STRONG GRAVITATIONAL LENSING BY THE SUPER-MASSIVE cD GALAXY IN ABELL 3827

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carrasco, E. R.; Gomez, P. L.; Lee, H.

2010-06-01

We have discovered strong gravitational lensing features in the core of the nearby cluster Abell 3827 by analyzing Gemini South GMOS images. The most prominent strong lensing feature is a highly magnified, ring-shaped configuration of four images around the central cD galaxy. GMOS spectroscopic analysis puts this source at z {approx} 0.2. Located {approx}20'' away from the central galaxy is a secondary tangential arc feature which has been identified as a background galaxy with z {approx} 0.4. We have modeled the gravitational potential of the cluster core, taking into account the mass from the cluster, the brightest cluster galaxy (BCG),more » and other galaxies. We derive a total mass of (2.7 {+-} 0.4) x 10{sup 13} M {sub sun} within 37 h {sup -1} kpc. This mass is an order of magnitude larger than that derived from X-ray observations. The total mass derived from lensing data suggests that the BCG in this cluster is perhaps the most massive galaxy in the nearby universe.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogle, Patrick M.; Lanz, Lauranne; Nader, Cyril

We report the discovery of spiral galaxies that are as optically luminous as elliptical brightest cluster galaxies, with r-band monochromatic luminosity L{sub r} = 8–14L* (4.3–7.5 × 10{sup 44} erg s{sup −1}). These super spiral galaxies are also giant and massive, with diameter D = 57–134 kpc and stellar mass M{sub stars} = 0.3–3.4 × 10{sup 11}M{sub ⊙}. We find 53 super spirals out of a complete sample of 1616 SDSS galaxies with redshift z < 0.3 and L{sub r} > 8L*. The closest example is found at z = 0.089. We use existing photometry to estimate their stellar masses and star formation rates (SFRs). The SDSS and Wide-field Infrared Survey Explorer colors aremore » consistent with normal star-forming spirals on the blue sequence. However, the extreme masses and rapid SFRs of 5–65 M{sub ⊙} yr{sup −1} place super spirals in a sparsely populated region of parameter space, above the star-forming main sequence of disk galaxies. Super spirals occupy a diverse range of environments, from isolation to cluster centers. We find four super spiral galaxy systems that are late-stage major mergers—a possible clue to their formation. We suggest that super spirals are a remnant population of unquenched, massive disk galaxies. They may eventually become massive lenticular galaxies after they are cut off from their gas supply and their disks fade.« less

Discovery of Super-Thin Disks in Nearby Edge-on Spiral Galaxies

NASA Astrophysics Data System (ADS)

Schechtman-Rook, A.; Bershady, M. A.

2014-03-01

We report the identification of a super-thin disk (hz˜ 60 pc) in the edge-on spiral galaxy NGC 891. This component is only apparent after we perform a physically motivated attenuation correction, based on detailed radiation transfer models, to our sub-arcsecond resolution near-infrared imaging. In addition to the super-thin disk, we also find several structural features near the center of NGC 891, including an inner disk truncation at ˜3 kpc. Inner disk truncations may be commonplace among massive spiral galaxies, possibly due to the effects of instabilities, such as bars. Having successfully demonstrated our methods, we are poised to apply them to a small sample of nearby edge-on galaxies, consisting both of massive and low-mass spirals.

FAST TRACK COMMUNICATION The Bel-Robinson tensor for topologically massive gravity

NASA Astrophysics Data System (ADS)

Deser, S.; Franklin, J.

2011-02-01

We construct, and establish the (covariant) conservation of, a 4-index 'super stress tensor' for topologically massive gravity. Separately, we discuss its invalidity in quadratic curvature models and suggest a generalization.

Digging for red nuggets: discovery of hot haloes surrounding massive, compact, relic galaxies

NASA Astrophysics Data System (ADS)

Werner, N.; Lakhchaura, K.; Canning, R. E. A.; Gaspari, M.; Simionescu, A.

2018-07-01

We present the results of Chandra X-ray observations of the isolated, massive, compact, relic galaxies MRK 1216 and PGC 032873. Compact massive galaxies observed at z > 2, also called red nuggets, formed in quick dissipative events and later grew by dry mergers into the local giant ellipticals. Due to the stochastic nature of mergers, a few of the primordial massive galaxies avoided the mergers and remained untouched over cosmic time. We find that the hot atmosphere surrounding MRK 1216 extends far beyond the stellar population and has a 0.5-7 keV X-ray luminosity of LX = (7.0 ± 0.2) × 1041 erg s-1, which is similar to the nearby X-ray bright giant ellipticals. The hot gas has a short central cooling time of ˜50 Myr and the galaxy has an ˜13-Gyr-old stellar population. The presence of an X-ray atmosphere with a short nominal cooling time and the lack of young stars indicate the presence of a sustained heating source, which prevented star formation since the dissipative origin of the galaxy 13 Gyr ago. The central temperature peak and the presence of radio emission in the core of the galaxy indicate that the heating source is radio-mechanical active galactic nucleus (AGN) feedback. Given that both MRK 1216 and PGC 032873 appear to have evolved in isolation, the order of magnitude difference in their current X-ray luminosity could be traced back to a difference in the ferocity of the AGN outbursts in these systems. Finally, we discuss the potential connection between the presence of hot haloes around such massive galaxies and the growth of super-/overmassive black holes via chaotic cold accretion.

Keck Observations of the Gas Dynamics at the Galactic Center

NASA Astrophysics Data System (ADS)

Campbell, Randall; Ciurlo, Anna; Morris, Mark; Sitarski, Breann N.; Ghez, Andrea M.; Do, Tuan

2018-06-01

In the central parsec of the Milky Way Galaxy the environment of the super-massive black hole (SMBH) presents a complicated mixture of stars, gas, and dust. These inner few tens of arcseconds of the GC have been observed at high resolution with Keck for 20 years with the primary goal of monitoring stars orbiting the SMBH. However, the gas features and their dynamics can also be closely examined using this unique baseline of data. In particular, observations with the Keck OSIRIS integral field spectrometer allow us to examine of the dynamical properties of the gas and to possibly identify new “G-type” objects, or dusty stellar objects. We present a study of morphology and orbital dynamics of sub-parsec scale gas features in the central region.

Canibalismo Extremo y Lente Gravitacional Intensa en el Cúmulo de Galaxias Abell 3827

NASA Astrophysics Data System (ADS)

Díaz, R. J.; West, M.; Bergmann, M.; Carrasco, E. R.; Gomez, P.; Lee, H.; Miller, B.; Turner, J.

Abell 3827 is one of the most massive known clusters and at its center we observe an extreme example of galactic canibalism: a super giant elliptical galaxy in its formation process, devoring five massive galaxies at the same time. Using high spatial resolution Gemini+GMOS imagery and multi-object spectroscopy, we derived the redshift (z=0.099) and the radial velocity dispersion of the 55 brightest galaxies in the cluster central region (1134 +- 125 km/s). The estimated virial mass is ~ 1E14 M(sun) inside a radius of 300 kpc of the cluster center. We have also found features corresponding to a strong gravitational lense, four anular features arranged in an Einstein Ring from a galaxy (z=0.2) at double redshift than the cluster, and a fifth arclet feature corresponding to the lensed light of a farther galaxy (z=0.4). The possible Einstein Ring is of small angular size and the gravitational lense morphology would confirm that the cluster is indeed very massive and dense. FULL TEXT IN SPANISH.

RUNAWAY MASSIVE STARS FROM R136: VFTS 682 IS VERY LIKELY A 'SLOW RUNAWAY'

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Sambaran; Kroupa, Pavel; Oh, Seungkyung, E-mail: sambaran@astro.uni-bonn.de, E-mail: pavel@astro.uni-bonn.de, E-mail: skoh@astro.uni-bonn.de

2012-02-10

We conduct a theoretical study on the ejection of runaway massive stars from R136-the central massive, starburst cluster in the 30 Doradus complex of the Large Magellanic Cloud. Specifically, we investigate the possibility of the very massive star (VMS) VFTS 682 being a runaway member of R136. Recent observations of the above VMS, by virtue of its isolated location and its moderate peculiar motion, have raised the fundamental question of whether isolated massive star formation is indeed possible. We perform the first realistic N-body computations of fully mass-segregated R136-type star clusters in which all the massive stars are in primordialmore » binary systems. These calculations confirm that the dynamical ejection of a VMS from an R136-like cluster, with kinematic properties similar to those of VFTS 682, is common. Hence, the conjecture of isolated massive star formation is unnecessary to account for this VMS. Our results are also quite consistent with the ejection of 30 Dor 016, another suspected runaway VMS from R136. We further note that during the clusters' evolution, mergers of massive binaries produce a few single stars per cluster with masses significantly exceeding the canonical upper limit of 150 M{sub Sun }. The observations of such single super-canonical stars in R136, therefore, do not imply an initial mass function with an upper limit greatly exceeding the accepted canonical 150 M{sub Sun} limit, as has been suggested recently, and they are consistent with the canonical upper limit.« less

Radiation pressure in super star cluster formation

NASA Astrophysics Data System (ADS)

Tsang, Benny T.-H.; Milosavljević, Miloš

2018-05-01

The physics of star formation at its extreme, in the nuclei of the densest and the most massive star clusters in the universe—potential massive black hole nurseries—has for decades eluded scrutiny. Spectroscopy of these systems has been scarce, whereas theoretical arguments suggest that radiation pressure on dust grains somehow inhibits star formation. Here, we harness an accelerated Monte Carlo radiation transport scheme to report a radiation hydrodynamical simulation of super star cluster formation in turbulent clouds. We find that radiation pressure reduces the global star formation efficiency by 30-35%, and the star formation rate by 15-50%, both relative to a radiation-free control run. Overall, radiation pressure does not terminate the gas supply for star formation and the final stellar mass of the most massive cluster is ˜1.3 × 106 M⊙. The limited impact as compared to in idealized theoretical models is attributed to a radiation-matter anti-correlation in the supersonically turbulent, gravitationally collapsing medium. In isolated regions outside massive clusters, where the gas distribution is less disturbed, radiation pressure is more effective in limiting star formation. The resulting stellar density at the cluster core is ≥108 M⊙ pc-3, with stellar velocity dispersion ≳ 70 km s-1. We conclude that the super star cluster nucleus is propitious to the formation of very massive stars via dynamical core collapse and stellar merging. We speculate that the very massive star may avoid the claimed catastrophic mass loss by continuing to accrete dense gas condensing from a gravitationally-confined ionized phase.

Chandra Provides New View of Biggest Construction Sites in Universe

NASA Astrophysics Data System (ADS)

2003-05-01

Images made by NASA's Chandra X-ray Observatory have revealed two distant cosmic construction sites buzzing with activity. This discovery shows how super massive black holes control the growth of massive galaxies in the distant universe. X-rays were detected from vast clouds of high-energy particles around the galaxies 3C294 and 4C41.17, which are 10 and 12 billion light years from Earth, respectively. The energetic particles were left over from past explosive events that can be traced through the X-ray and radio jets back to the super massive black holes located in the centers of the galaxies. "These galaxies are revealing an energetic phase in which a super massive black hole transfers considerable energy into the gas surrounding the galaxies," said Andrew Fabian of England's Cambridge University, lead author of a paper on 3C294 to appear in an upcoming issue of the Monthly Notices of the Royal Astronomical Society. "This appears to be crucial in explaining the puzzling properties of present-day galaxies, especially those that group together in large clusters," he said. The picture that is emerging is of a grand cosmic cycle. A dense region of intergalactic gas cools to form several smaller galaxies, which merge to form a larger galaxy with a super massive black hole. The galaxy and its central black hole continue to grow until the energy generated by jets from the vicinity of the voracious black hole stops the fall of matter into the black hole. Millions of years after the jet activity subsides, matter will resume falling into the black hole and the cycle begins anew. 4C41.17 and 3C294 4C41.17 Both 3C294 and 4C41.17 reside in regions of space containing unusually high numbers of galaxies. The gas and galaxies surrounding these galaxies will eventually collapse to form galaxy clusters, some of the most massive objects in the universe. Although 3C294 and 4C41.17 will grow to gargantuan sizes, through the accumulation of surrounding matter that forms hundreds of billions of stars, their growth does not go unchecked. "It's as if nature tries to impose a weight limit on the size of the most massive galaxies," said Caleb Scharf of Columbia University, N.Y., and lead author of a paper on 4C41.17 to be published in The Astrophysical Journal. "The Chandra observations have given us an important clue as to how this occurs. The high energy jets give the super massive black holes an extended reach to regulate the growth of these galaxies," he said. In 3C294 and 4C41.17, the hot swirling infernos around their super massive black holes have launched magnetized jets of high energy particles first identified by radio telescopes. These jets, which were also detected by Chandra, have swept up clouds of dust and gas and have helped trigger the formation of billions of new stars. The dusty, star-forming clouds of 4C41.17, the most powerful source of infrared radiation ever observed, are embedded in even larger clouds of gas. Astronomers recently used the Keck Observatory to observe these larger clouds, which have a temperature of 10,000 degree Celsius gas. These clouds are leftover material from the galaxy's formation and should have cooled rapidly by radiation in the absence of a heat source. Animation of How Supermassive Black Holes Affect the Formation of Massive Galaxies Animation of How Supermassive Black Holes Affect the Formation of Massive Galaxies "Significantly, the warm gas clouds coincide closely with the largest extent of the X-ray emission," said Michiel Reuland of Lawrence Livermore National Laboratory, Livermore, Calif., a coauthor on the 4C41.17 paper and a paper describing Keck Observatory work. "The Chandra results show that high energy particles or radiation can supply the necessary energy to light up these clouds," he said. Most of the X-rays from 4C41.17 and 3C294 are due to collisions of energetic electrons with the cosmic background of photons produced in the hot early universe. Because these galaxies are far away, their observed radiation originated when the universe was younger and the background was more intense. This effect enhances the X-radiation and helps astronomers to study extremely distant galaxies. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program, and TRW, Inc., Redondo Beach, Calif., is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, Mass., for the Office of Space Science, NASA Headquarters, Washington. Images and additional information about this result are available at: http://chandra.harvard.edu and http://chandra.nasa.gov

Panchromatic observations of dwarf starburst galaxies: Infant super star clusters and a low-luminosity AGN

NASA Astrophysics Data System (ADS)

Reines, Amy Ellen

2011-01-01

Globular star clusters and supermassive black holes are fundamental components of today's massive galaxies, with origins dating back to the very early universe. Both globular clusters and the seeds of supermassive black holes are believed to have formed in the progenitors of modern massive galaxies, although the details are poorly understood. Direct observations of these low-mass, distant, and hence faint systems are unobtainable with current capabilities. However, gas-rich dwarf starburst galaxies in the local universe, analogous in many ways to protogalaxies at high-redshift, can provide critical insight into the early stages of galaxy evolution including the formation of globular clusters and massive black holes. This thesis presents a panchromatic study of nearby dwarf starburst galaxies harboring nascent globular clusters still embedded in their birth material. Infant clusters are identified via their production of thermal radio emission at centimeter wavelengths, which comes from dense gas ionized by young massive stars. By combining radio observations with complementary data at ultraviolet, optical and infrared wavelengths, we obtain a comprehensive view of massive clusters emerging from their gaseous and dusty birth cocoons. This thesis also presents the first example of a nearby dwarf starburst galaxy hosting an actively accreting massive central black hole. The black hole in this dwarf galaxy is unusual in that it is not associated with a bulge, a nuclear star cluster, or any other well-defined nucleus, likely reflecting an early phase of black hole and galaxy evolution that has not been previously observed.

Young and Exotic Stellar Zoo

NASA Astrophysics Data System (ADS)

2005-03-01

Summary Super star clusters are groups of hundreds of thousands of very young stars packed into an unbelievably small volume. They represent the most extreme environments in which stars and planets can form. Until now, super star clusters were only known to exist very far away, mostly in pairs or groups of interacting galaxies. Now, however, a team of European astronomers [1] have used ESO's telescopes to uncover such a monster object within our own Galaxy, the Milky Way, almost, but not quite, in our own backyard! The newly found massive structure is hidden behind a large cloud of dust and gas and this is why it took so long to unveil its true nature. It is known as "Westerlund 1" and is a thousand times closer than any other super star cluster known so far. It is close enough that astronomers may now probe its structure in some detail. Westerlund 1 contains hundreds of very massive stars, some shining with a brilliance of almost one million suns and some two-thousand times larger than the Sun (as large as the orbit of Saturn)! Indeed, if the Sun were located at the heart of this remarkable cluster, our sky would be full of hundreds of stars as bright as the full Moon. Westerlund 1 is a most unique natural laboratory for the study of extreme stellar physics, helping astronomers to find out how the most massive stars in our Galaxy live and die. From their observations, the astronomers conclude that this extreme cluster most probably contains no less than 100,000 times the mass of the Sun, and all of its stars are located within a region less than 6 light-years across. Westerlund 1 thus appears to be the most massive compact young cluster yet identified in the Milky Way Galaxy. PR Photo 09a/05: The Super Star Cluster Westerlund 1 (2.2m MPG/ESO + WFI) PR Photo 09b/05: Properties of Young Massive Clusters Super Star Clusters Stars are generally born in small groups, mostly in so-called "open clusters" that typically contain a few hundred stars. From a wide range of observations, astronomers infer that the Sun itself was born in one such cluster, some 4,500 million years ago. In some active ("starburst") galaxies, scientists have observed violent episodes of star formation (see, for example, ESO Press Photo 31/04), leading to the development of super star clusters, each containing several million stars. Such events were obviously common during the Milky Way's childhood, more than 12,000 million years ago: the many galactic globular clusters - which are nearly as old as our Galaxy (e.g. ESO PR 20/04) - are indeed thought to be the remnants of early super star clusters. All super star clusters so far observed in starburst galaxies are very distant. It is not possible to distinguish their individual stars, even with the most advanced technology. This dramatically complicates their study and astronomers have therefore long been eager to find such clusters in our neighbourhood in order to probe their structure in much more detail. Now, a team of European astronomers [1] has finally succeeded in doing so, using several of ESO's telescopes at the La Silla observatory (Chile). Westerlund 1 ESO PR Photo 09a/05 ESO PR Photo 09a/05 The Super Star Cluster Westerlund 1 (2.2m MPG/ESO + WFI) [Preview - JPEG: 400 x 472 pix - 58k] [Normal - JPEG: 800 x 943 pix - 986k] [Full Res - JPEG: 1261 x 1486 pix - 2.4M] Caption: ESO PR Photo 09a/05 is a composite image of the super star cluster "Westerlund 1" from 2.2-m MPG/ESO Wide-Field Imager (WFI) observations. The image covers a 5 x 5 arcmin sky region and is based on observations made in the V-band (550 nm, 2 min exposure time, associated to the blue channel), R-band (650nm, 1 min, green channel) and I-band (784nm, 18 sec, red channel). Only the central CCD of WFI was used, as the entire cluster fits comfortably inside it. The foreground stars appear blue, while the hot massive members of the cluster look orange, and the cool massive ones come out red. The open cluster Westerlund 1 is located in the Southern constellation Ara (the Altar). It was discovered in 1961 from Australia by Swedish astronomer Bengt Westerlund, who later moved from there to become ESO Director in Chile (1970 - 74). This cluster is behind a huge interstellar cloud of gas and dust, which blocks most of its visible light. The dimming factor is more than 100,000 - and this is why it has taken so long to uncover the true nature of this particular cluster. In 2001, the team of astronomers identified more than a dozen extremely hot and peculiar massive stars in the cluster, so-called "Wolf-Rayet" stars. They have since studied Westerlund 1 extensively with various ESO telescopes. They used images from the Wide Field Imager (WFI) attached to the 2.2-m ESO/MPG as well as from the SUperb Seeing Imager 2 (SuSI2) camera on the ESO 3.5-m New Technology Telescope (NTT). From these observations, they were able to identify about 200 cluster member stars. To establish the true nature of these stars, the astronomers then performed spectroscopic observations of about one quarter of them. For this, they used the Boller & Chivens spectrograph on the ESO 1.52-m telescope and the ESO Multi-Mode Instrument (EMMI) on the NTT. An Exotic Zoo These observations have revealed a large population of very bright and massive, quite extreme stars. Some would fill the solar system space within the orbit of Saturn (about 2,000 times larger than the Sun!), others are as bright as a million Suns. Westerlund 1 is obviously a fantastic stellar zoo, with a most exotic population and a true astronomical bonanza. All stars identified are evolved and very massive, spanning the full range of stellar oddities from Wolf-Rayet stars, OB supergiants, Yellow Hypergiants (nearly as bright as a million Suns) and Luminous Blue Variables (similar to the exceptional Eta Carinae object - see ESO PR 31/03). All stars so far analysed in Westerlund 1 weigh at least 30-40 times more than the Sun. Because such stars have a rather short life - astronomically speaking - Westerlund 1 must be very young. The astronomers determine an age somewhere between 3.5 and 5 million years. So, Westerlund 1 is clearly a "newborn" cluster in our Galaxy! The Most Massive Cluster ESO PR Photo 09b/05 ESO PR Photo 09b/05 Properties of Young Massive Clusters [Preview - JPEG: 400 x 511 pix - 20k] [Normal - JPEG: 800 x 1021 pix - 122k] Caption: ESO PR Photo 09b/05 shows the properties of young massive clusters in our Galaxy and in the Large Magellanic Clouds, as well as of Super Star Clusters in star-forming galaxies. The diagram shows the mass and radius of these clusters and also the position of Westerlund 1 (indicated Wd 1). Westerlund 1 is incredibly rich in monster stars - just as one example, it contains as many Yellow Hypergiants as were hitherto known in the entire Milky Way! "If the Sun were located at the heart of Westerlund 1, the sky would be full of stars, many of them brighter than the full Moon", comments Ignacio Negueruela of the Universidad de Alicante in Spain and member of the team. The large quantity of very massive stars implies that Westerlund 1 must contain a huge number of stars. "In our Galaxy, explains Simon Clark of the University College London (UK) and one of the authors of this study, "there are more than 100 solar-like stars for every star weighing 10 times as much as the Sun. The fact that we see hundreds of massive stars in Westerlund 1 means that it probably contains close to half a million stars, but most of these are not bright enough to peer through the obscuring cloud of gas and dust". This is ten times more than any other known young clusterin the Milky Way. Westerlund 1 is presumably much more massive than the dense clusters of heavy stars present in the central region of our Galaxy, like the Arches and Quintuplet clusters. Further deep infrared observations will be required to confirm this. This super star cluster now provides astronomers with a unique perspective towards one of the most extreme environments in the Universe. Westerlund 1 will certainly provide new opportunities in the long-standing quest for more and finer details about how stars, and especially massive ones, do form. ... and the Most Dense The large number of stars in Westerlund 1 was not the only surprise awaiting Clark and his colleagues. From their observations, the team members also found that all these stars are packed into an amazingly small volume of space, indeed less than 6 light-years across. In fact, this is more or less comparable to the 4 light-year distance to the star nearest to the Sun, Proxima Centauri! It is incredible: the concentration in Westerlund 1 is so high that the mean separation between stars is quite similar to the extent of the Solar System. "With so many stars in such a small volume, some of them may collide", envisages Simon Clark. "This could lead to the formation of an intermediate-mass black hole more massive than 100 solar masses. It may well be that such a monster has already formed at the core of Westerlund 1." The huge population of massive stars in Westerlund 1 suggests that it will have a very significant impact on its surroundings. The cluster contains so many massive stars that in a time span of less than 40 million years, it will be the site of more than 1,500 supernovae. A gigantic firework that may drive a fountain of galactic material! Because Westerlund 1 is at a distance of only about 10,000 light-years, high-resolution cameras such as NAOS/CONICA on ESO's Very Large Telescope can resolve its individual stars. Such observations are now starting to reveal smaller stars in Westerlund 1, including some that are less massive than the Sun. Astronomers will thus soon be able to study this exotic galactic zoo in great depth. More information The research presented in this ESO Press Release will soon appear in the leading research journal Astronomy and Astrophysics ("On the massive stellar population of the Super Star Cluster Westerlund 1" by J.S. Clark and colleagues). The PDF file is available at the A&A web site. A second paper ("Further Wolf-Rayet stars in the starburst cluster Westerlund 1", by Ignacio Negueruela and Simon Clark) will also soon be published in Astronomy and Astrophysics. It is available as astro-ph/0503303. A Spanish press release issued by Universidad de Alicante is available on the web site of Ignacio Negueruela.

Constraints and Superspin for SuperPoincare Algebras in Diverse Dimensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pasqua, Andrea; Zumino, Bruno

2004-04-27

We generalize to arbitrary dimension the construction of a covariant and supersymmetric constraint for the massless superPoincare algebra, which was given for the eleven-dimensional case in a previous work. We also contrast it with a similar construction appropriate to the massive case. Finally we show that the constraint uniquely fixes the representation of the algebra.

The SUNBIRD survey: characterizing the super star cluster populations of intensely star-forming galaxies

NASA Astrophysics Data System (ADS)

Randriamanakoto, Zara; Väisänen, Petri

2017-03-01

Super star clusters (SSCs) represent the youngest and most massive form of known gravitationally bound star clusters in the Universe. They are born abundantly in environments that trigger strong and violent star formation. We investigate the properties of these massive SSCs in a sample of 42 nearby starbursts and luminous infrared galaxies. The targets form the sample of the SUperNovae and starBursts in the InfraReD (SUNBIRD) survey that were imaged using near-infrared (NIR) K-band adaptive optics mounted on the Gemini/NIRI and the VLT/NaCo instruments. Results from i) the fitted power-laws to the SSC K-band luminosity functions, ii) the NIR brightest star cluster magnitude - star formation rate (SFR) relation and iii) the star cluster age and mass distributions have shown the importance of studying SSC host galaxies with high SFR levels to determine the role of the galactic environments in the star cluster formation, evolution and disruption mechanisms.

Supermassive and super-hungry

NASA Image and Video Library

2016-01-04

This NASA/ESA Hubble Space Telescope image shows the spiral galaxy NGC 4845, located over 65 million light-years away in the constellation of Virgo (The Virgin). The galaxy’s orientation clearly reveals the galaxy’s striking spiral structure: a flat and dust-mottled disc surrounding a bright galactic bulge. NGC 4845’s glowing centre hosts a gigantic version of a black hole, known as a supermassive black hole. The presence of a black hole in a distant galaxy like NGC 4845 can be inferred from its effect on the galaxy’s innermost stars; these stars experience a strong gravitational pull from the black hole and whizz around the galaxy’s centre much faster than otherwise. From investigating the motion of these central stars, astronomers can estimate the mass of the central black hole — for NGC 4845 this is estimated to be hundreds of thousands times heavier than the Sun. This same technique was also used to discover the supermassive black hole at the centre of our own Milky Way — Sagittarius A* — which hits some four million times the mass of the Sun (potw1340a). The galactic core of NGC 4845 is not just supermassive, but also super-hungry. In 2013 researchers were observing another galaxy when they noticed a violent flare at the centre of NGC 4845. The flare came from the central black hole tearing up and feeding off an object many times more massive than Jupiter. A brown dwarf or a large planet simply strayed too close and was devoured by the hungry core of NGC 4845.

Dynamics of supernova remnants in the Galactic centre.

NASA Astrophysics Data System (ADS)

Bortolas, E.; Mapelli, M.; Spera, M.

The Galactic centre (GC) is a unique place to study the extreme dynamical processes occurring near a super-massive black hole (SMBH). Here we simulate a large set of binaries orbiting the SMBH while the primary member undergoes a supernova (SN) explosion, in order to study the impact of SN kicks on the orbits of stars and dark remnants in the GC. We find that SN explosions are efficient in scattering neutron stars and other light stars on new (mostly eccentric) orbits, while black holes (BHs) tend to retain memory of the orbit of their progenitor star. SN kicks are thus unable to eject BHs from the GC: a cusp of dark remnants may be lurking in the central parsec of our Galaxy.

Observing the Super-Massive Black Hole of the Galactic center with Simbol-X .

NASA Astrophysics Data System (ADS)

Goldwurm, A.

The Center of our Galaxy is one of the prime objective of the Simbol-X mission. This region of several square degrees around the dynamical center of the galaxy hosts a large variety of high energy sources and violent phenomena that involve different non-thermal processes contributing to the hard X-ray emission from the region. Here we present in detail the case for the observation of Sgr A*, the super-massive black hole of the galactic nucleus, with Simbol-X, stressing on the presently open questions and on the crucial measurements that will be performed in the hard X-ray domain with this formation-flying hard X-ray focussing telescope expected to flight in the next decade.

The star-forming complex LMC-N79 as a future rival to 30 Doradus

NASA Astrophysics Data System (ADS)

Ochsendorf, Bram B.; Zinnecker, Hans; Nayak, Omnarayani; Bally, John; Meixner, Margaret; Jones, Olivia C.; Indebetouw, Remy; Rahman, Mubdi

2017-11-01

Within the early Universe, `extreme' star formation may have been the norm rather than the exception1,2. Super star clusters (with masses greater than 105 solar masses) are thought to be the modern-day analogues of globular clusters, relics of a cosmic time (redshift z ≳ 2) when the Universe was filled with vigorously star-forming systems3. The giant H ii region 30 Doradus in the Large Magellanic Cloud is often regarded as a benchmark for studies of extreme star formation4. Here, we report the discovery of a massive embedded star-forming complex spanning about 500 pc in the unexplored southwest region of the Large Magellanic Cloud, which manifests itself as a younger, embedded twin of 30 Doradus. Previously known as N79, this region has a star-formation efficiency greater than that of 30 Doradus, by a factor of about 2, as measured over the past 0.5 Myr. Moreover, at the heart of N79 lies the most luminous infrared compact source discovered with large-scale infrared surveys of the Large Magellanic Cloud and Milky Way, possibly a precursor to the central super star cluster of 30 Doradus, R136. The discovery of a nearby candidate super star cluster may provide invaluable information to understand how extreme star formation proceeds in the current and high-redshift Universe.

BINARY BLACK HOLES, GAS SLOSHING, AND COLD FRONTS IN THE X-RAY HALO HOSTING 4C+37.11

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrade-Santos, Felipe; Bogdán, Ákos; Forman, William R.

We analyzed deep Chandra ACIS-I exposures of the cluster-scale X-ray halo surrounding the radio source 4C+37.11. This remarkable system hosts the closest resolved pair of super-massive black holes and an exceptionally luminous elliptical galaxy, the likely product of a series of past mergers. We characterize the halo with r {sub 500} ∼ 0.95 Mpc, M {sub 500} = 2.5 ± 0.2 × 10{sup 14} M {sub ⊙}, kT = 4.6 ± 0.2 keV, and a gas mass of M {sub g,500} = 2.2 ± 0.1 × 10{sup 13} M {sub ⊙}. The gas mass fraction within r {sub 500} ismore » f {sub g} = 0.09 ± 0.01. The entropy profile shows large non-gravitational heating in the central regions. We see several surface brightness jumps, associated with substantial temperature and density changes but approximate pressure equilibrium, implying that these are sloshing structures driven by a recent merger. A residual intensity image shows a core spiral structure closely matching that seen in the Perseus cluster, although at z = 0.055 the spiral pattern is less distinct. We infer that the most recent merger occurred 1–2 Gyr ago and that the event that brought the two observed super-massive black holes to the system core is even older. Under this interpretation, the black hole binary pair has, unusually, remained at a parsec-scale separation for more than 2 Gyr.« less

Hot super-Earths and giant planet cores from different migration histories

NASA Astrophysics Data System (ADS)

Cossou, Christophe; Raymond, Sean N.; Hersant, Franck; Pierens, Arnaud

2014-09-01

Planetary embryos embedded in gaseous protoplanetary disks undergo Type I orbital migration. Migration can be inward or outward depending on the local disk properties but, in general, only planets more massive than several M⊕ can migrate outward. Here we propose that an embryo's migration history determines whether it becomes a hot super-Earth or the core of a giant planet. Systems of hot super-Earths (or mini-Neptunes) form when embryos migrate inward and pile up at the inner edge of the disk. Giant planet cores form when inward-migrating embryos become massive enough to switch direction and migrate outward. We present simulations of this process using a modified N-body code, starting from a swarm of planetary embryos. Systems of hot super-Earths form in resonant chains with the innermost planet at or interior to the disk inner edge. Resonant chains are disrupted by late dynamical instabilities triggered by the dispersal of the gaseous disk. Giant planet cores migrate outward toward zero-torque zones, which move inward and eventually disappear as the disk disperses. Giant planet cores migrate inward with these zones and are stranded at ~1-5 AU. Our model reproduces several properties of the observed extra-solar planet populations. The frequency of giant planet cores increases strongly when the mass in solids is increased, consistent with the observed giant exoplanet - stellar metallicity correlation. The frequency of hot super-Earths is not a function of stellar metallicity, also in agreement with observations. Our simulations can reproduce the broad characteristics of the observed super-Earth population.

A RAPIDLY EVOLVING REGION IN THE GALACTIC CENTER: WHY S-STARS THERMALIZE AND MORE MASSIVE STARS ARE MISSING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Xian; Amaro-Seoane, Pau, E-mail: Xian.Chen@aei.mpg.de, E-mail: Pau.Amaro-Seoane@aei.mpg.de

2014-05-10

The existence of ''S-stars'' within a distance of 1'' from Sgr A* contradicts our understanding of star formation, due to Sgr A* 's forbiddingly violent environment. A suggested possibility is that they form far away and were brought in by some fast dynamical process, since they are young. Nonetheless, all conjectured mechanisms either fail to reproduce their eccentricities—without violating their young age—or cannot explain the problem of {sup i}nverse mass segregation{sup :} the fact that lighter stars (the S-stars) are closer to Sgr A* and more massive ones, Wolf-Rayet (WR) and O-stars, are farther out. In this Letter we proposemore » that the mechanism responsible for both the distribution of the eccentricities and the paucity of massive stars is the Kozai-Lidov-like resonance induced by a sub-parsec disk recently discovered in the Galactic center. Considering that the disk probably extended to a smaller radius in the past, we show that in as short as (a few) 10{sup 6} yr, the stars populating the innermost 1'' region would redistribute in angular-momentum space and recover the observed ''super-thermal'' distribution. Meanwhile, WR and O-stars in the same region intermittently attain ample eccentricities that will lead to their tidal disruptions by the central massive black hole. Our results provide new evidences that Sgr A* was powered several millions years ago by an accretion disk as well as by tidal stellar disruptions.« less

Super-AGB Stars and their Role as Electron Capture Supernova Progenitors

NASA Astrophysics Data System (ADS)

Doherty, Carolyn L.; Gil-Pons, Pilar; Siess, Lionel; Lattanzio, John C.

2017-11-01

We review the lives, deaths and nucleosynthetic signatures of intermediate-mass stars in the range ≈6-12 M⊙, which form super-AGB stars near the end of their lives. The critical mass boundaries both between different types of massive white dwarfs (CO, CO-Ne, ONe), and between white dwarfs and supernovae, are examined along with the relative fraction of super-AGB stars that end life either as an ONe white dwarf or as a neutron star (or an ONeFe white dwarf), after undergoing an electron capture supernova event. The contribution of the other potential single-star channel to electron-capture supernovae, that of the failed massive stars, is also discussed. The factors that influence these different final fates and mass limits, such as composition, rotation, the efficiency of convection, the nuclear reaction rates, mass-loss rates, and third dredge-up efficiency, are described. We stress the importance of the binary evolution channels for producing electron-capture supernovae. Recent nucleosynthesis calculations and elemental yield results are discussed and a new set of s-process heavy element yields is presented. The contribution of super-AGB star nucleosynthesis is assessed within a Galactic perspective, and the (super-)AGB scenario is considered in the context of the multiple stellar populations seen in globular clusters. A brief summary of recent works on dust production is included. Last, we conclude with a discussion of the observational constraints and potential future advances for study into these stars on the low mass/high mass star boundary.

X-Ray Mosaic of Milky Way Taken by the Chandra X-Ray Observatory

NASA Technical Reports Server (NTRS)

2001-01-01

The Chandra X-Ray Observatory (CXO) has made a sturning, high-energy panorama of the central regions of our Milky Way galaxy. The findings are an important step toward understanding the most active area of the Milky Way as well as other galaxies throughout the universe. This 400 by 900-light-year mosaic of several CXO images reveals hundreds of white dwarf stars, neutron stars, and black holes bathed in an incandescent fog of miltimillion-degree gas. The diffuse x-ray emission seems to be related to the turmoil and density of matter in the inner Milky Way. Stars are forming there at a much more rapid rate than in the galactic 'suburbs.' Many of the most massive stars in the galaxy are located in the galactic center and are furiously boiling off their outer layers in searing stellar winds. Supernova explosions are far more common in the region and send shock waves booming through the inner galaxy. The super massive black hole at the center of the galaxy is located inside the bright white patch in the center of the image. The colors indicate x-ray energy bands-red (low), green (medial), and blue (high). A supernova occurs when a massive star has used up its nuclear fuel and the pressure drops in the central core of the star. The matter in the core is crushed by gravity to higher and higher densities, and temperatures reach billions of degrees. Under these extreme conditions, nuclear reactions occur violently and catastrophically reversing the collapse. A thermonuclear shock wave races through the now expanding stellar debris, fusing lighter elements into heavier ones and producing a brilliant visual outburst. (Photo credit: NASA/UMass/D. Wang et al)

History of Chandra X-Ray Observatory

NASA Image and Video Library

2001-07-01

The Chandra X-Ray Observatory (CXO) has made a sturning, high-energy panorama of the central regions of our Milky Way galaxy. The findings are an important step toward understanding the most active area of the Milky Way as well as other galaxies throughout the universe. This 400 by 900-light-year mosaic of several CXO images reveals hundreds of white dwarf stars, neutron stars, and black holes bathed in an incandescent fog of miltimillion-degree gas. The diffuse x-ray emission seems to be related to the turmoil and density of matter in the inner Milky Way. Stars are forming there at a much more rapid rate than in the galactic "suburbs." Many of the most massive stars in the galaxy are located in the galactic center and are furiously boiling off their outer layers in searing stellar winds. Supernova explosions are far more common in the region and send shock waves booming through the inner galaxy. The super massive black hole at the center of the galaxy is located inside the bright white patch in the center of the image. The colors indicate x-ray energy bands-red (low), green (medial), and blue (high). A supernova occurs when a massive star has used up its nuclear fuel and the pressure drops in the central core of the star. The matter in the core is crushed by gravity to higher and higher densities, and temperatures reach billions of degrees. Under these extreme conditions, nuclear reactions occur violently and catastrophically reversing the collapse. A thermonuclear shock wave races through the now expanding stellar debris, fusing lighter elements into heavier ones and producing a brilliant visual outburst. (Photo credit: NASA/UMass/D. Wang et al)

Radiation hydrodynamics of super star cluster formation

NASA Astrophysics Data System (ADS)

Tsang, Benny Tsz Ho; Milos Milosavljevic

2018-01-01

Throughout the history of the Universe, the nuclei of super star clusters represent the most active sites for star formation. The high densities of massive stars within the clusters produce intense radiation that imparts both energy and momentum on the surrounding star-forming gas. Theoretical claims based on idealized geometries have claimed the dominant role of radiation pressure in controlling the star formation activity within the clusters. In order for cluster formation simulations to be reliable, numerical schemes have to be able to model accurately the radiation flows through the gas clumps at the cluster nuclei with high density contrasts. With a hybrid Monte Carlo radiation transport module we developed, we performed 3D radiation hydrodynamical simulations of super star cluster formation in turbulent clouds. Furthermore, our Monte Carlo radiation treatment provides a native capability to produce synthetic observations, which allows us to predict observational indicators and to inform future observations. We found that radiation pressure has definite, but minor effects on limiting the gas supply for star formation, and the final mass of the most massive cluster is about one million solar masses. The ineffective forcing was due to the density variations inside the clusters, i.e. radiation takes the paths of low densities and avoids forcing on dense clumps. Compared to a radiation-free control run, we further found that the presence of radiation amplifies the density variations. The core of the resulting cluster has a high stellar density, about the threshold required for stellar collisions and merging. The very massive star that form from the stellar merging could continue to gain mass from the surrounding gas reservoir that is gravitationally confined by the deep potential of the cluster, seeding the potential formation of a massive black hole.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bromley, Benjamin C.; Kenyon, Scott J., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu

Correlations in the orbits of several minor planets in the outer solar system suggest the presence of a remote, massive Planet Nine. With at least 10 times the mass of the Earth and a perihelion well beyond 100 au, Planet Nine poses a challenge to planet formation theory. Here we expand on a scenario in which the planet formed closer to the Sun and was gravitationally scattered by Jupiter or Saturn onto a very eccentric orbit in an extended gaseous disk. Dynamical friction with the gas then allowed the planet to settle in the outer solar system. We explore thismore » possibility with a set of numerical simulations. Depending on how the gas disk evolves, scattered super-Earths or small gas giants settle on a range of orbits, with perihelion distances as large as 300 au. Massive disks that clear from the inside out on million-year timescales yield orbits that allow a super-Earth or gas giant to shepherd the minor planets as observed. A massive planet can achieve a similar orbit in a persistent, low-mass disk over the lifetime of the solar system.« less

Deep learning massively accelerates super-resolution localization microscopy.

PubMed

Ouyang, Wei; Aristov, Andrey; Lelek, Mickaël; Hao, Xian; Zimmer, Christophe

2018-06-01

The speed of super-resolution microscopy methods based on single-molecule localization, for example, PALM and STORM, is limited by the need to record many thousands of frames with a small number of observed molecules in each. Here, we present ANNA-PALM, a computational strategy that uses artificial neural networks to reconstruct super-resolution views from sparse, rapidly acquired localization images and/or widefield images. Simulations and experimental imaging of microtubules, nuclear pores, and mitochondria show that high-quality, super-resolution images can be reconstructed from up to two orders of magnitude fewer frames than usually needed, without compromising spatial resolution. Super-resolution reconstructions are even possible from widefield images alone, though adding localization data improves image quality. We demonstrate super-resolution imaging of >1,000 fields of view containing >1,000 cells in ∼3 h, yielding an image spanning spatial scales from ∼20 nm to ∼2 mm. The drastic reduction in acquisition time and sample irradiation afforded by ANNA-PALM enables faster and gentler high-throughput and live-cell super-resolution imaging.

UVIT observations of the star-forming ring in NGC 7252: Evidence of possible AGN feedback suppressing central star formation

NASA Astrophysics Data System (ADS)

George, K.; Joseph, P.; Mondal, C.; Devaraj, A.; Subramaniam, A.; Stalin, C. S.; Côté, P.; Ghosh, S. K.; Hutchings, J. B.; Mohan, R.; Postma, J.; Sankarasubramanian, K.; Sreekumar, P.; Tandon, S. N.

2018-05-01

Context. Some post-merger galaxies are known to undergo a starburst phase that quickly depletes the gas reservoir and turns it into a red-sequence galaxy, though the details are still unclear. Aims: Here we explore the pattern of recent star formation in the central region of the post-merger galaxy NGC 7252 using high-resolution ultraviolet (UV) images from the UVIT on ASTROSAT. Methods: The UVIT images with 1.2 and 1.4 arcsec resolution in the FUV and NUV are used to construct a FUV-NUV colour map of the central region. Results: The FUV-NUV pixel colour map for this canonical post-merger galaxy reveals a blue circumnuclear ring of diameter 10'' (3.2 kpc) with bluer patches located over the ring. Based on a comparison to single stellar population models, we show that the ring is comprised of stellar populations with ages ≲300 Myr, with embedded star-forming clumps of younger age (≲150Myr). Conclusions: The suppressed star formation in the central region, along with the recent finding of a large amount of ionised gas, leads us to speculate that this ring may be connected to past feedback from a central super-massive black hole that has ionised the hydrogen gas in the central 4'' 1.3 kpc.

An Astrophysical Laboratory: Understanding and Exploiting the Young Massive Cluster Westerlund 1

NASA Astrophysics Data System (ADS)

Clark, S.; Negueruela, I.; Ritchie, B.; Najarro, P.; Langer, N.; Crowther, P.; Bartlett, L.; Fenech, D.; González-Fernández, C.; Goodwin, S.; Lohr, M.; Prinja, R.

2015-03-01

Westerlund 1 provides a unique opportunity to probe the physics of massive stars, from birth to death and beyond, as well as the formation and evolution of a super star cluster that appears destined to evolve into a globular cluster. We highlight the result of current studies of this cluster, its diverse stellar constituents and immediate environment, concluding with a summary of future research avenues enabled by ESO facilities.

Development and Applications of a Modular Parallel Process for Large Scale Fluid/Structures Problems

NASA Technical Reports Server (NTRS)

Guruswamy, Guru P.; Byun, Chansup; Kwak, Dochan (Technical Monitor)

2001-01-01

A modular process that can efficiently solve large scale multidisciplinary problems using massively parallel super computers is presented. The process integrates disciplines with diverse physical characteristics by retaining the efficiency of individual disciplines. Computational domain independence of individual disciplines is maintained using a meta programming approach. The process integrates disciplines without affecting the combined performance. Results are demonstrated for large scale aerospace problems on several supercomputers. The super scalability and portability of the approach is demonstrated on several parallel computers.

Climbing to the top of the galactic mass ladder: evidence for frequent prolate-like rotation among the most massive galaxies

NASA Astrophysics Data System (ADS)

Krajnović, Davor; Emsellem, Eric; den Brok, Mark; Marino, Raffaella Anna; Schmidt, Kasper Borello; Steinmetz, Matthias; Weilbacher, Peter M.

2018-07-01

We present the stellar velocity maps of 25 massive early-type galaxies located in dense environments observed with MUSE. Galaxies are selected to be brighter than MK = -25.7 mag, reside in the core of the Shapley Super Cluster or be the brightest galaxy in clusters richer than the Virgo Cluster. We thus targeted galaxies more massive than 1012 M⊙ and larger than 10 kpc (half-light radius). The velocity maps show a large variety of kinematic features: oblate-like regular rotation, kinematically distinct cores, and various types of non-regular rotation. The kinematic misalignment angles show that massive galaxies can be divided into two categories: those with small or negligible misalignment and those with misalignment consistent with being 90°. Galaxies in this latter group, comprising just under half of our galaxies, have prolate-like rotation (rotation around the major axis). Among the brightest cluster galaxies the incidence of prolate-like rotation is 50 per cent, while for a magnitude limited sub-sample of objects within the Shapley Super Cluster (mostly satellites), 35 per cent of galaxies show prolate-like rotation. Placing our galaxies on the mass-size diagram, we show that they all fall on a branch extending almost an order of magnitude in mass and a factor of 5 in size from the massive end of galaxies, previously recognized as associated with major dissipation-less mergers. The presence of galaxies with complex kinematics and, particularly, prolate-like rotators suggests, according to current numerical simulations, that the most massive galaxies grow predominantly through dissipation-less equal-mass mergers.

Climbing to the top of the galactic mass ladder: evidence for frequent prolate-like rotation among the most massive galaxies

NASA Astrophysics Data System (ADS)

Krajnović, Davor; Emsellem, Eric; den Brok, Mark; Marino, Raffaella Anna; Schmidt, Kasper Borello; Steinmetz, Matthias; Weilbacher, Peter M.

2018-04-01

We present the stellar velocity maps of 25 massive early-type galaxies located in dense environments observed with MUSE. Galaxies are selected to be brighter than MK = -25.7 magnitude, reside in the core of the Shapley Super Cluster or be the brightest galaxy in clusters richer than the Virgo Cluster. We thus targeted galaxies more massive than 1012 M⊙ and larger than 10 kpc (half-light radius). The velocity maps show a large variety of kinematic features: oblate-like regular rotation, kinematically distinct cores and various types of non-regular rotation. The kinematic misalignment angles show that massive galaxies can be divided into two categories: those with small or negligible misalignment, and those with misalignment consistent with being 90°. Galaxies in this latter group, comprising just under half of our galaxies, have prolate-like rotation (rotation around the major axis). Among the brightest cluster galaxies the incidence of prolate-like rotation is 50 per cent, while for a magnitude limited sub-sample of objects within the Shapley Super Cluster (mostly satellites), 35 per cent of galaxies show prolate-like rotation. Placing our galaxies on the mass - size diagram, we show that they all fall on a branch extending almost an order of magnitude in mass and a factor of 5 in size from the massive end of galaxies, previously recognised as associated with major dissipation-less mergers. The presence of galaxies with complex kinematics and, particularly, prolate-like rotators suggests, according to current numerical simulations, that the most massive galaxies grow predominantly through dissipation-less equal-mass mergers.

Prototyping an active neutron veto for SuperCDMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calkins, Robert; Loer, Ben

2015-08-17

Neutrons, originating cosmogenically or from radioactive decays, can produce signals in dark matter detectors that are indistinguishable from Weakly Interacting Massive Particles (WIMPs). To combat this background for the SuperCDMS SNOLAB experiment, we are investigating designs for an active neutron veto within the constrained space of the compact SuperCDMS passive shielding. The current design employs an organic liquid scintillator mixed with an agent to enhance thermal neutron captures, with the scintillation light collected using wavelength-shifting fibers and read out by silicon photo-multipliers. We will describe the proposed veto and its predicted efficiency in detail and give some recent results frommore » our R&D and prototyping efforts.« less

Prototyping an Active Neutron Veto for SuperCDMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calkins, Robert; Loer, Ben

2015-08-17

Neutrons, originating cosmogenically or from radioactive decays, can produce signals in dark matter detectors that are indistinguishable from Weakly Interacting Massive Particles (WIMPs). To combat this background for the SuperCDMS SNOLAB experiment, we are investigating designs for an active neutron veto within the constrained space of the compact SuperCDMS passive shielding. The current design employs an organic liquid scintillator mixed with an agent to enhance thermal neutron captures, with the scintillation light collected using wavelength-shifting fibers and read out by silicon photo-multipliers. We will describe the proposed veto and its predicted efficiency in detail and give some recent results frommore » our R&D and prototyping efforts.« less

Theoretical models of highly magnetic white dwarf stars that violate the Chandrasekhar Limit

NASA Astrophysics Data System (ADS)

Shah, Hridaya

2017-08-01

Until recently, white dwarf (WD) stars were believed to be no more massive than 1.44 solar masses (M ⊙ ). This belief has been changed now with the observations of over-luminous or 'peculiar' Type la supernovae that have lead researchers to hypothesize the existence of WDs in the mass range 2.4 - 2.8 M ⊙ . This discovery also raises some doubt over the reliability of the Type Ia supernova as a standard candle. It is thought that these super-massive WDs are their most likely progenitors and that they probably have a very strong magnetic field inside them. A degenerate electron gas in a magnetic field, such as that present inside this star, will be Landau quantized. Magnetic field changes the momentum space of electrons which in turn changes their density of states (DOS) and that in turn changes the equation of state (EoS) of matter inside the star, as opposed to that without a field. When this change in the DOS is taken into account and a link between the DOS and the EoS is established, as is done in this work, I find a physical reason behind the theoretical mass-radius (M-R) relations of a super-massive WD. I start with different equations of state with at most three Landau levels occupied and then construct stellar models of magnetic WDs (MWDs) using the same. I also show the M-R relations of these stars for a particular chosen value of maximum electron Fermi energy. Once a multiple Landau level system of electrons is considered, I find that it leads to such an EoS that gives multiple branches in the MR relations. Super-massive MWDs are obtained only when the Landau level occupancy is limited to just one level and some of the mass values fall within the mass range given above.

The secular tidal disruption of stars by low-mass Super Massive Black Holes secondaries in galactic nuclei

NASA Astrophysics Data System (ADS)

Fragione, Giacomo; Leigh, Nathan

2018-06-01

Stars passing too close to a super massive black hole (SMBH) can produce tidal disruption events (TDEs). Since the resulting stellar debris can produce an electromagnetic flare, TDEs are believed to probe the presence of single SMBHs in galactic nuclei, which otherwise remain dark. In this paper, we show how stars orbiting an IMBH secondary are perturbed by an SMBH primary. We find that the evolution of the stellar orbits are severely affected by the primary SMBH due to secular effects and stars orbiting with high inclinations with respect to the SMBH-IMBH orbital plane end their lives as TDEs due to Kozai-Lidov oscillations, hence illuminating the secondary SMBH/IMBH. Above a critical SMBH mass of ≈1.15 × 108 M⊙, no TDE can occur for typical stars in an old stellar population since the Schwarzschild radius exceeds the tidal disruption radius. Consequently, any TDEs due to such massive SMBHs will remain dark. It follows that no TDEs should be observed in galaxies more massive than ≈4.15 × 1010 M⊙, unless a lower-mass secondary SMBH or IMBH is also present. The secular mechanism for producing TDEs considered here therefore offers a useful probe of SMBH-SMBH/IMBH binarity in the most massive galaxies. We further show that the TDE rate can be ≈10-4 - 10-3 yr-1, and that most TDEs occur on ≈0.5 Myr. Finally, we show that stars may be ejected with velocities up to thousands of km s-1, which could contribute to the observed population of Galactic hypervelocity stars.

Topics in Higher-Derivative Supergravity and N = 2 Yang-Mills Theories

NASA Astrophysics Data System (ADS)

Hindawi, Ahmed Abdel-Ati

1997-09-01

In Part I of the thesis we discuss higher-derivative theories of gravity. We start by discussing the field content of quadratic higher-derivative gravity, together with a new example of a massless spin-two field consistently coupled to gravity. The full quadratic gravity theory is shown to be equivalent to a canonical second-order theory of a massive scalar field, a massive spin-two symmetric tensor field and gravity. It is shown that flat-space is the only stable vacuum, and that the spin-two field around it is always ghost-like. We give a procedure for exhibiting the new propagating degrees of freedom in a generic higher-derivative gravity, at the full non-linear level. We show that around any vacuum the elementary excitations remain the massless graviton, a massive scalar field and a massive ghost-like spin-two field. In Part II of the thesis we extend our investigations to the realm of supergravity. We consider the general form of quadratic (1, 1) supergravity in two dimensions. It is demonstrated that the theory possesses stable vacua with vanishing cosmological constant which spontaneously break supersymmetry. We then consider higher-derivative N=1 supergravity in four dimensions. We construct two classes of higher-derivative supergravity theories. They are found to be equivalent to Einstein supergravity coupled to one or two chiral superfields and have a rich vacuum structure. It is demonstrated that theories of the second class can possess a stable vacuum with vanishing cosmological constant that spontaneously breaks supersymmetry. We then proceed to show how spontaneous supersymmetry breaking in the vacuum state of higher-derivative supergravity is transmitted, as explicit soft supersymmetry-breaking terms, to the effective Lagrangian of the standard electroweak model. In Part III we use central charge superspace to give a geometrical construction of the N=2 Abelian vector-tensor multiplet consisting, under N=1 supersymmetry, of one vector and one linear multiplet. We derive the component field supersymmetry and central charge transformations, and show that there is a super-Lagrangian, the higher components of which are all total derivatives, allowing us to construct superfield and component actions.

Search for bosonic super-WIMP interactions with the XENON100 experiment

NASA Astrophysics Data System (ADS)

Aprile, E.; Aalbers, J.; Agostini, F.; Alfonsi, M.; Althueser, L.; Amaro, F. D.; Anthony, M.; Arneodo, F.; Barrow, P.; Baudis, L.; Bauermeister, B.; Benabderrahmane, M. L.; Berger, T.; Breur, P. A.; Brown, A.; Brown, A.; Brown, E.; Bruenner, S.; Bruno, G.; Budnik, R.; Bütikofer, L.; Calvén, J.; Capelli, C.; Cardoso, J. M. R.; Cichon, D.; Coderre, D.; Colijn, A. P.; Conrad, J.; Cussonneau, J. P.; Decowski, M. P.; de Perio, P.; di Gangi, P.; di Giovanni, A.; Diglio, S.; Eurin, G.; Fei, J.; Ferella, A. D.; Fieguth, A.; Fulgione, W.; Gallo Rosso, A.; Galloway, M.; Gao, F.; Garbini, M.; Geis, C.; Goetzke, L. W.; Greene, Z.; Grignon, C.; Hasterok, C.; Hogenbirk, E.; Howlett, J.; Itay, R.; Kaminsky, B.; Kazama, S.; Kessler, G.; Kish, A.; Landsman, H.; Lang, R. F.; Lellouch, D.; Levinson, L.; Lin, Q.; Lindemann, S.; Lindner, M.; Lombardi, F.; Lopes, J. A. M.; Manfredini, A.; Maris, I.; Marrodán Undagoitia, T.; Masbou, J.; Massoli, F. V.; Masson, D.; Mayani, D.; Messina, M.; Micheneau, K.; Molinario, A.; Morâ, K.; Murra, M.; Naganoma, J.; Ni, K.; Oberlack, U.; Pakarha, P.; Pelssers, B.; Persiani, R.; Piastra, F.; Pienaar, J.; Pizzella, V.; Piro, M.-C.; Plante, G.; Priel, N.; Ramírez García, D.; Rauch, L.; Reichard, S.; Reuter, C.; Rizzo, A.; Rupp, N.; Dos Santos, J. M. F.; Sartorelli, G.; Scheibelhut, M.; Schindler, S.; Schreiner, J.; Schumann, M.; Scotto Lavina, L.; Selvi, M.; Shagin, P.; Silva, M.; Simgen, H.; Sivers, M. V.; Stein, A.; Thers, D.; Tiseni, A.; Trinchero, G.; Tunnell, C.; Vargas, M.; Wang, H.; Wang, Z.; Wei, Y.; Weinheimer, C.; Wittweg, C.; Wulf, J.; Ye, J.; Zhang, Y.; Zhu, T.; Xenon Collaboration

2017-12-01

We present results of searches for vector and pseudoscalar bosonic super-weakly interacting massive particles (WIMPs), which are dark matter candidates with masses at the keV-scale, with the XENON100 experiment. XENON100 is a dual-phase xenon time projection chamber operated at the Laboratori Nazionali del Gran Sasso. A profile likelihood analysis of data with an exposure of 224.6 live days ×34 kg showed no evidence for a signal above the expected background. We thus obtain new and stringent upper limits in the (8 - 125 ) keV /c2 mass range, excluding couplings to electrons with coupling constants of ga e>3 ×10-13 for pseudo-scalar and α'/α >2 ×10-28 for vector super-WIMPs, respectively. These limits are derived under the assumption that super-WIMPs constitute all of the dark matter in our galaxy.

Mass Chart for Dead Stars and Black Holes

NASA Image and Video Library

2014-10-08

This chart illustrates relative masses of super-dense cosmic objects, ranging from white dwarfs to supermassive black holes encased in the cores of most galaxies. The first three dead stars left all form when stars more massive than our sun explode.

Super central configurations of the n-body problem

NASA Astrophysics Data System (ADS)

Xie, Zhifu

2010-04-01

In this paper, we consider the inverse problem of central configurations of the n-body problem. For a given q =(q1,q2,…,qn)ε(Rd)n, let S(q ) be the admissible set of masses by S(q )={m =(m1,…,mn)∣miεR+, q is a central configurationfor m}. For a given m εS(q), let Sm(q) be the permutational admissible set about m =(m1,m2,…,mn) by Sm(q)={m'∣m'εS(q), m'≠m and m' is apermutation of m}. Here, q is called a super central configuration if there exists m such that Sm(q) is nonempty. For any q in the planar four-body problem, q is not a super central configuration as an immediate consequence of a theorem proved by MacMillan and Bartky ["Permanent configurations in the problem of four bodies," Trans. Am. Math. Soc. 34, 838 (1932)]. The main discovery in this paper is the existence of super central configurations in the collinear three-body problem. We proved that for any q in the collinear three-body problem and any m εS(q), Sm(q) has at most one element and the detailed classification of Sm(q) is provided.

The Nearest Black Holes

NASA Technical Reports Server (NTRS)

Garcia, Michael R.; Oliversen, Ronald J. (Technical Monitor)

2002-01-01

The goal of this program is to study black holes, both in our Galaxy and in nearby galaxies. We aim to study both "stellar mass" x-ray binaries containing black holes (both in our Galaxy and in nearby galaxies), and super-massive black holes in nearby galaxies.

The Nearest Black Hole

NASA Technical Reports Server (NTRS)

Oliversen, Ronald (Technical Monitor); Garcia, Michael

2005-01-01

The goal of this program is to study black holes, both in our Galaxy and in nearby galaxies. We aim to study both 'stellar mass' x-ray binaries containing black holes (both in our Galaxy and in nearby galaxies), and super-massive black holes in nearby galaxies.

Formation metrology and control for large separated optics space telescopes

NASA Technical Reports Server (NTRS)

Mettler, E.; Quadrelli, M.; Breckenridge, W.

2002-01-01

In this paper we present formation flying performance analysis initial results for a representative large space telescope composed of separated optical elements [Mett 02]. A virtual-structure construct (an equivalent rigid body) is created by unique metrology and control that combines both centralized and decentralized methods. The formation may be in orbit at GEO for super-resolution Earth observation, as in the case of Figure 1, or it may be in an Earth-trailing orbit for astrophysics, Figure 2. Extended applications are envisioned for exo-solar planet interferometric imaging by a formation of very large separated optics telescopes, Figure 3. Space telescopes, with such large apertures and f/10 to f/100 optics, are not feasible if connected by massive metering structures. Instead, the new virtual-structure paradigm of information and control connectivity between the formation elements provides the necessary spatial rigidity and alignment precision for the telescope.

The growth efficiency of high-redshift black holes

NASA Astrophysics Data System (ADS)

Pacucci, Fabio; Volonteri, Marta; Ferrara, Andrea

2015-09-01

The observational evidence that Super-Massive Black Holes (M• ˜ 109-10 M⊙) are already in place less than 1 Gyr after the big bang poses stringent time constraints on the growth efficiency of their seeds. Among proposed possibilities, the formation of massive (˜103-6 M⊙) seeds and/or the occurrence of super-Eddington (dot{M}>dot{M}_{Edd}) accretion episodes may contribute to the solution of this problem. In this work, using a set of astrophysically motivated initial conditions, we analytically and numerically investigate the accretion flow on to high-redshift (z ˜ 10) black holes to understand the physical requirements favouring rapid and efficient growth. Our model identifies a `feeding-dominated' accretion regime and a `feedback-limited' one, the latter being characterized by intermittent (duty cycles D ≲ 0.5) and inefficient growth, with recurring outflow episodes. We find that low-mass seeds (≲103-4 M⊙) evolve in the feedback-limited regime, while more massive seeds (≳105-6 M⊙) grow very rapidly as they are found in the feeding-dominated regime. In addition to the standard accretion model with a fixed matter-energy conversion factor (ɛ = 0.1), we have also explored slim disc models, appropriate for super-Eddington accretion, where radiation is trapped in the disc and the radiative efficiency is reduced (ɛ ≲ 0.04), which may ensure a continuous growth with dot{M} ≫ dot{M}_{Edd} (up to {˜ } 300 dot{M}_{Edd} in our simulations). Under these conditions, outflows play a negligible role and a black hole can accrete 80-100 per cent of the gas mass of the host halo (˜107 M⊙) in ˜10 Myr, while in feedback-limited systems we predict that black holes can accrete only up to ˜15 per cent of the available mass.

Modeling quasar central engine as a relativistic radiating star

NASA Astrophysics Data System (ADS)

Singh, Ksh. Newton; Pant, Neeraj

2015-01-01

Long ago Hoyle & Fowler attempted to model the central engine of quasars as hot super-massive stars supported by radiation pressure. Whereas the model of Hoyle & Fowler was Newtonian, here we make a toy model of quasar central engines as ultra relativistic ultrahot plasma or as a ball of radiation. Accordingly, we consider general relativistic gravitational collapse including emission of radiation. More specifically, we discuss a new class of radiating fluid ball exact solution in conformally-flat metric which is quasi-static and contracting at negligible rate. The problem is solved by assuming that the metric potential is separable in to radial and time dependent parts. It is found the gravitational mass of the radiating ball M→0 as comoving time t→∞ in conformity of the idea of an "Eternally Collapsing Object" (ECO) which has been claimed to be the true nature of the so-called "Black Holes". In particular, we consider here a quasi-static radiation ball having M≈9.507×107 M ⊙, a radius of ≈2×1014 km, and a luminosity L ∞≈9.1×1046 erg/s. Prima-facie, such an ECO solution is compatible with the central compact object of a quasar having comoving lifetime of ≈107 yr and a distantly observed lifetime ( u) which could be higher by many orders of magnitude.

The Red Spiral Galaxy UGC11680: Clues for the Inside-Out Quenching.

NASA Astrophysics Data System (ADS)

Bárcenas, J.; Sanchez, S. F.

2016-06-01

Broadly, galaxies can be divided in two groups, thanks to the Color-Magnitude Diagram: the lively star formation ones, ``The blue Cloud'' and galaxies which halted their star formation, ``The Red Sequence''. It is a currently accepted that the galaxies start their lifespan as a blue objects, turning red when they stop to assembly more mass and thus more stars. Nevertheless, This change need to be quick (˜ 1 Gyr), due to the dearth of galaxies between this two populations (the so called ``green valley'').Previous works have found two distinct stellar mass assembly modes, they are termed as ``the inside-out'' and ``the outside-in'' growth scenarios in the literature. In the ``inside-out'' scenario, mass assembly is finished in the galactic central region. In some cases, the inflow gas can fuel the central SuperMassive BlackHole. The subsequent AGN feedback will then shut-off the central star formation. One possible case of this scenario is the galaxy UGC11680, an unusual face-on red spiral galaxy with an AGN type 2, at the red sequence belonging to the CALIFA survey. We used the so called fossil method to study its star formation history and try to understand what happened to its stellar populations.

Catastrophic impact of typhoon waves on coral communities in the Ryukyu Islands under global warming

NASA Astrophysics Data System (ADS)

Hongo, Chuki; Kawamata, Hideki; Goto, Kazuhisa

2012-06-01

Typhoon-generated storm waves generally cause mechanical damage to coral communities on present-day reefs, and the magnitude and extent of damage is predicted to increase in the near future as a result of global warming. Therefore, a comprehensive understanding of potential future scenarios of reef ecosystems is of prime interest. This study assesses the current status of coral communities on Ibaruma reef, Ryukyu Islands, on the basis of field observations, engineering and fluid dynamic models, and calculations of wave motion, and predicts the potential effects of a super-extreme typhoon (incident wave height,H = 20 m; wave period, T = 20 s) on the reef. On the present-day reef, massive corals occur in shallow lagoons and tabular corals occur from the reef crest to the reef slope. The observed distribution of corals, which is frequently attacked by moderate (H = 10 m, T = 10 s) and extreme (H = 10 m, T = 15 s) typhoons, is consistent with the predictions of engineering models. Moreover, this study indicates that if a super-extreme typhoon attacks the reef in the near future, massive corals will survive in the shallow lagoons but tabular corals on the reef crest and reef slope will be severely impacted. The findings imply that super-extreme typhoons will cause a loss of species diversity, as the tabular corals are important reef builders and are critical to the maintenance of reef ecosystems. Consequently, reef restoration is a key approach to maintaining reef ecosystems in the wake of super-extreme typhoons.

THE INFLUENCE OF PRESSURE-DEPENDENT VISCOSITY ON THE THERMAL EVOLUTION OF SUPER-EARTHS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stamenkovic, Vlada; Noack, Lena; Spohn, Tilman

2012-03-20

We study the thermal evolution of super-Earths with a one-dimensional (1D) parameterized convection model that has been adopted to account for a strong pressure dependence of the viscosity. A comparison with a 2D spherical convection model shows that the derived parameterization satisfactorily represents the main characteristics of the thermal evolution of massive rocky planets. We find that the pressure dependence of the viscosity strongly influences the thermal evolution of super-Earths-resulting in a highly sluggish convection regime in the lower mantles of those planets. Depending on the effective activation volume and for cooler initial conditions, we observe with growing planetary massmore » even the formation of a conductive lid above the core-mantle boundary (CMB), a so-called CMB-lid. For initially molten planets our results suggest no CMB-lids but instead a hot lower mantle and core as well as sluggish lower mantle convection. This implies that the initial interior temperatures, especially in the lower mantle, become crucial for the thermal evolution-the thermostat effect suggested to regulate the interior temperatures in terrestrial planets does not work for massive planets if the viscosity is strongly pressure dependent. The sluggish convection and the potential formation of the CMB-lid reduce the convective vigor throughout the mantle, thereby affecting convective stresses, lithospheric thicknesses, and heat fluxes. The pressure dependence of the viscosity may therefore also strongly affect the propensity of plate tectonics, volcanic activity, and the generation of a magnetic field of super-Earths.« less

An Introverted Starburst: Gas and SSC Formation in NGC 5253

NASA Astrophysics Data System (ADS)

Turner, J. L.; Beck, S. C.

2004-06-01

High resolution Brackett line spectroscopy with the Keck Telescope reveals relatively narrow recombination lines toward the embedded young super star cluster nebula in NGC 5253. The gas within this nebula is almost certainly gravitationally bound by the massive and compact young star cluster.

Clarification of the formation process of the super massive black hole by Infrared astrometric satellite, Small-JASMINE

NASA Astrophysics Data System (ADS)

Yano, Taihei; JASMINE-WG

2018-04-01

Small-JASMINE (hearafter SJ), infrared astrometric satellite, will measure the positions and the proper motions which are located around the Galactic center, by operating at near infrared wave-lengths. SJ will clarify the formation process of the super massive black hole (hearafter SMBH) at the Galactic center. In particular, SJ will determine whether the SMBH was formed by a sequential merging of multiple black holes. The clarification of this formation process of the SMBH will contribute to a better understanding of merging process of satellite galaxies into the Galaxy, which is suggested by the standard galaxy formation scenario. A numerical simulation (Tanikawa and Umemura, 2014) suggests that if the SMBH was formed by the merging process, then the dynamical friction caused by the black holes have influenced the phase space distribution of stars. The phase space distribution measured by SJ will make it possible to determine the occurrences of the merging process.

Super-Eddington accreting massive black holes as long-lived cosmological standards.

PubMed

Wang, Jian-Min; Du, Pu; Valls-Gabaud, David; Hu, Chen; Netzer, Hagai

2013-02-22

Super-Eddington accreting massive black holes (SEAMBHs) reach saturated luminosities above a certain accretion rate due to photon trapping and advection in slim accretion disks. We show that these SEAMBHs could provide a new tool for estimating cosmological distances if they are properly identified by hard x-ray observations, in particular by the slope of their 2-10 keV continuum. To verify this idea we obtained black hole mass estimates and x-ray data for a sample of 60 narrow line Seyfert 1 galaxies that we consider to be the most promising SEAMBH candidates. We demonstrate that the distances derived by the new method for the objects in the sample get closer to the standard luminosity distances as the hard x-ray continuum gets steeper. The results allow us to analyze the requirements for using the method in future samples of active black holes and to demonstrate that the expected uncertainty, given large enough samples, can make them into a useful, new cosmological ruler.

No tension between assembly models of super massive black hole binaries and pulsar observations.

PubMed

Middleton, Hannah; Chen, Siyuan; Del Pozzo, Walter; Sesana, Alberto; Vecchio, Alberto

2018-02-08

Pulsar timing arrays are presently the only means to search for the gravitational wave stochastic background from super massive black hole binary populations, considered to be within the grasp of current or near-future observations. The stringent upper limit from the Parkes Pulsar Timing Array has been interpreted as excluding (>90% confidence) the current paradigm of binary assembly through galaxy mergers and hardening via stellar interaction, suggesting evolution is accelerated or stalled. Using Bayesian hierarchical modelling we consider implications of this upper limit for a range of astrophysical scenarios, without invoking stalling, nor more exotic physical processes. All scenarios are fully consistent with the upper limit, but (weak) bounds on population parameters can be inferred. Recent upward revisions of the black hole-galaxy bulge mass relation are disfavoured at 1.6σ against lighter models. Once sensitivity improves by an order of magnitude, a non-detection will disfavour the most optimistic scenarios at 3.9σ.

Hubble Sees a Supermassive and Super-hungry Galaxy

NASA Image and Video Library

2016-01-08

This NASA/ESA Hubble Space Telescope image shows the spiral galaxy NGC 4845, located over 65 million light-years away in the constellation of Virgo (The Virgin). The galaxy’s orientation clearly reveals the galaxy’s striking spiral structure: a flat and dust-mottled disk surrounding a bright galactic bulge. NGC 4845’s glowing center hosts a gigantic version of a black hole, known as a supermassive black hole. The presence of a black hole in a distant galaxy like NGC 4845 can be inferred from its effect on the galaxy’s innermost stars; these stars experience a strong gravitational pull from the black hole and whizz around the galaxy’s center much faster than otherwise. From investigating the motion of these central stars, astronomers can estimate the mass of the central black hole — for NGC 4845 this is estimated to be hundreds of thousands times heavier than the sun. This same technique was also used to discover the supermassive black hole at the center of our own Milky Way — Sagittarius A* — which hits some four million times the mass of the sun. The galactic core of NGC 4845 is not just supermassive, but also super-hungry. In 2013 researchers were observing another galaxy when they noticed a violent flare at the center of NGC 4845. The flare came from the central black hole tearing up and feeding off an object many times more massive than Jupiter. A brown dwarf or a large planet simply strayed too close and was devoured by the hungry core of NGC 4845. Image credit: ESA/Hubble & NASA and S. Smartt (Queen's University Belfast) NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Galaxy And Mass Assembly (GAMA): A “No Smoking” Zone for Giant Elliptical Galaxies?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khosroshahi, Habib G.; Raouf, Mojtaba; Miraghaei, Halime

We study the radio emission of the most massive galaxies in a sample of dynamically relaxed and unrelaxed galaxy groups from the Galaxy and Mass Assembly survey. The dynamical state of the group is defined by the stellar dominance of the brightest group galaxy (BGG), e.g., the luminosity gap between the two most luminous members, and the offset between the position of the BGG and the luminosity centroid of the group. We find that the radio luminosity of the largest galaxy in the group strongly depends on its environment, such that the BGGs in dynamically young (evolving) groups are anmore » order of magnitude more luminous in the radio than those with a similar stellar mass but residing in dynamically old (relaxed) groups. This observation has been successfully reproduced by a newly developed semi-analytic model that allows us to explore the various causes of these findings. We find that the fraction of radio-loud BGGs in the observed dynamically young groups is ∼2 times that of the dynamically old groups. We discuss the implications of this observational constraint on the central galaxy properties in the context of galaxy mergers and the super massive black hole accretion rate.« less

NGC 5195 IN M51: FEEDBACK “BURPS” AFTER A MASSIVE MEAL?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlegel, E. M.; Jones, C.; Machacek, M.

2016-06-01

We describe a double-arc-like X-ray structure lying ∼15″–30″ (∼0.8–1.7 kpc) south of the NGC 5195 nucleus, visible in the merged exposures of long Chandra pointings of M51. The curvature and orientation of the arcs argues for a nuclear origin. The arcs are radially separated by ∼15″ (∼1 kpc), but are rotated relative to each other by ∼30°. From an archival image, we find a slender H α -emitting region just outside the outer edge of the outer X-ray arc, suggesting that the X-ray-emitting gas plowed up and displaced the H α -emitting material from the galaxy core. Star formation maymore » have commenced in that arc. H α emission is present at the inner arc, but appears more complex in structure. In contrast to an explosion expected to be azimuthally symmetric, the X-ray arcs suggest a focused outflow. We interpret the arcs as episodic outbursts from the central super-massive black hole (SMBH). We conclude that NGC 5195 represents the nearest galaxy exhibiting on-going, large-scale outflows of gas, in particular, two episodes of a focused outburst of the SMBH. The arcs represent a clear demonstration of feedback.« less

The Fate of Super-AGB Stars at Low Metallicity

NASA Astrophysics Data System (ADS)

Decressin, T.; Siess, L.; Charbonnel, C.; Leclair, G.

2005-11-01

Super-AGBs are stars massive enough to ignite carbon off center and to climb the asymptotic giant branch (where they undergo thermal pulses) after core carbon exhaustion. The destiny of these stars, ONe white dwarfs or neutron stars, depends essentially on the ability of the mass loss to peel the stellar envelope before the core reaches the critical mass for electron captures to occur. Here, we focus on a super-AGB stars of 8.5 Msolar at Z=0.0001 and investigate the effects of various mass loss prescriptions. We study the interplay between mass loss and diffusive overshooting below the convective envelope. The former determines the duration of the AGB phase and the final state of the star; the latter affects the increase of the core mass and the nucleosynthesis as well.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Madau, Piero; Haardt, Francesco; Dotti, Massimo

We consider super-critical accretion with angular momentum onto stellar-mass black holes as a possible mechanism for growing billion-solar-mass black holes from light seeds at early times. We use the radiatively inefficient ''slim disk'' solution—advective, optically thick flows that generalize the standard geometrically thin disk model—to show how mildly super-Eddington intermittent accretion may significantly ease the problem of assembling the first massive black holes when the universe was less than 0.8 Gyr old. Because of the low radiative efficiencies of slim disks around non-rotating as well as rapidly rotating black holes, the mass e-folding timescale in this regime is nearly independent ofmore » the spin parameter. The conditions that may lead to super-critical growth in the early universe are briefly discussed.« less

Geometric structures of super-(Diff(S/sup 1/)/S/sup 1/)*

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidke, W.B.; Vokos, S.P.

Superconformal invariance is of central importance to a perturbative and non-perturbative formulation of stringy theory. The group that describes the invariances of the superstring is the super-Virasoro group, Super-Diff(S/sup 1/). The super-reparameterizations of the circle that leave a point fixed compose the quotient space Super-(Diff(S/sup 1/)/S/sup 1/). We investigate the holomorphic geometry of this infinite-dimensional Kaehler supermanifold and calculate its curvature. copyright 1989 Academic Press, Inc.

Results from the Super Cryogenic Dark Matter Search Experiment at Soudan

DOE PAGES

Agnese, R.; Aramaki, T.; Arnquist, I. J.; ...

2018-02-09

Here, we report the result of a blinded search for weakly interacting massive particles (WIMPs) using the majority of the SuperCDMS Soudan data set. With an exposure of 1690 kg d, a single candidate event is observed, consistent with expected backgrounds. This analysis (combined with previous Ge results) sets an upper limit on the spin-independent WIMP–nucleon cross section of 1.4×10 -44 (1.0×10 -44) cm 2 at 46 GeV/c 2. These results set the strongest limits for WIMP–germanium-nucleus interactions for masses >12 GeV/c 2.

Results from the Super Cryogenic Dark Matter Search Experiment at Soudan

NASA Astrophysics Data System (ADS)

Agnese, R.; Aramaki, T.; Arnquist, I. J.; Baker, W.; Balakishiyeva, D.; Banik, S.; Barker, D.; Basu Thakur, R.; Bauer, D. A.; Binder, T.; Bowles, M. A.; Brink, P. L.; Bunker, R.; Cabrera, B.; Caldwell, D. O.; Calkins, R.; Cartaro, C.; Cerdeño, D. G.; Chang, Y.; Chen, Y.; Cooley, J.; Cornell, B.; Cushman, P.; Daal, M.; Di Stefano, P. C. F.; Doughty, T.; Fascione, E.; Figueroa-Feliciano, E.; Fritts, M.; Gerbier, G.; Germond, R.; Ghaith, M.; Godfrey, G. L.; Golwala, S. R.; Hall, J.; Harris, H. R.; Hong, Z.; Hoppe, E. W.; Hsu, L.; Huber, M. E.; Iyer, V.; Jardin, D.; Jastram, A.; Jena, C.; Kelsey, M. H.; Kennedy, A.; Kubik, A.; Kurinsky, N. A.; Loer, B.; Lopez Asamar, E.; Lukens, P.; MacDonell, D.; Mahapatra, R.; Mandic, V.; Mast, N.; Miller, E. H.; Mirabolfathi, N.; Mohanty, B.; Morales Mendoza, J. D.; Nelson, J.; Orrell, J. L.; Oser, S. M.; Page, K.; Page, W. A.; Partridge, R.; Penalver Martinez, M.; Pepin, M.; Phipps, A.; Poudel, S.; Pyle, M.; Qiu, H.; Rau, W.; Redl, P.; Reisetter, A.; Reynolds, T.; Roberts, A.; Robinson, A. E.; Rogers, H. E.; Saab, T.; Sadoulet, B.; Sander, J.; Schneck, K.; Schnee, R. W.; Scorza, S.; Senapati, K.; Serfass, B.; Speller, D.; Stein, M.; Street, J.; Tanaka, H. A.; Toback, D.; Underwood, R.; Villano, A. N.; von Krosigk, B.; Welliver, B.; Wilson, J. S.; Wilson, M. J.; Wright, D. H.; Yellin, S.; Yen, J. J.; Young, B. A.; Zhang, X.; Zhao, X.; SuperCDMS Collaboration

2018-02-01

We report the result of a blinded search for weakly interacting massive particles (WIMPs) using the majority of the SuperCDMS Soudan data set. With an exposure of 1690 kg d, a single candidate event is observed, consistent with expected backgrounds. This analysis (combined with previous Ge results) sets an upper limit on the spin-independent WIMP-nucleon cross section of 1.4 ×10-44 (1.0 ×10-44) cm2 at 46 GeV /c2 . These results set the strongest limits for WIMP-germanium-nucleus interactions for masses >12 GeV /c2.

Results from the Super Cryogenic Dark Matter Search Experiment at Soudan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agnese, R.; Aramaki, T.; Arnquist, I. J.

Here, we report the result of a blinded search for weakly interacting massive particles (WIMPs) using the majority of the SuperCDMS Soudan data set. With an exposure of 1690 kg d, a single candidate event is observed, consistent with expected backgrounds. This analysis (combined with previous Ge results) sets an upper limit on the spin-independent WIMP–nucleon cross section of 1.4×10 -44 (1.0×10 -44) cm 2 at 46 GeV/c 2. These results set the strongest limits for WIMP–germanium-nucleus interactions for masses >12 GeV/c 2.

Results from the Super Cryogenic Dark Matter Search Experiment at Soudan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agnese, R.; Aramaki, T.; Arnquist, I. J.

We report the result of a blinded search for Weakly Interacting Massive Particles (WIMPs) using the full SuperCDMS Soudan dataset. With an exposure of 1690 kg days, a single event was observed after unblinding, consistent with expected backgrounds. This analysis (combined with previous Ge results) sets an upper limit on the spin-independent WIMP-nucleon cross section of 1.4x10^-44 (1.0x10^-44) cm^2 at 46 GeV/c^2 . These results set the strongest limits for WIMP-germanium-nucleus interactions for masses >12 GeV/c^2.

Lower limit on dark matter production at the CERN Large Hadron Collider.

PubMed

Feng, Jonathan L; Su, Shufang; Takayama, Fumihiro

2006-04-21

We evaluate the prospects for finding evidence of dark matter production at the CERN Large Hadron Collider. We consider weakly interacting massive particles (WIMPs) and superWIMPs and characterize their properties through model-independent parametrizations. The observed relic density then implies lower bounds on dark matter production rates as functions of a few parameters. For WIMPs, the resulting signal is indistinguishable from background. For superWIMPs, however, this analysis implies significant production of metastable charged particles. For natural parameters, these rates may far exceed Drell-Yan cross sections and yield spectacular signals.

SuperTIGER: On the Cosmic Ray Charge Frontier

NASA Astrophysics Data System (ADS)

Brandt, Theresa J.

2017-08-01

The Super Trans-Iron Galactic Element Recorder (SuperTIGER) was designed to measure significant statistics particularly for cosmic rays (CRs) with charge > 30. These heaviest nuclei are some 10^3-10^5 times rarer than the lighter elements. With the longest science flight to date on a Long Duration Balloon in 2012-13, SuperTIGER has collected >1200 of these rare nuclei and millions of lighter CR events. After the instrument spent two winters in Antarctica, we recovered it and are completing preparations for a second flight. We present results from the first flight, including the highest statistical precision measurements of CR charges from 30-40 to date. We anticipate even greater improvements with our second flight, this coming austral summer, 2017-18 from McMurdo, Antarctica. The results show enhanced numbers of elements formed in massive stars relative to solar system values, and thus give insight into the origin of Galactic CRs, likely in OB associations, and into the atomic processes which accelerate nuclei.

Detecting and Discriminating Gravitational Microlensing in the SuperMACHO Survey

NASA Astrophysics Data System (ADS)

Garg, Arti

2010-02-01

The SuperMACHO Project is a 5 year survey to determine the nature of the lens population responsible for the excess gravitational microlensing rate toward the Large Magellanic Cloud observed by the MACHO project. The MACHO results indicate a large population of compact lenses toward the clouds, and the observed lensing rate is consistent with a Milky Way halo comprised of up to ˜20% Massive Compact Halo Objects (MACHO's), dark matter that is most likely baryonic. This work describes the method by which gravitational microlensing is detected in the SuperMACHO survey. Based on the MACHO findings and the SuperMACHO observing strategy and selection criteria, we expect <10-6 of the sources monitored to be lensed at any time. Our detection criteria are designed to minimize false positives while preserving a statistically significant detection rate. We provide an overview of the detection criteria. We also discuss the selection criteria used to discriminate between microlensing and other astrophysical transients. )

Luminous blue variables and the fates of very massive stars

NASA Astrophysics Data System (ADS)

Smith, Nathan

2017-09-01

Luminous blue variables (LBVs) had long been considered massive stars in transition to the Wolf-Rayet (WR) phase, so their identification as progenitors of some peculiar supernovae (SNe) was surprising. More recently, environment statistics of LBVs show that most of them cannot be in transition to the WR phase after all, because LBVs are more isolated than allowed in this scenario. Additionally, the high-mass H shells around luminous SNe IIn require that some very massive stars above 40 M⊙ die without shedding their H envelopes, and the precursor outbursts are a challenge for understanding the final burning sequences leading to core collapse. Recent evidence suggests a clear continuum in pre-SN mass loss from super-luminous SNe IIn, to regular SNe IIn, to SNe II-L and II-P, whereas most stripped-envelope SNe seem to arise from a separate channel of lower-mass binary stars rather than massive WR stars. This article is part of the themed issue 'Bridging the gap: from massive stars to supernovae'.

Supersonic gas streams enhance the formation of massive black holes in the early universe.

PubMed

Hirano, Shingo; Hosokawa, Takashi; Yoshida, Naoki; Kuiper, Rolf

2017-09-29

The origin of super-massive black holes in the early universe remains poorly understood. Gravitational collapse of a massive primordial gas cloud is a promising initial process, but theoretical studies have difficulty growing the black hole fast enough. We report numerical simulations of early black hole formation starting from realistic cosmological conditions. Supersonic gas motions left over from the Big Bang prevent early gas cloud formation until rapid gas condensation is triggered in a protogalactic halo. A protostar is formed in the dense, turbulent gas cloud, and it grows by sporadic mass accretion until it acquires 34,000 solar masses. The massive star ends its life with a catastrophic collapse to leave a black hole-a promising seed for the formation of a monstrous black hole. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

A magnetar model for the hydrogen-rich super-luminous supernova iPTF14hls

NASA Astrophysics Data System (ADS)

Dessart, Luc

2018-02-01

Transient surveys have recently revealed the existence of H-rich super-luminous supernovae (SLSN; e.g., iPTF14hls, OGLE-SN14-073) that are characterized by an exceptionally high time-integrated bolometric luminosity, a sustained blue optical color, and Doppler-broadened H I lines at all times. Here, I investigate the effect that a magnetar (with an initial rotational energy of 4 × 1050 erg and field strength of 7 × 1013 G) would have on the properties of a typical Type II supernova (SN) ejecta (mass of 13.35 M⊙, kinetic energy of 1.32 × 1051 erg, 0.077 M⊙ of 56Ni) produced by the terminal explosion of an H-rich blue supergiant star. I present a non-local thermodynamic equilibrium time-dependent radiative transfer simulation of the resulting photometric and spectroscopic evolution from 1 d until 600 d after explosion. With the magnetar power, the model luminosity and brightness are enhanced, the ejecta is hotter and more ionized everywhere, and the spectrum formation region is much more extended. This magnetar-powered SN ejecta reproduces most of the observed properties of SLSN iPTF14hls, including the sustained brightness of ‑18 mag in the R band, the blue optical color, and the broad H I lines for 600 d. The non-extreme magnetar properties, combined with the standard Type II SN ejecta properties, offer an interesting alternative to the pair-unstable super-massive star model recently proposed, which involves a highly energetic and super-massive ejecta. Hence, such Type II SLSNe may differ from standard Type II SNe exclusively through the influence of a magnetar.

Breeding Super-Earths and Birthing Super-puffs in Transitional Disks

NASA Astrophysics Data System (ADS)

Lee, Eve J.; Chiang, Eugene

2016-02-01

The riddle posed by super-Earths (1-4R⊕, 2-20M⊕) is that they are not Jupiters: their core masses are large enough to trigger runaway gas accretion, yet somehow super-Earths accreted atmospheres that weigh only a few percent of their total mass. We show that this puzzle is solved if super-Earths formed late, as the last vestiges of their parent gas disks were about to clear. This scenario would seem to present fine-tuning problems, but we show that there are none. Ambient gas densities can span many (in one case up to 9) orders of magnitude, and super-Earths can still robustly emerge after ˜0.1-1 Myr with percent-by-weight atmospheres. Super-Earth cores are naturally bred in gas-poor environments where gas dynamical friction has weakened sufficiently to allow constituent protocores to gravitationally stir one another and merge. So little gas is present at the time of core assembly that cores hardly migrate by disk torques: formation of super-Earths can be in situ. The basic picture—that close-in super-Earths form in a gas-poor (but not gas-empty) inner disk, fed continuously by gas that bleeds inward from a more massive outer disk—recalls the largely evacuated but still accreting inner cavities of transitional protoplanetary disks. We also address the inverse problem presented by super-puffs: an uncommon class of short-period planets seemingly too voluminous for their small masses (4-10R⊕, 2-6M⊕). Super-puffs most easily acquire their thick atmospheres as dust-free, rapidly cooling worlds outside ˜1 AU where nebular gas is colder, less dense, and therefore less opaque. Unlike super-Earths, which can form in situ, super-puffs probably migrated in to their current orbits; they are expected to form the outer links of mean-motion resonant chains, and to exhibit greater water content. We close by confronting observations and itemizing remaining questions.

Water-Assisted Highly Efficient Synthesis of Impurity-Free Single-Walled Carbon Nanotubes-``Super-Growth''

NASA Astrophysics Data System (ADS)

Hata, Kenji

2005-03-01

We demonstrate an extremely efficient chemical vapour deposition synthesis of single-walled carbon nanotubes where the activity and lifetime of the catalysts are enhanced by water [1]. Water-stimulated enhanced catalytic activity results in massive growth of super-dense and vertically-aligned nanotube forests with heights up to 2.5 millimeters that can be easily separated from the catalysts, providing nanotube material with carbon purity above 99.98%. Moreover, patterned highly organized intrinsic nanotube structures were successfully fabricated. The water-assisted synthesis method addresses many critical problems that currently plague carbon nanotube synthesis. [1] K. Hata, et al., Science, 306, 1362 (2004).

Death or Survival? Determining the nature of SNe IIn-P explosions

NASA Astrophysics Data System (ADS)

Mauerhan, Jon

2016-10-01

An increasing number of transients classifiable as interacting supernovae of Type IIn have become the subject of intense debate, as the death or survival of the precursor star is unclear. This is because giant non-terminal eruptions from massive luminous blue variable (LBV) stars can spectroscopically resemble SNe IIn and achieve comparable luminosities via shock interaction with pre-existing circumstellar material (CSM). The stellar origin of the new SNe IIn-P class of explosions is particularly controversial. Competing interpretations predict stellar progenitors with very different initial masses and explosion outcomes: 1) non-terminal super-Eddington eruptions from LBVs; 2) collapsars from very massive stars that should die within their natal OB associations; and 3) electron-capture SNe from super-AGB stars with dense CSM envelopes. To resolve the uncertain origin of SNe IIn-P, we propose a simple and inexpensive optical imaging experiment to see if there is a luminous surviving star remaining at the site. UV imaging is also proposed to determine the nature of a UV source detected in pre-explosion GALEX images, and to survey the progenitor's environment for sibling O-type stars.

Tori sequences as remnants of multiple accreting periods of Kerr SMBHs

NASA Astrophysics Data System (ADS)

Pugliese, D.; Stuchlík, Z.

2018-03-01

Super-massive black holes (SMBHs) hosted in active galactic nuclei (AGNs) can be characterized by multi-accreting periods as the attractors interact with the environment during their life-time. These multi-accretion episodes should leave traces in the matter orbiting the attractor. Counterrotating and even misaligned structures orbiting around the SMBHs would be consequences of these episodes. Our task in this work is to consider situations where such accretions occur and to trace their remnants represented by several toroidal accreting fluids, corotating or counterrotating relative to the central Kerr attractor, and created in various regimes during the evolution of matter configurations around SMBHs. We focus particularly on the emergence of matter instabilities, i.e., tori collisions, accretion onto the central Kerr black hole, or creation of jet-like structures (proto-jets). Each orbiting configuration is governed by the general relativistic hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluid. We prove that sequences of configurations and hot points, where an instability occurs, characterize the Kerr SMBHs, depending mainly on their spin-mass ratios. The occurrence of tori accretion or collision are strongly constrained by the fluid rotation with respect to the central black hole and the relative rotation with respect to each other. Our investigation provides characteristic of attractors where traces of multi-accreting episodes can be found and observed.

Star trapping and metallicity enrichment in quasars and active galactic nuclei

NASA Technical Reports Server (NTRS)

Artymowicz, Pawel; Lin, D. N. C.; Wampler, E. J.

1993-01-01

Recent observational evidence suggests that the metallicity in quasars within a wide range of redshifts, in particular in gas flowing out of the nuclear regions, may be approximately redshift-independent and comparable with or larger than solar. It is plausible that the nuclear metallicity can be internally generated and maintained at approximately time-stationary values in quasars. We identify and estimate efficiency of a mechanism for rapid metallicity enrichment of quasar nuclear gas (in general, in active galactic nuclei) based on star-gas interactions and equivalent to an unusual mode of massive star formation. The mechanism involves capture of low-mass stars from the host galaxy's nucleus by the assemblages of clouds or by accretion disks orbiting the central massive objects (e.g., black holes). Trapping of stars within gaseous disks/clouds occurs through resonant density and bending wave excitation, as well as by hydrodynamical drag. The time scale for trapping stars with total mass equal to that of disk fragment/cloud is of order Hubble time and is remarkably model-independent. Our results show that the described mechanism can produce features suggested by observations, for example, the (super) solar gas metallicity in the nucleus. Thus the observed metallicities in high-redshift quasars do not necessarily imply that global star formation and efficient chemical changes have occurred in their host galaxies at very early cosmological epochs.

Ultrafast outflows in Super-Eddington Tidal Disruption Events

NASA Astrophysics Data System (ADS)

Kara, Erin

2017-08-01

The disruption of a star from the strong tidal forces of a supermassive black hole can cause the stellar debris to fall back towards the black hole at super Eddington rates. Efficient circularization of the debris can lead to the formation of an accretion disc with luminosities close to or potentially exceeding Eddington limit. Most super-Eddington accretion flow models (including recent magnetohydrodynamic simulations) predict large scale height, optically thick equatorial winds at relativistic velocities. In this talk, we will present observational results from two of the most well-observed X-ray emitting Tidal Disruption Events, Swift J1644+57 and ASASSN-14li. Both of these objects show evidence for massive outflows at tens of percent of the speed of light. The outflow in Swift J1644+57 was detected via blue shifted emission and reverberation of the iron K alpha line, and ASASSN-14li shows a potential P Cygni profile of the OVIII line. We will discuss the constraints that these observations put on the geometry of the super-Eddington accretion flows in tidal disruption events.

Inner Super-Earths, Outer Gas Giants: How Pebble Isolation and Migration Feedback Keep Jupiters Cold

NASA Astrophysics Data System (ADS)

Fung, Jeffrey; Lee, Eve J.

2018-06-01

The majority of gas giants (planets of masses ≳102 M ⊕) are found to reside at distances beyond ∼1 au from their host stars. Within 1 au, the planetary population is dominated by super-Earths of 2–20 M ⊕. We show that this dichotomy between inner super-Earths and outer gas giants can be naturally explained should they form in nearly inviscid disks. In laminar disks, a planet can more easily repel disk gas away from its orbit. The feedback torque from the pile-up of gas inside the planet’s orbit slows down and eventually halts migration. A pressure bump outside the planet’s orbit traps pebbles and solids, starving the core. Gas giants are born cold and stay cold: more massive cores are preferentially formed at larger distances, and they barely migrate under disk feedback. We demonstrate this using two-dimensional hydrodynamical simulations of disk–planet interaction lasting up to 105 years: we track planet migration and pebble accretion until both come to an end by disk feedback. Whether cores undergo runaway gas accretion to become gas giants or not is determined by computing one-dimensional gas accretion models. Our simulations show that in an inviscid minimum mass solar nebula, gas giants do not form inside ∼0.5 au, nor can they migrate there while the disk is present. We also explore the dependence on disk mass and find that gas giants form further out in less massive disks.

Energy extraction of a spinning particle via the super Penrose process from an extremal Kerr black hole

NASA Astrophysics Data System (ADS)

Liu, Yan; Liu, Wen-Biao

2018-03-01

The energy extraction of the collisional Penrose process has been investigated in recent years. Previous researchers mainly concentrated on the case of nonspin massive or massless particles, and they discovered that when the collision occurs near the horizon of extremal rotating black holes, the arbitrary large efficiency can be achieved with the particle's angular momentum below the critical value as L1<2 . In this paper, the energy extraction of spinning massive particles is calculated via the super Penrose process. We obtain the dependence of the impact factor and the turning points on the particle's spin s . The super Penrose process can occur only when s ≤1 and J1<2 , where J1 is the spinning particle's angular momentum. It is found that the efficiency of the energy extraction is monotonously increasing with the particle's spin s increasing for s <1 , and it can become arbitrarily high when the collision occurs close to the horizon. We compare the maximum extracted energy of spinning particles with that of the nonspin case and find a significant increase of the extracted energy. When s →1 , the maximum extracted energy can be orders of magnitude larger than that of the nonspin case. For the astrophysical black holes, the large efficiency is also obtained. Naturally, when the particle's spin s ≪1 , we can degenerate the result back to the nonspin case.

A Multi-Wavelength View of Radio Galaxy Hercules A

NASA Image and Video Library

2017-12-08

Spectacular jets powered by the gravitational energy of a super massive black hole in the core of the elliptical galaxy Hercules A illustrate the combined imaging power of two of astronomy's cutting-edge tools, the Hubble Space Telescope's Wide Field Camera 3, and the recently upgraded Karl G. Jansky Very Large Array (VLA) radio telescope in New Mexico. To view a video of this go to: bit.ly/Ue2ypS Some two billion light-years away, the yellowish elliptical galaxy in the center of the image appears quite ordinary as seen by Hubble in visible wavelengths of light. The galaxy is roughly 1,000 times more massive than the Milky Way and harbors a 2.5-billion-solar-mass central black hole that is 1,000 times more massive than the black hole in the Milky Way. But the innocuous-looking galaxy, also known as 3C 348, has long been known as the brightest radio-emitting object in the constellation Hercules. Emitting nearly a billion times more power in radio wavelengths than our Sun, the galaxy is one of the brightest extragalactic radio sources in the entire sky. Credit: NASA, ESA, S. Baum and C. O'Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA) To read more about this image go to: 1.usa.gov/Yu7uvX NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Luminous blue variables and the fates of very massive stars.

PubMed

Smith, Nathan

2017-10-28

Luminous blue variables (LBVs) had long been considered massive stars in transition to the Wolf-Rayet (WR) phase, so their identification as progenitors of some peculiar supernovae (SNe) was surprising. More recently, environment statistics of LBVs show that most of them cannot be in transition to the WR phase after all, because LBVs are more isolated than allowed in this scenario. Additionally, the high-mass H shells around luminous SNe IIn require that some very massive stars above 40  M ⊙ die without shedding their H envelopes, and the precursor outbursts are a challenge for understanding the final burning sequences leading to core collapse. Recent evidence suggests a clear continuum in pre-SN mass loss from super-luminous SNe IIn, to regular SNe IIn, to SNe II-L and II-P, whereas most stripped-envelope SNe seem to arise from a separate channel of lower-mass binary stars rather than massive WR stars.This article is part of the themed issue 'Bridging the gap: from massive stars to supernovae'. © 2017 The Author(s).

Three-Dimensional Nanobiocomputing Architectures With Neuronal Hypercells

DTIC Science & Technology

2007-06-01

Neumann architectures, and CMOS fabrication. Novel solutions of massive parallel distributed computing and processing (pipelined due to systolic... and processing platforms utilizing molecular hardware within an enabling organization and architecture. The design technology is based on utilizing a...Microsystems and Nanotechnologies investigated a novel 3D3 (Hardware Software Nanotechnology) technology to design super-high performance computing

The Journey to Teaching Online: A Case Study of Faculty Preparation and Experiences in Online Teaching

ERIC Educational Resources Information Center

Chi, Angel

2013-01-01

When Bill Gates published his book "The Road Ahead" (1995), he summarized the transformative implications of the personal computing revolution and described a future profoundly changed by the arrival of a global information super highway. Almost twenty years later, the tsunami of online programs and the MOOCs (massive online open…

What drives the formation of massive stars and clusters?

NASA Astrophysics Data System (ADS)

Ochsendorf, Bram; Meixner, Margaret; Roman-Duval, Julia; Evans, Neal J., II; Rahman, Mubdi; Zinnecker, Hans; Nayak, Omnarayani; Bally, John; Jones, Olivia C.; Indebetouw, Remy

2018-01-01

Galaxy-wide surveys allow to study star formation in unprecedented ways. In this talk, I will discuss our analysis of the Large Magellanic Cloud (LMC) and the Milky Way, and illustrate how studying both the large and small scale structure of galaxies are critical in addressing the question: what drives the formation of massive stars and clusters?I will show that ‘turbulence-regulated’ star formation models do not reproduce massive star formation properties of GMCs in the LMC and Milky Way: this suggests that theory currently does not capture the full complexity of star formation on small scales. I will also report on the discovery of a massive star forming complex in the LMC, which in many ways manifests itself as an embedded twin of 30 Doradus: this may shed light on the formation of R136 and 'Super Star Clusters' in general. Finally, I will highlight what we can expect in the next years in the field of star formation with large-scale sky surveys, ALMA, and our JWST-GTO program.

LISA: Astrophysics Out to z Approximately 10 with Low-Frequency Gravitational Waves

NASA Technical Reports Server (NTRS)

Stebbins, Robin T.

2008-01-01

This viewgraph presentation reviews the Laser Interferometer Space Antenna (LISA). LISA os a joint ESA-NASA project to design, build and operate a space-based gravitational wave detector. The 5 million Kilometer long detector will consist of three spacecraft orbiting the Sun in a triangular formation. Space-Time strains induced by gravitational waves are detected by measuring changes in the separation of fiducial masses with laser interferometry. LISA is expected to detect signals from merging massive black holes, compact stellar objects spiraling into super massive black holes in galactic nuclei, thousands of close binaries of compact objects in the Milky way and possible backgrounds of cosmological origin.

Improving safety in high-speed work zones : a Super 70 study.

DOT National Transportation Integrated Search

2011-01-01

Super 70 was an urban reconstruction project (March-November 2007) along I-70 in the central part of Indianapolis. INDOT : applied in that project several innovative and traditional solutions. This study investigates the safety effect of the solution...

BREEDING SUPER-EARTHS AND BIRTHING SUPER-PUFFS IN TRANSITIONAL DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Eve J.; Chiang, Eugene, E-mail: evelee@berkeley.edu, E-mail: echiang@astro.berkeley.edu

The riddle posed by super-Earths (1–4R{sub ⊕}, 2–20M{sub ⊕}) is that they are not Jupiters: their core masses are large enough to trigger runaway gas accretion, yet somehow super-Earths accreted atmospheres that weigh only a few percent of their total mass. We show that this puzzle is solved if super-Earths formed late, as the last vestiges of their parent gas disks were about to clear. This scenario would seem to present fine-tuning problems, but we show that there are none. Ambient gas densities can span many (in one case up to 9) orders of magnitude, and super-Earths can still robustlymore » emerge after ∼0.1–1 Myr with percent-by-weight atmospheres. Super-Earth cores are naturally bred in gas-poor environments where gas dynamical friction has weakened sufficiently to allow constituent protocores to gravitationally stir one another and merge. So little gas is present at the time of core assembly that cores hardly migrate by disk torques: formation of super-Earths can be in situ. The basic picture—that close-in super-Earths form in a gas-poor (but not gas-empty) inner disk, fed continuously by gas that bleeds inward from a more massive outer disk—recalls the largely evacuated but still accreting inner cavities of transitional protoplanetary disks. We also address the inverse problem presented by super-puffs: an uncommon class of short-period planets seemingly too voluminous for their small masses (4–10R{sub ⊕}, 2–6M{sub ⊕}). Super-puffs most easily acquire their thick atmospheres as dust-free, rapidly cooling worlds outside ∼1 AU where nebular gas is colder, less dense, and therefore less opaque. Unlike super-Earths, which can form in situ, super-puffs probably migrated in to their current orbits; they are expected to form the outer links of mean-motion resonant chains, and to exhibit greater water content. We close by confronting observations and itemizing remaining questions.« less

Bright vigorous winds as signposts of supermassive black hole birth

NASA Astrophysics Data System (ADS)

Fiacconi, Davide; Rossi, Elena M.

2016-01-01

The formation of supermassive black holes is still an outstanding question. In the quasi-star scenario, black hole seeds experience an initial super-Eddington growth, that in less than a million years may leave a 104-105 M⊙ black hole at the centre of a protogalaxy at z ˜ 20-10. Super-Eddington accretion, however, may be accompanied by vigorous mass-loss that can limit the amount of mass that reaches the black hole. In this paper, we critically assess the impact of radiative driven winds, launched from the surface of the massive envelopes from which the black hole accretes. Solving the full wind equations coupled with the hydrostatic structure of the envelope, we find mass outflows with rates between a few tens and 104 M⊙ yr-1, mainly powered by advection luminosity within the outflow. We therefore confirm the claim by Dotan et al. that mass losses can severely affect the black hole seed early growth within a quasi-star. In particular, seeds with mass >104 M⊙ can only form within mass reservoirs ≳107 M⊙, unless they are refilled at huge rates (≳100 M⊙ yr-1). This may imply that only very massive haloes (>109 M⊙) at those redshifts can harbour massive seeds. Contrary to previous claims, these winds are expected to be relatively bright (1044-1047 erg s-1), blue (Teff ˜ 8000 K) objects, that while eluding the Hubble Space Telescope, could be observed by the James Webb Space Telescope.

The Nearest Black Holes

NASA Technical Reports Server (NTRS)

Garcia, M.; Oliversen, Ronald J. (Technical Monitor)

2004-01-01

The goal of this program is to study black holes, both in our Galaxy and in nearby galaxies. We aim to study both 'stellar mass' x-ray binaries containing black holes (both in our Galaxy and in nearby galaxies), and super-massive black holes in nearby galaxies. This program facilitate this study by funding related travel, computer equipment, and partial salary for a post-doc.

The Nearest Black Holes

NASA Technical Reports Server (NTRS)

Oliversen, Ronald J. (Technical Monitor); Garcia, M.

2003-01-01

The goal of this program is to study black holes, both in our Galaxy and in nearby galaxies. We aim to study both 'stellar mass' x-ray binaries containing black holes (both in our Galaxy and in nearby galaxies), and super-massive black holes in nearby galaxies. This program facilitates this study by funding related travel, computer equipment, and partial salary for a post-doc.

Super-massive binary black holes in galaxies. Dynamical models and observed structures in Arp 5, 87, 214, 240, and NGC 4027, 6946

NASA Astrophysics Data System (ADS)

Anosova, Joanna P.

2017-06-01

On 14 Sept, 2015 The LIGO reported the first direct detection of gravitational waves and the first direct observation of a binary black hole. These observations demonstrate the existence of binary black holes in stellar systems predicted by Einstein in his general theory of relativity a century earlier.A lot of violent and complicated phenomena take place on different scales in the Universe. Many of them may be caused by multiple centers of gravitational attraction: planetary rings, accretion discs of various scales, peculiar structures of single galaxies and interacting galaxies. In this work, we show that various features of celestial objects can be understood by assuming the existence of two dominant centers of gravity in stellar systems.We study numerically the dynamical evolution of models with the central super-massive binary black holes and extended shells with numerous low-mass particles inside and around the orbits of binaries. These particles could be star clusters or gas and dust complexes. We consider several tens of thousands of initial conditions for the general three-body problem and compile them. We studied the dynamical evolution of all spherical shells together and separately. Our method permits us to study the individual trajectories of particles, their close double and triple approaches, and inspect the time-depending structures in the models. Multiple runs of the models allow us to classify the numerous strong triple interactions of the binary components with low-mass particles; frequently, the "gravitational slingshot" effect occurs in the center of systems. Such strong interactions of bodies are results in various structures with "dumb-bell" bars, close and open spirals, different types of flows, jets etc. These structures are often very similar the observed structures of galaxies.We found some combinations of the initial conditions and model parameters that produce at some time similar structures as that found in the galaxies Arp 5, 87, 214, 240, and NGC 4027, 6946. Our Figures show results of such comparison and the past and future evolution of our models.

Tidal Disruption Events Across Cosmic Time

NASA Astrophysics Data System (ADS)

Fialkov, Anastasia; Loeb, Abraham

2017-01-01

Tidal disruption events (TDEs) of stars by single or binary super-massive black holes illuminate the environment around quiescent black holes in galactic nuclei allowing to probe dorment black holes. We predict the TDE rates expected to be detected by next-generation X-ray surveys. We include events sourced by both single and binary super-massive black holes assuming that 10% of TDEs lead to the formation of relativistic jets and are therefore observable to higher redshifts. Assigning the Eddington luminosity to each event, we show that if the occupation fraction of intermediate black holes is high, more than 90% of the brightest TDE might be associated with merging black holes which are potential sources for eLISA. Next generation telescopes with improved sensitivities should probe dim local TDE events as well as bright events at high redshifts. We show that an instrument which is 50 times more sensitive than the Swift Burst Alert Telescope (BAT) is expected to trigger ~10 times more events than BAT. Majority of these events originate at low redshifts (z<0.5) if the occupation fraction of IMBHs is high and at high-redshift (z>2) if it is low.

SuperWASP J015100.23-100524.2: A SPOTTED SHALLOW-CONTACT BINARY BELOW THE PERIOD LIMIT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qian, S. B.; Zhang, B.; He, J. J.

2015-10-15

SuperWASP J015100.23-100524.2 (hereafter J015100) is an eclipsing binary with an orbital period of 0.d2145 that is below the short-period limit of contact binary stars. Complete light curves of J015100 in B, V, R, and I bands are presented and are analyzed with the Wilson–Devinney method. It has been discovered that J015100 is a shallow-contact binary (f = 14.6(±2.7)%) with a mass ratio of 3.128. It is a W-type contact binary where the less massive component is about 130 K hotter than the more massive one. The asymmetries of light curves are explained as one dark spot on the more massivemore » component. The detection of J015100 as a contact binary below the period limit suggests that contact binaries below this limit are not rapidly destroyed. This shallow-contact system may be formed from a detached short-period binary similar to DV Psc (Sp. = K4/K5; P = 0.d30855) via orbital shrinkage due to angular momentum loss through magnetic stellar wind.« less

AN INDIRECT SEARCH FOR WEAKLY INTERACTING MASSIVE PARTICLES IN THE SUN USING 3109.6 DAYS OF UPWARD-GOING MUONS IN SUPER-KAMIOKANDE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, T.; Abe, K.; Hayato, Y.

2011-12-01

We present the result of an indirect search for high energy neutrinos from Weakly Interacting Massive Particle (WIMP) annihilation in the Sun using upward-going muon (upmu) events at Super-Kamiokande. Data sets from SKI-SKIII (3109.6 days) were used for the analysis. We looked for an excess of neutrino signal from the Sun as compared with the expected atmospheric neutrino background in three upmu categories: stopping, non-showering, and showering. No significant excess was observed. The 90% C.L. upper limits of upmu flux induced by WIMPs of 100 GeV c{sup -2} were 6.4 Multiplication-Sign 10{sup -15} cm{sup -2} s{sup -1} and 4.0 Multiplication-Signmore » 10{sup -15} cm{sup -2} s{sup -1} for the soft and hard annihilation channels, respectively. These limits correspond to upper limits of 4.5 Multiplication-Sign 10{sup -39} cm{sup -2} and 2.7 Multiplication-Sign 10{sup -40} cm{sup -2} for spin-dependent WIMP-nucleon scattering cross sections in the soft and hard annihilation channels, respectively.« less

The influence of microlensing on spectral line shapes generated by a relativistic accretion disc

NASA Astrophysics Data System (ADS)

Popović, L. Č; Mediavilla, E. G.; Muñoz, J. A.

2001-10-01

We study the influence of gravitational microlensing on the spectral line profiles originating from a relativistic accretion disc. Using the Chen & Halpern model for the disc, we show the noticeable changes that microlensing can induce in the line shape when the Einstein radius associated with the microlens is of a size comparable to that of the accretion disc. Of special interest is the relative enhancement between the blue and red peaks of the line when an off-center microlens affects the approaching and receding parts of the accretion disc asymmetrically. In an AGN formed by a super-massive binary in which the accretion disc is located around one of the super-massive companions (the primary), we discuss the possibility of microlensing by the secondary. In this case the ratio between the blue and red peaks of the line profile would depend on the orbital phase. We have also considered the more standard configuration of microlensing by a star-sized object in an intervening galaxy and find that microlensing may also be detected in the broad emission lines of multiply imaged QSOs. The changes observed in the line profile of Arp 102 B are taken as a reference for exploring both scenarios.

Quantum tunneling and quasinormal modes in the spacetime of the Alcubierre warp drive

NASA Astrophysics Data System (ADS)

Jusufi, Kimet; Sakallı, İzzet; Övgün, Ali

2018-01-01

In a seminal paper, Alcubierre showed that Einstein's theory of general relativity appears to allow a super-luminal motion. In the present study, we use a recent eternal-warp-drive solution found by Alcubierre to study the effect of Hawking radiation upon an observer located within the warp drive in the framework of the quantum tunneling method. We find the same expression for the Hawking temperatures associated with the tunneling of both massive vector and scalar particles, and show this expression to be proportional to the velocity of the warp drive. On the other hand, since the discovery of gravitational waves, the quasinormal modes (QNMs) of black holes have also been extensively studied. With this purpose in mind, we perform a QNM analysis of massive scalar field perturbations in the background of the eternal-Alcubierre-warp-drive spacetime. Our analytical analysis shows that massive scalar perturbations lead to stable QNMs.

Crystal structure and equation of state of Fe-Si alloys at super-Earth core conditions

PubMed Central

Fratanduono, Dayne E.; Coppari, Federica; Newman, Matthew G.; Duffy, Thomas S.

2018-01-01

The high-pressure behavior of Fe alloys governs the interior structure and dynamics of super-Earths, rocky extrasolar planets that could be as much as 10 times more massive than Earth. In experiments reaching up to 1300 GPa, we combine laser-driven dynamic ramp compression with in situ x-ray diffraction to study the effect of composition on the crystal structure and density of Fe-Si alloys, a potential constituent of super-Earth cores. We find that Fe-Si alloy with 7 weight % (wt %) Si adopts the hexagonal close-packed structure over the measured pressure range, whereas Fe-15wt%Si is observed in a body-centered cubic structure. This study represents the first experimental determination of the density and crystal structure of Fe-Si alloys at pressures corresponding to the center of a ~3–Earth mass terrestrial planet. Our results allow for direct determination of the effects of light elements on core radius, density, and pressures for these planets. PMID:29707632

Crystal structure and equation of state of Fe-Si alloys at super-Earth core conditions

DOE PAGES

Wicks, June K.; Smith, Raymond F.; Fratanduono, Dayne E.; ...

2018-04-25

In this paper, the high-pressure behavior of Fe alloys governs the interior structure and dynamics of super-Earths, rocky extrasolar planets that could be as much as ten times more massive than Earth. In experiments reaching up to 1300 GPa, we combine laser-driven dynamic ramp compression with in situ X-ray diffraction to study the effect of composition on the crystal structure and density of Fe-Si alloys, a potential constituent of super-Earth cores. We find that Fe-7wt.%Si adopts the hexagonal close packed (hcp) structure over the measured pressure range, whereas Fe-15wt.%Si is observed in a body-centered cubic (bcc) structure. This study representsmore » the first experimental determination of the density and crystal structure of Fe-Si alloys at pressures corresponding to the center of a ~3 Earth-mass terrestrial planet. Our results allow for direct determination of the effects of light elements on core radius, density, and pressures for such planets.« less

Small Seed Black Hole Growth in Various Accretion Regimes

NASA Astrophysics Data System (ADS)

Gerling-Dunsmore, Hannalore J.; Hopkins, Philip F.

2016-03-01

Observational evidence indicates a population of super massive black holes (SMBHs) (~109 -1010M⊙) formed within 1 Gyr after the Big Bang. One proposed means of SMBH formation is accretion onto small seed black holes (BHs) (~ 100M⊙). However, the existence of SMBHs within 1 Gyr requires rapid growth, but conventional models of accretion fail to grow the seed BHs quickly enough. Super Eddington accretion (Ṁ >ṀEddington) may aid in improving growth efficiency. We study small seed BH growth via accretion in 3D, using the magneto-hydrodynamics+gravity code GIZMO. In particular, we consider a BH in a high density turbulent star-forming cloud, and ask whether or not the BH can capture sufficient gas to grow rapidly. We consider both Eddington-limited and super Eddington regimes, and resolve physics on scales from 0.1 pc to 1 kpc while including detailed models for stellar feedback physics, including stellar winds, supernovae, radiation pressure, and photo-ionization. We present results on the viability of different small seed BHs growing into SMBH candidates.

Crystal structure and equation of state of Fe-Si alloys at super-Earth core conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wicks, June K.; Smith, Raymond F.; Fratanduono, Dayne E.

In this paper, the high-pressure behavior of Fe alloys governs the interior structure and dynamics of super-Earths, rocky extrasolar planets that could be as much as ten times more massive than Earth. In experiments reaching up to 1300 GPa, we combine laser-driven dynamic ramp compression with in situ X-ray diffraction to study the effect of composition on the crystal structure and density of Fe-Si alloys, a potential constituent of super-Earth cores. We find that Fe-7wt.%Si adopts the hexagonal close packed (hcp) structure over the measured pressure range, whereas Fe-15wt.%Si is observed in a body-centered cubic (bcc) structure. This study representsmore » the first experimental determination of the density and crystal structure of Fe-Si alloys at pressures corresponding to the center of a ~3 Earth-mass terrestrial planet. Our results allow for direct determination of the effects of light elements on core radius, density, and pressures for such planets.« less

Growing massive black holes through supercritical accretion of stellar-mass seeds

NASA Astrophysics Data System (ADS)

Lupi, A.; Haardt, F.; Dotti, M.; Fiacconi, D.; Mayer, L.; Madau, P.

2016-03-01

The rapid assembly of the massive black holes that power the luminous quasars observed at z ˜ 6-7 remains a puzzle. Various direct collapse models have been proposed to head-start black hole growth from initial seeds with masses ˜105 M⊙, which can then reach a billion solar mass while accreting at the Eddington limit. Here, we propose an alternative scenario based on radiatively inefficient supercritical accretion of stellar-mass holes embedded in the gaseous circumnuclear discs (CNDs) expected to exist in the cores of high-redshift galaxies. Our sub-pc resolution hydrodynamical simulations show that stellar-mass holes orbiting within the central 100 pc of the CND bind to very high density gas clumps that arise from the fragmentation of the surrounding gas. Owing to the large reservoir of dense cold gas available, a stellar-mass black hole allowed to grow at super-Eddington rates according to the `slim-disc' solution can increase its mass by three orders of magnitudes within a few million years. These findings are supported by simulations run with two different hydro codes, RAMSES based on the Adaptive Mesh Refinement technique and GIZMO based on a new Lagrangian Godunov-type method, and with similar, but not identical, sub-grid recipes for star formation, supernova feedback, black hole accretion and feedback. The low radiative efficiency of supercritical accretion flows are instrumental to the rapid mass growth of our black holes, as they imply modest radiative heating of the surrounding nuclear environment.

Early BHs: simulations and observations

NASA Astrophysics Data System (ADS)

Cappelluti, Nico; di-Matteo, Tiziana; Schawinski, Kevin; Fragos, Tassos

We report recent investigations in the field of Early Black Holes. We summarize recent theoretical and observational efforts to understand how Black Holes formed and eventually evolved into Super Massive Black Holes at high-z. This paper makes use of state of the art computer simulations and multiwavelength surveys. Although non conclusive, we present results and hypothesis that pose exciting challenges to modern astrophysics and to future facilities.

String Theory Origin of Dyonic N=8 Supergravity and Its Chern-Simons Duals.

PubMed

Guarino, Adolfo; Jafferis, Daniel L; Varela, Oscar

2015-08-28

We clarify the higher-dimensional origin of a class of dyonic gaugings of D=4  N=8 supergravity recently discovered, when the gauge group is chosen to be ISO(7). This dyonically gauged maximal supergravity arises from consistent truncation of massive IIA supergravity on S^6, and its magnetic coupling constant descends directly from the Romans mass. The critical points of the supergravity uplift to new four-dimensional anti-de Sitter space (AdS4) massive type IIA vacua. We identify the corresponding three-dimensional conformal field theory (CFT3) duals as super-Chern-Simons-matter theories with simple gauge group SU(N) and level k given by the Romans mass. In particular, we find a critical point that uplifts to the first explicit N=2 AdS4 massive IIA background. We compute its free energy and that of the candidate dual Chern-Simons theory by localization to a solvable matrix model, and find perfect agreement. This provides the first AdS4/CFT3 precision match in massive type IIA string theory.

Looking for early black holes signatures in the anisotropies of Cosmic backgrounds

NASA Astrophysics Data System (ADS)

Cappelluti, Nico

2016-04-01

We currently do not know how Super Massive Black Holes are seeded and grow to form the observed massive QSO at z~7. This is puzzling, because at that redshift the Universe was still too young to allow the growth of such massive black holes from stellar remnant black hole seeds. Theoretical models, taking into account the paucity of metals in the early Universe, explain this by invoking the formation of massive black holes seeds at z>10 as Direct Collapse Black holes of remnants of dead POPIII stars. As of today we cannot claim any detection of any high-z (z>7) black hole in their early stage of life. However, our recent measures of the arcminute scale joint fluctuations of the Cosmic X-ray Background and the Cosmic Infrared Background by Chandra and Spitzer can be explained by a population of highly absorbed z>10 Direct Collapse Black Holes.I will review the recent discoveries obtained with different instruments and by different teams and critically discuss these findings and the interpretations.

Super Kitchen Centralizes Food Service

ERIC Educational Resources Information Center

Modern Schools, 1975

1975-01-01

To centralize food service within the entire Pittsburgh school district, a 90,000-square-foot food service preparation building contains cranes and monorails to move 500-pound capacity vats throughout the kitchen. (Author/MLF)

Super: a web server to rapidly screen superposable oligopeptide fragments from the protein data bank.

PubMed

Collier, James H; Lesk, Arthur M; Garcia de la Banda, Maria; Konagurthu, Arun S

2012-07-01

Searching for well-fitting 3D oligopeptide fragments within a large collection of protein structures is an important task central to many analyses involving protein structures. This article reports a new web server, Super, dedicated to the task of rapidly screening the protein data bank (PDB) to identify all fragments that superpose with a query under a prespecified threshold of root-mean-square deviation (RMSD). Super relies on efficiently computing a mathematical bound on the commonly used structural similarity measure, RMSD of superposition. This allows the server to filter out a large proportion of fragments that are unrelated to the query; >99% of the total number of fragments in some cases. For a typical query, Super scans the current PDB containing over 80,500 structures (with ∼40 million potential oligopeptide fragments to match) in under a minute. Super web server is freely accessible from: http://lcb.infotech.monash.edu.au/super.

The II Zw 40 Supernebula: 30 Doradus on Steroids

NASA Astrophysics Data System (ADS)

Leitherer, Claus

2015-10-01

We propose COS G140L spectroscopy of the enigmatic nearby blue compact dwarf galaxy II Zw 40. The galaxy hosts a nuclear super star cluster with a luminosity 10 times that of 30 Doradus, the most powerful giant HII region in the Local Group. The super star cluster has been suggested to be the ionizing source of a supernebula detected via its free-free radiation in the radio. The physical conditions, however, are much more complex, as demonstrated by the detection of the nebular He II and the mid-infrared line of [O IV] 25.9. These lines are unlikely to be related to hot stars and require a different powering source. II Zw 40 shares many similarities with the related blue compact dwarfs NGC 5253 and Henize 2-10, both of which have been studied extensively with HST, yet no ultraviolet spectroscopy has ever been obtained for II Zw 40. This small 4-orbit proposal will provide the necessary UV data to study the massive-star content directly. We will determine reddening, age, and the stellar initial mass function and perform a comparison with the local benchmark 30 Doradus. In particular we will investigate whether the hot stars are able to power the supernebula and the nebular high-excitation lines. Our modeling will utilize the latest generation of stellar evolutionary tracks with and without stellar rotation. If the stars fall short in terms of spectral hardness and luminosity, II Zw 40 may become the second candidate for a central black hole in a young starburst after Henize 2-10.

Quasar feedback revealed by giant molecular outflows

NASA Astrophysics Data System (ADS)

Feruglio, C.; Maiolino, R.; Piconcelli, E.; Menci, N.; Aussel, H.; Lamastra, A.; Fiore, F.

2010-07-01

In the standard scenario for galaxy evolution young star-forming galaxies transform into red bulge-dominated spheroids, where star formation has been quenched. To explain this transformation, a strong negative feedback generated by accretion onto a central super-massive black hole is often invoked. The depletion of gas resulting from quasar-driven outflows should eventually stop star-formation across the host galaxy and lead the black hole to “suicide” by starvation. Direct observational evidence for a major quasar feedback onto the host galaxy is still missing, because outflows previously observed in quasars are generally associated with the ionized component of the gas, which only accounts for a minor fraction of the total gas content, and typically occurrs in the central regions. We used the IRAM PdB Interferometer to observe the CO(1-0) transition in Mrk 231, the closest quasar known. Thanks to the wide band we detected broad wings of the CO line, with velocities of up to 750 km s-1 and spatially resolved on the kpc scale. These broad CO wings trace a giant molecular outflow of about 700 M_⊙/year, far larger than the ongoing star-formation rate (~200 M_⊙/year) observed in the host galaxy. This wind will totally expel the cold gas reservoir in Mrk 231 in about 107 yrs, therefore halting the star-formation activity on the same timescale. The inferred kinetic energy in the molecular outflow is ~1.2 × 1044 erg/s, corresponding to a few percent of the AGN bolometric luminosity, which is very close to the fraction expected by models ascribing quasar feedback to highly supersonic shocks generated by radiatively accelerated nuclear winds. Instead, the contribution by the SNe associated with the starburst fall short by several orders of magnitude to account for the kinetic energy observed in the outflow. The direct observational evidence for quasar feedback reported here provides solid support to the scenarios ascribing the observed properties of local massive galaxies to quasar-induced large-scale winds.

Underground neutrino detectors for particle and astroparticle Science: The Giant Liquid Argon Charge Imaging ExpeRiment (GLACIER)

NASA Astrophysics Data System (ADS)

Rubbia, André

2009-06-01

The current focus of the CERN program is the Large Hadron Collider (LHC), however, CERN is engaged in long baseline neutrino physics with the CNGS project and supports T2K as recognized CERN RE13, and for good reasons: a number of observed phenomena in high-energy physics and cosmology lack their resolution within the Standard Model of particle physics; these puzzles include the origin of neutrino masses, CP-violation in the leptonic sector, and baryon asymmetry of the Universe. They will only partially be addressed at LHC. A positive measurement of sin2 2θ13 > 0.01 would certainly give a tremendous boost to neutrino physics by opening the possibility to study CP violation in the lepton sector and the determination of the neutrino mass hierarchy with upgraded conventional super-beams. These experiments (so called 'Phase II') require, in addition to an upgraded beam power, next generation very massive neutrino detectors with excellent energy resolution and high detection efficiency in a wide neutrino energy range, to cover 1st and 2nd oscillation maxima, and excellent particle identification and p0 background suppression. Two generations of large water Cherenkov detectors at Kamioka (Kamiokande and Super-Kamiokande) have been extremely successful. And there are good reasons to consider a third generation water Cherenkov detector with an order of magnitude larger mass than Super-Kamiokande for both non-accelerator (proton decay, supernovae,...) and accelerator-based physics. On the other hand, a very massive underground liquid Argon detector of about 100 kton could represent a credible alternative for the precision measurements of 'Phase II' and aim at significantly new results in neutrino astroparticle and non-accelerator-based particle physics (e.g. proton decay).

Improving timing sensitivity in the microhertz frequency regime: limits from PSR J1713+0747 on gravitational waves produced by super-massive black-hole binaries

NASA Astrophysics Data System (ADS)

Perera, B. B. P.; Stappers, B. W.; Babak, S.; Keith, M. J.; Antoniadis, J.; Bassa, C. G.; Caballero, R. N.; Champion, D. J.; Cognard, I.; Desvignes, G.; Graikou, E.; Guillemot, L.; Janssen, G. H.; Karuppusamy, R.; Kramer, M.; Lazarus, P.; Lentati, L.; Liu, K.; Lyne, A. G.; McKee, J. W.; Osłowski, S.; Perrodin, D.; Sanidas, S. A.; Sesana, A.; Shaifullah, G.; Theureau, G.; Verbiest, J. P. W.; Taylor, S. R.

2018-05-01

We search for continuous gravitational waves (CGWs) produced by individual super-massive black-hole binaries (SMBHBs) in circular orbits using high-cadence timing observations of PSR J1713+0747. We observe this millisecond pulsar using the telescopes in the European Pulsar Timing Array (EPTA) with an average cadence of approximately 1.6 days over the period between April 2011 and July 2015, including an approximately daily average between February 2013 and April 2014. The high-cadence observations are used to improve the pulsar timing sensitivity across the GW frequency range of 0.008 - 5 μHz. We use two algorithms in the analysis, including a spectral fitting method and a Bayesian approach. For an independent comparison, we also use a previously published Bayesian algorithm. We find that the Bayesian approaches provide optimal results and the timing observations of the pulsar place a 95 per cent upper limit on the sky-averaged strain amplitude of CGWs to be ≲ 3.5 × 10-13 at a reference frequency of 1 μHz. We also find a 95 per cent upper limit on the sky-averaged strain amplitude of low-frequency CGWs to be ≲ 1.4 × 10-14 at a reference frequency of 20 nHz.

Feedback in the Antennae Galaxies (NGC 4038/9): I. High-Resolution Infrared Spectroscopy of Winds from Super Star Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilbert, A; Graham, J

2007-06-05

We present high-resolution (R {approx} 24,600) near-IR spectroscopy of the youngest super star clusters (SSCs) in the prototypical starburst merger, the Antennae Galaxies. These SSCs are young (3-7 Myr old) and massive (10{sup 5}-10{sup 7} M{sub {circle_dot}} for a Kroupa IMF) and their spectra are characterized by broad, extended Brackett {gamma} emission, so we refer to them as emission-line clusters (ELCs) to distinguish them from older SSCs. The Br {gamma} lines of most ELCs have supersonic widths (60-110 km s{sup -1} FWHM) and non-Gaussian wings whose velocities exceed the clusters escape velocities. This high-velocity unbound gas is flowing out inmore » winds that are powered by the clusters massive O and W-R stars over the course of at least several crossing times. The large sizes of some ELCs relative to those of older SSCs may be due to expansion caused by these outflows; many of the ELCs may not survive as bound stellar systems, but rather dissipate rapidly into the field population. The observed tendency of older ELCs to be more compact than young ones is consistent with the preferential survival of the most concentrated clusters at a given age.« less

dbSUPER: a database of super-enhancers in mouse and human genome

PubMed Central

Khan, Aziz; Zhang, Xuegong

2016-01-01

Super-enhancers are clusters of transcriptional enhancers that drive cell-type-specific gene expression and are crucial to cell identity. Many disease-associated sequence variations are enriched in super-enhancer regions of disease-relevant cell types. Thus, super-enhancers can be used as potential biomarkers for disease diagnosis and therapeutics. Current studies have identified super-enhancers in more than 100 cell types and demonstrated their functional importance. However, a centralized resource to integrate all these findings is not currently available. We developed dbSUPER (http://bioinfo.au.tsinghua.edu.cn/dbsuper/), the first integrated and interactive database of super-enhancers, with the primary goal of providing a resource for assistance in further studies related to transcriptional control of cell identity and disease. dbSUPER provides a responsive and user-friendly web interface to facilitate efficient and comprehensive search and browsing. The data can be easily sent to Galaxy instances, GREAT and Cistrome web-servers for downstream analysis, and can also be visualized in the UCSC genome browser where custom tracks can be added automatically. The data can be downloaded and exported in variety of formats. Furthermore, dbSUPER lists genes associated with super-enhancers and also links to external databases such as GeneCards, UniProt and Entrez. dbSUPER also provides an overlap analysis tool to annotate user-defined regions. We believe dbSUPER is a valuable resource for the biology and genetic research communities. PMID:26438538

THE OBSERVED M-{sigma} RELATIONS IMPLY THAT SUPER-MASSIVE BLACK HOLES GROW BY COLD CHAOTIC ACCRETION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nayakshin, Sergei; King, Andrew R.; Power, Chris

We argue that current observations of M-{sigma} relations for galaxies can be used to constrain theories of super-massive black holes (SMBHs) feeding. In particular, assuming that SMBH mass is limited only by the feedback on the gas that feeds it, we show that SMBHs fed via a planar galaxy-scale gas flow, such as a disk or a bar, should be much more massive than their counterparts fed by quasi-spherical inflows. This follows from the relative inefficiency of active galactic nucleus feedback on a flattened inflow. We find that even under the most optimistic conditions for SMBH feedback on flattened inflows,more » the mass at which the SMBH expels the gas disk and terminates its own growth is a factor of several higher than the one established for quasi-spherical inflows. Any beaming of feedback away from the disk and any disk self-shadowing strengthen this result further. Contrary to this theoretical expectation, recent observations have shown that SMBHs in pseudobulge galaxies (which are associated with barred galaxies) are typically under- rather than overmassive when compared with their classical bulge counterparts at a fixed value of {sigma}. We conclude from this that SMBHs are not fed by large (100 pc to many kpc) scale gas disks or bars, most likely because such planar flows are turned into stars too efficiently to allow any SMBH growth. Based on this and other related observational evidence, we argue that most SMBHs grow by chaotic accretion of gas clouds with a small and nearly randomly distributed direction of angular momentum.« less

Ultra-Heavy Galactic Cosmic Ray Abundances from the SuperTIGER Instrument: evidence for an OB association origin of GCR

NASA Astrophysics Data System (ADS)

Murphy, Ryan; Supertiger Collaboration

2017-01-01

We report Galactic Cosmic Ray (GCR) abundances of elements from 26Fe to 40Zr measured by the SuperTIGER (Trans-Iron Galactic Element Recorder) instrument during 55 days of exposure on a long-duration balloon flight over Antarctica. SuperTIGER measures charge (Z) and energy (E) using a combination of three scintillator and two Cherenkov detectors, and employs a scintillating fiber hodoscope for event trajectory determination. These observations resolve elemental abundances in this charge range with single-element resolution and good statistics. We also derived GCR source abundances, which support a model of cosmic-ray origin in which the source material consists of a mixture of 19-6+ 11 % material from massive stars and 81% normal interstellar medium (ISM) material with solar system abundances. The results also show a preferential acceleration, ordered by atomic mass (A), of refractory elements over volatile elements by a factor of 4. Both the refractory and volatile elements show a mass-dependent enhancement with similar mass dependence. (now AIP Congressional Science Fellow).

Central pedicled breast reduction technique in male patients after massive weight loss.

PubMed

Stoff, Alexander; Velasco-Laguardia, Fernando J; Richter, Dirk F

2012-03-01

Male patients after massive weight loss often suffer from redundant skin and soft tissue in the anterior and lateral chest region, causing various deformities of pseudogynecomastia. Techniques with free or pedicled nipple-areola complex (NAC) transposition are widely accepted. The authors present their approach to male breast reduction with preservation of the NAC on a central dermoglandular pedicle and a wide elliptical tissue excision of breast and lateral thorax tissue in combination with liposuction. Male breast reduction was performed on patients after moderate to massive weight loss due to diet or bariatric procedures. Former procedures included free nipple-areola grafts or inferior pedicled techniques for NAC preservation. As a modification, we performed a central pedicled breast reduction on nine male patients with excessive liposuction of the pedicle and a horizontal elliptical skin removal, allowing for sufficient tissue removal at the lateral thorax. From October 2010 until June 2011, nine male patients had central pedicled breast reconstructions after massive weight loss. Mean age was 29.1 years, mean preoperative body mass index was 29.2, and mean preoperative weight loss was 63.9 kg. The chest wall improvement was rated "very good" by eight patients. No major complications occurred in all nine patients. Male chest deformities after massive weight loss can be dealt by several approaches. The optimal scar positioning and the preservation of NAC may be the most challenging aspects of these procedures. Therefore, the preservation of the NAC on a central dermoglandular pedicle with a horizontal submammary scar course may optimize the esthetic outcome.

M32 analogs? A population of massive ultra-compact dwarf and compact elliptical galaxies in intermediate-redshift clusters

DOE PAGES

Zhang, Yuanyuan; Bell, Eric F.

2017-01-13

Here, we report the discovery of relatively massive, M32-like ultra compact dwarf (UCD) and compact elliptical (CE) galaxy candidates inmore » $$0.2\\lt z\\lt 0.6$$ massive galaxy clusters imaged by the Cluster Lensing And Supernova survey with Hubble (CLASH) survey. Examining the nearly unresolved objects in the survey, we identify a sample of compact objects concentrated around the cluster central galaxies with colors similar to cluster red sequence galaxies. Their colors and magnitudes suggest stellar masses around $${10}^{9}{M}_{\\odot }$$. More than half of these galaxies have half-light radii smaller than 200 pc, falling into the category of massive UCDs and CEs, with properties similar to M32. The properties are consistent with a tidal stripping origin, but we cannot rule out the possibility that they are early-formed compact objects trapped in massive dark matter halos. The 17 CLASH clusters studied in this work on average contain 2.7 of these objects in their central 0.3 Mpc and 0.6 in their central 50 kpc. Our study demonstrates the possibility of statistically characterizing UCDs/CEs with a large set of uniform imaging survey data.« less

M32 analogs? A population of massive ultra-compact dwarf and compact elliptical galaxies in intermediate-redshift clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yuanyuan; Bell, Eric F.

Here, we report the discovery of relatively massive, M32-like ultra compact dwarf (UCD) and compact elliptical (CE) galaxy candidates inmore » $$0.2\\lt z\\lt 0.6$$ massive galaxy clusters imaged by the Cluster Lensing And Supernova survey with Hubble (CLASH) survey. Examining the nearly unresolved objects in the survey, we identify a sample of compact objects concentrated around the cluster central galaxies with colors similar to cluster red sequence galaxies. Their colors and magnitudes suggest stellar masses around $${10}^{9}{M}_{\\odot }$$. More than half of these galaxies have half-light radii smaller than 200 pc, falling into the category of massive UCDs and CEs, with properties similar to M32. The properties are consistent with a tidal stripping origin, but we cannot rule out the possibility that they are early-formed compact objects trapped in massive dark matter halos. The 17 CLASH clusters studied in this work on average contain 2.7 of these objects in their central 0.3 Mpc and 0.6 in their central 50 kpc. Our study demonstrates the possibility of statistically characterizing UCDs/CEs with a large set of uniform imaging survey data.« less

Near-infrared structure of fast and slow-rotating disk galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schechtman-Rook, Andrew; Bershady, Matthew A., E-mail: andrew@astro.wisc.edu

We investigate the stellar disk structure of six nearby edge-on spiral galaxies using high-resolution JHK {sub s}-band images and three-dimensional radiative transfer models. To explore how mass and environment shape spiral disks, we selected galaxies with rotational velocities between 69 km s{sup –1} 150 km s{sup –1}) galaxies, only NGC 4013 has the super-thin+thin+thick nested disk structure seen in NGC 891 and the Milky Way, albeit with decreased oblateness, while NGC 1055, a disturbed massive spiral galaxy, contains disks with h{sub z} ≲ 200 pc. NGC 4565, another fast-rotator, contains a prominent ring at a radius ∼5 kpc but nomore » super-thin disk. Despite these differences, all fast-rotating galaxies in our sample have inner truncations in at least one of their disks. These truncations lead to Freeman Type II profiles when projected face-on. Slow-rotating galaxies are less complex, lacking inner disk truncations and requiring fewer disk components to reproduce their light distributions. Super-thin disk components in undisturbed disks contribute ∼25% of the total K {sub s}-band light, up to that of the thin-disk contribution. The presence of super-thin disks correlates with infrared flux ratios; galaxies with super-thin disks have f{sub K{sub s}}/f{sub 60} {sub μm}≤0.12 for integrated light, consistent with super-thin disks being regions of ongoing star-formation. Attenuation-corrected vertical color gradients in (J – K {sub s}) correlate with the observed disk structure and are consistent with population gradients with young-to-intermediate ages closer to the mid-plane, indicating that disk heating—or cooling—is a ubiquitous phenomenon.« less

CEMPlifying reionization

NASA Astrophysics Data System (ADS)

Sharma, Mahavir; Theuns, Tom; Frenk, Carlos

2018-05-01

The massive stars that ionised the Universe have short lifetimes and can only be studied near the time of formation, but any low mass stars that formed contemporaneously might be observable in the local Universe today. We study the abundance pattern and spatial distribution of these `siblings of reionizers' (SoRs) in the EAGLE cosmological hydrodynamical simulation. SoRs tend to be enriched to super-solar levels in α-elements compared to iron. In EAGLE galaxies resembling the Milky Way, ˜40 percent of carbon-enhanced metal poor (CEMP) stars are SoRs. Conversely, ˜10 percent of all SoRs are CEMP stars. This fraction increases to ≳ 50 percent for SoRs of metallicity [Fe/H]<-4, and at such low metallicities, most of the CEMP stars are of CEMP-no subtype that are lacking neutron capture elements. Although these numbers may well depend on the details of the physical models implemented in EAGLE, the trends we describe are robust as they result from the strong feedback from star formation in early galaxies, itself a key ingredient of most current models of galaxy formation. We further find that most SoRs today reside in halos with mass Mh≳1012 M⊙, and 50 percent of them are in the halo of their central galaxy (distance >10 kpc), mainly because they were accreted onto their current host rather than formed in-situ. To a good approximation, the SoRs are CEMP-no stars that reside in the stellar halos of massive galaxies, with nearly half of them contributing to the intracluster light in groups and clusters.

Super: a web server to rapidly screen superposable oligopeptide fragments from the protein data bank

PubMed Central

Collier, James H.; Lesk, Arthur M.; Garcia de la Banda, Maria; Konagurthu, Arun S.

2012-01-01

Searching for well-fitting 3D oligopeptide fragments within a large collection of protein structures is an important task central to many analyses involving protein structures. This article reports a new web server, Super, dedicated to the task of rapidly screening the protein data bank (PDB) to identify all fragments that superpose with a query under a prespecified threshold of root-mean-square deviation (RMSD). Super relies on efficiently computing a mathematical bound on the commonly used structural similarity measure, RMSD of superposition. This allows the server to filter out a large proportion of fragments that are unrelated to the query; >99% of the total number of fragments in some cases. For a typical query, Super scans the current PDB containing over 80 500 structures (with ∼40 million potential oligopeptide fragments to match) in under a minute. Super web server is freely accessible from: http://lcb.infotech.monash.edu.au/super. PMID:22638586

Earth observations taken from Discovery during STS-85 mission - Typhoon Winnie

NASA Image and Video Library

1997-08-15

S85-E-5092 (14 August 1997) --- Flying directly over the eye just before 3 p.m. (EST), Aug. 15, the STS-85 crew members captured this image of Super Typhoon Winnie. The massive typhoon is located about half way between Japan and New Guinea in the Pacific Ocean. The Canadian-built robot arm of Discovery, being used in operations with CRISTA-SPAS on this mission, is partially visible in left foreground.

Superspace geometrical realization of the N-extended super Virasoro algebra and its dual

NASA Astrophysics Data System (ADS)

Curto, C.; Gates, S. J., Jr.; Rodgers, V. G. J.

2000-05-01

We derive properties of N-extended /GR super Virasoro algebras. These include adding central extensions, identification of all primary fields and the action of the adjoint representation on its dual. The final result suggest identification with the spectrum of fields in supergravity theories and superstring/M-theory constructed from NSR N-extended supersymmetric /GR Virasoro algebras.

Minimal massive 3D gravity

NASA Astrophysics Data System (ADS)

Bergshoeff, Eric; Hohm, Olaf; Merbis, Wout; Routh, Alasdair J.; Townsend, Paul K.

2014-07-01

We present an alternative to topologically massive gravity (TMG) with the same ‘minimal’ bulk properties; i.e. a single local degree of freedom that is realized as a massive graviton in linearization about an anti-de Sitter (AdS) vacuum. However, in contrast to TMG, the new ‘minimal massive gravity’ has both a positive energy graviton and positive central charges for the asymptotic AdS-boundary conformal algebra.

Electrically charged: An effective mechanism for soft EOS supporting massive neutron star

NASA Astrophysics Data System (ADS)

Jing, ZhenZhen; Wen, DeHua; Zhang, XiangDong

2015-10-01

The massive neutron star discoverer announced that strange particles, such as hyperons should be ruled out in the neutron star core as the soft Equation of State (EOS) can-not support a massive neutron star. However, many of the nuclear theories and laboratory experiments support that at high density the strange particles will appear and the corresponding EOS of super-dense matters will become soft. This situation promotes a challenge between the astro-observation and nuclear physics. In this work, we introduce an effective mechanism to answer this challenge, that is, if a neutron star is electrically charged, a soft EOS will be equivalently stiffened and thus can support a massive neutron star. By employing a representative soft EOS, it is found that in order to obtain an evident effect on the EOS and thus increasing the maximum stellar mass by the electrostatic field, the total net charge should be in an order of 1020 C. Moreover, by comparing the results of two kind of charge distributions, it is found that even for different distributions, a similar total charge: ~ 2.3 × 1020 C is needed to support a ~ 2.0 M ⊙ neutron star.

SOWFA + Super Controller User's Manual

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleming, P.; Gebraad, P.; Churchfield, M.

2013-08-01

SOWFA + Super Controller is a modification of the NREL's SOWFA tool which allows for a user to apply multiturbine or centralized wind plant control algorithms within the high-fidelity SOWFA simulation environment. The tool is currently a branch of the main SOWFA program, but will one day will be merged into a single version. This manual introduces the tool and provides examples such that a usercan implement their own super controller and set up and run simulations. The manual only discusses enough about SOWFA itself to allow for the customization of controllers and running of simulations, and details of SOWFAmore » itself are reported elsewhere Churchfield and Lee (2013); Churchfield et al. (2012). SOWFA + Super Controller, and this manual, are in alpha mode.« less

Nature and origin of a Pleistocene-age massive ground-ice body exposed in the Chapman Lake moraine complex, central Yukon Territory, Canada

NASA Astrophysics Data System (ADS)

Lacelle, Denis; Lauriol, Bernard; Clark, Ian D.; Cardyn, Raphaelle; Zdanowicz, Christian

2007-09-01

A massive ground-ice body was found exposed in the headwall of a thaw flow developed within the Chapman Lake terminal moraine complex on the Blackstone Plateau (Ogilvie Mountains, central Yukon Territory), which is contemporaneous to the Reid glaciation. Based on visible cryostructures in the 4-m-high headwall, two units were identified: massive ground ice, overlain sharply by 2 m of icy diamicton. The nature and origin of the Chapman Lake massive ground ice was determined using cryostratigraphy, petrography, stable O-H isotopes and the molar concentration of occluded gases (CO 2, O 2, N 2 and Ar) entrapped in the ice, a new technique in the field of periglacial geomorphology that allows to distinguish between glacial and non-glacial intrasedimental ice. Collectively, the results indicate that the Chapman Lake massive ground ice formed by firn densification with limited melting-refreezing and underwent deformation near its margin. Given that the massive ground-ice body consists of relict glacier ice, it suggests that permafrost persisted, at least locally, on plateau areas in the central Yukon Territory since the middle Pleistocene. In addition, the d value of Chapman Lake relict glacier ice suggests that the ice covering the area during the Reid glaciation originated from a local alpine glaciation in the Ogilvie Mountains.

Group quenching and galactic conformity at low redshift

NASA Astrophysics Data System (ADS)

Treyer, M.; Kraljic, K.; Arnouts, S.; de la Torre, S.; Pichon, C.; Dubois, Y.; Vibert, D.; Milliard, B.; Laigle, C.; Seibert, M.; Brown, M. J. I.; Grootes, M. W.; Wright, A. H.; Liske, J.; Lara-Lopez, M. A.; Bland-Hawthorn, J.

2018-06-01

We quantify the quenching impact of the group environment using the spectroscopic survey Galaxy and Mass Assembly to z ˜ 0.2. The fraction of red (quiescent) galaxies, whether in groups or isolated, increases with both stellar mass and large-scale (5 Mpc) density. At fixed stellar mass, the red fraction is on average higher for satellites of red centrals than of blue (star-forming) centrals, a galactic conformity effect that increases with density. Most of the signal originates from groups that have the highest stellar mass, reside in the densest environments, and have massive, red only centrals. Assuming a colour-dependent halo-to-stellar-mass ratio, whereby red central galaxies inhabit significantly more massive haloes than blue ones of the same stellar mass, two regimes emerge more distinctly: at log (Mhalo/M⊙) ≲ 13, central quenching is still ongoing, conformity is no longer existent, and satellites and group centrals exhibit the same quenching excess over field galaxies at all mass and density, in agreement with the concept of `group quenching'; at log (Mh/M⊙) ≳ 13, a cut-off that sets apart massive (log (M⋆/M⊙) > 11), fully quenched group centrals, conformity is meaningless, and satellites undergo significantly more quenching than their counterparts in smaller haloes. The latter effect strongly increases with density, giving rise to the density-dependent conformity signal when both regimes are mixed. The star formation of blue satellites in massive haloes is also suppressed compared to blue field galaxies, while blue group centrals and the majority of blue satellites, which reside in low-mass haloes, show no deviation from the colour-stellar mass relation of blue field galaxies.

Dynamical Processes Near the Super Massive Black Hole at the Galactic Center

NASA Astrophysics Data System (ADS)

Antonini, Fabio

2011-01-01

Observations of the stellar environment near the Galactic center provide the strongest empirical evidence for the existence of massive black holes in the Universe. Theoretical models of the Milky Way nuclear star cluster fail to explain numerous properties of such environment, including the presence of very young stars close to the super massive black hole (SMBH) and the more recent discovery of a parsec-scale core in the central distribution of the bright late-type (old) stars. In this thesis we present a theoretical study of dynamical processes near the Galactic center, strongly related to these issues. Using different numerical techniques we explore the close environment of a SMBH as catalyst for stellar collisions and mergers. We study binary stars that remain bound for several revolutions around the SMBH, finding that in the case of highly inclined binaries the Kozai resonance can lead to large periodic oscillations in the internal binary eccentricity and inclination. Collisions and mergers of the binary elements are found to increase significantly for multiple orbits around the SMBH. In collisions involving a low-mass and a high-mass star, the merger product acquires a high core hydrogen abundance from the smaller star, effectively resetting the nuclear evolution clock to a younger age. This process could serve as an important source of young stars at the Galactic center. We then show that a core in the old stars can be naturally explained in a scenario in which the Milky Way nuclear star cluster (NSC) is formed via repeated inspiral of globular clusters into the Galactic center. We present results from a set of N -body simulations of this process, which show that the fundamental properties of the NSC, including its mass, outer density profile and velocity structure, are also reproduced. Chandrasekhar's dynamical friction formula predicts no frictional force on a test body in a low-density core, regardless of its density, due to the absence of stars moving more slowly than the local circular velocity. We have tested this prediction using large-scale N -body experiments. The rate of orbital decay never drops precisely to zero, because stars moving faster than the test body also contribute to the frictional force. When the contribution from the fast-moving stars is included in the expression for the dynamical friction force, and the changes induced by the massive body on the stellar distribution are taken into account, Chandrasekhar's theory is found to reproduce the rate of orbital decay remarkably well. However, this rate is still substantially smaller than the rate predicted by Chandrasekhar's formula in its most widely-used forms, implying longer time scales for inspiral. Motivated by recent observations that suggest a parsec-scale core around the Galactic center SMBH, we investigated the evolution of a population of stellar-mass black holes (BHs) as they spiral in to the center of the Galaxy. After ˜ 10 Gyr, we find that the density of BHs can remain substantially less than the density in stars at all radii; we conclude that it would be unjustified to assume that the spatial distribution of BHs at the Galactic center is well described by steady-state models.

Search for dark matter WIMPs using upward through-going muons in Super-Kamiokande

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desai, S.; Earl, M.; Kearns, E.

2004-10-15

We present the results of indirect searches for Weakly Interacting Massive Particles (WIMPs), with 1679.6 live days of data from the Super-Kamiokande detector using neutrino-induced upward through-going muons. The search is performed by looking for an excess of high energy muon neutrinos from WIMP annihilations in the Sun, the core of the Earth, and the Galactic Center, as compared to the number expected from the atmospheric neutrino background. No statistically significant excess was seen. We calculate the flux limits in various angular cones around each of the above celestial objects. We obtain conservative model-independent upper limits on the WIMP-nucleon crossmore » section as a function of WIMP mass, and compare these results with the corresponding results from direct dark matter detection experiments.« less

The Early Growth of the First Black Holes

NASA Astrophysics Data System (ADS)

Johnson, Jarrett L.; Haardt, Francesco

2016-03-01

With detections of quasars powered by increasingly massive black holes at increasingly early times in cosmic history over the past decade, there has been correspondingly rapid progress made on the theory of early black hole formation and growth. Here, we review the emerging picture of how the first massive black holes formed from the primordial gas and then grew to supermassive scales. We discuss the initial conditions for the formation of the progenitors of these seed black holes, the factors dictating the initial masses with which they form, and their initial stages of growth via accretion, which may occur at super-Eddington rates. Finally, we briefly discuss how these results connect to large-scale simulations of the growth of supermassive black holes in the first billion years after the Big Bang.

Big data mining analysis method based on cloud computing

NASA Astrophysics Data System (ADS)

Cai, Qing Qiu; Cui, Hong Gang; Tang, Hao

2017-08-01

Information explosion era, large data super-large, discrete and non-(semi) structured features have gone far beyond the traditional data management can carry the scope of the way. With the arrival of the cloud computing era, cloud computing provides a new technical way to analyze the massive data mining, which can effectively solve the problem that the traditional data mining method cannot adapt to massive data mining. This paper introduces the meaning and characteristics of cloud computing, analyzes the advantages of using cloud computing technology to realize data mining, designs the mining algorithm of association rules based on MapReduce parallel processing architecture, and carries out the experimental verification. The algorithm of parallel association rule mining based on cloud computing platform can greatly improve the execution speed of data mining.

Variation of fundamental constants on sub- and super-Hubble scales: From the equivalence principle to the multiverse

NASA Astrophysics Data System (ADS)

Uzan, Jean-Philippe

2013-02-01

Fundamental constants play a central role in many modern developments in gravitation and cosmology. Most extensions of general relativity lead to the conclusion that dimensionless constants are actually dynamical fields. Any detection of their variation on sub-Hubble scales would signal a violation of the Einstein equivalence principle and hence a lead to gravity beyond general relativity. On super-Hubble scales, or maybe should we say on super-universe scales, such variations are invoked as a solution to the fine-tuning problem, in connection with an anthropic approach.

A LUMINOUS, FAST RISING UV-TRANSIENT DISCOVERED BY ROTSE: A TIDAL DISRUPTION EVENT?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vinkó, J.; Wheeler, J. C.; Chatzopoulos, E.

2015-01-01

We present follow-up observations of an optical transient (OT) discovered by ROTSE on 2009 January 21. Photometric monitoring was carried out with ROTSE-IIIb in the optical and Swift in the UV up to +70 days after discovery. The light curve showed a fast rise time of ∼10 days followed by a steep decline over the next 60 days, which was much faster than that implied by {sup 56}Ni—{sup 56}Co radioactive decay. The Sloan Digital Sky Survey Data Release 10 database contains a faint, red object at the position of the OT, which appears slightly extended. This and other lines ofmore » evidence suggest that the OT is of extragalactic origin, and this faint object is likely the host galaxy. A sequence of optical spectra obtained with the 9.2 m Hobby-Eberly Telescope between +8 and +45 days after discovery revealed a hot, blue continuum with no visible spectral features. A few weak features that appeared after +30 days probably originated from the underlying host. Fitting synthetic templates to the observed spectrum of the host galaxy revealed a redshift of z = 0.19. At this redshift, the peak magnitude of the OT is close to –22.5, similar to the brightest super-luminous supernovae; however, the lack of identifiable spectral features makes the massive stellar death hypothesis less likely. A more plausible explanation appears to be the tidal disruption of a Sun-like star by the central supermassive black hole. We argue that this transient likely belongs to a class of super-Eddington tidal disruption events.« less

The Nature and Origin of UCDs in the Coma Cluster

NASA Astrophysics Data System (ADS)

Chiboucas, Kristin; Tully, R. Brent; Madrid, Juan; Phillipps, Steven; Carter, David; Peng, Eric

2018-01-01

UCDs are super massive star clusters found largely in dense regions but have also been found around individual galaxies and in smaller groups. Their origin is still under debate but currently favored scenarios include formation as giant star clusters, either as the brightest globular clusters or through mergers of super star clusters, themselves formed during major galaxy mergers, or as remnant nuclei from tidal stripping of nucleated dwarf ellipticals. Establishing the nature of these enigmatic objects has important implications for our understanding of star formation, star cluster formation, the missing satellite problem, and galaxy evolution. We are attempting to disentangle these competing formation scenarios with a large survey of UCDs in the Coma cluster. Using ACS two-passband imaging from the HST/ACS Coma Cluster Treasury Survey, we are using colors and sizes to identify the UCD cluster members. With a large size limited sample of the UCD population within the core region of the Coma cluster, we are investigating the population size, properties, and spatial distribution, and comparing that with the Coma globular cluster and nuclear star cluster populations to discriminate between the threshing and globular cluster scenarios. In previous work, we had found a possible correlation of UCD colors with host galaxy and a possible excess of UCDs around a non-central giant galaxy with an unusually large globular cluster population, both suggestive of a globular cluster origin. With a larger sample size and additional imaging fields that encompass the regions around these giant galaxies, we have found that the color correlation with host persists and the giant galaxy with unusually large globular cluster population does appear to host a large UCD population as well. We present the current status of the survey.

Surprise: Dwarf Galaxy Harbors Supermassive Black Hole

NASA Astrophysics Data System (ADS)

2011-01-01

The surprising discovery of a supermassive black hole in a small nearby galaxy has given astronomers a tantalizing look at how black holes and galaxies may have grown in the early history of the Universe. Finding a black hole a million times more massive than the Sun in a star-forming dwarf galaxy is a strong indication that supermassive black holes formed before the buildup of galaxies, the astronomers said. The galaxy, called Henize 2-10, 30 million light-years from Earth, has been studied for years, and is forming stars very rapidly. Irregularly shaped and about 3,000 light-years across (compared to 100,000 for our own Milky Way), it resembles what scientists think were some of the first galaxies to form in the early Universe. "This galaxy gives us important clues about a very early phase of galaxy evolution that has not been observed before," said Amy Reines, a Ph.D. candidate at the University of Virginia. Supermassive black holes lie at the cores of all "full-sized" galaxies. In the nearby Universe, there is a direct relationship -- a constant ratio -- between the masses of the black holes and that of the central "bulges" of the galaxies, leading them to conclude that the black holes and bulges affected each others' growth. Two years ago, an international team of astronomers found that black holes in young galaxies in the early Universe were more massive than this ratio would indicate. This, they said, was strong evidence that black holes developed before their surrounding galaxies. "Now, we have found a dwarf galaxy with no bulge at all, yet it has a supermassive black hole. This greatly strengthens the case for the black holes developing first, before the galaxy's bulge is formed," Reines said. Reines, along with Gregory Sivakoff and Kelsey Johnson of the University of Virginia and the National Radio Astronomy Observatory (NRAO), and Crystal Brogan of the NRAO, observed Henize 2-10 with the National Science Foundation's Very Large Array radio telescope and with the Hubble Space Telescope. They found a region near the center of the galaxy that strongly emits radio waves with characteristics of those emitted by super-fast "jets" of material spewed outward from areas close to a black hole. They then searched images from the Chandra X-Ray Observatory that showed this same, radio-bright region to be strongly emitting energetic X-rays. This combination, they said, indicates an active, black-hole-powered, galactic nucleus. "Not many dwarf galaxies are known to have massive black holes," Sivakoff said. While central black holes of roughly the same mass as the one in Henize 2-10 have been found in other galaxies, those galaxies all have much more regular shapes. Henize 2-10 differs not only in its irregular shape and small size but also in its furious star formation, concentrated in numerous, very dense "super star clusters." "This galaxy probably resembles those in the very young Universe, when galaxies were just starting to form and were colliding frequently. All its properties, including the supermassive black hole, are giving us important new clues about how these black holes and galaxies formed at that time," Johnson said. The astronomers reported their findings in the January 9 online edition of Nature, and at the American Astronomical Society's meeting in Seattle, WA.

[WN] central stars of planetary nebulae

NASA Astrophysics Data System (ADS)

Todt, H.; Miszalski, B.; Toalá, J. A.; Guerrero, M. A.

2017-10-01

While most of the low-mass stars stay hydrogen-rich on their surface throughout their evolution, a considerable fraction of white dwarfs as well as central stars of planetary nebulae have a hydrogen-deficient surface composition. The majority of these H-deficient central stars exhibit spectra very similar to massive Wolf-Rayet stars of the carbon sequence, i.e. with broad emission lines of carbon, helium, and oxygen. In analogy to the massive Wolf-Rayet stars, they are classified as [WC] stars. Their formation, which is relatively well understood, is thought to be the result of a (very) late thermal pulse of the helium burning shell. It is therefore surprising that some H-deficient central stars which have been found recently, e.g. IC 4663 and Abell 48, exhibit spectra that resemble those of the massive Wolf-Rayet stars of the nitrogen sequence, i.e. with strong emission lines of nitrogen instead of carbon. This new type of central stars is therefore labelled [WN]. We present spectral analyses of these objects and discuss the status of further candidates as well as the evolutionary status and origin of the [WN] stars.

Science in 60 – Searching for Dark Matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albert, Andrea

2016-09-30

Nearly 14,000 feet up the slopes of Mexico's Sierra Negra volcano, a unique observatory called HAWC (High-Altitude Water Cherenkov Gamma Ray Observatory) is providing insight into some of the most violent phenomena in the known universe, such as supernovae explosions and the evolution of super massive black holes. For Dr. Andrea Albert, the Marie Curie Distinguished Postdoctoral Fellow at Los Alamos National Lab, HAWC provides another distinct opportunity: a way to search for signals from dark matter.

Dense CO in Mrk 71-A: Superwind Suppressed in a Young Super Star Cluster

NASA Astrophysics Data System (ADS)

Oey, M. S.; Herrera, C. N.; Silich, Sergiy; Reiter, Megan; James, Bethan L.; Jaskot, A. E.; Micheva, Genoveva

2017-11-01

We report the detection of CO(J=2-1) coincident with the super star cluster (SSC) Mrk 71-A in the nearby Green Pea analog galaxy, NGC 2366. Our observations with the Northern Extended Millimeter Array reveal a compact, ˜7 pc, molecular cloud whose mass ({10}5 {M}⊙ ) is similar to that of the SSC, consistent with a high star formation efficiency, on the order of 0.5. There are two spatially distinct components separated by 11 {km} {{{s}}}-1. If expanding, these could be due to momentum-driven stellar wind feedback. Alternatively, we may be seeing remnants of the infalling, colliding clouds responsible for triggering the SSC formation. The kinematics are also consistent with a virialized system. These extreme, high-density, star-forming conditions inhibit energy-driven feedback; the co-spatial existence of a massive, molecular cloud with the SSC supports this scenario, and we quantitatively confirm that any wind-driven feedback in Mrk 71-A is momentum-driven, rather than energy-driven. Since Mrk 71-A is a candidate Lyman continuum emitter, this implies that energy-driven superwinds may not be a necessary condition for the escape of ionizing radiation. In addition, the detection of nebular continuum emission yields an accurate astrometric position for the Mrk 71-A. We also detect four other massive molecular clouds in this giant star-forming complex.

Space Weathering of Super-Earths: Model Simulations of Exospheric Sodium Escape from 61 Virgo b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoneda, M.; Berdyugina, S.; Kuhn, J.

Rocky exoplanets are expected to be eroded by space weather in a similar way as in the solar system. In particular, Mercury is one of the dramatically eroded planets whose material continuously escapes into its exosphere and further into space. This escape is well traced by sodium atoms scattering sunlight. Due to solar wind impact, micrometeorite impacts, photo-stimulated desorption and thermal desorption, sodium atoms are released from surface regolith. Some of these released sodium atoms are escaping from Mercury’s gravitational-sphere. They are dragged anti-Sun-ward and form a tail structure. We expect similar phenomena on exoplanets. The hot super-Earth 61 Virmore » b orbiting a G3V star at only 0.05 au may show a similar structure. Because of its small separation from the star, the sodium release mechanisms may be working more efficiently on hot super-Earths than on Mercury, although the strong gravitational force of Earth-sized or even more massive planets may be keeping sodium atoms from escaping from the planet. Here, we performed model simulations for Mercury (to verify our model) and 61 Vir b as a representative super-Earth. We have found that sodium atoms can escape from this exoplanet due to stellar wind sputtering and micrometeorite impacts, to form a sodium tail. However, in contrast to Mercury, the tail on this hot super-Earth is strongly aligned with the anti-starward direction because of higher light pressure. Our model suggests that 61 Vir b seems to have an exo-base atmosphere like that of Mercury.« less

IN SITU ACCRETION OF HYDROGEN-RICH ATMOSPHERES ON SHORT-PERIOD SUPER-EARTHS: IMPLICATIONS FOR THE KEPLER-11 PLANETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ikoma, M.; Hori, Y., E-mail: ikoma@eps.s.u-tokyo.ac.jp, E-mail: yasunori.hori@nao.ac.jp

2012-07-01

Motivated by recent discoveries of low-density super-Earths with short orbital periods, we have investigated in situ accretion of H-He atmospheres on rocky bodies embedded in dissipating warm disks, by simulating quasi-static evolution of atmospheres that connect to the ambient disk. We have found that the atmospheric evolution has two distinctly different outcomes, depending on the rocky body's mass: while the atmospheres on massive rocky bodies undergo runaway disk-gas accretion, those on light rocky bodies undergo significant erosion during disk dispersal. In the atmospheric erosion, the heat content of the rocky body that was previously neglected plays an important role. Wemore » have also realized that the atmospheric mass is rather sensitive to disk temperature in the mass range of interest in this study. Our theory is applied to recently detected super-Earths orbiting Kepler-11 to examine the possibility that the planets are rock-dominated ones with relatively thick H-He atmospheres. The application suggests that the in situ formation of the relatively thick H-He atmospheres inferred by structure modeling is possible only under restricted conditions, namely, relatively slow disk dissipation and/or cool environments. This study demonstrates that low-density super-Earths provide important clues to understanding of planetary accretion and disk evolution.« less

Characterizing the UV environment of GJ1214b

NASA Astrophysics Data System (ADS)

Desert, Jean-Michel

2010-09-01

The recent detection of a super-Earth transiting a nearby low-mass star GJ1214 {Charbonneau et al., 2009} has opened the door to testing the predictions of low mass planet atmosphere theories. Theoretical models predict that low mass planets are likely to exist with atmospheres that can vary widely in their composition and structure. Some super-Earths may be able to retain massive hydrogen-rich atmospheres. Others might never accumulate hydrogen or experience significant escape of lightweight elements, resulting in atmospheres more like those of the terrestrial planets in our Solar System. Planets which orbit close to their parent stars, such as close-in hot-Jupiters and super-Earths, are exposed to strong XEUV flux that influence their atmospheres and may trigger atmospheric escape processes. This phenomenon, which shapes planetary atmospheres, determines the evolution of the planet. This can also dramatically enhance the detectability of a heavily irradiated hydrogen atmosphere when the planet transits in front of its parent star. We propose to use HST/STIS/G140M to determine the intensity and variability of the Lyman-alpha chromospheric emission line and provide observational constraints to super-Earth atmospheric models. We propose to coordinate this measurement with a planetary transit in order to detect large upper atmospheric signatures if present. This short measurement also enables us to determine whether a larger program dedicated to upper atmospheric study is feasible for a following cycle.

Eta Carinae: Viewed from Multiple Vantage Points

NASA Technical Reports Server (NTRS)

Gull, Theodore

2007-01-01

The central source of Eta Carinae and its ejecta is a massive binary system buried within a massive interacting wind structure which envelops the two stars. However the hot, less massive companion blows a small cavity in the very massive primary wind, plus ionizes a portion of the massive wind just beyond the wind-wind boundary. We gain insight on this complex structure by examining the spatially-resolved Space Telescope Imaging Spectrograph (STIS) spectra of the central source (0.1") with the wind structure which extends out to nearly an arcsecond (2300AU) and the wind-blown boundaries, plus the ejecta of the Little Homunculus. Moreover, the spatially resolved Very Large Telescope/UltraViolet Echelle Spectrograph (VLT/UVES) stellar spectrum (one arcsecond) and spatially sampled spectra across the foreground lobe of the Homunculus provide us vantage points from different angles relative to line of sight. Examples of wind line profiles of Fe II, and the.highly excited [Fe III], [Ne III], [Ar III] and [S III)], plus other lines will be presented.

The rotating wind of the quasar PG 1700+518.

PubMed

Young, S; Axon, D J; Robinson, A; Hough, J H; Smith, J E

2007-11-01

It is now widely accepted that most galaxies undergo an active phase, during which a central super-massive black hole generates vast radiant luminosities through the gravitational accretion of gas. Winds launched from a rotating accretion disk surrounding the black hole are thought to play a critical role, allowing the disk to shed angular momentum that would otherwise inhibit accretion. Such winds are capable of depositing large amounts of mechanical energy in the host galaxy and its environs, profoundly affecting its formation and evolution, and perhaps regulating the formation of large-scale cosmological structures in the early Universe. Although there are good theoretical grounds for believing that outflows from active galactic nuclei originate as disk winds, observational verification has proven elusive. Here we show that structures observed in polarized light across the broad Halpha emission line in the quasar PG 1700+518 originate close to the accretion disk in an electron scattering wind. The wind has large rotational motions (approximately 4,000 km s(-1)), providing direct observational evidence that outflows from active galactic nuclei are launched from the disks. Moreover, the wind rises nearly vertically from the disk, favouring launch mechanisms that impart an initial acceleration perpendicular to the disk plane.

The Redshifted Hydrogen Balmer and Metastable He 1 Absorption Line System in Mini-FeLoBAL Quasar SDSS J112526.12+002901.3: A Parsec-scale Accretion Inflow?

NASA Astrophysics Data System (ADS)

Shi, Xi-Heng; Jiang, Peng; Wang, Hui-Yuan; Zhang, Shao-Hua; Ji, Tuo; Liu, Wen-Juan; Zhou, Hong-Yan

2016-10-01

The accretion of the interstellar medium onto central super-massive black holes is widely accepted as the source of the gigantic energy released by the active galactic nuclei. However, few pieces of observational evidence have been confirmed directly demonstrating the existence of the inflows. The absorption line system in the spectra of quasar SDSS J112526.12+002901.3 presents an interesting example in which the rarely detected hydrogen Balmer and metastable He I absorption lines are found redshifted to the quasar's rest frame along with the low-ionization metal absorption lines Mg II, Fe II, etc. The repeated SDSS spectroscopic observations suggest a transverse velocity smaller than the radial velocity. The motion of the absorbing medium is thus dominated by infall. The He I* lines present a powerful probe to the strength of ionizing flux, while the Balmer lines imply a dense environment. With the help of photoionization simulations, we find that the absorbing medium is exposed to the radiation with ionization parameter U ≈ 10-1.8, and the density is n({{H}})≈ {10}9 {{cm}}-3. Thus the absorbing medium is located ˜4 pc away from the central engine. According to the similarity in the distance and physical conditions between the absorbing medium and the torus, we strongly propose the absorption line system as a candidate for the accretion inflow, which originates in the inner surface of the torus.

GJ 832c: A Super-Earth in the Habitable Zone

NASA Astrophysics Data System (ADS)

Wittenmyer, Robert A.; Tuomi, Mikko; Butler, R. P.; Jones, H. R. A.; Anglada-Escudé, Guillem; Horner, Jonathan; Tinney, C. G.; Marshall, J. P.; Carter, B. D.; Bailey, J.; Salter, G. S.; O'Toole, S. J.; Wright, D.; Crane, J. D.; Schectman, S. A.; Arriagada, P.; Thompson, I.; Minniti, D.; Jenkins, J. S.; Diaz, M.

2014-08-01

We report the detection of GJ 832c, a super-Earth orbiting near the inner edge of the habitable zone of GJ 832, an M dwarf previously known to host a Jupiter analog in a nearly circular 9.4 yr orbit. The combination of precise radial-velocity measurements from three telescopes reveals the presence of a planet with a period of 35.68 ± 0.03 days and minimum mass (m sin i) of 5.4 ± 1.0 Earth masses. GJ 832c moves on a low-eccentricity orbit (e = 0.18 ± 0.13) toward the inner edge of the habitable zone. However, given the large mass of the planet, it seems likely that it would possess a massive atmosphere, which may well render the planet inhospitable. Indeed, it is perhaps more likely that GJ 832c is a "super-Venus," featuring significant greenhouse forcing. With an outer giant planet and an interior, potentially rocky planet, the GJ 832 planetary system can be thought of as a miniature version of our own solar system. This paper includes data gathered with the 6.5 m Magellan Telescopes located at the Las Campanas Observatory, Chile.

Super-Eddington Accretion in Tidal Disruption Events: the Impact of Realistic Fallback Rates on Accretion Rates

NASA Astrophysics Data System (ADS)

Wu, Samantha; Coughlin, Eric R.; Nixon, Chris

2018-04-01

After the tidal disruption of a star by a massive black hole, disrupted stellar debris can fall back to the hole at a rate significantly exceeding its Eddington limit. To understand how black hole mass affects the duration of super-Eddington accretion in tidal disruption events, we first run a suite of simulations of the disruption of a Solar-like star by a supermassive black hole of varying mass to directly measure the fallback rate onto the hole, and we compare these fallback rates to the analytic predictions of the "frozen-in" model. Then, adopting a Zero-Bernoulli Accretion flow as an analytic prescription for the accretion flow around the hole, we investigate how the accretion rate onto the black hole evolves with the more accurate fallback rates calculated from the simulations. We find that numerically-simulated fallback rates yield accretion rates onto the hole that can, depending on the black hole mass, be nearly an order of magnitude larger than those predicted by the frozen-in approximation. Our results place new limits on the maximum black hole mass for which super-Eddington accretion occurs in tidal disruption events.

The early growth of the first black holes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Jarrett L.; Haardt, Francesco

With detections of quasars powered by increasingly massive black holes at increasingly early times in cosmic history over the past decade, there has been correspondingly rapid progress made on the theory of early black hole formation and growth. Here, we review the emerging picture of how the first massive black holes formed from the primordial gas and then grew to supermassive scales. We discuss the initial conditions for the formation of the progenitors of these seed black holes, the factors dictating the initial masses with which they form, and their initial stages of growth via accretion, which may occur atmore » super-Eddington rates. Lastly, we briefly discuss how these results connect to large-scale simulations of the growth of supermassive black holes in the first billion years after the Big Bang.« less

The early growth of the first black holes

DOE PAGES

Johnson, Jarrett L.; Haardt, Francesco

2016-03-04

With detections of quasars powered by increasingly massive black holes at increasingly early times in cosmic history over the past decade, there has been correspondingly rapid progress made on the theory of early black hole formation and growth. Here, we review the emerging picture of how the first massive black holes formed from the primordial gas and then grew to supermassive scales. We discuss the initial conditions for the formation of the progenitors of these seed black holes, the factors dictating the initial masses with which they form, and their initial stages of growth via accretion, which may occur atmore » super-Eddington rates. Lastly, we briefly discuss how these results connect to large-scale simulations of the growth of supermassive black holes in the first billion years after the Big Bang.« less

The Lyman-alpha glow of gas falling into the dark matter halo of a z = 3 galaxy.

PubMed

Weidinger, Michael; Møller, Palle; Fynbo, Johan Peter Uldall

2004-08-26

Quasars are the visible signatures of gas falling into the deep potential well of super-massive black holes in the centres of distant galaxies. It has been suggested that quasars are formed when two massive galaxies collide and merge, leading to the prediction that quasars should be found in the centres of regions of largest overdensity in the early Universe. In dark matter (DM)-dominated models of the early Universe, massive DM halos are predicted to attract the surrounding gas, which falls towards their centres. The neutral gas is not detectable in emission by itself, but gas falling into the ionizing cone of such a quasar will glow in the Lyman-alpha line of hydrogen, effectively imaging the DM halo. Here we present a Lyalpha image of a DM halo at redshift z = 3, along with a two-dimensional spectrum of the gaseous halo. Our observations are best understood in the context of the standard model for DM haloes; we infer a mass of (2 - 7) x 10(12) solar masses (M(\\circ)) for the halo.

Science in 60 – Searching for Dark Matter

ScienceCinema

Albert, Andrea

2018-06-12

Nearly 14,000 feet up the slopes of Mexico's Sierra Negra volcano, a unique observatory called HAWC (High-Altitude Water Cherenkov Gamma Ray Observatory) is providing insight into some of the most violent phenomena in the known universe, such as supernovae explosions and the evolution of super massive black holes. For Dr. Andrea Albert, the Marie Curie Distinguished Postdoctoral Fellow at Los Alamos National Lab, HAWC provides another distinct opportunity: a way to search for signals from dark matter.

Development and Applications of a Modular Parallel Process for Large Scale Fluid/Structures Problems

NASA Technical Reports Server (NTRS)

Guruswamy, Guru P.; Kwak, Dochan (Technical Monitor)

2002-01-01

A modular process that can efficiently solve large scale multidisciplinary problems using massively parallel supercomputers is presented. The process integrates disciplines with diverse physical characteristics by retaining the efficiency of individual disciplines. Computational domain independence of individual disciplines is maintained using a meta programming approach. The process integrates disciplines without affecting the combined performance. Results are demonstrated for large scale aerospace problems on several supercomputers. The super scalability and portability of the approach is demonstrated on several parallel computers.

Analytical study of a Kerr-Sen black hole and a charged massive scalar field

NASA Astrophysics Data System (ADS)

Bernard, Canisius

2017-11-01

It is reported that Kerr-Newman and Kerr-Sen black holes are unstable to perturbations of charged massive scalar field. In this paper, we study analytically the complex frequencies which characterize charged massive scalar fields in a near-extremal Kerr-Sen black hole. For near-extremal Kerr-Sen black holes and for charged massive scalar fields in the eikonal large-mass M ≫μ regime, where M is the mass of the black hole, and μ is the mass of the charged scalar field, we have obtained a simple expression for the dimensionless ratio ωI/(ωR-ωc) , where ωI and ωR are, respectively, the imaginary and real parts of the frequency of the modes, and ωc is the critical frequency for the onset of super-radiance. We have also found our expression is consistent with the result of Hod [Phys. Rev. D 94, 044036 (2016), 10.1103/PhysRevD.94.044036] for the case of a near-extremal Kerr-Newman black hole and the result of Zouros and Eardly [Ann. Phys. (N.Y.) 118, 139 (1979), 10.1016/0003-4916(79)90237-9] for the case of neutral scalar fields in the background of a near-extremal Kerr black hole.

Biomimetic Models for An Ecological Approach to Massively-Deployed Sensor Networks

NASA Technical Reports Server (NTRS)

Jones, Kennie H.; Lodding, Kenneth N.; Olariu, Stephan; Wilson, Larry; Xin, Chunsheng

2005-01-01

Promises of ubiquitous control of the physical environment by massively-deployed wireless sensor networks open avenues for new applications that will redefine the way we live and work. Due to small size and low cost of sensor devices, visionaries promise systems enabled by deployment of massive numbers of sensors ubiquitous throughout our environment working in concert. Recent research has concentrated on developing techniques for performing relatively simple tasks with minimal energy expense, assuming some form of centralized control. Unfortunately, centralized control is not conducive to parallel activities and does not scale to massive size networks. Execution of simple tasks in sparse networks will not lead to the sophisticated applications predicted. We propose a new way of looking at massively-deployed sensor networks, motivated by lessons learned from the way biological ecosystems are organized. We demonstrate that in such a model, fully distributed data aggregation can be performed in a scalable fashion in massively deployed sensor networks, where motes operate on local information, making local decisions that are aggregated across the network to achieve globally-meaningful effects. We show that such architectures may be used to facilitate communication and synchronization in a fault-tolerant manner, while balancing workload and required energy expenditure throughout the network.

Rapid growth of black holes accompanied with hot or warm outflows exposed to anisotropic super-Eddington radiation

NASA Astrophysics Data System (ADS)

Takeo, Eishun; Inayoshi, Kohei; Ohsuga, Ken; Takahashi, Hiroyuki R.; Mineshige, Shin

2018-05-01

We perform two-dimensional radiation hydrodynamical simulations of accretion flows on to a black hole (BH) with a mass of 103 ≤ MBH/ M⊙ ≲ 106 in order to study rapid growth of BHs in the early Universe. For spherically symmetric flows, hyper-Eddington accretion from outside the Bondi radius can occur unimpeded by radiation feedback when MBH ≳ 104 M⊙(n∞/105 cm - 3) - 1(T∞/104 K)3/2, where the density and temperature of ambient gas are initially set to n∞ = 105 cm-3 and T∞ = 104 K. Here, we study accretion flows exposed to anisotropic radiation from a nuclear accretion disc with a luminosity higher than the Eddington value (LEdd) due to collimation towards the bipolar directions. We find that, unlike the spherically symmetric case, even less massive BHs with MBH < 104 M⊙ can be fed at high accretion rates of ≳ LEdd/c2 through the equatorial region, while ionized regions expand towards the poles producing hot outflows with T ˜ 105 K. For more massive BHs with MBH ≳ 5 × 105 M⊙, intense inflows of neutral gas through the equator totally cover the central radiating region due to the non-radial gas motions. Because of efficient recombination by hydrogen, the entire flow settles in neutral and warm gas with T ≃ 8000 K. The BH is fed at a rate of ˜5 × 104LEdd/c2 (a half of the inflow rate from the Bondi radius). Moreover, radiation momentum absorbed by neutral hydrogen produces warm outflows towards the bipolar directions at ˜ 10 per cent of the BH feeding rate and with a velocity several times higher than the escaping value.

THE FORMATION OF SECONDARY STELLAR GENERATIONS IN MASSIVE YOUNG STAR CLUSTERS FROM RAPIDLY COOLING SHOCKED STELLAR WINDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wünsch, R.; Palouš, J.; Ehlerová, S.

We study a model of rapidly cooling shocked stellar winds in young massive clusters and estimate the circumstances under which secondary star formation, out of the reinserted winds from a first stellar generation (1G), is possible. We have used two implementations of the model: a highly idealized, computationally inexpensive, spherically symmetric semi-analytic model, and a complex, three-dimensional radiation-hydrodynamic, simulation; they are in a good mutual agreement. The results confirm our previous findings that, in a cluster with 1G mass 10{sup 7} M {sub ⊙} and half-mass–radius 2.38 pc, the shocked stellar winds become thermally unstable, collapse into dense gaseous structuresmore » that partially accumulate inside the cluster, self-shield against ionizing stellar radiation, and form the second generation (2G) of stars. We have used the semi-analytic model to explore a subset of the parameter space covering a wide range of the observationally poorly constrained parameters: the heating efficiency, η {sub he}, and the mass loading, η {sub ml}. The results show that the fraction of the 1G stellar winds accumulating inside the cluster can be larger than 50% if η {sub he} ≲ 10%, which is suggested by the observations. Furthermore, for low η {sub he}, the model provides a self-consistent mechanism predicting 2G stars forming only in the central zones of the cluster. Finally, we have calculated the accumulated warm gas emission in the H30 α recombination line, analyzed its velocity profile, and estimated its intensity for super star clusters in interacting galaxies NGC4038/9 (Antennae) showing that the warm gas should be detectable with ALMA.« less

Forming supermassive black holes by accreting dark and baryon matter

NASA Astrophysics Data System (ADS)

Hu, Jian; Shen, Yue; Lou, Yu-Qing; Zhang, Shuangnan

2006-01-01

Given a large-scale mixture of self-interacting dark matter (SIDM) particles and baryon matter distributed in the early Universe, we advance here a two-phase accretion scenario for forming supermassive black holes (SMBHs) with masses around ~109Msolar at high redshifts z(>~6). The first phase is conceived to involve a rapid quasi-spherical and quasi-steady Bondi accretion of mainly SIDM particles embedded with baryon matter on to seed black holes (BHs) created at redshifts z<~ 30 by the first generation of massive Population III stars; this earlier phase rapidly gives birth to significantly enlarged seed BH masses of during z~ 20-15, where σ0 is the cross-section per unit mass of SIDM particles and Cs is the velocity dispersion in the SIDM halo referred to as an effective `sound speed'. The second phase of BH mass growth is envisaged to proceed primarily via baryon accretion, eventually leading to SMBH masses of MBH~ 109Msolar such SMBHs may form either by z~ 6 for a sustained accretion at the Eddington limit or later at lower z for sub-Eddington mean accretion rates. In between these two phases, there is a transitional yet sustained diffusively limited accretion of SIDM particles which in an eventual steady state would be much lower than the accretion rates of the two main phases. We intend to account for the reported detections of a few SMBHs at early epochs, e.g. Sloan Digital Sky Survey (SDSS) 1148+5251 and so forth, without necessarily resorting to either super-Eddington baryon accretion or very frequent BH merging processes. Only extremely massive dark SIDM haloes associated with rare peaks of density fluctuations in the early Universe may harbour such early SMBHs or quasars. Observational consequences are discussed. During the final stage of accumulating a SMBH mass, violent feedback in circumnuclear environs of a galactic nucleus leads to the central bulge formation and gives rise to the familiar empirical MBH-σb correlation inferred for nearby normal galaxies with σb being the stellar velocity dispersion in the galactic bulge; in our scenario, the central SMBH formation precedes that of the galactic bulge.

Magellan/PFS Radial Velocities of GJ 9827, a Late K dwarf at 30 pc with Three Transiting Super-Earths

NASA Astrophysics Data System (ADS)

Teske, Johanna K.; Wang, Sharon; Wolfgang, Angie; Dai, Fei; Shectman, Stephen A.; Butler, R. Paul; Crane, Jeffrey D.; Thompson, Ian B.

2018-04-01

The Kepler mission showed us that planets with sizes between that of Earth and Neptune appear to be the most common type in our Galaxy. These “super-Earths” continue to be of great interest for exoplanet formation, evolution, and composition studies. However, the number of super-Earths with well-constrained mass and radius measurements remains small (40 planets with σ mass < 25%), due in part to the faintness of their host stars causing ground-based mass measurements to be challenging. Recently, three transiting super-Earth planets were detected by the K2 mission around the nearby star GJ 9827/HIP 115752, at only 30 pc away. The radii of the planets span the “radius gap” detected by Fulton et al. (2017), and all orbit within ∼6.5 days, easing follow-up observations. Here, we report radial velocity (RV) observations of GJ 9827, taken between 2010 and 2016 with the Planet Finder Spectrograph on the Magellan II Telescope. We employ two different RV analysis packages, SYSTEMIC and RADVEL, to derive masses and thus densities of the GJ 9827 planets. We also test a Gaussian Process regression analysis but find the correlated stellar noise is not well constrained by the PFS data and that the GP tends to over-fit the RV semi-amplitudes resulting in a lower K value. Our RV observations are not able to place strong mass constraints on the two outer planets (c and d) but do indicate that planet b, at 1.64 R ⊕ and ∼8 M ⊕, is one of the most massive (and dense) super-Earth planets detected to date.

Examining the Center: Positions, Dominance, and Star Formation Rates of Most Massive Group Galaxies at Intermediate Redshift

NASA Astrophysics Data System (ADS)

Connelly, Jennifer L.; Parker, Laura C.; McGee, Sean; Mulchaey, John S.; Finoguenov, Alexis; Balogh, Michael; Wilman, David; Group Environment Evolution Collaboration

2015-01-01

The group environment is believed to be the stage for many galaxy transformations, helping evolve blue star-forming galaxies to red passive ones. In local studies of galaxy clusters, the central member is usually a single dominant giant galaxy at the center of the potential with little star formation thought to be the result of galaxy mergers. In nearby groups, a range of morphologies and star formation rates are observed and the formation history is less clear. Further, the position and dominance of the central galaxy cannot be assumed in groups, which are less massive and evolved than clusters. To understand the connections between global group properties and properties of the central group galaxy at intermediate redshift, we examine galaxy groups from the Group Environment and Evolution Collaboration (GEEC) catalog, including both optically- and X-ray-selected groups at redshift z~0.4. The sample is diverse, containing a range in overall mass and evolutionary state. The number of groups is significant, membership is notably complete, and measurements span the IR to the UV allowing the properties of the members to be connected to those of the host groups. Having investigated trends in the global group properties previously, including mass and velocity substructure, we turn our attention now to the galaxy populations, focusing on the central regions of these systems. The most massive and second most massive group galaxies are identified by their stellar mass. The positions of the most massive galaxies (MMGs) are determined with respect to both the luminosity-weighted and X-ray center. Star formation rates are used to explore the fraction of passive/quiescent versus star-forming MMGs and the dominance of the MMGs in our group sample is also tested. Determinations of these characteristics and trends constitute the important first steps toward a detailed understanding of the relationships between the properties of host groups and their most massive galaxies and the environmental effects involved in the evolution of such objects.

The Galactic Centre source G2 was unlikely born in any of the known massive binaries

NASA Astrophysics Data System (ADS)

Calderón, D.; Cuadra, J.; Schartmann, M.; Burkert, A.; Plewa, P.; Eisenhauer, F.; Habibi, M.

2018-05-01

The source G2 has already completed its pericentre passage around Sgr A*, the super-massive black hole in the centre of our Galaxy. Although it has been monitored for 15 years, its astrophysical nature and origin still remain unknown. In this work, we aim to test the hypothesis of G2 being the result of a stellar wind collision. To do so, we study the motion and final fate of gas clumps formed as a result of collisions of stellar winds in massive binaries. Our approach is based on a test-particle model in order to describe the trajectories of such clumps. The model takes into account the gravitational field of Sgr A*, the interaction of the clumps with the interstellar medium as well as their finite lifetimes. Our analysis allows us to reject the hypothesis based on four arguments: i) if G2 has followed a purely Keplerian orbit since its formation, it cannot have been produced in any of the known massive binaries since their motions are not consistent; ii) in general, gas clumps are evaporated through thermal conduction on very short timescale (<100 yr) before getting close enough to Sgr A*; iii) IRS 16SW, the best candidate for the origin of G2, cannot generate clumps as massive as G2; and iv) clumps ejected from IRS 16SW describe trajectories significantly different to the observed motion of G2.

Theories of central engine for long gamma-ray bursts

NASA Astrophysics Data System (ADS)

Nagataki, Shigehiro

2018-02-01

Long GRBs are the most powerful explosions in the universe since the Big Bang. At least, some fraction of long GRBs are born from the death of massive stars. Likewise, only some fraction of massive stars that satisfy additional special conditions explode as long GRBs associated with supernovae/hypernovae. In this paper, we discuss the explosion mechanism of long GRBs associated with hypernovae: ‘the central engine of long GRBs’. The central engine of long GRBs is very different from that of core-collapse supernovae, although the mechanism of the engine is still not firmly established. In this paper, we review theoretical studies of the central engine of long GRBs. First, we discuss possible progenitor stars. Then several promising mechanisms of the central engine—such as black hole and magnetar formation—will be reviewed. We will also mention some more exotic models. Finally, we describe prospects for future studies of the central engine of long GRBs.

Inferring the Growth of Massive Galaxies Using Bayesian Spectral Synthesis Modeling

NASA Astrophysics Data System (ADS)

Stillman, Coley Michael; Poremba, Megan R.; Moustakas, John

2018-01-01

The most massive galaxies in the universe are typically found at the centers of massive galaxy clusters. Studying these galaxies can provide valuable insight into the hierarchical growth of massive dark matter halos. One of the key challenges of measuring the stellar mass growth of massive galaxies is converting the measured light profiles into stellar mass. We use Prospector, a state-of-the-art Bayesian spectral synthesis modeling code, to infer the total stellar masses of a pilot sample of massive central galaxies selected from the Sloan Digital Sky Survey. We compare our stellar mass estimates to previous measurements, and present some of the quantitative diagnostics provided by Prospector.

Coagulation calculations of icy planet formation around 0.1-0.5 M {sub ☉} stars: Super-Earths from large planetesimals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kenyon, Scott J.; Bromley, Benjamin C., E-mail: skenyon@cfa.harvard.edu, E-mail: bromley@physics.utah.edu

2014-01-01

We investigate formation mechanisms for icy super-Earth-mass planets orbiting at 2-20 AU around 0.1-0.5 M {sub ☉} stars. A large ensemble of coagulation calculations demonstrates a new formation channel: disks composed of large planetesimals with radii of 30-300 km form super-Earths on timescales of ∼1 Gyr. In other gas-poor disks, a collisional cascade grinds planetesimals to dust before the largest planets reach super-Earth masses. Once icy Earth-mass planets form, they migrate through the leftover swarm of planetesimals at rates of 0.01-1 AU Myr{sup –1}. On timescales of 10 Myr to 1 Gyr, many of these planets migrate through the diskmore » of leftover planetesimals from semimajor axes of 5-10 AU to 1-2 AU. A few percent of super-Earths might migrate to semimajor axes of 0.1-0.2 AU. When the disk has an initial mass comparable with the minimum-mass solar nebula, scaled to the mass of the central star, the predicted frequency of super-Earths matches the observed frequency.« less

The mass function of black holes 1

NASA Astrophysics Data System (ADS)

Natarajan, Priyamvada; Volonteri, Marta

2012-05-01

In this paper, we compare the observationally derived black hole mass function (BHMF) of luminous (>1045-1046 erg s-1) broad-line quasars (BLQSOs) at 1 < z < 4.5 drawn from the Sloan Digital Sky Survey (SDSS) presented by Kelly et al., with models of merger-driven black hole (BH) growth in the context of standard hierarchical structure formation models. In these models, we explore two distinct black hole seeding prescriptions at the highest redshifts: 'light seeds'- remnants of Population III stars and 'massive seeds' that form from the direct collapse of pre-galactic discs. The subsequent merger triggered mass build-up of the black hole population is tracked over cosmic time under the assumption of a fixed accretion rate as well as rates drawn from the distribution derived by Merloni & Heinz. Four model snapshots at z= 1.25, 2, 3.25 and 4.25 are compared with the SDSS-derived BHMFs of BLQSOs. We find that the light seed models fall short of reproducing the observationally derived mass function of BLQSOs at MBH > 109 M⊙ throughout the redshift range; the massive seed models with a fixed accretion rate of 0.3 Edd, or with accretion rates drawn from the Merloni & Heinz distribution provide the best fit to the current observational data at z > 2, although they overestimate the high-mass end of the mass function at lower redshifts. At low redshifts, a drastic drop in the accretion rate is observed and this is explained as arising due to the diminished gas supply available due to consumption by star formation or changes in the geometry of the inner feeding regions. Therefore, the overestimate at the high-mass end of the black hole mass function for the massive seed models can be easily modified, as the accretion rate is likely significantly lower at these epochs than what we assume. For the Merloni & Heinz model, examining the Eddington ratio distributions fEdd, we find that they are almost uniformly sampled from fEdd= 10-2 to 1 at z≃ 1, while at high redshift, current observations suggest accretion rates close to Eddington, if not mildly super-Eddington, at least for these extremely luminous quasars. Our key findings are that the duty cycle of super-massive black holes powering BLQSOs increases with increasing redshift for all models and models with Population III remnants as black hole seeds are unable to fit the observationally derived BHMFs for BLQSOs, lending strong support for the massive seeding model.

Quantum entanglement for systems of identical bosons: I. General features

NASA Astrophysics Data System (ADS)

Dalton, B. J.; Goold, J.; Garraway, B. M.; Reid, M. D.

2017-02-01

These two accompanying papers are concerned with two mode entanglement for systems of identical massive bosons and the relationship to spin squeezing and other quantum correlation effects. Entanglement is a key quantum feature of composite systems in which the probabilities for joint measurements on the composite sub-systems are no longer determined from measurement probabilities on the separate sub-systems. There are many aspects of entanglement that can be studied. This two-part review focuses on the meaning of entanglement, the quantum paradoxes associated with entangled states, and the important tests that allow an experimentalist to determine whether a quantum state—in particular, one for massive bosons is entangled. An overall outcome of the review is to distinguish criteria (and hence experiments) for entanglement that fully utilize the symmetrization principle and the super-selection rules that can be applied to bosonic massive particles. In the first paper (I), the background is given for the meaning of entanglement in the context of systems of identical particles. For such systems, the requirement is that the relevant quantum density operators must satisfy the symmetrization principle and that global and local super-selection rules prohibit states in which there are coherences between differing particle numbers. The justification for these requirements is fully discussed. In the second quantization approach that is used, both the system and the sub-systems are modes (or sets of modes) rather than particles, particles being associated with different occupancies of the modes. The definition of entangled states is based on first defining the non-entangled states—after specifying which modes constitute the sub-systems. This work mainly focuses on the two mode entanglement for massive bosons, but is put in the context of tests of local hidden variable theories, where one may not be able to make the above restrictions. The review provides the detailed arguments necessary for the conclusions of a recent paper, where the question of how to rigorously demonstrate the entanglement of a two-mode Bose-Einstein condensate (BEC) has been examined. In the accompanying review paper (II), we consider spin squeezing and other tests for entanglement that have been proposed for two-mode bosonic systems. We apply the approach of review (I) to determine which tests, and which modifications of the tests, are useful for detecting entanglement in massive bosonic (BEC), as opposed to photonic, systems. Several new inequalities are derived, a theory for the required two-mode interferometry is presented, and key experiments to date are analyzed.

Detection of Sagittarius A* at 330 MHz With the Very Large Array

DTIC Science & Technology

2004-01-20

our Galaxy’s central massive black hole , at 330 MHz with the Very Large Array. Implications for the spectrum and emission processes of Sgr A * are... A East, the Sgr A West H ii region, and Sgr A *, recently established as our Galaxy’s central massive black hole (e.g., Ghez et al. 2000; Eckart et al...toward Sgr A *. This could be explained by a localized clearing of the ambient gas accomplished either through the direct influence of the black hole

Recurrent X-ray Emission Variations of Eta Carinae and the Binary Hypothesis

NASA Technical Reports Server (NTRS)

Ishibashi, K.; Corcoran, M. F.; Davidson, K.; Swank, J. H.; Petre, R.; Drake, S. A.; Damineki, A.; White, S.

1998-01-01

Recent studies suggest that, the super-massive star eta Carinae may have a massive stellar companion (Damineli, Conti, and Lopes 1997), although the dense ejecta surrounding the star make this claim hard to test using conventional methods. Settling this question is critical for determining the current evolutionary state and future evolution of the star. We address this problem by an unconventional method: If eta Carinae is a binary, X-ray emission should be produced in shock waves generated by wind-wind collisions in the region between eta Carinae and its companion. Detailed X-ray monitoring of eta Carinae for more that) 2 years shows that the observed emission generally resembles colliding-wind X-ray emission, but with some significant discrepancies. Furthermore, periodic X-ray "flaring" may provide an additional clue to determine the presence of a companion star and for atmospheric pulsation in eta Carinae.

Template based parallel checkpointing in a massively parallel computer system

DOEpatents

Archer, Charles Jens [Rochester, MN; Inglett, Todd Alan [Rochester, MN

2009-01-13

A method and apparatus for a template based parallel checkpoint save for a massively parallel super computer system using a parallel variation of the rsync protocol, and network broadcast. In preferred embodiments, the checkpoint data for each node is compared to a template checkpoint file that resides in the storage and that was previously produced. Embodiments herein greatly decrease the amount of data that must be transmitted and stored for faster checkpointing and increased efficiency of the computer system. Embodiments are directed to a parallel computer system with nodes arranged in a cluster with a high speed interconnect that can perform broadcast communication. The checkpoint contains a set of actual small data blocks with their corresponding checksums from all nodes in the system. The data blocks may be compressed using conventional non-lossy data compression algorithms to further reduce the overall checkpoint size.

a Snapshot Survey of X-Ray Selected Central Cluster Galaxies

NASA Astrophysics Data System (ADS)

Edge, Alastair

1999-07-01

Central cluster galaxies are the most massive stellar systems known and have been used as standard candles for many decades. Only recently have central cluster galaxies been recognised to exhibit a wide variety of small scale {<100 pc} features that can only be reliably detected with HST resolution. The most intriguing of these are dust lanes which have been detected in many central cluster galaxies. Dust is not expected to survive long in the hostile cluster environment unless shielded by the ISM of a disk galaxy or very dense clouds of cold gas. WFPC2 snapshot images of a representative subset of the central cluster galaxies from an X-ray selected cluster sample would provide important constraints on the formation and evolution of dust in cluster cores that cannot be obtained from ground-based observations. In addition, these images will allow the AGN component, the frequency of multiple nuclei, and the amount of massive-star formation in central cluster galaxies to be ass es sed. The proposed HST observatio ns would also provide high-resolution images of previously unresolved gravitational arcs in the most massive clusters in our sample resulting in constraints on the shape of the gravitational potential of these systems. This project will complement our extensive multi-frequency work on this sample that includes optical spectroscopy and photometry, VLA and X-ray images for the majority of the 210 targets.

The algebra of supertraces for 2+1 super de Sitter gravity

NASA Technical Reports Server (NTRS)

Urrutia, L. F.; Waelbroeck, H.; Zertuche, F.

1993-01-01

The algebra of the observables for 2+1 super de Sitter gravity, for one genus of the spatial surface is calculated. The algebra turns out to be an infinite Lie algebra subject to non-linear constraints. The constraints are solved explicitly in terms of five independent complex supertraces. These variables are the true degrees of freedom of the system and their quantized algebra generates a new structure which is referred to as a 'central extension' of the quantum algebra SU(2)q.

Modelling the multiwavelength emission of Ultraluminous X-ray sources accreting above Eddington

NASA Astrophysics Data System (ADS)

Ambrosi, E.; Zampieri, L.

2017-10-01

Understanding ULXs requires a comprehensive modelling of their multiwavelength emission properties. We compute the optical-through-X-ray emission of ULXs assuming that they are binary systems with stellar-mass or massive-stellar Black Holes and considering the possibility that a non-standard disc sets in when the mass transfer rate (\\dot{M}) becomes highly super-Eddington. The emission model is applied to self-consistent simulations of ULX binaries. We compare our color-magnitude diagrams (CMDs) with those in the literature and find significant differences in the post main sequence evolution. When the donor is on the main-sequence and \\dot{M} is mildly super-Eddington, the behaviour of the system is similar to that found in previous investigations. However, when the donor star leaves the main-sequence and \\dot{M} becomes highly super-Eddington, the optical luminosity of the system is systematically larger and the colours show a markedly different evolution. The emission properties depend on the variable shielding of the outer disc and donor induced by the changing inner disc structure. We determine also the effects caused by the onset of a strong optically thick outflow. CMDs in various photometric systems are compared to the observed properties of the optical counterparts of several ULXs, obtaining updated constraints on their donor mass and accretion rate.

The Formation of Cluster Populations Through Direct Galaxy Collisions

NASA Astrophysics Data System (ADS)

Peterson, Bradley W.; Smith, Beverly J.; Struck, Curtis

2016-01-01

Much progress has been made on the question of how globular clusters form. In particular, the study of extragalactic populations of young, high-mass clusters ("super star clusters") has revealed a class of objects can evolve into globular clusters. The process by which these clusters form, and how many survive long enough to become globular clusters, is not wholly understood. Here, we use new data on the colliding galaxy system Arp 261 to investigate the possibility that young, massive clusters form in greater numbers during direct galaxy collisions, compared to less direct tidal collisions.

The Transiting Exocomets of HD 172555

NASA Technical Reports Server (NTRS)

Grady, C. A.; Brown, Alex; Kamp, Inga; Riviere-Marichalar, Pablo; Roberge, Aki; Welsh, Barry

2016-01-01

While most attention has been garnered by searches for super-Jovian mass exo-planets the presence of minor bodies can be detected, at least through their dissociation products in suitably oriented systems. The principal detection technique is line-of-sight absorption spectroscopy of systems viewed close to edge-on. I review what we have learned about such bodies in beta Pictoris, and HD 172555, their link to more massive bodies in their systems, and what this tells us about the frequency and potential locations of Jovian-mass bodies in advance of their direct imaging detection.

SuperCDMS Prototype Detector Design and Testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kennedy, Allison Blair

A substantial amount of astrophysical evidence indicates that approximately a quarter of all energy in the universe is composed of a nonluminous, and nonbaryonic \\dark" matter. Of the potential dark matter particle candidates, Weakly Interacting Massive Particles, or WIMPs, is particularly well motivated. As a means to directly detect WIMP interactions with baryonic matter, the Cryogenic Dark Matter Search (CDMS) project was established, operating at the Soudan Underground Laboratory from 2003 - 2015, under the CDMS II and SuperCDMS Soudan experiments. CDMS detectors simultaneously measure the ionization and phonon energies of recoil events in Si and Ge crystals kept atmore » cryogenic temperatures in a low-background environment. The ratio of ionization energy to recoil energy serves as a discrimination parameter to separate nuclear recoil events from the electron-recoil background. The next installation, SuperCDMS SNOLAB, is preparing for future operation, with an initial payload of eighteen Ge and six Si, 100 mm diameter, 33 mm thick detectors. Of this initial payload, eight Ge and four Si detectors will operate in a high-voltage ( 100 V) mode, which have an increased sensitivity to low-mass WIMPs due to decreased energy thresholds. The SuperCDMS test facility at University of Minnesota aids in the detector R&D and characterization of prototype detectors, as part of the scale-up eort for Super- CDMS SNOLAB. This thesis presents the rst full ionization and phonon characterization study of a 100 mm diameter, 33 mm thick prototype Ge detector with interleaved phonon and ionization channels. Measurements include ionization collection eciency, surface event rejection capabilities, and successful demonstration of nuclear recoil event discrimination. Results indicate that 100 mm diameter, interleaved Ge detectors show potential for use in SuperCDMS SNOLAB. As part of detector R&D, the Minnesota test facility also looks beyond the next stage of SuperCDMS, investigating larger individual detectors as a means to easily scale up the sensitive mass of future searches. This thesis presents the design and initial testing results of a prototype 150 mm diameter, 33 mm thick silicon ionization detector, which is 5.2 times larger than those used in SuperCDMS at Soudan and 2.25 times larger than those planned for use at SuperCDMS SNOLAB. In addition, the detector was operated with contact-free ionization electrodes to minimize bias leakage currents, which can limit operation at high bias voltages. The results show promise for the operation of both large volume silicon detectors and contact-free ionization electrodes for scaling up detector mass and bias.« less

Mineral potential for volcanogenic massive sulfide deposits in the Islamic Republic of Mauritania, (phase V, deliverable 77): Chapter L in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

USGS Publications Warehouse

Taylor, Cliff D.; Giles, Stuart A.

2015-01-01

Potential for base- and precious-metal-bearing volcanogenic massive sulfide deposits (VMS) exists in Mauritania in the greenstone belts of the southwestern Rgueïbat Shield and in the allochthonous portions of the central and southern Mauritanides. Additional potential exists for VMS deposits within the Tiris Complex of the central Rgueïbat Shield. Volcanosedimentary successions of Paleoproterozoic rocks of the northeastern portion of the Rgueïbat Shield are also permissive for volcanogenic massive sulfide deposits. These types of mineral occurrences are common features of marine volcanosedimentary successions worldwide and can be of almost any age, although Proterozoic examples are less abundant.

A NEW HYBRID N-BODY-COAGULATION CODE FOR THE FORMATION OF GAS GIANT PLANETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bromley, Benjamin C.; Kenyon, Scott J., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu

2011-04-20

We describe an updated version of our hybrid N-body-coagulation code for planet formation. In addition to the features of our 2006-2008 code, our treatment now includes algorithms for the one-dimensional evolution of the viscous disk, the accretion of small particles in planetary atmospheres, gas accretion onto massive cores, and the response of N-bodies to the gravitational potential of the gaseous disk and the swarm of planetesimals. To validate the N-body portion of the algorithm, we use a battery of tests in planetary dynamics. As a first application of the complete code, we consider the evolution of Pluto-mass planetesimals in amore » swarm of 0.1-1 cm pebbles. In a typical evolution time of 1-3 Myr, our calculations transform 0.01-0.1 M{sub sun} disks of gas and dust into planetary systems containing super-Earths, Saturns, and Jupiters. Low-mass planets form more often than massive planets; disks with smaller {alpha} form more massive planets than disks with larger {alpha}. For Jupiter-mass planets, masses of solid cores are 10-100 M{sub +}.« less

ORBITAL STABILITY OF MULTI-PLANET SYSTEMS: BEHAVIOR AT HIGH MASSES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morrison, Sarah J.; Kratter, Kaitlin M., E-mail: morrison@lpl.arizona.edu, E-mail: kkratter@email.arizona.edu

2016-06-01

In the coming years, high-contrast imaging surveys are expected to reveal the characteristics of the population of wide-orbit, massive, exoplanets. To date, a handful of wide planetary mass companions are known, but only one such multi-planet system has been discovered: HR 8799. For low mass planetary systems, multi-planet interactions play an important role in setting system architecture. In this paper, we explore the stability of these high mass, multi-planet systems. While empirical relationships exist that predict how system stability scales with planet spacing at low masses, we show that extrapolating to super-Jupiter masses can lead to up to an ordermore » of magnitude overestimate of stability for massive, tightly packed systems. We show that at both low and high planet masses, overlapping mean-motion resonances trigger chaotic orbital evolution, which leads to system instability. We attribute some of the difference in behavior as a function of mass to the increasing importance of second order resonances at high planet–star mass ratios. We use our tailored high mass planet results to estimate the maximum number of planets that might reside in double component debris disk systems, whose gaps may indicate the presence of massive bodies.« less

A Rare Encounter with Very Massive Stars in NGC~3125-A1

NASA Astrophysics Data System (ADS)

Wofford, A.; Leitherer, C.; Chandar, R.; Bouret, J. C.

2014-09-01

Super star cluster A1 in the nearby starburst galaxy NGC~3125 shows broad He II λ1640 emission (FWHM ~ 1200 km/s) of unprecedented strength (equivalent width, EW = 7.1+/-0.4 angstroms). Previous attempts to characterize A1's massive star content were hampered by the low resolution of the UV spectrum and the lack of co-spatial panchromatic data. We obtained far-UV to near-IR spectroscopy of the two principal emitting regions in the galaxy with the Space Telescope Imaging Spectrograph and the Cosmic Origins Spectrograph on board the Hubble Space Telescope. We use these data to derive the ages, reddenings, masses, and Wolf-Rayet (WR) to O star ratios of three compact clusters in the galaxy. We rule out that the extraordinary HeII lambda 1640 emission and OV lambda 1371 absorption in A1 are due to an extremely flat upper Initial Mass Function (IMF), and suggest that they originate in the winds of Very Massive Stars ( > 120 Msun, VMS). In order to reproduce the properties of peculiar clusters such as A1, the stellar evolution tracks implemented in Starburst99 need to be extended to masses >120 Msun.

The fate of scattered planets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bromley, Benjamin C.; Kenyon, Scott J., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu

2014-12-01

As gas giant planets evolve, they may scatter other planets far from their original orbits to produce hot Jupiters or rogue planets that are not gravitationally bound to any star. Here, we consider planets cast out to large orbital distances on eccentric, bound orbits through a gaseous disk. With simple numerical models, we show that super-Earths can interact with the gas through dynamical friction to settle in the remote outer regions of a planetary system. Outcomes depend on planet mass, the initial scattered orbit, and the evolution of the time-dependent disk. Efficient orbital damping by dynamical friction requires planets atmore » least as massive as the Earth. More massive, longer-lived disks damp eccentricities more efficiently than less massive, short-lived ones. Transition disks with an expanding inner cavity can circularize orbits at larger distances than disks that experience a global (homologous) decay in surface density. Thus, orbits of remote planets may reveal the evolutionary history of their primordial gas disks. A remote planet with an orbital distance ∼100 AU from the Sun is plausible and might explain correlations in the orbital parameters of several distant trans-Neptunian objects.« less

A catalogue of clusters of galaxies identified from all sky surveys of 2MASS, WISE, and SuperCOSMOS

NASA Astrophysics Data System (ADS)

Wen, Z. L.; Han, J. L.; Yang, F.

2018-03-01

We identify 47 600 clusters of galaxies from photometric data of Two Micron All Sky Survey (2MASS), Wide-field Infrared Survey Explorer (WISE), and SuperCOSMOS, among which 26 125 clusters are recognized for the first time and mostly in the sky outside the Sloan Digital Sky Survey (SDSS) area. About 90 per cent of massive clusters of M500 > 3 × 1014 M⊙ in the redshift range of 0.025 < z < 0.3 have been detected from such survey data, and the detection rate drops down to 50 per cent for clusters with a mass of M500 ˜ 1 × 1014 M⊙. Monte Carlo simulations show that the false detection rate for the whole cluster sample is less than 5 per cent. By cross-matching with ROSAT and XMM-Newton sources, we get 779 new X-ray cluster candidates which have X-ray counterparts within a projected offset of 0.2 Mpc.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wittenmyer, Robert A.; Horner, Jonathan; Tinney, C. G.

We report the detection of GJ 832c, a super-Earth orbiting near the inner edge of the habitable zone of GJ 832, an M dwarf previously known to host a Jupiter analog in a nearly circular 9.4 yr orbit. The combination of precise radial-velocity measurements from three telescopes reveals the presence of a planet with a period of 35.68 ± 0.03 days and minimum mass (m sin i) of 5.4 ± 1.0 Earth masses. GJ 832c moves on a low-eccentricity orbit (e = 0.18 ± 0.13) toward the inner edge of the habitable zone. However, given the large mass of themore » planet, it seems likely that it would possess a massive atmosphere, which may well render the planet inhospitable. Indeed, it is perhaps more likely that GJ 832c is a 'super-Venus', featuring significant greenhouse forcing. With an outer giant planet and an interior, potentially rocky planet, the GJ 832 planetary system can be thought of as a miniature version of our own solar system.« less

Melting curve of SiO2 at multimegabar pressures: implications for gas giants and super-Earths.

PubMed

González-Cataldo, Felipe; Davis, Sergio; Gutiérrez, Gonzalo

2016-05-23

Ultrahigh-pressure phase boundary between solid and liquid SiO2 is still quite unclear. Here we present predictions of silica melting curve for the multimegabar pressure regime, as obtained from first principles molecular dynamics simulations. We calculate the melting temperatures from three high pressure phases of silica (pyrite-, cotunnite-, and Fe2P-type SiO2) at different pressures using the Z method. The computed melting curve is found to rise abruptly around 330 GPa, an increase not previously reported by any melting simulations. This is in close agreement with recent experiments reporting the α-PbO2-pyrite transition around this pressure. The predicted phase diagram indicates that silica could be one of the dominant components of the rocky cores of gas giants, as it remains solid at the core of our Solar System's gas giants. These results are also relevant to model the interior structure and evolution of massive super-Earths.

Melting curve of SiO2 at multimegabar pressures: implications for gas giants and super-Earths

PubMed Central

González-Cataldo, Felipe; Davis, Sergio; Gutiérrez, Gonzalo

2016-01-01

Ultrahigh-pressure phase boundary between solid and liquid SiO2 is still quite unclear. Here we present predictions of silica melting curve for the multimegabar pressure regime, as obtained from first principles molecular dynamics simulations. We calculate the melting temperatures from three high pressure phases of silica (pyrite-, cotunnite-, and Fe2P-type SiO2) at different pressures using the Z method. The computed melting curve is found to rise abruptly around 330 GPa, an increase not previously reported by any melting simulations. This is in close agreement with recent experiments reporting the α-PbO2–pyrite transition around this pressure. The predicted phase diagram indicates that silica could be one of the dominant components of the rocky cores of gas giants, as it remains solid at the core of our Solar System’s gas giants. These results are also relevant to model the interior structure and evolution of massive super-Earths. PMID:27210813

How Does the Low-Rank Matrix Decomposition Help Internal and External Learnings for Super-Resolution.

PubMed

Wang, Shuang; Yue, Bo; Liang, Xuefeng; Jiao, Licheng

2018-03-01

Wisely utilizing the internal and external learning methods is a new challenge in super-resolution problem. To address this issue, we analyze the attributes of two methodologies and find two observations of their recovered details: 1) they are complementary in both feature space and image plane and 2) they distribute sparsely in the spatial space. These inspire us to propose a low-rank solution which effectively integrates two learning methods and then achieves a superior result. To fit this solution, the internal learning method and the external learning method are tailored to produce multiple preliminary results. Our theoretical analysis and experiment prove that the proposed low-rank solution does not require massive inputs to guarantee the performance, and thereby simplifying the design of two learning methods for the solution. Intensive experiments show the proposed solution improves the single learning method in both qualitative and quantitative assessments. Surprisingly, it shows more superior capability on noisy images and outperforms state-of-the-art methods.

Water cycling between ocean and mantle: Super-earths need not be waterworlds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cowan, Nicolas B.; Abbot, Dorian S., E-mail: n-cowan@northwestern.edu

2014-01-20

Large terrestrial planets are expected to have muted topography and deep oceans, implying that most super-Earths should be entirely covered in water, so-called waterworlds. This is important because waterworlds lack a silicate weathering thermostat so their climate is predicted to be less stable than that of planets with exposed continents. In other words, the continuously habitable zone for waterworlds is much narrower than for Earth-like planets. A planet's water is partitioned, however, between a surface reservoir, the ocean, and an interior reservoir, the mantle. Plate tectonics transports water between these reservoirs on geological timescales. Degassing of melt at mid-ocean ridgesmore » and serpentinization of oceanic crust depend negatively and positively on seafloor pressure, respectively, providing a stabilizing feedback on long-term ocean volume. Motivated by Earth's approximately steady-state deep water cycle, we develop a two-box model of the hydrosphere and derive steady-state solutions to the water partitioning on terrestrial planets. Critically, hydrostatic seafloor pressure is proportional to surface gravity, so super-Earths with a deep water cycle will tend to store more water in the mantle. We conclude that a tectonically active terrestrial planet of any mass can maintain exposed continents if its water mass fraction is less than ∼0.2%, dramatically increasing the odds that super-Earths are habitable. The greatest source of uncertainty in our study is Earth's current mantle water inventory: the greater its value, the more robust planets are to inundation. Lastly, we discuss how future missions can test our hypothesis by mapping the oceans and continents of massive terrestrial planets.« less

Framework for Detection and Localization of Extreme Climate Event with Pixel Recursive Super Resolution

NASA Astrophysics Data System (ADS)

Kim, S. K.; Lee, J.; Zhang, C.; Ames, S.; Williams, D. N.

2017-12-01

Deep learning techniques have been successfully applied to solve many problems in climate and geoscience using massive-scaled observed and modeled data. For extreme climate event detections, several models based on deep neural networks have been recently proposed and attend superior performance that overshadows all previous handcrafted expert based method. The issue arising, though, is that accurate localization of events requires high quality of climate data. In this work, we propose framework capable of detecting and localizing extreme climate events in very coarse climate data. Our framework is based on two models using deep neural networks, (1) Convolutional Neural Networks (CNNs) to detect and localize extreme climate events, and (2) Pixel recursive recursive super resolution model to reconstruct high resolution climate data from low resolution climate data. Based on our preliminary work, we have presented two CNNs in our framework for different purposes, detection and localization. Our results using CNNs for extreme climate events detection shows that simple neural nets can capture the pattern of extreme climate events with high accuracy from very coarse reanalysis data. However, localization accuracy is relatively low due to the coarse resolution. To resolve this issue, the pixel recursive super resolution model reconstructs the resolution of input of localization CNNs. We present a best networks using pixel recursive super resolution model that synthesizes details of tropical cyclone in ground truth data while enhancing their resolution. Therefore, this approach not only dramat- ically reduces the human effort, but also suggests possibility to reduce computing cost required for downscaling process to increase resolution of data.

Reduced gas accretion on super-Earths and ice giants

NASA Astrophysics Data System (ADS)

Lambrechts, M.; Lega, E.

2017-10-01

A large fraction of giant planets have gaseous envelopes that are limited to about 10% of their total mass budget. Such planets are present in the solar system (Uranus, Neptune) and are frequently observed in short periods around other stars (the so-called super-Earths). In contrast to these observations, theoretical calculations based on the evolution of hydrostatic envelopes argue that such low-mass envelopes cannot be maintained around cores exceeding five Earth masses. Instead, under nominal disk conditions, these planets would acquire massive envelopes through runaway gas accretion within the lifetime of the protoplanetary disk. In this work we show that planetary envelopes are not in hydrostatic balance, which slows down envelope growth. A series of 3D global, radiative hydrodynamical simulations reveal a steady-state gas flow, which enters through the poles and exits in the disk midplane. Gas is pushed through the outer envelope in about ten orbital timescales. In regions of the disk that are not significantly dust-depleted, envelope accretion onto cores of about five Earth masses can get stalled as the gas flow enters the deep interior. Accreted solids sublimate deep in the convective interior, but small opacity-providing grains are trapped in the flow and do not settle, which further prevents rapid envelope accretion. The transition to runaway gas accretion can however be reached when cores grow larger than typical super-Earths, beyond 15 Earth masses, and preferably when disk opacities are below κ = 1 cm2/g. These findings offer an explanation for the typical low-mass envelopes around the cores of super-Earths.

Unveiling the High Energy Obscured Universe: Hunting Collapsed Objects Physics

NASA Technical Reports Server (NTRS)

Ubertini, P.; Bazzano, A.; Cocchi, M.; Natalucci, L.; Bassani, L.; Caroli, E.; Stephen, J. B.; Caraveo, P.; Mereghetti, S.; Villa, G.

2005-01-01

A large part of energy from space is coming from collapsing stars (SN, Hypernovae) and collapsed stars (black holes, neutron stars and white dwarfs). The peak of their energy release is in the hard-X and gamma-ray wavelengths where photons are insensitive to absorption and can travel from the edge the Universe or the central core of the Galaxy without loosing the primordial information of energy, time signature and polarization. The most efficient process to produce energetic photons is gravitational accretion of matter from a "normal" star onto a collapsed companion (LGxMcollxdMacc/dtx( 1Rdisc)-dMacc/dt x c2), exceeding by far the nuclear reaction capability to generate high energy quanta. Thus our natural laboratory for "in situ" investigations are collapsed objects in which matter and radiation co-exist in extreme conditions of temperature and density due to gravitationally bent geometry and magnetic fields. This is a unique opportunity to study the physics of accretion flows in stellar mass and super-massive Black Holes (SMBHs), plasmoids generated in relativistic jets in galactic microQSOs and AGNs, ionised plasma interacting at the touching point of weakly magnetized NS surface, GRB/Supernovae connection, and the mysterious origins of "dark" GRB and X-ray flash.

Searching for intermediate-mass black holes in galaxies with low-luminosity AGN: a multiple-method approach

NASA Astrophysics Data System (ADS)

Koliopanos, F.; Ciambur, B.; Graham, A.; Webb, N.; Coriat, M.; Mutlu-Pakdil, B.; Davis, B.; Godet, O.; Barret, D.; Seigar, M.

2017-10-01

Intermediate Mass Black Holes (IMBHs) are predicted by a variety of models and are the likely seeds for super massive BHs (SMBHs). However, we have yet to establish their existence. One method, by which we can discover IMBHs, is by measuring the mass of an accreting BH, using X-ray and radio observations and drawing on the correlation between radio luminosity, X-ray luminosity and the BH mass, known as the fundamental plane of BH activity (FP-BH). Furthermore, the mass of BHs in the centers of galaxies, can be estimated using scaling relations between BH mass and galactic properties. We are initiating a campaign to search for IMBH candidates in dwarf galaxies with low-luminosity AGN, using - for the first time - three different scaling relations and the FP-BH, simultaneously. In this first stage of our campaign, we measure the mass of seven LLAGN, that have been previously suggested to host central IMBHs, investigate the consistency between the predictions of the BH scaling relations and the FP-BH, in the low mass regime and demonstrate that this multiple method approach provides a robust average mass prediction. In my talk, I will discuss our methodology, results and next steps of this campaign.

Mass and size growth of early-type galaxies by dry mergers in cluster environments

NASA Astrophysics Data System (ADS)

Oogi, Taira; Habe, Asao; Ishiyama, Tomoaki

2016-02-01

We perform dry merger simulations to investigate the role of dry mergers in the size growth of early-type galaxies in high-density environments. We replace the virialized dark matter haloes obtained by a large cosmological N-body simulation with N-body galaxy models consisting of two components, a stellar bulge and a dark matter halo, which have higher mass resolution than the cosmological simulation. We then resimulate nine cluster-forming regions, whose masses range from 1 × 1014 to 5 × 1014 M⊙. Masses and sizes of stellar bulges are also assumed to satisfy the stellar mass-size relation of high-z compact massive early-type galaxies. We find that dry major mergers considerably contribute to the mass and size growth of central massive galaxies. One or two dry major mergers double the average stellar mass and quadruple the average size between z = 2 and 0. These growths favourably agree with observations. Moreover, the density distributions of our simulated central massive galaxies grow from the inside-out, which is consistent with recent observations. The mass-size evolution is approximated as R∝ M_{{ast }}^{α }, with α ˜ 2.24. Most of our simulated galaxies are efficiently grown by dry mergers, and their stellar mass-size relations match the ones observed in the local Universe. Our results show that the central galaxies in the cluster haloes are potential descendants of high-z (z ˜ 2-3) compact massive early-type galaxies. This conclusion is consistent with previous numerical studies which investigate the formation and evolution of compact massive early-type galaxies.

A Faster Parallel Algorithm and Efficient Multithreaded Implementations for Evaluating Betweenness Centrality on Massive Datasets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Madduri, Kamesh; Ediger, David; Jiang, Karl

2009-05-29

We present a new lock-free parallel algorithm for computing betweenness centrality of massive small-world networks. With minor changes to the data structures, our algorithm also achieves better spatial cache locality compared to previous approaches. Betweenness centrality is a key algorithm kernel in the HPCS SSCA#2 Graph Analysis benchmark, which has been extensively used to evaluate the performance of emerging high-performance computing architectures for graph-theoretic computations. We design optimized implementations of betweenness centrality and the SSCA#2 benchmark for two hardware multithreaded systems: a Cray XMT system with the ThreadStorm processor, and a single-socket Sun multicore server with the UltraSparc T2 processor.more » For a small-world network of 134 million vertices and 1.073 billion edges, the 16-processor XMT system and the 8-core Sun Fire T5120 server achieve TEPS scores (an algorithmic performance count for the SSCA#2 benchmark) of 160 million and 90 million respectively, which corresponds to more than a 2X performance improvement over the previous parallel implementations. To better characterize the performance of these multithreaded systems, we correlate the SSCA#2 performance results with data from the memory-intensive STREAM and RandomAccess benchmarks. Finally, we demonstrate the applicability of our implementation to analyze massive real-world datasets by computing approximate betweenness centrality for a large-scale IMDb movie-actor network.« less

Super-Eight: The brightest z~8 Galaxies

NASA Astrophysics Data System (ADS)

Holwerda, Benne; Bouwens, R.; Bradley, L.; Calvi, V.; Illingworth, G.; Labbe, I.; Magee, D.; Oesch, P.; Roberts-Borsani, G.; Smit, R.

2016-08-01

What are the properties of the most massive z~8 galaxies ('Super-Eights') and how luminous can these galaxies become at that epoch? Answering these questions is challenging due to the rarity of luminous z~8 galaxies and the large field-to-field variations in their volume densities. Indeed, the full wide-area CANDELS program only shows 3 z~8 galaxy candidates brighter than 25.5 mag and all of these candidates conspicuously lie in the same CANDELS field (EGS). One of our strongest new probes for particularly luminous z~8 galaxies are the WFC3 Pure-Parallel (PP) programs. Particularly intriguing are 8 bright z~8 candidates in these observations. These candidates have similar luminosities as the 3 brightest z~8 candidates from CANDELS (all spectroscopically confirmed). However, the uncertain contamination levels at extreme bright end of z~8 selection mean that follow-up observations are critical. We propose highly-efficient pointed HST and Spitzer/IRAC observations to determine if these candidates are indeed at z~8. We estimate that anywhere from 50 to 100% of the targeted sources will be confirmed to be at z~8 based on our results from CANDELS. The estimate is very uncertain due to very large cosmic variance in the CANDELS result and contamination from rare low-redshift sources. When combined with CANDELS, our observations would provide us the strongest current constraints on the volume density of bright, massive galaxies in the early Universe (serving as a guide to models of their build-up) and also provide valuable targets for future spectroscopy (e.g. with JWST), useful for probing the ionization state of the IGM.

Super-Eight: The brightest z 8 Galaxies

NASA Astrophysics Data System (ADS)

Holwerda, Benne

2016-10-01

What are the properties of the most massive z 8 galaxies (Super-Eights) and how luminous can these galaxies become at that epoch? Answering these questions is challenging due to the rarity of luminous z 8 galaxies and the large field-to-field variations in their volume densities. Indeed, the full wide-area CANDELS program only shows 3 z 8 galaxy candidates brighter than 25.5 mag and all of these candidates conspicuously lie in the same CANDELS field (EGS). One of our strongest new probes for particularly luminous z 8 galaxies are the WFC3 Pure-Parallel (PP) programs. Particularly intriguing are 8 bright z 8 candidates in these observations. These candidates have similar luminosities as the 3 brightest z 8 candidates from CANDELS (all spectroscopically confirmed). However, the uncertain contamination levels at extreme bright end of z 8 selection mean that follow-up observations are critical. We propose highly-efficient pointed HST and Spitzer/IRAC observations to determine if these candidates are indeed at z 8. We estimate that anywhere from 50 to 100% of the targeted sources will be confirmed to be at z 8 based on our results from CANDELS. The estimate is very uncertain due to very large cosmic variance in the CANDELS result and contamination from rare low-redshift sources.When combined with CANDELS, our observations would provide us the strongest current constraints on the volume density of bright, massive galaxies in the early Universe (serving as a guide to models of their build-up) and also provide valuable targets for future spectroscopy (e.g. with JWST), useful for probing the ionization state of the IGM.

The salt-responsive transcriptome of chickpea roots and nodules via deepSuperSAGE

PubMed Central

2011-01-01

Background The combination of high-throughput transcript profiling and next-generation sequencing technologies is a prerequisite for genome-wide comprehensive transcriptome analysis. Our recent innovation of deepSuperSAGE is based on an advanced SuperSAGE protocol and its combination with massively parallel pyrosequencing on Roche's 454 sequencing platform. As a demonstration of the power of this combination, we have chosen the salt stress transcriptomes of roots and nodules of the third most important legume crop chickpea (Cicer arietinum L.). While our report is more technology-oriented, it nevertheless addresses a major world-wide problem for crops generally: high salinity. Together with low temperatures and water stress, high salinity is responsible for crop losses of millions of tons of various legume (and other) crops. Continuously deteriorating environmental conditions will combine with salinity stress to further compromise crop yields. As a good example for such stress-exposed crop plants, we started to characterize salt stress responses of chickpeas on the transcriptome level. Results We used deepSuperSAGE to detect early global transcriptome changes in salt-stressed chickpea. The salt stress responses of 86,919 transcripts representing 17,918 unique 26 bp deepSuperSAGE tags (UniTags) from roots of the salt-tolerant variety INRAT-93 two hours after treatment with 25 mM NaCl were characterized. Additionally, the expression of 57,281 transcripts representing 13,115 UniTags was monitored in nodules of the same plants. From a total of 144,200 analyzed 26 bp tags in roots and nodules together, 21,401 unique transcripts were identified. Of these, only 363 and 106 specific transcripts, respectively, were commonly up- or down-regulated (>3.0-fold) under salt stress in both organs, witnessing a differential organ-specific response to stress. Profiting from recent pioneer works on massive cDNA sequencing in chickpea, more than 9,400 UniTags were able to be linked to UniProt entries. Additionally, gene ontology (GO) categories over-representation analysis enabled to filter out enriched biological processes among the differentially expressed UniTags. Subsequently, the gathered information was further cross-checked with stress-related pathways. From several filtered pathways, here we focus exemplarily on transcripts associated with the generation and scavenging of reactive oxygen species (ROS), as well as on transcripts involved in Na+ homeostasis. Although both processes are already very well characterized in other plants, the information generated in the present work is of high value. Information on expression profiles and sequence similarity for several hundreds of transcripts of potential interest is now available. Conclusions This report demonstrates, that the combination of the high-throughput transcriptome profiling technology SuperSAGE with one of the next-generation sequencing platforms allows deep insights into the first molecular reactions of a plant exposed to salinity. Cross validation with recent reports enriched the information about the salt stress dynamics of more than 9,000 chickpea ESTs, and enlarged their pool of alternative transcripts isoforms. As an example for the high resolution of the employed technology that we coin deepSuperSAGE, we demonstrate that ROS-scavenging and -generating pathways undergo strong global transcriptome changes in chickpea roots and nodules already 2 hours after onset of moderate salt stress (25 mM NaCl). Additionally, a set of more than 15 candidate transcripts are proposed to be potential components of the salt overly sensitive (SOS) pathway in chickpea. Newly identified transcript isoforms are potential targets for breeding novel cultivars with high salinity tolerance. We demonstrate that these targets can be integrated into breeding schemes by micro-arrays and RT-PCR assays downstream of the generation of 26 bp tags by SuperSAGE. PMID:21320317

The salt-responsive transcriptome of chickpea roots and nodules via deepSuperSAGE.

PubMed

Molina, Carlos; Zaman-Allah, Mainassara; Khan, Faheema; Fatnassi, Nadia; Horres, Ralf; Rotter, Björn; Steinhauer, Diana; Amenc, Laurie; Drevon, Jean-Jacques; Winter, Peter; Kahl, Günter

2011-02-14

The combination of high-throughput transcript profiling and next-generation sequencing technologies is a prerequisite for genome-wide comprehensive transcriptome analysis. Our recent innovation of deepSuperSAGE is based on an advanced SuperSAGE protocol and its combination with massively parallel pyrosequencing on Roche's 454 sequencing platform. As a demonstration of the power of this combination, we have chosen the salt stress transcriptomes of roots and nodules of the third most important legume crop chickpea (Cicer arietinum L.). While our report is more technology-oriented, it nevertheless addresses a major world-wide problem for crops generally: high salinity. Together with low temperatures and water stress, high salinity is responsible for crop losses of millions of tons of various legume (and other) crops. Continuously deteriorating environmental conditions will combine with salinity stress to further compromise crop yields. As a good example for such stress-exposed crop plants, we started to characterize salt stress responses of chickpeas on the transcriptome level. We used deepSuperSAGE to detect early global transcriptome changes in salt-stressed chickpea. The salt stress responses of 86,919 transcripts representing 17,918 unique 26 bp deepSuperSAGE tags (UniTags) from roots of the salt-tolerant variety INRAT-93 two hours after treatment with 25 mM NaCl were characterized. Additionally, the expression of 57,281 transcripts representing 13,115 UniTags was monitored in nodules of the same plants. From a total of 144,200 analyzed 26 bp tags in roots and nodules together, 21,401 unique transcripts were identified. Of these, only 363 and 106 specific transcripts, respectively, were commonly up- or down-regulated (>3.0-fold) under salt stress in both organs, witnessing a differential organ-specific response to stress.Profiting from recent pioneer works on massive cDNA sequencing in chickpea, more than 9,400 UniTags were able to be linked to UniProt entries. Additionally, gene ontology (GO) categories over-representation analysis enabled to filter out enriched biological processes among the differentially expressed UniTags. Subsequently, the gathered information was further cross-checked with stress-related pathways. From several filtered pathways, here we focus exemplarily on transcripts associated with the generation and scavenging of reactive oxygen species (ROS), as well as on transcripts involved in Na+ homeostasis. Although both processes are already very well characterized in other plants, the information generated in the present work is of high value. Information on expression profiles and sequence similarity for several hundreds of transcripts of potential interest is now available. This report demonstrates, that the combination of the high-throughput transcriptome profiling technology SuperSAGE with one of the next-generation sequencing platforms allows deep insights into the first molecular reactions of a plant exposed to salinity. Cross validation with recent reports enriched the information about the salt stress dynamics of more than 9,000 chickpea ESTs, and enlarged their pool of alternative transcripts isoforms. As an example for the high resolution of the employed technology that we coin deepSuperSAGE, we demonstrate that ROS-scavenging and -generating pathways undergo strong global transcriptome changes in chickpea roots and nodules already 2 hours after onset of moderate salt stress (25 mM NaCl). Additionally, a set of more than 15 candidate transcripts are proposed to be potential components of the salt overly sensitive (SOS) pathway in chickpea. Newly identified transcript isoforms are potential targets for breeding novel cultivars with high salinity tolerance. We demonstrate that these targets can be integrated into breeding schemes by micro-arrays and RT-PCR assays downstream of the generation of 26 bp tags by SuperSAGE.

Super Blood Moon Lunar Eclipse

NASA Image and Video Library

2017-12-08

What time will you be able to view the Super Moon Eclipse? The images below show times to view it for Eastern Daylight Time (EDT), Central Daylight Time (CDT), Mountain Daylight Time (MDT) and Pacific Daylight Time (PDT). All of South America and most of North and Central America will see the entire eclipse, while those west of roughly 120°W will see it in progress at moonrise. You won’t need special equipment to see it. Just go outside and look up! NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Formation of intermediate-mass black holes through runaway collisions in the first star clusters

NASA Astrophysics Data System (ADS)

Sakurai, Yuya; Yoshida, Naoki; Fujii, Michiko S.; Hirano, Shingo

2017-12-01

We study the formation of massive black holes in the first star clusters. We first locate star-forming gas clouds in protogalactic haloes of ≳107 M⊙ in cosmological hydrodynamics simulations and use them to generate the initial conditions for star clusters with masses of ∼105 M⊙. We then perform a series of direct-tree hybrid N-body simulations to follow runaway stellar collisions in the dense star clusters. In all the cluster models except one, runaway collisions occur within a few million years, and the mass of the central, most massive star reaches ∼400-1900 M⊙. Such very massive stars collapse to leave intermediate-mass black holes (IMBHs). The diversity of the final masses may be attributed to the differences in a few basic properties of the host haloes such as mass, central gas velocity dispersion and mean gas density of the central core. Finally, we derive the IMBH mass to cluster mass ratios, and compare them with the observed black hole to bulge mass ratios in the present-day Universe.

A Massive Central Peak and a Low Peak Ring in Gale Crater - Important Influences on the Formation of Mt. Sharp

NASA Technical Reports Server (NTRS)

Allen, Carlton C.

2015-01-01

The Curiosity rover is exploring 155 km diameter Gale crater and Mt. Sharp, Gale's high central mound. This study addresses the central peak and proposed peak ring, and their influence on the overall morphology of the mountain.

The Search for New Luminous Blue Variable Stars: Near-Infrared Spectroscopy of Stars With 24 micron Shells

NASA Astrophysics Data System (ADS)

Stringfellow, Guy; Gvaramadze, Vasilii

2010-02-01

Luminous Blue Variable (LBV) stars represent an extremely rare class of very luminous and massive stars. Only about a dozen confirmed Galactic LBV stars are known to date, which precludes us from determining a solid evolutionary connection between LBV and other intermediate (e.g. Ofpe/WN9, WNL) phases in the life of very massive stars. The known LBV stars each have their own unique properties, so new discoveries add insight into the properties and evolutionary status of LBVs and massive stars; even one new discovery of objects of this type could provide break-through results in the understanding of the intermediate stages of massive star evolution. We have culled a prime sample of possible LBV candidates from the Spitzer 24 (micron) archival data. All have circumstellar nebulae, rings, and shells (typical of LBVs and related stars) surrounding reddened central stars. Spectroscopic followup of about two dozen optically visible central stars associated with the shells from this sample showed that they are either candidate LBVs, late WN-type Wolf-Rayet stars or blue supergiants. We propose infrared spectroscopic observations of the central stars for a large fraction (23 stars) of our northern sample to determine their nature and discover additional LBV candidates. These stars have no plausible optical counterparts, so infrared spectra are needed. This program requires two nights of Hale time using TripleSpec.

Dissolved Massive Metal-rich Globular Clusters Can Cause the Range of UV Upturn Strengths Found among Early-type Galaxies

NASA Astrophysics Data System (ADS)

Goudfrooij, Paul

2018-04-01

I discuss a scenario in which the ultraviolet (UV) upturn of giant early-type galaxies (ETGs) is primarily due to helium-rich stellar populations that formed in massive metal-rich globular clusters (GCs), which subsequently dissolved in the strong tidal field in the central regions of the massive host galaxy. These massive GCs are assumed to show UV upturns similar to those observed recently in M87, the central giant elliptical galaxy in the Virgo cluster of galaxies. Data taken from the literature reveal a strong correlation between the strength of the UV upturn and the specific frequency of metal-rich GCs in ETGs. Adopting a Schechter function parameterization of GC mass functions, simulations of long-term dynamical evolution of GC systems show that the observed correlation between UV upturn strength and GC specific frequency can be explained by variations in the characteristic truncation mass {{ \\mathcal M }}{{c}} such that {{ \\mathcal M }}{{c}} increases with ETG luminosity in a way that is consistent with observed GC luminosity functions in ETGs. These findings suggest that the nature of the UV upturn in ETGs and the variation of its strength among ETGs are causally related to that of helium-rich populations in massive GCs, rather than intrinsic properties of field stars in massive galactic spheroids. With this in mind, I predict that future studies will find that [N/Fe] decreases with increasing galactocentric radius in massive ETGs, and that such gradients have the largest amplitudes in ETGs with the strongest UV upturns.

Massive sulfide metallogenesis at a late Mesozoic sediment-covered spreading axis: Evidence from the Franciscan complex and contemporary analogues

USGS Publications Warehouse

Koski, Randolph A.; Lamons, Roberta C.; Dumoulin, Julie A.; Bouse, Robin M.

1993-01-01

The Island Mountain deposit, an anomalous massive sulfide in the Central belt of the Franciscan subduction complex, northern California Coast Ranges, formed during hydrothermal activity in a sediment-dominated paleo-sea-floor environment. Although the base of the massive sulfide is juxtaposed against a 500-m-wide melange band, its gradational upper contact within a coherent sequence of sandstone, siltstone, and mudstone indicates that hydrothermal activity was concurrent with turbidite deposition. Accumulations of sulfide breccia and clastic sulfide were produced by mass wasting of the sulfide mound prior to burial by turbidites. The bulk composition of sulfide samples (pyrrhotite rich; high Cu, As, and Au contents; radiogenic Pb isotope ratios) is consistent with a hydrothermal system dominated by fluid-sediment interaction. On the basis of a comparison with possible contemporary tectonic analogues at the southern Gorda Ridge and the Chile margin triple junction, we propose that massive sulfide mineralization in the Central belt of the Franciscan complex resulted from hydrothermal activity at a late Mesozoic sediment-covered ridge axis prior to collision with the North American plate.

Massive sulfide metallogenesis at a late Mesozoic sediment-covered spreading axis: Evidence from the Franciscan complex and contemporary analogues

NASA Astrophysics Data System (ADS)

Koski, Randolph A.; Lamons, Roberta C.; Dumoulin, Julie A.; Bouse, Robin M.

1993-02-01

The Island Mountain deposit, an anomalous massive sulfide in the Central belt of the Franciscan subduction complex, northern California Coast Ranges, formed during hydrothermal activity in a sediment-dominated paleo-sea-floor environment. Although the base of the massive sulfide is juxtaposed against a 500-m-wide melange band, its gradational upper contact within a coherent sequence of sandstone, siltstone, and mudstone indicates that hydrothermal activity was concurrent with turbidite deposition. Accumulations of sulfide breccia and clastic sulfide were produced by mass wasting of the sulfide mound prior to burial by turbidites. The bulk composition of sulfide samples (pyrrhotite rich; high Cu, As, and Au contents; radiogenic Pb isotope ratios) is consistent with a hydrothermal system dominated by fluid-sediment interaction. On the basis of a comparison with possible contemporary tectonic analogues at the southern Gorda Ridge and the Chile margin triple junction, we propose that massive sulfide mineralization in the Central belt of the Franciscan complex resulted from hydrothermal activity at a late Mesozoic sediment-covered ridge axis prior to collision with the North American plate.

Central Venous Catheter Placement in the Left Internal Jugular Vein Complicated by Perforation of the Left Brachiocephalic Vein and Massive Hemothorax: A Case Report.

PubMed

Wetzel, Lindsay R; Patel, Priyesh R; Pesa, Nicholas L

2017-07-01

An elderly male presented for emergent repair of a ruptured abdominal aortic aneurysm. For anticipated volume resuscitation, vasopressor administration, and hemodynamic monitoring, a large-bore central venous catheter was placed in the left internal jugular vein under ultrasound guidance before surgical incision. Initially, there were no readily apparent signs of venous perforation. However, a massive left hemothorax developed because of perforation of the brachiocephalic vein and violation of the pleural space. This case report discusses both prevention and management of such a complication.

The dynamics and fueling of active nuclei

NASA Technical Reports Server (NTRS)

Norman, C.; Silk, J.

1983-01-01

It is generally believed that quasars and active galactic nuclei produce their prodigious luminosities in connection with the release of gravitational energy associated with accretion and infall of matter onto a compact central object. In the present analysis, it is assumed that the central object is a massive black hole. The fact that a black hole provides the deepest possible central potential well does imply that it is the most natural candidate for the central engine. It is also assumed that the quasar is associated with the nucleus of a conventional galaxy. A number of difficulties arise in connection with finding a suitable stellar fueling model. A simple scheme is discussed for resolving these difficulties. Attention is given to fueling in a nonaxisymmetric potential, the effects of a massive accretion disk, and the variability in the disk luminosity caused by star-disk collisions assuming that the energy deposited in the disk is radiated.

Butterfly effect in 3D gravity

NASA Astrophysics Data System (ADS)

Qaemmaqami, Mohammad M.

2017-11-01

We study the butterfly effect by considering shock wave solutions near the horizon of the anti-de Sitter black hole in some three-dimensional gravity models including 3D Einstein gravity, minimal massive 3D gravity, new massive gravity, generalized massive gravity, Born-Infeld 3D gravity, and new bigravity. We calculate the butterfly velocities of these models and also we consider the critical points and different limits in some of these models. By studying the butterfly effect in the generalized massive gravity, we observe a correspondence between the butterfly velocities and right-left moving degrees of freedom or the central charges of the dual 2D conformal field theories.

On the Formation of Massive Stars

NASA Technical Reports Server (NTRS)

Yorke, Harold W.; Sonnhalter, Cordula

2002-01-01

We calculate numerically the collapse of slowly rotating, nonmagnetic, massive molecular clumps of masses 30,60, and 120 Stellar Mass, which conceivably could lead to the formation of massive stars. Because radiative acceleration on dust grains plays a critical role in the clump's dynamical evolution, we have improved the module for continuum radiation transfer in an existing two-dimensional (axial symmetry assumed) radiation hydrodynamic code. In particular, rather than using "gray" dust opacities and "gray" radiation transfer, we calculate the dust's wavelength-dependent absorption and emission simultaneously with the radiation density at each wavelength and the equilibrium temperatures of three grain components: amorphous carbon particles. silicates, and " dirty ice " -coated silicates. Because our simulations cannot spatially resolve the innermost regions of the molecular clump, however, we cannot distinguish between the formation of a dense central cluster or a single massive object. Furthermore, we cannot exclude significant mass loss from the central object(s) that may interact with the inflow into the central grid cell. Thus, with our basic assumption that all material in the innermost grid cell accretes onto a single object. we are able to provide only an upper limit to the mass of stars that could possibly be formed. We introduce a semianalytical scheme for augmenting existing evolutionary tracks of pre-main-sequence protostars by including the effects of accretion. By considering an open outermost boundary, an arbitrary amount of material could, in principal, be accreted onto this central star. However, for the three cases considered (30, 60, and 120 Stellar Mass originally within the computation grid), radiation acceleration limited the final masses to 3 1.6, 33.6, and 42.9 Stellar Mass, respectively, for wavelength-dependent radiation transfer and to 19.1, 20.1, and 22.9 Stellar Mass. for the corresponding simulations with gray radiation transfer. Our calculations demonstrate that massive stars can in principle be formed via accretion through a disk. The accretion rate onto the central source increases rapidly after one initial free-fall time and decreases monotonically afterward. By enhancing the nonisotropic character of the radiation field, the accretion disk reduces the effects of radiative acceleration in the radial direction - a process we call the "flashlight effect." The flashlight effect is further amplified in our case by including the effects of frequency-dependent radiation transfer. We conclude with the warning that a careful treatment of radiation transfer is a mandatory requirement for realistic simulations of the formation of massive stars.

Surprise: Dwarf Galaxy Harbors Supermassive Black Hole

NASA Astrophysics Data System (ADS)

2011-01-01

The surprising discovery of a supermassive black hole in a small nearby galaxy has given astronomers a tantalizing look at how black holes and galaxies may have grown in the early history of the Universe. Finding a black hole a million times more massive than the Sun in a star-forming dwarf galaxy is a strong indication that supermassive black holes formed before the buildup of galaxies, the astronomers said. The galaxy, called Henize 2-10, 30 million light-years from Earth, has been studied for years, and is forming stars very rapidly. Irregularly shaped and about 3,000 light-years across (compared to 100,000 for our own Milky Way), it resembles what scientists think were some of the first galaxies to form in the early Universe. "This galaxy gives us important clues about a very early phase of galaxy evolution that has not been observed before," said Amy Reines, a Ph.D. candidate at the University of Virginia. Supermassive black holes lie at the cores of all "full-sized" galaxies. In the nearby Universe, there is a direct relationship -- a constant ratio -- between the masses of the black holes and that of the central "bulges" of the galaxies, leading them to conclude that the black holes and bulges affected each others' growth. Two years ago, an international team of astronomers found that black holes in young galaxies in the early Universe were more massive than this ratio would indicate. This, they said, was strong evidence that black holes developed before their surrounding galaxies. "Now, we have found a dwarf galaxy with no bulge at all, yet it has a supermassive black hole. This greatly strengthens the case for the black holes developing first, before the galaxy's bulge is formed," Reines said. Reines, along with Gregory Sivakoff and Kelsey Johnson of the University of Virginia and the National Radio Astronomy Observatory (NRAO), and Crystal Brogan of the NRAO, observed Henize 2-10 with the National Science Foundation's Very Large Array radio telescope and with the Hubble Space Telescope. They found a region near the center of the galaxy that strongly emits radio waves with characteristics of those emitted by super-fast "jets" of material spewed outward from areas close to a black hole. They then searched images from the Chandra X-Ray Observatory that showed this same, radio-bright region to be strongly emitting energetic X-rays. This combination, they said, indicates an active, black-hole-powered, galactic nucleus. "Not many dwarf galaxies are known to have massive black holes," Sivakoff said. While central black holes of roughly the same mass as the one in Henize 2-10 have been found in other galaxies, those galaxies all have much more regular shapes. Henize 2-10 differs not only in its irregular shape and small size but also in its furious star formation, concentrated in numerous, very dense "super star clusters." "This galaxy probably resembles those in the very young Universe, when galaxies were just starting to form and were colliding frequently. All its properties, including the supermassive black hole, are giving us important new clues about how these black holes and galaxies formed at that time," Johnson said. The astronomers reported their findings in the January 9 online edition of Nature, and at the American Astronomical Society's meeting in Seattle, WA. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. More information, including images and other multimedia, can be found at: http://chandra.harvard.edu and http://chandra.nasa.gov

Growing Cutting-edge X-ray Optics

ScienceCinema

Conley, Ray

2018-03-02

Ever imagined that an Xbox controller could help open a window into a world spanning just one billionth of a meter? Brookhaven Lab's Ray Conley grows cutting-edge optics called multilayer Laue lenses (MLL) one atomic layer at a time to focus high-energy x-rays to within a single nanometer. To achieve this focusing feat, Ray uses a massive, custom-built atomic deposition device, an array of computers, and a trusty Xbox controller. These lenses will be deployed at the Lab's National Synchrotron Light Source II, due to begin shining super-bright light on pressing scientific puzzles in 2015.

A Celestial Reference Frame at X/ka-Band (8.4/32 Ghz) for Deep Space Navigation

NASA Technical Reports Server (NTRS)

Jacobs, C. S.; Clark, J. E.; Garcia-Miro, C.; Horiuchi, S.; Romero-Wolf, A.; Snedeker, L.; Sotuela, I.

2012-01-01

Deep space tracking and navigation are done in a quasi-inertial reference frame based upon the angular positions of distant active galactic nuclei (AGN). These objects, which are found at extreme distances characterized by median redshifts of z = 1, are ideal for reference frame definition because they exhibit no measurable parallax or proper motion. They are thought to be powered by super massive black holes whose gravitational energy drives galactic sized relativistic jets. These jets produce synchrotron emissions which are detectable by modern radio techniques such as Very Long baseline Interferometry (VLBI).

Application of activation methods on the Dubna experimental transmutation set-ups.

PubMed

Stoulos, S; Fragopoulou, M; Adloff, J C; Debeauvais, M; Brandt, R; Westmeier, W; Krivopustov, M; Sosnin, A; Papastefanou, C; Zamani, M; Manolopoulou, M

2003-02-01

High spallation neutron fluxes were produced by irradiating massive heavy targets with proton beams in the GeV range. The experiments were performed at the Dubna High Energy Laboratory using the nuclotron accelerator. Two different experimental set-ups were used to produce neutron spectra convenient for transmutation of radioactive waste by (n,x) reactions. By a theoretical analysis neutron spectra can be reproduced from activation measurements. Thermal-epithermal and fast-super-fast neutron fluxes were estimated using the 197Au, 238U (n,gamma) and (n,2n) reactions, respectively. Depleted uranium transmutation rates were also studied in both experiments.

There Are (super)Giants in the Sky: Searching for Misidentified Massive Stars in Algorithmically-Selected Quasar Catalogs

NASA Astrophysics Data System (ADS)

Dorn-Wallenstein, Trevor Z.; Levesque, Emily

2017-11-01

Thanks to incredible advances in instrumentation, surveys like the Sloan Digital Sky Survey have been able to find and catalog billions of objects, ranging from local M dwarfs to distant quasars. Machine learning algorithms have greatly aided in the effort to classify these objects; however, there are regimes where these algorithms fail, where interesting oddities may be found. We present here an X-ray bright quasar misidentified as a red supergiant/X-ray binary, and a subsequent search of the SDSS quasar catalog for X-ray bright stars misidentified as quasars.

The growth of central and satellite galaxies in cosmological smoothed particle hydrodynamics simulations

NASA Astrophysics Data System (ADS)

Simha, Vimal; Weinberg, David H.; Davé, Romeel; Gnedin, Oleg Y.; Katz, Neal; Kereš, Dušan

2009-10-01

We examine the accretion and merger histories of central and satellite galaxies in a smoothed particle hydrodynamics (SPH) cosmological simulation that resolves galaxies down to 7 × 109Msolar. Most friends-of-friends haloes in the simulation have a distinct central galaxy, typically 2-5 times more massive than the most massive satellite. As expected, satellites have systematically higher assembly redshifts than central galaxies of the same baryonic mass, and satellites in more massive haloes form earlier. However, contrary to the simplest expectations, satellite galaxies continue to accrete gas and convert it to stars; the gas accretion declines steadily over a period of 0.5-1 Gyr after the satellite halo merges with a larger parent halo. Satellites in a cluster mass halo eventually begin to lose baryonic mass. Typically, satellites in our simulation are 0.1-0.2 mag bluer than in models that assume no gas accretion on to satellites after a halo merger. Since z = 1, 27 per cent of central galaxies (above 3 × 1010Msolar) and 22 per cent of present-day satellite galaxies have merged with a smaller system above a 1:4 mass ratio; about half of the satellite mergers occurred after the galaxy became a satellite and half before. In effect, satellite galaxies can remain `central' objects of halo substructures, with continuing accretion and mergers, making the transition in assembly histories and physical properties a gradual one. Implementing such a gradual transformation in semi-analytic models would improve their agreement with observed colour distributions of satellite galaxies in groups and with the observed colour dependence of galaxy clustering.

SED Modeling of 20 Massive Young Stellar Objects

NASA Astrophysics Data System (ADS)

Tanti, Kamal Kumar

In this paper, we present the spectral energy distributions (SEDs) modeling of twenty massive young stellar objects (MYSOs) and subsequently estimated different physical and structural/geometrical parameters for each of the twenty central YSO outflow candidates, along with their associated circumstellar disks and infalling envelopes. The SEDs for each of the MYSOs been reconstructed by using 2MASS, MSX, IRAS, IRAC & MIPS, SCUBA, WISE, SPIRE and IRAM data, with the help of a SED Fitting Tool, that uses a grid of 2D radiative transfer models. Using the detailed analysis of SEDs and subsequent estimation of physical and geometrical parameters for the central YSO sources along with its circumstellar disks and envelopes, the cumulative distribution of the stellar, disk and envelope parameters can be analyzed. This leads to a better understanding of massive star formation processes in their respective star forming regions in different molecular clouds.

Visualization of Pulsar Search Data

NASA Astrophysics Data System (ADS)

Foster, R. S.; Wolszczan, A.

1993-05-01

The search for periodic signals from rotating neutron stars or pulsars has been a computationally taxing problem to astronomers for more than twenty-five years. Over this time interval, increases in computational capability have allowed ever more sensitive searches, covering a larger parameter space. The volume of input data and the general presence of radio frequency interference typically produce numerous spurious signals. Visualization of the search output and enhanced real-time processing of significant candidate events allow the pulsar searcher to optimally processes and search for new radio pulsars. The pulsar search algorithm and visualization system presented in this paper currently runs on serial RISC based workstations, a traditional vector based super computer, and a massively parallel computer. A description of the serial software algorithm and its modifications for massively parallel computing are describe. The results of four successive searches for millisecond period radio pulsars using the Arecibo telescope at 430 MHz have resulted in the successful detection of new long-period and millisecond period radio pulsars.

The effective hyper-Kähler potential in the N = 2 supersymmetric QCD

NASA Astrophysics Data System (ADS)

Ketov, Sergei V.

1997-02-01

The effective low-energy hyper-Kähler potential for a massive N = 2 matter in N = 2 super-QCD is investigated. TheN = 2 extended supersymmetry severely restricts the N = 2 matter self-couplings so that their exact form can be fixed by a few parameters, which is apparent in the N = 2 harmonic superspace. In the N = 2 QED with a single matter hypermultiplet, the one-loop perturbative calculations lead to the Taub-NUT hyper-Kähler metric in the massive case, and a free metric in the massless case. It is remarkable that the naive non-renormalization `theorem' does not apply. There exists a manifestly N = 2 supersymmetric duality transformation converting the low-energy effective action for the N = 2 QED hypermultiplet into a sum of the quadratic and the improved (non-polynomial) actions for an N = 2 tensor multiplet. The duality transformation also gives a simple connection between the low-energy effective action in the N = 2 harmonic superspace and the component results.

Prospects for Probing Strong Gravity with a Pulsar-Black Hole System

NASA Technical Reports Server (NTRS)

Wex, N.; Liu, K.; Eatough, R. P.; Kramer, M.; Cordes, J. M.; Lazio, T. J. W.

2012-01-01

The discovery of a pulsar (PSR) in orbit around a black hole (BH) is expected to provide a superb new probe of relativistic gravity and BH properties. Apart from a precise mass measurement for the BH, one could expect a clean verification of the dragging of space-time caused by the BH spin. In order to measure the quadrupole moment of the BH for testing the no-hair theorem of general relativity (GR), one has to hope for a sufficiently massive BH. In this respect, a PSR orbiting the super-massive BH in the center of our Galaxy would be the ultimate laboratory for gravity tests with PSRs. But even for gravity theories that predict the same properties for BHs as GR, a PSR-BH system would constitute an excellent test system, due to the high grade of asymmetry in the strong field properties of these two components. Here we highlight some of the potential gravity tests that one could expect from different PSR-BH systems.

Cerro Xalapaxco: An Unusual Tuff Cone with Multiple Explosion Craters, in Central Mexico (Puebla)

NASA Technical Reports Server (NTRS)

Abrams, M. J.; Siebe, C.

1994-01-01

The Xalapaxco tuff cone is located on the northeast flank of La Malinche stratovolcano in central Mexico. An unusually large number (10) of explosion craters, concentrated on the central and on the uphill side of the cone, expose alternating beds of stratified surge deposits and massive fall deposits.

Production of deuterium, tritium, and He 3 in central Pb + Pb collisions at 20 A , 30 A , 40 A , 80 A , and 158 A  GeV at the CERN Super Proton Synchrotron

DOE PAGES

Anticic, T.; Baatar, B.; Bartke, J.; ...

2016-10-13

Production of d, t, and 3He nuclei in central Pb + Pb interactions was studied at five collision energies (more » $$\\sqrt{s}$$$_ {NN}$$= 6.3, 7.6, 8.8, 12.3, and 17.3 GeV) with the NA49 detector at the CERN Super Proton Synchrotron.Transverse momentum spectra, rapidity distributions, and particle ratios were measured. Yields are compared to predictions of statistical models. Phase-space distributions of light nuclei are discussed and compared to those of protons in the context of a coalescence approach. Finally, the coalescence parameters B 2 and B 3, as well as coalescence radii for d and 3He were determined as a function of transverse mass at all energies.« less

Pacifier Stiffness Alters the Dynamics of the Suck Central Pattern Generator.

PubMed

Zimmerman, Emily; Barlow, Steven M

2008-06-01

Variation in pacifier stiffness on non-nutritive suck (NNS) dynamics was examined among infants born prematurely with a history of respiratory distress syndrome. Three types of silicone pacifiers used in the NICU were tested for stiffness, revealing the Super Soothie™ nipple is 7 times stiffer than the Wee™ or Soothie™ pacifiers even though shape and displaced volume are identical. Suck dynamics among 20 preterm infants were subsequently sampled using the Soothie™ and Super Soothie™ pacifiers during follow-up at approximately 3 months of age. ANOVA revealed significant differences in NNS cycles/min, NNS amplitude, NNS cycles/burst, and NNS cycle periods as a function of pacifier stiffness. Infants modify the spatiotemporal output of their suck central pattern generator when presented with pacifiers with significantly different mechanical properties. Infants show a non-preference to suck due to high stiffness in the selected pacifier. Therefore, excessive pacifier stiffness may decrease ororhythmic patterning and impact feeding outcomes.

Pacifier Stiffness Alters the Dynamics of the Suck Central Pattern Generator

PubMed Central

Zimmerman, Emily; Barlow, Steven M.

2008-01-01

Variation in pacifier stiffness on non-nutritive suck (NNS) dynamics was examined among infants born prematurely with a history of respiratory distress syndrome. Three types of silicone pacifiers used in the NICU were tested for stiffness, revealing the Super Soothie™ nipple is 7 times stiffer than the Wee™ or Soothie™ pacifiers even though shape and displaced volume are identical. Suck dynamics among 20 preterm infants were subsequently sampled using the Soothie™ and Super Soothie™ pacifiers during follow-up at approximately 3 months of age. ANOVA revealed significant differences in NNS cycles/min, NNS amplitude, NNS cycles/burst, and NNS cycle periods as a function of pacifier stiffness. Infants modify the spatiotemporal output of their suck central pattern generator when presented with pacifiers with significantly different mechanical properties. Infants show a non-preference to suck due to high stiffness in the selected pacifier. Therefore, excessive pacifier stiffness may decrease ororhythmic patterning and impact feeding outcomes. PMID:19492006

A possible relation between flare activity in super-luminous supernovae and gamma-ray bursts

NASA Astrophysics Data System (ADS)

Yu, Yun-Wei; Li, Shao-Ze

2017-09-01

Significant undulations appear in the light curve of a recently discovered super-luminous supernova (SLSN) SN 2015bn after the first peak, while the underlying profile of the light curve can be explained well by a continuous energy supply from a central engine, possibly the spin-down of a millisecond magnetar. We propose that these undulations are caused by an intermittent pulsed energy supply, indicating the energetic flare activity of the central engine of the SLSN. Many post-burst flares were discovered during X-ray afterglow observations of gamma-ray bursts (GRBs). We find that the SLSN flares described here approximately obey the empirical correlation between the luminosity and time-scale of GRB flares, extrapolated to the relevant longer time-scales of SLSN flares. This somewhat confirms the possible connection between these two different phenomena, as recently suggested by Yu et al.

Super-Eddington Accretion in the Ultraluminous X-Ray Source NGC 1313 X-2: An Ephemeral Feast

NASA Astrophysics Data System (ADS)

Weng, Shan-Shan; Zhang, Shuang-Nan; Zhao, Hai-Hui

2014-01-01

We investigate the X-ray spectrum, variability, and the surrounding ionized bubble of NGC 1313 X-2 to explore the physics of super-Eddington accretion. Beyond the Eddington luminosity, the accretion disk of NGC 1313 X-2 is truncated at a large radius (~50 times the innermost stable circular orbit), and displays the similar evolution track with both luminous Galactic black-hole and neutron star X-ray binaries (XRBs). In super-critical accretion, the speed of radiatively driven outflows from the inner disk is mildly relativistic. Such ultra-fast outflows would be overionized and might produce weak Fe K absorption lines, which may be detected by the coming X-ray mission Astro-H. If NGC 1313 X-2 is a massive stellar XRB, the high luminosity indicates that an ephemeral feast is held in the source. That is, the source must be accreting at a hyper-Eddington mass rate to give the super-Eddington emission over ~104-105 yr. The expansion of the surrounding bubble nebula with a velocity of ~100 km s-1 might indicate that it has existed over ~106 yr and is inflated by the radiatively driven outflows from the transient with a duty cycle of activity of ~ a few percent. Alternatively, if the surrounding bubble nebula is produced by line-driven winds, less energy is required than the radiatively driven outflow scenario, and the radius of the Strömgren radius agrees with the nebula size. Our results are in favor of the line-driven winds scenario, which can avoid the conflict between the short accretion age and the apparently much longer bubble age inferred from the expansion velocity in the nebula.

Super-Eddington stellar winds driven by near-surface energy deposition

NASA Astrophysics Data System (ADS)

Quataert, Eliot; Fernández, Rodrigo; Kasen, Daniel; Klion, Hannah; Paxton, Bill

2016-05-01

We develop analytic and numerical models of the properties of super-Eddington stellar winds, motivated by phases in stellar evolution when super-Eddington energy deposition (via, e.g. unstable fusion, wave heating, or a binary companion) heats a region near the stellar surface. This appears to occur in the giant eruptions of luminous blue variables (LBVs), Type IIn supernovae progenitors, classical novae, and X-ray bursts. We show that when the wind kinetic power exceeds Eddington, the photons are trapped and behave like a fluid. Convection does not play a significant role in the wind energy transport. The wind properties depend on the ratio of a characteristic speed in the problem v_crit˜ (dot{E} G)^{1/5} (where dot{E} is the heating rate) to the stellar escape speed near the heating region vesc(rh). For vcrit ≳ vesc(rh), the wind kinetic power at large radii dot{E}_w ˜ dot{E}. For vcrit ≲ vesc(rh), most of the energy is used to unbind the wind material and thus dot{E}_w ≲ dot{E}. Multidimensional hydrodynamic simulations without radiation diffusion using FLASH and one-dimensional hydrodynamic simulations with radiation diffusion using MESA are in good agreement with the analytic predictions. The photon luminosity from the wind is itself super-Eddington but in many cases the photon luminosity is likely dominated by `internal shocks' in the wind. We discuss the application of our models to eruptive mass-loss from massive stars and argue that the wind models described here can account for the broad properties of LBV outflows and the enhanced mass-loss in the years prior to Type IIn core-collapse supernovae.

The Disruptive Potential of the Massive Open Online Course: A Literature Review

ERIC Educational Resources Information Center

Jacoby, Jean

2014-01-01

The Massive Open Online Course (MOOC) is a rapidly evolving phenomenon which has stimulated discussion in universities around the world. A central theme of these discussions, and much of the published literature on the phenomenon, is the potential of the MOOC to disrupt the way universities do business. The aim of this narrative literature review…

The annual amount of lightning in just 20 minutes: the October 25th, 2015 super-cell thunderstorm over central Israel

NASA Astrophysics Data System (ADS)

Yair, Y.; Ziv, B.; Lynn, B. H.; Evgeni, K.

2016-12-01

An exceptionally rare Eastern Mediterranean super-cell thunderstorm occurred during the morning hours of October 25th 2015. The storm developed within the northern tip of a Red-Sea trough (extending from Sudan to the Southeastern Mediterranean Sea) off the Egyptian coastline near Alexandria and moved north-west, crossing the Israeli coast just north of Tel-Aviv at 0900 local time. Deep convective cells developed rapidly over the sea, with thunderclouds exhibiting cloud top temperatures colder than -70°C (18 km) and radar reflectivity cores > 65 dBz at 10 km. The storms were accompanied by intensive lightning activity, severe hail, downbursts, and intense rain. The super-cell subsided upon reaching the Jordan rift in eastern Israel. The super-cell caused 1 fatality, extensive flooding and agricultural damages. It also impacted the national electrical network with power outages lasting for 3 days in central Israel. More than 17,000 cloud-to-ground lightning strokes were registered by the lightning detection system of the Israeli Electrical Corporation, exceeding the annual average for the entire country. The average cloud-to-ground flash rates between 0940-0950 and 0950-1000 (local time) were greater than 436 and 430 strokes per minute respectively, exceeding the global record flash rates found in the Argentina-Paraguay border (Zipser et al., 2006). This was the most powerful thunderstorm ever observed in Israel since lightning detection became operational in 1997. Medium-range forecast models such as ECMWF and the GFS missed the timing and severity of this unusual storm. We will present a mesoscale and microphysical analysis of this event to better understand the origins and severity of this rare super-cell. WRF high-resolution simulations with lightning assimilation (Fierro et al., 2012; Lynn et al., 2015) coupled with the Dynamic Lightning Scheme (Lynn et al., 2012) will be used in order to evaluate the performance of the WRF for accurately nowcasting such events.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ginsburg, A.; Bally, J.; Battersby, C.

We search the {lambda} = 1.1 mm Bolocam Galactic Plane Survey for clumps containing sufficient mass to form {approx}10{sup 4} M{sub Sun} star clusters. Eighteen candidate massive proto-clusters are identified in the first Galactic quadrant outside of the central kiloparsec. This sample is complete to clumps with mass M{sub clump} > 10{sup 4} M{sub Sun} and radius r {approx}< 2.5 pc. The overall Galactic massive cluster formation rate is CFR(M{sub cluster} > 10{sup 4}) {approx}<5 Myr{sup -1}, which is in agreement with the rates inferred from Galactic open clusters and M31 massive clusters. We find that all massive proto-clusters inmore » the first quadrant are actively forming massive stars and place an upper limit of {tau}{sub starless} < 0.5 Myr on the lifetime of the starless phase of massive cluster formation. If massive clusters go through a starless phase with all of their mass in a single clump, the lifetime of this phase is very short.« less

Isolating signatures of major cloud-cloud collisions using position-velocity diagrams

NASA Astrophysics Data System (ADS)

Haworth, T. J.; Tasker, E. J.; Fukui, Y.; Torii, K.; Dale, J. E.; Shima, K.; Takahira, K.; Habe, A.; Hasegawa, K.

2015-06-01

Collisions between giant molecular clouds are a potential mechanism for triggering the formation of massive stars, or even super star clusters. The trouble is identifying this process observationally and distinguishing it from other mechanisms. We produce synthetic position-velocity diagrams from models of cloud-cloud collisions, non-interacting clouds along the line of sight, clouds with internal radiative feedback and a more complex cloud evolving in a galactic disc, to try and identify unique signatures of collision. We find that a broad bridge feature connecting two intensity peaks, spatially correlated but separated in velocity, is a signature of a high-velocity cloud-cloud collision. We show that the broad bridge feature is resilient to the effects of radiative feedback, at least to around 2.5 Myr after the formation of the first massive (ionizing) star. However for a head-on 10 km s-1 collision, we find that this will only be observable from 20 to 30 per cent of viewing angles. Such broad-bridge features have been identified towards M20, a very young region of massive star formation that was concluded to be a site of cloud-cloud collision by Torii et al., and also towards star formation in the outer Milky Way by Izumi et al.

Gargantuan Super Spiral Galaxies Loom Large in the Cosmos

NASA Image and Video Library

2016-03-17

In archived NASA data, researchers have discovered "super spiral" galaxies that dwarf our own spiral galaxy, the Milky Way, and compete in size and brightness with the largest galaxies in the universe. The unprecedented galaxies have long hidden in plain sight by mimicking the appearance of typical spirals. Three examples of super spirals are presented here in images taken by the Sloan Digital Sky Survey. The super spiral on the left (Figure 1), catalogued as 2MASX J08542169+0449308, contains two galactic nuclei, instead of just the usual one, and thus looks like two eggs frying in a pan. The central image (Figure 2) shows a super spiral designated 2MASX J16014061+2718161, and it also contains the double nuclei. On the right (Figure 3), a huge galaxy with the moniker SDSS J094700.08+254045.7 stands as one of the biggest and brightest super spirals. The mega-galaxy's starry disk and spiral arms stretch about 320,000 light-years across, or more than three times the breadth of the Milky Way. These double nuclei, which are known to result from the recent merger of two galaxies, could offer a vital hint about the potential origin of super spirals. Researchers speculate that a special merger involving two, gas-rich spiral galaxies could see their pooled gases settle down into a new, larger stellar disk -- presto, a super spiral. The super spirals were discovered using the NASA/IPAC Extragalactic Database, or NED, an online repository containing information on over 100 million galaxies. NED brings together a wealth of data from many different projects, including ultraviolet light observations from the Galaxy Evolution Explorer, visible light from Sloan Digital Sky Survey, infrared light from the 2-Micron All-Sky Survey, and links to data from other missions such as NASA's Spitzer Space Telescope and Wide-Field Infrared Survey Explorer, or WISE. http://photojournal.jpl.nasa.gov/catalog/PIA20064

The X-ray footprint of the circumnuclear disc

NASA Astrophysics Data System (ADS)

Mossoux, Enmanuelle; Eckart, Andreas

2018-03-01

We studied the central regions of the Galactic Centre to determine if the circumnuclear disc (CND) acts as an absorber or a barrier for the central X-rays diffuse emission. After reprocessing 4.6 Ms of Chandra observations, we were able to detect, for the first time, a depression in the X-ray luminosity of the diffuse emission whose size and location correspond to those of the CND. We extracted the X-ray spectra for various regions inside the CND footprint as well as for the region where the footprint is observed and for a region located outside the footprint. We simultaneously fitted these spectra as an optically thin plasma whose absorption by the interstellar medium (ISM) and by the local plasma were fitted independently using the Markov chain Monte Carlo method. The hydrogen column density of the ISM is 7.5 × 1022 cm-2. The X-ray diffuse emission inside the CND footprint is formed by a 2T plasma of 1 and 4 keV with slightly super-solar abundances except for the iron and carbon that are sub-solar. The plasma from the CND, in turn, is better described by a 1T model with abundances and local hydrogen column density that are very different from those of the innermost regions. The large iron abundance in this region confirms that the CND is dominated by the shock-heated ejecta of the Sgr A East supernova remnant. We deduced that the CND rather acts as a barrier for the Galactic Centre plasma and that the plasma located outside the CND may correspond to the collimated outflow possibly created by Sgr A* or the interaction between the wind of massive stars and the mini-spiral material.

Flat-top beam for laser-stimulated pain

NASA Astrophysics Data System (ADS)

McCaughey, Ryan; Nadeau, Valerie; Dickinson, Mark

2005-04-01

One of the main problems during laser stimulation in human pain research is the risk of tissue damage caused by excessive heating of the skin. This risk has been reduced by using a laser beam with a flattop (or superGaussian) intensity profile, instead of the conventional Gaussian beam. A finite difference approximation to the heat conduction equation has been applied to model the temperature distribution in skin as a result of irradiation by flattop and Gaussian profile CO2 laser beams. The model predicts that a 15 mm diameter, 15 W, 100 ms CO2 laser pulse with an order 6 superGaussian profile produces a maximum temperature 6 oC less than a Gaussian beam with the same energy density. A superGaussian profile was created by passing a Gaussian beam through a pair of zinc selenide aspheric lenses which refract the more intense central region of the beam towards the less intense periphery. The profiles of the lenses were determined by geometrical optics. In human pain trials the superGaussian beam required more power than the Gaussian beam to reach sensory and pain thresholds.

Hubble Space Telescope imaging of the central star forming region in NGC 1140 (exp 1)

NASA Technical Reports Server (NTRS)

Hunter, Deidre A.; O'Connell, Robert W.; Gallagher, John S. Iii

1994-01-01

We present broadband images taken with the Hubble Space Telescope's Planetary Camera of the central supergiant H II region in the amorphous galaxy NGC 1140. These images allow observations to a resolution of about 13 pc at the galaxy, and they reveal that its central 1/2 kpc contains 6-7 blue, luminous, compact super star clusters, many of which would be comparable in luminosity to globular clusters at the same age. A blue arc-shaped structure near the center may be a grouping of less luminous, R136/NGC 2070-sized clusters or a sheet of OB stars. Additional somewhat less luminous and redder clusters are also found farther out from the center. If these clusters are older, they too could have had luminosities comparable to those of the central six clusters at a comparable age. Thus, we find that NGC 1140 is remarkable in the number of extreme clusters that it has formed recently in a relatively small area of the galaxy. Since NGC 1140 exhibits global characteristics that are consistent with a recent merger, these clusters are likely to be a product of that event. This galaxy adds to the number of cases where rapid star formation has evidently produced super star clusters.

Interventional Management of Massive Hemothorax Due to Inadvertent Puncture of an Aberrant Right Subclavian Artery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jahnke, Thomas, E-mail: thomas.jahnke@gmx.net; Schaefer, Phillip Jost; Heller, Martin

2008-07-15

We report a case of massive hemothorax due to inadvertent puncture of an aberrant right subclavian artery during central venous access. Iatrogenic laceration at the origin of the right internal thoracic artery was successfully treated with coil embolization of the internal thoracic artery followed by stent-graft placement into the subclavian artery. Due to its elongated and abnormal course, an aberrant right subclavian artery may predispose to inadvertent puncture during vein catheterization and should be recognized as a potential threat for such procedures. Our case emphasizes that ultrasound guidance should be used routinely for central venous lines wherever possible.

Planetary Habitability over Cosmic-Time Based on Cosmic-Ray Levels

NASA Astrophysics Data System (ADS)

Mason, Paul A.; Biermann, Peter L.

2016-01-01

Extreme cosmic-ray (CR) fluxes have a negative effect on life when flux densities are high enough to cause excessive biological, especially DNA, damage. The CR history of a planet plays an important role in its potential surface habitation. Both global and local CR conditions determine the ability of life to survive for astrobiologically relevant time periods. We highlight two CR life-limiting factors: 1) General galactic activity, starburst and AGN, was up by about a factor of 30 at redshift 1 - 2, per comoving frame, averaged over all galaxies. And 2) AGN activity is highly intermittent, so extreme brief but powerful bursts (Her A for example) can be detrimental at great distances. This means that during such brief bursts of AGN activity the extragalactic CRs might even overpower the local galactic CRs. But as shown by the starburst galaxy M82, the local CRs in a starburst can also be quite high. Moreover, in our cosmic neighborhood we have several super-massive black holes. These are in M31, M32, M81, NGC5128 (Cen A), and in our own Galaxy, all within about 4 Mpc today. Within about 20 Mpc today there are many more super-massive black holes. Cen A is of course the most famous one now, since it may be a major source of the ultra-high-energy CRs (UHECRs). Folding in what redshift means in terms of cosmic time, this implies that there may have been little chance for life to survive much earlier than Earth's starting epoch. We speculate, on whether the very slow start oflife on Earth is connected to the decay of disturbing CR activity.

Super-Eddington accreting massive black holes explore high-z cosmology: Monte-Carlo simulations

NASA Astrophysics Data System (ADS)

Cai, Rong-Gen; Guo, Zong-Kuan; Huang, Qing-Guo; Yang, Tao

2018-06-01

In this paper, we simulate Super-Eddington accreting massive black holes (SEAMBHs) as the candles to probe cosmology for the first time. SEAMBHs have been demonstrated to be able to provide a new tool for estimating cosmological distance. Thus, we create a series of mock data sets of SEAMBHs, especially in the high redshift region, to check their abilities to probe the cosmology. To fulfill the potential of the SEAMBHs on the cosmology, we apply the simulated data to three projects. The first is the exploration of their abilities to constrain the cosmological parameters, in which we combine different data sets of current observations such as the cosmic microwave background from Planck and type Ia supernovae from Joint Light-curve Analysis (JLA). We find that the high redshift SEAMBHs can help to break the degeneracies of the background cosmological parameters constrained by Planck and JLA, thus giving much tighter constraints of the cosmological parameters. The second uses the high redshift SEAMBHs as the complements of the low redshift JLA to constrain the early expansion rate and the dark energy density evolution in the cold dark matter frame. Our results show that these high redshift SEAMBHs are very powerful on constraining the early Hubble rate and the evolution of the dark energy density; thus they can give us more information about the expansion history of our Universe, which is also crucial for testing the Λ CDM model in the high redshift region. Finally, we check the SEAMBH candles' abilities to reconstruct the equation of state for dark energy at high redshift. In summary, our results show that the SEAMBHs, as the rare candles in the high redshift region, can provide us a new and independent observation to probe cosmology in the future.

A Faster Parallel Algorithm and Efficient Multithreaded Implementations for Evaluating Betweenness Centrality on Massive Datasets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Madduri, Kamesh; Ediger, David; Jiang, Karl

2009-02-15

We present a new lock-free parallel algorithm for computing betweenness centralityof massive small-world networks. With minor changes to the data structures, ouralgorithm also achieves better spatial cache locality compared to previous approaches. Betweenness centrality is a key algorithm kernel in HPCS SSCA#2, a benchmark extensively used to evaluate the performance of emerging high-performance computing architectures for graph-theoretic computations. We design optimized implementations of betweenness centrality and the SSCA#2 benchmark for two hardware multithreaded systems: a Cray XMT system with the Threadstorm processor, and a single-socket Sun multicore server with the UltraSPARC T2 processor. For a small-world network of 134 millionmore » vertices and 1.073 billion edges, the 16-processor XMT system and the 8-core Sun Fire T5120 server achieve TEPS scores (an algorithmic performance count for the SSCA#2 benchmark) of 160 million and 90 million respectively, which corresponds to more than a 2X performance improvement over the previous parallel implementations. To better characterize the performance of these multithreaded systems, we correlate the SSCA#2 performance results with data from the memory-intensive STREAM and RandomAccess benchmarks. Finally, we demonstrate the applicability of our implementation to analyze massive real-world datasets by computing approximate betweenness centrality for a large-scale IMDb movie-actor network.« less

THE RELATION BETWEEN GALAXY MORPHOLOGY AND ENVIRONMENT IN THE LOCAL UNIVERSE: AN RC3-SDSS PICTURE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilman, David J.; Erwin, Peter

2012-02-20

We present results of an analysis of the local (z {approx} 0) morphology-environment relation for 911 bright (M{sub B} < -19) galaxies, based on matching classical RC3 morphologies with the Sloan Digital Sky Survey based group catalog of Yang et al., which includes halo mass estimates. This allows us to study how the relative fractions of spirals, lenticulars, and ellipticals depend on halo mass over a range of 10{sup 11.7}-10{sup 14.8} h{sup -1} M{sub Sun }, from isolated single-galaxy halos to massive groups and low-mass clusters. We pay particular attention to how morphology relates to central versus satellite status (wheremore » 'central' galaxies are the most massive within their halo). The fraction of galaxies which are elliptical is a strong function of stellar mass; it is also a strong function of halo mass, but only for central galaxies. We interpret this as evidence for a scenario where elliptical galaxies are always formed, probably via mergers, as central galaxies within their halos, with satellite ellipticals being previously central galaxies accreted onto a larger halo. The overall fraction of galaxies which are S0 increases strongly with halo mass, from {approx}10% to {approx}70%. Here, too, we find striking differences between the central and satellite populations. 20% {+-} 2% of central galaxies with stellar masses M{sub *} > 10{sup 10.5} M{sub Sun} are S0 regardless of halo mass, but satellite S0 galaxies are only found in massive (>10{sup 13} h{sup -1} M{sub Sun }) halos, where they are 69% {+-} 4% of the M{sub *} > 10{sup 10.5} M{sub Sun} satellite population. This suggests two channels for forming S0 galaxies: one which operates for central galaxies and another which transforms lower-mass (M{sub *} {approx}< 10{sup 11} M{sub Sun }) accreted spirals into satellite S0 galaxies in massive halos. Analysis of finer morphological structure (bars and rings in disk galaxies) shows some trends with stellar mass, but none with halo mass; this is consistent with other recent studies which indicate that bars are not strongly influenced by galaxy environment. Radio sources in high-mass central galaxies are common, similarly so for elliptical and S0 galaxies, with a frequency that increases with the halo mass. Emission-line active galactic nuclei (mostly LINERs) are more common in S0s, but show no strong trends with environment.« less

Average is Over

NASA Astrophysics Data System (ADS)

Eliazar, Iddo

2018-02-01

The popular perception of statistical distributions is depicted by the iconic bell curve which comprises of a massive bulk of 'middle-class' values, and two thin tails - one of small left-wing values, and one of large right-wing values. The shape of the bell curve is unimodal, and its peak represents both the mode and the mean. Thomas Friedman, the famous New York Times columnist, recently asserted that we have entered a human era in which "Average is Over" . In this paper we present mathematical models for the phenomenon that Friedman highlighted. While the models are derived via different modeling approaches, they share a common foundation. Inherent tipping points cause the models to phase-shift from a 'normal' bell-shape statistical behavior to an 'anomalous' statistical behavior: the unimodal shape changes to an unbounded monotone shape, the mode vanishes, and the mean diverges. Hence: (i) there is an explosion of small values; (ii) large values become super-large; (iii) 'middle-class' values are wiped out, leaving an infinite rift between the small and the super large values; and (iv) "Average is Over" indeed.

Eddington limit for a gaseous stratus with finite optical depth

NASA Astrophysics Data System (ADS)

Fukue, Jun

2015-06-01

The Eddington luminosity of a spherical source is usually defined for a uniformly extending normal plasma. We usually suppose that the gas can accrete to the central object at the sub-Eddington luminosity, while it would be blown off from the central luminous source in the super-Eddington case. We reconsider this central dogma of the Eddington limit under the radiative transfer effect for the purely scattering case, using analytical and numerical methods. For the translucent isolated gas cloud (stratus) with finite optical depth, the concept of the Eddington luminosity is drastically changed. In an heuristic way, we find that the critical condition is approximately expressed as Γ = (1 + μ* + τc)/2, where Γ (=L/LE) is the central luminosity L normalized by the Eddington luminosity LE, τc is the optical depth of the stratus, and μ* (=√{1-R_*^2/R^2}) is the direction cosine of the central object, R* being the radius of the central object, and R the distance from the central object. When the optical depth of the stratus is around unity, the classical Eddington limit roughly holds for the stratus; Γ ˜ 1. However, when the optical depth is greater than unity, the critical condition becomes roughly Γ ˜ τc/2, and the stratus would infall on to the central source even at the highly super-Eddington luminosity. When the optical depth is less than unity, on the other hand, the critical condition reduces to Γ ≳ (1 + μ*)/2, and the stratus could be blown off in some limited ranges, depending on μ*. This new concept of the Eddington limit for the isolated stratus could drastically change the accretion and outflow physics of highly inhomegeneous plasmas, with relevance for astrophysical jets and winds and supermassive black hole formation.

Black-hole-regulated star formation in massive galaxies.

PubMed

Martín-Navarro, Ignacio; Brodie, Jean P; Romanowsky, Aaron J; Ruiz-Lara, Tomás; van de Ven, Glenn

2018-01-18

Supermassive black holes, with masses more than a million times that of the Sun, seem to inhabit the centres of all massive galaxies. Cosmologically motivated theories of galaxy formation require feedback from these supermassive black holes to regulate star formation. In the absence of such feedback, state-of-the-art numerical simulations fail to reproduce the number density and properties of massive galaxies in the local Universe. There is, however, no observational evidence of this strongly coupled coevolution between supermassive black holes and star formation, impeding our understanding of baryonic processes within galaxies. Here we report that the star formation histories of nearby massive galaxies, as measured from their integrated optical spectra, depend on the mass of the central supermassive black hole. Our results indicate that the black-hole mass scales with the gas cooling rate in the early Universe. The subsequent quenching of star formation takes place earlier and more efficiently in galaxies that host higher-mass central black holes. The observed relation between black-hole mass and star formation efficiency applies to all generations of stars formed throughout the life of a galaxy, revealing a continuous interplay between black-hole activity and baryon cooling.

Black-hole-regulated star formation in massive galaxies

NASA Astrophysics Data System (ADS)

Martín-Navarro, Ignacio; Brodie, Jean P.; Romanowsky, Aaron J.; Ruiz-Lara, Tomás; van de Ven, Glenn

2018-01-01

Supermassive black holes, with masses more than a million times that of the Sun, seem to inhabit the centres of all massive galaxies. Cosmologically motivated theories of galaxy formation require feedback from these supermassive black holes to regulate star formation. In the absence of such feedback, state-of-the-art numerical simulations fail to reproduce the number density and properties of massive galaxies in the local Universe. There is, however, no observational evidence of this strongly coupled coevolution between supermassive black holes and star formation, impeding our understanding of baryonic processes within galaxies. Here we report that the star formation histories of nearby massive galaxies, as measured from their integrated optical spectra, depend on the mass of the central supermassive black hole. Our results indicate that the black-hole mass scales with the gas cooling rate in the early Universe. The subsequent quenching of star formation takes place earlier and more efficiently in galaxies that host higher-mass central black holes. The observed relation between black-hole mass and star formation efficiency applies to all generations of stars formed throughout the life of a galaxy, revealing a continuous interplay between black-hole activity and baryon cooling.

A single population of red globular clusters around the massive compact galaxy NGC 1277

NASA Astrophysics Data System (ADS)

Beasley, Michael A.; Trujillo, Ignacio; Leaman, Ryan; Montes, Mireia

2018-03-01

Massive galaxies are thought to form in two phases: an initial collapse of gas and giant burst of central star formation, followed by the later accretion of material that builds up their stellar and dark-matter haloes. The systems of globular clusters within such galaxies are believed to form in a similar manner. The initial central burst forms metal-rich (spectrally red) clusters, whereas more metal-poor (spectrally blue) clusters are brought in by the later accretion of less-massive satellites. This formation process is thought to result in the multimodal optical colour distributions that are seen in the globular cluster systems of massive galaxies. Here we report optical observations of the massive relic-galaxy candidate NGC 1277—a nearby, un-evolved example of a high-redshift ‘red nugget’ galaxy. We find that the optical colour distribution of the cluster system of NGC 1277 is unimodal and entirely red. This finding is in strong contrast to other galaxies of similar and larger stellar mass, the cluster systems of which always exhibit (and are generally dominated by) blue clusters. We argue that the colour distribution of the cluster system of NGC 1277 indicates that the galaxy has undergone little (if any) mass accretion after its initial collapse, and use simulations of possible merger histories to show that the stellar mass due to accretion is probably at most ten per cent of the total stellar mass of the galaxy. These results confirm that NGC 1277 is a genuine relic galaxy and demonstrate that blue clusters constitute an accreted population in present-day massive galaxies.

A single population of red globular clusters around the massive compact galaxy NGC 1277.

PubMed

Beasley, Michael A; Trujillo, Ignacio; Leaman, Ryan; Montes, Mireia

2018-03-22

Massive galaxies are thought to form in two phases: an initial collapse of gas and giant burst of central star formation, followed by the later accretion of material that builds up their stellar and dark-matter haloes. The systems of globular clusters within such galaxies are believed to form in a similar manner. The initial central burst forms metal-rich (spectrally red) clusters, whereas more metal-poor (spectrally blue) clusters are brought in by the later accretion of less-massive satellites. This formation process is thought to result in the multimodal optical colour distributions that are seen in the globular cluster systems of massive galaxies. Here we report optical observations of the massive relic-galaxy candidate NGC 1277-a nearby, un-evolved example of a high-redshift 'red nugget' galaxy. We find that the optical colour distribution of the cluster system of NGC 1277 is unimodal and entirely red. This finding is in strong contrast to other galaxies of similar and larger stellar mass, the cluster systems of which always exhibit (and are generally dominated by) blue clusters. We argue that the colour distribution of the cluster system of NGC 1277 indicates that the galaxy has undergone little (if any) mass accretion after its initial collapse, and use simulations of possible merger histories to show that the stellar mass due to accretion is probably at most ten per cent of the total stellar mass of the galaxy. These results confirm that NGC 1277 is a genuine relic galaxy and demonstrate that blue clusters constitute an accreted population in present-day massive galaxies.

Ultra-long Gamma-Ray Bursts from the Collapse of Blue Supergiant Stars: An End-to-end Simulation

NASA Astrophysics Data System (ADS)

Perna, Rosalba; Lazzati, Davide; Cantiello, Matteo

2018-05-01

Ultra-long gamma-ray bursts (ULGRBs) are a distinct class of GRBs characterized by durations of several thousands of seconds, about two orders of magnitude longer than those of standard long GRBs (LGRBs). The driving engine of these events has not yet been uncovered, and ideas range from magnetars, to tidal disruption events, to extended massive stars, such as blue super giants (BSG). BSGs, a possible endpoint of stellar evolution, are attractive for the relatively long freefall times of their envelopes, allowing accretion to power a long-lasting central engine. At the same time, their large radial extension poses a challenge to the emergence of a jet. Here, we perform an end-to-end simulation aimed at assessing the viability of BSGs as ULGRB progenitors. The evolution to the core-collapse of a BSG star model is calculated with the MESA code. We then compute the accretion rate for the fraction of envelope material with enough angular momentum to circularize and form an accretion disk, and input the corresponding power into a jet, which we evolve through the star envelope with the FLASH code. Our simulation shows that the jet can emerge, and the resulting light curves resemble those observed in ULGRBs, with durations T 90 ranging from ≈4000 s to ≈104 s, depending on the viewing angle.

Slugs and Snails and Puppy Dog Tails: jets from an unconventional angle

NASA Astrophysics Data System (ADS)

Harris, D. E.

2015-03-01

We discuss some aspects of extragalactic jets originating from super massive black holes in the centres of active galaxies (and quasars). We start with a short review of sizes and flavors and then argue that the emission we detect across the electromagnetic spectrum does not come from the essence of the jet, but is rather a product of the jet. We go on to discuss some topics concerning synchrotron emission from jets, mainly aspects of knots. Finally we discuss the emission processes for the X-rays and describe a current experiment with LOFAR designed to test a requirement of inverse Compton models.

Research Studies on Advanced Optical Module/Head Designs for Optical Data Storage

NASA Technical Reports Server (NTRS)

1992-01-01

Preprints are presented from the recent 1992 Optical Data Storage meeting in San Jose. The papers are divided into the following topical areas: Magneto-optical media (Modeling/design and fabrication/characterization/testing); Optical heads (holographic optical elements); and Optical heads (integrated optics). Some representative titles are as follow: Diffraction analysis and evaluation of several focus and track error detection schemes for magneto-optical disk systems; Proposal for massively parallel data storage system; Transfer function characteristics of super resolving systems; Modeling and measurement of a micro-optic beam deflector; Oxidation processes in magneto-optic and related materials; and A modal analysis of lamellar diffraction gratings in conical mountings.

Chandra X-Ray Observatory Image of Sagittarius A

NASA Technical Reports Server (NTRS)

2003-01-01

A 2 week observation through the optic eye of the Chandra X-Ray Observatory revealed this sturning explosion occurring in the super massive black hole at the Milky Way's center, known as Sagittarius A or Sgr A*. Huge lobes of 20-million degree Centigrade gas ( red loops in image) flank both sides of the black hole and extend over dozens of light years indicating that enormous explosions occurred several times over the last 10 thousand years. Weighing in at 3-million times the mass of the sun, the Sgr A* is a starved black hole, possibly because explosive events in the past have cleared much of the gas around it.

History of Chandra X-Ray Observatory

NASA Image and Video Library

2003-01-06

A 2 week observation through the optic eye of the Chandra X-Ray Observatory revealed this sturning explosion occurring in the super massive black hole at the Milky Way's center, known as Sagittarius A or Sgr A*. Huge lobes of 20-million degree Centigrade gas ( red loops in image) flank both sides of the black hole and extend over dozens of light years indicating that enormous explosions occurred several times over the last 10 thousand years. Weighing in at 3-million times the mass of the sun, the Sgr A* is a starved black hole, possibly because explosive events in the past have cleared much of the gas around it.

Dusty Starbursts within a z=3 Large Scale Structure revealed by ALMA

NASA Astrophysics Data System (ADS)

Umehata, Hideki

The role of the large-scale structure is one of the most important theme in studying galaxy formation and evolution. However, it has been still mystery especially at z>2. On the basis of our ALMA 1.1 mm observations in a z ~ 3 protocluster field, it is suggested that submillimeter galaxies (SMGs) preferentially reside in the densest environment at z ~ 3. Furthermore we find a rich cluster of AGN-host SMGs at the core of the protocluster, combining with Chandra X-ray data. Our results indicate the vigorous star-formation and accelerated super massive black hole (SMBH) growth in the node of the cosmic web.

The formation of high-mass stars and stellar clusters in the extreme environment of the Central Molecular Zone

NASA Astrophysics Data System (ADS)

Walker, Daniel Lewis

2017-08-01

The process of converting gas into stars underpins much of astrophysics, yet many fundamental questions surrounding this process remain unanswered. For example - how sensitive is star formation to the local environmental conditions? How do massive and dense stellar clusters form, and how does this crowded environment influence the stars that form within it? How do the most massive stars form and is there an upper limit to the stellar initial mass function (IMF)? Answering questions such as these is crucial if we are to construct an end-to-end model of how stars form across the full range of conditions found throughout the Universe. The research described in this thesis presents a study that utilises a multi-scale approach to identifying and characterising the early precursors to young massive clusters and high-mass proto-stars, with a specific focus on the extreme environment in the inner few hundred parsecs of the Milky Way - the Central Molecular Zone (CMZ). The primary sources of interest that are studied in detail belong to the Galactic centre dust ridge - a group of six high-mass (M 10^(4-5) Msun), dense (R 1-3 pc, n > 10^(4) cm^(-3)), and quiescent molecular clouds. These properties make these clouds ideal candidates for representing the earliest stages of high-mass star and cluster formation. The research presented makes use of single-dish and interferometric far-infrared and (sub-)millimetre observations to study their global and small-scale properties. A comparison of the known young massive clusters (YMCs) and their likely progenitors (the dust ridge clouds) in the CMZ shows that the stellar content of YMCs is much more dense and centrally concentrated than the gas in the clouds. If these clouds are truly precursors to massive clusters, the resultant stellar population would have to undergo significant dynamical evolution to reach central densities that are typical of YMCs. This suggests that YMCs in the CMZ are unlikely to form monolithically. Extending this study to include YMCs in the Galactic disc again shows that the known population of YMC precursor clouds throughout the Galaxy are not sufficiently dense or central concentrated that they could form a cluster that then expands due to gas expulsion. The data also reveal an evolutionary trend, in which clouds contract and accrete gas towards their central regions along with concurrent star formation. This is argued to favour a conveyor-belt mode of YMC formation and is again not consistent with a monolithic formation event. High angular resolution observations of the dust ridge clouds with the Submillimeter Array are presented. They reveal an embedded population of compact and massive cores, ranging from 50 - 2150 Msun within radii of 0.1 - 0.25 pc. These are likely formation sites of high-mass stars and clusters, and are strong candidates for representing the initial conditions of extremely massive stars. Two of these cores are found to be young, high-mass proto-stars, while the remaining 13 are quiescent. Comparing these cores with high-mass proto-stars in the Galactic disc, along with models in which star formation is regulated by turbulence, shows that these cores are consistent with the idea that the critical density threshold for star formation is greater in the turbulent environment at the Galactic centre.

Network Analysis of an Emergent Massively Collaborative Creation on Video Sharing Website

NASA Astrophysics Data System (ADS)

Hamasaki, Masahiro; Takeda, Hideaki; Nishimura, Takuichi

The Web technology enables numerous people to collaborate in creation. We designate it as massively collaborative creation via the Web. As an example of massively collaborative creation, we particularly examine video development on Nico Nico Douga, which is a video sharing website that is popular in Japan. We specifically examine videos on Hatsune Miku, a version of a singing synthesizer application software that has inspired not only song creation but also songwriting, illustration, and video editing. As described herein, creators of interact to create new contents through their social network. In this paper, we analyzed the process of developing thousands of videos based on creators' social networks and investigate relationships among creation activity and social networks. The social network reveals interesting features. Creators generate large and sparse social networks including some centralized communities, and such centralized community's members shared special tags. Different categories of creators have different roles in evolving the network, e.g., songwriters gather more links than other categories, implying that they are triggers to network evolution.

SALT Spectroscopy of Evolved Massive Stars

NASA Astrophysics Data System (ADS)

Kniazev, A. Y.; Gvaramadze, V. V.; Berdnikov, L. N.

2017-06-01

Long-slit spectroscopy with the Southern African Large Telescope (SALT) of central stars of mid-infrared nebulae detected with the Spitzer Space Telescope and Wide-Field Infrared Survey Explorer (WISE) led to the discovery of numerous candidate luminous blue variables (cLBVs) and other rare evolved massive stars. With the recent advent of the SALT fiber-fed high-resolution echelle spectrograph (HRS), a new perspective for the study of these interesting objects is appeared. Using the HRS we obtained spectra of a dozen newly identified massive stars. Some results on the recently identified cLBV Hen 3-729 are presented.

REVIEWS OF TOPICAL PROBLEMS: Birth and life of massive black holes

NASA Astrophysics Data System (ADS)

Dokuchaev, V. I.

1991-06-01

The problems of massive black holes in galactic nuclei of different types are reviewed. The dynamical evolution of compact star systems ends naturally in a gigantic concentrated mass of gas, containing an admixture of surviving stars, that unavoidably collapses into a black hole. The subsequent joint evolution of the remnant star system with a massive black hole at the center leads either to the phenomenon of a bright central source in the nuclei of active galaxies and quasars or to the opposite case of a "dead" frozen black hole in the nucleus of a normal galaxy.

The last 6 Gyr of dark matter assembly in massive galaxies from the Kilo Degree Survey

NASA Astrophysics Data System (ADS)

Tortora, C.; Napolitano, N. R.; Roy, N.; Radovich, M.; Getman, F.; Koopmans, L. V. E.; Verdoes Kleijn, G. A.; Kuijken, K. H.

2018-01-01

We study the dark matter (DM) assembly in the central regions of massive early-type galaxies up to z ∼ 0.65. We use a sample of ∼3800 massive (log M⋆/M⊙ > 11.2) galaxies with photometry and structural parameters from 156 deg2 of the Kilo Degree Survey (KiDS), and spectroscopic redshifts and velocity dispersions from Sloan Digital Sky Survey (SDSS). We obtain central total-to-stellar mass ratios, Mdyn/M⋆, and DM fractions, by determining dynamical masses, Mdyn, from Jeans modelling of SDSS aperture velocity dispersions and stellar masses, M⋆, from KiDS galaxy colours. We first show how the central DM fraction correlates with structural parameters, mass and density proxies, and demonstrate that most of the local correlations are still observed up to z ∼ 0.65; at fixed M⋆, local galaxies have larger DM fraction, on average, than their counterparts at larger redshift. We also interpret these trends with a non-universal initial mass function (IMF), finding a strong evolution with redshift, which contrast independent observations and is at odds with the effect of galaxy mergers. For a fixed IMF, the galaxy assembly can be explained, realistically, by mass and size accretion, which can be physically achieved by a series of minor mergers. We reproduce both the Re-M⋆ and Mdyn/M⋆-M⋆ evolution with stellar and dark mass changing at a different rate. This result suggests that the main progenitor galaxy is merging with less massive systems, characterized by a smaller Mdyn/M⋆, consistently with results from halo abundance matching.

Emergent Adaptive Noise Reduction from Communal Cooperation of Sensor Grid

NASA Technical Reports Server (NTRS)

Jones, Kennie H.; Jones, Michael G.; Nark, Douglas M.; Lodding, Kenneth N.

2010-01-01

In the last decade, the realization of small, inexpensive, and powerful devices with sensors, computers, and wireless communication has promised the development of massive sized sensor networks with dense deployments over large areas capable of high fidelity situational assessments. However, most management models have been based on centralized control and research has concentrated on methods for passing data from sensor devices to the central controller. Most implementations have been small but, as it is not scalable, this methodology is insufficient for massive deployments. Here, a specific application of a large sensor network for adaptive noise reduction demonstrates a new paradigm where communities of sensor/computer devices assess local conditions and make local decisions from which emerges a global behaviour. This approach obviates many of the problems of centralized control as it is not prone to single point of failure and is more scalable, efficient, robust, and fault tolerant

Anomaly cancellation for super- W -gravity

NASA Astrophysics Data System (ADS)

Mansfield, P.; Spence, B.

1991-08-01

We generalise the description of minimal superconformal models coupled to supergravity, due to Distler, Hlousek and Kawaii, to super- W -gravity. When the chiral algebra is the generalisation of the W-algebra associated to any contragredient Lie superalgebra the total central charge vanishes as a result of Lie superalgebra identities. When the algebra has only fermionic simple roots there is N = 1 superconformal invariance and for this case we describe the Lax operators and construct gravitationally dressed primary superfields of weight zero. We also prove the anomaly cancellation associated with the generalised non-abelian Toda theories. Address from 1 October 1991: Physics Department, Imperial College, London SW7 2BZ, UK.

Observation of the ballooning mode that limits the operation space of the high-density super-dense-core plasma in the LHD

NASA Astrophysics Data System (ADS)

Ohdachi, S.; Watanabe, K. Y.; Tanaka, K.; Suzuki, Y.; Takemura, Y.; Sakakibara, S.; Du, X. D.; Bando, T.; Narushima, Y.; Sakamoto, R.; Miyazawa, J.; Motojima, G.; Morisaki, T.; LHD Experiment Group

2017-06-01

The central beta of the super-dense-core (SDC) plasma in the large helical device (LHD) is limited by a large scale MHD event called ‘core density collapse’ (CDC). The detailed measurement reveals that a new type of ballooning mode, quite localized in space and destabilized from the 3D nature of Heliotron devices, is the cause of the CDC. It is the first observation of an unstable mode in a region with global negative magnetic shear. Avoidance of the excitation of this mode is a key to expand the operational limit of the LHD.

NASA Spacecraft Shows Before/After of Typhoon Haiyan Devastation

NASA Image and Video Library

2013-11-20

On Nov. 8, 2013, NASA Terra spacecraft acquired this image of Super Typhoon Haiyan as it tore across the central Philippines, leaving a trail of destruction in its path. Among the worst-hit areas is eastern Leyte island and the city of Tacloban.

A Weak Bar Potential and Massive Core in the Seyfert 2 Galaxy NGC 3079: CO(1--0) observations using the Nobeyama Millimeter Array

NASA Astrophysics Data System (ADS)

Koda, J.; Sofue, Y.; Kohno, K.; Okumura, S. K.; Irwin, Judith A.

We present our recent 12CO (1-0) observations in the central molecular disk of the Hα/radio lobe galaxy NGC 3079 with the Nobeyama Millimeter Array. We show four kinematically distinct components in the observed molecular disk: a main disk, spiral arms, a nuclear disk and a nuclear core. We discuss their possible origins using a simple orbit-analysis model in a weak bar potential. We show that three of the four components are well-understood by typical gaseous orbits in a weak bar, such as gaseous x1- and x2-orbits. The main disk and spiral arms are well-understood as the gaseous x1-orbits and their associated crowding, respectively. The nuclear disk is naturally explained by the x2-orbits. However, the nuclear core, showing a high velocity of about 200kmps at a radius of about 100pc, cannot be explained by those gaseous orbits in a bar. Furthermore, no other orbits, derived by bars, cannot be responsible for the nuclear core. Thus we discuss that this component should be attributed to a central massive core with a dynamical mass of about 109Msun within the central 100pc radius. This mass is three orders of magnitude more massive than that of a central black hole in this galaxy. More detailed descriptions are presented in Koda et al. (2002).

Edema fluid accumulation within necrotic brain tissue as a cause of the mass effect of cerebral contusion in head trauma patients.

PubMed

Katayama, Y; Kawamata, T

2003-01-01

The early massive edema caused by severe cerebral contusion results in progressive intracranial pressure (ICP) elevation and clinical deterioration within 24-72 hours post-trauma. Surgical excision of the necrotic brain tissue represents the only therapy, which can provide satisfactory control of the elevated ICP and clinical deterioration. In order to elucidate the mechanisms underlying the early massive edema, we have carried out a series of detailed clinical studies. Diffusion magnetic resonance (MR) imaging and apparent diffusion co-efficient (ADC) mapping suggest that cells in the central area of contusion undergo shrinkage, disintegration and homogenization, whereas cellular swelling is predominant in the peripheral area during the period of 24-72 hours post-trauma. The ADC values in the central and peripheral areas are maximally dissociated during this period. A large amount of edema fluid accumulates within the necrotic brain tissue of the central area beginning at approximately 24 hours post-trauma. We have found that fluid-blood interface formation within the central area does not represent an uncommon finding in various neuroimaging examinations of cerebral contusions, indicating layering of red blood cells within the necrotic brain tissue accumulating voluminous edema fluid. Intravenous slow infusion of gadolinium-DTPA and delayed MR imaging revealed that the central area of contusion can be enhanced at 24-48 hours post-trauma. implying that water supply from the blood vessels is not completely interrupted. Necrotic brain tissue sampled from the central area of contusion during surgery demonstrates a very high osmolality. It appears that the capacitance for edema fluid accumulation increases in the central area, whereas cellular swelling in the peripheral area elevates the resistance for edema fluid propagation. Combination of these circumstances may facilitate edema fluid accumulation in the central area. We also suggest that the dissociation of ADC values and high osmolality within the necrotic brain tissue may generate an osmotic potential across the central and peripheral areas and contribute to the early massive edema caused by cerebral contusion.

Very massive runaway stars from three-body encounters

NASA Astrophysics Data System (ADS)

Gvaramadze, Vasilii V.; Gualandris, Alessia

2011-01-01

Very massive stars preferentially reside in the cores of their parent clusters and form binary or multiple systems. We study the role of tight very massive binaries in the origin of the field population of very massive stars. We performed numerical simulations of dynamical encounters between single (massive) stars and a very massive binary with parameters similar to those of the most massive known Galactic binaries, WR 20a and NGC 3603-A1. We found that these three-body encounters could be responsible for the origin of high peculiar velocities (≥70 km s-1) observed for some very massive (≥60-70 M⊙) runaway stars in the Milky Way and the Large Magellanic Cloud (e.g. λ Cep, BD+43°3654, Sk -67°22, BI 237, 30 Dor 016), which can hardly be explained within the framework of the binary-supernova scenario. The production of high-velocity massive stars via three-body encounters is accompanied by the recoil of the binary in the opposite direction to the ejected star. We show that the relative position of the very massive binary R145 and the runaway early B-type star Sk-69°206 on the sky is consistent with the possibility that both objects were ejected from the central cluster, R136, of the star-forming region 30 Doradus via the same dynamical event - a three-body encounter.

Hubble Observes One-of-a-Kind Star Nicknamed ‘Nasty’

NASA Image and Video Library

2015-03-21

Astronomers using NASA’s Hubble Space Telescope have uncovered surprising new clues about a hefty, rapidly aging star whose behavior has never been seen before in our Milky Way galaxy. In fact, the star is so weird that astronomers have nicknamed it “Nasty 1,” a play on its catalog name of NaSt1. The star may represent a brief transitory stage in the evolution of extremely massive stars. First discovered several decades ago, Nasty 1 was identified as a Wolf-Rayet star, a rapidly evolving star that is much more massive than our sun. The star loses its hydrogen-filled outer layers quickly, exposing its super-hot and extremely bright helium-burning core. But Nasty 1 doesn’t look like a typical Wolf-Rayet star. The astronomers using Hubble had expected to see twin lobes of gas flowing from opposite sides of the star, perhaps similar to those emanating from the massive star Eta Carinae, which is a Wolf-Rayet candidate. Instead, Hubble revealed a pancake-shaped disk of gas encircling the star. The vast disk is nearly 2 trillion miles wide, and may have formed from an unseen companion star that snacked on the outer envelope of the newly formed Wolf-Rayet. Based on current estimates, the nebula surrounding the stars is just a few thousand years old, and as close as 3,000 light-years from Earth. Credits: NASA/Hubble

Pre-supernova outbursts via wave heating in massive stars - II. Hydrogen-poor stars

NASA Astrophysics Data System (ADS)

Fuller, Jim; Ro, Stephen

2018-05-01

Pre-supernova (SN) outbursts from massive stars may be driven by hydrodynamical wave energy emerging from the core of the progenitor star during late nuclear-burning phases. Here, we examine the effects of wave heating in stars containing little or no hydrogen, i.e. progenitors of Type IIb/Ib SNe. Because there is no massive hydrogen envelope, wave energy is thermalized near the stellar surface where the overlying atmospheric mass is small but the optical depth is large. Wave energy can thus unbind this material, driving an optically thick, super-Eddington wind. Using 1D hydrodynamic MESA simulations of ˜5 M⊙ He stars, we find that wave heating can drive pre-SN outbursts composed of a dense wind whose mass-loss rate can exceed ˜0.1 M⊙ yr-1. The wind terminal velocities are a few 100 km s-1, and outburst luminosities can reach ˜106 L⊙. Wave-driven outbursts may be linked with observed or inferred pre-SN outbursts of Type Ibn/transitional/transformational SNe, and pre-SN wave-driven mass loss is a good candidate to produce these types of SNe. However, we also show that non-linear wave breaking in the core of the star may prevent such outbursts in stars with thick convective helium-burning shells. Hence, only a limited subset of SN progenitors is likely to experience wave-driven pre-SN outbursts.

Signatures of primordial black hole dark matter

NASA Astrophysics Data System (ADS)

Belotsky, K. M.; Dmitriev, A. E.; Esipova, E. A.; Gani, V. A.; Grobov, A. V.; Khlopov, M. Yu.; Kirillov, A. A.; Rubin, S. G.; Svadkovsky, I. V.

2014-11-01

The nonbaryonic dark matter of the Universe is assumed to consist of new stable forms of matter. Their stability reflects symmetry of micro-world and mechanisms of its symmetry breaking. In the early Universe heavy metastable particles can dominate, leaving primordial black holes (PBHs) after their decay, as well as the structure of particle symmetry breaking gives rise to cosmological phase transitions, from which massive black holes (BHs) and/or their clusters can originate. PBHs can be formed in such transitions within a narrow interval of masses about 1017g and, avoiding severe observational constraints on PBHs, can be a candidate for the dominant form of dark matter. PBHs in this range of mass can give solution of the problem of reionization in the Universe at the redshift z 5-10. Clusters of massive PBHs can serve as a nonlinear seeds for galaxy formation, while PBHs evaporating in such clusters can provide an interesting interpretation for the observations of point-like gamma-ray sources. Analysis of possible PBH signatures represents a universal probe for super-high energy physics in the early Universe in studies of indirect effects of the dark matter.

Radio transients from newborn black holes

NASA Astrophysics Data System (ADS)

Kashiyama, Kazumi; Hotokezaka, Kenta; Murase, Kohta

2018-05-01

We consider radio emission from a newborn black hole (BH), which is accompanied by a mini-disk with a mass of ≲ M⊙. Such a disk can be formed from an outer edge of the progenitor's envelope, especially for metal-poor massive stars and/or massive stars in close binaries. The disk accretion rate is typically super-Eddington and an ultrafast outflow with a velocity of ˜0.1-0.3 c will be launched into the circumstellar medium. The outflow forms a collisionless shock, and electrons are accelerated and emit synchrotron emission in radio bands with a flux of ˜ 10^{26-30} erg s^{-1} Hz^{-1} days to decades after the BH formation. The model predicts not only a fast UV/optical transient but also quasi-simultaneous inverse-Compton X-ray emission ˜ a few days after the BH formation, and the discovery of the radio counterpart with coordinated searches will enable us to identify this type of transients. The occurrence rate can be 0.1 - 10 % of the core-collapse supernova rate, which makes them a promising target of dedicated radio observations such as the Jansky VLA Sky Survey.

Constraints on Galactic Cosmic-Ray Origins from Elemental Composition Measurements

NASA Astrophysics Data System (ADS)

Binns, W. R.; Christian, E. R.; Cummings, A. C.; Denolfo, G. A.; Israel, M. H.; Lave, K. A.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.; von Rosenvinge, T. T.; Wiedenbeck, M. E.

2017-01-01

We present measurements of the abundances of ultra-heavy (Z>29) cosmic rays made by the CRIS instrument on NASA's Advanced Composition Explorer satellite. The data set corresponds to 6413 days of data collection between December 4, 1997 and May 31, 2016. The charge resolution that we obtain is excellent, exhibiting essentially complete separation of adjacent charges in the Z>28 range. We detected 196 events over the charge range of Z =30-40. Our measured abundances show that the ordering of refractory and volatile elements with atomic mass is greatly improved when compared to a mix of massive star outflow and SN ejecta with normal ISM, rather than pure ISM. Additionally, the refractory and volatile elements have similar slopes and refractory elements are preferentially accelerated by a factor of 4. The measured abundances support a model in which 20% of cosmic ray source material is from massive star outflow and ejecta and 80% is from normal ISM. Our abundances show generally good agreement with the TIGER and SuperTIGER results. This research is supported by NASA under Grant # NNX13AH66G.

Stratigraphic setting and mineralogy of the Arctic volcanogenic massive sulfide prospect, Ambler district, Alaska.

USGS Publications Warehouse

Schmidt, J.M.

1986-01-01

The Arctic prospect, south central Brooks Range, is among the 30 largest of 508 volcanic-hosted massive sulphide deposits in the world. The massive sulphide lenses are interlayered with graphitic schist between metamorphosed rhyolite porphyries in Middle Devonian to early Mississippian metamorphosed volcanic, volcaniclastic and sedimentary rocks. Hydrothermal alteration is of three types: chloritic, phyllic s.l., and pyrite-phengite, each type strata-distinctively and respectively below, in, and above the sulphides. Maximum alteration conforms with metal zoning in the sulfides to suggest predominantly northwestward dispersal from a linear vent area in the elongate basin containing the deposit.-G.J.N.

Reconciling the Stellar and Nebular Spectra of High-redshift Galaxies

NASA Astrophysics Data System (ADS)

Steidel, Charles C.; Strom, Allison L.; Pettini, Max; Rudie, Gwen C.; Reddy, Naveen A.; Trainor, Ryan F.

2016-08-01

We present a combined analysis of rest-frame far-UV (FUV; 1000-2000 Å) and rest-frame optical (3600-7000 Å) composite spectra formed from very deep Keck/LRIS and Keck/MOSFIRE observations of a sample of 30 star-forming galaxies with z=2.40+/- 0.11, selected to be broadly representative of the full KBSS-MOSFIRE spectroscopic survey. Since the same massive stars are responsible for the observed FUV continuum and for the excitation of the observed nebular emission, a self-consistent stellar population synthesis model should simultaneously match the details of the FUV stellar+nebular continuum and—when inserted as the excitation source in photoionization models—predict all observed nebular emission line ratios. We find that only models including massive star binaries, having low stellar metallicity ({Z}* /{Z}⊙ ≃ 0.1) but relatively high nebular (ionized gas-phase) abundances ({Z}{{neb}}/{Z}⊙ ≃ 0.5), can successfully match all of the observational constraints. We show that this apparent discrepancy is naturally explained by highly super-solar O/Fe (≃ 4{--}5 {({{O}}/{Fe})}⊙ ), expected for a gas whose enrichment is dominated by the products of core-collapse supernovae. While O dominates the physics of the ionized gas (and thus the nebular emission lines), Fe dominates the extreme-UV (EUV) and FUV opacity and controls the mass-loss rate from massive stars, resulting in particularly dramatic effects for massive stars in binary systems. This high nebular excitation—caused by the hard EUV spectra of Fe-poor massive stars—is much more common at high redshift (z≳ 2) than low redshift due to systematic differences in the star formation history of typical galaxies. Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

The Evolution and Stability of Massive Stars

NASA Astrophysics Data System (ADS)

Shiode, Joshua Hajime

Massive stars are the ultimate source for nearly all the elements necessary for life. The first stars forge these elements from the sparse set of ingredients supplied by the Big Bang, and distribute enriched ashes throughout their galactic homes via their winds and explosive deaths. Subsequent generations follow suit, assembling from the enriched ashes of their predecessors. Over the last several decades, the astrophysics community has developed a sophisticated theoretical picture of the evolution of these stars, but it remains an incomplete accounting of the rich set of observations. Using state of the art models of massive stars, I have investigated the internal processes taking place throughout the life-cycles of stars spanning those from the first generation ("Population III") to the present-day ("Population I"). I will argue that early-generation stars were not highly unstable to perturbations, contrary to a host of past investigations, if a correct accounting is made for the viscous effect of convection. For later generations, those with near solar metallicity, I find that this very same convection may excite gravity-mode oscillations that produce observable brightness variations at the stellar surface when the stars are near the main sequence. If confirmed with modern high-precision monitoring experiments, like Kepler and CoRoT, the properties of observed gravity modes in massive stars could provide a direct probe of the poorly constrained physics of gravity mode excitation by convection. Finally, jumping forward in stellar evolutionary time, I propose and explore an entirely new mechanism to explain the giant eruptions observed and inferred to occur during the final phases of massive stellar evolution. This mechanism taps into the vast nuclear fusion luminosity, and accompanying convective luminosity, in the stellar core to excite waves capable of carrying a super-Eddington luminosity out to the stellar envelope. This energy transfer from the core to the envelope has the potential to unbind a significant amount of mass in close proximity to a star's eventual explosion as a core collapse supernova.

Crozer-Chester Medical Center Burn Research Project

DTIC Science & Technology

2013-09-01

description of findings reported for CT scans, echocardiograms, cardiac catheterizations , chest x-ray reports, and measurements of central venous pressure...epithelial autografts (CEA) in patients with massive burn injuries.  Central venous catheter exchange strategies in patients with acute burn injury at...had complete data. Culture data were stratified by type: sputum (SCx) (5.4 ±4.7 Cx/Patient), central venous catheter (CVCx) (2.1 ±2.4 Cx/Patient

POTS to broadband ... cable modems.

PubMed

Kabachinski, Jeff

2003-01-01

There have been 3 columns talking about broadband communications and now at the very end when it's time to compare using a telco or cableco, I'm asking does it really matter? So what if I can actually get the whole 30 Mbps with a cable network when the website I'm connecting to is running on an ISDN line at 128 Kbps? Broadband offers a lot more bandwidth than the connections many Internet servers have today. Except for the biggest websites, many servers connect to the Internet with a switched 56-Kbps, ISDN, or fractional T1 line. Even with the big websites, my home network only runs a 10 Mbps Ethernet connection to my cable modem. Maybe it doesn't matter that the cable lines are shared or that I can only get 8 Mbps from an ADSL line. Maybe the ISP that I use has a T1 line connection to the Internet so my new ADSL modem has a fatter pipe than my provider! (See table 1). It all makes me wonder what's in store for us in the future. PC technology has increased exponentially in the last 10 years with super fast processor speeds, hard disks of hundreds of gigabytes, and amazing video and audio. Internet connection speeds have failed to keep the same pace. Instead of hundreds of times better or faster--modem speeds are barely 10 times faster. Broadband connections offer some additional speed but still not comparable growth as broadband connections are still in their infancy. Rather than trying to make use of existing communication paths, maybe we need a massive infrastructure makeover of something new. How about national wireless access points so we can connect anywhere, anytime? To use the latest and fastest wireless technology you will simply need to buy another $9.95 WLAN card or download the latest super slick WLAN compression/encryption software. Perhaps it is time for a massive infra-restructuring. Consider the past massive infrastructure efforts. The telcos needed to put in their wiring infrastructure starting in the 1870s before telephones were useful to the masses. CATV was a minor player in the TV broadcast business before they installed their cabling infrastructure and went national. Even automobiles were fairly useless until roads were paved and the highway infrastructure was built!

Low-mass White Dwarfs with Hydrogen Envelopes as a Missing Link in the Tidal Disruption Menu

NASA Astrophysics Data System (ADS)

Law-Smith, Jamie; MacLeod, Morgan; Guillochon, James; Macias, Phillip; Ramirez-Ruiz, Enrico

2017-06-01

We construct a menu of objects that can give rise to bright flares when disrupted by massive black holes (BHs), ranging from planets to evolved stars. Through their tidal disruption, main sequence and evolved stars can effectively probe the existence of otherwise quiescent supermassive BHs, and white dwarfs can probe intermediate mass BHs. Many low-mass white dwarfs possess extended hydrogen envelopes, which allow for the production of prompt flares in disruptive encounters with moderately massive BHs of 105-{10}7 {M}⊙ —masses that may constitute the majority of massive BHs by number. These objects are a missing link in two ways: (1) for probing moderately massive BHs and (2) for understanding the hydrodynamics of the disruption of objects with tenuous envelopes. A flare arising from the tidal disruption of a 0.17 {M}⊙ white dwarf by a {10}5 {M}⊙ {BH} reaches a maximum between 0.6 and 11 days, with a peak fallback rate that is usually super-Eddington and results in a flare that is likely brighter than a typical tidal disruption event. Encounters stripping only the envelope can provide hydrogen-only fallback, while encounters disrupting the core evolve from H- to He-rich fallback. While most tidal disruption candidates observed thus far are consistent with the disruptions of main sequence stars, the rapid timescales of nuclear transients such as Dougie and PTF10iya are naturally explained by the disruption of low-mass white dwarfs. As the number of observed flares continues to increase, the menu presented here will be essential for characterizing nuclear BHs and their environments through tidal disruptions.

The dark nemesis of galaxy formation: why hot haloes trigger black hole growth and bring star formation to an end

NASA Astrophysics Data System (ADS)

Bower, Richard G.; Schaye, Joop; Frenk, Carlos S.; Theuns, Tom; Schaller, Matthieu; Crain, Robert A.; McAlpine, Stuart

2017-02-01

Galaxies fall into two clearly distinct types: `blue-sequence' galaxies which are rapidly forming young stars, and `red-sequence' galaxies in which star formation has almost completely ceased. Most galaxies more massive than 3 × 1010 M⊙ follow the red sequence, while less massive central galaxies lie on the blue sequence. We show that these sequences are created by a competition between star formation-driven outflows and gas accretion on to the supermassive black hole at the galaxy's centre. We develop a simple analytic model for this interaction. In galaxies less massive than 3 × 1010 M⊙, young stars and supernovae drive a high-entropy outflow which is more buoyant than any tenuous corona. The outflow balances the rate of gas inflow, preventing high gas densities building up in the central regions. More massive galaxies, however, are surrounded by an increasingly hot corona. Above a halo mass of ˜1012 M⊙, the outflow ceases to be buoyant and star formation is unable to prevent the build-up of gas in the central regions. This triggers a strongly non-linear response from the black hole. Its accretion rate rises rapidly, heating the galaxy's corona, disrupting the incoming supply of cool gas and starving the galaxy of the fuel for star formation. The host galaxy makes a transition to the red sequence, and further growth predominantly occurs through galaxy mergers. We show that the analytic model provides a good description of galaxy evolution in the EAGLE hydrodynamic simulations. So long as star formation-driven outflows are present, the transition mass scale is almost independent of subgrid parameter choice.

Overview of the NASA Suborbital Program

NASA Astrophysics Data System (ADS)

Jones, W. Vernon

2014-08-01

The NASA Suborbital Program consists of Sounding Rocket and Balloon Projects managed, respectively, by the Heliophysics and Astrophysics Divisions of the Science Mission Directorate, which maintains “Program” Offices at the NASA Wallops Flight Facility. Suborbital missions have for several decades enabled investigations with significant results from relatively modest investments. Some have been competitive with orbital missions, while others have enabled orbital missions. NASA launches suborbital missions from sites established in the U.S. and around the world to meet investigators’ needs. A sea change in scientific ballooning occurred with the inauguration of 8 - 20 day flights around Antarctica in the early 1990’s. The U.S. National Science Foundation supports these circumpolar flights, which have been spectacularly successful with many investigations utilizing multiple flights of payloads that are recovered, refurbished, and reused to minimize life-cycle costs. The attainment of 25 - 32 day and 35 - 55 day flights in two and three circumnavigations, respectively, of the Antarctic continent has greatly increased expectations of scientific users. The 55-day Super-TIGER flight over Antarctica during the 2012-13 season broke the 42-day CREAM record during the 2004-05 season, as well as the 54-day super pressure balloon test flight in 2008-09. Qualification of super pressure flights to support 1000 kg science instruments for up to 100 days at 33 km have proceeded in parallel with plans to increase the altitude for less massive instruments requiring less atmospheric overburden. The nearly constant volume of super-pressure balloons allows stable altitude flights at non-polar latitudes. Long-duration flights in both polar and non-polar regions will confirm the important contributions that ballooning can make in traditional Astrophysics, Solar and Heliophysics, and Earth Science disciplines. With two comets approaching the sun in 2013-14, the Planetary Science community has shown increased interest in remote observations of comets, planets, and other objects in the Solar System.

MTL distributed magnet measurement system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nogiec, J.M.; Craker, P.A.; Garbarini, J.P.

1993-04-01

The Magnet Test Laboratory (MTL) at the Superconducting Super collider Laboratory will be required to precisely and reliably measure properties of magnets in a production environment. The extensive testing of the superconducting magnets comprises several types of measurements whose main purpose is to evaluate some basic parameters characterizing magnetic, mechanic and cryogenic properties of magnets. The measurement process will produce a significant amount of data which will be subjected to complex analysis. Such massive measurements require a careful design of both the hardware and software of computer systems, having in mind a reliable, maximally automated system. In order to fulfillmore » this requirement a dedicated Distributed Magnet Measurement System (DMMS) is being developed.« less

General Relativistic Magnetohydrodynamics Simulations of Tilted Black Hole Accretion Flows and Their Radiative Properties

NASA Astrophysics Data System (ADS)

Shiokawa, Hotaka; Gammie, C. F.; Dolence, J.; Noble, S. C.

2013-01-01

We perform global General Relativistic Magnetohydrodynamics (GRMHD) simulations of non-radiative, magnetized disks that are initially tilted with respect to the black hole's spin axis. We run the simulations with different size and tilt angle of the tori for 2 different resolutions. We also perform radiative transfer using Monte Carlo based code that includes synchrotron emission, absorption and Compton scattering to obtain spectral energy distribution and light curves. Similar work was done by Fragile et al. (2007) and Dexter & Fragile (2012) to model the super massive black hole SgrA* with tilted accretion disks. We compare our results of fully conservative hydrodynamic code and spectra that include X-ray, with their results.

A modified detector concept for SuperCDMS: The HiZIP and its charge performance

NASA Astrophysics Data System (ADS)

Page, Kedar Mohan

SuperCDMS is a leading direct dark matter search experiment which uses solid state detectors (Ge crystals) at milliKelvin temperatures to look for nuclear recoils caused by dark matter interactions in the detector. 'Weakly Interacting Massive Particles' (WIMPs) are the most favoured dark matter candidate particles. SuperCDMS, like many other direct dark matter search experiments, primarily looks for WIMPs. The measurement of both the ionization and the lattice vibration (phonon) signals from an interaction in the detector allow it to discriminate against electron recoils which are the main source of background for WIMP detection. SuperCDMS currently operates about 9 kgs worth of germanium detectors at the Soudan underground lab in northern Minnesota. In its next phase, SuperCDMS SNOLAB, it plans to use 100-200 kg of target mass (Ge) which would allow it to probe more of the interesting and unexplored parameter space for WIMPs predicted by theoretical models. The SuperCDMS Queen's Test Facility is a detector testing facility which is intended to serve detector testing and detector research and development purposes for the SuperCDMS experiment. A modified detector called the 'HiZIP' (Half-iZIP), which is reduced in complexity in comparison to the currently used iZIP (interleaved Z-sensitive Ionization and Phonon mediated) detectors, is studied in this thesis. The HiZIP detector design also serves to discriminate against background from multiple scatter events occurring close to the surfaces in a single detector. Studies carried out to compare the surface event leakage in the HiZIP detector using limited information from iZIP data taken at SuperCDMS test facility at UC Berkley produce a highly conservative upper limit of 5 out of 10,000 events at 90% confidence level. This upper limit is the best among many different HiZIP configurations that were investigated and is comparable to the upper limit calculated for an iZIP detector in the same way using the same data. A real HiZIP device operated at Queen's Test Facility produced an exposure limited 90% upper limit of about 1 in 100 events for surface event leakage. The data used in these studies contain true nuclear recoil events from cosmogenic and ambient neutrons. This background was not subtracted in the calculation of the upper limits stated above and hence they are highly conservative. A surface event source was produced by depositing lead-210 from radon exposure onto a copper plate. This source was then used to take data for a surface event discrimination study of the HiZIP detector operated at Queen's Test Facility. A study of the contribution of the noise from capacitive crosstalk between charge sensors in a HiZIP detector configuration was investigated, confirming the expectation that no significant drop in performance is to be expected due to this effect.

Impacts of SST anomalies in the Indian-Pacific basin on Northwest Pacific tropical cyclone activities during three super El Niño years

NASA Astrophysics Data System (ADS)

Zhan, Ruifen; Chen, Baode; Ding, Yihui

2018-01-01

This study investigated the impact of sea surface temperature (SST) in several important areas of the Indian-Pacific basin on tropical cyclone (TC) activity over the western North Pacific (WNP) during the developing years of three super El Niño events (1982, 1997, and 2015) based on observations and numerical simulations. During the super El Niño years, TC intensity was enhanced considerably, TC days increased, TC tracks mostly recurved along the coasts, and fewer TCs made landfall in China. These characteristics are similar to the strong ENSO-TC relationship but further above the climatological means than in strong El Niño years. It indicates that super El Niño events play a dominant role in the intensities and tracks of WNP TCs. However, there were clear differences in both numbers and positions of TC genesis among the different super El Niño years. These features could be attributed to the collective impact of SST anomalies (SSTAs) in the tropical central-eastern Pacific and East Indian Ocean (EIO) and the SST gradient (SSTG) between the southwestern Pacific and the western Pacific warm pool. During 2015, the EIO SSTA was extremely warm and the anomalous anticyclone in the western WNP was enhanced, resulting in fewer TCs than normal. In 1982, the EIO SSTA and spring SSTG showed negative anomalies, followed by an increased anomalous cyclone in the western WNP and equatorial vertical wind shear. This intensified the conversion of eddy kinetic energy from large-scale flows, favorable for the westward shift of TC genesis. Consequently, anomalous TC activities during the super El Niño years resulted mainly from combined SSTA impacts of different key areas over the Indian-Pacific basin.

High-Mass Stars in the Centers of Young Dense Clusters: Mass Segregation, Binary Mergers and Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Zinnecker, H.

We start by discussing dense, young star-clusters, particularly the 30 Doradus cluster with its core R136. The question of mass segregation and core collapse of the massive stars is addressed. Analytical estimates of relaxation times and collision times predict that the central N=10 subsystem of massive stars in the R136 core will evolve dynamically in such a way and fast enough (i.e. within their main-sequence lifetime of a few Myr) that a dominant massive binary system is formed whose orbit will shrink to a point where merging of the components appears inevitable. The merger product will be spinning rapidly, and we put forward the idea that this rare and very massive object might be the perfect precursor of a gamma-ray burst (collapsar).

The Tarantula Nebula as a template for extragalactic star forming regions from VLT/MUSE and HST/STIS

NASA Astrophysics Data System (ADS)

Crowther, Paul A.; Caballero-Nieves, Saida M.; Castro, Norberto; Evans, Christopher J.

2017-11-01

We present VLT/MUSE observations of NGC 2070, the dominant ionizing nebula of 30 Doradus in the LMC, plus HST/STIS spectroscopy of its central star cluster R136. Integral Field Spectroscopy (MUSE) and pseudo IFS (STIS) together provides a complete census of all massive stars within the central 30×30 parsec2 of the Tarantula. We discuss the integrated far-UV spectrum of R136, of particular interest for UV studies of young extragalactic star clusters. Strong He iiλ1640 emission at very early ages (1-2 Myr) from very massive stars cannot be reproduced by current population synthesis models, even those incorporating binary evolution and very massive stars. A nebular analysis of the integrated MUSE dataset implies an age of ~4.5 Myr for NGC 2070. Wolf-Rayet features provide alternative age diagnostics, with the primary contribution to the integrated Wolf-Rayet bumps arising from R140 rather than the more numerous H-rich WN stars in R136. Caution should be used when interpreting spatially extended observations of extragalactic star-forming regions.

Evolution and alteration in situ of a massive iron duricrust in Central Africa

NASA Astrophysics Data System (ADS)

Bitom, Dieudonné; Volkoff, Boris; Abossolo-Angue, Monique

2003-08-01

A soil sequence with iron duricrust is described in an area covered by tropical rain forest in South Cameroon. The dismantling of the iron duricrust is documented through a close observation of a soft duricrust, which corresponds to a transitional stage in the degradation of a massive iron duricrust into a loose nodular horizon. In the initial massive and hematitic duricrust, nodular shapes are progressively formed. The nodules and the internodular matrix remain hematitic. The internodular matrix undergoes goethitization and a pronounced deferruginisation before loosening; the primary structure of the iron duricrust is maintained, however, due to internodular bridges, relics of internodular matrix which escaped the process of goethitization. The iron is gradually released from these hematitic bridges, which become softer. This leads to the collapse of the initial structures of the iron duricrust and to the formation of a loose nodular material with a clayey matrix containing kaolinite and goethite. Many loose nodular horizons, which are found all over Central Africa, may have been formed by such alteration of a former iron duricrust.

The definition of environment and its relation to the quenching of galaxies at z = 1-2 in a hierarchical Universe

NASA Astrophysics Data System (ADS)

Fossati, M.; Wilman, D. J.; Fontanot, F.; De Lucia, G.; Monaco, P.; Hirschmann, M.; Mendel, J. T.; Beifiori, A.; Contini, E.

2015-01-01

A well-calibrated method to describe the environment of galaxies at all redshifts is essential for the study of structure formation. Such a calibration should include well-understood correlations with halo mass, and the possibility to identify galaxies which dominate their potential well (centrals), and their satellites. Focusing on z ˜ 1 and 2, we propose a method of environmental calibration which can be applied to the next generation of low- to medium-resolution spectroscopic surveys. Using an up-to-date semi-analytic model of galaxy formation, we measure the local density of galaxies in fixed apertures on different scales. There is a clear correlation of density with halo mass for satellite galaxies, while a significant population of low-mass centrals is found at high densities in the neighbourhood of massive haloes. In this case, the density simply traces the mass of the most massive halo within the aperture. To identify central and satellite galaxies, we apply an observationally motivated stellar mass rank method which is both highly pure and complete, especially in the more massive haloes where such a division is most meaningful. Finally, we examine a test case for the recovery of environmental trends: the passive fraction of galaxies and its dependence on stellar and halo mass for centrals and satellites. With careful calibration, observationally defined quantities do a good job of recovering known trends in the model. This result stands even with reduced redshift accuracy, provided the sample is deep enough to preserve a wide dynamic range of density.

Massive Young Stellar Objects in the Galactic Center. 1; Spectroscopic Identification from Spitzer/IRS Observations

NASA Technical Reports Server (NTRS)

An, Deokkeun; Ramirez, Solange V.; Sellgren, Kris; Arendt, Richard G.; Boogert, A. C. Adwin; Robitaille, Thomas P.; Schultheis, Mathias; Cotera, Angela S.; Smith, Howard A.; Stolovy, Susan R.

2011-01-01

We present results from our spectroscopic study, using the Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope, designed to identify massive young stellar objects (YSOs) in the Galactic Center (GC). Our sample of 107 YSO candidates was selected based on IRAC colors from the high spatial resolution, high sensitivity Spitzer/IRAC images in the Central Molecular Zone (CMZ), which spans the central approximately 300 pc region of the Milky Way Galaxy. We obtained IRS spectra over 5 micron to 35 micron using both high- and low-resolution IRS modules. We spectroscopically identify massive YSOs by the presence of a 15.4 micron shoulder on the absorption profile of 15 micron CO2 ice, suggestive of CO2 ice mixed with CH30H ice on grains. This 15.4 micron shoulder is clearly observed in 16 sources and possibly observed in an additional 19 sources. We show that 9 massive YSOs also reveal molecular gas-phase absorption from C02, C2H2, and/or HCN, which traces warm and dense gas in YSOs. Our results provide the first spectroscopic census of the massive YSO population in the GC. We fit YSO models to the observed spectral energy distributions and find YSO masses of 8 - 23 solar Mass, which generally agree with the masses derived from observed radio continuum emission. We find that about 50% of photometrically identified YSOs are confirmed with our spectroscopic study. This implies a preliminary star formation rate of approximately 0.07 solar mass/yr at the GC.

Quantifying the impact of weak, strong, and super ties in scientific careers

PubMed Central

Petersen, Alexander Michael

2015-01-01

Scientists are frequently faced with the important decision to start or terminate a creative partnership. This process can be influenced by strategic motivations, as early career researchers are pursuers, whereas senior researchers are typically attractors, of new collaborative opportunities. Focusing on the longitudinal aspects of scientific collaboration, we analyzed 473 collaboration profiles using an egocentric perspective that accounts for researcher-specific characteristics and provides insight into a range of topics, from career achievement and sustainability to team dynamics and efficiency. From more than 166,000 collaboration records, we quantify the frequency distributions of collaboration duration and tie strength, showing that collaboration networks are dominated by weak ties characterized by high turnover rates. We use analytic extreme value thresholds to identify a new class of indispensable super ties, the strongest of which commonly exhibit >50% publication overlap with the central scientist. The prevalence of super ties suggests that they arise from career strategies based upon cost, risk, and reward sharing and complementary skill matching. We then use a combination of descriptive and panel regression methods to compare the subset of publications coauthored with a super tie to the subset without one, controlling for pertinent features such as career age, prestige, team size, and prior group experience. We find that super ties contribute to above-average productivity and a 17% citation increase per publication, thus identifying these partnerships—the analog of life partners—as a major factor in science career development. PMID:26261301

Eleven-Year Retrospective Report of Super-Selective Venous Sampling for the Evaluation of Recurrent or Persistent Hyperparathyroidism in 32 Patients.

PubMed

Habibollahi, Peiman; Shin, Benjamin; Shamchi, Sara P; Wachtel, Heather; Fraker, Douglas L; Trerotola, Scott O

2018-01-01

Parathyroid venous sampling (PAVS) is usually reserved for patients with persistent or recurrent hyperparathyroidism after parathyroidectomy with inconclusive noninvasive imaging studies. A retrospective study was performed to evaluate the diagnostic efficacy of super-selective PAVS (SSVS) in patients needing revision neck surgery with inconclusive imaging. Patients undergoing PAVS between 2005 and 2016 due to persistent or recurrent hyperparathyroidism following surgery were reviewed. PAVS was performed in all patients using super-selective technique. Single-value measurements within central neck veins performed as part of super-selective PAVS were used to simulate selective venous sampling (SVS) and allow for comparison to data, which might be obtained in a non-super-selective approach. 32 patients (mean age 51 ± 15 years; 8 men and 24 women) met inclusion and exclusion criteria. The sensitivity and positive predictive value (PPV) of SSVS for localizing the source of elevated PTH to a limited area in the neck or chest was 96 and 84%, respectively. Simulated SVS, on the other hand, had a sensitivity of 28% and a PPV of 89% based on the predefined gold standard. SSVS had a significantly higher sensitivity compared to simulated SVS (p < 0.001). SSVS is highly effective in localizing the source of hyperparathyroidism in patients undergoing revision surgery for hyperparathyroidism in whom noninvasive imaging studies are inconclusive. SSVS data had also markedly higher sensitivity for localizing disease in these patients compared to simulated SVS.

The structure and stability of orbits in Hoag-like ring systems

NASA Astrophysics Data System (ADS)

Bannikova, Elena Yu

2018-05-01

Ring galaxies are amazing objects exemplified by the famous case of Hoag's Object. Here the mass of the central galaxy may be comparable to the mass of the ring, making it a difficult case to model mechanically. In a previous paper, it was shown that the outer potential of a torus (ring) can be represented with good accuracy by the potential of a massive circle with the same mass. This approach allows us to simplify the problem of the particle motion in the gravitational field of a torus associated with a central mass by replacing the torus with a massive circle. In such a system, there is a circle of unstable equilibrium that we call `Lagrangian circle' (LC). Stable circular orbits exist only in some region limited by the last possible circular orbit related to the disappearance of the extrema of the effective potential. We call this orbit `the outermost stable circular orbit' (OSCO) by analogy with the innermost stable circular orbit (ISCO) in the relativistic case of a black hole. Under these conditions, there is a region between OSCO and LC where the circular motion is not possible due to the competition between the gravitational forces by the central mass and the ring. As a result, a gap in the matter distribution can form in Hoag-like system with massive rings.

Theoretical Developments in Understanding Massive Star Formation

NASA Technical Reports Server (NTRS)

Yorke, Harold W.; Bodenheimer, Peter

2007-01-01

Except under special circumstances massive stars in galactic disks will form through accretion. The gravitational collapse of a molecular cloud core will initially produce one or more low mass quasi-hydrostatic objects of a few Jupiter masses. Through subsequent accretion the masses of these cores grow as they simultaneously evolve toward hydrogen burning central densities and temperatures. We review the evolution of accreting (proto-)stars, including new results calculated with a publicly available stellar evolution code written by the authors.

High-Resolution, Wide-Field Imaging of the Galactic Center Region at 330 MHz

DTIC Science & Technology

2004-10-01

associated with the massive black hole in the center of our galaxy, Sgr A *, is slightly circularly polarized at higher frequencies (Bower et al. 1999...axy’s central massive black hole , was detected utilizing a subset of these data. This is the first detection of this source at comparable frequencies...first detection of Sagittarius A * in this frequency range. Key words: Galaxy: center — radio continuum: general — techniques: interferometric 1

An Analysis Framework for Understanding the Origin of Nuclear Activity in Low-power Radio Galaxies

NASA Astrophysics Data System (ADS)

Lin, Yen-Ting; Huang, Hung-Jin; Chen, Yen-Chi

2018-05-01

Using large samples containing nearly 2300 active galaxies of low radio luminosity (1.4 GHz luminosity between 2 × 1023 and 3 × 1025 W Hz‑1, essentially low-excitation radio galaxies) at z ≲ 0.3, we present a self-contained analysis of the dependence of the nuclear radio activity on both intrinsic and extrinsic properties of galaxies, with the goal of identifying the best predictors of the nuclear radio activity. While confirming the established result that stellar mass must play a key role on the triggering of radio activities, we point out that for the central, most massive galaxies, the radio activity also shows a strong dependence on halo mass, which is not likely due to enhanced interaction rates in denser regions in massive, cluster-scale halos. We thus further investigate the effects of various properties of the intracluster medium (ICM) in massive clusters on the radio activities, employing two standard statistical tools, principle component analysis and logistic regression. It is found that ICM entropy, local cooling time, and pressure are the most effective in predicting the radio activity, pointing to the accretion of gas cooling out of a hot atmosphere to be the likely origin in triggering such activities in galaxies residing in massive dark matter halos. Our analysis framework enables us to logically discern the mechanisms responsible for the radio activity separately for central and satellite galaxies.

An X-ray survey of the central molecular zone: Variability of the Fe Kα emission line

NASA Astrophysics Data System (ADS)

Terrier, R.; Clavel, M.; Soldi, S.; Goldwurm, A.; Ponti, G.; Morris, M. R.; Chuard, D.

2018-05-01

There is now abundant evidence that the luminosity of the Galactic super-massive black hole (SMBH) has not always been as low as it is nowadays. The observation of varying non-thermal diffuse X-ray emission in molecular complexes in the central 300 pc has been interpreted as delayed reflection of a past illumination by bright outbursts of the SMBH. The observation of different variability timescales of the reflected emission in the Sgr A molecular complex can be well explained if the X-ray emission of at least two distinct and relatively short events (i.e. about 10 yr or less) is currently propagating through the region. The number of such events or the presence of a long-duration illumination are open questions. Variability of the reflected emission all over of the central 300 pc, in particular in the 6.4 keV Fe Kα line, can bring strong constraints. To do so we performed a deep scan of the inner 300 pc with XMM-Newton in 2012. Together with all the archive data taken over the course of the mission, and in particular a similar albeit more shallow scan performed in 2000-2001, this allows for a detailed study of variability of the 6.4 keV line emission in the region, which we present here. We show that the overall 6.4 keV emission does not strongly vary on average, but variations are very pronounced on smaller scales. In particular, most regions showing bright reflection emission in 2000-2001 significantly decrease by 2012. We discuss those regions and present newly illuminated features. The absence of bright steady emission argues against the presence of an echo from an event of multi-centennial duration and most, if not all, of the emission can likely be explained by a limited number of relatively short (i.e. up to 10 yr) events. Images of the Fe Kα emission as FITS files are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A102

Simultaneous Ultraviolet Line and Continuum Variability Studies in Seyfert 1 Galaxies and Quasars

NASA Astrophysics Data System (ADS)

Honnappa, Vijayakumar; Prabhakar, Vedavvathi

Simultaneous Ultraviolet Line and Continuum Variability Studies in Seyfert 1 Galaxies and Quasars Vijayakumar H. Doddamani*and P. Vedavathi Department of Physics, Bangalore University, Bangalore-560056, *Corresponding author:drvkdmani@gmail.com, Abstract The line and continuum flux variability is a hallmark phenomenon of Seyfert 1 galaxies and quasars. Large amplitude luminosity variability is observed in AGNs from x-rays through radio waves over a wide-ranging timescales from minutes to years. The combinations of high luminosity and short variability time scales suggests, that the power of AGN is produced by a phenomena more efficient in terms of energy release per unit mass than ordinary stellar processes. The basic structure of AGNs thus developed based on the variability studies consists of a central super massive black hole surrounded by an accretion disk or more generally optically thick plasma radiating brightly at UV and soft X-ray wavelengths. The variability studies have been important tools of understanding the physics of the central regions of AGNs, which in general cannot be resolved with the existing or planned ground and space telescopes. Therefore, we have undertaken a study of the simultaneous ultraviolet line and continuum flux variability studies in MRK501, ESOB113-IG45 (also called as Fairall 9), MRK1506, MRK1095 V*GQCOM, PG1211+143, MRK205, PG1226+023 (also known as 3C273), PG1351+640, MRK 1383, MRK876 and QSO2251-178 as these objects have been repeatedly observed by IUE satellite over several years.. It is observed that Fairall 9, MRK 1095 and 3C273 exhibit the large amplitude variability (» 30 times) over the observed timescale, which spans several years. The remaining nine objects exhibit small amplitude (» 5 times) variability over the long time scale of observations. The highest amplitude variability is observed in Lya with a least in the MgII line. The amplitude of variability decreases in the order of Lya, CIV and Mg II, lines. These results suggest that the BLR is spatially stratified into different regions from the central compact nuclear engine. Keywords: Active galaxies, Seyfert galaxies, Quasars, Line and continuum, Variability, Supermassive black hole

Massive binaries in R136 using Hubble

NASA Astrophysics Data System (ADS)

Caballero-Nieves, Saida; Crowther, Paul; Bostroem, K. Azalee; Maíz Apellániz, Jesus

2014-09-01

We have undertaken a complete HST/STIS spectroscopic survey of R136, the young, central dense starburst cluster of the LMC 30 Doradus nebula, which hosts the most massive stars currently known. Our CCD datasets, comprising 17 adjacent 0.2"×52" long slits, were split across Cycles 19 and 20 to allow us to search for spectroscopic binaries. We will present the results of our survey, including a comparison with the massive-star population in the wider 30 Doradus region from the VLT Flames Tarantula survey. We will also describe upcoming HST/FGS observations, which will probe intermediate-separation binaries in R136, and discuss this cluster in the context of unresolved young extragalactic star clusters.

A Disk Origin for S-Stars in the Galactic Center?

NASA Astrophysics Data System (ADS)

Haislip, G.; Youdin, A. N.

2005-12-01

Young massive stars in the central 0.5" of our Galaxy probe dynamics around supermassive black holes, and challenge our understanding of star formation in extreme environments. Recent observations (Ghez et al. 2005, Eisenhauer et al. 2005) show large eccentricities and a seemingly random distribution of inclinations, which seems to contradict formation in a disk. We investigate scenarios in which the massive S-stars are born with circular, coplanar orbits and perturbed to their current relaxed state. John Chambers' MERCURY code is modified to include post-Newtonian corrections to the gravitational central force of a Schwarzchild hole and Lense-Thirring precession about a Kerr black hole. The role of resonant relaxation (Rauch & Tremaine, 1996) of angular momentum between S-stars and a background stellar halo is studied in this context.

ngVLA Key Science Goal 3: Charting the Assembly, Structure, and Evolution of Galaxies Over Cosmic Time

NASA Astrophysics Data System (ADS)

Riechers, Dominik A.; Bolatto, Alberto D.; Carilli, Chris; Casey, Caitlin M.; Decarli, Roberto; Murphy, Eric Joseph; Narayanan, Desika; Walter, Fabian; ngVLA Galaxy Assembly through Cosmic Time Science Working Group, ngVLA Galaxy Ecosystems Science Working Group

2018-01-01

The Next Generation Very Large Array (ngVLA) will fundamentally advance our understanding of the formation processes that lead to the assembly of galaxies throughout cosmic history. The combination of large bandwidth with unprecedented sensitivity to the critical low-level CO lines over virtually the entire redshift range will open up the opportunity to conduct large-scale, deep cold molecular gas surveys, mapping the fuel for star formation in galaxies over substantial cosmic volumes. Imaging of the sub-kiloparsec scale distribution and kinematic structure of molecular gas in both normal main-sequence galaxies and large starbursts back to early cosmic epochs will reveal the physical processes responsible for star formation and black hole growth in galaxies over a broad range in redshifts. In the nearby universe, the ngVLA has the capability to survey the structure of the cold, star-forming interstellar medium at parsec-resolution out to the Virgo cluster. A range of molecular tracers will be accessible to map the motion, distribution, and physical and chemical state of the gas as it flows in from the outer disk, assembles into clouds, and experiences feedback due to star formation or accretion into central super-massive black holes. These investigations will crucially complement studies of the star formation and stellar mass histories with the Large UV/Optical/Infrared Surveyor and the Origins Space Telescope, providing the means to obtain a comprehensive picture of galaxy evolution through cosmic times.

Probing the end of reionization with the near zones of z ≳ 6 QSOs

NASA Astrophysics Data System (ADS)

Keating, Laura C.; Haehnelt, Martin G.; Cantalupo, Sebastiano; Puchwein, Ewald

2015-11-01

QSO near zones are an important probe of the ionization state of the intergalactic medium (IGM) at z ˜ 6-7, at the end of reionization. We present here high-resolution cosmological 3D radiative transfer simulations of QSO environments for a wide range of host halo masses, 1010-12.5 M⊙. Our simulated near zones reproduce both the overall decrease of observed near-zone sizes at 6 < z < 7 and their scatter. The observable near-zone properties in our simulations depend only very weakly on the mass of the host halo. The size of the H II region expanding into the IGM is generally limited by (super-)Lyman Limit systems loosely associated with (low-mass) dark matter haloes. This leads to a strong dependence of near-zone size on direction and drives the large observed scatter. In the simulation centred on our most massive host halo, many sightlines show strong red damping wings even for initial volume averaged neutral hydrogen fractions as low as ˜10-3. For QSO lifetimes long enough to allow growth of the central supermassive black hole while optically bright, we can reproduce the observed near zone of ULAS J1120+0641 only with an IGM that is initially neutral. Our results suggest that larger samples of z > 7 QSOs will provide important constraints on the evolution of the neutral hydrogen fraction and thus on how late reionization ends.

A Stellar Dynamical Black Hole Mass for the Reverberation Mapped AGN NGC 5273

NASA Astrophysics Data System (ADS)

Batiste, Merida; Bentz, Misty C.; Valluri, Monica; Onken, Christopher A.

2018-01-01

We present preliminary results from stellar dynamical modeling of the mass of the central super-massive black hole (MBH) in the active galaxy NGC 5273. NGC 5273 is one of the few AGN with a secure MBH measurement from reverberation-mapping that is also nearby enough to measure MBH with stellar dynamical modeling. Dynamical modeling and reverberation-mapping are the two most heavily favored methods of direct MBH determination in the literature, however the specific limitations of each method means that there are very few galaxies for which both can be used. To date only two such galaxies, NGC 3227 and NGC 4151, have MBH determinations from both methods. Given this small sample size, it is not yet clear that the two methods give consistent results. Moreover, given the inherent uncertainties and potential systematic biases in each method, it is likewise unclear whether one method should be preferred over the other. This study is part of an ongoing project to increase the sample of galaxies with secure MBH measurements from both methods, so that a direct comparison may be made. NGC 5273 provides a particularly valuable comparison because it is free of kinematic substructure (e.g. the presence of a bar, as is the case for NGC 4151) which can complicate and potentially bias results from stellar dynamical modeling. I will discuss our current results as well as the advantages and limitations of each method, and the potential sources of systematic bias that may affect comparison between results.

An intermediate-mass black hole in the centre of the globular cluster 47 Tucanae.

PubMed

Kızıltan, Bülent; Baumgardt, Holger; Loeb, Abraham

2017-02-08

Intermediate-mass black holes should help us to understand the evolutionary connection between stellar-mass and super-massive black holes. However, the existence of intermediate-mass black holes is still uncertain, and their formation process is therefore unknown. It has long been suspected that black holes with masses 100 to 10,000 times that of the Sun should form and reside in dense stellar systems. Therefore, dedicated observational campaigns have targeted globular clusters for many decades, searching for signatures of these elusive objects. All candidate signatures appear radio-dim and do not have the X-ray to radio flux ratios required for accreting black holes. Based on the lack of an electromagnetic counterpart, upper limits of 2,060 and 470 solar masses have been placed on the mass of a putative black hole in 47 Tucanae (NGC 104) from radio and X-ray observations, respectively. Here we show there is evidence for a central black hole in 47 Tucanae with a mass of solar masses when the dynamical state of the globular cluster is probed with pulsars. The existence of an intermediate-mass black hole in the centre of one of the densest clusters with no detectable electromagnetic counterpart suggests that the black hole is not accreting at a sufficient rate to make it electromagnetically bright and therefore, contrary to expectations, is gas-starved. This intermediate-mass black hole might be a member of an electromagnetically invisible population of black holes that grow into supermassive black holes in galaxies.

University of Maryland MRSEC - Education: Resources

Science.gov Websites

. University of Maryland Materials Research Science and Engineering Center Home About Us Leadership Moments in MSE The Materials Science and Engineering Career Resources Center Materials Research Society Central Super Science Fair Projects: Ideas, Topics, & Experiments All Science Fair Projects Science

Expressed Willingness and Competence of Home Economics Teachers to Instruct Occupational Classes.

ERIC Educational Resources Information Center

Bowden, Shirley

A questionnaire and Super's Work Values Inventory were mailed to all teachers of home economics in junior and senior high schools and community colleges in five central California counties to investigate their expressed willingness and competence to offer occupational classes. It was also desired to determine any relationship between willingness…

Are Compton-thick AGNs the Missing Link between Mergers and Black Hole Growth?

NASA Astrophysics Data System (ADS)

Kocevski, Dale D.; Brightman, Murray; Nandra, Kirpal; Koekemoer, Anton M.; Salvato, Mara; Aird, James; Bell, Eric F.; Hsu, Li-Ting; Kartaltepe, Jeyhan S.; Koo, David C.; Lotz, Jennifer M.; McIntosh, Daniel H.; Mozena, Mark; Rosario, David; Trump, Jonathan R.

2015-12-01

We examine the host morphologies of heavily obscured active galactic nuclei (AGNs) at z∼ 1 to test whether obscured super-massive black hole growth at this epoch is preferentially linked to galaxy mergers. Our sample consists of 154 obscured AGNs with {N}{{H}}\\gt {10}23.5 {{cm}}-2 and z\\lt 1.5. Using visual classifications, we compare the morphologies of these AGNs to control samples of moderately obscured (1022 cm{}-2\\lt {N}{{H}}\\lt {10}23.5 {{cm}}-2) and unobscured ({N}{{H}}\\lt {10}22 {{cm}}-2) AGN. These control AGNs have similar redshifts and intrinsic X-ray luminosities to our heavily obscured AGN. We find that heavily obscured AGNs are twice as likely to be hosted by late-type galaxies relative to unobscured AGNs ({65.3}-4.6+4.1% versus {34.5}-2.7+2.9%) and three times as likely to exhibit merger or interaction signatures ({21.5}-3.3+4.2% versus {7.8}-1.3+1.9%). The increased merger fraction is significant at the 3.8σ level. If we exclude all point sources and consider only extended hosts, we find that the correlation between the merger fraction and obscuration is still evident, although at a reduced statistical significance (2.5σ ). The fact that we observe a different disk/spheroid fraction versus obscuration indicates that the viewing angle cannot be the only thing differentiating our three AGN samples, as a simple unification model would suggest. The increased fraction of disturbed morphologies with obscuration supports an evolutionary scenario, in which Compton-thick AGNs are a distinct phase of obscured super-massive black hole (SMBH) growth following a merger/interaction event. Our findings also suggest that some of the merger-triggered SMBH growth predicted by recent AGN fueling models may be hidden among the heavily obscured, Compton-thick population.

Liquid plasma use during "super" massive transfusion protocol.

PubMed

Allen, Casey J; Shariatmadar, Sherry; Meizoso, Jonathan P; Hanna, Mena M; Mora, Jose L; Ray, Juliet J; Namias, Nicholas; Dudaryk, Roman; Proctor, Kenneth G

2015-12-01

A massive transfusion protocol (MTP) presents a logistical challenge for most blood banks and trauma centers. We compare the ratio of packed red blood cells (PRBC) and plasma transfused over serial time points in those requiring MTP (10-30 U PRBC/24 h) to those requiring "super" MTP (S-MTP; >30 U PRBC/24 h) and test the hypothesis that changes in allocation of blood products with use of readily transfusable liquid plasma (LP) improves the ratio of PRBC and plasma during S-MTP. All transfused trauma patients (n = 1305) from January 01, 2009-April, 03, 2015 were reviewed. PRBC:plasma ratio was compared for MTP (n = 277) and S-MTP (n = 61) patients, before and after the availability of LP at our institution. Data are reported as mean ± standard deviation or median (interquartile range). Age was 41 ± 19 y, 52% blunt mechanism, injury severity score 32 ± 16, and 46.3% mortality. In 24 h, requirements were 17 (14) U PRBC and 10 (11) U plasma, with a PRBC:plasma of 1.6 (0.8). Within the first hour, PRBC:plasma for S-MTP versus MTP was 2.1:1 versus 1.7:1 (P = 0.017). With LP, S-MTP patients received significantly lower PRBC:plasma at the first hour (P < 0.001). Before institutional changes, PRBC:plasma positively correlated with PRBC transfused at hour 1 (r = 0.410, R(2) = 0.168, P < 0.001); after institutional changes and the advent of LP, there was no correlation (r = 0.177, R(2) = 0.031, P = 0.219). Within the first hour of transfusion, units of PRBC transfused positively correlated with PRBC:plasma, and patients receiving S-MTP had higher PRBC:plasma than those receiving MTP. Changes in our institution's MTP protocol to include LP improved the early PRBC:plasma transfused in patients requiring S-MTP. Copyright © 2015 Elsevier Inc. All rights reserved.

Clearing Residual Planetesimals by Sweeping Secular Resonances in Transitional Disks: A Lone-planet Scenario for the Wide Gaps in Debris Disks around Vega and Fomalhaut

NASA Astrophysics Data System (ADS)

Zheng, Xiaochen; Lin, Douglas N. C.; Kouwenhoven, M. B. N.; Mao, Shude; Zhang, Xiaojia

2017-11-01

Extended gaps in the debris disks of both Vega and Fomalhaut have been observed. These structures have been attributed to tidal perturbations by multiple super-Jupiter gas giant planets. Within the current observational limits, however, no such massive planets have been detected. Here we propose a less stringent “lone-planet” scenario to account for the observed structure with a single eccentric gas giant and suggest that clearing of these wide gaps is induced by its sweeping secular resonance. With a series of numerical simulations, we show that the gravitational potential of the natal disk induces the planet to precess. At the locations where its precession frequency matches the precession frequency the planet imposes on the residual planetesimals, their eccentricity is excited by its resonant perturbation. Due to the hydrodynamic drag by the residual disk gas, the planetesimals undergo orbital decay as their excited eccentricities are effectively damped. During the depletion of the disk gas, the planet’s secular resonance propagates inward and clears a wide gap over an extended region of the disk. Although some residual intermediate-size planetesimals may remain in the gap, their surface density is too low to either produce super-Earths or lead to sufficiently frequent disruptive collisions to generate any observable dusty signatures. The main advantage of this lone-planet sweeping-secular-resonance model over the previous multiple gas giant tidal truncation scenario is the relaxed requirement on the number of gas giants. The observationally inferred upper mass limit can also be satisfied provided the hypothetical planet has a significant eccentricity. A significant fraction of solar or more massive stars bear gas giant planets with significant eccentricities. If these planets acquired their present-day kinematic properties prior to the depletion of their natal disks, their sweeping secular resonance would effectively impede the retention of neighboring planets and planetesimals over a wide range of orbital semimajor axes.

Local structure-based image decomposition for feature extraction with applications to face recognition.

PubMed

Qian, Jianjun; Yang, Jian; Xu, Yong

2013-09-01

This paper presents a robust but simple image feature extraction method, called image decomposition based on local structure (IDLS). It is assumed that in the local window of an image, the macro-pixel (patch) of the central pixel, and those of its neighbors, are locally linear. IDLS captures the local structural information by describing the relationship between the central macro-pixel and its neighbors. This relationship is represented with the linear representation coefficients determined using ridge regression. One image is actually decomposed into a series of sub-images (also called structure images) according to a local structure feature vector. All the structure images, after being down-sampled for dimensionality reduction, are concatenated into one super-vector. Fisher linear discriminant analysis is then used to provide a low-dimensional, compact, and discriminative representation for each super-vector. The proposed method is applied to face recognition and examined using our real-world face image database, NUST-RWFR, and five popular, publicly available, benchmark face image databases (AR, Extended Yale B, PIE, FERET, and LFW). Experimental results show the performance advantages of IDLS over state-of-the-art algorithms.

The Formation and Evolution of Star Clusters in Interacting Galaxies

NASA Astrophysics Data System (ADS)

Maji, Moupiya; Zhu, Qirong; Li, Yuexing; Charlton, Jane; Hernquist, Lars; Knebe, Alexander

2017-08-01

Observations of globular clusters show that they have universal lognormal mass functions with a characteristic peak at ˜ 2× {10}5 {M}⊙ , but the origin of this peaked distribution is highly debated. Here we investigate the formation and evolution of star clusters (SCs) in interacting galaxies using high-resolution hydrodynamical simulations performed with two different codes in order to mitigate numerical artifacts. We find that massive SCs in the range of ˜ {10}5.5{--}{10}7.5 {M}⊙ form preferentially in the highly shocked regions produced by galaxy interactions. The nascent cluster-forming clouds have high gas pressures in the range of P/k˜ {10}8{--}{10}12 {{K}} {{cm}}-3, which is ˜ {10}4{--}{10}8 times higher than the typical pressure of the interstellar medium but consistent with recent observations of a pre-super-SC cloud in the Antennae Galaxies. Furthermore, these massive SCs have quasi-lognormal initial mass functions with a peak around ˜ {10}6 {M}⊙ . The number of clusters declines with time due to destructive processes, but the shape and the peak of the mass functions do not change significantly during the course of galaxy collisions. Our results suggest that gas-rich galaxy mergers may provide a favorable environment for the formation of massive SCs such as globular clusters, and that the lognormal mass functions and the unique peak may originate from the extreme high-pressure conditions of the birth clouds and may survive the dynamical evolution.

Radiation-Induced Central Nervous System Death - A study of the Pathologic Findings in Monkeys Irradiated with Massive Doses of Cobalt-60 (Gamma) Radiation

DTIC Science & Technology

1959-04-01

U.S. DEPARTMENT OF COMMERCE National Technical Information Service AD-AO36 168 RADIATION-INDUCED CENTRAL NERVOUS SYSTEM DEATH - A STUDY OF THE...ý." - ý " . :..’ýý.ý-. .. , . ý 4 ý .. -- ’ý.- -!:;:ý’,. 1,ý,-: WJiAUOK4KOUED CENTRAL NERVOUS SYSTEM NT A Study of the Pathologic Findings in...University SCHOOL OF AVIATION MEDICINE, USAF Randolph AFB, Texas April 1959 7757-. AdIAIONH-INDUCED CENTRAL NEVOUS $Y$194 DUTH A Study of the Pathologic

Star formation in galaxy mergers with realistic models of stellar feedback and the interstellar medium

NASA Astrophysics Data System (ADS)

Hopkins, Philip F.; Cox, Thomas J.; Hernquist, Lars; Narayanan, Desika; Hayward, Christopher C.; Murray, Norman

2013-04-01

We use hydrodynamic simulations with detailed, explicit models for stellar feedback to study galaxy mergers. These high-resolution (˜1 pc) simulations follow the formation and destruction of individual giant molecular clouds (GMC) and star clusters. We find that the final starburst is dominated by in situ star formation, fuelled by gas which flows inwards due to global torques. The resulting high gas density results in rapid star formation. The gas is self-gravitating, and forms massive (≲1010 M⊙) GMC and subsequently super star clusters (with masses up to 108 M⊙). However, in contrast to some recent simulations, the bulk of new stars which eventually form the central bulge are not born in super-clusters which then sink to the centre of the galaxy. This is because feedback efficiently disperses GMC after they turn several per cent of their mass into stars. In other words, most of the mass that reaches the nucleus does so in the form of gas. The Kennicutt-Schmidt law emerges naturally as a consequence of feedback balancing gravitational collapse, independent of the small-scale star formation microphysics. The same mechanisms that drive this relation in isolated galaxies, in particular radiation pressure from infrared photons, extend, with no fine-tuning, over seven decades in star formation rate (SFR) to regulate star formation in the most extreme starburst systems with densities ≳104 M⊙ pc-2. This feedback also drives super-winds with large mass-loss rates; however, a significant fraction of the wind material falls back on to the discs at later times, leading to higher post-starburst SFRs in the presence of stellar feedback. This suggests that strong active galactic nucleus feedback may be required to explain the sharp cut-offs in SFR that are observed in post-merger galaxies. We compare the results to those from simulations with no explicit resolution of GMC or feedback [`effective equation-of-state' (EOS) models]. We find that global galaxy properties are similar between EOS and resolved-feedback models. The relic structure and mass profile, and the total mass of stars formed in the nuclear starburst are quite similar, as is the morphological structure during and after mergers (tails, bridges, etc.). Disc survival in sufficiently gas rich mergers is similar in the two cases, and the new models follow the same scalings as derived for the efficiency of disc re-formation after a merger as derived from previous work with the simplified EOS models. While the global galaxy properties are similar between EOS and feedback models, subgalaxy-scale properties and the SFRs can be quite different: the more detailed models exhibit significantly higher star formation in tails and bridges (especially in shocks), and allow us to resolve the formation of super star clusters. In the new models, the star formation is more strongly time-variable and drops more sharply between close passages. The instantaneous burst enhancement can be higher or lower, depending on the details of the orbit and initial structural properties of the galaxies; first-passage bursts are more sensitive to these details than those at the final coalescence.

A Massive Star Census of the Starburst Cluster R136

NASA Astrophysics Data System (ADS)

Crowther, Paul

2011-10-01

We propose to carry out a comprehensive census of the most massive stars in the central parsec {4"} of the starburst cluster, R136, which powers the Tarantula Nebula in the LMC. R136 is both sufficiently massive that the upper mass function is richly populated and young enough that its most massive stars have yet to explode as supernovae. The identification of very massive stars in R136, up to 300 solar masses, raises general questions of star formation, binarity and feedback in young massive clusters. The proposed STIS spectral survey of 36 stars more massive than 50 solar masses within R136 is ground-breaking, of legacy value, and is specifically tailored to a} yield physical properties; b} detect the majority of binaries by splitting observations between Cycles 19 and 20; c} measure rotational velocities, relevant for predictions of rotational mixing; d} quantify mass-loss properties for very massive stars; e} determine surface compositions; f} measure radial velocities, relevant for runaway stars and cluster dynamics; g} quantify radiative and mechanical feedback. This census will enable the mass function of very massive stars to be measured for the first time, as a result of incomplete and inadequate spectroscopy to date. It will also perfectly complement our Tarantula Survey, a ground-based VLT Large Programme, by including the most massive stars that are inaccessible to ground-based visual spectroscopy due to severe crowding. These surveys, together with existing integrated UV and optical studies will enable 30 Doradus to serve as a bona-fide template for unresolved extragalactic starburst regions.

A Massive Star Census of the Starburst Cluster R136

NASA Astrophysics Data System (ADS)

Crowther, Paul

2012-10-01

We propose to carry out a comprehensive census of the most massive stars in the central parsec {4"} of the starburst cluster, R136, which powers the Tarantula Nebula in the LMC. R136 is both sufficiently massive that the upper mass function is richly populated and young enough that its most massive stars have yet to explode as supernovae. The identification of very massive stars in R136, up to 300 solar masses, raises general questions of star formation, binarity and feedback in young massive clusters. The proposed STIS spectral survey of 36 stars more massive than 50 solar masses within R136 is ground-breaking, of legacy value, and is specifically tailored to a} yield physical properties; b} detect the majority of binaries by splitting observations between Cycles 19 and 20; c} measure rotational velocities, relevant for predictions of rotational mixing; d} quantify mass-loss properties for very massive stars; e} determine surface compositions; f} measure radial velocities, relevant for runaway stars and cluster dynamics; g} quantify radiative and mechanical feedback. This census will enable the mass function of very massive stars to be measured for the first time, as a result of incomplete and inadequate spectroscopy to date. It will also perfectly complement our Tarantula Survey, a ground-based VLT Large Programme, by including the most massive stars that are inaccessible to ground-based visual spectroscopy due to severe crowding. These surveys, together with existing integrated UV and optical studies will enable 30 Doradus to serve as a bona-fide template for unresolved extragalactic starburst regions.

On the curious spectrum of duality invariant higher-derivative gravity

NASA Astrophysics Data System (ADS)

Hohm, Olaf; Naseer, Usman; Zwiebach, Barton

2016-08-01

We analyze the spectrum of the exactly duality and gauge invariant higher-derivative double field theory. While this theory is based on a chiral CFT and does not correspond to a standard string theory, our analysis illuminates a number of issues central in string theory. The full quadratic action is rewritten as a two-derivative theory with additional fields. This allows for a simple analysis of the spectrum, which contains two massive spin-2 ghosts and massive scalars, in addition to the massless fields. Moreover, in this formulation, the massless or tensionless limit α ' → ∞ is non-singular and leads to an enhanced gauge symmetry. We show that the massive modes can be integrated out exactly at the quadratic level, leading to an infinite series of higher-derivative corrections. Finally, we present a ghost-free massive extension of linearized double field theory, which employs a novel mass term for the dilaton and metric.

First Spectroscopic Identification of Massive Young Stellar Objects in the Galactic Center

NASA Technical Reports Server (NTRS)

An, Deokkeun; Ramirez, V.; Sellgren, Kris; Arendt, Richard G.; Boogert, A. C.; Schultheis, Mathias; Stolovy, Susan R.; Cotera, Angela S.; Robitaille, Thomas P.; Smith, Howard A.

2009-01-01

We report the detection of several molecular gas-phase and ice absorption features in three photometrically-selected young stellar object (YSO) candidates in the central 280 pc of the Milky Way. Our spectra, obtained with the Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope, reveal gas-phase absorption from CO2 (15.0 microns), C2H2 (13.7 microns) and HCN (14.0 microns). We attribute this absorption to warm, dense gas in massive YSOs. We also detect strong and broad 15 microns CO2 ice absorption features, with a remarkable double-peaked structure. The prominent long-wavelength peak is due to CH3OH-rich ice grains, and is similar to those found in other known massive YSOs. Our IRS observa.tions demonstra.te the youth of these objects, and provide the first spectroscopic identification of massive YSOs in the Galactic Center.

PREFACE: Astronomy at High Angular Resolution 2011: The central kiloparsec in galactic nuclei

NASA Astrophysics Data System (ADS)

Iserlohe, Christof; Karas, Vladimir; Krips, Melanie; Eckart, Andreas; Britzen, Silke; Fischer, Sebastian

2012-07-01

We are pleased to present the proceedings from the Astronomy at High Angular Resolution 2011: The central kiloparsec in galactic nuclei conference. The conference took place in the Physikzentrum of the Deutsche Physikalische Gesellschaft (DPG), Bad Honnef, Germany, from 28 August to 2 September 2011. It was the second conference of this kind, following the Astronomy at High Angular Resolution conference held in Bad Honnef, three years earlier in 2008. The main objective of the conference was to frame the discussion of the broad range of physical processes that occur in the central 100pc of galactic nuclei. In most cases, this domain is difficult to probe through observations. This is mainly because of the lack of angular resolution, the brightness of the central engine and possible obscurations through dust and gas, which play together in the central regions of host galaxies of galactic nuclei within a broad range of activity. The presence of large amounts of molecular and atomic (both neutral and ionized) gas, dust and central engines with outflows and jets implies that the conditions for star formation in these regions are very special, and probably different from those in the disks of host galaxies. Numerous presentations covering a broad range of topics, both theoretical and experimental, those related to research on Active Galactic Nuclei and on a wide range of observed wavelengths were submitted to the Scientific Organizing Committee. Presentations have been grouped into six sessions: The nuclei of active galaxies The Galactic Center The immediate environment of Super Massive Black Holes The physics of nuclear jets and the interaction of the interstellar medium The central 100pc of the nuclear environment Star formation in that region The editors thank all participants of the AHAR 2011 conference for their enthusiasm and their numerous and vivid contributions to this conference. We would especially like to thank John Hugh Seiradakis from the Aristotle University of Thessaloniki in Greece for giving the dinner talk on the most astounding ancient Antikythera mechanism. We would also like to thank Victor Gomer and the staff of the Physikzentrum of the Deutsche Physikalische Gesellschaft in Bad Honnef where the conference took place. Last but not least we would like to thank all unnamed helpers, without whom the organisation of this conference would not have been possible. Financial support for this conference was granted by the Deutsche Forschungsgemeinschaft (DFG) Sonderforschungsbereich project number SFB 956. We also acknowledge support from the European Community Framework Programme 7, Advanced Radio Astronomy in Europe, grant agreement no. 227290. Christof Iserlohe, Vladimir Karas, Melanie Krips, Andreas Eckart, Silke Britzen and Sebastian Fischer The Editors Conference photograph Conference Group Photo, 1 September 2011 The PDF also contains additional photographs from the conference and the Contents of the Proceedings.

The central spheroids of Milky Way mass-sized galaxies

NASA Astrophysics Data System (ADS)

Tissera, Patricia B.; Machado, Rubens E. G.; Carollo, Daniela; Minniti, Dante; Beers, Timothy C.; Zoccali, Manuela; Meza, Andres

2018-01-01

We study the properties of the central spheroids located within 10 kpc of the centre of mass of Milky Way mass-sized galaxies simulated in a cosmological context. The simulated central regions are dominated by stars older than 10 Gyr, mostly formed in situ, with a contribution of ∼30 per cent from accreted stars. These stars formed in well-defined starbursts, although accreted stars exhibit sharper and earlier ones. The fraction of accreted stars increases with galactocentric distance, so that at a radius of ∼8-10 kpc, a fraction of ∼40 per cent, on average, is detected. Accreted stars are slightly younger, lower metallicity, and more α-enhanced than in situ stars. A significant fraction of old stars in the central regions come from a few (2-3) massive satellites (∼1010 M⊙). The bulge components receive larger contributions of accreted stars formed in dwarfs smaller than ∼109.5 M⊙. The difference between the distributions of ages and metallicities of old stars is thus linked to the accretion histories - those central regions with a larger fraction of accreted stars are those with contributions from more massive satellites. The kinematical properties of in situ and accreted stars are consistent with the latter being supported by their velocity dispersions, while the former exhibit clear signatures of rotational support. Our simulations demonstrate a range of characteristics, with some systems exhibiting a co-existing bar and spheroid in their central regions, resembling in some respect the central region of the Milky Way.

Analysis of Superconducting Dipole Coil of 11 GeV Super High Momentum Spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Eric; Cheng, Gary; Lassiter, Steve R.

2015-06-01

Jefferson Lab is constructing five Super High Momentum Spectrometer (SHMS) superconducting magnets for the 12 GeV Upgrade. This paper reports measured coil material properties and the results of the extensive finite element analysis (FEA) for the dipole coil. To properly define the smeared orthotropic material of the coil, a detailed coil model is set up to compute material parameters because not all parameters were measured. Stress and strain acceptance criteria are discussed. Eight load steps are defined. The preheat temperature of the force collar is optimized under two loading scenarios so that the positive pressure between the inner coil andmore » central spacer is maintained while there is not too much squeeze to the coil.« less

Ore mineralogy and textural zonation in the world-class epithermal Waihi Vein System, Hauraki Goldfield

USGS Publications Warehouse

Mauk, Jeffrey L.; Skinner, Erin G; Fyfe, Sarah J; Menzies, Andrew H; Lowers, Heather A.; Koenig, Alan E.

2016-01-01

The Waihi district in the Hauraki Goldfield of New Zealand contains adularia-sericite epithermal gold-silver veins that have produced more than 7.7 Moz gold. The outermost veins of the district (Martha, Favona, Moonlight, and Cowshed) contain abundant colloform, cherty, and black quartz fill textures, with minor crustiform and massive quartz. The central veins (Amaranth, Trio, and Union) contain predominantly massive and crustiform textures, and these veins are also commonly coarser grained than outermost veins. Pyrite, sphalerite, galena, chalcopyrite, electrum, and acanthite occur in both outermost and central veins; base metal sulfide minerals typically increase in abundance in deeper samples. Antimony-, arsenic-, and selenium-bearing minerals are most abundant in the Favona and Moonlight veins, whereas base metal sulfide minerals are more abundant in the central veins at Correnso. Throughout the Waihi vein system, electrum is by far the most widespread, abundant, and significant gold-bearing mineral, but LA-ICP-MS analyses show that arsenian pyrite also contains some gold. Mineralogical and textural data are consistent with the central veins forming at a deeper structural level, or from hydrothermal fluids with different chemistry, or both.

CANDELS Sheds Light on the Environmental Quenching of Low-mass Galaxies

NASA Astrophysics Data System (ADS)

Guo, Yicheng; Bell, Eric F.; Lu, Yu; Koo, David C.; Faber, Sandra M.; CANDELS

2018-01-01

We investigate the environmental quenching of galaxies, especially those with stellar masses (M*) smaller than 10^9.5 M⊙, beyond the local universe. Essentially all local low-mass quenched galaxies (QGs) are believed to live close to massive central galaxies, which is a demonstration of environmental quenching. We use CANDELS data to test whether or not such a dwarf QG--massive central galaxy connection exists beyond the local universe. For this purpose, we only need a statistically representative, rather than a complete, sample of low-mass galaxies, which enables our study out to z > 1.5. For each low-mass galaxy, we measure the projected distance (dproj) to its nearest massive (M* > 10^10.5 M⊙) neighbor within a redshift range. At a given z and M*, the environmental quenching effect is considered to be observed if the dproj distribution of QGs is significantly skewed toward lower values than that of star-forming galaxies (SFGs). For galaxies with 10^8 M⊙ < M* < 10^10 M⊙, such a difference between the dproj distributions of quenched and star-forming populations is detected up to z ˜ 1. Also, about 10% of the quenched galaxies in our sample are located between two and four virial radii (R_Vir) of the massive halos. The median projected distance from low-mass QGs to their massive neighbors (dproj/R_Vir) decreases with satellite M* at M* < 10^9.5 M⊙, but increases with satellite M* at M* > 10^9.5 M⊙. This trend suggests a smooth, if any, transition of the quenching timescale around M* of 10^9.5 M⊙ at 0.5 < z < 1.0.

CANDELS Sheds Light on the Environmental Quenching of Low-mass Galaxies

NASA Astrophysics Data System (ADS)

Guo, Yicheng; Bell, Eric F.; Lu, Yu; Koo, David C.; Faber, S. M.; Koekemoer, Anton M.; Kurczynski, Peter; Lee, Seong-Kook; Papovich, Casey; Chen, Zhu; Dekel, Avishai; Ferguson, Henry C.; Fontana, Adriano; Giavalisco, Mauro; Kocevski, Dale D.; Nayyeri, Hooshang; Pérez-González, Pablo G.; Pforr, Janine; Rodríguez-Puebla, Aldo; Santini, Paola

2017-06-01

We investigate the environmental quenching of galaxies, especially those with stellar masses (M *) < 109.5 M ⊙, beyond the local universe. Essentially all local low-mass quenched galaxies (QGs) are believed to live close to massive central galaxies, which is a demonstration of environmental quenching. We use CANDELS data to test whether or not such a dwarf QG-massive central galaxy connection exists beyond the local universe. For this purpose, we only need a statistically representative, rather than complete, sample of low-mass galaxies, which enables our study to z ≳ 1.5. For each low-mass galaxy, we measure the projected distance (d proj) to its nearest massive neighbor (M * > 1010.5 M ⊙) within a redshift range. At a given z and M *, the environmental quenching effect is considered to be observed if the d proj distribution of QGs ({d}{proj}Q) is significantly skewed toward lower values than that of star-forming galaxies ({d}{proj}{SF}). For galaxies with 108 M ⊙ < M * < 1010 M ⊙, such a difference between {d}{proj}Q and {d}{proj}{SF} is detected up to z ˜ 1. Also, about 10% of the quenched galaxies in our sample are located between two and four virial radii (R Vir) of the massive halos. The median projected distance from low-mass QGs to their massive neighbors, {d}{proj}Q/{R}{Vir}, decreases with satellite M * at M * ≲ 109.5 M ⊙, but increases with satellite M * at M * ≳ 109.5 M ⊙. This trend suggests a smooth, if any, transition of the quenching timescale around M * ˜ 109.5 M ⊙ at 0.5 < z < 1.0.

Growing massive black holes in a Local Group environment: the central supermassive, slowly sinking and ejected populations

NASA Astrophysics Data System (ADS)

Micic, Miroslav; Holley-Bockelmann, Kelly; Sigurdsson, Steinn

2011-06-01

We explore the growth of ≤107 M⊙ black holes that reside at the centres of spiral and field dwarf galaxies in a Local Group type of environment. We use merger trees from a cosmological N-body simulation known as Via Lactea 2 (VL-2) as a framework to test two merger-driven semi-analytic recipes for black hole growth that include dynamical friction, tidal stripping and gravitational wave recoil in over 20 000 merger tree realizations. First, we apply a Fundamental Plane limited (FPL) model to the growth of Sgr A*, which drives the central black hole to a maximum mass limited by the black hole Fundamental Plane after every merger. Next, we present a new model that allows for low-level prolonged gas accretion (PGA) during the merger. We find that both models can generate an Sgr A* mass black hole. We predict a population of massive black holes in local field dwarf galaxies - if the VL-2 simulation is representative of the growth of the Local Group, we predict up to 35 massive black holes (≤106 M⊙) in Local Group field dwarfs. We also predict that hundreds of ≤105 M⊙ black holes fail to merge, and instead populate the Milky Way halo, with the most massive of them at roughly the virial radius. In addition, we find that there may be hundreds of massive black holes ejected from their hosts into the nearby intergalactic medium due to gravitational wave recoil. We discuss how the black hole population in the Local Group field dwarfs may help to constrain the growth mechanism for Sgr A*.

Diagnosis and Management of Combined Central Diabetes Insipidus and Cerebral Salt Wasting Syndrome After Traumatic Brain Injury.

PubMed

Wu, Xuehai; Zhou, Xiaolan; Gao, Liang; Wu, Xing; Fei, Li; Mao, Ying; Hu, Jin; Zhou, Liangfu

2016-04-01

Combined central diabetes insipidus and cerebral salt wasting syndrome after traumatic brain injury (TBI) is rare, is characterized by massive polyuria leading to severe water and electrolyte disturbances, and usually is associated with very high mortality mainly as a result of delayed diagnosis and improper management. We retrospectively reviewed the clinical presentation, management, and outcomes of 11 patients who developed combined central diabetes insipidus and cerebral salt wasting syndrome after traumatic brain injury to define distinctive features for timely diagnosis and proper management. The most typical clinical presentation was massive polyuria (10,000 mL/24 hours or >1000 mL/hour) refractory to vasopressin alone but responsive to vasopressin plus cortisone acetate. Other characteristic presentations included low central venous pressure, high brain natriuretic peptide precursor level without cardiac dysfunction, high 24-hour urine sodium excretion and hypovolemia, and much higher urine than serum osmolarity; normal serum sodium level and urine specific gravity can also be present. Timely and adequate infusion of sodium chloride was key in treatment. Of 11 patients, 5 had a good prognosis 3 months later (Extended Glasgow Outcome Scale score ≥6), 1 had an Extended Glasgow Outcome Scale score of 4, 2 died in the hospital of brain hernia, and 3 developed a vegetative state. For combined diabetes insipidus and cerebral salt wasting syndrome after traumatic brain injury, massive polyuria is a major typical presentation, and intensive monitoring of fluid and sodium status is key for timely diagnosis. To achieve a favorable outcome, proper sodium chloride supplementation and cortisone acetate and vasopressin coadministration are key. Copyright © 2016 Elsevier Inc. All rights reserved.

Small-world network model of propagation of the AIDS epidemic

NASA Astrophysics Data System (ADS)

Shi, Pengliang; Small, Michael

2004-03-01

Sexual contact and intravenus drug-use are the most common modes of transmission of HIV-AIDS. In this paper, homogenerous and heterogeneous models are proposed to model the dynamics in a system contains Small-World clusters. Four high risk groups: intravenus drug-users (D); homosexuals (H); individuals with multiple-sexual partners (M) and prostitutes (P), are classified using two models. Both networks are embedded among a background (low-risk) population using rich-get-richer preferential attachment. When a network is established, an epidemic is simulated in it by seeding randomly. We compare the two epidemic networks in detail and consider the effect of different levels of control policies in both. This study highlights two main conclusions: (i) set high protection coefficient for a massive-linkage-vertex (i.e. protect the highly connected individuals); and, (ii) a quick removal for the infected massive-linkage-veterx from the network is essential (rapidly quarantine infected individuals). While these conclusions may be intuitive, they indicate a necessary change of public policy toward prostitution in some developing countries such as China and India. An active effort to prevent possible infection from super-spreader is recommended.

The Elephant in the Room: Effects of Distant, Massive Companions on Planetary System Architectures

NASA Astrophysics Data System (ADS)

Knutson, Heather

2016-06-01

Over the past two decades ongoing radial velocity and transit surveys have been astoundingly successful in detecting thousands of new planetary systems around nearby stars. These systems include apparently single gas giant planets on short period orbits, closely packed systems of up to 5-6 “super-Earths”, and relatively empty systems with either one or no small planets interior to 0.5 AU. Despite our success in cataloguing the diverse properties of these systems, we are still struggling to develop narratives that can explain their apparently divergent formation and migration histories. This is in large part due to our lack of knowledge about the potential presence of massive outer companions in these systems, which can play a pivotal role in the shaping the final properties of the inner planets. In my talk I will discuss current efforts to complete the census for known planetary systems by searching for outer gas giant planets with long term radial velocity monitoring and wide separation stellar companions with high contrast imaging and spectroscopy. I will then demonstrate how statistical constraints on this population of outer companions can be used to test current theories for planet formation and migration.

The metallicity dependence of WR winds

NASA Astrophysics Data System (ADS)

Hainich, R.; Shenar, T.; Sander, A.; Hamann, W.-R.; Todt, H.

2017-11-01

Wolf-Rayet (WR) stars are the most advanced stage in the evolution of the most massive stars. The strong feedback provided by these objects and their subsequent supernova (SN) explosions are decisive for a variety of astrophysical topics such as the cosmic matter cycle. Consequently, understanding the properties of WR stars and their evolution is indispensable. A crucial but still not well known quantity determining the evolution of WR stars is their mass-loss rate. Since the mass loss is predicted to increase with metallicity, the feedback provided by these objects and their spectral appearance are expected to be a function of the metal content of their host galaxy. This has severe implications for the role of massive stars in general and the exploration of low metallicity environments in particular. Hitherto, the metallicity dependence of WR star winds was not well studied. In this contribution, we review the results from our comprehensive spectral analyses of WR stars in environments of different metallicities, ranging from slightly super-solar to SMC-like metallicities. Based on these studies, we derived empirical relations for the dependence of the WN mass-loss rates on the metallicity and iron abundance, respectively.

The Influence of Host Galaxies in Type Ia Supernova Cosmology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uddin, Syed A.; Mould, Jeremy; Lidman, Chris

We use a sample of 1338 spectroscopically confirmed and photometrically classified Type Ia supernovae (SNe Ia) sourced from Carnegie Supernova Project, Center for Astrophysics Supernova Survey, Sloan Digital Sky Survey-II, and SuperNova Legacy Survey SN samples to examine the relationships between SNe Ia and the galaxies that host them. Our results provide confirmation with improved statistical significance that SNe Ia, after standardization, are on average more luminous in massive hosts (significance >5 σ ), and decline more rapidly in massive hosts (significance >9 σ ) and in hosts with low specific star formation rates (significance >8 σ ). We studymore » the variation of these relationships with redshift and detect no evolution. We split SNe Ia into pairs of subsets that are based on the properties of the hosts and fit cosmological models to each subset. Including both systematic and statistical uncertainties, we do not find any significant shift in the best-fit cosmological parameters between the subsets. Among different SN Ia subsets, we find that SNe Ia in hosts with high specific star formation rates have the least intrinsic scatter ( σ {sub int} = 0.08 ± 0.01) in luminosity after standardization.« less

Flows of X-ray gas reveal the disruption of a star by a massive black hole.

PubMed

Miller, Jon M; Kaastra, Jelle S; Miller, M Coleman; Reynolds, Mark T; Brown, Gregory; Cenko, S Bradley; Drake, Jeremy J; Gezari, Suvi; Guillochon, James; Gultekin, Kayhan; Irwin, Jimmy; Levan, Andrew; Maitra, Dipankar; Maksym, W Peter; Mushotzky, Richard; O'Brien, Paul; Paerels, Frits; de Plaa, Jelle; Ramirez-Ruiz, Enrico; Strohmayer, Tod; Tanvir, Nial

2015-10-22

Tidal forces close to massive black holes can violently disrupt stars that make a close approach. These extreme events are discovered via bright X-ray and optical/ultraviolet flares in galactic centres. Prior studies based on modelling decaying flux trends have been able to estimate broad properties, such as the mass accretion rate. Here we report the detection of flows of hot, ionized gas in high-resolution X-ray spectra of a nearby tidal disruption event, ASASSN-14li in the galaxy PGC 043234. Variability within the absorption-dominated spectra indicates that the gas is relatively close to the black hole. Narrow linewidths indicate that the gas does not stretch over a large range of radii, giving a low volume filling factor. Modest outflow speeds of a few hundred kilometres per second are observed; these are below the escape speed from the radius set by variability. The gas flow is consistent with a rotating wind from the inner, super-Eddington region of a nascent accretion disk, or with a filament of disrupted stellar gas near to the apocentre of an elliptical orbit. Flows of this sort are predicted by fundamental analytical theory and more recent numerical simulations.

The Influence of Host Galaxies in Type Ia Supernova Cosmology

NASA Astrophysics Data System (ADS)

Uddin, Syed A.; Mould, Jeremy; Lidman, Chris; Ruhlmann-Kleider, Vanina; Zhang, Bonnie R.

2017-10-01

We use a sample of 1338 spectroscopically confirmed and photometrically classified Type Ia supernovae (SNe Ia) sourced from Carnegie Supernova Project, Center for Astrophysics Supernova Survey, Sloan Digital Sky Survey-II, and SuperNova Legacy Survey SN samples to examine the relationships between SNe Ia and the galaxies that host them. Our results provide confirmation with improved statistical significance that SNe Ia, after standardization, are on average more luminous in massive hosts (significance >5σ), and decline more rapidly in massive hosts (significance >9σ) and in hosts with low specific star formation rates (significance >8σ). We study the variation of these relationships with redshift and detect no evolution. We split SNe Ia into pairs of subsets that are based on the properties of the hosts and fit cosmological models to each subset. Including both systematic and statistical uncertainties, we do not find any significant shift in the best-fit cosmological parameters between the subsets. Among different SN Ia subsets, we find that SNe Ia in hosts with high specific star formation rates have the least intrinsic scatter (σ int = 0.08 ± 0.01) in luminosity after standardization.

Unveiling the nucleus of NGC 7172

NASA Astrophysics Data System (ADS)

Smajić, S.; Fischer, S.; Zuther, J.; Eckart, A.

2012-08-01

Aims: We present the results of near-infrared (NIR) H + K European Southern Observatory SINFONI integral field spectroscopy (IFS) of the Seyfert 2 galaxy NGC 7172. We investigate the central 800 pc, concentrating on excitation conditions, morphology, and stellar content. NGC 7172 was selected from a sample of the ten nearest Seyfert 2 galaxies from the Veron-Cetty & Veron catalogue. All objects were chosen as test cases for adaptive optics (AO) assisted observations that allow a detailed study (at high spatial and spectral resolution) of the nuclear and host environments. NGC 7172 has a prominent dustlane crossing the central galaxy region from east to west, which makes it an ideal candidate to investigate the effect of obscuration by strong galactic extinction on (active) galaxies and their classification. Methods: The NIR is less influenced by dust extinction than optical light and is sensitive to the mass-dominating stellar populations. SINFONI integral field spectroscopy combines NIR imaging and spectroscopy and provides us with the opportunity to analyze several emission and absorption lines to investigate the stellar populations and ionization mechanisms over the 4″ × 4″ field of view (FOV). Results: We present emission and absorption line measurements in the central 800 pc of NGC 7172. The detection of [Si vi] and broad Paα and Brγ components are clear signs of an accreting super-massive black hole hiding behind the prominent dustlane at visible wavelengths. Hot temperatures of about 1300 K are indicative of a dusty torus in the nuclear region. Narrow components of Paα and Brγ enable us to make an extinction measurement. Our measures of the molecular hydrogen lines, hydrogen recombination lines, and [Fe ii] indicate that the excitation of these lines is caused by an active galactic nucleus. The central region of the galactic disk is predominantly inhabited by gas, dust, and an old K-M type giant stellar population. The gaseous, molecular, and stellar velocity maps show a related disturbed disk structure and similar velocities. Conclusions: We find evidence of nuclear activity located behind the prominent dustlane crossing the central region of the galaxy. The nucleus of NGC 7172, which is optically classified as a Seyfert 2 nucleus without any trace of broad emission lines, is a Seyfert 1 nucleus either surrounded by a molecular dust torus or hidden behind the strong galactic extinction. Our observation provides support for the unified model scheme. However, an evolutionary scenario cannot be ruled out by our observation. Based on the ESO-VLT STS-Cologne GTO proposal ID: 083.B-0620(A).

Terrestrial black holes as sources of super-high energy radiation

NASA Astrophysics Data System (ADS)

Trofimenko, A. P.; Gurin, V. S.

1993-04-01

The study proposes small black holes which can be located in the earth's interior as sources of superhigh energy radiation; their origin is not constrained to the big bang. The intensity and spectrum of massless and massive particle radiation due to the Hawking effect for black holes with masses of 10 exp 8 to 10 exp 16 are estimated. The possibility of their detection according to a number of features (high particle energies, thermal energetic spectrum, transientness or an explicit trend to intensity and energy increase, and some expressed direction of emission associated with source localization) is explored. The rates of the radiation of massless particles with spin-1/2 and with spin-1 are illustrated in graphic form.

Observational Progress in Identifying and Characterizing Tidal Disruption Flares

NASA Astrophysics Data System (ADS)

Cenko, S. Bradley

I present an overview of observational efforts across the electromagnetic spectrum to identify and study tidal disruption flares (TDFs), when a star wanders too close to a super-massive black hole and is torn apart by tidal forces. In particular I will focus on four unexpected surprises that challenge the most basic analytic picture of these events: 1) large inferred radii for the optical/UV-emitting material; 2) the ubiquity of outflows, detected at radio, X-ray, and UV wavelengths, ranging from speeds of 100 km/s to near the speed of light; 3) the peculiar atomic abundances observed in the UV and optical spectra of these objects; and, 4) the preference for these events to occur in post-starburst galaxies.

Proxy-equation paradigm: A strategy for massively parallel asynchronous computations

NASA Astrophysics Data System (ADS)

Mittal, Ankita; Girimaji, Sharath

2017-09-01

Massively parallel simulations of transport equation systems call for a paradigm change in algorithm development to achieve efficient scalability. Traditional approaches require time synchronization of processing elements (PEs), which severely restricts scalability. Relaxing synchronization requirement introduces error and slows down convergence. In this paper, we propose and develop a novel "proxy equation" concept for a general transport equation that (i) tolerates asynchrony with minimal added error, (ii) preserves convergence order and thus, (iii) expected to scale efficiently on massively parallel machines. The central idea is to modify a priori the transport equation at the PE boundaries to offset asynchrony errors. Proof-of-concept computations are performed using a one-dimensional advection (convection) diffusion equation. The results demonstrate the promise and advantages of the present strategy.

Supernovae, supernebulae, and nucleosynthesis

NASA Astrophysics Data System (ADS)

Wheeler, J. Craig; Harkness, Robert P.; Barkat, Zalman; Swartz, Douglas

1986-10-01

Supernova atmosphere calculations continue to show that variants of previously calculated carbon-deflagration models provide a good representation of the maximum light spectra of classical type Ia supernovae including the ultraviolet deficit. Careful consideration of the conditions leading to central thermonuclear runaway of degenerate carbon shows that runaway can, however, lead to detonation and direct conflict with observations. As witnessed by the spectra of type Ib supernovae, massive stars are expected to be the primary source of oxygen. Estimates of the absolute production of oxygen in massive stars suggest that if all stars more massive than ≡12 M_sun; explode as supernovae, oxygen would be overproduced in the solar neighborhood, an effect exacerbated by the recent increase in the reaction rate for 12C(α, γ)16O.

Star formation in infrared bright and infrared faint starburst interacting galaxies

NASA Technical Reports Server (NTRS)

Lamb, Susan A.; Bushouse, Howard A.; Towns, John W.

1990-01-01

Short wavelength IUE spectra of Arp 248b and UGC 8315N are combined with optical spectra and interpreted using a combination of spectrum synthesis and spectral diagnostics to place constraints on the massive star populations of the central regions of these galaxies and to deduce information about the star formation histories in the last 10(exp 8) years. The authors find that both galaxies have substantial fractions of their optical light coming from massive stars and that Arp 248b may be dominated in the UV by WR stars. The UV spectra are dominated by radiation from evolved massive stars and the authors place and age on the burst in Arp 248b of a few tens of millions of years.

Dynamics and stellar population of the Galactic Center (French Title: Étude de la cinématique et de la population stellaire du Centre Galactique)

NASA Astrophysics Data System (ADS)

Paumard, Thibaut

2003-09-01

The central parsec of the Galaxy has been observed using BEAR spectroimagery at high spectral resolution (up to 21 km/s) and medium spatial resolution (0.5"), in Bracket gamma (2.16 microns) and He I (2.06 microns), and high resolution imaging. These data were used to study the young, massive stars of the central parsec, and the structure and dynamics of ionized gas in Sgr A West. The stellar population has been separated into two groups: the IRS 16 complex of 6 LBVs, and at least 20 Wolf-Rayets. The IRS 13E complex has been identified as a cluster of at least 6 massive stars. All this is consistent with the young stars being born in a massive cluster a few tens of parsecs from the Galactic Centre. Providing a deep insight into the morphology of Sgr A West, our data allowed us to derive a kinematic model for the Northern Arm. Our results are in agreement with the idea that the Minispiral is made of ionisation fronts of wider neutral clouds, gravitationally stretched, coming from the CND.

Super-spinning compact objects and models of high-frequency quasi-periodic oscillations observed in Galactic microquasars

NASA Astrophysics Data System (ADS)

Kotrlová, Andrea; Török, Gabriel; Šrámková, Eva; Stuchlík, Zdeněk

2014-12-01

We have previously applied several models of high-frequency quasi-periodic oscillations (HF QPOs) to estimate the spin of the central Kerr black hole in the three Galactic microquasars, GRS 1915+105, GRO J1655-40, and XTE J1550-564. Here we explore the alternative possibility that the central compact body is a super-spinning object (or a naked singularity) with the external space-time described by Kerr geometry with a dimensionless spin parameter a ≡ cJ/GM2> 1. We calculate the relevant spin intervals for a subset of HF QPO models considered in the previous study. Our analysis indicates that for all but one of the considered models there exists at least one interval of a> 1 that is compatible with constraints given by the ranges of the central compact object mass independently estimated for the three sources. For most of the models, the inferred values of a are several times higher than the extreme Kerr black hole value a = 1. These values may be too high since the spin of superspinars is often assumed to rapidly decrease due to accretion when a ≫ 1. In this context, we conclude that only the epicyclic and the Keplerian resonance model provides estimates that are compatible with the expectation of just a small deviation from a = 1.

ATLASGAL - towards a complete sample of massive star forming clumps

NASA Astrophysics Data System (ADS)

Urquhart, J. S.; Moore, T. J. T.; Csengeri, T.; Wyrowski, F.; Schuller, F.; Hoare, M. G.; Lumsden, S. L.; Mottram, J. C.; Thompson, M. A.; Menten, K. M.; Walmsley, C. M.; Bronfman, L.; Pfalzner, S.; König, C.; Wienen, M.

2014-09-01

By matching infrared-selected, massive young stellar objects (MYSOs) and compact H II regions in the Red MSX Source survey to massive clumps found in the submillimetre ATLASGAL (APEX Telescope Large Area Survey of the Galaxy) survey, we have identified ˜1000 embedded young massive stars between 280° < ℓ < 350° and 10° < ℓ < 60° with | b | < 1.5°. Combined with an existing sample of radio-selected methanol masers and compact H II regions, the result is a catalogue of ˜1700 massive stars embedded within ˜1300 clumps located across the inner Galaxy, containing three observationally distinct subsamples, methanol-maser, MYSO and H II-region associations, covering the most important tracers of massive star formation, thought to represent key stages of evolution. We find that massive star formation is strongly correlated with the regions of highest column density in spherical, centrally condensed clumps. We find no significant differences between the three samples in clump structure or the relative location of the embedded stars, which suggests that the structure of a clump is set before the onset of star formation, and changes little as the embedded object evolves towards the main sequence. There is a strong linear correlation between clump mass and bolometric luminosity, with the most massive stars forming in the most massive clumps. We find that the MYSO and H II-region subsamples are likely to cover a similar range of evolutionary stages and that the majority are near the end of their main accretion phase. We find few infrared-bright MYSOs associated with the most massive clumps, probably due to very short pre-main-sequence lifetimes in the most luminous sources.

Supermassive black holes and their feedback effects in the IllustrisTNG simulation

NASA Astrophysics Data System (ADS)

Weinberger, Rainer; Springel, Volker; Pakmor, Rüdiger; Nelson, Dylan; Genel, Shy; Pillepich, Annalisa; Vogelsberger, Mark; Marinacci, Federico; Naiman, Jill; Torrey, Paul; Hernquist, Lars

2018-06-01

We study the population of supermassive black holes (SMBHs) and their effects on massive central galaxies in the IllustrisTNG cosmological hydrodynamical simulations of galaxy formation. The employed model for SMBH growth and feedback assumes a two-mode scenario in which the feedback from active galactic nuclei occurs through a kinetic, comparatively efficient mode at low accretion rates relative to the Eddington limit, and in the form of a thermal, less efficient mode at high accretion rates. We show that the quenching of massive central galaxies happens coincidently with kinetic-mode feedback, consistent with the notion that active supermassive black cause the low specific star formation rates observed in massive galaxies. However, major galaxy mergers are not responsible for initiating most of the quenching events in our model. Up to black hole masses of about 108.5 M⊙, the dominant growth channel for SMBHs is in the thermal mode. Higher mass black holes stay mainly in the kinetic mode and gas accretion is self-regulated via their feedback, which causes their Eddington ratios to drop, with SMBH mergers becoming the main channel for residual mass growth. As a consequence, the quasar luminosity function is dominated by rapidly accreting, moderately massive black holes in the thermal mode. We show that the associated growth history of SMBHs produces a low-redshift quasar luminosity function and a redshift zero black hole mass - stellar bulge mass relation in good agreement with observations, whereas the simulation tends to over-predict the high-redshift quasar luminosity function.

Forming spectroscopic massive protobinaries by disc fragmentation

NASA Astrophysics Data System (ADS)

Meyer, D. M.-A.; Kuiper, R.; Kley, W.; Johnston, K. G.; Vorobyov, E.

2018-01-01

The surroundings of massive protostars constitute an accretion disc which has numerically been shown to be subject to fragmentation and responsible for luminous accretion-driven outbursts. Moreover, it is suspected to produce close binary companions which will later strongly influence the star's future evolution in the Hertzsprung-Russel diagram. We present three-dimensional gravitation-radiation-hydrodynamic numerical simulations of 100 M⊙ pre-stellar cores. We find that accretion discs of young massive stars violently fragment without preventing the (highly variable) accretion of gaseous clumps on to the protostars. While acquiring the characteristics of a nascent low-mass companion, some disc fragments migrate on to the central massive protostar with dynamical properties showing that its final Keplerian orbit is close enough to constitute a close massive protobinary system, having a young high- and a low-mass components. We conclude on the viability of the disc fragmentation channel for the formation of such short-period binaries, and that both processes - close massive binary formation and accretion bursts - may happen at the same time. FU-Orionis-type bursts, such as observed in the young high-mass star S255IR-NIRS3, may not only indicate ongoing disc fragmentation, but also be considered as a tracer for the formation of close massive binaries - progenitors of the subsequent massive spectroscopic binaries - once the high-mass component of the system will enter the main-sequence phase of its evolution. Finally, we investigate the Atacama Large (sub-)Millimeter Array observability of the disc fragments.

Recent Results and Near Term Outlook for the NASA Balloon Science Program

NASA Astrophysics Data System (ADS)

Jones, William Vernon

Long-duration and conventional balloon flights in the traditional Astrophysics, Solar and Heliophysics, and Earth Science disciplines have continued in both polar and non-polar regions since the 39th COSPAR Assembly in Mysore, India. One of these established a new flight record of 55 days over Antarctica during the 2012-2013 austral season. That Super-TIGER science flight broke both the 42-day record of the CREAM science flight during the 2004-2005 season and the 54-day super pressure balloon test flight in 2008-2009. With two comets approaching the sun in 2013-2014, the Planetary Science community has shown increased interest in remote observations of comets, planets, and other objects in the Solar System. All of the above science disciplines are interested in super pressure balloon (SPB) flights, which have been under development by NASA, and which were strongly supported by the Astro2010 Decadal Study. A 532,152 m3 (18.8 MCF) SPB with a major gamma ray astrophysics payload is planned for an ultra-long duration balloon (ULDB) test flight around and from Antarctica during the upcoming 2014-2015 season. Flights for SPB qualification to support 1000 kg science instruments to 33 km altitude have proceeded in parallel with planning for options to increase the altitude for less massive instruments that require less atmospheric overburden. The nearly constant SPB volume will provide stable altitude long-duration flights at non-polar latitudes, thereby supporting a much broader range of scientific investigations. Scientific ballooning continues to complement and enable space missions, while training young scientists and systems engineers for the workforce needed to conduct future missions. Highlights of results from past balloon-borne measurements and expected results from ongoing and planned balloon-borne experiments will be presented.

Extreme supernova models for the super-luminous transient ASASSN-15LH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatzopoulos, Emmanouil; Wheeler, John C.; Vinko, J.

The recent discovery of the unprecedentedly super-luminous transient ASASSN-15lh (or SN 2015L) with its UV-bright secondary peak challenges all the power-input models that have been proposed for super-luminous supernovae. Here we examine some of the few viable interpretations of ASASSN-15lh in the context of a stellar explosion, involving combinations of one or more power inputs. We model the light curve of ASASSN-15lh with a hybrid model that includes contributions from magnetar spin-down energy and hydrogen-poor circumstellar interaction. We also investigate models of pure circumstellar interaction with a massive hydrogen-deficient shell and discuss the lack of interaction features in the observedmore » spectra. We find that, as a supernova, ASASSN-15lh can be best modeled by the energetic core-collapse of an ~40 M ⊙ star interacting with a hydrogen-poor shell of ~20 M ⊙. The circumstellar shell and progenitor mass are consistent with a rapidly rotating pulsational pair-instability supernova progenitor as required for strong interaction following the final supernova explosion. Additional energy injection by a magnetar with an initial period of 1–2 ms and magnetic field of 0.1–1 × 10 14 G may supply the excess luminosity required to overcome the deficit in single-component models, but this requires more fine-tuning and extreme parameters for the magnetar, as well as the assumption of efficient conversion of magnetar energy into radiation. As a result, we thus favor a single-input model where the reverse shock formed in a strong SN ejecta–circumstellar matter interaction following a very powerful core-collapse SN explosion can supply the luminosity needed to reproduce the late-time UV-bright plateau.« less

Extreme supernova models for the super-luminous transient ASASSN-15LH

DOE PAGES

Chatzopoulos, Emmanouil; Wheeler, John C.; Vinko, J.; ...

2016-09-07

The recent discovery of the unprecedentedly super-luminous transient ASASSN-15lh (or SN 2015L) with its UV-bright secondary peak challenges all the power-input models that have been proposed for super-luminous supernovae. Here we examine some of the few viable interpretations of ASASSN-15lh in the context of a stellar explosion, involving combinations of one or more power inputs. We model the light curve of ASASSN-15lh with a hybrid model that includes contributions from magnetar spin-down energy and hydrogen-poor circumstellar interaction. We also investigate models of pure circumstellar interaction with a massive hydrogen-deficient shell and discuss the lack of interaction features in the observedmore » spectra. We find that, as a supernova, ASASSN-15lh can be best modeled by the energetic core-collapse of an ~40 M ⊙ star interacting with a hydrogen-poor shell of ~20 M ⊙. The circumstellar shell and progenitor mass are consistent with a rapidly rotating pulsational pair-instability supernova progenitor as required for strong interaction following the final supernova explosion. Additional energy injection by a magnetar with an initial period of 1–2 ms and magnetic field of 0.1–1 × 10 14 G may supply the excess luminosity required to overcome the deficit in single-component models, but this requires more fine-tuning and extreme parameters for the magnetar, as well as the assumption of efficient conversion of magnetar energy into radiation. As a result, we thus favor a single-input model where the reverse shock formed in a strong SN ejecta–circumstellar matter interaction following a very powerful core-collapse SN explosion can supply the luminosity needed to reproduce the late-time UV-bright plateau.« less

Complex dynamics in a simple model of pulsations for super-asymptotic giant branch stars.

PubMed

Munteanu, Andreea; Garcia-Berro, Enrique; Jose, Jordi; Petrisor, Emilia

2002-06-01

When intermediate mass stars reach their last stages of evolution they show pronounced oscillations. This phenomenon happens when these stars reach the so-called asymptotic giant branch (AGB), which is a region of the Hertzsprung-Russell diagram located at about the same region of effective temperatures but at larger luminosities than those of regular giant stars. The period of these oscillations depends on the mass of the star. There is growing evidence that these oscillations are highly correlated with mass loss and that, as the mass loss increases, the pulsations become more chaotic. In this paper we study a simple oscillator which accounts for the observed properties of this kind of stars. This oscillator was first proposed and studied in Icke et al. [Astron. Astrophys. 258, 341 (1992)] and we extend their study to the region of more massive and luminous stars -the region of super-AGB stars. The oscillator consists of a periodic nonlinear perturbation of a linear Hamiltonian system. The formalism of dynamical systems theory has been used to explore the associated Poincare map for the range of parameters typical of those stars. We have studied and characterized the dynamical behavior of the oscillator as the parameters of the model are varied, leading us to explore a sequence of local and global bifurcations. Among these, a tripling bifurcation is remarkable, which allows us to show that the Poincare map is a nontwist area preserving map. Meandering curves, hierarchical-islands traps and sticky orbits also show up. We discuss the implications of the stickiness phenomenon in the evolution and stability of the super-AGB stars. (c) 2002 American Institute of Physics.

Combining the Complete Active Space Self-Consistent Field Method and the Full Configuration Interaction Quantum Monte Carlo within a Super-CI Framework, with Application to Challenging Metal-Porphyrins.

PubMed

Li Manni, Giovanni; Smart, Simon D; Alavi, Ali

2016-03-08

A novel stochastic Complete Active Space Self-Consistent Field (CASSCF) method has been developed and implemented in the Molcas software package. A two-step procedure is used, in which the CAS configuration interaction secular equations are solved stochastically with the Full Configuration Interaction Quantum Monte Carlo (FCIQMC) approach, while orbital rotations are performed using an approximated form of the Super-CI method. This new method does not suffer from the strong combinatorial limitations of standard MCSCF implementations using direct schemes and can handle active spaces well in excess of those accessible to traditional CASSCF approaches. The density matrix formulation of the Super-CI method makes this step independent of the size of the CI expansion, depending exclusively on one- and two-body density matrices with indices restricted to the relatively small number of active orbitals. No sigma vectors need to be stored in memory for the FCIQMC eigensolver--a substantial gain in comparison to implementations using the Davidson method, which require three or more vectors of the size of the CI expansion. Further, no orbital Hessian is computed, circumventing limitations on basis set expansions. Like the parent FCIQMC method, the present technique is scalable on massively parallel architectures. We present in this report the method and its application to the free-base porphyrin, Mg(II) porphyrin, and Fe(II) porphyrin. In the present study, active spaces up to 32 electrons and 29 orbitals in orbital expansions containing up to 916 contracted functions are treated with modest computational resources. Results are quite promising even without accounting for the correlation outside the active space. The systems here presented clearly demonstrate that large CASSCF calculations are possible via FCIQMC-CASSCF without limitations on basis set size.

Molecular line study of massive star-forming regions from the Red MSX Source survey

NASA Astrophysics Data System (ADS)

Yu, Naiping; Wang, Jun-Jie

2014-05-01

In this paper, we have selected a sample of massive star-forming regions from the Red MSX Source survey, in order to study star formation activities (mainly outflow and inflow signatures). We have focused on three molecular lines from the Millimeter Astronomy Legacy Team Survey at 90 GHz: HCO+(1-0), H13CO+(1-0) and SiO(2-1). According to previous observations, our sources can be divided into two groups: nine massive young stellar object candidates (radio-quiet) and 10 H II regions (which have spherical or unresolved radio emissions). Outflow activities have been found in 11 sources, while only three show inflow signatures in all. The high outflow detection rate means that outflows are common in massive star-forming regions. The inflow detection rate was relatively low. We suggest that this was because of the beam dilution of the telescope. All three inflow candidates have outflow(s). The outward radiation and thermal pressure from the central massive star(s) do not seem to be strong enough to halt accretion in G345.0034-00.2240. Our simple model of G318.9480-00.1969 shows that it has an infall velocity of about 1.8 km s-1. The spectral energy distribution analysis agrees our sources are massive and intermediate-massive star formation regions.

Analysis of spatial autocorrelation patterns of heavy and super-heavy rainfall in Iran

NASA Astrophysics Data System (ADS)

Rousta, Iman; Doostkamian, Mehdi; Haghighi, Esmaeil; Ghafarian Malamiri, Hamid Reza; Yarahmadi, Parvane

2017-09-01

Rainfall is a highly variable climatic element, and rainfall-related changes occur in spatial and temporal dimensions within a regional climate. The purpose of this study is to investigate the spatial autocorrelation changes of Iran's heavy and super-heavy rainfall over the past 40 years. For this purpose, the daily rainfall data of 664 meteorological stations between 1971 and 2011 are used. To analyze the changes in rainfall within a decade, geostatistical techniques like spatial autocorrelation analysis of hot spots, based on the Getis-Ord G i statistic, are employed. Furthermore, programming features in MATLAB, Surfer, and GIS are used. The results indicate that the Caspian coast, the northwest and west of the western foothills of the Zagros Mountains of Iran, the inner regions of Iran, and southern parts of Southeast and Northeast Iran, have the highest likelihood of heavy and super-heavy rainfall. The spatial pattern of heavy rainfall shows that, despite its oscillation in different periods, the maximum positive spatial autocorrelation pattern of heavy rainfall includes areas of the west, northwest and west coast of the Caspian Sea. On the other hand, a negative spatial autocorrelation pattern of heavy rainfall is observed in central Iran and parts of the east, particularly in Zabul. Finally, it is found that patterns of super-heavy rainfall are similar to those of heavy rainfall.

Extreme Transients in the High Energy Universe

NASA Technical Reports Server (NTRS)

Kouveliotou, Chryssa

2013-01-01

The High Energy Universe is rich in diverse populations of objects spanning the entire cosmological (time)scale, from our own present-day Milky Way to the re-ionization epoch. Several of these are associated with extreme conditions irreproducible in laboratories on Earth. Their study thus sheds light on the behavior of matter under extreme conditions, such as super-strong magnetic fields (in excess of 10^14 G), high gravitational potentials (e.g., Super Massive Black Holes), very energetic collimated explosions resulting in relativistic jet flows (e.g., Gamma Ray Bursts, exceeding 10^53 ergs). In the last thirty years, my work has been mostly focused on two apparently different but potentially linked populations of such transients: magnetars (highly magnetized neutron stars) and Gamma Ray Bursts (strongly beamed emission from relativistic jets), two populations that constitute unique astrophysical laboratories, while also giving us the tools to probe matter conditions in the Universe to redshifts beyond z=10, when the first stars and galaxies were assembled. I did not make this journey alone I have either led or participated in several international collaborations studying these phenomena in multi-wavelength observations; solitary perfection is not sufficient anymore in the world of High Energy Astrophysics. I will describe this journey, present crucial observational breakthroughs, discuss key results and muse on the future of this field.

The X-Ray Globular Cluster Population in NGC 1399

NASA Technical Reports Server (NTRS)

Angelini, Lorella; Loewenstein, Michael; Mushotzky, Richard F.; White, Nicholas E. (Technical Monitor)

2001-01-01

We report on X-ray sources detected in the Chandra images of the elliptical galaxy NGC 1399 and identified with globular clusters (GCs). The 8'x 8' Chandra image shows that a large fraction of the 2-10 keV X-ray emission is resolved into point sources, with a luminosity threshold of 5 x 10 (exp 37) ergs s-1. These sources are most likely Low Mass X-ray Binaries (LMXBs). More than 70% of the X-ray sources, in a region imaged by Hubble Space Telescope (HST), are located within GCs. Many of these sources have super-Eddington luminosity (for an accreting neutron star) and their average luminosity is higher than the remaining sources. This association suggests that, in giant elliptical galaxies, luminous X-ray binaries preferentially form in GCs. The spectral properties of the GC and non-GC sources are in most cases similar to those of LMXBs in our galaxy. Two of the brightest sources, one of which is in GC, have a much softer spectra as seen in the high state black hole. The "apparent" super-Eddington luminosity in many cases may be due to multiple LMXB systems within individual GC, but with some of the most extreme luminous systems containing massive black holes.

Search for Neutrinos from Annihilation of Captured Low-Mass Dark Matter Particles in the Sun by Super-Kamiokande

NASA Astrophysics Data System (ADS)

Choi, K.; Abe, K.; Haga, Y.; Hayato, Y.; Iyogi, K.; Kameda, J.; Kishimoto, Y.; Miura, M.; Moriyama, S.; Nakahata, M.; Nakano, Y.; Nakayama, S.; Sekiya, H.; Shiozawa, M.; Suzuki, Y.; Takeda, A.; Tomura, T.; Wendell, R. A.; Irvine, T.; Kajita, T.; Kametani, I.; Kaneyuki, K.; Lee, K. P.; Nishimura, Y.; Okumura, K.; McLachlan, T.; Labarga, L.; Kearns, E.; Raaf, J. L.; Stone, J. L.; Sulak, L. R.; Berkman, S.; Tanaka, H. A.; Tobayama, S.; Goldhaber, M.; Carminati, G.; Kropp, W. R.; Mine, S.; Renshaw, A.; Smy, M. B.; Sobel, H. W.; Ganezer, K. S.; Hill, J.; Hong, N.; Kim, J. Y.; Lim, I. T.; Akiri, T.; Himmel, A.; Scholberg, K.; Walter, C. W.; Wongjirad, T.; Ishizuka, T.; Tasaka, S.; Jang, J. S.; Learned, J. G.; Matsuno, S.; Smith, S. N.; Hasegawa, T.; Ishida, T.; Ishii, T.; Kobayashi, T.; Nakadaira, T.; Nakamura, K.; Oyama, Y.; Sakashita, K.; Sekiguchi, T.; Tsukamoto, T.; Suzuki, A. T.; Takeuchi, Y.; Bronner, C.; Hirota, S.; Huang, K.; Ieki, K.; Ikeda, M.; Kikawa, T.; Minamino, A.; Nakaya, T.; Suzuki, K.; Takahashi, S.; Fukuda, Y.; Itow, Y.; Mitsuka, G.; Mijakowski, P.; Hignight, J.; Imber, J.; Jung, C. K.; Yanagisawa, C.; Ishino, H.; Kibayashi, A.; Koshio, Y.; Mori, T.; Sakuda, M.; Yano, T.; Kuno, Y.; Tacik, R.; Kim, S. B.; Okazawa, H.; Choi, Y.; Nishijima, K.; Koshiba, M.; Totsuka, Y.; Yokoyama, M.; Martens, K.; Marti, Ll.; Vagins, M. R.; Martin, J. F.; de Perio, P.; Konaka, A.; Wilking, M. J.; Chen, S.; Zhang, Y.; Wilkes, R. J.; Super-Kamiokande Collaboration

2015-04-01

Super-Kamiokande (SK) can search for weakly interacting massive particles (WIMPs) by detecting neutrinos produced from WIMP annihilations occurring inside the Sun. In this analysis, we include neutrino events with interaction vertices in the detector in addition to upward-going muons produced in the surrounding rock. Compared to the previous result, which used the upward-going muons only, the signal acceptances for light (few-GeV /c2-200 -GeV /c2 ) WIMPs are significantly increased. We fit 3903 days of SK data to search for the contribution of neutrinos from WIMP annihilation in the Sun. We found no significant excess over expected atmospheric-neutrino background and the result is interpreted in terms of upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel. We set the current best limits on the spin-dependent WIMP-proton cross section for WIMP masses below 200 GeV /c2 (at 10 GeV /c2 , 1.49 ×10-39 cm2 for χ χ →b b ¯ and 1.31 ×10-40 cm2 for χ χ →τ+τ- annihilation channels), also ruling out some fraction of WIMP candidates with spin-independent coupling in the few-GeV /c2 mass range.

Mobility Data Analytics Center.

DOT National Transportation Integrated Search

2016-01-01

Mobility Data Analytics Center aims at building a centralized data engine to efficiently manipulate : large-scale data for smart decision making. Integrating and learning the massive data are the key to : the data engine. The ultimate goal of underst...

The Core-Collapse Supernova-Black Hole Connection

NASA Astrophysics Data System (ADS)

O'Connor, Evan

The death of a massive star is typically associated with a bright optical transient known as a core-collapse supernova. However, there is growing evidence that not all massive stars end their lives with a brillant optical display, but rather in a whimper. These failed supernovae, or unnovae, result from the central engine failing to turn the initial implosion of the iron core into an explosion that launches the supernova shock wave, unbinds the majority of the star, and creates the supernova as we know it. In these unnovae, the failure of the central engine is soon followed by the collapse of the would-be neutron star into a stellar mass black hole. Instead of the bright optical display following successful supernovae, little to no optical emission is expected from typical failed supernovae as most of the material quietly accretes onto the black hole. This makes the hunt for failed supernovae difficult. In this chapter for the Handbook of Supernovae, I present the growing observational evidence for failed supernovae and discuss the current theoretical understanding of how and in what stars the supernova central engine fails.

Hubble peers inside a celestial geode

NASA Astrophysics Data System (ADS)

2004-08-01

celestial geode hi-res Size hi-res: 148 Kb Credits: ESA/NASA, Yäel Nazé (University of Liège, Belgium) and You-Hua Chu (University of Illinois, Urbana, USA) Hubble peers inside a celestial geode In this unusual image, the NASA/ESA Hubble Space Telescope captures a rare view of the celestial equivalent of a geode - a gas cavity carved by the stellar wind and intense ultraviolet radiation from a young hot star. Real geodes are handball-sized, hollow rocks that start out as bubbles in volcanic or sedimentary rock. Only when these inconspicuous round rocks are split in half by a geologist, do we get a chance to appreciate the inside of the rock cavity that is lined with crystals. In the case of Hubble's 35 light-year diameter ‘celestial geode’ the transparency of its bubble-like cavity of interstellar gas and dust reveals the treasures of its interior. Low resolution version (JPG format) 148 Kb High resolution version (TIFF format) 1929 Kb Acknowledgment: This image was created with the help of the ESA/ESO/NASA Photoshop FITS Liberator. Real geodes are handball-sized, hollow rocks that start out as bubbles in volcanic or sedimentary rock. Only when these inconspicuous round rocks are split in half by a geologist, do we get a chance to appreciate the inside of the rock cavity that is lined with crystals. In the case of Hubble's 35 light-year diameter ‘celestial geode’ the transparency of its bubble-like cavity of interstellar gas and dust reveals the treasures of its interior. The object, called N44F, is being inflated by a torrent of fast-moving particles (what astronomers call a 'stellar wind') from an exceptionally hot star (the bright star just below the centre of the bubble) once buried inside a cold dense cloud. Compared with our Sun (which is losing mass through the so-called 'solar wind'), the central star in N44F is ejecting more than a 100 million times more mass per second and the hurricane of particles moves much faster at 7 million km per hour (as opposed to less than 1.5 million km per hour for our Sun). Because the bright central star does not exist in empty space but is surrounded by an envelope of gas, the stellar wind collides with this gas, pushing it out, like a snow plough. This forms a bubble, whose striking structure is clearly visible in the crisp Hubble image. The nebula N44F is one of a handful of known interstellar bubbles. Bubbles like these have been seen around evolved massive stars (called 'Wolf-Rayet stars'), and also around clusters of stars (where they are called 'super-bubbles'). But they have rarely been viewed around isolated stars, as is the case here. On closer inspection N44F harbours additional surprises. The interior wall of its gaseous cavity is lined with several four to eight light-year high finger-like columns of cool dust and gas. (The structure of these 'columns' is similar to the Eagle Nebula’s iconic 'Pillars of Creation' photographed by Hubble a decade ago, and is seen in a few other nebulae as well). The fingers are created by a blistering ultraviolet radiation from the central star. Like wind socks caught in a gale, they point in the direction of the energy flow. These pillars look small in this image only because they are much farther away from us then the Eagle Nebula’s pillars. N44F is located about 160 000 light-years in the neighbouring dwarf galaxy the Large Magellanic Cloud, in the direction of the southern constellation Dorado. N44F is part of the larger N44 complex, which contains a large super-bubble, blown out by the combined action of stellar winds and multiple supernova explosions. N44 itself is roughly 1000 light-years across. Several compact star-forming regions, including N44F, are found along the rim of the central super-bubble. This image was taken with Hubble's Wide Field Planetary Camera 2, using filters that isolate light emitted by sulphur (shown in blue, a 1200-second exposure) and hydrogen gas (shown in red, a 1000-second exposure).

Growth and evolution of satellites in a Jovian massive disc

NASA Astrophysics Data System (ADS)

Moraes, R. A.; Kley, W.; Vieira Neto, E.

2018-03-01

The formation of satellite systems in circum-planetary discs is considered to be similar to the formation of rocky planets in a proto-planetary disc, especially super-Earths. Thus, it is possible to use systems with large satellites to test formation theories that are also applicable to extrasolar planets. Furthermore, a better understanding of the origin of satellites might yield important information about the environment near the growing planet during the last stages of planet formation. In this work, we investigate the formation and migration of the Jovian satellites through N-body simulations. We simulated a massive, static, low-viscosity, circum-planetary disc in agreement with the minimum mass sub-nebula model prescriptions for its total mass. In hydrodynamic simulations, we found no signs of gaps, therefore type II migration is not expected. Hence, we used analytic prescriptions for type I migration, eccentricity and inclination damping, and performed N-body simulations with damping forces added. Detailed parameter studies showed that the number of final satellites is strong influenced by the initial distribution of embryos, the disc temperature, and the initial gas density profile. For steeper initial density profiles, it is possible to form systems with multiple satellites in resonance while a flatter profile favours the formation of satellites close to the region of the Galilean satellites. We show that the formation of massive satellites such as Ganymede and Callisto can be achieved for hotter discs with an aspect ratio of H/r ˜ 0.15 for which the ice line was located around 30RJ.

The Eta Carinae Homunculus in Full 3D with X-Shooter and Shape

NASA Technical Reports Server (NTRS)

Steffen, Wolfgang; Teodoro, Mairan; Madura, Thomas I.; Groh, Jose H.; Gull, Theodore R.; Mehner, Andrea; Corcoran, Michael F.; Damineli, Augusto; Hamaguchi, Kenji

2014-01-01

Massive stars like Eta Carinae are extremely rare in comparison to stars such as the Sun, and currently we know of only a handful of stars with masses of more than 100 solar mass in the Milky Way. Such massive stars were much more frequent in the early history of the Universe and had a huge impact on its evolution. Even among this elite club, Eta Car is outstanding, in particular because of its giant eruption around 1840 that produced the beautiful bipolar nebula now known as the Homunculus. In this study, we used detailed spatio-kinematic information obtained from X-shooter spectra to reconstruct the 3D structure of the Homunculus. The small-scale features suggest that the central massive binary played a significant role in shaping the Homunculus.

Coronagraphic imaging of circumstellar material around evolved massive stars

NASA Astrophysics Data System (ADS)

Lomax, Jamie R.; Levesque, Emily; Wisniewski, John

2018-01-01

While many astronomical subfields (e.g. the solar, exoplanet, and disk communities) have been using coronagraphy to combat contrast ratio problems for years, the use of coronagraphic imaging techniques to probe the circumstellar environments of massive stars has been surprisingly underutilized. While current extreme adaptive optics coronagraphic imaging systems (e.g. GPI on Gemini South, SPHERE at the VLT, and SCExAO at Subaru) were built for the sole purpose of detecting exoplanets, their ability to provide large contrast ratios and small inner working angles means they can detect gas, dust, and companions that are closer to the central star than ever before. In this poster we present pilot studies of evolved massive stars using several coronagraphic imaging systems and summarize potential science gains this technique might provide.

On the curious spectrum of duality invariant higher-derivative gravity

DOE PAGES

Hohm, Olaf; Naseer, Usman; Zwiebach, Barton

2016-08-31

Here, we analyze the spectrum of the exactly duality and gauge invariant higher-derivative double field theory. While this theory is based on a chiral CFT and does not correspond to a standard string theory, our analysis illuminates a number of issues central in string theory. The full quadratic action is rewritten as a two-derivative theory with additional fields. This allows for a simple analysis of the spectrum, which contains two massive spin-2 ghosts and massive scalars, in addition to the massless fields. Moreover, in this formulation, the massless or tensionless limit α' → ∞ is non-singular and leads to anmore » enhanced gauge symmetry. We show that the massive modes can be integrated out exactly at the quadratic level, leading to an infinite series of higher-derivative corrections. Lastly, we present a ghost-free massive extension of linearized double field theory, which employs a novel mass term for the dilaton and metric.« less

Macrophages and the Viral Dissemination Super Highway

PubMed Central

Klepper, Arielle; Branch, Andrea D

2016-01-01

Monocytes and macrophages are key components of the innate immune system yet they are often the victims of attack by infectious agents. This review examines the significance of viral infection of macrophages. The central hypothesis is that macrophage tropism enhances viral dissemination and persistence, but these changes may come at the cost of reduced replication in cells other than macrophages. PMID:26949751

Whole-rock and sulfide-mineral geochemical data for samples from volcanogenic massive sulfide deposits of the Bonnifield district, east-central Alaska

USGS Publications Warehouse

Dusel-Bacon, Cynthia; Slack, John F.; Koenig, Alan E.; Foley, Nora K.; Oscarson, Robert L.; Gans, Kathleen D.

2011-01-01

This Open-File Report presents geochemical data for outcrop and drill-core samples from volcanogenic massive sulfide deposits and associated metaigneous and metasedimentary rocks in the Wood River area of the Bonnifield mining district, northern Alaska Range, east-central Alaska. The data consist of major- and trace-element whole-rock geochemical analyses, and major- and trace-element analyses of sulfide minerals determined by electron microprobe and laser ablation—inductively coupled plasma—mass spectrometry (LA-ICP-MS) techniques. The PDF consists of text, appendix explaining the analytical methods used for the analyses presented in the data tables, a sample location map, and seven data tables. The seven tables are also available as spreadsheets in several file formats. Descriptions and discussions of the Bonnifield deposits are given in Dusel-Bacon and others (2004, 2005, 2006, 2007, 2010).

The nature of the central parsec of the Galaxy

NASA Technical Reports Server (NTRS)

Lacy, J. H.; Townes, C. H.; Hollenbach, D. J.

1982-01-01

Observations of infrared fine-structure line emission from compact clouds of ionized gas in the galactic center have been reported by Lacy et al (1979, 1980). These observations suggest the existence of a central black hole of nearly 3,000,000 solar masses and require mechanisms to generate, ionize, and dispose of the gas clouds. It is found that the best model to fulfill these requirements involves cloud generation through disruption of red giants by stellar collisions, ionization by a population of stars which is affected either by enhanced metal abundances or the death of the most massive stars, and gas disposal by star formation. Although the existence of a massive black hole cannot be ruled out, it would play no necessary role in this model and may cause the tidal disruption of stars at a rate such that their accretion into the black hole would produce more radiation than is observed.

A Mega-fire event in Central Russia: fire weather, radiative, and optical properties of the atmosphere, and consequences for subboreal forest plants

Treesearch

Nataly Y. Chubarova; Nickolay G. Prilepsky; Alexei N. Rublev; Allen R. Riebau

2009-01-01

In 2002, a major drought and prolonged high temperatures occurred in central Russia that resulted in unprecedented wildland fires. These fires occurred under extreme fire danger conditions and were impossible for the Russian authorities to extinguish. It is perhaps somewhat unique that the fires were first burning peat bogs and later forests, causing very massive smoke...

Central Nervous System Symptoms Due to Transient Methemoglobinemia in a Child With G6PD Deficiency.

PubMed

Sharma, Shreya; Srinivasaraghavan, Rangan; Krishnamurthy, Sriram

2017-01-01

The authors herein report a 5-year-old child who presented with massive hemolysis, irritability, and cyanosis. The final diagnosis was glucose-6-phosphate dehydrogenase deficiency with associated central nervous system symptoms probably because of concomitantly acquired methemoglobinemia following oxidant drug exposure. The associated acute-onset anemia would have contributed to the development of cerebral anoxia-related seizures and encephalopathy.

Early-type Galaxy Spin Evolution in the Horizon-AGN Simulation

NASA Astrophysics Data System (ADS)

Choi, Hoseung; Yi, Sukyoung K.; Dubois, Yohan; Kimm, Taysun; Devriendt, Julien. E. G.; Pichon, Christophe

2018-04-01

Using the Horizon-AGN simulation data, we study the relative role of mergers and environmental effects in shaping the spin of early-type galaxies (ETGs) after z ≃ 1. We follow the spin evolution of 10,037 color-selected ETGs more massive than {10}10 {M}ȯ that are divided into four groups: cluster centrals (3%), cluster satellites (33%), group centrals (5%), and field ETGs (59%). We find a strong mass dependence of the slow rotator fraction, f SR, and the mean spin of massive ETGs. Although we do not find a clear environmental dependence of f SR, a weak trend is seen in the mean value of the spin parameter driven by the satellite ETGs as they gradually lose their spin as their environment becomes denser. Galaxy mergers appear to be the main cause of total spin changes in 94% of the central ETGs of halos with {M}vir}> {10}12.5 {M}ȯ , but only 22% of satellite and field ETGs. We find that non-merger-induced tidal perturbations better correlate with the galaxy spin down in satellite ETGs than in mergers. Given that the majority of ETGs are not central in dense environments, we conclude that non-merger tidal perturbation effects played a key role in the spin evolution of ETGs observed in the local (z < 1) universe.

Precise weak lensing constraints from deep high-resolution Ks images: VLT/HAWK-I analysis of the super-massive galaxy cluster RCS2 J 232727.7-020437 at z = 0.70

NASA Astrophysics Data System (ADS)

Schrabback, Tim; Schirmer, Mischa; van der Burg, Remco F. J.; Hoekstra, Henk; Buddendiek, Axel; Applegate, Douglas; Bradač, Maruša; Eifler, Tim; Erben, Thomas; Gladders, Michael D.; Hernández-Martín, Beatriz; Hildebrandt, Hendrik; Hoag, Austin; Klaes, Dominik; von der Linden, Anja; Marchesini, Danilo; Muzzin, Adam; Sharon, Keren; Stefanon, Mauro

2018-03-01

We demonstrate that deep good-seeing VLT/HAWK-I Ks images complemented with g + z-band photometry can yield a sensitivity for weak lensing studies of massive galaxy clusters at redshifts 0.7 ≲ z ≲ 1.1, which is almost identical to the sensitivity of HST/ACS mosaics of single-orbit depth. Key reasons for this good performance are the excellent image quality frequently achievable for Ks imaging from the ground, a highly effective photometric selection of background galaxies, and a galaxy ellipticity dispersion that is noticeably lower than for optically observed high-redshift galaxy samples. Incorporating results from the 3D-HST and UltraVISTA surveys we also obtained a more accurate calibration of the source redshift distribution than previously achieved for similar optical weak lensing data sets. Here we studied the extremely massive galaxy cluster RCS2 J232727.7-020437 (z = 0.699), combining deep VLT/HAWK-I Ks images (point spread function with a 0.''35 full width at half maximum) with LBT/LBC photometry. The resulting weak lensing mass reconstruction suggests that the cluster consists of a single overdensity, which is detected with a peak significance of 10.1σ. We constrained the cluster mass to M200c/(1015 M⊙) = 2.06-0.26+0.28(stat.) ± 0.12(sys.) assuming a spherical Navarro, Frenk & White model and simulation-based priors on the concentration, making it one of the most massive galaxy clusters known in the z ≳ 0.7 Universe. We also cross-checked the HAWK-I measurements through an analysis of overlapping HST/ACS images, yielding fully consistent estimates of the lensing signal. Based on observations conducted with the ESO Very Large Telescope, the Large Binocular Telescope, and the NASA/ESA Hubble Space Telescope, as detailed in the acknowledgements.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yagi, Kent; Tanaka, Takahiro; Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502

We calculate how strongly one can put constraints on alternative theories of gravity such as Brans-Dicke and massive graviton theories with LISA. We consider inspiral gravitational waves from a compact binary composed of a neutron star and an intermediate mass black hole in Brans-Dicke (BD) theory and that composed of a super massive black hole in massive graviton theories. We use the restricted second post-Newtonian waveforms including the effects of spins. We also take both precession and eccentricity of the orbit into account. For simplicity, we set the fiducial value for the spin of one of the binary constituents tomore » zero so that we can apply the approximation called simple precession. We perform the Monte Carlo simulations of 10{sup 4} binaries, estimating the determination accuracy of binary parameters including the BD parameter {omega}{sub BD} and the Compton wavelength of graviton {lambda}{sub g} for each binary using the Fisher matrix method. We find that including both the spin-spin coupling {sigma} and the eccentricity e into the binary parameters reduces the determination accuracy by an order of magnitude for the Brans-Dicke case, while it has less influence on massive graviton theories. On the other hand, including precession enhances the constraint on {omega}{sub BD} only 20% but it increases the constraint on {lambda}{sub g} by several factors. Using a (1.4+1000)M{sub {center_dot}}neutron star/black hole binary of SNR={radical}(200), one can put a constraint {omega}{sub BD}>6944, while using a (10{sup 7}+10{sup 6})M{sub {center_dot}}black hole/black hole binary at 3 Gpc, one can put {lambda}{sub g}>3.10x10{sup 21} cm, on average. The latter is 4 orders of magnitude stronger than the one obtained from the solar system experiment. These results are consistent with previous results within uncontrolled errors and indicate that the effects of precession and eccentricity must be taken carefully in the parameter estimation analysis.« less

A Rare Encounter with Very Massive Stars in NGC 3125-A1

NASA Astrophysics Data System (ADS)

Wofford, Aida; Leitherer, Claus; Chandar, Rupali; Bouret, Jean-Claude

2014-02-01

Super star cluster A1 in the nearby starburst galaxy NGC 3125 is characterized by broad He II λ1640 emission (FWHM ~ 1200 km s-1) of unprecedented strength (equivalent width, EW = 7.1 ± 0.4 Å). Previous attempts to characterize the massive star content in NGC 3125-A1 were hampered by the low resolution of the UV spectrum and the lack of co-spatial panchromatic data. We obtained far-UV to near-IR spectroscopy of the two principal emitting regions in the galaxy with the Space Telescope Imaging Spectrograph and the Cosmic Origins Spectrograph on board the Hubble Space Telescope. We use these data to study three clusters in the galaxy, A1, B1, and B2. We derive cluster ages of 3-4 Myr, intrinsic reddenings of E(B - V) = 0.13, 0.15, and 0.13, and cluster masses of 1.7 × 105, 1.4 × 105, and 1.1 × 105 M ⊙, respectively. A1 and B2 show O V λ1371 absorption from massive stars, which is rarely seen in star-forming galaxies, and have Wolf-Rayet (WR) to O star ratios of N(WN5-6)/N(O) = 0.23 and 0.10, respectively. The high N(WN5-6)/N(O) ratio of A1 cannot be reproduced by models that use a normal initial mass function (IMF) and generic WR star line luminosities. We rule out that the extraordinary He II λ1640 emission and O V λ1371 absorption of A1 are due to an extremely flat upper IMF exponent, and suggest that they originate in the winds of very massive (>120 M ⊙) stars. In order to reproduce the properties of peculiar clusters such as A1, the present grid of stellar evolution tracks implemented in Starburst99 needs to be extended to masses >120 M ⊙.

Central Stars of Mid-Infrared Nebulae Discovered with Spitzer and WISE

NASA Astrophysics Data System (ADS)

Gvaramadze, V. V.; Kniazev, A. Y.

2017-02-01

Searches for compact mid-IR nebulae with the Spitzer Space Telescope and the Wide-field Infrared Survey Explorer (WISE), accompanied by spectroscopic observations of central stars of these nebulae led to the discovery of many dozens of massive stars at different evolutionary stages, of which the most numerous are candidate luminous blue variables (LBVs). In this paper, we give a census of candidate and confirmed Galactic LBVs revealed with Spitzer and WISE, and present some new results of spectroscopic observations of central stars of mid-IR nebulae.

GALEX Wide-field Ultraviolet Imaging of NGC 5128 (Centaurus-A)

NASA Technical Reports Server (NTRS)

Neff, S. G.; Shiminovich, D.; Martin, C. D.

2004-01-01

We present new wide-field ultraviolet (UV) observations of the nearby active galaxy NGC 5128 (Centaurus A). The GALEX images provide 3.5 sec - 5.5 sec resolution over a 1.2 degree field, in two broad bands (1350- 1800A and 1800-3000A, centered at 1550A and 2200A). We detect ultraviolet emission associated with the radio and X-ray jets in both bands, extending out to a distance of approx. 40kpc from the galaxy nucleus. We compare the radio, X-ray, and UV jets, and discuss the feasibility of jet-induced star formation. We show how the UV emission relates to the optical filaments: HI and CO clouds, stellar shells, X-ray arcs, and young star chains previously reported by other authors. In the central region of NGC 5128, we detect UV emission from young super-star-clusters and associated ionized gas located along the near edge and on the upper surface of the dusty warped disk. All of the UV emission in the galaxy appears to result from intense star formation in the disk; none appears to be associated with the old stellar population of the main galaxy body, and no UV emission from the AGN is detected. We estimate the numbers and ages of the massive young stars present, and the associated ionized gas masses. Finally, we compare Cen-A to high redshift radio galaxies which were much more numerous in the earlier universe. The GALEX satellite is a NASA Small Explorer, launched in April 2003. We gratefully acknowledge NASA's support for construction, operation, and science analysis for the GALEX mission.

The Cold Side of Galaxy Formation: Dense Gas Through Cosmic Time

NASA Astrophysics Data System (ADS)

Riechers, Dominik A.; ngVLA Galaxy Assembly through Cosmic Time Science Working Group, ngVLA Galaxy Ecosystems Science Working Group

2018-01-01

The processes that lead to the formation and evolution of galaxies throughout the history of the Universe involve the complex interplay between hierarchical merging of dark matter halos, accretion of primordial and recycled gas, transport of gas within galaxy disks, accretion onto central super-massive black holes, and the formation of molecular clouds which subsequently collapse and fragment. The resulting star formation and black hole accretion provide large sources of energy and momentum that light up galaxies and lead to feedback. The ngVLA will be key to further understand how gas is accreted onto galaxies, and the processes that regulate the growth of galaxies through cosmic history. It will reveal how and on which timescales star formation and black hole accretion impact the gas in galaxies, and how the physical properties and chemical state of the gas change as gas cycles between different phases for different galaxy populations over a broad range in redshifts. The ngVLA will have the capability to carry out unbiased, large cosmic volume surveys at virtually any redshift down to an order of magnitude lower gas masses than currently possible in the critical low-level CO lines, thus exposing the evolution of gaseous reservoirs from the earliest epochs to the peak of the cosmic history of star formation. It will also image routinely and systematically the sub-kiloparsec scale distribution and kinematic structure of molecular gas in both normal main-sequence galaxies and large starbursts. The ngVLA thus is poised to revolutionize our understanding of galaxy evolution through cosmic time.

Newly Discovered Be Stars in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Reid, W. A.

2016-11-01

The Large Magellanic Cloud (LMC) is a excellent laboratory in which to analyse and compare the distinctive characteristics of massive and luminous emission-line stars. In particular, the known and almost co-equal distance to all objects greatly assists the study of comparative luminosities. The original UKST Hα survey covering the central 25deg2 of the LMC revealed 518 Be stars, 413 of which were new discoveries. By extending the survey to cover the entire LMC area of 64 deg2, an additional 415 emission-line stars were identified. Most of the additions have now been spectroscopically observed, with the majority being confirmed as Be stars. The flux, equivalent width, and width at half maximum of the main emission-lines for each of the ˜800 spectroscopically observed LMC Be stars were measured in order to understand their elemental composition and the interaction of the extended circumstellar disk. After subtracting foreground or ambient dust and gas emission, 130 or 22% of B stars were classified as type B[e], characterized by the presence of forbidden emission lines such as [SII], [NII], [OIII] and [OII]. With de-reddened data, the first V-band and Hα luminosity functions were constructed for these stars in the LMC. The magnitudes were then compared using U, B, V, I, R, near-IR J, H, K and mid-IR photometry from the Magellanic Cloud Emission-Line Survey, SuperCOSMOS, 2MASS, and WISE where available. Correlations of varying strength between the optical, IR and Hα magnitudes are shown and discussed.