Infra-red sources in the H II region W3.
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Wynn-Williams, C. G.↗
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Isolated Stroemgren spheres as a source of galactic H alpha emission
The isolated H alpha emission features reported by Reynolds et al. are identified with Stroemgren spheres surrounding observed O stars; the root mean square electron densities and Stroemgren radii are calculated from the observed emission measure and stellar type. The density has an average value of 2 per cu cm but increases to 3.3 per cu cm for stars within 200 pc of the galactic plane. An analysis of the Catalogue of Galactic O Stars shows that enhanced H alpha emission is observed around all known O stars. The diffuse component of H alpha emission is what one would expect from the line-of-sight overlapping of isolated Stroemgren spheres surrounding B stars and appears to correlate with features on extinction maps, as derived. There is no compelling reason to suggest any large-scale intercloud ionization from H alpha data alone.
Elmergreen, B. G.↗
Scalable Deterministic State-of-the-Art: The Omega_h Open-Source Adaptation Library.
Abstract not provided.
Ibanez, Daniel Alejandro↗
A kinematic search for supernova remnants in giant extragalactic H II regions
We have obtained velocity fields of the Giant H II complexes NGC 5471 in M101, NGC 2363 in NGC 2366, and the largest H II region in NGC 2403 from H-alpha observations using the TAURUS imaging Fabry-Perot interferometer. We have detected five H-alpha sources with velocity profiles which are broad when compared with the surrounding H II region. Region B in NGC 5471 has been previously determined to contain a supernova remnant by the presence of nonthermal radio continuum radiation and enhanced (O I) and (S II) emission (Skillman 1985) and broad H-alpha emission (Chu & Kennicutt 1986). Two broad H-alpha sources in NGC 2363 coincide with regions where strong splitting has been found in the (O III) line (Roy et al. 1991). Two more broad H-alpha sources have been identified in the largest H II region in NGC 2403. Very Large Array (VLA) radio continuum observations with a resolution of 2 sec at lambda(6) and lambda(20) cm of all 3 H II complexes are presented. In addition, high resolution (subarcsecond) VLA images of NGC 5471 were made at lambda(2) and lambda(6) cm. The presence of a nonthermal source in region NGC 5471 B was confirmed while region NGC 5471 A appears to be dominated by thermal emission. The nonthermal spectral index in NGC 2363 A indicates the existence of none or more supernova remnants at the position of a large velocity width source detected in H-alpha emission. No similar nonthermal sources were detected in NGC 2403 #1. Supernovae explosions and stellar winds are considered as causes for these large velocity width sources (LVWS). If the emission from the LVWSs is attributed to single supernova remnants, they are unusually luminous in both nonthermal radio continuum and H-alpha emision. The very large H-alpha luminosities could be a result of high velocity gas being ionized by the neighboring stellar cluster.
Yang, Hui↗
Dynamics of the reaction of C{sub 3}(a{sup 3}Π{sub u}) radicals with C{sub 2}H{sub 2}: A new source for the formation of C{sub 5}H
The reaction C{sub 3}(a{sup 3}Π{sub u}) + C{sub 2}H{sub 2} → C{sub 5}H + H was investigated at collision energy 10.9 kcal mol{sup −1} that is less than the enthalpy of ground-state reaction C{sub 3}(X{sup 1}Σ{sub g}{sup +}) + C{sub 2}H{sub 2} → C{sub 5}H + H. C{sub 3}(a{sup 3}Π{sub u}) radicals were synthesized from 1% C{sub 4}F{sub 6}/He by pulsed high-voltage discharge. The title reaction was conducted in a crossed molecular-beam apparatus equipped with a quadrupole-mass filter. Product C{sub 5}H was interrogated with time-of-flight spectroscopy and synchrotron vacuum-ultraviolet ionization. Reactant C{sub 3}(a{sup 3}Π{sub u}) and product C{sub 5}H were identified using photoionization spectroscopy. The ionization thresholds of C{sub 3}(X{sup 1}Σ{sub g}{sup +}) and C{sub 3}(a{sup 3}Π{sub u}) are determined as 11.6 ± 0.2 eV and 10.0 ± 0.2 eV, respectively. The C{sub 5}H product is identified as linear pentynylidyne that has an ionization energy 8.4 ± 0.2 eV. The title reaction releases translational energy 10.6 kcal mol{sup −1} in average and has an isotropic product angular distribution. The quantum-chemical calculation indicates that the C{sub 3}(a{sup 3}Π{sub u}) radical attacks one of the carbon atoms of C{sub 2}H{sub 2} and subsequently a hydrogen atom is ejected to form C{sub 5}H + H, in good agreement with the experimental observation. As far as we are aware, the C{sub 3}(a{sup 3}Π{sub u}) + C{sub 2}H{sub 2} reaction is investigated for the first time. This work gives an implication for the formation of C{sub 5}H from the C{sub 3}(a{sup 3}Π{sub u}) + C{sub 2}H{sub 2} reaction occurring in a combustion or discharge process of C{sub 2}H{sub 2}.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Ion source and injection line for high intensity medical cyclotron
A 14 MeV high intensity compact cyclotron, CYCIAE-14, was built at China Institute of Atomic Energy (CIAE). An injection system based on the external H− ion source was used on CYCIAE-14 so as to provide high intensity beam, while most positron emission tomography cyclotrons adopt internal ion source. A beam intensity of 100 μA/14 MeV was extracted from the cyclotron with a small multi-cusp H− ion source (CIAE-CH-I type) and a short injection line, which the H− ion source of 3 mA/25 keV H− beam with emittance of 0.3π mm mrad and the injection line of with only 1.2 m from the extraction of ion source to the medial plane of the cyclotron. To increase the extracted beam intensity of the cyclotron, a new ion source (CIAE-CH-II type) of 9.1 mA was used, with maximum of 500 μA was achieved from the cyclotron. The design and test results of the ion source and injection line optimized for high intensity acceleration will be given in this paper.
43 PARTICLE ACCELERATORS↗
Negative hydrogen ion sources for particle accelerators: Sustainability issues and recent improvements in long-term operations
High brightness, negative hydrogen ion sources are used extensively in scientific facilities operating worldwide. Negative hydrogen beams have become the preferred means of filling circular accelerators and storage rings as well as enabling efficient extraction from cyclotrons. Several well-known facilities now have considerable experience with operating a variety of sources such as RF-, filament-, magnetron- and Penning-type H- ion sources. These facilities include the US Spallation Neutron Source (SNS), Japan Proton Accelerator Research Complex (J-PARC), Rutherford Appleton Laboratory (RAL-ISIS), Los Alamos Neutron Science Center (LANSCE), Fermi National Accelerator Laboratory (FNAL), Brookhaven National Laboratory (BNL), numerous installations of D-Pace (licenced by TRIUMF) ion sources used mainly on cyclotrons and, most recently, the CERN-LINAC-1 injector. This report first summarizes the current performance of these ion sources in routine, daily operations with attention toward source service-periods and availability metrics. Sustainability issues encountered at each facility are also reported and categorized to identify areas of common concern and key issues. Recent ion source improvements to address these issues are also discussed as well as plans for meeting future facility upgrade requirements.
Welton, Robert F.↗
TIDAL TAILS OF MINOR MERGERS. II. COMPARING STAR FORMATION IN THE TIDAL TAILS OF NGC 2782
The peculiar spiral NGC 2782 is the result of a minor merger with a mass ratio {approx}4: 1 occurring {approx}200 Myr ago. This merger produced a molecular and H I-rich, optically bright eastern tail and an H I-rich, optically faint western tail. Non-detection of CO in the western tail by Braine et al. suggested that star formation had not yet begun. However, deep UBVR and H{alpha} narrowband images show evidence of recent star formation in the western tail, though it lacks massive star clusters and cluster complexes. Using Herschel PACS spectroscopy, we discover 158 {mu}m [C II] emission at the location of the three most luminous H{alpha} sources in the eastern tail, but not at the location of the even brighter H{alpha} source in the western tail. The western tail is found to have a normal star formation efficiency (SFE), but the eastern tail has a low SFE. The lack of CO and [C II] emission suggests that the western tail H II region may have a low carbon abundance and be undergoing its first star formation. The western tail is more efficient at forming stars, but lacks massive clusters. We propose that the low SFE in the eastern tail may be due to its formation as a splash region where gas heating is important even though it has sufficient molecular and neutral gas to make massive star clusters. The western tail, which has lower gas surface density and does not form high-mass star clusters, is a tidally formed region where gravitational compression likely enhances star formation.
79 ASTRONOMY AND ASTROPHYSICS↗
Effect of Coulomb collision on the negative ion extraction mechanism in negative ion sources
To improve the H{sup −} ion beam optics, it is necessary to understand the energy relaxation process of surface produced H{sup −} ions in the extraction region of Cs seeded H{sup −} ion sources. Coulomb collisions of charged particles have been introduced to the 2D3V-PIC (two dimension in real space and three dimension in velocity space particle-in-cell) model for the H{sup −} extraction by using the binary collision model. Due to Coulomb collision, the lower energy part of the ion energy distribution function of H{sup −} ions has been greatly increased. The mean kinetic energy of the surface produced H{sup −} ions has been reduced to 0.65 eV from 1.5 eV. It has been suggested that the beam optics of the extracted H{sup −} ion beam is strongly affected by the energy relaxation process due to Coulomb collision.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Operation and development status of the J-PARC ion source
A cesium-free H{sup −} ion source driven with a LaB{sub 6} filament is being operated at the Japan Proton Accelerator Research Complex (J-PARC) without any serious trouble since the restoration from the March 2011 earthquake. The H{sup −} ion current from the ion source is routinely restricted approximately 19 mA for the lifetime of the filament. In order to increase the beam power at the linac beam operation (January to February 2013), the beam current from the ion source was increased to 22 mA. At this operation, the lifetime of the filament was estimated by the reduction in the filament current. According to the steep reduction in the filament current, the break of the filament was predicted. Although the filament has broken after approximately 10 h from the steep current reduction, the beam operation was restarted approximately 8 h later by the preparation for the exchange of new filament. At the study time for the 3 GeV rapid cycling synchrotron (April 2013), the ion source was operated at approximately 30 mA for 8 days. As a part of the beam current upgrade plan for the J-PARC, the front end test stand consisting of the ion source and the radio frequency quadrupole is under preparation. The RF-driven H{sup −} ion source developed for the J-PARC 2nd stage requirements will be tested at this test stand.
43 PARTICLE ACCELERATORS↗
A Novel Hollow Fiber Membrane Reactor for High Purity H 2 Generation from Thermal Catalytic NH 3 Decomposition (Final Report)
Ammonia (NH 3 ), as a promising carbon neutral liquid fuel (CNLF) and an effective H 2 source, can be synthesized from air and water (N 2 extracted from air and H 2 from water) using renewable energy sources. To produce H 2 as an intermediate, it is essential to develop effective and economic NH 3 decomposition technologies. We have been developing an innovative hollow fiber membrane reactor for high purity H 2 generation from thermal catalytic NH 3 decomposition. The objective of the proposed research is to fabricate a compact and robust prototype with high energy efficiency (>80%) to deliver high purity (>99%) H2 at high rate per volume (>0.15 g H 2 /h/cm 3 ) from NH3 decomposition at low temperature (<450 °C) and high conversion (>99%). Our overall technical approach is to effectively combine an active catalyst for NH 3 decomposition with a selective H 2 membrane separation process in a novel, compact modular system to generate high purity H 2 and simultaneously achieve high NH 3 conversion and optimize the entire system energy efficiency. This novel integrated membrane reactor design, together with low-cost, highly active Ru-based catalyst, makes it most appropriate for the project objective. The proposed applied research and development work, therefore, represents an innovative and transformational solution to H 2 generation from thermal catalytic NH 3 decomposition. During the course of our research we i) synthesized and characterized ruthenium(Ru)-based catalysts, evaluated their catalytic performance for NH 3 decomposition and optimized the catalyst composition and performance based on machine learning, ii) prepared SAPO-34, MFI membranes on α-alumina hollow fibers and measured their performance for H 2 /N 2 , H 2 /N 2 /NH 3 separation and evaluated carbon molecular sieve (CMS) and Pd/Ag membranes for H 2 /N 2 , H 2 /N 2 /NH 3 separation at different conditions, iii) designed and evaluated several types of membrane reactors for H 2 production from NH 3 decomposition, and iv) evaluated the H 2 delivery cost base on catalysts development, membrane development and membrane reactor. For 3,1,12 RuYK catalyst, H 2 productivity of 6.35 mmol/min/gcat with NH 3 conversion of 95~98% was achieved at 5 bar and 400 °C; for SAPO-34 membrane, the best membrane showed H 2 permeance of 7.56×10 -7 mol/(m 2 ∙s∙Pa) and H 2 /N 2 selectivity of 23.1 at 20 °C; For CMS and Pd/Ag membranes, both showed superior stability for 71%H 2 /24%N 2 /5%NH 3 mixture separation at 450 °C and 7 bar for over 120 h; for the membrane reactor, high H 2 purity of >99.99% with NH 3 conversion of >99.4% were achieved in Pd/Ag membrane reactor at 450 °C, and the NH 3 concentration was always below 10 ppb in H 2 product. The H 2 generation rate was calculated to be as high as 0.47 g/h/cm 3 and the energy efficiency was calculated to be 88%. The membrane reactor showed superior stability for over 370 h and high H 2 purity, H 2 production rate and NH 3 conversion. Based on calculation, the H 2 delivery cost can be as low as $3.66/kg.
08 HYDROGEN↗
GAS KINEMATICS IN Ly{alpha} NEBULAE
Exploring the origin of Ly{alpha} nebulae ('blobs') at high redshift requires measurements of their gas kinematics that are impossible with only the resonant, optically thick Ly{alpha} line. To define gas motions relative to the systemic velocity of the blob, the Ly{alpha} line must be compared with an optically thin line like H{alpha} {lambda}6563, which is not much altered by radiative transfer effects and is more concentrated about the galaxies embedded in the nebula's core. We obtain optical and near-IR (NIR) spectra of the two brightest Ly{alpha} blobs (CDFS-LAB01 and CDFS-LAB02) from the Yang et al. sample using the Magellan/Magellan Echellette Spectrograph optical and Very Large Telescope/SINFONI NIR spectrographs. Both the Ly{alpha} and H{alpha} lines confirm that these blobs lie at the survey redshift, z {approx} 2.3. Within each blob, we detect several H{alpha} sources, which roughly correspond to galaxies seen in Hubble Space Telescope rest-frame UV images. The H{alpha} detections show that these galaxies have large internal velocity dispersions ({sigma}{sub v} = 130-190 km s{sup -1}) and that, in the one system (LAB01), where we can reliably extract profiles for two H{alpha} sources, their velocity difference is {Delta}v {approx} 440 km s{sup -1}. The presence of multiple galaxies within the blobs, and those galaxies' large velocity dispersions and large relative motion, is consistent with our previous finding that Ly{alpha} blobs inhabit massive dark matter halos that will evolve into those typical of present-day rich clusters and that the embedded galaxies may eventually become brightest cluster galaxies. To determine whether the gas near the embedded galaxies is predominantly infalling or outflowing, we compare the Ly{alpha} and H{alpha} line centers, finding that Ly{alpha} is not offset ({Delta}v{sub Ly{alpha}} = +0 km s{sup -1}) in LAB01 and redshifted by only +230 km s{sup -1} in LAB02. These offsets are small compared to those of Lyman break galaxies, which average +450 km s{sup -1} and extend to about +700 km s{sup -1}. In LAB02, we detect C II {lambda}1334 and Si II {lambda}1526 absorption lines, whose blueward shifts of {approx}200 km s{sup -1} are consistent with the small outflow implied by the redward shift of Ly{alpha}. We test and rule out the simplest infall models and those outflow models with super/hyperwinds, which require large outflow velocities. Because of the unknown geometry of the gas distribution and the possibility of multiple sources of Ly{alpha} emission embedded in the blobs, a larger sample and more sophisticated models are required to test more complex or a wider range of infall and outflow scenarios.
79 ASTRONOMY AND ASTROPHYSICS↗
SIMULTANEOUS OBSERVATIONS OF SiO AND H{sub 2}O MASERS TOWARD KNOWN STELLAR H{sub 2}O MASER SOURCES
We present the results of simultaneous observations of SiO v = 1, 2, {sup 29}SiO v = 0, J = 1-0, and H{sub 2}O 6{sub 16}-5{sub 23} maser lines toward 152 known stellar H{sub 2}O maser sources using the Yonsei 21 m radio telescope of the Korean VLBI Network from 2009 June to 2011 January. Both SiO and H{sub 2}O masers were detected from 62 sources with a detection rate of 40.8%. The SiO-only maser emission without H{sub 2}O maser detection was detected from 27 sources, while the H{sub 2}O-only maser without SiO maser detection was detected from 22 sources. Therefore, the overall SiO maser emission was detected from 89 sources, resulting in a detection rate of 58.6%. We have identified 70 new detections of the SiO maser emission. For both H{sub 2}O and SiO maser detected sources, the peak and integrated antenna temperatures of SiO masers are stronger than those of H{sub 2}O masers in both Mira variables and OH/IR stars and the relative intensity ratios of H{sub 2}O to SiO masers in OH/IR stars are larger than those in Mira variables. In addition, distributions of 152 observed sources were investigated in the IRAS two-color diagram.
79 ASTRONOMY AND ASTROPHYSICS↗
The Infrared Properties of Sources Matched in the Wise All-Sky and Herschel ATLAS Surveys
We describe the infrared properties of sources detected over approx 36 sq deg of sky in the GAMA 15-hr equatorial field, using data from both the Herschel Astrophysical Terahertz Large-Area Survey (HATLAS) and Wide-field Infrared Survey (WISE). With 5sigma point-source depths of 34 and 0.048 mJy at 250 micron and 3.4 micron, respectively, we are able to identify 50.6% of the H-ATLAS sources in the WISE survey, corresponding to a surface density of approx 630 deg(exp -2). Approximately two-thirds of these sources have measured spectroscopic or optical/near-IR photometric redshifts of z < 1. For sources with spectroscopic redshifts at z < 0.3, we find a linear correlation between the infrared luminosity at 3.4 micron and that at 250 micron, with +/- 50% scatter over approx 1.5 orders of magnitude in luminosity, approx 10(exp 9) - 10(exp 10.5) Solar Luminosity By contrast, the matched sources without previously measured redshifts (r approx > 20.5) have 250-350 micron flux density ratios that suggest either high-redshift galaxies (z approx > 1.5) or optically faint low-redshift galaxies with unusually low temperatures (T approx < 20). Their small 3.4-250 micron flux ratios favor a high-redshift galaxy population, as only the most actively star-forming galaxies at low redshift (e.g., Arp 220) exhibit comparable flux density ratios. Furthermore, we find a relatively large AGN fraction (approx 30%) in a 12 micron flux-limited subsample of H-ATLAS sources, also consistent with there being a significant population of high-redshift sources in the no-redshift sample
Bond, Nicholas A.↗
Reinterpreting the infrared spectrum of H + HCN: Methylene amidogen radical and its coproducts
The methylene amidogen radical (H 2 CN) plays a role in high-energy material combustion and extraterresterial atmospheres. Recent theoretical work has struggled to match experimental assignments for its CN and antisymmetric CH 2 stretching frequencies (ν 2 and ν 5 ), which were reported to occur at 1725 and 3103 cm –1 . Herein, we compute the vibrational energy levels of this molecule by extrapolating quadruples-level coupled- cluster theory to the complete basis limit and adding corrections for vibrational anharmonicity. This level of theory predicts that ν 2 and ν 5 should occur at 1646 and 2892 cm –1 , at odds with the experimental assignments. To investigate the possibility of defects in our theoretical treatment, we analyze the sensitivity of our approach to each of its contributing approximations. Our analysis suggests that the observed deviation from experiment is too large to be explained as an accumulation of errors, leading us to conclude that these transitions were misassigned. To help resolve this discrepancy, we investigate possible byproducts of the H + HCN reaction, which was the source of H 2 CN in the original experiment. In particular, we predict vibrational spectra for cis -HCNH, trans -HCNH, and H 2 CNH using high-level coupled-cluster computations. Based on these results, we reassign the transition at 1725 cm –1 to ν 3 of trans-HCNH, yielding excellent agreement. Supporting this identification, we assign a known contaminant peak at 886 cm –1 to ν 5 of the same conformer. Our computations suggest that the peak observed at 3103 cm –1 , however, does not belong to any of the aforementioned species. To facilitate further investigation, we use structure and bonding arguments to narrow the range of possible candidates. Furthermore, these arguments lead us to tentatively put forth formaldazine [(H 2 CN) 2 ] as a suggestion for further study, which we support with additional computations.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
An expanded kinetics model describing injector region desorption
During the initial stages of electron beam injection, absorbed or entrained material can be released into the nascent beam pulse by thermal desorption or electron beam impact. These processes, and subsequent ionization and dissociation, are examined assuming a prototypical temporal beam pulse. An expanded set of kinetic equations that includes thermal desorption, electron-stimulated ion emission, electron impact dissociation, electron impact ionization, and thermal decomposition of adsorbed water molecules is developed. Estimates of the three most important ionized species H 2 O + , H + and OH + are provided for typical injector conditions. Electron impact dissociative ionization of neutral H 2 O is the dominant source of H + under these conditions. Since the abundance of thermally desorbed neutral H 2 O has an exponential rate, the production of H+ is likewise controlled by this exponential desorption rate. Thus thermal management of the confining walls could suppress proton production in the injector region. Thermal decomposition of H 2 O will not be a contributing physical process in the injector region on time scales less than a μs. The formalism is sufficiently flexible to include entrained hydrogen.
42 ENGINEERING↗
Chemical studies of H chondrites. 5: Temporal variations of sources
We report Cl-36 (301-kyr half-life) data obtained by accelerator mass spectrometry allowing nominal terrestrial ages to be determined for 39 Antarctic H4-6 chondrites for which contents of volatile trace elements are known. The compositional difference between these Antarctic meteorites and 58 non-Antarctic falls increases with terrestrial age and, using multivariate statistical techniques, becomes highly significant for Antarctic samples with ages greater than 50 kyr. The compositional difference is inconsistent with trivial causes such as weathering and seems to reflect differences in thermal histories of parent sources. Temporal source variations for the H chondrite flux on Earth thus exist not only on a short-term, 40 years, basis (Dodd et al., 1993) but also on a long-term, greater than 50 kyr, basis.
Michlovich, Edward S.↗
A New Method to Use Chandra Data to Resolve the X-Ray Halos Around Point Sources and Its Application to Cygnus X-1
The excellent angular resolution, good energy resolution and broad energy band make Chandra ACIS the best instrument for studying the X-ray halos around some galactic x-ray point sources caused by the dust scattering of X-rays in the interstellar medium, but direct images of bright sources of b r i g h t sources obtained with ACIS usually from severe pile- UP - Making use of the fact that an isotropic image could be reconstructed from it's projection on any direction, we can reconstruct the images of the X-ray halos from data obtained with the regular HETGS and/or the CC mode. With the reconstructed high resolution images, we can probe the X-ray halos as close as 1 arcsecond to their associated point sources.
Yao, Y.↗