbit.  The flares occur when the lost material—equal to three times the mass of Jupiter at each pass—falls in towards the black hole.

The astronomers are unsure how long the flares will persist. The star can’t lose mass forever, and while scientists can estimate the amount of mass it loses during each orbit, they don’t know how much it had originally.

“We plan to keep predicting and observing these bursts or as long as we can,” said second author Benjamin Shappee, also of UH Mānoa (and a Carnegie alumnus). “This rare find could reveal new details about black hole physics.”

Source: Carnagie Science/News

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The Earliest Supermassive Black Hole and Quasar in the Universe

Artist’s impression of quasar J0313-1806 (labelled). An artist’s impression of quasar J0313-1806 showing the supermassive black hole and the extremely high velocity wind. The quasar, seen just 670 million years after the Big Bang, is 1000 times more luminous than the Milky Way, and is powered by the earliest known supermassive black hole, which weighs in at more than 1.6 billion times the mass of the Sun. Credit: NOIRLab/NSF/AURA/J. da Silva. download TIFF/JPEG

The most distant quasar known has been discovered. The quasar, observed just 670 million years after the Big Bang, is 1000 times more luminous than the Milky Way. It is powered by the earliest known supermassive black hole, which weighs in at more than 1.6 billion times the mass of the Sun. Seen more than 13 billion years ago, this fully formed distant quasar is also the earliest yet discovered, providing astronomers with insight into the formation of massive galaxies in the early Universe. The result was released today at the January 2021 meeting of the American Astronomical Society.

Quasars, which are powered by the feeding frenzies of colossal supermassive black holes, are the most energetic objects in the Universe. They occur when gas in the superheated accretion disk around a supermassive black hole is inexorably drawn inwards, shedding energy across the electromagnetic spectrum. The amount of electromagnetic radiation emitted by quasars is enormous, with the most massive examples easily outshining entire galaxies. Today, an international team of astronomers has announced the discovery of J0313-1806, the most distant quasar known to date.[1]

“The most distant quasars are crucial for understanding how the earliest black holes formed and for understanding cosmic reionization — the last major phase transition of our Universe,” said Xiaohui Fan, study co-author and Regents Professor of Astronomy at the University of Arizona.[2]

J0313-1806 is seen more than 13 billion years ago. As the most distant quasar known, it is also the earliest, being fully formed only about 670 million years after the Big Bang. The new quasar is more than ten trillion times as luminous as our Sun — meaning that it pours out one thousand times more energy than the entire Milky Way Galaxy. The source of this quasar’s power is a supermassive black hole 1.6 billion times as massive as the Sun — the earliest black hole currently known to exist in the Universe.[3]

The presence of such a massive black hole so early in the Universe’s history challenges theories of black hole formation as astronomers need to explain how it came into existence when it barely had the time to do so. Feige Wang, NASA Hubble fellow at the University of Arizona and lead author of the research paper, explains: “Black holes created by the very first massive stars could not have grown this large in only a few hundred million years.”

The observations that led to this discovery were made using a variety of telescopes, including three National Science Foundation NOIRLab facilities — the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory, Gemini South, and Gemini North. Data from the Blanco Telescope, taken as part of the DESI Legacy Imaging Surveys, which are served to the astronomical community via the Astro Data Lab at NOIRLab’s Community Science and Data Center (CSDC), helped to first identify J0313-1806, while Gemini South observations were used to confirm its identity as a quasar. High-quality spectra from two Maunakea observatories in Hawai‘i — Gemini North and W. M. Keck Observatory — were used to measure the mass of the central supermassive black hole.

“The most distant quasars and earliest black holes are important markers in the history of the Universe,” said Program Director Martin Still of the National Science Foundation. “The researchers combined several of NSF’s NOIRLab facilities to make this discovery.”

As well as weighing the monster black hole, the Gemini North and Keck Observatory observations uncovered an extremely fast outflow emanating from the quasar in the form of a high-velocity wind, which is traveling at 20% of the speed of light. “The energy released by such an extreme high-velocity outflow is large enough to impact the star formation in the entire quasar host galaxy,” said Jinyi Yang, Peter A. Strittmatter postdoctoral fellow of Steward Observatory at the University of Arizona. This is the earliest known example of a quasar sculpting the growth of its host galaxy, making J0313-1806 a promising target for future observations.

The galaxy hosting J0313-1806 is undergoing a spurt of star formation, producing new stars 200 times faster than the Milky Way. The combination of this intense star formation, the luminous quasar, and the high-velocity outflow make J0313-1806 and its host galaxy a promising natural laboratory for understanding the growth of supermassive black holes and their host galaxies in the early Universe.

“This would be a great target to investigate the formation of the earliest supermassive black holes,” concluded Feige Wang. “We also hope to learn more about the effect of quasar outflows on their host galaxy — as well as to learn how the most massive galaxies formed in the early Universe.”

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Notes

[1] At a redshift of 7.64.

[2] There are two phase transitions of the Universe.

[3] Distance and time are closely entwined in astronomy, as the light from distant objects takes time to reach observers here on Earth. We see the Sun as it was 8 minutes ago, and our latest observations of the heart of the Milky Way show it as it was over 25,000 years ago. The further astronomers look from Earth, the further back in time they see.

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More information

This research was presented in the paper “A Luminous Quasar at Redshift 7.642” at the 237th meeting of the American Astronomical Society. The study has been accepted in The Astrophysical Journal Letters.

The team was composed of Feige Wang (Steward Observatory, University of Arizona), Jinyi Yang (Steward Observatory, University of Arizona), Xiaohui Fan (Steward Observatory, University of Arizona), Joseph F. Hennawi (University of California, Santa Barbara and Max Planck Institute for Astronomy), Aaron J. Barth (University of California, Irvine), Eduardo Banados (Max Planck Institute for Astronomy), Fuyan Bian (European Southern Observatory), Konstantina Boutsia (European Southern Observatory), Thomas Connor (Jet Propulsion Laboratory), Frederick B. Davies (Lawrence Berkeley National Laboratory and Max Planck Institute for Astronomy), Roberto Decarl (INAF), Anna-Christina Eilers (MIT-Kavli Institute for Astrophysics and Space Research), Emanuele Paolo Farina (Max Planck Institute for Astrophysics), Richard Green (Steward Observatory, University of Arizona), Linhua Jiang (Kavli Institute for Astronomy and Astrophysics, Peking University), Jiang-Tao Li (University of Michigan), Chiara Mazzucchelli (European Southern Observatory), Riccardo Nanni (University of California, Santa Barbara), Jan-Torge Schindler (Max Planck Institute for Astronomy), Bram Venemans (Max Planck Institute for Astronomy), Fabian Walter (Max Planck Institute for Astronomy), Xue-Bing Wu (Kavli Institute for Astronomy and Astrophysics and Department of Astronomy, Peking University), Minghao Yue (Steward Observatory, University of Arizona).

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Links

• Research paper
• Photos of the Víctor M. Blanco 4-meter Telescope
• Photos of Gemini North
• Photos of Gemini South
• Keck Observatory release

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Contacts:

Xiaohui Fan
University of Arizona
Cell: +1 520 360 0956
Email: fan@as.arizona.edu 

Feige Wang 
University of Arizona
Cell: +1 520 360 3967
Email: feigewang@arizona.edu 

Amanda Kocz
Press and Internal Communications Officer
NSF’s NOIRLab
Cell: +1 626-524-5884
Email: amanda.kocz@noirlab.edu 

Source:  Gemini Observatory/News

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Roman Space Telescope Could Image 100 Hubble Ultra Deep Fields at Once

Roman Ultra Deep Fiels
Credits: NASA, ESA, and A. Koekemoer (STScI)
Acknowledgement: Digitized Sky Survey
Release images | Release videos

One of the Hubble Space Telescope’s most iconic images is the Hubble Ultra Deep Field, which unveiled myriad galaxies across the universe, stretching back to within a few hundred million years of the Big Bang. Hubble peered at a single patch of seemingly empty sky for hundreds of hours beginning in September 2003, and astronomers unveiled the galaxy tapestry in 2004, with more observations in subsequent years.

NASA’s upcoming Nancy Grace Roman Space Telescope will be able to photograph an area of the sky at least 100 times larger than Hubble with the same crisp sharpness. Among the many observations that will be enabled by this wide view of the cosmos, astronomers are considering the possibility and scientific potential of a Roman Space Telescope “ultra-deep field.” Such an observation could reveal new insights into subjects ranging from star formation during the universe’s youth to the way galaxies cluster together in space.

Roman will enable new science in all areas of astrophysics, from the solar system to the edge of the observable universe. Much of Roman’s observing time will be dedicated to surveys over wide swaths of the sky. However, some observing time will also be available for the general astronomical community to request other projects. A Roman ultra deep field could greatly benefit the scientific community, say astronomers.

“As a community science concept, there could be exciting science returns from ultra-deep field observations by Roman. We would like to engage the astronomical community to think about ways in which they could take advantage of Roman’s capabilities,” said Anton Koekemoer of the Space Telescope Science Institute in Baltimore, Maryland. Koekemoer presented the Roman ultra-deep field idea at the 237th meeting of the American Astronomical Society, on behalf of a group of astronomers spanning more than 30 institutions.

As an example, a Roman ultra-deep field could be similar to the Hubble Ultra Deep Field – looking in a single direction for a few hundred hours to build up an extremely detailed image of very faint, distant objects. Yet while Hubble snagged thousands of galaxies this way, Roman would collect millions. As a result, it would enable new science and vastly improve our understanding of the universe.

Structure and History of the Universe

Perhaps most exciting is the possibility of studying the very early universe, which corresponds to the most distant galaxies. Those galaxies are also the rarest: for example, only a handful are seen in the Hubble Ultra Deep Field.

Thanks to Roman’s wide field of view and near-infrared data of similar quality to Hubble’s, it could discover many hundreds, or possibly thousands, of these youngest, most distant galaxies, interspersed among the millions of other galaxies. That would let astronomers measure how they group together in space as well as their ages and how their stars have formed.

“Roman would also yield powerful synergies with current and future telescopes on the ground and in space, including NASA’s James Webb Space Telescope space, including NASA’s James Webb Space Telescopece and others,” said Koekemoer.

Moving forward in cosmic time, Roman would pick up additional galaxies that existed about 800 million to 1 billion years after the big bang. At that time, galaxies were just beginning to group together into clusters under the influence of dark matter. While researchers have simulated this process of forming large-scale structures, a Roman ultra-deep field would provide real world examples to test those simulations.

Star Formation Over Cosmic Time

The early universe also experienced a firestorm of star formation. Stars were being born at rates hundreds of times faster than what we see today. In particular, astronomers are eager to study “cosmic dawn” and “cosmic noon,” which together cover a time 500 million to 3 billion years after the big bang when most star formation was happening, as well as when supermassive black holes were most active.

“Because Roman’s field of view is so large, it will be game changing. We would be able to sample not just one environment in a narrow field of view, but instead a variety of environments captured by Roman’s wide-eyed view. This will give us a better sense of where and when star formation was happening,” explained Sangeeta Malhotra of NASA Goddard Space Flight Center in Greenbelt, Maryland. Malhotra is a co-investigator on the Roman science investigation teams working on cosmic dawn, and has led programs that do deep spectroscopy with Hubble, to learn about distant, young galaxies.

Astronomers are eager to measure star formation rates in this distant epoch, which could influence a variety of factors such as the amount of heavy elements observed. Rates of star formation might depend on whether or not a galaxy lies within a large cluster. Roman will be capable of taking faint spectra that will show distinct “fingerprints” of these elements, and give accurate distances (called redshifts) of galaxies.

“Population experts might ask, what differences are there between people who live in big cities, versus those in suburbia, or rural areas? Similarly, as astronomers we can ask, do the most active star forming galaxies live in very clustered regions, or just at the edges of clusters, or do they live in isolation?” Malhotra said.

Big Data and Machine Learning

One of the greatest challenges of the Roman mission will be learning how to analyze the abundance of scientific information in the public datasets that it will produce. In a sense, Roman will create new opportunities not only in terms of sky coverage, but also in data mining.

A Roman ultra-deep field would contain information on millions of galaxies – far too many to be studied by researchers one at a time. Machine learning—a form of artificial intelligence—will be needed to process the massive database. While this is a challenge, it also offers an opportunity. “You could explore completely new questions that you couldn’t previously address,” stated Koekemoer.

“The discovery potential enabled by the huge datasets from the Roman mission could lead to breakthroughs in our understanding of the universe, beyond what we might currently envision,” Koekemoer added. “That could be Roman’s lasting legacy for the scientific community: not only in answering the science questions we think we can address, but also new questions that we have yet to think of.”

 

Contact

Christine Pulliam
Space Telescope Science Institute, Baltimore, Md.
410-338-4366
cpulliam@stsci.edu

Related Links

• The Astro 2020 white paper by A. Koekemoer et al.

• NASA's Roman Portal

Source: HubbleSite/News

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Microquasars: The “Elusive” Gamma-Ray Emitters

Artistic view of a microquasar
Credit: NASA/ CXC/M.Weiss

Microquasars are Galactic binary systems composed of a star and a compact object (a black hole or a neutron star) that eats up matter from its companion, usually via an accretion disk, giving rise to relativistic jets, i.e. beams of particles moving almost at the speed of light. These jets, which can be either intermittent or persistent structures depending on the specific state of the system, emanate from the vicinity of the compact object and can expand light years away from the binary system. 

The word “microquasar” was used for the first time in 1992 to describe the Galactic binary system 1E1740.7–2942, characterized by radio-emitting double-sided jets [1]. The jets resembled the relativistic collimated outflows launched by quasars (active galaxies with supermassive black holes at the centre that devour its surrounding material), although, in the latter case, the powerful jets reach distances of up to millions of light years. Thus, we can say that microquasars, as their name suggests, are the little siblings of the quasars, sharing multiple similarities. One of the advantages of studying microquasars is that, given their smaller size, processes inside the system and jets happen on a shorter timescale, allowing scientists to analyze rapid variabilities in their emission.

Microquasars’ outflows are efficient sites of extreme particle acceleration and are responsible for transient and persistent non-thermal radiation, spanning from radio to gamma-ray energies. Nevertheless, the emission at GeV and TeV energies from microquasars has only been sporadically observed up to this point, making these systems a class of non-thermal emitters that is actually “elusive” in the gamma-ray energy range. With its improved sensitivity compared to the current gamma-ray instruments, CTA will be fundamental to the study of these systems and the physical processes inside the jets. In particular, two microquasars, SS 433 and Cygnus X-1, have been drawing attention over the past few years.

 Prolonged observations of SS 433 with the High Altitude Water Cherenkov (HAWC) observatory were able to resolve two lobes at energies of ~20 TeV related the terminal parts of its jets, where the relativistic outflows interact with the surrounding environment [2]. According to the authors, to produce such a TeV signal, the system needs to accelerate particles up to PeV energies along the jets and, therefore, SS 433 might be a so-called Galactic PeVatron. Furthermore, a recent study with the Fermi-LAT has reported sub-TeV persistent emission from a site lying in the proximity of the eastern lobe [3]. Still some mysteries remain: What is the maximum energy to which the particles are accelerated in the jets? Does gamma-ray emission occur near or inside the binary system? What are the exact acceleration sites and mechanisms? CTA’s excellent angular resolution will play a key role in answering these questions.

 In the Cygnus region, three microquasars have been observed above 50 MeV: Cygnus X-1, Cygnus X-3 and V404 Cygni (see e.g. [4,5]). The case of Cygnus X-1 is intriguing. At GeV energies, short-time transient emission [6] and persistent emission coming from the jets [7] have been detected, while at TeV energies, only a hint during a short hard X-ray flare has been reported by MAGIC [8]. Therefore, even though theoretically predicted, a clear TeV component has not yet been detected. According to recent simulations, the CTA-North array, located in La Palma (Spain), would detect a short transient event, similar to the hint reported by MAGIC, in just a few minutes, and would be able to characterize the TeV persistent emission from the jet with a set of prolonged observations (see Figure 1).

Figure 1: CTA-North (100 GeV – 1 TeV) simulations for Cygnus X-1. Panel a.: After 30 minutes observation of a transient event, similar to the hint reported by MAGIC, CTA would clearly detect a TeV signal. Panel b.: 5h (grey triangles) and 50h observation (black points), assuming that the spectrum follows the Fermi-LAT 4FGL power-law; CTA would detect persistent emission after a few hours. Panel c.: 50h observation, assuming that the spectrum is consistent with the theoretical jet leptonic model of [9]; CTA would need more than 50 hours to detect a persistent TeV signal. The MAGIC upper limits (violet squares) in panels b and c are referred to ~83 hours of observation [10].

With CTA, we expect to unveil the timing of a possible TeV flare in a multi-wavelength context, the maximum limit of acceleration along the jets, the nature of the emission mechanisms (leptonic/hadronic) responsible for the very high-energy gamma-ray radiation and more.  Particularly, CTA’s unprecedented sensitivity between 20 GeV to 300 TeV will allow us to delve into these sources like never before: at the lowest energies, we will be able to comprehend the physics mechanisms between the GeV and TeV gamma-ray component (e.g., in Cygnus X-1) and, at the highest energies, we will be able to open a new window at the high end of the electromagnetic spectrum to study the jet-medium interaction (e.g., in SS 433). Thanks to CTA’s improved angular resolution, lower energy threshold and fast telescope repositioning to respond to external triggers for transient events, a better understanding of the physics of extreme particle acceleration in microquasars will finally be well within our grasp.

Written by: Giovanni Piano

References:

[1] Mirabel, I. F. et al., Nature 358, 215 (1992)
[2] Abeysekara, A. U. et al. (HAWC Collaboration), Nature 562, 82 (2018)
[3] Li, Jian et al., https://doi.org/10.1038/s41550-020-1164-6, Nat Astron (2020)
[4] Tavani, M. et al., Nature 462, 620 (2009)
[5] Piano, G. et al., ApJ 839, id. 84 (2017)
[6] Sabatini, S. et al., ApJL 712, L10 (2010)
[7] Zanin, R. et al., A&A 596, id. A55 (2016)
[8] Albert, J. et al., ApJ 665, L51 (2007)
[9] Zdziarski, A. A. et al., MNRAS 471, 3657 (2017)
[10] Ahnen, M. L. et al., MNRAS 472, 3474 (2017)

Source: Cherenkov Telescope Array/News

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When Galaxies Collide: Hubble Showcases 6 Beautiful Galaxy Mergers

PR Image heic2101a

Hubble Showcases 6 Galaxy Mergers 

 

PR Image heic2101b

Peculiar galaxy NGC 3256

 

PR Image heic2101c

NGC 1614 

 

PR Image heic2101d

Snakes and Stones 

 

PR Image heic2101e

NGC 3690 

 

PR Image heic2101f

Colliding galaxies 

 

PR Image heic2101g

Beauty From Chaos

 

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Videos

PR Video heic2101a

Hubble Showcases 6 Galaxy Mergers

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To celebrate a new year, the NASA/ESA Hubble Space Telescope has published a montage of six beautiful galaxy mergers. Each of these merging systems was studied as part of the recent HiPEEC survey to investigate the rate of new star formation within such systems. These interactions are a key aspect of galaxy evolution and are among the most spectacular events in the lifetime of a galaxy.

It is during rare merging events that galaxies undergo dramatic changes in their appearance and in their stellar content. These systems are excellent laboratories to trace the formation of star clusters under extreme physical conditions.

The Milky Way typically forms star clusters with masses that are 10 thousand times the mass of our Sun. This doesn’t compare to the masses of the star clusters forming in colliding galaxies, which can reach millions of times the mass of our Sun.

These dense stellar systems are also very luminous. Even after the collision, when the resulting galactic system begins to fade into a more quiescent phase, these very massive star clusters will shine throughout their host galaxy, as long-lasting witnesses of past merging events.

By studying the six galaxy mergers shown here, the Hubble imaging Probe of Extreme Environments and Clusters (HiPEEC) survey has investigated how star clusters are affected during collisions by the rapid changes that drastically increase the rate at which new stars are formed in these galaxies. Hubble’s capabilities have made it possible to resolve large star-forming “knots” into numerous compact young star clusters. Hubble’s ultraviolet and near-infrared observations of these systems have been used to derive star cluster ages, masses, and extinctions and to analyse the star formation rate within these six merging galaxies. The HiPEEC study reveals that the star cluster populations undergo large and rapid variations in their properties, with the most massive clusters formed towards the end of the merger phase.

Each of the merging systems shown here has been previously published  by Hubble, as early as 2008 and as recently as October 2020. To celebrate it’s 18th anniversary in 2008, the Hubble Space Telescope released a collection of 59 images of merging galaxies, which can be explored here.

Source: ESA/Hubble/News 

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More Information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The HiPEEC survey was completed as part of the Hubble Space Telescope program GO 14066 (PI: A. Adamo). A repository with the study’s final data and catalogues is available here in the MAST Archive.

The international team of astronomers in this study consists of A. Adamo, K. Hollyhead, M. Messa, J. E. Ryon, V. Bajaj, A. Runholm, A. Aalto, D. Calzeti, J. S. Gallagher, M. J. Hayes, J. M. D. Kruijssen, S. König, S. S. Larsen, J. Melinder, E. Sabbi, L. J. Smith, and G. Östlin.

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Links

• Images of Hubble 
• Science paper

 

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Contacts

Bethany Downer
ESA/Hubble Chief Communications Officer
Email: Bethany.Downer@esahubble.org

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Algorithmic improvements for radio interferometry

The 27 antennas of the Very Large Array (VLA) in New Mexico observe the sky simultaneously, forming a single virtual telescope with a gigantic diameter. Credit: NRAO/AUI/NSF

Schematic illustration of an interferometer: A larger distance of two sources in the sky leads to an increased difference in travel time (marked red) as does a larger distance between antennae. Antennae placed at larger distances are therefore able to resolve smaller structures, while antennas placed closely together are more sensitive to larger structures.© MPA 

Central region of a typical radio interferometric coverage. The colours of the individual data points indicate the observed strength of spatial fluctuations of the flux density. © MPA

Radio telescopes observe the sky in a very indirect fashion. Sky images in the radio frequency range therefore have to be computed using sophisticated algorithms. Scientists at the MPI for Astrophysics have developed a series of improvements for these algorithms, which help to improve the telescopes' resolution considerably.

Optical telescopes produce data, which are a direct representation of the observed object's brightness distribution, i.e. an image in the conventional sense, which can be used for further analysis without additional processing. In radio interferometry (i.e. the high-resolution observation of the sky at radio frequencies), the situation is more complicated: here one does not obtain the sky brightness at a specific location, but rather data points indicating the amount, frequency and direction of brightness fluctuations.

If these data points were arranged on a regular two-dimensional grid, converting them to a normal image would be straightforward, but unfortunately no radio telescope design exists which could produce this arrangement. Realistic data point distributions often exhibit complex, inhomogeneous patterns (see fig. 3). Further complications arise if the individual antennae are not placed perfectly on a single plane, and/or if the observed sky region is too large to be approximated by a flat surface. In this case, additional correction terms have to be applied during the image generation, which further increases the computational cost.

The operation described above is called "gridding" and in practice various different implementations exist. Some are not particularly accurate (usually because they date back to the early times of radio astronomy, when computational power was very limited and many approximations and simplifications had to be made). Others provide good accuracy, but often are not fast enough to process the huge amounts of data produced by contemporary radio telescopes in an acceptable amount of time.

Scientists at MPA have now used various approaches – both from both radio astronomy itself and from unrelated scientific areas – to implement a new version of the gridding operation. This new implementation produces very accurate results while at the same time consuming considerably less CPU time and computer memory.

Gridding, however, is only one of several components necessary to produce realistic images from interferometric observations. To suppress noise in the data and eliminate the directional changes in antenna sensitivity, sophisticated iterative algorithms are employed. Traditionally, very often a variant of the so-called CLEAN algorithm is used, which is comparatively quick but does not provide an uncertainty estimate for the resulting image. In contrast to CLEAN-based methods, the MPA scientists developed an (admittedly significantly slower) approach, which delivers physically motivated results including error bars, making use of Information Field Theory and Bayesian statistics.

Three different image reconstructions of the radio galaxy Cygnus A from VLA interferometry data. Two small regions (a bright and a dark one, respectively), have been enlarged for easier comparison. Top panel: naive Fourier transform without optimization. Middle panel: reconstruction using the CLEAN algorithm. A higher resolution is reached, but some unphysical structures are generated, especially in the darker regions. Bottom panel: reconstruction using Bayesian imaging and Information Field Theory. Resolution in the bright areas is further improved, yet no artefacts are visible in the dark areas.For a larger view of image reconstructions B and C, please see below. © MPA; reconstruction middle image: NRAO, Klasse Richard A. Perley

Fig. 4 shows a comparison of the two methods. The observed astrophysical source is the radio galaxy Cygnus A with a supermassive black hole (weighing more than a billion solar masses) at its centre. Two jets, observable at radio wavelengths, leave this centre and at some point encounter the intergalactic medium, where they are reflected and start to emit very brightly. The back-flows create large volumes of radio-bright gas, which can be observed with radio interferometers like the VLA.

The image obtained with the new algorithm exhibits significantly better spatial resolution in the bright image regions, since the signal-to-noise ratio in these areas is much higher. At the same time, it does not show the pronounced structures in the darker regions from the CLEAN results; presumably these structures are artefacts of the CLEAN algorithm which do not correspond to real features on the sky.

The methods presented here essentially open up two new possibilities for radio astronomy: they allow re-processing of already existing data sets, in order to gain additional insights from the improved images. For future observations, there may now be an option to reach the desired image quality with shorter observation times, thanks to the improvements in the algorithms, allowing for a higher overall number of observations. Source: Max Planck Institute for Astrophysics

Other scientific disciplines such as medical imaging, especially magneto-resonance tomography (MRT) employ imaging techniques that are closely related to those in radio interferometry. It is therefore possible that the insights gained from these developments will be beneficial in these areas as well.

 Additional information:

The two last images from Fig 4 can be enlarged separately below.

Image reconstruction with the CLEAN algorithm.
© MPA; reconstruction: NRAO, Klasse Richard A. Perley

Image reconstruction with the new algorithm developed at MPA.
© MPA

 

Source: Max Planck Institute for Astrophysics

 

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Authors

Arras, Philipp Arras
PhD student
Tel: 2034
Martin Reinecke
Scientific Staff

Enßlin, Torsten Enßlin
Scientific Staff
Tel.:2243

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Original publications

1. P. Arras, R.A. Perley, H.L. Bester, R. Leike, O. Smirnov, R. Westermann, T.A. Enßlin Comparison of classical and Bayesian imaging in radio interferometry. Cygnus A with CLEAN and resolve A&A, Forthcoming article
Source/ DOI 

 

2. Philipp Arras, Martin Reinecke, Rüdiger Westermann, Torsten A. Enßlin
Efficient wide-field radio interferometry response A&A, accepted 

Source/DOI

3.Ye, H.
Accurate image reconstruction in radio interferometry
Doctoral thesis
Source/DOI

4. Alex H. Barnett, Jeremy F. Magland, Ludvig af Klinteberg A parallel non-uniform fast Fourier transform library based on an "exponential of semicircle" kernel SIAM Journal on Scientific Computing, 41, 5, C479--C504, 2019 

Source 

 

5. Enßlin, Torsten A. 

Information theory for fields Annalen der Physik 2019, 1800127

DOI

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