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.

Is there a cluster in the massive star forming region IRAS 20126+4104?

NASA Astrophysics Data System (ADS)

Montes, V. A.; Hofner, Peter; Anderson, C.; Rosero, V.

2017-03-01

A Chandra X-ray Observatory ACIS-I observation and a 6 cm continuum radio observation with the Karl G. Jansky Very Large Array (VLA) together with a multiwavelength study in infrared (2MASS and Spitzer) and optical (USNO-B1.0) shows an increasing surface density of X-ray sources toward the massive protostar. There are at least 43 YSOs within 1.2 pc distance from the massive protostar. This number is consistent with typical B-type stars clusters (Lada & Lada 2003).

The Birth of Disks Around Protostars

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-03-01

The dusty disks around young stars make the news regularly due to their appeal as the birthplace of early exoplanets. But how do disks like these first form and evolve around their newly born protostars? New observations from the Atacama Large Millimeter/submillimeter Array (ALMA) are helping us to better understand this process.Formation from CollapseStars are born from the gravitational collapse of a dense cloud of molecular gas. Long before they start fusing hydrogen at their centers when they are still just hot overdensities in the process of contracting we call them protostars. These low-mass cores are hidden at the hearts of the clouds of molecular gas from which they are born.Aerial image of the Atacama Large Millimeter/submillimeter Array. [EFE/Ariel Marinkovic]During this contraction phase, before a protostar transitions to a pre-main-sequence star (which it does by blowing away its outer gas envelope, halting the stars growth), much of the collapsing material will spin into a centrifugally supported Keplerian disk that surrounds the young protostar. Later, these circumstellar disks will become the birthplace for young planets something for which weve seen observational evidence in recent years.But how do these Keplerian disks which eventually have scales of hundreds of AU first form and grow around protostars? We need observations of these disks in their early stages of formation to understand their birth and evolution a challenging prospect, given the obscuring molecular gas that hides them at these stages. ALMA, however, is up to the task: it can peer through to the center of the gas clouds to see the emission from protostellar cores and their surroundings.ALMA observations of the protostar Lupus 3 MMS. The molecular outflows from the protostar are shown in panel a. Panel b shows the continuum emission, which has a compact component that likely traces a disk surrounding the protostar. [Adapted from Yen et al. 2017]New Disks Revealed?In a recent

The molecular inventory around protostars: water, organic molecules, and the missing oxygen problem

NASA Astrophysics Data System (ADS)

Neufeld, David A.

2018-06-01

Massive star formation is accompanied by significant chemical evolution in the surrounding interstellar gas. Here, grains are heated up and icy mantles evaporate, releasing a rich inventory of water and organic molecules into the gas-phase within “hot core” regions surrounding massive protostars. Because molecules on the grain surface present broad infrared features without rotational structure, only the most abundant molecules can be identified unambiguously in the solid phase; once released into the gas-phase, however, where they are free to rotate, the constituents of grain mantles can be identified easily by means of rotational spectroscopy at millimeter and submillimeter wavelengths or through rovibrational spectroscopy in the mid-infrared. While observations of pure-rotational emission lines provide a broad view of hot core chemistry, absorption line spectroscopy of rovibrational transitions can probe the very hottest material closest to the protostar. With access to the mid-infrared spectral region from above 99% of Earth’s water vapor, SOFIA provides a unique platform for high-resolution rovibrational spectroscopy of water and organic molecules, many of which have vibrational transitions in the 5 – 8 micron spectral region that is unobservable from the ground. High spectral resolution is essential for disentangling the rotational structure and providing reliable measurements of the molecular column densities and temperatures. Future SOFIA observations will help elucidate the inventory of water and organic molecules around young protostars, and can address a puzzle related to the “oxygen budget” in the interstellar medium: surprisingly, the main interstellar reservoirs of the third-most abundant element in the Universe have yet to be identified.

Multi-Wavelength Views of Protostars in IC 1396

NASA Image and Video Library

2003-12-18

This archival image from 2003 captured by NASA Spitzer Space Telescope captured the Elephant Trunk Nebula, an elongated dark globule within the emission nebula IC 1396 in the constellation of Cepheus.

Young Stellar Populations in MYStIX Star-forming Regions: Candidate Protostars

NASA Astrophysics Data System (ADS)

Romine, Gregory; Feigelson, Eric D.; Getman, Konstantin V.; Kuhn, Michael A.; Povich, Matthew S.

2016-12-01

The Massive Young Star-Forming Complex in Infrared and X-ray (MYStIX) project provides a new census on stellar members of massive star-forming regions within 4 kpc. Here the MYStIX Infrared Excess catalog and Chandra-based X-ray photometric catalogs are mined to obtain high-quality samples of Class I protostars using criteria designed to reduce extragalactic and Galactic field star contamination. A total of 1109 MYStIX Candidate Protostars (MCPs) are found in 14 star-forming regions. Most are selected from protoplanetary disk infrared excess emission, but 20% are found from their ultrahard X-ray spectra from heavily absorbed magnetospheric flare emission. Two-thirds of the MCP sample is newly reported here. The resulting samples are strongly spatially associated with molecular cores and filaments on Herschel far-infrared maps. This spatial agreement and other evidence indicate that the MCP sample has high reliability with relatively few “false positives” from contaminating populations. But the limited sensitivity and sparse overlap among the infrared and X-ray subsamples indicate that the sample is very incomplete with many “false negatives.” Maps, tables, and source descriptions are provided to guide further study of star formation in these regions. In particular, the nature of ultrahard X-ray protostellar candidates without known infrared counterparts needs to be elucidated.

YOUNG STELLAR POPULATIONS IN MYStIX STAR-FORMING REGIONS: CANDIDATE PROTOSTARS

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

Romine, Gregory; Feigelson, Eric D.; Getman, Konstantin V.

The Massive Young Star-Forming Complex in Infrared and X-ray (MYStIX) project provides a new census on stellar members of massive star-forming regions within 4 kpc. Here the MYStIX Infrared Excess catalog and Chandra -based X-ray photometric catalogs are mined to obtain high-quality samples of Class I protostars using criteria designed to reduce extragalactic and Galactic field star contamination. A total of 1109 MYStIX Candidate Protostars (MCPs) are found in 14 star-forming regions. Most are selected from protoplanetary disk infrared excess emission, but 20% are found from their ultrahard X-ray spectra from heavily absorbed magnetospheric flare emission. Two-thirds of the MCP sample ismore » newly reported here. The resulting samples are strongly spatially associated with molecular cores and filaments on Herschel far-infrared maps. This spatial agreement and other evidence indicate that the MCP sample has high reliability with relatively few “false positives” from contaminating populations. But the limited sensitivity and sparse overlap among the infrared and X-ray subsamples indicate that the sample is very incomplete with many “false negatives.” Maps, tables, and source descriptions are provided to guide further study of star formation in these regions. In particular, the nature of ultrahard X-ray protostellar candidates without known infrared counterparts needs to be elucidated.« less

Protostars and Planets VI

NASA Astrophysics Data System (ADS)

Beuther, Henrik; Klessen, Ralf S.; Dullemond, Cornelis P.; Henning, Thomas

The Protostars and Planets book and conference series has been a long-standing tradition that commenced with the first meeting led by Tom Gehrels and held in Tucson, Arizona, in 1978. The goal then, as it still is today, was to bridge the gap between the fields of star and planet formation as well as the investigation of planetary systems and planets. As Tom Gehrels stated in the preface to the first Protostars and Planets book, "Cross-fertilization of information and understanding is bound to occur when investigators who are familiar with the stellar and interstellar phases meet with those who study the early phases of solar system formation." The central goal remained the same for the subsequent editions of the books and conferences Protostars and Planets II in 1984, Protostars and Planets III in 1990, Protostars and Planets IV in 1998, and Protostars and Planets V in 2005, but has now been greatly expanded by the flood of new discoveries in the field of exoplanet science. The original concept of the Protostars and Planets series also formed the basis for the sixth conference in the series, which took place on July 15-20, 2013. It was held for the first time outside of the United States in the bustling university town of Heidelberg, Germany. The meeting attracted 852 participants from 32 countries, and was centered around 38 review talks and more than 600 posters. The review talks were expanded to form the 38 chapters of this book, written by a total of 250 contributing authors. This Protostars and Planets volume reflects the current state-of-the-art in star and planet formation, and tightly connects the fields with each other. It is structured into four sections covering key aspects of molecular cloud and star formation, disk formation and evolution, planetary systems, and astrophysical conditions for life. All poster presentations from the conference can be found at www.ppvi.org. In the eight years that have passed since the fifth conference and book in the

The Cluster Environment of Two High-mass Protostars

NASA Astrophysics Data System (ADS)

Montes, Virginie; Hofner, Peter

2017-06-01

Characterizing the environment and stellar population in which high-mass stars form is an important step to decide between the main massive star formation theories. In the monolithic collapse model, the mass of the core will determine the final stellar mass (e.g., McKee & Tan 2003). In contrast, in the competitive accretion model (e.g., Bonnell & Bate 2006), the mass of the high-mass star is related to the properties of the cluster. As dynamical processes substantially affect the appearance of a cluster, we study early stages of high-mass star formation. These regions often show extended emission from hot dust at infrared wavelengths, which can cause difficulties to define the cluster. We use a multi-wavelength technique to study nearby high-mass star clusters, based on X-ray observations with the Chandra X-Ray Telescope, in conjunction with infrared data and VLA data. The technique relies on the fact that YSOs are particularly bright in X-ray and that contamination is relatively small. X-ray observations allow us to determine the cluster size. The cluster membership and YSOs classification is established using infrared identification of the X-ray sources, and color-color and color-magnitude diagrams.In this talk, I will present our findings on the cluster study of two high-mass star forming regions: IRAS 20126+4104 and IRAS 16562-3959. While most massive stars appear to be formed in rich a cluster environment, those two sources are candidates for the formation of massive stars in a relatively poor cluster. In contrast to what was found in previous studies (Qiu et al. 2008), the dominant B0-type protostar in IRAS 20126+4104 is associated with a small cluster of low-mass stars. I will also show our current work on IRAS 16562-3959, which contains one of the most luminous O-type protostars in the Galaxy. In the vicinity of this particularly interesting region there is a multitude of small clusters, for which I will present how their stellar population differ from the

Into the Darkness: Interstellar Extinction Near the Cepheus OB3 Molecular Cloud

NASA Astrophysics Data System (ADS)

Fitzpatrick, Edward L.; Jacklin, S.; Massa, D.

2014-01-01

We present the results of a followup investigation to a study performed by Massa and Savage (1984, ApJ, 279, 310) of the properties of UV interstellar extinction in the region of the Cepheus OB3 molecular cloud. That study was performed using UV photometry and spectro-photometry from the ANS and IUE satellites. We have extended this study into the IR, utilizing the uniform database of IR photometry available from the 2MASS project. This is a part of a larger program whose goal is to study the properties of extinction in localized regions, where we hope to find clues to dust grain growth and destruction processes through spatial correlations of extinction with distinct environmental properties. Similarly to Massa and Savage’s UV results, we find that the IR extinction properties on the Cepheus OB3 region vary systematically with the apparent proximity of the target stars to the molecular cloud. We also find that the UV extinction and the IR extinction are crudely correlated. The methodology leading to these results and their implications are discussed.

Luminosity variations of protostars at the Hayashi stage

NASA Astrophysics Data System (ADS)

Abdulmyanov, T. R.

2017-09-01

In the present paper, the luminosity variations of protostars at the Hayashi stage are considered. According to the density wave model, the luminosity of protostars will have significant variations throughout the Hayashi stage. The initial moments of the formation of protoplanetary rings of the Solar system and the luminosity of the protostar for these moments are obtained.

Searching for Young Stars in Cepheus C

NASA Astrophysics Data System (ADS)

Evans, Sam; Rebull, Luisa; Rutherford, Thomas; Stalnaker, Olivia; Taylor, John; Efsits, Gabriel; Harl, Linda; Keil, Shayna; Learman, Duncan; Leonard, Liam; Russell, Aaron

2018-01-01

We used archival Herschel Space Observatory data to search for young stellar objects (YSOs) in the Cepheus C region of the molecular cloud Cepheus OB3. Previous work by Gutermuth et al. (2009) identified 114 YSO candidates in this region based on Spitzer/IRAC data. Work by Orr et al. (2016) refined a list of approximately 300 young star candidates to 245 likely YSOs. Our initial search focused on longer infrared wavelength data – Herschel (70, 160, 250, 350, 500 μm) archival data and SCUBA (450, 850 μm) data from the literature (DiFrancesco et al. 2008). Through image inspection and catalog matching, we assembled a list of 54 candidate YSOs detected at wavelengths longer than 22 μm. For each source, we constructed a spectral energy distribution (SED) by aggregating available shorter wavelength data from the literature and assembling photometry from released PACS catalogs, preliminary SPIRE catalogs, and our own photometric measurements. We also created color-color and color-magnitude diagrams to see how these sources compared to each other, other populations of YSOs, and objects in extragalactic regions. Each source was then classified based on its SED shape and its locations on color-color and color-magnitude diagrams. From the initial list of 54 candidates, we suspect all are likely YSOs, some of which are very embedded; ~40% are likely SED Class I or 0. Approximately 20% of the 54 sources have not been previously identified. By beginning the investigation of YSOs in this region, we are adding to the body of YSO knowledge which can be used to understand the process of star formation. This research was made possible through the NASA/IPAC Teacher Archive Research Program (NITARP) and was funded by NASA Astrophysics Data Program.

Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud

NASA Astrophysics Data System (ADS)

Sheehan, Patrick D.; Eisner, Josh A.

2017-12-01

Class I protostars are thought to represent an early stage in the lifetime of protoplanetary disks, when they are still embedded in their natal envelope. Here we measure the disk masses of 10 Class I protostars in the Taurus Molecular Cloud to constrain the initial mass budget for forming planets in disks. We use radiative transfer modeling to produce synthetic protostar observations and fit the models to a multi-wavelength data set using a Markov Chain Monte Carlo fitting procedure. We fit these models simultaneously to our new Combined Array for Research in Millimeter-wave Astronomy 1.3 mm observations that are sensitive to the wide range of spatial scales that are expected from protostellar disks and envelopes so as to be able to distinguish each component, as well as broadband spectral energy distributions compiled from the literature. We find a median disk mass of 0.018 {M}ȯ on average, more massive than the Taurus Class II disks, which have median disk mass of ∼ 0.0025 {M}ȯ . This decrease in disk mass can be explained if dust grains have grown by a factor of 75 in grain size, indicating that by the Class II stage, at a few Myr, a significant amount of dust grain processing has occurred. However, there is evidence that significant dust processing has occurred even during the Class I stage, so it is likely that the initial mass budget is higher than the value quoted here.

Fission of Rapidly Rotating Protostars

NASA Astrophysics Data System (ADS)

Lozier, Jennifer L.; Michael, S.; Durisen, R. H.; Imamura, J. N.

2006-12-01

It has long been conjectured that close binary star systems might form through the fission of a rapidly rotating and contracting protostar (for a review see Durisen & Tohline 1985). Protostars that are axisymmetric beyond the point of dynamic bar-like mode instability do not fission (Imamura et al. 2000), but contracting non-axisymmetric protostars might encounter bifurcations of surface shape leading to fission. In addition, they may be susceptible to hydrodynamic instabilities, first described by Lebovitz & Lifschitz (1996), whose nonlinear effects are still unknown. We will present a series of hydrodynamic simulations of rapidly rotating polytropic protostars to investigate fission in contracting protostars. The initial model is an equilibrium configuration with T/|W| ≈ 0.14, where T is the rotational kinetic energy and W is the total gravitational energy. It is given a bar-like cos(2φ) density perturbation with an amplitude of .02, .10 or .25. These perturbed polytropes are then cooled by reducing the polytropic constant K where P = Kρ1+1/n. Here P is the pressure, ρ is the density and n is the polytropic index, here chosen to be 3/2. As the polytrope contracts, we find no strong signal of a growing instability. All simulations evolve through to the dynamic bar-like mode instability point at T/|W|≈ 0.27 and produce a ring around a bar, not a binary. However, there is some indication of amplitude growth at a T/|W|≈0.22. We are investigating this growth further with follow-up simulations that start at an equilibrium model with a T/|W| ≈ 0.22. This enables us to study growth in this regime with higher resolution and slower contraction rates. This work has been supported by the National Science Foundation through grant AST-0452975 (astronomy REU program to Indiana University).

OH maser proper motions in Cepheus A

NASA Astrophysics Data System (ADS)

Migenes, V.; Cohen, R. J.; Brebner, G. C.

1992-02-01

MERLIN measurements made between 1982 and 1989 reveal proper motions of OH masers in the source Cepheus A. The proper motions are typically a few milliarcsec per year, and are mainly directed away from the central H II regions. Statistical analysis of the data suggests an expansion time-scale of some 300 yr. The distance of the source implied by the proper motions is 320+140/-80 pc, assuming that the expansion is isotropic. The proper motions can be reconciled with the larger distance of 730 pc which is generally accepted, provided that the masers are moving at large angles to the line of sight. The expansion time-scale agrees with that of the magnetic field decay recently reported by Cohen, et al. (1990).

CO outflows from high-mass Class 0 protostars in Cygnus-X

NASA Astrophysics Data System (ADS)

Duarte-Cabral, A.; Bontemps, S.; Motte, F.; Hennemann, M.; Schneider, N.; André, Ph.

2013-10-01

Context. The earliest phases of the formation of high-mass stars are not well known. It is unclear whether high-mass cores in monolithic collapse exist or not, and what the accretion process and origin of the material feeding the precursors of high-mass stars are. As outflows are natural consequences of the accretion process, they represent one of the few (indirect) tracers of accretion. Aims: We aim to search for individual outflows from high-mass cores in Cygnus X and to study the characteristics of the detected ejections. We compare these to what has been found for the low-mass protostars, to understand how ejection and accretion change and behave with final stellar mass. Methods: We used CO (2-1) PdBI observations towards six massive dense clumps, containing a total of 9 high-mass cores. We estimated the bolometric luminosities and masses of the 9 high-mass cores and measured the energetics of outflows. We compared our sample to low-mass objects studied in the literature and developed simple evolutionary models to reproduce the observables. Results: We find that 8 out of 9 high-mass cores are driving clear individual outflows. They are therefore true equivalents of Class 0 protostars in the high-mass regime. The remaining core, CygX-N53 MM2, has only a tentative outflow detection. It could be one of the first examples of a true individual high-mass prestellar core. We also find that the momentum flux of high-mass objects has a linear relation to the reservoir of mass in the envelope, as a scale up of the relations previously found for low-mass protostars. This suggests a fundamental proportionality between accretion rates and envelope masses. The linear dependency implies that the timescale for accretion is similar for high- and low-mass stars. Conclusions: The existence of strong outflows driven by high-mass cores in Cygnus X clearly indicates that high-mass Class 0 protostars exist. The collapsing envelopes of these Class 0 objects have similar sizes and a

Opacity Limit for Supermassive Protostars

NASA Astrophysics Data System (ADS)

Becerra, Fernando; Marinacci, Federico; Inayoshi, Kohei; Bromm, Volker; Hernquist, Lars E.

2018-04-01

We present a model for the evolution of supermassive protostars from their formation at {M}\\star ≃ 0.1 {M}ȯ until their growth to {M}\\star ≃ {10}5 {M}ȯ . To calculate the initial properties of the object in the optically thick regime, we follow two approaches: one based on idealized thermodynamic considerations, and another based on a more detailed one-zone model. Both methods derive a similar value of {n}{{F}}≃ 2× {10}17 {cm}}-3 for the density of the object when opacity becomes important, i.e., the opacity limit. The subsequent evolution of the growing protostar is determined by the accretion of gas onto the object and can be described by a mass–radius relation of the form {R}\\star \\propto {M}\\star 1/3 during the early stages, and of the form {R}\\star \\propto {M}\\star 1/2 when internal luminosity becomes important. For the case of a supermassive protostar, this implies that the radius of the star grows from {R}\\star ≃ 0.65 {au} to {R}\\star ≃ 250 {au} during its evolution. Finally, we use this model to construct a subgrid recipe for accreting sink particles in numerical simulations. A prime ingredient thereof is a physically motivated prescription for the accretion radius and the effective temperature of the growing protostar embedded inside it. From the latter, we can conclude that photoionization feedback can be neglected until very late in the assembly process of the supermassive object.

Stellar Properties of Embedded Protostars: Progress and Prospects

NASA Technical Reports Server (NTRS)

Greene, Thomas

2006-01-01

Until now, high extinctions have prevented direct observation of the central objects of self-embedded, accreting protostars. However, sensitive high dispersion spectrographs on large aperture telescopes have allowed us to begin studying the stellar astrophysical properties of dozens of embedded low mass protostars in the nearest regions of star formation. These high dispersion spectra allow, for the first time, direct measurements of their stellar effective temperatures, surface gravities, rotation velocities, radial velocities (and spectroscopic binarity), mass accretion properties, and mass outflow indicators. Comparisons of the stellar properties with evolutionary models also allow us to estimate masses and constrain ages. We find that these objects have masses similar to those of older, more evolved T Tauri stars, but protostars have higher mean rotation velocities and angular momenta. Most protostars indicate high mass accretion or outflow, but some in Taurus-Auriga appear to be relatively quiescent. These new results are testing, expanding, and refining the standard star formation paradigm, and we explore how to expand this work further.

YSOVAR: The Age of the Cepheus C Star Cluster

NASA Astrophysics Data System (ADS)

Luna, Jessica; Covey, K.; YSOVAR

2014-01-01

We constructed a spectroscopic Hertzsprung-Russell diagram for the Cepheus C (Ceph C) sub-cluster, which we use to generate the first quantitative measurement of this young cluster’s age. Using two TripleSpec spectrographs, on the 3.5m telescope at Apache Point Ob- servatory and the 200” telescope at Palomar Observatory, we obtained near infrared (NIR) spectra for 31 candidate Ceph C members. By comparing our target spectra to a large library of dwarf, sub-giant, and giant star templates, we measured spectral types for candidate Ceph C members ranging from F2 to M2.5. We converted each YSO’s ST into a Teff estimate using the ST to Teff relation recently published by Pecaut et al. (2013). Using our spectroscopically derived extinction estimates to deredden spectral energy distributions constructed from 2MASS and Spitzer photometry, we measured each YSO’s bolometric luminosity. Placing each candidate Ceph C member on an HR Dia- gram, we used Dartmouth pre-main sequence evolutionary tracks to estimate the mass and age of each YSO. We measure a median stellar age for the Ceph C cluster of ˜10 Myrs or less. We also detect a large systematic effect in our ages, however, such that cooler, low mass mem- bers have substantially smaller inferred ages than their higher mass counterparts. We are working to understand the root cause of this systematic effect, but this first estimate of Ceph C’s age will advance our understanding of the cluster’s relationship to other sub clusters in Cepheus, and place the Ceph C cluster in context among other local star forming regions. This research was funded by the NSF through grant number AST-1004107.

Massive black hole factories: Supermassive and quasi-star formation in primordial halos

NASA Astrophysics Data System (ADS)

Schleicher, Dominik R. G.; Palla, Francesco; Ferrara, Andrea; Galli, Daniele; Latif, Muhammad

2013-10-01

Context. Supermassive stars and quasi-stars (massive stars with a central black hole) are both considered as potential progenitors for the formation of supermassive black holes. They are expected to form from rapidly accreting protostars in massive primordial halos. Aims: We explore how long rapidly accreting protostars remain on the Hayashi track, implying large protostellar radii and weak accretion luminosity feedback. We assess the potential role of energy production in the nuclear core, and determine what regulates the evolution of such protostars into quasi-stars or supermassive stars. Methods: We followed the contraction of characteristic mass shells in rapidly accreting protostars, and inferred the timescales for them to reach nuclear densities. We compared the characteristic timescales for nuclear burning with those for which the extended protostellar envelope can be maintained. Results: We find that the extended envelope can be maintained up to protostellar masses of 3.6 × 108 ṁ3 M⊙, where ṁ denotes the accretion rate in solar masses per year. We expect the nuclear core to exhaust its hydrogen content in 7 × 106 yr. If accretion rates ṁ ≫ 0.14 can still be maintained at this point, a black hole may form within the accreting envelope, leading to a quasi-star. Alternatively, the accreting object will gravitationally contract to become a main-sequence supermassive star. Conclusions: Due to the limited gas reservoir in typical 107 M⊙ dark matter halos, the accretion rate onto the central object may drop at late times, implying the formation of supermassive stars as the typical outcome of direct collapse. However, if high accretion rates are maintained, a quasi-star with an interior black hole may form.

Magnetic Fields and Multiple Protostar Formation

NASA Astrophysics Data System (ADS)

Boss, A. P.

2001-12-01

Recent observations of star-forming regions suggest that binary and multiple young stars are the rule rather than the exception, and implicate fragmentation as the likely mechanism for their formation. Most numerical hydrodynamical calculations of fragmentation have neglected the possibly deleterious effects of magnetic fields, in spite of ample evidence for the importance of magnetic support of pre-collapse clouds. We present here the first numerical hydrodynamical survey of the full effects of magnetic fields on the collapse and fragmentation of dense cloud cores. The models are calculated with a three dimensional, finite differences code which solves the equations of hydrodynamics, gravitation, and radiative transfer in the Eddington and diffusion approximations. Magnetic field effects are included through two simple approximations: magnetic pressure is added to the gas pressure, and magnetic tension is approximated by gravity dilution once collapse is well underway. Ambipolar diffusion of the magnetic field leading to cloud collapse is treated approximately as well. Models are calculated for a variety of initial cloud density profiles, shapes, and rotation rates. We find that in spite of the inclusion of magnetic field effects, dense cloud cores are capable of fragmenting into binary and multiple protostar systems. Initially prolate clouds tend to fragment into binary protostars, while initially oblate clouds tend to fragment into multiple protostar systems containing a small number (of order four) of fragments. The latter are likely to be subject to rapid orbital evolution, with close encounters possibly leading to the ejection of fragments. Contrary to expectation, magnetic tension effects appear to enhance fragmentation, allowing lower mass fragments to form than would otherwise be possible, because magnetic tension helps to prevent a central density singularity from forming and producing a dominant single object. Magnetically-supported dense cloud cores

X-RAY AND RADIO OBSERVATIONS OF THE MASSIVE STAR-FORMING REGION IRAS 20126+4104

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

Montes, V. A.; Hofner, P.; Anderson, C.

2015-08-15

We present results from Chandra ACIS-I and Karl G. Jansky Very Large Array 6 cm continuum observations of the IRAS 20126+4104 massive star-forming region. We detect 150 X-ray sources within the 17′ × 17′ ACIS-I field, and a total of 13 radio sources within the 9.′2 primary beam at 4.9 GHz. Among these observtions are the first 6 cm detections of the central sources reported by Hofner et al., namely, I20N1, I20S, and I20var. A new variable radio source is also reported. Searching the 2MASS archive, we identified 88 near-infrared (NIR) counterparts to the X-ray sources. Only four of the X-raymore » sources had 6 cm counterparts. Based on an NIR color–color analysis and on the Besançon simulation of Galactic stellar populations, we estimate that approximately 80 X-ray sources are associated with this massive star-forming region. We detect an increasing surface density of X-ray sources toward the massive protostar and infer the presence of a cluster of at least 43 young stellar objects within a distance of 1.2 pc from the massive protostar.« less

The SOFIA Massive (SOMA) Star Formation Survey. I. Overview and First Results

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

De Buizer, James M.; Shuping, Ralph; Liu, Mengyao

We present an overview and first results of the Stratospheric Observatory For Infrared Astronomy Massive (SOMA) Star Formation Survey, which is using the FORCAST instrument to image massive protostars from ∼10 to 40 μ m. These wavelengths trace thermal emission from warm dust, which in Core Accretion models mainly emerges from the inner regions of protostellar outflow cavities. Dust in dense core envelopes also imprints characteristic extinction patterns at these wavelengths, causing intensity peaks to shift along the outflow axis and profiles to become more symmetric at longer wavelengths. We present observational results for the first eight protostars in themore » survey, i.e., multiwavelength images, including some ancillary ground-based mid-infrared (MIR) observations and archival Spitzer and Herschel data. These images generally show extended MIR/FIR emission along directions consistent with those of known outflows and with shorter wavelength peak flux positions displaced from the protostar along the blueshifted, near-facing sides, thus confirming qualitative predictions of Core Accretion models. We then compile spectral energy distributions and use these to derive protostellar properties by fitting theoretical radiative transfer models. Zhang and Tan models, based on the Turbulent Core Model of McKee and Tan, imply the sources have protostellar masses m {sub *} ∼ 10–50 M {sub ⊙} accreting at ∼10{sup −4}–10{sup −3} M {sub ⊙} yr{sup −1} inside cores of initial masses M {sub c} ∼ 30–500 M {sub ⊙} embedded in clumps with mass surface densities Σ{sub cl} ∼ 0.1–3 g cm{sup −2}. Fitting the Robitaille et al. models typically leads to slightly higher protostellar masses, but with disk accretion rates ∼100× smaller. We discuss reasons for these differences and overall implications of these first survey results for massive star formation theories.« less

A highly embedded protostar in SFO 18: IRAS 05417+0907

NASA Astrophysics Data System (ADS)

Saha, Piyali; Gopinathan, Maheswar; Puravankara, Manoj; Sharma, Neha; Soam, Archana

2018-04-01

Bright-rimmed clouds, located at the periphery of relatively evolved HIT regions, are considered to be the sites of star formation possibly triggered by the implosion caused due to the ionizing radiation from nearby massive stars. SFO 18 is one such region showing a bright-rim on the side facing the 0-type star, A Ori. A point source, IRAS 05417+0907, is detected towards the high density region of the cloud. A molecular outflow has been found to be associated with the source. The outflow is directed towards a Herbig-Haro object, HH 175. From the Spitzer and WISE observations, we show evidence of a physical connection between the molecular outflow, IRAS 05417+0907 and the HH object. The spectral energy distribution constructed using multi-wavelength data shows that the point source is most likely a highly embedded protostar.

X-ray emitting class I protostars in the Serpens dark cloud

NASA Astrophysics Data System (ADS)

Preibisch, T.

2004-12-01

We analyze a set of three individual XMM-Newton X-ray observation of the Serpens dark cloud. In addition to the 45 sources already reported in the analysis of the first of these XMM-Newton observations by Preibisch (\\cite{Preibisch2003), the complete combined data set leads to the detection of X-ray emission from four of the 19 known class I protostars in the region. The set of three observations allows us to study the variability of the sources on timescales from minutes to several months. The lightcurves of two of the four X-ray detected class I protostars show evidence for significant variability; the data suggest at least four flare-like events on these objects. This relatively high level of variability in the X-ray emission from the class I protostars is in qualitative agreement with the result by Imanishi et al. (\\cite{Imanishi2001}), who found that the class I protostars in the ρ Ophiuchi dark cloud show a higher level of variability than that of more evolved class II and class III young stellar objects. This may support non-coronal X-ray emission mechanisms for class I protostars and is in agreement with the predictions of models that assume magnetic interactions between the protostar and its surrounding disk as a source of high-energy emission. We also find a strong variation (by a factor of ˜10) in the X-ray luminosity of the class II object EC 74 between the three observations, which may be explained by a long duration flare or by rotational modulation. Finally, we find no evidence for X-ray emission from the five class 0 protostars in the region.

Submillimeter-wave Observations of Complex Organic Molecules in Southern Massive Star Forming Regions

NASA Astrophysics Data System (ADS)

Kamegai, Kazuhisa; Sakai, Takeshi; Sakai, Nami; Hirota, Tomoya; Yamamoto, Satoshi

2013-03-01

Submillimeter-wave observations of complex organic molecules toward southern massive star forming regions were carried out with ASTE 10m telescope. Methyl formate (HCOOCH3) and dimethyl ether (CH3OCH3) were detected in some molecular cloud cores with young protostars. Differences in chemical composition among neighboring cores were also found.

SOFIA Science Imagery

NASA Image and Video Library

2017-09-14

SCI2016_0006: Map of Cepheus E emphasizing the jets of material flowing to the upper left and lower right from the protostar. The protostar itself is the central yellow-red 'blob" in the colored background map of hydrogen emission made at a wavelength of 4.5 microns by the Spitzer infrared space telescope. The contour curves show the strength of emission from cool carbon monoxide gas measured by the Plateau de Bure radio telescope located in the French Alps. Lefloch et al. used GREAT on SOFIA to measure the amount and velocity of hot carbon monoxide gas at multiple positions along both "wings" of the outflow jet. Credit: Lefloch et al. 2015 Figure 1

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.

CO in Protostars (COPS): Herschel-SPIRE Spectroscopy of Embedded Protostars

NASA Astrophysics Data System (ADS)

Yang, Yao-Lun; Green, Joel D.; Evans, Neal J.; COPS Team

2017-06-01

Molecular emission from early stage protostars reveals the properties of the surrounding gas and the underlying physical processes that govern the early stage of star formation. The CO in Protostars (COPS) Herschel program observes 27 embedded protostars with SPIRE, including several molecular species, such as CO, 13CO, H2O, and HCO+, allowing us to investigate the processes that regulate the early stage of star formation across a large sample of sources. We detect CO rotational lines from Jup = 4 to 36, 13CO lines from Jup = 5 to 10, and six H2O lines, along with atomic lines, such as [N II] and [C I]. We have created an uniformly calibrated dataset with the data from Dust, Ice, and Gas In Time (DIGIT) Herschel Key Program and archival photometry, in which we characterize each source by its spectral energy distribution and evolutionary class. We detect 323 lines from 25 sources from which we successfully extracted 1D spectra, and 3068 lines from 27 sources observed in all spatial pixels of SPIRE. We analyze the correlations of the line strengths of every line pair from all lines detected in our sample with two methods from ASURV package, Spearman's ρ, which test whether the line strengths relation can be described by a monotonic function, and the Kendall z-value, which quantifies the similarity of the ordering of the line strengths of two lines. We notice that the distribution of correlations shows a systematic tendency coinciding with the wavelength coverages of the instruments, suggesting an instrumental bias. Within each module, the correlations of two CO line pairs show high correlations, which decrease as the difference of the upper J-level of the two CO lines increases. The smooth gradients of the distribution of correlations hint that the temperature and density of CO gas are continuously varying throughout the embedding envelope. If all CO gas in the envelope shares a same temperature or density, the correlations would be strong for two CO lines

Radiation transfer of models of massive star formation. III. The evolutionary sequence

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

Zhang, Yichen; Tan, Jonathan C.; Hosokawa, Takashi, E-mail: yichen.zhang@yale.edu, E-mail: jt@astro.ufl.edu, E-mail: takashi.hosokawa@phys.s.u-tokyo.ac.jp

2014-06-20

We present radiation transfer simulations of evolutionary sequences of massive protostars forming from massive dense cores in environments of high mass surface densities, based on the Turbulent Core Model. The protostellar evolution is calculated with a multi-zone numerical model, with the accretion rate regulated by feedback from an evolving disk wind outflow cavity. The disk evolution is calculated assuming a fixed ratio of disk to protostellar mass, while the core envelope evolution assumes an inside-out collapse of the core with a fixed outer radius. In this framework, an evolutionary track is determined by three environmental initial conditions: the core massmore » M{sub c} , the mass surface density of the ambient clump Σ{sub cl}, and the ratio of the core's initial rotational to gravitational energy β {sub c}. Evolutionary sequences with various M{sub c} , Σ{sub cl}, and β {sub c} are constructed. We find that in a fiducial model with M{sub c} = 60 M {sub ☉}, Σ{sub cl} = 1 g cm{sup –2}, and β {sub c} = 0.02, the final mass of the protostar reaches at least ∼26 M {sub ☉}, making the final star formation efficiency ≳ 0.43. For each of the evolutionary tracks, radiation transfer simulations are performed at selected stages, with temperature profiles, spectral energy distributions (SEDs), and multiwavelength images produced. At a given stage, the envelope temperature depends strongly on Σ{sub cl}, with higher temperatures in a higher Σ{sub cl} core, but only weakly on M{sub c} . The SED and MIR images depend sensitively on the evolving outflow cavity, which gradually widens as the protostar grows. The fluxes at ≲ 100 μm increase dramatically, and the far-IR peaks move to shorter wavelengths. The influence of Σ{sub cl} and β {sub c} (which determines disk size) are discussed. We find that, despite scatter caused by different M{sub c} , Σ{sub cl}, β {sub c}, and inclinations, sources at a given evolutionary stage appear in similar

The VLA Nascent Disk And Multiplicity Survey of Perseus Protostars (VANDAM). III. Extended Radio Emission from Protostars in Perseus

NASA Astrophysics Data System (ADS)

Tychoniec, Łukasz; Tobin, John J.; Karska, Agata; Chandler, Claire; Dunham, Michael M.; Li, Zhi-Yun; Looney, Leslie W.; Segura-Cox, Dominique; Harris, Robert J.; Melis, Carl; Sadavoy, Sarah I.

2018-01-01

Centimeter continuum emission from protostars offers insight into the innermost part of the outflows, as shock-ionized gas produces free–free emission. We observed a complete population of Class 0 and I protostars in the Perseus molecular cloud at 4.1 and 6.4 cm with resolution and sensitivity superior to previous surveys. From a total of 71 detections, eight sources exhibit resolved emission at 4.1 cm and/or 6.4 cm. In this paper, we focus on this subsample, analyzing their spectral indices along the jet and their alignment with respect to the large-scale molecular outflow. Spectral indices for fluxes integrated toward the position of the protostar are consistent with free–free thermal emission. The value of the spectral index along a radio jet decreases with distance from the protostar. For six sources, emission is well aligned with the outflow central axis, showing that we observe the ionized base of the jet. This is not the case for two sources, where we note misalignment of the emission with respect to the large-scale outflow. This might indicate that the emission does not originate in the radio jet, but rather in an ionized outflow cavity wall or disk surface. For five of the sources, the spectral indices along the jet decrease well below the thermal free–free limit of ‑0.1 with > 2σ significance. This is indicative of synchrotron emission, meaning that high-energy electrons are being produced in the outflows close to the disk. This result can have far-reaching implications for the chemical composition of the embedded disks.

Magnetic Protostars

NASA Astrophysics Data System (ADS)

Glagolevskij, Yu. V.

2015-09-01

A possible variant of the evolution of magnetic protostars "before the Hayashi phase" is discussed. Arguments are given in support of the following major properties of magnetic stars: (1) global magnetic dipole fields with predominant orientation of the magnetic lines of force in the plane of the equator of revolution; (2) slow rotation; (3) complex, two and three dipole structures of the magnetic field in a large part of the stars; (4) partition of stars into magnetic and normal in a proportion of 1:10 occurs during the period when the protostellar clouds undergo gravitational collapse "before the Hayashi phase."

Fragmentation of protostars dust shells at the Hayashi stage

NASA Astrophysics Data System (ADS)

Abdulmyanov, T. R.

2017-09-01

The aim of this study is to determine the density variations of a protostars dust shells at the Hayashi stage. The simplified model of the density wave perturbations are obtained on the base hydrodynamic equations. According to this model, the fragmentation of dust shells may occur at the stage of slow compression of protostar. Using the solution of the wave equation, the 3-D profiles of the density of the dust shell are defined.

COPS-GREAT: CO in ProtoStars with GREAT

NASA Astrophysics Data System (ADS)

Kristensen, Lars

2013-10-01

Low-mass embedded protostars drive strong bipolar jets, which shock the surrounding gas on 100-1000 AU scales and entrain colder gas in outflows on 10,000 AU and larger scales. The aim of this proposal is to analyze the transition between shocks and entrainment and to quantify the mass in each component. We plan to do this by observing the CO 13-12 line with GREAT in five sources. Outflows from young protostars are a major source of feedback on both protostellar and cloud scales. However, our understanding of how they entrain or impact the protostellar envelope is still in its infancy. High-J CO observations are required to analyze in detail the transition where the outflowing gas goes from being colder (T ~ 100 K) entrained outflowing gas to being directly excited by the shocks causing the entrainment. These observations will allow us to quantify the amount of currently shocked gas with respect to the entrained gas, as well as examine shock properties as a function of velocity, and thereby quantify the feedback from a protostar on its natal material.

VizieR Online Data Catalog: MYStIX candidate protostars (Romine+, 2016)

NASA Astrophysics Data System (ADS)

Romine, G.; Feigelson, E. D.; Getman, K. V.; Kuhn, M. A.; Povich, M. S.

2017-04-01

The present study seeks protostars from the Massive Young Star-forming complex in Infrared and X-ray (MYStIX) survey catalogs. We combine objects with protostellar infrared SEDs and 4.5um excesses with X-ray sources exhibiting ultrahard spectra denoting very heavy obscuration. These criteria filter away nearly all of the older Class II-III stars and contaminant populations, but give very incomplete samples. The result is a list of 1109 protostellar candidates in 14 star-forming regions. See sections 1 and 2 for further explanations. The reliability of the catalog is strengthened because a large majority (86%) are found to be associated with dense cores seen in Herschel 500um maps that trace cold dust emission. However, the candidate list requires more detailed study for confirmation and cannot be viewed as an unbiased view of star formation in the clouds. (3 data files).

Methanol ice in the protostar GL 2136

NASA Technical Reports Server (NTRS)

Skinner, C. J.; Tielens, A. G. G. M.; Barlow, M. J.; Justtanont, K.

1992-01-01

We present ground-based spectra in the 10 and 20 micron atmospheric windows of the deeply embedded protostar GL 2136. These reveal narrow absorption features at 9.7 and 8.9 microns, which we ascribe to the CO-stretch and CH3 rock (respectively) of solid methanol in grain mantles. The peak position of the 9.7 micron band implies that methanol is an important ice mantle component. However, the CH3OH/H2O abundance ratio derived from the observed column densities is only 0.1. This discrepancy suggests that the solid methanol and water ice are located in independent grain components. These independent components may reflect chemical differentiation during grain mantle formation and/or partial outgassing close to the protostar.

Formation of massive seed black holes via collisions and accretion

NASA Astrophysics Data System (ADS)

Boekholt, T. C. N.; Schleicher, D. R. G.; Fellhauer, M.; Klessen, R. S.; Reinoso, B.; Stutz, A. M.; Haemmerlé, L.

2018-05-01

Models aiming to explain the formation of massive black hole seeds, and in particular the direct collapse scenario, face substantial difficulties. These are rooted in rather ad hoc and fine-tuned initial conditions, such as the simultaneous requirements of extremely low metallicities and strong radiation backgrounds. Here, we explore a modification of such scenarios where a massive primordial star cluster is initially produced. Subsequent stellar collisions give rise to the formation of massive (104-105 M⊙) objects. Our calculations demonstrate that the interplay among stellar dynamics, gas accretion, and protostellar evolution is particularly relevant. Gas accretion on to the protostars enhances their radii, resulting in an enhanced collisional cross-section. We show that the fraction of collisions can increase from 0.1 to 1 per cent of the initial population to about 10 per cent when compared to gas-free models or models of protostellar clusters in the local Universe. We conclude that very massive objects can form in spite of initial fragmentation, making the first massive protostellar clusters viable candidate birth places for observed supermassive black holes.

Water D/H Ratio In Low-Mass Protostars

NASA Astrophysics Data System (ADS)

Persson, Magnus V.; Jørgensen, Jes K.; van Dishoeck, Ewine F.; Harsono, Daniel

2013-07-01

Water is an important molecule for our life on Earth, but its way from formation on the surfaces of dust grains to planets and the accompanying chemical processing are not well understood. Through evaporation in the warm inner regions of protostars, water brings complex organics and other species previously locked up in the ice into the gas phase. The water deuterium fractionation (HDO/H2O abundance ratio) has traditionally been used to infer the amount of water that was brought to the Earth by comets. Deducing this ratio in the warm gas of deeply-embedded low-mass protostars allows to extend the discussion of the origin of Earth's water to earlier evolutionary stages. This poster present high-angular resolution, ground based interferometric observations of both HDO and H2(18)O water isotopologues toward several Class~0 low-mass protostars. The emission is compact, and stems from the inner few 100 AU in all sources. The derived amount of deuterium fractionation in water, obtained assuming LTE and optically thin emission, is the same within the uncertainties in all sources and shows only small enhancements compared with Earth's oceans and solar system's comets.

On the nature of the deeply embedded protostar OMC-2 FIR 4

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

Furlan, E.; Megeath, S. T.; Fischer, W. J.

We use mid-infrared to submillimeter data from the Spitzer, Herschel, and Atacama Pathfinder Experiment telescopes to study the bright submillimeter source OMC-2 FIR 4. We find a point source at 8, 24, and 70 μm, and a compact, but extended source at 160, 350, and 870 μm. The peak of the emission from 8 to 70 μm, attributed to the protostar associated with FIR 4, is displaced relative to the peak of the extended emission; the latter represents the large molecular core the protostar is embedded within. We determine that the protostar has a bolometric luminosity of 37 L {submore » ☉}, although including more extended emission surrounding the point source raises this value to 86 L {sub ☉}. Radiative transfer models of the protostellar system fit the observed spectral energy distribution well and yield a total luminosity of most likely less than 100 L {sub ☉}. Our models suggest that the bolometric luminosity of the protostar could be as low as 12-14 L {sub ☉}, while the luminosity of the colder (∼20 K) extended core could be around 100 L {sub ☉}, with a mass of about 27 M {sub ☉}. Our derived luminosities for the protostar OMC-2 FIR 4 are in direct contradiction with previous claims of a total luminosity of 1000 L {sub ☉}. Furthermore, we find evidence from far-infrared molecular spectra and 3.6 cm emission that FIR 4 drives an outflow. The final stellar mass the protostar will ultimately achieve is uncertain due to its association with the large reservoir of mass found in the cold core.« less

Co in Protostars (cops): Herschel-Spire Spectroscopy of Embedded Protostars

NASA Astrophysics Data System (ADS)

Yang, Yao-Lun; Green, Joel D.; Evans, Neal J., II

2017-06-01

Protostars form from cold dense cores dominated by molecular gas and dust, showing excess continuum and rich spectra beyond 100 μm that are best observed by Herschel Space Observatory. Molecular emission reveals the properties of the surrounding gas and the underlying physical processes that govern the early stage of star formation. The CO in Protostars (COPS) Herschel program observes 27 embedded protostars with SPIRE, including several dominant molecular species, such as CO, ^{13}CO, H_{2}O, and HCO^{+}. The COPS dataset covers a unique wavelength range, allowing us to investigate the early stage of star formation across a large sample of sources. We detect CO rotational lines from J_{up} = 4 to 36, ^{13}CO lines from J_{up} = 5 to 10, and six H_{2}O lines, along with [N II] and [C I]. We have created an uniformly calibrated dataset with the data from Dust, Ice, and Gas In Time (DIGIT) Herschel Key Program and archival photometry, in which we characterize each source by its spectral energy distribution and evolutionary class. With an automatic line fitting pipeline, we detect 323 lines from 25 sources from which we successfully extracted 1D spectra, and 3068 lines from 27 sources observed in all spatial pixels of SPIRE. We analyze the correlations of the line strengths of every line pair from all lines detected with two methods from ASURV package, Spearman's ρ, which test whether the line strengths relation can be described by a monotonic function, and the Kendall z-value, which quantifies the similarity of the ordering of the line strengths of two lines. The distribution of correlations shows a systematic tendency coinciding with the wavelength coverages of the instruments, suggesting that the correlations should only be compared within the lines observed by each module. Within each module, the correlations of two CO line pairs show high correlations, which decrease as the difference of the upper J-level of the two CO lines increases. The smooth gradients of

COPS-GREAT2: CO in ProtoStars with GREAT

NASA Astrophysics Data System (ADS)

Yildiz, Umut

Low-mass embedded protostars drive strong bipolar jets, which shock the surrounding gas on 100-1000 AU scales and entrain colder gas in outflows on 10,000 AU and larger scales. The aim of this proposal is to analyze the transition between shocks and entrainment and to quantify the mass in each component. We plan to do this by observing the CO 11-10 line with GREAT in nine sources. Outflows from young protostars are a major source of feedback on both protostellar and cloud scales. However, our understanding of how they entrain or impact the protostellar envelope is still in its infancy. High-J CO observations are required to analyze in detail the transition where the outflowing gas goes from being colder (T 100 K) entrained outflowing gas to being directly excited by the shocks causing the entrainment. These observations will allow us to quantify the amount of currently shocked gas with respect to the entrained gas, as well as examine shock properties as a function of velocity, and thereby quantify the feedback from a protostar on its natal material.

Water and complex organic molecules in the warm inner regions of solar-type protostars

NASA Astrophysics Data System (ADS)

Coutens, A.; Jørgensen, J. K.; Persson, M. V.; Lykke, J. M.; Taquet, V.; van Dishoeck, E. F.; Vastel, C.; Wampfler, S. F.

2015-12-01

Water and complex organic molecules play an important role in the emergence of Life. They have been detected in different types of astrophysical environments (protostars, prestellar cores, outflows, protoplanetary disks, comets, etc). In particular, they show high abundances towards the warm inner regions of protostars, where the icy grain mantles thermally desorb. Can a part of the molecular content observed in these regions be preserved during the star formation process and incorporated into asteroids and comets, that can deliver it to planetary embryos through impacts? By comparison with cometary studies, interferometric observations of solar-type protostars can help to address this important question. We present recent results obtained with the Plateau de Bure interferometer about water deuteration, glycolaldehyde and ethylene glycol towards the low-mass protostar NGC 1333 IRAS2A.

From bipolar to quadrupolar - The collimation processes of the Cepheus A outflow

NASA Technical Reports Server (NTRS)

Torrelles, Jose M.; Verdes-Montenegro, Lourdes; Ho, Paul T. P.; Rodriguez, Luis F.; Canto, Jorge

1993-01-01

Results of new K-band observations of the (1, 1) and (2, 2) ammonia lines toward Cepheus A are reported. The lines are mapped with approximately 2 arcsec of angular resolution and 0.3 km/s of velocity resolution. A sensitivity of 10 mJy has been achieved. The observations reveal details of the spatial and kinematics structure of the ambient high-density gas. It is suggested that the interstellar high-density gas is diverting and redirecting the outflow in the sense that the quadrupolar structure of the molecular outflow is produced by the interaction with the ammonia condensationss, with Cep A-1 and Cep A-3 splitting in two halves, respectively the blue- and redshifted lobes of an east-west bipolar molecular outflow.

VizieR Online Data Catalog: Deconvolved Spitzer images of 89 protostars (Velusamy+, 2014)

NASA Astrophysics Data System (ADS)

Velusamy, T.; Langer, W. D.; Thompson, T.

2016-03-01

The sample of Class 0 protostars, H2 jets, and outflow sour selected for HiRes deconvolution of Spitzer images are listed in Table1. The majority of our target protostellar objects were selected from "The Youngest Protostars" webpage hosted by the University of Kent (http://astro.kent.ac.uk/protostars/old/), which are based on the young Class 0 objects compiled by Froebrich 2005 (cat. J/ApJS/156/169). In addition to these objects, our sample includes some Herbig-Haro (HH) sources and a few well known jet outflow sources. Our sample also includes one high-mass protostar (IRAS20126+4104; cf. Caratti o Garatti et al., 2008A&A...485..137C) to demonstrate the use of HiRes for such sources. Our choice for target selection was primarily based on the availability of Spitzer images in IRAC and MIPS bands in the archives and the feasibility for reprocessing based on the published Spitzer images wherever available. (1 data file).

EVLA Observation of Centimeter Continuum Emission from Protostars in Serpens South

NASA Astrophysics Data System (ADS)

Kern, Nicholas S.; Tobin, John J.; Keown, Jared A.; Gutermuth, Robert A.

2015-01-01

Serpens South is a protocluster with an unusually high abundance of Class 0 and I protostars, suggesting it is in a very early phase of star formation and may eventually form a star cluster. Following its discovery in 2008 with the Spitzer space telescope, infrared and millimeter observations and analysis quickly followed, however, Serpens South has yet to be fully explored in the radio. Radio observations at centimeter wavelengths have long been used as a tool to probe the dynamical processes of young protostars that are still heavily shrouded in their protostellar envelopes and thus cannot be seen at longer wavelengths. Radio observations then become an important tool in understanding Serpens South due to its young age. To this end, we have conducted EVLA C band continuum observations of the central region of the Serpens South protostellar cluster in order to map the centimeter continuum emission in a region of high Class 0 / I protostellar surface density. We report the detection of centimeter emission corresponding to protostars identified by Spitzer, and to protostars identified but blended by Herschel. We characterize their centimeter emission, and put them in context with previous Spitzer and Herschel infrared and far-infrared observations, as well as IRAM millimeter observations. Additionally, we make an assessment of the protostars' bolometric luminosity, and compare them to the known protostellar 3.6 cm to 6.0 cm luminosity vs. bolometric luminosity relation. With the EVLA, we present a mid-resolution map of centimeter emission from the central region of Serpens South with the highest sensitivity to date, with a beam size of ~5 arcseconds and rms on the order of 15 microJansky.

The Red MSX Source Survey: The Massive Young Stellar Population of Our Galaxy

NASA Astrophysics Data System (ADS)

Lumsden, S. L.; Hoare, M. G.; Urquhart, J. S.; Oudmaijer, R. D.; Davies, B.; Mottram, J. C.; Cooper, H. D. B.; Moore, T. J. T.

2013-09-01

We present the Red MSX Source survey, the largest statistically selected catalog of young massive protostars and H II regions to date. We outline the construction of the catalog using mid- and near-infrared color selection. We also discuss the detailed follow up work at other wavelengths, including higher spatial resolution data in the infrared. We show that within the adopted selection bounds we are more than 90% complete for the massive protostellar population, with a positional accuracy of the exciting source of better than 2 arcsec. We briefly summarize some of the results that can be obtained from studying the properties of the objects in the catalog as a whole; we find evidence that the most massive stars form: (1) preferentially nearer the Galactic center than the anti-center; (2) in the most heavily reddened environments, suggestive of high accretion rates; and (3) from the most massive cloud cores.

Definitive X-Ray Detection of the Class 0 Protostar HOPS 383

NASA Astrophysics Data System (ADS)

Grosso, Nicolas

2016-09-01

We have identified in the Chandra archive a possible pre-outburst X-ray counterpart to the protostar HOPS 383, the first and only Class 0 protostar thus far observed to undergo an accretion outburst. We propose ACIS-I and contemporaneous CT-4m near-IR observations to confirm and to identify the source of this X-ray emission and to measure the presumed increase in X-ray flux during the accretion outburst.

LUMINOSITY FUNCTIONS OF SPITZER-IDENTIFIED PROTOSTARS IN NINE NEARBY MOLECULAR CLOUDS

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

Kryukova, E.; Megeath, S. T.; Allen, T. S.

2012-08-15

We identify protostars in Spitzer surveys of nine star-forming (SF) molecular clouds within 1 kpc: Serpens, Perseus, Ophiuchus, Chamaeleon, Lupus, Taurus, Orion, Cep OB3, and Mon R2, which combined host over 700 protostar candidates. These clouds encompass a variety of SF environments, including both low-mass and high-mass SF regions, as well as dense clusters and regions of sparsely distributed star formation. Our diverse cloud sample allows us to compare protostar luminosity functions in these varied environments. We combine near- and mid-infrared photometry from the Two Micron All Sky Survey and Spitzer to create 1-24 {mu}m spectral energy distributions (SEDs). Usingmore » protostars from the c2d survey with well-determined bolometric luminosities, we derive a relationship between bolometric luminosity, mid-IR luminosity (integrated from 1-24 {mu}m), and SED slope. Estimations of the bolometric luminosities for protostar candidates are combined to create luminosity functions for each cloud. Contamination due to edge-on disks, reddened Class II sources, and galaxies is estimated and removed from the luminosity functions. We find that luminosity functions for high-mass SF clouds (Orion, Mon R2, and Cep OB3) peak near 1 L{sub Sun} and show a tail extending toward luminosities above 100 L{sub Sun }. The luminosity functions of the low-mass SF clouds (Serpens, Perseus, Ophiuchus, Taurus, Lupus, and Chamaeleon) do not exhibit a common peak, however the combined luminosity function of these regions peaks below 1 L{sub Sun }. Finally, we examine the luminosity functions as a function of the local surface density of young stellar objects. In the Orion molecular clouds, we find a significant difference between the luminosity functions of protostars in regions of high and low stellar density, the former of which is biased toward more luminous sources. This may be the result of primordial mass segregation, although this interpretation is not unique. We compare our

Astronomers puzzle over a peculiar age-defying massive star

NASA Image and Video Library

2017-12-08

An age-defying star designated as IRAS 19312+1950 exhibits features characteristic of a very young star and a very old star. The object stands out as extremely bright inside a large, chemically rich cloud of material, as shown in this image from NASA’s Spitzer Space Telescope. A NASA-led team of scientists thinks the star – which is about 10 times as massive as our sun and emits about 20,000 times as much energy – is a newly forming protostar. That was a big surprise because the region had not been known as a stellar nursery before. But the presence of a nearby interstellar bubble, which indicates the presence of a recently formed massive star, also supports this idea. Read more: go.nasa.gov/2bMza9d Image Credit: NASA/JPL-Caltech

Discovery of ``isolated'' co-moving T Tauri stars in Cepheus

NASA Astrophysics Data System (ADS)

Guillout, P.; Frasca, A.; Klutsch, A.; Marilli, E.; Montes, D.

2010-09-01

Context. During the course of a large spectroscopic survey of X-ray active late-type stars in the solar neighbourhood, we discovered four lithium-rich stars packed within just a few degrees on the sky. Although located in a sky area rich in CO molecular regions and dark clouds, the Cepheus-Cassiopeia complex, these very young stars are projected several degrees away from clouds in front of an area void of interstellar matter. As such, they are very good “isolated” T Tauri star candidates. Aims: We present optical observations of these stars conducted with 1-2 m class telescopes. We acquired high-resolution optical spectra as well as photometric data allowing us to investigate in detail their nature and physical parameters with the aim of testing the “runaway” and “in-situ” formation scenarios. Their kinematical properties are also analyzed to investigate their possible connection to already known stellar kinematic groups. Methods: We use the cross-correlation technique and other tools developed by us to derive accurate radial and rotational velocities and perform an automatic spectral classification. The spectral subtraction technique is used to infer chromospheric activity level in the Hα line core and clean the spectra of photospheric lines before measuring the equivalent width of the lithium absorption line. Results: Both physical (lithium content, chromospheric, and coronal activities) and kinematical indicators show that all stars are very young, with ages probably in the range 10-30 Myr. In particular, the spectral energy distribution of TYC 4496-780-1 displays a strong near- and far-infrared excess, typical of T Tauri stars still surrounded by an accretion disc. They also share the same Galactic motion, proving that they form a homogeneous moving group of stars with the same origin. Conclusions: The most plausible explanation of how these “isolated” T Tauri stars formed is the “in-situ” model, although accurate distances are needed to

Massive Infrared-Quiet Dense Cores: Unveiling the Initial Conditions of High-Mass Star Formation

NASA Astrophysics Data System (ADS)

Motte, F.; Bontemps, S.; Schneider, N.; Schilke, P.; Menten, K. M.

2008-05-01

As Th. Henning said at the conference, cold precursors of high-mass stars are now ``hot topics''. We here propose some observational criteria to identify massive infrared-quiet dense cores which can host the high-mass analogs of Class~0 protostars and pre-stellar condensations. We also show how far-infrared to millimeter imaging surveys of entire complexes forming OB stars are starting to unveil the initial conditions of high-mass star formation.

The Massive Star-forming Regions Omnibus X-ray Catalog, Second Installment

NASA Astrophysics Data System (ADS)

Townsley, Leisa K.; Broos, Patrick S.; Garmire, Gordon P.; Anderson, Gemma E.; Feigelson, Eric D.; Naylor, Tim; Povich, Matthew S.

2018-04-01

We present the second installment of the Massive Star-forming Regions (MSFRs) Omnibus X-ray Catalog (MOXC2), a compilation of X-ray point sources detected in Chandra/ACIS observations of 16 Galactic MSFRs and surrounding fields. MOXC2 includes 13 ACIS mosaics, three containing a pair of unrelated MSFRs at different distances, with a total catalog of 18,396 point sources. The MSFRs sampled range over distances of 1.3 kpc to 6 kpc and populations varying from single massive protostars to the most massive Young Massive Cluster known in the Galaxy. By carefully detecting and removing X-ray point sources down to the faintest statistically significant limit, we facilitate the study of the remaining unresolved X-ray emission. Through comparison with mid-infrared images that trace photon-dominated regions and ionization fronts, we see that the unresolved X-ray emission is due primarily to hot plasmas threading these MSFRs, the result of feedback from the winds and supernovae of massive stars. The 16 MSFRs studied in MOXC2 more than double the MOXC1 sample, broadening the parameter space of ACIS MSFR explorations and expanding Chandra's substantial contribution to contemporary star formation science.

Fermi observations of Cassiopeia and Cepheus: Diffuse gamma-ray emission in the outer galaxy

DOE PAGES

Abdo, A. A.

2010-01-15

Here, we present the analysis of the interstellar γ-ray emission measured by the Fermi Large Area Telescope toward a region in the second Galactic quadrant at 100° ≤ l ≤ 145° and –15° ≤ b ≤ +30°. This region encompasses the prominent Gould Belt clouds of Cassiopeia, Cepheus, and the Polaris flare, as well as atomic and molecular complexes at larger distances, like that associated with NGC 7538 in the Perseus arm. The good kinematic separation in velocity between the local, Perseus, and outer arms, and the presence of massive complexes in each of them, make this region well suitedmore » to probe cosmic rays (CRs) and the interstellar medium beyond the solar circle. Furthermore, the γ-ray emissivity spectrum of the gas in the Gould Belt is consistent with expectations based on the locally measured CR spectra. The γ-ray emissivity decreases from the Gould Belt to the Perseus arm, but the measured gradient is flatter than expectations for CR sources peaking in the inner Galaxy as suggested by pulsars. The X CO = N(H 2)/W CO conversion factor is found to increase from (0.87 ± 0.05) × 10 20 cm –2 (K km s –1) –1 in the Gould Belt to (1.9 ± 0.2) × 10 20 cm –2 (K km s –1) –1 in the Perseus arm. We also derive masses for the molecular clouds under study. Dark gas, not properly traced by radio and microwave surveys, is detected in the Gould Belt through a correlated excess of dust and γ-ray emission: its mass amounts to ~50% of the CO-traced mass.« less

The VLA Nascent Disk and Multiplicity Survey of Perseus Protostars (VANDAM). II. Multiplicity of Protostars in the Perseus Molecular Cloud

NASA Astrophysics Data System (ADS)

Tobin, John J.; Looney, Leslie W.; Li, Zhi-Yun; Chandler, Claire J.; Dunham, Michael M.; Segura-Cox, Dominique; Sadavoy, Sarah I.; Melis, Carl; Harris, Robert J.; Kratter, Kaitlin; Perez, Laura

2016-02-01

We present a multiplicity study of all known protostars (94) in the Perseus molecular cloud from a Karl G. Jansky Very Large Array survey at Ka-band (8 mm and 1 cm) and C-band (4 and 6.6 cm). The observed sample has a bolometric luminosity range between 0.1 L⊙ and ˜33 L⊙, with a median of 0.7 L⊙. This multiplicity study is based on the Ka-band data, having a best resolution of ˜0.″065 (15 au) and separations out to ˜43″ (10,000 au) can be probed. The overall multiplicity fraction (MF) is found to be 0.40 ± 0.06 and the companion star fraction (CSF) is 0.71 ± 0.06. The MF and CSF of the Class 0 protostars are 0.57 ± 0.09 and 1.2 ± 0.2, and the MF and CSF of Class I protostars are both 0.23 ± 0.08. The distribution of companion separations appears bi-modal, with a peak at ˜75 au and another peak at ˜3000 au. Turbulent fragmentation is likely the dominant mechanism on >1000 au scales and disk fragmentation is likely to be the dominant mechanism on <200 au scales. Toward three Class 0 sources we find companions separated by <30 au. These systems have the smallest separations of currently known Class 0 protostellar binary systems. Moreover, these close systems are embedded within larger (50-400 au) structures and may be candidates for ongoing disk fragmentation.

Searching for Correlations with the HCO+ 4-3 Molecular Spectra of Protostars

NASA Astrophysics Data System (ADS)

Acikgoz, Ogulcan; Basturk, Seda

The assignment is based on HCO+ J=4-3 spectral line molecular observations of protostars from the James Clerk Maxwell Telescope, which has the 15 m diameter dish and located in Mauna Kea, Hawaii, USA. Data of 20 protostars are taken from the public LOMASS database and analyzed. We looked for correlations between a few observational quantities. We thank Dr Umut Yildiz (NASA/JPL-Caltech) for providing data and his comments and support to our research project.

The Green Bank Ammonia Survey: Observations of Hierarchical Dense Gas Structures in Cepheus-L1251

NASA Astrophysics Data System (ADS)

Keown, Jared; Di Francesco, James; Kirk, Helen; Friesen, Rachel K.; Pineda, Jaime E.; Rosolowsky, Erik; Ginsburg, Adam; Offner, Stella S. R.; Caselli, Paola; Alves, Felipe; Chacón-Tanarro, Ana; Punanova, Anna; Redaelli, Elena; Seo, Young Min; Matzner, Christopher D.; Chun-Yuan Chen, Michael; Goodman, Alyssa A.; Chen, How-Huan; Shirley, Yancy; Singh, Ayushi; Arce, Hector G.; Martin, Peter; Myers, Philip C.

2017-11-01

We use Green Bank Ammonia Survey observations of NH3 (1, 1) and (2, 2) emission with 32″ FWHM resolution from a ˜10 pc2 portion of the Cepheus-L1251 molecular cloud to identify hierarchical dense gas structures. Our dendrogram analysis of the NH3 data results in 22 top-level structures, which reside within 13 lower-level parent structures. The structures are compact (0.01 {pc}≲ {R}{eff}≲ 0.1 {pc}) and are spatially correlated with the highest H2 column density portions of the cloud. We also compare the ammonia data to a catalog of dense cores identified by higher-resolution (18.″2 FWHM) Herschel Space Observatory observations of dust continuum emission from Cepheus-L1251. Maps of kinetic gas temperature, velocity dispersion, and NH3 column density, derived from detailed modeling of the NH3 data, are used to investigate the stability and chemistry of the ammonia-identified and Herschel-identified structures. We show that the dust and dense gas in the structures have similar temperatures, with median T dust and T K measurements of 11.7 ± 1.1 K and 10.3 ± 2.0 K, respectively. Based on a virial analysis, we find that the ammonia-identified structures are gravitationally dominated, yet may be in or near a state of virial equilibrium. Meanwhile, the majority of the Herschel-identified dense cores appear to be not bound by their own gravity and instead confined by external pressure. CCS (20 - 10) and HC5N (9-8) emission from the region reveal broader line widths and centroid velocity offsets when compared to the NH3 (1, 1) emission in some cases, likely due to these carbon-based molecules tracing the turbulent outer layers of the dense cores.

Spectroscopic Detection of a Stellar-like Photosphere in an Accreting Protostar

NASA Technical Reports Server (NTRS)

Greene, Thomas P.; Lada, Charles J.; DeVincenzi, Donald L. (Technical Monitor)

2002-01-01

We present high-resolution (R is approximately equal to 18,000), high signal-to-noise 2 micron spectra of two luminous, X-ray flaring Class I protostars in the rho Ophiuchi cloud acquired with the NIRSPEC (near infrared spectrograph) of the Keck II telescope. We present the first spectrum of a highly veiled, strongly accreting protostar which shows photospheric absorption features and demonstrates the stellar nature of its central core. We find the spectrum of the luminous (L (sub bol) = 10 solar luminosity) protostellar source, YLW 15, to be stellar-like with numerous atomic and molecular absorption features, indicative of a K5 IV/V spectral type and a continuum veiling r(sub k) = 3.0. Its derived stellar luminosity (3 stellar luminosity) and stellar radius (3.1 solar radius) are consistent with those of a 0.5 solar mass pre-main-sequence star. However, 70% of its bolometric luminosity is due to mass accretion, whose rate we estimate to be 1.7 x 10(exp -6) solar masses yr(exp -1). We determine that excess infrared emission produced by the circumstellar accretion disk, the inner infalling envelope, and accretion shocks at the surface of the stellar core of YLW 15 all contribute significantly to its near-IR (infrared) continuum veiling. Its rotational velocity v sin i = 50 km s(exp -1) is comparable to those of flat-spectrum protostars but considerably higher than those of classical T Tauri stars in the rho Oph cloud. The protostar may be magnetically coupled to its circumstellar disk at a radius of 2 - 3 R(sub *). It is also plausible that this protostar can shed over half its angular momentum and evolve into a more slowly rotating classical T Tauri star by remaining coupled to its circumstellar disk (at increasing radius) as its accretion rate drops by an order of magnitude during the rapid transition between the Class I and Class II phases of evolution. The spectrum of WL 6 does not show any photospheric absorption features, and we estimate that its continuum

Infrared Observations of Hot Gas and Cold Ice Toward the Low Mass Protostar Elias 29

NASA Technical Reports Server (NTRS)

Boogert, A. C. A.; Tielens, A. G. G. M.; Ceccarelli, C.; Boonman, A. M. S.; vanDishoeck, E. F.; Keane, J. V.; Whittet, D. C. B.; deGraauw, T.

2000-01-01

We have obtained the full 1-200 micrometer spectrum of the low luminosity (36 solar luminosity Class I protostar Elias 29 in the rho Ophiuchi molecular cloud. It provides a unique opportunity to study the origin and evolution of interstellar ice and the interrelationship of interstellar ice and hot core gases around low mass protostars. We see abundant hot CO and H2O gas, as well as the absorption bands of CO, CO2, H2O and "6.85 micrometer" ices. We compare the abundances and physical conditions of the gas and ices toward Elias 29 with the conditions around several well studied luminous, high mass protostars. The high gas temperature and gas/solid ratios resemble those of relatively evolved high mass objects (e.g. GL 2591). However, none of the ice band profiles shows evidence for significant thermal processing, and in this respect Elias 29 resembles the least evolved luminous protostars, such as NGC 7538 : IRS9. Thus we conclude that the heating of the envelope of the low mass object Elias 29 is qualitatively different from that of high mass protostars. This is possibly related to a different density gradient of the envelope or shielding of the ices in a circumstellar disk. This result is important for our understanding of the evolution of interstellar ices, and their relation to cometary ices.

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.

Massive 70 μm quiet clumps I: evidence of embedded low/intermediate-mass star formation activity

NASA Astrophysics Data System (ADS)

Traficante, A.; Fuller, G. A.; Billot, N.; Duarte-Cabral, A.; Merello, M.; Molinari, S.; Peretto, N.; Schisano, E.

2017-10-01

Massive clumps, prior to the formation of any visible protostars, are the best candidates to search for the elusive massive starless cores. In this work, we investigate the dust and gas properties of massive clumps selected to be 70 μm quiet, therefore good starless candidates. Our sample of 18 clumps has masses 300 ≲ M ≲ 3000 M⊙, radius 0.54 ≤ R ≤ 1.00 pc, surface densities Σ ≥ 0.05 g cm-2 and luminosity/mass ratio L/M ≤ 0.3. We show that half of these 70 μm quiet clumps embed faint 24 μm sources. Comparison with GLIMPSE counterparts shows that five clumps embed young stars of intermediate stellar mass up to ≃5.5 M⊙. We study the clump dynamics with observations of N2H+ (1-0), HNC (1-0) and HCO+ (1-0) made with the IRAM 30 m telescope. Seven clumps have blue-shifted spectra compatible with infall signatures, for which we estimate a mass accretion rate 0.04≲ \\dot{M}≲ 2.0× 10^{-3} M⊙ yr-1, comparable with values found in high-mass protostellar regions, and free-fall time of the order of tff ≃ 3 × 105 yr. The only appreciable difference we find between objects with and without embedded 24 μm sources is that the infall rate appears to increase from 24 μm dark to 24 μm bright objects. We conclude that all 70 μm quiet objects have similar properties on clump scales, independently of the presence of an embedded protostar. Based on our data, we speculate that the majority, if not all of these clumps, may already embed faint, low-mass protostellar cores. If these clumps are to form massive stars, this must occur after the formation of these lower mass stars.

VizieR Online Data Catalog: H2O + CH3OH maser survey of Orion protostar

NASA Astrophysics Data System (ADS)

Kang, M.; Lee, J.-E.; Choi, M.; Choi, Y.; Kim, K.-T.; di Francesco, J.; Park, Y.-S.

2015-04-01

Out of the protostars listed in the Herschel Orion Protostar Survey (HOPS) catalogue (Fischer et al. 2010A&A...518L.122F; Stutz et al. 2013, J/ApJ/767/36), we selected protostars showing line wings in the CO(J=2->1) line spectra obtained with the Seoul Radio Astronomy Observatory 6m telescope. In the Orion molecular cloud complex 99 protostars were observed using the KVN 21m radio antennas in the single-dish telescope mode during the 2010 Mar-2010 Jun and 2011-2012 observing seasons. The observations were carried out with the KVN Yonsei telescope at Seoul, the KVN Ulsan telescope at Ulsan, and the KVN Tamna telescope at Seogwipo, Korea. The target lines were the H2O(616->523) (22.23508GHz) line and the CH3OH (70->61 A+), (80->71A+), and (6-1->50E) lines at 44.06943, 95.169516, and 132.890800GHz, respectively. (6 data files).

High-velocity Interstellar Bullets in IRAS 05506+2414: A Very Young Protostar

NASA Technical Reports Server (NTRS)

Sahai, Raghvendra; Claussen, Mark; Sanchez Contreras, Carmen; Morris, Mark; Sarkar, Geetanjali

2008-01-01

We have made a serendipitous discovery of an enigmatic outflow source, IRAS 05506+2414 (hereafter IRAS 05506), as part of a multiwavelength survey of pre-planetary nebulae (PPNs). The HST optical and near-infrared images show a bright compact central source with a jet-like extension, and a fan-like spray of high-velocity (with radial velocities up to 350 km/s) elongated knots which appear to emanate from it. These structures are possibly analogous to the near-IR bullets'' seen in the Orion Nebula. Interferometric observations at 2.6 mm show the presence of a continuum source and a high-velocity CO outflow, which is aligned with the optical jet structure. IRAS 05506 is most likely not a PPN. We find extended NH3 (1,1) emission toward IRAS 05506; these data, together with the combined presence of far-IR emission, H2O and OH masers, and CO and CS J=2-1 emission, strongly argue for a dense, dusty star-forming core associated with IRAS 05506. IRAS 05506 is probably an intermediate-mass or massive protostar, and the very short timescale (200 yr) of its outflows indicates that it is very young. If IRAS 05506 is a massive star, then the lack of radio continuum and the late G to early K spectral type we find from our optical spectra imply that in this object we are witnessing the earliest stages of its life, while its temperature is still too low to provide sufficient UV flux for ionization.

Two protostar candidates in the bright-rimmed dark cloud LDN 1206

NASA Technical Reports Server (NTRS)

Ressler, Michael E.; Shure, Mark

1991-01-01

The discovery of several near IR objects associated with two IRAS point sources in the LDN 1206 region is reported. IRAS 22272 + 6358A is probably a 'protostar' which is seen only in scattered light at near-IR wavelengths because of heavy obscuration by an almost edge-on circumstellar disk. In contrast, IRAS 22272 + 6358B is directly visible at these wavelengths and is perhaps an object which lies between protostars and T-Tauri stars in its evolution. Both direct and polarimetric K-band images of the region are presented, as well as spectral energy distributions constructed from J, H, K, L, L-prime, and M data and published far-IR and mm data.

Herschel Shines Light on the Episodic Evolutionary Sequence of Protostars

NASA Astrophysics Data System (ADS)

Green, Joel D.; DIGIT; FOOSH; COPS Teams

2014-01-01

New far-infrared and submillimeter spectroscopic capabilities, along with moderate spatial and spectral resolution, provide the opportunity to study the diversity of shocks, accretion processes, and compositions of the envelopes of developing protostellar objects in nearby molecular clouds. We present the "COPS" (CO in Protostars) sample; a statistical analysis of the full sample of 30 Class 0/I protostars from the "DIGIT" Key project using Herschel-PACS/SPIRE 50-700 micron spectroscopy. We consider the sample as a whole in characteristic spectral lines, using a standardized data reduction procedure for all targets, and analyze the differences in the continuum and gas over the full sample, presenting an overview of trends. We compare the sources in evolutionary state, envelope mass, and gas properties to more evolved sources from the"FOOSH'' (FUor) samples.

Molecular Anions in Protostars, Prestellar Cores and Dark Clouds

NASA Technical Reports Server (NTRS)

Cordiner, Martin; Charnley, Steven; Buckle, Jane; Wash, Catherine; Millar, Tom

2011-01-01

From our recent survey work using the Green Bank Telescope, microwave emission lines from the hydrocarbon anion C6H(-) and its parent neutral C6H have been detected in six new sources. Using HC3N = 10(exp -9) emission maps, we targeted the most carbon-chain-rich sources for our anion survey, which included the low-mass Class 0 protostar L1251A-IRS3, the prestellar cores L1389-SMM1 and L1512, and the interstellar clouds Ll172A, TMC-1C and L1495B. Derived [C6H(-)]/[C6H] anion-to-neutral ratios are approximately 1-10. The greatest C6H(-) column densities are found in the quiescent clouds TMC-1C and L1495B, but the anion-to-neutral ratios are greatest in the prestellar cores and protostars. These results are interpreted in terms of the physical and chemical properties of the sources, and the implications for molecular cloud chemistry are discussed.

Observations of Carbon Chain Chemistry in the Envelopes of Low-Mass Protostars

NASA Technical Reports Server (NTRS)

Cordiner, M.; Charnley, S.; Buckle, J. V.; Walsh, C.; Millar, T. J.

2012-01-01

Observational results are reported from our surveys in the Northern Hemisphere (using the Onsala 20 m telescope) and the Southern Hemisphere (using the Mopra 22 m telescope) to search for 3 mm emission lines from carbon-chain-bearing species and other complex molecules in the envelopes of low-mass protostars. Based on a sample of approximately 60 sources, we find that carbon-chain-bearing species including HC3N (and C4H) are highly abundant in the vicinity of more than half of the observed protostars. The origin and evolution of these species, including their likely incorporation into ices in protoplanetary disks will be discussed

Is Episodic Accretion Necessary to Resolve the Luminosity Problem in Low-Mass Protostars?

NASA Astrophysics Data System (ADS)

Sevrinsky, Raymond Andrew; Dunham, Michael

2017-01-01

In this contribution, we compare the results of protostellar accretion simulations for scenarios both containing and lacking episodic accretion activity. We determine synthetic observational signatures for collapsing protostars by taking hydrodynamical simulations predicting highly variable episodic accretion events, filtering out the stochastic behavior by applying power law fits to the mass accretion rates onto the disk and central star, and using the filtered rates as inputs to two-dimensional radiative transfer calculations. The spectral energy distributions generated by these calculations are used to calculate standard observational signatures of Lbol and Tbol, and compared directly to a sample of 230 embedded protostars. We explore the degree to which these continually declining accretion models successfully reproduce the observed spread of protostellar luminosities, and examine their consistency with the prior variable models to investigate the degree to which episodic accretion bursts are necessary in protostellar formation theories to match observations of field protostars. The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. 1262851, and by the Smithsonian Institution.

Variability of young stars: Determination of rotational periods of weak-line T Tauri stars in the Cepheus-Cassiopeia star-forming region

NASA Astrophysics Data System (ADS)

Koeltzsch, A.; Mugrauer, M.; Raetz, St.; Schmidt, T. O. B.; Roell, T.; Eisenbeiss, T.; Hohle, M. M.; Vaňko, M.; Ginski, Ch.; Marka, C.; Moualla, M.; Schreyer, K.; Broeg, Ch.; Neuhäuser, R.

2009-05-01

We report on observation and determination of rotational periods of ten weak-line T Tauri stars in the Cepheus-Cassiopeia star-forming region. Observations were carried out with the Cassegrain-Teleskop-Kamera (CTK) at University Observatory Jena between 2007 June and 2008 May. The periods obtained range between 0.49 d and 5.7 d, typical for weak-line and post T Tauri stars. Based on observations obtained with telescopes of the University Observatory Jena, which is operated by the Astrophysical Institute of the Friedrich-Schiller-University.

Constraining the Abundances of Complex Organics in the Inner Regions of Solar-type Protostars

NASA Astrophysics Data System (ADS)

Taquet, Vianney; López-Sepulcre, Ana; Ceccarelli, Cecilia; Neri, Roberto; Kahane, Claudine; Charnley, Steven B.

2015-05-01

The high abundances of Complex Organic Molecules (COMs) with respect to methanol, the most abundant COM, detected toward low-mass protostars, tend to be underpredicted by astrochemical models. This discrepancy might come from the large beam of the single-dish telescopes, encompassing several components of the studied protostar, commonly used to detect COMs. To address this issue, we have carried out multi-line observations of methanol and several COMs toward the two low-mass protostars NGC 1333-IRAS 2A and -IRAS 4A with the Plateau de Bure interferometer at an angular resolution of 2″, resulting in the first multi-line detection of the O-bearing species glycolaldehyde and ethanol and of the N-bearing species ethyl cyanide toward low-mass protostars other than IRAS 16293. The high number of detected transitions from COMs (more than 40 methanol transitions for instance) allowed us to accurately derive the source size of their emission and the COM column densities. The COM abundances with respect to methanol derived toward IRAS 2A and IRAS 4A are slightly, but not substantitally, lower than those derived from previous single-dish observations. The COM abundance ratios do not vary significantly with the protostellar luminosity, over five orders of magnitude, implying that low-mass hot corinos are quite chemically rich as high-mass hot cores. Astrochemical models still underpredict the abundances of key COMs, such as methyl formate or di-methyl ether, suggesting that our understanding of their formation remains incomplete.

How Do Stars Gain Their Mass? A JCMT/SCUBA-2 Transient Survey of Protostars in Nearby Star-forming Regions

NASA Astrophysics Data System (ADS)

Herczeg, Gregory J.; Johnstone, Doug; Mairs, Steve; Hatchell, Jennifer; Lee, Jeong-Eun; Bower, Geoffrey C.; Chen, Huei-Ru Vivien; Aikawa, Yuri; Yoo, Hyunju; Kang, Sung-Ju; Kang, Miju; Chen, Wen-Ping; Williams, Jonathan P.; Bae, Jaehan; Dunham, Michael M.; Vorobyov, Eduard I.; Zhu, Zhaohuan; Rao, Ramprasad; Kirk, Helen; Takahashi, Satoko; Morata, Oscar; Lacaille, Kevin; Lane, James; Pon, Andy; Scholz, Aleks; Samal, Manash R.; Bell, Graham S.; Graves, Sarah; Lee, E.'lisa M.; Parsons, Harriet; He, Yuxin; Zhou, Jianjun; Kim, Mi-Ryang; Chapman, Scott; Drabek-Maunder, Emily; Chung, Eun Jung; Eyres, Stewart P. S.; Forbrich, Jan; Hillenbrand, Lynne A.; Inutsuka, Shu-ichiro; Kim, Gwanjeong; Kim, Kyoung Hee; Kuan, Yi-Jehng; Kwon, Woojin; Lai, Shih-Ping; Lalchand, Bhavana; Lee, Chang Won; Lee, Chin-Fei; Long, Feng; Lyo, A.-Ran; Qian, Lei; Scicluna, Peter; Soam, Archana; Stamatellos, Dimitris; Takakuwa, Shigehisa; Tang, Ya-Wen; Wang, Hongchi; Wang, Yiren

2017-11-01

Most protostars have luminosities that are fainter than expected from steady accretion over the protostellar lifetime. The solution to this problem may lie in episodic mass accretion—prolonged periods of very low accretion punctuated by short bursts of rapid accretion. However, the timescale and amplitude for variability at the protostellar phase is almost entirely unconstrained. In A James Clerk Maxwell Telescope/SCUBA-2 Transient Survey of Protostars in Nearby Star-forming Regions, we are monitoring monthly with SCUBA-2 the submillimeter emission in eight fields within nearby (< 500 pc) star-forming regions to measure the accretion variability of protostars. The total survey area of ˜1.6 deg2 includes ˜105 peaks with peaks brighter than 0.5 Jy/beam (43 associated with embedded protostars or disks) and 237 peaks of 0.125-0.5 Jy/beam (50 with embedded protostars or disks). Each field has enough bright peaks for flux calibration relative to other peaks in the same field, which improves upon the nominal flux calibration uncertainties of submillimeter observations to reach a precision of ˜2%-3% rms, and also provides quantified confidence in any measured variability. The timescales and amplitudes of any submillimeter variation will then be converted into variations in accretion rate and subsequently used to infer the physical causes of the variability. This survey is the first dedicated survey for submillimeter variability and complements other transient surveys at optical and near-IR wavelengths, which are not sensitive to accretion variability of deeply embedded protostars.

Locally linear embedding: dimension reduction of massive protostellar spectra

NASA Astrophysics Data System (ADS)

Ward, J. L.; Lumsden, S. L.

2016-09-01

We present the results of the application of locally linear embedding (LLE) to reduce the dimensionality of dereddened and continuum subtracted near-infrared spectra using a combination of models and real spectra of massive protostars selected from the Red MSX Source survey data base. A brief comparison is also made with two other dimension reduction techniques; principal component analysis (PCA) and Isomap using the same set of spectra as well as a more advanced form of LLE, Hessian locally linear embedding. We find that whilst LLE certainly has its limitations, it significantly outperforms both PCA and Isomap in classification of spectra based on the presence/absence of emission lines and provides a valuable tool for classification and analysis of large spectral data sets.

Collapse and Fragmentation of Molecular Cloud Cores. VII. Magnetic Fields and Multiple Protostar Formation

NASA Astrophysics Data System (ADS)

Boss, Alan P.

2002-04-01

Recent observations of star-forming regions suggest that binary and multiple young stars are the rule rather than the exception and implicate fragmentation as the likely mechanism for their formation. Most numerical hydrodynamic calculations of fragmentation have neglected the possibly deleterious effects of magnetic fields, despite ample evidence for the importance of magnetic support of precollapse clouds. We present here the first numerical hydrodynamic survey of the collapse and fragmentation of initially magnetically supported clouds that takes into account several magnetic field effects in an approximate manner. The models are calculated with a three-dimensional, finite differences code that solves the equations of hydrodynamics, gravitation, and radiative transfer in the Eddington and diffusion approximations. Magnetic field effects are included through two simple approximations: magnetic pressure is added to the gas pressure, and magnetic tension is approximated by gravity dilution once collapse is well underway. Ambipolar diffusion of the magnetic field leading to cloud collapse is treated approximately as well. Models are calculated for a variety of initial cloud density profiles, shapes, and rotation rates. We find that in spite of the inclusion of magnetic field effects, dense cloud cores are capable of fragmenting into binary and multiple protostar systems. Initially prolate clouds tend to fragment into binary protostars, while initially oblate clouds tend to fragment into multiple protostar systems containing a small number (of the order of 4) of fragments. The latter are likely to be subject to rapid orbital evolution, with close encounters possibly leading to the ejection of fragments. Contrary to expectation, magnetic tension effects appear to enhance fragmentation, allowing lower mass fragments to form than would otherwise be possible, because magnetic tension helps to prevent a central density singularity from forming and producing a dominant

Uncovering the Protostars in Serpens South with ALMA: Continuum Sources and Their Outflow Activity

NASA Astrophysics Data System (ADS)

Plunkett, Adele; Arce, H.; Corder, S.; Dunham, M.

2017-06-01

Serpens South is an appealing protostellar cluster to study due the combination of several factors: (1) a high protostar fraction that shows evidence for very recent and ongoing star formation; (2) iconic clustered star formation along a filamentary structure; (3) its relative proximity within a few hundred parsecs. An effective study requires the sensitivity, angular and spectral resolution, and mapping capabilities recently provided with ALMA. Here we present a multi-faceted data set acquired from Cycles 1 through 3 with ALMA, including maps of continuum sources and molecular outflows throughout the region, as well as a more focused kinematical study of the protostar that is the strongest continuum source at the cluster center. Together these data span spatial scales over several orders of magnitude, allowing us to investigate the outflow-driving sources and the impact of the outflows on the cluster environment. Currently, we focus on the census of protostars in the cluster center, numbering about 20, including low-flux, low-mass sources never before detected in mm-wavelengths and evidence for multiplicity that was previously unresolved.

Water in embedded low-mass protostars: cold envelopes and warm outflows

NASA Astrophysics Data System (ADS)

Kristensen, Lars E.; van Dishoeck, Ewine; Mottram, Joseph; Schmalzl, Markus; Visser, Ruud

2015-08-01

As stars form, gas from the parental cloud is transported through the molecular envelope to the protostellar disk from which planets eventually form. Water plays a crucial role in such systems: it forms the backbone of the oxygen chemistry, it is a unique probe of warm and hot gas, and it provides a unique link between the grain surface and gas-phase chemistries. The distribution of water, both as ice and gas, is a fundamental question to our understanding of how planetary systems, such as the Solar System, form.The Herschel Space Observatory observed many tens of embedded low-mass protostars in a suite of gas-phase water transitions in several programs (e.g. Water in Star-forming regions with Herschel, WISH, and the William Herschel Line Legacy Survey, WILL), and related species (e.g. CO in Protostars with HIFI, COPS-HIFI). I will summarize what Herschel has revealed about the water distribution in the cold outer molecular envelope of low-mass protostars, and the warm gas in outflows, the two components predominantly traced by Herschel observations. I will present our current understanding of where the water vapor is in protostellar systems and the underlying physical and chemical processes leading to this distribution. Through these dedicated observational surveys and complementary modeling efforts, we are now at a stage where we can quantify where the water is during the early stages of star formation.

CONSTRAINING THE ABUNDANCES OF COMPLEX ORGANICS IN THE INNER REGIONS OF SOLAR-TYPE PROTOSTARS

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

Taquet, Vianney; Charnley, Steven B.; López-Sepulcre, Ana

The high abundances of Complex Organic Molecules (COMs) with respect to methanol, the most abundant COM, detected toward low-mass protostars, tend to be underpredicted by astrochemical models. This discrepancy might come from the large beam of the single-dish telescopes, encompassing several components of the studied protostar, commonly used to detect COMs. To address this issue, we have carried out multi-line observations of methanol and several COMs toward the two low-mass protostars NGC 1333-IRAS 2A and -IRAS 4A with the Plateau de Bure interferometer at an angular resolution of 2″, resulting in the first multi-line detection of the O-bearing species glycolaldehydemore » and ethanol and of the N-bearing species ethyl cyanide toward low-mass protostars other than IRAS 16293. The high number of detected transitions from COMs (more than 40 methanol transitions for instance) allowed us to accurately derive the source size of their emission and the COM column densities. The COM abundances with respect to methanol derived toward IRAS 2A and IRAS 4A are slightly, but not substantitally, lower than those derived from previous single-dish observations. The COM abundance ratios do not vary significantly with the protostellar luminosity, over five orders of magnitude, implying that low-mass hot corinos are quite chemically rich as high-mass hot cores. Astrochemical models still underpredict the abundances of key COMs, such as methyl formate or di-methyl ether, suggesting that our understanding of their formation remains incomplete.« less

Radiative transfer modelling of W33A MM1: 3-D structure and dynamics of a complex massive star forming region

NASA Astrophysics Data System (ADS)

Izquierdo, Andrés F.; Galván-Madrid, Roberto; Maud, Luke T.; Hoare, Melvin G.; Johnston, Katharine G.; Keto, Eric R.; Zhang, Qizhou; de Wit, Willem-Jan

2018-05-01

We present a composite model and radiative transfer simulations of the massive star forming core W33A MM1. The model was tailored to reproduce the complex features observed with ALMA at ≈0.2 arcsec resolution in CH3CN and dust emission. The MM1 core is fragmented into six compact sources coexisting within ˜1000 au. In our models, three of these compact sources are better represented as disc-envelope systems around a central (proto)star, two as envelopes with a central object, and one as a pure envelope. The model of the most prominent object (Main) contains the most massive (proto)star (M⋆ ≈ 7 M⊙) and disc+envelope (Mgas ≈ 0.4 M⊙), and is the most luminous (LMain ˜ 104 L⊙). The model discs are small (a few hundred au) for all sources. The composite model shows that the elongated spiral-like feature converging to the MM1 core can be convincingly interpreted as a filamentary accretion flow that feeds the rising stellar system. The kinematics of this filament is reproduced by a parabolic trajectory with focus at the center of mass of the region. Radial collapse and fragmentation within this filament, as well as smaller filamentary flows between pairs of sources are proposed to exist. Our modelling supports an interpretation where what was once considered as a single massive star with a ˜103 au disc and envelope, is instead a forming stellar association which appears to be virialized and to form several low-mass stars per high-mass object.

Probing the core of Cepheus A - Millimeter and submillimeter observations

NASA Astrophysics Data System (ADS)

Moriarty-Schieven, G. H.; Snell, R. L.; Hughes, V. A.

1991-06-01

Moderate and high angular resolution (40-7 arcsec) maps are presented of the core of the Cepheus A star-forming region using CS J = 3-2 and J = 7-6 emission, which traces the dense gas component of the cloud core, and using far-infrared (450 and 800 microns) continuum emission tracing the warm dust component. Three regimes in the core are traced by these observations: (1) a small (about 0.14 pc), nearly circular central core of high density (1-10 x 10 to the 6th/cu cm) and temperature (30-100 K) containing at least 25 percent of the mass and which contains the active early-type star formation; (2) an extended (0.5 x 0.25 pc), NE-SW oriented core of mass 200-300 solar masses, temperature 30-40 K, and average density nH2 of about 10 to the 5th/cu cm and which, together with the central core, contains 60-80 percent of the total core mass; and (3) an extended core envelope of dimensions 0.5 x 0.85 pc oriented primarily north-south, and a lower density. The velocity structure of the core suggests that it is being disrupted by the high-velocity winds driving the molecular outflow and is not due to a rotating circumstellar disk.

Modeling Protostar Envelopes and Disks Seen With ALMA: A Focus on L1527 Kinematics

NASA Astrophysics Data System (ADS)

Terebey, Susan; Flores Rivera, Lizxandra; Willacy, Karen

2018-06-01

ALMA probes continuum and spectral line emission from protostars that comes from both the envelope and circumstellar disk. The dust and gas emit on a variety of spatial scales, ranging from sub-arcseconds for disks to roughly 10 arcseconds for envelopes for nearby protostars. We present models of what ALMA should detect that incorporate a self-consistent collapse solution, radiative transfer, and realistic dust properties. Molecular abundances are also calculated; we present results for CO and isotopologues for the Class 0 source L1527. Results for the outer disk show that there can be significant differences from standard assumptions due to the effect of CO freeze out and non-Keplerian dynamics.

Therapeutic lipid target achievements among high and highest risk patients: results from the CEPHEUS study in the Arabian Gulf.

PubMed

Al-Rasadi, Khalid; Al-Zakwani, Ibrahim; Al Mahmeed, Wael; Arafah, Mohamed; Al-Hinai, Ali T; Shehab, Abdullah; Al Tamimi, Omer; Alawadhi, Mahmoud

2014-12-01

To determine lipid target achievements of low-density lipoprotein cholesterol (LDL-C), non-high density lipoprotein cholesterol (non-HDL-C) and apolipoprotein B (apo B) in the Centralized Pan-Middle East Survey on the undertreatment of hypercholesterolemia (CEPHEUS) in Arabian Gulf States patients with high and highest risk according to the joint Consensus Statement of the American Diabetes Association (ADA) and American College of Cardiology Foundation (ACC). CEPHEUS was conducted in patients (≥ 18 years of age) in six Middle Eastern countries between November 2009 and July 2010 on lipid lowering drugs (LLDs). Serum samples collected included total cholesterol (TC), LDL-C, HDL-C, triglycerides (TGs), apo B, and apolipoprotein A1 (apo A1). The overall mean age of the cohort (n = 5275) was 56 ± 13 years, 58% (n = 3060) were male and 69% (n = 3635) were highest risk. LDL-C target was achieved in 25%, non-HDL-C in 36% and apo B in 38% of patients in the highest risk cohort compared with LDL-C 46%, non-HDL-C 58% and apo B 51% in the high risk group. In patients with TGs ≥ 2.2 mmol/L, LDL-C target was achieved in 16% and apo B in 15% of patients in the highest risk group compared with LDL-C 32% and apo B 22% in the high risk cohort. Despite being on LLDs, a large proportion of high and highest risk patients in the Arabian Gulf are not at recommended lipid targets and remain at a substantial residual risk for cardiovascular diseases. Apo B may be used as an additional target in patients with triglycerides ≥ 2.2 mmol/L. The findings should be interpreted in light of the study's limitations.

Photometry and Classification of Stars around the Reflection Nebula NGC 7023 IN Cepheus. I. A Catalog of Magnitudes, Color Indices and Spectral Types of 1240 Stars

NASA Astrophysics Data System (ADS)

Zdanavičius, K.; Zdanavičius, J.; Straižys, V.; Kotovas, A.

The catalog contains magnitudes and color indices of 1240 stars down to ˜ 16.7 mag in V measured in the seven-color Vilnius photometric system in the area of 1.5 square degrees around the reflection nebula NGC 7023 in Cepheus. For most of the stars spectral types determined from the photometric data are given. A large number of visual binaries with separations between 3'' and 10'' are identified using the DSS2 images.

Massive Stars and Star Clusters in the Era of JWST

NASA Astrophysics Data System (ADS)

Klein, Richard

radiative transfer with both ionizing and non-ionizing radiation that accurately handle both the direct radiation from stars and the diffuse infrared radiation field that builds up when direct radiation is reprocessed by dust grains. Our simulations include all of the relevant feedback effects such as radiative heating, radiation pressure, photodissociation and photoionization, protostellar outflows and stellar winds. The challenge in simulating the formation of massive stars and massive clusters is to include all these feedback effects self-consistently as they occur collectively. We are in an excellent position to do so. The results of these simulations will be directly relevant to the interpretation of observations with JWST, which will probe cluster formation in both the nearby and distant universe, and with SOFIA, which can observe high-mass star formation in the Galaxy. We shall make direct comparison with observations of massive protostars in the Galactic disk. We shall also compare with observations of star clusters that form in dense environments, such as the Galactic Center and in merging galaxies (e.g., the Antennae), and in low metallicity environments, such as the dwarf starburst galaxy I Zw 18. Once our simulations have been benchmarked with observations of massive protostars in the Galaxy and massive protoclusters in the local universe, they will provide the theoretical basis for interpreting observations of the formation of massive star clusters at high redshift with JWST. What determines the maximum mass of a star? How does stellar feedback affect the formation of individual stars and the formation of massive star clusters and how the answers to these questions evolve with cosmic time. The proposed research will provide high-resolution input to the study of stellar feedback on galaxy formation with a significantly more accurate treatment of the physics, particularly the radiative transfer that is so important for feedback.

PROTOSTELLAR OUTFLOWS AND RADIATIVE FEEDBACK FROM MASSIVE STARS. II. FEEDBACK, STAR-FORMATION EFFICIENCY, AND OUTFLOW BROADENING

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

Kuiper, Rolf; Turner, Neal J.; Yorke, Harold W., E-mail: rolf.kuiper@uni-tuebingen.de, E-mail: Neal.J.Turner@jpl.nasa.gov, E-mail: Harold.W.Yorke@jpl.nasa.gov

2016-11-20

We perform two-dimensional axially symmetric radiation hydrodynamic simulations to assess the impact of outflows and radiative force feedback from massive protostars by varying when the protostellar outflow starts, and to determine the ratio of ejection to accretion rates and the strength of the wide-angle disk wind component. The star-formation efficiency, i.e., the ratio of final stellar mass to initial core mass, is dominated by radiative forces and the ratio of outflow to accretion rates. Increasing this ratio has three effects. First, the protostar grows slower with a lower luminosity at any given time, lowering radiative feedback. Second, bipolar cavities clearedmore » by the outflow become larger, further diminishing radiative feedback on disk and core scales. Third, the higher momentum outflow sweeps up more material from the collapsing envelope, decreasing the protostar's potential mass reservoir via entrainment. The star-formation efficiency varies with the ratio of ejection to accretion rates from 50% in the case of very weak outflows to as low as 20% for very strong outflows. At latitudes between the low-density bipolar cavity and the high-density accretion disk, wide-angle disk winds remove some of the gas, which otherwise would be part of the accretion flow onto the disk; varying the strength of these wide-angle disk winds, however, alters the final star-formation efficiency by only ±6%. For all cases, the opening angle of the bipolar outflow cavity remains below 20° during early protostellar accretion phases, increasing rapidly up to 65° at the onset of radiation pressure feedback.« less

Sun-sized Water Vapor Masers in Cepheus A

NASA Astrophysics Data System (ADS)

Sobolev, A. M.; Moran, J. M.; Gray, M. D.; Alakoz, A.; Imai, H.; Baan, W. A.; Tolmachev, A. M.; Samodurov, V. A.; Ladeyshchikov, D. A.

2018-03-01

We present the first VLBI observations of a Galactic water maser (in Cepheus A) made with a very long baseline interferometric array involving the RadioAstron Earth-orbiting satellite station as one of its elements. We detected two distinct components at ‑16.9 and 0.6 km s‑1 with a fringe spacing of 66 μas. In total power, the 0.6 km s‑1 component appears to be a single Gaussian component of strength 580 Jy and width of 0.7 km s‑1. Single-telescope monitoring showed that its lifetime was only eight months. The absence of a Zeeman pattern implies the longitudinal magnetic field component is weaker than 120 mG. The space–Earth cross power spectrum shows two unresolved components smaller than 15 μas, corresponding to a linear scale of 1.6 × 1011 cm, about the diameter of the Sun, for a distance of 700 pc, separated by 0.54 km s‑1 in velocity and by 160 ± 35 μas in angle. This is the smallest angular structure ever observed in a Galactic maser. The brightness temperatures are greater than 2 × 1014 K, and the line widths are 0.5 km s‑1. Most of the flux (about 87%) is contained in a halo of angular size of 400 ± 150 μas. This structure is associated with the compact H II region HW3diii. We have probably picked up the most prominent peaks in the angular size range of our interferometer. We discuss three dynamical models: (1) Keplerian motion around a central object, (2) two chance overlapping clouds, and (3) vortices caused by flow around an obstacle (i.e., von Kármán vortex street) with a Strouhal number of about 0.3.

Deuterated water in low-mass protostars

NASA Astrophysics Data System (ADS)

Coutens, Audrey; Vastel, Charlotte; Chess Collaboration; Wish Collaboration; Hexos Collaboration

2013-07-01

In addition to its dominant role in the cooling of warm gas and in the oxygen chemistry, water is a primordial species in the emergence of life, and comets may have brought a large fraction to Earth to form the oceans. Observations of deuterated water are an important complement for studies of H2O to understand how water forms and how it has evolved from cold prestellar cores to protoplanetary disks and consequently oceans for the Earth's specific, but probably not isolated, case. Several deuterated water transitions were observed with the Herschel/HIFI (Heterodyne Instrument for Far Infrared) instrument towards three low-mass protostars: IRAS 16293-2422, NGC1333 IRAS4A and NGC1333 IRAS4B. In the first source, both HDO and D2O lines are detected, thanks to the unbiased spectral survey carried out by the CHESS key program (Vastel et al. 2010, Coutens et al. 2013a). In the framework of a collaboration between the CHESS, WISH and HEXOS programs, two HDO key lines were observed towards the two other protostars. In addition, complementary observations were carried out with several ground-based single-dish telescopes (IRAM-30m, JCMT, APEX). We used the non-LTE RATRAN spherical model (Hogerheijde & van der Tak 2000) to determine the HDO abundance distribution throughout the protostellar envelope. An abundance jump at 100 K is required to reproduce the line profiles. Indeed, water molecules trapped in the icy grain mantles thermally desorb in the hot corinos, the inner warm regions of the protostellar envelopes. We also obtain that it is necessary to add a water-rich external absorbing layer to reproduce the absorbing components of the HDO and D2O fundamental transitions in all sources (Coutens et al. 2012, 2013a,b). The results derived for the different sources will be then presented and discussed.

Radio outburst from a massive (proto)star. When accretion turns into ejection

NASA Astrophysics Data System (ADS)

Cesaroni, R.; Moscadelli, L.; Neri, R.; Sanna, A.; Caratti o Garatti, A.; Eisloffel, J.; Stecklum, B.; Ray, T.; Walmsley, C. M.

2018-05-01

Context. Recent observations of the massive young stellar object S255 NIRS 3 have revealed a large increase in both methanol maser flux density and IR emission, which have been interpreted as the result of an accretion outburst, possibly due to instabilities in a circumstellar disk. This indicates that this type of accretion event could be common in young/forming early-type stars and in their lower mass siblings, and supports the idea that accretion onto the star may occur in a non-continuous way. Aims: As accretion and ejection are believed to be tightly associated phenomena, we wanted to confirm the accretion interpretation of the outburst in S255 NIRS 3 by detecting the corresponding burst of the associated thermal jet. Methods: We monitored the radio continuum emission from S255 NIRS 3 at four bands using the Karl G. Jansky Very Large Array. The millimetre continuum emission was also observed with both the Northern Extended Millimeter Array of IRAM and the Atacama Large Millimeter/Submillimeter Array. Results: We have detected an exponential increase in the radio flux density from 6 to 45 GHz starting right after July 10, 2016, namely 13 months after the estimated onset of the IR outburst. This is the first ever detection of a radio burst associated with an IR accretion outburst from a young stellar object. The flux density at all observed centimetre bands can be reproduced with a simple expanding jet model. At millimetre wavelengths we infer a marginal flux increase with respect to the literature values and we show this is due to free-free emission from the radio jet. Conclusions: Our model fits indicate a significant increase in the jet opening angle and ionized mass loss rate with time. For the first time, we can estimate the ionization fraction in the jet and conclude that this must be low (<14%), lending strong support to the idea that the neutral component is dominant in thermal jets. Our findings strongly suggest that recurrent accretion + ejection

The Envelope Kinematics and a Possible Disk around the Class 0 Protostar within BHR7

NASA Astrophysics Data System (ADS)

Tobin, John J.; Bos, Steven P.; Dunham, Michael M.; Bourke, Tyler L.; van der Marel, Nienke

2018-04-01

We present a characterization of the protostar embedded within the BHR7 dark cloud, based on both photometric measurements from the near-infrared to millimeter and interferometric continuum and molecular line observations at millimeter wavelengths. We find that this protostar is a Class 0 system, the youngest class of protostars, measuring its bolometric temperature to be 50.5 K, with a bolometric luminosity of 9.3 L ⊙. The near-infrared and Spitzer imaging show a prominent dark lane from dust extinction separating clear bipolar outflow cavities. Observations of 13CO (J=2\\to 1), C18O (J=2\\to 1), and other molecular lines with the Submillimeter Array (SMA) exhibit a clear rotation signature on scales <1300 au. The rotation can be traced to an inner radius of ∼170 au and the rotation curve is consistent with an R ‑1 profile, implying that angular momentum is being conserved. Observations of the 1.3 mm dust continuum with the SMA reveal a resolved continuum source, extended in the direction of the dark lane, orthogonal to the outflow. The deconvolved size of the continuum indicates a radius of ∼100 au for the continuum source at the assumed distance of 400 pc. The visibility amplitude profile of the continuum emission cannot be reproduced by an envelope alone and needs a compact component. Thus, we posit that the resolved continuum source could be tracing a Keplerian disk in this very young system. If we assume that the continuum radius traces a Keplerian disk (R ∼ 120 au) the observed rotation profile is consistent with a protostar mass of 1.0 M ⊙.

Episodic accretion in binary protostars emerging from self-gravitating solar mass cores

NASA Astrophysics Data System (ADS)

Riaz, R.; Vanaverbeke, S.; Schleicher, D. R. G.

2018-06-01

Observations show a large spread in the luminosities of young protostars, which are frequently explained in the context of episodic accretion. We tested this scenario with numerical simulations that follow the collapse of a solar mass molecular cloud using the GRADSPH code, thereby varying the strength of the initial perturbations and temperature of the cores. A specific emphasis of this paper is to investigate the role of binaries and multiple systems in the context of episodic accretion and to compare their evolution to the evolution in isolated fragments. Our models form a variety of low-mass protostellar objects including single, binary, and triple systems in which binaries are more active in exhibiting episodic accretion than isolated protostars. We also find a general decreasing trend in the average mass accretion rate over time, suggesting that the majority of the protostellar mass is accreted within the first 105 years. This result can potentially help to explain the surprisingly low average luminosities in the majority of the protostellar population.

Infrared spectra of rotating protostars

NASA Technical Reports Server (NTRS)

Adams, F. C.; Shu, F. H.

1986-01-01

Earlier calculations of the infrared emission expected from stars in the process of being made are corrected to include the most important observable effects of rotation and generalized. An improved version of the spherical model of a previous paper is developed, and the corresponding emergent spectral energy distributions are calculated for the theoretically expected mass infall rate in the cores of cool and quiescent molecular clouds. The dust grain opacity model and the temperature profile parameterization are improved. It is shown that the infrared spectrum of the IRAS source 04264+2426, which is associated with a Herbig-Haro object, can be adequately represented in terms of a rotating and accreting protostar. This strengthens the suggestion that collimated outflows in young stellar objects originate when a stellar wind tries to emerge and reverse the swirling pattern of infall which gave birth to the central star.

Photometry and Classification of Stars in the Direction of the Dark Cloud Tgu 619 IN Cepheus. I. a Catalog of Magnitudes, Color Indices and Spectral Types of 1304 Stars

NASA Astrophysics Data System (ADS)

Zdanavičius, K.; Zdanavičius, J.; Straižys, V.; Maskoliūnas, M.

The catalog contains magnitudes and color indices of 1304 stars down to ˜ 16.6 mag in V measured in the seven-color Vilnius photometric system in the area of 1.5 square degrees with the center at Galactic coordinates 102.4°, +15.5°, containing the dark cloud TGU 619 in the Cepheus Flare. For most of the stars spectral and luminosity classes determined from the photometric data are given.

Detection of glycolaldehyde toward the solar-type protostar NGC 1333 IRAS2A

NASA Astrophysics Data System (ADS)

Coutens, A.; Persson, M. V.; Jørgensen, J. K.; Wampfler, S. F.; Lykke, J. M.

2015-04-01

Glycolaldehyde is a key molecule in the formation of biologically relevant molecules such as ribose. We report its detection with the Plateau de Bure interferometer toward the Class 0 young stellar object NGC 1333 IRAS2A, which is only the second solar-type protostar for which this prebiotic molecule is detected. Local thermodynamic equilibrium analyses of glycolaldehyde, ethylene glycol (the reduced alcohol of glycolaldehyde), and methyl formate (the most abundant isomer of glycolaldehyde) were carried out. The relative abundance of ethylene glycol to glycolaldehyde is found to be ~5 - higher than in the Class 0 source IRAS 16293-2422 (~1), but similar to the lower limits derived in comets (≥3-6). The different ethylene glycol-to-glycolaldehyde ratios in the two protostars might be related to different CH3OH:CO compositions of the icy grain mantles. In particular, a more efficient hydrogenation on the grains in NGC 1333 IRAS2A would favor the formation of both methanol and ethylene glycol. In conclusion, it is possible that like NGC 1333 IRAS2A, other low-mass protostars show high ethylene glycol-to-glycolaldehyde abundance ratios. The cometary ratios might consequently be inherited from earlier stages of star formation if the young Sun experienced conditions similar to NGC 1333 IRAS2A. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).Figures 3-4 and Table 1 are available in electronic form at http://www.aanda.org

ORPHANED PROTOSTARS

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

Reipurth, Bo; Connelley, Michael; Mikkola, Seppo

2010-12-10

We explore the origin of a population of distant companions ({approx}1000-5000 AU) to Class I protostellar sources recently found by Connelley and coworkers, who noted that the companion fraction diminished as the sources evolved. Here, we present N-body simulations of unstable triple systems embedded in dense cloud cores. Many companions are ejected into unbound orbits and quickly escape, but others are ejected with insufficient momentum to climb out of the potential well of the cloud core and associated binary. These loosely bound companions reach distances of many thousands of AU before falling back and eventually being ejected into escapes asmore » the cloud cores gradually disappear. We use the term orphans to denote protostellar objects that are dynamically ejected from their placental cloud cores, either escaping or for a time being tenuously bound at large separations. Half of all triple systems are found to disintegrate during the protostellar stage, so if multiple systems are a frequent outcome of the collapse of a cloud core, then orphans should be common. Bound orphans are associated with embedded close protostellar binaries, but escaping orphans can travel as far as {approx}0.2 pc during the protostellar phase. The steep climb out of a potential well ensures that orphans are not kinematically distinct from young stars born with a less violent pre-history. The identification of orphans outside their heavily extincted cloud cores will allow the detailed study of protostars high up on their Hayashi tracks at near-infrared and in some cases even at optical wavelengths.« less

Early Science Planning of Protoplanetary Disks and Protostars in the Orion Nebula Cluster Using SOFIA/FORCAST

NASA Astrophysics Data System (ADS)

Hoadley, Keri; Adams, J. D.; Herter, T. L.; Gull, G.; Henderson, C.; Schoenwald, J.; Keller, L.; Megeath, T. S.

2011-01-01

The Faint Object Camera for the SOFIA Telescope (FORCAST) is a mid-infrared facility instrument for the Stratospheric Observatory For Infrared Astronomy (SOFIA). In late May of this year, FORCAST achieved first light on SOFIA during a Telescope Assembly characterization flight, successfully taking photometry of Jupiter, its moons, and M82 from an altitude of 35,000 ft. Analysis of images of Jupiter and one of its moons, Ganymede, show the in-flight sensitivity to be comparable to that expected from preflight (lab) measurements and models. In preparation for SOFIA Short Science, we constructed Spectral Energy Distributions (SEDs) for known proplyds and protostars (Smith et al. 2005) in the core of the Orion molecular cloud using 2MASS (Skrutskie et al. 2006), IRAC on Spitzer, TReCS on Gemini South (Smith et al. 2005), and 880mm SCUBA data (Mann and Williams 2009). FORCAST will provide important wavelength coverage (20 - 40 microns) which when used in conjunction with previous data will constrain the physical properties of the proplyds and protostars. We fit the observed SEDs with those from radiative transfer models for circumstellar disks and protostars from Robitaille et al (2006, 2007). With these models, we can extrapolate into the 20 - 40 micron region of FORCAST and determine the range of models that FORCAST is capable of detecting. Using the FORCAST sensitivity model and the SEDs of known proplyds, we expect to detect 67% of the proplyds found by other investigations. However, detectability will be greatly influenced by the presence of structures in the diffuse dust emission associated with the HII region complex. Comparing FORCAST observations with the radiative transfer models will help to understand the physical properties of proplyds and protostars, and perhaps illuminate the impact of their environments, such as photoevaporation of disks and effects from crowding.

Chasing discs around O-type (proto)stars: Evidence from ALMA observations

NASA Astrophysics Data System (ADS)

Cesaroni, R.; Sánchez-Monge, Á.; Beltrán, M. T.; Johnston, K. G.; Maud, L. T.; Moscadelli, L.; Mottram, J. C.; Ahmadi, A.; Allen, V.; Beuther, H.; Csengeri, T.; Etoka, S.; Fuller, G. A.; Galli, D.; Galván-Madrid, R.; Goddi, C.; Henning, T.; Hoare, M. G.; Klaassen, P. D.; Kuiper, R.; Kumar, M. S. N.; Lumsden, S.; Peters, T.; Rivilla, V. M.; Schilke, P.; Testi, L.; van der Tak, F.; Vig, S.; Walmsley, C. M.; Zinnecker, H.

2017-06-01

Context. Circumstellar discs around massive stars could mediate the accretion onto the star from the infalling envelope, and could minimize the effects of radiation pressure. Despite such a crucial role, only a few convincing candidates have been provided for discs around deeply embedded O-type (proto)stars. Aims: In order to establish whether disc-mediated accretion is the formation mechanism for the most massive stars, we have searched for circumstellar, rotating discs around a limited sample of six luminous (>105L⊙) young stellar objects. These objects were selected on the basis of their IR and radio properties in order to maximize the likelihood of association with disc+jet systems. Methods: We used ALMA with 0.̋2 resolution to observe a large number of molecular lines typical of hot molecular cores. In this paper we limit our analysis to two disc tracers (methyl cyanide, CH3CN, and its isotopologue, 13CH3CN), and an outflow tracer (silicon monoxide, SiO). Results: We reveal many cores, although their number depends dramatically on the target. We focus on the cores that present prominent molecular line emission. In six of these a velocity gradient is seen across the core,three of which show evidence of Keplerian-like rotation. The SiO data reveal clear but poorly collimated bipolar outflow signatures towards two objects only. This can be explained if real jets are rare (perhaps short-lived) in very massive objects and/or if stellar multiplicity significantly affects the outflow structure.For all cores with velocity gradients, the velocity field is analysed through position-velocity plots to establish whether the gas is undergoing rotation with νrot ∝ R- α, as expected for Keplerian-like discs. Conclusions: Our results suggest that in three objects we are observing rotation in circumstellar discs, with three more tentative cases, and one core where no evidence for rotation is found. In all cases but one, we find that the gas mass is less than the mass of

ALMA Observations of SMM11 Reveal an Extremely Young Protostar in Serpens Main Cluster

NASA Astrophysics Data System (ADS)

Aso, Yusuke; Ohashi, Nagayoshi; Aikawa, Yuri; Machida, Masahiro N.; Saigo, Kazuya; Saito, Masao; Takakuwa, Shigehisa; Tomida, Kengo; Tomisaka, Kohji; Yen, Hsi-Wei; Williams, Jonathan P.

2017-11-01

We report the discovery of an extremely young protostar, SMM11, located in the associated submillimeter condensation in the Serpens Main cluster using the Atacama Large Millimeter/submillimeter Array (ALMA) during its Cycle 3 at 1.3 mm and an angular resolution of ˜ 0\\buildrel{\\prime\\prime}\\over{.} 5˜ 210 {AU}. SMM11 is a Class 0 protostar without any counterpart at 70 μm or shorter wavelengths. The ALMA observations show 1.3 mm continuum emission associated with a collimated 12CO bipolar outflow. Spitzer and Herschel data show that SMM11 is extremely cold ({T}{bol} = 26 K) and faint ({L}{bol} ≲ 0.9 {L}⊙ ). We estimate the inclination angle of the outflow to be ˜ 80^\\circ , almost parallel to the plane of the sky, from simple fitting using a wind-driven-shell model. The continuum visibilities consist of Gaussian and power-law components, suggesting a spherical envelope with a radius of ˜600 au around the protostar. The estimated low C18O abundance, X(C18O) = 1.5-3 × {10}-10, is also consistent with its youth. The high outflow velocity, a few 10 {km} {{{s}}}-1 at a few 1000 au, is much higher than theoretical simulations of first hydrostatic cores, and we suggest that SMM11 is a transitional object right after the second collapse of the first core.

A distance-limited sample of massive molecular outflows

NASA Astrophysics Data System (ADS)

Maud, L. T.; Moore, T. J. T.; Lumsden, S. L.; Mottram, J. C.; Urquhart, J. S.; Hoare, M. G.

2015-10-01

We have observed 99 mid-infrared-bright, massive young stellar objects and compact H II regions drawn from the Red MSX source survey in the J = 3-2 transition of 12CO and 13CO, using the James Clerk Maxwell Telescope. 89 targets are within 6 kpc of the Sun, covering a representative range of luminosities and core masses. These constitute a relatively unbiased sample of bipolar molecular outflows associated with massive star formation. Of these, 59, 17 and 13 sources (66, 19 and 15 per cent) are found to have outflows, show some evidence of outflow, and have no evidence of outflow, respectively. The time-dependent parameters of the high-velocity molecular flows are calculated using a spatially variable dynamic time-scale. The canonical correlations between the outflow parameters and source luminosity are recovered and shown to scale with those of low-mass sources. For coeval star formation, we find the scaling is consistent with all the protostars in an embedded cluster providing the outflow force, with massive stars up to ˜30 M⊙ generating outflows. Taken at face value, the results support the model of a scaled-up version of the accretion-related outflow-generation mechanism associated with discs and jets in low-mass objects with time-averaged accretion rates of ˜10-3 M⊙ yr-1 on to the cores. However, we also suggest an alternative model, in which the molecular outflow dynamics are dominated by the entrained mass and are unrelated to the details of the acceleration mechanism. We find no evidence that outflows contribute significantly to the turbulent kinetic energy of the surrounding dense cores.

Proper motions of collimated jets from intermediate-mass protostars in the Carina Nebula

NASA Astrophysics Data System (ADS)

Reiter, Megan; Kiminki, Megan M.; Smith, Nathan; Bally, John

2017-10-01

We present proper motion measurements of 37 jets and HH objects in the Carina Nebula measured in two epochs of H α images obtained ˜10 yr apart with Hubble Space Telescope/Advanced Camera for Surveys (ACS). Transverse velocities in all but one jet are faster than ≳ 25 km s-1, confirming that the jet-like H α features identified in the first epoch images trace outflowing gas. Proper motions constrain the location of the jet-driving source and provide kinematic confirmation of the intermediate-mass protostars that we identify for 20/37 jets. Jet velocities do not correlate with the estimated protostar mass and embedded driving sources do not have slower jets. Instead, transverse velocities (median ˜75 km s-1) are similar to those in jets from low-mass stars. Assuming a constant velocity since launch, we compute jet dynamical ages (median ˜104 yr). If continuous emission from inner jets traces the duration of the most recent accretion bursts, then these episodes are sustained longer (median ˜700 yr) than the typical decay time of an FU Orionis outburst. These jets can carry appreciable momentum that may be injected into the surrounding environment. The resulting outflow force, dP/dt, lies between that measured in low- and high-mass sources, despite the very different observational tracers used. Smooth scaling of the outflow force argues for a common physical process underlying outflows from protostars of all masses. This latest kinematic result adds to a growing body of evidence that intermediate-mass star formation proceeds like a scaled-up version of the formation of low-mass stars.

Herschel/PACS far-IR spectral imaging of a jet from an intermediate mass protostar in the OMC-2 region

NASA Astrophysics Data System (ADS)

González-García, B.; Manoj, P.; Watson, D. M.; Vavrek, R.; Megeath, S. T.; Stutz, A. M.; Osorio, M.; Wyrowski, F.; Fischer, W.; Tobin, J. J.; Sánchez-Portal, M.; Diaz Rodriguez, A. K.; Wilson, T. L.

2016-11-01

We present the first detection of a jet in the far-IR [O I] lines from an intermediate mass protostar. This jet was detected in a Herschel/PACS spectral mapping study in the [O I] lines of OMC-2 FIR 3 and FIR 4, two of the most luminous protostars in Orion outside of the Orion Nebula. The spatial morphology of the fine structure line emission reveals the presence of an extended photodissociation region (PDR) and a narrow, but intense jet connecting the two protostars. The jet seen in [O I] emission is spatially aligned with the Spitzer/IRAC 4.5 μm jet and the CO (6-5) molecular outflow centered on FIR 3. The mass-loss rate derived from the total [O I] 63 μm line luminosity of the jet is 7.7 × 10-6M⊙ yr-1, more than an order of magnitude higher than that measured for typical low-mass class 0 protostars. The implied accretion luminosity is significantly higher than the observed bolometric luminosity of FIR 4, indicating that the [O I] jet is unlikely to be associated with FIR 4. We argue that the peak line emission seen toward FIR 4 originates in the terminal shock produced by the jet driven by FIR 3. The higher mass-loss rate that we find for FIR 3 is consistent with the idea that intermediate-mass protostars drive more powerful jets than their low-mass counterparts. Our results also call into question the nature of FIR 4. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.The final reduced Herschel data used in this paper (FITS) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/596/A26

Massive pre-main-sequence stars in M17

NASA Astrophysics Data System (ADS)

Ramírez-Tannus, M. C.; Kaper, L.; de Koter, A.; Tramper, F.; Bik, A.; Ellerbroek, L. E.; Ochsendorf, B. B.; Ramírez-Agudelo, O. H.; Sana, H.

2017-08-01

The formation process of massive stars is still poorly understood. Massive young stellar objects (mYSOs) are deeply embedded in their parental clouds; these objects are rare, and thus typically distant, and their reddened spectra usually preclude the determination of their photospheric parameters. M17 is one of the best-studied H II regions in the sky, is relatively nearby, and hosts a young stellar population. We have obtained optical to near-infrared spectra of previously identified candidate mYSOs and a few OB stars in this region with X-shooter on the ESO Very Large Telescope. The large wavelength coverage enables a detailed spectroscopic analysis of the photospheres and circumstellar disks of these candidate mYSOs. We confirm the pre-main-sequence (PMS) nature of six of the stars and characterise the O stars. The PMS stars have radii that are consistent with being contracting towards the main sequence and are surrounded by a remnant accretion disk. The observed infrared excess and the double-peaked emission lines provide an opportunity to measure structured velocity profiles in the disks. We compare the observed properties of this unique sample of young massive stars with evolutionary tracks of massive protostars and propose that these mYSOs near the western edge of the H II region are on their way to become main-sequence stars ( 6-20 M⊙) after having undergone high mass accretion rates (Ṁacc 10-4-10-3M⊙yr-1). Their spin distribution upon arrival at the zero age main-sequence is consistent with that observed for young B stars, assuming conservation of angular momentum and homologous contraction. Based on observations collected at the European Southern Observatory at Paranal, Chile (ESO programmes 60.A-9404(A), 085.D-0741, 089.C-0874(A), and 091.C-0934(B)).The full normalised X-shooter spectra are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/604/A78

Massive star formation in 100,000 years from turbulent and pressurized molecular clouds.

PubMed

McKee, Christopher F; Tan, Jonathan C

2002-03-07

Massive stars (with mass m* > 8 solar masses Mmiddle dot in circle) are fundamental to the evolution of galaxies, because they produce heavy elements, inject energy into the interstellar medium, and possibly regulate the star formation rate. The individual star formation time, t*f, determines the accretion rate of the star; the value of the former quantity is currently uncertain by many orders of magnitude, leading to other astrophysical questions. For example, the variation of t*f with stellar mass dictates whether massive stars can form simultaneously with low-mass stars in clusters. Here we show that t*f is determined by the conditions in the star's natal cloud, and is typically about 105yr. The corresponding mass accretion rate depends on the pressure within the cloud--which we relate to the gas surface density--and on both the instantaneous and final stellar masses. Characteristic accretion rates are sufficient to overcome radiation pressure from about 100M middle dot in circle protostars, while simultaneously driving intense bipolar gas outflows. The weak dependence of t*f on the final mass of the star allows high- and low-mass star formation to occur nearly simultaneously in clusters.

A distance-limited sample of massive star-forming cores from the RMS

NASA Astrophysics Data System (ADS)

Maud, L. T.; Lumsden, S. L.; Moore, T. J. T.; Mottram, J. C.; Urquhart, J. S.; Cicchini, A.

2015-09-01

We analyse C18O (J = 3-2) data from a sample of 99 infrared (IR)-bright massive young stellar objects (MYSOs) and compact H II regions that were identified as potential molecular-outflow sources in the Red MSX Source survey. We extract a distance-limited (D < 6 kpc) sample shown to be representative of star formation covering the transition between the source types. At the spatial resolution probed, Larson-like relationships are found for these cores, though the alternative explanation, that Larson's relations arise where surface-density-limited samples are considered, is also consistent with our data. There are no significant differences found between source properties for the MYSOs and H II regions, suggesting that the core properties are established prior to the formation of massive stars, which subsequently have little impact at the later evolutionary stages investigated. There is a strong correlation between dust-continuum and C18O-gas masses, supporting the interpretation that both trace the same material in these IR-bright sources. A clear linear relationship is seen between the independently established core masses and luminosities. The position of MYSOs and compact H II regions in the mass-luminosity plane is consistent with the luminosity expected from the most massive protostar in the cluster when using an ˜40 per cent star formation efficiency and indicates that they are at a similar evolutionary stage, near the end of the accretion phase.

A Detached Protostellar Disk around a ˜0.2 M ⊙ Protostar in a Possible Site of a Multiple Star Formation in a Dynamical Environment in Taurus

NASA Astrophysics Data System (ADS)

Tokuda, Kazuki; Onishi, Toshikazu; Saigo, Kazuya; Hosokawa, Takashi; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro; Machida, Masahiro N.; Tomida, Kengo; Kunitomo, Masanobu; Kawamura, Akiko; Fukui, Yasuo; Tachihara, Kengo

2017-11-01

We report ALMA observations in 0.87 mm continuum and 12CO (J = 3-2) toward a very low-luminosity (<0.1 L ⊙) protostar, which is deeply embedded in one of the densest cores, MC27/L1521F, in Taurus with an indication of multiple star formation in a highly dynamical environment. The beam size corresponds to ˜20 au, and we have clearly detected blueshifted/redshifted gas in 12CO associated with the protostar. The spatial/velocity distributions of the gas show there is a rotating disk with a size scale of ˜10 au, a disk mass of ˜10-4 M ⊙, and a central stellar mass of ˜0.2 M ⊙. The observed disk seems to be detached from the surrounding dense gas, although it is still embedded at the center of the core whose density is ˜106 cm-3. The current low-outflow activity and the very low luminosity indicate that the mass accretion rate onto the protostar is extremely low in spite of a very early stage of star formation. We may be witnessing the final stage of the formation of ˜0.2 M ⊙ protostar. However, we cannot explain the observed low luminosity with the standard pre-main-sequence evolutionary track unless we assume cold accretion with an extremely small initial radius of the protostar (˜0.65 {R}⊙ ). These facts may challenge our current understanding of the low mass star formation, in particular the mass accretion process onto the protostar and the circumstellar disk.

A substellar-mass protostar and its outflow of IRAS 15398–3359 revealed by subarcsecond-resolution observations of H{sub 2}CO and CCH

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

Oya, Yoko; Sakai, Nami; Watanabe, Yoshimasa

2014-11-10

Subarcsecond (0.''5) images of H{sub 2}CO and CCH line emission have been obtained in the 0.8 mm band toward the low-mass protostar IRAS 15398–3359 in the Lupus 1 cloud as one of the Cycle 0 projects of the Atacama Large Millimeter/Submillimeter Array. We have detected a compact component concentrated in the vicinity of the protostar and a well-collimated outflow cavity extending along the northeast-southwest axis. The inclination angle of the outflow is found to be about 20°, or almost edge-on, based on the kinematic structure of the outflow cavity. This is in contrast to previous suggestions of a more pole-onmore » geometry. The centrally concentrated component is interpreted by use of a model of the infalling rotating envelope with the estimated inclination angle and the mass of the protostar is estimated to be less than 0.09 M {sub ☉}. Higher spatial resolution data are needed to infer the presence of a rotationally supported disk for this source, hinted at by a weak high-velocity H{sub 2}CO emission associated with the protostar.« less

Weak and compact radio emission in early massive star formation regions: an ionized jet toward G11.11–0.12P1

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

Rosero, V.; Hofner, P.; McCoy, M.

2014-12-01

We report 1.3 cm and 6 cm continuum observations toward the massive proto-stellar candidate G11.11–0.12P1 using the Karl G. Jansky Very Large Array. We detect a string of four unresolved radio continuum sources coincident with the mid-infrared source in G11P1. The continuum sources have positive spectral indices consistent with a thermal (free-free) ionized jet. The most likely origins of the ionized gas are shocks due to the interaction of a stellar wind with the surrounding high-density material. We also present NIR United Kingdom Infrared Telescope (UKIRT) archival data that show an extended structure detected only at K band (2.2 μm),more » which is oriented perpendicular to the jet, and that may be scattered light from a circumstellar disk around the massive protostar. Our observations plus the UKIRT archival data thus provide new evidence that a disk/jet system is present in the massive proto-stellar candidate located in the G11.11–0.12P1 core.« less

Evidence for disks at an early stage in class 0 protostars?

NASA Astrophysics Data System (ADS)

Gerin, M.; Pety, J.; Commerçon, B.; Fuente, A.; Cernicharo, J.; Marcelino, N.; Ciardi, A.; Lis, D. C.; Roueff, E.; Wootten, H. A.; Chapillon, E.

2017-10-01

Aims: The formation epoch of protostellar disks is debated because of the competing roles of rotation, turbulence, and magnetic fields in the early stages of low-mass star formation. Magnetohydrodynamics simulations of collapsing cores predict that rotationally supported disks may form in strongly magnetized cores through ambipolar diffusion or misalignment between the rotation axis and the magnetic field orientation. Detailed studies of individual sources are needed to cross check the theoretical predictions. Methods: We present 0.06-0.1'' resolution images at 350 GHz toward B1b-N and B1b-S, which are young class 0 protostars, possibly first hydrostatic cores. The images have been obtained with ALMA, and we compare these data with magnetohydrodynamics simulations of a collapsing turbulent and magnetized core. Results: The submillimeter continuum emission is spatially resolved by ALMA. Compact structures with optically thick 350 GHz emission are detected toward both B1b-N and B1b-S, with 0.2 and 0.35'' radii (46 and 80 au at the Perseus distance of 230 pc), within a more extended envelope. The flux ratio between the compact structure and the envelope is lower in B1b-N than in B1b-S, in agreement with its earlier evolutionary status. The size and orientation of the compact structure are consistent with 0.2'' resolution 32 GHz observations obtained with the Very Large Array as a part of the VANDAM survey, suggesting that grains have grown through coagulation. The morphology, temperature, and densities of the compact structures are consistent with those of disks formed in numerical simulations of collapsing cores. Moreover, the properties of B1b-N are consistent with those of a very young protostar, possibly a first hydrostatic core. These observations provide support for the early formation of disks around low-mass protostars. The reduced images and datacubes are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via

First detection of cyanamide (NH2CN) towards solar-type protostars

NASA Astrophysics Data System (ADS)

Coutens, A.; Willis, E. R.; Garrod, R. T.; Müller, H. S. P.; Bourke, T. L.; Calcutt, H.; Drozdovskaya, M. N.; Jørgensen, J. K.; Ligterink, N. F. W.; Persson, M. V.; Stéphan, G.; van der Wiel, M. H. D.; van Dishoeck, E. F.; Wampfler, S. F.

2018-05-01

Searches for the prebiotically relevant cyanamide (NH2CN) towards solar-type protostars have not been reported in the literature. We present here the first detection of this species in the warm gas surrounding two solar-type protostars, using data from the Atacama Large Millimeter/Submillimeter Array Protostellar Interferometric Line Survey (PILS) of IRAS 16293-2422 B and observations from the IRAM Plateau de Bure Interferometer of NGC 1333 IRAS2A. We also detected the deuterated and 13C isotopologs of NH2CN towards IRAS 16293-2422 B. This is the first detection of NHDCN in the interstellar medium. Based on a local thermodynamic equilibrium analysis, we find that the deuteration of cyanamide ( 1.7%) is similar to that of formamide (NH2CHO), which may suggest that these two molecules share NH2 as a common precursor. The NH2CN/NH2CHO abundance ratio is about 0.2 for IRAS 16293-2422 B and 0.02 for IRAS2A, which is comparable to the range of values found for Sgr B2. We explored the possible formation of NH2CN on grains through the NH2 + CN reaction using the chemical model MAGICKAL. Grain-surface chemistry appears capable of reproducing the gas-phase abundance of NH2CN with the correct choice of physical parameters.

First Magnetic Field Detection on a Class I Protostar

NASA Astrophysics Data System (ADS)

Johns-Krull, Christopher M.; Greene, Thomas P.; Doppmann, Greg W.; Covey, Kevin R.

2009-08-01

Strong stellar magnetic fields are believed to truncate the inner accretion disks around young stars, redirecting the accreting material to the high latitude regions of the stellar surface. In the past few years, observations of strong stellar fields on T Tauri stars with field strengths in general agreement with the predictions of magnetospheric accretion theory have bolstered this picture. Currently, nothing is known about the magnetic field properties of younger, more embedded Class I young stellar objects. It is believed that protostars accrete much of their final mass during the Class I phase, but the physics governing this process remains poorly understood. Here, we use high-resolution near-infrared spectra obtained with NIRSPEC on Keck and with Phoenix on Gemini South to measure the magnetic field properties of the Class I protostar WL 17. We find clear signatures of a strong stellar magnetic field. Analysis of this data suggests a surface average field strength of 2.9 ± 0.43 kG on WL 17. We present our field measurements and discuss how they fit with the general model of magnetospheric accretion in young stars. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil), and SECYT (Argentina). The Phoenix data were obtained under the program: GS-2006A-C-12.

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

Centralized pan-Middle East Survey on the undertreatment of hypercholesterolemia: results from the CEPHEUS study in Arabian Gulf countries.

PubMed

Arafah, Mohamed; Al-Hinai, Ali T; Al Mahmeed, Wael; Al-Rasadi, Khalid; Al Tamimi, Omer; Al Herz, Shorook; Al Anazi, Faisal; Al Nemer, Khalid; Metwally, Othman; Alkhadra, Akram; Fakhry, Mohammed; Elghetany, Hossam; Medani, Abdel Razak; Yusufali, Afzal Hussein; Al Jassim, Obaid; Al Hallaq, Omar; Baslaib, Fahad Omar Ahmed S; Alawadhi, Mahmoud; Amin, Haitham; Al-Hashmi, Khamis; Shehab, Abdullah

2014-11-01

The Centralized pan-Middle East Survey on the undertreatment of hypercholesterolemia (CEPHEUS) survey evaluated the attainment of low-density lipoprotein cholesterol (LDL-C) goals among patients on lipid-lowering drugs (LLDs) according to the updated National Cholesterol Education Program (NCEP)-Adult Treatment Panel (ATP-III) guideline. The survey was conducted in 6 Arabian Gulf countries. Patients aged ≥18 years on LLDs for at least ≥3 months (stable medication for ≥6 weeks) were recruited. Fasting blood samples were collected at a single visit. In this survey, 5276 (58.2% male) patients were included in the final analysis. The LDL-C goal was attained in 91.1% of low-risk, 52.7% of high-risk, and 32.0% in very-high-risk categories. Goal attainment was directly related to female gender, age<40 years, history of diabetes, and family history of cardiovascular disease. The results of this survey highlight the suboptimal management of hypercholesterolemia across Arabian Gulf countries. © The Author(s) 2013.

Multi-wavelength investigations on feedback of massive star formation

NASA Astrophysics Data System (ADS)

Yuan, Jinghua

2014-05-01

outflow driven by a massive protostar. Multi-wavelength observations based on classical tracers of outflows are highly necessary. Extensive investigations of IRAS 18114-1825 may contribute to our understanding of massive star formation in early stage.

The JCMT Transient Survey: Detection of Submillimeter Variability in a Class I Protostar EC 53 in Serpens Main

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

Yoo, Hyunju; Cho, Jungyeon; Lee, Jeong-Eun

During the protostellar phase of stellar evolution, accretion onto the star is expected to be variable, but this suspected variability has been difficult to detect because protostars are deeply embedded. In this paper, we describe a submillimeter luminosity burst of the Class I protostar EC 53 in Serpens Main, the first variable found during our dedicated JCMT/SCUBA-2 monitoring program of eight nearby star-forming regions. EC 53 remained quiescent for the first six months of our survey, from 2016 February to August. The submillimeter emission began to brighten in 2016 September, reached a peak brightness of 1.5 times the faint state,more » and has been decaying slowly since 2017 February. The change in submillimeter brightness is interpreted as dust heating in the envelope, generated by a luminosity increase of the protostar of a factor of ≥4. The 850 μ m light curve resembles the historical K -band light curve, which varies by a factor of ∼6 with a 543 period and is interpreted as accretion variability excited by interactions between the accretion disk and a close binary system. The predictable detections of accretion variability observed at both near-infrared and submillimeter wavelengths make the system a unique test-bed, enabling us to capture the moment of the accretion burst and to study the consequences of the outburst on the protostellar disk and envelope.« less

Radiation-hydrodynamical simulations of massive star formation using Monte Carlo radiative transfer - II. The formation of a 25 solar-mass star

NASA Astrophysics Data System (ADS)

Harries, Tim J.; Douglas, Tom A.; Ali, Ahmad

2017-11-01

We present a numerical simulation of the formation of a massive star using Monte Carlo-based radiation hydrodynamics (RHD). The star forms via stochastic disc accretion and produces fast, radiation-driven bipolar cavities. We find that the evolution of the infall rate (considered to be the mass flux across a 1500 au spherical boundary) and the accretion rate on to the protostar, are broadly consistent with observational constraints. After 35 kyr the star has a mass of 25 M⊙ and is surrounded by a disc of mass 7 M⊙ and 1500 au radius, and we find that the velocity field of the disc is close to Keplerian. Once again these results are consistent with those from recent high-resolution studies of discs around forming massive stars. Synthetic imaging of the RHD model shows good agreement with observations in the near- and far-IR, but may be in conflict with observations that suggest that massive young stellar objects are typically circularly symmetric in the sky at 24.5 μm. Molecular line simulations of a CH3CN transition compare well with observations in terms of surface brightness and line width, and indicate that it should be possible to reliably extract the protostellar mass from such observations.

Nature of shocks revealed by SOFIA OI observations in the Cepheus E protostellar outflow

NASA Astrophysics Data System (ADS)

Gusdorf, A.; Anderl, S.; Lefloch, B.; Leurini, S.; Wiesemeyer, H.; Güsten, R.; Benedettini, M.; Codella, C.; Godard, B.; Gómez-Ruiz, A. I.; Jacobs, K.; Kristensen, L. E.; Lesaffre, P.; Pineau des Forêts, G.; Lis, D. C.

2017-06-01

Context. Protostellar jets and outflows are key features of the star-formation process, and primary processes of the feedback of young stars on the interstellar medium. Understanding the underlying shocks is necessary to explain how jet and outflow systems are launched, and to quantify their chemical and energetic impacts on the surrounding medium. Aims: We performed a high-spectral resolution study of the [OI]63μm emission in the outflow of the intermediate-mass Class 0 protostar Cep E-mm. The goal is to determine the structure of the outflow, to constrain the chemical conditions in the various components, and to understand the nature of the underlying shocks, thus probing the origin of the mass-loss phenomenon. Methods: We present observations of the O I 3P1 → 3P2, OH between 2Π1/2J = 3/2 and J = 1/2 at 1837.8 GHz, and CO (16-15) lines with the GREAT receiver onboard SOFIA towards three positions in the Cep E protostellar outflow: Cep E-mm (the driving protostar), Cep E-BI (in the southern lobe), and Cep E-BII (the terminal position in the southern lobe). Results: The CO (16-15) line is detected at all three positions. The [OI]63μm line is detected in Cep E-BI and BII, whereas the OH line is not detected. In Cep E-BII, we identify three kinematical components in O I and CO. These were already detected in CO transitions and relate to spatial components: the jet, the HH377 terminal bow-shock, and the outflow cavity. We measure line temperature and line integrated intensity ratios for all components. The O I column density is higher in the outflow cavity than in the jet, which itself is higher than in the terminal shock. The terminal shock is the region where the abundance ratio of O I to CO is the lowest (about 0.2), whereas the jet component is atomic (N(O I)/N(CO) 2.7). In the jet, we compare the [OI]63μm observations with shock models that successfully fit the integrated intensity of 10 CO lines. We find that these models most likely do not fit the [OI]63�

CO bandhead emission of massive young stellar objects: determining disc properties

NASA Astrophysics Data System (ADS)

Ilee, J. D.; Wheelwright, H. E.; Oudmaijer, R. D.; de Wit, W. J.; Maud, L. T.; Hoare, M. G.; Lumsden, S. L.; Moore, T. J. T.; Urquhart, J. S.; Mottram, J. C.

2013-03-01

Massive stars play an important role in many areas of astrophysics, but numerous details regarding their formation remain unclear. In this paper we present and analyse high-resolution (R ˜ 30 000) near-infrared 2.3 μm spectra of 20 massive young stellar objects (MYSOs) from the Red MSX Source (RMS) data base, in the largest such study of CO first overtone bandhead emission to date. We fit the emission under the assumption it originates from a circumstellar disc in Keplerian rotation. We explore three approaches to modelling the physical conditions within the disc - a disc heated mainly via irradiation from the central star, a disc heated mainly via viscosity, and a disc in which the temperature and density are described analytically. We find that the models described by heating mechanisms are inappropriate because they do not provide good fits to the CO emission spectra. We therefore restrict our analysis to the analytic model, and obtain good fits to all objects that possess sufficiently strong CO emission, suggesting circumstellar discs are the source of this emission. On average, the temperature and density structure of the discs correspond to geometrically thin discs, spread across a wide range of inclinations. Essentially all the discs are located within the dust sublimation radius, providing strong evidence that the CO emission originates close to the central protostar, on astronomical unit scales. In addition, we show that the objects in our sample appear no different to the general population of MYSOs in the RMS data base, based on their near- and mid-infrared colours. The combination of observations of a large sample of MYSOs with CO bandhead emission and our detailed modelling provide compelling evidence of the presence of small-scale gaseous discs around such objects, supporting the scenario in which massive stars form via disc accretion.

VizieR Online Data Catalog: SOFIA Massive (SOMA) Star Formation Survey. I. (De Buizer+, 2017)

NASA Astrophysics Data System (ADS)

De Buizer, J. M.; Liu, M.; Tan, J. C.; Zhang, Y.; Beltran, M. T.; Shuping, R.; Staff, J. E.; Tanaka, K. E. I.; Whitney, B.

2018-02-01

The following eight sources, AFGL 4029, AFGL 437, IRAS 07299-1651, G35.20-0.74, G45.45+0.05, IRAS 20126+4104, Cepheus A, and NGC 7538 IRS9, were observed by SOFIA with the FORCAST instrument (see Table 1). Data were taken on multiple flights spanning the Early Science period, Cycle 1, and Cycle 2 SOFIA observing cycles (spanning 2011 May to 2014 June). (4 data files).

Complex Organic Molecules tracing shocks along the outflow cavity in the high-mass protostar IRAS 20126+4104.

PubMed

Palau, Aina; Walsh, Catherine; Sánchez-Monge, Álvaro; Girart, Josep M; Cesaroni, Riccardo; Jiménez-Serra, Izaskun; Fuente, Asunción; Zapata, Luis A; Neri, Roberto

2017-06-01

We report on subarcsecond observations of complex organic molecules (COMs) in the high-mass protostar IRAS 20126+4104 with the Plateau de Bure Interferometer in its most extended configurations. In addition to the simple molecules SO, HNCO and H 2 13 CO, we detect emission from CH 3 CN, CH 3 OH, HCOOH, HCOOCH 3 , CH 3 OCH 3 , CH 3 CH 2 CN, CH 3 COCH 3 , NH 2 CN, and (CH 2 OH) 2 . SO and HNCO present a X-shaped morphology consistent with tracing the outflow cavity walls. Most of the COMs have their peak emission at the putative position of the protostar, but also show an extension towards the south(east), coinciding with an H 2 knot from the jet at about 800-1000 au from the protostar. This is especially clear in the case of H 2 13 CO and CH 3 OCH 3 . We fitted the spectra at representative positions for the disc and the outflow, and found that the abundances of most COMs are comparable at both positions, suggesting that COMs are enhanced in shocks as a result of the passage of the outflow. By coupling a parametric shock model to a large gas-grain chemical network including COMs, we find that the observed COMs should survive in the gas phase for ∼ 2000 yr, comparable to the shock lifetime estimated from the water masers at the outflow position. Overall, our data indicate that COMs in IRAS 20126+4104 may arise not only from the disc, but also from dense and hot regions associated with the outflow.

Complex Organic Molecules tracing shocks along the outflow cavity in the high-mass protostar IRAS 20126+4104

PubMed Central

Palau, Aina; Walsh, Catherine; Sánchez-Monge, Álvaro; Girart, Josep M.; Cesaroni, Riccardo; Jiménez-Serra, Izaskun; Fuente, Asunción; Zapata, Luis A.; Neri, Roberto

2017-01-01

We report on subarcsecond observations of complex organic molecules (COMs) in the high-mass protostar IRAS 20126+4104 with the Plateau de Bure Interferometer in its most extended configurations. In addition to the simple molecules SO, HNCO and H213CO, we detect emission from CH3CN, CH3OH, HCOOH, HCOOCH3, CH3OCH3, CH3CH2CN, CH3COCH3, NH2CN, and (CH2OH)2. SO and HNCO present a X-shaped morphology consistent with tracing the outflow cavity walls. Most of the COMs have their peak emission at the putative position of the protostar, but also show an extension towards the south(east), coinciding with an H2 knot from the jet at about 800–1000 au from the protostar. This is especially clear in the case of H213CO and CH3OCH3. We fitted the spectra at representative positions for the disc and the outflow, and found that the abundances of most COMs are comparable at both positions, suggesting that COMs are enhanced in shocks as a result of the passage of the outflow. By coupling a parametric shock model to a large gas-grain chemical network including COMs, we find that the observed COMs should survive in the gas phase for ∼ 2000 yr, comparable to the shock lifetime estimated from the water masers at the outflow position. Overall, our data indicate that COMs in IRAS 20126+4104 may arise not only from the disc, but also from dense and hot regions associated with the outflow. PMID:28579644

CARBON CHAINS AND METHANOL TOWARD EMBEDDED PROTOSTARS

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

Graninger, Dawn M.; Wilkins, Olivia H.; Öberg, Karin I., E-mail: dgraninger@cfa.harvard.edu

2016-03-10

Large interstellar organic molecules are potential precursors of prebiotic molecules. Their formation pathways and chemical relationships with one another and simpler molecules are therefore of great interest. In this paper we address the relationships between two classes of large organic molecules, carbon chains and saturated complex organic molecules at the early stages of star formation through observations of C{sub 4}H and CH{sub 3}OH. We surveyed these molecules with the IRAM 30 m telescope toward 16 deeply embedded low-mass protostars selected from the Spitzer c2d ice survey. We find that CH{sub 3}OH and C{sub 4}H are positively correlated, indicating that thesemore » two classes of molecules can coexist during the embedded protostellar stage. The C{sub 4}H/CH{sub 3}OH gas abundance ratio tentatively correlates with the CH{sub 4}/CH{sub 3}OH ice abundance ratio in the same lines of sight. This relationship supports a scenario where carbon chain formation in protostellar envelopes begins with CH{sub 4} ice desorption.« less

The discovery of low-mass pre-main-sequence stars in Cepheus OB3b

NASA Astrophysics Data System (ADS)

Pozzo, M.; Naylor, T.; Jeffries, R. D.; Drew, J. E.

2003-05-01

We report the discovery of a low-mass pre-main-sequence (PMS) stellar population in the younger subgroup of the Cepheus OB3 association, Cep OB3b, using UBVI CCD photometry and follow-up spectroscopy. The optical survey covers approximately 1300 arcmin2 on the sky and gives a global photometric and astrometric catalogue for more than 7000 objects. The location of a PMS population is well defined in a V versus (V-I) colour-magnitude diagram. Multifibre spectroscopic results for optically selected PMS candidates confirm the T Tauri nature for 10 objects, with equal numbers of classical TTS (CTTS) and weak-line TTS (WTTS). There are six other objects that we classify as possible PMS stars. The newly discovered TTS stars have masses in the range ~0.9-3.0 Msolar and ages from <1 to nearly 10 Myr, based on the Siess, Dufour & Forestini isochrones. Their location close to the O and B stars of the association (especially the O7n star) demonstrates that low-mass star formation is indeed possible in such an apparently hostile environment dominated by early-type stars and that the latter must have been less effective in eroding the circumstellar discs of their lower-mass siblings compared with other OB associations (e.g. λ-Ori). We attribute this to the nature of the local environment, speculating that the bulk of molecular material, which shielded low-mass stars from the ionizing radiation of their early-type siblings, has only recently been removed.

CO in Protostars (COPS): Herschel-SPIRE Spectroscopy of Embedded Protostars

NASA Astrophysics Data System (ADS)

Yang, Yao-Lun; Green, Joel; COPS Team

2018-01-01

We present full spectral scans from 200 μm - 670 μm of 27 Class 0/I protostellar sources, obtained with Herschel-SPIRE, as part of the "COPS-SPIRE" Open Time program, complementary to the DIGIT and WISH Key programs. Only 16 of 27 protostars have the same Class classification with Tbol and Lbol/Lsubmm. We found that the spectral index at 500 μm evolves with Lbol/Lsubmm, suggesting that it may be sensitive to the evolution during the Class 0 phase by probing the envelope. We identify rotational transitions of CO lines from J = 4→3 to J = 13→12, along with a number of lines of 13CO, HCO+, H2O, and [C I] lines. The ratios of 12CO to 13CO suggest that 12CO emission remains optically thick until Jup > 17. We fit up to four components of temperature from the rotational diagram with flexible break points which separate the components. The distribution of rotational temperature shows a primary population around 100 K with a secondary population at 400 K. We quantify the correlations of each line pair found in our dataset, and find the strength of correlation of CO lines decreases as the difference of J-level between two CO lines increases. The multiple origins of CO emission previously revealed by velocity-resolved profiles is consistent with this smooth distribution, if each origin contributes to a wide range of CO lines with significant overlap in the CO ladder. The spatial extent of the CO emission is investigated by projecting the flux ratio from the outer spatial pixel (spaxel) to the central spaxel as a function of azimuthal angle, which allows us to identify the bipolarity of the morphology. We find that the morphology of CO emission is more centralized and less bipolar at higher J lines. The difference of the maximum and minimum ratios in the projected profile (peak-to-valley difference) quantifies the bipolarity of the identified bipolar feature. We found the peak-to-valley difference declines as the J-level increases, suggesting that the bipolar feature is

CO in Protostars (COPS): Herschel-SPIRE Spectroscopy of Embedded Protostars

NASA Astrophysics Data System (ADS)

Yang, Yao-Lun; Green, Joel D.; Evans, Neal J., II; Lee, Jeong-Eun; Jørgensen, Jes K.; Kristensen, Lars E.; Mottram, Joseph C.; Herczeg, Gregory; Karska, Agata; Dionatos, Odysseas; Bergin, Edwin A.; Bouwman, Jeroen; van Dishoeck, Ewine F.; van Kempen, Tim A.; Larson, Rebecca L.; Yıldız, Umut A.

2018-06-01

We present full spectral scans from 200 to 670 μm of 26 Class 0+I protostellar sources obtained with Herschel-SPIRE as part of the “COPS-SPIRE” Open Time program, complementary to the DIGIT and WISH Key Programs. Based on our nearly continuous, line-free spectra from 200 to 670 μm, the calculated bolometric luminosities (L bol) increase by 50% on average, and the bolometric temperatures (T bol) decrease by 10% on average, in comparison with the measurements without Herschel. Fifteen protostars have the same class using T bol and L bol/L smm. We identify rotational transitions of CO lines from J=4\\to 3 to J=13\\to 12, along with emission lines of 13CO, HCO+, H2O, and [C I]. The ratios of 12CO to 13CO indicate that 12CO emission remains optically thick for J up < 13. We fit up to four components of temperature from the rotational diagram with flexible break points to separate the components. The distribution of rotational temperatures shows a primary population around 100 K with a secondary population at ∼350 K. We quantify the correlations of each line pair found in our data set and find that the strength of the correlation of CO lines decreases as the difference between J levels between two CO lines increases. The multiple origins of CO emission previously revealed by velocity-resolved profiles are consistent with this smooth distribution if each physical component contributes to a wide range of CO lines with significant overlap in the CO ladder. We investigate the spatial extent of CO emission and find that the morphology is more centrally peaked and less bipolar at high-J lines. We find the CO emission observed with SPIRE related to outflows, which consists of two components, the entrained gas and shocked gas, as revealed by our rotational diagram analysis, as well as the studies with velocity-resolved CO emission. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important

Nonaxisymmetric Dynamic Instabilities of Rotating Polytropes. II. Torques, Bars, and Mode Saturation with Applications to Protostars and Fizzlers

NASA Astrophysics Data System (ADS)

Imamura, James N.; Durisen, Richard H.; Pickett, Brian K.

2000-01-01

Dynamic nonaxisymmetric instabilities in rapidly rotating stars and protostars have a range of potential applications in astrophysics, including implications for binary formation during protostellar cloud collapse and for the possibility of aborted collapse to neutron star densities at late stages of stellar evolution (``fizzlers''). We have recently presented detailed linear analyses for polytropes of the most dynamically unstable global modes, the barlike modes. These produce bar distortions in the regions near the rotation axis but have trailing spiral arms toward the equator. In this paper, we use our linear eigenfunctions to predict the early nonlinear behavior of the dynamic instability and compare these ``quasi-linear'' predictions with several fully nonlinear hydrodynamics simulations. The comparisons demonstrate that the nonlinear saturation of the barlike instability is due to the self-interaction gravitational torques between the growing central bar and the spiral arms, where angular momentum is transferred outward from bar to arms. We also find a previously unsuspected resonance condition that accurately predicts the mass of the bar regions in our own simulations and in those published by other researchers. The quasi-linear theory makes other accurate predictions about consequences of instability, including properties of possible end-state bars and increases in central density, which can be large under some conditions. We discuss in some detail the application of our results to binary formation during protostellar collapse and to the formation of massive rotating black holes.

The Herschel-PACS Legacy of Low-mass Protostars: The Properties of Warm and Hot Gas Components and Their Origin in Far-UV Illuminated Shocks

NASA Astrophysics Data System (ADS)

Karska, Agata; Kaufman, Michael J.; Kristensen, Lars E.; van Dishoeck, Ewine F.; Herczeg, Gregory J.; Mottram, Joseph C.; Tychoniec, Łukasz; Lindberg, Johan E.; Evans, Neal J., II; Green, Joel D.; Yang, Yao-Lun; Gusdorf, Antoine; Itrich, Dominika; Siódmiak, Natasza

2018-04-01

Recent observations from Herschel allow the identification of important mechanisms responsible both for the heating of the gas that surrounds low-mass protostars and for its subsequent cooling in the far-infrared. Shocks are routinely invoked to reproduce some properties of the far-IR spectra, but standard models fail to reproduce the emission from key molecules, e.g., H2O. Here, we present the Herschel Photodetector Array Camera and Spectrometer (PACS) far-IR spectroscopy of 90 embedded low-mass protostars (Class 0/I). The Herschel-PACS spectral maps, covering ∼55–210 μm with a field of view of ∼50″, are used to quantify the gas excitation conditions and spatial extent using rotational transitions of H2O, high-J CO, and OH, as well as [O I] and [C II]. We confirm that a warm (∼300 K) CO reservoir is ubiquitous and that a hotter component (760 ± 170 K) is frequently detected around protostars. The line emission is extended beyond ∼1000 au spatial scales in 40/90 objects, typically in molecular tracers in Class 0 and atomic tracers in Class I objects. High-velocity emission (≳90 km s‑1) is detected in only 10 sources in the [O I] line, suggesting that the bulk of [O I] arises from gas that is moving slower than typical jets. Line flux ratios show an excellent agreement with models of C-shocks illuminated by ultraviolet (UV) photons for pre-shock densities of ∼105 cm‑3 and UV fields 0.1–10 times the interstellar value. The far-IR molecular and atomic lines are a unique diagnostic of feedback from UV emission and shocks in envelopes of deeply embedded protostars.

FORMALDEHYDE AND METHANOL DEUTERATION IN PROTOSTARS: FOSSILS FROM A PAST FAST HIGH-DENSITY PRE-COLLAPSE PHASE

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

Taquet, V.; Ceccarelli, C.; Kahane, C.

Extremely high deuteration of several molecules has been observed around low-mass protostars for a decade. Among them, formaldehyde and methanol present particularly high deuteration, with observations of abundant doubly and triply deuterated forms. Both species are thought to be mainly formed on interstellar grains during the low-temperature and dense pre-collapse phase by H and D atom additions on the iced CO. We present here a theoretical study of the formaldehyde and methanol deuteration obtained with our gas-grain model, GRAINOBLE. This model takes into account the multilayer nature of the mantle and explores the robustness of the results against the uncertaintiesmore » of poorly constrained chemical and surface model parameters. The comparison of the model predictions with the observations leads to two major results: (1) the observed high deuteration is obtained during the last phase of the pre-collapse stage, when the density reaches {approx}5 Multiplication-Sign 10{sup 6} cm{sup -3}, and this phase is fast, lasting only several thousands years; and (2) D and H abstraction and substitution reactions are crucial in making up the observed deuteration ratios. This work shows the power of chemical composition as a tool to reconstruct the past history of protostars.« less

Deuterated formaldehyde in the low-mass protostar HH212

NASA Astrophysics Data System (ADS)

Sahu, Dipen; Minh, Y. C.; Lee, Chin-Fei; Liu, Sheng-Yuan; Das, Ankan; Chakrabarti, S. K.; Sivaraman, Bhala

2018-04-01

HH212, a nearby (400 pc) object in Orion, is a class 0 protostellar system with a Keplerian disc and collimated bipolar SiO jets. Deuterated water, HDO, and a deuterated complex molecule, methanol (CH2DOH), have been reported in the source. Here, we report the HDCO (deuterated formaldehyde) line observation from Atacama Large Millimeter Array data to probe the inner region of HH212. We compare HDCO line with other molecular lines to understand the possible chemistry and physics of the source. The distribution of HDCO emission suggests that it may be associated with the base of the outflow. The emission also shows a rotation but it is not associated with the Keplerian rotation of disc or the rotating infalling envelope, rather it is associated with the outflow as previously seen in C34S. From the possible deuterium fractionation, we speculate that the gas phase formation of deuterated formaldehyde is active in the central hot region of the low-mass protostar system, HH212.

Detection of OD towards the low-mass protostar IRAS 16293-2422

NASA Astrophysics Data System (ADS)

Parise, B.; Du, F.; Liu, F.-C.; Belloche, A.; Wiesemeyer, H.; Güsten, R.; Menten, K. M.; Hübers, H.-W.; Klein, B.

2012-06-01

Context. Although water is an essential and widespread molecule in star-forming regions, its chemical formation pathways are still not very well constrained. Observing the level of deuterium fractionation of OH, a radical involved in the water chemical network, is a promising way to infer its chemical origin. Aims: We aim at understanding the formation mechanisms of water by investigating the origin of its deuterium fractionation. This can be achieved by observing the abundance of OD towards the low-mass protostar IRAS 16293-2422, where the HDO distribution is already known. Methods: Using the GREAT receiver on board SOFIA, we observed the ground-state OD transition at 1391.5 GHz towards the low-mass protostar IRAS 16293-2422. We also present the detection of the HDO 111-000 line using the APEX telescope. We compare the OD/HDO abundance ratio inferred from these observations with the predictions of chemical models. Results: The OD line is detected in absorption towards the source continuum. This is the first detection of OD outside the solar system. The SOFIA observation, coupled to the observation of the HDO 111-000 line, provides an estimate of the abundance ratio OD/HDO ~ 17-90 in the gas where the absorption takes place. This value is fairly high compared with model predictions. This may be reconciled if reprocessing in the gas by means of the dissociative recombination of H2DO+ further fractionates OH with respect to water. Conclusions: The present observation demonstrates the capability of the SOFIA/GREAT instrument to detect the ground transition of OD towards star-forming regions in a frequency range that was not accessible before. Dissociative recombination of H2DO+ may play an important role in setting a high OD abundance. Measuring the branching ratios of this reaction in the laboratory will be of great value for chemical models. Figure 5 is available in electronic form at http://www.aanda.org

Star Formation Under the Outflow: The Discovery of a Non-thermal Jet from OMC-2 FIR 3 and Its Relationship to the Deeply Embedded FIR 4 Protostar

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

Osorio, Mayra; Díaz-Rodríguez, Ana K.; Anglada, Guillem

We carried out multiwavelength (0.7–5 cm), multi-epoch (1994–2015) Very Large Array (VLA) observations toward the region enclosing the bright far-IR sources FIR 3 (HOPS 370) and FIR 4 (HOPS 108) in OMC-2. We report the detection of 10 radio sources, 7 of them identified as young stellar objects. We image a well-collimated radio jet with a thermal free–free core (VLA 11) associated with the Class I intermediate-mass protostar HOPS 370. The jet features several knots (VLA 12N, 12C, 12S) of non-thermal radio emission (likely synchrotron from shock-accelerated relativistic electrons) at distances of ∼7500–12,500 au from the protostar, in a regionmore » where other shock tracers have been previously identified. These knots are moving away from the HOPS 370 protostar at ∼100 km s{sup −1}. The Class 0 protostar HOPS 108, which itself is detected as an independent, kinematically decoupled radio source, falls in the path of these non-thermal radio knots. These results favor the previously proposed scenario in which the formation of HOPS 108 is triggered by the impact of the HOPS 370 outflow with a dense clump. However, HOPS 108 has a large proper motion velocity of ∼30 km s{sup −1}, similar to that of other runaway stars in Orion, whose origin would be puzzling within this scenario. Alternatively, an apparent proper motion could result because of changes in the position of the centroid of the source due to blending with nearby extended emission, variations in the source shape, and/or opacity effects.« less

The onset of energetic particle irradiation in Class 0 protostars

NASA Astrophysics Data System (ADS)

Favre, C.; López-Sepulcre, A.; Ceccarelli, C.; Dominik, C.; Caselli, P.; Caux, E.; Fuente, A.; Kama, M.; Le Bourlot, J.; Lefloch, B.; Lis, D.; Montmerle, T.; Padovani, M.; Vastel, C.

2017-12-01

Context. The early stages of low-mass star formation are likely to be subject to intense ionization by protostellar energetic MeV particles. As a result, the surrounding gas is enriched in molecular ions, such as HCO+ and N2H+. Nonetheless, this phenomenon remains poorly understood for Class 0 objects. Recently, based on Herschel observations taken as part of the key programme Chemical HErschel Surveys of Star forming regions (CHESS), a very low HCO+/N2H+ abundance ratio of about three to four, has been reported towards the protocluster OMC-2 FIR4. This finding suggests a cosmic-ray ionization rate in excess of 10-14 s-1, much higher than the canonical value of ζ = 3 × 10-17 s-1 (value expected in quiescent dense clouds). Aims: We aim to assess the specificity of OMC-2 FIR4, we have extended this study to a sample of sources in low- and intermediate mass. More specifically, we seek to measure the HCO+/N2H+ abundance ratio from high energy lines (J ≥ 6) towards this source sample in order to infer the flux of energetic particles in the warm and dense gas surrounding the protostars. Methods: We have used observations performed with the Heterodyne Instrument for the Far-Infrared spectrometer on board the Herschel Space Observatory towards a sample of nine protostars. Results: We report HCO+/N2H+ abundance ratios in the range of five up to 73 towards our source sample. The large error bars do not allow us to conclude whether OMC-2 FIR4 is a peculiar source. Nonetheless, an important result is that the measured HCO+/N2H+ ratio does not vary with the source luminosity. At the present time, OMC-2 FIR4 remains the only source where a high flux of energetic particles is clearly evident. More sensitive and higher angular resolution observations are required to further investigate this process. Herschel is an ESA space observatory with science instruments provided by European-led principal investigator consortia and with important participation from NASA.

Dark Globule in IC 1396 (IRAC)

NASA Technical Reports Server (NTRS)

2003-01-01

[figure removed for brevity, see original site] Click on image for larger view of inset

NASA's Spitzer Space Telescope image of a glowing stellar nursery provides a spectacular contrast to the opaque cloud seen in visible light (inset). The Elephant's Trunk Nebula is an elongated dark globule within the emission nebula IC 1396 in the constellation of Cepheus. Located at a distance of 2,450 light-years, the globule is a condensation of dense gas that is barely surviving the strong ionizing radiation from a nearby massive star. The globule is being compressed by the surrounding ionized gas. The dark globule is seen in silhouette at visible-light wavelengths, backlit by the illumination of a bright star located to the left of the field of view.

The Spitzer Space Telescope pierces through the obscuration to reveal the birth of new protostars, or embryonic stars, and previously unseen young stars. The infrared image was obtained by Spitzer's infrared array camera. The image is a four-color composite of invisible light, showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8.0 microns (red). The filamentary appearance of the globule results from the sculpting effects of competing physical processes. The winds from a massive star, located to the left of the image, produce a dense circular rim comprising the 'head' of the globule and a swept-back tail of gas.

A pair of young stars (LkHa 349 and LkHa 349c) that formed from the dense gas has cleared a spherical cavity within the globule head. While one of these stars is significantly fainter than the other in the visible-light image, they are of comparable brightness in the infrared Spitzer image. This implies the presence of a thick and dusty disc around LkHa 349c. Such circumstellar discs are the precursors of planetary systems. They are much thicker in the early stages of stellar formation when the placental planet-forming material (gas and dust) is still

Rotation-Infall Motion around the Protostar IRAS 16293-2422 Traced by Water Maser Emission

NASA Astrophysics Data System (ADS)

Imai, Hiroshi; Iwata, Takahiro; Miyoshi, Makoto

1999-08-01

We made VLBI observations of the water maser emission associated with a protostar, IRAS 16293-2422, using the Kashima-Nobeyama Interferometer (KNIFE) and the Japanese domestic VLBI network (J-Net).\\footnote[2]. These distributions of water maser features showed the blue-shifted and red-shifted components separated in the north-south direction among three epochs spanning three years. The direction of the separation was perpendicular to the molecular outflow and parallel to the elongation of the molecular disk. These steady distributions were successfully modeled by a rotating-infalling disk with an outer radius of 100 AU around a central object with a mass of 0.3 MO . The local specific angular momentum of the disk was calculated to be 0.2-1.0times 10-3 km s-1 pc at a radius of 20-100 AU. This value is roughly equal to that of the disk of IRAS 00338+6312 in L1287 and those of the molecular disks around the protostars in the Taurus molecular cloud. The relatively large disk radius of about 100 AU traced by water maser emission suggests that impinging clumps onto the disk should be hotter than 200 K to excite the water maser emission. Mizusawa, Nobeyama, and Kagoshima stations are operated by staff members of National Astronomical Observatory of the Ministry of Education, Science, Sports and Culture. Kashima station is operated by staff members of Communications Research Laboratory of the Ministry of Posts and Telecomunications. The recent status of J-Net is seen in the WWW home page: http://www.nro.nao.ac.jp/\\ \\ miyaji/Jnet.

SPECTRAL LINE SURVEY TOWARD THE YOUNG MASSIVE PROTOSTAR NGC 2264 CMM3 IN THE 4 mm, 3 mm, AND 0.8 mm BANDS

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

Watanabe, Yoshimasa; Sakai, Nami; López-Sepulcre, Ana

2015-08-20

Spectral line survey observations are conducted toward the high-mass protostar candidate NGC 2264 CMM3 in the 4, 3, and 0.8 mm bands with the Nobeyama 45 m telescope and the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope. In total, 265 emission lines are detected in the 4 and 3 mm bands, and 74 emission lines in the 0.8 mm band. As a result, 36 molecular species and 30 isotopologues are identified. In addition to the fundamental molecular species, many emission lines of carbon-chain molecules such as HC{sub 5}N, C{sub 4}H, CCS, and C{sub 3}S are detected in the 4more » and 3 mm bands. Deuterated molecular species are also detected with relatively strong intensities. On the other hand, emission lines of complex organic molecules such as HCOOCH{sub 3} and CH{sub 3}OCH{sub 3} are found to be weak. For the molecules for which multiple transitions are detected, rotation temperatures are derived to be 7–33 K except for CH{sub 3}OH. Emission lines with high upper-state energies (E{sub u} > 150 K) are detected for CH{sub 3}OH, indicating the existence of a hot core. In comparison with the chemical composition of the Orion KL, carbon-chain molecules and deuterated molecules are found to be abundant in NGC 2264 CMM3, while sulfur-bearing species and complex organic molecules are deficient. These characteristics indicate the chemical youth of NGC 2264 CMM3 in spite of its location at the center of the cluster forming core, NGC 2264 C.« less

Water masers in NGC7538 region

NASA Astrophysics Data System (ADS)

Kameya, Osamu

We observed H2O masers towards NGC7538 molecular-cloud core using VERA (VLBI Experiment of Radio Astrometry). This region is in the Perseus arm at a distance of about 2.7 kpc and is famous for its multiple, massive star formation. There are three areas there, N(IRS1-3), E(IRS9), and S(IRS11), each having a strong IR source(s), ultra-compact HII region(s), bipolar outflow, high-density core, and OH/H2O/CH3OH masers. We made differential VLBI observations towards the NGC7538 H2O maser sources at N and S and a reference source, Cepheus A H2O maser, simultaneously. The Cepheus A region is separated by 2 degrees from the NGC7538 region. The positions of H2O masers in N and S regions, distributed around the ultra-compact HII regions, are basically consistent with those found by means of interferometric observations of past 29 years. The masers may come from interface regions between the ultra-compact HII regions and the environments of dense molecular gas.

Deuterated methanol on a solar system scale around the HH212 protostar

NASA Astrophysics Data System (ADS)

Bianchi, E.; Codella, C.; Ceccarelli, C.; Taquet, V.; Cabrit, S.; Bacciotti, F.; Bachiller, R.; Chapillon, E.; Gueth, F.; Gusdorf, A.; Lefloch, B.; Leurini, S.; Podio, L.; Rygl, K. L. J.; Tabone, B.; Tafalla, M.

2017-10-01

Context. Deuterium fractionation is a valuable tool for understanding the chemical evolution during the process that leads to the formation of a Sun-like planetary system. Aims: Methanol is thought to be mainly formed during the prestellar phase, and its deuterated form keeps a memory of the conditions at that epoch. The unique combination of high angular resolution and sensitivity provided by ALMA enables us to measure methanol deuteration in the planet formation region around a Class 0 protostar and to understand its origin. Methods: We mapped both the 13CH3OH and CH2DOH distribution in the inner regions ( 100 au) of the HH212 system in Orion B. To this end, we used ALMA Cycle 1 and Cycle 4 observations in Band 7 with angular resolution down to 0.̋15. Results: We detected 6 lines of 13CH3OH and 13 lines of CH2DOH with upper level energies of up to 438 K in temperature units. We derived a rotational temperature of (171 ± 52) K and column densities of 7 × 1016 cm-2 (13CH3OH) and 1 × 1017 cm-2 (CH2DOH), respectively. This yields a D/H ratio of (2.4 ± 0.4) × 10-2, which is lower by an order of magnitude than previously measured values using single-dish telescopes toward protostars located in Perseus. Our findings are consistent with the higher dust temperatures in Orion B with respect to the temperature derived for the Perseus cloud. The emission traces a rotating structure extending up to 45 au from the jet axis, which is elongated by 90 au along the jet axis. So far, the origin of the observed emission appears to be related with the accretion disc. Only higher spatial resolution measurements will be able to distinguish between different possible scenarios, however: disc wind, disc atmosphere, or accretion shocks.

LINEAR POLARIZATION OF CLASS I METHANOL MASERS IN MASSIVE STAR-FORMING REGIONS

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

Kang, Ji-hyun; Byun, Do-Young; Kim, Kee-Tae

Class I methanol masers are found to be good tracers of the interaction between outflows from massive young stellar objects with their surrounding media. Although polarization observations of Class II methanol masers have been able to provide information about magnetic fields close to the central (proto)stars, polarization observations of Class I methanol masers are rare, especially at 44 and 95 GHz. We present the results of linear polarization observations of 39 Class I methanol maser sources at 44 and 95 GHz. These two lines are observed simultaneously with one of the 21 m Korean VLBI Network telescopes in single-dish mode.more » Approximately 60% of the observed sources have fractional polarizations of a few percent in at least one transition. This is the first reported detection of linear polarization of the 44 GHz methanol maser. The two maser transitions show similar polarization properties, indicating that they trace similar magnetic environments, although the fraction of the linear polarization is slightly higher at 95 GHz. We discuss the association between the directions of polarization angles and outflows. We also discuss some targets having different polarization properties at both lines, including DR21(OH) and G82.58+0.20, which show the 90° polarization angle flip at 44 GHz.« less

Massive, wide binaries as tracers of massive star formation

NASA Astrophysics Data System (ADS)

Griffiths, Daniel W.; Goodwin, Simon P.; Caballero-Nieves, Saida M.

2018-05-01

Massive stars can be found in wide (hundreds to thousands au) binaries with other massive stars. We use N-body simulations to show that any bound cluster should always have approximately one massive wide binary: one will probably form if none are present initially, and probably only one will survive if more than one is present initially. Therefore, any region that contains many massive wide binaries must have been composed of many individual subregions. Observations of Cyg OB2 show that the massive wide binary fraction is at least a half (38/74), which suggests that Cyg OB2 had at least 30 distinct massive star formation sites. This is further evidence that Cyg OB2 has always been a large, low-density association. That Cyg OB2 has a normal high-mass initial mass function (IMF) for its total mass suggests that however massive stars form, they `randomly sample' the IMF (as the massive stars did not `know' about each other).

Star Formation near Berkeley 59: Embedded Protostars

NASA Astrophysics Data System (ADS)

Rosvick, J. M.; Majaess, D.

2013-12-01

A group of suspected protostars in a dark cloud northwest of the young (~2 Myr) cluster Berkeley 59 and two sources in a pillar south of the cluster have been studied in order to determine their evolutionary stages and ascertain whether their formation was triggered by Berkeley 59. Narrowband near-infrared observations from the Observatoire du Mont Mégantic, 12CO (J = 3-2) and SCUBA-2 (450 and 850 μm) observations from the JCMT, 2MASS, and WISE images, and data extracted from the IPHAS survey catalog were used. Of 12 sources studied, two are Class I objects, while three others are flat/Class II, one of which is a T Tauri candidate. A weak CO outflow and two potential starless cores are present in the cloud, while the pillar possesses substructure at different velocities, with no outflows present. The CO spectra of both regions show peaks in the range v LSR = -15 to -17 km s-1, which agrees with the velocity adopted for Berkeley 59 (-15.7 km s-1), while spectral energy distribution models yield an average interstellar extinction AV and distance of 15 ± 2 mag and 830 ± 120 pc, respectively, for the cloud, and 6.9 mag and 912 pc for the pillar, indicating that the regions are in the same vicinity as Berkeley 59. The formation of the pillar source appears to have been triggered by Berkeley 59. It is unclear whether Berkeley 59 triggered the association's formation.

Constraining the Abundances of Complex Organics in the Inner Regions of Solar-Type Protostars

NASA Astrophysics Data System (ADS)

López-Sepulcre, A.; Taquet, V.; Ceccarelli, C.; Neri, R.; Kahane, C.; Charnley, S. B.

2015-12-01

We present arcsecond-resolution observations, obtained with the IRAM Plateau de Bure interferometer, of multiple complex organic molecules in two hot corino protostars: IRAS 2A and IRAS 4A, in the NGC 1333 star-forming region. The distribution of the line emission is very compact, indicating the presence of COMs is mostly concentrated in the inner hot corino regions. A comparison of the COMs abundances with astrochemical models favours a gas-phase formation route for CH3OCH3, and a grain formation of C2H5OH, C2H5CN, and HCOCH2OH. The high abundances of methyl formate (HCOOCH3) remain underpredicted by an order of magnitude.

Massive Stars

NASA Astrophysics Data System (ADS)

Livio, Mario; Villaver, Eva

2009-11-01

Participants; Preface Mario Livio and Eva Villaver; 1. High-mass star formation by gravitational collapse of massive cores M. R. Krumholz; 2. Observations of massive star formation N. A. Patel; 3. Massive star formation in the Galactic center D. F. Figer; 4. An X-ray tour of massive star-forming regions with Chandra L. K. Townsley; 5. Massive stars: feedback effects in the local universe M. S. Oey and C. J. Clarke; 6. The initial mass function in clusters B. G. Elmegreen; 7. Massive stars and star clusters in the Antennae galaxies B. C. Whitmore; 8. On the binarity of Eta Carinae T. R. Gull; 9. Parameters and winds of hot massive stars R. P. Kudritzki and M. A. Urbaneja; 10. Unraveling the Galaxy to find the first stars J. Tumlinson; 11. Optically observable zero-age main-sequence O stars N. R. Walborn; 12. Metallicity-dependent Wolf-Raynet winds P. A. Crowther; 13. Eruptive mass loss in very massive stars and Population III stars N. Smith; 14. From progenitor to afterlife R. A. Chevalier; 15. Pair-production supernovae: theory and observation E. Scannapieco; 16. Cosmic infrared background and Population III: an overview A. Kashlinsky.

Magnetic Stars After the Hayashi Phase. II.

NASA Astrophysics Data System (ADS)

Glagolevskij, Yu. V.

2016-09-01

The properties of magnetic stars derived from observational data are analyzed. The degree of "magnetic" braking of parent protostars, which depends the magnetic field and mass, is studied. The conditions under which magnetic and "normal" nonmagnetic stars are separated, which appear to depend only on the rotational velocity of the protostars, are examined. The reasons for differences in the average magnitudes of the magnetic field in massive and low-mass magnetic stars are analyzed. The magnetic field structures of magnetic stars and their stability over time (rigidity of rotation) are examined.

Water deuterium fractionation in the low-mass protostar NGC1333-IRAS2A

NASA Astrophysics Data System (ADS)

Liu, F.-C.; Parise, B.; Kristensen, L.; Visser, R.; van Dishoeck, E. F.; Güsten, R.

2011-03-01

Context. Although deuterium enrichment of water may provide an essential piece of information in the understanding of the formation of comets and protoplanetary systems, only a few studies up to now have aimed at deriving the HDO/H2O ratio in low-mass star forming regions. Previous studies of the molecular deuteration toward the solar-type class 0 protostar, IRAS 16293-2422, have shown that the D/H ratio of water is significantly lower than other grain-surface-formed molecules. It is not clear if this property is general or particular to this source. Aims: In order to see if the results toward IRAS 16293-2422 are particular, we aimed at studying water deuterium fractionation in a second low-mass solar-type protostar, NGC1333-IRAS2A. Methods: Using the 1-D radiative transfer code RATRAN, we analyzed five HDO transitions observed with the IRAM 30 m, JCMT, and APEX telescopes. We assumed that the abundance profile of HDO in the envelope is a step function, with two different values in the inner warm (T > 100 K) and outer cold (T < 100 K) regions of the protostellar envelope. Results: The inner and outer abundance of HDO is found to be well constrained at the 3σ level. The obtained HDO inner and outer fractional abundances are xHDO_in = 6.6 × 10-8-1.0 × 10-7(3σ) and x^{HDO}out=9×10-11= 9 × 10-11-1.0-1.8 × 10-9(3σ). These values are close to those in IRAS 16293-2422, which suggests that HDO may be formed by the same mechanisms in these two solar-type protostars. Taking into account the (rather poorly onstrained) H2O abundance profile deduced from Herschel observations, the derived HDO/H2O in the inner envelope is ≥1% and in the outer envelope it is 0.9%-18%. These values are more than one order of magnitude higher than what is measured in comets. If the same ratios apply to the protosolar nebula, this would imply that there is some efficient reprocessing of the material between the protostellar and cometary phases. Conclusions: The H2O inner fractional

Refining Models of L1527-IRS

NASA Astrophysics Data System (ADS)

Baker Metzler-Winslow, Elizabeth; Terebey, Susan

2018-06-01

This project examines the Class 0/Class 1 protostar L1527-IRS (hereby referred to as L1527) in the interest of creating a more accurate computational model. In a Class 0/Class I protostar like L1527, the envelope is massive, the protostar is growing in mass, and the disk is a small fraction of the protostar mass. Recent work based on ALMA data indicates that L1527, located in the constellation Taurus (about 140 parsecs from Earth), is about ~0.44 solar masses. Existing models were able to fit the spectral energy distribution of L1527 by assuming a puffed-up inner disk. However, the inclusion of the puffed-up disk results in a portion of the disk coinciding with the outflow cavities, a physically unsatisfying arrangement. This project tests models which decrease the size of the disk and increase the density of the outflow cavities (hypothesizing that some dust from the walls of the outflow cavities is swept up into the cavity itself) against existing observational data, and finds that these models fit the data relatively well.

Modelling water in the envelopes of low-mass protostars

NASA Astrophysics Data System (ADS)

van Kempen, Tim A.; Jørgensen, Jes K.; Hogerheijde, Michiel R.; van Dishoeck, Ewine F.

Using sophisticated spherically symmetric radiative transfer models for gas and dust, we simulate the emission of H2O and its isotopes for the circumstellar envelopes around class 0 protostars, as preparatory science for the ESA cornerstone mission Herschel and its spectrometer, HIFI. L483mm is taken as an example. We probe a wide range of models in which dust, freeze-out and a large variety of abundance structures and optical depths are taken into account. A sample of water lines is selected that are observable by Herschel. Expected fluxes for these lines are derived from the models, convolved with the Herschel beam size. 1. Introduction Water has been detected by the LWS instruments aboard ISO in low-mass protostars (e.g. Ceccarelli et al. 1999, Giannini et al. 2001). The origin of the water lines is still subject of discussion, however. It has been theorized to originate in both the outflow and the quiescent infalling envelope. Ceccarelli et al. (1999) place the water in the small (200 AU), dense (> 107cm-3) and warm (> 100 K) region of the protostellar envelope. The ESA Herschel mission and in particular the HIFI instrument are particularly well suited to observe rotational far-infrared and submillimeter water lines in these environments and test the various models. 2. Approach We started with the physical structure deduced by Jørgensen (2004) for L483mm (Lbol = 9Lsol, Menv10K = 4.4Msol, D=200 pc), giving the density and temperature profiles for a typical protostellar envelope. These profiles are the result of a dust radiative transfer calculation with DUSTY (Ivezic & Elitzur, 1997). The line radiative transfer is subsequently calculated through RATRAN, developed by Hogerheijde & van der Tak (2000). The dust to gas ratio has been set at 1:100, the dust opacities are approximated by the OH5 (Ossenkopf & Henning 1994) at a density of 106cm-3. To simulate the abundance of the water molecule, we have used trial abundances with the assumption that water freezes out

Properties of Protostars in the Elephant Trunk in the Globule IC 1396A

NASA Astrophysics Data System (ADS)

Reach, William T.; Faied, Dohy; Rho, Jeonghee; Boogert, Adwin; Tappe, Achim; Jarrett, Thomas H.; Morris, Patrick; Cambrésy, Laurent; Palla, Francesco; Valdettaro, Riccardo

2009-01-01

Extremely red objects, identified in the early Spitzer Space Telescope observations of the bright-rimmed globule IC 1396A and photometrically classified as Class I protostars and Class II T Tauri stars based on their mid-infrared (mid-IR) colors, were spectroscopically observed at 5.5-38 μm (Spitzer Infrared Spectrograph), at the 22 GHz water maser frequency (National Radio Astronomy Observatory Green Bank Telescope), and in the optical (Palomar Hale 5 m) to confirm their nature and further elucidate their properties. The sources photometrically identified as Class I, including IC 1396A:α, γ, δ, epsilon, and ζ, are confirmed as objects dominated by accretion luminosity from dense envelopes, with accretion rates 1-10 × 10-6 M sun yr-1 and present stellar masses 0.1-2 M sun. The Class I sources have extremely red continua, still rising at 38 μm, with a deep silicate absorption at 9-11 μm, weaker silicate absorption around 18 μm, and weak ice features including CO2 at 15.2 μm and H2O at 6 μm. The ice/silicate absorption ratio in the envelope is exceptionally low for the IC 1396A protostars, compared to those in nearby star-forming regions, suggesting that the envelope chemistry is altered by the radiation field or globule pressure. Only one 22 GHz water maser was detected in IC 1396A; it is coincident with a faint mid-IR source, offset from near the luminous Class I protostar IC 1396A:γ. The maser source, IC 1396A:γ b , has luminosity less than 0.1 L sun, the first H2O maser from such a low-luminosity object. Two near-infrared (NIR) H2 knots on opposite sides of IC 1396A:γ reveal a jet, with an axis clearly distinct from the H2O maser of IC 1396A:γ b . The objects photometrically classified as Class II, including IC 1396A:β, θ, Two Micron All Sky Survey (2MASS)J 21364964+5722270, 2MASSJ 21362507+5727502, LkHα 349c, Tr 37 11-2146, and Tr 37 11-2037, are confirmed as stars with warm, luminous disks, with a silicate emission feature at 9-11 μm, and

Protostellar accretion traced with chemistry. High-resolution C18O and continuum observations towards deeply embedded protostars in Perseus

NASA Astrophysics Data System (ADS)

Frimann, Søren; Jørgensen, Jes K.; Dunham, Michael M.; Bourke, Tyler L.; Kristensen, Lars E.; Offner, Stella S. R.; Stephens, Ian W.; Tobin, John J.; Vorobyov, Eduard I.

2017-06-01

Context. Understanding how accretion proceeds is a key question of star formation, with important implications for both the physical and chemical evolution of young stellar objects. In particular, very little is known about the accretion variability in the earliest stages of star formation. Aims: Our aim is to characterise protostellar accretion histories towards individual sources by utilising sublimation and freeze-out chemistry of CO. Methods: A sample of 24 embedded protostars are observed with the Submillimeter Array (SMA) in context of the large program "Mass Assembly of Stellar Systems and their Evolution with the SMA" (MASSES). The size of the C18O-emitting region, where CO has sublimated into the gas-phase, is measured towards each source and compared to the expected size of the region given the current luminosity. The SMA observations also include 1.3 mm continuum data, which are used to investigate whether or not a link can be established between accretion bursts and massive circumstellar disks. Results: Depending on the adopted sublimation temperature of the CO ice, between 20% and 50% of the sources in the sample show extended C18O emission indicating that the gas was warm enough in the past that CO sublimated and is currently in the process of refreezing; something which we attribute to a recent accretion burst. Given the fraction of sources with extended C18O emission, we estimate an average interval between bursts of 20 000-50 000 yr, which is consistent with previous estimates. No clear link can be established between the presence of circumstellar disks and accretion bursts, however the three closest known binaries in the sample (projected separations <20 AU) all show evidence of a past accretion burst, indicating that close binary interactions may also play a role in inducing accretion variability.

The protostar OMC-2 FIR 4: Results from the CHESS Herschel/HIFI spectral survey

NASA Astrophysics Data System (ADS)

Kama, Mihkel; Lopez-Sepulcre, Ana; Ceccarelli, Cecilia; Dominik, Carsten; Caux, Emmanuel; Fuente, Asuncion

2013-07-01

The intermediate-mass protostar OMC-2 FIR 4 in Orion is the focus of several ongoing studies, including a CHESS key programme Herschel/HIFI spectral survey. In this poster, we review recent CHESS results on this source, including the properties of the central hot core, the presence of a compact outflow, the spatial variation of the chemical composition, and the discovery of a tenuous foreground cloud. The HIFI spectrum of FIR 4 contains 719 lines from 40 species and isotopologs. Cooling by lines detectable with our sensitivity contributes 2% of the total in the 480 to 1900 GHz range. The total line flux is dominated by CO, followed by H2O and CH3OH. Initial comparisons with spectral surveys of other sources will also be presented.

History of the solar-type protostar IRAS 16293-2422 as told by the cyanopolyynes

NASA Astrophysics Data System (ADS)

Jaber Al-Edhari, A.; Ceccarelli, C.; Kahane, C.; Viti, S.; Balucani, N.; Caux, E.; Faure, A.; Lefloch, B.; Lique, F.; Mendoza, E.; Quenard, D.; Wiesenfeld, L.

2017-01-01

Context. Cyanopolyynes are chains of carbon atoms with an atom of hydrogen and a CN group on either side. They are detected almost everywhere in the interstellar medium (ISM), as well as in comets. In the past, they have been used to constrain the age of some molecular clouds, since their abundance is predicted to be a strong function of time. Finally, cyanopolyynes can potentially contain a large portion of molecular carbon. Aims: We present an extensive study of the cyanopolyynes distribution in the solar-type protostar IRAS 16293-2422. The goals are (I) to obtain a census of the cyanopolyynes in this source and of their isotopologues; (II) to derive how their abundance varies across the protostar envelope; and (III) to obtain constraints on the history of IRAS 16293-2422 by comparing the observations with the predictions of a chemical model. Methods: We analysed the data from the IRAM-30 m unbiased millimeter and submillimeter spectral survey towards IRAS 16293-2422 named TIMASSS. The derived spectral line energy distribution (SLED) of each detected cyanopolyyne was compared with the predictions from the radiative transfer code GRenoble Analysis of Protostellar Envelope Spectra (GRAPES) to derive the cyanopolyyne abundances across the envelope of IRAS 16293-2422. Finally, the derived abundances were compared with the predictions of the chemical model UCL_CHEM. Results: We detect several lines from cyanoacetylene (HC3N) and cyanodiacetylene (HC5N), and report the first detection of deuterated cyanoacetylene, DC3N, in a solar-type protostar. We found that the HC3N abundance is roughly constant ( 1.3 × 10-11) in the outer cold envelope of IRAS 16293-2422, and it increases by about a factor 100 in the inner region where the dust temperature exceeds 80 K, namely when the volcano ice desorption is predicted to occur. The HC5N has an abundance similar to HC3N in the outer envelope and about a factor of ten lower in the inner region. The comparison with the chemical

The Destructive Birth of Massive Stars and Massive Star Clusters

NASA Astrophysics Data System (ADS)

Rosen, Anna; Krumholz, Mark; McKee, Christopher F.; Klein, Richard I.; Ramirez-Ruiz, Enrico

2017-01-01

Massive stars play an essential role in the Universe. They are rare, yet the energy and momentum they inject into the interstellar medium with their intense radiation fields dwarfs the contribution by their vastly more numerous low-mass cousins. Previous theoretical and observational studies have concluded that the feedback associated with massive stars' radiation fields is the dominant mechanism regulating massive star and massive star cluster (MSC) formation. Therefore detailed simulation of the formation of massive stars and MSCs, which host hundreds to thousands of massive stars, requires an accurate treatment of radiation. For this purpose, we have developed a new, highly accurate hybrid radiation algorithm that properly treats the absorption of the direct radiation field from stars and the re-emission and processing by interstellar dust. We use our new tool to perform a suite of three-dimensional radiation-hydrodynamic simulations of the formation of massive stars and MSCs. For individual massive stellar systems, we simulate the collapse of massive pre-stellar cores with laminar and turbulent initial conditions and properly resolve regions where we expect instabilities to grow. We find that mass is channeled to the massive stellar system via gravitational and Rayleigh-Taylor (RT) instabilities. For laminar initial conditions, proper treatment of the direct radiation field produces later onset of RT instability, but does not suppress it entirely provided the edges of the radiation-dominated bubbles are adequately resolved. RT instabilities arise immediately for turbulent pre-stellar cores because the initial turbulence seeds the instabilities. To model MSC formation, we simulate the collapse of a dense, turbulent, magnetized Mcl = 106 M⊙ molecular cloud. We find that the influence of the magnetic pressure and radiative feedback slows down star formation. Furthermore, we find that star formation is suppressed along dense filaments where the magnetic field is

The magnetic field structure around protostars. Submillimetre polarimetry of VLA 1623 and S 106-IR/FIR.

NASA Astrophysics Data System (ADS)

Holland, W. S.; Greaves, J. S.; Ward-Thompson, D.; Andre, P.

1996-05-01

We present 800μm polarization observations of the young low-mass candidate protostar VLA 1623, and of the high-mass young stellar object S 106-IR and its companion candidate protostar S 106-FIR. The polarized emission due to aligned dust grains has been used to derive the magnetic field direction around both sources. In the case of VLA 1623 we find that the field direction is almost exactly perpendicular to the extremely well-collimated CO outflow. This suggests that the large-scale magnetic field in the cloud cannot be responsible for the collimation of the outflow. However, the data may be consistent with a recent magneto-hydrodynamic model where the field follows stream lines through the central plane of a `cored apple' accretion structure. In S 106 our observations indicate a magnetic field along the dust lane connecting the IR/FIR sources, and perpendicular to the bipolar HII region. A model consistent both with these data, and previous Zeeman measurements, is presented, in which the large-scale magnetic field is poloidal, but is either twisted into a toroidal morphology, or highly `pinched-in', in the flattened dust lane. We also present a synopsis of recent submillimetre polarimetry observations of young disk/outflow sources. For high-mass objects, the data are consistent with super-critical collapse models, and there is evidence for varying degrees of field compression. There is also a correlation of net field orientation with source distance, which is explained by the inclusion of varying amounts of ambient cloud material within the telescope beam. For the few low-mass objects for which data is available, the polarization is less affected by ambient material, and there is some evidence that different outflow models may apply in different sources.

An X-ray Observation of the L1251 Dark Cloud

NASA Technical Reports Server (NTRS)

Simon, Theodore

2006-01-01

An X-ray image of the L1251 dark cloud in Cepheus was obtained with the XMM-Newton telescope. More than three dozen sources were detected above a 3 delta limit in X-ray luminosity of L(sub X = 10(exp 29) ergs/s. Among the detections are eight optically visible T Tauri stars, which had been identified in earlier work from their emission at H(alpha). The two strongest X-ray sources have steady luminosities of L(sub X) approx. 10(exp 31) ergs/s and are at the saturation limit for X-ray activity in late-type stars, L(sub X)/L(sub bol) approx. 10(exp -3). X-ray emission was also observed from two CO emission cores in L1251, core C (L1251A) and core E (L1251B). Both regions contain high-velocity molecular gas, bright IRAS sources (Class I protostars), thermal radio sources, and Herbig-Haro (HH) jets. In L1251A strong X-ray emission was discovered in close proximity to the near-inbred and radio source IRSA/VLA 7 and to IRAS 22343+7501. IRSA/VLA 7 thus appears to be the most likely source of the molecular and HH outflows in L1251A. In L1251B X-ray emission was observed from a visible T Tauri star, KP2-44, which is thought to be the driving source for HH 189. Also reported is the tentative detection of X-ray emission from VLA 3, a thermal radio continuum source in L1251B that is closely associated with the extreme Class I protostar IRAS 22376+7455.

Analysis of Extreme Star Formation Environments in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Nayak, Omnarayani

2018-01-01

My thesis is on three extreme star forming environments in the Large Magellanic Cloud: 30 Doradus, N159, and N79. These three regions are at different evolutionary stage of forming stars. N79 is at a very young stage, just starting its star formation activity. N159 is currently actively forming several massive YSOs. And 30 Doradus has already passed it peak star formation, and several protostars are no longer shrouded by gas and dust, and are starting to be more visible in the optical wavelengths. I analyze the CO molecular gas clouds with ALMA in 30 Doradus, N159, and N79. I identify all massive YSOs within the ALMA footprint of all three regions. My thesis is on relating the star formation activity in 30 Doradus, N159, and N79 to the high density gas in which these protostars form. I find that not all massive young stellar objects are associated with CO gas, higher mass clumps tend to form higher mass stars, and lower mass clumps tend to not be gravitationally bound however the larger clouds are bound. I use ancillary SOFIA data and Magellan FIRE data to place constraints on the outflow rate from the massive protostars, constrain the temperature of the gas, determine the spectral type of the young stellar objects, and estimate the extinction. Looking at the interplay between dense molecular gas and the newly forming stars in a stellar nursery will shed light on how these stars formed: filamentary collision, monolithic collapse, or competitive accretion. The Large Magellanic Cloud has been the subject of star formation studies for decades due to its proximity to the Milky Way (50 kpc), a nearly face-on orientation, and a low metallicity (0.5 solar) similar to that of galaxies at the peak of star formation in the universe (z~2). Thus, my thesis probes the chemical and physical conditions necessary for massive star formation in an environment more typical of the peak of star formation in the universe.

The Formation and Early Evolution of Embedded Massive Star Clusters

NASA Astrophysics Data System (ADS)

Barnes, Peter

We propose to combine Spitzer, WISE, Herschel, and other archival spacecraft data with an existing ground- and space-based mm-wave to near-IR survey of molecular clouds over a large portion of the Milky Way, in order to systematically study the formation and early evolution of massive stars and star clusters, and provide new observational calibrations for a theoretical paradigm of this key astrophysical problem. Central Objectives: The Galactic Census of High- and Medium-mass Protostars (CHaMP) is a large, unbiased, uniform, and panchromatic survey of massive star and cluster formation and early evolution, covering 20°x6° of the Galactic Plane. Its uniqueness lies in the comprehensive molecular spectroscopy of 303 massive dense clumps, which have also been included in several archival spacecraft surveys. Our objective is a systematic demographic analysis of massive star and cluster formation, one which has not been possible without knowledge of our CHaMP cloud sample, including all clouds with embedded clusters as well as those that have not yet formed massive stars. For proto-clusters deeply embedded within dense molecular clouds, analysis of these space-based data will: 1. Yield a complete census of Young Stellar Objects in each cluster. 2. Allow systematic measurements of embedded cluster properties: spectral energy distributions, luminosity functions, protostellar and disk fractions, and how these vary with cluster mass, age, and density. Combined with other, similarly complete and unbiased infrared and mm data, CHaMP's goals include: 3. A detailed comparison of the embedded stellar populations with their natal dense gas to derive extinction maps, star formation efficiencies and feedback effects, and the kinematics, physics, and chemistry of the gas in and around the clusters. 4. Tying the demographics, age spreads, and timescales of the clusters, based on pre-Main Sequence evolution, to that of the dense gas clumps and Giant Molecular Clouds. 5. A

The Spectral Energy Distribution of the Earliest Phases of Massive Star Formation from the Spizter and Herschel Archives

NASA Astrophysics Data System (ADS)

Klein, Randolf; Looney, Leslie; Henning, Thomas; Chakrabarti, Sukanya; Shenoy, Sachin

2015-08-01

Infrared Dark Clouds (IRDCs) are very good candidates for the earliest phases of massive star formation, but can only be found in regions with high infrared background. We have searched for early phases among cold and massive (M>100M⊙) cloud cores by selecting cores from millimeter continuum surveys (Faundez et al. 2004, Sridharan et al. 2005, Klein et al. 2005, Beltran et al. 2006) without associations at short wavelengths. We compared the millimeter continuum peak positions with IR and radio catalogs (2MASS, MSX, IRAS, and NVSS) and excluded cores that had sources associated with the cores' peaks. We compiled a list of 173 cores in over 117 regions that are candidates for very early phases of Massive Star Formation (MSF). Now with the Spitzer and Herschel archives, these cores can be characterized further. The GLIMPSE and MIPSGAL programs alone covered 86 of these regions. The Herschel Archive adds even longer wavelengths. We are compiling this data set to construct the complete spectral energy distribution (SED) in the mid- and far-infrared with good spatial resolution and broad spectral coverage. This allow us to disentangle the complex regions and model the SED of the deeply embedded protostars/clusters.We will be presenting the IR properties of all cores and their embedded source, attempt a characterization, and order the cores in an evolutionary sequence. The resulting properties can be compared to e.g. IRDCs, a class of objects suggested to be the earliest stages of MSF. With the relative large number of cores, we can try to answer questions like: How homogeneous or diverse are our regions in terms of their evolutionary stage? Where do our embedded sources fit in the evolutionary sequence of IRDCs, hot molecular cores, ultra-compact HII regions, etc? How is the MSF shaping the environment and vice versa? Can we extrapolate to the initial conditions of MSF using our evolutionary sequence?

The Magnetic Field of the Class I Protostar WL 17

NASA Astrophysics Data System (ADS)

Johns-Krull, Christopher M.; Greene, T. P.; Doppmann, G.; Covey, K. R.

2007-12-01

Strong stellar magnetic fields are believed to truncate the inner accretion disks around young stars, redirecting the accreting material to the high latitude regions of the stellar surface. In the past few years, observations of strong stellar fields on Classical T Tauri stars [class II young stellar objects (YSOs)] with field strengths in general agreement with the predictions of magnetopsheric accretion theory have bolstered this picture. Currently, nothing is known about the magnetic field properties of younger, more embedded class I YSOs. It is during this protostellar evolutionary phase that stars accrete most of their final mass, but the physics governing this process remains poorly understood. Here, we use high resolution near infrared spectra obtained with NIRSPEC on Keck and with PHOENIX on Gemini South to measure the magnetic field properties of the class I protostar WL 17. We find clear signatures of a strong stellar magnetic field. Initial analysis of this data suggests a surface average field strength of 3.6 kG on the surface of WL 17. This is the highest mean surface field detected to date on any YSO. We present our field measurements and discuss how they fit with the general model of magnetospheric accretion in young stars.

3D modelling of HCO+ and its isotopologues in the low-mass proto-star IRAS16293-2422

NASA Astrophysics Data System (ADS)

Quénard, D.; Bottinelli, S.; Caux, E.; Wakelam, V.

2018-07-01

Ions and electrons play an important role in various stages of the star formation process. By following the magnetic field of their environment and interacting with neutral species, they slow down the gravitational collapse of the proto-star envelope. This process (known as ambipolar diffusion) depends on the ionization degree, which can be derived from the HCO+ abundance. We present a study of HCO+ and its isotopologues (H13CO+ , HC18O+ , DCO+ , and D13CO+) in the low-mass proto-star IRAS16293-2422. The structure of this object is complex, and the HCO+emission arises from the contribution of a young NW-SE outflow, the proto-stellar envelope, and the foreground cloud. We aim at constraining the physical parameters of these structures using all the observed transitions. For the young NW-SE outflow, we derive Tkin= 180-220 K and n(H2) = (4-7)× 106 cm-3 with an HCO+abundance of (3-5)× 10-9. Following previous studies, we demonstrate that the presence of a cold (Tkin≤ 30 K) and low density [n(H2) ≤ 1 × 104 cm-3] foreground cloud is also necessary to reproduce the observed line profiles. We have used the gas-grain chemical code NAUTILUS to derive the HCO+ abundance profile across the envelope and the external regions where X(HCO+) ≳ 1 × 10-9 dominate the envelope emission. From this, we derive an ionization degree of 10-8.9 ≲ x( e) ≲ 10-7.9. The ambipolar diffusion time-scale is ˜5 times the free-fall time-scale, indicating that the magnetic field starts to support the source against gravitational collapse and the magnetic field strength is estimated to be 6-46μG.

3D modelling of HCO+ and its isotopologues in the low-mass proto-star IRAS16293-2422

NASA Astrophysics Data System (ADS)

Quénard, D.; Bottinelli, S.; Caux, E.; Wakelam, V.

2018-04-01

Ions and electrons play an important role in various stages of the star formation process. By following the magnetic field of their environment and interacting with neutral species, they slow down the gravitational collapse of the proto-star envelope. This process (known as ambipolar diffusion) depends on the ionisation degree, which can be derived from the HCO+abundance. We present a study of HCO+and its isotopologues (H13CO+, HC18O+, DCO+, and D13CO+) in the low-mass proto-star IRAS16293-2422. The structure of this object is complex, and the HCO+emission arises from the contribution of a young NW-SE outflow, the proto-stellar envelope and the foreground cloud. We aim at constraining the physical parameters of these structures using all the observed transitions. For the young NW-SE outflow, we derive Tkin = 180 - 220 K and n(H2) = (4 - 7) × 106 cm-3 with an HCO+abundance of (3 - 5) × 10-9. Following previous studies, we demonstrate that the presence of a cold (Tkin≤30 K) and low density (n(H2) ≤ 1 × 104 cm-3) foreground cloud is also necessary to reproduce the observed line profiles. We have used the gas-grain chemical code NAUTILUS to derive the HCO+abundance profile across the envelope and the external regions where X(HCO+)≳ 1 × 10-9 dominate the envelope emission. From this, we derive an ionisation degree of 10-8.9 ≲ x(e) ≲ 10-7.9. The ambipolar diffusion timescale is ˜5 times the free-fall timescale, indicating that the magnetic field starts to support the source against gravitational collapse and the magnetic field strength is estimated to be 6 - 46 μG.

A Photometrically and Morphologically Variable Infrared Nebula IN L483

NASA Astrophysics Data System (ADS)

Connelley, Michael S.; Hodapp, Klaus W.; Fuller, Gary A.

2009-03-01

We present narrow and broad K-band observations of the Class 0/I source IRAS 18148-0440 that span 17 years. The infrared nebula associated with this protostar in the L483 dark cloud is both morphologically and photometrically variable on a timescale of only a few months. This nebula appears to be an infrared analog to other well known optically visible variable nebulae associated with young stars, such as Hubble's Variable Nebula. Along with Cepheus A, this is one of the first large variable nebulae to be found that is only visible in the infrared. The variability of this nebula is most likely due to changing illumination of the cloud rather than any motion of the structure in the nebula. Both morphological and photometric changes are observed on a timescale only a few times longer than the light crossing time of the nebula, suggesting very rapid intrinsic changes in the illumination of the nebula. Our narrowband observations also found that H2 knots are found nearly twice as far to the east of the source as to its west, and that H2 emission extends farther east of the source than the previously known CO outflow.

First detection of ND in the solar-mass protostar IRAS16293-2422

NASA Astrophysics Data System (ADS)

Bacmann, A.; Caux, E.; Hily-Blant, P.; Parise, B.; Pagani, L.; Bottinelli, S.; Maret, S.; Vastel, C.; Ceccarelli, C.; Cernicharo, J.; Henning, T.; Castets, A.; Coutens, A.; Bergin, E. A.; Blake, G. A.; Crimier, N.; Demyk, K.; Dominik, C.; Gerin, M.; Hennebelle, P.; Kahane, C.; Klotz, A.; Melnick, G.; Schilke, P.; Wakelam, V.; Walters, A.; Baudry, A.; Bell, T.; Benedettini, M.; Boogert, A.; Cabrit, S.; Caselli, P.; Codella, C.; Comito, C.; Encrenaz, P.; Falgarone, E.; Fuente, A.; Goldsmith, P. F.; Helmich, F.; Herbst, E.; Jacq, T.; Kama, M.; Langer, W.; Lefloch, B.; Lis, D.; Lord, S.; Lorenzani, A.; Neufeld, D.; Nisini, B.; Pacheco, S.; Pearson, J.; Phillips, T.; Salez, M.; Saraceno, P.; Schuster, K.; Tielens, X.; van der Tak, F. F. S.; van der Wiel, M. H. D.; Viti, S.; Wyrowski, F.; Yorke, H.; Faure, A.; Benz, A.; Coeur-Joly, O.; Cros, A.; Güsten, R.; Ravera, L.

2010-10-01

Context. In the past decade, much progress has been made in characterising the processes leading to the enhanced deuterium fractionation observed in the ISM and in particular in the cold, dense parts of star forming regions such as protostellar envelopes. Very high molecular D/H ratios have been found for saturated molecules and ions. However, little is known about the deuterium fractionation in radicals, even though simple radicals often represent an intermediate stage in the formation of more complex, saturated molecules. The imidogen radical NH is such an intermediate species for the ammonia synthesis in the gas phase. Many of these light molecules however have their fundamental transitions in the submillimetre domain and their detection is hampered by the opacity of the atmosphere at these wavelengths. Herschel/HIFI represents a unique opportunity to study the deuteration and formation mechanisms of species not observable from the ground. Aims: We searched here for the deuterated radical ND in order to determine the deuterium fractionation of imidogen and constrain the deuteration mechanism of this species. Methods: We observed the solar-mass Class 0 protostar IRAS16293-2422 with the heterodyne instrument HIFI in Bands 1a (480-560 GHz), 3b (858-961 GHz), and 4a (949-1061 GHz) as part of the Herschel key programme CHESS (Chemical HErschel Survey of Star forming regions). Results: The deuterated form of the imidogen radical ND was detected and securely identified with 2 hyperfine component groups of its fundamental transition (N = 0-1) at 522.1 and 546.2 GHz, in absorption against the continuum background emitted from the nascent protostar. The 3 groups of hyperfine components of its hydrogenated counterpart NH were also detected in absorption. The absorption arises from the cold envelope, where many deuterated species have been shown to be abundant. The estimated column densities are ~2 × 1014 cm-2 for NH and ~ 1.3 × 1014 cm-2 for ND. We derive a very high

Infrared and Optical Spectroscopy of Protostars in the Elephant Trunk Nebula

NASA Astrophysics Data System (ADS)

Faied, Dohy; Reach, W. T.; Tappe, A.; Rho, J.

2006-12-01

We present Spitzer Space Telescope observations of the optically dark globule IC1396A. We have identified red objects located within the molecular globule to be Class I protostars, and objects scattered near the globule are found to be Class II T-Tauri stars surrounded by warm, luminous disks. We obtained simultaneous optical and infrared spectra (5.5 40 microns) with the Palomar Hale 200 inch telescope. The Class I sources were observed to have extremely red continua, rising at 24 microns, with deep silicate absorption at 9-11 microns, and weaker silicate absorption at around 12 microns. Some of these sources also display weak ice features such as CO2 and H2O. In contrast, the Class II sources have strong H-alpha emission and silicate emission features at 9-11 microns, indicative of circumstellar disks. These results all suggest that star formation within this globule is occurring at two different stages the first stage, leading to the Class II sources located in the center of the globule, and a second, very recent one (less than 100,000 yr ago) that is occurring within the globule. This second phase was likely triggered by the wind and radiation of the central O-type star of the IC 1396 H II region.

The JCMT Gould Belt Survey: A First Look at IC 5146

NASA Astrophysics Data System (ADS)

Johnstone, D.; Ciccone, S.; Kirk, H.; Mairs, S.; Buckle, J.; Berry, D. S.; Broekhoven-Fiene, H.; Currie, M. J.; Hatchell, J.; Jenness, T.; Mottram, J. C.; Pattle, K.; Tisi, S.; Di Francesco, J.; Hogerheijde, M. R.; Ward-Thompson, D.; Bastien, P.; Bresnahan, D.; Butner, H.; Chen, M.; Chrysostomou, A.; Coudé, S.; Davis, C. J.; Drabek-Maunder, E.; Duarte-Cabral, A.; Fich, M.; Fiege, J.; Friberg, P.; Friesen, R.; Fuller, G. A.; Graves, S.; Greaves, J.; Gregson, J.; Holland, W.; Joncas, G.; Kirk, J. M.; Knee, L. B. G.; Marsh, K.; Matthews, B. C.; Moriarty-Schieven, G.; Mowat, C.; Nutter, D.; Pineda, J. E.; Salji, C.; Rawlings, J.; Richer, J.; Robertson, D.; Rosolowsky, E.; Rumble, D.; Sadavoy, S.; Thomas, H.; Tothill, N.; Viti, S.; White, G. J.; Wouterloot, J.; Yates, J.; Zhu, M.

2017-02-01

We present 450 and 850 μm submillimeter continuum observations of the IC 5146 star-forming region taken as part of the James Clerk Maxwell Telescope Gould Belt Survey. We investigate the location of bright submillimeter (clumped) emission with the larger-scale molecular cloud through comparison with extinction maps, and find that these denser structures correlate with higher cloud column density. Ninety-six individual submillimeter clumps are identified using FellWalker, and their physical properties are examined. These clumps are found to be relatively massive, ranging from 0.5 {M}⊙ to 116 {M}⊙ with a mean mass of 8 {M}⊙ and a median mass of 3.7 {M}⊙ . A stability analysis for the clumps suggests that the majority are (thermally) Jeans stable, with M/{M}J< 1. We further compare the locations of known protostars with the observed submillimeter emission, finding that younger protostars, I.e., Class 0 and I sources, are strongly correlated with submillimeter peaks and that the clumps with protostars are among the most Jeans unstable. Finally, we contrast the evolutionary conditions in the two major star-forming regions within IC 5146: the young cluster associated with the Cocoon Nebula and the more distributed star formation associated with the Northern Streamer filaments. The Cocoon Nebula appears to have converted a higher fraction of its mass into dense clumps and protostars, the clumps are more likely to be Jeans unstable, and a larger fraction of these remaining clumps contain embedded protostars. The Northern Streamer, however, has a larger number of clumps in total and a larger fraction of the known protostars are still embedded within these clumps.

Massive Submucosal Ganglia in Colonic Inertia.

PubMed

Naemi, Kaveh; Stamos, Michael J; Wu, Mark Li-Cheng

2018-02-01

- Colonic inertia is a debilitating form of primary chronic constipation with unknown etiology and diagnostic criteria, often requiring pancolectomy. We have occasionally observed massively enlarged submucosal ganglia containing at least 20 perikarya, in addition to previously described giant ganglia with greater than 8 perikarya, in cases of colonic inertia. These massively enlarged ganglia have yet to be formally recognized. - To determine whether such "massive submucosal ganglia," defined as ganglia harboring at least 20 perikarya, characterize colonic inertia. - We retrospectively reviewed specimens from colectomies of patients with colonic inertia and compared the prevalence of massive submucosal ganglia occurring in this setting to the prevalence of massive submucosal ganglia occurring in a set of control specimens from patients lacking chronic constipation. - Seven of 8 specimens affected by colonic inertia harbored 1 to 4 massive ganglia, for a total of 11 massive ganglia. One specimen lacked massive ganglia but had limited sampling and nearly massive ganglia. Massive ganglia occupied both superficial and deep submucosal plexus. The patient with 4 massive ganglia also had 1 mitotically active giant ganglion. Only 1 massive ganglion occupied the entire set of 10 specimens from patients lacking chronic constipation. - We performed the first, albeit distinctly small, study of massive submucosal ganglia and showed that massive ganglia may be linked to colonic inertia. Further, larger studies are necessary to determine whether massive ganglia are pathogenetic or secondary phenomena, and whether massive ganglia or mitotically active ganglia distinguish colonic inertia from other types of chronic constipation.

Masers in Disks due to Gravitational Instabilities

NASA Astrophysics Data System (ADS)

Mejia, A. C.; Durisen, R. H.; Pickett, B. K.; Hartquist, T. W.

2001-12-01

Evidence suggests that some masers associated with massive protostars may originate in the outer regions of large circumstellar disks, at radii of 100's to 1000's of AU from the central mass. This is particularly true for methanol (CH3OH), where linear distributions of masers are found with disk-like kinematics. In 3D hydrodynamics simulations we have made to study the effects of gravitational instabilities in the outer parts of disks around young low-mass stars, the nonlinear development of the instabilities leads to a complex of intersecting spiral shocks, clumps, and arclets within the disk and to significant time-dependent, nonaxisymmetric distortions of the disk surface. A rescaling of our disk simulations to the case of a massive protostar shows that conditions in the disturbed outer disk seem conducive to the appearance of masers if it is viewed edge-on. This work was supported by NASA Origins Program Grant NAGW5-4342, by the Alexander von Humboldt Foundation, and by NASA Planetary Geology and Geophysics Program Grant NAG5-10262.

Massive graviton geons

NASA Astrophysics Data System (ADS)

Aoki, Katsuki; Maeda, Kei-ichi; Misonoh, Yosuke; Okawa, Hirotada

2018-02-01

We find vacuum solutions such that massive gravitons are confined in a local spacetime region by their gravitational energy in asymptotically flat spacetimes in the context of the bigravity theory. We call such self-gravitating objects massive graviton geons. The basic equations can be reduced to the Schrödinger-Poisson equations with the tensor "wave function" in the Newtonian limit. We obtain a nonspherically symmetric solution with j =2 , ℓ=0 as well as a spherically symmetric solution with j =0 , ℓ=2 in this system where j is the total angular momentum quantum number and ℓ is the orbital angular momentum quantum number, respectively. The energy eigenvalue of the Schrödinger equation in the nonspherical solution is smaller than that in the spherical solution. We then study the perturbative stability of the spherical solution and find that there is an unstable mode in the quadrupole mode perturbations which may be interpreted as the transition mode to the nonspherical solution. The results suggest that the nonspherically symmetric solution is the ground state of the massive graviton geon. The massive graviton geons may decay in time due to emissions of gravitational waves but this timescale can be quite long when the massive gravitons are nonrelativistic and then the geons can be long-lived. We also argue possible prospects of the massive graviton geons: applications to the ultralight dark matter scenario, nonlinear (in)stability of the Minkowski spacetime, and a quantum transition of the spacetime.

Probing the CO and methanol snow lines in young protostars. Results from the CALYPSO IRAM-PdBI survey

NASA Astrophysics Data System (ADS)

Anderl, S.; Maret, S.; Cabrit, S.; Belloche, A.; Maury, A. J.; André, Ph.; Codella, C.; Bacmann, A.; Bontemps, S.; Podio, L.; Gueth, F.; Bergin, E.

2016-06-01

Context. So-called snow lines, indicating regions where abundant volatiles freeze out onto the surface of dust grains, play an important role for planet growth and bulk composition in protoplanetary disks. They can already be observed in the envelopes of the much younger, low-mass Class 0 protostars, which are still in their early phase of heavy accretion. Aims: We aim to use the information on the sublimation regions of different kinds of ices to understand the chemistry of the envelope, its temperature and density structure, and the history of the accretion process. This information is crucial to get the full picture of the early protostellar collapse and the subsequent evolution of young protostars. Methods: As part of the CALYPSO IRAM Large Program, we have obtained observations of C18O, N2H+, and CH3OH towards nearby Class 0 protostars with the IRAM Plateau de Bure interferometer at sub-arcsecond resolution. For four of these sources, we have modeled the emission using a chemical code coupled with a radiative transfer module. Results: We observe an anti-correlation of C18O and N2H+ in NGC 1333-IRAS4A, NGC 1333-IRAS4B, L1157, and L1448C, with N2H+ forming a ring (perturbed by the outflow) around the centrally peaked C18O emission. This emission morphology, which is due to N2H+ being chemically destroyed by CO, reveals the CO and N2 ice sublimation regions in these protostellar envelopes with unprecedented resolution. We also observe compact methanol emission towards three of the sources. Based on our chemical model and assuming temperature and density profiles from the literature, we find that for all four sources the CO snow line appears further inwards than expected from the binding energy of pure CO ices (~855 K). The emission regions of models and observations match for a higher value of the CO binding energy of 1200 K, corresponding to a dust temperature of ~24 K at the CO snow line. The binding energy for N2 ices is modeled at 1000 K, also higher than for

Constraining the physical structure of the inner few 100 AU scales of deeply embedded low-mass protostars

NASA Astrophysics Data System (ADS)

Persson, M. V.; Harsono, D.; Tobin, J. J.; van Dishoeck, E. F.; Jørgensen, J. K.; Murillo, N.; Lai, S.-P.

2016-05-01

Context. The physical structure of deeply embedded low-mass protostars (Class 0) on scales of less than 300 AU is still poorly constrained. While molecular line observations demonstrate the presence of disks with Keplerian rotation toward a handful of sources, others show no hint of rotation. Determining the structure on small scales (a few 100 AU) is crucial for understanding the physical and chemical evolution from cores to disks. Aims: We determine the presence and characteristics of compact, disk-like structures in deeply embedded low-mass protostars. A related goal is investigating how the derived structure affects the determination of gas-phase molecular abundances on hot-core scales. Methods: Two models of the emission, a Gaussian disk intensity distribution and a parametrized power-law disk model, are fitted to subarcsecond resolution interferometric continuum observations of five Class 0 sources, including one source with a confirmed Keplerian disk. Prior to fitting the models to the de-projected real visibilities, the estimated envelope from an independent model and any companion sources are subtracted. For reference, a spherically symmetric single power-law envelope is fitted to the larger scale emission (~1000 AU) and investigated further for one of the sources on smaller scales. Results: The radii of the fitted disk-like structures range from ~90-170 AU, and the derived masses depend on the method. Using the Gaussian disk model results in masses of 54-556 × 10-3 M⊙, and using the power-law disk model gives 9-140 × 10-3 M⊙. While the disk radii agree with previous estimates the masses are different for some of the sources studied. Assuming a typical temperature distribution (r-0.5), the fractional amount of mass in the disk above 100 K varies from 7% to 30%. Conclusions: A thin disk model can approximate the emission and physical structure in the inner few 100 AU scales of the studied deeply embedded low-mass protostars and paves the way for

Triggered star-formation in the bright rimmed globule IC1396A

NASA Astrophysics Data System (ADS)

Patel, Nimesh A.; Sicilia-Aguilar, Aurora; Goldsmith, Paul

2015-01-01

IC1396 is a well known HII region and molecular cloud complex surrounding the Trumpler 37 cluster of OB stars in the Cepheus OB2 association. The dense, elephant trunk shaped globules in this region typically show bright rims facing the central exciting O6 star HD~206267. This region, at a distance of 870 pc, is an excellent astrophysical laboratory for studying the feedback effects of massive stars on neighboring molecular clouds. Triggered star formation occurs when dense cores (which would otherwise remain stable) are compressed and made unstable by the sustained energy input from the OB association. Observationally it remains challenging to prove whether the onset of star-formation in such globules is triggered or spontaneous.Using the Submillimeter Array (SMA), we observed IC1396 globule A (Pottasch 1958 nomenclature), targeting four newly discovered protostars from recent Herschel PACS observations. Here we present 230 GHz molecular line (CO, 13CO, C18O, N2D+ and H2CO) and continuum results for the source IC1396A-PACS-1 (Sicilia-Aguilar et al. 2014). This is a Class 0 source very close to the edge of the ionization front and Herschel observations show this to be a most promisingcase of triggered star-formation. The SMA 230 GHz continuum source has a flux density of 280 mJy. We estimate a dust mass of about 0.1 Msun in this source which appears very compact in our 5" beam. CO, 13CO and C18O emission is largely resolved out by the interferometer and will require combined imaging with single-dish observations. (We have a parallel ongoing study being carried out with the IRAM 30m telescope). SMA N2D+ emission peaks on the continuum sourceand is partially resolved. H2CO emission appears to avoid the peak of continuum and N2D+, suggesting depletion. Both the morphology and kinematics in H2CO emission are indicative of internal disturbance, away from the PDR region into the globule.

Multiple Gaps in the Disk of the Class I Protostar GY 91

NASA Astrophysics Data System (ADS)

Sheehan, Patrick D.; Eisner, Josh A.

2018-04-01

We present the highest spatial resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations to date of the Class I protostar GY 91 in the ρ Ophiuchus L1688 molecular cloud complex. Our 870 μm and 3 mm dust continuum maps show that the GY 91 disk has a radius of ∼80 au, and an inclination of ∼40°, but most interestingly that the disk has three dark lanes located at 10, 40, and 70 au. We model these features assuming they are gaps in the disk surface density profile and find that their widths are 7, 30, and 10 au. These gaps bear a striking resemblance to the gaps seen in the HL Tau disk, suggesting that there may be Saturn-mass planets hiding in the disk. To constrain the relative ages of GY 91 and HL Tau, we also model the disk and envelope of HL Tau and find that they are of similar ages, although GY 91 may be younger. Although snow lines and magnetic dead zones can also produce dark lanes, if planets are indeed carving these gaps then Saturn-mass planets must form within the first ∼0.5 Myr of the lifetime of protoplanetary disks.

Grain growth in Class I protostar Per-emb-50: a dust continuum analysis with NOEMA & SMA .

NASA Astrophysics Data System (ADS)

Agurto-Gangas, C.; Pineda, J. E.; Testi, L.; Caselli, P.; Szucs, L.; Tazzari, M.; Dunham, M.; Stephens, I. W.; Miotello, A.

A good understanding of when dust grains grow from sub-micrometer to millimeter sizes occurs is crucial for models of planet formation. This provides the first step towards the production of pebbles and planetesimals in protoplanetary disks. Thanks to detailed studies of the spectral index in Class II disks, it is well established that Class II objects have already dust grains of millimetres sizes, however, it is not clear when in the star formation process this grain growth occurs. Here, we present interferometric data from NOEMA at 3 mm and SMA at 1.3 mm of the Class I protostar, Per-emb-50, to determine the flux density spectral index at mm-wavelengths of the unresolved disk and the surrounding envelope. We find a spectral index in the unresolved disk 30% smaller than the envelope, alpha env=2.18, comparable to values obtained toward Class 0 sources.

Observations Of Polarized Dust Emission In Protostars: How To Reconstruct Magnetic Field Properties?

NASA Astrophysics Data System (ADS)

Maury, Anaëlle; Galametz, M.; Girart; Guillet; Hennebelle, P.; Houde; Rao; Valdivia, V.; Zhang, Q.

2017-10-01

I will present our ALMA Cycle 2 polarized dust continuum data towards the Class 0 protostar B335 where the absence of detected rotational motions in the inner envelope might suggest an efficient magnetic braking at work to inhibit the formation of a large disk. The Band 6 data we obtained shows an intriguing polarized vectors topology, which could either suggest (i) at least two different grain alignment mechanisms at work in B335 to produce the observed polarization pattern, or (ii) an interferometric bias leading to filtering of the polarized signal that is different from the filtering of Stokes I. I will discuss both options, proposing multi-wavelength and multi observatory (ALMA Band3 data in Cycle 5, NIKA2Pol camera on the IRAM-30m) strategies to lift the degeneracy when using polarization observations as a proxy of magnetic fields in dense astrophysical environments. This observational effort in the framework of the MagneticYSOs project, is also supported by our development of an end-to-end chain of ALMA synthetic observations of the polarization from non-ideal MHD simulations of protostellar collapse (see complementary contributions by V. Valdivia and M. Galametz).

Multiplicity of Massive Stars

NASA Astrophysics Data System (ADS)

Zinnecker, Hans

We review the multiplicity of massive stars by compiling the abstracts of the most relevant papers in the field. We start by discussing the massive stars in the Orion Trapezium Cluster and in other Galactic young clusters and OB associations, and end with the R136 cluster in the LMC. The multiplicity of field O-stars and runaway OB stars is also reviewed. The results of both visual and spectroscopic surveys are presented, as well as data for eclipsing systems. Among the latter, we find the most massive known binary system WR20a, with two ~,80M_⊙ components in a 3 day orbit. Some 80% of the wide visual binaries in stellar associations are in fact hierarchical triple systems, where typically the more massive of the binary components is itself a spectroscopic or even eclipsing binary pair. The multiplicity (number of companions) of massive star primaries is significantly higher than for low-mass solar-type primaries or for young low-mass T Tauri stars. There is also a striking preponderance of very close nearly equal mass binary systems (the origin of which has recently been explained in an accretion scenario). Finally, we offer a new idea as to the origin of massive Trapezium systems, frequently found in the centers of dense young clusters.

Topologically massive magnetic monopoles

NASA Astrophysics Data System (ADS)

Aliev, A. N.; Nutku, Y.; Saygili, K.

2000-10-01

We show that in the Maxwell-Chern-Simons theory of topologically massive electrodynamics the Dirac string of a monopole becomes a cone in anti-de Sitter space with the opening angle of the cone determined by the topological mass, which in turn is related to the square root of the cosmological constant. This proves to be an example of a physical system, a priori completely unrelated to gravity, which nevertheless requires curved spacetime for its very existence. We extend this result to topologically massive gravity coupled to topologically massive electrodynamics within the framework of the theory of Deser, Jackiw and Templeton. The two-component spinor formalism, which is a Newman-Penrose type approach for three dimensions, is extended to include both the electrodynamical and gravitational topologically massive field equations. Using this formalism exact solutions of the coupled Deser-Jackiw-Templeton and Maxwell-Chern-Simons field equations for a topologically massive monopole are presented. These are homogeneous spaces with conical deficit. Pure Einstein gravity coupled to the Maxwell-Chern-Simons field does not admit such a monopole solution.

An ALMA Survey of Planet Forming Disks in Rho Ophiuchus

NASA Astrophysics Data System (ADS)

Cox, Erin Guilfoil; Looney, Leslie; Harris, Robert J.; Dong, Jiayin; Segura-Cox, Dominique; Tobin, John J.; Sadavoy, Sarah; Li, Zhi-Yun; Dunham, Michael; Perez, Laura M.; Chandler, Claire J.; Kratter, Kaitlin M.; Melis, Carl; Chiang, Hsin-Fang

2017-01-01

Relatively evolved (~ 1 Myr old) protostars with little residual natal envelope, but massive disks, are commonly assumed to be the sites of ongoing planet formation. Critical to our study of these objects is information about the available mass reservior and dust structure, as they directly tie in to how much mass is available for planets as well as the modes of planet formation that occur (i.e., core-accretion vs. gravitational instability). Millimeter-wave observations provide this critical information as continuum emission is relatively optically thin, allowing for mass estimates, and the availability of high-resolution interferometry, allowing structure constraints. We present high-resolution observations of the population of Class II protostars in the Rho-Ophiuchus cloud (d ~ 130 pc). Our survey observed ~50 of these older protostars at 870µm, using the Atacama Large Millimeter/submillimeter Array (ALMA). Out of these sources, there are ~10 transition disks, where we see a ring of dust emission surrounding the central protostar -- indicative of ongoing planet formation -- as well as many binary systems. Both of these stages have implications for star and planet formation. We present results from both 1-D and 2-D disk modeling, where we try to understand disk substructure that might indicate on-going planet formation, in particular, transition disk cavities, disk gaps, and asymmetries in the dust emission.

Cassiopeia

NASA Astrophysics Data System (ADS)

Murdin, P.

2000-11-01

(abbrev. Cas, gen. Cassiopeiae; area 598 sq. deg.) A northern constellation which lies between Cepheus and Andromeda, and culminates at midnight in early October. It is named after Queen Cassiopeia, wife of King Cepheus and mother of Andromeda in Greek mythology, and is usually shown on early celestial charts as a seated figure. Its brightest stars were cataloged by Ptolemy (c. AD 100-175) in the ...

MassiveNuS: cosmological massive neutrino simulations

NASA Astrophysics Data System (ADS)

Liu, Jia; Bird, Simeon; Zorrilla Matilla, José Manuel; Hill, J. Colin; Haiman, Zoltán; Madhavacheril, Mathew S.; Petri, Andrea; Spergel, David N.

2018-03-01

The non-zero mass of neutrinos suppresses the growth of cosmic structure on small scales. Since the level of suppression depends on the sum of the masses of the three active neutrino species, the evolution of large-scale structure is a promising tool to constrain the total mass of neutrinos and possibly shed light on the mass hierarchy. In this work, we investigate these effects via a large suite of N-body simulations that include massive neutrinos using an analytic linear-response approximation: the Cosmological Massive Neutrino Simulations (MassiveNuS). The simulations include the effects of radiation on the background expansion, as well as the clustering of neutrinos in response to the nonlinear dark matter evolution. We allow three cosmological parameters to vary: the neutrino mass sum Mν in the range of 0–0.6 eV, the total matter density Ωm, and the primordial power spectrum amplitude As. The rms density fluctuation in spheres of 8 comoving Mpc/h (σ8) is a derived parameter as a result. Our data products include N-body snapshots, halo catalogues, merger trees, ray-traced galaxy lensing convergence maps for four source redshift planes between zs=1–2.5, and ray-traced cosmic microwave background lensing convergence maps. We describe the simulation procedures and code validation in this paper. The data are publicly available at http://columbialensing.org.

Holographically viable extensions of topologically massive and minimal massive gravity?

NASA Astrophysics Data System (ADS)

Altas, Emel; Tekin, Bayram

2016-01-01

Recently [E. Bergshoeff et al., Classical Quantum Gravity 31, 145008 (2014)], an extension of the topologically massive gravity (TMG) in 2 +1 dimensions, dubbed as minimal massive gravity (MMG), which is free of the bulk-boundary unitarity clash that inflicts the former theory and all the other known three-dimensional theories, was found. Field equations of MMG differ from those of TMG at quadratic terms in the curvature that do not come from the variation of an action depending on the metric alone. Here we show that MMG is a unique theory and there does not exist a deformation of TMG or MMG at the cubic and quartic order (and beyond) in the curvature that is consistent at the level of the field equations. The only extension of TMG with the desired bulk and boundary properties having a single massive degree of freedom is MMG.

Probing the water and CO snow lines in the young protostar NGC 1333-IRAS4B

NASA Astrophysics Data System (ADS)

Anderl, Sibylle; Maret, Sébastien; André, Philippe; Maury, Anaëlle; Belloche, Arnaud; Cabrit, Sylvie; Codella, Claudio; Lefloch, Bertrand

2015-08-01

Today, we believe that the onset of life requires free energy, water, and complex, probably carbon-based chemistry. In the interstellar medium, complex organic molecules seem to mostly form in reactions happening on the icy surface of dust grains, such that they are released into the gas phase when the dust is heated. The resulting “snow lines”, marking regions where ices start to sublimate, play an important role for planet growth and bulk composition in protoplanetary disks. However, they can already be observed in the envelopes of the much younger, low-mass Class 0 protostars that are still in their early phase of heavy accretion. The information on the sublimation regions of different kinds of ices can be used to understand the chemistry of the envelope, its temperature and density structure, and may even hint at the history of the accretion process. Accordingly, it is a crucial piece of information in order to get the full picture of how organic chemistry evolves already at the earliest stages of the formation of sun-like stars. As part of the CALYPSO Large Program (http://irfu.cea.fr/Projets/Calypso/), we have obtained observations of C18O, N2H+ and CH3OH towards the Class 0 protostar NGC 1333-IRAS4B with the IRAM Plateau de Bure interferometer at sub-arcsecond resolution. Of these we use the methanol observations as a proxy for the water snow line, assuming methanol is trapped in water ice. The observed anti-correlation of C18O and N2H+, with N2H+ forming a ring around the centrally peaked C18O emission, reveals for the first time the CO snow line in this protostellar envelope, with a radius of ~300 AU. The methanol emission is much more compact than that of C18O, and traces the water snow line with a radius of ~40 AU. We have modeled the emission using a chemical model coupled with a radiative transfer module. We find that the CO snow line appears further inwards than expected from the binding energy of pure CO ices. This may hint at CO being frozen out

Star Formation in the Eagle Nebula

NASA Astrophysics Data System (ADS)

Oliveira, J. M.

2008-12-01

M16 (the Eagle Nebula) is a striking star forming region, with a complex morphology of gas and dust sculpted by the massive stars in NGC 6611. Detailed studies of the famous ``elephant trunks'' dramatically increased our understanding of the massive star feedback into the parent molecular cloud. A rich young stellar population (2-3 Myr) has been identified, from massive O-stars down to substellar masses. Deep into the remnant molecular material, embedded protostars, Herbig-Haro objects and maser sources bear evidence of ongoing star formation in the nebula, possibly triggered by the massive cluster members. M 16 is a excellent template for the study of star formation under the hostile environment created by massive O-stars. This review aims at providing an observational overview not only of the young stellar population but also of the gas remnant of the star formation process.

COLA with massive neutrinos

NASA Astrophysics Data System (ADS)

Wright, Bill S.; Winther, Hans A.; Koyama, Kazuya

2017-10-01

The effect of massive neutrinos on the growth of cold dark matter perturbations acts as a scale-dependent Newton's constant and leads to scale-dependent growth factors just as we often find in models of gravity beyond General Relativity. We show how to compute growth factors for ΛCDM and general modified gravity cosmologies combined with massive neutrinos in Lagrangian perturbation theory for use in COLA and extensions thereof. We implement this together with the grid-based massive neutrino method of Brandbyge and Hannestad in MG-PICOLA and compare COLA simulations to full N-body simulations of ΛCDM and f(R) gravity with massive neutrinos. Our implementation is computationally cheap if the underlying cosmology already has scale-dependent growth factors and it is shown to be able to produce results that match N-body to percent level accuracy for both the total and CDM matter power-spectra up to klesssim 1 h/Mpc.

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.

The rate and latency of star formation in dense, massive clumps in the Milky Way

NASA Astrophysics Data System (ADS)

Heyer, M.; Gutermuth, R.; Urquhart, J. S.; Csengeri, T.; Wienen, M.; Leurini, S.; Menten, K.; Wyrowski, F.

2016-04-01

Context. Newborn stars form within the localized, high density regions of molecular clouds. The sequence and rate at which stars form in dense clumps and the dependence on local and global environments are key factors in developing descriptions of stellar production in galaxies. Aims: We seek to observationally constrain the rate and latency of star formation in dense massive clumps that are distributed throughout the Galaxy and to compare these results to proposed prescriptions for stellar production. Methods: A sample of 24 μm-based Class I protostars are linked to dust clumps that are embedded within molecular clouds selected from the APEX Telescope Large Area Survey of the Galaxy. We determine the fraction of star-forming clumps, f∗, that imposes a constraint on the latency of star formation in units of a clump's lifetime. Protostellar masses are estimated from models of circumstellar environments of young stellar objects from which star formation rates are derived. Physical properties of the clumps are calculated from 870 μm dust continuum emission and NH3 line emission. Results: Linear correlations are identified between the star formation rate surface density, ΣSFR, and the quantities ΣH2/τff and ΣH2/τcross, suggesting that star formation is regulated at the local scales of molecular clouds. The measured fraction of star forming clumps is 23%. Accounting for star formation within clumps that are excluded from our sample due to 24 μm saturation, this fraction can be as high as 31%, which is similar to previous results. Dense, massive clumps form primarily low mass (<1-2 M⊙) stars with emergent 24 μm fluxes below our sensitivity limit or are incapable of forming any stars for the initial 70% of their lifetimes. The low fraction of star forming clumps in the Galactic center relative to those located in the disk of the Milky Way is verified. Full Tables 2-4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130

A Complex Organic Slushy Bathing Low-Mass Protostars

NASA Astrophysics Data System (ADS)

Drozdovskaya, Maria; Walsh, Catherine; Visser, Ruud; Harsono, Daniel; van Dishoeck, Ewine

2015-08-01

Complex organic molecules are ubiquitous companions of young forming stars. They were first observed in hot cores surrounding high-mass protostars [e.g., 1], but have since also been detected in the environs of several low-mass counterparts [e.g., 2]. Recent studies have shown that colder envelopes and positions with impinging outflows may also glow with emission from complex organic species [e.g., 3, 4]. For this meeting, I would like to present physicochemical modeling results on the synthesis of complex organics in an envelope-cavity system that is subject to non-thermal processing. This includes wavelength-dependent radiative transfer calculations with RADMC [5] and a comprehensive gas-grain chemical network [6]. The results show that the morphology of such a system delineates three distinct regions: the cavity wall layer with time-dependent and species-variant enhancements; a torus rich in complex organic ices, but not reflected in gas-phase abundances; and the remaining outer envelope abundant in simpler solid and gaseous molecules. Within the adopted paradigm, complex organic molecules are demonstrated to have unique lifetimes and be grouped into early and late species [7]. Key chemical processes for forming and destroying complex organic molecules will be discussed. In addition, the results of adding newly experimentally verified routes [8] into the existing chemical networks will be shown.[1] Blake G. A., Sutton E. C., Masson C. R., Phillips T. G., 1987, ApJ, 315, 621[2] Jørgensen J. K., Favre C., Bisschop S. E., Bourke T. L., van Dishoeck E. F., Schmalzl M., 2012, ApJ, 757, L4[3] Arce H. G., Santiago-García J., Jørgensen J. K., Tafalla M., Bachiller R., 2008, ApJ, 681, L21[4] Öberg K. I., Bottinelli S., Jørgensen J. K., van Dishoeck E. F., 2010, ApJ, 716, 825[5] Dullemond C. P., Dominik C., 2004, A&A, 417, 159[6] Walsh C., Millar T. J., Nomura H., Herbst E., Widicus Weaver S., Aikawa Y., Laas J. C., Vasyunin A. I., 2014, A&A, 563, A33[7] Drozdovskaya

Massive Stars in M31

NASA Astrophysics Data System (ADS)

Lomax, Jamie R.; Peters, Matthew; Wisniewski, John; Dalcanton, Julianne; Williams, Benjamin; Lutz, Julie; Choi, Yumi; Sigut, Aaron

2017-11-01

Massive stars are intrinsically rare and therefore present a challenge to understand from a statistical perspective, especially within the Milky Way. We recently conducted follow-up observations to the Panchromatic Hubble Andromeda Treasury (PHAT) survey that were designed to detect more than 10,000 emission line stars, including WRs, by targeting regions in M31 previously known to host large numbers of young, massive clusters and very young stellar populations. Because of the existing PHAT data, we are able to derive an effective temperature, bolarimetric luminosity, and extinction for each of our detected stars. We report on preliminary results of the massive star population of our dataset and discuss how our results compare to previous studies of massive stars in M31.

Rise of the First Super-Massive Stars

NASA Astrophysics Data System (ADS)

Regan, John A.; Downes, Turlough P.

2018-05-01

We use high resolution adaptive mesh refinement simulations to model the formation of massive metal-free stars in the early Universe. By applying Lyman-Werner (LW) backgrounds of 100 J21 and 1000 J21 respectively we construct environments conducive to the formation of massive stars. We find that only in the case of the higher LW backgrounds are super-critical accretion rates realised that are necessary for super-massive star (SMS) formation. Mild fragmentation is observed for both backgrounds. Violent dynamical interactions between the stars that form in the more massive halo formed (1000 J21 background) results in the eventual expulsion of the two most massive stars from the halo. In the smaller mass halo (100 J21 background) mergers of stars occur before any multibody interactions and a single massive Pop III star is left at the centre of the halo at the end of our simulation. Feedback from the very massive Pop III stars is not effective in generating a large HII region with ionising photons absorbed within a few thousand AU of the star. In all cases a massive black hole seed is the expected final fate of the most massive objects. The seed of the massive Pop III star which remained at the centre of the less massive halo experiences steady accretion rates of almost 10-2M_{⊙}/yr and if these rates continue could potentially experience super-Eddington accretion rates in the immediate aftermath of collapsing into a black hole.

Inconsistency of topologically massive hypergravity

NASA Technical Reports Server (NTRS)

Aragone, C.; Deser, S.

1985-01-01

The coupled topologically massive spin-5/2 gravity system in D = 3 dimensions whose kinematics represents dynamical propagating gauge invariant massive spin-5/2 and spin-2 excitations, is shown to be inconsistent, or equivalently, not locally hypersymmetric. In contrast to D = 4, the local constraints on the system arising from failure of the fermionic Bianchi identities do not involve the 'highest spin' components of the field, but rather the auxiliary spinor required to construct a consistent massive model.

The ALMA-PILS survey: the sulphur connection between protostars and comets: IRAS 16293-2422 B and 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Drozdovskaya, Maria N.; van Dishoeck, Ewine F.; Jørgensen, Jes K.; Calmonte, Ursina; van der Wiel, Matthijs H. D.; Coutens, Audrey; Calcutt, Hannah; Müller, Holger S. P.; Bjerkeli, Per; Persson, Magnus V.; Wampfler, Susanne F.; Altwegg, Kathrin

2018-06-01

The evolutionary past of our Solar system can be pieced together by comparing analogous low-mass protostars with remnants of our Protosolar Nebula - comets. Sulphur-bearing molecules may be unique tracers of the joint evolution of the volatile and refractory components. ALMA Band 7 data from the large unbiased Protostellar Interferometric Line Survey are used to search for S-bearing molecules in the outer disc-like structure, ˜60 au from IRAS 16293-2422 B, and are compared with data on 67P/Churyumov-Gerasimenko (67P/C-G) stemming from the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instrument aboard Rosetta. Species such as SO2, SO, OCS, CS, H2CS, H2S, and CH3SH are detected via at least one of their isotopologues towards IRAS 16293-2422 B. The search reveals a first-time detection of OC33S towards this source and a tentative first-time detection of C36S towards a low-mass protostar. The data show that IRAS 16293-2422 B contains much more OCS than H2S in comparison to 67P/C-G; meanwhile, the SO/SO2 ratio is in close agreement between the two targets. IRAS 16293-2422 B has a CH3SH/H2CS ratio in range of that of our Solar system (differences by a factor of 0.7-5.3). It is suggested that the levels of UV radiation during the initial collapse of the systems may have varied and have potentially been higher for IRAS 16293-2422 B due to its binary nature; thereby, converting more H2S into OCS. It remains to be conclusively tested if this also promotes the formation of S-bearing complex organics. Elevated UV levels of IRAS 16293-2422 B and a warmer birth cloud of our Solar system may jointly explain the variations between the two low-mass systems.

The Formation and Fragmentation of Primordial Protostellar Discs

NASA Astrophysics Data System (ADS)

Clark, Paul C.; Glover, Simon C. O.; Smith, Rowan J.; Greif, Thomas H.; Klessen, Ralf S.; Bromm, Volker

2010-11-01

We study the formation and evolution of the protostellar discs that form around the first stars in the Universe. Using sink particles, we replace the gravitationally bound gas at densities higher than 1015 cm-3 and radii greater than 3 AU from the central protostellar core, with an accreting point mass that is able to gravitationally interact with the surrounding gas. We find the disc is gravitationally (or `Toomre') unstable, and is dominated by a strong m = 2 spiral mode. Although the angular momentum transport is dominated by a combination of gravitational torques and Reynolds stresses, which are extremely efficient mechanisms, the disc is unable to process the infalling material and grows increasingly gravitationally unstable. During the build-up of the disc, the temperature in the gas is regulated by a combination of H2 line cooling, collision-induced emission and H2 dissociation, which together help to offset heating from the gravitational collapse and feedback from the protostar. Once the disc starts to fragment, H2 dissociation keeps the gas almost isothermal as the collapse of the fragment progresses. The fragmentation occurs when the protostar/disc system is only 230 yr old and at a distance of ~20 AU from its sibling, by which point the central protostar has a mass of ~1 Msolar. Given the angular momentum of the new protostellar system, it is likely that the protostars will grow to become a massive binary system.

ALMA’s Polarized View of 10 Protostars in the Perseus Molecular Cloud

NASA Astrophysics Data System (ADS)

Cox, Erin G.; Harris, Robert J.; Looney, Leslie W.; Li, Zhi-Yun; Yang, Haifeng; Tobin, John J.; Stephens, Ian

2018-03-01

We present 870 μm ALMA dust polarization observations of 10 young Class 0/I protostars in the Perseus Molecular Cloud. At ∼0.″35 (80 au) resolution, all of our sources show some degree of polarization, with most (9/10) showing significantly extended emission in the polarized continuum. Each source has incredibly intricate polarization signatures. In particular, all three disk-candidates have polarization vectors roughly along the minor axis, which is indicative of polarization produced by dust scattering. On ∼100 au scales, the polarization is at a relatively low level (≲1%) and is quite ordered. In sources with significant envelope emission, the envelope is typically polarized at a much higher (≳5%) level and has a far more disordered morphology. We compute the cumulative probability distributions for both the small (disk-scale) and large (envelope-scale) polarization percentage. We find that the two are intrinsically different, even after accounting for the different detection thresholds in the high/low surface brightness regions. We perform Kolmogorov–Smirnov and Anderson–Darling tests on the distributions of angle offsets of the polarization from the outflow axis. We find disk-candidate sources are different from the non-disk-candidate sources. We conclude that the polarization on the 100 au scale is consistent with the signature of dust scattering for disk-candidates and that the polarization on the envelope-scale in all sources may come from another mechanism, most likely magnetically aligned grains.

Nonsingular universe in massive gravity's rainbow

NASA Astrophysics Data System (ADS)

Hendi, S. H.; Momennia, M.; Eslam Panah, B.; Panahiyan, S.

2017-06-01

One of the fundamental open questions in cosmology is whether we can regard the universe evolution without singularity like a Big Bang or a Big Rip. This challenging subject stimulates one to regard a nonsingular universe in the far past with an arbitrarily large vacuum energy. Considering the high energy regime in the cosmic history, it is believed that Einstein gravity should be corrected to an effective energy dependent theory which could be acquired by gravity's rainbow. On the other hand, employing massive gravity provided us with solutions to some of the long standing fundamental problems of cosmology such as cosmological constant problem and self acceleration of the universe. Considering these aspects of gravity's rainbow and massive gravity, in this paper, we initiate studying FRW cosmology in the massive gravity's rainbow formalism. At first, we show that although massive gravity modifies the FRW cosmology, but it does not itself remove the big bang singularity. Then, we generalize the massive gravity to the case of energy dependent spacetime and find that massive gravity's rainbow can remove the early universe singularity. We bring together all the essential conditions for having a nonsingular universe and the effects of both gravity's rainbow and massive gravity generalizations on such criteria are determined.

Massive gravity in three dimensions.

PubMed

Bergshoeff, Eric A; Hohm, Olaf; Townsend, Paul K

2009-05-22

A particular higher-derivative extension of the Einstein-Hilbert action in three spacetime dimensions is shown to be equivalent at the linearized level to the (unitary) Pauli-Fierz action for a massive spin-2 field. A more general model, which also includes "topologically-massive" gravity as a special case, propagates the two spin-2 helicity states with different masses. We discuss the extension to massive N-extended supergravity, and we present a "cosmological" extension that admits an anti-de Sitter vacuum.

Massive binary stars as a probe of massive star formation

NASA Astrophysics Data System (ADS)

Kiminki, Daniel C.

2010-10-01

Massive stars are among the largest and most influential objects we know of on a sub-galactic scale. Binary systems, composed of at least one of these stars, may be responsible for several types of phenomena, including type Ib/c supernovae, short and long gamma ray bursts, high-velocity runaway O and B-type stars, and the density of the parent star clusters. Our understanding of these stars has met with limited success, especially in the area of their formation. Current formation theories rely on the accumulated statistics of massive binary systems that are limited because of their sample size or the inhomogeneous environments from which the statistics are collected. The purpose of this work is to provide a higher-level analysis of close massive binary characteristics using the radial velocity information of 113 massive stars (B3 and earlier) and binary orbital properties for the 19 known close massive binaries in the Cygnus OB2 Association. This work provides an analysis using the largest amount of massive star and binary information ever compiled for an O-star rich cluster like Cygnus OB2, and compliments other O-star binary studies such as NGC 6231, NGC 2244, and NGC 6611. I first report the discovery of 73 new O or B-type stars and 13 new massive binaries by this survey. This work involved the use of 75 successful nights of spectroscopic observation at the Wyoming Infrared Observatory in addition to observations obtained using the Hydra multi-object spectrograph at WIYN, the HIRES echelle spectrograph at KECK, and the Hamilton spectrograph at LICK. I use these data to estimate the spectrophotometric distance to the cluster and to measure the mean systemic velocity and the one-sided velocity dispersion of the cluster. Finally, I compare these data to a series of Monte Carlo models, the results of which indicate that the binary fraction of the cluster is 57 +/- 5% and that the indices for the power law distributions, describing the log of the periods, mass

Cold CO Gas in the Envelopes of FU Orionis-type Young Eruptive Stars

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

Kóspál, Á.; Ábrahám, P.; Moór, A.

FU Orionis-type objects (FUors) are young stellar objects experiencing large optical outbursts due to highly enhanced accretion from the circumstellar disk onto the star. FUors are often surrounded by massive envelopes, which play a significant role in the outburst mechanism. Conversely, the subsequent eruptions might gradually clear up the obscuring envelope material and drive the protostar on its way to become a disk-only T Tauri star. Here we present an APEX {sup 12}CO and {sup 13}CO survey of eight southern and equatorial FUors. We measure the mass of the gaseous material surrounding our targets, locate the source of the COmore » emission, and derive physical parameters for the envelopes and outflows, where detected. Our results support the evolutionary scenario where FUors represent a transition phase from envelope-surrounded protostars to classical T Tauri stars.« less

Unraveling the 10 micron "silicate" feature of protostars: the detection of frozen interstellar ammonia

NASA Technical Reports Server (NTRS)

Lacy, J. H.; Faraji, H.; Sandford, S. A.; Allamandola, L. J.

1998-01-01

We present infrared spectra of four embedded protostars in the 750-1230 cm-1 (13.3-8.1 microns) range. For NGC 7538 IRS 9, a new band is reported at 1110 cm-1 (9.01 microns, and several others may be present near 785, 820, 900, 1030, and 1075 cm-1 (12.7, 12.2, 11.1, 9.71, and 9.30 microns). The band 1110 cm-1 is attributed to frozen NH3. Its position and width imply that the NH3 is frozen in a polar, H2O-rich interstellar ice component. The NH3/H2O ice ratio inferred for NGC 7538 IRS 9 is 0.1, making NH3 as important a component as CH3OH and CO2 in the polar ices along this line of sight. At these concentrations, hydrogen bonding between the NH3 and H2O can account for much of the enigmatic low-frequency wing on the 3240 cm-1 (3.09 microns) H2O interstellar ice band. The strength of the implied NH3 deformation fundamental at 1624 cm-1 (6.158 microns) can also account for the absorption at this position reported by ISO.

Outflows, infall and evolution of a sample of embedded low-mass protostars. The William Herschel Line Legacy (WILL) survey

NASA Astrophysics Data System (ADS)

Mottram, J. C.; van Dishoeck, E. F.; Kristensen, L. E.; Karska, A.; San José-García, I.; Khanna, S.; Herczeg, G. J.; André, Ph.; Bontemps, S.; Cabrit, S.; Carney, M. T.; Drozdovskaya, M. N.; Dunham, M. M.; Evans, N. J.; Fedele, D.; Green, J. D.; Harsono, D.; Johnstone, D.; Jørgensen, J. K.; Könyves, V.; Nisini, B.; Persson, M. V.; Tafalla, M.; Visser, R.; Yıldız, U. A.

2017-04-01

Context. Herschel observations of water and highly excited CO (J > 9) have allowed the physical and chemical conditions in the more active parts of protostellar outflows to be quantified in detail for the first time. However, to date, the studied samples of Class 0/I protostars in nearby star-forming regions have been selected from bright, well-known sources and have not been large enough for statistically significant trends to be firmly established. Aims: We aim to explore the relationships between the outflow, envelope and physical properties of a flux-limited sample of embedded low-mass Class 0/I protostars. Methods: We present spectroscopic observations in H2O, CO and related species with Herschel HIFI and PACS, as well as ground-based follow-up with the JCMT and APEX in CO, HCO+ and isotopologues, of a sample of 49 nearby (d < 500 pc) candidate protostars selected from Spitzer and Herschel photometric surveys of the Gould Belt. This more than doubles the sample of sources observed by the WISH and DIGIT surveys. These data are used to study the outflow and envelope properties of these sources. We also compile their continuum spectral energy distributions (SEDs) from the near-IR to mm wavelengths in order to constrain their physical properties (e.g. Lbol, Tbol and Menv). Results: Water emission is dominated by shocks associated with the outflow, rather than the cooler, slower entrained outflowing gas probed by ground-based CO observations. These shocks become less energetic as sources evolve from Class 0 to Class I. Outflow force, measured from low-J CO, also decreases with source evolutionary stage, while the fraction of mass in the outflow relative to the total envelope (I.e. Mout/Menv) remains broadly constant between Class 0 and I. The median value of 1% is consistent with a core to star formation efficiency on the order of 50% and an outflow duty cycle on the order of 5%. Entrainment efficiency, as probed by FCO/Ṁacc, is also invariant with source

Search of massive star formation with COMICS

NASA Astrophysics Data System (ADS)

Okamoto, Yoshiko K.

2004-04-01

Mid-infrared observations is useful for studies of massive star formation. Especially COMICS offers powerful tools: imaging survey of the circumstellar structures of forming massive stars such as massive disks and cavity structures, mass estimate from spectroscopy of fine structure lines, and high dispersion spectroscopy to census gas motion around formed stars. COMICS will open the next generation infrared studies of massive star formation.

COMPUTATIONAL MODELING OF THE CLASS I LOW-MASS PROTOSTAR ELIAS 29 APPLYING OPTICAL CONSTANTS OF ICES PROCESSED BY HIGH ENERGY COSMIC RAY ANALOGS

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

Rocha, W. R. M.; Pilling, S., E-mail: willrobson88@hotmail.com, E-mail: sergiopilling@yahoo.com.br

2015-04-10

We present a study of the effects of high energy cosmic rays (CRs) over the astrophysical ices, observed toward the embedded class I protostar Elias 29, by using computational modeling and laboratory data. Its spectrum was observed with the Infrared Space Observatory (ISO) covering 2.3–190 μm. The modeling employed the three-dimensional Monte Carlo radiative transfer code RADMC-3D and laboratory data of bombarded ice grains by CR analogs and unprocessed ices (not bombarded). We are assuming that Elias 29 has a self-irradiated disk with inclination i = 60.°0, surrounded by an envelope with a bipolar cavity. The results show that absorptionmore » features toward Elias 29 are better reproduced by assuming a combination between unprocessed astrophysical ices at low temperature (H{sub 2}O, CO, CO{sub 2}) and bombarded ices (H{sub 2}O:CO{sub 2}) by high energy CRs. Evidences of the ice processing around Elias 29 can be observed by the good fitting around 5.5–8.0 μm, by polar and apolar ice segregation in 15.15–15.25 μm, and by the presence of the CH{sub 4} and HCOOH ices. Given that non-nitrogen compounds were employed in this work, we assume that absorption around 5.5–8.0 μm should not be associated with the NH{sub 4}{sup +} ion (see the 2003 work of Shutte and Khanna ), but more probably with aliphatic ethers (e.g., R1-OCH{sub 2}-R2), CH{sub 3}CHO, and related species. The results obtained in this paper are important because they show that the environment around protostars is better modeled considering processed samples and, consequently, demonstrate the chemical evolution of the astrophysical ices.« less

Discovery of the Rotating Molecular Outflow and Disk in the CLASS-0/I Protostar [BHB2007]#11 in Pipe

NASA Astrophysics Data System (ADS)

Chihomi, Hara; Ryohei, Kawabe; Yoshito, Shimajiri; Junko, Ueda; Takashi, Tsukagoshi; Yasutaka, Kurono; Kazuya, Saigo; Fumitaka, Nakamura; Masao, Saito; Wilner, David

2013-07-01

The loss of angular momentum is inevitable in star formation processes, and the transportation of angular momentum by a molecular flow is widely thought to be one of the important processes. We present the results of our 2'h resolution Submillimeter Array (SMA) observations in CO, 13CO, and C18O(2-1) emissions toward a low-mass Class-0/I protostar, [BHB2007]#11 (hereafter B59#11) at the nearby star forming region, Barnard 59 in the Pipe Nebula (d=130 pc). B59#11 ejects a molecular outflow whose axis lies almost on the plane of the sky, and one of the best targets to investigate the envelope/disk rotation and the velocity structure of the molecular outflow. The 13CO and C18O observations have revealed that a compact (r ˜ 800 AU) and elongated structure of dense gas is associated with B59#11, which orients perpendicular to the outflow axis. Their distributions show the velocity gradients along their major axes, which are considered to arise from the envelope/disk rotation. The specific angular momentum is estimated to be (1.6+/-0.6)e-3 km/s pc. The power-law index of the radial profile of the rotation velocity changes from steeper one, i.e., ˜ -1 to -1/2 at a radius of 140 AU, suggesting the Keplerian disk is formed inside the radius. The central stellar mass is estimated to be ˜1.3 Msun. A collimated molecular outflow is detected from the CO observations. We found in the outflow a velocity gradient which direction is the same as that seen in the dense gas. This is interpreted to be due to the outflow rotation. The specific angular momentum of the outflow is comparable to that of the envelope, suggesting that this outflow play an important role to the ejection of the angular momentum from the envelope/disk system. This is the first case where both the Keplerian disk and the rotation of the molecular outflow were found in the Class-0 or I protostar, and provides one of good targets for ALMA to address the angular momentum ejection in course of star formation.

Heavy water stratification in a low-mass protostar

NASA Astrophysics Data System (ADS)

Coutens, A.; Vastel, C.; Cazaux, S.; Bottinelli, S.; Caux, E.; Ceccarelli, C.; Demyk, K.; Taquet, V.; Wakelam, V.

2013-05-01

Context. Despite the low elemental deuterium abundance in the Galaxy, enhanced molecular deuterium fractionation has been found in the environments of low-mass star-forming regions and, in particular, the Class 0 protostar IRAS 16293-2422. Aims: The key program Chemical HErschel Surveys of Star forming regions (CHESS) aims at studying the molecular complexity of the interstellar medium. The high sensitivity and spectral resolution of the Herschel/HIFI (Heterodyne Instrument for Far-Infrared) instrument provide a unique opportunity to observe the fundamental 11,1-00,0 transition of ortho-D2O at 607 GHz and the higher energy 21,2-10,1 transition of para-D2O at 898 GHz, both of which are inaccessible from the ground. Methods: The ortho-D2O transition at 607 GHz was previously detected. We present in this paper the first tentative detection for the para-D2O transition at 898 GHz. The spherical Monte Carlo radiative transfer code RATRAN was used to reproduce the observed line profiles of D2O with the same method that was used to reproduce the HDO and H218O line profiles in IRAS 16293-2422. Results: As for HDO, the absorption component seen on the D2O lines can only be reproduced by adding an external absorbing layer, possibly created by the photodesorption of the ices at the edges of the molecular cloud. The D2O column density is found to be about 2.5 × 1012 cm-2 in this added layer, leading to a D2O/H2O ratio of about 0.5%. At a 3σ uncertainty, upper limits of 0.03% and 0.2% are obtained for this ratio in the hot corino and the colder envelope of IRAS 16293-2422, respectively. Conclusions: The deuterium fractionation derived in our study suggests that the ices present in IRAS 16293-2422 formed on warm dust grains (~15-20 K) in dense (~104-5 × 104 cm-3) translucent clouds. These results allow us to address the earliest phases of star formation and the conditions in which ices form. Based on Herschel/HIFI observations. Herschel is an ESA space observatory with

The efficiency of seismic attributes to differentiate between massive and non-massive carbonate successions for hydrocarbon exploration activity

NASA Astrophysics Data System (ADS)

Sarhan, Mohammad Abdelfattah

2017-12-01

The present work investigates the efficiency of applying volume seismic attributes to differentiate between massive and non-massive carbonate sedimentary successions on using seismic data. The main objective of this work is to provide a pre-drilling technique to recognize the porous carbonate section (probable hydrocarbon reservoirs) based on seismic data. A case study from the Upper Cretaceous - Eocene carbonate successions of Abu Gharadig Basin, northern Western Desert of Egypt has been tested in this work. The qualitative interpretations of the well-log data of four available wells distributed in the study area, namely; AG-2, AG-5, AG-6 and AG-15 wells, has confirmed that the Upper Cretaceous Khoman A Member represents the massive carbonate section whereas the Eocene Apollonia Formation represents the non-massive carbonate unit. The present work have proved that the most promising seismic attributes capable of differentiating between massive and non-massive carbonate sequences are; Root Mean Square (RMS) Amplitude, Envelope (Reflection Strength), Instantaneous Frequency, Chaos, Local Flatness and Relative Acoustic Impedance.

Binary interaction dominates the evolution of massive stars.

PubMed

Sana, H; de Mink, S E; de Koter, A; Langer, N; Evans, C J; Gieles, M; Gosset, E; Izzard, R G; Le Bouquin, J-B; Schneider, F R N

2012-07-27

The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, x-ray binaries, and gamma-ray bursts. Unambiguous constraints on the fraction of massive stars affected by binary interaction were lacking. We simultaneously measured all relevant binary characteristics in a sample of Galactic massive O stars and quantified the frequency and nature of binary interactions. More than 70% of all massive stars will exchange mass with a companion, leading to a binary merger in one-third of the cases. These numbers greatly exceed previous estimates and imply that binary interaction dominates the evolution of massive stars, with implications for populations of massive stars and their supernovae.

MASSIVE+: The Growth Histories of MASSIVE Survey Galaxies from their Globular Cluster Colors

NASA Astrophysics Data System (ADS)

Blakeslee, John

2017-08-01

The MASSIVE survey is targeting the 100 most massive galaxies within 108 Mpc that are visible in the northern sky. These most massive galaxies in the present-day universe reside in a surprisingly wide variety of environments, from rich clusters to fossil groups to near isolation. We propose to use WFC3/UVIS and ACS to carry out a deep imaging study of the globular cluster populations around a selected subset of the MASSIVE targets. Though much is known about GC systems of bright galaxies in rich clusters, we know surprisingly little about the effects of environment on these systems. The MASSIVE sample provides a golden opportunity to learn about the systematics of GC systems and what they can tell us about environmental drivers on the evolution of the highest mass galaxies. The most pressing questions to be addressed include: (1) Do isolated giants have the same constant mass fraction of GCs to total halo mass as BCGs of similar luminosity? (2) Do their GC systems show the same color (metallicity) distribution, which is an outcome of the mass spectrum of gas-rich halos during hierarchical growth? (3) Do the GCs in isolated high-mass galaxies follow the same radial distribution versus metallicity as in rich environments (a test of the relative importance of growth by accretion)? (4) Do the GCs of galaxies in sparse environments follow the same mass function? Our proposed second-band imaging will enable us to secure answers to these questions and add enormously to the legacy value of existing HST imaging of the highest mass galaxies in the universe.

Observations of nitrogen isotope fractionation in deeply embedded protostars

NASA Astrophysics Data System (ADS)

Wampfler, S. F.; Jørgensen, J. K.; Bizzarro, M.; Bisschop, S. E.

2014-12-01

Context. The terrestrial planets, comets, and meteorites are significantly enriched in 15N compared to the Sun and Jupiter. While the solar and jovian nitrogen isotope ratio is believed to represent the composition of the protosolar nebula, a still unidentified process has caused 15N-enrichment in the solids. Several mechanisms have been proposed to explain the variations, including chemical fractionation. However, observational results that constrain the fractionation models are scarce. While there is evidence of 15N-enrichment in prestellar cores, it is unclear how the signature evolves into the protostellar phases. Aims: The aim of this study is to measure the 14N/15N ratio around three nearby, embedded low- to intermediate-mass protostars. Methods: Isotopologues of HCN and HNC were used to probe the 14N/15N ratio. A selection of J = 3-2 and 4-3 transitions of H13CN, HC15N, HN13C, and H15NC was observed with the Atacama Pathfinder EXperiment telescope (APEX). The 14N/15N ratios were derived from the integrated intensities assuming a standard 12C/13C ratio. The assumption of optically thin emission was verified using radiative transfer modeling and hyperfine structure fitting. Results: Two sources, IRAS 16293A and R CrA IRS7B, show 15N-enrichment by a factor of ~1.5-2.5 in both HCN and HNC with respect to the solar composition. IRAS 16293A falls in the range of typical prestellar core values. Solar composition cannot be excluded for the third source, OMC-3 MMS6. Furthermore, there are indications of a trend toward increasing 14N/15N ratios with increasing outer envelope temperature. Conclusions: The enhanced 15N abundances in HCN and HNC found in two Class 0 sources (14N /15N ~ 160-290) and the tentative trend toward a temperature-dependent 14N/15N ratio are consistent with the chemical fractionation scenario, but 14N/15N ratios from additional tracers are indispensable for testing the models. Spatially resolved observations are needed to distinguish between

The evolution of massive stars

NASA Technical Reports Server (NTRS)

1982-01-01

The hypotheses underlying theoretical studies of the evolution of massive model stars with and without mass loss are summarized. The evolutionary tracks followed by the models across theoretical Hertzsprung-Russell (HR) diagrams are compared with the observed distribution of B stars in an HR diagram. The pulsational properties of models of massive star are also described.

Condensate of massive graviton and dark matter

NASA Astrophysics Data System (ADS)

Aoki, Katsuki; Maeda, Kei-ichi

2018-02-01

We study coherently oscillating massive gravitons in the ghost-free bigravity theory. This coherent field can be interpreted as a condensate of the massive gravitons. We first define the effective energy-momentum tensor of the coherent massive gravitons in a curved spacetime. We then study the background dynamics of the Universe and the cosmic structure formation including the effects of the coherent massive gravitons. We find that the condensate of the massive graviton behaves as a dark matter component of the Universe. From the geometrical point of view the condensate is regarded as a spacetime anisotropy. Hence, in our scenario, dark matter is originated from the tiny deformation of the spacetime. We also discuss a production of the spacetime anisotropy and find that the extragalactic magnetic field of a primordial origin can yield a sufficient amount for dark matter.

The formation of massive molecular filaments and massive stars triggered by a magnetohydrodynamic shock wave

NASA Astrophysics Data System (ADS)

Inoue, Tsuyoshi; Hennebelle, Patrick; Fukui, Yasuo; Matsumoto, Tomoaki; Iwasaki, Kazunari; Inutsuka, Shu-ichiro

2018-05-01

Recent observations suggest an that intensive molecular cloud collision can trigger massive star/cluster formation. The most important physical process caused by the collision is a shock compression. In this paper, the influence of a shock wave on the evolution of a molecular cloud is studied numerically by using isothermal magnetohydrodynamics simulations with the effect of self-gravity. Adaptive mesh refinement and sink particle techniques are used to follow the long-time evolution of the shocked cloud. We find that the shock compression of a turbulent inhomogeneous molecular cloud creates massive filaments, which lie perpendicularly to the background magnetic field, as we have pointed out in a previous paper. The massive filament shows global collapse along the filament, which feeds a sink particle located at the collapse center. We observe a high accretion rate \\dot{M}_acc> 10^{-4} M_{⊙}yr-1 that is high enough to allow the formation of even O-type stars. The most massive sink particle achieves M > 50 M_{⊙} in a few times 105 yr after the onset of the filament collapse.

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.

The Bolocam Galactic Plane Survey. XIV. Physical Properties of Massive Starless and Star-forming Clumps

NASA Astrophysics Data System (ADS)

Svoboda, Brian E.; Shirley, Yancy L.; Battersby, Cara; Rosolowsky, Erik W.; Ginsburg, Adam G.; Ellsworth-Bowers, Timothy P.; Pestalozzi, Michele R.; Dunham, Miranda K.; Evans, Neal J., II; Bally, John; Glenn, Jason

2016-05-01

We sort 4683 molecular clouds between 10° < ℓ < 65° from the Bolocam Galactic Plane Survey based on observational diagnostics of star formation activity: compact 70 μm sources, mid-IR color-selected YSOs, H2O and CH3OH masers, and UCH II regions. We also present a combined NH3-derived gas kinetic temperature and H2O maser catalog for 1788 clumps from our own GBT 100 m observations and from the literature. We identify a subsample of 2223 (47.5%) starless clump candidates (SCCs), the largest and most robust sample identified from a blind survey to date. Distributions of flux density, flux concentration, solid angle, kinetic temperature, column density, radius, and mass show strong (>1 dex) progressions when sorted by star formation indicator. The median SCC is marginally subvirial (α ˜ 0.7) with >75% of clumps with known distance being gravitationally bound (α < 2). These samples show a statistically significant increase in the median clump mass of ΔM ˜ 170-370 M ⊙ from the starless candidates to clumps associated with protostars. This trend could be due to (I) mass growth of the clumps at \\dot{M}˜ 200{--}440 M ⊙ Myr-1 for an average freefall 0.8 Myr timescale, (II) a systematic factor of two increase in dust opacity from starless to protostellar phases, and/or (III) a variation in the ratio of starless to protostellar clump lifetime that scales as ˜M -0.4. By comparing to the observed number of CH3OH maser containing clumps, we estimate the phase lifetime of massive (M > 103 M ⊙) starless clumps to be 0.37 ± 0.08 Myr (M/103 M ⊙)-1 the majority (M < 450 M ⊙) have phase lifetimes longer than their average freefall time.

Massive transfusion and nonsurgical hemostatic agents.

PubMed

Perkins, Jeremy G; Cap, Andrew P; Weiss, Brendan M; Reid, Thomas J; Bolan, Charles D; Bolan, Charles E

2008-07-01

Hemorrhage in trauma is a significant challenge, accounting for 30% to 40% of all fatalities, second only to central nervous system injury as a cause of death. However, hemorrhagic death is the leading preventable cause of mortality in combat casualties and typically occurs within 6 to 24 hrs of injury. In cases of severe hemorrhage, massive transfusion may be required to replace more than the entire blood volume. Early prediction of massive transfusion requirements, using clinical and laboratory parameters, combined with aggressive management of hemorrhage by surgical and nonsurgical means, has significant potential to reduce early mortality. Although the classification of massive transfusion varies, the most frequently used definition is ten or more units of blood in 24 hrs. Transfusion of red blood cells is intended to restore blood volume, tissue perfusion, and oxygen-carrying capacity; platelets, plasma, and cryoprecipitate are intended to facilitate hemostasis through prevention or treatment of coagulopathy. Massive transfusion is uncommon in civilian trauma, occurring in only 1% to 3% of trauma admissions. As a result of a higher proportion of penetrating injury in combat casualties, it has occurred in approximately 8% of Operation Iraqi Freedom admissions and in as many as 16% during the Vietnam conflict. Despite its potential to reduce early mortality, massive transfusion is not without risk. It requires extensive blood-banking resources and is associated with high mortality. This review describes the clinical problems associated with massive transfusion and surveys the nonsurgical management of hemorrhage, including transfusion of blood products, use of hemostatic bandages/agents, and treatment with hemostatic medications.

Fluid/gravity correspondence for massive gravity

NASA Astrophysics Data System (ADS)

Pan, Wen-Jian; Huang, Yong-Chang

2016-11-01

In this paper, we investigate the fluid/gravity correspondence in the framework of massive Einstein gravity. Treating the gravitational mass terms as an effective energy-momentum tensor and utilizing the Petrov-like boundary condition on a timelike hypersurface, we find that the perturbation effects of massive gravity in bulk can be completely governed by the incompressible Navier-Stokes equation living on the cutoff surface under the near horizon and nonrelativistic limits. Furthermore, we have concisely computed the ratio of dynamical viscosity to entropy density for two massive Einstein gravity theories, and found that they still saturate the Kovtun-Son-Starinets (KSS) bound.

Positive signs in massive gravity

NASA Astrophysics Data System (ADS)

Cheung, Clifford; Remmen, Grant N.

2016-04-01

We derive new constraints on massive gravity from unitarity and analyticity of scattering amplitudes. Our results apply to a general effective theory defined by Einstein gravity plus the leading soft diffeomorphism-breaking corrections. We calculate scattering amplitudes for all combinations of tensor, vector, and scalar polarizations. The high-energy behavior of these amplitudes prescribes a specific choice of couplings that ameliorates the ultraviolet cutoff, in agreement with existing literature. We then derive consistency conditions from analytic dispersion relations, which dictate positivity of certain combinations of parameters appearing in the forward scattering amplitudes. These constraints exclude all but a small island in the parameter space of ghost-free massive gravity. While the theory of the "Galileon" scalar mode alone is known to be inconsistent with positivity constraints, this is remedied in the full massive gravity theory.

Change in the chemical composition of infalling gas forming a disk around a protostar.

PubMed

Sakai, Nami; Sakai, Takeshi; Hirota, Tomoya; Watanabe, Yoshimasa; Ceccarelli, Cecilia; Kahane, Claudine; Bottinelli, Sandrine; Caux, Emmanuel; Demyk, Karine; Vastel, Charlotte; Coutens, Audrey; Taquet, Vianney; Ohashi, Nagayoshi; Takakuwa, Shigehisa; Yen, Hsi-Wei; Aikawa, Yuri; Yamamoto, Satoshi

2014-03-06

IRAS 04368+2557 is a solar-type (low-mass) protostar embedded in a protostellar core (L1527) in the Taurus molecular cloud, which is only 140 parsecs away from Earth, making it the closest large star-forming region. The protostellar envelope has a flattened shape with a diameter of a thousand astronomical units (1 AU is the distance from Earth to the Sun), and is infalling and rotating. It also has a protostellar disk with a radius of 90 AU (ref. 6), from which a planetary system is expected to form. The interstellar gas, mainly consisting of hydrogen molecules, undergoes a change in density of about three orders of magnitude as it collapses from the envelope into the disk, while being heated from 10 kelvin to over 100 kelvin in the mid-plane, but it has hitherto not been possible to explore changes in chemical composition associated with this collapse. Here we report that the unsaturated hydrocarbon molecule cyclic-C3H2 resides in the infalling rotating envelope, whereas sulphur monoxide (SO) is enhanced in the transition zone at the radius of the centrifugal barrier (100 ± 20 AU), which is the radius at which the kinetic energy of the infalling gas is converted to rotational energy. Such a drastic change in chemistry at the centrifugal barrier was not anticipated, but is probably caused by the discontinuous infalling motion at the centrifugal barrier and local heating processes there.

Magnetically regulated collapse in the B335 protostar? I. ALMA observations of the polarized dust emission

NASA Astrophysics Data System (ADS)

Maury, A. J.; Girart, J. M.; Zhang, Q.; Hennebelle, P.; Keto, E.; Rao, R.; Lai, S.-P.; Ohashi, N.; Galametz, M.

2018-06-01

The role of the magnetic field during protostellar collapse is poorly constrained from an observational point of view, although it could be significant if we believe state-of-the-art models of protostellar formation. We present polarimetric observations of the 233 GHz thermal dust continuum emission obtained with ALMA in the B335 Class 0 protostar. Linearly polarized dust emission arising from the circumstellar material in the envelope of B335 is detected at all scales probed by our observations (50 to 1000 au). The magnetic field structure producing the dust polarization has a very ordered topology in the inner envelope, with a transition from a large-scale poloidal magnetic field, in the outflow direction, to strongly pinched in the equatorial direction. This is probably due to magnetic field lines being dragged along the dominating infall direction since B335 does not exhibit prominent rotation. Our data and their qualitative comparison to a family of magnetized protostellar collapse models show that, during the magnetized collapse in B335, the magnetic field is maintaining a high level of organization from scales 1000 au to 50 au: this suggests the field is dynamically relevant and capable of influencing the typical outcome of protostellar collapse, such as regulating the disc size in B335.

Update on massive transfusion.

PubMed

Pham, H P; Shaz, B H

2013-12-01

Massive haemorrhage requires massive transfusion (MT) to maintain adequate circulation and haemostasis. For optimal management of massively bleeding patients, regardless of aetiology (trauma, obstetrical, surgical), effective preparation and communication between transfusion and other laboratory services and clinical teams are essential. A well-defined MT protocol is a valuable tool to delineate how blood products are ordered, prepared, and delivered; determine laboratory algorithms to use as transfusion guidelines; and outline duties and facilitate communication between involved personnel. In MT patients, it is crucial to practice damage control resuscitation and to administer blood products early in the resuscitation. Trauma patients are often admitted with early trauma-induced coagulopathy (ETIC), which is associated with mortality; the aetiology of ETIC is likely multifactorial. Current data support that trauma patients treated with higher ratios of plasma and platelet to red blood cell transfusions have improved outcomes, but further clinical investigation is needed. Additionally, tranexamic acid has been shown to decrease the mortality in trauma patients requiring MT. Greater use of cryoprecipitate or fibrinogen concentrate might be beneficial in MT patients from obstetrical causes. The risks and benefits for other therapies (prothrombin complex concentrate, recombinant activated factor VII, or whole blood) are not clearly defined in MT patients. Throughout the resuscitation, the patient should be closely monitored and both metabolic and coagulation abnormalities corrected. Further studies are needed to clarify the optimal ratios of blood products, treatment based on underlying clinical disorder, use of alternative therapies, and integration of laboratory testing results in the management of massively bleeding patients.

Positive signs in massive gravity

DOE PAGES

Cheung, Clifford; Remmen, Grant N.

2016-04-01

Here, we derive new constraints on massive gravity from unitarity and analyticity of scattering amplitudes. Our results apply to a general effective theory defined by Einstein gravity plus the leading soft diffeomorphism-breaking corrections. We calculate scattering amplitudes for all combinations of tensor, vector, and scalar polarizations. Furthermore, the high-energy behavior of these amplitudes prescribes a specific choice of couplings that ameliorates the ultraviolet cutoff, in agreement with existing literature. We then derive consistency conditions from analytic dispersion relations, which dictate positivity of certain combinations of parameters appearing in the forward scattering amplitudes. These constraints exclude all but a small islandmore » in the parameter space of ghost-free massive gravity. And while the theory of the "Galileon" scalar mode alone is known to be inconsistent with positivity constraints, this is remedied in the full massive gravity theory.« less

The Class 0 Protostar BHR71: Herschel Observations and Dust Continuum Models

NASA Astrophysics Data System (ADS)

Yang, Yao-Lun; Evans, Neal J., II; Green, Joel D.; Dunham, Michael M.; Jørgensen, Jes K.

2017-02-01

We use Herschel spectrophotometry of BHR71, an embedded Class 0 protostar, to provide new constraints on its physical properties. We detect 645 (non-unique) spectral lines among all spatial pixels. At least 61 different spectral lines originate from the central region. A CO rotational diagram analysis shows four excitation temperature components, 43, 197, 397, and 1057 K. Low-J CO lines trace the outflow while the high-J CO lines are centered on the infrared source. The low-excitation emission lines of {{{H}}}2{{O}} trace the large-scale outflow, while the high-excitation emission lines trace a small-scale distribution around the equatorial plane. We model the envelope structure using the dust radiative transfer code, hyperion, incorporating rotational collapse, an outer static envelope, outflow cavity, and disk. The evolution of a rotating collapsing envelope can be constrained by the far-infrared/millimeter spectral energy distribution along with the azimuthally averaged radial intensity profile, and the structure of the outflow cavity plays a critical role at shorter wavelengths. Emission at 20-40 μm requires a cavity with a constant-density inner region and a power-law density outer region. The best-fit model has an envelope mass of 19 {M}⊙ inside a radius of 0.315 pc and a central luminosity of 18.8 {L}⊙ . The time since collapse began is 24,630-44,000 years, most likely around 36,000 years. The corresponding mass infall rate in the envelope (1.2 × 10-5 {M}⊙ {{yr}}-1) is comparable to the stellar mass accretion rate, while the mass-loss rate estimated from the CO outflow is 20% of the stellar mass accretion rate. We find no evidence for episodic accretion.

The formation and fragmentation of disks around primordial protostars.

PubMed

Clark, Paul C; Glover, Simon C O; Smith, Rowan J; Greif, Thomas H; Klessen, Ralf S; Bromm, Volker

2011-02-25

The very first stars to form in the universe heralded an end to the cosmic dark ages and introduced new physical processes that shaped early cosmic evolution. Until now, it was thought that these stars lived short, solitary lives, with only one extremely massive star, or possibly a very wide binary system, forming in each dark-matter minihalo. Here we describe numerical simulations that show that these stars were, to the contrary, often members of tight multiple systems. Our results show that the disks that formed around the first young stars were unstable to gravitational fragmentation, possibly producing small binary and higher-order systems that had separations as small as the distance between Earth and the Sun.

Exact solutions in 3D new massive gravity.

PubMed

Ahmedov, Haji; Aliev, Alikram N

2011-01-14

We show that the field equations of new massive gravity (NMG) consist of a massive (tensorial) Klein-Gordon-type equation with a curvature-squared source term and a constraint equation. We also show that, for algebraic type D and N spacetimes, the field equations of topologically massive gravity (TMG) can be thought of as the "square root" of the massive Klein-Gordon-type equation. Using this fact, we establish a simple framework for mapping all types D and N solutions of TMG into NMG. Finally, we present new examples of types D and N solutions to NMG.

Exact Solutions in 3D New Massive Gravity

NASA Astrophysics Data System (ADS)

Ahmedov, Haji; Aliev, Alikram N.

2011-01-01

We show that the field equations of new massive gravity (NMG) consist of a massive (tensorial) Klein-Gordon-type equation with a curvature-squared source term and a constraint equation. We also show that, for algebraic type D and N spacetimes, the field equations of topologically massive gravity (TMG) can be thought of as the “square root” of the massive Klein-Gordon-type equation. Using this fact, we establish a simple framework for mapping all types D and N solutions of TMG into NMG. Finally, we present new examples of types D and N solutions to NMG.

The Circumgalactic Medium in Massive Halos

NASA Astrophysics Data System (ADS)

Chen, Hsiao-Wen

This chapter presents a review of the current state of knowledge on the cool (T ˜ 104 K) halo gas content around massive galaxies at z ≈ 0. 2-2. Over the last decade, significant progress has been made in characterizing the cool circumgalactic gas in massive halos of M h ≈ 1012-14 M⊙ at intermediate redshifts using absorption spectroscopy. Systematic studies of halo gas around massive galaxies beyond the nearby universe are made possible by large spectroscopic samples of galaxies and quasars in public archives. In addition to accurate and precise constraints for the incidence of cool gas in massive halos, detailed characterizations of gas kinematics and chemical compositions around massive quiescent galaxies at z ≈ 0. 5 have also been obtained. Combining all available measurements shows that infalling clouds from external sources are likely the primary source of cool gas detected at d ≳ 100 d\\gtrsim 100 kpc frommassive quiescent galaxies. The origin of the gas closer in is currently less certain, but SNe Ia driven winds appear to contribute significantly to cool gas found at d < 100 kpc. In contrast, cool gas observed at d ≲ 200 d\\lesssim 200 kpc from luminous quasars appears to be intimately connected to quasar activities on parsec scales. The observed strong correlation between cool gas covering fraction in quasar host halos and quasar bolometric luminosity remains a puzzle. Combining absorption-line studies with spatially resolved emission measurements of both gas and galaxies is the necessary next step to address remaining questions.

Trisomy 13 and Massive Fetomaternal Hemorrhage

PubMed Central

Matsui, Ryoko; Suzuki, Shunji; Ito, Marie; Terada, Yusuke; Kumasaka, Sakae

2015-01-01

This is the first case report of trisomy 13 complicated by massive fetomaternal hemorrhage (FMH). A pale male infant weighing 2,950 g was delivered with low Apgar scores by emergency cesarean section due to non-reassuring fetal status. The umbilical arterial pH and hemoglobin level were 6.815 and 6.9 g/dL (normal: 13 - 22 g/dL), respectively. The maternal hemoglobin-F and serum alpha-fetoprotein levels were 6.0% (normal: < 1.0%) and 1,150 ng/mL (4.1 multiple of median), respectively. The neonate was diagnosed as having trisomy 13 by a subsequent chromosome examination. In the placenta, massive intervillous thrombosis was observed microscopically. This placental finding has been reported to be associated with both preeclampsia and massive FMH. In addition, the incidence of preeclampsia in pregnancies complicated by trisomy 13 has been reported to be significantly higher than normal karyotype populations. Therefore, the current finding may support the association between trisomy 13 and the incidence of massive FMH. PMID:26015824

High Resolution 4.7 Micron Keck/NIRSPEC Spectra of Protostars. 1; Ices and Infalling Gas in the Disk of L1489 IRS

NASA Technical Reports Server (NTRS)

Boogert, A. C. A.; Hogerheijde, M. R.; Blake, G. A.

2001-01-01

We explore the infrared M band (4.7 micron) spectrum of the class I protostar L1489 IRS in the Taurus Molecular Cloud. This is the highest resolution wide coverage spectrum at this wavelength of a low mass protostar observed to date (R =25,000; (Delta)v =12 km s(exp -1). A large number of narrow absorption lines of gas phase (12)CO, (13)CO, and C(sup 18)O are detected, as well as a prominent band of solid (12)CO. The gas phase (12)CO lines have red shifted absorption wings (up to 100 km s(exp -1)), which likely originate from warm disk material falling toward the central object. Both the isotopes and the extent of the (12)CO line wings are successfully fitted with a contracting disk model of this evolutionary transitional object. This shows that the inward motions seen in millimeter wave emission lines continue to within approx. 0.1 AU from the star. The amount of high velocity infalling gas is however overestimated by this model, suggesting that only part of the disk is infalling, e.g. a hot surface layer or hot gas in magnetic field tubes. The colder parts of the disk are traced by the prominent CO ice band. The band profile results from CO in 'polar' ices (CO mixed with H2O), and CO in 'apolar' ices. At the high spectral resolution, the 'apolar' component is, for the first time, resolved into two distinct components, likely due to pure CO and CO mixed with CO2, O2 and/or N2. The ices have probably experienced thermal processing in the upper disk layer traced by our pencil absorption beam: much of the volatile 'apolar' ices has evaporated, the depletion factor of CO onto grains is remarkably low (approx. 7%), and the CO2 traced in the CO band profile was possibly formed energetically. This study shows that high spectral resolution 4.7 micron observations provide important and unique information on the dynamics and structure of protostellar disks and the origin and evolution of ices in these disks.

Colliding Winds in Massive Binaries

NASA Astrophysics Data System (ADS)

Thaller, M. L.

1998-12-01

In close binary systems of massive stars, the individual stellar winds will collide and form a bow shock between the stars, which may have significant impact on the mass-loss and evolution of the system. The existence of such a shock can be established through orbital-phase related variations in the UV resonance lines and optical emission lines. High density regions near the shock will produce Hα and Helium I emission which can be used to map the mass-flow structure of the system. The shock front between the stars may influence the balance of mass-loss versus mass-transfer in massive binary evolution, as matter lost to one star due to Roche lobe overflow may hit the shock and be deflected before it can accrete onto the surface of the other star. I have completed a high-resolution spectroscopic survey of 37 massive binaries, and compared the incidence and strength of emission to an independent survey of single massive stars. Binary stars show a statistically significant overabundance of optical emission, especially when one of the binary stars is in either a giant or supergiant phase of evolution. Seven systems in my survey exhibited clear signs of orbital phase related emission, and for three of the stars (HD 149404, HD 152248, and HD 163181), I present qualitative models of the mass-flow dynamics of the systems.

Investigation of the status quo of massive blood transfusion in China and a synopsis of the proposed guidelines for massive blood transfusion

PubMed Central

Yang, Jiang-Cun; Wang, Qiu-Shi; Dang, Qian-Li; Sun, Yang; Xu, Cui-Xiang; Jin, Zhan-Kui; Ma, Ting; Liu, Jing

2017-01-01

Abstract The aim of this study was to provide an overview of massive transfusion in Chinese hospitals, identify the important indications for massive transfusion and corrective therapies based on clinical evidence and supporting experimental studies, and propose guidelines for the management of massive transfusion. This multiregion, multicenter retrospective study involved a Massive Blood Transfusion Coordination Group composed of 50 clinical experts specializing in blood transfusion, cardiac surgery, anesthesiology, obstetrics, general surgery, and medical statistics from 20 tertiary general hospitals across 5 regions in China. Data were collected for all patients who received ≥10 U red blood cell transfusion within 24 hours in the participating hospitals from January 1 2009 to December 31 2010, including patient demographics, pre-, peri-, and post-operative clinical characteristics, laboratory test results before, during, and after transfusion, and patient mortality at post-transfusion and discharge. We also designed an in vitro hemodilution model to investigate the changes of blood coagulation indices during massive transfusion and the correction of coagulopathy through supplement blood components under different hemodilutions. The experimental data in combination with the clinical evidence were used to determine the optimal proportion and timing for blood component supplementation during massive transfusion. Based on the findings from the present study, together with an extensive review of domestic and international transfusion-related literature and consensus feedback from the 50 experts, we drafted the guidelines on massive blood transfusion that will help Chinese hospitals to develop standardized protocols for massive blood transfusion. PMID:28767599

Bridging the gap: from massive stars to supernovae

PubMed Central

Crowther, Paul A.; Janka, Hans-Thomas; Langer, Norbert

2017-01-01

Almost since the beginning, massive stars and their resultant supernovae have played a crucial role in the Universe. These objects produce tremendous amounts of energy and new, heavy elements that enrich galaxies, encourage new stars to form and sculpt the shapes of galaxies that we see today. The end of millions of years of massive star evolution and the beginning of hundreds or thousands of years of supernova evolution are separated by a matter of a few seconds, in which some of the most extreme physics found in the Universe causes the explosive and terminal disruption of the star. Key questions remain unanswered in both the studies of how massive stars evolve and the behaviour of supernovae, and it appears the solutions may not lie on just one side of the explosion or the other or in just the domain of the stellar evolution or the supernova astrophysics communities. The need to view massive star evolution and supernovae as continuous phases in a single narrative motivated the Theo Murphy international scientific meeting ‘Bridging the gap: from massive stars to supernovae’ at Chicheley Hall, UK, in June 2016, with the specific purpose of simultaneously addressing the scientific connections between theoretical and observational studies of massive stars and their supernovae, through engaging astronomers from both communities. This article is part of the themed issue ‘Bridging the gap: from massive stars to supernovae’. PMID:28923995

Bridging the gap: from massive stars to supernovae.

PubMed

Maund, Justyn R; Crowther, Paul A; Janka, Hans-Thomas; Langer, Norbert

2017-10-28

Almost since the beginning, massive stars and their resultant supernovae have played a crucial role in the Universe. These objects produce tremendous amounts of energy and new, heavy elements that enrich galaxies, encourage new stars to form and sculpt the shapes of galaxies that we see today. The end of millions of years of massive star evolution and the beginning of hundreds or thousands of years of supernova evolution are separated by a matter of a few seconds, in which some of the most extreme physics found in the Universe causes the explosive and terminal disruption of the star. Key questions remain unanswered in both the studies of how massive stars evolve and the behaviour of supernovae, and it appears the solutions may not lie on just one side of the explosion or the other or in just the domain of the stellar evolution or the supernova astrophysics communities. The need to view massive star evolution and supernovae as continuous phases in a single narrative motivated the Theo Murphy international scientific meeting 'Bridging the gap: from massive stars to supernovae' at Chicheley Hall, UK, in June 2016, with the specific purpose of simultaneously addressing the scientific connections between theoretical and observational studies of massive stars and their supernovae, through engaging astronomers from both communities.This article is part of the themed issue 'Bridging the gap: from massive stars to supernovae'. © 2017 The Author(s).

Observed Luminosity Spread in Young Clusters and FU Ori Stars: A Unified Picture

NASA Astrophysics Data System (ADS)

Baraffe, I.; Vorobyov, E.; Chabrier, G.

2012-09-01

The idea that non-steady accretion during the embedded phase of protostar evolution can produce the observed luminosity spread in the Herzsprung-Russell diagram (HRD) of young clusters has recently been called into question. Observations of FU Ori, for instance, suggest an expansion of the star during strong accretion events, whereas the luminosity spread implies a contraction of the accreting objects, decreasing their radiating surface. In this paper, we present a global scenario based on calculations coupling episodic accretion histories derived from numerical simulations of collapsing cloud prestellar cores of various masses and subsequent protostar evolution. Our calculations show that, assuming an initial protostar mass Mi ~ 1 M Jup, typical of the second Larson's core, both the luminosity spread in the HRD and the inferred properties of FU Ori events (mass, radius, accretion rate) can be explained by this scenario, providing two conditions. First, there must be some variation within the fraction of accretion energy absorbed by the protostar during the accretion process. Second, the range of this variation should increase with increasing accretion burst intensity and thus with the initial core mass and final star mass. The numerical hydrodynamics simulations of collapsing cloud prestellar cores indeed show that the intensity of the accretion bursts correlates with the mass and initial angular momentum of the prestellar core. Massive prestellar cores with high initial angular momentum are found to produce intense bursts characteristic of FU Ori-like events. Our results thus suggest a link between the burst intensities and the fraction of accretion energy absorbed by the protostar, with some threshold in the accretion rate, of the order of 10-5 M ⊙ yr-1, delimitating the transition from "cold" to "hot" accretion. Such a transition might reflect a change in the accretion geometry with increasing accretion rate, i.e., a transition from magnetospheric or thin

The complex chemistry of outflow cavity walls exposed: the case of low-mass protostars

NASA Astrophysics Data System (ADS)

Drozdovskaya, Maria N.; Walsh, Catherine; Visser, Ruud; Harsono, Daniel; van Dishoeck, Ewine F.

2015-08-01

Complex organic molecules are ubiquitous companions of young low-mass protostars. Recent observations suggest that their emission stems, not only from the traditional hot corino, but also from offset positions. In this work, 2D physicochemical modelling of an envelope-cavity system is carried out. Wavelength-dependent radiative transfer calculations are performed and a comprehensive gas-grain chemical network is used to simulate the physical and chemical structure. The morphology of the system delineates three distinct regions: the cavity wall layer with time-dependent and species-variant enhancements; a torus rich in complex organic ices, but not reflected in gas-phase abundances and the remaining outer envelope abundant in simpler solid and gaseous molecules. Strongly irradiated regions, such as the cavity wall layer, are subject to frequent photodissociation in the solid phase. Subsequent recombination of the photoproducts leads to frequent reactive desorption, causing gas-phase enhancements of several orders of magnitude. This mechanism remains to be quantified with laboratory experiments. Direct photodesorption is found to be relatively inefficient. If radicals are not produced directly in the icy mantle, the formation of complex organics is impeded. For efficiency, a sufficient number of FUV photons needs to penetrate the envelope, and elevated cool dust temperatures need to enable grain-surface radical mobility. As a result, a high stellar luminosity and a sufficiently wide cavity favour chemical complexity. Furthermore within this paradigm, complex organics are demonstrated to have unique lifetimes and be grouped into early (formaldehyde, ketene, methanol, formic acid, methyl formate, acetic acid and glycolaldehyde) and late (acetaldehyde, dimethyl ether and ethanol) species.

Properties of Massive Stars in Primitive Galaxies

NASA Technical Reports Server (NTRS)

Heap, Sara

2012-01-01

According to R. Dave, the phases of galaxy formation are distinguished by their halo mass and governing feedback mechanism. Galaxies in the birth phase (our "primitive galaxies") have a low halo mass (M<10(exp 9) Msun); and star formation is affected by photoionizing radiation of massive stars. In contrast, galaxies in the growth phase (e.g. Lyman Break galaxies) are more massive (M=10(exp 9)-10(exp 12) Msun); star formation is fueled by cold accretion but modulated by strong outflows from massive stars. I Zw 18 is a local blue, compact dwarf galaxy that meets the requirements for a birth-phase galaxy: halo mass <10(exp 9) Msun, strong photo ionizing radiation, no galactic outflow, and very low metallicity, log(O/H)=7.2. We will describe the properties of massive stars in I Zw 18 based on analysis of ultraviolet spectra obtained with HST.

Topologically massive gravity and Ricci-Cotton flow

NASA Astrophysics Data System (ADS)

Lashkari, Nima; Maloney, Alexander

2011-05-01

We consider topologically massive gravity (TMG), which is three-dimensional general relativity with a cosmological constant and a gravitational Chern-Simons term. When the cosmological constant is negative the theory has two potential vacuum solutions: anti-de Sitter space and warped anti-de Sitter space. The theory also contains a massive graviton state which renders these solutions unstable for certain values of the parameters and boundary conditions. We study the decay of these solutions due to the condensation of the massive graviton mode using Ricci-Cotton flow, which is the appropriate generalization of Ricci flow to TMG. When the Chern-Simons coupling is small the AdS solution flows to warped AdS by the condensation of the massive graviton mode. When the coupling is large the situation is reversed, and warped AdS flows to AdS. Minisuperspace models are constructed where these flows are studied explicitly.

Neutron stars structure in the context of massive gravity

NASA Astrophysics Data System (ADS)

Hendi, S. H.; Bordbar, G. H.; Eslam Panah, B.; Panahiyan, S.

2017-07-01

Motivated by the recent interests in spin-2 massive gravitons, we study the structure of neutron star in the context of massive gravity. The modifications of TOV equation in the presence of massive gravity are explored in 4 and higher dimensions. Next, by considering the modern equation of state for the neutron star matter (which is extracted by the lowest order constrained variational (LOCV) method with the AV18 potential), different physical properties of the neutron star (such as Le Chatelier's principle, stability and energy conditions) are investigated. It is shown that consideration of the massive gravity has specific contributions into the structure of neutron star and introduces new prescriptions for the massive astrophysical objects. The mass-radius relation is examined and the effects of massive gravity on the Schwarzschild radius, average density, compactness, gravitational redshift and dynamical stability are studied. Finally, a relation between mass and radius of neutron star versus the Planck mass is extracted.

On the Nature of the Enigmatic Object IRAS 19312+1950: A Rare Phase of Massive Star Formation?

NASA Technical Reports Server (NTRS)

Cordiner, M. A.; Boogert, A. C. A.; Charnley, S. B.; Justtanont, K.; Cox, N. L. J.; Smith, R. G.; Tielens, A. G. G. M.; Wirstrom, E. S.; Milam, S. N.; Keane, J. V.

2016-01-01

IRAS?19312+1950 is a peculiar object that has eluded firm characterization since its discovery, with combined maser properties similar to an evolved star and a young stellar object (YSO). To help determine its true nature, we obtained infrared spectra of IRAS?19312+1950 in the range 5-550 microns using the Herschel and Spitzer space observatories. The Herschel PACS maps exhibit a compact, slightly asymmetric continuum source at 170 microns, indicative of a large, dusty circumstellar envelope. The far-IR CO emission line spectrum reveals two gas temperature components: approx. = 0.22 Stellar Mass of material at 280+/-18 K, and ˜1.6 Me of material at 157+/-3 K. The OI 63 micron line is detected on-source but no significant emission from atomic ions was found. The HIFI observations display shocked, high-velocity gas with outflow speeds up to 90 km/s along the line of sight. From Spitzer spectroscopy, we identify ice absorption bands due to H2O at 5.8 microns and CO2 at 15 microns. The spectral energy distribution is consistent with a massive, luminous (approx. 2 × 10(exp 4) Stellar Luminosity) central source surrounded by a dense, warm circumstellar disk and envelope of total mass approx. 500-700 Stellar Mass with large bipolar outflow cavities. The combination of distinctive far-IR spectral features suggest that IRAS19312+1950 should be classified as an accreting, high-mass YSO rather than an evolved star. In light of this reclassification, IRAS19312+1950 becomes only the fifth high-mass protostar known to exhibit SiO maser activity, and demonstrates that 18 cm OH maser line ratios may not be reliable observational discriminators between evolved stars and YSOs.

ON THE NATURE OF THE ENIGMATIC OBJECT IRAS 19312+1950: A RARE PHASE OF MASSIVE STAR FORMATION?

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

Cordiner, M. A.; Charnley, S. B.; Milam, S. N.

IRAS 19312+1950 is a peculiar object that has eluded firm characterization since its discovery, with combined maser properties similar to an evolved star and a young stellar object (YSO). To help determine its true nature, we obtained infrared spectra of IRAS 19312+1950 in the range 5–550 μ m using the Herschel and Spitzer space observatories. The Herschel PACS maps exhibit a compact, slightly asymmetric continuum source at 170 μ m, indicative of a large, dusty circumstellar envelope. The far-IR CO emission line spectrum reveals two gas temperature components: ≈0.22 M {sub ⊙} of material at 280 ± 18 K, andmore » ≈1.6 M {sub ⊙} of material at 157 ± 3 K. The O i 63 μ m line is detected on-source but no significant emission from atomic ions was found. The HIFI observations display shocked, high-velocity gas with outflow speeds up to 90 km s{sup −1} along the line of sight. From Spitzer spectroscopy, we identify ice absorption bands due to H{sub 2}O at 5.8 μ m and CO{sub 2} at 15 μ m. The spectral energy distribution is consistent with a massive, luminous (∼2 × 10{sup 4} L {sub ⊙}) central source surrounded by a dense, warm circumstellar disk and envelope of total mass ∼500–700 M {sub ⊙}, with large bipolar outflow cavities. The combination of distinctive far-IR spectral features suggest that IRAS 19312+1950 should be classified as an accreting, high-mass YSO rather than an evolved star. In light of this reclassification, IRAS 19312+1950 becomes only the fifth high-mass protostar known to exhibit SiO maser activity, and demonstrates that 18 cm OH maser line ratios may not be reliable observational discriminators between evolved stars and YSOs.« less

Massive spin-2 scattering and asymptotic superluminality

NASA Astrophysics Data System (ADS)

Hinterbichler, Kurt; Joyce, Austin; Rosen, Rachel A.

2018-03-01

We place model-independent constraints on theories of massive spin-2 particles by considering the positivity of the phase shift in eikonal scattering. The phase shift is an asymptotic S-matrix observable, related to the time delay/advance experienced by a particle during scattering. Demanding the absence of a time advance leads to constraints on the cubic vertices present in the theory. We find that, in theories with massive spin-2 particles, requiring no time advance means that either: (i) the cubic vertices must appear as a particular linear combination of the Einstein-Hilbert cubic vertex and an h μν 3 potential term or (ii) new degrees of freedom or strong coupling must enter at parametrically the mass of the massive spin-2 field. These conclusions have implications for a variety of situations. Applied to theories of large- N QCD, this indicates that any spectrum with an isolated massive spin-2 at the bottom must have these particular cubic self-couplings. Applied to de Rham-Gabadadze-Tolley massive gravity, the constraint is in accord with results obtained from a shockwave calculation: of the two free dimensionless parameters in the theory there is a one parameter line consistent with a subluminal phase shift.

Massive Stars in Interactive Binaries

NASA Astrophysics Data System (ADS)

St.-Louis, Nicole; Moffat, Anthony F. J.

Massive stars start their lives above a mass of ~8 time solar, finally exploding after a few million years as core-collapse or pair-production supernovae. Above ~15 solar masses, they also spend most of their lives driving especially strong, hot winds due to their extreme luminosities. All of these aspects dominate the ecology of the Universe, from element enrichment to stirring up and ionizing the interstellar medium. But when they occur in close pairs or groups separated by less than a parsec, the interaction of massive stars can lead to various exotic phenomena which would not be seen if there were no binaries. These depend on the actual separation, and going from wie to close including colliding winds (with non-thermal radio emission and Wolf-Rayet dust spirals), cluster dynamics, X-ray binaries, Roche-lobe overflow (with inverse mass-ratios and rapid spin up), collisions, merging, rejuventation and massive blue stragglers, black-hole formation, runaways and gamma-ray bursts. Also, one wonders whether the fact that a massive star is in a binary affects its parameters compared to its isolated equivalent. These proceedings deal with all of these phenomena, plus binary statistics and determination of general physical properties of massive stars, that would not be possible with their single cousins. The 77 articles published in these proceedings, all based on oral talks, vary from broad revies to the lates developments in the field. About a third of the time was spent in open discussion of all participants, both for ~5 minutes after each talk and 8 half-hour long general dialogues, all audio-recorded, transcribed and only moderately edited to yield a real flavour of the meeting. The candid information in these discussions is sometimes more revealing than the article(s) that preceded them and also provide entertaining reading. The book is suitable for researchers and graduate students interested in stellar astrophysics and in various physical processes involved when

Black holes in massive gravity as heat engines

NASA Astrophysics Data System (ADS)

Hendi, S. H.; Eslam Panah, B.; Panahiyan, S.; Liu, H.; Meng, X.-H.

2018-06-01

The paper at hand studies the heat engine provided by black holes in the presence of massive gravity. The main motivation is to investigate the effects of massive gravity on different properties of the heat engine. It will be shown that massive gravity parameters modify the efficiency of engine on a significant level. Furthermore, it will be pointed out that it is possible to have a heat engine for non-spherical black holes in massive gravity, and therefore, we will study the effects of horizon topology on the properties of heat engine. Surprisingly, it will be shown that the highest efficiency for the heat engine belongs to black holes with the hyperbolic horizon, while the lowest one belongs to the spherical black holes.

Exact solutions of massive gravity in three dimensions

NASA Astrophysics Data System (ADS)

Chakhad, Mohamed

In recent years, there has been an upsurge in interest in three-dimensional theories of gravity. In particular, two theories of massive gravity in three dimensions hold strong promise in the search for fully consistent theories of quantum gravity, an understanding of which will shed light on the problems of quantum gravity in four dimensions. One of these theories is the "old" third-order theory of topologically massive gravity (TMG) and the other one is a "new" fourth-order theory of massive gravity (NMG). Despite this increase in research activity, the problem of finding and classifying solutions of TMG and NMG remains a wide open area of research. In this thesis, we provide explicit new solutions of massive gravity in three dimensions and suggest future directions of research. These solutions belong to the Kundt class of spacetimes. A systematic analysis of the Kundt solutions with constant scalar polynomial curvature invariants provides a glimpse of the structure of the spaces of solutions of the two theories of massive gravity. We also find explicit solutions of topologically massive gravity whose scalar polynomial curvature invariants are not all constant, and these are the first such solutions. A number of properties of Kundt solutions of TMG and NMG, such as an identification of solutions which lie at the intersection of the full nonlinear and linearized theories, are also derived.

Infrared Spectro-Interferometry of Massive Stars: Disks, Winds, Outflows, and Stellar Multiplicity

NASA Astrophysics Data System (ADS)

Kraus, Stefan

2007-06-01

complemented with archival Spitzer/IRS spectra. Surprisingly, we found that passive disk models, which can reproduce the SED well, are in strong conflict with the interferometric data. However, when including emission from an optically thick inner gaseous disk, good quantitative agreement was found for all observables, suggesting that MWC 147 harbours a still actively accreting disk. NGC 7538 IRS1/2: NGC 7538 IRS1 is a high-mass (O7-type) protostar with a CO outflow, an associated ultracompact H II region, and a linear methanol maser structure, which might trace a Keplerian-rotating circumstellar disk. We investigated the NIR morphology of the source with unprecedented resolution using NIR bispectrum speckle interferometry obtained at the BTA 6 m and the MMT 6.5 m telescopes. Our high-dynamic range images show fan-shaped outflow structures, in which we detected 18 stars and several blobs of diffuse emission. Complementary archival Spitzer/IRAC images were used to relate the detected structures with the outflow at larger scales. We found a misalignment of various outflow axes and interpreted this in the context of a disk precession model, also using molecular hydrodynamic simulations. As a possible triggering mechanism, we identified non-coplanar tidal interaction of an (yet undiscovered) close companion with the circumbinary disk. Finally, our observations resolved the nearby massive protostar NGC 7538 IRS2 as a close binary with a separation of 195 mas, finding indications for shock interaction between the outflows from IRS1 and IRS2. Theta 1 Orionis C/D: Located in the Orion Trapezium Cluster, Theta 1 C is one of the youngest and nearest high-mass (O5-O7) stars. The star is also known to be a close binary system. We traced the orbital motion from 1997.8 to 2004.8 using visual and NIR bispectrum speckle interferometry at the BTA 6 m telescope. In 2005.9, we obtained first IOTA long-baseline interferometry on the Theta 1 C system, allowing us to derive preliminary solutions

Interactions in Massive Colliding Wind Binaries

NASA Technical Reports Server (NTRS)

Corcoran, M.

2012-01-01

The most massive stars (M> 60 Solar Mass) play crucial roles in altering the chemical and thermodynamic properties of their host galaxies. Stellar mass is the fundamental stellar parameter that determines their ancillary properties and which ultimately determines the fate of these stars and their influence on their galactic environs. Unfortunately, stellar mass becomes observationally and theoretically less well constrained as it increases. Theory becomes uncertain mostly because very massive stars are prone to strong, variable mass loss which is difficult to model. Observational constraints are uncertain too. Massive stars are rare, and massive binary stars (needed for dynamical determination of mass) are rarer still: and of these systems only a fraction have suitably high orbital inclinations for direct photometric and spectroscopic radial-velocity analysis. Even in the small number of cases in which a high-inclination binary near the upper mass limit can be identified, rotational broadening and contamination of spectral line features from thick circumstellar material (either natal clouds or produced by strong stellar wind driven mass loss from one or both of he stellar components) biases the analysis. In the wilds of the upper HR diagram, we're often left with indirect and circumstantial means of determining mass, a rather unsatisfactory state of affairs.

Holographic heat engine within the framework of massive gravity

NASA Astrophysics Data System (ADS)

Mo, Jie-Xiong; Li, Gu-Qiang

2018-05-01

Heat engine models are constructed within the framework of massive gravity in this paper. For the four-dimensional charged black holes in massive gravity, it is shown that the existence of graviton mass improves the heat engine efficiency significantly. The situation is more complicated for the five-dimensional neutral black holes since the constant which corresponds to the third massive potential also contributes to the efficiency. It is also shown that the existence of graviton mass can improve the heat engine efficiency. Moreover, we probe how the massive gravity influences the behavior of the heat engine efficiency approaching the Carnot efficiency.

Inverse relationship between cirrhosis and massive tumours in hepatocellular carcinoma.

PubMed

Sarpel, Umut; Ayo, Diego; Lobach, Iryna; Xu, Ruliang; Newman, Elliot

2012-11-01

A subset of patients with hepatocellular carcinoma (HCC) present with massive tumours. It is unknown why certain patients develop these massive tumours, and whether this presentation is specific to the underlying viral aetiology or patient demographics such as gender, race and age. All patients with HCC at Bellevue Hospital Center, New York from 1998 to 2012 were identified and relevant demographic and clinical information was collected. Computed tomography/magnetic resonance imaging (CT/MRI) images were reviewed and the maximal tumour diameter on axial sections was recorded. Cirrhosis was defined histologically or by radiographical criteria. The two cohorts of massive and non-massive HCC were compared. A total of 361 patients with HCC were identified, of which 58 were categorized as having a massive HCC using a 13 cm size cut-off. Univariate and multivariate analysis demonstrated a significant association of massive HCC with age <40 years; hepatitis B or Asian ethnicity; and a lack of cirrhosis or platelet count >100. Massive HCC represents a tumour subtype that is associated with young, chronic hepatitis B carriers with non-cirrhotic livers. The clinical implications of this finding are that patients with massive HCC are typically excellent resection candidates barring the presence of gross vascular invasion or distant metastases. © 2012 International Hepato-Pancreato-Biliary Association.

Accretion and outflow in the proplyd-like objects near Cygnus OB2

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

Guarcello, M. G.; Drake, J. J.; Wright, N. J.

2014-09-20

Cygnus OB2 is the most massive association within 2 kpc from the Sun, hosting hundreds of massive stars, thousands of young low mass members, and some sights of active star formation in the surrounding cloud. Recently, 10 photoevaporating proplyd-like objects with tadpole-shaped morphology were discovered in the outskirts of the OB association, approximately 6-14 pc away from its center. The classification of these objects is ambiguous, being either evaporating residuals of the parental cloud that are hosting a protostar inside or disk-bearing stars with an evaporating disk, such as the evaporating proplyds observed in the Trapezium Cluster in Orion. Inmore » this paper, we present a study based on low-resolution optical spectroscopic observations made with the Optical System for Imaging and low Resolution Integrated Spectroscopy, mounted on the 10.4 m Gran Telescopio CANARIAS, of two of these protostars. The spectrum of one of the objects shows evidence of accretion but not of outflows. In the latter object, the spectra show several emission lines indicating the presence of an actively accreting disk with outflow. We present estimates of the mass loss rate and the accretion rate from the disk, showing that the former exceeds the latter as observed in other known objects with evaporating disks. We also show evidence of a strong variability in the integrated flux observed in these objects as well as in the accretion and outflow diagnostics.« less

Modeling populations of rotationally mixed massive stars

NASA Astrophysics Data System (ADS)

Brott, I.

2011-02-01

Massive stars can be considered as cosmic engines. With their high luminosities, strong stellar winds and violent deaths they drive the evolution of galaxies through-out the history of the universe. Despite the importance of massive stars, their evolution is still poorly understood. Two major issues have plagued evolutionary models of massive stars until today: mixing and mass loss On the main sequence, the effects of mass loss remain limited in the considered mass and metallicity range, this thesis concentrates on the role of mixing in massive stars. This thesis approaches this problem just on the cross road between observations and simulations. The main question: Do evolutionary models of single stars, accounting for the effects of rotation, reproduce the observed properties of real stars. In particular we are interested if the evolutionary models can reproduce the surface abundance changes during the main-sequence phase. To constrain our models we build a population synthesis model for the sample of the VLT-FLAMES Survey of Massive stars, for which star-formation history and rotational velocity distribution are well constrained. We consider the four main regions of the Hunter diagram. Nitrogen un-enriched slow rotators and nitrogen enriched fast rotators that are predicted by theory. Nitrogen enriched slow rotators and nitrogen unenriched fast rotators that are not predicted by our model. We conclude that currently these comparisons are not sufficient to verify the theory of rotational mixing. Physical processes in addition to rotational mixing appear necessary to explain the stars in the later two regions. The chapters of this Thesis have been published in the following Journals: Ch. 2: ``Rotating Massive Main-Sequence Stars I: Grids of Evolutionary Models and Isochrones'', I. Brott, S. E. de Mink, M. Cantiello, N. Langer, A. de Koter, C. J. Evans, I. Hunter, C. Trundle, J.S. Vink submitted to Astronomy & Astrop hysics Ch. 3: ``The VLT-FLAMES Survey of Massive

Suboptimal control of lipid levels: results from the non-interventional Centralized Pan-Russian Survey of the Undertreatment of Hypercholesterolemia II (CEPHEUS II).

PubMed

Boytsov, Sergey; Logunova, Natalia; Khomitskaya, Yunona

2017-12-16

Elevated levels of low-density lipoprotein cholesterol (LDL-C) and glycosylated hemoglobin (HbA1c) are risk factors for cardiovascular complications. This study evaluated LDL-C goal attainment in Russian clinical practice among patients with moderate to very high cardiovascular risk. The study also assessed LDL-C goal attainment in patients prescribed lipid-lowering therapy for primary compared with secondary cardiovascular disease (CVD) prevention, predictors of LDL-C goal attainment, and the proportion of individuals with diabetes mellitus who achieved HbA1c < 7%. The Centralized Pan-Russian Survey on the Undertreatment of Hypercholesterolemia in Russia II (CEPHEUS II) was a multicenter, non-interventional, cross-sectional study conducted in the Russian Federation from September 2014 to November 2015. Participants were aged ≥ 18 years, were receiving a stable dose of lipid-lowering medication and had a moderate to very high cardiovascular risk. The primary variable was the proportion of patients reaching LDL-C goals established by the Fifth Joint European Task Force guidelines. Secondary analyses used McNemar and χ 2 tests. Data from 2703 patients were analyzed; 91.2% had a very high cardiovascular risk and 24.0% had been diagnosed with diabetes mellitus. Overall, 17.4% of patients (95% confidence interval [CI] 15.9-18.8%) achieved LDL-C goals. Investigators estimated this proportion at 21.8% (95% CI 20.3-23.4%). LDL-C goals were achieved by more patients in the primary CVD prevention subgroup than in the secondary CVD prevention subgroup (19.7% vs 16.1%, p = 0.017). Patient-related factors associated with a decreased likelihood of achieving LDL-C goals included having ischemic heart disease or a family history of premature coronary heart disease, forgetting to take hypercholesterolemia treatment or considering it acceptable to miss prescribed doses more than once per week, and dissatisfaction with or concern about lipid-lowering therapy. Overall, 367

Critical N = (1, 1) general massive supergravity

NASA Astrophysics Data System (ADS)

Deger, Nihat Sadik; Moutsopoulos, George; Rosseel, Jan

2018-04-01

In this paper we study the supermultiplet structure of N = (1, 1) General Massive Supergravity at non-critical and critical points of its parameter space. To do this, we first linearize the theory around its maximally supersymmetric AdS3 vacuum and obtain the full linearized Lagrangian including fermionic terms. At generic values, linearized modes can be organized as two massless and 2 massive multiplets where supersymmetry relates them in the standard way. At critical points logarithmic modes appear and we find that in three of such points some of the supersymmetry transformations are non-invertible in logarithmic multiplets. However, in the fourth critical point, there is a massive logarithmic multiplet with invertible supersymmetry transformations.

Massive infrared clusters in the Milky Way

NASA Astrophysics Data System (ADS)

Chené, André-Nicolas; Ramírez Alegría, Sebastian; Borissova, Jordanka; Hervé, Anthony; Martins, Fabrice; Kuhn, Michael; Minniti, Dante; VVV Science Team

2017-11-01

Our position in the Milky Way (MW) is both a blessing and a curse. We are nearby to many star clusters, but the dust that is a product of their very existence obscures them. Also, many massive young clusters are expected to be located near, or across the Galactic Center, where the dust extinction is extreme (A V > 15 mag) and can be better penetrated by infrared photons. This paper reviews the discoveries and the study of new MW massive stars and massive clusters made possible by near infrared observations that are part of the VISTA Variables in the Vía Láctea (VVV) survey. It discusses what the studies of their fundamental parameters have taught us.

The Census of Complex Organic Molecules in the Solar-type Protostar IRAS16293-2422

NASA Astrophysics Data System (ADS)

Jaber, Ali A.; Ceccarelli, C.; Kahane, C.; Caux, E.

2014-08-01

Complex organic molecules (COMs) are considered to be crucial molecules, since they are connected with organic chemistry, at the basis of terrestrial life. More pragmatically, they are molecules which in principle are difficult to synthesize in harsh interstellar environments and, therefore, are a crucial test for astrochemical models. Current models assume that several COMs are synthesized on lukewarm grain surfaces (gsim30-40 K) and released in the gas phase at dust temperatures of gsim100 K. However, recent detections of COMs in lsim20 K gas demonstrate that we still need important pieces to complete the puzzle of COMs formation. Here, we present a complete census of the oxygen- and nitrogen-bearing COMs, previously detected in different Interstellar Medium (ISM) regions, toward the solar-type protostar IRAS16293-2422. The census was obtained from the millimeter-submillimeter unbiased spectral survey TIMASSS. Of the 29 COMs searched for, 6 were detected: methyl cyanide, ketene, acetaldehyde, formamide, dimethyl ether, and methyl formate. Multifrequency analysis of the last five COMs provides clear evidence that they are present in the cold (lsim30 K) envelope of IRAS16293-2422, with abundances of 0.03-2 × 10-10. Our data do not allow us to support the hypothesis that the COMs abundance increases with increasing dust temperature in the cold envelope, as expected if COMs were predominately formed on lukewarm grain surfaces. Finally, when also considering other ISM sources, we find a strong correlation over five orders of magnitude between methyl formate and dimethyl ether, and methyl formate and formamide abundances, which may point to a link between these two couples of species in cold and warm gas.

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.

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

Massive-Star Magnetospheres: Now in 3-D!

NASA Astrophysics Data System (ADS)

Townsend, Richard

Magnetic fields are unexpected in massive stars, due to the absence of a dynamo convection zone beneath their surface layers. Nevertheless, kilogauss-strength, ordered fields were detected in a small subset of these stars over three decades ago, and the intervening years have witnessed the steady expansion of this subset. A distinctive feature of magnetic massive stars is that they harbor magnetospheres --- circumstellar environments where the magnetic field interacts strongly with the star's radiation-driven wind, confining it and channelling it into energetic shocks. A wide range of observational signatures are associated with these magnetospheres, in diagnostics ranging from X-rays all the way through to radio emission. Moreover, these magnetospheres can play an important role in massive-star evolution, by amplifying angular momentum loss in the wind. Recent progress in understanding massive-star magnetospheres has largely been driven by magnetohydrodynamical (MHD) simulations. However, these have been restricted to two- dimensional axisymmetric configurations, with three-dimensional configurations possible only in certain special cases. These restrictions are limiting further progress; we therefore propose to develop completely general three-dimensional models for the magnetospheres of massive stars, on the one hand to understand their observational properties and exploit them as plasma-physics laboratories, and on the other to gain a comprehensive understanding of how they influence the evolution of their host star. For weak- and intermediate-field stars, the models will be based on 3-D MHD simulations using a modified version of the ZEUS-MP code. For strong-field stars, we will extend our existing Rigid Field Hydrodynamics (RFHD) code to handle completely arbitrary field topologies. To explore a putative 'photoionization-moderated mass loss' mechanism for massive-star magnetospheres, we will also further develop a photoionization code we have recently

Far-infrared observations of a massive cluster forming in the Monoceros R2 filament hub

NASA Astrophysics Data System (ADS)

Rayner, T. S. M.; Griffin, M. J.; Schneider, N.; Motte, F.; Könyves, V.; André, P.; Di Francesco, J.; Didelon, P.; Pattle, K.; Ward-Thompson, D.; Anderson, L. D.; Benedettini, M.; Bernard, J.-P.; Bontemps, S.; Elia, D.; Fuente, A.; Hennemann, M.; Hill, T.; Kirk, J.; Marsh, K.; Men'shchikov, A.; Nguyen Luong, Q.; Peretto, N.; Pezzuto, S.; Rivera-Ingraham, A.; Roy, A.; Rygl, K.; Sánchez-Monge, Á.; Spinoglio, L.; Tigé, J.; Treviño-Morales, S. P.; White, G. J.

2017-10-01

We present far-infrared observations of Monoceros R2 (a giant molecular cloud at approximately 830 pc distance, containing several sites of active star formation), as observed at 70 μm, 160 μm, 250 μm, 350 μm, and 500 μm by the Photodetector Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging Receiver (SPIRE) instruments on the Herschel Space Observatory as part of the Herschel imaging survey of OB young stellar objects (HOBYS) Key programme. The Herschel data are complemented by SCUBA-2 data in the submillimetre range, and WISE and Spitzer data in the mid-infrared. In addition, C18O data from the IRAM 30-m Telescope are presented, and used for kinematic information. Sources were extracted from the maps with getsources, and from the fluxes measured, spectral energy distributions were constructed, allowing measurements of source mass and dust temperature. Of177 Herschel sources robustly detected in the region (a detection with high signal-to-noise and low axis ratio at multiple wavelengths), including protostars and starless cores, 29 are found in a filamentary hub at the centre of the region (a little over 1% of the observed area). These objects are on average smaller, more massive, and more luminous than those in the surrounding regions (which together suggest that they are at a later stage of evolution), a result that cannot be explained entirely by selection effects. These results suggest a picture in which the hub may have begun star formation at a point significantly earlier than the outer regions, possibly forming as a result of feedback from earlier star formation. Furthermore, the hub may be sustaining its star formation by accreting material from the surrounding filaments. Full Tables 4 and D.1-D.9 and the C180 datacube are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A22

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.

Driven and decaying turbulence simulations of low–mass star formation: From clumps to cores to protostars

DOE PAGES

Offner, Stella S. R.; Klein, Richard I.; McKee, Christopher F.

2008-10-20

Molecular clouds are observed to be turbulent, but the origin of this turbulence is not well understood. As a result, there are two different approaches to simulating molecular clouds, one in which the turbulence is allowed to decay after it is initialized, and one in which it is driven. We use the adaptive mesh refinement (AMR) code, Orion, to perform high-resolution simulations of molecular cloud cores and protostars in environments with both driven and decaying turbulence. We include self-gravity, use a barotropic equation of state, and represent regions exceeding the maximum grid resolution with sink particles. We analyze the propertiesmore » of bound cores such as size, shape, line width, and rotational energy, and we find reasonable agreement with observation. At high resolution the different rates of core accretion in the two cases have a significant effect on protostellar system development. Clumps forming in a decaying turbulence environment produce high-multiplicity protostellar systems with Toomre Q unstable disks that exhibit characteristics of the competitive accretion model for star formation. In contrast, cores forming in the context of continuously driven turbulence and virial equilibrium form smaller protostellar systems with fewer low-mass members. Furthermore, our simulations of driven and decaying turbulence show some statistically significant differences, particularly in the production of brown dwarfs and core rotation, but the uncertainties are large enough that we are not able to conclude whether observations favor one or the other.« less

HOW TO FIND YOUNG MASSIVE CLUSTER PROGENITORS

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

Bressert, E.; Longmore, S.; Testi, L.

2012-10-20

We propose that bound, young massive stellar clusters form from dense clouds that have escape speeds greater than the sound speed in photo-ionized gas. In these clumps, radiative feedback in the form of gas ionization is bottled up, enabling star formation to proceed to sufficiently high efficiency so that the resulting star cluster remains bound even after gas removal. We estimate the observable properties of the massive proto-clusters (MPCs) for existing Galactic plane surveys and suggest how they may be sought in recent and upcoming extragalactic observations. These surveys will potentially provide a significant sample of MPC candidates that willmore » allow us to better understand extreme star-formation and massive cluster formation in the Local Universe.« less

Nucleosynthesis in the first massive stars

NASA Astrophysics Data System (ADS)

Choplin, Arthur; Meynet, Georges; Maeder, André; Hirschi, Raphael; Chiappini, Cristina

2018-01-01

The nucleosynthesis in the first massive stars may be constrained by observing the surface composition of long-lived very iron-poor stars born around 10 billion years ago from material enriched by their ejecta. Many interesting clues on physical processes having occurred in the first stars can be obtained based on nuclear aspects. First, in these first massive stars, mixing must have occurred between the H-burning and the He-burning zone during their nuclear lifetimes; Second, only the outer layers of these massive stars have enriched the material from which the very iron-poor stars, observed today in the halo of the MilkyWay, have formed. These two basic requirements can be obtained by rotating stellar models at very low metallicity. In the present paper, we discuss the arguments supporting this view and illustrate the sensitivity of the results concerning the [Mg/Al] ratio on the rate of the reaction 23Na(p,γ)24Mg.

Massive and Open

ERIC Educational Resources Information Center

Fasimpaur, Karen

2013-01-01

MOOCs--massive open online courses--are all the rage these days, with hundreds of thousands of participants signing up and investors plunking down millions to get a piece of the pie. Why is there so much excitement about this new disruptive form of online learning, and how does this model apply to professional learning for teachers? Traditional…

Massively parallel information processing systems for space applications

NASA Technical Reports Server (NTRS)

Schaefer, D. H.

1979-01-01

NASA is developing massively parallel systems for ultra high speed processing of digital image data collected by satellite borne instrumentation. Such systems contain thousands of processing elements. Work is underway on the design and fabrication of the 'Massively Parallel Processor', a ground computer containing 16,384 processing elements arranged in a 128 x 128 array. This computer uses existing technology. Advanced work includes the development of semiconductor chips containing thousands of feedthrough paths. Massively parallel image analog to digital conversion technology is also being developed. The goal is to provide compact computers suitable for real-time onboard processing of images.

Young Star Clusters: Keys to Understanding Massive Stars

NASA Astrophysics Data System (ADS)

Davies, B.

2012-12-01

Young, coeval clusters of stars provide the perfect laboratory in which to test our understanding of how massive stars evolve. Early optical observations limited us to a handful of low-mass clusters within 1kpc. However, thanks to the recent progress in infrared astronomy, the Milky Way's population of young massive star clusters is now beginning to be revealed. Here, I will review the recent progress made in this field, what it has told us about the evolution of massive stars to supernova and beyond, the prospects for this field, and some issues that should be taken into account when interpreting the results.

NON-AQUEOUS DISSOLUTION OF MASSIVE PLUTONIUM

DOEpatents

Reavis, J.G.; Leary, J.A.; Walsh, K.A.

1959-05-12

A method is presented for obtaining non-aqueous solutions or plutonium from massive forms of the metal. In the present invention massive plutonium is added to a salt melt consisting of 10 to 40 weight per cent of sodium chloride and the balance zinc chloride. The plutonium reacts at about 800 deg C with the zinc chloride to form a salt bath of plutonium trichloride, sodium chloride, and metallic zinc. The zinc is separated from the salt melt by forcing the molten mixture through a Pyrex filter.

Topical perspective on massive threading and parallelism.

PubMed

Farber, Robert M

2011-09-01

Unquestionably computer architectures have undergone a recent and noteworthy paradigm shift that now delivers multi- and many-core systems with tens to many thousands of concurrent hardware processing elements per workstation or supercomputer node. GPGPU (General Purpose Graphics Processor Unit) technology in particular has attracted significant attention as new software development capabilities, namely CUDA (Compute Unified Device Architecture) and OpenCL™, have made it possible for students as well as small and large research organizations to achieve excellent speedup for many applications over more conventional computing architectures. The current scientific literature reflects this shift with numerous examples of GPGPU applications that have achieved one, two, and in some special cases, three-orders of magnitude increased computational performance through the use of massive threading to exploit parallelism. Multi-core architectures are also evolving quickly to exploit both massive-threading and massive-parallelism such as the 1.3 million threads Blue Waters supercomputer. The challenge confronting scientists in planning future experimental and theoretical research efforts--be they individual efforts with one computer or collaborative efforts proposing to use the largest supercomputers in the world is how to capitalize on these new massively threaded computational architectures--especially as not all computational problems will scale to massive parallelism. In particular, the costs associated with restructuring software (and potentially redesigning algorithms) to exploit the parallelism of these multi- and many-threaded machines must be considered along with application scalability and lifespan. This perspective is an overview of the current state of threading and parallelize with some insight into the future. Published by Elsevier Inc.

Observational properties of massive black hole binary progenitors

NASA Astrophysics Data System (ADS)

Hainich, R.; Oskinova, L. M.; Shenar, T.; Marchant, P.; Eldridge, J. J.; Sander, A. A. C.; Hamann, W.-R.; Langer, N.; Todt, H.

2018-01-01

Context. The first directly detected gravitational waves (GW 150914) were emitted by two coalescing black holes (BHs) with masses of ≈ 36 M⊙ and ≈ 29 M⊙. Several scenarios have been proposed to put this detection into an astrophysical context. The evolution of an isolated massive binary system is among commonly considered models. Aims: Various groups have performed detailed binary-evolution calculations that lead to BH merger events. However, the question remains open as to whether binary systems with the predicted properties really exist. The aim of this paper is to help observers to close this gap by providing spectral characteristics of massive binary BH progenitors during a phase where at least one of the companions is still non-degenerate. Methods: Stellar evolution models predict fundamental stellar parameters. Using these as input for our stellar atmosphere code (Potsdam Wolf-Rayet), we compute a set of models for selected evolutionary stages of massive merging BH progenitors at different metallicities. Results: The synthetic spectra obtained from our atmosphere calculations reveal that progenitors of massive BH merger events start their lives as O2-3V stars that evolve to early-type blue supergiants before they undergo core-collapse during the Wolf-Rayet phase. When the primary has collapsed, the remaining system will appear as a wind-fed high-mass X-ray binary. Based on our atmosphere models, we provide feedback parameters, broad band magnitudes, and spectral templates that should help to identify such binaries in the future. Conclusions: While the predicted parameter space for massive BH binary progenitors is partly realized in nature, none of the known massive binaries match our synthetic spectra of massive BH binary progenitors exactly. Comparisons of empirically determined mass-loss rates with those assumed by evolution calculations reveal significant differences. The consideration of the empirical mass-loss rates in evolution calculations will

Embeddings of the "New Massive Gravity"

NASA Astrophysics Data System (ADS)

Dalmazi, D.; Mendonça, E. L.

2016-07-01

Here we apply different types of embeddings of the equations of motion of the linearized "New Massive Gravity" in order to generate alternative and even higher-order (in derivatives) massive gravity theories in D=2+1. In the first part of the work we use the Weyl symmetry as a guiding principle for the embeddings. First we show that a Noether gauge embedding of the Weyl symmetry leads to a sixth-order model in derivatives with either a massive or a massless ghost, according to the chosen overall sign of the theory. On the other hand, if the Weyl symmetry is implemented by means of a Stueckelberg field we obtain a new scalar-tensor model for massive gravitons. It is ghost-free and Weyl invariant at the linearized level around Minkowski space. The model can be nonlinearly completed into a scalar field coupled to the NMG theory. The elimination of the scalar field leads to a nonlocal modification of the NMG. In the second part of the work we prove to all orders in derivatives that there is no local, ghost-free embedding of the linearized NMG equations of motion around Minkowski space when written in terms of one symmetric tensor. Regarding that point, NMG differs from the Fierz-Pauli theory, since in the latter case we can replace the Einstein-Hilbert action by specific f(R,Box R) generalizations and still keep the theory ghost-free at the linearized level.

Growth histories in bimetric massive gravity

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

Berg, Marcus; Buchberger, Igor; Enander, Jonas

2012-12-01

We perform cosmological perturbation theory in Hassan-Rosen bimetric gravity for general homogeneous and isotropic backgrounds. In the de Sitter approximation, we obtain decoupled sets of massless and massive scalar gravitational fluctuations. Matter perturbations then evolve like in Einstein gravity. We perturb the future de Sitter regime by the ratio of matter to dark energy, producing quasi-de Sitter space. In this more general setting the massive and massless fluctuations mix. We argue that in the quasi-de Sitter regime, the growth of structure in bimetric gravity differs from that of Einstein gravity.

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.

Massive stars in the Sagittarius Dwarf Irregular Galaxy

NASA Astrophysics Data System (ADS)

Garcia, Miriam

2018-02-01

Low metallicity massive stars hold the key to interpret numerous processes in the past Universe including re-ionization, starburst galaxies, high-redshift supernovae, and γ-ray bursts. The Sagittarius Dwarf Irregular Galaxy [SagDIG, 12+log(O/H) = 7.37] represents an important landmark in the quest for analogues accessible with 10-m class telescopes. This Letter presents low-resolution spectroscopy executed with the Gran Telescopio Canarias that confirms that SagDIG hosts massive stars. The observations unveiled three OBA-type stars and one red supergiant candidate. Pending confirmation from high-resolution follow-up studies, these could be the most metal-poor massive stars of the Local Group.

The census of complex organic molecules in the solar-type protostar IRAS16293-2422

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

Jaber, Ali A.; Ceccarelli, C.; Kahane, C.

2014-08-10

Complex organic molecules (COMs) are considered to be crucial molecules, since they are connected with organic chemistry, at the basis of terrestrial life. More pragmatically, they are molecules which in principle are difficult to synthesize in harsh interstellar environments and, therefore, are a crucial test for astrochemical models. Current models assume that several COMs are synthesized on lukewarm grain surfaces (≳30-40 K) and released in the gas phase at dust temperatures of ≳100 K. However, recent detections of COMs in ≲20 K gas demonstrate that we still need important pieces to complete the puzzle of COMs formation. Here, we presentmore » a complete census of the oxygen- and nitrogen-bearing COMs, previously detected in different Interstellar Medium (ISM) regions, toward the solar-type protostar IRAS16293-2422. The census was obtained from the millimeter-submillimeter unbiased spectral survey TIMASSS. Of the 29 COMs searched for, 6 were detected: methyl cyanide, ketene, acetaldehyde, formamide, dimethyl ether, and methyl formate. Multifrequency analysis of the last five COMs provides clear evidence that they are present in the cold (≲30 K) envelope of IRAS16293-2422, with abundances of 0.03-2 × 10{sup –10}. Our data do not allow us to support the hypothesis that the COMs abundance increases with increasing dust temperature in the cold envelope, as expected if COMs were predominately formed on lukewarm grain surfaces. Finally, when also considering other ISM sources, we find a strong correlation over five orders of magnitude between methyl formate and dimethyl ether, and methyl formate and formamide abundances, which may point to a link between these two couples of species in cold and warm gas.« less

The Rb problem in massive AGB stars.

NASA Astrophysics Data System (ADS)

Pérez-Mesa, V.; García-Hernández, D. A.; Zamora, O.; Plez, B.; Manchado, A.; Karakas, A. I.; Lugaro, M.

2017-03-01

The asymptotic giant branch (AGB) is formed by low- and intermediate-mass stars (0.8 M_{⊙} < M < 8 M_{⊙}) in their last nuclear-burning phase, when they develop thermal pulses (TP) and suffer extreme mass loss. AGB stars are the main contributor to the enrichment of the interstellar medium (ISM) and thus to the chemical evolution of galaxies. In particular, the more massive AGB stars (M > 4 M_{⊙}) are expected to produce light (e.g., Li, N) and heavy neutron-rich s-process elements (such as Rb, Zr, Ba, Y, etc.), which are not formed in lower mass AGB stars and Supernova explosions. Classical chemical analyses using hydrostatic atmospheres revealed strong Rb overabundances and high [Rb/Zr] ratios in massive AGB stars of our Galaxy and the Magellanic Clouds (MC), confirming for the first time that the ^{22}Ne neutron source dominates the production of s-process elements in these stars. The extremely high Rb abundances and [Rb/Zr] ratios observed in the most massive stars (specially in the low-metallicity MC stars) uncovered a Rb problem; such extreme Rb and [Rb/Zr] values are not predicted by the s-process AGB models, suggesting fundamental problems in our present understanding of their atmospheres. We present more realistic dynamical model atmospheres that consider a gaseous circumstellar envelope with a radial wind and we re-derive the Rb (and Zr) abundances in massive Galactic AGB stars. The new Rb abundances and [Rb/Zr] ratios derived with these dynamical models significantly resolve the problem of the mismatch between the observations and the theoretical predictions of the more massive AGB stars.

Acausality of massive gravity.

PubMed

Deser, S; Waldron, A

2013-03-15

We show, by analyzing its characteristics, that the ghost-free, 5 degree of freedom, Wess-Zumino massive gravity model admits superluminal shock wave solutions and thus is acausal. Ironically, this pathology arises from the very constraint that removes the (sixth) Boulware-Deser ghost mode.

Pseudoangiomatous stromal hyperplasia causing massive breast enlargement

PubMed Central

Bourke, Anita Geraldine; Tiang, Stephen; Harvey, Nathan; McClure, Robert

2015-01-01

Pseudoangiomatous stromal hyperplasia (PASH) of the breast is a benign mesenchymal proliferative process, initially described by Vuitch et al. We report an unusual case of a 46-year-old woman who presented with a 6-week history of bilateral massive, asymmetrical, painful enlargement of her breasts, without a history of trauma. On clinical examination, both breasts were markedly enlarged and oedematous, but there were no discrete palpable masses. Preoperative image-guided core biopsies and surgery showed PASH. PASH is increasingly recognised as an incidental finding on image-guided core biopsy performed for screen detected lesions. There are a few reported cases of PASH presenting as rapid breast enlargement. In our case, the patient presented with painful, asymmetrical, massive breast enlargement. Awareness needs to be raised of this entity as a differential diagnosis in massive, painful breast enlargement. PMID:26475873

Primordial inhomogeneities from massive defects during inflation

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

Firouzjahi, Hassan; Karami, Asieh; Rostami, Tahereh, E-mail: firouz@ipm.ir, E-mail: karami@ipm.ir, E-mail: t.rostami@ipm.ir

2016-10-01

We consider the imprints of local massive defects, such as a black hole or a massive monopole, during inflation. The massive defect breaks the background homogeneity. We consider the limit that the physical Schwarzschild radius of the defect is much smaller than the inflationary Hubble radius so a perturbative analysis is allowed. The inhomogeneities induced in scalar and gravitational wave power spectrum are calculated. We obtain the amplitudes of dipole, quadrupole and octupole anisotropies in curvature perturbation power spectrum and identify the relative configuration of the defect to CMB sphere in which large observable dipole asymmetry can be generated. Wemore » observe a curious reflection symmetry in which the configuration where the defect is inside the CMB comoving sphere has the same inhomogeneous variance as its mirror configuration where the defect is outside the CMB sphere.« less

Massive Binaries in the R 136 Cluster

NASA Astrophysics Data System (ADS)

Morrell, N. I.; Massey, P.; Degioia-Eastwood, K.; Penny, L. R.; Gies, D. R.; Tsitkin, Y.; Darnell, E.

2008-08-01

As part of a large project aimed to the discovery and follow up of massive eclipsing systems in young clusters and stellar associations, we have obtained V-band CCD imaging of the R136 cluster in 30 Doradus, and high resolution spectroscopy of several among the variable stars we found there. Here we summarize our preliminary analysis of light and radial velocity variations for 4 massive multiple systems in the R136 cluster.

VizieR Online Data Catalog: The Red MSX Source Survey: massive protostars (Lumsden+, 2013)

NASA Astrophysics Data System (ADS)

Lumsden, S. L.; Hoare, M. G.; Urquhart, J. S.; Oudmaijer, R. D.; Davies, B.; Mottram, J. C.; Cooper, H. D. B.; Moore, T. J. T.

2013-10-01

The Midcourse Space Experiment (MSX) satellite mission included an astronomy experiment (SPIRIT III) designed to acquire mid-infrared photometry of sources in the Galactic plane (b<5°). MSX had a raw resolution of 18.3", a beam size 50 times smaller than that of IRAS at 12 and 25um. MSX observed six bands between 4 and 21um, of which the four between 8 and 21um are sensitive to astronomical sources. We used v2.3 of the MSX PSC (Egan et al. 2003, Cat. V/114) as our basic input, restricting ourselves to the main Galactic plane catalog, which excludes sources seen in only a single observing pass and those seen in multiple passes but with low significance. We restricted our catalog to 10

The Dynamics of Massive Starless Cores with ALMA

NASA Astrophysics Data System (ADS)

Tan, Jonathan C.; Kong, Shuo; Butler, Michael J.; Caselli, Paola; Fontani, Francesco

2013-12-01

How do stars that are more massive than the Sun form, and thus how is the stellar initial mass function (IMF) established? Such intermediate- and high-mass stars may be born from relatively massive pre-stellar gas cores, which are more massive than the thermal Jeans mass. The turbulent core accretion model invokes such cores as being in approximate virial equilibrium and in approximate pressure equilibrium with their surrounding clump medium. Their internal pressure is provided by a combination of turbulence and magnetic fields. Alternatively, the competitive accretion model requires strongly sub-virial initial conditions that then lead to extensive fragmentation to the thermal Jeans scale, with intermediate- and high-mass stars later forming by competitive Bondi-Hoyle accretion. To test these models, we have identified four prime examples of massive (~100 M ⊙) clumps from mid-infrared extinction mapping of infrared dark clouds. Fontani et al. found high deuteration fractions of N2H+ in these objects, which are consistent with them being starless. Here we present ALMA observations of these four clumps that probe the N2D+ (3-2) line at 2.''3 resolution. We find six N2D+ cores and determine their dynamical state. Their observed velocity dispersions and sizes are broadly consistent with the predictions of the turbulent core model of self-gravitating, magnetized (with Alfvén Mach number mA ~ 1) and virialized cores that are bounded by the high pressures of their surrounding clumps. However, in the most massive cores, with masses up to ~60 M ⊙, our results suggest that moderately enhanced magnetic fields (so that mA ~= 0.3) may be needed for the structures to be in virial and pressure equilibrium. Magnetically regulated core formation may thus be important in controlling the formation of massive cores, inhibiting their fragmentation, and thus helping to establish the stellar IMF.

Massive QCD Amplitudes at Higher Orders

NASA Astrophysics Data System (ADS)

Moch, S.; Mitov, A.

2007-11-01

We consider the factorisation properties of on-shell QCD amplitudes with massive partons in the limit when all kinematical invariants are large compared to the parton mass and discuss the structure of their infrared singularities. The dimensionally regulated soft poles and the large collinear logarithms of the parton masses exponentiate to all orders. Based on this factorisation a simple relation between massless and massive scattering amplitudes in gauge theories can be established. We present recent applications of this relation for the calculation of the two-loop virtual QCD corrections to the hadro-production of heavy quarks.

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.

Age-Defying Star

NASA Image and Video Library

2016-08-29

An age-defying star called IRAS 19312+1950 exhibits features characteristic of a very young star and a very old star. The object stands out as extremely bright inside a large, chemically rich cloud of material, as shown in this image from NASA's Spitzer Space Telescope. IRAS 19312+1950 is the bright red star in the center of this image. A NASA-led team of scientists thinks the star -- which is about 10 times as massive as our sun and emits about 20,000 times as much energy -- is a newly forming protostar. That was a big surprise, because the region had not been known as a stellar nursery before. But the presence of a nearby interstellar bubble, which indicates the presence of a recently formed massive star, also supports this idea. http://photojournal.jpl.nasa.gov/catalog/PIA20914

Subspace Methods for Massive and Messy Data

DTIC Science & Technology

2017-07-12

Subspace Methods for Massive and Messy Data The views, opinions and/or findings contained in this report are those of the author(s) and should not...AGENCY NAME(S) AND ADDRESS (ES) U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 REPORT DOCUMENTATION PAGE 11. SPONSOR...Number: W911NF-14-1-0634 Organization: University of Michigan - Ann Arbor Title: Subspace Methods for Massive and Messy Data Report Term: 0-Other

The singular behavior of massive QCD amplitudes

NASA Astrophysics Data System (ADS)

Mitov, Alexander; Moch, Sven-Olaf

2007-05-01

We discuss the structure of infrared singularities in on-shell QCD amplitudes with massive partons and present a general factorization formula in the limit of small parton masses. The factorization formula gives rise to an all-order exponentiation of both, the soft poles in dimensional regularization and the large collinear logarithms of the parton masses. Moreover, it provides a universal relation between any on-shell amplitude with massive external partons and its corresponding massless amplitude. For the form factor of a heavy quark we present explicit results including the fixed-order expansion up to three loops in the small mass limit. For general scattering processes we show how our constructive method applies to the computation of all singularities as well as the constant (mass-independent) terms of a generic massive n-parton QCD amplitude up to the next-to-next-to-leading order corrections.

DEEPLY EMBEDDED PROTOSTELLAR POPULATION IN THE 20 km s{sup −1} CLOUD OF THE CENTRAL MOLECULAR ZONE

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

Lu, Xing; Gu, Qiusheng; Zhang, Qizhou

2015-12-01

We report the discovery of a population of deeply embedded protostellar candidates in the 20 km s{sup −1} cloud, one of the massive molecular clouds in the Central Molecular Zone (CMZ) of the Milky Way, using interferometric submillimeter continuum and H{sub 2}O maser observations. The submillimeter continuum emission shows five 1 pc scale clumps, each of which further fragments into several 0.1 pc scale cores. We identify 17 dense cores, among which 12 are gravitationally bound. Among the 18 H{sub 2}O masers detected, 13 coincide with the cores and probably trace outflows emanating from the protostars. There are also 5more » gravitationally bound dense cores without H{sub 2}O maser detection. In total, the 13 masers and 5 cores may represent 18 protostars with spectral types later than B1 or potentially growing more massive stars at earlier evolutionary stages, given the non-detection in the centimeter radio continuum. In combination with previous studies of CH{sub 3}OH masers, we conclude that the star formation in this cloud is at an early evolutionary phase, before the presence of any significant ionizing or heating sources. Our findings indicate that star formation in this cloud may be triggered by a tidal compression as it approaches pericenter, similar to the case of G0.253+0.016 but with a higher star formation rate, and demonstrate that high angular resolution, high-sensitivity maser, and submillimeter observations are promising techniques to unveil deeply embedded star formation in the CMZ.« less

Eta Carinae in the Context of the Most Massive Stars

NASA Technical Reports Server (NTRS)

Gull, Theodore R.; Damineli, Augusto

2009-01-01

Eta Car, with its historical outbursts, visible ejecta and massive, variable winds, continues to challenge both observers and modelers. In just the past five years over 100 papers have been published on this fascinating object. We now know it to be a massive binary system with a 5.54-year period. In January 2009, Car underwent one of its periodic low-states, associated with periastron passage of the two massive stars. This event was monitored by an intensive multi-wavelength campaign ranging from -rays to radio. A large amount of data was collected to test a number of evolving models including 3-D models of the massive interacting winds. August 2009 was an excellent time for observers and theorists to come together and review the accumulated studies, as have occurred in four meetings since 1998 devoted to Eta Car. Indeed, Car behaved both predictably and unpredictably during this most recent periastron, spurring timely discussions. Coincidently, WR140 also passed through periastron in early 2009. It, too, is a intensively studied massive interacting binary. Comparison of its properties, as well as the properties of other massive stars, with those of Eta Car is very instructive. These well-known examples of evolved massive binary systems provide many clues as to the fate of the most massive stars. What are the effects of the interacting winds, of individual stellar rotation, and of the circumstellar material on what we see as hypernovae/supernovae? We hope to learn. Topics discussed in this 1.5 day Joint Discussion were: Car: the 2009.0 event: Monitoring campaigns in X-rays, optical, radio, interferometry WR140 and HD5980: similarities and differences to Car LBVs and Eta Carinae: What is the relationship? Massive binary systems, wind interactions and 3-D modeling Shapes of the Homunculus & Little Homunculus: what do we learn about mass ejection? Massive stars: the connection to supernovae, hypernovae and gamma ray bursters Where do we go from here? (future

Ongoing Massive Star Formation in NGC 604

NASA Astrophysics Data System (ADS)

Martínez-Galarza, J. R.; Hunter, D.; Groves, B.; Brandl, B.

2012-12-01

NGC 604 is the second most massive H II region in the Local Group, thus an important laboratory for massive star formation. Using a combination of observational and analytical tools that include Spitzer spectroscopy, Herschel photometry, Chandra imaging, and Bayesian spectral energy distribution fitting, we investigate the physical conditions in NGC 604 and quantify the amount of massive star formation currently taking place. We derive an average age of 4 ± 1 Myr and a total stellar mass of 1.6+1.6 - 1.0 × 105 M ⊙ for the entire region, in agreement with previous optical studies. Across the region, we find an effect of the X-ray field on both the abundance of aromatic molecules and the [Si II] emission. Within NGC 604, we identify several individual bright infrared sources with diameters of about 15 pc and luminosity-weighted masses between 103 M ⊙ and 104 M ⊙. Their spectral properties indicate that some of these sources are embedded clusters in process of formation, which together account for ~8% of the total stellar mass in the NGC 604 system. The variations of the radiation field strength across NGC 604 are consistent with a sequential star formation scenario, with at least two bursts in the last few million years. Our results indicate that massive star formation in NGC 604 is still ongoing, likely triggered by the earlier bursts.

Topologically massive higher spin gravity

NASA Astrophysics Data System (ADS)

Bagchi, Arjun; Lal, Shailesh; Saha, Arunabha; Sahoo, Bindusar

2011-10-01

We look at the generalisation of topologically massive gravity (TMG) to higher spins, specifically spin-3. We find a special "chiral" point for the spin-three, analogous to the spin-two example, which actually coincides with the usual spin-two chiral point. But in contrast to usual TMG, there is the presence of a non-trivial trace and its logarithmic partner at the chiral point. The trace modes carry energy opposite in sign to the traceless modes. The logarithmic partner of the traceless mode carries negative energy indicating an instability at the chiral point. We make several comments on the asymptotic symmetry and its possible deformations at this chiral point and speculate on the higher spin generalisation of LCFT2 dual to the spin-3 massive gravity at the chiral point.

Research on the Orbital Period of Massive Binaries

NASA Astrophysics Data System (ADS)

Zhao, E.; Qain, S.

2011-12-01

Massive binary is the kind of binary, whose spectral type is earlier than B5. Research on massive binary plays an important role in the mass and angular momentum transfer or loss between the components, and the evolution of binary. Some massive binaries are observed and analyzed, including O-type binary LY Aur, B-type contact binary RZ Pyx and B-type semi-detached binary AI Cru. It is found that all of their periods have a long-term increasing, which indicates that the system is undergoing a Case A slow mass transfer stage on the nuclear time-scale of the secondary. Moreover, analysis show a cyclic change of orbital period, which can be explained by the light-travel effect time of the third body.

Low-metallicity (sub-SMC) massive stars

NASA Astrophysics Data System (ADS)

Garcia, Miriam; Herrero, Artemio; Najarro, Francisco; Camacho, Inés; Lennon, Daniel J.; Urbaneja, Miguel A.; Castro, Norberto

2017-11-01

The double distance and metallicity frontier marked by the SMC has been finally broken with the aid of powerful multi-object spectrographs installed at 8-10m class telescopes. VLT, GTC and Keck have enabled studies of massive stars in dwarf irregular galaxies of the Local Group with poorer metal-content than the SMC. The community is working to test the predictions of evolutionary models in the low-metallicity regime, set the new standard for the metal-poor high-redshift Universe, and test the extrapolation of the physics of massive stars to environments of decreasing metallicity. In this paper, we review current knowledge on this topic.

The Evolution of Low-Metallicity Massive Stars

NASA Astrophysics Data System (ADS)

Szécsi, Dorottya

2016-07-01

Massive star evolution taking place in astrophysical environments consisting almost entirely of hydrogen and helium - in other words, low-metallicity environments - is responsible for some of the most intriguing and energetic cosmic phenomena, including supernovae, gamma-ray bursts and gravitational waves. This thesis aims to investigate the life and death of metal-poor massive stars, using theoretical simulations of the stellar structure and evolution. Evolutionary models of rotating, massive stars (9-600 Msun) with an initial metal composition appropriate for the low-metallicity dwarf galaxy I Zwicky 18 are presented and analyzed. We find that the fast rotating models (300 km/s) become a particular type of objects predicted only at low-metallicity: the so-called Transparent Wind Ultraviolet INtense (TWUIN) stars. TWUIN stars are fast rotating massive stars that are extremely hot (90 kK), very bright and as compact as Wolf-Rayet stars. However, as opposed to Wolf-Rayet stars, their stellar winds are optically thin. As these hot objects emit intense UV radiation, we show that they can explain the unusually high number of ionizing photons of the dwarf galaxy I Zwicky 18, an observational quantity that cannot be understood solely based on the normal stellar population of this galaxy. On the other hand, we find that the most massive, slowly rotating models become another special type of object predicted only at low-metallicity: core-hydrogen-burning cool supergiant stars. Having a slow but strong stellar wind, these supergiants may be important contributors in the chemical evolution of young galactic globular clusters. In particular, we suggest that the low mass stars observed today could form in a dense, massive and cool shell around these, now dead, supergiants. This scenario is shown to explain the anomalous surface abundances observed in these low mass stars, since the shell itself, having been made of the mass ejected by the supergiant’s wind, contains nuclear

Massive Star Formation Viewed through Extragalactic-Tinted Glasses

NASA Astrophysics Data System (ADS)

Willis, Sarah; Marengo, M.; Smith, H. A.; Allen, L.

2014-01-01

Massive Galactic star forming regions are the local analogs to the luminous star forming regions that dominate the emission from star forming galaxies. Their proximity to us enables the characterization of the full range of stellar masses that form in these more massive environments, improving our understanding of star formation tracers used in extragalactic studies. We have surveyed a sample of massive star forming regions with a range of morphologies and luminosities to probe the star formation activity in a variety of environments. We have used Spitzer IRAC and deep ground based J, H, Ks observations to characterize the Young Stellar Object (YSO) content of 6 massive star forming regions. These YSOs provide insight into the rate and efficiency of star formation within these regions, and enable comparison with nearby, low mass star forming regions as well as extreme cases of Galactic star formation including ‘mini-starburst’ regions. In addition, we have conducted an in-depth analysis of NGC 6334 to investigate how the star formation activity varies within an individual star forming region, using Herschel data in the far-infrared to probe the earliest stages of the ongoing star formation activity.

METHOD OF DISSOLVING MASSIVE PLUTONIUM

DOEpatents

Facer, J.F.; Lyon, W.L.

1960-06-28

Massive plutonium can be dissolved in a hot mixture of concentrated nitric acid and a small quantity of hydrofluoric acid. A preliminary oxidation with water under superatmospheric pressure at 140 to 150 deg C is advantageous

Massive Symbolic Mathematical Computations and Their Applications

DTIC Science & Technology

1988-08-16

NUMBER ORGANIZATION (if appi cable) AFOSR I A_ /__ I F49620-87- C -0113 Bc. ADDRESS (City, Stare, and ZIP Code) %. SOURCE OF FUNDING NUMBERS PROGRAM PROJECT...TASK WORK UNIT - < ’/I/ "//ELEMENT NO. NO. NO. ACCESSION NO. /,, AF,; c 9r ;- 6 (4/tL’ " ’ ’! /K’, 11 TITLE (Incoue Secuirty Classification) Massive...DARPA R & D Status Report AFOSR.m. 8 8-1 12Contract No. F49620-87- C -0113 MASSIVE SYMBOLIC MATHEMATICAL COMPUTATIONS AND THEIR APPLICATIONS Quarterly

Observational studies of regions of massive star formation

NASA Astrophysics Data System (ADS)

Cooper, Heather Danielle Blythe

2013-03-01

Massive stars have a profound influence on their surroundings. However, relatively little is known about their formation. The study of massive star formation is hindered by a lack of observational evidence, primarily due to difficulties observing massive stars at early stages in their development. The Red MSX Source survey (RMS survey) is a valuable tool with which to address these issues. Near-infrared H- and K-band spectra were taken for 247 candidate massive young stellar objects (MYSOs), selected from the RMS survey. 195 (∼80%) of the targets are YSOs, of which 131 are massive YSOs (LBOL>5E3L⊙, M>8 M⊙). This is the largest spectroscopic study of massive YSOs to date. This study covers minimally obscured objects right through to very red, dusty sources. Almost all YSOs show some evidence for emission lines, though there is a wide variety of observed properties, with HI, H2 Fe II, and CO among the most commonly observed lines. Evidence for disks and outflows was frequently seen. Comparisons of Brγ and H2 emission with low mass YSOs suggest that the emission mechanism for these lines is the same for low-, intermediate-, and high-mass YSOs, i.e. high-mass YSOs appear to resemble scaled-up versions of low-mass YSOs. It was found that the YSOs form an evolutionary sequence, based on their spectra, consistent with the existing theoretical models. Type I YSOs have strong H2 emission, no ionized lines, and are redder than the other two subtypes. As such, these are considered to be the youngest sources. The Type III sources are bluest, and therefore considered to be the oldest subtype. They have strong H I lines and fluorescent Fe II 1.6878 μm emission. They may also have weak H2 emission. Type III sources may even be beginning to form a mini-H II region. XSHOOTER data from 10 Herbig Be stars were analysed. The evidence suggests that winds and disks are common among Herbig stars, as they are among their main sequence classical Be star counterparts. Line

MASGOMAS project: building a bona-fide catalog of massive star cluster candidates

NASA Astrophysics Data System (ADS)

Herrero, Artemio; Rübke, Klaus; Ramírez Alegría, Sebastián; Garcia, Miriam; Marín-Franch, Antonio

2017-11-01

MASGOMAS (MAssive Stars in Galactic Obscured MAssive clusterS) is a project aiming at discovering OB stars in Galactic, dust enshrouded, star-forming massive clusters (Marín-Franch et al. 2009, A&A 502, 559). The project has gone through different phases of increasing automatization, that have allowed us to discover massive clusters like MASGOMAS-1 (Ramírez Alegría et al. 2012, A&A 541, A75) (with M~20,000 M⊙).

Near infrared observations of S155. evidence of induced star formation?

NASA Astrophysics Data System (ADS)

Hunt, L. K.; Lisi, F.; Felli, M.; Tofani, G.

At the interface of the giant molecular cloud Cepheus OB3, S155 represents one of the most interesting examples of bright rim produced by the ionization of a nearby O-star. The interaction between the ionized HII region S155 and the hot molecular core Cepheus B may constitute the ideal site for new stars, according to the sequential star-formation theory. Past observations of molecular lines have shown the evidence of a hot spot in the cloud core, probably a compact region associated to a young stellar object. New J,H,K images recently obtained with the ARNICA array at the TIRGO telescope give evidence of stars with strong near-infrared excess, which must represent the newest generation of young stars.

The Tadpole and the Wriggler

NASA Image and Video Library

2014-04-14

A bright blue tadpole appears to swim through the inky blackness of space. Known as IRAS 20324+4057, but dubbed "the Tadpole," this clump of gas and dust has given birth to a bright, "protostar," one of the earliest steps in building a star. This image was taken by NASA's Hubble Space Telescope, and released publicly, in 2012. There are actually multiple protostars within this tadpole's 'head," but the glowing yellow one in this image is the most luminous and massive. When this protostar has gathered together enough mass from its surroundings, it will eventually emerge as a fully-fledged young star. The intense blue glow is caused by nearby stars firing ultraviolet radiation at IRAS 20324+4057, which also sculpts its tail into a long, wiggly shape. In total, this clump spans roughly a light-year from head to tail-tip, and contains gas weighing almost four times the mass of the sun. Framed against a background of distant stars, IRAS 20324+4057 is making its way through the Cygnus OB2 association, a loose cluster of stars some 4,700 light-years from Earth in the constellation Cygnus. This association is one of the largest clusters known, and is famed for its heavyweight members. It contains some of the hottest, most massive and most luminous stars known, some of which are about two million times more luminous than the sun. The Tadpole is not alone in this interstellar pond. Just out of view, to the bottom right of this image, lies another curious object dubbed "the Goldfish" by astronomers. The Goldfish is about half the length of IRAS 20324+4057, and is also thought to be a globule of gas that is being both lit up and sculpted by radiation from cluster stars. Completing this trio is a small clump of blue gas, informally nicknamed "the Wriggler" by some astronomers, visible in the bottom left of this Hubble image. All three objects have the same orientation in the sky and appear to be brighter on their northern sides, leading astronomers to believe they are being

Spin-3 topologically massive gravity

NASA Astrophysics Data System (ADS)

Chen, Bin; Long, Jiang; Wu, Jun-bao

2011-11-01

In this Letter, we study the spin-3 topologically massive gravity (TMG), paying special attention to its properties at the chiral point. We propose an action describing the higher spin fields coupled to TMG. We discuss the traceless spin-3 fluctuations around the AdS3 vacuum and find that there is an extra local massive mode, besides the left-moving and right-moving boundary massless modes. At the chiral point, such extra mode becomes massless and degenerates with the left-moving mode. We show that at the chiral point the only degrees of freedom in the theory are the boundary right-moving graviton and spin-3 field. We conjecture that spin-3 chiral gravity with generalized Brown-Henneaux boundary condition is holographically dual to 2D chiral CFT with classical W3 algebra and central charge cR = 3 l / G.

A clinical update on massive ovarian oedema - a pseudotumour?

PubMed

Praveen, Rs; Pallavi, Vr; Rajashekar, K; Usha, A; Umadevi, K; Bafna, Ud

2013-01-01

Benign massive ovarian oedema is a rare clinical entity arising from the ovaries, and it poses a significant clinical challenge as it can be easily mistaken for neoplasm. Due to the lack of pathognomonic clinical features or characteristic hallmarks on non-invasive diagnostic modalities and the dependence on the final histopathology, the efforts of the surgeon have been deviated from performing fertility-sparing surgery on young women. The lack of standardised guidelines due to the rarity of this condition calls for a review of the literature to enable the clinician to formulate treatment guidelines. A Medline search on the PubMed database for literature published in English from 1969 to 2011 was done using the keywords 'massive ovarian oedema, massive ovarian oedema case report or case series, and pseudotumour of ovary'. A total of 177 women who had undergone a variety of treatments were retrieved. We also report the management options we used for four women presenting to us between August 2000 and October 2011, as well as a review of the literature. A total of 177 cases of massive ovarian oedema were identified. Out of these cases 151 (85.3%) were primary massive ovarian oedema; secondary massive ovarian oedema was identified in 26 (14.7%) cases. A salpingo-oophorectomy was done in 145 (81.9%) cases, 12 (6.8%) cases had an abdominal hysterectomy with bilateral salpingo-oophorectomy. A total of 76 (42.9%) cases intraoperatively were found to have ovarian torsions, and one patient with primary massive ovarian oedema had ascites. Conservative treatment was carried out in 20 (11.3%) patients; 14 of these had a wedge biopsy with frozen section and with or without ovarian suspension, one patient had diagnostic laparotomy, and five cases had only ultrasonographic or magnetic resonance imaging monitoring and symptomatic treatment. The four cases treated at the regional cancer institute from 2000 to 2011 revealed that the first three cases had salpingo-oophorectomy and

Collaborative Calibrated Peer Assessment in Massive Open Online Courses

ERIC Educational Resources Information Center

Boudria, Asma; Lafifi, Yacine; Bordjiba, Yamina

2018-01-01

The free nature and open access courses in the Massive Open Online Courses (MOOC) allow the facilities of disseminating information for a large number of participants. However, the "massive" propriety can generate many pedagogical problems, such as the assessment of learners, which is considered as the major difficulty facing in the…

Hypocalcemia in trauma patients receiving massive transfusion.

PubMed

Giancarelli, Amanda; Birrer, Kara L; Alban, Rodrigo F; Hobbs, Brandon P; Liu-DeRyke, Xi

2016-05-01

Massive transfusion protocol (MTP) is increasingly used in civilian trauma resuscitation. Calcium is vital for coagulation, but hypocalcemia commonly occurs during massive transfusion due to citrate and serum calcium chelation. This study was conducted to determine the incidence of hypocalcemia and severe hypocalcemia in trauma patients who receive massive transfusion and to compare characteristics of patients with severe versus nonsevere hypocalcemia. This was a retrospective study of trauma patients who received massive transfusion between January 2009 and November 2013. The primary outcome was the incidence of hypocalcemia (ionized calcium [iCa] < 1.12 mmol/L) and severe hypocalcemia (iCa < 0.90 mmol/L). Secondary outcomes included calcium monitoring, calcium replacement, and correction of coagulopathy. There were 156 patients included; 152 (97%) experienced hypocalcemia, and 111 (71%) had severe hypocalcemia. Patients were stratified into iCa ≥ 0.90 (n = 45) and iCa < 0.90 (n = 111). There were no differences in demographics or baseline laboratories except the severe hypocalcemia group had higher baseline activated partial thromboplastin time (29.7 [23.7-50.9] versus 25.8 [22.3-35.9], P = 0.003), higher lactic acid (5.8 [4.1-9.8] versus 4.0 [3.1-7.8], P = 0.019), lower platelets (176 [108-237] versus 208 [169-272], P = 0.003), and lower pH (7.14 [6.98-7.28] versus 7.23 [7.14-7.33], P = 0.019). Mortality was higher in the severe hypocalcemia group (49% versus 24%, P = 0.007). Patients in the iCa < 0.90 group received more blood products (34 [23-58] versus 22 [18-30] units, P < 0.001), and calcium chloride (4 [2-7] versus 3 [1-4] g, P = 0.002), but there was no difference in duration of MTP or final iCa. Neither group reached a median iCa > 1.12. Hypocalcemia is common during MTP, and vigilant monitoring is warranted. Research is needed to effectively manage hypocalcemia during massive transfusion. Copyright © 2016 Elsevier Inc. All rights reserved.

Wide-field SCUBA-2 observations of NGC 2264: submillimetre clumps and filaments

NASA Astrophysics Data System (ADS)

Buckle, J. V.; Richer, J. S.

2015-10-01

We present wide-field observations of the NGC 2264 molecular cloud in the dust continuum at 850 and 450 μm using SCUBA-2 on the James Clerk Maxwell Telescope. Using 12CO 3 → 2 molecular line data, we determine that emission from CO contaminates the 850 μm emission at levels ˜30 per cent in localized regions associated with high-velocity molecular outflows. Much higher contamination levels of 60 per cent are seen in shocked regions near the massive star S Mon. If not removed, the levels of CO contamination would contribute an extra 13 per cent to the dust mass in NGC 2264. We use the FELLWALKER routine to decompose the dust into clumpy structures, and a Hessian-based routine to decompose the dust into filamentary structures. The filaments can be described as a hub-filament structure, with lower column density filaments radiating from the NGC 2264 C protocluster hub. Above mean filament column densities of 2.4 × 1022 cm-2, star formation proceeds with the formation of two or more protostars. Below these column densities, filaments are starless, or contain only a single protostar.

Near-Infrared Mass Loss Diagnostics for Massive Stars

NASA Technical Reports Server (NTRS)

Sonneborn, George; Bouret, J. C.

2010-01-01

Stellar wind mass loss is a key process which modifies surface abundances, luminosities, and other physical properties of hot, massive stars. Furthermore, mass loss has to be understood quantitatively in order to accurately describe and predict massive star evolution. Two urgent problems have been identified that challenge our understanding of line-driven winds, the so-called weak-wind problem and wind clumping. In both cases, mass-loss rates are drastically lower than theoretically expected (up to a factor 1001). Here we study how the expected spectroscopic capabilities of the James Webb Space Telescope (JWST), especially NIRSpec, could be used to significantly improve constraints on wind density structures (clumps) and deep-seated phenomena in stellar winds of massive stars, including OB, Wolf-Rayet and LBV stars. Since the IR continuum of objects with strong winds is formed in the wind, IR lines may sample different depths inside the wind than UV-optical lines and provide new information about the shape of the velocity field and clumping properties. One of the most important applications of IR line diagnostics will be the measurement of mass-loss rates in massive stars with very weak winds by means of the H I Bracket alpha line, which has been identified as one of the most promising diagnostics for this problem.

Photon emission from massive projectile impacts on solids.

PubMed

Fernandez-Lima, F A; Pinnick, V T; Della-Negra, S; Schweikert, E A

2011-01-01

First evidence of photon emission from individual impacts of massive gold projectiles on solids for a number of projectile-target combinations is reported. Photon emission from individual impacts of massive Au(n) (+q) (1 ≤ n ≤ 400; q = 1-4) projectiles with impact energies in the range of 28-136 keV occurs in less than 10 ns after the projectile impact. Experimental observations show an increase in the photon yield from individual impacts with the projectile size and velocity. Concurrently with the photon emission, electron emission from the impact area has been observed below the kinetic emission threshold and under unlikely conditions for potential electron emission. We interpret the puzzling electron emission and correlated luminescence observation as evidence of the electronic excitation resulting from the high-energy density deposited by massive cluster projectiles during the impact.

Photon emission from massive projectile impacts on solids

PubMed Central

Fernandez-Lima, F. A.; Pinnick, V. T.; Della-Negra, S.; Schweikert, E. A.

2011-01-01

First evidence of photon emission from individual impacts of massive gold projectiles on solids for a number of projectile-target combinations is reported. Photon emission from individual impacts of massive Aun+q (1 ≤ n ≤ 400; q = 1–4) projectiles with impact energies in the range of 28–136 keV occurs in less than 10 ns after the projectile impact. Experimental observations show an increase in the photon yield from individual impacts with the projectile size and velocity. Concurrently with the photon emission, electron emission from the impact area has been observed below the kinetic emission threshold and under unlikely conditions for potential electron emission. We interpret the puzzling electron emission and correlated luminescence observation as evidence of the electronic excitation resulting from the high-energy density deposited by massive cluster projectiles during the impact. PMID:21603128

ALFIL: A Crowd Simulation Serious Game for Massive Evacuation Training and Awareness

ERIC Educational Resources Information Center

García-García, César; Fernández-Robles, José Luis; Larios-Rosillo, Victor; Luga, Hervé

2012-01-01

This article presents the current development of a serious game for the simulation of massive evacuations. The purpose of this project is to promote self-protection through awareness of the procedures and different possible scenarios during the evacuation of a massive event. Sophisticated behaviors require massive computational power and it has…

Massive ovarian oedema: a misleading clinical entity.

PubMed

Machairiotis, Nikolaos; Stylianaki, Aikaterini; Kouroutou, Paraskevi; Sarli, Polixeni; Alexiou, Nikolaos Konstantinos; Efthymiou, Elias; Maras, Athanasios; Alexiou, Nikolaos Georgios; Nikolaou, Spyridon Evaggelos; Courcoutsakis, Nikolaos; Papakonstantinou, Eleni; Zarogoulidis, Paul; Barbetakis, Nikolaos; Paliouras, Dimitrios; Gogakos, Apostolos; Machairiotis, Christodoulos

2016-02-03

Massive ovarian oedema is a rare non-neoplastic clinicopathologic entity has a higher incidence in women during their second and third life decade. The oedema can be presented in one or both ovaries as a result of partial intermittent torsion of the ovarian pedicle that interferes to the venal and lymphatic drainage of the ovary. We present a clinical case of a 16 year old with massive ovarian oedema and we performed a review of the literature. The pathophysiology of this entity is very complex. We tried to perform a complete review of the literature and focus on the complexity of this entity as far as its pathophysiological backround is concerned and as far as its clinical presentation is concerned. In conclusion, massive ovarian oedema is a rare, multi disease mimicking clinical entity, with an acute or progressive clinical presentation. It has also to be a part of our differential diagnosis in cases of acute abdominal pain and we have to try to treat her conservatively, in order to preserve fertility.

Massive star evolution and SN 1987A

NASA Technical Reports Server (NTRS)

Arnett, David

1991-01-01

The evolution of massive stars through hydrogen and helium burning is addressed. A set of stellar evolutionary sequences for mass/solar mass of 15, 20, and 25, and metallicity of 0.002, 0.005, 0.007, 0.010, and 0.20 are presented; semiconvection is restricted to operating slower than the local thermal time scale. Using these sequences, simple models of the massive star content of the LMC are found to agree moderately well with the new observational data of Fitzpatrick and Garmany (1990). LMC supergiants were detected only in their postmain-sequence phases, so that 5-10 times more massive stars are there but not identified as such. It is argued that SN 1987A exhibits the normal evolution of a single star of about 20 solar mases having LMC abundances. Despite the variety of envelope behavior, the structure of the core at collapse is rather similar for the stars of a given mass. Variations due to different rates of mass loss are likely to be larger than those due to composition.

Relativistic N-body simulations with massive neutrinos

NASA Astrophysics Data System (ADS)

Adamek, Julian; Durrer, Ruth; Kunz, Martin

2017-11-01

Some of the dark matter in the Universe is made up of massive neutrinos. Their impact on the formation of large scale structure can be used to determine their absolute mass scale from cosmology, but to this end accurate numerical simulations have to be developed. Due to their relativistic nature, neutrinos pose additional challenges when one tries to include them in N-body simulations that are traditionally based on Newtonian physics. Here we present the first numerical study of massive neutrinos that uses a fully relativistic approach. Our N-body code, gevolution, is based on a weak-field formulation of general relativity that naturally provides a self-consistent framework for relativistic particle species. This allows us to model neutrinos from first principles, without invoking any ad-hoc recipes. Our simulation suite comprises some of the largest neutrino simulations performed to date. We study the effect of massive neutrinos on the nonlinear power spectra and the halo mass function, focusing on the interesting mass range between 0.06 eV and 0.3 eV and including a case for an inverted mass hierarchy.

Satisfying the Einstein-Podolsky-Rosen criterion with massive particles

NASA Astrophysics Data System (ADS)

Peise, J.; Kruse, I.; Lange, K.; Lücke, B.; Pezzè, L.; Arlt, J.; Ertmer, W.; Hammerer, K.; Santos, L.; Smerzi, A.; Klempt, C.

2016-03-01

In 1935, Einstein, Podolsky and Rosen (EPR) questioned the completeness of quantum mechanics by devising a quantum state of two massive particles with maximally correlated space and momentum coordinates. The EPR criterion qualifies such continuous-variable entangled states, as shown successfully with light fields. Here, we report on the production of massive particles which meet the EPR criterion for continuous phase/amplitude variables. The created quantum state of ultracold atoms shows an EPR parameter of 0.18(3), which is 2.4 standard deviations below the threshold of 1/4. Our state presents a resource for tests of quantum nonlocality with massive particles and a wide variety of applications in the field of continuous-variable quantum information and metrology.

Water in star-forming regions with Herschel (WISH). II. Evolution of 557 GHz 110-101 emission in low-mass protostars

NASA Astrophysics Data System (ADS)

Kristensen, L. E.; van Dishoeck, E. F.; Bergin, E. A.; Visser, R.; Yıldız, U. A.; San Jose-Garcia, I.; Jørgensen, J. K.; Herczeg, G. J.; Johnstone, D.; Wampfler, S. F.; Benz, A. O.; Bruderer, S.; Cabrit, S.; Caselli, P.; Doty, S. D.; Harsono, D.; Herpin, F.; Hogerheijde, M. R.; Karska, A.; van Kempen, T. A.; Liseau, R.; Nisini, B.; Tafalla, M.; van der Tak, F.; Wyrowski, F.

2012-06-01

Context. Water is a key tracer of dynamics and chemistry in low-mass star-forming regions, but spectrally resolved observations have so far been limited in sensitivity and angular resolution, and only data from the brightest low-mass protostars have been published. Aims: The first systematic survey of spectrally resolved water emission in 29 low-mass (L < 40 L⊙) protostellar objects is presented. The sources cover a range of luminosities and evolutionary states. The aim is to characterise the line profiles to distinguish physical components in the beam and examine how water emission changes with protostellar evolution. Methods: H2O was observed in the ground-state 110-101 transition at 557 GHz (Eup/kB ~ 60 K) as single-point observations with the Heterodyne Instrument for the Far-Infrared (HIFI) on Herschel in 29 deeply embedded Class 0 and I low-mass protostars. Complementary far-IR and sub-mm continuum data (including PACS data from our programme) are used to constrain the spectral energy distribution (SED) of each source. H2O intensities are compared to inferred envelope properties, e.g., mass and density, outflow properties and CO 3-2 emission. Results: H2O emission is detected in all objects except one (TMC1A). The line profiles are complex and consist of several kinematic components tracing different physical regions in each system. In particular, the profiles are typically dominated by a broad Gaussian emission feature, indicating that the bulk of the water emission arises in outflows, not in the quiescent envelope. Several sources show multiple shock components appearing in either emission or absorption, thus constraining the internal geometry of the system. Furthermore, the components include inverse P-Cygni profiles in seven sources (six Class 0, one Class I) indicative of infalling envelopes, and regular P-Cygni profiles in four sources (three Class I, one Class 0) indicative of expanding envelopes. Molecular "bullets" moving at ≳50 km s-1 with

Stochastic quantization and holographic Wilsonian renormalization group of free massive fermion

NASA Astrophysics Data System (ADS)

Moon, Sung Pil

2018-06-01

We examine a suggested relation between stochastic quantization and the holographic Wilsonian renormalization group in the massive fermion case on Euclidean AdS space. The original suggestion about the general relation between the two theories is posted in arXiv:1209.2242. In the previous researches, it is already verified that scalar fields, U(1) gauge fields, and massless fermions are consistent with the relation. In this paper, we examine the relation in the massive fermion case. Contrary to the other case, in the massive fermion case, the action needs particular boundary terms to satisfy boundary conditions. We finally confirm that the proposed suggestion is also valid in the massive fermion case.

The Evolution of the Multiplicity of Embedded Protostars. I. Sample Properties and Binary Detections

NASA Astrophysics Data System (ADS)

Connelley, Michael S.; Reipurth, Bo; Tokunaga, Alan T.

2008-06-01

We present the observational results of a near-infrared survey of a large sample of Class I protostars designed to determine the Class I binary separation distribution from ~100 AU to ~5000 AU. We have selected targets from a new sample of 267 nearby candidate Class I objects. This sample is well understood, consists of mostly Class I young stellar objects (YSOs) within 1 kpc, has targets selected from the whole sky, and is not biased by previous studies of star formation. We have observed 189 Class I YSOs north of δ = -40° at the H, K, and L' bands, with a median angular resolution of 0farcs33 at L'. We determine our detection limit for close binary companions by observing artificial binaries. We choose a contrast limit and an outer detection limit to minimize contamination and to ensure that a candidate companion is gravitationally bound. Our survey uses observations at the L' rather than the K band for the detection of binary companions since there is less scattered light and better seeing at L'. This paper presents the positions of our targets, the near-IR photometry of sources detected in our fields at L', as well as the observed properties of the 89 detected companions (73 of which are newly discovered). Although we have chosen contrast and separation limits to minimize contamination, we expect that there are about six stars identified as binary companions that are due to contamination. Finder charts at L' for each field are shown to facilitate future studies of these objects. The Infrared Telescope Facility is operated by the University of Hawaii under Cooperative Agreement no. NCC 5-538 with the National Aeronautics and Space Administration, Science Mission Directorate, Planetary Astronomy Program. The United Kingdom Infrared Telescope is operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the U.K. Based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical

Spontaneous Lorentz and diffeomorphism violation, massive modes, and gravity

NASA Astrophysics Data System (ADS)

Bluhm, Robert; Fung, Shu-Hong; Kostelecký, V. Alan

2008-03-01

Theories with spontaneous local Lorentz and diffeomorphism violation contain massless Nambu-Goldstone modes, which arise as field excitations in the minimum of the symmetry-breaking potential. If the shape of the potential also allows excitations above the minimum, then an alternative gravitational Higgs mechanism can occur in which massive modes involving the metric appear. The origin and basic properties of the massive modes are addressed in the general context involving an arbitrary tensor vacuum value. Special attention is given to the case of bumblebee models, which are gravitationally coupled vector theories with spontaneous local Lorentz and diffeomorphism violation. Mode expansions are presented in both local and spacetime frames, revealing the Nambu-Goldstone and massive modes via decomposition of the metric and bumblebee fields, and the associated symmetry properties and gauge fixing are discussed. The class of bumblebee models with kinetic terms of the Maxwell form is used as a focus for more detailed study. The nature of the associated conservation laws and the interpretation as a candidate alternative to Einstein-Maxwell theory are investigated. Explicit examples involving smooth and Lagrange-multiplier potentials are studied to illustrate features of the massive modes, including their origin, nature, dispersion laws, and effects on gravitational interactions. In the weak static limit, the massive mode and Lagrange-multiplier fields are found to modify the Newton and Coulomb potentials. The nature and implications of these modifications are examined.

A Massive-born Neutron Star with a Massive White Dwarf Companion

NASA Astrophysics Data System (ADS)

Cognard, Ismaël; Freire, Paulo C. C.; Guillemot, Lucas; Theureau, Gilles; Tauris, Thomas M.; Wex, Norbert; Graikou, Eleni; Kramer, Michael; Stappers, Benjamin; Lyne, Andrew G.; Bassa, Cees; Desvignes, Gregory; Lazarus, Patrick

2017-08-01

We report on the results of a 4 year timing campaign of PSR J2222-0137, a 2.44 day binary pulsar with a massive white dwarf (WD) companion, with the Nançay, Effelsberg, and Lovell radio telescopes. Using the Shapiro delay for this system, we find a pulsar mass m p = 1.76 ± 0.06 M ⊙ and a WD mass m c = 1.293 ± 0.025 M ⊙. We also measure the rate of advance of periastron for this system, which is marginally consistent with the general relativity prediction for these masses. The short lifetime of the massive WD progenitor star led to a rapid X-ray binary phase with little (< 10-2 M ⊙) mass accretion onto the neutron star; hence, the current pulsar mass is, within uncertainties, its birth mass, which is the largest measured to date. We discuss the discrepancy with previous mass measurements for this system; we conclude that the measurements presented here are likely to be more accurate. Finally, we highlight the usefulness of this system for testing alternative theories of gravity by tightly constraining the presence of dipolar radiation. This is of particular importance for certain aspects of strong-field gravity, like spontaneous scalarization, since the mass of PSR J2222-0137 puts that system into a poorly tested parameter range.

The Formation and Gravitational-wave Detection of Massive Stellar Black Hole Binaries

NASA Astrophysics Data System (ADS)

Belczynski, Krzysztof; Buonanno, Alessandra; Cantiello, Matteo; Fryer, Chris L.; Holz, Daniel E.; Mandel, Ilya; Miller, M. Coleman; Walczak, Marek

2014-07-01

If binaries consisting of two ~100 M ⊙ black holes exist, they would serve as extraordinarily powerful gravitational-wave sources, detectable to redshifts of z ~ 2 with the advanced LIGO/Virgo ground-based detectors. Large uncertainties about the evolution of massive stars preclude definitive rate predictions for mergers of these massive black holes. We show that rates as high as hundreds of detections per year, or as low as no detections whatsoever, are both possible. It was thought that the only way to produce these massive binaries was via dynamical interactions in dense stellar systems. This view has been challenged by the recent discovery of several >~ 150 M ⊙ stars in the R136 region of the Large Magellanic Cloud. Current models predict that when stars of this mass leave the main sequence, their expansion is insufficient to allow common envelope evolution to efficiently reduce the orbital separation. The resulting black hole-black hole binary remains too wide to be able to coalesce within a Hubble time. If this assessment is correct, isolated very massive binaries do not evolve to be gravitational-wave sources. However, other formation channels exist. For example, the high multiplicity of massive stars, and their common formation in relatively dense stellar associations, opens up dynamical channels for massive black hole mergers (e.g., via Kozai cycles or repeated binary-single interactions). We identify key physical factors that shape the population of very massive black hole-black hole binaries. Advanced gravitational-wave detectors will provide important constraints on the formation and evolution of very massive stars.

Classical and quantum cosmology of minimal massive bigravity

NASA Astrophysics Data System (ADS)

Darabi, F.; Mousavi, M.

2016-10-01

In a Friedmann-Robertson-Walker (FRW) space-time background we study the classical cosmological models in the context of recently proposed theory of nonlinear minimal massive bigravity. We show that in the presence of perfect fluid the classical field equations acquire contribution from the massive graviton as a cosmological term which is positive or negative depending on the dynamical competition between two scale factors of bigravity metrics. We obtain the classical field equations for flat and open universes in the ordinary and Schutz representation of perfect fluid. Focusing on the Schutz representation for flat universe, we find classical solutions exhibiting singularities at early universe with vacuum equation of state. Then, in the Schutz representation, we study the quantum cosmology for flat universe and derive the Schrodinger-Wheeler-DeWitt equation. We find its exact and wave packet solutions and discuss on their properties to show that the initial singularity in the classical solutions can be avoided by quantum cosmology. Similar to the study of Hartle-Hawking no-boundary proposal in the quantum cosmology of de Rham, Gabadadze and Tolley (dRGT) massive gravity, it turns out that the mass of graviton predicted by quantum cosmology of the minimal massive bigravity is large at early universe. This is in agreement with the fact that at early universe the cosmological constant should be large.

A Royal Celebration

NASA Image and Video Library

2012-01-10

This enormous section of the Milky Way galaxy is a mosaic of images from NASA Wide-field Infrared Survey Explorer. The constellations Cassiopeia and Cepheus are featured in this 1,000-square degree expanse.

The MASSIVE Survey. VI. The Spatial Distribution and Kinematics of Warm Ionized Gas in the Most Massive Local Early-type Galaxies

NASA Astrophysics Data System (ADS)

Pandya, Viraj; Greene, Jenny E.; Ma, Chung-Pei; Veale, Melanie; Ene, Irina; Davis, Timothy A.; Blakeslee, John P.; Goulding, Andy D.; McConnell, Nicholas J.; Nyland, Kristina; Thomas, Jens

2017-03-01

We present the first systematic investigation of the existence, spatial distribution, and kinematics of warm ionized gas as traced by the [O II] 3727 Å emission line in 74 of the most massive galaxies in the local universe. All of our galaxies have deep integral-field spectroscopy from the volume- and magnitude-limited MASSIVE survey of early-type galaxies with stellar mass {log}({M}* /{M}⊙ )> 11.5 (M K < -25.3 mag) and distance D < 108 Mpc. Of the 74 galaxies in our sample, we detect warm ionized gas in 28, which yields a global detection fraction of 38 ± 6% down to a typical [O II] equivalent width limit of 2 Å. MASSIVE fast rotators are more likely to have gas than MASSIVE slow rotators with detection fractions of 80 ± 10% and 28 ± 6%, respectively. The spatial extents span a wide range of radii (0.6-18.2 kpc; 0.1-4R e ), and the gas morphologies are diverse, with 17/28 ≈ 61 ± 9% being centrally concentrated, 8/28 ≈ 29 ± 9% exhibiting clear rotation out to several kiloparsecs, and 3/28 ≈ 11 ± 6% being extended but patchy. Three out of four fast rotators show kinematic alignment between the stars and gas, whereas the two slow rotators with robust kinematic measurements available exhibit kinematic misalignment. Our inferred warm ionized gas masses are roughly ˜105 M ⊙. The emission line ratios and radial equivalent width profiles are generally consistent with excitation of the gas by the old underlying stellar population. We explore different gas origin scenarios for MASSIVE galaxies and find that a variety of physical processes are likely at play, including internal gas recycling, cooling out of the hot gaseous halo, and gas acquired via mergers.

Kundt solutions of minimal massive 3D gravity

NASA Astrophysics Data System (ADS)

Deger, Nihat Sadik; Sarıoǧlu, Ã.-zgür

2015-11-01

We construct Kundt solutions of minimal massive gravity theory and show that, similar to topologically massive gravity (TMG), most of them are constant scalar invariant (CSI) spacetimes that correspond to deformations of round and warped (A)dS. We also find an explicit non-CSI Kundt solution at the merger point. Finally, we give their algebraic classification with respect to the traceless Ricci tensor (Segre classification) and show that their Segre types match with the types of their counterparts in TMG.

Complexity growth in minimal massive 3D gravity

NASA Astrophysics Data System (ADS)

Qaemmaqami, Mohammad M.

2018-01-01

We study the complexity growth by using "complexity =action " (CA) proposal in the minimal massive 3D gravity (MMG) model which is proposed for resolving the bulk-boundary clash problem of topologically massive gravity (TMG). We observe that the rate of the complexity growth for Banados-Teitelboim-Zanelli (BTZ) black hole saturates the proposed bound by physical mass of the BTZ black hole in the MMG model, when the angular momentum parameter and the inner horizon of black hole goes to zero.

New and Topologically Massive Gravity, from the Outside In

NASA Astrophysics Data System (ADS)

Cunliff, Colin

This thesis examines the asymptotically anti-de Sitter solutions of higher-derivative gravity in 2+1 dimensions, using a Fefferman-Graham-like approach that expands solutions from the boundary (at infinity) into the interior. First, solutions of topologically massive gravity (TMG) are analyzed for values of the mass parameter in the range mu ≥ 1. The traditional Fefferman-Graham expansion fails to capture the dynamics of TMG, and new terms in the asymptotic expansion are needed to include the massive graviton modes. The linearized modes of Carlip, Deser, Waldron and Wise map onto the non-Einstein solutions for all μ, with nonlinear corrections appearing at higher order in the expansion. A similar result is found for new massive gravity (NMG), where the asymptotic behavior of massive gravitons is found to depend on the coupling parameter m2. Additionally, new boundary conditions are discovered for a range of values -1 < 2m2 l2 < 1 at which non-Einstein modes decay more slowly than the rate required for Brown-Henneaux boundary conditions. The holographically renormalized stress tensor is computed for these modes, and the relevant counterterms are identified up to unphysical ambiguities.

Collisions in primordial star clusters. Formation pathway for intermediate mass black holes

NASA Astrophysics Data System (ADS)

Reinoso, B.; Schleicher, D. R. G.; Fellhauer, M.; Klessen, R. S.; Boekholt, T. C. N.

2018-06-01

Collisions were suggested to potentially play a role in the formation of massive stars in present day clusters, and have likely been relevant during the formation of massive stars and intermediate mass black holes within the first star clusters. In the early Universe, the first stellar clusters were particularly dense, as fragmentation typically only occurred at densities above 109 cm-3, and the radii of the protostars were enhanced as a result of larger accretion rates, suggesting a potentially more relevant role of stellar collisions. We present here a detailed parameter study to assess how the number of collisions and the mass growth of the most massive object depend on the properties of the cluster. We also characterize the time evolution with three effective parameters: the time when most collisions occur, the duration of the collisions period, and the normalization required to obtain the total number of collisions. We apply our results to typical Population III (Pop. III) clusters of about 1000 M⊙, finding that a moderate enhancement of the mass of the most massive star by a factor of a few can be expected. For more massive Pop. III clusters as expected in the first atomic cooling halos, we expect a more significant enhancement by a factor of 15-32. We therefore conclude that collisions in massive Pop. III clusters were likely relevant to form the first intermediate mass black holes.

New massive members of Cygnus OB2

NASA Astrophysics Data System (ADS)

Berlanas, S. R.; Herrero, A.; Comerón, F.; Pasquali, A.; Motta, C. Bertelli; Sota, A.

2018-04-01

Context. The Cygnus complex is one of the most powerful star forming regions at a close distance from the Sun ( 1.4 kpc). Its richest OB association Cygnus OB2 is known to harbor many tens of O-type stars and hundreds of B-type stars, providing a large homogeneous population of OB stars that can be analyzed. Many studies of its massive population have been developed in the last decades, although the total number of OB stars is still incomplete. Aim. Our aim is to increase the sample of O and B members of Cygnus OB2 and its surroundings by spectroscopically classifying 61 candidates as possible OB-type members of Cygnus OB2, using new intermediate resolution spectroscopy. Methods: We have obtained intermediate resolution (R 5000) spectra for all of the OB-type candidates between 2013 and 2017. We thus performed a spectral classification of the sample using HeI-II and metal lines rates, as well as the Marxist Ghost Buster (MGB) software for O-type stars and the IACOB standards catalog for B-type stars. Results: From the whole sample of 61 candidates, we have classified 42 stars as new massive OB-type stars, earlier than B3, in Cygnus OB2 and surroundings, including 11 O-type stars. The other candidates are discarded as they display later spectral types inconsistent with membership in the association. We have also obtained visual extinctions for all the new confirmed massive OB members, placing them in a Hertzsprung-Russell Diagram using calibrations for Teff and luminosity. Finally, we have studied the age and extinction distribution of our sample within the region. Conclusions: We have obtained new blue intermediate-resolution spectra suitable for spectral classification of 61 OB candidates in Cygnus OB2 and surroundings. The confirmation of 42 new OB massive stars (earlier than B3) in the region allows us to increase the young massive population known in the field. We have also confirmed the correlation between age and Galactic longitude previously found in the

The formation and gravitational-wave detection of massive stellar black hole binaries

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

Belczynski, Krzysztof; Walczak, Marek; Buonanno, Alessandra

2014-07-10

If binaries consisting of two ∼100 M{sub ☉} black holes exist, they would serve as extraordinarily powerful gravitational-wave sources, detectable to redshifts of z ∼ 2 with the advanced LIGO/Virgo ground-based detectors. Large uncertainties about the evolution of massive stars preclude definitive rate predictions for mergers of these massive black holes. We show that rates as high as hundreds of detections per year, or as low as no detections whatsoever, are both possible. It was thought that the only way to produce these massive binaries was via dynamical interactions in dense stellar systems. This view has been challenged by themore » recent discovery of several ≳ 150 M{sub ☉} stars in the R136 region of the Large Magellanic Cloud. Current models predict that when stars of this mass leave the main sequence, their expansion is insufficient to allow common envelope evolution to efficiently reduce the orbital separation. The resulting black hole-black hole binary remains too wide to be able to coalesce within a Hubble time. If this assessment is correct, isolated very massive binaries do not evolve to be gravitational-wave sources. However, other formation channels exist. For example, the high multiplicity of massive stars, and their common formation in relatively dense stellar associations, opens up dynamical channels for massive black hole mergers (e.g., via Kozai cycles or repeated binary-single interactions). We identify key physical factors that shape the population of very massive black hole-black hole binaries. Advanced gravitational-wave detectors will provide important constraints on the formation and evolution of very massive stars.« less

Three-dimensional massive gravity and the bigravity black hole

NASA Astrophysics Data System (ADS)

Bañados, Máximo; Theisen, Stefan

2009-11-01

We study three-dimensional massive gravity formulated as a theory with two dynamical metrics, like the f-g theories of Isham-Salam and Strathdee. The action is parity preserving and has no higher derivative terms. The spectrum contains a single massive graviton. This theory has several features discussed recently in TMG and NMG. We find warped black holes, a critical point, and generalized Brown-Henneaux boundary conditions.

Trigger-Happy Cloud

NASA Image and Video Library

2009-08-12

This composite image, combining data from NASA Chandra X-ray Observatory and Spitzer Space Telescope shows the star-forming cloud Cepheus B, located in our Milky Way galaxy about 2,400 light years from Earth

Massive stars: flare activity due to infalls of comet-like bodies

NASA Astrophysics Data System (ADS)

Ibadov, Subhon; Ibodov, Firuz S.

2015-01-01

Passages of comet-like bodies through the atmosphere/chromosphere of massive stars at velocities more than 600 km/s will be accompanied, due to aerodynamic effects as crushing and flattening, by impulse generation of hot plasma within a relatively very thin layer near the stellar surface/photosphere as well as ``blast'' shock wave, i.e., impact-generated photospheric stellar/solar flares. Observational manifestations of such high-temperature phenomena will be eruption of the explosive layer's hot plasma, on materials of the star and ``exploding'' comet nuclei, into the circumstellar environment and variable anomalies in chemical abundances of metal atoms/ions like Fe, Si etc. Interferometric and spectroscopic observations/monitoring of young massive stars with dense protoplanetary discs are of interest for massive stars physics/evolution, including identification of mechanisms for massive stars variability.

Dynamical Models for High-Energy Emission from Massive Stars

NASA Astrophysics Data System (ADS)

Owocki, Stanley %FAA(University of Delaware)

Massive stars are prominent sources of X-rays and gamma-rays detected by both targeted and survey observations from orbiting telescopes like Chandra, XMM/Newton, RXTE, and Fermi. Such high-energy emissions represent key probes of the dynamics of massive-star mass loss, and their penetration through many magnitudes of visible interstellar extinction makes them effective beacons of massive stars in distant reaches of the Galaxy, and in young, active star-forming regions. The project proposed here will develop a comprehensive theoretical framework for interpreting both surveys and targeted observations of high-energy emission from massive stars. It will build on our team's extensive experience in both theoretical models and observational analyses for three key types of emission mechanisms in the stellar wind outflows of these stars, namely: 1) Embedded Wind Shocks (EWS) arising from internal instabilities in the wind driving; 2) shocks in Colliding Wind Binary (CWB) systems; and 3) High-Mass X-ray Binaries (HMXB) systems with interaction between massive-star wind with a compact companion (neutron star or black hole). Taking advantage of commonalities in the treatment of radiative driving, hydrodynamics, shock heating and cooling, and radiation transport, we will develop radiation hydrodynamical models for the key observational signatures like energy distribution, emission line spectrum, and variability, with an emphasis on how these can be used in affiliated analyses of both surveys like the recent Chandra mapping of the Carina association, and targeted observations of galactic X-ray and gamma-ray sources associated with each of the above specific model types. The promises of new clumping-insensitive diagnostics of mass loss rates, and the connection to mass transfer and binarity, all have broad relevance for understanding the origin, evolution, and fate of massive stars, in concert with elements of NASA's Strategic Subgoal 3D. Building on our team's expertise, the

The 2nd Symposium on the Frontiers of Massively Parallel Computations

NASA Technical Reports Server (NTRS)

Mills, Ronnie (Editor)

1988-01-01

Programming languages, computer graphics, neural networks, massively parallel computers, SIMD architecture, algorithms, digital terrain models, sort computation, simulation of charged particle transport on the massively parallel processor and image processing are among the topics discussed.

First results from the CALYPSO IRAM-PdBI survey. II. Resolving the hot corino in the Class 0 protostar NGC 1333-IRAS2A

NASA Astrophysics Data System (ADS)

Maury, A. J.; Belloche, A.; André, Ph.; Maret, S.; Gueth, F.; Codella, C.; Cabrit, S.; Testi, L.; Bontemps, S.

2014-03-01

Aims: We investigate the origin of complex organic molecules (COMs) in the gas phase around the low-mass Class 0 protostar NGC 1333-IRAS2A, to determine if the COM emission lines trace an embedded disk, shocks from the protostellar jet, or the warm inner parts of the protostellar envelope. Methods: In the framework of the CALYPSO IRAM Plateau de Bure survey, we obtained large bandwidth spectra at sub-arcsecond resolution towards NGC 1333-IRAS2A. We identify the emission lines towards the central protostar and perform Gaussian fits to constrain the size of the emitting region for each of these lines, tracing various physical conditions and scales. Results: The emission of numerous COMs such as methanol, ethylene glycol, and methyl formate is spatially resolved by our observations. This allows us to measure, for the first time, the size of the COM emission inside the protostellar envelope, finding that it originates from a region of radius 40-100 AU, centered on the NGC 1333-IRAS2A protostellar object. Our analysis shows no preferential elongation of the COM emission along the jet axis, and therefore does not support the hypothesis that COM emission arises from shocked envelope material at the base of the jet. Down to similar sizes, the dust continuum emission is well reproduced with a single power-law envelope model, and therefore does not favor the hypothesis that COM emission arises from the thermal sublimation of grains embedded in a circumstellar disk. Finally, the typical scale ~60 AU observed for COM emission is consistent with the size of the inner envelope where Tdust > 100 K is expected. Our data therefore strongly suggest that the COM emission traces the hot corino in IRAS2A, i.e., the warm inner envelope material where the icy mantles of dust grains evaporate because they are passively heated by the central protostellar object. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG

Explaining the luminosity spread in young clusters: proto and pre-main sequence stellar evolution in a molecular cloud environment

NASA Astrophysics Data System (ADS)

Jensen, Sigurd S.; Haugbølle, Troels

2018-02-01

Hertzsprung-Russell diagrams of star-forming regions show a large luminosity spread. This is incompatible with well-defined isochrones based on classic non-accreting protostellar evolution models. Protostars do not evolve in isolation of their environment, but grow through accretion of gas. In addition, while an age can be defined for a star-forming region, the ages of individual stars in the region will vary. We show how the combined effect of a protostellar age spread, a consequence of sustained star formation in the molecular cloud, and time-varying protostellar accretion for individual protostars can explain the observed luminosity spread. We use a global magnetohydrodynamic simulation including a sub-scale sink particle model of a star-forming region to follow the accretion process of each star. The accretion profiles are used to compute stellar evolution models for each star, incorporating a model of how the accretion energy is distributed to the disc, radiated away at the accretion shock, or incorporated into the outer layers of the protostar. Using a modelled cluster age of 5 Myr, we naturally reproduce the luminosity spread and find good agreement with observations of the Collinder 69 cluster, and the Orion Nebular Cluster. It is shown how stars in binary and multiple systems can be externally forced creating recurrent episodic accretion events. We find that in a realistic global molecular cloud model massive stars build up mass over relatively long time-scales. This leads to an important conceptual change compared to the classic picture of non-accreting stellar evolution segmented into low-mass Hayashi tracks and high-mass Henyey tracks.

Spontaneous massive haemothorax caused by rupture of an intercostal vein

PubMed Central

Ke, H‐Y; Lee, S‐C; Tzao, C; Chang, H; Liao, G‐S; Cheng, Y‐L

2006-01-01

Spontaneous massive haemothorax is rare. We describe a healthy 44 year old woman who experience sudden onset chest pain while sleeping. Chest radiograph revealed massive right pleural effusion. Progressive dyspnoea, cold sweating, and tachycardia developed later. A tube thoracostomy was performed immediately and massive haemothorax was noted. An emergency thoracotomy was performed because of unstable vital signs. Disruption of the right third intercostal vein with continuous bleeding was observed, and suture ligation of the vein was performed. The total blood loss was about 4000 ml. The patient recovered uneventfully, and her condition at follow up visits to the outpatient department was satisfactory. PMID:16921070

The Most Massive Heartbeat: Finding the Pulse of ι Orionis

NASA Astrophysics Data System (ADS)

Pablo, Herbert; Richardson, Noel; Fuller, Jim; Moffat, Anthony F. J.; BEST and Ritter Observing Team

2017-11-01

ι Orionis is a massive binary system consisting of O9III + B1 III/IV stars. Though the system has been well studied, much about its fundamental properties have been difficult to determine. In this paper we report on the discovery of the heartbeat phenomenon in ι Orionis making it the most massive heartbeat system currently known. Using this phenomenon we have found empirical values for the masses and radii of both components. Moreover, we report the detection of tidally induced oscillations in an O-type star for the first time. These discoveries open a new avenue for exploring asteroseismology in massive stars.

A clinical update on massive ovarian oedema – a pseudotumour?

PubMed Central

Praveen, RS; Pallavi, VR; Rajashekar, K; Usha, A; Umadevi, K; Bafna, UD

2013-01-01

Objective: Benign massive ovarian oedema is a rare clinical entity arising from the ovaries, and it poses a significant clinical challenge as it can be easily mistaken for neoplasm. Due to the lack of pathognomonic clinical features or characteristic hallmarks on non-invasive diagnostic modalities and the dependence on the final histopathology, the efforts of the surgeon have been deviated from performing fertility-sparing surgery on young women. The lack of standardised guidelines due to the rarity of this condition calls for a review of the literature to enable the clinician to formulate treatment guidelines. Methods and Material: A Medline search on the PubMed database for literature published in English from 1969 to 2011 was done using the keywords ‘massive ovarian oedema, massive ovarian oedema case report or case series, and pseudotumour of ovary’. A total of 177 women who had undergone a variety of treatments were retrieved. We also report the management options we used for four women presenting to us between August 2000 and October 2011, as well as a review of the literature. Result: A total of 177 cases of massive ovarian oedema were identified. Out of these cases 151 (85.3%) were primary massive ovarian oedema; secondary massive ovarian oedema was identified in 26 (14.7%) cases. A salpingo-oophorectomy was done in 145 (81.9%) cases, 12 (6.8%) cases had an abdominal hysterectomy with bilateral salpingo-oophorectomy. A total of 76 (42.9%) cases intraoperatively were found to have ovarian torsions, and one patient with primary massive ovarian oedema had ascites. Conservative treatment was carried out in 20 (11.3%) patients; 14 of these had a wedge biopsy with frozen section and with or without ovarian suspension, one patient had diagnostic laparotomy, and five cases had only ultrasonographic or magnetic resonance imaging monitoring and symptomatic treatment. The four cases treated at the regional cancer institute from 2000 to 2011 revealed that the first

Using Massively Multiplayer Online Role-Playing Games for Online Learning

ERIC Educational Resources Information Center

Childress, Marcus D.; Braswell, Ray

2006-01-01

This article addresses the use of a massively multiplayer online role-playing game (MMORPG) to foster communication and interaction and to facilitate cooperative learning in an online course. The authors delineate the definition and history of massively multiplayer online games (MMOGs), and describe current uses of MMORPGs in education, including…

Long-term outcomes of patients receiving a massive transfusion after trauma.

PubMed

Mitra, Biswadev; Gabbe, Belinda J; Kaukonen, Kirsi-Maija; Olaussen, Alexander; Cooper, David J; Cameron, Peter A

2014-10-01

Resuscitation of patients presenting with hemorrhagic shock after major trauma has evolved to incorporate multiple strategies to maintain tissue perfusion and oxygenation while managing coagulation disorders. We aimed to study changes across time in long-term outcomes in patients with major trauma. A retrospective observational study in a single major trauma center in Australia was conducted. We included all patients with major trauma and massive blood transfusion within the first 24 h during a 6-year period (from 2006 to 2011). The main outcome measures were Glasgow Outcome Score-Extended (GOSE) and work capacity at 6 and 12 months. There were 5,915 patients with major trauma of which 365 (6.2%; 95% confidence interval [95% CI], 5.6 - 6.8) received a massive transfusion. The proportion of major trauma patients receiving a massive transfusion decreased across time from 8.2% to 4.4% (P < 0.01). There were statistically significant trends toward lower volumes of red blood cell transfusion and higher ratios of fresh-frozen plasma to red blood cells (P < 0.01). Among massively transfused patients, there was no significant change in measured outcomes during the study period, with a persistent 23% mortality in hospital, 52% unfavorable GOSE at 6 months, and 44% unfavorable GOSE at 12 months. Massive transfusion was independently associated with unfavorable outcomes at 6 months after injury (adjusted odds ratio, 1.56; 95% CI, 1.05 - 2.31) but not at 12 months (adjusted odds ratio, 0.85; 95% CI, 0.72 - 1.01). A significant reduction in massive transfusion rates was observed. Unfavorable long-term outcomes among patients receiving a massive transfusion after trauma were frequent with a substantial proportion of survivors experiencing poor functional status 1 year after injury.

Fulminant massive gas gangrene caused by Clostridium perfringens.

PubMed

Kuroda, Shoji; Okada, Yumi; Mita, Masaki; Okamoto, Yasuo; Kato, Hirotaka; Ueyama, Shigemitsu; Fujii, Ikuzo; Morita, Sumiharu; Yoshida, Yasuaki

2005-05-01

Clostridium perfringens (C.P) gas gangrene is one of the most fulminant infectious diseases. We encountered fulminant massive gas gangrene in a 56- year-old man with alcoholic liver cirrhosis. The patient died 14 hours after diagnosis of gas gangrene (54 hours after admission). Dramatic changes in abdominal CT imaging revealed development of a massive volume of gas in the intra-portal vein, retroperitoneum and abdominal subcutaneous tissue within 24 hours. We also proved C.P infection by immunohistological staining, leading to a diagnosis of C.P gas gangrene.

RAMA: A file system for massively parallel computers

NASA Technical Reports Server (NTRS)

Miller, Ethan L.; Katz, Randy H.

1993-01-01

This paper describes a file system design for massively parallel computers which makes very efficient use of a few disks per processor. This overcomes the traditional I/O bottleneck of massively parallel machines by storing the data on disks within the high-speed interconnection network. In addition, the file system, called RAMA, requires little inter-node synchronization, removing another common bottleneck in parallel processor file systems. Support for a large tertiary storage system can easily be integrated in lo the file system; in fact, RAMA runs most efficiently when tertiary storage is used.

Gravitational lensing of photons coupled to massive particles

NASA Astrophysics Data System (ADS)

Glicenstein, J.-F.

2018-04-01

The gravitational deflection of massless and massive particles, both with and without spin, has been extensively studied. This paper discusses the lensing of a particle which oscillates between two interaction eigenstates. The deflection angle, lens equation and time delay between images are derived in a model of photon to hidden-photon oscillations. In the case of coherent oscillations, the coupled photon behaves as a massive particle with a mass equal to the product of the coupling constant and hidden-photon mass. The conditions for observing coherent photon-hidden photon lensing are discussed.

Galaxy bispectrum from massive spinning particles

NASA Astrophysics Data System (ADS)

Moradinezhad Dizgah, Azadeh; Lee, Hayden; Muñoz, Julian B.; Dvorkin, Cora

2018-05-01

Massive spinning particles, if present during inflation, lead to a distinctive bispectrum of primordial perturbations, the shape and amplitude of which depend on the masses and spins of the extra particles. This signal, in turn, leaves an imprint in the statistical distribution of galaxies; in particular, as a non-vanishing galaxy bispectrum, which can be used to probe the masses and spins of these particles. In this paper, we present for the first time a new theoretical template for the bispectrum generated by massive spinning particles, valid for a general triangle configuration. We then proceed to perform a Fisher-matrix forecast to assess the potential of two next-generation spectroscopic galaxy surveys, EUCLID and DESI, to constrain the primordial non-Gaussianity sourced by these extra particles. We model the galaxy bispectrum using tree-level perturbation theory, accounting for redshift-space distortions and the Alcock-Paczynski effect, and forecast constraints on the primordial non-Gaussianity parameters marginalizing over all relevant biases and cosmological parameters. Our results suggest that these surveys would potentially be sensitive to any primordial non-Gaussianity with an amplitude larger than fNL≈ 1, for massive particles with spins 2, 3, and 4. Interestingly, if non-Gaussianities are present at that level, these surveys will be able to infer the masses of these spinning particles to within tens of percent. If detected, this would provide a very clear window into the particle content of our Universe during inflation.

Molecular Cloud Structures and Massive Star Formation in N159

NASA Astrophysics Data System (ADS)

Nayak, O.; Meixner, M.; Fukui, Y.; Tachihara, K.; Onishi, T.; Saigo, K.; Tokuda, K.; Harada, R.

2018-02-01

The N159 star-forming region is one of the most massive giant molecular clouds (GMCs) in the Large Magellanic Cloud (LMC). We show the 12CO, 13CO, CS molecular gas lines observed with ALMA in N159 west (N159W) and N159 east (N159E). We relate the structure of the gas clumps to the properties of 24 massive young stellar objects (YSOs) that include 10 newly identified YSOs based on our search. We use dendrogram analysis to identify properties of the molecular clumps, such as flux, mass, linewidth, size, and virial parameter. We relate the YSO properties to the molecular gas properties. We find that the CS gas clumps have a steeper size–linewidth relation than the 12CO or 13CO gas clumps. This larger slope could potentially occur if the CS gas is tracing shocks. The virial parameters of the 13CO gas clumps in N159W and N159E are low (<1). The threshold for massive star formation in N159W is 501 M ⊙ pc‑2, and the threshold for massive star formation in N159E is 794 M ⊙ pc‑2. We find that 13CO is more photodissociated in N159E than N159W. The most massive YSO in N159E has cleared out a molecular gas hole in its vicinity. All the massive YSO candidates in N159E have a more evolved spectral energy distribution type in comparison to the YSO candidates in N159W. These differences lead us to conclude that the giant molecular cloud complex in N159E is more evolved than the giant molecular cloud complex in N159W.

Phenomenology in minimal theory of massive gravity

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

Felice, Antonio De; Mukohyama, Shinji; Kavli Institute for the Physics and Mathematics of the Universe

2016-04-15

We investigate the minimal theory of massive gravity (MTMG) recently introduced. After reviewing the original construction based on its Hamiltonian in the vielbein formalism, we reformulate it in terms of its Lagrangian in both the vielbein and the metric formalisms. It then becomes obvious that, unlike previous attempts in the literature of Lorentz-violating massive gravity, not only the potential but also the kinetic structure of the action is modified from the de Rham-Gabadadze-Tolley (dRGT) massive gravity theory. We confirm that the number of physical degrees of freedom in MTMG is two at fully nonlinear level. This proves the absence ofmore » various possible pathologies such as superluminality, acausality and strong coupling. Afterwards, we discuss the phenomenology of MTMG in the presence of a dust fluid. We find that on a flat homogeneous and isotropic background we have two branches. One of them (self-accelerating branch) naturally leads to acceleration without the genuine cosmological constant or dark energy. For this branch both the scalar and the vector modes behave exactly as in general relativity (GR). The phenomenology of this branch differs from GR in the tensor modes sector, as the tensor modes acquire a non-zero mass. Hence, MTMG serves as a stable nonlinear completion of the self-accelerating cosmological solution found originally in dRGT theory. The other branch (normal branch) has a dynamics which depends on the time-dependent fiducial metric. For the normal branch, the scalar mode sector, even though as in GR only one scalar mode is present (due to the dust fluid), differs from the one in GR, and, in general, structure formation will follow a different phenomenology. The tensor modes will be massive, whereas the vector modes, for both branches, will have the same phenomenology as in GR.« less

The nature of ultra-massive lens galaxies

NASA Astrophysics Data System (ADS)

Canameras, Raoul

2017-08-01

During the past decade, strong gravitational lensing analyses have contributed tremendously to the characterization of the inner properties of massive early-type galaxies, beyond the local Universe. Here we intend to extend studies of this kind to the most massive lens galaxies known to date, well outside the mass limits investigated by previous lensing surveys. This will allow us to probe the physics of the likely descendants of the most violent episodes of star formation and of the compact massive galaxies at high redshift. We propose WFC3 imaging (F438W and F160W) of four extremely massive early-type lens galaxies at z 0.5, in order to put them into context with the evolutionary trends of ellipticals as a function of mass and redshift. These systems were discovered in the SDSS and show one single main lens galaxy with a stellar mass above 1.5x10^12 Msun and large Einstein radii. Our high-resolution spectroscopic follow-up with VLT/X-shooter provides secure lens and source redshifts, between 0.3 and 0.7 and between 1.5 and 2.5, respectively, and confirm extreme stellar velocity dispersions > 400 km/s for the lenses. The excellent angular resolution of the proposed WFC3 imaging - not achievable from the ground - is the remaining indispensable piece of information to :(1) Resolve the lens structural parameters and obtain robust measurements of their stellar mass distributions,(2) Model the amount and distribution of the lens total masses and measure their M/L ratios and stellar IMF with joint strong lensing and stellar dynamics analyses,(3) Enhance our on-going lens models through the most accurate positions and morphologies of the blue multiply-imaged sources.

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'.

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).

Weighing the Most Massive Stars

NASA Astrophysics Data System (ADS)

Moffat, Anthony; Schnurr, Olivier; Chené, André-Nicolas; St-Louis, Nicole

2005-08-01

HR diagrams of the brightest stars in nearby galaxies indicate that there exists an upper luminosity limit to star formation. One can assign real masses of stars at that limit, although with low confidence because of uncertainties in current stellar models. Understanding the physics of massive stars is important because these stars dominate the light and ecology of the Universe, not only at the present epoch, but also and especially during the first generation of stars (pop III), expected to be dominated by stars in the range 100-1000 solar masses. The only viable way to determine (or calibrate) masses is by "weighing" them in binary systems. The most massive stars are expected to be formed in the most massive, densest young stellar clusters, like the core R136 of 30 Dor in the Large Magellanic Cloud or its much closer clone NGC 3603 in the Galaxy. Telescopes in space or adaptive-optics systems on large groundbased telescopes are needed to cleanly resolve such stars in order to obtain the necessary high-precision radial velocities and light curves to define the orbits and obtain the masses. We discuss recent progress on this topic, with emphasis on our own attempt to determine the masses of the components of the brightest star (A1, a known main-sequence eclipsing system of type WN6ha + O3: and period 3.7724 d) in the core of NGC 3603, first using HST/STIS (instrument failure) then using VLT/SINFONI (in progress). With A1 being one magnitude intrinsically brighter than the current record holder WR20a (WN6ha + WN6ha, P = 3.686 d, 83 + 82 solar mass), we expect masses for A1 of ~ 100 solar mass if L .M3, or more likely, ~200 solar mass if L . M

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.

Helicity amplitudes for QCD with massive quarks

NASA Astrophysics Data System (ADS)

Ochirov, Alexander

2018-04-01

The novel massive spinor-helicity formalism of Arkani-Hamed, Huang and Huang provides an elegant way to calculate scattering amplitudes in quantum chromodynamics for arbitrary quark spin projections. In this note we compute two families of tree-level QCD amplitudes with one massive quark pair and n - 2 gluons. The two cases include all gluons with identical helicity and one opposite-helicity gluon being color-adjacent to one of the quarks. Our results naturally incorporate the previously known amplitudes for both quark spins quantized along one of the gluonic momenta. In the all-multiplicity formulae presented here the spin quantization axes can be tuned at will, which includes the case of the definite-helicity quark states.

Fast, Massively Parallel Data Processors

NASA Technical Reports Server (NTRS)

Heaton, Robert A.; Blevins, Donald W.; Davis, ED

1994-01-01

Proposed fast, massively parallel data processor contains 8x16 array of processing elements with efficient interconnection scheme and options for flexible local control. Processing elements communicate with each other on "X" interconnection grid with external memory via high-capacity input/output bus. This approach to conditional operation nearly doubles speed of various arithmetic operations.

Granulosa cell tumor induced massive recurrence of post hysterectomy leiomyoma

PubMed Central

Chalanki, Mohana Vamsy; Dattatreya, Satya; Padmaja, Parvathaneni; Dayal, Monal; Parakh, Megha; Rao, Vatturi Venkata Satya Prabhakar

2014-01-01

The authors report a very unusual occurrence of a massive recurrence of leiomyoma from post hysterectomy stump diagnosed on fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18-FDG PET/CT). The case also has an additional complexity of granulosa cell tumor (GCT) of ovary probably contributing to the recurrence and massive size. PMID:25210289

THE PREVALENCE AND IMPACT OF WOLF–RAYET STARS IN EMERGING MASSIVE STAR CLUSTERS

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

Sokal, Kimberly R.; Johnson, Kelsey E.; Indebetouw, Rémy

We investigate Wolf–Rayet (WR) stars as a source of feedback contributing to the removal of natal material in the early evolution of massive star clusters. Despite previous work suggesting that massive star clusters clear out their natal material before the massive stars evolve into the WR phase, WR stars have been detected in several emerging massive star clusters. These detections suggest that the timescale for clusters to emerge can be at least as long as the time required to produce WR stars (a few million years), and could also indicate that WR stars may be providing the tipping point inmore » the combined feedback processes that drive a massive star cluster to emerge. We explore the potential overlap between the emerging phase and the WR phase with an observational survey to search for WR stars in emerging massive star clusters hosting WR stars. We select candidate emerging massive star clusters from known radio continuum sources with thermal emission and obtain optical spectra with the 4 m Mayall Telescope at Kitt Peak National Observatory and the 6.5 m MMT.{sup 4} We identify 21 sources with significantly detected WR signatures, which we term “emerging WR clusters.” WR features are detected in ∼50% of the radio-selected sample, and thus we find that WR stars are commonly present in currently emerging massive star clusters. The observed extinctions and ages suggest that clusters without WR detections remain embedded for longer periods of time, and may indicate that WR stars can aid, and therefore accelerate, the emergence process.« less

Thought Leaders during Crises in Massive Social Networks

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

Corley, Courtney D.; Farber, Robert M.; Reynolds, William

The vast amount of social media data that can be gathered from the internet coupled with workflows that utilize both commodity systems and massively parallel supercomputers, such as the Cray XMT, open new vistas for research to support health, defense, and national security. Computer technology now enables the analysis of graph structures containing more than 4 billion vertices joined by 34 billion edges along with metrics and massively parallel algorithms that exhibit near-linear scalability according to number of processors. The challenge lies in making this massive data and analysis comprehensible to an analyst and end-users that require actionable knowledge tomore » carry out their duties. Simply stated, we have developed language and content agnostic techniques to reduce large graphs built from vast media corpora into forms people can understand. Specifically, our tools and metrics act as a survey tool to identify thought leaders' -- those members that lead or reflect the thoughts and opinions of an online community, independent of the source language.« less

Does massive intraabdominal free gas require surgical intervention?

PubMed

Furihata, Tadashi; Furihata, Makoto; Ishikawa, Kunibumi; Kosaka, Masato; Satoh, Naoki; Kubota, Keiichi

2016-08-28

We describe a rare case of an 81-year-old man who presented with severe epigastralgia. A chest radiograph showed massive free gas bilaterally in the diaphragmatic spaces. Computed tomography (CT) scan also showed massive free gas in the peritoneal cavity with portal venous gas. We used a wait-and-see approach and carefully considered surgery again when the time was appropriate. The patient received conservative therapy with fasting, an intravenous infusion of antibiotics, and nasogastric intubation. The patient soon recovered and was able to start eating meals 4 d after treatment; thus, surgical intervention was avoided. Thereafter, colonoscopy examination showed pneumatosis cystoides intestinalis in the ascending colon. On retrospective review, CT scan demonstrated sporadic air-filled cysts in the ascending colon. The present case taught us a lesson: the presence of massive intraabdominal free gas with portal venous gas does not necessarily require surgical intervention. Pneumatosis cystoides intestinalis should be considered as a potential causative factor of free gas with portal venous gas when making the differential diagnosis.

Reconstructing evolutionary trees in parallel for massive sequences.

PubMed

Zou, Quan; Wan, Shixiang; Zeng, Xiangxiang; Ma, Zhanshan Sam

2017-12-14

Building the evolutionary trees for massive unaligned DNA sequences is challenging and crucial. However, reconstructing evolutionary tree for ultra-large sequences is hard. Massive multiple sequence alignment is also challenging and time/space consuming. Hadoop and Spark are developed recently, which bring spring light for the classical computational biology problems. In this paper, we tried to solve the multiple sequence alignment and evolutionary reconstruction in parallel. HPTree, which is developed in this paper, can deal with big DNA sequence files quickly. It works well on the >1GB files, and gets better performance than other evolutionary reconstruction tools. Users could use HPTree for reonstructing evolutioanry trees on the computer clusters or cloud platform (eg. Amazon Cloud). HPTree could help on population evolution research and metagenomics analysis. In this paper, we employ the Hadoop and Spark platform and design an evolutionary tree reconstruction software tool for unaligned massive DNA sequences. Clustering and multiple sequence alignment are done in parallel. Neighbour-joining model was employed for the evolutionary tree building. We opened our software together with source codes via http://lab.malab.cn/soft/HPtree/ .

Infrared Color Selection of Massive Galaxies at z > 3

NASA Astrophysics Data System (ADS)

Wang, T.; Elbaz, D.; Schreiber, C.; Pannella, M.; Shu, X.; Willner, S. P.; Ashby, M. L. N.; Huang, J.-S.; Fontana, A.; Dekel, A.; Daddi, E.; Ferguson, H. C.; Dunlop, J.; Ciesla, L.; Koekemoer, A. M.; Giavalisco, M.; Boutsia, K.; Finkelstein, S.; Juneau, S.; Barro, G.; Koo, D. C.; Michałowski, M. J.; Orellana, G.; Lu, Y.; Castellano, M.; Bourne, N.; Buitrago, F.; Santini, P.; Faber, S. M.; Hathi, N.; Lucas, R. A.; Pérez-González, P. G.

2016-01-01

We introduce a new color selection technique to identify high-redshift, massive galaxies that are systematically missed by Lyman-break selection. The new selection is based on the H160 (H) and Infrared Array Camera (IRAC) 4.5 μm bands, specifically H-[4.5]\\gt 2.25 mag. These galaxies, called “HIEROs,” include two major populations that can be separated with an additional J - H color. The populations are massive and dusty star-forming galaxies at z\\gt 3 ({JH}-{blue}) and extremely dusty galaxies at z≲ 3 ({JH}-{red}). The 350 arcmin2 of the GOODS-North and GOODS-South fields with the deepest Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) near-infrared and IRAC data contain as many as 285 HIEROs down to [4.5]\\lt 24 mag. Inclusion of the most extreme HIEROs, not even detected in the H band, makes this selection particularly complete for the identification of massive high-redshift galaxies. We focus here primarily on {JH}-{blue} (z\\gt 3) HIEROs, which have a median photometric redshift < z> ˜ 4.4 and stellar mass {M}*˜ {10}10.6 {M}⊙ and are much fainter in the rest-frame UV than similarly massive Lyman-break galaxies (LBGs). Their star formation rates (SFRs), derived from their stacked infrared spectral energy distributions (SEDs), reach ˜240 {M}⊙ yr-1, leading to a specific SFR, {{sSFR}}\\equiv {{SFR}}/{M}*˜ 4.2 Gyr-1, suggesting that the sSFRs for massive galaxies continue to grow at z\\gt 2 but at a lower growth rate than from z = 0 to z = 2. With a median half-light radius of 2 kpc, including ˜ 20% as compact as quiescent (QS) galaxies at similar redshifts, {JH}-{blue} HIEROs represent perfect star-forming progenitors of the most massive ({M}*≳ {10}11.2 {M}⊙ ) compact QS galaxies at z˜ 3 and have the right number density. HIEROs make up ˜ 60% of all galaxies with {M}*\\gt {10}10.5 {M}⊙ identified at z\\gt 3 from their photometric redshifts. This is five times more than LBGs with nearly no overlap between the two populations

THE LOCATION, CLUSTERING, AND PROPAGATION OF MASSIVE STAR FORMATION IN GIANT MOLECULAR CLOUDS

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

Ochsendorf, Bram B.; Meixner, Margaret; Chastenet, Jérémy

Massive stars are key players in the evolution of galaxies, yet their formation pathway remains unclear. In this work, we use data from several galaxy-wide surveys to build an unbiased data set of ∼600 massive young stellar objects, ∼200 giant molecular clouds (GMCs), and ∼100 young (<10 Myr) optical stellar clusters (SCs) in the Large Magellanic Cloud. We employ this data to quantitatively study the location and clustering of massive star formation and its relation to the internal structure of GMCs. We reveal that massive stars do not typically form at the highest column densities nor centers of their parentmore » GMCs at the ∼6 pc resolution of our observations. Massive star formation clusters over multiple generations and on size scales much smaller than the size of the parent GMC. We find that massive star formation is significantly boosted in clouds near SCs. However, whether a cloud is associated with an SC does not depend on either the cloud’s mass or global surface density. These results reveal a connection between different generations of massive stars on timescales up to 10 Myr. We compare our work with Galactic studies and discuss our findings in terms of GMC collapse, triggered star formation, and a potential dichotomy between low- and high-mass star formation.« less

The RMS survey: galactic distribution of massive star formation

NASA Astrophysics Data System (ADS)

Urquhart, J. S.; Figura, C. C.; Moore, T. J. T.; Hoare, M. G.; Lumsden, S. L.; Mottram, J. C.; Thompson, M. A.; Oudmaijer, R. D.

2014-01-01

We have used the well-selected sample of ˜1750 embedded, young, massive stars identified by the Red MSX Source (RMS) survey to investigate the Galactic distribution of recent massive star formation. We present molecular line observations for ˜800 sources without existing radial velocities. We describe the various methods used to assign distances extracted from the literature and solve the distance ambiguities towards approximately 200 sources located within the solar circle using archival H I data. These distances are used to calculate bolometric luminosities and estimate the survey completeness (˜2 × 104 L⊙). In total, we calculate the distance and luminosity of ˜1650 sources, one third of which are above the survey's completeness threshold. Examination of the sample's longitude, latitude, radial velocities and mid-infrared images has identified ˜120 small groups of sources, many of which are associated with well-known star formation complexes, such as G305, G333, W31, W43, W49 and W51. We compare the positional distribution of the sample with the expected locations of the spiral arms, assuming a model of the Galaxy consisting of four gaseous arms. The distribution of young massive stars in the Milky Way is spatially correlated with the spiral arms, with strong peaks in the source position and luminosity distributions at the arms' Galactocentric radii. The overall source and luminosity surface densities are both well correlated with the surface density of the molecular gas, which suggests that the massive star formation rate per unit molecular mass is approximately constant across the Galaxy. A comparison of the distribution of molecular gas and the young massive stars to that in other nearby spiral galaxies shows similar radial dependences. We estimate the total luminosity of the embedded massive star population to be ˜0.76 × 108 L⊙, 30 per cent of which is associated with the 10 most active star-forming complexes. We measure the scaleheight as a

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.

Massive Young Star and its Cradle

NASA Image and Video Library

2010-07-14

This star-forming region, captured by NASA Spitzer Space Telescope, is dominated by the bright, young star IRAS 13481-6124; it is the first massive baby star for which astronomers could obtain a detailed look at the dusty disk closely encircling it.

Has Research on Collaborative Learning Technologies Addressed Massiveness? A Literature Review

ERIC Educational Resources Information Center

Manathunga, Kalpani; Hernández-Leo, Davinia

2015-01-01

There is a growing interest in understanding to what extent innovative educational technologies can be used to support massive courses. Collaboration is one of the main desired elements in massive learning actions involving large communities of participants. Accumulated research in collaborative learning technologies has proposed and evaluated…

Massive vulvar edema in a woman with preeclampsia: a case report.

PubMed

Daponte, Alexandros; Skentou, Hara; Dimopoulos, Konstantinos D; Kallitsaris, Athanasios; Messinis, Ioannis E

2007-11-01

Massive vulvar edema in a woman with preeclampsia preceded the development of massive ascites and impending eclampsia. A 17-year-old preeclamptic, primiparous woman was admitted with preeclampsia and massive vulvar edema. Other causes were excluded. The vulvar edema increased as the blood pressure and ascites increased, and a severe headache developed. Cesarean section for increasing preclampsia was performed. In the puerperium, the blood pressure improved and vulvar edema resolved. The clinical picture of the vulvar edema correlated with the severity of the preeclampsia. The presence of vulvar edema in women with preeclampsia should indicate immediate admission to the hospital. These patients must be considered as at high risk, and close monitoring must be instituted. In our case, vulvar edema preceded massive ascites development. We assume a common development mechanism for these signs in preeclampsia, due mainly to increased capillary permeability and hypoalbuminemia. The attending physician must be prepared for immediate delivery and possible preeclampsia complications in these patients.

The structure of the Cepheus E protostellar outflow: The jet, the bowshock, and the cavity

NASA Astrophysics Data System (ADS)

Lefloch, B.; Gusdorf, A.; Codella, C.; Eislöffel, J.; Neri, R.; Gómez-Ruiz, A. I.; Güsten, R.; Leurini, S.; Risacher, C.; Benedettini, M.

2015-09-01

Context. Protostellar outflows are a crucial ingredient of the star-formation process. However, the physical conditions in the warm outflowing gas are still poorly known. Aims: We present a multi-transition, high spectral resolution CO study of the outflow of the intermediate-mass Class 0 protostar Cep E-mm. The goal is to determine the structure of the outflow and to constrain the physical conditions of the various components in order to understand the origin of the mass-loss phenomenon. Methods: We have observed the J = 12-11, J = 13-12, and J = 16-15 CO lines at high spectral resolution with SOFIA/GREAT and the J = 5-4, J = 9-8, and J = 14-13 CO lines with HIFI/Herschel towards the position of the terminal bowshock HH377 in the southern outflow lobe. These observations were complemented with maps of CO transitions obtained with the IRAM 30 m telescope (J = 1-0, 2-1), the Plateau de Bure interferometer (J = 2-1), and the James Clerk Maxwell Telescope (J = 3-2, 4-3). Results: We identify three main components in the protostellar outflow: the jet, the cavity, and the bowshock, with a typical size of 1.7″ × 21″, 4.5″, and 22″ × 10″, respectively. In the jet, the emission from the low-J CO lines is dominated by a gas layer at Tkin = 80-100 K, column density N(CO) = 9 × 1016 cm-2, and density n(H2) = (0.5-1) × 105 cm-3; the emission of the high-J CO lines arises from a warmer (Tkin = 400-750 K), denser (n(H2) = (0.5-1) × 106 cm-3), lower column density (N(CO) = 1.5 × 1016 cm-2) gas component. Similarly, in the outflow cavity, two components are detected: the emission of the low-J lines is dominated by a gas layer of column density N(CO) = 7 × 1017 cm-2 at Tkin = 55-85 K and density in the range (1-8) × 105 cm-3; the emission of the high-J lines is dominated by a hot, denser gas layer with Tkin = 500-1500K, n(H2) = (1-5) × 106 cm-3, and N(CO) = 6 × 1016 cm-2. A temperature gradient as a function of the velocity is found in the high-excitation gas

a UV Spectral Library of Metal-Poor Massive Stars

NASA Astrophysics Data System (ADS)

Robert, Carmelle

1994-01-01

We propose to use the FOS to build a snapshot library of UV spectra of a sample of about 50 metal-poor massive stars located in the Magellanic Clouds. The majority of libraries already existing contains spectra of hot stars with chemical abundances close to solar. The high spectral resolution achieves with the FOS will be a major factor for the uniqueness of this new library. UV spectral libraries represent fundamental tools for the study of the massive star populations of young star-forming regions. Massive stars, which are impossible to identify directly in the optical-IR part of a composite spectrum, display on the other hand key signatures in the UV region. These signatures are mainly broad, metallicity dependent spectral features formed in the hot star winds. They require a high spectral resolution (of the order of 200-300 km/s) for an adequate study. A spectral library of metal-poor massive stars represents also a unique source of data for a stellar atmosphere analysis. Within less then 10 min we will obtain a high signal-to-noise ratio of at least 30. Finally, since short exposure times are possible, this proposal makes extremely good use of the capabilities of HST. We designed an observing strategy which yields a maximum scientific return at a minimum cost of spacecraft time.

Very Massive Stars in the local Universe

NASA Astrophysics Data System (ADS)

Vink, Jorick S.; Heger, Alexander; Krumholz, Mark R.; Puls, Joachim; Banerjee, S.; Castro, N.; Chen, K.-J.; Chenè, A.-N.; Crowther, P. A.; Daminelli, A.; Gräfener, G.; Groh, J. H.; Hamann, W.-R.; Heap, S.; Herrero, A.; Kaper, L.; Najarro, F.; Oskinova, L. M.; Roman-Lopes, A.; Rosen, A.; Sander, A.; Shirazi, M.; Sugawara, Y.; Tramper, F.; Vanbeveren, D.; Voss, R.; Wofford, A.; Zhang, Y.

2015-03-01

Recent studies have claimed the existence of very massive stars (VMS) up to 300 M ⊙ in the local Universe. As this finding may represent a paradigm shift for the canonical stellar upper-mass limit of 150 M ⊙, it is timely to discuss the status of the data, as well as the far-reaching implications of such objects. We held a Joint Discussion at the General Assembly in Beijing to discuss (i) the determination of the current masses of the most massive stars, (ii) the formation of VMS, (iii) their mass loss, and (iv) their evolution and final fate. The prime aim was to reach broad consensus between observers and theorists on how to identify and quantify the dominant physical processes.

Massive ovarian edema, due to adjacent appendicitis.

PubMed

Callen, Andrew L; Illangasekare, Tushani; Poder, Liina

2017-04-01

Massive ovarian edema is a benign clinical entity, the imaging findings of which can mimic an adnexal mass or ovarian torsion. In the setting of acute abdominal pain, identifying massive ovarian edema is a key in avoiding potential fertility-threatening surgery in young women. In addition, it is important to consider other contributing pathology when ovarian edema is secondary to another process. We present a case of a young woman presenting with subacute abdominal pain, whose initial workup revealed marked enlarged right ovary. Further imaging, diagnostic tests, and eventually diagnostic laparoscopy revealed that the ovarian enlargement was secondary to subacute appendicitis, rather than a primary adnexal process. We review the classic ultrasound and MRI imaging findings and pitfalls that relate to this diagnosis.

Facial transplantation for massive traumatic injuries.

PubMed

Alam, Daniel S; Chi, John J

2013-10-01

This article describes the challenges of facial reconstruction and the role of facial transplantation in certain facial defects and injuries. This information is of value to surgeons assessing facial injuries with massive soft tissue loss or injury. Copyright © 2013 Elsevier Inc. All rights reserved.

Massive plexiform neurofibromas in childhood: natural history and management issues.

PubMed

Serletis, Demitre; Parkin, Patricia; Bouffet, Eric; Shroff, Manohar; Drake, James M; Rutka, James T

2007-05-01

The authors review their experience with massive plexiform neurofibromas (PNs) in patients with pediatric neurofibromatosis Type 1 (NF1) to better characterize the natural history and management of these complex lesions. The authors performed a retrospective review of data obtained in seven patients with NF1 in whom massive PNs were diagnosed at The Hospital for Sick Children in Toronto, Ontario, Canada. These patients attended routine follow-up examinations conducted by a number of specialists, and serial neuroimaging studies were obtained to monitor disease progression. The most common presenting feature of PN was that of a painful, expanding lesion. Furthermore, two patients harbored multiple, distinct PNs affecting different body sites. With respect to management, two patients were simply observed, undergoing serial neuroimaging studies; two patients underwent biopsy sampling of their plexiform lesions; two patients underwent attempted medical treatment (farnesyl transferase inhibitor, R11577, and cyclophosphamide chemotherapy); and three patients required surgical debulking of their PNs because the massive growth of these tumors caused functional compromise. Ultimately, one patient died of respiratory complications due to progressive growth of the massive PN lesion. In this review of their experience, the authors found certain features that underscore the presentation and natural history of PNs. The management of these complex lesions, however, remains unclear. Slow-growing PNs may be observed conservatively, but the authors' experience suggests that resection should be considered in selected cases involving significant deterioration or functional compromise. Nevertheless, patients with massive PNs will benefit from close surveillance by a team of specialists to monitor for ongoing disease progression.

A massive, quiescent galaxy at a redshift of 3.717.

PubMed

Glazebrook, Karl; Schreiber, Corentin; Labbé, Ivo; Nanayakkara, Themiya; Kacprzak, Glenn G; Oesch, Pascal A; Papovich, Casey; Spitler, Lee R; Straatman, Caroline M S; Tran, Kim-Vy H; Yuan, Tiantian

2017-04-05

Finding massive galaxies that stopped forming stars in the early Universe presents an observational challenge because their rest-frame ultraviolet emission is negligible and they can only be reliably identified by extremely deep near-infrared surveys. These surveys have revealed the presence of massive, quiescent early-type galaxies appearing as early as redshift z ≈ 2, an epoch three billion years after the Big Bang. Their age and formation processes have now been explained by an improved generation of galaxy-formation models, in which they form rapidly at z ≈ 3-4, consistent with the typical masses and ages derived from their observations. Deeper surveys have reported evidence for populations of massive, quiescent galaxies at even higher redshifts and earlier times, using coarsely sampled photometry. However, these early, massive, quiescent galaxies are not predicted by the latest generation of theoretical models. Here we report the spectroscopic confirmation of one such galaxy at redshift z = 3.717, with a stellar mass of 1.7 × 10 11 solar masses. We derive its age to be nearly half the age of the Universe at this redshift and the absorption line spectrum shows no current star formation. These observations demonstrate that the galaxy must have formed the majority of its stars quickly, within the first billion years of cosmic history in a short, extreme starburst. This ancestral starburst appears similar to those being found by submillimetre-wavelength surveys. The early formation of such massive systems implies that our picture of early galaxy assembly requires substantial revision.

A massive, quiescent galaxy at a redshift of 3.717

NASA Astrophysics Data System (ADS)

Glazebrook, Karl; Schreiber, Corentin; Labbé, Ivo; Nanayakkara, Themiya; Kacprzak, Glenn G.; Oesch, Pascal A.; Papovich, Casey; Spitler, Lee R.; Straatman, Caroline M. S.; Tran, Kim-Vy H.; Yuan, Tiantian

2017-04-01

Finding massive galaxies that stopped forming stars in the early Universe presents an observational challenge because their rest-frame ultraviolet emission is negligible and they can only be reliably identified by extremely deep near-infrared surveys. These surveys have revealed the presence of massive, quiescent early-type galaxies appearing as early as redshift z ≈ 2, an epoch three billion years after the Big Bang. Their age and formation processes have now been explained by an improved generation of galaxy-formation models, in which they form rapidly at z ≈ 3-4, consistent with the typical masses and ages derived from their observations. Deeper surveys have reported evidence for populations of massive, quiescent galaxies at even higher redshifts and earlier times, using coarsely sampled photometry. However, these early, massive, quiescent galaxies are not predicted by the latest generation of theoretical models. Here we report the spectroscopic confirmation of one such galaxy at redshift z = 3.717, with a stellar mass of 1.7 × 1011 solar masses. We derive its age to be nearly half the age of the Universe at this redshift and the absorption line spectrum shows no current star formation. These observations demonstrate that the galaxy must have formed the majority of its stars quickly, within the first billion years of cosmic history in a short, extreme starburst. This ancestral starburst appears similar to those being found by submillimetre-wavelength surveys. The early formation of such massive systems implies that our picture of early galaxy assembly requires substantial revision.

Massive units deposited by bedload transport in sheet flow mode

NASA Astrophysics Data System (ADS)

Viparelli, E.; Hernandez Moreira, R. R.; Jafarinik, S.; Sanders, S.; Huffman, B.; Parker, G.; Kendall, C.

2017-12-01

A sandy massive (structureless) unit overlying a basal erosional surface and underlying a parallel or cross-laminated unit often characterizes turbidity current and coastal storm deposits. The basal massive units are thought to be the result of relatively rapid deposition of suspended sediment. However, suspension-based models fail to explain how basal massive units can be emplaced for long distances, far away from the source and can contain gravel particles as floating clasts. Here we present experimental results that can significantly change the understanding of the processes forming turbidity current and coastal storm deposits. The experiments were performed in open channel flow mode in the Hydraulics Laboratory at the University of South Carolina. The sediment was a mixture of sand size particles with a geometric mean diameter of 0.95 mm and a geometric standard deviation of 1.65. Five experiments were performed with a flow rate of 30 l/s and sediment feed rates varying between 1.5 kg/min and 20 kg/min. Each experiment was characterized by two phases, 1) the equilibration phase, in which we waited for the system to reach equilibrium condition, and 2) the aggradation phase, in which we slowly raised the water surface base level to induce channel bed aggradation under the same transport conditions observed over the equilibrium bed. Our experiments show that sandy massive units can be the result of deposition from a thick bedload layer of colliding grains, the sheet flow layer. The presence of this sheet flow layer explains how a strong, sustained current can emplace extensive massive units containing gravel clasts. Although our experiments were conducted in open-channel mode, observations of bedload driven by density underflows suggest that our results are directly applicable to sheet flows driven by deep-sea turbidity currents. More specifically, we believe that this mechanism offers an explanation for massive turbidites that heretofore have been identified as

Cosmic string loops as the seeds of super-massive black holes

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

Bramberger, Sebastian F.; Brandenberger, Robert H.; Jreidini, Paul

2015-06-01

Recent discoveries of super-massive black holes at high redshifts indicate a possible tension with the standard ΛCDM paradigm of early universe cosmology which has difficulties in explaining the origin of the required nonlinear compact seeds which trigger the formation of these super-massive black holes. Here we show that cosmic string loops which result from a scaling solution of strings formed during a phase transition in the very early universe lead to an additional source of compact seeds. The number density of string-induced seeds dominates at high redshifts and can help trigger the formation of the observed super-massive black holes.

Ghosts, strong coupling, and accidental symmetries in massive gravity

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

Deffayet, C.; GReCO/IAP, 98 bis boulevard Arago, 75014 Paris; Rombouts, J.-W.

2005-08-15

We show that the strong self-interaction of the scalar polarization of a massive graviton can be understood in terms of the propagation of an extra ghostlike degree of freedom, thus relating strong coupling to the sixth degree of freedom discussed by Boulware and Deser in their Hamiltonian analysis of massive gravity. This enables one to understand the Vainshtein recovery of solutions of massless gravity as being due to the effect of the exchange of this ghost, which gets frozen at distances larger than the Vainshtein radius. Inside this region, we can trust the two-field Lagrangian perturbatively, while at larger distancesmore » one can use the higher derivative formulation. We also compare massive gravity with other models, namely, deconstructed theories of gravity, as well as the Dvali-Gabadadze-Porrati model. In the latter case, we argue that the Vainshtein recovery process is of a different nature, not involving a ghost degree of freedom.« less

The Massive Star-Forming Regions Omnibus X-Ray Catalog

NASA Astrophysics Data System (ADS)

Townsley, Leisa K.; Broos, Patrick S.; Garmire, Gordon P.; Bouwman, Jeroen; Povich, Matthew S.; Feigelson, Eric D.; Getman, Konstantin V.; Kuhn, Michael A.

2014-07-01

We present the Massive Star-forming Regions (MSFRs) Omnibus X-ray Catalog (MOXC), a compendium of X-ray point sources from Chandra/ACIS observations of a selection of MSFRs across the Galaxy, plus 30 Doradus in the Large Magellanic Cloud. MOXC consists of 20,623 X-ray point sources from 12 MSFRs with distances ranging from 1.7 kpc to 50 kpc. Additionally, we show the morphology of the unresolved X-ray emission that remains after the cataloged X-ray point sources are excised from the ACIS data, in the context of Spitzer and WISE observations that trace the bubbles, ionization fronts, and photon-dominated regions that characterize MSFRs. In previous work, we have found that this unresolved X-ray emission is dominated by hot plasma from massive star wind shocks. This diffuse X-ray emission is found in every MOXC MSFR, clearly demonstrating that massive star feedback (and the several-million-degree plasmas that it generates) is an integral component of MSFR physics.

Massive star formation at high spatial resolution

NASA Astrophysics Data System (ADS)

Pascucci, Ilaria

2004-05-01

This thesis studies the early phases of massive stars and their impact on the surrounding. The capabilities of continuum radiative transfer (RT) codes to interpret the observations are also investigated. The main results of this work are: 1) Two massive star-forming regions are observed in the infrared. The thermal emission from the ultra-compact H II regions is resolved and the spectral type of the ionizing stars is estimated. The hot cores are not detected thus implying line-of-sight extinction larger than 200 visual magnitude. 2) The first mid-infrared interferometric measurements towards a young massive star resolve thermal emission on scales of 30-50 AU probing the size of the predicted disk. The visibility curve differs from those of intermediate-mass stars. 3) The close vicinity of Θ1C Ori are imaged using the NACO adaptive optics system. The binary proplyd Orion 168-326 and its interaction with the wind from Θ1C Ori are resolved. A proplyd uniquely seen face-on is also identified. 4) Five RT codes are compared in a disk configuration. The solutions provide the first 2D benchmark and serve to test the reliability of other RT codes. The images/visibilities from two RT codes are compared for a distorted disk. The parameter range in which such a distortion is detectable with MIDI is explored.

Complexity-action duality of the shock wave geometry in a massive gravity theory

NASA Astrophysics Data System (ADS)

Miao, Yan-Gang; Zhao, Long

2018-01-01

On the holographic complexity dual to the bulk action, we investigate the action growth for a shock wave geometry in a massive gravity theory within the Wheeler-DeWitt (WDW) patch at the late time limit. For a global shock wave, the graviton mass does not affect the action growth in the bulk, i.e., the complexity on the boundary, showing that the action growth (complexity) is the same for both the Einstein gravity and the massive gravity. Nevertheless, for a local shock wave that depends on transverse coordinates, the action growth (complexity) caused by the boundary disturbance (perturbation) is proportional to the butterfly velocity for the two gravity theories, but the butterfly velocity of the massive gravity theory is smaller than that of the Einstein gravity theory, indicating that the action growth (complexity) of the massive gravity is depressed by the graviton mass. In addition, we extend the black hole thermodynamics of the massive gravity and obtain the right Smarr formula.

Role of Massive Stars in the Evolution of Primitive Galaxies

NASA Technical Reports Server (NTRS)

Heap, Sara

2012-01-01

An important factor controlling galaxy evolution is feedback from massive stars. It is believed that the nature and intensity of stellar feedback changes as a function of galaxy mass and metallicity. At low mass and metallicity, feedback from massive stars is mainly in the form of photoionizing radiation. At higher mass and metallicity, it is in stellar winds. IZw 18 is a local blue, compact dwarf galaxy that meets the requirements for a primitive galaxy: low halo mass greater than 10(exp 9)Msun, strong photoionizing radiation, no galactic outflow, and very low metallicity,log(O/H)+12=7.2. We will describe the properties of massive stars and their role in the evolution of IZw 18, based on analysis of ultraviolet images and spectra obtained with HST.

Massive star winds interacting with magnetic fields on various scales

NASA Astrophysics Data System (ADS)

David-Uraz, A.; Petit, V.; Erba, C.; Fullerton, A.; Walborn, N.; MacInnis, R.

2018-01-01

One of the defining processes which govern massive star evolution is their continuous mass loss via dense, supersonic line-driven winds. In the case of those OB stars which also host a surface magnetic field, the interaction between that field and the ionized outflow leads to complex circumstellar structures known as magnetospheres. In this contribution, we review recent developments in the field of massive star magnetospheres, including current efforts to characterize the largest magnetosphere surrounding an O star: that of NGC 1624-2. We also discuss the potential of the "analytic dynamical magnetosphere" (ADM) model to interpret multi-wavelength observations. Finally, we examine the possible effects of — heretofore undetected — small-scale magnetic fields on massive star winds and compare their hypothetical consequences to existing, unexplained observations.

The massive stellar population of W49: A spectroscopic survey

NASA Astrophysics Data System (ADS)

Wu, Shi-Wei; Bik, Arjan; Bestenlehner, Joachim M.; Henning, Thomas; Pasquali, Anna; Brandner, Wolfgang; Stolte, Andrea

2016-05-01

Context. Massive stars form on different scales that range from large, dispersed OB associations to compact, dense starburst clusters. The complex structure of regions of massive star formation and the involved short timescales provide a challenge for our understanding of their birth and early evolution. As one of the most massive and luminous star-forming region in our Galaxy, W49 is the ideal place to study the formation of the most massive stars. Aims: By classifying the massive young stars that are deeply embedded in the molecular cloud of W49, we aim to investigate and trace the star formation history of this region. Methods: We analyse near-infrared K-band spectroscopic observations of W49 from LBT/LUCI combined with JHK images obtained with NTT/SOFI and LBT/LUCI. Based on JHK-band photometry and K-band spectroscopy, the massive stars are placed in a Hertzsprung Russell diagram. By comparison with evolutionary models, their age and hence the star formation history of W49 can be investigated. Results: Fourteen O-type stars, as well as two young stellar objects (YSOs), are identified by our spectroscopic survey. Eleven O stars are main sequence stars with subtypes ranging from O3 to O9.5 and masses ranging from ~20 M⊙ to ~120 M⊙. Three of the O stars show strong wind features and are considered to be Of-type supergiants with masses beyond 100 M⊙. The two YSOs show CO emission, which is indicative of the presence of circumstellar disks in the central region of the massive cluster. The age of the cluster is estimated as ~1.5 Myr, with star formation continuing in different parts of the region. The ionising photons from the central massive stars have not yet cleared the molecular cocoon surrounding the cluster. W49 is comparable to extragalactic star-forming regions, and it provides us with a unique chance to study a starburst in detail. Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among

Massive blood transfusion during hospitalization for delivery in New York State, 1998-2007.

PubMed

Mhyre, Jill M; Shilkrut, Alexander; Kuklina, Elena V; Callaghan, William M; Creanga, Andreea A; Kaminsky, Sari; Bateman, Brian T

2013-12-01

To define the frequency, risk factors, and outcomes of massive transfusion in obstetrics. The State Inpatient Dataset for New York (1998-2007) was used to identify all delivery hospitalizations for hospitals that reported at least one delivery-related transfusion per year. Multivariable logistic regression analysis was performed to examine the relationship between maternal age, race, and relevant clinical variables and the risk of massive blood transfusion defined as 10 or more units of blood recorded. Massive blood transfusion complicated 6 of every 10,000 deliveries with cases observed even in the smallest facilities. Risk factors with the strongest independent associations with massive blood transfusion included abnormal placentation (1.6/10,000 deliveries, adjusted odds ratio [OR] 18.5, 95% confidence interval [CI] 14.7-23.3), placental abruption (1.0/10,000, adjusted OR 14.6, 95% CI 11.2-19.0), severe preeclampsia (0.8/10,000, adjusted OR 10.4, 95% CI 7.7-14.2), and intrauterine fetal demise (0.7/10,000, adjusted OR 5.5, 95% CI 3.9-7.8). The most common etiologies of massive blood transfusion were abnormal placentation (26.6% of cases), uterine atony (21.2%), placental abruption (16.7%), and postpartum hemorrhage associated with coagulopathy (15.0%). A disproportionate number of women who received a massive blood transfusion experienced severe morbidity including renal failure, acute respiratory distress syndrome, sepsis, and in-hospital death. Massive blood transfusion was infrequent, regardless of facility size. In the presence of known risk for receipt of massive blood transfusion, women should be informed of this possibility, should deliver in a well-resourced facility if possible, and should receive appropriate blood product preparation and venous access in advance of delivery. : II.

The TESIS Project: Revealing Massive Early-Type Galaxies at z > 1

NASA Astrophysics Data System (ADS)

Saracco, P.; Longhetti, M.; Severgnini, P.; Della Ceca, R.; Braito, V.; Bender, R.; Drory, N.; Feulner, G.; Hopp, U.; Mannucci, F.; Maraston, C.

How and when present-day massive early-type galaxies built up and what type of evolution has characterized their growth (star formation and/or merging) still remain open issues. The different competing scenarios of galaxy formation predict much different properties of early-type galaxies at z > 1. The "monolithic" collapse predicts that massive spheroids formed at high redshift (z > 2.5-3) and that their comoving density is constant at z < 2.5-3 since they evolve only in luminosity. On the contrary, in the hierarchical scenario massive spheroids are built up through subsequent mergers reaching their final masses at z < 1.5 [3,5]. As a consequence, massive systems are very rare at z > 1, their comoving density decreases from z = 0 to z ~ 1.5 and they should experience their last burst of star formation at z < 1.5, concurrent with the merging event(s) of their formation. These opposed predicted properties of early-types at z > 1 can be probed observationally once a well defined sample of massive early-types at z > 1 is available. We are constructing such a sample through a dedicated near-IR very low resolution (λ/Δλ≃50) spectroscopic survey (TNG EROs Spectroscopic Identification Survey, TESIS, [6]) of a complete sample of 30 bright (K < 18.5) Extremely Red Objects (EROs).

Evolution and Nucleosynthesis of Massive Stars

NASA Astrophysics Data System (ADS)

Meynet, Georges; Maeder, André; Choplin, Arthur; Takahashi, Koh; Ekström, Sylvia; Hirschi, Raphael; Chiappini, Cristina; Eggenberger, Patrick

Massive stars are rapid nuclear reactors that play a key role in injecting new synthesized elements in the interstellar medium. Depending on the strengths of the stellar winds on the efficiency of mixing processes, the masses and the chemical compositions of their ejecta can be dramatically different. In a first part, we describe two types of rotating models differing by the physics involved and discussing various consequences. In a second part, we focus on the impacts of rotation in massive stars at very low metallicity. Various nucleosynthetic signatures pointing towards the need for some extra-mixing in the first generation of stars are presented. This extra-mixing has great chance to be driven by rotation for the following reasons: 1) when the metallicity decreases, the formation of fast rotators seem to be favored; 2) rotational mixing is more efficient at low metallicities; 3) primary nitrogen is produced only at low metallicities a fact that can be well explained by more efficient rotational mixing at low metallicities.

Visser's massive graviton bimetric theory revisited

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

Roany, Alain de; Chauvineau, Bertrand; Freitas Pacheco, Jose A. de

2011-10-15

A massive gravity theory was proposed by Visser in the late 1990s. This theory, based on a background metric b{sub {alpha}{beta}} and on an usual dynamical metric g{sub {alpha}{beta}} has the advantage of being free of ghosts as well as discontinuities present in other massive theories proposed in the past. In the present investigation, the equations of Visser's theory are revisited with particular care on the related conservation laws. It will be shown that a multiplicative factor is missing in the graviton tensor originally derived by Visser, which has no incidence on the weak field approach but becomes important inmore » the strong field regime when, for instance, cosmological applications are considered. In this case, contrary to some previous claims found in the literature, we conclude that a nonstatic background metric is required in order to obtain a solution able to mimic the {Lambda}CDM cosmology.« less

Probing massive stars around gamma-ray burst progenitors

NASA Astrophysics Data System (ADS)

Lu, Wenbin; Kumar, Pawan; Smoot, George F.

2015-10-01

Long gamma-ray bursts (GRBs) are produced by ultra-relativistic jets launched from core collapse of massive stars. Most massive stars form in binaries and/or in star clusters, which means that there may be a significant external photon field (EPF) around the GRB progenitor. We calculate the inverse-Compton scattering of EPF by the hot electrons in the GRB jet. Three possible cases of EPF are considered: the progenitor is (I) in a massive binary system, (II) surrounded by a Wolf-Rayet-star wind and (III) in a dense star cluster. Typical luminosities of 1046-1050 erg s-1 in the 1-100 GeV band are expected, depending on the stellar luminosity, binary separation (I), wind mass-loss rate (II), stellar number density (III), etc. We calculate the light curve and spectrum in each case, taking fully into account the equal-arrival time surfaces and possible pair-production absorption with the prompt γ-rays. Observations can put constraints on the existence of such EPFs (and hence on the nature of GRB progenitors) and on the radius where the jet internal dissipation process accelerates electrons.

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.

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

Bosonization of fermions coupled to topologically massive gravity

NASA Astrophysics Data System (ADS)

Fradkin, Eduardo; Moreno, Enrique F.; Schaposnik, Fidel A.

2014-03-01

We establish a duality between massive fermions coupled to topologically massive gravity (TMG) in d=3 space-time dimensions and a purely gravity theory which also will turn out to be a TMG theory but with different parameters: the original graviton mass in the TMG theory coupled to fermions picks up a contribution from fermion bosonization. We obtain explicit bosonization rules for the fermionic currents and for the energy-momentum tensor showing that the identifications do not depend explicitly on the parameters of the theory. These results are the gravitational analog of the results for 2+1 Abelian and non-Abelian bosonization in flat space-time.

A high abundance of massive galaxies 3-6 billion years after the Big Bang.

PubMed

Glazebrook, Karl; Abraham, Roberto G; McCarthy, Patrick J; Savaglio, Sandra; Chen, Hsiao-Wen; Crampton, David; Murowinski, Rick; Jørgensen, Inger; Roth, Kathy; Hook, Isobel; Marzke, Ronald O; Carlberg, R G

2004-07-08

Hierarchical galaxy formation is the model whereby massive galaxies form from an assembly of smaller units. The most massive objects therefore form last. The model succeeds in describing the clustering of galaxies, but the evolutionary history of massive galaxies, as revealed by their visible stars and gas, is not accurately predicted. Near-infrared observations (which allow us to measure the stellar masses of high-redshift galaxies) and deep multi-colour images indicate that a large fraction of the stars in massive galaxies form in the first 5 Gyr (refs 4-7), but uncertainties remain owing to the lack of spectra to confirm the redshifts (which are estimated from the colours) and the role of obscuration by dust. Here we report the results of a spectroscopic redshift survey that probes the most massive and quiescent galaxies back to an era only 3 Gyr after the Big Bang. We find that at least two-thirds of massive galaxies have appeared since this era, but also that a significant fraction of them are already in place in the early Universe.

The architecture of tomorrow's massively parallel computer

NASA Technical Reports Server (NTRS)

Batcher, Ken

1987-01-01

Goodyear Aerospace delivered the Massively Parallel Processor (MPP) to NASA/Goddard in May 1983, over three years ago. Ever since then, Goodyear has tried to look in a forward direction. There is always some debate as to which way is forward when it comes to supercomputer architecture. Improvements to the MPP's massively parallel architecture are discussed in the areas of data I/O, memory capacity, connectivity, and indirect (or local) addressing. In I/O, transfer rates up to 640 megabytes per second can be achieved. There are devices that can supply the data and accept it at this rate. The memory capacity can be increased up to 128 megabytes in the ARU and over a gigabyte in the staging memory. For connectivity, there are several different kinds of multistage networks that should be considered.

Fates of the most massive primordial stars

NASA Astrophysics Data System (ADS)

Chen, Ke-Jung; Heger, Alexander; Almgren, Ann; Woosley, Stan

2012-09-01

We present our results of numerical simulations of the most massive primordial stars. For the extremely massive non-rotating Pop III stars over 300Msolar, they would simply die as black holes. But the Pop III stars with initial masses 140 - 260Msolar may have died as gigantic explosions called pair-instability supernovae (PSNe). We use a new radiation-hydrodynamics code CASTRO to study evolution of PSNe. Our models follow the entire explosive burning and the explosion until the shock breaks out from the stellar surface. In our simulations, we find that fluid instabilities occurred during the explosion. These instabilities are driven by both nuclear burning and hydrodynamical instability. In the red supergiant models, fluid instabilities can lead to significant mixing of supernova ejecta and alter the observational signature.

The low-metallicity starburst NGC346: massive-star population and feedback

NASA Astrophysics Data System (ADS)

Oskinova, Lida

2017-08-01

The Small Magellanic Cloud (SMC) is ideal to study young, massive stars at low metallicity. The compact cluster NGC346 contains about half of all O-type stars in the entire SMC. The massive-star population of this cluster powers N66, the brightest and largest HII region in the SMC. We propose to use HST-STIS to slice NGC346 with 20 long-slit exposures, in order to obtain the UV spectra of most of the massive early-type stars of this cluster. Archival data of 13 exposures that cover already a minor part of this cluster will be included in our analyses. Our aim is to quantitatively analyze virtually the whole massive-star population of NGC346. We have already secured the optical spectra of all massive stars in the field with the integral-field spectrograph MUSE at the ESO-VLT. However, for the determination of the stellar-wind parameters, i.e. the mass-loss rates and the wind velocities, ultraviolet spectra are indispensable. Our advanced Potsdam Wolf-Rayet (PoWR) code will be used for modeling the stellar and wind spectra in the course of the analysis. Finally, we will obtain:(a) the fundamental stellar and wind parameters of all stars brighter than spectral type B2V in the field, which, e,g,, will constrain the initial mass function in this young low-metallicity starburst;(b) mass-loss rates of many more OB-type stars at SMC metallicity than hitherto known, allowing to better constrain their metallicity dependence;(c) the integrated feedback by ionizing radiation and stellar winds of the whole massive-star population of NGC346, which will be used as input to model the ecology of the giant HII region N66.These HST UV data will be of high legacy value.

Formation and pre-MS Evolution of Massive Stars with Growing Accretion

NASA Astrophysics Data System (ADS)

Maeder, A.; Behrend, R.

2002-10-01

We briefly describe the three existing scenarios for forming massive stars and emphasize that the arguments often used to reject the accretion scenario for massive stars are misleading. It is usually not accounted for the fact that the turbulent pressure associated to large turbulent velocities in clouds necessarily imply relatively high accretion rates for massive stars. We show the basic difference between the formation of low and high mass stars based on the values of the free fall time and of the Kelvin-Helmholtz timescale, and define the concept of birthline for massive stars. Due to D-burning, the radius and location of the birthline in the HR diagram, as well as the lifetimes are very sensitive to the accretion rate dM/dt(accr). If a form dM/dt(accr) propto A(M/Msun)phi is adopted, the observations in the HR diagram and the lifetimes support a value of A approx 10-5 Msun/yr and a value of phi > 1. Remarkably, such a law is consistent with the relation found by Churchwell and Henning et al. between the outflow rates and the luminosities of ultracompact HII regions, if we assume that a fraction 0.15 to 0.3 of the global inflow is accreted. The above relation implies high dM/dt(accr) approx 10-3 Msun/yr for the most massive stars. The physical possibility of such high dM/dt(accr) is supported by current numerical models. Finally, we give simple analytical arguments in favour of the growth of dM/dt(accr) with the already accreted mass. We also suggest that due to Bondi-Hoyle accretion, the formation of binary stars is largely favoured among massive stars in the accretion scenario.

Multiplicity in Early Stellar Evolution

NASA Astrophysics Data System (ADS)

Reipurth, B.; Clarke, C. J.; Boss, A. P.; Goodwin, S. P.; Rodríguez, L. F.; Stassun, K. G.; Tokovinin, A.; Zinnecker, H.

Observations from optical to centimeter wavelengths have demonstrated that multiple systems of two or more bodies is the norm at all stellar evolutionary stages. Multiple systems are widely agreed to result from the collapse and fragmentation of cloud cores, despite the inhibiting influence of magnetic fields. Surveys of class 0 protostars with millimeter interferometers have revealed a very high multiplicity frequency of about 2/3, even though there are observational difficulties in resolving close protobinaries, thus supporting the possibility that all stars could be born in multiple systems. Near-infrared adaptive optics observations of class I protostars show a lower binary frequency relative to the class 0 phase, a declining trend that continues through the class II/III stages to the field population. This loss of companions is a natural consequence of dynamical interplay in small multiple systems, leading to ejection of members. We discuss observational consequences of this dynamical evolution, and its influence on circumstellar disks, and we review the evolution of circumbinary disks and their role in defining binary mass ratios. Special attention is paid to eclipsing PMS binaries, which allow for observational tests of evolutionary models of early stellar evolution. Many stars are born in clusters and small groups, and we discuss how interactions in dense stellar environments can significantly alter the distribution of binary separations through dissolution of wider binaries. The binaries and multiples we find in the field are the survivors of these internal and external destructive processes, and we provide a detailed overview of the multiplicity statistics of the field, which form a boundary condition for all models of binary evolution. Finally, we discuss various formation mechanisms for massive binaries, and the properties of massive trapezia.

The Structure of the Star-forming Cluster RCW 38

NASA Astrophysics Data System (ADS)

Winston, E.; Wolk, S. J.; Bourke, T. L.; Megeath, S. T.; Gutermuth, R.; Spitzbart, B.

2011-12-01

We present a study of the structure of the high-mass star-forming region RCW 38 and the spatial distribution of its young stellar population. Spitzer Infrared Array Camera (IRAC) photometry (3-8 μm) is combined with Two Micron All Sky Survey near-IR data to identify young stellar objects (YSOs) by IR-excess emission from their circumstellar material. Chandra X-ray data are used to identify class III pre-main-sequence stars lacking circumstellar material. We identify 624 YSOs: 23 class 0/I and 90 flat spectrum protostars, 437 class II stars, and 74 class III stars. We also identify 29 (27 new) O star candidates over the IRAC field. Seventy-two stars exhibit IR-variability, including 7 class 0/I and 12 flat spectrum YSOs. A further 177 tentative candidates are identified by their location in the IRAC [3.6] versus [3.6]-[5.8] color-magnitude diagram. We find strong evidence of subclustering in the region. Three subclusters were identified surrounding the central cluster, with massive and variable stars in each subcluster. The central region shows evidence of distinct spatial distributions of the protostars and pre-main-sequence stars. A previously detected IR cluster, DB2001_Obj36, has been established as a subcluster of RCW 38. This suggests that star formation in RCW 38 occurs over a more extended area than previously thought. The gas-to-dust ratio is examined using the X-ray derived hydrogen column density, N H and the K-band extinction, and found to be consistent with the diffuse interstellar medium, in contrast with Serpens and NGC 1333. We posit that the high photoionizing flux of massive stars in RCW 38 affects the agglomeration of the dust grains.

Upper stellar mass limit by radiative feedback at low-metallicities: metallicity and accretion rate dependence

NASA Astrophysics Data System (ADS)

Fukushima, Hajime; Omukai, Kazuyuki; Hosokawa, Takashi

2018-02-01

We investigate the upper stellar mass limit set by radiative feedback for a forming star with various accretion rates and metallicities. Thus, we numerically solve the structures of both a protostar and its surrounding accretion envelope assuming a spherical symmetric and steady flow. The optical depth of the dust cocoon, a dusty part of the accretion envelope, differs for direct light from the stellar photosphere and diffuse light re-emitted as dust thermal emission. As a result, varying the metallicity qualitatively changes the way that the radiative feedback suppresses the accretion flow. With a fixed accretion rate of 10-3 M⊙ yr-1, both direct and diffuse light jointly operate to prevent mass accretion at Z ≳ 10-1 Z⊙. At Z ≲ 10-1 Z⊙, the diffuse light is no longer effective and the direct light solely limits the mass accretion. At Z ≲ 10-3 Z⊙, formation of the H II region plays an important role in terminating the accretion. The resultant upper mass limit increases with decreasing metallicity, from a few × 10 M⊙ to ∼103 M⊙ over Z = 1 Z⊙-10-4 Z⊙. We also illustrate how the radiation spectrum of massive star-forming cores changes with decreasing metallicity. First, the peak wavelength of the spectrum, which is located around 30 μm at 1 Z⊙, shifts to < 3 μm at Z ≲ 0.1 Z⊙. Secondly, a characteristic feature at 10 μm due to the amorphous silicate band appears as a dip at 1 Z⊙, but changes to a bump at Z ≲ 0.1 Z⊙. Using these spectral signatures, we can search massive accreting protostars in nearby low-metallicity environments with upcoming observations.

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

Hunter, T. R.; Brogan, C. L.; Indebetouw, R.

Based on sub-arcsecond Atacama Large Millimeter/submillimeter Array (ALMA) and Submillimeter Array (SMA) 1.3 mm continuum images of the massive protocluster NGC 6334I obtained in 2015 and 2008, we find that the dust emission from MM1 has increased by a factor of 4.0 ± 0.3 during the intervening years, and undergone a significant change in morphology. The continuum emission from the other cluster members (MM2, MM4, and the UCH ii region MM3 = NGC 6334F) has remained constant. Long-term single-dish maser monitoring at HartRAO finds that multiple maser species toward NGC 6334I flared beginning in early 2015, a few months beforemore » our ALMA observation, and some persist in that state. New ALMA images obtained in 2016 July–August at 1.1 and 0.87 mm confirm the changes with respect to SMA 0.87 mm images from 2008, and indicate that the (sub)millimeter flaring has continued for at least a year. The excess continuum emission, centered on the hypercompact H ii region MM1B, is extended and elongated (1.″6 × 1.″0 ≈ 2100 × 1300 au) with multiple peaks, suggestive of general heating of the surrounding subcomponents of MM1, some of which may trace clumps in a fragmented disk rather than separate protostars. In either case, these remarkable increases in maser and dust emission provide direct observational evidence of a sudden accretion event in the growth of a massive protostar yielding a sustained luminosity surge by a factor of 70 ± 20, analogous to the largest events in simulations by Meyer et al. This target provides an excellent opportunity to assess the impact of such a rare event on a protocluster over many years.« less

High-mass Star Formation through Filamentary Collapse and Clump-fed Accretion in G22

NASA Astrophysics Data System (ADS)

Yuan, Jinghua; Li, Jin-Zeng; Wu, Yuefang; Ellingsen, Simon P.; Henkel, Christian; Wang, Ke; Liu, Tie; Liu, Hong-Li; Zavagno, Annie; Ren, Zhiyuan; Huang, Ya-Fang

2018-01-01

How mass is accumulated from cloud-scale down to individual stars is a key open question in understanding high-mass star formation. Here, we present the mass accumulation process in a hub-filament cloud G22 that is composed of four supercritical filaments. Velocity gradients detected along three filaments indicate that they are collapsing with a total mass infall rate of about 440 M ⊙ Myr‑1, suggesting the hub mass would be doubled in six free-fall times, adding up to ∼2 Myr. A fraction of the masses in the central clumps C1 and C2 can be accounted for through large-scale filamentary collapse. Ubiquitous blue profiles in HCO+ (3–2) and 13CO (3–2) spectra suggest a clump-scale collapse scenario in the most massive and densest clump C1. The estimated infall velocity and mass infall rate are 0.31 km s‑1 and 7.2 × 10‑4 M ⊙ yr‑1, respectively. In clump C1, a hot molecular core (SMA1) is revealed by the Submillimeter Array observations and an outflow-driving high-mass protostar is located at the center of SMA1. The mass of the protostar is estimated to be 11–15 M ⊙ and it is still growing with an accretion rate of 7 × 10‑5 M ⊙ yr‑1. The coexistent infall in filaments, clump C1, and the central hot core in G22 suggests that pre-assembled mass reservoirs (i.e., high-mass starless cores) may not be required to form high-mass stars. In the course of high-mass star formation, the central protostar, the core, and the clump can simultaneously grow in mass via core-fed/disk accretion, clump-fed accretion, and filamentary/cloud collapse.

Postoperative Infection in the Setting of Massive Intraoperative Blood Loss.

PubMed

Leylek, Melike; Poliquin, Vanessa; Al-Wazzan, Ahmad; Dean, Erin; Altman, Alon D

2016-12-01

To determine the local rates of massive intraoperative blood loss and subsequent infectious morbidity for patients undergoing gynaecologic laparotomy. We performed a retrospective chart review of all patients undergoing gynaecologic laparotomy between January 1, 2013 and December 31, 2013 to identify cases of massive intraoperative blood loss (defined as ≥1 L estimated intraoperative blood loss, a postoperative reduction in hemoglobin concentration of ≥40 g/L, or a perioperative blood transfusion). For cases meeting these criteria, we abstracted further data to assess the rate of postoperative infectious morbidity (defined as a positive wound swab culture, positive urine culture, or satisfying the 1991 criteria for systemic inflammatory response syndrome). The rate of massive intraoperative blood loss was 13.5% (n = 69). The average age in this cohort was 50.4 years (range 18-84 years) and the average BMI was 27.9 kg/m 2 . Perioperative transfusion was required in 31.9% (n = 22). Notably, 26.1% of patients (n = 18) met one of our primary endpoints for postoperative infectious morbidity. A further 10.1% (n = 7) had morbidities including hyponatremia, wound dehiscence, intra-abdominal abscess, positive blood cultures, acute respiratory distress syndrome, myocardial infarction, intensive care unit admission, or death. Our rate of massive intraoperative blood loss during gynaecologic laparotomy was found to be 13.5%, and our rate of postoperative infectious morbidity subsequent to massive intraoperative blood loss was 26.1%. Copyright © 2016 The Society of Obstetricians and Gynaecologists of Canada/La Société des obstétriciens et gynécologues du Canada. Published by Elsevier Inc. All rights reserved.

Massive and Distant Clusters of WISE Survey (MaDCoWS)

NASA Astrophysics Data System (ADS)

Brodwin, Mark; MaDCoWS Collaboration

2018-06-01

The Massive and Distant Clusters of WISE Survey (MaDCoWS) is a comprehensive program to detect and characterize the most massive galaxy clusters in the Universe at z ~ 1, and is the only all-sky survey sensitive to galaxy clusters at this epoch. The foundation for this program is data from the NASA Wide-field Infrared Survey Explorer (WISE). The primary goal is to study the evolution of massive galaxies in the most overdense environments at z > 1 when star formation and AGN activity may be peaking in these structures. Spitzer follow-up imaging of 2000 MaDCoWS clusters has allowed us to select the richest and/or most distant clusters for detailed study. To date we have spectroscopically confirmed over 35 MaDCoWS clusters, spanning a wide range of masses (2-11 x 10^14 Msun), out to z = 1.5. This includes the discovery of the most massive z > 1.15 cluster found to date, as well as a cluster at z = 1.23 that is lensing a z = 2.22 supernova Ia. Multiwavelength follow-up observations of these distant clusters, currently underway, will permit several novel studies of galaxy evolution in rich cluster environments at z > 1.

The Dark Heart of the King

NASA Image and Video Library

2010-09-29

NASA Wide-field Infrared Survey Explorer captured this image of a hidden star-forming cloud of dust and gas located in the constellation of Cepheus. What appears to the naked eye as the blackness of space is in fact a dark nebula.

VizieR Online Data Catalog: Massive early-type galaxies (Buitrago+, 2013)

NASA Astrophysics Data System (ADS)

Buitrago, F.; Trujillo, I.; Conselice, C. J.; Haussler, B.

2013-08-01

Present-day massive galaxies are composed mostly of early-type objects. It is unknown whether this was also the case at higher redshifts. In a hierarchical assembling scenario the morphological content of the massive population is expected to change with time from disc-like objects in the early Universe to spheroid-like galaxies at present. In this paper we have probed this theoretical expectation by compiling a large sample of massive (Mstellar>=1011h-270M⊙) galaxies in the redshift interval 0massive galaxy population has changed from ~20-30 per cent at z~3 to~70 per cent at z=0. Early-type galaxies have been the predominant morphological class for massive galaxies since only z~1. (1 data file).

Cerro de Pasco and other massive sulfide deposits of central Peru

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

Cheney, E.S.

1985-01-01

The famous Cerro de Pasco Pb-Zn-Ag deposit historically has been considered to be hydrothermally derived from an adjacent Tertiary volcanic vent. However, texturally massive pyrite-chert and pyrite-sphalerite-galena in the deposit have the same strike and cross folds as the adjacent pre-Tertiary strata. Both the deposit and the strata are cut by one of the large Longitudinal Faults. Both dikes and pyrite-enargite veins associated with the vent cut the massive sulfides; fragments of massive pyrite occur in the vent. A few examples of laminated pyrite and chert, banded pyrite and chert, banded pyrite and sphalerite, and banded pyrite, sphalerite, and galenamore » are preserved in the massive sulfide portion of the deposit. The deposit has the composition and zoning patterns typical of shale-hosted massive sulfides. Cerro de Pasco probably in part of the pelitic Devonian Excelsior formation. The Colquijirca deposit 8 km to the south and the San Cristobal district 110 km to the south likewise have been considered to be Tertiary volcanic hydrothermal deposits. Colquijirca consists of stratigraphically controlled mantos of layered pyrite, chert and tuff in the Tertiary Calera formation. The mantos of the San Cristobal district are along the upper contact of the pyritic, Permian, Catalina felsic volcanic rocks; some ore consists of laminated pyrite and sphalerite. Tertiary plutons are conspicuously absent at San Cristobal, and the ores are brecciated by Tertiary folding.« less

The halo model in a massive neutrino cosmology

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

Massara, Elena; Villaescusa-Navarro, Francisco; Viel, Matteo, E-mail: emassara@sissa.it, E-mail: villaescusa@oats.inaf.it, E-mail: viel@oats.inaf.it

2014-12-01

We provide a quantitative analysis of the halo model in the context of massive neutrino cosmologies. We discuss all the ingredients necessary to model the non-linear matter and cold dark matter power spectra and compare with the results of N-body simulations that incorporate massive neutrinos. Our neutrino halo model is able to capture the non-linear behavior of matter clustering with a ∼20% accuracy up to very non-linear scales of k = 10 h/Mpc (which would be affected by baryon physics). The largest discrepancies arise in the range k = 0.5 – 1 h/Mpc where the 1-halo and 2-halo terms are comparable and are present also inmore » a massless neutrino cosmology. However, at scales k < 0.2 h/Mpc our neutrino halo model agrees with the results of N-body simulations at the level of 8% for total neutrino masses of < 0.3 eV. We also model the neutrino non-linear density field as a sum of a linear and clustered component and predict the neutrino power spectrum and the cold dark matter-neutrino cross-power spectrum up to k = 1 h/Mpc with ∼30% accuracy. For masses below 0.15 eV the neutrino halo model captures the neutrino induced suppression, casted in terms of matter power ratios between massive and massless scenarios, with a 2% agreement with the results of N-body/neutrino simulations. Finally, we provide a simple application of the halo model: the computation of the clustering of galaxies, in massless and massive neutrinos cosmologies, using a simple Halo Occupation Distribution scheme and our halo model extension.« less

Integrands for QCD rational terms and {N} = {4} SYM from massive CSW rules

NASA Astrophysics Data System (ADS)

Elvang, Henriette; Freedman, Daniel Z.; Kiermaier, Michael

2012-06-01

We use massive CSW rules to derive explicit compact expressions for integrands of rational terms in QCD with any number of external legs. Specifically, we present all- n integrands for the one-loop all-plus and one-minus gluon amplitudes in QCD. We extract the finite part of spurious external-bubble contributions systematically; this is crucial for the application of integrand-level CSW rules in theories without supersymmetry. Our approach yields integrands that are independent of the choice of CSW reference spinor even before integration. Furthermore, we present a recursive derivation of the recently proposed massive CSW-style vertex expansion for massive tree amplitudes and loop integrands on the Coulomb-branch of {N} = {4} SYM. The derivation requires a careful study of boundary terms in all-line shift recursion relations, and provides a rigorous (albeit indirect) proof of the recently proposed construction of massive amplitudes from soft-limits of massless on-shell amplitudes. We show that the massive vertex expansion manifestly preserves all holomorphic and half of the anti-holomorphic supercharges, diagram-by-diagram, even off-shell.

Accretion Signatures on Massive Young Stellar Objects

NASA Astrophysics Data System (ADS)

Navarete, F.; Damineli, A.; Barbosa, C. L.; Blum, R. D.

2015-01-01

We present preliminary results from a survey of molecular H2 (2.12 μm) emission in massive young stellar objects (MYSO) candidates selected from the Red MSX Source survey. We observed 354 MYSO candidates through the H2 S(1) 1-0 transition (2.12 μm) and an adjacent continuum narrow-band filters using the Spartan/SOAR and WIRCam/CFHT cameras. The continuum-subtracted H2 maps were analyzed and extended H2 emission was found in 50% of the sample (178 sources), and 38% of them (66) have polar morphology, suggesting collimated outflows. The polar-like structures are more likely to be driven on radio-quiet sources, indicating that these structures occur during the pre-ultra compact H ii phase. We analyzed the continuum images and found that 54% (191) of the sample displayed extended continuum emission and only ~23% (80) were associated to stellar clusters. The extended continuum emission is correlated to the H2 emission and those sources within stellar clusters does display diffuse H2 emission, which may be due to fluorescent H2 emission. These results support the accretion scenario for massive star formation, since the merging of low-mass stars would not produce jet-like structures. Also, the correlation between jet-like structures and radio-quiet sources indicates that higher inflow rates are required to form massive stars in a typical timescale less than 105 years.

Emergent universe with wormholes in massive gravity

NASA Astrophysics Data System (ADS)

Paul, B. C.; Majumdar, A. S.

2018-03-01

An emergent universe (EU) scenario is proposed to obtain a universe free from big-bang singularity. In this framework the present universe emerged from a static Einstein universe phase in the infinite past. A flat EU scenario is found to exist in Einstein’s gravity with a non-linear equation of state (EoS). It has been shown subsequently that a physically realistic EU model can be obtained considering cosmic fluid composed of interacting fluids with a non-linear equation of state. It results a viable cosmological model accommodating both early inflation and present accelerating phases. In the present paper, the origin of an initial static Einstein universe needed in the EU model is explored in a massive gravity theory which subsequently emerged to be a dynamically evolving universe. A new gravitational instanton solution in a flat universe is obtained in the massive gravity theory which is a dynamical wormhole that might play an important role in realizing the origin of the initial state of the emergent universe. The emergence of a Lorentzian universe from a Euclidean gravity is understood by a Wick rotation τ = i t . A universe with radiation at the beginning finally transits into the present observed universe with a non-linear EoS as the interactions among the fluids set in. Thus a viable flat EU scenario where the universe stretches back into time infinitely, with no big bang is permitted in a massive gravity.

A dust-obscured massive maximum-starburst galaxy at a redshift of 6.34.

PubMed

Riechers, Dominik A; Bradford, C M; Clements, D L; Dowell, C D; Pérez-Fournon, I; Ivison, R J; Bridge, C; Conley, A; Fu, Hai; Vieira, J D; Wardlow, J; Calanog, J; Cooray, A; Hurley, P; Neri, R; Kamenetzky, J; Aguirre, J E; Altieri, B; Arumugam, V; Benford, D J; Béthermin, M; Bock, J; Burgarella, D; Cabrera-Lavers, A; Chapman, S C; Cox, P; Dunlop, J S; Earle, L; Farrah, D; Ferrero, P; Franceschini, A; Gavazzi, R; Glenn, J; Solares, E A Gonzalez; Gurwell, M A; Halpern, M; Hatziminaoglou, E; Hyde, A; Ibar, E; Kovács, A; Krips, M; Lupu, R E; Maloney, P R; Martinez-Navajas, P; Matsuhara, H; Murphy, E J; Naylor, B J; Nguyen, H T; Oliver, S J; Omont, A; Page, M J; Petitpas, G; Rangwala, N; Roseboom, I G; Scott, D; Smith, A J; Staguhn, J G; Streblyanska, A; Thomson, A P; Valtchanov, I; Viero, M; Wang, L; Zemcov, M; Zmuidzinas, J

2013-04-18

Massive present-day early-type (elliptical and lenticular) galaxies probably gained the bulk of their stellar mass and heavy elements through intense, dust-enshrouded starbursts--that is, increased rates of star formation--in the most massive dark-matter haloes at early epochs. However, it remains unknown how soon after the Big Bang massive starburst progenitors exist. The measured redshift (z) distribution of dusty, massive starbursts has long been suspected to be biased low in z owing to selection effects, as confirmed by recent findings of systems with redshifts as high as ~5 (refs 2-4). Here we report the identification of a massive starburst galaxy at z = 6.34 through a submillimetre colour-selection technique. We unambiguously determined the redshift from a suite of molecular and atomic fine-structure cooling lines. These measurements reveal a hundred billion solar masses of highly excited, chemically evolved interstellar medium in this galaxy, which constitutes at least 40 per cent of the baryonic mass. A 'maximum starburst' converts the gas into stars at a rate more than 2,000 times that of the Milky Way, a rate among the highest observed at any epoch. Despite the overall downturn in cosmic star formation towards the highest redshifts, it seems that environments mature enough to form the most massive, intense starbursts existed at least as early as 880 million years after the Big Bang.

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.

How Massive Single Stars End Their Life

NASA Technical Reports Server (NTRS)

Heger, A.; Fryer, C. L.; Woosley, S. E.; Langer, N.; Hartmann, D. H.

2003-01-01

How massive stars die-what sort of explosion and remnant each produces-depends chiefly on the masses of their helium cores and hydrogen envelopes at death. For single stars, stellar winds are the only means of mass loss, and these are a function of the metallicity of the star. We discuss how metallicity, and a simplified prescription for its effect on mass loss, affects the evolution and final fate of massive stars. We map, as a function of mass and metallicity, where black holes and neutron stars are likely to form and where different types of supernovae are produced. Integrating over an initial mass function, we derive the relative populations as a function of metallicity. Provided that single stars rotate rapidly enough at death, we speculate on stellar populations that might produce gamma-ray bursts and jet-driven supernovae.

H II REGIONS, EMBEDDED PROTOSTARS, AND STARLESS CORES IN SHARPLESS 2-157

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

Chen, Chian-Chou; Williams, Jonathan P.; Pandian, Jagadheep D., E-mail: ccchen@ifa.hawaii.edu, E-mail: jpw@ifa.hawaii.edu, E-mail: jagadheep@iist.ac.in

2012-06-20

We present arcsecond resolution 1.4 mm observations of the high-mass star-forming region, Sharpless 2-157, that reveal the cool dust associated with the first stages of star formation. These data are compared with archival images at optical, infrared, and radio wavelengths, and complemented with new arcsecond resolution mid-infrared data. We identify a dusty young H II region, numerous infrared sources within the cluster envelope, and four starless condensations. Three of the cores lie in a line to the south of the cluster peak, but the most massive one is right at the center and associated with a jumble of bright radiomore » and infrared sources. This presents an interesting juxtaposition of high- and low-mass star formation within the same cluster which we compare with similar observations of other high-mass star-forming regions and discuss in the context of cluster formation theory.« less

On The Detachment of Massive Trans-Neptunian Objects

NASA Astrophysics Data System (ADS)

Fleisig, Jacob; Madigan, Ann-Marie; Zderic, Alexander

2018-06-01

Our Solar System contains a large population of icy bodies stretching well beyond the orbit of Neptune. These objects, known collectively as the Scattered Disk, are remnants from the early formation of the Solar System that were scattered outward from their birth location by Neptune. But not all fit the bill.Sedna, one particularly massive Trans-Neptunian Object (TNO), does not conform to the scattering pattern. Its orbital eccentricity (e) is much lower than expected for a scattered object. This means its perihelion distance (proportional to 1-e) is much larger than the orbit of Neptune, or that it is “detached” from the main Solar System. Many more TNOs share similarities with Sedna. These observations suggest that there is a large population of detached TNOs that have a dynamical history different than that of the objects scattered by Neptune.The physical mechanism by which these massive minor planets become detached is currently unknown. However, we have discovered a phenomenon, driven by differential precession between TNOs of different masses and mutual secular gravitational torques, that naturally detach massive minor planets. This mechanism could have notable consequences for the outer Solar System and may shed some light on the origin of the detached population of minor planets near the Scattered Disk.

Spontaneous hemothorax following thrombolytic and anticoagulant therapy for massive pulmonary embolism.

PubMed

Wang, Chung-Cheng; Ng, Chip-Jin; Seak, Chen-Ken; Seak, Chen-June

2013-06-01

Massive spontaneous hemothorax following combined thrombolytic and anticoagulant therapy for pulmonary embolism(PE) is a rare event that is little documented in the literature. Here, we describe a rare case of spontaneous hemothorax in a 23-year-old woman with underlying systemic lupus erythematosus following combined administration of tissue plasminogen activator and low-molecular-weight heparin for massive PE. This report of our successful treatment of this case by video-assisted thoracoscopic thoracotomy demonstrates that although the occurrence is rare, massive hemothorax following anticoagulant and/or thrombolytic therapy for PE should be suspected if patients experience chest pain, dyspnea, or signs of anemia, and follow-up physical examination and hemogram should be performed to facilitate diagnosis of this life-threatening complication.

Highly accurate quantitative spectroscopy of massive stars in the Galaxy

NASA Astrophysics Data System (ADS)

Nieva, María-Fernanda; Przybilla, Norbert

2017-11-01

Achieving high accuracy and precision in stellar parameter and chemical composition determinations is challenging in massive star spectroscopy. On one hand, the target selection for an unbiased sample build-up is complicated by several types of peculiarities that can occur in individual objects. On the other hand, composite spectra are often not recognized as such even at medium-high spectral resolution and typical signal-to-noise ratios, despite multiplicity among massive stars is widespread. In particular, surveys that produce large amounts of automatically reduced data are prone to oversight of details that turn hazardous for the analysis with techniques that have been developed for a set of standard assumptions applicable to a spectrum of a single star. Much larger systematic errors than anticipated may therefore result because of the unrecognized true nature of the investigated objects, or much smaller sample sizes of objects for the analysis than initially planned, if recognized. More factors to be taken care of are the multiple steps from the choice of instrument over the details of the data reduction chain to the choice of modelling code, input data, analysis technique and the selection of the spectral lines to be analyzed. Only when avoiding all the possible pitfalls, a precise and accurate characterization of the stars in terms of fundamental parameters and chemical fingerprints can be achieved that form the basis for further investigations regarding e.g. stellar structure and evolution or the chemical evolution of the Galaxy. The scope of the present work is to provide the massive star and also other astrophysical communities with criteria to evaluate the quality of spectroscopic investigations of massive stars before interpreting them in a broader context. The discussion is guided by our experiences made in the course of over a decade of studies of massive star spectroscopy ranging from the simplest single objects to multiple systems.

Blood transfusion and the anaesthetist: management of massive haemorrhage

PubMed Central

Thomas, D; Wee, M; Clyburn, P; Walker, I; Brohi, K; Collins, P; Doughty, H; Isaac, J; Mahoney, PF; Shewry, L

2010-01-01

Hospitals must have a major haemorrhage protocol in place and this should include clinical, laboratory and logistic responses. Immediate control of obvious bleeding is of paramount importance (pressure, tourniquet, haemostatic dressings). The major haemorrhage protocol must be mobilised immediately when a massive haemorrhage situation is declared. A fibrinogen < 1 g.l−1 or a prothrombin time (PT) and activated partial thromboplastin time (aPTT) of > 1.5 times normal represents established haemostatic failure and is predictive of microvascular bleeding. Early infusion of fresh frozen plasma (FFP; 15 ml.kg−1) should be used to prevent this occurring if a senior clinician anticipates a massive haemorrhage. Established coagulopathy will require more than 15 ml.kg−1 of FFP to correct. The most effective way to achieve fibrinogen replacement rapidly is by giving fibrinogen concentrate or cryoprecipitate if fibrinogen is unavailable. 1:1:1 red cell:FFP:platelet regimens, as used by the military, are reserved for the most severely traumatised patients. A minimum target platelet count of 75 × 109.l−1 is appropriate in this clinical situation. Group-specific blood can be issued without performing an antibody screen because patients will have minimal circulating antibodies. O negative blood should only be used if blood is needed immediately. In hospitals where the need to treat massive haemorrhage is frequent, the use of locally developed shock packs may be helpful. Standard venous thromboprophylaxis should be commenced as soon as possible after haemostasis has been secured as patients develop a prothrombotic state following massive haemorrhage. PMID:20963925

Revealing evolved massive stars with Spitzer

NASA Astrophysics Data System (ADS)

Gvaramadze, V. V.; Kniazev, A. Y.; Fabrika, S.

2010-06-01

Massive evolved stars lose a large fraction of their mass via copious stellar wind or instant outbursts. During certain evolutionary phases, they can be identified by the presence of their circumstellar nebulae. In this paper, we present the results of a search for compact nebulae (reminiscent of circumstellar nebulae around evolved massive stars) using archival 24-μm data obtained with the Multiband Imaging Photometer for Spitzer. We have discovered 115 nebulae, most of which bear a striking resemblance to the circumstellar nebulae associated with luminous blue variables (LBVs) and late WN-type (WNL) Wolf-Rayet (WR) stars in the Milky Way and the Large Magellanic Cloud (LMC). We interpret this similarity as an indication that the central stars of detected nebulae are either LBVs or related evolved massive stars. Our interpretation is supported by follow-up spectroscopy of two dozen of these central stars, most of which turn out to be either candidate LBVs (cLBVs), blue supergiants or WNL stars. We expect that the forthcoming spectroscopy of the remaining objects from our list, accompanied by the spectrophotometric monitoring of the already discovered cLBVs, will further increase the known population of Galactic LBVs. This, in turn, will have profound consequences for better understanding the LBV phenomenon and its role in the transition between hydrogen-burning O stars and helium-burning WR stars. We also report on the detection of an arc-like structure attached to the cLBV HD 326823 and an arc associated with the LBV R99 (HD 269445) in the LMC. Partially based on observations collected at the German-Spanish Astronomical Centre, Calar Alto, jointly operated by the Max-Planck-Institut für Astronomie Heidelberg and the Instituto de Astrofísica de Andalucía (CSIC). E-mail: vgvaram@mx.iki.rssi.ru (VVG); akniazev@saao.ac.za (AYK); fabrika@sao.ru (SF)

Chemical and Physical Picture of IRAS 16293–2422 Source B at a Sub-arcsecond Scale Studied with ALMA

NASA Astrophysics Data System (ADS)

Oya, Yoko; Moriwaki, Kana; Onishi, Shusuke; Sakai, Nami; López–Sepulcre, Ana; Favre, Cécile; Watanabe, Yoshimasa; Ceccarelli, Cecilia; Lefloch, Bertrand; Yamamoto, Satoshi

2018-02-01

We have analyzed the OCS, H2CS, CH3OH, and HCOOCH3 data observed toward the low-mass protostar IRAS 16293–2422 Source B at a sub-arcsecond resolution with ALMA. A clear chemical differentiation is seen in their distributions; OCS and H2CS are extended with a slight rotation signature, while CH3OH and HCOOCH3 are concentrated near the protostar. Such a chemical change in the vicinity of the protostar is similar to the companion (Source A) case. The extended component is interpreted by the infalling-rotating envelope model with a nearly face-on configuration. The radius of the centrifugal barrier of the infalling-rotating envelope is roughly evaluated to be (30–50) au. The observed lines show the inverse P-Cygni profile, indicating the infall motion within a few 10 au from the protostar. The nearly pole-on geometry of the outflow lobes is inferred from the SiO distribution, and thus, the infalling and outflowing motions should coexist along the line of sight to the protostar. This implies that the infalling gas is localized near the protostar and the current launching points of the outflow have an offset from the protostar. A possible mechanism for this configuration is discussed.

Channel Acquisition for Massive MIMO-OFDM With Adjustable Phase Shift Pilots

NASA Astrophysics Data System (ADS)

You, Li; Gao, Xiqi; Swindlehurst, A. Lee; Zhong, Wen

2016-03-01

We propose adjustable phase shift pilots (APSPs) for channel acquisition in wideband massive multiple-input multiple-output (MIMO) systems employing orthogonal frequency division multiplexing (OFDM) to reduce the pilot overhead. Based on a physically motivated channel model, we first establish a relationship between channel space-frequency correlations and the channel power angle-delay spectrum in the massive antenna array regime, which reveals the channel sparsity in massive MIMO-OFDM. With this channel model, we then investigate channel acquisition, including channel estimation and channel prediction, for massive MIMO-OFDM with APSPs. We show that channel acquisition performance in terms of sum mean square error can be minimized if the user terminals' channel power distributions in the angle-delay domain can be made non-overlapping with proper phase shift scheduling. A simplified pilot phase shift scheduling algorithm is developed based on this optimal channel acquisition condition. The performance of APSPs is investigated for both one symbol and multiple symbol data models. Simulations demonstrate that the proposed APSP approach can provide substantial performance gains in terms of achievable spectral efficiency over the conventional phase shift orthogonal pilot approach in typical mobility scenarios.

Imprints of fast-rotating massive stars in the Galactic Bulge.

PubMed

Chiappini, Cristina; Frischknecht, Urs; Meynet, Georges; Hirschi, Raphael; Barbuy, Beatriz; Pignatari, Marco; Decressin, Thibaut; Maeder, André

2011-04-28

The first stars that formed after the Big Bang were probably massive, and they provided the Universe with the first elements heavier than helium ('metals'), which were incorporated into low-mass stars that have survived to the present. Eight stars in the oldest globular cluster in the Galaxy, NGC 6522, were found to have surface abundances consistent with the gas from which they formed being enriched by massive stars (that is, with higher α-element/Fe and Eu/Fe ratios than those of the Sun). However, the same stars have anomalously high abundances of Ba and La with respect to Fe, which usually arises through nucleosynthesis in low-mass stars (via the slow-neutron-capture process, or s-process). Recent theory suggests that metal-poor fast-rotating massive stars are able to boost the s-process yields by up to four orders of magnitude, which might provide a solution to this contradiction. Here we report a reanalysis of the earlier spectra, which reveals that Y and Sr are also overabundant with respect to Fe, showing a large scatter similar to that observed in extremely metal-poor stars, whereas C abundances are not enhanced. This pattern is best explained as originating in metal-poor fast-rotating massive stars, which might point to a common property of the first stellar generations and even of the 'first stars'.

A Collection of Economic and Social Data from Glitch, a Massively Multiplayer Online Game

DTIC Science & Technology

2013-03-05

A Collection of Economic and Social Data from Glitch, a Massively Multiplayer Online Game Peter M. Landwehr March 5, 2013 CMU-ISR-13...massively multiplayer online games (MMOG) - social and cultural model embedding technologies. Additional support was provided by CASOS — the center for...SUBTITLE A Collection of Economic and Social Data from Glitch, a Massively Multiplayer Online Game 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM

Efficient, massively parallel eigenvalue computation

NASA Technical Reports Server (NTRS)

Huo, Yan; Schreiber, Robert

1993-01-01

In numerical simulations of disordered electronic systems, one of the most common approaches is to diagonalize random Hamiltonian matrices and to study the eigenvalues and eigenfunctions of a single electron in the presence of a random potential. An effort to implement a matrix diagonalization routine for real symmetric dense matrices on massively parallel SIMD computers, the Maspar MP-1 and MP-2 systems, is described. Results of numerical tests and timings are also presented.

Theoretical Near-IR Spectra for Surface Abundance Studies of Massive Stars

NASA Technical Reports Server (NTRS)

Sonneborn, George; Bouret, J.

2011-01-01

We present initial results of a study of abundance and mass loss properties of O-type stars based on theoretical near-IR spectra computed with state-of-the-art stellar atmosphere models. The James Webb Space Telescope (JWST) will be a powerful tool to obtain high signal-to-noise ratio near-IR (1-5 micron) spectra of massive stars in different environments of local galaxies. Our goal is to analyze model near-IR spectra corresponding to those expected from NIRspec on JWST in order to map the wind properties and surface composition across the parameter range of 0 stars and to determine projected rotational velocities. As a massive star evolves, internal coupling, related mixing, and mass loss impact its intrinsic rotation rate. These three parameters form an intricate loop, where enhanced rotation leads to more mixing which in turn changes the mass loss rate, the latter thus affecting the rotation rate. Since the effects of rotation are expected to be much more pronounced at low metallicity, we pay special attention to models for massive stars in the the Small Magellanic Cloud. This galaxy provides a unique opportunity to probe stellar evolution, and the feedback of massive stars on galactic evol.ution in conditions similar to the epoch of maximal star formation. Plain-Language Abstract: We present initial results of a study of abundance and mass loss properties of massive stars based on theoretical near-infrared (1-5 micron) spectra computed with state-of-the-art stellar atmosphere models. This study is to prepare for observations by the James Webb Space Telescope.

Analysis of Massively Separated Flows of Aircraft Using Detached Eddy Simulation

NASA Astrophysics Data System (ADS)

Morton, Scott

2002-08-01

An important class of turbulent flows of aerodynamic interest are those characterized by massive separation, e.g., the flow around an aircraft at high angle of attack. Numerical simulation is an important tool for analysis, though traditional models used in the solution of the Reynolds-averaged Navier-Stokes (RANS) equations appear unable to accurately account for the time-dependent and three-dimensional motions governing flows with massive separation. Large-eddy simulation (LES) is able to resolve these unsteady three-dimensional motions, yet is cost prohibitive for high Reynolds number wall-bounded flows due to the need to resolve the small scale motions in the boundary layer. Spalart et. al. proposed a hybrid technique, Detached-Eddy Simulation (DES), which takes advantage of the often adequate performance of RANS turbulence models in the "thin," typically attached regions of the flow. In the separated regions of the flow the technique becomes a Large Eddy Simulation, directly resolving the time-dependent and unsteady features that dominate regions of massive separation. The current work applies DES to a 70 degree sweep delta wing at 27 degrees angle of attack, a geometrically simple yet challenging flowfield that exhibits the unsteady three-dimensional massively separated phenomena of vortex breakdown. After detailed examination of this basic flowfield, the method is demonstrated on three full aircraft of interest characterized by massive separation, the F-16 at 45 degrees angle of attack, the F-15 at 65 degree angle of attack (with comparison to flight test), and the C-130 in a parachute drop condition at near stall speed with cargo doors open.

Eruptive Massive Vector Particles of 5-Dimensional Kerr-Gödel Spacetime

NASA Astrophysics Data System (ADS)

Övgün, A.; Sakalli, I.

2018-02-01

In this paper, we investigate Hawking radiation of massive spin-1 particles from 5-dimensional Kerr-Gödel spacetime. By applying the WKB approximation and the Hamilton-Jacobi ansatz to the relativistic Proca equation, we obtain the quantum tunneling rate of the massive vector particles. Using the obtained tunneling rate, we show how one impeccably computes the Hawking temperature of the 5-dimensional Kerr-Gödel spacetime.

Massive thoracoabdominal aortic thrombosis in a patient with iatrogenic Cushing syndrome.

PubMed

Kim, Dong Hun; Choi, Dong-Hyun; Lee, Young-Min; Kang, Joon Tae; Chae, Seung Seok; Kim, Bo-Bae; Ki, Young-Jae; Kim, Jin Hwa; Chung, Joong-Wha; Koh, Young-Youp

2014-01-01

Massive thoracoabdominal aortic thrombosis is a rare finding in patients with iatrogenic Cushing syndrome in the absence of any coagulation abnormality. It frequently represents an urgent surgical situation. We report the case of an 82-year-old woman with massive aortic thrombosis secondary to iatrogenic Cushing syndrome. A follow-up computed tomography scan showed a decreased amount of thrombus in the aorta after anticoagulation therapy alone.

Massive Open Online Courses (MOOCs): Insights and Challenges from a Psychological Perspective

ERIC Educational Resources Information Center

Terras, Melody M.; Ramsay, Judith

2015-01-01

Massive open online courses (MOOCs) offer an exciting range of opportunities to widen access and participation in education. The massive and open nature of MOOCs places the control of learning at the discretion of the learner. Therefore, it is essential to understand learner behaviour. This paper examines the psychological considerations inherent…

Assessment Approaches in Massive Open Online Courses: Possibilities, Challenges and Future Directions

ERIC Educational Resources Information Center

Xiong, Yao; Suen, Hoi K.

2018-01-01

The development of massive open online courses (MOOCs) has launched an era of large-scale interactive participation in education. While massive open enrolment and the advances of learning technology are creating exciting potentials for lifelong learning in formal and informal ways, the implementation of efficient and effective assessment is still…

Anaesthetic management of a child with massive extracranial arteriovenous malformation

PubMed Central

Shamim, Faisal; Ullah, Hameed; Rehman, Azhar

2012-01-01

Vascular tumors affect the head and neck commonly but arteriovenous malformations are rare. Vascular malformations are often present at birth and grow with the patient, usually only becoming significant later in childhood. Embolization has been the mainstay of treatment in massive and complex arteriovenous malformations. We present a case of massive extracranial arteriovenous malformation in a 7-year-old boy causing significant workload on right heart and respiratory distress. The management of angioembolization under general anaesthesia and anaesthetic concerns are presented. PMID:22345959

Massive splenic infarction in Saudi patients with sickle cell anemia: a unique manifestation.

PubMed

Jama, Ali Hassan Al; Salem, Ahmed Hassan Al; Dabbous, Ibrahim Abdalla Al

2002-03-01

Splenic infarcts are common in patients with sickle cell anemia (SCA), but these are usually small and repetitive, leading ultimately to autosplenectomy. Massive splenic infarcts on the other hand are extremely rare. This is a report of our experience with 8 (4 males and 4 females) cases of massive splenic infarction in patients with SCA. Their ages ranged from 16 to 36 years (mean 22 years). Three presented with left upper quadrant abdominal pain and massive splenic infarction on admission, while the other 5 developed massive splenic infarction while in hospital. In 5 the precipitating factors were high altitude, postoperative, postpartum, salmonella septicemia, and strenuous exercise in one each, while the remaining 3 had severe generalized vasoocclusive crises. Although both ultrasound and CT scan of the abdomen were of diagnostic value, we found CT scan more accurate in delineating the size of infarction. All our patients were managed conservatively with I.V. fluids, analgesia, and blood transfusion when necessary. Diagnostic aspiration under ultrasound guidance was necessary in two patients to differentiate between massive splenic infarction and splenic abscess. Two patients required splenectomy during the same admission because of suspicion of secondary infection and abscess formation, while a third patient had splenectomy 2 months after the attack because of persistent left upper quadrant abdominal pain. In all the 3 histology of the spleen showed congestive splenomegaly with massive infarction. All of our patients survived. Two patients subsequently developed autosplenectomy while the remaining 3 continue to have persistent but asymptomatic splenomegaly. Massive splenic infarction is a rare and unique complication of SCA in the Eastern Province of Saudi Arabia, and for early diagnosis and treatment, physicians caring for these patients should be aware of such a complication.

The JCMT Transient Survey: Stochastic and Secular Variability of Protostars and Disks In the Submillimeter Region Observed over 18 Months

NASA Astrophysics Data System (ADS)

Johnstone, Doug; Herczeg, Gregory J.; Mairs, Steve; Hatchell, Jennifer; Bower, Geoffrey C.; Kirk, Helen; Lane, James; Bell, Graham S.; Graves, Sarah; Aikawa, Yuri; Chen, Huei-Ru Vivien; Chen, Wen-Ping; Kang, Miju; Kang, Sung-Ju; Lee, Jeong-Eun; Morata, Oscar; Pon, Andy; Scicluna, Peter; Scholz, Aleks; Takahashi, Satoko; Yoo, Hyunju; The JCMT Transient Team

2018-02-01

We analyze results from the first 18 months of monthly submillimeter monitoring of eight star-forming regions in the JCMT Transient Survey. In our search for stochastic variability in 1643 bright peaks, only the previously identified source, EC 53, shows behavior well above the expected measurement uncertainty. Another four sources—two disks and two protostars—show moderately enhanced standard deviations in brightness, as expected for stochastic variables. For the two protostars, this apparent variability is the result of single epochs that are much brighter than the mean. In our search for secular brightness variations that are linear in time, we measure the fractional brightness change per year for 150 bright peaks, 50 of which are protostellar. The ensemble distribution of slopes is well fit by a normal distribution with σ ∼ 0.023. Most sources are not rapidly brightening or fading at submillimeter wavelengths. Comparison against time-randomized realizations shows that the width of the distribution is dominated by the uncertainty in the individual brightness measurements of the sources. A toy model for secular variability reveals that an underlying Gaussian distribution of linear fractional brightness change σ = 0.005 would be unobservable in the present sample, whereas an underlying distribution with σ = 0.02 is ruled out. Five protostellar sources, 10% of the protostellar sample, are found to have robust secular measures deviating from a constant flux. The sensitivity to secular brightness variations will improve significantly with a sample over a longer time duration, with an improvement by factor of two expected by the conclusion of our 36 month survey.

Arthroscopic Repair for Chronic Massive Rotator Cuff Tears: A Systematic Review.

PubMed

Henry, Patrick; Wasserstein, David; Park, Sam; Dwyer, Tim; Chahal, Jaskarndip; Slobogean, Gerard; Schemitsch, Emil

2015-12-01

To systematically review the available evidence for arthroscopic repair of chronic massive rotator cuff tears and identify patient demographics, pre- and post-operative functional limitations, reparability and repair techniques, and retear rates. Medline, Embase, the Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials were searched to identify all clinical papers describing arthroscopic repair of chronic massive rotator cuff tears. Papers were excluded if a definition of "massive" was not provided, if the definition of "massive" was considered inappropriate by agreement between the 2 reviewers, or if patients with smaller tears were also included in the study population. Study quality and clinical outcome data were pooled and summarized. There were 18 papers that met the eligibility criteria; they involved 954 patients with a mean age of 63 (range, 37 to 87), 48% of whom were female. There were 5 prospective and 13 retrospective study designs. The overall study quality was poor according to the Modified Coleman Methodology Score. Of the 954 repairs, 81% were complete repairs and 19% were partial repairs. The follow-up range was between 33 and 52 months, and the mean duration between symptom onset and surgery was 24 months. Single-row repairs were performed in 56% or patients, and double-row repairs were performed in 44%. A pooled analysis demonstrated an improvement in visual analog scale from 5.9 to 1.7, active range of motion from 125° to 169°, and the Constant-Murley score from 49 to 74. The pooled retear rate was 79%. Arthroscopic repair of chronic massive rotator cuff tears is associated with complete repair in the majority of cases and consistently improves pain, range of motion, and functional outcome scores; however, the retear rate is high. Existing research on massive rotator cuff repair is limited to poor- to fair-quality studies. Level IV, systematic review including Level IV studies. Copyright © 2015

Kinematics of the inner thousand AU region around the young massive star AFGL 2591-VLA3: a massive disk candidate?

NASA Astrophysics Data System (ADS)

Wang, K.-S.; van der Tak, F. F. S.; Hogerheijde, M. R.

2012-07-01

Context. Recent detections of disks around young high-mass stars support the idea of massive star formation through accretion rather than coalescence, but the detailed kinematics in the equatorial region of the disk candidates is not well known, which limits our understanding of the accretion process. Aims: This paper explores the kinematics of the gas around a young massive star with millimeter-wave interferometry to improve our understanding of the formation of massive stars though accretion. Methods: We use Plateau de Bure interferometric images to probe the environment of the nearby (~1 kpc) and luminous (~20 000 L⊙) high-mass (10-16 M⊙) young star AFGL 2591-VLA3 in continuum and in lines of HDO, H_218O and SO2 in the 115 and 230 GHz bands. Radiative transfer calculations are employed to investigate the kinematics of the source. Results: At ~0.5″ (500 AU) resolution, the line images clearly resolve the velocity field of the central compact source (diameter of ~800 AU) and show linear velocity gradients in the northeast-southwest direction. Judging from the disk-outflow geometry, the observed velocity gradient results from rotation and radial expansion in the equatorial region of VLA3. Radiative transfer calculations suggest that the velocity field is consistent with sub-Keplerian rotation plus Hubble-law like expansion. The line profiles of the observed molecules suggest a layered structure, with HDO emission arising from the disk mid-plane, H_218O from the warm mid-layer, and SO2 from the upper disk. Conclusions: We propose AFGL 2591-VLA3 as a new massive disk candidate, with peculiar kinematics. The rotation of this disk is sub-Keplerian, probably due to magnetic braking, while the stellar wind may be responsible for the expansion of the disk. The expansion motion may also be an indirect evidence of disk accretion in the very inner region because of the conservation of angular momentum. The sub-Keplerian rotation discovered in our work suggests that

What are the Progenitors of Compace, Massive, Quiescent Galaxies at z (equals) 2.3? The Population of Massive Galaxies at z (greater than) 3 From NMBS AND CANDELS

NASA Technical Reports Server (NTRS)

Stefanon, Mauro; Marchesini, Danilo; Rudnick, Gregory H.; Brammer, Gabriel B.; Tease, Katherine Whitaker

2013-01-01

Using public data from the NEWFIRM Medium-Band Survey (NMBS) and the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS), we investigate the population of massive galaxies at z > 3. The main aim of this work is to identify the potential progenitors of z 2 compact, massive, quiescent galaxies (CMQGs), furthering our understanding of the onset and evolution of massive galaxies. Our work is enabled by high-resolution images from CANDELS data and accurate photometric redshifts, stellar masses, and star formation rates (SFRs) from 37-band NMBS photometry. The total number of massive galaxies at z > 3 is consistent with the number of massive, quiescent galaxies (MQGs) at z 2, implying that the SFRs for all of these galaxies must be much lower by z 2. We discover four CMQGs at z > 3, pushing back the time for which such galaxies have been observed. However, the volume density for these galaxies is significantly less than that of galaxies at z < 2 with similar masses, SFRs, and sizes, implying that additional CMQGs must be created in the intervening 1 Gyr between z = 3 and z = 2. We find five star-forming galaxies at z 3 that are compact (Re < 1.4 kpc) and have stellar mass M* > 1010.6M; these galaxies are likely to become members of the massive, quiescent, compact galaxy population at z 2. We evolve the stellar masses and SFRs of each individual z > 3 galaxy adopting five different star formation histories (SFHs) and studying the resulting population of massive galaxies at z = 2.3. We find that declining or truncated SFHs are necessary to match the observed number density of MQGs at z 2, whereas a constant delayed-exponential SFH would result in a number density significantly smaller than observed. All of our assumed SFHs imply number densities of CMQGs at z 2 that are consistent with the observed number density. Better agreement with the observed number density of CMQGs at z 2 is obtained if merging is included in the analysis and better still if

Deducing the Milky Way's Massive Cluster Population

NASA Astrophysics Data System (ADS)

Hanson, M. M.; Popescu, B.; Larsen, S. S.; Ivanov, V. D.

2010-11-01

Recent near-infrared surveys of the galactic plane have been used to identify new massive cluster candidates. Follow up study indicates about half are not true, gravitationally-bound clusters. These false positives are created by high density fields of unassociated stars, often due to a sight-line of reduced extinction. What is not so easy to estimate is the number of false negatives, clusters which exist but are not currently being detected by our surveys. In order to derive critical characteristics of the Milky Way's massive cluster population, such as cluster mass function and cluster lifetimes, one must be able to estimate the characteristics of these false negatives. Our group has taken on the daunting task of attempting such an estimate by first creating the stellar cluster imaging simulation program, MASSCLEAN. I will present our preliminary models and methods for deriving the biases of current searches.

Massive Smash-up at Vega Artist Concept

NASA Image and Video Library

2005-01-10

This artist concept illustrates how a massive collision of objects perhaps as large as the planet Pluto smashed together to create the dust ring around the nearby star Vega. New observations from NASA's Spitzer Space Telescope indicate the collision took place within the last one million years. Astronomers think that embryonic planets smashed together, shattered into pieces, and repeatedly crashed into other fragments to create ever finer debris. In the image, a collision is seen between massive objects that measured up to 2,000 kilometers (about 1,200 miles) in diameter. Scientists say the big collision initiated subsequent collisions that created dust particles around the star that were a few microns in size. Vega's intense light blew these fine particles to larger distances from the star, and also warmed them to emit heat radiation that can be detected by Spitzer's infrared detectors. http://photojournal.jpl.nasa.gov/catalog/PIA07217

Magnetic fields in the formation of massive stars.

PubMed

Girart, Josep M; Beltrán, Maria T; Zhang, Qizhou; Rao, Ramprasad; Estalella, Robert

2009-06-12

Massive stars play a crucial role in the production of heavy elements and in the evolution of the interstellar medium, yet how they form is still a matter of debate. We report high-angular-resolution submillimeter observations toward the massive hot molecular core (HMC) in the high-mass star-forming region G31.41+0.31. We find that the evolution of the gravitational collapse of the HMC is controlled by the magnetic field. The HMC is simultaneously contracting and rotating, and the magnetic field lines threading the HMC are deformed along its major axis, acquiring an hourglass shape. The magnetic energy dominates over the centrifugal and turbulence energies, and there is evidence of magnetic braking in the contracting core.

Holographic thermalization and generalized Vaidya-AdS solutions in massive gravity

NASA Astrophysics Data System (ADS)

Hu, Ya-Peng; Zeng, Xiao-Xiong; Zhang, Hai-Qing

2017-02-01

We investigate the effect of massive graviton on the holographic thermalization process. Before doing this, we first find out the generalized Vaidya-AdS solutions in the de Rham-Gabadadze-Tolley (dRGT) massive gravity by directly solving the gravitational equations. Then, we study the thermodynamics of these Vaidya-AdS solutions by using the Misner-Sharp energy and unified first law, which also shows that the massive gravity is in a thermodynamic equilibrium state. Moreover, we adopt the two-point correlation function at equal time to explore the thermalization process in the dual field theory, and to see how the graviton mass parameter affects this process from the viewpoint of AdS/CFT correspondence. Our results show that the graviton mass parameter will increase the holographic thermalization process.

Massive pericardial effusion and rhabdomyolysis secondary to untreated severe hypothyroidism: the first report.

PubMed

Zare-Khormizi, M R; Rahmanian, M; Pourrajab, F; Akbarnia, S

2014-10-01

Hypothyroidism is an endocrine disease with various clinical manifestations. It is a rare cause for rhabdomyolysis and massive pericardial effusion. We describe a case of severe hypothyroidism secondary to autoimmune hashimoto thyroiditis with massive pericardial effusion and rhabdomyolysis. Improvement of mentioned complications after hypothyroidism treatment and rule out of other possible causes are supportive clues that hypothyroidism is the main cause of patient's rare presentation. With the best of our knowledge, it is the first report of rhabdomyolysis and massive pericardial effusion coincidence in a patient of adult population with primary uncontrolled hypothyroidism for years.

Colony size as a species character in massive reef corals

NASA Astrophysics Data System (ADS)

Soong, Keryea

1993-07-01

In a study of seven massive, Caribbean corals, I have found major differences in reproductive behavior between species with large maximum colony sizes and species with smaller maximum colony sizes. Four species ( Diploria clivosa, D. strigosa, Montastrea cavernosa, Siderastrea siderea) which are large (<1000 cm2 in surface area) broadcast gametes during a short spawning season. Their puberty size is relatively large (>100 cm2, except M. cavernosa). In contrast, two small massive species (<100 cm2, Favia fragum and S. radians), and one medium-sized (100 1000 cm2, Porites astreoides) massive species, brood larvae during an extended season (year-round in Panama). The puberty size of the small species is only 2 4 cm2. Given these close associations between maximum colony sizes and a number of fundamental reproductive attributes, greater attention should be given to the colony size distributions of different species of reef corals in nature, since many important life history and population characters may be inferred.

Light element production by low energy nuclei from massive stars

NASA Technical Reports Server (NTRS)

Vangioni-Flam, E.; Casse, M.; Ramaty, R.

1997-01-01

The Orion complex is a source of gamma rays attributed to the de-excitation of fast carbon and oxygen nuclei excited through interactions with ambient hydrogen and helium. This has consequences for the production and evolution of light isotopes in the Galaxy, as massive stars appear as prolific sources of C-O rich low energy nuclei. The different stages of massive star evolution are considered in relation to the acceleration of nuclei to moderate energies. It is concluded that the low energy nuclear component originating from massive stars plays a larger role than the usual Galactic cosmic rays in shaping the evolution of Li-6, Be-9, B-10 and B-11, especially in the early Galactic evolution. The enhancement of the B-11/B-10 ratio observed in meteorites and in the interstellar medium is attributed to the interaction of low energy carbon nuclei with ambient H and to a lesser degree, to neutrino spallation.

HIGH-RESOLUTION 8 mm AND 1 cm POLARIZATION OF IRAS 4A FROM THE VLA NASCENT DISK AND MULTIPLICITY (VANDAM) SURVEY

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

Cox, Erin G.; Harris, Robert J.; Looney, Leslie W.

2015-12-01

Magnetic fields can regulate disk formation, accretion, and jet launching. Until recently, it has been difficult to obtain high-resolution observations of the magnetic fields of the youngest protostars in the critical region near the protostar. The VANDAM survey is observing all known protostars in the Perseus Molecular Cloud. Here we present the polarization data of IRAS 4A. We find that with ∼0.″2 (50 AU) resolution at λ = 8.1 and 10.3 mm, the inferred magnetic field is consistent with a circular morphology, in marked contrast with the hourglass morphology seen on larger scales. This morphology is consistent with frozen-in fieldmore » lines that were dragged in by rotating material entering the infall region. The field morphology is reminiscent of rotating circumstellar material near the protostar. This is the first polarization detection of a protostar at these wavelengths. We conclude from our observations that the dust emission is optically thin with β ∼ 1.3, suggesting that millimeter-/centimeter-sized grains have grown and survived in the short lifetime of the protostar.« less

The Evolution of the Multiplicity of Embedded Protostars. II. Binary Separation Distribution and Analysis

NASA Astrophysics Data System (ADS)

Connelley, Michael S.; Reipurth, Bo; Tokunaga, Alan T.

2008-06-01

We present the Class I protostellar binary separation distribution based on the data tabulated in a companion paper. We verify the excess of Class I binary stars over solar-type main-sequence stars in the separation range from 500 AU to 4500 AU. Although our sources are in nearby star-forming regions distributed across the entire sky (including Orion), none of our objects are in a high stellar density environment. A log-normal function, used by previous authors to fit the main-sequence and T Tauri binary separation distributions, poorly fits our data, and we determine that a log-uniform function is a better fit. Our observations show that the binary separation distribution changes significantly during the Class I phase, and that the binary frequency at separations greater than 1000 AU declines steadily with respect to spectral index. Despite these changes, the binary frequency remains constant until the end of the Class I phase, when it drops sharply. We propose a scenario to account for the changes in the Class I binary separation distribution. This scenario postulates that a large number of companions with a separation greater than ~1000 AU were ejected during the Class 0 phase, but remain gravitationally bound due to the significant mass of the Class I envelope. As the envelope dissipates, these companions become unbound and the binary frequency at wide separations declines. Circumstellar and circumbinary disks are expected to play an important role in the orbital evolution at closer separations. This scenario predicts that a large number of Class 0 objects should be non-hierarchical multiple systems, and that many Class I young stellar objects (YSOs) with a widely separated companion should also have a very close companion. We also find that Class I protostars are not dynamically pristine, but have experienced dynamical evolution before they are visible as Class I objects. Our analysis shows that the Class I binary frequency and the binary separation

The singular behavior of one-loop massive QCD amplitudes with one external soft gluon

NASA Astrophysics Data System (ADS)

Bierenbaum, Isabella; Czakon, Michał; Mitov, Alexander

2012-03-01

We calculate the one-loop correction to the soft-gluon current with massive fermions. This current is process independent and controls the singular behavior of one-loop massive QCD amplitudes in the limit when one external gluon becomes soft. The result derived in this work is the last missing process-independent ingredient needed for numerical evaluation of observables with massive fermions at hadron colliders at the next-to-next-to-leading order.

On massive carbide precipitation during high temperature low cycle fatigue in alloy 800H

NASA Technical Reports Server (NTRS)

Sankararao, K. Bhanu; Schuster, H.; Halford, G. R.

1994-01-01

The effect of strain rate on massive precipitation and the mechanism for the occurrence of massive precipitation of M23C6 in alloy 800H is investigated during elevated temperature low cycle fatigue testing. It was observed that large M23C6 platelets were in the vicinity of grain and incoherent twin boundaries. The strain controlled fatigue testing at higher strain rates that promoted cyclic hardening enabled massive precipitation to occur more easily.

Propagation peculiarities of mean field massive gravity

DOE PAGES

Deser, S.; Waldron, A.; Zahariade, G.

2015-07-28

Massive gravity (mGR) describes a dynamical “metric” on a fiducial, background one. We investigate fluctuations of the dynamics about mGR solutions, that is about its “mean field theory”. Analyzing mean field massive gravity (m¯GR) propagation characteristics is not only equivalent to studying those of the full non-linear theory, but also in direct correspondence with earlier analyses of charged higher spin systems, the oldest example being the charged, massive spin 3/2 Rarita–Schwinger (RS) theory. The fiducial and mGR mean field background metrics in the m¯GR model correspond to the RS Minkowski metric and external EM field. The common implications in bothmore » systems are that hyperbolicity holds only in a weak background-mean-field limit, immediately ruling both theories out as fundamental theories; a situation in stark contrast with general relativity (GR) which is at least a consistent classical theory. Moreover, even though both m¯GR and RS theories can still in principle be considered as predictive effective models in the weak regime, their lower helicities then exhibit superluminal behavior: lower helicity gravitons are superluminal as compared to photons propagating on either the fiducial or background metric. Thus our approach has uncovered a novel, dispersive, “crystal-like” phenomenon of differing helicities having differing propagation speeds. As a result, this applies both to m¯GR and mGR, and is a peculiar feature that is also problematic for consistent coupling to matter.« less

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

Runaway Massive Stars from R136: VFTS 682 is Very Likely a "Slow Runaway"

NASA Astrophysics Data System (ADS)

Banerjee, Sambaran; Kroupa, Pavel; Oh, Seungkyung

2012-02-01

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 primordial 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 ⊙. 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 ⊙ limit, as has been suggested recently, and they are consistent with the canonical upper limit.

Interstitial pulmonary fibrosis and progressive massive fibrosis related to smoking methamphetamine with talc as filler.

PubMed

Baylor, Peter A; Sobenes, Juan R; Vallyathan, Val

2013-05-01

We present a case of interstitial pulmonary fibrosis accompanied by radiographic evidence of progressive massive fibrosis in a patient who had a 15-20 year history of almost daily recreational inhalation of methamphetamine. Mineralogical analysis confirmed the presence of talc on biopsy of the area of progressive massive fibrosis. The coexistence of interstitial pulmonary fibrosis and progressive massive fibrosis suggests that prolonged recreational inhalation of methamphetamine that has been "cut" with talc can result in sufficient amount of talc being inhaled to result in interstitial pulmonary fibrosis and progressive massive fibrosis in the absence of other causes.

The MASSIVE Survey - X. Misalignment between Kinematic and Photometric Axes and Intrinsic Shapes of Massive Early-Type Galaxies

NASA Astrophysics Data System (ADS)

Ene, Irina; Ma, Chung-Pei; Veale, Melanie; Greene, Jenny E.; Thomas, Jens; Blakeslee, John P.; Foster, Caroline; Walsh, Jonelle L.; Ito, Jennifer; Goulding, Andy D.

2018-06-01

We use spatially resolved two-dimensional stellar velocity maps over a 107″ × 107″ field of view to investigate the kinematic features of 90 early-type galaxies above stellar mass 1011.5M⊙ in the MASSIVE survey. We measure the misalignment angle Ψ between the kinematic and photometric axes and identify local features such as velocity twists and kinematically distinct components. We find 46% of the sample to be well aligned (Ψ < 15°), 33% misaligned, and 21% without detectable rotation (non-rotators). Only 24% of the sample are fast rotators, the majority of which (91%) are aligned, whereas 57% of the slow rotators are misaligned with a nearly flat distribution of Ψ from 15° to 90°. 11 galaxies have Ψ ≳ 60° and thus exhibit minor-axis ("prolate") rotation in which the rotation is preferentially around the photometric major axis. Kinematic misalignments occur more frequently for lower galaxy spin or denser galaxy environments. Using the observed misalignment and ellipticity distributions, we infer the intrinsic shape distribution of our sample and find that MASSIVE slow rotators are consistent with being mildly triaxial, with mean axis ratios of b/a = 0.88 and c/a = 0.65. In terms of local kinematic features, 51% of the sample exhibit kinematic twists of larger than 20°, and 2 galaxies have kinematically distinct components. The frequency of misalignment and the broad distribution of Ψ reported here suggest that the most massive early-type galaxies are mildly triaxial, and that formation processes resulting in kinematically misaligned slow rotators such as gas-poor mergers occur frequently in this mass range.

Noncommutative massive unquenched ABJM

NASA Astrophysics Data System (ADS)

Bea, Yago; Jokela, Niko; Pönni, Arttu; Ramallo, Alfonso V.

2018-05-01

In this paper, we study noncommutative massive unquenched Chern-Simons matter theory using its gravity dual. We construct this novel background by applying a TsT-transformation on the known parent commutative solution. We discuss several aspects of this solution to the Type IIA supergravity equations of motion and, amongst others, check that it preserves 𝒩 = 1 supersymmetry. We then turn our attention to applications and investigate how dynamical flavor degrees of freedom affect numerous observables of interest. Our framework can be regarded as a key step toward the construction of holographic quantum Hall states on a noncommutative plane.

Outcomes from massive paracetamol overdose: a retrospective observational study

PubMed Central

Marks, Daniel J. B.; Dargan, Paul I.; Archer, John R. H.; Davies, Charlotte L.; Dines, Alison M.; Wood, David M.

2017-01-01

LINKED ARTICLE This article is commented on by Bateman DN and Dear JW. Should we treat very large paracetamol overdose differently? Br J Clin Pharmacol 2017; 83: 1163–5. https://doi.org/10.1111/bcp.13279 Aims Treatment of paracetamol (acetaminophen) overdose with acetylcysteine is standardized, with dose determined only by patient weight. The validity of this approach for massive overdoses has been questioned. We systematically compared outcomes in massive and non‐massive overdoses, to guide whether alternative treatment strategies should be considered, and whether the ratio between measured timed paracetamol concentrations (APAPpl) and treatment nomogram thresholds at those time points (APAPt) provides a useful assessment tool. Methods This is a retrospective observational study of all patients (n = 545) between 2005 and 2013 admitted to a tertiary care toxicology service with acute non‐staggered paracetamol overdose. Massive overdoses were defined as extrapolated 4‐h plasma paracetamol concentrations >250 mg l−1, or reported ingestions ≥30 g. Outcomes (liver injury, coagulopathy and kidney injury) were assessed in relation to reported dose and APAPpl:APAPt ratio (based on a treatment line through 100 mg l−1 at 4 h), and time to acetylcysteine. Results Ingestions of ≥30 g paracetamol correlated with higher peak serum aminotransferase (r = 0.212, P < 0.0001) and creatinine (r = 0.138, P = 0.002) concentrations. Acute liver injury, hepatotoxicity and coagulopathy were more frequent with APAPpl:APAPt ≥ 3 with odds ratios (OR) and 95% confidence intervals (CI) of 9.19 (5.04–16.68), 35.95 (8.80–158.1) and 8.34 (4.43–15.84), respectively (P < 0.0001). Heightened risk persisted in patients receiving acetylcysteine within 8 h of overdose. Conclusion Patients presenting following massive paracetamol overdose are at higher risk of organ injury, even when acetylcysteine is administered early. Enhanced therapeutic strategies

Outcomes from massive paracetamol overdose: a retrospective observational study.

PubMed

Marks, Daniel J B; Dargan, Paul I; Archer, John R H; Davies, Charlotte L; Dines, Alison M; Wood, David M; Greene, Shaun L

2017-06-01

This article is commented on by Bateman DN and Dear JW. Should we treat very large paracetamol overdose differently? Br J Clin Pharmacol 2017; 83: 1163-5. https://doi.org/10.1111/bcp.13279 AIMS: Treatment of paracetamol (acetaminophen) overdose with acetylcysteine is standardized, with dose determined only by patient weight. The validity of this approach for massive overdoses has been questioned. We systematically compared outcomes in massive and non-massive overdoses, to guide whether alternative treatment strategies should be considered, and whether the ratio between measured timed paracetamol concentrations (APAP pl ) and treatment nomogram thresholds at those time points (APAP t ) provides a useful assessment tool. This is a retrospective observational study of all patients (n = 545) between 2005 and 2013 admitted to a tertiary care toxicology service with acute non-staggered paracetamol overdose. Massive overdoses were defined as extrapolated 4-h plasma paracetamol concentrations >250 mg l -1 , or reported ingestions ≥30 g. Outcomes (liver injury, coagulopathy and kidney injury) were assessed in relation to reported dose and APAP pl :APAP t ratio (based on a treatment line through 100 mg l -1 at 4 h), and time to acetylcysteine. Ingestions of ≥30 g paracetamol correlated with higher peak serum aminotransferase (r = 0.212, P < 0.0001) and creatinine (r = 0.138, P = 0.002) concentrations. Acute liver injury, hepatotoxicity and coagulopathy were more frequent with APAP pl :APAP t  ≥ 3 with odds ratios (OR) and 95% confidence intervals (CI) of 9.19 (5.04-16.68), 35.95 (8.80-158.1) and 8.34 (4.43-15.84), respectively (P < 0.0001). Heightened risk persisted in patients receiving acetylcysteine within 8 h of overdose. Patients presenting following massive paracetamol overdose are at higher risk of organ injury, even when acetylcysteine is administered early. Enhanced therapeutic strategies should be considered in those who have an APAP pl

THE ROLE OF THE MAGNETOROTATIONAL INSTABILITY IN MASSIVE STARS

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

Wheeler, J. Craig; Kagan, Daniel; Chatzopoulos, Emmanouil, E-mail: wheel@astro.as.utexas.edu

2015-01-20

The magnetorotational instability (MRI) is key to physics in accretion disks and is widely considered to play some role in massive star core collapse. Models of rotating massive stars naturally develop very strong shear at composition boundaries, a necessary condition for MRI instability, and the MRI is subject to triply diffusive destabilizing effects in radiative regions. We have used the MESA stellar evolution code to compute magnetic effects due to the Spruit-Tayler (ST) mechanism and the MRI, separately and together, in a sample of massive star models. We find that the MRI can be active in the later stages ofmore » massive star evolution, leading to mixing effects that are not captured in models that neglect the MRI. The MRI and related magnetorotational effects can move models of given zero-age main sequence mass across ''boundaries'' from degenerate CO cores to degenerate O/Ne/Mg cores and from degenerate O/Ne/Mg cores to iron cores, thus affecting the final evolution and the physics of core collapse. The MRI acting alone can slow the rotation of the inner core in general agreement with the observed ''initial'' rotation rates of pulsars. The MRI analysis suggests that localized fields ∼10{sup 12} G may exist at the boundary of the iron core. With both the ST and MRI mechanisms active in the 20 M {sub ☉} model, we find that the helium shell mixes entirely out into the envelope. Enhanced mixing could yield a population of yellow or even blue supergiant supernova progenitors that would not be standard SN IIP.« less

Massive Multi-Agent Systems Control

NASA Technical Reports Server (NTRS)

Campagne, Jean-Charles; Gardon, Alain; Collomb, Etienne; Nishida, Toyoaki

2004-01-01

In order to build massive multi-agent systems, considered as complex and dynamic systems, one needs a method to analyze and control the system. We suggest an approach using morphology to represent and control the state of large organizations composed of a great number of light software agents. Morphology is understood as representing the state of the multi-agent system as shapes in an abstract geometrical space, this notion is close to the notion of phase space in physics.

Successful management of trachea stenosis with massive substernal goiter via thacheobronchial stent

PubMed Central

2013-01-01

A case of 65 year-old Chinese male patient with severe tracheal stenosis due to a massive substernal goiter, is presented. MRI and CT scan revealed that the massive substernal goiter was 9.3 × 6.1 × 4.7 cm in size, displacing the trachea and adjacent large vessels to the patient’s right contributing to severe intrathoracic trachea compression up to 6 cm in length and the narrowest caliber of the trachea only 3.0 mm in diameter. To the best of our knowledge, optimal airway management for the massive substernal goiter resection was considered to be temporary tracheobronchial stent placement pre-operation. PMID:24228633

Near infrared observations of S 155. Evidence of induced star formation?

NASA Astrophysics Data System (ADS)

Hunt, L. K.; Lisi, F.; Felli, M.; Tofani, G.

In order to investigate the possible existence of embedded objects of recent formation in the area of the Cepheus B - Sh2-155 interface, the authors have observed the region of the compact radio continuum source with the new near infrared camera ARNICA and the TIRGO telescope.

An excess of massive stars in the local 30 Doradus starburst

NASA Astrophysics Data System (ADS)

Schneider, F. R. N.; Sana, H.; Evans, C. J.; Bestenlehner, J. M.; Castro, N.; Fossati, L.; Gräfener, G.; Langer, N.; Ramírez-Agudelo, O. H.; Sabín-Sanjulián, C.; Simón-Díaz, S.; Tramper, F.; Crowther, P. A.; de Koter, A.; de Mink, S. E.; Dufton, P. L.; Garcia, M.; Gieles, M.; Hénault-Brunet, V.; Herrero, A.; Izzard, R. G.; Kalari, V.; Lennon, D. J.; Maíz Apellániz, J.; Markova, N.; Najarro, F.; Podsiadlowski, Ph.; Puls, J.; Taylor, W. D.; van Loon, J. Th.; Vink, J. S.; Norman, C.

2018-01-01

The 30 Doradus star-forming region in the Large Magellanic Cloud is a nearby analog of large star-formation events in the distant universe. We determined the recent formation history and the initial mass function (IMF) of massive stars in 30 Doradus on the basis of spectroscopic observations of 247 stars more massive than 15 solar masses (M☉). The main episode of massive star formation began about 8 million years (My) ago, and the star-formation rate seems to have declined in the last 1 My. The IMF is densely sampled up to 200 M☉ and contains 32 ± 12% more stars above 30 M☉ than predicted by a standard Salpeter IMF. In the mass range of 15 to 200 M☉, the IMF power-law exponent is 1.90‑0.26+0.37, shallower than the Salpeter value of 2.35.

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.

Color Magnitude Diagrams of Old, Massive GCs in M31

NASA Astrophysics Data System (ADS)

Caldwell, Nelson; Williams, B.; Dolphin, A. E.; Johnson, L. C.; Weisz, D. R.

2013-01-01

Multicolor stellar photometry of HST data of M31 collected as part of the PHAT project has been performed using the DOLPHOT suite of programs. We present results of color-magnitude diagrams created in F475W and F814W (BI) of more than 50 massive, old clusters. These are clusters in or projected on the disk. We compare the metallicities derived from the color of the giant branch stars with that derived from integrated light spectroscopy. As well, we compare the ages of massive, young clusters with those found from spectra.

Escape of gravitational radiation from the field of massive bodies

NASA Technical Reports Server (NTRS)

Price, Richard H.; Pullin, Jorge; Kundu, Prasun K.

1993-01-01

We consider a compact source of gravitational waves of frequency omega in or near a massive spherically symmetric distribution of matter or a black hole. Recent calculations have led to apparently contradictory results for the influence of the massive body on the propagation of the waves. We show here that the results are in fact consistent and in agreement with the 'standard' viewpoint in which the high-frequency compact source produces the radiation as if in a flat background, and the background curvature affects the propagation of these waves.

The Evolution of Massive Stars: a Selection of Facts and Questions

NASA Astrophysics Data System (ADS)

Vanbeveren, D.

In the present paper we discuss a selection of facts and questions related to observations and evolutionary calculations of massive single stars and massive stars in interacting binaries. We focus on the surface chemical abundances, the role of stellar winds, the early Be-stars, the high mass X-ray binaries and the effects of rotation on stellar evolution. Finally, we present an unconventionally formed object scenario (UFO-scenario) of WR binaries in dense stellar environments.

Massive Galaxies at z=2-3: A Large Population of Disky Star-Forming Systems?

NASA Astrophysics Data System (ADS)

Weinzirl, Tim; Jogee, S.; GOODS-NICMOS Collaboration

2011-01-01

The assembly modes via which galaxies develop their present-day mass and structure remain hotly debated. We explore this issue using one of the largest samples of massive galaxies (166 with stellar mass Mstar ≥ 5 × 1010 M⊙) at z=1-3 with NICMOS F160W observations from the GOODS NICMOS Survey (GNS), along with complementary ACS, Spitzer, and Chandra data. Our findings are: (1) The majority of the massive galaxies at z=2-3 have a disky structure (as characterized by the index of single-component Sersic profiles). Most are also compact with half-light radii less than 2 kpc. These massive galaxies at z=2-3 appear to be radically different in structure from their more massive descendants at z 0. Through artificial redshfiting experiments based on redshifted simulated NICMOS data of such massive z 0 elliptical, S0, and spiral galaxies, we show that most of this difference in structure is not due to cosmological or instrumental effects. This implies that significant structural evolution is needed to convert the massive z=2-3 systems into their z 0 elliptical and S0 descendants, and places important constraints on the associated evolutionary mechanisms (e.g., major mergers and cold accretion). (2) Using IR luminosities inferred from Spitzer detections, we find that over z=1-3, the mean star formation rate (SFR) rises substantially, even if AGN candidates are excluded. SFRs of several hundred solar masses per year or higher are common. The results imply a much higher average cold gas fraction than exists in z 0 galaxies. (3) We identify AGN candidates using a variety of techniques (X-ray properties, IR power-law, and IR-to-optical excess) and classify about one-third of the massive galaxies at z=1-3 as AGN hosts. The AGN fraction rises with redshift and is 40% at z=2-3. A significant fraction of the AGN candidates have disky structures although they host massive black holes.

Predicting the need for massive transfusion in trauma patients: the Traumatic Bleeding Severity Score.

PubMed

Ogura, Takayuki; Nakamura, Yoshihiko; Nakano, Minoru; Izawa, Yoshimitsu; Nakamura, Mitsunobu; Fujizuka, Kenji; Suzukawa, Masayuki; Lefor, Alan T

2014-05-01

The ability to easily predict the need for massive transfusion may improve the process of care, allowing early mobilization of resources. There are currently no clear criteria to activate massive transfusion in severely injured trauma patients. The aims of this study were to create a scoring system to predict the need for massive transfusion and then to validate this scoring system. We reviewed the records of 119 severely injured trauma patients and identified massive transfusion predictors using statistical methods. Each predictor was converted into a simple score based on the odds ratio in a multivariate logistic regression analysis. The Traumatic Bleeding Severity Score (TBSS) was defined as the sum of the component scores. The predictive value of the TBSS for massive transfusion was then validated, using data from 113 severely injured trauma patients. Receiver operating characteristic curve analysis was performed to compare the results of TBSS with the Trauma-Associated Severe Hemorrhage score and the Assessment of Blood Consumption score. In the development phase, five predictors of massive transfusion were identified, including age, systolic blood pressure, the Focused Assessment with Sonography for Trauma scan, severity of pelvic fracture, and lactate level. The maximum TBSS is 57 points. In the validation study, the average TBSS in patients who received massive transfusion was significantly greater (24.2 [6.7]) than the score of patients who did not (6.2 [4.7]) (p < 0.01). The area under the receiver operating characteristic curve, sensitivity, and specificity for a TBSS greater than 15 points was 0.985 (significantly higher than the other scoring systems evaluated at 0.892 and 0.813, respectively), 97.4%, and 96.2%, respectively. The TBSS is simple to calculate using an available iOS application and is accurate in predicting the need for massive transfusion. Additional multicenter studies are needed to further validate this scoring system and further

The environment of young massive clusters

NASA Astrophysics Data System (ADS)

Vanzi, L.; Sauvage, M.

2006-06-01

We observed a sample of Blue Dwarf Galaxies in the Ks (2.2 μm) and Lα (3.7 μm) IR bands at the ESO VLT with ISAAC. The purpose of the observations was to study the population of young massive clusters and the conditions under which they are formed. The sample galaxies included: Tol 1924-416, Tol 35, Pox 36, UM 462, He 2-10, II Zw 40, Tol 3, NGC 1705, NGC 5408, IC 4662, NGC 5253. They were selected to have evidence for star formation and firm detection by IRAS. All galaxies observed turned to be very rich of young massive clusters in Ks. Only few clusters, about 8%, showed counterparts in Lα. Most L' sources can be associated to radio thermal sources, with the only exception of the NGC 1705's one. For two galaxies, NGC 5408 and IC 4662, we derived the cluster luminosity functions finding them consistent with a power law of index about -2. We compared the numbers and luminosities of the clusters with the star formation rate of the host galaxy and could not find any evidence of a relation.

A Systematic Review of the Socio-Ethical Aspects of Massive Online Open Courses

ERIC Educational Resources Information Center

Rolfe, Vivien

2015-01-01

Massive open online courses (MOOCs) offer learners across the globe unprecedented access to education. Through sophisticated e-learning technologies and web approaches, MOOCs attract massive scale participation and global interest. Some commercial ventures place social equality at the heart of their missions, claiming to empower communities by…

R144: a very massive binary likely ejected from R136 through a binary-binary encounter

NASA Astrophysics Data System (ADS)

Oh, Seungkyung; Kroupa, Pavel; Banerjee, Sambaran

2014-02-01

R144 is a recently confirmed very massive, spectroscopic binary which appears isolated from the core of the massive young star cluster R136. The dynamical ejection hypothesis as an origin for its location is claimed improbable by Sana et al. due to its binary nature and high mass. We demonstrate here by means of direct N-body calculations that a very massive binary system can be readily dynamically ejected from an R136-like cluster, through a close encounter with a very massive system. One out of four N-body cluster models produces a dynamically ejected very massive binary system with a mass comparable to R144. The system has a system mass of ≈355 M⊙ and is located at 36.8 pc from the centre of its parent cluster, moving away from the cluster with a velocity of 57 km s-1 at 2 Myr as a result of a binary-binary interaction. This implies that R144 could have been ejected from R136 through a strong encounter with another massive binary or single star. In addition, we discuss all massive binaries and single stars which are ejected dynamically from their parent cluster in the N-body models.

NGC 346: Looking in the Cradle of a Massive Star Cluster

NASA Astrophysics Data System (ADS)

Gouliermis, Dimitrios A.; Hony, Sacha

2017-03-01

How does a star cluster of more than few 10,000 solar masses form? We present the case of the cluster NGC 346 in the Small Magellanic Cloud, still embedded in its natal star-forming region N66, and we propose a scenario for its formation, based on observations of the rich stellar populations in the region. Young massive clusters host a high fraction of early-type stars, indicating an extremely high star formation efficiency. The Milky Way galaxy hosts several young massive clusters that fill the gap between young low-mass open clusters and old massive globular clusters. Only a handful, though, are young enough to study their formation. Moreover, the investigation of their gaseous natal environments suffers from contamination by the Galactic disk. Young massive clusters are very abundant in distant starburst and interacting galaxies, but the distance of their hosting galaxies do not also allow a detailed analysis of their formation. The Magellanic Clouds, on the other hand, host young massive clusters in a wide range of ages with the youngest being still embedded in their giant HII regions. Hubble Space Telescope imaging of such star-forming complexes provide a stellar sampling with a high dynamic range in stellar masses, allowing the detailed study of star formation at scales typical for molecular clouds. Our cluster analysis on the distribution of newly-born stars in N66 shows that star formation in the region proceeds in a clumpy hierarchical fashion, leading to the formation of both a dominant young massive cluster, hosting about half of the observed pre-main-sequence population, and a self-similar dispersed distribution of the remaining stars. We investigate the correlation between stellar surface density (and star formation rate derived from star-counts) and molecular gas surface density (derived from dust column density) in order to unravel the physical conditions that gave birth to NGC 346. A power law fit to the data yields a steep correlation between these

The EMCC / DARPA Massively Parallel Electromagnetic Scattering Project

NASA Technical Reports Server (NTRS)

Woo, Alex C.; Hill, Kueichien C.

1996-01-01

The Electromagnetic Code Consortium (EMCC) was sponsored by the Advanced Research Program Agency (ARPA) to demonstrate the effectiveness of massively parallel computing in large scale radar signature predictions. The EMCC/ARPA project consisted of three parts.

Probing Massive Black Hole Populations and Their Environments with LISA

NASA Astrophysics Data System (ADS)

Katz, Michael; Larson, Shane

2018-01-01

With the adoption of the LISA Mission Proposal by the European Space Agency in response to its call for L3 mission concepts, gravitational wave measurements from space are on the horizon. With data from the Illustris large-scale cosmological simulation, we provide analysis of LISA detection rates accompanied by characterization of the merging Massive Black Holes (MBH) and their host galaxies. MBHs of total mass $\\sim10^6-10^9 M_\\odot$ are the main focus of this study. Using a precise treatment of the dynamical friction evolutionary process prior to gravitational wave emission, we evolve MBH simulation particle mergers from $\\sim$kpc scales until coalescence to achieve a merger distribution. Using the statistical basis of the Illustris output, we Monte-carlo synthesize many realizations of the merging massive black hole population across space and time. We use those realizations to build mock LISA detection catalogs to understand the impact of LISA mission configurations on our ability to probe massive black hole merger populations and their environments throughout the visible Universe.

Increasing the reach of forensic genetics with massively parallel sequencing.

PubMed

Budowle, Bruce; Schmedes, Sarah E; Wendt, Frank R

2017-09-01

The field of forensic genetics has made great strides in the analysis of biological evidence related to criminal and civil matters. More so, the discipline has set a standard of performance and quality in the forensic sciences. The advent of massively parallel sequencing will allow the field to expand its capabilities substantially. This review describes the salient features of massively parallel sequencing and how it can impact forensic genetics. The features of this technology offer increased number and types of genetic markers that can be analyzed, higher throughput of samples, and the capability of targeting different organisms, all by one unifying methodology. While there are many applications, three are described where massively parallel sequencing will have immediate impact: molecular autopsy, microbial forensics and differentiation of monozygotic twins. The intent of this review is to expose the forensic science community to the potential enhancements that have or are soon to arrive and demonstrate the continued expansion the field of forensic genetics and its service in the investigation of legal matters.

Gravitational Wave Signals from the First Massive Black Hole Seeds

NASA Astrophysics Data System (ADS)

Hartwig, Tilman; Agarwal, Bhaskar; Regan, John A.

2018-05-01

Recent numerical simulations reveal that the isothermal collapse of pristine gas in atomic cooling haloes may result in stellar binaries of supermassive stars with M* ≳ 104M⊙. For the first time, we compute the in-situ merger rate for such massive black hole remnants by combining their abundance and multiplicity estimates. For black holes with initial masses in the range 104 - 6M⊙ merging at redshifts z ≳ 15 our optimistic model predicts that LISA should be able to detect 0.6 mergers per year. This rate of detection can be attributed, without confusion, to the in-situ mergers of seeds from the collapse of very massive stars. Equally, in the case where LISA observes no mergers from heavy seeds at z ≳ 15 we can constrain the combined number density, multiplicity, and coalesence times of these high-redshift systems. This letter proposes gravitational wave signatures as a means to constrain theoretical models and processes that govern the abundance of massive black hole seeds in the early Universe.

Analysis of crossover between local and massive separation on airfoils

NASA Technical Reports Server (NTRS)

Barnett, Mark

1987-01-01

The occurrence of massive separation on airfoils operating at high Reynolds number poses an important problem to the aerodynamicist. In the present study, the phenomenon of crossover, induced by airfoil thickness, between local separation and massive separation is investigated for low speed (incompressible), symmetric flow past realistic airfoil geometries. This problem is studied both for the infinite Reynolds number asymptotic limit using triple-deck theory and for finite Reynolds number using interacting boundary-layer theory. Numerical results are presented which illustrate how the flow evolves from local to massive separation as the airfoil thickness is increased. The results of the triple-deck and the interacting boundary-layer analyses are found to be in qualitative agreement for the NACA four digit series and an uncambered supercritical airfoil. The effect of turbulence on the evolution of the flow is also considered. Solutions are presented for turbulent flows past a NACA 0014 airfoil and a circular cylinder. For the latter case, the calculated surface pressure distribution is found to agree well with experimental data if the proper eddy pressure level is specified.

Critical Discussions on the Massive Open Online Course (MOOC) in India and China

ERIC Educational Resources Information Center

Trehan, Sangeeta; Sanzgiri, Janesh; Li, Chenxi; Wang, Rongsheng; Joshi, Rakesh Mohan

2017-01-01

Massive Open Online Courses (MOOCs) have been a relatively recent entrant in the field of online learning, yet with their "massiveness" and "openness" were posited to have the potential to transform learning and development in developing countries by providing willing learners with ready access to knowledge and Higher Education…

Tourmaline in Appalachian - Caledonian massive sulphide deposits and its exploration significance.

USGS Publications Warehouse

Slack, J.F.

1982-01-01

Tourmaline is a common gangue mineral in several types of stratabound mineral deposits, including some massive base-metal sulphide ores of the Appalachian - Caledonian orogen. It is most abundant (sometimes forming massive foliated tourmalinite) in sediment-hosted deposits, such as those at the Elizabeth Cu mine and the Ore Knob Cu mine (North Carolina, USA). Trace amounts of tourmaline occur associated with volcanic-hosted deposits in the Piedmont and New England and also in the Trondheim district. Tourmaline associated with the massive sulphide deposits are Mg- rich dravites with major- and trace-element compositions significantly different from schorl. It is suggested that the necessary B was produced by submarine exhalative processes as a part of the same hydrothermal system that deposited the ores. An abundance of dravite in non-evaporitic terrains is believed to indicate proximity to former subaqueous fumarolic centres.-R.A.H.

Structure, Dynamics, and Deuterium Fractionation of Massive Pre-stellar Cores

NASA Astrophysics Data System (ADS)

Goodson, Matthew D.; Kong, Shuo; Tan, Jonathan C.; Heitsch, Fabian; Caselli, Paola

2016-12-01

High levels of deuterium fraction in N2H+ are observed in some pre-stellar cores. Single-zone chemical models find that the timescale required to reach observed values ({D}{frac}{{{N}}2{{{H}}}+}\\equiv {{{N}}}2{{{D}}}+/{{{N}}}2{{{H}}}+≳ 0.1) is longer than the free-fall time, possibly 10 times longer. Here, we explore the deuteration of turbulent, magnetized cores with 3D magnetohydrodynamics simulations. We use an approximate chemical model to follow the growth in abundances of N2H+ and N2D+. We then examine the dynamics of the core using each tracer for comparison to observations. We find that the velocity dispersion of the core as traced by N2D+ appears slightly sub-virial compared to predictions of the Turbulent Core Model of McKee & Tan, except at late times just before the onset of protostar formation. By varying the initial mass surface density, the magnetic energy, the chemical age, and the ortho-to-para ratio of H2, we also determine the physical and temporal properties required for high deuteration. We find that low initial ortho-to-para ratios (≲ 0.01) and/or multiple free-fall times (≳ 3) of prior chemical evolution are necessary to reach the observed values of deuterium fraction in pre-stellar cores.

Supersymmetric solutions of N =(1 ,1 ) general massive supergravity

NASA Astrophysics Data System (ADS)

Deger, N. S.; Nazari, Z.; Sarıoǧlu, Ö.

2018-05-01

We construct supersymmetric solutions of three-dimensional N =(1 ,1 ) general massive supergravity (GMG). Solutions with a null Killing vector are, in general, pp-waves. We identify those that appear at critical points of the model, some of which do not exist in N =(1 ,1 ) new massive supergravity (NMG). In the timelike case, we find that many solutions are common with NMG, but there is a new class that is genuine to GMG, two members of which are stationary Lifshitz and timelike squashed AdS spacetimes. We also show that in addition to the fully supersymmetric AdS vacuum, there is a second AdS background with a nonzero vector field that preserves 1 /4 supersymmetry.

Diagnostic validity of hematologic parameters in evaluation of massive pulmonary embolism.

PubMed

Ates, Hale; Ates, Ihsan; Kundi, Harun; Yilmaz, Fatma Meric

2017-09-01

The aim of this study was to determine the hematologic parameter with the highest diagnostic differentiation in the identification of massive acute pulmonary embolism (APE). A retrospective study was performed on patients diagnosing with APE between June 2014 and June 2016. All radiological and laboratory parameters of patients were scanned through the electronic information management system of the hospital. PLR was obtained from the ratio of platelet count to lymphocyte count, NLR was obtained from the ratio of neutrophil count to lymphocyte count, WMR was obtained from white blood cell in mean platelet volume ratio, MPR was obtained from the ratio of mean platelet volume to platelet count, and RPR was obtained from the ratio of red distribution width to platelet count. Six hundred and thirty-nine patients consisting of 292 males (45.7%) and 347 females (54.3%) were included in the research. Independent predictors of massive risk as compared to sub-massive group were; pulmonary arterial systolic pressure (PASP) (OR=1.40; P=.001), PLR (OR=1.59; P<.001), NLR (OR=2.22; P<.001), WMR (OR=1.22; P<.001), MPR (OR=0.33; P<.001), and RPR (OR=0.68; P<.001). Upon evaluation of the diagnostic differentiation of these risk factors for massive APE by employing receiver operating characteristic curve analysis, it was determined that PLR (AUC±SE=0.877±0.015; P<.001), and NLR (AUC±SE=0.893±0.013; P<.001) have similar diagnostic differentiation in diagnosing massive APE and these two parameters are superior over PASP, MPR, WMR, and RPR. We determined that the levels of NLR and PLR are superior to other parameters in the determination of clinical severity in APE cases. © 2016 Wiley Periodicals, Inc.

THE DISCOVERY OF A MASSIVE CLUSTER OF RED SUPERGIANTS WITH GLIMPSE

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

Alexander, Michael J.; Kobulnicky, Henry A.; Clemens, Dan P.

We report the discovery of a previously unknown massive Galactic star cluster at l = 29.{sup 0}22, b = -0.{sup 0}20. Identified visually in mid-IR images from the Spitzer GLIMPSE survey, the cluster contains at least eight late-type supergiants, based on follow-up near-IR spectroscopy, and an additional 3-6 candidate supergiant members having IR photometry consistent with a similar distance and reddening. The cluster lies at a local minimum in the {sup 13}CO column density and 8 {mu}m emission. We interpret this feature as a hole carved by the energetic winds of the evolving massive stars. The {sup 13}CO hole seenmore » in molecular maps at V {sub LSR} {approx} 95 km s{sup -1} corresponds to near/far kinematic distances of 6.1/8.7 {+-} 1 kpc. We calculate a mean spectrophotometric distance of 7.0{sup +3.7} {sub -2.4} kpc, broadly consistent with the kinematic distances inferred. This location places it near the northern end of the Galactic bar. For the mean extinction of A{sub V} = 12.6 {+-} 0.5 mag (A{sub K} = 1.5 {+-} 0.1 mag), the color-magnitude diagram of probable cluster members is well fit by isochrones in the age range 18-24 Myr. The estimated cluster mass is {approx}20,000 M {sub sun}. With the most massive original cluster stars likely deceased, no strong radio emission is detected in this vicinity. As such, this red supergiant (RSG) cluster is representative of adolescent massive Galactic clusters that lie hidden behind many magnitudes of dust obscuration. This cluster joins two similar RSG clusters as residents of the volatile region where the end of our Galaxy's bar joins the base of the Scutum-Crux spiral arm, suggesting a recent episode of widespread massive star formation there.« less

A butterfly-shaped 'Papillon Nebula' yields secrets of massive star birth

NASA Astrophysics Data System (ADS)

1999-06-01

The newly found massive newborn stars are in one of our satellite galaxies, the Large Magellanic Cloud (LMC), 170,000 light-years away - right in our cosmic backyard. The Hubble image shows a view of a turbulent cauldron of starbirth, unromantically called N159. Fierce stellar winds from the hot newborn massive stars sculpt ridges, arcs and filaments in the vast cloud, which is over 150 light-years across. This is the clearest image ever obtained of this region. Seen for the first time is the butterfly-shaped or 'Papillon' (French for butterfly) nebula, buried in the centre of the maelstrom of glowing gases and dark dust. The unprecedented details of the structure of the Papillon, itself less than 2 light-years in size (about 1/2000th of a degree in the sky), are seen in the inset. This bipolar shape might be explained by the outflow of gas from the massive star (over 10 times the mass of our Sun) hidden in the central absorption zone. Such stars are so hot and bright that the pressure created by their light halts the infall of gas and directs it away from the star in two opposite directions. This mechanism is not fully understood, but presumably the outflow is constrained around the star's equator and directed to escape along the star's rotation axis. This observation is part of a search for young massive stars in the LMC. This butterfly-shaped nebula is considered to be a rare class of compact 'blob' around newborn, massive stars. The red in this true-colour image comes from the emission of hydrogen and the yellow from hotter oxygen gas. The picture was taken on 5 September 1998 with Wide Field Planetary Camera 2.

Learner Satisfaction with Massive Open Online Courses

ERIC Educational Resources Information Center

Gameel, Bahaa G.

2017-01-01

This study investigates factors that influence learners' satisfaction with massive open online courses (MOOCs). Framed by the theory of independent learning and teaching, the three types of interaction model, and the technology acceptance model, this study analyzed data collected from 1,786 learners enrolled in four MOOCs. Results show that the…

Perturbation Theory of Massive Yang-Mills Fields

DOE R&D Accomplishments Database

Veltman, M.

1968-08-01

Perturbation theory of massive Yang-Mills fields is investigated with the help of the Bell-Treiman transformation. Diagrams containing one closed loop are shown to be convergent if there are more than four external vector boson lines. The investigation presented does not exclude the possibility that the theory is renormalizable.

Hawking radiation and the boomerang behavior of massive modes near a horizon

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

Jannes, G.; Low Temperature Laboratory, Aalto University School of Science, PO Box 15100, 00076 Aalto; Maiessa, P.

2011-05-15

We discuss the behavior of massive modes near a horizon based on a study of the dispersion relation and wave packet simulations of the Klein-Gordon equation. We point out an apparent paradox between two (in principle equivalent) pictures of black-hole evaporation through Hawking radiation. In the picture in which the evaporation is due to the emission of positive-energy modes, one immediately obtains a threshold for the emission of massive particles. In the picture in which the evaporation is due to the absorption of negative-energy modes, such a threshold apparently does not exist. We resolve this paradox by tracing the evolutionmore » of the positive-energy massive modes with an energy below the threshold. These are seen to be emitted and move away from the black-hole horizon, but they bounce back at a 'red horizon' and are reabsorbed by the black hole, thus compensating exactly for the difference between the two pictures. For astrophysical black holes, the consequences are curious but do not affect the terrestrial constraints on observing Hawking radiation. For analogue-gravity systems with massive modes, however, the consequences are crucial and rather surprising.« less

Hawking radiation and the boomerang behavior of massive modes near a horizon

NASA Astrophysics Data System (ADS)

Jannes, G.; Maïssa, P.; Philbin, T. G.; Rousseaux, G.

2011-05-01

We discuss the behavior of massive modes near a horizon based on a study of the dispersion relation and wave packet simulations of the Klein-Gordon equation. We point out an apparent paradox between two (in principle equivalent) pictures of black-hole evaporation through Hawking radiation. In the picture in which the evaporation is due to the emission of positive-energy modes, one immediately obtains a threshold for the emission of massive particles. In the picture in which the evaporation is due to the absorption of negative-energy modes, such a threshold apparently does not exist. We resolve this paradox by tracing the evolution of the positive-energy massive modes with an energy below the threshold. These are seen to be emitted and move away from the black-hole horizon, but they bounce back at a “red horizon” and are reabsorbed by the black hole, thus compensating exactly for the difference between the two pictures. For astrophysical black holes, the consequences are curious but do not affect the terrestrial constraints on observing Hawking radiation. For analogue-gravity systems with massive modes, however, the consequences are crucial and rather surprising.

Synthetic observations of protostellar multiple systems

NASA Astrophysics Data System (ADS)

Lomax, O.; Whitworth, A. P.

2018-04-01

Observations of protostars are often compared with synthetic observations of models in order to infer the underlying physical properties of the protostars. The majority of these models have a single protostar, attended by a disc and an envelope. However, observational and numerical evidence suggests that a large fraction of protostars form as multiple systems. This means that fitting models of single protostars to observations may be inappropriate. We produce synthetic observations of protostellar multiple systems undergoing realistic, non-continuous accretion. These systems consist of multiple protostars with episodic luminosities, embedded self-consistently in discs and envelopes. We model the gas dynamics of these systems using smoothed particle hydrodynamics and we generate synthetic observations by post-processing the snapshots using the SPAMCART Monte Carlo radiative transfer code. We present simulation results of three model protostellar multiple systems. For each of these, we generate 4 × 104 synthetic spectra at different points in time and from different viewing angles. We propose a Bayesian method, using similar calculations to those presented here, but in greater numbers, to infer the physical properties of protostellar multiple systems from observations.

After massive weight loss: patients' expectations of body contouring surgery.

PubMed

Kitzinger, Hugo B; Abayev, Sara; Pittermann, Anna; Karle, Birgit; Bohdjalian, Arthur; Langer, Felix B; Prager, Gerhard; Frey, Manfred

2012-04-01

Massive weight loss following bariatric surgery leads to excess skin with functional and aesthetic impairments. Surplus skin can then contribute to problems with additional weight loss or gain. The aims of the current study were to evaluate the frequency of massive soft tissue development in gastric bypass patients, to determine whether males and females experience similar post-bypass body changes, and to learn about the expectations and impairments related to body contouring surgery. A questionnaire addressing information on the satisfaction of body image, quality of life, and expectation of body contouring surgery following massive weight loss was mailed to 425 patients who had undergone gastric bypass surgery between 2003 and 2009. Of these 425 individuals, 252 (59%) patients completed the survey. Ninety percent of women and 88% of men surveyed rated their appearance following massive weight loss as satisfactory, good, or very good. However, 96% of all patients developed surplus skin, which caused intertriginous dermatitis and itching. In addition, patients reported problems with physical activity (playing sports) and finding clothing that fit appropriately. Moreover, 75% of female and 68% of male patients reported desiring body contouring surgery. The most important expectation of body contouring surgery was improved appearance, followed by improved self-confidence and quality of life. Surplus skin resulting from gastric bypass surgery is a common issue that causes functional and aesthetic impairments in patients. Consequently, this increases the desire for body contouring surgery with high expectations for the aesthetic outcome as well as improved life satisfaction.

A massive protocluster of galaxies at a redshift of z ≈ 5.3.

PubMed

Capak, Peter L; Riechers, Dominik; Scoville, Nick Z; Carilli, Chris; Cox, Pierre; Neri, Roberto; Robertson, Brant; Salvato, Mara; Schinnerer, Eva; Yan, Lin; Wilson, Grant W; Yun, Min; Civano, Francesca; Elvis, Martin; Karim, Alexander; Mobasher, Bahram; Staguhn, Johannes G

2011-02-10

Massive clusters of galaxies have been found that date from as early as 3.9 billion years (3.9 Gyr; z = 1.62) after the Big Bang, containing stars that formed at even earlier epochs. Cosmological simulations using the current cold dark matter model predict that these systems should descend from 'protoclusters'-early overdensities of massive galaxies that merge hierarchically to form a cluster. These protocluster regions themselves are built up hierarchically and so are expected to contain extremely massive galaxies that can be observed as luminous quasars and starbursts. Observational evidence for this picture, however, is sparse because high-redshift protoclusters are rare and difficult to observe. Here we report a protocluster region that dates from 1 Gyr (z = 5.3) after the Big Bang. This cluster of massive galaxies extends over more than 13 megaparsecs and contains a luminous quasar as well as a system rich in molecular gas. These massive galaxies place a lower limit of more than 4 × 10(11) solar masses of dark and luminous matter in this region, consistent with that expected from cosmological simulations for the earliest galaxy clusters.

Shifting from Stewardship to Analytics of Massive Science Data

NASA Astrophysics Data System (ADS)

Crichton, D. J.; Doyle, R.; Law, E.; Hughes, S.; Huang, T.; Mahabal, A.

2015-12-01

Currently, the analysis of large data collections is executed through traditional computational and data analysis approaches, which require users to bring data to their desktops and perform local data analysis. Data collection, archiving and analysis from future remote sensing missions, be it from earth science satellites, planetary robotic missions, or massive radio observatories may not scale as more capable instruments stress existing architectural approaches and systems due to more continuous data streams, data from multiple observational platforms, and measurements and models from different agencies. A new paradigm is needed in order to increase the productivity and effectiveness of scientific data analysis. This paradigm must recognize that architectural choices, data processing, management, analysis, etc are interrelated, and must be carefully coordinated in any system that aims to allow efficient, interactive scientific exploration and discovery to exploit massive data collections. Future observational systems, including satellite and airborne experiments, and research in climate modeling will significantly increase the size of the data requiring new methodological approaches towards data analytics where users can more effectively interact with the data and apply automated mechanisms for data reduction, reduction and fusion across these massive data repositories. This presentation will discuss architecture, use cases, and approaches for developing a big data analytics strategy across multiple science disciplines.

[Massive trichuriasis in an adult diagnosed by colonoscopy].

PubMed

Sapunar, J; Gil, L C; Gil, J G

1999-01-01

A case of massive trichuriasis in a 37-year-old female from a rural locality of the Metropolitan Region of Chile, with antecedents of alcoholism, chronic hepatic damage and portal cavernomatosis, is presented. Since 12 year ago she has had geophagia. In the last six months she has frequently presented liquid diarrhea, colic abdominal pains, tenesmus and sensation of abdominal distention. Clinical and laboratory tests confirmed her hepatic affection associated with a celiac disease with anemia and hypereosinophilia. Within a week diarrhea became worse and dysentery appeared. A colonoscopy revealed an impressive and massive trichuriasis. The patient was successfully treated with two cures of 200 mg tablets of mebendazole twice daily for three days with a week interval. After the first cure she evacuated a big amount of Tricuris trichiura, fecal evacuations became normal, geophagia disappeared and recovered 4 kg of body weight.