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News Article | April 28, 2017
Site: www.eurekalert.org

A team of researchers in Japan modeled the two rings around Chariklo, the smallest body in the Solar System known to have rings (Figure 1). This is the first time an entire ring system has been simulated using realistic sizes for the ring particles while also taking into account collisions and gravitational interactions between the particles. The team's simulation revealed information about the size and density of the particles in the rings. By considering both the detailed structure and the global picture for the first time, the team found that Chariklo's inner ring should be unstable without help. It is possible the ring particles are much smaller than predicted or that an undiscovered shepherd satellite around Chariklo is stabilizing the ring. In order to elucidate the detailed structure and evolution of Chariklo's rings, Dr. Shugo Michikoshi (Kyoto Women's University/University of Tsukuba) and Prof. Eiichiro Kokubo (National Astronomical Observatory of Japan, NAOJ) performed simulations of the rings by using the supercomputer ATERUI*1 at NAOJ. They calculated the motions of 345 million ring particles with the realistic size of a few meters taking into account the inelastic collisions and mutual gravitational attractions between the particles. Thanks to ATERUI's many CPUs and the small size of Chariklo's ring system, the researchers successfully performed the first ever global simulation with realistic sized particles.*2 Their results show that the density of the ring particles must be less than half the density of Chariklo itself. Their results also showed that a striped pattern, known as "self-gravity wakes," forms in the inner ring due to interactions between the particles (Figure 2). These self-gravity wakes accelerate the break-up of the ring. The team recalculated the expected lifetime of Chariklo's rings based on their results and found it to be only 1 to 100 years, much shorter than previous estimates. This is so short that it's surprising the ring is still there. The research team suggested two possibilities to explain the continued existence of the ring. "Small ring particles is one possibility. If the size of the ring particles is only a few millimeters, the rings can be maintained for 10 million years. Another possibility is the existence of an undiscovered shepherd satellite which slows down the dissolution of the rings." explains Prof. Kokubo. Dr. Michikoshi adds, "The interaction between the rings and a satellite is also an important process in Saturn's rings. To better understand the effect of a satellite on ring structure, we plan to construct a new model for the formation of Chariklo's rings." Ring systems, such as the iconic rings around Saturn and Uranus, are composed of particles ranging from centimeters to meters in size. Until now, the difficultly of calculating the trajectories and mutual interactions of all these particles had confounded attempts to study rings through computer simulations. Previous researchers have either simulated only a portion of a ring system ignoring the overall structure, or used unrealistically large particles and ignored the detailed structures. In 2014, two rings separated by a gap were discovered around Chariklo, the largest known centaur. Centaurs are small bodies wandering between Jupiter and Neptune. Although Chariklo is only hundreds of kilometers in size, its rings are as opaque as those around Saturn and Uranus. Thus Chariklo offered an ideal chance to model a complete ring system. *1 "ATERUI" is a supercomputer for astrophysical simulations in the Center for Computational Astrophysics, NAOJ. Its theoretical peak performance is 1.058 Pflops. It is installed at NAOJ Mizusawa Campus in Oshu City, Iwate, Japan. (Related Aeticle: Supercomputer for Astronomy "ATERUI" Upgraded to Double its Speed. (November 13, 2014)) *2 This study used the general-purpose high-performance library for particle simulations FDPS (Framework for Developing Particle Simulator), which was developed by RIKEN Advanced Institute for Computational Science. On parallel computers such as ATERUI, FDPS calculates particle interactions with the ideal load balancing efficiently. By developing the new simulation code with FDPS, the research team succeeded in global simulations of the rings.


News Article | April 25, 2017
Site: phys.org

High-redshift quasars and galaxies (at redshift higher than 5.0) are useful probes of the early universe in many respects. They offer essential clues on the evolution of the intergalactic medium, quasar evolution, early supermassive black hole growth, as well as evolution of galaxies through cosmic times. Generally speaking, they enable scientists to study the universe when it looked much different than it does today. Recently, Matsuoka's team has presented the results from the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, which uses multi-band photometry data provided by the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) survey. HSC is a wide-field camera installed on the Subaru 8.2 m telescope located at the summit of Maunakea, Hawaii and operated by NAOJ. The researchers selected nearly 50 photometric candidates from the HSC-SSP source catalog and then observed them with spectrographs on the Subaru Telescope and the Gran Telescopio Canarias (GTC), located on the island on the Canary Island of La Palma, Spain. The observations resulted in the identification of 24 new quasars and eight new luminous galaxies at redshift between 5.7 and 6.8. "We took optical spectra of 48 candidates with GTC/OSIRIS and Subaru/FOCAS, and newly discovered 24 quasars and 8 luminous galaxies at 5.7 According to the study, the newly detected quasars have lower luminosity than most of the previously known high-redshift quasi-stellar objects, in contrast to the new galaxies, which have extremely high luminosity when compared to other galaxies found at similar redshift. The quasar with the highest redshift (6.8) described in the paper received designation J1429 − 0104, while the one with the lowest redshift (5.92) was named J0903 + 0211. Among the new galaxies, J1628 + 4312 was found at the highest redshift (6.03) and J2237 − 0006 at the lowest (5.77). J2237 − 0006 is also the most luminous newly found galaxy. Meanwhile, the researchers revealed that the SHELLQs project continues, and more new quasars are being discovered, which will be reported in forthcoming papers. "Further survey observations and follow-up studies of the identified objects, including the construction of the quasar luminosity function at z ∼ 6, are ongoing," they wrote in the paper. The authors also noted that they plan to conduct follow-up observations of the newly discovered quasars and galaxies at various wavelengths from sub-millimeter/radio to X-ray. Several of these objects have already been observed with the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, near-infrared spectrographs on the Gemini telescope, located in Hawaii and the Very Large Telescope (VLT), also in Chile. More information: Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). II. Discovery of 32 Quasars and Luminous Galaxies at 5.7 arxiv.org/abs/1704.05854 Abstract We present spectroscopic identification of 32 new quasars and luminous galaxies discovered at 5.7 10^(43) erg/s) and narrow (


News Article | April 28, 2017
Site: phys.org

Visualization was constructed from simulation of Chariklo's double ring. The movie clip can be downloaded from the URL. Credit: Shugo Michikoshi, Eiichiro Kokubo, Hirotaka Nakayama, 4D2U Project, NAOJ A team of researchers in Japan modeled the two rings around Chariklo, the smallest body in the Solar System known to have rings (Figure 1). This is the first time an entire ring system has been simulated using realistic sizes for the ring particles while also taking into account collisions and gravitational interactions between the particles. The team's simulation revealed information about the size and density of the particles in the rings. By considering both the detailed structure and the global picture for the first time, the team found that Chariklo's inner ring should be unstable without help. It is possible the ring particles are much smaller than predicted or that an undiscovered shepherd satellite around Chariklo is stabilizing the ring. In order to elucidate the detailed structure and evolution of Chariklo's rings, Dr. Shugo Michikoshi (Kyoto Women's University/University of Tsukuba) and Prof. Eiichiro Kokubo (National Astronomical Observatory of Japan, NAOJ) performed simulations of the rings by using the supercomputer ATERUI at NAOJ. They calculated the motions of 345 million ring particles with the realistic size of a few meters taking into account the inelastic collisions and mutual gravitational attractions between the particles. Thanks to ATERUI's many CPUs and the small size of Chariklo's ring system, the researchers successfully performed the first ever global simulation with realistic sized particles. Their results show that the density of the ring particles must be less than half the density of Chariklo itself. Their results also showed that a striped pattern, known as "self-gravity wakes," forms in the inner ring due to interactions between the particles (Figure 2). These self-gravity wakes accelerate the break-up of the ring. The team recalculated the expected lifetime of Chariklo's rings based on their results and found it to be only 1 to 100 years, much shorter than previous estimates. This is so short that it's surprising the ring is still there. The research team suggested two possibilities to explain the continued existence of the ring. "Small ring particles is one possibility. If the size of the ring particles is only a few millimeters, the rings can be maintained for 10 million years. Another possibility is the existence of an undiscovered shepherd satellite which slows down the dissolution of the rings." explains Prof. Kokubo. Dr. Michikoshi adds, "The interaction between the rings and a satellite is also an important process in Saturn's rings. To better understand the effect of a satellite on ring structure, we plan to construct a new model for the formation of Chariklo's rings." Ring systems, such as the iconic rings around Saturn and Uranus, are composed of particles ranging from centimeters to meters in size. Until now, the difficultly of calculating the trajectories and mutual interactions of all these particles had confounded attempts to study rings through computer simulations. Previous researchers have either simulated only a portion of a ring system ignoring the overall structure, or used unrealistically large particles and ignored the detailed structures. In 2014, two rings separated by a gap were discovered around Chariklo, the largest known centaur. Centaurs are small bodies wandering between Jupiter and Neptune. Although Chariklo is only hundreds of kilometers in size, its rings are as opaque as those around Saturn and Uranus. Thus Chariklo offered an ideal chance to model a complete ring system. Explore further: The Lords of the Rings among centaurs More information: Shugo Michikoshi et al, Simulating the Smallest Ring World of Chariklo, The Astrophysical Journal (2017). DOI: 10.3847/2041-8213/aa6256


News Article | April 17, 2017
Site: www.eurekalert.org

IMAGE:  Artist concept of the planetary body 2014 UZ224, more informally known as DeeDee. ALMA was able to observe the faint millimeter-wavelength "glow " emitted by the object, confirming it is roughly... view more Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have revealed extraordinary details about a recently discovered far-flung member of our solar system, the planetary body 2014 UZ224, more informally known as DeeDee. At about three times the current distance of Pluto from the Sun, DeeDee is the second most distant known trans-Neptunian object (TNO) with a confirmed orbit, surpassed only by the dwarf planet Eris. Astronomers estimate that there are tens-of-thousands of these icy bodies in the outer solar system beyond the orbit of Neptune. The new ALMA data reveal, for the first time, that DeeDee is roughly 635 kilometers across, or about two-thirds the diameter of the dwarf planet Ceres, the largest member of our asteroid belt. At this size, DeeDee should have enough mass to be spherical, the criteria necessary for astronomers to consider it a dwarf planet, though it has yet to receive that official designation. "Far beyond Pluto is a region surprisingly rich with planetary bodies. Some are quite small but others have sizes to rival Pluto, and could possibly be much larger," said David Gerdes, a scientist with the University of Michigan and lead author on a paper appearing in the Astrophysical Journal Letters. "Because these objects are so distant and dim, it's incredibly difficult to even detect them, let alone study them in any detail. ALMA, however, has unique capabilities that enabled us to learn exciting details about these distant worlds." Currently, DeeDee is about 92 astronomical units (AU) from the Sun. An astronomical unit is the average distance from the Earth to the Sun, or about 150 million kilometers. At this tremendous distance, it takes DeeDee more than 1,100 years to complete one orbit. Light from DeeDee takes nearly 13 hours to reach Earth. Gerdes and his team announced the discovery of DeeDee in the fall of 2016. They found it using the 4-meter Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile as part of ongoing observations for the Dark Energy Survey, an optical survey of about 12 percent of the sky that seeks to understand the as-yet mysterious force that is accelerating the expansion of the universe. The Dark Energy Survey produces vast troves of astronomical images, which give astronomers the opportunity to also search for distant solar system objects. The initial search, which includes nearly 15,000 images, identified more than 1.1 billion candidate objects. The vast majority of these turned out to be background stars and even more distant galaxies. A small fraction, however, were observed to move slowly across the sky over successive observations, the telltale sign of a TNO. One such object was identified on 12 separate images. The astronomers informally dubbed it DeeDee, which is short for Distant Dwarf. The optical data from the Blanco telescope enabled the astronomers to measure DeeDee's distance and orbital properties, but they were unable to determine its size or other physical characteristics. It was possible that DeeDee was a relatively small member of our solar system, yet reflective enough to be detected from Earth. Or, it could be uncommonly large and dark, reflecting only a tiny portion of the feeble sunlight that reaches it; both scenarios would produce identical optical data. Since ALMA observes the cold, dark universe, it is able to detect the heat - in the form of millimeter-wavelength light - emitted naturally by cold objects in space. The heat signature from a distant solar system object would be directly proportional to its size. "We calculated that this object would be incredibly cold, only about 30 degrees Kelvin, just a little above absolute zero," said Gerdes. While the reflected visible light from DeeDee is only about as bright as a candle seen halfway the distance to the moon, ALMA was able to quickly home in on the planetary body's heat signature and measure its brightness in millimeter-wavelength light. This allowed astronomers to determine that it reflects only about 13 percent of the sunlight that hits it. That is about the same reflectivity of the dry dirt found on a baseball infield. By comparing these ALMA observations to the earlier optical data, the astronomers had the information necessary to calculate the object's size. "ALMA picked it up fairly easily," said Gerdes. "We were then able to resolve the ambiguity we had with the optical data alone." Objects like DeeDee are cosmic leftovers from the formation of the solar system. Their orbits and physical properties reveal important details about the formation of planets, including Earth. This discovery is also exciting because it shows that it is possible to detect very distant, slowly moving objects in our own solar system. The researchers note that these same techniques could be used to detect the hypothesized "Planet Nine" that may reside far beyond DeeDee and Eris. "There are still new worlds to discover in our own cosmic backyard," concludes Gerdes. "The solar system is a rich and complicated place." The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.


News Article | February 24, 2017
Site: phys.org

Since that first sighting, SN 1987A has continued to fascinate astronomers with its spectacular light show. Located in the nearby Large Magellanic Cloud, it is the nearest supernova explosion observed in hundreds of years and the best opportunity yet for astronomers to study the phases before, during, and after the death of a star. To commemorate the 30th anniversary of SN 1987A, new images, time-lapse movies, a data-based animation based on work led by Salvatore Orlando at INAF-Osservatorio Astronomico di Palermo, Italy, and a three-dimensional model are being released. By combining data from NASA's Hubble Space Telescope and Chandra X-ray Observatory, as well as the international Atacama Large Millimeter/submillimeter Array (ALMA), astronomers—and the public—can explore SN 1987A like never before. Hubble has repeatedly observed SN 1987A since 1990, accumulating hundreds of images, and Chandra began observing SN 1987A shortly after its deployment in 1999. ALMA, a powerful array of 66 antennas, has been gathering high-resolution millimeter and submillimeter data on SN 1987A since its inception. "The 30 years' worth of observations of SN 1987A are important because they provide insight into the last stages of stellar evolution," said Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and the Gordon and Betty Moore Foundation in Palo Alto, California. The latest data from these powerful telescopes indicate that SN 1987A has passed an important threshold. The supernova shock wave is moving beyond the dense ring of gas produced late in the life of the pre-supernova star when a fast outflow or wind from the star collided with a slower wind generated in an earlier red giant phase of the star's evolution. What lies beyond the ring is poorly known at present, and depends on the details of the evolution of the star when it was a red giant. "The details of this transition will give astronomers a better understanding of the life of the doomed star, and how it ended," said Kari Frank of Penn State University who led the latest Chandra study of SN 1987A. Supernovas such as SN 1987A can stir up the surrounding gas and trigger the formation of new stars and planets. The gas from which these stars and planets form will be enriched with elements such as carbon, nitrogen, oxygen and iron, which are the basic components of all known life. These elements are forged inside the pre-supernova star and during the supernova explosion itself, and then dispersed into their host galaxy by expanding supernova remnants. Continued studies of SN 1987A should give unique insight into the early stages of this dispersal. Some highlights from studies involving these telescopes include: Hubble studies have revealed that the dense ring of gas around the supernova is glowing in optical light, and has a diameter of about a light-year. The ring was there at least 20,000 years before the star exploded. A flash of ultraviolet light from the explosion energized the gas in the ring, making it glow for decades. The central structure visible inside the ring in the Hubble image has now grown to roughly half a light-year across. Most noticeable are two blobs of debris in the center of the supernova remnant racing away from each other at roughly 20 million miles an hour. From 1999 until 2013, Chandra data showed an expanding ring of X-ray emission that had been steadily getting brighter. The blast wave from the original explosion has been bursting through and heating the ring of gas surrounding the supernova, producing X-ray emission. In the past few years, the ring has stopped getting brighter in X-rays. From about February 2013 until the last Chandra observation analyzed in September 2015 the total amount of low-energy X-rays has remained constant. Also, the bottom left part of the ring has started to fade. These changes provide evidence that the explosion's blast wave has moved beyond the ring into a region with less dense gas. This represents the end of an era for SN 1987A. Beginning in 2012, astronomers used ALMA to observe the glowing remains of the supernova, studying how the remnant is actually forging vast amounts of new dust from the new elements created in the progenitor star. A portion of this dust will make its way into interstellar space and may become the building blocks of future stars and planets in another system. These observations also suggest that dust in the early universe likely formed from similar supernova explosions. Astronomers also are still looking for evidence of a black hole or a neutron star left behind by the blast. They observed a flash of neutrinos from the star just as it erupted. This detection makes astronomers quite certain a compact object formed as the center of the star collapsed—either a neutron star or a black hole—but no telescope has uncovered any evidence for one yet. Astronomers combined observations from three different observatories to produce this colorful, multiwavelength image of the intricate remains of Supernova 1987A. Credit: NASA, ESA, and A. Angelich (NRAO/AUI/NSF); Hubble credit: NASA, ESA, and R. Kirshner (Harvard-Smithsonian Center for Astrophysics and Gordon and Betty Moore Foundation) Chandra credit: NASA/CXC/Penn State/K. Frank et al.; ALMA credit: ALMA (ESO/NAOJ/NRAO) and R. Indebetouw (NRAO/AUI/NSF) Explore further: Space image: New supernova remnant lights up


News Article | February 24, 2017
Site: www.eurekalert.org

Three decades ago, astronomers spotted one of the brightest exploding stars in more than 400 years. The titanic supernova, called Supernova 1987A (SN 1987A), blazed with the power of 100 million suns for several months following its discovery on Feb. 23, 1987. Since that first sighting, SN 1987A has continued to fascinate astronomers with its spectacular light show. Located in the nearby Large Magellanic Cloud, it is the nearest supernova explosion observed in hundreds of years and the best opportunity yet for astronomers to study the phases before, during, and after the death of a star. To commemorate the 30th anniversary of SN 1987A, new images, time-lapse movies, a data-based animation based on work led by Salvatore Orlando at INAF-Osservatorio Astronomico di Palermo, Italy, and a three-dimensional model are being released. By combining data from NASA's Hubble Space Telescope and Chandra X-ray Observatory, as well as the international Atacama Large Millimeter/submillimeter Array (ALMA), astronomers -- and the public -- can explore SN 1987A like never before. Hubble has repeatedly observed SN 1987A since 1990, accumulating hundreds of images, and Chandra began observing SN 1987A shortly after its deployment in 1999. ALMA, a powerful array of 66 antennas, has been gathering high-resolution millimeter and submillimeter data on SN 1987A since its inception. "The 30 years' worth of observations of SN 1987A are important because they provide insight into the last stages of stellar evolution," said Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and the Gordon and Betty Moore Foundation in Palo Alto, California. The latest data from these powerful telescopes indicate that SN 1987A has passed an important threshold. The supernova shock wave is moving beyond the dense ring of gas produced late in the life of the pre-supernova star when a fast outflow or wind from the star collided with a slower wind generated in an earlier red giant phase of the star's evolution. What lies beyond the ring is poorly known at present, and depends on the details of the evolution of the star when it was a red giant. "The details of this transition will give astronomers a better understanding of the life of the doomed star, and how it ended," said Kari Frank of Penn State University who led the latest Chandra study of SN 1987A. Supernovas such as SN 1987A can stir up the surrounding gas and trigger the formation of new stars and planets. The gas from which these stars and planets form will be enriched with elements such as carbon, nitrogen, oxygen and iron, which are the basic components of all known life. These elements are forged inside the pre-supernova star and during the supernova explosion itself, and then dispersed into their host galaxy by expanding supernova remnants. Continued studies of SN 1987A should give unique insight into the early stages of this dispersal. Some highlights from studies involving these telescopes include: Hubble studies have revealed that the dense ring of gas around the supernova is glowing in optical light, and has a diameter of about a light-year. The ring was there at least 20,000 years before the star exploded. A flash of ultraviolet light from the explosion energized the gas in the ring, making it glow for decades. The central structure visible inside the ring in the Hubble image has now grown to roughly half a light-year across. Most noticeable are two blobs of debris in the center of the supernova remnant racing away from each other at roughly 20 million miles an hour. From 1999 until 2013, Chandra data showed an expanding ring of X-ray emission that had been steadily getting brighter. The blast wave from the original explosion has been bursting through and heating the ring of gas surrounding the supernova, producing X-ray emission. In the past few years, the ring has stopped getting brighter in X-rays. From about February 2013 until the last Chandra observation analyzed in September 2015 the total amount of low-energy X-rays has remained constant. Also, the bottom left part of the ring has started to fade. These changes provide evidence that the explosion's blast wave has moved beyond the ring into a region with less dense gas. This represents the end of an era for SN 1987A. Beginning in 2012, astronomers used ALMA to observe the glowing remains of the supernova, studying how the remnant is actually forging vast amounts of new dust from the new elements created in the progenitor star. A portion of this dust will make its way into interstellar space and may become the building blocks of future stars and planets in another system. These observations also suggest that dust in the early universe likely formed from similar supernova explosions. Astronomers also are still looking for evidence of a black hole or a neutron star left behind by the blast. They observed a flash of neutrinos from the star just as it erupted. This detection makes astronomers quite certain a compact object formed as the center of the star collapsed -- either a neutron star or a black hole -- but no telescope has uncovered any evidence for one yet. These latest visuals were made possible by combining several sources of information including simulations by Salvatore Orlando and collaborators that appear in this paper: https:/ . The Chandra study by Frank et al. can be found online at http://lanl. . Recent ALMA results on SN 87A are available at https:/ . The Chandra program is managed by NASA's Marshall Space Flight Center in Huntsville, Alabama, for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations. 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 conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of South Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.


News Article | February 15, 2017
Site: www.eurekalert.org

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered a surprising connection between a supermassive black hole and the galaxy where it resides. Powerful radio jets from the black hole - which normally suppress star formation - are stimulating the production of cold gas in the galaxy's extended halo of hot gas. This newly identified supply of cold, dense gas could eventually fuel future star birth as well as feed the black hole itself. The researchers used ALMA to study a galaxy at the heart of the Phoenix Cluster, an uncommonly crowded collection of galaxies about 5.7 billion light-years from Earth. The central galaxy in this cluster harbors a supermassive black hole that is in the process of devouring star-forming gas, which fuels a pair of powerful jets that erupt from the black hole in opposite directions into intergalactic space. Astronomers refer to this type of black-hole powered system as an active galactic nucleus (AGN). Earlier research with NASA's Chandra X-ray observatory revealed that the jets from this AGN are carving out a pair of giant "radio bubbles," huge cavities in the hot, diffuse plasma that surrounds the galaxy. These expanding bubbles should create conditions that are too inhospitable for the surrounding hot gas to cool and condense, which are essential steps for future star formation. The latest ALMA observations, however, reveal long filaments of cold molecular gas condensing around the outer edges of the radio bubbles. These filaments extend up to 82,000 light-years from either side of the AGN. They collectively contain enough material to make about 10 billion suns. "With ALMA we can see that there's a direct link between these radio bubbles inflated by the supermassive black hole and the future fuel for galaxy growth," said Helen Russell, an astronomer with the University of Cambridge, UK, and lead author on a paper appearing in the Astrophysical Journal. "This gives us new insights into how a black hole can regulate future star birth and how a galaxy can acquire additional material to fuel an active black hole." The new ALMA observations reveal previously unknown connections between an AGN and the abundance of cold molecular gas that fuels star birth. "To produce powerful jets, black holes must feed on the same material that the galaxy uses to make new stars," said Michael McDonald, an astrophysicist at the Massachusetts Institute of Technology in Cambridge and coauthor on the paper. "This material powers the jets that disrupt the region and quenches star formation. This illustrates how black holes can slow the growth of their host galaxies." Without a significant source of heat, the most massive galaxies in the universe would be forming stars at extreme rates that far exceed observations. Astronomers believe that the heat, in the form of radiation and jets from an actively feeding supermassive black hole, prevents overcooling of the cluster's hot gas atmosphere, suppressing star formation. This story, however, now appears more complex. In the Phoenix Cluster, Russell and her team found an additional process that ties the galaxy and its black hole together. The radio jets that heat the core of the cluster's hot atmosphere also appear to stimulate the production of the cold gas required to sustain the AGN. "That's what makes this result so surprising," said Brian McNamara, an astronomer at the University of Waterloo, Ontario, and co-author on the paper. "This supermassive black hole is regulating the growth of the galaxy by blowing bubbles and heating the gases around it. Remarkably, it also is cooling enough gas to feed itself." This result helps astronomers understand the workings of the cosmic "thermostat" that controls the launching of radio jets from the supermassive black hole. "This could also explain how the most massive black holes were able to both suppress run-away starbursts and regulate the growth of their host galaxies over the past six billion years or so of cosmic history," noted Russell. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.


News Article | February 28, 2017
Site: www.eurekalert.org

Figuring out the fate of the Universe is one step closer. The first massive dataset of a "cosmic census" is released using the largest digital camera on the Subaru Telescope. Beautiful images are available for public at large. The first dataset from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) was released to the public on February 27th, 2017. HSC-SSP is a large survey being done using HSC, which is an optical imaging camera mounted at the prime focus of the Subaru Telescope. HSC has 104 scientific CCDs (for a total of 870 million pixels) and a 1.77 square-degree field of view. The National Astronomical Observatory of Japan (NAOJ) has embarked on the HSC-SSP survey in collaboration with the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) in Japan, the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan, and Princeton University in the United States. The project will take 300 nights over 5-6 years. This survey consists of three layers; Wide, Deep, and UltraDeep, using optical and near infrared wavelengths in five broad bands (g, r, i, z, y) and four narrow-band filters. This release includes data from the first 1.7 years (61.5 nights of observations beginning in 2014). The observed areas covered by the Wide, Deep, and UltraDeep layers are 108, 26, and 4 square degrees, respectively. The limiting magnitudes, which refer to the depth (Note) of the observations, are 26.4, 26.6 and 27.3 mag in r-band (about 620 nm wavelength), respectively, allowing observations of some of the most distant galaxies in the universe. In the multi-band images, images are extremely sharp, with star images only 0.6 to 0.8 arcseconds across. 1 arcsecond equals 3600th part of a degree. These high-quality data will allow a unprecedented view into the nature and evolution of galaxies and dark matter. This first public dataset already contains 70 million galaxies and stars. It demonstrates that HSC-SSP is making the most of the performance of the Subaru Telescope and HSC. In 2015, using HSC observations over 2.3 square degrees of sky, nine clumps of dark matter, each weighing as much a galaxy cluster were discovered from their weak lensing signature (Miyazaki et al. 2015, ApJ 807, 22, "Properties of Weak Lensing Clusters Detected on Hyper Suprime-Cam 2.3 Square Degree Field"). The HSC-SSP data release covers about 50 times more sky than was used in this study, showing the potential of these data to reveal the statistical properties of dark matter. The total amount of data taken so far comprises 80 terabytes, which is comparable to the size of about 10 million images by a general digital camera. Since it is difficult to search such a huge dataset with standard tools, NAOJ has developed a dedicated database and interface for ease of access and use of the data. "Since 2014, we have been observing the sky with HSC, which can capture a wide-field image with high resolution," said Dr. Satoshi Miyazaki, the leader of the HSC-SSP. "We believe the data release will lead to many exciting astronomical results, from exploring the nature of dark matter and dark energy, as well as asteroids in our own solar system objects and galaxies in the early universe. SSP team members are now preparing a number of scientific papers based on these data. We plan to publish them in a special issue of the Publications of Astronomical Society of Japan. Moreover, we hope that interested members of the public will also access the data and enjoy the real universe imaged by the Subaru telescope, one of the largest the world." "Depth" of an observation refers to how dim objects can be studied. The light collection power of large aperture mirror (8.2 m for the Subaru Telescope) is the crucial factor, as well as the exposure time. For astronomical objects of the same intrinsic brightness, depth is literally how far one can look.


News Article | March 1, 2017
Site: www.eurekalert.org

The universe has come into sharper focus with the release this week of new images from the one of the largest telescopes in the world. A multinational collaboration led by the National Astronomical Observatory of Japan that includes Princeton University scientists has published a "cosmic census" of a large swath of the night sky containing roughly 100 million stars and galaxies, including some of the most distant objects in the universe. These high-quality images allow an unprecedented view into the nature and evolution of galaxies and dark matter. The images and accompanying data were collected using a digital optical-imaging camera on the Subaru Telescope, located at the Mauna Kea Observatory in Hawaii. The camera, known as Hyper Suprime-Cam, is mounted directly in the optical path, at the "prime focus," of the Subaru Telescope. A single image from the camera captures an amount of sky equal to the area of about nine full moons. The project, known as the Hyper Suprime-Cam Subaru Strategic Program, is led by the National Astronomical Observatory of Japan (NAOJ) in collaboration with the Kavli Institute for the Physics and Mathematics of the Universe in Japan, the Academia Sinica Institute of Astronomy and Astrophysics in Taiwan, and Princeton University. The release includes data from the first one-and-a-half years of the project, consisting of 61.5 nights of observations beginning in 2014. The project will take 300 nights over five to six years. The data will allow researchers to look for previously undiscovered galaxies and to search for dark matter, which is matter that neither emits nor absorbs light but which can be detected via its effects on gravity. A 2015 study using Hyper Suprime-Cam sur-veyed 2.3 square degrees of sky and found gravitational signatures of nine clumps of dark matter, each weighing as much as a galaxy cluster (Miyazaki et al., 2015). The current data release covers about 50 times more sky than was used in that study, showing the potential of these data to reveal the statistical properties of dark matter. The survey consists of three layers: a Wide survey that will eventually cover an area equal to 7000 full moons, or 1400 square degrees; a Deep survey that will look farther into the universe and encompass 26 square degrees; and an UltraDeep survey that will cover 3.5 square degrees and penetrate deep into space, allowing observations of some of the most distant galaxies in the universe. The surveys use optical and near infrared wavelengths in five broad wavelength bands (green, red, infrared, z, and y) and four narrow-band filters. In the multi-band images, the images are extremely sharp, with star images only 0.6 to 0.8 arcseconds across. (One arcsecond equals 3600th part of a degree.) The ability to capture images from deep in space is made possible by the light-collection power of the Subaru Telescope's mirror, which has an aperture of 8.2 meters, as well as the image exposure time. The depth into space that one can look is measured in terms of the magnitude, or brightness of objects that can be seen from Earth in a given wavelength band. The depths of the three surveys are characterized by magnitudes in the red band of 26.4, 26.6 and 27.3 in the Wide, Deep and Ultradeep data, respectively. As the survey continues, the Deep and Ultradeep surveys will be able to image fainter objects. The Hyper Suprime-Cam contains 104 scientific charge-coupled devices (CCDs) for a total of 870 million pixels. The total amount of data taken so far comprises 80 terabytes, which is comparable to the size of about 10 million images by a typical digital camera, and covers 108 square degrees. Because it is difficult to search such a huge dataset with standard tools, NAOJ has developed a dedicated database and interface for ease of access and use of the data. "Since 2014, we have been observing the sky with HSC, which can capture a wide-field image with high resolution," said Satoshi Miyazaki, the leader of the project and a scientist at NAOJ. "We believe the data release will lead to many exciting astronomical results, from exploring the nature of dark matter and dark energy, as well as asteroids in our own solar system and galaxies in the early universe. The team members are now preparing a number of scientific papers based on these data. We plan to publish them in a special issue of the Publication of Astronomical Society of Japan. Moreover, we hope that interested members of the public will also access the data and enjoy the real universe imaged by the Subaru telescope, one of the largest the world." At Princeton, the project is co-led by Michael Strauss and Robert Lupton of the De-partment of Astrophysical Sciences. "The HSC data are really beautiful," Strauss said. "Princeton scientists are using these data to explore the nature of merging galaxies, to search for the most distant quasars in the universe, to map the outer reaches of the Milky Way Galaxy, and for many other projects. We are delighted to make these won-derful images available to the world-wide astronomical community." Funding for the HSC Project was provided in part by the following grants: Grant-in-Aid for Scientific Research (B) JP15340065; Grant-in-Aid for Scientific Research on Priority Areas JP18072003; and the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST) entitled, "Uncovering the origin and future of the Universe-ultra-wide-field imaging and spectroscopy reveal the nature of dark matter and dark energy." Funding was also provided by Princeton University.


News Article | February 24, 2017
Site: phys.org

A three-color composite of the mid-infrared images of Saturn on Jan. 23, 2008 captured with COMICS on the Subaru Telescope. The Cassini Division and the C ring appear bright. Color differences reflect the temperatures; the warmer part is blue, the cooler part is red. Credit: NAOJ A team of researchers has succeeded in measuring the brightnesses and temperatures of Saturn's rings using the mid-infrared images taken by the Subaru Telescope in 2008. The images are the highest resolution ground-based views ever made. They reveal that, at that time, the Cassini Division and the C ring were brighter than the other rings in the mid-infrared light and that the brightness contrast appeared to be the inverse of that seen in the visible light (Figure 1). The data give important insights into the nature of Saturn's rings. The beautiful appearance of Saturn and its rings has always fascinated people. The rings consist of countless numbers of ice particles orbiting above Saturn's equator. However, their detailed origin and nature remain unknown. Spacecraft- and ground-based telescopes have tackled that mystery with many observations at various wavelengths and methods. The international Cassini mission led by NASA has been observing Saturn and its rings for more than 10 years, and has released a huge number of beautiful images. The Subaru Telescope also has observed Saturn several times over the years. Dr. Hideaki Fujiwara, Subaru Public Information Officer/Scientist, analyzed data taken in January 2008 using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the telescope to produce a beautiful image of Saturn for public information purposes. During the analysis, he noticed that the appearance of Saturn's rings in the mid-infrared part of the spectrum was totally different from what is seen in the visible light Saturn's main rings consist of the C, B, and A rings, each with different populations of particles. The Cassini Division separates the B and A rings. The 2008 image shows that the Cassini Division and the C ring are brighter in the mid-infrared wavelengths than the B and A rings appear to be (Figure 1). This brightness contrast is the inverse of how they appear in the visible light, where the B and A rings are always brighter than the Cassini Division and the C ring (Figure 2). "Thermal emission" from ring particles is observed in the mid-infrared, where warmer particles are brighter. The team measured the temperatures of the rings from the images, which revealed that the Cassini Division and the C ring are warmer than the B and A rings. The team concluded that this was because the particles in the Cassini Division and C ring are more easily heated by solar light due to their sparser populations and darker surfaces. On the other hand, in the visible light, observers see sunlight being reflected by the ring particles. Therefore, the B and A rings, with their dense populations of particles, always seem bright in the visible wavelengths, while the Cassini Division and the C ring appear faint. The difference in the emission process explains the inverse brightnesses of Saturn's rings between the mid-infrared and the visible-light views. It turns out that the Cassini Division and the C ring are not always brighter than the B and A rings, even in the mid-infrared. The team investigated images of Saturn's rings taken in April 2005 with COMICS, and found that the Cassini Division and the C ring were fainter than the B and A rings at that time, which is the same contrast to what was seen in the visible light (Figure 3). The team concluded that the "inversion" of the brightness of Saturn's rings between 2005 and 2008 was caused by the seasonal change in the ring opening angle to the Sun and Earth. Since the rotation axis of Saturn inclines compared to its orbital plane around the Sun, the ring opening angle to the Sun changes over a 15-year cycle. This makes a seasonal variation in the solar heating of the ring particles. The change in the opening angle viewed from the Earth affects the apparent filling factor of the particles in the rings. These two variations - the temperature and the observed filling factor of the particles - led to the change in the mid-infrared appearance of Saturn's rings. The data taken with the Subaru Telescope revealed that the Cassini Division and the C ring are sometimes bright in the mid-infrared though they are always faint in visible light. "I am so happy that the public information activities of the Subaru Telescope, of which I am in charge, led to this scientific finding," said Dr. Fujiwara. "We are going to observe Saturn again in May 2017 and hope to investigate the nature of Saturn's rings further by taking advantages of observations with space missions and ground-based telescopes." This research is published in Astronomy & Astrophysics, Volume 599, A29 and posted on-line on February 23, 2017 (Fujiwara et al., 2017, "Seasonal variation of the radial brightness contrast of Saturn's rings viewed in mid-infrared by Subaru/COMICS"). More information: Hideaki Fujiwara et al, Seasonal variation of the radial brightness contrast of Saturn's rings viewed in mid-infrared by Subaru/COMICS, Astronomy & Astrophysics (2017). DOI: 10.1051/0004-6361/201527529

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