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Sample records for foreground damped ly-alpha

  1. Magnetic fields in damped Ly-alpha systems

    NASA Technical Reports Server (NTRS)

    Wolfe, A. M.; Lanzetta, K. M.; Oren, A. L.

    1992-01-01

    The probability of Faraday rotation in various types of metal-line absorbers is computed by combining the incidence of Faraday rotation in a sample of radio-selected QSOs with the incidence of foreground metal-line absorption. The sample is divided into subsets with and without damped Ly-alpha absorption. The probability of Faraday rotation is significantly higher in the damped subset. The probability is higher in the damped subset than in nondamped subsets selected on the basis of Mg II or C IV absorption. From evidence linking damped systems to the progenitors of galactic disks and the Mg II systems to the progenitors of galactic halos, it is concluded that magnetic fields were significantly higher in protogalactic disks than in protogalactic halos. It is estimated that the B fields in two damped Ly-alpha systems with z of about 2 are a few micro-Gauss.

  2. Discovery of a Ly-alpha galaxy near a damped Ly-alpha absorber at z = 2.3

    NASA Technical Reports Server (NTRS)

    Lowenthal, James D.; Hogan, Craig J.; Green, Richard F.; Caulet, Adeline; Woodgate, Bruce E.; Brown, Larry; Foltz, Craig B.

    1991-01-01

    The detection of a galaxy associated with the damped Ly-alpha absorbing cloud seen at z = 2.309 toward the QSO PHL 957 is reported. In addition to a strong but narrow Ly-alpha emission line and weaker C IV and He II lines, the object shows continuum at V about 24, with a slope rising slightly toward the red. This is similar to what is seen in high-redshift radio galaxies, but this galaxy does not correspond to any known radio source. The detected emission lines and continuum are most easily interpreted as light from hot, recently formed stars, implying a sizable star formation rate and a scarcity of dust. The spatial correlation of the absorbing cloud and the companion galaxy supports the interpretation of damped Ly-alpha clouds as objects fundamentally different from the lower column density Ly-alpha forest clouds, which show weak or no clustering.

  3. THE FUNDAMENTAL PLANE OF DAMPED Ly{alpha} SYSTEMS

    SciTech Connect

    Neeleman, Marcel; Wolfe, Arthur M.; Prochaska, J. Xavier

    2013-05-20

    Using a sample of 100 H I-selected damped Ly{alpha} (DLA) systems, observed with the High Resolution Echelle Spectrometer on the Keck I telescope, we present evidence that the scatter in the well-studied correlation between the redshift and metallicity of a DLA is largely due to the existence of a mass-metallicity relationship at each redshift. To describe the fundamental relations that exist between redshift, metallicity, and mass, we use a fundamental plane description, which is described by the following equation: [M/H] = (- 1.9 {+-} 0.5) + (0.74 {+-} 0.21) {center_dot} log {Delta}v{sub 90} - (0.32 {+-} 0.06) {center_dot} z. Here, we assert that the velocity width, {Delta}v{sub 90}, which is defined as the velocity interval containing 90% of the integrated optical depth, traces the mass of the underlying dark matter halo. This description provides two significant improvements over the individual descriptions of the mass-metallicity correlation and metallicity-redshift correlation. Firstly, the fundamental equation reduces the scatter around both relationships by about 20%, providing a more stringent constraint on numerical simulations modeling DLAs. Secondly, it confirms that the dark matter halos that host DLAs satisfy a mass-metallicity relationship at each redshift between redshifts 2 through 5.

  4. ASYMMETRIC ABSORPTION PROFILES OF Ly{alpha} AND Ly{beta} IN DAMPED Ly{alpha} SYSTEMS

    SciTech Connect

    Lee, Hee-Won

    2013-08-01

    Damped Ly{alpha} systems observed in the quasar spectra are characterized by a high neutral hydrogen column density, N{sub HI} > 2 x 10{sup 20} cm{sup -2}. The absorption wing profiles are often fitted using the Voigt function due to the fact that the scattering cross section near the resonant line center is approximately described by the Lorentzian function. Since a hydrogen atom has infinitely many p states that participate in the electric dipole interaction, the cross section starts to deviate from the Lorentzian in an asymmetric way in the line wing regions. We investigate this asymmetry in the absorption line profiles around Ly{alpha} and Ly{beta} as a function of the neutral hydrogen column density N{sub HI}. In terms of {Delta}{lambda} {identical_to} {lambda} - {lambda}{sub {alpha}}, we expand the Kramers-Heisenberg formula around Ly{alpha} to find {sigma}({lambda}) {approx_equal} (0.5f{sub 12}){sup 2}{sigma}{sub T}({Delta}{lambda}/{lambda}{sub {alpha}}){sup -2}[1 + 3.792({Delta}{lambda}/{lambda}{sub {alpha}})], where f{sub 12} and {sigma}{sub T} are the oscillator strength of Ly{alpha} and the Thomson scattering cross section, respectively. In terms of {Delta}{lambda}{sub 2} {identical_to} {lambda} - {lambda}{sub {beta}} in the vicinity of Ly{beta}, the total scattering cross section, given as the sum of cross sections for Rayleigh and Raman scattering, is shown to be {sigma}({lambda}) {approx_equal} {sigma}{sub T}(0.5f{sub 13}){sup 2}(1 + R{sub 0})({Delta}{lambda}{sub 2}/{lambda}{sub {beta}}){sup -2}[1 - 24.68({Delta}{lambda}{sub 2}/{lambda}{sub {beta}})] with f{sub 13} and the factor R{sub 0} = 0.1342 being the oscillator strength for Ly{beta} and the ratio of the Raman cross section to Rayleigh cross section, respectively. A redward asymmetry develops around Ly{alpha}, whereas a blue asymmetry is obtained for Ly{beta}. The absorption center shifts are found to be almost proportional to the neutral hydrogen column density.

  5. A Search For Multiple Images of QSOs Seen Through Damped Ly-alpha Absorbers

    NASA Astrophysics Data System (ADS)

    Falco, Emilio

    1996-07-01

    We propose to obtain high-resolution images of a sample of QSOs with strong damped Ly-alpha absorption in their spectra. The observations would determine whether these QSOs are multiply imaged by gravitational lensing. It is widely believed that damped Ly-alpha absorption occurs in HI disks of spiral galaxies. Gravitational lensing is then inevitable for lines of sight passing close to the centers of these systems. For typical spiral galaxies, the resulting image separation is expected to be in the range 0.1''-0.5'' and can only be detected with HST at optical wavelengths. Because the neutral -hydrogen column density increases on average towards the center of galaxies, strong Ly-alpha absorption provides an efficient ``flag'' for gravitationally lensed QSOs with small image separations. Bartelmann & Loeb {1995, ApJ, in press} have shown that the frequency of multiple images is enhanced by 1-2 orders of magnitude in samples of QSOs with strong damped Ly-alpha absorption {N_ HI> 10^21 cm^-2}, compared to the overall QSO population. For this proposal, we have selected those QSOs most likely to exhibit gravitational lensing, from the published list of QSOs with damped Ly-alpha absorption. If lensing is found in this QSO sample, it will have important cosmological implications. First, it will confirm the association of damped Ly-alpha systems with galactic potential wells. Second, the magnification bias associated with lensing would make the appearance of damped systems more likely, and therefore affect estimates of the neutral-hydrogen fraction in the Universe {Bartelmann & Loeb 1995}. Third, the cosmological history of HI is linked to the process of galaxy formation and evolution {Lanzetta, Wolfe, & Turnshek 1995, ApJ, 440, 435}. Finally, the lensing frequency provides a sensitive probe of the cosmological constant.

  6. Survey for z>3 damped Ly alpha absorption systems: the evolution of neutral gas

    NASA Technical Reports Server (NTRS)

    Storrie-Lombardi, L. J.; Wolfe, A. M.

    2000-01-01

    We have completed spectroscopic observations using LRIS on the Keck 1 telescope of 30 very high redshift quasars, 11 selected for the presence of damped Ly alpha absorption systems and 19 with redshifts z>3.5 not previously surveyed for absorption systems.

  7. A Faraday rotation search for magnetic fields in quasar damped Ly alpha absorption systems

    NASA Technical Reports Server (NTRS)

    Oren, Abraham L.; Wolfe, Arthur M.

    1995-01-01

    We present the results of a Faraday rotation survey of 61 radio-bright QSOs conducted at the National Radio Astronomy Observatory (NRAO) Very Large Array (VLA). The Galactic contribution to the Faraday rotation is estimated and subtracted to determine the extragalactic rotation measure (RRM) for each source. Eleven of these QSOs are known to exhibit damped Ly alpha absorption. The rate of incidence of significant Faraday rotation of these 11 sources is compared to the remaining 50 and is found to be higher at the 99.8% confidence level. However, as this is based upon only two detections of Faraday rotation in the damped Ly alpha sample, the result is only tentative. If the two detections in the damped Ly alpha sample are dug to the absorbing systems, then the inferred rotation measure induced by these systems is roughly 250 rad/sq m. The two detections were for the two lowest redshift absorbers in the sample. We find that a rotation measure of 250 rad/sq m would have gone undetected for any other absorber in the damped Ly alpha sample due to the 1/(1 + 2) squared dilution of the observed RRM with redshift. Thus the data are consistent with, but do not prove, the hypothesis that Faraday rotation is a generic property of damped Ly alpha absorbers. We do not confirm the suggestion that the amplitude of RRMs increases with redshift. Rather, the data are consistent with no redshift evolution. We find that the uncertainty in the estimation of the Galactic rotation measure (GRM) is a more serious problem than previously realized for extra-galactic Faraday rotation studies of QSO absorbers. A careful analysis of current methods for estimating GRM indicate that it can be determined to an accuracy of about 15 - 20 rad/sq m. Previous studies underestimated this uncertainty by more than a factor of 2. Due to this uncertainty, rotation measures such as we suspect are associated with damped Ly alpha absorption systems can only be detected at redshifts less than z approximately

  8. The Dust-to-Gas Ratio in the Damped Ly alpha Clouds Towards the Gravitationally Lensed QSO 0957+561

    NASA Technical Reports Server (NTRS)

    Zuo, Lin; Beaver, E. A.; Burbidge, E. Margaret; Cohen, Ross D.; Junkkarinen, Vesa T.; Lyons, R. W.

    1997-01-01

    We present HST/FOS spectra of the two bright images (A and B) of the gravitationally lensed QSO 0957+561 in the wavelength range 2200-3300 A. We find that the absorption system (Z(sub abs)) = 1.3911) near z(sub em) is a weak, damped Ly alpha system with strong Ly alpha absorption lines seen in both images. However, the H(I) column densities are different, with the line of sight to image A intersecting a larger column density. The continuum shapes of the two spectra differ in the sense that the flux level of image A increases more slowly toward shorter wavelengths than that of image B. We explain this as the result of differential reddening by dust grains in the damped Ly alpha absorber. A direct outcome of this explanation is a determination of the dust-to-gas ratio, k, in the damped Ly alpha system. We derive k = 0.55 + 0.18 for a simple 1/lambda extinction law and k = 0.31 + 0.10 for the Galactic extinction curve. For gravitationally lensed systems with damped Ly alpha absorbers, our method is a powerful tool for determining the values and dispersion of k, and the shapes of extinction curves, especially in the FUV and EUV regions. We compare our results with previous work.

  9. METALLICITY EVOLUTION OF DAMPED Ly{alpha} SYSTEMS OUT TO z {approx} 5

    SciTech Connect

    Rafelski, Marc; Wolfe, Arthur M.; Neeleman, Marcel; Mendez, Alexander J.; Prochaska, J. Xavier

    2012-08-20

    We present chemical abundance measurements for 47 damped Ly{alpha} (DLA) systems, 30 at z > 4, observed with the Echellette Spectrograph and Imager and the High Resolution Echelle Spectrometer on the Keck telescopes. H I column densities of the DLAs are measured with Voigt profile fits to the Ly{alpha} profiles, and we find an increased number of false DLA identifications with Sloan Digital Sky Survey at z > 4 due to the increased density of the Ly{alpha} forest. Ionic column densities are determined using the apparent optical depth method, and we combine our new metallicity measurements with 195 from previous surveys to determine the evolution of the cosmic metallicity of neutral gas. We find the metallicity of DLAs decreases with increasing redshift, improving the significance of the trend and extending it to higher redshifts, with a linear fit of -0.22 {+-} 0.03 dex per unit redshift from z = 0.09-5.06. The metallicity 'floor' of Almost-Equal-To 1/600 solar continues out to z {approx} 5, despite our sensitivity for finding DLAs with much lower metallicities. However, this floor is not statistically different from a steep tail to the distribution. We also find that the intrinsic scatter of metallicity among DLAs of {approx}0.5 dex continues out to z {approx} 5. In addition, the metallicity distribution and the {alpha}/Fe ratios of z > 2 DLAs are consistent with being drawn from the same parent population with those of halo stars. It is therefore possible that the halo stars in the Milky Way formed out of gas that commonly exhibits DLA absorption at z > 2.

  10. CHEMICAL ENRICHMENT IN THE CARBON-ENHANCED DAMPED Ly{alpha} SYSTEM BY POPULATION III SUPERNOVAE

    SciTech Connect

    Kobayashi, Chiaki; Tominaga, Nozomu; Nomoto, Ken'ichi

    2011-04-01

    We show that the recently observed elemental abundance pattern of the carbon-rich metal-poor damped Ly{alpha} (DLA) system is in excellent agreement with the nucleosynthesis yields of faint core-collapse supernovae of primordial stars. The observed abundance pattern is not consistent with the nucleosynthesis yields of pair-instability supernovae. The DLA abundance pattern is very similar to that of carbon-rich extremely metal-poor (EMP) stars, and the contributions from low-mass stars and/or binary effects should be very small in DLAs. This suggests that chemical enrichment by the first stars in the first galaxies is driven by core-collapse supernovae from {approx}20 to 50 M{sub sun} stars and also supports the supernova scenario as the enrichment source of EMP stars in the Milky Way Galaxy.

  11. CONSTRAINING STELLAR PROPERTIES OF INTERVENING DAMPED Ly{alpha} AND Mg II ABSORBING GALAXIES TOWARD GRB 050730

    SciTech Connect

    Minowa, Y.; Okoshi, K.; Kobayashi, N.; Takami, H.

    2012-09-15

    We performed multiband deep imaging of the field around GRB 050730 to identify the host galaxies of intervening absorbers, which consist of a damped Ly{alpha} absorption (DLA) system at z{sub abs} = 3.564, a sub-DLA system at z{sub abs} = 3.022, and strong Mg II absorption systems at z{sub abs} = 1.773 and 2.253. Our observations were performed after the gamma-ray burst afterglow had disappeared. Thus, our imaging survey has a higher sensitivity to the host galaxies of the intervening absorbers than the normal imaging surveys in the direction of QSOs, for which the QSO glare tends to hide the foreground galaxies. In this deep imaging survey, we could not detect any unambiguous candidates for the host galaxies of the intervening absorbers. Using the 3{sigma} upper limit of the flux in the optical to mid-infrared observing bands, which corresponds to the UV to optical bands in the rest frame of the intervening absorbers, we constrained the star formation rates and stellar masses of the hosts. We estimated the star formation rates for the intervening absorbers to be {approx}< 2.5 M{sub Sun} yr{sup -1} for z > 3 DLAs and {approx}< 1.0 M{sub Sun} yr{sup -1} for z {approx} 2 Mg II systems. Their stellar masses are estimated to be several times 10{sup 9} M{sub Sun} or smaller for all intervening galaxies. These properties are comparable to dwarf galaxies, rather than the massive star-forming galaxies commonly seen in the z > 2 galaxy surveys based on emission-line selection or color selection.

  12. A SUPER-DAMPED Ly{alpha} QUASI-STELLAR OBJECT ABSORBER AT z = 2.2

    SciTech Connect

    Kulkarni, Varsha P.; Som, Debopam; Meiring, Joseph; Peroux, Celine; York, Donald G.; Khare, Pushpa; Lauroesch, James T.

    2012-04-20

    We report the discovery of a 'super-damped' Ly{alpha} absorber at z{sub abs} = 2.2068 toward quasi-stellar object (QSO) Q1135-0010 in the Sloan Digital Sky Survey (SDSS) and follow-up Very Large Telescope (VLT) UVES spectroscopy. A Voigt profile fit to the damped Ly{alpha} (DLA) line indicates log N{sub Hi}= 22.05 {+-} 0.1. This is the second QSO DLA discovered to date with such high N{sub Hi}. We derive element abundances [Si/H] = -1.10 {+-} 0.10, [Zn/H] = -1.06 {+-} 0.10, [Cr/H] = -1.55 {+-} 0.10, [Ni/H] = -1.60 {+-} 0.10, [Fe/H] = -1.76 {+-} 0.10, [Ti/H] = -1.69 {+-} 0.11, [P/H] = -0.93 {+-} 0.23, and [Cu/H] = -0.75 {+-} 0.14. Our data indicate detection of Ly{alpha} emission in the DLA trough, implying a star formation rate (SFR) of {approx}10 M{sub Sun} yr{sup -1} in the absence of dust attenuation. C II* {lambda}1336 absorption is also detected, suggesting SFR surface density -2

  13. Metal Abundances and Physical Conditions in Two Damped LY alpha Systems toward HS 1946+7658

    NASA Astrophysics Data System (ADS)

    Lu, Limin; Savage, Blair D.; Tripp, Todd M.; Meyer, David M.

    1995-07-01

    Quasar metal absorption systems represent some of the best opportunities to study the properties and evolution of galaxies at high red shifts. We present a study of metal abundances and physical conditions in two damped Lyα systems at z = 2.8443 and z = 1.7382 toward the quasar HS 1946 + 7658. The analyses are based on a high-resolution (FWHM = 20 km s-1), high signal-to-noise ratio (40-80 per resolution element) spectrum of the quasar. Ion column densities are determined from a combination of profile fitting and the apparent optical depth method. Special efforts are exercised to minimize the effects of the line saturation problem. We also incorporate recently improved oscillator strengths for a number of important transitions. The z = 2.8443 system is found to have an absolute Fe metallicity of 2.4-2.6 dex below solar, where the large range mainly reflects uncertainties in the ionization corrections. The absolute metallicity of the z = 1.7382 system cannot be determined because its H I column density is unknown. We find an apparent overabundance of Si to Fe relative to their solar ratio by about a factor of 2 in both systems. We also find an overabundance of Si to Al relative to solar by a factor of 3 in the z = 2.8443 system, and an underabundance of Mn to Fe relative to solar by a factor of 3 in the z = 1.7382 system. Photoionization calculations suggest that these abundance ratios are not likely to be significantly biased by ionization effects. More likely, either these ratios represent the intrinsic abundance ratios in the gas, or the gas actually has solar relative abundances with the observed abundance patterns being produced by dust depletion effects. However, the apparent underabundance of Mn to Fe relative to solar argues against the latter interpretation. Interestingly, the observed relative abundance patterns are similar to those seen in Galactic low-metallicity stars, and they can be explained by theories of heavy-element nucleosynthesis in the early

  14. CHEMICAL ENRICHMENT OF DAMPED Ly{alpha} SYSTEMS AS A DIRECT CONSTRAINT ON POPULATION III STAR FORMATION

    SciTech Connect

    Kulkarni, Girish; Hennawi, Joseph F.; Rollinde, Emmanuel; Vangioni, Elisabeth

    2013-08-01

    Observations of damped Ly{alpha} absorbers (DLAs) can be used to measure gas-phase metallicities at large cosmological look-back times with high precision. Furthermore, relative abundances can still be measured accurately deep into the reionization epoch (z > 6) using transitions redward of Ly{alpha}, even though Gunn-Peterson absorption precludes measurement of neutral hydrogen. In this paper, we study the chemical evolution of DLAs using a model for the coupled evolution of galaxies and the intergalactic medium (IGM), which is constrained by a variety of observations. Our goal is to explore the influence of Population III stars on the abundance patterns of DLAs to determine the degree to which abundance measurements can discriminate between different Population III stellar initial mass functions (IMFs). We include effects, such as inflows onto galaxies due to cosmological accretion and outflows from galaxies due to supernova feedback. A distinct feature of our model is that it self-consistently calculates the effect of Population III star formation on the reionization of an inhomogeneous IGM, thus allowing us to calculate the thermal evolution of the IGM and implement photoionization feedback on low-mass galaxy formation. We find that if the critical metallicity of Population III to II/I transition is {approx}< 10{sup -4} Z{sub Sun }, then the cosmic Population III star formation rate drops to zero for z < 8. Nevertheless, at high redshift (z {approx} 6), chemical signatures of Population III stars remain in low-mass galaxies (halo mass {approx}< 10{sup 9} M{sub Sun }). This is because photoionization feedback suppresses star formation in these galaxies until relatively low redshift (z {approx} 10), and the chemical record of their initial generation of Population III stars is retained. We model DLAs as these low-mass galaxies, and assign to them a mass-dependent H I absorption cross-section in order to predict the expected distribution of DLA abundance ratios

  15. A search for molecular hydrogen and dust in the z = 2. 796 damped Ly-alpha absorber toward Q1337+113

    SciTech Connect

    Lanzetta, K.M.; Wolfe, A.M.; Turnshek, D.A.; Space Telescope Science Institute, Baltimore, MD )

    1989-09-01

    Spectroscopic and spectrophotometric observations and analyses are presented with the aim of ascertaining the presence of molecular hydrogen and dust in the damped Ly-alpha absorber toward Q1337+113. These observations are not sensitive to dust abundances. It is found that the abundance ratios of the metal elements are consistent with solar values, and that the C exp 0 column density is at least 200 times lower than for the H II region toward Zeta Oph. These results are consistent with a lack of dust in the absorber. A model of the equilibrium abundance of H2 is constructed, and the observed limit to the fractional H2 abundance is found capable of placing an independent upper limit on the dust content of the absorber at less than one-third the Galactic value. 58 refs.

  16. Directly Imaging Damped Ly-Alpha Galaxies at Redshifts Greater Than 2. III: The Star Formation Rates of Neutral Gas Reservoirs at Redshifts of Approximately 2.7

    NASA Technical Reports Server (NTRS)

    Fumagalli, Michele; OMeara, John M.; Prochaska, J. Xavier; Rafelski, Marc; Kanekar, Nissim

    2014-01-01

    We present results from a survey designed to probe the star formation properties of 32 damped Ly alpha systems (DLAs) at redshifts of approximately 2.7. By using the "double-DLA" technique that eliminates the glare of the bright background quasars, we directly measure the rest-frame FUV flux from DLAs and their neighbouring galaxies. At the position of the absorbing gas, we place stringent constraints on the unobscured star formation rates (SFRs) of DLAs to 2 sigma limits of psi less than 0.09-0.27 solar mass yr(exp -1), corresponding to SFR surface densities sigma(sub sfr) less than 10(exp -2.6)-10(exp -1.5) solar mass yr(exp -1) kpc(exp -2). The implications of these limits for the star formation law, metal enrichment, and cooling rates of DLAs are examined. By studying the distribution of impact parameters as a function of SFRs for all the galaxies detected around these DLAs, we place new direct constraints on the bright end of the UV luminosity function of DLA hosts. We find that less than or equal to 13% of the hosts have psi greater than or equal to 2 solar mass yr(exp -1) at impact parameters b(sub dla) less than or equal to (psi/solar mass yr(exp -1))(exp 0.8) + 6 kpc, differently from current samples of confirmed DLA galaxies. Our observations also disfavor a scenario in which the majority of DLAs arise from bright LBGs at distances 20 less than or equal to b(sub dla) less than 100 kpc. These new findings corroborate a picture in which DLAs do not originate from highly star forming systems that are coincident with the absorbers, and instead suggest that DLAs are associated with faint, possibly isolated, star-forming galaxies. Potential shortcomings of this scenario and future strategies for further investigation are discussed.

  17. THE ALFALFA H I ABSORPTION PILOT SURVEY: A WIDE-AREA BLIND DAMPED Ly{alpha} SYSTEM SURVEY OF THE LOCAL UNIVERSE

    SciTech Connect

    Darling, Jeremy; Macdonald, Erin P.; Haynes, Martha P.; Giovanelli, Riccardo E-mail: e.macdonald@physics.gla.ac.uk E-mail: riccardo@astro.cornell.edu

    2011-11-20

    We present the results of a pilot survey for neutral hydrogen (H I) 21 cm absorption in the Arecibo Legacy Fast Arecibo L-Band Feed Array (ALFALFA) Survey. This project is a wide-area 'blind' search for H I absorption in the local universe, spanning -650 km s{sup -1} < cz < 17, 500 km s{sup -1} and covering 517.0 deg{sup 2} (7% of the full ALFALFA survey). The survey is sensitive to H I absorption lines stronger than 7.7 mJy (8983 radio sources) and is 90% complete for lines stronger than 11.0 mJy (7296 sources). The total redshift interval sensitive to all damped Ly{alpha} (DLA) systems (N{sub H{sub i}}{>=}2 Multiplication-Sign 10{sup 20} cm{sup -2}) is {Delta}z = 7.0 (129 objects, assuming T{sub s} = 100 K and covering fraction unity); for super-DLAs (N{sub H{sub i}}{>=}2 Multiplication-Sign 10{sup 21} cm{sup -2}) it is {Delta}z = 128.2 (2353 objects). We re-detect the intrinsic H I absorption line in UGC 6081 but detect no intervening absorption line systems. We compute a 95% confidence upper limit on the column density frequency distribution function f(N{sub H{sub i}},X) spanning four orders of magnitude in column density, 10{sup 19} (T{sub s} /100 K) (1/f) cm{sup -2}

  18. A METAL-STRONG AND DUST-RICH DAMPED Ly{alpha} ABSORPTION SYSTEM TOWARD THE QUASAR SDSS J115705.52+615521.7

    SciTech Connect

    Wang Jianguo; Ge Jian; Hamann, Fred; Xavier Prochaska, J.

    2012-11-20

    We report the discovery of an unusual, extremely dust-rich and metal-strong damped Ly{alpha} absorption system (DLA) at a redshift z{sub a} = 2.4596 toward the quasar SDSS J115705.52+615521.7 with an emission-line redshift z{sub e} = 2.5125. The quasar spectrum, taken in the Sloan Digital Sky Survey, shows a very red color and a number of metal absorption lines, including C II, Al II, Si II, Fe II, and Zn II, which are confirmed and further characterized by follow-up spectroscopy made with the Multiple Mirror Telescope. Its neutral hydrogen column density N {sub HI} = 10{sup 21.8{+-}0.2} cm{sup -2} is among the highest values measured in quasar DLAs. The measured metal column density is N {sub ZnII} Almost-Equal-To 10{sup 13.8} cm{sup -2}, which is about 1.5 times larger than the largest value in any previously observed quasar DLAs. We derive the extinction curve of the dusty DLA using a new technique, which is an analog of the 'pair method' widely used to measure extinction curves in the Milky Way (MW). The best-fit curve is an MW-like law with a significant broad feature centered around 2175 A in the rest frame of the absorber. The measured extinction A{sub V} Almost-Equal-To 0.92 mag is unprecedentedly high in quasar DLAs. After applying an extinction correction, the i-band absolute magnitude of the quasar is as high as M{sub i} Almost-Equal-To -29.4 mag, placing it as one of the most luminous quasars ever known. The large gas-phase relative abundance of [Zn/Fe] Almost-Equal-To 1.0 indicates that metals are heavily depleted onto dust grains in the absorber. The dust depletion level is between that of the warm and cool clouds in the MW. This discovery is suggestive of the existence of a rare yet important population of dust-rich DLAs with both high metallicities and high column densities, which may have significant impact on the measurement of the cosmic evolution of neutral gas mass density and metallicity.

  19. METALLICITIES, DUST, AND MOLECULAR CONTENT OF A QSO-DAMPED Ly{alpha} SYSTEM REACHING log N(H I) = 22: AN ANALOG TO GRB-DLAs

    SciTech Connect

    Guimaraes, R.; Noterdaeme, P.; Petitjean, P.; Ledoux, C.; Srianand, R.; Rahmani, H.; Lopez, S.

    2012-06-15

    We present the elemental abundance and H{sub 2} content measurements of a damped Ly{alpha} (DLA) system with an extremely large H I column density, log N(H I) (cm{sup -2}) = 22.0 {+-} 0.10, at z{sub abs} = 3.287 toward the QSO SDSS J081634+144612. We measure column densities of H{sub 2}, C I, C I*, Zn II, Fe II, Cr II, Ni II, and Si II from a high signal-to-noise and high spectral resolution VLT-UVES spectrum. The overall metallicity of the system is [Zn/H] = -1.10 {+-} 0.10 relative to solar. Two molecular hydrogen absorption components are seen at z = 3.28667 and 3.28742 (a velocity separation of Almost-Equal-To 52 km s{sup -1}) in rotational levels up to J = 3. We derive a total H{sub 2} column density of log N(H{sub 2}) (cm{sup -2}) = 18.66 and a mean molecular fraction of f = 2N(H{sub 2})/[2N(H{sub 2}) + N(H I)] = 10{sup -3.04{+-}0.37}, typical of known H{sub 2}-bearing DLA systems. From the observed abundance ratios we conclude that dust is present in the interstellar medium of this galaxy, with an enhanced abundance in the H{sub 2}-bearing clouds. However, the total amount of dust along the line of sight is not large and does not produce any significant reddening of the background QSO. The physical conditions in the H{sub 2}-bearing clouds are constrained directly from the column densities of H{sub 2} in different rotational levels, C I and C I*. The kinetic temperature is found to be T Almost-Equal-To 75 K and the particle density lies in the range n{sub H} = 50-80 cm{sup -3}. The neutral hydrogen column density of this DLA is similar to the mean H I column density of DLAs observed at the redshift of {gamma}-ray bursts (GRBs). We explore the relationship between GRB-DLAs and the high column density end of QSO-DLAs finding that the properties (metallicity and depletion) of DLAs with log N(H I) > 21.5 in the two populations do not appear to be significantly different.

  20. The solar Ly-alpha line profile

    NASA Technical Reports Server (NTRS)

    Woods, Thomas N.; Rottman, Gary J.; White, O. R.; Fontenla, Juan; Avrett, E. H.

    1995-01-01

    Solar Ly-alpha irradiance measurements from the SOLar STellar Irradiance Comparison Experiment (SOLSTICE) on the Upper Atmosphere Research Satellite (UARS) have been made since 1991 October with a spectral resolution of 0.1 nm. The uniqueness of the small molecular oxygen cross section near Ly-alpha permits the Ly-alpha radiation to penetrate much deeper into the atmosphere than the other emissions near Ly-alpha. We have taken advantage of this phenomenon by performing solar occultation experiments near the Ly-alpha to evaluate precisely the instrument scattered light contribution. After correcting for scattered light, the broad wings of the solar Ly-alpha line can be extracted out to 5 nm from line center with a typical accuracy of +/-20%. The variability in the Ly-alpha wings near 2 nm from line center is about one-half that of the Ly-alpha core emission, defined within 0.1 nm from line center. These Ly-alpha profile measurements are found to be consistent with the Skylab radiance measurements and theoretical models of the Ly-alpha line profiles computed using partial redistribution of photons in the source function.

  1. THE BOSS Ly{alpha} FOREST SAMPLE FROM SDSS DATA RELEASE 9

    SciTech Connect

    Lee, Khee-Gan; Bailey, Stephen; Carithers, William; Schlegel, David J.; Bartsch, Leslie E.; Dawson, Kyle S.; Bolton, Adam S.; Kirkby, David; Margala, Daniel; Blomqvist, Michael; Lundgren, Britt; Palanque-Delabrouille, Nathalie; Yeche, Christophe; Borde, Arnaud; Weinberg, David H.; Aubourg, Eric; Bautista, Julian; and others

    2013-03-15

    We present the BOSS Lyman-{alpha} (Ly{alpha}) Forest Sample from SDSS Data Release 9, comprising 54,468 quasar spectra with z{sub qso} > 2.15 suitable for Ly{alpha} forest analysis. This data set probes the intergalactic medium with absorption redshifts 2.0 < z{sub {alpha}} < 5.7 over an area of 3275 deg{sup 2}, and encompasses an approximate comoving volume of 20 h {sup -3} Gpc{sup 3}. With each spectrum, we have included several products designed to aid in Ly{alpha} forest analysis: improved sky masks that flag pixels where data may be unreliable, corrections for known biases in the pipeline estimated noise, masks for the cores of damped Ly{alpha} systems and corrections for their wings, and estimates of the unabsorbed continua so that the observed flux can be converted to a fractional transmission. The continua are derived using a principal component fit to the quasar spectrum redward of rest-frame Ly{alpha} ({lambda} > 1216 A), extrapolated into the forest region and normalized by a linear function to fit the expected evolution of the Ly{alpha} forest mean flux. The estimated continuum errors are {approx}< 5% rms. We also discuss possible systematics arising from uncertain spectrophotometry and artifacts in the flux calibration; global corrections for the latter are provided. Our sample provides a convenient starting point for users to analyze clustering in BOSS Ly{alpha} forest data, and it provides a fiducial data set that can be used to compare results from different analyses of baryon acoustic oscillations in the Ly{alpha} forest. The full data set is available from the SDSS-III DR9 Web site.

  2. Lyman-alpha emission from the damped Lyman-alpha system toward H0836 + 113

    NASA Technical Reports Server (NTRS)

    Wolfe, A. M.; Lanzetta, K. M.; Turnshek, D. A.; Oke, J. B.

    1992-01-01

    This study presents results of a comprehensive search for Ly-alpha emission from the 2.466-redshift damped Ly-alpha system toward the QSO H0836 + 113. Deep CCD images of the field surrounding the QSO were acquired with a narrow-band filter tuned to the wavelength centroid of the 2.466-redshift damped Ly-alpha line. Two superposed objects, one extended and the other compact, were detected within 4 arcsec of the QSO. Evidence is presented indicating that the extended object, seen only in the narrow-band frames, was detected in the light of Ly-alpha line radiation emitted by the damped system, while the compact object, seen with the broadband filters and in the narrow-band frames acquired with superior seeing, was detected in the light of the continuum radiation emitted by a foreground Mg II galaxy with a redshift of 0.79. Accurate spectra of the QSO were also obtained in order to observe the spatially unresolved Ly-alpha emission feature reported to exist at the bottom of the damped Ly-alpha absorption trough.

  3. A Ly{alpha} HALO AROUND A QUASAR AT REDSHIFT z = 6.4

    SciTech Connect

    Willott, Chris J.; Chet, Savironi; Hutchings, John B.; Bergeron, Jacqueline

    2011-12-15

    We present long-slit spectroscopic data that reveal extended Ly{alpha} emission around the z = 6.417 radio-quiet quasar CFHQS J2329-0301. The Ly{alpha} emission is extended over 15 kpc and has a luminosity of >8 Multiplication-Sign 10{sup 36} W, comparable to the most luminous Ly{alpha} halos known. The emission has complex kinematics, in part due to foreground absorption, which only partly covers the extended nebula. The velocity ranges from -500 km s{sup -1} to +500 km s{sup -1}, with a peak remarkably close to the systemic velocity identified by broad Mg II emission of the quasar. There is no evidence for infall or outflow of the halo gas. We speculate that the Ly{alpha} emission mechanism is recombination after quasar photoionization of gas sitting within a high-mass dark matter halo. The immense Ly{alpha} luminosity indicates a higher covering factor of cold gas compared with typical radio-quiet quasars at lower redshift.

  4. GAS KINEMATICS IN Ly{alpha} NEBULAE

    SciTech Connect

    Yang Yujin; Jahnke, Knud; Zabludoff, Ann; Eisenstein, Daniel; Dave, Romeel; Shectman, Stephen A.; Kelson, Daniel D.

    2011-07-10

    Exploring the origin of Ly{alpha} nebulae ('blobs') at high redshift requires measurements of their gas kinematics that are impossible with only the resonant, optically thick Ly{alpha} line. To define gas motions relative to the systemic velocity of the blob, the Ly{alpha} line must be compared with an optically thin line like H{alpha} {lambda}6563, which is not much altered by radiative transfer effects and is more concentrated about the galaxies embedded in the nebula's core. We obtain optical and near-IR (NIR) spectra of the two brightest Ly{alpha} blobs (CDFS-LAB01 and CDFS-LAB02) from the Yang et al. sample using the Magellan/Magellan Echellette Spectrograph optical and Very Large Telescope/SINFONI NIR spectrographs. Both the Ly{alpha} and H{alpha} lines confirm that these blobs lie at the survey redshift, z {approx} 2.3. Within each blob, we detect several H{alpha} sources, which roughly correspond to galaxies seen in Hubble Space Telescope rest-frame UV images. The H{alpha} detections show that these galaxies have large internal velocity dispersions ({sigma}{sub v} = 130-190 km s{sup -1}) and that, in the one system (LAB01), where we can reliably extract profiles for two H{alpha} sources, their velocity difference is {Delta}v {approx} 440 km s{sup -1}. The presence of multiple galaxies within the blobs, and those galaxies' large velocity dispersions and large relative motion, is consistent with our previous finding that Ly{alpha} blobs inhabit massive dark matter halos that will evolve into those typical of present-day rich clusters and that the embedded galaxies may eventually become brightest cluster galaxies. To determine whether the gas near the embedded galaxies is predominantly infalling or outflowing, we compare the Ly{alpha} and H{alpha} line centers, finding that Ly{alpha} is not offset ({Delta}v{sub Ly{alpha}} = +0 km s{sup -1}) in LAB01 and redshifted by only +230 km s{sup -1} in LAB02. These offsets are small compared to those of Lyman break

  5. Clearings in Ly-alpha forests

    NASA Astrophysics Data System (ADS)

    Kovner, Israel; Rees, Martin J.

    1989-10-01

    At sufficient resolution, QSO spectra can be examined for patches of reduced H I column density in Ly-alpha clouds. Statistics of these clearings can constrain the fraction of the ionizing background contributed by compact sources and (possibly) their lifetimes and beaming. This is demonstrated first in a simple Euclidean setup and then in a model which takes into account the expansion of the universe and the cosmological evolution of the factors involved. The expected number of clearings in a Ly-alpha forest extending back to the formation epoch of compact sources of ionizing radiation (CSIRs) is about 1/4, if the CSIRs are important ionizing agents, and if the transience of CSIRs is unimportant. The particular properties of the CSIR population, e.g., their luminosity function, have little importance. However, expected number of clearings can be much larger if the CSIR lifetimes are short compared to the light crossing times of the domains of dominance, or if the CSIRs turned on sharply at a time when the ionization rate due to competing processes was low.

  6. Uranian H Ly-alpha emission - The interstellar wind source

    NASA Technical Reports Server (NTRS)

    Yelle, R. V.; Sandel, B. R.

    1986-01-01

    IUE observation of Uranian emissions in hydrogen Lyman alpha (H Ly-alpha) over the past four years have recently been summarized by Clarke et al. (1985). Over this time period they find an average H Ly-alpha brightness of 1260 R which they estimate is composed of 200 R of solar scattered radiation and 1060 R from a collisional source. A third component, not considered by previous authors, is the reflection of H Ly-alpha emissions from the interstellar wind. Hydrogen in the interstellar wind forms an extended source of H Ly-alpha whose importance relative to the solar flux increases with distance from the sun. The present paper demonstrates that scattering of interstellar H Ly-alpha is more important than scattering of solar H Ly-alpha for reasonable values of H column abundance and, in fact, may make up 10-40 percent of the observed signal. Large H column abundances are still required to explain the H Ly-alpha brightness solely on the basis of resonant scattering; therefore it is likely that the emissions are due in part to collisional sources and in part to the scattering of interstellar H Ly-alpha with solar scattering playing a minor role.

  7. THE PROPAGATION OF Ly{alpha} IN EVOLVING PROTOPLANETARY DISKS

    SciTech Connect

    Bethell, Thomas J.; Bergin, Edwin A.

    2011-10-01

    We study the role resonant scattering plays in the transport of Ly{alpha} photons in accreting protoplanetary disk systems subject to varying degrees of dust settling. While the intrinsic stellar far-UV (FUV) spectrum of accreting T Tauri systems may already be dominated by a strong, broad Ly{alpha} line ({approx}80% of the FUV luminosity), we find that resonant scattering further enhances the Ly{alpha} density in the deep molecular layers of the disk. Ly{alpha} is scattered downward efficiently by the photodissociated atomic hydrogen layer that exists above the molecular disk. In contrast, FUV-continuum photons pass unimpeded through the photodissociation layer and (forward-)scatter inefficiently off dust grains. Using detailed, adaptive grid Monte Carlo radiative transfer simulations we show that the resulting Ly{alpha}/FUV-continuum photon density ratio is strongly stratified; FUV-continuum-dominated in the photodissociation layer and Ly{alpha}-dominated field in the molecular disk. The enhancement is greatest in the interior of the disk (r {approx} 1 AU) but is also observed in the outer disk (r {approx} 100 AU). The majority of the total disk mass is shown to be increasingly Ly{alpha} dominated as dust settles toward the midplane.

  8. DISCOVERY OF A GIANT Ly{alpha} EMITTER NEAR THE REIONIZATION EPOCH

    SciTech Connect

    Ouchi, Masami; McCarthy, Patrick J.; Momcheva, Ivelina; Dressler, Alan; Ono, Yoshiaki; Shimasaku, Kazuhiro; Okamura, Sadanori; Hayashi, Masao; Egami, Eiichi; Saito, Tomoki; Oguri, Masamune; Farrah, Duncan; Kashikawa, Nobunari; Iye, Masanori; Nakanishi, Kouichiro; Furusawa, Hisanori; Akiyama, Masayuki; Dunlop, James S.; Mortier, Angela M. J.; Cirasuolo, Michele

    2009-05-10

    We report the discovery of a giant Ly{alpha} emitter (LAE) with a Spitzer/Infrared Array Camera (IRAC) counterpart near the reionization epoch at z = 6.595. The giant LAE is found from the extensive 1 deg{sup 2} Subaru narrowband survey for z = 6.6 LAEs in the Subaru/XMM-Newton Deep Survey (SXDS) field, and subsequently identified by deep spectroscopy of Keck/DEIMOS and Magellan/IMACS. Among our 207 LAE candidates, this LAE is not only the brightest narrowband object with L(Ly{alpha}) = 3.9 {+-} 0.2 x 10{sup 43} erg s{sup -1} in our survey volume of 10{sup 6} Mpc{sup 3}, but also a spatially extended Ly{alpha} nebula with the largest isophotal area whose major axis is at least {approx_equal}3''. This object is more likely to be a large Ly{alpha} nebula with a size of {approx}>17 kpc than to be a strongly lensed galaxy by a foreground object. Our Keck spectrum with medium-high spectral and spatial resolutions suggests that the velocity width is v {sub FWHM} = 251 {+-} 21 km s{sup -1}, and that the line-center velocity changes by {approx_equal}60 km s{sup -1} in a 10 kpc range. The stellar mass and star formation rate are estimated to be 0.9-5.0 x 10{sup 10} M {sub sun} and >34 M {sub sun} yr{sup -1}, respectively, from the combination of deep optical to infrared images of Subaru, UKIDSS-Ultra Deep Survey, and Spitzer/IRAC. Although the nature of this object is not yet clearly understood, this could be an important object for studying cooling clouds accreting onto a massive halo, or forming-massive galaxies with significant outflows contributing to cosmic reionization and metal enrichment of intergalactic medium.

  9. Ly alpha and IR galaxy companions of high redshift damped Ly alpha QSO absorbers

    NASA Technical Reports Server (NTRS)

    Caulet, Adeline; Mccaughrean, Mark

    1993-01-01

    We have used a Near-Infrared Camera and Multi-Object Spectrometer (NICMOS3) HgCdTe 256x256 array detector with the Infrared (IR) camera on the 2.3m telescope at Steward Observatory to image several Quasi-Stellar Object (QSO) fields. The limiting magnitude is K'(2.1 microns) = 21.0 - 21.5 mag per square arcsec for a 3 sigma detection in 3 hours of in-field chopping observations. Each QSO line-of-sight samples several known absorbers with Mg2(lambda)2796-2803 A and/or C4(lambda)1548-1551 A absorption doublets. The equivalent width distributions of the low and high ionization absorption lines of the absorber sample are identical to those of the parent population of all absorbers. This selection process, used already for a spectroscopic survey of Mg2 absorption lines in C4-selected absorption systems at high z, gives a methodical approach to observing, reduces the observer biases, and makes a more efficient use of telescope time. This selection guarantees that imaging of the sample of QSO fields will provide complete sampling of the whole population of high z QSO absorbers. Follow-up optical and IR spectroscopy of these objects is scheduled for redshift measurement and confirmation of the absorbing galaxies and the cluster members.

  10. THE LINE POLARIZATION WITHIN A GIANT Ly{alpha} NEBULA

    SciTech Connect

    Prescott, Moire K. M.; Smith, Paul S.; Schmidt, Gary D.; Dey, Arjun

    2011-04-01

    Recent theoretical work has suggested that Ly{alpha} nebulae could be substantially polarized in the Ly{alpha} emission line, depending on the geometry, kinematics, and powering mechanism at work. Polarization observations can therefore provide a useful constraint on the source of ionization in these systems. In this Letter, we present the first Ly{alpha} polarization measurements for a giant Ly{alpha} nebula at z{approx} 2.656. We do not detect any significant linear polarization of the Ly{alpha} emission: P{sub Ly{alpha}} = 2.6% {+-} 2.8% (corrected for statistical bias) within a single large aperture. The current data also do not show evidence for the radial polarization gradient predicted by some theoretical models. These results rule out singly scattered Ly{alpha} (e.g., from the nearby active galactic nucleus, AGN) and may be inconsistent with some models of backscattering in a spherical outflow. However, the effects of seeing, diminished signal-to-noise ratio, and angle averaging within radial bins make it difficult to put strong constraints on the radial polarization profile. The current constraints may be consistent with higher density outflow models, spherically symmetric infall models, photoionization by star formation within the nebula or the nearby AGN, resonant scattering, or non-spherically symmetric cold accretion (i.e., along filaments). Higher signal-to-noise ratio data probing to higher spatial resolution will allow us to harness the full diagnostic power of polarization observations in distinguishing between theoretical models of giant Ly{alpha} nebulae.

  11. EXTENDED Ly{alpha} EMISSION AROUND STAR-FORMING GALAXIES

    SciTech Connect

    Zheng Zheng; Cen Renyue; Weinberg, David; Trac, Hy; Miralda-Escude, Jordi

    2011-10-01

    Ly{alpha} photons that escape the interstellar medium of star-forming galaxies may be resonantly scattered by neutral hydrogen atoms in the circumgalactic and intergalactic media, thereby increasing the angular extent of the galaxy's Ly{alpha} emission. We present predictions of this extended, low surface brightness Ly{alpha} emission based on radiative transfer modeling in a cosmological reionization simulation. The extended emission can be detected from stacked narrowband images of Ly{alpha} emitters (LAEs) or of Lyman break galaxies (LBGs). Its average surface brightness profile has a central cusp, then flattens to an approximate plateau beginning at an inner characteristic scale below {approx}0.2 Mpc (comoving), then steepens again beyond an outer characteristic scale of {approx}1 Mpc. The inner scale marks the transition from scattered light of the central source to emission from clustered sources, while the outer scale marks the spatial extent of scattered emission from these clustered sources. Both scales tend to increase with halo mass, UV luminosity, and observed Ly{alpha} luminosity. The extended emission predicted by our simulation is already within reach of deep narrowband photometry using large ground-based telescopes. Such observations would test radiative transfer models of emission from LAEs and LBGs, and they would open a new window on the circumgalactic environment of high-redshift star-forming galaxies.

  12. RADIATIVE TRANSFER MODELING OF Ly{alpha} EMITTERS. I. STATISTICS OF SPECTRA AND LUMINOSITY

    SciTech Connect

    Zheng Zheng; Cen Renyue; Trac, Hy; Miralda-Escude, Jordi

    2010-06-10

    We combine a cosmological reionization simulation with box size of 100 h {sup -1} Mpc on a side and a Monte Carlo Ly{alpha} radiative transfer code to model Ly{alpha} Emitters (LAEs) at z {approx} 5.7. The model introduces Ly{alpha} radiative transfer as the single factor for transforming the intrinsic Ly{alpha} emission properties into the observed ones. Spatial diffusion of Ly{alpha} photons from radiative transfer results in extended Ly{alpha} emission and only the central part with high surface brightness can be observed. Because of radiative transfer, the appearance of LAEs depends on density and velocity structures in circumgalactic and intergalactic media as well as the viewing angle, which leads to a broad distribution of apparent (observed) Ly{alpha} luminosity for a given intrinsic Ly{alpha} luminosity. Radiative transfer also causes frequency diffusion of Ly{alpha} photons. The resultant Ly{alpha} line is asymmetric with a red tail. The peak of the Ly{alpha} line shifts toward longer wavelength and the shift is anti-correlated with the apparent-to-intrinsic Ly{alpha} luminosity ratio. The simple radiative transfer model provides a new framework for studying LAEs. It is able to explain an array of observed properties of z {approx} 5.7 LAEs in Ouchi et al., producing Ly{alpha} spectra, morphology, and apparent Ly{alpha} luminosity function (LF) similar to those seen in observation. The broad distribution of apparent Ly{alpha} luminosity at fixed UV luminosity provides a natural explanation for the observed UV LF, especially the turnover toward the low luminosity end. The model also reproduces the observed distribution of Ly{alpha} equivalent width (EW) and explains the deficit of UV bright, high EW sources. Because of the broad distribution of the apparent-to-intrinsic Ly{alpha} luminosity ratio, the model predicts effective duty cycles and Ly{alpha} escape fractions for LAEs.

  13. Ly{alpha} COOLING EMISSION FROM GALAXY FORMATION

    SciTech Connect

    Faucher-Giguere, Claude-Andre; Keres, Dusan; Dijkstra, Mark; Hernquist, Lars; Zaldarriaga, Matias

    2010-12-10

    Recent numerical and analytical studies have shown that galaxies accrete most of their baryons via the cold mode, from streams with temperatures T {approx} 10{sup 4}-10{sup 5} K. At these temperatures, the streams should radiate primarily in the Ly{alpha} line and have therefore been proposed as a model to power the extended, high-redshift objects known as Ly{alpha} blobs, and may also be relevant for powering a range of less luminous Ly{alpha} sources. We introduce a new Ly{alpha} radiative transfer code, {alpha}RT, and calculate the transport of the Ly{alpha} emission from cold accretion in cosmological hydrodynamical simulations. In this paper, we describe our methodology, and address physical and numerical issues that are critical to making accurate predictions for the cooling luminosity, but that have been mostly neglected or treated simplistically so far. In particular, we highlight the importance of self-shielding and of properly treating sub-resolution models in numerical simulations. Most existing simulations do not self-consistently incorporate these effects, which can lead to order-of-magnitude errors in the predicted cooling luminosity. Using a combination of post-processing ionizing radiative transfer and re-simulation techniques, we develop an approximation to the consistent evolution of the self-shielded gas. We quantify the dependence of the Ly{alpha} cooling luminosity on halo mass at z = 3 for the simplified problem of pure gas accretion embedded in the cosmic radiation background and without feedback, and present radiative transfer results for a particular system. While pure cooling in massive halos (without additional energy input from star formation and active galactic nuclei) is in principle sufficient to produce L{sub {alpha}} {approx} 10{sup 43}-10{sup 44} erg s{sup -1} blobs, this requires including energy released in gas of density sufficient to form stars, but which is kept 100% gaseous in our optimistic estimates. Excluding emission from

  14. PROBING PRIMORDIAL MAGNETIC FIELDS USING Ly{alpha} CLOUDS

    SciTech Connect

    Pandey, Kanhaiya L.; Sethi, Shiv K.

    2013-01-01

    From previous studies of the effect of primordial magnetic fields on early structure formation, we know that the presence of primordial magnetic fields during early structure formation could induce more perturbations at small scales (at present 1-10 h {sup -1} Mpc) as compared to the usual {Lambda}CDM theory. Matter power spectra over these scales are effectively probed by cosmological observables such as shear correlation and Ly{alpha} clouds. In this paper we discuss the implications of primordial magnetic fields on the distribution of Ly{alpha} clouds. We simulate the line-of-sight density fluctuation including the contribution coming from the primordial magnetic fields. We compute the evolution of Ly{alpha} opacity for this case and compare our theoretical estimates of Ly{alpha} opacity with the existing data to constrain the parameters of the primordial magnetic fields. We also discuss the case when the two density fields are correlated. Our analysis yields an upper bound of roughly 0.3-0.6 nG on the magnetic field strength for a range of nearly scale-invariant models, corresponding to a magnetic field power spectrum index n {approx_equal} -3.

  15. SIZING UP Ly{alpha} AND LYMAN BREAK GALAXIES

    SciTech Connect

    Malhotra, Sangeeta; Rhoads, James E.; McLinden, Emily; Finkelstein, Steven L.; Hathi, Nimish; Nilsson, Kim; Pirzkal, Norbert

    2012-05-10

    We measure the sizes for a sample of 174 Ly{alpha}-selected galaxies with broadband imaging with the Hubble Space Telescope. Over the redshift range 2.25 < z < 6, Ly{alpha}-selected galaxies have a characteristic, constant, small size in rest-frame ultraviolet (UV) light. Coupled with a characteristic star formation intensity (i.e., UV luminosity per unit area), this can explain their non-evolving ultraviolet continuum luminosity function. This is in contrast to Lyman break galaxies (LBGs) over the same redshift range, which have been previously shown to increase in linear size as H(z){sup -1}. The compact physical size seems to be a critical determining factor in whether a galaxy will show Ly{alpha} emission or not. The L{sub *} of LBGs and its evolution with redshift can be derived from a simple model where the star formation intensity has an upper limit set by feedback processes, independent of redshift. The increase in L{sub *} of LBGs is mainly driven by the increase in linear size over redshifts for z = 2-7. Since Ly{alpha} galaxies do not grow in linear size, they do not show an increase in L{sub *}.

  16. EVIDENCE FOR SPATIALLY COMPACT Ly{alpha} EMISSION IN z = 3.1 Ly{alpha}-EMITTING GALAXIES

    SciTech Connect

    Bond, Nicholas A.; Gawiser, Eric; Feldmeier, John J.; Matkovic, Ana; Gronwall, Caryl; Ciardullo, Robin E-mail: gawiser@physics.rutgers.ed E-mail: matkovic@astro.psu.ed E-mail: rbc@astro.psu.ed

    2010-06-20

    We present the results of a high spatial resolution study of the line emission in a sample of z = 3.1 Ly{alpha}-emitting galaxies (LAEs) in the Extended Chandra Deep Field-South. Of the eight objects with coverage in our HST/WFPC2 narrowband imaging, two have clear detections and two are barely detected ({approx}2 {sigma}). The clear detections are within {approx}0.5 kpc of the centroid of the corresponding rest-UV continuum source, suggesting that the line-emitting gas and young stars in LAEs are spatially coincident. The brightest object exhibits extended emission with a half-light radius of {approx}1.5 kpc, but a stack of the remaining LAE surface brightness profiles is consistent with the WFPC2 point-spread function. This suggests that the Ly{alpha} emission in these objects originates from a compact ({approx}<2 kpc) region and cannot be significantly more extended than the far-UV continuum emission ({approx}<1 kpc). Comparing our WFPC2 photometry to previous ground-based measurements of their monochromatic fluxes, we find at 95% (99.7%) confidence that we cannot be missing more than 22% (32%) of the Ly{alpha} emission.

  17. HUBBLE SPACE TELESCOPE IMAGING OF Ly{alpha} EMISSION AT z {approx} 4.4

    SciTech Connect

    Finkelstein, Steven L.; Finkelstein, Keely D.; Cohen, Seth H.; Windhorst, Rogier A.; Malhotra, Sangeeta; Rhoads, James E.; Ryan, Russell E.; Hathi, Nimish P.; McCarthy, Patrick J.; Anderson, Jay; Grogin, Norman A.; Koekemoer, Anton M.; Mutchler, Max; Bond, Howard E.; O'Connell, Robert W.; Balick, Bruce; Calzetti, Daniela; Disney, Michael J.; Dopita, Michael A.; Frogel, Jay A.

    2011-07-01

    We present the highest redshift detections of resolved Ly{alpha} emission, using Hubble Space Telescope (HST)/Advanced Camera for Surveys F658N narrowband-imaging data taken in parallel with the Wide Field Camera 3 Early Release Science program in the GOODS Chandra Deep Field-South. We detect Ly{alpha} emission from three spectroscopically confirmed z = 4.4 Ly{alpha} emitting galaxies (LAEs), more than doubling the sample of LAEs with resolved Ly{alpha} emission. Comparing the light distribution between the rest-frame ultraviolet continuum and narrowband images, we investigate the escape of Ly{alpha} photons at high redshift. While our data do not support a positional offset between the Ly{alpha} and rest-frame ultraviolet (UV) continuum emission, the half-light radius in one out of the three galaxies is significantly (>1{sigma}) larger in Ly{alpha} than in the rest-frame UV continuum. Stacking the three LAEs in both the narrowband and UV continuum images, we find that the Ly{alpha} light appears larger than the rest-frame UV at 4.2{sigma} significance. This Ly{alpha} flux detected with HST is a factor of 4-10 less than observed in similar filters from the ground. These results together imply that the Ly{alpha} emission is not strictly confined to its indigenous star-forming regions. Rather, for at least one object the Ly{alpha} emission is more extended, with the missing HST flux possibly existing in a diffuse outer halo. This suggests that the radiative transfer of Ly{alpha} photons in high-redshift LAEs is complicated, with the interstellar-medium geometry and/or outflows playing a significant role in galaxies at these redshifts.

  18. RADIATIVE TRANSFER MODELING OF Ly{alpha} EMITTERS. II. NEW EFFECTS ON GALAXY CLUSTERING

    SciTech Connect

    Zheng Zheng; Cen Renyue; Trac, Hy; Miralda-Escude, Jordi

    2011-01-01

    We study the clustering properties of z {approx} 5.7 Ly{alpha} emitters (LAEs) in a cosmological reionization simulation with a full Ly{alpha} radiative transfer calculation. Ly{alpha} radiative transfer substantially modifies the intrinsic Ly{alpha} emission properties, compared to observed ones, depending on the density and velocity structure environment around the Ly{alpha}-emitting galaxy. This environment-dependent Ly{alpha} selection introduces new features in LAE clustering, suppressing (enhancing) the line-of-sight (transverse) density fluctuations and giving rise to scale-dependent galaxy bias. In real space, the contours of the three-dimensional two-point correlation function of LAEs appear to be prominently elongated along the line of sight on large scales, an effect that is opposite to and much stronger than the linear redshift-space distortion effect. The projected two-point correlation function is greatly enhanced in amplitude by a factor of up to a few, compared to the case without the environment-dependent selection effect. The new features in LAE clustering can be understood with a simple, physically motivated model, where Ly{alpha} selection depends on matter density, velocity, and their gradients. We discuss the implications and consequences of the effects on galaxy clustering from Ly{alpha} selection in interpreting clustering measurements and in constraining cosmology and reionization from LAEs.

  19. A SUCCESSFUL BROADBAND SURVEY FOR GIANT Ly{alpha} NEBULAE. II. SPECTROSCOPIC CONFIRMATION

    SciTech Connect

    Prescott, Moire K. M.; Dey, Arjun; Jannuzi, Buell T.

    2013-01-01

    Using a systematic broadband search technique, we have carried out a survey for large Ly{alpha} nebulae (or Ly{alpha} {sup b}lobs{sup )} at 2 {approx}< z {approx}< 3 within 8.5 deg{sup 2} of the NOAO Deep Wide-Field Survey Booetes field, corresponding to a total survey comoving volume of Almost-Equal-To 10{sup 8} h {sup -3} {sub 70} Mpc{sup 3}. Here, we present our spectroscopic observations of candidate giant Ly{alpha} nebulae. Of 26 candidates targeted, 5 were confirmed to have Ly{alpha} emission at 1.7 {approx}< z {approx}< 2.7, 4 of which were new discoveries. The confirmed Ly{alpha} nebulae span a range of Ly{alpha} equivalent widths, colors, sizes, and line ratios, and most show spatially extended continuum emission. The remaining candidates did not reveal any strong emission lines, but instead exhibit featureless, diffuse, blue continuum spectra. Their nature remains mysterious, but we speculate that some of these might be Ly{alpha} nebulae lying within the redshift desert (i.e., 1.2 {approx}< z {approx}< 1.6). Our spectroscopic follow-up confirms the power of using deep broadband imaging to search for the bright end of the Ly{alpha} nebula population across enormous comoving volumes.

  20. Extended Ly-alpha emission associated with 3C 294

    NASA Technical Reports Server (NTRS)

    Mccarthy, Patrick J.; Spinrad, Hyron; Dickinson, Mark; Van Breugel, Wil; Liebert, James; Djorgovski, S.; Eisenhardt, Peter

    1990-01-01

    Optical, IR, and radio observations of the powerful radio source 3C 294, which is surrounded by a large cloud of ionized gas, are presented. The galaxy is faint in the rest-frame UV, yet has a near-IR luminosity that is typical of radio galaxies at redshifts of order two. In contrast to the large extent of the ionized gas, the K-band image is quite compact. The emission-line cloud is closely aligned with the radio source axis and has an ionization state indicative of ionization by a nonstellar source. The velocity field of the gas has both large ordered motions and large turbulent components. The total mass required to keep the gas bound to the system is comparable to present-day massive galaxies and their halos. The velocity fields of the high-ionization lines are systematically different from Ly-alpha in a manner that is not easily understood.

  1. A Ly{alpha} GALAXY AT REDSHIFT z = 6.944 IN THE COSMOS FIELD

    SciTech Connect

    Rhoads, James E.; Hibon, Pascale; Malhotra, Sangeeta; Cooper, Michael; Weiner, Benjamin E-mail: James.Rhoads@asu.edu E-mail: m.cooper@uci.edu

    2012-06-20

    Ly{alpha} emitting galaxies can be used to study cosmological reionization, because a neutral intergalactic medium (IGM) scatters Ly{alpha} photons into diffuse halos whose surface brightness falls below typical survey detection limits. Here, we present the Ly{alpha} emitting galaxy LAE J095950.99+021219.1, identified at redshift z = 6.944 in the COSMOS field using narrowband imaging and follow-up spectroscopy with the IMACS instrument on the Magellan I Baade telescope. With a single object spectroscopically confirmed so far, our survey remains consistent with a wide range of IGM neutral fraction at z Almost-Equal-To 7, but further observations are planned and will help clarify the situation. Meantime, the object we present here is only the third Ly{alpha}-selected galaxy to be spectroscopically confirmed at z {approx}> 7, and is {approx}2-3 times fainter than the previously confirmed z Almost-Equal-To 7 Ly{alpha} galaxies.

  2. Ly(alpha) Photolysis in the Primitive Solar Nebula

    NASA Astrophysics Data System (ADS)

    Gladstone, G. Randall

    1998-01-01

    This is the final report for the third year of work on this project. Our proposal was to quantitatively investigate the importance of photochemistry in the solar nebula. In the generally accepted theory for the chemical evolution of the primitive solar nebula, Prinn and Fegley argued that photochemistry is unimportant, and that thermochemistry controls the relative abundances of molecular species throughout the planet-forming region. They provided useful estimates of the chemical energy available to the solar nebula from a variety of sources, and established that even the small photolysis rate due to starlight is more important than the photolysis rate from direct sunlight (although small, the UV flux from starlight could have processed a non-negligible fraction of the solar nebula. The reason for this is that the opacity of the disk was so large that direct sunlight could only penetrate to 0.1 AU or so, despite the expectation that the protosun, if comparable to a T-Tauri star, would be emitting up to 104 more H I Ly(alpha) photons than the current sun. We developed a Monte Carlo resonance fine radiative transfer code, capable of accurately calculating the radiation field of H I Ly(alpha), He I 584 A, and He II 304 A emissions throughout the nebula and the nearby interstellar medium in which it is embedded. We applied the code to two appropriate models of the primitive solar nebula. Our model provided the photolysis rates of various species over the entire surface layer of the nebula, and from this we evaluated the importance of UV photochemistry due to backscattered solar UV resonance line emissions on different parts of the nebula. The results discussed below were presented.

  3. Ly(alpha) Photolysis in the Primitive Solar Nebula

    NASA Technical Reports Server (NTRS)

    Gladstone, G. Randall

    1998-01-01

    This is the final report for the third year of work on this project. Our proposal was to quantitatively investigate the importance of photochemistry in the solar nebula. In the generally accepted theory for the chemical evolution of the primitive solar nebula, Prinn and Fegley argued that photochemistry is unimportant, and that thermochemistry controls the relative abundances of molecular species throughout the planet-forming region. They provided useful estimates of the chemical energy available to the solar nebula from a variety of sources, and established that even the small photolysis rate due to starlight is more important than the photolysis rate from direct sunlight (although small, the UV flux from starlight could have processed a non-negligible fraction of the solar nebula. The reason for this is that the opacity of the disk was so large that direct sunlight could only penetrate to 0.1 AU or so, despite the expectation that the protosun, if comparable to a T-Tauri star, would be emitting up to 10(exp 4) more H I Ly(alpha) photons than the current sun. We developed a Monte Carlo resonance fine radiative transfer code, capable of accurately calculating the radiation field of H I Ly(alpha), He I 584 A, and He II 304 A emissions throughout the nebula and the nearby interstellar medium in which it is embedded. We applied the code to two appropriate models of the primitive solar nebula. Our model provided the photolysis rates of various species over the entire surface layer of the nebula, and from this we evaluated the importance of UV photochemistry due to backscattered solar UV resonance line emissions on different parts of the nebula. The results discussed below were presented.

  4. THE UV-CONTINUUM PROPERTIES OF Ly{alpha}-SELECTED GALAXIES AT z = 6.5

    SciTech Connect

    Cowie, Lennox L.; Hu, Esther M.; Songaila, Antoinette E-mail: acowie@ifa.hawaii.edu

    2011-07-10

    We report the first space-based very deep near-infrared continuum observations of a uniform sample of z = 6.5 galaxies with log(L(Ly{alpha})) = 42.5-43 erg s{sup -1} selected from narrowband line searches and with spectroscopically confirmed Ly{alpha} emission. The 1.4 {mu}m Hubble Space Telescope WFC3 observations are deep enough (AB(1{sigma}) = 28.75) to measure individual continuum magnitudes at this redshift for all of the objects. We compare the results with continuum-selected samples at the same redshift and find that Ly{alpha} emission is present in 24% of all galaxies with M{sub AB}(1350 A) < -20 at z = 6.5. The error in this quantity is dominated by systematic uncertainties, which could be as large as multiplicative factors of three. The Ly{alpha} galaxies are extended but small (size <1 kpc), and have star formation rates of approximately 10 M{sub sun} yr{sup -1}. We find a mean L(Ly{alpha})/{nu}L{sub {nu}} at 1400 A to be 0.08, with the seven objects showing a range from 0.026 to 0.26, implying that there is little sign of destruction of the Ly{alpha} line. All of the properties of the z = 6.5 sample appear to be very similar to those of Ly{alpha} emitters at lower redshifts.

  5. Ly{alpha} DOMINANCE OF THE CLASSICAL T TAURI FAR-ULTRAVIOLET RADIATION FIELD

    SciTech Connect

    Schindhelm, Eric; France, Kevin; Brown, Alexander; Herczeg, Gregory J.; Bergin, Edwin; Yang Hao; Brown, Joanna M.; Linsky, Jeffrey L.; Valenti, Jeff

    2012-09-01

    Far-ultraviolet (FUV) radiation plays an important role in determining chemical abundances in protoplanetary disks. H I Lyman {alpha} (Ly{alpha}) is suspected to be the dominant component of the FUV emission from Classical T Tauri Stars (CTTSs), but is difficult to measure directly due to circumstellar and interstellar H I absorption. To better characterize the intrinsic Ly{alpha} radiation, we present FUV spectra of 14 CTTSs taken with the Hubble Space Telescope Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph instruments. H{sub 2} fluorescence, commonly seen in the spectra of CTTSs, is excited by Ly{alpha} photons, providing an indirect measure of the Ly{alpha} flux incident upon the warm disk surface. We use observed H{sub 2} progression fluxes to reconstruct the CTTS Ly{alpha} profiles. The Ly{alpha} flux correlates with total measured FUV flux, in agreement with an accretion-related source of FUV emission. With a geometry-independent analysis, we confirm that in accreting T Tauri systems Ly{alpha} radiation dominates the FUV flux ({approx}1150 A -1700 A). In the systems surveyed this one line comprises 70%-90% of the total FUV flux.

  6. COMPUTING INTRINSIC LY{alpha} FLUXES OF F5 V TO M5 V STARS

    SciTech Connect

    Linsky, Jeffrey L.; France, Kevin; Ayres, Tom

    2013-04-01

    The Ly{alpha} emission line dominates the far-ultraviolet spectra of late-type stars and is a major source for photodissociation of important molecules including H{sub 2}O, CH{sub 4}, and CO{sub 2} in exoplanet atmospheres. The incident flux in this line illuminating an exoplanet's atmosphere cannot be measured directly as neutral hydrogen in the interstellar medium (ISM) attenuates most of the flux reaching the Earth. Reconstruction of the intrinsic Ly{alpha} line has been accomplished for a limited number of nearby stars, but is not feasible for distant or faint host stars. We identify correlations connecting the intrinsic Ly{alpha} flux with the flux in other emission lines formed in the stellar chromosphere, and find that these correlations depend only gradually on the flux in the other lines. These correlations, which are based on Hubble Space Telescope spectra, reconstructed Ly{alpha} line fluxes, and irradiance spectra of the quiet and active Sun, are required for photochemical models of exoplanet atmospheres when intrinsic Ly{alpha} fluxes are not available. We find a tight correlation of the intrinsic Ly{alpha} flux with stellar X-ray flux for F5 V to K5 V stars, but much larger dispersion for M stars. We also show that knowledge of the stellar effective temperature and rotation rate can provide reasonably accurate estimates of the Ly{alpha} flux for G and K stars, and less accurate estimates for cooler stars.

  7. Ly(alpha) emission and absorption features in the spectra of galaxies

    NASA Technical Reports Server (NTRS)

    Chen, W. L.; Neufeld, David A.

    1994-01-01

    The combined effects of interstellar dust absorption and of scattering by hydrogen atoms may give rise to a Ly(alpha) spectral feature of negative equivalent width, as has been observed in several star-forming galaxies. By considering the transfer of Ly(alpha) line radiation and of neighboring stellar continuum radiation within a dusty galaxy, we find that dust absorption has three effects: (1) it reduces the apparent ultraviolet continuum luminosity at all wavelengths; (2) it preferentially decreases the apparent Ly(alpha) line luminosity from H II regions; and (3) it creates an 'attenuation feature' in the continuum spectrum -- centered at the Ly(alpha) rest frequency -- which occurs because the attenuation of the stellar continuum radiation increases as the Ly(alpha) rest frequency is approached, due to the effects of scattering by hydrogen atoms. For plausible values of the galactic dust content and of the disk thickness, these effects can lead to a negative net Ly(alpha) equivalent width, even for galaxies in which the unattenuated spectrum would show a strong Ly(alpha) emission line.

  8. HUBBLE SPACE TELESCOPE NARROWBAND SEARCH FOR EXTENDED Ly{alpha} EMISSION AROUND TWO z > 6 QUASARS

    SciTech Connect

    Decarli, Roberto; Walter, Fabian; Yang Yujin; Hennawi, Joseph F.; Rix, Hans-Walter; Venemans, Bram P.; Carilli, Chris L.; Fan Xiahoui; Kurk, Jaron; Riechers, Dominik; Strauss, Michael A.

    2012-09-10

    We search for extended Ly{alpha} emission around two z > 6 quasars, SDSS J1030+0524 (z = 6.309) and SDSS J1148+5251 (z = 6.419) using Wide Field Camera 3 narrowband filters on board the Hubble Space Telescope. For each quasar, we collected two deep, narrowband images, one sampling the Ly{alpha} line+continuum at the quasar redshifts and one of the continuum emission redward of the line. After carefully modeling the point-spread function, we find no evidence for extended Ly{alpha} emission. These observations set 2{sigma} limits of L(Ly{alpha}, extended) <3.2 Multiplication-Sign 10{sup 44} erg s{sup -1} for J1030+0524 and L(Ly{alpha}, extended) <2.5 Multiplication-Sign 10{sup 44} erg s{sup -1} for J1148+5251. Given the star formation rates typically inferred from (rest-frame) far-infrared measurements of z {approx} 6 quasars, these limits are well below the intrinsic bright Ly{alpha} emission expected from the recombination of gas photoionized by the quasars or by the star formation in the host galaxies, and point toward significant Ly{alpha} suppression or dust attenuation. However, small extinction values have been observed along the line of sight to the nuclei, thus reddening has to be coupled with other mechanisms for Ly{alpha} suppression (e.g., resonance scattering). No Ly{alpha} emitting companions are found, down to a 5{sigma} sensitivity of {approx}1 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} arcsec{sup -2} (surface brightness) and {approx}5 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} (assuming point sources).

  9. THE LUMINOSITY FUNCTION OF Ly{alpha} EMITTERS AT REDSHIFT z = 7.7

    SciTech Connect

    Tilvi, Vithal; Rhoads, James E.; Hibon, Pascale; Malhotra, Sangeeta; Wang Junxian; Veilleux, Sylvain; Swaters, Rob; Krug, Hannah; Probst, Ron; Dickinson, Mark; Finkelstein, Steven L.

    2010-10-01

    Ly{alpha} emission lines should be attenuated in a neutral intergalactic medium. Therefore, the visibility of Ly{alpha} emitters at high redshifts can serve as a valuable probe of reionization at about the 50% level. We present an imaging search for z = 7.7 Ly{alpha} emitting galaxies using an ultra-narrowband filter (filter width = 9 A) on the NEWFIRM imager at the Kitt Peak National Observatory. We found four candidate Ly{alpha} emitters in a survey volume of 1.4x10{sup 4} Mpc{sup 3}, with a line flux brighter than 6 x 10{sup -18} erg cm{sup -2} s{sup -1} (5{sigma} in 2'' aperture). We also performed a detailed Monte Carlo simulation incorporating the instrumental effects to estimate the expected number of Ly{alpha} emitters in our survey and found that we should expect to detect one Ly{alpha} emitter, assuming a non-evolving Ly{alpha} luminosity function (LF) between z = 6.5 and z = 7.7. Even if one of the present candidates is spectroscopically confirmed as a z {approx} 8 Ly{alpha} emitter, it would indicate that there is no significant evolution of the Ly{alpha} LF from z = 3.1 to z {approx} 8. While firm conclusions would need both spectroscopic confirmations and larger surveys to boost the number counts of galaxies, we successfully demonstrate the feasibility of sensitive near-infrared (1.06 {mu}m) narrowband searches using custom filters designed to avoid the OH emission lines that make up most of the sky background.

  10. WERE PROGENITORS OF LOCAL L* GALAXIES Ly{alpha} EMITTERS AT HIGH REDSHIFT?

    SciTech Connect

    Yajima, Hidenobu; Li Yuexing; Zhu Qirong; Gronwall, Caryl; Ciardullo, Robin; Abel, Tom

    2012-08-01

    The Ly{alpha} emission has been observed from galaxies over a redshift span z {approx} 0-8.6. However, the evolution of high-redshift Ly{alpha} emitters (LAEs), and the link between these populations and local galaxies, remains poorly understood. Here, we investigate the Ly{alpha} properties of progenitors of a local L* galaxy by combining cosmological hydrodynamic simulations with three-dimensional radiative transfer calculations using the new ART{sup 2} code. We find that the main progenitor (the most massive one) of a Milky-Way-like galaxy has a number of Ly{alpha} properties close to those of observed LAEs at z {approx} 2-6, but most of the fainter ones appear to fall below the detection limits of current surveys. The Ly{alpha} photon escape fraction depends sensitively on a number of physical properties of the galaxy, such as mass, star formation rate, and metallicity, as well as galaxy morphology and orientation. Moreover, we find that high-redshift LAEs show blueshifted Ly{alpha} line profiles characteristic of gas inflow, and that the Ly{alpha} emission by excitation cooling increases with redshift, and becomes dominant at z {approx}> 6. Our results suggest that some observed LAEs at z {approx} 2-6 with luminosity of L{sub Ly{alpha}} {approx} 10{sup 42}-10{sup 43} erg s{sup -1} may be similar to the main progenitor of the Milky Way at high redshift, and that they may evolve into present-day L* galaxies.

  11. A SUCCESSFUL BROADBAND SURVEY FOR GIANT Ly{alpha} NEBULAE. I. SURVEY DESIGN AND CANDIDATE SELECTION

    SciTech Connect

    Prescott, Moire K. M.; Dey, Arjun; Jannuzi, Buell T.

    2012-04-01

    Giant Ly{alpha} nebulae (or Ly{alpha} 'blobs') are likely sites of ongoing massive galaxy formation, but the rarity of these powerful sources has made it difficult to form a coherent picture of their properties, ionization mechanisms, and space density. Systematic narrowband Ly{alpha} nebula surveys are ongoing, but the small redshift range covered and the observational expense limit the comoving volume that can be probed by even the largest of these surveys and pose a significant problem when searching for such rare sources. We have developed a systematic search technique designed to find large Ly{alpha} nebulae at 2 {approx}< z {approx}< 3 within deep broadband imaging and have carried out a survey of the 9.4 deg{sup 2} NOAO Deep Wide-Field Survey Booetes field. With a total survey comoving volume of Almost-Equal-To 10{sup 8} h{sup -3}{sub 70} Mpc{sup 3}, this is the largest volume survey for Ly{alpha} nebulae ever undertaken. In this first paper in the series, we present the details of the survey design and a systematically selected sample of 79 candidates, which includes one previously discovered Ly{alpha} nebula.

  12. An IUE survey of interstellar H I Ly alpha absorption. 1: Column densities

    NASA Technical Reports Server (NTRS)

    Diplas, Athanassios; Savage, Blair D.

    1994-01-01

    We measure Galactic interstellar neutral hydrogen column densities by analyzing archival interstellar Ly alpha absorption line data toward 554 B2 and hotter stars observed at high resolution with the IUE satellite. This study more than doubles the number of lines of sight with measures of N(H I) based on Ly alpha. We have included the scattered light background correction algorithm of Bianchi and Bohlin in our data reduction. We use the correlation between the Balmer discontinuity (c sub 1) index and the stellar Ly alpha absorption in order to assess the effects of stellar Ly alpha contamination. Approximately 40% of the B stars with measured (c sub 1) index, exhibit serious stellar Ly alpha contamination. One table contains the derived values of the interstellar N(H I) for 393 stars with at most small amounts of stellar contamination. Another lists the observed values of total N(H I) for 161 stars with suspected stellar Ly alpha contamination and/or uncertain stellar parameters.

  13. X-RAY CONSTRAINTS ON THE Ly{alpha} ESCAPE FRACTION

    SciTech Connect

    Zheng Zhenya; Wang Junxian; Malhotra, Sangeeta; Rhoads, James E.; Finkelstein, Steven L.; Gawiser, Eric; Gronwall, Caryl; Ciardullo, Robin; Guaita, Lucia; Nilsson, Kim K.

    2012-02-10

    We have co-added the X-ray flux of all known Ly{alpha} emitters (LAEs) in the 4 Ms Chandra Deep Field South (CDF-S) region, achieving the tightest upper limits yet on the X-ray to Ly{alpha} ratio. We use the X-ray data to place sensitive upper limits on the average unobscured star formation rate (SFR{sub X}) in these galaxies. A very small fraction of Ly{alpha} galaxies in the field are individually detected in the X-rays, implying a low fraction of active galactic nucleus activity. After excluding the few X-ray-detected LAEs, we stack the undetected LAEs located in the 4 Ms CDF-S data and 250 ks Extended CDF-S (ECDF-S) data, and compute a 1{sigma} upper limit on SFR{sub X} < 1.6, 14, 28, 28, 140, 440, 880 M{sub Sun} yr{sup -1} for LAEs located at z {approx} 0.3 and z = 2.1, 3.1, 3.2, 4.5, 5.7, and 6.5, respectively. The upper limit of SFR{sub X} in LAEs can be then compared to SFR{sub Ly{alpha}} derived from Ly{alpha} line and thus can constrain on the Ly{alpha} escape fraction (f{sup Esc}{sub Ly{alpha}}). The f{sup Esc}{sub Ly{alpha}} from X-ray at z {approx} 0.3 is substantially larger than that from UV or H{alpha}. Three X-ray-detected LAE galaxies at z {approx} 0.3 show f{sup Esc}{sub Ly{alpha}} {approx} 3%-22%, and the average Ly{alpha} escape fraction from stacking the X-ray-undetected LAEs show f{sup Esc}{sub Ly{alpha}} > 28% at 3{sigma} significance level at the same redshift. We derive a lower limit on f{sup Esc}{sub Ly{alpha}} > 14% (84% confidence level, 1{sigma} lower limit) for LAEs at redshift z {approx} 2.1 and z {approx} 3.1-3.2. At z > 4, the current LAE samples are not of sufficient size to constrain SFR{sub X} well. By averaging all the LAEs at z > 2, the X-ray non-detection constrains f{sup Esc}{sub Ly{alpha}} > 17% (84% confidence level, 1{sigma} lower limit), and rejects f{sup Esc}{sub Ly{alpha}} < 5.7% at the 99.87% confidence level from 2.1 < z < 6.5.

  14. The Ly(alpha) Line Profiles of Ultraluminous Infrared Galaxies: Fast Winds and Lyman Continuum Leakage

    NASA Technical Reports Server (NTRS)

    Martin, Crystal L.; Dijkstra, Mark; Henry, Alaina L.; Soto, Kurt T.; Danforth, Charles W.; Wong, Joseph

    2015-01-01

    We present new Hubble Space Telescope Cosmic Origins Spectrograph far-ultraviolet (far-UV) spectroscopy and Keck Echellete optical spectroscopy of 11 ultraluminous infrared galaxies (ULIRGs), a rare population of local galaxies experiencing massive gas inflows, extreme starbursts, and prominent outflows. We detect Ly(alpha) emission from eight ULIRGs and the companion to IRAS09583+4714. In contrast to the P Cygni profiles often seen in galaxy spectra, the Ly(alpha) profiles exhibit prominent, blueshifted emission out to Doppler shifts exceeding -1000 km/s in three H II-dominated and two AGN-dominated ULIRGs. To better understand the role of resonance scattering in shaping the Ly(alpha) line profiles, we directly compare them to non-resonant emission lines in optical spectra. We find that the line wings are already present in the intrinsic nebular spectra, and scattering merely enhances the wings relative to the line core. The Ly(alpha) attenuation (as measured in the COS aperture) ranges from that of the far-UV continuum to over 100 times more. A simple radiative transfer model suggests the Ly(alpha) photons escape through cavities which have low column densities of neutral hydrogen and become optically thin to the Lyman continuum in the most advanced mergers. We show that the properties of the highly blueshifted line wings on the Ly(alpha) and optical emission-line profiles are consistent with emission from clumps of gas condensing out of a fast, hot wind. The luminosity of the Ly(alpha) emission increases nonlinearly with the ULIRG bolometric luminosity and represents about 0.1-1% of the radiative cooling from the hot winds in the H II-dominated ULIRGs.

  15. INTENSITY MAPPING OF Ly{alpha} EMISSION DURING THE EPOCH OF REIONIZATION

    SciTech Connect

    Silva, Marta B.; Santos, Mario G.; Gong, Yan; Cooray, Asantha; Bock, James

    2013-02-15

    We calculate the absolute intensity and anisotropies of the Ly{alpha} radiation field present during the epoch of reionization. We consider emission from both galaxies and the intergalactic medium (IGM) and take into account the main contributions to the production of Ly{alpha} photons: recombinations, collisions, continuum emission from galaxies, and scattering of Lyn photons in the IGM. We find that the emission from individual galaxies dominates over the IGM with a total Ly{alpha} intensity (times frequency) of about (1.43-3.57) Multiplication-Sign 10{sup -8} erg s{sup -1} cm{sup -2} sr{sup -1} at a redshift of 7. This intensity level is low, so it is unlikely that the Ly{alpha} background during reionization can be established by an experiment aiming at an absolute background light measurement. Instead, we consider Ly{alpha} intensity mapping with the aim of measuring the anisotropy power spectrum that has rms fluctuations at the level of 1 Multiplication-Sign 10{sup -16} [erg s{sup -1} cm{sup -2} sr{sup -1}]{sup 2} at a few Mpc scales. These anisotropies could be measured with a spectrometer at near-IR wavelengths from 0.9 to 1.4 {mu}m with fields in the order of 0.5 to 1 deg{sup 2}. We recommend that existing ground-based programs using narrowband filters also pursue intensity fluctuations to study statistics on the spatial distribution of faint Ly{alpha} emitters. We also discuss the cross-correlation signal with 21 cm experiments that probe H I in the IGM during reionization. A dedicated sub-orbital or space-based Ly{alpha} intensity mapping experiment could provide a viable complimentary approach to probe reionization, when compared to 21 cm experiments, and is likely within experimental reach.

  16. FILAMENTARY LARGE-SCALE STRUCTURE TRACED BY SIX Ly{alpha} BLOBS AT z = 2.3

    SciTech Connect

    Erb, Dawn K.; Bogosavljevic, Milan; Steidel, Charles C.

    2011-10-10

    Extended nebulae of Ly{alpha} emission ('Ly{alpha} blobs') are known to be associated with overdense regions at high redshift. Here we present six large Ly{alpha} blobs in a previously known protocluster with galaxy overdensity {delta} {approx} 7 at z = 2.3; this is the richest field of giant Ly{alpha} blobs detected to date. The blobs have linear sizes of {approx}> 100 kpc and Ly{alpha} luminosities of {approx}10{sup 43} erg s{sup -1}. The positions of the blobs define two linear filaments with an extent of at least 12 comoving Mpc; these filaments intersect at the center of one of the blobs. Measurement of the position angles of the blobs indicates that five of the six are aligned with these filaments to within {approx}10{sup 0}, suggesting a connection between the physical processes powering extended Ly{alpha} emission and those driving structure on larger scales.

  17. Confirmation of a Steep Luminosity Function for Ly alpha Emitters at z 5.7: a Major Component of Reionization

    NASA Technical Reports Server (NTRS)

    Dressler, Alan; Henry, Alaina L.; Martin, Crystal L.; Sawicki, Marcin; McCarthy, Patrick; Villaneuva, Edward

    2014-01-01

    We report the first direct and robust measurement of the faint-end slope of the Ly-alpha emitter (LAE) luminosity function at z = 5.7. Candidate LAEs from a low-spectral-resolution blind search with IMACS on Magellan- Baade were targeted at higher resolution to distinguish high redshift LAEs from foreground galaxies. All but 2 of our 42 single-emission-line systems are fainter than F = 2.0×10(exp-17) ergs s(exp-1) cm(exp-2), making these the faintest emission-lines observed for a z = 5.7 sample with known completeness, an essential property for determining the faint end slope of the LAE luminosity function. We find 13 LAEs as compared to 29 foreground galaxies, in very good agreement with the modeled foreground counts predicted in Dressler et al. (2011a) that had been used to estimate a faint-end slope of alpha = -2.0 for the LAE luminosity function. A 32% LAE fraction, LAE/(LAE+foreground) within the flux interval F = 2-20 × 10(exp-18) ergs s(exp-1) cm(exp-2) constrains the faint end slope of the luminosity function to -1.95 greater than alpha greater than -2.35 (1 delta). We show how this steep LF should provide, to the limit of our observations, more than 20% of the flux necessary to maintain ionization at z = 5.7, with a factor-of-ten extrapolation in flux reaching more than 55%. We suggest that this bodes well for a comparable contribution by similar, low-mass star forming galaxies at higher-redshift - within the reionization epoch at z greater than approximately 7, only 250 Myr earlier - and that such systems provide a substantial, if not dominant, contribution to the late-stage reionization of the IGM.

  18. PROFILES OF Ly{alpha} EMISSION LINES OF THE EMITTERS AT z = 3.1

    SciTech Connect

    Yamada, T.; Morimoto, N.; Matsuda, Y.; Kousai, K.; Hayashino, T.; Umemura, M.

    2012-05-20

    We present the results of the observations of the Ly{alpha} line profiles of 91 emission-line galaxies at z = 3.1 with a spectral resolution of {lambda}/{delta}{lambda}(FWHM) Almost-Equal-To 1700 or 180 km s{sup -1}. A significant fraction of {approx}50% of the observed objects show the characteristic double peaks in their Ly{alpha} profile. The red peak is much stronger than the blue one for most of the cases. The red peaks themselves also show weak but significant asymmetry and their widths are correlated with the velocity separation of the red and the blue peaks. This implies that the peaks are not isolated multiple components with different velocities but parts of a single line that are modified by the absorption and/or scattering by the associated neutral hydrogen gas. The characteristic profile can be naturally explained by scattering in the expanding shell of the neutral hydrogen surrounding the Ly{alpha} emitting region while the attenuation by the intergalactic medium should also be considered. Our results suggest that the star formation in these Ly{alpha} emitters are dominated by young burst-like events that produce the intrinsic Ly{alpha} emission as well as the gas outflow.

  19. Ly{alpha} RADIATIVE TRANSFER IN COSMOLOGICAL SIMULATIONS USING ADAPTIVE MESH REFINEMENT

    SciTech Connect

    Laursen, Peter; Razoumov, Alexei O.; Sommer-Larsen, Jesper E-mail: razoumov@ap.smu.ca

    2009-05-01

    A numerical code for solving various Ly{alpha} radiative transfer (RT) problems is presented. The code is suitable for an arbitrary, three-dimensional distribution of Ly{alpha} emissivity, gas temperature, density, and velocity field. Capable of handling Ly{alpha} RT in an adaptively refined grid-based structure, it enables detailed investigation of the effects of clumpiness of the interstellar (or intergalactic) medium. The code is tested against various geometrically and physically idealized configurations for which analytical solutions exist, and subsequently applied to three different simulated high-resolution 'Lyman-break galaxies', extracted from high-resolution cosmological simulations at redshift z = 3.6. Proper treatment of the Ly{alpha} scattering reveals a diversity of surface brightness (SB) and line profiles. Specifically, for a given galaxy the maximum observed SB can vary by an order of magnitude, and the total flux by a factor of 3-6, depending on the viewing angle. This may provide an explanation for differences in observed properties of high-redshift galaxies, and in particular a possible physical link between Lyman-break galaxies and regular Ly{alpha} emitters.

  20. POLARIZED EXTENDED Ly{alpha} EMISSION FROM A z = 2.3 RADIO GALAXY

    SciTech Connect

    Humphrey, A.; Vernet, J.; Fosbury, R. A. E.; Villar-Martin, M.; Di Serego Alighieri, S.; Cimatti, A.

    2013-05-01

    We present spatially resolved spectropolarimetric measurements of the 100 kpc scale gaseous environment of the z = 2.34 radio galaxy TXS 0211-122. The polarization level of the narrow Ly{alpha} emission is low centrally (P < 5%), but rises to P = 16.4% {+-} 4.6% in the eastern part of the nebula, indicating that the nebula is at least partly powered by the scattering of Ly{alpha} photons by H I. Not only is this the first detection of polarized Ly{alpha} around a radio-loud active galaxy, it is also the second detection to date for any kind of Ly{alpha} nebula. We also detect a pair of diametrically opposed UV continuum sources along the slit, at the outer edges of the Ly{alpha} nebula, which we suggest may be the limb of a dusty shell, related to the large-scale H I absorbers often associated with high-z radio galaxies.

  1. DIFFUSE Ly{alpha} EMITTING HALOS: A GENERIC PROPERTY OF HIGH-REDSHIFT STAR-FORMING GALAXIES

    SciTech Connect

    Steidel, Charles C.; Bogosavljevic, Milan; Shapley, Alice E.; Kollmeier, Juna A.; Reddy, Naveen A.; Erb, Dawn K.; Pettini, Max

    2011-08-01

    Using a sample of 92 UV continuum-selected, spectroscopically identified galaxies with (z) = 2.65, all of which have been imaged in the Ly{alpha} line with extremely deep narrow-band imaging, we examine galaxy Ly{alpha} emission profiles to very faint surface brightness limits. The galaxy sample is representative of spectroscopic samples of Lyman break galaxies (LBGs) at similar redshifts in terms of apparent magnitude, UV luminosity, inferred extinction, and star formation rate and was assembled without regard to Ly{alpha} emission properties. Approximately 45% (55%) of the galaxy spectra have Ly{alpha} appearing in net absorption (emission), with {approx_equal} 20% satisfying commonly used criteria for the identification of 'Ly{alpha} emitters' (LAEs; W{sub 0}(Ly{alpha}) {>=} 20 A). We use extremely deep stacks of rest-UV continuum and continuum-subtracted Ly{alpha} images to show that all sub-samples exhibit diffuse Ly{alpha} emission to radii of at least 10'' ({approx}80 physical kpc). The characteristic exponential scale lengths for Ly{alpha} line emission exceed that of the {lambda}{sub 0} = 1220 A UV continuum light by factors of {approx}5-10. The surface brightness profiles of Ly{alpha} emission are strongly suppressed relative to the UV continuum light in the inner few kpc, by amounts that are tightly correlated with the galaxies' observed spectral morphology; however, all galaxy sub-subsamples, including that of galaxies for which Ly{alpha} appears in net absorption in the spectra, exhibit qualitatively similar diffuse Ly{alpha} emission halos. Accounting for the extended Ly{alpha} emission halos, which generally would not be detected in the slit spectra of individual objects or with typical narrow-band Ly{alpha} imaging, increases the total Ly{alpha} flux (and rest equivalent width W{sub 0}(Ly{alpha})) by an average factor of {approx}5, and by a much larger factor for the 80% of LBGs not classified as LAEs. We argue that most, if not all, of the observed

  2. Measurement of the Relative Intensity of the Ly-(alpha) Lines in Fe 25+

    SciTech Connect

    Wong, K L; Beiersdorfer, P; Reed, K J; Osterheld, A L

    2002-06-18

    The intensity of the polarized Ly-{alpha}{sub 1} (2p{sub 3/2} {yields} 1s{sub 1/2}) transition has been measured relative to that of the unpolarized Ly-{alpha}{sub 2} (2p{sub 1/2} {yields} 1s{sub 1/2}) transition in Fe{sup 25+}. The measurements were made with the Livermore electron beam ion trap EBIT-II for beam energies from threshold to 2.5 times threshold. The results are compared to the corresponding intensity ratio predicted using excitation cross sections from distorted-wave calculations, which includes polarization, the M1(2s{sub 1/2} {yields} 1s{sub 1/2}) transition, and cascade contributions. Discrepancies are found that tend to confirm a recent report of a measurement of the Ly-{alpha} lines in Ti{sup 21+} performed on the Tokyo electron beam ion trap.

  3. AN ATLAS OF z = 5.7 AND z = 6.5 Ly{alpha} EMITTERS ,

    SciTech Connect

    Hu, E. M.; Cowie, L. L.; Barger, A. J.; Capak, P.; Kakazu, Y.; Trouille, L. E-mail: cowie@ifa.hawaii.ed E-mail: trouille@astro.wisc.ed E-mail: kakazu@astro.caltech.ed

    2010-12-10

    We present an atlas of 88 z {approx} 5.7 and 30 z {approx} 6.5 Ly{alpha} emitters obtained from a wide-field narrowband survey. We combined deep narrowband imaging in 120 A bandpass filters centered at 8150 A and 9140 A with deep BVRIz broadband imaging to select high-redshift galaxy candidates over an area of 4180 arcmin{sup 2}. The goal was to obtain a uniform selection of comparable depth over the seven targeted fields in the two filters. For the GOODS-North region of the Hubble Deep Field-North field, we also selected candidates using a 120 A filter centered at 9210 A. We made spectroscopic observations with Keck DEIMOS of nearly all the candidates to obtain the final sample of Ly{alpha} emitters. At the 3.3 A resolution of the DEIMOS observations the asymmetric profile for Ly{alpha} emission can be clearly seen in the spectra of nearly all the galaxies. We show that the spectral profiles are surprisingly similar for many of the galaxies and that the composite spectral profiles are nearly identical at z = 5.7 and z = 6.5. We analyze the distributions of line widths and Ly{alpha} equivalent widths and find that the lines are marginally narrower at the higher redshift, with median values of 0.77 A at z = 6.5 and 0.92 A at z = 5.7. The line widths have a dependence on the Ly{alpha} luminosity of the form {approx}L {sup 0.3}{sub {alpha}}. We compare the surface densities and the luminosity functions at the two redshifts and find that there is a multiplicative factor of two decrease in the number density of bright Ly{alpha} emitters from z = 5.7 to z = 6.5, while the characteristic luminosity is unchanged.

  4. NEW RESULTS FROM THE MAGELLAN IMACS SPECTROSCOPIC Ly{alpha} SURVEY: NICMOS OBSERVATIONS OF Ly{alpha} EMITTERS AT z = 5.7

    SciTech Connect

    Henry, Alaina L.; Martin, Crystal L.; Dressler, Alan; McCarthy, Patrick; Sawicki, Marcin

    2010-08-10

    We present NICMOS J {sub 110} (rest-frame 1200-2100 A) observations of the three z = 5.7 Ly{alpha} emitters discovered in the blind multislit spectroscopic survey by Martin et al. These images confirm the presence of the two sources that were previously only seen in spectroscopic observations. The third source, which is undetected in our J {sub 110} observations, has been detected in narrowband imaging of the Cosmic Origins Survey, so our non-detection implies a rest-frame equivalent width >146 A (3{sigma}). The two J {sub 110}-detected sources have more modest rest-frame equivalent widths of 30-40 A, but all three are typical of high-redshift Ly{alpha} emitters. In addition, the J {sub 110}-detected sources have UV luminosities that are within a factor of 2 of L*{sub UV}, and sizes that appear compact (r {sub hl{approx}} 0.''15) in our NIC2 images-consistent with a redshift of 5.7. We use these UV-continuum and Ly{alpha} measurements to estimate the i {sub 775}-z {sub 850} colors of these galaxies and show that at least one and possibly all three would be missed by the i-dropout Lyman break galaxy selection. These observations help demonstrate the utility of multislit narrowband spectroscopy as a technique for finding faint emission-line galaxies.

  5. Ly{alpha} EMISSION FROM HIGH-REDSHIFT SOURCES IN COSMOS

    SciTech Connect

    Mallery, Ryan P.; Mobasher, Bahram; Hemmati, Shoubaneh; Capak, Peter; Kakazu, Yuko; Masters, Dan; Scoville, Nick; Scarlata, Claudia; Salvato, Mara; McCracken, Henry

    2012-12-01

    We investigate spectroscopically measured Ly{alpha} equivalent widths (EWs) and escape fractions of 244 sources of which 95 are Lyman break galaxies (LBGs) and 106 Lyman alpha emitters (LAEs) at z {approx} 4.2, z {approx} 4.8, and z {approx} 5.6 selected from intermediate and narrowband observations. The sources were selected from the Cosmic Evolution Survey and observed with the DEIMOS spectrograph. We find that the distribution of EWs shows no evolution with redshift for both the LBG selected sources and the intermediate/narrowband LAEs. We also find that the Ly{alpha} escape fraction of intermediate/narrowband LAEs is on average higher and has a larger variation than the escape fraction of LBG selected sources. The escape fraction does not show a dependence with redshift. Similar to what has been found for LAEs at low redshifts, the sources with the highest extinctions show the lowest escape fractions. The range of escape fractions increases with decreasing extinction. This is evidence that the dust extinction is the most important factor affecting the escape of Ly{alpha} photons, but at low extinctions other factors, such as the H I covering fraction and gas kinematics, can be just as effective at inhibiting the escape of Ly{alpha} photons.

  6. CHEMISTRY OF A PROTOPLANETARY DISK WITH GRAIN SETTLING AND Ly{alpha} RADIATION

    SciTech Connect

    Fogel, Jeffrey K. J.; Bethell, Thomas J.; Bergin, Edwin A.; Calvet, Nuria; Semenov, Dmitry E-mail: tbethell@umich.edu E-mail: ncalvet@umich.edu

    2011-01-01

    We present results from a model of the chemical evolution of protoplanetary disks. In our models, we directly calculate the changing propagation and penetration of a high energy radiation field with Ly{alpha} radiation included. We also explore the effect on our models of including dust grain settling. We find that, in agreement with earlier studies, the evolution of dust grains plays a large role in determining how deep the UV radiation penetrates into the disk. Significant grain settling at the midplane leads to much smaller freeze-out regions and a correspondingly larger molecular layer, which leads to an increase in column density for molecular species such as CO, CN, and SO. The inclusion of Ly{alpha} radiation impacts the disk chemistry through specific species that have large photodissociation cross sections at 1216 A. These include HCN, NH{sub 3}, and CH{sub 4}, for which the column densities are decreased by an order of magnitude or more due to the presence of Ly{alpha} radiation in the UV spectrum. A few species, such as CO{sub 2} and SO, are enhanced by the presence of Ly{alpha} radiation, but rarely by more than a factor of a few.

  7. THE HANLE EFFECT OF Ly{alpha} IN A MAGNETOHYDRODYNAMIC MODEL OF THE SOLAR TRANSITION REGION

    SciTech Connect

    Stepan, J.; Trujillo Bueno, J.; Carlsson, M.; Leenaarts, J.

    2012-10-20

    In order to understand the heating of the solar corona it is crucial to obtain empirical information on the magnetic field in its lower boundary (the transition region). To this end, we need to measure and model the linear polarization produced by scattering processes in strong UV lines, such as the hydrogen Ly{alpha} line. The interpretation of the observed Stokes profiles will require taking into account that the outer solar atmosphere is highly structured and dynamic, and that the height of the transition region may well vary from one place in the atmosphere to another. Here, we report on the Ly{alpha} scattering polarization signals we have calculated in a realistic model of an enhanced network region, resulting from a state-of-the-art radiation magnetohydrodynamic simulation. This model is characterized by spatially complex variations of the physical quantities at transition region heights. The results of our investigation lead us to emphasize that scattering processes in the upper solar chromosphere should indeed produce measurable linear polarization in Ly{alpha}. More importantly, we show that via the Hanle effect the model's magnetic field produces significant changes in the emergent Q/I and U/I profiles. Therefore, we argue that by measuring the polarization signals produced by scattering processes and the Hanle effect in Ly{alpha} and contrasting them with those computed in increasingly realistic atmospheric models, we should be able to decipher the magnetic, thermal, and dynamic structure of the upper chromosphere and transition region of the Sun.

  8. COMPLETING THE CENSUS OF Ly{alpha} EMITTERS AT THE REIONIZATION EPOCH

    SciTech Connect

    Kashikawa, Nobunari; Iye, Masanori; Shimasaku, Kazuhiro; Okamura, Sadanori; Matsuda, Yuichi; Egami, Eiichi; Jiang, Linhua; Nagao, Tohru; Taniguchi, Yoshiaki; Shioya, Yasuhiro; Ouchi, Masami; Ota, Kazuaki; Malkan, Matthew A.; Hattori, Takashi; Ly, Chun; Furusawa, Hisanori; Shibuya, Takatoshi; Ishizaki, Yoshifumi; Toshikawa, Jun

    2011-06-20

    We carried out extended spectroscopic confirmations of Ly{alpha} emitters (LAEs) at z = 6.5 and 5.7 in the Subaru Deep Field. Now, the total number of spectroscopically confirmed LAEs is 45 and 54 at z = 6.5 and 5.7, respectively, and at least 81% (70%) of our photometric candidates at z = 6.5 (5.7) have been spectroscopically identified as real LAEs. We made careful measurements of the Ly{alpha} luminosity, both photometrically and spectroscopically, to accurately determine the Ly{alpha} and rest-UV luminosity functions (LFs). The substantially improved evaluation of the Ly{alpha} LF at z = 6.5 shows an apparent deficit from z = 5.7 at least at the bright end, and a possible decline even at the faint end, though small uncertainties remain. The rest-UV LFs at z = 6.5 and 5.7 are in good agreement, at least at the bright end, in clear contrast to the differences seen in the Ly{alpha} LF. These results imply an increase in the neutral fraction of the intergalactic medium from z = 5.7 to 6.5. The rest-frame equivalent width (EW{sub 0}) distribution at z = 6.5 seems to be systematically smaller than z = 5.7, and it shows an extended tail toward larger EW{sub 0}. The bright end of the rest-UV LF can be reproduced from the observed Ly{alpha} LF and a reasonable EW{sub 0}-UV luminosity relation. Integrating this rest-UV LF provides the first measurement of the contribution of LAEs to the photon budget required for reionization. The derived UV LF suggests that the fractional contribution of LAEs to the photon budget among Lyman break galaxies significantly increases toward faint magnitudes. Low-luminosity LAEs could dominate the ionizing photon budget, though this inference depends strongly on the uncertain faint-end slope of the Ly{alpha} LF.

  9. DUST EXTINCTION AND METALLICITIES OF STAR-FORMING Ly{alpha} EMITTING GALAXIES AT LOW REDSHIFT

    SciTech Connect

    Finkelstein, Steven L.; Papovich, Casey; Cohen, Seth H.; Malhotra, Sangeeta; Rhoads, James E.; Moustakas, John

    2011-06-01

    We present the results of an optical spectroscopic study of 12 GALEX-discovered star-forming Ly{alpha} emitting galaxies (LAEs) at z {approx} 0.3. We measure the emission-line fluxes from these galaxies by fitting their observed spectra to stellar population models in order to correct for underlying stellar absorption. We revisit earlier stellar population model fitting results, finding that excluding now-known active galactic nuclei lowers the typical stellar population age and stellar mass of this sample to {approx}300 Myr and {approx}4 x 10{sup 9} M{sub sun}, respectively. We calculate their dust extinction using the Balmer decrement, and find a typical visual attenuation of A{sub V} {approx} 0.3 mag, similar to that seen in some high-redshift LAEs. Comparing the ratios of Ly{alpha}/H{alpha} and the Ly{alpha} equivalent widths to the measured dust extinction, we find that the interstellar media (ISMs) in these objects appear to be neither enhancing nor seriously attenuating the Ly{alpha} equivalent widths, as would be the case in a quasi-clumpy ISM. Lastly, we perform a detailed analysis of the gas-phase metallicities of these galaxies, and we find that most galaxies in our sample have Z {approx}< 0.4 Z{sub sun}. We find that at a fixed stellar mass, these low-redshift LAE analogs are offset by {approx}0.3-0.6 dex lower metallicity from the general galaxy population at similar redshifts based on the local mass-metallicity relationship. This implies that galaxies with Ly{alpha} in emission may be systematically more metal-poor than star-forming galaxies at the same stellar mass and redshift, similar to preliminary results at z {approx} 2.

  10. WARM GAS IN THE VIRGO CLUSTER. I. DISTRIBUTION OF Ly{alpha} ABSORBERS

    SciTech Connect

    Yoon, Joo Heon; Putman, Mary E.; Bryan, Greg L.; Thom, Christopher; Chen, Hsiao-Wen

    2012-08-01

    The first systematic study of the warm gas (T = 10{sup 4-5} K) distribution across a galaxy cluster is presented using multiple background QSOs in and around the Virgo Cluster. We detect 25 Ly{alpha} absorbers (N{sub HI} = 10{sup 13.1-15.4} cm{sup -2}) in the Virgo velocity range toward 9 of 12 QSO sightlines observed with the Cosmic Origin Spectrograph, with a cluster impact parameter range of 0.36-1.65 Mpc (0.23-1.05 R{sub vir}). Including 18 Ly{alpha} absorbers previously detected by STIS or GHRS toward 7 of 11 background QSOs in and around the Virgo Cluster, we establish a sample of 43 absorbers toward a total of 23 background probes for studying the incidence of Ly{alpha} absorbers in and around the Virgo Cluster. With these absorbers, we find (1) warm gas is predominantly in the outskirts of the cluster and avoids the X-ray-detected hot intracluster medium (ICM). Also, Ly{alpha} absorption strength increases with cluster impact parameter. (2) Ly{alpha}-absorbing warm gas traces cold H I-emitting gas in the substructures of the Virgo Cluster. (3) Including the absorbers associated with the surrounding substructures, the warm gas covering fraction (100% for N{sub HI} > 10{sup 13.1} cm{sup -2}) is in agreement with cosmological simulations. We speculate that the observed warm gas is part of large-scale gas flows feeding the cluster both in the ICM and galaxies.

  11. LOGNORMAL INTENSITY DISTRIBUTION OF THE FAR-ULTRAVIOLET CONTINUUM BACKGROUND SHORTWARD OF Ly{alpha}

    SciTech Connect

    Seon, Kwang-Il

    2013-07-20

    The diffuse far-ultraviolet (FUV) continuum radiation 'longward' of Ly{alpha} (1216 A) is well known to correlate with the dust emission at 100 {mu}m. However, it has been claimed that the FUV continuum background 'shortward' of Ly{alpha} shows very weak or no correlation with the 100 {mu}m emission. In this paper, the observational data of the diffuse FUV radiation by the Far Ultraviolet Spectroscopic Explorer (FUSE) are reexamined in order to investigate the correlation between the diffuse FUV radiation shortward of Ly{alpha} and the 100 {mu}m emission. Large fluctuations were confirmed in the linear-linear correlation plots, but good correlations were found in the log-log plots. The large fluctuations in the linear-linear plots, and thus poor correlations, between the FUV and 100 {mu}m intensities were attributed to the lognormal property of the FUV intensity distribution. The standard deviation of the intensity distribution of the FUV radiation shortward of Ly{alpha} was found to be {sigma}{sub logI} = 0.16-0.25. The result is consistent with that obtained not only for the FUV radiation longward of 1216 A but also with the dust column density measurements of various molecular clouds. This implies that most of the diffuse FUV radiation shortward of Ly{alpha} is dust-scattered light in the turbulent interstellar medium. The diffuse FUV data obtained from the Voyager missions were also investigated. However, much wider random fluctuations were found compared with the FUSE data, which is most likely due to the systematic difficulties in data reduction of the Voyager data.

  12. Monitoring Ly-Alpha Emission From the Blazar 3C 279

    NASA Technical Reports Server (NTRS)

    Koratkar, Anuradha; Pian, Elena; Urry, C. Megan; Pesce, Joseph E.

    1998-01-01

    The blazar 3C 279 is well studied and shows frequent large continuum flares from radio to gamma-ray wavelengths. There have been a number of multiwavelength observations of 3C 279, and hence there are extensive ultraviolet data for this object available in the UV archives. In this paper we present Ly-alpha emission line measurements for 3C 279 using all the archival IUE SWP spectra from 1988 to 1996 and all archival Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) G190H spectra from 1992 to 1996. Individual archival IUE spectra of 3C 279 show weak Ly-alpha emission at approximately 1868 A (z = 0.536), which is easily seen in the co-added data. The Ly-alpha emission is observed in all the HST/FOS spectra. The strength of Ly-alpha is nearly constant (approximately 5 x 10(exp -14) erg/sq cm.s), while the 1750 A continuum varies by a factor of approximately 50, from approximately 0.6 to 31.6 x 10(exp -15) ergs/sq cm.s.A. The behavior of the Ly-alpha emission line flux and continuum flux is similar to that of the only other well observed blazar, 3C 273, which shows constant line flux while the continuum varies by a factor of approximately 3. This near-constancy of emission-line flux in the two best-studied blazars suggests that the highly variable beamed continuum is not a significant source of photoionization for the gas. Some other source, such as thermal emission from an accretion disk, must be providing a significant fraction of the photoionizing flux in these objects. The large amplitude variability seen at gamma-ray energies must be due to changes in the energetic electrons in the jet rather than changes in the external photon field.

  13. The Evolution of Ly-alpha Emitting Galaxies Between z = 2.1 and z = 3.l

    NASA Technical Reports Server (NTRS)

    Ciardullo, Robin; Gronwall,Caryl; Wolf, Christopher; McCathran, Emily; Bond, Nicholas A.; Gawiser, Eric; Guaita, Lucia; Feldmeier, John J.; Treister, Ezequiel; Padilla, Nelson; Francke, Harold; Matkovic, Ana; Altmann, Martin; Herrera, David

    2011-01-01

    We describe the results of a new, wide-field survey for z= 3.1 Ly-alpha emission-line galaxies (LAEs) in the Extended Chandra Deep Field South (ECDF-S). By using a nearly top-hat 5010 Angstrom filter and complementary broadband photometry from the MUSYC survey, we identify a complete sample of 141 objects with monochromatic fluxes brighter than 2.4E-17 ergs/cm^2/s and observers-frame equivalent widths greater than 80 Angstroms (i.e., 20 Angstroms in the rest-frame of Ly-alpha). The bright-end of this dataset is dominated by x-ray sources and foreground objects with GALEX detections, but when these interlopers are removed, we are still left with a sample of 130 LAE candidates, 39 of which have spectroscopic confirmations. This sample overlaps the set of objects found in an earlier ECDF-S survey, but due to our filter's redder bandpass, it also includes 68 previously uncataloged sources. We confirm earlier measurements of the z=3.1 LAE emission-line luminosity function, and show that an apparent anti-correlation between equivalent width and continuum brightness is likely due to the effect of correlated errors in our heteroskedastic dataset. Finally, we compare the properties of z=3.1 LAEs to LAEs found at z=2.1. We show that in the approximately 1 Gyr after z approximately 3, the LAE luminosity function evolved significantly, with L * fading by approximately 0.4 mag, the number density of sources with L greater than 1.5E42 ergs/s declining by approximately 50%, and the equivalent width scalelength contracting from 70^{+7}_{-5} Angstroms to 50^{+9}_{-6} Angstroms. When combined with literature results, our observations demonstrate that over the redshift range z approximately 0 to z approximately 4, LAEs contain less than approximately 10% of the star-formation rate density of the universe.

  14. EXTENDED Ly{alpha} EMISSION FROM INTERACTING GALAXIES AT HIGH REDSHIFTS

    SciTech Connect

    Yajima, Hidenobu; Li Yuexing; Zhu Qirong

    2013-08-20

    Recent observations have discovered a population of extended Ly{alpha} sources, dubbed Ly{alpha} blobs (LABs), at high redshift z {approx} 2-6.6. These LABs typically have a luminosity of L {approx} 10{sup 42}-10{sup 44} erg s{sup -1}, and a size of tens of kiloparsecs, with some giant ones reaching up to D {approx} 100 kpc. However, the origin of these LABs is not well understood. In this paper, we investigate a merger model for the formation of LABs by studying Ly{alpha} emission from interacting galaxies at high redshifts by means of a combination of hydrodynamics simulations with three-dimensional radiative transfer calculations. Our galaxy simulations focus on a set of binary major mergers of galaxies with a mass range of 3-7 Multiplication-Sign 10{sup 12} M{sub Sun} in the redshift range z {approx} 3-7, and we use the newly improved ART{sup 2} code to perform the radiative transfer calculations, which couple multi-wavelength continuum, ionization of hydrogen, and Ly{alpha} line emission. We find that intense star formation and enhanced cooling induced by gravitational interaction produce strong Ly{alpha} emission from these merging galaxies. The Ly{alpha} emission appears to be extended due to the extended distribution of sources and gas. During the close encounter of galaxy progenitors when the star formation rate peaks at {approx}10{sup 3} M{sub Sun} yr{sup -1}, our model produces LABs with luminosity of L {approx} 10{sup 42}-10{sup 44} erg s{sup -1}, and size of D {approx} 10-20 kpc at z > 6 and D {approx} 20-50 kpc at z {approx} 3, in broad agreement with observations in the same redshift range. Our results suggest that merging galaxies may produce some typical LABs as observed, but the giant ones may be produced by mergers more massive than those in our model, or a combination of mergers and cold accretion from filaments on a large scale.

  15. GAS MOTION STUDY OF Ly{alpha} EMITTERS AT z {approx} 2 USING FUV AND OPTICAL SPECTRAL LINES {sup ,}

    SciTech Connect

    Hashimoto, Takuya; Shimasaku, Kazuhiro; Nakajima, Kimihiko; Ouchi, Masami; Ono, Yoshiaki; Rauch, Michael; Janice Lee; Okamura, Sadanori

    2013-03-01

    We present the results of Magellan/MMIRS and Keck/NIRSPEC spectroscopy for five Ly{alpha} emitters (LAEs) at z {approx_equal} 2.2 for which high-resolution FUV spectra from Magellan/MagE are available. We detect nebular emission lines including H{alpha} on the individual basis and low-ionization interstellar (LIS) absorption lines in a stacked FUV spectrum, and measure average offset velocities of the Ly{alpha} line, {Delta}v {sub Ly{alpha}}, and LIS absorption lines, {Delta}v {sub abs}, with respect to the systemic velocity defined by the nebular lines. For a sample of eight z {approx} 2-3 LAEs without active galactic nucleus from our study and the literature, we obtain {Delta}v {sub Ly{alpha}} = 175 {+-} 35 km s{sup -1}, which is significantly smaller than that of Lyman-break Galaxies (LBGs), {Delta}v {sub Ly{alpha}} {approx_equal} 400 km s{sup -1}. The stacked FUV spectrum gives {Delta}v {sub abs} = -179 {+-} 73 km s{sup -1}, comparable to that of LBGs. These positive {Delta}v {sub Ly{alpha}} and negative {Delta}v {sub abs} suggest that LAEs also have outflows. In contrast to LBGs, however, the LAEs' {Delta}v {sub Ly{alpha}} is as small as |{Delta}v {sub abs}|, suggesting low neutral hydrogen column densities. Such a low column density with a small number of resonant scattering may cause the observed strong Ly{alpha} emission of LAEs. We find an anti-correlation between Ly{alpha} equivalent width (EW) and {Delta}v {sub Ly{alpha}} in a compilation of LAE and LBG samples. Although its physical origin is not clear, this anti-correlation result appears to challenge the hypothesis that a strong outflow, by means of a reduced number of resonant scattering, produces a large EW. If LAEs at z > 6 have similarly small {Delta}v {sub Ly{alpha}} values, constraints on the reionization history derived from the Ly{alpha} transmissivity may need to be revised.

  16. Ly{alpha} EMITTING GALAXIES AS EARLY STAGES IN GALAXY FORMATION

    SciTech Connect

    Cowie, Lennox L.; Barger, Amy J.; Hu, Esther M.

    2011-09-10

    We present optical spectroscopy of two samples of Galaxy Evolution Explorer grism selected Ly{alpha} emitters (LAEs): one at z = 0.195-0.44 and the other at z = 0.65-1.25. We have also observed a comparison sample of galaxies in the same redshift intervals with the same UV magnitude distributions but with no detected Ly{alpha}. We use the optical spectroscopy to eliminate active galactic nuclei and to obtain the optical emission-line properties of the samples. We compare the luminosities of the LAEs in the two redshift intervals and show that there is dramatic evolution in the maximum Ly{alpha} luminosity over z = 0-1. Focusing on the z = 0.195-0.44 samples alone, we show that there are tightly defined relations between all of the galaxy parameters and the rest-frame equivalent width (EW) of H{alpha}. The higher EW(H{alpha}) sources all have lower metallicities, bluer colors, smaller sizes, and less extinction, consistent with their being in the early stages of the galaxy formation process. We find that 75% {+-} 12% of the LAEs have EW(H{alpha}) >100 A and, conversely, that 31% {+-} 13% of galaxies with EW(H{alpha}) >100 A are LAEs. We correct the broadband magnitudes for the emission-line contributions and use spectral synthesis fits to estimate the ages of the galaxies. We find a median age of 1.1 x 10{sup 8} yr for the LAE sample and 1.4 x 10{sup 9} yr for the UV-continuum sample without detected Ly{alpha}. The median metallicity of the LAE sample is 12 + log (O/H) = 8.24, or about 0.4 dex lower than the UV-continuum sample.

  17. EFFECT OF DUST ON Ly{alpha} PHOTON TRANSFER IN AN OPTICALLY THICK HALO

    SciTech Connect

    Yang Yang; Shu Chiwang; Roy, Ishani; Fang Lizhi

    2011-10-01

    We investigate the effects of dust on Ly{alpha} photons emergent from an optically thick medium by solving the integro-differential equation of radiative transfer of resonant photons. To solve the differential equations numerically, we use the weighted essentially non-oscillatory method. Although the effects of dust on radiative transfer are well known, the resonant scattering of Ly{alpha} photons makes the problem non-trivial. For instance, if the medium has an optical depth of dust absorption and scattering of {tau}{sub a} >> 1, {tau} >> 1, and {tau} >> {tau}{sub a}, the effective absorption optical depth in a random walk scenario would be equal to {radical}({tau}{sub a}({tau}{sub a}+{tau})). We show, however, that for a resonant scattering at frequency {nu}{sub 0}, the effective absorption optical depth would be even larger than {tau}({nu}{sub 0}). If the cross section of dust scattering and absorption is frequency-independent, the double-peaked structure of the frequency profile given by the resonant scattering is basically dust-independent. That is, dust causes neither narrowing nor widening of the width of the double-peaked profile. One more result is that the timescales of the Ly{alpha} photon transfer in an optically thick halo are also basically independent of the dust scattering, even when the scattering is anisotropic. This is because those timescales are mainly determined by the transfer in the frequency space, while dust scattering, either isotropic or anisotropic, does not affect the behavior of the transfer in the frequency space when the cross section of scattering is wavelength-independent. This result does not support the speculation that dust will lead to the smoothing of the brightness distribution of a Ly{alpha} photon source with an optically thick halo.

  18. Ly{alpha} ESCAPE FROM z {approx} 0.03 STAR-FORMING GALAXIES: THE DOMINANT ROLE OF OUTFLOWS

    SciTech Connect

    Wofford, Aida; Leitherer, Claus; Salzer, John

    2013-03-10

    The usefulness of H I Ly{alpha} photons for characterizing star formation in the distant universe is limited by our understanding of the astrophysical processes that regulate their escape from galaxies. These processes can only be observed in detail out to a few Multiplication-Sign 100 Mpc. Past nearby (z < 0.3) spectroscopic studies are based on small samples and/or kinematically unresolved data. Taking advantage of the high sensitivity of Hubble Space Telescope's Cosmic Origins Spectrograph (COS), we observed the Ly{alpha} lines of 20 H{alpha}-selected galaxies located at =0.03. The galaxies cover a broad range of luminosity, oxygen abundance, and reddening. In this paper, we characterize the observed Ly{alpha} lines and establish correlations with fundamental galaxy properties. We find seven emitters. These host young ({<=}10 Myr) stellar populations have rest-frame equivalent widths in the range 1-12 A, and have Ly{alpha} escape fractions within the COS aperture in the range 1%-12%. One emitter has a double-peaked Ly{alpha} with peaks 370 km s{sup -1} apart and a stronger blue peak. Excluding this object, the emitters have Ly{alpha} and O I {lambda}1302 offsets from H{alpha} in agreement with expanding-shell models and Lyman break galaxies observations. The absorbers have offsets that are almost consistent with a static medium. We find no one-to-one correspondence between Ly{alpha} emission and age, metallicity, or reddening. Thus, we confirm that Ly{alpha} is enhanced by outflows and is regulated by the dust and H I column density surrounding the hot stars.

  19. ON THE (NON-)ENHANCEMENT OF THE Ly{alpha} EQUIVALENT WIDTH BY A MULTIPHASE INTERSTELLAR MEDIUM

    SciTech Connect

    Laursen, Peter; Duval, Florent; Oestlin, Goeran

    2013-04-01

    It has been suggested that radiative transfer effects may explain the unusually high equivalent widths (EWs) of the Ly{alpha} line, observed occasionally from starburst galaxies, especially at high redshifts. If the dust is locked up inside high-density clouds dispersed in an empty intercloud medium, the Ly{alpha} photons could scatter off of the surfaces of the clouds, effectively having their journey confined to the dustless medium. The continuum radiation, on the other hand, does not scatter, and would thus be subject to absorption inside the clouds. This scenario is routinely invoked when Ly{alpha} EWs higher than what is expected theoretically are observed, although the ideal conditions under which the results are derived usually are not considered. Here we systematically examine the relevant physical parameters in this idealized framework, testing whether any astrophysically realistic scenarios may lead to such an effect. It is found that although clumpiness indeed facilitates the escape of Ly{alpha}, it is highly unlikely that any real interstellar media should result in a preferential escape of Ly{alpha} over continuum radiation. Other possible causes are discussed, and it is concluded that the observed high EWs are more likely to be caused by cooling radiation from cold accretion and/or anisotropic escape of the Ly{alpha} radiation.

  20. The Local Ly(alpha) Forest: Association of Clouds with Superclusters and Voids

    NASA Technical Reports Server (NTRS)

    Stocke, John T.; Shull, J. Michael; Penton, Steve; Donahue, Megan; Carilli, Chris

    1995-01-01

    The Goddard High Resolution Spectrograph aboard the Hubble Space Telescope was used with the G160M grating to obtain high-resolution (6.2 A) spectra of three very bright active galactic nuclei located behind voids in the nearby distribution of bright galaxies (i.e., CfA and Arecibo redshift survey regions). A total of eight definite (greater than or equal to 4 sigma) Ly(alpha) absorption lines were discovered ranging in equivalent width from 26 to 240 mA at Galactocentric velocities 1740-7740 km/s. Of these eight systems, we locate seven in supercluster structures and one, in the sight line of Mrk 501 at 7740 km/s, in a void. In addition, one of two tentative (3-4 sigma) Ly(alpha) absorption lines are found in voids. Thus, the voids are not entirely devoid of matter, and not all Ly(alpha) clouds are associated with galaxies. Also, since the path lengths through voids and superclusters probed by our observations thus far are nearly equal, there is some statistical evidence that the Ly(alpha) clouds avoid the voids. The nearest galaxy neighbors to these absorbing clouds are 0.45-5.9 Mpc away, too far to be physically associated by most models. The lower equivalent width absorption lines (W(sub lambda) less than or equal to 100 mA) are consistent with random locations with respect to galaxies and may be truly intergalactic, similar to the bulk of the Ly(alpha) forest seen at high z. These results on local Ly(alpha) clouds are in full agreement with those found by Morris et al. (1993) for the 3C 273 sight line but are different from the results for higher equivalent width systems where closer cloud-galaxy associations were found by Lanzetta et al. (1994). Pencil-beam optical and 21 cm radio line observations of the area of sky surrounding Mrk 501 fail to find faint galaxies near the velocities of the Ly(alpha) clouds in that sight line. Specifically, for the 'void absorption' system at 7740 km/s, we find no galaxy at comparable redshift to the absorber within 100 h

  1. A GRAVITATIONAL LENS MODEL FOR THE Ly{alpha} EMITTER LAE 221724+001716 AT z = 3.1 IN THE SSA 22 FIELD {sup ,}

    SciTech Connect

    Nakahiro, Y.; Kajisawa, M.; Tanaka, A. R.; Hamada, K.; Taniguchi, Y.; Shioya, Y.; Kobayashi, M. A. R.; Inoue, A. K.; Iwata, I.; Matsuda, Y.; Hayashino, T.

    2013-04-01

    During the course of our Lyman continuum imaging survey, we found that the spectroscopically confirmed Ly{alpha} emitter LAE 221724+001716 at z = 3.10 in the SSA 22 field shows strong Lyman continuum emission ({lambda}{sub rest} {approx} 900 A) that escapes from this galaxy. However, another recent spectroscopic survey revealed that the supposed Lyman continuum emission could arise from a foreground galaxy at z = 1.76 if the emission line newly detected from the galaxy at {lambda}{sub obs} Almost-Equal-To 3360 A is Ly{alpha}. If this is the case, as the angular separation between these two galaxies is very small ( Almost-Equal-To 0.''6), LAE 221724+001716 at z = 3.10 could be amplified by the gravitational lensing caused by this intervening galaxy. Here we present a possible gravitational lens model for the system of LAE 221724+001716. First, we estimate the stellar mass of the intervening galaxy as M{sub *} {approx} 3.5 Multiplication-Sign 10{sup 9} M{sub Sun} from its UV luminosity and {approx}3.0 Multiplication-Sign 10{sup 7}-2.4 Multiplication-Sign 10{sup 9} M{sub Sun} through the spectral energy distribution fitting. Then, we find that the gravitational magnification factor ranges from 1.01 to 1.16 using the so-called singular isothermal sphere model for strong lensing. While LAE 221724+001716 is the first system of an LAE-LAE lensing reported so far, the estimated magnification factor is not so significant because the stellar mass of the intervening galaxy is small.

  2. FIRST SPECTROSCOPIC MEASUREMENTS OF [O III] EMISSION FROM Ly{alpha} SELECTED FIELD GALAXIES AT z {approx} 3.1

    SciTech Connect

    McLinden, Emily M.; Rhoads, James E.; Malhotra, Sangeeta; Hibon, Pascale; Richardson, Mark L. A.; Finkelstein, Steven L.; Cresci, Giovanni; Quirrenbach, Andreas; Pasquali, Anna; Bian Fuyan; Fan Xiaohui; Woodward, Charles E.

    2011-04-01

    We present the first spectroscopic measurements of the [O III] 5007 A line in two z {approx} 3.1 Ly{alpha} emitting galaxies (LAEs) using the new near-infrared instrument LUCIFER1 on the 8.4 m Large Binocular Telescope. We also describe the optical imaging and spectroscopic observations used to identify these LAEs. Using the [O III] line we have measured accurate systemic redshifts for these two galaxies, and discovered a velocity offset between the [O III] and Ly{alpha} lines in both, with the Ly{alpha} line peaking 342 and 125 km s{sup -1} redward of the systemic velocity. These velocity offsets imply that there are powerful outflows in high-redshift LAEs. They also ease the transmission of Ly{alpha} photons through the interstellar medium and intergalactic medium around the galaxies. By measuring these offsets directly, we can refine both Ly{alpha}-based tests for reionization, and Ly{alpha} luminosity function measurements where the Ly{alpha} forest affects the blue wing of the line. Our work also provides the first direct constraints on the strength of the [O III] line in high-redshift LAEs. We find [O III] fluxes of 7 and 36 x10{sup -17} erg s{sup -1} cm{sup -2} in two z {approx} 3.1 LAEs. These lines are strong enough to dominate broadband flux measurements that include the line (in this case, K{sub s} -band photometry). Spectral energy distribution fits that do not account for the lines would therefore overestimate the 4000 A (and/or Balmer) break strength in such galaxies, and hence also the ages and stellar masses of such high-z galaxies.

  3. MEAN-FLUX-REGULATED PRINCIPAL COMPONENT ANALYSIS CONTINUUM FITTING OF SLOAN DIGITAL SKY SURVEY Ly{alpha} FOREST SPECTRA

    SciTech Connect

    Lee, Khee-Gan; Spergel, David N.; Suzuki, Nao

    2012-02-15

    Continuum fitting is an important aspect of Ly{alpha} forest science, since errors in the derived optical depths scale with the fractional continuum error. However, traditional methods of estimating continua in noisy and moderate-resolution spectra (e.g., Sloan Digital Sky Survey, SDSS; S/N {approx}< 10 pixel{sup -1} and R {approx} 2000), such as power-law extrapolation or dividing by the mean spectrum, achieve no better than {approx}15% rms accuracy. To improve on this, we introduce mean-flux-regulated principal component analysis (MF-PCA) continuum fitting. In this technique, PCA fitting is carried out redward of the quasar Ly{alpha} line in order to provide a prediction for the shape of the Ly{alpha} forest continuum. The slope and amplitude of this continuum prediction is then corrected using external constraints for the Ly{alpha} forest mean flux. This requires prior knowledge of the mean flux, (F), but significantly improves the accuracy of the flux transmission, F {identical_to} exp (- {tau}), estimated from each pixel. From tests on mock spectra, we find that MF-PCA reduces the errors to 8% rms in S/N {approx} 2 spectra, and <5% rms in spectra with S/N {approx}> 5. The residual Fourier power in the continuum is decreased by a factor of a few in comparison with dividing by the mean continuum, enabling Ly{alpha} flux power spectrum measurements to be extended to {approx}2 Multiplication-Sign larger scales. Using this new technique, we make available continuum fits for 12,069 z > 2.3 Ly{alpha} forest spectra from SDSS Data Release 7 for use by the community. This technique is also applicable to future releases of the ongoing Baryon Oscillations Spectroscopic Survey, which obtains spectra for {approx}150, 000 Ly{alpha} forest spectra at low signal-to-noise (S/N {approx} 2).

  4. RESOLVING THE GALAXIES WITHIN A GIANT Ly{alpha} NEBULA: WITNESSING THE FORMATION OF A GALAXY GROUP?

    SciTech Connect

    Prescott, Moire K. M.; Dey, Arjun; Jannuzi, Buell T.; Brodwin, Mark; Chaffee, Frederic H.; Desai, Vandana; Soifer, B. T.; Eisenhardt, Peter; Le Floc'h, Emeric; Matsuda, Yuichi

    2012-06-20

    Detailed analysis of the substructure of Ly{alpha} nebulae can put important constraints on the physical mechanisms at work and the properties of galaxies forming within them. Using high-resolution Hubble Space Telescope (HST) imaging of a Ly{alpha} nebula at z Almost-Equal-To 2.656, we have taken a census of the compact galaxies in the vicinity, used optical/near-infrared colors to select system members, and put constraints on the morphology of the spatially extended emission. The system is characterized by (1) a population of compact, low-luminosity ({approx}0.1 L*) sources-17 primarily young, small (R{sub e} Almost-Equal-To 1-2 kpc), disky galaxies including an obscured active galactic nucleus-that are all substantially offset ({approx}>20 kpc) from the line-emitting nebula; (2) the lack of a central galaxy at or near the peak of the Ly{alpha} emission; and (3) several nearly coincident, spatially extended emission components-Ly{alpha}, He II, and UV continuum-that are extremely smooth. These morphological findings are difficult to reconcile with theoretical models that invoke outflows, cold flows, or resonant scattering, suggesting that while all of these physical phenomena may be occurring, they are not sufficient to explain the powering and large extent of Ly{alpha} nebulae. In addition, although the compact galaxies within the system are irrelevant as power sources, the region is significantly overdense relative to the field galaxy population (by at least a factor of four). These observations provide the first estimate of the luminosity function of galaxies within an individual Ly{alpha} nebula system and suggest that large Ly{alpha} nebulae may be the seeds of galaxy groups or low-mass clusters.

  5. SEARCHING FOR z {approx} 7.7 Ly{alpha} EMITTERS IN THE COSMOS FIELD WITH NEWFIRM

    SciTech Connect

    Krug, Hannah B.; Veilleux, Sylvain; Tilvi, Vithal; Malhotra, Sangeeta; Rhoads, James; Hibon, Pascale; Swaters, Rob

    2012-02-01

    The study of Ly{alpha} emission in the high-redshift universe is a useful probe of the epoch of reionization, as the Ly{alpha} line should be attenuated by the intergalactic medium (IGM) at low to moderate neutral hydrogen fractions. Here we present the results of a deep and wide imaging search for Ly{alpha} emitters in the Cosmological Evolution Survey field. We have used two ultra-narrowband filters (filter width of {approx}8-9 A) on the NOAO Extremely Wide-Field Infrared Mosaic camera, installed on the Mayall 4 m telescope at Kitt Peak National Observatory, in order to isolate Ly{alpha} emitters at z = 7.7; such ultra-narrowband imaging searches have proved to be excellent at detecting Ly{alpha} emitters. We found 5{sigma} detections of four candidate Ly{alpha} emitters in a survey volume of 2.8 Multiplication-Sign 10{sup 4} Mpc{sup 3} (total survey area {approx}760 arcmin{sup 2}). Each candidate has a line flux greater than 8 Multiplication-Sign 10{sup -18} erg s{sup -1} cm{sup -2}. Using these results to construct a luminosity function and comparing to previously established Ly{alpha} luminosity functions at z = 5.7 and z = 6.5, we find no conclusive evidence for evolution of the luminosity function between z = 5.7 and z = 7.7. Statistical Monte Carlo simulations suggest that half of these candidates are real z = 7.7 targets, and spectroscopic follow-up will be required to verify the redshift of these candidates. However, our results are consistent with no strong evolution in the neutral hydrogen fraction of the IGM between z = 5.7 and z = 7.7, even if only one or two of the z = 7.7 candidates are spectroscopically confirmed.

  6. CONSTRAINTS ON QUASAR LIFETIMES AND BEAMING FROM THE He II Ly{alpha} FOREST

    SciTech Connect

    Furlanetto, Steven R.; Lidz, Adam

    2011-07-10

    We show that comparisons of He II Ly{alpha} forest lines of sight to nearby quasar populations can strongly constrain the lifetimes and emission geometry of quasars. By comparing the He II and H I Ly{alpha} forests along a particular line of sight, one can trace fluctuations in the hardness of the radiation field (which are driven by fluctuations in the He II ionization rate). Because this high-energy background is highly variable-thanks to the rarity of the bright quasars that dominate it and the relatively short attenuation lengths of these photons-it is straightforward to associate features in the radiation field with their source quasars. Here we quantify how finite lifetimes and beamed emission geometries affect these expectations. Finite lifetimes induce a time delay that displaces the observed radiation peak relative to the quasar. For beamed emission, geometry dictates that sources invisible to the observer can still create a peak in the radiation field. We show that both these models produce substantial populations of 'bare' peaks (without an associated quasar) for reasonable parameter values (lifetimes {approx}10{sup 6}-10{sup 8} yr and beaming angles {approx}< 90 deg.). A comparison to existing quasar surveys along two He II Ly{alpha} forest lines of sight rules out isotropic emission and infinite lifetime at high confidence; they can be accommodated either by moderate beaming or lifetimes {approx}10{sup 7}-10{sup 8} yr. We also show that the distribution of radial displacements between peaks and their quasars can unambiguously distinguish these two models, although larger statistical samples are needed.

  7. THRESHOLD PROBABILITY FUNCTIONS AND THERMAL INHOMOGENEITIES IN THE Ly{alpha} FOREST

    SciTech Connect

    Lee, Khee-Gan; Spergel, David N. E-mail: dns@astro.princeton.edu

    2011-06-10

    We introduce to astrophysics the threshold probability functions S{sub 2}, C{sub 2}, and D{sub 2} first derived by Torquato et al., which effectively samples the flux probability distribution function (PDF) of the Ly{alpha} forest at different spatial scales. These statistics are tested on mock Ly{alpha} forest spectra based on various toy models for He II reionization, with homogeneous models with various temperature-density relations as well as models with temperature inhomogeneities. These mock samples have systematics and noise added to simulate the latest Sloan Digital Sky Survey Data Release 7 (SDSS DR7) data. We find that the flux PDF from SDSS DR7 can be used to constrain the temperature-density relation {gamma} (where T{proportional_to}(1 + {Delta}){sup {gamma}-1}) of the intergalactic medium (IGM) at z = 2.5 to a precision of {Delta}{gamma} = 0.2 at {approx}4{sigma} confidence. The flux PDF is degenerate to temperature inhomogeneities in the IGM arising from He II reionization, but we find S{sub 2} can detect these inhomogeneities at {approx}3{sigma}, with the assumption that the flux continuum of the Ly{alpha} forest can be determined to 9% accuracy, approximately the error from current fitting methods. If the flux continuum can be determined to 3% accuracy, then S{sub 2} is capable of constraining the characteristic scale of temperature inhomogeneities, with {approx}4{sigma} differentiation between toy models with hot bubble radii of 50 h{sup -1} Mpc and 25 h{sup -1} Mpc.

  8. BROAD Ly{alpha} EMISSION FROM THREE NEARBY BL LACERTAE OBJECTS

    SciTech Connect

    Stocke, John T.; Danforth, Charles W.; Perlman, Eric S. E-mail: stocke@casa.colorado.edu

    2011-05-10

    We present far-UV HST/COS spectra of four nearby BL Lac objects. BL Lac spectra are dominated by a smooth, power-law continuum which arises in a relativistic jet. However, the spectra are not necessarily featureless; weak, broad- and/or narrow-line emission is sometimes seen in high-quality optical spectra. We present detections of Ly{alpha} emission in HST/COS spectra of Mrk 421 (z = 0.030) and PKS 2005-489 (z = 0.071) as well as an archival HST/GHRS observation of Mrk 501 (z = 0.0337). Archival HST/STIS observations of PKS 2155-304 (z = 0.116) show no Ly{alpha} emission to a very low upper limit. Using the assumption that the broad-line region (BLR) clouds are symmetrically placed around the active galactic nucleus (AGN), we use these measured Ly{alpha} emission features to constrain either the relativistic {Gamma} values for the ionizing continuum produced by the jet (in the ionization-bounded case) or the mass of warm gas (in the density-bounded case). While realistic {Gamma} values can be obtained for all four cases, the values for Mrk 421 and PKS 2155-304 are high enough to suggest that covering factors of BLR clouds of {approx}1%-2% might be required to provide consistency with earlier values of Doppler boosting and viewing angles suggested for this class of BL Lacs. This discrepancy also exists in the case of M 87, where the amount of Doppler boosting in our direction is expected to be minimal, again suggestive of a small covering factor of BLR clouds. If, as these small covering factors might suggest, the assumptions of a density-bounded model could be more correct, then the observed Ly{alpha} luminosities require that BL Lac/FR 1 nuclei possess very little warm gas (10{sup -4} to 10{sup -5} M{sub sun}) as suggested by Guilbert et al. If these clouds are in pressure balance with a hotter ({approx}10{sup 6} K) gas, the BLR contains too little mass to power the AGN by accretion alone.

  9. STATISTICS OF 207 Ly{alpha} EMITTERS AT A REDSHIFT NEAR 7: CONSTRAINTS ON REIONIZATION AND GALAXY FORMATION MODELS

    SciTech Connect

    Ouchi, Masami; Ota, Kazuaki; Shimasaku, Kazuhiro; Yoshida, Makiko; Ono, Yoshiaki; Okamura, Sadanori; Furusawa, Hisanori; Kashikawa, Nobunari; Iye, Masanori; Kodama, Tadayuki; Saito, Tomoki; Akiyama, Masayuki; Yamada, Toru; Simpson, Chris; Yoshida, Michitoshi

    2010-11-01

    We present the Ly{alpha} luminosity function (LF), clustering measurements, and Ly{alpha} line profiles based on the largest sample to date of 207 Ly{alpha} emitters (LAEs) at z = 6.6 on the 1 deg{sup 2} sky of Subaru/XMM-Newton Deep Survey field. Our z = 6.6 Ly{alpha} LF including cosmic variance estimates yields the best-fit Schechter parameters of {phi}* = 8.5{sup +3.0}{sub -2.2} x 10{sup -4} Mpc{sup -3} and L*{sub Ly{alpha}} = 4.4{sup +0.6}{sub -0.6} x 10{sup 42} erg s{sup -1} with a fixed {alpha} = -1.5, and indicates a decrease from z = 5.7 at the {approx}>90% confidence level. However, this decrease is not large, only {approx_equal}30% in Ly{alpha} luminosity, which is too small to have been identified in the previous studies. A clustering signal of z = 6.6 LAEs is detected for the first time. We obtain the correlation length of r{sub 0}= 2-5 h {sup -1}{sub 100} Mpc and a bias of b= 3-6, and find no significant boost of clustering amplitude by reionization at z = 6.6. The average hosting dark halo mass inferred from clustering is 10{sup 10}-10{sup 11} M{sub sun}, and a duty cycle of LAE population is roughly {approx}1%, albeit with large uncertainties. The average of our high-quality Keck/DEIMOS spectra shows an FWHM velocity width of 251 {+-} 16 km s{sup -1}. We find no large evolution of the Ly{alpha} line profile from z = 5.7 to 6.6, and no anti-correlation between Ly{alpha} luminosity and line width at z = 6.6. The combination of various reionization models and our observational results about the LF, clustering, and line profile indicates that there would exist a small decrease of the intergalactic medium's (IGM's) Ly{alpha} transmission owing to reionization, but that the hydrogen IGM is not highly neutral at z = 6.6. Our neutral-hydrogen fraction constraint implies that the major reionization process took place at z {approx}> 7.

  10. SYSTEMATIC CONTINUUM ERRORS IN THE Ly{alpha} FOREST AND THE MEASURED TEMPERATURE-DENSITY RELATION

    SciTech Connect

    Lee, Khee-Gan

    2012-07-10

    Continuum fitting uncertainties are a major source of error in estimates of the temperature-density relation (usually parameterized as a power-law, T {proportional_to} {Delta}{sup {gamma}-1}) of the intergalactic medium through the flux probability distribution function (PDF) of the Ly{alpha} forest. Using a simple order-of-magnitude calculation, we show that few percent-level systematic errors in the placement of the quasar continuum due to, e.g., a uniform low-absorption Gunn-Peterson component could lead to errors in {gamma} of the order of unity. This is quantified further using a simple semi-analytic model of the Ly{alpha} forest flux PDF. We find that under(over)estimates in the continuum level can lead to a lower (higher) measured value of {gamma}. By fitting models to mock data realizations generated with current observational errors, we find that continuum errors can cause a systematic bias in the estimated temperature-density relation of ({delta}({gamma})) Almost-Equal-To -0.1, while the error is increased to {sigma}{sub {gamma}} Almost-Equal-To 0.2 compared to {sigma}{sub {gamma}} Almost-Equal-To 0.1 in the absence of continuum errors.

  11. Effects of excitation laser wavelength on Ly-{alpha} and He-{alpha} line emission from nitrogen plasmas

    SciTech Connect

    Harilal, S. S.; Miloshevsky, G. V.; Sizyuk, T.; Hassanein, A.

    2013-01-15

    Laser-produced nitrogen plasmas emitting radiation at 2.48 nm (Ly-{alpha}) and 2.88 nm (He-{alpha}) are considered potential efficient sources for water-window (WW) microscopy. The atomic and optical properties of nitrogen plasma and influence of the laser wavelength on the line emission in the WW range are investigated. It is found that the optimal temperatures for maximum emission from Ly-{alpha} and He-{alpha} spectral lines are 40-60 eV and 80-100 eV, respectively. The WW line emission and the conversion efficiency (CE) are estimated for three distinct Nd:YAG laser wavelengths (1064 nm, 532 nm, and 266 nm). The calculated CEs are compared with experimentally observed CE values. It is found that 1064 nm wavelength provides the highest CE from laser to Ly-{alpha} and He-{alpha} radiation.

  12. SEARCH FOR z {approx} 6.96 Ly{alpha} EMITTERS WITH MAGELLAN/IMACS IN THE COSMOS FIELD

    SciTech Connect

    Hibon, P.; Malhotra, S.; Rhoads, J.; Willott, C.

    2011-11-10

    We report a search for z {approx} 6.96 Ly{alpha} emitters (LAEs) using a narrowband filter, centered at 9680 A with the Inamori-Magellan Area Camera and Spectrograph instrument on the Magellan telescope at Las Campanas Observatory. We obtain a sample of six LAE candidates of luminosity {approx}10{sup 42} erg s{sup -1} in a total area of 465 arcmin{sup 2} corresponding to a comoving volume of {approx}72,000 Mpc{sup 3}. From this result, we derive a Ly{alpha} luminosity function (LF) at z {approx} 6.96 and compare our sample with the only z {approx} 6.96 LAE spectroscopically confirmed to date. We find no evolution between the z = 5.7 and z {approx} 7 Ly{alpha} LFs if a majority of our candidates are confirmed. Spectroscopic confirmation for this sample will enable more robust conclusions.

  13. A FLUX-LIMITED SAMPLE OF z {approx} 1 Ly{alpha} EMITTING GALAXIES IN THE CHANDRA DEEP FIELD SOUTH ,

    SciTech Connect

    Barger, A. J.; Wold, I. G. B.; Cowie, L. L.

    2012-04-20

    We describe a method for obtaining a flux-limited sample of Ly{alpha} emitters from Galaxy Evolution Explorer (GALEX) grism data. We show that the multiple GALEX grism images can be converted into a three-dimensional (two spatial axes and one wavelength axis) data cube. The wavelength slices may then be treated as narrowband images and searched for emission-line galaxies. For the GALEX NUV grism data, the method provides a Ly{alpha} flux-limited sample over the redshift range z = 0.67-1.16. We test the method on the Chandra Deep Field South field, where we find 28 Ly{alpha} emitters with faint continuum magnitudes (NUV > 22) that are not present in the GALEX pipeline sample. We measure the completeness by adding artificial emitters and measuring the fraction recovered. We find that we have an 80% completeness above a Ly{alpha} flux of 10{sup -15} erg cm{sup -2} s{sup -1}. We use the UV spectra and the available X-ray data and optical spectra to estimate the fraction of active galactic nuclei in the selection. We report the first detection of a giant Ly{alpha} blob at z < 1, though we find that these objects are much less common at z = 1 than at z = 3. Finally, we compute limits on the z {approx} 1 Ly{alpha} luminosity function and confirm that there is a dramatic evolution in the luminosity function over the redshift range z = 0-1.

  14. PANORAMIC SURVEY OF Ly{alpha} EMITTERS AT z = 3.1

    SciTech Connect

    Yamada, T.; Nakamura, Y.; Morimoto, N.; Matsuda, Y.; Hayashino, T.; Yamauchi, R.; Kousai, K.; Umemura, M.

    2012-04-15

    We present the results of the extensive narrowband survey of Ly{alpha} emission-line objects at z = 3.1 in the 1.38 deg{sup 2} area surrounding the high-density region of star-forming galaxies at z = 3.09 in the SSA22 field, as well as in the 1.04 deg{sup 2} area of the three separated general blank fields. In total, of 2161 Ly{alpha} emitters, there are 1394 in the SSA22 fields and 767 in the general fields detected at the narrowband AB magnitude limit of 25.73, which corresponds to the line flux of Almost-Equal-To 1.8 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} or the luminosity of Almost-Equal-To 1.5 Multiplication-Sign 10{sup 42} erg s{sup -1} at z = 3.1, above the observed equivalent-width threshold, Almost-Equal-To 190 A. The average surface number density of the emitters at z = 3.1 in the general fields above the thresholds is 0.20 {+-} 0.01 arcmin{sup -2}. The SSA22 high-density region at z = 3.09, whose peak local density is six times that of the average, is found to be the most prominent outstanding structure in the whole surveyed area and is firmly identified as a robust 'protocluster'. We also compared the overdensity of the 100 arcmin{sup 2} and 700 arcmin{sup 2} areas which contain the protocluster with the expected fluctuation of the dark matter as well as those of the model galaxies in cosmological simulations. We found that the peak height values of the overdensity are 8-10 and 3-4 times the expected standard deviations for the counts of Ly{alpha} emitters at z = 3.1 in the corresponding volume, respectively. We conclude that the structure at z = 3.09 in the SSA22 field is a very significant and rare density peak up to the scale of Almost-Equal-To 60 Mpc.

  15. THE FAINT-END SLOPE OF THE REDSHIFT 5.7 Ly{alpha} LUMINOSITY FUNCTION

    SciTech Connect

    Henry, Alaina L.; Martin, Crystal L.; Dressler, Alan; McCarthy, Patrick; Sawicki, Marcin

    2012-01-10

    Using new Keck DEIMOS spectroscopy, we examine the origin of the steep number counts of ultra-faint emission-line galaxies recently reported by Dressler et al. We confirm six Ly{alpha} emitters (LAEs), three of which have significant asymmetric line profiles with prominent wings extending 300-400 km s{sup -1} redward of the peak emission. With these six LAEs, we revise our previous estimate of the number of faint LAEs in the Dressler et al. survey. Combining these data with the density of bright LAEs in the Cosmic Evolution Survey and Subaru Deep Field provides the best constraints to date on the redshift 5.7 LAE luminosity function (LF). Schechter function parameters, {phi}* = 4.5 Multiplication-Sign 10{sup -4} Mpc{sup -3}, L* = 9.1 Multiplication-Sign 10{sup 42} erg s{sup -1}, and {alpha} = -1.70, are estimated using a maximum likelihood technique with a model for slit-losses. To place this result in the context of the UV-selected galaxy population, we investigate how various parameterizations of the Ly{alpha} equivalent width distribution, along with the measured UV-continuum LF, affect shape and normalization of the Ly{alpha} LF. The nominal model, which uses z {approx} 6 equivalent widths from the literature, falls short of the observed space density of LAEs at the bright end, possibly indicating a need for higher equivalent widths. This parameterization of the equivalent width distribution implies that as many as 50% of our faintest LAEs should have M{sub UV} > -18.0, rendering them undetectable in even the deepest Hubble Space Telescope surveys at this redshift. Hence, ultra-deep emission-line surveys find some of the faintest galaxies ever observed at the end of the reionization epoch. Such faint galaxies likely enrich the intergalactic medium with metals and maintain its ionized state in the post-reionization era. Observations of these objects provide a glimpse of the building blocks of present-day galaxies at an early time.

  16. LARGE-SCALE FLUCTUATIONS IN THE He II Ly{alpha} FOREST AND He II REIONIZATION

    SciTech Connect

    Furlanetto, Steven R.; Dixon, Keri L.

    2010-05-01

    We examine large-scale fluctuations in the He II Ly{alpha} forest transmission during and after He II reionization. We use a simple Monte Carlo model to distribute quasars throughout a large volume and compute the resulting radiation field along one-dimensional skewers. In agreement with previous studies, we find that the rarity of these sources induces order unity fluctuations in the mean optical depth after reionization, even when averaged over large segments ({approx}10-100Mpc across). We compare our models to existing data along five He II Ly{alpha} forest lines of sight spanning z {approx} 2-3.2. The large cosmic variance contained in our model plausibly explains many of the observed fluctuations at z {approx_lt} 2.5. But our models cannot accommodate the large fluctuations toward high optical depths on {approx}30Mpc scales observed at z {approx} 2.7-2.9, and the measured optical depths ({tau}{sub eff} {approx_gt} 4) at z>2.9 are difficult to explain with a smoothly evolving mean radiation field. In order to better understand these data, we construct a toy model of He II reionization, in which we assume that regions with the smallest radiation fields in a post-reionization universe (or farthest from strong ionizing sources) are completely dark during reionization. The observed fluctuations fit much more comfortably into this model, and we therefore argue that, according to present data, He II reionization does not complete until z {approx_lt} 2.9.

  17. The discovery of six Ly{alpha} emitters near a radio galaxy at z {approx} 5.2

    SciTech Connect

    Venemans, B P; Rottgering, H A; Overzier, R A; Miley, G K; De Breuck, C; Kurk, J D; van Breugel, W; Carilli, C L; Ford, H; Heckman, T; McCarthy, P; Pentericci, L

    2004-09-15

    The authors present the results of narrow-band and broad-band imaging with the Very Large Telescope of the field surrounding the radio galaxy TN J0924-2201 at z = 5.2. 14 candidate Ly{alpha} emitters with an observed equivalent width of at least 124 {angstrom} were detected. Spectroscopy of 8 of these objects revealed 6 having redshifts similar to that of the radio galaxy. The density of emitters near the radio galaxy is a factor 3-4 higher than in the field, and comparable to the density of Ly{alpha} emitters in the protocluster 1338-1942 at z = 4.1. The Ly{alpha} emitters near TN J0924-2201 could therefore be part of a structure that will evolve into a 10{sup 15} M{sub {circle_dot}} cluster. These observations confirm that substantial clustering of Ly{alpha} emitters occur at z > 5 and strengthen the idea that radio galaxies in the early Universe pinpoint regions of high density.

  18. DEEP LBT/LUCI SPECTROSCOPY OF AN Ly{alpha} EMITTER CANDIDATE AT z {approx_equal} 7.7

    SciTech Connect

    Jiang Linhua; Bian Fuyan; Fan Xiaohui; McGreer, Ian D.; Stark, Daniel P.; Clement, Benjamin; Egami, Eiichi; Krug, Hannah B.

    2013-07-01

    We present deep spectroscopic observations of an Ly{alpha} emitter (LAE) candidate at z {approx_equal} 7.7 using the infrared spectrograph LUCI on the 2 Multiplication-Sign 8.4 m Large Binocular Telescope (LBT). The candidate is the brightest among the four z {approx_equal} 7.7 LAE candidates found in a narrowband imaging survey by Krug et al. Our spectroscopic data include a total of 7.5 hr of integration with LBT/LUCI and are deep enough to significantly (3.2{sigma}-4.9{sigma}) detect the Ly{alpha} emission line of this candidate based on its Ly{alpha} flux 1.2 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} estimated from the narrowband photometry. However, we do not find any convincing signal at the expected position of its Ly{alpha} emission line, suggesting that this source is not an LAE at z {approx_equal} 7.7. The non-detection in this work, together with the previous studies of z {approx_equal} 7.7 LAEs, puts a strong constraint on the bright-end Ly{alpha} luminosity function (LF) at z {approx_equal} 7.7. We find a rapid evolution of the Ly{alpha} LF from z {approx_equal} 6.5 to 7.7: the upper limit of the z {approx_equal} 7.7 LF is more than five times lower than the z {approx_equal} 6.5 LF at the bright end (f{>=} 1.0 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} or L{>=} 6.9 Multiplication-Sign 10{sup 42} erg s{sup -1}). This is likely caused by an increasing neutral fraction in the intergalactic medium that substantially attenuates Ly{alpha} emission at z {approx_equal} 7.7.

  19. STRONG FIELD-TO-FIELD VARIATION OF Ly{alpha} NEBULAE POPULATIONS AT z {approx_equal} 2.3

    SciTech Connect

    Yang Yujin; Zabludoff, Ann; Eisenstein, Daniel; Dave, Romeel E-mail: azabludoff@as.arizona.ed E-mail: rad@as.arizona.ed

    2010-08-20

    Understanding the nature of distant Ly{alpha} nebulae, aka 'blobs', and connecting them to their present-day descendants requires constraining their number density, clustering, and large-scale environment. To measure these basic quantities, we conduct a deep narrowband imaging survey in four different fields, Chandra Deep Field South (CDFS), Chandra Deep Field North (CDFN), and two COSMOS subfields, for a total survey area of 1.2 deg{sup 2}. We discover 25 blobs at z = 2.3 with Ly{alpha} luminosities of L{sub Ly{alpha}=} (0.7-8) x 10{sup 43} erg s{sup -1} and isophotal areas of A{sub iso} = 10-60 {open_square}arcsec. The transition from compact Ly{alpha} emitters (LAEs; A{sub iso} {approx} a few {open_square}arcsec ) to extended Ly{alpha} blobs (A {sub iso} > 10 {open_square}arcsec) is continuous, suggesting a single family perhaps governed by similar emission mechanisms. Surprisingly, most blobs (16/25) are in one survey field, the CDFS. The six brightest, largest blobs with L {sub Ly{alpha} {approx}}> 1.5x10{sup 43} erg s{sup -1} and A{sub iso} > 16 {open_square}arcsec lie only in the CDFS. These large, bright blobs have a field-to-field variance of {sigma} {sub v} {approx}> 1.5 (150%) about their number density n {approx}1.0{sup +1.8}{sub -0.6}x 10{sup -5} Mpc{sup -3}. This variance is large, significantly higher than that of unresolved LAEs ({sigma} {sub v} {approx} 0.3 or 30%), and can adversely affect comparisons of blob number densities and luminosity functions (LFs) among different surveys. Our deep, blind survey allows us to construct a reliable blob LF. We compare the statistics of our blobs with dark matter halos in a 1 h {sup -1} Gpc cosmological N-body simulation. At z = 2.3, n implies that each bright, large blob could occupy a halo of M{sub halo} {approx}>10{sup 13} M{sub sun} if most halos have detectable blobs. The predicted variance in n is consistent with that observed and corresponds to a bias of {approx}7. Blob halos lie at the high end of the

  20. HUBBLE/COS OBSERVATIONS OF THE Ly{alpha} FOREST TOWARD THE BL Lac OBJECT 1ES 1553+113

    SciTech Connect

    Danforth, Charles W.; Keeney, Brian A.; Stocke, John T.; Shull, J. Michael; Yao Yangsen

    2010-09-01

    We present new moderate-resolution, far-ultraviolet spectra from the Hubble Space Telescope/Cosmic Origins Spectrograph (HST/COS) of the BL Lac object 1ES 1553+113 covering the wavelength range 1135 A < {lambda} < 1795 A. The data show a smooth continuum with a wealth of narrow (b < 100 km s{sup -1}) absorption features arising in the interstellar medium and intergalactic medium. These features include 41 Ly{alpha} absorbers at 0 < z{sub abs} < 0.43, 14 of which are detected in multiple Lyman lines and 6 of which show absorption in one or more metal lines. We analyze a metal-rich triplet ({Delta}cz {approx} 1000 km s{sup -1}) of Ly{alpha} absorbers at z{sub abs} {approx} 0.188 in which O VI, N V, and C III absorption is detected. Silicon ions (Si III, Si IV) are not detected to fairly strong upper limits and we use the measured Si III/C III upper limit to derive an abundance limit (C/Si) {>=} 4(C/Si){sub sun} for the strongest component of the absorber complex. Galaxy redshift surveys show a number of massive galaxies at approximately the same redshift as this absorption complex, suggesting that it arises in a large-scale galaxy filament. As one of the brightest extragalactic X-ray and {gamma}-ray sources, 1ES 1553+113 is of great interest to the high-energy astrophysics community. With no intrinsic emission or absorption features, 1ES 1553+113 has no direct redshift determination. We use intervening Ly{alpha} absorbers to place a direct limit on the redshift: z{sub em}>0.395 based on a confirmed Ly{alpha}+O VI absorber and z{sub em}>0.433 based on a single-line detection of Ly{alpha}. The current COS data are only sensitive to Ly{alpha} absorbers at z < 0.47, but we present statistical arguments that z{sub em} {approx}< 0.58 (at a 1{sigma} confidence limit) based on the non-detection of any Ly{beta} absorbers at z>0.4.

  1. STACKED REST-FRAME ULTRAVIOLET SPECTRA OF Ly{alpha}-EMITTING AND CONTINUUM-SELECTED GALAXIES AT 2 < z < 3.5

    SciTech Connect

    Berry, Michael; Gawiser, Eric; Guaita, Lucia; Padilla, Nelson; Francke, Harold; Treister, Ezequiel; Blanc, Guillermo A.; Ciardullo, Robin; Gronwall, Caryl

    2012-04-10

    We present properties of individual and composite rest-UV spectra of continuum- and narrowband-selected star-forming galaxies (SFGs) at a redshift of 2 < z < 3.5 discovered by the MUSYC collaboration in the Extended Chandra Deep Field-South. Among our sample of 81 UV-bright SFGs, 59 have R < 25.5, of which 32 have rest-frame equivalent widths of W{sub Ly{alpha}} > 20 A, the canonical limit to be classified as an Ly{alpha}-emitting galaxy. We divide our data set into subsamples based on properties that we are able to measure for each individual galaxy: Ly{alpha} equivalent width, rest-frame UV colors, and redshift. Among our subsample of galaxies with R < 25.5, those with rest frame W{sub Ly{alpha}} > 20 A have bluer UV continua, weaker low-ionization interstellar absorption lines, weaker C IV absorption, and stronger Si II* nebular emission than those with W{sub Ly{alpha}} < 20 A. We measure a velocity offset of {Delta}v {approx} 600 km s{sup -1} between Ly{alpha} emission and low-ionization absorption, which does not vary substantially among any of our subsamples. We find that the interstellar component, as opposed to the stellar component, dominates the high-ionization absorption line profiles. We find that the low- and high-ionization Si ionization states have similar kinematic properties, yet the low-ionization absorption is correlated with Ly{alpha} emission and the high-ionization absorption is not. These trends are consistent with outflowing neutral gas being in the form of neutral clouds embedded in ionized gas as previously suggested by Steidel et al. Moreover, our galaxies with bluer UV colors have stronger Ly{alpha} emission, weaker low-ionization absorption, and more prominent nebular emission line profiles. From a redshift of 2.7 < z < 3.5 to 2.0 < z < 2.7, our subsample of galaxies with W{sub Ly{alpha}} < 20 Angstrom-Sign shows no significant evolution in their physical properties or the nature of their outflows. Among our data set, UV-bright galaxies

  2. PHOTODESORPTION OF SOLID CO{sub 2} BY LY{alpha}

    SciTech Connect

    Bahr, D. A.; Baragiola, R. A.

    2012-12-10

    We measured desorption of atoms and molecules from films of solid carbon dioxide in an ultrahigh vacuum from 6 to 60 K under irradiation with Ly{alpha} (121.6 nm, 10.2 eV) photons, an important process in the balance between gas phase and condensed molecules in the interstellar medium. The measurements use microgravimetry and mass spectrometry during irradiation and temperature programmed desorption after irradiation. At low photon fluences, the desorption flux consists mainly of O atoms and, after {approx}10{sup 17} photons cm{sup -2}, it is dominated by CO with smaller amount of O{sub 2}, C, and CO{sub 2}, with the presence of O{sub 2} indicating solid-state chemical reactions. At high fluences (up to 10{sup 18} photons cm{sup -2}){sub ,} the desorption yields saturate at values much higher than in previous studies. The yields (molecules/photon), derived assuming stoichiometric desorption, reach 0.014 at 6 K, growing to {approx}0.2 at 50 and 60 K. Warming the films during irradiation gives rise to pressure spikes that suggest desorption of trapped species in pores or at defects, possibly assisted by radical-induced reactions. Such an effect could be significant for radiation-processed CO{sub 2}-coated interstellar grains that are heated by, i.e., cosmic ray impacts or grain-grain collisions. We discuss the experiments considering photochemical mechanisms and compare them to the results of ion irradiation.

  3. Copernicus observations of Ly-alpha and Mg II emission from HR 1099 /V711 Tauri/ and UX Ari

    NASA Technical Reports Server (NTRS)

    Weiler, E. J.

    1978-01-01

    Ultraviolet observations of two RS CVn binaries obtained with Copernicus are described. High-resolution (0.05 A) U1 observations indicate that both HR 1099 and UX Ari display broad Ly-alpha emission. The Ly-alpha emission strength from HR 1099 is variable and seems to be correlated with orbital phase, while the UX Ari results indicate no significant variation. Moderate resolution (0.51 A) V2 scans of both systems show variable Mg II h and k emission-line profiles which usually matched the velocity of the more active star in each binary. Additionally, displaced emission components were seen at velocities of up to + or - 250 km/s, indicative of high-velocity gas motions. The radial velocities of these emission features from HR 1099 are marginally correlated with orbital phase. Highly active and variable chromospheric phenomena are found to be the most consistent explanation of these results.

  4. PHYSICAL PROPERTIES OF Ly{alpha} EMITTERS AT z {approx} 0.3 FROM UV-TO-FIR MEASUREMENTS

    SciTech Connect

    Oteo, I.; Bongiovanni, A.; Perez Garcia, A. M.; Cepa, J.; Pintos-Castro, I.; Ederoclite, A.; Sanchez-Portal, M.; Altieri, B.; Perez-Martinez, R.; Andreani, P.; Aussel, H.; Daddi, E.; Elbaz, D.; Le Floc'h, E.; Cimatti, A.; and others

    2012-06-01

    The analysis of the physical properties of low-redshift Ly{alpha} emitters (LAEs) can provide clues in the study of their high-redshift analogs. At z {approx} 0.3, LAEs are bright enough to be detected over almost the entire electromagnetic spectrum and it is possible to carry out a more precise and complete study than at higher redshifts. In this work, we examine the UV and IR emission, dust attenuation, star formation rate (SFR), and morphology of a sample of 23 GALEX-discovered star-forming LAEs at z {approx} 0.3 with direct UV (GALEX), optical (ACS), and FIR (PACS and MIPS) data. Using the same UV and IR limiting luminosities, we find that LAEs at z {approx} 0.3 tend to be less dusty, have slightly higher total SFRs, have bluer UV continuum slopes, and are much smaller than other galaxies that do not exhibit Ly{alpha} emission in their spectrum (non-LAEs). These results suggest that at z {approx} 0.3, Ly{alpha} photons tend to escape from small galaxies with low dust attenuation. Regarding their morphology, LAEs belong to Irr/merger classes, unlike non-LAEs. Size and morphology represent the most noticeable difference between LAEs and non-LAEs at z {approx} 0.3. Furthermore, the comparison of our results with those obtained at higher redshifts indicates either that the Ly{alpha} technique picks up different kind of galaxies at different redshifts or that the physical properties of LAEs are evolving with redshift.

  5. SEARCH FOR z {approx} 7 Ly{alpha} EMITTERS WITH THE SUPRIME-CAM AT THE SUBARU TELESCOPE

    SciTech Connect

    Hibon, P.; Kashikawa, N.; Iye, M.; Shibuya, T.; Willott, C.

    2012-01-10

    We report a search for z = 7 Ly{alpha} emitters (LAEs) using a custom-made narrowband filter centered at 9755 A with the Suprime-Cam instrument installed at the Subaru telescope. We observed two different fields and obtained two samples of seven LAEs, of which four are robust in each field. We cover the luminosity range of 9.10{sup 42}-2.10{sup 43} erg s{sup -1} in comoving volumes of {approx}4 Multiplication-Sign 10{sup 5} and 4.3 Multiplication-Sign 10{sup 5} Mpc{sup 3}. From this result, we derived possible z {approx} 7 Ly{alpha} luminosity functions for the full samples and for a subsample of four objects in each field. We do not observe, in each case, any strong evolution between the z = 6.5 and z {approx} 7 Ly{alpha} luminosity functions. Spectroscopic confirmation for these candidate samples is required to establish a definitive measure of the luminosity function at z {approx} 7.

  6. Ly-alpha and white light observations of a CME during the Spartan 201-1 mission

    NASA Technical Reports Server (NTRS)

    Hassler, Don M.; Strachan, Leonard; Gardner, L. D.; Kohl, J. L.; Guhathakurta, Madhulika; Fisher, Richard R.; Strong, K.

    1994-01-01

    A coronal mass ejection (CME) near a large active region on the west limb was observed with the white light coronograph (WLC) and ultraviolet coronal spectrometer (UVCS) on the Spartan 201 satellite at 9:42 UT on 12 Apr. 1993. Soft X-ray images of the region below the CME were obtained out to 1.7 solar radii with the soft X-ray telescope (SXT) on Yohkoh. After the event, the formation of a new helmet streamer could be seen in the polarized brightness (pB) images from the Mk III coronograph at Mauna Loa. The CME was observed from Spartan 201 in two different pB images obtained 14 min apart using the WLC, and was observed moving through the field-of-view of the UVCS integrated intensity slit. Ly-alpha intensities in the same region of the corona were obtained one orbit earlier (prior to the CME) using the Ly-alpha profile slit of the UVCS. These are the first Ly-alpha observations of a CME and may help constrain models of the electron temperature on CME's.

  7. Spectral Energy Distribution Fitting of Hetdex Pilot Survey Ly-alpha Emitters in Cosmos and Goods-N

    NASA Technical Reports Server (NTRS)

    Hagen, Alex; Ciardullo, Robin; Cronwall, Caryl; Acquaviva, Viviana; Bridge, Joanna; Zeimann, Gregory R.; Blanc, Guillermo; Bond, Nicholas; Finkelstein, Steven L.; Song, Mimi; Gawiser, Eric; Fox, Derek B.; Gebhardt, Henry; Malz, A. I; Schneider, Donald P.; Drory, Niv; Gebhardt, Karl; Hill, Gary J.

    2014-01-01

    We use broadband photometry extending from the rest-frame UV to the near-IR to fit the individual spectral energy distributions of 63 bright (L(Ly-alpha) greater than 10(exp 43) erg s(exp -1) Ly-alpha emitting galaxies (LAEs) in the redshift range 1.9 less than z less than 3.6. We find that these LAEs are quite heterogeneous, with stellar masses that span over three orders of magnitude, from 7.5 greater than logM/solar mass less than 10.5. Moreover, although most LAEs have small amounts of extinction, some high-mass objects have stellar reddenings as large as E(B - V ) is approximately 0.4. Interestingly, in dusty objects the optical depths for Ly-alpha and the UV continuum are always similar, indicating that Lya photons are not undergoing many scatters before escaping their galaxy. In contrast, the ratio of optical depths in low-reddening systems can vary widely, illustrating the diverse nature of the systems. Finally, we show that in the star-formation-rate-log-mass diagram, our LAEs fall above the "main-sequence" defined by z is approximately 3 continuum selected star-forming galaxies. In this respect, they are similar to submillimeter-selected galaxies, although most LAEs have much lower mass.

  8. PROBING THE INTERGALACTIC MEDIUM/GALAXY CONNECTION. V. ON THE ORIGIN OF Ly{alpha} AND O VI ABSORPTION AT z < 0.2

    SciTech Connect

    Prochaska, J. Xavier; Chen, H.-W.; Mulchaey, J.; Cooksey, K. E-mail: bjw@as.arizona.edu E-mail: mulchaey@obs.carnegiescience.edu

    2011-10-20

    We analyze the association of galaxies with Ly{alpha} and O VI absorption, the most commonly detected transitions of the low-z intergalactic medium (IGM), in the fields of 14 quasars with z{sub em} = 0.06-0.57. Confirming previous studies, we observe a high covering fraction for Ly{alpha} absorption to impact parameter {rho} = 300 h{sup -1}{sub 72} kpc: 33/37 of our L > 0.01 L* galaxies show Ly{alpha} equivalent width W{sup Ly{alpha}} {>=} 50 mA. Galaxies of all luminosity L > 0.01 L* and spectral type are surrounded by a diffuse and ionized circumgalactic medium (CGM), whose baryonic mass is estimated at {approx}10{sup 10.5{+-}0.3} M{sub sun} for a constant N{sub H} = 10{sup 19} cm{sup -2}. The virialized halos and extended CGM of present-day galaxies are responsible for most strong Ly{alpha} absorbers (W{sup Ly{alpha}} > 300 mA) but cannot reproduce the majority of observed lines in the Ly{alpha} forest. We conclude that the majority of Ly{alpha} absorption with W{sup Ly{alpha}} = 30-300 mA occurs in the cosmic web predicted by cosmological simulations and estimate a characteristic width for these filaments of {approx}400 h{sup -1}{sub 72} kpc. Regarding O VI, we observe a near unity covering fraction to {rho} = 200 h{sup -1}{sub 72} kpc for L > 0.1 L* galaxies and to {rho} = 300 h{sup -1}{sub 72} kpc for sub-L* (0.1 L* < L < L*) galaxies. Similar to our Ly{alpha} results, stronger O VI systems (W{sup 1031} > 70 mA) arise in the virialized halos of L > 0.1 L* galaxies. Unlike Ly{alpha}, the weaker O VI systems (W{sup 1031} {approx} 30 mA) arise in the extended CGM of sub-L* galaxies. The majority of O VI gas observed in the low-z IGM is associated with a diffuse medium surrounding individual galaxies with L {approx} 0.3 L* and rarely originates in the so-called warm-hot IGM (predicted by cosmological simulations.

  9. THE DISCOVERY OF A LARGE Ly{alpha}+He II NEBULA AT z {approx} 1.67: A CANDIDATE LOW METALLICITY REGION?

    SciTech Connect

    Prescott, Moire K. M.; Dey, Arjun; Jannuzi, Buell T. E-mail: dey@noao.edu

    2009-09-01

    We have discovered a {approx}45 kpc Ly{alpha} nebula (or Ly{alpha} 'blob') at z {approx} 1.67 which exhibits strong, spatially extended He II emission and very weak C IV and C III] emission. This is the first spatially extended Ly{alpha}+He II emitter observed and the lowest redshift Ly{alpha} blob yet found. Strong Ly{alpha} and He II{lambda}1640 emission in the absence of metal lines has been proposed as a unique observational signature of primordial galaxy formation (e.g., from gravitational cooling radiation or Population III star formation), but no convincing examples of spatially extended Ly{alpha}+He II emitters have surfaced either in Ly{alpha}-emitting galaxy surveys at high redshifts (z > 4) or in studies of Ly{alpha} nebulae at lower redshifts. From comparisons with photoionization models, we find that the observed line ratios in this nebula are consistent with low metallicity gas (Z {approx}< 10{sup -2}-10{sup -3} Z{sub sun}), but that this conclusion depends on the unknown ionization parameter of the system. The large He II equivalent width ({approx}37 {+-} 10 A) and the large He II/Ly{alpha} ratio (0.12 {+-} 0.04) suggest that the cloud is being illuminated by a hard ionizing continuum, either an active galactic nucleus (AGN) or very low metallicity stars, or perhaps powered by gravitational cooling radiation. Thus far there is no obvious sign of a powerful AGN in or near the system, so in order to power the nebula while remaining hidden from view even in the mid-infrared, the AGN would need to be heavily obscured. Despite the strong Ly{alpha}+He II emission, it is not yet clear what is the dominant power source for this nebula. The system therefore serves as an instructive example of how the complexities of true astrophysical sources will complicate matters when attempting to use a strong Ly{alpha}+He II signature as a unique tracer of primordial galaxy formation.

  10. KECK SPECTROSCOPY OF LYMAN-BREAK GALAXIES AND ITS IMPLICATIONS FOR THE UV-CONTINUUM AND Ly{alpha} LUMINOSITY FUNCTIONS AT z > 6

    SciTech Connect

    Jiang Linhua; Egami, Eiichi; Walth, Gregory; Kashikawa, Nobunari; Matsuda, Yuichi; Shimasaku, Kazuhiro; Nagao, Tohru; Ota, Kazuaki; Ouchi, Masami

    2011-12-10

    We present Keck spectroscopic observations of z > 6 Lyman-break galaxy (LBG) candidates in the Subaru Deep Field (SDF). The candidates were selected as i'-dropout objects down to z' = 27 AB magnitudes from an ultra-deep SDF z'-band image. With the Keck spectroscopy we identified 19 LBGs with prominent Ly{alpha} emission lines at 6 {<=} z {<=} 6.4. The median value of the Ly{alpha} rest-frame equivalent widths (EWs) is {approx}50 A, with four EWs >100 A. This well-defined spectroscopic sample spans a UV-continuum luminosity range of -21.8 {<=} M{sub UV} {<=} -19.5 (0.6 {approx} 5 L*{sub UV}) and a Ly{alpha} luminosity range of (0.3-3) Multiplication-Sign 10{sup 43} erg s{sup -1} (0.3-3 L*{sub Ly{alpha}}). We derive the UV and Ly{alpha} luminosity functions (LFs) from our sample at (z) {approx} 6.2 after we correct for sample incompleteness. We find that our measurement of the UV LF is consistent with the results of previous studies based on photometric LBG samples at 5 < z < 7. Our Ly{alpha} LF is also generally in agreement with the results of Ly{alpha}-emitter surveys at z {approx} 5.7 and 6.6. This study shows that deep spectroscopic observations of LBGs can provide unique constraints on both the UV and Ly{alpha} LFs at z > 6.

  11. A MEASUREMENT OF SMALL-SCALE STRUCTURE IN THE 2.2 {<=} z {<=} 4.2 Ly{alpha} FOREST

    SciTech Connect

    Lidz, Adam; Faucher-Giguere, Claude-Andre; McQuinn, Matthew; Zaldarriaga, Matias; Hernquist, Lars; Dutta, Suvendra; Dall'Aglio, Aldo; Fechner, Cora

    2010-07-20

    The amplitude of fluctuations in the Ly{alpha} forest on small spatial scales is sensitive to the temperature of the intergalactic medium (IGM) and its spatial fluctuations. The temperature of the IGM and its spatial variations contain important information about hydrogen and helium reionization. We present a new measurement of the small-scale structure in the Ly{alpha} forest from 40 high resolution, high signal-to-noise ratio, VLT spectra for absorbing gas at redshifts between 2.2 {<=} z {<=} 4.2. We convolve each Ly{alpha} forest spectrum with a suitably chosen Morlet wavelet filter, which allows us to extract the amount of small-scale structure in the forest as a function of position across each spectrum. We monitor contamination from metal line absorbers. We present a first comparison of these measurements with high-resolution hydrodynamic simulations of the Ly{alpha} forest that track more than 2 billion particles. This comparison suggests that the IGM temperature close to the cosmic mean density (T {sub 0}) peaks at a redshift near z = 3.4, at which point it is greater than 20, 000 K at {approx}>2{sigma} confidence. The temperature at lower redshift is consistent with the fall-off expected from adiabatic cooling (T {sub 0} {proportional_to} (1 + z){sup 2}), after the peak temperature is reached near z = 3.4. In our highest redshift bin, centered around z = 4.2, the results favor a temperature of T {sub 0} = 15-20, 000 K. However, owing mostly to uncertainties in the mean transmitted flux at this redshift, a cooler IGM model with T {sub 0} = 10, 000 K is only disfavored at the 2{sigma} level here, although such cool IGM models are strongly discrepant with the z {approx} 3-3.4 measurement. We do not detect large spatial fluctuations in the IGM temperature at any redshift covered by our data set. The simplest interpretation of our measurements is that He II reionization completes sometime near z {approx} 3.4, although statistical uncertainties are still large

  12. PHOTOMETRIC PROPERTIES OF Ly{alpha} EMITTERS AT z {approx} 4.86 IN THE COSMOS 2 SQUARE DEGREE FIELD

    SciTech Connect

    Shioya, Y.; Taniguchi, Y.; Nagao, T.; Saito, T.; Trump, J.; Sasaki, S. S.; Ideue, Y.; Nakajima, A.; Matsuoka, K.; Murayama, T.; Scoville, N. Z.; Capak, P.; Ellis, R. S.; Sanders, D. B.; Kartaltepe, J.; Mobasher, B.; Aussel, H.; Koekemoer, A.; Carilli, C.; Garilli, B.

    2009-05-01

    We present results of a survey for Ly{alpha} emitters at z {approx} 4.86 based on optical narrowband ({lambda} {sub c} = 7126 A, {delta}{lambda} = 73 A) and broadband (B, V, r', i', and z') observations of the Cosmic Evolution Survey field using Suprime-Cam on the Subaru Telescope. We find 79 Ly{alpha} emitter (LAE) candidates at z {approx} 4.86 over a contiguous survey area of 1.83 deg{sup 2}, down to the Ly{alpha} line flux of 1.47 x 10{sup -17} erg s{sup -1} cm{sup -2}. We obtain the Ly{alpha} luminosity function with a best-fit Schechter parameters of log L* = 42.9{sup +0.5} {sub -0.3} erg s{sup -1} and {phi}* = 1.2{sup +8.0} {sub -1.1} x 10{sup -4} Mpc{sup -3} for {alpha} = -1.5 (fixed). The two-point correlation function for our LAE sample is {xi}(r) = (r/4.4{sup +5.7} {sub -2.9} Mpc){sup -1.90{+-}}{sup 0.22}. In order to investigate the field-to-field variations of the properties of Ly{alpha} emitters, we divide the survey area into nine tiles of 0.{sup 0}5 x 0.{sup 0}5 each. We find that the number density varies with a factor of {approx_equal}2 from field to field with high statistical significance. However, we find no significant field-to-field variance when we divide the field into four tiles with 0.{sup 0}7 x 0.{sup 0}7 each. We conclude that at least 0.5 deg{sup 2} survey area is required to derive averaged properties of LAEs at z {approx} 5, and our survey field is wide enough to overcome the cosmic variance.

  13. THE ANGULAR DISTRIBUTION OF Ly{alpha} RESONANT PHOTONS EMERGING FROM AN OPTICALLY THICK MEDIUM

    SciTech Connect

    Yang Yang; Shu Chiwang; Roy, Ishani; Fang Lizhi

    2013-07-20

    We investigate the angular distribution of Ly{alpha} photons scattering or emerging from an optically thick medium. Since the evolution of specific intensity I in frequency space and angular space are coupled with each other, we first develop the WENO numerical solver to find the time-dependent solutions of the integro-differential equation of I in frequency and angular space simultaneously. We first show that the solutions with the Eddington approximation, which assume that I is linearly dependent on the angular variable {mu}, yield similar frequency profiles of the photon flux as those without the Eddington approximation. However, the solutions of the {mu} distribution evolution are significantly different from those given by the Eddington approximation. First, the angular distribution of I is found to be substantially dependent on the frequency of the photons. For photons with the resonant frequency {nu}{sub 0}, I contains only a linear term of {mu}. For photons with frequencies at the double peaks of the flux, the {mu}-distribution is highly anisotropic; most photons are emitted radially forward. Moreover, either at {nu}{sub 0} or at the double peaks, the {mu} distributions actually are independent of the initial {mu} distribution of photons of the source. This is because the photons with frequencies either at {nu}{sub 0} or the double peaks undergo the process of forgetting their initial conditions due to resonant scattering. We also show that the optically thick medium is a collimator of photons at the double peaks. Photons from the double peaks form a forward beam with a very small opening angle.

  14. Ly{alpha} EMITTERS AT z = 7 IN THE SUBARU/XMM-NEWTON DEEP SURVEY FIELD: PHOTOMETRIC CANDIDATES AND LUMINOSITY FUNCTION

    SciTech Connect

    Ota, Kazuaki; Ouchi, Masami; Iye, Masanori; Kashikawa, Nobunari; Kobayashi, Masakazu A. R.; Morokuma, Tomoki; Furusawa, Hisanori; Shimasaku, Kazuhiro; Totani, Tomonori; Nagashima, Masahiro; Harayama, Atsushi; Kodaka, Natsuki; Tajitsu, Akito; Hattori, Takashi

    2010-10-10

    We conducted a deep narrowband NB973 (FWHM = 200 A centered at 9755 A) survey of z = 7 Ly{alpha} emitters (LAEs) in the Subaru/XMM-Newton Deep Survey Field, using the fully depleted CCDs newly installed on the Subaru Telescope Suprime-Cam, which is twice more sensitive to z = 7 Ly{alpha} at {approx}1 {mu}m than the previous CCDs. Reaching the depth 0.5 mag deeper than our previous survey in the Subaru Deep Field that led to the discovery of a z = 6.96 LAE, we detected three probable z = 7 LAE candidates. Even if all the candidates are real, the Ly{alpha} luminosity function (LF) at z = 7 shows a significant deficit from the LF at z = 5.7 determined by previous surveys. The LAE number and Ly{alpha} luminosity densities at z = 7 are {approx}7.7%-54% and {approx}5.5%-39%, respectively, of those at z = 5.7, to the Ly{alpha} line luminosity limit of L(Ly{alpha}) {approx}> 9.2 x 10{sup 42} erg s{sup -1}. This could be due to evolution of the LAE population at these epochs as a recent galaxy evolution model predicts that the LAE modestly evolves from z = 5.7 to 7. However, even after correcting for this effect of galaxy evolution on the decrease in LAE number density, the z = 7 Ly{alpha} LF still shows a deficit from z = 5.7 LF. This might reflect the attenuation of Ly{alpha} emission by neutral hydrogen remaining at the epoch of reionization and suggests that reionization of the universe might not be complete yet at z = 7. If we attribute the density deficit to reionization, the intergalactic medium transmission for Ly{alpha} photons at z = 7 would be 0.4 {<=} T {sup IGM}{sub Ly{alpha} {<=}} 1, supporting the possible higher neutral fraction at the earlier epochs at z > 6 suggested by the previous surveys of z = 5.7-7 LAEs, z {approx} 6 quasars, and z > 6 gamma-ray bursts.

  15. SPECTROSCOPIC CONFIRMATION OF THREE z-DROPOUT GALAXIES AT z = 6.844-7.213: DEMOGRAPHICS OF Ly{alpha} EMISSION IN z {approx} 7 GALAXIES

    SciTech Connect

    Ono, Yoshiaki; Shimasaku, Kazuhiro; Nakajima, Kimihiko; Ouchi, Masami; Mobasher, Bahram; Nayyeri, Hooshang; Dickinson, Mark; Kartaltepe, Jeyhan S.; Penner, Kyle; Weiner, Benjamin J.; Stern, Daniel; Kashikawa, Nobunari; Spinrad, Hyron

    2012-01-10

    We present the results of our ultra-deep Keck/DEIMOS spectroscopy of z-dropout galaxies in the Subaru Deep Field and Great Observatories Origins Deep Survey's northern field. For 3 out of 11 objects, we detect an emission line at {approx}1 {mu}m with a signal-to-noise ratio of {approx}10. The lines show asymmetric profiles with high weighted skewness values, consistent with being Ly{alpha}, yielding redshifts of z = 7.213, 6.965, and 6.844. Specifically, we confirm the z = 7.213 object in two independent DEIMOS runs with different spectroscopic configurations. The z = 6.965 object is a known Ly{alpha} emitter, IOK-1, for which our improved spectrum at a higher resolution yields a robust skewness measurement. The three z-dropouts have Ly{alpha} fluxes of 3 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} and rest-frame equivalent widths EW{sup Ly{alpha}}{sub 0} = 33-43 A. Based on the largest spectroscopic sample of 43 z-dropouts, which is the combination of our and previous data, we find that the fraction of Ly{alpha}-emitting galaxies (EW{sup Ly{alpha}}{sub 0} > 25 A) is low at z {approx} 7; 17% {+-} 10% and 24% {+-} 12% for bright (M{sub UV} {approx_equal} -21) and faint (M{sub UV} {approx_equal} -19.5) galaxies, respectively. The fractions of Ly{alpha}-emitting galaxies drop from z {approx} 6 to 7 and the amplitude of the drop is larger for faint galaxies than for bright galaxies. These two pieces of evidence would indicate that the neutral hydrogen fraction of the intergalactic medium increases from z {approx} 6 to 7 and that the reionization proceeds from high- to low-density environments, as suggested by an inside-out reionization model.

  16. FIRST SPECTROSCOPIC EVIDENCE FOR HIGH IONIZATION STATE AND LOW OXYGEN ABUNDANCE IN Ly{alpha} EMITTERS ,

    SciTech Connect

    Nakajima, Kimihiko; Shimasaku, Kazuhiro; Hashimoto, Takuya; Ono, Yoshiaki; Ouchi, Masami; Lee, Janice C.

    2013-05-20

    We present results from Keck/NIRSPEC and Magellan/MMIRS follow-up spectroscopy of Ly{alpha} emitters (LAEs) at z = 2.2 identified in our Subaru narrowband survey. We successfully detect H{alpha} emission from seven LAEs, and perform a detailed analysis of six LAEs free from active galactic nucleus activity, two out of which, CDFS-3865 and COSMOS-30679, have [O II] and [O III] line detections. They are the first [O II]-detected LAEs at high-z, and their [O III]/[O II] ratios and R23-indices provide the first simultaneous determinations of ionization parameter and oxygen abundance for LAEs. CDFS-3865 has a very high ionization parameter (q{sub ion}=2.5{sup +1.7}{sub -0.8} Multiplication-Sign 10{sup 8} cm s{sup -1}) and a low oxygen abundance (12+ log (O/H)=7.84{sup +0.24}{sub -0.25}) in contrast with moderate values of other high-z galaxies such as Lyman break galaxies (LBGs). COSMOS-30679 also possesses a relatively high ionization parameter (q{sub ion}=8{sup +10}{sub -4} Multiplication-Sign 10{sup 7} cm s{sup -1}) and a low oxygen abundance (12+ log (O/H)=8.18{sup +0.28}{sub -0.28}). Both LAEs appear to fall below the mass-metallicity relation of z {approx} 2 LBGs. Similarly, a low metallicity of 12 + log (O/H) < 8.4 is independently indicated for typical LAEs from a composite spectrum and the [N II]/H{alpha} index. Such high ionization parameters and low oxygen abundances can be found in local star-forming galaxies, but this extreme local population occupies only {approx}0.06% of the Sloan Digital Sky Survey spectroscopic galaxy sample with a number density {approx}100 times smaller than that of LAEs. With their high ionization parameters and low oxygen abundances, LAEs would represent an early stage of galaxy formation dominated by massive stars in compact star-forming regions. High-q{sub ion} galaxies like LAEs would produce ionizing photons efficiently with a high escape fraction achieved by density-bounded H II regions, which would significantly contribute to

  17. FORMATION OF METAL-POOR GLOBULAR CLUSTERS IN Ly{alpha} EMITTING GALAXIES IN THE EARLY UNIVERSE

    SciTech Connect

    Elmegreen, Bruce G.; Malhotra, Sangeeta; Rhoads, James

    2012-09-20

    The size, mass, luminosity, and space density of Ly{alpha} emitting (LAE) galaxies observed at intermediate to high redshift agree with expectations for the properties of galaxies that formed metal-poor halo globular clusters (GCs). The low metallicity of these clusters is the result of their formation in low-mass galaxies. Metal-poor GCs could enter spiral galaxies along with their dwarf galaxy hosts, unlike metal-rich GCs, which form in the spirals themselves. Considering an initial GC mass larger than the current mass to account for multiple stellar populations, and considering the additional clusters that are likely to form with massive clusters, we estimate that each GC with a mass today greater than 2 Multiplication-Sign 10{sup 5} M{sub Sun} was likely to have formed among a total stellar mass {approx}> 3 Multiplication-Sign 10{sup 7} M{sub Sun }, a molecular mass {approx}> 10{sup 9} M{sub Sun }, and 10{sup 7} to 10{sup 9} M{sub Sun} of older stars, depending on the relative gas fraction. The star formation rate would have been several M{sub Sun} yr{sup -1} lasting for {approx}10{sup 7} yr, and the Ly{alpha} luminosity would have been {approx}> 10{sup 42} erg s{sup -1}. Integrating the LAE galaxy luminosity function above this minimum, considering the average escape probability for Ly{alpha} photons (25%), and then dividing by the probability that a dwarf galaxy is observed in the LAE phase (0.4%), we find agreement between the comoving space density of LAEs and the average space density of metal-poor GCs today. The local galaxy WLM, with its early starburst and old GC, could be an LAE remnant that did not get into a galaxy halo because of its remote location.

  18. INFERENCES ON THE DISTRIBUTION OF Ly{alpha} EMISSION OF z {approx} 7 AND z {approx} 8 GALAXIES

    SciTech Connect

    Treu, Tommaso; Auger, Matthew W.; Trenti, Michele; Stiavelli, Massimo; Bradley, Larry D.

    2012-03-01

    Spectroscopic confirmation of galaxies at z {approx} 7 and above has been extremely difficult, owing to a drop in intensity of Ly{alpha} emission in comparison with samples at z {approx} 6. This crucial finding could potentially signal the ending of cosmic reionization. However, it is based on small data sets, often incomplete and heterogeneous in nature. We introduce a flexible Bayesian framework, useful to interpret such evidence. Within this framework, we implement two simple phenomenological models: a smooth one where the distribution of Ly{alpha} is attenuated by a factor {epsilon}{sub s} with respect to z {approx} 6 and a patchy one where a fraction {epsilon}{sub p} is absorbed/non-emitted while the rest is unabsorbed. From a compilation of 39 observed z {approx} 7 galaxies, we find {epsilon}{sub s} = 0.69 {+-} 0.12 and {epsilon}{sub p} = 0.66 {+-} 0.16. The models can be used to compute fractions of emitters above any equivalent width W. For W > 25 A, we find X{sup 25}{sub z=7} = 0.37 {+-} 0.11 (0.14 {+-} 0.06) for galaxies fainter (brighter) than M{sub UV} = -20.25 for the patchy model, consistent with previous work, but with smaller uncertainties by virtue of our full use of the data. At z {approx} 8 we combine new deep (5{sigma} flux limit 10{sup -17} erg s{sup -1} cm{sup -2}) Keck/NIRSPEC observations of a bright Y-dropout identified by our Brightest of Reionization Galaxies Survey, with those of three objects from the literature and find that the inference is inconclusive. We compute predictions for future near-infrared spectroscopic surveys and show that it is challenging but feasible to constrain the distribution of Ly{alpha} emitters at z {approx} 8 and distinguish between models.

  19. AVERAGE METALLICITY AND STAR FORMATION RATE OF Ly{alpha} EMITTERS PROBED BY A TRIPLE NARROWBAND SURVEY

    SciTech Connect

    Nakajima, Kimihiko; Shimasaku, Kazuhiro; Ono, Yoshiaki; Okamura, Sadanori; Ouchi, Masami; Lee, Janice C.; Ly, Chun; Foucaud, Sebastien; Dale, Daniel A.; Salim, Samir; Finn, Rose; Almaini, Omar

    2012-01-20

    We present the average metallicity and star formation rate (SFR) of Ly{alpha} emitters (LAEs) measured from our large-area survey with three narrowband (NB) filters covering the Ly{alpha}, [O II]{lambda}3727, and H{alpha}+[N II] lines of LAEs at z = 2.2. We select 919 z = 2.2 LAEs from Subaru/Suprime-Cam NB data in conjunction with Magellan/IMACS spectroscopy. Of these LAEs, 561 and 105 are observed with KPNO/NEWFIRM near-infrared NB filters whose central wavelengths are matched to redshifted [O II] and H{alpha} nebular lines, respectively. By stacking the near-infrared images of the LAEs, we successfully obtain average nebular-line fluxes of LAEs, the majority of which are too faint to be identified individually by NB imaging or deep spectroscopy. The stacked object has an H{alpha} luminosity of 1.7 Multiplication-Sign 10{sup 42} erg s{sup -1} corresponding to an SFR of 14 M{sub Sun} yr{sup -1}. We place, for the first time, a firm lower limit to the average metallicity of LAEs of Z {approx}> 0.09 Z{sub Sun} (2{sigma}) based on the [O II]/(H{alpha}+[N II]) index together with photoionization models and empirical relations. This lower limit of metallicity rules out the hypothesis that LAEs, so far observed at z {approx} 2, are extremely metal-poor (Z < 2 Multiplication-Sign 10{sup -2} Z{sub Sun }) galaxies at the 4{sigma} level. This limit is higher than a simple extrapolation of the observed mass-metallicity relation of z {approx} 2 UV-selected galaxies toward lower masses (5 Multiplication-Sign 10{sup 8} M{sub Sun }), but roughly consistent with a recently proposed fundamental mass-metallicity relation when the LAEs' relatively low SFR is taken into account. The H{alpha} and Ly{alpha} luminosities of our NB-selected LAEs indicate that the escape fraction of Ly{alpha} photons is {approx}12%-30%, much higher than the values derived for other galaxy populations at z {approx} 2.

  20. RESOLVING THE OPTICAL EMISSION LINES OF Ly{alpha} BLOB ''B1'' AT z = 2.38: ANOTHER HIDDEN QUASAR

    SciTech Connect

    Overzier, R. A.; Nesvadba, N. P. H.; Dijkstra, M.; Hatch, N. A.; Lehnert, M. D.; Villar-Martin, M.; Wilman, R. J.; Zirm, A. W.

    2013-07-10

    We have used the SINFONI near-infrared integral field unit on the Very Large Telescope to resolve the optical emission line structure of one of the brightest (L{sub Ly{alpha}} Almost-Equal-To 10{sup 44} erg s{sup -1}) and nearest (z Almost-Equal-To 2.38) of all Ly{alpha} blobs (LABs). The target, known in the literature as object {sup B}1{sup ,} lies at a redshift where the main optical emission lines are accessible in the observed near-infrared. We detect luminous [O III] {lambda}{lambda}4959, 5007 and H{alpha} emission with a spatial extent of at least 32 Multiplication-Sign 40 kpc (4'' Multiplication-Sign 5''). The dominant optical emission line component shows relatively broad lines (600-800 km s{sup -1}, FWHM) and line ratios consistent with active galactic nucleus (AGN) photoionization. The new evidence for AGN photoionization, combined with previously detected C IV and luminous, warm infrared emission, suggest that B1 is the site of a hidden quasar. This is confirmed by the fact that [O II] is relatively weak compared with [O III] (extinction-corrected [O III]/[O II] of about 3.8), which is indicative of a high, Seyfert-like ionization parameter. From the extinction-corrected [O III] luminosity we infer a bolometric AGN luminosity of {approx}3 Multiplication-Sign 10{sup 46} erg s{sup -1}, and further conclude that the obscured AGN may be Compton-thick given existing X-ray limits. The large line widths observed are consistent with clouds moving within the narrow-line region of a luminous QSO. The AGN scenario is capable of producing sufficient ionizing photons to power the Ly{alpha}, even in the presence of dust. By performing a census of similar objects in the literature, we find that virtually all luminous LABs harbor obscured quasars. Based on simple duty-cycle arguments, we conclude that AGNs are the main drivers of the Ly{alpha} in LABs rather than the gravitational heating and subsequent cooling suggested by cold stream models. We also conclude that the

  1. A SEARCH FOR OXYGEN IN THE LOW-DENSITY Ly{alpha} FOREST USING THE SLOAN DIGITAL SKY SURVEY

    SciTech Connect

    Pieri, Matthew M.; Frank, Stephan; Mathur, Smita; Weinberg, David H.; York, Donald G.; Oppenheimer, Benjamin D.

    2010-06-20

    We use 2167 Sloan Digital Sky Survey quasar spectra to search for low-density oxygen in the intergalactic medium (IGM). Oxygen absorption is detected on a pixel-by-pixel basis by its correlation with Ly{alpha} forest absorption. We have developed a novel locally calibrated pixel (LCP) search method that uses adjacent regions of the spectrum to calibrate interlopers and spectral artifacts, which would otherwise limit the measurement of O VI absorption. Despite the challenges presented by searching for weak O VI within the Ly{alpha} forest in spectra of moderate resolution and signal-to-noise, we find a highly significant detection of absorption by oxygen at 2.7 < z < 3.2 (the null hypothesis has a {chi}{sup 2} = 80 for nine data points). We interpret our results using synthetic spectra generated from a log-normal density field assuming a mixed quasar-galaxy photoionizing background and that it dominates the ionization fraction of detected O VI. The LCP search data can be fit by a constant metallicity model with [O/H] = -2.15{sup +0.07}{sub -0.09} but also by models in which low-density regions are unenriched and higher density regions have a higher metallicity. The density-dependent enrichment model by Aguirre et al. is also an acceptable fit. All our successful models have similar mass-weighted oxygen abundance, corresponding to [(O/H){sub MW}] = -2.45 {+-} 0.06. This result can be used to find the cosmic oxygen density in the Ly{alpha} forest, {Omega}{sub Oxy,IGM} = 1.4({+-}0.2) x 10{sup -6} {approx} 3 x 10{sup -4{Omega}}{sub b}. This is the tightest constraint on the mass-weighted mean oxygen abundance and the cosmic oxygen density in the Ly{alpha} forest to date and indicates that it contains {approx}16% of the total expected metal production by star formation up to z = 3.

  2. A spectroscopic study of damped Lyman-alpha systems in the Las Campanas/Palomar survey

    NASA Technical Reports Server (NTRS)

    Lu, Limin; Wolfe, Arthur M.; Turnshek, David A.; Lanzetta, Kenneth M.

    1993-01-01

    The present intermediate-resolution spectra of nine QSOs contain 15 candidate damped Ly-alpha absorption features which are part of a sample of candidate damped Ly-alpha absorption lines. Ten of the 15 candidates are confirmed to have these features; eight of the ten have neutral hydrogen column density greater than 2 x 10 exp 20/sq cm. A simple curve-of-growth analysis is conducted for seven of the ten confirmed Ly-alpha systems, in order to characterize the kinematics of the absorbing gas; the deduced velocity dispersion, which is too large to be compatible with the simple velocity structure indicated by the 21-cm absorption data, is interpreted as grounds for a two-phase model encompassing a quiescent H I gas and a turbulent gas that dominates the equivalent widths of associated metal lines.

  3. THE KINEMATICS OF MULTIPLE-PEAKED Ly{alpha} EMISSION IN STAR-FORMING GALAXIES AT z {approx} 2-3

    SciTech Connect

    Kulas, Kristin R.; Shapley, Alice E.; Kollmeier, Juna A.; Zheng Zheng; Steidel, Charles C.; Hainline, Kevin N.

    2012-01-20

    We present new results on the Ly{alpha} emission-line kinematics of 18 z {approx} 2-3 star-forming galaxies with multiple-peaked Ly{alpha} profiles. With our large spectroscopic database of UV-selected star-forming galaxies at these redshifts, we have determined that {approx}30% of such objects with detectable Ly{alpha} emission display multiple-peaked emission profiles. These profiles provide additional constraints on the escape of Ly{alpha} photons due to the rich velocity structure in the emergent line. Despite recent advances in modeling the escape of Ly{alpha} from star-forming galaxies at high redshifts, comparisons between models and data are often missing crucial observational information. Using Keck II NIRSPEC spectra of H{alpha} (z {approx} 2) and [O III]{lambda}5007 (z {approx} 3), we have measured accurate systemic redshifts, rest-frame optical nebular velocity dispersions, and emission-line fluxes for the objects in the sample. In addition, rest-frame UV luminosities and colors provide estimates of star formation rates and the degree of dust extinction. In concert with the profile sub-structure, these measurements provide critical constraints on the geometry and kinematics of interstellar gas in high-redshift galaxies. Accurate systemic redshifts allow us to translate the multiple-peaked Ly{alpha} profiles into velocity space, revealing that the majority (11/18) display double-peaked emission straddling the velocity-field zero point with stronger red-side emission. Interstellar absorption-line kinematics suggest the presence of large-scale outflows for the majority of objects in our sample, with an average measured interstellar absorption velocity offset of ({Delta}v{sub abs}) = -230 km s{sup -1}. A comparison of the interstellar absorption kinematics for objects with multiple- and single-peaked Ly{alpha} profiles indicate that the multiple-peaked objects are characterized by significantly narrower absorption line widths. We compare our data with the

  4. A SEARCH FOR C II 158 {mu}m LINE EMISSION IN HCM 6A, A Ly{alpha} EMITTER AT z = 6.56

    SciTech Connect

    Kanekar, Nissim; Wagg, Jeff; Chary, Ranga Ram; Carilli, Christopher L.

    2013-07-10

    We report a Plateau de Bure Interferometer search for C II 158 {mu}m emission from HCM 6A, a lensed Ly{alpha} emitter (LAE) at z = 6.56. Our non-detections of C II 158 {mu}m line emission and 1.2 mm radio continuum emission yield 3{sigma} limits of L{sub CII} < 6.4 x 10{sup 7} x ({Delta}V/100 km s{sup -1}){sup 1/2} L{sub Sun} for the C II 158 {mu}m line luminosity and S{sub 1.2mm} < 0.68 mJy for the 1.2 mm flux density. The local conversion factor between L{sub CII} and the star formation rate (SFR) yields an SFR < 4.7 M{sub Sun} yr{sup -1}, Almost-Equal-To 2 times lower than that inferred from the ultraviolet (UV) continuum, suggesting that the local factor may not be applicable in high-z LAEs. The non-detection of 1.2 mm continuum emission yields a total SFR < 28 M{sub Sun} yr{sup -1}; any obscured star formation is thus within a factor of two of the visible star formation. Our best-fit model to the rest-frame UV/optical spectral energy distribution of HCM 6A yields a stellar mass of 1.3 Multiplication-Sign 10{sup 9} M{sub Sun} and an SFR of Almost-Equal-To 10 M{sub Sun} yr{sup -1}, with negligible dust obscuration. We fortuitously detect CO J = 3-2 emission from a z = 0.375 galaxy in the foreground cluster A370, and obtain a CO line luminosity of L'(CO) > (8.95 {+-} 0.79) Multiplication-Sign 10{sup 8} K km s{sup -1} pc{sup 2} and a molecular gas mass of M(H{sub 2}) > (4.12 {+-} 0.36) Multiplication-Sign 10{sup 9} M{sub Sun }, for a CO-to-H{sub 2} conversion factor of 4.6 M{sub Sun} (K km s{sup -1} pc{sup 2}){sup -1}.

  5. CONSTRAINTS ON HYPERLUMINOUS QSO LIFETIMES VIA FLUORESCENT Ly{alpha} EMITTERS AT Z {approx_equal} 2.7

    SciTech Connect

    Trainor, Ryan; Steidel, Charles C.

    2013-09-20

    We present observations of a population of Ly{alpha} emitters (LAEs) exhibiting fluorescent emission via the reprocessing of ionizing radiation from nearby hyperluminous QSOs. These LAEs are part of a survey at redshifts 2.5 < z < 2.9 combining narrow-band photometric selection and spectroscopic follow-up to characterize the emission mechanisms, physical properties, and three-dimensional locations of the emitters with respect to their nearby hyperluminous QSOs. These data allow us to probe the radiation field, and thus the radiative history, of the QSOs, and we determine that most of the eight QSOs in our sample have been active and of comparable luminosity for a time 1 Myr {approx}< t{sub Q} {approx}< 20 Myr. Furthermore, we find that the ionizing QSO emission must have an opening angle {theta} {approx} 30 Degree-Sign or larger relative to the line of sight.

  6. THE HANLE EFFECT OF THE HYDROGEN Ly{alpha} LINE FOR PROBING THE MAGNETISM OF THE SOLAR TRANSITION REGION

    SciTech Connect

    Trujillo Bueno, Javier; Stepan, JirI; Casini, Roberto E-mail: stepan@iac.es

    2011-09-01

    We present some theoretical predictions concerning the amplitude and magnetic sensitivity of the linear-polarization signals produced by scattering processes in the hydrogen Ly{alpha} line of the solar transition region. To this end, we have calculated the atomic-level polarization (population imbalances and quantum coherences) induced by anisotropic radiation pumping in semiempirical and hydrodynamical models of the solar atmosphere, taking into account radiative transfer and the Hanle effect caused by the presence of organized and random magnetic fields. The line-center amplitudes of the emergent linear-polarization signals are found to vary typically between 0.1% and 1%, depending on the scattering geometry and the strength and orientation of the magnetic field. The results shown here encourage the development of UV polarimeters for sounding rockets and space telescopes with the aim of opening up a diagnostic window for magnetic field measurements in the upper chromosphere and transition region of the Sun.

  7. THE HETDEX PILOT SURVEY. II. THE EVOLUTION OF THE Ly{alpha} ESCAPE FRACTION FROM THE ULTRAVIOLET SLOPE AND LUMINOSITY FUNCTION OF 1.9 < z < 3.8 LAEs

    SciTech Connect

    Blanc, Guillermo A.; Adams, Joshua J.; Gebhardt, Karl; Hao Lei; Fry, Alexander B.; Jeong, Donghui; Komatsu, Eiichiro; Murphy, Jeremy D.; Hill, Gary J.; Drory, Niv; Bender, Ralf; Hopp, Ulrich; Kelzenberg, Ralf; Ciardullo, Robin; Gronwall, Caryl; Schneider, Donald P.; Finkelstein, Steven L.; Gawiser, Eric; MacQueen, Phillip; Roth, Martin M.

    2011-07-20

    We study the escape of Ly{alpha} photons from Ly{alpha} emitting galaxies (LAEs) and the overall galaxy population using a sample of 99 LAEs at 1.9 < z < 3.8 detected through integral-field spectroscopy of blank fields by The Hobby Eberly Telescope Dark Energy Experiment Pilot Survey. For 89 LAEs with broadband counterparts we measure ultraviolet (UV) luminosities and UV slopes, and estimate E(B - V) under the assumption of a constant intrinsic UV slope for LAEs. These quantities are used to estimate dust-corrected star formation rates (SFRs). Comparison between the observed Ly{alpha} luminosity and that predicted by the dust-corrected SFR yields the Ly{alpha} escape fraction. We also measure the Ly{alpha} luminosity function and luminosity density ({rho}{sub Ly{alpha}}) at 2 < z < 4. Using this and other measurements from the literature at 0.3 < z < 7.7 we trace the redshift evolution of {rho}{sub Ly{alpha}.} We compare it to the expectations from the star formation history of the universe and characterize the evolution of the Ly{alpha} escape fraction of galaxies. LAEs at 2 < z < 4 selected down to a luminosity limit of L(Ly{alpha}) > (3-6) x 10{sup 42} erg s{sup -1} (0.25-0.5 L*), have a mean (E(B - V)) = 0.13 {+-} 0.01, implying an attenuation of {approx}70% in the UV. They show a median UV uncorrected SFR = 11 M{sub sun} yr{sup -1}, dust-corrected SFR = 34 M{sub sun} yr{sup -1}, and Ly{alpha} equivalent widths (EWs) which are consistent with normal stellar populations. We measure a median Ly{alpha} escape fraction of 29%, with a large scatter and values ranging from a few percent to 100%. The Ly{alpha} escape fraction in LAEs correlates with E(B - V) in a way that is expected if Ly{alpha} photons suffer from similar amounts of dust extinction as UV continuum photons. This result implies that a strong enhancement of the Ly{alpha} EW with dust, due to a clumpy multi-phase interstellar medium (ISM), is not a common process in LAEs at these redshifts. It also

  8. THE Ly{alpha} LINES OF H I AND He II: A DIFFERENTIAL HANLE EFFECT FOR EXPLORING THE MAGNETISM OF THE SOLAR TRANSITION REGION

    SciTech Connect

    Trujillo Bueno, Javier; Stepan, Jiri; Belluzzi, Luca E-mail: stepan@iac.es

    2012-02-10

    The Ly{alpha} line of He II at 304 Angstrom-Sign is one of the spectral lines of choice for EUV channels of narrowband imagers on board space telescopes, which provide spectacular intensity images of the outer solar atmosphere. Since the magnetic field information is encoded in the polarization of the spectral line radiation, it is important to investigate whether the He II line radiation from the solar disk can be polarized, along with its magnetic sensitivity. Here we report some theoretical predictions concerning the linear polarization signals produced by scattering processes in this strong emission line of the solar transition region, taking into account radiative transfer and the Hanle effect caused by the presence of organized and random magnetic fields. We find that the fractional polarization amplitudes are significant ({approx}1%), even when considering the wavelength-integrated signals. Interestingly, the scattering polarization of the Ly{alpha} line of He II starts to be sensitive to the Hanle effect for magnetic strengths B {approx}> 100 G (i.e., for magnetic strengths of the order of and larger than the Hanle saturation field of the hydrogen Ly{alpha} line at 1216 Angstrom-Sign ). We therefore propose simultaneous observations of the scattering polarization in both Ly{alpha} lines to facilitate magnetic field measurements in the upper solar chromosphere. Even the development of a narrowband imaging polarimeter for the He II 304 Angstrom-Sign line alone would be already of great diagnostic value for probing the solar transition region.

  9. A Luminosity Function of Ly(alpha)-Emitting Galaxies at Z [Approx. Equal to] 4.5(Sup 1),(Sup 2)

    NASA Technical Reports Server (NTRS)

    Dawson, Steve; Rhoads, James E.; Malhotra, Sangeeta; Stern, Daniel; Wang, JunXian; Dey, Arjun; Spinrad, Hyron; Jannuzi, Buell T.

    2007-01-01

    We present a catalog of 59 z [approx. equal to] 4:5 Ly(alpha)-emitting galaxies spectroscopically confirmed in a campaign of Keck DEIMOS follow-up observations to candidates selected in the Large Are (LALA) narrowband imaging survey.We targeted 97 candidates for spectroscopic follow-up; by accounting for the variety of conditions under which we performed spectroscopy, we estimate a selection reliability of approx.76%. Together with our previous sample of Keck LRIS confirmations, the 59 sources confirmed herein bring the total catalog to 73 spectroscopically confirmed z [approx. equal to] 4:5 Ly(alpha)- emitting galaxies in the [approx. equal to] 0.7 deg(exp 2) covered by the LALA imaging. As with the Keck LRIS sample, we find that a nonnegligible fraction of the co rest-frame equivalent widths (W(sub lambda)(sup rest)) that exceed the maximum predicted for normal stellar populations: 17%-31%(93%confidence) of the detected galaxies show (W(sub lambda)(sup rest)) 12%-27% (90% confidence) show (W(sub lambda)(sup rest)) > 240 A. We construct a luminosity function of z [approx. equal to] 4.5 Ly(alpha) emission lines for comparison to Ly(alpha) luminosity function < 6.6. We find no significant evidence for Ly(alpha) luminosity function evolution from z [approx. equal to] 3 to z [approx. equal to] 6. This result supports the conclusion that the intergalactic me largely reionized from the local universe out to z [approx. equal to] 6.5. It is somewhat at odds with the pronounced drop in the cosmic star formation rate density recently measured between z approx. 3 an z approx. 6 in continuum-selected Lyman-break galaxies, and therefore potentially sheds light on the relationship between the two populations.

  10. THE FIRST SYSTEMATIC SURVEY FOR Ly{alpha} EMITTERS AT z = 7.3 WITH RED-SENSITIVE SUBARU/SUPRIME-CAM

    SciTech Connect

    Shibuya, Takatoshi; Kashikawa, Nobunari; Iye, Masanori; Ota, Kazuaki; Ouchi, Masami; Furusawa, Hisanori; Shimasaku, Kazuhiro; Hattori, Takashi

    2012-06-20

    We have performed deep imaging surveys for Ly{alpha} emitters (LAEs) at redshift {approx}7.3 in two blank fields, the Subaru Deep Field (SDF) and the Subaru/XMM-Newton Deep survey Field (SXDF), using the Subaru/Suprime-Cam equipped with new red-sensitive CCDs and a new narrowband filter, NB1006 ({lambda}{sub c} = 10052 Angstrom-Sign , FWHM {Delta}{lambda} = 214 A). We identified four objects as LAE candidates that exhibit luminosity excess in NB1006. By carrying out deep follow-up spectroscopy for three of them using Subaru/FOCAS and Keck/DEIMOS, a definitively asymmetric emission line is detected for one of them, SXDF-NB1006-2. Assuming this line is Ly{alpha}, this object is an LAE at z = 7.215 which has a luminosity of 1.2{sup +1.5}{sub -0.6} Multiplication-Sign 10{sup 43} erg s{sup -1} and a weighted skewness S{sub {omega}} = 4.90 {+-} 0.86. Another object, SDF-NB1006-2, shows variable photometry and is thus probably a quasar (QSO) or an active galactic nucleus. It shows an asymmetric emission line at 10076 A which may be due to either Ly{alpha} at z = 7.288 or [O II] at z = 1.703. The third object, SDF-NB1006-1, is likely a galaxy with temporal luminosity enhancement associated with a supernova explosion, as the brightness of this object varies between the observed epochs. Its spectrum does not show any emission lines. The inferred decrease in the number density of LAEs toward higher redshift is n{sup z={sup {sup 7.3}{sub Ly{alpha}}}}/n{sub Ly{alpha}}{sup z={sup {sup 5.7}}} = 0.05{sup +0.11}{sub -0.05} from z = 5.7 to 7.3 down to L{sup Ly{alpha}} = 1.0 Multiplication-Sign 10{sup 43} erg s{sup -1}. The present result is consistent with the interpretation in previous studies that the neutral hydrogen fraction is rapidly increasing from z = 5.7 to 7.3.

  11. He II lambda 1640/lambda 4686 and Ly-alpha/H-beta ratios in the extraordinary Seyfert galaxy Markarian 359

    NASA Technical Reports Server (NTRS)

    Macalpine, G. M.; Davidson, K.; Gull, T. R.; Wu, C.-C.

    1985-01-01

    The exceptionally narrow-lined Seyfert 1 galaxy Mrk 359 is ideally suited for determining reddening via the He II lambda 1640/lambda 4686 emission-line ratio. Here the validity of He II lines as a reddening indicator for quasars and Seyfert galaxies is reexamined and confirmed in the context of the most complete photoionization models available. In addition, lambda 1640 equivalent width measurements are shown to support previous contentions of substantial differences between observed and intrinsic quasar far-ultraviolet continua. Then IUE satellite and ground-based spectral data are presented, with the surprising result that both the lambda 1640/lambda 4686 and Ly-alpha/H-beta ratios do not differ greatly from case B recombination values in Mrk 359. This object is only slightly reddened, and it shows no evidence for extended, high-optical-depth H(+)/H(0) transition regions in the line-emitting gas. The very narrow lines and lack of deep transition regions and/or reddening may be related. In addition, Mrk 359 has low luminosity compared with most other Seyfert 1 galaxies, measured emission lines suggest an unusually high ionization parameter, and there is a hint of low nitrogen abundance. Further work is needed to examine possible relationships among all these peculiar properties.

  12. CHARACTERIZATION OF THE DISTRIBUTION OF THE Ly{alpha} EMITTERS IN THE 53W002 FIELD AT z = 2.4

    SciTech Connect

    Mawatari, K.; Yamada, T.; Nakamura, Y.; Hayashino, T.; Matsuda, Y.

    2012-11-10

    We present the results of our wide-field narrowband imaging of the field around the radio galaxy 53W002 at z = 2.390 with Subaru/Suprime-Cam. A custom-made filter, NB413, centered at 4140 A with a width of 83 A is used to observe the 31' Multiplication-Sign 24' area around the radio galaxy. We detected 204 Ly{alpha} emitters (LAEs) at z = 2.4 with a rest-frame equivalent width larger than 25 A to the depth of 26 AB mag (in NB413). The entire LAE population in the 53W002 field has an average number density and distributions of equivalent width and size that are similar to those of other fields at z {approx} 2. We identify a significant high-density region (53W002F-HDR) that spreads over Almost-Equal-To 5' Multiplication-Sign 4' near 53W002, where the LAE number density is nearly four times as large as the average of the entire field. Using the probability distribution function of density fluctuation, we evaluate the rareness probability of 53W002F-HDR to be 0.9{sup +2.4} {sub -0.62}%, which corresponds to a moderately rich structure. No notable environmental dependency at the comoving scale of 10 Mpc is found for the distributions of the Ly{alpha} equivalent width and luminosity in the field. We also detected four Ly{alpha} blobs, one of which is newly discovered. They are all located in the rims of high-density regions. The biased location and unique morphologies in Ly{alpha} suggest that galaxy interaction plays a key role in their formation.

  13. H Ly-alpha transmittance of thin foils of C, Si/C, and Al/C for keV particle detectors

    NASA Technical Reports Server (NTRS)

    Drake, V. A.; Sandel, B. R.; Jenkins, D. G.; Hsieh, K. C.

    1992-01-01

    A class of instruments designed for remote sensing of space plasmas by measuring energetic neutral atoms (ENA) uses a thin foil as both a signal generator and a light shield. An ENA imager must look directly at the ENA source region, which is also usually an intense source of H Ly-alpha (1216 A) photons. It is desirable to minimize the energy threshold for ENA detectors, at the same time maximizing the blocking of H Ly-alpha. Optimizing filter design to meet these two contrary requirements has led us to measure the transmittance of thin C, Si/C, and Al/C foils at H Ly-alpha. Our results indicate that (1) transmittance of less than 0.0007 can be achieved with 7 micro-g/sq cm Si on 1.7 micro-g/sq cm C; (2) an Si/C composite foil with a thin carbon layer is more effective in blocking UV radiation while having the lowest energy threshold of all the foils measured; and (3) transmittance of Si/C foils of known Si and C thicknesses cannot be accurately predicted, but must be measured.

  14. HST/COS SPECTRA OF DF Tau AND V4046 Sgr: FIRST DETECTION OF MOLECULAR HYDROGEN ABSORPTION AGAINST THE Ly{alpha} EMISSION LINE

    SciTech Connect

    Yang Hao; Linsky, Jeffrey L.; France, Kevin E-mail: jlinsky@jilau1.colorado.edu

    2011-03-20

    We report the first detection of molecular hydrogen (H{sub 2}) absorption in the Ly{alpha} emission line profiles of two classical T Tauri stars (CTTSs), DF Tau and V4046 Sgr, observed by the Hubble Space Telescope/Cosmic Origins Spectrograph. This absorption is the energy source for many of the Lyman-band H{sub 2} fluorescent lines commonly seen in the far-ultraviolet spectra of CTTSs. We find that the absorbed energy in the H{sub 2} pumping transitions from a portion of the Ly{alpha} line significantly differ from the amount of energy in the resulting fluorescent emission. By assuming additional absorption in the H I Ly{alpha} profile along our light of sight, we can correct the H{sub 2} absorption/emission ratios so that they are close to unity. The required H I absorption for DF Tau is at a velocity close to the radial velocity of the star, consistent with H I absorption in the edge-on disk and interstellar medium. For V4046 Sgr, a nearly face-on system, the required absorption is between +100 km s{sup -1} and +290 km s{sup -1}, most likely resulting from H I gas in the accretion columns falling onto the star.

  15. X-RAY PROPERTIES OF THE z {approx} 4.5 Ly{alpha} EMITTERS IN THE CHANDRA DEEP FIELD SOUTH REGION

    SciTech Connect

    Zheng, Z. Y.; Wang, J. X.; Finkelstein, S. L.; Finkelstein, K. D.; Malhotra, S.; Rhoads, J. E. E-mail: jxw@ustc.edu.c

    2010-07-20

    We report the first X-ray detection of Ly{alpha} emitters (LAEs) at redshift z {approx} 4.5. One source (J033127.2-274247) is detected in the Extended Chandra Deep Field-South (ECDF-S) X-ray data and has been spectroscopically confirmed as a z = 4.48 quasar with L{sub X} = 4.2 x 10{sup 44} erg s{sup -1}. The single detection gives an Ly{alpha} quasar density of {approx} 2.7{sup +6.2} {sub -2.2} x 10{sup -6} Mpc{sup -3}, consistent with the X-ray luminosity function of quasars. Another 22 LAEs in the central Chandra Deep Field-South region are not detected individually, but their co-added counts yield an S/N = 2.4 (p = 99.83%) detection at soft band, with an effective exposure time of {approx}36 Ms. Further analysis of the equivalent width (EW) distribution shows that all the signals come from 12 LAE candidates with EW{sub rest}< 400 A and 2 of them contribute about half of the signal. From follow-up spectroscopic observations, we find that one of the two is a low-redshift emission-line galaxy, and the other is a Lyman break galaxy at z = 4.4 with little or no Ly{alpha} emission. Excluding these two and combined with ECDF-S data, we derive a 3{sigma} upper limit on the average X-ray flux of F {sub 0.5-2.0keV} < 1.6 x 10{sup -18} erg cm{sup -2} s{sup -1}, which corresponds to an average luminosity of (L {sub 0.5-2keV}) <2.4 x 10{sup 42} erg s{sup -1} for z {approx} 4.5 LAEs. If the average X-ray emission is due to star formation, it corresponds to a star formation rate (SFR) of <180-530 M {sub sun} yr{sup -1}. We use this SFR {sub X} as an upper limit of the unobscured SFR to constrain the escape fraction of Ly{alpha} photons and find a lower limit of f{sub esc,Ly{alpha}} > 3%-10%. However, our upper limit on the SFR {sub X} is {approx}7 times larger than the upper limit on SFR {sub X} on z {approx} 3.1 LAEs in the same field and at least 30 times higher than the SFR estimated from Ly{alpha} emission. From the average X-ray-to-Ly{alpha} line ratio, we estimate that

  16. STIS Observations of the Ly\\Alpha Bright Jet Associated with the Herbig Ae Star HD163296

    NASA Technical Reports Server (NTRS)

    Devine, David; Grady, C. A.; Woodgate, B.; Palunas, P.; Linsky, J. L.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We present follow-up HST/Space Telescope Imaging Spectrograph (STIS) observations of the Ly-alpha bright jet associated with the near-ZAMS Herbig Ae star HD163296. The proper motions and radial velocities of the knots in the flow are consistent with a collimated outflow inclined by 40 deg relative to the plane of the sky with a flow velocity that varies from 350 to 500 km/s along the jet. A new knot is visible in the jet at a projected distance of 0.33 arcsec (40 AU) from the central star. The knot has a dynamical age of only seven months, making it the youngest HH knot ever observed. We did not detect any emission from the counterjet within 2.5 arcsec of the source, which is consistent with absorption due to a uniform 450 AU radius disk tilted at 50 deg relative to the line of sight. We also present observations made with the Goddard Fabry-Perot Imager which show additional, more distant knots along the blue and red shifted outflow lobes, and discuss the collimation of the jet and implications for a magnetosphere associated with HD 163296. Support for this study was provided by HST STIS GTO funding through support to the NOAO, in response to the NASA A/O OSSA-4-84 through the Hubble Space Telescope Project at GSFC, as well as NASA grant NRA-98-03-UVG-O11. NOAO is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation. Data analysis facilities were provided by the Laboratory for Astronomy & Solar Physics, NASA/GSFC.

  17. The Influence of the Photoionizing Radiation Spectrum on Metal-Line Ratios in Ly(alpha) Forest Clouds

    NASA Technical Reports Server (NTRS)

    Giroux, Mark L.; Shull, J. Michael

    1997-01-01

    Recent measurements of Si IV/C IV ratios in the high-redshift Ly(alpha) forest (Songaila & Cowie, AJ, 112, 335 (1996a); Savaglio et at., A&A (in press) (1997)) have opened a new window on chemical enrichment and the first generations of stars. However, the derivation of accurate Si/C abundances requires reliable ionization corrections, which are strongly dependent on the spectral shape of the metagalactic ionizing background and on the 'local effects' of hot stars in nearby galaxies. Recent models have assumed power-law quasar ionizing backgrounds plus a decrement at 4 Ryd to account for He II attenuation in intervening clouds. However, we show that realistic ionizing backgrounds based on cosmological radiative transfer models produce more complex ionizing spectra between 1-5 Ryd that are critical to interpreting ions of Si and C. We also make a preliminary investigation of the effects of He II ionization front nonoverlap. Because the attenuation and reemission by intervening clouds enhance Si IV relative to C the observed high Si IV/C IV ratios do not require an unrealistic Si overproduction (Si/C greater than or equal to 3 (Si/C)(solar mass)). If the ionizing spectrum is dominated by 'local effects' from massive stars, even larger Si IV/C IV ratios are possible. However, unless stellar radiation dominates quasars by more than a factor of 10, we confirm the evidence for some Si overproduction by massive stars; values Si/C approx. 2(Si/C)(solar mass) fit the measurements better than solar abundances. Ultimately, an adequate interpretation of the ratios of C IV, Si IV, and C II may require hot, collisionally ionized gas in a multiphase medium.

  18. PRESENT-DAY DESCENDANTS OF z = 3 Ly{alpha}-EMITTING GALAXIES IN THE MILLENNIUM-II HALO MERGER TREES

    SciTech Connect

    Walker-Soler, Jean P.; Gawiser, Eric; Bond, Nicholas A.; Padilla, Nelson; Francke, Harold

    2012-06-20

    Using the Millennium-II Simulation dark matter sub-halo merger histories, we created mock catalogs of Ly{alpha}-emitting (LAE) galaxies at z = 3.1 to study the properties of their descendants. Several models were created by selecting the sub-halos to match the number density and typical dark matter mass determined from observations of these galaxies. We used mass-based and age-based selection criteria to study their effects on descendant populations at z {approx_equal} 2, 1, and 0. For the models that best represent LAEs at z = 3.1, the z = 0 descendants have a median dark matter halo mass of 10{sup 12.7} M{sub Sun }, with a wide scatter in masses (50% between 10{sup 11.8} and 10{sup 13.7} M{sub Sun }). Our study differentiated between central and satellite sub-halos and found that {approx}55% of z = 0 descendants are central sub-halos with M{sub Median} {approx} 10{sup 12}. This confirms that central z = 0 descendants of z = 3.1 LAEs have halo masses typical of L*-type galaxies. The satellite sub-halos reside in group/cluster environments with dark matter masses around 10{sup 14} M{sub Sun }. The median descendant mass is robust to various methods of age determination, but it could vary by a factor of five due to current observational uncertainties in the clustering of LAEs used to determine their typical z = 3.1 dark matter mass.

  19. THE CURIOUS CASE OF Ly{alpha} EMITTERS: GROWING YOUNGER FROM z {approx} 3 to z {approx} 2?

    SciTech Connect

    Acquaviva, Viviana; Vargas, Carlos; Gawiser, Eric; Guaita, Lucia

    2012-06-01

    Ly{alpha} emitting (LAE) galaxies are thought to be progenitors of present-day L* galaxies. Clustering analyses have suggested that LAEs at z {approx} 3 might evolve into LAEs at z {approx} 2, but it is unclear whether the physical nature of these galaxies is compatible with this hypothesis. Several groups have investigated the properties of LAEs using spectral energy distribution (SED) fitting, but direct comparison of their results is complicated by inconsistencies in the treatment of the data and in the assumptions made in modeling the stellar populations, which are degenerate with the effects of galaxy evolution. By using the same data analysis pipeline and SED fitting software on two stacked samples of LAEs at z = 3.1 and z = 2.1, and by eliminating several systematic uncertainties that might cause a discrepancy, we determine that the physical properties of these two samples of galaxies are dramatically different. LAEs at z = 3.1 are found to be old (age {approx}1 Gyr) and metal-poor (Z < 0.2 Z{sub Sun }), while LAEs at z = 2.1 appear to be young (age {approx}50 Myr) and metal-rich (Z > Z{sub Sun }). The difference in the observed stellar ages makes it very unlikely that z 3.1 LAEs evolve directly into z = 2.1 LAEs. Larger samples of galaxies, studies of individual objects, and spectroscopic measurements of metallicity at these redshifts are needed to confirm this picture, which is difficult to reconcile with the effects of 1 Gyr of cosmological evolution.

  20. The {ital b} Distribution and the Velocity Structure of Absorption Peaks in the Ly{alpha} Forest

    SciTech Connect

    Hui, L.

    1999-06-01

    A theory is developed that relates the observed {ital b} parameter of a Ly{alpha} absorption line to the velocity curvature of the corresponding peak in the optical depth fluctuation. Its relation to the traditional interpretation of {ital b} as the thermal broadening width is discussed. It is demonstrated that, independent of the details of the cosmological model, the differential {ital b} distribution has a high-{ital b} asymptote of dN/db{proportional_to}b{sup {minus}m}, where m{ge}5, when we make the reasonable assumption that low-curvature fluctuations are statistically favored over high-curvature ones. There in general always exist lines much broader than the thermal width. We develop a linear perturbative analysis of the optical depth fluctuation, which yields a single-parameter prediction for the full {ital b} distribution. In addition to exhibiting the high-velocity tail, it qualitatively explains the observed sharp low-{ital b} cutoff{emdash}a simple reflection of the fact that high-curvature fluctuations are relatively rare. Although the existence of the high-{ital b} asymptote, which is independent of the validity of the linear expansion, is consistent with the observed {ital b} distribution, a detailed comparison of the linear prediction with six observational data sets indicates that higher order corrections are not negligible. The perturbative analysis nonetheless offers valuable insights into the dependence of the {ital b} distribution on cosmological parameters such as {Omega} and the power spectrum. A key parameter is the effective smoothing scale of the optical depth fluctuation, which is in turn determined by three scales: the thermal broadening width, the baryon smoothing scale (approximately the Jeans scale), and the observation/simulation resolution. The first two are determined by reionization history, but are comparable in general, whereas the third varies by about an order of magnitude in current hydrodynamic simulations. Studies with non

  1. A NEW POPULATION OF HIGH-z, DUSTY Ly{alpha} EMITTERS AND BLOBS DISCOVERED BY WISE: FEEDBACK CAUGHT IN THE ACT?

    SciTech Connect

    Bridge, Carrie R.; Blain, Andrew; Borys, Colin J. K.; Griffith, Roger L.; Tsai, Chao-Wei; Petty, Sara; Farrah, Duncan; Benford, Dominic; Eisenhardt, Peter; Stern, Daniel; Wu Jingwen; Jarrett, Tom; Lonsdale, Carol; Stanford, Spencer A.; Wright, Edward L.

    2013-06-01

    By combining data from the NASA Wide-field Infrared Survey Explorer (WISE) mission with optical spectroscopy from the W. M. Keck telescope, we discover a mid-IR color criterion that yields a 78% success rate in identifying rare, typically radio-quiet, 1.6 {approx}< z {approx}< 4.6 dusty Ly{alpha} emitters (LAEs). Of these, at least 37% have emission extended on scales of 30-100 kpc and are considered Ly{alpha} ''blobs'' (LABs). The objects have a surface density of only {approx}0.1 deg{sup -2}, making them rare enough that they have been largely missed in deep, small area surveys. We measured spectroscopic redshifts for 92 of these galaxies, and find that the LAEs (LABs) have a median redshift of 2.3 (2.5). The WISE photometry coupled with data from Herschel (Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA) reveals that these galaxies are in the Hyper Luminous IR galaxy regime (L{sub IR} {approx}> 10{sup 13}-10{sup 14} L{sub Sun }) and have warm colors. They are typically more luminous and warmer than other dusty, z {approx} 2 populations such as submillimeter-selected galaxies and dust-obscured galaxies. These traits are commonly associated with the dust being illuminated by intense active galactic nucleus activity. We hypothesize that the combination of spatially extended Ly{alpha}, large amounts of warm IR-luminous dust, and rarity (implying a short-lived phase) can be explained if the galaxies are undergoing brief, intense ''feedback'' transforming them from an extreme dusty starburst/QSO into a mature galaxy.

  2. PHYSICAL PROPERTIES OF SPECTROSCOPICALLY CONFIRMED GALAXIES AT z {>=} 6. II. MORPHOLOGY OF THE REST-FRAME UV CONTINUUM AND Ly{alpha} EMISSION

    SciTech Connect

    Jiang Linhua; Windhorst, Rogier A.; Cohen, Seth H.; Mechtley, Matthew; Egami, Eiichi; Fan Xiaohui; Dave, Romeel; Finlator, Kristian; Kashikawa, Nobunari; Ouchi, Masami; Shimasaku, Kazuhiro

    2013-08-20

    We present a detailed structural and morphological study of a large sample of spectroscopically confirmed galaxies at z {>=} 6 using deep Hubble Space Telescope (HST) near-IR broad-band images and Subaru Telescope optical narrow-band images. The galaxy sample consists of 51 Ly{alpha} emitters (LAEs) at z {approx_equal} 5.7, 6.5, and 7.0, and 16 Lyman break galaxies (LBGs) at 5.9 {<=} z {<=} 6.5. These galaxies exhibit a wide range of rest-frame UV continuum morphology in the HST images, from compact features to multiple component systems. The fraction of merging/interacting galaxies reaches 40%-50% at the brightest end of M{sub 1500} {<=} -20.5 mag. The intrinsic half-light radii r{sub hl,in}, after correcting for point-spread function (PSF) broadening, are roughly between r{sub hl,in} {approx_equal} 0.''05 (0.3 kpc) and 0.''3 (1.7 kpc) at M{sub 1500} {<=} -19.5 mag. The median r{sub hl,in} value is 0.''16 ({approx}0.9 kpc). This is consistent with the sizes of bright LAEs and LBGs at z {>=} 6 found in previous studies. In addition, more luminous galaxies tend to be larger and exhibit a weak size-luminosity relation, r{sub hl,in}{proportional_to}L {sup 0.14} at M{sub 1500} {<=} -19.5 mag. The slope of 0.14 is significantly flatter than those in fainter LBG samples. We discuss the morphology of z {>=} 6 galaxies with nonparametric methods, including the concentration, asymmetry, and smoothness system and the Gini and M{sub 20} parameters, and demonstrate their validity through simulations. We search for extended Ly{alpha} emission halos around LAEs at z {approx_equal} 5.7 and 6.5 by stacking a number of narrow-band images. We do not find evidence of extended Ly{alpha} halos predicted by cosmological simulations. Such halos, if they exist, could be weaker than predicted. Finally, we investigate positional misalignment between the UV continuum and Ly{alpha} emissions in LAEs. While the two positions are generally consistent, several merging galaxies show significant

  3. PHYSICAL PROPERTIES OF SPECTROSCOPICALLY CONFIRMED GALAXIES AT z {>=} 6. I. BASIC CHARACTERISTICS OF THE REST-FRAME UV CONTINUUM AND Ly{alpha} EMISSION

    SciTech Connect

    Jiang Linhua; Mechtley, Matthew; Cohen, Seth H.; Windhorst, Rogier A.; Egami, Eiichi; Fan Xiaohui; Dave, Romeel; Finlator, Kristian; Kashikawa, Nobunari; Ouchi, Masami; Shimasaku, Kazuhiro

    2013-08-01

    We present deep Hubble Space Telescope near-IR and Spitzer mid-IR observations of a large sample of spectroscopically confirmed galaxies at z {>=} 6. The sample consists of 51 Ly{alpha} emitters (LAEs) at z {approx_equal} 5.7, 6.5, and 7.0, and 16 Lyman break galaxies (LBGs) at 5.9 {<=} z {<=} 6.5. The near-IR images were mostly obtained with WFC3 in the F125W and F160W bands, and the mid-IR images were obtained with IRAC in the 3.6 {mu}m and 4.5 {mu}m bands. Our galaxies also have deep optical imaging data from Subaru Suprime-Cam. We utilize the multi-band data and secure redshifts to derive their rest-frame UV properties. These galaxies have steep UV-continuum slopes roughly between {beta} {approx_equal} -1.5 and -3.5, with an average value of {beta} {approx_equal} -2.3, slightly steeper than the slopes of LBGs in previous studies. The slope shows little dependence on UV-continuum luminosity except for a few of the brightest galaxies. We find a statistically significant excess of galaxies with slopes around {beta} {approx_equal} -3, suggesting the existence of very young stellar populations with extremely low metallicity and dust content. Our galaxies have moderately strong rest-frame Ly{alpha} equivalent width (EW) in a range of {approx}10 to {approx}200 A. The star formation rates are also moderate, from a few to a few tens of solar masses per year. The LAEs and LBGs in this sample share many common properties, implying that LAEs represent a subset of LBGs with strong Ly{alpha} emission. Finally, the comparison of the UV luminosity functions between LAEs and LBGs suggests that there exists a substantial population of faint galaxies with weak Ly{alpha} emission (EW < 20 A) that could be the dominant contribution to the total ionizing flux at z {>=} 6.

  4. A DEEP SEARCH FOR CO J = 2-1 EMISSION FROM A Ly{alpha} BLOB AT z {approx} 6.595

    SciTech Connect

    Wagg, Jeff; Kanekar, Nissim

    2012-06-01

    We have used the Green Bank Telescope to carry out a deep search for redshifted CO J = 2-1 line emission from an extended (>17 kpc) Ly{alpha} blob (LAB), 'Himiko', at z {approx} 6.595. Our non-detection of CO J = 2-1 emission places the strong 3{sigma} upper limit of L'{sub CO} < 1.8 Multiplication-Sign 10{sup 10} Multiplication-Sign ({Delta}V/250){sup 1/2} K km s{sup -1} pc{sup 2} on the CO line luminosity. This is comparable to the best current limits on the CO line luminosity in LABs at z {approx} 3 and lower-luminosity Ly{alpha} emitters at z {approx}> 6.5. High-z LABs appear to have lower CO line luminosities than the host galaxies of luminous quasars and submillimeter galaxies at similar redshifts, despite their high stellar mass. Although the CO-to-H{sub 2} conversion factor is uncertain for galaxies in the early universe, we assume X{sub CO} = 0.8 M{sub Sun} (K km s{sup -1} pc{sup 2}){sup -1} to obtain the limit M(H{sub 2}) <1.4 Multiplication-Sign 10{sup 10} M{sub Sun} on Himiko's molecular gas mass; this is a factor of {approx}> 2.5 lower than the stellar mass in the z {approx} 6.595 LAB.

  5. Damped Lyman-alpha absorption by disk galaxies with large redshifts. III. Intermediate-resolution spectroscopy

    SciTech Connect

    Turnshek, D.A.; Wolfe, A.M.; Lanzetta, K.M.; Briggs, F.H.; Cohen, R.D.; Multiple Mirror Telescope Observatory, Tucson, AZ; Pittsburgh Univ., PA; California Univ., La Jolla )

    1989-09-01

    New intermediate-resolution spectroscopy for six members of a sample of 68 moderate- to high-redshift QSOs is presented. Evidence is reported which indicates that seven strong absorption features in the QSO spectra are due to damped Ly-alpha absorption. A standard curve-of-growth analysis on five of the damped systems is performed, and relevant properties are tabulated and discussed. Six of the seven damped Ly-alpha systems have H I column densities of 2 x 10 to the 20th/sq cm or larger, while the remaining system has an H I column density of about 10 to the 20th/sq cm. It is suggested that damped Ly-alpha systems arise when a sight line intercepts a high-redshift protogalaxy disk containing a quiescent cloud component characterized by high column density and low effective velocity dispersion. At the same time, the sight line usually intercepts a broader turbulent component, which is identified as the halo, characterized by much lower column density and higher effective velocity dispersion. 42 refs.

  6. A Ly{alpha} EMITTER WITH AN EXTREMELY LARGE REST-FRAME EQUIVALENT WIDTH OF {approx}900 A AT z = 6.5: A CANDIDATE POPULATION III-DOMINATED GALAXY?

    SciTech Connect

    Kashikawa, Nobunari; Hayashi, Masao; Iye, Masanori; Nagao, Tohru; Ota, Kazuaki; Toshikawa, Jun; Ishizaki, Yoshifumi; Shibuya, Takatoshi; Egami, Eiichi; Jiang, Linhua; Ly, Chun; Malkan, Matthew A.; Matsuda, Yuichi; Shimasaku, Kazuhiro; Taniguchi, Yoshiaki; Shioya, Yasuhiro

    2012-12-20

    We have identified a very interesting Ly{alpha} emitter (LAE), whose Ly{alpha} emission line has an extremely large observed equivalent width of EW{sub 0} = 436{sup +422}{sub -{sub 149}} A, which corresponds to an extraordinarily large intrinsic rest-frame equivalent width of EW{sup int}{sub 0} = 872{sup +844}{sub -{sub 298}} A after the average intergalactic absorption correction. The object was spectroscopically confirmed to be a real LAE by its apparent asymmetric Ly{alpha} line profile detected at z = 6.538. The continuum emission of the object was definitely detected in our deep z'-band image; thus, its EW{sub 0} was reliably determined. Follow-up deep near-infrared spectroscopy revealed emission lines of neither He II {lambda}1640 as an apparent signature of Population III (Pop III) nor C IV {lambda}1549 as proof of an active nucleus. No detection of the short-lived He II {lambda}1640 line is not necessarily inconsistent with the interpretation that the underlying stellar population of the object is dominated by Pop III. We found that the observed extremely large EW{sub 0} of the Ly{alpha} emission and the upper limit on the EW{sub 0} of the He II {lambda}1640 emission can be explained by population synthesis models favoring a very young age less than 2-4 Myr and massive metal-poor (Z < 10{sup -5}) or even metal-free stars. The observed large EW{sub 0} of Ly{alpha} is insufficiently explained by Population I/II synthesis models with Z {>=} 10{sup -3}. However, we cannot conclusively rule out the possibility that this object is composed of a normal stellar population with a clumpy dust distribution, which could enhance the Ly{alpha} EW{sub 0}, though its significance is still unclear.

  7. Damped Lyman-alpha absorption by disk galaxies with large redshifts. IV - More intermediate-resolution spectroscopy

    NASA Technical Reports Server (NTRS)

    Wolfe, Arthur M.; Turnshek, David A.; Lanzetta, Kenneth M.; Lu, Limin

    1993-01-01

    Intermediate-resolution spectra of six QSOs exhibiting seven Ly-alpha absorption troughs that are candidates for damped Ly-alpha absorption lines are presented. The metal content of the confirmed damped systems is investigated by examining the metal-line velocity profiles, and by performing curve-of-growth analyses for four of the six confirmed damped systems. The low-ionization lines associated with the z(metals) = 2.0399 damped system toward Q0458-020 have velocity widths up to 10 times wider than the width of the 21-cm absorption feature found at the same redshift. Since the 21-cm absorption arises in a low velocity dispersion layer of H I that extends more than 8/h kpc transverse to the line of sight, the H I absorption cannot arise from the same clouds responsible for the bulk of the metal-line absorption. This is strong evidence for a two-component model consisting of high column density 'quiescent' gas which gives rise to damped Ly-alpha and 21-cm absorption, and low column density 'turbulent' gas which dominates equivalent widths of saturated metal lines.

  8. EVOLUTION IN THE CONTINUUM MORPHOLOGICAL PROPERTIES OF Ly{alpha}-EMITTING GALAXIES FROM z = 3.1 TO z = 2.1

    SciTech Connect

    Bond, Nicholas A.; Gawiser, Eric; Guaita, Lucia; Padilla, Nelson; Gronwall, Caryl; Ciardullo, Robin; Lai, Kamson

    2012-07-10

    We present a rest-frame ultraviolet morphological analysis of 108 z {approx_equal} 2.1 Ly{alpha} emitters (LAEs) in the Extended Chandra Deep Field South and compare it to a similar sample of 171 LAEs at z {approx_equal} 3.1. Using Hubble Space Telescope images from the Galaxy Evolution from Morphology and SEDs survey, Great Observatories Origins Deep Survey, and Hubble Ultradeep Field, we measure size and photometric component distributions, where photometric components are defined as distinct clumps of UV-continuum emission. At both redshifts, >80% of LAEs have observed half-light radii <2 kpc, but the median half-light radius rises from 0.95 {+-} 0.04 kpc at z 3.1 to 1.41 {+-} 0.14 kpc at z = 2.1. A similar evolution is seen in the sizes of individual rest-UV components, but there is no evidence for evolution in the number of multi-component systems. In the z = 2.1 sample, we see clear correlations between the size of an LAE and other physical properties derived from its spectral energy distribution (SED). LAEs are found to be larger for galaxies with higher stellar mass, star formation rate, and dust obscuration, but there is no evidence for a trend between equivalent width and half-light radius at either redshift. The presence of these correlations suggests that a wide range of objects are being selected by LAE surveys at z {approx} 2, including a significant fraction of objects for which a massive and moderately extended population of old stars underlies the young starburst giving rise to the Ly{alpha} emission.

  9. STELLAR POPULATIONS OF Ly{alpha} EMITTERS AT z {approx} 6-7: CONSTRAINTS ON THE ESCAPE FRACTION OF IONIZING PHOTONS FROM GALAXY BUILDING BLOCKS

    SciTech Connect

    Ono, Yoshiaki; Shimasaku, Kazuhiro; Okamura, Sadanori; Masami Ouchi; Dunlop, James; Farrah, Duncan; McLure, Ross

    2010-12-01

    We investigate the stellar populations of Ly{alpha} emitters (LAEs) at z = 5.7 and 6.6 in a 0.65 deg{sup 2} sky of the Subaru/XMM-Newton Deep Survey (SXDS) Field, using deep images taken with the Subaru/Suprime-Cam, United Kingdom Infrared Telescope/Wide Field Infrared Camera, and Spitzer/Infrared Array Camera (IRAC). We produce stacked multiband images at each redshift from 165 (z = 5.7) and 91 (z = 6.6) IRAC-undetected objects to derive typical spectral energy distributions (SEDs) of z {approx} 6-7 LAEs for the first time. The stacked LAEs have as blue UV continua as the Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) z-dropout galaxies of similar M{sub UV}, with a spectral slope {beta} {approx} -3, but at the same time they have red UV-to-optical colors with detection in the 3.6 {mu}m band. Using SED fitting we find that the stacked LAEs have low stellar masses of {approx}(3-10) x 10{sup 7} M{sub sun}, very young ages of {approx}1-3 Myr, negligible dust extinction, and strong nebular emission from the ionized interstellar medium, although the z = 6.6 object is fitted similarly well with high-mass models without nebular emission; inclusion of nebular emission reproduces the red UV-to-optical colors while keeping the UV colors sufficiently blue. We infer that typical LAEs at z {approx} 6-7 are building blocks of galaxies seen at lower redshifts. We find a tentative decrease in the Ly{alpha} escape fraction from z = 5.7 to 6.6, which may imply an increase in the intergalactic medium neutral fraction. From the minimum contribution of nebular emission required to fit the observed SEDs, we place an upper limit on the escape fraction of ionizing photons of f {sup ion}{sub esc} {approx} 0.6 at z = 5.7 and {approx}0.9 at z = 6.6. We also compare the stellar populations of our LAEs with those of stacked HST/WFC3 z-dropout galaxies.

  10. THE SCATTERING POLARIZATION OF THE Ly{alpha} LINES OF H I AND He II TAKING INTO ACCOUNT PARTIAL FREQUENCY REDISTRIBUTION AND J-STATE INTERFERENCE EFFECTS

    SciTech Connect

    Belluzzi, Luca; Trujillo Bueno, Javier; Stepan, Jiri

    2012-08-10

    Recent theoretical investigations have pointed out that the cores of the Ly{alpha} lines of H I and He II should show measurable scattering polarization signals when observing the solar disk, and that the magnetic sensitivity, through the Hanle effect, of such linear polarization signals is suitable for exploring the magnetism of the solar transition region. Such investigations were carried out in the limit of complete frequency redistribution (CRD) and neglecting quantum interference between the two upper J-levels of each line. Here we relax both approximations and show that the joint action of partial frequency redistribution and J-state interference produces much more complex fractional linear polarization (Q/I) profiles, with large amplitudes in their wings. Such wing polarization signals turn out to be very sensitive to the temperature structure of the atmospheric model, so that they can be exploited for constraining the thermal properties of the solar chromosphere. Finally, we show that the approximation of CRD without J-state interference is however suitable for estimating the amplitude of the linear polarization signals in the core of the lines, where the Hanle effect operates.

  11. Automotive headlighting: effect of foreground illumination.

    PubMed

    Olson, P L; Sivak, M

    1983-12-01

    Described are studies of the relationship between the level of foreground illumination provided by automotive headlamps and the driver's eye-fixation pattern and ability to identify objects ahead of the car. Analysis indicates that the driver's eye fixations tended to move further from the car at high levels of foreground illumination. There were no differences in distance of target identification as a function of level of foreground illumination. PMID:6664782

  12. Quadratic Damping

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2012-01-01

    Quadratic friction involves a discontinuous damping term in equations of motion in order that the frictional force always opposes the direction of the motion. Perhaps for this reason this topic is usually omitted from beginning texts in differential equations and physics. However, quadratic damping is more realistic than viscous damping in many…

  13. Recognizing foreground-background interaction

    NASA Astrophysics Data System (ADS)

    Jenkins, Jeffrey; Szu, Harold

    2010-04-01

    Can the background affect a foreground target in distant, low-quality imagery? If it does, it might occur in our mind, or perhaps it may represent a snapshot of our early vision. An affirmative answer, one way or another, may affect our current understanding of this phenomena and potentially for related applications. How can we be sure about this in the psycho-physical sense? We begin with the physiology of our brain's homeostasis, of which an isothermal equilibrium is characterized by the minimum of Helmholtz isothermal Free Energy: A = U - T0S >= 0, where T0 = 37°C, the Boltzmann Entropy S = KB1n(W), and U is the unknown internal energy to be computed.

  14. Landau damping

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2010-10-01

    Section 2.5.8 of the Handbook of Accelerator Physics and Engineering on Landau damping is rewritten. An solvable example is first given to demonstrate the interplay between Landau damping and decoherence. This example is an actual one when the beam oscillatory motion is driven by a wake force. The dispersion relation is derived and its implication on Landau damping is illustrated. The rest of the article touches on the Landau damping of transverse and longitudinal beam oscillations. The stability criteria are given for a bunched beam and the changes of the criteria when the beam is lengthened and becomes unbunched.

  15. Coulomb Damping

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2012-01-01

    Viscous damping is commonly discussed in beginning differential equations and physics texts but dry friction or Coulomb friction is not despite dry friction being encountered in many physical applications. One reason for avoiding this topic is that the equations involve a jump discontinuity in the damping term. In this article, we adopt an energy…

  16. Nearby Galaxies as Damped Lyman alpha Absorbers

    NASA Astrophysics Data System (ADS)

    Rao, Sandhya

    1993-12-01

    The evolution of the neutral hydrogen content of galaxies as a function of time is an important constraint on processes in galactic evolution. We present a comprehensive, statistical description of the HI content and distribution within galaxies at the present epoch and compare these statistics with the properties of HI associated with ``damped Lyman alpha '' absorption systems at high redshift that are observed in the spectra of QSOs. Omega_ {HI}(z=0), the HI mass density at the present epoch relative to the present critical mass density, is found to be (2.3 +/- 0.6) times 10(-4) h75(-1) , consistent with the decreasing trend of the HI content with time deduced from QSO absorption line statistics for redshifts from about 4 to 0.5 (Lanzetta 1993). Spiral galaxies contain an overwhelming 94% of this neutral hydrogen mass. The rest is contained in irregulars (3%), and S0s plus ellipticals (3%). Spirals also offer the largest cross-section to line-of-sight absorption of light from QSOs. By considering nearby spirals as potential absorbers, the interception probability as a function of the HI column density, N(HI), is derived for comparison with the cross-sections inferred from observations of damped Lyman alpha systems. Consistent with previous studies, the comparison shows that the damped Ly alpha lines are created by absorbers that subtend larger cross-sections than present-day spirals by a factor of 5 implying that galaxies were either larger or more numerous at z ~ 2.5. We are also investigating the statistics of damped Lyman alpha absorbers in the redshift range 0.2 1.5.

  17. BFORE: The B-mode Foreground Experiment

    NASA Astrophysics Data System (ADS)

    Niemack, Michael D.; Ade, Peter; de Bernardis, Francesco; Boulanger, Francois; Bryan, Sean; Devlin, Mark; Dunkley, Joanna; Eales, Steve; Gomez, Haley; Groppi, Chris; Henderson, Shawn; Hillbrand, Seth; Hubmayr, Johannes; Mauskopf, Philip; McMahon, Jeff; Miville-Deschênes, Marc-Antoine; Pascale, Enzo; Pisano, Giampaolo; Novak, Giles; Scott, Douglas; Soler, Juan; Tucker, Carole

    2016-08-01

    The B-mode Foreground Experiment (BFORE) is a proposed NASA balloon project designed to make optimal use of the sub-orbital platform by concentrating on three dust foreground bands (270, 350, and 600 GHz) that complement ground-based cosmic microwave background (CMB) programs. BFORE will survey ˜ 1/4 of the sky with 1.7-3.7 arcminute resolution, enabling precise characterization of the Galactic dust that now limits constraints on inflation from CMB B-mode polarization measurements. In addition, BFORE's combination of frequency coverage, large survey area, and angular resolution enables science far beyond the critical goal of measuring foregrounds. BFORE will constrain the velocities of thousands of galaxy clusters, provide a new window on the cosmic infrared background, and probe magnetic fields in the interstellar medium. We review the BFORE science case, timeline, and instrument design, which is based on a compact off-axis telescope coupled to {>}10,000 superconducting detectors.

  18. BFORE: The B-mode Foreground Experiment

    NASA Astrophysics Data System (ADS)

    Niemack, Michael D.; Ade, Peter; de Bernardis, Francesco; Boulanger, Francois; Bryan, Sean; Devlin, Mark; Dunkley, Joanna; Eales, Steve; Gomez, Haley; Groppi, Chris; Henderson, Shawn; Hillbrand, Seth; Hubmayr, Johannes; Mauskopf, Philip; McMahon, Jeff; Miville-Deschênes, Marc-Antoine; Pascale, Enzo; Pisano, Giampaolo; Novak, Giles; Scott, Douglas; Soler, Juan; Tucker, Carole

    2015-12-01

    The B-mode Foreground Experiment (BFORE) is a proposed NASA balloon project designed to make optimal use of the sub-orbital platform by concentrating on three dust foreground bands (270, 350, and 600 GHz) that complement ground-based cosmic microwave background (CMB) programs. BFORE will survey ˜ 1/4 of the sky with 1.7-3.7 arcminute resolution, enabling precise characterization of the Galactic dust that now limits constraints on inflation from CMB B-mode polarization measurements. In addition, BFORE's combination of frequency coverage, large survey area, and angular resolution enables science far beyond the critical goal of measuring foregrounds. BFORE will constrain the velocities of thousands of galaxy clusters, provide a new window on the cosmic infrared background, and probe magnetic fields in the interstellar medium. We review the BFORE science case, timeline, and instrument design, which is based on a compact off-axis telescope coupled to {>}10,000 superconducting detectors.

  19. TOWER, WEST ELEVATION, SHOWING CONNECTION PIPES FOR TURNOUTS 22 (FOREGROUND) ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    TOWER, WEST ELEVATION, SHOWING CONNECTION PIPES FOR TURNOUTS 22 (FOREGROUND) AND 24. NOTE “LAZY JACK” TEMPERATURE COMPENSATOR IN FOREGROUND. - Baltimore & Ohio Railroad, Z Tower, State Route 46, Keyser, Mineral County, WV

  20. GENERAL VIEW OF SITE LOOKING SOUTHWEST. JUPITER 'HOP' STAND, FOREGROUND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    GENERAL VIEW OF SITE LOOKING SOUTHWEST. JUPITER 'HOP' STAND, FOREGROUND CENTER, REDSTONE TEST STAND FOREGROUND RIGHT, SATURN I C TEST STAND BACKGROUND LEFT. - Marshall Space Flight Center, Redstone Rocket (Missile) Test Stand, Dodd Road, Huntsville, Madison County, AL

  1. 2. VIEW SHOWING SOUTHWEST FACE OF BATTERY OFFICES FOREGROUND, DIRECTOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. VIEW SHOWING SOUTHWEST FACE OF BATTERY OFFICES FOREGROUND, DIRECTOR PIT LEFT MIDDLE-GROUND. AND HEIGHT FINDER RIGHT FOREGROUND, LOOKING NORTHEAST - Fort Cronkhite, Anti-Aircraft Battery No. 1, Battery Offices, Wolf Ridge, Sausalito, Marin County, CA

  2. 4. Log chicken house (far left foreground), log bunkhouse (far ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. Log chicken house (far left foreground), log bunkhouse (far left background), one-room log cabin (left of center background), log root cellar (center), post-and-beam center in foreground, and blacksmith shop (far right foreground). View to southeast. - William & Lucina Bowe Ranch, County Road 44, 0.1 mile northeast of Big Hole River Bridge, Melrose, Silver Bow County, MT

  3. Modeling the Extragalactic Epoch of Reionization Foreground

    NASA Astrophysics Data System (ADS)

    Carroll, Patricia A.

    The Epoch of Reionization represents a largely unexplored yet fundamental chapter of the early universe. During this period, spanning several hundred million years, the first stars and galaxies formed and the Hydrogen-dominated intergalactic medium transitioned from a predominantly neutral to ionized state. Modern efforts to study exactly when and how reionization occurred are largely focused on the distribution of neutral Hydrogen gas and its evolution in response to the increasing abundance of luminous objects and ionizing flux. The Murchison Widefield Array is a low frequency radio interferometer designed as a first generation EoR experiment. The predominant systematic difficulty in making a detection of the primordial HI signal is the overwhelmingly bright emission from the intervening foreground galaxies and quasars. This thesis presents novel survey methods used to create a highly precise and reliable catalog of discrete extragalactic sources for the purposes of both calibration and foreground removal.

  4. GARDEN (FOREGROUND), GARAGE (CENTER), AND PUMPHOUSE, LOOKING NORTHWEST Irvine ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    GARDEN (FOREGROUND), GARAGE (CENTER), AND PUMPHOUSE, LOOKING NORTHWEST - Irvine Ranch Agricultural Headquarters, Carillo Tenant House, Southwest of Intersection of San Diego & Santa Ana Freeways, Irvine, Orange County, CA

  5. 20. CAMPANILE WITH DOWNING URN IN FOREGROUND, LOOKING SOUTHWEST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    20. CAMPANILE WITH DOWNING URN IN FOREGROUND, LOOKING SOUTHWEST - Smithsonian Institution Building, 1000 Jefferson Drive, between Ninth & Twelfth Streets, Southwest, Washington, District of Columbia, DC

  6. VIEW OF MARISCAL WORKS INCLUDING (POSSIBLE SOOT FURNACE), FOREGROUND, CONDENSERS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF MARISCAL WORKS INCLUDING (POSSIBLE SOOT FURNACE), FOREGROUND, CONDENSERS AND ORE BIN FOUNDATION ABOVE, LOOKING NORTHWEST. - Mariscal Quicksilver Mine & Reduction Works, Terlingua, Brewster County, TX

  7. 18. VIEW OF MARISCAL WORKS INCLUDING (POSSIBLE SOOT FURNACE), FOREGROUND, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. VIEW OF MARISCAL WORKS INCLUDING (POSSIBLE SOOT FURNACE), FOREGROUND, CONDENSERS, AND ORE BIN FOUNDATION ABOVE, LOOKING NORTHWEST. - Mariscal Quicksilver Mine & Reduction Works, Terlingua, Brewster County, TX

  8. A moving foreground objects extraction method under camouflage effect

    NASA Astrophysics Data System (ADS)

    Zhu, Zhen-zhen; Li, Jing-yue; Yang, Si-si; Zhou, Hong

    2015-07-01

    This paper discusses the problem of segmenting foreground objects with apertures or discontinuities under camouflage effect and the optical physics model is introduced into foreground detection. A moving foreground objects extraction method based on color invariants is proposed in which color invariants are used as descriptors to model the background and do the foreground segmentation. It makes full use of the color spectral information and spatial configuration. Experimental results demonstrate that the proposed method performs well in various situations of color similarity and meets the demand of real-time performance.

  9. NORTH AND WEST SIDES OF OIL HOUSE IN RIGHT FOREGROUND, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    NORTH AND WEST SIDES OF OIL HOUSE IN RIGHT FOREGROUND, WITH EMBANKMENT (MI-100-A) IN LEFT FOREGROUND, AND POWERHOUSE (MI-100-B) AND SUBSTATION (MI-100-C) AT CENTER AND LEFT BACKGROUND. VIEW TO SOUTHEAST - Hardy Hydroelectric Plant, Oil House, 6928 East Thirty-sixth Street, Newaygo, Newaygo County, MI

  10. 2. VIEW OF EAST TAILING DAM (FOREGROUND), LOOKING EAST SOUTHEAST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. VIEW OF EAST TAILING DAM (FOREGROUND), LOOKING EAST SOUTHEAST UP WASH TOWARD ORE BIN, OVERBURDEN, ADITS, AND ROAD SHOWN IN CA-290-1. MILL SITE IS UP AND TO THE RIGHT OF THIS VIEW. STANDARD FIFTY-GALLON DRUM IN FOREGROUND GIVES SCALE OF WALL. - Skidoo Mine, Park Route 38 (Skidoo Road), Death Valley Junction, Inyo County, CA

  11. VIEW TO EAST OF CRYSTALLIZATION LABORATORY (CENTER LEFT FOREGROUND), PAINT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW TO EAST OF CRYSTALLIZATION LABORATORY (CENTER LEFT FOREGROUND), PAINT APPLICATION BUILDING (CENTER BACKGROUND), AND c1944-1950 c1944-1950 POST-U.S. RADIUM ADDITION ADDITIONS TO EACH BUILDING (RIGHT FOREGROUND AND BACKGROUND) - United States Radium Corporation, 422-432 Alden Street, Orange, Essex County, NJ

  12. Robust Background Subtraction with Foreground Validation for Urban Traffic Video

    SciTech Connect

    Cheung, S S; Kamath, C

    2004-01-15

    Identifying moving objects in a video sequence is a fundamental and critical task in many computer-vision applications. Background subtraction techniques are commonly used to separate foreground moving objects from the background. Most background subtraction techniques assume a single rate of adaptation, which is inadequate for complex scenes such as a traffic intersection where objects are moving at different and varying speeds. In this paper, we propose a foreground validation algorithm that first builds a foreground mask using a slow-adapting Kalman filter, and then validates individual foreground pixels by a simple moving object model, built using both the foreground and background statistics as well as the frame difference. Ground-truth experiments with urban traffic sequences show that our proposed algorithm significantly improves upon results using only Kalman filter or frame-differencing, and outperforms other techniques based on mixture of Gaussians, median filter, and approximated media filter.

  13. Statistical Diagnostics to Identify Galactic Foregrounds in B -Mode Maps

    NASA Astrophysics Data System (ADS)

    Kamionkowski, Marc; Kovetz, Ely D.

    2014-11-01

    Recent developments in the search for inflationary gravitational waves in the cosmic microwave background polarization motivate the search for new diagnostics to distinguish the Galactic foreground contribution to B modes from the cosmic signal. We show that B modes from these foregrounds should exhibit a local hexadecapolar departure in power from statistical isotropy (SI). We present a simple algorithm to search for a uniform SI violation of this sort, as may arise in a sufficiently small patch of sky. We then show how to search for these effects if the orientation of the SI violation varies across the survey region, as is more likely to occur in surveys with more sky coverage. If detected, these departures from Gaussianity would indicate some level of Galactic foreground contamination in the B -mode maps. Given uncertainties about foreground properties, though, caution should be exercised in attributing a null detection to an absence of foregrounds.

  14. Cross-correlation analysis of CMB with foregrounds for residuals

    NASA Astrophysics Data System (ADS)

    Aluri, Pavan K.; Rath, Pranati K.

    2016-06-01

    In this paper, we try to probe whether a clean cosmic microwave background (CMB) map obtained from the raw satellite data using a cleaning procedure is sufficiently clean. Specifically, we study if there are any foreground residuals still present in the cleaned data using a cross-correlation statistic. Residual contamination is expected to be present, primarily, in the Galactic plane due to the high emission from our own Galaxy. A foreground mask is applied conventionally to avoid biases in the estimated quantities of interest due to foreground leakage. Here, we map foreground residuals, if present, in the unmasked region i.e. outside a CMB analysis mask. Further locally extended foreground-contaminated regions, found eventually, are studied to understand them better. The few contaminated regions thus identified may be used to slightly extend the available masks to make them more stringent.

  15. Solution Accounts for Structural Damping

    NASA Technical Reports Server (NTRS)

    Roussos, L. A.; Hyer, M. W.; Thornton, E. A.

    1982-01-01

    New analytical technique determines dynamic response of damped structures dominated by internal structural damping mechanisms. Though structural damping is often negligible compared with damping due to air friction and friction in joints, structural damping can be of major importance in structures having heavy damping treatments or in outer-space structures. Finite-element model includes nonlinear, nonviscous internal damping.

  16. Magnetic Damping For Maglev

    DOE PAGESBeta

    Zhu, S.; Cai, Y.; Rote, D. M.; Chen, S. S.

    1998-01-01

    Magnetic damping is one of the important parameters that control the response and stability of maglev systems. An experimental study to measure magnetic damping directly is presented. A plate attached to a permanent magnet levitated on a rotating drum was tested to investigate the effect of various parameters, such as conductivity, gap, excitation frequency, and oscillation amplitude, on magnetic damping. The experimental technique is capable of measuring all of the magnetic damping coefficients, some of which cannot be measured indirectly.

  17. Damped leaf flexure hinge

    NASA Astrophysics Data System (ADS)

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage.

  18. Damped leaf flexure hinge.

    PubMed

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage. PMID:26026549

  19. Overview of operational apron. Painted warning sign in foreground. View ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Overview of operational apron. Painted warning sign in foreground. View to north - Offutt Air Force Base, Looking Glass Airborne Command Post, Operational & Hangar Access Aprons, Spanning length of northeast half of Project Looking Glass Historic District, Bellevue, Sarpy County, NE

  20. 7. INTERIOR OF BUILDING 242, SHOWING GANTRY HOIST IN FOREGROUND. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. INTERIOR OF BUILDING 242, SHOWING GANTRY HOIST IN FOREGROUND. VIEW TO SOUTHWEST. - Rocky Mountain Arsenal, Chlorine Production Cell Building, 405 feet South of December Seventh Avenue; 330 feet West of D Street, Commerce City, Adams County, CO

  1. 2. MAGAZINE P, WITH ENTRANCE DOOR IN FOREGROUND, LOOKING NORTHEAST. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. MAGAZINE P, WITH ENTRANCE DOOR IN FOREGROUND, LOOKING NORTHEAST. - NIKE Missile Base C-84, Underground Storage Magazines & Launcher-Loader Assemblies, Easternmost portion of launch area, Barrington, Cook County, IL

  2. 9. FLUME BOX Y, LOOKING SOUTH. CANAL IN FOREGROUND FOLLOWS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. FLUME BOX Y, LOOKING SOUTH. CANAL IN FOREGROUND FOLLOWS HILLSIDE INTO DRAINAGE; FLUME HEADING TO RIGHT CROSSED GULCH ON A TRESTLE. - Snake River Ditch, Headgate on north bank of Snake River, Dillon, Summit County, CO

  3. 25. CAFETERIA Note remains of tile floor in foreground. Food ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    25. CAFETERIA Note remains of tile floor in foreground. Food cooked on the stove was served to workers in the eating area to the left of the counter (off picture). - Hovden Cannery, 886 Cannery Row, Monterey, Monterey County, CA

  4. SECTION D, WITH FLAT GROUP BURIAL MARKER AT RIGHT FOREGROUND. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    SECTION D, WITH FLAT GROUP BURIAL MARKER AT RIGHT FOREGROUND. VIEW TO NORTHWEST. - Rock Island National Cemetery, Rock Island Arsenal, 0.25 mile north of southern tip of Rock Island, Rock Island, Rock Island County, IL

  5. Contextual view showing building 253 in foreground; camera facing southeast. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Contextual view showing building 253 in foreground; camera facing southeast. - Mare Island Naval Shipyard, Supply Building, Walnut Avenue, southeast corner of Walnut Avenue & Fifth Street, Vallejo, Solano County, CA

  6. Context view looking west from hill with tree in foreground. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Context view looking west from hill with tree in foreground. Entist Mountains are in distance. - Badger Mountain Lookout, .125 mile northwest of Badger Mountain summit, East Wenatchee, Douglas County, WA

  7. Elevation from east. White Holly in foreground, with White Sage ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Elevation from east. White Holly in foreground, with White Sage behind. - U.S. Coast Guard Cutter WHITE HOLLY, U.S. Coast Guard 8th District Base, 4640 Urquhart Street, New Orleans, Orleans Parish, LA

  8. 33. Coal Fuel Elevator (diagonal in foreground), Fuel Elevator (left), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    33. Coal Fuel Elevator (diagonal in foreground), Fuel Elevator (left), Fuel Storage Bins (center), and Power Plant (right) Photographs taken by Joseph E.B. Elliot - Huber Coal Breaker, 101 South Main Street, Ashley, Luzerne County, PA

  9. 2. Long view east, with bridge in foreground, showing length ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. Long view east, with bridge in foreground, showing length of Carquinez Strait with Benecia Martinez Bridge in background. - Carquinez Bridge, Spanning Carquinez Strait at Interstate 80, Vallejo, Solano County, CA

  10. EVAPORATOR FLOOR, CELL ONE IN FOREGROUND, CRYSTALLIZER MEZZANINE TO REAR, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    EVAPORATOR FLOOR, CELL ONE IN FOREGROUND, CRYSTALLIZER MEZZANINE TO REAR, OLIVER MUD FILTER WING TO RIGHT REAR. VIEW FROM NORTHEAST - Lihue Plantation Company, Sugar Mill Building, Haleko Road, Lihue, Kauai County, HI

  11. BOILING HOUSE, INTERIOR, SECOND FLOOR, GARVER CLARIFIER IN FOREGROUND, TOPS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    BOILING HOUSE, INTERIOR, SECOND FLOOR, GARVER CLARIFIER IN FOREGROUND, TOPS OF LONG TUBE EVAPORATORS IN BACKGROUND. VIEW FROM NORTHWEST - Kekaha Sugar Company, Sugar Mill Building, 8315 Kekaha Road, Kekaha, Kauai County, HI

  12. 17. VIEW OF UNDERSTRUCTURE, SWAY BRACING IN FOREGROUND, COLUMNS, AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. VIEW OF UNDERSTRUCTURE, SWAY BRACING IN FOREGROUND, COLUMNS, AND DECK SOFFIT, LOOKING NORTHEAST TO NORTH ABUTMENT - Chili Bar Bridge, Spanning South Fork of American River at State Highway 193, Placerville, El Dorado County, CA

  13. 44. Blue Coal Corporation Office Building (foreground), Huber Breaker (left), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    44. Blue Coal Corporation Office Building (foreground), Huber Breaker (left), Retail Coal Storage Bins (far center) Photograph taken by George Harven - Huber Coal Breaker, 101 South Main Street, Ashley, Luzerne County, PA

  14. CONTEXTUAL VIEW FROM HOTEL; HAMILTON BUNGALOW IN FOREGROUND; BUNGALOW NO. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    CONTEXTUAL VIEW FROM HOTEL; HAMILTON BUNGALOW IN FOREGROUND; BUNGALOW NO. 3 DIRECTLY BEHIND; HINDS & CONNER AND "A" BUNGALOWS IN REAR. VISTA DEL ARROYO HOTEL ON RIGHT - Vista del Arroyo Hotel, 125 South Grand Avenue, Pasadena, Los Angeles County, CA

  15. Building 202, with shop area in foreground, also showing test ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Building 202, with shop area in foreground, also showing test cell of test stand A and a portion of stand B. - Rocket Engine Testing Facility, GRC Building No. 202, NASA Glenn Research Center, Cleveland, Cuyahoga County, OH

  16. 12. June 1988 INTERIOR, SOUTHWEST CORNER; SHOWING FIREFINDER (FOREGROUND), LIGHTNING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. June 1988 INTERIOR, SOUTHWEST CORNER; SHOWING FIREFINDER (FOREGROUND), LIGHTNING STOOL AND BED (BOTH TO RIGHT OF FIREFINDER) - Suntop Lookout, Forest Road 510, Mt. Baker-Snoqualmie National Forest, Greenwater, Pierce County, WA

  17. El Tovar steam tunnel breaker box in foreground. Note El ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    El Tovar steam tunnel breaker box in foreground. Note El Tovar stone vault in alignment with tunnel. - Grand Canyon Village Utilities, Grand Canyon National Park, Grand Canyon Village, Coconino County, AZ

  18. NORTH AND EAST SIDES, WITH READY MAGAZINE 155 IN FOREGROUND, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    NORTH AND EAST SIDES, WITH READY MAGAZINE 155 IN FOREGROUND, VIEW FACING SOUTH-SOUTHWEST. - Naval Air Station Barbers Point, Torpedo & Bombsight Shop & Storehouse, Midway Street between Enterprise & Ranger Streets, Ewa, Honolulu County, HI

  19. Looking east along Porter Avenue, management engineering in foreground; supply ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Looking east along Porter Avenue, management engineering in foreground; supply department storehouse (building no. 5) (Haer no. PA-387-1) to left. - Naval Base Philadelphia-Philadelphia Naval Shipyard, Management Engineering, League Island, Philadelphia, Philadelphia County, PA

  20. 19. View west, foreground, north facade of Forest East Suites, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    19. View west, foreground, north facade of Forest East Suites, background north & east facades of Forest Hall. - Lake Placid Club, Forest Wing, East side of Mirror Lake Drive, North of State Route 86 & Main, North Elba, Essex County, NY

  1. 27. View east, foreground north facade of Forest Hall, background ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    27. View east, foreground north facade of Forest Hall, background north facade of Forest East Suites. - Lake Placid Club, Forest Wing, East side of Mirror Lake Drive, North of State Route 86 & Main, North Elba, Essex County, NY

  2. 13. AERIAL VIEW SHOWING IN THE FOREGROUND, EXCAVATION FOR THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. AERIAL VIEW SHOWING IN THE FOREGROUND, EXCAVATION FOR THE SPILLWAY APRON.... Volume XVII, No. 12, December 26, 1939. - Prado Dam, Spillway, Santa Ana River near junction of State Highways 71 & 91, Corona, Riverside County, CA

  3. GENERAL VIEW LOOKING NORTH TOWARDS THE OUTBUILDINGS. PATH IN FOREGROUND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    GENERAL VIEW LOOKING NORTH TOWARDS THE OUTBUILDINGS. PATH IN FOREGROUND EXTENDS NORTHWESTERLY FROM THE SCHUYLKILL RIVER TO THE HOUSE - John Bartram House & Garden, 54th Street & Lindbergh Boulevard, Philadelphia, Philadelphia County, PA

  4. 2. LONG VIEW NORTHWEST, EASTBOUND BRIDGE IN FOREGROUND, WESTBOUND BRIDGE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. LONG VIEW NORTHWEST, EASTBOUND BRIDGE IN FOREGROUND, WESTBOUND BRIDGE IN BACKGROUND - Willow Run Expressway Bridge No. R01, Spanning Conrail Railway, eastbound, at US-10, Ypsilanti, Washtenaw County, MI

  5. BOILER SHOP, NORTH END, WITH DROP PIT IN FOREGROUND AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    BOILER SHOP, NORTH END, WITH DROP PIT IN FOREGROUND AND SP 2902 PASSENGER CAR UNDER RESTORATION, LOOKING SOUTHEAST. - Southern Pacific, Sacramento Shops, Boiler Shop, 111 I Street, Sacramento, Sacramento County, CA

  6. 11. Span 2 foreground, Span 3 beyondunderneath from riverbank vicinity ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. Span 2- foreground, Span 3 beyond-underneath from riverbank vicinity Pier 1 toward Pier 2 in river. - Monongahela Connecting Railroad Company, Main Bridge, Spanning Monongahela River at mile post 3.1, Pittsburgh, Allegheny County, PA

  7. 3. View west. North elevation Walpole span in foreground, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. View west. North elevation - Walpole span in foreground, link span; Westminster span in background. - Walpole-Westminster Bridge, Spanning Connecticut River between Walpole, NH & Westminster, VT, Walpole, Cheshire County, NH

  8. 11. View underside of draw span, with fender in foreground ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. View underside of draw span, with fender in foreground and concrete deck spans and pile visible at rear, looking northeast - Colonel Alexander Scammell Memorial Bridge, Spanning Bellamy River at U.S. Route 4, Dover, Strafford County, NH

  9. 2. DETAIL VIEW OF ON RIGHT FOREGROUND FIXED SPAN TO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. DETAIL VIEW OF ON RIGHT FOREGROUND FIXED SPAN TO TRANSITIONAL MOVEABLE SPAN TO FLOATING SPAN IN MIDDLEGROUND - Lacey V. Murrow Memorial Floating Bridge, Spanning Lake Washington at I-90, Seattle, King County, WA

  10. DETAIL OF SLATE SWITCHBOARD IN FOREGROUND, WITH PANELS FOR #1 ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF SLATE SWITCHBOARD IN FOREGROUND, WITH PANELS FOR #1 AND #2 GENERATORS . PHOTO BY JET LOWE, HAER, 1995. - Elwha River Hydroelectric System, Elwha Hydroelectric Dam & Plant, Port Angeles, Clallam County, WA

  11. 57. INTERIOR OF SEAPLANE HANGAR (BLDG. 2). PLANES IN FOREGROUND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    57. INTERIOR OF SEAPLANE HANGAR (BLDG. 2). PLANES IN FOREGROUND ARE VOUGHT-SIKOUSKY OSZU-1'S OF THE NEUTRALITY PATROL. USN PHOTO, FEBRUARY 27, 1941. - Quonset Point Naval Air Station, Roger Williams Way, North Kingstown, Washington County, RI

  12. 3. EAST ELEVATION, SHOWING RAISED APRON BERM IN FOREGROUND. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. EAST ELEVATION, SHOWING RAISED APRON BERM IN FOREGROUND. - Loring Air Force Base, Double Cantilever Hangar, East of Arizona Road, west of southern portion of Taxiway J, Limestone, Aroostook County, ME

  13. 1. NORTHWEST FRONT, SOUTHWEST SIDE (SPRING HOUSE IN FOREGROUND; BATH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. NORTHWEST FRONT, SOUTHWEST SIDE (SPRING HOUSE IN FOREGROUND; BATH HOUSE AT REAR) (4 x 5 negative; 5 x 7 print) - Salt Sulphur Springs, Spring House, U.S. Route 219, Salt Sulphur Springs, Monroe County, WV

  14. 1. LOOKING NORTH, SHOWING IODINE SPRING (FOREGROUND), SALT SULPHUR SPRING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. LOOKING NORTH, SHOWING IODINE SPRING (FOREGROUND), SALT SULPHUR SPRING (LEFT BACKGROUND), AND TWIN COTTAGES (UPPER RIGHT) (4 x 5 negative; 5 x 7 print) - Salt Sulpher Springs, U.S. Route 219, Salt Sulphur Springs, Monroe County, WV

  15. Redwood tanks in foreground with old rain shed (Building No. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Redwood tanks in foreground with old rain shed (Building No. 43) and steel tanks in background. - Hawaii Volcanoes National Park Water Collection System, Hawaii Volcanoes National Park, Volcano, Hawaii County, HI

  16. Eastern end of bridge, detail of valor statue in foreground ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Eastern end of bridge, detail of valor statue in foreground and sacrifice statue at right. - Arlington Memorial Bridge, Spanning Potomac River between Lincoln Memorial & Arlington National Cemetery, Washington, District of Columbia, DC

  17. 12. NEW YORK SIDE, HUDSON RIVER VENTILATION BUILDING IN FOREGROUND; ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. NEW YORK SIDE, HUDSON RIVER VENTILATION BUILDING IN FOREGROUND; NEW JERSEY SIDE, HUDSON RIVEN VENTILATION BUILDING IN BACKGROUND - Holland Tunnel, Beneath Hudson River between New York & Jersey City, New York County, NY

  18. PIQUETTE AVENUE STREETSCAPE WITH STUDEBAKER CORPORATION IN FOREGROUND. 411 PIQUETTE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    PIQUETTE AVENUE STREETSCAPE WITH STUDEBAKER CORPORATION IN FOREGROUND. 411 PIQUETTE AVENUE IN CENTER, AND FORD PIQIETTE PLANT ON THE OTHER SIDE. (Duplicate color view of HAER MI-349-1) - 411 Piquette Avenue (Industrial), Detroit, MI

  19. Outlet Works, from foreground: Deschutes River, Stilling Basin, Outlet Opening, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Outlet Works, from foreground: Deschutes River, Stilling Basin, Outlet Opening, Valve House, dam embankment, and Emergency Gates Control Tower, view to southwest - Wickiup Dam, Outlet Works, Deschutes River, La Pine, Deschutes County, OR

  20. 61. View of exhaust air vent (foreground), escape hatch, and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    61. View of exhaust air vent (foreground), escape hatch, and elevator doors at launch pad "A" with building 157, sentry control box on right, looking southwest - Nike Missile Battery MS-40, County Road No. 260, Farmington, Dakota County, MN

  1. 10. CONTEXTUAL VIEW WEST OF FEATURE 14 IN FOREGROUND, WITH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. CONTEXTUAL VIEW WEST OF FEATURE 14 IN FOREGROUND, WITH FEATURES 7, 6, 8, AND 2 IN BACKGROUND. - Juniata Mill Complex, 22.5 miles Southwest of Hawthorne, between Aurora Crater & Aurora Peak, Hawthorne, Mineral County, NV

  2. VIEW OF INTERIOR SPACE WITH VERSON HYDROPRESS IN FOREGROUND, FACING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF INTERIOR SPACE WITH VERSON HYDROPRESS IN FOREGROUND, FACING SOUTHWEST. - Douglas Aircraft Company Long Beach Plant, Aircraft Parts Shipping & Receiving Building, 3855 Lakewood Boulevard, Long Beach, Los Angeles County, CA

  3. VIEW OF CARILLON MEMORIAL WITH 5 SERVICE MEDALS IN FOREGROUND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF CARILLON MEMORIAL WITH 5 SERVICE MEDALS IN FOREGROUND AND GETTYSBURG ADDRESS TABLET IN BACKGROUND. VIEW TO SOUTHEAST. - Leavenworth National Cemetery, 150 Muncie Road, Leavenworth, Leavenworth County, KS

  4. SECTION 1, WITH BIVOUAC OF THE DEAD TABLET IN FOREGROUND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    SECTION 1, WITH BIVOUAC OF THE DEAD TABLET IN FOREGROUND AND FLAGPOLE IN BACKGROUND. VIEW TO EAST. - Crown Hill Cemetery, Crown Hill National Cemetery, 700 West Thirty-eighth Street, Indianapolis, Marion County, IN

  5. 6. View looking east of north elevation. IN the foreground ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. View looking east of north elevation. IN the foreground is the ornamental wrought iron railing of the old Superior Avenue Viaduct. - Detroit Superior High Level Bridge, Cleveland, Cuyahoga County, OH

  6. 1. View of tower with cabin in the right foreground, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. View of tower with cabin in the right foreground, facing southeast - Cold Mountain Fire Lookout Station, Lookout Tower, Krassel District, Frank Church River of No Return Wilderness, Dixie, Idaho County, ID

  7. POWER HOUSE, DISMANTLED TURBOGENERATOR IN RIGHT FOREGROUND WITH TURBOGENERATOR AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    POWER HOUSE, DISMANTLED TURBO-GENERATOR IN RIGHT FOREGROUND WITH TURBO-GENERATOR AND OFFICE BEYOND. RAILED AREA IS A STAIRWELL. VIEW FROM NORTHWEST - Kekaha Sugar Company, Sugar Mill Building, 8315 Kekaha Road, Kekaha, Kauai County, HI

  8. 1. DETAIL, NORTHEAST VIEW (REMAINDER OF SHAFTTURNING MECHANISM IN FOREGROUND). ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. DETAIL, NORTHEAST VIEW (REMAINDER OF SHAFT-TURNING MECHANISM IN FOREGROUND). - Vanadium Corporation of America (VCA) Naturita Mill, Brick Skimmer Salt Roaster, 3 miles Northwest of Naturita, between Highway 141 & San Miguel River, Naturita, Montrose County, CO

  9. View of Chapel Park, showing bomb shelters at right foreground, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of Chapel Park, showing bomb shelters at right foreground, from building 746 parking lot across Walnut Avenue; camera facing north. - Mare Island Naval Shipyard, East of Nave Drive, Vallejo, Solano County, CA

  10. View of Antenna #1 (foreground), and Antenna #2 surface doors. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of Antenna #1 (foreground), and Antenna #2 surface doors. Image looking northeast - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

  11. Probing B-mode foregrounds using estimators of isotropy violation

    NASA Astrophysics Data System (ADS)

    Rotti, Aditya; Huffenberger, Kevin

    2016-01-01

    We propose an isotropy-violation test as a diagnostic for foreground contamination to the Cosmic Microwave Background (CMB). Using polarized Planck 353 GHz data, we construct a map that indicates B-mode foreground dust emission, and helps to indicate the least contaminated lines-of-sight. This estimate, constructed in harmonic space via the bipolar spherical harmonic basis, has higher signal-to-noise than previous estimates of the dust B-mode power. We compare the contamination levels in several low-foreground regions of the sky, including the BICEP2 region. This information, and similar statistics, may be useful to ground-based CMB projects when planning observations to hunt for primordial B-mode signatures. Today, this tool can assess clean portions of the sky, but in the future it will allow null tests for foreground contamination in claimed detections of primordial B-modes.

  12. 1. VIEW, LOOKING NORTH, SHOWING GROTON BRIDGE (FOREGROUND) AND HIGHWAY ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. VIEW, LOOKING NORTH, SHOWING GROTON BRIDGE (FOREGROUND) AND HIGHWAY BRIDGE (BACKGROUND) - New York, New Haven & Hartford Railroad, Groton Bridge, Spanning Thames River between New London & Groton, New London, New London County, CT

  13. 5. View, oxidizer waste tanks and containment basin in foreground ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. View, oxidizer waste tanks and containment basin in foreground with Systems Integration Laboratory (T-28) uphill in background, looking northeast. - Air Force Plant PJKS, Systems Integration Laboratory, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  14. View facing north, Structure 162 in foreground, as Transmission Line ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View facing north, Structure 16-2 in foreground, as Transmission Line turns at intersection of Powerline Road and US 87 - Havre Rainbow Transmission Line, Havre City to Great Falls vicinity, Montana, Great Falls, Cascade County, MT

  15. 7. Shed and keeper' house with helicopter pad in foreground, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. Shed and keeper' house with helicopter pad in foreground, view east, southwest and northwest sides - Goat Island Light Station, Goat Island, next to entrance to Cape Porpoise Harbor, just south of Trott Island, Cape Porpoise, York County, ME

  16. ERECTING SHOP, EAST SIDE, LOOKING SOUTH. LEFT FOREGROUND BREAK IN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    ERECTING SHOP, EAST SIDE, LOOKING SOUTH. LEFT FOREGROUND BREAK IN WALL IS FOR PASSAGE OF STEAM-POWERED BELTING FROM POWERHOUSE. - Southern Pacific, Sacramento Shops, Erecting Shop, 111 I Street, Sacramento, Sacramento County, CA

  17. 6. Water treatment plant, view NE, berm in foreground ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. Water treatment plant, view NE, berm in foreground - Fort Benton Water Treatment Plant, Filtration Plant, Lots 9-13 of Block 7, Fort Benton Original Townsite at Missouri River, Fort Benton, Chouteau County, MT

  18. 5. Water treatment plant, view to N, berm in foreground ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. Water treatment plant, view to N, berm in foreground - Fort Benton Water Treatment Plant, Filtration Plant, Lots 9-13 of Block 7, Fort Benton Original Townsite at Missouri River, Fort Benton, Chouteau County, MT

  19. 4. Water treatment plant, view to NW, berm in foreground ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. Water treatment plant, view to NW, berm in foreground - Fort Benton Water Treatment Plant, Filtration Plant, Lots 9-13 of Block 7, Fort Benton Original Townsite at Missouri River, Fort Benton, Chouteau County, MT

  20. 8. Water treatment plant, view to SE, berm in foreground ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. Water treatment plant, view to SE, berm in foreground covering settling tank - Fort Benton Water Treatment Plant, Filtration Plant, Lots 9-13 of Block 7, Fort Benton Original Townsite at Missouri River, Fort Benton, Chouteau County, MT

  1. 7. Water treatment plant, view to E, berm in foreground ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. Water treatment plant, view to E, berm in foreground covering settling tank - Fort Benton Water Treatment Plant, Filtration Plant, Lots 9-13 of Block 7, Fort Benton Original Townsite at Missouri River, Fort Benton, Chouteau County, MT

  2. 1. OVERALL VIEW OF VIADUCT, WITH JEFFERSON STREET IN FOREGROUND, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. OVERALL VIEW OF VIADUCT, WITH JEFFERSON STREET IN FOREGROUND, LOOKING SOUTH ALONG SIXTH STREET - Sixth Street Viaduct, Spanning Burlington Northern Railroad & Valley Street, Burlington, Des Moines County, IA

  3. First floor interior, showing mess room in left foreground and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    First floor interior, showing mess room in left foreground and main hall in right background. View to southwest. - Fort David A. Russell, Artillery Barracks, Randall Avenue between Sixth & Fifth Streets, Cheyenne, Laramie County, WY

  4. 7. General view of stockyards showing cattle pens in foreground, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. General view of stockyards showing cattle pens in foreground, south Omaha in background, and livestock exchange building to right. View to east. - South Omaha Union Stock Yards, 2900 "O" Plaza, Omaha, Douglas County, NE

  5. 53. VIEW OF PASSENGER SPEEDER 04 IN FOREGROUND, BOOM SPEEDER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    53. VIEW OF PASSENGER SPEEDER 04 IN FOREGROUND, BOOM SPEEDER 75 IN BACKGROUND LEFT, AND BOOM SPEEDER 59 IN BACKGROUND RIGHT - Electron Hydroelectric Project, Along Puyallup River, Electron, Pierce County, WA

  6. View looking southeast. Buildings in foreground from right to left, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View looking southeast. Buildings in foreground from right to left, building nos. 1009 (Bighorn), 1007 (Osage/Columbine), 1006 (Arapahoe) and 1010 (Laundry). - McGraw Ranch, McGraw Ranch Road, Estes Park, Larimer County, CO

  7. 20. OUTLET (FOREGROUND) AND WEIR (BACKGROUND) OF DEER FLAT CALDWELL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    20. OUTLET (FOREGROUND) AND WEIR (BACKGROUND) OF DEER FLAT CALDWELL CANAL ON DOWNSTREAM FACE OF UPPER EMBANKMENT. VIEW TO NORTH. - Boise Project, Deer Flat Embankments, Lake Lowell, Nampa, Canyon County, ID

  8. OBLIQUE VIEW WITH ABOVEGROUND PORTION IN THE FOREGROUND. VIEW FACING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    OBLIQUE VIEW WITH ABOVE-GROUND PORTION IN THE FOREGROUND. VIEW FACING SOUTHWEST - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, Battery Command Center, Ford Island, Pearl City, Honolulu County, HI

  9. DETAIL OF THREE DOORS FOR READY AMMUNITION BOXES (IN FOREGROUND). ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF THREE DOORS FOR READY AMMUNITION BOXES (IN FOREGROUND). NOTE THE STEEL PLATES IN THE BACKGROUND - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, Battery Command Center, Ford Island, Pearl City, Honolulu County, HI

  10. Interior oblique view with wagon in foreground; camera facing southwest. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Interior oblique view with wagon in foreground; camera facing southwest. - Mare Island Naval Shipyard, Mechanics Shop, Waterfront Avenue, west side between A Street & Third Street, Vallejo, Solano County, CA

  11. 1. LOOKING WEST ON LEHIGH CANAL, GRAPHITE MILL IN FOREGROUND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. LOOKING WEST ON LEHIGH CANAL, GRAPHITE MILL IN FOREGROUND - Pettinos Brothers Graphite Manufacturing Mill, On Sand Island, south side of Lehigh Canal, west of Hill-to-Hill Bridge, Bethlehem, Northampton County, PA

  12. BOILING HOUSE, INTERIOR, SECOND FLOOR, SYRUP TANKS IN RIGHT FOREGROUND, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    BOILING HOUSE, INTERIOR, SECOND FLOOR, SYRUP TANKS IN RIGHT FOREGROUND, HIGH GRADE VACUUM PANS BEYOND THE SYRUP TANKS. VIEW FROM THE SOUTH - Kekaha Sugar Company, Sugar Mill Building, 8315 Kekaha Road, Kekaha, Kauai County, HI

  13. THE TRUSS BRIDGE SEGMENT OF THE TRIBOROUGH BRIDGE IN FOREGROUND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    THE TRUSS BRIDGE SEGMENT OF THE TRIBOROUGH BRIDGE IN FOREGROUND AND THE HELL GATE BRIDGE IN THE BACKGROUND ADJACENT TO THE SUSPENSION SEGMENT OF THE TRIBOROUGH BRIDGE. - Triborough Bridge, Passing through Queens, Manhattan & the Bronx, Queens (subdivision), Queens County, NY

  14. 2. Salmon Creek Diversion Dam, overview, diversion weir center foreground, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. Salmon Creek Diversion Dam, overview, diversion weir center foreground, headworks overflow weir to center left, view to east - Salmon Creek Diversion Dam, Salmon Creek, Okanogan, Okanogan County, WA

  15. Southeast corner with overhead crane in foreground Bureau of ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Southeast corner with overhead crane in foreground - Bureau of Mines Boulder City Experimental Station, Titanium Development Plant, Date Street north of U.S. Highway 93, Boulder City, Clark County, NV

  16. 6. GENE WASH DAM, LOOKING NORTHWEST. SURVEY REFLECTOR IN FOREGROUND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. GENE WASH DAM, LOOKING NORTHWEST. SURVEY REFLECTOR IN FOREGROUND FOR MONITORING MOVEMENT OF DAM AND EARTH. - Gene Wash Reservoir & Dam, 2 miles west of Parker Dam, Parker Dam, San Bernardino County, CA

  17. 97. VIEW OF PIER EXTENSION WITH RAMP IN FOREGROUND AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    97. VIEW OF PIER EXTENSION WITH RAMP IN FOREGROUND AND 4TH TEE IN BACKGROUND, LOOKING SOUTHWEST FROM 3RD TEE - Huntington Beach Municipal Pier, Pacific Coast Highway at Main Street, Huntington Beach, Orange County, CA

  18. 89. LOCK 13 EAST. WOODEN TIMBERS (FOREGROUND LEFT AND RIGHT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    89. LOCK 13 EAST. WOODEN TIMBERS (FOREGROUND LEFT AND RIGHT OF LOCK ENTRANCE) ARE BEING USED AS BUMPERS TO HELP GUIDE SHIP INTO LOCK WHILE AVOIDING CONTACT WITH WALLS. - Morris Canal, Phillipsburg, Warren County, NJ

  19. 2. GATELIFTING SPUR GEAR DRIVE IN FOREGROUND, ATTACHED TO A ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. GATE-LIFTING SPUR GEAR DRIVE IN FOREGROUND, ATTACHED TO A GENERAL ELECTRIC COMPANY CRANE MOTOR, WITH COMPANION SOLENOID BRAKE IN RIGHT BACKGROUND, WITH BOTH MOUNTED ON A CONCRETE PEDESTAL. PORTIONS OF THE STEEL DERRICK LIFTING FRAME ARE VISIBLE IN THE FOREGROUND AND BACKGROUND, LOOKING EAST/NORTHEAST. - Washington Water Power Spokane River Upper Falls Hydroelectric Development, Gates & Gate-Lifting Mechanisms, Spokane River, approximately 0.5 mile northeast of intersection of Spokane Falls Boulevard & Post Street, Spokane, Spokane County, WA

  20. RMS active damping augmentation

    NASA Technical Reports Server (NTRS)

    Gilbert, Michael G.; Scott, Michael A.; Demeo, Martha E.

    1992-01-01

    The topics are presented in viewgraph form and include: RMS active damping augmentation; potential space station assembly benefits to CSI; LaRC/JSC bridge program; control law design process; draper RMS simulator; MIMO acceleration control laws improve damping; potential load reduction benefit; DRS modified to model distributed accelerations; accelerometer location; Space Shuttle aft cockpit simulator; simulated shuttle video displays; SES test goals and objectives; and SES modifications to support RMS active damping augmentation.

  1. Magnetic damping for maglev

    SciTech Connect

    Chen, S.S.; Zhu, S.; Cai, Y.; Rote, D.M.

    1994-12-31

    Magnetic damping is one of the important parameters to control the response and stability of maglev systems. An experimental study is presented to measure the magnetic damping using a direct method. A plate attached to a permanent magnet levitated on a rotating drum was tested to investigate the effect of various parameters on magnetic damping such as conductivity, gap, excitation frequency, and oscillation amplitude. The experimental technique is capable of measuring all magnetic damping coefficients, some of which can not be measured by an indirect method.

  2. Decoherence and Landau-Damping

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2005-12-01

    The terminologies, decoherence and Landau damping, are often used concerning the damping of a collective instability. This article revisits the difference and relation between decoherence and Landau damping. A model is given to demonstrate how Landau damping affects the rate of damping coming from decoherence.

  3. Signals and Images Foreground/Background Joint Estimation and Separation

    NASA Astrophysics Data System (ADS)

    Ait-El-Fquih, Boujemaa; Mohammad-Djafari, Ali

    2011-03-01

    This paper is devoted to a foreground/background joint estimation and separation problem. We first observe that this problem is modeled by a conditionally linear and Gaussian hidden Markov chain (CLGHMC). We next propose a filtering algorithm in the general non-linear and non Gaussian conditionally hidden Markov chain (CHMC), allowing the propagation of the filtering densities associated to the foreground and the background. We then focus on the particular case of our CLGHMC in which these filtering densities are weighted sums of Gaussian distributions; the parameters of each Gaussian are computed by using the Kalman filter algorithm, while the weights are computed by using the particle filter algorithm. We finally perform some simulations to highlight the interest of our method in both signals and images foreground/backgound joint estimation and separation.

  4. Improving video foreground segmentation with an object-like pool

    NASA Astrophysics Data System (ADS)

    Cheng, Xiaoliu; Lv, Wei; Liu, Huawei; You, Xing; Li, Baoqing; Yuan, Xiaobing

    2015-03-01

    Foreground segmentation in video frames is quite valuable for object and activity recognition, while the existing approaches often demand training data or initial annotation, which is expensive and inconvenient. We propose an automatic and unsupervised method of foreground segmentation given an unlabeled and short video. The pixel-level optical flow and binary mask features are converted into the normal probabilistic superpixels, therefore, they are adaptable to build the superpixel-level conditional random field which aims to label the foreground and background. We exploit the fact that the appearance and motion features of the moving object are temporally and spatially coherent in general, to construct an object-like pool and background-like pool via the previous segmented results. The continuously updated pools can be regarded as the "prior" knowledge of the current frame to provide a reliable way to learn the features of the object. Experimental results demonstrate that our approach exceeds the current methods, both qualitatively and quantitatively.

  5. Predicting Ly-alpha intensities in coronal streamers

    NASA Technical Reports Server (NTRS)

    Noci, Giancarlo; Poletto, Giannina; Suess, Steven T.; Wang, A.-H.; Wu, S. T.

    1992-01-01

    SOHO (Solar and Heliospheric Observatory) UVCS (Ultraviolet Coronagraph Spectrometer) will make long term observations of coronal streamers in UV lines, providing a new tool for the analysis of structures which have been known for decades but are still far from being adequately described. Work to evaluate the Lyman alpha brightness of coronal streamers is reported, adopting the streamer models obtained, via a time dependent numerical relaxation technique. This will yield understanding on the role of geometric versus physical factors in determining the streamer lyman alpha intensity and provide guidelines for UVCS observational operations. Future prospects along this line of research are summarized.

  6. Extended LY alpha -absorbing Halos around Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Bowen, David V.; Blades, J. Chris; Pettini, Max

    1996-06-01

    In order to establish the Lyα absorption cross section of present-day galaxies, we have identified 38 galaxies with z = 0-0.08 that lie within 40-500 h^-1^ kpc of the line of sight to a QSO observed with the Faint Object Spectrograph aboard the Hubble Space Telescope (HST). Including three galaxies in the field of 3C 273 investigated by previous authors, we find that nine of 41 galaxies have associated Lyα absorption. If the identified Lyα absorption systems are genuinely associated with the galaxies, then the covering factor of gas around galaxies remains roughly constant at ~40% between 100 and 300 h^-1^ kpc. Beyond 300 h^-1^ kpc, the incidence of absorption drops sharply. We conclude that (1) nearby galaxies do not possess Lyα-absorbing halos beyond 300 h^-1^ kpc in radius and (2) the covering factor of present-day galaxies between 50 and 300 h^-1^ kpc is 44% at an equivalent width limit of W >= 0.3 A. For the nine galaxies with associated Lyα absorption lines, differences in the galaxies systemic velocities and the velocity of the absorption line, {DELTA}v, range over +/- 300 km s^-1^, consistent with the distribution found at redshifts > 0.1 by Lanzetta et al. and Le Brun, Bergeron, & Boisse. Values of {DELTA}v spanning several hundred km s^-1^ are probably real for some of the QSO-galaxy pairs, however, and do not simply arise from errors in measuring cz_gal_ or cz_abs_. This suggests that the absorbing clouds are kinematically tied to the galaxy disks and that the distribution of {DELTA}v may arise because of the effects of galaxy inclination. We find no evidence for a correlation between Lyα equivalent width and galaxy line-of-sight separation, which weakens the argument that the identified galaxies are directly associated with the Lyα lines. Also, we find that absorption does not arise only from bright galaxies, since there are several examples in which low-luminosity galaxies apparently cause absorption. Yet we show that the absorbing halos around galaxies cannot be independent of galaxy luminosity because if all low- redshift galaxies were surrounded by extended halos, the number of Lyα absorption systems found in HST spectra would be much larger than has recently been determined. This result leads us to question whether the galaxies are actually responsible for the Lyα absorption lines or whether the association in redshift is fortuitous. Our results support the picture suggested by others that Lyα lines arise in filaments or sheets that connect and contain the overdense regions that galaxies inhabit. This conclusion, however, remains at odds with the results of Lanzetta et al., who find that Lyα systems are more intimately linked with galaxies. It may be, therefore, that we are seeing an evolution of the way in which Ly& lines associate with galaxies over the last few billion years. We suggest that at least some of the Lyα clouds that are not associated with galaxies at z ~ 0.5 have been slowly merging with galaxies over time, creating larger but less uniform gas distributions around the galaxies we see today.

  7. Obscuration of LY alpha Photons in Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Giavalisco, Mauro; Koratkar, Anuradha; Calzetti, Daniela

    1996-08-01

    We present a new study of the correlations between the Lyα emission, the UV extinction, and the metal content in a sample of 21 local, low-metallicity starburst galaxies from archival IUE spectra. We have consistently reextracted all the spectra using the optimal extraction algorithm by Kinney and coworkers, and we have also included galaxies not previously studied. In 40% of the cases our new measures of the Lyα equivalent width, Walpha_, differ from those reported in the literature by up to 50% of their value. The new measures show no significant correlation with either the obscuration of the UV continuum or the Balmer decrement, and only a very weak correlation with the metal index [O/H]. Using the flux ratio Lyα/Hβ instead of Walpha_ to take into account differences in the ionizing conditions of the nebular gas does not change these results. This shows that the extinction vicissitudes of the Lyα and nonresonant radiations have been decoupled during their propagations through the ISM. We interpret this as evidence that the ISM in the sample galaxies is, on average, highly inhomogeneous and that the transport of Lyα photons is primarily controlled by the ISM geometry rather than by the amount of dust. If the ISM geometry is mainly the result of the energy release from the star formation activity, we speculate that a similar phenomenology was also present at high redshifts. As the median of the absolute value of Walpha_ in our sample is relatively large, the line can be efficiently used to measure the redshifts of primeval galaxy candidates at redshifts 2 <~ z <~ 7 via optical spectroscopy with the 10 m class telescopes.

  8. Turbine blade damping study

    NASA Technical Reports Server (NTRS)

    Dominic, R. J.

    1984-01-01

    Research results and progress on the performance of bladed systems is reported the different topics discussed include: the study of turbine blade damping; forced vibrations of friction damped beam moistures in two dimensions; and a users manual for a computer program for dynamic analysis of bladed systems.

  9. Damped acceleration cavities

    SciTech Connect

    Palmer, R.B.

    1988-07-01

    Structures with slots to strongly damp higher order longitudinal and transverse modes should allow the use, in linear colliders, of multiple bunches, and thus attain luminosities of over 10/sup 34/cm/sup /minus/2/sec/sup /minus/1/. Preliminary measurements on model structures suggest that such damping can be achieved. 10 refs., 9 figs.

  10. Turbojet engine blade damping

    NASA Technical Reports Server (NTRS)

    Srinivasan, A. V.; Cutts, D. G.; Sridhar, S.

    1981-01-01

    The potentials of various sources of nonaerodynamic damping in engine blading are evaluated through a combination of advanced analysis and testing. The sources studied include material hysteresis, dry friction at shroud and root disk interfaces as well as at platform type external dampers. A limited seris of tests was conducted to evaluate damping capacities of composite materials (B/AL, B/AL/Ti) and thermal barrier coatings. Further, basic experiments were performed on titanium specimens to establish the characteristics of sliding friction and to determine material damping constants J and n. All the tests were conducted on single blades. Mathematical models were develthe several mechanisms of damping. Procedures to apply this data to predict damping levels in an assembly of blades are developed and discussed.

  11. Operational apron with pit hydrants in foreground, aircraft in background. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Operational apron with pit hydrants in foreground, aircraft in background. View to west - Offutt Air Force Base, Looking Glass Airborne Command Post, Operational & Hangar Access Aprons, Spanning length of northeast half of Project Looking Glass Historic District, Bellevue, Sarpy County, NE

  12. 20. View from rear door; space in foreground is transverse ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    20. View from rear door; space in foreground is transverse room connecting north and south cell blocks; room at right center with screened window was presumably visiting room; view to southwest, 65mm lens with electronic flash illumination. - Tule Lake Project Jail, Post Mile 44.85, State Route 139, Newell, Modoc County, CA

  13. Integrated foreground segmentation and boundary matting for live videos.

    PubMed

    Minglun Gong; Yiming Qian; Li Cheng

    2015-04-01

    The objective of foreground segmentation is to extract the desired foreground object from input videos. Over the years, there have been significant amount of efforts on this topic. Nevertheless, there still lacks a simple yet effective algorithm that can process live videos of objects with fuzzy boundaries (e.g., hair) captured by freely moving cameras. This paper presents an algorithm toward this goal. The key idea is to train and maintain two competing one-class support vector machines at each pixel location, which model local color distributions for both foreground and background, respectively. The usage of two competing local classifiers, as we have advocated, provides higher discriminative power while allowing better handling of ambiguities. By exploiting this proposed machine learning technique, and by addressing both foreground segmentation and boundary matting problems in an integrated manner, our algorithm is shown to be particularly competent at processing a wide range of videos with complex backgrounds from freely moving cameras. This is usually achieved with minimum user interactions. Furthermore, by introducing novel acceleration techniques and by exploiting the parallel structure of the algorithm, near real-time processing speed (14 frames/s without matting and 8 frames/s with matting on a midrange PC & GPU) is achieved for VGA-sized videos. PMID:25675459

  14. OVERVIEW, HANGAR No. 3 (FOREGROUND), HANGAR No. 4 (CENTER), AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    OVERVIEW, HANGAR No. 3 (FOREGROUND), HANGAR No. 4 (CENTER), AND HANGAR No. 5 (BACKGROUND), FROM AIRCRAFT PARKING APRON, VIEW FACING NORTH - U.S. Marine Corps Base Hawaii, Kaneohe Bay, Hangar No. 4, First Street between A & B Streets, Kailua, Honolulu County, HI

  15. 34. Coal Fuel Elevator (diagonal in foreground), Fuel Elevator (left), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    34. Coal Fuel Elevator (diagonal in foreground), Fuel Elevator (left), Fuel Storage Bins (center), and Power Plant (far center), and Retail Coal Storage Bins (right) Photograph taken by George Harven - Huber Coal Breaker, 101 South Main Street, Ashley, Luzerne County, PA

  16. Detail of north end of the Electrical Shop (foreground) and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of north end of the Electrical Shop (foreground) and Sheet Metal Shop, note the metal-frame windows in the Electrical Shop, view facing east - Kahului Cannery, Plant No. 28, Boiler House, Sheet Metal and Electrical Shops, 120 Kane Street, Kahului, Maui County, HI

  17. 25. White Plains Road Bridge in foreground; Unionport Road Bridge ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    25. White Plains Road Bridge in foreground; Unionport Road Bridge in background. Van Nest, Bronx Co., NY. Sec. 4207, MP 12.75./78. - Northeast Railroad Corridor, Amtrak Route between New Jersey/New York & New York/Connecticut State Lines, New York County, NY

  18. 14. ELEVATED CAMERA STAND IN FOREGROUND, FIRING CONTROL BLOCKHOUSE (BLDG. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. ELEVATED CAMERA STAND IN FOREGROUND, FIRING CONTROL BLOCKHOUSE (BLDG. 0545) IN CENTER, AIR SUPPLY BUILDING AND PROTECTIVE BERM IN BACKGROUND. Looking north northeast from Camera Road. - Edwards Air Force Base, South Base Sled Track, Edwards Air Force Base, North of Avenue B, between 100th & 140th Streets East, Lancaster, Los Angeles County, CA

  19. 6. GENERAL VIEW OF INTERNAL POLICE POST IN FOREGROUND AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. GENERAL VIEW OF INTERNAL POLICE POST IN FOREGROUND AND MILITARY POLICE POST IN BACKGROUND ALONG ENTRANCE ROAD, LOOKING NORTHEAST - Manzanar War Relocation Center, Owens Valley off U.S. Highway 395, 6 miles South of Independence, Independence, Inyo County, CA

  20. 24. VIEW, LOOKING NORTHEAST, SHOWING MAIN TRANSMISSION IN LEFT FOREGROUND, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    24. VIEW, LOOKING NORTHEAST, SHOWING MAIN TRANSMISSION IN LEFT FOREGROUND, GASOLINE-POWERED WAUKESHA AUXILIARY DRIVE MOTOR AT CENTER, AND ONE OF TWO MAIN ELECTRIC DRIVE MOTORS AT LEFT CENTER - Sacramento River Bridge, Spanning Sacramento River at California State Highway 275, Sacramento, Sacramento County, CA

  1. 9. Looking northeast, foreground Clenny Run Road, duck pond and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. Looking northeast, foreground Clenny Run Road, duck pond and Clenny Run, with intersection of State Routes 92 and 100 beyond, Brandywine Creek State Park in background, mixed deciduous trees along top of hill - Winterthur Farms, Intersection State Routes 92 & 100, Intersection State Routes 92 & 100, Winterthur, New Castle County, DE

  2. 21. VIEW, LOOKING WESTNORTHWEST, SHOWING TRANSMISSION, IN FOREGROUND, ATTACHED TO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    21. VIEW, LOOKING WEST-NORTHWEST, SHOWING TRANSMISSION, IN FOREGROUND, ATTACHED TO REDUCTION GEAR HOUSING WHICH IS FLANKED BY THE TWO MAIN ELECTRIC DRIVE MOTORS, WITH ELECTRICAL CABINETS AND OPERATOR'S DESK IN BACKGROUND - Sacramento River Bridge, Spanning Sacramento River at California State Highway 275, Sacramento, Sacramento County, CA

  3. 2. VIEW OF ROOT CELLAR (Feature 11) IN FOREGROUND, WITH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. VIEW OF ROOT CELLAR (Feature 11) IN FOREGROUND, WITH REAR ROOF OF HOUSE (Feature 10) AT LEFT, AND ROOF OF BUTCHER SHOP/FREIGHT DEPOT (Feature 9) IN CENTER, LOOKING SOUTHWEST - Leesburg Townsite, Root Cellar, Napias Creek, Salmon, Lemhi County, ID

  4. View of Corto Square. Access ramp in foreground to Building ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of Corto Square. Access ramp in foreground to Building No. 30. Buildings No. 25, 26, 34, and 32 left to right at rear, looking north - Easter Hill Village, Bordered by South Twenty-sixth Street, South Twenty-eighth Street, Hinkley Avenue, Foothill Avenue & Corto Square, Richmond, Contra Costa County, CA

  5. 16. FOREGROUND (LEFT TO RIGHT) EXHAUST AND INTAKE DUCTS. SOUTH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    16. FOREGROUND (LEFT TO RIGHT) EXHAUST AND INTAKE DUCTS. SOUTH SIDE AND WEST FRONT OF LAUNCH CONTROL SUPPORT BUILDING IN BACKGROUND. VIEW TO NORTH. - Minuteman III ICBM Launch Control Facility November-1, 1.5 miles North of New Raymer & State Highway 14, New Raymer, Weld County, CO

  6. 113. VIEW OF MACHINE SHOP FROM WEST. AREA IN FOREGROUND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    113. VIEW OF MACHINE SHOP FROM WEST. AREA IN FOREGROUND WAS ONCE ENCLOSED AS PART OF THE SHOP. THE TRAM LINE AND SNOWSHED RAN TO THE RIGHT (SOUTH) TO EAGLE MINE PORTAL. - Bald Mountain Gold Mill, Nevada Gulch at head of False Bottom Creek, Lead, Lawrence County, SD

  7. 7. VIEW TO NORTH SHOWING SEWER CONSTRUCTION IN FOREGROUND AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. VIEW TO NORTH SHOWING SEWER CONSTRUCTION IN FOREGROUND AND BUILDING F IN THE LEFT BACKGROUND. 8X10 black and white gelatin print. United States Coast Guard, Air Station Contract 1247, Sewer System. 1956. - U.S. Coast Guard Air Station San Francisco, 1020 North Access Road, San Francisco, San Francisco County, CA

  8. 1. PERSPECTIVE VIEW, FROM THE NORTHEAST ATOP EAST WING (FOREGROUND), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. PERSPECTIVE VIEW, FROM THE NORTHEAST ATOP EAST WING (FOREGROUND), OF GREAT KIVA (RECONSTUCTED IN BACKGROUND) AND A SMALLER KIVA (MIDDLE GROUND) - Aztec Ruins, Great Kiva, New Mexico 44 near junction of U.S. 550, Aztec, San Juan County, NM

  9. 23. BACKING DRUM IN FOREGROUND. MAIN ENGINE STEP DRUM IN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    23. BACKING DRUM IN FOREGROUND. MAIN ENGINE STEP DRUM IN CENTER. TO RIGHT NOTE CYLINDER, PISTON ROD CROSSHEAD. AT END OF CRANKSHAFT NOTE WRIST PIN AND CRANE DISK. - Dredge CINCINNATI, Docked on Ohio River at foot of Lighthill Street, Pittsburgh, Allegheny County, PA

  10. Ford Service Building in foreground with new facade covering front ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Ford Service Building in foreground with new facade covering front elevation. Original facade can be seen on side. Original was eight-story reinforced concrete Albert Kahn design with exposed structural frame. One-story addition on north side. Stone veneer covers south and west facades of the building in strips - Ford Service Building, 7310 Woodward Avenue, Detroit, MI

  11. View of Plum Street regulator in foreground, containing 18" vitrified ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of Plum Street regulator in foreground, containing 18" vitrified clay pipe, in background are the Riverfront Park and the Route 51 Bridge. WPA retaining wall (Haer no. Pa-398) is right. - Plum Street Regulator, Plum Street at Monongahela River, Allegheny County, PA

  12. 2. In the foreground is the fan which removed fumes ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. In the foreground is the fan which removed fumes from the galvanizing area in building #8. In the background are the waste treatment tanks for the acids and alkali used in the zinc-electro-plating process. - American Chain & Cable Company, East Princess Street (400 Block), York, York County, PA

  13. INTERIOR, NORTH ENGINE IN FOREGROUND LOOKING EAST ON FIRST FLOOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR, NORTH ENGINE IN FOREGROUND LOOKING EAST ON FIRST FLOOR (INDICATED AS SECOND FLOOR BY CURRENT OWNER). - Colt Fire Arms Company, East Armory Building, 36-150 Huyshope Avenue, 17-170 Van Dyke Avenue, 49 Vredendale Avenue, Hartford, Hartford County, CT

  14. View of Antenna #2 (foreground), and Antenna #1 surface doors. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of Antenna #2 (foreground), and Antenna #1 surface doors. Orientation Target #1 in background. Image looking northwest - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

  15. View of Antenna #1 (foreground), and Antenna #2 surface doors. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of Antenna #1 (foreground), and Antenna #2 surface doors. Orientation Target #2 in background. Image looking northeast - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

  16. OBLIQUE VIEW OF REAR SIDE WITH UNIT A IN FOREGROUND. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    OBLIQUE VIEW OF REAR SIDE WITH UNIT A IN FOREGROUND. NOTE THE FLOOR TO CEILING WINDOWS OF THE LIVING ROOM. VIEW FACING NORTHWEST - Camp H.M. Smith and Navy Public Works Center Manana Title VII (Capehart) Housing, U-Shaped Three-Bedroom Duplex Type 3, Acacia Road, Birch Circle, and Cedar Drive, Pearl City, Honolulu County, HI

  17. 18. INTERIOR VIEW OF ROUGH FORGED TOOLS (FOREGROUND) WHICH ARE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. INTERIOR VIEW OF ROUGH FORGED TOOLS (FOREGROUND) WHICH ARE PRE-HEATED IN THE FURNACE (REAR RIGHT) AND THEN FORGED WITH THE BRADLEY HAMMER (LEFT) AS SHOWN BY JAMES GLASPELL - Warwood Tool Company, Foot of Nineteenth Street, Wheeling, Ohio County, WV

  18. View of unit 42 flywheel with plant crew in foreground. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of unit 42 flywheel with plant crew in foreground. From left to right; Asst Superintendent James L. Wine; Paul W. Bragg; Garry N. Dobbins, Robert L. Gregory. - Burnsville Natural Gas Pumping Station, Saratoga Avenue between Little Kanawha River & C&O Railroad line, Burnsville, Braxton County, WV

  19. 4. View, fuel waste tanks and containment basin in foreground ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. View, fuel waste tanks and containment basin in foreground with Systems Integration Laboratory (T-28) uphill in background, looking southeast. At the extreme right is the Long-Term Oxidizer Silo (T-28B) and the Oxidizer Conditioning Structure (T-28D). - Air Force Plant PJKS, Systems Integration Laboratory, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  20. 2. COW HOUSE AT RIGHT FOREGROUND. There is an identical ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. COW HOUSE AT RIGHT FOREGROUND. There is an identical cow house opposite from the one pictured. In the background are: Robinson-Aiken Slave Building and Kitchens (SC-276) on left, and Robinson-Aiken Service Building and Stable (SC-275) on right. - Robinson-Aiken Cow House, 48 Elizabeth Street, Charleston, Charleston County, SC

  1. 78. (Credit JTL) Mixing chambers (19241926) in foreground, looking west ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    78. (Credit JTL) Mixing chambers (1924-1926) in foreground, looking west along south facade of station. Settling basins to left, new filter house (1942) in background. Aerators added in 1930-31 to remove carbon dioxide from water. - McNeil Street Pumping Station, McNeil Street & Cross Bayou, Shreveport, Caddo Parish, LA

  2. 7. POWERHOUSE, FOREGROUND ON CEILING EXCITER FLATBELT PULLEYS, BACK RIGHT, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. POWERHOUSE, FOREGROUND ON CEILING EXCITER FLATBELT PULLEYS, BACK RIGHT, WOODEN PERSONAL FACILITY LOCATED IN POWERHOUSE LOWER LEVEL LOOKING SOUTH - Dayville Mills Hydroelectric Facility, Powerhouse, North side of Route 101, .5 mile west of Route 395, Killingly Center, Windham County, CT

  3. View looking southeast. Buildings in foreground from right to left, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View looking southeast. Buildings in foreground from right to left, building nos. 1009 (Bighorn), 1007 (Osage/Columbine), 1006 (Arapahoe) and 1010 (Laundry). - Fitzsimons General Hospital, Water Storage Tank, North Cooper Street & East McClouskey Avenue, Aurora, Adams County, CO

  4. A LINE POLE 1 IN FOREGROUND AND MYSTIC LAKE POWERHOUSE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    A LINE POLE 1 IN FOREGROUND AND MYSTIC LAKE POWERHOUSE IN BACKGROUND. A LINE POLE 1 IS A MODERN REPLACEMENT STRUCTURE WITH BROWN PORCELAIN SUSPENSION-TYPE INSULATORS. VIEW TO EAST. - Mystic Lake Hydroelectric Facility, Electric Transmission A Line, Along West Rosebud Creek, Fishtail, Stillwater County, MT

  5. 8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER No. 2., AND GENERATOR UNITS BEHIND EXCITER No. 2 IN BACKGROUND. EXCITER No. 1 GENERATOR HAS A COVER OVER TOP HALF OF COMMUTATOR ELEMENT. VIEW TO NORTHWEST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  6. 7. VIEW OF THE MODERN SUBSTATION (FOREGROUND), WITH THE OLD ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. VIEW OF THE MODERN SUBSTATION (FOREGROUND), WITH THE OLD SWITCHING BUILDING IN THE BACKGROUND, LOOKING SOUTHWEST. - Washington Water Power Company Post Falls Power Plant, Middle Channel Powerhouse & Dam, West of intersection of Spokane & Fourth Streets, Post Falls, Kootenai County, ID

  7. 3. TAINTER GATES (LEFT FOREGROUND) AND ROLLING SECTOR GATE AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. TAINTER GATES (LEFT FOREGROUND) AND ROLLING SECTOR GATE AND SPILLWAY (BACKGROUND) OF THE NORTH CHANNEL DAM, LOOKING SOUTH. - Washington Water Power Company Post Falls Power Plant, North Channel Dam, West of intersection of Spokane & Fourth Streets, Post Falls, Kootenai County, ID

  8. INTERIOR VIEW, NORTH QUARRY, LOOKING WEST. IN THE FOREGROUND ON ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR VIEW, NORTH QUARRY, LOOKING WEST. IN THE FOREGROUND ON THE FIRST BENCH, POWDER HILLS ARE PRIMED FOR DOLOMITE EXTRACTION. ON THE SECOND BENCH, THE DRILL TEAM IS LAYING OUT THE NEXT SHOTS. - Wade Sand & Gravel Company, North Quarry, State Highway 78, Thomas, Jefferson County, AL

  9. 72. NORTHEAST SIDE OF NITROGEN EXCHANGERS IN FOREGROUND; FUEL APRON ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    72. NORTHEAST SIDE OF NITROGEN EXCHANGERS IN FOREGROUND; FUEL APRON IN BACKGROUND. NORTHEAST CORNER OF WEST CAMERA TOWER ALSO IN BACKGROUND. - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 East, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  10. 18. CLOSEUP OF NITROGEN REGENERATOR IN FOREGROUND AND VERMICULITE STORAGE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. CLOSE-UP OF NITROGEN REGENERATOR IN FOREGROUND AND VERMICULITE STORAGE TOWER FOR THE LINDE 1000 TONS PER DAY HIGH PURITY OXYGEN MAKING PLANT. - U.S. Steel Duquesne Works, Fuel & Utilities Plant, Along Monongahela River, Duquesne, Allegheny County, PA

  11. 23. DETAIL OF PIPELINE PIERS, LOOKING EAST. FOREGROUND IS SLOPED ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    23. DETAIL OF PIPELINE PIERS, LOOKING EAST. FOREGROUND IS SLOPED TYPE, NEXT ONE IS PERPENDICULAR TYPE A COMPRESSION COUPLING, USED TO REPAIR A BROKEN PIPE SECTION, CAN BE SEEN AT BOTTOM. - Kalaupapa Water Supply System, Waikolu Valley to Kalaupapa Settlement, Island of Molokai, Kalaupapa, Kalawao County, HI

  12. 52. VIEW OF HONEYWELL PROPELLANT UTILIZATION TEST SET (FOREGROUND) AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    52. VIEW OF HONEYWELL PROPELLANT UTILIZATION TEST SET (FOREGROUND) AND GENERAL ELECTRIC AIRBORNE BEACON EQUIPMENT TEST SET LOCATED IMMEDIATELY SOUTH OF DEMULTIPLEX BAY, IN THE SOUTHWEST CORNER OF THE TELEMETRY ROOM (ROOM 106) - Vandenberg Air Force Base, Space Launch Complex 3, Launch Operations Building, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  13. Damping models in elastography

    NASA Astrophysics Data System (ADS)

    McGarry, Matthew D. J.; Berger, Hans-Uwe; Van Houten, Elijah E. W.

    2007-03-01

    Current optimization based Elastography reconstruction algorithms encounter difficulties when the motion approaches resonant conditions, where the model does a poor job of approximating the real behavior of the material. Model accuracy can be improved through the addition of damping effects. These effects occur in-vivo due to the complex interaction between microstructural elements of the tissue; however reconstruction models are typically formulated at larger scales where the structure can be treated as a continuum. Attenuation behavior in an elastic continuum can be described as a mixture of inertial and viscoelastic damping effects. In order to develop a continuum damping model appropriate for human tissue, the behavior of each aspect of this proportional, or Rayleigh damping needs to be characterized. In this paper we investigate the nature of these various damping representations with a goal of best describing in-vivo behavior of actual tissue in order to improve the accuracy and performance of optimization based elastographic reconstruction. Inertial damping effects are modelled using a complex density, where the imaginary part is equivalent to a damping coefficient, and the effects of viscoelasticity are modelled through the use of complex shear moduli, where the real and imaginary parts represent the storage and loss moduli respectively. The investigation is carried out through a combination of theoretical analysis, numerical experiment, investigation of gelatine phantoms and comparison with other continua such as porous media models.

  14. Spatial cyclotron damping

    NASA Technical Reports Server (NTRS)

    Olson, C. L.

    1970-01-01

    To examine spatial electron cyclotron damping in a uniform Vlasov plasma, it is noted that the plasma response to a steady-state transverse excitation consists of several terms (dielectric-pole, free-streaming, and branch-cut), but that the cyclotron-damped pole term is the dominant term for z l = c/w sub ce provided (w sub pe/w sub ce) squared (c/a) is much greater than 1. If the latter inequality does not hold, then the free-streaming and branch-cut terms persist well past z = c/w sub ce as w sub 1 approaches w sub ce, making experimental measurement of cyclotron damping essentially impossible. Considering only (w sub pe/w sub ce) squared (c/a) is much greater than 1, it is shown how collisional effects should be estimated and how a finite-width excitation usually has little effect on the cyclotron-damped part of the response. Criteria is established concerning collisional damping, measurable damping length sizes, and allowed uncertainty in the magnetic field Beta. Results of numerical calculations, showing the regions in the appropriate parameter spaces that meet these criteria, are presented. From these results, one can determine the feasibility of, or propose parameter values for, an experiment designed to measure spatial cyclotron damping. It is concluded that the electron temperature T sub e should be at least 1 ev., and preferably 10 ev. or higher, for a successful experiment.

  15. STREAK damping. Technical report

    SciTech Connect

    Baker, J.; Peyton, S.; Freiberg, H.

    1989-12-01

    This report documents a study aimed at improving the damping in STREAK. A form and value for an artificial viscosity is recommended which appears to control ringing and overshoots without overdamping.

  16. DAMPs, ageing, and cancer: The 'DAMP Hypothesis'.

    PubMed

    Huang, Jin; Xie, Yangchun; Sun, Xiaofang; Zeh, Herbert J; Kang, Rui; Lotze, Michael T; Tang, Daolin

    2015-11-01

    Ageing is a complex and multifactorial process characterized by the accumulation of many forms of damage at the molecular, cellular, and tissue level with advancing age. Ageing increases the risk of the onset of chronic inflammation-associated diseases such as cancer, diabetes, stroke, and neurodegenerative disease. In particular, ageing and cancer share some common origins and hallmarks such as genomic instability, epigenetic alteration, aberrant telomeres, inflammation and immune injury, reprogrammed metabolism, and degradation system impairment (including within the ubiquitin-proteasome system and the autophagic machinery). Recent advances indicate that damage-associated molecular pattern molecules (DAMPs) such as high mobility group box 1, histones, S100, and heat shock proteins play location-dependent roles inside and outside the cell. These provide interaction platforms at molecular levels linked to common hallmarks of ageing and cancer. They can act as inducers, sensors, and mediators of stress through individual plasma membrane receptors, intracellular recognition receptors (e.g., advanced glycosylation end product-specific receptors, AIM2-like receptors, RIG-I-like receptors, and NOD1-like receptors, and toll-like receptors), or following endocytic uptake. Thus, the DAMP Hypothesis is novel and complements other theories that explain the features of ageing. DAMPs represent ideal biomarkers of ageing and provide an attractive target for interventions in ageing and age-associated diseases. PMID:25446804

  17. Damping of nanomechanical resonators.

    PubMed

    Unterreithmeier, Quirin P; Faust, Thomas; Kotthaus, Jörg P

    2010-07-01

    We study the transverse oscillatory modes of nanomechanical silicon nitride strings under high tensile stress as a function of geometry and mode index m≤9. Reproducing all observed resonance frequencies with classical elastic theory we extract the relevant elastic constants. Based on the oscillatory local strain we successfully predict the observed mode-dependent damping with a single frequency-independent fit parameter. Our model clarifies the role of tensile stress on damping and hints at the underlying microscopic mechanisms. PMID:20867737

  18. Non-Gaussianity in the foreground-reduced CMB maps

    SciTech Connect

    Bernui, A.; Reboucas, M. J.

    2010-03-15

    A detection or nondetection of primordial non-Gaussianity by using the cosmic microwave background radiation (CMB) data is crucial not only to discriminate inflationary models but also to test alternative scenarios. Non-Gaussianity offers, therefore, a powerful probe of the physics of the primordial Universe. The extraction of primordial non-Gaussianity is a difficult enterprise since several effects of a nonprimordial nature can produce non-Gaussianity. Given the far-reaching consequences of such a non-Gaussianity for our understanding of the physics of the early Universe, it is important to employ a range of different statistical tools to quantify and/or constrain its amount in order to have information that may be helpful for identifying its causes. Moreover, different indicators can in principle provide information about distinct forms of non-Gaussianity that can be present in CMB data. Most of the Gaussianity analyses of CMB data have been performed by using part-sky frequency, where the mask is used to deal with the galactic diffuse foreground emission. However, full-sky map seems to be potentially more appropriate to test for Gaussianity of the CMB data. On the other hand, masks can induce bias in some non-Gaussianity analyses. Here we use two recent large-angle non-Gaussianity indicators, based on skewness and kurtosis of large-angle patches of CMB maps, to examine the question of non-Gaussianity in the available full-sky five-year and seven-year Wilkinson Microwave Anisotropy Probe (WMAP) maps. We show that these full-sky foreground-reduced maps present a significant deviation from Gaussianity of different levels, which vary with the foreground-reducing procedures. We also make a Gaussianity analysis of the foreground-reduced five-year and seven-year WMAP maps with a KQ75 mask, and compare with the similar analysis performed with the corresponding full-sky foreground-reduced maps. This comparison shows a significant reduction in the levels of non

  19. The effect of foreground mitigation strategy on EoR window recovery

    NASA Astrophysics Data System (ADS)

    Chapman, Emma; Zaroubi, Saleem; Abdalla, Filipe B.; Dulwich, Fred; Jelić, Vibor; Mort, Benjamin

    2016-05-01

    The removal of the Galactic and extragalactic foregrounds remains a major challenge for those wishing to make a detection of the Epoch of Reionization (EoR) 21 cm signal. Multiple methods of modelling these foregrounds with varying levels of assumption have been trialled and shown promising recoveries on simulated data. Recently however there has been increased discussion of using the expected shape of the foregrounds in Fourier space to define an EoR window free of foreground contamination. By carrying out analysis within this window only, one can avoid the foregrounds and any statistical bias they might introduce by instead removing these foregrounds. In this paper, we discuss the advantages and disadvantages of both foreground removal and foreground avoidance. We create a series of simulations with noise levels in line with both current and future experiments and compare the recovered statistical cosmological signal from foreground avoidance and a simplified, frequency independent foreground removal model. We find that for current generation experiments, while foreground avoidance enables a better recovery at kperp > 0.6 Mpc-1, foreground removal is able to recover significantly more signal at small klos for both current and future experiments. We also relax the assumption that the foregrounds are smooth. For line-of-sight variations only, foreground removal is able to make a good signal recovery even at 1 per cent while foreground avoidance is compromised significantly. We find that both methods perform well for foreground models with line-of-sight and spatial variations around 0.1 per cent however at levels larger than this both methods are compromised.

  20. Damping modeling in Timoshenko beams

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Wang, Y.

    1992-01-01

    Theoretical and numerical results of damping model studies for composite material beams using the Timoshenko theory is presented. Based on the damping models developed for Euler-Bernoulli beams, the authors develop damping methods for both bending and shear in investigation of Timoshenko beams. A computational method for the estimation of the damping parameters is given. Experimental data with high-frequency excitation were used to test Timoshenko beam equations with different types of damping models for bending and shear in various combinations.

  1. Stopped object detection by learning foreground model in videos.

    PubMed

    Maddalena, Lucia; Petrosino, Alfredo

    2013-05-01

    The automatic detection of objects that are abandoned or removed in a video scene is an interesting area of computer vision, with key applications in video surveillance. Forgotten or stolen luggage in train and airport stations and irregularly parked vehicles are examples that concern significant issues, such as the fight against terrorism and crime, and public safety. Both issues involve the basic task of detecting static regions in the scene. We address this problem by introducing a model-based framework to segment static foreground objects against moving foreground objects in single view sequences taken from stationary cameras. An image sequence model, obtained by learning in a self-organizing neural network image sequence variations, seen as trajectories of pixels in time, is adopted within the model-based framework. Experimental results on real video sequences and comparisons with existing approaches show the accuracy of the proposed stopped object detection approach. PMID:24808423

  2. View north towards yard Triple Stub Switch in foreground. The ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View north towards yard Triple Stub Switch in foreground. The three tracks lead into the East Railroad's Shop complex and Roundhouse. The Steel Hopper Car was used to haul coal and was in the process of being rebuilt but in 1956, when the railroad ended freight operations. As a result it was never completed and was left outside - East Broad Top Railroad & Coal Company, State Route 994, West of U.S. Route 522, Rockhill Furnace, Huntingdon County, PA

  3. The foreground wedge and 21-cm BAO surveys

    NASA Astrophysics Data System (ADS)

    Seo, Hee-Jong; Hirata, Christopher M.

    2016-03-01

    Redshifted H I 21 cm emission from unresolved low-redshift large-scale structure is a promising window for ground-based baryon acoustic oscillations (BAO) observations. A major challenge for this method is separating the cosmic signal from the foregrounds of Galactic and extra-Galactic origins that are stronger by many orders of magnitude than the former. The smooth frequency spectrum expected for the foregrounds would nominally contaminate only very small k∥ modes; however, the chromatic response of the telescope antenna pattern at this wavelength to the foreground introduces non-smooth structure, pervasively contaminating the cosmic signal over the physical scales of our interest. Such contamination defines a wedged volume in Fourier space around the transverse modes that is inaccessible for the cosmic signal. In this paper, we test the effect of this contaminated wedge on the future 21-cm BAO surveys using Fisher information matrix calculation. We include the signal improvement due to the BAO reconstruction technique that has been used for galaxy surveys and test the effect of this wedge on the BAO reconstruction as a function of signal to noises and incorporate the results in the Fisher matrix calculation. We find that the wedge effect expected at z = 1-2 is very detrimental to the angular diameter distances: the errors on angular diameter distances increased by 3-4.4 times, while the errors on H(z) increased by a factor of 1.5-1.6. We conclude that calibration techniques that clean out the foreground `wedge' would be extremely valuable for constraining angular diameter distances from intensity-mapping 21-cm surveys.

  4. View of east entrance to Flume Tunnel #2. In foreground, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of east entrance to Flume Tunnel #2. In foreground, covered decking (covered by debris) protects the flume below it (not visible). The extreme top of the tunnel entrance is visible in the middle of the picture, just beyond the covered decking. This is typical of gravity tunnel entrances and the only photograph representing these features in the system. Looking south - Childs-Irving Hydroelectric Project, Childs System, Flume Tunnel No. 2, Forest Service Road 708/502, Camp Verde, Yavapai County, AZ

  5. 3. AERIAL VIEW FROM THE EAST OF (FOREGROUND TO BACKGROUND) ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. AERIAL VIEW FROM THE EAST OF (FOREGROUND TO BACKGROUND) SLC-3 AIR FORCE BUILDING (BLDG. 761), TECHNICAL SUPPORT BUILDING (BLDG. 762/762A), ENTRY CONTROL POINT (BLDG. 768), AND LOB (BLDG. 763). EAST SIDE OF SLC-3E MOBILE SERVICE TOWER (MST) VISIBLE IN UPPER LEFT CORNER. - Vandenberg Air Force Base, Space Launch Complex 3, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  6. 4. View in foreground of the deck of the Viaduct. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. View in foreground of the deck of the Viaduct. The ornamental wrought iron railing, sandstone sidewalks, and cobblestone roadway are visible. The bridge accommodated two streetcar lines flanked by two lanes of vehicular traffic. In the background is the Detroit- Superior High Level Bridge, which replaced the viaduct. View is looking Southwest. - Superior Avenue Viaduct, Cleveland East & West side, Cuyahoga Valley Vicinity, Cleveland, Cuyahoga County, OH

  7. OBLIQUE VIEW OF REAR SIDE WITH UNIT B IN FOREGROUND. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    OBLIQUE VIEW OF REAR SIDE WITH UNIT B IN FOREGROUND. NOTE THE GABLE VENT AND CONCRETE SLAB OF THE CARPORT (TO THE RIGHT OF UNIT B). VIEW FACING NORTHEAST - Camp H.M. Smith and Navy Public Works Center Manana Title VII (Capehart) Housing, U-Shaped Three-Bedroom Duplex Type 3, Acacia Road, Birch Circle, and Cedar Drive, Pearl City, Honolulu County, HI

  8. VIEW SHOWING THE ENTRY THROUGH THE RETAINING WALL (FOREGROUND) TO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW SHOWING THE ENTRY THROUGH THE RETAINING WALL (FOREGROUND) TO THE CONCRETE SLAB. NOTE THE 1¾" MOUNTING BOLTS FOR THE STEEL PLATE BASE OF THE 5" GUN, SET IN THE GUN BLOCK. STEEL REINFORCING RODS PROTRUDING FROM THE BROKEN TOPS OF THE RETAINING WALLS ARE ALSO VISIBLE. VIEW FACING EAST - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, South Gun Emplacement, Ford Island, Pearl City, Honolulu County, HI

  9. Foreground-induced biases in CMB polarimeter self-calibration

    NASA Astrophysics Data System (ADS)

    Abitbol, Maximilian H.; Hill, James; Johnson, Bradley

    2016-06-01

    Precise polarization measurements of the cosmic microwave background (CMB) require accurate knowledge of the instrument orientation relative to the sky frame used to define the cosmological Stokes parameters. Suitable celestial calibration sources that could be used to measure the polarimeter orientation angle are limited, so current experiments commonly `self-calibrate.' The self-calibration method exploits the theoretical fact that the EB and TB cross-spectra of the CMB vanish in the standard cosmological model, so any detected EB and TB signals must be due to systematic errors. However, this assumption neglects the fact that polarized Galactic foregrounds in a given portion of the sky may have non-zero EB and TB cross-spectra. If these foreground signals remain in the observations, then they will bias the self-calibrated telescope polarization angle and produce a spurious B-mode signal. In this paper, we estimate the foreground-induced bias for various instrument configurations and then expand the self-calibration formalism to account for polarized foreground signals. Assuming the EB correlation signal for dust is in the range constrained by angular power spectrum measurements from Planck at 353 GHz (scaled down to 150 GHz), then the bias is negligible for high angular resolution experiments, which have access to CMB-dominated high 'ell' modes with which to self-calibrate. Low-resolution experiments observing particularly dusty sky patches can have a bias as large as 0.5°. A miscalibration of this magnitude generates a spurious BB signal corresponding to a tensor-to-scalar ratio of approximately r ~ 2 × 10-3, within the targeted range of planned experiments.

  10. INTERIOR VIEW, NORTH QUARRY, LOOKING WEST. IN THE FOREGROUND ON ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR VIEW, NORTH QUARRY, LOOKING WEST. IN THE FOREGROUND ON THE FIRST BENCH, POWDER HILLS ARE PRIMED FOR DOLOMITE EXTRACTION. ON THE SECOND BENCH, THE DRILL TEAM IS LAYING OUT THE NEXT SHOTS. ON THE TOP BENCH, A 245 CATERPILLAR LOADER FILLS A 55-TON CATERPILLAR ROCK TRUCK WITH EXTRACTED DOLOMITE FOR TRANSPORT TO THE DOLOMITE CRUSHING AND SCREENING PLANT. - Wade Sand & Gravel Company, North Quarry, State Highway 78, Thomas, Jefferson County, AL

  11. Foreground-induced biases in CMB polarimeter self-calibration

    NASA Astrophysics Data System (ADS)

    Abitbol, Maximilian H.; Hill, J. Colin; Johnson, Bradley R.

    2016-04-01

    Precise polarization measurements of the cosmic microwave background (CMB) require accurate knowledge of the instrument orientation relative to the sky frame used to define the cosmological Stokes parameters. Suitable celestial calibration sources that could be used to measure the polarimeter orientation angle are limited, so current experiments commonly `self-calibrate.' The self-calibration method exploits the theoretical fact that the EB and TB cross-spectra of the CMB vanish in the standard cosmological model, so any detected EB and TB signals must be due to systematic errors. However, this assumption neglects the fact that polarized Galactic foregrounds in a given portion of the sky may have non-zero EB and TB cross-spectra. If these foreground signals remain in the observations, then they will bias the self-calibrated telescope polarization angle and produce a spurious B-mode signal. In this paper, we estimate the foreground-induced bias for various instrument configurations and then expand the self-calibration formalism to account for polarized foreground signals. Assuming the EB correlation signal for dust is in the range constrained by angular power spectrum measurements from Planck at 353 GHz (scaled down to 150 GHz), then the bias is negligible for high angular resolution experiments, which have access to CMB-dominated high ℓ modes with which to self-calibrate. Low-resolution experiments observing particularly dusty sky patches can have a bias as large as 0.5°. A miscalibration of this magnitude generates a spurious BB signal corresponding to a tensor-to-scalar ratio of approximately r ˜ 2 × 10-3, within the targeted range of planned experiments.

  12. SPIDER OPTIMIZATION. II. OPTICAL, MAGNETIC, AND FOREGROUND EFFECTS

    SciTech Connect

    O'Dea, D. T.; Clark, C. N.; Contaldi, C. R.; Ade, P. A. R.; Amiri, M.; Burger, B.; Davis, G.; Benton, S. J.; Bock, J. J.; Crill, B. P.; Dore, O.; Filippini, J. P.; Bond, J. R.; Farhang, M.; Bonetti, J. A.; Bryan, S.; Chiang, H. C.; Fraisse, A. A.; Fissel, L. M.; Gandilo, N. N.

    2011-09-01

    SPIDER is a balloon-borne instrument designed to map the polarization of the cosmic microwave background (CMB) with degree-scale resolution over a large fraction of the sky. SPIDER's main goal is to measure the amplitude of primordial gravitational waves through their imprint on the polarization of the CMB if the tensor-to-scalar ratio, r, is greater than 0.03. To achieve this goal, instrumental systematic errors must be controlled with unprecedented accuracy. Here, we build on previous work to use simulations of SPIDER observations to examine the impact of several systematic effects that have been characterized through testing and modeling of various instrument components. In particular, we investigate the impact of the non-ideal spectral response of the half-wave plates, coupling between focal-plane components and Earth's magnetic field, and beam mismatches and asymmetries. We also present a model of diffuse polarized foreground emission based on a three-dimensional model of the Galactic magnetic field and dust, and study the interaction of this foreground emission with our observation strategy and instrumental effects. We find that the expected level of foreground and systematic contamination is sufficiently low for SPIDER to achieve its science goals.

  13. CMB multipole measurements in the presence of foregrounds

    NASA Astrophysics Data System (ADS)

    de Oliveira-Costa, Angélica; Tegmark, Max

    2006-07-01

    Most analysis of cosmic microwave background spherical harmonic coefficients aℓm has focused on estimating the power spectrum Cℓ=⟨|aℓm|2⟩ rather than the coefficients themselves. We present a minimum-variance method for measuring aℓm given anisotropic noise, incomplete sky coverage and foreground contamination, and apply it to the Wilkinson Microwave Anisotropy Probe (WMAP) data. Our method is shown to constitute lossless data compression in the sense that the widely used quadratic estimators of the power spectrum Cℓ can be computed directly from our aℓm-estimators. As the Galactic cut is increased, the error bars Δaℓm on low multipoles go from being dominated by foregrounds to being dominated by leakage from other multipoles, with the intervening minimum defining the optimal cut. Applying our method to the WMAP quadrupole and octopole as an illustration, we investigate the robustness of the previously reported “axis of evil” alignment to Galactic cut and foreground contamination.

  14. Experiments with particle damping

    NASA Astrophysics Data System (ADS)

    Hollkamp, Joseph J.; Gordon, Robert W.

    1998-06-01

    High cycle fatigue in jet engines is a current military concern. The vibratory stresses that cause fatigue can be reduced by adding damping. However, the high temperatures that occur in the gas turbine greatly hinder the application of mature damping technologies. One technology which may perform in the harsh environment is particle damping. Particle damping involves placing metallic or ceramic particles inside structural cavities. As the cavity vibrates, energy is dissipated through particle collisions. Performance is influenced by many parameters including the type, shape, and size of the particles; the amount of free volume for the particles to move in; density of the particles; and the level of vibration. This paper presents results from a series of experiments designed to gain an appreciation of the important parameters. The experimental setup consists of a cantilever beam with drilled holes. These holes are partially filled with particles. The types of particles, location of the particles, fill level, and other parameters are varied. Damping is estimated for each configuration. Trends in the results are studied to determine the influence of the varied parameter.

  15. Damped flexible seal

    DOEpatents

    DuBois, Neil J.; Amaral, Antonio M.

    1992-10-27

    A damped flexible seal assembly for a torpedo isolates the tailcone thereof rom vibrational energy present in the drive shaft assembly. A pair of outside flanges, each of which include an inwardly facing groove and an O-ring constrained therein, provide a watertight seal against the outer non-rotating surface of the drive shaft assembly. An inside flange includes an outwardly-facing groove and an O-ring constrained therein, and provides a watertight seal against the inner surface of the tail cone. Two cast-in-place elastomeric seals provide a watertight seal between the flanges and further provide a damping barrier between the outside flanges and the inside flanges for damping vibrational energy present in the drive shaft assembly before the energy can reach the tailcone through the seal assembly.

  16. DAMPs and autophagy

    PubMed Central

    Zhang, Qiuhong; Kang, Rui; Zeh, III, Herbert J.; Lotze, Michael T.; Tang, Daolin

    2013-01-01

    Autophagy is a lysosome-mediated catabolic process involving the degradation of intracellular contents (e.g., proteins and organelles) as well as invading microbes (e.g., parasites, bacteria and viruses). Multiple forms of cellular stress can stimulate this pathway, including nutritional imbalances, oxygen deprivation, immunological response, genetic defects, chromosomal anomalies and cytotoxic stress. Damage-associated molecular pattern molecules (DAMPs) are released by stressed cells undergoing autophagy or injury, and act as endogenous danger signals to regulate the subsequent inflammatory and immune response. A complex relationship exists between DAMPs and autophagy in cellular adaption to injury and unscheduled cell death. Since both autophagy and DAMPs are important for pathogenesis of human disease, it is crucial to understand how they interplay to sustain homeostasis in stressful or dangerous environments. PMID:23388380

  17. First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Foreground Emission

    NASA Technical Reports Server (NTRS)

    Bennett, C. L.; Hill, R. S.; Hinshaw, G.; Nolta, M. R.; Odegard, N.; Page, L.; Spergel, D. N.; Weiland, J. L.; Wright, E. L.; Halpern, M.

    2003-01-01

    The WMAP mission has mapped the full sky to determine the geometry, content, and evolution of the universe. Full sky maps are made in five microwave frequency bands to separate the temperature anisotropy of the cosmic microwave background (CMB) from foreground emission, including diffuse Galactic emission and Galactic and extragalactic point sources. We define masks that excise regions of high foreground emission, so CMB analyses can became out with minimal foreground contamination. We also present maps and spectra of the individual emission components, leading to an improved understanding of Galactic astrophysical processes. The effectiveness of template fits to remove foreground emission from the WMAP data is also examined. These efforts result in a CMB map with minimal contamination and a demonstration that the WMAP CMB power spectrum is insensitive to residual foreground emission. We use a Maximum Entropy Method to construct a model of the Galactic emission components. The observed total Galactic emission matches the model to less than 1% and the individual model components are accurate to a few percent. We find that the Milky Way resembles other normal spiral galaxies between 408 MHz and 23 GHz, with a synchrotron spectral index that is flattest (beta(sub s) approx. -2.5) near star-forming regions, especially in the plane, and steepest (beta(sub s) approx. -3) in the halo. This is consistent with a picture of relativistic cosmic ray electron generation in star-forming regions and diffusion and convection within the plane. The significant synchrotron index steepening out of the plane suggests a diffusion process in which the halo electrons are trapped in the Galactic potential long enough to suffer synchrotron and inverse Compton energy losses and hence a spectral steepening. The synchrotron index is steeper in the WMAP bands than in lower frequency radio surveys, with a spectral break near 20 GHz to beta(sub s) less than -3. The modeled thermal dust spectral

  18. Process Damping Parameters

    NASA Astrophysics Data System (ADS)

    Turner, Sam

    2011-12-01

    The phenomenon of process damping as a stabilising effect in milling has been encountered by machinists since milling and turning began. It is of great importance when milling aerospace alloys where maximum surface speed is limited by excessive tool wear and high speed stability lobes cannot be attained. Much of the established research into regenerative chatter and chatter avoidance has focussed on stability lobe theory with different analytical and time domain models developed to expand on the theory first developed by Trusty and Tobias. Process damping is a stabilising effect that occurs when the surface speed is low relative to the dominant natural frequency of the system and has been less successfully modelled and understood. Process damping is believed to be influenced by the interference of the relief face of the cutting tool with the waveform traced on the cut surface, with material properties and the relief geometry of the tool believed to be key factors governing performance. This study combines experimental trials with Finite Element (FE) simulation in an attempt to identify and understand the key factors influencing process damping performance in titanium milling. Rake angle, relief angle and chip thickness are the variables considered experimentally with the FE study looking at average radial and tangential forces and surface compressive stress. For the experimental study a technique is developed to identify the critical process damping wavelength as a means of measuring process damping performance. For the range of parameters studied, chip thickness is found to be the dominant factor with maximum stable parameters increased by a factor of 17 in the best case. Within the range studied, relief angle was found to have a lesser effect than expected whilst rake angle had an influence.

  19. Note: Tesla transformer damping

    NASA Astrophysics Data System (ADS)

    Reed, J. L.

    2012-07-01

    Unexpected heavy damping in the two winding Tesla pulse transformer is shown to be due to small primary inductances. A small primary inductance is a necessary condition of operability, but is also a refractory inefficiency. A 30% performance loss is demonstrated using a typical "spiral strip" transformer. The loss is investigated by examining damping terms added to the transformer's governing equations. A significant alteration of the transformer's architecture is suggested to mitigate these losses. Experimental and simulated data comparing the 2 and 3 winding transformers are cited to support the suggestion.

  20. Damping seals for turbomachinery

    NASA Technical Reports Server (NTRS)

    Vonpragenau, G. L.

    1985-01-01

    Rotor whirl stabilization of high performance turbomachinery which operates at supercritical speed is discussed. Basic whirl driving forces are reviewed. Stabilization and criteria are discussed. Damping seals are offered as a solution to whirl and high vibration problems. Concept, advantages, retrofitting, and limits of damping seals are explained. Dynamic and leakage properties are shown to require a rough stator surface for stability and efficiency. Typical seal characteristics are given for the case of the high pressure oxidizer turbopump of the Space Shuttle. Ways of implementation and bearing load effects are discussed.

  1. Damping seal for turbomachinery

    NASA Technical Reports Server (NTRS)

    Vonpragenau, G. L. (Inventor)

    1985-01-01

    A damping seal between a high speed rotor member and stator member that separates pressurized fluid compartments is described. It is characterized by the rotor member having a smooth outer surface and the stator member having its bore surface roughened by a plurality of pockets or depressions.

  2. Exotic damping ring lattices

    SciTech Connect

    Palmer, R.B.

    1987-05-01

    This paper looks at, and compares three types of damping ring lattices: conventional, wiggler lattice with finite ..cap alpha.., wiggler lattice with ..cap alpha.. = 0, and observes the attainable equilibrium emittances for the three cases assuming a constraint on the attainable longitudinal impedance of 0.2 ohms. The emittance obtained are roughly in the ratio 4:2:1 for these cases.

  3. Photocopy of photograph entitled, on back, "Bldg in foreground ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of photograph entitled, on back, "Bldg in foreground - 1st hospital". That building is 511 and in the background is the Red Cross Building with steeple. The photograph dates to the 1920's and in the Fitzsimons Army Medical Center Public Affairs Office, building 120. Photograph in public domain as it is not copyrighted. Compare to CO-172-5. - Fitzsimons General Hospital, Bounded by East Colfax to south, Peoria Street to west, Denver City/County & Adams County Line to north, & U.S. Route 255 to east, Aurora, Adams County, CO

  4. Detectability of tensor modes in the presence of foregrounds

    NASA Astrophysics Data System (ADS)

    Amarie, Mihail; Hirata, Christopher; Seljak, Uroš

    2005-12-01

    In inflationary models gravitational waves are produced in the early universe and generate B-type polarization in the cosmic microwave background (CMB). Since B polarization is only generated by gravity waves it does not suffer from the usual cosmic variance. A perfect decomposition of the CMB into B-modes and E-modes would require data from the entire sky, which in practice is not possible because of the foreground contaminants. This leads to mixing of E polarization into B, which introduces cosmic variance contamination of B polarization and reduces sensitivity to gravity wave amplitude even in absence of detector noise. We present numerical results for the uncertainty in the tensor-to-scalar ratio using the Fisher matrix formalism for various resolutions and considering several cuts of the sky, using the foreground model based on dust maps and assuming 90 GHz operating frequency. We find that the usual scaling △((T)/(S))∝fsky-1/2 is significantly degraded and becomes △((T)/(S))∝fsky-2 for fsky>0.7. This dependence is affected only weakly by the choice of sky cuts. To put this into a context of what is required level of foreground cleaning, to achieve a T/S=10-3 detection at 3σ one needs to observe 15% of the sky as opposed to naive expectation of 0.3%. To prevent contamination over this large sky area at required level one must be able to remove polarized dust emission at or better than 0.1% of unpolarized intensity, assuming the cleanest part of the sky has been chosen. To achieve T/S=10-4 detection at 3σ one needs to observe 70% of the sky, which is only possible if dust emission is removed everywhere over this region at 0.01% level. Reaching T/S=10-2 should be easier: 1% of the sky is needed over which polarized emission needs to be removed at 1% of unpolarized intensity if the cleanest region is chosen. These results suggest that foreground contamination may make it difficult to achieve levels below T/S=10-3.

  5. Damping formulas and experimental values of damping in flutter models

    NASA Technical Reports Server (NTRS)

    Coleman, Robert P

    1940-01-01

    The problem of determining values of structural damping for use in flutter calculations is discussed. The concept of equivalent viscous damping is reviewed and its relation to the structural damping coefficient g introduced in NACA Technical Report No. 685 is shown. The theory of normal modes is reviewed and a number of methods are described for separating the motions associated with different modes. Equations are developed for use in evaluating the damping parameters from experimental data. Experimental results of measurements of damping in several flutter models are presented.

  6. S Orionis 70: Just a Foreground Field Brown Dwarf?

    NASA Astrophysics Data System (ADS)

    Burgasser, Adam J.; Kirkpatrick, J. Davy; McGovern, Mark R.; McLean, Ian S.; Prato, L.; Reid, I. Neill

    2004-04-01

    We examine recent claims that the T-type brown dwarf S Ori 053810.1-203626 (S Ori 70) is a spectroscopically verified low-mass (3+5-1 MJup) member of the 1-8 Myr σ Orionis cluster. Comparative arguments by Martín & Zapatero Osorio asserting that S Ori 70 exhibits low surface gravity spectral features indicative of youth and low mass are invalidated by the fact that their comparison object was not the field T dwarf 2MASS 0559-1404, but rather a nearby background star. Instead, we find that the 1-2.5 μm spectra of S Ori 70 are well matched to older (age~few Gyr) field T6-T7 dwarfs. Moreover, we find that spectral model fits to late-type field T dwarf spectra tend to yield low surface gravities (logg=3.0-3.5), and thus young ages (<~5 Myr) and low masses (<~3 MJup), inconsistent with expected and/or empirical values. Finally, we show that the identification of one T dwarf in the field imaged by Zapatero Osorio et al. is statistically consistent with the expected foreground contamination. Based on the reexamined evidence, we conclude that S Ori 70 may simply be an old, massive (30-60 MJup) field brown dwarf lying in the foreground of the σ Orionis cluster. This interpretation should be considered before presuming the existence of so-called ``cluster planets.''

  7. Observational and theoretical advances in cosmological foreground emission

    NASA Astrophysics Data System (ADS)

    Stevenson, Matthew A.

    Observational and theoretical work towards the separation of foreground emission from the cosmic microwave background is described. The bulk of this work is in the design, construction, and commissioning of the C-Band All-Sky Survey (C-BASS), an experiment to produce a template of the Milky Way Galaxy's polarized synchrotron emission. Theoretical work is the derivation of an analytical approximation to the emission spectrum of spinning dust grains. The performance of the C-BASS experiment is demonstrated through a preliminary, deep survey of the North Celestial Pole region. A comparison to multiwavelength data is performed, and the thermal and systematic noise properties of the experiment are explored. The systematic noise has been minimized through careful data processing algorithms, implemented both in the experiment's Field Programmable Gate Array (FPGA) based digital backend and in the data analysis pipeline. Detailed descriptions of these algorithms are presented. The analytical function of spinning dust emission is derived through the application of careful approximations, with each step tested against numerical calculations. This work is intended for use in the parameterized separation of cosmological foreground components and as a framework for interpreting and comparing the variety of anomalous microwave emission observations.

  8. Damping seals for turbomachinery

    NASA Technical Reports Server (NTRS)

    Vonpragenau, G. L.

    1982-01-01

    A rotor seal is proposed that restricts leakage like a labyrinth seal, but extends the stabilizing speed range beyond twice the first critical speed. The dynamic parameters were derived from bulk flow equations without requiring a dominant axial flow. The flow is considered incompressible and turbulent. Damping seals are shown to be feasible for extending the speed range of high performance turbomachinery beyond the limit imposed by conventional seals.

  9. Methods for improving damping. Part 3: Damping material data

    NASA Astrophysics Data System (ADS)

    1992-12-01

    ESDU 92001 presents modulus and loss factor for 27 damping materials in the form of reduced temperature nomograms which allow the effects of frequency and temperature on those properties to be considered simultaneously. The data were supplied by 5 manufacturers, and their addresses in the UK and US are provided. The information is a necessary input in computational procedures, described in ESDU 91013, dealing with the application of layered damping treatments to beam- and plate-like structures. Notes are included on the measurement and reliability of the damping quantities that affect the variability allowances to be made when assessing a damping treatment for a particular application. Factors to be considered when selecting a damping material are discussed. Approximate relationships between the elastic properties of damping materials are given.

  10. Illumination and Reflectance Estimation with its Application in Foreground Detection

    PubMed Central

    Tu, Gang Jun; Karstoft, Henrik; Pedersen, Lene Juul; Jørgensen, Erik

    2015-01-01

    In this paper, we introduce a novel approach to estimate the illumination and reflectance of an image. The approach is based on illumination-reflectance model and wavelet theory. We use a homomorphic wavelet filter (HWF) and define a wavelet quotient image (WQI) model based on dyadic wavelet transform. The illumination and reflectance components are estimated by using HWF and WQI, respectively. Based on the illumination and reflectance estimation we develop an algorithm to segment sows in grayscale video recordings which are captured in complex farrowing pens. Experimental results demonstrate that the algorithm can be applied to detect the domestic animals in complex environments such as light changes, motionless foreground objects and dynamic background. PMID:26343675

  11. Differentiating salt marsh species using foreground/background analysis

    SciTech Connect

    Zhang, M.; Pinzon, J.; Ustin, S.L.; Rejmankova, E.

    1996-10-01

    Three California salt marsh plant species have distinctive morphologies that could be remotely sensed by airborne spectrometers because the architectures create differences in canopy reflectance characteristics. This paper presents a method to differentiate wetland species using a modified spectral mixture analysis termed hierarchical foreground and background analysis (HFBA). To validate this approach, the method was applied to field spectral data from several salt marshes. Foreground and background analysis allows the user to direct analysis along a specified axis of variance by identifying vectors through the n-dimensional spectral volume by identifying vectors that comprise the information of selected subset of spectra which emphasizes the presence of a discriminative signature of interest. The goal of FBA is to project spectral variation along the most relevant axis of variance that maximizes spectral differences between groups, while minimizing spectral variation within each group. For this work, we selected a training set that allowed us to create HFBA vectors which efficiently discriminate species based on canopy spectral characteristics. Results indicated that the dominant species in these salts marshes could be clearly differentiated with greater than 90% certainty from field collected canopy spectrometer data. Hundred percent of Spartina and 79% of Salicornia were correctly classified at the first level of classification. The accuracy of classification for Salicornia improved to 87% in the second level of classification. The unclassified spectral samples were related to extraordinary conditions within the wetlands such as extreme biomass, salinity and nitrogen conditions. These patterns were apparent in AVIRIS (Airborne Visible/infrared Imaging Spectrometer) images which showed distinct zonation corresponding to the distributions of these species in the marsh. Results were confirmed by field reconnaissance. 19 refs., 3 figs., 4 tabs.

  12. On damping mechanisms in beams

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Inman, D. J.

    1989-01-01

    A partial differential equation model of a cantilevered beam with a tip mass at its free end is used to study damping in a composite. Four separate damping mechanisms consisting of air damping, strain rate damping, spatial hysteresis and time hysteresis are considered experimentally. Dynamic tests were performed to produce time histories. The time history data is then used along with an approximate model to form a sequence of least squares problems. The solution of the least squares problem yields the estimated damping coefficients. The resulting experimentally determined analytical model is compared with the time histories via numerical simulation of the dynamic response. The procedure suggested here is compared with a standard modal damping ratio model commonly used in experimental modal analysis.

  13. Damping measurements in flowing water

    NASA Astrophysics Data System (ADS)

    Coutu, A.; Seeley, C.; Monette, C.; Nennemann, B.; Marmont, H.

    2012-11-01

    Fluid-structure interaction (FSI), in the form of mass loading and damping, governs the dynamic response of water turbines, such as Francis turbines. Water added mass and damping are both critical quantities in evaluating the dynamic response of the turbine component. Although the effect of fluid added mass is well documented, fluid damping, a critical quantity to limit vibration amplitudes during service, and therefore to help avoiding possible failure of the turbines, has received much less attention in the literature. This paper presents an experimental investigation of damping due to FSI. The experimental setup, designed to create dynamic characteristics similar to the ones of Francis turbine blades is discussed, together with the experimental protocol and examples of measurements obtained. The paper concludes with the calculated damping values and a discussion on the impact of the observed damping behaviour on the response of hydraulic turbine blades to FSI.

  14. Magnetically Damped Furnace (MDF)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The Magnetically Damped Furnace (MDF) breadboard is being developed in response to NASA's mission and goals to advance the scientific knowledge of microgravity research, materials science, and related technologies. The objective of the MDF is to dampen the fluid flows due to density gradients and surface tension gradients in conductive melts by introducing a magnetic field during the sample processing. The MDF breadboard will serve as a proof of concept that the MDF performance requirements can be attained within the International Space Station resource constraints.

  15. The Joint Damping Experiment (JDX)

    NASA Technical Reports Server (NTRS)

    Folkman, Steven L.; Bingham, Jeff G.; Crookston, Jess R.; Dutson, Joseph D.; Ferney, Brook D.; Ferney, Greg D.; Rowsell, Edwin A.

    1997-01-01

    The Joint Damping Experiment (JDX), flown on the Shuttle STS-69 Mission, is designed to measure the influence of gravity on the structural damping of a high precision three bay truss. Principal objectives are: (1) Measure vibration damping of a small-scale, pinjointed truss to determine how pin gaps give rise to gravity-dependent damping rates; (2) Evaluate the applicability of ground and low-g aircraft tests for predicting on-orbit behavior; and (3) Evaluate the ability of current nonlinear finite element codes to model the dynamic behavior of the truss. Damping of the truss was inferred from 'Twang' tests that involve plucking the truss structure and recording the decay of the oscillations. Results are summarized as follows. (1) Damping, rates can change by a factor of 3 to 8 through changing the truss orientation; (2) The addition of a few pinned joints to a truss structure can increase the damping by a factor as high as 30; (3) Damping is amplitude dependent; (4) As gravity induced preloads become large (truss long axis perpendicular to gravity vector) the damping is similar to non-pinjointed truss; (5) Impacting in joints drives higher modes in structure; (6) The torsion mode disappears if gravity induced preloads are low.

  16. New concepts for damping rings

    SciTech Connect

    Raimondi, P.; Wolski, A.

    2002-05-30

    The requirements for very low emittance and short damping time in the damping rings of future linear colliders, naturally lead to very small beta functions and dispersion in the ring arcs. This makes it difficult to make chromatic correction while maintaining good dynamics. We have therefore developed a lattice with very simple arcs (designed to give the best product of emittance and damping time), and with separate chromatic correction in a dedicated section. The chromatic correction is achieved using a series of non-interleaved sextupole pairs. The performance of such a solution is comparable to that of current damping ring designs, while there are a number of potential advantages.

  17. 4. OVERVIEW LOOKING NORTHEAST, BLD 5 RIGHT FOREGROUND, BLDG. 44/16 ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. OVERVIEW LOOKING NORTHEAST, BLD 5 RIGHT FOREGROUND, BLDG. 44/16 LEFT FOREGROUND. - Fafnir Bearing Plant, Bounded on North side by Myrtle Street, on South side by Orange Street, on East side by Booth Street & on West side by Grove Street, New Britain, Hartford County, CT

  18. The DAMPE mission

    NASA Astrophysics Data System (ADS)

    Wu, Jian; Guo, Jianhua; Chang, Jin; Cai, Mingsheng

    2016-07-01

    The DArk Matter Particle Explorer (DAMPE) was launched into space on Dec.17, 2015 to a 500km dawn-to-dusk sun-synchronous orbit aiming at detecting high energy electron(gamma) as well as cosmic heavy ions up to 10TeV and 1PeV respectively to try to understand the mechanisms of particle acceleration in celestial sources and the propagation of cosmic rays in the Galaxy, to probe the nature of dark matter, a form of matter necessary to account for gravitational effects observed in very large scale structures such as anomalies in the rotation of galaxies and the gravitational lensing of light by galaxy clusters that cannot be accounted for by the quantity of observed matter , and to study the high-energy behavior of gamma-ray bursts, pulsars, Active Galaxy Nuclei and other transients,etc. After months' commissioning, DAMPE has been in the observational mode. This paper reports the status of its detectors and latest results collected so far.

  19. Statistical diagnostics to identify galactic foregrounds in B-mode maps.

    PubMed

    Kamionkowski, Marc; Kovetz, Ely D

    2014-11-01

    Recent developments in the search for inflationary gravitational waves in the cosmic microwave background polarization motivate the search for new diagnostics to distinguish the Galactic foreground contribution to B modes from the cosmic signal. We show that B modes from these foregrounds should exhibit a local hexadecapolar departure in power from statistical isotropy (SI). We present a simple algorithm to search for a uniform SI violation of this sort, as may arise in a sufficiently small patch of sky. We then show how to search for these effects if the orientation of the SI violation varies across the survey region, as is more likely to occur in surveys with more sky coverage. If detected, these departures from Gaussianity would indicate some level of Galactic foreground contamination in the B-mode maps. Given uncertainties about foreground properties, though, caution should be exercised in attributing a null detection to an absence of foregrounds. PMID:25415897

  20. Damping Vibration at an Impeller

    NASA Technical Reports Server (NTRS)

    Hager, J. A.; Rowan, B. F.

    1982-01-01

    Vibration of pump shaft is damped at impeller--where vibration-induced deflections are greatest--by shroud and seal. Damping reduces vibrational motion of shaft at bearings and load shaft places on them. Flow through clearance channel absorbs vibration energy.

  1. The Latest Results from DAMPE

    NASA Astrophysics Data System (ADS)

    Chang, Jin

    2016-07-01

    DArk Matter Particle Explorer (DAMPE) successfully launched on Dec.17, 2015 is the first Chinese astronomical satellite that can measure 2 GeV-10 TeV electrons and gamma-rays with unprecedented energy resolution. In this talk I will introduce the design, the beam-test, the on-orbit calibration and some preliminary results of DAMPE.

  2. Surge-damping vacuum valve

    DOEpatents

    Bullock, Jack C.; Kelly, Benjamin E.

    1980-01-01

    A valve having a mechanism for damping out flow surges in a vacuum system which utilizes a slotted spring-loaded disk positioned adjacent the valve's vacuum port. Under flow surge conditions, the differential pressure forces the disk into sealing engagement with the vacuum port, thereby restricting the flow path to the slots in the disk damping out the flow surge.

  3. Damping seal verification setup

    NASA Technical Reports Server (NTRS)

    Cappel, K. L.

    1985-01-01

    The heart of the Space Shuttle Main Engine (SSME) is a set of turbopumps that propel cryogenic fluids at very high pressures and flow rates, at rotor speeds up to 37,000 rpm. Bushing seals that cause the flow in the fluid film to become turbulent, by means of a multiplicity of pockets, were shown theoretically not only to inhibit subsynchronous whirl, but to reduce leakage as well. However, experimental data that relate these two desirable characteristics to such parameters as pocket depth, Reynolds number (based on clearance and axial flow rate), and rotating speed are limited. To obtain the required data, NASA's Marshall Space Flight Center (MSFC) commissioned Wyle Laboratories to design, build and operate a test rig in which the damping efficacy and leakage reduction of typical candidate seals are to be evaluated.

  4. Damping measurements using operational data

    SciTech Connect

    James, G.H.; Carne, T.G.; Veers, P.S.

    1996-08-01

    The authors have measured modal damping using strain-gauge data from an operating wind turbine. This new technique for measuring modal damping is easier and less expensive than previously used methods. Auto-correlation and cross-correlation functions of the strain-gauge data have been shown to consist of decaying sinusoids which correspond to the modal frequencies and damping ratios of the wind turbine. The authors have verified the method by extracting damping values from an analytically generated data set. Actual operating response data from the DOE/Sandia 34-m Test Bed has been used to calculate modal damping ratios as a function of rotor rotation rate. This capability will allow more accurate fatigue life prediction and control.

  5. Damping Bearings In High-Speed Turbomachines

    NASA Technical Reports Server (NTRS)

    Von Pragenau, George L.

    1994-01-01

    Paper presents comparison of damping bearings with traditional ball, roller, and hydrostatic bearings in high-speed cryogenic turbopumps. Concept of damping bearings described in "Damping Seals and Bearings for a Turbomachine" (MFS-28345).

  6. COSMOG: Cosmology Oriented Sub-mm Modeling of Galactic Foregrounds

    NASA Technical Reports Server (NTRS)

    Kashlinsky, A.; Leisawitz, D.

    2004-01-01

    With upcoming missions in mid- and far-Infrared there is a need for software packages to reliably simulate the planned observations. This would help in both planning the observation and scanning strategy and in developing the concepts of the far-off missions. As this workshop demonstrated, many of the new missions are to be in the far-IR range of the electromagnetic spectrum and at the same time will map the sky with a sub-arcsec angular resolution. We present here a computer package for simulating foreground maps for the planned sub-mm and far-IR missions. such as SPECS. The package allows to study confusion limits and simulate cosmological observations for specified sky location interactively and in real time. Most of the emission at wavelengths long-ward of approximately 50 microns is dominated by Galactic cirrus and Zodiacal dust emission. Stellar emission at these wavelengths is weak and is for now neglected. Cosmological sources (distant and not-so-distant) galaxies for specified cosmologies will be added. Briefly, the steps that the algorithm goes through is described.

  7. Possible signature of distant foreground in the Planck data

    NASA Astrophysics Data System (ADS)

    Yershov, V. N.; Orlov, V. V.; Raikov, A. A.

    2014-12-01

    By using the Planck map of the cosmic microwave background (CMB) radiation, we have checked and confirmed the existence of a correlation between supernova (SN) redshifts, zSN, and CMB temperature fluctuations at the SNe locations, TSN, which we previously reported for the Wilkinson Microwave Anisotropy Probe data. The Pearson correlation coefficient for the Planck data is r = +0.38 ± 0.08, which indicates that the correlation is statistically significant (the signal is about 5σ above the noise level). The correlation becomes even stronger for the Type Ia subsample of SNe, rIa = +0.45 ± 0.09, whereas for the rest of the SNe it is vanishing. By checking the slopes of the regression lines TSN/zSN for Planck's different frequency bands, we have also excluded the possibility of this anomaly being caused by the Sunyaev-Zeldovich effect. The remaining possibility is some, unaccounted for, contribution to the CMB from distant (z > 0.3) foreground through either the integrated Sachs-Wolfe effect or thermal emission from intergalactic matter.

  8. Epoch of reionization window. II. Statistical methods for foreground wedge reduction

    NASA Astrophysics Data System (ADS)

    Liu, Adrian; Parsons, Aaron R.; Trott, Cathryn M.

    2014-07-01

    For there to be a successful measurement of the 21 cm epoch of reionization (EoR) power spectrum, it is crucial that strong foreground contaminants be robustly suppressed. These foregrounds come from a variety of sources (such as Galactic synchrotron emission and extragalactic point sources), but almost all share the property of being spectrally smooth and, when viewed through the chromatic response of an interferometer, occupy a signature "wedge" region in cylindrical k⊥k∥ Fourier space. The complement of the foreground wedge is termed the "EoR window" and is expected to be mostly foreground-free, allowing clean measurements of the power spectrum. This paper is a sequel to a previous paper that established a rigorous mathematical framework for describing the foreground wedge and the EoR window. Here, we use our framework to explore statistical methods by which the EoR window can be enlarged, thereby increasing the sensitivity of a power spectrum measurement. We adapt the Feldman-Kaiser-Peacock approximation (commonly used in galaxy surveys) for 21 cm cosmology and also compare the optimal quadratic estimator to simpler estimators that ignore covariances between different Fourier modes. The optimal quadratic estimator is found to suppress foregrounds by an extra factor of ˜105 in power at the peripheries of the EoR window, boosting the detection of the cosmological signal from 12σ to 50σ at the midpoint of reionization in our fiducial models. If numerical issues can be finessed, decorrelation techniques allow the EoR window to be further enlarged, enabling measurements to be made deep within the foreground wedge. These techniques do not assume that foreground is Gaussian distributed, and we additionally prove that a final round of foreground subtraction can be performed after decorrelation in a way that is guaranteed to have no cosmological signal loss.

  9. An Overview of DNA Microarray Grid Alignment and Foreground Separation Approaches

    NASA Astrophysics Data System (ADS)

    Bajcsy, Peter

    2006-12-01

    This paper overviews DNA microarray grid alignment and foreground separation approaches. Microarray grid alignment and foreground separation are the basic processing steps of DNA microarray images that affect the quality of gene expression information, and hence impact our confidence in any data-derived biological conclusions. Thus, understanding microarray data processing steps becomes critical for performing optimal microarray data analysis. In the past, the grid alignment and foreground separation steps have not been covered extensively in the survey literature. We present several classifications of existing algorithms, and describe the fundamental principles of these algorithms. Challenges related to automation and reliability of processed image data are outlined at the end of this overview paper.

  10. Self-Damping Sprung Wheel

    NASA Technical Reports Server (NTRS)

    Weddendorf, Bruce

    1993-01-01

    Self-damping sprung wheel provides shock-absorbing suspension for wheelchair, reducing user's discomfort when traversing rough terrain or obstacles. Pair of self-damping sprung wheels installed in place of conventional large rear wheels of standard wheelchair, which user operates in conventional manner. Rim deflects in vicinity of contact with ground or floor. Includes inner and outer hoops bending when obstacle encountered. Shear deformation of elastomeric hoop between them absorbs energy. Thus, three hoops act together as damping spring. Alternative version of wheel designed for bicycle.

  11. Gilbert damping in noncollinear ferromagnets.

    PubMed

    Yuan, Zhe; Hals, Kjetil M D; Liu, Yi; Starikov, Anton A; Brataas, Arne; Kelly, Paul J

    2014-12-31

    The precession and damping of a collinear magnetization displaced from its equilibrium are well described by the Landau-Lifshitz-Gilbert equation. The theoretical and experimental complexity of noncollinear magnetizations is such that it is not known how the damping is modified by the noncollinearity. We use first-principles scattering theory to investigate transverse domain walls (DWs) of the important ferromagnetic alloy Ni80Fe20 and show that the damping depends not only on the magnetization texture but also on the specific dynamic modes of Bloch and Néel DWs in ways that were not theoretically predicted. Even in the highly disordered Ni80Fe20 alloy, the damping is found to be remarkably nonlocal. PMID:25615368

  12. Damping measurements using operational data

    SciTech Connect

    James, G.H.; Carne, T.G.; Veers, P.S.

    1991-01-01

    We have measured modal damping using strain-gauge data from an operating wind turbine. Previously, such measurements were difficult and expensive. Auto-correlation and cross-correlation functions of the strain-gauge data have been shown to consist of decaying sinusoids which correspond to the modal frequencies and damping ratios of the wind turbine. We have verified the method by extracting damping values from an analytically generated data set. Actual operating response data from the DOE/Sandia 34-meter Test Bed has been used to calculate modal damping ratios as a function of rotor rotation rate. This capability will allow more accurate fatigue life prediction and control. 16 refs., 3 figs., 2 tabs.

  13. THE APPLICATION OF CONTINUOUS WAVELET TRANSFORM BASED FOREGROUND SUBTRACTION METHOD IN 21 cm SKY SURVEYS

    SciTech Connect

    Gu Junhua; Xu Haiguang; Wang Jingying; Chen Wen; An Tao

    2013-08-10

    We propose a continuous wavelet transform based non-parametric foreground subtraction method for the detection of redshifted 21 cm signal from the epoch of reionization. This method works based on the assumption that the foreground spectra are smooth in frequency domain, while the 21 cm signal spectrum is full of saw-tooth-like structures, thus their characteristic scales are significantly different. We can distinguish them in the wavelet coefficient space easily and perform the foreground subtraction. Compared with the traditional spectral fitting based method, our method is more tolerant to complex foregrounds. Furthermore, we also find that when the instrument has uncorrected response error, our method can also work significantly better than the spectral fitting based method. Our method can obtain similar results with the Wp smoothing method, which is also a non-parametric method, but our method consumes much less computing time.

  14. 20. VIEW OF NEWER 7LEVER INTERLOCKING MACHINE IN FOREGROUND, NEXT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    20. VIEW OF NEWER 7-LEVER INTERLOCKING MACHINE IN FOREGROUND, NEXT TO ORIGINAL INTERLOCKING MACHINE, THIRD FLOOR - South Station Tower No. 1 & Interlocking System, Dewey Square, Boston, Suffolk County, MA

  15. MAIN GENERATOR EXCITER UNIT IN FOREGROUND, WITH CYCLOPS 75TON CRANE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    MAIN GENERATOR EXCITER UNIT IN FOREGROUND, WITH CYCLOPS 75-TON CRANE IN BACKGROUND. PHOTO BY JET LOWE, HAER, 1995. - Elwha River Hydroelectric System, Glines Hydroelectric Dam & Plant, Port Angeles, Clallam County, WA

  16. A novel ensemble method to integrate with different technologies for moving foreground detection

    NASA Astrophysics Data System (ADS)

    Chan, Yi-Tung; Wang, Shuenn-Jyi; Tsai, Chung-Hsien; Lin, Pei-Ru; Chen, Wen-Pin

    2015-12-01

    Moving foreground detection can be used for the intelligent surveillance system and computer vision as an important step for many applications. Previous researchers have developed many different moving foreground detection technologies, such as background subtraction and optical flow. However, as far as we knew, there was few literature investigated ensemble method in integrate with various foreground detection technologies in real-time. In this paper, we present a new approach inspired from the ensemble system of machine learning to detect moving foreground by using weighted matrix with spatial characteristics. Furthermore, the weighted values can be automatically scaled over time for optimal flexibility and parameterization in our method. The experimental results demonstrate that the proposed method can not only provide compared performance with the state-of-the-art methods, but also satisfy real-time applications.

  17. East façade, Burton Park Club House, with Amphitheater in foreground, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    East façade, Burton Park Club House, with Amphitheater in foreground, view to north from Amphitheater stage (90 mm lens). - Burton Park, Club House & Amphitheater, Adjacent ot south end of Chestnut Avenue, San Carlos, San Mateo County, CA

  18. View of slow sand filters with pump house/chlorinator in foreground. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of slow sand filters with pump house/chlorinator in foreground. Clear well tank located behind pump house and trees. - Hawaii Volcanoes National Park Water Collection System, Hawaii Volcanoes National Park, Volcano, Hawaii County, HI

  19. FACILITY 810A, DINING ROOM IN FOREGROUND WITH LIVING ROOM AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    FACILITY 810A, DINING ROOM IN FOREGROUND WITH LIVING ROOM AND ITS FIREPLACE IN BACKGROUND, VIEW FACING NORTH. - Schofield Barracks Military Reservation, Duplex Housing Type with Corner Entries, Between Hamilton & Tidball Streets near Williston Avenue, Wahiawa, Honolulu County, HI

  20. The Application of Continuous Wavelet Transform Based Foreground Subtraction Method in 21 cm Sky Surveys

    NASA Astrophysics Data System (ADS)

    Gu, Junhua; Xu, Haiguang; Wang, Jingying; An, Tao; Chen, Wen

    2013-08-01

    We propose a continuous wavelet transform based non-parametric foreground subtraction method for the detection of redshifted 21 cm signal from the epoch of reionization. This method works based on the assumption that the foreground spectra are smooth in frequency domain, while the 21 cm signal spectrum is full of saw-tooth-like structures, thus their characteristic scales are significantly different. We can distinguish them in the wavelet coefficient space easily and perform the foreground subtraction. Compared with the traditional spectral fitting based method, our method is more tolerant to complex foregrounds. Furthermore, we also find that when the instrument has uncorrected response error, our method can also work significantly better than the spectral fitting based method. Our method can obtain similar results with the Wp smoothing method, which is also a non-parametric method, but our method consumes much less computing time.

  1. Vibration damping method and apparatus

    DOEpatents

    Redmond, James M.; Barney, Patrick S.; Parker, Gordon G.; Smith, David A.

    1999-01-01

    The present invention provides vibration damping method and apparatus that can damp vibration in more than one direction without requiring disassembly, that can accommodate varying tool dimensions without requiring re-tuning, and that does not interfere with tool tip operations and cooling. The present invention provides active dampening by generating bending moments internal to a structure such as a boring bar to dampen vibration thereof.

  2. Vibration damping method and apparatus

    DOEpatents

    Redmond, J.M.; Barney, P.S.; Parker, G.G.; Smith, D.A.

    1999-06-22

    The present invention provides vibration damping method and apparatus that can damp vibration in more than one direction without requiring disassembly, that can accommodate varying tool dimensions without requiring re-tuning, and that does not interfere with tool tip operations and cooling. The present invention provides active dampening by generating bending moments internal to a structure such as a boring bar to dampen vibration thereof. 38 figs.

  3. The impact of foregrounds on redshift space distortion measurements with the highly redshifted 21-cm line

    NASA Astrophysics Data System (ADS)

    Pober, Jonathan C.

    2015-02-01

    The highly redshifted 21-cm line of neutral hydrogen has become recognized as a unique probe of cosmology from relatively low redshifts (z ˜ 1) up through the Epoch of Reionization (EoR) (z ˜ 8) and even beyond. To date, most work has focused on recovering the spherically averaged power spectrum of the 21-cm signal, since this approach maximizes the signal to noise in the initial measurement. However, like galaxy surveys, the 21-cm signal is affected by redshift space distortions, and is inherently anisotropic between the line of sight and transverse directions. A measurement of this anisotropy can yield unique cosmological information, potentially even isolating the matter power spectrum from astrophysical effects. However, in interferometric measurements, foregrounds also have an anisotropic footprint between the line of sight and transverse directions: the so-called foreground `wedge'. Although foreground subtraction techniques are actively being developed, a `foreground avoidance' approach of simply ignoring contaminated modes has arguably proven most successful to date. In this work, we analyse the effect of this foreground anisotropy in recovering the redshift space distortion signature in 21-cm measurements at both high and intermediate redshifts. We find the foreground wedge corrupts nearly all of the redshift space signal for even the largest proposed EoR experiments (Hydrogen Epoch of Reionization Array and the Square Kilometre Array), making cosmological information unrecoverable without foreground subtraction. The situation is somewhat improved at lower redshifts, where the redshift-dependent mapping from observed coordinates to cosmological coordinates significantly reduces the size of the wedge. Using only foreground avoidance, we find that a large experiment like Canadian Hydrogen Intensity Mapping Experiment can place non-trivial constraints on cosmological parameters.

  4. OPENING THE 21 cm EPOCH OF REIONIZATION WINDOW: MEASUREMENTS OF FOREGROUND ISOLATION WITH PAPER

    SciTech Connect

    Pober, Jonathan C.; Parsons, Aaron R.; Ali, Zaki; Aguirre, James E.; Moore, David F.; Bradley, Richard F.; Carilli, Chris L.; DeBoer, Dave; Dexter, Matthew; MacMahon, Dave; Gugliucci, Nicole E.; Jacobs, Daniel C.; Klima, Patricia J.; Manley, Jason; Walbrugh, William P.; Stefan, Irina I.

    2013-05-10

    We present new observations with the Precision Array for Probing the Epoch of Reionization with the aim of measuring the properties of foreground emission for 21 cm epoch of reionization (EoR) experiments at 150 MHz. We focus on the footprint of the foregrounds in cosmological Fourier space to understand which modes of the 21 cm power spectrum will most likely be compromised by foreground emission. These observations confirm predictions that foregrounds can be isolated to a {sup w}edge{sup -}like region of two-dimensional (k , k{sub Parallel-To })-space, creating a window for cosmological studies at higher k{sub Parallel-To} values. We also find that the emission extends past the nominal edge of this wedge due to spectral structure in the foregrounds, with this feature most prominent on the shortest baselines. Finally, we filter the data to retain only this ''unsmooth'' emission and image its specific k{sub Parallel-To} modes. The resultant images show an excess of power at the lowest modes, but no emission can be clearly localized to any one region of the sky. This image is highly suggestive that the most problematic foregrounds for 21 cm EoR studies will not be easily identifiable bright sources, but rather an aggregate of fainter emission.

  5. Five-Year Wilkinson Microwave Anisotropy Probe (WMAP1) Observations: Galactic Foreground Emission

    NASA Technical Reports Server (NTRS)

    Gold, B.; Bennett, C.L.; Larson, D.; Hill, R.S.; Odegard, N.; Weiland, J.L.; Hinshaw, G.; Kogut, A.; Wollack, E.; Page, L.; Dunkley, J.; Jarosik, N.; Spergel, N.; Halpern, M.; Komatsu, E.; Meyer, S.S.; Nolta, M.R.; Wright, E.L.

    2008-01-01

    We present a new estimate of foreground emission in the WMAP data, using a Markov chain Monte Carlo (MCMC) method. The new technique delivers maps of each foreground component for a variety of foreground models, error estimates of the uncertainty of each foreground component, and provides an overall goodness-of-fit measurement. The resulting foreground maps are in broad agreement with those from previous techniques used both within the collaboration and by other authors. We find that for WMAP data, a simple model with power-law synchrotron, free-free, and thermal dust components fits 90% of the sky with a reduced X(sup 2) (sub v) of 1.14. However, the model does not work well inside the Galactic plane. The addition of either synchrotron steepening or a modified spinning dust model improves the fit. This component may account for up to 14% of the total flux at Ka-band (33 GHz). We find no evidence for foreground contamination of the CMB temperature map in the 85% of the sky used for cosmological analysis.

  6. Opening the 21 cm Epoch of Reionization Window: Measurements of Foreground Isolation with PAPER

    NASA Astrophysics Data System (ADS)

    Pober, Jonathan C.; Parsons, Aaron R.; Aguirre, James E.; Ali, Zaki; Bradley, Richard F.; Carilli, Chris L.; DeBoer, Dave; Dexter, Matthew; Gugliucci, Nicole E.; Jacobs, Daniel C.; Klima, Patricia J.; MacMahon, Dave; Manley, Jason; Moore, David F.; Stefan, Irina I.; Walbrugh, William P.

    2013-05-01

    We present new observations with the Precision Array for Probing the Epoch of Reionization with the aim of measuring the properties of foreground emission for 21 cm epoch of reionization (EoR) experiments at 150 MHz. We focus on the footprint of the foregrounds in cosmological Fourier space to understand which modes of the 21 cm power spectrum will most likely be compromised by foreground emission. These observations confirm predictions that foregrounds can be isolated to a "wedge"-like region of two-dimensional (k , k ∥)-space, creating a window for cosmological studies at higher k ∥ values. We also find that the emission extends past the nominal edge of this wedge due to spectral structure in the foregrounds, with this feature most prominent on the shortest baselines. Finally, we filter the data to retain only this "unsmooth" emission and image its specific k ∥ modes. The resultant images show an excess of power at the lowest modes, but no emission can be clearly localized to any one region of the sky. This image is highly suggestive that the most problematic foregrounds for 21 cm EoR studies will not be easily identifiable bright sources, but rather an aggregate of fainter emission.

  7. The effects of the space environment on damping materials and damping designs on flexible structures

    NASA Technical Reports Server (NTRS)

    Kluesener, M. F.

    1984-01-01

    The effects of space environments on damping materials and damping designs on flexible structures were investigated. The following items were examined: damping of flexible spacecraft appendages; composite loss factor (n sub s) vs. time in high vacuum for damped test beams and damping of flexible structures. The STEP experiments show inherent damping of flexible structures in space effective possible damping design configurations for space structures, effects of passively damped components on the system loss factor of flexible structures and the effect of space environment on properties of damping materials.

  8. Circular polarization of the CMB: Foregrounds and detection prospects

    NASA Astrophysics Data System (ADS)

    King, Soma; Lubin, Philip

    2016-07-01

    The cosmic microwave background (CMB) is one of the finest probes of cosmology. Its all-sky temperature and linear polarization fluctuations have been measured precisely at a level of δ T /TCMB˜10-6 . In contrast, circular polarization (C P ) of the CMB has not been precisely explored. The current upper limit on the C P of the CMB is at a level of δ V /TCMB˜10-4 and is limited on large scales. Some of the cosmologically important sources which can induce a C P in the CMB include early Universe symmetry breaking, a primordial magnetic field, galaxy clusters, and Pop III stars (also known as the first stars). Among these sources, Pop III stars are expected to induce the strongest signal with levels strongly dependent on the frequency of observation and on the number, Np, of the Pop III stars per halo. Optimistically, a C P signal in the CMB resulting from the Pop III stars could be at a level of δ V /TCMB˜2 ×10-7 in scales of 1° at 10 GHz, which is much smaller than the currently existing upper limits on the C P measurements. Primary foregrounds in the cosmological C P detection will come from the galactic synchrotron emission, which is naturally (intrinsically) circularly polarized. We use data-driven models of the galactic magnetic field, thermal electron density, and relativistic electron density to simulate all-sky maps of the galactic C P . This work also points out that the galactic C P levels are important below 50 GHz and is an important factor for telescopes aiming to detect primordial B modes using C P as a systematic rejection channel. In this paper, we focus on a SNR evaluation for the detectability of the Pop III induced C P signal in the CMB. We find that a SNR higher than unity is achievable, for example, with a 10 m telescope and an observation time of 20 months at 10 GHz, if Np≥100 . We also find that, if frequency of observation and resolution of the beam is appropriately chosen, a SNR higher than unity is possible with Np≥10 and

  9. The 21-cm emission from the reionization epoch: extended and point source foregrounds

    NASA Astrophysics Data System (ADS)

    Di Matteo, Tiziana; Ciardi, Benedetta; Miniati, Francesco

    2004-12-01

    Fluctuations in the redshifted 21-cm emission from neutral hydrogen probe the epoch of reionization. We examine the observability of this signal and the impact of extragalactic foreground radio sources (both extended and point-like). We use cosmological simulations to predict the angular correlation functions of intensity fluctuations due to unresolved radio galaxies, cluster radio haloes and relics and free-free emission from the interstellar and intergalactic medium at the frequencies and angular scales relevant for the proposed 21-cm tomography. In accord with previous findings, the brightness temperature fluctuations due to foreground sources are much larger than those from the primary 21-cm signal at all scales. In particular, diffuse cluster radio emission, which has been previously neglected, provides the most significant foreground contamination. However, we show that the contribution to the angular fluctuations at scales θ>~ 1 arcmin is dominated by the spatial clustering of bright foreground sources. This excess can be removed if sources above flux levels S>~ 0.1 mJy (out to redshifts of z~ 1 and z~ 2 for diffuse and point sources, respectively) are detected and removed. Hence, efficient source removal may be sufficient to allow the detection of angular fluctuations in the 21-cm emission free of extragalactic foregrounds at θ>~ 1 arcmin. In addition, the removal of sources above S= 0.1 mJy also reduces the foreground fluctuations to roughly the same level as the 21-cm signal at scales θ<~ 1 arcmin. This should allow the substraction of the foreground components in frequency space, making it possible to observe in detail the topology and history of reionization.

  10. IMAGING THE EPOCH OF REIONIZATION: LIMITATIONS FROM FOREGROUND CONFUSION AND IMAGING ALGORITHMS

    SciTech Connect

    Vedantham, Harish; Udaya Shankar, N.; Subrahmanyan, Ravi

    2012-02-01

    Tomography of redshifted 21 cm transition from neutral hydrogen using Fourier synthesis telescopes is a promising tool to study the Epoch of Reionization (EoR). Limiting the confusion from Galactic and extragalactic foregrounds is critical to the success of these telescopes. The instrumental response or the point-spread function (PSF) of such telescopes is inherently three dimensional with frequency mapping to the line-of-sight (LOS) distance. EoR signals will necessarily have to be detected in data where continuum confusion persists; therefore, it is important that the PSF has acceptable frequency structure so that the residual foreground does not confuse the EoR signature. This paper aims to understand the three-dimensional PSF and foreground contamination in the same framework. We develop a formalism to estimate the foreground contamination along frequency, or equivalently LOS dimension, and establish a relationship between foreground contamination in the image plane and visibility weights on the Fourier plane. We identify two dominant sources of LOS foreground contamination-'PSF contamination' and 'gridding contamination'. We show that PSF contamination is localized in LOS wavenumber space, beyond which there potentially exists an 'EoR window' with negligible foreground contamination where we may focus our efforts to detect EoR. PSF contamination in this window may be substantially reduced by judicious choice of a frequency window function. Gridding and imaging algorithms create additional gridding contamination and we propose a new imaging algorithm using the Chirp Z Transform that significantly reduces this contamination. Finally, we demonstrate the analytical relationships and the merit of the new imaging algorithm for the case of imaging with the Murchison Widefield Array.

  11. Timoshenko systems with indefinite damping

    NASA Astrophysics Data System (ADS)

    Muñoz Rivera, Jaime E.; Racke, Reinhard

    2008-05-01

    We consider the Timoshenko system in a bounded domain . The system has an indefinite damping mechanism, i.e. with a damping function a=a(x) possibly changing sign, present only in the equation for the rotation angle. We shall prove that the system is still exponentially stable under the same conditions as in the positive constant damping case, and provided and , for [epsilon] small enough. The decay rate will be described explicitly. In the arguments, we shall also give a new proof of exponential stability for the constant case . Moreover, we give a precise description of the decay rate and demonstrate that the system has the spectrum determined growth (SDG) property, i.e. the type of the induced semigroup coincides with the spectral bound for its generator.

  12. Landau damping of auroral hiss

    NASA Technical Reports Server (NTRS)

    Morgan, D. D.; Gurnett, D. A.; Menietti, J. D.; Winningham, J. D.; Burch, J. L.

    1994-01-01

    Auroral hiss is observed to propagate over distances comparable to an Earth radius from its source in the auroral oval. The role of Landau damping is investigated for upward propagating auroral hiss. By using a ray tracing code and a simplified model of the distribution function, the effect of Landau damping is calculated for auroral hiss propagation through the environment around the auroral oval. Landau damping is found to be the likely mechanism for explaining some of the one-sided auroral hiss funnels observed by Dynamics Explorer 1. It is also found that Landau damping puts a lower limit on the wavelength of auroral hiss. Poleward of the auroral oval, Landau damping is found in a typical case to limit omega/k(sub parallel) to values of 3.4 x 10(exp 4) km/s or greater, corresponding to resonance energies of 3.2 keV or greater and wavelengths of 2 km or greater. For equatorward propagation, omega/k(sub parallel) is limited to values greater than 6.8 x 10(exp 4) km/s, corresponding to resonance energies greater than 13 keV and wavelengths greater than 3 km. Independent estimates based on measured ratios of the magnetic to electric field intensity also show that omega/k(sub parallel) corresponds to resonance energies greater than 1 keV and wavelengths greater than 1 km. These results lead to the difficulty that upgoing electron beams sufficiently energetic to directly generate auroral hiss of the inferred wavelength are not usually observed. A partial transmission mechanism utilizing density discontinuities oblique to the magnetic field is proposed for converting auroral hiss to wavelengths long enough to avoid damping of the wave over long distances. Numerous reflections of the wave in an upwardly flared density cavity could convert waves to significantly increased wavelengths and resonance velocities.

  13. Landau damping of auroral hiss

    SciTech Connect

    Morgan, D.D.; Gurnett, D.A.; Menietti, J.D.; Winningham, J.D.; Burch, J.L.

    1994-02-01

    Auroral hiss is observed to propagate over distances comparable to an Earth radius from its source in the auroral oval. The role of Landau damping is investigated for upward propagating auroral hiss. By using a ray tracing code and a simplified model of the distribution function, the effect of Landau damping is calculated for auroral hiss propagation through the environment around the auroral oval. Landau damping is found to be the likely mechanism for explaining some of the one-sided auroral hiss funnels observed by Dynamics Explorer 1. It is also found that Landau damping puts a lower limit on the wavelength of auroral hiss. Poleward of the auroral oval, Landau damping is found in a typical case to limit {omega}/k{parallel} to values of 3.4 x 10{sup 4} km/s or greater, corresponding to resonance energies of 3.2 keV or greater and wavelengths of 2 km or greater. For equatorward propagation, {omega}/k{parallel} is limited to values greater than 6.8 x 10{sup 4} km/s, corresponding to resonance energies greater than 13 keV and wavelengths greater than 3 km. Independent estimates based on measured ratios of the magnetic to electric field intensity also show that {omega}/k{parallel} corresponds to resonance energies greater than 1 keV and wavelengths greater than 1 km. These results lead to the difficulty that upgoing electron beams sufficiently energetic to directly generate auroral hiss of the inferred wavelength are not usually observed. A partial transmission mechanism utilizing density discontinuities oblique to the magnetic field is proposed for converting auroral hiss to wavelengths long enough to avoid damping of the wave over long distances. Numerous reflections of the wave in an upwardly flared density cavity could convert waves to significantly increased wavelengths and resonance velocities. 36 refs., 12 figs., 4 tabs.

  14. Damped vacuum states of light

    NASA Astrophysics Data System (ADS)

    Philbin, T. G.

    2016-09-01

    We consider one-dimensional propagation of quantum light in the presence of a block of material, with a full account of dispersion and absorption. The electromagnetic zero-point energy for some frequencies is damped (suppressed) by the block below the free-space value, while for other frequencies it is increased. We also calculate the regularized (Casimir) zero-point energy at each frequency and find that it too is damped below the free-space value (zero) for some frequencies. The total Casimir energy is positive.

  15. Structural damping studies at cryogenic temperatures

    NASA Technical Reports Server (NTRS)

    Young, Clarence P., Jr.; Buehrle, Ralph D.

    1994-01-01

    Results of an engineering study to measure changes in structural damping properties of two cryogenic wind tunnel model systems and two metallic test specimens at cryogenic temperatures are presented. Data are presented which indicate overall, a trend toward reduced structural damping at cryogenic temperatures (-250 degrees F) when compared with room temperature damping properties. The study was focused on structures and materials used for model systems tested in the National Transonic Facility (NTF). The study suggests that the significant reductions in damping at extremely cold temperatures are most likely associated with changes in mechanical joint compliance damping rather than changes in material (solid) damping.

  16. A FOREGROUND-CLEANED COSMIC MICROWAVE BACKGROUND MAP FROM NON-GAUSSIANITY MEASUREMENT

    SciTech Connect

    Saha, Rajib

    2011-10-01

    In this Letter, we present a new method to estimate a foreground-cleaned cosmic microwave background (CMB) map at a resolution of 1{sup 0} by minimizing the non-Gaussian properties of the cleaned map which arise dominantly due to diffuse foreground emission components from the Milky Way. We employ simple kurtosis statistic as the measure of non-Gaussian properties and perform a linear combination of five frequency maps provided by the Wilkinson Microwave Anisotropy Probe (WMAP) in its seven-year data release in such a way that the cleaned map has a minimum kurtosis which leads to a non-Gaussianity-minimized, foreground-cleaned CMB map. We validate the method by performing Monte Carlo simulations. To minimize any residual foreground contamination from the cleaned map we flag out the region near the galactic plane based upon results from simulations. Outside the masked region our new estimate of the CMB map matches well with the WMAP's Internal Linear Combination (ILC) map. A simple pseudo-C{sub l} -based CMB TT power spectrum derived from the non-Gaussianity minimized map reproduces the earlier results of WMAP's power spectrum. An important advantage of the method is that it does not introduce any negative bias in angular power spectrum in the low multipole regime, unlike usual ILC method. Comparing our results with the previously published results we argue that CMB results are robust with respect to specific foreground removal algorithms employed.

  17. The Effects of Polarized Foregrounds on 21 cm Epoch of Reionization Power Spectrum Measurements

    NASA Astrophysics Data System (ADS)

    Moore, David F.; Aguirre, James E.; Parsons, Aaron R.; Jacobs, Daniel C.; Pober, Jonathan C.

    2013-06-01

    Experiments aimed at detecting highly-redshifted 21 cm emission from the epoch of reionization (EoR) are plagued by the contamination of foreground emission. A potentially important source of contaminating foregrounds may be Faraday-rotated, polarized emission, which leaks into the estimate of the intrinsically unpolarized EoR signal. While these foregrounds' intrinsic polarization may not be problematic, the spectral structure introduced by the Faraday rotation could be. To better understand and characterize these effects, we present a simulation of the polarized sky between 120 and 180 MHz. We compute a single visibility, and estimate the three-dimensional power spectrum from that visibility using the delay spectrum approach presented in Parsons et al. Using the Donald C. Backer Precision Array to Probe the Epoch of Reionization as an example instrument, we show the expected leakage into the unpolarized power spectrum to be several orders of magnitude above the expected 21 cm EoR signal.

  18. THE EFFECTS OF POLARIZED FOREGROUNDS ON 21 cm EPOCH OF REIONIZATION POWER SPECTRUM MEASUREMENTS

    SciTech Connect

    Moore, David F.; Aguirre, James E.; Parsons, Aaron R.; Pober, Jonathan C.; Jacobs, Daniel C.

    2013-06-01

    Experiments aimed at detecting highly-redshifted 21 cm emission from the epoch of reionization (EoR) are plagued by the contamination of foreground emission. A potentially important source of contaminating foregrounds may be Faraday-rotated, polarized emission, which leaks into the estimate of the intrinsically unpolarized EoR signal. While these foregrounds' intrinsic polarization may not be problematic, the spectral structure introduced by the Faraday rotation could be. To better understand and characterize these effects, we present a simulation of the polarized sky between 120 and 180 MHz. We compute a single visibility, and estimate the three-dimensional power spectrum from that visibility using the delay spectrum approach presented in Parsons et al. Using the Donald C. Backer Precision Array to Probe the Epoch of Reionization as an example instrument, we show the expected leakage into the unpolarized power spectrum to be several orders of magnitude above the expected 21 cm EoR signal.

  19. Dealing with damping-off

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Damping-off is a common disease that rots and kills both seeds and recently germinated seedlings. The disease is caused by number of different soilborne pathogens, including true fungi (Botrytis, Fusarium, and Rhizoctonia species) and oomycetes (Phytophthora and Pythium species). The seedlings of mo...

  20. Red cell DAMPs and inflammation.

    PubMed

    Mendonça, Rafaela; Silveira, Angélica A A; Conran, Nicola

    2016-09-01

    Intravascular hemolysis, or the destruction of red blood cells in the circulation, can occur in numerous diseases, including the acquired hemolytic anemias, sickle cell disease and β-thalassemia, as well as during some transfusion reactions, preeclampsia and infections, such as those caused by malaria or Clostridium perfringens. Hemolysis results in the release of large quantities of red cell damage-associated molecular patterns (DAMPs) into the circulation, which, if not neutralized by innate protective mechanisms, have the potential to activate multiple inflammatory pathways. One of the major red cell DAMPs, heme, is able to activate converging inflammatory pathways, such as toll-like receptor signaling, neutrophil extracellular trap formation and inflammasome formation, suggesting that this DAMP both activates and amplifies inflammation. Other potent DAMPs that may be released by the erythrocytes upon their rupture include heat shock proteins (Hsp), such as Hsp70, interleukin-33 and Adenosine 5' triphosphate. As such, hemolysis represents a major inflammatory mechanism that potentially contributes to the clinical manifestations that have been associated with the hemolytic diseases, such as pulmonary hypertension and leg ulcers, and likely plays a role in specific complications of sickle cell disease such as endothelial activation, vaso-occlusive processes and tissue injury. PMID:27251171

  1. Foreground Cleaning for Cosmic Microwave Background Polarimeters in the Presence of Instrumental Effects

    NASA Astrophysics Data System (ADS)

    Bao, Chaoyun

    The Cosmic Microwave Background (CMB) B-mode polarization signal offers a direct probe of inflation, a period of exponential expansion in the extreme early universe. The inflationary CMB B-mode polarization signal, however, is subject to the contamination of polarized galactic thermal dust foreground emission. A robust foreground cleaning method is essential for CMB polarimeters targeting the inflationary B-mode signal. In this thesis I present my work on developing foreground cleaning algorithms particularly in the presence of instrumental effects. One of the instrumental effects I focus on in this work is the frequency dependent polarization rotation effect such as the one caused by an achromatic half-wave plate (AHWP). As an example, I use the AHWP of the E and B Experiment (EBEX) in this work and study the relation between the frequency dependent rotation effect and the characteristic parameters of the AHWP. To address the effect of an AHWP while removing galactic dust foreground contamination, I developed two foreground cleaning algorithms: a simple method that assumes perfect knowledge of the AHWP and a few simplifying assumptions, and a more sophisticated algorithm based on maximum likelihood method. Based on simulation results, the maximum likelihood foreground cleaning algorithm can recover CMB B-mode signal without any bias in the presence of band shape uncertainty, frequency dependent rotation effect and instrumental noise with realistic measurement accuracy of instrumental parameters. In this thesis I also present my work on calculating the atmospheric loading in the millimeter wave regime for sub-orbital CMB experiments such as EBEX. Having a proper prediction of the atmospheric loading is an important input to detector designs for CMB experiments.

  2. Damped Oscillator with Delta-Kicked Frequency

    NASA Technical Reports Server (NTRS)

    Manko, O. V.

    1996-01-01

    Exact solutions of the Schrodinger equation for quantum damped oscillator subject to frequency delta-kick describing squeezed states are obtained. The cases of strong, intermediate, and weak damping are investigated.

  3. Video background tracking and foreground extraction via L1-subspace updates

    NASA Astrophysics Data System (ADS)

    Pierantozzi, Michele; Liu, Ying; Pados, Dimitris A.; Colonnese, Stefania

    2016-05-01

    We consider the problem of online foreground extraction from compressed-sensed (CS) surveillance videos. A technically novel approach is suggested and developed by which the background scene is captured by an L1- norm subspace sequence directly in the CS domain. In contrast to conventional L2-norm subspaces, L1-norm subspaces are seen to offer significant robustness to outliers, disturbances, and rank selection. Subtraction of the L1-subspace tracked background leads then to effective foreground/moving objects extraction. Experimental studies included in this paper illustrate and support the theoretical developments.

  4. Squeezed states of damped oscillator chain

    NASA Technical Reports Server (NTRS)

    Manko, O. V.

    1993-01-01

    The Caldirola-Kanai model of one-dimensional damped oscillator is extended to the chain of coupled parametric oscillators with damping. The correlated and squeezed states for the chain of coupled parametric oscillators with damping are constructed. Based on the concept of the integrals of motion, it is demonstrated how squeezing phenomenon arises due to parametric excitation.

  5. Passive damping for space truss structures

    NASA Technical Reports Server (NTRS)

    Chen, Gun-Shing; Wada, Ben K.

    1988-01-01

    Theoretical and experimental studies of passive damping techniques in truss-type structures are presented, with emphasis on the use of viscoelastic damping in the parallel load path. The constraining member length is shown to be a convenient design variable for enhancing damping performance. Results are presented for integral damping members made of thin-wall aluminum tubes, concentric constraining members, and viscoelastic materials in a six-bay truss structure at low frequency and low dynamic strain conditions. Integral members with graphite/epoxy constraining members exhibited relatively low damping values due to the possible polymer interaction during the cocure stage.

  6. Forced oscillations with linear and nonlinear damping

    NASA Astrophysics Data System (ADS)

    Li, Aijun; Ma, Li; Keene, David; Klingel, Joshua; Payne, Marvin; Wang, Xiao-jun

    2016-01-01

    A general solution is derived for the differential equations of forced oscillatory motion with both linear damping ( ˜v ) and nonlinear damping ( ˜v2 ). Experiments with forced oscillators are performed using a flat metal plate with a drag force due to eddy currents and a flat piece of stiffened cardboard with a drag force due to air resistance serving as the linear and nonlinear damping, respectively. Resonance of forced oscillations for different damping forces and quality factors is demonstrated. The experimental measurements and theoretical calculations are in good agreement, and damping constants are determined.

  7. Clipped viscous damping with negative stiffness for semi-active cable damping

    NASA Astrophysics Data System (ADS)

    Weber, F.; Boston, C.

    2011-04-01

    This paper investigates numerically and experimentally clipped viscous damping with negative stiffness for semi-active cable damping. From simulations it is concluded that unclipped and clipped viscous damping with negative stiffness is equivalent to unclipped and clipped LQR. It is shown that optimized unclipped viscous damping with negative stiffness generates critical cable damping by an anti-node at the actuator position. The resulting curvature at the actuator position is larger than the curvature close to the anchors due to the disturbance forces which may lead to premature cable fatigue at the actuator position. Optimized clipped viscous damping with negative stiffness does not show this drawback, can be implemented using a semi-active damper and produces twice as much cable damping as optimal viscous damping. Close to the optimal tuning, it leads to approximately the same control force as optimal semi-active friction damping with negative stiffness, which explains the superior cable damping. The superior damping results from the negative stiffness that increases the damper motion. Clipped viscous damping with negative stiffness is validated on a strand cable with a magneto-rheological damper. The measured cable damping is twice that achieved by emulated viscous damping, which confirms the numerical results. A tuning rule for clipped viscous damping with negative stiffness of real cables with flexural rigidity is given.

  8. Foreground Characterization for the Murchison Widefield Array Using the Jansky Very Large Array

    NASA Astrophysics Data System (ADS)

    Busch, Michael P.; Bowman, Judd D.; Kittiwisit, Piyanat; Jacobs, Danny

    2016-01-01

    One of the most compelling questions in astrophysics today is how the process of galaxy formation unfolded during the Epoch of Reionization (EoR). A new generation of radio telescopes, including the Murchison Widefield Array (MWA) and others, are attempting to capture the redshifted 21cm signal from neutral hydrogen during the EoR. Mapping the reionization of the intergalactic medium (IGM) is one of the core objectives of 21 cm observatories. A pressing concern of these observations is the bright foreground sources in the telescope's sidelobes outside the primary beam of the MWA. These sources, including AGN, radio galaxies and local Galactic sources, are numerous and difficult to deal with. These foreground contaminants are five orders of magnitude brighter than the redshifted 21 cm emission expected from the IGM during the EoR. The Jansky Very Large Array (JVLA) in New Mexico can provide sensitive characterization of these sources in the MWA's northern sidelobe. We observed 100 bright radio sources using the JVLA in P-band and characterized these sources by extracting the spectral fits and fluxes for each source. By creating a foreground model for these data, the MWA will be able to better subtract these sources from future EoR measurements. We report the current status of the creation of the foreground model.

  9. A foreground object features-based stereoscopic image visual comfort assessment model

    NASA Astrophysics Data System (ADS)

    Jin, Xin; Jiang, G.; Ying, H.; Yu, M.; Ding, S.; Peng, Z.; Shao, F.

    2014-11-01

    Since stereoscopic images provide observers with both realistic and discomfort viewing experience, it is necessary to investigate the determinants of visual discomfort. By considering that foreground object draws most attention when human observing stereoscopic images. This paper proposes a new foreground object based visual comfort assessment (VCA) metric. In the first place, a suitable segmentation method is applied to disparity map and then the foreground object is ascertained as the one having the biggest average disparity. In the second place, three visual features being average disparity, average width and spatial complexity of foreground object are computed from the perspective of visual attention. Nevertheless, object's width and complexity do not consistently influence the perception of visual comfort in comparison with disparity. In accordance with this psychological phenomenon, we divide the whole images into four categories on the basis of different disparity and width, and exert four different models to more precisely predict its visual comfort in the third place. Experimental results show that the proposed VCA metric outperformance other existing metrics and can achieve a high consistency between objective and subjective visual comfort scores. The Pearson Linear Correlation Coefficient (PLCC) and Spearman Rank Order Correlation Coefficient (SROCC) are over 0.84 and 0.82, respectively.

  10. A fast method for power spectrum and foreground analysis for 21 cm cosmology

    NASA Astrophysics Data System (ADS)

    Dillon, Joshua S.; Liu, Adrian; Tegmark, Max

    2013-02-01

    We develop and demonstrate an acceleration of the Liu and Tegmark quadratic estimator formalism for inverse variance foreground subtraction and power spectrum estimation in 21 cm tomography from O(N3) to O(Nlog⁡N), where N is the number of voxels of data. This technique makes feasible the megavoxel scale analysis necessary for current and upcoming radio interferometers by making only moderately restrictive assumptions about foreground models and survey geometry. We exploit iterative and Monte Carlo techniques and the symmetries of the foreground covariance matrices to quickly estimate the 21 cm brightness temperature power spectrum, P(k∥,k⊥), the Fisher information matrix, the error bars, the window functions, and the bias. We also extend the Liu and Tegmark foreground model to include bright point sources with known positions in a way that scales as O[(Nlog⁡N)×(Npointsources)]≤O(N5/3). As a first application of our method, we forecast error bars and window functions for the upcoming 128-tile deployment of the Murchinson Widefield Array, showing that 1000 hours of observation should prove sufficiently sensitive to detect the power spectrum signal from the Epoch of Reionization.

  11. NORTH EMBANKMENT IN FOREGROUND, WITH (LR) SUBSTATION (MI98D), POWERHOUSE (MI98C), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    NORTH EMBANKMENT IN FOREGROUND, WITH (L-R) SUBSTATION (MI-98-D), POWERHOUSE (MI-98-C), AND COOKE DAM POND IN BACKGROUND. VIEW TO SOUTH - Cooke Hydroelectric Plant, North Embankment, Cook Dam Road at Au Sable River, Oscoda, Iosco County, MI

  12. 9. Acircuit weather cover in foreground, personnel access hatch, transporter/erector ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. A-circuit weather cover in foreground, personnel access hatch, transporter/erector grounding points at right center - Ellsworth Air Force Base, Delta Flight, Launch Facility D-6, 4 miles north of Badlands National Park Headquarters, 4.5 miles east of Jackson County line on county road, Interior, Jackson County, SD

  13. OBLIQUE VIEW SHOING THE OR&L BRIDGE IN THE FOREGROUND. NOTE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    OBLIQUE VIEW SHOING THE OR&L BRIDGE IN THE FOREGROUND. NOTE THE ARC-PLAN END STACHION AND THE RELATIONSHIP BETWEEN THE OR&L BRIDGE AND THE WAIKELE CANAL BRIDGE, WHICH CAN BE SEEN IN THE BACKGROUND. VIEW FACING WEST. - Waikele Canal Bridge and Highway Overpass, Farrington Highway and Waikele Stream, Waipahu, Honolulu County, HI

  14. The effect of foreground subtraction on cosmological measurements from intensity mapping

    NASA Astrophysics Data System (ADS)

    Wolz, L.; Abdalla, F. B.; Blake, C.; Shaw, J. R.; Chapman, E.; Rawlings, S.

    2014-07-01

    We model a 21-cm intensity mapping survey in the redshift range 0.01 < z < 1.5 designed to simulate the skies as seen by future radio telescopes such as the Square Kilometre Array, including instrumental noise and Galactic foregrounds. In our pipeline, we remove the Galactic foregrounds with a fast independent component analysis technique. We present the power spectrum of the large-scale matter distribution, C(ℓ), before and after the application of this foreground removal method and calculate the systematic errors. Our simulations show a certain level of bias remains in the power spectrum at all scales ℓ < 400. At large-scales ℓ < 30 this bias is particularly significant. We measure the impact of these systematics in two ways: first we fit cosmological parameters to the broad-band shape of the C(ℓ) where we find that the best fit is significantly shifted at the 2-3σ level depending on masking and noise levels. However, secondly, we recover cosmic distances without biases at all simulated redshifts by fitting the baryon acoustic oscillations in the C(ℓ). We conclude that further advances in foreground removal are needed in order to recover unbiased information from the broad-band shape of the C(ℓ), however, intensity mapping experiments will be a powerful tool for mapping cosmic distances across a wide redshift range.

  15. Effects of Numerical Versus Foreground-Only Icon Displays on Understanding of Risk Magnitudes.

    PubMed

    Stone, Eric R; Gabard, Alexis R; Groves, Aislinn E; Lipkus, Isaac M

    2015-01-01

    The aim of this work is to advance knowledge of how to measure gist and verbatim understanding of risk magnitude information and to apply this knowledge to address whether graphics that focus on the number of people affected (the numerator of the risk ratio, i.e., the foreground) are effective displays for increasing (a) understanding of absolute and relative risk magnitudes and (b) risk avoidance. In 2 experiments, the authors examined the effects of a graphical display that used icons to represent the foreground information on measures of understanding (Experiments 1 and 2) and on perceived risk, affect, and risk aversion (Experiment 2). Consistent with prior findings, this foreground-only graphical display increased perceived risk and risk aversion; however, it also led to decreased understanding of absolute (although not relative) risk magnitudes. Methodologically, this work shows the importance of distinguishing understanding of absolute risk from understanding of relative risk magnitudes, and the need to assess gist knowledge of both types of risk. Substantively, this work shows that although using foreground-only graphical displays is an appealing risk communication strategy to increase risk aversion, doing so comes at the cost of decreased understanding of absolute risk magnitudes. PMID:26065633

  16. 140° view showing: Pigeon Wash, foreground; Lake Mead NRA Approved ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    140° view showing: Pigeon Wash, foreground; Lake Mead NRA Approved Road 148, middleground; and part of the Cockscomb Range, background. This negative forms a 360° composite panoramic when joined with AZ-2-78 and AZ-2-79. See AZ-2-89 for color version. - Tassi Ranch, Tassi Springs, Littlefield, Mohave County, AZ

  17. Foreground contamination in Lyα intensity mapping during the epoch of reionization

    SciTech Connect

    Gong, Yan; Cooray, Asantha; Silva, Marta; Santos, Mario G.

    2014-04-10

    The intensity mapping of Lyα emission during the epoch of reionization will be contaminated by foreground emission lines from lower redshifts. We calculate the mean intensity and the power spectrum of Lyα emission at z ∼ 7 and estimate the uncertainties according to the relevant astrophysical processes. We find that the low-redshift emission lines from 6563 Å Hα, 5007 Å [O III], and 3727 Å [O II] will be strong contaminants on the observed Lyα power spectrum. We make use of both the star formation rate and luminosity functions to estimate the mean intensity and power spectra of the three foreground lines at z ∼ 0.5 for Hα, z ∼ 0.9 for [O III], and z ∼ 1.6 for [O II], as they will contaminate the Lyα emission at z ∼ 7. The [O II] line is found to be the strongest. We analyze the masking of the bright survey pixels with a foreground line above some line intensity threshold as a way to reduce the contamination in an intensity mapping survey. We find that the foreground contamination can be neglected if we remove pixels with fluxes above 1.4 × 10{sup –20} W m{sup –2}.

  18. Limits on foreground subtraction from chromatic beam effects in global redshifted 21 cm measurements

    NASA Astrophysics Data System (ADS)

    Mozdzen, T. J.; Bowman, J. D.; Monsalve, R. A.; Rogers, A. E. E.

    2016-02-01

    Foreground subtraction in global redshifted 21 cm measurements is limited by frequency-dependent (chromatic) structure in antenna beam patterns. Chromatic beams couple angular structures in Galactic foreground emission to spectral structures that may not be removed by smooth functional forms. We report results for simulations based on two dipole antennas used by the Experiment to Detect the Global EoR Signature (EDGES). The residual levels in simulated foreground-subtracted spectra are found to differ substantially between the two antennas, suggesting that antenna design must be carefully considered. Residuals are also highly dependent on the right ascension and declination of the antenna pointing, with rms values differing by as much as a factor of 20 across pointings. For EDGES and other ground-based experiments with zenith pointing antennas, right ascension and declination correspond directly to the local sidereal time and the latitude of the deployment site, hence chromatic beam effects should be taken into account when selecting sites. We introduce the `blade' dipole antenna and show, via simulations, that it has better chromatic performance than the `fourpoint' antenna previously used for EDGES. The blade antenna yields 1-5 mK residuals across the entire sky after a 5-term polynomial is removed from simulated spectra, whereas the fourpoint antenna typically requires a 6-term polynomial for comparable residuals. For both antennas, the signal-to-noise ratio of recovered 21 cm input signals peaks for a 5-term polynomial foreground fit given realistic thermal noise levels.

  19. Overview of RyantoRainbow Line 1 (foreground) and Line 2 (center) ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Overview of Ryan-to-Rainbow Line 1 (foreground) and Line 2 (center) in context with Morony-to-Rainbow 100kv Transmission Line (background) about on-half mile southwest of Ryan Dam. View to north - Ryan Hydroelectric Facility, Ryan-to-Rainbow 100 kV Transmission Line, West bank of Missouri River, northeast of Great Falls, Great Falls, Cascade County, MT

  20. THE LISA GRAVITATIONAL WAVE FOREGROUND: A STUDY OF DOUBLE WHITE DWARFS

    SciTech Connect

    Ruiter, Ashley J.; Belczynski, Krzysztof; Larson, Shane L. E-mail: kbelczyn@nmsu.ed E-mail: gabriel.j.williams@gmail.co

    2010-07-10

    Double white dwarfs (WDs) are expected to be a source of confusion-limited noise for the future gravitational wave observatory LISA. In a specific frequency range, this 'foreground noise' is predicted to rise above the instrumental noise and hinder the detection of other types of signals, e.g., gravitational waves arising from stellar-mass objects inspiraling into massive black holes. In many previous studies, only detached populations of compact object binaries have been considered in estimating the LISA gravitational wave foreground signal. Here, we investigate the influence of compact object detached and Roche-Lobe overflow (RLOF) Galactic binaries on the shape and strength of the LISA signal. Since >99% of remnant binaries that have orbital periods within the LISA sensitivity range are WD binaries, we consider only these binaries when calculating the LISA signal. We find that the contribution of RLOF binaries to the foreground noise is negligible at low frequencies, but becomes significant at higher frequencies, pushing the frequency at which the foreground noise drops below the instrumental noise to >6 mHz. We find that it is important to consider the population of mass-transferring binaries in order to obtain an accurate assessment of the foreground noise on the LISA data stream. However, we estimate that there still exists a sizeable number ({approx}11,300) of Galactic double WD binaries that will have a signal-to-noise ratio >5, and thus will be potentially resolvable with LISA. We present the LISA gravitational wave signal from the Galactic population of WD binaries, show the most important formation channels contributing to the LISA disk and bulge populations, and discuss the implications of these new findings.

  1. Residual foreground contamination in the WMAP data and bias in non-Gaussianity estimation

    SciTech Connect

    Chingangbam, Pravabati; Park, Changbom E-mail: cbp@kias.re.kr

    2013-02-01

    We analyze whether there is any residual foreground contamination in the cleaned WMAP 7 years data for the differential assemblies, Q, V and W. We calculate the correlation between the foreground map, from which long wavelength correlations have been subtracted, and the foreground reduced map for each differential assembly after applying the Galaxy and point sources masks. We find positive correlations for all the differential assemblies, with high statistical significance. For Q and V, we find that a large fraction of the contamination comes from pixels where the foreground maps have positive values larger than three times the rms values. These findings imply the presence of residual contamination from Galactic emissions and unresolved point sources. We redo the analysis after masking the extended point sources cataloque of Scodeller et al. [7] and find a drop in the correlation and corresponding significance values. To quantify the effect of the residual contamination on the search for primordial non-Gaussianity in the CMB we add estimated contaminant fraction to simulated Gaussian CMB maps and calculate the characteristic non-Gaussian deviation shapes of Minkowski Functionals that arise due to the contamination. We find remarkable agreement of these deviation shapes with those measured from WMAP data, which imply that a major fraction of the observed non-Gaussian deviation comes from residual foreground contamination. We also compute non-Gaussian deviations of Minkowski Functionals after applying the point sources mask of Scodeller et al. and find a decrease in the overall amplitudes of the deviations which is consistent with a decrease in the level of contamination.

  2. Targeting damage-associated molecular pattern molecules (DAMPs) and DAMP receptors in melanoma.

    PubMed

    Boone, Brian A; Lotze, Michael T

    2014-01-01

    Damage-associated molecular pattern molecules (DAMPs) are proteins released from cells under stress due to nutrient deprivation, hypoxia, trauma, or treatment with chemotherapy, among a variety of other causes. When released, DAMPs activate innate immunity, providing a pathway to a systemic inflammatory response in the absence of infection. By regulating inflammation in the tumor microenvironment, promoting angiogenesis, and increasing autophagy with evasion of apoptosis, DAMPs facilitate cancer growth. DAMPs and DAMP receptors have a key role in melanoma pathogenesis. Due to their crucial role in the development of melanoma and chemoresistance, DAMPs represent intriguing targets at a time when novel treatments are desperately needed. PMID:24258998

  3. Introduction to DAMPE event reconstruction (On behalf of DAMPE collaboration)

    NASA Astrophysics Data System (ADS)

    Zang, Jingjing

    2016-07-01

    The Dark Matter Particle Explorer (DAMPE) is a high energy particle physics experiment satellite, launched on 17 Dec 2015. To measure basic attributes of cosmic ray particles, DAMPE is equipped with four sub-detectors, BGO calorimeter (BGO), plastic scintillator detector (PSD), silicon tungsten tracker (STK) and neutron detector (NUD). On orbit, the high energy particle data are acquired and recorded by well-designed Data Acquisition system. After that, a series of elaborate event reconstruction algorithms are implemented to determine the energy, direction and particle ID of each event. The energy reconstruction algorithm firstly treats the sum of the BGO crystal energy as the overall energy estimator and various corrections are performed to calculate energy leakage from side and back of the calorimeter. The track reconstruction starts with cluster finding in STK, then shower axis of BGO and barycentre of clusters are used to extract seed of tracks. These seeds will be projected on the next layer by Kalman Filter method which will finally give location and direction of particle tracks. Based on shower development in BGO and tracks reconstructed by STK, we also combine data from PSD and NUD and developed a series of algorithms to evaluate particle's charge and identification. In this talk, we will describe technical strategies of event reconstruction and provide their basic performance.

  4. ICAN/DAMP-integrated composite analyzer with damping analysis capabilities: User's manual

    NASA Technical Reports Server (NTRS)

    Saravanos, Dimitrious A.; Sanfeliz, Jose G.

    1992-01-01

    This manual describes the use of the computer code ICAN/DAMP (Integrated Composite Analyzer with Damping Analysis Capabilities) for the prediction of damping in polymer-matrix composites. The code is written in FORTRAN 77 and is a version of the ICAN (Integrated Composite ANalyzer) computer program. The code incorporates a new module for synthesizing the material damping from micromechanics to laminate level. Explicit micromechanics equations based on hysteretic damping are programmed relating the on-axis damping capacities to the fiber and matrix properties and fiber volume ratio. The damping capacities of unidirectional composites subjected to off-axis loading are synthesized from on-axis damping values. The hygrothermal effect on the damping performance of unidirectional composites caused by temperature and moisture variation is modeled along with the damping contributions from interfacial friction between broken fibers and matrix. The temperature rise is continuously vibrating composite plies and composite laminates is also estimated. The ICAN/DAMP user's manual provides descriptions of the damping analysis module's functions, structure, input requirements, output interpretation, and execution requirements. It only addresses the changes required to conduct the damping analysis and is used in conjunction with the 'Second Generation Integrated Composite Analyzer (ICAN) Computer Code' user's manual (NASA TP-3290).

  5. Viscous damping for base isolated structures

    SciTech Connect

    Lee, D.; Hussain, S.; Retamal, E.

    1995-12-01

    Seismic Base Isolation can use elastomeric pads, sliding plates or inverted pendulums. Each method can include an energy dissipation means, but only as some kind of hysteretic damping. Hysteretic damping has limitations in terms of energy absorption and may tend to excite higher modes in some cases. It`s possible to avoid these problems with viscous dampers. Viscous damping adds energy dissipation through loads that are 900 out of phase with bending and shear loads so even with damping levels as high as 40% of critical adverse side effects tend to be minimal. This paper presents basic theory of viscous damping, and also describes a sample project. Viscous dampers being built for the new San Bernardino Medical Center reduce both deflections and loads by 50% compared with high damping elastomer base isolation bearings by themselves.

  6. CHARACTERIZATION OF DAMPING IN BOLTED LAP JOINTS

    SciTech Connect

    C. MALONEY; D. PEAIRS; ET AL

    2000-08-01

    The dynamic response of a jointed beam was measured in laboratory experiments. The data were analyzed and the system was mathematically modeled to establish plausible representations of joint damping behavior. Damping is examined in an approximate, local linear framework using log decrement and half power bandwidth approaches. in addition, damping is modeled in a nonlinear framework using a hybrid surface irregularities model that employs a bristles-construct. Experimental and analytical results are presented.

  7. Understanding the damped SHM without ODEs

    NASA Astrophysics Data System (ADS)

    Ng, Chiu-king

    2016-03-01

    Instead of solving ordinary differential equations (ODEs), the damped simple harmonic motion (SHM) is surveyed qualitatively from basic mechanics and quantitatively by the instrumentality of a graph of velocity against displacement. In this way, the condition b≥slant \\sqrt{4mk}~ for the occurrence of the non-oscillating critical damping and heavy-damping is derived. Besides, we prove in the under-damping, the oscillation is isochronous and the diminishing amplitude satisfies a rule of ‘constant ratio’. All are done on a non-ODE basis.

  8. Damping constant estimation in magnetoresistive readers

    SciTech Connect

    Stankiewicz, Andrzej Hernandez, Stephanie

    2015-05-07

    The damping constant is a key design parameter in magnetic reader design. Its value can be derived from bulk or sheet film ferromagnetic resonance (FMR) line width. However, dynamics of nanodevices is usually defined by presence of non-uniform modes. It triggers new damping mechanisms and produces stronger damping than expected from traditional FMR. This work proposes a device-level technique for damping evaluation, based on time-domain analysis of thermally excited stochastic oscillations. The signal is collected using a high bandwidth oscilloscope, by direct probing of a biased reader. Recorded waveforms may contain different noise signals, but free layer FMR is usually a dominating one. The autocorrelation function is a reflection of the damped oscillation curve, averaging out stochastic contributions. The damped oscillator formula is fitted to autocorrelation data, producing resonance frequency and damping constant values. Restricting lag range allows for mitigation of the impact of other phenomena (e.g., reader instability) on the damping constant. For a micromagnetically modeled reader, the technique proves to be much more accurate than the stochastic FMR line width approach. Application to actual reader waveforms yields a damping constant of ∼0.03.

  9. The next linear collider damping ring lattices

    SciTech Connect

    Wolski, Andrzej; Corlett, John N.

    2001-06-20

    We report on the lattice design of the Next Linear Collider (NLC) damping rings. The damping rings are required to provide low emittance electron and positron bunch trains to the NLC linacs, at a rate of 120 Hz. We present an optical design, based on a theoretical minimum emittance (TME) lattice, to produce the required normalized extracted beam emittances gex = 3 mm-mrad and gey = 0.02 mm mrad. An assessment of dynamic aperture and non-linear effects is given. The positron pre-damping ring, required to reduce the emittance of the positron beam such that it may be accepted by a main damping ring, is also described.

  10. Viscous damped space structure for reduced jitter

    NASA Technical Reports Server (NTRS)

    Wilson, James F.; Davis, L. Porter

    1987-01-01

    A technique to provide modal vibration damping in high performance space structures was developed which uses less than one once of incompressible fluid. Up to 50 percent damping can be achieved which can reduce the settling times of the lowest structural mode by as much as 50 to 1. This concept allows the designers to reduce the weight of the structure while improving its dynamic performance. Damping by this technique is purely viscous and has been shown by test to be linear over 5 orders of input magnitude. Amplitudes as low as 0.2 microinch were demonstrated. Damping in the system is independent of stiffness and relatively insensitive to temperature.

  11. Phenomenology of chiral damping in noncentrosymmetric magnets

    NASA Astrophysics Data System (ADS)

    Akosa, Collins Ashu; Miron, Ioan Mihai; Gaudin, Gilles; Manchon, Aurélien

    2016-06-01

    A phenomenology of magnetic chiral damping is proposed in the context of magnetic materials lacking inversion symmetry. We show that the magnetic damping tensor acquires a component linear in magnetization gradient in the form of Lifshitz invariants. We propose different microscopic mechanisms that can produce such a damping in ferromagnetic metals, among which local spin pumping in the presence of an anomalous Hall effect and an effective "s-d" Dzyaloshinskii-Moriya antisymmetric exchange. The implication of this chiral damping in terms of domain-wall motion is investigated in the flow and creep regimes.

  12. Damping constant estimation in magnetoresistive readers

    NASA Astrophysics Data System (ADS)

    Stankiewicz, Andrzej; Hernandez, Stephanie

    2015-05-01

    The damping constant is a key design parameter in magnetic reader design. Its value can be derived from bulk or sheet film ferromagnetic resonance (FMR) line width. However, dynamics of nanodevices is usually defined by presence of non-uniform modes. It triggers new damping mechanisms and produces stronger damping than expected from traditional FMR. This work proposes a device-level technique for damping evaluation, based on time-domain analysis of thermally excited stochastic oscillations. The signal is collected using a high bandwidth oscilloscope, by direct probing of a biased reader. Recorded waveforms may contain different noise signals, but free layer FMR is usually a dominating one. The autocorrelation function is a reflection of the damped oscillation curve, averaging out stochastic contributions. The damped oscillator formula is fitted to autocorrelation data, producing resonance frequency and damping constant values. Restricting lag range allows for mitigation of the impact of other phenomena (e.g., reader instability) on the damping constant. For a micromagnetically modeled reader, the technique proves to be much more accurate than the stochastic FMR line width approach. Application to actual reader waveforms yields a damping constant of ˜0.03.

  13. Demagnified gravitational waves from cosmological double neutron stars and gravitational wave foreground cleaning around 1 Hz

    SciTech Connect

    Seto, Naoki

    2009-11-15

    Gravitational waves (GWs) from cosmological double neutron star binaries (NS+NS) can be significantly demagnified by the strong gravitational lensing effect, and the proposed future missions such as the Big Bang Observer or Deci-hertz Interferometer Gravitational Wave Observatory might miss some of the demagnified GW signals below a detection threshold. The undetectable binaries would form a GW foreground, which might hamper detection of a very weak primordial GW signal. We discuss the outlook of this potential problem, using a simple model based on the singular isothermal sphere lens profile. Fortunately, it is expected that, for a presumable merger rate of NS+NSs, the residual foreground would be below the detection limit {omega}{sub GW,lim}{approx}10{sup -16} realized with the Big Bang Observer/Deci-hertz Interferometer Gravitational Wave Observatory by correlation analysis.

  14. BICEP2/Keck - Planck joint analysis and prospects for Galactic foreground removal from CMB observations

    NASA Astrophysics Data System (ADS)

    Crill, Brendan

    2015-08-01

    The joint analysis of 150 GHz polarized maps from BICEP2 and Keck Array at 150 GHz with Planck data at 353 GHzallowed the removal of Galactic dust contamination from the measurement of lensed B-modes in the deep (57 nK deg)BICEP2/Keck maps as well as setting an upper limit on the primordial gravitational wave background from inflation. We present this analysis, describe prospects for polarized foreground cleaning of future suborbitalmeasurements of CMB, and additionally describe Planck's measurements of the spatial correlation of polarizedemission from synchrotron and dust at high galactic latitude, which complicates the removal of Galactic foregrounds at the foregroundminimum of 70-100 GHz.

  15. Foreground removal from Planck Sky Model temperature maps using a MLP neural network

    NASA Astrophysics Data System (ADS)

    Nørgaard-Nielsen, H. U.; Hebert, K.

    2009-08-01

    Unfortunately, the Cosmic Microwave Background (CMB) radiation is contaminated by emission originating in the Milky Way (synchrotron, free-free and dust emission). Since the cosmological information is statistically in nature, it is essential to remove this foreground emission and leave the CMB with no systematic errors. To demonstrate the feasibility of a simple multilayer perceptron (MLP) neural network for extracting the CMB temperature signal, we have analyzed a specific data set, namely the Planck Sky Model maps, developed for evaluation of different component separation methods before including them in the Planck data analysis pipeline. It is found that a MLP neural network can provide a CMB map of about 80 % of the sky to a very high degree uncorrelated with the foreground components. Also the derived power spectrum shows little evidence for systematic errors.

  16. A GREEN BANK TELESCOPE SURVEY FOR H I 21 cm ABSORPTION IN THE DISKS AND HALOS OF LOW-REDSHIFT GALAXIES

    SciTech Connect

    Borthakur, Sanchayeeta; Tripp, Todd M.; Yun, Min S.; Meiring, Joseph D.; Bowen, David V.; York, Donald G.; Momjian, Emmanuel

    2011-01-20

    We present an H I 21 cm absorption survey with the Green Bank Telescope (GBT) of galaxy-quasar pairs selected by combining galaxy data from the Sloan Digital Sky Survey (SDSS) and radio sources from the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey. Our sample consists of 23 sight lines through 15 low-redshift foreground galaxy-background quasar pairs with impact parameters ranging from 1.7 kpc up to 86.7 kpc. We detected one absorber in the GBT survey from the foreground dwarf galaxy, GQ1042+0747, at an impact parameter of 1.7 kpc and another possible absorber in our follow-up Very Large Array (VLA) imaging of the nearby foreground galaxy UGC 7408. The line widths of both absorbers are narrow (FWHM of 3.6 and 4.8km s{sup -1}). The absorbers have sub-damped Ly{alpha} column densities, and most likely originate in the disk gas of the foreground galaxies. We also detected H I emission from three foreground galaxies including UGC 7408. Although our sample contains both blue and red galaxies, the two H I absorbers as well as the H I emissions are associated with blue galaxies. We discuss the physical conditions in the 21 cm absorbers and some drawbacks of the large GBT beam for this type of survey.

  17. Acoustic transducer with damping means

    DOEpatents

    Smith, Richard W.; Adamson, Gerald E.

    1976-11-02

    An ultrasonic transducer specifically suited to high temperature sodium applications is described. A piezoelectric active element is joined to the transducer faceplate by coating the faceplate and juxtaposed active element face with wetting agents specifically compatible with the bonding procedure employed to achieve the joint. The opposite face of the active element is fitted with a backing member designed to assure continued electrical continuity during adverse operating conditions which can result in the fracturing of the active element. The fit is achieved employing a spring-loaded electrode operably arranged to electrically couple the internal transducer components, enclosed in a hermetically sealed housing, to accessory components normally employed in transducer applications. Two alternative backing members are taught for assuring electrical continuity. The first employs a resilient, discrete multipoint contact electrode in electrical communication with the active element face. The second employs a resilient, elastomeric, electrically conductive, damped member in electrical communication with the active element face in a manner to effect ring-down of the transducer. Each embodiment provides continued electrical continuity within the transducer in the event the active element fractures, while the second provides the added benefit of damping.

  18. Relaxation damping in oscillating contacts

    PubMed Central

    Popov, M.; Popov, V.L.; Pohrt, R.

    2015-01-01

    If a contact of two purely elastic bodies with no sliding (infinite coefficient of friction) is subjected to superimposed oscillations in the normal and tangential directions, then a specific damping appears, that is not dependent on friction or dissipation in the material. We call this effect “relaxation damping”. The rate of energy dissipation due to relaxation damping is calculated in a closed analytic form for arbitrary axially-symmetric contacts. In the case of equal frequency of normal and tangential oscillations, the dissipated energy per cycle is proportional to the square of the amplitude of tangential oscillation and to the absolute value of the amplitude of normal oscillation, and is dependent on the phase shift between both oscillations. In the case of low frequency tangential oscillations with superimposed high frequency normal oscillations, the dissipation is proportional to the ratio of the frequencies. Generalization of the results for macroscopically planar, randomly rough surfaces as well as for the case of finite friction is discussed. PMID:26549011

  19. Relaxation damping in oscillating contacts

    NASA Astrophysics Data System (ADS)

    Popov, M.; Popov, V. L.; Pohrt, R.

    2015-11-01

    If a contact of two purely elastic bodies with no sliding (infinite coefficient of friction) is subjected to superimposed oscillations in the normal and tangential directions, then a specific damping appears, that is not dependent on friction or dissipation in the material. We call this effect “relaxation damping”. The rate of energy dissipation due to relaxation damping is calculated in a closed analytic form for arbitrary axially-symmetric contacts. In the case of equal frequency of normal and tangential oscillations, the dissipated energy per cycle is proportional to the square of the amplitude of tangential oscillation and to the absolute value of the amplitude of normal oscillation, and is dependent on the phase shift between both oscillations. In the case of low frequency tangential oscillations with superimposed high frequency normal oscillations, the dissipation is proportional to the ratio of the frequencies. Generalization of the results for macroscopically planar, randomly rough surfaces as well as for the case of finite friction is discussed.

  20. Superconductive material and magnetic field for damping and levitation support and damping of cryogenic instruments

    NASA Technical Reports Server (NTRS)

    Dolgin, Benjamin P. (Inventor)

    1994-01-01

    A superconductive load bearing support without a mechanical contact and vibration damping for cryogenic instruments in space is presented. The levitation support and vibration damping is accomplished by the use of superconducting magnets and the 'Meissner' effect. The assembly allows for transfer of vibration energy away from the cryogenic instrument which then can be damped by the use of either an electronic circuit or conventional vibration damping mean.

  1. SPERTI Terminal Building (PER604) is under construction in foreground, with ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    SPERT-I Terminal Building (PER-604) is under construction in foreground, with vertical metal siding partially affixed to gable end of building. Utility lines are laid in shallow trench to Reactor Pit and Instrument Cell Buildings also under construction in distance. Photographer: R.G. Larsen. Date: April 22, 1955. INEEL negative no. 55-1001 - Idaho National Engineering Laboratory, SPERT-I & Power Burst Facility Area, Scoville, Butte County, ID

  2. From Foreground to Background: How Task-Neutral Context Influences Contextual Cueing of Visual Search

    PubMed Central

    Zang, Xuelian; Geyer, Thomas; Assumpção, Leonardo; Müller, Hermann J.; Shi, Zhuanghua

    2016-01-01

    Selective attention determines the effectiveness of implicit contextual learning (e.g., Jiang and Leung, 2005). Visual foreground-background segmentation, on the other hand, is a key process in the guidance of attention (Wolfe, 2003). In the present study, we examined the impact of foreground-background segmentation on contextual cueing of visual search in three experiments. A visual search display, consisting of distractor ‘L’s and a target ‘T’, was overlaid on a task-neutral cuboid on the same depth plane (Experiment 1), on stereoscopically separated depth planes (Experiment 2), or spread over the entire display on the same depth plane (Experiment 3). Half of the search displays contained repeated target-distractor arrangements, whereas the other half was always newly generated. The task-neutral cuboid was constant during an initial training session, but was either rotated by 90° or entirely removed in the subsequent test sessions. We found that the gains resulting from repeated presentation of display arrangements during training (i.e., contextual-cueing effects) were diminished when the cuboid was changed or removed in Experiment 1, but remained intact in Experiments 2 and 3 when the cuboid was placed in a different depth plane, or when the items were randomly spread over the whole display but not on the edges of the cuboid. These findings suggest that foreground-background segmentation occurs prior to contextual learning, and only objects/arrangements that are grouped as foreground are learned over the course of repeated visual search. PMID:27375530

  3. 28. VIEW SOUTH FROM SLC3W MST STATION 63. FOREGROUND LEFT: ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    28. VIEW SOUTH FROM SLC-3W MST STATION 63. FOREGROUND LEFT: THEODOLITE SHELTER (BLDG. 786) CENTER LEFT TO RIGHT: GLOBAL POSITIONING SYSTEM AZIMUTH STATION (BLDG. 775), PYROTECHNIC SHED (BLDG. 757), PORTABLE GUARD SHED, METEOROLOGICAL SHED (BLDG. 756), METEOROLOGICAL TOWER. BACKGROUND CENTER TO RIGHT: STORAGE SHED (BLDG. 776), LIQUID OXYGEN APRON, SLC-3E MST, TOP OF SLC-3E FUEL STORAGE TANK. - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 West, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  4. STS-82 Discovery Rollout to Pad 39-A (Flag in foreground)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The Space Shuttle Discovery on its Mobile Launch Platform makes its slow 3.4-mile trek from the Vehicle Assembly Building to Launch Pad 39A in preparation for the STS-82 mission. In foreground is the U.S. flag at the Press Site area. A seven- member crew will perform the second servicing of the orbiting Hubble Space Telescope (HST) during the 10-day STS-82 mission, which is targeted for a Feb. 11 liftoff.

  5. Bayesian Semi-blind Component Separation for Foreground Removal in Interferometric 21 cm Observations

    NASA Astrophysics Data System (ADS)

    Zhang, Le; Bunn, Emory F.; Karakci, Ata; Korotkov, Andrei; Sutter, P. M.; Timbie, Peter T.; Tucker, Gregory S.; Wandelt, Benjamin D.

    2016-01-01

    In this paper, we present a new Bayesian semi-blind approach for foreground removal in observations of the 21 cm signal measured by interferometers. The technique, which we call H i Expectation-Maximization Independent Component Analysis (HIEMICA), is an extension of the Independent Component Analysis technique developed for two-dimensional (2D) cosmic microwave background maps to three-dimensional (3D) 21 cm cosmological signals measured by interferometers. This technique provides a fully Bayesian inference of power spectra and maps and separates the foregrounds from the signal based on the diversity of their power spectra. Relying only on the statistical independence of the components, this approach can jointly estimate the 3D power spectrum of the 21 cm signal, as well as the 2D angular power spectrum and the frequency dependence of each foreground component, without any prior assumptions about the foregrounds. This approach has been tested extensively by applying it to mock data from interferometric 21 cm intensity mapping observations under idealized assumptions of instrumental effects. We also discuss the impact when the noise properties are not known completely. As a first step toward solving the 21 cm power spectrum analysis problem, we compare the semi-blind HIEMICA technique to the commonly used Principal Component Analysis. Under the same idealized circumstances, the proposed technique provides significantly improved recovery of the power spectrum. This technique can be applied in a straightforward manner to all 21 cm interferometric observations, including epoch of reionization measurements, and can be extended to single-dish observations as well.

  6. Erasing the Variable: Empirical Foreground Discovery for Global 21 cm Spectrum Experiments

    NASA Technical Reports Server (NTRS)

    Switzer, Eric R.; Liu, Adrian

    2014-01-01

    Spectral measurements of the 21 cm monopole background have the promise of revealing the bulk energetic properties and ionization state of our universe from z approx. 6 - 30. Synchrotron foregrounds are orders of magnitude larger than the cosmological signal, and are the principal challenge faced by these experiments. While synchrotron radiation is thought to be spectrally smooth and described by relatively few degrees of freedom, the instrumental response to bright foregrounds may be much more complex. To deal with such complexities, we develop an approach that discovers contaminated spectral modes using spatial fluctuations of the measured data. This approach exploits the fact that foregrounds vary across the sky while the signal does not. The discovered modes are projected out of each line-of-sight of a data cube. An angular weighting then optimizes the cosmological signal amplitude estimate by giving preference to lower-noise regions. Using this method, we show that it is essential for the passband to be stable to at least approx. 10(exp -4). In contrast, the constraints on the spectral smoothness of the absolute calibration are mainly aesthetic if one is able to take advantage of spatial information. To the extent it is understood, controlling polarization to intensity leakage at the approx. 10(exp -2) level will also be essential to rejecting Faraday rotation of the polarized synchrotron emission. Subject headings: dark ages, reionization, first stars - methods: data analysis - methods: statistical

  7. Erasing the variable: empirical foreground discovery for global 21 cm spectrum experiments

    SciTech Connect

    Switzer, Eric R.; Liu, Adrian

    2014-10-01

    Spectral measurements of the 21 cm monopole background have the promise of revealing the bulk energetic properties and ionization state of our universe from z ∼ 6-30. Synchrotron foregrounds are orders of magnitude larger than the cosmological signal and are the principal challenge faced by these experiments. While synchrotron radiation is thought to be spectrally smooth and described by relatively few degrees of freedom, the instrumental response to bright foregrounds may be much more complex. To deal with such complexities, we develop an approach that discovers contaminated spectral modes using spatial fluctuations of the measured data. This approach exploits the fact that foregrounds vary across the sky while the signal does not. The discovered modes are projected out of each line of sight of a data cube. An angular weighting then optimizes the cosmological signal amplitude estimate by giving preference to lower-noise regions. Using this method, we show that it is essential for the passband to be stable to at least ∼10{sup –4}. In contrast, the constraints on the spectral smoothness of the absolute calibration are mainly aesthetic if one is able to take advantage of spatial information. To the extent it is understood, controlling polarization to intensity leakage at the ∼10{sup –2} level will also be essential to rejecting Faraday rotation of the polarized synchrotron emission.

  8. Saliency-Aware Nonparametric Foreground Annotation Based on Weakly Labeled Data.

    PubMed

    Cao, Xiaochun; Zhang, Changqing; Fu, Huazhu; Guo, Xiaojie; Tian, Qi

    2016-06-01

    In this paper, we focus on annotating the foreground of an image. More precisely, we predict both image-level labels (category labels) and object-level labels (locations) for objects within a target image in a unified framework. Traditional learning-based image annotation approaches are cumbersome, because they need to establish complex mathematical models and be frequently updated as the scale of training data varies considerably. Thus, we advocate the nonparametric method, which has shown potential in numerous applications and turned out to be attractive thanks to its advantages, i.e., lightweight training load and scalability. In particular, we exploit the salient object windows to describe images, which is beneficial to image retrieval and, thus, the subsequent image-level annotation and localization tasks. Our method, namely, saliency-aware nonparametric foreground annotation, is practical to alleviate the full label requirement of training data, and effectively addresses the problem of foreground annotation. The proposed method only relies on retrieval results from the image database, while pretrained object detectors are no longer necessary. Experimental results on the challenging PASCAL VOC 2007 and PASCAL VOC 2008 demonstrate the advance of our method. PMID:26529788

  9. Tuned vibration absorbers with nonlinear viscous damping for damped structures under random load

    NASA Astrophysics Data System (ADS)

    Shum, K. M.

    2015-06-01

    The classical problem for the application of a tuned vibration absorber is to minimize the response of a structural system, such as displacement, velocity, acceleration or to maximize the energy dissipated by tuned vibration absorber. The development of explicit optimal absorber parameters is challenging for a damped structural system since the fixed points no longer exist in the frequency response curve. This paper aims at deriving a set of simple design formula of tuned vibration absorber with nonlinear viscous damping based on the frequency tuning for harmonic load for a damped structural system under white noise excitation. The vibration absorbers being considered include tuned mass damper (TMD) and liquid column vibration absorber (LCVA). Simple approximate expression for the standard deviation velocity response of tuned vibration absorber for damped primary structure is also derived in this study to facilitate the estimation of the damping coefficient of TMD with nonlinear viscous damping and the head loss coefficient of LCVA. The derived results indicate that the higher the structural inherent damping the smaller the supplementary damping provided by a tuned vibration absorber. Furthermore, the optimal damping of tuned vibration absorber is shown to be independent of structural damping when it is tuned using the frequency tuning for harmonic load. Finally, the derived closed-form expressions are demonstrated to be capable of predicting the optimal parameters of tuned vibration absorbers with sufficient accuracy for preliminary design of tuned vibration absorbers with nonlinear viscous damping for a damped primary structure.

  10. Double troughs in broad absorption line quasars and Ly-alpha-N V line-locking

    NASA Technical Reports Server (NTRS)

    Korista, Kirk T.; Voit, G. M.; Morris, Simon L.; Weymann, Ray J.

    1993-01-01

    It was investigated whether the double trough (DT) structure in the mean C IV BAL trough reported by Weymann et al. (1991) is real or due to statistical fluctuations of BAL troughs over random outflow velocities in a limited sample. A sample of 72 BAL QSOs with C IV BAL troughs was analyzed. It is found that only 22 percent of the sample explicitly exhibits the DT feature; when present the DTs are deep. A Monte Carlo simulation of the mean C IV BAL suggests that the DT feature is real at only the 95-98 percent level.

  11. The Local LY alpha Forest: Association of Clouds with Superclusters and Voids

    NASA Astrophysics Data System (ADS)

    Stocke, John T.; Shull, J. Michael; Penton, Steve; Donahue, Megan; Carilli, Chris

    1995-09-01

    The Goddard High Resolution Spectrograph aboard the Hubble Space Telescope was used with the G160M grating to obtain high-resolution (0.2 Å) spectra of three very bright active galactic nuclei located behind voids in the nearby distribution of bright galaxies (i.e., CfA and Arecibo redshift survey regions). A total of eight definite (≥ 4 σ) Lyα absorption lines were discovered ranging in equivalent width from 26 to 240 mÅ at Galactocentric velocities 1740-7740 km 5-1 Of these eight systems, we locate seven in supercluster structures and one, in the sight line of Mrk 501 at 7740 km s-1, in a void. In addition, one of two tentative (3-4 σ) Lyα absorption lines are found in voids. Thus, the voids are not entirely devoid of matter, and not all Lyα clouds are associated with galaxies. Also, since the path lengths through voids and superclusters probed by our observations thus far are nearly equal, there is some statistical evidence that the Lyα clouds avoid the voids. The nearest galaxy neighbors to these absorbing clouds are 0.45-5.9 Mpc away, too far to be physically associated by most models. The lower equivalent width absorption lines (Wλ ≤ 100 mÅ) are consistent with random locations with respect to galaxies and may be truly intergalactic, similar to the bulk of the Lyα forest seen at high z. These results on local Lyα clouds are in full agreement with those found by Morris et al. (1993) for the 3C 273 sight line but are different from the results for higher equivalent width systems where closer cloud-galaxy associations were found by Lanzetta et al. (1994). Pencil-beam optical and 21 cm radio line observations of the area of sky surrounding Mrk 501 fail to find faint galaxies near the velocities of the Lyα clouds in that sight line. Specifically, for the "void absorption" system at 7740 km s-1, we find no galaxy at comparable redshift to the absorber within 100 h-175 kpc (H0 = 75 h75 km s-1 Mpc-1) with an absolute magnitude of B ≤ -16 and no object with H I mass ≥ 7 × 108 h-275 Msun within 500 h-175 kpc. Thus, neither a faint optical galaxy nor a gas-rich, optically dim or low surface brightness galaxy is present close to this absorber.

  12. Cross section for Ly-alpha emission by electron impact on methane

    NASA Technical Reports Server (NTRS)

    Orient, O. J.; Srivastava, S. K.

    1981-01-01

    Utilizing Lyman-alpha emission cross sections for H2 as secondary standards, absolute values of Lyman-alpha emission cross sections for CH4 have been obtained for electron impact energies varying from threshold to 100 eV. A crossed electron beam-molecular beam geometry was employed and the Lyman-alpha radiation was detected at 90 deg and 45 deg with respect to the incident electron beam by a solar blind photomultiplier in tandem with an oxygen filter. The results are compared with previous measurements. Appreciable differences among the various experimental data are found.

  13. Statistical analysis of the cosmic microwave background: Power spectra and foregrounds

    NASA Astrophysics Data System (ADS)

    O'Dwyer, Ian J.

    2005-11-01

    In this thesis I examine some of the challenges associated with analyzing Cosmic Microwave Background (CMB) data and present a novel approach to solving the problem of power spectrum estimation, which is called MAGIC (MAGIC Allows Global Inference of Covariance). In light of the computational difficulty of a brute force approach to power spectrum estimation, I review several approaches which have been applied to the problem and show an example application of such an approximate method to experimental CMB data from the Background Emission Anisotropy Scanning Telescope (BEAST). I then introduce MAGIC, a new approach to power spectrum estimation; based on a Bayesian statistical analysis of the data utilizing Gibbs Sampling. I demonstrate application of this method to the all-sky Wilkinson Microwave Anistropy Probe WMAP data. The results are in broad agreement with those obtained originally by the WMAP team. Since MAGIC generates a full description of each C l it is possible to examine several issues raised by the best-fit WMAP power spectrum, for example the perceived lack of power at low ℓ. It is found that the distribution of C ℓ's at low l are significantly non-Gaussian and, based on the exact analysis presented here, the "low quadrupole issue" can be attributed to a statistical fluctuation. Finally, I examine the effect of Galactic foreground contamination on CMB experiments and describe the principle foregrounds. I show that it is possible to include the foreground components in a self-consistent fashion within the statistical framework of MAGIC and give explicit examples of how this might be achieved. Foreground contamination will become an increasingly important issue in CMB data analysis and the ability of this new algorithm to produce an exact power spectrum in a computationally feasible time, coupled with the foreground component separation and removal is an exciting development in CMB data analysis. When considered with current algorithmic developments

  14. Damping device for a stationary labyrinth seal

    NASA Technical Reports Server (NTRS)

    El-Aini, Yehia M. (Inventor); Mitchell, William S. (Inventor); Roberts, Lawrence P. (Inventor); Montgomery, Stuart K. (Inventor); Davis, Gary A. (Inventor)

    2010-01-01

    A stationary labyrinth seal system includes a seal housing having an annular cavity, a plurality of damping devices, and a retaining ring. The damping devices are positioned within the annular cavity and are maintained within the annular cavity by the retaining ring.

  15. HOME DAMPNESS AND RESPIRATORY MORBIDITY IN CHILDREN

    EPA Science Inventory

    This study examined the relationship between measures of home dampness and respiratory illness and symptoms in a cohort of 4,625 eight- to 12-year old children in six U.S. cities. ome dampness was characterized from questionnaire reports of mold or mildew damage inside the home, ...

  16. Study for ILC Damping Ring at KEKB

    SciTech Connect

    Flanagan, J.W.; Fukuma, H.; Kanazawa, K.I.; Koiso, H.; Masuzawa, M.; Ohmi, Kazuhito; Ohnishi, Y.; Oide, Katsunobu; Suetsugu, Y.; Tobiyama, M.; Pivi, M.; /SLAC

    2011-11-04

    ILC damping ring consists of very low emittance electron and positron storage rings. It is necessary for ILC damping ring to study electron cloud effects in such low emittance positron ring. We propose a low emittance operation of KEKB to study the effects.

  17. Passive damping in EDS maglev systems.

    SciTech Connect

    Rote, D. M.

    2002-05-03

    There continues to be strong interest in the subjects of damping and drag forces associated with electrodynamic suspension (EDS) systems. While electromagnetic drag forces resist the forward motion of a vehicle and therefore consume energy, damping forces control, at least in part, the response of the vehicle to disturbances. Ideally, one would like to reduce the drag forces as much as possible while retaining adequate damping forces to insure dynamic stability and satisfactory ride quality. These two goals turn out to be difficult to achieve in practice. It is well known that maglev systems tend to be intrinsically under damped. Consequently it is often necessary in a practical system design to enhance the damping passively or actively. For reasons of cost and simplicity, it is desirable to rely as much as possible on passive damping mechanisms. In this paper, rough estimates are made of the passive damping and drag forces caused by various mechanisms in EDS systems. No attention will be given to active control systems or secondary suspension systems which are obvious ways to augment passive damping mechanisms if the latter prove to be inadequate.

  18. Understanding the Damped SHM without ODEs

    ERIC Educational Resources Information Center

    Ng, Chiu-king

    2016-01-01

    Instead of solving ordinary differential equations (ODEs), the damped simple harmonic motion (SHM) is surveyed qualitatively from basic mechanics and quantitatively by the instrumentality of a graph of velocity against displacement. In this way, the condition b ? [square root]4mk for the occurrence of the non-oscillating critical damping and…

  19. Status report of RMS active damping augmentation

    NASA Technical Reports Server (NTRS)

    Gilbert, Mike; Demeo, Martha E.

    1993-01-01

    A status report of Remote Manipulator System (RMS) active damping augmentation is presented. Topics covered include: active damping augmentation; benefits of RMS ADA; simulated payload definition; sensor and actuator definition; ADA control law design; Shuttle Engineering Simulator (SES) real-time simulation; and astronaut evaluation.

  20. Large space structure damping design

    NASA Technical Reports Server (NTRS)

    Pilkey, W. D.; Haviland, J. K.

    1983-01-01

    Several FORTRAN subroutines and programs were developed which compute complex eigenvalues of a damped system using different approaches, and which rescale mode shapes to unit generalized mass and make rigid bodies orthogonal to each other. An analytical proof of a Minimum Constrained Frequency Criterion (MCFC) for a single damper is presented. A method to minimize the effect of control spill-over for large space structures is proposed. The characteristic equation of an undamped system with a generalized control law is derived using reanalysis theory. This equation can be implemented in computer programs for efficient eigenvalue analysis or control quasi synthesis. Methods to control vibrations in large space structure are reviewed and analyzed. The resulting prototype, using electromagnetic actuator, is described.

  1. VIBRATION DAMPING AND SHOCK MOUNT

    DOEpatents

    Stevens, D.J.; Forman, G.W.

    1963-12-10

    A shock absorbing mount in which vibrations are damped by an interference fit between relatively movable parts of the mount is described. A pair of generally cup-shaped parts or members have skirt portions disposed in an oppositely facing nesting relationship with the skirt of one member frictionally engaging the skirt of the other. The outermost skirt may be slotted to provide spring-like segments which embrace the inner skirt for effecting the interference fit. Belleville washers between the members provide yieldable support for a load carried by the mount. When a resonant frequency of vibration forces acting upon the moumt attains a certain level the kinetic energy of these forces is absorbed by sliding friction between the parts. (AEC)

  2. Landau damping in a turbulent setting

    SciTech Connect

    Plunk, G. G.

    2013-03-15

    To address the problem of Landau damping in kinetic turbulence, we consider the forcing of the linearized Vlasov equation by a stationary random source. It is found that the time-asymptotic density response is dominated by resonant particle interactions that are synchronized with the source. The energy consumption of this response is calculated, implying an effective damping rate, which is the main result of this paper. Evaluating several cases, it is found that the effective damping rate can differ from the Landau damping rate in magnitude and also, remarkably, in sign. A limit is demonstrated in which the density and current become phase-locked, which causes the effective damping to be negligible; this result offers a fresh perspective from which to reconsider recent observations of kinetic turbulence satisfying critical balance.

  3. Damping characteristics of damaged fiber composite components

    NASA Technical Reports Server (NTRS)

    Eberle, K.

    1986-01-01

    Defects in fiber composite components produce changes with respect to the vibrational characteristics of the material. These changes can be recognized in the form of a frequency shift or an alteration of the damping process. The present investigation is concerned with questions regarding the possibility of a utilization of the changes in suitable defect-detecting inspection procedures. A description is given of a method for measuring the damping characteristics of a specimen. This method provides a spectrum of the damping coefficients of the sample as a basis for a comprehensive evaluation of the damping behavior. The correlation between defects and change in the damping characteristics is demonstrated with the aid of results obtained in measurements involving specimens of carbon-fiber composites and a component consisting of glass-fiber-reinforced plastics.

  4. Experimental Investigation of the Damping Behavior of the Particle Damping in the Transient Vibrations

    NASA Astrophysics Data System (ADS)

    Chavan, Shrirang Pandurang; Kale, Arvind Kamalakar; Mulla, Faiz Abdulkadar

    2016-01-01

    Particle damping is a non linear type of damping in which energy of the vibratory system is dissipated by the impact and the frictional losses made by the particles used for the damping purposes. The particle damping technique is useful over other types of damping as it is temperature independent. So it is reliable over wide temperature range and hence is essentially used in the cryogenic and the gas turbine related applications. For experimentation, cantilever beam with particle enclosure attached to its free end has been extensively used and the effect of the particle material, particle size, mass ratio and enclosure height on the damping performance has been studied [1]. For a small weight penalty, rather large amounts of damping can be achieved [2].

  5. Validation Of Equivalent Viscous Damping Methodologies

    NASA Astrophysics Data System (ADS)

    Vaquer Araujo, Xavier; Fransen, S. H. J. A.; Germes, S.; Thiry, N.

    2012-07-01

    An important step in the design and verification process of spacecraft structures is the coupled dynamic analysis with the launch vehicle in the low-frequency domain. To obtain accurate predictions of the satellite’s dynamic environment it is essential that the damping of the system is correctly defined and taken into account within the resolution methodologies for the Coupled Loads Analysis (CLA). When working with finite element models, the materials’ damping is characterized by structural damping ratios. In addition, most of the load cases present in the CLA are transient excitations so the resolution of the equations of motion must be done in the time domain. Unfortunately, transient analyses cannot be carried out using structural damping models. Thus, a transformation from a structural to a viscous damping characterization is necessary. Nevertheless, this transformation is not trivial. There exist many methodologies aiming at computing an equivalent viscous damping matrix of the system so it can be used in transient analyses. This paper describes the results obtained in the validation of equivalent viscous damping methodologies used in the European Space Agency. This work permitted to identify the limitations of these methodologies and to come up with an enhanced methodology that predicts more reliable results.

  6. Bounce harmonic Landau damping of plasma waves

    NASA Astrophysics Data System (ADS)

    Anderegg, F.; Affolter, M.; Kabantsev, A. A.; Dubin, D. H. E.; Ashourvan, A.; Driscoll, C. F.

    2016-05-01

    We present measurements of bounce harmonic Landau damping due to z-variations in the plasma potential, created by an azimuthally symmetric "squeeze" voltage Vs applied to the cylindrical wall. Traditional Landau damping on spatially uniform plasma is weak in regimes where the wave phase velocity vp h≡ω/k is large compared to the thermal velocity. However, z-variations in plasma density and potential create higher spatial harmonics, which enable resonant wave damping by particles with bounce-averaged velocities vp h/n , where n is an integer. In our geometry, the applied squeeze predominantly generates a resonance at vp h/3 . Wave-coherent laser induced fluorescence measurements of particle velocities show a distinctive Landau damping signature at vp h/3 , with amplitude proportional to the applied Vs. The measured (small amplitude) wave damping is then proportional to Vs2 , in quantitative agreement with theory over a range of 20 in temperature. Significant questions remain regarding "background" bounce harmonic damping due to ubiquitous confinement fields and regarding the saturation of this damping at large wave amplitudes.

  7. Sunyaev-Zel'dovich effect or not? Detecting the main foreground effect of most galaxy clusters

    NASA Astrophysics Data System (ADS)

    Xiao, Weike; Chen, Chen; Zhang, Bin; Wu, Yongfeng; Dai, Mi

    2013-05-01

    Galaxy clusters are the most massive objects in the Universe and comprise a high-temperature intracluster medium of about 107 K, believed to offer a main foreground effect for cosmic microwave background (CMB) data in the form of the thermal Sunyaev-Zel'dovich (SZ) effect. This assumption has been confirmed by SZ signal detection in hundreds of clusters but, in comparison with the huge numbers of clusters within optically selected samples from Sloan Digital Sky Survey (SDSS) data, this only accounts for a few per cent of clusters. Here we introduce a model-independent new method to confirm the assumption that most galaxy clusters can offer the thermal SZ signal as their main foreground effect. For the Wilkinson Microwave Anisotropy Probe (WMAP) seven-year data (and a given galaxy cluster sample), we introduced a parameter d1 as the nearest-neighbour cluster angular distance of each pixel, then we classified data pixels as `to be' (d1 → 0 case) or `not to be' (d1 large enough) affected by the sample clusters. By comparing the statistical results of these two kinds of pixels, we can see how the sample clusters affect the CMB data directly. We find that the Planck Early Sunyaev-Zel'dovich (ESZ) sample and X-ray samples (˜102 clusters) can lead to obvious temperature depression in the WMAP seven-year data, which confirms the SZ effect prediction. However, each optically selected sample (>104 clusters) shows an opposite result: the mean temperature rises to about 10 μK. This unexpected qualitative scenario implies that the main foreground effect of most clusters is not always the expected SZ effect. This may be the reason why the SZ signal detection result is lower than expected from the model.

  8. Characterizing foreground for redshifted 21 cm radiation: 150 MHz Giant Metrewave Radio Telescope observations

    NASA Astrophysics Data System (ADS)

    Ghosh, Abhik; Prasad, Jayanti; Bharadwaj, Somnath; Ali, Sk. Saiyad; Chengalur, Jayaram N.

    2012-11-01

    Foreground removal is a major challenge for detecting the redshifted 21 cm neutral hydrogen (H I) signal from the Epoch of Reionization. We have used 150 MHz Giant Metrewave Radio Telescope observations to characterize the statistical properties of the foregrounds in four different fields of view. The measured multifrequency angular power spectrum Cℓ(Δν) is found to have values in the range 104-2 × 104 mK2 across 700 ≤ ℓ ≤ 2 × 104 and Δν ≤ 2.5 MHz, which is consistent with model predictions where point sources are the most dominant foreground component. The measured Cℓ(Δν) does not show a smooth Δν dependence, which poses a severe difficulty for foreground removal using polynomial fitting. The observational data were used to assess point source subtraction. Considering the brightest source (˜1 Jy) in each field, we find that the residual artefacts are less than 1.5 per cent in the most sensitive field (FIELD I). Considering all the sources in the fields, we find that the bulk of the image is free of artefacts, the artefacts being localized to the vicinity of the brightest sources. We have used FIELD I, which has an rms noise of 1.3 mJy beam-1, to study the properties of the radio source population to a limiting flux of 9 mJy. The differential source count is well fitted with a single power law of slope -1.6. We find there is no evidence for flattening of the source counts towards lower flux densities which suggests that source population is dominated by the classical radio-loud active galactic nucleus. The diffuse Galactic emission is revealed after the point sources are subtracted out from FIELD I. We find Cℓ ∝ ℓ-2.34 for 253 ≤ ℓ ≤ 800 which is characteristic of the Galactic synchrotron radiation measured at higher frequencies and larger angular scales. We estimate the fluctuations in the Galactic synchrotron emission to be ℓ(ℓ+1)Cℓ/2π≃10 K at ℓ = 800 (θ > 10 arcmin). The measured Cℓ is dominated by

  9. Robust forecasts on fundamental physics from the foreground-obscured, gravitationally-lensed CMB polarization

    NASA Astrophysics Data System (ADS)

    Errard, Josquin; Feeney, Stephen M.; Peiris, Hiranya V.; Jaffe, Andrew H.

    2016-03-01

    Recent results from the BICEP, Keck Array and Planck Collaborations demonstrate that Galactic foregrounds are an unavoidable obstacle in the search for evidence of inflationary gravitational waves in the cosmic microwave background (CMB) polarization. Beyond the foregrounds, the effect of lensing by intervening large-scale structure further obscures all but the strongest inflationary signals permitted by current data. With a plethora of ongoing and upcoming experiments aiming to measure these signatures, careful and self-consistent consideration of experiments' foreground- and lensing-removal capabilities is critical in obtaining credible forecasts of their performance. We investigate the capabilities of instruments such as Advanced ACTPol, BICEP3 and Keck Array, CLASS, EBEX10K, PIPER, Simons Array, SPT-3G and SPIDER, and projects as COrE+, LiteBIRD-ext, PIXIE and Stage IV, to clean contamination due to polarized synchrotron and dust from raw multi-frequency data, and remove lensing from the resulting co-added CMB maps (either using iterative CMB-only techniques or through cross-correlation with external data). Incorporating these effects, we present forecasts for the constraining power of these experiments in terms of inflationary physics, the neutrino sector, and dark energy parameters. Made publicly available through an online interface, this tool enables the next generation of CMB experiments to foreground-proof their designs, optimize their frequency coverage to maximize scientific output, and determine where cross-experimental collaboration would be most beneficial. We find that analyzing data from ground, balloon and space instruments in complementary combinations can significantly improve component separation performance, delensing, and cosmological constraints over individual datasets. In particular, we find that a combination of post-2020 ground- and space-based experiments could achieve constraints such as σ(r)~1.3×10-4, σ(nt)~0.03, σ( ns )~1.8×10

  10. STS-79 Atlantis rolls back to the VAB (flag in foreground)

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Space Shuttle Atlantis passes by the Turn Basin and the American flag at the Press Site, in foreground, en route to the Vehicle Assembly Building, where it will be sheltered from the threat of Hurricane Fran. Atlantis is rolling back from Launch Pad 39A, where it was undergoing preparations for Mission STS-79. This marks the second rollback for Atlantis since July because of hurricane threats. The threat of Hurricane Bertha forced the rollback of Atlantis in July. Atlantis currently is scheduled for launch on the fourth Shuttle-Mir docking mission around mid- September.

  11. Toward an understanding of foreground emission in the BICEP2 region

    SciTech Connect

    Flauger, Raphael; Hill, J. Colin; Spergel, David N. E-mail: jch@astro.princeton.edu

    2014-08-01

    BICEP2 has reported the detection of a degree-scale B-mode polarization pattern in the Cosmic Microwave Background (CMB) and has interpreted the measurement as evidence for primordial gravitational waves. Motivated by the profound importance of the discovery of gravitational waves from the early Universe, we examine to what extent a combination of Galactic foregrounds and lensed E-modes could be responsible for the signal. We reanalyze the BICEP2 results and show that the 100 ×150 GHz and 150 ×150 GHz data are consistent with a cosmology with r=0.2 and negligible foregrounds, but also with a cosmology with r=0 and a significant dust polarization signal. We give independent estimates of the dust polarization signal in the BICEP2 region using a number of different approaches: (1) data-driven models based on Planck 353 GHz intensity, polarization fractions inferred from the same Planck data used by the BICEP2 team but corrected for CMB and CIB contributions, and polarization angles from starlight polarization data or the Planck sky model; (2) the same set of pre-Planck models used by the BICEP2 team but taking into account the higher polarization fractions observed in the CMB- and CIB-corrected map; (3) a measurement of neutral hydrogen gas column density N{sub HI} in the BICEP2 region combined with an extrapolation of a relation between HI column density and dust polarization derived by Planck; and (4) a dust polarization map based on digitized Planck data, which we only use as a final cross-check. While these approaches are consistent with each other, the expected amplitude of the dust polarization power spectrum remains uncertain by about a factor of three. The lower end of the prediction leaves room for a primordial contribution, but at the higher end the dust in combination with the standard CMB lensing signal could account for the BICEP2 observations, without requiring the existence of primordial gravitational waves. By measuring the cross-correlations between

  12. Continuum damping of ideal toroidal Alfven eigenmodes

    SciTech Connect

    Zhang, X.D.; Zhang, Y.Z.; Mahajan, S.M.

    1993-08-01

    A perturbation theory based on the two dimensional (2D) ballooning transform is systematically developed for ideal toroidal Alfven eigenmodes (TAEs). A formula, similar to the Fermi golden rule for decaying systems in quantum mechanics, is derived for the continuum damping rate of the TAE; the decay (damping) rate is expressed explicitly in terms of the coupling of the TAE to the continuum spectrum. Numerical results are compared with previous calculations. It is found that in some narrow intervals of the parameter m{cflx {epsilon}} the damping rate varies very rapidly. These regions correspond precisely to the root missing intervals of the numerical solution by Rosenbluth et al.

  13. A Resonant Damping Study Using Piezoelectric Materials

    NASA Technical Reports Server (NTRS)

    Min, J. B.; Duffy, K. P.; Choi, B. B.; Morrison, C. R.; Jansen, R. H.; Provenza, A. J.

    2008-01-01

    Excessive vibration of turbomachinery blades causes high cycle fatigue (HCF) problems requiring damping treatments to mitigate vibration levels. Based on the technical challenges and requirements learned from previous turbomachinery blade research, a feasibility study of resonant damping control using shunted piezoelectric patches with passive and active control techniques has been conducted on cantilever beam specimens. Test results for the passive damping circuit show that the optimum resistive shunt circuit reduces the third bending resonant vibration by almost 50%, and the optimum inductive circuit reduces the vibration by 90%. In a separate test, active control reduced vibration by approximately 98%.

  14. Saturation of Gyrokinetic Turbulence through Damped Eigenmodes

    SciTech Connect

    Hatch, D. R.; Terry, P. W.; Jenko, F.; Merz, F.; Nevins, W. M.

    2011-03-18

    In the context of toroidal gyrokinetic simulations, it is shown that a hierarchy of damped modes is excited in the nonlinear turbulent state. These modes exist at the same spatial scales as the unstable eigenmodes that drive the turbulence. The larger amplitude subdominant modes are weakly damped and exhibit smooth, large-scale structure in velocity space and in the direction parallel to the magnetic field. Modes with increasingly fine-scale structure are excited to decreasing amplitudes. In aggregate, damped modes define a potent energy sink. This leads to an overlap of the spatial scales of energy injection and peak dissipation, a feature that is in contrast with more traditional turbulent systems.

  15. Oscillation damped movement of suspended objects

    SciTech Connect

    Jones, J.F.; Petterson, B.J.

    1988-01-01

    Transportation of objects using overhead cranes or manipulators can induce pendulum motion of the object. Residual oscillation from transportation typically must be damped or allowed to decay before the next process can take place. By properly programming the acceleration of the transporting device (e.g., crane) an oscillation damped transport and swing free stop is obtainable. This paper reviews the theory associated with oscillation damped trajectories for simply suspended objects and describes a particular implementation using a CIMCORP XR 6100 gantry robot. 8 refs., 7 figs., 1 tab.

  16. Turbine blade friction damping study

    NASA Technical Reports Server (NTRS)

    Dominic, R. J.

    1985-01-01

    A lumped parameter method, implemented on a VAX 11/780 computer shows that the primary parameters affecting the performance of the friction damper of the first stage turbine of the SSME high pressure fuel pump are: the damper-blade coefficient of friction; the normal force applied to the friction interface; the amplitude of the periodic forcing function; the relative phase angle of the forcing functions for adjacent blades bridged by a damper (effectively, the engine order of the forcing function); and the amount of hysteretic damping that acts to limit the vibration amplitude of the blade in its resonance modes. The low order flexural resonance vibration modes of HPFTP blades without dampers, with production dampers, and with two types of lightweight experimental dampers were evaluated in high speed spin pit tests. Results agree with those of the analytical study in that blades fitted with production friction dampers experienced the airfoil-alone flexural resonance mode, while those without dampers or with lighter weight dampers did not. No blades fitted with dampers experienced the whole blade flexural resonance mode during high speed tests, while those without dampers did.

  17. Artificial Compressibility with Entropic Damping

    NASA Astrophysics Data System (ADS)

    Clausen, Jonathan; Roberts, Scott

    2012-11-01

    Artificial Compressibility (AC) methods relax the strict incompressibility constraint associated with the incompressible Navier-Stokes equations. Instead, they rely on an artificial equation of state relating pressure and density fluctuations through a numerical Mach number. Such methods are not new: the first AC methods date back to Chorin (1967). More recent applications can be found in the lattice-Boltzmann method, which is a kinetic/mesoscopic method that converges to an AC form of the Navier-Stokes equations. With computing hardware trending towards massively parallel architectures in order to achieve high computational throughput, AC style methods have become attractive due to their local information propagation and concomitant parallelizable algorithms. In this work, we examine a damped form of AC in the context of finite-difference and finite-element methods, with a focus on achieving time-accurate simulations. Also, we comment on the scalability of the various algorithms. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  18. Turbulent Damping without Eddy Viscosity

    NASA Astrophysics Data System (ADS)

    Thalabard, Simon

    2015-11-01

    The intrinsic Non-Gaussianity of turbulence may explain why the standard Quasi-Normal cumulant discard closures can fail dramatically, an example being the development of negative energy spectra in Millionshtchikov's 1941 Quasi-Normal (QN) theory. While Orszag's 1977 EDQNM provides an ingenious patch to the issue, the reason why QN fails so badly is not so clear. Is it because of the Gaussian Ansatz itself? Or rather its inconsistent use? The purpose of the talk is to argue in favor of the latter option, using the lights of a new ``optimal closure'' recently exposed by [Turkington,2013], which allows Gaussians to be used consistently with an intrinsic damping. The key to this apparent paradox lies in a clear distinction between the ensemble averages and their proxies, most easily grasped provided one uses the Liouville equation rather than the cumulant hierarchy as a starting point. Schematically said, closure is achieved by minimizing a lack-of-fit residual, that retains the intrinsic features of the dynamics. For the sake of clarity, I will discuss the optimal closure on a problem where it can be entirely implemented and compared to DNS: the relaxation of an arbitrarily far from equilibrium energy shell towards the Gibbs equilibrium for truncated Euler dynamics.

  19. Eigensolutions of non-proportionally damped systems based on continuous damping sensitivity

    NASA Astrophysics Data System (ADS)

    Lázaro, Mario

    2016-02-01

    The viscous damping model has been widely used to represent dissipative forces in structures under mechanical vibrations. In multiple degree of freedom systems, such behavior is mathematically modeled by a damping matrix, which in general presents non-proportionality, that is, it does not become diagonal in the modal space of the undamped problem. Eigensolutions of non-proportional systems are usually estimated assuming that the modal damping matrix is diagonally dominant (neglecting the off-diagonal terms) or, in the general case, using the state-space approach. In this paper, a new closed-form expression for the complex eigenvalues of non-proportionally damped system is proposed. The approach is derived assuming small damping and involves not only the diagonal terms of the modal damping matrix, but also the off-diagonal terms, which appear under higher order. The validity of the proposed approach is illustrated through a numerical example.

  20. Linear collisionless Landau damping in Hilbert space

    NASA Astrophysics Data System (ADS)

    Zocco, Alessandro

    2015-08-01

    The equivalence between the Laplace transform (Landau, J. Phys. USSR 10 (1946), 25) and Hermite transform (Zocco and Schekochihin, Phys. Plasmas 18, 102309 (2011)) solutions of the linear collisionless Landau damping problem is proven.

  1. Nucleon exchange in damped nuclear reactions

    SciTech Connect

    Randrup, J.

    1986-04-01

    Starting from the general context of one-body nuclear dynamics, the nucleon-exchange mechanism in damped nuclear reactions is discussed. Some of its characteristic effects on various dinuclear observables are highlighted and a few recent advances are described.

  2. Magnetic Damping in Ferromagnetic Thin Films

    NASA Astrophysics Data System (ADS)

    Oogane, Mikihiko; Wakitani, Takeshi; Yakata, Satoshi; Yilgin, Resul; Ando, Yasuo; Sakuma, Akimasa; Miyazaki, Terunobu

    2006-05-01

    We determined the Gilbert damping constants of Fe-Co-Ni and Co-Fe-B alloys with various compositions and half-metallic Co2MnAl Heusler alloy films prepared by magnetron sputtering. The ferromagnetic resonance (FMR) technique was used to determine the damping constants of the prepared films. The out-of-plane angular dependences of the resonance field (HR) and line width (Δ Hpp) of FMR spectra were measured and fitted using the Landau-Lifshitz-Gilbert (LLG) equation. The experimental results fitted well, considering the inhomogeneities of the films in the fitting. The damping constants of the metallic films were much larger than those of bulk ferrimagnetic insulators and were roughly proportional to (g-2)2, where g is the Lande g factor. We discuss the origin of magnetic damping, considering spin-orbit and s-d interactions.

  3. Damping Wiggler Study at KEK-ATF

    SciTech Connect

    Naito, T.; Hayano, H.; Honda, Y.; Kubo, K.; Kuriki, M.; Kuroda, S.; Muto, T.; Terunuma, N.; Urakawa, J.; Sakai, H.; Nakamura, N.; Korostelev, M.; Zimmermann, F.; Ross, Marc; /SLAC

    2006-02-07

    The effects of damping wiggler magnets have been studied at KEK-ATF damping ring, which is a 1.3 GeV storage ring capable of producing ultra-low emittance electron beams. The fast beam damping is a significant issue for the damping ring. The tuning method with 4 sets of wiggler magnets was investigated for the ultra-low emittance beam. The effect on the beam quality, which is related to the transverse (x and y) and the longitudinal (z and {Delta}p/p), has been measured by the wire scanner, SR monitor, the laser wire, streak camera and the energy spread monitor. We report on the operational condition and the measurement results.

  4. Concepts and effects of damping in isolators

    NASA Technical Reports Server (NTRS)

    Kerley, J.

    1984-01-01

    A series of innovative designs and inventions which led to the solution of many aerospace vibration and shock problems through damping techniques is presented. The design of damped airborne structures has presented a need for such creative innovation. The primary concern was to discover what concepts were necessary for good structural damping. Once these concepts are determined and converted into basic principles, the design of hardware follows. The following hardware and techniques were developed in support of aerospace program requirements: shipping containers, alignment cables for precision mechanisms, isolation of small components such as relays and flight instruments, isolation for heavy flight equipment, coupling devices, universal joints, use of wire mesh to replace cable, isolation of 16-dB, 5000 lb horn, and compound damping devices to get better isolation from shock and vibration in a high steady environment.

  5. Simplified Model of Nonlinear Landau Damping

    SciTech Connect

    N. A. Yampolsky and N. J. Fisch

    2009-07-16

    The nonlinear interaction of a plasma wave with resonant electrons results in a plateau in the electron distribution function close to the phase velocity of the plasma wave. As a result, Landau damping of the plasma wave vanishes and the resonant frequency of the plasma wave downshifts. However, this simple picture is invalid when the external driving force changes the plasma wave fast enough so that the plateau cannot be fully developed. A new model to describe amplification of the plasma wave including the saturation of Landau damping and the nonlinear frequency shift is proposed. The proposed model takes into account the change of the plasma wave amplitude and describes saturation of the Landau damping rate in terms of a single fluid equation, which simplifies the description of the inherently kinetic nature of Landau damping. A proposed fluid model, incorporating these simplifications, is verified numerically using a kinetic Vlasov code.

  6. Coarse-graining Landau-Lifshitz damping

    NASA Astrophysics Data System (ADS)

    Feng, Xuebing; Visscher, P. B.

    2001-06-01

    High speed switching in magnetic materials is usually studied with the Landau-Lifshitz (LL) equation, which describes damping through a phenomenological coefficient. The results of micromagnetic calculations based on the LL equation have been observed to depend strongly on the cell size. We take a coarse-graining or renormalization-group approach to this cell size dependence: from a simulation using cell size L, we look at the dynamics of a cell of size 2L and determine an effective damping coefficient that describes the larger-scale dynamics. This can be thought of as a Green-Kubo calculation of the effective damping coefficient. In principle, this makes it possible to coarse grain from the atomic scale to determine the micromagnetic damping coefficient.

  7. Oscillation damping means for magnetically levitated systems

    DOEpatents

    Post, Richard F.

    2009-01-20

    The present invention presents a novel system and method of damping rolling, pitching, or yawing motions, or longitudinal oscillations superposed on their normal forward or backward velocity of a moving levitated system.

  8. Active damping and compensation of satellite appendages

    NASA Astrophysics Data System (ADS)

    Charon, W.; Baier, H.

    1993-10-01

    Future space missions will employ large and, for lightweight reasons, extremely flexible structures with very high performance requirements such as high pointing accuracy and stability, and high shape precision. This requires actively damping out vibrations induced by spacecraft maneuvers. The damping of the solar array vibrations is a characteristic task for such active interface devices. The example of an active interface for damping the bending vibrations of large conventional solar arrays is addressed. Other typical active components are active tube sections for damping the vibrations of large booms, and interfaces between satellite and vibrating large masts carrying high precision reflectors or measurement systems. The mechanical properties of the interfaces and the technological requirements related to their development are determined. New 'smart' materials are prominent among current concerns. Piezoelectric polymer foils bonded to structural shell surfaces, embedded thin piezoceramics plates, and embedded fiber optics sensors, as well as the implementation of materials such as memory alloys, are here addressed.

  9. Random vibrations of quadratic damping systems. [optimum damping analysis for automobile suspension system

    NASA Technical Reports Server (NTRS)

    Sireteanu, T.

    1974-01-01

    An oscillating system with quadratic damping subjected to white noise excitation is replaced by a nonlinear, statistically equivalent system for which the associated Fokker-Planck equation can be exactly solved. The mean square responses are calculated and the optimum damping coefficient is determined with respect to the minimum mean square acceleration criteria. An application of these results to the optimization of automobile suspension damping is given.

  10. RESEARCH PAPER: Foreground removal of 21 cm fluctuation with multifrequency fitting

    NASA Astrophysics Data System (ADS)

    He, Li-Ping

    2009-06-01

    The 21 centimeter (21 cm) line emission from neutral hydrogen in the intergalactic medium (IGM) at high redshifts is strongly contaminated by foreground sources such as the diffuse Galactic synchrotron emission and free-free emission from the Galaxy, as well as emission from extragalactic radio sources, thus making its observation very complicated. However, the 21 cm signal can be recovered through its structure in frequency space, as the power spectrum of the foreground contamination is expected to be smooth over a wide band in frequency space while the 21 cm fluctuations vary significantly. We use a simple polynomial fitting to reconstruct the 21 cm signal around four frequencies 50, 100, 150 and 200MHz with an especially small channel width of 20 kHz. Our calculations show that this multifrequency fitting approach can effectively recover the 21 cm signal in the frequency range 100 ~ 200 MHz. However, this method doesn't work well around 50 MHz because of the low intensity of the 21 cm signal at this frequency. We also show that the fluctuation of detector noise can be suppressed to a very low level by taking long integration times, which means that we can reach a sensitivity of approx10 mK at 150 MHz with 40 antennas in 120 hours of observations.

  11. Skewness and kurtosis as indicators of non-Gaussianity in galactic foreground maps

    NASA Astrophysics Data System (ADS)

    Ben-David, Assaf; von Hausegger, Sebastian; Jackson, Andrew D.

    2015-11-01

    Observational cosmology is entering an era in which high precision will be required in both measurement and data analysis. Accuracy, however, can only be achieved with a thorough understanding of potential sources of contamination from foreground effects. Our primary focus will be on non-Gaussian effects in foregrounds. This issue will be crucial for coming experiments to determine B-mode polarization. We propose a novel method for investigating a data set in terms of skewness and kurtosis in locally defined regions that collectively cover the entire sky. The method is demonstrated on two sky maps: (i) the SMICA map of Cosmic Microwave Background fluctuations provided by the Planck Collaboration and (ii) a version of the Haslam map at 408 MHz that describes synchrotron radiation. We find that skewness and kurtosis can be evaluated in combination to reveal local physical information. In the present case, we demonstrate that the statistical properties of both maps in small local regions are predominantly Gaussian. This result was expected for the SMICA map. It is surprising that it also applies for the Haslam map given its evident large scale non-Gaussianity. The approach described here has a generality and flexibility that should make it useful in a variety of astrophysical and cosmological contexts.

  12. Can residuals of the solar system foreground explain low multipole anomalies of the CMB?

    SciTech Connect

    Hansen, M.; Kim, J.; Frejsel, A.M.; Ramazanov, S.; Naselsky, P.; Zhao, W.; Burigana, C. E-mail: jkim@nbi.dk E-mail: sabir_ra@nbi.dk E-mail: wzhao7@nbi.ku.dk

    2012-10-01

    The low multipole anomalies of the Cosmic Microwave Background has received much attention during the last few years. It is still not ascertained whether these anomalies are indeed primordial or the result of systematics or foregrounds. An example of a foreground, which could generate some non-Gaussian and statistically anisotropic features at low multipole range, is the very symmetric Kuiper Belt in the outer solar system. In this paper, expanding upon the methods presented in [1], we investigate the contributions from the Kuiper Belt objects (KBO) to the WMAP ILC 7 map, whereby we can minimize the contrast in power between even and odd multipoles in the CMB, discussed in [2,3]. We submit our KBO de-correlated CMB signal to several tests, to analyze its validity, and find that incorporation of the KBO emission can decrease the quadrupole-octupole alignment and parity asymmetry problems, provided that the KBO signals has a non-cosmological dipole modulation, associated with the statistical anisotropy of the ILC 7 map. Additionally, we show that the amplitude of the dipole modulation, within a 2σ interval, is in agreement with the corresponding amplitudes, discussed in [4].

  13. Foreground marker controlled watershed on digital radiographic image for weld discontinuity detection

    NASA Astrophysics Data System (ADS)

    Abd Halim, Suhaila; Zahid, Akhma; Abdul Razak, Nurul Syafinaz; Ibrahim, Arsmah; Manurung, Yupiter HP; Jayes, Mohd Idris

    2013-04-01

    Radiography is one of the most common and widely used non-destructive testing (NDT) technique in inspecting weld discontinuity in welded joints. Conventionally, radiography inspector is requires to do the inspection analysis manually on weld discontinuity based on visual characteristics such as location, shape, length and density. The results can be very subjective, time consuming and inconsistent. Hence, semi-automated inspection using digital image processing and segmentation technique can be applied for weld discontinuity detection. The goal of this work is to detect the weld discontinuity on digital radiographic image using Foreground Marker Controlled Watershed. It is usually implemented in image processing because it always generates closed contour for each region in the image. In this paper, image enhancement on radiographic image is aim to remove image noise and improve image contrast. Then, marker controlled watershed with foreground markers is applied on the image to detect the discontinuity. The accuracy of the technique is evaluated using Receiver Operating Characteristic (ROC) curve. The accuracy of the technique has been compared with the ground truth and the result shows that the accuracy is 67% and area under the curve is 0.7134. The application of image processing technique in detecting weld discontinuity is able to assist radiographer to improve the inconsistent results in evaluating the radiographic image.

  14. Foregrounding the Background: Cognitive Science as the Study of Embodied Context

    NASA Astrophysics Data System (ADS)

    Scott Jordan, J.; Bai, Jiuyang; Cialdella, Vincent; Schloesser, Daniel S.

    In contemporary cognitive science, context is implicitly conceptualized as the constellation of background factors against which an object or event is treated as foreground. This approach to context is due to our ontological commitments to realism and its assertion that reality exists, as it does, independently of observers. The present chapter proposes that realism is an insufficient ontological starting point for cognitive science because it leads one to potentially accept the distinction between relative properties (e.g., weight) and intrinsic properties (e.g., mass). Many contemporary physicists and philosophers criticize this view because of its implicit assertion that intrinsic properties exist in a manner that is completely independent of context. Interestingly, alternatives to intrinsic properties often seem very much like the notion of `internal relations' espoused by late 19th- and early 20th century idealist philosophers. Wild Systems theory (Jordan, 2013) is presented as a framework for cognitive science that is consistent with such a thoroughly relational view of reality. Specifically, WST conceptualizes organisms as embodiments of context that are thoroughly, relationally embedded within the contexts they embody. Within WST, context is foregrounded instead of being treated as background, as cognitive science becomes the study of embodied contexts.

  15. Quantum damped oscillator I: Dissipation and resonances

    SciTech Connect

    Chruscinski, Dariusz

    2006-04-15

    Quantization of a damped harmonic oscillator leads to so called Bateman's dual system. The corresponding Bateman's Hamiltonian, being a self-adjoint operator, displays the discrete family of complex eigenvalues. We show that they correspond to the poles of energy eigenvectors and the corresponding resolvent operator when continued to the complex energy plane. Therefore, the corresponding generalized eigenvectors may be interpreted as resonant states which are responsible for the irreversible quantum dynamics of a damped harmonic oscillator.

  16. Effect of material damping on bone remodelling.

    PubMed

    Misra, J C; Samanta, S

    1987-01-01

    This paper considers the effect of internal material damping on the stresses, strains, and surface and internal remodelling behaviour in a section of axisymmetrical bone with a force-fitted axially oriented medullary pin. The bone response to several loading situations is modelled using visco-elastic equations. An approximate method is developed to analyse the proposed mathematical model. By considering a numerical example, the effect of material damping on the remodelling stresses is quantified. PMID:3584150

  17. Spatial versus time hysteresis in damping mechanisms

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Fabiano, R. H.; Wang, Y.; Inman, D. J.; Cudney, H., Jr.

    1988-01-01

    A description is given of continuing investigations on the task of estimating internal damping mechanisms in flexible structures. Specifically, two models for internal damping in Euler-Bernoulli beams are considered: spatial hysteresis and time hysteresis. A theoretically sound computational algorithm for estimation is described, and experimental results are discussed. It is concluded that both models perform well in the sense that they accurately predict response for the experiments conducted.

  18. Turbine blade with tuned damping structure

    SciTech Connect

    Campbell, Christian X.; Messmann, Stephen J.

    2015-09-01

    A turbine blade is provided comprising: a root; an airfoil comprising an external wall extending radially from the root and having a radially outermost portion; and a damping structure. The external wall may comprise first and second side walls joined together to define an inner cavity of the airfoil. The damping structure may be positioned within the airfoil inner cavity and coupled to the airfoil so as to define a tuned mass damper.

  19. Embedded absorbers for helicopter rotor lag damping

    NASA Astrophysics Data System (ADS)

    Byers, Lynn; Gandhi, Farhan

    2009-09-01

    Radial and chordwise damped vibration absorbers embedded in the rotor blade are compared for rotor lag damping augmentation. Results show that the radial absorber is more effective in transferring damping to the rotor blade lag mode. The chordwise absorber needs to be at a more outboard location and have a larger mass to introduce levels of lag damping comparable to that introduced by the radial absorber. The 1/rev amplitude of a chordwise absorber at the blade tip, per degree of blade lead-lag motion in forward flight, is of the order of 35% of the blade chord, and such a stroke might be difficult to accommodate. The 1/rev amplitude of a radial absorber at 70% span (having significantly lower mass than the chordwise absorber and producing comparable lag damping) is of the order of 4% of the rotor blade span. The static displacement of the radial absorber under centrifugal load needs to be limited using a frequency-dependent (high static stiffness, low dynamic stiffness) or nonlinear spring. The chordwise absorber can also undergo a large static displacement under the chordwise component of the centrifugal load if there is an offset from the feather axis, and this would again have to be limited using a strategy such as a frequency-dependent spring. Significant advantages of the radial absorber are—higher lag damping, lower absorber mass, space for absorber mass travel, and no chordwise travel of blade center of gravity reducing susceptibility to aeroelastic instability and dynamic pitch-link loads.

  20. Damping of Sound Waves in Strong Centrifugal Field

    NASA Astrophysics Data System (ADS)

    Bogovalov, S. V.; Kislov, V. A.; Tronin, I. V.

    A method for numerical calculation of the sound wave damping and dispersion law in a strong centrifugal field of the order of 106 g is considered. The damping is defined from the width of the resonance peak for different wave vectors. In the strong centrifugal field damping of the sound waves essentially exceeds the damping in the quiescent gas.