17,628 research outputs found
ERTS-1 data user investigation of the use of ERTS imagery in reservoir management and operation
There are no author-identified significant results in this report
Novel String Banana Template Method of Track Reconstruction for high Multiplicity Events with Significant Multiple Scattering
Novel String Banana Template Method (SBTM) for track reconstruction in high
multiplicity events in non-uniform magnetic field spectrometer with emphasis on
the lowest momenta tracks with significant Multiple Scattering (MS) is
described. Two steps model of track with additional parameter/s which takes
into account MS for this particular track is introduced. SBTM is time efficient
and demonstrates better resolutions than another method equivalent to the Least
Squares method (LSM).Comment: 3 pages, 3 figures, DPF2004 Proceeding, International Journal of
Modern Physics
Retrieval information file relating to assigned frequencies, part 2 Final report, Jan. - Sep. 1969
Retrieval information file relating to assigned frequencies for use on IBM 360 compute
Deconvolution of Images from BLAST 2005: Insight into the K3-50 and IC 5146 Star-forming Regions
We present an implementation of the iterative flux-conserving Lucy-Richardson (L-R) deconvolution method of image restoration for maps produced by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST). Compared to the direct Fourier transform method of deconvolution, the L-R operation restores images with better-controlled background noise and increases source detectability. Intermediate iterated images are useful for studying extended diffuse structures, while the later iterations truly enhance point sources to near the designed diffraction limit of the telescope. The L-R method of deconvolution is efficient in resolving compact sources in crowded regions while simultaneously conserving their respective flux densities. We have analyzed its performance and convergence extensively through simulations and cross-correlations of the deconvolved images with available high-resolution maps. We present new science results from two BLAST surveys, in the Galactic regions K3-50 and IC 5146, further demonstrating the benefits of performing this deconvolution. We have resolved three clumps within a radius of 4'.5 inside the star-forming molecular cloud containing K3-50. Combining the well-resolved dust emission map with available multi-wavelength data, we have constrained the spectral energy distributions (SEDs) of five clumps to obtain masses (M), bolometric luminosities (L), and dust temperatures (T). The L-M diagram has been used as a diagnostic tool to estimate the evolutionary stages of the clumps. There are close relationships between dust continuum emission and both 21 cm radio continuum and ^(12)CO molecular line emission. The restored extended large-scale structures in the Northern Streamer of IC 5146 have a strong spatial correlation with both SCUBA and high-resolution extinction images. A dust temperature of 12 K has been obtained for the central filament. We report physical properties of ten compact sources, including six associated protostars, by fitting SEDs to multi-wavelength data. All of these compact sources are still quite cold (typical temperature below ~ 16 K) and are above the critical Bonner-Ebert mass. They have associated low-power young stellar objects. Further evidence for starless clumps has also been found in the IC 5146 region
Correlations in the (Sub)millimeter Background from ACT × BLAST
We present measurements of the auto- and cross-frequency correlation power spectra of the cosmic (sub)millimeter background at 250, 350, and 500 μm (1200, 860, and 600 GHz) from observations made with the Balloon-borne Large Aperture Submillimeter Telescope (BLAST); and at 1380 and 2030 μm (218 and 148 GHz) from observations made with the Atacama Cosmology Telescope (ACT). The overlapping observations cover 8.6 deg^2 in an area relatively free of Galactic dust near the south ecliptic pole. The ACT bands are sensitive to radiation from the cosmic microwave background, to the Sunyaev-Zel'dovich effect from galaxy clusters, and to emission by radio and dusty star-forming galaxies (DSFGs), while the dominant contribution to the BLAST bands is from DSFGs. We confirm and extend the BLAST analysis of clustering with an independent pipeline and also detect correlations between the ACT and BLAST maps at over 25σ significance, which we interpret as a detection of the DSFGs in the ACT maps. In addition to a Poisson component in the cross-frequency power spectra, we detect a clustered signal at 4σ, and using a model for the DSFG evolution and number counts, we successfully fit all of our spectra with a linear clustering model and a bias that depends only on redshift and not on scale. Finally, the data are compared to, and generally agree with, phenomenological models for the DSFG population. This study demonstrates the constraining power of the cross-frequency correlation technique to constrain models for the DSFGs. Similar analyses with more data will impose tight constraints on future models
A Wilson-Yukawa model with undoubled chiral fermions in 2D
We consider the fermion spectrum in the strong coupling vortex phase of a
lattice fermion-scalar model with a global , in 2D, in the
context of a recently proposed two-cutoff lattice formulation. The fermion
doublers are made massive by a strong Wilson-Yukawa coupling, but in contrast
with the standard formulation of these models, in which the light fermion
spectrum was found to be massive and vectorlike, we find massless undoubled
fermions with chiral quantum numbers at finite lattice spacing. When the global
symmetry is gauged, this model is expected to give rise to a chiral gauge
theory.Comment: 34 pages, late
Documentation of a ground hydrology parameterization for use in the GISS atmospheric general circulation model
The moisture transport processes related to the earth's surface relevant to the ground circulation model GCM are presented. The GHM parametrizations considered are: (1) ground wetness and soil parameters; (2) precipitation; (3) evapotranspiration; (4) surface storage of snow and ice; and (5) runout. The computational aspects of the GHM using computer programs and flow charts are described
Evidence for Environmental Changes in the Submillimeter Dust Opacity
The submillimeter opacity of dust in the diffuse interstellar medium (ISM) in the Galactic plane has been quantified using a pixel-by-pixel correlation of images of continuum emission with a proxy for column density. We used multi-wavelength continuum data: three Balloon-borne Large Aperture Submillimeter Telescope bands at 250, 350, and 500 μm and one IRAS band at 100 μm. The proxy is the near-infrared color excess, E(J – K_s), obtained from the Two Micron All Sky Survey. Based on observations of stars, we show how well this color excess is correlated with the total hydrogen column density for regions of moderate extinction. The ratio of emission to column density, the emissivity, is then known from the correlations, as a function of frequency. The spectral distribution of this emissivity can be fit by a modified blackbody, whence the characteristic dust temperature T and the desired opacity σ_e(1200) at 1200 GHz or 250 μm can be obtained. We have analyzed 14 regions near the Galactic plane toward the Vela molecular cloud, mostly selected to avoid regions of high column density (N_H > 10^(22) cm^(–2)) and small enough to ensure a uniform dust temperature. We find σ_e(1200) is typically (2-4) × 10^(–25) cm^2 H^(–1) and thus about 2-4 times larger than the average value in the local high Galactic latitude diffuse atomic ISM. This is strong evidence for grain evolution. There is a range in total power per H nucleon absorbed (and re-radiated) by the dust, reflecting changes in the strength of the interstellar radiation field and/or the dust absorption opacity. These changes in emission opacity and power affect the equilibrium T, which is typically 15 K, colder than at high latitudes. Our analysis extends, to higher opacity and lower temperature, the trend of increasing σ_e(1200) with decreasing T that was found at high latitudes. The recognition of changes in the emission opacity raises a cautionary flag because all column densities deduced from dust emission maps, and the masses of compact structures within them, depend inversely on the value adopted
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