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News Article | December 20, 2016
Site: www.eurekalert.org

Astronomers have gotten their first look at exactly where most of today's stars were born. To do so, they used the National Science Foundation's Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA) to look at distant galaxies seen as they were some 10 billion years ago. At that time, the Universe was experiencing its peak rate of star formation. Most stars in the present Universe were born then. "We knew that galaxies in that era were forming stars prolifically, but we didn't know what those galaxies looked like, because they are shrouded in so much dust that almost no visible light escapes them," said Wiphu Rujopakam, of the Kavli Institute for the Physics and Mathematics of the Universe at the University of Tokyo and Chulalongkorn University in Bangkok, who was lead author on the research paper. Radio waves, unlike visible light, can get through the dust. However, in order to reveal the details of such distant -- and faint -- galaxies, the astronomers had to make the most sensitive images ever made with the VLA. The new observations, using the VLA and ALMA, have answered longstanding questions about just what mechanisms were responsible for the bulk of star formation in those galaxies. They found that intense star formation in the galaxies they studied most frequently occured throughout the galaxies, as opposed to much smaller regions in present-day galaxies with similar high star-formation rates. The astronomers used the VLA and ALMA to study galaxies in the Hubble Ultra Deep Field, a small area of sky observed since 2003 with NASA's Hubble Space Telescope (HST). The HST made very long exposures of the area to detect galaxies in the far-distant Universe, and numerous observing programs with other telescopes have followed up on the HST work. "We used the VLA and ALMA to see deeply into these galaxies, beyond the dust that obscured their innards from Hubble," said Kristina Nyland, of the National Radio Astronomy Observatory (NRAO). "The VLA showed us where star formation was occurring, and ALMA revealed the cold gas that is the fuel for star formation," she added. "In this study, we made the most sensitive image ever made with the VLA," said Preshanth Jagannathan, also of NRAO. "If you took your cellphone, which transmits a weak radio signal, and put it at more than twice the distance to Pluto, near the outer edge of the solar system, its signal would be roughly as strong as what we detected from these galaxies," he added. The study of the galaxies was done by an international team of astronomers. Others involved include James Dunlop of the University of Edinburgh and Rob Ivison of the University of Edinburgh and the European Southern Observatory. The researchers reported their findings in the Dec. 1 issue of the Astrophysical Journal. 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. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.


News Article | November 21, 2016
Site: www.eurekalert.org

An international team led by researchers from Tohoku University has found an extremely faint dwarf satellite galaxy of the Milky Way. The team's discovery is part of the ongoing Subaru Strategic Survey using Hyper Suprime-Cam. The satellite, named Virgo I, lies in the direction of the constellation Virgo. At the absolute magnitude of -0.8 in the optical waveband, it may well be the faintest satellite galaxy yet found. Its discovery suggests the presence of a large number of yet-undetected dwarf satellites in the halo of the Milky Way and provides important insights into galaxy formation through hierarchical assembly of dark matter. Currently, some 50 satellite galaxies to the Milky Way have been identified. About 40 of them are faint and diffuse and belong to the category of so-called "dwarf spheroidal galaxies". Many recently discovered dwarf galaxies, especially those seen in systematic photometric surveys such as the Sloan Digital Sky Survey (SDSS) and the Dark Energy Survey (DES) are very faint with absolute luminosity in the optical waveband below -8 magnitude. These are so-called "ultra-faint dwarf galaxies". However, previous searches made use of telescopes with a diameter of 2.5 to 4 meters, so only satellites relatively close to the Sun or those with higher magnitudes were identified. Those that are more distant or faint ones in the halo of the Milky Way are yet to be detected. The combination of the large aperture of 8.2-meter Subaru Telescope and the large field-of-view Hyper Suprime-Cam (HSC) instrument is very powerful in this study. It enables an efficient search for very faint dwarf satellites over large areas of the sky. The first step in searching out a new dwarf galaxy is to identify an over density of stars in the sky, using photometric data. Next is to assess that the over dense appearance is not due to line-of-sight or accidental juxtapositions of unrelated dense fields, but is really a stellar system. The standard method for doing this is to look for a characteristic distribution of stars in the color-magnitude diagram (comparable to the Hertzsprung-Russell diagram). Stars in a general field shows no particular patterns in this diagram. Daisuke Homma, a graduate student at Tohoku University, found Virgo I under the guidance of his advisor, Masashi Chiba, and their international collaborators. "We have carefully examined the early data of the Subaru Strategic Survey with HSC and found an apparent over density of stars in Virgo with very high statistical significance, showing a characteristic pattern of an ancient stellar system in the color-magnitude diagram," he said. "Surprisingly, this is one of the faintest satellites, with absolute magnitude of -0.8 in the optical waveband. This is indeed a galaxy, because it is spatially extended with a radius of 124 light years - systematically larger than a globular cluster with comparable luminosity." The faintest dwarf satellites identified so far was Segue I, discovered by SDSS (-1.5 mag) and Cetus II in DES (0.0 mag). Cetus II is yet to be confirmed, as it is too compact as a galaxy. Virgo I may ultimately turn out to be the faintest one ever discovered. It lies at a distance of 280,000 light years from the Sun, and such a remote galaxy with faint brightness has not been identified in previous surveys. It is beyond the reach of SDSS, which has previously surveyed the same area in the direction of the constellation Virgo. According to Chiba, the leader of this search project, the discovery has profound implications. "This discovery implies hundreds of faint dwarf satellites waiting to be discovered in the halo of the Milky Way," he said. "How many satellites are indeed there and what properties they have, will give us an important clue of understanding how the Milky Way formed and how dark matter contributed to it." Formation of galaxies like the Milky Way is thought to proceed through the hierarchical assembly of dark matter, forming dark halos, and through the subsequent infall of gas and star formation affected by gravity. Standard models of galaxy formation in the context of the so-called cold dark matter (CDM) theory predict the presence of hundreds of small dark halos orbiting in a Milky Way-sized dark halo and a comparable number of luminous satellite companions. However, only tens of satellites have ever been identified. This falls well short of a theoretical predicted number, which is part of the so-called "missing satellite problem". Astronomers may need to consider other types of dark matter than CDM or to invoke baryonic physics suppressing galaxy formation to explain the shortfall in the number of satellites. Another possibility is that they have seen only a fraction of all the satellites associated with the Milky Way due to various observational biases. The issue remains unsolved. One of the motivations for the Subaru Strategic Survey using HSC is to do increase observations in the search for Milky Way satellites. The early data from this survey is what led to the discovery of Virgo I. This program will continue to explore much wider areas of the sky and is expected to find more satellites like Virgo I. These tiny companions to be discovered in the near future may tell us much more about history of the Milky Way's formation. Daisuke Homma (Tohoku University, Japan), Masashi Chiba (Tohoku University, Japan), Sakurako Okamoto (Shanghai Astronomical Observatory, China), Yutaka Komiyama (National Astronomical Observatory of Japan (NAOJ), Japan), Masayuki Tanaka (NAOJ, Japan), Mikito Tanaka (Tohoku University, Japan), Miho N. Ishigaki (Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), University of Tokyo, Japan), Masayuki Akiyama (Tohoku University, Japan), Nobuo Arimoto (Subaru Telescope, NAOJ, USA), Jose A, Garmilla (Princeton University, USA), Robert H. Lupton (Princeton University, USA), Michael A. Strauss (Princeton University, USA), Hisanori Furusawa (NAOJ, Japan), Satoshi Miyazaki (NAOJ, Japan), Hitoshi Murayama (Kavli IPMU, WPI, University of Tokyo, Japan), Atsushi J. Nishizawa (Nagoya University, Japan), Masahiro Takada (Kavli IPMU, WPI, University of Tokyo, Japan), Tomonori Usuda (NAOJ, Japan), Shiang-Yu Wang (Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan) Leo II: An Old Dwarf Galaxy with Juvenescent Heart http://subarutelescope.


News Article | December 20, 2016
Site: phys.org

At that time, the Universe was experiencing its peak rate of star formation. Most stars in the present Universe were born then. "We knew that galaxies in that era were forming stars prolifically, but we didn't know what those galaxies looked like, because they are shrouded in so much dust that almost no visible light escapes them," said Wiphu Rujopakam, of the Kavli Institute for the Physics and Mathematics of the Universe at the University of Tokyo and Chulalongkorn University in Bangkok, who was lead author on the research paper. Radio waves, unlike visible light, can get through the dust. However, in order to reveal the details of such distant—and faint—galaxies, the astronomers had to make the most sensitive images ever made with the VLA. The new observations, using the VLA and ALMA, have answered longstanding questions about just what mechanisms were responsible for the bulk of star formation in those galaxies. They found that intense star formation in the galaxies they studied most frequently occured throughout the galaxies, as opposed to much smaller regions in present-day galaxies with similar high star-formation rates. The astronomers used the VLA and ALMA to study galaxies in the Hubble Ultra Deep Field, a small area of sky observed since 2003 with NASA's Hubble Space Telescope (HST). The HST made very long exposures of the area to detect galaxies in the far-distant Universe, and numerous observing programs with other telescopes have followed up on the HST work. "We used the VLA and ALMA to see deeply into these galaxies, beyond the dust that obscured their innards from Hubble," said Kristina Nyland, of the National Radio Astronomy Observatory (NRAO). "The VLA showed us where star formation was occurring, and ALMA revealed the cold gas that is the fuel for star formation," she added. "In this study, we made the most sensitive image ever made with the VLA," said Preshanth Jagannathan, also of NRAO. "If you took your cellphone, which transmits a weak radio signal, and put it at more than twice the distance to Pluto, near the outer edge of the solar system, its signal would be roughly as strong as what we detected from these galaxies," he added. The study of the galaxies was done by an international team of astronomers. Others involved include James Dunlop of the University of Edinburgh and Rob Ivison of the University of Edinburgh and the European Southern Observatory. The researchers reported their findings in the Dec. 1 issue of the Astrophysical Journal. Explore further: Forming stars in the early universe More information: W. Rujopakarn et al. VLA AND ALMA IMAGING OF INTENSE GALAXY-WIDE STAR FORMATION IN∼ 2 GALAXIES, The Astrophysical Journal (2016). DOI: 10.3847/0004-637X/833/1/12 , arxiv.org/abs/1607.07710


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

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." 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." Explore further: Tracing the cosmic web with star-forming galaxies in the distant universe


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 2, 2017
Site: www.chromatographytechniques.com

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 surveyed 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."


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 | January 25, 2016
Site: phys.org

An international team of researchers, including Carnegie Mellon University's Rachel Mandelbaum, has shown that the relationship between galaxy clusters and their surrounding dark matter halo is more complex than previously thought. The researchers' findings, published in Physical Review Letters today, are the first to use observational data to show that, in addition to mass, a galaxy cluster's formation history plays a role in how it interacts with its environment. There is a connection between galaxy clusters and their dark matter halos that holds a great deal of information about the universe's content of dark matter and accelerating expansion due to dark energy. Galaxy clusters are groupings of hundreds to thousands of galaxies bound together by gravity, and are the most massive structures found in the universe. These clusters are embedded in a halo of invisible dark matter. Traditionally, cosmologists have predicted and interpreted clustering by calculating just the masses of the clusters and their halos. However, theoretical studies and cosmological simulations suggested that mass is not the only element at play—something called assembly bias, which takes into account when and how a galaxy cluster formed, also could impact clustering. "Simulations have shown us that assembly bias should be part of our picture," said Mandelbaum, a member of Carnegie Mellon's McWilliams Center for Cosmology. "Confirming this observationally is an important piece of understanding galaxy and galaxy cluster formation and evolution." In the current study, the research team, led by Hironao Miyatake, Surhud More and Masahiro Takada of the Kavli Institute for the Physics and Mathematics of the Universe, analyzed observational data from the Sloan Digital Sky Survey's DR8 galaxy catalog. Using this data, they demonstrated that when and where galaxies group together within a cluster impacts the cluster's relationship with its dark matter environment. The researchers divided close to 9,000 galaxy clusters into two groups based on the spatial distribution of the galaxies in each cluster. One group consisted of clusters with galaxies aggregated at the center and the other consisted of clusters in which the galaxies were more diffuse. They then used a technique called gravitational lensing to show that, while the two groups of clusters had the same mass, they interacted with their environment much differently. The group of clusters with diffuse galaxies were much more clumpy than the group of clusters that had their galaxies close to the center. "Measuring the way galaxy clusters clump together on large scales is a linchpin of modern cosmology. We can go forward knowing that mass might not be the only factor in clustering," Mandelbaum said. Explore further: Dark matter and galaxies part ways in collision between hefty galaxy clusters More information: Evidence of Halo Assembly Bias in Massive Clusters, Physical Review Letters, dx.doi.org/10.1103/PhysRevLett.116.041301 , journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.041301 , On Arxiv: journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.041301


Late last year, in a pair of research papers, Space Warps announced the discovery of 29 new gravitational lenses. These arced or blobby features, seen in images of deep space, are actually distant galaxies whose light has been bent by the mass of foreground galaxies. Scientists prize these rare, cosmic phenomena because they offer tantalizing glimpses of objects too distant and dim to be otherwise seen. This haul of lenses was obtained over an 8-month period by about 37,000 Space Warps volunteers who reviewed 430,000 digital images in a massive, online photo library. Automated computer programs have identified most of the approximately 500 gravitational lenses discovered to date. However, computers failed to flag the 29 lenses the Space Warps volunteers spotted. "Human beings are very good at pattern recognition. The dynamic range that our eyes and our brains offer is much greater than a computer algorithm," said Anupreeta More, a project researcher at the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) at the University of Tokyo and a co-principal investigator for Space Warps. More was one of the three astrophysicists who participated in a roundtable discussion, hosted by The Kavli Foundation, about the growing role that citizen scientists are playing in astrophysics. More and her colleagues designed Space Warps to take advantage of these human abilities. So far, besides the 29 new gravitational lens candidates, Space Warpers have also turned up a never-before-seen lensing scenario that looks like a red ring in the project's image archive. Researchers are still working out the source of this red ring, which they suspect is the warped features of a background galaxy containing a supermassive black hole as well as regions of new star formation. Discovering such strange, new phenomena is a hallmark of citizen science. Among the most famous examples is Hanny's Voorwerp, a galaxy-size gas cloud discovered in 2007 in a project called Galaxy Zoo, one of the earliest astronomy projects. "Citizen scientists... have really enabled us to produce important findings. They've inspired us with their dedication and productivity," said Aprajita Verma, a senior researcher in the department of physics at the University of Oxford and also a co-principal investigator for Space Warps. "We've learned from our analysis that basically anyone who joins Space Warps has an impact on the results." As astronomical datasets continue to increase in size, there will be no shortage of opportunities for eager citizen scientists. For instance, the Large Synoptic Survey Telescope, opening in 2022, will collect 30 terabytes of data nightly as it observes the whole sky every few days from the vantage of the Southern Hemisphere. Computerized object-recognition programs will certainly play an important role in analyzing these data, but human volunteers are likely to remain integral. "I think there will be citizen involvement for a long while and it will become more interesting as we use machines to do more of the routine work and filter the data," said Chris Lintott, a professor of astrophysics and the citizen science lead at the University of Oxford. "The tasks for citizen scientists will involve more varied things—more of the unusual, Hanny's Voorwerp-type of discoveries." Lintott, who is also a co-founder of Galaxy Zoo and the principal investigator for the Zooniverse citizen science web portal, added: "Plus, a lot of unusual discoveries will need to be followed up, and I'd like to see citizen scientists get further into the process of analysis. Without them, I think we're going to end up with a pile of interesting objects which professional scientists just don't have time to deal with." More information: Read the full conversation with astrophysicists Anupreeta More, Aprajita Verma and Chris Lintott on The Kavli Foundation website: www.kavlifoundation.org/science-spotlights/crowdsourcing-universe-how-citizen-scientists-are-driving-discovery


News Article | January 10, 2016
Site: phys.org

Astronomers from the Sloan Digital Sky Survey (SDSS) this morning announced the results of a new study that reveals the true origin of puzzling light from nearby galaxies. Results were presented at the 227th meeting of the American Astronomical Society in Kissimmee, Florida. "We now know that white dwarfs, not central black holes, explain these observations," says Francesco Belfiore, the lead author of the study and a graduate student at the University of Cambridge. "Because we know that white dwarfs are to blame, we are much closer to understanding how galaxies retire from the star-formation business." To solve the mystery, Belfiore's team looked at the thin interstellar gas that lies between stars in nearby galaxies. They used information from the emission lines of the spectra of that hot, glowing gas to decode what energy source lights it up. Understanding the origin of these emission lines is far from straightforward. In particular, astronomers have long been puzzled by the energy source for a particular state of gas in galaxies: The source must be hotter than newly formed stars but cooler than the radiation from a violently accreting black hole, like a quasar. The leading theory used to be that this gas was lit by a wimpy active galactic nucleus, which is only accreting very small amounts of gas. This idea was supported by the fact that nuclear regions of many galaxies show such Low-Ionization Nuclear Emission-line Regions, which were therefore called LINERs. "LINERs are a 35-year-old puzzle," says Belfiore. "In recent years, several astronomers have argued against the mainstream interpretation and presented evidence that not all LINERs are due to black holes. The new SDSS data gave us a chance to take a new look at this question and evaluate possible alternative theories. Previous spectroscopic observations were insufficient because they generally covered only a small portion of a galaxy near its center. A new SDSS instrument, called MaNGA (MApping Nearby Galaxies at Apache Point Observatory), is now capable of obtaining spectroscopic data for the whole galaxy at once. "To get the data we need, we use a simple but innovative design," says Kevin Bundy from the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), Principal Investigator for the MaNGA survey and co-author of the study. "We tie together a few dozen optical fibers into a large hexagonal bundle and point them at a galaxy. The bundle covers most of the galaxy and each fiber measures the spectrum at a different point." Belfiore and his collaborators used the MaNGA data to map the state of gas and stars throughout more than 600 LINER galaxies. 'By taking advantage of the fact that MaNGA can get data for an entire galaxy at once, we have revealed that the sources lighting the gas up must be distributed throughout the galaxy, even tens of thousands of light years away from the central black hole. This proves that the emission lines we see cannot all be due to central black holes," says Belfiore. Claudia Maraston of the University of Portsmouth, a co-author of the study, explains the most likely answer to the LINER puzzle. "White dwarfs are revealed as stars lose their outer gas envelopes and expose their hot cores, which still glows at millions of degrees. These newly-exposed white dwarfs are the ideal sources to light up the interstellar gas and produce the emission lines we see," says Maraston. Although this mechanism was originally suggested to be important only in elliptical galaxies, the new MaNGA data reveals that it is in fact common in both elliptical and spiral galaxies. "In the spiral galaxies, the gas shining as LINERs is the dying gasp of star formation being quenched as gas reservoirs are depleted in inner regions and star formation moves to the outer suburbs. In the elliptical galaxies, where almost all star formation occurred rapidly in the early days of the Universe, this glowing gas represents a 'rejuvenation' of the dormant galaxy," says Belfiore. "Donated gas, from dying stars within the galaxy or from a merging galaxy, is now able to intercept the extreme radiation and make the galaxy shine again, albeit only as a LINER." With the extensive mapping of low-ionization emission-line regions outside of the nuclei of galaxies, far removed from central supermassive black holes, but close to newly born white dwarfs, the 'N' for 'nuclear' in the LINER acronym must disappear. The truth, then, is this: many galaxies are LIERs.

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