From Science News: “The M87 black hole image showed the best way to measure black hole masses”

From Science News

April 22, 2019
Lisa Grossman

Its diameter suggests the black hole is 6.5 billion times the mass of the sun.

SUPERMASSIVE SOURCE The gases and stars in galaxy Messier 87, shown in this composite image from the Chandra X-ray telescope and the Very Large Array, gave different numbers for the mass of the galaxy’s supermassive black hole.

NASA/Chandra X-ray Telescope

NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

The measure of a black hole is what it does with its stars.

That’s one lesson astronomers are taking from the first-ever picture of a black hole, released on April 10 by an international telescope team (SN Online: 4/10/19).

SHADOW SIZE The Event Horizon Telescope captured the first image of M87’s black hole. That image showed that the black hole’s mass is about 6.5 billion times the mass of the sun, close to what astronomers expected based on the galaxy’s stars.

That image confirmed that the mass of the supermassive black hole in the center of galaxy Messier 87 is close to what astronomers expected from how nearby stars orbit — solving a long-standing debate over how best to measure a black hole’s mass.

The black hole in Messier 87, which is located about 55 million light-years from Earth, is the first black hole whose mass has been calculated by three precise methods: measuring the motion of stars, the swirl of surrounding gases and now, thanks to the Event Horizon Telescope imaging project, the diameter of the black hole’s shadow.

EHT map

In 1978, the first mass estimates to track the motions of stars whipping around the great gravitational center found that the stars must be orbiting something containing about 5 billion times the mass of the sun. A more precise estimate in 2011 using a similar stellar technique bumped its heft up to 6.6 billion times the mass of the sun.

Star S0-2 Andrea Ghez Keck/UCLA Galactic Center Group at SGR A*, the supermassive black hole at the center of the milky way

Meanwhile, astronomers in 1994 made another estimate by tracing how gases closer to the black hole than the stars swirl around the behemoth. That technique suggested that the black hole was 2.4 billion solar masses, which was revised in 2013 to 3.5 billion solar masses.

For years, it wasn’t clear which technique got closer to the truth.

Now the EHT picture showing a glowing orange ring of gases and dust around the black hole has solved the conflict. According to Einstein’s general theory of relativity, the diameter of the dark space in the center of the image — the black hole’s shadow — is directly related to its mass.

“Bigger black holes cast bigger shadows,” EHT team member Michael Johnson, an astrophysicist at the Harvard Smithsonian Center for Astrophysics, said April 12 at a talk at MIT. “Easy check, we can see whether one or the other of these [mass measuring methods] is correct.” The shadow of M87’s black hole yielded a diameter of 38 billion kilometers, which let astronomers calculate a mass of 6.5 billion suns [The Astrophysical Journal Letters]— very close to the mass suggested by the motion of stars.

The size of the shadow also negated the idea that the black hole is a wormhole, a theoretical bridge between distant points in spacetime (SN: 5/31/14, p. 16). If M87’s black hole had been a wormhole, theory predicts it should look smaller than it does. “It’s a stunning confirmation” of general relativity, Johnson said. “We instantly rule out all these exotic possibilities.”

The mass confirmation may boost confidence in current simulations for how black holes develop, says Priyamvada Natarajan, a Yale University astrophysicist who was not involved with the EHT project. Most black hole mass estimates already use the stellar technique, in part because it’s easier to track a galaxy’s stars from farther away.

STARS AND STREAKS Astrophysicists have used both stars and gases to weigh in on the mass of the black hole in the galaxy NGC 4258, shown in this composite image. P.Ogle et al/Caltech/CXC/NASA, R.Gendler, STScI/NASA, Caltech-JPL/NASA, VLA/NRAO/NSF

SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory

Two other black holes whose masses have been measured in multiple ways, the Milky Way’s Sagittarius A* [Astronomy and Astrophysics] and the galaxy NGC 4258’s black hole, also suggest the star method works better. “These three cases now offer renewed faith in our current method,” Natarajan says.

That faith won’t solve the most pressing black hole problems, such as how black holes grew so big so fast in the early universe — at least not right away (SN Online: 3/16/18). The gas versus star measurement of the M87 black hole mass differed by only a factor of two, which is not enough to explain how it got so massive in the first place. A black hole could double its mass in about a million years, at most.

“What we don’t know is how we get supermassive black holes within a billion years,” says Hannalore Gerling-Dunsmore, a former Caltech physicist who is joining the University of Colorado Boulder later this year. She was not on the EHT team. “Once you’re already that big, what’s a million years between friends?”

See the full article here .

NSF press conference on the EHT Messier 87 Black Hole project

European Research Council press conference on the EHT Messier 87 Black Hole project

Katie Bouman on the EHT Messier 87 Black Hole project at Caltech

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From University of Maryland CMNS: “The Past, Present and Future of Gravitational Wave Astronomy”

From University of Maryland

CMNS

Matthew Wright
301-405-9267
mewright@umd.edu

UMD Astronomy Professor Coleman Miller co-authored wide-ranging review article for 150th anniversary of the journal Nature.

Coleman Miller, University of Maryland Astronomy Professor and Co-Director of the Joint Space-Science Institute. Miller co-authored a new review of the past, present, and future of gravitational wave astronomy for the journal Nature. Image credit: Coleman Miller.

When Albert Einstein published his general theory of relativity in 1915, he gave the scientific community a wealth of theoretical predictions about the nature of space, time, matter and gravity. Unlike much of his prior work, however, general relativity wasn’t easily testable with experiments and direct observation.

That all changed a century later, on September 14, 2015, when the twin Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors registered gravitational waves from the merger of two black holes.

For the first time, the scientific community had definitive support for one of the greatest predictions arising from Einstein’s general theory of relativity—that the acceleration of massive objects can produce ripples in the fabric of spacetime.

In just three short years since that initial observation, LIGO has made or contributed to a landslide of new discoveries, helping to usher in the age of gravitational wave astronomy. University of Maryland Astronomy Professor Coleman Miller, an expert in the theory and modeling of gravity, co-authored a review of the past, present, and future of gravitational wave astronomy for the journal Nature, published on April 25, 2019. The article is part of a series that celebrates the 150th anniversary of the journal, which was first published on November 4, 1869.

“Direct observation of gravitational waves was an important test of general relativity that gave us access to information we simply didn’t have before,” said Miller, who is also a co-director of the Joint Space-Science Institute (JSI), a partnership between UMD and NASA’s Goddard Space Flight Center. “There is a very limited set of ways we can get information about the distant universe beyond our solar system. We were missing a lot of non-trivial events before we could detect gravitational waves. To offer some perspective: the final plunge of a black hole merger emits tens of times more energy in gravitational waves than all the stars in the visible universe radiate within the same period of time.”

Miller is a co-author of more than 20 publications related to gravitational radiation. Although he served as the chair of the LIGO Program Advisory Committee for four years (2010-2014), Miller has not been directly involved in LIGO’s science operations. This provides him with a uniquely knowledgeable, yet scientifically objective, viewpoint on the topic.

Co-authored with Nicolás Yunes of Montana State University, the review article traces the early history of attempts to investigate general relativity, including several indirect observations and theoretical work. Then, Miller and Yunes describe the contributions of UMD Physics Professor Joseph Weber (1919-2000), who was the first to suggest that it was physically possible to detect and measure gravitational waves.

Beginning in the 1960s, Weber designed, built and operated a pair of solid aluminum bars—one near UMD’s campus and another just outside Chicago—which he suggested would resonate like a bell when struck by passing gravitational waves. Thus began a decades-long scientific quest that would involve hundreds of scientists the world over, including many UMD faculty and staff members and alumni. The physics community eventually settled on a completely different interferometer design that would become the basis for LIGO’s twin detector facilities in Livingston, Louisiana, and Hanford, Washington.

The collision of two black holes—a tremendously powerful event detected for the first time ever by the Laser Interferometer Gravitational-Wave Observatory, or LIGO on September 14, 2015—is seen in this still from a computer simulation. LIGO detected gravitational waves, or ripples in space and time generated as the black holes spiraled in toward each other, collided, and merged. This simulation shows how the merger would appear to human eyes. It was created by solving equations from Albert Einstein’s general theory of relativity using the LIGO data. Illustration: SXS.

With the help of UMD Physics Professor and JSI Fellow Peter Shawhan and UMD College Park Professor of Physics Alessandra Buonanno—both principal investigators with the LIGO Scientific Collaboration—the construction and fine-tuning of the detectors resulted in LIGO’s historic first observation in 2015. Just two years later, in 2017, LIGO project leads Rainer Weiss of the Massachusetts Institute of Technology and Kip Thorne and Barry Barish of Caltech were recognized with the Nobel Prize in physics for the groundbreaking observation.

LIGO followed the initial 2015 detection with several more observations of black hole mergers. But another major turning point came on August 17, 2017, when scientists across the world made the first direct observation of a merger between two neutron stars—the dense, collapsed cores that remain after large stars die in a supernova. The merger was the first cosmological event observed in both gravitational waves and—with the help of a large array of ground- and space-based telescopes—the entire spectrum of light, from gamma rays to radio waves.

“This event gave us instant confirmation that gravitational waves travel at a speed that is indistinguishable from the speed of light,” Miller explained. “For years, there have been alternate theories of gravity that would explain what dark matter is thought to do. But many of these relied on gravitational waves reacting to the gravity of massive objects differently than light does. This was not found to be the case in the wake of a neutron star merger, so observing this event eliminated a wide swath of these theories immediately.”

The neutron star merger also yielded the first direct observation of a kilonova—a massive explosion now believed to create most of the heavy elements in the universe. Led by UMD’s Eleonora Troja, an associate research scientist in the Department of Astronomy, an early analysis of the kilonova suggested that the explosion produced a staggering amount of platinum and gold, with a combined mass several hundred times that of Earth.

This iconc illustration depicts the merger of two neutron stars. The rippling spacetime grid represents gravitational waves that travel out from the collision, while the narrow beams show the burst of gamma rays launched just seconds after the gravitational waves. Swirling clouds of material ejected from the merging stars glow with visible and other wavelengths of light. Image credit: National Science Foundation/LIGO/Sonoma State University/A. Simonnet

This finding alone strongly swung the needle toward a conclusion that all elements heavier than iron are all produced in neutron star mergers,” Miller explained. “That’s very exciting.”

On April 1, 2019, LIGO began its third observing run, after a series of upgrades to its lasers, mirrors and other components. While Miller is hesitant to set his own expectations too high, he is hopeful that the latest round will yield some new surprises.

“The universe will give us what it will give us. That said, it would be wonderful to see a merger between a black hole and a neutron star,” Miller said. “And a few extra double neutron star mergers certainly wouldn’t hurt.”

Looking further down the line, Miller and Yunes also assessed the prospects for observing the gravitational wave background. This ever-present hum of gravitational waves is thought to contain the fingerprints of orbiting black holes, neutron stars and other massive objects. These pairs of objects may be tens, hundreds or even thousands of years away from merging—and thus are unable to produce a spike in gravitational waves detectable with current technology. Miller likens the effort to adjusting one’s ears to the din of conversation in a crowded room.

“Imagine arriving at a party. At first, you can see that everyone is talking, but the sound registers quietly, if at all,” Miller said. “Then your hearing gets better. You’re not yet able to hear every individual, but you can hear the sum total. Then, as your hearing gets better, you can hear some nearby conversations and can distinguish between people who are near and far.”

Within the next few years, the International Pulsar Timing Array (IPTA) collaboration could become the first to detect the subtle drone from thousands of pairs of supermassive black holes.

With the help of the world’s largest radio telescopes, IPTA will carefully track deviations in the precise, clock-like flashing of roughly 100 small, rotating neutron stars called millisecond pulsars. These deviations will help IPTA detect gravitational fluctuations from orbiting pairs of supermassive black holes, each of which contains billions of times the mass of the sun.

The next big step in gravitational wave astronomy will be the launch of the Laser Interferometer Space Antenna (LISA) mission, led by the European Space Agency in partnership with NASA.

ESA/NASA eLISA space based, the future of gravitational wave research

This trio of satellites, currently slated for deployment by 2034, will be sensitive to a lower range of gravitational wave frequencies than LIGO. As such, LISA should be able to observe events that LIGO cannot detect, such as mergers that involve one or more supermassive black holes.

“A lot can happen in 15 years. In the meantime, I plan to eat my vegetables so I can be around to appreciate LISA’s findings when the satellites are launched,” Miller said. “The excitement in the astrophysical community is only increasing. Expectation of new discovery has been one the enduring excitements of gravitational wave astronomy.”

See the full article here .

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About CMNS

The thirst for new knowledge is a fundamental and defining characteristic of humankind. It is also at the heart of scientific endeavor and discovery. As we seek to understand our world, across a host of complexly interconnected phenomena and over scales of time and distance that were virtually inaccessible to us a generation ago, our discoveries shape that world. At the forefront of many of these discoveries is the College of Computer, Mathematical, and Natural Sciences (CMNS).

CMNS is home to 12 major research institutes and centers and to 10 academic departments: astronomy, atmospheric and oceanic science, biology, cell biology and molecular genetics, chemistry and biochemistry, computer science, entomology, geology, mathematics, and physics.

Our Faculty

Our faculty are at the cutting edge over the full range of these disciplines. Our physicists fill in major gaps in our fundamental understanding of matter, participating in the recent Higgs boson discovery, and demonstrating the first-ever teleportation of information between atoms. Our astronomers probe the origin of the universe with one of the world’s premier radio observatories, and have just discovered water on the moon. Our computer scientists are developing the principles for guaranteed security and privacy in information systems.

Our Research

Driven by the pursuit of excellence, the University of Maryland has enjoyed a remarkable rise in accomplishment and reputation over the past two decades. By any measure, Maryland is now one of the nation’s preeminent public research universities and on a path to become one of the world’s best. To fulfill this promise, we must capitalize on our momentum, fully exploit our competitive advantages, and pursue ambitious goals with great discipline and entrepreneurial spirit. This promise is within reach. This strategic plan is our working agenda.

The plan is comprehensive, bold, and action oriented. It sets forth a vision of the University as an institution unmatched in its capacity to attract talent, address the most important issues of our time, and produce the leaders of tomorrow. The plan will guide the investment of our human and material resources as we strengthen our undergraduate and graduate programs and expand research, outreach and partnerships, become a truly international center, and enhance our surrounding community.

Our success will benefit Maryland in the near and long term, strengthen the State’s competitive capacity in a challenging and changing environment and enrich the economic, social and cultural life of the region. We will be a catalyst for progress, the State’s most valuable asset, and an indispensable contributor to the nation’s well-being. Achieving the goals of Transforming Maryland requires broad-based and sustained support from our extended community. We ask our stakeholders to join with us to make the University an institution of world-class quality with world-wide reach and unparalleled impact as it serves the people and the state of Maryland.

Our researchers are also at the cusp of the new biology for the 21st century, with bioscience emerging as a key area in almost all CMNS disciplines. Entomologists are learning how climate change affects the behavior of insects, and earth science faculty are coupling physical and biosphere data to predict that change. Geochemists are discovering how our planet evolved to support life, and biologists and entomologists are discovering how evolutionary processes have operated in living organisms. Our biologists have learned how human generated sound affects aquatic organisms, and cell biologists and computer scientists use advanced genomics to study disease and host-pathogen interactions. Our mathematicians are modeling the spread of AIDS, while our astronomers are searching for habitable exoplanets.

Our Education

CMNS is also a national resource for educating and training the next generation of leaders. Many of our major programs are ranked among the top 10 of public research universities in the nation. CMNS offers every student a high-quality, innovative and cross-disciplinary educational experience that is also affordable. Strongly committed to making science and mathematics studies available to all, CMNS actively encourages and supports the recruitment and retention of women and minorities.

Our Students

Our students have the unique opportunity to work closely with first-class faculty in state-of-the-art labs both on and off campus, conducting real-world, high-impact research on some of the most exciting problems of modern science. 87% of our undergraduates conduct research and/or hold internships while earning their bachelor’s degree. CMNS degrees command respect around the world, and open doors to a wide variety of rewarding career options. Many students continue on to graduate school; others find challenging positions in high-tech industry or federal laboratories, and some join professions such as medicine, teaching, and law.

From Nautilus: “First Black-Hole Image: It’s Not Looks That Count”

From Nautilus

Apr 11, 2019
Sabine Hossenfelder

FIRST LOOK: The Event Horizon Telescope measures wavelength in the millimeter regime, too long to be seen by eye, but ideally suited to the task of imaging a black hole: The gas surrounding the black hole is almost transparent at this wavelength and the light travels to Earth almost undisturbed. Since we cannot see light of such wavelength by eye, the released telescope image shows the observed signal shifted into the visible range.Event Horizon Telescope Collaboration.

“The Day Feynman Worked Out Black-Hole Radiation on My Blackboard”

After a few minutes, Richard Feynman had worked out the process of spontaneous emission, which is what Stephen Hawking became famous for a year later.Wikicommons.

The Italian 14th-century painter, Giotto di Bondone, when asked by the Pope to prove his talent, is said to have swung his arm and drawn a perfect circle. But geometric perfection is limited by the medium. Inspect a canvas closely enough, and every circle will eventually appear grainy. If perfection is what you seek, don’t look at man-made art, look at the sky. More precisely, look at a black hole.

Looking at a black hole is what the Event Horizon Telescope has done for the past 12 years. Yesterday, the collaboration released the long-awaited results from its first full run in April 2017. Contrary to expectation, their inaugural image is not, as many expected, Sagittarius A*, the black hole at the center of the Milky Way. Instead, it is the supermassive black hole in the elliptic galaxy Messier 87, about 55 million light-years from here. This black hole weighs in at 6.5 billion times the mass of our sun, and is considerably larger than the black hole in our own galaxy [1,000 times the size of SGR A*]. So, even though the Messier 87 black hole is a thousand times farther away than Sagittarius A*, it still appears half the size in the sky.

The Event Horizon Telescope (EHT) is not less remarkable than the objects it observes. With a collaboration of 200 people, the EHT uses not a single telescope, but a global network of nine telescopes. Its sites, from Greenland to the South Pole and from Hawaii to the French Alps, act in concert as one. Together, the collaboration commands a telescope the size of planet Earth, staring at a tiny patch in the northern sky that contains the Messier-87 black hole.

Event Horizon Telescope Array

Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

Atacama Pathfinder EXperiment

Combined Array for Research in Millimeter-wave Astronomy (CARMA)

Atacama Submillimeter Telescope Experiment (ASTE)

Caltech Submillimeter Observatory (CSO)

IRAM 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada,, Altitude 2,850 m (9,350 ft)

Institut de Radioastronomie Millimetrique (IRAM) 30m

James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

Large Millimeter Telescope Alfonso Serrano

CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft)

Submillimeter Array Hawaii SAO

ESO/NRAO/NAOJ ALMA Array, Chile [recently added]

South Pole Telescope SPTPOL [recently added]

Future Array/Telescopes

NOEMA (NOrthern Extended Millimeter Array) will double the number of its 15 meter antennas of its predecessor from six to twelve, located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters

NSF CfA Greenland telescope

Greenland Telescope

ARO 12m Radio Telescope, Kitt Peak National Observatory, Arizona, USA, Altitude 1,914 m (6,280 ft)

ARO 12m Radio Telescope

In theory, black holes are regions of space where the gravitational pull is so large that everything, including light, becomes trapped for eternity. The surface of the trapping region is called the “event horizon.” It has no substance; it is a property of space itself. In the simplest case, the event horizon is a sphere—a perfect sphere, made of nothing.

In reality, it’s complicated. Astrophysicists have had evidence for the existence of black holes since the 1990s, but so far all observations have been indirect—inferred from the motion of visible stars and gas, leaving doubt as to whether the dark object really possesses the defining event horizon. It turned out difficult to actually see a black hole. Trouble is, they’re black. They trap light. And while Stephen Hawking proved that black holes must emit radiation due to quantum effects, this quantum glow is far too feeble to observe.

But much like the prisoners in Plato’s cave, we can see black holes by observing the shadows they cast. Black holes attract gas from their environment. This gas collects in a spinning disk, and heats up as it spirals into the event horizon, pushing around electric charges. This gives rise to strong magnetic fields that can create a “jet,” a narrow, directed stream of particles leaving the black hole at almost the speed of light. But whatever strays too close to the event horizon falls in and vanishes without a trace.

At the same time black holes bend rays of light, bend them so strongly, indeed, that looking at the front of a black hole, we can see part of the disk behind it. The light that just about manages to escape reveals what happens nearby the horizon. It is an asymmetric image that the astrophysicists expect, brighter on the side of the black hole where the material surrounding it moves toward us, and darker where it moves away from us. The hot gas combined with the gravitational lensing creates the unique observable signature that the EHT looks out for.

The experimental challenge is formidable. The network’s telescopes must synchronize their data-taking using atomic clocks. Weather conditions must be favorable at all locations simultaneously. Once recorded, the amount of data is so staggeringly large, it must be shipped on hard disks to central locations for processing.

The theoretical challenges are not any lesser. Black holes bend light so much that it can wrap around the horizon multiple times. The resulting image is too complicated to capture in simple equations. Though the math had been known since the 1920s, it wasn’t until 1978 that physicists got a first glimpse of what a black hole would actually look like. In that year, the French astrophysicist Jean-Pierre Luminet programmed the calculation on an IBM 7040 using punchcards. He drew the image by hand.

Today, astrophysicists use computers many times more powerful to predict the accretion of gas onto the black hole and how the light bends before reaching us. Still, the partly turbulent motion of the gas, the electric and magnetic fields created by it, and the intricacies of the particle’s interactions are not fully understood.

The EHT’s observations agree with expectation. But this result is more than just another triumph of Einstein’s theory of general relativity. It is also a triumph of the astronomers’ resourcefulness. They joined hands and brains to achieve what they could not have done separately. And while their measurement settles a long-standing question—yes, black holes really do have event horizons!—it is also the start of further exploration. Physicists hope that the observations will help them understand better the extreme conditions in the accretion disk, the role of magnetic fields in jet formation, and the way supermassive black holes affect galaxy formation.

When the Pope received Giotto’s circle, it was not the image itself that impressed him. It was the courtier’s report that the artist produced it without the aid of a compass. This first image of a black hole, too, is remarkable not so much for its appearance, but for its origin. A black sphere, spanning 40 billion kilometers, drawn on a background of hot gas by the greatest artist of all: Nature herself.

See the full article here .

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Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

The Astrophysical Journal Letters: “Focus on the First Event Horizon Telescope Results”

The Astrophysical Journal Letters

April 10, 2019
Shep Doeleman (EHT Director) on behalf of the EHT Collaboration

Figure 1. EHT images of M87 on four different observing nights. In each panel, the white circle shows the resolution of the EHT. All four images are dominated by a bright ring with enhanced emission in the south. From Paper IV (Figure 15).

We report the first image of a black hole.

This Focus Issue shows ultra-high angular resolution images of radio emission from the supermassive black hole believed to lie at the heart of galaxy Messier 87 (Figure 1). A defining feature of the images is an irregular but clear bright ring, whose size and shape agree closely with the expected lensed photon orbit of a 6.5 billion solar mass black hole. Soon after Einstein introduced general relativity, theorists derived the full analytic form of the photon orbit, and first simulated its lensed appearance in the 1970s. By the 2000s, it was possible to sketch the “shadow” formed in the image when synchrotron emission from an optically thin accretion flow is lensed in the black hole’s gravity. During this time, observational evidence began to build for the existence of black holes at the centers of active galaxies, and in our own Milky Way [SGR A*]. In particular, a steady progression in radio astronomy enabled very long baseline interferometry (VLBI) observations at ever-shorter wavelengths, targeting supermassive black holes with the largest apparent event horizons: Messier 87, and Sgr A* in the Galactic Center. The compact sizes of these two sources were confirmed by studies at 1.3mm, first exploiting baselines that ran from Hawai’i to the mainland US, then with increased resolution on baselines to Spain and Chile.

Over the past decade, the EHT extended these first measurements of size to mount the more ambitious campaign of imaging the shadow itself. During 5-11 April 2017, the Event Horizon Telescope (EHT) observed Messier 87 and calibrators on four separate days using an array that included eight radio telescopes at six geographic locations: Arizona (USA), Chile, Hawai’i (USA), Mexico, the South Pole, and Spain (Figure 2). Years of preparation (and an astonishing spate of planet-wide good weather) paid off with an extraordinary multi-petabyte yield of data. The results presented here, from observations through images to interpretation, issue from a team of instrument, algorithm, software, modeling, and theoretical experts, following a tremendous effort by a group of scientists that span all career stages, from undergraduates to senior members of the field. More than 200 members from 59 institutes in 20 countries and regions have devoted years to the effort, all unified by a common scientific vision.

Figure 2. A map of the EHT. Stations active in 2017 and 2018 are shown with connecting lines and labeled in yellow, sites in commission are labeled in green, and legacy sites are labeled in red. From Paper II (Figure 1).

The sequence of Letters in this issue provides the full scope of the project and the conclusions drawn to date. Paper II opens with a description of the EHT array, the technical developments that enabled precursor detections, and the full range of observations reported here. Through the deployment of novel instrumentation at existing facilities, the collaboration created a new telescope with unique capabilities for black hole imaging. Paper III details the observations, data processing, calibration algorithms, and rigorous validation protocols for the final data products used for analysis. Paper IV gives the full process and approach to image reconstruction. The final images emerged after a rigorous evaluation of traditional imaging algorithms and new techniques tailored to the EHT instrument–alongside many months of testing the imaging algorithms through the analysis of synthetic data sets. Paper V uses newly assembled libraries of general relativistic magnetohydrodynamic (GRMHD) simulations and advanced ray-tracing to analyze the images and data in the context of black hole accretion and jet-launching. Paper VI employs model fits, comparison of simulations to data, and feature extraction from images to derive formal estimates of the lensed emission ring size and shape, black hole mass, and constraints on the nature of the black hole and the space-time surrounding it. Paper I is a concise summary.

Our image of the shadow confines the mass of Messier 87 to within its photon orbit, providing the strongest case for the existence of supermassive black holes. These observations are consistent with Doppler brightening of relativistically moving plasma close to the black hole lensed around the photon orbit. They strengthen the fundamental connection between active galactic nuclei and central engines powered by accreting black holes through an entirely new approach. In the coming years, the EHT Collaboration will extend efforts to include full polarimetry, mapping of magnetic fields on horizon scales, investigations of time variability, and increased resolution through shorter wavelength observations.

In short, this work signals the development of a new field of research in astronomy and physics as we zero in on precision images of black holes on horizon scales. The prospects for sharpening our focus even further are excellent.

First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
The Event Horizon Telescope Collaboration et al. 2019 ApJL 875 L1

First M87 Event Horizon Telescope Results. II. Array and Instrumentation
The Event Horizon Telescope Collaboration et al. 2019 ApJL 875 L2

First M87 Event Horizon Telescope Results. III. Data Processing and Calibration
The Event Horizon Telescope Collaboration et al. 2019 ApJL 875 L3

First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
The Event Horizon Telescope Collaboration et al. 2019 ApJL 875 L4

First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
The Event Horizon Telescope Collaboration et al. 2019 ApJL 875 L5

First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
The Event Horizon Telescope Collaboration et al. 2019 ApJL 875 L6

See the full article here .

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Netherlands Institute for Radio Astronomy (ASTRON): “Energy loss gives unexpected insights in evolution of quasar jets”

Netherlands Institute for Radio Astronomy (ASTRON)

The radio jet of the quasar 4C+19.44, powered by a supermassive black hole lying in the center of its host galaxy and shining at long radio wavelengths as seen by the LOFAR radio telescope (magenta). The background image shows neighboring galaxies in the visible light highlighted thanks to the Hubble Space Telescope (cyan and orange) having the radio jet passing into the dark voids of intergalactic space (Harris et al. 2019). Image Credit: NASA/HST/LOFAR; Courtesy of J. DePasquale

An international team of astrophysicists observed for the first time that the jet of a quasar is less powerful on long radio wavelengths than earlier predicted. This discovery gives new insights in the evolution of quasar jets. They made this observation using the international Low Frequency Array (LOFAR) telescope [below], that produced high resolution radio images of quasar 4C+19.44 located over 5 billion light-years from Earth.

Supermassive black holes, many millions of times more massive than our Sun reside in the central regions of galaxies. They grow even larger by attracting and consuming nearby gas and dust. If they consume material rapidly, the infalling matter shines brightly and the source is known as a quasar. Some of this infalling matter is not digested, but instead is ejected in the form of so-called jets that punch through the surrounding galaxy and into intergalactic space for millions of light years. These jets, shining brightly at radio wavelengths, are composed of particles accelerated up to nearly the speed of light, but exactly how these particles achieve energies not attainable on the Earth is yet to be completely solved.

The discovery on quasar 4C+19.44 gives new insights to the balance between the energy in the field surrounding the quasar and that residing in the quasar jet. This finding indicates to an intrinsic property of the source rather than due to absorption effects. It implies that the energy budget available to accelerate particles and the balance between energy stored in particles and in the magnetic field, is less than expected.

“This is an important discovery that will be used for the years to come to improve simulations of jets. We observed for the first time a new signature of particle acceleration in the power emitted of quasar jets at long radio wavelengths. An unexpected behaviour that changes our interpretation on their evolution.” Said Prof. Francesco Massaro from University of Turin. “We knew that this was already discovered in other cosmic sources but it was never before observed in quasars.”

The international team of astrophysicists had observed the jet of the quasar 4C+19.44 at short radio wavelengths, in visible light, and X-ray wavelengths. The addition of the LOFAR images allowed astrophysicists to make this discovery. LOFAR is the first radio facility operating at long radio wavelengths, which produces sharp images with a resolution similar to that of the Hubble Space Telescope.

“We have been able to perform this experiment thanks to the highest resolution ever achieved at these long radio wavelengths, made possible by LOFAR.” Said Dr Adam Deller, an astrophysicist of the Swinburne University of Technology who contributed to the LOFAR data analysis and imaging of 4C +19.44 while at ASTRON in the Netherlands, heart of the LOFAR collaboration.

Dr Raymond Oonk, an astronomer at ASTRON and Leiden University and Dr Javier Moldon, astronomer at the University of Manchester, explained that “We have developed new calibration techniques for LOFAR and this has allowed us to separate compact radio structures in the quasar jet known as radio knots, and measure their emitted light. This result was unexpected and demands to future deeper investigations. New insights and clues on particle acceleration will come soon thanks to the international stations of LOFAR.”

The observation performed on the radio jet of 4C+19.44 was designed by Dr D. E. Harris, supervisor of Prof. Francesco Massaro, while working at the Harvard-Smithsonian Center for Astrophysics, several years ago. He performed the observation in collaboration with Dr Raffaella Morganti and his friends and colleagues at ASTRON. He only got the opportunity to see preliminary results as he passed away on 2015 December 6th. This publication, published in the first March issue of The Astrophysical Journal, is in memory of a career spanned much of the history of radio astronomy.

See the full article here .

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LOFAR is a radio telescope composed of an international network of antenna stations and is designed to observe the universe at frequencies between 10 and 250 MHz. Operated by ASTRON, the network includes stations in the Netherlands, Germany, Sweden, the U.K., France, Poland and Ireland.

ASTRON LOFAR Radio Antenna Bank, Netherlands

Westerbork Synthesis Radio Telescope (WSRT)

ASTRON was founded in 1949, as the Foundation for Radio radiation from the Sun and Milky Way (SRZM). Its original charge was to develop and operate radio telescopes, the first being systems using surplus wartime radar dishes. The organisation has grown from twenty employees in the early 1960’s to about 180 staff members today.

From AAS NOVA: ” Missing Halos in the High-Energy Sky”

From AAS NOVA

18 March 2019
Susanna Kohler

This composite image reveals Centaurus A, a galaxy with an active nucleus spewing fast-moving jets into its surroundings. Active galactic nuclei like this one produce extremely high-energy photons. [ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)]

Wide Field Imager on the 2.2 meter MPG/ESO telescope at Cerro LaSilla

MPG/ESO 2.2 meter telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres

ESO/MPIfR APEX high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft)

NASA/Chandra X-ray Telescope

What’s going on in our high-energy sky? Powerful phenomena abound in our universe, and they can produce photons with tremendous energies. A new study explores a high-energy mystery from one of these sources: active galactic nuclei, or AGN.

Gamma rays span a broad range of energies in the most energetic part of the electromagnetic spectrum. Very high-energy gamma rays initially emitted from AGN have energies above 100 GeV, but these are reprocessed by interactions with background photons to energies of 1–100 GeV. [Ulflund]

Where Are the Gamma Rays?

Active galactic nuclei — the accreting supermassive black holes lurking at the centers of some galaxies — dot our universal landscape, spewing out very high-energy gamma-ray photons within jets moving at nearly the speed of light. These energetic photons speed across the sky — but they don’t travel unencumbered.

Theory predicts that this energetic emission should be effectively reprocessed as it slams into the cosmic microwave background, generating a compact sheath of gamma-ray emission in the 1–100 GeV range, beamed forward in the direction of the jets emitted from each AGN. But there’s a problem: we don’t see this expected flux.

Galactic coordinates of the sources used to generate the authors’ stacked analysis. Two types of AGN-containing galaxies are included: FR I and FR II galaxies. [Broderick et al. 2019]

One possible explanation for the missing light is that these traveling photons could be deflected from their path by a strong, large-scale magnetic field threading through intergalactic space. This would convert the compact, forward-beamed sheath into a more diffuse, harder-to-spot gamma-ray halo around each AGN. In a new study, a team of scientists led by Avery Broderick (University of Waterloo and the Perimeter Institute for Theoretical Physics, Canada) has gone on the hunt for these missing gamma-ray halos.

Perimeter Institute in Waterloo, Canada

Stacks of Galaxies

Though the proposed gamma-ray halos may be too faint to spot individually, Broderick and collaborators suggest that by stacking a bunch of gamma-ray observations of off-axis AGN on top of one another, we should easily be able to detect their combined halo — if it exists.

The process of aligning the jets in two different radio images: an FR I galaxy (top) and an FR II galaxy (bottom). [Broderick et al. 2019]

To do this, the AGN must first be oriented in the same direction. Broderick and collaborators use radio observations of AGN jets pointed off our line of sight to identify each jet’s orientation. They determine the transformations needed to align each of the radio jets, and then apply this transformation to corresponding Fermi-telescope gamma-ray observations of the active galaxies. The result is a sample of nearly 9,000 gamma-ray observations of AGN, all oriented in the same direction.

Broderick and collaborators then stack these observations and compare their results to a model of what we would expect to see if an intergalactic magnetic field were deflecting the gamma-ray photons, generating a faint halo around the AGN.

Still No Halos

Top: the authors’ stacked gamma-ray observations for FR I (left) and FR II (right) galaxies. Bottom: the expected signals if gamma-ray halos were present. The observations clearly rule out the presence of faint halos. [Broderick et al. 2019]

Intriguingly, the authors find no hint of a combined gamma-ray halo. Their non-detection places strict limits on the strength of the intergalactic magnetic field allowed in this picture, and it rules out magnetic fields as an explanation for why we don’t see the gamma rays we expect from AGN.

What does this mean? Broderick and collaborators argue that this requires us to consider brand new physics in high-energy processes. There must be some unexpected mechanism that prevents the creation of the expected gamma-ray halos, either because the highest-energy emission is suppressed in gamma-ray bright AGN, or because some process affects this emission before it can lead to the generation of halos. The mystery deepens!

Citation

“Missing Gamma-Ray Halos and the Need for New Physics in the Gamma-Ray Sky,” Avery E. Broderick et al 2018 ApJ 868 87.
https://iopscience.iop.org/article/10.3847/1538-4357/aae5f2/meta

See the full article here .

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AAS Mission and Vision Statement

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

From Harvard-Smithsonian Center for Astrophysics: “Bright X-Ray Galactic Nuclei”

From Harvard-Smithsonian Center for Astrophysics

A Chandra X-Ray Observatory image of a field of galaxies in the costellation Bootes. A new study of 703 galaxies with supermassive black holes in this field finds that although infrared from dust and X-ray emission from the nucleus tend to be correlated, the infrared emitted by the supermassive black holes is not well correlated with the dust, suggesting the role of our viewing angle of a torus around the black hole nuclei. X-ray: NASA/CXC/CfA/R.Hickox et al.; Moon: NASA/JPL

All massive galaxies are believed to host supermassive black holes (SMBH) at their centers that grow by accreting mass from their environment. The current picture also imagines that the black holes grow in size as their host galaxy evolves, perhaps because galaxy evolution includes accretion triggered, for example, by galaxy mergers. This general picture has been substantiated by two lines of data.

The peak epoch of black hole accretion can be measured by observations of nuclear activity, and coincides with the peak epoch of star formation in the universe about ten billion years after the big bang. Star formation is associated with disruptions that stir up the gas and induce accretion. Moreover, the local universe shows a tight correlation between SMBH mass, host galaxy bulge mass, and the spread of stellar velocities. These methods (but with weaker confirmation) can similarly estimate the sizes of SMBH in galaxies in the earlier universe, and find that SMBH growth and galaxy growth are co-evolutionary processes. Indeed, it seems the processes may regulate each other over time to produce the galaxy and SMBH sizes we observe today.

Both central black hole growth and star formation are fed by the abundance of molecular gas and dust that can be traced by the infrared emitted by the dust.

Dust grains, heated by the radiation from young stars and AGN accretion, emit strongly in the infrared. Since AGN activity also produces X-rays, the expectation is that AGN should track strong dust emission and that X-ray and infrared emission should be correlated.

CfA astronomer Mojegan Azadi was a member of a team that examined 703 galaxies with active SMBH nuclei using both X-ray data from Chandra and infrared from Spitzer and Herschel, the largest sample to date making this comparison. Although the team did find a trend consistent with the infrared correlating with AGN X-ray activity over a wide range of cases, they did not find one when compared with the AGN’s infrared (not- X-ray) contributions.

Since the AGN infrared comes largely from a dusty emitting torus around the SMBH, the difference could point to the role of the angle with which we view the torus. These results help to refine the current models of AGN activity, but the authors note that more sensitive, deeper observations should be able to sort out more clearly the physical processes associated with the AGN.

Science paper:
Infrared Contributions of X-Ray Selected Active Galactic Nuclei in Dusty Star-forming Galaxies
Arianna Brown, Hooshang Nayyeri, Asantha Cooray, Jingzhe Ma, Ryan C. Hickox, and Mojegan Azadi
The Astrophysical Journal

See the full article here .

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The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

From AAS NOVA: “Giant Stars in Our Black Hole’s Neighborhood”

From AAS NOVA

15 March 2019
Kerry Hensley

This infrared view from Spitzer cuts through the dust in the galactic plane to reveal the center of the Milky Way. Infrared observations are critical for studying the stars at the center of the galaxy, which are visible as the bright spot in the center of this image. [NASA/JPL-Caltech/S. Stolovy (Spitzer Science Center/Caltech)]

NASA/Spitzer Infrared Telescope

How does a supermassive black hole affect its stellar neighbors? One way to explore this question is by searching for old, giant stars in the extreme environs of the galactic center.

Crowded Quarters

Dark dust lanes block the visible light from the galactic center, hiding the dense star cluster located there. [Dave Young]

The supermassive black hole at the center of our galaxy likely plays a huge role in the evolution and dynamics of stars in its neighborhood, as well as in how they are spatially distributed.

Theory predicts that old, giant stars near the galactic center should be arrayed in a “cusp”-like distribution, with the number of stars per square arcsecond increasing sharply toward the central black hole. Faint red giants seem to follow the expected distribution, but brighter red giants — which can be probed closer to the center of the galaxy — do not. Instead, these stars appear to follow a “core”-like distribution, with fewer stars than expected within the central arcsecond of the galaxy.

Many theories have been proposed to explain the apparent lack of bright red giants near the galactic center, from stellar collisions to tidal disruption by the supermassive black hole. While these factors may play a role, it’s also possible that observational challenges have prevented astronomers from fully cataloging the stellar population at the galactic center.

Giant stars from this study (black stars) on an H-R diagram with the theoretical isochrones used to determine the stellar ages. [Habibi et al. 2019]

Tracking Down Missing Stars

Observing stars so close to the galactic center is tricky — it’s crowded there, and starlight is highly extincted by dust clouds in the galactic plane at many wavelengths. In order to probe the stellar population near the galactic center, a team led by Maryam Habibi (Max Planck Institute for Extraterrestrial Physics, Germany) analyzed more than a decade’s worth of near-infrared stellar spectra from the SINFONI spectrograph on ESO’s Very Large Telescope.

ESO SINFONI installed at the Cassegrain focus of UT3 on the VLT

ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
•KUEYEN (UT2; The Moon ),
•MELIPAL (UT3; The Southern Cross ), and
•YEPUN (UT4; Venus – as evening star).
elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo,

The spectra used in this study were collected with the help of adaptive optics, in which the telescope’s mirror is deformed slightly to correct for the effects of turbulence in Earth’s atmosphere in close to real time — critical for observations of individual stars in a field as crowded as the galactic center!

Glistening against the awesome backdrop of the night sky above ESO_s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT, a major asset of the Adaptive Optics system

By co-adding multiple epochs of spectra to tease out faint spectral features, the authors derived the effective temperature, spectral type, age, mass, and radius for each target star. Their deeper spectra allowed them to identify old giants that had previously been misclassified as younger stars, bringing the number of known giants to 21.

Cusp Versus Core

Combining their new observations of bright giants within the central arcsecond with previously observed giants farther from the galactic center, the authors find that the distribution of bright giants can be described by a power law with an exponent of 0.34 ± 0.04 — definitively ruling out a core-like distribution.

Does this mean the galactic center’s core–cusp problem has been solved? While many of the missing giants have been found, the authors estimate that there are still stars awaiting discovery in the crowded interior of our galaxy, including some of the brightest red giants. Future observations should help us understand the complex distribution of stellar populations in the galactic center.

Citation

“Spectroscopic Detection of a Cusp of Late-type Stars Around the Central Black Hole in the Milky Way,” M. Habibi et al 2019 ApJL 872 L15.
https://iopscience.iop.org/article/10.3847/2041-8213/ab03cf/meta

See the full article here .

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AAS Mission and Vision Statement

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009

From Princeton University: “Astronomers discover 83 supermassive black holes in the early universe”

From Princeton University

March 13, 2019
Liz Fuller-Wright

Astronomers from Japan, Taiwan and Princeton University have discovered 83 quasars powered by supermassive black holes in the distant universe, from a time when the universe was less than 10 percent of its present age.

“It is remarkable that such massive dense objects were able to form so soon after the Big Bang,” said Michael Strauss, a professor of astrophysical sciences at Princeton University who is one of the co-authors of the study. “Understanding how black holes can form in the early universe, and just how common they are, is a challenge for our cosmological models.”

This finding increases the number of black holes known at that epoch considerably, and reveals, for the first time, how common they are early in the universe’s history. In addition, it provides new insight into the effect of black holes on the physical state of gas in the early universe in its first billion years. The research appears in a series of five papers published in The Astrophysical Journal and the Publications of the Astronomical Observatory of Japan.

Light from one of the most distant quasars known, powered by a supermassive black hole lying 13.05 billion light-years away from Earth. The image was obtained by the Hyper Suprime-Cam (HSC) mounted on the Subaru Telescope. The other objects in the field are mostly stars in our Milky Way or galaxies along the line of sight. Image courtesy of the National Astronomical Observatory of Japan

NAOJ Subaru Hyper Suprime-Cam

NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level

Supermassive black holes, found at the centers of galaxies, can be millions or even billions of times more massive than the sun. While they are prevalent today, it is unclear when they first formed, and how many existed in the distant early universe. A supermassive black hole becomes visible when gas accretes onto it, causing it to shine as a “quasar.” Previous studies have been sensitive only to the very rare, most luminous quasars, and thus the most massive black holes. The new discoveries probe the population of fainter quasars, powered by black holes with masses comparable to most black holes seen in the present-day universe.

An artist’s impression of a quasar. A supermassive black hole sits at the center, and the gravitational energy of material accreting onto it is released as light.
Image courtesy of Yoshiki Matsuoka

HSC has a gigantic field-of-view — 1.77 degrees across, or seven times the area of the full moon — mounted on one of the largest telescopes in the world. The HSC team is surveying the sky over the course of 300 nights of telescope time, spread over five years.

The team selected distant quasar candidates from the sensitive HSC survey data. They then carried out an intensive observational campaign to obtain spectra of those candidates, using three telescopes: the Subaru Telescope [above]; the Gran Telescopio Canarias on the island of La Palma in the Canaries, Spain; and the Gemini South Telescope in Chile.

Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level

Gemini/South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

The team selected distant quasar candidates from the sensitive HSC survey data. They then carried out an intensive observational campaign to obtain spectra of those candidates, using three telescopes: the Subaru Telescope; the Gran Telescopio Canarias on the island of La Palma in the Canaries, Spain; and the Gemini South Telescope in Chile. The survey has revealed 83 previously unknown very distant quasars. Together with 17 quasars already known in the survey region, the researchers found that there is roughly one supermassive black hole per cubic giga-light-year — in other words, if you chunked the universe into imaginary cubes that are a billion light-years on a side, each would hold one supermassive black hole.

The 100 quasars identified from the HSC data. The top seven rows show the 83 newly discovered quasars while the bottom two rows represent 17 previously known quasars in the survey area. They appear extremely red due to the cosmic expansion and absorption of light in intergalactic space. All the images were obtained by HSC.
Image courtesy of the National Astronomical Observatory of Japan

The sample of quasars in this study are about 13 billion light-years away from the Earth; in other words, we are seeing them as they existed 13 billion years ago. As the Big Bang took place 13.8 billion years ago, we are effectively looking back in time, seeing these quasars and supermassive black holes as they appeared only about 800 million years after the creation of the (known) universe.

If the history of the universe from the Big Bang to the present were laid out on a football field, Earth and our solar system would not appear until our own 33-yard line. Life appeared just inside the 28-yard line and dinosaurs went extinct halfway between the 1-yard line and the goal. All of human history, since hominids first climbed out of trees, takes place within an inch of the goal line. On this timeline, the supermassive black holes discovered by Princeton astrophysicist Michael Strauss and his international team of colleagues would appear back on the universe’s 6-yard line, very shortly after the Big Bang itself.
Image by Kyle McKernan, Office of Communications

The survey has revealed 83 previously unknown very distant quasars. Together with 17 quasars already known in the survey region, the researchers found that there is roughly one supermassive black hole per cubic giga-light-year — in other words, if you chunked the universe into imaginary cubes that are a billion light-years on a side, each would hold one supermassive black hole.

It is widely accepted that the hydrogen in the universe was once neutral, but was “reionized” — split into its component protons and electrons — around the time when the first generation of stars, galaxies and supermassive black holes were born, in the first few hundred million years after the Big Bang. This is a milestone of cosmic history, but astronomers still don’t know what provided the incredible amount of energy required to cause the reionization. A compelling hypothesis suggests that there were many more quasars in the early universe than detected previously, and it is their integrated radiation that reionized the universe.

“However, the number of quasars we observed shows that this is not the case,” explained Robert Lupton, a 1985 Princeton Ph.D. alumnus who is a senior research scientist in astrophysical sciences. “The number of quasars seen is significantly less than needed to explain the reionization.” Reionization was therefore caused by another energy source, most likely numerous galaxies that started to form in the young universe.

The present study was made possible by the world-leading survey ability of Subaru and HSC. “The quasars we discovered will be an interesting subject for further follow-up observations with current and future facilities,” said Yoshiki Matsuoka, a former Princeton postdoctoral researcher now at Ehime University in Japan, who led the study. “We will also learn about the formation and early evolution of supermassive black holes, by comparing the measured number density and luminosity distribution with predictions from theoretical models.”

Based on the results achieved so far, the team is looking forward to finding yet more distant black holes and discovering when the first supermassive black hole appeared in the universe.

The HSC collaboration includes astronomers from Japan, Taiwan and Princeton University. The HSC instrumentation and software were developed by the National Astronomical Observatory of Japan (NAOJ), the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), the University of Tokyo, the High Energy Accelerator Research Organization (KEK), the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan (ASIAA), and Princeton University. Funding was contributed by the FIRST program from Japanese Cabinet Office, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the Japan Society for the Promotion of Science (JSPS), Japan Science and Technology Agency (JST), the Toray Science Foundation, NAOJ, Kavli IPMU, KEK, ASIAA, and Princeton University.

The results of the present study are published in the following five papers — the second paper in particular.

[1] “Discovery of the First Low-luminosity Quasar at z > 7”, by Yoshiki Matsuoka1, Masafusa Onoue2, Nobunari Kashikawa3,4,5, Michael A Strauss6, Kazushi Iwasawa7, Chien-Hsiu Lee8, Masatoshi Imanishi4,5, Tohru Nagao and 40 co-authors, including Princeton astrophysicists James Bosch, James Gunn, Robert Lupton and Paul Price, appeared in the Feb. 6 issue of The Astrophysical Journal Letters, 872 (2019),

[2] “Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). V. Quasar Luminosity Function and Contribution to Cosmic Reionization at z = 6,” appeared in the Dec. 20 issue of The Astrophysical Journal, 869 (2018), 150

[3] “Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). IV. Discovery of 41 Quasars and Luminous Galaxies at 5.7 ≤ z ≤ 6.9,” was published July 3, 2018 in The Astrophysical Journal Supplement Series, 237 (2018), 5

[4] “Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). II. Discovery of 32 quasars and luminous galaxies at 5.7 < z ≤ 6.8,” was published July 5, 2017 in Publications of the Astronomical Society of Japan, 70 (2018), S35

[5] “Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). I. Discovery of 15 Quasars and Bright Galaxies at 5.7 < z < 6.9”, was published Aug. 25, 2016 in The Astrophysical Journal, 828 (2016), 26 .

See the full article here .

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About Princeton: Overview

Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

From AAS NOVA: “First Disrupted Star for a New Survey”

From AAS NOVA

6 March 2019
Susanna Kohler

Artist’s impression of a glowing stream of material produced when a star is shredded by a supermassive black hole. [NASA/JPL-Caltech]

What happens when a black hole makes a meal out of a passing star? So far, we’ve only detected a few dozen candidate tidal disruption events to help us answer this question — but now a new player is in the observing game.

Snacks for Black Holes

When a star passes within the tidal radius of a supermassive black hole, things don’t end well for the star. After the unfortunate object is torn apart by gravitational forces, some of the resulting debris accretes onto the black hole, causing a multi-wavelength flare.

To date, we’ve observed this flare emission from several dozen candidate tidal disruption events (TDEs), but many of them were only noticed significantly after the moment of disruption, when the flare emission is already ramping back down again. We also have only a handful of detections of TDEs across multiple wavelengths.

Zwicky Transient Facility (ZTF) instrument installed on the 1.2m diameter Samuel Oschin Telescope at Palomar Observatory in California. Courtesy Caltech Optical Observatories

In short, TDE observations thus far — though tantalizing — aren’t yet enough to help us complete the picture of what happens when a star is torn apart by a supermassive black hole. Clearly, the next step is to gather many more such observations! Luckily, a new tool has recently come online that will help us do exactly that: the Zwicky Transient Facility (ZTF)

A New Player

ZTF is a wide-field optical survey that hunts for transient objects in our night sky. ZTF images image the entire northern sky once every three nights, and the plane of the Milky Way twice a night. By scanning the same regions frequently, the survey can detect and monitor rapidly changing objects — like a suddenly rising tidal disruption flare.

ZTF began its first major public observing survey in mid-March 2018. In the weeks before that, ZTF was still in its commissioning phase, testing the camera and the alert pipeline. It was in this time that the survey detected its first tidal disruption event candidate, AT2018zr.

ZTF optical and Swift ultraviolet and optical light curves for AT2018zr. The data capture both the sudden rise and gradual decay of the flare. [van Velzen et al. 2019]

NASA Neil Gehrels Swift Observatory

Early View of Destruction

The transient AT2018zr triggered a ZTF alert on 6 March 2018. In the weeks that followed, it was observed by additional telescopes across a number of wavelength bands. In a new publication led by Sjoert van Velzen (University of Maryland and New York University), team members detailed the ZTF and multi-wavelength follow-up observations of AT2018zr.

By reprocessing earlier ZTF image frames, van Veltzen and collaborators found that ZTF had actually captured this tidal disruption event starting in early February, 50 days before the peak of the flare light curve. These detailed optical observations, combined with the broadband follow-up, provide an unusually complete view of this flare.

The host of AT2018zr, as observed by the Sloan Digital Sky Survey before the TDE occurred. [SDSS]

SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude2,788 meters (9,147 ft)

Harbingers of Data to Come

With many more events like AT2018zr, we can hope to build a large sample of flares that will finally shed light on TDE processes. ZTF is conveniently poised to start producing those observations; estimates suggest that, now that ZTF is fully operational, it will produce ~30 TDE detections per year.

What’s more, ZTF is providing researchers with a chance to test clever analysis techniques in advance of an even larger flood of data: the upcoming Large Synoptic Survey Telescope (LSST) is expected to detect ~1,000 TDEs per year!

LSST

LSST Camera, built at SLAC

LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

While only one event, AT2018zr is likely something more — the beginning of a new era for TDE observations.
Citation

“The First Tidal Disruption Flare in ZTF: From Photometric Selection to Multi-wavelength Characterization,” Sjoert van Velzen et al 2019 ApJ 872 198.
https://iopscience.iop.org/article/10.3847/1538-4357/aafe0c/meta

See the full article here .

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