The angular power spectrum of dust-obscured galaxies and its impact on Sunyaev Zel'dovich studies

NASA Astrophysics Data System (ADS)

Montaña, A. A.; Sanchez-Argüelles, D. O.; Hughes, D. H.; Wilson, G. W.; Gaztañaga, E.

2011-10-01

In this work we measure the angular power spectrum (APS) of the population of (sub-)millimetric galaxies (SMGs) using 1.1 mm wavelength observations obtained with the AzTEC camera on the Atacama Submillimeter Telescope Experiment (ASTE) and the James Clerk Maxwell Telescope (JCMT). The sample of survey fields allows us to compare the properties of the APS of the (sub-)mm galaxy population towards unbiased and potentially overdense regions of the Universe. Furthermore, our measurements provide a strong constraint to the impact that the SMGs have on the APS of the primary and secondary CMB anisotropies, which are being measured by the new generation of arcminute resolution SZE experiments at millimeter wavelengths.

On the Nature of the First Galaxies Selected at 350 Micrometers

NASA Technical Reports Server (NTRS)

Khan, Sophia A.; Chanial, Pierre F.; Willner, S. P.; Pearson, Chris P.; Ashby, M. L. N.; Benford, Dominic J.; Clements, David L.; Dye, Simon; Farrah, Duncan; Fazio, G. G.;

Rotation of the asymptotic giant branch star R Doradus

NASA Astrophysics Data System (ADS)

Vlemmings, W. H. T.; Khouri, T.; Beck, E. De; Olofsson, H.; García-Segura, G.; Villaver, E.; Baudry, A.; Humphreys, E. M. L.; Maercker, M.; Ramstedt, S.

2018-05-01

High-resolution observations of the extended atmospheres of asymptotic giant branch (AGB) stars can now directly be compared to the theories that describe stellar mass loss. Using Atacama Large Millimeter/submillimeter Array (ALMA) high angular resolution (30 × 42 mas) observations, we have for the first time resolved stellar rotation of an AGB star, R Dor. We measure an angular rotation velocity of ωR sin i = (3.5 ± 0.3) × 10-9 rad s-1, which indicates a rotational velocity of |υrot sin i| = 1.0 ± 0.1 km s-1 at the stellar surface (R* = 31.2 mas at 214 GHz). The rotation axis projected on the plane of the sky has a position angle Φ = 7 ± 6°. We find that the rotation of R Dor is two orders of magnitude faster than expected for a solitary AGB star that will have lost most of its angular momentum. Its rotational velocity is consistent with angular momentum transfer from a close companion. As a companion has not been directly detected, we suggest R Dor has a low-mass, close-in companion. The rotational velocity approaches the critical velocity, set by the local sound speed in the extended envelope, and is thus expected to affect the mass-loss characteristics of R Dor.

Chemistry and Star Formation: A Love-Hate Relationship

NASA Astrophysics Data System (ADS)

Jiménez-Serra, Izaskun; Zhang, Qizhou; Patel, Nimesh; Lu, Xing; Wang, Ke; Testi, Leonardo; Caselli, Paola; Martin-Pintado, Jesus

2014-06-01

The development of the broad bandwidth receivers at the Submillimeter Array (SMA) a decade ago opened up the possibility to observe tens of molecular lines at high angular resolution simultaneously. The unprecedented wealth of molecular line data provided by the SMA allowed for the first time detailed studies of the chemistry in star-forming regions. These studies have revealed that chemistry is a useful tool to pin down the internal physical structure and the physical processes involved in the process of low-mass and high-mass star formation. In this talk, I will review the most important advances in our understanding of the star-formation process through chemistry thanks to the SMA, and I will present the challenges that will be faced in the next decade in this field of research thanks to the advent of new instrumentation such as the Atacama Large Millimeter/Submillimeter Array and the Square Kilometer Array.

ON THE CLUSTERING OF SUBMILLIMETER GALAXIES

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

Williams, Christina C.; Giavalisco, Mauro; Yun, Min S.

2011-06-01

We measure the angular two-point correlation function of submillimeter galaxies (SMGs) from 1.1 mm imaging of the COSMOS field with the AzTEC camera and ASTE 10 m telescope. These data yield one of the largest contiguous samples of SMGs to date, covering an area of 0.72 deg{sup 2} down to a 1.26 mJy beam{sup -1} (1{sigma}) limit, including 189 (328) sources with S/N {>=}3.5 (3). We can only set upper limits to the correlation length r{sub 0}, modeling the correlation function as a power law with pre-assigned slope. Assuming existing redshift distributions, we derive 68.3% confidence level upper limits ofmore » r{sub 0} {approx}< 6-8h{sup -1} Mpc at 3.7 mJy and r{sub 0} {approx}< 11-12 h{sup -1} Mpc at 4.2 mJy. Although consistent with most previous estimates, these upper limits imply that the real r{sub 0} is likely smaller. This casts doubts on the robustness of claims that SMGs are characterized by significantly stronger spatial clustering (and thus larger mass) than differently selected galaxies at high redshift. Using Monte Carlo simulations we show that even strongly clustered distributions of galaxies can appear unclustered when sampled with limited sensitivity and coarse angular resolution common to current submillimeter surveys. The simulations, however, also show that unclustered distributions can appear strongly clustered under these circumstances. From the simulations, we predict that at our survey depth, a mapped area of 2 deg{sup 2} is needed to reconstruct the correlation function, assuming smaller beam sizes of future surveys (e.g., the Large Millimeter Telescope's 6'' beam size). At present, robust measures of the clustering strength of bright SMGs appear to be below the reach of most observations.« less

Protoplanetary Disk Properties in the Orion Nebula Cluster: Initial Results from Deep, High-resolution ALMA Observations

NASA Astrophysics Data System (ADS)

Eisner, J. A.; Arce, H. G.; Ballering, N. P.; Bally, J.; Andrews, S. M.; Boyden, R. D.; Di Francesco, J.; Fang, M.; Johnstone, D.; Kim, J. S.; Mann, R. K.; Matthews, B.; Pascucci, I.; Ricci, L.; Sheehan, P. D.; Williams, J. P.

2018-06-01

We present Atacama Large Millimeter Array 850 μm continuum observations of the Orion Nebula Cluster that provide the highest angular resolution (∼0.″1 ≈ 40 au) and deepest sensitivity (∼0.1 mJy) of the region to date. We mosaicked a field containing ∼225 optical or near-IR-identified young stars, ∼60 of which are also optically identified “proplyds.” We detect continuum emission at 850 μm toward ∼80% of the proplyd sample, and ∼50% of the larger sample of previously identified cluster members. Detected objects have fluxes of ∼0.5–80 mJy. We remove submillimeter flux due to free–free emission in some objects, leaving a sample of sources detected in dust emission. Under standard assumptions of isothermal, optically thin disks, submillimeter fluxes correspond to dust masses of ∼0.5–80 Earth masses. We measure the distribution of disk sizes, and find that disks in this region are particularly compact. Such compact disks are likely to be significantly optically thick. The distributions of submillimeter flux and inferred disk size indicate smaller, lower-flux disks than in lower-density star-forming regions of similar age. Measured disk flux is correlated weakly with stellar mass, contrary to studies in other star-forming regions that found steeper correlations. We find a correlation between disk flux and distance from the massive star θ 1 Ori C, suggesting that disk properties in this region are influenced strongly by the rich cluster environment.

A Resolved Near-Infrared Image of the Inner Cavity in the GM Aur Transitional Disk

NASA Technical Reports Server (NTRS)

Oh, Daehyeon; Hashimoto, Jun; Carson, Joseph C.; Janson, Markus; Kwon, Jungmi; Nakagawa, Takao; Mayama, Satoshi; Uyama, Taichi; Grady, Carol A.; McElwain, Michael W.

2016-01-01

We present high-contrast H-band polarized intensity (PI) images of the transitional disk around the young solar like star GM Aur. The near-infrared direct imaging of the disk was derived by polarimetric differential imaging using the Subaru 8.2 m Telescope and HiCIAO. An angular resolution and an inner working angle of 0 07 and radius approximately 0 05, respectively, were obtained. We clearly resolved a large inner cavity, with a measured radius of 18+/ 2 au, which is smaller than that of a submillimeter interferometric image (28 au). This discrepancy in the cavity radii at near-infrared and submillimeter wavelengths may be caused by a 34M(sub Jup) planet about 20 au away from the star, near the edge of the cavity. The presence of a near-infrared inner cavity is a strong constraint on hypotheses for inner cavity formation in a transitional disk. A dust filtration mechanism has been proposed to explain the large cavity in the submillimeter image, but our results suggest that this mechanism must be combined with an additional process. We found that the PI slope of the outer disk is significantly different from the intensity slope obtained from HSTNICMOS, and this difference may indicate the grain growth process in the disk.

Brain single-photon emission CT physics principles.

PubMed

Accorsi, R

2008-08-01

The basic principles of scintigraphy are reviewed and extended to 3D imaging. Single-photon emission computed tomography (SPECT) is a sensitive and specific 3D technique to monitor in vivo functional processes in both clinical and preclinical studies. SPECT/CT systems are becoming increasingly common and can provide accurately registered anatomic information as well. In general, SPECT is affected by low photon-collection efficiency, but in brain imaging, not all of the large FOV of clinical gamma cameras is needed: The use of fan- and cone-beam collimation trades off the unused FOV for increased sensitivity and resolution. The design of dedicated cameras aims at increased angular coverage and resolution by minimizing the distance from the patient. The corrections needed for quantitative imaging are challenging but can take advantage of the relative spatial uniformity of attenuation and scatter. Preclinical systems can provide submillimeter resolution in small animal brain imaging with workable sensitivity.

ALMA Observations of Dust Polarization and Molecular Line Emission from the Class 0 Protostellar Source Serpens SMM1

NASA Astrophysics Data System (ADS)

Hull, Charles L. H.; Girart, Josep M.; Tychoniec, Łukasz; Rao, Ramprasad; Cortés, Paulo C.; Pokhrel, Riwaj; Zhang, Qizhou; Houde, Martin; Dunham, Michael M.; Kristensen, Lars E.; Lai, Shih-Ping; Li, Zhi-Yun; Plambeck, Richard L.

2017-10-01

We present high angular resolution dust polarization and molecular line observations carried out with the Atacama Large Millimeter/submillimeter Array (ALMA) toward the Class 0 protostar Serpens SMM1. By complementing these observations with new polarization observations from the Submillimeter Array (SMA) and archival data from the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and the James Clerk Maxwell Telescopes (JCMT), we can compare the magnetic field orientations at different spatial scales. We find major changes in the magnetic field orientation between large (˜0.1 pc) scales—where the magnetic field is oriented E-W, perpendicular to the major axis of the dusty filament where SMM1 is embedded—and the intermediate and small scales probed by CARMA (˜1000 au resolution), the SMA (˜350 au resolution), and ALMA (˜140 au resolution). The ALMA maps reveal that the redshifted lobe of the bipolar outflow is shaping the magnetic field in SMM1 on the southeast side of the source; however, on the northwestern side and elsewhere in the source, low-velocity shocks may be causing the observed chaotic magnetic field pattern. High-spatial-resolution continuum and spectral-line observations also reveal a tight (˜130 au) protobinary system in SMM1-b, the eastern component of which is launching an extremely high-velocity, one-sided jet visible in both {CO}(J=2\\to 1) and {SiO}(J=5\\to 4); however, that jet does not appear to be shaping the magnetic field. These observations show that with the sensitivity and resolution of ALMA, we can now begin to understand the role that feedback (e.g., from protostellar outflows) plays in shaping the magnetic field in very young, star-forming sources like SMM1.

Design and fabrication of two-dimensional semiconducting bolometer arrays for HAWC and SHARC-II

NASA Astrophysics Data System (ADS)

Voellmer, George M.; Allen, Christine A.; Amato, Michael J.; Babu, Sachidananda R.; Bartels, Arlin E.; Benford, Dominic J.; Derro, Rebecca J.; Dowell, C. D.; Harper, D. A.; Jhabvala, Murzy D.; Moseley, S. H.; Rennick, Timothy; Shirron, Peter J.; Smith, W. W.; Staguhn, Johannes G.

2003-02-01

The High resolution Airborne Wideband Camera (HAWC) and the Submillimeter High Angular Resolution Camera II (SHARC II) will use almost identical versions of an ion-implanted silicon bolometer array developed at the National Aeronautics and Space Administration's Goddard Space Flight Center (GSFC). The GSFC "Pop-Up" Detectors (PUD's) use a unique folding technique to enable a 12 × 32-element close-packed array of bolometers with a filling factor greater than 95 percent. A kinematic Kevlar suspension system isolates the 200 mK bolometers from the helium bath temperature, and GSFC - developed silicon bridge chips make electrical connection to the bolometers, while maintaining thermal isolation. The JFET preamps operate at 120 K. Providing good thermal heat sinking for these, and keeping their conduction and radiation from reaching the nearby bolometers, is one of the principal design challenges encountered. Another interesting challenge is the preparation of the silicon bolometers. They are manufactured in 32-element, planar rows using Micro Electro Mechanical Systems (MEMS) semiconductor etching techniques, and then cut and folded onto a ceramic bar. Optical alignment using specialized jigs ensures their uniformity and correct placement. The rows are then stacked to create the 12 × 32-element array. Engineering results from the first light run of SHARC II at the Caltech Submillimeter Observatory (CSO) are presented.

SPECS: the kilometer-baseline far-IR interferometer in NASA's space science roadmap

NASA Astrophysics Data System (ADS)

Leisawitz, David T.; Abel, Tom; Allen, Ronald J.; Benford, Dominic J.; Blain, Andrew; Bombardelli, Claudio; Calzetti, Daniela; DiPirro, Michael J.; Ehrenfreund, Pascale; Evans, Neal J., II; Fischer, Jacqueline; Harwit, Martin; Hyde, Tristram T.; Kuchner, Marc J.; Leitner, Jesse A.; Lorenzini, Enrico C.; Mather, John C.; Menten, Karl M.; Moseley, Samuel H., Jr.; Mundy, Lee G.; Nakagawa, Takao; Neufeld, David A.; Pearson, John C.; Rinehart, Stephen A.; Roman, Juan; Satyapal, Shobita; Silverberg, Robert F.; Stahl, H. Philip; Swain, Mark R.; Swanson, Theodore D.; Traub, Wesley A.; Wright, Edward L.; Yorke, Harold W.

2004-10-01

Ultimately, after the Single Aperture Far-IR (SAFIR) telescope, astrophysicists will need a far-IR observatory that provides angular resolution comparable to that of the Hubble Space Telescope. At such resolution galaxies at high redshift, protostars, and nascent planetary systems will be resolved, and theoretical models for galaxy, star, and planet formation and evolution can be subjected to important observational tests. This paper updates information provided in a 2000 SPIE paper on the scientific motivation and design concepts for interferometric missions SPIRIT (the Space Infrared Interferometric Telescope) and SPECS (the Submillimeter Probe of the Evolution of Cosmic Structure). SPECS is a kilometer baseline far-IR/submillimeter imaging and spectral interferometer that depends on formation flying, and SPIRIT is a highly-capable pathfinder interferometer on a boom with a maximum baseline in the 30 - 50 m range. We describe recent community planning activities, remind readers of the scientific rationale for space-based far-infrared imaging interferometry, present updated design concepts for the SPIRIT and SPECS missions, and describe the main issues currently under study. The engineering and technology requirements for SPIRIT and SPECS, additional design details, recent technology developments, and technology roadmaps are given in a companion paper in the Proceedings of the conference on New Frontiers in Stellar Interferometry.

A RESOLVED NEAR-INFRARED IMAGE OF THE INNER CAVITY IN THE GM Aur TRANSITIONAL DISK

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

Oh, Daehyeon; Yang, Yi; Hashimoto, Jun

We present high-contrast H -band polarized intensity (PI) images of the transitional disk around the young solar-like star GM Aur. The near-infrared direct imaging of the disk was derived by polarimetric differential imaging using the Subaru 8.2 m Telescope and HiCIAO. An angular resolution and an inner working angle of 0.″07 and r ∼ 0.″05, respectively, were obtained. We clearly resolved a large inner cavity, with a measured radius of 18 ± 2 au, which is smaller than that of a submillimeter interferometric image (28 au). This discrepancy in the cavity radii at near-infrared and submillimeter wavelengths may be causedmore » by a 3–4 M {sub Jup} planet about 20 au away from the star, near the edge of the cavity. The presence of a near-infrared inner cavity is a strong constraint on hypotheses for inner cavity formation in a transitional disk. A dust filtration mechanism has been proposed to explain the large cavity in the submillimeter image, but our results suggest that this mechanism must be combined with an additional process. We found that the PI slope of the outer disk is significantly different from the intensity slope obtained from HST /NICMOS, and this difference may indicate the grain growth process in the disk.« less

Design consideration of a multipinhole collimator with septa for ultra high-resolution silicon drift detector modules

NASA Astrophysics Data System (ADS)

Min, Byung Jun; Choi, Yong; Lee, Nam-Yong; Lee, Kisung; Ahn, Young Bok; Joung, Jinhun

2009-07-01

The aim of this study was to design a multipinhole (MP) collimator with lead vertical septa coupled to a high-resolution detector module containing silicon drift detectors (SDDs) with an intrinsic resolution approaching the sub-millimeter level. Monte Carlo simulations were performed to determine pinhole parameters such as pinhole diameter, focal length, and number of pinholes. Effects of parallax error and collimator penetration were investigated for the new MP collimator design. The MP detector module was evaluated using reconstructed images of resolution and mathematical cardiac torso (MCAT) phantoms. In addition, the reduced angular sampling effect was investigated over 180°. The images were reconstructed using dedicated maximum likelihood expectation maximization (MLEM) algorithm. An MP collimator with 81-pinhole was designed with a 2-mm-diameter pinhole and a focal length of 40 mm . Planar sensitivity and resolution obtained using the devised MP collimator were 3.9 cps/μCi and 6 mm full-width at half-maximum (FWHM) at a 10 cm distance. The parallax error and penetration ratio were significantly improved using the proposed MP collimation design. The simulation results demonstrated that the proposed MP detector provided enlarged imaging field of view (FOV) and improved the angular sampling effect in resolution and MCAT phantom studies. Moreover, the novel design enables tomography images by simultaneously obtaining eight projections with eight-detector modules located along the 180° orbit surrounding a patient, which allows designing of a stationary cardiac SPECT. In conclusion, the MP collimator with lead vertical septa was designed to have comparable system resolution and sensitivity to those of the low-energy high-resolution (LEHR) collimator per detector. The system sensitivity with an eight-detector configuration would be four times higher than that with a standard dual-detector cardiac SPECT.

Human brain diffusion tensor imaging at submillimeter isotropic resolution on a 3 Tesla clinical MRI scanner

PubMed Central

Chang, Hing-Chiu; Sundman, Mark; Petit, Laurent; Guhaniyogi, Shayan; Chu, Mei-Lan; Petty, Christopher; Song, Allen W.; Chen, Nan-kuei

2015-01-01

The advantages of high-resolution diffusion tensor imaging (DTI) have been demonstrated in a recent post-mortem human brain study (Miller et al., NeuroImage 2011;57(1):167–181), showing that white matter fiber tracts can be much more accurately detected in data at submillimeter isotropic resolution. To our knowledge, in vivo human brain DTI at submillimeter isotropic resolution has not been routinely achieved yet because of the difficulty in simultaneously achieving high resolution and high signal-to-noise ratio (SNR) in DTI scans. Here we report a 3D multi-slab interleaved EPI acquisition integrated with multiplexed sensitivity encoded (MUSE) reconstruction, to achieve high-quality, high-SNR and submillimeter isotropic resolution (0.85 × 0.85 × 0.85 mm3) in vivo human brain DTI on a 3 Tesla clinical MRI scanner. In agreement with the previously reported post-mortem human brain DTI study, our in vivo data show that the structural connectivity networks of human brains can be mapped more accurately and completely with high-resolution DTI as compared with conventional DTI (e.g., 2 × 2 × 2 mm3). PMID:26072250

A submillimeter background galaxy projected on the debris disk of HD95086 revealed by ALMA

NASA Astrophysics Data System (ADS)

Zapata, Luis A.; Ho, Paul T. P.; Rodríguez, Luis F.

2018-06-01

We present sensitive observations carried out with the Atacama Large Millimeter/Submillimeter Array (ALMA) of the dusty debris disc HD 95086. These observations were made in bands 6 (223 GHz) and 7 (338 GHz) with an angular resolution of about 1 arcsec, which allowed us to resolve well the debris disc with a deconvolved size of 7.0 × 6.0 arcsec2 and with an inner depression of about 2 arcsec. We do not detect emission from the star itself and the possible inner dusty belt. We also do not detect CO (J = 2-1) and (J = 3-2) emission, excluding the possibility of an evolved gaseous primordial disc as noted in previous studies of HD95086. We estimated a lower limit for the gas mass of ≤0.01 M⊕ for the debris disc of HD95086. From the mm. emission, we computed a dust mass for the debris disc HD95086 of 0.5 ± 0.2 M⊕, resulting in a dust-to-gas ratio of ≥50. Finally, we confirm the detection of a strong submillimeter source to the north-west of the disc (ALMA-SMM1) revealed by recent ALMA observations. This new source might be interpreted as a planet in formation on the periphery of the debris disc HD 95086 or as a strong impact between dwarf planets. However, given the absence of the proper motions of ALMA-SMM1 similar to those reported in the debris disc (estimated from these new ALMA observations) and for the optical star, this is more likely to be a submillimeter background galaxy.

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.

ALMA BAND 8 CONTINUUM EMISSION FROM ORION SOURCE I

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

Hirota, Tomoya; Matsumoto, Naoko; Machida, Masahiro N.

2016-12-20

We have measured continuum flux densities of a high-mass protostar candidate, a radio source I in the Orion KL region (Orion Source I) using the Atacama Large Millimeter/Submillimeter Array (ALMA) at band 8 with an angular resolution of 0.″1. The continuum emission at 430, 460, and 490 GHz associated with Source I shows an elongated structure along the northwest–southeast direction perpendicular to the so-called low-velocity bipolar outflow. The deconvolved size of the continuum source, 90 au × 20 au, is consistent with those reported previously at other millimeter/submillimeter wavelengths. The flux density can be well fitted to the optically thick blackbody spectral energy distribution, and the brightness temperaturemore » is evaluated to be 700–800 K. It is much lower than that in the case of proton–electron or H{sup −} free–free radiations. Our data are consistent with the latest ALMA results by Plambeck and Wright, in which the continuum emission was proposed to arise from the edge-on circumstellar disk via thermal dust emission, unless the continuum source consists of an unresolved structure with a smaller beam filling factor.« less

PLANET SHADOWS IN PROTOPLANETARY DISKS. II. OBSERVABLE SIGNATURES

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

Jang-Condell, Hannah

2009-07-20

We calculate simulated images of disks perturbed by embedded small planets. These 10-50 M{sub +} bodies represent the growing cores of giant planets. We examine scattered light and thermal emission from these disks over a range of wavelengths, taking into account the wavelength-dependent opacity of dust in the disk. We also examine the effect of inclination on the observed perturbations. We find that the perturbations are best observed in the visible to mid-infrared (mid-IR). Scattered light images reflect shadows produced at the surface of perturbed disks, while the infrared images follow thermal emission from the surface of the disk, showingmore » cooled/heated material in the shadowed/brightened regions. At still longer wavelengths in the submillimeter, the perturbation fades as the disk becomes optically thin and surface features become overwhelmed by emission closer toward the midplane of the disk. With the construction of telescopes such as TMT, GMT, and ALMA due in the next decade, there is a real possibility of observing planets forming in disks in the optical and submillimeter. However, having the angular resolution to observe the features in the mid-IR will remain a challenge.« less

ALMA Observations of the Archetypal “Hot Core” That Is Not: Orion-KL

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

Orozco-Aguilera, M. T.; Zapata, Luis A.; Hirota, Tomoya

We present sensitive high angular resolution (∼0.″1–0.″3) continuum Atacama Large Millimeter/Submillimeter Array (ALMA) observations of the archetypal hot core located in the Orion Kleinmann-Low (KL) region. The observations were made in five different spectral bands (bands 3, 6, 7, 8, and 9) covering a very broad range of frequencies (149–658 GHz). Apart from the well-known millimeter emitting objects located in this region (Orion Source I and BN), we report the first submillimeter detection of three compact continuum sources (ALMA1–3) in the vicinities of the Orion-KL hot molecular core. These three continuum objects have spectral indices between 1.47 and 1.56, andmore » brightness temperatures between 100 and 200 K at 658 GHz, suggesting that we are seeing moderate, optically thick dust emission with possible grain growth. However, as these objects are not associated with warm molecular gas, and some of them are farther out from the molecular core, we thus conclude that they cannot heat the molecular core. This result favors the hypothesis that the hot molecular core in Orion-KL core is heated externally.« less

Submillimeter detection of stratospheric OH and further line assignments in the stratospheric emission spectrum

NASA Technical Reports Server (NTRS)

Carli, B.; Mencaraglia, F.; Bonetti, A.; Dinelli, B. M.; Forni, F.

1983-01-01

Hydroxyl radical has been identified in submillimeter stratospheric emission spectra measured with an unapodized resolution of 0.0033 per cm. Many features due to vibrationally excited ozone have also been detected. The contribution to the submillimeter atmospheric spectrum of NO, NO2, and HBr is discussed.

A Submillimeter Resolution PET Prototype Evaluated With an 18F Inkjet Printed Phantom

NASA Astrophysics Data System (ADS)

Schneider, Florian R.; Hohberg, Melanie; Mann, Alexander B.; Paul, Stephan; Ziegler, Sibylle I.

2015-10-01

This work presents a submillimeter resolution PET (Positron Emission Tomography) scanner prototype based on SiPM/MPPC arrays (Silicon Photomultiplier/Multi Pixel Photon Counter). Onto each active area a 1 ×1 ×20 mm3 LYSO (Lutetium-Yttrium-Oxyorthosilicate) scintillator crystal is coupled one-to-one. Two detector modules facing each other in a distance of 10.0 cm have been set up with in total 64 channels that are digitized by SADCs (Sampling Analog to Digital Converters) with 80 MHz, 10 bit resolution and FPGA (Field Programmable Gate Array) based extraction of energy and time information. Since standard phantoms are not sufficient for testing submillimeter resolution at which positron range is an issue, a 18F inkjet printed phantom has been used to explore the limit in spatial resolution. The phantom could be successfully reconstructed with an iterative MLEM (Maximum Likelihood Expectation Maximization) and an analytically calculated system matrix based on the DRF (Detector Response Function) model. The system yields a coincidence time resolution of 4.8 ns FWHM, an energy resolution of 20%-30% FWHM and a spatial resolution of 0.8 mm.

FIR/THz Space Interferometry: Science Opportunities, Mission Concepts, and Technical Challenges

NASA Technical Reports Server (NTRS)

Leisawitz, David

2007-01-01

Sensitive far-IR imaging and spectroscopic measurements of astronomical objects on sub-arcsecond angular scales are essential to our understanding of star and planet formation, the formation and evolution of galaxies, and to the detection and characterization of extrasolar planets. Cold single-aperture telescopes in space, such as the Spitzer Space Telescope and the Herschel Space Observatory, are very sensitive, but they lack the necessary angular resolution by two or more orders of magnitude. Far-IR space interferometers will address this need in the coming decades. Several mission concepts have already been studied, including in the US the Space Infrared Interferometric Telescope (SPIRIT) and the more ambitious Submillimeter Probe of the Evolution of Cosmic Structure (SPECS). This talk will describe science goals and summarize alternative concepts for future FIR/THz space interferometry missions. Small arrays of sensitive, fast, direct detectors are a key enabling technology for SPIRIT and SPECS. I will describe the technology requirements for far-IR interferometry, including the detector requirements, and their derivation from the mission science goals and instrument concepts.

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

The Molecular Envelope around the Red Supergiant VY CMa

NASA Astrophysics Data System (ADS)

Muller, S.; Dinh-V-Trung; Lim, J.; Hirano, N.; Muthu, C.; Kwok, S.

2007-02-01

We present millimeter interferometric observations of the molecular envelope around the red supergiant VY CMa with the Submillimeter Array (SMA). The high angular resolution (<2") allows us to derive the structure of the envelope as observed in the 1.3 mm continuum, 12CO(2-1), 13CO(2-1), and SO(65-54) lines emission. The circumstellar envelope is resolved into three components: (1) a dense, compact, and dusty central component, embedded in (2) a more diffuse and extended envelope, and (3) a high-velocity component. We construct a simple model, consisting of a spherically symmetric slowly expanding envelope and bipolar outflows with a wide opening angle (~120°) viewed close to the line of sight (i=15deg). Our model can explain the main features of the SMA data and previous single-dish CO multiline observations. An episode of enhanced mass loss along the bipolar direction is inferred from our modeling. The SMA data provide a better understanding of the complicated morphology seen in the optical/IR high-resolution observations.

Science with the wideband Submillimeter Array: A Strategy for the Decade 2017-2027

NASA Astrophysics Data System (ADS)

Wilner, D.; Keto, E.; Bower, G.; Ching, T. C.; Gurwell, M.; Hirano, N.; Keating, G.; Lai, S. P.; Patel, N.; Petitpas, G.; Qi, C.; Sridharan, T. K.; Urata, Y.; Young, K.; Zhang, Q.; Zhao, J.-H.

2017-01-01

The Submillimeter Array (SMA) comprises eight movable 6-meter diameter antennas sited on Maunakea, Hawaii, designed for high spatial and spectral resolution observations at submillimeter wavelengths. Pioneering observations with the SMA have provided new insights into a wide variety of astrophysical phenomena, including the formation and evolution of galaxies, stars and planets, and the nature of the supermassive black hole at the center of the Milky Way. Following careful deliberation, the SMA project is embarking on an ambitious, staged, strategic upgrade that will increase its instantaneous bandwidth and dramatically improve its observational sensitivity and speed. The unique capabilities of this ultra-wideband SMA - the "wSMA" promise to spark a new era of forefront discoveries. In brief, the wSMA upgrade will provide a core receiver set providing dual-polarization observing bands covering the 345 GHz and 230 GHz atmospheric windows, each with 32 GHz of spectral coverage. Together with upgrades of the signal transport system and digital correlator, this brings a factor of 16 increase in instantaneous bandwidth from the original SMA capability. For continuum observations, speed increases linearly with bandwidth to a given level of sensitivity, enabling more observations to the same depth in the same amount of time. Or, for a given amount of time, the sensitivity increases as the square root of bandwidth, enabling deeper observations. For line observations, spectral coverage increases linearly with bandwidth, enabling observations of many lines simultaneously, all at high spectral resolution. In effect, every wSMA observation of an astronomical source is an imaging spectral line survey, and an enormous amount of information can be extracted from such data in conjunction with physical, chemical and dynamical models. This whitepaper elaborates on illustrative examples in key scientific areas, including the evolutionary state of protostellar sources, the chemistry of evolved star envelopes, the constituents of planetary atmospheres, starburst galaxies in the local Universe and at high redshifts, and even low-mass galaxies at high redshifts through the technique of intensity mapping. The wSMA speeds up observations to allow systematic, comparative studies of large numbers of spectral surveys for the first time. The wSMA also will be ideally suited for the study of sources in the time domain. Illustrative examples include the variability of the accretion flow onto the SgrA* black hole, capturing emission from gamma ray bursts from massive star deaths in the early universe and the mergers of compact objects that produce gravitational waves, and resolved spectroscopy of the pristine material that escapes from comets as they traverse the inner Solar System. The wSMA will be complementary to the larger international Atacama Large Millimeter/ submillimeter Array (ALMA) in Chile, which followed the SMA into submillimeter interferometry in 2011. The immense time pressure on ALMA from its many constituencies only creates an increasing need for the wSMA, notably for the large class of observations that do not require ALMA's full sensitivity or angular resolution, as well as for unique submillimeter access to the northern sky. The wSMA will play a leading role in select science areas in the ALMA era, including those requiring long-term programs to build large samples, or rapid response based on flexible scheduling, as well as for high risk seed studies specifically designed for subsequent ALMA follow-up. In addition, the wSMA will be a critical station for submillimeter VLBI observations of supermassive black holes in the global Event Horizon Telescope, which will be bolstered by the inclusion of ALMA in 2017. Finally, the wSMA design explicitly incorporates open space for additional instrumentation to pursue new and compelling science goals and technical innovations, continuing its role as a pathfinder for submillimeter astronomy.

Mission Concept for the Single Aperture Far-Infrared (SAFIR) Observatory

NASA Technical Reports Server (NTRS)

Benford, Dominic J.; Amato, Michael J.; Mather, John C.; Moseley, S. Harvey, Jr.

2004-01-01

We have developed a preliminary but comprehensive mission concept for SAFIR, as a 10 m-class far-infrared and submillimeter observatory that would begin development later in this decade to meet the needs outlined above. Its operating temperature (< or = 4K) and instrument complement would be optimized to reach the natural sky confusion limit in the far-infrared with diffraction-limited performance down to at least the atmospheric cutoff, lambda > or approx. 40 microns. This would provide a point source sensitivity improvement of several orders of magnitude over that of the Spitzer Space Telescope (previously SIRTF) or the Herschel Space Observatory. Additionally, it would have an angular resolution 12 times finer than that of Spitzer and three times finer than Herschel. This sensitivity and angular resolution are necessary to perform imaging and spectroscopic studies of individual galaxies in the early universe. We have considered many aspects of the SAFIR mission, including the telescope technology (optical design, materials, and packaging), detector needs and technologies, cooling method and required technology developments, attitude and pointing, power systems, launch vehicle, and mission operations. The most challenging requirements for this mission are operating temperature and aperture size of the telescope, and the development of detector arrays. SAFIR can take advantage of much of the technology under development for JWST, but with much less stringent requirements on optical accuracy.

A Massive Molecular Outflow in the Dense Dust Core AGAL G337.916-00.477

NASA Astrophysics Data System (ADS)

Torii, Kazufumi; Hattori, Yusuke; Hasegawa, Keisuke; Ohama, Akio; Yamamoto, Hiroaki; Tachihara, Kengo; Tokuda, Kazuki; Onishi, Toshikazu; Hattori, Yasuki; Ishihara, Daisuke; Kaneda, Hidehiro; Fukui, Yasuo

2017-05-01

Massive molecular outflows erupting from high-mass young stellar objects (YSOs) provide important clues to understanding the mechanism of high-mass star formation. Based on new CO J = 3-2 and J = 1-0 observations using the Atacama Submillimeter Telescope Experiment (ASTE) and Mopra telescope facilities, we discovered a massive bipolar outflow associated with the dense dust core AGAL G337.916-00.477 (AGAL337.9-S), located 3.48 kpc from the Sun. The outflow lobes have extensions of less than 1 pc—and thus were not fully resolved in the angular resolutions of ASTE and Mopra—and masses of ˜50 M ⊙. The maximum velocities of the outflow lobes are as high as 36-40 {km} {{{s}}}-1. Our analysis of the infrared and submillimeter data indicates that AGAL337.9-S is in an early evolutionary stage of high-mass star formation, having the total far-infrared luminosity of ˜ 5× {10}4 {L}⊙ . We also found that another dust core, AGAL G337.922-00.456 (AGAL337.9-N), located 2‧ north of AGAL337.9-S, is a high-mass YSO in an earlier evolutionary stage than AGAL337.9-S, as it is less bright in the mid-infrared than AGAL337.9-S.

The Dust and [C II] Morphologies of Redshift ∼4.5 Sub-millimeter Galaxies at ∼200 pc Resolution: The Absence of Large Clumps in the Interstellar Medium at High-redshift

NASA Astrophysics Data System (ADS)

Gullberg, B.; Swinbank, A. M.; Smail, I.; Biggs, A. D.; Bertoldi, F.; De Breuck, C.; Chapman, S. C.; Chen, C.-C.; Cooke, E. A.; Coppin, K. E. K.; Cox, P.; Dannerbauer, H.; Dunlop, J. S.; Edge, A. C.; Farrah, D.; Geach, J. E.; Greve, T. R.; Hodge, J.; Ibar, E.; Ivison, R. J.; Karim, A.; Schinnerer, E.; Scott, D.; Simpson, J. M.; Stach, S. M.; Thomson, A. P.; van der Werf, P.; Walter, F.; Wardlow, J. L.; Weiss, A.

2018-05-01

We present deep, high-resolution (0.″03, 200 pc) ALMA Band 7 observations covering the dust continuum and [C II] λ157.7 μm emission in four z ∼ 4.4–4.8 sub-millimeter galaxies (SMGs) selected from the ALESS and AS2UDS surveys. The data show that the rest-frame 160 μm (observed 345 GHz) dust emission is consistent with smooth morphologies on kpc scales for three of the sources. One source, UDS 47.0, displays apparent substructure, but this is also consistent with a smooth morphology—as indicated by simulations showing that smooth exponential disks can appear clumpy when observed at the high angular resolution (0.″03) and depth of these observations ({σ }345{GHz}∼ 27{--}47 μJy beam‑1). The four SMGs are bright [C II] emitters. We extract [C II] spectra from the high-resolution data, and recover ∼20%–100% of the [C II] flux and ∼40%–80% of the dust continuum emission, compared to the previous lower-resolution observations. When tapered to 0.″2 resolution, our maps recover ∼80%–100% of the continuum emission, indicating that ∼60% of the emission is resolved out on ∼200 pc scales. We find that the [C II] emission in high-redshift galaxies is more spatially extended than the rest-frame 160 μm dust continuum by a factor of 1.6 ± 0.4. By considering the {L}[{{C}{{II}}]}/{L}FIR} ratio as a function of the star formation rate surface density ({{{Σ }}}SFR}), we revisit the [C II] deficit and suggest that the decline in the {L}[{{C}{{II}}]}/{L}FIR} ratio as a function of {{{Σ }}}SFR} is consistent with local processes. We also explore the physical drivers that may be responsible for these trends and can give rise to the properties found in the densest regions of SMGs.

Homogeneous Analysis of the Dust Morphology of Transition Disks Observed with ALMA: Investigating Dust Trapping and the Origin of the Cavities

NASA Astrophysics Data System (ADS)

Pinilla, P.; Tazzari, M.; Pascucci, I.; Youdin, A. N.; Garufi, A.; Manara, C. F.; Testi, L.; van der Plas, G.; Barenfeld, S. A.; Canovas, H.; Cox, E. G.; Hendler, N. P.; Pérez, L. M.; van der Marel, N.

2018-05-01

We analyze the dust morphology of 29 transition disks (TDs) observed with Atacama Large (sub-)Millimeter Array (ALMA) at (sub-)millimeter emission. We perform the analysis in the visibility plane to characterize the total flux, cavity size, and shape of the ring-like structure. First, we found that the M dust–M ⋆ relation is much flatter for TDs than the observed trends from samples of class II sources in different star-forming regions. This relation demonstrates that cavities open in high (dust) mass disks, independent of the stellar mass. The flatness of this relation contradicts the idea that TDs are a more evolved set of disks. Two potential reasons (not mutually exclusive) may explain this flat relation: the emission is optically thick or/and millimeter-sized particles are trapped in a pressure bump. Second, we discuss our results of the cavity size and ring width in the context of different physical processes for cavity formation. Photoevaporation is an unlikely leading mechanism for the origin of the cavity of any of the targets in the sample. Embedded giant planets or dead zones remain as potential explanations. Although both models predict correlations between the cavity size and the ring shape for different stellar and disk properties, we demonstrate that with the current resolution of the observations, it is difficult to obtain these correlations. Future observations with higher angular resolution observations of TDs with ALMA will help discern between different potential origins of cavities in TDs.

Micro-Spec: A High Performance Compact Spectrometer for Submillimeter Astronomy

NASA Technical Reports Server (NTRS)

Hsieh, Wen-Ting; Moseley, Harvey; Stevenson, Thomas; Brown, Ari; Patel, Amil; U-Yen, Kongpop; Ehsan, Negar; Caltado, Giuseppe; Wollock, Edward

2012-01-01

We describe the micro-Spec, an extremely compact high performance spectrometer for the submillimeter and millimeter spectral ranges. We have designed a fully integrated submillimeter spectrometer based on superconducting microstrip technology and fabricated its critical elements. Using low loss transmission lines, we can produce a fully integrated high resolution submillimeter spectrometer on a single four inch Si wafer. A resolution of 500 can readily be achieved with standard fabrication tolerance, higher with phase trimming. All functions of the spectrometer are integrated - light is coupled to the micro strip circuit with a planar antenna, the spectra discrimination is achieved using a synthetic grating, orders are separated using a built-in planar filter, and the light is detected using photon counting Microwave Kinetic Inductance Detectors (MKID). We will discus the design principle of the instrument, describe its technical advantages, and report the progress on the development of the instrument.

Mu-Spec: A High Performance Compact Spectrometer for Submillimeter Astronomy

NASA Technical Reports Server (NTRS)

Hsieh, Wen-Ting; Moseley, Harvey; Stevenson, Thomas; Brown, Ari; Patel, Amil; U-yen, Kongpop; Ehsan, Negar; Cataldo, Giuseppe; Wollack, Ed

2012-01-01

We describe the Mu-Spec, an extremely compact high performance spectrometer for the submillimeter and millimeter spectral ranges. We have designed a fully integrated submillimeter spectrometer based on superconducting microstrip technology and fabricated its critical elements. Using low loss transmission lines, we can produce a fully integrated high resolution submillimeter spectrometer on a single four inch Si wafer. A resolution of 500 can readily be achieved with standard fabrication tolerance, higher with phase trimming. All functions of the spectrometer are integrated - light is coupled to the microstrip circuit with a planar antenna, the spectra discrimination is achieved using a synthetic grating, orders are separated using a built-in planar filter, and the light is detected using photon counting Microwave Kinetic Inductance Detectors (MKID). We will discus the design principle of the instrument, describe its technical advantages, and report the progress on the development of the instrument.

HELICAL MAGNETIC FIELDS IN THE NGC 1333 IRAS 4A PROTOSTELLAR OUTFLOWS

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

Ching, Tao-Chung; Lai, Shih-Ping; Zhang, Qizhou

We present Submillimeter Array polarization observations of the CO J = 3–2 line toward NGC 1333 IRAS 4A. The CO Stokes I maps at an angular resolution of ∼1″ reveal two bipolar outflows from the binary sources of NGC 1333 IRAS 4A. The kinematic features of the CO emission can be modeled by wind-driven outflows at ∼20° inclined from the plane of the sky. Close to the protostars the CO polarization, at an angular resolution of ∼2.″3, has a position angle approximately parallel to the magnetic field direction inferred from the dust polarizations. The CO polarization direction appears to vary smoothly frommore » an hourglass field around the core to an arc-like morphology wrapping around the outflow, suggesting a helical structure of magnetic fields that inherits the poloidal fields at the launching point and consists of toroidal fields at a farther distance of outflow. The helical magnetic field is consistent with the theoretical expectations for launching and collimating outflows from a magnetized rotating disk. Considering that the CO polarized emission is mainly contributed from the low-velocity and low-resolution data, the helical magnetic field is likely a product of the wind–envelope interaction in the wind-driven outflows. The CO data reveal a PA of ∼30° deflection in the outflows. The variation in the CO polarization angle seems to correlate with the deflections. We speculate that the helical magnetic field contributes to ∼10° deflection of the outflows by means of Lorentz force.« less

Submillimeter heterodyne detection of interstellar carbon monoxide at 434 micrometers

NASA Technical Reports Server (NTRS)

Fetterman, H. R.; Clifton, B. J.; Peck, D. D.; Tannenwald, P. E.; Koepf, G. A.; Goldsmith, P. F.; Erickson, N. R.; Buhl, D.; Mcavoy, N.

1981-01-01

Laser heterodyne observations of submillimeter emissions from carbon monoxide in the Orion molecular cloud are reported. High frequency and spatial resolution observations were made at the NASA Infrared Telescope Facility on Mauna Kea by the use of an optically pumped laser local oscillator and quasi-optical Schottky diode mixer for heterodyne detection of the J = 6 - 5 rotational transition of CO at 434 microns. Spectral analysis of the 434-micron emission indicates that the emitting gas is optically thin and is at a temperature above 180 K. Results thus demonstrate the potential contributions of ground-based high-resolution submillimeter astronomy to the study of active regions in interstellar molecular clouds.

Atlas of stratospheric submillimeter lines. I - The 7-20 kayser interval

NASA Technical Reports Server (NTRS)

Baldecchi, M. G.; Carli, B.; Mencaraglia, F.; Bonetti, A.; Carlotti, M.

1984-01-01

The stratospheric emission in the submillimeter spectral region has been measured from 38.2 km altitude with a resolution of 0.0033 kayser. In most cases this resolution makes possible the separation of contributions caused by the individual rotational transitions. An atlas of the observed features is given as a guide to both the measurements of minor stratospheric constituents concentration and the evaluation of stratospheric transparency for the measurement of nontelluric sources.

NGC 7538 IRS. 1. Interaction of a Polarized Dust Spiral and a Molecular Outflow

NASA Astrophysics Data System (ADS)

Wright, M. C. H.; Hull, Charles L. H.; Pillai, Thushara; Zhao, Jun-Hui; Sandell, Göran

2014-12-01

We present dust polarization and CO molecular line images of NGC 7538 IRS 1. We combined data from the Submillimeter Array, the Combined Array for Research in Millimeter-wave Astronomy, and the James Clerk Maxwell Telescope to make images with ~2.''5 resolution at 230 and 345 GHz. The images show a remarkable spiral pattern in both the dust polarization and molecular outflow. These data dramatically illustrate the interplay between a high infall rate onto IRS 1 and a powerful outflow disrupting the dense, clumpy medium surrounding the star. The images of the dust polarization and the CO outflow presented here provide observational evidence for the exchange of energy and angular momentum between the infall and the outflow. The spiral dust pattern, which rotates through over 180° from IRS 1, may be a clumpy filament wound up by conservation of angular momentum in the infalling material. The redshifted CO emission ridge traces the dust spiral closely through the MM dust cores, several of which may contain protostars. We propose that the CO maps the boundary layer where the outflow is ablating gas from the dense gas in the spiral.

Warm water deuterium fractionation in IRAS 16293-2422. The high-resolution ALMA and SMA view

NASA Astrophysics Data System (ADS)

Persson, M. V.; Jørgensen, J. K.; van Dishoeck, E. F.

2013-01-01

Context. Measuring the water deuterium fractionation in the inner warm regions of low-mass protostars has so far been hampered by poor angular resolution obtainable with single-dish ground- and space-based telescopes. Observations of water isotopologues using (sub)millimeter wavelength interferometers have the potential to shed light on this matter. Aims: To measure the water deuterium fractionation in the warm gas of the deeply-embedded protostellar binary IRAS 16293-2422. Methods: Observations toward IRAS 16293-2422 of the 53,2 - 44,1 transition of H218O at 692.07914 GHz from Atacama Large Millimeter/submillimeter Array (ALMA) as well as the 31,3 - 22,0 of H218O at 203.40752 GHz and the 31,2 - 22,1 transition of HDO at 225.89672 GHz from the Submillimeter Array (SMA) are presented. Results: The 692 GHz H218O line is seen toward both components of the binary protostar. Toward one of the components, "source B", the line is seen in absorption toward the continuum, slightly red-shifted from the systemic velocity, whereas emission is seen off-source at the systemic velocity. Toward the other component, "source A", the two HDO and H218O lines are detected as well with the SMA. From the H218O transitions the excitation temperature is estimated at 124 ± 12 K. The calculated HDO/H2O ratio is (9.2 ± 2.6) × 10-4 - significantly lower than previous estimates in the warm gas close to the source. It is also lower by a factor of ~5 than the ratio deduced in the outer envelope. Conclusions: Our observations reveal the physical and chemical structure of water vapor close to the protostars on solar-system scales. The red-shifted absorption detected toward source B is indicative of infall. The excitation temperature is consistent with the picture of water ice evaporation close to the protostar. The low HDO/H2O ratio deduced here suggests that the differences between the inner regions of the protostars and the Earth's oceans and comets are smaller than previously thought. Appendix A is available in electronic form at http://www.aanda.org

The Role of Coherent Detection

NASA Technical Reports Server (NTRS)

Zmuidzinas, J.

2004-01-01

Many interesting astronomical objects, such as galaxies, molecular clouds, PDRs, star - forming regions, protostars, evolved stars, planets, and comets, have rich submillimeter spectra. In order to avoid line blending, and to be able to resolve the line shape, it is often necessary to measure these spectra at high resolution. This paper discusses the relative advantages and limitations of coherent and direct detection for high resolution spectroscopy in the submillimeter and far - infrared. In principle, direct detection has a fundamental sensitivity advantage. In practice, it is di.cult to realize this advantage given the sensitivities of existing detectors and reasonable constraints on the instrument volume. Thus, coherent detection can be expected to play an important role in submillimeter and far - infrared astrophysics well into the future.

Multiplicity of High-z Submillimeter Galaxies from Cosmological Simulations

NASA Astrophysics Data System (ADS)

Ball, David; Narayanan, Desika; Hopkins, Philip F.; Turk, Matthew

2015-01-01

Sub-millimeter galaxies (or SMG's) are some of the most luminous galaxies in the universe, yet are nearly invisible in the optical. Theorists have long struggled to simulate SMG's and accurately match their spectral properties and abundance to observations. Recent high-resolution observations, however, suggest that what were previously thought to be single sub-millimeter sources on the sky, may break up into multiple components when viewed with sufficient resolving power. Here, we present a combination of high-resolution cosmological hydrodynamic zoom simulations of massive galaxies in formation with a new dust radiative transfer package in order to understand this multiplicity in simulated SMGs. We find that multiplicity is a natural element of SMG formation as numerous subhalos bombard the central during its peak growth phase

CO(J = 3-2) on-the-fly mapping of the nearby spiral galaxies NGC 628 and NGC 7793: Spatially resolved CO(J = 3-2) star-formation law

NASA Astrophysics Data System (ADS)

Muraoka, Kazuyuki; Takeda, Miho; Yanagitani, Kazuki; Kaneko, Hiroyuki; Nakanishi, Kouichiro; Kuno, Nario; Sorai, Kazuo; Tosaki, Tomoka; Kohno, Kotaro

2016-04-01

We present the results of CO(J = 3-2) on-the-fly mappings of two nearby non-barred spiral galaxies, NGC 628 and NGC 7793, with the Atacama Submillimeter Telescope Experiment at an effective angular resolution of 25″. We successfully obtained global distributions of CO(J = 3-2) emission over the entire disks at a sub-kpc resolution for both galaxies. We examined the spatially resolved (sub-kpc) relationship between CO(J = 3-2) luminosities (L^' }_CO(3-2)) and infrared (IR) luminosities (LIR) for NGC 628, NGC 7793, and M 83, and compared it with global luminosities of a JCMT (James Clerk Maxwell Telescope) Nearby Galaxy Legacy Survey sample. We found a striking linear L^' }_CO(3-2)-LIR correlation over the four orders of magnitude, and the correlation is consistent even with that for ultraluminous IR galaxies and submillimeter-selected galaxies. In addition, we examined the spatially resolved relationship between CO(J = 3-2) intensities (ICO(3-2)) and extinction-corrected star formation rates (SFRs) for NGC 628, NGC 7793, and M 83, and compared it with that for Giant Molecular Clouds in M 33 and 14 nearby galaxy centers. We found a linear ICO(3-2)-SFR correlation with ˜1 dex scatter. We conclude that the CO(J = 3-2) star-formation law (i.e., linear L^' }_CO(3-2)-LIR and ICO(3-2)-SFR correlations) is universally applicable to various types and spatial scales of galaxies; from spatially resolved nearby galaxy disks to distant IR-luminous galaxies, within ˜1 dex scatter.

Development of Low-Noise High Value Chromium Silicide Resistors for Cryogenic Detector Applications

NASA Technical Reports Server (NTRS)

Jhabvala, Murzy; Babu, Sachi; Monroy, Carlos; Darren, C.; Krebs, Carolyn A. (Technical Monitor)

2001-01-01

Extremely high sensitivity detectors, such as silicon bolometers are required in many NASA missions for detection of photons from the x-ray to the far infrared regions. Typically, these detectors are cooled to well below the liquid helium (LHe) temperature (4.2 K) to achieve the maximum detection performance. As photoconductors, they are generally operated with a load resistor and a pre-set bias voltage, which is then coupled to the input gate of a source-follower Field Effect Transistor (FET) circuit. It is imperative that the detector system signal to noise performance be limited by the noise of the detector and not by the noise of the external components. The load resistor value is selected to optimize the detector performance. These two criteria tend to be contradictory in that these detectors require load resistors in the hundreds of megaohms, which leads to a higher Johnson noise. Additionally, the physical size of the resistor must be small for device integration as required by such missions as the NASA High Resolution Airborne Wide-Band Camera (HAWC) instrument and the Submillimeter High Angular Resolution Camera (SHARC) for the Caltech Submillimeter Observatory (CSO). We have designed, fabricated and characterized thin film resistors using a CrSi/TiW/Al metal system on optical quality quartz substrates. The resistor values range from 100 megaohms to over 650 megaohms and are Johnson noise limited at LHe temperatures. The resistor film is sputtered with a sheet resistance ranging from 300 ohms to 1600 ohms and the processing sequence developed for these devices allows for chemically fine tuning the sheet resistance in-situ. The wafer fabrication process was of sufficiently high yield (>80%) providing clusters of good resistors for integrated multiple detector channels, a very important feature in the assembly of these two instruments.

New assignments in the submillimeter emission spectrum of the stratosphere

NASA Technical Reports Server (NTRS)

Carli, B.; Mencaraglia, F.; Bonetti, A.

1982-01-01

New line assignments in the spectrum of the stratospheric submillimeter emission, measured with unapodized resolution of 0.0033/cm, have been made. Positive evidence for the presence of symmetric and asymmetric ozone isotopes, water vapor excited to the (010) level, and HCN is given.

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.

THE DISTRIBUTION OF DEUTERATED FORMALDEHYDE WITHIN ORION-KL

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

Favre, Cécile; Bergin, Edwin A.; Neill, Justin L.

2015-08-01

We report the first high angular resolution imaging (3.″4 × 3.″0) of deuterated formaldehyde (HDCO) toward Orion-KL, carried out with the Submillimeter Array. We find that the spatial distribution of the formaldehyde emission systematically differs from that of methanol: while methanol is found toward the inner part of the region, HDCO is found in colder gas that wraps around the methanol emission on four sides. The HDCO/H{sub 2}CO ratios are determined to be 0.003–0.009 within the region, up to an order of magnitude higher than the D/H measured for methanol. These findings strengthen the previously suggested hypothesis that there aremore » differences in the chemical pathways leading to HDCO (via deuterated gas-phase chemistry) and deuterated methanol (through conversion of formaldehyde into methanol on the surface of icy grain mantles)« less

From ATLASGAL to SEDIGISM: Towards a Complete 3D View of the Dense Galactic Interstellar Medium

NASA Astrophysics Data System (ADS)

Schuller, F.; Urquhart, J.; Bronfman, L.; Csengeri, T.; Bontemps, S.; Duarte-Cabral, A.; Giannetti, A.; Ginsburg, A.; Henning, T.; Immer, K.; Leurini, S.; Mattern, M.; Menten, K.; Molinari, S.; Muller, E.; Sánchez-Monge, A.; Schisano, E.; Suri, S.; Testi, L.; Wang, K.; Wyrowski, F.; Zavagno, A.

2016-09-01

The ATLASGAL survey has provided the first unbiased view of the inner Galactic Plane at sub-millimetre wavelengths. This is the largest ground-based survey of its kind to date, covering 420 square degrees at a wavelength of 870 µm. The reduced data, consisting of images and a catalogue of > 104 compact sources, are available from the ESO Science Archive Facility through the Phase 3 infrastructure. The extremely rich statistics of this survey initiated several follow-up projects, including spectroscopic observations to explore molecular complexity and high angular resolution imaging with the Atacama Large Millimeter/submillimeter Array (ALMA), aimed at resolving individual protostars. The most extensive follow-up project is SEDIGISM, a 3D mapping of the dense interstellar medium over a large fraction of the inner Galaxy. Some notable results of these surveys are highlighted.

Broadband Direct Detection Submillimeter Spectrometer with Multiplexed Superconducting Transition Edge Thermometer Bolometers

NASA Technical Reports Server (NTRS)

Benford, D. J.; Ames, T. A.; Chervenak, J. A.; Moseley, S. H.; Shafer, R. A.; Staguhn, J. G.; Voellmer, G. M.; Pajot, F.; Rioux, C.; Phillips, T. G.;

Submillimeter Remote Sensing of Planetary and Cometary Atmospheres and LRO/LCROSS Observations of the Moon

NASA Technical Reports Server (NTRS)

Chin, Gordon

2011-01-01

Submillimeter remote sensing of planetary and cometary atmospheres have been proposed for Venus and Mars while MIRO on Rosetta will observe the coma of Comet 67P/Churyumov - Cierasimenko in December 2015, UARS and AURA MLS have observed millimeter and submillimeter molecule emissions in the Earth's stratosphere for many decades, Observations of submillimeter wave molecular emissions provide a wealth of information not obtainable by alternative techniques. Submillimeter line emissions exhibit linear temperature dependence, insensitivity to aerosol scattering, extinction, and have separated transitions with well determined line-shapes. These observations have high sensitivities to trace chemical species and can; 1) Fully resolve the line profiles of molecules with high resolution, 2) Provide deterministic retrievals of species abundance, temperature, and pressure, and 3) Measure Doppler shifts of detected molecules for wind velocities.

Angular Momentum in Disk Wind Revealed in the Young Star MWC 349A

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

Zhang, Qizhou; Claus, Brian; Watson, Linda

Disk winds are thought to play a critical role in star birth. As winds extract excess angular momentum from accretion disks, matter in the disk can be transported inward to the star to fuel mass growth. However, observational evidence of wind carrying angular momentum has been very limited. We present Submillimeter Array (SMA) observations of the young star MWC 349A in the H26 α and H30 α recombination lines. The high signal-to-noise ratios made possible by the maser emission process allow us to constrain the relative astrometry of the maser spots to milli-arcsecond precision. Previous observations of the H30 αmore » line with the SMA and the Plateau de Bure interferometer (PdBI) showed that masers are distributed in the disk and wind. Our new high-resolution observations of the H26 α line reveal differences in spatial distribution from that of the H30 α line. H26 α line masers in the disk are excited in a thin annulus with a radius of about 25 au, while the H30 α line masers are formed in a slightly larger annulus with a radius of 30 au. This is consistent with expectations for maser excitation in the presence of an electron density variation of approximately R {sup −4}. In addition, the H30 α and H26 α line masers arise from different parts in the wind. This difference is also expected from maser theory. The wind component of both masers exhibits line-of-sight velocities that closely follow a Keplerian law. This result provides strong evidence that the disk wind extracts significant angular momentum, thereby facilitating mass accretion in the young star.« less

Submillimeter atmospheric FTS at the geographic South Pole

NASA Astrophysics Data System (ADS)

Chamberlin, Richard A.; Martin, Robert N.; Martin, Christopher L.; Stark, Antony A.

2003-02-01

A submillimeter Fourier Transform Spectrometer of the Martin-Puplett type was constructed and deployed to the geographical South Pole in 2001. The instrument operates from about 300 GHz to almost 2 THz and was used over winter to acquire atmospheric spectra with resolution as fine as 250 MHz. The main motivation for constructing and deploying this FTS was for astronomical site testing, but the obtained spectra can have important secondary uses in atmospheric science and transmission model validation. Some preliminary, low spectral resolution site testing results are presented here.

Direct measurement of additional Ar-H2O vibration-rotation-tunneling bands in the millimeter-submillimeter range

NASA Astrophysics Data System (ADS)

Zou, Luyao; Widicus Weaver, Susanna L.

2016-06-01

Three new weak bands of the Ar-H2O vibration-rotation-tunneling spectrum have been measured in the millimeter wavelength range. These bands were predicted from combination differences based on previously measured bands in the submillimeter region. Two previously reported submillimeter bands were also remeasured with higher frequency resolution. These new measurements allow us to obtain accurate information on the Coriolis interaction between the 101 and 110 states. Here we report these results and the associated improved molecular constants.

High-resolution submillimeter-wave radiometry of supersonic flow

NASA Technical Reports Server (NTRS)

Dionne, G. F.; Weiss, J. A.; Fitzgerald, J. F.; Fetterman, H. R.; Litvak, M. M.

1983-01-01

The recent development of a high-resolution submillimeter-wave heterodyne radiometer has made possible the first measurements of H2O molecule rotational line excitation temperatures and detailed profiles in supersonic flow. Absorption signals were measured across the flow for the 2/11/ from 2//02/ (752 GHz) para-H2O rotational transition against a hot background. These signals decrease downstream owing to the volume expansion of the gas away from the sonic nozle exit in the high-vacuum chamber. Radiative transfer calculations based on the large-velocity-gradient approximation and multilevel statistical equilibrium agree with these results and with the measured spectral line shapes. The data reveal nearly isentropic gas expansion and cooling. These studies have shown that submillimeter-wave heterodyne radiometry can be useful for remote sensing of supersonic flow with low mass flux, provided the signal transmission is through a dry or thin atmosphere.

Isotopic Ratios in Nitriles from Submillimeter Spectroscopy Using SMA and ALMA

NASA Astrophysics Data System (ADS)

Gurwell, Mark A.; Moreno, Raphael; Vinatier, Sandrine; Lellouch, Emmanuel; Butler, Bryan J.; Moullet, Arielle; Lara, Luisa; Hidayat, Taufiq

2016-10-01

We present submillimeter spectroscopic observations of Titan obtained using the Submillimeter Array (SMA) in 2011, and the Atacama Large Millimeter/Submillimeter Array (ALMA) in 2012, some of which have previously been presented but not fully analyzed (1, 2, 3). The SMA observations were obtained at low spatial resolution, providing disk average spectra, but the ALMA observations provide low resolution mapping of Titan (~0.4"-0.6" when Titan was 0.77" surface diameter). We will present detailed radiative transfer analysis of detected spectral lines to derive isotopic ratios in two nitriles: HCN (D/H, 13C/12C, 15N/14N) and HC3N (15N/14N). The analysis makes use of nearly concurrent CIRS temperature profiles as important constraints for the vertical profiles of these species, allowing high precision measurements of the ratios. Finally, we will highlight current and future ALMA observations that will allow monitoring of non-symmetric molecular species in Titan's upper atmosphere from Earth, beyond the end of the Cassini mission.(1) Gurwell et al (2011) EPSC-DPS Joint Meeting 2011, p270. (2) Moreno et al (2014) EPSC 2014 Abstracts, Vol. 9, id. EPSC2014-438. (3) Moreno etal (2014), DPS meeting #46, id.211.19

Advantages of cortical surface reconstruction using submillimeter 7 T MEMPRAGE.

PubMed

Zaretskaya, Natalia; Fischl, Bruce; Reuter, Martin; Renvall, Ville; Polimeni, Jonathan R

2018-01-15

Recent advances in MR technology have enabled increased spatial resolution for routine functional and anatomical imaging, which has created demand for software tools that are able to process these data. The availability of high-resolution data also raises the question of whether higher resolution leads to substantial gains in accuracy of quantitative morphometric neuroimaging procedures, in particular the cortical surface reconstruction and cortical thickness estimation. In this study we adapted the FreeSurfer cortical surface reconstruction pipeline to process structural data at native submillimeter resolution. We then quantified the differences in surface placement between meshes generated from (0.75 mm) 3 isotropic resolution data acquired in 39 volunteers and the same data downsampled to the conventional 1 mm 3 voxel size. We find that when processed at native resolution, cortex is estimated to be thinner in most areas, but thicker around the Cingulate and the Calcarine sulci as well as in the posterior bank of the Central sulcus. Thickness differences are driven by two kinds of effects. First, the gray-white surface is found closer to the white matter, especially in cortical areas with high myelin content, and thus low contrast, such as the Calcarine and the Central sulci, causing local increases in thickness estimates. Second, the gray-CSF surface is placed more interiorly, especially in the deep sulci, contributing to local decreases in thickness estimates. We suggest that both effects are due to reduced partial volume effects at higher spatial resolution. Submillimeter voxel sizes can therefore provide improved accuracy for measuring cortical thickness. Copyright © 2017 Elsevier Inc. All rights reserved.

Imaging X-ray spectrophotometers

NASA Technical Reports Server (NTRS)

Hailey, C. J.; Hamilton, T. T.; Ku, W. H.-M.

1981-01-01

A new instrument which combines the good energy resolution of the gas scintillation proportional counter with the high position resolution of the microchannel plate is proposed. A study of the factors which determine the combined energy and position resolution of the new instrument is discussed. Submillimeter position resolution along with good energy resolution (8% fwhm at 6 keV) should be achievable.

Cool stars, stellar systems, and the sun; Proceedings of the 7th Cambridge Workshop, Tucson, AZ, Oct. 9-12, 1991

NASA Technical Reports Server (NTRS)

Giampapa, Mark S. (Editor); Bookbinder, Jay A. (Editor)

1992-01-01

Consideration is given to HST observations of late-type stars, molecular absorption in the UV spectrum of Alpha Ori, EUV emission from late-type stars, Rosat observations of the Pleiades cluster, a deep ROSAT observation of the Hyades cluster, optical spectroscopy detected by EXOSAT, stellar photospheric convection, a structure of the solar X-ray corona, magnetic surface images of the BY Dra Star HD 82558, a Zebra interpretatin of BY Dra stars, optical flares on II Peg, a low-resolution spectroscopic survey of post-T tauri candidates, millimeter and sub-millimeter emission from flare stars, and activity in tidally interacting binaries. Attention is also given to modeling stellar angular momentum evolution, extended 60-micron emission from nearby Mira variables, the PANDORA atmosphere program, the global properties of active regions, oscillations in a stratified atmosphere, lithium abundances in northern RS CVn binaries, a new catalog of cool dwarf stars, the Far UV Spectrograph Explorer, and development of reflecting coronagraphs.

Facilities for US radioastronomy

NASA Technical Reports Server (NTRS)

Thaddeus, P.

1982-01-01

An overview of the radio-astronomy field is given, and prospects ready for construction at NASA are presented. A very-long-baseline array consisting of ten 25 m antennas, with a limiting wavelength of 7 mm and an angular resolution at that wavelength of 2 x 10 to the 4th arcsec is discussed. Eighty percent of the phase information will be obtained by closure around the 36 independent triangles, and high quality aperture-synthesis maps will be produced at all wavelengths. The 25 m telescope will be capable of several applications including the discovery of new molecules in our galaxy (in particular, the envelope of the evolved carbon star IRC + 10216), the detection of CO to distances of perhaps 100 million light years, and the understanding of the events which occur as stars are formed from molecular clouds, and as energy is fed back into the molecular gas by new stars. The submillimeter-wave telescope contains the last atmospheric radio windows where astronomical observations can be made from the earth's surface. The need for funding is stressed.

NANOCOSMOS: a trip to the nanoworld

NASA Astrophysics Data System (ADS)

Ruiz Zelmanovitch, N.; Castellanos, M.

2017-03-01

Cosmic dust is made in evolved stars. However, the processes involved in the formation and evolution of dust remain unknown so far. The project ''Gas and dust from stars to the laboratory: exploring the NANOCOSMOS'', takes advantage of the new observational capabilities (increased angular resolution) of the Atacama Large Millimeter/submillimeter Array (ALMA) to unveil the physical and chemical conditions in the dust formation zone of evolved stars. These observations, in combination with novel top-level ultra-high vacuum experiments and astrophysical modelling, will provide a cutting-edge view of cosmic dust. The importance of publishing scientific results based on NANOCOSMOS in the scientific literature goes without saying. But it is also important and a stated NANOCOSMOS objective to disseminate the achievements of the project and its scientific and technological results to a wider audience. In this presentation we will discuss the tools used to spread them to the society. This presentation is structured as follows: 1. What is Astrochemistry?; 2. What is NANOCOSMOS?; 3. Outreach in the NANOCOSMOS programme; 4. Conclusions.

The Space Infrared Interferometric Telescope (SPIRIT): Recent Study Results and Plans

NASA Astrophysics Data System (ADS)

Leisawitz, David; SPIRIT Mission Study Team

2007-12-01

SPIRIT was recommended in the 2002 "Community Plan for Far-IR/Submillimeter Space Astronomy.” A structurally connected interferometer, SPIRIT provides sensitive sub-arcsecond angular resolution images and integral field spectroscopy in the 25 to 400 micron wavelength range. SPIRIT was designed to revolutionize our understanding of planetary system formation, reveal otherwise-undetectable planets through the disk perturbations they induce, spectroscopically probe the atmospheres of extrasolar giant planets in orbits typical of most of the planets in our solar system, and yield significant new insight into the processes associated with galaxy formation and development. This paper updates previously presented study results and describes future study plans. Our SPIRIT mission concept study proposal was peer reviewed and selected by NASA for support under the Origins Probe Mission Concept Study program. NASA's Goddard Space Flight Center and four industry partners - Ball Aerospace, Boeing, Lockheed-Martin, and Northrop-Grumman - contributed generously the study. The Origins Probe study results were reviewed by an Advisory Review Panel.

Study of the Imaging Capabilities of SPIRIT/SPECS Concept Interferometers

NASA Technical Reports Server (NTRS)

Allen, Ronald J.

2002-01-01

Several new space science mission concepts under development at NASA-GSFC for astronomy are intended to carry out synthetic imaging using Michelson interferometers or direct (Fizeau) imaging with sparse apertures. Examples of these mission concepts include the Stellar Imager (SI), the Space Infrared Interferometric Telescope (SPIRIT), the Submillimeter Probe of the Evolution of Cosmic Structure (SPECS), and the Fourier-Kelvin Stellar Interferometer (FKSI). We have been developing computer-based simulators for these missions. These simulators are aimed at providing a quantitative evaluation of the imaging capabilities of the mission by modeling the performance on different realistic targets in terms of sensitivity, angular resolution, and dynamic range. Both Fizeau and Michelson modes of operation can be considered. Our work is based on adapting a computer simulator called imSIM which was initially written for the Space Interferometer Mission in order to simulate the imaging mode of new missions such as those listed. This report covers the activities we have undertaken to provide a preliminary version of a simulator for the SPIRIT mission concept.

VizieR Online Data Catalog: High-mass starless clump candidates from ATLASGAL (Yuan+, 2017)

NASA Astrophysics Data System (ADS)

Yuan, J.; Wu, Y.; Ellingsen, S. P.; Evans, N. J., II; Henkel, C.; Wang, K.; Liu, H.-L.; Liu, T.; Li, J.-Z.; Zavagno, A.

2017-08-01

This work is based on data from several Galactic plane surveys covering wavelengths from mid-IR to submillimeter. The sample of dense clumps from the ATLASGAL survey (Schuller+ 2009A&A...504..415S) provides the basis for our investigation. The ATLASGAL survey mapped 420 square degrees of the Galactic plane between -80°

ORIGIN AND KINEMATICS OF THE ERUPTIVE FLOW FROM XZ TAU REVEALED BY ALMA

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

Zapata, Luis A.; Galván-Madrid, Roberto; Carrasco-González, Carlos

2015-09-20

We present high angular resolution (∼0.″94) {sup 12}CO(1-0) Atacama Large Millimeter/submillimeter Array (ALMA) observations obtained during the 2014 long baseline campaign from the eruptive bipolar flow from the multiple XZ Tau stellar system discovered by the Hubble Space Telescope (HST). These observations reveal, for the first time, the kinematics of the molecular flow. The kinematics of the different ejections close to XZ Tau reveal a rotating and expanding structure with a southeast–northwest velocity gradient. The youngest eruptive bubbles unveiled in the optical HST images are inside of this molecular expanding structure. Additionally, we report a very compact and collimated bipolarmore » outflow emanating from XZ Tau A, which indicates that the eruptive outflow is indeed originating from this object. The mass (3 × 10{sup −7} M{sub ⊙}) and energetics (E{sub kin} = 3 × 10{sup 37} erg) for the collimated outflow are comparable to those found in molecular outflows associated with young brown dwarfs.« less

New LMT High Resolution Imaging and CO Spectroscopic Studies of the Brightest AzTEC 1.1mm Sources

NASA Astrophysics Data System (ADS)

Yun, Min S.; Aretxaga, Itziar; Hughes, David; Montana, A.; Pope, A.; Bruzual, Gustavo; Ferrusca, D.; Rosa Gonzalez, D.; Sanchez-Arguelles, D.; Narayanan, G.; Wilson, Grant; Gim, Hansung; Ibarra, H.; Mo, H.; Lowenthal, James; Zavala, J.; Carrasco, L.; Chavez, M.; Valazquez, M.; Zeballos, M.; Vega, O.; Schloerb, P.; Cybulsky, J. R.; Casey, Caitlin M.; Tang, Y.

2015-08-01

A substantial population of quiescent galaxies with stellar masses exceeding 10 billion solar masses have been found to z~4, suggesting a rapid formation and quenching of massive galaxies at z~6 or earlier. The submillimeter bright galaxies (SMGs) with SFR > 100-1000 solar masses per year represent natural candidates for the progenitor systems undergoing an epoch of rapid formation and cessation of stellar mass build up. Many of the most luminous SMGs are also extremely red and faint in the optical, suggesting a high redshift and are beyond the reach of the current optical spectroscopic redshift surveys. There is also a growing concern that these most luminous SMGs may be blends of several unrelated sources as a result of a poor angular resolution of the existing surveys (18" & 28" for the AzTEC 1.1mm surveys on JCMT and ASTE, respectively). We have obtained new 8" resolution AzTEC images of 40 brightest AzTEC sources previously found in the GOODS and COSMOS fields using the Large Millimeter Telescope (LMT) to examine the multiplicity question and for the identification of multi-wavelength counterparts. We have also conducted a CO redshift survey using the Redshift Search Receiver on the LMT. We will report the results of these analysis and several new CO redshifts.

Design and Performance of A High Resolution Micro-Spec: An Integrated Sub-Millimeter Spectrometer

NASA Technical Reports Server (NTRS)

Barrentine, Emily M.; Cataldo, Giuseppe; Brown, Ari D.; Ehsan, Negar; Noroozian, Omid; Stevenson, Thomas R.; U-Yen, Kongpop; Wollack, Edward J.; Moseley, S. Harvey

2016-01-01

Micro-Spec is a compact sub-millimeter (approximately 100 GHz--1:1 THz) spectrometer which uses low loss superconducting microstrip transmission lines and a single-crystal silicon dielectric to integrate all of the components of a diffraction grating spectrometer onto a single chip. We have already successfully evaluated the performance of a prototype Micro-Spec, with spectral resolving power, R=64. Here we present our progress towards developing a higher resolution Micro-Spec, which would enable the first science returns in a balloon flight version of this instrument. We describe modifications to the design in scaling from a R=64 to a R=256 instrument, as well as the ultimate performance limits and design concerns when scaling this instrument to higher resolutions.

A Massive Bipolar Outflow and a Dusty Torus with Large Grains in the Preplanetary Nebula IRAS 22036+5306

NASA Technical Reports Server (NTRS)

Sahai, Raghvendra; Young, K.; Patel, N. A.; Sanchez Contreras, C.; Morris, M.

2006-01-01

We report high angular resolution (approx.1") CO J=3-2 interferometric mapping using the Submillimeter Array (SMA) of IRAS 22036+5306 (I22036), a bipolar preplanetary nebula (PPN) with knotty jets discovered in our HST snapshot survey of young PPNs. In addition, we have obtained supporting lower resolution (approx.10") CO and 13CO J=1-0 observations with the Owens Valley Radio Observatory (OVRO) interferometer, as well as optical long-slit echelle spectra at the Palomar Observatory. The CO J=3-2 observations show the presence of a very fast (approx.220 km/s), highly collimated, massive (0.03 Solar Mass) bipolar outflow with a very large scalar momentum (about 10(exp 39) g cm/s), and the characteristic spatiokinematic structure of bow shocks at the tips of this outflow. The H(alpha) line shows an absorption feature blueshifted from the systemic velocity by approx.100 km/s, which most likely arises in neutral interface material between the fast outflow and the dense walls of the bipolar lobes at low latitudes. The fast outflow in I22036, as in most PPNs, cannot be driven by radiation pressure. We find an unresolved source of submillimeter (and millimeter-wave) continuum emission in I22036, implying a very substantial mass (0.02-0.04 Solar Mass) of large (radius > or approx.1 mm), cold (< or approx.50 K) dust grains associated with I22036's toroidal waist. We also find that the C-13/C-12 ratio in I22036 is very high (0.16), close to the maximum value achieved in equilibrium CNO nucleosynthesis (0.33). The combination of the high circumstellar mass (i.e., in the extended dust shell and the torus) and the high C-13/C-12 ratio in I22036 provides strong support for this object having evolved from a massive (> or approx.4 Solar Mass) progenitor in which hot-bottom-burning has occurred.

Distributed Framework for Dynamic Telescope and Instrument Control

NASA Astrophysics Data System (ADS)

Ames, Troy J.; Case, Lynne

2002-12-01

Traditionally, instrument command and control systems have been developed specifically for a single instrument. Such solutions are frequently expensive and are inflexible to support the next instrument development effort. NASA Goddard Space Flight Center is developing an extensible framework, known as Instrument Remote Control (IRC) that applies to any kind of instrument that can be controlled by a computer. IRC combines the platform independent processing capabilities of Java with the power of the Extensible Markup Language (XML). A key aspect of the architecture is software that is driven by an instrument description, written using the Instrument Markup Language (IML). IML is an XML dialect used to describe graphical user interfaces to control and monitor the instrument, command sets and command formats, data streams, communication mechanisms, and data processing algorithms. The IRC framework provides the ability to communicate to components anywhere on a network using the JXTA protocol for dynamic discovery of distributed components. JXTA (see http://www.jxta.org) is a generalized protocol that allows any devices connected by a network to communicate in a peer-to-peer manner. IRC uses JXTA to advertise a device?s IML and discover devices of interest on the network. Devices can join or leave the network and thus join or leave the instrument control environment of IRC. Currently, several astronomical instruments are working with the IRC development team to develop custom components for IRC to control their instruments. These instruments include: High resolution Airborne Wideband Camera (HAWC), a first light instrument for the Stratospheric Observatory for Infrared Astronomy (SOFIA); Submillimeter And Far Infrared Experiment (SAFIRE), a principal investigator instrument for SOFIA; and Fabry-Perot Interferometer Bolometer Research Experiment (FIBRE), a prototype of the SAFIRE instrument, used at the Caltech Submillimeter Observatory (CSO). Most recently, we have been working with the Submillimetre High Angular Resolution Camera IInd Generation (SHARCII) at the CSO to investigate using IRC capabilities with the SHARC instrument.

THE ARIZONA RADIO OBSERVATORY CO MAPPING SURVEY OF GALACTIC MOLECULAR CLOUDS. IV. THE NGC 1333 CLOUD IN PERSEUS IN CO J = 2-1 AND {sup 13}CO J = 2-1

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

Bieging, John H.; Revelle, Melissa; Peters, William L.

2014-09-01

We mapped the NGC 1333 section of the Perseus Molecular Cloud in the J = 2-1 emission lines of {sup 12}CO and {sup 13}CO over a 50' × 60' region (3.4 × 4.1 pc at the cloud distance of 235 pc), using the Arizona Radio Observatory Heinrich Hertz Submillimeter Telescope. The angular resolution is 38'' (0.04 pc) and velocity resolution is 0.3 km s{sup –1}. We compare our velocity moment maps with known positions of young stellar objects (YSOs) and (sub)millimeter dust continuum emission. The CO emission is brightest at the center of the cluster of YSOs, but is detectedmore » over the full extent of the mapped region at ≥10 × rms. The morphology of the CO channel maps shows a kinematically complex structure, with many elongated features extending from the YSO cluster outward by ∼1 pc. One notable feature appears as a narrow serpentine structure that curves and doubles back, with a total length of ∼3 pc. The {sup 13}CO velocity channel maps show evidence for many low-density cavities surrounded by partial shell-like structures, consistent with previous studies. Maps of the velocity moments show localized effects of bipolar outflows from embedded YSOs, as well as a large-scale velocity gradient around the central core of YSOs, suggestive of large-scale turbulent cloud motions determining the location of current star formation. The CO/{sup 13}CO intensity ratios show the distribution of the CO opacity, which exhibits a complex kinematic structure. Identified YSOs are located mainly at the positions of greatest CO opacity. The maps are available for download as FITS files.« less

RESOLVING GIANT MOLECULAR CLOUDS IN NGC 300: A FIRST LOOK WITH THE SUBMILLIMETER ARRAY

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

Faesi, Christopher M.; Lada, Charles J.; Forbrich, Jan

2016-04-20

We present the first high angular resolution study of giant molecular clouds (GMCs) in the nearby spiral galaxy NGC 300, based on observations from the Submillimeter Array (SMA). We target eleven 500 pc sized regions of active star formation within the galaxy in the {sup 12}CO( J = 2-1) line at 40 pc spatial and 1 km s{sup −1} spectral resolution and identify 45 individual GMCs. We characterize the physical properties of these GMCs, and find that they are similar to GMCs in the disks of the Milky Way and other nearby spiral galaxies. For example, the GMC mass spectrummore » in our sample has a slope of 1.80 ± 0.07. Twelve clouds are spatially resolved by our observations, of which ten have virial mass estimates that agree to within a factor of two with mass estimates derived directly from {sup 12}CO integrated intensity, suggesting that the majority of these GMCs are bound. The resolved clouds show consistency with Larson’s fundamental relations between size, linewidth, and mass observed in the Milky Way. We find that the linewidth scales with the size as Δ V ∝ R {sup 0.52±0.20}, and the median surface density in the subsample is 54 M {sub ⊙} pc{sup −2}. We detect {sup 13}CO in four GMCs and find a mean {sup 12}CO/{sup 13}CO flux ratio of 6.2. Our interferometric observations recover between 30% and 100% of the integrated intensity from the APEX single dish {sup 12}CO observations of Faesi et al., suggesting the presence of low-mass GMCs and/or diffuse gas below our sensitivity limit. The fraction of APEX emission recovered increases with the SMA total intensity, as well as with the star formation rate.« less

Distributed Framework for Dynamic Telescope and Instrument Control

NASA Technical Reports Server (NTRS)

Ames, Troy J.; Case, Lynne

2002-01-01

Traditionally, instrument command and control systems have been developed specifically for a single instrument. Such solutions are frequently expensive and are inflexible to support the next instrument development effort. NASA Goddard Space Flight Center is developing an extensible framework, known as Instrument Remote Control (IRC) that applies to any kind of instrument that can be controlled by a computer. IRC combines the platform independent processing capabilities of Java with the power of the Extensible Markup Language (XML). A key aspect of the architecture is software that is driven by an instrument description, written using the Instrument Markup Language (IML). IML is an XML dialect used to describe graphical user interfaces to control and monitor the instrument, command sets and command formats, data streams, communication mechanisms, and data processing algorithms. The IRC framework provides the ability to communicate to components anywhere on a network using the JXTA protocol for dynamic discovery of distributed components. JXTA (see httD://www.jxta.org,) is a generalized protocol that allows any devices connected by a network to communicate in a peer-to-peer manner. IRC uses JXTA to advertise a device's IML and discover devices of interest on the network. Devices can join or leave the network and thus join or leave the instrument control environment of IRC. Currently, several astronomical instruments are working with the IRC development team to develop custom components for IRC to control their instruments. These instruments include: High resolution Airborne Wideband Camera (HAWC), a first light instrument for the Stratospheric Observatory for Infrared Astronomy (SOFIA); Submillimeter And Far Infrared Experiment (SAFIRE), a Principal Investigator instrument for SOFIA; and Fabry-Perot Interferometer Bolometer Research Experiment (FIBRE), a prototype of the SAFIRE instrument, used at the Caltech Submillimeter Observatory (CSO). Most recently, we have been working with the Submillimetre High Angular Resolution Camera IInd Generation (SHARCII) at the CSO to investigate using IRC capabilities with the SHARC instrument.

Molecular jet of IRAS 04166+2706

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

Wang, Liang-Yao; Shang, Hsien; Su, Yu-Nung

2014-01-01

The molecular outflow from IRAS 04166+2706 was mapped with the Submillimeter Array at a 350 GHz continuum and CO J = 3-2 at an angular resolution of ∼1''. The field of view covers the central arcminute, which contains the inner four pairs of knots of the molecular jet. On the channel map, conical structures are clearly present in the low-velocity range (|V – V {sub 0}| < 10 km s{sup –1}), and the highly collimated knots appear in the extremely high velocity range (50 >|V – V {sub 0}| > 30 km s{sup –1}). The higher angular resolution of ∼1''more » reveals the first blue-shifted knot (B1) that was missing in previous Plateau de Bure Interferometer observation of Santiago-García et al. at an offset of ∼6'' to the northeast of the central source. This identification completes the symmetric sequence of knots in both the blue- and red-shifted lobes of the outflow. The innermost knots R1 and B1 have the highest velocities within the sequence. Although the general features appear to be similar to previous CO J = 2-1 images in Santiago-García et al., the emission in CO J = 3-2 almost always peaks further away from the central source than that of CO J = 2-1 in the red-shifted lobe of the channel maps. This gives rise to a gradient in the line-ratio map of CO J = 3-2/J = 2-1 from head to tail within a knot. A large velocity gradient analysis suggests that the differences may reflect a higher gas kinetic temperature at the head. We also explore possible constraints imposed by the nondetection of SiO J = 8-7.« less

The Molecular Gas Environment in the 20 km s{sup −1} Cloud in the Central Molecular Zone

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

Lu, Xing; Gu, Qiusheng; Zhang, Qizhou

We recently reported a population of protostellar candidates in the 20 km s{sup −1} cloud in the Central Molecular Zone of the Milky Way, traced by H{sub 2}O masers in gravitationally bound dense cores. In this paper, we report molecular line studies with high angular resolution (∼3″) of the environment of star formation in this cloud. Maps of various molecular line transitions as well as the continuum at 1.3 mm are obtained using the Submillimeter Array. Five NH{sub 3} inversion lines and the 1.3 cm continuum are observed with the Karl G. Jansky Very Large Array. The interferometric observations aremore » complemented with single-dish data. We find that the CH{sub 3}OH, SO, and HNCO lines, which are usually shock tracers, are better correlated spatially with the compact dust emission from dense cores among the detected lines. These lines also show enhancement in intensities with respect to SiO intensities toward the compact dust emission, suggesting the presence of slow shocks or hot cores in these regions. We find gas temperatures of ≳100 K at 0.1 pc scales based on RADEX modeling of the H{sub 2}CO and NH{sub 3} lines. Although no strong correlations between temperatures and linewidths/H{sub 2}O maser luminosities are found, in high-angular-resolution maps we note several candidate shock-heated regions offset from any dense cores, as well as signatures of localized heating by protostars in several dense cores. Our findings suggest that at 0.1 pc scales in this cloud star formation and strong turbulence may together affect the chemistry and temperature of the molecular gas.« less

Continuous-wave Submillimeter-wave Gyrotrons

PubMed Central

Han, Seong-Tae; Griffin, Robert G.; Hu, Kan-Nian; Joo, Chan-Gyu; Joye, Colin D.; Mastovsky, Ivan; Shapiro, Michael A.; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Torrezan, Antonio C.; Woskov, Paul P.

2007-01-01

Recently, dynamic nuclear polarization enhanced nuclear magnetic resonance (DNP/NMR) has emerged as a powerful technique to obtain significant enhancements in spin spectra from biological samples. For DNP in modern NMR systems, a high power continuous-wave source in the submillimeter wavelength range is necessary. Gyrotrons can deliver tens of watts of CW power at submillimeter wavelengths and are well suited for use in DNP/NMR spectrometers. To date, 140 GHz and 250 GHz gyrotrons are being employed in DNP spectrometer experiments at 200 MHz and 380 MHz at MIT. A 460 GHz gyrotron, which has operated with 8 W of CW output power, will soon be installed in a 700 MHz NMR spectrometer. High power radiation with good spectral and spatial resolution from these gyrotrons should provide NMR spectrometers with high signal enhancement through DNP. Also, these tubes operating at submillimeter wavelengths should have important applications in research in physics, chemistry, biology, materials science and medicine. PMID:17404605

The Circumstellar Environment of Low Mass Star Forming Regions

NASA Technical Reports Server (NTRS)

Butner, Harold M.

1999-01-01

The final technical report of the NASA grant project is presented. The goals of the grant were to: (1) analyze the data from the Far-Infrared (FIR) Camera on board the Kuiper Airborne Observatory (KAO); (2) acquire additional data at other wavelengths for models and (4) to develop source models for the Young stellar objects (YSOs)under study. The complete Spectral Energy Distribution (SED) from 10 microns out to 1.3 mm for all sources being studied have been obtained. The FIR imaging data was processed to reveal the maximum angular resolution possible, which allows us to model the disk. To model the disk we have the high resolution millimeter interferometry data. In summary the results to date are: (1) the vast majority of embedded YSOs in Taurus are compact at 100 microns. The models mos consistent with our data and other observations are either dominated by disk emissions, or envelopes that have relatively steep density gradients; (2) the submillimeter/millimeter photometer suggests that models are very successful. Disk emission plays an important role and must be considered when predicting the overall emission. (3) in the two cases, where we seem to have extended emission, we have to investigate other possible source models than a Shu collapse.

Arcsecond Resolution Mapping of Sulfur Dioxide Emission in the Circumstellar Envelope of VY Canis Majoris

NASA Astrophysics Data System (ADS)

Fu, Roger R.; Moullet, Arielle; Patel, Nimesh A.; Biersteker, John; Derose, Kimberly L.; Young, Kenneth H.

2012-02-01

We report Submillimeter Array observations of SO2 emission in the circumstellar envelope (CSE) of the red supergiant VY Canis Majoris, with an angular resolution of ≈1''. SO2 emission appears in three distinct outflow regions surrounding the central continuum peak emission that is spatially unresolved. No bipolar structure is noted in the sources. A fourth source of SO2 is identified as a spherical wind centered at the systemic velocity. We estimate the SO2 column density and rotational temperature assuming local thermal equilibrium (LTE) as well as perform non-LTE radiative transfer analysis using RADEX. Column densities of SO2 are found to be ~1016 cm-2 in the outflows and in the spherical wind. Comparison with existing maps of the two parent species OH and SO shows the SO2 distribution to be consistent with that of OH. The abundance ratio f_{SO_{2}}/f_{SO} is greater than unity for all radii larger than 3 × 1016 cm. SO2 is distributed in fragmented clumps compared to SO, PN, and SiS molecules. These observations lend support to specific models of circumstellar chemistry that predict f_{SO_{2}}/f_{SO}>1 and may suggest the role of localized effects such as shocks in the production of SO2 in the CSE.

Distribution and Kinematics of the HCN (3-2) Emission Down to the Innermost Region in the Envelope of the O-rich Star W Hydrae

NASA Astrophysics Data System (ADS)

Muller, Sébastien; Dinh-V-Trung; He, Jin-Hua; Lim, Jeremy

2008-09-01

We report high angular resolution observations of the HCN (3-2) line emission in the circumstellar envelope of the O-rich star W Hya with the Submillimeter Array. The proximity of this star allows us to image its molecular envelope with a spatial resolution of just ~40 AU, corresponding to about 10 times the stellar diameter. We resolve the HCN (3-2) emission and find that it is centrally peaked and has a roughly spherically symmetrical distribution. This shows that HCN is formed in the innermost region of the envelope (within ~10 stellar radii), which is consistent with predictions from pulsation-driven shock chemistry models, and rules out the scenario in which HCN forms through photochemical reactions in the outer envelope. Our model suggests that the envelope decreases steeply in temperature and increases smoothly in velocity with radius, inconsistent with the standard model for mass-loss driven by radiative pressure on dust grains. We detect a velocity gradient of ~5 km s-1 in the northwest-southeast direction over the central 40 AU. This velocity gradient is reminiscent of that seen in OH maser lines, and could be caused by the rotation of the envelope or by a weak bipolar outflow.

Instrumentation for Kinetic-Inductance-Detector-Based Submillimeter Radio Astronomy

NASA Astrophysics Data System (ADS)

Duan, Ran

A substantial amount of important scientific information is contained within astronomical data at the submillimeter and far-infrared (FIR) wavelengths, including information regarding dusty galaxies, galaxy clusters, and star-forming regions; however, these wavelengths are among the least-explored fields in astronomy because of the technological difficulties involved in such research. Over the past 20 years, considerable efforts have been devoted to developing submillimeter- and millimeter-wavelength astronomical instruments and telescopes. The number of detectors is an important property of such instruments and is the subject of the current study. Future telescopes will require as many as hundreds of thousands of detectors to meet the necessary requirements in terms of the field of view, scan speed, and resolution. A large pixel count is one benefit of the development of multiplexable detectors that use kinetic inductance detector (KID) technology. This dissertation presents the development of a KID-based instrument including a portion of the millimeter-wave bandpass filters and all aspects of the readout electronics, which together enabled one of the largest detector counts achieved to date in submillimeter-/millimeter-wavelength imaging arrays: a total of 2304 detectors. The work presented in this dissertation has been implemented in the MUltiwavelength Submillimeter Inductance Camera (MUSIC), a new instrument for the Caltech Submillimeter Observatory (CSO).

Throughput of diffraction-limited field optics systems for infrared and millimetric telescopes

NASA Technical Reports Server (NTRS)

Hildebrand, R. H.; Winston, R.

1982-01-01

Telescopes for submillimeter wavelengths have point spread functions some millimeters or centimeters in diameter, but the detectors may be only fractions of a millimeter in size. Thus a field aperture and collecting optics are needed. Optimizing the aperture by a calculation of the effects of diffraction on signal and resolution as a function of size of the collecting aperture is shown. Calculations are compared to experimental results from observations of Mars at submillimeter wavelengths.

Precise Selenodetic Coordinate System on Artificial Light Refers

NASA Astrophysics Data System (ADS)

Bagrov, Alexander; Pichkhadze, Konstantin M.; Sysoev, Valentin

Historically a coordinate system for the Moon was established on the base of telescopic observations from the Earth. As the angular resolution of Earth-to-Space telescopic observations is limited by Earth atmosphere, and is ordinary worse then 1 ang. second, the mean accuracy of selenodetic coordinates is some angular minutes, which corresponds to errors about 900 meters for positions of lunar objects near center of visible lunar disk, and at least twice more when objects are near lunar poles. As there are no Global Positioning System nor any astronomical observation instruments on the Moon, we proposed to use an autonomous light beacon on the Luna-Globe landing module to fix its position on the surface of the moon ant to use it as refer point for fixation of spherical coordinates system for the Moon. The light beacon is designed to be surely visible by orbiting probe TV-camera. As any space probe has its own stars-orientation system, there is not a problem to calculate a set of directions to the beacon and to the referent stars in probe-centered coordinate system during flight over the beacon. Large number of measured angular positions and time of each observation will be enough to calculate both orbital parameters of the probe and selenodetic coordinates of the beacon by methods of geodesy. All this will allow fixing angular coordinates of any feature of lunar surface in one global coordinate system, referred to the beacon. The satellite’s orbit plane contains ever the center mass of main body, so if the beacon will be placed closely to a lunar pole, we shall determine pole point position of the Moon with accuracy tens times better then it is known now. When angular accuracy of self-orientation by stars of the orbital module of Luna-Glob mission will be 6 angular seconds, then being in circular orbit with height of 200 km the on-board TV-camera will allow calculation of the beacon position as well as 6" corresponding to spatial resolution of the camera. It mean that coordinates of the beacon will be determined with accuracy not worse then 6 meters on the lunar surface. Much more accuracy can be achieved if orbital probe will use as precise angular measurer as optical interferometer. The limiting accuracy of proposed method is far above any reasonable level, because it may be sub-millimeter one. Theoretical analysis shows that for achievement of 1-meter accuracy of coordinate measuring over lunar globe it will be enough to disperse over it surface some 60 light beacons. Designed by Lavochkin Association light beacon is autonomous one, and it will work at least 10 years, so coordinate frame of any other lunar mission could use established selenodetic coordinates during this period. The same approach may be used for establishing Martial coordinates system.

Science Questions for the Post-SIRTF and Herschel Era

NASA Technical Reports Server (NTRS)

Werner, Michael

2004-01-01

The contents include the following: 1. SIRTF. Long wavelength surveys planned for SIRTF. Galaxy Discovery Rates for Future Missions. Impact of SIRTF s Improved Resolution at 160um: Resolving the Background. 2. Polarimetry. Submillimeter Polarimetry - The State of Play. Magnetic Vectors Across the Orion Molecular Cloud Core. Neutral and Ionized Molecular Spectral Lines. Variation of Polarization With Wavelength. The Polarization Spectrum. Submillimeter Polarimetry - Looking Ahead. 3.Confusion. Confusion at 500, 600 micron. 4. Extragalactic Science. Do Massive Black Holes and Galaxy Bulges form Together? 5. Galactic Science. Can We See the First Generations of Stars and Metal Formation? The Birth of Planets and the Origins of Life. Spatial Resolution at 100 microns. Far-ir/Sub-mm Transitions of Linear Carbon Clusters. Predicted Spectra of Glycine.

The AzTEC/SMA Interferometric Imaging Survey of Submillimeter-selected High-redshift Galaxies

NASA Astrophysics Data System (ADS)

Younger, Joshua D.; Fazio, Giovanni G.; Huang, Jia-Sheng; Yun, Min S.; Wilson, Grant W.; Ashby, Matthew L. N.; Gurwell, Mark A.; Peck, Alison B.; Petitpas, Glen R.; Wilner, David J.; Hughes, David H.; Aretxaga, Itziar; Kim, Sungeun; Scott, Kimberly S.; Austermann, Jason; Perera, Thushara; Lowenthal, James D.

2009-10-01

We present results from a continuing interferometric survey of high-redshift submillimeter galaxies (SMGs) with the Submillimeter Array, including high-resolution (beam size ~2 arcsec) imaging of eight additional AzTEC 1.1 mm selected sources in the COSMOS field, for which we obtain six reliable (peak signal-to-noise ratio (S/N) >5 or peak S/N >4 with multiwavelength counterparts within the beam) and two moderate significance (peak S/N >4) detections. When combined with previous detections, this yields an unbiased sample of millimeter-selected SMGs with complete interferometric follow up. With this sample in hand, we (1) empirically confirm the radio-submillimeter association, (2) examine the submillimeter morphology—including the nature of SMGs with multiple radio counterparts and constraints on the physical scale of the far infrared—of the sample, and (3) find additional evidence for a population of extremely luminous, radio-dim SMGs that peaks at higher redshift than previous, radio-selected samples. In particular, the presence of such a population of high-redshift sources has important consequences for models of galaxy formation—which struggle to account for such objects even under liberal assumptions—and dust production models given the limited time since the big bang.

Millimeter and submillimeter wave spectroscopy of propanal

NASA Astrophysics Data System (ADS)

Zingsheim, Oliver; Müller, Holger S. P.; Lewen, Frank; Jørgensen, Jes K.; Schlemmer, Stephan

2017-12-01

The rotational spectra of the two stable conformers syn- and gauche-propanal (CH3CH2CHO) were studied in the millimeter and submillimeter wave regions from 75 to 500 GHz with the Cologne (Sub-)Millimeter wave Spectrometer. Furthermore, the first excited states associated with the aldehyde torsion and with the methyl torsion, respectively, of the syn-conformer were analyzed. The newly obtained spectroscopic parameters yield better predictions, thus fulfill sensitivity and resolution requirements in new astronomical observations in order to unambiguously assign pure rotational transitions of propanal. This is demonstrated on a radio astronomical spectrum from the Atacama Large Millimeter/submillimeter Array Protostellar Interferometric Line Survey (ALMA-PILS). In particular, an accurate description of observed splittings, caused by internal rotation of the methyl group in the syn-conformer and by tunneling rotation interaction from two stable degenerate gauche-conformers, is reported. The rotational spectrum of propanal is of additional interest because of its two large amplitude motions pertaining to the methyl and the aldehyde group, respectively.

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.

Geo-PET: A novel generic organ-pet for small animal organs and tissues

NASA Astrophysics Data System (ADS)

Sensoy, Levent

Reconstructed tomographic image resolution of small animal PET imaging systems is improving with advances in radiation detector development. However the trend towards higher resolution systems has come with an increase in price and system complexity. Recent developments in the area of solid-state photomultiplication devices like silicon photomultiplier arrays (SPMA) are creating opportunities for new high performance tools for PET scanner design. Imaging of excised small animal organs and tissues has been used as part of post-mortem studies in order to gain detailed, high-resolution anatomical information on sacrificed animals. However, this kind of ex-vivo specimen imaging has largely been limited to ultra-high resolution muCT. The inherent limitations to PET resolution have, to date, excluded PET imaging from these ex-vivo imaging studies. In this work, we leverage the diminishing physical size of current generation SPMA designs to create a very small, simple, and high-resolution prototype detector system targeting ex-vivo tomographic imaging of small animal organs and tissues. We investigate sensitivity, spatial resolution, and the reconstructed image quality of a prototype small animal PET scanner designed specifically for imaging of excised murine tissue and organs. We aim to demonstrate that a cost-effective silicon photomultiplier (SiPM) array based design with thin crystals (2 mm) to minimize depth of interaction errors might be able to achieve sub-millimeter resolution. We hypothesize that the substantial decrease in sensitivity associated with the thin crystals can be compensated for with increased solid angle detection, longer acquisitions, higher activity and wider acceptance energy windows (due to minimal scatter from excised organs). The constructed system has a functional field of view (FoV) of 40 mm diameter, which is adequate for most small animal specimen studies. We perform both analytical (3D-FBP) and iterative (ML-EM) methods in order to reconstruct tomographic images. Results demonstrate good agreement between the simulation and the prototype. Our detector system with pixelated crystals is able to separate small objects as close as 1.25 mm apart, whereas spatial resolution converges to the theoretical limit of 1.6 mm (half the size of the smallest detecting element), which is to comparable to the spatial resolution of the existing commercial small animal PET systems. Better system spatial resolution is achievable with new generation SiPM detector boards with 1 mm x 1 mm cell dimensions. We demonstrate through Monte Carlo simulations that it is possible to achieve sub-millimeter spatial image resolution (0.7 mm for our scanner) in complex objects using monolithic crystals and exploiting the light-sharing mechanism among the neighboring detector cells. Results also suggest that scanner (or object) rotation minimizes artifacts arising from poor angular sampling, which is even more significant in smaller PET designs as the gaps between the sensitive regions of the detector have a more exaggerated effect on the overall reconstructed image quality when the design is more compact. Sensitivity of the system, on the other hand, can be doubled by adding two additional detector heads resulting in a, fully closed, 4? geometry.

Tracing the Origins of Nitrogen Bearing Organics Toward Orion KL with Alma

NASA Astrophysics Data System (ADS)

Carroll, Brandon; Crockett, Nathan; Wilkins, Olivia H.; Bergin, Edwin; Blake, Geoffrey

2017-06-01

A comprehensive analysis of a broadband 1.2 THz wide spectral survey of the Orion Kleinmann-Low nebula (Orion KL) has shown that nitrogen bearing complex organics trace systematically hotter gas than O-bearing organics toward this source. The origin of this O/N dichotomy remains a mystery. If complex molecules originate from grain surfaces, N-bearing species may be more difficult to remove from grain surfaces than O-bearing organics. Theoretical studies, however, have shown that hot (T=300 K) gas phase chemistry can produce high abundances of N-bearing organics while suppressing the formation of O-bearing complex molecules. In order to distinguish these distinct formation pathways we have obtained extremely high angular resolution observations of methyl cyanide (CH_3CN) using the Atacama Large Millimeter/Submillimeter Array (ALMA) toward Orion KL. By simultaneously imaging ^{13}CH_3CN and CH_2DCN we map the temperature structure and D/H ratio of CH_3CN. We will present updated results of these observations and discuss their implications for the formation of N-bearing organics in the interstellar medium.

Tracing the Origins of Nitrogen Bearing Organics Toward Orion KL with Alma

NASA Astrophysics Data System (ADS)

Carroll, Brandon; Crockett, Nathan; Bergin, Edwin; Blake, Geoffrey

2016-06-01

A comprehensive analysis of a broadband 1.2 THz wide spectral survey of the Orion Kleinmann-Low nebula (Orion KL) from the Herschel Space Telescope has shown that nitrogen bearing complex organics trace systematically hotter gas than O-bearing organics toward this source. The origin of this O/N dichotomy remains a mystery. If complex molecules originate from grain surfaces, N-bearing species may be more difficult to remove from grain surfaces than O-bearing organics. Theoretical studies, however, have shown that hot (T=300 K) gas phase chemistry can produce high abundances of N-bearing organics while suppressing the formation of O-bearing complex molecules. In order to distinguish these distinct formation pathways we have obtained extremely high angular resolution observations of methyl cyanide (CH_3CN) using the Atacama Large Millimeter/Submillimeter Array (ALMA) toward Orion KL. By simultaneously imaging 13CH_3CN and CH_2DCN we map the temperature structure and D/H ratio of CH_3CN. We will present the initial results of these observations and discuss their implications for the formation of N-bearing organics in the interstellar medium.

The Planck Dusty Gravitationally Enhanced subMillimeter Sources (GEMS)

NASA Astrophysics Data System (ADS)

Frye, Brenda

2015-10-01

The brightest, strongly lensed high-redshift galaxies are veritable gems to study intense star formation in the early Universe. How do the high and irregular clumpy stellar and gas mass surface densities, strong radiation fields, and high turbulence regulate the rapid growth of these galaxies? We will use HST/WFC3 to investigate the stellar component of 6 of the brightest high-redshift sub-millimeter galaxies on the sky, which were recently discovered with the Planck all-sky survey. All are giant arcs or partial Einstein rings with angular sizes up to 17 in shallow CFHT K-band or Spitzer/IRAC imaging. FIR luminosities are 10^13-14 L_sun, with dust SEDs strongly dominated by intense star formation near the maximum possible rates (maximal starbursts). All have spectroscopic redshifts z=2.2-3.6 and magnification factors >/=20. We already have multiwavelength data sets to characterize their gas and dust column densities and kinematics, and propose here to acquire deep, high-resolution rest-frame optical imaging to study the stellar populations and morphologies. With WFC3 imaging in F110W & F160W we will: (1) constrain the stellar morphologies, ages, and mass-to-light ratios (2) Identify clumps and measure their properties to test several clump formation scenarios(3) Enhance our on-going lens modeling through the most accurate positions, morphologies and colorsOnly the brightest of the arc clumps are visible from the ground in the NIR. To register the flux along the full extent of the arcs, and importantly to probe individual star forming regions of the size of 30 Dor at z 2-3 in the brightest high-z sub-mm galaxies requires HST.

MAPPING THE RELEASE OF VOLATILES IN THE INNER COMAE OF COMETS C/2012 F6 (LEMMON) AND C/2012 S1 (ISON) USING THE ATACAMA LARGE MILLIMETER/SUBMILLIMETER ARRAY

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

Cordiner, M. A.; Milam, S. N.; Mumma, M. J.

2014-09-01

Results are presented from the first cometary observations using the Atacama Large Millimeter/Submillimeter Array (ALMA), including measurements of the spatially resolved distributions of HCN, HNC, H{sub 2}CO, and dust within the comae of two comets: C/2012 F6 (Lemmon) and C/2012 S1 (ISON), observed at heliocentric distances of 1.5 AU and 0.54 AU, respectively. These observations (with angular resolution ≈0.''5), reveal an unprecedented level of detail in the distributions of these fundamental cometary molecules, and demonstrate the power of ALMA for quantitative measurements of the distributions of molecules and dust in the inner comae of typical bright comets. In both comets, HCN ismore » found to originate from (or within a few hundred kilometers of) the nucleus, with a spatial distribution largely consistent with spherically symmetric, uniform outflow. By contrast, the HNC distributions are clumpy and asymmetrical, with peaks at cometocentric radii ∼500-1000 km, consistent with release of HNC in collimated outflow(s). Compared to HCN, the H{sub 2}CO distribution in comet Lemmon is very extended. The interferometric visibility amplitudes are consistent with coma production of H{sub 2}CO and HNC from unidentified precursor material(s) in both comets. Adopting a Haser model, the H{sub 2}CO parent scale length is found to be a few thousand kilometers in Lemmon and only a few hundred kilometers in ISON, consistent with the destruction of the precursor by photolysis or thermal degradation at a rate that scales in proportion to the solar radiation flux.« less

Sub-mm CO Measurements of the Orion Molecular Cloud

NASA Astrophysics Data System (ADS)

Wilson, T. L.; Muders, D.; Kramer, C.; Henkel, C.

2000-05-01

Images of a >3' region around the Orion KL source have been made in the J=4-3 (461 GHz) and J=7-6 (806 GHz) lines of CO with angular resolutions of 18'' and 13'', using the 10-meter Heinrich Hertz Telescope (HHT) of the Sub-Millimeter Telescope Observatory (SMTO). This region contains a variety of objects: (1) the Hot Core (a region containing complex molecules) and Orion KL outflow (NE of the center of the 10'' diameter Hot Core, and very likely associated with the continuum source `I' (Menten & Reid 1995 ApJ 445, L157)), (2) another outflow source, Orion-S ( ~100'' south of the Hot Core (Rodriguez-Franco et al. 1999 A&A 344, L57)), (3) the ionized-neutral interface at the rear of the Orion HII region, and (4) the Orion Bar feature (an ionized-neutral interface to the SW of the HII region). Regions (3) and (4) are examples of `Photon Dominated Regions' or `PDR's'. The sub-mm CO lines are emitted from warm gas; the J=7-6 line is emitted from an energy level 156 Kelvin above the ground state. The excellent pointing and low sidelobes of the HHT allow accurate comparisons with high r! esolution CO images in lower J lines and images of other species. Our J=7-6 CO image was made with the Harvard-Smithsonian Center for Astrophysics Hot Electron Bolometer (Kawamura et al. 1999 IEEE Trans. on Appl. Superconductivity 9, 3753. The HHT is operated by the Submillimeter Telescope Observatory on behalf of the Max-Planck-Institut f. Radioastronomie and Steward Observatory of The University of Arizona. We thank the CfA receiver group for providing the Hot Electron Bolometer used to take the J=7-6 CO line data.

Investigating the Early Evolution of Planetary Systems with ALMA and the Next Generation Very Large Array

NASA Astrophysics Data System (ADS)

Ricci, Luca; Liu, Shang-Fei; Isella, Andrea; Li, Hui

2018-02-01

We investigate the potential of the Atacama Large Millimeter/submillimeter Array (ALMA) and the Next Generation Very Large Array (ngVLA) to observe substructures in nearby young disks which are due to the gravitational interaction between disk material and planets close to the central star. We simulate the gas and dust dynamics in the disk using the LA-COMPASS hydrodynamical code. We generate synthetic images for the dust continuum emission at submillimeter to centimeter wavelengths and simulate ALMA and ngVLA observations. We explore the parameter space of some of the main disk and planet properties that would produce substructures that can be visible with ALMA and the ngVLA. We find that ngVLA observations with an angular resolution of 5 milliarcsec at 3 mm can reveal and characterize gaps and azimuthal asymmetries in disks hosting planets with masses down to ≈ 5 {M}\\oplus ≈ 1{--}5 {au} from a solar-like star in the closest star-forming regions, whereas ALMA can detect gaps down to planetary masses of ≈ 20 {M}\\oplus at 5 au. Gaps opened by super-Earth planets with masses ≈ 5{--}10 {M}\\oplus are detectable by the ngVLA in the case of disks with low viscosity (α ∼ {10}-5) and low pressure scale height (h ≈ 0.025 au at 5 au). The ngVLA can measure the proper motion of azimuthal asymmetric structures associated with the disk–planet interaction as well as possible circumplanetary disks on timescales as short as one to a few weeks for planets at 1–5 au from the star.

Radio Interferometry with the SMA: Uncovering Hidden Star Formation in Our Extreme Galactic Center

NASA Astrophysics Data System (ADS)

Gutierrez, Elizabeth; Battersby, Cara; MacGregor, Meredith Ann

2018-01-01

Radio interferometry provides the best tool to identify embedded star-forming cores in cold, dense, molecular clouds of gas and dust. Observations at long, submillimeter wavelengths can be used to investigate the physical properties in the youngest stages of star formation. Interferometers provide the resolution necessary to resolve small scale structures like dense cores where star formation is expected to occur. CMZoom is the first large area survey of the Central Molecular Zone (CMZ) at high resolution in the submillimeter, allowing us to identify early sites of star formation. The survey uses both the subcompact and compact configurations of the Submillimeter Array (SMA) interferometric radio telescope. The CMZ, or the inner 500 pc of the Milky Way Galaxy, is a high extinction region comprised of hot, dense, and turbulent molecular gas. This region is forming about an order of magnitude fewer stars than predicted based on simple star formation prescriptions. Here, we present new high resolution images of G0.068-0.075, a region from the CMZoom survey, obtained using CASA. We highlight the importance of interferometric observations of different baseline lengths by comparing the spatial information obtained through different configurations. We will use these new images, in conjunction with the rest of the CMZoom survey, to reveal the mechanisms driving star formation at the center of the galaxy.

Multiframe super resolution reconstruction method based on light field angular images

NASA Astrophysics Data System (ADS)

Zhou, Shubo; Yuan, Yan; Su, Lijuan; Ding, Xiaomin; Wang, Jichao

2017-12-01

The plenoptic camera can directly obtain 4-dimensional light field information from a 2-dimensional sensor. However, based on the sampling theorem, the spatial resolution is greatly limited by the microlenses. In this paper, we present a method of reconstructing high-resolution images from the angular images. First, the ray tracing method is used to model the telecentric-based light field imaging process. Then, we analyze the subpixel shifts between the angular images extracted from the defocused light field data and the blur in the angular images. According to the analysis above, we construct the observation model from the ideal high-resolution image to the angular images. Applying the regularized super resolution method, we can obtain the super resolution result with a magnification ratio of 8. The results demonstrate the effectiveness of the proposed observation model.

Gaps, rings, and non-axisymmetric structures in protoplanetary disks. From simulations to ALMA observations

NASA Astrophysics Data System (ADS)

Flock, M.; Ruge, J. P.; Dzyurkevich, N.; Henning, Th.; Klahr, H.; Wolf, S.

2015-02-01

Aims: Recent observations by the Atacama Large Millimeter/submillimeter Array (ALMA) of disks around young stars revealed distinct asymmetries in the dust continuum emission. In this work we wish to study axisymmetric and non-axisymmetric structures that are generated by the magneto-rotational instability in the outer regions of protoplanetary disks. We combine the results of state-of-the-art numerical simulations with post-processing radiative transfer (RT) to generate synthetic maps and predictions for ALMA. Methods: We performed non-ideal global 3D magneto-hydrodynamic (MHD) stratified simulations of the dead-zone outer edge using the FARGO MHD code PLUTO. The stellar and disk parameters were taken from a parameterized disk model applied for fitting high-angular resolution multi-wavelength observations of various circumstellar disks. We considered a stellar mass of M∗ = 0.5 M⊙ and a total disk mass of about 0.085 M∗. The 2D initial temperature and density profiles were calculated consistently from a given surface density profile and Monte Carlo radiative transfer. The 2D Ohmic resistivity profile was calculated using a dust chemistry model. We considered two values for the dust-to-gas mass ratio, 10-2 and 10-4, which resulted in two different levels of magnetic coupling. The initial magnetic field was a vertical net flux field. The radiative transfer simulations were performed with the Monte Carlo-based 3D continuum RT code MC3D. The resulting dust reemission provided the basis for the simulation of observations with ALMA. Results: All models quickly turned into a turbulent state. The fiducial model with a dust-to-gas mass ratio of 10-2 developed a large gap followed by a jump in surface density located at the dead-zone outer edge. The jump in density and pressure was strong enough to stop the radial drift of particles at this location. In addition, we observed the generation of vortices by the Rossby wave instability at the jump location close to 60 AU. The vortices were steadily generated and destroyed at a cycle of 40 local orbits. The RT results and simulated ALMA observations predict that it is feasible to observe these large-scale structures that appear in magnetized disks without planets. Neither the turbulent fluctuations in the disk nor specific times of the model can be distinguished on the basis of high-angular resolution submillimeter observations alone. The same applies to the distinction between gaps at the dead-zone edges and planetary gaps, to the distinction between turbulent and simple unperturbed disks, and to the asymmetry created by the vortex.

First Astronomical Use of Multiplexed Transition Edge Sensor Bolometers

NASA Technical Reports Server (NTRS)

Staguhn, J. G.; Ames, T. A.; Benford, D. J.; Chervenak, J. A.; Grossman, E. N.; Irwin, K. D.; Khan, S. A.; Maffei, B.; Moseley, S. H.; Pajot, F.

2004-01-01

We present performance results based on the first astronomical use of multiplexed superconducting bolometers. The Fabry-Perot Interferometer Bolometer Research Experiment (FIBRE) is a broadband submillimeter spectrometer that achieved first light in June 2001 at the Caltech Submillimeter Observatory (CSO). FIBRE's detectors are superconducting transition edge sensor (TES) bolometers read out by a SQUID multiplexer. The Fabry-Perot uses a low resolution grating to order sort the incoming light. A linear bolometer array consisting of 16 elements detects this dispersed light, capturing 5 orders simultaneously from one position on the sky. With tuning of the Fabry-Perot over one free spectral range, a spectrum covering Delta lambda/lambda = 1/7 at a resolution of delta lambda/lambda approx. 1/1200 can be acquired. This spectral resolution is sufficient to resolve Doppler-broadened line emission from external galaxies. FIBRE operates in the 350 m and 450 m bands. These bands cover line emission from the important star formation tracers neutral carbon (CI) and carbon monoxide (CO). We have verified that the multiplexed bolometers are photon noise limited even with the low power present in moderate resolution spectrometry.

First Astronomical Use Of Multiplexed Transition Edge Bolometers

NASA Technical Reports Server (NTRS)

Benford, D. J.; Chervenak, J. A.; Grossman, E. N.; Irwin, K. D.; DeKotwara, S. A.; Maffei, B.; Moseley, S. H.; Pajot, F.; Phillips, T. G.; Reintsema, C. D.

2001-01-01

We present performance results based on the first astronomical use of multiplexed superconducting bolometers. The Fabry-Perot Interferometer Bolometer Research Experiment (FIBRE) is a broadband submillimeter spectrometer that achieved first light in June 2001 at the Caltech Submillimeter Observatory (CSO). FIBRE's detectors are superconducting transition edge sensor (TES) bolometers read out by a SQUID multiplexer. The Fabry-Perot uses a low resolution grating to order sort the incoming light. A linear bolometer array consisting of 16 elements detects this dispersed light, capturing five orders simultaneously from one position on the sky. With tuning of the Fabry-Perot over one free spectral range, a spectrum covering delta-lamda/lamda = 1/7 at a resolution of delta-lamda/lamda = 1/1200 can be acquired. This spectral resolution is sufficient to resolve doppler broadened line emission from external galaxies. FIBRE operates in the 350 micrometer and 450 micrometer bands. These bands cover line emission from the important PDR tracers neutral carbon [CI] and carbon monoxide (CO). We have verified that the multiplexed bolometers are photon noise limited even with the low power present in moderate resolution spectrometry.

ALMA deep field in SSA22: Blindly detected CO emitters and [C II] emitter candidates

NASA Astrophysics Data System (ADS)

Hayatsu, Natsuki H.; Matsuda, Yuichi; Umehata, Hideki; Yoshida, Naoki; Smail, Ian; Swinbank, A. Mark; Ivison, Rob; Kohno, Kotaro; Tamura, Yoichi; Kubo, Mariko; Iono, Daisuke; Hatsukade, Bunyo; Nakanishi, Kouichiro; Kawabe, Ryohei; Nagao, Tohru; Inoue, Akio K.; Takeuchi, Tsutomu T.; Lee, Minju; Ao, Yiping; Fujimoto, Seiji; Izumi, Takuma; Yamaguchi, Yuki; Ikarashi, Soh; Yamada, Toru

2017-06-01

We report the identification of four millimeter line-emitting galaxies with the Atacama Large Milli/submillimeter Array (ALMA) in SSA22 Field (ADF22). We analyze the ALMA 1.1-mm survey data, with an effective survey area of 5 arcmin2, frequency ranges of 253.1-256.8 and 269.1-272.8 GHz, angular resolution of 0{^''.}7 and rms noise of 0.8 mJy beam-1 at 36 km s-1 velocity resolution. We detect four line-emitter candidates with significance levels above 6σ. We identify one of the four sources as a CO(9-8) emitter at z = 3.1 in a member of the proto-cluster known in this field. Another line emitter with an optical counterpart is likely a CO(4-3) emitter at z = 0.7. The other two sources without any millimeter continuum or optical/near-infrared counterpart are likely to be [C II] emitter candidates at z = 6.0 and 6.5. The equivalent widths of the [C II] candidates are consistent with those of confirmed high-redshift [C II] emitters and candidates, and are a factor of 10 times larger than that of the CO(9-8) emitter detected in this search. The [C II] luminosity of the candidates are 4-7 × 108 L⊙. The star formation rates (SFRs) of these sources are estimated to be 10-20 M⊙ yr-1 if we adopt an empirical [C II] luminosity-SFR relation. One of them has a relatively low S/N ratio, but shows features characteristic of emission lines. Assuming that at least one of the two candidates is a [C II] emitter, we derive a lower limit of [C II]-based star formation rate density (SFRD) at z ˜ 6. The resulting value of >10-2 M⊙ yr-1 Mpc-3 is consistent with the dust-uncorrected UV-based SFRD. Future millimeter/submillimeter surveys can be used to detect a number of high-redshift line emitters, with which to study the star formation history in the early universe.

THE AzTEC/SMA INTERFEROMETRIC IMAGING SURVEY OF SUBMILLIMETER-SELECTED HIGH-REDSHIFT GALAXIES

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

Younger, Joshua D.; Fazio, Giovanni G.; Huang Jiasheng

We present results from a continuing interferometric survey of high-redshift submillimeter galaxies (SMGs) with the Submillimeter Array, including high-resolution (beam size approx2 arcsec) imaging of eight additional AzTEC 1.1 mm selected sources in the COSMOS field, for which we obtain six reliable (peak signal-to-noise ratio (S/N) >5 or peak S/N >4 with multiwavelength counterparts within the beam) and two moderate significance (peak S/N >4) detections. When combined with previous detections, this yields an unbiased sample of millimeter-selected SMGs with complete interferometric follow up. With this sample in hand, we (1) empirically confirm the radio-submillimeter association, (2) examine the submillimeter morphology-includingmore » the nature of SMGs with multiple radio counterparts and constraints on the physical scale of the far infrared-of the sample, and (3) find additional evidence for a population of extremely luminous, radio-dim SMGs that peaks at higher redshift than previous, radio-selected samples. In particular, the presence of such a population of high-redshift sources has important consequences for models of galaxy formation-which struggle to account for such objects even under liberal assumptions-and dust production models given the limited time since the big bang.« less

Characterization of a sub-assembly of 3D position sensitive cadmium zinc telluride detectors and electronics from a sub-millimeter resolution PET system.

PubMed

Abbaszadeh, Shiva; Gu, Yi; Reynolds, Paul D; Levin, Craig S

2016-09-21

Cadmium zinc telluride (CZT) offers key advantages for small animal positron emission tomography (PET), including high spatial and energy resolution and simple metal deposition for fabrication of very small pixel arrays. Previous studies have investigated the intrinsic spatial, energy, and timing resolution of an individual sub-millimeter resolution CZT detector. In this work we present the first characterization results of a system of these detectors. The 3D position sensitive dual-CZT detector module and readout electronics developed in our lab was scaled up to complete a significant portion of the final PET system. This sub-system was configured as two opposing detection panels containing a total of twelve [Formula: see text] mm monolithic CZT crystals for proof of concept. System-level characterization studies, including optimizing the trigger threshold of each channel's comparators, were performed. 68 Ge and 137 Cs radioactive isotopes were used to characterize the energy resolution of all 468 anode channels in the sub-system. The mean measured global 511 keV photopeak energy resolution over all anodes was found to be [Formula: see text]% FWHM after correction for photon interaction depth-dependent signal variation. The measured global time resolution was 37 ns FWHM, a parameter to be further optimized, and the intrinsic spatial resolution was 0.76 mm FWHM.

Tethered Formation Configurations: Meeting the Scientific Objectives of Large Aperture and Interferometric Science

NASA Technical Reports Server (NTRS)

Farley, Rodger E.; Quinn, David A.; Brodeur, Stephen J. (Technical Monitor)

2001-01-01

With the success of the Hubble Space Telescope, it has become apparent that new frontiers of science and discovery are made every time an improvement in imaging resolution is made. For the HST working primarily in the visible and near-visible spectrum, this meant designing, building, and launching a primary mirror approximately three meters in diameter. Conventional thinking tells us that accomplishing a comparable improvement in resolution at longer wavelengths for Earth and Space Science applications requires a corresponding increase in the size of the primary mirror. For wavelengths in the sub-millimeter range, a very large telescope with an effective aperture in excess of one kilometer in diameter would be needed to obtain high quality angular resolution. Realistically a single aperture this large is practically impossible. Fortunately such large apertures can be constructed synthetically. Possibly as few as three 34 meter diameter mirrors flying in precision formation could be used to collect light at these longer wavelengths permitting not only very large virtual aperture science to be carried out, but high-resolution interferometry as well. To ensure the longest possible mission duration, a system of tethered spacecraft will be needed to mitigate the need for a great deal of propellant. A spin-stabilized, tethered formation will likely meet these requirements. Several configurations have been proposed which possibly meet the needs of the Space Science community. This paper discusses two of them, weighing the relative pros and cons of each concept. The ultimate goal being to settle on a configuration which combines the best features of structure, tethers, and formation flying to meet the ambitious requirements necessary to make future large synthetic aperture and interferometric science missions successful.

Tethered Formation Configurations: Meeting the Scientific Objectives of Large Aperture and Interferometric Science

NASA Technical Reports Server (NTRS)

Farley, Rodger E.; Quinn, David A.

2004-01-01

With the success of the Hubble Space Telescope, it has become apparent that new frontiers of science and discovery are made every time an improvement in imaging resolution is made. For the HST working primarily in the visible and near-visible spectrum, this meant designing, building and launching a primary mirror approximately three meters in diameter. Conventional thinking tells us that accomplishing a comparable improvement in resolution at longer wavelengths for Earth and Space Science applications requires a corresponding increase in the size of the primary mirror. For wavelengths in the sub-millimeter range, a very large telescope with an effective aperture in excess of one kilometer in diameter would be needed to obtain high quality angular resolution. Realistically a single aperture this large is practically impossible. Fortunately such large apertures can be constructed synthetically. Possibly as few as three 3 - 4 meter diameter mirrors flying in precision formation could be used to collect light at these longer wavelengths permitting not only very large virtual aperture science to be carried out, but high-resolution interferometry as well. To ensure the longest possible mission duration, a system of tethered spacecraft will be needed to mitigate the need for a great deal of propellant. A spin-stabilized, tethered formation will likely meet these requirements. Several configurations have been proposed which possibly meet the needs of the Space Science community. This paper discusses two of them, weighing the relative pros and cons of each concept. The ultimate goal being to settle on a configuration which combines the best features of structure, tethers and formation flying to meet the ambitious requirements necessary to make future large synthetic aperture and interferometric science missions successful.

THE DISK-OUTFLOW SYSTEM IN THE S255IR AREA OF HIGH-MASS STAR FORMATION

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

Zinchenko, I.; Zemlyanukha, P.; Liu, S.-Y.

We report the results of our observations of the S255IR area with the Submillimeter Array (SMA) at 1.3 mm in the very extended configuration and at 0.8 mm in the compact configuration as well as with the IRAM 30 m at 0.8 mm. The best achieved angular resolution is about 0.4 arcsec. The dust continuum emission and several tens of molecular spectral lines are observed. The majority of the lines is detected only toward the S255IR-SMA1 clump, which represents a rotating structure (probably a disk) around the young massive star. The achieved angular resolution is still insufficient to make anymore » conclusions about the Keplerian or non-Keplerian character of the rotation. The temperature of the molecular gas reaches 130–180 K. The size of the clump is about 500 AU. The clump is strongly fragmented as follows from the low beam-filling factor. The mass of the hot gas is significantly lower than the mass of the central star. A strong DCN emission near the center of the hot core most probably indicates a presence of a relatively cold (≲80 K) and rather massive clump there. High-velocity emission is observed in the CO line as well as in lines of high-density tracers HCN, HCO{sup +}, CS and other molecules. The outflow morphology obtained from a combination of the SMA and IRAM 30 m data is significantly different from that derived from the SMA data alone. The CO emission detected with the SMA traces only one boundary of the outflow. The outflow is most probably driven by jet bow shocks created by episodic ejections from the center. We detected a dense high velocity clump associated apparently with one of the bow shocks. The outflow strongly affects the chemical composition of the surrounding medium.« less

THE BOLOCAM GALACTIC PLANE SURVEY. VIII. A MID-INFRARED KINEMATIC DISTANCE DISCRIMINATION METHOD

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

Ellsworth-Bowers, Timothy P.; Glenn, Jason; Battersby, Cara

2013-06-10

We present a new distance estimation method for dust-continuum-identified molecular cloud clumps. Recent (sub-)millimeter Galactic plane surveys have cataloged tens of thousands of these objects, plausible precursors to stellar clusters, but detailed study of their physical properties requires robust distance determinations. We derive Bayesian distance probability density functions (DPDFs) for 770 objects from the Bolocam Galactic Plane Survey in the Galactic longitude range 7. Degree-Sign 5 {<=} l {<=} 65 Degree-Sign . The DPDF formalism is based on kinematic distances, and uses any number of external data sets to place prior distance probabilities to resolve the kinematic distance ambiguity (KDA)more » for objects in the inner Galaxy. We present here priors related to the mid-infrared absorption of dust in dense molecular regions and the distribution of molecular gas in the Galactic disk. By assuming a numerical model of Galactic mid-infrared emission and simple radiative transfer, we match the morphology of (sub-)millimeter thermal dust emission with mid-infrared absorption to compute a prior DPDF for distance discrimination. Selecting objects first from (sub-)millimeter source catalogs avoids a bias towards the darkest infrared dark clouds (IRDCs) and extends the range of heliocentric distance probed by mid-infrared extinction and includes lower-contrast sources. We derive well-constrained KDA resolutions for 618 molecular cloud clumps, with approximately 15% placed at or beyond the tangent distance. Objects with mid-infrared contrast sufficient to be cataloged as IRDCs are generally placed at the near kinematic distance. Distance comparisons with Galactic Ring Survey KDA resolutions yield a 92% agreement. A face-on view of the Milky Way using resolved distances reveals sections of the Sagittarius and Scutum-Centaurus Arms. This KDA-resolution method for large catalogs of sources through the combination of (sub-)millimeter and mid-infrared observations of molecular cloud clumps is generally applicable to other dust-continuum Galactic plane surveys.« less

High angular resolution at LBT

NASA Astrophysics Data System (ADS)

Conrad, A.; Arcidiacono, C.; Bertero, M.; Boccacci, P.; Davies, A. G.; Defrere, D.; de Kleer, K.; De Pater, I.; Hinz, P.; Hofmann, K. H.; La Camera, A.; Leisenring, J.; Kürster, M.; Rathbun, J. A.; Schertl, D.; Skemer, A.; Skrutskie, M.; Spencer, J. R.; Veillet, C.; Weigelt, G.; Woodward, C. E.

2015-12-01

High angular resolution from ground-based observatories stands as a key technology for advancing planetary science. In the window between the angular resolution achievable with 8-10 meter class telescopes, and the 23-to-40 meter giants of the future, LBT provides a glimpse of what the next generation of instruments providing higher angular resolution will provide. We present first ever resolved images of an Io eruption site taken from the ground, images of Io's Loki Patera taken with Fizeau imaging at the 22.8 meter LBT [Conrad, et al., AJ, 2015]. We will also present preliminary analysis of two data sets acquired during the 2015 opposition: L-band fringes at Kurdalagon and an occultation of Loki and Pele by Europa (see figure). The light curves from this occultation will yield an order of magnitude improvement in spatial resolution along the path of ingress and egress. We will conclude by providing an overview of the overall benefit of recent and future advances in angular resolution for planetary science.

Bayesian Deconvolution for Angular Super-Resolution in Forward-Looking Scanning Radar

PubMed Central

Zha, Yuebo; Huang, Yulin; Sun, Zhichao; Wang, Yue; Yang, Jianyu

2015-01-01

Scanning radar is of notable importance for ground surveillance, terrain mapping and disaster rescue. However, the angular resolution of a scanning radar image is poor compared to the achievable range resolution. This paper presents a deconvolution algorithm for angular super-resolution in scanning radar based on Bayesian theory, which states that the angular super-resolution can be realized by solving the corresponding deconvolution problem with the maximum a posteriori (MAP) criterion. The algorithm considers that the noise is composed of two mutually independent parts, i.e., a Gaussian signal-independent component and a Poisson signal-dependent component. In addition, the Laplace distribution is used to represent the prior information about the targets under the assumption that the radar image of interest can be represented by the dominant scatters in the scene. Experimental results demonstrate that the proposed deconvolution algorithm has higher precision for angular super-resolution compared with the conventional algorithms, such as the Tikhonov regularization algorithm, the Wiener filter and the Richardson–Lucy algorithm. PMID:25806871

Millimeter and Submillimeter Wave Spectroscopy of Higher Energy Conformers of 1,2-PROPANEDIOL

NASA Astrophysics Data System (ADS)

Zakharenko, Olena; Bossa, Jean-Baptiste; Lewen, Frank; Schlemmer, Stephan; Müller, Holger S. P.

2017-06-01

We have performed a study of the millimeter/submillimeter wave spectrum of four higher energy conformers of 1,2-propanediol (continuation of the previous study on the three lowest energy conformers. The present analysis of rotational transitions carried out in the frequency range 38 - 400 GHz represents a significant extension of previous microwave work. The new data were combined with previously-measured microwave transitions and fitted using a Watson's S-reduced Hamiltonian. The final fits were within experimental accuracy, and included spectroscopic parameters up to sixth order of angular momentum, for the ground states of the four higher energy conformers following previously studied ones: g'Ga, gG'g', aGg' and g'Gg. The present analysis provides reliable frequency predictions for astrophysical detection of 1,2-propanediol by radio telescope arrays at millimeter wavelengths. J.-B. Bossa, M.H. Ordu, H.S.P. Müller, F. Lewen, S. Schlemmer, A&A 570 (2014) A12)

RadioAstron Maser Observations: a Record in Angular Resolution

NASA Astrophysics Data System (ADS)

Sobolev, A. M.; Shakhvorostova, N. N.; Alakoz, A. V.; Baan, W. A.; RadioAstron Maser Team

2017-06-01

Extremely long baselines of the space-ground interferometer RadioAstron allow to achieve ultra-high angular resolutions. The possibility of detection of a maser emission with resolutions about tens of micro-arcseconds was arguable before successful experiments reported in this paper. We present the results of the maser survey obtained by RadioAstron during first 5 years of operation. Extremely high angular resolution of 11 microarcseconds have been achieved in observations of the megamaser galaxy NGC 4258. For the galaxy at the distance about 7 Mpc this corresponds to linear resolution around 80 AU. Very compact features with angular sizes about 20 micro-arcseconds have been detected in star-forming regions of our Galaxy. Corresponding linear sizes are about 5-10 millions of kilometers.

Goal-based angular adaptivity applied to a wavelet-based discretisation of the neutral particle transport equation

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

Goffin, Mark A., E-mail: mark.a.goffin@gmail.com; Buchan, Andrew G.; Dargaville, Steven

2015-01-15

A method for applying goal-based adaptive methods to the angular resolution of the neutral particle transport equation is presented. The methods are applied to an octahedral wavelet discretisation of the spherical angular domain which allows for anisotropic resolution. The angular resolution is adapted across both the spatial and energy dimensions. The spatial domain is discretised using an inner-element sub-grid scale finite element method. The goal-based adaptive methods optimise the angular discretisation to minimise the error in a specific functional of the solution. The goal-based error estimators require the solution of an adjoint system to determine the importance to the specifiedmore » functional. The error estimators and the novel methods to calculate them are described. Several examples are presented to demonstrate the effectiveness of the methods. It is shown that the methods can significantly reduce the number of unknowns and computational time required to obtain a given error. The novelty of the work is the use of goal-based adaptive methods to obtain anisotropic resolution in the angular domain for solving the transport equation. -- Highlights: •Wavelet angular discretisation used to solve transport equation. •Adaptive method developed for the wavelet discretisation. •Anisotropic angular resolution demonstrated through the adaptive method. •Adaptive method provides improvements in computational efficiency.« less

Spatial and Angular Resolution Enhancement of Light Fields Using Convolutional Neural Networks

NASA Astrophysics Data System (ADS)

Gul, M. Shahzeb Khan; Gunturk, Bahadir K.

2018-05-01

Light field imaging extends the traditional photography by capturing both spatial and angular distribution of light, which enables new capabilities, including post-capture refocusing, post-capture aperture control, and depth estimation from a single shot. Micro-lens array (MLA) based light field cameras offer a cost-effective approach to capture light field. A major drawback of MLA based light field cameras is low spatial resolution, which is due to the fact that a single image sensor is shared to capture both spatial and angular information. In this paper, we present a learning based light field enhancement approach. Both spatial and angular resolution of captured light field is enhanced using convolutional neural networks. The proposed method is tested with real light field data captured with a Lytro light field camera, clearly demonstrating spatial and angular resolution improvement.

Spatial and Angular Resolution Enhancement of Light Fields Using Convolutional Neural Networks.

PubMed

Gul, M Shahzeb Khan; Gunturk, Bahadir K

2018-05-01

Light field imaging extends the traditional photography by capturing both spatial and angular distribution of light, which enables new capabilities, including post-capture refocusing, post-capture aperture control, and depth estimation from a single shot. Micro-lens array (MLA) based light field cameras offer a cost-effective approach to capture light field. A major drawback of MLA based light field cameras is low spatial resolution, which is due to the fact that a single image sensor is shared to capture both spatial and angular information. In this paper, we present a learning based light field enhancement approach. Both spatial and angular resolution of captured light field is enhanced using convolutional neural networks. The proposed method is tested with real light field data captured with a Lytro light field camera, clearly demonstrating spatial and angular resolution improvement.

Design of Multishell Sampling Schemes with Uniform Coverage in Diffusion MRI

PubMed Central

Caruyer, Emmanuel; Lenglet, Christophe; Sapiro, Guillermo; Deriche, Rachid

2017-01-01

Purpose In diffusion MRI, a technique known as diffusion spectrum imaging reconstructs the propagator with a discrete Fourier transform, from a Cartesian sampling of the diffusion signal. Alternatively, it is possible to directly reconstruct the orientation distribution function in q-ball imaging, providing so-called high angular resolution diffusion imaging. In between these two techniques, acquisitions on several spheres in q-space offer an interesting trade-off between the angular resolution and the radial information gathered in diffusion MRI. A careful design is central in the success of multishell acquisition and reconstruction techniques. Methods The design of acquisition in multishell is still an open and active field of research, however. In this work, we provide a general method to design multishell acquisition with uniform angular coverage. This method is based on a generalization of electrostatic repulsion to multishell. Results We evaluate the impact of our method using simulations, on the angular resolution in one and two bundles of fiber configurations. Compared to more commonly used radial sampling, we show that our method improves the angular resolution, as well as fiber crossing discrimination. Discussion We propose a novel method to design sampling schemes with optimal angular coverage and show the positive impact on angular resolution in diffusion MRI. PMID:23625329

High-resolution three-dimensional imaging radar

NASA Technical Reports Server (NTRS)

Cooper, Ken B. (Inventor); Chattopadhyay, Goutam (Inventor); Siegel, Peter H. (Inventor); Dengler, Robert J. (Inventor); Schlecht, Erich T. (Inventor); Mehdi, Imran (Inventor); Skalare, Anders J. (Inventor)

2010-01-01

A three-dimensional imaging radar operating at high frequency e.g., 670 GHz, is disclosed. The active target illumination inherent in radar solves the problem of low signal power and narrow-band detection by using submillimeter heterodyne mixer receivers. A submillimeter imaging radar may use low phase-noise synthesizers and a fast chirper to generate a frequency-modulated continuous-wave (FMCW) waveform. Three-dimensional images are generated through range information derived for each pixel scanned over a target. A peak finding algorithm may be used in processing for each pixel to differentiate material layers of the target. Improved focusing is achieved through a compensation signal sampled from a point source calibration target and applied to received signals from active targets prior to FFT-based range compression to extract and display high-resolution target images. Such an imaging radar has particular application in detecting concealed weapons or contraband.

A Study of Imaging Interferometer Simulators

NASA Technical Reports Server (NTRS)

Allen, Ronald J.

2002-01-01

Several new space science mission concepts under development at NASA-GSFC for astronomy are intended to carry out synthetic imaging using Michelson interferometers or direct (Fizeau) imaging with sparse apertures. Examples of these mission concepts include the Stellar Imager (SI), the Space Infrared Interferometric Telescope (SPIRIT), the Submillimeter Probe of the Evolution of Cosmic Structure (SPECS), and the Fourier-Kelvin Stellar Interferometer (FKSI). We have been developing computer-based simulators for these missions. These simulators are aimed at providing a quantitative evaluation of the imaging capabilities of the mission by modelling the performance on different realistic targets in terms of sensitivity, angular resolution, and dynamic range. Both Fizeau and Michelson modes of operation can be considered. Our work is based on adapting a computer simulator called imSIM, which was initially written for the Space Interferometer Mission in order to simulate the imaging mode of new missions such as those listed. In a recent GSFC-funded study we have successfully written a preliminary version of a simulator SISIM for the Stellar Imager and carried out some preliminary studies with it. In a separately funded study we have also been applying these methods to SPECS/SPIRIT.

Super-resolution and ultra-sensitivity of angular rotation measurement based on SU(1,1) interferometers using homodyne detection

NASA Astrophysics Data System (ADS)

Liu, Jun; Li, Shitao; Wei, Dong; Gao, Hong; Li, Fuli

2018-02-01

We theoretically explore the angular rotation measurement sensitivity of SU(1,1) interferometers with a coherent beam and a vacuum beam input by using orbital angular momentum (OAM). Compared with the OAM in an SU(2) interferometer, the SU(1,1) interferometer employing homodyne detection can further surpass the angular rotation shot noise limit \\tfrac{1}{2l\\sqrt{N}} and improve the resolution and sensitivity of angular rotation measurement. Two models are considered, one is that OAM is carried by a probe beam and the other one is a pump beam with the OAM. The sensitivity can be improved by higher OAM and nonlinear process with a large gain. The resolution can be enhanced in the case that the pump beam has OAM. Moreover, we present a brief discussion on the variation of resolution and sensitivity in the presence of photon loss.

TU-H-CAMPUS-TeP2-03: High Sensitivity and High Resolution Fiber Based Micro-Detector for Sub-Millimeter Preclinical Dosimetry

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

Izaguirre, E; Pokhrel, S; Knewtson, T

2016-06-15

Purpose: Current precision of small animal and cell micro-irradiators has continuously increased during the past years. Currently, preclinical irradiators can deliver sub-millimeter fields with micrometric precision but there are no water equivalent dosimeters to determine small field profiles and dose in the orthovoltage range of energies with micrometric resolution and precision. We have developed a fiber based micro-dosimeter with the resolution and dosimetric accuracy required for radiobiological research. Methods: We constructed two prototypes of micro-dosimeters based on different compositions of fiber scintillators to study the spatial resolution and dosimetric precision of small animal and cell micro-irradiators. The first has greenmore » output and the second has blue output. The blue output dosimeter has the highest sensitivity because it matches the spectral sensitivity of silicon photomultipliers. A blue detector with 500um cross section was built and tested respect to a CC01 ion chamber, film, and the 1500um green output detector. Orthovoltage fields from 1×1mm2 to 5×5mm2 were used for detector characteristics comparison. Results: The blue fiber dosimeter shows great agreement with films and matches dose measurements with the gold-standard ion chamber for 5×5mm2 fields. The detector has the appropriate sensitivity to measure fields from 1×1mm2 to larger sizes with a 1% dosimetric accuracy. The spatial resolution is in the sub-millimeter range and the spectral matching with the photomultiplier allows reducing the sensor cross section even further than the presented prototype. These results suggest that scintillating fibers combined with silicon photomultipliers is the appropriate technology to pursue micro-dosimetry for small animals and disperse cell samples. Conclusion: The constructed detectors establish a new landmark for the resolution and sensitivity of fiber based microdetectors. The validation of the detector in our small animal and cell irradiator shows that they are appropriate for preclinical and micro single cell irradiation quality assurance and dosimetry.« less

Abundance and Temperature Variations in Titan's Atmosphere as Revealed by ALMA

NASA Astrophysics Data System (ADS)

Thelen, A. E.; Nixon, C. A.; Chanover, N.; Molter, E.; Cordiner, M. A.; Serigano, J., IV; Irwin, P. G.; Charnley, S. B.; Teanby, N. A.

2016-12-01

Photochemistry in Titan's atmosphere produces a wealth of organic molecular species through the dissociation of it's main constituents: N2 and CH4. Chemical species including hydrocarbons (CXHY) and nitriles (CXHY[CN]Z) exhibit latitudinal variations in abundance as observed by Cassini, attributed to atmospheric circulation and Titan's seasonal cycle. Flux calibration images of Titan taken by the Atacama Large Millimeter/Submillimeter Array (ALMA) with beam sizes smaller than Titan's angular diameter ( 0.7'') allow for measurements of rotational transition lines in spatially resolved regions of Titan's disk. We present nitrile abundance profiles and temperature measurements derived from CO lines obtained by ALMA in 2014, as Titan transitioned into northern summer. Vertical profiles in Titan's lower/middle atmosphere were retrieved by modeling high resolution ALMA spectra using the Non-linear Optimal Estimator for MultivariatE Spectral analySIS (NEMESIS) radiative transfer code. We present a comparison of the abundance variations of chemical species to measurements made using Cassini data. Temperature profiles derived from CO lines are compared to Cassini Composite Infrared Spectrometer temperature fields. The techniques presented here will allow us to determine temporal changes in Titan's atmospheric chemical composition after the end of the Cassini mission by utilizing high resolution ALMA data. Comparisons of chemical species with strong abundance enhancements over the poles will inform our knowledge of chemical lifetimes in Titan's atmosphere, and allow us to observe the important changes in production and circulation of numerous organic molecules which are attributed to Titan's seasons.

The feasibility study on 3-dimensional fluorescent x-ray computed tomography using the pinhole effect for biomedical applications.

PubMed

Sunaguchi, Naoki; Yuasa, Tetsuya; Hyodo, Kazuyuki; Zeniya, Tsutomu

2013-01-01

We propose a 3-dimensional fluorescent x-ray computed tomography (CT) pinhole collimator, aimed at providing molecular imaging with quantifiable measures and sub-millimeter spatial resolution. In this study, we demonstrate the feasibility of this concept and investigate imaging properties such as spatial resolution, contrast resolution and quantifiable measures, by imaging physical phantoms using a preliminary imaging system developed with monochromatic synchrotron x rays constructed at the BLNE-7A experimental line at KEK, Japan.

SMILES/AOS: acousto-optical spectrometer for high resolution submillimeter-wave spectroscopy

NASA Astrophysics Data System (ADS)

Mazuray, L.; Barthès, J.-C.; Bayle, F.; Castel, D.; Claviere, P.; Delbru, F.; Doittau, P.-O.; Gladin, L.; Guilleux, P.; Halbout, S.; Lavielle, D.; Varin, J.-L.; de Zotti, S.; Rosolen, C.; Ozeki, H.

2017-11-01

An acousto-optical spectrometer (AOS) is employed in order to meet scientific mission objectives of submillimeter-wave limb-emission sounder (SMILES) to be aboard the Japanese Experiment Module (JEM) of International space station (ISS). AOS is developed by ASTRIUM for the Japanese space agency (NASDA). The capability of multi channel detection with AOS is suitable for observing multi-chemical species in a wide frequency region. Low noise of the AOS enables us to obtain the spectra with a very high sensitivity. Several technical concerns relating to important instrumental characteristics of AOS are discussed and expected performance of the design are overviewed.

Measurement of middle and upper atmospheric horizontal winds with a submillimeter/THz limb sounder: results from JEM/SMILES and simulation study for SMILES-2

NASA Astrophysics Data System (ADS)

Baron, Philippe; Manago, Naohiro; Ozeki, Hiroyuki; Yoshihisa, Irimajiri; Donal, Murtagh; Yoshinori, Uzawa; Satoshi, Ochiai; Masato, Shiotani; Makoto, Suzuki

2016-04-01

In a near future, ESA will launch the Atmospheric Dynamics Mission (ADM) equipped with a lidar for measuring tropospheric and lower stratospheric winds. NASA will continue a long-term series of upper atmospheric wind measurements (altitudes >80 km) with the new Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) on the Ionospheric Connection Explorer (ICON) satellite. No mission is planned to observe winds in the middle atmosphere (30-80 km), though they are recognized as essential parameters for understanding atmospheric dynamics and the vertical coupling between atmospheric regions. They are also promising data for improving long-term weather forecast and climate modelling. It has been demonstrated with the Superconducting Submillimeter Wave Limb Emission Sounder (SMILES, Oct 2009 - Apr 2010) that a 4-K cooled microwave radiometer can provide data to fill the altitude gap in the wind measurements. Its possible successor named SMILES-2, is being designed in Japan for the study of the middle and upper atmospheric chemistry and dynamics (O3, H2O, T, atomic O, OH, HO2, ClO, BrO, ...). If realized, the instrument will measure sub-millimeter and THz molecular spectral lines (616-150 μm) with high sensitivity and frequency resolution. The SMILES-2 characteristics are very well suited for horizontal wind observations between 20 km to more than 160 km. The best performances are found between 35-90 km where the retrieval precision is better than 3 m/s for a vertical resolution of 2-3 km [1]. In this presentation, we summarize the results obtained from SMILES and assess the measurement performances of SMILES-2 to measure horizontal winds. [1] P. Baron, N. Manago, H. Ozeki, Y. Irimajiri, D. Murtagh, Y. Uzawa, S. Ochiai, M. Shiotani, M. Suzuki: "Measurement of stratospheric and mesospheric winds with a SubMillimeter wave limb sounder: Results from JEM/SMILES and simulation study for SMILES-2"; Proc. of SPIE Remote sensing, 96390N-96390N-20, 2015

SU-F-T-559: High-Resolution Scintillating Fiber Array for In-Vivo Real-Time SRS and SBRT Patient QA

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

Knewtson, T; Pokhrel, S; University of Tennessee Health Science Center, Memphis, TN

2016-06-15

Purpose: A high-resolution scintillating fiber detector was built for in-vivo real-time patient specific quality assurance (QA). The detector is designed for stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS) to monitor treatment delivery and detect real-time deviations from planned dose to increase patient safety and treatment accuracy. Methods: The detector consists of two high-density scintillating fiber arrays layered to form an X-Y grid which can be attached to the accessory tray of a medical linac for SBRT and cone SRS treatment QA. Fiber arrays consist of 128 scintillating fibers embedded within a precision-machined, high-transmission polymer substrate with 0.8mm pitch. Themore » fibers are coupled on both ends to high-sensitivity photodetectors and the output is recorded through a high-speed analog-to-digital converter to capture the linac pulse sequence as treatment delivery progresses. The detector has a software controlled 360 degree rotational system to capture angular beam projections for high-resolution beam profile reconstruction. Results: The detector was validated using SRS cone sizes from 6mm to 34mm and MLC defined field sizes from 5×5mm2 to 100×100mm2. The detector output response is linear with dose and is dose rate independent. Each field can be reconstructed accurately with a spatial resolution of 0.8mm and the current beam output is displayed every 50msec. Dosimetric errors of 1% with respect to the treatment plan can be identified and clinically significant deviations from the expected treatment can be displayed in real-time to alert the therapists. Conclusion: The high resolution detector is capable of reconstructing beam profiles in real-time with submillimeter resolution and 1% dose resolution. This system has the ability to project in-vivo both spatial and dosimetric errors during SBRT and SRS treatments when only a non-clinically significant fraction of the intended dose was delivered. The device has the potential to establish new standards for in-vivo patient specific QA.« less

The Millimeter Sky Transparency Imager (MiSTI)

NASA Astrophysics Data System (ADS)

Tamura, Yoichi; Kawabe, Ryohei; Kohno, Kotaro; Fukuhara, Masayuki; Momose, Munetake; Ezawa, Hajime; Kuboi, Akihito; Sekiguchi, Tomohiko; Kamazaki, Takeshi; Vila-Vilaró, Baltasar; Nakagawa, Yuki; Okada, Norio

2011-04-01

The Millimeter Sky Transparency Imager (MiSTI) is a small millimeter-wave scanning telescope with a 25-cm diameter dish operating at 183 GHz. MiSTI is installed at Atacama, Chile, and it measures emission from atmospheric water vapor and its fluctuations to estimate atmospheric absorption in the millimeter to submillimeter range. MiSTI observes the water vapor distribution at a spatial resolution of 0.°5, and it is sensitive enough to detect an excess path length of lesssim0.05 mm for an integration time of 1 s. By comparing the MiSTI measurements with those by a 220 GHz tipper, we validated that the 183 GHz measurements of MiSTI are correct, down to the level of any residual systematic errors in the 220 GHz measurements. Since 2008, MiSTI has provided real-time (every 1 hr) monitoring of the all-sky opacity distribution and atmospheric transmission curves in the (sub)millimeter through the internet, allowing us to know the (sub)millimeter sky conditions at Atacama.

VizieR Online Data Catalog: Planck Catalog of Compact Sources Release 1 (Planck, 2013)

NASA Astrophysics Data System (ADS)

Planck Collaboration

2013-03-01

Planck is a European Space Agency (ESA) mission, with significant contributions from the U.S. National Aeronautics and Space Agency (NASA). It is the third generation of space-based cosmic microwave background experiments, after the Cosmic Background Explorer (COBE) and the Wilkinson Microwave Anisotropy Probe (WMAP). Planck was launched on 14 May 2009 on an Ariane 5 rocket from Kourou, French Guiana. Following a cruise to the Earth-Sun L2 Lagrange point, cooling and in orbit checkout, Planck initiated the First Light Survey on 13 August 2009. Since then, Planck has been continuously measuring the intensity of the sky over a range of frequencies from 30 to 857GHz (wavelengths of 1cm to 350μm) with spatial resolutions ranging from about 33' to 5' respectively. The Low Frequency Instrument (LFI) on Planck provides temperature and polarization information using radiometers which operate between 30 and 70GHz. The High Frequency Instrument (HFI) uses pairs of polarization-sensitive bolometers at each of four frequencies between 100 and 353GHz but does not measure polarization information in the two upper HFI bands at 545 and 857GHz. The lowest frequencies overlap with WMAP, and the highest frequencies extend far into the submillimeter in order to improve separation between Galactic foregrounds and the cosmic microwave background (CMB). By extending to wavelengths longer than those at which the Infrared Astronomical Satellite (IRAS) operated, Planck is providing an unprecedented window into dust emission at far-infrared and submillimeter wavelengths. The PCCS (Planck Catalog of Compact Sources) is the list of sources detected in the first 15 months of Planck "nominal" mission. It consists of nine single-frequency catalogues of compact sources, both Galactic and extragalactic, detected over the entire sky. The PCCS covers the frequency range 30-857 GHz with higher sensitivity (it is 90% complete at 180mJy in the best channel) and better angular resolution than previous all-sky surveys in the microwave band. By construction its reliability is >80% and more than 65% of the sources have been detected at least in two contiguous Planck channels. Many of the Planck PCCS sources can be associated with stars with dust shells, stellar cores, radio galaxies, blazars, infrared luminous galaxies and Galactic interstellar medium features. (12 data files).

Submillimeter Spectroscopy with SOFIA

NASA Technical Reports Server (NTRS)

Erickson, E.; Gisten, R.; Moseley, H.; Poglitsch, A.; Zmuidzinas, J.

2005-01-01

Four submillimeter spectrometers are being developed for use on SOFIA, the Stratospheric Observatory for Infrared Astronomy. They will be nearly diffraction limited by SOFIA'S 2.5 m telescope, giving for example images of 8.5 arc seconds FWHM at 100 microns. The instruments are FlFI LS, an integral-field imaging grating spectrometer (MPE) covering 40-210 microns with 150 km/s resolution; SAFIRE an imaging Fabry-Perot spectrometer covering 100-'650 microns with resolution 200 km/s, and two heterodyne receivers with resolving powers up to 0.03 km/s: GREAT covering bands from 158-187 um, 110-125, and 62-65 microns, and CASIMIR, operating from 150-264 and 508-588 microns. These instruments will enable a variety of studies including topics relating to the origins of stars, planets, and biogenic materials in the interstallar medium of our own and other galaxies. Opportunities for observing with these and the other SOFIA instruments will be available to general investigators. SOFIA is a joint project of NASA in the U.S. and DLR in Germany.

Overview of the Design, Fabrication and Performance Requirements of Micro-Spec, an Integrated Submillimeter Spectrometer

NASA Technical Reports Server (NTRS)

Barrentine, Emily M.; Noroozian, Omid; Brown, Ari D.; Cataldo, Giuseppe; Ehsan, Negar; Hsieh, Wen-Ting; Stevenson, Thomas R.; U-Yen, Kongpop; Wollack, Edward J.; Moseley, S. Harvey

2015-01-01

Micro-Spec is a compact submillimeter (350-700 GHz) spectrometer which uses low loss superconducting niobium microstrip transmission lines and a single-crystal silicon dielectric to integrate all of the components of a grating-analog spectrometer onto a single chip. Here we present details of the fabrication and design of a prototype Micro-Spec spectrometer with resolution, R64, where we use a high-yield single-flip wafer bonding process to realize instrument components on a 0.45 m single-crystal silicon dielectric. We discuss some of the electromagnetic design concerns (such as loss, stray-light, cross-talk, and fabrication tolerances) for each of the spectrometer components and their integration into the instrument as a whole. These components include a slot antenna with a silicon lens for optical coupling, a phase delay transmission line network, parallel plate waveguide interference region, and aluminum microstrip transmission line kinetic inductance detectors with extremely low cross-talk and immunity to stray light. We have demonstrated this prototype spectrometer with design resolution of R64. Given the optical performance of this prototype, we will also discuss the extension of this design to higher resolutions suitable for balloon-flight.

Millimeter and Sub-millimeter High Resolution Spectroscopy: New Frontiers with ALMA

NASA Astrophysics Data System (ADS)

Ziurys, Lucy M.

2016-06-01

It is becoming increasingly clear that new laboratory data will be critical for the next decade of observations with the Atacama Large Millimeter Array (ALMA). The high spatial resolution offered by ALMA will probe new regions of molecular complexity, including the inner envelopes of evolved stars, regions dominated by UV radiation, and the densest cores of molecular clouds. New molecular lines will be discovered in the wide wavelength range covered by the ALMA bands, and high resolution, gas-phase spectroscopy are needed to provide crucial “rest frequencies.” In particular, highly accurate methods that measure millimeter and sub-millimeter rotational transitions, such as direct absorption and Fourier transform mm-wave techniques, are important, especially when coupled to exotic molecular production schemes. Recent ALMA studies of SH+ and larger organic species have already demonstrated the need for laboratory measurements. New laboratory work will likely be required for circumstellar refractory molecules, radicals and ions generated near photon-dominated regions (PDRs), and large, organic-type species. This talk will give an overview of current contributions of laboratory spectroscopy to ALMA observations, summarize relevant spectroscopic techniques, and provide input into future prospects and directions.

γ-ray telescopes using conversions to e+e- pairs: event generators, angular resolution and polarimetry

NASA Astrophysics Data System (ADS)

Gros, P.; Bernard, D.

2017-02-01

We benchmark various available event generators in Geant4 and EGS5 in the light of ongoing projects for high angular-resolution pair-conversion telescopes at low energy. We compare the distributions of key kinematic variables extracted from the geometry of the three final state particles. We validate and use as reference an exact generator using the full 5D differential cross-section of the conversion process. We focus in particular on the effect of the unmeasured recoiling nucleus on the angular resolution. We show that for high resolution trackers, the choice of the generator affects the estimated resolution of the telescope. We also show that the current available generator are unable to describe accurately a linearly polarised photon source.

Studying AGN Jets At Extreme Angular Resolution

NASA Astrophysics Data System (ADS)

Bruni, Gabriele

2016-10-01

RadioAstron is a 10m antenna orbiting on the Russian Speckt-R spacecraft, launched in 2011. Performing radio interferometry with a global array of ground telescopes, it is providing record angular resolution. The Key Science Project on AGN polarization is exploiting it to study in great detail the configuration of magnetic fields in AGN jets, and understand their formation and collimation. To date, the project has already achieved the highest angular resolution image ever obtained in Astronomy, and detected brightness temperatures exceeding the ones predicted by theory of AGN.

ALMA OBSERVATIONS OF Ly α BLOB 1: HALO SUBSTRUCTURE ILLUMINATED FROM WITHIN

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

Geach, J. E.; Narayanan, D.; Matsuda, Y.

2016-11-20

We present new Atacama Large Millimeter/Submillimeter Array (ALMA) 850 μ m continuum observations of the original Ly α Blob (LAB) in the SSA22 field at z = 3.1 (SSA22-LAB01). The ALMA map resolves the previously identified submillimeter source into three components with a total flux density of S {sub 850} = 1.68 ± 0.06 mJy, corresponding to a star-formation rate of ∼150 M {sub ⊙} yr{sup -1}. The submillimeter sources are associated with several faint ( m ≈ 27 mag) rest-frame ultraviolet sources identified in Hubble Space Telescope Imaging Spectrograph (STIS) clear filter imaging ( λ ≈ 5850 Å). Onemore » of these companions is spectroscopically confirmed with the Keck Multi-Object Spectrometer For Infra-Red Exploration to lie within 20 projected kpc and 250 km s{sup -1} of one of the ALMA components. We postulate that some of these STIS sources represent a population of low-mass star-forming satellites surrounding the central submillimeter sources, potentially contributing to their growth and activity through accretion. Using a high-resolution cosmological zoom simulation of a 10{sup 13} M {sub ⊙} halo at z = 3, including stellar, dust, and Ly α radiative transfer, we can model the ALMA+STIS observations and demonstrate that Ly α photons escaping from the central submillimeter sources are expected to resonantly scatter in neutral hydrogen, the majority of which is predicted to be associated with halo substructure. We show how this process gives rise to extended Ly α emission with similar surface brightness and morphology to observed giant LABs.« less

A development roadmap for critical technologies needed for TALC: a deployable 20m annular space telescope

NASA Astrophysics Data System (ADS)

Sauvage, Marc; Amiaux, Jérome; Austin, James; Bello, Mara; Bianucci, Giovanni; Chesné, Simon; Citterio, Oberto; Collette, Christophe; Correia, Sébastien; Durand, Gilles A.; Molinari, Sergio; Pareschi, Giovanni; Penfornis, Yann; Sironi, Giorgia; Valsecchi, Giuseppe; Verpoort, Sven; Wittrock, Ulrich

2016-07-01

Astronomy is driven by the quest for higher sensitivity and improved angular resolution in order to detect fainter or smaller objects. The far-infrared to submillimeter domain is a unique probe of the cold and obscured Universe, harboring for instance the precious signatures of key elements such as water. Space observations are mandatory given the blocking effect of our atmosphere. However the methods we have relied on so far to develop increasingly larger telescopes are now reaching a hard limit, with the JWST illustrating this in more than one way (e.g. it will be launched by one of the most powerful rocket, it requires the largest existing facility on Earth to be qualified). With the Thinned Aperture Light Collector (TALC) project, a concept of a deployable 20 m annular telescope, we propose to break out of this deadlock by developing novel technologies for space telescopes, which are disruptive in three aspects: • An innovative deployable mirror whose topology, based on stacking rather than folding, leads to an optimum ratio of collecting area over volume, and creates a telescope with an eight times larger collecting area and three times higher angular resolution compared to JWST from the same pre-deployed volume; • An ultra-light weight segmented primary mirror, based on electrodeposited Nickel, Composite and Honeycomb stacks, built with a replica process to control costs and mitigate the industrial risks; • An active optics control layer based on piezo-electric layers incorporated into the mirror rear shell allowing control of the shape by internal stress rather than by reaction on a structure. We present in this paper the roadmap we have built to bring these three disruptive technologies to technology readiness level 3. We will achieve this goal through design and realization of representative elements: segments of mirrors for optical quality verification, active optics implemented on representative mirror stacks to characterize the shape correction capabilities, and mechanical models for validation of the deployment concept. Accompanying these developments, a strong system activity will ensure that the ultimate goal of having an integrated system can be met, especially in terms of (a) scalability toward a larger structure, and (b) verification philosophy.

The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid in the interstellar medium

NASA Astrophysics Data System (ADS)

Coutens, A.; Jørgensen, J. K.; van der Wiel, M. H. D.; Müller, H. S. P.; Lykke, J. M.; Bjerkeli, P.; Bourke, T. L.; Calcutt, H.; Drozdovskaya, M. N.; Favre, C.; Fayolle, E. C.; Garrod, R. T.; Jacobsen, S. K.; Ligterink, N. F. W.; Öberg, K. I.; Persson, M. V.; van Dishoeck, E. F.; Wampfler, S. F.

2016-05-01

Formamide (NH2CHO) has previously been detected in several star-forming regions and is thought to be a precursor for different prebiotic molecules. Its formation mechanism is still debated, however. Observations of formamide, related species, and their isopotologues may provide useful clues to the chemical pathways leading to their formation. The Protostellar Interferometric Line Survey (PILS) represents an unbiased, high angular resolution and sensitivity spectral survey of the low-mass protostellar binary IRAS 16293-2422 with the Atacama Large Millimeter/submillimeter Array (ALMA). For the first time, we detect the three singly deuterated forms of NH2CHO (NH2CDO, cis- and trans-NHDCHO), as well as DNCO towards the component B of this binary source. The images reveal that the different isotopologues are all present in the same region. Based on observations of the 13C isotopologues of formamide and a standard 12C/13C ratio, the deuterium fractionation is found to be similar for the three different forms with a value of about 2%. The DNCO/HNCO ratio is also comparable to the D/H ratio of formamide (~1%). These results are in agreement with the hypothesis that NH2CHO and HNCO are chemically related through grain-surface formation.

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.

ALMA Detection of Extended [C II] Emission in Himiko at z = 6.6

NASA Astrophysics Data System (ADS)

Carniani, S.; Maiolino, R.; Smit, R.; Amorín, R.

2018-02-01

Himiko is one of the most luminous Lyα emitters at z = 6.595. It has three star-forming clumps detected in the rest-frame UV, with a total SFR = 20 M ⊙ yr‑1. We report the Atacama Large Millimeter/submillimeter Array (ALMA) detection of the [C II]158 μm line emission in this Galaxy with a significance of 8σ. The total [C II] luminosity (L [C II] = 1.2 × 108 L ⊙) is fully consistent with the local L [C II]–SFR relation. The ALMA high-angular resolution reveals that the [C II] emission is made of two distinct components. The brightest [C II] clump is extended over 4 kpc and is located on the peak of the Lyα nebula, which is spatially offset by 1 kpc relative to the brightest UV clump. The second [C II] component is spatially unresolved (size <2 kpc) and coincident with one of the three UV clumps. While the latter component is consistent with the local L [C II]–SFR relation, the other components are scattered above and below the local relation. We shortly discuss the possible origin of the [C II] components and their relation with the star-forming clumps traced by the UV emission.

Myofiber Architecture of the Human Atria as Revealed by Submillimeter Diffusion Tensor Imaging.

PubMed

Pashakhanloo, Farhad; Herzka, Daniel A; Ashikaga, Hiroshi; Mori, Susumu; Gai, Neville; Bluemke, David A; Trayanova, Natalia A; McVeigh, Elliot R

2016-04-01

Accurate knowledge of the human atrial fibrous structure is paramount in understanding the mechanisms of atrial electric function in health and disease. Thus far, such knowledge has been acquired from destructive sectioning, and there is a paucity of data about atrial fiber architecture variability in the human population. In this study, we have developed a customized 3-dimensional diffusion tensor magnetic resonance imaging sequence on a clinical scanner that makes it possible to image an entire intact human heart specimen ex vivo at submillimeter resolution. The data from 8 human atrial specimens obtained with this technique present complete maps of the fibrous organization of the human atria. The findings demonstrate that the main features of atrial anatomy are mostly preserved across subjects although the exact location and orientation of atrial bundles vary. Using the full tractography data, we were able to cluster, visualize, and characterize the distinct major bundles in the human atria. Furthermore, quantitative characterization of the fiber angles across the atrial wall revealed that the transmural fiber angle distribution is heterogeneous throughout different regions of the atria. The application of submillimeter diffusion tensor magnetic resonance imaging provides an unprecedented level of information on both human atrial structure, as well as its intersubject variability. The high resolution and fidelity of this data could enhance our understanding of structural contributions to atrial rhythm and pump disorders and lead to improvements in their targeted treatment. © 2016 American Heart Association, Inc.

Angular resolution of the gaseous micro-pixel detector Gossip

NASA Astrophysics Data System (ADS)

Bilevych, Y.; Blanco Carballo, V.; van Dijk, M.; Fransen, M.; van der Graaf, H.; Hartjes, F.; Hessey, N.; Koppert, W.; Nauta, S.; Rogers, M.; Romaniouk, A.; Veenhof, R.

2011-06-01

Gossip is a gaseous micro-pixel detector with a very thin drift gap intended for a high rate environment like at the pixel layers of ATLAS at the sLHC. The detector outputs not only the crossing point of a traversing MIP, but also the angle of the track, thus greatly simplifying track reconstruction. In this paper we describe a testbeam experiment to examine the angular resolution of the reconstructed track segments in Gossip. We used here the low diffusion gas mixture DME/CO 2 50/50. An angular resolution of 20 mrad for perpendicular tracks could be obtained from a 1.5 mm thin drift volume. However, for the prototype detector used at the testbeam experiment, the resolution of slanting tracks was worsened by poor time resolution of the pixel chip used.

First-generation science cases for ground-based terahertz telescopes

NASA Astrophysics Data System (ADS)

Hirashita, Hiroyuki; Koch, Patrick M.; Matsushita, Satoki; Takakuwa, Shigehisa; Nakamura, Masanori; Asada, Keiichi; Liu, Hauyu Baobab; Urata, Yuji; Wang, Ming-Jye; Wang, Wei-Hao; Takahashi, Satoko; Tang, Ya-Wen; Chang, Hsian-Hong; Huang, Kuiyun; Morata, Oscar; Otsuka, Masaaki; Lin, Kai-Yang; Tsai, An-Li; Lin, Yen-Ting; Srinivasan, Sundar; Martin-Cocher, Pierre; Pu, Hung-Yi; Kemper, Francisca; Patel, Nimesh; Grimes, Paul; Huang, Yau-De; Han, Chih-Chiang; Huang, Yen-Ru; Nishioka, Hiroaki; Lin, Lupin Chun-Che; Zhang, Qizhou; Keto, Eric; Burgos, Roberto; Chen, Ming-Tang; Inoue, Makoto; Ho, Paul T. P.

2016-02-01

Ground-based observations at terahertz (THz) frequencies are a newly explorable area of astronomy in the coming decades. We discuss science cases for a first-generation 10-m class THz telescope, focusing on the Greenland Telescope as an example of such a facility. We propose science cases and provide quantitative estimates for each case. The largest advantage of ground-based THz telescopes is their higher angular resolution (˜ 4″ for a 10-m dish), as compared to space or airborne THz telescopes. Thus, high-resolution mapping is an important scientific argument. In particular, we can isolate zones of interest for Galactic and extragalactic star-forming regions. The THz windows are suitable for observations of high-excitation CO lines and [N II] 205-μm lines, which are scientifically relevant tracers of star formation and stellar feedback. Those lines are the brightest lines in the THz windows, so they are suitable for the initiation of ground-based THz observations. THz polarization of star-forming regions can also be explored since it traces the dust population contributing to the THz spectral peak. For survey-type observations, we focus on "sub-THz" extragalactic surveys, the uniqueness of which is detecting galaxies at redshifts z ˜ 1-2, where the dust emission per comoving volume is the largest in the history of the Universe. Finally we explore possibilities of flexible time scheduling, which enables us to monitor active galactic nuclei, and to target gamma-ray burst afterglows. For these objects, THz and submillimeter wavelength ranges have not yet been explored.

Nobeyama Radio Observatory

NASA Astrophysics Data System (ADS)

Murdin, P.

2000-11-01

Nobeyama Radio Observatory has telescopes at millimeter and submillimeter wavelengths. It was established in 1982 as an observatory of Tokyo Astronomical Observatory (NATIONAL ASTRONOMICAL OBSERVATORY, JAPAN since 1987), and operates the 45 m telescope, Nobeyama Millimeter Array, and Radioheliograph. High-resolution images of star forming regions and molecular clouds have revealed many aspects of...

Replicated Wolter-I X-ray Optics for Lightweight, High Angular Resolution, Large Collecting Area X-Ray Telescopes

NASA Technical Reports Server (NTRS)

Joy, M.; Bilbro, J.; Elsner, R.; Jones, W.; Kolodziejczak, J.; Petruzzo, J.; ODell, S.; Weisskopf, M.

1997-01-01

The next generation of orbiting x-ray observatories will require high angular resolution telescopes that have an order of magnitude greater collecting area in the 0.1-10 keV spectral region than those currently under construction, but with a much lower weight and cost per unit area. Replicated Wolter-I x-ray optics have the potential to meet this requirement. The currently demonstrated capabilities of replicated Wolter-I optics will be described, and a development plan for creating lightweight, high angular resolution, large effective area x-ray telescopes will be presented.

Sub-Millimeter Heterodyne Focal-Plane Arrays for High-Resolution Astronomical Spectroscopy

NASA Astrophysics Data System (ADS)

Goldsmith, Paul F.

2017-09-01

Spectral lines are vital tools for astronomy, particularly for studying the interstellar medium, which is widely distributed throughout the volume of our Milky Way and of other galaxies. Broadband emissions, including synchrotron, free-free, and thermal dust emissions give astronomers important information. However, they do not give information about the motions of, for example, interstellar clouds, the filamentary structures found within them, star-forming dense cores, and photon-dominated regions energized by massive young stars. For study of the interstellar medium, spectral lines at sub-millimeter wavelengths are particularly important, for two reasons. First, they offer the unique ability to observe a variety of important molecules, atoms, and ions, which are the most important gas coolants (fine-structure lines of ionized and neutral carbon, neutral oxygen), probes of physical conditions (high-J transitions of CO, HF, fine-structure lines of ionized nitrogen), and of obvious biogenic importance (H2O). In addition, high-resolution observations of spectral lines offer the unique ability to disentangle the complex motions within these regions and, in some cases, to determine their arrangement along the line of sight. To accomplish this, spectral resolution high enough to resolve the spectral lines of interest is required. We can measure the resolution of the spectrometer in terms of its resolution, R = f/δf, where f is the rest frequency of the line, and δJ is the frequency resolution of the spectrometer. More-active sources can be advantageously studied with R = 3 × 10^5, while more quiescent sources require R as high as 10^7.

Sideband-Separating, Millimeter-Wave Heterodyne Receiver

NASA Technical Reports Server (NTRS)

Ward, John S.; Bumble, Bruce; Lee, Karen A.; Kawamura, Jonathan H.; Chattopadhyay, Goutam; Stek, paul; Stek, Paul

2010-01-01

Researchers have demonstrated a submillimeter-wave spectrometer that combines extremely broad bandwidth with extremely high sensitivity and spectral resolution to enable future spacecraft to measure the composition of the Earth s troposphere in three dimensions many times per day at spatial resolutions as high as a few kilometers. Microwave limb sounding is a proven remote-sensing technique that measures thermal emission spectra from molecular gases along limb views of the Earth s atmosphere against a cold space background.

First detection of equatorial dark dust lane in a protostellar disk at submillimeter wavelength

PubMed Central

Lee, Chin-Fei; Li, Zhi-Yun; Ho, Paul T. P.; Hirano, Naomi; Zhang, Qizhou; Shang, Hsien

2017-01-01

In the earliest (so-called “Class 0”) phase of Sun-like (low-mass) star formation, circumstellar disks are expected to form, feeding the protostars. However, these disks are difficult to resolve spatially because of their small sizes. Moreover, there are theoretical difficulties in producing these disks in the earliest phase because of the retarding effects of magnetic fields on the rotating, collapsing material (so-called “magnetic braking”). With the Atacama Large Millimeter/submillimeter Array (ALMA), it becomes possible to uncover these disks and study them in detail. HH 212 is a very young protostellar system. With ALMA, we not only detect but also spatially resolve its disk in dust emission at submillimeter wavelength. The disk is nearly edge-on and has a radius of ~60 astronomical unit. It shows a prominent equatorial dark lane sandwiched between two brighter features due to relatively low temperature and high optical depth near the disk midplane. For the first time, this dark lane is seen at submillimeter wavelength, producing a “hamburger”-shaped appearance that is reminiscent of the scattered-light image of an edge-on disk in optical and near infrared light. Our observations open up an exciting possibility of directly detecting and characterizing small disks around the youngest protostars through high-resolution imaging with ALMA, which provides strong constraints on theories of disk formation. PMID:28439561

Deployment Testing of Flexible Composite Hinges in Bi-Material Beams

NASA Technical Reports Server (NTRS)

Sauder, Jonathan F.; Trease, Brian

2016-01-01

Composites have excellent properties for strength, thermal stability, and weight. However, they are traditionally highly rigid, and when used in deployable structures require hinges bonded to the composite material, which increases complexity and opportunities for failure. Recent research in composites has found by adding an elastomeric soft matrix, often silicone instead of an epoxy, the composite becomes flexible. This work explores the deployment repeatability of silicone matrix composite hinges which join rigid composite beams. The hinges were found to have sub-millimeter linear deployment repeatability, and sub-degree angular deployment repeatability. Also, an interesting relaxation effect was discovered, as a hinges deployment error would decrease with time.

Adaptive Optics Imaging of Solar System Objects

NASA Technical Reports Server (NTRS)

Roddier, Francois; Owen, Toby

1999-01-01

Most solar system objects have never been observed at wavelengths longer than the R band with an angular resolution better than 1". The Hubble Space Telescope itself has only recently been equipped to observe in the infrared. However, because of its small diameter, the angular resolution is lower than that one can now achieved from the ground with adaptive optics, and time allocated to planetary science is limited. We have successfully used adaptive optics on a 4-m class telescope to obtain 0.1" resolution images of solar system objects in the far red and near infrared (0.7-2.5 microns), aE wavelengths which best discl"lmlnate their spectral signatures. Our efforts have been put into areas of research for which high angular resolution is essential.

Correction of eddy current distortions in high angular resolution diffusion imaging.

PubMed

Zhuang, Jiancheng; Lu, Zhong-Lin; Vidal, Christine Bouteiller; Damasio, Hanna

2013-06-01

To correct distortions caused by eddy currents induced by large diffusion gradients during high angular resolution diffusion imaging without any auxiliary reference scans. Image distortion parameters were obtained by image coregistration, performed only between diffusion-weighted images with close diffusion gradient orientations. A linear model that describes distortion parameters (translation, scale, and shear) as a function of diffusion gradient directions was numerically computed to allow individualized distortion correction for every diffusion-weighted image. The assumptions of the algorithm were successfully verified in a series of experiments on phantom and human scans. Application of the proposed algorithm in high angular resolution diffusion images markedly reduced eddy current distortions when compared to results obtained with previously published methods. The method can correct eddy current artifacts in the high angular resolution diffusion images, and it avoids the problematic procedure of cross-correlating images with significantly different contrasts resulting from very different gradient orientations or strengths. Copyright © 2012 Wiley Periodicals, Inc.

Chiral resolution of spin angular momentum in linearly polarized and unpolarized light

PubMed Central

Hernández, R. J.; Mazzulla, A.; Provenzano, C.; Pagliusi, P.; Cipparrone, G.

2015-01-01

Linearly polarized (LP) and unpolarized (UP) light are racemic entities since they can be described as superposition of opposite circularly polarized (CP) components of equal amplitude. As a consequence they do not carry spin angular momentum. Chiral resolution of a racemate, i.e. separation of their chiral components, is usually performed via asymmetric interaction with a chiral entity. In this paper we provide an experimental evidence of the chiral resolution of linearly polarized and unpolarized Gaussian beams through the transfer of spin angular momentum to chiral microparticles. Due to the interplay between linear and angular momentum exchange, basic manipulation tasks, as trapping, spinning or orbiting of micro-objects, can be performed by light with zero helicity. The results might broaden the perspectives for development of miniaturized and cost-effective devices. PMID:26585284

Optical fiber sensors-based temperature distribution measurement in ex vivo radiofrequency ablation with submillimeter resolution.

PubMed

Macchi, Edoardo Gino; Tosi, Daniele; Braschi, Giovanni; Gallati, Mario; Cigada, Alfredo; Busca, Giorgio; Lewis, Elfed

2014-01-01

Radiofrequency thermal ablation (RFTA) induces a high-temperature field in a biological tissue having steep spatial (up to 6°C∕mm) and temporal (up to 1°C∕s) gradients. Applied in cancer care, RFTA produces a localized heating, cytotoxic for tumor cells, and is able to treat tumors with sizes up to 3 to 5 cm in diameter. The online measurement of temperature distribution at the RFTA point of care has been previously carried out with miniature thermocouples and optical fiber sensors, which exhibit problems of size, alteration of RFTA pattern, hysteresis, and sensor density worse than 1 sensor∕cm. In this work, we apply a distributed temperature sensor (DTS) with a submillimeter spatial resolution for the monitoring of RFTA in porcine liver tissue. The DTS demodulates the chaotic Rayleigh backscattering pattern with an interferometric setup to obtain the real-time temperature distribution. A measurement chamber has been set up with the fiber crossing the tissue along different diameters. Several experiments have been carried out measuring the space-time evolution of temperature during RFTA. The present work showcases the temperature monitoring in RFTA with an unprecedented spatial resolution and is exportable to in vivo measurement; the acquired data can be particularly useful for the validation of RFTA computational models.

Fourier spectroscopy of the stratospheric emission

NASA Technical Reports Server (NTRS)

Carli, B.; Mencaraglia, F.; Bonetti, A.

1980-01-01

Stratospheric emission spectra in the submillimeter range have been recorded with a resolution of 0.0033/cm with a balloon-borne interferometer. Several minor atmospheric constituents have been identified in a preliminary analysis of the spectra; these are water vapor, oxygen, ozone isotopes, nitric acid, nitrous oxide, hydrofluoric and hydrochloric acids, and carbon monoxide.

Scanning SQUID microscopy of a ferromanganese crust from the northwestern Pacific: Submillimeter scale magnetostratigraphy as a new tool for age determination and mapping of environmental magnetic parameters

NASA Astrophysics Data System (ADS)

Noguchi, A.; Oda, H.; Yamamoto, Y.; Usui, A.; Sato, M.; Kawai, J.

2017-06-01

Ferromanganese crusts record long-term deep-sea environmental changes. Thus, providing their reliable high-resolution age models is important. We applied a magnetostratigraphic technique to estimate the growth rate of a ferromanganese crust using scanning SQUID (superconducting quantum interference device) microscope (SSM). SSM is designed to map the magnetic field across thin sections with submillimeter resolution. The crust sample was taken from the Takuyo-Daigo Seamount, northwestern Pacific, and recorded a limited supply of dust and sediment from continents. After drift correction and removal of spike noises, the magnetic field values were stacked within the areas of high signal-to-noise ratios. By correlating the obtained profiles with a standard geomagnetic polarity timescale, we obtained an average growth rate of 3.37 ± 0.06 mm/Ma, which is consistent with that obtained by 10Be/9Be geochronology (2.93 ± 0.15 mm/Ma). S ratio mapping shows low values after 3 Ma, associated with voids between columnar structures.

Towards a Full-sky, High-resolution Dust Extinction Map with WISE and Planck

NASA Astrophysics Data System (ADS)

Meisner, Aaron M.; Finkbeiner, D. P.

2014-01-01

We have recently completed a custom processing of the entire WISE 12 micron All-sky imaging data set. The result is a full-sky map of diffuse, mid-infrared Galactic dust emission with angular resolution of 15 arcseconds, and with contaminating artifacts such as compact sources removed. At the same time, the 2013 Planck HFI maps represent a complementary data set in the far-infrared, with zero-point relatively immune to zodiacal contamination and angular resolution superior to previous full-sky data sets at similar frequencies. Taken together, these WISE and Planck data products present an opportunity to improve upon the SFD (1998) dust extinction map, by virtue of enhanced angular resolution and potentially better-controlled systematics on large scales. We describe our continuing efforts to construct and test high-resolution dust extinction and temperature maps based on our custom WISE processing and Planck HFI data.

Simulated cosmic microwave background maps at 0.5 deg resolution: Basic results

NASA Technical Reports Server (NTRS)

Hinshaw, G.; Bennett, C. L.; Kogut, A.

1995-01-01

We have simulated full-sky maps of the cosmic microwave background (CMB) anisotropy expected from cold dark matter (CDM) models at 0.5 deg and 1.0 deg angular resolution. Statistical properties of the maps are presented as a function of sky coverage, angular resolution, and instrument noise, and the implications of these results for observability of the Doppler peak are discussed. The rms fluctuations in a map are not a particularly robust probe of the existence of a Doppler peak; however, a full correlation analysis can provide reasonable sensitivity. We find that sensitivity to the Doppler peak depends primarily on the fraction of sky covered, and only secondarily on the angular resolution and noise level. Color plates of the simulated maps are presented to illustrate the anisotropies.

Kiloparsec-scale Dust Disks in High-redshift Luminous Submillimeter Galaxies

NASA Astrophysics Data System (ADS)

Hodge, J. A.; Swinbank, A. M.; Simpson, J. M.; Smail, I.; Walter, F.; Alexander, D. M.; Bertoldi, F.; Biggs, A. D.; Brandt, W. N.; Chapman, S. C.; Chen, C. C.; Coppin, K. E. K.; Cox, P.; Dannerbauer, H.; Edge, A. C.; Greve, T. R.; Ivison, R. J.; Karim, A.; Knudsen, K. K.; Menten, K. M.; Rix, H.-W.; Schinnerer, E.; Wardlow, J. L.; Weiss, A.; van der Werf, P.

2016-12-01

We present high-resolution (0.″16) 870 μm Atacama Large Millimeter/submillimeter Array (ALMA) imaging of 16 luminous ({L}{IR}˜ 4× {10}12 {L}⊙ ) submillimeter galaxies (SMGs) from the ALESS survey of the Extended Chandra Deep Field South. This dust imaging traces the dust-obscured star formation in these z˜ 2.5 galaxies on ˜1.3 kpc scales. The emission has a median effective radius of R e = 0.″24 ± 0.″02, corresponding to a typical physical size of {R}e= 1.8 ± 0.2 kpc. We derive a median Sérsic index of n = 0.9 ± 0.2, implying that the dust emission is remarkably disk-like at the current resolution and sensitivity. We use different weighting schemes with the visibilities to search for clumps on 0.″12 (˜1.0 kpc) scales, but we find no significant evidence for clumping in the majority of cases. Indeed, we demonstrate using simulations that the observed morphologies are generally consistent with smooth exponential disks, suggesting that caution should be exercised when identifying candidate clumps in even moderate signal-to-noise ratio interferometric data. We compare our maps to comparable-resolution Hubble Space Telescope {H}160-band images, finding that the stellar morphologies appear significantly more extended and disturbed, and suggesting that major mergers may be responsible for driving the formation of the compact dust disks we observe. The stark contrast between the obscured and unobscured morphologies may also have implications for SED fitting routines that assume the dust is co-located with the optical/near-IR continuum emission. Finally, we discuss the potential of the current bursts of star formation to transform the observed galaxy sizes and light profiles, showing that the z˜ 0 descendants of these SMGs are expected to have stellar masses, effective radii, and gas surface densities consistent with the most compact massive ({M}* ˜ 1-2 × 1011 {M}⊙ ) early-type galaxies observed locally.

Taking the Measure of Massive Stars and their Environments with the CHARA Array Long-baseline Interferometer

NASA Astrophysics Data System (ADS)

Gies, Douglas R.

2017-11-01

Most massive stars are so distant that their angular diameters are too small for direct resolution. However, the observational situation is now much more favorable, thanks to new opportunities available with optical/IR long-baseline interferometry. The Georgia State University Center for High Angular Resolution Astronomy Array at Mount Wilson Observatory is a six-telescope instrument with a maximum baseline of 330 meters, which is capable of resolving stellar disks with diameters as small as 0.2 milliarcsec. The distant stars are no longer out of range, and many kinds of investigations are possible. Here we summarize a number of studies involving angular diameter measurements and effective temperature estimates for OB stars, binary and multiple stars (including the σ Orionis system), and outflows in Luminous Blue Variables. An enlarged visitors program will begin in 2017 that will open many opportunities for new programs in high angular resolution astronomy.

Measurement method for roll angular displacement with a high resolution by using diffraction gratings and a heterodyne interferometer

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

Tang, Shanzhi, E-mail: shanzhit@gmail.com; School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049; Wang, Zhao

The roll angle measurement is difficult to be achieved directly using a typical commercial interferometer due to its low sensitivity in axial direction, where the axial direction is orthogonal to the plane of the roll angular displacement. A roll angle measurement method combined diffraction gratings with a laser heterodyne interferometer is discussed in this paper. The diffraction grating placed in the plane of a roll angular displacement and the interferometer arranged in the plane's orthogonal direction, constitute the measurement pattern for the roll angle with high resolution. The roll angular displacement, considered as the linear, can be tested precisely whenmore » the corresponding angle is very small. Using the proposed method, the angle roll measurement obtains the high resolution of 0.002{sup ″}. Experiment has proved its feasibility and practicability.« less

Estimation of physiological sub-millimeter displacement with CW Doppler radar.

PubMed

Jia Xu; Xiaomeng Gao; Padasdao, Bryson E; Boric-Lubecke, Olga

2015-01-01

Doppler radar physiological sensing has been studied for non-contact detection of vital signs including respiratory and heartbeat rates. This paper presents the first micrometer resolution Wi-Fi band Doppler radar for sub-millimeter physiological displacement measurement. A continuous-wave Doppler radar working at 2.4GHz is used for the measurement. It is intended for estimating small displacements on the body surface resulting from physiological activity. A mechanical mover was used as target, and programmed to conduct sinusoidal motions to simulate pulse motions. Measured displacements were compared with a reference system, which indicates a superior performance in accuracy for having absolute errors less than 10μm, and relative errors below 4%. It indicates the feasibility of highly accurate non-contact monitoring of physiological movements using Doppler radar.

High resolution phoswich gamma-ray imager utilizing monolithic MPPC arrays with submillimeter pixelized crystals

NASA Astrophysics Data System (ADS)

Kato, T.; Kataoka, J.; Nakamori, T.; Kishimoto, A.; Yamamoto, S.; Sato, K.; Ishikawa, Y.; Yamamura, K.; Kawabata, N.; Ikeda, H.; Kamada, K.

2013-05-01

We report the development of a high spatial resolution tweezers-type coincidence gamma-ray camera for medical imaging. This application consists of large-area monolithic Multi-Pixel Photon Counters (MPPCs) and submillimeter pixelized scintillator matrices. The MPPC array has 4 × 4 channels with a three-side buttable, very compact package. For typical operational gain of 7.5 × 105 at + 20 °C, gain fluctuation over the entire MPPC device is only ± 5.6%, and dark count rates (as measured at the 1 p.e. level) amount to <= 400 kcps per channel. We selected Ce-doped (Lu,Y)2(SiO4)O (Ce:LYSO) and a brand-new scintillator, Ce-doped Gd3Al2Ga3O12 (Ce:GAGG) due to their high light yield and density. To improve the spatial resolution, these scintillators were fabricated into 15 × 15 matrices of 0.5 × 0.5 mm2 pixels. The Ce:LYSO and Ce:GAGG scintillator matrices were assembled into phosphor sandwich (phoswich) detectors, and then coupled to the MPPC array along with an acrylic light guide measuring 1 mm thick, and with summing operational amplifiers that compile the signals into four position-encoded analog outputs being used for signal readout. Spatial resolution of 1.1 mm was achieved with the coincidence imaging system using a 22Na point source. These results suggest that the gamma-ray imagers offer excellent potential for applications in high spatial medical imaging.

High-resolution laser spectroscopy between 0.9 and 14.3 THz in a supersonic beam: Rydberg-Rydberg transitions of atomic Xe at intermediate n values

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

Haase, Christa; Agner, Josef A.; Merkt, Frederic

2013-06-28

A laser-based, pulsed, narrow-band source of submillimeter-wave radiation has been developed that is continuously tunable from 0.1 THz to 14.3 THz. The source is based on difference-frequency mixing in the nonlinear crystal trans-4{sup Prime }-(dimethylamino)-N-methyl-4-stilbazolium tosylate. By varying the pulse length, the bandwidth of the submillimeter-wave radiation can be adjusted between 85 MHz and 2.8 MHz. This new radiation source has been integrated in a vacuum-ultraviolet-submillimeter-ware double-resonance spectrometer, with which low-frequency transitions of atoms and molecules in supersonic beams can be detected mass-selectively by photoionization and time-of-flight mass spectrometry. The properties of the radiation source and spectrometer are demonstrated inmore » a study of 33f Leftwards-Arrow nd Rydberg-Rydberg transitions in Xe with n in the range 16-31. The frequency calibration of the submillimeter-wave radiation was performed with an accuracy of 2.8 MHz. The narrowest lines observed experimentally have a full-width at half-maximum of {approx}3 MHz, which is sufficient to fully resolve the hyperfine structure of the Rydberg-Rydberg transitions of {sup 129}Xe and {sup 131}Xe. A total of 72 transitions were measured in the range between 0.937 THz and 14.245 THz and their frequencies are compared with frequencies calculated by multichannel quantum defect theory.« less

X-Ray Diffractive Optics

NASA Technical Reports Server (NTRS)

Dennis, Brian; Li, Mary; Skinner, Gerald

2013-01-01

X-ray optics were fabricated with the capability of imaging solar x-ray sources with better than 0.1 arcsecond angular resolution, over an order of magnitude finer than is currently possible. Such images would provide a new window into the little-understood energy release and particle acceleration regions in solar flares. They constitute one of the most promising ways to probe these regions in the solar atmosphere with the sensitivity and angular resolution needed to better understand the physical processes involved. A circular slit structure with widths as fine as 0.85 micron etched in a silicon wafer 8 microns thick forms a phase zone plate version of a Fresnel lens capable of focusing approx. =.6 keV x-rays. The focal length of the 3-cm diameter lenses is 100 microns, and the angular resolution capability is better than 0.1 arcsecond. Such phase zone plates were fabricated in Goddard fs Detector Development Lab. (DDL) and tested at the Goddard 600-microns x-ray test facility. The test data verified that the desired angular resolution and throughput efficiency were achieved.

Effects of inlet boundary conditions, on the computed flow in the Turbine-99 draft tube, using OpenFOAM and CFX

NASA Astrophysics Data System (ADS)

Nilsson, H.; Cervantes, M. J.

2012-11-01

The flow in the Turbine-99 Kaplan draft tube was thoroughly investigated at three workshops (1999, 2001, 2005), which aimed at determining the state of the art of draft tube simulations. The flow is challenging due to the different flow phenomena appearing simultaneously such as unsteadiness, separation, swirl, turbulence, and a strong adverse pressure gradient. The geometry and the experimentally determined inlet boundary conditions were provided to the Turbine-99 workshop participants. At the final workshop, angular resolved inlet velocity boundary conditions were provided. The rotating non-axi-symmetry of the inlet flow due to the runner blades was thus included. The effect of the rotating angular resolution was however not fully investigated at that workshop. The first purpose of this work is to further investigate this effect. Several different inlet boundary conditions are applied - the angular resolved experimental data distributed at the Turbine-99 workshop, the angular resolved results of a runner simulation with interpolated values using different resolution in the tangential and radial directions, and an axi-symmetric variant of the same numerical data. The second purpose of this work is to compare the results from the OpenFOAM and CFX CFD codes, using as similar settings as possible. The present results suggest that the experimental angular inlet boundary conditions proposed to the workshop are not adequate to simulate accurately the flow in the T-99 draft tube. The reason for this is that the experimental phase-averaged data has some important differences compared to the previously measured time-averaged data. Using the interpolated data from the runner simulation as inlet boundary condition however gives good results as long as the resolution of that data is sufficient. It is shown that the difference between the results using the angular-resolved and the corresponding symmetric inlet data is very small, suggesting that the importance of the angular resolution is small. The results from OpenFOAM and CFX are very similar as long as the inlet data resolution is fine enough. CFX seems to be more sensitive to that resolution.

Cloud Structure of Galactic OB Cluster-forming Regions from Combining Ground- and Space-based Bolometric Observations

NASA Astrophysics Data System (ADS)

Lin, Yuxin; Liu, Hauyu Baobab; Li, Di; Zhang, Zhi-Yu; Ginsburg, Adam; Pineda, Jaime E.; Qian, Lei; Galván-Madrid, Roberto; McLeod, Anna Faye; Rosolowsky, Erik; Dale, James E.; Immer, Katharina; Koch, Eric; Longmore, Steve; Walker, Daniel; Testi, Leonardo

2016-09-01

We have developed an iterative procedure to systematically combine the millimeter and submillimeter images of OB cluster-forming molecular clouds, which were taken by ground-based (CSO, JCMT, APEX, and IRAM-30 m) and space telescopes (Herschel and Planck). For the seven luminous (L\\gt {10}6 L ⊙) Galactic OB cluster-forming molecular clouds selected for our analyses, namely W49A, W43-Main, W43-South, W33, G10.6-0.4, G10.2-0.3, and G10.3-0.1, we have performed single-component, modified blackbody fits to each pixel of the combined (sub)millimeter images, and the Herschel PACS and SPIRE images at shorter wavelengths. The ˜10″ resolution dust column density and temperature maps of these sources revealed dramatically different morphologies, indicating very different modes of OB cluster-formation, or parent molecular cloud structures in different evolutionary stages. The molecular clouds W49A, W33, and G10.6-0.4 show centrally concentrated massive molecular clumps that are connected with approximately radially orientated molecular gas filaments. The W43-Main and W43-South molecular cloud complexes, which are located at the intersection of the Galactic near 3 kpc (or Scutum) arm and the Galactic bar, show a widely scattered distribution of dense molecular clumps/cores over the observed ˜10 pc spatial scale. The relatively evolved sources G10.2-0.3 and G10.3-0.1 appear to be affected by stellar feedback, and show a complicated cloud morphology embedded with abundant dense molecular clumps/cores. We find that with the high angular resolution we achieved, our visual classification of cloud morphology can be linked to the systematically derived statistical quantities (I.e., the enclosed mass profile, the column density probability distribution function (N-PDF), the two-point correlation function of column density, and the probability distribution function of clump/core separations). In particular, the massive molecular gas clumps located at the center of G10.6-0.4 and W49A, which contribute to a considerable fraction of their overall cloud masses, may be special OB cluster-forming environments as a direct consequence of global cloud collapse. These centralized massive molecular gas clumps also uniquely occupy much higher column densities than what is determined by the overall fit of power-law N-PDF. We have made efforts to archive the derived statistical quantities of individual target sources, to permit comparisons with theoretical frameworks, numerical simulations, and other observations in the future.

Electromagnetic microscope compared with a conventional pulsed eddy-current probe

NASA Astrophysics Data System (ADS)

Podney, Walter N.

1998-03-01

A superconductive probe presently can detect a crack at a rivet hole that is two to three times smaller than the smallest crack detectable by a conventional probe. As the technology matures and noise resolution approaches a limit set by SQUIDS, approximately 1 fH, it will enable detecting submillimeter cracks down to approximately 15 mm.

Multi-pinhole SPECT Imaging with Silicon Strip Detectors

PubMed Central

Peterson, Todd E.; Shokouhi, Sepideh; Furenlid, Lars R.; Wilson, Donald W.

2010-01-01

Silicon double-sided strip detectors offer outstanding instrinsic spatial resolution with reasonable detection efficiency for iodine-125 emissions. This spatial resolution allows for multiple-pinhole imaging at low magnification, minimizing the problem of multiplexing. We have conducted imaging studies using a prototype system that utilizes a detector of 300-micrometer thickness and 50-micrometer strip pitch together with a 23-pinhole collimator. These studies include an investigation of the synthetic-collimator imaging approach, which combines multiple-pinhole projections acquired at multiple magnifications to obtain tomographic reconstructions from limited-angle data using the ML-EM algorithm. Sub-millimeter spatial resolution was obtained, demonstrating the basic validity of this approach. PMID:20953300

Josephson frequency meter for millimeter and submillimeter wavelengths

NASA Technical Reports Server (NTRS)

Anischenko, S. E.; Larkin, S. Y.; Chaikovsky, V. I.; Kabayev, P. V.; Kamyshin, V. V.

1995-01-01

Frequency measurements of electromagnetic oscillations of millimeter and submillimeter wavebands with frequency growth due to a number of reasons become more and more difficult. First, these frequencies are considered to be cutoffs for semiconductor converting devices and one has to use optical measurement methods instead of traditional ones with frequency transfer. Second, resonance measurement methods are characterized by using relatively narrow bands and optical ones are limited in frequency and time resolution due to the limited range and velocity of movement of their mechanical elements as well as the efficiency of these optical techniques decrease with the increase of wavelength due to diffraction losses. That requires a priori information on the radiation frequency band of the source involved. Method of measuring frequency of harmonic microwave signals in millimeter and submillimeter wavebands based on the ac Josephson effect in superconducting contacts is devoid of all the above drawbacks. This approach offers a number of major advantages over the more traditional measurement methods, that is one based on frequency conversion, resonance and interferometric techniques. It can be characterized by high potential accuracy, wide range of frequencies measured, prompt measurement and the opportunity to obtain a panoramic display of the results as well as full automation of the measuring process.

An Imperfectly Passive Nature: Bright Submillimeter Emission from Dust-obscured Star Formation in the z = 3.717 “Passive” System, ZF 20115

NASA Astrophysics Data System (ADS)

Simpson, J. M.; Smail, Ian; Wang, Wei-Hao; Riechers, D.; Dunlop, J. S.; Ao, Y.; Bourne, N.; Bunker, A.; Chapman, S. C.; Chen, Chian-Chou; Dannerbauer, H.; Geach, J. E.; Goto, T.; Harrison, C. M.; Hwang, H. S.; Ivison, R. J.; Kodama, Tadayuki; Lee, C.-H.; Lee, H.-M.; Lee, M.; Lim, C.-F.; Michałowski, M. J.; Rosario, D. J.; Shim, H.; Shu, X. W.; Swinbank, A. M.; Tee, W.-L.; Toba, Y.; Valiante, E.; Wang, Junxian; Zheng, X. Z.

2017-07-01

The identification of high-redshift, massive galaxies with old stellar populations may pose challenges to some models of galaxy formation. However, to securely classify a galaxy as quiescent, it is necessary to exclude significant ongoing star formation, something that can be challenging to achieve at high redshifts. In this Letter, we analyze deep ALMA/870 μm and SCUBA-2/450 μm imaging of the claimed “post-starburst” galaxy ZF 20115 at z = 3.717 that exhibits a strong Balmer break and absorption lines. The rest-frame far-infrared imaging identifies a luminous starburst 0.″4 ± 0.″1 (˜3 kpc in projection) from the position of the ultraviolet/optical emission and is consistent with lying at the redshift of ZF 20115. The star-forming component, with an obscured star formation rate of {100}-70+15 {M}⊙ {{yr}}-1, is undetected in the rest-frame ultraviolet but contributes significantly to the lower angular resolution photometry at rest-frame wavelengths ≳3500 Å. This contribution from the obscured starburst, especially in the Spitzer/IRAC wavebands, significantly complicates the determination of a reliable stellar mass for the ZF 20015 system, and we conclude that this source does not pose a challenge to current models of galaxy formation. The multi-wavelength observations of ZF 20115 unveil a complex system with an intricate and spatially varying star formation history. ZF 20115 demonstrates that understanding high-redshift obscured starbursts will only be possible with multi-wavelength studies that include high-resolution observations, available with the James Webb Space Telescope, at mid-infrared wavelengths.

ABSENCE OF SIGNIFICANT COOL DISKS IN YOUNG STELLAR OBJECTS EXHIBITING REPETITIVE OPTICAL OUTBURSTS

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

Liu, Hauyu Baobab; Hirano, Naomi; Takami, Michihiro

2016-01-10

We report Submillimeter Array 1.3 mm high angular resolution observations toward the four EXor-type outbursting young stellar objects VY Tau, V1118 Ori, V1143 Ori, and NY Ori. The data mostly show low dust masses M{sub dust} in the associated circumstellar disks. Among the sources, NY Ori possesses a relatively massive disk with M{sub dust} ∼ 9 × 10{sup −4}M{sub ⊙}. V1118 Ori has a marginal detection equivalent to M{sub dust} ∼ 6 × 10{sup −5}M{sub ⊙}. V1143 Ori has a non-detection also equivalent to M{sub dust} < 6 × 10{sup −5}M{sub ⊙}. For the nearest source, VY Tau, we get a surprising non-detection that provides a stringent upper limit M{sub dust} < 6 × 10{sup −6}M{sub ⊙}.more » We interpret our findings as suggesting that the gas and dust reservoirs that feed the short-duration, repetitive optical outbursts seen in some EXors may be limited to the small-scale, innermost region of their circumstellar disks. This hot dust may have escaped our detection limits. Follow-up, more sensitive millimeter observations are needed to improve our understanding of the triggering mechanisms of EXor-type outbursts.« less

Building Blocks of Dust and Large Organic Molecules: a Coordinated Laboratory and Astronomical Study of AGB Stars

NASA Astrophysics Data System (ADS)

McCarthy, Michael C.; Gottlieb, Carl A.; Cernicharo, Jose

2017-06-01

The increased sensitivity and angular resolution of high-altitude ground-based interferometers in the sub-millimeter band has enabled the physics and chemistry of carbon- and oxygen-rich evolved stars to be re-examined at an unprecedented level of detail. Observations of rotational lines in the inner envelope - the region within a few stellar radii of the central star where the molecular seeds of dust are formed - allows one to critically assess models of dust growth. Interferometric observations of the outer envelope provide stringent tests of neutral and ionized molecule formation. All of the astronomical studies are crucially dependent on precise laboratory measurements of the rotational spectra of new species and of vibrationally excited levels of known molecules and their rare isotopic species. By means of a closely coordinated laboratory and astronomical program, a number of exotic species including the disilicon carbide SiCSi, titanium oxides TiO and TiO_2, and carbon chain anions ranging from CN^- to C_8H^- have recently been observed in evolved stars. This talk will provide overview of these findings, and how they impact current models of the ``chemical laboratories'' of evolved stars. Ongoing laboratory studies of small silicon-bearing molecules such as H_2SiO_2 and vibrationally excited SiC_2 will be highlighted.

A Cavity of Large Grains in the Disk around the Group II Herbig Ae/Be Star HD 142666

NASA Astrophysics Data System (ADS)

Rubinstein, A. E.; Macías, E.; Espaillat, C. C.; Zhang, K.; Calvet, N.; Robinson, C.

2018-06-01

Herbig Ae/Be (HAeBe) stars have been classified into Group I or Group II, and were initially thought to be flared and flat disks, respectively. Several Group I sources have been shown to have large gaps, suggesting ongoing planet formation, while no large gaps have been found in the disks of Group II sources. We analyzed the disk around the Group II source, HD 142666, using irradiated accretion disk modeling of the broadband spectral energy distribution along with the 1.3 mm spatial brightness distribution traced by Atacama Large Millimeter and Submillimeter Array (ALMA) observations. Our model reproduces the available data, predicting a high degree of dust settling in the disk, which is consistent with the Group II classification of HD 142666. In addition, the observed visibilities and synthesized image could only be reproduced when including a depletion of large grains out to ∼ 16 au in our disk model, although the ALMA observations did not have enough angular resolution to fully resolve the inner parts of the disk. These results may suggest that some disks around Group II HAeBe stars have cavities of large grains as well. Further ALMA observations of Group II sources are needed to discern how commonly cavities occur in this class of objects, as well as to reveal their possible origins.

Report on the ESO Workshop ''Astronomy at High Angular Resolution''

NASA Astrophysics Data System (ADS)

Boffin, H.; Schmidtobreick, L.; Hussain, G.; Berger, J.-Ph.

2015-03-01

A workshop took place in Brussels in 2000 on astrotomography, a generic term for indirect mapping techniques that can be applied to a huge variety of astrophysical systems, ranging from planets, single stars and binaries to active galactic nuclei. It appeared to be timely to revisit the topic given the many past, recent and forthcoming improvements in telescopes and instrumentation. We therefore decided to repeat the astrotomography workshop, but to put it into the much broader context of high angular resolution astronomy. Many techniques, from lucky and speckle imaging, adaptive optics to interferometry, are now widely employed to achieve high angular resolution and they have led to an amazing number of new discoveries. A summary of the workshop themes is presented.

Lunar Occultations as a Simple Tool for High Angular Resolution Astronomy

NASA Astrophysics Data System (ADS)

Richichi, Andrea

1999-08-01

At the turn of the millennium, modern astronomy is seeing the creation of several new impressive facilities. Among them, large telescopes and long baseline interferometers are beginning to break the limitations imposed by seeing and to push our angular resolution limits at the level of the millisecond of arc. In this race for the state-of-the-art in angular resolution, one should not forget the considerable aid which has been provided for some decades by the more humble technique of lunar occultations. Although burdened with obvious limitations in the choice of the sources, this latter method has two main features that can make it attractive for the modern amateur astronomer: it is simple, and can be implemented also at realtively small telescopes.

k-space and q-space: combining ultra-high spatial and angular resolution in diffusion imaging using ZOOPPA at 7 T.

PubMed

Heidemann, Robin M; Anwander, Alfred; Feiweier, Thorsten; Knösche, Thomas R; Turner, Robert

2012-04-02

There is ongoing debate whether using a higher spatial resolution (sampling k-space) or a higher angular resolution (sampling q-space angles) is the better way to improve diffusion MRI (dMRI) based tractography results in living humans. In both cases, the limiting factor is the signal-to-noise ratio (SNR), due to the restricted acquisition time. One possible way to increase the spatial resolution without sacrificing either SNR or angular resolution is to move to a higher magnetic field strength. Nevertheless, dMRI has not been the preferred application for ultra-high field strength (7 T). This is because single-shot echo-planar imaging (EPI) has been the method of choice for human in vivo dMRI. EPI faces several challenges related to the use of a high resolution at high field strength, for example, distortions and image blurring. These problems can easily compromise the expected SNR gain with field strength. In the current study, we introduce an adapted EPI sequence in conjunction with a combination of ZOOmed imaging and Partially Parallel Acquisition (ZOOPPA). We demonstrate that the method can produce high quality diffusion-weighted images with high spatial and angular resolution at 7 T. We provide examples of in vivo human dMRI with isotropic resolutions of 1 mm and 800 μm. These data sets are particularly suitable for resolving complex and subtle fiber architectures, including fiber crossings in the white matter, anisotropy in the cortex and fibers entering the cortex. Copyright © 2011 Elsevier Inc. All rights reserved.

Millimeter and Submillimeter Survey of the R Coronae Australis Region

NASA Astrophysics Data System (ADS)

Groppi, Christopher E.; Kulesa, Craig; Walker, Christopher; Martin, Christopher L.

2004-09-01

Using a combination of data from the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO), the Arizona Radio Observatory Kitt Peak 12 m telescope, and the Arizona Radio Observatory 10 m Heinrich Hertz Telescope, we have studied the most active part of the R CrA molecular cloud in multiple transitions of carbon monoxide, HCO+, and 870 μm continuum emission. Since R CrA is nearby (130 pc), we are able to obtain physical spatial resolution as high as 0.01 pc over an area of 0.16 pc2, with velocity resolution finer than 1 km s-1. Mass estimates of the protostar driving the millimeter-wave emission derived from HCO+, dust continuum emission, and kinematic techniques point to a young, deeply embedded protostar of ~0.5-0.75 Msolar, with a gaseous envelope of similar mass. A molecular outflow is driven by this source that also contains at least 0.8 Msolar of molecular gas with ~0.5 Lsolar of mechanical luminosity. HCO+ lines show the kinematic signature of infall motions, as well as bulk rotation. The source is most likely a Class 0 protostellar object not yet visible at near-IR wavelengths. With the combination of spatial and spectral resolution in our data set, we are able to disentangle the effects of infall, rotation, and outflow toward this young object.

A measurement of the cosmic microwave background from the high Chilean Andes

NASA Astrophysics Data System (ADS)

Miller, Amber Dawn

A measurement of the angular spectrum of the Cosmic Microwave Background (CMB) between l = 50 and l = 400 is described. Data were obtained using HEMT radiometers at 30 and 40 GHz with angular resolutions of ≈1 deg and ≈0.7 deg respectively and with SIS based receivers at 144 GHz with angular resolution of ≈0.2 deg. Observations were made from Cerro Toco in the Chilean altiplano at an altitude of 17,000 feet in the Northern Chilean Andes. We find that the angular spectrum rises from l = 50 to a peak at l ≈ 200 and falls off at higher angular scales. A peak in the angular spectrum with amplitude, deltaTl ≈ 85muK is thus located for the first time with a single instrument at l ≈ 200. In addition, we find that the detected anisotropy has the spectrum of the CMB. Cosmological implications of this result are discussed.

A goal-based angular adaptivity method for thermal radiation modelling in non grey media

NASA Astrophysics Data System (ADS)

Soucasse, Laurent; Dargaville, Steven; Buchan, Andrew G.; Pain, Christopher C.

2017-10-01

This paper investigates for the first time a goal-based angular adaptivity method for thermal radiation transport, suitable for non grey media when the radiation field is coupled with an unsteady flow field through an energy balance. Anisotropic angular adaptivity is achieved by using a Haar wavelet finite element expansion that forms a hierarchical angular basis with compact support and does not require any angular interpolation in space. The novelty of this work lies in (1) the definition of a target functional to compute the goal-based error measure equal to the radiative source term of the energy balance, which is the quantity of interest in the context of coupled flow-radiation calculations; (2) the use of different optimal angular resolutions for each absorption coefficient class, built from a global model of the radiative properties of the medium. The accuracy and efficiency of the goal-based angular adaptivity method is assessed in a coupled flow-radiation problem relevant for air pollution modelling in street canyons. Compared to a uniform Haar wavelet expansion, the adapted resolution uses 5 times fewer angular basis functions and is 6.5 times quicker, given the same accuracy in the radiative source term.

The NGC 1614 interacting galaxy. Molecular gas feeding a "ring of fire"

NASA Astrophysics Data System (ADS)

König, S.; Aalto, S.; Muller, S.; Beswick, R. J.; Gallagher, J. S.

2013-05-01

Minor mergers frequently occur between giant and gas-rich low-mass galaxies and can provide significant amounts of interstellar matter to refuel star formation and power active galactic nuclei (AGN) in the giant systems. Major starbursts and/or AGN result when fresh gas is transported and compressed in the central regions of the giant galaxy. This is the situation in the starburst minor merger NGC 1614, whose molecular medium we explore at half-arcsecond angular resolution through our observations of 12CO (2-1) emission using the Submillimeter Array (SMA). We compare our 12CO (2-1) maps with optical and Paα, Hubble Space Telescope and high angular resolution radio continuum images to study the relationships between dense molecular gas and the NGC 1614 starburst region. The most intense 12CO emission occurs in a partial ring with ~230 pc radius around the center of NGC 1614, with an extension to the northwest into the dust lane that contains diffuse molecular gas. We resolve ten giant molecular associations (GMAs) in the ring, which has an integrated molecular mass of ~8 × 108 M⊙. Our interferometric observations filter out a large part of the 12CO (1-0) emission mapped at shorter spacings, indicating that most of the molecular gas is diffuse and that GMAs only exist near and within the circumnuclear ring. The molecular ring is uneven with most of the mass on the western side, which also contains GMAs extending into a pronounced tidal dust lane. The spatial and kinematic patterns in our data suggest that the northwest extension of the ring is a cosmic umbilical cord that is feeding molecular gas associated with the dust lane and tidal debris into the nuclear ring, which contains the bulk of the starburst activity. The astrophysical process for producing a ring structure for the final resting place of accreted gas in NGC 1614 is not fully understood, but the presence of numerous GMAs suggests an orbit-crowding or resonance phenomenon. There is some evidence that star formation is progressing radially outward within the ring, indicating that a self-triggering mechanism may also affect star formation processes. The net result of this merger therefore very likely increases the central concentration of stellar mass in the NGC 1614 remnant giant system.

Atmospheric absorption measurements in the region of 1 mm wavelength.

NASA Technical Reports Server (NTRS)

Emery, R.

1972-01-01

A Froome-type plasma-metal-junction device (1962) was used in high-resolution radiation transmission measurements in the atmosphere at wavelengths from 0.5 to 3.0 mm. The experimental and theoretical results for water vapor absorption lines in two submillimeter wavelength windows were compared, showing that this technique provided a much higher wavelength accuracy than more conventional optical-type spectroscopy.

Probing Galaxy Formation and Evolution with Space Born Sub-Millimeter Telescopes

NASA Technical Reports Server (NTRS)

Dwek, Eli; Arendt, Richard G.; Moseley, Harvey; Benford, Dominic; Shafer, Richard; Mather, John; Oegerle, William (Technical Monitor)

2002-01-01

A major unresolved question in cosmology is how the complex system of galaxies we see in the present universe evolved from an almost perfectly smooth beginning. Multiwavelength observations of galaxies have revealed that a significant fraction of their UV-visible starlight is absorbed and reradiated by dust at infrared JR) and submillimeter wavelengths. The cumulative IR-submm. emission from galaxies since the epoch of recombination, the cosmic IR background, has recently been recorded by the COBE satellite. The COBE observations in combination with recent submm surveys conducted with the SCUBA on the 15 m JCMT have shown that most of the radiation from star formation that has taken place in the early stages of galaxy evolution is reradiated by dust at submm wavelengths. Therefore, submm telescopes offer a unique probe of the early stages of galaxy formation and evolution. This talk will: (1) consider the impact of telescope diameter on the depth of the survey (what redshift can be probed) at different wavelengths; (2) discuss the relative scientific merits of high-resolution narrow-field surveys versus lower resolution deep surveys; and (3) show how both strategies offer complementary information crucial to our understanding of the structure and evolution of galaxies in the universe.

Restoring the spatial resolution of refocus images on 4D light field

NASA Astrophysics Data System (ADS)

Lim, JaeGuyn; Park, ByungKwan; Kang, JooYoung; Lee, SeongDeok

2010-01-01

This paper presents the method for generating a refocus image with restored spatial resolution on a plenoptic camera, which functions controlling the depth of field after capturing one image unlike a traditional camera. It is generally known that the camera captures 4D light field (angular and spatial information of light) within a limited 2D sensor and results in reducing 2D spatial resolution due to inevitable 2D angular data. That's the reason why a refocus image is composed of a low spatial resolution compared with 2D sensor. However, it has recently been known that angular data contain sub-pixel spatial information such that the spatial resolution of 4D light field can be increased. We exploit the fact for improving the spatial resolution of a refocus image. We have experimentally scrutinized that the spatial information is different according to the depth of objects from a camera. So, from the selection of refocused regions (corresponding depth), we use corresponding pre-estimated sub-pixel spatial information for reconstructing spatial resolution of the regions. Meanwhile other regions maintain out-of-focus. Our experimental results show the effect of this proposed method compared to existing method.

Rapidly-Indexing Incremental-Angle Encoder

NASA Technical Reports Server (NTRS)

Christon, Philip R.; Meyer, Wallace W.

1989-01-01

Optoelectronic system measures relative angular position of shaft or other device to be turned, also measures absolute angular position after device turned through small angle. Relative angular position measured with fine resolution by optoelectronically counting finely- and uniformly-spaced light and dark areas on encoder disk as disk turns past position-sensing device. Also includes track containing coarsely- and nonuniformly-spaced light and dark areas, angular widths varying in proportion to absolute angular position. This second track provides gating and indexing signal.

Investigation of passive atmospheric sounding using millimeter and submillimeter wavelength channels

NASA Technical Reports Server (NTRS)

Gasiewski, Albin J.; Kunkee, D. B.; Jackson, D. M.; Blackwell, W.; Sharpe, S.

1994-01-01

Progress by the Georgia Institute of Technology's Laboratory for Radio-science and Remote Sensing in developing techniques for passive microwave retrieval of water vapor profiles and cloud and precipitation parameters using millimeter and submillimeter wavelength channels is reviewed. Channels of particular interest are in the tropospheric transmission windows at 90, 166, 220, 340, and 410 GHz and centered around the water vapor lines at 183 and 325 GHz. Collectively, these channels have potential application in high-resolution precipitation mapping (e.g., from geosynchronous orbit), remote sensing of cloud and precipitation parameters, including cirrus ice mass, and improved retrieval of water vapor profiles. During the period from January 1, 1994 through June 30, 1994 research activities focussed on calibrating and interpreting data from the Millimeter-Wave Imaging Radiometer (MIR). The MIR was deployed on the NASA ER-2 during the Convective Atmospheric Moisture Experiment (CAMEX, September-October 1993) to obtain the first submillimeter-wave tropospheric imagery of convective precipitations. A 325-GHz radiometer consisted of a submillimeter-wave DSB receiver with three IF channels at +/- 1, 3, and 8.5 GHz, and approximately 14 dB DSB noise figure was successfully operated during these experiments. Activities supported under this grant include a study of the impact of local oscillator reflections from the MIR calibration loads, the development of optimal gain and offset filters for radiometric calibration, and the modeling and interpretation of the MIR 325-GHz data over both clear and cloudy atmospheres. In addition, polarimetric radiometer measurements and modeling for ocean surface and atmospheric cloud-ice studies_were supported.

Hierarchical imaging of the human knee

NASA Astrophysics Data System (ADS)

Schulz, Georg; Götz, Christian; Deyhle, Hans; Müller-Gerbl, Magdalena; Zanette, Irene; Zdora, Marie-Christine; Khimchenko, Anna; Thalmann, Peter; Rack, Alexander; Müller, Bert

2016-10-01

Among the clinically relevant imaging techniques, computed tomography (CT) reaches the best spatial resolution. Sub-millimeter voxel sizes are regularly obtained. For investigations on true micrometer level lab-based μCT has become gold standard. The aim of the present study is the hierarchical investigation of a human knee post mortem using hard X-ray μCT. After the visualization of the entire knee using a clinical CT with a spatial resolution on the sub-millimeter range, a hierarchical imaging study was performed using a laboratory μCT system nanotom m. Due to the size of the whole knee the pixel length could not be reduced below 65 μm. These first two data sets were directly compared after a rigid registration using a cross-correlation algorithm. The μCT data set allowed an investigation of the trabecular structures of the bones. The further reduction of the pixel length down to 25 μm could be achieved by removing the skin and soft tissues and measuring the tibia and the femur separately. True micrometer resolution could be achieved after extracting cylinders of several millimeters diameters from the two bones. The high resolution scans revealed the mineralized cartilage zone including the tide mark line as well as individual calcified chondrocytes. The visualization of soft tissues including cartilage, was arranged by X-ray grating interferometry (XGI) at ESRF and Diamond Light Source. Whereas the high-energy measurements at ESRF allowed the simultaneous visualization of soft and hard tissues, the low-energy results from Diamond Light Source made individual chondrocytes within the cartilage visual.

High-Resolution Submillimeter and Near-Infrared Studies of the Transition Disk around Sz 91

NASA Technical Reports Server (NTRS)

Tsukagoshi, Takashi; Momose, Munetake; Hashimoto, Jun; Kudo, Tomoyuki; Andrews, Sean; Saito, Masao; Kitamura, Yoshimi; Ohashi, Nagayoshi; Wilner, David; Kawabe, Ryohei;

CHARRON: Code for High Angular Resolution of Rotating Objects in Nature

NASA Astrophysics Data System (ADS)

Domiciano de Souza, A.; Zorec, J.; Vakili, F.

2012-12-01

Rotation is one of the fundamental physical parameters governing stellar physics and evolution. At the same time, spectrally resolved optical/IR long-baseline interferometry has proven to be an important observing tool to measure many physical effects linked to rotation, in particular, stellar flattening, gravity darkening, differential rotation. In order to interpret the high angular resolution observations from modern spectro-interferometers, such as VLTI/AMBER and VEGA/CHARA, we have developed an interferometry-oriented numerical model: CHARRON (Code for High Angular Resolution of Rotating Objects in Nature). We present here the characteristics of CHARRON, which is faster (≃q10-30 s per model) and thus more adapted to model-fitting than the first version of the code presented by Domiciano de Souza et al. (2002).

Angular difference feature extraction for urban scene classification using ZY-3 multi-angle high-resolution satellite imagery

NASA Astrophysics Data System (ADS)

Huang, Xin; Chen, Huijun; Gong, Jianya

2018-01-01

Spaceborne multi-angle images with a high-resolution are capable of simultaneously providing spatial details and three-dimensional (3D) information to support detailed and accurate classification of complex urban scenes. In recent years, satellite-derived digital surface models (DSMs) have been increasingly utilized to provide height information to complement spectral properties for urban classification. However, in such a way, the multi-angle information is not effectively exploited, which is mainly due to the errors and difficulties of the multi-view image matching and the inaccuracy of the generated DSM over complex and dense urban scenes. Therefore, it is still a challenging task to effectively exploit the available angular information from high-resolution multi-angle images. In this paper, we investigate the potential for classifying urban scenes based on local angular properties characterized from high-resolution ZY-3 multi-view images. Specifically, three categories of angular difference features (ADFs) are proposed to describe the angular information at three levels (i.e., pixel, feature, and label levels): (1) ADF-pixel: the angular information is directly extrapolated by pixel comparison between the multi-angle images; (2) ADF-feature: the angular differences are described in the feature domains by comparing the differences between the multi-angle spatial features (e.g., morphological attribute profiles (APs)). (3) ADF-label: label-level angular features are proposed based on a group of urban primitives (e.g., buildings and shadows), in order to describe the specific angular information related to the types of primitive classes. In addition, we utilize spatial-contextual information to refine the multi-level ADF features using superpixel segmentation, for the purpose of alleviating the effects of salt-and-pepper noise and representing the main angular characteristics within a local area. The experiments on ZY-3 multi-angle images confirm that the proposed ADF features can effectively improve the accuracy of urban scene classification, with a significant increase in overall accuracy (3.8-11.7%) compared to using the spectral bands alone. Furthermore, the results indicated the superiority of the proposed ADFs in distinguishing between the spectrally similar and complex man-made classes, including roads and various types of buildings (e.g., high buildings, urban villages, and residential apartments).

Complex organics in IRAS 4A revisited with ALMA and PdBI: Striking contrast between two neighbouring protostellar cores

NASA Astrophysics Data System (ADS)

López-Sepulcre, A.; Sakai, N.; Neri, R.; Imai, M.; Oya, Y.; Ceccarelli, C.; Higuchi, A. E.; Aikawa, Y.; Bottinelli, S.; Caux, E.; Hirota, T.; Kahane, C.; Lefloch, B.; Vastel, C.; Watanabe, Y.; Yamamoto, S.

2017-10-01

Context. Hot corinos are extremely rich in complex organic molecules (COMs). Accurate abundance measurements of COMs in such objects are crucial to constrain astrochemical models. In the particular case of close binary systems this can only be achieved through high angular resolution imaging. Aims: We aim to perform an interferometric study of multiple COMs in NGC 1333 IRAS 4A, which is a protostellar binary hosting hot corino activity, at an angular resolution that is sufficient to distinguish easily the emission from the two cores separated by 1.8''. Methods: We used the Atacama Large (sub-)Millimeter Array (ALMA) in its 1.2 mm band and the IRAM Plateau de Bure Interferometer (PdBI) at 2.7 mm to image, with an angular resolution of 0.5'' (120 au) and 1'' (235 au), respectively, the emission from 11 different organic molecules in IRAS 4A. This allowed us to clearly disentangle A1 and A2, the two protostellar cores. For the first time, we were able to derive the column densities and fractional abundances simultaneously for the two objects, allowing us to analyse the chemical differences between them. Results: Molecular emission from organic molecules is concentrated exclusively in A2, while A1 appears completely devoid of COMs or even simpler organic molecules, such as HNCO, even though A1 is the strongest continuum emitter. The protostellar core A2 displays typical hot corino abundances and its deconvolved size is 70 au. In contrast, the upper limits we placed on COM abundances for A1 are extremely low, lying about one order of magnitude below prestellar values. The difference in the amount of COMs present in A1 and A2 ranges between one and two orders of magnitude. Our results suggest that the optical depth of dust emission at these wavelengths is unlikely to be sufficiently high to completely hide a hot corino in A1 similar in size to that in A2. Thus, the significant contrast in molecular richness found between the two sources is most probably real. We estimate that the size of a hypothetical hot corino in A1 should be less than 12 au. Conclusions: Our results favour a scenario in which the protostar in A2 is either more massive and/or subject to a higher accretion rate than A1, as a result of inhomogeneous fragmentation of the parental molecular clump. This naturally explains the smaller current envelope mass in A2 with respect to A1 along with its molecular richness. The extremely low abundances of organic molecules in A1 with respect to those in A2 demonstrate that the dense inner regions of a young protostellar core lacking hot corino activity may be poorer in COMs than the outer protostellar envelope. The reduced datacube is 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/606/A121

Investigation of Passive Atmospheric Sounding Using Millimeter- and Submillimeter- Wavelength Channels

NASA Technical Reports Server (NTRS)

Gasiewski, Albin J.

1996-01-01

This report summarizes progress made during the period from July 1, 1994 through June 30, 1996 on the development of satellite-based observational techniques for high resolution imaging of precipitation and sounding of atmospheric ice and water vapor using passive microwave radiometers in the millimeter (MMW)- and submillimeter (SMMW)-wavelength. This is being achieved by radiative transfer modeling a millimeter and submillimeter wave frequencies and by the development and operation of an airborne millimeter wave imaging radiometer (MIR). The MIR has been used in both airborne and ground-based experiments. Its primary application is to provide calibrated radiometric imagery to verify MMW and SMMW radiative transfer models in clear air, cloud, and precipitation and to develop retrieval techniques using MMW and SMMW channels. The MIR imagery over convective storm cells has been used to illustrate the potentially useful cloud and water vapor sensing and storm-cell mapping capabilities of SMMW channels. The radiometric data has also been used to analyze radiative transfer model discrepancies caused by water vapor errors in radiosondes. The MMW and SMMW channels can be used to extend the altitude that water vapor sounding can be performed up into the lower stratosphere. Together, the use of both SMMW and MMW channels are expected to provide additional observational degrees of freedom related to cloud ice particle size.

Josephson frequency meter for millimeter and submillimeter wavelengths

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

Anischenko, S.E.; Larkin, S.Y.; Chaikovsky, V.I.

1994-12-31

Frequency measurements of electromagnetic oscillations of millimeter and submillimeter wavebands with frequency growth due to a number of reasons become more and more difficult. First, these frequencies are considered to be cutoff for semiconductor converting devices and one has to use optical measurement methods instead of traditional ones with frequency transfer. Second, resonance measurement methods are characterized by using relatively narrow bands and optical ones are limited in frequency and time resolution due to the limited range and velocity of movement of their mechanical elements as well as the efficiency of these optical techniques decreases with the increase of wavelengthmore » due to diffraction losses. That requires the apriori information on the radiation frequency band of the source involved. Method of measuring frequency of harmonic microwave signals in millimeter and submillimeter wavebands based on the ac Josephson effect in superconducting contacts is devoid of all the above drawbacks. This approach offers a number of major advantages over the more traditional measurement methods, that is the one based on frequency conversion, resonance and interferrometric techniques. It can be characterized by high potential accuracy, wide range of frequencies measured, prompt measurement and the opportunity to obtain panoramic display of the results as well as full automation of the measuring process.« less

Submillimeter Wave Astronomy Satellite (SWAS) Launch and Early Orbit Support Experiences

NASA Technical Reports Server (NTRS)

Kirschner, S.; Sedlak, J.; Challa, M.; Nicholson, A.; Sande, C.; Rohrbaugh, D.

1999-01-01

The Submillimeter Wave Astronomy Satellite (SWAS) was successfully launched on December 6, 1998 at 00:58 UTC. The two year mission is the fourth in the series of Small Explorer (SMEX) missions. SWAS is dedicated to the study of star formation and interstellar chemistry. SWAS was injected into a 635 km by 650 km orbit with an inclination of nearly 70 deg by an Orbital Sciences Corporation Pegasus XL launch vehicle. The Flight Dynamics attitude and navigation teams supported all phases of the early mission. This support included orbit determination, attitude determination, real-time monitoring, and sensor calibration. This paper reports the main results and lessons learned concerning navigation, support software, star tracker performance, magnetometer and gyroscope calibrations, and anomaly resolution. This includes information on spacecraft tip-off rates, first-day navigation problems, target acquisition anomalies, star tracker anomalies, and significant sensor improvements due to calibration efforts.

Hacking for astronomy: can 3D printers and open-hardware enable low-cost sub-/millimeter instrumentation?

NASA Astrophysics Data System (ADS)

Ferkinhoff, Carl

2014-07-01

There have been several exciting developments in the technologies commonly used n in the hardware hacking community. Advances in low cost additive-manufacturing processes (i.e. 3D-printers) and the development of openhardware projects, which have produced inexpensive and easily programmable micro-controllers and micro-computers (i.e. Arduino and Raspberry Pi) have opened a new door for individuals seeking to make their own devices. Here we describe the potential for these technologies to reduce costs in construction and development of submillimeter/millimeter astronomical instrumentation. Specifically we have begun a program to measure the optical properties of the custom plastics used in 3D-printers as well as the printer accuracy and resolution to assess the feasibility of directly printing sub- /millimeter transmissive optics. We will also discuss low cost designs for cryogenic temperature measurement and control utilizing Arduino and Raspberry Pi.

Aerosol Retrieval from Multiangle Multispectral Photopolarimetric Measurements: Importance of Spectral Range and Angular Resolution

NASA Technical Reports Server (NTRS)

Wu, L.; Hasekamp, O.; Van Diedenhoven, B.; Cairns, B.

2015-01-01

We investigated the importance of spectral range and angular resolution for aerosol retrieval from multiangle photopolarimetric measurements over land. For this purpose, we use an extensive set of simulated measurements for different spectral ranges and angular resolutions and subsets of real measurements of the airborne Research Scanning Polarimeter (RSP) carried out during the PODEX and SEAC4RS campaigns over the continental USA. Aerosol retrievals performed from RSP measurements show good agreement with ground-based AERONET measurements for aerosol optical depth (AOD), single scattering albedo (SSA) and refractive index. Furthermore, we found that inclusion of shortwave infrared bands (1590 and/or 2250 nm) significantly improves the retrieval of AOD, SSA and coarse mode microphysical properties. However, accuracies of the retrieved aerosol properties do not improve significantly when more than five viewing angles are used in the retrieval.

An Outflow-shaped Magnetic Field Toward the Class 0 Protostellar Source Serpens SMM1

NASA Astrophysics Data System (ADS)

Hull, Charles; Girart, Josep M.; Tychoniec, Lukasz; Rao, Ramprasad; Cortés, Paulo; Pokhrel, Riwaj; Zhang, Qizhou; Houde, Martin; Dunham, Michael; Kristensen, Lars; Lai, Shih-Ping; Li, Zhi-Yun; Plambeck, Richard

2018-01-01

The results from the polarization system at the Atacama Large Millimeter/submillimeter Array (ALMA) have begun both to expand and to confound our understanding of the role of the magnetic field in low-mass star formation. Here we show the highest resolution and highest sensitivity polarization images made to date toward the very young, intermediate-mass Class 0 protostellar source Serpens SMM1, the brightest source in the Serpens Main star-forming region. These ALMA observations achieve ~140 AU resolution, allowing us to probe dust polarization—and thus magnetic field orientation—in the innermost regions surrounding the protostar. By complementing these observations with polarization observations from the Submillimeter Array (SMA) and archival data from the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and the James Clerk Maxwell Telescopes (JCMT), we can compare the magnetic field orientations at different spatial scales. We find major changes in the magnetic field orientation between large (~0.1 pc) scales—where the magnetic field is oriented E–W, perpendicular to the major axis of the dusty filament where SMM1 is embedded—and the intermediate and small scales probed by CARMA (~1000 au resolution), the SMA (~350 au resolution), and ALMA. The ALMA maps reveal that the redshifted lobe of the bipolar outflow is clearly shaping the magnetic field in SMM1 on the southeast side of the source. High-spatial-resolution continuum and spectral-line observations also reveal a tight (~130 au) protobinary system in SMM1-b, the eastern component of which is launching an extremely high-velocity, one-sided jet visible in both CO(2-1) and SiO(5-4); however, that jet does not appear to be shaping the magnetic field. These observations show that with the sensitivity and resolution of ALMA, we can now begin to understand the role that feedback (e.g., from protostellar outflows) plays in shaping the magnetic field in very young, star-forming sources like SMM1.

Materials characterisation by angle-resolved scanning transmission electron microscopy.

PubMed

Müller-Caspary, Knut; Oppermann, Oliver; Grieb, Tim; Krause, Florian F; Rosenauer, Andreas; Schowalter, Marco; Mehrtens, Thorsten; Beyer, Andreas; Volz, Kerstin; Potapov, Pavel

2016-11-16

Solid-state properties such as strain or chemical composition often leave characteristic fingerprints in the angular dependence of electron scattering. Scanning transmission electron microscopy (STEM) is dedicated to probe scattered intensity with atomic resolution, but it drastically lacks angular resolution. Here we report both a setup to exploit the explicit angular dependence of scattered intensity and applications of angle-resolved STEM to semiconductor nanostructures. Our method is applied to measure nitrogen content and specimen thickness in a GaN x As 1-x layer independently at atomic resolution by evaluating two dedicated angular intervals. We demonstrate contrast formation due to strain and composition in a Si- based metal-oxide semiconductor field effect transistor (MOSFET) with Ge x Si 1-x stressors as a function of the angles used for imaging. To shed light on the validity of current theoretical approaches this data is compared with theory, namely the Rutherford approach and contemporary multislice simulations. Inconsistency is found for the Rutherford model in the whole angular range of 16-255 mrad. Contrary, the multislice simulations are applicable for angles larger than 35 mrad whereas a significant mismatch is observed at lower angles. This limitation of established simulations is discussed particularly on the basis of inelastic scattering.

Method for improving the angular resolution of a neutron scatter camera

DOEpatents

Mascarenhas, Nicholas; Marleau, Peter; Gerling, Mark; Cooper, Robert Lee; Mrowka, Stanley; Brennan, James S.

2012-12-25

An instrument that will directly image the fast fission neutrons from a special nuclear material source wherein the neutron detection efficiency is increased has been described. Instead of the previous technique that uses a time-of-flight (TOF) between 2 widely spaced fixed planes of neutron detectors to measure scatter neutron kinetic energy, we now use the recoil proton energy deposited in the second of the 2 scatter planes which can now be repositioned either much closer together or further apart. However, by doubling the separation distance between the 2 planes from 20 cm to a distance of 40 cm we improved the angular resolution of the detector from about 12.degree. to about 10.degree.. A further doubling of the separation distance to 80 cm provided an addition improvement in angular resolution of the detector to about 6.degree. without adding additional detectors or ancillary electronics. The distance between planes also may be dynamically changed using a suitable common technique such as a gear- or motor-drive to toggle between the various positions. The angular resolution of this new configuration, therefore, is increased at the expanse of detection sensitivity. However, the diminished sensitivity may be acceptable for those applications where the detector is able to interrogate a particular site for an extended period.

Spatiotemporal characteristics and vascular sources of neural-specific and -nonspecific fMRI signals at submillimeter columnar resolution

PubMed Central

Moon, Chan Hong; Fukuda, Mitsuhiro; Kim, Seong-Gi

2012-01-01

The neural specificity of hemodynamic-based functional magnetic resonance imaging (fMRI) signals are dependent on both the vascular regulation and the sensitivity of the applied fMRI technique to different types and sizes of blood vessels. In order to examine the specificity of MRI-detectable hemodynamic responses, submillimeter blood oxygenation-level dependent (BOLD) and cerebral blood volume (CBV) fMRI studies were performed in a well-established cat orientation column model at 9.4 Tesla. Neural-nonspecific and -specific signals were separated by comparing the fMRI responses of orthogonal orientation stimuli. The BOLD response was dominantly neural-nonspecific, mostly originating from pial and intracortical emerging veins, and thus was highly correlated with baseline blood volume. Uneven baseline CBV may displace or distort small functional domains in high-resolution BOLD maps. The CBV response in the parenchyma exhibited dual spatiotemporal characteristics, a fast and early neural-nonspecific response (with 4.3-s time constant) and a slightly slower and delayed neural-specific response (with 9.4-s time constant). The nonspecific CBV signal originates from early-responding arteries and arterioles, while the specific CBV response, which is not correlated with baseline blood volume, arises from late-responding microvessels including small pre-capillary arterioles and capillaries. Our data indicate that although the neural specificity of CBV fMRI signals is dependent on stimulation duration, high-resolution functional maps can be obtained from steady-state CBV studies. PMID:22960251

Angular width of the Cherenkov radiation with inclusion of multiple scattering

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

Zheng, Jian, E-mail: jzheng@ustc.edu.cn

2016-06-15

Visible Cherenkov radiation can offer a method of the measurement of the velocity of charged particles. The angular width of the radiation is important since it determines the resolution of the velocity measurement. In this article, the angular width of Cherenkov radiation with inclusion of multiple scattering is calculated through the path-integral method, and the analytical expressions are presented. The condition that multiple scattering processes dominate the angular distribution is obtained.

Formation, Detection and the Distribution of Complex Organic Molecules with the Atacama Large Millimeter/submillimeter Array (ALMA)

NASA Astrophysics Data System (ADS)

Remijan, Anthony John

2015-08-01

The formation and distribution of complex organic material in astronomical environments continues to be a focused research area in astrochemistry. For several decades now, emphasis has been placed on the millimeter/submillimeter regime of the radio spectrum for trying to detect new molecular species and to constrain the chemical formation route of complex molecules by comparing and contrasting their relative distributions towards varying astronomical environments. This effort has been extremely laborious as millimeter/submillimeter facilities have been only able to detect and map the distribution of the strongest transition(s) of the simplest organic molecules. Even then, these single transition "chemical maps" have been very low spatial resolution because early millimeter/submillimeter facilities did not have access to broadband spectral coverage or the imaging capabilities to truly ascertain the morphology of the molecular emission. In the era of ALMA, these limitations have been greatly lifted. Broadband spectral line surveys now hold the key to uncovering the full molecular complexity in astronomical environments. In addition, searches for complex organic material is no longer limited to investigating the strongest lines of the simplest molecules toward the strongest sources of emission in the Galaxy. ALMA is issuing a new era of exploration as the search for complex molecules will now be available to an increased suite of sources in the Galaxy and our understanding of the formation of this complex material will be greatly increased as a result. This presentation will highlight the current and future ALMA capabilities in the search for complex molecules towards astronomical environments, highlight the recent searches that ALMA scientists have conducted from the start of ALMA Early Science and provide the motivation for the next suite of astronomical searches to investigate our pre-biotic origins in the universe.

Model-based cartilage thickness measurement in the submillimeter range

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

Streekstra, G. J.; Strackee, S. D.; Maas, M.

2007-09-15

Current methods of image-based thickness measurement in thin sheet structures utilize second derivative zero crossings to locate the layer boundaries. It is generally acknowledged that the nonzero width of the point spread function (PSF) limits the accuracy of this measurement procedure. We propose a model-based method that strongly reduces PSF-induced bias by incorporating the PSF into the thickness estimation method. We estimated the bias in thickness measurements in simulated thin sheet images as obtained from second derivative zero crossings. To gain insight into the range of sheet thickness where our method is expected to yield improved results, sheet thickness wasmore » varied between 0.15 and 1.2 mm with an assumed PSF as present in the high-resolution modes of current computed tomography (CT) scanners [full width at half maximum (FWHM) 0.5-0.8 mm]. Our model-based method was evaluated in practice by measuring layer thickness from CT images of a phantom mimicking two parallel cartilage layers in an arthrography procedure. CT arthrography images of cadaver wrists were also evaluated, and thickness estimates were compared to those obtained from high-resolution anatomical sections that served as a reference. The thickness estimates from the simulated images reveal that the method based on second derivative zero crossings shows considerable bias for layers in the submillimeter range. This bias is negligible for sheet thickness larger than 1 mm, where the size of the sheet is more than twice the FWHM of the PSF but can be as large as 0.2 mm for a 0.5 mm sheet. The results of the phantom experiments show that the bias is effectively reduced by our method. The deviations from the true thickness, due to random fluctuations induced by quantum noise in the CT images, are of the order of 3% for a standard wrist imaging protocol. In the wrist the submillimeter thickness estimates from the CT arthrography images correspond within 10% to those estimated from the anatomical sections. We present a method that yields virtually unbiased thickness estimates of cartilage layers in the submillimeter range. The good agreement of thickness estimates from CT images with estimates from anatomical sections is promising for clinical application of the method in cartilage integrity staging of the wrist and the ankle.« less

HerMES: ALMA Imaging of Herschel-selected Dusty Star-forming Galaxies

NASA Astrophysics Data System (ADS)

Bussmann, R. S.; Riechers, D.; Fialkov, A.; Scudder, J.; Hayward, C. C.; Cowley, W. I.; Bock, J.; Calanog, J.; Chapman, S. C.; Cooray, A.; De Bernardis, F.; Farrah, D.; Fu, Hai; Gavazzi, R.; Hopwood, R.; Ivison, R. J.; Jarvis, M.; Lacey, C.; Loeb, A.; Oliver, S. J.; Pérez-Fournon, I.; Rigopoulou, D.; Roseboom, I. G.; Scott, Douglas; Smith, A. J.; Vieira, J. D.; Wang, L.; Wardlow, J.

2015-10-01

The Herschel Multi-tiered Extragalactic Survey (HerMES) has identified large numbers of dusty star-forming galaxies (DSFGs) over a wide range in redshift. A detailed understanding of these DSFGs is hampered by the limited spatial resolution of Herschel. We present 870 μm 0.″45 resolution imaging obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) of a sample of 29 HerMES DSFGs that have far-infrared (FIR) flux densities that lie between the brightest of sources found by Herschel and fainter DSFGs found via ground-based surveys in the submillimeter region. The ALMA imaging reveals that these DSFGs comprise a total of 62 sources (down to the 5σ point-source sensitivity limit in our ALMA sample; σ ≈ 0.2 {mJy}). Optical or near-infrared imaging indicates that 36 of the ALMA sources experience a significant flux boost from gravitational lensing (μ \\gt 1.1), but only six are strongly lensed and show multiple images. We introduce and make use of uvmcmcfit, a general-purpose and publicly available Markov chain Monte Carlo visibility-plane analysis tool to analyze the source properties. Combined with our previous work on brighter Herschel sources, the lens models presented here tentatively favor intrinsic number counts for DSFGs with a break near 8 {mJy} at 880 μ {{m}} and a steep fall-off at higher flux densities. Nearly 70% of the Herschel sources break down into multiple ALMA counterparts, consistent with previous research indicating that the multiplicity rate is high in bright sources discovered in single-dish submillimeter or FIR surveys. The ALMA counterparts to our Herschel targets are located significantly closer to each other than ALMA counterparts to sources found in the LABOCA ECDFS Submillimeter Survey. Theoretical models underpredict the excess number of sources with small separations seen in our ALMA sample. The high multiplicity rate and small projected separations between sources seen in our sample argue in favor of interactions and mergers plausibly driving both the prodigious emission from the brightest DSFGs as well as the sharp downturn above {S}880=8 {mJy}. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

High-resolution submillimeter and near-infrared studies of the transition disk around Sz 91

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

Tsukagoshi, Takashi; Momose, Munetake; Hashimoto, Jun

2014-03-10

To reveal the structures of a transition disk around a young stellar object in Lupus, Sz 91 , we have performed aperture synthesis 345 GHz continuum and CO(3-2) observations with the Submillimeter Array (∼1''-3'' resolution) and high-resolution imaging of polarized intensity at the K{sub s} -band using the HiCIAO instrument on the Subaru Telescope (0.''25 resolution). Our observations successfully resolved the inner and outer radii of the dust disk to be 65 and 170 AU, respectively, which indicates that Sz 91 is a transition disk source with one of the largest known inner holes. The model fitting analysis of themore » spectral energy distribution reveals an H{sub 2} mass of 2.4 × 10{sup –3} M {sub ☉} in the cold (T < 30 K) outer part at 65 AU 3 × 10{sup –9} M {sub ☉}) of hot (T ∼ 180 K) dust possibly remains inside the inner hole of the disk. The structure of the hot component could be interpreted as either an unresolved self-luminous companion body (not directly detected in our observations) or a narrow ring inside the inner hole. Significant CO(3-2) emission with a velocity gradient along the major axis of the dust disk is concentrated on the Sz 91 position, suggesting a rotating gas disk with a radius of 420 AU. The Sz 91 disk is possibly a rare disk in an evolutionary stage immediately after the formation of protoplanets because of the large inner hole and the lower disk mass than other transition disks studied thus far.« less

High-Resolution Submillimeter and Near-Infrared Studies of the Transition Disk Around Sz 91

NASA Technical Reports Server (NTRS)

Tsukagoshi, Takashi; Momose, Munetake; Abe, Lyu; Akiyama, Eiji; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph; Currie, Thayne; Egner, Sebastian E.; Goto, Miwa;

Full-sky, High-resolution Maps of Interstellar Dust

NASA Astrophysics Data System (ADS)

Meisner, Aaron Michael

We present full-sky, high-resolution maps of interstellar dust based on data from the Wide-field Infrared Survey Explorer (WISE) and Planck missions. We describe our custom processing of the entire WISE 12 micron All-Sky imaging data set, and present the resulting 15 arcsecond resolution, full-sky map of diffuse Galactic dust emission, free of compact sources and other contaminating artifacts. Our derived 12 micron dust map offers angular resolution far superior to that of all other existing full-sky, infrared dust emission maps, revealing a wealth of small-scale filamentary structure. We also apply the Finkbeiner et al. (1999) two-component thermal dust emission model to the Planck HFI maps. We derive full-sky 6.1 arcminute resolution maps of dust optical depth and temperature by fitting this two-component model to Planck 217-857 GHz along with DIRBE/IRAS 100 micron data. In doing so, we obtain the first ever full-sky 100-3000 GHz Planck-based thermal dust emission model, as well as a dust temperature correction with ~10 times enhanced angular resolution relative to DIRBE-based temperature maps. Analyzing the joint Planck/DIRBE dust spectrum, we show that two-component models provide a better fit to the 100-3000 GHz emission than do single-MBB models, though by a lesser margin than found by Finkbeiner et al. (1999) based on FIRAS and DIRBE. We find that, in diffuse sky regions, our two-component 100-217 GHz predictions are on average accurate to within 2.2%, while extrapolating the Planck Collaboration (2013) single-MBB model systematically underpredicts emission by 18.8% at 100 GHz, 12.6% at 143 GHz and 7.9% at 217 GHz. We calibrate our two-component optical depth to reddening, and compare with reddening estimates based on stellar spectra. We find the dominant systematic problems in our temperature/reddening maps to be zodiacal light on large angular scales and the cosmic infrared background anisotropy on small angular scales. Future work will focus on combining our WISE 12 micron dust map and Planck dust model to create a next-generation, full-sky dust extinction map with angular resolution several times better than Schlegel et al. (1998).

X-ray optics for the LAMAR facility, an overview. [Large Area Modular Array of Reflectors

NASA Technical Reports Server (NTRS)

Gorenstein, P.

1979-01-01

The paper surveys the Large Area Modular Array of Reflectors (LAMAR), the concept of which is based on meeting two major requirements in X-ray astronomy, large collecting area and moderately good or better angular resolution for avoiding source confusion and imaging source fields. It is shown that the LAMAR provides the same sensitivity and signal to noise in imaging as a single large telescope having the same area and angular resolution but is a great deal less costly to develop, construct, and integrate into a space mission. Attention is also given to the LAMAR modular nature which will allow for an evolutionary development from a modest size array on Spacelab to a Shuttle launched free flyer. Finally, consideration is given to manufacturing methods which show promise of making LAMAR meet the criteria of good angular resolution, relatively low cost, and capability for fast volume production.

Understanding deformation with high angular resolution electron backscatter diffraction (HR-EBSD)

NASA Astrophysics Data System (ADS)

Britton, T. B.; Hickey, J. L. R.

2018-01-01

High angular resolution electron backscatter diffraction (HR-EBSD) affords an increase in angular resolution, as compared to ‘conventional’ Hough transform based EBSD, of two orders of magnitude, enabling measurements of relative misorientations of 1 x 10-4 rads (~ 0.006°) and changes in (deviatoric) lattice strain with a precision of 1 x 10-4. This is achieved through direct comparison of two or more diffraction patterns using sophisticated cross-correlation based image analysis routines. Image shifts between zone axes in the two-correlated diffraction pattern are measured with sub-pixel precision and this realises the ability to measure changes in interplanar angles and lattice orientation with a high degree of sensitivity. These shifts are linked to strains and lattice rotations through simple geometry. In this manuscript, we outline the basis of the technique and two case studies that highlight its potential to tackle real materials science challenges, such as deformation patterning in polycrystalline alloys.

Scientific Benefit of Enlarging Gravitational Wave Detector Networks

NASA Astrophysics Data System (ADS)

Chu, Qi; Wen, Linqing; Blair, David

2012-06-01

Localising the sources of gravitational waves (GWs) in the sky is crucial to observing the electromagnetic counterparts of GW sources. The localisation capability is poor by a single GW detector yet can be improved by adding more detectors to the detector network. In this paper we review recent studies on scientific benefits of global detector networks and focus on their localisation capability. We employ Wen-Chen's formula to compare this merit of current and future detector networks for localising gravitational wave bursts. We find that the addition of a new detector located in Japan, or India, or Australia will increase angular resolution 3~5 fold with respect to current LIGO-Virgo network, and that the angular resolution improvement by adding a single detector in Australia is comparable to that achieved by adding detectors in both India and Japan. A six-site network achieves a 11-fold improvement in angular resolution compared with the existing three-site network.

Development of a High Angular Resolution Diffusion Imaging Human Brain Template

PubMed Central

Varentsova, Anna; Zhang, Shengwei; Arfanakis, Konstantinos

2014-01-01

Brain diffusion templates contain rich information about the microstructure of the brain, and are used as references in spatial normalization or in the development of brain atlases. The accuracy of diffusion templates constructed based on the diffusion tensor (DT) model is limited in regions with complex neuronal micro-architecture. High angular resolution diffusion imaging (HARDI) overcomes limitations of the DT model and is capable of resolving intravoxel heterogeneity. However, when HARDI is combined with multiple-shot sequences to minimize image artifacts, the scan time becomes inappropriate for human brain imaging. In this work, an artifact-free HARDI template of the human brain was developed from low angular resolution multiple-shot diffusion data. The resulting HARDI template was produced in ICBM-152 space based on Turboprop diffusion data, was shown to resolve complex neuronal micro-architecture in regions with intravoxel heterogeneity, and contained fiber orientation information consistent with known human brain anatomy. PMID:24440528

High resolution tip-tilt positioning system for a next generation MLL-based x-ray microscope

DOE PAGES

Xu, Weihe; Schlossberger, Noah; Xu, Wei; ...

2017-11-15

Multilayer Laue lenses (MLLs) are x-ray focusing optics with the potential to focus hard x-rays down to a single nanometer level. In order to achieve point focus, an MLL microscope needs to have the capability to perform tip-tilt motion of MLL optics and to hold the angular position for an extended period of time. Here, we present a 2D tip-tilt system that can achieve an angular resolution of over 100 microdegree with a working range of 4°, by utilizing a combination of laser interferometer and mini retroreflector. The linear dimensions of the developed system are about 30 mm in allmore » directions, and the thermal dissipation of the system during operation is negligible. Compact design and high angular resolution make the developed system suitable for MLL optics alignment in the next generation of MLL-based x-ray microscopes.« less

High resolution tip-tilt positioning system for a next generation MLL-based x-ray microscope

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

Xu, Weihe; Schlossberger, Noah; Xu, Wei

Multilayer Laue lenses (MLLs) are x-ray focusing optics with the potential to focus hard x-rays down to a single nanometer level. In order to achieve point focus, an MLL microscope needs to have the capability to perform tip-tilt motion of MLL optics and to hold the angular position for an extended period of time. Here, we present a 2D tip-tilt system that can achieve an angular resolution of over 100 microdegree with a working range of 4°, by utilizing a combination of laser interferometer and mini retroreflector. The linear dimensions of the developed system are about 30 mm in allmore » directions, and the thermal dissipation of the system during operation is negligible. Compact design and high angular resolution make the developed system suitable for MLL optics alignment in the next generation of MLL-based x-ray microscopes.« less

Inelastic hyperspectral lidar for aquatic ecosystems monitoring and landscape plant scanning test

NASA Astrophysics Data System (ADS)

Zhao, Guangyu; Malmqvist, Elin; Rydhmer, Klas; Strand, Alfred; Bianco, Giuseppe; Hansson, Lars-Anders; Svanberg, Sune; Brydegaard, Mikkel

2018-04-01

We have developed an aquatic inelastic hyperspectral lidar with unrestricted focal-depth and enough sensitivity and spatio-temporal resolution to detect and resolve position and behavior of individual sub-millimeter aquatic organisms. We demonstrate ranging with monitoring of elastic echoes, water Raman signals and fluorescence from chlorophyllbearing phytoplankton and dye tagged organisms. The system is based on a blue CW diode laser and a Scheimpflug optical arrangement.

Second-Generation Design of Micro-Spec: A Medium-Resolution, Submillimeter-Wavelength Spectrometer-on-a-Chip

NASA Astrophysics Data System (ADS)

Cataldo, G.; Barrentine, E. M.; Bulcha, B. T.; Ehsan, N.; Hess, L. A.; Noroozian, O.; Stevenson, T. R.; U-Yen, K.; Wollack, E. J.; Moseley, S. H.

2018-04-01

Micro-Spec (µ-Spec) is a direct-detection spectrometer which integrates all the components of a diffraction-grating spectrometer onto a ˜ 10-cm^2 chip through the use of superconducting microstrip transmission lines on a single-crystal silicon substrate. A second-generation µ-Spec is being designed to operate with a spectral resolution of 512 in the submillimeter (500-1000 µm, 300-600 GHz) wavelength range, a band of interest for several spectroscopic applications in astrophysics. High-altitude balloon missions would provide the first test bed to demonstrate the µ-Spec technology in a space-like environment and would be an economically viable venue for multiple observation campaigns. This work reports on the current status of the instrument design and will provide a brief overview of each instrument subsystem. Particular emphasis will be given to the design of the spectrometer's two-dimensional diffractive region, through which the light of different wavelengths is focused on the detectors along the focal plane. An optimization process is employed to generate geometrical configurations of the diffractive region that satisfy specific requirements on spectrometer size, operating spectral range, and performance. An optical design optimized for balloon missions will be presented in terms of geometric layout, spectral purity, and efficiency.

Quadratic Finite Element Method for 1D Deterministic Transport

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

Tolar, Jr., D R; Ferguson, J M

2004-01-06

In the discrete ordinates, or SN, numerical solution of the transport equation, both the spatial ({und r}) and angular ({und {Omega}}) dependences on the angular flux {psi}{und r},{und {Omega}}are modeled discretely. While significant effort has been devoted toward improving the spatial discretization of the angular flux, we focus on improving the angular discretization of {psi}{und r},{und {Omega}}. Specifically, we employ a Petrov-Galerkin quadratic finite element approximation for the differencing of the angular variable ({mu}) in developing the one-dimensional (1D) spherical geometry S{sub N} equations. We develop an algorithm that shows faster convergence with angular resolution than conventional S{sub N} algorithms.

Advanced designs for non-imaging submillimeter-wave Winston cone concentrators

NASA Astrophysics Data System (ADS)

Nelson, A. O.; Grossman, E. N.

2014-05-01

We describe the design and simulation of several non-imaging concentrators designed to couple submillimeter wavelength radiation from free space into highly overmoded, rectangular, WR-10 waveguide. Previous designs are altered to improve the uniformity of efficiency rather than the efficiency itself. The concentrators are intended for use as adapters between instruments using overmoded WR-10 waveguide as input or output and sources propagating through free space. Previous simulation and measurement have shown that the angular response is primarily determined by the Winston cone and is well predicted by geometric optics theory while the efficiencies are primarily determined by the transition section. Additionally, previous work has shown insensitivity to polarization, orientation and beam size. Several separate concentrator designs are studied, all of which use a Winston cone (also known as a compound parabolic concentrator) with an input diameter ranging from 4 mm to 16 mm, and "throat" diameters of less than 0.5 mm to 4 mm as the initial interface. The use of various length adiabatic circular-to-rectangular transition sections is investigated, along with the effect of an additional, 25 mm waveguide section designed to model the internal waveguide of the power meter. Adapters without a transition section and a rectangular Winston cone throat aperture and double cone configurations are also studied. Adapters are analyzed in simulation for consistent efficiency across the opening aperture.

Modern Paradigm of Star Formation in the Galaxy

NASA Astrophysics Data System (ADS)

Sobolev, A. M.

2017-06-01

Understanding by the scientific community of the star formation processes in the Galaxy undergone significant changes in recent years. This is largely due to the development of the observational basis of astronomy in the infrared and submillimeter ranges. Analysis of new observational data obtained in the course of the Herschel project, by radio interferometer ALMA and other modern facilities significantly advanced our understanding of the structure of the regions of star formation, young stellar object vicinities and provided comprehensive data on the mass function of proto-stellar objects in a number of star-forming complexes of the Galaxy. Mapping of the complexes in molecular radio lines allowed to study their spatial and kinematic structure on the spatial scales of tens and hundreds of parsecs. The next breakthrough in this field can be achieved as a result of the planned project “Spektr-MM” (Millimetron) which implies a significant improvement in angular resolution and sensitivity. The use of sensitive interferometers allowed to investigate the details of star formation processes at small spatial scales - down to the size of the solar system (with the help of the ALMA), and even the Sun (in the course of the space project “Spektr-R” = RadioAstron). Significant contribution to the study of the processes of accretion is expected as a result of the project “Spektr-UV” (WSO-UV = “World Space Observatory - Ultraviolet”). Complemented with significant theoretical achievements obtained observational data have greatly promoted our understanding of the star formation processes.

Asymmetric 2D spatial beam filtering by photonic crystals

NASA Astrophysics Data System (ADS)

Gailevicius, D.; Purlys, V.; Maigyte, L.; Gaizauskas, E.; Peckus, M.; Gadonas, R.; Staliunas, K.

2016-04-01

Spatial filtering techniques are important for improving the spatial quality of light beams. Photonic crystals (PhCs) with a selective spatial (angular) transmittance can also provide spatial filtering with the added benefit transversal symmetries, submillimeter dimensions and monolithic integration in other devices, such as micro-lasers or semiconductor lasers. Workable bandgap PhC configurations require a modulated refractive index with period lengths that are approximately less than the wavelength of radiation. This imposes technical limitations, whereby the available direct laser write (DLW) fabrication techniques are limited in resolution and refractive index depth. If, however, a deflection mechanism is chosen instead, a functional filter PhC can be produced that is operational in the visible wavelength regime. For deflection based PhCs glass is an attractive choice as it is highly stable medium. 2D and 3D PhC filter variations have already been produced on soda-lime glass. However, little is known about how to control the scattering of PhCs when approaching the smallest period values. Here we look into the internal structure of the initially symmetric geometry 2D PhCs and associating it with the resulting transmittance spectra. By varying the DLW fabrication beam parameters and scanning algorithms, we show that such PhCs contain layers that are comprised of semi-tilted structure voxels. We show the appearance of asymmetry can be compensated in order to circumvent some negative effects at the cost of potentially maximum scattering efficiency.

Dynamical Imaging with Interferometry

NASA Astrophysics Data System (ADS)

Johnson, Michael D.; Bouman, Katherine L.; Blackburn, Lindy; Chael, Andrew A.; Rosen, Julian; Shiokawa, Hotaka; Roelofs, Freek; Akiyama, Kazunori; Fish, Vincent L.; Doeleman, Sheperd S.

2017-12-01

By linking widely separated radio dishes, the technique of very long baseline interferometry (VLBI) can greatly enhance angular resolution in radio astronomy. However, at any given moment, a VLBI array only sparsely samples the information necessary to form an image. Conventional imaging techniques partially overcome this limitation by making the assumption that the observed cosmic source structure does not evolve over the duration of an observation, which enables VLBI networks to accumulate information as Earth rotates and changes the projected array geometry. Although this assumption is appropriate for nearly all VLBI, it is almost certainly violated for submillimeter observations of the Galactic center supermassive black hole, Sagittarius A* (Sgr A*), which has a gravitational timescale of only ∼ 20 s and exhibits intrahour variability. To address this challenge, we develop several techniques to reconstruct dynamical images (“movies”) from interferometric data. Our techniques are applicable to both single-epoch and multiepoch variability studies, and they are suitable for exploring many different physical processes including flaring regions, stable images with small time-dependent perturbations, steady accretion dynamics, or kinematics of relativistic jets. Moreover, dynamical imaging can be used to estimate time-averaged images from time-variable data, eliminating many spurious image artifacts that arise when using standard imaging methods. We demonstrate the effectiveness of our techniques using synthetic observations of simulated black hole systems and 7 mm Very Long Baseline Array observations of M87, and we show that dynamical imaging is feasible for Event Horizon Telescope observations of Sgr A*.

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

Lieman-Sifry, Jesse; Hughes, A. Meredith; Flaherty, Kevin M.

We present a CO(2-1) and 1240 μ m continuum survey of 23 debris disks with spectral types B9-G1, observed at an angular resolution of 0.″5–1″ with the Atacama Large Millimeter/Submillimeter Array (ALMA). The sample was selected for large infrared excess and age ∼10 Myr, to characterize the prevalence of molecular gas emission in young debris disks. We identify three CO-rich debris disks, plus two additional tentative (3 σ) CO detections. Twenty disks were detected in the continuum at the >3 σ level. For the 12 disks in the sample that are spatially resolved by our observations, we perform an independentmore » analysis of the interferometric continuum visibilities to constrain the basic dust disk geometry, as well as a simultaneous analysis of the visibilities and broadband spectral energy distribution to constrain the characteristic grain size and disk mass. The gas-rich debris disks exhibit preferentially larger outer radii in their dust disks, and a higher prevalence of characteristic grain sizes smaller than the blowout size. The gas-rich disks do not exhibit preferentially larger dust masses, contrary to expectations for a scenario in which a higher cometary destruction rate would be expected to result in a larger mass of both CO and dust. The three debris disks in our sample with strong CO detections are all around A stars: the conditions in disks around intermediate-mass stars appear to be the most conducive to the survival or formation of CO.« less

DEATH-STAR: Silicon and photovoltaic fission fragment detector arrays for light-ion induced fission correlation studies

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

Koglin, J. D.; Burke, J. T.; Fisher, S. E.

Here, the Direct Excitation Angular Tracking pHotovoltaic-Silicon Telescope ARray (DEATH-STAR) combines a series of 12 silicon detectors in a ΔE–E configuration for charged particle identification with a large-area array of 56 photovoltaic (solar) cells for detection of fission fragments. The combination of many scattering angles and fission fragment detectors allows for an angular-resolved tool to study reaction cross sections using the surrogate method, anisotropic fission distributions, and angular momentum transfers through stripping, transfer, inelastic scattering, and other direct nuclear reactions. The unique photovoltaic detectors efficiently detect fission fragments while being insensitive to light ions and have a timing resolution ofmore » 15.63±0.37 ns. Alpha particles are detected with a resolution of 35.5 keV 1σ at 7.9 MeV. Measured fission fragment angular distributions are also presented.« less

DEATH-STAR: Silicon and Photovoltaic Fission Fragment Detector Arrays for Light-Ion Induced Fission Correlation Studies

NASA Astrophysics Data System (ADS)

Koglin, J. D.; Burke, J. T.; Fisher, S. E.; Jovanovic, I.

2017-05-01

The Direct Excitation Angular Tracking pHotovoltaic-Silicon Telescope ARray (DEATH-STAR) combines a series of 12 silicon detectors in a ΔE - E configuration for charged particle identification with a large-area array of 56 photovoltaic (solar) cells for detection of fission fragments. The combination of many scattering angles and fission fragment detectors allows for an angular-resolved tool to study reaction cross sections using the surrogate method, anisotropic fission distributions, and angular momentum transfers through stripping, transfer, inelastic scattering, and other direct nuclear reactions. The unique photovoltaic detectors efficiently detect fission fragments while being insensitive to light ions and have a timing resolution of 15.63±0.37 ns. Alpha particles are detected with a resolution of 35.5 keV 1σ at 7.9 MeV. Measured fission fragment angular distributions are also presented.

DEATH-STAR: Silicon and photovoltaic fission fragment detector arrays for light-ion induced fission correlation studies

DOE PAGES

Koglin, J. D.; Burke, J. T.; Fisher, S. E.; ...

2017-02-20

Here, the Direct Excitation Angular Tracking pHotovoltaic-Silicon Telescope ARray (DEATH-STAR) combines a series of 12 silicon detectors in a ΔE–E configuration for charged particle identification with a large-area array of 56 photovoltaic (solar) cells for detection of fission fragments. The combination of many scattering angles and fission fragment detectors allows for an angular-resolved tool to study reaction cross sections using the surrogate method, anisotropic fission distributions, and angular momentum transfers through stripping, transfer, inelastic scattering, and other direct nuclear reactions. The unique photovoltaic detectors efficiently detect fission fragments while being insensitive to light ions and have a timing resolution ofmore » 15.63±0.37 ns. Alpha particles are detected with a resolution of 35.5 keV 1σ at 7.9 MeV. Measured fission fragment angular distributions are also presented.« less

Arcsecond and Sub-arcsedond Imaging with X-ray Multi-Image Interferometer and Imager for (very) small sattelites

NASA Astrophysics Data System (ADS)

Hayashida, K.; Kawabata, T.; Nakajima, H.; Inoue, S.; Tsunemi, H.

2017-10-01

The best angular resolution of 0.5 arcsec is realized with the X-ray mirror onborad the Chandra satellite. Nevertheless, further better or comparable resolution is anticipated to be difficult in near future. In fact, the goal of ATHENA telescope is 5 arcsec in the angular resolution. We propose a new type of X-ray interferometer consisting simply of an X-ray absorption grating and an X-ray spectral imaging detector, such as X-ray CCDs or new generation CMOS detectors, by stacking the multi images created with the Talbot interferenece (Hayashida et al. 2016). This system, now we call Multi Image X-ray Interferometer Module (MIXIM) enables arcseconds resolution with very small satellites of 50cm size, and sub-arcseconds resolution with small sattellites. We have performed ground experiments, in which a micro-focus X-ray source, grating with pitch of 4.8μm, and 30 μm pixel detector placed about 1m from the source. We obtained the self-image (interferometirc fringe) of the grating for wide band pass around 10keV. This result corresponds to about 2 arcsec resolution for parrallel beam incidence. The MIXIM is usefull for high angular resolution imaging of relatively bright sources. Search for super massive black holes and resolving AGN torus would be the targets of this system.

Power-Law Template for IR Point Source Clustering

NASA Technical Reports Server (NTRS)

Addison, Graeme E.; Dunkley, Joanna; Hajian, Amir; Viero, Marco; Bond, J. Richard; Das, Sudeep; Devlin, Mark; Halpern, Mark; Hincks, Adam; Hlozek, Renee;

High Resolution Optical Imaging through the Atmosphere

DTIC Science & Technology

1989-12-28

34Iterative Blind Deconvolution Method and its Applications’, Opt. Lett., 13, p.54 7 . Fienup, J.R. 1978, Opt. Lett., 3, 27. Karovska , M., Nisenson, P., and...Noyes, R. (1987), ’High Angular Resolution Speckle Imaging of Alpha Ori", BAAS, Vol.19, No. 2. Karovska , M., Koechlin, L., Nisenson, P., Papaliolios...Publishers. Karovska , M., Nisenson, P., Papaliolios, C., Stendley, C. (1989), "High Angular Speckle Observations of SN1987A. Days 40-580.", BAAS, Vol

Grazing Incidence Nickel Replicated Optics for Hard X-ray Telescopes

NASA Technical Reports Server (NTRS)

Peturzzo, J. J., III; Elsner, R. F.; Joy, M. K.; ODell, S. L.; Weisskopf, M. C.

1997-01-01

The requirements for future hard x-ray (up to 50 keV) telescopes are lightweight, high angular resolution optics with large collecting areas. Grazing incidence replicated optics are an excellent candidate for this, type of mission, providing better angular resolution, comparable area/unit mass, and simpler fabrication than multilayer-coated foils. Most importantly, the technology to fabricate the required optics currently exists. A comparison of several hard x-ray telescope designs will be presented.

A Cryogenic, Insulating Suspension System for the High Resolution Airborne Wideband Camera (HAWC)and Submillemeter And Far Infrared Experiment (SAFIRE) Adiabatic Demagnetization Refrigerators (ADRs)

NASA Technical Reports Server (NTRS)

Voellmer, George M.; Jackson, Michael L.; Shirron, Peter J.; Tuttle, James G.

2002-01-01

The High Resolution Airborne Wideband Camera (HAWC) and the Submillimeter And Far Infrared Experiment (SAFIRE) will use identical Adiabatic Demagnetization Refrigerators (ADR) to cool their detectors to 200mK and 100mK, respectively. In order to minimize thermal loads on the salt pill, a Kevlar suspension system is used to hold it in place. An innovative, kinematic suspension system is presented. The suspension system is unique in that it consists of two parts that can be assembled and tensioned offline, and later bolted onto the salt pill.

High Angular Resolution and Lightweight X-Ray Optics for Astronomical Missions

NASA Technical Reports Server (NTRS)

Zhang, W. W.; Biskach, M. P.; Blake, P. N.; Chan, K. W.; Evans, T. C.; Hong, M.; Jones, W. D.; Jones, W. D.; Kolos, L. D.; Mazzarella, J. M.;

The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII): High Angular Resolution Astronomy at Far-Infrared Wavelengths

NASA Technical Reports Server (NTRS)

Rinehart, Stephen A.

2008-01-01

Astronomical studies at infrared wavelengths have dramatically improved our understanding of the universe, and observations with Spitzer, the upcoming Herschel mission. and SOFIA will continue to provide exciting new discoveries. The comparatively low spatial resolution of these missions, however. is insufficient to resolve the physical scales on which mid- to far-infrared emission arises, resulting in source and structure ambiguities that limit our ability to answer key science questions. Interferometry enables high angular resolution at these wavelengths. We have proposed a new high altitude balloon experiment, the Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII). High altitude operation makes far-infrared (30- 300micron) observations possible, and BETTII's 8-meter baseline provides unprecedented angular resolution (-0.5 arcsec) in this band. BETTII will use a double- Fourier instrument to simultaneously obtain both spatial and spectral informatioT. he spatially resolved spectroscopy provided by BETTII will address key questions about the nature of disks in young cluster stars and active galactic nuclei and the envelopes of evolved stars. BETTII will also lay the groundwork for future space interferometers.

A Noninvasive Platform for Imaging and Quantifying Oil Storage in Submillimeter Tobacco Seed1[W][OA

PubMed Central

Fuchs, Johannes; Neuberger, Thomas; Rolletschek, Hardy; Schiebold, Silke; Nguyen, Thuy Ha; Borisjuk, Nikolai; Börner, Andreas; Melkus, Gerd; Jakob, Peter; Borisjuk, Ljudmilla

2013-01-01

While often thought of as a smoking drug, tobacco (Nicotiana spp.) is now considered as a plant of choice for molecular farming and biofuel production. Here, we describe a noninvasive means of deriving both the distribution of lipid and the microtopology of the submillimeter tobacco seed, founded on nuclear magnetic resonance (NMR) technology. Our platform enables counting of seeds inside the intact tobacco capsule to measure seed sizes, to model the seed interior in three dimensions, to quantify the lipid content, and to visualize lipid gradients. Hundreds of seeds can be simultaneously imaged at an isotropic resolution of 25 µm, sufficient to assess each individual seed. The relative contributions of the embryo and the endosperm to both seed size and total lipid content could be assessed. The extension of the platform to a range of wild and cultivated Nicotiana species demonstrated certain evolutionary trends in both seed topology and pattern of lipid storage. The NMR analysis of transgenic tobacco plants with seed-specific ectopic expression of the plastidial phosphoenolpyruvate/phosphate translocator, displayed a trade off between seed size and oil concentration. The NMR-based assay of seed lipid content and topology has a number of potential applications, in particular providing a means to test and optimize transgenic strategies aimed at the manipulation of seed size, seed number, and lipid content in tobacco and other species with submillimeter seeds. PMID:23232144

A Spatially Resolved Study of Cold Dust, Molecular Gas, H II Regions, and Stars in the z = 2.12 Submillimeter Galaxy ALESS67.1

NASA Astrophysics Data System (ADS)

Chen, Chian-Chou; Hodge, J. A.; Smail, Ian; Swinbank, A. M.; Walter, Fabian; Simpson, J. M.; Calistro Rivera, Gabriela; Bertoldi, F.; Brandt, W. N.; Chapman, S. C.; da Cunha, Elisabete; Dannerbauer, H.; De Breuck, C.; Harrison, C. M.; Ivison, R. J.; Karim, A.; Knudsen, K. K.; Wardlow, J. L.; Weiß, A.; van der Werf, P. P.

2017-09-01

We present detailed studies of a z = 2.12 submillimeter galaxy, ALESS67.1, using sub-arcsecond resolution ALMA, adaptive optics-aided VLT/SINFONI, and Hubble Space Telescope (HST)/CANDELS data to investigate the kinematics and spatial distributions of dust emission (870 μm continuum), 12CO(J = 3–2), strong optical emission lines, and visible stars. Dynamical modeling of the optical emission lines suggests that ALESS67.1 is not a pure rotating disk but a merger, consistent with the apparent tidal features revealed in the HST imaging. Our sub-arcsecond resolution data set allows us to measure half-light radii for all the tracers, and we find a factor of 4–6 smaller sizes in dust continuum compared to all the other tracers, including 12CO; also, ultraviolet (UV) and Hα emission are significantly offset from the dust continuum. The spatial mismatch between the UV continuum and the cold dust and gas reservoir supports the explanation that geometrical effects are responsible for the offset of the dusty galaxy on the IRX–β diagram. Using a dynamical method we derive an {α }CO}=1.8+/- 1.0, consistent with other submillimeter galaxies (SMGs) that also have resolved CO and dust measurements. Assuming a single {α }CO} value we also derive resolved gas and star formation rate surface densities, and find that the core region of the galaxy (≲ 5 kpc) follows the trend of mergers on the Schmidt–Kennicutt relationship, whereas the outskirts (≳ 5 kpc) lie on the locus of normal star-forming galaxies, suggesting different star formation efficiencies within one galaxy. Our results caution against using single size or morphology for different tracers of the star formation activity and gas content of galaxies, and therefore argue the need to use spatially resolved, multi-wavelength observations to interpret the properties of SMGs, and perhaps even for z> 1 galaxies in general.

Spatial resolution limits for the isotropic-3D PET detector X’tal cube

NASA Astrophysics Data System (ADS)

Yoshida, Eiji; Tashima, Hideaki; Hirano, Yoshiyuki; Inadama, Naoko; Nishikido, Fumihiko; Murayama, Hideo; Yamaya, Taiga

2013-11-01

Positron emission tomography (PET) has become a popular imaging method in metabolism, neuroscience, and molecular imaging. For dedicated human brain and small animal PET scanners, high spatial resolution is needed to visualize small objects. To improve the spatial resolution, we are developing the X’tal cube, which is our new PET detector to achieve isotropic 3D positioning detectability. We have shown that the X’tal cube can achieve 1 mm3 uniform crystal identification performance with the Anger-type calculation even at the block edges. We plan to develop the X’tal cube with even smaller 3D grids for sub-millimeter crystal identification. In this work, we investigate spatial resolution of a PET scanner based on the X’tal cube using Monte Carlo simulations for predicting resolution performance in smaller 3D grids. For spatial resolution evaluation, a point source emitting 511 keV photons was simulated by GATE for all physical processes involved in emission and interaction of positrons. We simulated two types of animal PET scanners. The first PET scanner had a detector ring 14.6 cm in diameter composed of 18 detectors. The second PET scanner had a detector ring 7.8 cm in diameter composed of 12 detectors. After the GATE simulations, we converted the interacting 3D position information to digitalized positions for realistic segmented crystals. We simulated several X’tal cubes with cubic crystals from (0.5 mm)3 to (2 mm)3 in size. Also, for evaluating the effect of DOI resolution, we simulated several X’tal cubes with crystal thickness from (0.5 mm)3 to (9 mm)3. We showed that sub-millimeter spatial resolution was possible using cubic crystals smaller than (1.0 mm)3 even with the assumed physical processes. Also, the weighted average spatial resolutions of both PET scanners with (0.5 mm)3 cubic crystals were 0.53 mm (14.6 cm ring diameter) and 0.48 mm (7.8 cm ring diameter). For the 7.8 cm ring diameter, spatial resolution with 0.5×0.5×1.0 mm3 crystals was improved 39% relative to the (1 mm)3 cubic crystals. On the other hand, spatial resolution with (0.5 mm)3 cubic crystals was improved 47% relative to the (1 mm)3 cubic crystals. The X’tal cube promises better spatial resolution for the 3D crystal block with isotropic resolution.

Organic molecules, ions, and rare isotopologues in the remnant of the stellar-merger candidate, CK Vulpeculae (Nova 1670)

NASA Astrophysics Data System (ADS)

Kamiński, T.; Menten, K. M.; Tylenda, R.; Karakas, A.; Belloche, A.; Patel, N. A.

2017-11-01

Context. CK Vulpeculae (CK Vul) is an enigmatic star whose outburst was observed in 1670-72. A stellar-merger event was proposed to explain its ancient eruption. Aims: We aim to investigate the composition of the molecular gas recently discovered in the remnant of CK Vul. Deriving the chemical, elemental, and isotopic composition is crucial for identifying the nature of the object and obtaining clues on its progenitor(s). Methods: We observed millimeter and submillimeter-wave spectra of CK Vul using the IRAM 30 m and APEX telescopes. Radiative-transfer modeling of the observed molecular features was performed to yield isotopic ratios for various elements. Results: The spectra of CK Vul reveal a very rich molecular environment of low excitation (Tex ≲ 12 K). Atomic carbon and twenty-seven different molecules, including two ions, were identified. They range from simple diatomic to complex polyatomic species of up to seven atoms large. The chemical composition of the molecular gas is indicative of carbon and nitrogen-driven chemistry but oxides are also present. Additionally, the abundance of fluorine may be enhanced. The spectra are rich in isotopologues that are very rare in most known sources. All stable isotopes of C, N, O, Si, and S are observed and their isotopic ratios are derived. Conclusions: The composition of the remnant's molecular gas is most peculiar and gives rise to a very unique millimeter and submillimeter spectrum. The observation of ions and complex molecules suggests the presence of a photoionizing source but its nature (a central star or shocks) remains unknown. The elemental and isotopic composition of the gas cannot be easily reconciled with standard stellar nucleosynthesis but processing in hot CNO cycles and partial helium burning can explain most of the chemical peculiarities. The isotopic ratios of CK Vul are remarkably close to those of presolar "nova grains" but the link of Nova 1670 to objects responsible for these grains is unclear. The accuracy of isotopic ratios can be improved by future observations at higher angular resolutions and with realistic models of the kinematical structure of the remnant. The reduced spectra 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/A78

First Surface-resolved Results with the Infrared Optical Telescope Array Imaging Interferometer: Detection of Asymmetries in Asymptotic Giant Branch Stars

NASA Astrophysics Data System (ADS)

Ragland, S.; Traub, W. A.; Berger, J.-P.; Danchi, W. C.; Monnier, J. D.; Willson, L. A.; Carleton, N. P.; Lacasse, M. G.; Millan-Gabet, R.; Pedretti, E.; Schloerb, F. P.; Cotton, W. D.; Townes, C. H.; Brewer, M.; Haguenauer, P.; Kern, P.; Labeye, P.; Malbet, F.; Malin, D.; Pearlman, M.; Perraut, K.; Souccar, K.; Wallace, G.

2006-11-01

We have measured nonzero closure phases for about 29% of our sample of 56 nearby asymptotic giant branch (AGB) stars, using the three-telescope Infrared Optical Telescope Array (IOTA) interferometer at near-infrared wavelengths (H band) and with angular resolutions in the range 5-10 mas. These nonzero closure phases can only be generated by asymmetric brightness distributions of the target stars or their surroundings. We discuss how these results were obtained and how they might be interpreted in terms of structures on or near the target stars. We also report measured angular sizes and hypothesize that most Mira stars would show detectable asymmetry if observed with adequate angular resolution.

A High Angular Resolution Survey of Massive Stars in Cygnus OB2: Results from the Hubble Space Telescope Fine Guidance Sensors

DTIC Science & Technology

2014-02-01

F. J. Moffat9, and N. R. Walborn2 1 Center for High Angular Resolution Astronomy, Department of Physics and Astronomy, Georgia State University, P.O...Martin Drive, Baltimore, MD 21218, USA; nelan@stsci.edu, walborn@stsci.edu 3 Department of Natural Sciences, University of South Carolina Beaufort, 1 ...Online-only material: figure set 1 . INTRODUCTION Massive stars (10M) play a fundamental role in the evo- lution of the universe, from influencing

Angular resolution of stacked resistive plate chambers

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

Samuel, Deepak; Onikeri, Pratibha B.; Murgod, Lakshmi P., E-mail: deepaksamuel@cuk.ac.in, E-mail: pratibhaonikeri@gmail.com, E-mail: lakshmipmurgod@gmail.com

We present here detailed derivations of mathematical expressions for the accuracy in the arrival direction of particles estimated using a set of stacked resistive plate chambers (RPCs). The expressions are validated against experimental results using data collected from the prototype detectors (without magnet) of the upcoming India-based Neutrino Observatory (INO). We also present a theoretical estimate of angular resolution of such a setup. In principle, these expressions can be used for any other detector with an architecture similar to that of RPCs.

Chemistry of a newly detected circumbinary disk in Ophiuchus

NASA Astrophysics Data System (ADS)

Artur de la Villarmois, Elizabeth; Kristensen, Lars E.; Jørgensen, Jes K.; Bergin, Edwin A.; Brinch, Christian; Frimann, Søren; Harsono, Daniel; Sakai, Nami; Yamamoto, Satoshi

2018-06-01

Context. Astronomers recently started discovering exoplanets around binary systems. Therefore, understanding the formation and evolution of circumbinary disks and their environment is crucial for a complete scenario of planet formation. Aims: The purpose of this paper is to present the detection of a circumbinary disk around the system Oph-IRS67 and analyse its chemical and physical structure. Methods: We present high-angular-resolution (0.''4, 60 AU) observations of C17O, H13CO+, C34S, SO2, C2H and c-C3H2 molecular transitions with the Atacama Large Millimeter/submillimeter Array (ALMA) at wavelengths of 0.8 mm. The spectrally and spatially resolved maps reveal the kinematics of the circumbinary disk as well as its chemistry. Molecular abundances are estimated using the non-local thermodynamic equilibrium (LTE) radiative-transfer tool RADEX. Results: The continuum emission agrees with the position of Oph-IRS67 A and B, and reveals the presence of a circumbinary disk around the two sources. The circumbinary disk has a diameter of 620 AU and is well traced by C17O and H13CO+ emission. Two further molecular species, C2H and c-C3H2, trace a higher-density region which is spatially offset from the sources ( 430 AU). Finally, SO2 shows compact and broad emission around only one of the sources, Oph-IRS67 B. The molecular transitions which trace the circumbinary disk are consistent with a Keplerian profile on smaller disk scales (≲200 AU) and an infalling profile for larger envelope scales (≳200 AU). The Keplerian fit leads to an enclosed mass of 2.2 M⊙. Inferred CO abundances with respect to H2 are comparable to the canonical ISM value of 2.7 × 10-4, reflecting that freeze-out of CO in the disk midplane is not significant. Conclusions: Molecular emission and kinematic studies prove the existence and first detection of the circumbinary disk associated with the system Oph-IRS67. The high-density region shows a different chemistry than the disk, being enriched in carbon chain molecules. The lack of methanol emission agrees with the scenario where the extended disk dominates the mass budget in the innermost regions of the protostellar envelope, generating a flat density profile where less material is exposed to high temperatures, and thus, complex organic molecules would be associated with lower column densities. Finally, Oph-IRS67 is a promising candidate for proper motion studies and the detection of both circumstellar disks with higher-angular-resolution observations.

Sub-millimeter wave frequency heterodyne detector system

NASA Technical Reports Server (NTRS)

Siegel, Peter H. (Inventor); Dengler, Robert (Inventor); Mueller, Eric R. (Inventor)

2009-01-01

The present invention relates to sub-millimeter wave frequency heterodyne imaging systems. More specifically, the present invention relates to a sub-millimeter wave frequency heterodyne detector system for imaging the magnitude and phase of transmitted power through or reflected power off of mechanically scanned samples at sub-millimeter wave frequencies.

Sub-millimeter wave frequency heterodyne detector system

NASA Technical Reports Server (NTRS)

Siegel, Peter H. (Inventor); Dengler, Robert (Inventor); Mueller, Eric R. (Inventor)

2010-01-01

The present invention relates to sub-millimeter wave frequency heterodyne imaging systems. More specifically, the present invention relates to a sub-millimeter wave frequency heterodyne detector system for imaging the magnitude and phase of transmitted power through or reflected power off of mechanically scanned samples at sub-millimeter wave frequencies.

Review and latest news from the VEGA/CHARA facility

NASA Astrophysics Data System (ADS)

Nardetto, N.; Mourard, D.; Perraut, K.; Tallon-Bosc, I.; Meilland, A.; Stee, P.; Ligi, R.; Challouf, M.; Clausse, J.-M.; Berio, P.; Spang, A.

2014-12-01

The VEGA instrument located at the focus of the Center for High Angular Resolution Astronomy (CHARA) array in California is a collaborating project between the Lagrange laboratory in Nice, where it has been developed (Mourard et al. 2009, 2011), the IPAG (Grenoble) and CRAL (Lyon) laboratories, and the CHARA group at Mount Wilson Observatory. The outcome from this international collaboration is to provide to the community a visible spectro-interferometer with an unprecedented angular resolution of 0.3 milli-second of arc (mas) together with a spectral resolution of 5000 or 30000. With such an instrument it becomes possible to determine simultaneously the size and the kinematic of the photosphere and/or of the circumstellar environment of the star as a function of the wavelength, which basically means for each spectral channel in the continuum and/or within spectral lines (in Hα for instance). The only limitation is to get enough signal to noise ratio in each spectral channel. We can currently reach a limiting magnitude of 8 in visible in medium spectral resolution (5000) and 4.5 in high resolution (30000). In this proceeding, we illustrate the two main subjects studied with the VEGA instrument, namely (1) how angular diameters are useful to accurately derive the fundamental parameters of stars, (2) how the spectral resolution can allow to study the kinematical structure of stars or even to derive chromatic images of stellar objects.

ZEUS-2: a second generation submillimeter grating spectrometer for exploring distant galaxies

NASA Astrophysics Data System (ADS)

Ferkinhoff, Carl; Nikola, Thomas; Parshley, Stephen C.; Stacey, Gordon J.; Irwin, Kent D.; Cho, Hsiao-Mei; Halpern, Mark

2010-07-01

ZEUS-2, the second generation (z)Redshift and Early Universe Spectrometer, like its predecessor is a moderate resolution (R~1000) long-slit, echelle grating spectrometer optimized for the detection of faint, broad lines from distant galaxies. It is designed for studying star-formation across cosmic time. ZEUS-2 employs three TES bolometer arrays (555 pixels total) to deliver simultaneous, multi-beam spectra in up to 4 submillimeter windows. The NIST Boulder-built arrays operate at ~100mK and are readout via SQUID multiplexers and the Multi-Channel Electronics from the University of British Columbia. The instrument is cooled via a pulse-tube cooler and two-stage ADR. Various filter configurations give ZEUS-2 access to 7 different telluric windows from 200 to 850 micron enabling the simultaneous mapping of lines from extended sources or the simultaneous detection of the 158 micron [CII] line and the [NII] 122 or 205 micron lines from z = 1-2 galaxies. ZEUS-2 is designed for use on the CSO, APEX and possibly JCMT.

Investigation of passive atmospheric sounding using millimeter and submillimeter wavelength channels

NASA Technical Reports Server (NTRS)

Gasiewski, A. J.; Adelberg, L. K.; Kunkee, D. B.; Jackson, D. M.

1993-01-01

Progress by investigators at the Georgia Institute of Technology in the development of techniques for passive microwave retrieval of water vapor, cloud, and precipitation parameters using millimeter- and sub-millimeter wavelength channels is reviewed. Channels of particular interest are in the tropospheric transmission windows at 90, 166, 220, 340, and 410 GHz and centered around the water vapor lines at 183 and 325 GHz. Collectively, these channels have potential application in high-resolution mapping (e.g., from geosynchronous orbit), remote sensing of cloud and precipitation parameters, and retrieval of water vapor profiles. During the period from 1 Jan. 1993 through 30 Jun. 1993 the Millimeter-wave Imaging Radiometer (MIR) completed data flights during a two-month long deployment in conjunction with TOGA/COARE. Coincident data was collected from several other ground-based, airborne, and satellite sensors, including the NASA/MSFC AMPR, MIT MTS, DMSP SSM/T-2 satellite, collocated radiosondes, ground- and aircraft-based radiometers and cloud lidars, airborne infrared imagers, solar flux probes, and airborne cloud particle sampling probes.

Imaging of Stellar Surfacess Using Radio Facilities Including ALMA

NASA Astrophysics Data System (ADS)

O'Gorman, Eamon

2018-04-01

Until very recently, studies focusing on imaging stars at continuum radio wavelengths (here defined as submillimeter, millimeter, and centimeter wavelengths) has been scarce. These studies have mainly been carried out with the Very Large Array on a handful of evolved stars (i.e., Asymptotic Giant Branch and Red Supergiant stars) whereby their stellar disks have just about been spatially resolved. Some of these results however, have challenged our historical views on the nature of evolved star atmospheres. Now, the very long baselines of the Atacama Large Millimeter/submillimeter Array and the newly upgraded Karl G. Jansky Very Large Array provide a new opportunity to image these atmospheres at unprecedented spatial resolution and sensitivity across a much wider portion of the radio spectrum. In this talk I will first provide a history of stellar radio imaging and then discuss some recent exciting ALMA results. Finally I will present some brand new multi-wavelength ALMA and VLA results for the famous red supergiant Antares.

Development of a high angular resolution diffusion imaging human brain template.

PubMed

Varentsova, Anna; Zhang, Shengwei; Arfanakis, Konstantinos

2014-05-01

Brain diffusion templates contain rich information about the microstructure of the brain, and are used as references in spatial normalization or in the development of brain atlases. The accuracy of diffusion templates constructed based on the diffusion tensor (DT) model is limited in regions with complex neuronal micro-architecture. High angular resolution diffusion imaging (HARDI) overcomes limitations of the DT model and is capable of resolving intravoxel heterogeneity. However, when HARDI is combined with multiple-shot sequences to minimize image artifacts, the scan time becomes inappropriate for human brain imaging. In this work, an artifact-free HARDI template of the human brain was developed from low angular resolution multiple-shot diffusion data. The resulting HARDI template was produced in ICBM-152 space based on Turboprop diffusion data, was shown to resolve complex neuronal micro-architecture in regions with intravoxel heterogeneity, and contained fiber orientation information consistent with known human brain anatomy. Copyright © 2014 Elsevier Inc. All rights reserved.

THE MASSIVE PROTOSTELLAR CLUSTER NGC 6334I AT 220 au RESOLUTION: DISCOVERY OF FURTHER MULTIPLICITY, DIVERSITY, AND A HOT MULTI-CORE

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

Brogan, C. L.; Hunter, T. R.; Indebetouw, R.

2016-12-01

We present Very Large Array and Atacama Large Millimeter/submillimeter Array imaging of the deeply embedded protostellar cluster NGC 6334I from 5 cm to 1.3 mm at angular resolutions as fine as 0.″17 (220 au). The dominant hot core MM1 is resolved into seven components at 1.3 mm, clustered within a radius of 1000 au. Four of the components have brightness temperatures >200 K, radii ∼300 au, minimum luminosities ∼10{sup 4} L {sub ⊙}, and must be centrally heated. We term this new phenomenon a “hot multi-core.” Two of these objects also exhibit compact free–free emission at longer wavelengths, consistent withmore » a hypercompact H ii region (MM1B) and a jet (MM1D). The spatial kinematics of the water maser emission centered on MM1D are consistent with it being the origin of the high-velocity bipolar molecular outflow seen in CO. The close proximity of MM1B and MM1D (440 au) suggests a proto-binary or a transient bound system. Several components of MM1 exhibit steep millimeter spectral energy distributions indicative of either unusual dust spectral properties or time variability. In addition to resolving MM1 and the other hot core (MM2) into multiple components, we detect five new millimeter and two new centimeter sources. Water masers are detected for the first time toward MM4A, confirming its membership in the protocluster. With a 1.3 mm brightness temperature of 97 K coupled with a lack of thermal molecular line emission, MM4A appears to be a highly optically thick 240  L {sub ⊙} dust core, possibly tracing a transient stage of massive protostellar evolution. The nature of the strongest water maser source CM2 remains unclear due to its combination of non-thermal radio continuum and lack of dust emission.« less

Chemistry of the High-mass Protostellar Molecular Clump IRAS 16562–3959

NASA Astrophysics Data System (ADS)

Guzmán, Andrés E.; Guzmán, Viviana V.; Garay, Guido; Bronfman, Leonardo; Hechenleitner, Federico

2018-06-01

We present molecular line observations of the high-mass molecular clump IRAS 16562‑3959 taken at 3 mm using the Atacama Large Millimeter/submillimeter Array at 1.″7 angular resolution (0.014 pc spatial resolution). This clump hosts the actively accreting high-mass young stellar object (HMYSO) G345.4938+01.4677, which is associated with a hypercompact H II region. We identify and analyze emission lines from 22 molecular species (encompassing 34 isomers) and classify them into two groups, depending on their spatial distribution within the clump. One of these groups gathers shock tracers (e.g., SiO, SO, HNCO) and species formed in dust grains like methanol (CH3OH), ethenone or ketene (H2CCO), and acetaldehyde (CH3CHO). The second group collects species closely resembling the dust continuum emission morphology and are formed mainly in the gas phase, like hydrocarbons (CCH, c-C3H2, CH3CCH), cyanopolyynes (HC3N and HC5N), and cyanides (HCN and CH3C3N). Emission from complex organic molecules (COMs) like CH3OH, propanenitrile (CH3CH2CN), and methoxymethane (CH3OCH3) arise from gas in the vicinity of a hot molecular core (T ≳ 100 K) associated with the HMYSO. Other COMs such as propyne (CH3CCH), acrylonitrile (CH2CHCN), and acetaldehyde seem to better trace warm (T ≲ 80 K) dense gas. In addition, deuterated ammonia (NH2D) is detected mostly in the outskirts of IRAS 16562‑3959 and associated with near-infrared dark globules, probably gaseous remnants of the clump’s prestellar phase. The spatial distribution of molecules in IRAS 16562‑3959 supports the view that in protostellar clumps, chemical tracers associated with different evolutionary stages—starless to hot cores/H II regions—exist coevally.

A contracting circumbinary molecular ring around Ori 139-409 with an inner cavity of about 140 au

NASA Astrophysics Data System (ADS)

Zapata, Luis A.; Schilke, Peter; Ho, Paul T. P.

2010-03-01

We present sensitive and subarcsecond resolution (~0.7 arcsec) CH3OH(7-2,6-6-2,5) line and 890-μm continuum observations, made with the Submillimeter Array (SMA), towards the hot molecular circumbinary ring associated with the young multiple star Ori 139-409. The CH3OH(7-2,6-6-2,5) emission from the ring is well resolved at this angular resolution, revealing an inner cavity with a size of about 140 au. A local thermodynamic equilibrium model of a Keplerian disc with an inner cavity of the same size confirms the presence of this cavity. Additionally, this model suggests that the circumbinary ring is contracting with a velocity of Vinf ~ 1.5kms-1 towards the binary central compact circumstellar discs reported at a wavelength of 7 mm. The inner central cavity seems to be formed by the tidal effects of the young stars in the middle of the ring. The ring does not appear to be a stationary object. Furthermore, the infall velocity we determine is about a factor of 3 slower than the free-fall velocity corresponding to the dynamical mass. This would correspond to a mass accretion rate of about 10-5 Msolar yr-1. We have found that the dust emission associated with Ori 139-409 appears to be arising from the circumstellar discs, with no strong contribution from the molecular gas ring. Furthermore, a simple comparison with other classical molecular dusty rings (e.g. GG Tau, UZ Tau and UY Aur) suggests that Ori 139-409 could be one of the youngest circumbinary rings reported to date. Finally, our results confirm that the circumbinary rings are actively funnelling fresh gas material to the central compact binary circumstellar discs (i.e. to the protostars in the very early phases of their evolution).

The Massive Protostellar Cluster NGC 6334I at 220 au Resolution: Discovery of Further Multiplicity, Diversity, and a Hot Multi-core

NASA Astrophysics Data System (ADS)

Brogan, C. L.; Hunter, T. R.; Cyganowski, C. J.; Chandler, C. J.; Friesen, R.; Indebetouw, R.

2016-12-01

We present Very Large Array and Atacama Large Millimeter/submillimeter Array imaging of the deeply embedded protostellar cluster NGC 6334I from 5 cm to 1.3 mm at angular resolutions as fine as 0.″17 (220 au). The dominant hot core MM1 is resolved into seven components at 1.3 mm, clustered within a radius of 1000 au. Four of the components have brightness temperatures >200 K, radii ˜300 au, minimum luminosities ˜104 L ⊙, and must be centrally heated. We term this new phenomenon a “hot multi-core.” Two of these objects also exhibit compact free-free emission at longer wavelengths, consistent with a hypercompact H II region (MM1B) and a jet (MM1D). The spatial kinematics of the water maser emission centered on MM1D are consistent with it being the origin of the high-velocity bipolar molecular outflow seen in CO. The close proximity of MM1B and MM1D (440 au) suggests a proto-binary or a transient bound system. Several components of MM1 exhibit steep millimeter spectral energy distributions indicative of either unusual dust spectral properties or time variability. In addition to resolving MM1 and the other hot core (MM2) into multiple components, we detect five new millimeter and two new centimeter sources. Water masers are detected for the first time toward MM4A, confirming its membership in the protocluster. With a 1.3 mm brightness temperature of 97 K coupled with a lack of thermal molecular line emission, MM4A appears to be a highly optically thick 240 L ⊙ dust core, possibly tracing a transient stage of massive protostellar evolution. The nature of the strongest water maser source CM2 remains unclear due to its combination of non-thermal radio continuum and lack of dust emission.

Adaptive optics and interferometry

NASA Technical Reports Server (NTRS)

Beichman, Charles A.; Ridgway, Stephen

1991-01-01

Adaptive optics and interferometry, two techniques that will improve the limiting resolution of optical and infrared observations by factors of tens or even thousands, are discussed. The real-time adjustment of optical surfaces to compensate for wavefront distortions will improve image quality and increase sensitivity. The phased operation of multiple telescopes separated by large distances will make it possible to achieve very high angular resolution and precise positional measurements. Infrared and optical interferometers that will manipulate light beams and measure interference directly are considered. Angular resolutions of single telescopes will be limited to around 10 milliarcseconds even using the adaptive optics techniques. Interferometry would surpass this limit by a factor of 100 or more. Future telescope arrays with 100-m baselines (resolution of 2.5 milliarcseconds at a 1-micron wavelength) are also discussed.

SMART-X: Square Meter, Arcsecond Resolution Telescope for X-rays

NASA Astrophysics Data System (ADS)

Vikhlinin, Alexey; SMART-X Collaboration

2013-04-01

SMART-X is a concept for a next-generation X-ray observatory with large-area, 0.5" angular resolution grazing incidence adjustable X-ray mirrors, high-throughput critical angle transmission gratings, and X-ray microcalorimeter and CMOS-based imager in the focal plane. High angular resolution is enabled by new technology based on controlling the shape of mirror segments using thin film piezo actuators deposited on the back surface. Science applications include observations of growth of supermassive black holes since redshifts of ~10, ultra-deep surveys over 10's of square degrees, galaxy assembly at z=2-3, as well as new opportunities in the high-resolution X-ray spectroscopy and time domains. We also review the progress in technology development, tests, and mission design over the past year.

The X-Ray Optics for the High Angular Resolution Imager (HARI)

NASA Technical Reports Server (NTRS)

Weisskopf, M. C.

2010-01-01

This slide presentation shows the basic parameters of the x-ray optics, the housing,a graph of the effective area vs energy, another graph showing the angular off-set vs HEW, and a series of graphs showing the detector offsets and tilts,

Deformable complex network for refining low-resolution X-ray structures

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

Zhang, Chong; Wang, Qinghua; Ma, Jianpeng, E-mail: jpma@bcm.edu

2015-10-27

A new refinement algorithm called the deformable complex network that combines a novel angular network-based restraint with a deformable elastic network model in the target function has been developed to aid in structural refinement in macromolecular X-ray crystallography. In macromolecular X-ray crystallography, building more accurate atomic models based on lower resolution experimental diffraction data remains a great challenge. Previous studies have used a deformable elastic network (DEN) model to aid in low-resolution structural refinement. In this study, the development of a new refinement algorithm called the deformable complex network (DCN) is reported that combines a novel angular network-based restraint withmore » the DEN model in the target function. Testing of DCN on a wide range of low-resolution structures demonstrated that it constantly leads to significantly improved structural models as judged by multiple refinement criteria, thus representing a new effective refinement tool for low-resolution structural determination.« less

Design of discrete and continuous super-resolving Toraldo pupils in the microwave range.

PubMed

Olmi, Luca; Bolli, Pietro; Mugnai, Daniela

2018-03-20

The concept of super-resolution refers to various methods for improving the angular resolution of an optical imaging system beyond the classical diffraction limit. In optical microscopy, several techniques have been successfully developed with the aim of narrowing the central lobe of the illumination point spread function. In astronomy, however, no similar techniques can be used. A feasible method to design antennas and telescopes with angular resolution better than the diffraction limit consists of using variable transmittance pupils. In particular, discrete binary phase masks (0 or π ) with finite phase-jump positions, known as Toraldo pupils (TPs), have the advantage of being easy to fabricate but offer relatively little flexibility in terms of achieving specific trade-offs between design parameters, such as the angular width of the main lobe and the intensity of sidelobes. In this paper, we show that a complex transmittance filter (equivalent to a continuous TP, i.e., consisting of infinitely narrow concentric rings) can achieve more easily the desired trade-off between design parameters. We also show how the super-resolution effect can be generated with both amplitude- and phase-only masks and confirm the expected performance with electromagnetic numerical simulations in the microwave range.

Wide-angle display-type retarding field analyzer with high energy and angular resolutions

NASA Astrophysics Data System (ADS)

Muro, Takayuki; Ohkochi, Takuo; Kato, Yukako; Izumi, Yudai; Fukami, Shun; Fujiwara, Hidenori; Matsushita, Tomohiro

2017-12-01

Deployments of spherical grids to obtain high energy and angular resolutions for retarding field analyzers (RFAs) having acceptance angles as large as or larger than ±45° were explored under the condition of using commercially available microchannel plates with effective diameters of approximately 100 mm. As a result of electron trajectory simulations, a deployment of three spherical grids with significantly different grid separations instead of conventional equidistant separations showed an energy resolving power (E/ΔE) of 3200 and an angular resolution of 0.6°. The mesh number of the wire mesh retarding grid used for the simulation was 250. An RFA constructed with the simulated design experimentally showed an E/ΔE of 1100 and an angular resolution of 1°. Using the RFA and synchrotron radiation of 900 eV, photoelectron diffraction (PED) measurements were performed for single-crystal graphite. A clear C 1s PED pattern was observed even when the differential energy of the RFA was set at 0.5 eV. Further improvement of the energy resolution was theoretically examined under the assumption of utilizing a retarding grid fabricated by making a large number of radially directed cylindrical holes through a partial spherical shell instead of using a wire mesh retarding grid. An E/ΔE of 14 500 was predicted for a hole design with a diameter of 60 μm and a depth of 100 μm. A retarding grid with this hole design and a holed area corresponding to an acceptance angle of ±7° was fabricated. An RFA constructed with this retarding grid experimentally showed an E/ΔE of 1800. Possible reasons for the experimental E/ΔE lower than the theoretical values are discussed.

RadioAstron Science Program Five Years after Launch: Main Science Results

NASA Astrophysics Data System (ADS)

Kardashev, N. S.; Alakoz, A. V.; Andrianov, A. S.; Artyukhov, M. I.; Baan, W.; Babyshkin, V. E.; Bartel, N.; Bayandina, O. S.; Val'tts, I. E.; Voitsik, P. A.; Vorobyov, A. Z.; Gwinn, C.; Gomez, J. L.; Giovannini, G.; Jauncey, D.; Johnson, M.; Imai, H.; Kovalev, Y. Y.; Kurtz, S. E.; Lisakov, M. M.; Lobanov, A. P.; Molodtsov, V. A.; Novikov, B. S.; Pogodin, A. V.; Popov, M. V.; Privesenzev, A. S.; Rudnitski, A. G.; Rudnitski, G. M.; Savolainen, T.; Smirnova, T. V.; Sobolev, A. M.; Soglasnov, V. A.; Sokolovsky, K. V.; Filippova, E. N.; Khartov, V. V.; Churikova, M. E.; Shirshakov, A. E.; Shishov, V. I.; Edwards, P.

2017-12-01

The RadioAstron ground-space interferometer provides the highest angular resolution achieved now in astronomy. The detection of interferometric fringes from quasars with this angular resolution on baselines of 100-200 thousand km suggests the brightness temperatures which exceed the Compton limit by two orders of magnitude. Polarimetric measurements on ground-space baselines have revealed fine structure testifying to recollimation shocks on scales of 100-250 μas and a helical magnetic field near the base of radio emission in BL Lacertae. Substructure within a the scattering disk of pulsar emission on interferometer baselines (from 60000 to 250000 km) was discovered. This substructure is produced by action of the interstellar interferometer with an effective baseline of about 1 AU and the effective angular resolution of better than 1 μas. Diameters of scattering disks were measured for several pulsars, and distances to diffusing screens were evaluated. The ground-space observations of sources of the maser radiation in lines of water and hydroxyl have shown that the maser sources in star-forming regions remain unresolved on baselines, which considerably exceed the Earth diameter. These very compact and bright features with angular sizes of about 20-60 μas correspond to linear sizes of about 5-10 million km (several solar diameters).

A high-resolution full-field range imaging system

NASA Astrophysics Data System (ADS)

Carnegie, D. A.; Cree, M. J.; Dorrington, A. A.

2005-08-01

There exist a number of applications where the range to all objects in a field of view needs to be obtained. Specific examples include obstacle avoidance for autonomous mobile robots, process automation in assembly factories, surface profiling for shape analysis, and surveying. Ranging systems can be typically characterized as being either laser scanning systems where a laser point is sequentially scanned over a scene or a full-field acquisition where the range to every point in the image is simultaneously obtained. The former offers advantages in terms of range resolution, while the latter tend to be faster and involve no moving parts. We present a system for determining the range to any object within a camera's field of view, at the speed of a full-field system and the range resolution of some point laser scans. Initial results obtained have a centimeter range resolution for a 10 second acquisition time. Modifications to the existing system are discussed that should provide faster results with submillimeter resolution.

Focusing X-Ray Telescopes

NASA Technical Reports Server (NTRS)

O'Dell, Stephen; Brissenden, Roger; Davis, William; Elsner, Ronald; Elvis, Martin; Freeman, Mark; Gaetz, Terrance; Gorenstein, Paul; Gubarev, Mikhall; Jerlus, Diab;

Adjustable Grazing-Incidence X-Ray Optics

NASA Technical Reports Server (NTRS)

O'Dell, Stephen L.; Reid, Paul B.

2015-01-01

With its unique subarcsecond imaging performance, NASA's Chandra X-ray Observatory illustrates the importance of fine angular resolution for x-ray astronomy. Indeed, the future of x-ray astronomy relies upon x-ray telescopes with comparable angular resolution but larger aperture areas. Combined with the special requirements of nested grazing-incidence optics, mass, and envelope constraints of space-borne telescopes render such advances technologically and programmatically challenging. The goal of this technology research is to enable the cost-effective fabrication of large-area, lightweight grazing-incidence x-ray optics with subarcsecond resolution. Toward this end, the project is developing active x-ray optics using slumped-glass mirrors with thin-film piezoelectric arrays for correction of intrinsic or mount-induced distortions.

High resolution, wide field of view, real time 340GHz 3D imaging radar for security screening

NASA Astrophysics Data System (ADS)

Robertson, Duncan A.; Macfarlane, David G.; Hunter, Robert I.; Cassidy, Scott L.; Llombart, Nuria; Gandini, Erio; Bryllert, Tomas; Ferndahl, Mattias; Lindström, Hannu; Tenhunen, Jussi; Vasama, Hannu; Huopana, Jouni; Selkälä, Timo; Vuotikka, Antti-Jussi

2017-05-01

The EU FP7 project CONSORTIS (Concealed Object Stand-Off Real-Time Imaging for Security) is developing a demonstrator system for next generation airport security screening which will combine passive and active submillimeter wave imaging sensors. We report on the development of the 340 GHz 3D imaging radar which achieves high volumetric resolution over a wide field of view with high dynamic range and a high frame rate. A sparse array of 16 radar transceivers is coupled with high speed mechanical beam scanning to achieve a field of view of 1 x 1 x 1 m3 and a 10 Hz frame rate.

Shower disc sampling and the angular resolution of gamma-ray shower detectors

NASA Technical Reports Server (NTRS)

Lambert, A.; Lloyd-Evans, J.

1985-01-01

As part of the design study for the new UHE gamma ray detector being constsructed at Haverah Park, a series of experiments using scintillators operated side-by-side in 10 to the 15th power eV air showers are undertaken. Investigation of the rms sampling fluctuations in the shower disc arrival time yields an upper limit to the intrinsic sampling uncertainty, sigma sub rms = (1.1 + or - 0.1)ns, implying an angular resolution capability 1 deg for an inter-detector spacing of approximately 25 m.

A new model-independent approach for finding the arrival direction of an extensive air shower

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

Hedayati, H. Kh., E-mail: hedayati@kntu.ac.ir

2016-11-01

A new accurate method for reconstructing the arrival direction of an extensive air shower (EAS) is described. Compared to existing methods, it is not subject to minimization of a function and, therefore, is fast and stable. This method also does not need to know detailed curvature or thickness structure of an EAS. It can have angular resolution of about 1 degree for a typical surface array in central regions. Also, it has better angular resolution than other methods in the marginal area of arrays.

The Future of X-Ray Optics

NASA Technical Reports Server (NTRS)

Weisskopf, Martin C.

2013-01-01

The most important next step is the development of X-ray optics comparable to (or better than) Chandra in angular resolution that far exceed Chandra s effective area. Use the long delay to establish an adequately funded, competitive technology program along the lines I have recommended. Don't be diverted from this objective, except for Explorer-class missions. Progress in X-ray optics, with emphasis on the angular resolution, is central to the paradigm-shifting discoveries and the contributions of X-ray astronomy to multiwavelength astrophysics over the past 51 years.

MIPS - The Multiband Imaging Photometer for SIRTF. [Multiband Imaging Photometer for SIRTF

NASA Technical Reports Server (NTRS)

Rieke, G. H.; Lada, C.; Lebofsky, M.; Low, F.; Strittmatter, P.; Young, E.; Arens, J.; Beichman, C.; Gautier, T. N.; Werner, M.

1986-01-01

The Multiband Imaging Photometer for SIRTF (MIPS) is to be designed to reach as closely as possible the fundamental sensitivity and angular resolution limits for SIRTF over the 3 to 700 micron spectral region. It will use high performance photoconductive detectors from 3 to 200 micron with integrating JFET amplifiers. From 200 to 700 microns, the MIPS will use a bolometer cooled by an adiabatic demagnetization refrigerator. Over much of its operating range, the MIPS will make possible observations at and beyond the conventional Rayleigh diffraction limit of angular resolution.

MIPS - The Multiband Imaging Photometer for SIRTF

NASA Technical Reports Server (NTRS)

Rieke, G. H.; Lada, C.; Lebofsky, M.; Low, F.; Strittmatter, P.; Young, E.; Beichman, C.; Gautier, T. N.; Mould, J.; Werner, M.

1986-01-01

The Multiband Imaging Photometer System (MIPS) for SIRTF is to be designed to reach as closely as possible the fundamental sensitivity and angular resolution limits for SIRTF over the 3 to 700 microns spectral region. It will use high performance photoconductive detectors from 3 to 200 microns with integrating JFET amplifiers. From 200 to 700 microns, the MIPS will use a bolometer cooled by an adiabatic demagnetization refrigerator. Over much of its operating range, the MIPS will make possible observations at and beyond the conventional Rayleigh diffraction limit of angular resolution.

Power-Law Template for Infrared Point-Source Clustering

NASA Technical Reports Server (NTRS)

Addison, Graeme E; Dunkley, Joanna; Hajian, Amir; Viero, Marco; Bond, J. Richard; Das, Sudeep; Devlin, Mark J.; Halpern, Mark; Hincks, Adam D; Hlozek, Renee;

Stratospheric Observatory for Infrared Astronomy (SOFIA)

NASA Astrophysics Data System (ADS)

Becklin, E. E.; Tielens, A. G. G. M.; Gehrz, R. D.; Callis, H. H. S.

2007-09-01

The joint U.S. and German SOFIA project to develop and operate a 2.5-meter infrared airborne telescope in a Boeing 747-SP is now in its final stages of development. Flying in the stratosphere, SOFIA allows observations throughout the infrared and submillimeter region with an average transmission of >= 80%. The SOFIA instrument complement includes broadband imagers, moderate resolution spectrographs capable of resolving broad features due to dust and large molecules, and high resolution spectrometers suitable for kinematic studies of molecular and atomic gas lines at km/s resolution. These instruments will enable SOFIA to make unique contributions to a broad array of science topics. First science flights will begin in 2009, and the observatory is expected to operate for more than 20 years. The sensitivity, characteristics, science instrument complement, and examples of first light science are discussed.

Laboratory Rotational Spectroscopy of the Interstellar Diatomic Hydride Ion SH+ (X 3Σ-)

NASA Astrophysics Data System (ADS)

Halfen, DeWayne; Ziurys, Lucy M.

2016-06-01

Diatomic hydride are among the most common molecular species in the interstellar medium (ISM). The low molecular mass and thus moments of inertia cause their rotational spectra to lie principally in the submillimeter and far-infrared regions. Diatomic hydrides, both neutral (MH) and ionic (MH+) forms, are also basic building blocks of interstellar chemistry. In ionic form, they may be the “hidden” carriers of refractory elements in dense gas. They are therefore extremely good targets for space-borne and airborne platforms such as Herschel, SOFIA, and SAFIR. However, in order to detect these species in the ISM, their rotational spectra must first be measured in the laboratory. To date, there is very little high resolution data available for many hydride species, in particular the ionic form. Using submillimeter/THz direct absorption methods in the Ziurys laboratory, spectra of the interstellar diatomic hydride SH+ (X 3Σ-) have been recorded. Recent work has concerned measurement of all three fine structure components of the fundamental rotational transition N = 1 ← 0 in the range 345 - 683 GHz. SH+ was generated from H2S and argon in an AC discharge. The data have been analyzed, and spectroscopic constants for this species have been refined. SH+ is found in Photon Dominated Regions (PDRs) and X-ray Dominated Regions (XDRs) and is thought to trace energetic processes in the ISM. These current measurements confirm recent observations of this species at submillimeter/THz wavelengths with ALMA and other ground-based telescopes.

Discovery of a Lensed Ultrabright Submillimeter Galaxy at z = 2.0439

NASA Astrophysics Data System (ADS)

Díaz-Sánchez, A.; Iglesias-Groth, S.; Rebolo, R.; Dannerbauer, H.

2017-07-01

We report an ultrabright lensed submillimeter galaxy (SMG) at z = 2.0439, WISE J132934.18+224327.3, identified as a result of a full-sky cross-correlation of the AllWISE and Planck compact source catalogs aimed to search for bright analogs of the SMG SMM J2135, the Cosmic Eyelash. Inspection of archival SCUBA-2 observations of the candidates revealed a source with fluxes ({S}850μ {{m}}=130 mJy) consistent with the Planck measurements. The centroid of the SCUBA-2 source coincides within 1 arcsec with the position of the AllWISE mid-IR source, and, remarkably, with an arc-shaped lensed galaxy in HST images at visible wavelengths. Low-resolution rest-frame UV-optical spectroscopy of this lensed galaxy obtained with 10.4 m GTC reveals the typical absorption lines of a starburst galaxy. Gemini-N near-IR spectroscopy provided a clear detection of {{{H}}}α emission. The lensed source appears to be gravitationally magnified by a massive foreground galaxy cluster lens at z = 0.44 modeling with Lenstool indicates a lensing amplification factor of 11 ± 2. We determine an intrinsic rest-frame 8-1000 μm luminosity, {L}{IR}, of (1.3+/- 0.1)× {10}13 {L}⊙ , and a likely star formation rate (SFR) of ˜ 500{--}2000 {M}⊙ {{yr}}-1. The SED shows a remarkable similarity with the Cosmic Eyelash from optical-mid/IR to submillimeter/radio, albeit at higher fluxes.

ALMA OBSERVATIONS OF SPT-DISCOVERED, STRONGLY LENSED, DUSTY, STAR-FORMING GALAXIES

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

Hezaveh, Y. D.; Marrone, D. P.; Spilker, J. S.

2013-04-20

We present Atacama Large Millimeter/submillimeter Array (ALMA) 860 {mu}m imaging of four high-redshift (z = 2.8-5.7) dusty sources that were detected using the South Pole Telescope (SPT) at 1.4 mm and are not seen in existing radio to far-infrared catalogs. At 1.''5 resolution, the ALMA data reveal multiple images of each submillimeter source, separated by 1''-3'', consistent with strong lensing by intervening galaxies visible in near-IR imaging of these sources. We describe a gravitational lens modeling procedure that operates on the measured visibilities and incorporates self-calibration-like antenna phase corrections as part of the model optimization, which we use to interpretmore » the source structure. Lens models indicate that SPT0346-52, located at z = 5.7, is one of the most luminous and intensely star-forming sources in the universe with a lensing corrected FIR luminosity of 3.7 Multiplication-Sign 10{sup 13} L{sub Sun} and star formation surface density of 4200 M{sub Sun} yr{sup -1} kpc{sup -2}. We find magnification factors of 5 to 22, with lens Einstein radii of 1.''1-2.''0 and Einstein enclosed masses of 1.6-7.2 Multiplication-Sign 10{sup 11} M{sub Sun }. These observations confirm the lensing origin of these objects, allow us to measure their intrinsic sizes and luminosities, and demonstrate the important role that ALMA will play in the interpretation of lensed submillimeter sources.« less

Second generation stationary digital breast tomosynthesis system with faster scan time and wider angular span.

PubMed

Calliste, Jabari; Wu, Gongting; Laganis, Philip E; Spronk, Derrek; Jafari, Houman; Olson, Kyle; Gao, Bo; Lee, Yueh Z; Zhou, Otto; Lu, Jianping

2017-09-01

The aim of this study was to characterize a new generation stationary digital breast tomosynthesis system with higher tube flux and increased angular span over a first generation system. The linear CNT x-ray source was designed, built, and evaluated to determine its performance parameters. The second generation system was then constructed using the CNT x-ray source and a Hologic gantry. Upon construction, test objects and phantoms were used to characterize system resolution as measured by the modulation transfer function (MTF), and artifact spread function (ASF). The results indicated that the linear CNT x-ray source was capable of stable operation at a tube potential of 49 kVp, and measured focal spot sizes showed source-to-source consistency with a nominal focal spot size of 1.1 mm. After construction, the second generation (Gen 2) system exhibited entrance surface air kerma rates two times greater the previous s-DBT system. System in-plane resolution as measured by the MTF is 7.7 cycles/mm, compared to 6.7 cycles/mm for the Gen 1 system. As expected, an increase in the z-axis depth resolution was observed, with a decrease in the ASF from 4.30 mm to 2.35 mm moving from the Gen 1 system to the Gen 2 system as result of an increased angular span. The results indicate that the Gen 2 stationary digital breast tomosynthesis system, which has a larger angular span, increased entrance surface air kerma, and faster image acquisition time over the Gen 1 s-DBT system, results in higher resolution images. With the detector operating at full resolution, the Gen 2 s-DBT system can achieve an in-plane resolution of 7.7 cycles per mm, which is better than the current commercial DBT systems today, and may potentially result in better patient diagnosis. © 2017 American Association of Physicists in Medicine.

SU-E-T-510: Calculation of High Resolution and Material-Specific Photon Energy Deposition Kernels.

PubMed

Huang, J; Childress, N; Kry, S

2012-06-01

To calculate photon energy deposition kernels (EDKs) used for convolution/superposition dose calculation at a higher resolution than the original Mackie et al. 1988 kernels and to calculate material-specific kernels that describe how energy is transported and deposited by secondary particles when the incident photon interacts in a material other than water. The high resolution EDKs for various incident photon energies were generated using the EGSnrc user-code EDKnrc, which forces incident photons to interact at the center of a 60 cm radius sphere of water. The simulation geometry is essentially the same as the original Mackie calculation but with a greater number of scoring voxels (48 radial, 144 angular bins). For the material-specific EDKs, incident photons were forced to interact at the center of a 1 mm radius sphere of material (lung, cortical bone, silver, or titanium) surrounded by a 60 cm radius water sphere, using the original scoring voxel geometry implemented by Mackie et al. 1988 (24 radial, 48 angular bins). Our Monte Carlo-calculated high resolution EDKs showed excellent agreement with the Mackie kernels, with our kernels providing more information about energy deposition close to the interaction site. Furthermore, our EDKs resulted in smoother dose deposition functions due to the finer resolution and greater number of simulation histories. The material-specific EDK results show that the angular distribution of energy deposition is different for incident photons interacting in different materials. Calculated from the angular dose distribution for 300 keV incident photons, the expected polar angle for dose deposition () is 28.6° for water, 33.3° for lung, 36.0° for cortical bone, 44.6° for titanium, and 58.1° for silver, showing a dependence on the material in which the primary photon interacts. These high resolution and material-specific EDKs have implications for convolution/superposition dose calculations in heterogeneous patient geometries, especially at material interfaces. © 2012 American Association of Physicists in Medicine.

Angular-domain scattering interferometry.

PubMed

Shipp, Dustin W; Qian, Ruobing; Berger, Andrew J

2013-11-15

We present an angular-scattering optical method that is capable of measuring the mean size of scatterers in static ensembles within a field of view less than 20 μm in diameter. Using interferometry, the method overcomes the inability of intensity-based models to tolerate the large speckle grains associated with such small illumination areas. By first estimating each scatterer's location, the method can model between-scatterer interference as well as traditional single-particle Mie scattering. Direct angular-domain measurements provide finer angular resolution than digitally transformed image-plane recordings. This increases sensitivity to size-dependent scattering features, enabling more robust size estimates. The sensitivity of these angular-scattering measurements to various sizes of polystyrene beads is demonstrated. Interferometry also allows recovery of the full complex scattered field, including a size-dependent phase profile in the angular-scattering pattern.

The relationship between Class I and Class II methanol masers at high angular resolution

NASA Astrophysics Data System (ADS)

McCarthy, T. P.; Ellingsen, S. P.; Voronkov, M. A.; Cimò, G.

2018-06-01

We have used the Australia Telescope Compact Array (ATCA) to make the first high-resolution observations of a large sample of class I methanol masers in the 95-GHz (80-71A+) transition. The target sources consist of a statistically complete sample of 6.7-GHz class II methanol masers with an associated 95-GHz class I methanol maser, enabling a detailed study of the relationship between the two methanol maser classes at arcsecond angular resolution. These sources have been previously observed at high resolution in the 36- and 44-GHz transitions, allowing comparison between all three class I maser transitions. In total, 172 95-GHz maser components were detected across the 32 target sources. We find that at high resolution, when considering matched maser components, a 3:1 flux density ratio is observed between the 95- and 44-GHz components, consistent with a number of previous lower angular resolution studies. The 95-GHz maser components appear to be preferentially located closer to the driving sources and this may indicate that this transition is more strongly inverted nearby to background continuum sources. We do not observe an elevated association rate between 95-GHz maser emission and more evolved sources, as indicated by the presence of 12.2-GHz class II masers. We find that in the majority of cases where both class I and class II methanol emission is observed, some component of the class I emission is associated with a likely outflow candidate.

Inferring a Gap in the Group II Disk of the Herbig Ae/Be Star HD 142666

NASA Astrophysics Data System (ADS)

Ezra Rubinstein, Adam; Macías, Enrique; Espaillat, Catherine; Calvet, Nuria; Robinson, Connor; Zhang, Ke

2018-01-01

Disks around Herbig Ae/Be (HAeBe) stars have been classified into Group I or Group II, which are thought to be flared and flat disks respectively. Most Group I disks have been shown to have large gaps, suggesting ongoing planet formation, while no large gaps have been found in Group II disks. We analyzed the Group II disk of HD 142666 using irradiated accretion disk modeling of the broad-band spectral energy distribution along with the 1.3 millimeter spatial brightness distribution traced by Atacama Large Millimeter and Submillimeter Array (ALMA) observations. Our model is able to reproduce the available data, predicting a high degree of settling in the disk, which is consistent with the Group II classification of HD 142666. Although the ALMA observations did not have enough angular resolution to fully resolve the inner parts of the disk, the observed visibilities and synthesized image can only be reproduced when including a gap between ~5 to 12 au in our disk model. In addition, we also infer that the disk has an outer radius of ~65 au, which may be evidence of radial migration of dust or an unseen, low-mass companion that is truncating the outer disk. These results may suggest that Group II disks around HAeBe stars have gaps, possibly carved by young giant planets in the disk. Further ALMA observations of HD 142666 and other Group II disks are needed to discern if gaps are common in this class of objects, as well as to reveal their possible origin.

ALMA observations of protoplanetary disks

NASA Astrophysics Data System (ADS)

Hogerheijde, Michiel

2015-08-01

The Universe is filled with planetary systems, as recent detections of exo-planets have shown. Such systems grow out of disks of gas and dust that surround newly formed stars. The ground work for our understanding of the structure, composition, and evolution of such disks has been laid with infrared telescopes in the 1980's, 1990's, and 2000's, as well as with millimeter interferometers operating in the United States, France, and Japan. With the construction of the Atacama Large Millimeter / submillimeter Array, a new era of studying planet-forming disks has started. The unprecedented leap in sensitivity and angular resolution that ALMA offers, has truely revolutionized our understanding of disks. No longer featureless objects consisting of gas and smalll dust, they are now seen to harbor a rich structure and chemistry. The ongoing planet-formation process sculpts many disks into systems of rings and arcs; grains grown to millimeter-sizes collect in high-pressure areas where they could grow out to asteroids or comets or further generations of planets. This wealth of new information directly addresses bottlenecks in our theoretical understanding of planet formation, such as the question how grains can grow past the 'meter-sized' barrier or overcome the 'drift barrier', and how gas and ice evolve together and ultimately determine the elemental compositions of both giant and terrestrial planets. I will review the recent ALMA results on protoplanetary disks, presenting results on individual objects and from the first populations studies. I will conclude with a forward look, on what we might expect from ALMA in this area for the years and decades to come.

3.3 CM JVLA OBSERVATIONS OF TRANSITIONAL DISKS: SEARCHING FOR CENTIMETER PEBBLES

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

Zapata, Luis A.; Rodríguez, Luis F.; Palau, Aina, E-mail: lzapata@crya.unam.mx

We present sensitive (rms-noises ∼4–25 μ Jy) and high angular resolution (∼1″–2″) 8.9 GHz (3.3 cm) Karl G. Jansky Very Large Array radio continuum observations of 10 presumed transitional disks associated with young low-mass stars. We report the detection of radio continuum emission in 5 out of the 10 objects (RXJ1615, UX Tau A, LkCa15, RXJ1633, and SR 24s). In the case of LkCa15, the centimeter emission is extended, and has a similar morphology to that of the transitional disk observed at millimeter wavelengths with an inner depression. For these five detections, we construct the spectral energy distributions from themore » centimeter to submillimeter wavelengths, and find that they can be well fitted with a single (RXJ1633 and UX Tau A) or a two-component power law (LkCa15, RXJ1615, and SR 24s). For the cases where a single power law fits the data well, the centimeter emission is likely produced by optically thin dust with large grains (i.e., centimeter-size pebbles) present in the transitional disks. For the cases where a double power law fits the data, the centimeter emission might be produced by the combination of photoevaporation and a free–free jet. We conclude that RXJ1633 and UX Tau A are excellent examples of transitional disks where the structure of the emission from centimeter/millimeter pebbles can be studied. In the other cases, some other physical emitting mechanisms are also important in the centimeter regime.« less

3.3 CM JVLA Observations of Transitional Disks: Searching for Centimeter Pebbles

NASA Astrophysics Data System (ADS)

Zapata, Luis A.; Rodríguez, Luis F.; Palau, Aina

2017-01-01

We present sensitive (rms-noises ˜4-25 μJy) and high angular resolution (˜1″-2″) 8.9 GHz (3.3 cm) Karl G. Jansky Very Large Array radio continuum observations of 10 presumed transitional disks associated with young low-mass stars. We report the detection of radio continuum emission in 5 out of the 10 objects (RXJ1615, UX Tau A, LkCa15, RXJ1633, and SR 24s). In the case of LkCa15, the centimeter emission is extended, and has a similar morphology to that of the transitional disk observed at millimeter wavelengths with an inner depression. For these five detections, we construct the spectral energy distributions from the centimeter to submillimeter wavelengths, and find that they can be well fitted with a single (RXJ1633 and UX Tau A) or a two-component power law (LkCa15, RXJ1615, and SR 24s). For the cases where a single power law fits the data well, the centimeter emission is likely produced by optically thin dust with large grains (I.e., centimeter-size pebbles) present in the transitional disks. For the cases where a double power law fits the data, the centimeter emission might be produced by the combination of photoevaporation and a free-free jet. We conclude that RXJ1633 and UX Tau A are excellent examples of transitional disks where the structure of the emission from centimeter/millimeter pebbles can be studied. In the other cases, some other physical emitting mechanisms are also important in the centimeter regime.

PLANETARY SYSTEM FORMATION IN THE PROTOPLANETARY DISK AROUND HL TAURI

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

Akiyama, Eiji; Hasegawa, Yasuhiro; Hayashi, Masahiko

2016-02-20

We reprocess the Atacama Large Millimeter/Submillimeter Array (ALMA) long-baseline science verification data taken toward HL Tauri. Assuming the observed gaps are opened up by currently forming, unseen bodies, we estimate the mass of such hypothetical bodies based on the following two approaches: the Hill radius analysis and a more elaborate approach developed from the angular momentum transfer analysis in gas disks. For the former, the measured gap widths are used for estimating the mass of the bodies, while for the latter, the measured gap depths are utilized. We show that their masses are comparable to or less than the mass of Jovian planets.more » By evaluating Toomre’s gravitational instability (GI) condition and cooling effect, we find that the GI might be a mechanism to form the bodies in the outer region of the disk. As the disk might be gravitationally unstable only in the outer region of the disk, inward planetary migration would be needed to construct the current architecture of the observed disk. We estimate the gap-opening mass and show that type II migration might be able to play such a role. Combining GIs with inward migration, we conjecture that all of the observed gaps may be a consequence of bodies that might have originally formed at the outer part of the disk, and have subsequently migrated to the current locations. While ALMA’s unprecedented high spatial resolution observations can revolutionize our picture of planet formation, more dedicated observational and theoretical studies are needed to fully understand the HL Tauri images.« less

Molecular Gas Properties in M83 from CO PDFs

NASA Astrophysics Data System (ADS)

Egusa, Fumi; Hirota, Akihiko; Baba, Junichi; Muraoka, Kazuyuki

2018-02-01

We have obtained 12CO(1–0) data of the nearby barred spiral galaxy M83 from Atacama Large Millimeter/submillimeter Array and Nobeyama 45 m observations. By combining these two data sets, the total CO flux has been recovered, and a high angular resolution (2\\prime\\prime corresponding to ∼40 pc at the distance of M83) has been achieved. The field of view is 3\\prime corresponding to ∼3.4 kpc and covers the galactic center, bar, and spiral arm regions. In order to investigate how these galactic structures affect gas properties, we have created a probability distribution function (PDF) of the CO integrated intensity ({I}CO}), peak temperature, and velocity dispersion for a region with each structure. We find that the {I}CO} PDF for the bar shows a bright-end tail while that for the arm does not. As the star formation efficiency is lower in the bar, this difference in PDF shape is contrary to the trend in Milky Way studies where the bright-end tail is found for star-forming molecular clouds. While the peak temperature PDFs are similar for the bar and arm regions, velocity dispersion in the bar is systematically larger than in the arm. This large velocity dispersion is likely a major cause of the bright-end tail and of suppressed star formation. We also investigate an effect of stellar feedback to PDF profiles and find that the different {I}CO} PDFs between bar and arm regions cannot be explained by the feedback effect, at least at the current spatial scale.

QUEST FOR COSMOS SUBMILLIMETER GALAXY COUNTERPARTS USING CARMA AND VLA: IDENTIFYING THREE HIGH-REDSHIFT STARBURST GALAXIES

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

Smolcic, V.; Navarrete, F.; Bertoldi, F.

2012-05-01

We report on interferometric observations at 1.3 mm at 2''-3'' resolution using the Combined Array for Research in Millimeter-wave Astronomy. We identify multi-wavelength counterparts of three submillimeter galaxies (SMGs; F{sub 1m} > 5.5 mJy) in the COSMOS field, initially detected with MAMBO and AzTEC bolometers at low, {approx}10''-30'', resolution. All three sources-AzTEC/C1, Cosbo-3, and Cosbo-8-are identified to coincide with positions of 20 cm radio sources. Cosbo-3, however, is not associated with the most likely radio counterpart, closest to the MAMBO source position, but with that farther away from it. This illustrates the need for intermediate-resolution ({approx}2'') mm-observations to identify themore » correct counterparts of single-dish-detected SMGs. All of our three sources become prominent only at NIR wavelengths, and their mm-to-radio flux based redshifts suggest that they lie at redshifts z {approx}> 2. As a proof of concept, we show that photometric redshifts can be well determined for SMGs, and we find photometric redshifts of 5.6 {+-} 1.2, 1.9{sup +0.9}{sub -0.5}, and {approx}4 for AzTEC/C1, Cosbo-3, and Cosbo-8, respectively. Using these we infer that these galaxies have radio-based star formation rates of {approx}> 1000 M{sub Sun} yr{sup -1}and IR luminosities of {approx}10{sup 13} L{sub Sun} consistent with properties of high-redshift SMGs. In summary, our sources reflect a variety of SMG properties in terms of redshift and clustering, consistent with the framework that SMGs are progenitors of z {approx} 2 and today's passive galaxies.« less

Timing considerations for preclinical MRgRT: effects of ion diffusion, SNR and imaging times on FXG gel calibration

NASA Astrophysics Data System (ADS)

Welch, M.; Foltz, W. D.; Jaffray, D. A.

2015-01-01

Sub-millimeter resolution images are required for gel dosimeters to be used in preclinical research, which is challenging for MR probed ferrous xylenol-orange (FXG) dosimeters due to ion diffusion and inadequate SNR. A preclinical 7 T MR, small animal irradiator and FXG dosimeters were used in all experiments. Ion diffusion was analyzed using high resolution (0.2 mm/pixel) T1 MR images collected every 5 minutes, post-irradiation, for an hour. Using Fick's second law, ion diffusion was approximated for the first hour post-irradiation. SNR, T1 map precision and calibration fit were determined for two MR protocols: (1) 10 minute acquisition, 0.35mm/pixel and 3mm slices, (2) 45 minute acquisition, 0. 25 mm/pixel and 2 mm slices. SNR and T1 map precision were calculated using a Monte Carlo simulation. Calibration curves were determined by plotting R1 relaxation rates versus depth dose data, and fitting a linear trend line. Ion diffusion was estimated as 0.003mm2 in the first hour post-irradiation. For protocols (1) and (2) respectively, Monte Carlo simulation predicted T1 precisions of 3% and 5% within individual voxels using experimental SNRs; the corresponding measured T1 precisions were 8% and 12%. The linear trend lines reported slopes of 27 ± 3 Gy*s (R2: 0.80 ± 0.04) and 27 ± 4 Gy*s (R2: 0.90 ± 0.04). Ion diffusion is negligible within the first hour post-irradiation, and an accurate and reproducible calibration can be achieved in a preclinical setting with sub-millimeter resolution.

Multi-resolution anisotropy studies of ultrahigh-energy cosmic rays detected at the Pierre Auger Observatory

NASA Astrophysics Data System (ADS)

Aab, A.; Abreu, P.; Aglietta, M.; Samarai, I. Al; Albuquerque, I. F. M.; Allekotte, I.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Anastasi, G. A.; Anchordoqui, L.; Andrada, B.; Andringa, S.; Aramo, C.; Arqueros, F.; Arsene, N.; Asorey, H.; Assis, P.; Aublin, J.; Avila, G.; Badescu, A. M.; Balaceanu, A.; Barreira Luz, R. J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Billoir, P.; Biteau, J.; Blaess, S. G.; Blanco, A.; Blazek, J.; Bleve, C.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Borodai, N.; Botti, A. M.; Brack, J.; Brancus, I.; Bretz, T.; Bridgeman, A.; Briechle, F. L.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, L.; Cancio, A.; Canfora, F.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Chavez, A. G.; Chinellato, J. A.; Chudoba, J.; Clay, R. W.; Colalillo, R.; Coleman, A.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Cronin, J.; D'Amico, S.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; de Jong, S. J.; De Mauro, G.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; Debatin, J.; Deligny, O.; Di Giulio, C.; Di Matteo, A.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; D'Olivo, J. C.; dos Anjos, R. C.; Dova, M. T.; Dundovic, A.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Fick, B.; Figueira, J. M.; Filipčič, A.; Fratu, O.; Freire, M. M.; Fujii, T.; Fuster, A.; Gaior, R.; García, B.; Garcia-Pinto, D.; Gaté, F.; Gemmeke, H.; Gherghel-Lascu, A.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Głas, D.; Glaser, C.; Golup, G.; Gómez Berisso, M.; Gómez Vitale, P. F.; González, N.; Gorgi, A.; Gorham, P.; Gouffon, P.; Grillo, A. F.; Grubb, T. D.; Guarino, F.; Guedes, G. P.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Hasankiadeh, Q.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huege, T.; Hulsman, J.; Insolia, A.; Isar, P. G.; Jandt, I.; Jansen, S.; Johnsen, J. A.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Katkov, I.; Keilhauer, B.; Kemp, E.; Kemp, J.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Kuempel, D.; Kukec Mezek, G.; Kunka, N.; Kuotb Awad, A.; LaHurd, D.; Lauscher, M.; Legumina, R.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; Lopes, L.; López, R.; López Casado, A.; Luce, Q.; Lucero, A.; Malacari, M.; Mallamaci, M.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Mariş, I. C.; Marsella, G.; Martello, D.; Martinez, H.; Martínez Bravo, O.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melo, D.; Menshikov, A.; Messina, S.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Mockler, D.; Mollerach, S.; Montanet, F.; Morello, C.; Mostafá, M.; Müller, A. L.; Müller, G.; Muller, M. A.; Müller, S.; Mussa, R.; Naranjo, I.; Nellen, L.; Nguyen, P. H.; Niculescu-Oglinzanu, M.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, H.; Núñez, L. A.; Ochilo, L.; Oikonomou, F.; Olinto, A.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.; Pech, M.; Pedreira, F.; Pȩkala, J.; Pelayo, R.; Peña-Rodriguez, J.; Pereira, L. A. S.; Perlín, M.; Perrone, L.; Peters, C.; Petrera, S.; Phuntsok, J.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Ramos-Pollan, R.; Rautenberg, J.; Ravignani, D.; Revenu, B.; Ridky, J.; Risse, M.; Ristori, P.; Rizi, V.; Rodrigues de Carvalho, W.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rogozin, D.; Roncoroni, M. J.; Roth, M.; Roulet, E.; Rovero, A. C.; Ruehl, P.; Saffi, S. J.; Saftoiu, A.; Salazar, H.; Saleh, A.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santos, E. M.; Santos, E.; Sarazin, F.; Sarmento, R.; Sarmiento, C. A.; Sato, R.; Schauer, M.; Scherini, V.; Schieler, H.; Schimp, M.; Schmidt, D.; Scholten, O.; Schovánek, P.; Schröder, F. G.; Schulz, A.; Schulz, J.; Schumacher, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sigl, G.; Silli, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sonntag, S.; Sorokin, J.; Squartini, R.; Stanca, D.; Stanič, S.; Stasielak, J.; Stassi, P.; Strafella, F.; Suarez, F.; Suarez Durán, M.; Sudholz, T.; Suomijärvi, T.; Supanitsky, A. D.; Swain, J.; Szadkowski, Z.; Taboada, A.; Taborda, O. A.; Tapia, A.; Theodoro, V. M.; Timmermans, C.; Todero Peixoto, C. J.; Tomankova, L.; Tomé, B.; Torralba Elipe, G.; Torri, M.; Travnicek, P.; Trini, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van Bodegom, P.; van den Berg, A. M.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Vergara Quispe, I. D.; Verzi, V.; Vicha, J.; Villaseñor, L.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weindl, A.; Wiencke, L.; Wilczyński, H.; Winchen, T.; Wittkowski, D.; Wundheiler, B.; Yang, L.; Yelos, D.; Yushkov, A.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zepeda, A.; Zimmermann, B.; Ziolkowski, M.; Zong, Z.; Zuccarello, F.

2017-06-01

We report a multi-resolution search for anisotropies in the arrival directions of cosmic rays detected at the Pierre Auger Observatory with local zenith angles up to 80o and energies in excess of 4 EeV (4 × 1018 eV). This search is conducted by measuring the angular power spectrum and performing a needlet wavelet analysis in two independent energy ranges. Both analyses are complementary since the angular power spectrum achieves a better performance in identifying large-scale patterns while the needlet wavelet analysis, considering the parameters used in this work, presents a higher efficiency in detecting smaller-scale anisotropies, potentially providing directional information on any observed anisotropies. No deviation from isotropy is observed on any angular scale in the energy range between 4 and 8 EeV. Above 8 EeV, an indication for a dipole moment is captured; while no other deviation from isotropy is observed for moments beyond the dipole one. The corresponding p-values obtained after accounting for searches blindly performed at several angular scales, are 1.3 × 10-5 in the case of the angular power spectrum, and 2.5 × 10-3 in the case of the needlet analysis. While these results are consistent with previous reports making use of the same data set, they provide extensions of the previous works through the thorough scans of the angular scales.

A Multi-instrument and Multi-wavelength High Angular Resolution Study of MWC 614: Quantum Heated Particles Inside the Disk Cavity

NASA Astrophysics Data System (ADS)

Kluska, Jacques; Kraus, Stefan; Davies, Claire L.; Harries, Tim; Willson, Matthew; Monnier, John D.; Aarnio, Alicia; Baron, Fabien; Millan-Gabet, Rafael; Ten Brummelaar, Theo; Che, Xiao; Hinkley, Sasha; Preibisch, Thomas; Sturmann, Judit; Sturmann, Laszlo; Touhami, Yamina

2018-03-01

High angular resolution observations of young stellar objects are required to study the inner astronomical units of protoplanetary disks in which the majority of planets form. As they evolve, gaps open up in the inner disk regions and the disks are fully dispersed within ∼10 Myr. MWC 614 is a pretransitional object with a ∼10 au radius gap. We present a set of high angular resolution observations of this object including SPHERE/ZIMPOL polarimetric and coronagraphic images in the visible, Keck/NIRC2 near-infrared (NIR) aperture masking observations, and Very Large Telescope Interferometer (AMBER, MIDI, and PIONIER) and Center for High Angular Resolution Astronomy (CLASSIC and CLIMB) long-baseline interferometry at infrared wavelengths. We find that all the observations are compatible with an inclined disk (i ∼ 55° at a position angle of ∼20°–30°). The mid-infrared data set confirms that the disk inner rim is at 12.3 ± 0.4 au from the central star. We determined an upper mass limit of 0.34 M ⊙ for a companion inside the cavity. Within the cavity, the NIR emission, usually associated with the dust sublimation region, is unusually extended (∼10 au, 30 times larger than the theoretical sublimation radius) and indicates a high dust temperature (T ∼ 1800 K). As a possible result of companion-induced dust segregation, quantum heated dust grains could explain the extended NIR emission with this high temperature. Our observations confirm the peculiar state of this object where the inner disk has already been accreted onto the star, exposing small particles inside the cavity to direct stellar radiation. Based on observations made with the Keck observatory (NASA program ID N104N2) and with ESO telescopes at the Paranal Observatory (ESO program IDs 073.C-0720, 077.C-0226, 077.C-0521, 083.C-0984, 087.C-0498(A), 190.C-0963, 095.C-0883) and with the Center for High Angular Resolution Astronomy observatory.

A Broadband X-Ray Imaging Spectroscopy with High-Angular Resolution: the FORCE Mission

NASA Technical Reports Server (NTRS)

Mori, Koji; Tsuru, Takeshi Go; Nakazawac, Kazuhiro; Ueda, Yoshihiro; Okajima, Takashi; Murakami, Hiroshi; Awaki, Hisamitsu; Matsumoto, Hironori; Fukazawai, Yasushi; Tsunemi, Hiroshi;

A broadband x-ray imaging spectroscopy with high-angular resolution: the FORCE mission

NASA Astrophysics Data System (ADS)

Mori, Koji; Tsuru, Takeshi Go; Nakazawa, Kazuhiro; Ueda, Yoshihiro; Okajima, Takashi; Murakami, Hiroshi; Awaki, Hisamitsu; Matsumoto, Hironori; Fukazawa, Yasushi; Tsunemi, Hiroshi; Takahashi, Tadayuki; Zhang, William W.

2016-07-01

We are proposing FORCE (Focusing On Relativistic universe and Cosmic Evolution) as a future Japan-lead Xray observatory to be launched in the mid 2020s. Hitomi (ASTRO-H) possesses a suite of sensitive instruments enabling the highest energy-resolution spectroscopy in soft X-ray band, a broadband X-ray imaging spectroscopy in soft and hard X-ray bands, and further high energy coverage up to soft gamma-ray band. FORCE is the direct successor to the broadband X-ray imaging spectroscopy aspect of Hitomi (ASTRO-H) with significantly higher angular resolution. The current design of FORCE defines energy band pass of 1-80 keV with angular resolution of < 15 in half-power diameter, achieving a 10 times higher sensitivity above 10 keV compared to any previous missions with simultaneous soft X-ray coverage. Our primary scientific objective is to trace the cosmic formation history by searching for "missing black holes" in various mass-scales: "buried supermassive black holes (SMBHs)" (> 104 M⊙) residing in the center of galaxies in a cosmological distance, "intermediate-mass black holes" (102-104 M⊙) acting as the possible seeds from which SMBHs grow, and "orphan stellar-mass black holes" (< 102 M⊙) without companion in our Galaxy. In addition to these missing BHs, hunting for the nature of relativistic particles at various astrophysical shocks is also in our scope, utilizing the broadband X-ray coverage with high angular-resolution. FORCE are going to open a new era in these fields. The satellite is proposed to be launched with the Epsilon vehicle that is a Japanese current solid-fuel rocket. FORCE carries three identical pairs of Super-mirror and wide-band X-ray detector. The focal length is currently planned to be 10 m. The silicon mirror with multi-layer coating is our primary choice to achieve lightweight, good angular optics. The detector is a descendant of hard X-ray imager onboard Hitomi (ASTRO-H) replacing its silicon strip detector with SOI-CMOS silicon pixel detector, allowing an extension of the low energy threshold down to 1 keV or even less.

Phosphorus Imaging as a Tool for Studying the pH Metabolism in Living Insects

NASA Astrophysics Data System (ADS)

Skibbe, U.; Christeller, J. T.; Eccles, C. D.; Laing, W. A.; Callaghan, P. T.

1995-09-01

Comparative 31P NMR and 1H NMR imaging experiments at submillimeter pixel resolution were carried out, using a specially constructed solenoidal RF coil. Chemical-shift imaging is used to provide pH maps from the midgut of a Lepidopteran larvae and to demonstrate physiological dependence in the resulting images, The titration curve of pH versus chemical shift for inorganic phosphate is extended beyond the "normal" biological range to the strong alkaline limit.

LDR system concepts and technology

NASA Technical Reports Server (NTRS)

Pittman, B.

1985-01-01

The Large Deployable Reflector is a 20 meter diameter infrared/submillimeter telescope planned for the late 1990's. The Astronomy Survey Committee of the National Academy of Sciences (Field Committee) recommended LDR as one of the two space based observatories that should start development in the 80's. LDR's large aperture will give it unequaled resolution in the wavelength range from 30 to 1000 microns. To meet LDR performance goals will call for advances in several technology disciplines including: optics, controls, thermal control, detectors, cryogenic cooling, and large space structures.

A device to measure the effects of strong magnetic fields on the image resolution of PET scanners

NASA Astrophysics Data System (ADS)

Burdette, D.; Albani, D.; Chesi, E.; Clinthorne, N. H.; Cochran, E.; Honscheid, K.; Huh, S. S.; Kagan, H.; Knopp, M.; Lacasta, C.; Mikuz, M.; Schmalbrock, P.; Studen, A.; Weilhammer, P.

2009-10-01

Very high resolution images can be achieved in small animal PET systems utilizing solid state silicon pad detectors. As these systems approach sub-millimeter resolutions, the range of the positron is becoming the dominant contribution to image blur. The size of the positron range effect depends on the initial positron energy and hence the radioactive tracer used. For higher energy positron emitters, such as Ga68 and Tc94m, which are gaining importance in small animal studies, the width of the annihilation point distribution dominates the spatial resolution. This positron range effect can be reduced by embedding the field of view of the PET scanner in a strong magnetic field. In order to confirm this effect experimentally, we developed a high resolution PET instrument based on silicon pad detectors that can operate in a 7 T magnetic field. In this paper, we describe the instrument and present initial results of a study of the effects of magnetic fields up to 7 T on PET image resolution for Na22 and Ga68 point sources.

Empirical single sample quantification of bias and variance in Q-ball imaging.

PubMed

Hainline, Allison E; Nath, Vishwesh; Parvathaneni, Prasanna; Blaber, Justin A; Schilling, Kurt G; Anderson, Adam W; Kang, Hakmook; Landman, Bennett A

2018-02-06

The bias and variance of high angular resolution diffusion imaging methods have not been thoroughly explored in the literature and may benefit from the simulation extrapolation (SIMEX) and bootstrap techniques to estimate bias and variance of high angular resolution diffusion imaging metrics. The SIMEX approach is well established in the statistics literature and uses simulation of increasingly noisy data to extrapolate back to a hypothetical case with no noise. The bias of calculated metrics can then be computed by subtracting the SIMEX estimate from the original pointwise measurement. The SIMEX technique has been studied in the context of diffusion imaging to accurately capture the bias in fractional anisotropy measurements in DTI. Herein, we extend the application of SIMEX and bootstrap approaches to characterize bias and variance in metrics obtained from a Q-ball imaging reconstruction of high angular resolution diffusion imaging data. The results demonstrate that SIMEX and bootstrap approaches provide consistent estimates of the bias and variance of generalized fractional anisotropy, respectively. The RMSE for the generalized fractional anisotropy estimates shows a 7% decrease in white matter and an 8% decrease in gray matter when compared with the observed generalized fractional anisotropy estimates. On average, the bootstrap technique results in SD estimates that are approximately 97% of the true variation in white matter, and 86% in gray matter. Both SIMEX and bootstrap methods are flexible, estimate population characteristics based on single scans, and may be extended for bias and variance estimation on a variety of high angular resolution diffusion imaging metrics. © 2018 International Society for Magnetic Resonance in Medicine.

The Submillimeter Wave Electron Cyclotron Emission Diagnostic for the Alcator C-Mod Tokamak.

NASA Astrophysics Data System (ADS)

Hsu, Thomas C.

This thesis describes the engineering design, construction, and operation of a high spatial resolution submillimeter wave diagnostic for electron temperature measurements on Alcator C-Mod. Alcator C-Mod is a high performance compact tokamak capable of producing diverted, shaped plasmas with a major radius of 0.67 meters, minor radius of 0.21 centimeters, plasma current of 3 MA. The maximum toroidal field is 9 Tesla on the magnetic axis. The ECE diagnostic includes three primary components: a 10.8 meter quasioptical transmission line, a rapid scanning Michelson interferometer, and a vacuum compatible calibration source. Due to the compact size and high field of the tokamak the ECE system was designed to have a spectral range from 100 to 1000 GHz with frequency resolution of 5 GHz and spatial resolution of one centimeter. The beamline uses all reflecting optical elements including two off-axis parabolic mirrors with diameters of 20 cm. and focal lengths of 2.7 meters. Techniques are presented for grinding and finishing the mirrors to sufficient surface quality to permit optical alignment of the system. Measurements of the surface figure confirm the design goal of 1/4 wavelength accuracy at 1000 GHz. Extensive broadband tests of the spatial resolution of the ECE system are compared to a fundamental mode Gaussian beam model, a three dimensional vector diffraction model, and a geometric optics model. The Michelson interferometer is a rapid scanning polarization instrument which has an apodized frequency resolution of 5 GHz and a minimum scan period of 7.5 milliseconds. The novel features of this instrument include the use of precision linear bearings to stabilize the moving mirror and active counterbalancing to reduce vibration. Beam collimation within the instrument is done with off-axis parabolic mirrors. The Michelson also includes a 2-50 mm variable aperture and two signal attenuators constructed from crossed wire grid polarizers. To make full use of the advantages of an evacuated optical path a dual element in-situ calibration source was designed and constructed. The calibration source operates as a thermal blackbody at temperatures from 77K to 373K and base pressures down to 10^{-7} torr. The top element of the source serves as a room temperature reference while the lower element can be heated or cooled by the circulation of an appropriate fluid through the internal heat transfer tubes. The submillimeter absorbing bodies of both elements are made from arrays of knife edge tiles cast from thermally conductive, alumina filled epoxy. A boundary element heat transfer model of the tiles was constructed which indicates temperature uniformity within 1.5 percent. Operation during the 1993 startup of Alcator C -Mod demonstrates the excellent potential of the new instruments. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253 -1690.) (Abstract shortened by UMI.).

Revealing the subfemtosecond dynamics of orbital angular momentum in nanoplasmonic vortices

NASA Astrophysics Data System (ADS)

Spektor, G.; Kilbane, D.; Mahro, A. K.; Frank, B.; Ristok, S.; Gal, L.; Kahl, P.; Podbiel, D.; Mathias, S.; Giessen, H.; Meyer zu Heringdorf, F.-J.; Orenstein, M.; Aeschlimann, M.

2017-03-01

The ability of light to carry and deliver orbital angular momentum (OAM) in the form of optical vortices has attracted much interest. The physical properties of light with a helical wavefront can be confined onto two-dimensional surfaces with subwavelength dimensions in the form of plasmonic vortices, opening avenues for thus far unknown light-matter interactions. Because of their extreme rotational velocity, the ultrafast dynamics of such vortices remained unexplored. Here we show the detailed spatiotemporal evolution of nanovortices using time-resolved two-photon photoemission electron microscopy. We observe both long- and short-range plasmonic vortices confined to deep subwavelength dimensions on the scale of 100 nanometers with nanometer spatial resolution and subfemtosecond time-step resolution. Finally, by measuring the angular velocity of the vortex, we directly extract the OAM magnitude of light.

Characterisation and comparison of event generators for pair conversion: A crucial step for future low energy gamma telescope

NASA Astrophysics Data System (ADS)

Gros, P.; Bernard, D.

2017-05-01

Gamma ray astronomy suffers from a sensitivity gap between 0.1 and 100Mev. With high angular resolution for the electrons, it will also be possible to probe the linear polarisation of the photons. An accurate simulation is necessary to correctly design and compare these detectors. We establish baseline distributions of key kinematic variables as simulated by a 5D, exact down to threshold, and polarised event generator. We compare them to simulations with the low energy electromagnetic models available in Geant4 and in EGS5. We show that different generators give a different picture of the optimal angular resolution of pair telescopes. We also show that, of all the simulations we used, only the full 5D generator describes accurately the angular asymmetry in the case of polarised photons.

The Physics and Chemistry of Oxygen-Rich Circumstellar Envelopes as Traced by Simple Molecules

NASA Astrophysics Data System (ADS)

Wong, Ka Tat

2018-04-01

The physics and chemistry of the circumstellar envelopes (CSEs) of evolved stars are not fully understood despite decades of research. This thesis addresses two issues in the study of the CSEs of oxygen-rich (O-rich) evolved stars. In the first project, the ammonia (NH3) chemistry of O-rich stars is investigated with multi-wavelength observations; in the second project, the extended atmosphere and inner wind of the archetypal asymptotic giant branch (AGB) star o Ceti (Mira) is studied with high-angular resolution observations. One of the long-standing mysteries in circumstellar chemistry is the perplexing overabundance of the NH3 molecule. NH3 in O-rich evolved stars has been found in much higher abundance, by several orders of magnitude, than that expected in equilibrium chemistry. Several mechanisms have been suggested in the literature to explain this high NH3 abundance, including shocks in the inner wind, photodissociation of nitrogen by interstellar ultraviolet radiation, and nitrogen enrichment in stellar nucleosynthesis; however, none of these suggestions can fully explain the abundances of NH3 and various other molecular species in the CSEs of O-rich stars. In order to investigate the distribution of NH3 in O-rich CSEs, observations of the spectral lines of NH3 from a diverse sample of evolved stars and in different wavelength regimes are necessary. In this thesis, the NH3 line emission and absorption from four O-rich stars are studied. These targets include the AGB star IK Tauri, the pre-planetary nebula OH 231.8+4.2, the red supergiant VY Canis Majoris, and the yellow hypergiant IRC +10420. The amount of NH3 observational data has increased drastically thanks to the recent advancement of instrumentation. Observations of NH3 rotational line emission at submillimetre/far-infrared wavelengths were possible with the Herschel Space Observatory (2009–2013). The new wideband correlator in the upgraded Karl G. Janksy Very Large Array (VLA) provided data of multiple radio inversion lines of NH3. Furthermore, mid-infrared absorption of NH3 has been observed by the NASA Infrared Telescope Facility (IRTF) for IK Tau and VY CMa. Full radiative transfer modelling including mid-infrared pumping to the first vibrationally excited state (v2=1) has been carried out to reproduce the observed emission and absorption spectra and to retrieve the NH3 abundances in the targets. It is found that the NH3 emission in the CSEs of the targets arises from localised spatial-kinematic structures in which the gas density may be higher than in the surrounding gas. Circumstellar shocks may contribute to, but cannot fully account for, the formation of the molecule. Besides circumstellar chemistry, our understanding of the dust formation and wind-driving mechanisms of oxygen-rich evolved stars is still incomplete. One of the obstacles in the past was the difficulty in imaging the dust condensation and wind acceleration zones due to the lack of high-angular resolution instruments. Thanks to the Atacama Large Millimeter/submillimeter Array (ALMA), which has the longest baseline of about 15 km, we are now able to produce high-fidelity images at unprecedented angular resolutions of tens of milliarcseconds (mas) in the (sub)millimetre regime. Such angular resolutions, which are comparable to the stellar radii of nearby objects, are necessary to understand the gas dynamics and chemical evolution in the pulsating atmosphere and dust formation zone of nearby AGB stars. The eponymous Mira-type long-period variable, o Cet, was observed as a Science Verification target during the first ALMA Long Baseline Campaign that took place in 2014. The observations produced images of the stellar radio photosphere and the molecular transitions of SiO and H2O at an angular resolution of about 30 mas near 220 GHz (1.3 mm). The millimetre stellar disc of o Cet was resolved and modelled. More importantly, this is the first time that molecular line absorption against the background stellar continuum has been clearly imaged in the (sub)millimetre wavelength regime. Through radiative transfer modelling of the SiO and H2O line absorption and emission, it is found that during the ALMA observations, the extended atmosphere of the star exhibited infall motions in general with a shock front of velocity

Spiral Transformation for High-Resolution and Efficient Sorting of Optical Vortex Modes.

PubMed

Wen, Yuanhui; Chremmos, Ioannis; Chen, Yujie; Zhu, Jiangbo; Zhang, Yanfeng; Yu, Siyuan

2018-05-11

Mode sorting is an essential function for optical multiplexing systems that exploit the orthogonality of the orbital angular momentum mode space. The familiar log-polar optical transformation provides a simple yet efficient approach whose resolution is, however, restricted by a considerable overlap between adjacent modes resulting from the limited excursion of the phase along a complete circle around the optical vortex axis. We propose and experimentally verify a new optical transformation that maps spirals (instead of concentric circles) to parallel lines. As the phase excursion along a spiral in the wave front of an optical vortex is theoretically unlimited, this new optical transformation can separate orbital angular momentum modes with superior resolution while maintaining unity efficiency.

Spiral Transformation for High-Resolution and Efficient Sorting of Optical Vortex Modes

NASA Astrophysics Data System (ADS)

Wen, Yuanhui; Chremmos, Ioannis; Chen, Yujie; Zhu, Jiangbo; Zhang, Yanfeng; Yu, Siyuan

2018-05-01

Mode sorting is an essential function for optical multiplexing systems that exploit the orthogonality of the orbital angular momentum mode space. The familiar log-polar optical transformation provides a simple yet efficient approach whose resolution is, however, restricted by a considerable overlap between adjacent modes resulting from the limited excursion of the phase along a complete circle around the optical vortex axis. We propose and experimentally verify a new optical transformation that maps spirals (instead of concentric circles) to parallel lines. As the phase excursion along a spiral in the wave front of an optical vortex is theoretically unlimited, this new optical transformation can separate orbital angular momentum modes with superior resolution while maintaining unity efficiency.

Development of a combined microSPECT/CT system for small animal imaging

NASA Astrophysics Data System (ADS)

Sun, Mingshan

Modern advances in the biomedical sciences have placed increased attention on small animals such as mice and rats as models of human biology and disease in biological research and pharmaceutical development. Their small size and fast breeding rate, their physiologic similarity to human, and, more importantly, the availability of sophisticated genetic manipulations, all have made mice and rats the laboratory mammals of choice in these experimental studies. However, the increased use of small animals in biomedical research also calls for new instruments that can measure the anatomic and metabolic information noninvasively with adequate spatial resolution and measurement sensitivity to facilitate these studies. This dissertation describes the engineering development of a combined single photon emission computed tomography (SPECT) and X-ray computed tomography (CT) system dedicated for small animals imaging. The system aims to obtain both the anatomic and metabolic images with submillimeter spatial resolution in a way that the data can be correlated to provide improved image quality and to offer more complete biological evaluation for biomedical studies involving small animals. The project requires development of complete microSPECT and microCT subsystems. Both subsystems are configured with a shared gantry and animal bed with integrated instrumentation for data acquisition and system control. The microCT employs a microfocus X-ray tube and a CCD-based detector for low noise, high resolution imaging. The microSPECT utilizes three semiconductor detectors coupled with pinhole collimators. A significant contribution of this dissertation project is the development of iterative algorithms with geometrical compensation that allows radionuclide images to be reconstructed at submillimeter spatial resolution, but with significantly higher detection efficiency than conventional methods. Both subsystems are capable of helical scans, offering lengthened field of view and improved axial resolution. System performance of both modalities is characterized with phantoms and animals. The microSPECT shows 0.6 mm resolution and 60 cps/MBq detection efficiency for imaging mice with 0.5 mm pinholes. The microCT achieves 120 mum spatial resolution on detector but with a relatively low detective quantum efficiency of 0.2 at the zero frequency. The combined system demonstrates a flexible platform for instrumentation development and a valuable tool for biomedical research. In summary, this dissertation describes the development of a combined SPECT/CT system for imaging the physiological function and anatomical structure in small animals.

TeraHertz Space Telescope (TST)

NASA Astrophysics Data System (ADS)

Dunn, Marina Madeline; Lesser, David; O'Dougherty, Stephan; Swift, Brandon; Pat, Terrance; Cortez, German; Smith, Steve; Goldsmith, Paul; Walker, Christopher K.

2017-01-01

The Terahertz Space Telescope (TST) utilizes breakthrough inflatable technology to create a ~25 m far-infrared observing system at a fraction of the cost of previous space telescopes. As a follow-on to JWST and Herschel, TST will probe the FIR/THz regime with unprecedented sensitivity and angular resolution, answering fundamental questions concerning the origin and destiny of the cosmos. Prior and planned space telescopes have barely scratched the surface of what can be learned in this wavelength region. TST will pick up where JWST and Herschel leave off. At ~30µm TST will have ~10x the sensitivity and ~3x the angular resolution of JWST. At longer wavelengths it will have ~1000x the sensitivity of Herschel and ~7 times the angular resolution. TST can achieve this at low cost through the innovative use of inflatable technology. A recently-completed NIAC Phase II study (Large Balloon Reflector) validated, both analytically and experimentally, the concept of a large inflatable spherical reflector and demonstrated critical telescope functions. In our poster we will introduce the TST concept and compare its performance to past, present, and proposed far-infrared observatories.

Photoelectron angular distributions from rotationally resolved autoionizing states of N 2

DOE PAGES

Chartrand, A. M.; McCormack, E. F.; Jacovella, U.; ...

2017-12-08

The single-photon, photoelectron-photoion coincidence spectrum of N 2 has been recorded at high (~1.5 cm -1) resolution in the region between the N 2 + X 2Σ g +, v + = 0 and 1 ionization thresholds by using a double imaging spectrometer and intense vacuum-ultraviolet light from the Synchrotron SOLEIL. This approach provides the relative photoionization cross section, the photoelectron energy distribution, and the photoelectron angular distribution as a function of photon energy. The region of interest contains autoionizing valence states, vibrationally autoionizing Rydberg states converging to vibrationally excited levels of the N 2 + X 2Σ g +more » ground state, and electronically autoionizing states converging to the N 2 + A 2Π and B 2Σ u + states. The wavelength resolution is sufficient to resolve rotational structure in the autoionizing states, but the electron energy resolution is insufficient to resolve rotational structure in the photoion spectrum. Here, a simplified approach based on multichannel quantum defect theory is used to predict the photoelectron angular distribution parameters, β, and the results are in reasonably good agreement with experiment.« less

Slumped glass optics with interfacing ribs for high angular resolution x-ray astronomy: a progress report

NASA Astrophysics Data System (ADS)

Civitani, M.; Basso, S.; Brizzolari, C.; Ghigo, M.; Pareschi, G.; Salmaso, B.; Spiga, D.; Vecchi, G.; Breunig, E.; Burwitz, V.; Hartner, G. D.; Menz, B.

2015-09-01

The Slumped Glass Optics technology, developed at INAF/OAB since a few years, is becoming a competitive solution for the realization of the future X-ray telescopes with a very large collecting area, as e.g. the proposed Athena, with more than 2 m2 effective area at 1 keV and with a high angular resolution (5'' HEW). The developed technique is based on modular elements, named X-ray Optical Units (XOUs), made of several layers of thin foils of glass, previously formed by direct hot slumping in cylindrical configuration, and then stacked in a Wolter-I configuration, through interfacing ribs. The achievable global angular resolution of the optics relies on the surface shape accuracy of the slumped foils, on the smoothness of the mirror surfaces and on the correct integration and co-alignment of the mirror segments achieved with a dedicated Integration Machine (IMA). In this paper we provide an update of the project development, reporting on the last results achieved. In particular, we will present the results obtained with full illumination X-ray tests for the last developed prototypes.

Silicon pore optics for the international x-ray observatory

NASA Astrophysics Data System (ADS)

Wille, E.; Wallace, K.; Bavdaz, M.; Collon, M. J.; Günther, R.; Ackermann, M.; Beijersbergen, M. W.; Riekerink, M. O.; Blom, M.; Lansdorp, B.; de Vreede, L.

2017-11-01

Lightweight X-ray Wolter optics with a high angular resolution will enable the next generation of X-ray telescopes in space. The International X-ray Observatory (IXO) requires a mirror assembly of 3 m2 effective area (at 1.5 keV) and an angular resolution of 5 arcsec. These specifications can only be achieved with a novel technology like Silicon Pore Optics, which is developed by ESA together with a consortium of European industry. Silicon Pore Optics are made of commercial Si wafers using process technology adapted from the semiconductor industry. We present the manufacturing process ranging from single mirror plates towards complete focusing mirror modules mounted in flight configuration. The performance of the mirror modules is tested using X-ray pencil beams or full X-ray illumination. In 2009, an angular resolution of 9 arcsec was achieved, demonstrating the improvement of the technology compared to 17 arcsec in 2007. Further development activities of Silicon Pore Optics concentrate on ruggedizing the mounting system and performing environmental tests, integrating baffles into the mirror modules and assessing the mass production.

Production of thin glass mirrors by hot slumping for x-ray telescopes: present process and ongoing development

NASA Astrophysics Data System (ADS)

Salmaso, B.; Basso, S.; Brizzolari, C.; Civitani, M.; Ghigo, M.; Pareschi, G.; Spiga, D.; Tagliaferri, G.; Vecchi, G.

2014-07-01

Thin glass foils are considered good candidates to build a segmented X-ray telescope with effective area as large as 2 m2 and angular resolution better than 5 arcsec. In order to produce thin glass mirror segments, we developed a direct hot slumping technique assisted by pressure, in which the shape of a mould is replicated onto the optical surface of the glass. In this paper we present the result obtained with AF32 (by Schott) and EAGLE XG (by Corning) glass types. The selected mould material is Zerodur K20, as it does not require any anti-sticking layer and has a good matching, in terms of Coefficient of Thermal Expansion, with both glass types. Our group already produced a few prototypes, reaching angular resolution near 20 arcsec. In this work, relevant steps forward aimed at attaining a 5 arcsec angular resolution are described, along with the tuning of few key parameters in the slumping process. The results obtained on a newly procured cylindrical Zerodur K20 mould are presented.

A concordant scenario to explain FU Orionis from deep centimeter and millimeter interferometric observations

NASA Astrophysics Data System (ADS)

Liu, Hauyu Baobab; Vorobyov, Eduard I.; Dong, Ruobing; Dunham, Michael M.; Takami, Michihiro; Galván-Madrid, Roberto; Hashimoto, Jun; Kóspál, Ágnes; Henning, Thomas; Tamura, Motohide; Rodríguez, Luis F.; Hirano, Naomi; Hasegawa, Yasuhiro; Fukagawa, Misato; Carrasco-Gonzalez, Carlos; Tazzari, Marco

2017-06-01

Aims: The aim of this work is to constrain properties of the disk around the archetype FU Orionis object, FU Ori, with as good as 25 au resolution. Methods: We resolved FU Ori at 29-37 GHz using the Karl G. Jansky Very Large Array (JVLA) in the A-array configuration, which provided the highest possible angular resolution to date at this frequency band ( 0.07 arcsec). We also performed complementary JVLA 8-10 GHz observations, Submillimeter Array (SMA) 224 GHz and 272 GHz observations, and compared these with archival Atacama Large Millimeter Array (ALMA) 346 GHz observations to obtain the spectral energy distributions (SEDs). Results: Our 8-10 GHz observations do not find evidence for the presence of thermal radio jets, and constrain the radio jet/wind flux to at least 90 times lower than the expected value from the previously reported bolometric luminosity-radio luminosity correlation. The emission at frequencies higher than 29 GHz may be dominated by the two spatially unresolved sources, which are located immediately around FU Ori and its companion FU Ori S, respectively. Their deconvolved radii at 33 GHz are only a few au, which is two orders of magnitude smaller in linear scale than the gaseous disk revealed by the previous Subaru-HiCIAO 1.6 μm coronagraphic polarization imaging observations. We are struck by the fact that these two spatially compact sources contribute to over 50% of the observed fluxes at 224 GHz, 272 GHz, and 346 GHz. The 8-346 GHz SEDs of FU Ori and FU Ori S cannot be fit by constant spectral indices (over frequency), although we cannot rule out that it is due to the time variability of their (sub)millimeter fluxes. Conclusions: The more sophisticated models for SEDs considering the details of the observed spectral indices in the millimeter bands suggest that the >29 GHz emission is contributed by a combination of free-free emission from ionized gas and thermal emission from optically thick and optically thin dust components. We hypothesize that dust in the innermost parts of the disks (≲0.1 au) has been sublimated, and thus the disks are no longer well shielded against the ionizing photons. The estimated overall gas and dust mass based on SED modeling, can be as high as a fraction of a solar mass, which is adequate for developing disk gravitational instability. Our present explanation for the observational data is that the massive inflow of gas and dust due to disk gravitational instability or interaction with a companion/intruder, was piled up at the few-au scale due to the development of a deadzone with negligible ionization. The piled up material subsequently triggered the thermal instability and the magnetorotational instability when the ionization fraction in the inner sub-au scale region exceeded a threshold value, leading to the high protostellar accretion rate.

SPICA, Stellar Parameters and Images with a Cophased Array: a 6T visible combiner for the CHARA array.

PubMed

Mourard, Denis; Bério, Philippe; Perraut, Karine; Clausse, Jean-Michel; Creevey, Orlagh; Martinod, Marc-Antoine; Meilland, Anthony; Millour, Florentin; Nardetto, Nicolas

2017-05-01

High angular resolution studies of stars in the optical domain have highly progressed in recent years. After the results obtained with the visible instrument Visible spEctroGraph and polArimeter (VEGA) on the Center for High Angular Resolution Astronomy (CHARA) array and the recent developments on adaptive optics and fibered interferometry, we have started the design and study of a new six-telescope visible combiner with single-mode fibers. It is designed as a low spectral resolution instrument for the measurement of the angular diameter of stars to make a major step forward in terms of magnitude and precision with respect to the present situation. For a large sample of bright stars, a medium spectral resolution mode will allow unprecedented spectral imaging of stellar surfaces and environments for higher accuracy on stellar/planetary parameters. To reach the ultimate performance of the instrument in terms of limiting magnitude (Rmag≃8 for diameter measurements and Rmag≃4 to 5 for imaging), Stellar Parameters and Images with a Cophased Array (SPICA) includes the development of a dedicated fringe tracking system in the H band to reach "long" (200 ms to 30 s) exposures of the fringe signal in the visible.

Evaluation of beam tracking strategies for the THOR-CSW solar wind instrument

NASA Astrophysics Data System (ADS)

De Keyser, Johan; Lavraud, Benoit; Prech, Lubomir; Neefs, Eddy; Berkenbosch, Sophie; Beeckman, Bram; Maggiolo, Romain; Fedorov, Andrei; Baruah, Rituparna; Wong, King-Wah; Amoros, Carine; Mathon, Romain; Génot, Vincent

2017-04-01

We compare different beam tracking strategies for the Cold Solar Wind (CSW) plasma spectrometer on the ESA M4 THOR mission candidate. The goal is to intelligently select the energy and angular windows the instrument is sampling and to adapt these windows as the solar wind properties evolve, with the aim to maximize the velocity distribution acquisition rate while maintaining excellent energy and angular resolution. Using synthetic data constructed using high-cadence measurements by the Faraday cup instrument on the Spektr-R mission (30 ms resolution), we test the performance of energy beam tracking with or without angular beam tracking. The algorithm can be fed both by data acquired by the plasma spectrometer during the previous measurement cycle, or by data from another instrument, in casu the Faraday Cup (FAR) instrument foreseen on THOR. We verify how these beam tracking algorithms behave for different sizes of the energy and angular windows, and for different data integration times, in order to assess the limitations of the algorithm and to avoid situations in which the algorithm loses track of the beam.

Observation of the shadowing of cosmic rays by the Moon using a deep underground detector

NASA Astrophysics Data System (ADS)

Ambrosio, M.; Antolini, R.; Aramo, C.; Auriemma, G.; Baldini, A.; Barbarino, G. C.; Barish, B. C.; Battistoni, G.; Bellotti, R.; Bemporad, C.; Bernardini, P.; Bilokon, H.; Bisi, V.; Bloise, C.; Bower, C.; Bussino, S.; Cafagna, F.; Calicchio, M.; Campana, D.; Carboni, M.; Castellano, M.; Cecchini, S.; Cei, F.; Chiarella, V.; Choudhary, B. C.; Coutu, S.; de Benedictis, L.; de Cataldo, G.; Dekhissi, H.; de Marzo, C.; de Mitri, I.; Derkaoui, J.; de Vincenzi, M.; di Credico, A.; Erriquez, O.; Favuzzi, C.; Forti, C.; Fusco, P.; Giacomelli, G.; Giannini, G.; Giglietto, N.; Giorgini, M.; Grassi, M.; Gray, L.; Grillo, A.; Guarino, F.; Guarnaccia, P.; Gustavino, C.; Habig, A.; Hanson, K.; Heinz, R.; Huang, Y.; Iarocci, E.; Katsavounidis, E.; Kearns, E.; Kim, H.; Kyriazopoulou, S.; Lamanna, E.; Lane, C.; Levin, D. S.; Lipari, P.; Longley, N. P.; Longo, M. J.; Maaroufi, F.; Mancarella, G.; Mandrioli, G.; Manzoor, S.; Neri, A. Margiotta; Marini, A.; Martello, D.; Marzari-Chiesa, A.; Mazziotta, M. N.; Mazzotta, C.; Michael, D. G.; Mikheyev, S.; Miller, L.; Monacelli, P.; Montaruli, T.; Monteno, M.; Mufson, S.; Musser, J.; Nicoló, D.; Orth, C.; Osteria, G.; Ouchrif, M.; Palamara, O.; Patera, V.; Patrizii, L.; Pazzi, R.; Peck, C. W.; Petrera, S.; Pistilli, P.; Popa, V.; Pugliese, V.; Rainò, A.; Reynoldson, J.; Ronga, F.; Rubizzo, U.; Satriano, C.; Satta, L.; Scapparone, E.; Scholberg, K.; Sciubba, A.; Serra-Lugaresi, P.; Severi, M.; Sioli, M.; Sitta, M.; Spinelli, P.; Spinetti, M.; Spurio, M.; Steinberg, R.; Stone, J. L.; Sulak, L. R.; Surdo, A.; Tarlè, G.; Togo, V.; Ugolotti, D.; Vakili, M.; Walter, C. W.; Webb, R.

1999-01-01

Using data collected by the MACRO experiment during the years 1989-1996, we show evidence for the shadow of the Moon in the underground cosmic ray flux with a significance of 3.6σ. This detection of the shadowing effect is the first by an underground detector. A maximum-likelihood analysis is used to determine that the angular resolution of the apparatus is 0.9°+/-0.3°. These results demonstrate MACRO's capabilities as a muon telescope by confirming its absolute pointing ability and quantifying its angular resolution.

An optical VLA on the Moon

NASA Technical Reports Server (NTRS)

Burke, Bernard F.

1992-01-01

Optical observations on the Earth must cope with the refractive disturbances of the atmosphere, perturbations by the day-to-night thermal cycle, vibrations induced by the wind, and the bending of the telescope by gravity. These all conspire to limit telescope performance. In particular, in trying to improve angular resolution, there seems to be a practical limit of the order of a few tenths of an arc-second for the realizable angular resolution of single-aperture telescopes, largely imposed by the atmosphere, although other structural limitations would appear as limits at one-tenth of an arc-second or so.

The Space High Angular Resolution Probe for the Infrared (SHARP-IR)

NASA Technical Reports Server (NTRS)

Rinehart, S. A.; Rizzo, M. J.; Leisawitz, D. T.; Staguhn, J. G.; Dipirro, M.; Mentzell, J. E.; Juanola-Parramon, R.; Dhabal, A.; Mundy, L. G.; Moseley, S. H.;

Determining neutrino mass from the cosmic microwave background alone.

PubMed

Kaplinghat, Manoj; Knox, Lloyd; Song, Yong-Seon

2003-12-12

Distortions of cosmic microwave background temperature and polarization maps caused by gravitational lensing, observable with high angular resolution and high sensitivity, can be used to measure the neutrino mass. Assuming two massless species and one with mass m(nu), we forecast sigma(m(nu))=0.15 eV from the Planck satellite and sigma(m(nu))=0.04 eV from observations with twice the angular resolution and approximately 20 times the sensitivity. A detection is likely at this higher sensitivity since the observation of atmospheric neutrino oscillations requires Deltam(2)(nu) greater, similar (0.04 eV)(2).

Role of CT in Congenital Heart Disease.

PubMed

Rajiah, Prabhakar; Saboo, Sachin S; Abbara, Suhny

2017-01-01

Congenital heart diseases (CHD) are being increasingly encountered in cardiac imaging due to improved outcomes from surgical and interventional techniques. Imaging plays an important role in the evaluation of CHD, both prior to and after surgeries and interventions. Computed tomography (CT) has several advantages in the evaluation of these disorders, particularly its high spatial resolution, multi-planar reconstruction capabilities at sub-millimeter isotropic resolution, good temporal resolution, wide field of view, and rapid turnaround time, which minimizes the need for sedation and anesthesia in young children or children with disabilities. With modern scanners, images can be acquired as fast as within one heartbeat. Although there is a risk of ionizing radiation, the radiation dose can be minimized by using several dose reduction strategies. There is a risk of contrast nephrotoxicity in patients with renal dysfunction. In this article, we will review the role of CT in the evaluation of several congenital heart diseases, both in children and adults.

Spectroscopic observations with the Stratospheric Observatory for Infrared Astronomy (SOFIA)

NASA Astrophysics Data System (ADS)

Becklin, E. E.; Tielens, A. G. G. M.; Callis, H. H. S.

The joint US and German SOFIA project to develop and operate a 2.5-meter infrared airborne telescope in a Boeing 747-SP is now in its final stages of development. Flying in the stratosphere, SOFIA allows observations through the infrared and submillimeter region, with an average transmission of greater than 80%. SOFIA is characterized by a wide instrument complement ranging from broadband imagers, through moderate resolution spectrographs capable of resolving broad features due to dust and large molecules, to high-resolution spectrometers suitable for kinematic studies of molecular and atomic gas lines at km/s resolution. This broad range in instruments will enable SOFIA to make unique contributions to a broad array of science topics. First science flights will begin in 2009 and the observatory is expected to operate for over 20 years. The sensitivity, characteristics, science instrument complement, and examples of first light spectroscopic science are discussed.

Stratospheric Observatory for Infrared Astronomy (sofia)

NASA Astrophysics Data System (ADS)

Becklin, E. E.; Tielens, A. G. G. M.; Callis, H. H. S.

The joint U.S. and German SOFIA project to develop and operate a 2.5-meter infrared airborne telescope in a Boeing 747-SP is now in its final stages of development. Flying in the stratosphere, SOFIA allows observations through the infrared and submillimeter region, with an average transmission of ≳ 80%. SOFIA is characterized by a wide instrument complement ranging from broadband imagers, through moderate resolution spectrographs capable of resolving broad features due to dust and large molecules, to high resolution spectrometers suitable for kinematic studies of molecular and atomic gas lines at km/s resolution. This broad range in instruments will enable SOFIA to make unique contributions to a broad array of science topics. First science flights will begin in 2009 and the observatory is expected to operate for over 20 years. The sensitivity, characteristics, science instrument complement, and examples of first light science are discussed.

Stratospheric Observatory for Infrared Astronomy (SOFIA)

NASA Astrophysics Data System (ADS)

Becklin, E. E.; Gehrz, R. D.

2009-08-01

The joint U.S. and German SOFIA project to develop and operate a 2.5-meter infrared airborne telescope in a Boeing 747-SP is in its final stages of development. Flying in the stratosphere, SOFIA allows observations throughout the infrared and submillimeter region, with an average transmission of greater than 80%. SOFIA's first generation instrument complement includes high-speed photometers, broadband imagers, moderate resolution spectrographs capable of resolving broad features due to dust and large molecules, and high resolution spectrometers suitable for kinematic studies of molecular and atomic gas lines at km/s resolution. These instruments will enable SOFIA to make unique contributions to a broad array of science topics. First science flights will begin in 2010, and the observatory is expected to operate for more than 20 years. The sensitivity, characteristics, science instrument complement, future instrument opportunities and examples of first light science will be discussed.

Open Science CBS Neuroimaging Repository: Sharing ultra-high-field MR images of the brain.

PubMed

Tardif, Christine Lucas; Schäfer, Andreas; Trampel, Robert; Villringer, Arno; Turner, Robert; Bazin, Pierre-Louis

2016-01-01

Magnetic resonance imaging at ultra high field opens the door to quantitative brain imaging at sub-millimeter isotropic resolutions. However, novel image processing tools to analyze these new rich datasets are lacking. In this article, we introduce the Open Science CBS Neuroimaging Repository: a unique repository of high-resolution and quantitative images acquired at 7 T. The motivation for this project is to increase interest for high-resolution and quantitative imaging and stimulate the development of image processing tools developed specifically for high-field data. Our growing repository currently includes datasets from MP2RAGE and multi-echo FLASH sequences from 28 and 20 healthy subjects respectively. These datasets represent the current state-of-the-art in in-vivo relaxometry at 7 T, and are now fully available to the entire neuroimaging community. Copyright © 2015 Elsevier Inc. All rights reserved.

Progress in passive submillimeter-wave video imaging

NASA Astrophysics Data System (ADS)

Heinz, Erik; May, Torsten; Born, Detlef; Zieger, Gabriel; Peiselt, Katja; Zakosarenko, Vyacheslav; Krause, Torsten; Krüger, André; Schulz, Marco; Bauer, Frank; Meyer, Hans-Georg

2014-06-01

Since 2007 we are developing passive submillimeter-wave video cameras for personal security screening. In contradiction to established portal-based millimeter-wave scanning techniques, these are suitable for stand-off or stealth operation. The cameras operate in the 350GHz band and use arrays of superconducting transition-edge sensors (TES), reflector optics, and opto-mechanical scanners. Whereas the basic principle of these devices remains unchanged, there has been a continuous development of the technical details, as the detector array, the scanning scheme, and the readout, as well as system integration and performance. The latest prototype of this camera development features a linear array of 128 detectors and a linear scanner capable of 25Hz frame rate. Using different types of reflector optics, a field of view of 1×2m2 and a spatial resolution of 1-2 cm is provided at object distances of about 5-25m. We present the concept of this camera and give details on system design and performance. Demonstration videos show its capability for hidden threat detection and illustrate possible application scenarios.

Multiwavelength Properties of Faint Submillimeter Galaxies with Archival ALMA Data

NASA Astrophysics Data System (ADS)

Patil, Pallavi; Lacy, Mark; Nyland, Kristina

2018-01-01

Detection of Faint submillimeter galaxies was made possible by large improvements in the spatial resolution and sensitivity by interferometric observations. These galaxies are a dominant contributor to the extragalactic background light at millimeter wavelengths and are likely to play a significant role in galaxy evolution. We present a catalog of 28 such galaxies with S(1.1 mm) < 1.0 mJy that have 13-band optical/near IR photometry (Spitzer DeepDrill, VIDEO, CFHTLS, and HSC) and serendipitous detections in ALMA band 6. ALMA 1.1 mm continuum observations were cross-matched with the K-band VIDEO catalog in the XMM-LSS field to identify multiwavelength counterparts. A forced Photometry approach based on the Tractor image modeling code is used to construct the catalog. The median photometric redshift of the sample is z ~ 1.96 along with two high redshift candidates at z ~ 5. We have provided population statistics using multiband photometry and estimated galaxy properties such as dust and gas masses. We aim to provide a detailed characterization of this population to ultimately devise better selection techniques for future wide-area sky surveys.

MIRO Computational Model

NASA Technical Reports Server (NTRS)

Broderick, Daniel

2010-01-01

A computational model calculates the excitation of water rotational levels and emission-line spectra in a cometary coma with applications for the Micro-wave Instrument for Rosetta Orbiter (MIRO). MIRO is a millimeter-submillimeter spectrometer that will be used to study the nature of cometary nuclei, the physical processes of outgassing, and the formation of the head region of a comet (coma). The computational model is a means to interpret the data measured by MIRO. The model is based on the accelerated Monte Carlo method, which performs a random angular, spatial, and frequency sampling of the radiation field to calculate the local average intensity of the field. With the model, the water rotational level populations in the cometary coma and the line profiles for the emission from the water molecules as a function of cometary parameters (such as outgassing rate, gas temperature, and gas and electron density) and observation parameters (such as distance to the comet and beam width) are calculated.

[An effective method for improving the imaging spatial resolution of terahertz time domain spectroscopy system].

PubMed

Zhang, Zeng-yan; Ji, Te; Zhu, Zhi-yong; Zhao, Hong-wei; Chen, Min; Xiao, Ti-qiao; Guo, Zhi

2015-01-01

Terahertz radiation is an electromagnetic radiation in the range between millimeter waves and far infrared. Due to its low energy and non-ionizing characters, THz pulse imaging emerges as a novel tool in many fields, such as material, chemical, biological medicine, and food safety. Limited spatial resolution is a significant restricting factor of terahertz imaging technology. Near field imaging method was proposed to improve the spatial resolution of terahertz system. Submillimeter scale's spauial resolution can be achieved if the income source size is smaller than the wawelength of the incoming source and the source is very close to the sample. But many changes were needed to the traditional terahertz time domain spectroscopy system, and it's very complex to analyze sample's physical parameters through the terahertz signal. A method of inserting a pinhole upstream to the sample was first proposed in this article to improve the spatial resolution of traditional terahertz time domain spectroscopy system. The measured spatial resolution of terahertz time domain spectroscopy system by knife edge method can achieve spatial resolution curves. The moving stage distance between 10 % and 90 Yo of the maximum signals respectively was defined as the, spatial resolution of the system. Imaging spatial resolution of traditional terahertz time domain spectroscopy system was improved dramatically after inserted a pinhole with diameter 0. 5 mm, 2 mm upstream to the sample. Experimental results show that the spatial resolution has been improved from 1. 276 mm to 0. 774 mm, with the increment about 39 %. Though this simple method, the spatial resolution of traditional terahertz time domain spectroscopy system was increased from millimeter scale to submillimeter scale. A pinhole with diameter 1 mm on a polyethylene plate was taken as sample, to terahertz imaging study. The traditional terahertz time domain spectroscopy system and pinhole inserted terahertz time domain spectroscopy system were applied in the imaging experiment respectively. The relative THz-power loss imaging of samples were use in this article. This method generally delivers the best signal to noise ratio in loss images, dispersion effects are cancelled. Terahertz imaging results show that the sample's boundary was more distinct after inserting the pinhole in front of, sample. The results also conform that inserting pinhole in front of sample can improve the imaging spatial resolution effectively. The theoretical analyses of the method which improve the spatial resolution by inserting a pinhole in front of sample were given in this article. The analyses also indicate that the smaller the pinhole size, the longer spatial coherence length of the system, the better spatial resolution of the system. At the same time the terahertz signal will be reduced accordingly. All the experimental results and theoretical analyses indicate that the method of inserting a pinhole in front of sample can improve the spatial resolution of traditional terahertz time domain spectroscopy system effectively, and it will further expand the application of terahertz imaging technology.

Spatial Angular Compounding Technique for H-Scan Ultrasound Imaging.

PubMed

Khairalseed, Mawia; Xiong, Fangyuan; Kim, Jung-Whan; Mattrey, Robert F; Parker, Kevin J; Hoyt, Kenneth

2018-01-01

H-Scan is a new ultrasound imaging technique that relies on matching a model of pulse-echo formation to the mathematics of a class of Gaussian-weighted Hermite polynomials. This technique may be beneficial in the measurement of relative scatterer sizes and in cancer therapy, particularly for early response to drug treatment. Because current H-scan techniques use focused ultrasound data acquisitions, spatial resolution degrades away from the focal region and inherently affects relative scatterer size estimation. Although the resolution of ultrasound plane wave imaging can be inferior to that of traditional focused ultrasound approaches, the former exhibits a homogeneous spatial resolution throughout the image plane. The purpose of this study was to implement H-scan using plane wave imaging and investigate the impact of spatial angular compounding on H-scan image quality. Parallel convolution filters using two different Gaussian-weighted Hermite polynomials that describe ultrasound scattering events are applied to the radiofrequency data. The H-scan processing is done on each radiofrequency image plane before averaging to get the angular compounded image. The relative strength from each convolution is color-coded to represent relative scatterer size. Given results from a series of phantom materials, H-scan imaging with spatial angular compounding more accurately reflects the true scatterer size caused by reductions in the system point spread function and improved signal-to-noise ratio. Preliminary in vivo H-scan imaging of tumor-bearing animals suggests this modality may be useful for monitoring early response to chemotherapeutic treatment. Overall, H-scan imaging using ultrasound plane waves and spatial angular compounding is a promising approach for visualizing the relative size and distribution of acoustic scattering sources. Copyright © 2018 World Federation for Ultrasound in Medicine and Biology. Published by Elsevier Inc. All rights reserved.

Multi-resolution anisotropy studies of ultrahigh-energy cosmic rays detected at the Pierre Auger Observatory

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

Aab, A.; Abreu, P.; Andringa, S.

2017-06-01

We report a multi-resolution search for anisotropies in the arrival directions of cosmic rays detected at the Pierre Auger Observatory with local zenith angles up to 80{sup o} and energies in excess of 4 EeV (4 × 10{sup 18} eV). This search is conducted by measuring the angular power spectrum and performing a needlet wavelet analysis in two independent energy ranges. Both analyses are complementary since the angular power spectrum achieves a better performance in identifying large-scale patterns while the needlet wavelet analysis, considering the parameters used in this work, presents a higher efficiency in detecting smaller-scale anisotropies, potentially providingmore » directional information on any observed anisotropies. No deviation from isotropy is observed on any angular scale in the energy range between 4 and 8 EeV. Above 8 EeV, an indication for a dipole moment is captured; while no other deviation from isotropy is observed for moments beyond the dipole one. The corresponding p -values obtained after accounting for searches blindly performed at several angular scales, are 1.3 × 10{sup −5} in the case of the angular power spectrum, and 2.5 × 10{sup −3} in the case of the needlet analysis. While these results are consistent with previous reports making use of the same data set, they provide extensions of the previous works through the thorough scans of the angular scales.« less

Multi-resolution anisotropy studies of ultrahigh-energy cosmic rays detected at the Pierre Auger Observatory

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

Aab, A.; Abreu, P.; Aglietta, M.

We report a multi-resolution search for anisotropies in the arrival directions of cosmic rays detected at the Pierre Auger Observatory with local zenith angles up to 80(o) and energies in excess of 4 EeV (4 × 10 18 eV). This search is conducted by measuring the angular power spectrum and performing a needlet wavelet analysis in two independent energy ranges. Both analyses are complementary since the angular power spectrum achieves a better performance in identifying large-scale patterns while the needlet wavelet analysis, considering the parameters used in this work, presents a higher efficiency in detecting smaller-scale anisotropies, potentially providing directional information onmore » any observed anisotropies. No deviation from isotropy is observed on any angular scale in the energy range between 4 and 8 EeV. Above 8 EeV, an indication for a dipole moment is captured, while no other deviation from isotropy is observed for moments beyond the dipole one. The corresponding p-values obtained after accounting for searches blindly performed at several angular scales, are 1.3 × 10 -5 in the case of the angular power spectrum, and 2.5 × 10 -3 in the case of the needlet analysis. While these results are consistent with previous reports making use of the same data set, they provide extensions of the previous works through the thorough scans of the angular scales.« less

Small FDIRC designs

DOE PAGES

Dey, B.; Ratcliff, B.; Va’vra, J.

2017-02-16

In this article, we explore the angular resolution limits attainable in small FDIRC designs taking advantage of the new highly pixelated detectors that are now available. Since the basic FDIRC design concept attains its particle separation performance mostly in the angular domain as measured by two-dimensional pixels, this paper relies primarily on a pixel-based analysis, with additional chromatic corrections using the time domain, requiring single photon timing resolution at a level of 100–200 ps only. This approach differs from other modern DIRC design concepts such as TOP or TORCH detectors, whose separation performances rely more strongly on time-dependent analyses. Inmore » conclusion, we find excellent single photon resolution with a geometry where individual bars are coupled to a single plate, which is coupled in turn to a cylindrical lens focusing camera.« less

Small FDIRC designs

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

Dey, B.; Ratcliff, B.; Va’vra, J.

In this article, we explore the angular resolution limits attainable in small FDIRC designs taking advantage of the new highly pixelated detectors that are now available. Since the basic FDIRC design concept attains its particle separation performance mostly in the angular domain as measured by two-dimensional pixels, this paper relies primarily on a pixel-based analysis, with additional chromatic corrections using the time domain, requiring single photon timing resolution at a level of 100–200 ps only. This approach differs from other modern DIRC design concepts such as TOP or TORCH detectors, whose separation performances rely more strongly on time-dependent analyses. Inmore » conclusion, we find excellent single photon resolution with a geometry where individual bars are coupled to a single plate, which is coupled in turn to a cylindrical lens focusing camera.« less

Review of SPECT collimator selection, optimization, and fabrication for clinical and preclinical imaging

PubMed Central

Van Audenhaege, Karen; Van Holen, Roel; Vandenberghe, Stefaan; Vanhove, Christian; Metzler, Scott D.; Moore, Stephen C.

2015-01-01

In single photon emission computed tomography, the choice of the collimator has a major impact on the sensitivity and resolution of the system. Traditional parallel-hole and fan-beam collimators used in clinical practice, for example, have a relatively poor sensitivity and subcentimeter spatial resolution, while in small-animal imaging, pinhole collimators are used to obtain submillimeter resolution and multiple pinholes are often combined to increase sensitivity. This paper reviews methods for production, sensitivity maximization, and task-based optimization of collimation for both clinical and preclinical imaging applications. New opportunities for improved collimation are now arising primarily because of (i) new collimator-production techniques and (ii) detectors with improved intrinsic spatial resolution that have recently become available. These new technologies are expected to impact the design of collimators in the future. The authors also discuss concepts like septal penetration, high-resolution applications, multiplexing, sampling completeness, and adaptive systems, and the authors conclude with an example of an optimization study for a parallel-hole, fan-beam, cone-beam, and multiple-pinhole collimator for different applications. PMID:26233207

Planetary submillimeter spectroscopy

NASA Technical Reports Server (NTRS)

Klein, M. J.

1988-01-01

The aim is to develop a comprehensive observational and analytical program to study solar system physics and meterology by measuring molecular lines in the millimeter and submillimeter spectra of planets and comets. A primary objective is to conduct observations with new JPL and Caltech submillimeter receivers at the Caltech Submillimeter Observatory (CSO) on Mauna Kea, Hawaii. A secondary objective is to continue to monitor the time variable planetary phenomena (e.g., Jupiter and Uranus) at centimeter wavelength using the NASA antennas of the Deep Space Network (DSN).

Cryogenic Amplifier Based Receivers at Submillimeter Wavelengths

NASA Technical Reports Server (NTRS)

Chattopadhyay, Goutam; Reck, Theodore and; Schlecht, Erich; Lin, Robert; Deal, William

2012-01-01

The operating frequency of InP high electron mobility transistor (HEMT) based amplifiers has moved well in the submillimeter-wave frequencies over the last couple of years. Working amplifiers with usable gain in waveguide packages has been reported beyond 700 GHz. When cooled cryogenically, they have shown substantial improvement in their noise temperature. This has opened up the real possibility of cryogenic amplifier based heterodyne receivers at submillimeter wavelengths for ground-based, air-borne, and space-based instruments for astrophysics, planetary, and Earth science applications. This paper provides an overview of the science applications at submillimeter wavelengths that will benefit from this technology. It also describes the current state of the InP HEMT based cryogenic amplifier receivers at submillimeter wavelengths.

A sub-millimeter resolution PET detector module using a multi-pixel photon counter array

NASA Astrophysics Data System (ADS)

Song, Tae Yong; Wu, Heyu; Komarov, Sergey; Siegel, Stefan B.; Tai, Yuan-Chuan

2010-05-01

A PET block detector module using an array of sub-millimeter lutetium oxyorthosilicate (LSO) crystals read out by an array of surface-mount, semiconductor photosensors has been developed. The detector consists of a LSO array, a custom acrylic light guide, a 3 × 3 multi-pixel photon counter (MPPC) array (S10362-11-050P, Hamamatsu Photonics, Japan) and a readout board with a charge division resistor network. The LSO array consists of 100 crystals, each measuring 0.8 × 0.8 × 3 mm3 and arranged in 0.86 mm pitches. A Monte Carlo simulation was used to aid the design and fabrication of a custom light guide to control distribution of scintillation light over the surface of the MPPC array. The output signals of the nine MPPC are multiplexed by a charge division resistor network to generate four position-encoded analog outputs. Flood image, energy resolution and timing resolution measurements were performed using standard NIM electronics. The linearity of the detector response was investigated using gamma-ray sources of different energies. The 10 × 10 array of 0.8 mm LSO crystals was clearly resolved in the flood image. The average energy resolution and standard deviation were 20.0% full-width at half-maximum (FWHM) and ±5.0%, respectively, at 511 keV. The timing resolution of a single MPPC coupled to a LSO crystal was found to be 857 ps FWHM, and the value for the central region of detector module was 1182 ps FWHM when ±10% energy window was applied. The nonlinear response of a single MPPC when used to read out a single LSO was observed among the corner crystals of the proposed detector module. However, the central region of the detector module exhibits significantly less nonlinearity (6.5% for 511 keV). These results demonstrate that (1) a charge-sharing resistor network can effectively multiplex MPPC signals and reduce the number of output signals without significantly degrading the performance of a PET detector and (2) a custom light guide to permit light sharing among multiple MPPC and to diffuse and direct scintillation light can reduce the nonlinearity of the detector response within the limited dynamic range of a typical MPPC. As a result, the proposed PET detector module has the potential to be refined for use in high-resolution PET insert applications.

A sub-millimeter resolution PET detector module using a multi-pixel photon counter array.

PubMed

Song, Tae Yong; Wu, Heyu; Komarov, Sergey; Siegel, Stefan B; Tai, Yuan-Chuan

2010-05-07

A PET block detector module using an array of sub-millimeter lutetium oxyorthosilicate (LSO) crystals read out by an array of surface-mount, semiconductor photosensors has been developed. The detector consists of a LSO array, a custom acrylic light guide, a 3 x 3 multi-pixel photon counter (MPPC) array (S10362-11-050P, Hamamatsu Photonics, Japan) and a readout board with a charge division resistor network. The LSO array consists of 100 crystals, each measuring 0.8 x 0.8 x 3 mm(3) and arranged in 0.86 mm pitches. A Monte Carlo simulation was used to aid the design and fabrication of a custom light guide to control distribution of scintillation light over the surface of the MPPC array. The output signals of the nine MPPC are multiplexed by a charge division resistor network to generate four position-encoded analog outputs. Flood image, energy resolution and timing resolution measurements were performed using standard NIM electronics. The linearity of the detector response was investigated using gamma-ray sources of different energies. The 10 x 10 array of 0.8 mm LSO crystals was clearly resolved in the flood image. The average energy resolution and standard deviation were 20.0% full-width at half-maximum (FWHM) and +/-5.0%, respectively, at 511 keV. The timing resolution of a single MPPC coupled to a LSO crystal was found to be 857 ps FWHM, and the value for the central region of detector module was 1182 ps FWHM when +/-10% energy window was applied. The nonlinear response of a single MPPC when used to read out a single LSO was observed among the corner crystals of the proposed detector module. However, the central region of the detector module exhibits significantly less nonlinearity (6.5% for 511 keV). These results demonstrate that (1) a charge-sharing resistor network can effectively multiplex MPPC signals and reduce the number of output signals without significantly degrading the performance of a PET detector and (2) a custom light guide to permit light sharing among multiple MPPC and to diffuse and direct scintillation light can reduce the nonlinearity of the detector response within the limited dynamic range of a typical MPPC. As a result, the proposed PET detector module has the potential to be refined for use in high-resolution PET insert applications.

A sub-millimeter resolution PET detector module using a multi-pixel photon counter array

PubMed Central

Song, Tae Yong; Wu, Heyu; Komarov, Sergey; Siegel, Stefan B; Tai, Yuan-Chuan

2010-01-01

A PET block detector module using an array of sub-millimeter lutetium oxyorthosilicate (LSO) crystals read out by an array of surface-mount, semiconductor photosensors has been developed. The detector consists of a LSO array, a custom acrylic light guide, a 3 × 3 multi-pixel photon counter (MPPC) array (S10362-11-050P, Hamamatsu Photonics, Japan) and a readout board with a charge division resistor network. The LSO array consists of 100 crystals, each measuring 0.8 × 0.8 × 3 mm3 and arranged in 0.86 mm pitches. A Monte Carlo simulation was used to aid the design and fabrication of a custom light guide to control distribution of scintillation light over the surface of the MPPC array. The output signals of the nine MPPC are multiplexed by a charge division resistor network to generate four position-encoded analog outputs. Flood image, energy resolution and timing resolution measurements were performed using standard NIM electronics. The linearity of the detector response was investigated using gamma-ray sources of different energies. The 10 × 10 array of 0.8 mm LSO crystals was clearly resolved in the flood image. The average energy resolution and standard deviation were 20.0% full-width at half-maximum (FWHM) and ±5.0%, respectively, at 511 keV. The timing resolution of a single MPPC coupled to a LSO crystal was found to be 857 ps FWHM, and the value for the central region of detector module was 1182 ps FWHM when ±10% energy window was applied. The nonlinear response of a single MPPC when used to read out a single LSO was observed among the corner crystals of the proposed detector module. However, the central region of the detector module exhibits significantly less nonlinearity (6.5% for 511 keV). These results demonstrate that (1) a charge-sharing resistor network can effectively multiplex MPPC signals and reduce the number of output signals without significantly degrading the performance of a PET detector and (2) a custom light guide to permit light sharing among multiple MPPC and to diffuse and direct scintillation light can reduce the nonlinearity of the detector response within the limited dynamic range of a typical MPPC. As a result, the proposed PET detector module has the potential to be refined for use in high-resolution PET insert applications. PMID:20393236

An angle encoder for super-high resolution and super-high accuracy using SelfA

NASA Astrophysics Data System (ADS)

Watanabe, Tsukasa; Kon, Masahito; Nabeshima, Nobuo; Taniguchi, Kayoko

2014-06-01

Angular measurement technology at high resolution for applications such as in hard disk drive manufacturing machines, precision measurement equipment and aspherical process machines requires a rotary encoder with high accuracy, high resolution and high response speed. However, a rotary encoder has angular deviation factors during operation due to scale error or installation error. It has been assumed to be impossible to achieve accuracy below 0.1″ in angular measurement or control after the installation onto the rotating axis. Self-calibration (Lu and Trumper 2007 CIRP Ann. 56 499; Kim et al 2011 Proc. MacroScale; Probst 2008 Meas. Sci. Technol. 19 015101; Probst et al Meas. Sci. Technol. 9 1059; Tadashi and Makoto 1993 J. Robot. Mechatronics 5 448; Ralf et al 2006 Meas. Sci. Technol. 17 2811) and cross-calibration (Probst et al 1998 Meas. Sci. Technol. 9 1059; Just et al 2009 Precis. Eng. 33 530; Burnashev 2013 Quantum Electron. 43 130) technologies for a rotary encoder have been actively discussed on the basis of the principle of circular closure. This discussion prompted the development of rotary tables which achieve reliable and high accuracy angular verification. We apply these technologies for the development of a rotary encoder not only to meet the requirement of super-high accuracy but also to meet that of super-high resolution. This paper presents the development of an encoder with 221 = 2097 152 resolutions per rotation (360°), that is, corresponding to a 0.62″ signal period, achieved by the combination of a laser rotary encoder supplied by Magnescale Co., Ltd and a self-calibratable encoder (SelfA) supplied by The National Institute of Advanced Industrial Science & Technology (AIST). In addition, this paper introduces the development of a rotary encoder to guarantee ±0.03″ accuracy at any point of the interpolated signal, with respect to the encoder at the minimum resolution of 233, that is, corresponding to a 0.0015″ signal period after interpolation of 212 (= 4096) divisions through the interpolator.

Time-resolved orbital angular momentum spectroscopy

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

Noyan, Mehmet A.; Kikkawa, James M.

We introduce pump-probe magneto-orbital spectroscopy, wherein Laguerre-Gauss optical pump pulses impart orbital angular momentum to the electronic states of a material and subsequent dynamics are studied with 100 fs time resolution. The excitation uses vortex modes that distribute angular momentum over a macroscopic area determined by the spot size, and the optical probe studies the chiral imbalance of vortex modes reflected off the sample. First observations in bulk GaAs yield transients that evolve on time scales distinctly different from population and spin relaxation, as expected, but with surprisingly large lifetimes.

Shadow image on the retina of a defocused eye

NASA Astrophysics Data System (ADS)

Lenskii, A. V.

1994-04-01

Some visual conditions for transparent objects positioned within and beyond the accommodation limits on the path of the light traveling from a remote source of a small angular size are theoretically considered for the naked eye with a strong ametropia. The resolving power and admissible angular size of the light source are evaluated. The predicted possibility of seeing sufficiently extended transparent gratings at such distances has found that the density of ruling of the grating-object is higher than the ultimate angular resolution of the normal eye.

Improving angular resolution with Scan-MUSIC algorithm for real complex targets using 35-GHz millimeter-wave radar

NASA Astrophysics Data System (ADS)

Ly, Canh

2004-08-01

Scan-MUSIC algorithm, developed by the U.S. Army Research Laboratory (ARL), improves angular resolution for target detection with the use of a single rotatable radar scanning the angular region of interest. This algorithm has been adapted and extended from the MUSIC algorithm that has been used for a linear sensor array. Previously, it was shown that the SMUSIC algorithm and a Millimeter Wave radar can be used to resolve two closely spaced point targets that exhibited constructive interference, but not for the targets that exhibited destructive interference. Therefore, there were some limitations of the algorithm for the point targets. In this paper, the SMUSIC algorithm is applied to a problem of resolving real complex scatterer-type targets, which is more useful and of greater practical interest, particular for the future Army radar system. The paper presents results of the angular resolution of the targets, an M60 tank and an M113 Armored Personnel Carrier (APC), that are within the mainlobe of a Κα-band radar antenna. In particular, we applied the algorithm to resolve centroids of the targets that were placed within the beamwidth of the antenna. The collected coherent data using the stepped-frequency radar were compute magnitudely for the SMUSIC calculation. Even though there were significantly different signal returns for different orientations and offsets of the two targets, we resolved those two target centroids when they were as close as about 1/3 of the antenna beamwidth.

Science requirements and optimization of the silicon pore optics design for the Athena mirror

NASA Astrophysics Data System (ADS)

Willingale, R.; Pareschi, G.; Christensen, F.; den Herder, J.-W.; Ferreira, D.; Jakobsen, A.; Ackermann, M.; Collon, M.; Bavdaz, M.

2014-07-01

The science requirements for the Athena X-ray mirror are to provide a collecting area of 2 m2 at 1 keV, an angular resolution of ~5 arc seconds half energy eidth (HEW) and a field of view of diameter 40-50 arc minutes. This combination of area and angular resolution over a wide field are possible because of unique features of the Silicon pore optics (SPO) technology used. Here we describe the optimization and modifications of the SPO technology required to achieve the Athena mirror specification and demonstrate how the optical design of the mirror system impacts on the scientific performance of Athena.

REVIEWS OF TOPICAL PROBLEMS: Global phase-stable radiointerferometric systems

NASA Astrophysics Data System (ADS)

Dravskikh, A. F.; Korol'kov, Dimitrii V.; Pariĭskiĭ, Yu N.; Stotskiĭ, A. A.; Finkel'steĭn, A. M.; Fridman, P. A.

1981-12-01

We discuss from a unitary standpoint the possibility of building a phase-stable interferometric system with very long baselines that operate around the clock with real-time data processing. The various problems involved in the realization of this idea are discussed: the methods of suppression of instrumental and tropospheric phase fluctuations, the methods for constructing two-dimensional images and determining the coordinates of radio sources with high angular resolution, and the problem of the optimal structure of the interferometric system. We review in detail the scientific problems from the various branches of natural science (astrophysics, cosmology, geophysics, geodynamics, astrometry, etc.) whose solution requires superhigh angular resolution.

The usability of the optical parametric amplification of light for high-angular-resolution imaging and fast astrometry

NASA Astrophysics Data System (ADS)

Kurek, A. R.; Stachowski, A.; Banaszek, K.; Pollo, A.

2018-05-01

High-angular-resolution imaging is crucial for many applications in modern astronomy and astrophysics. The fundamental diffraction limit constrains the resolving power of both ground-based and spaceborne telescopes. The recent idea of a quantum telescope based on the optical parametric amplification (OPA) of light aims to bypass this limit for the imaging of extended sources by an order of magnitude or more. We present an updated scheme of an OPA-based device and a more accurate model of the signal amplification by such a device. The semiclassical model that we present predicts that the noise in such a system will form so-called light speckles as a result of light interference in the optical path. Based on this model, we analysed the efficiency of OPA in increasing the angular resolution of the imaging of extended targets and the precise localization of a distant point source. According to our new model, OPA offers a gain in resolved imaging in comparison to classical optics. For a given time-span, we found that OPA can be more efficient in localizing a single distant point source than classical telescopes.

X-ray Interferometry with Transmissive Beam Combiners for Ultra-High Angular Resolution Astronomy

NASA Technical Reports Server (NTRS)

Skinner, G. K.; Krismanic, John F.

2009-01-01

Abstract Interferometry provides one of the possible routes to ultra-high angular resolution for X-ray and gamma-ray astronomy. Sub-micro-arc-second angular resolution, necessary to achieve objectives such as imaging the regions around the event horizon of a super-massive black hole at the center of an active galaxy, can be achieved if beams from parts of the incoming wavefront separated by 100s of meters can be stably and accurately brought together at small angles. One way of achieving this is by using grazing incidence mirrors. We here investigate an alternative approach in which the beams are recombined by optical elements working in transmission. It is shown that the use of diffractive elements is a particularly attractive option. We report experimental results from a simple 2-beam interferometer using a low-cost commercially available profiled film as the diffractive elements. A rotationally symmetric filled (or mostly filled) aperture variant of such an interferometer, equivalent to an X-ray axicon, is shown to offer a much wider bandpass than either a Phase Fresnel Lens (PFL) or a PFL with a refractive lens in an achromatic pair. Simulations of an example system are presented.

VECC array for Nuclear fast Timing and angUlar corRElation studies (VENTURE)

NASA Astrophysics Data System (ADS)

Alam, S. S.; Bhattacharjee, T.; Banerjee, D.; Saha, A.; Pandit, Deepak; Mondal, D.; Mukhopadhyay, S.; Pal, Surajit; Bhaskar, P.; Das, S. K.; Banerjee, S. R.

2017-12-01

The VECC array for Nuclear fast Timing and angUlar corRElation studies (VENTURE) has been developed using several fast Cerium-Bromide (CeBr3) scintillators coupled to Hamamatsu R9779 Photomultiplier tubes. The CeBr3 detector has been characterised for the spectroscopic properties like energy response, energy resolution, timing resolution and detection efficiency. The response and efficiency of the detector have been compared with the results obtained from a Monte Carlo simulation with GEANT3 package. A time resolution of 144(1) ps and 109(1) ps was obtained for a single detector using 622-512 keV and 1173-1332 keV cascades respectively. The Generalised Centroid Difference (GCD) method has been employed with CeBr3 detectors by measuring the level lifetimes for the 511.9 keV level of 106Pd and the 160.6 and 383.8 keV levels of 133Cs. The angular correlation measurement was performed for the 1173-1332 keV cascade in 60Ni and the 228-49 keV cascade of 132I nucleus, populated from the decay of 132Te produced via 238U(α, f) reaction.

Detection of atomic oxygen and further line assignments in the far-infrared stratospheric spectrum

NASA Technical Reports Server (NTRS)

Carli, B.; Mencaraglia, F.; Bonetti, A.; Carlotti, M.; Nolt, I.

1985-01-01

Recent progress in high-resolution measurement of sub-millimeter and far-infrared emission in the stratosphere is reviewed. Attention is given to the results of recent balloon measurements of the minor stratospheric constituents in the spectral range 40-190 per cm. Emission spectra are presented for HCl; HF; and OH. Emission spectra were also obtained for atomic oxygen; hydrobromic acid; and hydroperoxyl radical. The possibility of detecting HO2 and H2O2 in the far-infrared is also briefly discussed.

Motivation and Prospects for Spatio-spectral Interferometry in the Far-infrared

NASA Technical Reports Server (NTRS)

Leisawitz, David

2013-01-01

Consensus developed through a series of workshops, starting in 1998. Compelling science case for high angular resolution imaging and spectroscopy, and mission concepts. A robust plan - it has evolved over the years, but has consistently called for high resolution.

A study of the effects of strong magnetic fields on the image resolution of PET scanners

NASA Astrophysics Data System (ADS)

Burdette, Don J.

Very high resolution images can be achieved in small animal PET systems utilizing solid state silicon pad detectors. In such systems using detectors with sub-millimeter intrinsic resolutions, the range of the positron is the largest contribution to the image blur. The size of the positron range effect depends on the initial positron energy and hence the radioactive tracer used. For higher energy positron emitters, such as 68Ga and 94mTc, the variation of the annihilation point dominates the spatial resolution. In this study two techniques are investigated to improve the image resolution of PET scanners limited by the range of the positron. One, the positron range can be reduced by embedding the PET field of view in a strong magnetic field. We have developed a silicon pad detector based PET instrument that can operate in strong magnetic fields with an image resolution of 0.7 mm FWHM to study this effect. Two, iterative reconstruction methods can be used to statistically correct for the range of the positron. Both strong magnetic fields and iterative reconstruction algorithms that statistically account for the positron range distribution are investigated in this work.

High precision moving magnet chopper for variable operation conditions

NASA Technical Reports Server (NTRS)

Aicher, Winfried; Schmid, Manfred

1994-01-01

In the context of an ESTEC technology contract, a Chopping Mechanism was developed and built with the Far Infrared and Submillimeter Telescope (FIRST) astronomy mission as a reference. The task of the mechanism is to tilt the subreflector of the telescope with an assumed mass of 2.5 kg about one chopping axis at nominal frequencies of up to 5 Hz and chopping angles of up to +/- 11.25 mrad with high efficiency (minimum time for position change). The chopping axis is required to run through the subreflector vertex. After performing a concept trade-off also considering the low operational temperatures in the 130 K range, a design using moving magnet actuators was found to be the favorite one. In addition, a bearing concept using flexible pivots was chosen to meet the high chopping accuracy required. With this approach, a very reliable design could be realized, since the actuators work without any mechanical contact between its moving and fixed parts, and the only bearings used are two flexible pivots supporting the subreflector mounting interface. The mechanism was completely built in titanium in a lightweight and stiff design. The moving magnet actuators were designed to meet the stringent requirements for minimum risetime (time necessary to move from one angular position to a new one) in the 20 msec range. The angular position and the corresponding chopping frequency as well can be arbitrarily selected by the user.

Submillimeter Spectroscopy of the Out-Of Bending State ν_{20} of C_2H_5CN

NASA Astrophysics Data System (ADS)

Pearson, John C.; Brauer, Carolyn S.; Yu, Shanshan; Drouin, Brian J.

2009-06-01

Propionitrile is a well known interstellar molecule that is a closely associated with warm dust near ultra compact H_{II} regions. In these regions the C_2H_5CN column can reach 10^{17} and the rotational temperature often equals the vibrational temperature and exceeds 200 K, populating all the low-lying vibrational states. The rotational spectrum of the third lowest excited vibrational state, the 378 cm^{-1} out-of-plane bending state, ν_{20}, of propionitrile, which was previously identified at millimeter wavelengths in both the laboratory and the interstellar medium, has been characterized to high angular momentum quantum numbers. This state is surprisingly isolated considering its proximity to the overtone of the in-plane bend, 2ν_{13}, the excited torsional state of the in-plane bend, ν_{13}+ν_{21}, and the second excited torsional state, 2ν_{21}, which lie approximately 35 cm^{-1} higher. The only surprising aspect is the presence of significantly larger torsional A-E splitting than observed in either the ground state or the ν_{13} in the absence of a resonance with ν_{21}. Because ν_{20} has been observed in high mass star forming cores in the millimeter, its higher angular momentum lines are known to be a major source of line confusion in high mass star forming cores. The spectrum, constants and determined barriers will be presented.

The large area high resolution gamma ray astrophysics facility - HR-GRAF

NASA Astrophysics Data System (ADS)

Fenyves, E. J.; Chaney, R. C.; Hoffman, J. H.; Cline, D. B.; Atac, M.; Park, J.; White, S. R.; Zych, A. D.; Tumer, Q. T.; Hughes, E. B.

1990-03-01

The long-term program is described in terms of its equipment, scientific objectives, and long-range scientific studies. A prototype of a space-based large-area high-resolution gamma-ray facility (HR-GRAF) is being developed to examine pointlike and diffuse gamma-ray sources in the range 1 MeV-100 GeV. The instrument for the facility is proposed to have high angular and energy resolution and very high sensitivity to permit the study of the proposed objects. The primary research targets include the mapping of galactic gamma radiation, observing the angular variations of diffuse gamma rays, and studying the Galactic center with particular emphasis on the hypothetical black hole. Also included in the research plans are obtaining data on gamma-ray bursters, investigating the transmission of gamma rays from cold dark matter, and studying nuclear gamma-ray lines.

Characterization of novel preclinical dose distributions for micro irradiator

NASA Astrophysics Data System (ADS)

Kodra, J.; Miles, D.; Yoon, S. W.; Kirsch, D. G.; Oldham, M.

2017-05-01

This work explores and demonstrates the feasibility of utilizing new 3D printing techniques to implement advanced micro radiation therapy for pre-clinical small animal studies. 3D printed blocks and compensators were designed and printed from a strong x-ray attenuating material at sub-millimeter resolution. These techniques enable a powerful range of new preclinical treatment capabilities including grid therapy, lattice therapy, and IMRT treatment. At small scales, verification of these treatments is exceptionally challenging, and high resolution 3D dosimetry (0.5mm3) is an essential capability to characterize and verify these capabilities, Here, investigate the 2D and 3D dosimetry of several novel pre-clinical treatments using a combination of EBT film and Presage/optical-CT 3D dosimetry in rodent-morphic dosimeters.

The high resolution submillimetre spectrum of the stratosphere

NASA Technical Reports Server (NTRS)

Carli, B.

1984-01-01

The structure of the stratospheric spectrum, measured with a resolution of 0.0033/cm unapodized in the 7-90/cm spectral interval is described. The spectra from measurements recorded on April 24, 1979 from a balloon-borne platform at about 39 km altitude launched from the National Scientific Balloon Facility of Palestine, TX are presented. The main spectroscopic constituents include a few strong and saturated lines due to the rotational spectrum of water vapor, to magnetic dipole transitions of oxygen, and to the rotational spectrum of ozone. It is shown that the lines of ozone prevent the positive identification of the contribution to the submillimeter spectrum of several minor constituents such as HF, HCl, HCN, HNO3, and N2O. The assignments which are possible in the spectra are revised.

Localization accuracy of compact binary coalescences detected by the third-generation gravitational-wave detectors and implication for cosmology

NASA Astrophysics Data System (ADS)

Zhao, Wen; Wen, Linqing

2018-03-01

We use the Fisher information matrix to investigate the angular resolution and luminosity distance uncertainty for coalescing binary neutron stars (BNSs) and neutron star-black hole binaries (NSBHs) detected by the third-generation (3G) gravitational-wave (GW) detectors. Our study focuses on an individual 3G detector and a network of up to four 3G detectors at different locations including the United States, Europe, China, and Australia for the proposed Einstein Telescope (ET) and Cosmic Explorer (CE) detectors. In particular, we examine the effect of the Earth's rotation, as GW signals from BNS and low-mass NSBH systems could be hours long for 3G detectors. In this case, an individual detector can be effectively treated as a detector network with long baselines formed by the trajectory of the detector as it rotates with the Earth. Therefore, a single detector or two-detector networks could also be used to localize the GW sources effectively. We find that a time-dependent antenna beam-pattern function can help better localize BNS and NSBH sources, especially edge-on ones. The medium angular resolution for one ET-D detector is around 150 deg2 for BNSs at a redshift of z =0.1 , which improves rapidly with a decreasing low-frequency cutoff flow in sensitivity. The medium angular resolution for a network of two CE detectors in the United States and Europe, respectively, is around 20 deg2 at z =0.2 for the simulated BNS and NSBH samples. While for a network of two ET-D detectors, the similar angular resolution can be achieved at a much higher redshift of z =0.5 . The angular resolution of a network of three detectors is mainly determined by the baselines between detectors regardless of the CE or ET detector type. The medium angular resolution of BNS for a network of three detectors of the ET-D or CE type in the United States, Europe, and Australia is around 10 deg2 at z =2 . We discuss the implications of our results for multimessenger astronomy and, in particular, for using GW sources as independent tools to constrain the Hubble constant H0, the deceleration parameter q0, and the equation-of-state (EoS) of dark energy. We find that, in general, if 10 BNSs or NSBHs at z =0.1 with known redshifts are detected by 3G networks consisting of two ET-like detectors, H0 can be measured with an accuracy of 0.9%. If 1000 face-on BNSs at z <2 are detected with known redshifts, we are able to achieve Δ q0=0.002 for the deceleration parameter, or Δ w0=0.03 and Δ wa=0.2 for EoS of dark energy, respectively.

Investigation of the Chromosphere-Corona Interface with the Upgraded Very High Angular Resolution Ultraviolet Telescope (VAULT2.0)

NASA Astrophysics Data System (ADS)

Vourlidas, Angelos; Beltran, Samuel Tun; Chintzoglou, Georgios; Eisenhower, Kevin; Korendyke, Clarence; Feldman, Ronen; Moser, John; Shea, John; Johnson-Rambert, Mary; McMullin, Don; Stenborg, Guillermo; Shepler, Ed; Roberts, David

2016-03-01

Very high angular resolution ultraviolet telescope (VAULT2.0) is a Lyman-alpha (Lyα; 1216Å) spectroheliograph designed to observe the upper chromospheric region of the solar atmosphere with high spatial (<0.5‧‧) and temporal (8s) resolution. Besides being the brightest line in the solar spectrum, Lyα emission arises at the temperature interface between coronal and chromospheric plasmas and may, hence, hold important clues about the transfer of mass and energy to the solar corona. VAULT2.0 is an upgrade of the previously flown VAULT rocket and was launched successfully on September 30, 2014 from White Sands Missile Range (WSMR). The target was AR12172 midway toward the southwestern limb. We obtained 33 images at 8s cadence at arc second resolution due to hardware problems. The science campaign was a resounding success, with all space and ground-based instruments obtaining high-resolution data at the same location within the AR. We discuss the science rationale, instrument upgrades, and performance during the first flight and present some preliminary science results.

Multiple Disk Gaps and Rings Generated by a Single Super-Earth

NASA Astrophysics Data System (ADS)

Dong, Ruobing; Li, Shengtai; Chiang, Eugene; Li, Hui

2017-07-01

We investigate the observational signatures of super-Earths (i.e., planets with Earth-to-Neptune mass), which are the most common type of exoplanet discovered to date, in their natal disks of gas and dust. Combining two-fluid global hydrodynamics simulations with a radiative transfer code, we calculate the distributions of gas and of submillimeter-sized dust in a disk perturbed by a super-Earth, synthesizing images in near-infrared scattered light and the millimeter-wave thermal continuum for direct comparison with observations. In low-viscosity gas (α ≲ {10}-4), a super-Earth opens two annular gaps to either side of its orbit by the action of Lindblad torques. This double gap and its associated gas pressure gradients cause dust particles to be dragged by gas into three rings: one ring sandwiched between the two gaps, and two rings located at the gap edges farthest from the planet. Depending on the system parameters, additional rings may manifest for a single planet. A double gap located at tens of au from a host star in Taurus can be detected in the dust continuum by the Atacama Large Millimeter Array (ALMA) at an angular resolution of ∼0\\buildrel{\\prime\\prime}\\over{.} 03 after two hours of integration. Ring and gap features persist in a variety of background disk profiles, last for thousands of orbits, and change their relative positions and dimensions depending on the speed and direction of planet migration. Candidate double gaps have been observed by ALMA in systems such as HL Tau (D5 and D6) and TW Hya (at 37 and 43 au); we submit that each double gap is carved by one super-Earth in nearly inviscid gas.

ALMA OBSERVATIONS OF THE DEBRIS DISK AROUND THE YOUNG SOLAR ANALOG HD 107146

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

Ricci, L.; Carpenter, J. M.; Fu, B.

We present the Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations at a wavelength of 1.25 mm of the debris disk surrounding the ∼100 Myr old solar analog HD 107146. The continuum emission extends from about 30 to 150 AU from the central star with a decrease in the surface brightness at intermediate radii. We analyze the ALMA interferometric visibilities using debris disk models with radial profiles for the dust surface density parameterized as (1) a single power law, (2) a single power law with a gap, and (3) a double power law. We find that models with a gap of radial widthmore » ∼8 AU at a distance of ∼80 AU from the central star, as well as double power-law models with a dip in the dust surface density at ∼70 AU provide significantly better fits to the ALMA data than single power-law models. We discuss possible scenarios for the origin of the HD 107146 debris disk using models of planetesimal belts in which the formation of Pluto-sized objects trigger disruptive collisions of large bodies, as well as models that consider the interaction of a planetary system with a planetesimal belt and spatial variation of the dust opacity across the disk. If future observations with higher angular resolution and sensitivity confirm the fully depleted gap structure discussed here, a planet with a mass of approximately a few Earth masses in a nearly circular orbit at ∼80 AU from the central star would be a possible explanation for the presence of the gap.« less

High-resolution imaging gamma-ray spectroscopy with externally segmented germanium detectors

NASA Technical Reports Server (NTRS)

Callas, J. L.; Mahoney, W. A.; Varnell, L. S.; Wheaton, W. A.

1993-01-01

Externally segmented germanium detectors promise a breakthrough in gamma-ray imaging capabilities while retaining the superb energy resolution of germanium spectrometers. An angular resolution of 0.2 deg becomes practical by combining position-sensitive germanium detectors having a segment thickness of a few millimeters with a one-dimensional coded aperture located about a meter from the detectors. Correspondingly higher angular resolutions are possible with larger separations between the detectors and the coded aperture. Two-dimensional images can be obtained by rotating the instrument. Although the basic concept is similar to optical or X-ray coded-aperture imaging techniques, several complicating effects arise because of the penetrating nature of gamma rays. The complications include partial transmission through the coded aperture elements, Compton scattering in the germanium detectors, and high background count rates. Extensive electron-photon Monte Carlo modeling of a realistic detector/coded-aperture/collimator system has been performed. Results show that these complicating effects can be characterized and accounted for with no significant loss in instrument sensitivity.

Compressive light field imaging

NASA Astrophysics Data System (ADS)

Ashok, Amit; Neifeld, Mark A.

2010-04-01

Light field imagers such as the plenoptic and the integral imagers inherently measure projections of the four dimensional (4D) light field scalar function onto a two dimensional sensor and therefore, suffer from a spatial vs. angular resolution trade-off. Programmable light field imagers, proposed recently, overcome this spatioangular resolution trade-off and allow high-resolution capture of the (4D) light field function with multiple measurements at the cost of a longer exposure time. However, these light field imagers do not exploit the spatio-angular correlations inherent in the light fields of natural scenes and thus result in photon-inefficient measurements. Here, we describe two architectures for compressive light field imaging that require relatively few photon-efficient measurements to obtain a high-resolution estimate of the light field while reducing the overall exposure time. Our simulation study shows that, compressive light field imagers using the principal component (PC) measurement basis require four times fewer measurements and three times shorter exposure time compared to a conventional light field imager in order to achieve an equivalent light field reconstruction quality.

High-resolution bottom-loss estimation using the ambient-noise vertical coherence function.

PubMed

Muzi, Lanfranco; Siderius, Martin; Quijano, Jorge E; Dosso, Stan E

2015-01-01

The seabed reflection loss (shortly "bottom loss") is an important quantity for predicting transmission loss in the ocean. A recent passive technique for estimating the bottom loss as a function of frequency and grazing angle exploits marine ambient noise (originating at the surface from breaking waves, wind, and rain) as an acoustic source. Conventional beamforming of the noise field at a vertical line array of hydrophones is a fundamental step in this technique, and the beamformer resolution in grazing angle affects the quality of the estimated bottom loss. Implementation of this technique with short arrays can be hindered by their inherently poor angular resolution. This paper presents a derivation of the bottom reflection coefficient from the ambient-noise spatial coherence function, and a technique based on this derivation for obtaining higher angular resolution bottom-loss estimates. The technique, which exploits the (approximate) spatial stationarity of the ambient-noise spatial coherence function, is demonstrated on both simulated and experimental data.

InP HEMT Integrated Circuits for Submillimeter Wave Radiometers in Earth Remote Sensing

NASA Technical Reports Server (NTRS)

Deal, William R.; Chattopadhyay, Goutam

2012-01-01

The operating frequency of InP integrated circuits has pushed well into the Submillimeter Wave frequency band, with amplification reported as high as 670 GHz. This paper provides an overview of current performance and potential application of InP HEMT to Submillimeter Wave radiometers for earth remote sensing.

Preliminary submillimeter spectroscopic measurements using a submillimeter heterodyne radiometer

NASA Technical Reports Server (NTRS)

Safren, H. G.; Stabnow, W. R.; Bufton, J. L.; Peruso, C. J.; Rossey, C. E.; Walker, H. E.

1982-01-01

A submillimeter heterodyne radiometer uses a submillimeter laser, pumped by a CO2 laser, as a local oscillator and a room temperature Schottky barrier diode as the first IF mixer. The radiometer can resolve spectral lines in the submillimeter region of the spectrum (arising from pure rotational molecular transitions) to within 0.3 MHz, using acousto-optic spectrum analyzer which measures the power spectrum by simultaneously sampling 0.3 MHz wide channels over a 100 MHz bandwidth spanning the line. Preliminary observations of eight spectral lines of H2O2, CO, NH3 and H2O, all lying in the 434-524 micrometer wavelength range are described. All eight lines were observed using two local oscillator frequencies obtained by operating the submillimeter laser with either methyl fluoride (CH3F) or formic acid (HCOOH) as the lasing gas. Sample calculations of line parameters from the observed data show good agreement with established values. One development goal is the size and weight reduction of the package to make it suitable for balloon or shuttle experiments to detect trace gases in the upper atmosphere.

Faint Submillimeter Galaxies Behind Lensing Clusters

NASA Astrophysics Data System (ADS)

Hsu, Li-Yen; Lauchlan Cowie, Lennox; Barger, Amy J.; Desai, Vandana; Murphy, Eric J.

2017-01-01

Faint submillimeter galaxies are the major contributors to the submillimeter extragalactic background light and hence the dominant star-forming population in the dusty universe. Determining how much these galaxies overlap the optically selected samples is critical to fully account for the cosmic star formation history. Observations of massive cluster fields are the best way to explore this faint submillimeter population, thanks to gravitational lensing effects. We have been undertaking a lensing cluster survey with the SCUBA-2 camera on the James Clerk Maxwell Telescope to map nine galaxy clusters, including the northern five clusters in the HST Frontier Fields program. We have also been using the Submillimeter Array and the Very Large Array to determine the accurate positions of our detected sources. Our observations have discovered high-redshift dusty galaxies with far-infrared luminosities similar to that of the Milky Way or luminous infrared galaxies. Some of these galaxies are still undetected in deep optical and near-infrared images. These results suggest that a substantial amount of star formation in even the faint submillimeter population may be hidden from rest-frame optical surveys.

Evidence for a Major Merger Origin of High-Redshift Submillimeter Galaxies

NASA Astrophysics Data System (ADS)

Conselice, Christopher J.; Chapman, Scott C.; Windhorst, Rogier A.

2003-10-01

Submillimeter-detected galaxies located at redshifts z>1 host a major fraction of the bolometric luminosity at high redshifts due to thermal emission from heated dust grains, yet the nature of these objects remains a mystery. The major problem in understanding their origin is whether the dust-heating mechanism is predominantly caused by star formation or active galactic nuclei and what triggered this activity. We address this issue by examining the structures of 11 submillimeter galaxies imaged with STIS on the Hubble Space Telescope. We argue that ~61%+/-21% of these submillimeter sources are undergoing an active major merger using the CAS (concentration, asymmetry, clumpiness) quantitative morphological system. We rule out at ~5 σ confidence that these submillimeter galaxies are normal Hubble types at high redshift. This merger fraction appears to be higher than for Lyman break galaxies undergoing mergers at similar redshifts. Using reasonable constraints on the stellar masses of Lyman break galaxies and these submillimeter sources, we further argue that at redshifts z~2-3, systems with high stellar masses are more likely than lower mass galaxies to be involved in major mergers.

Report of the submillimeter splinter group

NASA Astrophysics Data System (ADS)

Harris, A. I.; Lequeux, J.

1992-12-01

The aim of the submillimeter splinter group of the LIST (Lunar Interferometry Study Team) was to examine the scientific and technical aspects of a submillimeter interferometer with an emphasis on heterodyne detection. The main elements of the scientific logic that lead to the conclusions that a heterodyne submillimeter array should have a collecting area of at order 1000 sq m are summarized. This conclusion is based on sensitivity constraints and the following points: anything that can be done from the ground, will be; an instrument as complex and expensive as a large submillimeter interferometer must be capable of significant extragalactic observations; and no matter what the future scientific trends are, looking at the main coolants will always be important. It is clear that an instrument of this size is several steps past the next generation of spaceborne observatories.

Submillimeter wave detection with superconducting tunnel diodes

NASA Technical Reports Server (NTRS)

Wengler, Michael J.

1992-01-01

Superconductor-Insulator-Superconductor (SIS) diodes are the detector elements in the most sensitive heterodyne receivers available from 100 to 500 GHz. SIS mixers are the front end of radio astronomical systems around the world. SIS mixer technology is being extended to 1 THz and higher frequencies for eventual use on spaceborne astronomical experiments. Here is a short review of submillimeter SIS mixers. The role of impedance matching in the proper design of an SIS mixer is described. A variety of methods for achieving good impedance match at submillimeter frequencies are presented. The experimental state of the submillimeter SIS mixer art is described and summarized.

A stable submillimeter laser local oscillator for heterodyne radiometry and spectroscopy

NASA Technical Reports Server (NTRS)

Koepf, G. A.; Fetterman, H. R.; Mcavoy, N.

1980-01-01

A submillimeter laser with off-axis pump beam injection is described. This design concept achieves complete isolation of the pump laser with respect to the pump radiation reflected from the submillimeter resonator. Active line independent stabilization of the pump laser is obtained by the use of an external tunable etalon as a frequency reference. The submillimeter output power is constant to within 4% over periods of hours. Mean frequency drifts of less than 2 parts in 100 million per minute were measured by mixing with very high harmonics of an X-band synthesizer in a planar Schottky diode.

ALMA deep field in SSA22: Survey design and source catalog of a 20 arcmin2 survey at 1.1 mm

NASA Astrophysics Data System (ADS)

Umehata, Hideki; Hatsukade, Bunyo; Smail, Ian; Alexander, David M.; Ivison, Rob J.; Matsuda, Yuichi; Tamura, Yoichi; Kohno, Kotaro; Kato, Yuta; Hayatsu, Natsuki H.; Kubo, Mariko; Ikarashi, Soh

2018-06-01

To search for dust-obscured star-formation activity in the early Universe, it is essential to obtain a deep and wide submillimeter/millimeter map. The advent of the Atacama Large Millimeter/submillimeter Array (ALMA) has enabled us to obtain such maps with sufficiently high spatial resolution to be free from source confusion. We present a new 1.1 mm-wave map obtained by ALMA in the SSA22 field. The field contains a remarkable proto-cluster at z = 3.09; therefore, it is an ideal region to investigate the role of a large-scale cosmic web on dust-obscured star formation. The typical 1σ depth of our map is 73 μJy beam-1 with a {0^{^''.}5} resolution. Combining the present survey with earlier, archived observations, we map an area of 20 arcmin2 (71 comoving Mpc2 at z = 3.09). Within the combined survey area we have detected 35 sources at a signal-to-noise ratio (S/N) >5, with flux densities of S1.1mm = 0.43-5.6 mJy, equivalent to star-formation rates of ≳100-1000 M⊙ yr-1 at z = 3.09, for a Chabrier initial mass function: 17 sources out of 35 are new detections. The cumulative number counts show an excess by a factor of three to five compared to blank fields. The excess suggests enhanced, dust-enshrouded star-formation activity in the proto-cluster on a 10 comoving Mpc scale, indicating accelerated galaxy evolution in this overdense region.

Passive 350 GHz Video Imaging Systems for Security Applications

NASA Astrophysics Data System (ADS)

Heinz, E.; May, T.; Born, D.; Zieger, G.; Anders, S.; Zakosarenko, V.; Meyer, H.-G.; Schäffel, C.

2015-10-01

Passive submillimeter-wave imaging is a concept that has been in the focus of interest as a promising technology for personal security screening for a number of years. In contradiction to established portal-based millimeter-wave scanning techniques, it allows for scanning people from a distance in real time with high throughput and without a distinct inspection procedure. This opens up new possibilities for scanning, which directly address an urgent security need of modern societies: protecting crowds and critical infrastructure from the growing threat of individual terror attacks. Considering the low radiometric contrast of indoor scenes in the submillimeter range, this objective calls for an extremely high detector sensitivity that can only be achieved using cooled detectors. Our approach to this task is a series of passive standoff video cameras for the 350 GHz band that represent an evolving concept and a continuous development since 2007. Arrays of superconducting transition-edge sensors (TES), operated at temperatures below 1 K, are used as radiation detectors. By this means, background limited performance (BLIP) mode is achieved, providing the maximum possible signal to noise ratio. At video rates, this leads to a temperature resolution well below 1 K. The imaging system is completed by reflector optics based on free-form mirrors. For object distances of 5-25 m, a field of view up to 2 m height and a diffraction-limited spatial resolution in the order of 1-2 cm is provided. Opto-mechanical scanning systems are part of the optical setup and capable of frame rates of up to 25 frames per second.

Forming Disc Galaxies In Major Mergers: Radial Density Profiles And Angular Momentum

NASA Astrophysics Data System (ADS)

Peschken, Nicolas; Athanassoula, E.; Rodionov, S. A.; Lambert, J. C.

2017-06-01

In Athanassoula et al. (2016), we used high resolution N-body hydrodynamical simulations to model the major merger between two disc galaxies with a hot gaseous halo each, and showed that the remnant is a spiral galaxy. The two discs are destroyed by the collision, but after the merger, accretion from the surrounding gaseous halo allows the building of a new disc in the remnant galaxy. In Peschken et al. (2017), we used these simulations to study the radial surface density profiles of the remnant galaxies with downbending profiles (type II), i.e. composed of an inner and an outer exponential disc separated by a break. We analyzed the effect of angular momentum on these profiles, and found that the inner and outer disc scalelengths, as well as the break radius, all increase linearly with the total angular momentum of the initial merging system. Following the angular momentum redistribution in our simulations, we find that the disc angular momentum is acquired via accretion from the gaseous halo. Furthermore, high angular momentum systems give more angular momentum to their discs, which affects directly their radial density profile.

The Atacama Cosmology Telescope: The Polarization-Sensitive ACTPol Instrument

NASA Technical Reports Server (NTRS)

Thornton, R. J.; Ade, P. A. R.; Aiola, S.; Angile, F. E.; Amiri, M.; Beall, J. A.; Becker, D. T.; Cho, H.-M.; Choi, S. K.; Corlies, P.;

The Atacama Cosmology Telescope: The Polarization-sensitive ACTPol Instrument

NASA Astrophysics Data System (ADS)

Thornton, R. J.; Ade, P. A. R.; Aiola, S.; Angilè, F. E.; Amiri, M.; Beall, J. A.; Becker, D. T.; Cho, H.-M.; Choi, S. K.; Corlies, P.; Coughlin, K. P.; Datta, R.; Devlin, M. J.; Dicker, S. R.; Dünner, R.; Fowler, J. W.; Fox, A. E.; Gallardo, P. A.; Gao, J.; Grace, E.; Halpern, M.; Hasselfield, M.; Henderson, S. W.; Hilton, G. C.; Hincks, A. D.; Ho, S. P.; Hubmayr, J.; Irwin, K. D.; Klein, J.; Koopman, B.; Li, Dale; Louis, T.; Lungu, M.; Maurin, L.; McMahon, J.; Munson, C. D.; Naess, S.; Nati, F.; Newburgh, L.; Nibarger, J.; Niemack, M. D.; Niraula, P.; Nolta, M. R.; Page, L. A.; Pappas, C. G.; Schillaci, A.; Schmitt, B. L.; Sehgal, N.; Sievers, J. L.; Simon, S. M.; Staggs, S. T.; Tucker, C.; Uehara, M.; van Lanen, J.; Ward, J. T.; Wollack, E. J.

2016-12-01

The Atacama Cosmology Telescope (ACT) makes high angular resolution measurements of anisotropies in the Cosmic Microwave Background (CMB) at millimeter wavelengths. We describe ACTPol, an upgraded receiver for ACT, which uses feedhorn-coupled, polarization-sensitive detector arrays, a 3° field of view, 100 mK cryogenics with continuous cooling, and meta material antireflection coatings. ACTPol comprises three arrays with separate cryogenic optics: two arrays at a central frequency of 148 GHz and one array operating simultaneously at both 97 GHz and 148 GHz. The combined instrument sensitivity, angular resolution, and sky coverage are optimized for measuring angular power spectra, clusters via the thermal Sunyaev–Zel’dovich (SZ) and kinetic SZ signals, and CMB lensing due to large-scale structure. The receiver was commissioned with its first 148 GHz array in 2013, observed with both 148 GHz arrays in 2014, and has recently completed its first full season of operations with the full suite of three arrays. This paper provides an overview of the design and initial performance of the receiver and related systems.

A new multidimensional diagnostic method for measuring the properties of intense ion beams

NASA Astrophysics Data System (ADS)

Yasuike, Kazuhito; Miyamoto, Shuji; Nakai, Sadao

1996-02-01

A new arrayed pinhole camera (APC) diagnostic method for intense ion beams has been developed. The APC diagnostic technique permits the acquisition of the angular divergences and the ion fluxes of high intensity ion beams, in one shot, with a spatial resolution on the source of better than 1 mm and an effective angular divergence resolution of better than 10 mrad. A prototype time integrated APC has been designed and evaluated. The demonstration experiments have been performed on a Reiden-IV, 1 MV and 1 Ω pulsed power machine [1 T W (tera-watt or trillion watts)]. Proton beams of 0.7 MeV, with a pulse duration of ˜50 ns and an ion current density of about 100 A/cm2, were generated in an applied-Br type ion diode source using paraffin-filled grooves. These experimental results show that the APC can measure nonuniformities in the ion beam intensity generated from the ion source and the dependence of beam angular divergence on ion beam intensity.

High-resolution mapping reveals linkage between genes in common bean cultivar Ouro Negro conferring resistance to the rust, anthracnose, and angular leaf spot diseases

USDA-ARS?s Scientific Manuscript database

Rust, Anthracnose, and angular leaf spot are major diseases of common bean in the world and most particularly in the Americas and Africa, which are the largest common bean production regions of the world. The Mesoamerican black-seeded cultivar Ouro Negro is unusual in that it has resistance to all t...

Stratospheric Observatory for Infrared Astronomy (SOFIA): Infrared Sensor Development and Science Capabilities

NASA Astrophysics Data System (ADS)

Nelson, J.; Ruzek, M.

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a unique airborne observatory designed to operate in the lower stratosphere to altitudes as high as 45,000 feet and above 99.8 percent of Earths obscuring atmospheric water vapor. SOFIA's capabilities enable science and observations that will complement and extend past, present and future infrared (IR) telescopes in wavelength range, angular and spectral resolution, and observing flexibility. The joint U.S. and German SOFIA project to develop and operate a 2.5-meter infrared airborne telescope in a Boeing 747-SP is nearing readiness for for open door flights and demonstration of early science results. Flying in the stratosphere, SOFIA allows observations throughout the infrared and submillimeter region. The SOFIA instrument complement includes broadband imagers, moderate resolution spectrographs capable of resolving broad features due to dust and large molecules, and high resolution spectrometers suitable for kinematic studies of molecular and atomic gas lines at high resolution. First science flights will begin in early 2010. A great strength of SOFIA is the enormous breadth of its capabilities and the flexibility with which those capabilities can be modified and improved to take advantage of advances in infrared technology. This paper and presentation will highlight the following points: A 2.5-meter effective-diameter optical-quality telescope for diffraction-limited imaging beyond 25 micrometers, giving the sharpest view of the sky provided by any current or developmental IR telescope operating in the 30-60 micrometers region; Wavelength coverage from 0.3 micrometers to 1.6 mm and high resolution spectroscopy (R to 105) at wavelengths between 5 and 150 micrometers; An 8 arcmin FOV allowing use of very large detector arrays; Ready observer access to science instruments which can be serviced in flight and changed between flights; A low-risk ability to incorporate new science-enabling instrument technologies and to create a whole "new" observatory several times during the lifetime of the facility; Opportunity for continuous training of instrumentalists to develop and test the next generation of instrumentation for both suborbital and space applications; Mobility, which allows access to the entire sky and a vastly increased number of stellar occultation events; Unique opportunities for educators and journalists to participate first-hand in exciting astronomical observations. The mid- and far-IR wavelength regions are key to studying the dusty universe. SOFIA science emphasizes four major themes: Star and planet formation; the interstellar medium of the Milky Way; Galaxies and the galactic center; and Planetary science. These capabilities will enable a wide range of science investigations over SOFIA's 20-year operational lifetime. This paper will address SOFIA's nine first-light science instruments, capabilities, and development.

Lucky Imaging in Astronomy

NASA Astrophysics Data System (ADS)

Brandner, Wolfgang; Hormuth, Felix

Lucky Imaging improves the angular resolution of astronomical observations hampered by atmospheric turbulence ("seeing"). Unlike adaptive optics, Lucky Imaging is a passive observing technique with individual integration times comparable to the atmospheric coherence time. Thanks to the advent of essentially noise free "Electron multiplying CCD" detectors, Lucky Imaging saw a renewed interest in the past decade. It is now routinely used at a number of 2-5-m class telescopes, such as ESO's NTT. We review the history of Lucky Imaging, present the technical implementation, describe the data analysis philosophy, and show some recent results obtained with this technique. We also discuss the advantages and limitations of Lucky Imaging compared to other passive and active high angular resolution observing techniques.

Note: A versatile mass spectrometer chamber for molecular beam and temperature programmed desorption experiments

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

Tonks, James P., E-mail: james.tonks@awe.co.uk; AWE Plc, Aldermaston, Reading, Berkshire RG7 4PR; Galloway, Ewan C., E-mail: ewan.galloway@awe.co.uk

2016-08-15

A dual purpose mass spectrometer chamber capable of performing molecular beam scattering (MBS) and temperature programmed desorption (TPD) is detailed. Two simple features of this design allow it to perform these techniques. First, the diameter of entrance aperture to the mass spectrometer can be varied to maximize signal for TPD or to maximize angular resolution for MBS. Second, the mass spectrometer chamber can be radially translated so that it can be positioned close to the sample to maximize signal or far from the sample to maximize angular resolution. The performance of this system is described and compares well with systemsmore » designed for only one of these techniques.« less

Microwave, Millimeter, Submillimeter, and Far Infrared Spectral Databases

NASA Technical Reports Server (NTRS)

Pearson, J. C.; Pickett, H. M.; Drouin, B. J.; Chen, P.; Cohen, E. A.

2002-01-01

The spectrum of most known astrophysical molecules is derived from transitions between a few hundred to a few hundred thousand energy levels populated at room temperature. In the microwave and millimeter wave regions. spectroscopy is almost always performed with traditional microwave techniques. In the submillimeter and far infrared microwave technique becomes progressively more technologically challenging and infrared techniques become more widely employed as the wavelength gets shorter. Infrared techniques are typically one to two orders of magnitude less precise but they do generate all the strong features in the spectrum. With microwave technique, it is generally impossible and rarely necessary to measure every single transition of a molecular species, so careful fitting of quantum mechanical Hamiltonians to the transitions measured are required to produce the complete spectral picture of the molecule required by astronomers. The fitting process produces the most precise data possible and is required in the interpret heterodyne observations. The drawback of traditional microwave technique is that precise knowledge of the band origins of low lying excited states is rarely gained. The fitting of data interpolates well for the range of quantum numbers where there is laboratory data, but extrapolation is almost never precise. The majority of high resolution spectroscopic data is millimeter or longer in wavelength and a very limited number of molecules have ever been studied with microwave techniques at wavelengths shorter than 0.3 millimeters. The situation with infrared technique is similarly dire in the submillimeter and far infrared because the black body sources used are competing with a very significant thermal background making the signal to noise poor. Regardless of the technique used the data must be archived in a way useful for the interpretation of observations.

High resolution study of the ν2 and ν5 rovibrational fundamental bands of thionyl chloride: Interplay of an evolutionary algorithm and a line-by-line analysis

NASA Astrophysics Data System (ADS)

Roucou, Anthony; Dhont, Guillaume; Cuisset, Arnaud; Martin-Drumel, Marie-Aline; Thorwirth, Sven; Fontanari, Daniele; Meerts, W. Leo

2017-08-01

The ν2 and ν5 fundamental bands of thionyl chloride (SOCl2) were measured in the 420 cm-1-550 cm-1 region using the FT-far-IR spectrometer exploiting synchrotron radiation on the AILES beamline at SOLEIL. A straightforward line-by-line analysis is complicated by the high congestion of the spectrum due to both the high density of SOCl2 rovibrational bands and the presence of the ν2 fundamental band of sulfur dioxide produced by hydrolysis of SOCl2 with residual water. To overcome this difficulty, our assignment procedure for the main isotopologues 32S16O35Cl2 and 32S16O35Cl37Cl alternates between a direct fit of the spectrum, via a global optimization technique, and a traditional line-by-line analysis. The global optimization, based on an evolutionary algorithm, produces rotational constants and band centers that serve as useful starting values for the subsequent spectroscopic analysis. This work helped to identify the pure rotational submillimeter spectrum of 32S16O35Cl2 in the v2=1 and v5=1 vibrational states of Martin-Drumel et al. [J. Chem. Phys. 144, 084305 (2016)]. As a by-product, the rotational transitions of the v4=1 far-IR inactive state were identified in the submillimeter spectrum. A global fit gathering all the microwave, submillimeter, and far-IR data of thionyl chloride has been performed, showing that no major perturbation of rovibrational energy levels occurs for the main isotopologue of the molecule.

SMA Spectral Line Survey of the Proto-Planetary Nebula CRL 618

NASA Astrophysics Data System (ADS)

Patel, Nimesh A.; Gottlieb, Carl; Young, Ken; Kaminski, Tomasz Tomek; McCarthy, Michael; Menten, Karl; Primiani, Rurik; Lee, Chin-Fei; Gupta, Harshal

2018-01-01

Carbon-rich Asymptotic Giant Branch (AGB) stars are major sources of gas and dust in the interstellar medium. AGB stars remain in their evolutionary stage for 1 to 10 Myrs, during which they have very high mass loss rates that increase at the end. During the brief (~1000 yr) period in the evolution from the AGB to the Planetary Nebula (PN) stage there are dramatic changes in the morphology from nearly spherical symmetry, to bipolar, quadrupolar and more complex structures, with the development of both slow and fast (100 km/s) outflows. The molecular composition of these objects' cirumstellar envelopes also evolves from being similar to that of parent AGB star (mainly diatomic and small polyatomic species), to more complex molecules (including ions).We have started an observational study of a sample of Proto-Planetary nebulae (PPN) with the Submillimeter Array to carry out spectral-line surveys of ~60 GHz frequency coverage in the 345 GHz band (similar to our published IRC+10216 line survey of 2011). Here we present preliminary results from the line survey of the carbon-rich PPN CRL 618, covering a frequency range of 281.9 to 359.4 GHz. Observations were carried out in January 2016 and September 2017, with the SMA in compact (3" angular resolution) and very extended (0.5") configurations, respectively.More than 1100 lines were detected in CRL 618. The majority of them can be attributed to HC3N and c-C3H2, and their isotopologues. About 350 lines are as yet unassigned. The continuum emission is unresolved even at 0.5" resolution. Several hydrogen recombination lines are detected from the central HII region. Lines of CO, HCO+, CS show the fast outflow wings, while the majority of molecular emission arises from a compact region of about 1" diameter. We present LTEmodeling and rotation temperature diagram analysis of HC3N, c-C3H2, CH3CN, and their isotopologues. We plan to observe another PPN, CRL 2688 with the SMA in 2018. Together, these imaging line surveys will provide observational constraints on models of the chemical evolution from AGB stars to Planetary Nebulae.

The Fourier-Kelvin Stellar Interferometer Mission Concept

NASA Technical Reports Server (NTRS)

Danchi, W. C.; Allen, R.; Benford, D.; Gezari, D.; Leisawitz, D.; Mundy, L.; Oegerle, William (Technical Monitor)

2002-01-01

The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for an imaging interferometer for the mid-infrared spectral region (5-30 microns). FKSI is conceived as a scientific and technological precursor to TPF as well as Space Infrared Interferometric Telescope (SPIRIT), Submillimeter Probe Evolution of Cosmic Structure (SPECS), and Single Aperture for Infrared Observatory (SAFIR). It will also be a high angular resolution system complementary to Next Generation Space Telescope (NGST). The scientific emphasis of the mission is on the evolution of protostellar systems, from just after the collapse of the precursor molecular cloud core, through the formation of the disk surrounding the protostar, the formation of planets in the disk, and eventual dispersal of the disk material. FKSI will also search for brown dwarfs and Jupiter mass and smaller planets, and could also play a very powerful role in the investigation of the structure of active galactic nuclei and extra-galactic star formation. We are in the process of studying alternative interferometer architectures and beam combination techniques, and evaluating the relevant science and technology tradeoffs. Some of the technical challenges include the development of the cryocooler systems necessary for the telescopes and focal plane array, light and stiff but well-damped truss systems to support the telescopes, and lightweight and coolable optical telescopes. The goal of the design study is to determine if a mid-infrared interferometry mission can be performed within the cost and schedule requirements of a Discovery class mission. At the present time we envision the FKSI as comprised of five one meter diameter telescopes arranged along a truss structure in a linear non-redundant array, cooled to 35 K. A maximum baseline of 20 meters gives a nominal resolution of 26 mas at 5 microns. Using a Fizeau beam combination technique, a simple focal plane camera could be used to obtain both Fourier and spectral data simultaneously for a given orientation of the array. The spacecraft will be rotated to give sufficient Fourier data to reconstruct complex images of a broad range of astrophysical sources.

PECULIAR NEAR-NUCLEUS OUTGASSING OF COMET 17P/HOLMES DURING ITS 2007 OUTBURST

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

Qi, Chunhua; Gurwell, Mark A.; Wilner, David J.

2015-01-20

We present high angular resolution Submillimeter Array observations of the outbursting Jupiter family comet 17P/Holmes on 2007 October 26-29, achieving a spatial resolution of 2.''5, or ∼3000 km at the comet distance. The observations resulted in detections of the rotational lines CO 3-2, HCN 4-3, H{sup 13}CN 4-3, CS 7-6, H{sub 2}CO 3{sub 1,} {sub 2}-2{sub 1,} {sub 1}, H{sub 2}S 2{sub 2,} {sub 0}-2{sub 1,} {sub 1}, and multiple CH{sub 3}OH lines, along with the associated dust continuum at 221 and 349 GHz. The continuum has a spectral index of 2.7 ± 0.3, slightly steeper than blackbody emission from large dust particles.more » From the imaging data, we identify two components in the molecular emission. One component is characterized by a relatively broad line width (∼1 km s{sup –1} FWHM) exhibiting a symmetric outgassing pattern with respect to the nucleus position. The second component has a narrower line width (<0.5 km s{sup –1} FWHM) with the line center redshifted by 0.1-0.2 km s{sup –1} (cometocentric frame), and shows a velocity shift across the nucleus position with the position angle gradually changing from 66° to 30° within the four days of observations. We determine distinctly different CO/HCN ratios for each of the components. For the broad-line component we find CO/HCN < 7, while in the narrow-line component, CO/HCN = 40 ± 5. We hypothesize that the narrow-line component originates from the ice grain halo found in near-nucleus photometry, believed to be created by sublimating recently released ice grains around the nucleus during the outburst. In this interpretation, the high CO/HCN ratio of this component reflects the more pristine volatile composition of nucleus material released in the outburst.« less

Probing Protoplanetary Disks: From Birth to Planets

NASA Astrophysics Data System (ADS)

Cox, Erin Guilfoil

2018-01-01

Disks are very important in the evolution of protostars and their subsequent planets. How early disks can form has implications for early planet formation. In the youngest protostars (i.e., Class 0 sources) magnetic fields can control disk growth. When the field is parallel to the collapsing core’s rotation axis, infalling material loses angular momentum and disks form in later stages. Sub-/millimeter polarization continuum observations of Class 0 sources at ~1000 au resolution support this idea. However, in the inner (~100 au), denser regions, it is unknown if the polarization only traces aligned dust grains. Recent theoretical studies have shown that self-scattering of thermal emission in the disk may contribute significantly to the polarization. Determining the scattering contribution in these sources is important to disentangle the magnetic field. At older times (the Class II phase), the disk structure can both act as a modulator and signpost of planet formation, if there is enough of a mass reservoir. In my dissertation talk, I will present results that bear on disk evolution at both young and late ages. I will present 8 mm polarization results of two Class 0 protostars (IRAS 4A and IC348 MMS) from the VLA at ~50 au resolution. The inferred magnetic field of IRAS 4A has a circular morphology, reminiscent of material being dragged into a rotating structure. I will show results from SOFIA polarization data of the area surrounding IRAS 4A at ~4000 au. I will also present ALMA 850 micron polarization data of ten protostars in the Perseus Molecular Cloud. Most of these sources show very ordered patterns and low (~0.5%) polarization in their inner regions, while having very disordered patterns and high polarization patterns in their extended emission that may suggest different mechanisms in the inner/outer regions. Finally, I will present results from our ALMA dust continuum survey of protoplanetary disks in Rho Ophiuchus; we measured both the sizes and fluxes of 49 pre main-sequence stellar systems and detected either gaps or cavities in ~6 of these sources. Combined, these results build upon how early protoplanetary disks can form around young protostars and thus how early planets can begin to form.

A Mission to Study Water Throughout The Universe

NASA Astrophysics Data System (ADS)

Goldsmith, Paul F.

2015-08-01

A variety of recent observations have revealed important new information about the distribution of water in the universe, and dramatically expanded its role as a tracer of key stages in the formation of stars and planetary systems. These include water in planetary atmospheres, an asteroid (Ceres), and comets in the solar system by Herschel and Rosetta. Observations of the protoplanetary disk TWHydra have revealed emission from water. Herschel observations of water in a collapsing cloud core (in combination with other molecular lines) have been able to determine the velocity field. Water has also been extensively studied in diffuse interstellar clouds and has been showed to be a valuable tracer of physical conditions and chemistry in these regions. A space mission dedicated to observations of water throughout the universe is appropriate and timely. A critical unifying characteristic of all of the above is that the line widths are very narrow and so high spectral resolution is essential. This means that for the water lines throughout the submillimeter spectral region, heterodyne systems are required. For such systems, the thermal emission from the telescope is negligible so a cold telescope is not necessary. Technology advances allow focal plane array systems with 16 and possibly 64 pixels to frequencies as high as 5 GHz. There have been significant reduction in system noise, but increasing the collecting area is the main way to significantly improve the sensitivity. We have been developing a concept for a space mission that will employ a 8m-9m diameter telescope with a suite of heterodyne focal plane array receivers and broadband digital spectrometers. The collecting area will be factor >5 greater than that of Herschel, and the angular resolution improved by a factor ~2.5. The telescope can be folded to allow a relatively low cost Falcon 9 launch. The surface accuracy should allow observations up to ~2 THz frequency, including a variety of ortho- and para-H2O lines. Other key tracers of the interstellar medium such as C+ and OI can also be covered, making this an enormously exciting concept for future studies of the solar system, the Milky Way, and nearby galaxies.

Extreme Ultraviolet Fractional Orbital Angular Momentum Beams from High Harmonic Generation

PubMed Central

Turpin, Alex; Rego, Laura; Picón, Antonio; San Román, Julio; Hernández-García, Carlos

2017-01-01

We investigate theoretically the generation of extreme-ultraviolet (EUV) beams carrying fractional orbital angular momentum. To this end, we drive high-order harmonic generation with infrared conical refraction (CR) beams. We show that the high-order harmonic beams emitted in the EUV/soft x-ray regime preserve the characteristic signatures of the driving beam, namely ringlike transverse intensity profile and CR-like polarization distribution. As a result, through orbital and spin angular momentum conservation, harmonic beams are emitted with fractional orbital angular momentum, and they can be synthesized into structured attosecond helical beams –or “structured attosecond light springs”– with rotating linear polarization along the azimuth. Our proposal overcomes the state of the art limitations for the generation of light beams far from the visible domain carrying non-integer orbital angular momentum and could be applied in fields such as diffraction imaging, EUV lithography, particle trapping, and super-resolution imaging. PMID:28281655

Anisotropy of the Cosmic Microwave Background Radiation on Large and Medium Angular Scales

NASA Technical Reports Server (NTRS)

Houghton, Anthony; Timbie, Peter

1998-01-01

This grant has supported work at Brown University on measurements of the 2.7 K Cosmic Microwave Background Radiation (CMB). The goal has been to characterize the spatial variations in the temperature of the CMB in order to understand the formation of large-scale structure in the universe. We have concurrently pursued two measurements using millimeter-wave telescopes carried aloft by scientific balloons. Both systems operate over a range of wavelengths, chosen to allow spectral removal of foreground sources such as the atmosphere, Galaxy, etc. The angular resolution of approx. 25 arcminutes is near the angular scale at which the most structure is predicted by current models to be visible in the CMB angular power spectrum. The main goal is to determine the angular scale of this structure; in turn we can infer the density parameter, Omega, for the universe as well as other cosmological parameters, such as the Hubble constant.

A Submillimeter Survey of Dust Continuum Emission in Local Dust-Obscured Galaxies

NASA Astrophysics Data System (ADS)

Lee, Jong Chul; Hwang, Ho Seong; Lee, Gwang-Ho

2015-08-01

Dusty star-forming galaxies are responsible for the bulk of cosmic star formation at 1

A balloon-borne payload for imaging hard X-rays and gamma rays from solar flares

NASA Technical Reports Server (NTRS)

Crannell, Carol J.; Dennis, Brian R.; Orwig, Larry E.; Schmahl, Edward J.; Lang, Frederic L.; Starr, Richard; Norris, Jay P.; Greene, Michael E.; Hurford, Gordon J.; Johnson, W. N.

1991-01-01

Hard X-rays and gamma rays provide direct evidence of the roles of accelerated particles in solar flares. An approach that employs a spatial Fourier-transform technique for imaging the sources of these emissions is described, and the development of a balloon-borne imaging device based on this instrumental technique is presented. The detectors, together with the imaging optics, are sensitive to hard X-ray and gamma-ray emission in the energy-range from 20 to 700 keV. This payload, scheduled for its first flight in June 1992, will provide 11-arc second angular resolution and millisecond time resolution with a whole-sun field of view. For subsequent flights, the effective detector area can be increased by as much as a factor of four, and imaging optics with angular resolution as fine as 2 arcsec can be added to the existing gondola and metering structures.

Two-Dimensional Micro-/Nanoradian Angle Generator with High Resolution and Repeatability Based on Piezo-Driven Double-Axis Flexure Hinge and Three Capacitive Sensors.

PubMed

Tan, Xinran; Zhu, Fan; Wang, Chao; Yu, Yang; Shi, Jian; Qi, Xue; Yuan, Feng; Tan, Jiubin

2017-11-19

This study presents a two-dimensional micro-/nanoradian angle generator (2D-MNAG) that achieves high angular displacement resolution and repeatability using a piezo-driven flexure hinge for two-dimensional deflections and three capacitive sensors for output angle monitoring and feedback control. The principal error of the capacitive sensor for precision microangle measurement is analyzed and compensated for; so as to achieve a high angle output resolution of 10 nrad (0.002 arcsec) and positioning repeatability of 120 nrad (0.024 arcsec) over a large angular range of ±4363 μrad (±900 arcsec) for the 2D-MNAG. The impact of each error component, together with the synthetic error of the 2D-MNAG after principal error compensation are determined using Monte Carlo simulation for further improvement of the 2D-MNAG.

Two-Dimensional Micro-/Nanoradian Angle Generator with High Resolution and Repeatability Based on Piezo-Driven Double-Axis Flexure Hinge and Three Capacitive Sensors

PubMed Central

Tan, Xinran; Zhu, Fan; Wang, Chao; Yu, Yang; Shi, Jian; Qi, Xue; Yuan, Feng; Tan, Jiubin

2017-01-01

This study presents a two-dimensional micro-/nanoradian angle generator (2D-MNAG) that achieves high angular displacement resolution and repeatability using a piezo-driven flexure hinge for two-dimensional deflections and three capacitive sensors for output angle monitoring and feedback control. The principal error of the capacitive sensor for precision microangle measurement is analyzed and compensated for; so as to achieve a high angle output resolution of 10 nrad (0.002 arcsec) and positioning repeatability of 120 nrad (0.024 arcsec) over a large angular range of ±4363 μrad (±900 arcsec) for the 2D-MNAG. The impact of each error component, together with the synthetic error of the 2D-MNAG after principal error compensation are determined using Monte Carlo simulation for further improvement of the 2D-MNAG. PMID:29156595

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

Adams, B.W.; et al.

The Large Area Picosecond PhotoDetector (LAPPD) Collaboration was formed in 2009 to develop large-area photodetectors capable of time resolutions measured in pico-seconds, with accompanying sub-millimeter spatial resolution. During the next three and one-half years the Collaboration developed the LAPPD design of 20 x 20 cm modules with gains greater thanmore » $10^7$ and non-uniformity less than $$15\\%$$, time resolution less than 50 psec for single photons and spatial resolution of 700~microns in both lateral dimensions. We describe the R\\&D performed to develop large-area micro-channel plate glass substrates, resistive and secondary-emitting coatings, large-area bialkali photocathodes, and RF-capable hermetic packaging. In addition, the Collaboration developed the necessary electronics for large systems capable of precise timing, built up from a custom low-power 15-GigaSample/sec waveform sampling 6-channel integrated circuit and supported by a two-level modular data acquisition system based on Field-Programmable Gate Arrays for local control, data-sparcification, and triggering. We discuss the formation, organization, and technical successes and short-comings of the Collaboration. The Collaboration ended in December 2012 with a transition from R\\&D to commercialization.« less

A sub-millimeter resolution detector module for small-animal PET applications

NASA Astrophysics Data System (ADS)

Sacco, I.; Dohle, R.; Fischer, P.; Gola, A.; Piemonte, C.; Ritzert, M.

2017-01-01

We present a gamma detection module optimized for very high resolution PET applications, able to resolve arrays of scintillating crystals with sub-millimeter pitch. The detector is composed of a single ceramic substrate (LTCC): it hosts four flip-chip mounted PETA5 ASICs on the bottom side and an array of SiPM sensors on the top surface, fabricated in HD-RGB technology by FBK. Each chip has 36 channels, for a maximum of 144 readout channels on a sensitive area of about 32 mm × 32 mm. The module is MR-compatible. The thermal decoupling of the readout electronics from the photon sensors is obtained with an efficient internal liquid channel, integrated within the ceramic substrate. Two modules have been designed, based on different SiPM topologies: • Light spreader-based: an array of 12 × 12 SiPMs, with an overall pitch of 2.5 mm, is coupled with a scintillators array using a 1 mm thick glass plate. The light from one crystal is spread over a group of SiPMs, which are read out in parallel using PETA5 internal neighbor logic. • Interpolating SiPM-based: ISiPMs are intrinsic position-sensitive sensors. The photon diodes in the array are connected to one of the four available outputs so that the center of gravity of any bunch of detected photons can be reconstructed using a proper weight function of the read out amplitudes. An array of ISiPMs, each 7.5 mm× 5 mm sized, is directly coupled with the scintillating crystals. Both modules can clearly resolve LYSO arrays with a pitch of only 0.833 mm. The detector can be adjusted for clinical PET, where it has already shown ToF resolution of about 230 ps CRT at FWHM. The module designs, their features and results are described.

Cortical lamina-dependent blood volume changes in human brain at 7 T.

PubMed

Huber, Laurentius; Goense, Jozien; Kennerley, Aneurin J; Trampel, Robert; Guidi, Maria; Reimer, Enrico; Ivanov, Dimo; Neef, Nicole; Gauthier, Claudine J; Turner, Robert; Möller, Harald E

2015-02-15

Cortical layer-dependent high (sub-millimeter) resolution functional magnetic resonance imaging (fMRI) in human or animal brain can be used to address questions regarding the functioning of cortical circuits, such as the effect of different afferent and efferent connectivities on activity in specific cortical layers. The sensitivity of gradient echo (GE) blood oxygenation level-dependent (BOLD) responses to large draining veins reduces its local specificity and can render the interpretation of the underlying laminar neural activity impossible. The application of the more spatially specific cerebral blood volume (CBV)-based fMRI in humans has been hindered by the low sensitivity of the noninvasive modalities available. Here, a vascular space occupancy (VASO) variant, adapted for use at high field, is further optimized to capture layer-dependent activity changes in human motor cortex at sub-millimeter resolution. Acquired activation maps and cortical profiles show that the VASO signal peaks in gray matter at 0.8-1.6mm depth, and deeper compared to the superficial and vein-dominated GE-BOLD responses. Validation of the VASO signal change versus well-established iron-oxide contrast agent based fMRI methods in animals showed the same cortical profiles of CBV change, after normalization for lamina-dependent baseline CBV. In order to evaluate its potential of revealing small lamina-dependent signal differences due to modulations of the input-output characteristics, layer-dependent VASO responses were investigated in the ipsilateral hemisphere during unilateral finger tapping. Positive activation in ipsilateral primary motor cortex and negative activation in ipsilateral primary sensory cortex were observed. This feature is only visible in high-resolution fMRI where opposing sides of a sulcus can be investigated independently because of a lack of partial volume effects. Based on the results presented here, we conclude that VASO offers good reproducibility, high sensitivity and lower sensitivity than GE-BOLD to changes in larger vessels, making it a valuable tool for layer-dependent fMRI studies in humans. Copyright © 2014 Elsevier Inc. All rights reserved.

First Observations of the Magnetic Field inside the Pillars of Creation: Results from the BISTRO Survey

NASA Astrophysics Data System (ADS)

Pattle, Kate; Ward-Thompson, Derek; Hasegawa, Tetsuo; Bastien, Pierre; Kwon, Woojin; Lai, Shih-Ping; Qiu, Keping; Furuya, Ray; Berry, David; JCMT BISTRO Survey Team

2018-06-01

We present the first high-resolution, submillimeter-wavelength polarimetric observations of—and thus direct observations of the magnetic field morphology within—the dense gas of the Pillars of Creation in M16. These 850 μm observations, taken as part of the B-Fields in Star-forming Region Observations Survey (BISTRO) using the POL-2 polarimeter on the Submillimeter Common-User Bolometer Array 2 (SCUBA-2) camera on the James Clerk Maxwell Telescope (JCMT), show that the magnetic field runs along the length of the Pillars, perpendicular to and decoupled from the field in the surrounding photoionized cloud. Using the Chandrasekhar–Fermi method we estimate a plane-of-sky magnetic field strength of 170–320 μG in the Pillars, consistent with their having been formed through the compression of gas with initially weak magnetization. The observed magnetic field strength and morphology suggests that the magnetic field may be slowing the Pillars’ evolution into cometary globules. We thus hypothesize that the evolution and lifetime of the Pillars may be strongly influenced by the strength of the coupling of their magnetic field to that of their parent photoionized cloud—i.e., that the Pillars’ longevity results from magnetic support.

SWARM: A 32 GHz Correlator and VLBI Beamformer for the Submillimeter Array

NASA Astrophysics Data System (ADS)

Primiani, Rurik A.; Young, Kenneth H.; Young, André; Patel, Nimesh; Wilson, Robert W.; Vertatschitsch, Laura; Chitwood, Billie B.; Srinivasan, Ranjani; MacMahon, David; Weintroub, Jonathan

2016-03-01

A 32GHz bandwidth VLBI capable correlator and phased array has been designed and deployeda at the Smithsonian Astrophysical Observatory’s Submillimeter Array (SMA). The SMA Wideband Astronomical ROACH2 Machine (SWARM) integrates two instruments: a correlator with 140kHz spectral resolution across its full 32GHz band, used for connected interferometric observations, and a phased array summer used when the SMA participates as a station in the Event Horizon Telescope (EHT) very long baseline interferometry (VLBI) array. For each SWARM quadrant, Reconfigurable Open Architecture Computing Hardware (ROACH2) units shared under open-source from the Collaboration for Astronomy Signal Processing and Electronics Research (CASPER) are equipped with a pair of ultra-fast analog-to-digital converters (ADCs), a field programmable gate array (FPGA) processor, and eight 10 Gigabit Ethernet (GbE) ports. A VLBI data recorder interface designated the SWARM digital back end, or SDBE, is implemented with a ninth ROACH2 per quadrant, feeding four Mark6 VLBI recorders with an aggregate recording rate of 64 Gbps. This paper describes the design and implementation of SWARM, as well as its deployment at SMA with reference to verification and science data.

Mach-Zehnder Fourier transform spectrometer for astronomical spectroscopy at submillimeter wavelengths

NASA Astrophysics Data System (ADS)

Naylor, David A.; Gom, Bradley G.; Schofield, Ian; Tompkins, Gregory; Davis, Gary R.

2003-02-01

Astronomical spectroscopy at submillimeter wavelengths holds much promise for fields as diverse as the study of planetary atmospheres, molecular clouds and extragalactic sources. Fourier transform spectrometers (FTS) represent an important class of spectrometers well suited to observations that require broad spectral coverage at intermediate spectral resolution. In this paper we present the design and performance of a novel FTS, which has been developed for use at the James Clerk Maxwell Telescope (JCMT). The design uses two broadband intensity beamsplitters in a Mach-Zehnder configuration, which provide access to all four interferometer ports while maintaining a high and uniform efficiency over a broad spectral range. Since the interferometer processes both polarizations it is twice as efficient as the Martin-Puplett interferometer (MPI). As with the MPI, the spatial separation of the two input ports allows a reference blackbody to be viewed at all times in one port, while continually viewing the astronomical source in the other. Furthermore, by minimizing the size of the optical beam at the beamsplitter, the design is well suited to imaging Fourier transform spectroscopy (IFTS) as evidenced by its selection for the SPIRE instrument on Herschel.

The Millimeter-Wave Spectrum of Propanal

NASA Astrophysics Data System (ADS)

Zingsheim, Oliver; Müller, Holger S. P.; Lewen, Frank; Schlemmer, Stephan

2017-06-01

The microwave spectrum of propanal, also known as propionaldehyde, CH_3CH_2CHO, has been investigated in the laboratory already since 1964^1 and has also been detected in space^2. Recently, propanal was detected with the Atacama Large Millimeter/submillimeter Array (ALMA), Protostellar Interferometric Line Survey (PILS)^3. The high sensitivity and resolution of ALMA indicated small discrepancies between observed and predicted rotational spectra of propanal. As higher accuracies are desired the spectrum of propanal was measured up to 500 GHz with the Cologne (Sub-)Millimeter spectrometer. Propanal has two stable conformers, syn and gauche, which differ mainly in the rotation of the aldehyd group with respect to the rigid C-atom framework of the molecule. We extensively studied both of them. The lower syn-conformer shows small splittings caused by the internal rotation of the methyl group, whereas the spectrum of gauche-propanal is complicated due to the tunneling rotation interaction from two stable degenerate conformers. Additionally, we analyzed vibrationally excited states. ^1 Butcher et al., J. Chem. Phys. 40 6 (1964) ^2 Hollis et al., Astrophys. J. 610 L21 (2004) ^3 Lykke et al., A&A 597 A53 (2017)

High-Resolution X-Ray Telescopes

NASA Technical Reports Server (NTRS)

ODell, Stephen L.; Brissenden, Roger J.; Davis, William; Elsner, Ronald F.; Elvis, Martin; Freeman, Mark; Gaetz, Terry; Gorenstein, Paul; Gubarev, Mikhail V.

2010-01-01

Fundamental needs for future x-ray telescopes: a) Sharp images => excellent angular resolution. b) High throughput => large aperture areas. Generation-X optics technical challenges: a) High resolution => precision mirrors & alignment. b) Large apertures => lots of lightweight mirrors. Innovation needed for technical readiness: a) 4 top-level error terms contribute to image size. b) There are approaches to controlling those errors. Innovation needed for manufacturing readiness. Programmatic issues are comparably challenging.

The Normalization of Surface Anisotropy Effects Present in SEVIRI Reflectances by Using the MODIS BRDF Method

NASA Technical Reports Server (NTRS)

Proud, Simon Richard; Zhang, Qingling; Schaaf, Crystal; Fensholt, Rasmus; Rasmussen, Mads Olander; Shisanya, Chris; Mutero, Wycliffe; Mbow, Cheikh; Anyamba, Assaf; Pak, Ed;

Dislocation Content Measured Via 3D HR-EBSD Near a Grain Boundary in an AlCu Oligocrystal

NASA Technical Reports Server (NTRS)

Ruggles, Timothy; Hochhalter, Jacob; Homer, Eric

2016-01-01

Interactions between dislocations and grain boundaries are poorly understood and crucial to mesoscale plasticity modeling. Much of our understanding of dislocation-grain boundary interaction comes from atomistic simulations and TEM studies, both of which are extremely limited in scale. High angular resolution EBSD-based continuum dislocation microscopy provides a way of measuring dislocation activity at length scales and accuracies relevant to crystal plasticity, but it is limited as a two-dimensional technique, meaning the character of the grain boundary and the complete dislocation activity is difficult to recover. However, the commercialization of plasma FIB dual-beam microscopes have made 3D EBSD studies all the more feasible. The objective of this work is to apply high angular resolution cross correlation EBSD to a 3D EBSD data set collected by serial sectioning in a FIB to characterize dislocation interaction with a grain boundary. Three dimensional high angular resolution cross correlation EBSD analysis was applied to an AlCu oligocrystal to measure dislocation densities around a grain boundary. Distortion derivatives associated with the plasma FIB serial sectioning were higher than expected, possibly due to geometric uncertainty between layers. Future work will focus on mitigating the geometric uncertainty and examining more regions of interest along the grain boundary to glean information on dislocation-grain boundary interaction.

A lower limit to the accretion disc radius in the low-luminosity AGNNGC 1052 derived from high-angular resolution data

NASA Astrophysics Data System (ADS)

Reb, Lennart; Fernández-Ontiveros, Juan A.; Prieto, M. Almudena; Dolag, Klaus

2018-07-01

We investigate the central sub-arcsec region of the low-luminosity active galactic nucleusNGC 1052, using a high-angular resolution data set that covers 10 orders of magnitude in frequency. This allows us to infer the continuum emission within the innermost ˜17 pc around the black hole to be of non-thermal, synchrotron origin and to set a limit to the maximum contribution of a standard accretion disc. Assuming the canonical 10 per cent mass-light conversion efficiency for the standard accretion disc, its inferred accretion power would be too low by one order of magnitude to account for the observed continuum luminosity. We thus introduce a truncated accretion disc and derive a truncation radius to mass-light conversion efficiency relation, which we use to reconcile the inferred accretion power with the continuum luminosity. As a result we find that a disc providing the necessary accretion power must be truncated at rtr ≳ 26 rg, consistent with the inner radius derived from the observations of the Fe Kα line in the X-ray spectrum of this nucleus. This is the first time to derive a limit on the truncation radius of the accretion disc from high-angular resolution data only.

A lower limit to the accretion disc radius in the low-luminosity AGN NGC 1052 derived from high-angular resolution data

NASA Astrophysics Data System (ADS)

Reb, Lennart; Fernández-Ontiveros, Juan A.; Prieto, M. Almudena; Dolag, Klaus

2018-05-01

We investigate the central sub-arcsec region of the low-luminosity active galactic nucleus NGC 1052, using a high-angular resolution dataset that covers 10 orders of magnitude in frequency. This allows us to infer the continuum emission within the innermost ˜17 pc around the black hole to be of non-thermal, synchrotron origin and to set a limit to the maximum contribution of a standard accretion disc. Assuming the canonical 10 per cent mass-light conversion efficiency for the standard accretion disc, its inferred accretion power would be too low by one order of magnitude to account for the observed continuum luminosity. We thus introduce a truncated accretion disc and derive a truncation radius to mass-light conversion efficiency relation, which we use to reconcile the inferred accretion power with the continuum luminosity. As a result we find that a truncated disc providing the necessary accretion power must be truncated at rtr ≳ 26 rg, consistent with the inner radius derived from the observations of the Fe Kα line in the X-ray spectrum of this nucleus. This is the first time to derive a limit on the truncation radius of the accretion disc from high-angular resolution data only.

International Conference on Infrared and Millimeter Waves, 16th, Ecole Polytechnique Federale de Lausanne, Switzerland, Aug. 26-30, 1991, Conference Digest

NASA Astrophysics Data System (ADS)

Siegrist, M. R.; Tran, T. M.; Tran, M. Q.

1991-10-01

Consideration is given to millimeter waves (MMW), submillimeter waves, materials properties, and gyrotrons/FEL. Particular attention is given to MMW sources, detectors and mixers; MMW systems, devices and antennas; guided propagation; high Tc superconductors; semiconductors; MMW astronomy and atmospheric physics; lasers, submillimeter devices, and plasma diagnostics; and submillimeter detectors.

High resolution T2(*)-weighted Magnetic Resonance Imaging at 3 Tesla using PROPELLER-EPI.

PubMed

Krämer, Martin; Reichenbach, Jürgen R

2014-05-01

We report the application of PROPELLER-EPI for high resolution T2(*)-weighted imaging with sub-millimeter in-plane resolution on a clinical 3 Tesla scanner. Periodically rotated blades of a long-axis PROPELLER-EPI sequence were acquired with fast gradient echo readout and acquisition matrix of 320 × 50 per blade. Images were reconstructed by using 2D-gridding, phase and geometric distortion correction and compensation of resonance frequency drifts that occurred during extended measurements. To characterize these resonance frequency offsets, short FID calibration measurements were added to the PROPELLER-EPI sequence. Functional PROPELLER-EPI was performed with volunteers using a simple block design of right handed finger tapping. Results indicate that PROPELLER-EPI can be employed for fast, high resolution T2(*)-weighted imaging provided geometric distortions and possible resonance frequency drifts are properly corrected. Even small resonance frequency drifts below 10 Hz as well as non-corrected geometric distortions degraded image quality substantially. In the initial fMRI experiment image quality and signal-to-noise ratio was sufficient for obtaining high resolution functional activation maps. Copyright © 2014. Published by Elsevier GmbH.

Optical simulations for design, alignment, and performance prediction of silicon pore optics for the ATHENA x-ray telescope (Conference Presentation)

NASA Astrophysics Data System (ADS)

Spiga, D.; Della Monica Ferreira, D.; Shortt, B.; Bavdaz, M.; Bergback Knudsen, E.; Bianucci, G.; Christensen, F.; Civitani, M.; Collon, M.; Conconi, P.; Fransen, S.; Marioni, F.; Massahi, S.; Pareschi, G.; Salmaso, B.; Jegers, A. S.; Tayabaly, K.; Valsecchi, G.; Westergaard, N.; Wille, E.

2017-09-01

The ATHENA X-ray observatory is a large-class ESA approved mission, with launch scheduled in 2028. The technology of silicon pore optics (SPO) was selected as baseline to assemble ATHENA's optic with hundreds of mirror modules, obtained by stacking wedged and ribbed silicon wafer plates onto silicon mandrels to form the Wolter-I configuration. In the current configuration, the optical assembly has a 3 m diameter and a 2 m2 effective area at 1 keV, with a required angular resolution of 5 arcsec. The angular resolution that can be achieved is chiefly the combination of 1) the focal spot size determined by the pore diffraction, 2) the focus degradation caused by surface and profile errors, 3) the aberrations introduced by the misalignments between primary and secondary segments, 4) imperfections in the co-focality of the mirror modules in the optical assembly. A detailed simulation of these aspects is required in order to assess the fabrication and alignment tolerances; moreover, the achievable effective area and angular resolution depend on the mirror module design. Therefore, guaranteeing these optical performances requires: a fast design tool to find the most performing solution in terms of mirror module geometry and population, and an accurate point spread function simulation from local metrology and positioning information. In this paper, we present the results of simulations in the framework of ESA-financed projects (SIMPOSiuM, ASPHEA, SPIRIT), in preparation of the ATHENA X-ray telescope, analyzing the mentioned points: 1) we deal with a detailed description of diffractive effects in an SPO mirror module, 2) we show ray-tracing results including surface and profile defects of the reflective surfaces, 3) we assess the effective area and angular resolution degradation caused by alignment errors between SPO mirror module's segments, and 4) we simulate the effects of co-focality errors in X-rays and in the UV optical bench used to study the mirror module alignment and integration.

A comparison of multi-spectral, multi-angular, and multi-temporal remote sensing datasets for fractional shrub canopy mapping in Arctic Alaska

USGS Publications Warehouse

Selkowitz, D.J.

2010-01-01

Shrub cover appears to be increasing across many areas of the Arctic tundra biome, and increasing shrub cover in the Arctic has the potential to significantly impact global carbon budgets and the global climate system. For most of the Arctic, however, there is no existing baseline inventory of shrub canopy cover, as existing maps of Arctic vegetation provide little information about the density of shrub cover at a moderate spatial resolution across the region. Remotely-sensed fractional shrub canopy maps can provide this necessary baseline inventory of shrub cover. In this study, we compare the accuracy of fractional shrub canopy (> 0.5 m tall) maps derived from multi-spectral, multi-angular, and multi-temporal datasets from Landsat imagery at 30 m spatial resolution, Moderate Resolution Imaging SpectroRadiometer (MODIS) imagery at 250 m and 500 m spatial resolution, and MultiAngle Imaging Spectroradiometer (MISR) imagery at 275 m spatial resolution for a 1067 km2 study area in Arctic Alaska. The study area is centered at 69 ??N, ranges in elevation from 130 to 770 m, is composed primarily of rolling topography with gentle slopes less than 10??, and is free of glaciers and perennial snow cover. Shrubs > 0.5 m in height cover 2.9% of the study area and are primarily confined to patches associated with specific landscape features. Reference fractional shrub canopy is determined from in situ shrub canopy measurements and a high spatial resolution IKONOS image swath. Regression tree models are constructed to estimate fractional canopy cover at 250 m using different combinations of input data from Landsat, MODIS, and MISR. Results indicate that multi-spectral data provide substantially more accurate estimates of fractional shrub canopy cover than multi-angular or multi-temporal data. Higher spatial resolution datasets also provide more accurate estimates of fractional shrub canopy cover (aggregated to moderate spatial resolutions) than lower spatial resolution datasets, an expected result for a study area where most shrub cover is concentrated in narrow patches associated with rivers, drainages, and slopes. Including the middle infrared bands available from Landsat and MODIS in the regression tree models (in addition to the four standard visible and near-infrared spectral bands) typically results in a slight boost in accuracy. Including the multi-angular red band data available from MISR in the regression tree models, however, typically boosts accuracy more substantially, resulting in moderate resolution fractional shrub canopy estimates approaching the accuracy of estimates derived from the much higher spatial resolution Landsat sensor. Given the poor availability of snow and cloud-free Landsat scenes in many areas of the Arctic and the promising results demonstrated here by the MISR sensor, MISR may be the best choice for large area fractional shrub canopy mapping in the Alaskan Arctic for the period 2000-2009.

Characterization of surface tilt of foundations for high-precision radio-astronomic antennas

NASA Astrophysics Data System (ADS)

Hoff, Brian D.; Puga, Jose P.

2010-07-01

The Atacama Large Millimeter/Submillimeter Array (ALMA) is a joint project between astronomical organizations in Europe, North America, and East Asia, in collaboration with the Republic of Chile. ALMA will consist of at least 54 twelve-meter antennas operating in the millimeter and sub-millimeter wavelength range. It will be located at an altitude above 5000m in the Chajnantor Plateau in northern Chile. There are 192 antenna foundations under construction at ALMA's Array Operations Site (AOS). Interchangeability between foundations will permit a variety of array configurations. Foundations provide the physical interface to the bedrock, as well as to the underground signal and power cable conduits. To achieve ALMA's precision requirements, the antenna pointing angular error budget is strict with anticipated non-repeatable error on the order of a few arc seconds. This level of precision imposes rigorous requirements on antenna foundations. The objective of this study is to demonstrate the methodology of precision tilt measurements combined with finite element simulation predictions to portray the qualitative nature of the antenna foundation surface deformation. Characteristics of foundation surface tilt have been examined in detail. Although the actual foundation has demonstrated much less resistance to tilt than the finite element representation, the simulation has predicted some key characteristics of the tilt pattern. The large deviations from the ideal have incited speculations into the compliance of materials, ambiguities in the construction, thermal effects and several other aspects described herein. This research has served as groundwork to characterize ALMA's foundation surface behavior on a micro-degree level and to identify subsequent studies to pursue. This in turn has contributed to the diagnosis of antenna pointing anomalies.

Orbital angular momentum light in microscopy

PubMed Central

2017-01-01

Light with a helical phase has had an impact on optical imaging, pushing the limits of resolution or sensitivity. Here, special emphasis will be given to classical light microscopy of phase samples and to Fourier filtering techniques with a helical phase profile, such as the spiral phase contrast technique in its many variants and areas of application. This article is part of the themed issue ‘Optical orbital angular momentum’. PMID:28069768

X-ray-induced acoustic computed tomography of concrete infrastructure

NASA Astrophysics Data System (ADS)

Tang, Shanshan; Ramseyer, Chris; Samant, Pratik; Xiang, Liangzhong

2018-02-01

X-ray-induced Acoustic Computed Tomography (XACT) takes advantage of both X-ray absorption contrast and high ultrasonic resolution in a single imaging modality by making use of the thermoacoustic effect. In XACT, X-ray absorption by defects and other structures in concrete create thermally induced pressure jumps that launch ultrasonic waves, which are then received by acoustic detectors to form images. In this research, XACT imaging was used to non-destructively test and identify defects in concrete. For concrete structures, we conclude that XACT imaging allows multiscale imaging at depths ranging from centimeters to meters, with spatial resolutions from sub-millimeter to centimeters. XACT imaging also holds promise for single-side testing of concrete infrastructure and provides an optimal solution for nondestructive inspection of existing bridges, pavement, nuclear power plants, and other concrete infrastructure.

Developing Wide-Field Spatio-Spectral Interferometry for Far-Infrared Space Applications

NASA Technical Reports Server (NTRS)

Leisawitz, David; Bolcar, Matthew R.; Lyon, Richard G.; Maher, Stephen F.; Memarsadeghi, Nargess; Rinehart, Stephen A.; Sinukoff, Evan J.

2012-01-01

Interferometry is an affordable way to bring the benefits of high resolution to space far-IR astrophysics. We summarize an ongoing effort to develop and learn the practical limitations of an interferometric technique that will enable the acquisition of high-resolution far-IR integral field spectroscopic data with a single instrument in a future space-based interferometer. This technique was central to the Space Infrared Interferometric Telescope (SPIRIT) and Submillimeter Probe of the Evolution of Cosmic Structure (SPECS) space mission design concepts, and it will first be used on the Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII). Our experimental approach combines data from a laboratory optical interferometer (the Wide-field Imaging Interferometry Testbed, WIIT), computational optical system modeling, and spatio-spectral synthesis algorithm development. We summarize recent experimental results and future plans.

Bringing the Visible Universe into Focus with Robo-AO

PubMed Central

Baranec, Christoph; Riddle, Reed; Law, Nicholas M.; Ramaprakash, A.N.; Tendulkar, Shriharsh P.; Bui, Khanh; Burse, Mahesh P.; Chordia, Pravin; Das, Hillol K.; Davis, Jack T.C.; Dekany, Richard G.; Kasliwal, Mansi M.; Kulkarni, Shrinivas R.; Morton, Timothy D.; Ofek, Eran O.; Punnadi, Sujit

2013-01-01

The angular resolution of ground-based optical telescopes is limited by the degrading effects of the turbulent atmosphere. In the absence of an atmosphere, the angular resolution of a typical telescope is limited only by diffraction, i.e., the wavelength of interest, λ, divided by the size of its primary mirror's aperture, D. For example, the Hubble Space Telescope (HST), with a 2.4-m primary mirror, has an angular resolution at visible wavelengths of ~0.04 arc seconds. The atmosphere is composed of air at slightly different temperatures, and therefore different indices of refraction, constantly mixing. Light waves are bent as they pass through the inhomogeneous atmosphere. When a telescope on the ground focuses these light waves, instantaneous images appear fragmented, changing as a function of time. As a result, long-exposure images acquired using ground-based telescopes - even telescopes with four times the diameter of HST - appear blurry and have an angular resolution of roughly 0.5 to 1.5 arc seconds at best. Astronomical adaptive-optics systems compensate for the effects of atmospheric turbulence. First, the shape of the incoming non-planar wave is determined using measurements of a nearby bright star by a wavefront sensor. Next, an element in the optical system, such as a deformable mirror, is commanded to correct the shape of the incoming light wave. Additional corrections are made at a rate sufficient to keep up with the dynamically changing atmosphere through which the telescope looks, ultimately producing diffraction-limited images. The fidelity of the wavefront sensor measurement is based upon how well the incoming light is spatially and temporally sampled1. Finer sampling requires brighter reference objects. While the brightest stars can serve as reference objects for imaging targets from several to tens of arc seconds away in the best conditions, most interesting astronomical targets do not have sufficiently bright stars nearby. One solution is to focus a high-power laser beam in the direction of the astronomical target to create an artificial reference of known shape, also known as a 'laser guide star'. The Robo-AO laser adaptive optics system2,3 employs a 10-W ultraviolet laser focused at a distance of 10 km to generate a laser guide star. Wavefront sensor measurements of the laser guide star drive the adaptive optics correction resulting in diffraction-limited images that have an angular resolution of ~0.1 arc seconds on a 1.5-m telescope. PMID:23426078

Bringing the visible universe into focus with Robo-AO.

PubMed

Baranec, Christoph; Riddle, Reed; Law, Nicholas M; Ramaprakash, A N; Tendulkar, Shriharsh P; Bui, Khanh; Burse, Mahesh P; Chordia, Pravin; Das, Hillol K; Davis, Jack T C; Dekany, Richard G; Kasliwal, Mansi M; Kulkarni, Shrinivas R; Morton, Timothy D; Ofek, Eran O; Punnadi, Sujit

2013-02-12

The angular resolution of ground-based optical telescopes is limited by the degrading effects of the turbulent atmosphere. In the absence of an atmosphere, the angular resolution of a typical telescope is limited only by diffraction, i.e., the wavelength of interest, λ, divided by the size of its primary mirror's aperture, D. For example, the Hubble Space Telescope (HST), with a 2.4-m primary mirror, has an angular resolution at visible wavelengths of ~0.04 arc seconds. The atmosphere is composed of air at slightly different temperatures, and therefore different indices of refraction, constantly mixing. Light waves are bent as they pass through the inhomogeneous atmosphere. When a telescope on the ground focuses these light waves, instantaneous images appear fragmented, changing as a function of time. As a result, long-exposure images acquired using ground-based telescopes--even telescopes with four times the diameter of HST--appear blurry and have an angular resolution of roughly 0.5 to 1.5 arc seconds at best. Astronomical adaptive-optics systems compensate for the effects of atmospheric turbulence. First, the shape of the incoming non-planar wave is determined using measurements of a nearby bright star by a wavefront sensor. Next, an element in the optical system, such as a deformable mirror, is commanded to correct the shape of the incoming light wave. Additional corrections are made at a rate sufficient to keep up with the dynamically changing atmosphere through which the telescope looks, ultimately producing diffraction-limited images. The fidelity of the wavefront sensor measurement is based upon how well the incoming light is spatially and temporally sampled. Finer sampling requires brighter reference objects. While the brightest stars can serve as reference objects for imaging targets from several to tens of arc seconds away in the best conditions, most interesting astronomical targets do not have sufficiently bright stars nearby. One solution is to focus a high-power laser beam in the direction of the astronomical target to create an artificial reference of known shape, also known as a 'laser guide star'. The Robo-AO laser adaptive optics system, employs a 10-W ultraviolet laser focused at a distance of 10 km to generate a laser guide star. Wavefront sensor measurements of the laser guide star drive the adaptive optics correction resulting in diffraction-limited images that have an angular resolution of ~0.1 arc seconds on a 1.5-m telescope.

Photoacoustic tomography using a Michelson interferometer with quadrature phase detection

NASA Astrophysics Data System (ADS)

Speirs, Rory W.; Bishop, Alexis I.

2013-07-01

We present a pressure sensor based on a Michelson interferometer, for use in photoacoustic tomography. Quadrature phase detection is employed allowing measurement at any point on the mirror surface without having to retune the interferometer, as is typically required by Fabry-Perot type detectors. This opens the door to rapid full surface detection, which is necessary for clinical applications. Theory relating acoustic pressure to detected acoustic particle displacements is used to calculate the detector sensitivity, which is validated with measurement. Proof-of-concept tomographic images of blood vessel phantoms have been taken with sub-millimeter resolution at depths of several millimeters.

The Stratospheric Observatory for Infrared Astronomy (sofia)

NASA Astrophysics Data System (ADS)

Joseph, R. D.

2009-08-01

The SOFIA is a 2.5-meter telescope built into a Boeing 747 airplane. It will fly at altitudes between 12-14 km above 99.8% of the atmospheric water vapor, making possible observations throughout the far-infrared and submillimeter spectral region. Nine focal plane instruments providing imaging and low-to-high resolution spectroscopy will be available. It will be operated as a guest observer facility. The first call for ``Early Basic Science'' will be issued in December 2009, the call for Demonstration Science will be issued early in 2010, and the call for Cycle 0 Guest Investigator programs is planned for January 2011.

433 micron laser heterodyne observations of galactic CO from Mauna Kea

NASA Technical Reports Server (NTRS)

Buhl, D.; Chin, G.; Koepf, G. A.; Fetterman, H. R.; Peck, D. D.; Clifton, B. J.; Tannenwald, P. E.; Goldsmith, P. F.; Erickson, N. R.; Mcavoy, N.

1981-01-01

A submillimeter heterodyne radiometer, developed for astronomical applications, uses an optically pumped laser local oscillator and a quasi-optical Schottky diode mixer. The resultant telescope-mounted system, which has a noise temperature less than 4000 K (double sideband) and high frequency and spatial resolution, has been used to detect the J = 6 to 5 rotational transition of carbon monoxide at 434 micrometers in the Orion molecular clouds. The measurements, when compared with previous millimeter-wave data, indicate that the broad carbon monoxide emission feature is produced by an optically thin gas whose temperature exceeds 180 K.

A combined Compton and coded-aperture telescope for medium-energy gamma-ray astrophysics

NASA Astrophysics Data System (ADS)

Galloway, Michelle; Zoglauer, Andreas; Boggs, Steven E.; Amman, Mark

2018-06-01

A future mission in medium-energy gamma-ray astrophysics would allow for many scientific advancements, such as a possible explanation for the excess positron emission from the Galactic center, a better understanding of nucleosynthesis and explosion mechanisms in Type Ia supernovae, and a look at the physical forces at play in compact objects such as black holes and neutron stars. Additionally, further observation in this energy regime would significantly extend the search parameter space for low-mass dark matter. In order to achieve these objectives, an instrument with good energy resolution, good angular resolution, and high sensitivity is required. In this paper we present the design and simulation of a Compton telescope consisting of cubic-centimeter cadmium zinc telluride detectors as absorbers behind a silicon tracker with the addition of a passive coded mask. The goal of the design was to create a very sensitive instrument that is capable of high angular resolution. The simulated telescope achieved energy resolutions of 1.68% FWHM at 511 keV and 1.11% at 1809 keV, on-axis angular resolutions in Compton mode of 2.63° FWHM at 511 keV and 1.30° FWHM at 1809 keV, and is capable of resolving sources to at least 0.2° at lower energies with the use of the coded mask. An initial assessment of the instrument in Compton-imaging mode yields an effective area of 183 cm2 at 511 keV and an anticipated all-sky sensitivity of 3.6 × 10-6 photons cm-2 s-1 for a broadened 511 keV source over a two-year observation time. Additionally, combining a coded mask with a Compton imager to improve point-source localization for positron detection has been demonstrated.

The Advanced Pair Telescope (APT) Mission Concept

NASA Technical Reports Server (NTRS)

Hunter, Stanley; Buckley, James H.

2008-01-01

We present a mission concept for the Advanced Pair Telescope (APT), a high-energy gamma-ray instrument with an order of magnitude improvement in sensitivity, 6 sr field of view, and angular resolution a factor of 3-10 times that of GLAST. With its very wide instantaneous field-of-view and large effective area, this instrument would be capable of detecting GRBs at very large redshifts, would enable a very high resolution study of SNRs and PWN, and could provide hour-scale temporal resolution of transients from many AGN and galactic sources. The APT instrument will consist of a Xe time-projection-chamber tracker that bridges the energy regime between Compton scattering and pair production and will provide an unprecedented improvement in angular resolution; a thick scintillating-fiber trackerlcalorimeter that will provide sensitivity and energy resolution to higher energies and will possess a factor of 10 improvement in geometric factor over GLAST; and an anticoincidence detector using scintillator-tiles to reject charged particles. After the anticipated 10-years of GLAST operation , the APT instrument would provide continued coverage of the critial high-energy gamma-ray band (between 30 MeV to 100 GeV), providing an essential component of broad-band multiwavelength studies of the high-energy universe.

Survey of the galactic disk from 1 = -150 deg to 1 = 82 deg in the submillimeter range

NASA Technical Reports Server (NTRS)

Caux, Emmanuel; Serra, Guy

1987-01-01

The first almost complete survey of the galactic disk from 1 = -150 deg to 1 = 82 deg in the submillimeter range (effective wavelength = 380 microns), performed with the AGLAE balloon-borne instrument modified to include a submillimeter channel, is reported. The instrumentation and observational procedures are described, as are the signal processing and calibration. The results are presented as a profile of the submillimeter brightness of the galactic disk displayed as a function of the galactic longitude. This profile exhibits diffuse emission all along the disk with bright peaks associated with resolved sources. The averaged galactic spectrum is in agreement with a temperature distribution of the interstellar cold dust.

Angular Resolution of an EAS Array for Gamma Ray Astronomy at Energies Greater Than 5 x 10 (13) Ev

NASA Technical Reports Server (NTRS)

Apte, A. R.; Gopalakrishnan, N. V.; Tonwar, S. C.; Uma, V.

1985-01-01

A 24 detector extensive air shower array is being operated at Ootacamund (2300 m altitude, 11.4 deg N latitude) in southern India for a study of arrival directions of showers of energies greater than 5 x 10 to the 13th power eV. Various configurations of the array of detectors have been used to estimate the accuracy in determination of arrival angle of showers with such an array. These studies show that it is possible to achieve an angular resolution of better than 2 deg with the Ooty array for search for point sources of Cosmic gamma rays at energies above 5 x 10 to the 13th power eV.

Curved position-sensitive detector for X-ray crystallography

NASA Astrophysics Data System (ADS)

Izumi, T.

1980-11-01

A new curved position-sensitive proportional detector has been constructed for X-ray crystallography. A very hard steel wire 0.2 mm in diameter was used as a single anode wire. It was bent to a radius of 6.5 cm and was suspended elastically in a wide 160° 2θ angular aperture. An amplifier and ADC-per-cathode strip system was made in order to encode the position. The spatial resolution is better than 0.37 mm (fwhm) along the curved anode wire, and this value corresponds to an angular resolution of 0.28° in 2θ. It is shown that a thick hard anode wire is quite suitable for use as a curved position-sensitive detector.

The Advanced Gamma-ray Imaging System (AGIS): Extragalactic Science

NASA Astrophysics Data System (ADS)

Coppi, Paolo S.; Extragalactic Science Working Group; AGIS Collaboration

2010-03-01

The Advanced Gamma-ray Imaging System (AGIS), a proposed next-generation array of Cherenkov telescopes, will provide an unprecedented view of the high energy universe. We discuss how AGIS, with its larger effective area, improved angular resolution, lower threshold, and an order of magnitude increase in sensitivity, impacts the extragalactic science possible in the very high energy domain. Likely source classes detectable by AGIS include AGN, GRBs, clusters, star-forming galaxies, and possibly the cascade radiation surrounding powerful cosmic accelerators. AGIS should see many of the sources discovered by Fermi. With its better sensitivity and angular resolution, AGIS then becomes a key instrument for identifying and characterizing Fermi survey sources, the majority of which will have limited Fermi photon statistics and localizations.

Focal Plane Detectors for the Advanced Gamma-Ray Imaging System (AGIS)

NASA Astrophysics Data System (ADS)

Wagner, R. G.; Byrum, K.; Drake, G.; Funk, S.; Otte, N.; Smith, A.; Tajima, H.; Williams, D.

2009-05-01

The Advanced Gamma-Ray Imaging System (AGIS) is a concept for the next generation observatory in ground-based very high energy gamma-ray astronomy. It is being designed to achieve a significant improvement in sensitivity compared to current Imaging Air Cherenkov Telescope (IACT) Arrays. One of the main requirements in order that AGIS fulfills this goal will be to achieve higher angular resolution than current IACTs. Simulations show that a substantial improvement in angular resolution may be achieved if the pixel size is reduced to 0.05 deg, i.e. two to three times smaller than for current IACT cameras. Here we present results from testing of alternatives being considered for AGIS, including both silicon photomultipliers (SiPMs) and multi-anode photomultipliers (MAPMTs).

High resolution energy-angle correlation measurement of hard x rays from laser-Thomson backscattering.

PubMed

Jochmann, A; Irman, A; Bussmann, M; Couperus, J P; Cowan, T E; Debus, A D; Kuntzsch, M; Ledingham, K W D; Lehnert, U; Sauerbrey, R; Schlenvoigt, H P; Seipt, D; Stöhlker, Th; Thorn, D B; Trotsenko, S; Wagner, A; Schramm, U

2013-09-13

Thomson backscattering of intense laser pulses from relativistic electrons not only allows for the generation of bright x-ray pulses but also for the investigation of the complex particle dynamics at the interaction point. For this purpose a complete spectral characterization of a Thomson source powered by a compact linear electron accelerator is performed with unprecedented angular and energy resolution. A rigorous statistical analysis comparing experimental data to 3D simulations enables, e.g., the extraction of the angular distribution of electrons with 1.5% accuracy and, in total, provides predictive capability for the future high brightness hard x-ray source PHOENIX (photon electron collider for narrow bandwidth intense x rays) and potential gamma-ray sources.

The Circumstellar Environment of Low Mass Star Forming Regions

NASA Technical Reports Server (NTRS)

Butner, Harold M.

1997-01-01

We have obtained the complete SED from 10 microns out to 1.3 mm for all of our sources. We have the FIR imaging data, processed to reveal the maximum angular resolution possible, which allows us to model the disk. To model the disk, we have high resolution millimeter interferometry data.

VizieR Online Data Catalog: APEX CO and HI observations of Lupus I (Gaczkowski+, 2017)

NASA Astrophysics Data System (ADS)

Gaczkowski, B.; Roccatagliata, V.; Flaischlen, S.; Kroell, D.; Krause, M. G. H. Burkert A.; Diehl, R.; Fierlinger, K.; Ngoumou, J.; Preibisch, T.

2017-11-01

The FITS files contain the data cubes corresponding to the 13C and C18O(3-2) lines. They were taken using the Atacama Pathfinder EXperiment (APEX) telescope, with an angular resolution of 30" and a velocity resolution of 0.1km/s. (2 data files).

Fabrication and characterization of a 0.5-mm lutetium oxyorthosilicate detector array for high-resolution PET applications.

PubMed

Stickel, Jennifer R; Qi, Jinyi; Cherry, Simon R

2007-01-01

With the increasing use of in vivo imaging in mouse models of disease, there are many interesting applications that demand imaging of organs and tissues with submillimeter resolution. Though there are other contributing factors, the spatial resolution in small-animal PET is still largely determined by the detector pixel dimensions. In this work, a pair of lutetium oxyorthosilicate (LSO) arrays with 0.5-mm pixels was coupled to multichannel photomultiplier tubes and evaluated for use as high-resolution PET detectors. Flood histograms demonstrated that most crystals were clearly identifiable. Energy resolution varied from 22% to 38%. The coincidence timing resolution was 1.42-ns full width at half maximum (FWHM). The intrinsic spatial resolution was 0.68-mm FWHM as measured with a 30-gauge needle filled with (18)F. The improvement in spatial resolution in a tomographic setting is demonstrated using images of a line source phantom reconstructed with filtered backprojection and compared with images obtained from 2 dedicated small-animal PET scanners. Finally, a projection image of the mouse foot is shown to demonstrate the application of these 0.5-mm LSO detectors to a biologic task. A pair of highly pixelated LSO detections has been constructed and characterized for use as high-spatial-resolution PET detectors. It appears that small-animal PET systems capable of a FWHM spatial resolution of 600 microm or less are feasible and should be pursued.

Modeling of beam customization devices in the pencil-beam splitting algorithm for heavy charged particle radiotherapy.

PubMed

Kanematsu, Nobuyuki

2011-03-07

A broad-beam-delivery system for radiotherapy with protons or ions often employs multiple collimators and a range-compensating filter, which offer complex and potentially useful beam customization. It is however difficult for conventional pencil-beam algorithms to deal with fine structures of these devices due to beam-size growth during transport. This study aims to avoid the difficulty with a novel computational model. The pencil beams are initially defined at the range-compensating filter with angular-acceptance correction for upstream collimation followed by stopping and scattering. They are individually transported with possible splitting near the aperture edge of a downstream collimator to form a sharp field edge. The dose distribution for a carbon-ion beam was calculated and compared with existing experimental data. The penumbra sizes of various collimator edges agreed between them to a submillimeter level. This beam-customization model will be used in the greater framework of the pencil-beam splitting algorithm for accurate and efficient patient dose calculation.

Cosmic evolution of star formation properties of galaxies

NASA Astrophysics Data System (ADS)

Kim, Sungeun

2014-01-01

Development of bolometer array and camera at submillimeter wavelength has played an important role in detecting submillimeter bright galaxies, so called submillimeter galaxies. These galaxies seem to be progenitors of present-day massive galaxies and account for their considerable contributions to the light from the early universe and their expected high star formation rates if there is a close link between the submillimeter galaxies and the star formation activities, and the interstellar dust in galaxies is mainly heated by the star light. We review assembly of submillimeter galaxies chosen from the AzTEC and the Herschel SPIRE/PACS data archives, and investigate their spectral energy distribution fits including the data at other wavelengths to deduce details about stellar parameters including star formation rates and parameters yielding the metallicity, composition and abundance in dust, and disc structure of these galaxies. This work has been supported in part by Mid-career Researcher Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology 2011-0028001.

A Weak Solar Burst Submillimeter Only Spectral Component During a GOES M Class Flare: Implications for its Emission Mechanisms

NASA Astrophysics Data System (ADS)

Cristiani, G. D.; Giménez de Castro, C. G.; Mandrini, C. H.; et al.

2008-09-01

Since the installation of the Submillimeter Solar Radio Telescope, a new spectral burst component was discovered at frequencies above 100 GHz, creating the THz bursts category. In all the reported cases, the events were X class flares and the THz component was increasing with frequency. We report for the first time an M class flare which shows a submillimeter radio spectral component different from the one in microwave classical bursts. Two successive flares of 2 minute duration occurred in active region NOAA 10226 with 2 minutes delay. They started at around 13:15 UT and had an M 6.8 maximum intensity in soft X-rays. The submillimeter flux density from the Solar Submillimeter Telescope (SST) is used in addition to microwave total Sun patrol telescope observations. Images with H filters from the H-alpha Solar Telescope for Argentina (HASTA) and in the extreme UV from the Extreme-ultraviolet Imaging Telescope (EIT) are used to characterize the flaring region. An extensive analysis of the magnetic topology evolution is derived from Michelson Doppler Imager (MDI) magnetograms and used to constrain the space of solutions for the possible emission mechanisms. The submillimeter component is observed at 212 GHz only. We have upper limits for the emission at 89.4and 405 GHz which are smaller than the observed flux density at 212 GHz. The analysis of the magnetic topology reveals a very compact and complex system of arches that reconnects at a low height, while from the soft X-ray observations we deduce that the flaring area is compact and dense (n=1e12 cm-3). The finding of a submillimeter only burst component in a medium size flare indicates that the phenomenon is more universal than shown until now. The multiwavelength analysis reveals that neither positron synchrotron nor free-free emission could produce the submillimeter component, which is explained here by synchrotron of accelerated electrons in a rather complex and compact magnetic configuration.

KINEMATICS OF THE OUTFLOW FROM THE YOUNG STAR DG TAU B: ROTATION IN THE VICINITIES OF AN OPTICAL JET

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

Zapata, Luis A.; Lizano, Susana; Rodríguez, Luis F.

2015-01-10

We present {sup 12}CO(2-1) line and 1300 μm continuum observations made with the Submillimeter Array of the young star DG Tau B. We find, in the continuum observations, emission arising from the circumstellar disk surrounding DG Tau B. The {sup 12}CO(2-1) line observations, on the other hand, revealed emission associated with the disk and the asymmetric outflow related with this source. Velocity asymmetries about the flow axis are found over the entire length of the flow. The amplitude of the velocity differences is of the order of 1-2 km s{sup –1} over distances of about 300-400 AU. We interpret themmore » as a result of outflow rotation. The sense of the outflow and disk rotation is the same. Infalling gas from a rotating molecular core cannot explain the observed velocity gradient within the flow. Magneto-centrifugal disk winds or photoevaporated disk winds can produce the observed rotational speeds if they are ejected from a Keplerian disk at radii of several tens of AU. Nevertheless, these slow winds ejected from large radii are not very massive, and cannot account for the observed linear momentum and angular momentum rates of the molecular flow. Thus, the observed flow is probably entrained material from the parent cloud. DG Tau B is a good laboratory to model in detail the entrainment process and see if it can account for the observed angular momentum.« less

Space Mirror Alignment System

NASA Technical Reports Server (NTRS)

Jau, Bruno M.; McKinney, Colin; Smythe, Robert F.; Palmer, Dean L.

2011-01-01

An optical alignment mirror mechanism (AMM) has been developed with angular positioning accuracy of +/-0.2 arcsec. This requires the mirror s linear positioning actuators to have positioning resolutions of +/-112 nm to enable the mirror to meet the angular tip/tilt accuracy requirement. Demonstrated capabilities are 0.1 arc-sec angular mirror positioning accuracy, which translates into linear positioning resolutions at the actuator of 50 nm. The mechanism consists of a structure with sets of cross-directional flexures that enable the mirror s tip and tilt motion, a mirror with its kinematic mount, and two linear actuators. An actuator comprises a brushless DC motor, a linear ball screw, and a piezoelectric brake that holds the mirror s position while the unit is unpowered. An interferometric linear position sensor senses the actuator s position. The AMMs were developed for an Astrometric Beam Combiner (ABC) optical bench, which is part of an interferometer development. Custom electronics were also developed to accommodate the presence of multiple AMMs within the ABC and provide a compact, all-in-one solution to power and control the AMMs.

High resolution gamma-ray spectroscopy and the fascinating angular momentum realm of the atomic nucleus

NASA Astrophysics Data System (ADS)

Riley, M. A.; Simpson, J.; Paul, E. S.

2016-12-01

In 1974 Aage Bohr and Ben Mottelson predicted the different ‘phases’ that may be expected in deformed nuclei as a function of increasing angular momentum and excitation energy all the way up to the fission limit. While admitting their picture was highly conjectural they confidently stated ‘...with the ingenious experimental approaches that are being developed, we may look forward with excitement to the detailed spectroscopic studies that will illuminate the behaviour of the spinning quantised nucleus’. High resolution gamma-ray spectroscopy has indeed been a major tool in studying the structure of atomic nuclei and has witnessed numerous significant advances over the last four decades. This article will select highlights from investigations at the Niels Bohr Institute, Denmark, and Daresbury Laboratory, UK, in the late 1970s and early 1980s, some of which have continued at other national laboratories in Europe and the USA to the present day. These studies illustrate the remarkable diversity of phenomena and symmetries exhibited by nuclei in the angular momentum-excitation energy plane that continue to surprise and fascinate scientists.

The Atacama Cosmology Telescope: The Polarization-Sensitive ACTPol Instrument

DOE PAGES

Thornton, R. J.; Ade, P. A. R.; Aiola, S.; ...

2016-12-09

The Atacama Cosmology Telescope (ACT) makes high angular resolution measurements of anisotropies in the Cosmic Microwave Background (CMB) at millimeter wavelengths. We describe ACTPol, an upgraded receiver for ACT, which uses feedhorn-coupled, polarization-sensitive detector arrays, a 3° field of view, 100 mK cryogenics with continuous cooling, and meta material antireflection coatings. ACTPol comprises three arrays with separate cryogenic optics: two arrays at a central frequency of 148 GHz and one array operating simultaneously at both 97 GHz and 148 GHz. The combined instrument sensitivity, angular resolution, and sky coverage are optimized for measuring angular power spectra, clusters via the thermalmore » Sunyaev–Zel'dovich (SZ) and kinetic SZ signals, and CMB lensing due to large-scale structure. The receiver was commissioned with its first 148 GHz array in 2013, observed with both 148 GHz arrays in 2014, and has recently completed its first full season of operations with the full suite of three arrays. This paper provides an overview of the design and initial performance of the receiver and related systems.« less

THE ATACAMA COSMOLOGY TELESCOPE: THE POLARIZATION-SENSITIVE ACTPol INSTRUMENT

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

Thornton, R. J.; Ade, P. A. R.; Aiola, S.

The Atacama Cosmology Telescope (ACT) makes high angular resolution measurements of anisotropies in the Cosmic Microwave Background (CMB) at millimeter wavelengths. We describe ACTPol, an upgraded receiver for ACT, which uses feedhorn-coupled, polarization-sensitive detector arrays, a 3° field of view, 100 mK cryogenics with continuous cooling, and meta material antireflection coatings. ACTPol comprises three arrays with separate cryogenic optics: two arrays at a central frequency of 148 GHz and one array operating simultaneously at both 97 GHz and 148 GHz. The combined instrument sensitivity, angular resolution, and sky coverage are optimized for measuring angular power spectra, clusters via the thermalmore » Sunyaev–Zel’dovich (SZ) and kinetic SZ signals, and CMB lensing due to large-scale structure. The receiver was commissioned with its first 148 GHz array in 2013, observed with both 148 GHz arrays in 2014, and has recently completed its first full season of operations with the full suite of three arrays. This paper provides an overview of the design and initial performance of the receiver and related systems.« less

The Atacama Cosmology Telescope: The Polarization-Sensitive ACTPol Instrument

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

Thornton, R. J.; Ade, P. A. R.; Aiola, S.

The Atacama Cosmology Telescope (ACT) makes high angular resolution measurements of anisotropies in the Cosmic Microwave Background (CMB) at millimeter wavelengths. We describe ACTPol, an upgraded receiver for ACT, which uses feedhorn-coupled, polarization-sensitive detector arrays, a 3° field of view, 100 mK cryogenics with continuous cooling, and meta material antireflection coatings. ACTPol comprises three arrays with separate cryogenic optics: two arrays at a central frequency of 148 GHz and one array operating simultaneously at both 97 GHz and 148 GHz. The combined instrument sensitivity, angular resolution, and sky coverage are optimized for measuring angular power spectra, clusters via the thermalmore » Sunyaev–Zel'dovich (SZ) and kinetic SZ signals, and CMB lensing due to large-scale structure. The receiver was commissioned with its first 148 GHz array in 2013, observed with both 148 GHz arrays in 2014, and has recently completed its first full season of operations with the full suite of three arrays. This paper provides an overview of the design and initial performance of the receiver and related systems.« less

High-resolution dust emission and the resolved star formation law in the z~4 submillimeter galaxy GN20

NASA Astrophysics Data System (ADS)

Hodge, Jacqueline; Riechers, Dominik A.; Decarli, Roberto; Walter, Fabian; Carilli, Chris Luke; Daddi, Emanuele; Dannerbauer, Helmut

2015-01-01

We present high-resolution observations of the 880μm (rest-frame far-infrared) continuum emission in the z=4.05 submillimeter galaxy GN20. These data, taken with the IRAM Plateau de Bure Interferometer (PdBI), allow us to resolve the obscured star formation on scales of 0.3'×0.2' (~2.1×1.3 kpc). The observations reveal a bright (16±1 mJy) dusty starburst centered on the cold molecular gas reservoir as traced by previous high-fidelity CO(2-1) imaging and showing a bar-like extension along the galaxy's major axis. The striking anti-correlation with the HST/WFC3 imaging suggests that the copious dust surrounding the starburst heavily obscures the rest-frame UV/optical light in all but one small region several kpc from the nucleus. A comparison with 1.2 mm PdBI data reveals no evidence for variations in the dust continuum slope across the source. A detailed star formation rate surface density map reveals values that peak at 119±8 M⊙ yr-1 kpc-2 in the galaxy's center, showing that the star formation in GN20 remains sub-Eddington on scales down to 3 kpc2. Lastly, we examine the resolved star formation law on the same scales, deriving a power law slope of ΣSFR ~ ΣH_22.1±1.0 and a mean depletion time of 130 Myr. Despite its disk-like morphology and the use of custom-derived CO-to-H2 conversion factors, GN20 lies roughly in-line with the other existing resolved starbursts and above the sequence of star forming disks, implying that the offset is not due solely to choice of conversion factor.

ALMACAL I: FIRST DUAL-BAND NUMBER COUNTS FROM A DEEP AND WIDE ALMA SUBMILLIMETER SURVEY, FREE FROM COSMIC VARIANCE

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

Oteo, I.; Ivison, R. J.; Zwaan, M. A.

We have exploited ALMA calibration observations to carry out a novel, wide, and deep submillimeter (submm) survey, almacal. These calibration data comprise a large number of observations of calibrator fields in a variety of frequency bands and array configurations. By gathering together data acquired during multiple visits to many ALMA calibrators, it is possible to reach noise levels which allow the detection of faint, dusty, star-forming galaxies (DSFGs) over a significant area. In this paper, we outline our survey strategy and report the first results. We have analyzed data for 69 calibrators, reaching depths of ∼25 μ Jy beam{sup −1}more » at sub-arcsec resolution. Adopting a conservative approach based on ≥5 σ detections, we have found 8 and 11 DSFGs in ALMA bands 6 and 7, respectively, with flux densities S {sub 1.2} m {sub m} ≥ 0.2 mJy. The faintest galaxies would have been missed by even the deepest Herschel surveys. Our cumulative number counts have been determined independently at 870 μ m and 1.2 mm from a sparse sampling of the astronomical sky, and are thus relatively free of cosmic variance. The counts are lower than reported previously by a factor of at least 2×. Future analyses will yield large, secure samples of DSFGs with redshifts determined via the detection of submm spectral lines. Uniquely, our strategy then allows for morphological studies of very faint DSFGs—representative of more normal star-forming galaxies than conventional submm galaxies—in fields where self-calibration is feasible, yielding milliarcsecond spatial resolution.« less

Submillimeter array observations of NGC 2264-C: molecular outflows and driving sources

NASA Astrophysics Data System (ADS)

Cunningham, Nichol; Lumsden, Stuart L.; Cyganowski, Claudia J.; Maud, Luke T.; Purcell, Cormac

2016-05-01

We present 1.3 mm Submillimeter Array (SMA) observations at ˜3 arcsec resolution towards the brightest section of the intermediate/massive star-forming cluster NGC 2264-C. The millimetre continuum emission reveals ten 1.3 mm continuum peaks, of which four are new detections. The observed frequency range includes the known molecular jet/outflow tracer SiO (5-4), thus providing the first high-resolution observations of SiO towards NGC 2264-C. We also detect molecular lines of 12 additional species towards this region, including CH3CN, CH3OH, SO, H2CO, DCN, HC3N, and 12CO. The SiO (5-4) emission reveals the presence of two collimated, high-velocity (up to 30 km s-1 with respect to the systemic velocity) bipolar outflows in NGC 2264-C. In addition, the outflows are traced by emission from 12CO, SO, H2CO, and CH3OH. We find an evolutionary spread between cores residing in the same parent cloud. The two unambiguous outflows are driven by the brightest mm continuum cores, which are IR-dark, molecular line weak, and likely the youngest cores in the region. Furthermore, towards the Red MSX Source AFGL 989-IRS1, the IR-bright and most evolved source in NGC 2264-C, we observe no molecular outflow emission. A molecular line rich ridge feature, with no obvious directly associated continuum source, lies on the edge of a low-density cavity and may be formed from a wind driven by AFGL 989-IRS1. In addition, 229 GHz class I maser emission is detected towards this feature.

Metrology Arrangement for Measuring the Positions of Mirrors of a Submillimeter Telescope

NASA Technical Reports Server (NTRS)

Abramovici, Alex; Bartman, Randall K.

2011-01-01

The position of the secondary mirror of a submillimeter telescope with respect to the primary mirror needs to be known .0.03 mm in three dimensions. At the time of this reporting, no convenient, reasonably priced arrangement that offers this capability exists. The solution proposed here relies on measurement devices developed and deployed for the GeoSAR mission, and later adapted for the ISAT (Innovative Space Based Radar Antenna Technology) demonstration. The measurement arrangement consists of four metrology heads, located on an optical bench, attached to the secondary mirror. Each metrology head has a dedicated target located at the edge of the primary mirror. One laser beam, launched from the head and returned by the target, is used to measure distance. Another beam, launched from a beacon on the target, is monitored by the metrology head and generates a measurement of the target position in the plane perpendicular to the laser beam. A 100-MHz modulation is carried by a collimated laser beam. The relevant wavelength is the RF one, 3 m, divided by two, because the light carries it to the target and back. The phase change due to travel to the target and back is measured by timing the zero-crossing of the RF modulation, using a 100-MHz clock. In order to obtain good resolution, the 100-MHz modulation signal is down-converted to 1 kHz. Then, the phase change corresponding to the round-trip to the target is carried by a 1-kHz signal. Since the 100-MHz clock beats 100,000 times during one period of the 1-kHz signal, the least-significant-bit (LSB) resolution is LSB = 0.015 mm.

Millimeter radiation from a 3D model of the solar atmosphere. II. Chromospheric magnetic field

NASA Astrophysics Data System (ADS)

Loukitcheva, M.; White, S. M.; Solanki, S. K.; Fleishman, G. D.; Carlsson, M.

2017-05-01

Aims: We use state-of-the-art, three-dimensional non-local thermodynamic equilibrium (non-LTE) radiative magnetohydrodynamic simulations of the quiet solar atmosphere to carry out detailed tests of chromospheric magnetic field diagnostics from free-free radiation at millimeter and submillimeter wavelengths (mm/submm). Methods: The vertical component of the magnetic field was deduced from the mm/submm brightness spectra and the degree of circular polarization synthesized at millimeter frequencies. We used the frequency bands observed by the Atacama Large Millimeter/Submillimeter Array (ALMA) as a convenient reference. The magnetic field maps obtained describe the longitudinal magnetic field at the effective formation heights of the relevant wavelengths in the solar chromosphere. Results: The comparison of the deduced and model chromospheric magnetic fields at the spatial resolution of both the model and current observations demonstrates a good correlation, but has a tendency to underestimate the model field. The systematic discrepancy of about 10% is probably due to averaging of the restored field over the heights contributing to the radiation, weighted by the strength of the contribution. On the whole, the method of probing the longitudinal component of the magnetic field with free-free emission at mm/submm wavelengths is found to be applicable to measurements of the weak quiet-Sun magnetic fields. However, successful exploitation of this technique requires very accurate measurements of the polarization properties (primary beam and receiver polarization response) of the antennas, which will be the principal factor that determines the level to which chromospheric magnetic fields can be measured. Conclusions: Consequently, high-resolution and high-precision observations of circularly polarized radiation at millimeter wavelengths can be a powerful tool for producing chromospheric longitudinal magnetograms.

A Detailed Comparison of Multidimensional Boltzmann Neutrino Transport Methods in Core-collapse Supernovae

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

Richers, Sherwood; Nagakura, Hiroki; Ott, Christian D.

The mechanism driving core-collapse supernovae is sensitive to the interplay between matter and neutrino radiation. However, neutrino radiation transport is very difficult to simulate, and several radiation transport methods of varying levels of approximation are available. We carefully compare for the first time in multiple spatial dimensions the discrete ordinates (DO) code of Nagakura, Yamada, and Sumiyoshi and the Monte Carlo (MC) code Sedonu, under the assumptions of a static fluid background, flat spacetime, elastic scattering, and full special relativity. We find remarkably good agreement in all spectral, angular, and fluid interaction quantities, lending confidence to both methods. The DOmore » method excels in determining the heating and cooling rates in the optically thick region. The MC method predicts sharper angular features due to the effectively infinite angular resolution, but struggles to drive down noise in quantities where subtractive cancellation is prevalent, such as the net gain in the protoneutron star and off-diagonal components of the Eddington tensor. We also find that errors in the angular moments of the distribution functions induced by neglecting velocity dependence are subdominant to those from limited momentum-space resolution. We briefly compare directly computed second angular moments to those predicted by popular algebraic two-moment closures, and we find that the errors from the approximate closures are comparable to the difference between the DO and MC methods. Included in this work is an improved Sedonu code, which now implements a fully special relativistic, time-independent version of the grid-agnostic MC random walk approximation.« less

A Detailed Comparison of Multidimensional Boltzmann Neutrino Transport Methods in Core-collapse Supernovae

DOE PAGES

Richers, Sherwood; Nagakura, Hiroki; Ott, Christian D.; ...

2017-10-03

The mechanism driving core-collapse supernovae is sensitive to the interplay between matter and neutrino radiation. However, neutrino radiation transport is very difficult to simulate, and several radiation transport methods of varying levels of approximation are available. In this paper, we carefully compare for the first time in multiple spatial dimensions the discrete ordinates (DO) code of Nagakura, Yamada, and Sumiyoshi and the Monte Carlo (MC) code Sedonu, under the assumptions of a static fluid background, flat spacetime, elastic scattering, and full special relativity. We find remarkably good agreement in all spectral, angular, and fluid interaction quantities, lending confidence to bothmore » methods. The DO method excels in determining the heating and cooling rates in the optically thick region. The MC method predicts sharper angular features due to the effectively infinite angular resolution, but struggles to drive down noise in quantities where subtractive cancellation is prevalent, such as the net gain in the protoneutron star and off-diagonal components of the Eddington tensor. We also find that errors in the angular moments of the distribution functions induced by neglecting velocity dependence are subdominant to those from limited momentum-space resolution. We briefly compare directly computed second angular moments to those predicted by popular algebraic two-moment closures, and we find that the errors from the approximate closures are comparable to the difference between the DO and MC methods. Finally, included in this work is an improved Sedonu code, which now implements a fully special relativistic, time-independent version of the grid-agnostic MC random walk approximation.« less

A Detailed Comparison of Multidimensional Boltzmann Neutrino Transport Methods in Core-collapse Supernovae

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

Richers, Sherwood; Nagakura, Hiroki; Ott, Christian D.

The mechanism driving core-collapse supernovae is sensitive to the interplay between matter and neutrino radiation. However, neutrino radiation transport is very difficult to simulate, and several radiation transport methods of varying levels of approximation are available. In this paper, we carefully compare for the first time in multiple spatial dimensions the discrete ordinates (DO) code of Nagakura, Yamada, and Sumiyoshi and the Monte Carlo (MC) code Sedonu, under the assumptions of a static fluid background, flat spacetime, elastic scattering, and full special relativity. We find remarkably good agreement in all spectral, angular, and fluid interaction quantities, lending confidence to bothmore » methods. The DO method excels in determining the heating and cooling rates in the optically thick region. The MC method predicts sharper angular features due to the effectively infinite angular resolution, but struggles to drive down noise in quantities where subtractive cancellation is prevalent, such as the net gain in the protoneutron star and off-diagonal components of the Eddington tensor. We also find that errors in the angular moments of the distribution functions induced by neglecting velocity dependence are subdominant to those from limited momentum-space resolution. We briefly compare directly computed second angular moments to those predicted by popular algebraic two-moment closures, and we find that the errors from the approximate closures are comparable to the difference between the DO and MC methods. Finally, included in this work is an improved Sedonu code, which now implements a fully special relativistic, time-independent version of the grid-agnostic MC random walk approximation.« less

A POD reduced order model for resolving angular direction in neutron/photon transport problems

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

Buchan, A.G., E-mail: andrew.buchan@imperial.ac.uk; Calloo, A.A.; Goffin, M.G.

2015-09-01

This article presents the first Reduced Order Model (ROM) that efficiently resolves the angular dimension of the time independent, mono-energetic Boltzmann Transport Equation (BTE). It is based on Proper Orthogonal Decomposition (POD) and uses the method of snapshots to form optimal basis functions for resolving the direction of particle travel in neutron/photon transport problems. A unique element of this work is that the snapshots are formed from the vector of angular coefficients relating to a high resolution expansion of the BTE's angular dimension. In addition, the individual snapshots are not recorded through time, as in standard POD, but instead theymore » are recorded through space. In essence this work swaps the roles of the dimensions space and time in standard POD methods, with angle and space respectively. It is shown here how the POD model can be formed from the POD basis functions in a highly efficient manner. The model is then applied to two radiation problems; one involving the transport of radiation through a shield and the other through an infinite array of pins. Both problems are selected for their complex angular flux solutions in order to provide an appropriate demonstration of the model's capabilities. It is shown that the POD model can resolve these fluxes efficiently and accurately. In comparison to high resolution models this POD model can reduce the size of a problem by up to two orders of magnitude without compromising accuracy. Solving times are also reduced by similar factors.« less

A Detailed Comparison of Multidimensional Boltzmann Neutrino Transport Methods in Core-collapse Supernovae

NASA Astrophysics Data System (ADS)

Richers, Sherwood; Nagakura, Hiroki; Ott, Christian D.; Dolence, Joshua; Sumiyoshi, Kohsuke; Yamada, Shoichi

2017-10-01

The mechanism driving core-collapse supernovae is sensitive to the interplay between matter and neutrino radiation. However, neutrino radiation transport is very difficult to simulate, and several radiation transport methods of varying levels of approximation are available. We carefully compare for the first time in multiple spatial dimensions the discrete ordinates (DO) code of Nagakura, Yamada, and Sumiyoshi and the Monte Carlo (MC) code Sedonu, under the assumptions of a static fluid background, flat spacetime, elastic scattering, and full special relativity. We find remarkably good agreement in all spectral, angular, and fluid interaction quantities, lending confidence to both methods. The DO method excels in determining the heating and cooling rates in the optically thick region. The MC method predicts sharper angular features due to the effectively infinite angular resolution, but struggles to drive down noise in quantities where subtractive cancellation is prevalent, such as the net gain in the protoneutron star and off-diagonal components of the Eddington tensor. We also find that errors in the angular moments of the distribution functions induced by neglecting velocity dependence are subdominant to those from limited momentum-space resolution. We briefly compare directly computed second angular moments to those predicted by popular algebraic two-moment closures, and we find that the errors from the approximate closures are comparable to the difference between the DO and MC methods. Included in this work is an improved Sedonu code, which now implements a fully special relativistic, time-independent version of the grid-agnostic MC random walk approximation.

Control of Rotational Energy and Angular Momentum Orientation with an Optical Centrifuge

NASA Astrophysics Data System (ADS)

Ogden, Hannah M.; Murray, Matthew J.; Mullin, Amy S.

2017-04-01

We use an optical centrifuge to trap and spin molecules to an angular frequency of 30 THz with oriented angular momenta and extremely high rotational energy and then investigate their subsequent collision dynamics with transient high resolution IR spectroscopy. The optical centrifuge is formed by combining oppositely-chirped pulses of 800 nm light, and overlapping them spatially and temporally. Polarization-sensitive Doppler-broadened line profiles characterize the anisotropic kinetic energy release of the super rotor molecules, showing that they behave like molecular gyroscopes. Studies are reported for collisions of CO2 super rotors with CO2, He and Ar. These studies reveal how mass, velocity and rotational adiabaticity impact the angular momentum relaxation and reorientation. Quantum scattering calculations provide insight into the J-specific collision cross sections that control the relaxation. NSF-CHE 105 8721.

IRC +10 216 in 3D: morphology of a TP-AGB star envelope

NASA Astrophysics Data System (ADS)

Guélin, M.; Patel, N. A.; Bremer, M.; Cernicharo, J.; Castro-Carrizo, A.; Pety, J.; Fonfría, J. P.; Agúndez, M.; Santander-García, M.; Quintana-Lacaci, G.; Velilla Prieto, L.; Blundell, R.; Thaddeus, P.

2018-02-01

During their late pulsating phase, AGB stars expel most of their mass in the form of massive dusty envelopes, an event that largely controls the composition of interstellar matter. The envelopes, however, are distant and opaque to visible and NIR radiation: their structure remains poorly known and the mass-loss process poorly understood. Millimeter-wave interferometry, which combines the advantages of longer wavelength, high angular resolution and very high spectral resolution is the optimal investigative tool for this purpose. Mm waves pass through dust with almost no attenuation. Their spectrum is rich in molecular lines and hosts the fundamental lines of the ubiquitous CO molecule, allowing a tomographic reconstruction of the envelope structure. The circumstellar envelope IRC +10 216 and its central star, the C-rich TP-AGB star closest to the Sun, are the best objects for such an investigation. Two years ago, we reported the first detailed study of the CO(2-1) line emission in that envelope, made with the IRAM 30-m telescope. It revealed a series of dense gas shells, expanding at a uniform radial velocity. The limited resolution of the telescope (HPBW 11″) did not allow us to resolve the shell structure. We now report much higher angular resolution observations of CO(2-1), CO(1-0), CN(2-1) and C4H(24-23) made with the SMA, PdB and ALMA interferometers (with synthesized half-power beamwidths of 3″, 1″ and 0.3″, respectively). Although the envelope appears much more intricate at high resolution than with an 11″ beam, its prevailing structure remains a pattern of thin, nearly concentric shells. The average separation between the brightest CO shells is 16″ in the outer envelope, where it appears remarkably constant. Closer to the star (<40″), the shell pattern is denser and less regular, showing intermediary arcs. Outside the small (r< 0.3'') dust formation zone, the gas appears to expand radially at a constant velocity, 14.5 km s-1, with small turbulent motions. Based on that property, we have reconstructed the 3D structure of the outer envelope and have derived the gas temperature and density radial profiles in the inner (r< 25'') envelope. The shell-intershell density contrast is found to be typically 3. The over-dense shells have spherical or slightly oblate shapes and typically extend over a few steradians, implying isotropic mass loss. The regular spacing of shells in the outer envelope supports the model of a binary star system with a period of 700 yr and a near face-on elliptical orbit. The companion fly-by triggers enhanced episodes of mass loss near periastron. The densification of the shell pattern observed in the central part of the envelope suggests a more complex scenario for the last few thousand years. This work was based on observations carried out with the IRAM, SMA and ALMA telescopes. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory (USA) and the Academia Sinica Institute of Astronomy and Astrophysics (Taiwan) and is funded by the Smithsonian Institution and the Academia Sinica. This paper makes use of the ALMA data: ADS/JAO.ALMA#2013.1.01215.S & ADS/JAO.ALMA#2013.1.00432.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan) and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.

Submillimeter Spectroscopy with a 500-1000 GHz SIS Receiver

NASA Technical Reports Server (NTRS)

Zmuidzinas, J.

1997-01-01

Sub-millimeter Spectroscopy with a 500-1000 GHz SIS Receiver, which extended over the period October 1, 1991 through January 31, 1997. The purpose of the grant was to fund the development and construction of a sensitive heterodyne receiver system for the submillimeter band (500-1000 GHz), using our newly-developed sensitive superconducting (SIS) detectors, and to carry out astronomical observations with this system aboard the NASA Kuiper Air- borne Observatory (a Lockheed C-141 aircraft carrying a 91 cm telescope). A secondary purpose of the grant was to stimulate the continued development of sensitive submillimeter detectors, in order to prepare for the next-generation airborne observatory, SOFIA, as well as future space missions (such as the ESA/NASA FIRST mission).

Digging deep into the ULIRG phenomenon: When radio beats dust

NASA Astrophysics Data System (ADS)

Pérez-Torres, M. A.

2013-05-01

Luminous and Ultra-Luminous Infrared Galaxies (U/LIRGs) do also radiate copious amounts of radio emission, both thermal (free-free) and non-thermal (mainly synchrotron). This is very handy since, unlike optical and infra-red observations, radio is not obscured by the ubiquitous dust present in U/LIRGs, which allows a direct view of the ongoing activity in the hearts of those prolific star-forming galaxies. Here, I first justify the need for this high-angular resolution radio studies of local U/LIRGs, discuss the energy budget and the magnetic field, as well as IC and synchrotron losses in U/LIRGs, and present some selected results obtained by our team on high-angular resolution radio continuum studies of U/LIRGs. Among other results, I show the impressive discovery of an extremely prolific supernova factory in the central ˜150 pc of the galaxy Arp 299-A (D = 45 Mpc) and the monitoring of a large number of very compact radio sources in it, the detection and precise location of the long-sought AGN in Arp 299-A. A movie summarizing those results can be found in http://www.iaa.es/ torres/research/arp299a.html. All those results demonstrate that very-high angular resolution studies of nearby U/LIRGs are of high relevance for the comprehension of both local and high-z starbursting galaxies.

The Advanced Energetic Pair Telescope (AdEPT}: A Future Medium-Energy Gamma-Ray Balloon (and Explorer?) Mission

NASA Technical Reports Server (NTRS)

Hunter, Stanley D.

2011-01-01

Gamma-ray astrophysics probes the highest energy, exotic phenomena in astrophysics. In the medium-energy regime, 0.1-200 MeV, many astrophysical objects exhibit unique and transitory behavior such as the transition from electron dominated to hadron dominated processes, spectral breaks, bursts, and flares. Medium-energy gamma-ray imaging however, continues to be a major challenge particularly because of high background, low effective area, and low source intensities. The sensitivity and angular resolution required to address these challenges requires a leap in technology. The Advance Energetic Pair Telescope (AdEPT) being developed at GSFC is designed to image gamma rays above 5 MeV via pair production with angular resolution of 1-10 deg. In addition AdEPT will, for the first time, provide high polarization sensitivity in this energy range. This performance is achieved by reducing the effective area in favor of enhanced angular resolution through the use of a low-density gaseous conversion medium. AdEPT is based on the Three-Dimensional Track Imager (3-DTI) technology that combines a large volume Negative Ion Time Projection Chamber (NITPC) with 2-D Micro-Well Detector (MWD) readout. I will review the major science topics addressable with medium-energy gamma-rays and discuss the current status of the AdEPT technology, a proposed balloon instrument, and the design of a future satellite mission.

Linear Transforms for Fourier Data on the Sphere: Application to High Angular Resolution Diffusion MRI of the Brain

PubMed Central

Haldar, Justin P.; Leahy, Richard M.

2013-01-01

This paper presents a novel family of linear transforms that can be applied to data collected from the surface of a 2-sphere in three-dimensional Fourier space. This family of transforms generalizes the previously-proposed Funk-Radon Transform (FRT), which was originally developed for estimating the orientations of white matter fibers in the central nervous system from diffusion magnetic resonance imaging data. The new family of transforms is characterized theoretically, and efficient numerical implementations of the transforms are presented for the case when the measured data is represented in a basis of spherical harmonics. After these general discussions, attention is focused on a particular new transform from this family that we name the Funk-Radon and Cosine Transform (FRACT). Based on theoretical arguments, it is expected that FRACT-based analysis should yield significantly better orientation information (e.g., improved accuracy and higher angular resolution) than FRT-based analysis, while maintaining the strong characterizability and computational efficiency of the FRT. Simulations are used to confirm these theoretical characteristics, and the practical significance of the proposed approach is illustrated with real diffusion weighted MRI brain data. These experiments demonstrate that, in addition to having strong theoretical characteristics, the proposed approach can outperform existing state-of-the-art orientation estimation methods with respect to measures such as angular resolution and robustness to noise and modeling errors. PMID:23353603

Development of the Advanced Energetic Pair Telescope (AdEPT) for Medium-Energy Gamma-Ray Astronomy

NASA Technical Reports Server (NTRS)

Hunter, Stanley D.; Bloser, Peter F.; Dion, Michael P.; McConnell, Mark L.; deNolfo, Georgia A.; Son, Seunghee; Ryan, James M.; Stecker, Floyd W.

2011-01-01

Progress in high-energy gamma-ray science has been dramatic since the launch of INTEGRAL, AGILE and FERMI. These instruments, however, are not optimized for observations in the medium-energy (approx.0.3< E(sub gamma)< approx.200 MeV) regime where many astrophysical objects exhibit unique, transitory behavior, such as spectral breaks, bursts, and flares. We outline some of the major science goals of a medium-energy mission. These science goals are best achieved with a combination of two telescopes, a Compton telescope and a pair telescope, optimized to provide significant improvements in angular resolution and sensitivity. In this paper we describe the design of the Advanced Energetic Pair Telescope (AdEPT) based on the Three-Dimensional Track Imager (3-DTI) detector. This technology achieves excellent, medium-energy sensitivity, angular resolution near the kinematic limit, and gamma-ray polarization sensitivity, by high resolution 3-D electron tracking. We describe the performance of a 30x30x30 cm3 prototype of the AdEPT instrument.

"Phoswich Wall": A charged-particle detector array for inverse-kinematic reactions with the Gretina/GRETA γ-ray arrays

NASA Astrophysics Data System (ADS)

Sarantites, D. G.; Reviol, W.; Elson, J. M.; Kinnison, J. E.; Izzo, C. J.; Manfredi, J.; Liu, J.; Jung, H. S.; Goerres, J.

2015-08-01

A high-efficiency, forward-hemisphere detector system for light charged particles and low-Z heavy ions, as obtained in an accelerator experiment, is described. It consists of four 8×8 pixel multianode photomultiplier tubes with 2.2-mm thick CsI(Tl) and 12 -μm thick fast-plastic scintillation detectors. Its phoswich structure allows individual Z resolution for 1H, 4He, 7Li, 4He+4He, 9Be, 11B, 12C, and 14N ions, which are target-like fragments detected in strongly inverse kinematics. The device design has been optimized for use with a 4π γ-ray array, and the main applications are transfer reactions and Coulomb excitation. A high-angular resolution for the detection of the target-like fragments is achieved which permits angular distributions to be measured in the rest frame of the projectile-like fragment with a resolution of ~ 2 °.

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

Zhang, Aiwu; Hohlmann, Marcus; Azmoun, Babak

Here, we study the position sensitivity of radial zigzag strips intended to read out large GEM detectors for tracking at future experiments. Zigzag strips can cover a readout area with fewer strips than regular straight strips while maintaining good spatial resolution. Consequently, they can reduce the number of required electronic channels and related cost for large-area GEM detector systems. A non-linear relation between incident particle position and hit position measured from charge sharing among zigzag strips was observed in a previous study. We significantly reduce this non-linearity by improving the interleaving of adjacent physical zigzag strips. Zigzag readout structures aremore » implemented on PCBs and on a flexible foil and are tested using a 10 cm × 10 cm triple-GEM detector scanned with a strongly collimated X-ray gun on a 2D motorized stage. Lastly, angular resolutions of 60–84 μrad are achieved with a 1.37 mrad angular strip pitch at a radius of 784 mm. On a linear scale this corresponds to resolutions below 100 μm.« less

LASER BIOLOGY AND MEDICINE: Optoacoustic laser monitoring of cooling and freezing of tissues

NASA Astrophysics Data System (ADS)

Larin, Kirill V.; Larina, I. V.; Motamedi, M.; Esenaliev, R. O.

2002-11-01

Real-time monitoring of cooling and freezing of tissues, cells, and other biological objects with a high spatial and time resolution, which is necessary for selective destruction of cancer and benign tumours during cryotherapy, as well as for preventing any damage to the structure and functioning of biological objects in cryobiology, is considered. The optoacoustic method, based on the measurement and analysis of acoustic waves induced by short laser pulses, is proposed for monitoring the cooling and freezing of the tissue. The effect of cooling and freezing on the amplitude and time profile of acoustic signals generated in real tissues and in a model object is studied. The experimental results indicate that the optoacoustic laser technique can be used for real-time monitoring of cooling and freezing of biological objects with a submillimeter spatial resolution and a high contrast.

Neutron Imaging Reveals Internal Plant Hydraulic Dynamics

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

Warren, Jeffrey; Bilheux, Hassina Z; Kang, Misun

2013-01-01

Many terrestrial ecosystem processes are constrained by water availability and transport within the soil. Knowledge of plant water fluxes is thus critical for assessing mechanistic processes linked to biogeochemical cycles, yet resolution of root structure and xylem water transport dynamics has been a particularly daunting task for the ecologist. Through neutron imaging, we demonstrate the ability to non-invasively monitor individual root functionality and water fluxes within Zea mays L. (maize) and Panicum virgatum L. (switchgrass) seedlings growing in a sandy medium. Root structure and growth were readily imaged by neutron radiography and neutron computed tomography. Seedlings were irrigated with watermore » or deuterium oxide and imaged through time as a growth lamp was cycled on to alter leaf demand for water. Sub-millimeter scale resolution reveals timing and magnitudes of root water uptake, redistribution within the roots, and root-shoot hydraulic linkages, relationships not well characterized by other techniques.« less

The Atacama Large Millimeter/submillimeter Array (alma): Early Results

NASA Astrophysics Data System (ADS)

Wootten, Alwyn

2012-06-01

New radioastronomical instruments, such as ALMA or the Jansky VLA, have increased spectral throughput by orders of magnitude over previously available capabilities. ALMA brings orders of magnitude increases in spectral sensitivity and spatial resolution over what has previously been available. These increased capabilities open new possibilities for studies of complex molecules in the interstellar medium. Complex interstellar molecules may form on the surfaces of interstellar grains, after which they may be liberated into the gas phase by shocks, radiation, or other external influences. Emission from complex molecules may be diluted owing to the large number of transitions large molecules may undergo, particularly in warm regions of interstellar clouds. High sensitivity and spatial resolution are necessary to explore the distributions and relationships of these molecules. Of particular interest are the distributions of large organic molecules. Observations which establish the relationships between various large molecules are now emerging from these new instruments and will be discussed.

Modelling high-resolution ALMA observations of strongly lensed highly star-forming galaxies detected by Herschel

NASA Astrophysics Data System (ADS)

Dye, S.; Furlanetto, C.; Dunne, L.; Eales, S. A.; Negrello, M.; Nayyeri, H.; van der Werf, P. P.; Serjeant, S.; Farrah, D.; Michałowski, M. J.; Baes, M.; Marchetti, L.; Cooray, A.; Riechers, D. A.; Amvrosiadis, A.

2018-06-01

We have modelled ˜0.1 arcsec resolution Atacama Large Millimetre/submillimeter Array imaging of six strong gravitationally lensed galaxies detected by the Herschel Space Observatory. Our modelling recovers mass properties of the lensing galaxies and, by determining magnification factors, intrinsic properties of the lensed submillimetre sources. We find that the lensed galaxies all have high ratios of star formation rate to dust mass, consistent with or higher than the mean ratio for high-redshift submillimetre galaxies and low-redshift ultra-luminous infrared galaxies. Source reconstruction reveals that most galaxies exhibit disturbed morphologies. Both the cleaned image plane data and the directly observed interferometric visibilities have been modelled, enabling comparison of both approaches. In the majority of cases, the recovered lens models are consistent between methods, all six having mass density profiles that are close to isothermal. However, one system with poor signal to noise shows mildly significant differences.

Coherence Volume of an Optical Wave Field with Broad Frequency and Angular Spectra

NASA Astrophysics Data System (ADS)

Lyakin, D. V.; Mysina, N. Yu.; Ryabukho, V. P.

2018-03-01

We consider the sizes of a region in a three-dimensional space in which an optical wave field excites mutually coherent perturbations. We discuss the conditions under which the length of this region along the direction of propagation of the wave field and, correspondingly, its volume are determined either by the width of the frequency spectrum of the field or by the width of its angular spectrum, or by the parameters of these spectra simultaneously. We obtain expressions for estimating extremely small values of the coherence volume of the fields with a broad frequency spectrum and an extremely broad angular spectrum. Using the notion of instantaneous speckle-modulation of the wave field, we give a physical interpretation to the occurrence of a limited coherence volume of the field. The length of the spatiotemporal coherence region in which mutually coherent perturbations occur at different times is determined. The coherence volume of a wave field that illuminates an object in high-resolution microscopy with frequency broadband light is considered. The conditions for the dominant influence of the angular or frequency spectra on the longitudinal length of the coherence region are given, and the conditions for the influence of the frequency spectrum width on the transverse coherence of the wave field are examined. We show that, when using fields with broad and ultrabroad spectra in high-resolution microscopy, this influence should be taken into account.

Magnetic effects in the paraxial regime of elastic electron scattering

NASA Astrophysics Data System (ADS)

Edström, Alexander; Lubk, Axel; Rusz, Ján

2016-11-01

Motivated by a recent claim [Phys. Rev. Lett. 116, 127203 (2016), 10.1103/PhysRevLett.116.127203] that electron vortex beams can be used to image magnetism at the nanoscale in elastic scattering experiments, using transmission electron microscopy, a comprehensive computational study is performed to study magnetic effects in the paraxial regime of elastic electron scattering in magnetic solids. Magnetic interactions from electron vortex beams, spin polarized electron beams, and beams with phase aberrations are considered, as they pass through ferromagnetic FePt or antiferromagnetic LaMnAsO. The magnetic signals are obtained by comparing the intensity over a disk in the diffraction plane for beams with opposite angular momentum or aberrations. The strongest magnetic signals are obtained from vortex beams with large orbital angular momentum, where relative magnetic signals above 10-3 are indicated for 10 ℏ orbital angular momentum, meaning that relative signals of one percent could be expected with the even larger orbital angular momenta, which have been produced in experimental setups. All results indicate that beams with low acceleration voltage and small convergence angles yield stronger magnetic signals, which is unfortunately problematic for the possibility of high spatial resolution imaging. Nevertheless, under atomic resolution conditions, relative magnetic signals in the order of 10-4 are demonstrated, corresponding to an increase with one order of magnitude compared to previous work.

Far Infrared All-Sky Survey

NASA Technical Reports Server (NTRS)

Richards, Paul L.

1998-01-01

Precise measurements of the angular power spectrum of the Cosmic Microwave Background (CMB) anisotropy will revolutionize cosmology. These measurements will discriminate between competing cosmological models and, if the standard inflationary scenario is correct, will determine each of the fundamental cosmological parameters with high precision. The astrophysics community has recognized this potential: the orbital experiments MAP and PLANCK, have been approved to measure CMB anisotropy. Balloon-borne experiments can realize much of this potential before these missions are launched. Additionally, properly designed balloon-borne experiments can complement MAP in frequency and angular resolution and can give the first realistic test of the instrumentation proposed for the high frequency instrument on PLANCK. The MAXIMA experiment is part of the MAXIMA/BOOMERANG collaboration which is doing balloon observations of the angular power spectrum of the Cosmic Microwave Background from l = 10 to l = 800. These experiments are designed to use the benefits of both North American and Antarctic long-duration ballooning to full advantage. We have developed several new technologies that together allow the power spectrum to be measured with unprecedented combination of angular resolution, beam throw, sensitivity, sky coverage and control of systematic effects. These technologies are the basis for the high frequency instrument for the PLANCK mission. Our measurements will strongly discriminate between models of the origin and evolution of structure in the universe and, for many models, will determine the value of the basic cosmological parameters to high precision.

A simple antireflection overcoat for opaque coatings in the submillimeter region

NASA Technical Reports Server (NTRS)

Smith, S. M.

1986-01-01

An antireflection overcoat for opaque baffle coatings in the far infrared (FIR)/submillimeter region was made from a simple Teflon spray-on lubricant. The Teflon overcoat reduced the specular reflectance of four different opaque coatings by nearly a factor of two. Analysis, based on the interference term of a reflecting-layer model, indicates that in the submillimeter region the reduced reflectance depends primarily on the refractive index of the overcoat and very little on its thickness.

Optics Requirements For The Generation-X X-Ray Telescope

NASA Technical Reports Server (NTRS)

O'Dell, S. .; Elsner, R. F.; Kolodziejczak, J. J.; Ramsey, B. D.; Weisskopf, M. C.; Zhang, W. W.; Content, D. A.; Petre, R.; Saha, T. T.; Reid, P. B.;

Marine algae are `taught' the basics of angular momentum

NASA Astrophysics Data System (ADS)

Allen, John Taylor

2017-11-01

Advanced modelling studies and high-resolution observations have shown that flows related to instability of the mesoscale ( 1-10 km scale) may provide both the fertilisation mechanism for nutrient-depleted (oligotrophic) surface waters and a subduction mechanism for the rapid export of phytoplankton biomass to the deep ocean. Here, a detailed multidisciplinary analysis of the data from an example high-resolution observational campaign is presented. The data provide direct observations of the transport of phytoplankton through baroclinic instability. Furthermore, the data confirm that this transport is constrained by the requirement to conserve angular momentum, expressed in a stratified water column as the conservation of potential vorticity. This constraint is clearly seen to produce long thin filaments of phytoplankton populations strained out along isopycnal vorticity annuli associated with mesoscale frontal instabilities.

Internal reflection sensors with high angular resolution

NASA Astrophysics Data System (ADS)

Shavirin, I.; Strelkov, O.; Vetskous, A.; Norton-Wayne, L.; Harwood, R.

1996-07-01

We discuss the use of total internal reflection for the production of sensors with high angular resolution. These sensors are intended for measurement of the angle between a sensor's axis and the direction to a source of radiation or reflecting object. Sensors of this type are used in controlling the position of machine parts in robotics and industry, orienting space vehicles and astronomic devices in relation to the Sun, and as autocollimators for checking angles of deviation. This kind of sensor was used in the Apollo space vehicle some 20 years ago. Using photodetectors with linear and area CCD arrays has opened up new application possibilities for appropriately designed sensors. A generalized methodology is presented applicable to a wide range of tasks. Some modifications that can improve the performance of the basic design are described.

Olivier Chesneau's Work on Low Mass Stars

NASA Astrophysics Data System (ADS)

Lagadec, E.

2015-12-01

During his too short career, Olivier Chesneau pioneered the study of the circumstellar environments of low mass evolved stars using very high angular resolution techniques. He applied state of the art high angular resolution techniques, such as optical interferometry and adaptive optics imaging, to the the study of a variety of objects, from AGB stars to Planetary Nebulae, via e.g. Born Again stars, RCB stars and Novae. I present here an overview of this work and most important results by focusing on the paths he followed and key encounters he made to reach these results. Olivier liked to work in teams and was very strong at linking people with complementary expertises to whom he would communicate his enthusiasm and sharp ideas. His legacy will live on through the many people he inspired.

Poster 8: ALMA observations of Titan : Vertical and spatial distributions of nitriles

NASA Astrophysics Data System (ADS)

Moreno, Raphael; Lellouch, Emmanuel; Vinatier, Sandrine; Gurwell, Mark; Moullet, Arielle; Lara, Luisa; Hidayat, Taufiq

2016-06-01

We report submm observations of Titan performed with the ALMA interferometer centered at the rotational frequencies of HCN(4-3) and HNC(4-3), i.e. 354 and 362 GHz. These measurements yielded disk-resolved emission spectra of Titan with an angular resolution of ˜0.47". Titan's angular surface diameter was 0.77". Data were acquired in summer 2012 near the greatest eastern and western elongations of Titan at a spectral resolution of 122 kHz (λ/dλ = 3106). We will present radiative transfer analysis of the acquired spectra. With the combination of all the detected rotational lines, we will constrain the atmospheric temperature, the spatial and vertical distribution HCN, HC3N, CH3CN, HNC, C2H5CN, as well as isotopic ratios.

MESAS: Measuring the Emission of Stellar Atmospheres at Submillimeter/millimeter Wavelengths

NASA Astrophysics Data System (ADS)

White, Jacob Aaron; Aufdenberg, Jason; Boley, A. C.; Hauschildt, Peter; Hughes, Meredith; Matthews, Brenda; Wilner, David

2018-06-01

In the early stages of planet formation, small dust grains grow to become millimeter-sized particles in debris disks around stars. These disks can in principle be characterized by their emission at submillimeter and millimeter wavelengths. Determining both the occurrence and abundance of debris in unresolved circumstellar disks of A-type main-sequence stars requires that the stellar photospheric emission be accurately modeled. To better constrain the photospheric emission for such systems, we present observations of Sirius A, an A-type star with no known debris, from the James Clerk Maxwell Telescope, Submillimeter Array, and Jansky Very Large Array at 0.45, 0.85, 0.88, 1.3, 6.7, and 9.0 mm. We use these observations to inform a PHOENIX model of Sirius A’s atmosphere. We find the model provides a good match to these data and can be used as a template for the submillimeter/millimeter emission of other early A-type stars where unresolved debris may be present. The observations are part of an ongoing observational campaign entitled Measuring the Emission of Stellar Atmospheres at Submillimeter/millimeter wavelengths.

High-resolution maps of real and illusory tactile activation in primary somatosensory cortex in individual monkeys with functional magnetic resonance imaging and optical imaging.

PubMed

Chen, Li M; Turner, Gregory H; Friedman, Robert M; Zhang, Na; Gore, John C; Roe, Anna W; Avison, Malcolm J

2007-08-22

Although blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) has been widely used to explore human brain function, questions remain regarding the ultimate spatial resolution of positive BOLD fMRI, and indeed the extent to which functional maps revealed by positive BOLD correlate spatially with maps obtained with other high-spatial-resolution mapping techniques commonly used in animals, such as optical imaging of intrinsic signal (OIS) and single-unit electrophysiology. Here, we demonstrate that the positive BOLD signal at 9.4T can reveal the fine topography of individual fingerpads in single-condition activation maps in nonhuman primates. These digit maps are similar to maps obtained from the same animal using intrinsic optical imaging. Furthermore, BOLD fMRI reliably resolved submillimeter spatial shifts in activation in area 3b previously identified with OIS (Chen et al., 2003) as neural correlates of the "funneling illusion." These data demonstrate that at high field, high-spatial-resolution topographic maps can be achieved using the positive BOLD signal, weakening previous notions regarding the spatial specificity of the positive BOLD signal.

Analysis strategies for high-resolution UHF-fMRI data.

PubMed

Polimeni, Jonathan R; Renvall, Ville; Zaretskaya, Natalia; Fischl, Bruce

2018-03-01

Functional MRI (fMRI) benefits from both increased sensitivity and specificity with increasing magnetic field strength, making it a key application for Ultra-High Field (UHF) MRI scanners. Most UHF-fMRI studies utilize the dramatic increases in sensitivity and specificity to acquire high-resolution data reaching sub-millimeter scales, which enable new classes of experiments to probe the functional organization of the human brain. This review article surveys advanced data analysis strategies developed for high-resolution fMRI at UHF. These include strategies designed to mitigate distortion and artifacts associated with higher fields in ways that attempt to preserve spatial resolution of the fMRI data, as well as recently introduced analysis techniques that are enabled by these extremely high-resolution data. Particular focus is placed on anatomically-informed analyses, including cortical surface-based analysis, which are powerful techniques that can guide each step of the analysis from preprocessing to statistical analysis to interpretation and visualization. New intracortical analysis techniques for laminar and columnar fMRI are also reviewed and discussed. Prospects for single-subject individualized analyses are also presented and discussed. Altogether, there are both specific challenges and opportunities presented by UHF-fMRI, and the use of proper analysis strategies can help these valuable data reach their full potential. Copyright © 2017 Elsevier Inc. All rights reserved.

Performance Evaluation of 98 CZT Sensors for Their Use in Gamma-Ray Imaging

NASA Astrophysics Data System (ADS)

Dedek, Nicolas; Speller, Robert D.; Spendley, Paul; Horrocks, Julie A.

2008-10-01

98 SPEAR sensors from eV Products have been evaluated for their use in a portable Compton camera. The sensors have a 5 mm times 5 mm times 5 mm CdZnTe crystal and are provided together with a preamplifier. The energy resolution was studied in detail for all sensors and was found to be 6% on average at 59.5 keV and 3% on average at 662 keV. The standard deviations of the corresponding energy resolution distributions are remarkably small (0.6% at 59.5 keV, 0.7% at 662 keV) and reflect the uniformity of the sensor characteristics. For a possible outside use the temperature dependence of the sensor performances was investigated for temperatures between 15 and 45 deg Celsius. A linear shift in calibration with temperature was observed. The energy resolution at low energies (81 keV) was found to deteriorate exponentially with temperature, while it stayed constant at higher energies (356 keV). A Compton camera built of these sensors was simulated. To obtain realistic energy spectra a suitable detector response function was implemented. To investigate the angular resolution of the camera a 137Cs point source was simulated. Reconstructed images of the point source were compared for perfect and realistic energy and position resolutions. The angular resolution of the camera was found to be better than 10 deg.

MEMS SoC: observer-based coplanar gyro-free inertial measurement unit

NASA Astrophysics Data System (ADS)

Chen, Tsung-Lin; Park, Sungsu

2005-09-01

This paper presents a novel design of a coplanar gyro-free inertial measurement unit (IMU) that consists of seven to nine single-axis linear accelerometers, and it can be utilized to perform the six DOF measurements for an object in motion. Unlike other gyro-fee IMUs, this design uses redundant accelerometers and state estimation techniques to facilitate the in situ and mass fabrication for the employed accelerometers. The alignment error from positioning accelerometers onto a measurement unit and the fabrication cost of an IMU can greatly be reduced. The outputs of the proposed design are three linear accelerations and three angular velocities. As compared to other gyro-free IMUs, the proposed design uses less integral operation and thus improves its sensing resolution and drifting problem. The sensing resolution of a gyro-free IMU depends on the sensing resolution of the employed accelerometers as well as the size of the measurement unit. Simulation results indicate that the sensing resolution of the proposed design is 2° s-1 for the angular velocity and 10 μg for the linear acceleration when nine single-axis accelerometers, each with 10 μg sensing resolution, are deployed on a 4 inch diameter disc. Also, thanks to the iterative EKF algorithm, the angle estimation error is within 10-3 deg at 2 s.

Submillimeter flux as a probe of molecular ISM mass in high-z galaxies

NASA Astrophysics Data System (ADS)

Liang, Lichen; Feldmann, Robert; Faucher-Giguère, Claude-André; Kereš, Dušan; Hopkins, Philip F.; Hayward, Christopher C.; Quataert, Eliot; Scoville, Nick Z.

2018-04-01

Recent long wavelength observations on the thermal dust continuum suggest that the Rayleigh-Jeans (RJ) tail can be used as a time-efficient quantitative probe of the dust and ISM mass in high-z galaxies. We use high-resolution cosmological simulations from the Feedback in Realistic Environment (FIRE) project to analyze the dust emission of M* ≳ 1010M⊙ galaxies at z = 2 - 4. Our simulations (MassiveFIRE) explicitly include various forms of stellar feedback, and they produce the stellar masses and star formation rates of high-z galaxies in agreement with observations. Using radiative transfer modelling, we show that sub-millimeter (sub-mm) luminosity and molecular ISM mass are tightly correlated and that the overall normalization is in quantitative agreement with observations. Notably, sub-mm luminosity traces molecular ISM mass even during starburst episodes as dust mass and mass-weighted temperature evolve only moderately between z = 4 and z = 2, including during starbursts. Our finding supports the empirical approach of using broadband sub-mm flux as a proxy for molecular gas content in high-z galaxies. We thus expect single-band sub-mm observations with ALMA to dramatically increase the sample size of high-z galaxies with reliable ISM masses in the near future.

Seasonal Variations in the CO Line Profile and the Retrieved Thermal/Pressure Structures in the Atmosphere of Mars

NASA Astrophysics Data System (ADS)

Khayat, Alain; Villanueva, G. L.; Mumma, M. J.; Riesen, T. E.; Tokunaga, A. T.

2013-10-01

We report retrievals of temperature vertical profiles up to 100 km over Tharsis and Syrtis regions on Mars obtained by inverting the strong rotational (3-2) line of carbon monoxide (CO) at 346 GHz. Observations of CO were made from mid Northern Spring to early Northern Summer on Mars (Ls= 36°-108°, 23 Nov, 2011 - 13 May, 2012) using the Caltech Submillimeter Observatory's (CSO) high-resolution heterodyne receiver (Barney) on top of Mauna Kea, Hawai'i. The temperature profiles were derived using our radiative transfer model that considers the latest spectroscopic constants for CO collisionally broadened by CO2. We observe notable changes of the line profile for different dates, which are directly related to seasonal variations in the thermal/pressure structure of the atmosphere. The seasonal variability of the martian CO line profile, the extracted temperature profiles, and comparisons with modeled profiles from the Mars Climate Database (Lewis et al, 1999) will be presented. We gratefully acknowledge support from the NASA Planetary Astronomy Program , NASA Astrobiology Institute, Planetary Atmospheres programs. This material is based upon work at the Caltech Submillimeter Observatory, which is operated by the California Institute of Technology under cooperative agreement with the National Science Foundation, grant number AST-0838261.

Elemental mapping of large samples by external ion beam analysis with sub-millimeter resolution and its applications

NASA Astrophysics Data System (ADS)

Silva, T. F.; Rodrigues, C. L.; Added, N.; Rizzutto, M. A.; Tabacniks, M. H.; Mangiarotti, A.; Curado, J. F.; Aguirre, F. R.; Aguero, N. F.; Allegro, P. R. P.; Campos, P. H. O. V.; Restrepo, J. M.; Trindade, G. F.; Antonio, M. R.; Assis, R. F.; Leite, A. R.

2018-05-01

The elemental mapping of large areas using ion beam techniques is a desired capability for several scientific communities, involved on topics ranging from geoscience to cultural heritage. Usually, the constraints for large-area mapping are not met in setups employing micro- and nano-probes implemented all over the world. A novel setup for mapping large sized samples in an external beam was recently built at the University of São Paulo employing a broad MeV-proton probe with sub-millimeter dimension, coupled to a high-precision large range XYZ robotic stage (60 cm range in all axis and precision of 5 μ m ensured by optical sensors). An important issue on large area mapping is how to deal with the irregularities of the sample's surface, that may introduce artifacts in the images due to the variation of the measuring conditions. In our setup, we implemented an automatic system based on machine vision to correct the position of the sample to compensate for its surface irregularities. As an additional benefit, a 3D digital reconstruction of the scanned surface can also be obtained. Using this new and unique setup, we have produced large-area elemental maps of ceramics, stones, fossils, and other sort of samples.

Submillimeter Spectroscopy of the R Coronae Australis Molecular Cloud Region

NASA Astrophysics Data System (ADS)

Dunn, Marina Madeline; Walker, Christopher K.; Pat, Terrance; Sirsi, Siddhartha; Swift, Brandon J.; Peters, William L.

2018-01-01

The Interstellar Medium is comprised of large amounts of gas and dust which coalesce to form stars. Observing in the Terahertz regime of the electromagnetic spectrum, approximately 0.3 -300 microns, allows astronomers to study the ISM in unprecedented detail. Using the high spectral resolution imaging system of the SuperCam receiver, a 64-pixel array previously installed on the Submillimeter Telescope on Mt. Graham, AZ, we have begun a 500 square degree survey of the galactic plane. This instrument was designed to do a complete survey of the Milky Way from the ground, with the main focus being to observe two specific transitions of the carbon monoxide molecule, 12CO(3-2) and 13CO(3-2), at 345 GHz. In this work, we present results from these observations for the R Coronae Australis (R Cr A) complex, a region in the southern hemisphere of the sky, using spectroscopic data from a portion of the survey to gain better insight into the life cycle of the ISM. The majority of stars being formed here are similar to the stellar class of the Sun, making it an excellent area of observing interest. Using these results, we attempt to better ascertain the large-scale structure and kinematics inside of the molecular cloud.

Center for Adaptive Optics | Jobs

Science.gov Websites

, 2015 University of Geneva Adaptive Optics Scientist or Engineer March 16, 2015 NRC-Herzberg Astronomy Max Planck Institute for Astronomy (MPIA) Post-doctoral Fellowships in High-angular Resolution

Appalachian Mountains

Atmospheric Science Data Center

2014-05-15

... Radiance Ellipsoid Product. MISR uses this enhanced sensitivity along with the angular variation in signal to monitor particulate ... of MISR's unique capability of providing moderately high spatial resolution, calibrated imagery at very oblique angles. Gradations ...

COTS Silicon diodes as radiation detectors in proton and heavy charged particle radiotherapy 1.

PubMed

Kaiser, Franz-Joachim; Bassler, Niels; Jäkel, Oliver

2010-08-01

Modern radiotherapy facilities for cancer treatment such as the Heavy Ion Therapy Center (HIT) in Heidelberg, Germany, allow for sub-millimeter precision in dose deposition. For measurement of such dose distributions and characterization of the particle beams, detectors with high spatial resolution are necessary. Here, a detector based on the commercially available COTS photodiode (BPW-34) is presented. When applied in hadronic beams of protons and carbon ions, the detector reproduces dose distribution well, but its response decreases rapidly by radiation damage. However, for MeV photon beams, the detector exhibits a similar behavior as found in diode detectors usually applied in radiotherapy.

Background-Limited Infrared-Submillimeter Spectroscopy (BLISS)

NASA Technical Reports Server (NTRS)

Bradford, Charles Matt

2004-01-01

The bulk of the cosmic far-infrared background light will soon be resolved into its individual sources with Spitzer, Astro-F, Herschel, and submm/mm ground-based cameras. The sources will be dusty galaxies at z approximately equal to 1-4. Their physical conditions and processes in these galaxies are directly probed with moderate-resolution spectroscopy from 20 micrometers to 1 mm. Currently large cold telescopes are being combined with sensitive direct detectors, offering the potential for mid-far-IR spectroscopy at the background limit (BLISS). The capability will allow routine observations of even modest high-redshift galaxies in a variety of lines. The BLISS instrument's capabilities are described in this presentation.

A Kinematic, Kevlar(registered) Suspension System for an ADR

NASA Technical Reports Server (NTRS)

Voellmer, George M.; Jackson, Michael L.; Shirron, Peter J.; Tuttle, James G.

2003-01-01

The High Resolution Airborne Wideband Camera (HAWC) and the Submillimeter And Far Infrared Experiment (SAFIRE) will use identical Adiabatic Demagnetization Refrigerators (ADR) to cool their bolometer detectors to 200mK and 100mK, respectively. In order to minimize thermal loads on the salt pill, a Kevlar@ suspension system is used to hold it in place. An innovative, kinematic suspension system is presented. The suspension system is unique in that it consists or two parts that can be assembled and tensioned offline, and later bolted onto the salt pill. The resulting assembly constrains each degree of freedom only once, yielding a kinematic, tensile structure.

CONNECTING ANGULAR MOMENTUM AND GALACTIC DYNAMICS: THE COMPLEX INTERPLAY BETWEEN SPIN, MASS, AND MORPHOLOGY

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

Teklu, Adelheid F.; Remus, Rhea-Silvia; Dolag, Klaus

The evolution and distribution of the angular momentum of dark matter (DM) halos have been discussed in several studies over the past decades. In particular, the idea arose that angular momentum conservation should allow us to infer the total angular momentum of the entire DM halo from measuring the angular momentum of the baryonic component, which is populating the center of the halo, especially for disk galaxies. To test this idea and to understand the connection between the angular momentum of the DM halo and its galaxy, we use a state-of-the-art, hydrodynamical cosmological simulation taken from the set of Magneticummore » Pathfinder simulations. Thanks to the inclusion of the relevant physical processes, the improved underlying numerical methods, and high spatial resolution, we successfully produce populations of spheroidal and disk galaxies self-consistently. Thus, we are able to study the dependence of galactic properties on their morphology. We find that (1) the specific angular momentum of stars in disk and spheroidal galaxies as a function of their stellar mass compares well with observational results; (2) the specific angular momentum of the stars in disk galaxies is slightly smaller compared to the specific angular momentum of the cold gas, in good agreement with observations; (3) simulations including the baryonic component show a dichotomy in the specific stellar angular momentum distribution when splitting the galaxies according to their morphological type (this dichotomy can also be seen in the spin parameter, where disk galaxies populate halos with slightly larger spin compared to spheroidal galaxies); (4) disk galaxies preferentially populate halos in which the angular momentum vector of the DM component in the central part shows a better alignment to the angular momentum vector of the entire halo; and (5) the specific angular momentum of the cold gas in disk galaxies is approximately 40% smaller than the specific angular momentum of the total DM halo and shows a significant scatter.« less

Low-cost enclosure for the sub-millimeter telescope

NASA Astrophysics Data System (ADS)

Ulich, B. L.; Hoffmann, W. F.; Davison, W. B.; Baars, J. W. M.; Mezger, P. G.

1984-01-01

The University of Arizona and the Max-Planck-Institut fuer Radioastronomie are collaborating to construct a submillimeter-wavelength radio telescope facility at the summit of Mt. Lemmon (2791 m above sea level) near Tucson, Arizona. A corotating building has been designed to protect the 10 m-diameter Submillimeter Telescope against storm damage, to provide large instrumentation rooms at the Nasmyth foci, and to minimize degradation of the reflector profile accuracy and pointing errors caused by wind forces and solar radiation.

Low-Cost Enclosure For The Sub-Millimeter Telescope

NASA Astrophysics Data System (ADS)

Ulich, Bobby L.; Hoffmann, William F.; Davison, Warren B.; Baars, Jacob W. M.; Mezger, Peter G.

1983-11-01

The University of Arizona and the Max-Planck-Institut fur Radioastronomie are collaborating to construct a sub-millimeter wavelength radio telescope facility at the summit of Mt. Lemmon (2791 m above sea level) near Tucson, Arizona. We have designed a corotating building to protect the 10 m diameter Sub-Millimeter Telescope (SMT) against storm damage, to provide large instrumentation rooms at the Nasmyth foci, and to minimize degradation of the reflector profile accuracy and pointing errors caused by wind forces and solar radiation.

ALMA, APEX and beyond

NASA Astrophysics Data System (ADS)

Zwaan, M.; Testi, L.

The Atacama Large Millimeter/submillimeter Array (ALMA) is currently being constructed at the 5000m Chajnantor plateau in the Chilean Andes. ALMA has been designed and is being built to deliver transformational science in the millimeter and submillimeter regime for many years to come. We briefly describe the project status and timeline. The Atacama Pathfinder Experiment (APEX), built at the same site, is already operational and proves to be an effective survey instrument. We discuss which niches in millimeter/submillimeter astronomy will remain open for a possible facility in Antarctica.

Anisotropic kinetic energy release and gyroscopic behavior of CO2 super rotors from an optical centrifuge.

PubMed

Murray, Matthew J; Ogden, Hannah M; Mullin, Amy S

2017-10-21

An optical centrifuge is used to generate an ensemble of CO 2 super rotors with oriented angular momentum. The collision dynamics and energy transfer behavior of the super rotor molecules are investigated using high-resolution transient IR absorption spectroscopy. New multipass IR detection provides improved sensitivity to perform polarization-dependent transient studies for rotational states with 76 ≤ J ≤ 100. Polarization-dependent measurements show that the collision-induced kinetic energy release is spatially anisotropic and results from both near-resonant energy transfer between super rotor molecules and non-resonant energy transfer between super rotors and thermal molecules. J-dependent studies show that the extent and duration of the orientational anisotropy increase with rotational angular momentum. The super rotors exhibit behavior akin to molecular gyroscopes, wherein molecules with larger amounts of angular momentum are less likely to change their angular momentum orientation through collisions.

Anisotropic kinetic energy release and gyroscopic behavior of CO2 super rotors from an optical centrifuge

NASA Astrophysics Data System (ADS)

Murray, Matthew J.; Ogden, Hannah M.; Mullin, Amy S.

2017-10-01

An optical centrifuge is used to generate an ensemble of CO2 super rotors with oriented angular momentum. The collision dynamics and energy transfer behavior of the super rotor molecules are investigated using high-resolution transient IR absorption spectroscopy. New multipass IR detection provides improved sensitivity to perform polarization-dependent transient studies for rotational states with 76 ≤ J ≤ 100. Polarization-dependent measurements show that the collision-induced kinetic energy release is spatially anisotropic and results from both near-resonant energy transfer between super rotor molecules and non-resonant energy transfer between super rotors and thermal molecules. J-dependent studies show that the extent and duration of the orientational anisotropy increase with rotational angular momentum. The super rotors exhibit behavior akin to molecular gyroscopes, wherein molecules with larger amounts of angular momentum are less likely to change their angular momentum orientation through collisions.

Semiclassical analysis of angular differential cross sections for single-electron capture in 250-eV H++H collisions

NASA Astrophysics Data System (ADS)

Frémont, F.

2015-05-01

A classical model based on the resolution of Hamilton equations of motion is used to determine the angular distribution of H projectiles following single-electron capture in H++H collisions at an incident projectile energy of 250 eV. At such low energies, the experimental charge-exchange probability and angular differential cross sections exhibit oscillatory structures that are classically related to the number of swaps the electron experiences between the target and the projectile during the collision. These oscillations are well reproduced by models based on quantum mechanics. In the present paper, the angular distribution of H projectiles is determined classically, at angles varying from 0.1° up to 7°. The variation in intensity due to interferences caused by the indiscernibility between different trajectories is calculated, and the role of these interferences is discussed.

The CHARA optical array

NASA Astrophysics Data System (ADS)

McAlister, Harold A.

1992-11-01

The Center for High Angular Resolution Astronomy (CHARA) was established in the College of Arts and Sciences at Georgia State University in 1984 with the goals of designing, constructing, and then operating a facility for very high spatial resolution astronomy. The interest in such a facility grew out of the participants' decade of activity in speckle interferometry. Although speckle interferometry continues to provide important astrophysical measurements of a variety of objects, many pressing problems require resolution far beyond that which can be expected from single aperture telescopes. In early 1986, CHARA received a grant from the National Science Foundation which has permitted a detailed exploration of the feasibility of constructing a facility which will provide a hundred-fold increase in angular resolution over what is possible by speckle interferometry at the largest existing telescopes. The design concept for the CHARA Array was developed initially with the contractural collaboration of United Technologies Optical Systems, Inc., in West Palm Beach, Florida, an arrangement that expired in August 1987. In late November 1987, the Georgia Tech Research Institute joined with CHARA to continue and complete the design concept study. Very high-resolution imaging at optical wavelengths is clearly coming of age in astronomy. The CHARA Array and other related projects will be important and necessary milestones along the way toward the development of a major national facility for high-resolution imaging--a true optical counterpart to the Very Large Array. Ground-based arrays and their scientific output will lead to high resolution facilities in space and, ultimately, on the Moon.

Thin fused silica optics for a high angular resolution and large collecting area X Ray telescope after Chandra

NASA Astrophysics Data System (ADS)

Pareschi, Giovanni; Citterio, Oberto; Civitani, Marta M; Basso, Stefano; Campana, Sergio; Conconi, Paolo; Ghigo, Mauro; Mattaini, Enrico; Moretti, Alberto; Parodi, Giancarlo; Tagliaferri, Gianpiero

2014-08-01

The implementation of an X-ray mission with high imaging capabilities, similar to those achieved with Chandra (<1 arcsec Half Energy Width, HEW), but with a much larger throughput is very attractive, even if challenging. For such a mission the scientific opportunities, in particular for the study of the early Universe, would remain at the state of the art for the next decades. Initially the ESA-led XEUS mission was proposed, with an effective area of several m2 and an angular resolution better than 2 arcsec HEW. Unfortunately, this mission was not implemented, mainly due to the costs and the low level of technology readiness. Currently the most advanced proposal for such a mission is the SMART-X project, led by CfA together with other US institutes. This project is based on adjustable segments of thin foil mirrors with piezo-electric actuators, aiming to achieve an effective area >2 m2 at 1 keV and an angular resolution better than 1 arcsec HEW. Another attractive technology to realize an X-ray telescope with similar characteristics is being developed at NASA/Goddard. In this case the mirrors are based on Si substrates that are super-polished and figured starting from a bulky Si ingot, from which they are properly cut. Here we propose an alternative method based on precise direct grinding, figuring and polishing of thin (a few mm) glass shells with innovative deterministic polishing methods. This is followed by a final correction via ion figuring to obtain the desired accuracy. For this purpose, a temporary stiffening structure is used to support the shell from the polishing operations up to its integration in the telescope supporting structure. This paper deals with the technological process under development, the results achieved so far and some mission scenarios based on this kind of optics, aiming to achieve an effective area more than 10 times larger than Chandra and an angular resolution of 1 arcsec HEW on axis and of a few arcsec off-axis across a large field of view (1o in diameter).

On-ground calibration of the Hitomi Hard X-ray Telescopes

NASA Astrophysics Data System (ADS)

Mori, Hideyuki; Miyazawa, Takuya; Awaki, Hisamitsu; Matsumoto, Hironori; Babazaki, Yasunori; Bandai, Ayako; Demoto, Tadatsugu; Furuzawa, Akihiro; Haba, Yoshito; Hayashi, Takayuki; Iizuka, Ryo; Ishibashi, Kazunori; Ishida, Manabu; Ishida, Naoki; Itoh, Masayuki; Iwase, Toshihiro; Kato, Hiroyoshi; Kobayashi, Hiroaki; Kosaka, Tatsuro; Kunieda, Hideyo; Kurashima, Shou; Kurihara, Daichi; Kuroda, Yuuji; Maeda, Yoshitomo; Meshino, Yoshifumi; Mitsuishi, Ikuyuki; Miyata, Yuusuke; Nagano, Housei; Namba, Yoshiharu; Ogasaka, Yasushi; Ogi, Keiji; Okajima, Takashi; Saji, Shigetaka; Shimasaki, Fumiya; Sato, Takuro; Sato, Toshiki; Shima, Naotsugu; Sugita, Satoshi; Suzuki, Yoshio; Tachibana, Kenji; Tachibana, Sasagu; Takizawa, Shun'ya; Tamura, Keisuke; Tawara, Yuzuru; Tomikawa, Kazuki; Torii, Tatsuharu; Uesugi, Kentaro; Yamashita, Koujun; Yamauchi, Shigeo

2018-01-01

We present x-ray characteristics of the Hard X-ray Telescopes (HXTs) on board the Hitomi (ASTRO-H) satellite. Measurements were conducted at the SPring-8 BL20B2 beamline and the ISAS/JAXA 27-m beamline. The angular resolution defined by a half-power diameter was 1.9‧ (HXT-1) and 2.1‧ (HXT-2) at 8 keV, 1.9‧ at 30 keV, and 1.8‧ at 50 keV. The effective area was found to be 620 cm2 at 8 keV, 178 cm2 at 30 keV, and 82 cm2 at 50 keV per mirror module. Although the angular resolutions were slightly worse than the requirement (1.7‧), the effective areas sufficiently exceeded the requirements of 150 cm2 at 30 keV and 55 cm2 at 50 keV. The off-axis measurements of the effective areas resulted in the field of view being 6.1‧ at 50 keV, 7.7‧ at 30 keV, and 9.7‧ at 8 keV in diameter. We confirmed that the main component of the stray x-ray light was significantly reduced by mounting the precollimator as designed. Detailed analysis of the data revealed that the angular resolution was degraded mainly by figure errors of mirror foils, and the angular resolution is completely explained by the figure errors, positioning errors of the foils, and conical approximation of the foil shape. We found that the effective areas were ˜80% of the designed values below 40 keV, whereas they steeply decline above 40 keV and become only ˜50%. We investigated this abrupt decline and found that neither the error of the multilayer design nor the errors of the incident angles induced by the positioning errors of the foils can be the cause. The reflection profile of each foil pair from the defocused image strongly suggests that the figure errors of the foils probably bring about the reduction in the effective areas at higher energies.

Future Prospects for Very High Angular Resolution Imaging in the UV/Optical

NASA Astrophysics Data System (ADS)

Allen, R. J.

2004-05-01

Achieving the most demanding science goals outlined by the previous speakers will ultimately require the development of coherent space-based arrays of UV/Optical light collectors spread over distances of hundreds of meters. It is possible to envisage ``in situ" assembly of large segmented filled-aperture telescopes in space using components ferried up with conventional launchers. However, the cost will grow roughly as the mass of material required, and this will ultimately limit the sizes of the apertures we can afford. Furthermore, since the collecting area and the angular resolution are coupled for diffraction-limited filled apertures, the sensitivity may be much higher than is actually required to do the science. Constellations of collectors deployed over large areas as interferometer arrays or sparse apertures offer the possibility of independently tailoring the angular resolution and the sensitivity in order to optimally match the science requirements. Several concept designs have been proposed to provide imaging data for different classes of targets such as protoplanetary disks, the nuclear regions of the nearest active galaxies, and the surfaces of stars of different types. Constellations of identical collectors may be built and launched at lower cost through mass production, but new challenges arise when they have to be deployed. The ``aperture" synthesized is only as good as the accuracy with which the individual collectors can be placed and held to the required figure. This ``station-keeping" problem is one of the most important engineering problems to be solved before the promise of virtually unlimited angular resolution in the UV/Optical can be realized. Among the attractive features of an array of free-flying collectors configured for imaging is the fact that the figure errors of the ``aperture" so produced may be much more random than is the case for monolithic or segmented telescopes. This can result in a significant improvement in the dynamic range and permit imaging of faint objects near much brighter extraneous nearby sources, a task presently reserved for specially-designed coronagraphs on filled apertures.

Tagged Neutron Source for API Inspection Systems with Greatly Enhanced Spatial Resolution

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

None

2012-06-04

We recently developed induced fission and transmission imaging methods with time- and directionally-tagged neutrons offer new capabilities for characterization of fissile material configurations and enhanced detection of special nuclear materials (SNM). An Advanced Associated Particle Imaging (API) generator with higher angular resolution and neutron yield than existing systems is needed to fully exploit these methods.

An alternative resolution to the Mansuripur paradox

NASA Astrophysics Data System (ADS)

Redfern, Francis

2016-04-01

In 2013 an article published online by the journal Science declared that the paradox proposed by Masud Mansuripur was resolved. This paradox concerns a point charge-Amperian magnetic dipole system as seen in a frame of reference where they are at rest and one in which they are moving. In the latter frame an electric dipole appears on the magnetic dipole. A torque is then exerted upon the electric dipole by the point charge, a torque that is not observed in the at-rest frame. Mansuripur points out this violates the relativity principle and suggests the Lorentz force responsible for the torque be replaced by the Einstein-Laub force. The resolution of the paradox reported by Science, based on numerous papers in the physics literature, preserves the Lorentz force but depends on the concept of hidden momentum. Here I propose a different resolution based on the overlooked fact that the charge-magnetic dipole system contains linear and angular electromagnetic field momentum. The time rate of change of the field angular-momentum in the frame through which the system is moving cancels that due to the charge-electric dipole interaction. From this point of view hidden momentum is not needed in the resolution of the paradox.

Landsat and Sentinel-2A Surface Albedo Estimation and Evaluation Against In Situ Measurements Across the US SURFRAD Network

NASA Astrophysics Data System (ADS)

Franch, B.; Skakun, S.; Vermote, E.; Roger, J. C.

2017-12-01

Surface albedo is an essential parameter not only for developing climate models, but also for most energy balance studies. While climate models are usually applied at coarse resolution, the energy balance studies, which are mainly focused on agricultural applications, require a high spatial resolution. The albedo, estimated through the angular integration of the BRDF, requires an appropriate angular sampling of the surface. However, Sentinel-2A sampling characteristics, with nearly constant observation geometry and low illumination variation, prevent from deriving a surface albedo product. In this work, we apply an algorithm developed to derive a Landsat surface albedo to Sentinel-2A. It is based on the BRDF parameters estimated from the MODerate Resolution Imaging Spectroradiometer (MODIS) CMG surface reflectance product (M{O,Y}D09) using the VJB method (Vermote et al., 2009). Sentinel-2A unsupervised classification images are used to disaggregate the BRDF parameters to the Sentinel-2 spatial resolution. We test the results over five different sites of the US SURFRAD network and plot the results versus albedo field measurements. Additionally, we also test this methodology using Landsat-8 images.

Online Mapping and Perception Algorithms for Multi-robot Teams Operating in Urban Environments

DTIC Science & Technology

2015-01-01

each method on a 2.53 GHz Intel i5 laptop. All our algorithms are hand-optimized, implemented in Java and single threaded. To determine which algorithm...approach would be to label all the pixels in the image with an x, y, z point. However, the angular resolution of the camera is finer than that of the...edge criterion. That is, each edge is either present or absent. In [42], edge existence is further screened by a fixed threshold for angular

Angularly resolved characterization of ion beams from laser-ultrathin foil interactions

NASA Astrophysics Data System (ADS)

Scullion, C.; Doria, D.; Romagnani, L.; Ahmed, H.; Alejo, A.; Ettlinger, O. C.; Gray, R. J.; Green, J.; Hicks, G. S.; Jung, D.; Naughton, K.; Padda, H.; Poder, K.; Scott, G. G.; Symes, D. R.; Kar, S.; McKenna, P.; Najmudin, Z.; Neely, D.; Zepf, M.; Borghesi, M.

2016-09-01

Methods and techniques used to capture and analyze beam profiles produced from the interaction of intense, ultrashort laser pulses and ultrathin foil targets using stacks of Radiochromic Film (RCF) and Columbia Resin #39 (CR-39) are presented. The identification of structure in the beam is particularly important in this regime, as it may be indicative of the dominance of specific acceleration mechanisms. Additionally, RCF can be used to deconvolve proton spectra with coarse energy resolution while mantaining angular information across the whole beam.

Developing Soft-Kill Capability for Light Armoured Vehicles through Battlefield Simulations

DTIC Science & Technology

2007-02-01

scripted so they can move, fire, sense, communicate and react without operator intervention. The entities, can interact with each other as well as manned...trace of the laser illuminator. The horizontal scan is 135◦ followed by a vertical angular displacement of 15◦ and retracement. The 15◦ vertical scan...properties based on combined characteristics. An example of a new detector is the laser detecting HARLID. With an angular resolution of ±1◦, it is a

Scalar and tensor spherical harmonics expansion of the velocity correlation in homogeneous anisotropic turbulence

DOE PAGES

Rubinstein, Robert; Kurien, Susan; Cambon, Claude

2015-06-22

The representation theory of the rotation group is applied to construct a series expansion of the correlation tensor in homogeneous anisotropic turbulence. The resolution of angular dependence is the main analytical difficulty posed by anisotropic turbulence; representation theory parametrises this dependence by a tensor analogue of the standard spherical harmonics expansion of a scalar. As a result, the series expansion is formulated in terms of explicitly constructed tensor bases with scalar coefficients determined by angular moments of the correlation tensor.