Science.gov

Sample records for gravity-driven lyman-alpha blobs

  1. [OIII] Emission and Gas Kinematics in a Lyman-alpha Blob at z ~ 3.1

    NASA Astrophysics Data System (ADS)

    McLinden, Emily; Rhoads, J. E.; Malhotra, S.; Hibon, P.; Tilvi, V.

    2013-01-01

    We present spectroscopic measurements of the [OIII] emission line from two subregions of strong Lyman-alpha emission in a radio-quiet Lyman-alpha blob (LAB). The blob under study is LAB1 at z ~ 3.1 first reported, by Steidel et al (2000). The [OIII] detections are from the two Lyman break galaxies embedded in the blob halo. We made our [OIII] measurements with LUCIFER on the 8.4m Large Binocular Telescope and NIRSPEC on 10m Keck Telescope. Comparing the redshift of the [OIII] to Lyman-alpha redshifts allows us to take a step towards understanding the kinematics of the gas in the blob. Using both LUCIFER and NIRSPEC we consistently find velocity offsets between the [OIII] and Lyman-alpha redshifts consistent with 0 km/s in both subregions studied (ranging from -43.88 ± 69.01 -- 36.58 ± 63.85 km/s). We discuss the possible implications of this result, as it could downplay the role of winds and outflows in powering the Lyman-alpha emission in this LAB, since a velocity offset between nebular emission lines and Lyman-alpha are often interpreted as evidence of large-scale outflows.

  2. Lyman Alpha Blobs in a Filament at z=2.38

    NASA Technical Reports Server (NTRS)

    Williger, G.; Francis, P.; Mushotzky, R.; Palunas, P.; Teplitz, H.; Weaver, K.; White, R.; Woodgate, B.

    2004-01-01

    Bright, extended Lyman-alpha nebulae (known as blobs) appear to be common in the densest environments at high redshift, and may be an important stage in galaxy evolution. Up to now, Chandra data have not distinguished between the possible excitation mechanisms, but suggest that we are seeing dense excitation mechanisms, but suggest that we are seeing dense intracluster gas either falling into forming galaxies (cooling flows) or being expelled into the intracluster medium, enriching it. Optical and X-ray evidence also suggests that some blobs harbor AGN. We took a 20 ksec exposure with Chandra of four Lyman-alpha blobs in a large filament at $z=2.38$, which completed the X-ray observations of all currently known blobs. We will present flux constraints for the blobs from the Chandra data and optical spectra of the field taken with the AAT+2dF (see accompanying poster by Woodgate et al.). Possible mechanisms for the extended emission of the Lyman-alpha blobs will be discussed.

  3. Gas kinematics of Lyman Alpha Blobs at z=2-3

    NASA Astrophysics Data System (ADS)

    Yang, Yujin

    2015-08-01

    High-redshift Lyman alpha nebulae (Ly-alpha "blobs", LABs) are the site of massive galaxy formation and their early interaction with the intergalactic medium. Research in the past decade has struggled to make progress on the question of what powers these huge Ly-alpha halos and whether the Ly-alpha-emitting gas is outflowing or infalling. First, I will present our optical and NIR spectroscopic observations for the Ly-alpha and the redshifted nebular emission lines such as [OII], [OIII] and Halpha. Using three independent measures --- the velocity offset between the Ly-alpha line and the nonresonant [O III] or Halpha line, the offset of stacked interstellar metal absorption lines, and the spectrally resolved [O III] line profile --- we study the kinematics of gas along the line of sight to galaxies within each blob center. All these kinematic measures show that there are only weak outflows, therefore excluding gas inflows and extreme hyper/superwinds as a source of the extended Ly-alpha emission. I will also present the first detection of molecular gas from a Ly-alpha blob and our on-going effort to characterize the physical conditions of its ISM. The large velocity gradient (LVG) modeling using PdBI observations of CO(3-2), CO(5-4), CO(7-6), CI(2-1) lines suggests that two-phase medium is required to explain the blob's CO SEDs and dust continuum.

  4. [O III] Emission and Gas Kinematics in a Lyman-alpha Blob at z ~ 3.1

    NASA Astrophysics Data System (ADS)

    McLinden, Emily M.; Malhotra, Sangeeta; Rhoads, James E.; Hibon, Pascale; Weijmans, Anne-Marie; Tilvi, Vithal

    2013-04-01

    We present spectroscopic measurements of the [O III] emission line from two subregions of strong Lyα emission in a radio-quiet Lyman-alpha blob (LAB). The blob under study is LAB1 at z ~ 3.1, and the [O III] detections are from the two Lyman break galaxies (LBGs) embedded in the blob halo. The [O III] measurements were made with LUCIFER on the 8.4 m Large Binocular Telescope and NIRSPEC on 10 m Keck Telescope. Comparing the redshift of the [O III] measurements to Lyα redshifts from SAURON allows us to take a step toward understanding the kinematics of the gas in the blob. Using both LUCIFER and NIRSPEC we find velocity offsets between the [O III] and Lyα redshifts that are modestly negative or consistent with 0 km s-1 in both subregions studied (ranging from -72 ± 42- + 6 ± 33 km s-1). A negative offset means Lyα is blueshifted with respect to [O III] a positive offset then implies Lyα is redshifted with respect to [O III]. These results may imply that outflows are not primarily responsible for Lyman alpha escape in this LAB, since outflows are generally expected to produce a positive velocity offset. In addition, we present an [O III] line flux upper limit on a third region of LAB1, a region that is unassociated with any underlying galaxy. We find that the [O III] upper limit from the galaxy-unassociated region of the blob is at least 1.4-2.5 times fainter than the [O III] flux from one of the LBG-associated regions and has an [O III] to Lyα ratio measured at least 1.9-3.4 times smaller than the same ratio measured from one of the LBGs.

  5. [O III] EMISSION AND GAS KINEMATICS IN A LYMAN-ALPHA BLOB AT z {approx} 3.1

    SciTech Connect

    McLinden, Emily M.; Malhotra, Sangeeta; Rhoads, James E.; Hibon, Pascale; Weijmans, Anne-Marie; Tilvi, Vithal

    2013-04-10

    We present spectroscopic measurements of the [O III] emission line from two subregions of strong Ly{alpha} emission in a radio-quiet Lyman-alpha blob (LAB). The blob under study is LAB1 at z {approx} 3.1, and the [O III] detections are from the two Lyman break galaxies (LBGs) embedded in the blob halo. The [O III] measurements were made with LUCIFER on the 8.4 m Large Binocular Telescope and NIRSPEC on 10 m Keck Telescope. Comparing the redshift of the [O III] measurements to Ly{alpha} redshifts from SAURON allows us to take a step toward understanding the kinematics of the gas in the blob. Using both LUCIFER and NIRSPEC we find velocity offsets between the [O III] and Ly{alpha} redshifts that are modestly negative or consistent with 0 km s{sup -1} in both subregions studied (ranging from -72 {+-} 42- + 6 {+-} 33 km s{sup -1}). A negative offset means Ly{alpha} is blueshifted with respect to [O III] a positive offset then implies Ly{alpha} is redshifted with respect to [O III]. These results may imply that outflows are not primarily responsible for Lyman alpha escape in this LAB, since outflows are generally expected to produce a positive velocity offset. In addition, we present an [O III] line flux upper limit on a third region of LAB1, a region that is unassociated with any underlying galaxy. We find that the [O III] upper limit from the galaxy-unassociated region of the blob is at least 1.4-2.5 times fainter than the [O III] flux from one of the LBG-associated regions and has an [O III] to Ly{alpha} ratio measured at least 1.9-3.4 times smaller than the same ratio measured from one of the LBGs.

  6. ALMA observations of a z ≈ 3.1 protocluster: star formation from active galactic nuclei and Lyman-alpha blobs in an overdense environment

    NASA Astrophysics Data System (ADS)

    Alexander, D. M.; Simpson, J. M.; Harrison, C. M.; Mullaney, J. R.; Smail, I.; Geach, J. E.; Hickox, R. C.; Hine, N. K.; Karim, A.; Kubo, M.; Lehmer, B. D.; Matsuda, Y.; Rosario, D. J.; Stanley, F.; Swinbank, A. M.; Umehata, H.; Yamada, T.

    2016-09-01

    We exploit Atacama Large Interferometer Array (ALMA) 870 μm observations to measure the star formation rates (SFRs) of eight X-ray detected active galactic nuclei (AGNs) in a z ≈ 3.1 protocluster, four of which reside in extended Lyα haloes (often termed Lyman-alpha blobs: LABs). Three of the AGNs are detected by ALMA and have implied SFRs of ≈220-410 M⊙ yr-1; the non-detection of the other five AGNs places SFR upper limits of ≲210 M⊙ yr-1. The mean SFR of the protocluster AGNs (≈110-210 M⊙ yr-1) is consistent (within a factor of ≈0.7-2.3) with that found for co-eval AGNs in the field, implying that the galaxy growth is not significantly accelerated in these systems. However, when also considering ALMA data from the literature, we find evidence for elevated mean SFRs (up-to a factor of ≈5.9 over the field) for AGNs at the protocluster core, indicating that galaxy growth is significantly accelerated in the central regions of the protocluster. We also show that all of the four protocluster LABs are associated with an ALMA counterpart within the extent of their Lyα emission. The SFRs of the ALMA sources within the LABs (≈150-410 M⊙ yr-1) are consistent with those expected for co-eval massive star-forming galaxies in the field. Furthermore, the two giant LABs (with physical extents of ≳100 kpc) do not host more luminous star formation than the smaller LABs, despite being an order of magnitude brighter in Lyα emission. We use these results to discuss star formation as the power source of LABs.

  7. The Lyman alpha coronagraph

    NASA Technical Reports Server (NTRS)

    Kohl, J. L.; Reeves, E. M.; Kirkham, B.

    1977-01-01

    The rocket-borne Lyman alpha coronagraph (RLAC) is to be used in the absence of a natural solar eclipse to determine coronal temperatures from measurements of the line width of Lyman-alpha and to determine neutral hydrogen densities of coronal material from the absolute intensity. The coronagraph consists of a 75-cm Fastie-Ebert scanning spectrometer with an AMR 641 photoelectric detection system, an off-axis parabolic primary mirror, and an occulting system. A special optical arrangement achieves rejection of radiation from the solar disk.

  8. Modeling Solar Lyman Alpha Irradiance

    NASA Technical Reports Server (NTRS)

    Pap, J.; Hudson, H. S.; Rottman, G. J.; Willson, R. C.; Donnelly, R. F.; London, J.

    1990-01-01

    Solar Lyman alpha irradiance is estimated from various solar indices using linear regression analyses. Models developed with multiple linear regression analysis, including daily values and 81-day running means of solar indices, predict reasonably well both the short- and long-term variations observed in Lyman alpha. It is shown that the full disk equivalent width of the He line at 1083 nm offers the best proxy for Lyman alpha, and that the total irradiance corrected for sunspot effect also has a high correlation with Lyman alpha.

  9. A New Population of High-z, Dusty Lyman-alpha Emitters and Blobs Discovered by WISE: Feedback Caught in the Act?

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

    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(exp -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(exp 13)-10(exp 14) Solar L) 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.

  10. Lyman alpha airglow observations from SORCE SOLSTICE

    NASA Astrophysics Data System (ADS)

    Dolinar, E.; Snow, M.; Holsclaw, G.; Thomas, G. E.; Woods, T. N.

    2010-12-01

    The Solar Stellar Irradiance Comparison Experiment (SOLSTICE) instrument on board the Solar Radiation Climate Experiment (SORCE) spacecraft in low Earth orbit observes stars every orbit for in-flight calibration. It also observes several star-free regions of the sky near the wavelength of Lyman alpha to correct for airglow emission in the stellar measurements. Although the airglow measurements are only taken during the eclipse portion of the orbit, the look directions cover nearly the entire anti-sunward hemisphere. This seven-year record of Lyman alpha airglow observations (2003-2010) shows the response of the Hydrogen geocorona to changes in the solar Lyman alpha irradiance over the solar cycle.

  11. Lyman Alpha Spicule Observatory (LASO)

    NASA Technical Reports Server (NTRS)

    Chamberlin, Phillip C.

    2011-01-01

    The Lyman Alpha Spicule Observatory (LASO) sounding rocket will observe smallscale eruptive events called "Rapid Blue-shifted Events" (RBEs) [Rouppe van der Voort et al., 2009], the on-disk equivalent of Type-II spicules, and extend observations that explore their role in the solar coronal heating problem [De Pontieu et al., 2011]. LASO utilizes a new and novel optical design to simultaneously observe two spatial dimensions at 4.2" spatial resolution (2.1" pixels) over a 2'x2' field of view with high spectral resolution of 66mAngstroms (33mAngstroms pixels) across a broad 20Angstrom spectral window. This spectral window contains three strong chromospheric and transition region emissions and is centered on the strong Hydrogen Lyman-a emission at 1216Angstroms. This instrument makes it possible to obtain new data crucial to the physical understanding of these phenomena and their role in the overall energy and momentum balance from the upper chromosphere to lower corona. LASO was submitted March 2011 in response to the ROSES SHP-LCAS call.

  12. Lyman Alpha Spicule Observatory (LASO)

    NASA Astrophysics Data System (ADS)

    Chamberlin, Phillip C.; Allred, J.; Airapetian, V.; Gong, Q.; Fontenla, J.; McIntosh, S.; de Pontieu, B.

    2011-05-01

    The Lyman Alpha Spicule Observatory (LASO) sounding rocket will observe small-scale eruptive events called "Rapid Blue-shifted Events” (RBEs), the on-disk equivalent of Type-II spicules, and extend observations that explore their role in the solar coronal heating problem. LASO utilizes a new and novel optical design to simultaneously observe two spatial dimensions at 4.2" spatial resolution (2.1” pixels) over a 2'x2' field of view with high spectral resolution of 66mÅ (33mÅ pixels) across a broad 20Å spectral window. This spectral window contains three strong chromospheric and transition region emissions and is centered on the strong Hydrogen Lyman-α emission at 1216Å. This instrument makes it possible to obtain new data crucial to the physical understanding of these phenomena and their role in the overall energy and momentum balance from the upper chromosphere to lower corona. LASO was submitted March 2011 in response to the ROSES SHP-LCAS call.

  13. Lyman Alpha Spicule Observatory (LASO)

    NASA Astrophysics Data System (ADS)

    Chamberlin, P. C.; Allred, J. C.; Airapetian, V.; Gong, Q.; Mcintosh, S. W.; De Pontieu, B.; Fontenla, J. M.

    2011-12-01

    The Lyman Alpha Spicule Observatory (LASO) sounding rocket will observe small-scale eruptive events called "Rapid Blue-shifted Events" (RBEs) [Rouppe van der Voort et al., 2009], the on-disk equivalent of Type-II spicules, and extend observations that explore their role in the solar coronal heating problem [De Pontieu et al., 2011]. LASO utilizes a new and novel optical design to simultaneously observe two spatial dimensions at 4.2" spatial resolution (2.1" pixels) over a 2'x2' field of view with high spectral resolution of 66mÅ (33mÅ pixels) across a broad 20Å spectral window. This spectral window contains three strong chromospheric and transition region emissions and is centered on the strong Hydrogen Lyman-α emission at 1216Å. This instrument makes it possible to obtain new data crucial to the physical understanding of these phenomena and their role in the overall energy and momentum balance from the upper chromosphere to lower corona. LASO was submitted March 2011 in response to the ROSES SHP-LCAS call.

  14. Lyman-alpha imagery of Comet Kohoutek

    NASA Technical Reports Server (NTRS)

    Carruthers, G. R.; Opal, C. B.; Page, T. L.; Meier, R. R.; Prinz, D. K.

    1974-01-01

    Electrographic imagery of Comet Kohoutek in the 1100-1500 A wavelength range was obtained from a sounding rocket on Jan. 8, 1974, and from the Skylab space station on 13 occasions between Nov. 26, 1973 and Feb. 2, 1974. These images are predominantly due to Lyman-alpha (1216 A) emission from the hydrogen coma of the comet. The rocket pictures have been calibrated for absolute sensitivity and a hydrogen production rate has been determined. However, the Skylab camera suffered degradation of its sensitivity during the mission, and its absolute sensitivity for each observation can only be estimated by comparison of the comet images with those taken by the rocket camera, with imagery of the geocoronal Lyman-alpha glow, of the moon in reflected Lyman-alpha, and of ultraviolet-bright stars. The rocket and geocoronal comparisons are used to derive a preliminary, qualitative history of the development of the cometary hydrogen coma and the associated hydrogen production rate.

  15. Shedding Lyman Alpha Light on Cosmological Reionization

    NASA Astrophysics Data System (ADS)

    Rhoads, James E.; Malhotra, Sangeeta; Ammons, S. Mark; Dressler, Alan; Gonzalez, Alicia; Finkelstein, Steven; Hibon, Pascale; Jiang, Tianxing; Lee, Janice; Mobasher, Bahram; Monson, Andy; Persson, S. Eric; Probst, Ronald; Swaters, Rob; Tilvi, Vithal S.; Veilleux, Sylvain; Wang, Junxian; Zabludoff, Ann; Zheng, Zhenya

    2015-08-01

    Lyman alpha photons are a powerful tool for studying reionization. They interact strongly with neutral hydrogen, so that neutral intergalactic gas acts to hide Lyman alpha light from our instruments. I will discuss two ongoing narrowband surveys to study the Epoch of Reionization. The Deep And Wide Narrowband (DAWN) survey is a 40 night NOAO survey program to look for Lyman alpha emission at redshift 7.7, using the NEWFIRM camera on the 4m Mayall Telescope at Kitt Peak National Observatory. The First Light And Reionization Experiment (FLARE) is pursuing a corresponding survey at redshift 8.8, using the FourStar camera on the Magellan telescope. Both surveys are motivated by the application of Lyman alpha lines to the study of reionization. Reionization marked the first global impact that gravitationally bound objects (stars and/or black holes) had on the universe around them, and also the last time that most hydrogen atoms did anything noteworthy. I will present results from both the DAWN and FLARE surveys, which have identified candidate galaxies near redshifts 7.7 and 8.8 in multiple fields.

  16. Lyman Alpha Photochemistry in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Fegley, Bruce, Jr.

    1997-01-01

    The purpose of the project "Lyman Alpha Photochemistry in the Solar Nebula" was to model photochemistry in the primitive solar nebula and the early solar systems. As part of the modeling, it was necessary to model the composition of the gas and dust accreted by the solar nebula. This final report contains a list of publications where the results of this project have been published.

  17. Lyman Alpha Mapping Project (LAMP) Brightness Maps

    NASA Astrophysics Data System (ADS)

    Retherford, Kurt D.; Gladstone, G.; Stern, S.; Egan, A. F.; Miles, P. F.; Parker, J. W.; Greathouse, T. K.; Davis, M. W.; Slater, D. C.; Kaufmann, D. E.; Versteeg, M. H.; Feldman, P. D.; Hurley, D. M.; Pryor, W. R.; Hendrix, A. R.

    2010-10-01

    The Lyman Alpha Mapping Project (LAMP) is an ultraviolet (UV) spectrograph on the Lunar Reconnaissance Orbiter (LRO) that is designed to map the lunar albedo at far-UV wavelengths. LAMP primarily measures interplanetary Hydrogen Lyman-alpha sky-glow and far-UV starlight reflected from the night-side lunar surface, including permanently shadowed regions (PSRs) near the poles. Dayside observations are also obtained. Brightness maps sorted by wavelength (including the Lyman-alpha wavelength of 121.6 nm) are reported for the polar regions, with a few regions of interest reported in more detail. LAMP's spectral range of 58 nm to 196 nm includes a water ice spectral feature near 160 nm, which provides a diagnostic tool for detecting water on the lunar surface that is complementary to recent discoveries using infrared and radio frequency techniques. Progress towards producing far-UV albedo maps and searching for water ice signatures will be reported. We'll discuss how LAMP data may address questions regarding how water is formed on the moon, transported through the lunar atmosphere, and deposited in the PSRs.

  18. Lyman alpha SMM/UVSP absolute calibration and geocoronal correction

    NASA Technical Reports Server (NTRS)

    Fontenla, Juan M.; Reichmann, Edwin J.

    1987-01-01

    Lyman alpha observations from the Ultraviolet Spectrometer Polarimeter (UVSP) instrument of the Solar Maximum Mission (SMM) spacecraft were analyzed and provide instrumental calibration details. Specific values of the instrument quantum efficiency, Lyman alpha absolute intensity, and correction for geocoronal absorption are presented.

  19. Variations in solar Lyman alpha irradiance on short time scales

    NASA Technical Reports Server (NTRS)

    Pap, J. M.

    1992-01-01

    Variations in solar UV irradiance at Lyman alpha are studied on short time scales (from days to months) after removing the long-term changes over the solar cycle. The SME/Lyman alpha irradiance is estimated from various solar indices using linear regression analysis. In order to study the nonlinear effects, Lyman alpha irradiance is modeled with a 5th-degree polynomial as well. It is shown that the full-disk equivalent width of the He line at 1083 nm, which is used as a proxy for the plages and active network, can best reproduce the changes observed in Lyman alpha. Approximately 72 percent of the solar-activity-related changes in Lyman alpha irradiance arise from plages and the network. The network contribution is estimated by the correlation analysis to be about 19 percent. It is shown that significant variability remains in Lyman alpha irradiance, with periods around 300, 27, and 13.5d, which is not explained by the solar activity indices. It is shown that the nonlinear effects cannot account for a significant part of the unexplained variation in Lyman alpha irradiance. Therefore, additional events (e.g., large-scale motions and/or a systematic difference in the area and intensity of the plages and network observed in the lines of Ca-K, He 1083, and Lyman alpha) may explain the discrepancies found between the observed and estimated irradiance values.

  20. 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.

  1. EUVL mask inspection at Hydrogen Lyman Alpha

    NASA Astrophysics Data System (ADS)

    Jota, Thiago S.; Milster, Tom D.

    2012-11-01

    Mask inspection is an outstanding challenge for Extreme Ultra-Violet Lithography (EUVL). The purpose of this investigation is to compare imaging characteristics of ArF and KrF inspection sources to imaging characteristics using a source at the Lyman-alpha line of Hydrogen at 121.6nm (HLA). HLA provides a raw resolution improvement of 37% to ArF and 51% to KrF, based on proportional wavelength scaling. The HLA wavelength is in an atmospheric transmission window, so a vacuum environment is not required. Our comparison uses rigorous vector imaging techniques to simulate partially coherent illumination schemes and reasonably accurate mask material properties and dimensions. Contrast is evaluated for representative spatial frequencies. Imaging and detection of defects are also considered with NILS and MEEF. The goal is high throughput inspection with maximum resolution, contrast, and sensitivity.

  2. A model for the disc Lyman alpha emission of Uranus

    SciTech Connect

    Jaffel, L.B.; Vidal-Madjar, A. ); Prange, R.; Emerich, C. ); McConnell, J.C. )

    1991-06-01

    A new efficient radiative transfer algorithm for inhomogeneous atmospheres has been used to simulate the limb to limb Lyman {alpha} reflectivities observed with the Voyager ultraviolet spectrometer during the flyby of Uranus. It was shown that complete frequency redistribution should be adequate to describe the disc emissions. The model atmosphere used was derived using a combination of Voyager measurements and modeling. Atomic H densities calculated had sources derivable directly from solar FUV and EUV fluxes. To fit the observations, four contributions are evaluated: (1) the resonance scattering of solar Lyman {alpha} radiation, (2) Rayleigh-Raman scattering of solar Lyman {alpha} radiation, (3) the resonance scattering of interplanetary Lyman {alpha} radiation, and (4) a possible internal source of unknown origin. From comparison with the observations, and provided that the published Voyager calibrations are correct, it is shown that only atmospheres with low eddy diffusion coefficients (K{sub H}{le}100 cm{sup 2} s{sup {minus}1}) and an internal source could simulate both the shape and the strength of the measured disc emission. The main results are then that the direct solar Lyman {alpha} scattering contribution (type 1 plus type 2) is of the order of 760 R, the scattering of interplanetary Lyman {alpha} contributes about 320 R, and a small additional internal source providing about 100-500 R is needed to match the measurements. Further, the analysis of the disc intensities suggests that there is no strong variation of K with latitude.

  3. Solar wind observations by Lyman alpha

    NASA Technical Reports Server (NTRS)

    Kyroelae, E.; Summanen, T.

    1995-01-01

    The interaction between the solar wind and the local interstellar matter takes place at two distinct regions. The plasma component of the interstellar matter meets the solar wind at the heliospheric interface region and it is excluded from entering into the heliosphere. The neutral component consisting mainly of the hydrogen atoms flows through the whole heliosphere. It gets, however, partly ionized by charge exchange collisions with solar wind protons and energetic photons from the Sun. The neutral atom trajectories are also affected by the radiation pressure from the Sun. While the properties of the interface region are still too sparsely known to be useful for solar wind studies the neutral H distribution near the Sun has been used successfully for this purpose. Measuring Lyman alpha light scattered by neutral hydrogen atoms can serve as a remote sensing measurement of the solar wind's three-dimensional and temporal distribution. In this work we will particularly focus on the solar cycle effects on the neutral hydrogen distribution and how it affects the solar wind monitoring.

  4. Variability of the Lyman alpha flux with solar activity

    SciTech Connect

    Lean, J.L.; Skumanich, A.

    1983-07-01

    A three-component model of the solar chromosphere, developed from ground based observations of the Ca II K chromospheric emission, is used to calculate the variability of the Lyman alpha flux between 1969 and 1980. The Lyman alpha flux at solar minimum is required in the model and is taken as 2.32 x 10/sup 11/ photons/cm/sup 2//s. This value occurred during 1975 as well as in 1976 near the commencement of solar cycle 21. The model predicts that the Lyman alpha flux increases to as much as 5 x 10/sup 11/ photons/cm/sup 2//s at the maximum of the solar cycle. The ratio of the average fluxes for December 1979 (cycle maximum) and July 1976 (cycle minimum) is 1.9. During solar maximum the 27-day solar rotation is shown to cause the Lyman alpha flux to vary by as much as 40% or as little as 5%. The model also shows that the Lyman alpha flux varies over intermediate time periods of 2 to 3 years, as well as over the 11-year sunspot cycle. We conclude that, unlike the sunspot number and the 10.7-cm radio flux, the Lyman alpha flux had a variability that was approximately the same during each of the past three cycles. Lyman alpha fluxes calculated by the model are consistent with measurements of the Lyman alpha flux made by 11 of a total of 14 rocket experiments conducted during the period 1969--1980. The model explains satisfactorily the absolute magnitude, long-term trends, and the cycle variability seen in the Lyman alpha irradiances by the OSO 5 satellite experiment. The 27-day variability observed by the AE-E satellite experiment is well reproduced. However, the magntidue of the AE-E 1 Lyman alpha irradiances are higher than the model calculations by between 40% and 80%. We suggest that the assumed calibration of the AE-E irradiances is in error.

  5. THE LYMAN ALPHA REFERENCE SAMPLE: EXTENDED LYMAN ALPHA HALOS PRODUCED AT LOW DUST CONTENT

    SciTech Connect

    Hayes, Matthew; Oestlin, Goeran; Duval, Florent; Guaita, Lucia; Melinder, Jens; Sandberg, Andreas; Schaerer, Daniel; Verhamme, Anne; Orlitova, Ivana; Mas-Hesse, J. Miguel; Oti-Floranes, Hector; Adamo, Angela; Atek, Hakim; Cannon, John M.; Herenz, E. Christian; Kunth, Daniel; Laursen, Peter

    2013-03-10

    We report on new imaging observations of the Lyman alpha emission line (Ly{alpha}), performed with the Hubble Space Telescope, that comprise the backbone of the Lyman alpha Reference Sample. We present images of 14 starburst galaxies at redshifts 0.028 < z < 0.18 in continuum-subtracted Ly{alpha}, H{alpha}, and the far ultraviolet continuum. We show that Ly{alpha} is emitted on scales that systematically exceed those of the massive stellar population and recombination nebulae: as measured by the Petrosian 20% radius, R{sub P20}, Ly{alpha} radii are larger than those of H{alpha} by factors ranging from 1 to 3.6, with an average of 2.4. The average ratio of Ly{alpha}-to-FUV radii is 2.9. This suggests that much of the Ly{alpha} light is pushed to large radii by resonance scattering. Defining the Relative Petrosian Extension of Ly{alpha} compared to H{alpha}, {xi}{sub Ly{alpha}} = R {sup Ly{alpha}}{sub P20}/R {sup H{alpha}}{sub P20}, we find {xi}{sub Ly{alpha}} to be uncorrelated with total Ly{alpha} luminosity. However, {xi}{sub Ly{alpha}} is strongly correlated with quantities that scale with dust content, in the sense that a low dust abundance is a necessary requirement (although not the only one) in order to spread Ly{alpha} photons throughout the interstellar medium and drive a large extended Ly{alpha} halo.

  6. Stellar lyman alpha emission and the local interstellar medium

    NASA Technical Reports Server (NTRS)

    Simon, Theodore

    1992-01-01

    Under the auspices of this ADP program, a systematic study was made of IUE archival images in order to extract spectra of the Lyman alpha region and to measure the stellar Lyman alpha flux for as many late-type stars as possible. The Lyman alpha resonance line is a powerful cooling channel for the hot chromospheres of solar-type stars, but has not been studied before in any systematic fashion across the H-R diagram. A major deterrent which has limited the use of Lyman alpha in the study of stellar chromospheres is the contamination of this spectral feature caused by the scattering of solar Lyman alpha photons in the Earth's exosphere. This scattered light is monochromatically imaged through the entrance slot of the IUE telescope and is superposed onto the stellar spectrum. In all but the shortest exposures with IUE, this 'geocoronal emission' overwhelms the stellar flux and makes it impossible to directly measure the strength of the stellar chromospheric feature. The IUESIPS processing contains no provision for correcting standard G.O. output products for this contamination. The first task was to develop a scheme for removing the geocoronal flux, specifically from low-dispersion spectra taken with the Short-Wavelength Camera of IUE. The strategy adopted was to fit a 'sky model' to the spatially-resolved geocoronal emission observed through the large science aperture of the telescope, using the spectral orders on either side of the central ones where the stellar emission is concentrated. The model emission was then subtracted from the observed image, leaving behind the corrected stellar Lyman alpha emission. The details of this fitting procedure are described. Having devised a successful method for removing the unwanted geocoronal emission, the correction procedure was applied to 366 archival images which, from inspection of the photowrites in the IUE browse file, seemed especially promising. In this survey, Lyman alpha emission were eventually detected in the

  7. Skylab observations of H I Lyman-alpha

    NASA Technical Reports Server (NTRS)

    Roussel-Dupre, D.

    1982-01-01

    The H I Lyman-alpha profiles obtained with the Skylab SO82-B spectrograph at spectral and spatial resolutions of 60 mA and 2 arcsec x 60 arcsec are presented. Profile variations are illustrated from center to limb, at different heights above the limb, and over a cell and network boundary. The Lyman-alpha core exhibits weak or no limb darkening, whereas the line wings show weak limb darkening. Above the limb, the Lyman-alpha core integrated intensity and line width remain in essence constant up to plus 12 arcsec and may result from resonance scattering of chromospheric radiation by coronal neutral hydrogen or from spicules. On the disk, intensities in the line core are seen as correlating well with the H-alpha network; however, the Lyman-alpha wing intensities are found to correlate better with the transition region lines. The average of profiles acquired over the cell and network region is found to be similar to profiles obtained in the cell.

  8. Variability of Lyman-alpha emission from Jupiter

    NASA Technical Reports Server (NTRS)

    Cochran, W. D.; Barker, E. S.

    1979-01-01

    The Jovian Lyman-alpha emission line was reobserved in 1978 March using the high-resolution spectrometer of the Copernicus satellite. An intensity of 8.3 plus or minus 2.9 kilorayleighs was measured. This value represents a significant increase in intensity over previous (1976) Copernicus observations, but is lower than the recent (1979) values obtained by Voyager 1 and IUE. The increase in intensity has been accompanied by a significant increase in line width giving strong support to the theory that the emission results from resonant scattering of the solar Lyman-alpha line by H atoms in the upper Jovian atmossphere. The strength of Jovian Lyman-alpha emission correlates well with the level of solar activity. The solar extreme ultraviolet radiation varies with the solar cycle. This radiation causes the dissociation of H2 and CH4 into H atoms in the Jovian atmosphere. Therefore, in times of high solar activity, the H column density will increase, causing the observed strong Jovian Lyman-alpha emission.

  9. Redistribution of radiation for the wings of Lyman-alpha

    NASA Technical Reports Server (NTRS)

    Yelnik, J.-B.; Burnett, K.; Cooper, J.; Ballagh, R. J.; Voslamber, D.

    1981-01-01

    Earlier work on redistribution of radiation by collisions for isolated lines is extended to overlapping lines, and an explicit expression for the frequency redistribution is given for Lyman-alpha. This expression is valid, even when the emitted photon is in the (non-impact) line wings. A simple physical explanation of the result is possible.

  10. Lyman Alpha Line Profile Observations from SORCE SOLSTICE

    NASA Astrophysics Data System (ADS)

    Snow, M. A.; Machol, J. L.; Woods, T. N.; Quemerais, E.; Gruyer, J.

    2015-12-01

    The SOLar-STellar Irradiance Comparison Experiment (SOLSTICE) on the SOlar Radiation and Climate Experiment (SORCE) makes daily measurements of the solar Lyman alpha profile with 0.1 nm spectral resolution. We will present analysis on how the shape of the line evolves over the solar cycle. For comparison, we have convolved observations from SUMER/SOHO with the SOLSTICE profile.

  11. Lyman-alpha observations of Comet West /1975n/

    NASA Technical Reports Server (NTRS)

    Opal, C. B.; Carruthers, G. R.

    1977-01-01

    The rate of hydrogen production of Comet West is studied through rocket observation of solar Lyman-alpha radiation resonantly scattered by the escaping hydrogen atoms. Two sets of Lyman-alpha exposure sequences are used to obtain computer-smoothed brightness contour (isophote) maps covering a density range of 100:1. A simple radial outflow model is applied to the contour maps to determine the rate of hydrogen production (3.2 by 10 to the 30th power atoms/sec.) Discrepancies between the observed shape of the outer isophotes and predicted models may be explained by optical depth effects, or by the presence of small pieces of the comet's nucleus distributed along the orbit. Hydrogen, carbon, and oxygen production for Comet West and Comet Kohoutek are compared; differences may be accounted for by variations in the composition or evolution of the two comets.

  12. New interpretations of extraterrestrial Lyman-alpha observations.

    NASA Technical Reports Server (NTRS)

    Blum, P. W.; Fahr, H. J.

    1972-01-01

    The solar Lyman-alpha radiation pressure affects the orbits and the velocities of the interstellar particles entering the solar system. This leads to enhanced particle losses in the heliosphere, since particles spend a longer time crossing it. This causes a stronger decrease of the density with decreasing distances from the sun than had been calculated without accounting for the radiation pressure. Furthermore, the emission pattern of the solar Lyman-alpha radiation is anisotropic and rotates with the sun in a 27-day period. This causes a temporal change in the location of the intensity extrema. At the same time it produces hydrogen density anisotropies with extrema deviating in their directions from those which had been calculated without consideration of the radiation pressure.

  13. The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)

    NASA Technical Reports Server (NTRS)

    Ishikawa, Shin-nosuke; Kano, R.; Kobayashi, K.; Bando, T.; Narukage, N..; Ishikawa, R.; Kubo, M.; Katsukawa, Y.; Suematsu, Y.; Hara, H.; Shimizu, T.; Sakao, T.; Ichimoto, K.; Giono, G.; Holloway, T.; Winebarger, A.; Cirtain, J.; DePontieu, B.; Casini, R.; Auchere F.; Bueno, J. Trujillo; Sainz, R. Manso; Belluzzi, L.; Ramos, A. Asensio; Stepan, J.; Carlsson, M.

    2014-01-01

    To Understand energy release process in the Sun including solar flares, it is essentially important to measure the magnetic field of the atmosphere of the Sun. Magnetic field measurement of the upper layers (upper chromosphere and above) was technically difficult and not well investigated yet. Upper chromosphere and transition region magnetic field measurement by Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) sounding rocket to be launched in 2015. The proposal is already selected and developments of the flight components are going.

  14. Photoelectron Emission and Lyman Alpha Measurements by the CHAMPS Rockets

    NASA Astrophysics Data System (ADS)

    Sternovsky, Z.; Robertson, S. H.; Dickson, S.; Gausa, M. A.; Friedrich, M.; Horanyi, M.

    2012-12-01

    The daytime CHAMPS (CHarge And mass of Meteoritic smoke ParticleS) sounding rocket carried a suit of instruments for the monitoring of photoemission current and Lyman alpha flux as a function of altitude. The results show that photoemission is significant down to 60-75 km altitude, depending on the photo-emitting surface. Lyman alpha was detected to about 65 km altitude. The daytime CHAMPS rocket launched on 13 October 13:50 UT from the Andøya Rocket Range, Norway. The CHAMPS instruments detected layers of particles, probably of meteoric origin, charged both positive and negative in the 63-93 km altitude range. The CHAMPS payloads were also designed to characterize the plasma environment and thus also carried Faraday rotation antennas and electron and ion probes. Solar UV plays an important role in charge balance for both the rocket body and meteoric smoke particles. Photoelectron emission was monitored by a set of three detectors consisting of an emitting surface (Platinum, Aluminum and Zirconium) biased at -10 V and placed behind a fine grid. The Al and Zr surfaces produced similar signals with photoemission measureable above 75 km altitude. The Pt surface emitted photoelectrons even below 60 km altitude. The different behavior of Pt can possibly be due to exposure to atomic oxygen, though further analysis is necessary. The solar Lyman alpha radiation was measured by a UV photodiode placed behind a pair or filters to reduce the contribution to the signal from visible light. Lyman alpha was detected down to 65 km altitude, which confirms that photo-detachment and photoelectric charging needs to be considered for the charge balance of particle layers in the mesosphere region. All instruments were calibrated at the facilities of the Laboratory for Atmospheric and Space Physics at the University of Colorado.

  15. Zenith angle dependence of the geocoronal Lyman-alpha glow.

    NASA Technical Reports Server (NTRS)

    Paresce, F.; Kumar, S.; Bowyer, S.

    1972-01-01

    Review of the observations made on the zenith angle dependence and intensity of the geocoronal hydrogen Lyman-alpha glow by means of one of four extreme ultraviolet photometers flown to an altitude of 264 km on a Nike Tomahawk rocket launched from Thumba, India, in March 1970. The results obtained are compared with Meier and Mange's (1970) theoretical predictions. The possible causes for the discrepancies found are discussed.

  16. Lyman alpha solar spectral irradiance line profile observations and models

    NASA Astrophysics Data System (ADS)

    Snow, Martin; Machol, Janet; Quemerais, Eric; Curdt, Werner; Kretschmar, Matthieu; Haberreiter, Margit

    2016-04-01

    Solar lyman alpha solar spectral irradiance measurements are available on a daily basis, but only the 1-nm integrated flux is typically published. The International Space Science Institute (ISSI) in Bern, Switzerland has sponsored a team to make higher spectral resolution data available to the community. Using a combination of SORCE/SOLSTICE and SOHO/SUMER observations plus empirical and semi-empirical modeling, we will produce a dataset of the line profile. Our poster will describe progress towards this goal.

  17. Dynamical and Stellar Masses of Lyman-alpha Galaxies

    NASA Astrophysics Data System (ADS)

    Rhoads, James E.; Malhotra, S.; McLinden, E.; Richardson, M. L.; Finkelstein, S. L.; Tilvi, V. S.

    2012-01-01

    We have observed strong nebular lines of [OIII] and H alpha for Lyman-alpha galaxies at z=2-3.1 using Keck+NIRSPEC, LBT+LUCIFER, and Gemini+NIFS. [OIII] 5007 is strong enough to dominate the 2 micron K band fluxes of these galaxies, and leads to an overestimate of the stellar mass of the galaxy by an order of magnitude. After correcting for the observed [OIII] lines, we infer low masses and young ages for these galaxies. We also use the physical widths of the rest-optical lines, combined with spatial sizes from HST imaging, to obtain direct dynamical mass estimates of Lyman alpha galaxies (which cannot be done using the resonantly scattered Lyman alpha line). Finally, we combine our stellar mass estimates and line widths to place these galaxies on the baryonic Tully-Fisher relation. We find that the stellar masses required to reproduce the observed light are lower than one would expect based on the galaxies' line widths. The stellar mass densities of these galaxies are comparable to those of elliptical galaxies today. We gratefully acknowledge support from NSF grant NSF-AST-0808165.

  18. The Lyman-alpha Imager onboard Solar Polar Orbit Telescope

    NASA Astrophysics Data System (ADS)

    Li, Baoquan; Li, Haitao; Zhou, Sizhong; Jiang, Bo

    2013-12-01

    Solar Polar ORbit Telescope (SPORT) was originally proposed in 2004 by the National Space Science Center, Chinese Academy of Sciences, which is currently being under background engineering study phase in China. SPORT will carry a suite of remote-sensing and in-situ instruments to observe coronal mass ejections (CMEs), solar high-latitude magnetism, and the fast solar wind from a polar orbit around the Sun. The Lyman-alpha Imager (LMI) is one of the key remotesensing instruments onboard SPORT with 45arcmin FOV, 2000mm effective focal length and 1.4arcsec/pixel spatial resolution . The size of LMI is φ150×1000mm, and the weight is less than10kg, including the 7kg telescope tube and 3kg electronic box. There are three 121.6nm filters used in the LMI optical path, so the 98% spectral purity image of 121.6nm can be achieved. The 121.6nm solar Lyman-alpha line is produced in the chromosphere and very sensitive to plasma temperature, plasma velocity and magnetism variation in the chromosphere. Solar Lyman-alpha disk image is an ideal tracker for corona magnetism variation.

  19. Analysis of solar Lyman alpha radiation in the heliosphere

    NASA Astrophysics Data System (ADS)

    Fayock, B.; Zank, G. P.; Heerikhuisen, J.

    2013-06-01

    Various NASA spacecraft have measured ultraviolet radiation in the heliosphere at different locations over time. Much of this data corresponds to back-scattered Lyman-alpha radiation from neutral hydrogen, particularly in the context of planetary atmospheric measurements and inferred solar activity. Less attention has been devoted to using this data in the context of large-scale heliospheric simulations with complex global models. A 3D Monte Carlo simulation has been developed for analysis of Lyman-alpha scattering using global heliospheric models developed within CSPAR as a background. The simulation tracks individual photons in a sun-centered spherical coordinate system with a radial limit of 1000 AU while retaining statistics for each cell within the grid space, which is defined by the global input data. Two of the statistics collected are the number of scatters and the total distance traveled by photons within a cell. Those photons directed towards the sun provide a measure of backscatter intensity that can be compared to antisolar observations of Lyman-alpha photons by spacecraft. Preliminary results reveal a similar trend of intensity between simulation in the upwind direction and reduced Voyager data, suggesting an accurate portrayal of neutral hydrogen in the heliosphere.

  20. Lyman alpha initiated winds in late-type stars

    NASA Technical Reports Server (NTRS)

    Haisch, B. M.; Van Der Hucht, K. A.; Linsky, J. L.

    1979-01-01

    One of the first major results of the IUE survey of late-type stars was the discovery of a sharp division in the HR diagram between stars with solar type spectra (chromosphere and transition region lines) and those with non-solar type spectra (only chromosphere lines). This result is especially interesting in view of observational evidence for mass loss from G and K giants and super-giants discussed recently by both Reimers and Stencel. In the present paper models of both hot coronae and cool wind flows are calculated using stellar model chromospheres as starting points for stellar wind calculations in order to investigate the possibility of having a 'supersonic transition locus' in the HR diagram dividing hot coronae from cool winds. It is concluded from these models that the Lyman-alpha flux may play an important role in determining the location of a stellar wind critical point. The interaction of Lyman-alpha radiation pressure with Alfven waves in producing strong, low temperature stellar winds in the star Arcturus is investigated.

  1. Weighing the Low-Redshift Lyman-alpha Forest

    NASA Technical Reports Server (NTRS)

    Shull, Mike

    2005-01-01

    In 2003-2004, our FUSE research group prepared several major surveys of the amount of baryonic matter in the intergalactic medium (IGM), using the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. These surveys include measurements of the Lyman-alpha absorption line of neutral hydrogen (H I), the far-ultraviolet (1032,1038 Angstrom) doublet of highly ionized oxygen ( O VI), the higher Lyman-series lines (Ly-beta, Ly-gamma, etc) of H I, and the 977 Angstrom line of c III. As an overview, our FUSE spectroscopic studies, taken together with data from the Hubble Space Telescope, show that approximately 30% of the normal matter is contained in intergalactic hydrogen gas clouds (the Lyman-alpha forest). Another 5-10% resides in hotter gas at temperatures of 10(exp 5) to 10(exp 6) K, visible in 0 VI and C III absorption. Along with the matter attributed to galaxies, we have now accounted for approximately HALF of all the baryonic matter in the universe. Where is the other half? That matter my exist in even hotter gas, invisible through the ultraviolet absorption lines, but perhaps detectable through X-ray absorption lines of more highly ionized oxygen and neon.

  2. Lyman-alpha forests cool warm dark matter

    NASA Astrophysics Data System (ADS)

    Baur, Julien; Palanque-Delabrouille, Nathalie; Yèche, Christophe; Magneville, Christophe; Viel, Matteo

    2016-08-01

    The free-streaming of keV-scale particles impacts structure growth on scales that are probed by the Lyman-alpha forest of distant quasars. Using an unprecedentedly large sample of medium-resolution QSO spectra from the ninth data release of SDSS, along with a state-of-the-art set of hydrodynamical simulations to model the Lyman-alpha forest in the non-linear regime, we issue one of the tightest bounds to date, from Ly-α data alone, on pure dark matter particles: mX>4.09 keV (95% CL) for early decoupled thermal relics such as a hypothetical gravitino, and correspondingly ms>24.4 keV (95% CL) for a non-resonantly produced right-handed neutrino. This limit depends on the value on ns, and Planck measures a higher value of ns than SDSS-III/BOSS. Our bounds thus change slightly when Ly-α data are combined with CMB data from Planck 2016. The limits shift to mX>2.96 keV (95% CL) and ms>16.0 keV (95% CL). Thanks to SDSS-III data featuring smaller uncertainties and covering a larger redshift range than SDSS-I data, our bounds confirm the most stringent results established by previous works and are further at odds with a purely non-resonantly produced sterile neutrino as dark matter.

  3. Measurement of precipitation induced FUV emission and Geocoronal Lyman Alpha from the IMI mission

    NASA Technical Reports Server (NTRS)

    Mende, Stephen B.; Fuselier, S. A.; Rairden, R. L.

    1995-01-01

    This final report describes the activities of the Lockheed Martin Palo Alto Research Laboratory in studying the measurement of ion and electron precipitation induced Far Ultra-Violet (FUV) emissions and Geocoronal Lyman Alpha for the NASA Inner Magnetospheric Imager (IMI) mission. this study examined promising techniques that may allow combining several FUV instruments that would separately measure proton aurora, electron aurora, and geocoronal Lyman alpha into a single instrument operated on a spinning spacecraft. The study consisted of two parts. First, the geocoronal Lyman alpha, proton aurora, and electron aurora emissions were modeled to determine instrument requirements. Second, several promising techniques were investigated to determine if they were suitable for use in an IMI-type mission. Among the techniques investigated were the Hydrogen gas cell for eliminating cold geocoronal Lyman alpha emissions, and a coded aperture spectrometer with sufficient resolution to separate Doppler shifted Lyman alpha components.

  4. Analysis of solar Lyman-alpha scattering in the heliosphere

    NASA Astrophysics Data System (ADS)

    Fayock, Brian

    Computational models of the global heliospheric interaction with the local interstellar medium have evolved to include very fine and complex physical details. While these models began from theory, the observations and measurements of various spacecraft have been able to provide comparisons to simulations over time, resulting in corrections, adjustments, or additions to certain aspects, and thus a better understanding of the problem. One aspect of great interest is the interaction of neutral hydrogen within the heliosphere. Its inclusion into models is quite complex and still in need of verification. The results of our model are able to provide such a verification. With an interest in neutral hydrogen, Pioneer 10, Voyager 1, and Voyager 2 can provide a relative measure of the local density of hydrogen at the location of the spacecraft by means of Lyman-alpha intensity observations. Their continuous collection of data at increasing radii has revealed trends of decreasing intensity that can be analyzed and compared with radiative transfer simulations performed on neutral hydrogen distributions resulting from the global heliospheric models. Many simulations have been developed in the past, but none has been able to provide results that match the long-term trend, until now. This thesis describes the analysis of Lyman-alpha radiation in the heliosphere by means of a new three-dimensional Monte Carlo radiative transfer technique applied to the background neutral hydrogen distribution provided by a state-of-the-art three-dimensional magnetohydrodynamic-neutral kinetic model, both of which have been developed within the Center for Space Plasma and Aeronomic Research at the University of Alabama in Huntsville. The results of backscatter intensity are compared directly to previously reduced Pioneer 10, Voyager 1, and Voyager 2 ultraviolet data sets, which describe the anti-solar intensity of Lyman-alpha radiation out to almost 50 astronomical units. The similarity between the

  5. Copernicus observations of interstellar absorption at Lyman alpha

    NASA Technical Reports Server (NTRS)

    Bohlin, R. C.

    1975-01-01

    Column densities NH of atomic hydrogen have been derived for 40 OB stars from spectral scans at Lyman alpha obtained by the Copernicus (OAO-3) satellite. The stars are all between 60 and 1100 pc away with a range of mean densities n sub H of 0.01 to 2.5 atoms cm-3. The gas to color-excess ratio in clouds varies from 1 to 3 times the mean outside of clouds. The presence of molecular hydrogen correlates with E(B-V), but the best tracer for H2 is atomic hydrogen. The mean density of the gas for all 40 stars is much smaller than the mean of 0.7 atoms cm-3 obtained from 21-cm observations, because the brightest stars with less than average amounts of matter in the line of sight were selected for observation.

  6. A model for the disc Lyman alpha emission of Uranus

    NASA Technical Reports Server (NTRS)

    Ben Jaffel, L.; Prange, R.; Emerich, C.; Vidal-Madjar, A.; Mcconnell, J. C.

    1991-01-01

    A new efficient radiative transfer algorithm for nonhomogeneous model atmospheres has been applied to the Uranian atmosphere. The contribution of the scatter solar Lyman-alpha to the Uranain emission is of the order of 300 R, and the Rayleigh contribution may reach 450 R for small values of the eddy diffusion coefficient (EDC). The total solar contribution may then reach about 750 R for a solar flux of 2.5 x 10 to the 11th photons/sq cm/s/A. A level of up to 400 R is confirmed in some directions for the interstellar wind contribution. The values of the atmospheric EDC necessary to mimic the observations are 50-100 sq cm/s. A small additional source located on the dayside Uranian atmosphere seems necessary correctly to fit the shape of the limb to limb intensity variation, especially near the limbs. Its contribution to the emergent intensity would range from 100 to 500 R.

  7. Spacelab Lyman Alpha-White Light Coronagraph Program

    NASA Technical Reports Server (NTRS)

    Kohl, J. L.

    1986-01-01

    The Spacelab Lyman Alpha Coronagraph (SLAC) of the Smithsonian Astrophysical Observatory (SAO) and the White Light Coronagraph (WLC) to be provided by the High Altitude Observatory (HAO) are two separate coronagraphs which would be operated in a joint fashion during Spacelab missions to be flown by the Space Shuttle. The two instruments would be used to perform joint observations of solar coronal structures from 1.2 to 8.0 solar radii from sun-center in vacuum ultraviolet and visible radiations. Temperatures, densities, and flow velocities throughout the solar wing acceleration region of the inner solar corona were measured. The Phase I Definition activity resulted in the successful definition and preliminary design of the experiment/instrumentation subsystem and associated software, ground support equipment and interfaces to the extended required to accurately estimate the scope of the investigation and prepare an Investigational Development Plan; the performance of the necessary functional, operations, and safety analyses necessary to complete the Experiment Requirements document.

  8. Coupling the emission of ionizing radiation and Lyman alpha

    NASA Astrophysics Data System (ADS)

    Scarlata, Claudia; Hayes, Matthew; Miller, Brendan P.; Pushnig, Johannes; Jansson, Gustav

    2016-01-01

    The class of objects that reionized the intergalactic hydrogen remains an observational and theoretical challenge. Recently, the shape of the Lyman-alpha (Lya) emission line profile has been proposed as a way to pre-select Lyman Continuum (LyC) leaking galaxies. We present results of deep spectroscopic observations obtained with the Cosmic Origin Spectrograph on the HST of a sample of 4 Lya-emitting galaxies at z~0.3, chosen to be candidate LyC leaking galaxies, on the grounds of blueshifted peaks of Lya emission/symmetric extended Lya wings. We do not detect ionizing radiation escaping from these objects, with upper 3sigma limits on the absolute escape fraction of LyC photons between 14 and 2%.

  9. Stellar Lyman-alpha emission and the local interstellar medium

    NASA Technical Reports Server (NTRS)

    Landsman, Wayne; Simon, Theodore

    1991-01-01

    The UV spectra now available in the IUE archives have been systematically searched for the presence of Lyman-alpha emission in late-type stars. The results provide the first survey of the behavior of the Ly-alpha emission line across most of the cool half of the H-R diagram. The normalized Ly-alpha emission flux is strongest in the chromospherically active RS CVn stars and in the dMe stars. The range of normalized flux values is much smaller among F-type stars than in stars of later spectral type. A dropoff appears in the flux levels of stars at B-V less than 0.30 mag. The measurements are used to search for evidence of possible high column density clouds in the local ISM. The cloud previously identified toward Alpha Oph may be seen in the reduced flux observed toward Beta Oph.

  10. Lyman-Alpha Observations of High Radial Velocity Stars

    NASA Astrophysics Data System (ADS)

    Bookbinder, Jay

    1990-12-01

    H I LYMAN -ALPHA (LY-A) IS ONE OF THE MOST IMPORTANT LINES EMITTED BY PLASMA IN THE TEMPERATURE RANGE OF 7000 TO 10 TO THE FIFTH POWER K IN LATE-TYPE STARS. IT IS A MAJOR COMPONENT OF THE TOTAL RADIATIVE LOSS RATE, AND IT PLAYS A CRUCIAL ROLE IN DETERMINING THE ATMOSPHERIC STRUCTURE AND IN FLUORESCING OTHER UV LINES. YET IT IS ALSO THE LEAST STUDIED MAJOR LINE IN THE FAR UV, BECAUSE MOST OF THE LINE FLUX IS ABSORBED BY THE ISM ALONG THE LINE OF SIGHT AND BECAUSE IT IS STRONGLY COMTAMINATED BY THE GEOCORONAL BACKGROUND. A KNOWLEDGE OF THE Ly-A PROFILE IS ALSO IMPORTANT FOR STUDIES OF DEUTERIUM IN THE INTERSTELLAR MEDIUM. BY OBSERVING HIGH RADIAL VELOCITY STARS WE WILL OBTAIN FOR THE FIRST TIME HIGH RESOLUTION SPECTRA OF THE CORE OF A STELLAR H I LYMAN-A EMISSION LINE PROFILE.

  11. Rotational modulation of hydrogen Lyman alpha flux from 44ii Bootis

    NASA Technical Reports Server (NTRS)

    Vilhu, O.; Neff, J. E.; Rahunen, T.

    1988-01-01

    Observations with IUE that cover the entire 6.4 hr orbital cycle of the late-type contact binary 44i Bootis are presented. Intrinsic stellar hydrogen Lyman alpha emission flux was determined from low-resolution IUE spectra, compensating for geocoronal emission and for interstellar absorption. The variation of the stellar Lyman alpha emission flux correlates well with the variation of the C II and C IV emission fluxes, and shows orbital modulation in phase with the visual light curve. The ratio of Lyman alpha to CII flux (15 to 20) is similar to that observed in solar active regions. Hydrogen Lyman alpha emission is thus one of the most important cooling channels in the outer atmosphere of 44i Boo. A high-resolution spectrum of the Lyman alpha line was obtained between orbital phases 0.0 and 0.6. The integrated flux in the observed high-resolution Lyman alpha profile is consistent with the fluxes determined using low-resolution spectra, and the composite profile indicates that both components of this binary have equally active chromospheres and transition regions. The uncertainty in the interstellar hydrogen column density cannot mimic the observed variation in the integrated Lyman alpha flux, because the stellar line is very much broader than the interstellar absorption.

  12. Io's Atmosphere Silhouetted in Transit by Jupiter Lyman-alpha

    NASA Astrophysics Data System (ADS)

    Retherford, Kurt

    2014-10-01

    Io's active volcanos both directly establish local gas plumes and indirectly establish a more global sublimation atmosphere, through plume deposited sulfur dioxide frost patches. Despite decades of study and recent observational advances the very basic question about the relative role of each of these sources is unresolved. The correlation between volcanic activity variability and Io's dramatic influence on numerous time-variable phenomenon in the Jupiter system cannot be causally linked until this answer is in hand. Our experienced team has developed a novel approach to use STIS in a new way to obtain global radial profiles of SO2 scale height distributions above both plume and sublimation dominated regions. We exploit the bright Lyman-alpha dayglow of Jupiter as a background illumination source together with the strongly absorptive nature of SO2 at 121.6 nm to image Io's atmosphere in silhouette with unprecedented detail during transit events. Our program provides the following key information for SO2: 1) First high-altitude (>400 km) radial measurements of tangential column densities and scale heights; 2) First clear measurement of sublimation densities at polar locations; 3) Volcanic densities for large and mid-sized plumes (possibly new ones); 4) Globally distributed limb profiles allowing strong distinctions between plume and sublimation dominated locations; 5) Repeated imaging on a few day and a few week timescales for improved plume variability constraints; and 6) Lyman-alpha reflectance imaging at Io central lon. ~180 deg, filling a gap in previous coverage. These new information are critical to breaking through an impasse in our understanding of Io's atmosphere.

  13. Monte Carlo treatment of Lyman-alpha radiation in a plane-parallel atmosphere.

    NASA Technical Reports Server (NTRS)

    Modali, S. B.; Brandt, J. C.; Kastner, S. O.

    1972-01-01

    A Monte Carlo technique involving Stokes vectors is used to obtain the state of polarization and intensity of solar Lyman-alpha photons as they diffuse through a plane-parallel homogeneous model of earth's hydrogen envelope. Fine structure of Lyman-alpha and Doppler redistribution of frequencies are taken into account. Comparison of the results with Heath's observed upper limit for polarization of 1.5 per cent implies an optical thickness tau greater than 7 and intensities of 8-10 kilorayleighs for a solar Lyman-alpha flux of 5.8 ergs per sq cm per sec.

  14. Analytic Lyman-alpha wing diagnostics and the chromospheric excitation balance in cool dwarfs

    NASA Technical Reports Server (NTRS)

    Gayley, K. G.

    1994-01-01

    I show that the Lyman alpha wings of cool dwarfs can be understood in terms of a very simple model, based on a simplified representation of the chromospheric hydrogen excitation balance and approximate analytic wing diagnostics in partial redistribution. Much of the complexity of the radiation transfer in the partially coherent and steeply temperature-sensitive Lyman alpha line is circumvented by this technique. The result is an expedient scheme for inverting the Lyman alpha wing profile to determine the characteristic free electron density and its gradient in the middle chromosphere. This represents an important new diagnostic for constraining chromospheric models and their radiative losses. I apply this diagnostic to the Lyman alpha wing profiles of the Sun and AU Mic and show that current instrumentation, most notably the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope, is capable of providing the necessary data.

  15. Mapping High-Velocity H-alpha and Lyman-alpha Emission from Supernova 1987A

    NASA Technical Reports Server (NTRS)

    France, Kevin; McCray, Richard; Fransson, Claes; Larsson, Josefin; Frank, Kari A.; Burrows, David N.; Challis, Peter; Kirshner, Robert P.; Chevalier, Roger A.; Garnavich, Peter; Heng, Kevin; Lawrence, Stephen S.; Lundqvist, Peter; Smith, Nathan; Sonneborn, George

    2015-01-01

    We present new Hubble Space Telescope images of high-velocity H-alpha and Lyman-alpha emission in the outer debris of SN 1987A. The H-alpha images are dominated by emission from hydrogen atoms crossing the reverse shock. For the first time we observe emission from the reverse shock surface well above and below the equatorial ring, suggesting a bipolar or conical structure perpendicular to the ring plane. Using the H-alpha imaging, we measure the mass flux of hydrogen atoms crossing the reverse shock front, in the velocity intervals (-7,500 < V(sub obs) < -2,800 km/s) and (1,000 < V(sub obs) < 7,500 km/s), ?M(sub H) = 1.2 × 10(exp -3) M/ y. We also present the first Lyman-alpha imaging of the whole remnant and new Chandra X-ray observations. Comparing the spatial distribution of the Lyman-alpha and X-ray emission, we observe that the majority of the high-velocity Lyman-alpha emission originates interior to the equatorial ring. The observed Lyman-alpha/H-alpha photon ratio, R(L-alpha/H-alpha) approx. = 17, is significantly higher than the theoretically predicted ratio of approx. = 5 for neutral atoms crossing the reverse shock front. We attribute this excess to Lyman-alpha emission produced by X-ray heating of the outer debris. The spatial orientation of the Lyman-alpha and X-ray emission suggests that X-ray heating of the outer debris is the dominant Lyman-alpha production mechanism in SN 1987A at this phase in its evolution.

  16. Copernicus measurement of the Jovian Lyman-alpha emission and its aeronomical significance

    NASA Technical Reports Server (NTRS)

    Atreya, S. K.; Kerr, R. B.; Upson, W. L., II; Festou, M. C.; Donahue, T. M.; Barker, E. S.; Cochran, W. D.; Bertaux, J. L.

    1982-01-01

    It is pointed out that the intensity of the Lyman-alpha emission is a good indicator of the principal aeronomical processes on the major planets. The high-resolution ultraviolet spectrometer aboard the Orbiting Astronomical Observatory Copernicus was used in 1980 April and May to detect the Jovian Lyman-alpha emission by spectroscopically discriminating it from other Doppler shifted Lyman-alpha emissions such as those of the geocorona, and the interplanetary medium. Taking into consideration the reported emission data, it appears that an unusually large energy input due to the particle precipitation in the auroral region must have been responsible for the large observed Lyman-alpha intensity during the Voyager encounter. At most other times, the observed Jovian Lyman-alpha intensity can be explained, within the range of statistical uncertainty, by a model that takes into consideration the solar EUV flux, the solar Lyman-alpha flux, the high exospheric temperature, and the eddy diffusion coefficient without energy input from the auroral sources.

  17. Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP)

    NASA Technical Reports Server (NTRS)

    Kano, Ryohei; Bando, Takamasa; Narukage, Noriyuki; Ishikawa, Ryoko; Kubo, Masahito; Katsukawa, Yukio; Ishikawa, Shin-­nosuke; Hara, Hirohisa; Suematsu, Yoshinori; Giono, Gabriel; Shimizu, Toshifumi; Sakao, Taro; Ichimoto, Kiyoshi; Goto, Motoshi; Winebarger, amy; Kobayashi, Ken; Trujullo Bueno, Javier; Auchere, Frederic

    2015-01-01

    Chromosphere, the transition layer of the sun is a region to switch to the magnetic pressure dominated from plasma pressure dominated, simultaneous observation of the detailed magnetic field measurement and plasma of dynamic phenomenon here is what is the frontier of the next solar physics. As This is a challenge that has just mentioned, even the next solar observation satellite plan SOLAR-C, in the experiments we had used a NASA sounding rocket for the first time in the SOLAR-C plan, will address the chromosphere-transition layer magnetic field measurement there. It is, is a Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) plan, the linear polarization of Lyman ?? emission lines chromosphere-transition layer shoots (121.6nm) were detected in 0.1 percent of high accuracy, a new technique called Hanre effect I get the magnetic field information of chromosphere-transition layer. In Japan, the US and Europe joint observation in November 2012 as a rocket experiment is adopted to NASA this plan that full-scale start-up, start from assembly work is 2014 spring flight observation device, currently, it is where the alignment of the optical elements have been implemented. After this, it is planned to continue with the performance evaluation towards the observation implementation of summer 2015. In addition to once again explain the contents of the plan In this presentation, we report an overview of the entire development and preparation current status.

  18. H I Lyman-alpha Equivalent Widths of Stellar Populations

    NASA Astrophysics Data System (ADS)

    Peña-Guerrero, María A.; Leitherer, Claus

    2013-12-01

    We have compiled a library of stellar Lyman-alpha (Lyα) equivalent widths in O and B stars using the model atmosphere codes CMFGEN and TLUSTY, respectively. The equivalent widths range from about 0 to 30 Å in absorption for early-O to mid-B stars. The purpose of this library is for the prediction of the underlying stellar Lyα absorption in stellar populations of star-forming galaxies with nebular Lyα emission. We implemented the grid of individual equivalent widths into the Starburst99 population synthesis code to generate synthetic Lyα equivalent widths for representative star formation histories. A starburst observed after 10 Myr will produce a stellar Lyα line with an equivalent width of ~ - 10 ± 4 Å in absorption for a Salpeter initial mass function. The lower value (deeper absorption) results from an instantaneous burst, and the higher value (shallower line) from continuous star formation. Depending on the escape fraction of nebular Lyα photons, the effect of stellar Lyα on the total profile ranges from negligible to dominant. If the nebular escape fraction is 10%, the stellar absorption and nebular emission equivalent widths become comparable for continuous star formation at ages of 10-20 Myr.

  19. Sub-Lyman-alpha observations of supernova remnants

    NASA Technical Reports Server (NTRS)

    Long, K. S.

    1993-01-01

    The first map of O VI lambda 1035 emission of the Cygnus Loop has now been obtained with Voyager. The first good spectra of the sub-Lyman-alpha region in the Cygnus Loop and in the Large Magellanic Cloud (LMC) remnant N49 have been obtained with the Hopkins Ultraviolet Telescope. The lines detected below 1200 A include S VI lambda lambda 933,945, C III lambda 977, N III lambda 991, and O VI lambda lambda 1032,1038. The O VI luminosities of the Cygnus Loop and of N49 exceed their soft X-ray luminosities. There is O VI emission at the primary shock front in the Cygnus Loop and from the bright optical filaments. The HUT spectra of the Cygnus Loop can be interpreted in terms of shocks with velocities of 170-190 km/s; the differences between the two spectra are due to the time since the beginning of the shock-cloud encounter.

  20. Variability of Lyman-alpha emission from Jupiter

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The Jovian Lyman-alpha emission line was again observed in 1978 using the high resolution spectrometer on the Copernicus satellite. In intensity of 8.4+3.0 kilo Rayleighs was measured. This value represents a significant increase in intensity over previous (1976) Copernicus observations, but is lower than the recent (1979) values obtained by Voyager I and IUE. The increase in intensity was accompanied by a significant increase in line width, giving strong support to the theory that the emission results from resonant scattering of the solar Ly-alpha line by H atoms in the upper Jovian atmosphere. The strength of Jovian Ly-alpha emission correlates well with the level of solar activity. The solar extreme ultraviolet radiation varies with the solar cycle. This radiation causes the dissociation of H2 and CH4 into H atoms in the Jovian atmosphere. Therefore, in times of high solar activity, the H column density will increase, causing the observed stronger Jovian Ly-alpha emission.

  1. Cosmology from the BOSS Lyman-Alpha Forest

    NASA Astrophysics Data System (ADS)

    Font-Ribera, Andreu; SDSS-III Collaboration

    2015-01-01

    After six years of observations, the Baryon Oscillation Spectroscopic Survey (BOSS) ended last summer, and recently made its data public (SDSS Data Release 12). During these years, it has used the SDSS telescope to obtain spectra of 1.5 million galaxies to get very accurate measurements of the Baryon Acoustic Oscillations (BAO) scale at redshift z ~0.5. At the same time, BOSS observed over 184 000 high redshift quasars (z>2.15) with the goal of detecting the BAO feature in the clustering of the intergalactic medium, using a technique known as the Lyman alpha forest (LyaF).In this talk I will overview several results from the LyaF working group in BOSS, including the measurement of BAO at z=2.4 both from the auto-correlation of the LyaF (Delubac et al. 2014), and from its cross-correlation with quasars (Font-Ribera et al. 2014). From the combination of these studies we are able to measure the expansion rate of the Universe 11 billion years ago with a 2% uncertainty.

  2. eLARS - extending the Lyman Alpha Reference Sample

    NASA Astrophysics Data System (ADS)

    Oestlin, Goeran

    2013-10-01

    Despite its pivotal importance in high-z astrophysics, Lyman alpha {LyA} imaging is a relatively unexplored territory, due to its reliance on HST for far UV imaging. Our team has pioneered systematic LyA imaging in the local universe and developed techniques for producing photometrically accurate images using HST. We recently finished LARS, the first systematic LyA imaging study of 14 UV+H-alpha selected starbursts in the local universe. We found further evidence for LyA variation on physical scales from 30 pc to several kpc, often in a manner uncorrelated with the UV continuum, H-alpha or the galaxy in general. Specifically, we find that when LyA is bright and when a lot of LyA manages to escape, it is always found in the form of a large scale halo. This is, in all such cases, more extended than the UV or H-alpha emission, but rarely symmetric.While these results are fascinating, LARS consists of extreme starbursts that contribute only a small fraction of the total UV and star-formation density at low and intermediate {z 2} redshifts. Given the importance of the LyA line for finding galaxies and for galaxy evolution studies it is imperative to now generalize the investigation and produce a fully representative quantitative framework. We here propose to image a sample of 28 local galaxies, dominated by more disk like objects {c.f. the irregular objects of LARS}, and the kind of objects than dominate the local FUV luminosity function. Specifically, we will investigate the effects of geometry and galaxy orientation of the emergent LyA emission.

  3. Development of Flight Slit-Jaw Optics for Chromospheric Lyman-Alpha SpectroPolarimeter

    NASA Technical Reports Server (NTRS)

    Kubo, Masahito; Suematsu, Yoshinori; Kano, Ryohei; Bando, Takamasa; Hara, Hirohisa; Narukage, Noriyuki; Katsukawa, Yukio; Ishikawa, Ryoko; Ishikawa, Shin-nosuke; Kobiki, Toshihiko; Tsuneta, Saku; Kobayashi, Ken; Winebarger, Amy; Takeyama, Norihide; Kanai, Yoshikazu; Sakakibara, Yoshiko

    2015-01-01

    In sounding rocket experiment CLASP, I have placed a slit a mirror-finished around the focal point of the telescope. The light reflected by the mirror surface surrounding the slit is then imaged in Slit-jaw optical system, to obtain the a-ray Lyman secondary image. This image, not only to use the real-time image in rocket flight rocket oriented direction selection, and also used as a scientific data showing the spatial structure of the Lyman alpha emission line intensity distribution and solar chromosphere around the observation area of the polarimetric spectroscope. Slit-jaw optical system is a two off-axis mirror unit part including a parabolic mirror and folding mirror, Lyman alpha transmission filter, the optical system magnification 1x consisting camera. The camera is supplied from the United States, and the other was carried out fabrication and testing in all the Japanese side. Slit-jaw optical system, it is difficult to access the structure, it is necessary to install the low place clearance. Therefore, influence the optical performance, the fine adjustment is necessary optical elements are collectively in the form of the mirror unit. On the other hand, due to the alignment of the solar sensor in the US launch site, must be removed once the Lyman alpha transmission filter holder including a filter has a different part from the mirror unit. In order to make the structure simple, stray light measures Aru to concentrate around Lyman alpha transmission filter. To overcome the difficulties of performing optical alignment in Lyman alpha wavelength absorbed by the atmosphere, it was planned 'following four steps in order to reduce standing time alignment me. 1. is measured in advance refractive index at Lyman alpha wavelength of Lyman alpha transmission filter (121.567nm), to prepare a visible light Firuwo having the same optical path length in the visible light (630nm).2. The mirror structure CLASP before mounting unit standing, dummy slit and camera standing

  4. Development of Flight Slit-Jaw Optics for Chromospheric Lyman-Alpha SpectroPolarimeter

    NASA Technical Reports Server (NTRS)

    Kubo, Masahito; Suematsu, Yoshinori; Kano, Ryohei; Bando, Takamasa; Hara, Hirohisa; Narukage, Noriyuki; Katsukawa, Yukio; Ishikawa, Ryoko; Ishikawa, Shin-nosuke; Kobiki, Toshihiko; Tsuneta, Saku; Kobayashi, Ken; Winebarger, Amy; Takeyama, Norihide; Kanai, Yoshikazu; Sakakibara, Yoshiko

    2015-01-01

    In sounding rocket experiment CLASP, I have placed a slit a mirror-finished around the focal point of the telescope. The light reflected by the mirror surface surrounding the slit is then imaged in Slit-jaw optical system, to obtain the alpha-ray Lyman secondary image. This image, not only to use the real-time image in rocket flight rocket oriented direction selection, and also used as a scientific data showing the spatial structure of the Lyman alpha emission line intensity distribution and solar chromosphere around the observation area of the polarimetric spectroscope. Slit-jaw optical system is a two off-axis mirror unit part including a parabolic mirror and folding mirror, Lyman alpha transmission filter, the optical system magnification 1x consisting camera. The camera is supplied from the United States, and the other was carried out fabrication and testing in all the Japanese side. Slit-jaw optical system, it is difficult to access the structure, it is necessary to install the low place clearance. Therefore, influence the optical performance, the fine adjustment is necessary optical elements are collectively in the form of the mirror unit. On the other hand, due to the alignment of the solar sensor in the US launch site, must be removed once the Lyman alpha transmission filter holder including a filter has a different part from the mirror unit. In order to make the structure simple, stray light measures Aru to concentrate around Lyman alpha transmission filter. To overcome the difficulties of performing optical alignment in Lyman alpha wavelength absorbed by the atmosphere, it was planned following four steps in order to reduce standing time alignment me. 1: is measured in advance refractive index at Lyman alpha wavelength of Lyman alpha transmission filter (121.567nm), to prepare a visible light Firuwo having the same optical path length in the visible light (630nm). 2: The mirror structure CLASP before mounting unit standing, dummy slit and camera standing

  5. Design and Fabrication of the All-Reflecting H-Lyman alpha Coronagraph/Polarimeter

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.; Johnson, R. Barry; Fineschi, Silvano; Walker, Arthur B. C., Jr.; Baker, Phillip C.; Zukic , Muamer; Kim, Jongmin

    1993-01-01

    We have designed, analyzed, and are now fabricating an All-Reflecting H-Lyman alpha Coronagraph/Polarimeter for solar research. This new instrument operates in a narrow bandpass centered at lambda 1215.7 A-the neutral hydrogen Lyman alpha (Ly-alpha) line. It is shorter and faster than the telescope which produced solar Ly-alpha images as a part of the MSSTA payload that was launched on May 13, 1991. The Ly-alpha line is produced and linearly polarized in the solar corona by resonance scattering, and the presence of a magnetic field modifies this polarization according to the Hanle effect. The Lyman alpha Coronagraph/Polarimeter instrument has been designed to measure coronal magnetic fields by interpreting, via the Hanle effect, the measured linear polarization of the coronal Ly-alpha line. Ultrasmooth mirrors, polarizers, and filters are being flow-polished for this instrument from CVD silicon carbide substrates. These optical components will be coated using advanced induced transmission and absorption thin film multilayer coatings, to optimize the reflectivity and polarization properties at 1215.7 A. We describe some of the solar imaging results obtained with the MSSTA Lyman alpha coronagraph. We also discuss the optical design parameters and fabrication plans for the All-Reflecting H-Lyman alpha Coronagraph/Polarimeter.

  6. New analysis of the Voyager UVS H Lyman-alpha emission of Saturn

    NASA Technical Reports Server (NTRS)

    Jaffel, L. Ben; Prange, R.; Sandel, B. R.; Yelle, R. V.; Emerich, C.; Feng, D.; Hall, D. T.

    1995-01-01

    The limb to limb Lyman-alpha reflectivities observed with the Voyager ultraviolet spectrometer (UVS) instruments during the fly-by of Saturn are reanalyzed using a revised H Lyman-alpha sensitivity for the Voyager 1 instrument. The new sensitivity reconciles the measured intensities to those of Voyager 2 and gives a coherent set of data. To fit the UV airglow observations, four sources are considered: (1) H resonance and H2 Rayleigh scattering of solar Lyman-alpha radiation, (2) the interplanetary Lyman-alpha radiation, (3) a possible internal source of unknown origin, (4) the possibility of atmospheric turbulence recently proposed to explain the Lyman-alpha bulge of Jupiter. The analysis supports neither a dominant collisional excitation source for the UV emissions nor the presence of strong atmospheric turbulence. The best fit, in terms of brightness but also in terms of shape of the limb to limb profile (that is to say independent on the absolute calibrations), is obtained for pure resonance and Rayleigh scattering of solar and interstellar wind line in an atmosphere enriched in atomic hydrogen up to three times the standard model. Influx of water from the rings of Saturn may provide a means for producing such enhanced H densities in the upper atmosphere.

  7. ZrCo as a new H2 storage and getter for Lyman alpha radiation sources

    NASA Astrophysics Data System (ADS)

    Woyke, Thomas; Schiller, Cornelius; Schmidt, Ulrich; Schober, Tilman; Zöger, Martin

    1995-01-01

    In the past, in sealed-off Lyman- alpha radiation sources (121.57 nm), uranium hydride was used as the hydrogen reservoir. We found that the zirconium-cobalt alloy ZrCo, which has similar thermodynamic properties, can also be used for hydrogen storage in such lamps. Like uranium, ZrCo acts as a getter for atmospheric contaminants. The advantage of the use of ZrCo lies in much easier and safer handling during production and disposal of the lamps. Using ZrCo, we succeeded in producing radiation sources with a large Lyman- alpha radiation output and high spectral purity, which were successfully applied in a Lyman- alpha fluorescence hygrometer for stratospheric observations.

  8. On the analysis of the H Lyman-alpha dayglow of Jupiter, Saturn and Uranus

    NASA Astrophysics Data System (ADS)

    Emerich, C.; Ben Jaffel, L.; Prange, R.

    1993-05-01

    A new radiative transfer model, particularly well adapted to calculations in inhomogeneous atmospheres, has been applied, during the last four years, to analyze new and older Lyman-alpha airglow data from three giant planets. We review all the results obtained so far. Several features which were not accounted for by using the previous transfer codes were satisfactorily simulated, using essentially the scattering of the solar and the interplanetary Lyman-alpha lines by hydrogen in the upper atmospheres. The search for a good fit both in intensity and in shape of the limb to limb data, and/or of the line profiles, provided constraints on the dynamics of the atmospheres, through the estimate of either the eddy diffusion coefficient, the total H column density, or of the possibility of some nonthermal turbulence processes at high altitude. Consequently, the need for an 'electroglow' process for the Lyman-alpha emission was considerably reduced and may be dismissed in the majority of cases.

  9. Theoretical Predictions of Large Scale Clustering in the Lyman-alpha Forest

    NASA Astrophysics Data System (ADS)

    Cieplak, Agnieszka M.; Slosar, Anze; Khandai, Nishikanta

    2015-01-01

    With the recent progress of Lyman-alpha forest power spectrum measurements, understanding of the bias between the measured flux and the underlying matter power spectrum is becoming crucial to the percent level cosmological interpretation of these measurements. Whereas previous theoretical studies of this bias have used N-body and hydro-PM simulations, we have run hydrodynamic simulations to study the response of the Lyman-alpha forest clustering to large wavelength modes of the underlying matter large-scale structure. Our results demonstrate that this can be simulated by evolving smaller, curved universe cosmologies, representing the same universe with different overdense patches. We use these to study the assumptions of the analytical bias formula derived by Seljak (2012), and compare these results with previous numerical methods of determining bias. With several forthcoming large data sets, such theoretical predictions are important to fully understand the clustering of the Lyman-alpha forest.

  10. Self-regulating galaxy formation. I - H II disk and Lyman-alpha pressure

    NASA Technical Reports Server (NTRS)

    Cox, D. P.

    1985-01-01

    The nascent interstellar medium and star formation model are incorporated into a scenario for the formation epoch of spiral galaxies. The structure, star formation time scale, and luminosity of a self-gravitating isothermal disk are evaluated as functions of the disk surface density. The importance of radiation pressure, particularly that of Lyman-alpha, in maintaining an inflated disk and halting infall is discussed. The Lyman-alpha pressure also supports a considerable halo of material in the vicinity of the disk. A first-order infall scenario and the time-dependent properties of the system it constructs are presented. Disk properties are evaluated at the epoch at which further material is supportable against infall by Lyman-alpha pressure. The two-dimensional family of disk galaxies whose scales and surface density are expressible in terms of fundamental constants and which arise from the three parameter sets of perturbations in the Hubble flow are determined.

  11. Lyman Alpha Emitting Galaxies in the Nearby Universe

    NASA Astrophysics Data System (ADS)

    Hayes, Matthew

    2015-07-01

    The Lyman alpha emission line (Lyα) of neutral hydrogen (Hi) is intrinsically the brightest emission feature in the spectrum of astrophysical nebulae, making it a very attractive observational feature with which to survey galaxies. Moreover as an ultraviolet resonance line, Lyα possesses several unique characteristics that make it useful to study the properties of the interstellar medium and ionising stellar population at all cosmic epochs. In this review, I present a summary of Lyα observations of galaxies in the nearby universe. By ultraviolet continuum selection, at the magnitudes reachable with current facilities, only ≈ 5% of the local galaxy population shows a Lyα equivalent width (W Lyα) that exceeds 20 Å. This fraction increases dramatically at higher redshifts, but only in the local universe can we study galaxies in detail and assemble unprecedented multi-wavelength datasets. I discuss many local Lyα observations, showing that when galaxies show net Lyα emission, they ubiquitously also produce large-scale halos of scattered Lyα, that dominate the integrated luminosity. Concerning global measurements, we discuss how W Lyα and the Lyα escape fraction (f Lyα esc) are higher (W Lyα ≳ 20 Å and f Lyα esc ≳ 10%) in galaxies that represent the less massive and younger end of the distribution for local objects. This is connected with various properties, such that Lyα-emitting galaxies have lower metal abundances (median value of 12 + log(O/H) ~ 8.1) and dust reddening. However, the presence of galactic outflows/winds is also vital to Doppler shift the Lyα line out of resonance with the atomic gas, and high W Lyα is found only among galaxies with winds faster than ~ 50 km s-1. The empirical evidence is then assembled into a coherent picture, and the requirement for star-formation-driven feedback is discussed in the context of an evolutionary sequence where the interstellar medium is accelerated and/or subject to hydrodynamical instabilities

  12. Lyman alpha emitter evolution in the reionization epoch

    NASA Astrophysics Data System (ADS)

    Dayal, P.; Ferrara, A.; Saro, A.; Salvaterra, R.; Borgani, S.; Tornatore, L.

    2009-12-01

    Combining cosmological smoothed particle hydrodynamics (SPH) simulations with a previously developed Lyα production/transmission model and the Early Reionization Model (ERM; reionization ends at redshift z ~ 7), we obtain Lyα and UV luminosity functions (LFs) for lyman alpha emitters (LAEs) at 5.7 <= z <= 7.6. Matching model results to observations at z ~ 5.7 requires escape fractions of Lyα,fα = 0.3, and UV (non-ionizing) continuum photons, fc = 0.22, corresponding to a colour excess, E(B - V) = 0.15. We find that (i) fc increases towards higher redshifts, due the decreasing mean dust content of galaxies, (ii) the evolution of fα/fc hints at the dust content of the interstellar medium becoming progressively inhomogeneous/clumped with decreasing redshift. Using the model assumptions, clustering of sources has little effect on the Lyα LF for a cosmic hydrogen neutral fraction χHI <= 10-4, a value attained at z <= 6.6 in the ERM. However, during the initial reionization phases (z >~ 7), the clustering photoionization boost becomes important. We quantify the physical properties of observed LAEs and their redshift evolution, for which we give handy analytical fitting functions. Halo (stellar) masses are in the range 10.0 < logMh < 11.8 (8.1 < logM* < 10.4) with Mh ~ M0.64*. The star formation rates are , mass-weighted mean ages are t* > 20 Myr at all redshifts, while the mean stellar metallicity increases from Z = 0.12Zsolar at z ~ 7.6 to Z = 0.22Zsolar at z ~ 5.7; both t* and Z positively correlate with stellar mass. The brightest LAEs are all characterized by large and intermediate ages (~200Myr), while objects in the faint end of the Lyα LF show large age and star formation rate spreads. With no more free parameters, the spectral energy distributions of three LAE at z ~ 5.7 observed by Lai et al. (2007) are well reproduced by an intermediate age (182-220 Myr) stellar population and the above E(B - V) value. The model uncertainties, mostly related to the

  13. The Lyman alpha reference sample. VII. Spatially resolved Hα kinematics

    NASA Astrophysics Data System (ADS)

    Herenz, Edmund Christian; Gruyters, Pieter; Orlitova, Ivana; Hayes, Matthew; Östlin, Göran; Cannon, John M.; Roth, Martin M.; Bik, Arjan; Pardy, Stephen; Otí-Floranes, Héctor; Mas-Hesse, J. Miguel; Adamo, Angela; Atek, Hakim; Duval, Florent; Guaita, Lucia; Kunth, Daniel; Laursen, Peter; Melinder, Jens; Puschnig, Johannes; Rivera-Thorsen, Thøger E.; Schaerer, Daniel; Verhamme, Anne

    2016-03-01

    We present integral field spectroscopic observations with the Potsdam Multi-Aperture Spectrophotometer of all 14 galaxies in the z ~ 0.1 Lyman Alpha Reference Sample (LARS). We produce 2D line-of-sight velocity maps and velocity dispersion maps from the Balmer α (Hα) emission in our data cubes. These maps trace the spectral and spatial properties of the LARS galaxies' intrinsic Lyα radiation field. We show our kinematic maps that are spatially registered onto the Hubble Space Telescope Hα and Lyman α (Lyα) images. We can conjecture a causal connection between spatially resolved Hα kinematics and Lyα photometry for individual galaxies, however, no general trend can be established for the whole sample. Furthermore, we compute the intrinsic velocity dispersion σ0, the shearing velocity vshear, and the vshear/σ0 ratio from our kinematic maps. In general LARS galaxies are characterised by high intrinsic velocity dispersions (54 km s-1 median) and low shearing velocities (65 km s-1 median). The vshear/σ0 values range from 0.5 to 3.2 with an average of 1.5. It is noteworthy that five galaxies of the sample are dispersion-dominated systems with vshear/σ0< 1, and are thus kinematically similar to turbulent star-forming galaxies seen at high redshift. When linking our kinematical statistics to the global LARS Lyα properties, we find that dispersion-dominated systems show higher Lyα equivalent widths and higher Lyα escape fractions than systems with vshear/σ0> 1. Our result indicates that turbulence in actively star-forming systems is causally connected to interstellar medium conditions that favour an escape of Lyα radiation. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).The reduced data cubes (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130

  14. OGO-5 measurements of the Lyman-alpha sky background in 1970 and 1971

    NASA Technical Reports Server (NTRS)

    Thomas, G. E.; Krassa, R. F.

    1974-01-01

    The results of measurements of the Lyman-alpha sky background emission at 1216 A, made by two different UV photometers during the last three 'spin-up' maneuvers (enabling more than 50% of the sky to be observed) are examined. The processed data revealed a smooth variation of Lyman-alpha brightness from a broad maximum near RA = 269 deg, declination = -20 deg to a broader minimum near RA = 50 deg, declination = +20 deg. The maximum/minimum intensity ratio is found to be on the order of 4.

  15. Properties of nearby interstellar hydrogen deduced from Lyman-alpha sky background measurements

    NASA Technical Reports Server (NTRS)

    Thomas, G. E.

    1972-01-01

    For a sufficiently rapid relative motion of the solar system and the nearby interstellar gas, neutral atoms may be expected to penetrate the heliosphere before becoming ionized. Recent satellite measurements of the Lyman alpha emission above the geocorona indicate such an interstellar wind of neutral hydrogen emerging from the direction of Sagittarius and reaching to within a few astronomical units of the sun. A detailed model of the scattering of solar Lyman alpha from the spatial distribution of neutral hydrogen in interplanetary space is presented. This asymmetric distribution is established by solar wind and solar ultraviolet ionization processes along the trajectories of the incoming hydrogen atoms. The values of the interstellar density, the relative velocity, and the gas temperature are adjusted to agree with the Lyman alpha measurements. The results may be interpreted in terms of two models, the cold model and the hot model of the interstellar gas, depending on whether galactic Lyman alpha emission is present at its maximum allowable value or negligibly small.

  16. A Sounding Rocket Experiment for the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)

    NASA Technical Reports Server (NTRS)

    Kubo, M.; Kano, R.; Kobayashi, K.; Ishikawa, R.; Bando, T.; Narukage, N.; Katsukawa, Y.; Ishikawa, S.; Suematsu, Y.; Hara, H.; Tsuneta, S.; Shimizu, T.; Sakao, T.; Ichimoto, K.; Winebarger, A.; Cirtain, J.; De Pontieu, B.; Casini, R.; Auchere, F.; Trujillo, Bueno J.; Manso, Sainz R.; Ramos, Asensio A.; Stepan, J.; Belluzi, L.; Carlsson, M.

    2014-01-01

    A sounding-rocket experiment called the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is presently under development to measure the linear polarization profiles caused by scattering processes and the Hanle effect in the hydrogen Lyman-alpha line (121.567nm). Accurate measurements of the linear polarization signals caused by scattering processes and the Hanle effect are essential to explore the strength and structures of weak magnetic fields. The primary target of future solar telescopes is to measure the weak magnetic field in outer solar atmospheres (from the chromosphere to the corona through the transition region). The hydrogen Lyman-alpha-line is one of the best lines for the diagnostics of magnetic fields in the outer solar atmospheres. CLASP is to be launched in 2015, and will provide, for the first time, the observations required for magnetic field measurements in the upper chromosphere and transition region. CLASP is designed to have a polarimetric sensitivity of 0.1% and a spectral resolution of 0.01nm for the Lyman-alpha line. CLASP will measure two orthogonal polarizations simultaneously for about 5-minute flight. Now the integration of flight mirrors and structures is in progress. In addition to our strategy to realize such a high-precision spectro-polarimetry in the UV, we will present a progress report on our pre-launch evaluation of optical and polarimetric performances of CLASP.

  17. A Lyman-alpha tunable acousto-optic filter for detecting superthermal flare protons

    NASA Technical Reports Server (NTRS)

    Mickey, Donald L.

    1994-01-01

    The goal of this project was to develop and characterize a narrow-band, tunable filter for use near the Lyman-alpha line of hydrogen at 121.6 nm. Such a filter could form the critical component of an instrument to observe asymmetries in the solar Lyman-alpha line, caused by energetic protons accelerated during the impulsive phase of solar flares. Characteristic charge-exchange nonthermal emission at Lyman alpha should be produced when sub-MeV protons are injected into the chromosphere, but no instrument suitable for their detection has been developed. Such an instrument would require a narrow-band (less than 0.01 nm) tunable filter with aperture and throughput consistent with imaging a solar active region at 0.1 second intervals. The development of acousto-optic tunable filters (AOTF) suitable for use as compact, simple tunable filters for astronomical work suggested an investigation into the use of an AOTF at Lyman-alpha.

  18. Resolving Lyman-alpha Emission On Physical Scales < 270 pc at z > 4

    NASA Astrophysics Data System (ADS)

    Bayliss, Matthew

    2014-10-01

    We propose ACS-WFC Ramp narrowband imaging of six strongly lensed Lyman-alpha Emitters (LAEs) at z > 4 that will spatially resolve the Lyman-alpha line emitting regions on scales < 270 pc. The best available observations (HST, Spitzer, 10m ground based telescopes) are unable to provide robust measurements of the structure of these galaxies from blank field studies, but strong gravitational lensing provides a unique opportunity to peer into the heart of young star forming galaxies at high redshift and address outstanding questions regarding their morphology and evolution. Strong lensing magnifies each of our target LAEs, increasing the effective spatial resolution of ACS-WFC such that the point spread function will correspond to physical scales < 270 parsecs within all six z > 4 galaxies. Additionally, the boost in flux due to gravitational lensing makes our proposed targets the brightest sources of their kind at these redshifts, in spite of the fact that they are intrinsically ~L* LAEs. The proposed observations will probe the morphological properties of Lyman-alpha and UV continuum emission in typical/representative high-redshift LAEs with signal-to-noise and spatial resolution comparable to studies of Lyman-alpha emitting galaxies in the z ~ 0.1 universe. The resulting data will bridge the gap between deep ground-based studies of blank field LAEs at high redshift, and detailed studies of low-redshift LAEs.

  19. A Search for z>6.5 Lyman-alpha Emitting Galaxies with WISP

    NASA Astrophysics Data System (ADS)

    Bagley, Micaela B.; Scarlata, Claudia; Dai, Yu Sophia; Rafelski, Marc; Baronchelli, Ivano; Colbert, James W.; Dominguez, Alberto; Hathi, Nimish P.; Henry, Alaina L.; Malkan, Matthew Arnold; Martin, Crystal L.; Mehta, Vihang; Pahl, Anthony; Ross, Nathaniel; Rutkowski, Michael J.; Teplitz, Harry I.; WISP Team

    2016-01-01

    The observed number density of Lyman-alpha emitting galaxies at z>6 provides an important probe of the reionization history of the universe. Because Lyman-alpha photons are very sensitive to the presence of neutral hydrogen, the evolution of the galaxy number density above redshift 6 can be used as a measurement on the progress of reionization. However, the Lyman-alpha luminosity function is currently poorly constrained at high-z. We present the results of a systematic search for Lyman-alpha emitters (LAEs) at redshifts of ~6.5 to 7.5 using the HST WFC3 Infrared Spectroscopic Parallels (WISP) survey. WISP's uncorrelated fields are well-suited to the study of bright LAEs, minimizing the effects of clustering introduced by a patchy reionization. From the 30 deepest WISP fields, we compile a sample of single-line emitters, confirm redshifts with broadband colors, and identify LAE candidates that have "dropped out" (are undetected at the 1 sigma level) of the WFC3 UVIS filters. By combining our results with other z~7 studies, we determine whether the number density of LAEs evolves past z~6.5.

  20. High efficiency SNAP survey for Lyman alpha emitters at low redshift

    NASA Astrophysics Data System (ADS)

    McCandliss, Stephan

    2014-10-01

    The goal of this proposal is to provide the first statistically significant survey of star-forming galaxies with Lyman alpha emission at redshifts 0.02 < z < 0.24. It will provide an overall assessment of the evolution in Lyman alpha luminosity at the lowest redshifts and allowed detailed studies of the physical processes that shape the Lyman alpha profile and govern escape in multi-phase, kinematic media. It will also provide a serendipitous search for star-forming galaxies with high LyC escape fractions that are analogous to those commonly invoked as being responsible for initiating and sustaining the epoch of reionization. The SNAP survey proposed here employing the G140L mode of COS offers a highly efficient means to examine the Lyman alpha emission properties of our candidate emitters and to inform our choice of objects that could warrant deeper integrations in future observations. These data have high UV legacy value and will be of broad interest to the star-forming galaxy community, so we have elected to waive the proprietary period.

  1. The Deepest Spectrum in the Universe? Line Emission from Lyman-alpha Clouds at z 3

    NASA Astrophysics Data System (ADS)

    Bunker, Andrew J.; Rauch, M.; Haehnelt, M.; Becker, G.; Marleau, F.; Graham, J.; Research, European; Inter-Galactic Medium, Training Network on the

    2007-12-01

    We present the results of an extremely deep long-slit optical spectroscopic search for low-luminosity Lyman-alpha emitters. Over several years we have accumulated 150-hours integration on a single field with 8-10m telescopes (VLT/FORS2, Gemini/GMOS and Keck/LRIS) at a spectral resolution of 300km/s. This is the deepest spectrum ever obtained - our 1 sigma sensitivity to line emission in a 1 arcsec2 aperture is 1019erg/cm2/s. We have significant detections of 30 emission line objects, which are most likely Lyman-alpha emitters at 2.7Lyman-alpha absorption clouds seen in QSO spectra (the Damped Lyman-alpha Systems and the Lyman-Limit Systems).

  2. Comparison between solar wind latitude distribution derived from Lyman-alpha observations and ULYSSES measurements

    NASA Astrophysics Data System (ADS)

    Quemarais, E.; Lallement, R.; Bertaux, J. L.; Sandel, B. R.

    1995-06-01

    The all-sky interplanetary Lyman-alpha pattern is sensitive to the latitude distribution of the solar wind because of destruction of neutral H by charge-exchange with solar wind protons. Lyman-alpha intensities recorded by Prognoz 5 and 6 in 1976 in a few parts of the sky were demonstrating a decrease of solar wind mass flux by about 30 % from equator to pole, when assuming a sinusoidal variation of this mass flux (harmonic distribution). A new analysis with a discrete variation with latitude has shown a decrease from 0 to 30 deg and then a plateau of constant mass flux up to the pole. This distribution bears a striking resemblance with Ulysses in-situ measurements, showing a clear similarity at 19 years interval. The Ulysses measurements were then used as a model input to calculate an all-sky Lyman-alpha pattern, either with a discrete model or with a harmonic solar wind variation with the same Ulysses equator-to-pole variation. There are conspicuous differences between the two Lyman-alpha patterns, in particular in the downwind region which are discussed in the context of future all-sky measurements with SWAN experiment on SOHO.

  3. Comparison between solar wind latitude distribution derived from Lyman-alpha observations and Ulysses measurements

    NASA Technical Reports Server (NTRS)

    Quemarais, E.; Lallement, R.; Bertaux, J. L.; Sandel, B. R.

    1995-01-01

    The all-sky interplanetary Lyman-alpha pattern is sensitive to the latitude distribution of the solar wind because of destruction of neutral H by charge-exchange with solar wind protons. Lyman-alpha intensities recorded by Prognoz 5 and 6 in 1976 in a few parts of the sky were demonstrating a decrease of solar wind mass flux by about 30 % from equator to pole, when assuming a sinusoidal variation of this mass flux (harmonic distribution). A new analysis with a discrete variation with latitude has shown a decrease from 0 to 30 deg and then a plateau of constant mass flux up to the pole. This distribution bears a striking resemblance with Ulysses in-situ measurements, showing a clear similarity at 19 years interval. The Ulysses measurements were then used as a model input to calculate an all-sky Lyman-alpha pattern, either with a discrete model or with a harmonic solar wind variation with the same Ulysses equator-to-pole variation. There are conspicuous differences between the two Lyman-alpha patterns, in particular in the downwind region which are discussed in the context of future all-sky measurements with SWAN experiment on SOHO.

  4. Simultaneous measurements of the hydrogen airglow emissions of Lyman alpha, Lyman beta, and Balmer alpha.

    NASA Technical Reports Server (NTRS)

    Weller, C. S.; Meier, R. R.; Tinsley, B. A.

    1971-01-01

    Comparison of Lyman-alpha, 740- to 1050-A, and Balmer-alpha airglow measurements made at 134 deg solar-zenith angle on Oct. 13, 1969, with resonance-scattering models of solar radiation. Model comparison with Lyman-alpha data fixes the hydrogen column abundance over 215 km to 2 x 10 to the 13th per cu cm within a factor of 2. Differences between the Lyman-alpha model and data indicate a polar-equatorial departure from spherical symmetry in the hydrogen distribution. A Lyman-beta model based on the hydrogen distribution found to fit the Lyman-alpha data fits the spatial variation of the 740- to 1050-A data well from 100 to 130 km, but it does not fit the data well at higher altitudes; thus the presence of more rapidly absorbed shorter-wavelength radiation is indicated. This same resonance-scattering model yields Balmer-alpha intensities that result in good spatial agreement with the Balmer-alpha measurements, but a fivefold increase in the measured solar line center Lyman-beta flux is required (as required for the Lyman-beta measurement). The intensity ratio of Lyman-beta and Balmer-alpha at night is found to be a simple measure of the hydrogen optical depth if measurements with good accuracy can be made in the visible and ultraviolet spectrum.

  5. Design and fabrication of the All-Reflecting H-Lyman-alpha Coronagraph/Polarimeter

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.; Johnson, R. B.; Fineschi, Silvano; Walker, Arthur B. C., Jr.; Baker, Phillip C.; Zukic, Muamer; Kim, Jongmin

    1993-01-01

    We have designed, analyzed, and are now fabricating an All-Reflecting H-Lyman-alpha Coronagraph/Polarimeter for solar research. This new instrument operates in a narrow bandpass centered at 215.7 A - the neutral hydrogen Ly-alpha line. It is shorter and faster than the telescope which produced solar Ly-alpha images as a part of the MSSTA payload that was launched on May 13, 1991. The Ly-alpha line is produced and linearly polarized in the solar corona by resonance scattering, and the presence of a magnetic field modifies this polarization according to the Hanle effect. The Lyman-alpha Coronagraph/Polarimeter instrument has been designed to measure coronal magnetic fields by interpreting, via the Hanle effect, the measured linear polarization of the coronal Ly-alpha line. Ultrasmooth mirrors, polarizers, and filters are being flow-polished for this instrument from CVD silicon carbide substrates. These optical components will be coated using advanced induced transmission and absorption thin film multilayer coatings to optimize the reflectivity and polarization properties at 1215.7 A. We describe some of the solar imaging results obtained with the MSSTA Lyman-alpha coronagraph. We also discuss the optical design parameters and fabrication plans for the All-Reflecting H-Lyman-alpha Coronagraph/Polarimeter.

  6. Seeing Galaxies Through the Forest: Spectral Stacking of Damped Lyman Alpha Systems

    NASA Astrophysics Data System (ADS)

    Yen, Steffi; Jorgenson, R.; Murphy, M.

    2013-01-01

    Damped Lyman alpha Systems (DLAs) are the highest column density (N(HI) >= 2x10^20 cm^-2) neutral gas absorbers detected in the sightlines to distant quasars. DLAs dominate the neutral gas mass content of the Universe from z=[0,5], suggesting that they are the reservoirs of neutral gas for star formation across cosmic time. However, the nature of DLAs is not fully understood because they are detected in absorption against the light of background quasars. The resulting spectra contain absorption from the Lyman alpha forest, a series of smaller neutral hydrogen lines, essentially filaments of neutral gas in the IGM. At high redshifts (z >= 2), the forest becomes quite thick, making it difficult to distinguish intervening forest lines from metal lines of the DLA. By employing the technique of spectral stacking, we essentially subtract the incoherent Lyman alpha forest lines, enabling us to measure metal lines that typically fall in the forest region, such as O VI, N V, and molecular hydrogen. In addition, the increased signal-to-noise ratio in the DLA stack allows us to search for the presence of weak metal lines and/or Lyman alpha emission not typically seen in a single DLA spectrum. We will present the results obtained from our stack of 97 high-resolution (FWHM ~ 8 km/s) VLT/UVES spectra. Initial analysis of the stack shows a possible detection of Lyman alpha emission in the DLA trough. We will combine this VLT/UVES stack with a previously created stack of ~110 Keck/HIRES spectra to create the highest signal-to-noise ratio, high-resolution DLA spectral stack. Analysis of this final stack will shed new light on our understanding of the role of DLAs in galaxy formation and evolution. This work was conducted by a Research Experience for Undergraduates (REU) position at the University of Hawai'i's Institute for Astronomy and funded by the NSF.

  7. Gravity-Driven Hydraulic Fractures

    NASA Astrophysics Data System (ADS)

    Germanovich, L. N.; Garagash, D.; Murdoch, L. C.; Robinowitz, M.

    2014-12-01

    This study is motived by a new method for disposing of nuclear waste by injecting it as a dense slurry into a hydraulic fracture that grows downward to great enough depth to permanently isolate the waste. Disposing of nuclear waste using gravity-driven hydraulic fractures is mechanically similar to the upward growth of dikes filled with low density magma. A fundamental question in both applications is how the injected fluid controls the propagation dynamics and fracture geometry (depth and breadth) in three dimensions. Analog experiments in gelatin [e.g., Heimpel and Olson, 1994; Taisne and Tait, 2009] show that fracture breadth (the short horizontal dimension) remains nearly stationary when the process in the fracture "head" (where breadth is controlled) is dominated by solid toughness, whereas viscous fluid dissipation is dominant in the fracture tail. We model propagation of the resulting gravity-driven (buoyant or sinking), finger-like fracture of stationary breadth with slowly varying opening along the crack length. The elastic response to fluid loading in a horizontal cross-section is local and can be treated similar to the classical Perkins-Kern-Nordgren (PKN) model of hydraulic fracturing. The propagation condition for a finger-like crack is based on balancing the global energy release rate due to a unit crack extension with the rock fracture toughness. It allows us to relate the net fluid pressure at the tip to the fracture breadth and rock toughness. Unlike the PKN fracture, where breadth is known a priori, the final breadth of a finger-like fracture is a result of processes in the fracture head. Because the head is much more open than the tail, viscous pressure drop in the head can be neglected leading to a 3D analog of Weertman's hydrostatic pulse. This requires relaxing the local elasticity assumption of the PKN model in the fracture head. As a result, we resolve the breadth, and then match the viscosity-dominated tail with the 3-D, toughness

  8. The Lyman alpha reference sample. VI. Lyman alpha escape from the edge-on disk galaxy Mrk 1486

    NASA Astrophysics Data System (ADS)

    Duval, Florent; Östlin, Göran; Hayes, Matthew; Zackrisson, Erik; Verhamme, Anne; Orlitova, Ivana; Adamo, Angela; Guaita, Lucia; Melinder, Jens; Cannon, John M.; Laursen, Peter; Rivera-Thorsen, Thoger; Herenz, E. Christian; Gruyters, Pieter; Mas-Hesse, J. Miguel; Kunth, Daniel; Sandberg, Andreas; Schaerer, Daniel; Månsson, Tore

    2016-03-01

    Context. Recent numerical simulations suggest that the strength of the Lyman alpha (Lyα) line of star-forming disk galaxies strongly depends on the inclination at which they are observed: from edge-on to face-on, we expect to see a change from a strongly attenuated Lyα line to a strong Lyα emission line. Aims: We aim to understand how a strong Lyα emission line is able to escape from the low-redshift highly inclined (edge-on) disk galaxy Mrk 1486 (z ~ 0.0338). To our knowledge, this work is the first observational study of Lyα transport inside an edge-on disk galaxy. Methods: Using a large set of HST imaging and spectroscopic data, we investigated the interstellar medium (ISM) structure and the dominant source of Lyα radiation inside Mrk 1486. Moreover, using a 3D Monte Carlo Lyα radiation transfer code, we studied the radiative transfer of Lyα and UV continuum photons inside a 3D geometry of neutral hydrogen (HI) and dust that models the ISM structure at the galaxy center. Our numerical simulations predicted the Lyα line profile that we then compared to the one observed in the HST/COS spectrum of Mrk 1486. Results: While a pronounced Lyα absorption line emerges from the disk of Mrk 1486, very extended Lyα structures are observed at large radii from the galaxy center: a large Lyα-halo and two very bright Lyα regions located slightly above and below the disk plane. The analysis of IFU Hα spectroscopic data of Mrk 1486 indicates the presence of two bipolar outflowing halos of HI gas at the same location as these two bright Lyα regions. Comparing different diagnostic diagrams (such as [OIII]5007/Hβ versus [OI]6300/Hα) to photo- and shock-ionization models, we find that the Lyα production of Mrk 1486 is dominated by photoionization inside the galaxy disk. From this perspective, our numerical simulations succeed in reproducing the strength and shape of the observed Lyα emission line of Mrk 1486 by assuming a scenario in which the Lyα photons are

  9. Estimation of the solar Lyman alpha flux from ground based measurements of the Ca II K line

    NASA Technical Reports Server (NTRS)

    Rottman, G. J.; Livingston, W. C.; White, O. R.

    1990-01-01

    Measurements of the solar Lyman alpha and Ca II K from October 1981 to April 1989 show a strong correlation (r = 0.95) that allows estimation of the Lyman alpha flux at 1 AU from 1975 to December 1989. The estimated Lyman alpha strength of 3.9 x 10 to the 11th + or - 0.15 x 10 to the 11th photons/s sq cm on December 7, 1989 is at the same maximum levels seen in Cycle 21. Relative to other UV surrogates (sunspot number, 10.7 cm radio flux, and He I 10830 line strength), Lyman alpha estimates computed from the K line track the SME measurements well from solar maximum, through solar minimum, and into Cycle 22.

  10. Feasibility of hydrogen density estimation from tomographic sensing of Lyman alpha emission

    NASA Astrophysics Data System (ADS)

    Waldrop, L.; Kamalabadi, F.; Ren, D.

    2015-12-01

    In this work, we describe the scientific motivation, basic principles, and feasibility of a new approach to the estimation of neutral hydrogen (H) density in the terrestrial exosphere based on the 3-D tomographic sensing of optically thin H emission at 121.6 nm (Lyman alpha). In contrast to existing techniques, Lyman alpha tomography allows for model-independent reconstruction of the underlying H distribution in support of investigations regarding the origin and time-dependent evolution of exospheric structure. We quantitatively describe the trade-off space between the measurement sampling rate, viewing geometry, and the spatial and temporal resolution of the reconstruction that is supported by the data. We demonstrate that this approach is feasible from either earth-orbiting satellites such as the stereoscopic NASA TWINS mission or from a CubeSat platform along a trans-exosphere trajectory such as that enabled by the upcoming Exploration Mission 1 launch.

  11. Competition between pressure and gravity confinement in Lyman Alpha forest observations

    NASA Technical Reports Server (NTRS)

    Charlton, Jane C.; Salpeter, Edwin E.; Linder, Suzanne M.

    1994-01-01

    A break in the distribution function of Lyman Alpha clouds (at a typical redshift of 2.5) has been reported by Petit-jean et al. (1993). This feature is what would be expected from a transition between pressure confinement and gravity confinement (as predicted in Charlton, Salpeter & Hogan 1993). The column density at which the feature occurs has been used to determine the external confining pressure approximately 10 per cu cm K, which could be due to a hot, intergalactic medium. For models that provide a good fit to the data, the contribution of the gas in clouds to omega is small. The specific shape of the distribution function at the transition (predicted by models to have a nonmonotonic slope) can serve as a diagnostic of the distribution of dark matter around Lyman Alpha forest clouds, and the present data already eliminate certain models.

  12. Polar solar wind and interstellar wind properties from interplanetary Lyman-alpha radiation measurements

    NASA Technical Reports Server (NTRS)

    Witt, N.; Blum, P. W.; Ajello, J. M.

    1981-01-01

    The analysis of Mariner 10 observations of Lyman-alpha resonance radiation shows an increase of interplanetary neutral hydrogen densities above the solar poles. This increase is caused by a latitudinal variation of the solar wind velocity and/or flux. Using both the Mariner 10 results and other solar wind observations, the values of the solar wind flux and velocity with latitude are determined for several cases of interest. The latitudinal variation of interplanetary hydrogen gas, arising from the solar wind latitudinal variation, is shown to be most pronounced in the inner solar system. From this result it is shown that spacecraft Lyman-alpha observations are more sensitive to the latitudinal anisotropy for a spacecraft location in the inner solar system near the downwind axis.

  13. Lyman-alpha imagery of comet Kohoutek, and far-UV magnitudes of stars

    NASA Technical Reports Server (NTRS)

    Page, T.

    1974-01-01

    The Apollo-16 S201 electronographic camera backup model was modified for use on the Skylab AMS-SAL, which reduced its 20 deg FOV to about 7 deg unvignetted. Over 500 frames were exposed by automatic sequencer through LiF and CaF2. The Lyman-alpha halo of comet Kohoutek has been analyzed for nine occasions, and its long, pointed tail was imaged in 1250-1600 A only near perihelion. Far-UV magnitudes and colors are being derived for about 200 stars, nebulae, and galaxies. Redshifted Lyman-alpha emission from intergalactic atomic hydrogen was not detected in 7 clusters of galaxies. About 25% of the exposed frames were degraded by water damage, electrical discharges, decline in photocathode sensitivity, and loss of AMS mirror reflectance.

  14. Lyman-alpha measurements of neutral hydrogen in the outer geocorona and in interplanetary space.

    NASA Technical Reports Server (NTRS)

    Thomas, G. E.; Bohlin, R. C.

    1972-01-01

    Results of hydrogen Lyman-alpha (1216 A) measurements made on a continuous basis by a two-channel photometer on Ogo 5 from March 1968 to June 1971. The highly elliptical orbit provided measurements of both the outer geocorona and of the 1216-A sky background emission, since geocoronal scattering is minimal at the apogee distance of 150,000 km. Selected data (through 1970) are presented, as well as an interpretation of the three principal discoveries to date - namely, (1) a pronounced antisolar enhancement of the geocoronal scattering beyond 70,000 km, which is regarded as evidence for a hydrogen 'geotail' produced by solar Lyman-alpha radiation pressure; (2) a clear correlation of periodic variations in the sky background emission with solar activity associated with solar rotation; and (3) an annual variation of the 1216-A sky background emission, caused by the earth's orbital motion within the cavity created by the solar wind in the nearby interstellar hydrogen.

  15. A Sounding Rocket Experiment for the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)

    NASA Astrophysics Data System (ADS)

    Kubo, M.; Kano, R.; Kobayashi, K.; Bando, T.; Narukage, N.; Ishikawa, R.; Tsuneta, S.; Katsukawa, Y.; Ishikawa, S.; Suematsu, Y.; Hara, H.; Shimizu, T.; Sakao, T.; Ichimoto, K.; Goto, M.; Holloway, T.; Winebarger, A.; Cirtain, J.; De Pontieu, B.; Casini, R.; Auchère, F.; Trujillo Bueno, J.; Manso Sainz, R.; Belluzzi, L.; Asensio Ramos, A.; Štěpán, J.; Carlsson, M.

    2014-10-01

    A sounding-rocket experiment called the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is presently under development to measure the linear polarization profiles in the hydrogen Lyman-alpha (Lyα) line at 121.567 nm. CLASP is a vacuum-UV (VUV) spectropolarimeter to aim for first detection of the linear polarizations caused by scattering processes and the Hanle effect in the Lyα line with high accuracy (0.1%). This is a fist step for exploration of magnetic fields in the upper chromosphere and transition region of the Sun. Accurate measurements of the linear polarization signals caused by scattering processes and the Hanle effect in strong UV lines like Lyα are essential to explore with future solar telescopes the strength and structures of the magnetic field in the upper chromosphere and transition region of the Sun. The CLASP proposal has been accepted by NASA in 2012, and the flight is planned in 2015.

  16. Variability of Lyman-alpha and the ultraviolet continuum of 3C 446

    NASA Technical Reports Server (NTRS)

    Bregman, J. N.; Glassgold, A. E.; Huggins, P. J.; Kinney, A. L.

    1986-01-01

    IUE observations have been conducted over the 1230-3175 A range for the violently variable quasar 3C 446, beginning in June 1980, at intervals of 1.2, 2.2, 0.5, and 0.4 yr. Strong absorption of the continuum was found below 1830 A, probably corresponding to a Lyman edge at z of 1.00 + or - 0.01. The absence of Mg II 2798 A absorption implies that the column density is in the lower end of the range, unless the gas is metal-poor. The Lyman-alpha emission line was detected in five spectra; relative to the number of ionizing protons, the line strengths are the same as in normal quasars, and line equivalent widths are small due to the continuum's rise redward of 912 A, which is much steeper than in normal quasars. The Lyman-alpha line and the nearby continuum vary so as to maintain constant equivalent width.

  17. Performance Characterization of UV Science Cameras Developed for the Chromospheric Lyman-Alpha Spectro-Polarimeter

    NASA Technical Reports Server (NTRS)

    Champey, Patrick; Kobayashi, Ken; Winebarger, Amy; Cirtain, Jonathan; Hyde, David; Robertson, Bryan; Beabout, Brent; Beabout, Dyana; Stewart, Mike

    2014-01-01

    The NASA Marshall Space Flight Center (MSFC) has developed a science camera suitable for sub-orbital missions for observations in the UV, EUV and soft X-ray. Six cameras will be built and tested for flight with the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), a joint National Astronomical Observatory of Japan (NAOJ) and MSFC sounding rocket mission. The goal of the CLASP mission is to observe the scattering polarization in Lyman-alpha and to detect the Hanle effect in the line core. Due to the nature of Lyman-alpha polarization in the chromosphere, strict measurement sensitivity requirements are imposed on the CLASP polarimeter and spectrograph systems; science requirements for polarization measurements of Q/I and U/I are 0.1 percent in the line core. CLASP is a dual-beam spectro- polarimeter, which uses a continuously rotating waveplate as a polarization modulator, while the waveplate motor driver outputs trigger pulses to synchronize the exposures. The CCDs are operated in frame-transfer mode; the trigger pulse initiates the frame transfer, effectively ending the ongoing exposure and starting the next. The strict requirement of 0.1 percent polarization accuracy is met by using frame-transfer cameras to maximize the duty cycle in order to minimize photon noise. Coating the e2v CCD57-10 512x512 detectors with Lumogen-E coating allows for a relatively high (30 percent) quantum efficiency at the Lyman-alpha line. The CLASP cameras were designed to operate with a gain of 2.0 +/- 0.5, less than or equal to 25 e- readout noise, less than or equal to 10 e-/second/pixel dark current, and less than 0.1percent residual non-linearity. We present the results of the performance characterization study performed on the CLASP prototype camera; system gain, dark current, read noise, and residual non-linearity.

  18. Performance Characterization of UV Science Cameras Developed for the Chromospheric Lyman-Alpha Spectro-Polarimeter

    NASA Technical Reports Server (NTRS)

    Champey, P.; Kobayashi, K.; Winebarger, A.; Cirtain, J.; Hyde, D.; Robertson, B.; Beabout, D.; Beabout, B.; Stewart, M.

    2014-01-01

    The NASA Marshall Space Flight Center (MSFC) has developed a science camera suitable for sub-orbital missions for observations in the UV, EUV and soft X-ray. Six cameras will be built and tested for flight with the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), a joint National Astronomical Observatory of Japan (NAOJ) and MSFC sounding rocket mission. The goal of the CLASP mission is to observe the scattering polarization in Lyman-alpha and to detect the Hanle effect in the line core. Due to the nature of Lyman-alpha polarization in the chromosphere, strict measurement sensitivity requirements are imposed on the CLASP polarimeter and spectrograph systems; science requirements for polarization measurements of Q/I and U/I are 0.1 percent in the line core. CLASP is a dual-beam spectro-polarimeter, which uses a continuously rotating waveplate as a polarization modulator, while the waveplate motor driver outputs trigger pulses to synchronize the exposures. The CCDs are operated in frame-transfer mode; the trigger pulse initiates the frame transfer, effectively ending the ongoing exposure and starting the next. The strict requirement of 0.1 percent polarization accuracy is met by using frame-transfer cameras to maximize the duty cycle in order to minimize photon noise. Coating the e2v CCD57-10 512x512 detectors with Lumogen-E coating allows for a relatively high (30 percent) quantum efficiency at the Lyman-alpha line. The CLASP cameras were designed to operate with 10 e-/pixel/second dark current, 25 e- read noise, a gain of 2.0 +/- 0.5 and 1.0 percent residual non-linearity. We present the results of the performance characterization study performed on the CLASP prototype camera; dark current, read noise, camera gain and residual non-linearity.

  19. Calculation of the quasi-energies and resonances behavior of the hydrogen Lyman-alpha problem

    NASA Technical Reports Server (NTRS)

    Ruyten, Wilhelmus M.

    1992-01-01

    Recently, Bakshi and Kalman presented numerical results for the quasi-energies of the n = 2 multiplet in the hydrogen Lyman-alpha transition for a plasma in which both strong static and oscillating electric fields are present. Recent work on related magnetic and optical resonance problems provides a simplified mathematical treatment, as well as greater insight into the complex resonance behavior of this interaction.

  20. Heliospheric interface modifications of interstellar neutral hydrogen compatible with Lyman alpha glow observations

    NASA Astrophysics Data System (ADS)

    Quemerais, E.; Lallement, R.; Bertaux, J. L.

    1992-11-01

    The paper presents results of calculations performed to interpret the interplanetary Lyman-alpha line shape measurements acquired aboard Prognoz 5 and 6 in 1976 and 1977. It is shown that some discrepancies between the Prognoz 5/6 data and a standard homogeneous model are alleviated when initial (far from the sun) velocity and temperature distributions varying with the distance to the stagnation line are considered.

  1. HETDEX: Developing the HET's Second Generation Low Resolution Spectrograph for Probing Lyman-alpha Emitting Galaxies

    NASA Astrophysics Data System (ADS)

    Chonis, Taylor S.; Hill, G. J.; Lee, H.; Tuttle, S. E.; Vattiat, B. L.; Gebhardt, K.; Finkelstein, S. L.; Adams, J. J.; HETDEX Collaboration

    2012-01-01

    HETDEX will map the power spectrum of 0.8 million blindly discovered Lyman-alpha Emitting Galaxies (LAE) using a revolutionary new array of massively replicated fiber-fed spectrographs dubbed the Visible Integral-Field Replicable Unit Spectrograph (VIRUS). In the era of the Hobby-Eberly Telescope wide-field upgrade and VIRUS, the current Low Resolution Spectrograph (LRS) must be replaced with a fiber instrument. We discuss the development of the second generation LRS (LRS2), which is a multi-channel instrument based on the VIRUS design. In its current design phase, it is fed by a 287 fiber microlens coupled integral field unit that covers 7” x 12” with 0.62” resolution. The instrument covers 3720 Å to 4700 Å at R ≈ 1900 and 4600 Å to 7000 Å at R ≈1200. With the purpose of making the instrument ideal for follow-up observations of LAE in the HETDEX survey, we discuss the science drivers for selecting the instrument's spectral resolution. We test the utility of the instrument and pilot a future study with LRS2 by presenting R ≈ 2000 spectra taken with the VIRUS prototype spectrograph (VIRUS-P) in a high-resolution mode at the McDonald Observatory Harlan J. Smith 2.7 m telescope. These LAE were originally discovered in the HETDEX Pilot Survey and their Lyman-alpha line profiles are constrained by near-infrared observations of rest-frame optical emission lines that set the systemic redshift of the galaxies. We discuss the velocity offsets of the Lyman-alpha line from the systemic line center and compare the line profiles to theoretical predictions and to similar observations for Lyman-break galaxies. Our observations provide an example of how LRS2 can be used to probe Lyman-alpha emission in 2 < z < 3 star forming galaxies.

  2. The intrinsic H I Lyman-alpha line profiles of late-type stars

    NASA Technical Reports Server (NTRS)

    Neff, J. E.; Landsman, W. B.; Bookbinder, J. A.; Linsky, J. L.

    1990-01-01

    The Lyman-alpha line of neutral hydrogen is probably the most important cooling channel for chromospheric plasma in late-type stars, yet it is also the least studied major line in the far ultraviolet. The scattering of much of the stellar Lyman-alpha flux by interstellar hydrogen, coupled with the geocoronal emission foreground, seriously complicates the analysis of the Lyman-alpha spectra. The influence of the local interstellar medium on the observed profiles was circumvented by observing stars with radial velocities sufficiently high to Doppler shift the center of the stellar emission line out of the interstellar absorption core. There are several stars that have high radial velocities by virtue of their presence in close binary systems. High resolution IUE (International Ultraviolet Explorer) spectra of Ly alpha line of two such eclipsing binary stars, AR Lac and TY Pyx, are obtained, at each orbital quadrature phase, when the projected orbital velocity is a maximum. By combining the spectra from opposite quadratures it is possible to piece together the entire stellar emission profiles. The third star in this study, delta Lep, is a single star with a high space velocity.

  3. Understanding the physics driving the values of Lyman-alpha forest bias parameters

    NASA Astrophysics Data System (ADS)

    Cieplak, Agnieszka M.; Slosar, Anze

    2016-01-01

    With the advancement of Lyman-alpha forest power spectrum measurements to larger scales and to greater precision, it is crucial that we also improve our understanding of the bias between the measured flux and the underlying matter power spectrum, especially for future percent level cosmology constraints. In order to develop an intuition for the physics driving the values of the density and velocity bias parameters of the Lyman-alpha forest, we have run a series of hydrodynamic SPH simulations to test existing approximations found in the literature. Through a series of progressively more realistic scenarios, we first introduce flux based on the Fluctuating Gunn Peterson Approximation, just using the density fields, then introduce redshift space distortions, as well as thermal broadening, and finally, analyzing the full hydrodynamic part of the simulations. We find surprising agreement between the analytical approximations developed by Seljak (2012) and the numerical methods in the limit of linear redshift space-distortions and no thermal broadening. Specifically, we find that the prediction of the analytical velocity bias expression is exact in the limit of no thermal broadening, and speculate that the measurement of this bias along with a small-scale measurement of the flux PDF, could yield a possible probe of the thermal state of the IGM. A deeper understanding of the large-scale Lyman-alpha biasing will also help us in using the large-scale clustering of the forest as a cosmological probe beyond baryon acoustic oscillations.

  4. Latitudinal distribution of solar wind as deduced from Lyman alpha measurements - an improved method

    NASA Astrophysics Data System (ADS)

    Summanen, T.; Lallement, R.; Bertaux, J. L.; Kyrola, E.

    1993-08-01

    In this work we examine the possibility of deducing the latitudinal distribution of the solar ionization rate using Prognoz 6 Lyman-alpha data in a more general and flexible way than previously examined. Using a so-called hot model for the hydrogen distribution and the optically thin model for the resonance scattering, theoretical Lyman-alpha intensity for the interstellar hydrogen is calculated and compared with the intensity data measured by Prognoz 6. Varying the latitudinal dependence of the ionization rate, the distributions which produce the best fit with the data are analyzed for four different measuring sessions. As a result, we get four ionization rate distributions that have two common features. The ionization rate is enhanced near the solar equator, and large broad plateaus exist around heliographic latitudes +/- 30 to +/- 70 deg. The latitudinal distribution of the average ionization rate about the solar minimum deviates clearly from the spherically symmetric and sinusoidally with the latitude-varying models used so far. The growth of the solar wind mass flux from the solar polar areas toward the equator corresponds to the earlier results found from Lyman-alpha measurements.

  5. The Lyman-alpha Solar Telescope for the ASO-S

    NASA Astrophysics Data System (ADS)

    Li, Hui

    2015-08-01

    The Lyman-alpha Solar Telescope (LST) is one of the payloads for the proposed Space-Borne Advanced Solar Observatory (ASO-S). LST consists of a Solar Disk Imager (SDI) with a field-of-view (FOV) of 1.2 Rsun, a Solar Corona Imager (SCI) with an FOV of 1.1 - 2.5 Rsun, and a full-disk White-light Solar Telescope (WST) with an FOV of 1.2 Rsun, which also serves as the guiding telescope. The SCI is designed to work at the Lyman-alpha waveband and white-light, while the SDI will work at the Lyman-alpha waveband only. The WST works both in visible (for guide) and ultraviolet (for science) white-light. The LST will observe the Sun from disk-center up to 2.5 solar radii for both solar flares and coronal mass ejections. In this presentation, I will give an introduction to LST, including scientific objectives, science requirement, instrument design and current status.

  6. Mapping of the Moon in the Ultraviolet: the Lyman Alpha Mapping Project

    NASA Astrophysics Data System (ADS)

    Horvath, D. G.; Retherford, K. D.; Gladstone, G. R.; Stern, S. A.; Egan, A. F.; Miles, P. F.; Parker, J. Wm.; Greathouse, T. K.; Davis, M. W.; Slater, D. C.; Kaufmann, D. E.; Versteeg, M. H.; Feldman, P. D.; Hurley, D. M.; Pryor, W. R.; Hendrix, A. R.

    2010-10-01

    The Lyman Alpha Mapping Project (LAMP) is an ultraviolet (UV) spectrograph on the Lunar Reconnaissance Orbiter (LRO) that is designed to map the lunar albedo at far-UV wavelengths. LAMP primarily measures interplanetary HI Lyman-alpha sky-glow and FUV starlight reflected from the night-side lunar surface, including permanently shadowed regions (PSRs) near the poles. Dayside observations are also obtained. Calibration data, collected monthly, will monitor instrument functionality. Brightness maps sorted by wavelength (including the Lyman-alpha wavelength of 121.6 nm) are reported for the polar regions, with a few regions of interest reported in more detail. LAMP's spectral range of 58 nm to 196 nm includes a water ice spectral feature near 160 nm, which provides a diagnostic tool for detecting water on the lunar surface that is complementary to recent discoveries using infrared and radio frequency techniques. Progress towards producing far-UV albedo maps and searching for water ice signatures will be reported. We'll discuss how LAMP data may address questions regarding how water is formed on the moon, transported through the lunar atmosphere, and deposited in the PSRs.

  7. Understanding the Large Scale Clustering of the Lyman-alpha Forest

    NASA Astrophysics Data System (ADS)

    Cieplak, Agnieszka; Slosar, Anze; Khandai, Nishikanta

    2015-04-01

    The Lyman-alpha forest has become a powerful probe of cosmological parameters by measuring large scale structure at intermediate redshift. With upcoming surveys increasing the scope of these measurements, understanding of the bias between the measured flux and the underlying matter power spectrum is becoming crucial to the percent level cosmological interpretation of these observations. We therefore employ cosmological hydrodynamic simulations to study the response of the Lyman-alpha forest clustering to large wavelength modes of the underlying matter large-scale structure and compare these to previous theoretical studies of this bias which used only N-body and hydro-PM simulations. We demonstrate this response by evolving smaller, curved universe cosmologies, representing the same universe with different overdense patches, and we use these to study the assumption of the analytical bias formula derived by Seljak (2012). A full theoretical understanding of this bias is important to fully understand the clustering of the Lyman-alpha forest and its cosmological implications.

  8. The Lyman Alpha Imaging-Monitor Experiment (LAIME) for TESIS/CORONAS-PHOTON

    NASA Astrophysics Data System (ADS)

    Damé, L.; Koutchmy, S.; Kuzin, S.; Lamy, P.; Malherbe, J.-M.; Noëns, J.-C.

    LAIME the Lyman Alpha Imaging-Monitor Experiment is a remarkably simple no mechanisms and compact 100x100x400 mm full Sun imager to be flown with TESIS on the CORONAS-PHOTON mission launch expected before mid-2008 As such it will be the only true chromospheric imager to be flown in the next years supporting TESIS EUV-XUV imaging SDO and the Belgian LYRA Lyman Alpha flux monitor on the ESA PROBA-2 microsatellite launch expected in September 2007 We will give a short description of this unique O60 mm aperture imaging telescope dedicated to the investigating of the magnetic sources of solar variability in the UV and chromospheric and coronal disruptive events rapid waves Moreton waves disparitions brusques of prominences filaments eruptions and CMEs onset The resolution pixel is 2 7 arcsec the field of view 1 4 solar radius and the acquisition cadence could be as high as 1 image minute The back thinned E2V CCD in the focal plane is using frame transfer to avoid shutter and mechanisms Further more the double Lyman Alpha filtering allows a 40 AA FWHM bandwidth and excellent rejection yet providing a vacuum seal design of the telescope MgF2 entrance window Structural stability of the telescope focal length 1 m is preserved by a 4-INVAR bars design with Aluminium compensation in a large pm 10 o around 20 o

  9. Blob Flowers.

    ERIC Educational Resources Information Center

    Canfield, Elaine

    2003-01-01

    Describes an art project called blob flowers in which fifth-grade students created pictures of flowers using watercolor and markers. Explains that the lesson incorporates ideas from art and science. Discusses in detail how the students created their flowers. (CMK)

  10. Searching for Lyman alpha emission from a possible Zel'dovich pancake

    NASA Technical Reports Server (NTRS)

    Cox, Caroline; Schulman, Eric; Bregman, Joel N.

    1993-01-01

    The detection of 2 x 10(exp 14) solar mass of neutral hydrogen at a redshift of 3.397 has been reported. Top-down theories of structure formation predict such a mass of hydrogen collapsing to form a protocluster of galaxies. We sought to observe this object in Lyman-alpha, which could be produced through ionization by the metagalactic ionizing radiation field or through internal ionization processes. On 29 Apr. 1992, the region of the reported HI emission for 1800 seconds with the 1.3 meter McGraw-Hill reflector at Michigan-Dartmouth-M.I.T. Observatory was observed. Because the H1 emission reported has a transverse scale of 300 sec, a 1/3.06 reducing camera and a Thomson CCD were used to obtain a field of view of about 600 sec by 840 sec. A filter 88 A wide, centered at 5354 A was used; Lyman-alpha emission at z = 3.4 is redshifted to 5347 A. In order to avoid saturating the CCD with a bright star in the field, nine 200 second exposures were taken. The combination of these images shows no obvious extended Lyman-alpha emission at a level of about 28 magnitudes per square arcsecond. The field observed also shows a distant cluster of galaxies. In order to determine if the cluster could in any way be associated with the cloud of neutral hydrogen at z = 3.4, we sought to estimate its redshift from the size and magnitude of the galaxies and of the cluster as a whole. Omega = 1 and H(sub O) = 50 km s(sup -1) Mpc(sup -1) were adopted; our redshift estimates range from z = 0.2 to z = 0.6. The cluster is clearly not associated with the HI cloud at z = 3.4.

  11. The effect of latitudinally varying solar wind flux on the Lyman alpha sky background

    NASA Astrophysics Data System (ADS)

    Summanen, T.; Kyrola, E.; Lallement, R.; Bertaux, J.-L.

    A model for the ionization rate, which accepts any latitudinal structure for the solar wind flux was used. It is possible to study different kinds of models for the latitudinal density structure, if the latitudinal dependence of the solar wind velocity is known (e.g., from interplanetary scintillation observations). Simulated measurements were compared with the Lyman alpha intensity data from Prognoz 5 and 6 satellites. The latest results are presented. The SOHO spacecraft, to be launched in 1995 to the first Lagrange point between the Sun and the Earth, will provide new data from the SWAN (a study of Solar Wind ANisotropies) experiment measuring Lymann alpha intensity.

  12. Spatially resolved Lyman-alpha emission from a virtual dwarf galaxy

    NASA Astrophysics Data System (ADS)

    Verhamme, Anne

    2015-02-01

    In the context of the first light of MUSE, Integral Field Unit (IFU) spectrograph of second generation installed recently at VLT, we compute mock IFU Lyman-alpha (lyα) observations of a virtual dwarf galaxy, to help understanding and interpreting forthcoming observations. This study is an extension of the work carried out in Verhamme et al. (2012), where we studied the spatially integrated lyα properties of a dwarf galaxy. With the same data, we now investigate the spatial variations of lyα spectra.

  13. Lyman-alpha fluorescence from hydrogen photofragments of CH4 and H2O

    NASA Technical Reports Server (NTRS)

    Wu, C. Y. R.; Judge, D. L.

    1981-01-01

    The process of H-Lyman-alpha fluorescence produced through photodissociation of CH4 and H2O provides an example for the usefulness of the detection of fluorescence of dissociation fragments as an aid in identifying some high lying Rydberg states. In the first experiment reported, an electron storage ring synchrotron radiation source was used. The fluorescence produced was detected with a solar blind photomultiplier and a Cs photocathode with a spectral sensitivity in the wavelength range from 1050 to 1950 A. In the second experiment considered, an intense atomic line source was employed.

  14. Signatures of solar wind latitudinal structure in interplanetary Lyman-alpha emissions - Mariner 10 observations

    NASA Technical Reports Server (NTRS)

    Kumar, S.; Broadfoot, A. L.

    1979-01-01

    A detailed analysis is conducted which shows that signatures in the interplanetary Lyman-alpha emissions observed in three different data sets from Mariner 10 (corresponding to different locations of the spacecraft) provide firm evidence that the intensity departures are correlated with a decrease in solar wind flux with increasing latitude. It is suggested that observations of the interplanetary emission can be used to monitor average solar wind activity at high latitudes. The asymmetry in the solar radiation field as a source of observed departures in L-alpha data is considered and attention is given to the interstellar hydrogen and helium density.

  15. Factors Affecting VUV Emission Spectrum near Lyman-{alpha} from a Hydrogen Plasma Source

    SciTech Connect

    Ogino, K.; Kasuya, T.; Shimamoto, S.; Wada, M.; Kimura, Y.; Nishiura, M.

    2011-09-26

    Vacuum ultra violet (VUV) emission spectra from plasmas near walls of different metallic materials were measured to estimate the effect upon the local production rate of vibrational excited hydrogen molecules due to plasma wall interaction. Among Cu, Mo, Ni, Ta and Ti, the intensity of band spectrum around Lyman-{alpha} had become the largest when Cu wall was used while it was the smallest for Ti. The role of particle reflection from the plasma electrode surface upon the H{sup -} production by a pure electron volume process is discussed.

  16. Evaluation of miniature vacuum ultraviolet lamps for stability and operating characteristics, Lyman-Alpha task

    NASA Technical Reports Server (NTRS)

    Hurd, W. A.

    1985-01-01

    Modifications required to change the near ultraviolet source in the Optical Contamination Monitor to a source with output at or near the Lyman-Alpha hydrogen line are discussed. The effort consisted of selecting, acquiring and testing candidate miniature ultraviolet lamps with significant output in or near 121.6 nm. The effort also included selection of a miniature dc high-voltage power supply capable of operating the lamp. The power supply was required to operate from available primary power supplied by the Optical Effect Module (DEM) and it should be flight qualified or have the ability to be qualified by the user.

  17. Evidence for Shocks and Increased SFE in the Lyman Alpha Reference Sample

    NASA Astrophysics Data System (ADS)

    Puschnig, Johannes; Hayes, Matthew; Östlin, Göran

    2015-02-01

    We report on first molecular gas observations in the Lyman Alpha Reference Sample (LARS; Hayes et al. 2013, 2014, Östlin et al. 2014), which were performed using the 45m telescope at the Nobeyama Radio Observatory (NRO). The beamsize at the observed 12CO (1-0) emission is ~ 15'' corresponding to ~ 12kpc at the given redshift of z ~ 0.04. We detected strong 12CO emission in LARS 3 (Arp 238), marginally detected LARS 8 (SDSS 1250+0734) and derived an upper limit for LARS 9 (IRAS 08208+2816).

  18. Photochemical decomposition of N2O by Lyman-alpha radiation: scientific basis for a chemical actinometer.

    PubMed

    Rajappan, Mahesh; Büttner, Michael; Cox, Charlie; Yates, John T

    2010-03-18

    A novel IR method for measuring the kinetics of N(2)O photodecomposition has been devised and used to calibrate the flux of Lyman-alpha (10.2 eV) radiation from a H(2)/Ar microwave discharge lamp. The photodecomposition of N(2)O occurs with a weak pressure dependence due to the operation of a wall effect consuming some photogenerated active oxygen species. This effect is removed by working at high N(2)O pressures. The Lyman-alpha flux from the lamp is 1.28 +/- 0.36 x 10(15) photons cm(-2) s(-1). PMID:20155946

  19. A Very Large Array search for emission from HI associated with nearby Lyman alpha absorbers

    NASA Technical Reports Server (NTRS)

    Van Gorkom, J. H.; Bahcall, J. N.; Jannuzi, B. T.; Schneider, D. P.

    1993-01-01

    We present a sensitive Very Large Array (VLA) search for H I emission from the vicinity of the Lyman alpha clouds in the Virgo Cluster, which were recently discovered with Hubble Space Telescope (HST) in absorption toward the nearest quasar 3C273. We searched an area of 40 by 40 arcmin centered on 3C273, covering a velocity range from 840 to 1840 km/s. The bandpass was self-calibrated on 3C273 leading to a spectral dynamic range of better than 10(exp 5) to 1. No H I was detected. The rms noise in the final images corresponds to a 3 sigma column density sensitivity of 2.8 x 10(exp 19) sq cm on scales of a few kpc. Small H I clouds could have been detected down to a few times 10(exp 6) solar mass. Our failure to detect H I emission at the higher column densities sets a lower limit to the radius of the Lyman alpha clouds of 3.9 kpc, assuming a spherical geometry.

  20. Performance Characterization of the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) CCD Cameras

    NASA Technical Reports Server (NTRS)

    Joiner, Reyann; Kobayashi, Ken; Winebarger, Amy; Champey, Patrick

    2014-01-01

    The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a sounding rocket instrument which is currently being developed by NASA's Marshall Space Flight Center (MSFC) and the National Astronomical Observatory of Japan (NAOJ). The goal of this instrument is to observe and detect the Hanle effect in the scattered Lyman-Alpha UV (121.6nm) light emitted by the Sun's Chromosphere to make measurements of the magnetic field in this region. In order to make accurate measurements of this effect, the performance characteristics of the three on-board charge-coupled devices (CCDs) must meet certain requirements. These characteristics include: quantum efficiency, gain, dark current, noise, and linearity. Each of these must meet predetermined requirements in order to achieve satisfactory performance for the mission. The cameras must be able to operate with a gain of no greater than 2 e(-)/DN, a noise level less than 25e(-), a dark current level which is less than 10e(-)/pixel/s, and a residual nonlinearity of less than 1%. Determining these characteristics involves performing a series of tests with each of the cameras in a high vacuum environment. Here we present the methods and results of each of these performance tests for the CLASP flight cameras.

  1. Performance Characterization of the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) CCD Cameras

    NASA Technical Reports Server (NTRS)

    Joiner, Reyann; Kobayashi, Ken; Winebarger, Amy; Champey, Patrick

    2014-01-01

    The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a sounding rocket instrument currently being developed by NASA's Marshall Space Flight Center (MSFC), the National Astronomical Observatory of Japan (NAOJ), and other partners. The goal of this instrument is to observe and detect the Hanle effect in the scattered Lyman-Alpha UV (121.6nm) light emitted by the Sun's chromosphere. The polarized spectrum imaged by the CCD cameras will capture information about the local magnetic field, allowing for measurements of magnetic strength and structure. In order to make accurate measurements of this effect, the performance characteristics of the three on- board charge-coupled devices (CCDs) must meet certain requirements. These characteristics include: quantum efficiency, gain, dark current, read noise, and linearity. Each of these must meet predetermined requirements in order to achieve satisfactory performance for the mission. The cameras must be able to operate with a gain of 2.0+/- 0.5 e--/DN, a read noise level less than 25e-, a dark current level which is less than 10e-/pixel/s, and a residual non- linearity of less than 1%. Determining these characteristics involves performing a series of tests with each of the cameras in a high vacuum environment. Here we present the methods and results of each of these performance tests for the CLASP flight cameras.

  2. Lyman-{alpha} constraints on warm and on warm-plus-cold dark matter models

    SciTech Connect

    Boyarsky, Alexey; Lesgourgues, Julien; Ruchayskiy, Oleg

    2009-05-15

    We revisit Lyman-{alpha} bounds on the dark matter mass in {Lambda} Warm Dark Matter ({Lambda}WDM) models, and derive new bounds in the case of mixed Cold plus Warm models ({Lambda}CWDM), using a set up which is a good approximation for several theoretically well-motivated dark matter models. We combine WMAP5 results with two different Lyman-{alpha} data sets, including observations from the Sloan Digital Sky Survey. We pay a special attention to systematics, test various possible sources of error, and compare the results of different statistical approaches. Expressed in terms of the mass of a non-resonantly produced sterile neutrino, our bounds read m{sub NRP} {>=} 8 keV (frequentist 99.7% confidence limit) or m{sub NRP} {>=} 12.1 keV (Bayesian 95% credible interval) in the pure {Lambda}WDM limit. For the mixed model, we obtain limits on the mass as a function of the warm dark matter fraction F{sub WDM}. Within the mass range studied here (5 keV < m{sub NRP} < {infinity}), we find that any mass value is allowed when F{sub WDM} < 0.6 (frequentist 99.7% confidence limit); similarly, the Bayesian joint probability on (F{sub WDM}, 1/m{sub NRP}) allows any value of the mass at the 95% confidence level, provided that F{sub WDM} < 0.35.

  3. The hydrogen coma of Comet P/Halley observed in Lyman-alpha using sounding rockets

    NASA Technical Reports Server (NTRS)

    Mccoy, R. P.; Meier, R. R.; Keller, H. U.; Opal, C. B.; Carruthers, G. R.

    1992-01-01

    Hydrogen Lyman-alpha (121.6 nm) images of Comet P/Halley were obtained using sounding rockets launched from White Sands Missile Range on 24.5 February and 13.5 March 1986. The second rocket was launched 13 hours before the fly-by of the Giotto spacecraft. An electrographic camera on both flights provided Lyman-alpha images covering a 20 field of view with 3 arcmin resolution. The data from both flights have been compared with a time-dependent model of hydrogen kinetics. To match the measured isophote contours, hydrogen sources with velocity components of 8 km/s and 20 km/s (from OH and H2O respectively) as well as a low velocity component (about 2 km/s) are required. This low velocity component is thought to result from thermalization of fast hydrogen atoms within the collision zone, providing an important diagnostic of temperature and density near the nucleus. Hydrogen production rates of 3.8 x 10 exp 30/s and 1.7 x 10 exp 30/s have been obtained for the two observations.

  4. Analysis of coronal H I Lyman alpha measurements from a rocket flight on 1979 April 13

    NASA Technical Reports Server (NTRS)

    Withbroe, G. L.; Kohl, J. L.; Weiser, H.; Noci, G.; Munro, R. H.

    1982-01-01

    It is noted that measurements of the profiles of resonantly scattered hydrogen Lyman-alpha coronal radiation have been used in determining hydrogen kinetic temperatures from 1.5 to 4 solar radii from sun center in a quiet region of the corona. Proton temperatures derived using the line widths decrease with height from 2.6 x 10 to the 6th K at 1.5 solar radii to 1.2 x 10 to the 6th K at 4 solar radii. These measurements, together with temperatures for lower heights determined from earlier Skylab and eclipse data, suggest that there is a maximum in the quiet coronal proton temperature at about 1.5 solar radii. Comparison of measured Lyman-alpha intensities with those calculated using a representative model for the radial variation of the coronal electron density yields information on the magnitude of the electron temperature gradient and suggests that the solar wind flow was subsonic for distances less than 4 solar radii.

  5. Magnetic Turbulence and Line Broadening in Simulations of Lyman-Alpha Absorption

    NASA Astrophysics Data System (ADS)

    Gurvich, Alex; Burkhart, Blakesley K.; Bird, Simeon

    2016-01-01

    We use the Illustris cosmological AREPO simulations to study the effects of gas turbulence and magnetic fields on measurements from the Lyman-Alpha forest. We generate simulated Lyman-Alpha spectra and plot the distributions of Column Density (CDD) and Doppler Width (b) both by adhering to the canonical method of fitting Voigt profiles to absorption lines and by directly measuring the column density and equivalent widths from snapshot data .We investigate the effects of additional unresolved gas turbulence in Illustris by adding an additional broadening term to the line profiles to mimic turbulent broadening. When we do this, we find a measurable effect in the CDD and an offset in the mean of the b distribution corresponding to the additional turbulence. We also compare different MHD runs in AREPO we find that the CDD can measurably differentiate between magnetic seed field at redshifts as low as z=0.1, but we do not find that the b distribution is affected at a detectable level. Our work suggests that the effects of turbulence and magnetic fields from z=2-0.1 can potentially be measured with these diagnostics. This work was supported in part by the NSF REU and DoD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution.

  6. Scattered Lyman-alpha radiation of comet 2012/S1 (ISON) observed by SUMER/SOHO

    NASA Astrophysics Data System (ADS)

    Curdt, W.; Boehnhardt, H.; Germerott, D.; Schuehle, U.; Solanki, S.; Teriaca, L.; Vincent, J.

    2014-07-01

    During its recent perihelion passage, comet ISON came so close to the Sun that it appeared in the field of view (FOV) of the SUMER spectrometer on SOHO and allowed unique observations at far-UV wavelengths with high spatial and temporal resolution. We report results of these observations completed during the comet's encounter with the Sun on November 28.75, 2013. Our data show the dust tail trailing behind the predicted position of the nucleus seen in Lyman-alpha emission as light from the solar disk that is scattered by micron-sized dust particles. The arrow-shaped tail is offset from the trajectory and not aligned with it. We model the dust emission and dynamics to reproduce the appearance of the tail. We could not detect any signature of cometary gas or plasma around the expected position of the nucleus and conclude that the out-gassing processes must have stopped before the comet entered our FOV. Also the model we used to reproduce the observed dust tail needs a sharp fall-off of the dust production hours before perihelion. We compare the radiance of the dust tail to the Lyman-alpha emission of the disk for an estimate of the dust column density. After observing 18 years mostly solar targets, this was the first time that SUMER completed spectroscopic observations of a comet.

  7. Mariner 6, 7, and 9 ultraviolet spectrometer experiment - Analysis of hydrogen Lyman alpha data

    NASA Technical Reports Server (NTRS)

    Anderson, D. E., Jr.

    1974-01-01

    Four Lyman alpha airglow measurements of the limb and disk of Mars, made by ultraviolet spectrometers on Mariner 6 and 7 in 1969 and Mariner 9 in 1971, are analyzed to determine the amount and distribution of atomic hydrogen above 80 km. The variation of atomic hydrogen with altitude is calculated by using time-independent chemical diffusion models from 80 to 250 km, and an exospheric model is used above 250 km. By employing radiative transfer theory that includes effects of pure absorption and accounts for temperature variations in the atmosphere, a spherical model of the airglow Lyman alpha emission is used to produce theoretical intensities for comparison with the data. It is found that (1) the exospheric temperature and distribution in 1971 are consistent with those determined in 1969, (2) the vertical optical depth above 80 km was 2.2 in 1969 and 5 in 1971, and (3) the derived atomic hydrogen distribution from 80 to 250 km requires a source of atomic hydrogen above 80 km. Comparison of observed profiles with chemical diffusion models implies a large downward flow of atomic hydrogen at 80 km coupled with a large upward flow of molecular hydrogen.-

  8. Lenses in the forest: cross--correlation of the Lyman-alpha flux with CMB lensing

    SciTech Connect

    Vallinotto, Alberto; Das, Sudeep; Spergel, David N.; Viel, Matteo; /Trieste Observ. /INFN, Trieste

    2009-03-01

    We present a theoretical estimate for a new observable: the cross-correlation between the Lyman-{alpha}-flux fluctuations in quasar (QSO) spectra and the convergence of the cosmic microwave background (CMB) as measured along the same line-of-sight. As a first step toward the assessment of its detectability, we estimate the signal-to-noise ratio using linear theory. Although the signal-to-noise is small for a single line-of-sight and peaks at somewhat smaller redshifts than those probed by the Lyman-{alpha} forest, we estimate a total signal-to-noise of 9 for cross-correlating QSO spectra of SDSSIII with Planck and 20 for cross-correlating with a future polarization based CMB experiment. The detection of this effect would be a direct measure of the neutral hydrogen-matter cross-correlation and could provide important information on the growth of structures at large scales in a redshift range which is still poorly probed by observations.

  9. Performance Characterization of the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) CCD Cameras

    NASA Astrophysics Data System (ADS)

    Joiner, R. K.; Kobayashi, K.; Winebarger, A. R.; Champey, P. R.

    2014-12-01

    The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a sounding rocket instrument which is currently being developed by NASA's Marshall Space Flight Center (MSFC) and the National Astronomical Observatory of Japan (NAOJ). The goal of this instrument is to observe and detect the Hanle effect in the scattered Lyman-Alpha UV (121.6nm) light emitted by the Sun's Chromosphere to make measurements of the magnetic field in this region. In order to make accurate measurements of this effect, the performance characteristics of the three on-board charge-coupled devices (CCDs) must meet certain requirements. These characteristics include: quantum efficiency, gain, dark current, noise, and linearity. Each of these must meet predetermined requirements in order to achieve satisfactory performance for the mission. The cameras must be able to operate with a gain of no greater than 2 e­-/DN, a noise level less than 25e-, a dark current level which is less than 10e-/pixel/s, and a residual non-linearity of less than 1%. Determining these characteristics involves performing a series of tests with each of the cameras in a high vacuum environment. Here we present the methods and results of each of these performance tests for the CLASP flight cameras.

  10. Properties of high-redshift Lyman-alpha clouds. I - Statistical analysis of the Schneider-Schmidt-Gunn quasars

    NASA Technical Reports Server (NTRS)

    Press, William H.; Rybicki, George B.; Schneider, Donald P.

    1993-01-01

    Techniques for statistical analysis of the Lyman-alpha forest in high-redshift quasars are developed, and applied to the low-resolution (25 A) spectra of 29 of the 33 quasars in the Schneider-Schmidt-Gunn sample. We extrapolate each quasar's continuum shortward of Lyman-alpha emission, then consider each spectral bin of each quasar to be an (approximately) independent measurement of the absorption due to the Lyman-alpha clouds. With several thousand such measurements thus available, we can obtain good determinations of some interesting properties of clouds in the redshift range 2.5-4.3 without actually resolving any single cloud. We find that the mean absorption increases with z approximately as a power law (1 + z) exp (gamma + 1) with gamma = 2.46 +/- 0.37. The mean ratio of Lyman-alpha to Lyman-beta absorption in the clouds is 0.476 +/- 0.054. We also detect, and obtain ratios, for Lyma-gamma, delta, and possibly epsilon.

  11. Indications for axial asymmetries in the interplanetary hydrogen distribution derived from Pioneer-10 Lyman-alpha data

    NASA Technical Reports Server (NTRS)

    Scherer, K.; Judge, D. L.

    1992-01-01

    It is presently noted that Pioneer 10's highly spatially resolved Lyman-alpha data exhibit a backscattered resonance glow with a persistent spatially-resolved asymmetry. The first harmonic amplitude ranges from about 5-10 percent of the mean value, and is observed continuously throughout the two years of this analysis period.

  12. Absolute wavelength measurement of the Lyman-{alpha} transitions of hydrogenic Mg{sup 11+}

    SciTech Connect

    Hoelzer, G.; Foerster, E.; Kloepfel, D.; Beiersdorfer, P.; Brown, G.V.; Crespo Lopez-Urrutia, J.R.; Widmann, K.

    1998-02-01

    The wavelengths of the 1s{sub 1/2}-2p{sub 1/2} and 1s{sub 1/2}-2p{sub 3/2} Lyman-{alpha} transitions have been measured in hydrogenic Mg{sup 11+} with an accuracy as high as 24 ppm. The measurement was carried out on an electron-beam ion trap and utilized a quasimonolithic crystal setup absolutely calibrated relative to optical standards. The resulting values for the two transitions were 0.84250{plus_minus}0.00004 and 0.84190{plus_minus}0.00002nm, respectively. The measurement confirms calculations of the 1s-2p wavelengths and tests the size of the 1s Lamb shift to within 13{percent}. {copyright} {ital 1998} {ital The American Physical Society}

  13. Nonadiabatic behavior of the polarization of electric-field-induced Lyman-. alpha. radiation

    SciTech Connect

    Plotzke, O.; Wille, U.; Hippler, R.; Lutz, H.O. Bereich Schwerionenphysik, Hahn-Meitner-Institut Berlin, Berlin )

    1990-12-10

    The linear polarization of Lyman-{alpha} radiation emitted when hydrogen atoms in the metastable 2{ital s}{sub 1/2} state traverse an external electric field is studied as a function of the effective rise time of the field for field strengths extending from very small values up to 6 keV/cm. With decreasing rise time, the measured polarization exhibits a transition from {ital adiabatic} to {ital sudden} behavior. The transition region is centered at a rise time which is approximately equal to the characteristic time associated with the 2{ital s}{sub 1/2-}2{ital p}{sub 1/2} Lamb splitting in the unperturbed hydrogen system. The experimental data are well described by the results of a time-dependent theory.

  14. Solar wind decrease at high heliographic latitudes detected from Prognoz interplanetary Lyman alpha mapping

    NASA Astrophysics Data System (ADS)

    Lallement, R.; Bertaux, J. L.; Kurt, V. G.

    1985-02-01

    New evidence for a latitudinal decrease of the solar wind mass flux is presented from observations of the interplanetary Lyman alpha emission collected in 1976 and 1977 with satellites Prognoz 5 and 6. The flow of interstellar hydrogen atoms in the solar system is ionized by EUV solar radiation and charge exchange with solar wind protons which accounts for about 80% of the total ionization rate. The resulting gradual decrease of the neutral H density from the upwind region down to the downwind region observed from Ly α intensity measurements allowed the determination of the absolute value of the total ionization rate β for one H atom at 1 AU against ionization. Collected in 1976 and 1977 at five places in the solar system, the measurements are compared to different models.

  15. Resonance-enhanced two-photon ionization of ions by Lyman alpha radiation in gaseous nebulae.

    PubMed

    Johansson, S; Letokhov, V

    2001-01-26

    One of the mysteries of nebulae in the vicinity of bright stars is the appearance of bright emission spectral lines of ions, which imply fairly high excitation temperatures. We suggest that an ion formation mechanism, based on resonance-enhanced two-photon ionization (RETPI) by intense H Lyman alpha radiation (wavelength of 1215 angstroms) trapped inside optically thick nebulae, can produce these spectral lines. The rate of such an ionization process is high enough for rarefied gaseous media where the recombination rate of the ions formed can be 10(-6) to 10(-8) per second for an electron density of 10(3) to 10(5) per cubic centimeter in the nebula. Under such conditions, the photo-ions formed may subsequently undergo further RETPI, catalyzed by intense He i and He ii radiation, which also gets enhanced in optically thick nebulae that contain enough helium. PMID:11158669

  16. Low-redshift Lyman-alpha absorption lines and the dark matter halos of disk galaxies

    NASA Technical Reports Server (NTRS)

    Maloney, Philip

    1992-01-01

    Ultraviolet observations of the low-redshift quasar 3C 273 using the Hubble Space Telescope have revealed many more Lyman-alpha absorption lines than would be expected from extrapolation of the absorption systems seen toward QSOs at z about 2. It is shown here that these absorption lines can plausibly be produced by gas at large radii in the disks of spiral and irregular galaxies; the gas is confined by the dark matter halos and ionized and heated by the extragalactic radiation field. This scenario does not require the extragalactic ionizing radiation field to decline as rapidly with decreasing z as the QSO emissivity. Observations of Ly-alpha absorption through the halos of known galaxies at low redshift will constrain both the extragalactic background and the properties of galactic halos.

  17. Glauber calculations of polarization of Lyman-alpha resulting from e/-/-H/1s/ collisions.

    NASA Technical Reports Server (NTRS)

    Gerjuoy, E.; Thomas, B. K.; Sheorey, V. B.

    1972-01-01

    We have calculated the polarization fraction of the Lyman-alpha radiation emitted in e/-/-H/1s/ collisions using the Glauber, Born, and various Vainshtein approximations, and have compared these predictions with observation. We find that the Born, Glauber and all forms of the Vainshtein yield results which are very close to each other and to the data in the energy range from 30 to 700 eV. The comparatively small differences between the various approximations are detailed in the text; also, the reason for the close agreement of the predicted polarization fractions - although the computed 1s-2p total and differential cross sections are not so close - is explained. With respect to the Glauber approximation, the importance of computing the phase integral along a direction perpendicular to the momentum transfer q at each value of q, is stressed.

  18. Mariner 9 ultraviolet spectrometer experiment - Mars airglow spectroscopy and variations in Lyman alpha.

    NASA Technical Reports Server (NTRS)

    Barth, C. A.; Stewart, A. I.; Hord, C. W.; Lane, A. L.

    1972-01-01

    Mariner 9 ultraviolet spectrometer observations show the Mars airglow consists principally of emissions that arise from the interaction of solar ultraviolet radiation with carbon dioxide, the principal constituent of the Mars atmosphere. Two minor constituents, atomic hydrogen and atomic oxygen, also produce airglow emissions. The airglow measurements show that ionized carbon dioxide is only a minor constituent of the ionosphere. Using the airglow measurements of atomic oxygen, it is possible to infer that the major ion is ionized molecular oxygen. The escape rate of atomic hydrogen measured by Mariner 9 is approximately the same as that measured two years earlier by Mariner 6 and 7. If the current escape rate has been operating for 4.5 billion years and if water vapor is the ultimate source, an amount of oxygen has been generated that is far in excess of that observed at present. Mariner 9 observations of Mars Lyman alpha emission over a period of 120 days show variations of 20%.

  19. Spectro-polarimetry of a Lyman-alpha Nebula at z=3.09

    NASA Astrophysics Data System (ADS)

    Beck, Melanie; Scarlata, Claudia; Hayes, Matthew

    2015-01-01

    We present a follow-up study to the imaging polarimetry performed by Hayes, Scarlata & Siana (2011) on one of the largest Lyman-alpha (Lya) nebula currently known, dubbed LAB1. We obtain deep, spatially resolved spectro-polarimetric measurements of LAB1, whose extended Lya emission is likely due to Lya photons produced from a powerful star-forming galaxy and scattered at large radii by the surrounding neutral gas. However, questions still remain on the precise nature of the kinematics in the system. We find spectrally integrated polarization consistent with our prior imaging results. We find wavelength dependent polarization consistent with zero at line center and rising to approximately 12% in the wing of the line profile which supports the idea of a large scale outflow. We discuss how the detected wavelength dependence of the Lya polarization can help in constraining the geometry of the scattering nebula.

  20. Imaging of High Redshift Starburst galaxies in the light of Lyman alpha

    NASA Astrophysics Data System (ADS)

    Beckwith, Steven

    1997-07-01

    The PI is the designated director for STScI but has no experience with HST. The purpose of this proposal is to gain experience with the facility by carrying out a modest observational program that is unique and will not conflict with any community programs. The proposed science is divided into priority 1 and priority 2, for 6 + 4 orbits. This division will allow allocation in parts, if the pressure on DDT is large and the total of 10 orbits unusually difficult to schedule. The priority 1 science is rather predictable and, hence, conservative, consisting of the brightest of the objects under study. The priority 2 science is somewhat riskier, because it is more difficult to estimate object brightnesses in the filters to be used on HST. Both priority 1 and priority 2 observations allow for a large degree of serendipity, because the fields are likely to have more starburst galaxies at the observed redshifts that may show up in Lyman alpha. Exploration of the high redshift u niverse and discovery of the most distant objects is still in its infancy. Only recently have the tools been available to detect normal galaxies at redshifts larger than one when the first galaxies were created {Pescarelle et al. 1996; Hu & McMahon 1996; Cowie & Hu 1998; Steidel et al. 1996}. It seems likely that young galaxies will have a variety of different signatures {Franceschini et al. 1998; Guideroni et al. 1997}, so that it will be necessary to use several diverse techniques to uncover all of them: searches at optical, infrared, x-ray, and radio wavelengths, for example. It is already known that many of the optically selected galaxies using the "dropout" technique are reddened by dust {Pettini et al. 1997}. We carried out two surveys for infrared emission-line galaxies by imaging through narrow {Resolving power 100} and broad band filters between 1 and 2.5 microns and identifying objects that appeared brighter in the narrow filters. Our first survey was designed to uncover emission lines at

  1. More confirmed damped Lyman-Alpha systems from the Las Campanas/Palomar survey

    NASA Technical Reports Server (NTRS)

    Lu, Limin; Wolfe, Arthur M.

    1994-01-01

    We present moderate-resolution spectra of six high-redshift quasars which contain nine candidate damped Lyman alpha absorption systems identified in the Las Campanas/Palomar survey of Lanzetta et al. (ApJS, 77, 1 (1991)). Eight of the nine candidate damped Lyman alpha absorption systems are confirmed (one tentative), including seven with N(H I) greater than or equal to 2 x 10(exp 20) /sq cm. The remaining one turns out to be due to blending of many narrow absorption lines. Accurate absorption redshifts, H I column densities, and metal-line equivalent widths are provided for these systems in order to facilitate future studies of detailed physical condition and chemical abundances. We briefly discuss the 18 other metal-line systems identified along these sight lines. The z(sub abs) = 2.6527 system toward Q 2231-00 is interesting in that it shows strong O VI (lambda) (lambda) 1031, 1037 absorption. The O VI ion is one of the best diagnostics of hot gas, and high resolution studies of the O VI absorption is likely to yield important clues regarding the ionization mechanism of the metal-line systems. Another system, at z(sub abs) = 2.3771 toward Q 2239-38, shows relatively strong Zn II and Cr II absorption, clearly indicating that it belongs to the same class absorbers as the damped Lyman systems. We have not obtained metal abundances for this system because the H(sub I) column density is not available. We also find a Lyman limit absorption system at z(sub abs)= 3.5090 toward Q 2239-38 which does not show obvious metal absorption lines. More sensitive observations are required to check on this interesting possibility.

  2. More confirmed damped Lyman-Alpha systems from the Las Campanas/Palomar survey

    NASA Astrophysics Data System (ADS)

    Lu, Limin; Wolfe, Arthur M.

    1994-07-01

    We present moderate-resolution spectra of six high-redshift quasars which contain nine candidate damped Lyman alpha absorption systems identified in the Las Campanas/Palomar survey of Lanzetta et al. (ApJS, 77, 1 (1991)). Eight of the nine candidate damped Lyman alpha absorption systems are confirmed (one tentative), including seven with N(H I) greater than or equal to 2 x 1020 /sq cm. The remaining one turns out to be due to blending of many narrow absorption lines. Accurate absorption redshifts, H I column densities, and metal-line equivalent widths are provided for these systems in order to facilitate future studies of detailed physical condition and chemical abundances. We briefly discuss the 18 other metal-line systems identified along these sight lines. The zabs = 2.6527 system toward Q 2231-00 is interesting in that it shows strong O VI (lambda) (lambda) 1031, 1037 absorption. The O VI ion is one of the best diagnostics of hot gas, and high resolution studies of the O VI absorption is likely to yield important clues regarding the ionization mechanism of the metal-line systems. Another system, at zabs = 2.3771 toward Q 2239-38, shows relatively strong Zn II and Cr II absorption, clearly indicating that it belongs to the same class absorbers as the damped Lyman systems. We have not obtained metal abundances for this system because the HI column density is not available. We also find a Lyman limit absorption system at zabs= 3.5090 toward Q 2239-38 which does not show obvious metal absorption lines. More sensitive observations are required to check on this interesting possibility.

  3. The Characteristic Dimension of Lyman-Alpha Forest Clouds Toward Q0957+561

    NASA Technical Reports Server (NTRS)

    Dolan, J. F.; Michalitsianos, A. G.; Hill, R. J.; Nguyen, Q. T.; Fisher, Richard (Technical Monitor)

    2000-01-01

    Far-ultraviolet spectra of the gravitational lens components Q0957+561 A and B were obtained with the Hubble Space Telescope Faint Object Spectrograph to investigate the characteristic dimension of Lyman-alpha forest clouds in the direction of the quasar. If one makes the usual assumption that the absorbing structures are spherical clouds with a single radius, that radius can be found analytically from the ratio of Lyman-alpha lines in only one line of sight to the number in both. A simple power series approximation to this solution, accurate everywhere to better than 1%, will be presented. Absorption lines in Q0957+561 having equivalent width greater than 0.3 A in the observer's frame not previously identified as interstellar lines, metal lines, or higher order Lyman lines were taken to be Ly-alpha forest lines. The existence of each line in this consistently selected set was then verified by its presence in two archival FOS spectra with approximately 1.5 times higher signal to noise than our spectra. Ly-alpha forest lines appear at 41 distinct wavelengths in the spectra of the two images. One absorption line in the spectrum of image A has no counterpart in the spectrum of image B, and one line in image B has no counterpart in image A. Based on the separation of the lines of sight over the redshift range searched for Ly-alpha forest lines, the density of the absorbing clouds in the direction of Q0957+561 must change significantly over a radius R = 160 (+120, -70) h (sup -1) (sub 50) kpc (H (sub 0) 50 h (sub 50) km s (sup -1) kpc (sup -1), q (sub 0) = 1/2). The 95% confidence interval on R extends from (50 950) h (sup -1) (sub 50) kpc.

  4. The Lyman alpha forest of the high-z quasar 0000-263

    NASA Technical Reports Server (NTRS)

    Penprase, Bryan; Gilmozzi, Roberto; Bowen, David; Madau, Piero

    1993-01-01

    Medium-resolution (delta(v) = 45 km/s) optical spectra of the bright, high-redshift (z = 4.1) quasar 0000-263 taken at the ESO 3.5-m NTT telescope were analyzed to determine the distribution of column densities, velocities and line widths of the Lyman-alpha forest absorption components. The values of NH, b, and z were determined by fitting Voigt profiles to the lines, and convolving with a Gaussian instrumental response function. Over 350 components with log N(sub H) greater than 13.2 were identified. An analysis of the dependence of the number of components with z reveals that the number evolution of components obeys the power law dN/dz varies as (1+z)(sup gamma), where gamma = 0.5 +/- 0.4 for the sample of 182 lines with log N(sub H) greater than 14.0. The distribution of component strengths is found to obey f(N(sub H)) varies as N(sub h)(sup -beta), where beta = -1.55 for components with log(N(sub H)) is greater than 14.7, and beta = -0.68 for the components with log(N(sub H)) greater than 13.5. A distinct break in the f(N(sub H)) histogram is also observed, at log(N(sub H)) is approximately 14.7. The results are briefly considered in the context of theoretical models of quasar Lyman alpha clouds and their evolution.

  5. Characteristics of the local interstellar hydrogen determined from PROGNOZ 5 and 6 interplanetary Lyman-alpha line profile measurements with a hydrogen absorption cell

    NASA Astrophysics Data System (ADS)

    Bertaux, J. L.; Lallement, R.; Kurt, V. G.; Mironova, E. N.

    1985-09-01

    The flow of interstellar H atoms in the solar system was observed through resonance scattering of solar Lyman-alpha protons with two Lyman-alpha photometers on the Prognoz 5 and 6 satellites. Data collected at five different locations in the solar system were compared with a model of the interstellar H flow, modified by solar interaction. Five parameters describing atomic hydrogen of the local interstellar medium and two parameters describing the solar interaction were derived simultaneously to give a good fit of the upwind hemisphere. The solar Lyman-alpha flux at line center was determined along with the ionization rate of H atoms.

  6. Galaxies Coming of Age in Cosmic Blobs

    NASA Astrophysics Data System (ADS)

    2009-06-01

    is a crucial stage of the evolution of galaxies and black holes - known as "feedback" - and one that astronomers have long been trying to understand. "We're seeing signs that the galaxies and black holes inside these blobs are coming of age and are now pushing back on the infalling gas to prevent further growth," said coauthor Bret Lehmer, also of Durham. "Massive galaxies must go through a stage like this or they would form too many stars and so end up ridiculously large by the present day." Chandra and a collection of other telescopes including Spitzer have observed 29 blobs in one large field in the sky dubbed "SSA22." These blobs, which are several hundred thousand light years across, are seen when the Universe is only about two billion years old, or roughly 15% of its current age. X-ray Chandra X-ray Image of Lyman Alpha Blobs In five of these blobs, the Chandra data revealed the telltale signature of growing supermassive black holes - a point-like source with luminous X- ray emission. These giant black holes are thought to reside at the centers of most galaxies today, including our own. Another three of the blobs in this field show possible evidence for such black holes. Based on further observations, including Spitzer data, the research team was able to determine that several of these galaxies are also dominated by remarkable levels of star formation. The radiation and powerful outflows from these black holes and bursts of star formation are, according to calculations, powerful enough to light up the hydrogen gas in the blobs they inhabit. In the cases where the signatures of these black holes were not detected, the blobs are generally fainter. The authors show that black holes bright enough to power these blobs would be too dim to be detected given the length of the Chandra observations. People Who Read This Also Read... Milky Way's Super-efficient Particle Accelerators Caught in The Act NASA Announces 2009 Astronomy and Astrophysics Fellows Cosmic

  7. The 27-day versus 13.5-day variations in the solar Lyman-alpha radiation and the radio wave absorption in the lower ionosphere over Europe

    NASA Technical Reports Server (NTRS)

    Delamorena, B. A.; Lastovicka, Jan; Rapoport, Z. TS.; Alberca, L.

    1989-01-01

    In order to clarify the question of solar periods in absorption, the pattern was studied of the solar Lyman-alpha radiation (the principal ionizing agent of the lower ionosphere) and of the radio wave absorption at five widely spaced places in Europe. When the solar Lyman-alpha flux variability is very well developed, then it dominates in the lower ionospheric variability. The most pronounced Lyman-alpha variation on time scale day-month is the solar rotation variation (about 27 days). When the Lyman-alpha variability is developed rather poorly, as it is typical for periods dominated by the 13.5 day variability, then the lower ionospheric variability appears to be dominated by variations of meteorological origin. The conclusions hold for all five widely spaced placed in Europe.

  8. Temporally Resolved Spectral Structure of 821 nm Broad-Area Laser Diode Seeder for Muonium Lyman-Alpha Generation

    NASA Astrophysics Data System (ADS)

    Okamura, Kotaro; Saito, Norihito; Miyazaki, Koji; Oishi, Yu; Louchev, Oleg; Iwasaki, Masahiko; Wada, Satoshi

    To match the Lyman-alpha bandwidth with the Doppler-broadening of thermal Muonium, 230 GHz bandwidth is required for the 821 nm output of OPO + OPA, hence that of their seeder. We selected a broad-area laser diode with bandwidth-selection using a thin solid etalon and successfully realized bandwidth- and wavelength- tunable output which satisfied the requirements.

  9. Performance Characterization of UV Science Cameras Developed for the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)

    NASA Technical Reports Server (NTRS)

    Champey, Patrick; Kobayashi, Ken; Winebarger, Amy; Cirtin, Jonathan; Hyde, David; Robertson, Bryan; Beabout, Brent; Beabout, Dyana; Stewart, Mike

    2014-01-01

    The NASA Marshall Space Flight Center (MSFC) has developed a science camera suitable for sub-orbital missions for observations in the UV, EUV and soft X-ray. Six cameras will be built and tested for flight with the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), a joint National Astronomical Observatory of Japan (NAOJ) and MSFC sounding rocket mission. The goal of the CLASP mission is to observe the scattering polarization in Lyman-alpha and to detect the Hanle effect in the line core. Due to the nature of Lyman-alpha polarization in the chromosphere, strict measurement sensitivity requirements are imposed on the CLASP polarimeter and spectrograph systems; science requirements for polarization measurements of Q/I and U/I are 0.1% in the line core. CLASP is a dual-beam spectro-polarimeter, which uses a continuously rotating waveplate as a polarization modulator, while the waveplate motor driver outputs trigger pulses to synchronize the exposures. The CCDs are operated in frame-transfer mode; the trigger pulse initiates the frame transfer, effectively ending the ongoing exposure and starting the next. The strict requirement of 0.1% polarization accuracy is met by using frame-transfer cameras to maximize the duty cycle in order to minimize photon noise. Coating the e2v CCD57-10 512x512 detectors with Lumogen-E coating allows for a relatively high (30%) quantum efficiency at the Lyman-$\\alpha$ line. The CLASP cameras were designed to operate with =10 e- /pixel/second dark current, = 25 e- read noise, a gain of 2.0 and =0.1% residual non-linearity. We present the results of the performance characterization study performed on the CLASP prototype camera; dark current, read noise, camera gain and residual non-linearity.

  10. The latitudinal dependence of the solar ionization rate as deduced from the Prognoz-6 Lyman-alpha measurements

    NASA Astrophysics Data System (ADS)

    Summanen, T.; Kyrola, E.; Lallement, R.; Bertaux, J. L.

    The latitudinal dependence of the solar ionization is studied using the Lyman-alpha measurements by the Prognoz-6 spacecraft during the solar minimum 1976-77. Applying a hot model for the interplanetary H-gas we have searched for an optimal ionization function to comply with the measurements. Using the optimal ionization function we have studied the latitudinal variation of the solar wind mass flux and the proton density.

  11. The Electron Excitation Function of H Lyman-(alpha) from Threshold to 1.8 keV

    NASA Technical Reports Server (NTRS)

    James, G. K.; Slevin, J. A.; Shemansky, D. E.; McConkey, J. W.; Dziczek, D.; Kanik, I.; Ajello, J. M.

    1996-01-01

    The excitation function of prompt Lyman-(alpha) radiation, produced by electron impact excitation of atomic hydrogen, has been measured for the first time over an extended energy range from threshold to 1.8 keV. Measurments were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source.

  12. COMPARISON OF PIONEER 10, VOYAGER 1, AND VOYAGER 2 ULTRAVIOLET OBSERVATIONS WITH ANTI-SOLAR LYMAN-ALPHA BACKSCATTER SIMULATIONS

    SciTech Connect

    Fayock, B.; Zank, G. P.; Heerikhuisen, J. E-mail: garyp.zank@gmail.com

    2013-09-20

    Observations made by ultraviolet (UV) detectors on board Pioneer 10, Voyager 1, and Voyager 2 can be used to analyze the distribution of neutral hydrogen throughout the heliosphere, including the interaction regions of the solar wind and local interstellar medium. Previous studies of the long-term trend of decreasing intensity with increasing heliocentric distance established the need for more sophisticated heliospheric models. Here we use state-of-the-art three-dimensional (3D) magnetohydrodynamic (MHD) neutral models to simulate Lyman-alpha backscatter as would be seen by the three spacecrafts, exploiting a new 3D Monte Carlo radiative transfer code under solar minimum conditions. Both observations and simulations of the UV backscatter intensity are normalized for each spacecraft flight path at {approx}15 AU, and we focus on the slope of decreasing intensity over an increasing heliocentric distance. Comparisons of simulations with Voyager 1 Lyman-alpha data results in a very close match, while the Pioneer 10 comparison is similar due to normalization, but not considered to be in agreement. The deviations may be influenced by a low resolution of photoionization in the 3D MHD-neutral model, a lack of solar cycle activity in our simulations, and possibly issues with instrumental sensitivity. Comparing the slope of Voyager 2 and the simulated intensities yields an almost identical match. Our results predict a large increase in the Lyman-alpha intensity as the hydrogen wall is approached, which would signal an imminent crossing of the heliopause.

  13. H I Lyman-alpha in the sun - The effects of partial redistribution in the line wings

    NASA Technical Reports Server (NTRS)

    Roussel-Dupre, D.

    1983-01-01

    A form for the Lyman-alpha redistribution function that is modified to include the effects of collisional coupling between different energy states is presented. It is noted that this extends the work of Yelnik et al. (1981) and Roussel-Dupre(1982). By separating the source function into its primary components at all heights, the formation of Lyman-alpha radiation is investigated in detail. Frequencies in the line wing can be mapped back in such a way that the heights of formation for a change in lambda of plus or minus 0.5-6 A span the entire solar chromosphere. The usefulness of the Lyman-alpha wing as an atmospheric probe, however, is limited by long thermalization lengths, which result from almost coherent scattering outside of the Doppler core. When the line profiles calculated from the chromospheric models of Vernazza et al. (1981) are compared with the quiet-sun observations of Roussel-Dupre, agreement is found in integrated core intensities and in the line wing shape and normalized center-to-limb behavior. The calculated wing intensities, however, are a factor of four too small.

  14. Primordial lithium in z~0, metal-poor damped Lyman alpha systems

    NASA Astrophysics Data System (ADS)

    Cooke, Ryan

    2013-10-01

    A longstanding challenge for the standard model of Big Bang Nucleosynthesis is to explain the discrepancy between the predicted and observed primordial lithium abundance; the most metal-poor stars are deficient in Li by a factor of 3-4 relative to the standard model prediction. We propose to use the combined efforts of HST+COS and ground-based optical echelle spectrographs, to measure the primordial Li abundance in clouds of near-pristine gas at low redshift. To this end, we have compiled a prime list of sure candidate low-redshift damped Lyman-alpha systems {DLAs} that are in front of bright quasars. This combination is essential to detect the weak Li absorption lines arising in the ISM of external galaxies. For a small investment of HST time, we will confirm these systems as new low-redshift DLAs - almost tripling the current number of known systems - and discern the optimum clouds where the primordial abundance of Li can be measured. The sought-after data will also provide new opportunities to study the detailed properties of DLAs and their host galaxies, as well as the greater environments in which they reside.

  15. Solar Cycle Variations of O VI and H I Lyman Alpha Intensities in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Miralles, M. P.; Panasyuk, A. V.; Strachan, L.; Gardner, L. D.; Suleiman, R. M.; Smith, P. L.; Kohl, J. L.

    2000-05-01

    UVCS/SOHO measurements of O VI (103.2 and 103.7 nm) and H I Lyman alpha intensities in the solar corona have been made from 1996 to the present spanning the rising phase of cycle 23. During solar minimum the corona consisted of large coronal holes at the poles and quiescent streamers at the equator. During the ascending phase of the cycle, the corona presented high latitude streamers and finally polar streamers as the Sun approached solar maximum. Recent observations of the solar corona show the presence of coronal holes at the equator and streamers at the poles. Our observations provide descriptions of these structures over the rising phase of the solar cycle. We compare the properties of quiescent equatorial streamers which occurred at solar minimum to high latitude and polar streamers observed toward solar maximum. We also compare solar minimum polar coronal holes to equatorial coronal holes present at solar maximum. We discuss how these results are related to the plasma properties. This work is supported by NASA under Grant NAG5-7822 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by PRODEX (Swiss contribution).

  16. Water vapor content in the polar atmosphere measured by Lyman-alpha/OH fluorescence method

    NASA Technical Reports Server (NTRS)

    Iwasaka, Y.; Saitoh, S.; Ono, A.

    1985-01-01

    The water vapor of the polar stratosphere possibly plays an important role in various aeronomical processes; for example, OH radical formation through photodissociation of H2O, formation of water cluster ions, radiative energy transfer in the lower stratosphere, condensation onto particulate matter, and so on. In addition to these, it has been speculated, from the viewpoint of global transport and/or budget of water vapor, that the polar stratosphere functions as an active sink. STANFORD (1973) emphasized the existence of the stratospheric Cist cloud in the polar stratosphere which brought a large loss rate of stratospheric water vapor through a so-called freeze-out of cloud particles from the stratosphere into the troposphere. However, these geophysically interesting problems unfortunately remain to be solved, owing to the lack of measurements on water vapor distribution and its temporal variation in the polar stratosphere. The water vapor content measured at Syowa Station (69.00 deg S, 39.35 deg E), Antarctica using a balloon-borne hygrometer (Lyman - alpha/OH fluorescence type) is discussed.

  17. The Moon's Permanently Shadowed Regions as Observed by LRO's Lyman Alpha Mapping Project (LAMP) Instrument

    NASA Astrophysics Data System (ADS)

    Gladstone, R.; Retherford, K. D.; Stern, S. A.; Egan, A.; Miles, P. F.; Versteeg, M.; Slater, D.; Davis, M. W.; Parker, J.; Kaufmann, D.; Greathouse, T. K.; Steffl, A. J.; Mukherjee, J.; Horvath, D.; Rojas, P.; Feldman, P. D.; Hurley, D. M.; Pryor, W. R.; Hendrix, A. R.

    2011-12-01

    Although of great interest for science and resource utilization, the Moon's permanently shadowed regions (PSRs) near each pole present difficult targets for remote sensing. The Lyman Alpha Mapping Project (LAMP) instrument on the Lunar Reconnaissance Orbiter (LRO) mission is able to map PSRs at far-ultraviolet (FUV) wavelengths using two faint sources of illumination from the night sky: the all-sky Lyα glow produced as interplanetary medium (IPM) H atoms scatter the Sun's Lyα emissions, and the much fainter source from UV-bright stars. Since the reflected light from these two sources produces only a few hundred events per second in the photon-counting LAMP instrument, building maps with useful signal-to-noise (SNR) ratios requires the careful accumulation of the observations from thousands of individual LRO orbits. In this talk we present the latest FUV albedo maps obtained by LAMP of the Moon's southern and northern polar regions. The results show that 1) most PSR regions are darker at all FUV wavelengths, consistent with their surface soils having much larger porosities than non-PSR regions (e.g., P~0.9 or so), and 2) most PSRs are somewhat "redder" (i.e., more reflective at the longer FUV wavelengths) than non-PSR regions, consistent with the presence of ~1-2% water frost at the surface.

  18. LAMP: The Lyman Alpha Mapping Project on NASA's Lunar Reconnaissance Orbiter Mission

    NASA Astrophysics Data System (ADS)

    Gladstone, G. Randall; Stern, S. Alan; Retherford, Kurt D.; Black, Ronald K.; Slater, David C.; Davis, Michael W.; Versteeg, Maarten H.; Persson, Kristian B.; Parker, Joel W.; Kaufmann, David E.; Egan, Anthony F.; Greathouse, Thomas K.; Feldman, Paul D.; Hurley, Dana; Pryor, Wayne R.; Hendrix, Amanda R.

    2010-01-01

    The Lyman Alpha Mapping Project (LAMP) is a far-ultraviolet (FUV) imaging spectrograph on NASA’s Lunar Reconnaissance Orbiter (LRO) mission. Its main objectives are to (i) identify and localize exposed water frost in permanently shadowed regions (PSRs), (ii) characterize landforms and albedos in PSRs, (iii) demonstrate the feasibility of using natural starlight and sky-glow illumination for future lunar surface mission applications, and (iv) characterize the lunar atmosphere and its variability. As a byproduct, LAMP will map a large fraction of the Moon at FUV wavelengths, allowing new studies of the microphysical and reflectance properties of the regolith. The LAMP FUV spectrograph will accomplish these objectives by measuring the signal reflected from the night-side lunar surface and in PSRs using both the interplanetary HI Lyman- α sky-glow and FUV starlight as light sources. Both these light sources provide fairly uniform, but faint, illumination. With the expected LAMP sensitivity, by the end of the primary 1-year LRO mission, the SNR for a Lyman- α albedo map should be >100 in polar regions >1 km2, providing useful FUV constraints to help characterize subtle compositional and structural features. The LAMP instrument is based on the flight-proven Alice series of spectrographs flying on the Rosetta comet mission and the New Horizons Pluto mission. A general description of the LAMP instrument and its initial ground calibration results are presented here.

  19. Non-parametric 3D map of the intergalactic medium using the Lyman-alpha forest

    NASA Astrophysics Data System (ADS)

    Cisewski, Jessi; Croft, Rupert A. C.; Freeman, Peter E.; Genovese, Christopher R.; Khandai, Nishikanta; Ozbek, Melih; Wasserman, Larry

    2014-05-01

    Visualizing the high-redshift Universe is difficult due to the dearth of available data; however, the Lyman-alpha forest provides a means to map the intergalactic medium at redshifts not accessible to large galaxy surveys. Large-scale structure surveys, such as the Baryon Oscillation Spectroscopic Survey (BOSS), have collected quasar (QSO) spectra that enable the reconstruction of H I density fluctuations. The data fall on a collection of lines defined by the lines of sight (LOS) of the QSO, and a major issue with producing a 3D reconstruction is determining how to model the regions between the LOS. We present a method that produces a 3D map of this relatively uncharted portion of the Universe by employing local polynomial smoothing, a non-parametric methodology. The performance of the method is analysed on simulated data that mimics the varying number of LOS expected in real data, and then is applied to a sample region selected from BOSS. Evaluation of the reconstruction is assessed by considering various features of the predicted 3D maps including visual comparison of slices, probability density functions (PDFs), counts of local minima and maxima, and standardized correlation functions. This 3D reconstruction allows for an initial investigation of the topology of this portion of the Universe using persistent homology.

  20. Latitudinal properties of the Lyman alpha and O VI profiles in the extended solar corona

    NASA Astrophysics Data System (ADS)

    Zangrilli, L.; Nicolosi, P.; Poletto, G.; Noci, G.; Romoli, M.; Kohl, J. L.

    1999-02-01

    We have analysed the latitudinal properties of the profiles of the H I Lyman alpha line at 1215.6 protect Angstroms and of the O VI doublet at 1031.9 protect Angstroms and 1037.6 protect Angstroms in the extended solar corona, between 1.5 R_sun and 2.0 R_sun. Observations have been performed with the UltraViolet Coronagraph Spectrometer (UVCS) on board the ESA-NASA solar satellite SOHO (SOlar and Heliospheric Observatory). The results show that these lines have quite a different behaviour with latitude: the Ly alpha line has larger full width at half maximum (FWHM) values in the streamer region and narrower ones towards polar latitudes, while the O VI lines have a minimum FWHM at the center of the streamer, which almost steadily increases towards polar regions. The observations have been analysed looking also for an interpretation in terms of selective heating mechanisms. The implications of our results for coronal heating theories are also examined. In particular we discuss the possibility for the presence of the ion-cyclotron coronal heating mechanism. Moreover, we point out an interesting correlation between the intensity of the coronal lines and their widths, which may be relevant to the open question of the different morphological features visible in the Ly alpha and O VI lines.

  1. Gravity-driven intrusions in stratified fluids

    NASA Astrophysics Data System (ADS)

    Maurer, Benjamin Dudley

    All natural fluids stratify. Stable stratifications, in which isobars and isopycnals are parallel, are capable of supporting internal wave motion. Unstable stratification, in which density and pressure gradients are not aligned, results in gravity-driven flow. Gravity currents are a subset of these flows in which horizontal density gradients sharpen and propagate horizontally, transporting mass, momentum, and energy. If the density of the gravity current is within the density extrema of the stably stratified ambient fluid, it propagates as an intrusion at an intermediate height. Through laboratory experiments and numerical simulations, this dissertation explores the influence of stratification on the dynamics of gravity-driven intrusions. Intrusions require stable stratification in the ambient fluid, which is capable of transporting momentum and energy away from the current in the form of internal waves. We investigate the constant velocity propagation of well-mixed intrusions propagating into a linearly stratified ambient fluid. Varying the level of neutral buoyancy, we quantify the corresponding variation in structure, momentum, and energy of the upstream wave field. Adjacent stable stratifications of differing vertical density structure necessarily entail horizontal density gradients. These gradients determine the hydrostatic pressure differences driving the ensuing gravity current. We examine the mid-depth, constant velocity propagation of one linearly stratified fluid into another more strongly linearly stratified fluid. Working from the available potential energy of the system and measurements of the intrusion thickness, we develop an energy model to describe the speed of the intrusion in terms of the ratio of the two buoyancy frequencies. Distinct from adjacent linear stratifications, adjacent discrete stratifications may create flow consisting of interleaving intrusions. Single intrusions into a two-layer ambient fluid are well understood. Limiting our

  2. Measurements of gravity driven granular channel flows

    NASA Astrophysics Data System (ADS)

    Facto, Kevin

    This dissertation presents experiments that studied two gravity driven granular channel flows. The first experiment used magnetic resonance imaging to measure the density and displacement distributions of poppy seeds flowing in a rough walled channel. Time-averaged measurements of normalized velocity and density showed little flow speed dependence. Instantaneous measurements, however, showed marked velocity dependence in the displacement distributions. There was evidence of aperiodic starting and stopping at lower flow speeds and the onset of density waves on a continuous flow at higher speeds. The second experiment measured forces in all three spatial directions at the boundary of a flow of steel balls. The relationship between the normal and the tangential forces were examined statistically and compared to the Coulomb friction model. For both large and small forces, the tangential and normal forces are unrelated, as there appears to be a strong tendency for the tangential force to maintain a value that will bear the weight the weight of the particles in flow.

  3. Galaxies Coming of Age in Cosmic Blobs

    NASA Astrophysics Data System (ADS)

    2009-06-01

    is a crucial stage of the evolution of galaxies and black holes - known as "feedback" - and one that astronomers have long been trying to understand. "We're seeing signs that the galaxies and black holes inside these blobs are coming of age and are now pushing back on the infalling gas to prevent further growth," said coauthor Bret Lehmer, also of Durham. "Massive galaxies must go through a stage like this or they would form too many stars and so end up ridiculously large by the present day." Chandra and a collection of other telescopes including Spitzer have observed 29 blobs in one large field in the sky dubbed "SSA22." These blobs, which are several hundred thousand light years across, are seen when the Universe is only about two billion years old, or roughly 15% of its current age. X-ray Chandra X-ray Image of Lyman Alpha Blobs In five of these blobs, the Chandra data revealed the telltale signature of growing supermassive black holes - a point-like source with luminous X- ray emission. These giant black holes are thought to reside at the centers of most galaxies today, including our own. Another three of the blobs in this field show possible evidence for such black holes. Based on further observations, including Spitzer data, the research team was able to determine that several of these galaxies are also dominated by remarkable levels of star formation. The radiation and powerful outflows from these black holes and bursts of star formation are, according to calculations, powerful enough to light up the hydrogen gas in the blobs they inhabit. In the cases where the signatures of these black holes were not detected, the blobs are generally fainter. The authors show that black holes bright enough to power these blobs would be too dim to be detected given the length of the Chandra observations. People Who Read This Also Read... Milky Way's Super-efficient Particle Accelerators Caught in The Act NASA Announces 2009 Astronomy and Astrophysics Fellows Cosmic

  4. Radiation Transport of Heliospheric Lyman-alpha from Combined Cassini and Voyager Data Sets

    NASA Technical Reports Server (NTRS)

    Pryor, W.; Gangopadhyay, P.; Sandel, B.; Forrester, T.; Quemerais, E.; Moebius, E.; Esposito, L.; Stewart, I.; McClintock, W.; Jouchoux, A.; Colwell, J.; Izmodenov, V.; Malama, Y.; Shemansky, D.; Ajello, J.; Hansen, C.; Bzowski, M.

    2008-01-01

    Heliospheric neutral hydrogen scatters solar Lyman-alpha radiation from the Sun with '27-day' intensity modulations observed near Earth due to the Sun's rotation combined with Earth's orbital motion. These modulations are increasingly damped in amplitude at larger distances from the Sun due to multiple scattering in the heliosphere, providing a diagnostic of the interplanetary neutral hydrogen density independent of instrument calibration. This paper presents Cassini data from 2003-2004 obtained downwind near Saturn at approximately 10 AU that at times show undamped '27-day' waves in good agreement with the single-scattering models of Pryor et al., 1992. Simultaneous Voyager 1 data from 2003- 2004 obtained upwind at a distance of 88.8-92.6 AU from the Sun show waves damped by a factor of -0.21. The observed degree of damping is interpreted in terms of Monte Carlo multiple-scattering calculations (e.g., Keller et al., 1981) applied to two heliospheric hydrogen two-shock density distributions (discussed in Gangopadhyay et al., 2006) calculated in the frame of the Baranov-Malama model of the solar wind interaction with the two-component (neutral hydrogen and plasma) interstellar wind (Baranov and Malama 1993, Izmodenov et al., 2001, Baranov and Izmodenov, 2006). We conclude that multiple scattering is definitely occurring in the outer heliosphere. Both models compare favorably to the data, using heliospheric neutral H densities at the termination shock of 0.085 cm(exp -3) and 0.095 cm(exp -3). This work generally agrees with earlier discussions of Voyager data in Quemerais et al., 1996 showing the importance of multiple scattering but is based on Voyager data obtained at larger distances from the Sun (with larger damping) simultaneously with Cassini data obtained closer to the Sun.

  5. The non-linear power spectrum of the Lyman alpha forest

    NASA Astrophysics Data System (ADS)

    Arinyo-i-Prats, Andreu; Miralda-Escudé, Jordi; Viel, Matteo; Cen, Renyue

    2015-12-01

    The Lyman alpha forest power spectrum has been measured on large scales by the BOSS survey in SDSS-III at z~ 2.3, has been shown to agree well with linear theory predictions, and has provided the first measurement of Baryon Acoustic Oscillations at this redshift. However, the power at small scales, affected by non-linearities, has not been well examined so far. We present results from a variety of hydrodynamic simulations to predict the redshift space non-linear power spectrum of the Lyα transmission for several models, testing the dependence on resolution and box size. A new fitting formula is introduced to facilitate the comparison of our simulation results with observations and other simulations. The non-linear power spectrum has a generic shape determined by a transition scale from linear to non-linear anisotropy, and a Jeans scale below which the power drops rapidly. In addition, we predict the two linear bias factors of the Lyα forest and provide a better physical interpretation of their values and redshift evolution. The dependence of these bias factors and the non-linear power on the amplitude and slope of the primordial fluctuations power spectrum, the temperature-density relation of the intergalactic medium, and the mean Lyα transmission, as well as the redshift evolution, is investigated and discussed in detail. A preliminary comparison to the observations shows that the predicted redshift distortion parameter is in good agreement with the recent determination of Blomqvist et al., but the density bias factor is lower than observed. We make all our results publicly available in the form of tables of the non-linear power spectrum that is directly obtained from all our simulations, and parameters of our fitting formula.

  6. Archival Search for METAL LINES in QUASAR LYMAN-ALPHA SYSTEMS

    NASA Astrophysics Data System (ADS)

    Tytler, David

    1995-07-01

    QSO Lyman-alpha forest absorption systems have traditionally been considered intergalactic primordial gas clouds, but new data suggest that many of them at high redshift contain metals with abundances of C/H eq -3, which means 10^-3 solar. We propose to search for metals in HST spectra of LyAlpha forest systems at low redshift. The search has two parts: first we look for 2 Sigma metal lines at the expected positions of known LyAlpha lines, and we estimate the number of chance identifications. Second, we align and coadd spectra at the expected positions of the metal lines in each LyAlpha systems. We will look for the strong metal lines {C IV, O VI, N V, C III, Mg X and Ne VIII} in this composite. There are five reasons why we expect to find metals. {1} We are finding C IV in LyAlpha clouds at high z. {2} The number of C IV systems increases with decreasing redshift. {3} In general, abundances should be higher at low z. {4} We are now identifying many low redshift LyAlpha lines with the outer regions of galaxies. {5} O VI should be stronger than C IV. O VI is not easily seen at high z because of confusion in the LyAlpha forest, but it will be accessible in HST data. With 100 LyAlpha systems from the HST spectra of 167 QSOs we should reach a limit of C/H <= -2.3 for C IV, and worse for other ions. If we find metals, we begin to determine if they are more common in LyAlpha clouds which are associated with galaxies, and especially whether they occur in clouds which are intergalactic.

  7. Solar wind decrease at high heliographic latitudes detected from Prognoz interplanetary Lyman alpha mapping

    SciTech Connect

    Lallement, R.; Bertaux, J.L.; Kurt, V.G.

    1985-02-01

    New evidence for a latitudinal decrease of the solar wind mass flux is presented from observations of the interplanetary Lyman alpha emission collected in 1976 and 1977 with satellites Prognoz 5 and 6. The flow of interstellar hydrogen atoms in the solar system is ionized by EUV solar radiation and charge exchange with solar wind protons which accounts for about 80% of the total ionization rate. The resulting gradual decrease of the neutral H density from the upwind region down to the downwind region observed from Ly ..cap alpha.. intensity measurements allowed the determination of the absolute value of the total ionization rate ..beta.. for one H atom at 1 AU against ionization. Collected in 1976 and 1977 at five places in the solar system, The measurements are first compared to a model which assumes isotropy of the EUV and solar wind. Strong departures are obvious toward high-latitude regions, especially when the observer is in the downwind region where the solar wind ionization has had more time to act (cumulative effect). A model was constructed which include a decrease of the ionization rate with heliographic latitude. The adjustment of data allowed for the measurement of the absolute value of the total ionization rate and implies a 50% latitude decrease of the ionization rate due to charge exchange with the solar wind, from ..beta../sub s//sub w/ = (3.9 +- 0.5) x 10/sup -8/ s/sup -1/ at the equator to ..beta../sub s//sub w/ = (2.0 +- 0.5) x 10/sup -8/ s/sup -1/ at the pole. The corresponding absolute value of the solar wind proton flux is (2.4-3.6) x 10/sup 8/ cm/sup -2/ s/sup -1/ at the equator and twice less at the pole if a constant velocity is assumed for the solar wind.

  8. The Lyman alpha reference sample. III. Properties of the neutral ISM from GBT and VLA observations

    SciTech Connect

    Pardy, Stephen A.; Cannon, John M.; Melinder, Jens E-mail: jcannon@macalester.edu; and others

    2014-10-20

    We present new H I imaging and spectroscopy of the 14 UV-selected star-forming galaxies in the Lyman Alpha Reference Sample (LARS), aimed for a detailed study of the processes governing the production, propagation, and escape of Lyα photons. New H I spectroscopy, obtained with the 100 m Green Bank Telescope (GBT), robustly detects the H I spectral line in 11 of the 14 observed LARS galaxies (although the profiles of two of the galaxies are likely confused by other sources within the GBT beam); the three highest redshift galaxies are not detected at our current sensitivity limits. The GBT profiles are used to derive fundamental H I line properties of the LARS galaxies. We also present new pilot H I spectral line imaging of five of the LARS galaxies obtained with the Karl G. Jansky Very Large Array (VLA). This imaging localizes the H I gas and provides a measurement of the total H I mass in each galaxy. In one system, LARS 03 (UGC 8335 or Arp 238), VLA observations reveal an enormous tidal structure that extends over 160 kpc from the main interacting systems and that contains >10{sup 9} M {sub ☉} of H I. We compare various H I properties with global Lyα quantities derived from Hubble Space Telescope measurements. The measurements of the Lyα escape fraction are coupled with the new direct measurements of H I mass and significantly disturbed H I velocities. Our robustly detected sample reveals tentative correlations between the total H I mass and linewidth, and key Lyα tracers. Further, on global scales, these data support a complex coupling between Lyα propagation and the H I properties of the surrounding medium.

  9. The Lyman alpha reference sample. II. Hubble space telescope imaging results, integrated properties, and trends

    SciTech Connect

    Hayes, Matthew; Östlin, Göran; Duval, Florent; Sandberg, Andreas; Guaita, Lucia; Melinder, Jens; Rivera-Thorsen, Thøger; Adamo, Angela; Schaerer, Daniel; Verhamme, Anne; Orlitová, Ivana; Mas-Hesse, J. Miguel; Otí-Floranes, Héctor; Cannon, John M.; Pardy, Stephen; Atek, Hakim; Kunth, Daniel; Laursen, Peter; Herenz, E. Christian

    2014-02-10

    We report new results regarding the Lyα output of galaxies, derived from the Lyman Alpha Reference Sample, and focused on Hubble Space Telescope imaging. For 14 galaxies we present intensity images in Lyα, Hα, and UV, and maps of Hα/Hβ, Lyα equivalent width (EW), and Lyα/Hα. We present Lyα and UV radial light profiles and show they are well-fitted by Sérsic profiles, but Lyα profiles show indices systematically lower than those of the UV (n ≈ 1-2 instead of ≳ 4). This reveals a general lack of the central concentration in Lyα that is ubiquitous in the UV. Photometric growth curves increase more slowly for Lyα than the far ultraviolet, showing that small apertures may underestimate the EW. For most galaxies, however, flux and EW curves flatten by radii ≈10 kpc, suggesting that if placed at high-z only a few of our galaxies would suffer from large flux losses. We compute global properties of the sample in large apertures, and show total Lyα luminosities to be independent of all other quantities. Normalized Lyα throughput, however, shows significant correlations: escape is found to be higher in galaxies of lower star formation rate, dust content, mass, and nebular quantities that suggest harder ionizing continuum and lower metallicity. Six galaxies would be selected as high-z Lyα emitters, based upon their luminosity and EW. We discuss the results in the context of high-z Lyα and UV samples. A few galaxies have EWs above 50 Å, and one shows f{sub esc}{sup Lyα} of 80%; such objects have not previously been reported at low-z.

  10. HETDEX: Probing the Chemical Evolution of the Universe with Lyman Alpha Emitting Galaxies

    NASA Astrophysics Data System (ADS)

    Finkelstein, Steven L.; Hill, G. J.; Gebhardt, K.; Blanc, G.; Drory, N.; HETDEX Collaboration

    2012-01-01

    The Hobby Eberly Telescope Dark Energy Experiment (HETDEX) will discover 0.8 million Lyman alpha emitting galaxies (LAEs) at 1.9 < z < 3.5 over 300 square degrees beginning in Fall 2012. This unprecedentedly large volume probed will allow the discovery of large samples of bright LAEs, enabling follow-up science which cannot be done for the bulk of the LAE population, as they form the faint end of the galaxy luminosity function. Combining the HETDEX sample with the new generation of multi-object near-infrared (NIR) spectrographs will allow direct measurements of LAE physical properties, which are of interest as LAEs appear similar to galaxies at very high redshifts (z > 7) , and LAEs are also the likely progenitors of present-day Milky Way-like galaxies. Here we present results from the HETDEX pilot survey, which discovered 100 LAEs with a single integral field spectrograph mounted on the McDonald Observatory 2.7m telescope. We have detected rest-frame optical emission lines from five of these galaxies with the single-slit NIR spectrograph NIRSPEC on the Keck II 10m telescope. From the ratio of the upper limit on the (undetected) [NII] flux to the observed Halpha line strength, all five LAEs appear to have low metallicities (< 50% solar). The brightest LAE in our sample lies significantly below the mass-metallicity relation for continuum-selected galaxies at the same redshift. The remaining LAEs may also lie below this relation, however their fainter Halpha fluxes result in higher limits on the [NII]/Halpha flux ratio. Thus deeper integrations, requiring multi-object spectrographs (MOS) to be feasible, are necessary. The field-of-view of the next generation of MOS NIR spectrographs will be able to simultaneously observe > 10 HETDEX LAEs to a much deeper depth, providing a significant boost in our ability to probe the chemical enrichment of this enigmatic galaxy population.

  11. On the Lack of Correlation Between Mg II 2796, 2803 Angstrom and Lyman alpha Emission in Lensed Star-Forming Galaxies

    NASA Technical Reports Server (NTRS)

    Rigby, Jane Rebecca; Bayliss, M. B.; Gladders, M. D.; Sharon, K.; Wuyts, E.; Dahle, H.

    2014-01-01

    We examine the Mg II 2796, 2803 Angstrom, Lyman alpha, and nebular line emission in five bright star-forming galaxies at 1.66 less than z less than 1.91 that have been gravitationally lensed by foreground galaxy clusters. All five galaxies show prominent Mg II emission and absorption in a P Cygni profile. We find no correlation between the equivalent widths of Mg II and Lyman alpha emission. The Mg II emission has a broader range of velocities than do the nebular emission line profiles; the Mg II emission is redshifted with respect to systemic by 100 to 200 km s(exp-1). When present, Lyman alpha is even more redshifted. The reddest components of Mg II and Lyman alpha emission have tails to 500-600 km s(exp-1), implying a strong outflow. The lack of correlation in the Mg II and Lyman alpha equivalent widths, the differing velocity profiles, and the high ratios of Mg II to nebular line fluxes together suggest that the bulk of Mg II emission does not ultimately arise as nebular line emission, but may instead be reprocessed stellar continuum emission.

  12. Remote diagnostic of the hydrogen wall through measurements of the backscattered solar Lyman alpha radiation by Voyager 1/UVS in 1993-2003

    NASA Astrophysics Data System (ADS)

    Katushkina, O. A.; Quémerais, E.; Izmodenov, V. V.; Alexashov, D. B.; Sandel, B. R.

    2016-01-01

    We perform a new analysis of the Lyman alpha data obtained by Voyager 1 during the spatial scans in 1993-2003 while Voyager 1 was at 53-88 AU from the Sun. These data are the important source of information on the hydrogen distribution in the outer heliosphere. A sophisticated global kinetic-MHD model of the heliospheric interface and a radiative transfer model are used for the analysis. It is shown for the first time that the ratio of the Lyman alpha intensities detected in the downwind and upwind lines of sight in the outer heliosphere is sensitive to the configuration (peak value and location) of the hydrogen wall. The hydrogen wall is a source of Doppler-shifted backscattered Lyman alpha photons, so it can be seen from inside the heliosphere. Therefore, Voyager 1/ultraviolet spectrometer (UVS) Lyman alpha data can be used for remote sensing of the hydrogen wall. We show that our current global model of the outer heliosphere, which is consistent with many other measurements including Lyman alpha data from both Voyager 1 and 2 in 1980-1993, provides a systematically larger downwind to upwind intensity ratio compared with the UVS data in 1993-2003. In order to decrease the ratio, a higher and/or closer hydrogen wall is needed.

  13. Neutrino Masses, Cosmological Parameters and Dark Energy from the Transmitted Flux in the Lyman-alpha Forest

    NASA Astrophysics Data System (ADS)

    Rossi, Graziano; Palanque-Delabrouille, N.; Yeche, C.; Borde, A.; Rich, J.; Viel, M.; Lesgourgues, J.

    2013-01-01

    The signature left in quasar spectra by the presence of neutral hydrogen in the Universe allows one to constrain the sum of the neutrino masses with unprecedented sensitivity, with respect to laboratory experiments. At the forefront of elementary particle physics and cosmology, this may also shed a new light on the neutrino mass hierarchy, and on the absolute mass scale of neutrinos. In addition, constrains on cosmological parameters and on the dark energy equation of state can be derived, from a joint parameter estimation. This however requires a detailed modeling of the line-of-sight power spectrum of the transmitted flux in the Lyman-alpha forest on scales ranging from a few to hundreds of Mpcs, which in turns demands for the inclusion and careful treatment of cosmological neutrinos. In particular, since massive neutrinos are known to significantly alter structure formation, one needs to quantify their free-streaming effect consistently. We develop here a new hydrodynamical code which incorporates cold dark matter, gas, and is also able to reproduce the impact of massive neutrinos on the one-dimensional power spectrum with a novel technique. In synergy with corresponding experimental work from state-of-the-art surveys such as BOSS, and with upcoming or future large-scale-structure probes (e.g. Planck, Euclid), this will allow one to constrain the sum of the neutrino massses and the main cosmological parameters with unprecedented statistical significance. The theoretical study presented here will be combined with topological techniques to investigate dark energy and the expansion history of the Universe directly from the Lyman-alpha transmitted flux. The method will be also relevant for BigBOSS, which is expected to produce Lyman-alpha forest data along ~600,000 distant QSOs, and the data will be used to study the line-of-sight one-dimensional fluctuations.

  14. Probing the High Redshift IGM: SPH+P{(3}) MG Simulations of the Lyman-alpha Forest

    NASA Astrophysics Data System (ADS)

    Wadsley, J.; Bond, J. R.

    1996-12-01

    Our understanding of the Lyman-alpha forest has received a great boost with the advent of the Keck Telescope and large 3D hydrodynamical simulations. We simulate the high redshift universe using the SPH technique with a P{(3}) MG (Particle-Particle Particle-MultiGrid) non-periodic gravity solver. We employ a high resolution (1 kpc) inner volume, essential for capturing the complex gas physics, larger medium and low resolution volumes surrounding it, essential for correct larger scale tidal fields, and a self-consistently applied, uniform tidal field to model the influence of ultra long waves. Such care is needed because the power per decade in the density fluctuations falls off very slowly in the dwarf galaxy regime of relevance to Lyman alpha clouds. The oft-used periodic boundary condition approach to simulations is ill-suited to proper treatment of the tides. We use constrained field realizations to probe a selection of environments, including voids, quiescent regions, proto-dwarf galaxies and regions experiencing strong tides, such as large galaxy halos and galaxy-galaxy filamentary bridges. We statistically combine our simulations to provide a more comprehensive sample of the universe, including ``rare event'' regions which are difficult to obtain in unrestricted FFT-based approaches. We fit Voigt profiles to the Lyman alpha spectra computed from our simulations direct comparison with the data, e.g., the column density distribution, line widths, temperatures, multiple line-of-sight correlations and the HI (and HeII) flux decrements. We demonstrate the importance of (1) the photoionizing UV flux level and history, (2) tidal environment and (3) differing cosmologies, including CDM and CDM+Lambda. With galaxy-scale rms fluctuations ~ 1 at z=3 and a UV choice motivated by proximity effect observations, the simulations give results in excellent agreement with the data.

  15. Solar minimum Lyman. alpha. sky background observations from Pioneer Venus orbiter ultraviolet spectrometer: Solar wind latitude variation

    SciTech Connect

    Ajello, J.M. )

    1990-09-01

    Measurements of interplanetary H I Lyman {alpha} over a large portion of the celestial sphere were made at the recent solar minimum by the Pioneer Venus orbiter ultraviolet spectrometer. These measurements were performed during a series of spacecraft maneuvers conducted to observe Halley's comet in early 1986. Analysis of these data using a model of the passage of interstellar wind hydrogen through the solar wind system shows that the rate of charge exchange with solar wind protons is 30% less over the solar poles than in the ecliptic. This result is in agreement with a similar experiment performed with Mariner 10 at the previous solar minimum.

  16. Solar minimum Lyman alpha sky background observations from Pioneer Venus orbiter ultraviolet spectrometer - Solar wind latitude variation

    NASA Technical Reports Server (NTRS)

    Ajello, J. M.

    1990-01-01

    Measurements of interplanetary H I Lyman alpha over a large portion of the celestial sphere were made at the recent solar minimum by the Pioneer Venus orbiter ultraviolet spectrometer. These measurements were performed during a series of spacecraft maneuvers conducted to observe Halley's comet in early 1986. Analysis of these data using a model of the passage of interstellar wind hydrogen through the solar system shows that the rate of charge exchange with solar wind protons is 30 percent less over the solar poles than in the ecliptic. This result is in agreement with a similar experiment performed with Mariner 10 at the previous solar minimum.

  17. Polarization measurements of the Lyman-(alpha)1 x-ray emission lines of hydrogenlike Ar17+ and Fe25+ at high electron impact energies

    SciTech Connect

    Robbins, D L; Beiersdorfer, P; Faenov, A Y; Pikuz, T A; Thorn, D B; Chen, H; Reed, K J; Smith, A J; Brown, G V; Kelley, R L; Kilbouren, C A; Porter, F S

    2006-01-29

    We have measured the polarization of the 2p{sub 3/2} {yields} 1s{sub 1/2} Lyman-{alpha}{sub 1} x-ray line of hydrogenlike Ar{sup 17+} and Fe{sup 25+} at electron impact energies ranging from 7 to 25 threshold units. The highly charged argon and iron ions were produced using the Lawrence Livermore National Laboratory SuperEBIT electron beam ion trap. A combination of two crystal spectrometers and a microcalorimeter were used to record the Lyman-{alpha} x-ray emission of Ar{sup 17+} and Fe{sup 25+} and to infer the polarization of the Lyman-{alpha}{sub 1} line. Our results show a systematic discrepancy with the predictions of distorted-wave calculations.

  18. THE LYMAN ALPHA MORPHOLOGY OF LOCAL STARBURST GALAXIES: RELEASE OF CALIBRATED IMAGES

    SciTech Connect

    Oestlin, Goeran; Hayes, Matthew; Kunth, Daniel; Atek, Hakim; Mas-Hesse, J. Miguel; Leitherer, Claus; Petrosian, Artashes E-mail: matthew.hayes@unige.ch

    2009-09-15

    We present reduced and calibrated high resolution Lyman-alpha (Ly{alpha}) images for a sample of six local star-forming galaxies. Targets were selected to represent a range in luminosity and metallicity and to include both known Ly{alpha} emitters and nonemitters. Far ultraviolet imaging was carried out with the Solar Blind Channel of the Advanced Camera for Surveys on the Hubble Space Telescope (HST) in the F122M (Ly{alpha} online) and F140LP (continuum) filters. The resulting Ly{alpha} images are the product of careful modeling of both the stellar and nebular continua, facilitated by supporting HST imaging at {lambda} {approx} 2200, 3300, 4400, 5500, H{alpha}, and 8000 A, combined with Starburst 99 evolutionary synthesis models, and prescriptions for dust extinction on the continuum. In all, the resulting morphologies in Ly{alpha}, H{alpha}, and UV continuum are qualitatively very different and we show that the bulk of Ly{alpha} emerges in a diffuse component resulting from resonant scattering events. Ly{alpha} escape fractions, computed from integrated H{alpha} luminosities and recombination theory, are found never to exceed 14%. Internal dust extinction is estimated in each pixel and used to correct Ly{alpha} fluxes. However, the extinction corrections are far too small (by factors from 2.6 to infinity) to reconcile the emerging global Ly{alpha} luminosities with standard recombination predictions. Surprisingly, when comparing the global equivalent widths of Ly{alpha} and H{alpha}, the two quantities appear to be anticorrelated, which may be due to the evolution of mechanical feedback from the starburst. This calls for caution in the interpretation of Ly{alpha} observations in terms of star formation rates. The images presented have a physical resolution 3 orders of magnitude better than attainable at high redshifts from the ground with current instrumentation and our images may therefore serve as useful templates for comparing with observations and modeling of

  19. Star Formation in Damped Lyman-alpha systems and the Outskirts of Lyman Break Galaxies

    NASA Astrophysics Data System (ADS)

    Rafelski, Marc Alexander

    In this thesis we begin to unify two pictures of the high redshift universe: absorption line systems such as damped Lyman alpha systems (DLAs) that provide the fuel for star formation, and compact star forming regions such as Lyman break galaxies (LBGs) which form the majority of stars. Wolfe & Chen (2006) find that the in situ star formation in DLAs is less than 5% of what is expected from the Kennicutt-Schmidt (KS) relation, but they do not constrain DLAs associated with bright star-forming regions such as LBGs. In this work we search for spatially-extended star formation in the outskirts of LBGs at z ∼3. To this end, we create a sample of z ∼3 LBGs in the Hubble Ultra Deep Field (UDF) by using photometric redshifts enabled by the introduction of an extremely deep u -band image. By stacking these galaxies, we find spatially extended low surface brightness emission around LBGs in the V -band image of the UDF, corresponding to the z ∼3 rest-frame far-ultraviolet light, which is a sensitive measure of star formation rates (SFRs). We connect this emission around LBGs to the expected emission from DLAs, and the results suggest that the SFR efficiency in such gas at z ∼3 is between factors of 10 and 50 lower than predictions based on the KS relation. This decreased efficiency is likely due to the lower metallicity of DLA gas. In addition, we measure the metallicity evolution of DLAs out to z ∼5, and find a continued decrease of metallicity with increasing redshift and a metallicity "floor"' around one thousandth of the solar value. We also compare the metallicity distribution and chemistry of DLAs and halo stars, and find that they are not inconsistent. Lastly, we study the photometric variability of stars in the Galactic center in order to further our understanding of the massive young stars forming in the presence of a super massive black hole. All together, these results improve our understanding of star formation and provide constraints for models and

  20. Lenses in the forest: cross correlation of the Lyman-alpha flux with cosmic microwave background lensing.

    PubMed

    Vallinotto, Alberto; Das, Sudeep; Spergel, David N; Viel, Matteo

    2009-08-28

    We present a theoretical estimate for a new observable: the cross correlation between the Lyman-alpha flux fluctuations in quasar spectra and the convergence of the cosmic microwave background as measured along the same line of sight. As a first step toward the assessment of its detectability, we estimate the signal-to-noise ratio using linear theory. Although the signal-to-noise is small for a single line of sight and peaks at somewhat smaller redshifts than those probed by the Lyman-alpha forest, we estimate a total signal-to-noise of 9 for cross correlating quasar spectra of SDSS-III with Planck and 20 for cross correlating with a future polarization based cosmic microwave background experiment. The detection of this effect would be a direct measure of the neutral hydrogen-matter cross correlation and could provide important information on the growth of structures at large scales in a redshift range which is still poorly probed. PMID:19792781

  1. Observations of a groove in the interplanetary Lyman alpha pattern as the signature of enhanced ionisation in the neutral sheet

    NASA Astrophysics Data System (ADS)

    Bertaux, J. L.; Quemerais, E.; Lallement, R.; Summanen, T.; Kyrola, E.

    1995-06-01

    We report several observations of the Lyman alpha interplanetary emission recorded by a photometer flown in 1976-1977 on board the Soviet spacecraft Prognoz-5 and Prognoz-6. Several scans made in a plane perpendicular to the sun were cutting through the maximum emission region. where the interstellar hydrogen is approaching nearest to the sun (upwind region). On each of these scans is observed a dip in the intensity curve near the ecliptic plane. about 30 deg wide and approximately equals 10% deep. They reveal the presence of a new feature of the interplanetary emission. a 'groove' aligned approximately with the ecliptic plane. This groove is present only near the upwind direction, and is interpreted as the result of enhanced ionisation of interstellar H by charge-exchange with the solar wind in a sheet of approximately 30 deg around the average position of the neutral sheet at this time of solar this Lyman alpha groove is a prime target for future observations with SWAN experiment on SOHO.

  2. Observations of a groove in the interplanetary Lyman alpha pattern as the signature of enhanced ionisation in the neutral sheet

    NASA Technical Reports Server (NTRS)

    Bertaux, J. L.; Quemerais, E.; Lallement, R.; Summanen, T.; Kyrola, E.

    1995-01-01

    We report several observations of the Lyman alpha interplanetary emission recorded by a photometer flown in 1976-1977 on board the Soviet spacecraft Prognoz-5 and Prognoz-6. Several scans made in a plane perpendicular to the sun were cutting through the maximum emission region. where the interstellar hydrogen is approaching nearest to the sun (upwind region). On each of these scans is observed a dip in the intensity curve near the ecliptic plane. about 30 deg wide and approximately equals 10% deep. They reveal the presence of a new feature of the interplanetary emission. a 'groove' aligned approximately with the ecliptic plane. This groove is present only near the upwind direction, and is interpreted as the result of enhanced ionisation of interstellar H by charge-exchange with the solar wind in a sheet of approximately 30 deg around the average position of the neutral sheet at this time of solar this Lyman alpha groove is a prime target for future observations with SWAN experiment on SOHO.

  3. Optical Alignment of the Chromospheric Lyman-Alpha SpectroPolarimeter using Sophisticated Methods to Minimize Activities under Vacuum

    NASA Technical Reports Server (NTRS)

    Giono, G.; Katsukawa, Y.; Ishikawa, R.; Narukage, N.; Kano, R.; Kubo, M.; Ishikawa, S.; Bando, T.; Hara, H.; Suematsu, Y.; Winebarger, A.; Kobayashi, K.

    2016-01-01

    The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a sounding-rocket instrument developed at the National Astronomical Observatory of Japan (NAOJ) as a part of an international collaboration. The in- strument main scientific goal is to achieve polarization measurement of the Lyman-alpha line at 121.56 nm emitted from the solar upper-chromosphere and transition region with an unprecedented 0.1% accuracy. For this purpose, the optics are composed of a Cassegrain telescope coated with a "cold mirror" coating optimized for UV reflection and a dual-channel spectrograph allowing for simultaneous observation of the two orthogonal states of polarization. Although the polarization sensitivity is the most important aspect of the instrument, the spatial and spectral resolutions of the instrument are also crucial to observe the chromospheric features and resolve the Ly- pro les. A precise alignment of the optics is required to ensure the resolutions, but experiments under vacuum conditions are needed since Ly-alpha is absorbed by air, making the alignment experiments difficult. To bypass this issue, we developed methods to align the telescope and the spectrograph separately in visible light. We will explain these methods and present the results for the optical alignment of the CLASP telescope and spectrograph. We will then discuss the combined performances of both parts to derive the expected resolutions of the instrument, and compare them with the flight observations performed on September 3rd 2015.

  4. Lyman alpha emitting galaxies at high redshift: Direct detection of young galaxies in a young universe

    NASA Astrophysics Data System (ADS)

    Dawson, Steven Arthur

    /DEIMOS follow-up observations to candidates selected in the Large Area Lyman Alpha (LALA) survey. We conclude that if there is evolution in the Lya luminosity function over these epochs, its significance is below the statistical uncertainty of these data. This result supports the conclusion from several smaller samples of high-redshift Lya---emitters that the intergalactic medium remains largely reionized from the local universe out to z [approximate] 6.5. However, it is somewhat at odds with the pronounced drop in the cosmic star formation rate density recently measured between z ~ 3 and z ~ 6 in Lyman-break galaxies, and therefore potentially sheds light on the relationship between the two populations. (Abstract shortened by UMI.)

  5. Lyman Alpha Camera for Io's SO2 atmosphere and Europa's water plumes

    NASA Astrophysics Data System (ADS)

    McEwen, Alfred S.; Sandel, Bill; Schneider, Nick

    2014-05-01

    The Student Lyman-Alpha Mapper (SLAM) was conceived for the Io Volcano Observer (IVO) mission proposal (McEwen et al., 2014) to determine the spatial and temporal variations in Io's SO2 atmosphere by recording the H Ly-α reflection over the disk (Feldman et al., 2000; Feaga et al., 2009). SO2 absorbs at H Ly-α, thereby modulating the brightness of sunlight reflected by the surface, and measures the density of the SO2 atmosphere and its variability with volcanic activity and time of day. Recently, enhancements at the Ly-α wavelength (121.57 nm) were seen near the limb of Europa and interpreted as active water plumes ~200 km high (Roth et al., 2014). We have a preliminary design for a very simple camera to image in a single bandpass at Ly-α, analogous to a simplified version of IMAGE EUV (Sandel et al. 2000). Our goal is at least 50 resolution elements across Io and/or Europa (~75 km/pixel), ~3x better than HST STIS, to be acquired at a range where the radiation noise is below 1E-4 hits/pixel/s. This goal is achieved with a Cassegrain-like telescope with a 10-cm aperture. The wavelength selection is achieved using a simple self-filtering mirror in combination with a solar-blind photocathode. A photon-counting detector based on a sealed image intensifier preserves the poisson statistics of the incoming photon flux. The intensifier window is coated with a solar-blind photocathode material (CsI). The location of each photon event is recorded by a position-sensitive anode based on crossed delay-line or wedge-and-strip technology. The sensitivity is 0.01 counts/pixel/sec/R, sufficient to estimate SO2 column abundances ranging from 1E15 to 1E17 per cm2 in a 5 min (300 sec) exposure. Sensitivity requirements to search for and image Europa plumes may be similar. Io's Ly-α brightness of ~3 kR exceeds the 0.8 kR brightness of Europa's plume reported by Roth et al. (2014), but the plume brightness is a direct measurement rather than inferring column abundance from

  6. On the detection of heliospheric interface properties from interstellar/interplanetary Lyman-alpha profiles - Example of Baranov's two-shock model

    NASA Astrophysics Data System (ADS)

    Quemerais, E.; Malama, Iu. G.; Lallement, R.; Bertaux, J. L.

    Interstellar/interplanetary neutral H atoms which are observed towards the upwind (UW) and downwind (DW) directions do not originate from the same region of the heliospheric interface. If the neutral/plasma coupling is not negligible, the variations of the plasma properties with the distance to the stagnation line are imprinted in the neutral atoms and in the relationship between the UW and DW Lyman-alpha spectral profiles, whatever the distance to the heliospheric shock and to the heliopause. This effect is checked both on the Prognoz 5/6 backscattered Lyman-alpha data and in the case of the Baranov type interface. Hydrogen absorption cell data interpretation is much improved when inhomogeneities of the interstellar wind are taken into account. Lyman-alpha profiles derived from the Monte Carlo neutral flow model of Malama (1990) show the predicted macroscopic effects. These results tend to show that information on the type of the interface at the heliopause can be derived from precise Lyman-alpha line shape measurements and from comparison with line shapes computed from a homogeneous interstellar flow model.

  7. Latitudinal structure and north-south asymmetry of the solar wind from Lyman-alpha remote sensing by SWAN

    NASA Astrophysics Data System (ADS)

    Bzowski, M.; Mäkinen, T.; Kyrölä, E.; Summanen, T.; Quémerais, E.

    2003-09-01

    Based on SWAN/SOHO observations carried out during 1996-2002, we analyze latitudinal profiles of the heliospheric backscatter Lyman-alpha radiation. We use these results to investigate the ionization field of neutral hydrogen in the inner heliosphere and the latitudinal distribution of the solar wind mass flux. The the depth and latitudinal range of the equatorial depression in the Lyman-alpha backscatter glow (the so-called ``groove'') are correlated with the corresponding parameters of the ionization field. We show that the groove is entirely due to latitudinal anisotropy of the solar wind, since, as we are able to demonstrate, the photoionization rate remains spherically symmetric throughout the solar cycle. During the last solar minimum the groove was well developed and stable. During the ascending phase of solar activity, it expanded in latitude (first south, then north), and disappeared altogether during the solar maximum. Shortly after the maximum it reappeared, but its structure was more complex than during the ascending phase. The groove feature is correlated with the equatorial band occupied by the slow solar wind, while the polar maxima of the Lyman-alpha intensity correspond to the fast solar wind from the polar holes. The groove observations (supported by appropriate modeling) show that during the last solar minimum the mass flux of the fast solar wind from the north and south polar holes were different from each other: a true north-south asymmetry between the polar regions was detected. During the solar minimum, the area occupied by the slow solar wind was quite stable and offset slightly to the south with respect to the solar equator: it extended to about 30° N and 35° S from the beginning of observations in May 1996 till 1998. Then it expanded by about 10degr north and south, and subsequently migrated towards southern latitudes, so that it engulfed the south pole in May/June 2000. The north region of the fast wind survived longer and disappeared

  8. Lyman-alpha line as a solar activity index for calculations of solar spectrum in the EUV region

    NASA Astrophysics Data System (ADS)

    Nusinov, Anatoliy; Kazachevskaya, Tamara; Katyushina, Valeria; Woods, Thomas

    It is investigated a possibility of retrieval of solar spectrum data using intensity observational data of the only solar spectral line L (Hydrogen Lyman-alpha, 121.6 nm).Using as an example spectra obtained by SEE instruments on TIMED satellite, it was shown, that both for lines and for continuum in the spectral range 27-105 nm, which is essential for ionization processes in the ionosphere, a correlation between their intensities and L was high. Therefore it becomes possible to use L measurements data as a natural solar activity index for calculations of EUV solar emission spectrum for solving aeronomical problems. It is noticed, that EUV model, obtained with using SEE data, does not allow to calculate correctly critical frequencies of ionospheric E-layer owing to low intensities of lines 97.7 and 102.6 nm, which produce the main part of ionization in ionospheric E-region.

  9. Enhancement of Lyman-. alpha. radiation following foil-induced dissociation of fast ionic hydrogen clusters H sub n sup +

    SciTech Connect

    Farizon, M.; Clouvas, A.; de Castro Faria, N.V.; Farizon-Mazuy, B.; Gaillard, M.J.; Gerlic, E. ); Denis, A.; Desesquelles, J.; Ouerdane, Y. )

    1991-01-01

    We have measured the Lyman-{alpha} radiation following foil breakup of hydrogen ionic clusters H{sub {ital n}}{sup +} ({ital n}=2 and {ital n}=3 to 61, odd) with velocities above and around the Bohr velocity. An enhancement of this radiation was observed and could reach a factor of 3 with respect to the proton case of the same velocity. Cluster mass number, velocity, and thickness dependences of the relative population of the 2{ital p} state in hydrogen fragments following H{sub {ital n}}{sup +} foil dissociation have been extracted. A specific collective effect on the 2{ital p}-state hydrogen has been observed and interpreted in terms of charge-exchange processes.

  10. Isotope effect in the photochemical decomposition of CO{sub 2} (ice) by Lyman-{alpha} radiation

    SciTech Connect

    Yuan Chunqing; Yates, John T. Jr.

    2013-04-21

    The photochemical decomposition of CO{sub 2}(ice) at 75 K by Lyman-{alpha} radiation (10.2 eV) has been studied using transmission infrared spectroscopy. An isotope effect in the decomposition of the CO{sub 2} molecule in the ice has been discovered, favoring {sup 12}CO{sub 2} photodecomposition over {sup 13}CO{sub 2} by about 10%. The effect is caused by electronic energy transfer from the excited CO{sub 2} molecule to the ice matrix, which favors quenching of the heavier electronically-excited {sup 13}CO{sub 2} molecule over {sup 12}CO{sub 2}. The effect is similar to the Menzel-Gomer-Redhead isotope effect in desorption from adsorbed molecules on surfaces when electronically excited. An enhancement of the rate of formation of lattice-trapped CO and CO{sub 3} species is observed for the photolysis of the {sup 12}CO{sub 2} molecule compared to the {sup 13}CO{sub 2} molecule in the ice. Only 0.5% of the primary photoexcitation results in O-CO bond dissociation to produce trapped-CO and trapped-CO{sub 3} product molecules and the majority of the electronically-excited CO{sub 2} molecules return to the ground state. Here either vibrational relaxation occurs (majority process) or desorption of CO{sub 2} occurs (minority process) from highly vibrationally-excited CO{sub 2} molecules in the ice. The observation of the {sup 12}C/{sup 13}C isotope effect in the Lyman-{alpha} induced photodecomposition of CO{sub 2} (ice) suggests that over astronomical time scales the isotope enrichment effect may distort historical information derived from isotope ratios in space wherever photochemistry can occur.

  11. Viscoelastic Suppression of Gravity-Driven Counterflow Instability

    NASA Astrophysics Data System (ADS)

    Beiersdorfer, P.; Layne, D.; Magee, E. W.; Katz, J. I.

    2011-02-01

    Attempts to achieve “top kill” of flowing oil wells by pumping dense drilling “muds,” i.e., slurries of dense minerals, from above will fail if the Kelvin-Helmholtz instability in the gravity-driven counterflow produces turbulence that breaks up the denser fluid into small droplets. Here we estimate the droplet size to be submillimeter for fast flows and suggest the addition of a shear-thickening or viscoelastic polymer to suppress turbulence. We find in laboratory experiments a variety of new physical effects for a viscoelastic shear-thickening liquid in a gravity-driven counterstreaming flow. There is a progression from droplet formation to complete turbulence suppression at the relevant high velocities. Thick descending columns show a viscoelastic analogue of the viscous buckling instability. Thinner streams form structures resembling globules on a looping filament.

  12. Viscoelastic suppression of gravity-driven counterflow instability.

    PubMed

    Beiersdorfer, P; Layne, D; Magee, E W; Katz, J I

    2011-02-01

    Attempts to achieve "top kill" of flowing oil wells by pumping dense drilling "muds," i.e., slurries of dense minerals, from above will fail if the Kelvin-Helmholtz instability in the gravity-driven counterflow produces turbulence that breaks up the denser fluid into small droplets. Here we estimate the droplet size to be submillimeter for fast flows and suggest the addition of a shear-thickening or viscoelastic polymer to suppress turbulence. We find in laboratory experiments a variety of new physical effects for a viscoelastic shear-thickening liquid in a gravity-driven counterstreaming flow. There is a progression from droplet formation to complete turbulence suppression at the relevant high velocities. Thick descending columns show a viscoelastic analogue of the viscous buckling instability. Thinner streams form structures resembling globules on a looping filament. PMID:21405442

  13. Variability of Solar UV Irradiance Related to Bright Magnetic Features Observed in Call K-Line: Relationship between Lyman alpha and K-line Report for UARS funding agency

    NASA Technical Reports Server (NTRS)

    Zirin, Harold; Cameron, Robert

    1999-01-01

    In this report we comment on the relationship between the Lyman alpha and Calcium K-line emission from the Sun. We firstly examine resolved Lyman alpha images (from TRACE) and resolved K-line images. We find that the Lyman alpha emission is consistent with a linear dependence on the K-line emission. As this is in conflict with the analysis of Johannesson et al.(1995, 1998) we proceed by comparing the disk integrated Lyman alpha flux as a function of ratio between the disk integrated Mg II core and wing fluxes (Johannesson et al (1998) having previously found a linear dependence between this index and the BBSO K-line index). We find that a reasonably good fit can be obtained, however note the discrepancies which lead Johannesson et al to consider the square root relationship. We suggest an alternative interpretation of the discrepancy.

  14. Three-dimensional exospheric hydrogen atom distributions obtained from observations of the geocorona in Lyman-alpha

    NASA Astrophysics Data System (ADS)

    Bailey, Justin J.

    Exospheric atomic hydrogen (H) resonantly scatters solar Lyman-alpha (121.567 nm) radiation, observed as the glow of the geocorona. Measurements of scattered solar photons allow one to probe time-varying three-dimensional distributions of exospheric H atoms. The Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) mission images the magnetosphere in energetic neutral atom (ENA) fluxes and additionally carries Lyman-alpha Detectors (LADs) to register line-of-sight intensities of the geocorona. This work details a process for preparing TWINS data such that LAD measurements can be used to obtain global H density distributions with three-dimensional asymmetries above 3 earth radii. Sequences of distributions are presented to investigate the dynamic exosphere, responding to seasonal variations between a summer solstice and autumnal equinox, as well as to solar and geomagnetic variations as described by commonly used indices. The distributions reveal asymmetries from day to night, north to south, and dawn to dusk. A nightside extension persists that is consistent with the location of a geotail. A seasonal north-south asymmetry occurs as solar illumination differs between the summer and winter polar regions. Pole-equator and less pronounced dawn-dusk asymmetries also appear, possibly due to a coupling effect via charge exchange with the polar wind and plasmasphere, respectively. A common phenomenon in geospace occurs as magnetospheric energetic ions collide with neutral background atoms and produce ENAs that, no longer bound by Earth's magnetic field, can travel large distances though space with minimal disturbance ---providing an opportunity for remote detection. Knowledge of the distribution of the primary neutral partner, exospheric H atoms, is therefore essential for the interpretation of ENA fluxes and subsequent retrieval of ion densities. An analysis is summarized that demonstrates the importance of exospheric H density distributions on reconstructing

  15. Polarization of Lyman-(alpha) Radiation from Atomic Hydrogen Excited by Electron Impact from Near-Threshold to 1800eV

    NASA Technical Reports Server (NTRS)

    James, G. K.; Slevin, J. A.; Dziczek, D.

    1996-01-01

    The polarization of Lyman-(alpha) radiation, produced by electron impact excitation of atomic hydrogen, has been measured for the first time over the extended energy range from near-threshold to 1800eV. Measurements were obtained in a crossed-beams experiment using a silica-reflection linear polarization analyzer in tandem with a vacuum ultraviolet (VUV) monochromator to isolate the emitted line radiation.

  16. Heating and ionization of stellar chromospheres by nonthermal proton beams: Implications for impulsive phase, redshifted Lyman-alpha radiation in stellar flares

    NASA Technical Reports Server (NTRS)

    Brosius, Jeffrey W.; Robinson, Richard D.; Maran, Stephen P.

    1995-01-01

    We investigate the physical basis for the timescale of impulsive-phase, redshifted Lyman-alpha emission in stellar flares on the assumption that it is determined by energy losses in a nonthermal proton beam that is penetrating the chromosphere from above. The temporal evolution of ionization and heating in representative model chromospheres subjected to such beams is calculated. The treatment of 'stopping' of beam protons takes into account their interactions with (1) electrons bound in neutral hydrogen, (2) nuclei of neutral hydrogen, (3) free electrons, and (4) ambient thermal protons. We find that, for constant incident beam flux, the system attains an equilibrium with the beam energy input to the chromosphere balanced by radiative losses. In equilibrium, the beam penetration depth is constant, and erosion of the chromosphere ceases. If the redshifted, impulsive-phase stellar flare Lyman-alpha emission is produced by downstreaming hydrogen formed through charge exchange between beam protons and ambient hydrogen, then the emission should end when the beam no longer reaches neutral hydrogen. The durations of representative emission events calculated on this assumption range from 0.1 to 14 s. The stronger the beam, the shorter the timescale over which the redshifted Lyman-alpha emission can be observed.

  17. Clasp/SJ Observation of Time Variations of Lyman-Alpha Emissions in a Solar Active Region

    NASA Technical Reports Server (NTRS)

    Ishikawa, S.; Kubo, M.; Katsukawa, Y.; Kano, R.; Narukage, N.; Ishikawa, R.; Bando, T.; Winebarger, A.; Kobayashi, K.; Trujillo Bueno, J.; Auchere, F.

    2016-01-01

    The Chromospheric Lyman-alpha SpectroPolarimeter (CLASP) is a sounding rocket experiment launched on September 3, 2015 to investigate the solar chromosphere, and the slit-jaw (SJ) optical system took Lya images with the high time cadence of 0.6 s. By the CLASP/SJ observation, many time variations in the solar chromosphere with the time scale of <1 minute were discovered (see the poster by Kubo et al., Pa-13). We focused on an active region and investigated the short (<30 s) time variations and relation to the coronal structure observed by SDO/AIA. We compared the Ly(alpha) time variations at footpoints of coronal magnetic fields observed by AIA 211 Å (approx.2 MK) and AIA 171 Å (0.6 MK), and non-loop regions. As the result, we found the <30 s Ly(alpha) time variations had more in the footpoint regions. On the other hand, the <30 s time variations had no dependency on the temperature of the loop.

  18. Analysis of hydrogen Lyman-alpha observations of the coma of Comet P/Halley near the perihelion

    NASA Technical Reports Server (NTRS)

    Smyth, William H.; Marconi, M. L.; Combi, Michael R.

    1995-01-01

    The pioneer Venus Orbiter Ultraviolet Spectrometer measurements of the Lyman-alpha intensity of atomic hydrogen excited by solar resonance scattering in the coma of Comet P/Halley acquired from December 28, 1985, to January 6, 1986, and from January 31, 1986, to March 6, 1986, are simulated with the Monte Carlo Particle Trajectory Model corrected for optical depth effects. Spatially detailed comparisons between data and model show excellent agreement and are used to infer that the highest cometary activity may not be at perihelion, but about 2 1/2 weeks before. An improved set of H2O production rates is presented for the period of time that the spectrometer was observing and is found to be consistent with the rates from other types of measurements. The apparent discrepancy between Stewart (1987) in early March and International Ultraviolet Explorer OH derived rates is resolved. The problem with the conversion of 18-cm OH radio brightness to H2O production rates is also discussed.

  19. Escape of about five per cent of Lyman-alpha photons from high-redshift star-forming galaxies.

    PubMed

    Hayes, Matthew; Ostlin, Göran; Schaerer, Daniel; Mas-Hesse, J Miguel; Leitherer, Claus; Atek, Hakim; Kunth, Daniel; Verhamme, Anne; de Barros, Stéphane; Melinder, Jens

    2010-03-25

    The Lyman-alpha (Lyalpha) emission line is the primary observational signature of star-forming galaxies at the highest redshifts, and has enabled the compilation of large samples of galaxies with which to study cosmic evolution. The resonant nature of the line, however, means that Lyalpha photons scatter in the neutral interstellar medium of their host galaxies, and their sensitivity to absorption by interstellar dust may therefore be greatly enhanced. This implies that the Lyalpha luminosity may be significantly reduced, or even completely suppressed. Hitherto, no unbiased empirical test of the escaping fraction (f(esc)) of Lyalpha photons has been performed at high redshifts. Here we report that the average f(esc) from star-forming galaxies at redshift z = 2.2 is just 5 per cent by performing a blind narrowband survey in Lyalpha and Halpha. This implies that numerous conclusions based on Lyalpha-selected samples will require upwards revision by an order of magnitude and we provide a benchmark for this revision. We demonstrate that almost 90 per cent of star-forming galaxies emit insufficient Lyalpha to be detected by standard selection criteria. Both samples show an anti-correlation of f(esc) with dust content, and we show that Lyalpha- and Halpha-selection recovers populations that differ substantially in dust content and f(esc). PMID:20336139

  20. Interplanetary Lyman-alpha observations with UVS on Voyager - Data, first analysis, implications for the ionization lifetime

    NASA Technical Reports Server (NTRS)

    Lallement, R.; Bertaux, J. L.; Chassefiere, E.; Sandel, B.

    1991-01-01

    A fraction of the measurements of the interplanetary Lyman-alpha background collected by the Ultraviolet Spectrometer during the cruise of Voyager 1 and 2 between 1977 and 1983 is presented and compared with results from current models of the interaction between the sun and the neutral interstellar gas. An analysis of two sets of data indicates that the same H atom lifetime cannot fit all the data. The actual ionization rate is inferred from the intensity gradient in the maximum emissivity region observed from a sidewind Voyager position at 6 AU, yielding a lifetime of about 1 exp 6 s at 1 AU, whereas the upwind/downwind intensity ratio in the inner solar system favors 2 x 10 exp 6 s, as measured by Voyager, Prognoz, and Pioneer Venus instruments. It is proposed that there is an excess of Ly-alpha emission in the downwind region which forces the model toward excessively high values of the lifetime. Possible explanations are discussed, like incorrect modeling or an additional source of H atoms.

  1. Interplanetary Lyman-alpha observations with UVS on Voyager - Data, first analysis, implications for the ionization lifetime

    NASA Astrophysics Data System (ADS)

    Lallement, R.; Bertaux, J. L.; Chassefiere, E.; Sandel, B.

    1991-12-01

    A fraction of the measurements of the interplanetary Lyman-alpha background collected by the Ultraviolet Spectrometer during the cruise of Voyager 1 and 2 between 1977 and 1983 is presented and compared with results from current models of the interaction between the sun and the neutral interstellar gas. An analysis of two sets of data indicates that the same H atom lifetime cannot fit all the data. The actual ionization rate is inferred from the intensity gradient in the maximum emissivity region observed from a sidewind Voyager position at 6 AU, yielding a lifetime of about 1 exp 6 s at 1 AU, whereas the upwind/downwind intensity ratio in the inner solar system favors 2 x 10 exp 6 s, as measured by Voyager, Prognoz, and Pioneer Venus instruments. It is proposed that there is an excess of Ly-alpha emission in the downwind region which forces the model toward excessively high values of the lifetime. Possible explanations are discussed, like incorrect modeling or an additional source of H atoms.

  2. In situ measurement of water vapor in the stratosphere with a cryogenically cooled Lyman-alpha hygrometer

    NASA Technical Reports Server (NTRS)

    Schwab, J. J.; Weinstock, E. M.; Nee, J. B.; Anderson, J. G.

    1990-01-01

    In situ measurements of water vapor in the stratosphere with a new instrument are reported. The instrument has been designed to observe daytime water vapor from a multiinstrument balloon gondola that simultaneously measures free radicals such as OH, HO2, and O3 in the stratosphere up to 40 km. Lyman-alpha photofragment fluorescence is used to measure water molecules in a flowing sample of ambient air. A brief description of the instrument is given, followed by the results of the first four balloon flights. The measured mixing ratio for this flight varies from 3.0-5.5 ppmv over the altitude range of 17-34 km. Adjustments in the cooling protocol for the flights of July 6, 1988, July 28, and August 25, 1989, result in a much higher signal-to-noise ratio. Profiles from these three flights are similar to, but somewhat higher, than the 1987 profile. Implications of measurements are discussed, as are the issues of short- and long-term variability of stratospheric water vapor.

  3. The Lyman-alpha glow of gas falling into the dark matter halo of a z = 3 galaxy.

    PubMed

    Weidinger, Michael; Møller, Palle; Fynbo, Johan Peter Uldall

    2004-08-26

    Quasars are the visible signatures of gas falling into the deep potential well of super-massive black holes in the centres of distant galaxies. It has been suggested that quasars are formed when two massive galaxies collide and merge, leading to the prediction that quasars should be found in the centres of regions of largest overdensity in the early Universe. In dark matter (DM)-dominated models of the early Universe, massive DM halos are predicted to attract the surrounding gas, which falls towards their centres. The neutral gas is not detectable in emission by itself, but gas falling into the ionizing cone of such a quasar will glow in the Lyman-alpha line of hydrogen, effectively imaging the DM halo. Here we present a Lyalpha image of a DM halo at redshift z = 3, along with a two-dimensional spectrum of the gaseous halo. Our observations are best understood in the context of the standard model for DM haloes; we infer a mass of (2 - 7) x 10(12) solar masses (M(\\circ)) for the halo. PMID:15329713

  4. Physical properties and evolutionary state of the Lyman alpha emitting starburst galaxy IRAS 08339+6517

    NASA Astrophysics Data System (ADS)

    Otí-Floranes, H.; Mas-Hesse, J. M.; Jiménez-Bailón, E.; Schaerer, D.; Hayes, M.; Östlin, G.; Atek, H.; Kunth, D.

    2014-06-01

    the release of mechanical energy in the first case, and by a large number of active high-mass X-ray binaries (HMXBs) in the second. In addition to the central compact emission blob, we have identified a diffuse Lyα emission component smoothly distributed over the whole central area of IRAS 08339+6517. This diffuse emission is spatially decoupled from the UV continuum, the Hα emission, or the Hα/Hβ ratio. Both locally and globally, the Lyα/Hα ratio is lower than the Case B predictions, even after reddening correction, with an overall Lyα escape fraction of only 4%. Conclusions: We conclude that in IRAS 08339+6517 the Lyα photons resonantly scattered by an outflowing shell of neutral gas are being smoothly redistributed over the whole central area of the galaxy. Their increased probability of being destroyed by dust would explain the low Lyα escape fraction measured. In any case, in the regions where the diffuse Lyα emission shows the largest Lyα/Hα ratios, no additional sources of Lyα emission are required, like ionization by hot plasma as proposed for Haro 2, another galaxy in our sample. These results stress again the importance of a proper correction of scattering and transfer effects when using Lyα to derive the star formation rate in high-redshift galaxies.

  5. Condensation during gravity driven ECC: Experiments with PACTEL

    SciTech Connect

    Munther, R.; Kalli, H.; Kouhia, J.

    1995-09-01

    This paper provides the results of the second series of gravity driven emergency core cooling (ECC) experiments with PACTEL (Parallel Channel Test Loop). The simulated accident was a small break loss-of-coolant accident (SBLOCA) with a break in a cold leg. The ECC flow was provided from a core makeup tank (CMT) located at a higher elevation than the main part of the primary system. The CMT was pressurized with pipings from the pressurizer and a cold leg. The tests indicated that steam condensation in the CMT can prevent ECC and lead to core uncovery.

  6. Basal entrainment by Newtonian gravity-driven flows

    NASA Astrophysics Data System (ADS)

    Bates, Belinda M.; Andreini, Nicolas; Ancey, Christophe

    2016-05-01

    Gravity-driven flows can erode the bed along which they descend and increase their mass by a factor of 10 or more. This process is called "basal entrainment." Although documented by field observations and laboratory experiments, it remains poorly understood. This paper examines what happens when a viscous gravity-driven flow generated by releasing a fixed volume of incompressible Newtonian fluid encounters a stationary layer (composed of fluid with the same density and viscosity). Models based on depth-averaged mass and momentum balance equations deal with bed-flow interfaces as shock waves. In contrast, we use an approach involving the long-wave approximation of the Navier-Stokes equations (lubrication theory), and in this context, bed-flow interfaces are acceleration waves that move quickly across thin stationary layers. The incoming flow digs down into the bed, pushing up downstream material, thus advancing the flow front. Extending the method used by Huppert ["The propagation of two-dimensional and axisymmetric viscous gravity currents over a rigid horizontal surface," J. Fluid Mech. 121, 43-58 (1982)] for modeling viscous dam-break waves, we end up with a nonlinear diffusion equation for the flow depth, which is solved numerically. Theory is compared with experimental results. Excellent agreement is found in the limit of low Reynolds numbers (i.e., for flow Reynolds numbers lower than 20) for the front position over time and flow depth profile.

  7. UV Spectral Variability and the Lyman-Alpha Forest in the Lensed Quasar Q0957+561

    NASA Technical Reports Server (NTRS)

    Dolan, J. F.; Michalitsianos, A. G.; Nguyen, Q. T.; Hill, R. J.

    1999-01-01

    Far-ultraviolet spectra of the gravitational lens components Q0957+561 A and B were obtained with the Hubble Space Telescope Faint Object Spectrograph (FOS) at five equally spaced epochs, one every two weeks. We confirm the flux variability of the quasar's Lyman-alpha and O VI lambda 1037 emission lines reported in IUE (International Ultraviolet Explorer) spectra. The fluxes in these lines vary on a time scale of weeks in the local rest frame (LRF), independently of each other and of the surrounding continuum. The individual spectra of each image were co-added to investigate the properties of the Lyman-alpha forest along the two lines of sight to the quasar. Absorption lines having equivalent width W (sub lambda) greater than or equal to 0.3 Angstroms in the LRF not previously identified as interstellar lines, metal lines, or higher order Lyman lines were taken to be LY-alpha forest lines. The existence of each line in this consistently selected set was then verified by its presence in two archival FOS spectra with approx. 1.5 times higher signal to noise than our co-added spectra. Ly-alpha forest lines with W (sub lambda) greater than or equal to 0.3 Angstroms appear at 42 distinct wavelengths in the spectra of the two images. Two absorption lines in the spectrum of image A have no counterpart at that wavelength in the spectrum of image B, and two lines in image B have no counterpart in image A. Based on the separation of the lines of sight at the redshift of the absorption lines appearing in only one spectrum, the density of the absorbing clouds in the direction of Q0957+561 must change significantly over a distance of 79 (+34, -26) h (sub 50) (sup -1) kpc in the simplified model where the absorbers are treated as spherical clouds and the characteristic dimension is the radius. (We adopt H (sub 0)= 50 h (sub 50) km s (sup -1) kpc (sup -1), q (sub 0) = 1/2, and LAMBDA = 0 throughout the paper.) The two limits define the 68% confidence interval on the

  8. Observations of interplanetary Lyman-alpha with the Galileo Ultraviolet Spectrometer: Multiple scattering effects at solar maximum

    NASA Technical Reports Server (NTRS)

    Ajello, J. M.; Pryor, W. R.; Barth, C. A.; Hord, C. W.; Stewart, A. I. F.; Simmons, K. E.; Hall, D. T.

    1994-01-01

    The Galileo Ultravilet Spectrometer Experiment (UVS) obtained a partial celestial sphere map of interplanetary Lyman-alpha (IP L alpha) on 13-14 December 1990 during the first Earth encounter. The Galileo spacecraft was near the downwind axis of the local interstellar medium flow. These UVS measurements sampled the downwind, anti-sunward hemisphere. The data were modeled using a hot model of the interplanetary hydrogen density distribution with the goal of studying multiple scattering effects in the inner solar system. The derived ratio in the downwind direction of the observed brightness and a single scattering model brightness, both normalized to unity in the upwind direction, is 1.82 +/- 0.2. This brightness ratio requires a multiple scattering correction which is 36% larger than can be accounted for by theoretical calculations. The hot model may require: (1) a temperature perturbation of the interstellar wind velocity distribution or (2) an additional downstream source of interplanetary hydrogen. However, a more likely exlanation which affects the hot model is the latitude dependence of the radiation pressure. This dependence, based on the known solar L alpha flux latitude variation at solar maximum, causes a downwind brightness enhancement by preferential focusing of H-atoms with trajectory planes containing the solar poles. This result implies that radiation pressure near the solar poles is nearly independent of solar cycle and is insufficient to lead to a net repulsion of hydrogen atoms by the sun, as can occur near the ecliptic plane during the solar maximum. In addition, the UVS performed 13 observations of IP L alpha while in cruise between Venus and the Earth in 3 directions fixed in ecliptic coordinates.

  9. Kinetic-Energy Distribution of D(2p) Atoms from Analysis of the D Lyman-Alpha Line Profile

    NASA Technical Reports Server (NTRS)

    Ciocca, M.; Ajello, Joseph M.; Liu, Xianming; Maki, Justin

    1997-01-01

    The kinetic-energy distribution of D(2p) atoms resulting from electron-impact dissociation of D2 has been measured. A high-resolution vacuum ultraviolet spectrometer was employed for the first measurement of the D Lyman-alpha (D L(alpha)) emission line profiles at 20- and 100-eV excitation energies. Analysis of the deconvoluted line profile of D L(alpha) at 100 eV reveals the existence of a narrow line central peak of 29+/-2 mA full width at half maximum and a broad pedestal wing structure about 190 mA wide. The wings of the line can be used to determine the fast atom distribution. The wings of D L(alpha) arise from dissociative excitation of a series of doubly excited states that cross the Franck-Condon region between 23 and 40 eV. The fast atom distribution at 100-eV electron impact energy spans the energy range from 1 to 10 eV with a peak value near 6 eV. Slow D(2p) atoms characterized by a distribution function with peak energy near 100 meV produce the central peak profile, which is nearly independent of the impact energy. The deconvoluted line profiles of the central peak at 20 eV for dissociative excitation of D2 and H2 are fitted with an analytical function for use in calibration of space flight instrumentation equipped with a D/H absorption cell. The kinetic-energy and line profile results are compared to similar measurements for H2. The absolute cross sections for the line center (slow atoms) and wings (fast atoms) and total emission line profile were measured from threshold to 400 eV. Analytical model coefficients are given for the energy dependence of the measured slow atom cross section.

  10. Lyman Alpha-emitting Galaxies at z = 2.1: Characterizing the Progenitors of Typical Present-day Galaxies

    NASA Astrophysics Data System (ADS)

    Gawiser, Eric J.; Guaita, L.; Padilla, N.; Francke, H.; Bond, N. A.; Gronwall, C.; Ciardullo, R.; Sinawa, S.; Feldmeier, J. J.; MUSYC Collaboration

    2010-01-01

    We discovered a sample of 261 Lyman alpha emitting (LAE) galaxies at z=2.1 in an ultra-deep 3727A narrow-band MUSYC image of the Extended Chandra Deep Field-South. LAEs were selected to have rest-frame equivalent widths >20A and emission line fluxes >3.7x10-17 ergs/cm2/s, corresponding to L_Lya>1.2x1042 ergs/s. 3% of the original candidates were detected in X-rays by Chandra, and 7% were detected in the rest-frame far-UV by GALEX; these objects were eliminated to minimize contamination by AGN and low-redshift galaxies. Our sample has median rest-frame EW=40A, and only a few galaxies have rest-frame EW bigger than 200A. Our results show that the luminosity function of LAEs at z=2.1 is consistent with that of LAEs at z=3.1 but with number density a factor of 1.8+-0.3 higher. We used the rest frame UV luminosity to estimate a median star formation rate of 4 Msun/yr. Clustering analysis reveals that LAEs at z=2.1 have r0=3+-0.5 Mpc, corresponding to b=1.0+-0.2, the lowest clustering bias of any high-redshift galaxy population. This implies that z=2.1 LAEs reside in dark matter halos with masses 1010 Msun, which are the lowest-mass halos yet probed at this redshift. We used the Sheth-Tormen conditional mass function to study the descendants of these LAEs and found that their typical present-day descendants are local galaxies with sub-L* and L* luminosities, like the Milky Way. We gratefully acknowledge grant support for this research from NSF, DOE, and NASA.

  11. Observation of Geocorona using Lyman Alpha Imaging CAmera (LAICA) onboard the very small deep space explorer PROCYON

    NASA Astrophysics Data System (ADS)

    Kameda, Shingo; Yoshikawa, Ichiro; Taguchi, Makoto; Sato, Masaki; Kuwabara, Masaki

    Exospheric hydrogen atoms resonantly scatter solar ultraviolet radiation at the wavelength of 121.567nm causing an ultraviolet glow. It is so called "geocorona". The past observational results suggest that geocorona extends to an altitude of about 20R _{E}, where the intensity of geocoronal emission is comparable with that of interplanetary hydrogen emission. Recently, Bailey and Gruntman (2013) newly reported abrupt temporary increases (from 6% to 17%) in the total number of hydrogen atoms in the spherical shell from a geocentric distance of 3 to 8 R _{E} during geomagnetic storms. However, the relation between hydrogen exosphere at high altitude and geomagnetic activity is still unclear. Past observation of the geocorona has mainly been performed using earth orbiters. Its altitude, e. g., 8 R _{E} is not adequately high for the observation of geocorona at high altitude. Observation of geocorona from deep space has been conducted in the Mariner 5, Apollo 16, and Nozomi mission. Among them, only Apollo 16 has a 2-D imager. Its FOV was about 10RE and was not wide enough for imaging the whole geocorona expanding to 20R _{E}. In June 2013, we proposed the LAICA (Lyman Alpha Imaging CAmera) instrument onboard the very small deep space explorer PROCYON, which is planned to be launched in Dec 2014. Its FOV ( 25R _{E}) is wide enough for imaging of the whole geocoronal distribution. We are planning to observe geocorona for more than one week with the temporal resolution of 2h. LAICA was approved in Oct 2013 and its development is now on-going. In this presentation, we will introduce the scientific objectives of LAICA and report the test result of the flight model.

  12. Performance characterization of UV science cameras developed for the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)

    NASA Astrophysics Data System (ADS)

    Champey, P.; Kobayashi, K.; Winebarger, A.; Cirtain, J.; Hyde, D.; Robertson, B.; Beabout, D.; Beabout, B.; Stewart, M.

    2014-07-01

    The NASA Marshall Space Flight Center (MSFC) has developed a science camera suitable for sub-orbital missions for observations in the UV, EUV and soft X-ray. Six cameras will be built and tested for flight with the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), a joint National Astronomical Observatory of Japan (NAOJ) and MSFC sounding rocket mission. The goal of the CLASP mission is to observe the scattering polarization in Lyman-α and to detect the Hanle effect in the line core. Due to the nature of Lyman-α polarizationin the chromosphere, strict measurement sensitivity requirements are imposed on the CLASP polarimeter and spectrograph systems; science requirements for polarization measurements of Q/I and U/I are 0.1% in the line core. CLASP is a dual-beam spectro-polarimeter, which uses a continuously rotating waveplate as a polarization modulator, while the waveplate motor driver outputs trigger pulses to synchronize the exposures. The CCDs are operated in frame-transfer mode; the trigger pulse initiates the frame transfer, effectively ending the ongoing exposure and starting the next. The strict requirement of 0.1% polarization accuracy is met by using frame-transfer cameras to maximize the duty cycle in order to minimize photon noise. The CLASP cameras were designed to operate with ≤ 10 e-/pixel/second dark current, ≤ 25 e- read noise, a gain of 2.0 +- 0.5 and ≤ 1.0% residual non-linearity. We present the results of the performance characterization study performed on the CLASP prototype camera; dark current, read noise, camera gain and residual non-linearity.

  13. In situ measurement of water vapor in the stratosphere with a cryogenically cooled Lyman-Alpha hygrometer

    SciTech Connect

    Schwab, J.J. ); Weinstock, E.M.; Nee, J.B.; Anderson, J.G. )

    1990-08-20

    In situ measurements of water vapor in the stratosphere with a new instrument are reported. The instrument has been designed to observe daytime water vapor from a multi-instrument balloon gondola that simultaneously measures free radicals such as OH, HO{sub 2}, and O{sub 3} in the stratosphere up to 40 km. Lyman-alpha photofragment fluorescence is used to measure water molecules in a flowing sample of ambient air. Outgassing from the interior walls of the instrument is avoided by cooling the walls with liquid nitrogen to a temperature near or below the dewpoint of the environment and by drawing air through the instrument with a fan. A brief description of the instrument is given, followed by the results of the first four balloon flights. Because frost formation in the scattering chamber resulted in a large and variable background, the data from July 15, 1987, have a relatively modest signal-to-noise ratio. The measured mixing ratio for this flight varies from 3.0-5.5 ppmv over the altitude range of 17-34 km. Adjustments in the cooling protocol for the flights of July 6, 1988, July 28, and August 25, 1989, result in a much higher signal-to-noise ratio. Profiles from these three flights are similar to, but somewhat higher, than the 1987 profile. The July 1988 and August 1989 profiles exhibit the highest mixing ratios, reaching peak values of about 6.5 ppmv near 35 km. Implications of these four measurements are discussed, as are the issues of short- and long-term variability of stratospheric water vapor.

  14. Measurements of Lyman Alpha Radiation from Collisions, 100 EV to 4000EV, of Negative Hydrogen Ions on Various Target Gases and Positive Hydrogen Ions on Xenon

    NASA Astrophysics Data System (ADS)

    Greenland, Glenn Blair

    This study reports measurements of cross sections for the production of Lyman alpha radiation from processes in which an ion is incident on a neutral target gas. Two kinds of processes were measured: the stripping of the extra electron from a negative hydro- gen ion leaving an excited neutral and the capture of an electron by a proton also leaving an excited neutral. In each case, radiation from the 2p state of the neutral hydrogen was detected. The projectile struck the static gas target with a kinetic energy between 100 and 4000 electron volts. The measurements used the ultraviolet absorption properties of molecular oxygen to isolate the Lyman alpha line. Cross sections for emission of Lyman alpha perpendicular to the incident beam were determined. The targets used in the stripping experiments were the atomic gases: helium, neon, argon, krypton and xenon, and the molecular gases: hydrogen, nitrogen and methane. The cross sections are rela- tively flat over the energy range investigated. All are slightly below 10('-16) cm('2) at 1000 eV. Only with the neon target does the cross section fall below 2 x 10('0-17) cm('2) at 100 electron volts. While the data appear to support the modeling of stripping with excitation as a two step process, this modeling may not be valid for excitation above 2p. Only a xenon target was used in the capture experiments. Careful measurements did not substantiate an earlier report of unusual structure('1) in this cross section. ('1)P. J. Martin, Ph.D. Dissertation, Univ. of Nebraska, 1975.

  15. The Detection of Lyman Alpha Radiation Formed by the Slowing Down of Protons and Tritons Produced by the 3He (n, tp) Reaction—A Model Study

    PubMed Central

    Cooper, John W.; Coplan, Michael A.; Hughes, Patrick P.

    2009-01-01

    The observation of Lyman alpha (Lα) radiation produced by the end products of the 3He (n,tp) reaction has suggested the possibility of a new method of cold thermal neutron detection. In order for this goal to be achieved, a basic understanding of how the Lα radiation is formed and how it may be detected, is needed. The model study described here is an attempt to provide this basic understanding and to provide quantitative results that can be used in designing future experiments.

  16. Trident: A three-pronged galaxy survey. I. Lyman alpha emitting galaxies at z ~ 2 in GOODS North

    NASA Astrophysics Data System (ADS)

    Sandberg, A.; Guaita, L.; Östlin, G.; Hayes, M.; Kiaeerad, F.

    2015-08-01

    Context. Lyman alpha (Lyα) emitting galaxies (LAEs) are used to probe the distant universe and are therefore important for galaxy evolution studies and for providing clues to the nature of the epoch of reionization. However, the exact circumstances under which Lyα escapes a galaxy are still not fully understood. Aims: The Trident project is designed to simultaneously examine Lyα, Hα, and Lyman continuum emission from galaxies at redshift z ~ 2, thus linking these three aspects of ionizing radiation in galaxies. In this paper, we outline the strategy of this project and examine the properties of LAEs in the GOODS North field. Methods: We performed a narrowband LAE survey in GOODS North using existing filters and two custom made filters at the Nordic Optical Telescope with MOSCA. We use complementary broadband archival data in the field to make a careful candidate selection and perform optical to near-IR SED fitting. We also estimate far-IR luminosities by matching our candidates to detections in Spitzer/MIPS 24 μm and Herschel/PACS catalogues. Results: We find a total of 25 LAE candidates, probing mainly the bright end of the LAE luminosity function with LLyα ~ 1-15 × 1042 erg s-1. They display a range of masses of ~ 0.5-50 × 109M⊙, and average ages from a few tens of Myr to 1 Gyr when assuming a constant star formation history. The majority of our candidates also show signs of recent elevated star formation. Three candidates have counterparts in the GOODS-Herschel far-IR catalogue, with luminosities consistent with ultra-luminous infrared galaxies (ULIRGs). Conclusions: The wide range of parameters derived from our SED fitting, as well as part of our sample being detected as ULIRGs, seems to indicate that at these Lyα luminosities, LAEs do not necessarily have to be young dwarfs, and that a lack of dust is not required for Lyα to escape. Based on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific

  17. Fluorescence Lyman-Alpha Stratospheric Hygrometer (FLASH): application on meteorological balloons, long duration balloons and unmanned aerial vehicles.

    NASA Astrophysics Data System (ADS)

    Lykov, Alexey; Khaykin, Sergey; Yushkov, Vladimir; Efremov, Denis; Formanyuk, Ivan; Astakhov, Valeriy

    The FLASH instrument is based on the fluorescent method, which uses H2O molecules photodissociation at a wavelength lambda=121.6 nm (Lalpha - hydrogen emission) followed by the measurement of the fluorescence of excited OH radicals. The source of Lyman-alpha radiation is a hydrogen discharge lamp while the detector of OH fluorescence at 308 -316 nm is a photomultiplier run in photon counting mode. The intensity of the fluorescent light as well as the instrument readings is directly proportional to the water vapor mixing ratio under stratospheric conditions with negligible oxygen absorption. Initially designed for rocket-borne application, FLASH has evolved into a light-weight balloon sonde (FLASH-B) for measurements in the upper troposphere and stratosphere on board meteorological and small plastic balloons. This configuration has been used in over 100 soundings at numerous tropical mid-latitude and polar locations within various international field campaigns. An airborne version of FLASH instrument is successfully utilized onboard stratospheric M55-Geophysica aircraft and tropospheric airborne laboratory YAK42-Roshydromet. The hygrometer was modified for application onboard stratospheric long-duration balloons (FLASH-LDB version). This version was successfully used onboard CNES super-pressure balloon launched from SSC Esrange in March 2007 and flown during 10 days. Special design for polar long duration balloon PoGOLite was created for testing work during polar day in June 2013. Installation and measurement peculiarities as well as observational results are presented. Observations of water vapour using FLASH-B instrument, being of high quality are rather costly as the payload recovery is often complicated and most of the time impossible. Following the goal to find a cost-efficient solution, FLASH was adapted for use onboard Unmanned Aerial Vehicles (UAV). This solution was only possible thanks to compactness and light-weight (0.5 kg) of FLASH instrument. The

  18. CONTINUUM SUBTRACTING LYMAN-ALPHA IMAGES: LOW-REDSHIFT STUDIES USING THE SOLAR BLIND CHANNEL OF HST/ACS

    SciTech Connect

    Hayes, Matthew; Oestlin, Goeran; Mas-Hesse, J. Miguel; Kunth, Daniel E-mail: ostlin@astro.su.se E-mail: kunth@iap.fr

    2009-09-15

    We are undertaking an imaging study of local star-forming galaxies in the Lyman-alpha (Ly{alpha}) emission line using the Solar Blind Channel (SBC) of the Advanced Camera for Surveys onboard the Hubble Space Telescope. Observations have been obtained in Ly{alpha} and H-alpha (H{alpha}) and six line-free continuum filters between {approx}1500 A and the I band. In a previous article, we demonstrated that the production of Ly{alpha} line-only images (i.e., continuum subtraction) in the SBC-only data set is nontrivial and that supporting data is a requirement. We here develop various methods of continuum subtraction and assess their relative performance using a variety of spectral energy distributions (SEDs) as input. We conclude that simple assumptions about the behavior of the ultraviolet continuum consistently lead to results that are wildly erroneous, and determine that a spectral fitting approach is essential. Moreover, fitting of a single component stellar or stellar+nebular spectrum is not always sufficient for realistic template SEDs and, in order to successfully recover the input observables, care must be taken to control the contribution of nebular gas and any underlying stellar population. Independent measurements of the metallicity must first be obtained, while details of the initial mass function play only a small role. We identify the need to bin together pixels in our data to obtain signal-to-noise ratios (S/Ns) of around 10 in each band before processing. At S/N = 10, we are able to recover Ly{alpha} fluxes accurate to within around 30% for Ly{alpha} lines with intrinsic equivalent width (W {sub Ly{alpha}}) of 10 A. This accuracy improves to {approx}<10% for W {sub Ly{alpha}} = 100 A. We describe the method of image processing applied to the observations presented in Oestlin et al. and the associated data release. We also present simulations for an observing strategy for an alternative low-redshift Ly{alpha} imaging campaign using ACS/SBC using adjacent

  19. At the Heart of Blobs

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This artist's concept illustrates one possible answer to the puzzle of the 'giant galactic blobs.' These blobs (red), first identified about five years ago, are mammoth clouds of intensely glowing material that surround distant galaxies (white). Astronomers using visible-light telescopes can see the glow of the blobs, but they didn't know what provides the energy to light them up. NASA's Spitzer Space Telescope set its infrared eyes on one well-known blob located 11 billion light-years away, and discovered three tremendously bright galaxies, each shining with the light of more than one trillion Suns, headed toward each other.

    Spitzer also observed three other blobs in the same galactic neighborhood and found equally bright galaxies within them. One of these blobs is also known to contain galaxies merging together. The findings suggest that galactic mergers might be the mysterious source of blobs.

    If so, then one explanation for how mergers produce such large clouds of material is that they trigger intense bursts of star formation. This star formation would lead to exploding massive stars, or supernovae, which would then shoot gases outward in a phenomenon known as superwinds. Blobs produced in this fashion are illustrated in this artist's concept.

  20. On the Accuracy of In Situ Water Vapor Measurements in the Troposphere and Lower Stratosphere with the Harvard Lyman-Alpha Hygrometer

    NASA Technical Reports Server (NTRS)

    Hintsa, Eric J.; Weinstock, Elliot M.; Anderson, James G.; May, Randy D.; Hurst, Dale F.

    1999-01-01

    In an effort to better constrain atmospheric water vapor mixing ratios and to understand the discrepancies between different measurements of water vapor in the stratosphere and troposphere, we have carefully examined data from the Harvard Lyman-alpha photofragment fluorescence hygrometer, which has flown on the NASA ER-2 aircraft from 1992 through 1998. The instrument is calibrated in the laboratory before and after each deployment, and the calibration is checked by direct absorption measurements in the troposphere. On certain flights, the ER-2 flew level tracks during which water vapor varied by up to 80 ppmv, under nearly constant atmospheric conditions. These flights provide a stringent test of our calibration via direct absorption and indicate agreement to within 3%. During the 1997 Photochemistry of Ozone Loss in the Arctic Region In Summer (POLARIS) mission, our Lyman-alpha instrument was compared with a new diode laser hygrometer from the Jet Propulsion Laboratory. Overall agreement was 5% during the June/July deployment and 1% for potential temperatures of 490 to 540 K. The accuracy of our instrument is shown to be +/-5 %, with an additional offset of at most 0.1 ppmv. Data from this instrument, combined with simultaneous measurements of CH4, and H2, are therefore ideal for studies of the hydrogen budget of the lower stratosphere.

  1. Lyman-Alpha aurora

    SciTech Connect

    Durrance, S.T.; Clarke, J.T.

    1984-10-01

    The existence of intense and variable H Ly a emission from Uranus is demonstrated utilizing the monochromatic imaging capabilities of the International Ultraviolet Explorer satellite. A series of 14 observations, using the IUE short wavelength spectrograph in low dispersion and covering the period from 3 March 1982 through 2 September 1983, shows the disk averaged Ly a brightness of Uranus to vary between 690 and 2230 Rayleighs. Model calculations indicates that 400 R of this emission can be attributed to resonant scattering of solar Ly a radiation. An upper limit of 100 R is obtained for the Raman scattering of solar Ly a by H2 (1280 A). This implies that 300 R is contributed to the planetary Ly a emission by Rayleigh scattering. In addition to being unexpectedly strong, the Uranian Ly a emission has been observed to vary by a factor of two in one 24 hr period and by about 50% in one 5 hr period.

  2. Basal entrainment by Newtonian gravity-driven flows

    NASA Astrophysics Data System (ADS)

    Bates, Belinda; Andreini, Nicolas; Ancey, Christophe

    2016-04-01

    Gravity-driven flows can erode the bed along which they descend and increase their mass by a factor of 10 or more. This process is called basal entrainment. Although documented by field observations and laboratory experiments, it remains poorly understood. We look into this issue by studying eroding dam-break waves. More specifically we would like to determine what happens when a viscous gravity-driven flow generated by releasing a fixed volume of incompressible Newtonian fluid encounters a stationary erodible layer (composed of fluid with the same density and viscosity). Models based on depth-averaged mass and momentum balance equations deal with bed-flow interfaces as shock waves. In contrast, we use an approach involving the long-wave approximation of the Navier-Stokes equations (lubrication theory), and in this context, bed-flow interfaces are acceleration waves that move quickly across thin stationary layers. The incoming flow digs down into the bed, pushing up downstream material, thus advancing the flow front. Extending the method used by Huppert [J. Fluid Mech. 121, 43--58 (1982)] for modelling viscous dam-break waves, we end up with a nonlinear diffusion equation for the flow depth, which is solved numerically. Theory is compared with experimental results. Excellent agreement is found in the limit of low Reynolds numbers (i.e., for flow Reynolds numbers lower than 20) for the front position over time and flow depth profile. The Newtonian model has sometimes been used to describe the flow behaviour of natural materials such as snow and debris suspensions, but the majority of existing approaches rely on more elaborate constitutive equations. So there is no direct application of the results presented here to real flow conditions. Yet, our study sheds light on the mechanisms involved in basal entrainment. We provide evidence that the whole layer of loose material is entrained quickly once the flow makes contact with the erodible layer. As this process occurs

  3. Biodegradation of Microcystins during Gravity-Driven Membrane (GDM) Ultrafiltration

    PubMed Central

    Kohler, Esther; Villiger, Jörg; Posch, Thomas; Derlon, Nicolas; Shabarova, Tanja; Morgenroth, Eberhard; Pernthaler, Jakob; Blom, Judith F.

    2014-01-01

    Gravity-driven membrane (GDM) ultrafiltration systems require little maintenance: they operate without electricity at ultra-low pressure in dead-end mode and without control of the biofilm formation. These systems are already in use for water purification in some regions of the world where adequate treatment and distribution of drinking water is not readily available. However, many water bodies worldwide exhibit harmful blooms of cyanobacteria that severely lower the water quality due to the production of toxic microcystins (MCs). We studied the performance of a GDM system during an artificial Microcystis aeruginosa bloom in lake water and its simulated collapse (i.e., the massive release of microcystins) over a period of 21 days. Presence of live or destroyed cyanobacterial cells in the feed water decreased the permeate flux in the Microcystis treatments considerably. At the same time, the microbial biofilms on the filter membranes could successfully reduce the amount of microcystins in the filtrate below the critical threshold concentration of 1 µg L−1 MC for human consumption in three out of four replicates after 15 days. We found pronounced differences in the composition of bacterial communities of the biofilms on the filter membranes. Bacterial genera that could be related to microcystin degradation substantially enriched in the biofilms amended with microcystin-containing cyanobacteria. In addition to bacteria previously characterized as microcystin degraders, members of other bacterial clades potentially involved in MC degradation could be identified. PMID:25369266

  4. Biodegradation of microcystins during gravity-driven membrane (GDM) ultrafiltration.

    PubMed

    Kohler, Esther; Villiger, Jörg; Posch, Thomas; Derlon, Nicolas; Shabarova, Tanja; Morgenroth, Eberhard; Pernthaler, Jakob; Blom, Judith F

    2014-01-01

    Gravity-driven membrane (GDM) ultrafiltration systems require little maintenance: they operate without electricity at ultra-low pressure in dead-end mode and without control of the biofilm formation. These systems are already in use for water purification in some regions of the world where adequate treatment and distribution of drinking water is not readily available. However, many water bodies worldwide exhibit harmful blooms of cyanobacteria that severely lower the water quality due to the production of toxic microcystins (MCs). We studied the performance of a GDM system during an artificial Microcystis aeruginosa bloom in lake water and its simulated collapse (i.e., the massive release of microcystins) over a period of 21 days. Presence of live or destroyed cyanobacterial cells in the feed water decreased the permeate flux in the Microcystis treatments considerably. At the same time, the microbial biofilms on the filter membranes could successfully reduce the amount of microcystins in the filtrate below the critical threshold concentration of 1 µg L(-1) MC for human consumption in three out of four replicates after 15 days. We found pronounced differences in the composition of bacterial communities of the biofilms on the filter membranes. Bacterial genera that could be related to microcystin degradation substantially enriched in the biofilms amended with microcystin-containing cyanobacteria. In addition to bacteria previously characterized as microcystin degraders, members of other bacterial clades potentially involved in MC degradation could be identified. PMID:25369266

  5. Noncommutative minisuperspace, gravity-driven acceleration, and kinetic inflation

    NASA Astrophysics Data System (ADS)

    Rasouli, S. M. M.; Moniz, Paulo Vargas

    2014-10-01

    In this paper, we introduce a noncommutative version of the Brans-Dicke (BD) theory and obtain the Hamiltonian equations of motion for a spatially flat Friedmann-Lemaître-Robertson-Walker universe filled with a perfect fluid. We focus on the case where the scalar potential as well as the ordinary matter sector are absent. Then, we investigate gravity-driven acceleration and kinetic inflation in this noncommutative BD cosmology. In contrast to the commutative case, in which the scale factor and BD scalar field are in a power-law form, in the noncommutative case the power-law scalar factor is multiplied by a dynamical exponential warp factor. This warp factor depends on the noncommutative parameter as well as the momentum conjugate associated to the BD scalar field. We show that the BD scalar field and the scale factor effectively depend on the noncommutative parameter. For very small values of this parameter, we obtain an appropriate inflationary solution, which can overcome problems within BD standard cosmology in a more efficient manner. Furthermore, a graceful exit from an early acceleration epoch towards a decelerating radiation epoch is provided. For late times, due to the presence of the noncommutative parameter, we obtain a zero acceleration epoch, which can be interpreted as the coarse-grained explanation.

  6. Blob-enhanced reconstruction technique

    NASA Astrophysics Data System (ADS)

    Castrillo, Giusy; Cafiero, Gioacchino; Discetti, Stefano; Astarita, Tommaso

    2016-09-01

    A method to enhance the quality of the tomographic reconstruction and, consequently, the 3D velocity measurement accuracy, is presented. The technique is based on integrating information on the objects to be reconstructed within the algebraic reconstruction process. A first guess intensity distribution is produced with a standard algebraic method, then the distribution is rebuilt as a sum of Gaussian blobs, based on location, intensity and size of agglomerates of light intensity surrounding local maxima. The blobs substitution regularizes the particle shape allowing a reduction of the particles discretization errors and of their elongation in the depth direction. The performances of the blob-enhanced reconstruction technique (BERT) are assessed with a 3D synthetic experiment. The results have been compared with those obtained by applying the standard camera simultaneous multiplicative reconstruction technique (CSMART) to the same volume. Several blob-enhanced reconstruction processes, both substituting the blobs at the end of the CSMART algorithm and during the iterations (i.e. using the blob-enhanced reconstruction as predictor for the following iterations), have been tested. The results confirm the enhancement in the velocity measurements accuracy, demonstrating a reduction of the bias error due to the ghost particles. The improvement is more remarkable at the largest tested seeding densities. Additionally, using the blobs distributions as a predictor enables further improvement of the convergence of the reconstruction algorithm, with the improvement being more considerable when substituting the blobs more than once during the process. The BERT process is also applied to multi resolution (MR) CSMART reconstructions, permitting simultaneously to achieve remarkable improvements in the flow field measurements and to benefit from the reduction in computational time due to the MR approach. Finally, BERT is also tested on experimental data, obtaining an increase of the

  7. Gravity-Driven Thin Film Flow of an Ellis Fluid.

    PubMed

    Kheyfets, Vitaly O; Kieweg, Sarah L

    2013-12-01

    The thin film lubrication approximation has been studied extensively for moving contact lines of Newtonian fluids. However, many industrial and biological applications of the thin film equation involve shear-thinning fluids, which often also exhibit a Newtonian plateau at low shear. This study presents new numerical simulations of the three-dimensional (i.e. two-dimensional spreading), constant-volume, gravity-driven, free surface flow of an Ellis fluid. The numerical solution was validated with a new similarity solution, compared to previous experiments, and then used in a parametric study. The parametric study centered around rheological data for an example biological application of thin film flow: topical drug delivery of anti-HIV microbicide formulations, e.g. hydroxyethylcellulose (HEC) polymer solutions. The parametric study evaluated how spreading length and front velocity saturation depend on Ellis parameters. A lower concentration polymer solution with smaller zero shear viscosity (η 0), τ 1/2, and λ values spread further. However, when comparing any two fluids with any possible combinations of Ellis parameters, the impact of changing one parameter on spreading length depends on the direction and magnitude of changes in the other two parameters. In addition, the isolated effect of the shear-thinning parameter, λ, on the front velocity saturation depended on τ 1/2. This study highlighted the relative effects of the individual Ellis parameters, and showed that the shear rates in this flow were in both the shear-thinning and plateau regions of rheological behavior, emphasizing the importance of characterizing the full range of shear-rates in rheological measurements. The validated numerical model and parametric study provides a useful tool for future steps to optimize flow of a fluid with rheological behavior well-described by the Ellis constitutive model, in a range of industrial and biological applications. PMID:25309029

  8. Gravity-Driven Thin Film Flow of an Ellis Fluid

    PubMed Central

    Kheyfets, Vitaly O.

    2014-01-01

    The thin film lubrication approximation has been studied extensively for moving contact lines of Newtonian fluids. However, many industrial and biological applications of the thin film equation involve shear-thinning fluids, which often also exhibit a Newtonian plateau at low shear. This study presents new numerical simulations of the three-dimensional (i.e. two-dimensional spreading), constant-volume, gravity-driven, free surface flow of an Ellis fluid. The numerical solution was validated with a new similarity solution, compared to previous experiments, and then used in a parametric study. The parametric study centered around rheological data for an example biological application of thin film flow: topical drug delivery of anti-HIV microbicide formulations, e.g. hydroxyethylcellulose (HEC) polymer solutions. The parametric study evaluated how spreading length and front velocity saturation depend on Ellis parameters. A lower concentration polymer solution with smaller zero shear viscosity (η0), τ1/2, and λ values spread further. However, when comparing any two fluids with any possible combinations of Ellis parameters, the impact of changing one parameter on spreading length depends on the direction and magnitude of changes in the other two parameters. In addition, the isolated effect of the shear-thinning parameter, λ, on the front velocity saturation depended on τ1/2. This study highlighted the relative effects of the individual Ellis parameters, and showed that the shear rates in this flow were in both the shear-thinning and plateau regions of rheological behavior, emphasizing the importance of characterizing the full range of shear-rates in rheological measurements. The validated numerical model and parametric study provides a useful tool for future steps to optimize flow of a fluid with rheological behavior well-described by the Ellis constitutive model, in a range of industrial and biological applications. PMID:25309029

  9. Interplanetary Lyman-alpha spectral profiles and intensities for both repulsive and attractive solar force fields Predicted absorption pattern by a hydrogen cell

    NASA Astrophysics Data System (ADS)

    Lallement, R.; Bertaux, J. L.; Dalaudier, F.

    1985-09-01

    The velocity of H atoms in the vicinity of the sun can be modified through ionization by solar-wind charge exchange and solar EUV photoionization, and through solar gravity. A computer-code model was developed to study these effects in detail; the model includes line profile computation in the repulsive case when the solar Lyman-alpha radiation pressure exceeds solar gravity. The model also predicts the distributions of the intensity I(phi) and reduction factor R(phi) of the intensity when the H cell is activated to observation planes perpendicular to the sun-earth line as a function of angle phi. This particular geometry applies to the space experiment flown on the Prognoz 5 and 6 spacecraft. The basic findings of the parametric study are presented.

  10. Rest-Optical Morphology of 2Lyman Alpha Emitters: Comparison with Rest-UV and Other High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Bond, Nicholas

    2013-10-01

    Lyman Alpha Emitting galaxies {LAEs} seen at redshifts 2 and 3 are progenitors of typical present-day galaxies like the Milky Way seen in their initial stage of star formation. LAEs are younger, lower in mass, and less chemically evolved than the better-studied Lyman break galaxies {LBGs}, and HST imaging probes the physical properties of these objects at sub-kiloparsec resolution.We will use archival WFC3-NIR images of the HUDF, CANDELS GOODS-S, and ERS GOODS-S to study the rest-frame optical morphology of 66 Lyman Alpha Emitters at z=2.1 and z=3.1, along with comparison samples of star-forming BzK galaxies and Lyman break galaxies at similar redshifts. For objects with sufficient signal-to-noise, we will determine Sersic profiles, CAS {Concentration/Asymmetry/clumpinesS}, and internal color dispersions. We will use an existing pipeline, which we developed and applied to rest-UV ACS images of these galaxies, enabling object-by-object comparisons of rest-optical and rest-UV morphology.Our results will reveal the nature of star formation in low-mass high-redshift galaxies where the bulk of present-day stars were formed and will provide a crucial point of comparison to the morphology of continuum-selected galaxies studied by the CANDELS team. We will illustrate if the distribution between clumpy and/or merger-driven star formation is correlated with galaxy properties such as mass or dust extinction. Our results will also improve the interpretation of morphological studies at z>4, where only rest-UV HST images are available. It will also allow for evolutionary comparisons with rest-UV morphologies at lower redshifts that are underway from UVUDF.

  11. Probing the Properties of Distant Galaxies and their Circumgalactic Medium with Damped, Sub-damped, and Super-damped Lyman-alpha Quasar Absorbers

    NASA Astrophysics Data System (ADS)

    Kulkarni, Varsha P.; Som, Debopam; Morrison, Sean; Peroux, Celine; York, Donald G.; Quiret, Samuel; Lauroesch, James Thomas; Khare, Pushpa; Aller, Monique C.

    2016-01-01

    Excellent tools to measure the chemical and physical properties of distant galaxies and their circumgalactic medium are provided by the high H I column density absorbers in quasar spectra. The damped Lyman-alpha absorbers [DLAs; log N(H I) >= 20.3] and the sub-DLA absorbers [19.0 <= log N(H I) < 20.3] dominate the neutral gas reservoir available for star formation. The super-DLAs [DLAs with log N(H I) >= 21.7] provide ideal laboratories to study the most gas-rich and potentially vigorously star-forming galaxies. We report a study of the DLAs (including super-DLAs) and sub-DLAs, based on observations from Keck, VLT, Magellan, and HST. We combine our results with the literature to examine trends between N(H I), metallicity, dust depletion, and gas velocity dispersion. We find that sub-DLAs have higher metallicities than DLAs at all redshifts studied, even after making ionization corrections. We find the super-DLAs have a relatively narrow range of metallicities. A much larger fraction of the super-DLAs lie close to or above the line [X/H] = 20.59 - log N(H I) in the metallicity versus N(H I) plot, compared to less gas-rich DLAs, suggesting that super-DLAs are more likely to be rich in molecules. Relative abundances of Si, S, Mn, Fe, Ni, and Zn suggest a mixture of dust depletion and alpha-enhancement. We confirm a strong correlation between metallicity and Fe depletion for DLAs, and also find a correlation between metallicity and Si depletion. For sub-DLAs at z < 0.5, we find [N/S] below the level for secondary N production. For some super-DLAs, we estimate star formation rates from potential detections of Lyman-alpha emission. We discuss constraints on electron densities from C II*/C II and Si II*/Si II. The DLAs and sub-DLAs appear to have different metallicity vs. velocity dispersion relations. We also find that the super-DLAs may have somewhat narrower velocity dispersions than the less gas-rich DLAs, and may arise in cooler/ less turbulent gas. We gratefully

  12. Origin and turbulence spreading of plasma blobs

    SciTech Connect

    Manz, P.; Birkenmeier, G.; Stroth, U.; Ribeiro, T. T.; Scott, B. D.; Carralero, D.; Müller, S. H.; Müller, H. W.; Wolfrum, E.; Fuchert, G.

    2015-02-15

    The formation of plasma blobs is studied by analyzing their trajectories in a gyrofluid simulation in the vicinity of the separatrix. Most blobs arise at the maximum radial electric field outside the separatrix. In general, blob generation is not bound to one particular radial position or instability. A simple model of turbulence spreading for the scrape-off layer is derived. The simulations show that the blob dynamics can be represented by turbulence spreading, which constitutes a substantial energy drive for far scrape-off layer turbulence and is a more suitable quantity to study blob generation compared to the skewness.

  13. Infrared Blobs : Time-dependent Flags

    NASA Astrophysics Data System (ADS)

    McCullough, P. R.; Mack, J.; Dulude, M.; Hilbert, B.

    2014-10-01

    We describe the creation of time-dependent flags for pixels associated with "blobs" on the WFC3 IR detector. We detect the blobs on flat fields obtained by repeated observations of the night side of the Earth. We provide the most complete census of IR blobs' positions, radii, and times of first appearance. In aggregate, a set of 46 blobs, 27 "strong" and 19 "medium" in their effective scattering cross section, affect slightly less than 1% of the pixels of the detector. A second set of 81 "weak" (and typically smaller) blobs affect another 1% of the pixels. In the past, the "blob" flag, bit 9 (i.e. value = 512) in the data quality (DQ) array described in Table 2.5 of the WFC3 Data Handbook (Rajan et al. 2010) has been a static 2-D array; henceforth a set of such arrays, each associated with a "use after" date corresponding to the appearance of one or more new blobs, can be used. We prepared such DQ arrays using the 46 "strong" and "medium" blobs and discuss why we did not include the fainter blobs therein. As an added data product, we create and test a blob flat field that corrects the effects of blobs on extended emission; however, it should not be applied if stellar photometry is the goal.

  14. Mechanism and computational model for Lyman-{alpha}-radiation generation by high-intensity-laser four-wave mixing in Kr-Ar gas

    SciTech Connect

    Louchev, Oleg A.; Saito, Norihito; Wada, Satoshi; Bakule, Pavel; Yokoyama, Koji; Ishida, Katsuhiko; Iwasaki, Masahiko

    2011-09-15

    We present a theoretical model combined with a computational study of a laser four-wave mixing process under optical discharge in which the non-steady-state four-wave amplitude equations are integrated with the kinetic equations of initial optical discharge and electron avalanche ionization in Kr-Ar gas. The model is validated by earlier experimental data showing strong inhibition of the generation of pulsed, tunable Lyman-{alpha} (Ly-{alpha}) radiation when using sum-difference frequency mixing of 212.6 nm and tunable infrared radiation (820-850 nm). The rigorous computational approach to the problem reveals the possibility and mechanism of strong auto-oscillations in sum-difference resonant Ly-{alpha} generation due to the combined effect of (i) 212.6-nm (2+1)-photon ionization producing initial electrons, followed by (ii) the electron avalanche dominated by 843-nm radiation, and (iii) the final breakdown of the phase matching condition. The model shows that the final efficiency of Ly-{alpha} radiation generation can achieve a value of {approx}5x10{sup -4} which is restricted by the total combined absorption of the fundamental and generated radiation.

  15. Lyman-alpha observations of the interplanetary hydrogen: support of a NASA sounding rocket program and study of the local interstellar medium

    NASA Astrophysics Data System (ADS)

    Vincent, Frederic

    2013-10-01

    Our proposal is to use the Hubble Space Telescope Imaging Spectrograph {HST /STIS} over a single orbit to make Lyman-alpha observations of the interplanetary hydrogen {IPH} during the April period of this year {2014}.These measurements will provide wavelength and flux calibration, in order to support the HYPE instrument {Hydrogen Polarimetric Explorer} that is planned to make spectro-polarimetric observations in April during a suborbital flight of a NASA sounding rocket {grant NNX08AI98G}. Cross-calibration will also be made with the SWAN instrument {Solar Wind Anisotropies} on the SOHO satellite {Solar and Heliospheric Observatory}. SWAN can provide flux calibration but without any spectral information, so only HST/STIS can provide the wavelength calibration.Moreover the scientific controversy on the physical properties of the local interstellar medium {LISM} is still going on. The recent observations of interstellar helium atoms by IBEX {Interstellar Boundaries Explorer} suggest that the LISM velocity vector may vary over time. Such a change should impact the bulk velocity of interplanetary hydrogen and should be detected by HST /STIS.

  16. A Catalog of z=3.1 Lyman Alpha Emitting Galaxies Discovered in Narrow-band Imaging of MUSYC 1030+05

    NASA Astrophysics Data System (ADS)

    Christenson, Holly; Gangolli, Nakul; Raney, Catie Ann; Walker, Jean P.; Gawiser, Eric J.; MUSYC Collaboration

    2016-01-01

    We present a catalog of ~200 Lyman Alpha Emitting galaxies (LAEs) at redshift z=3.1 found in a 5015 Å narrow-band image of the MUSYC 1030+05 field. We reduced raw optical images taken with the MOSAIC II CCD camera at the CTIO 4m telescope with the IRAF MSCRED package. The reduction included the crucial steps of bias subtraction, flat-field correction, cosmic ray and satellite trail rejection, astrometric calibration, tangent plane projection, weighted stacking, and sky background removal. Our initial catalog of sources detected in the narrow-band filter contains ~20,000 sources. We used additional photometric measurements in the MUSYC broad-band filters to identify LAEs via their flux density excess in the narrow-band. This catalog of LAEs will undergo further analysis to characterize how the number density, clustering, colors, and star formation rates of LAEs vary with position and evolve with redshift.We gratefully acknowledge support from NSF grants AST-1055919 & PHY-1263280.

  17. Edge Sheared Flows and Blob Dynamics

    NASA Astrophysics Data System (ADS)

    Myra, J. R.

    2012-10-01

    The dynamics of blob-filaments [S. I. Krasheninnikov, et al. J. Plasma Phys. 74, 679 (2008); D. A. D'Ippolito, et al., Phys. Plasmas 18, 060501 (2011)] in the strongly radially inhomogeneous edge and scrape-off-layer (SOL) region of a tokamak plasma is considered, with emphasis on sheared flow generation and interaction. The work is motivated by the potential importance of edge sheared flows for turbulence regulation, (e.g. the L-H transition), and the influence of flows on the character of emitted blob-filament structures which ultimately contact plasma-facing components. To study the dynamics of blobs and sheared flows, we employ both numerical simulations and experimental data analysis. The simulations use the fluid-based 2D curvature-interchange model embedded in the SOLT (SOL turbulence) code [D. A. Russell, et al, Phys. Plasmas 16, 122304 (2009)]. A blob-tracking algorithm has also been developed and applied to NSTX and Alcator C-Mod data. The algorithm is based on 2D time-resolved images from the gas puff imaging (GPI) diagnostic [S. J. Zweben, et al. Phys. Plasmas 9, 1981 (2002)]. The algorithm is able to track the blob motion and changes in blob structure, such as elliptical deformations, that can be affected by sheared flows. Results of seeded blob simulations are compared with the experimental data to determine the role of plasma parameters on the blob tracks and to evaluate the exchange of momentum between the blobs and flows. Seeded blob simulations are shown to reproduce many qualitative and quantitative features of the data including size, scale and direction of perpendicular (approximately poloidal) flows and the inferred Reynolds forces, poloidal reversal of blob tracks, and blob trapping and/or ejection. Simulation and experimental data comparisons permit the inference of dynamical mechanisms associated with blob motion and sheared flow generation in these shots, and their relation to previous theoretical work.

  18. Low Latitude Plasma Blobs: A Review

    NASA Astrophysics Data System (ADS)

    Kim, Vitaly P.; Hegai, Valery V.

    2016-03-01

    In recent years, there has been renewed activity in the study of local plasma density enhancements in the low latitude F region ionosphere (low latitude plasma blobs). Satellite, all-sky airglow imager, and radar measurements have identified the characteristics of these blobs, and their coupling to Equatorial Plasma Bubbles (EPBs). New information related to blobs has also been obtained from the Communication/Navigation Outage Forecasting System (C/NOFS) satellite. In this paper, we briefly review experimental, theoretical and modeling studies related to low latitude plasma blobs.

  19. X -Point Effect on Plasma Blob Dynamics

    NASA Astrophysics Data System (ADS)

    Avino, F.; Fasoli, A.; Furno, I.; Ricci, P.; Theiler, C.

    2016-03-01

    Plasma blob dynamics on the high-field side in the proximity of a magnetic field null (X point) is investigated in TORPEX. A significant acceleration of the blobs towards the X point is observed. Close to the X point the blobs break apart. The E ×B drifts associated with the blobs are measured, isolating the background drift component from the fluctuating contribution of the blob internal potential dipole. The time evolution of the latter is consistent with the fast blob dynamics. An analytical model based on charge conservation is derived for the potential dipole, including ion polarization, diamagnetic, and parallel currents. In the vicinity of the X point, a crucial role in determining the blob motion is played by the decrease of the poloidal magnetic field intensity. This variation increases the connection length that short circuits the potential dipole of the blob. Good quantitative agreement is found between the model and the experimental data in the initial accelerating phase of the blob dynamics.

  20. The Lyman-Alpha Forest in the Lensed Quasar Q0957+561 and the Characteristic Dimension of the Absorbing Clouds

    NASA Technical Reports Server (NTRS)

    Dolan, Joseph; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Far-ultraviolet spectra of the gravitational lens components Q0957+561 A and 9 were obtained with the Hubble Space Telescope Faint Object Spectrograph (FOS) at five equally spaced epochs, one every two weeks. We confirm the flux variability of the quasar's Lyman-alpha and 0 VI emission lines reported by Dolan et al. (1995) in IUE spectra. The fluxes in these lines vary on a time scale of weeks in the observer's rest frame, independently of each other and of the surrounding continuum. The individual spectra of each image were co-added to investigate the properties of the Lyman-alpha forest along the two lines of sight to the quasar. Absorption lines having equivalent width W > 0.3 A in the observer's frame not previously identified by Michalitsianos et al. (1997) as interstellar lines, metal lines, or higher order Lyman lines were taken to be Ly-alpha forest lines. The existence of each line in this consistently selected set was then verified by its presence in two archival FOS spectra with -1.5 times higher signal to noise than our co-added spectra. Ly-alpha forest lines with W > 0.3 A appear at 41 distinct wavelengths in the spectra of the two images. one absorption line in the spectrum of image A has no counterpart in the spectrum of image B and one line in image B has no counterpart in image A. Based on the separation of the lines of sight over the redshift range searched for Ly-forest lines, the density of the absorbing clouds in the direction of Q0957+561 must change significantly over a distance R = 160 (+120, -70)/ h(sub 50) kpc in the simplified model where the absorbers are treated as spherical clouds and the characteristic dimension, R, is the radius. (We adopt H(sub 0) = 50 h(sub 50) km/s/ kpc, q(sub 0) = 1/2, and lambda = 0 throughout the paper.) The 95% confidence interval on R extends from (50 - 950)/h(sub 50) kpc We show in the Appendix that the fraction of Ly-alpha forest lines that appear in only one spectrum can be expressed as a rapidly

  1. Lyman alpha escape in local starburst laboratories, a VLT/MUSE view of the ISM state and kinematics of ESO338-IG04 and Haro 11

    NASA Astrophysics Data System (ADS)

    Bik, Arjan; Östlin, Göran; Hayes, Matthew; Menacho, Veronica; Adamo, Angela; Melinder, Jens; Amram, Philippe

    2015-08-01

    Lyman alpha (Lyα) is one of the most important diagnostics in extra galactic astrophysics, however, its appearance strongly depends on the state and kinematics of the interstellar medium (ISM). To understand the relation between Lyα escape and ISM properties at high redshift detailed studies of the ISM and Lyα emission of local Lyα emitting galaxies are required.We present high quality integral field spectroscopy taken with VLT/MUSE of two local Lyman break galaxy analogues: ESO 338-IG04 and Haro 11, providing us with an unprecedented view of the state and kinematics of the ionized gas in the galaxy and their halos. I will present our recent results on studying the ISM state of these two galaxies. The data of both galaxies show that the mechanical and ionization feedback of the super star clusters in the galaxy modify the state and kinematics of the ISM substancially by creating highly ionized bubbles around the cluster, making the central part of the galaxy highly ionized. This shows that the HII regions around the individual clusters are density bounded, allowing the ionizing photons to escape and ionize the ISM further out.On larger scales however, we find remarkable differences. ESO 338-IG04 shows highly ionized cones and galaxy scale outflows all the way to the outskirts of the galaxy halo. Comparison with the cluster populations suggests that the mechanical feedback of the older (30 Myrs) cluster population is responsible for driving the outflows, while the youngest cluster have ionized some of those outflow cones with the EUV photons emitted by the massive stars. A comparison with the Lyα emission suggests that mainly the outflows facilitate Lyα escape. Haro 11 shows a much less clear relation between outflows and Lyα and most of the kinematics seem to be dominated by the merger which the galaxy is undergoing.

  2. A MINI X-RAY SURVEY OF SUB-DAMPED LYMAN-ALPHA ABSORPTION SYSTEMS: SEARCHING FOR ACTIVE GALACTIC NUCLEI FORMED IN PROTOGALAXIES

    SciTech Connect

    Chartas, G.; Asper, A.; Kulkarni, V. P. E-mail: kulkarni@sc.edu

    2013-10-01

    A significant fraction of the sub-damped Lyman-alpha (sub-DLA) absorption systems in quasar spectra appear to be metal-rich, including many with even super-solar element abundances. This raises the question whether some sub-DLAs may harbor active galactic nuclei (AGNs), since supersolar metallicities are observed in AGNs. Here, we investigate this question based on a mini-survey of 21 quasars known to contain sub-DLAs in their spectra. The X-ray observations were performed with the Chandra X-ray Observatory. In cases of no detection, we estimated upper limits for the X-ray luminosities of possible AGNs at the redshifts of the sub-DLAs. In six cases, we find possible X-ray emission within ∼1'' of the background quasar, which is consistent with the presence of a nearby X-ray source. If these nearby X-ray sources are at the redshifts of the sub-DLAs, then their estimated 0.2-10 keV luminosities range between 0.8 × 10{sup 44} h {sup –2} and 4.2 × 10{sup 44} h {sup –2} erg s{sup –1}, thus ruling out a normal late-type galaxy origin, and suggesting that the emission originates in a galactic nucleus near the center of a protogalaxy. The projected distances of these possible nearby X-ray sources from the background quasars lie in the range of 3-7 h {sup –1} kpc, which is consistent with our hypothesis that they represent AGNs centered on the sub-DLAs. Deeper follow-up X-ray and optical observations are required to confirm the marginal detections of X-rays from these sub-DLA galaxies.

  3. Diffusive smoothing of surfzone bathymetry by gravity-driven sediment transport

    NASA Astrophysics Data System (ADS)

    Moulton, M. R.; Elgar, S.; Raubenheimer, B.

    2012-12-01

    Gravity-driven sediment transport often is assumed to have a small effect on the evolution of nearshore morphology. Here, it is shown that down-slope gravity-driven sediment transport is an important process acting to smooth steep bathymetric features in the surfzone. Gravity-driven transport can be modeled as a diffusive term in the sediment continuity equation governing temporal (t) changes in bed level (h): ∂h/∂t ≈ κ ▽2h, where κ is a sediment diffusion coefficient that is a function of the bed shear stress (τb) and sediment properties, such as the grain size and the angle of repose. Field observations of waves, currents, and the evolution of large excavated holes (initially 10-m wide and 2-m deep, with sides as steep as 35°) in an energetic surfzone are consistent with diffusive smoothing by gravity. Specifically, comparisons of κ estimated from the measured bed evolution with those estimated with numerical model results for several transport theories suggest that gravity-driven sediment transport dominates the bed evolution, with κ proportional to a power of τb. The models are initiated with observed bathymetry and forced with observed waves and currents. The diffusion coefficients from the measurements and from the model simulations were on average of order 10-5 m2/s, implying evolution time scales of days for features with length scales of 10 m. The dependence of κ on τb varies for different transport theories and for high and low shear stress regimes. The US Army Corps of Engineers Field Research Facility, Duck, NC provided excellent logistical support. Funded by a National Security Science and Engineering Faculty Fellowship, a National Defense Science and Engineering Graduate Fellowship, and the Office of Naval Research.

  4. The Analysis of Data from Voyager's Ultraviolet Spectrometers: The Trend of Observed Interplanetary Lyman-alpha Intensity with Increasing Heliocentric Distance for Multiple Viewing Directions

    NASA Astrophysics Data System (ADS)

    Gilbert, C. R.; Fayock, B.; Heerikhuisen, J.; Zank, G. P.

    2014-12-01

    The motivation for this project was simple: to reduce raw data from the Ultraviolet Spectrometers on both Voyager Spacecraft to verify the results of a simulation of Lyman-alpha radiative transfer within a 3D MHD kinetic-neutral model of the heliosphere created at the University of Alabama in Huntsville. The heliospheric model, which self-consistently includes the interaction between ionized and neutral hydrogen, outputs a density map of neutral hydrogen. The Monte Carlo radiative transfer model then simulates the propagation and scattering of millions of photons through this density map and outputs the relative number of photons that should be seen by spacecraft at any point within 1000 AU of the sun. My project was to learn how to analyze the raw Voyager data and compare it to these simulations. There were several stages of analysis necessary to reduce to useful data. Records containing signals from sources other than the interplanetary medium, such as stars and planets, were discarded. The remaining records were averaged along regional lines of sight to achieve better signal to noise. The spectra were then corrected for inherent device flaws, such as channel-to-channel variations in sensitivity (fixed-pattern noise), dark counts due to the radioisotope thermal electric generator, and imperfections in the scattering of the diffraction grating. Records were then sorted and averaged to create a full-sky map consisting of 18 regions for each specified radial bin to match the cell spacing of the radiative transfer model. The results were then normalized to solar minimum to reduce variations in the data due to solar cycle oscillations. Initial results indicate an unexpected deviation from the models, but more analysis must be performed to determine if the discrepancy comes from the normalization of the data, insufficient angular resolution of the radiative transfer model, or the physics of the models themselves. Future work involves increasing the resolution of the

  5. Seeing the Lyman-Alpha Forest for the Trees: Constraints on the Thermal State of the IGM from SDSS-III/BOSS

    NASA Astrophysics Data System (ADS)

    Lee, Khee-Gan

    The Lyman-alpha (Lya) forest in the line-of-sight to distant quasars is an important probe of the intergalactic medium (IGM). The thermal properties of the IGM can provide insight the reionization history of the universe, as well as indirectly constraining energy sources in the universe such as galaxies and quasars. This thesis is concerned primarily with studying the IGM using moderate quality Lya forest data sets from large-scale spectroscopic surveys, such as the Sloan Digital Sky Survey (SDSS) and the Baryon Oscillations Spectroscopic Survey (BOSS). In Chapter 1, we study the potential of SDSS Lya forest data to study the IGM. Using simulated mock spectra, we show that the flux probability distribution function (PDF) of SDSS data can place interesting constraints on the spatially-averaged temperature-density relation (TDR) of the IGM. We also introduce the threshold probability functions, a one-dimensional two-point statistic adapted from material sciences that can be applied to SDSS data to detect ˜ 50 Mpc IGM thermal inhomogeneities arising from He II reionization. Chapter 2 discusses the effect of continuum biases in the TDR measured from high-resolution Lyalpha forest spectra in the context of recent evidence for an inverted (gamma < 1) TDR. We argue that forward modeling of continuum errors in mock spectra are necessary to make robust estimates of the TDR. Motivated by the importance of accurate continuum estimation in Lya forest analysis, Chapter 3 introduces the mean-flux regulated/principal component analysis (MF-PCA) continuum estimation technique. We show using mock spectra that this technique can achieve continuum accuracies of < 10% and < 4% in noisy spectra of S/N ˜ 2 and S/N ˜ 5, respectively. We have also publicly released ˜ 13,000 continua from SDSS Data Release 7. In Chapter 4, we measure the flux PDF from BOSS, drawing from an overall sample of ˜ 30,000 Lya forest sightlines. This uses a novel procedure for optimally combining the

  6. Design and Engineering Aspects of a Compact Lyman Alpha Photometer (LAP) for In-situ Measurements of D/H Ratio in Martian Atmosphere

    NASA Astrophysics Data System (ADS)

    Sridhar Raja, V. L. N.; Kalyani, K.; Mohan, Aparna; Chandran, Anand; Durga Pushpavalli, J. T.; Laxmiprasad, S. A.; Kamalakar, A. J.; Viswanathan, M.; Rao, M. V. H.

    2012-07-01

    One of the most challenging multidisciplinary problems in geophysics and atmospheric science is the study of the evolution and escape of planetary atmospheres. Owing to no or little intrinsic magnetic field, the upper atmosphere of the planet Mars is always exposed to the solar wind that triggers the photo-dissociation of water by producing H and D, which are subsequently lost to space over time. Measurements of the atmospheric deuterium to hydrogen abundance ratio (D/H ratio) are significantly vital not only to examine the escape process of the current atmosphere but also to infer the loss process of water in the evolutionary history of Martian atmosphere. Till date, observations of D/H ratio measurements of Mars revealed only local values at certain time or average values over the planetary atmosphere. The exact value of the pristine Martian D/H ratio is still considered to be an open question. This paper primarily focuses on the development of a compact ultraviolet photometer capable of providing present D/H ratio of Mars from spacecraft observations. An ultraviolet photometer named `Lyman Alpha Photometer-LAP' that is currently under development at our laboratory is compact, light weight with low-power consumption and supports the spacecraft operational altitude range of 200 km to 20000 km. LAP operates on the principle of resonant scattering and absorption at Lyman-a wavelengths of H and D i.e., 121.56 nm, 121.53 nm respectively and comprises of 25 mm (Φ) x 60 mm (l) cylindrical metal/glass based gas cells filled with pure H2 and D2 gases at 3 mbar pressure. Thermally dissociated H2 and D2 molecules (due to the heating of a filament inserted in the cell) in the cells absorb the incoming H2/D2 Lyman-a incident on the cell. A 15 nm bandwidth Lyman-a filter cuts-off the undesirable radiation and a solar-blind side-on type photo multiplier tube (PMT) is selected for photon detection. Proto-LAP that is currently under development is a compact instrument that

  7. Final Scientific/Technical Report, DE-FG02-08ER41561: "Lyman-alpha Emitting Galaxies at 2

    SciTech Connect

    Eric Gawiser

    2010-03-19

    Lyman Alpha Emitting (LAE) galaxies are a powerful tracer of large scale structure, making them an excellent probe of baryonic acoustic oscillations, which constrain the expansion history of the universe and hence the nature of the dark energy. The HETDEX Stage III dark energy experiment will utilize LAEs for this purpose, and they are under consideration as a tracer of structure for Stage IV ground- and space-based dark energy missions. Our successful investigation of LAEs at z=2.1 and z=3.1 now provides the best information on the number density and clustering bias of these galaxies over the redshift range that HETDEX will study. Connecting these star-forming galaxies to their host dark matter halos represents a major increase in scientific understanding, as we can now proceed with confidence in studying the spatial distribution of significantly larger samples. Our data also provided an empirical test of the Lyman Alpha Tomography technique, which has proven effective and can now be used to design future experiments to probe dark energy and dark matter properties.

  8. Anisotropic Lyman-alpha emission

    SciTech Connect

    Zheng, Zheng; Wallace, Joshua

    2014-10-20

    As a result of resonant scatterings off hydrogen atoms, Lyα emission from star-forming galaxies provides a probe of the (hardly isotropic) neutral gas environment around them. We study the effect of the environmental anisotropy on the observed Lyα emission by performing radiative transfer calculations for models of neutral hydrogen clouds with prescriptions of spatial and kinematic anisotropies. The environmental anisotropy leads to corresponding anisotropy in the Lyα flux and spectral properties and induces correlations among them. The Lyα flux (or observed luminosity) depends on the viewing angle and shows an approximate correlation with the initial Lyα optical depth in the viewing direction relative to those in all other directions. The distribution of Lyα flux from a set of randomly oriented clouds is skewed to high values, providing a natural contribution to the Lyα equivalent width (EW) distribution seen in observation. A narrower EW distribution is found at a larger peak offset of the Lyα line, similar to the trend suggested in observation. The peak offset appears to correlate with the line shape (full width at half-maximum and asymmetry), pointing to a possibility of using Lyα line features alone to determine the systemic redshifts of galaxies. The study suggests that anisotropies in the spatial and kinematic distributions of neutral hydrogen can be an important ingredient in shaping the observed properties of Lyα emission from star-forming galaxies. We discuss the implications of using Lyα emission to probe the circumgalactic and intergalactic environments of galaxies.

  9. The Lyman alpha reference sample

    NASA Astrophysics Data System (ADS)

    Adamo, Angela; Östlin, Göran; Hayes, Matthew; Melinder, Jens; Bik, Arjan

    2015-08-01

    The Lyman apha reference sample (LARS) is a major multiwavelength imaging and spectroscopic HST campaign of local normal star-forming galaxies, UV-luminous starburst systems, and luminous infrared galaxies. The aim of this survey is to probe what physical conditions and processes regulate the emission of Lyα radiation on local and global galactic scales. The Lyα line is widely used to identify and confirm galaxies in the distant universe, close to the epoch when the first galaxies formed and when the universe was reionized. However, the fact that Lyα is a resonant line makes it optically thick even at relatively low neutral hydrogen column densities, this means that the radiative transport of Lyα photons through galaxies is a complex problem where the structure, kinematics and dust content, and neutral hydrogen content of the interstellar medium all contribute to the process. In this poster we present the unique Lyα maps of the extended LARS sample (i.e. 42 galaxies). These initial results of the LARS survey reveal that when Lyα manages to escape it does so in the form of diffuse scattering halos.

  10. The moving boundary approach to modeling gravity-driven stable and unstable flow in soils

    NASA Astrophysics Data System (ADS)

    Brindt, Naaran; Wallach, Rony

    2016-04-01

    Many field and laboratory studies in the last 40 years have found that water flow in homogeneous soil profiles may occur in preferential flow pathways rather than in a laterally uniform wetting front, as expected from classical soil physics theory and expressed by the Richards equation. The water-content distribution within such gravity-driven fingers was found to be nonmonotonic due to water accumulation behind a sharp wetting front (denoted as saturation overshoot). The unstable flow was first related to soil coarseness. However, its appearance in water-repellent soils led the authors to hypothesize that gravity-driven unstable flow formation is triggered by a non-zero contact angle between water and soil particles. Despite its widespread occurrence, a macroscopic-type model describing the nonmonotonic water distribution and sharp wetting front is still lacking. The moving boundary approach, which divides the flow domain into two well-defined subdomains with a sharp change in fluid saturation between them, is suggested to replace the classical approach of solving the Richards equation for the entire flow domain. The upper subdomain consists of water and air, whose relationship varies with space and time following the imposed boundary condition at the soil surface as calculated by the Richards equation. The lower subdomain also consists of water and air, but their relationship remains constant following the predetermined initial condition. The moving boundary between the two subdomains is the sharp wetting front, whose location is part of the solution. As such, the problem is inherently nonlinear. The wetting front's movement is controlled by the dynamic water-entry pressure of the soil, which depends on soil wettability and the front's propagation rate. A lower soil wettability, which hinders the spontaneous invasion of dry pores and increases the water-entry pressure, induces a sharp wetting front and water accumulation behind it. The wetting front starts to

  11. Tomographic PIV: particles versus blobs

    NASA Astrophysics Data System (ADS)

    Champagnat, Frédéric; Cornic, Philippe; Cheminet, Adam; Leclaire, Benjamin; Le Besnerais, Guy; Plyer, Aurélien

    2014-08-01

    We present an alternative approach to tomographic particle image velocimetry (tomo-PIV) that seeks to recover nearly single voxel particles rather than blobs of extended size. The baseline of our approach is a particle-based representation of image data. An appropriate discretization of this representation yields an original linear forward model with a weight matrix built with specific samples of the system’s point spread function (PSF). Such an approach requires only a few voxels to explain the image appearance, therefore it favors much more sparsely reconstructed volumes than classic tomo-PIV. The proposed forward model is general and flexible and can be embedded in a classical multiplicative algebraic reconstruction technique (MART) or a simultaneous multiplicative algebraic reconstruction technique (SMART) inversion procedure. We show, using synthetic PIV images and by way of a large exploration of the generating conditions and a variety of performance metrics, that the model leads to better results than the classical tomo-PIV approach, in particular in the case of seeding densities greater than 0.06 particles per pixel and of PSFs characterized by a standard deviation larger than 0.8 pixels.

  12. The Development of Replicated Optical Integral Field Spectrographs and their Application to the Study of Lyman-alpha Emission at Moderate Redshifts

    NASA Astrophysics Data System (ADS)

    Chonis, Taylor Steven

    In the upcoming era of extremely large ground-based astronomical telescopes, the design of wide-field spectroscopic survey instrumentation has become increasingly complex due to the linear growth of instrument pupil size with telescope diameter for a constant spectral resolving power. The upcoming Visible Integral field Replicable Unit Spectrograph (VIRUS), a baseline array of 150 copies of a simple integral field spectrograph that will be fed by 3:36 x 104 optical fibers on the upgraded Hobby-Eberly Telescope (HET) at McDonald Observatory, represents one of the first uses of large-scale replication to break the relationship between instrument pupil size and telescope diameter. By dividing the telescope's field of view between a large number of smaller and more manageable instruments, the total information grasp of a traditional monolithic survey spectrograph can be achieved at a fraction of the cost and engineering complexity. To highlight the power of this method, VIRUS will execute the HET Dark Energy Experiment (HETDEX) and survey & 420 degrees2 of sky to an emission line flux limit of ˜ 10-17 erg s-1 cm -2 to detect ˜ 106 Lyman-alpha emitting galaxies (LAEs) as probes of large-scale structure at redshifts of 1:9 < z < 3:5. HETDEX will precisely measure the evolution of dark energy at that epoch, and will simultaneously amass an LAE sample that will be unprecedented for extragalactic astrophysics at the redshifts of interest. Large-scale replication has clear advantages to increasing the total information grasp of a spectrograph, but there are also challenges. In this dissertation, two of these challenges with respect to VIRUS are detailed. First, the VIRUS cryogenic system is discussed, specifically the design and tests of a novel thermal connector and internal camera croygenic components that link the 150 charge-coupled device detectors to the instrument's liquid nitrogen distribution system. Second, the design, testing, and mass production of the suite of

  13. In situ polymerized superhydrophobic and superoleophilic nanofibrous membranes for gravity driven oil-water separation.

    PubMed

    Tang, Xiaomin; Si, Yang; Ge, Jianlong; Ding, Bin; Liu, Lifang; Zheng, Gang; Luo, Wenjing; Yu, Jianyong

    2013-12-01

    Creating an efficient, cost-effective method that can provide simple, practical and high-throughput separation of oil-water mixtures has proved extremely challenging. This work responds to these challenges by designing, fabricating and evaluating a novel fluorinated polybenzoxazine (F-PBZ) modified nanofibrous membrane optimized to achieve gravity driven oil-water separation. The membrane design is then realized by a facile combination of electrospun poly(m-phenylene isophthalamide) (PMIA) nanofibers and an in situ polymerized F-PBZ functional layer incorporating SiO2 nanoparticles (SiO2 NPs). By employing the F-PBZ/SiO2 NP modification, the pristine hydrophilic PMIA nanofibrous membranes are endowed with promising superhydrophobicity with a water contact angle of 161° and superoleophilicity with an oil contact angle of 0°. This new membrane shows high thermal stability (350 °C) and good repellency to hot water (80 °C), and achieves an excellent mechanical strength of 40.8 MPa. Furthermore, the as-prepared membranes exhibited fast and efficient separation of oil-water mixtures by a solely gravity driven process, which makes them good candidates for industrial oil-polluted water treatments and oil spill cleanup, and also provided new insights into the design and development of functional nanofibrous membranes through F-PBZ modification. PMID:24100352

  14. Gravity-driven structures and rift basin evolution: Rio Muni Basin, offshore equatorial West Africa

    SciTech Connect

    Turner, J.P.

    1995-08-01

    Offshore Equatorial Guinea, west Africa, gravity-driven nappes, more than 1 km thick and 15 km from head to toe, provide key evidence in reconstructing the late synrift: evolution of this part of the South Atlantic margin basin system. Furthermore, Aptian-Cenomanian carbonate and clastic rocks in the nappes` allochthonous hanging walls are attracting interest as a new exploration play in west Africa. The nappes exhibit a range of geometries that suggest they share many of the same deformation processes as thin-skin thrust and linked extensional fault systems. Not only are these structures significant in their own right, representing a rare example of gravity tectonics in the virtual absence of major halokinesis, but their presence may record an other-wise undetectable process active during the transition from a rift basin to a passive continental margin. A review of Equatorial Guinea in its pre-Atlantic configuration, alongside neighboring basins in Brazil (the Sergipe-Alagoas basin) and Gabon, suggests that gravity gliding was sustained by a relatively steep, westward paleoslope promoted by east-ward offset of the locus of thermal uplift from the rift basin (i.e., a simple shear model of basin formation). In contrast to gravity-driven structures in most postrift settings, the Equatorial Guinea nappes developed at the close of the Aptian-Albian synrift episode in response to a growing bathymetric deep caused by rapid subsidence outpacing restricted sedimentation.

  15. On the continuum-scale simulation of gravity-driven fingers with hysteretic Richards equation: Trucation error induced numerical artifacts

    SciTech Connect

    ELIASSI,MEHDI; GLASS JR.,ROBERT J.

    2000-03-08

    The authors consider the ability of the numerical solution of Richards equation to model gravity-driven fingers. Although gravity-driven fingers can be easily simulated using a partial downwind averaging method, they find the fingers are purely artificial, generated by the combined effects of truncation error induced oscillations and capillary hysteresis. Since Richards equation can only yield a monotonic solution for standard constitutive relations and constant flux boundary conditions, it is not the valid governing equation to model gravity-driven fingers, and therefore is also suspect for unsaturated flow in initially dry, highly nonlinear, and hysteretic media where these fingers occur. However, analysis of truncation error at the wetting front for the partial downwind method suggests the required mathematical behavior of a more comprehensive and physically based modeling approach for this region of parameter space.

  16. A discontinuous Galerkin method for gravity-driven viscous fingering instabilities in porous media

    NASA Astrophysics Data System (ADS)

    Scovazzi, G.; Gerstenberger, A.; Collis, S. S.

    2013-01-01

    We present a new approach to the simulation of gravity-driven viscous fingering instabilities in porous media flow. These instabilities play a very important role during carbon sequestration processes in brine aquifers. Our approach is based on a nonlinear implementation of the discontinuous Galerkin method, and possesses a number of key features. First, the method developed is inherently high order, and is therefore well suited to study unstable flow mechanisms. Secondly, it maintains high-order accuracy on completely unstructured meshes. The combination of these two features makes it a very appealing strategy in simulating the challenging flow patterns and very complex geometries of actual reservoirs and aquifers. This article includes an extensive set of verification studies on the stability and accuracy of the method, and also features a number of computations with unstructured grids and non-standard geometries.

  17. Improvements on a gravity-driven low-rate particle feeder

    NASA Astrophysics Data System (ADS)

    Wan, Shaolong; Chen, Wei-Yin; Gowan, George

    2009-07-01

    A gravity-driven particle feeder has been modified to achieve sustained operation at steady rates. Particle reservoirs and rod for controlling the nozzle opening are completely redesigned. Particle attrition and rod wobbling are the two main contributors to the feed instabilities. They, in turn, are affected by the height of the particle bed, particle contact time with the moving rod, strength of the magnetic field, and the weight, shape, and position of the rod in the magnetic field. A secondary reservoir minimizes the residence time of particles in the main reservoir. Its shape, orientation, and connection with the main reservoir have profound influences on the feeding stabilities. Tests have been conducted with particles of different types, sizes, and feed rates; results showed good long-term and short-term stabilities.

  18. In situ polymerized superhydrophobic and superoleophilic nanofibrous membranes for gravity driven oil-water separation

    NASA Astrophysics Data System (ADS)

    Tang, Xiaomin; Si, Yang; Ge, Jianlong; Ding, Bin; Liu, Lifang; Zheng, Gang; Luo, Wenjing; Yu, Jianyong

    2013-11-01

    Creating an efficient, cost-effective method that can provide simple, practical and high-throughput separation of oil-water mixtures has proved extremely challenging. This work responds to these challenges by designing, fabricating and evaluating a novel fluorinated polybenzoxazine (F-PBZ) modified nanofibrous membrane optimized to achieve gravity driven oil-water separation. The membrane design is then realized by a facile combination of electrospun poly(m-phenylene isophthalamide) (PMIA) nanofibers and an in situ polymerized F-PBZ functional layer incorporating SiO2 nanoparticles (SiO2 NPs). By employing the F-PBZ/SiO2 NP modification, the pristine hydrophilic PMIA nanofibrous membranes are endowed with promising superhydrophobicity with a water contact angle of 161° and superoleophilicity with an oil contact angle of 0°. This new membrane shows high thermal stability (350 °C) and good repellency to hot water (80 °C), and achieves an excellent mechanical strength of 40.8 MPa. Furthermore, the as-prepared membranes exhibited fast and efficient separation of oil-water mixtures by a solely gravity driven process, which makes them good candidates for industrial oil-polluted water treatments and oil spill cleanup, and also provided new insights into the design and development of functional nanofibrous membranes through F-PBZ modification.Creating an efficient, cost-effective method that can provide simple, practical and high-throughput separation of oil-water mixtures has proved extremely challenging. This work responds to these challenges by designing, fabricating and evaluating a novel fluorinated polybenzoxazine (F-PBZ) modified nanofibrous membrane optimized to achieve gravity driven oil-water separation. The membrane design is then realized by a facile combination of electrospun poly(m-phenylene isophthalamide) (PMIA) nanofibers and an in situ polymerized F-PBZ functional layer incorporating SiO2 nanoparticles (SiO2 NPs). By employing the F-PBZ/SiO2 NP

  19. TRACKING STREAMER BLOBS INTO THE HELIOSPHERE

    SciTech Connect

    Sheeley, N. R.; Rouillard, A.P. E-mail: alexisrouillard@yahoo.co.u

    2010-05-20

    In this paper, we use coronal and heliospheric images from the Solar Terrestrial Relations Observatory (STEREO) spacecraft to track streamer blobs into the heliosphere and to observe them being swept up and compressed by the fast wind from low-latitude coronal holes. From an analysis of their elongation/time tracks, we discover a 'locus of enhanced visibility' where neighboring blobs pass each other along the line of sight and their corotating spiral is seen edge-on. The detailed shape of this locus accounts for a variety of east-west asymmetries and allows us to recognize the spiral of blobs by its signatures in the STEREO images: in the eastern view from STEREO-A, the leading edge of the spiral is visible as a moving wavefront where foreground ejections overtake background ejections against the sky and then fade. In the western view from STEREO-B, the leading edge is only visible close to the Sun-spacecraft line where the radial path of ejections nearly coincides with the line of sight. In this case, we can track large-scale waves continuously back to the lower corona and see that they originate as face-on blobs.

  20. Effects of parallel electron dynamics on plasma blob transport

    SciTech Connect

    Angus, Justin R.; Krasheninnikov, Sergei I.; Umansky, Maxim V.

    2012-08-15

    The 3D effects on sheath connected plasma blobs that result from parallel electron dynamics are studied by allowing for the variation of blob density and potential along the magnetic field line and using collisional Ohm's law to model the parallel current density. The parallel current density from linear sheath theory, typically used in the 2D model, is implemented as parallel boundary conditions. This model includes electrostatic 3D effects, such as resistive drift waves and blob spinning, while retaining all of the fundamental 2D physics of sheath connected plasma blobs. If the growth time of unstable drift waves is comparable to the 2D advection time scale of the blob, then the blob's density gradient will be depleted resulting in a much more diffusive blob with little radial motion. Furthermore, blob profiles that are initially varying along the field line drive the potential to a Boltzmann relation that spins the blob and thereby acts as an addition sink of the 2D potential. Basic dimensionless parameters are presented to estimate the relative importance of these two 3D effects. The deviation of blob dynamics from that predicted by 2D theory in the appropriate limits of these parameters is demonstrated by a direct comparison of 2D and 3D seeded blob simulations.

  1. Salt tectonics and gravity driven deformation: Structural guidelines for exploration in passive margin

    SciTech Connect

    Mauduit, T.; Gwenael G.; Brun, J.P.

    1995-08-01

    The West African Margin, (Gulf of Guinea) presents spectacular examples of gravity driven deformation above a salt decollement (i.e. growth faulting, rafts, diapirs and contractional structures) which have been documented by numerous Oil and Gas investigations. Seismic data demonstrate that the variation of deformation styles in space and time appear to be function of: regional geometry of the margin (i.e. value of basal slope and presence/absence of residual reliefs below the salt layers) and, mode, rate and repartition of sedimentation. The role and effects of the above parameters were analyzed using laboratory modeling investigation based on basic structural patterns identified through seismic data. Models are built with sand and silicone putty, that respectively represent the frictional behavior of upper Cretaceous-Cenozoic cover and the viscous behavior of the upper Aptian salt. They are scaled to fit observed natural configurations. Results are compared with examples from the Gulf of Guinea on the basis of seismic data. This approach allowed to better understand the evolution of the margin and therefore the reservoir distributions and traps geometries.

  2. Characterizing local forces and rearrangements inside a gravity-driven granular flow

    NASA Astrophysics Data System (ADS)

    Thackray, Emma; Nordstrom, Kerstin

    While the gravity-driven flow of a granular material in a silo geometry can be modeled by the Beverloo equation, the mesoscale-level particle rearrangements and interactions that drive this flow are not well-understood. We have constructed a quasi-two-dimensional system of bidisperse, millimeter-scale disks with photoelastic properties that make force networks within the material visible. The system is contained in an acrylic box with an adjustable bottom opening. We can approach the clogging transition by adjusting this opening and by adding external forcing to the top of the flowing pile. By placing the system between cross-polarizers, we can obtain high-speed video of this system during flow, and extract intensity signals that can be used to identify and quantify localized, otherwise indeterminate forces. We can simultaneously track individual particle motions, which can be used to identify shear transformation zones in the system. We are therefore able to correlate local forces with rearrangements within the system, and characterize the evolution of this interplay on the approach to the clogging transition.

  3. Gravity-driven instability of a thin liquid film underneath a soft solid

    NASA Astrophysics Data System (ADS)

    Lee, S. H.; Maki, K. L.; Flath, D.; Weinstein, S. J.; Kealey, C.; Li, W.; Talbot, C.; Kumar, S.

    2014-11-01

    The gravity-driven instability of a thin liquid film located underneath a soft solid material is considered. The equations and boundary conditions governing the solid deformation are systematically converted from a Lagrangian representation to an Eulerian representation, which is the natural framework for describing the liquid motion. This systematic conversion reveals that the continuity-of-velocity boundary condition at the liquid-solid interface is more complicated than has previously been assumed, even in the small-strain limit. We then make clear the conditions under which the commonly used simplified version of this boundary condition is valid. The small-strain approximation, lubrication theory, and linear stability analysis are applied to derive an expression for the growth rate of small-amplitude perturbations. Asymptotic analysis reveals that the coupling between the liquid and solid manifests itself as a lower effective liquid-air interfacial tension that leads to larger instability growth rates. Although this suggests that it is more difficult to maintain a stable liquid coating underneath a soft solid, the effect is expected to be weak for cases of practical interest.

  4. Modeling gravity-driven fingering in rough-walled fractures using modified percolation theory

    SciTech Connect

    Glass, R.J.

    1992-12-31

    Pore scale invasion percolation theory is modified for imbibition of.wetting fluids into fractures. The effects of gravity, local aperture field geometry, and local in-plane air/water interfacial curvatureare included in the calculation of aperture filling potential which controls wetted structure growth within the fracture. The inclusion of gravity yields fingers oriented in the direction of the gravitational gradient. These fingers widen and tend to meander and branch more as the gravitational gradient decreases. In-plane interfacial curvature also greatly affects the wetted structure in both horizontal and nonhorizontal fractures causing the formation of macroscopic wetting fronts. The modified percolation model is used to simulate imbibition into an analogue rough-walled fracture where both fingering and horizontal imbibition experiments were previously conducted. Comparison of numerical and experimental results showed reasonably good agreement. This process oriented physical and numerical modeling is-a necessary step toward including gravity-driven fingering in models of flow and transport through unsaturated, fractured rock.

  5. Comparative study of disinfectants for use in low-cost gravity driven household water purifiers.

    PubMed

    Patil, Rajshree A; Kausley, Shankar B; Balkunde, Pradeep L; Malhotra, Chetan P

    2013-09-01

    Point-of-use (POU) gravity-driven household water purifiers have been proven to be a simple, low-cost and effective intervention for reducing the impact of waterborne diseases in developing countries. The goal of this study was to compare commonly used water disinfectants for their feasibility of adoption in low-cost POU water purifiers. The potency of each candidate disinfectant was evaluated by conducting a batch disinfection study for estimating the concentration of disinfectant needed to inactivate a given concentration of the bacterial strain Escherichia coli ATCC 11229. Based on the concentration of disinfectant required, the size, weight and cost of a model purifier employing that disinfectant were estimated. Model purifiers based on different disinfectants were compared and disinfectants which resulted in the most safe, compact and inexpensive purifiers were identified. Purifiers based on bromine, tincture iodine, calcium hypochlorite and sodium dichloroisocyanurate were found to be most efficient, cost effective and compact with replacement parts costing US$3.60-6.00 for every 3,000 L of water purified and are thus expected to present the most attractive value proposition to end users. PMID:23981873

  6. Nonlinear Resonance Cones and Converging Plasma Blobs

    NASA Astrophysics Data System (ADS)

    Agmon, Nathan; Pribyl, Patrick; Gekelman, Walter; Wise, Joe; Katz, Cami; Ha, Chis; Baker, Bob

    2013-10-01

    Electric field resonance cones have been shown to create density disturbances in cold, magnetized plasmas. Two circular antennas in the LAPTAG experimental plasma device were used to create converging, nonlinear resonance cones. The nonlinear electrostatic field is produced by large amplitude RF (ERF/nkTe >> 1). A movable probe, powered by a computerized motor and consisting of three mutually orthogonal electric dipoles, is used to measure the electric field of the cones which become distorted at large amplitudes. A 2D movable Langmuir probe was used to determine localized density perturbations after turn-off of the RF power. A density blob moving at 3-5 times the ion sound speed has been observed to propagate away (for at least 20 cm) from the focus of the cone. Two ring antennas produced colliding blobs. The physics of the collision will be described. Work performed at the Basic Plasma Science Facility supported by DOE and NSF.

  7. Volcano seismicity and ground deformation unveil the gravity-driven magma discharge dynamics of a volcanic eruption.

    PubMed

    Ripepe, Maurizio; Donne, Dario Delle; Genco, Riccardo; Maggio, Giuseppe; Pistolesi, Marco; Marchetti, Emanuele; Lacanna, Giorgio; Ulivieri, Giacomo; Poggi, Pasquale

    2015-01-01

    Effusive eruptions are explained as the mechanism by which volcanoes restore the equilibrium perturbed by magma rising in a chamber deep in the crust. Seismic, ground deformation and topographic measurements are compared with effusion rate during the 2007 Stromboli eruption, drawing an eruptive scenario that shifts our attention from the interior of the crust to the surface. The eruption is modelled as a gravity-driven drainage of magma stored in the volcanic edifice with a minor contribution of magma supplied at a steady rate from a deep reservoir. Here we show that the discharge rate can be predicted by the contraction of the volcano edifice and that the very-long-period seismicity migrates downwards, tracking the residual volume of magma in the shallow reservoir. Gravity-driven magma discharge dynamics explain the initially high discharge rates observed during eruptive crises and greatly influence our ability to predict the evolution of effusive eruptions. PMID:25980642

  8. [Kinetic theory and boundary conditions for flows of highly inelastic spheres: Application to gravity driven granular flows down bumpy inclines

    SciTech Connect

    Richman, M.W.

    1992-01-01

    In this quarter, we extended our study of the effects of isotropic boundary vibrations to steady, gravity driven, inclined granular flows. These flows are more complex than those considered last quarter because of the presence of slip and mean velocity gradients at the boundary. Consequently, it was first necessary to modify the boundary conditions derived by Richman (1992) to account for corrections to the flow particle velocity distribution function from velocity gradients. In what follows we only summarize the results obtained.

  9. Radial convection of finite ion temperature, high amplitude plasma blobs

    SciTech Connect

    Wiesenberger, M. Kendl, A.; Madsen, J.

    2014-09-15

    We present results from simulations of seeded blob convection in the scrape-off-layer of magnetically confined fusion plasmas. We consistently incorporate high fluctuation amplitude levels and finite Larmor radius (FLR) effects using a fully nonlinear global gyrofluid model. This is in line with conditions found in tokamak scrape-off-layers (SOL) regions. Varying the ion temperature, the initial blob width, and the initial amplitude, we found an FLR dominated regime where the blob behavior is significantly different from what is predicted by cold-ion models. The transition to this regime is very well described by the ratio of the ion gyroradius to the characteristic gradient scale length of the blob. We compare the global gyrofluid model with a partly linearized local model. For low ion temperatures, we find that simulations of the global model show more coherent blobs with an increased cross-field transport compared to blobs simulated with the local model. The maximal blob amplitude is significantly higher in the global simulations than in the local ones. When the ion temperature is comparable to the electron temperature, global blob simulations show a reduced blob coherence and a decreased cross-field transport in comparison with local blob simulations.

  10. Laboratory and numerical simulations of gravity-driven coastal currents: Departures from geostrophic theory

    NASA Astrophysics Data System (ADS)

    Gregorio, S. O.; Haidvogel, D. B.; Thomas, P. J.; Taskinoglu, E. S.; Skeen, A. J.

    2011-09-01

    Laboratory realizations and numerical simulations of buoyant, gravity-driven coastal plumes are summarized and compared to the inviscid geostrophic theory of Thomas and Linden (2007). The lengths, widths and velocities of the buoyant currents, as well as their internal structure and dynamics, are studied. Agreement between the laboratory and numerical experiments and the geostrophic theory is found to depend on two non-dimensional parameters which characterize, respectively, the steepness of the plumes isopycnal interface ( I) and the strength of horizontal viscous forces ( EkH, the horizontal Ekman number). In general, the numerical and laboratory experiments are in good agreement when conducted at comparable values of I and EkH. The best agreement between experiments (both laboratory and numerical) and the geostrophic theory are found for the least viscous flows, though important departures from the theoretical predictions are nonetheless found, particularly in the early development of the plume system. At elevated values of the horizontal Ekman number, laboratory and numerical experiments depart more significantly from theory, e.g., in the rate of plume movement along the coast. A simple extension to the geostrophic theory suggests that the discrepancy between the theoretical and experimental propagation speed should be proportional to the square root of the horizontal Ekman number. The numerical simulations confirm this relationship. For some combinations of the non-dimensional parameters, instabilities develop in the seaward edge of the buoyant plumes. The laboratory and numerical experiments are used together to infer the region within parameter space within which the instabilities occur. Mixing of ambient and buoyant fluids by the plume-edge instabilities is explored using the numerical results.

  11. Optimization of gravity-driven membrane (GDM) filtration process for seawater pretreatment.

    PubMed

    Wu, Bing; Hochstrasser, Florian; Akhondi, Ebrahim; Ambauen, Noëmi; Tschirren, Lukas; Burkhardt, Michael; Fane, Anthony G; Pronk, Wouter

    2016-04-15

    Seawater pretreatment by gravity-driven membrane (GDM) filtration at 40 mbar has been investigated. In this system, a beneficial biofilm develops on the membrane that helps to stabilize flux. The effects of membrane type, prefiltration and system configuration on stable flux, biofilm layer properties and dissolved carbon removal were studied. The results show that the use of flat sheet PVDF membranes with pore sizes of 0.22 and 0.45 μm in GDM filtration achieved higher stabilized permeate fluxes (7.3-8.4 L/m(2)h) than that of flat sheet PES 100 kD membranes and hollow fibre PVDF 0.1 μm membranes. Pore constriction and cake filtration were identified as major membrane fouling mechanisms, but their relative contributions varied with filtration time for the various membranes. Compared to raw seawater, prefiltering of seawater with meshes at sizes of 10, 100 and 1000 μm decreased the permeate flux, which was attributed to removal of beneficial eukaryotic populations. Optical coherence tomography (OCT) showed that the porosity of the biofouling layer was more significantly related with permeate flux development rather than its thickness and roughness. To increase the contact time between the biofilm and the dissolved organics, a hybrid biofilm-submerged GDM reactor was evaluated, which displayed significantly higher permeate fluxes than the submerged GDM reactor. Although integrating the biofilm reactor with the membrane system displayed better permeate quality than the GDM filtration cells, it could not effectively reduce dissolved organic substances in the seawater. This may be attributed to the decomposition/degradation of solid organic substances in the feed and carbon fixation by the biofilm. Further studies of the dynamic carbon balance are required. PMID:26900974

  12. Seismogenic slump folds formed by gravity-driven tectonics down a negligible subaqueous slope

    NASA Astrophysics Data System (ADS)

    Alsop, G. Ian; Marco, Shmuel

    2013-10-01

    The Late Pleistocene Lisan Formation contains superb examples of soft-sediment deformation generated during gravity-driven slumping and failure down extremely gentle (< 1°) slopes towards the palaeo-Dead Sea Basin. Following a previously established framework, portions of individual slumps are broadly categorised into coherent, semi-coherent, and incoherent domains, reflecting increasing deformation and disarticulation of sediment. We present new structural data collected from each of these (overlapping) domains that demonstrate how the orientation of fold hinges and axial planes becomes more dispersed as slumps become increasingly incoherent. Such patterns are the reverse to that typically encountered in lithified rocks where increasing deformation results in clustering of linear elements towards the flow direction, and may reflect greater heterogeneity and disarticulation within slumps. Use of folds to determine palaeoslopes should therefore be limited to those from coherent slumps, where the opportunity for hinge dislocation and rotation is more limited. Within coherent and semi-coherent slumps, folds are reworked to create classic Type 1, 2 and 3 refold patterns during a single progressive deformation perhaps lasting just a matter of minutes. It is noteworthy that slump folds are typically lacking in smaller parasitic folds, implying that instantaneous development and/or limited viscosity contrasts have hindered the formation of second order folds. As deformation intensifies within semi-coherent to incoherent slumps, some fold hinges rotate towards the flow direction to create sheath folds. However, many fold hinges do not rotate into the flow direction, but rather roll downslope to form a new category of spiral folds. Extreme deformation may also generate semi-detached fold trains in which the short limbs of verging fold pairs are relatively thickened resulting in en-echelon X folds. The hinges of the sheared fold pair are reduced to apophyses, although these

  13. Modeling the shallow gravity-driven flows as saturated binary mixtures over temporally varying topography

    NASA Astrophysics Data System (ADS)

    Tai, Yih-Chin; Kuo, Chih-Yu

    2010-05-01

    Based on the "shallow water models over arbitrary topography" by Bouchut and Westdickenberg [2004], and the "Coulomb-mixture theory" by Iversion and Denlinger [2001], we propose a saturated binary mixture model over temporally varying topography, where the effects of the entrainment and deposition are considered. Due to the deposition or erosion processes, the interface between the moving material and the stagnant base is a non-material singular surface that moves with its own velocity. Its motion is thus determined by the mass exchange between the flowing layer and the ground. Through the introduction of the unified coordinate method (e.g. Hui [2004, 2007]) and dimension analysis, the leading-order depth-integrated mass and momentum equations are presented in the time-dependent and topography-fitted curvilinear coordinate system, where the evolving curvature effect is neatly included in the total derivative operator of the variable topography-fitted coordinates. The motion of the basal interface is postulated by function of basal friction coefficient, sliding velocity, local thickness of the flowing layer and a threshold kinetic energy. A shock-capturing numerical scheme is implemented to solve the derived equation system (e.g. Tai and Kuo [2008] or Tai and Lin [2008]). And the key features are investigated and illustrated by the numerical results. References: [1] F. Bouchut and M. Westdickenberg, "Gravity driven shallow water models for arbitrary topography." Commun. Math. Sci. 2, 359-389 (2004). [2] R.M. Iverson and R.P. Denlinger, "Flow of variably fluidized granular masses across three-dimensional terrain. Part 1 Coulomb mixture theory." J. Geophysical Research, 106, 537-552 (2001). [3] W.H. Hui, "A unified coordinates approach to computational Fluid dynamics." J. Comput. and Applied Math., 163, 15-28 (2004). [4] W.H. Hui. "The unified coordinate system in computational fluid dynamics." Commun. Comput. Phys., 2(4), 577-610 (2007). [5] Y.C. Tai and C.Y. Kuo, "A

  14. The formation of blobs from a pure interchange process

    SciTech Connect

    Zhu, P.; Sovinec, C. R.; Hegna, C. C.

    2015-02-15

    In this work, we focus on examining a pure interchange process in a shear-less slab configuration as a prototype mechanism for blob formation. We employ full magnetohydrodynamic simulations to demonstrate that the blob-like structures can emerge through the nonlinear development of a pure interchange instability originating from a pedestal-like transition region. In the early nonlinear stage, filamentary structures develop and extend in the direction of the effective gravity. The blob-like structures appear when the radially extending filaments break off and disconnect from the core plasma. The morphology and the dynamics of these filaments and blobs vary dramatically with a sensitive dependence on the dissipation mechanisms in the system and the initial perturbation. Despite the complexity in morphology and dynamics, the nature of the entire blob formation process in the shear-less slab configuration remains strictly interchange without involving any change in magnetic topology.

  15. The Effect of Surface Tension on the Gravity-driven Thin Film Flow of Newtonian and Power-law Fluids

    PubMed Central

    Hu, Bin; Kieweg, Sarah L.

    2012-01-01

    Gravity-driven thin film flow is of importance in many fields, as well as for the design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. There have been many prior works on gravity-driven thin films. However, the incorporation of surface tension effect has not been well studied for non-Newtonian fluids. After surface tension effect was incorporated into our 2D (i.e. 1D spreading) power-law model, we found that surface tension effect not only impacted the spreading speed of the microbicide gel, but also had an influence on the shape of the 2D spreading profile. We observed a capillary ridge at the front of the fluid bolus. Previous literature shows that the emergence of a capillary ridge is strongly related to the contact line fingering instability. Fingering instabilities during epithelial coating may change the microbicide gel distribution and therefore impact how well it can protect the epithelium. In this study, we focused on the capillary ridge in 2D flow and performed a series of simulations and showed how the capillary ridge height varies with other parameters, such as surface tension coefficient, inclination angle, initial thickness, and power-law parameters. As shown in our results, we found that capillary ridge height increased with higher surface tension, steeper inclination angle, bigger initial thickness, and more Newtonian fluids. This study provides the initial insights of how to optimize the flow and prevent the appearance of a capillary ridge and fingering instability. PMID:23687391

  16. The interchange instability in high-latitude plasma blobs

    SciTech Connect

    Chaturvedi, P.K.; Huba, J.D. )

    1987-04-01

    The stability of high-latitude plasma density enhancements (blobs) is analyzed with regard to the interchange mode (driven by neutral wind or equilibrium transverse electric field acting on the density gradient at the walls of the blobs). The effects arising from the finite parallel length of the blobs along the magnetic field lines are included in the analysis. Plasma regions of differing collisionalities, to which the blobs extend in altitude, are considered. The authors find that the finite parallel blob size results in a modest reduction in the growth rates of the small ({approx lt}1 km) and intermediate (1-10 km) scale sizes but severely reduces the growth rates for the large scale sizes (> 10 km) for the observed parallel blob lengths ({approximately}300-600 km). Further, it is found that the instability growth rates show a moderate reduction at higher altitudes (where ion-inertial effects may be dominant over the ion-neutral collisional effects). Thus the E{times} B instability is considered a plausible candidate for the scintillation-causing irregularities (1-10 km) associated with the high-latitude blobs.

  17. Interchange instability in high-latitude plasma blobs. Memorandum report

    SciTech Connect

    Chaturvedi, P.K.; Huba, J.D.

    1986-12-30

    The stability of high-latitude plasma-density enhancements (blobs) is analyzed with regard to the interchange model (driven by a neutral wind or transverse electric field acting on the density gradient at the walls of the blobs). The effects arising from the finite parallel length of the blobs along the magnetic field lines are included in the analysis. Plasma regions of differing collisionalities, to which the blobs extend in altitude, are considered. It was found that the finite-parallel blob size results in a modest reduction in the growth rates of the small somewhat < 1 km) and intermediate (1-10 km) scale sizes, but severely reduces the growth rates, for the large scale sizes (> 10 kms) for the observed parallel blob lengths (approx. 300-600 kms). Further, it is found that the instability growth rates show a moderate reduction at higher altitudes (where ion-inertial effects may be dominant over the ion-neutral collisional effects). Thus, the E x B instability is considered a plausible candidate for the scintillation causing irregularities (1-10 kms) associated with the high-latitude blobs.

  18. Blob structure and motion in the edge and SOL of NSTX

    DOE PAGESBeta

    Zweben, S. J.; Myra, J. R.; Davis, W. M.; D’Ippolito, D. A.; Gray, T. K.; Kaye, S. M.; LeBlanc, B. P.; Maqueda, R. J.; Russell, D. A.; Stotler, D. P.

    2016-01-28

    Here, the structure and motion of discrete plasma blobs (a.k.a. filaments) in the edge and scrape-off layer of NSTX is studied for representative Ohmic and H-mode discharges. Individual blobs were tracked in the 2D radial versus poloidal plane using data from the gas puff imaging diagnostic taken at 400 000 frames s-1. A database of blob amplitude, size, ellipticity, tilt, and velocity was obtained for ~45 000 individual blobs. Empirical relationships between various properties are described, e.g. blob speed versus amplitude and blob tilt versus ellipticity. The blob velocities are also compared with analytic models.

  19. Towards a quantitative prediction of the blob detection rate

    NASA Astrophysics Data System (ADS)

    Fuchert, G.; Carralero, D.; Manz, P.; Stroth, U.; Wolfrum, E.; ASDEX Upgrade Team

    2016-05-01

    To estimate the particle and energy flux to the plasma facing components of a future fusion power plant, the transport carried by filaments of increased pressure, called blobs, is of critical importance. To understand this transport the rate of the filaments has to be known. The novel approach presented here allows the prediction of both the blob generation and detection rates based on background plasma parameters only. The prediction is in a good overall agreement with recent experiments in ASDEX Upgrade.

  20. A comparison between laboratory and numerical simulations of gravity-driven coastal currents with a geostrophic theory

    NASA Astrophysics Data System (ADS)

    Gregorio, Sandy; Thomas, Peter; Haidvogel, Dale; Taskinoglu, Ezgi; Skeen, Andrew

    2011-11-01

    Laboratory and numerical simulations of buoyant, gravity-driven coastal currents are summarized and compared to the inviscid geostrophic theory of Thomas & Linden 2007. The lengths, widths and velocities of the buoyant currents are studied. Agreement between the laboratory and numerical experiments and the geostrophic theory is found to depend on two non-dimensional parameters which characterize, respectively, the steepness of the plumes isopycnal interface and the strength of horizontal viscous forces (quantified by the horizontal Ekman number). The best agreement between experiments (both laboratory and numerical) and the geostrophic theory are found for the least viscous flows. At elevated values of the horizontal Ekman number, laboratory and numerical experiments depart more significantly from theory. MEOM/LEGI from the 1st of October 2011.

  1. Modeling of large amplitude plasma blobs in three-dimensions

    SciTech Connect

    Angus, Justin R.; Umansky, Maxim V.

    2014-01-15

    Fluctuations in fusion boundary and similar plasmas often have the form of filamentary structures, or blobs, that convectively propagate radially. This may lead to the degradation of plasma facing components as well as plasma confinement. Theoretical analysis of plasma blobs usually takes advantage of the so-called Boussinesq approximation of the potential vorticity equation, which greatly simplifies the treatment analytically and numerically. This approximation is only strictly justified when the blob density amplitude is small with respect to that of the background plasma. However, this is not the case for typical plasma blobs in the far scrape-off layer region, where the background density is small compared to that of the blob, and results obtained based on the Boussinesq approximation are questionable. In this report, the solution of the full vorticity equation, without the usual Boussinesq approximation, is proposed via a novel numerical approach. The method is used to solve for the evolution of 2D and 3D plasma blobs in a regime where the Boussinesq approximation is not valid. The Boussinesq solution under predicts the cross field transport in 2D. However, in 3D, for parameters typical of current tokamaks, the disparity between the radial cross field transport from the Boussinesq approximation and full solution is virtually non-existent due to the effects of the drift wave instability.

  2. Lyman alpha radiation in external galaxies

    NASA Technical Reports Server (NTRS)

    Neufeld, David A.; Mckee, Christopher F.

    1990-01-01

    The Ly alpha line of atomic hydrogen is often a luminous component of the radiation emitted by distant galaxies. Except for those galaxies which have a substantial central source of non-stellar ionizing radiation, most of the Ly alpha radiation emitted by galaxies is generated within regions of the interstellar medium which are photoionized by starlight. Conversely, much of the energy radiated by photoionized regions is carried by the Ly alpha line. Only hot, massive stars are capable of ionizing hydrogen in the interstellar medium which surrounds them, and because such stars are necessarily short-lived, Ly alpha emission traces regions of active star formation. Researchers argue that the strength of the Ly alpha emission observed from external galaxies may be used to estimate quantitatively the dust content of the emitting region, while the Ly alpha line profile is sensitive to the presence of shock waves. Interstellar dust particles and shock waves are intimately associated with the process of star formation in two senses. First, both dust particles and shock waves owe their existence to stellar activity; second, they may both serve as agents which facilitate the formation of stars, shocks by triggering gravitational instabilities in the interstellar gas that they compress, and dust by shielding star-forming molecular clouds from the ionizing and dissociative effects of external UV radiation. By using Ly alpha observations as a probe of the dust content in diffuse gas at high redshift, we might hope to learn about the earliest epochs of star formation.

  3. Pressure-confined Lyman-alpha clouds

    NASA Technical Reports Server (NTRS)

    Baron, E.; Carswell, R. F.; Hogan, C. J.; Weymann, R. J.

    1989-01-01

    Results are presented of numerical models of pressure-confined spherical gas clouds which produce absorption resembling the low to intermediate atomic column density lines found in high-redshift QSO spectra. One-dimensional hydrodynamical models including electron conduction are described, and the rate equations are solved to find ionization and excitation states. Results are presented for both static and adiabatically expanding confining media covering a range of initial pressures. It is found that Ly-alpha lines are very similar over a wide range of conditions and that the most promising diagnostic of pressure is to compare the column density in H I to that in He I and He II. No single-pressure model can explain the wide range of observed H I column densities.

  4. Lyman alpha coronagraph research sounding rocket program

    NASA Technical Reports Server (NTRS)

    Parkinson, W. H.; Kohl, J. L.

    1985-01-01

    The ultraviolet light coronagraph was developed and successfully flown on three rocket flights on 13 April 1979, 16 February 1980 and 20 July 1982. During each of these flights, the Ultraviolet Light Coronagraph was flown jointly with the White Light Coronagraph provided by the High Altitude Observatory. Ultraviolet diagnostic techniques and instrumentation for determining the basic plasma parameters of solar wind acceleration regions in the extended corona were developed and verified and the understanding of the physics of the corona through the performance, analysis and interpretation of solar observations advanced. Valuable UV diagnostics can be performed in the absence of a natural solar eclipse.

  5. Lyman Alpha Searches at Redshift Z>7

    NASA Astrophysics Data System (ADS)

    Willis, Jon

    2007-05-01

    The ZEN survey is a narrow J-band survey for Ly-alpha emitting galaxies at z > 7. I will briefly review the pros and cons of narrow band observations before summarising the ZEN1 and ZEN2 searches based upon deep ISAAC pointings. I will then present ZEN3, consisting of wide field, narrow band observations of two fields using the CFHT WIRCam facility. I will conclude by reviewing the current sample of candidates and what we have learned about the z > 7 Ly-alpha emitting population.

  6. Pre-sheath density drop induced by ion-neutral friction along plasma blobs and implications for blob velocities

    SciTech Connect

    Furno, I.; Chabloz, V.; Fasoli, A.; Loizu, J.; Theiler, C.

    2014-01-15

    The pre-sheath density drop along the magnetic field in field-aligned, radially propagating plasma blobs is investigated in the TORPEX toroidal experiment [Fasoli et al., Plasma Phys. Controlled Fusion 52, 124020 (2010)]. Using Langmuir probes precisely aligned along the magnetic field, we measure the density n{sub se} at a poloidal limiter, where blobs are connected, and the upstream density n{sub 0} at a location half way to the other end of the blobs. The pre-sheath density drop n{sub se}/n{sub 0} is then computed and its dependence upon the neutral background gas pressure is studied. At low neutral gas pressures, the pre-sheath density drop is ≈0.4, close to the value of 0.5 expected in the collisionless case. In qualitative agreement with a simple model, this value decreases with increasing gas pressure. No significant dependence of the density drop upon the radial distance into the limiter shadow is observed. The effect of reduced blob density near the limiter on the blob radial velocity is measured and compared with predictions from a blob speed-versus-size scaling law [Theiler et al., Phys. Rev. Lett. 103, 065001 (2009)].

  7. What powers Lyα blobs?

    NASA Astrophysics Data System (ADS)

    Ao, Y.; Matsuda, Y.; Beelen, A.; Henkel, C.; Cen, R.; De Breuck, C.; Francis, P. J.; Kovács, A.; Lagache, G.; Lehnert, M.; Mao, M. Y.; Menten, K. M.; Norris, R. P.; Omont, A.; Tatemastu, K.; Weiß, A.; Zheng, Z.

    2015-09-01

    Lyα blobs (LABs) are spatially extended Lyα nebulae seen at high redshift. The origin of Lyα emission in the LABs is still unclear and under debate. To study their heating mechanism(s), we present Australia Telescope Compact Array (ATCA) observations of the 20 cm radio emission and Herschel PACS and SPIRE measurements of the far-infrared (FIR) emission toward the four LABs in the protocluster J2143-4423 at z = 2.38. Among the four LABs, B6 and B7 are detected in the radio with fluxes of 67±17 μJy and 77±16 μJy, respectively, and B5 is marginally detected at 3σ (51±16 μJy). For all detected sources, their radio positions are consistent with the central positions of the LABs. Among them, B6 and B7 are obviously also detected in the FIR. By fitting the data with different templates, we obtained redshifts of 2.20+0.30-0.35 for B6 and 2.20+0.45-0.30 for B7, which are consistent with the redshift of the Lyα emission within uncertainties, indicating that both FIR sources are likely associated with the LABs. The associated FIR emission in B6 and B7 and high star formation rates strongly favor star formation in galaxies as an important powering source for the Lyα emission in both LABs. However, the other two, B1 and B5, are predominantly driven by the active galactic nuclei or other sources of energy still to be specified, but not mainly by star formation. In general, the LABs are powered by quite diverse sources of energy. Herschel (Pilbratt et al. 2010) is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  8. Experimental and theoretical study of fluid-structure interactions in plunging hydrofoils and gravity-driven falling plates

    NASA Astrophysics Data System (ADS)

    Tian, Ruijun

    Two typical unsteady fluid-structure interaction problems have been investigated in the present study. One of them was about actively plunged flexible hydrofoil; the other was about gravity-driven falling plates in water. Real-time velocity field and dynamic response on the moving objects were measured to study these unsteady and highly nonlinear problems. For a long time, scientists have believed that bird and insect flight benefits greatly from the flexibility and morphing facility of their wings via flapping motion. A significant advantage flexible wing models have over quasi-steady rigid wing models is a much higher lift generation capability. Both experimental and computational studies have shown that the leading and trailing edge vortexes (LEV and TEV) play a major role in the efficient generation of such unconventionally high lift force. In this study, two NACA0012 miniature hydrofoils, one flexible and the other rigid, were actively plunged at various frequencies in a viscous glycerol-water solution to study the influence of flexibility. Two-dimensional, phase-locked particle image velocimetry (PIV) measurements were conducted to investigate the temporal and spacial development of LEVs and TEVs. Simultaneous measurements of lift and thrust forces were recorded to reveal the relationship between hydrodynamic force and the evolution of the surrounding flow field. Results from the flexible hydrofoil were compared to those from the rigid one in order to quantitatively analyze the effects of flexibility. The second problem focused on fluid-structure interaction of gravity driven falling plates. Falling leaves and paper cards in air has drawn plenty of research interest in the past decades to investigate the interaction between the fluid flow and the falling object. In this research, time-resolved PIV were employed to experimentally visualize the flow field evolution around the gravity-driven falling plates. The plates were made of different materials with

  9. Scattering of radio frequency waves by blobs in tokamak plasmas

    SciTech Connect

    Ram, Abhay K.; Hizanidis, Kyriakos; Kominis, Yannis

    2013-05-15

    The density fluctuations and blobs present in the edge region of magnetic fusion devices can scatter radio frequency (RF) waves through refraction, reflection, diffraction, and coupling to other plasma waves. This, in turn, affects the spectrum of the RF waves and the electromagnetic power that reaches the core of the plasma. The usual geometric optics analysis of RF scattering by density blobs accounts for only refractive effects. It is valid when the amplitude of the fluctuations is small, of the order of 10%, compared to the background density. In experiments, density fluctuations with much larger amplitudes are routinely observed, so that a more general treatment of the scattering process is needed. In this paper, a full-wave model for the scattering of RF waves by a blob is developed. The full-wave approach extends the range of validity well beyond that of geometric optics; however, it is theoretically and computationally much more challenging. The theoretical procedure, although similar to that followed for the Mie solution of Maxwell's equations, is generalized to plasmas in a magnetic field. Besides diffraction and reflection, the model includes coupling to a different plasma wave than the one imposed by the external antenna structure. In the model, it is assumed that the RF waves interact with a spherical blob. The plasma inside and around the blob is cold, homogeneous, and imbedded in a uniform magnetic field. After formulating the complete analytical theory, the effect of the blob on short wavelength electron cyclotron waves and longer wavelength lower hybrid waves is studied numerically.

  10. Gravity-driven hybrid membrane for oleophobic-superhydrophilic oil-water separation and water purification by graphene.

    PubMed

    Yoon, Hyun; Na, Seung-Heon; Choi, Jae-Young; Latthe, Sanjay S; Swihart, Mark T; Al-Deyab, Salem S; Yoon, Sam S

    2014-10-01

    We prepared a simple, low-cost membrane suitable for gravity-driven oil-water separation and water purification. Composite membranes with selective wettability were fabricated from a mixture of aqueous poly(diallyldimethylammonium chloride) solution, sodium perfluorooctanoate, and silica nanoparticles. Simply dip-coating a stainless steel mesh using this mixture produced the oil-water separator. The contact angles (CAs) of hexadecane and water on the prepared composite membranes were 95 ± 2° and 0°, respectively, showing the oleophobicity and superhydrophilicity of the membrane. In addition, a graphene plug was stacked below the membrane to remove water-soluble organics by adsorption. As a result, this multifunctional device not only separates hexadecane from water, but also purifies water by the permeation of the separated water through the graphene plug. Here, methylene blue (MB) was removed as a demonstration. Membranes were characterized by high-resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy to elucidate the origin of their selective wettability. PMID:25192514

  11. Effect of operation parameters on the flux stabilization of gravity-driven membrane (GDM) filtration system for decentralized water supply.

    PubMed

    Tang, Xiaobin; Ding, An; Qu, Fangshu; Jia, Ruibao; Chang, Haiqing; Cheng, Xiaoxiang; Liu, Bin; Li, Guibai; Liang, Heng

    2016-08-01

    A pilot-scale gravity-driven membrane (GDM) filtration system under low gravitational pressure without any pre-treatment, backwash, flushing, or chemical cleaning was carried out to investigate the effect of operation parameters (including operation pressure, aeration mode, and intermittent filtration) on the effluent quality and permeability development. The results revealed that GDM system exhibited an efficient performance for the removal of suspended substances and organic compounds. The stabilization of flux occurred and the average values of stable flux were 6.6, 8.1, and 8.6 Lm(-2) h(-1) for pressures of 65, 120, and 200 mbar, respectively. In contrast, flux stabilization was not observed under continuous and intermittent aeration conditions. However, aeration (especially continuous aeration) was effective to improve flux and alleviate membrane fouling during 1-month operation. Moreover, intermittent filtration would influence the stabilization of permeate flux, resulting in a higher stable flux (ranging from 6 to 13 Lm(-2) h(-1)). The stable flux significantly improved with the increase of intermittent period. Additionally, GDM systems exhibited an efficient recovery of flux after simple physical cleaning and the analyses of resistance reversibility demonstrated that most of the total resistance was hydraulic reversible resistance (50-75 %). Therefore, it is expected that the results of this study can develop strategies to increase membrane permeability and reduce energy consumption in GDM systems for decentralized water supply. PMID:27189452

  12. Dynamics of an Isolated Blob in the Presence of the X-Point

    SciTech Connect

    Cohen, R H; Ryutov, D D

    2005-10-10

    The interplay of X-point shearing and axial plasma redistribution along a moving flux tube is discussed. Blobs limited to the main scrape-off-layer and the blobs entirely confined in the divertor region are identified. A strong effect of the radial tilt of the divertor plate on ''divertor'' blobs is found.

  13. 3D seismic analysis of gravity-driven and basement influenced normal fault growth in the deepwater Otway Basin, Australia

    NASA Astrophysics Data System (ADS)

    Robson, A. G.; King, R. C.; Holford, S. P.

    2016-08-01

    We use three-dimensional (3D) seismic reflection data to analyse the structural style and growth of a normal fault array located at the present-day shelf-edge break and into the deepwater province of the Otway Basin, southern Australia. The Otway Basin is a Late Jurassic to Cenozoic, rift-to-passive margin basin. The seismic reflection data images a NW-SE (128-308) striking, normal fault array, located within Upper Cretaceous clastic sediments and which consists of ten fault segments. The fault array contains two hard-linked fault assemblages, separated by only 2 km in the dip direction. The gravity-driven, down-dip fault assemblage is entirely contained within the 3D seismic survey, is located over a basement plateau and displays growth commencing and terminating during the Campanian-Maastrichtian, with up to 1.45 km of accumulated throw (vertical displacement). The up-dip normal fault assemblage penetrates deeper than the base of the seismic survey, but is interpreted to be partially linked along strike at depth to major basement-involved normal faults that can be observed on regional 2D seismic lines. This fault assemblage displays growth initiating in the Turonian-Santonian and has accumulated up to 1.74 km of throw. Our detailed analysis of the 3D seismic data constraints post-Cenomanian fault growth of both fault assemblages into four evolutionary stages: [1] Turonian-Santonian basement reactivation during crustal extension between Australia and Antarctica. This either caused the upward propagation of basement-involved normal faults or the nucleation of a vertically isolated normal fault array in shallow cover sediments directly above the reactivated basement-involved faults; [2] continued Campanian-Maastrichtian crustal extension and sediment loading eventually created gravitational instability on the basement plateau, nucleating a second, vertically isolated normal fault array in the cover sediments; [3] eventual hard-linkage of fault segments in both fault

  14. Highly efficient and flexible electrospun carbon-silica nanofibrous membrane for ultrafast gravity-driven oil-water separation.

    PubMed

    Tai, Ming Hang; Gao, Peng; Tan, Benny Yong Liang; Sun, Darren D; Leckie, James O

    2014-06-25

    A novel free-standing and flexible electrospun carbon-silica composite nanofibrous membrane is newly introduced. The characterization results suggest that the electrospun composite nanofibers are constructed by carbon chains interpenetrated through a linear network of 3-dimensional SiO2. Thermogravimetric analysis indicates that the presence of insulating silica further improve the thermal resistance of the membrane. Additionally, the mechanical strength test shows that the membrane's toughness and flexibility can be enhanced if the concentration of SiO2 is maintained below 2.7 wt %. Thermal and chemical stability test show that the membrane's wettability properties can be sustained at an elevated temperature up to 300 °C and no discernible change in wettability was observed under highly acidic and basic conditions. After surface-coating with silicone oil for 30 mins, the composite membrane exhibits ultra-hydrophobic and superoleophilic properties with water and oil contact angles being 144.2 ± 1.2° and 0°, respectively. The enhanced flexibility and selective wetting property enables the membrane to serve as an effective substrate for separating free oil from water. Lab-scale oil-water separation test indicates that the membrane possesses excellent oil-water separation efficiency. In addition, its inherent property of high porosity allows oil-water separation to be performed in a gravity-driven process with high-flux. We anticipate that this study will open up a new avenue for fabrication of free-standing carbonaceous composite membrane with tunable flexibility for energy efficient and high-throughput production of clean water. PMID:24867399

  15. Activity of metazoa governs biofilm structure formation and enhances permeate flux during Gravity-Driven Membrane (GDM) filtration.

    PubMed

    Derlon, Nicolas; Koch, Nicolas; Eugster, Bettina; Posch, Thomas; Pernthaler, Jakob; Pronk, Wouter; Morgenroth, Eberhard

    2013-04-15

    The impact of different feed waters in terms of eukaryotic populations and organic carbon content on the biofilm structure formation and permeate flux during Gravity-Driven Membrane (GDM) filtration was investigated in this study. GDM filtration was performed at ultra-low pressure (65 mbar) in dead-end mode without control of the biofilm formation. Different feed waters were tested (River water, pre-treated river water, lake water, and tap water) and varied with regard to their organic substrate content and their predator community. River water was manipulated either by chemically inhibiting all eukaryotes or by filtering out macrozoobenthos (metazoan organisms). The structure of the biofilm was characterized at the meso- and micro-scale using Optical Coherence Tomography (OCT) and Confocal Laser Scanning Microscopy (CLSM), respectively. Based on Total Organic Carbon (TOC) measurements, the river waters provided the highest potential for bacterial growth whereas tap water had the lowest. An increasing content in soluble and particulate organic substrate resulted in increasing biofilm accumulation on membrane surface. However, enhanced biofilm accumulation did not result in lower flux values and permeate flux was mainly influenced by the structure of the biofilm. Metazoan organisms (in particular nematodes and oligochaetes) built-up protective habitats, which resulted in the formation of open and spatially heterogeneous biofilms composed of biomass patches. In the absence of predation by metazoan organisms, a flat and compact biofilm developed. It is concluded that the activity of metazoan organisms in natural river water and its impact on biofilm structure balances the detrimental effect of a high biofilm accumulation, thus allowing for a broader application of GDM filtration. Finally, our results suggest that for surface waters with high particulate organic carbon (POC) content, the use of worms is suitable to enhance POC removal before ultrafiltration units. PMID

  16. Gravity-driven fingering simulations for a thin liquid film flowing down the outside of a vertical cylinder.

    PubMed

    Mayo, Lisa C; McCue, Scott W; Moroney, Timothy J

    2013-05-01

    A numerical study is presented to examine the fingering instability of a gravity-driven thin liquid film flowing down the outer wall of a vertical cylinder. The lubrication approximation is employed to derive an evolution equation for the height of the film, which is dependent on a single parameter, the dimensionless cylinder radius. This equation is identified as a special case of that which describes thin film flow down an inclined plane. Fully three-dimensional simulations of the film depict a fingering pattern at the advancing contact line. We find the number of fingers observed in our simulations to be in excellent agreement with experimental observations and a linear stability analysis reported recently by Smolka and SeGall [Phys. Fluids 23, 092103 (2011)]. As the radius of the cylinder decreases, the modes of perturbation have an increased growth rate, thus increasing cylinder curvature partially acts to encourage the contact line instability. In direct competition with this behavior, a decrease in cylinder radius means that fewer fingers are able to form around the circumference of the cylinder. Indeed, for a sufficiently small radius, a transition is observed, at which point the contact line is stable to transverse perturbations of all wave numbers. In this regime, free surface instabilities lead to the development of wave patterns in the axial direction, and the flow features become perfectly analogous to the two-dimensional flow of a thin film down an inverted plane as studied by Lin and Kondic [Phys. Fluids 22, 052105 (2010)]. Finally, we simulate the flow of a single drop down the outside of the cylinder. Our results show that for drops with low volume, the cylinder curvature has the effect of increasing drop speed and hence promoting the phenomenon of pearling. In contrast, drops with much larger volume evolve to form single long rivulets with a similar shape to a finger formed in the aforementioned simulations. PMID:23767631

  17. Statistical study of the GNSS phase scintillation associated with two types of auroral blobs

    NASA Astrophysics Data System (ADS)

    Jin, Yaqi; Moen, Jøran I.; Miloch, Wojciech J.; Clausen, Lasse B. N.; Oksavik, Kjellmar

    2016-05-01

    This study surveys space weather effects on GNSS (Global Navigation Satellite System) signals in the nighttime auroral and polar cap ionosphere using scintillation receivers, all-sky imagers, and the European Incoherent Scatter Svalbard radar. We differentiate between two types of auroral blobs: blob type 1 (BT 1) which is formed when islands of high-density F region plasma (polar cap patches) enter the nightside auroral oval, and blob type 2 (BT 2) which are generated locally in the auroral oval by intense particle precipitation. For BT 1 blobs we have studied 41.4 h of data between November 2010 and February 2014. We find that BT 1 blobs have significantly higher scintillation levels than their corresponding polar cap patch; however, there is no clear relationship between the scintillation levels of the preexisting polar cap patch and the resulting BT 1 blob. For BT 2 blobs we find that they are associated with much weaker scintillations than BT 1 blobs, based on 20 h of data. Compared to patches and BT 2 blobs, the significantly higher scintillation level for BT 1 blobs implies that auroral dynamics plays an important role in structuring of BT 1 blobs.

  18. 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.

  19. He I absorption by Lyman-alpha clouds and low-redshift Lyman-alpha clouds

    NASA Technical Reports Server (NTRS)

    Miralda-Escude, Jordi; Ostriker, Jeremiah P.

    1992-01-01

    Sources and sinks of radiation are used to model the evolution of the metagalactic ionizing background radiation field. It is shown that, if the comoving number density of quasars approached constancy at high redshift, as suggested by some recent observations, the observed ionizing background might possibly have been produced by the observed quasars alone. Consideration is also given to the UV radiation from decaying neutrons proposed by Sciama (1990), as an extra possible source. If is found that, if the background spectrum were as soft as in the Sciama scenario, the observed Ly-alpha clouds would contain detectable amounts of neutral helium, producing an 'He I forest' almost as dense as the hydrogen forest, due to the 584-A transition 1s-squared-1s2p. It is argued that observations of the Ly-alpha forest contradict the Sciama hypothesis.

  20. Revisiting blob theory for DNA diffusivity in slitlike confinement

    PubMed Central

    Dai, Liang; Tree, Douglas R.; van der Maarel, Johan R. C.; Dorfman, Kevin D.; Doyle, Patrick S.

    2013-01-01

    Blob theory has been widely applied to describe polymer conformations and dynamics in nanoconfinement. In slit confinement, blob theory predicts a scaling exponent of 2/3 for polymer diffusivity as a function of slit height, yet a large body of experimental studies using DNA produce a scaling exponent significantly less than 2/3. In this work, we develop a theory that predicts that this discrepancy occurs because the segment correlation function for a semiflexible chain such as DNA does not follow the Flory exponent for length scales smaller than the persistence length. We show that these short length scale effects contribute significantly to the scaling for the DNA diffusivity, but do not appreciably affect the scalings for static properties. Our theory is fully supported by Monte Carlo simulations, quantitative agreement with DNA experiments, and the results reconcile this outstanding problem for confined polymers. PMID:23679643

  1. Revisiting Blob Theory for DNA Diffusivity in Slitlike Confinement

    NASA Astrophysics Data System (ADS)

    Dai, Liang; Tree, Douglas R.; van der Maarel, Johan R. C.; Dorfman, Kevin D.; Doyle, Patrick S.

    2013-04-01

    Blob theory has been widely applied to describe polymer conformations and dynamics in nanoconfinement. In slit confinement, blob theory predicts a scaling exponent of 2/3 for polymer diffusivity as a function of slit height, yet a large body of experimental studies using DNA produce a scaling exponent significantly less than 2/3. In this work, we develop a theory that predicts that this discrepancy occurs because the segment correlation function for a semiflexible chain such as DNA does not follow the Flory exponent for length scales smaller than the persistence length. We show that these short length scale effects contribute significantly to the scaling for the DNA diffusivity, but do not appreciably affect the scalings for static properties. Our theory is fully supported by Monte Carlo simulations, quantitative agreement with DNA experiments, and the results reconcile this outstanding problem for confined polymers.

  2. 2D numerical modeling of gravity-driven giant-scale deformation processes in the offshore Barreirinhas Basin (Brazil)

    NASA Astrophysics Data System (ADS)

    Cruciani, Francesco; Manconi, Andrea; Rinaldo Barchi, Massimiliano

    2014-05-01

    Gravity-driven deformation processes at continental passive margins occur at different scales, from small-scale turbidity currents and sediment slides, to large-scale mass transport complexes (MTCs), to the giant-scale deep water fold and thrust belts (DW-FTBs), which affect most or the entire sedimentary sequence. This kind of giant structures, quite widespread in passive margins, may be active for tens of millions of years. In this context, the Brazilian Atlantic margin hosts several well-known DW-FTBs detached on both shale and salt décollement. Despite of their relevant scientific and economic importance, the mechanical processes driving the onset and evolution of these giant-scale structures are still poorly investigated. In this work, we focus on the shale décollement DW-FTB of the Barreirinhas Basin, where the continental slope has been affected by multi-phase gravitational processes since the Late Cretaceous. This DW-FTB consists of a linked fault system of listric normal faults updip and thrust faults downdip, detached over a common concave upward décollement surface. From the onshore extensional to the offshore compressional domain the DW-FTB is about 50 km wide and involve a sedimentary sequence up to 5 km thick. Shortening within the compressional domain is accommodated almost entirely from a single thrust ramp with a large related anticline fold. Previous studies have shown that the main activity phases of the gravitational processes are closely linked to significant increases in the sediment supply within the basin. Indeed, the highest deformation rate, accounting for about 80% of the net strain, occurred in the Upper Miocene following a drainage rearrangement which led to the birth of the modern Amazon River drainage system. The Barreirinhas Basin DW-FTB entails a rather simple geometrical structure, which can be well schematized, therefore is particularly suitable for numerical simulations aimed to study and understand the dynamics of DW-FTB at

  3. Slow viscous gravity-driven interaction between a bubble and a free surface with unequal surface tensions

    NASA Astrophysics Data System (ADS)

    Guémas, Marine; Sellier, Antoine; Pigeonneau, Franck

    2015-04-01

    The axisymmetric gravity-driven dynamics of a bubble rising toward a free surface is addressed for gas-liquid interfaces having unequal surface tensions. The liquid flow is governed by the Stokes equations which are here solved using a boundary element method in axisymmetric configuration. Within this framework, two dimensionless numbers arise: the Bond number Bo1 based on the surface tension of the bubble interface and the surface tension ratio γ ˆ comparing the free surface and bubble surface tensions. Under a careful and discussed selection of the code key settings (number of boundary elements, initial bubble location, and distance beyond which the free surface is truncated), it has been possible to numerically and accurately track in time the bubble and free surface shapes for several values of ( Bo 1 , γ ˆ ) . The long-time shapes are found to deeply depend upon both Bo1 and γ ˆ and also to compare well with the shapes predicted in Princen and Mason ["Shape of a fluid drop at a fluid-liquid interface. II. Theory for three-phase systems," J. Colloid. Sci. 20, 246-266 (1965)] using a hydrostatic model in which both surfaces are touching. Similarly, the drainage dynamics of the liquid film thickness between the bubble and the free surface depends on ( Bo 1 , γ ˆ ) . The long-time film thickness exponentially decays in time and a so-called thinning rate α for which the numerical behaviors and a simple model reveal two basic behaviors: (i) at small Bond number, α behaves as 1/Bo1 and (ii) at large Bond number, α is nearly constant. In addition, it is found that in the entire range of the quantity χ = ( 1 + γ ˆ ) Bo 1 / ( 2 γ ˆ ) , the thinning rate α is well approximated by the function 1/(18χ) + α∞ with α∞ ≈ 0.158. Such a result also permits one to estimate the typical drainage time versus the initial bubble radius a, the liquid density ρ and viscosity μ, the gravity and the free surface, and bubble surface tensions.

  4. Gravity-Driven Flow of non-Newtonian Fluids in Heterogeneous Porous Media: a Theoretical and Experimental Analysis

    NASA Astrophysics Data System (ADS)

    Di Federico, V.; Longo, S.; Ciriello, V.; Chiapponi, L.

    2015-12-01

    A theoretical and experimental analysis of non-Newtonian gravity-driven flow in porous media with spatially variable properties is presented. The motivation for our study is the rheological complexity exhibited by several environmental contaminants (wastewater sludge, oil pollutants, waste produced by the minerals and coal industries) and remediation agents (suspensions employed to enhance the efficiency of in-situ remediation). Natural porous media are inherently heterogeneous, and this heterogeneity influences the extent and shape of the porous domain invaded by the contaminant or remediation agent. To grasp the combined effect of rheology and spatial heterogeneity, we consider: a) the release of a thin current of non-Newtonian power-law fluid into a 2-D, semi-infinite and saturated porous medium above a horizontal bed; b) perfectly stratified media, with permeability and porosity varying along the direction transverse (vertical) or parallel (horizontal) to the flow direction. This continuous variation of spatial properties is described by two additional parameters. In order to represent several possible spreading scenarios, we consider: i) instantaneous injection with constant mass; ii) continuous injection with time-variable mass; iii) instantaneous release of a mound of fluid, which can drain freely out of the formation at the origin (dipole flow). Under these assumptions, scalings for current length and thickness are derived in self similar form. An analysis of the conditions on model parameters required to avoid an unphysical or asymptotically invalid result is presented. Theoretical results are validated against multiple sets of experiments, conducted for different combinations of spreading scenarios and types of stratification. Two basic setups are employed for the experiments: I) direct flow simulation in an artificial porous medium constructed superimposing layers of glass beads of different diameter; II) a Hele-Shaw (HS) analogue made of two parallel

  5. Gravity-driven membrane filtration as pretreatment for seawater reverse osmosis: linking biofouling layer morphology with flux stabilization.

    PubMed

    Akhondi, Ebrahim; Wu, Bing; Sun, Shuyang; Marxer, Brigit; Lim, Weikang; Gu, Jun; Liu, Linbo; Burkhardt, Michael; McDougald, Diane; Pronk, Wouter; Fane, Anthony G

    2015-03-01

    In this study gravity-driven membrane (GDM) ultrafiltration is investigated for the pretreatment of seawater before reverse osmosis (RO). The impacts of temperature (21 ± 1 and 29 ± 1 °C) and hydrostatic pressure (40 and 100 mbar) on dynamic flux development and biofouling layer structure were studied. The data suggested pore constriction fouling was predominant at the early stage of filtration, during which the hydrostatic pressure and temperature had negligible effects on permeate flux. With extended filtration time, cake layer fouling played a major role, during which higher hydrostatic pressure and temperature improved permeate flux. The permeate flux stabilized in a range of 3.6 L/m(2) h (21 ± 1 °C, 40 mbar) to 7.3 L/m(2) h (29 ± 1 °C, 100 mbar) after slight fluctuations and remained constant for the duration of the experiments (almost 3 months). An increase in biofouling layer thickness and a variable biofouling layer structure were observed over time by optical coherence tomography and confocal laser scanning microscopy. The presence of eukaryotic organisms in the biofouling layer was observed by light microscopy and the microbial community structure of the biofouling layer was analyzed by sequences of 16S rRNA genes. The magnitude of permeate flux was associated with the combined effect of the biofouling layer thickness and structure. Changes in the biofouling layer structure were attributed to (1) the movement and predation behaviour of the eukaryotic organisms which increased the heterogeneous nature of the biofouling layer; (2) the bacterial debris generated by eukaryotic predation activity which reduced porosity; (3) significant shifts of the dominant bacterial species over time that may have influenced the biofouling layer structure. As expected, most of the particles and colloids in the feed seawater were removed by the GDM process, which led to a lower RO fouling potential. However, the dissolved organic carbon in the

  6. Gravity-driven creeping flow of two adjacent layers through a channel and down a plane wall

    NASA Astrophysics Data System (ADS)

    Pozrikidis, C.

    1998-09-01

    We study the stability of the interface between (a) two adjacent viscous layers flowing due to gravity through an inclined or vertical channel that is confined between two parallel plane walls, and (b) two superimposed liquid films flowing down an inclined or vertical plane wall, in the limit of Stokes flow. In the case of channel flow, linear stability analysis predicts that, when the fluids are stably stratified, the flow is neutrally stable when the surface tension vanishes and the channel is vertical, and stable otherwise. This behaviour contrasts with that of the gravity-driven flow of two superimposed films flowing down an inclined plane, where an instability has been identified when the viscosity of the fluid next to the plane is less than that of the top fluid, even in the absence of fluid inertia. We investigate the nonlinear stages of the motion subject to finite-amplitude two-dimensional perturbations by numerical simulations based on boundary-integral methods. In both cases of channel and film flow, the mathematical formulation results in integral equations for the unknown interface and free-surface velocity. The properties of the integral equation for multi-film flow are investigated with reference to the feasibility of computing a solution by the method of successive substitutions, and a deflation strategy that allows an iterative procedure is developed. In the case of channel flow, the numerical simulations show that disturbances of sufficiently large amplitude may cause permanent deformation in which the interface folds or develops elongated fingers. The ratio of the viscosities and densities of the two fluids plays an important role in determining the morphology of the emerging interfacial patterns. Comparing the numerical results with the predictions of a model based on the lubrication approximation shows that the simplified approach can only describe a limited range of motions. In the case of film flow down an inclined plane, we develop a method

  7. The Transition from Stable Creep to Stick-slip Instability in Gravity-driven Landslide Motion (Invited)

    NASA Astrophysics Data System (ADS)

    Iverson, R. M.; Schaeffer, D. G.

    2009-12-01

    Landslides provide accessible sites for studying diverse styles of displacement that may serve as analogs for fault slip in Earth's crust. Field observations and large-scale experiments demonstrate that landslides can exhibit slow, stable creep, episodic stick-slip, or runaway acceleration - similar to the diverse styles of motion inferred for faults and subduction zones. A mechanical model that explains all of these styles of landsliding considers gravity-driven motion of a water-saturated, poroelastic slide block regulated by pore-pressure change in a dilating or contracting basal shear zone that exchanges water with the block. If the shear zone exhibits rate-independent Coulomb friction, the stability of slide-block motion depends only on the sign of the Coulomb dilatancy angle, ψ (ψ > 0 implies dilation and stable creep; ψ < 0 implies contraction and runaway acceleration) and on evolution of ψ with displacement. If the shear zone exhibits nonlinearly rate-weakening friction together with ψ > 0, however, the model predicts that a transition (i.e., a Hopf bifurcation) occurs from stable, creeping motion to periodic stick-slip. The bifurcation is sharply demarcated by a line that transects a parameter space defined by the logarithms of two dimensionless parameters, one proportional to the ratio of the intrinsic timescales for downslope motion and pore-pressure diffusion in the slide block, and one proportional to the ratio of the intrinsic velocity scales for pore-fluid flow and rate-weakening of friction in the basal shear zone. In the unstable (upper) part of this parameter space, the amplitude and period of stick-slip oscillations increase with distance from the bifurcation line. Significantly, stick-slip behavior predicted by the model occurs in the absence of an elastic driving force; the elastic spring in classic spring-slider earthquake models is effectively replaced by pore-pressure diffusion, and the energy necessary to drive this dissipative but

  8. Cylindrical bubbles and blobs from a Class II Hydrophobin

    NASA Astrophysics Data System (ADS)

    Russo, Paul; Pham, Michael; Blalock, Brad

    2012-02-01

    Cerato ulmin is a class II hydrophobin. In aqueous suspensions, it easily forms cylindrical air bubbles and cylindrical oil blobs. The conditions for formation of these unusual structures will be discussed, along with scattering and microscopic investigations of their remarkable stability. Possible applications in diverse fields including polymer synthesis and oil spill remediation will be considered. Acknowledgment is made to Dr. Wayne C. Richards of the Canadian Forest Service for the gift of Cerato ulmin.

  9. Examining the Release Mechanism of Intermittent Streamer Blobs

    NASA Astrophysics Data System (ADS)

    Ozturk, D. S.; van der Holst, B.; Sokolov, I.; Gombosi, T. I.

    2015-12-01

    The white light images from the Large-Angle and Spectrometric Coronagraph (LASCO) C2 and C3 have shown small-scale periodic plasmoid releases from the tip of the Helmet Streamers. The density and velocity of these blobs show similarities with the slow solar wind. There are various scenarios proposed to comprehend the release mechanism for these plasmoids. Most widely accepted explanations include interchange reconnection and significant proton coronal heating at the streamer tip. A three-dimensional global coronal model will be used to examine this intermittent blob release over a several day period. We use the new real time version of Alfven Wave Solar Model (AWSoM-R) to decrease the computational costs. In AWSoM-R, the global magnetohydrodynamic (MHD) equations for the lower corona are solved along one-dimensional magnetic field line threads. The Alfven wave dissipation is partitioned into coronal heating of protons and electrons. We study how this heat partitioning affects plasmoid formation. We investigate the size and periodicity of the streamer blobs for Carrington Rotation 2109 (12 April 2011-09 May 2011) by constructing synthetic white light images from the time-dependent model and comparing our results with observations.

  10. BLOBS IN SPACE: THE LEGACY OF A NOVA

    NASA Technical Reports Server (NTRS)

    2002-01-01

    TThe prolific number of eruptions by the recurrent nova T Pyxidis has attracted the attention of many telescopes. The image on the left, taken by a ground-based telescope, shows shells of gas around the star that were blown off during several eruptions. Closer inspection by the Hubble Space Telescope (right-hand image), however, reveals that the shells are not smooth at all. In fact, this high-resolution image shows that the shells are actually more than 2,000 gaseous blobs packed into an area that is 1 light-year across. Resembling shrapnel from a shotgun blast, the blobs may have been produced by the nova explosion, the subsequent expansion of gaseous debris, or collisions between fast-moving and slow- moving gas from several eruptions. False color has been applied to this image to enhance details in the blobs. The ground-based image was taken Jan. 19, 1995 by the European Southern Observatory's New Technology Telescope in La Silla, Chile. The Hubble telescope picture is a compilation of data taken on Feb. 26, 1994, and June 16, Oct. 7, and Nov. 10, 1995, by the Wide Field and Planetary Camera 2. T Pyxidis is 6,000 light-years away in the dim southern constellation Pyxis, the Mariner's Compass. Credits: Mike Shara, Bob Williams, and David Zurek (Space Telescope Science Institute); Roberto Gilmozzi (European Southern Observatory); Dina Prialnik (Tel Aviv University); and NASA.

  11. On the propagation of blobs in the magnetotail: MHD simulations

    NASA Astrophysics Data System (ADS)

    Birn, J.; Nakamura, R.; Hesse, M.

    2013-09-01

    Using three-dimensional magnetohydrodynamic (MHD) simulations of the magnetotail, we investigate the fate of entropy-enhanced localized magnetic flux tubes ("blobs"). Such flux tubes may be the result of a slippage process that also generates entropy-depleted flux tubes ("bubbles") or of a rapid localized energy increase, for instance, from wave absorption. We confirm the expectation that the entropy enhancement leads to a tailward motion and that the speed and distance traveled into the tail increase with the entropy enhancement, even though the blobs tend to break up into pieces. The vorticity on the outside of the blobs twists the magnetic field and generates field-aligned currents predominantly of region-2 sense (earthward on the dusk side and tailward on the dawn side), which might provide a possibility for remote identification from the ground. The breakup, however, leads to more turbulent flow patterns, associated with opposite vorticity and the generation of region-1 sense field-aligned currents of lower intensity but approximately equal integrated magnitude.

  12. Assessment of RELAP5/MOD3.1 for gravity-driven injection experiment in the core makeup tank of the CARR Passive Reactor (CP-1300)

    SciTech Connect

    Lee, S.I.; No, H.C.; Bang, Y.S.; Kim, H.J.

    1996-10-01

    The objective of the present work is to improve the analysis capability of RELAP5/MOD3.1 on the direct contact condensation in the core makeup tank (CMT) of passive high-pressure injection system (PHPIS) in the CARR Passive Reactor (CP-1300). The gravity-driven injection experiment is conducted by using a small scale test facility to identify the parameters having significant effects on the gravity-driven injection and the major condensation modes. It turns out that the larger the water subcooling is, the more initiation of injection is delayed, and the sparger and the natural circulation of the hot water from the steam generator accelerate the gravity-driven injection. The condensation modes are divided into three modes: sonic jet, subsonic jet, and steam cavity. RELAP5/MOD3.1 is chosen to evaluate the cod predictability on the direct contact condensation in the CMT. It is found that the predictions of MOD3.1 are in better agreement with the experimental data than those of MOD3.0. From the nodalization study of the test section, the 1-node model shows better agreement with the experimental data than the multi-node models. RELAP5/MOD3.1 identifies the flow regime of the test section as vertical stratification. However, the flow regime observed in the experiment is the subsonic jet with the bubble having the vertical cone shape. To accurately predict the direct contact condensation in the CMT with RELAP5/MOD3.1, it is essential that a new set of the interfacial heat transfer coefficients and a new flow regime map for direct contact condensation in the CMT be developed.

  13. Controls of sedimentary supply and gravity driven deformation on the eastern Niger delta (Plio-Pleistocene) from the shoreline to the deep sea plain

    NASA Astrophysics Data System (ADS)

    Robin, Cécile; Guillocheau, François; Rouby, Delphine; Nalpas, Thierry; Jermannaud, Paul; Raillard, Stéphane

    2013-04-01

    We studied the evolution of the gravity flow sedimentary within a large shelf-edge delta (Eastern Niger delta) over the last 2,5Myr taking into account the influence of the contemporaneous gravity driven deformation and sedimentary supply. To do this, we mapped (i) the shoreline geometry and (ii) the associated turbiditic systems for 9 intervals using a classification based on three morphological end-members: erosive, constructive and depositional modes. We characterized the depositional profile of the passive margin delta from the littoral domain to the abyssal plain and its spatial and temporal variability. We showed that, at the scale of the delta, the depositional profile varied from (i) a shelf edge delta profile with a slope break at the location of the shoreline during progradation to (ii) a ramp profile characteristic of a mid-shelf delta during retrogradation. Thus, during a stratigraphic cycle, the delta front evolved from a prograding slope break during the development of the HST, to steepening clinoforms during the development of the LST that progressively flattened out during the TST to reach a ramp profile at the MFS. The turbiditic systems (including MTC) initiate near the shoreline, at the toe of the delta front. Also, they form preferentially down slope synthetic faults or within antithetic fault relays. They are initially erosive, becoming constructive further down slope and eventually depositional. They may become erosive again as they cut through the compressional structures. We showed that the stratigraphic state (progradation/retrogradation) controls the amount of sediment reaching the platform and strongly impacts the density of gravity flow sedimentary systems (low density during progradation and high density during progradation). On the other hand, the gravity driven deformation controls the slope of the sea-floor and, in doing so, their morphology (erosive/constructive/depositional). Within this framework, lateral migrations of the delta

  14. Justification of the Nonlinear Schrödinger Equation for the Evolution of Gravity Driven 2D Surface Water Waves in a Canal of Finite Depth

    NASA Astrophysics Data System (ADS)

    Düll, Wolf-Patrick; Schneider, Guido; Wayne, C. Eugene

    2016-05-01

    In 1968 V.E. Zakharov derived the Nonlinear Schrödinger equation for the two-dimensional water wave problem in the absence of surface tension, that is, for the evolution of gravity driven surface water waves, in order to describe slow temporal and spatial modulations of a spatially and temporarily oscillating wave packet. In this paper we give a rigorous proof that the wave packets in the two-dimensional water wave problem in a canal of finite depth can be approximated over a physically relevant timespan by solutions of the Nonlinear Schrödinger equation.

  15. Multiple scattering of radio frequency waves by blobs: homogenization of a mixture of blobs and the Waterman-Truell approach

    NASA Astrophysics Data System (ADS)

    Hizanidis, K.; Bairaktaris, F.; Valvis, S. I.; Ram, A. K.

    2015-11-01

    Radio frequency waves are of particular importance for heating and current drive in magnetized fusion plasmas. The scattering of these waves by a multitude of density fluctuations, such as blobs in the edge region, is studied by homogenizing the edge region populated by an ensemble of ellipsoidal plasma blobs immersed in an ambient background plasma. The effective permittivity tensor is formulated on the basis of a depolarization dyadic. In general, the interface between the homogenized slab and the ambient plasma is not necessarily aligned with the magnetic field line. The misalignment leads to changes in the propagation characteristics of the RF waves. The scattering of an incident wave is treated by considering the reflection and transmission through a composite plasma slab. This study is a generalization of; it applies to RF waves in plasmas interacting with ellipsoidal blobs of arbitrary shapes and sizes. Supported in part by the Hellenic National Programme on Controlled Thermonuclear Fusion associated with the EUROfusion Consortium, and by DoE.

  16. Fermi Blobs and the Symplectic Camel: A Geometric Picture of Quantum States

    NASA Astrophysics Data System (ADS)

    Gossona, Maurice A. De

    We have explained in previous work the correspondence between the standard squeezed coherent states of quantum mechanics, and quantum blobs, which are the smallest phase space units compatible with the uncertainty principle of quantum mechanics and having the symplectic group as a group of symmetries. In this work, we discuss the relation between quantum blobs and a certain level set (which we call "Fermi blob") introduced by Enrico Fermi in 1930. Fermi blobs allows us to extend our previous results not only to the excited states of the generalized harmonic oscillator in n dimensions, but also to arbitrary quadratic Hamiltonians. As is the case for quantum blobs, we can evaluate Fermi blobs using a topological notion, related to the uncertainty principle, the symplectic capacity of a phase space set. The definition of this notion is made possible by Gromov's symplectic non-squeezing theorem, nicknamed the "principle of the symplectic camel".

  17. Coeval gravity-driven and thick-skinned extensional tectonics in the mid-Cretaceous of the western Pyrenees

    NASA Astrophysics Data System (ADS)

    Bodego, Arantxa; Agirrezabala, Luis M.

    2010-05-01

    , which define a horst and graben system. Rollovers (unfaulted and faulted), hangingwall synclines and central domes are present in the hangingwalls of both listric and planar faults. Also, a fault-propagation fold, a forced fold and a roller have been interpreted. Synkinematic depositional systems and sediment-filled fissures are parallel to the NW- to N-trending tectonic structures. Based on the trend of tectonic structures, the orientation of sediment-filled fissures and the paleocurrent pattern of growth strata, a thin-skinned NE-SW to E-W extension has been deduced for the interior of the Lasarte sub-basin. Both the coincidence between the directions of extension and dip of the detachment layer and the characteristics of the deformation suggest a thin-skinned gravity-driven extensional tectonics caused by the dip of the detachment layer. Recorded extensional deformation event in the Lasarte sub-basin is contemporaneous with and would have been triggered by the extreme crustal thinning and mantle exhumation processes documented recently in both the Basque-Cantabrian Basin and the Pyrenees.

  18. The structure and poloidal dynamics of blob filaments in TJ-K

    NASA Astrophysics Data System (ADS)

    Garland, S.; Fuchert, G.; Ramisch, M.; Hirth, T.

    2016-04-01

    Relatively dense, field-aligned, filament-like structures (blobs) have been observed to propagate radially and poloidally through the scrape-off layer (SOL) in magnetically confined fusion plasmas, and contribute significantly to SOL transport. A detailed understanding of blob structure and dynamics, and their dependence on magnetic field geometry, is important in magnetic confinement physics for the prediction of heat loads on reactor wall facing components, as well as for understanding plasma confinement and neutral particle recycling. Experimentally deduced centre of mass poloidal blob velocity components, obtained using the conditional averaging technique, have been compared to an analytical blob model which has been simplified to express blob velocity in terms of the magnetic field curvature vector. Background flows are not incorporated into the analytical model, and must be added in to obtain good agreement with the experimental data. In addition, the 3D structure of blobs in TJ-K has been investigated using the conditional average of density fluctuations in two toroidally separated poloidal planes. Blobs are observed to be aligned to a flux tube near to the last closed flux surface, in the blob birth region. However at positions further along the blob trajectory, the structures do not deform according to the magnetic shear, rather they remain rigid, and retain their original form.

  19. Dynamics of coronal rain and descending plasma blobs in solar prominences. I. Fully ionized case

    SciTech Connect

    Oliver, R.; Soler, R.; Terradas, J.; Zaqarashvili, T. V.; Khodachenko, M. L.

    2014-03-20

    Observations of active regions and limb prominences often show cold, dense blobs descending with an acceleration smaller than that of free fall. The dynamics of these condensations falling in the solar corona is investigated in this paper using a simple fully ionized plasma model. We find that the presence of a heavy condensation gives rise to a dynamical rearrangement of the coronal pressure that results in the formation of a large pressure gradient that opposes gravity. Eventually this pressure gradient becomes so large that the blob acceleration vanishes or even points upward. Then, the blob descent is characterized by an initial acceleration phase followed by an essentially constant velocity phase. These two stages can be identified in published time-distance diagrams of coronal rain events. Both the duration of the first stage and the velocity attained by the blob increase for larger values of the ratio of blob to coronal density, for larger blob mass, and for smaller coronal temperature. Dense blobs are characterized by a detectable density growth (up to 60% in our calculations) and by a steepening of the density in their lower part, that could lead to the formation of a shock. They also emit sound waves that could be detected as small intensity changes with periods of the order of 100 s and lasting between a few and about 10 periods. Finally, the curvature of falling paths with large radii is only relevant when a very dense blob falls along inclined magnetic field lines.

  20. Experimental Pore-scale Study on the Dynamic Response of Blobs in Porous Media to Pressure Gradients

    NASA Astrophysics Data System (ADS)

    Hsu, S.; Hilpert, M.

    2012-12-01

    The dynamic response of blobs, which are trapped in porous media due to capillary forces, to applied pressure gradients is of interest to petroleum reservoir detection, enhanced oil recovery, and groundwater remediation. By performing planar laser-induced fluorescence experiments, we visualized the dynamics of blobs subject to steady and oscillatory pressure gradients in porous media. By analyzing blob images, we measured the 2D/3D contact angles and mean curvatures of the liquid-liquid interfaces and furthermore quantified the effects of contact angle hysteresis on blob mobilization. Once a blob was mobilized, the subsequent movement and interface behavior, such as contact line pinning, contact line slipping, and snap off, depended very much on the magnitude of the applied pressure gradient. We also revealed the flow patterns inside moving blobs by performing particle image velocimetry experiments. For an oscillatory pressure gradient, we showed that a trapped blob can exhibit resonance which can be exploited to enhance blob mobilization by seismic waves.

  1. Three-dimensional simulations of blob dynamics in a simple magnetized torus

    NASA Astrophysics Data System (ADS)

    Halpern, Federico D.; Cardellini, Annalisa; Ricci, Paolo; Jolliet, Sébastien; Loizu, Joaquim; Mosetto, Annamaria

    2014-02-01

    The propagation of blobs, structures of localized enhanced plasma pressure, is studied in global three-dimensional simulations of a simple magnetized torus. In particular, we carry out single-seeded blob simulations to explore the dependence of the blob velocity with respect to its size. It is found that the velocity scaling for two-dimensional blobs is satisfied in the parameter space where polarization currents are the dominant damping mechanism. On the other hand, three-dimensional blobs propagate faster than their two-dimensional counterparts in the parallel current damping regime. A detailed analysis of the charge and current balance reveals that, in fact, the difference in speed is due to an overestimation of the strength of the sheath current term in the two-dimensional model compared to the self-consistent three-dimensional model.

  2. Three-dimensional simulations of blob dynamics in a simple magnetized torus

    SciTech Connect

    Halpern, Federico D. Cardellini, Annalisa; Ricci, Paolo; Jolliet, Sébastien; Loizu, Joaquim; Mosetto, Annamaria

    2014-02-15

    The propagation of blobs, structures of localized enhanced plasma pressure, is studied in global three-dimensional simulations of a simple magnetized torus. In particular, we carry out single-seeded blob simulations to explore the dependence of the blob velocity with respect to its size. It is found that the velocity scaling for two-dimensional blobs is satisfied in the parameter space where polarization currents are the dominant damping mechanism. On the other hand, three-dimensional blobs propagate faster than their two-dimensional counterparts in the parallel current damping regime. A detailed analysis of the charge and current balance reveals that, in fact, the difference in speed is due to an overestimation of the strength of the sheath current term in the two-dimensional model compared to the self-consistent three-dimensional model.

  3. Submarine allochthonous salt sheets: Gravity-driven deformation of North African Cretaceous passive margin in Tunisia - Bled Dogra case study and nearby salt structures

    NASA Astrophysics Data System (ADS)

    Masrouhi, Amara; Bellier, Olivier; Ben Youssef, Mohamed; Koyi, Hemin

    2014-09-01

    We used structural, stratigraphic and sedimentologic data, together with a comparison of nearby structures and a Bouguer gravity map, to evaluate the evolution of the Bled Dogra salt structure (northern Tunisia) during the Cretaceous. Triassic salt sheets are recognized in the northwestern region of the Tunisian Atlas. These salt sheets are the result of Cretaceous thick and/or thin-skinned extension along the south Tethyan margin. The Bled Dogra salt structure is one of these submarine allochthonous salt sheets, which was emplaced during the Early Cretaceous. The geologic framework, during this period, produces conditions for a predominantly gravity-driven deformation: extension has produced space for the salt to rise; vigorous differential sedimentation created differential loading that resulted in the emplacement and extrusion of a large volume of Triassic salt and formation of large submarine salt sheets. Geologic field data suggest an interlayered Triassic salt sheet within Albian sequences. Salt was extruded at the sea floor during the Early-Middle Albian and was initially buried by Middle-Late Albian strata. The Coniacian corresponds to a second transgressive cover onto the salt sheet after the gliding of the first salt cover (Late Albian-Turonian). In addition, this northwest Tunisian area exposes evidences for salt flow and abundant slump features at the base of a northward facing submarine slope, which was probably dominant from the Early Cretaceous to Santonian. Two gravity deformation processes are recognized: gravity gliding and gravity spreading. Acting concurrently, these two processes appear indistinguishable in this geologic context. Like the present-day salt-involved passive margins - such as the northern Gulf of Mexico, the Atlantic margin of Morocco, the Brazilian Santos basin, the Angola margin, Cadiz in western Iberia, and the Red Sea - the North African Cretaceous passive margin in Tunisia provides evidences that deformation in a passive

  4. Blob dynamics in the TORPEX experiment: a multi-code validation

    NASA Astrophysics Data System (ADS)

    Riva, F.; Colin, C.; Denis, J.; Easy, L.; Furno, I.; Madsen, J.; Militello, F.; Naulin, V.; Nielsen, A. H.; Olsen, J. M. B.; Omotani, J. T.; Rasmussen, J. J.; Ricci, P.; Serre, E.; Tamain, P.; Theiler, C.

    2016-04-01

    Three-dimensional and two-dimensional seeded blob simulations are performed with five different fluid models, all based on the drift-reduced Braginskii equations, and the numerical results are compared among themselves and validated against experimental measurements provided by the TORPEX device (Fasoli et al 2006 Phys. Plasmas 13 055902). The five models are implemented in four simulation codes, typically used to simulate the plasma dynamics in the tokamak scrape-off layer, namely BOUT++ (Dudson et al 2009 Comput. Phys. Commun. 180 1467), GBS (Ricci et al 2012 Plasma Phys. Control. Fusion 54 124047), HESEL (Nielsen et al 2015 Phys. Lett. A 379 3097), and TOKAM3X (Tamain et al 2014 Contrib. Plasma Phys. 54 555). Three blobs with different velocities and different stability properties are simulated. The differences observed among the simulation results and the different levels of agreement with experimental measurements are investigated, increasing our confidence in our simulation tools and shedding light on the blob dynamics. The comparisons demonstrate that the radial blob dynamics observed in the three-dimensional simulations is in good agreement with experimental measurements and that, in the present experimental scenario, the two-dimensional model derived under the assumption of {{k}\\parallel}=0 is able to recover the blob dynamics observed in the three-dimensional simulations. Moreover, it is found that an accurate measurement of the blob temperature is important to perform reliable seeded blob simulations.

  5. 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.

  6. Rockglacier furrow-and-ridge morphology explained by gravity-driven buckle folding: A case study of the Murtèl rockglacier (Switzerland)

    NASA Astrophysics Data System (ADS)

    Frehner, Marcel; Gärtner-Roer, Isabelle; Ling, Anna H. M.

    2014-05-01

    Rockglaciers often feature a prominent transverse furrow-and-ridge morphology. Previous studies have suggested that these structures develop due to a longitudinal compressive flow in the lower part of a rockglacier. However, these hypotheses are mostly based on descriptive observations and not on mechanical considerations and therefore remained speculative. We propose that gravity-driven buckle folding is the dominating process leading to furrow-and-ridge morphology on rockglaciers. Buckle folding is the mechanical response to compression of a layered viscous material with significant mechanical contrast between the layers. The resulting buckle folds are common structures in rocks, which can be assumed viscous at elevated temperatures and pressures, and have extensively been studied in outcrops, experimentally, numerically, and analytically. In this cross-disciplinary study we use the buckle folding theory, which is well-established in the field of structural geology, and apply it to the field of rockglacier geomorphology. As a case study we use the Murtèl rockglacier in the Upper Engadin Valley (Switzerland), which features a very spectacular example of furrow-and-ridge morphology. The internal structure of the Murtèl rockglacier is well-studied and can be approximated by two layers: an upper mixed rock-ice layer and a lower almost pure ice layer, both exhibiting a viscous rheology. Such a simple structure is a prerequisite for applying the analytical buckle folding expressions. We use the Fold Geometry Toolbox (FGT) to analyze a 1 m-resolution digital elevation model (DEM) based on low-altitude aerial photographs. This software incorporates the analytical buckle folding expressions and hence provides a quantitative relationship between the observed wavelength (from DEM), layer thickness (from boreholes), and the effective viscosity ratio between the folded layer and the underlying ice. The geometrical parameters from the DEM and boreholes and the rheological

  7. Blob Dynamics in 3D BOUT Simulations of Tokamak Edge Turbulence

    SciTech Connect

    Russell, D; D'Ippolito, D; Myra, J; Nevins, W; Xu, X

    2004-08-23

    Propagating filaments of enhanced plasma density, or blobs, observed in 3D numerical simulations of a diverted, neutral-fueled tokamak are studied. Fluctuations of vorticity, electrical potential {phi}, temperature T{sub e} and current density J{sub {parallel}} associated with the blobs have a dipole structure perpendicular to the magnetic field and propagate radially with large E {center_dot} B drift velocities (> 1 km/s). The simulation results are consistent with a 3D blob dynamics model that incorporates increased parallel plasma resistivity (from neutral cooling of the X-point region), blob disconnection from the divertor sheath, X-point closure of the current loops, and collisional physics to sustain the {phi}, T{sub e}, J{sub {parallel}} dipoles.

  8. Experiments on the impact and turbulent coalescence of a blob at a liquid-liquid interface

    NASA Astrophysics Data System (ADS)

    Landeau, Maylis; Olson, Peter; Deguen, Renaud; Hirsh, Ben; Earth; Planetary Sciences Team

    2015-11-01

    We present experiments on finite liquid volumes, hereafter referred to as blobs, of variable densities impacting an interface between two immiscible liquids at high Reynolds and Weber numbers. Such processes occurred on a massive scale during the giant impacts that formed terrestrial planets and satellites, including the Earth and the Moon. We find that the fall distance of the blob controls an abrupt transition in coalescence regime and in the amount of mixing with the lower liquid. This transition coincides with a brief and global breakup of the impacting blob into drops. For small fall distances, the large-scale flow following impact behaves as a turbulent fountain: a mixture of immiscible liquids penetrates in the lower liquid, collapses and spreads along the immiscible interface. We derive an experimental scaling relation for turbulent mixing of the impacting blob with the lower liquid as a function of a Richardson number.

  9. Origin of the hot gas and radio blobs at the Galactic Centre

    NASA Technical Reports Server (NTRS)

    Wardle, Mark; Yusef-Zadeh, Farhad

    1992-01-01

    Radio continuum observations have shown a chain of blobs of emission leading from SgrA* to a small cavity which is located in one of the ionized gas streamers (the Bar) that orbit SgrA* and which is associated with hot gas. Further high-resolution radio images are presented here which show that the blobs are connected to SgrA* by a ridge of emission. It is suggested that the blobs are formed by the interaction of stellar winds from the IRS16 cluster with the gravitational potential of SgrA*. The hot gas then results from the dissipation of the kinetic energy of the blobs as they collide with the orbiting ionized streamer. These collisions are of dynamical significance for the motion of the Bar around the Galactic Center, and there should be detectable variability in the structure on a timescale of 10 yrs.

  10. Characterization of the blob generation region and blobby transport in a stellarator

    NASA Astrophysics Data System (ADS)

    Fuchert, G.; Birkenmeier, G.; Ramisch, M.; Stroth, U.

    2016-05-01

    Filaments of increased pressure (‘blobs’) in the scrape-off layer of toroidally confined magnetized plasmas are studied in the context of fusion research due to their relevance for confinement and wall safety. Analytical models in simple toroidal magnetic field geometries have proven useful to get a quantitative understanding of blob dynamics in tokamaks. However, their direct applicability to the more complicated stellarator geometry is far less studied. The experiments presented here show that in the stellarator TJ-K blobs are field-aligned structures occurring in scrape-off layer regions of negative mean normal curvature, which is in agreement with common blob models. Furthermore, it is shown that in TJ-K, in accordance with findings from tokamaks, blobs account for a significant fraction of the turbulent scrape-off layer transport of the order of several tens of percent.

  11. Bottom-up coarse-graining of a simple graphene model: the blob picture.

    PubMed

    Kauzlarić, David; Meier, Julia T; Español, Pep; Succi, Sauro; Greiner, Andreas; Korvink, Jan G

    2011-02-14

    The coarse-graining of a simple all-atom 2D microscopic model of graphene, in terms of "blobs" described by center of mass variables, is presented. The equations of motion of the coarse-grained variables take the form of dissipative particle dynamics (DPD). The coarse-grained conservative forces and the friction of the DPD model are obtained via a bottom-up procedure from molecular dynamics (MD) simulations. The separation of timescales for blobs of 24 and 96 carbon atoms is sufficiently pronounced for the Markovian assumption, inherent to the DPD model, to provide satisfactory results. In particular, the MD velocity autocorrelation function of the blobs is well reproduced by the DPD model, provided that the effect of friction and noise is taken into account. However, DPD cross-correlations between neighbor blobs show appreciable discrepancies with respect to the MD results. Possible extensions to mend these discrepancies are briefly outlined. PMID:21322660

  12. Blob current structures in TORPEX plasmas: experimental measurements and numerical simulations

    NASA Astrophysics Data System (ADS)

    Furno, I.; Theiler, C.; Lançon, D.; Fasoli, A.; Iraji, D.; Ricci, P.; Spolaore, M.; Vianello, N.

    2011-12-01

    In the simple magnetized torus TORPEX, field-aligned blobs originate from ideal interchange waves and propagate radially outward due to ∇B and curvature induced drifts. Time-resolved two-dimensional measurements of the field-aligned current density J∥ associated with blobs are obtained from conditionally sampled data from a single-sided Langmuir probe and a specially designed current probe. The profile of J∥ exhibits an asymmetric dipolar structure, which originates from the polarization of the blob and is consistent with sheath boundary conditions. The asymmetry results from the non-linear dependence of J∥ at the sheath edge upon the floating potential. Using internal measurements, we directly confirm the existence of two regimes, in which parallel currents to the sheath do or do not significantly damp charge separation and thus blob radial velocity. To investigate the effect of the observed asymmetry of J∥ on the blob motion, we carried out numerical simulations of seeded blobs, using a two-field fluid model, which evolves electron density and vorticity. Simulations are performed spanning a wide range of blob sizes covering both regimes. We use either the complete or a linearized form for the sheath dissipation term in the vorticity equation. The structure of the parallel current density and plasma potential is found to be different in the two cases. Asymmetric profiles are observed in simulations with the complete form, while symmetric profiles are obtained when a linearized form is used. Negligible effects are, however, observed in terms of blob radial velocity. The relevance of the present results for fusion devices is also discussed.

  13. Physics of blob displacement in a two-dimensional porous medium

    SciTech Connect

    Lenormand, R.; Zarcone, C.

    1988-03-01

    The evolution of the geometry of blobs is observed during displacements in a two-dimensional (2D) transparent micromodel, and such macroscopic parameters as pressure drop and recovery are monitored simultaneously. The results are in good agreement with experiments performed in real media and with theoretical calculations of the conditions required for blob mobilization when the presence of loops in the structure is taken into account.

  14. Intermittent Divertor Filaments in the National Spherical Torus Experiment and Their Relation to Midplane Blobs

    SciTech Connect

    R.J. Maqueda, D.P. Stotler and the NSTX Team.

    2010-05-19

    While intermittent filamentary structures, also known as blobs, are routinely seen in the low-field-side scrape-off layer of the National Spherical Torus Experiment (NSTX) (Ono et al 2000 Nucl. Fusion 40 557), fine structured filaments are also seen on the lower divertor target plates of NSTX. These filaments, not associated with edge localized modes, correspond to the interaction of the turbulent blobs seen near the midplane with the divertor plasma facing components. The fluctuation level of the neutral lithium light observed at the divertor, and the skewness and kurtosis of its probability distribution function, is similar to that of midplane blobs seen in Dα; e.g. increasing with increasing radii outside the outer strike point (OSP) (separatrix). In addition, their toroidal and radial movement agrees with the typical movement of midplane blobs. Furthermore, with the appropriate magnetic topology, i.e. mapping between the portion of the target plates being observed into the field of view of the midplane gas puff imaging diagnostic, very good correlation is observed between the blobs and the divertor filaments. The correlation between divertor plate filaments and midplane blobs is lost close to the OSP. This latter observation is consistent with the existence of ‘magnetic shear disconnection’ due to the lower X-point, as proposed by Cohen and Ryutov (1997 Nucl. Fusion 37 621).

  15. Gyrokinetic study of edge blobs and divertor heat-load footprint

    NASA Astrophysics Data System (ADS)

    Chang, C.-S.; Ku, S.-H.; Churchill, M.; Zweben, S.

    2014-10-01

    In an attempt to better understand the complicated physics of the inter-related ``intermittent plasma objects (blobs)'' and divertor heat-load footprint, the full-function gyrokinetic PIC code XGC1 has been used in realistic diverted geometry. Neoclassical and turbulence physics are simulated together self-consistently in the presence of Monte Carlo neutral particles. Blobs are modeled here as electrostatic nonlinear turbulence phenomenon. It is found that the ``blobs'' are generated, together with the ``holes,'' around the steep density gradient region. XGC1 reasserts the previous findings that blobs move out convectively into the scrape-off layer, while the holes move inward toward plasma core. The measured radial width of the divertor heat load, mapped to the outer midplane, is found to be much less than the median radial size of the intermittent plasma objects, but is rather closer to the width of neoclassical orbit excursion from pedestal to divertor, yielding approximately the 1/Ip-type scaling found from our previous pure neoclassical simulation or a heuristic neoclassical argument by Goldston. However, it also shows some spreading by the intermittent turbulence. In ITER plasma edge, where the ion banana width at separatrix becomes negligibly small compared to the meso-scale blob size, blobs may saturate the 1/Ip scaling.

  16. Effect of finite blob size on the current convective instability in the auroral ionosphere. Memorandum report

    SciTech Connect

    Huba, J.D.; Chaturvedi, P.K.

    1986-04-11

    It has been suggested that the current convective instability may be responsible for the structuring, i.e., generation of density irregularities, of density enhancements (known as blobs) in the auroral ionosphere. However, previous theories have neglected the finite extent of the blob along the geomagnetic field. In this paper, a nonlocal theory of the current convective instability is developed, which considers the finite extent of an ionospheric blob parallel to the geomagnetic field. It was found that the growth rate of the instability can be substantially reduced in the finite-sized blob case from the value obtained in the local approximation for an infinitely long blob. For auroral ionosphere parameters, the reduction in the growth rate for medium scale irregularities (1-10 km) can be one to two orders of magnitude for the typical observed values of blob sizes (approx. a few hundred km). Thus, it appears that the current convective instability is not a viable mechanism to generate scintillation causing irregularities, i.e., 1-10 km irregularities.

  17. Automated detection of microaneurysms using robust blob descriptors

    NASA Astrophysics Data System (ADS)

    Adal, K.; Ali, S.; Sidibé, D.; Karnowski, T.; Chaum, E.; Mériaudeau, F.

    2013-03-01

    Microaneurysms (MAs) are among the first signs of diabetic retinopathy (DR) that can be seen as round dark-red structures in digital color fundus photographs of retina. In recent years, automated computer-aided detection and diagnosis (CAD) of MAs has attracted many researchers due to its low-cost and versatile nature. In this paper, the MA detection problem is modeled as finding interest points from a given image and several interest point descriptors are introduced and integrated with machine learning techniques to detect MAs. The proposed approach starts by applying a novel fundus image contrast enhancement technique using Singular Value Decomposition (SVD) of fundus images. Then, Hessian-based candidate selection algorithm is applied to extract image regions which are more likely to be MAs. For each candidate region, robust low-level blob descriptors such as Speeded Up Robust Features (SURF) and Intensity Normalized Radon Transform are extracted to characterize candidate MA regions. The combined features are then classified using SVM which has been trained using ten manually annotated training images. The performance of the overall system is evaluated on Retinopathy Online Challenge (ROC) competition database. Preliminary results show the competitiveness of the proposed candidate selection techniques against state-of-the art methods as well as the promising future for the proposed descriptors to be used in the localization of MAs from fundus images.

  18. Numerical Analysis of Gravity-driven Spreading of Viscoelastic Fluids: Investigation of the Effect of Shear-thinning and Elastic Behavior

    NASA Astrophysics Data System (ADS)

    Hu, Bin; Kieweg, Sarah

    2011-11-01

    Many complex fluids of interest exhibit viscoelastic hehavior. Polymeric drug delivery vehicles, such as anti-HIV topical microbicides, are among these fluids. For the optimal design of microbicides, the combined effect of shear-thinning and elastic behavior on the gravity-driven spreading of viscoelastic fluids is studied. We develop a 2D model to simulate the fluids spreading down an incline using ANSYS POLYFLOW software package. Arbitrary Lagrangian-Eulerian (ALE) method combined with Lagrangian remeshing is applied to track the moving free surface of fluids during spreading. Adaptive meshing method is used to generate high quality mesh for the remeshing process. Based on an elastic viscous split stress (EVSS) approach, several differential viscoelastic constitutive models are studied to investigate the combined effect of shear-thinning and elastic behavior. Mesh convergence test and constant volume check are studied to verify the new model. Moreover, the new model with zero elasticity is compared with previous studies of Newtonian and power-law fluids.

  19. Gravity-driven transport of three engineered nanomaterials in unsaturated soils and their effects on soil pH and nutrient release.

    PubMed

    Conway, Jon R; Keller, Arturo A

    2016-07-01

    The gravity-driven transport of TiO2, CeO2, and Cu(OH)2 engineered nanomaterials (ENMs) and their effects on soil pH and nutrient release were measured in three unsaturated soils. ENM transport was found to be highly limited in natural soils collected from farmland and grasslands, with the majority of particles being retained in the upper 0-3 cm of the soil profile, while greater transport depth was seen in a commercial potting soil. Physical straining appeared to be the primary mechanism of retention in natural soils as ENMs immediately formed micron-scale aggregates, which was exacerbated by coating particles with Suwannee River natural organic matter (NOM) which promote steric hindrance. Small changes in soil pH were observed in natural soils contaminated with ENMs that were largely independent of ENM type and concentration, but differed from controls. These changes may have been due to enhanced release of naturally present pH-altering ions (Mg(2+), H(+)) in the soil via substitution processes. These results suggest ENMs introduced into soil will likely be highly retained near the source zone. PMID:27108211

  20. [Kinetic theory and boundary conditions for flows of highly inelastic spheres: Application to gravity driven granular flows down bumpy inclines]. Quarterly progress report, April 1, 1992--June 30, 1992

    SciTech Connect

    Richman, M.W.

    1992-12-01

    In this quarter, we extended our study of the effects of isotropic boundary vibrations to steady, gravity driven, inclined granular flows. These flows are more complex than those considered last quarter because of the presence of slip and mean velocity gradients at the boundary. Consequently, it was first necessary to modify the boundary conditions derived by Richman (1992) to account for corrections to the flow particle velocity distribution function from velocity gradients. In what follows we only summarize the results obtained.

  1. Accuracy Limits of the Blob Model for a Flexible Polymer Confined Inside a Cylindrical Nano-Channel

    NASA Astrophysics Data System (ADS)

    Hoseinpoor, S. Mohammad; Nikoofard, Narges; Zahedifar, Mostafa

    2016-05-01

    The blob model is a well-known scaling theory for polymers in confined environments. In this manuscript, the limitations of the blob model for a flexible polymer confined inside a nano-cylinder are clarified theoretically and using molecular dynamics simulations. In this model, the confined polymer is divided into smaller sections called blobs. The free energy of the confined polymer is accurate under the conditions that (1) the number of monomers inside each blob and (2) total number of the blobs is large enough. In simulations, we consider the opposite limit of extremely narrow nano-channels. Interestingly, the simulation results show that the theory can describe the statics of the confined polymer, even when the above two requirements are not satisfied. However, when simulation parameters are beyond the theoretical limits, the fluctuations in the radius of gyration of the confined polymer have a much stronger dependence on the diameter of the nano-channel than the blob model predicts.

  2. Constraints on Lyα Blob Number Densities at 2.1 and 3.1

    NASA Astrophysics Data System (ADS)

    Hay, John; Ciardullo, R.; Feldmeier, J. J.; Gronwall, C.; Hagen, A.; MUSYC Collaboration

    2014-01-01

    Ly-alpha blobs are thought to be associated with regions over dense in compact Lyα emitters (LAEs) at the intersection of dark matter filaments, and may be the progenitors of today's galaxy clusters. Thus, a blob census can help explain the structure and formation history of these rare objects. We report the results of a deep narrow-band survey for Lyα blobs in three ~0.3 deg^2 fields: the Extended Chandra Deep Field South (at z = 2.06 and z = 3.1), the Extended Hubble Deep Field South (at z = 2.06 and z = 3.12) and the MUSYC field SDSS 1030+05 (at z = 2.06). Our surveys cover a total volume of 0.923 x 10^6 Mpc^3 at z = 2.06, and 0.871 x 10^6 Mpc^3 at z = 3.1; they are sensitive to blobs which have rest-frame equivalent widths greater than 30 Angstrom, and resolved blobs whose isophotal areas, defined using a surface brightnesses limit equivalent to a value of 5.5 x 10^{-18 ergs/cm^2/s/arcsec^2 at z = 2.3, exceed a specified limit. We search for blobs expected in SDSS 1030+05 based on an observed over density of compact LAEs in the field (Gronwall et al, in prep.), and we use our results to place limits on the number density of low surface brightness blobs outside of clusters.

  3. a Spreading Blob Vortex Method for Viscous Bounded Flows.

    NASA Astrophysics Data System (ADS)

    Rossi, Louis Frank

    In this dissertation, I introduce a vortex method that is generally applicable to any two-dimensional, incompressible flow with or without boundaries. This method is deterministic, accurate, convergent, naturally adaptive, geometry independent and fully localized. For viscous flows, the vorticity distribution of each vortex element must evolve in addition to following a Lagrangian trajectory. My method relies upon an idea called core spreading. Core spreading is inconsistent by itself, but I have corrected it with a deterministic process known as "vortex fission" where one "fat" vortex is replaced by several "thinner" ones. Also, I examine rigorously a method for merging many blobs into one. This process maintains smaller problem sizes thus boosting the efficiency of the vortex method. To prove that this corrected core spreading method will converge uniformly, I adapted a continuous formalism to this grid-free scheme. This convergence theory does not rely on any form of grid. I only examine the linear problem where the flow field is specified, and treat the full nonlinear problem as a perturbation of the linear problem. The estimated rate of convergence is demonstrated to be sharp in several examples. Boundary conditions are approximated indirectly. The boundary is decomposed into a collection of small linear segments. I solve the no -slip and no-normal flow conditions simultaneously by superimposing a potential flow and injecting vorticity from the boundary consistent with the unsteady Rayleigh problem. Finally, the ultimate test for this new method is to simulate the wall jet. The simulations produce a dipole instability along the wall as observed in water tank and wind tunnel experiments and predicted by linear stability analysis. Moreover, the wavelength and height of these simulations agree quantitatively with experimental observations.

  4. Superhydrophobic meshes that can repel hot water and strong corrosive liquids used for efficient gravity-driven oil/water separation

    NASA Astrophysics Data System (ADS)

    Li, Jian; Kang, Ruimei; Tang, Xiaohua; She, Houde; Yang, Yaoxia; Zha, Fei

    2016-03-01

    Oil-polluted water has become a worldwide problem due to increasing industrial oily wastewater as well as frequent oil-spill pollution. Compared with underwater superoleophobic (water-removing) filtration membranes, superhydrophobic/superoleophilic (oil-removing) materials have advantages as they can be used for the filtration of heavy oil or the absorption of floating oil from water/oil mixtures. However, most of the superhydrophobic materials used for oil/water separation lose their superhydrophobicity when exposed to hot (e.g. >50 °C) water and strong corrosive liquids. Herein, we demonstrate superhydrophobic overlapped candle soot (CS) and silica coated meshes that can repel hot water (about 92 °C) and strong corrosive liquids, and were used for the gravity driven separation of oil-water mixtures in hot water and strong acidic, alkaline, and salty environments. To the best of our knowledge, we are unaware of any previously reported studies on the use of superhydrophobic materials for the separation of oil from hot water and corrosive aqueous media. In addition, the as-prepared robust superhydrophobic CS and silica coated meshes can separate a series of oils and organic solvents like kerosene, toluene, petroleum ether, heptane and chloroform from water with a separation efficiency larger than 99.0%. Moreover, the as-prepared coated mesh still maintained a separation efficiency above 98.5% and stable recyclability after 55 cycles of separation. The robust superhydrophobic meshes developed in this work can therefore be practically used as a highly efficient filtration membrane for the separation of oil from harsh water conditions, benefiting the environment and human health.Oil-polluted water has become a worldwide problem due to increasing industrial oily wastewater as well as frequent oil-spill pollution. Compared with underwater superoleophobic (water-removing) filtration membranes, superhydrophobic/superoleophilic (oil-removing) materials have advantages as

  5. Evolution of localized blobs of swirling or buoyant fluid with and without an ambient magnetic field

    SciTech Connect

    Davidson, P. A.; Sreenivasan, Binod; Aspden, A. J.

    2007-02-15

    We investigate the evolution of localized blobs of swirling or buoyant fluid in an infinite, inviscid, electrically conducting fluid. We consider the three cases of a strong imposed magnetic field, a weak imposed magnetic field, and no magnetic field. For a swirling blob in the absence of a magnetic field, we find, in line with others, that the blob bursts radially outward under the action of the centrifugal force, forming a thin annular vortex sheet. A simple model of this process predicts that the vortex sheet thins exponentially fast and that it moves radially outward with constant velocity. These predictions are verified by high-resolution numerical simulations. When an intense magnetic field is applied, this phenomenon is suppressed, with the energy and angular momentum of the blob now diffusing axially along the magnetic field lines, converting the blob into a columnar structure. For modest or weak magnetic fields, there are elements of both types of behavior, with the radial bursting dominating over axial diffusion for weak fields. However, even when the magnetic field is very weak, the flow structure is quite distinct to that of the nonmagnetic case. In particular, a small but finite magnetic field places a lower bound on the thickness of the annular vortex sheet and produces an annulus of counter-rotating fluid that surrounds the vortex core. The behavior of the buoyant blob is similar. In the absence of a magnetic field, it rapidly develops the mushroomlike shape of a thermal, with a thin vortex sheet at the top and sides of the mushroom. Again, a simple model of this process predicts that the vortex sheet at the top of the thermal thins exponentially fast and rises with constant velocity. These predictions are consistent with earlier numerical simulations. Curiously, however, it is shown that the net vertical momentum associated with the blob increases linearly in time, despite the fact that the vertical velocity at the front of the thermal is constant

  6. How Lyman Alpha Emission Depends on Galaxy Stellar Mass

    NASA Astrophysics Data System (ADS)

    Oyarzún, Grecco A.; Blanc, Guillermo A.; González, Valentino; Mateo, Mario; Bailey, John I., III; Finkelstein, Steven L.; Lira, Paulina; Crane, Jeffrey D.; Olszewski, Edward W.

    2016-04-01

    In this work, we show how the stellar mass (M *) of galaxies affects the 3 < z < 4.6 Lyα equivalent width (EW) distribution. To this end, we design a sample of 629 galaxies in the M * range 7.6\\lt {log}{M}*/{M}ȯ \\lt 10.6 from the 3D-HST/CANDELS survey. We perform spectroscopic observations of this sample using the Michigan/Magellan Fiber System, allowing us to measure Lyα fluxes and use 3D-HST/CANDELS ancillary data. In order to study the Lyα EW distribution dependence on M *, we split the whole sample in three stellar mass bins. We find that, in all bins, the distribution is best represented by an exponential profile of the form {dN}({M}*)/d{EW}={W}0{({M}*)}-1A({M}*){e}-{EW/{W}0({M}*)}. Through a Bayesian analysis, we confirm that lower M * galaxies have higher Lyα EWs. We also find that the fraction A of galaxies featuring emission and the e-folding scale W 0 of the distribution anti-correlate with M *, recovering expressions of the forms A({M}*)=-0.26(.13){log}{M}*/{M}ȯ +3.01(1.2) and {W}0({M}*)=-15.6(3.5){log}{M}*/{M}ȯ +166(34). These results are crucial for proper interpretation of Lyα emission trends reported in the literature that may be affected by strong M * selection biases.

  7. Properties of Lyman-alpha Absorbers at High-Redshift

    NASA Astrophysics Data System (ADS)

    Peroux, C.

    2001-09-01

    In recent years, an extremely successful method to observationally study early stages of galaxy formation has been provided by the study of quasar absorbers. Quasar absorption lines are systems intercepting our line-of-sight to a given quasar and thus produce a feature in the quasar spectrum. Damped Lyman-α systems (hereafter DLAs) have N (H I) > 2 × 1020 atoms cm-2, and were originally thought to be the precursors of present day disk galaxies but there is evidence that they may be dominated by gas-rich proto-dwarf galaxies representing the basic building blocks of hierarchical growth of structure. Since their detection is independent of their size, shape, and covering factor, they provide a unbiased method with which to study early galaxies. DLAs are a subset of Lyman-limit Systems (hereafter LLS) which have hydrogen column densities N (H I) > 1.6 × 1017 atoms cm-2. At z < 1, they are probably associated with galactic halos. Finally, the Lyman-α forest is composed of many small column density systems ranging from N (H I) =1012 to 1.6 × 1017 atoms cm-2. This thesis presents a sample of 66 bright z ⪆ 4 quasars observed with the 4 m Cerro Tololo Inter-American Observatory telescope and the 4.2 m William Hershel telescope. The first part of the study concentrates on the quasars themselves via the fitting of quasar continua and the measurement of continuum depression parameters characterising the mean absorption across the Lyman-α forest. The quasar spectra are then analysed to investigate the absorption systems they contain. This led to the discovery of 26 new DLAs, 34 LLS and many associated metal lines which enables the analysis of the evolution of the column density distribution, f(N,z), and the total mass in high-column density neutral hydrogen quasar absorbers. The observed number of LLS per unit redshift is used to constrain f(N,z) below the DLA limit in the range N(HI) = 1.6 × 1017 to 2× 1020 atoms cm-2. The joint analysis shows unambiguously that f(N,z) deviates significantly from a single power law and that a Γ-law distribution of the form f(N,z) = (f*/N*)(N/N*)-β exp(-N/N*) provides a better description of the observations. These results are further used to determine the amount of neutral gas contained in both DLAs and in systems with N(HI) ≥ 2 × 1019 atoms cm-2 (``sub-DLAs''). In the redshift range 2 -- 3, 85% of the neutral H I + He II mass density is in DLAs, however we find that at z>3.5 this fraction drops to 55% and that the remaining neutral gas mass lies in sub-DLAs. After correction of the observed mass in H I for this ``missing'' neutral gas the comoving mass density no longer shows any evidence for a decrease over the range z= 2 -- 5. The change in the column density distribution supports a picture, where at z>3.5, we may be directly observing the formation of high column density neutral hydrogen systems from lower column density units. Finally, predictions on the redshift evolution of the sub-DLAs number density are presented. Preliminary results from measuring their incidence from archival UVES echelle data seem in good agreement with our predictions.

  8. The HI Environment of Nearby Lyman-alpha Absorbers

    NASA Technical Reports Server (NTRS)

    VanGorkom, J. H.; Carilli, C. L.; Stocke, John T.; Perlman, Eric S.; Shull, J. Michael

    1996-01-01

    We present the results of a VLA and WSRT search for H I emission from the vicinity of seven nearby clouds, which were observed in Ly-alpha absorption with HST toward Mrk 335, Mrk 501, and PKS 2155-304. Around the absorbers, we searched a volume of 4O' x 40' x 1000 km/s; for one of the absorbers we probed a velocity range of only 600 km/s. The H I mass sensitivity (5 sigma) very close to the lines of sight varies from 5 x 10(exp 6) solar mass at best to 5 x 10(exp 8) solar mass at worst. We detected H I emission in the vicinity of four out of seven absorbers. The closest galaxy we find to the absorbers is a small dwarf galaxy at a projected distance of 68 h(exp -1) kpc from the sight line toward Mrk 335. This optically uncataloged galaxy has the same velocity (V = 1970 km/s) as one of the absorbers, is fainter than the SMC, and has an H I mass of only 4 x 10(exp 7) solar mass. We found a somewhat more luminous galaxy at exactly the velocity (V = 5100 km/s) of one of the absorbers toward PKS 2155-304 at a projected distance of 230 h(exp -1) kpc from the sight line. Two other, stronger absorbers toward PKS 2155-304 at V approx. 17,000 km/s appear to be associated with a loose group of three bright spiral galaxies, at projected distances of 300 to 600 h(exp -1) kpc. These results support the conclusions emerging from optical searches that most nearby Ly-alpha forest clouds trace the large-scale structures outlined by the optically luminous galaxies, although this is still based on small-number statistics. We do not find any evidence from the H I distribution or kinematics that there is a physical association between an absorber and its closest galaxy. While the absorbing clouds are at the systemic velocity of the galaxies, the H I extent of the galaxies is fairly typical, and at least an order of magnitude smaller than the projected distance to the sight line at which the absorbers are seen. On the other hand, we also do not find evidence against such a connection. In total, we detected H I emission from five galaxies, of which two were previously uncataloged and one did not have a known redshift. No H I emission was detected from the vicinity of the two absorbers, which are located in a void and a region of very low galaxy density; but the limits are somewhat less stringent than for the other sight lines. These results are similar to what has been found in optically unbiased H I surveys. Thus, presence of Ly-alpha absorbers does not significantly alter the H I detection rate in their environment.

  9. Fermi acceleration of Lyman-alpha photons by shocks

    NASA Technical Reports Server (NTRS)

    Neufeld, David A.; Mckee, Christopher F.

    1988-01-01

    The repeated scattering of Ly-alpha radiation across a shock front results in a systematic blueshift which may greatly exceed the shock velocity vs and is proportional to cube root of (Nvs), where N is the column density of hydrogen atoms on either side of the shock front. The blueshifting process is similar to the Fermi acceleration of cosmic rays and may be responsible for the blue asymmetric line profiles that have been observed in high-redshift Ly-alpha galaxies. The Ly-alpha line profile in 3C 326.1 is accounted for by a model in which shocks, driven into a population of interstellar clouds by a radio lobe, trigger the formation of ionizing stars and Fermi accelerate the Ly-alpha radiation emitted by H II regions surrounding those stars. Galaxy mergers, particularly between galaxies with low dust content, should produce Ly-alpha lines with strong blue wings.

  10. Equilibrium Slab Models of Lyman-Alpha Clouds

    NASA Technical Reports Server (NTRS)

    Charlton, Jane C.; Salpeter, Edwin E.; Hogan, Craig J.

    1993-01-01

    We model the L(sub y(alpha)) clouds as slabs of hydrogen with an ionizing extragalactic radiation field incident from both sides. In general, the equilibrium configuration of a slab at redshift z approx. less than 5 is determined by a balance of the gas pressure, gravity (including the effects of a dark matter halo), and the pressure exerted by the inter-galactic medium, P(sub ext). These models have been used to make predictions of the number of slabs as a function of the neutral hydrogen column density, N(sub H). A break in the curve is predicted at the transition between regimes where gravity and pressure are the dominant confining forces, with a less rapid decrease at larger N(sub H). The transition from optically thin to optically thick slabs leads to a gap in the distribution, whose location is governed largely by the spectrum of ionizing radiation. There are certain parallels between lines of sight through the outer HI disk of spiral galaxy with increasing radius, and the progression from damped, to Lyman limit, to forest clouds. We discuss briefly the possibility that at least some of the observed low z forest clouds may be a separate population, associated with galaxies, as suggested by the observations of Bahcall et al. This population could dominate the forest at present if the dark matter attached to galaxies should lead to gravity confinement for this disk population, while the isolated clouds remain pressure confined. The formalism developed in this paper will allow a more detailed study. We also discuss a more general parameter study of the equilibrium configuration of slabs, including mock gravity and L(sub y(alpha)) photon trapping.

  11. Spatial imaging of hydrogen Lyman-alpha emission from Jupiter

    NASA Technical Reports Server (NTRS)

    Clarke, J. T.; Weaver, H. A.; Feldman, P. D.; Moos, H. W.; Fastie, W. G.; Opal, C. B.

    1980-01-01

    A sounding rocket measurement of the H I L-alpha emission from Jupiter made on Dec. 1, 1978 shows limb darkening and an average disk brightness of 13 kR. This brightness is significantly higher than in previous measurements, and was confirmed by an IUE observation on Dec. 10, 1978. Comparison with a plane-parallel hydrogen layer model indicates that there is enhanced emission from the equatorial regions, reaching a peak near 80 deg longitude.

  12. The Spacelab Lyman alpha and white light coronagraphs program

    NASA Technical Reports Server (NTRS)

    Kohl, J. L.; Withbroe, G. L.; Weiser, H.; Macqueen, R. M.; Munro, R. H.

    1981-01-01

    The Harvard-Smithsonian Center for Astrophysics and the High Altitude Observatory have defined a joint coronagraphs experiment for a future Spacelab mission. The instrumentation package would include an ultraviolet light coronagraph to measure the intensity and profiles of spectral lines formed between 1.2 and 8 solar radii from sun center and a white light coronagraph to measure the intensity and polarization of visible light. The overall goals of the joint program are to use new coronal plasma diagnostic techniques to understand the physical processes and mechanisms operating in the solar corona, to understand the acceleration of high-speed and low-speed solar wind streams and to extrapolate this knowledge to other stars in order to help understand the physics of stellar coronae and stellar mass loss.

  13. Equilibrium slab models of Lyman-alpha clouds

    NASA Technical Reports Server (NTRS)

    Charlton, Jane C.; Salpeter, Edwin E.; Hogan, Craig J.

    1993-01-01

    Solutions for the equilibrium configuration of a slab with ionizing radiation incident equally from both sides are explored. Radiation effects (photoionization, Ly-alpha photon trapping, and mock gravity) as well as external pressure and self gravity (with and without dark matter) are included. The general formalism is applied to structure growth on small scales at very high z due to mock gravity on dust. Emphasis is placed on the application of slab models at z of less than 5, particularly those that may correspond to Ly-alpha forest, Lyman limit, and damped Ly-alpha systems. The regime with a dominant outward force contributed by trapping of Ly-alpha photons is discussed. General expressions are given for the equilibrium, including dark matter, assuming various relationships between the density of the dark matter halo and the total gas column density.

  14. Hydrocarbon photochemistry and Lyman alpha albedo of Jupiter

    NASA Technical Reports Server (NTRS)

    Yung, Y. L.; Strobel, D. F.

    1980-01-01

    A combined study of hydrocarbon and atomic hydrogen photochemistry is made to calculate self-consistently the L alpha albedo of Jupiter. It is shown that the L alpha emissions observed by Voyagers I and II can be explained by resonance scattering of sunlight. Precipitation of energetic particles from the magnetosphere can provide the large required source of atomic hydrogen, although the contribution of direct particle excitation to the disk-averaged brightness is insignificant. The variability of the L alpha brightness inferred from many observations in recent years is examined. The large difference in the brightness of the He 584 A resonance line observed by Pioneer and Voyager is briefly discussed. Driving the photochemistry by solar ultraviolet radiation alone yields a maximum mixing ratio of C2H6 + C2H2 at 0.01 atm of about 4 x 10 to the -6th. The possibility of additional CH4 dissociation from precipitation of magnetospheric particles is discussed. The photochemistry of C2H2 and C2H3 is sufficiently uncertain not to permit accurate calculations of their densities and the ratio C2H6/C2H2.

  15. A catalog of stellar Lyman-alpha fluxes

    NASA Technical Reports Server (NTRS)

    Landsman, Wayne; Simon, Theodore

    1993-01-01

    We present a catalog of stellar Ly-alpha emission fluxes, based on new and archival images obtained with the IUE spacecraft. The catalog includes 227 stars with detectable Ly-alpha emission fluxes, and upper limits on the Ly-alpha emission flux for another 48 stars. Multiple flux measurements are given for 52 stars. We present a model for correcting the observed Ly-alpha flux for attenuation by the local interstellar medium, and we apply this model to derive intrinsic Ly-alpha fluxes for 149 catalog stars which are located in low H I column density directions of the local interstellar medium. In our catalog, there are 14 late-A and early-F stars at B-V = 0.29 or less that show detectable emission at Ly-alpha. We find a linear correlation between the intrinsic Ly-alpha flux and C II 1335 A flux for stars with B-V greater than 0.60, but the A and F stars deviate from this relation in the sense that their Ly-alpha flux is too low. We also find a good correlation between Ly-alpha strength and coronal X-ray emission. This correlation holds over most of the H-R diagram, even for the F stars, where an X-ray deficit has previously been found relative to the transition region lines of C II and C IV.

  16. Coupling the emission of ionizing radiation and Lyman alpha

    NASA Astrophysics Data System (ADS)

    Hayes, Matthew

    2013-10-01

    The class of objects that reionized intergalactic hydrogen remains an observational and theoretical problem that is in contention for being the most prominent puzzle piece in contemporary astrophysics. The current consensus - determined almost entirely by ruling out bright active galaxies - is that the process was possibly begun and almost certainly finished by faint, lower-mass galaxies forming their early generations of stars. Recent observations of z 3 galaxies may even have identified the analog populations.However understanding how the emitted ionizing power of galaxies is causally related to their {robustly determined} physical properties is not a study that can be performed at high-z: neither the spatial information nor the standard multi-wavelength diagnostics are available. Moreover, on a case-by-case basis, the intervening IGM absorption is impossible to determine. These considerations have spawned a number of detailed studies with UV space telescopes, the synthesis of which however is that a characteristic population of Lyman continuum {LyC} emitting objects has not yet been identified. We show in this proposal that we have identified a characteristic trait in galaxy spectra that is highly indicative of LyC emission, by combining {a} high-z phenomenological studies, {b} new high-resolution UV spectra of local galaxies, and {c} sophisticated models of radiation transport. Believing that we have determined the signature, we propose to test the new hypothesis with deep spectroscopic observations with HST/COS under the Cycle 21 UV initiative.

  17. Detection of auroral hydrogen Lyman-Alpha emission from Uranus

    SciTech Connect

    Clarke, J.T.

    1982-12-15

    A series of observations of Uranus obtained with the short-wavelength spectrographs of the International Ultraviolet Explorer Observatory in 1982 April and June have revealed unexpectedly strong H Ly..cap alpha.. emission which varied between 430 and 850 Rayleighs in observed disk-averaged brightness over the course of these observations. The variability of the emission alone indicates that much of the emission must be produced by charged particle excitation of H in Uranus's upper atmosphere. In addition, comparison of these data with a model for resonant scattering of solar H Ly..cap alpha.. emission indicates that, over a wide range of model conditions, an emission brightness of even 430 Rayleighs (which was the lowest observed value) corresponds to an H column density on the order of 10/sup 17/ cm/sup -2/ in Uranus's upper atmosphere. At 20 AU from the Sun, solar EUV photodissociation of H/sub 2/ is insufficient to produce such a high column abundance of H, further supporting the identification of charged particle precipitation in Uranus's upper atmosphere. These data thus offer the first strong evidence for the presence of aurorae and therefore a magnetic field on Uranus.

  18. The Chromospheric Lyman Alpha SpectroPolarimeter (CLASP)

    NASA Astrophysics Data System (ADS)

    Kobayashi, K.; Tsuneta, S.; Trujillo Bueno, J.; Cirtain, J. W.; Bando, T.; Kano, R.; Hara, H.; Fujimura, D.; Ueda, K.; Ishikawa, R.; Watanabe, H.; Ichimoto, K.; Sakao, T.; de Pontieu, B.; Carlsson, M.; Casini, R.

    2010-12-01

    Magnetic fields in the solar chromosphere play a key role in the energy transfer and dynamics of the solar atmosphere. Yet a direct observation of the chromospheric magnetic field remains one of the greatest challenges in solar physics. While some advances have been made for observing the Zeeman effect in strong chromospheric lines, the effect is small and difficult to detect outside sunspots. The Hanle effect offers a promising alternative; it is sensitive to weaker magnetic fields (e.g., 5-500 G for Ly-Alpha), and while its magnitude saturates at stronger magnetic fields, the linear polarization signals remain sensitive to the magnetic field orientation. The Hanle effect is not only limited to off-limb observations. Because the chromosphere is illuminated by an anisotropic radiation field, the Ly-Alpha line is predicted to show linear polarization for on-disk, near-limb regions, and magnetic field is predicted to cause a measurable depolarization. At disk center, the Ly-Alpha radiation is predicted to be negligible in the absence of magnetic field, and linearly polarized to an order of 0.3% in the presence of an inclined magnetic field. The proposed CLASP sounding rocket instrument is designed to detect 0.3% linear polarization of the Ly-Alpha line at 1.5 arcsecond spatial resolution (0.7’’ pixel size) and 10 pm spectral resolution. The instrument consists of a 30 cm aperture Cassegrain telescope and a dual-beam spectropolarimeter. The telescope employs a ``cold mirror’’ design that uses multilayer coatings to reflect only the target wavelength range into the spectropolarimeter. The polarization analyzer consists of a rotating waveplate and a polarizing beamsplitter that comprises MgF2 plates placed at Brewster’s Angle. Each output beam of the polarizing beamsplitter, representing two orthogonal linear polarizations, is dispersed and focused using a separate spherical varied-line-space grating, and imaged with a separate 512x512 CCD camera. Prototypes of key optical components have been fabricated and tested. Instrument design is being finalized, and the experiment will be proposed for a 2014 flight aboard a NASA sounding rocket.

  19. Superhydrophobic meshes that can repel hot water and strong corrosive liquids used for efficient gravity-driven oil/water separation.

    PubMed

    Li, Jian; Kang, Ruimei; Tang, Xiaohua; She, Houde; Yang, Yaoxia; Zha, Fei

    2016-04-14

    Oil-polluted water has become a worldwide problem due to increasing industrial oily wastewater as well as frequent oil-spill pollution. Compared with underwater superoleophobic (water-removing) filtration membranes, superhydrophobic/superoleophilic (oil-removing) materials have advantages as they can be used for the filtration of heavy oil or the absorption of floating oil from water/oil mixtures. However, most of the superhydrophobic materials used for oil/water separation lose their superhydrophobicity when exposed to hot (e.g. >50 °C) water and strong corrosive liquids. Herein, we demonstrate superhydrophobic overlapped candle soot (CS) and silica coated meshes that can repel hot water (about 92 °C) and strong corrosive liquids, and were used for the gravity driven separation of oil-water mixtures in hot water and strong acidic, alkaline, and salty environments. To the best of our knowledge, we are unaware of any previously reported studies on the use of superhydrophobic materials for the separation of oil from hot water and corrosive aqueous media. In addition, the as-prepared robust superhydrophobic CS and silica coated meshes can separate a series of oils and organic solvents like kerosene, toluene, petroleum ether, heptane and chloroform from water with a separation efficiency larger than 99.0%. Moreover, the as-prepared coated mesh still maintained a separation efficiency above 98.5% and stable recyclability after 55 cycles of separation. The robust superhydrophobic meshes developed in this work can therefore be practically used as a highly efficient filtration membrane for the separation of oil from harsh water conditions, benefiting the environment and human health. PMID:26987990

  20. Superficial and deep-seated gravity-driven deformation horizons within basinal succession: the case study of Maiolica Formation, Gargano Promontory, Southern Italy

    NASA Astrophysics Data System (ADS)

    Jablonská, Danica; Di Celma, Claudio; Tondi, Emanuele

    2016-04-01

    Gravitational phenomena on the paleoslope of continental margins play a significant role both in redistribution of sediment and formation of new structural features within sedimentary basins worldwide. Mass-transport deposits (MTDs) represent important heterogeneities within the succession and occur on various scales (tens of centimetres to hundreds of metres). Small- to medium-scale MTDs (up to tens of meters) act as layers of different petrophysical properties, whereas large-scale MTDs (tens to hundreds of meters) form both stratigraphic and structural discontinuities (faults, thrusts, erosional surfaces, dykes or injections) within the succession. The Maiolica Formation, Early Cretaceous deep basinal succession cropping out in Gargano Promontory of Southeast Italy is represented by undisturbed intervals of flat-lying thin-bedded, cherty micritic limestone interstratified with intervals of lithologically similar, but structurally distorted beds. For this reason, the studied outcrops provide a good opportunity to characterize the geometry and the internal deformation of small- and medium-scale carbonate MTDs. At the outcrop scale, small- to medium-sized MTDs can be simply identified as sheets of deformed strata alternated with packages of undeformed beds. However, several observed features such as folded stylolites with radially oriented peaks within some of these deformed packages and the presence of large vertical clastic-dyke-like bodies in the succession suggest that some of these deformed packages represent deep-seated basal gliding horizons of large-scale MTDs. In this study, we present MTDs on two different scales that have a crucial influence on the evolution of slope to basinal successions. Moreover, we define the features that distinguish superficial MTDs from the deep-seated gravity-driven deformation horizons within basinal carbonates.

  1. Investigating the dynamics and density evolution of returning plasma blobs from the 2011 June 7 eruption

    SciTech Connect

    Carlyle, Jack; Williams, David R.; Van Driel-Gesztelyi, Lidia; Matthews, Sarah; Innes, Davina; Hillier, Andrew

    2014-02-20

    This work examines in-falling matter following an enormous coronal mass ejection on 2011 June 7. The material formed discrete concentrations, or blobs, in the corona and fell back to the surface, appearing as dark clouds against the bright corona. In this work we examined the density and dynamic evolution of these blobs in order to formally assess the intriguing morphology displayed throughout their descent. The blobs were studied in five wavelengths (94, 131, 171, 193, and 211 Å) using the Solar Dynamics Observatory Atmospheric Imaging Assembly, comparing background emission to attenuated emission as a function of wavelength to calculate column densities across the descent of four separate blobs. We found the material to have a column density of hydrogen of approximately 2 × 10{sup 19} cm{sup –2}, which is comparable with typical pre-eruption filament column densities. Repeated splitting of the returning material is seen in a manner consistent with the Rayleigh-Taylor instability. Furthermore, the observed distribution of density and its evolution is also a signature of this instability. By approximating the three-dimensional geometry (with data from STEREO-A), volumetric densities were found to be approximately 2 × 10{sup –14} g cm{sup –3}, and this, along with observed dominant length scales of the instability, was used to infer a magnetic field of the order 1 G associated with the descending blobs.

  2. Observations of Plasma Blobs by OI 630 nm Using ASI and Photometer over Kolhapur, India

    NASA Astrophysics Data System (ADS)

    Nade, D. P.; Sharma, A. K.; Nikte, S. S.; Chavan, G. A.; Ghodpage, R. N.; Patil, P. T.; Gurubaran, S.

    2014-08-01

    This paper presents observations of plasma blobs by nightglow OI 630.0 nm emissions using ground-based techniques, all sky imager and photometer from Kolhapur. The nightglow observations have been made at low latitude station, Kolhapur (16.42°N, 74.2°E, and 10.6°N dip lat.) during clear moonless nights for period of October 2011-April 2012. Generally, these occur 3 h after sunset (18:00 IST). Herein we have calculated velocities of plasma blobs using scanning method, introduced by Pimenta et al. (Adv Space Res 27:1219-1224, 2001). The average zonal drift velocity (eastward) of the plasma blobs were found to be 133 ms-1 and vary between 100 and 200 ms-1. The width (east-west expansion) and length (north-south expansion) of plasma blobs is calculated by recently developed method of Sharma et al. (Curr Sci 106(08):1085-1093, 2014b). Their mean width and length were in the range of 70-180 and 500-950 km respectively. The study shows that localized eastward polarization electric field plays an important role in the generation of plasma blobs.

  3. Lyman-alpha emission from the Lyman-alpha forest. [in high red shift quasar spectra due to molecular clouds

    NASA Technical Reports Server (NTRS)

    Hogan, Craig J.; Weymann, Ray J.

    1987-01-01

    It is suggested that high-dispersion long-slit spectra or very narrow-band etalon images of 'blank' sky could reveal patches of Ly-alpha line emission from the population of clouds whose absorption produces the 'Ly-alpha forest' in QSO spectra. A nonobservation can put limits on the ionizing background at high redshift which are better than those obtainable by direct measurements of background light.

  4. Gyrokinetic simulation of edge blobs and divertor heat-load footprint

    NASA Astrophysics Data System (ADS)

    Chang, C. S.; Ku, S.; Hager, R.; Churchill, M.; D'Azevedo, E.; Worley, P.

    2015-11-01

    Gyrokinetic study of divertor heat-load width Lq has been performed using the edge gyrokinetic code XGC1. Both neoclassical and electrostatic turbulence physics are self-consistently included in the simulation with fully nonlinear Fokker-Planck collision operation and neutral recycling. Gyrokinetic ions and drift kinetic electrons constitute the plasma in realistic magnetic separatrix geometry. The electron density fluctuations from nonlinear turbulence form blobs, as similarly seen in the experiments. DIII-D and NSTX geometries have been used to represent today's conventional and tight aspect ratio tokamaks. XGC1 shows that the ion neoclassical orbit dynamics dominates over the blob physics in setting Lq in the sample DIII-D and NSTX plasmas, re-discovering the experimentally observed 1/Ip type scaling. Magnitude of Lq is in the right ballpark, too, in comparison with experimental data. However, in an ITER standard plasma, XGC1 shows that the negligible neoclassical orbit excursion effect makes the blob dynamics to dominate Lq. Differently from Lq 1mm (when mapped back to outboard midplane) as was predicted by simple-minded extrapolation from the present-day data, XGC1 shows that Lq in ITER is about 1 cm that is somewhat smaller than the average blob size. Supported by US DOE and the INCITE program.

  5. A Linked List-Based Algorithm for Blob Detection on Embedded Vision-Based Sensors.

    PubMed

    Acevedo-Avila, Ricardo; Gonzalez-Mendoza, Miguel; Garcia-Garcia, Andres

    2016-01-01

    Blob detection is a common task in vision-based applications. Most existing algorithms are aimed at execution on general purpose computers; while very few can be adapted to the computing restrictions present in embedded platforms. This paper focuses on the design of an algorithm capable of real-time blob detection that minimizes system memory consumption. The proposed algorithm detects objects in one image scan; it is based on a linked-list data structure tree used to label blobs depending on their shape and node information. An example application showing the results of a blob detection co-processor has been built on a low-powered field programmable gate array hardware as a step towards developing a smart video surveillance system. The detection method is intended for general purpose application. As such, several test cases focused on character recognition are also examined. The results obtained present a fair trade-off between accuracy and memory requirements; and prove the validity of the proposed approach for real-time implementation on resource-constrained computing platforms. PMID:27240382

  6. A Linked List-Based Algorithm for Blob Detection on Embedded Vision-Based Sensors

    PubMed Central

    Acevedo-Avila, Ricardo; Gonzalez-Mendoza, Miguel; Garcia-Garcia, Andres

    2016-01-01

    Blob detection is a common task in vision-based applications. Most existing algorithms are aimed at execution on general purpose computers; while very few can be adapted to the computing restrictions present in embedded platforms. This paper focuses on the design of an algorithm capable of real-time blob detection that minimizes system memory consumption. The proposed algorithm detects objects in one image scan; it is based on a linked-list data structure tree used to label blobs depending on their shape and node information. An example application showing the results of a blob detection co-processor has been built on a low-powered field programmable gate array hardware as a step towards developing a smart video surveillance system. The detection method is intended for general purpose application. As such, several test cases focused on character recognition are also examined. The results obtained present a fair trade-off between accuracy and memory requirements; and prove the validity of the proposed approach for real-time implementation on resource-constrained computing platforms. PMID:27240382

  7. Detection of blob objects in microscopic zebrafish images based on gradient vector diffusion.

    PubMed

    Li, Gang; Liu, Tianming; Nie, Jingxin; Guo, Lei; Malicki, Jarema; Mara, Andrew; Holley, Scott A; Xia, Weiming; Wong, Stephen T C

    2007-10-01

    The zebrafish has become an important vertebrate animal model for the study of developmental biology, functional genomics, and disease mechanisms. It is also being used for drug discovery. Computerized detection of blob objects has been one of the important tasks in quantitative phenotyping of zebrafish. We present a new automated method that is able to detect blob objects, such as nuclei or cells in microscopic zebrafish images. This method is composed of three key steps. The first step is to produce a diffused gradient vector field by a physical elastic deformable model. In the second step, the flux image is computed on the diffused gradient vector field. The third step performs thresholding and nonmaximum suppression based on the flux image. We report the validation and experimental results of this method using zebrafish image datasets from three independent research labs. Both sensitivity and specificity of this method are over 90%. This method is able to differentiate closely juxtaposed or connected blob objects, with high sensitivity and specificity in different situations. It is characterized by a good, consistent performance in blob object detection. PMID:17654652

  8. Observations of Multiple Blobs in Homologous Solar Coronal Jets in Closed Loop

    NASA Astrophysics Data System (ADS)

    Zhang, Q. M.; Ji, H. S.; Su, Y. N.

    2016-03-01

    Coronal bright points (CBPs) and jets are ubiquitous small-scale brightenings that are often associated with each other. We here report our multiwavelength observations of two groups of homologous jets. The first group was observed by the Extreme-Ultraviolet Imager (EUVI) onboard the Solar TErrestrial RElations Observatory (STEREO) Behind spacecraft in 171 Å and 304 Å on 2014 September 10, from a location where no data from the Solar Dynamic Observatory (SDO) could be obtained. The jets (J1 - J6) recurred for six times with intervals of 5 - 15 minutes. They originated from the same primary CBP (BP1) and propagated in the northeast direction along large-scale, closed coronal loops. Two of the jets (J3 and J6) produced sympathetic CBPs (BP2 and BP3) after reaching the remote footpoints of the loops. The time delays between the peak times of BP1 and BP2 (BP3) are 240±75 s (300±75 s). The jets were not coherent. Instead, they were composed of bright and compact blobs. The sizes and apparent velocities of the blobs are 4.5 - 9 Mm and 140 - 380 km s-1. The arrival times of the multiple blobs in the jets at the far end of the loops indicate that the sympathetic CBPs are caused by jet flows and not by thermal conduction fronts. The second group was observed by the Atmospheric Imaging Assembly onboard SDO in various wavelengths on 2010 August 3. Similar to the first group, the jets originated from a short-lived BP at the boundary of Active Region 11092 and propagated along a small-scale, closed loop before flowing into the active region. Several tiny blobs with sizes of ˜1.7 Mm and an apparent velocity of ˜238 km s^{-1} were identified in the jets. We carried out differential emission measure (DEM) inversions to investigate the temperatures of the blobs, finding that the blobs were multithermal with an average temperature of 1.8 - 3.1 MK. The estimated number densities of the blobs were (1.7 - 2.8)×109 cm^{-3}.

  9. Statistical study of the GPS phase scintillation associated with plasma blobs

    NASA Astrophysics Data System (ADS)

    Jin, Yaqi; Miloch, Wojciech; Moen, Joran

    2016-04-01

    We present a study of the space weather effect of GNSS scintillation in the auroral/polar cap ionosphere with multi-instrument observations, including GNSS scintillation receiver, all-sky imager, and EISCAT radar. We focus on the period when polar cap patches (islands of high density F region plasma with density enhanced more than twice above the surrounding) exit the polar cap. When the patch exits into the nightside auroral region (and then it is termed blob), the GNSS phase scintillation can be enhanced; indicating that the blob is important for the scintillation study [Jin et al., 2014]. In the present study, we expand the data set to see how representative it is. From November of 2010 to February of 2014, 41.4 hours of data from all-sky imager were collected in 16 days when the airglow patches were observed to hit the nightside aurora and when the aurora covered a quarter of the all-sky imager field of view at Ny-Ålesund. The collocated GNSS scintillation receiver is used to study the scintillation impact. This study clearly shows that the scintillation level of a blob is higher than the scintillation level of the corresponding patch. However, no clear relation between the blob scintillation and the pre-conditioning of polar cap patches is found. Furthermore, the aurora alone did not produce strong scintillation. This implies that the aurora plays a role in structuring of the blob and increases its scintillation level. We also look into possible instability mechanisms which produce the plasma density irregularities.

  10. Blob-size distribution as a function of capillary number in sandstones

    SciTech Connect

    Chatzis, I.; Kuntamukkula, M.S.; Morrow, N.R.

    1984-09-01

    Changes that occur, with increase in capillary number, in the detailed structure of residual oil trapped in water-wet sandstone core samples, have been investigated. The technique of using a nonwetting phase which can be solidified and separated from the porous medium has been applied using styrene monomer as the nonwetting phase and 2% CaCl/sub 2/ brine as the wetting phase. The size distributions of residual oil blobs, obtained under various flow conditions, were measured by both image analysis and Coulter Counter techniques. Specific features of the results were checked by optical and electron microscopy. The changes in size distribution and shapes of blobs provide insight into the mechanisms of trapping and mobilization of residual oil.

  11. The influence of blobs on neutral particles in the scrape-off layer

    NASA Astrophysics Data System (ADS)

    Thrysøe, Alexander S.; Tophøj, Laust E. H.; Naulin, Volker; Rasmussen, Jens Juul; Madsen, Jens; Nielsen, Anders H.

    2016-04-01

    Interactions between plasma and neutrals are investigated with particular attention to the influence of large amplitude blob structures that mediate a significant particle and energy transport through the scrape-off layer (SOL). We perform a statistical analysis of the mean-field approximation for plasma parameters in the SOL, and this approximation is shown to be poor in a SOL with a high level of fluctuations, as the plasma fields are strongly correlated. A 1D neutral fluid model which account for both cold and hot neutrals is formulated and the effects of blobs on the ionization in the SOL and edge are investigated. Simulations suggest that neutrals originating from dissociation of hydrogen molecules only fuel in the outermost edge region of the plasma, whereas hot neutrals from charge exchange collisions penetrate deep into the bulk plasma. The results are recovered in a simplified 2D model.

  12. A Model Problem for Blob-Driven Tear Film Breakup (TBU)

    NASA Astrophysics Data System (ADS)

    Zhong, Lan; Ketelaar, C. F.; Braun, R. J.; Driscoll, T. A.; King-Smith, P. E.; Begley, Carolyn G.

    2015-11-01

    A model problem is developed to simulate tear film break up by assuming the existence of a flexible non-spreading blob with constant surfactant surface concentration. These assumptions model in vivo observations of an excess of tear film lipid that does not spread, with the surfactant concentration approximating the lipid layer. The model includes the effects of evaporation, osmolarity, surface tension, viscosity, the Marangoni effect and insoluble surfactant transport. The evaporative fluxes are input as representative functions based on data from experiments. A strong flow driven by surface tension gradient is observed from the numerical results, which may drive TBU at times compatible with in vivo observations. The TBU dynamics are studied as functions of blob size, surfactant properties and other parameters to establish regimes were TBU may be driven primarily by Marangoni effects. NSF grant 1412085 and NIH grant 1R01EY021794.

  13. Pore-scale Analysis of the effects of Contact Angle Hysteresis on Blob Mobilization in a Pore Doublet

    NASA Astrophysics Data System (ADS)

    Hsu, Shao-Yiu; Glantz, Roland; Hilpert, Markus

    2011-11-01

    The mobilization of residual oil blobs in porous media is of major interest to the petroleum industry. We studied the Jamin effect, which hampers the blob mobilization, experimentally in a pore doublet model and explain the Jamin effect through contact angle hysteresis. A liquid blob was trapped in one of the tubes of the pore doublet model and then subjected to different pressure gradients. We measured the contact angles (in 2D and 3D) as well as the mean curvatures of the blob. Due to gravity effects and hysteresis, the contact angles of the blob were initially (zero pressure gradient) non-uniform and exhibited a pronounced altitude dependence. As the pressure gradient was increased, the contact angles became more uniform and the altitude dependence of the contact angle decreased. At the same time, the mean curvature of the drainage interface increased, and the mean curvature of the imbibition interface decreased. The pressure drops across the pore model, which we inferred with our theory from the measured contact angles and mean curvatures, were in line with the directly measured pressure data. We not only show that a trapped blob can sustain a finite pressure gradient but also develop methods to measure the contact angles and mean curvatures in 3D.

  14. Dynamics of Coronal Rain and Descending Plasma Blobs in Solar Prominences. II. Partially Ionized Case

    NASA Astrophysics Data System (ADS)

    Oliver, R.; Soler, R.; Terradas, J.; Zaqarashvili, T. V.

    2016-02-01

    Coronal rain clumps and prominence knots are dense condensations with chromospheric to transition region temperatures that fall down in the much hotter corona. Their typical speeds are in the range 30-150 km s-1 and of the order of 10-30 km s-1, respectively, i.e., they are considerably smaller than free-fall velocities. These cold blobs contain a mixture of ionized and neutral material that must be dynamically coupled in order to fall together, as observed. We investigate this coupling by means of hydrodynamic simulations in which the coupling arises from the friction between ions and neutrals. The numerical simulations presented here are an extension of those of Oliver et al. to the partially ionized case. We find that, although the relative drift speed between the two species is smaller than 1 m s-1 at the blob center, it is sufficient to produce the forces required to strongly couple charged particles and neutrals. The ionization degree has no discernible effect on the main results of our previous work for a fully ionized plasma: the condensation has an initial acceleration phase followed by a period with roughly constant velocity, and, in addition, the maximum descending speed is clearly correlated with the ratio of initial blob to environment density.

  15. Effects of dust particles on the dynamics of blobs in the scrape off layer

    SciTech Connect

    Jovanovic, D.; De Angelis, U.; Fedele, R.; Pegoraro, F.

    2007-08-15

    A numerical study is presented of the evolution of plasma blobs in the scrape-off layer of a tokamak, in the presence of dust. Appropriate fluid model equations for the nonlinear interchange mode in a dusty plasma are derived, accounting for the attachment of electrons and ions, as well as for their scattering by the dust particulates, and the symmetry breaking between the electron and ion densities due to the dust charging. The dust is shown to introduce three new dissipative mechanisms that determine the blob dynamics, namely the sink of electrons by the attachment to the dust, the sink of the ion momentum by the attachment to, and scattering by, the dust, and the modification of the current outflow to the conductive wall due to the asymmetry between the electron and ion flows to the wall introduced by the dust. A new method for the detection of dust in a scrape-off layer during tokamak discharges is suggested, based on the qualitative difference between the blob dynamics in collisionless and dusty plasmas.

  16. Blob population dynamics during immiscible two-phase flows in reconstructed porous media

    NASA Astrophysics Data System (ADS)

    Yiotis, A. G.; Talon, L.; Salin, D.

    2013-03-01

    We study the dynamics of nonwetting liquid blobs during immiscible two-phase flows in stochastically reconstructed porous domains predominantly saturated by a wetting fluid. The flow problem is solved explicitly using a Lattice-Boltzmann model that captures both the bulk phase and interfacial dynamics of the process. We show that the nonwetting blobs undergo a continuous life cycle of dynamic breaking up and coalescence producing two populations of blobs, a mobile and a stranded one, that exchange continuously mass between them. The process reaches a “steady state” when the rates of coalescence and breaking up become equal, and the macroscopic flow variables remain practically constant with time. At steady state, mass partitioning between mobile and immobile populations depends strongly on the applied Bond number Bo and the initial nonwetting phase distributions. Three flow regimes are identified: a single-phase flow Darcy-type regime at low Bo numbers, a non-Darcy two-phase flow regime at intermediate values of Bo, where the capillary number scales as Ca∝Bo2, and a Darcy-type two-phase flow regime at higher values of Bo. Our numerical results are found to be in good agreement with recent experimental and theoretical works.

  17. The foundation of self-developing blob machines for spatial computing

    NASA Astrophysics Data System (ADS)

    Gruau, Frédéric; Eisenbeis, Christine; Maignan, Luidnel

    2008-07-01

    The current trend in electronics is to integrate more and more transistors on a chip and produce massive hardware resources. As a consequence, traditional computing models, which mainly compute in the temporal domain, do not work well anymore since it becomes increasingly difficult to orchestrate these massive-scale hardware resources in a centralized way. Spatial computing is a unifying term that embodies many unconventional computing models and means computing on a relatively homogeneous physical medium made of hardware components, where the communication time is dependent on the Euclidean distance between the components (locality constraint). This constraint makes the programming for high performance significantly more complex compared to classical non-spatial hardware because performance now depends on where computation happens in space (mapping problem). Blob computing is a new approach that addresses this parallel computing challenge in a radically new and unconventional way: it decouples the mapping of computations onto the hardware from the software programming while still elegantly exploiting the space of the underlying hardware. Hardware mapping of computations is done by a physical force-based approach that simulates forces between threads of computation (automata). Attractive forces are used to keep automata that need to communicate with each other closer while repulsive forces are used for load balancing. The advantage of these primitives is that they are simple enough to be implemented on an arbitrary computing medium. They form the basis of a runtime system (RTS) that transforms an arbitrary computing medium into an easier-to-program virtual machine called the blob machine. The basic objects of the blob machine are those automata, and the instructions let automata create new automata in specific ways so as to maintain a hierarchical organization (which facilitates both the mapping and the programming). We detail the basic instructions of the blob

  18. Study of self-consistent particle flows in a plasma blob with particle-in-cell simulations

    SciTech Connect

    Hasegawa, Hiroki Ishiguro, Seiji

    2015-10-15

    The self-consistent particle flows in a filamentary coherent structure along the magnetic field line in scrape-off layer (SOL) plasma (plasma blob) have been investigated by means of a three-dimensional electrostatic particle-in-cell simulation code. The presence of the spiral current system composed of the diamagnetic and parallel currents in a blob is confirmed by the particle simulation without any assumed sheath boundary models. Furthermore, the observation of the electron and ion parallel velocity distributions in a blob shows that those distributions are far from Maxwellian due to modification with the sheath formation and that the electron temperature on the higher potential side in a blob is higher than that on the lower potential side. Also, it is found that the ions on the higher potential side are accelerated more intensively along the magnetic field line than those on the lower potential side near the edge. This study indicates that particle simulations are able to provide an exact current closure to analysis of blob dynamics and will bring more accurate prediction of plasma transport in the SOL without any empirical assumptions.

  19. Observations of quasi-periodic scintillations and their possible relation to the dynamics of Es plasma blobs

    SciTech Connect

    Maruyama, Takashi )

    1991-06-01

    Quasi-periodic scintillations at a mid-latitude station, Wakkanai, Japan, are examined using 136-MHz geostationary satellite transmissions. Observations are compared with the ionospheric parameter obtained at the same station and random scintillation records. The results indicate that the quasi-periodic scintillations are most likely produced by plasma blobs within the sporadic E layers. Discussion focuses on characteristics of the ringing pattern which precedes and follows the primary deep fade-out, in field strength. In the majority of events the ringing pattern tends to develop after the distinct deep fade-out, i.e., the pattern is asymmetric. Quasi-periodic scintillation patterns are produced by the movement of plasma blobs in the case of geostationary satellite experiments. Thus the shape of the blob must be deformed so that a steep density gradient is attained on the backside. When the blob is highly deformed by the plasma instability which grows at the steep density gradient, burstlike random scintillations may be produced by the blob. 16 refs.

  20. Automatic laser beam alignment using blob detection for an environment monitoring spectroscopy

    NASA Astrophysics Data System (ADS)

    Khidir, Jarjees; Chen, Youhua; Anderson, Gary

    2013-05-01

    This paper describes a fully automated system to align an infra-red laser beam with a small retro-reflector over a wide range of distances. The component development and test were especially used for an open-path spectrometer gas detection system. Using blob detection under OpenCV library, an automatic alignment algorithm was designed to achieve fast and accurate target detection in a complex background environment. Test results are presented to show that the proposed algorithm has been successfully applied to various target distances and environment conditions.

  1. Finite Larmor Radius and Three-Dimensional Effects on the Blobs in the Scrape-Off Layer

    SciTech Connect

    Jovanovic, D.; Shukla, P. K.; Pegoraro, F.

    2008-10-15

    The nonlinear processes in the tokamak core edge and in the scrape-off layer are studied within the electrostatic interchange paradigm, with the collisions among the plasma particles and with the neutras, including the effects of the finite ion Larmor radius and of fully three-dimensional electron dynamics. These new three-dimensional model equations are solved numerically, to study the propagation of plasma blobs in the scrape-off layer. It is shown that the coupling with the resistive drift mode causes the transverse contraction and the rotation of the blob. The parallel resistivity and the finite ion temperature give rise to the symmetry breaking and the poloidal propagation of the blobs, while their stability is only weakly affected.

  2. Time scales of organic contaminant dissolution from complex source zones: coal tar pools vs. blobs

    NASA Astrophysics Data System (ADS)

    Eberhardt, Christina; Grathwohl, Peter

    2002-11-01

    Groundwater contamination due to complex organic mixtures such as coal tar, creosote and fuels is a widespread problem in industrialized regions. Although most compounds in these mixtures are biodegradable, the contaminant sources are very persistent for many decades after the contamination occurred (e.g., more than 100 years ago at gasworks sites). This limited bioavailability is due to slow dissolution processes. This study presents results from a large scale tank experiment (8 m long) on the long-term (354 days) dissolution kinetics of BTEX and PAHs from a 2.5 m long coal tar pool and 0.5 m long (smear) zone containing coal tar blobs distributed in a coarse sand. The results indicate (1) that Raoult's law holds for estimation of the saturation aqueous concentrations of the coal tar constituents, (2) that for the dissolution of smear zones longer than approximately 0.1 m and with more than 3-5% residual saturation, the local equilibrium assumption is valid and (3) that although very small (<0.1 mm), the transverse vertical dispersivity dominates the pool dissolution processes. Typical time scales for removal of the pollutants from the blob zone and the pool are in the order of a few weeks to more than 10,000 years, respectively.

  3. Time scales of organic contaminant dissolution from complex source zones: coal tar pools vs. blobs.

    PubMed

    Eberhardt, Christina; Grathwohl, Peter

    2002-11-01

    Groundwater contamination due to complex organic mixtures such as coal tar, creosote and fuels is a widespread problem in industrialized regions. Although most compounds in these mixtures are biodegradable, the contaminant sources are very persistent for many decades after the contamination occurred (e.g., more than 100 years ago at gasworks sites). This limited bioavailability is due to slow dissolution processes. This study presents results from a large scale tank experiment (8 m long) on the long-term (354 days) dissolution kinetics of BTEX and PAHs from a 2.5 m long coal tar pool and 0.5 m long (smear) zone containing coal tar blobs distributed in a coarse sand. The results inidicate (1) that Raoult's law holds for estimation of the saturation aqueous concentrations of the coal tar constituents, (2) that for the dissolution of smear zones longer than approximately 0.1 m and with more than 3-5% residual saturation, the local equilibrium assumption is valid and (3) that although very small (< 0.1 mm), the transverse vertical dispersivity dominates the pool dissolution processes. Typical time scales for removal of the pollutants from the blob zone and the pool are in the order of a few weeks to more than 10,000 years, respectively. PMID:12683639

  4. Automated Detection of Microaneurysms Using Scale-Adapted Blob Analysis and Semi-Supervised Learning

    SciTech Connect

    Adal, Kedir M.; Sidebe, Desire; Ali, Sharib; Chaum, Edward; Karnowski, Thomas Paul; Meriaudeau, Fabrice

    2014-01-07

    Despite several attempts, automated detection of microaneurysm (MA) from digital fundus images still remains to be an open issue. This is due to the subtle nature of MAs against the surrounding tissues. In this paper, the microaneurysm detection problem is modeled as finding interest regions or blobs from an image and an automatic local-scale selection technique is presented. Several scale-adapted region descriptors are then introduced to characterize these blob regions. A semi-supervised based learning approach, which requires few manually annotated learning examples, is also proposed to train a classifier to detect true MAs. The developed system is built using only few manually labeled and a large number of unlabeled retinal color fundus images. The performance of the overall system is evaluated on Retinopathy Online Challenge (ROC) competition database. A competition performance measure (CPM) of 0.364 shows the competitiveness of the proposed system against state-of-the art techniques as well as the applicability of the proposed features to analyze fundus images.

  5. Edge Zonal Flows and Blob Propagation in Alcator C-Mod

    SciTech Connect

    Zweben, S; Agostini, M; Davis, B; Grulke, O; Hager, R; Hughes, J; LaBombard, B; D'Ippolito, D A; Myra, J R; Russell, D A

    2011-07-25

    Here we describe recent measurements of the 2-D motion of turbulence in the edge and scrape-off layer (SOL) of the Alcator C-Mod tokamak. This data was taken using the outer midplane gas puff imaging (GPI) camera, which views a 6 cm radial by 6 cm poloidal region near the separatrix just below the outer midplane [1]. The data were taken in Ohmic or RF heated L-mode plasmas at 400,000 frames/sec for {approx}50 msec/shot using a Phantom 710 camera in a 64 x 64 pixel format. The resulting 2-D vs. time movies [2] can resolve the structure and motion of the turbulence on a spatial scale covering 0.3-6 cm. The images were analyzed using either a 2-D cross-correlation code (Sec. 2) or a 2-D blob tracking code (Sec. 3).

  6. Modelling the evolution of Ly α blobs and Ly α emitters

    NASA Astrophysics Data System (ADS)

    Smailagić, M.; Micic, M.; Martinović, N.

    2016-06-01

    In this work, we model the observed evolution in comoving number density of Lyman α blobs (LABs) as a function of redshift. Our model calculates LAB emission both from cooling radiation from the intergalactic gas accreting on to galaxies and from star formation (SF). We have used a dark matter (DM) cosmological simulation to which we applied empirical recipes for Ly α emission produced by cooling radiation and SF in every halo. Unlike previous work, the simulated volume in the DM simulation is large enough to produce an average LAB number density. For a range of redshifts, z ˜ 1-7, we compare our results with the observed luminosity functions of LABs and Lyman α emitters. Our cooling radiation luminosities appear to be too small to explain LAB luminosities at all redshifts. In contrast, for SF we obtained a good agreement with observed luminosity functions at all redshifts studied. We also discuss uncertainties that could influence the results obtained.

  7. Eruption of a plasma blob, associated M-class flare, and large-scale extreme-ultraviolet wave observed by SDO

    NASA Astrophysics Data System (ADS)

    Kumar, P.; Manoharan, P. K.

    2013-05-01

    We present a multiwavelength study of the formation and ejection of a plasma blob and associated extreme ultraviolet (EUV) waves in active region (AR) NOAA 11176, observed by SDO/AIA and STEREO on 25 March 2011. The EUV images observed with the AIA instrument clearly show the formation and ejection of a plasma blob from the lower atmosphere of the Sun at ~9 min prior to the onset of the M1.0 flare. This onset of the M-class flare happened at the site of the blob formation, while the blob was rising in a parabolic path with an average speed of ~300 km s. The blob also showed twisting and de-twisting motion in the lower corona, and the blob speed varied from ~10-540 km s. The faster and slower EUV wavefronts were observed in front of the plasma blob during its impulsive acceleration phase. The faster EUV wave propagated with a speed of ~785 to 1020 km s, whereas the slower wavefront speed varied in between ~245 and 465 km s. The timing and speed of the faster wave match the shock speed estimated from the drift rate of the associated type II radio burst. The faster wave experiences a reflection by the nearby AR NOAA 11177. In addition, secondary waves were observed (only in the 171 Å channel), when the primary fast wave and plasma blob impacted the funnel-shaped coronal loops. The Helioseismic Magnetic Imager (HMI) magnetograms revealed the continuous emergence of new magnetic flux along with shear flows at the site of the blob formation. It is inferred that the emergence of twisted magnetic fields in the form of arch-filaments/"anemone-type" loops is the likely cause for the plasma blob formation and associated eruption along with the triggering of M-class flare. Furthermore, the faster EUV wave formed ahead of the blob shows the signature of fast-mode MHD wave, whereas the slower wave seems to be generated by the field line compression by the plasma blob. The secondary wave trains originated from the funnel-shaped loops are probably the fast magnetoacoustic waves

  8. The Lamu Basin deepwater fold-and-thrust belt: An example of a margin-scale, gravity-driven thrust belt along the continental passive margin of East Africa

    NASA Astrophysics Data System (ADS)

    Cruciani, Francesco; Barchi, Massimiliano R.

    2016-03-01

    In recent decades, advances in seismic processing and acquisition of new data sets have revealed the presence of many deepwater fold-and-thrust belts (DW-FTBs), often developing along continental passive margins. These kinds of tectonic features have been intensively studied, due to their substantial interest. This work presents a regional-scale study of the poorly explored Lamu Basin DW-FTB, a margin-scale, gravity-driven system extending for more than 450 km along the continental passive margin of Kenya and southern Somalia (East Africa). A 2-D seismic data set was analyzed, consisting of both recently acquired high-quality data and old reprocessed seismic profiles, for the first detailed structural and stratigraphic interpretation of this DW-FTB. The system originated over an Early to mid-Cretaceous shale detachment due to a mainly gravity-spreading mechanism. Analysis of synkinematic strata indicates that the DW-FTB was active from the Late Cretaceous to the Early Miocene, but almost all of the deformation occurred before the Late Paleocene. The fold-and-thrust system displays a marked N-S variation in width, the northern portion being more than 150 km wide and the southern portion only a few dozen kilometers wide; this along-strike variation is thought to be related to the complex tectonosedimentary evolution of the continental margin at the Somalia-Kenya boundary, also reflected in the present-day bathymetry. Locally, a series of volcanic edifices stopped the basinward propagation of the DW-FTB. A landward change in the dominant structural style, from asymmetric imbricate thrust sheets to pseudo-symmetric detachment folds, is generally observed, related to the landward thickening of the detached shales.

  9. On the relation between Kaiser-Bessel blob and tube of response based modelling of the system matrix in iterative PET image reconstruction

    NASA Astrophysics Data System (ADS)

    Lougovski, Alexandr; Hofheinz, Frank; Maus, Jens; Schramm, Georg; van den Hoff, Jörg

    2015-05-01

    We investigate the question of how the blob approach is related to tube of response based modelling of the system matrix. In our model, the tube of response (TOR) is approximated as a cylinder with constant density (TOR-CD) and the cubic voxels are replaced by spheres. Here we investigate a modification of the TOR model that makes it effectively equivalent to the blob model, which models the intersection of lines of response (LORs) with radially variant basis functions (‘blobs’) replacing the cubic voxels. Implications of the achieved equivalence regarding the necessity of final resampling in blob-based reconstructions are considered. We extended TOR-CD to a variable density tube model (TOR-VD) that yields a weighting function (defining all system matrix elements) which is essentially identical to that of the blob model. The variable density of TOR-VD was modelled by a Gaussian and a Kaiser-Bessel function, respectively. The free parameters of both model functions were determined by fitting the corresponding weighting function to the weighting function of the blob model. TOR-CD and the best-fitting TOR-VD were compared to the blob model with a final resampling step (BLOB-RS) and without resampling (BLOB-NRS) in phantom studies. For three different contrast ratios and two different voxel sizes, resolution noise curves were generated. TOR-VD and BLOB-NRS lead to nearly identical images for all investigated contrast ratios and voxel sizes. Both models showed strong Gibbs artefacts at 4 mm voxel size, while at 2 mm voxel size there were no Gibbs artefacts visible. The spatial resolution was similar to the resolution with TOR-CD in all cases. The resampling step removed most of the Gibbs artefacts and reduced the noise level but also degraded the spatial resolution substantially. We conclude that the blob model can be considered just as a special case of a TOR-based reconstruction. The latter approach provides a more natural description of the detection process and

  10. The large-scale cross-correlation of Damped Lyman alpha systems with the Lyman alpha forest: first measurements from BOSS

    SciTech Connect

    Font-Ribera, Andreu; Miralda-Escudé, Jordi; Arnau, Eduard; Carithers, Bill; Ross, Nicholas P.; White, Martin; Lee, Khee-Gan; Noterdaeme, Pasquier; Pâris, Isabelle; Petitjean, Patrick; Rollinde, Emmanuel; Rich, James; Schneider, Donald P.; York, Donald G. E-mail: miralda@icc.ub.edu

    2012-11-01

    We present the first measurement of the large-scale cross-correlation of Lyα forest absorption and Damped Lyman α systems (DLA), using the 9th Data Release of the Baryon Oscillation Spectroscopic Survey (BOSS). The cross-correlation is clearly detected on scales up to 40h{sup −1}Mpc and is well fitted by the linear theory prediction of the standard Cold Dark Matter model of structure formation with the expected redshift distortions, confirming its origin in the gravitational evolution of structure. The amplitude of the DLA-Lyα cross-correlation depends on only one free parameter, the bias factor of the DLA systems, once the Lyα forest bias factors are known from independent Lyα forest correlation measurements. We measure the DLA bias factor to be b{sub D} = (2.17±0.20)β{sub F}{sup 0.22}, where the Lyα forest redshift distortion parameter β{sub F} is expected to be above unity. This bias factor implies a typical host halo mass for DLAs that is much larger than expected in present DLA models, and is reproduced if the DLA cross section scales with halo mass as M{sub h}{sup α}, with α = 1.1±0.1 for β{sub F} = 1. Matching the observed DLA bias factor and rate of incidence requires that atomic gas remains extended in massive halos over larger areas than predicted in present simulations of galaxy formation, with typical DLA proper sizes larger than 20 kpc in host halos of masses ∼ 10{sup 12}M{sub ☉}. We infer that typical galaxies at z ≅ 2 to 3 are surrounded by systems of atomic clouds that are much more extended than the luminous parts of galaxies and contain ∼ 10% of the baryons in the host halo.

  11. New method for probing Kerr space-time based on imaging observation of in-falling gas blob

    NASA Astrophysics Data System (ADS)

    Moriyama, Kotaro; Mineshige, Shin

    2016-06-01

    We propose a new observational method to probe the black hole space-time described by Einstein's theory. We consider a gas blob with an arc shape falling from the marginally stable orbit onto a black hole, carrying a finite amount of angular momentum. Previously, we proposed measuring the black hole spin from the flux variation data of the in-falling blob, assuming the Kerr space-time. We demonstrate here that we can independently measure the black hole spin solely by using the imaging data of the in-falling blob. We then introduce a Kerr-like hole (with one additional parameter which describes a stronger or weaker frame-dragging effect than that of the Kerr hole) and apply the two different methods of spin measurement: one based on the flux variation data and the other based on the imaging data. We obtain different spin values by the different methods for the Kerr-like hole. This is because these methods are sensitive to different components of the metric. We can in this way probe the black hole space-time through the comparison of the estimated spin values; that is, if the black hole space-time is described by the Kerr metric, all of them should coincide.

  12. Gravity driven instability in elastic solid layers.

    PubMed

    Mora, Serge; Phou, Ty; Fromental, Jean-Marc; Pomeau, Yves

    2014-10-24

    We demonstrate the instability of the free surface of a soft elastic solid facing downwards. Experiments are carried out using a gel of constant density ρ, shear modulus μ, put in a rigid cylindrical dish of depth h. When turned upside down, the free surface of the gel undergoes a normal outgoing acceleration g. It remains perfectly flat for ρgh/μ<α* with α*≃6, whereas a steady pattern spontaneously appears in the opposite case. This phenomenon results from the interplay between the gravitational energy and the elastic energy of deformation, which reduces the Rayleigh waves celerity and vanishes it at the threshold. PMID:25379940

  13. A Cosmology with a Gravity Driven Inflation

    NASA Astrophysics Data System (ADS)

    Enginol, Turan B.

    2015-08-01

    The theoretically expected value of Λ is some 10120 orders of magnitude larger than the current observational limits. Since Λ=8πc-2ρΛG, where the vacuum energy density ρΛ is constant, we argue that this discrepancy is due to a large value of G at the beginning which decreases to its present value at reheating. This suggests that initially gravity may have been a strong force. Inflation would then be driven by a large Gi, the variation range of G being similar to Λ. This may be a possible solution for the cosmological constant problem.A graceful exit from inflation occurs when ρr reaches the value ρΛ as radiation is created. Radiation is created through the decay of massive particle species φ with small mean lifetimes τ, which are produced by the fluctuations of the gravity field. We find that radiation energy density ρr increases sharply from the end of inflation at Rf to its maximum value and then decreases as R-3/2 until reheating at t=τ, continuing on to decrease with its natural pattern of R-4.Following Sciama's idea of gravitational induction, an equation of continuity for a possibly non-constant G is obtained using the equations of general relativity. This equation indicates that G is non-constant if radiation and/or matter is created, its solution for G having an inverse dependence on the sum of ρr, ρm, and ρΛ. Accordingly, with the sudden increase of ρr, G and therefore Λ fall off sharply from their values Gi and Λi at Rf, and continue to decrease as R-3/2. From reheating on they attain their constant values of the present epoch, namely G0 and Λ0.Our equation of cosmology, obtained by integrating the expression for the deceleration parameter q, gives two inflection points for R=R(t). The first one occurs at the recovery from inflation when ρr(R)=ρΛ. The second inflection is at R’, where R’

  14. Tornadolike gravity-driven vortex model

    NASA Technical Reports Server (NTRS)

    Deissler, R. G.; Boldman, D. R.

    1974-01-01

    The buoyancy-induced vorticity concentration produced as the fluid in a vortex accelerates vertically was studied. The boiloff from liquid nitrogen, to which a small amount of initial vorticity was added, provided a source of cool, heavy gas in which a concentration of vorticity took place. Condensation streamers made the flow visible. It is shown that the presence of a surface boundary layer is not necessary for the effective concentration of vorticity. A simple theoretical analysis of the phenomenon was also made. A radial contraction of the flow with vertical position and a characteristic hook shape in the top view of the streamlines were observed in both theory and experiment. The vorticity concentration observed may be similar to that which occurs in tornadoes.

  15. Fabrication of gravity-driven microfluidic device

    NASA Astrophysics Data System (ADS)

    Yamada, H.; Yoshida, Y.; Terada, N.; Hagihara, S.; Komatsu, T.; Terasawa, A.

    2008-12-01

    We have studied the micro total analysis system as a blood test. A microfluidic device with a three-pronged microchannel and artificial capillary vessels was fabricated. The microchannel is to transport blood, focus blood cells, and line them up. The vessels are to observe red blood cell deformation. An excimer laser was used to form grooves and so on. Numbers of thermosetting resin film and fluororesin were piled up on a cover glass. A laser fabricated part of the channel at the each film every lamination, and then a three-dimensional structure microchannel was fabricated. The channel sizes have widths of 50-150 μm and depths of 45 μm. Through holes used as artificial capillary vessels are made in the fluororesin having a minimum diameter of 5 μm and a length of 100 μm. As blood and a physiological saline are injected into the microchannel, the device stands upward facing the channel, and blood cells go into the vessels by the force of gravity and sheath flow of the saline. By gravity various groove patterns were made changing the width and length for measurement of blood focusing. Moreover, the red blood cell deformation was observed in the vessels with a microscope.

  16. Gravity-driven dense granular flows

    SciTech Connect

    ERTAS,DENIZ; GREST,GARY S.; HALSEY,THOMAS C.; DEVINE,DOV; SILBERT,LEONARDO E.

    2000-03-29

    The authors report and analyze the results of numerical studies of dense granular flows in two and three dimensions, using both linear damped springs and Hertzian force laws between particles. Chute flow generically produces a constant density profile that satisfies scaling relations suggestive of a Bagnold grain inertia regime. The type for force law has little impact on the behavior of the system. Failure is not initiated at the surface, consistent with the absence of surface flows and different principal stress directions at vs. below the surface.

  17. Gravity driven flows of bubble suspensions.

    NASA Astrophysics Data System (ADS)

    Zenit, Roberto; Koch, Donald L.; Sangani, Ashok K.

    1999-11-01

    Experiments on vertical and inclined channels were performed to study the behavior of a mono-dispersed bubble suspension for which the dual limit of large Reynolds number and small Weber number is satisfied. A uniform stream of 1.5 mm diameter bubbles is produced by a bank of identical capillaries and coalescence is inhibited by addition of salt to the water. Measurements of the liquid velocity and bubble-probe collision rate are obtained with a hot wire anemometer. The gas volume fraction, bubble velocity, velocity variance and chord length are measured using a dual impedance probe. Image analysis is used to quantify the distributions of bubble size and aspect ratio. For vertical channels the bubble velocity is observed to decrease as the bubble concentration increases in accord with the predictions of Spelt and Sangani (1998). The bubble velocity variance arises largely due to bubble-wall and bubble-bubble collisions. For inclined channels, the strength of the shear flow is controlled by the extent of bubble segregation and the effective viscosity of the bubble phase. The measurements are compared with solutions of the averaged equations of motion for a range of gas volume fractions and channel inclination angles.

  18. The average submillimetre properties of Lyman α blobs at z = 3

    NASA Astrophysics Data System (ADS)

    Hine, N. K.; Geach, J. E.; Matsuda, Y.; Lehmer, B. D.; Michałowski, M. J.; Farrah, D.; Spaans, M.; Oliver, S. J.; Smith, D. J. B.; Chapman, S. C.; Jenness, T.; Alexander, D. M.; Robson, I.; van der Werf, P.

    2016-08-01

    Ly α blobs (LABs) offer insight into the complex interface between galaxies and their circumgalactic medium. Whilst some LABs have been found to contain luminous star-forming galaxies and active galactic nuclei that could potentially power the Ly α emission, others appear not to be associated with obvious luminous galaxy counterparts. It has been speculated that LABs may be powered by cold gas streaming on to a central galaxy, providing an opportunity to directly observe the `cold accretion' mode of galaxy growth. Star-forming galaxies in LABs could be dust obscured and therefore detectable only at longer wavelengths. We stack deep Submillimetre Common User Bolometer Array 2 (SCUBA-2) observations of the Small Selected Area 22h field to determine the average 850 μm flux density of 34 LABs. We measure S850 = 0.6 ± 0.2 mJy for all LABs, but stacking the LABs by size indicates that only the largest third (area ≥1794 kpc2) have a mean detection, at 4.5σ, with S850 = 1.4 ± 0.3 mJy. Only two LABs (1 and 18) have individual SCUBA-2 >3.5σ detections at a depth of 1.1 mJy beam-1. We consider two possible mechanisms for powering the LABs and find that central star formation is likely to dominate the emission of Ly α, with cold accretion playing a secondary role.

  19. Edge instability regimes with applications to blob transport and the quasicoherent mode

    SciTech Connect

    Myra, J.R.; D'Ippolito, D.A.

    2005-09-15

    An analytic theory of the resistive X-point (RX) mode in the edge region of a diverted tokamak is developed by employing an outgoing-evanescent wave boundary condition along the field lines. This result is employed to deduce a new categorization of edge instabilities in the presence of X points. A regime diagram shows the relationship of the RX mode to the ideal and conventional resistive ballooning modes. In addition to describing growth rates of linear instabilities, the analysis also yields regimes and scalings for nonlinear convective ''blob'' propagation velocities. The regime diagram and a knowledge of experimental and BOUT code simulation results suggest that the quasicoherent mode seen in the Alcator C-Mod tokamak [M. Greenwald, R. Boivin, P. Bonoli et al., [Phys. Plasmas 6, 1943 (1999)] can be classified as an electromagnetic RX mode. Analytical scalings for the existence of this mode compare well with experimental trends, as does the solution of a model radial eigenvalue problem. Finally, using a finite Larmor radius assumption to eliminate the perpendicular wave number, the instability regime diagram can be converted to an edge phase space diagram. X-point physics adds a new region to this edge parameter space that is postulated to be the enhanced D-alpha regime.

  20. The average submillimetre properties of Lyman α blobs at z= 3

    NASA Astrophysics Data System (ADS)

    Hine, N. K.; Geach, J. E.; Matsuda, Y.; Lehmer, B. D.; Michałowski, M. J.; Farrah, D.; Spaans, M.; Oliver, S. J.; Smith, D. J. B.; Chapman, S. C.; Jenness, T.; Alexander, D. M.; Robson, I.; van der Werf, P.

    2016-08-01

    Ly-alpha blobs (LABs) offer insight into the complex interface between galaxies and their circumgalactic medium. Whilst some LABs have been found to contain luminous star-forming galaxies and active galactic nuclei that could potentially power the Ly-alpha emission, others appear not to be associated with obvious luminous galaxy counterparts. It has been speculated that LABs may be powered by cold gas streaming on to a central galaxy, providing an opportunity to directly observe the `cold accretion' mode of galaxy growth. Star-forming galaxies in LABs could be dust obscured and therefore detectable only at longer wavelengths. We stack deep SCUBA-2 observations of the SSA22 field to determine the average 850um flux density of 34 LABs. We measure S_850 = 0.6 +/- 0.2mJy for all LABs, but stacking the LABs by size indicates that only the largest third (area > 1794 kpc^2) have a mean detection, at 4.5 sigma, with S_850 = 1.4 +/- 0.3mJy. Only two LABs (1 and 18) have individual SCUBA-2 > 3.5 sigma detections at a depth of 1.1mJy/beam. We consider two possible mechanisms for powering the LABs and find that central star formation is likely to dominate the emission of Ly-alpha, with cold accretion playing a secondary role.

  1. Blob-Spring Model for the Dynamics of Ring Polymer in Obstacle Environment

    NASA Astrophysics Data System (ADS)

    Lele, Ashish K.; Iyer, Balaji V. S.; Juvekar, Vinay A.

    2008-07-01

    The dynamical behavior of cyclic macromolecules in a fixed obstacle (FO) environment is very different than the behavior of linear chains in the same topological environment; while the latter relax by a snake-like reptational motion from their chain ends the former can relax only by contour length fluctuations since they are endless. Duke, Obukhov and Rubinstein proposed a scaling model (the DOR model) to interpret the dynamical scaling exponents shown by Monte Carlo simulations of rings in a FO environment. We present a model (blob-spring model) to describe the dynamics of flexible and non-concatenated ring polymer in FO environment based on a theoretical formulation developed for the dynamics of an unentangled fractal polymer. We argue that the perpetual evolution of ring perimeter by the motion of contour segments results in an extra frictional load. Our model predicts self-similar dynamics with scaling exponents for the molecular weight dependence of diffusion coefficient and relaxation times that are in agreement with the scaling model proposed by Obukhov et al.

  2. The average submillimetre properties of Lyman-α Blobs at z = 3

    NASA Astrophysics Data System (ADS)

    Hine, N. K.; Geach, J. E.; Matsuda, Y.; Lehmer, B. D.; Michałowski, M. J.; Farrah, D.; Spaans, M.; Oliver, S. J.; Smith, D. J. B.; Chapman, S. C.; Jenness, T.; Alexander, D. M.; Robson, I.; van der Werf, P.

    2016-06-01

    Lyα blobs (LABs) offer insight into the complex interface between galaxies and their circumgalactic medium. Whilst some LABs have been found to contain luminous star-forming galaxies and active galactic nuclei that could potentially power the Lyα emission, others appear not to be associated with obvious luminous galaxy counterparts. It has been speculated that LABs may be powered by cold gas streaming on to a central galaxy, providing an opportunity to directly observe the `cold accretion' mode of galaxy growth. Star-forming galaxies in LABs could be dust obscured and therefore detectable only at longer wavelengths. We stack deep SCUBA-2 observations of the SSA22 field to determine the average 850μm flux density of 34 LABs. We measure S850 = 0.6±0.2mJy for all LABs, but stacking the LABs by size indicates that only the largest third (area ≥ 1794 kpc2) have a mean detection, at 4.5σ, with S850 = 1.4±0.3mJy. Only two LABs (1 and 18) have individual SCUBA-2 >3.5σ detections at a depth of 1.1mJy beam-1. We consider two possible mechanisms for powering the LABs and find that central star formation is likely to dominate the emission of Lyα, with cold accretion playing a secondary role.

  3. Three dimensional numerical simulation of the April 2000 CME event with a magnetized plasma blob model

    NASA Astrophysics Data System (ADS)

    Shen, Fang

    A three-dimensional time-dependent, numerical magnetohydrodynamic (MHD) model, with the asynchronous and parallel time-marching method is used to investigate the propagation of coronal mass ejections (CMEs) in the nonhomogenous background solar wind flow. The solar wind background with a self-consistent source surface structures as initial-boundary conditions is first presented, from the source surface of 2.5 Rs to the Earth's orbit (215 Rs) and beyond. The CMEs are simulated by means of a very simple flux rope model: a high density and high velocity magnetized plasma blob is superposed on a background steady state solar wind model with an initial velocity and launch direction. The dynamical interaction of a CME with the background solar wind flow between 2.5 and 220 Rs is investigated. We have chosen the well-defined halo-CME event of 4-6 April 2000 as a test case. In this validation study, we find that this 3D MHD model, with the asynchronous and parallel time-marching method, the self-consistent source surface and the simple flux rope model, provides a relatively satisfactory comparison with the ACE spacecraft observations at L1 point.

  4. The Blob, the Very Rare Massive Star and the Two Populations

    NASA Astrophysics Data System (ADS)

    2005-04-01

    young one, containing very massive stars, and an older one. Star numbered 17 is the main component of the Sk -71 51 cluster. From the unique images obtained and reproduced as ESO PR Photo 12b/05, the astronomers could study in great depth the properties of the 2341 stars lying towards the N214C region. This was done by putting them in a so-called colour-magnitude diagram, where the abscissa is the colour (representative of the temperature of the object) and the ordinate the magnitude (related to the intrinsic brightness). Plotting the temperature of stars against their intrinsic brightness reveals a typical distribution that reflects their different evolutionary stages. Two main stellar populations show up in this particular diagram (ESO PR Photo 12d/05): a main sequence, that is, stars that like the Sun are still centrally burning their hydrogen, and an evolved population. The main sequence is made up of stars with initial masses from roughly 2-4 to about 80 solar masses. The stars that follow the red line on ESO PR Photo 12d/05 are main sequence stars still very young, with an estimated age of about 1 million years only. The evolved population is mainly composed of much older and lower mass stars, having an age of 1,000 million years. From their work, the astronomers classified several massive O and B stars, which are associated with the H II region and therefore contribute to its ionisation. A Blob of Ionised Gas ESO PR Photo 12e/05 ESO PR Photo 12e/05 The Nebular Blob in N214C [Preview - JPEG: 400 x 455 pix - 182k] [Normal - JPEG: 800 x 909 pix - 682k] [Full Res - JPEG: 1228 x 1395 pix - 1.7M] Caption: ESO PR Photo 12e/05 zooms-in on the nebular blob lying ~ 60" (50 light-years) north of the Sk-71 51 cluster. The image is based on individual exposures taken through narrow-band filters around H-alpha (red), [O III] (green) and H-beta (blue). The field size is 104" x 101" on the sky, corresponding to roughly 85 by 82 light years. North is up and east to the left. A

  5. Nature of Axial Tail Instability and Bubble-Blob Formation in Near-Earth Plasma Sheet*

    NASA Astrophysics Data System (ADS)

    Zhu, P.; Raeder, J.; Hegna, C. C.; Sovinec, C. R.

    2011-12-01

    Previous global MHD simulations of substorm events have identified the dynamic presence of an axial tail instability with dawn-dusk symmetry in the near-Earth plasma sheet as a major cause of the initial loss of MHD equilibrium on closed field lines prior to the subsequent magnetic reconnection and substorm expansion onset processes [Raeder et al. 2010; Siscoe et al. 2009]. In this work, energy principle analysis indicates that a two-dimensional thin current sheet configuration in the magnetotail is typically stable to the axial mode within the framework of ideal MHD model. Linear resistive MHD calculations find axial tail instabilities on closed field lines in the generalized Harris sheet configurations. The properties of these instabilities are similar to the axial tail modes observed in the global MHD simulations. The axial tail mode is unstable in regimes of low Lundquist number and regions with small normal component of magnetic field. Mode growth and structure show both similarities and differences in comparison to the linear resistive tearing mode of a one-dimensional Harris sheet. Unlike the conventional tearing mode of Harris sheet, the linear axial tail instability does not involve any reconnection process. Instead, the nature of the mode is dominantly an interchange or slippage process among neighboring flux tubes as facilitated by dissipations such as resistivity. The formation of bubble-blob pairs in pressure and entropy distributions in the near-Earth plasma sheet is shown to be a natural component as well as consequence of this axial instability process. *Supported by NSF grants AGS-0902360 and PHY-0821899. REFERENCES: Raeder, J., P. Zhu, Y. Ge, and G. Siscoe (2010), Open Geospace General Circulation Model simulation of a substorm: Axial tail instability and ballooning mode preceding substorm onset, J. Geophys. Res., 115, A00I16, doi:10.1029/2010JA015876. Siscoe, G. L., M. M. Kuznetsova, and J. Raeder (2009), Search for an onset mechanism that

  6. Cross-field motion of plasma blob-filaments and related particle flux in an open magnetic field line configuration on QUEST

    NASA Astrophysics Data System (ADS)

    Liu, H. Q.; Hanada, K.; Nishino, N.; Ogata, R.; Ishiguro, M.; Gao, X.; Zushi, H.; Nakamura, K.; Fujisawa, A.; Idei, H.; Hasegawa, M.; Quest Group

    2013-07-01

    Blob-filaments have been observed by combined measurement with a fast camera and a movable Langmuir probe in an open magnetic field line configuration of electron cyclotron resonance (ECR) heating plasma in QUEST. Blob-filaments extended along field lines do correspond to over-dense plasma structures and propagated across the field lines to the outer wall. The radial velocity of the blob structure, Vb, was obtained by three methods and was dominantly driven by the E × B force. The radial velocity, size of the blob showed good agreements with the results obtained by sheath-connected interchange theoretical model. Vb corresponds to roughly 0.02-0.07 of the local sound speed (Cs) in QUEST. The higher moments (skewness S and kurtosis K) representing the shape of PDF of density fluctuation are studied. Their least squares fitting with quadratic polynomial is K = (1.60 ± 0.27)S2 - (0.46 ± 0.20). The larger blob structures, occurring only 10% of the time, can carry more than 60% loss of the entire radial particle flux.

  7. Capillary hysteresis in the pore space of a packing of spheres measured by the movement of blobs

    SciTech Connect

    Mason, G.; Yadav, G.D.

    1983-09-01

    The effect of the flow of surrounding liquid on the initial movement of a liquid blob in a packing of spheres was used to test the hypothesis that the capillary meniscus radius of a pore when filling is the same as the largest meniscus radius of the same pore when emptying. The agreement between experiment and theory confirmed this hypothesis and indicated that the multiple interconnections between the pores are instrumental in developing the capillary hysteresis exhibited by an assembly of pores. 12 references.

  8. Pinpointing the molecular gas within an Lyα blob at z ∼ 2.7

    SciTech Connect

    Yang, Yujin; Bertoldi, Frank; Bădescu, Toma; Walter, Fabian; Decarli, Roberto; Weiss, Axel; Dey, Arjun; Prescott, Moire K. M.

    2014-04-01

    We present IRAM Plateau de Bure Interferometer observations of the CO(3-2) and CO(5-4) line transitions from an Lyα blob at z ∼ 2.7 in order to investigate the gas kinematics, determine the location of the dominant energy source, and study the physical conditions of the molecular gas. CO line and dust continuum emissions are detected at the location of a strong MIPS source that is offset by ∼1.''5 from the Lyα peak. Neither of these emission components is resolved with the 1.''7 beam, showing that the gas and dust are confined to within ∼7 kpc from this galaxy. No millimeter source is found at the location of the Lyα peak, ruling out a central compact source of star formation as the power source for the Lyα emission. Combined with a spatially resolved spectrum of Lyα and He II, we constrain the kinematics of the extended gas using the CO emission as a tracer of the systemic redshift. Near the MIPS source, the Lyα profile is symmetric, and its line center agrees with that of the CO line, implying that there are no significant bulk flows and that the photo-ionization from the MIPS source might be the dominant source of the Lyα emission. In the region near the Lyα peak, the gas is slowly receding (∼100 km s{sup –1}) with respect to the MIPS source, thus making the hyper-/superwind hypothesis unlikely. We find a sub-thermal line ratio between two CO transitions, I {sub CO(5-4)}/I {sub CO(3-2)} = 0.97 ± 0.21. This line ratio is lower than the average values found in high-z submillimeter galaxies and QSOs but is consistent with the value found in the Galactic center, suggesting that there is a large reservoir of low-density molecular gas that is spread over the MIPS source and its vicinity.

  9. Eta Carinae: Linelist for the Emission Spectrum of the Weigelt Blobs in the 1700-10400Angstrom Wavelength Region

    NASA Technical Reports Server (NTRS)

    Zethson, T.; Johansson, S.; Hartman, H.; Gull, T. R.

    2011-01-01

    Aims. We present line identifications in the 1700 to 10400A region for the Weigelt Blobs B and D, located 0.1 to 0.3" NNW of Eta Carinae. The aim of this work is to characterize the behavior of these luminous, dense gas condensations in response to the broad maximum and short minimum states of Eta Carinae during its 5.54-year spectroscopic period. Methods. The observations were carried out during March 1998, the minimum spectrum, and in February 1999, early maximum spectrum, with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) from 1640 to 10400A using the 52"x0.1" aperture centered on Eta Carinae at position angle -28 degrees. Extractions of the reduced spectrum centered on Weigelt B and D, 0.28: in length along the slit, were used to identify the narrow, nebular emission lines, measure their wavelengths and estimate their fluxes. Results. A linelist of 1500 lines is presented for the maximum and minimum states of combined Weigelt blobs B and D. The spectra are dominated by emission lines from the iron-group elements, but include lines from lighter elements. They include parity permitted and forbidden lines. A number of lines are fluorescent lines pumped by H Ly alpha. Other lines show anomalous excitation.

  10. Lyman-alpha observations of Comet Kohoutek 1973 XII with Copernicus

    NASA Technical Reports Server (NTRS)

    Drake, J. F.; Jenkins, E. B.; Bertaux, J. L.; Festou, M.; Keller, H. U.

    1976-01-01

    Comet Kohoutek 1973 XII was observed with a telescope-spectrometer on the Copernicus satellite on six occasions over a 1-month period starting on January 29, 1974. Positive detection of the cometary Ly-alpha emission profile was obtained on January 29 and February 2. Earlier observations of the geocoronal Ly-alpha emission profile allowed an instrumental intensity calibration and confirmation of the computed instrumental profile for an extended source at the Ly-alpha wavelength. After allowing for broadening by the instrument, a hydrogen-outflow velocity of about 10.6 km/s is derived from the width of the Ly-alpha emission on January 29. The intensity calibration combined with an appropriate cometary model led to cometary water-production rates for January 29 and February 2. Only upper limits were obtained for Ly-alpha on and after February 14. Searches for OH and D led to negative results.

  11. Lyman-alpha observations in the vicinity of Saturn with Copernicus

    NASA Technical Reports Server (NTRS)

    Barker, E.; Cazes, S.; Emerich, C.; Vidal-Madjar, A.; Owen, T.

    1980-01-01

    For the first time, high-resolution Ly-alpha observations of the Saturn vicinity were completed with the Princeton spectrometer on board the Copernicus satellite. They showed that near a minimum solar activity the emissions related to several sources are 250 + or - 50 rayleighs for the interplanetary medium in a near-downwind direction, less than 100 rayleighs for the rings, 200 + or - 100 rayleighs for a torus linked to the Titan orbit, and 1400 + or - 450 rayleighs for the disk of Saturn. These results induce some constraints through the corresponding theoretical evaluations: the B ring as the primary source of the atoms for the ring emissions; an efficient production mechanism for hydrogen atoms in the Titan torus; and a slightly larger eddy diffusion coefficient in the Saturn atmosphere than in the Jupiter atmosphere near solar minimum.

  12. A search for Lyman-alpha emission in beta Lyrae from Copernicus

    NASA Technical Reports Server (NTRS)

    Kondo, Y.; Mccluskey, G. E., Jr.

    1974-01-01

    High-resolution (0.2 A) spectrophotometric observations of the complex eclipsing binary beta Lyrae were obtained with the Princeton Telescope Spectrometer on the Copernicus satellite. We discuss the search for L-alpha emission in beta Lyrae and compare the Copernicus results with the OAO-2 observations of the same binary system. The possible L-alpha emission features observed from OAO-2 are identified as blends of the emission lines of other elements in the vicinity of L-alpha.

  13. 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.

  14. 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.

  15. Lyman-Alpha Absorption at Low Redshifts and Hot Gas in Galactic Haloes

    NASA Astrophysics Data System (ADS)

    Mo, H. J.

    1994-08-01

    Motivated by the recent observation of Lanzetta et al. that most luminous galaxies at low redshifts produce Lyα absorptions at impact parameter l <~ 160 h^-1^ kpc, we propose that these absorbers are clouds confined by the pressure of ambient hot gas in galactic haloes. We determine the properties of this hot gas and of the absorption systems on the basis of observational and theoretical constraints. The absorbing clouds need to be replenished on a time-scale of about one orbital time (~10^9^ yr) in the galactic halo. The pressure and temperature of the gas at radius r~100 kpc are P = (10-100) cm^-3^ K and T = 10^5.5-6.5^ K. The model requires that about 10 per cent of the gas in low-redshift galactic haloes be in the hot phase. Such gas in galactic haloes emits X-rays with a bolometric luminosity of the order of 10^37-40^1 erg s^-1^. The likelihood that such gas exists in current models of galaxy formation is discussed.

  16. Are Pressure-Confined Clouds in Galactic Halos Possible for a Model of Lyman Alpha Clouds?

    NASA Astrophysics Data System (ADS)

    Miyahata, K.; Ikeuchi, S.

    Lanzetta et al (1995) found that most luminous galaxies at low redshifts produce Ly alpha absorptions at the mean impact parameter ~160h-1 kpc. Motivated by this observation, we propose the two-component protogalaxy model as a model for the Ly alpha cloud besed upon the previous work (MI 1995). In our model, the Ly alpha clouds are supposed to be stable cold clouds confined by the pressure of ambient hot gas in galactic halo. We determine the properties of these cold clouds and hot gas on the basis of theoretical and observational constraints. Especially, we take into account the stability of cold cloud in the galactic halo in addition to the general stability conditions in a two-component medium, and compare the derived quantities of Ly alpha cloud both cases in galactic halo and in intergalactic medium. We conclude that the condition that cloud is stable against both evaporation and tidal destruction by a hot galactic halo is very severe. As a result, at z ~0.5, it is concluded that a pressure-confined, stable spherical Ly alpha cloud of typical column density NHI = 1014 cm-2 cannot survive in the galactic halo, although much higher column density clouds of NHI = 1017 cm-2 can do there. We discuss how our result constraints an alternative model for a Ly alpha cloud which associates with galaxy observed by Lanzetta et.al.

  17. Hydrogen cells as narrowband geo-coronal Lyman-alpha rejection filters for astrophysical photometry

    NASA Astrophysics Data System (ADS)

    Redwine, Keith; McCandliss, Stephan R.; Fleming, Brian T.; Pelton, Russell

    2013-09-01

    The Johns Hopkins University rocket group is seeking to develop a hydrogen absorption cell to act as narrowband H I Lyα rejection filters for ultraviolet solar blind imaging detectors. A heated tungsten filament in the cell produces free atomic hydrogen by dissociation of molecular hydrogen contained in the cell. This creates a gas that is optically thick to the Lyα , effectively filtering out incident geo-coronal Lyα emission. This suppression of geo-coronal light will in principle make possible imaging observations of astrophysical sources into the far-UV below 1200 Å, down to the lithium-fluoride transmission edge near 1040Å. The flux attenuation of a hydrogen cell has been measured in a vacuum monochrometer testbed. The goal is to produce a usable hydrogen cell design that can be easily mounted on a detector for photometric observations of astronomical sources in the far-UV.

  18. Self-regulating galaxy formation. Part 1: HII disk and Lyman alpha pressure

    NASA Technical Reports Server (NTRS)

    Cox, D. P.

    1983-01-01

    Assuming a simple but physically based prototype for behavior of interstellar material during formation of a disk galaxy, coupled with the lowest order description of infall, a scenario is developed for self-regulated disk galaxy formation. Radiation pressure, particularly that of Lyman depha (from fluorescence conversion Lyman continuum), is an essential component, maintaining an inflated disk and stopping infall when only a small fraction of the overall perturbation has joined the disk. The resulting galaxies consist of a two dimensional family whose typical scales and surface density are expressable in terms of fundamental constants. The model leads naturally to galaxies with a rich circumgalactic environment and flat rotation curves (but is weak in its analysis of the subsequent evolution of halo material).

  19. Toward unbiased determination of the redshift evolution of Lyman-alpha forest clouds

    NASA Technical Reports Server (NTRS)

    Lu, Limin; Zuo, Lin

    1994-01-01

    The possibility of using D(sub A), the mean depression of a quasar spectrum due to Ly-alpha forest absorption, to study the number density evolution of the Ly-alpha forest clouds is examined in some detail. Current D(sub A) measurements are made against a continuum that is a power-law extrapolation from the continuum longward of Ly-alpha emission. Compared to the line-counting approach, the D(sub A)-method has the advantage that the D(sub A) measurements are not affected by line-blending effects. However, we find using low-redshift quasar spectra obtained with the Hubble Space Telescope (HST), where the true continuum in the Ly-alpha forest can be estimated fairly reliably because of the much lower density of the Ly-alpha forest lines, that the extrapolated continuum often deviates systematically from the true continuum in the forest region. Such systematic continuum errors introduce large errors in the D(sub A) measurements. The current D(sub A) measurements may also be significantly biased by the possible presence of the Gunn-Peterson absorption. We propose a modification to the existing D(sub A)-method, namely, to measure D(sub A) against a locally established continuum in the Ly-alpha forest. Under conditions that the quasar spectrum has good resolution and S/N to allow for a reliable estimate of the local continuum in the Ly-alpha forest, the modified D(sub A) measurements should be largely free of the systematic uncertainties suffered by the existing D(sub A) measurements. We also introduce a formalism based on the work of Zuo (1993) to simplify the application of the D(sub A)-method(s) to real data. We discuss the merits and limitations of the modified D(sub A)-method, and conclude that it is a useful alternative. Our findings that the extrapolated continuum from longward of Ly-alpha emission often deviates systematically from the true continuum in the Ly-alpha forest present a major problem in the study of the Gunn-Peterson absorption.

  20. Lyman Alpha Emitting Galaxies at 2 < z < 3: Towards a Calibrated Probe of Dark Energy

    SciTech Connect

    Caryl Gronwall

    2012-12-03

    The goal of this project was to establish the physical properties of Ly{alpha} emitting galaxies from redshifts of 2 to 3 in order to better calibrate the use of LAEs as probes of the large scale structure of the universe for upcoming dark energy experiments, such as the Hobby Eberly Telescope Dark Energy Experiment (HETDEX). We have obtained narrow-band imaging of the Extended Chandra Deep Field South (ECDF-S) in two different narrow-band filters centered at Ly{alpha} at z=2.1 and 3.1. The resulting of samples of LAEs were used to determine the LAE luminosity function, equivalent width distribution and clustering properties (bias) of LAEs at these redshifts. While the results from the ECDF-S appear robust, they are based on a single field. To explore the effects of cosmic variance and galaxy environment on the physical properties of LAEs, we have also obtained narrow-band data at both redshifts (z = 2:1 and 3:1) in three additional fields (SDSS 1030+-05, the Extended Hubble Deep Field South, and CW 1255+01). The narrow-band imaging data has been reduced and LAE catalogs are being generated. We have calculated preliminary luminosity functions, equivalent width distributions, and clustering properties. We have also obtained follow-up spectroscopy in the optical (using VLT/FORS) and in the near-infrared (using Magellan/MMIRS). Since individual LAEs have too little S/N to enable meaningful fits for stellar population parameters, our previous work has analyzed stacked Spectral Energy Distributions (SEDs). SED fitting was performed on several subsets of LAEs selected by their rest-UV luminosity, UV spectral slope, Ly alpha luminosity, Equivalent Width, or rest-optical (IRAC) luminosity.

  1. Solar cycle study of interplanetary Lyman-alpha variations - Pioneer Venus Orbiter sky background results

    NASA Technical Reports Server (NTRS)

    Ajello, J. M.; Stewart, A. I.; Thomas, G. E.; Graps, A.

    1987-01-01

    PVO observations of the interplanetary Ly-alpha (IPL) background, obtained over an entire solar cycle (SC) from 1979 to 1985, are compiled and analyzed statistically, along with data from other instruments and earlier solar cycles. The results are presented in extensive tables and graphs and characterized in detail. Findings reported include SC variation of 1.8 for the longitudinally averaged IPL intensity (in agreement with the variation of the 27-d disk-averaged integrated solar Ly-alpha flux), yearly averaged ecliptic H-atom lifetime at 1 AU equal to 1.0 Ms at solar minimum and 1.5 Ms at solar maximum, interplanetary H density equal to 0.07 + or - 0.01/cu cm, and interplanetary H/He within the heliopause but far from the sun of 7 + or - 3.

  2. Latitudinal dependence of solar proton flux derived from interplanetary Lyman alpha emission

    NASA Astrophysics Data System (ADS)

    Nakagawa, H.; Fukunishi, H.; Watanabe, S.; Takahashi, Y.; Taguchi, M.; Bertaux, J.; Quemerais, E.; Lallement, R.

    2004-12-01

    There is a uniform flow of the interplanetary hydrogen in the solar system. The distribution of interplanetary neutral hydrogen is sensitive to solar wind proton flux, which has a latitudinal distribution, because interplanetary neutral hydrogen atoms are mainly ionized through a process of charge-exchange with solar wind protons (contributing to 80% of the total ionization rate). Rucinski et al. [1996] estimated the ionization rate of the interplanetary hydrogen in an average solar activity condition: 6.4±0.14 [10E-7/s] for charge exchange with protons. The most practical technique for determining the latitudinal dependence of the interplanetary hydrogen is observation of resonant backscatter of solar Lyman ƒ¿ emission at 121.6 nm. The interplanetary Lyman ƒ¿ emission has been measured by the ultraviolet imaging spectrometer (UVS) on board the Nozomi spacecraft crusing on its Mars transfer orbit with a periapsis of 1 AU and an apoapsis 1.5 AU from the Sun. The field-of-view of UVS is perpendicular to the spin axis of the spacecraft, which is controlled toward the Earth. The spatial resolution of UVS is 1.41 degrees in a plane perpendicular to the spin axis and 0.29 degrees in a plane including the spin axis. Spatial distributions are obtained from the full sky scanning of UVS with spin and orbital motions of the Nozomi spacecraft. One-year UVS data enable us to construct a full sky image of Lyman ƒ¿ emission. We present the results obtained from Nozomi/UVS data analysis for the period of 1999-2002. From a fitting of model calculations to the observed data, it is confirmed that a latitudinal anisotropy with the higher ionization region at the equator is reduced toward solar maximum. Finally, higher ionization region are found at the poles than at the equator near solar maximum. Basically, this change is produced by variations in the latitudinal dependence of persistent solar wind proton flux. However, proton flux from transient CMEs also affects the distribution of the interplanetary hydrogen. We identify the effect of CMEs on the distribution of interplanetary hydrogen from the analysis of CME data collected by SOHO/LASCO.

  3. Ultraviolet observations of cool stars. VII - Local interstellar hydrogen and deuterium Lyman-alpha

    NASA Technical Reports Server (NTRS)

    Mcclintock, W.; Henry, R. C.; Linsky, J. L.; Moos, H. W.

    1978-01-01

    High-resolution Copernicus spectra of Epsilon Eri and Epsilon Ind containing interstellar hydrogen and deuterium L-alpha absorption lines are presented, reduced, and analyzed. Parameters of the interstellar hydrogen and deuterium toward these two stars are derived independently, without any assumptions concerning the D/H ratio. Copernicus spectra of Alpha Aur and Alpha Cen A are reanalyzed, and limits on the D/H number-density ratio consistent with the data for all four stars are considered. A comparison of the present estimates for the parameters of the local interstellar medium with those obtained by other techniques shows that there is no compelling evidence for significant variations in the hydrogen density and D/H ratio in the local interstellar medium. On this basis the hypothesis of an approaching local interstellar cloud proposed by Vidal-Madjar et al. (1978) is rejected

  4. On the evolution of Lyman alpha clouds based upon the Minihalo model

    NASA Technical Reports Server (NTRS)

    Murakami, Izumi; Ikeuchi, Satoru

    1993-01-01

    Intergalactic clouds confined by the gravity of cold dark matter (CDM), the so called mini-halo, is considered. Assuming a simplified evolution law of UV flux and mass function of gas clouds, number density evolution and H1 column density distribution can be reproduced by mini-halo model. Considering interaction between supersonic flow and a mini-halo, spatial correlation and the proximity effect of Ly-alpha forest can be investigated.

  5. Low redshift Lyman alpha absorption lines and the dark matter halos of disk galaxies

    NASA Technical Reports Server (NTRS)

    Maloney, Philip

    1993-01-01

    Recent observations using the Hubble Space Telescope of the z = 0.156 QSO 3C 273 have discovered a surprisingly large number of Ly-alpha absorption lines. In particular, Morris et al. found 9 certain and 7 possible Ly-alpha lines with equivalent widths above 25 mA. This is much larger (by a factor of 5-10) than the number expected from extrapolation of the high-redshift behavior of the Ly-alpha forest. Within the context of pressure-confined models for the Ly-alpha clouds, this behavior can be understood if the ionizing background declines sharply between z is approximately 2 and z is approximately 0. However, this requires that the ionizing photon flux drop as rapidly as the QSO volume emissivity; moreover, the absorbers must have a space density n(sub O) is approximately 2.6(N/10)h/((D/100 kpc)(sup 2)) Mpc(sup -3) where D is the present-day diameter of the absorbers. It is somewhat surprising that such necessarily fragile objects could have survived in such numbers to the present day. It is shown that it is plausible that the atomic hydrogen extents of spiral and irregular galaxies are large enough to produce the observed number of Ly-alpha absorption lines toward 3C 273, and that the neutral column densities and doppler b-values expected under these conditions fall in the range found by Morris et al. (1991).

  6. Neutrino masses and cosmology with Lyman-alpha forest power spectrum

    NASA Astrophysics Data System (ADS)

    Palanque-Delabrouille, Nathalie; Yèche, Christophe; Baur, Julien; Magneville, Christophe; Rossi, Graziano; Lesgourgues, Julien; Borde, Arnaud; Burtin, Etienne; LeGoff, Jean-Marc; Rich, James; Viel, Matteo; Weinberg, David

    2015-11-01

    We present constraints on neutrino masses, the primordial fluctuation spectrum from inflation, and other parameters of the ΛCDM model, using the one-dimensional Lyα-forest power spectrum measured by [1] from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III), complemented by Planck 2015 cosmic microwave background (CMB) data and other cosmological probes. This paper improves on the previous analysis by [2] by using a more powerful set of calibrating hydrodynamical simulations that reduces uncertainties associated with resolution and box size, by adopting a more flexible set of nuisance parameters for describing the evolution of the intergalactic medium, by including additional freedom to account for systematic uncertainties, and by using Planck 2015 constraints in place of Planck 2013. Fitting Lyα data alone leads to cosmological parameters in excellent agreement with the values derived independently from CMB data, except for a weak tension on the scalar index ns. Combining BOSS Lyα with Planck CMB constrains the sum of neutrino masses to ∑ mν < 0.12 eV (95% C.L.) including all identified systematic uncertainties, tighter than our previous limit (0.15 eV) and more robust. Adding Lyα data to CMB data reduces the uncertainties on the optical depth to reionization τ, through the correlation of τ with σ8. Similarly, correlations between cosmological parameters help in constraining the tensor-to-scalar ratio of primordial fluctuations r. The tension on ns can be accommodated by allowing for a running dns/d ln k. Allowing running as a free parameter in the fits does not change the limit on ∑ mν. We discuss possible interpretations of these results in the context of slow-roll inflation.

  7. C, N, O abundances in the most metal-poor damped Lyman alpha systems

    NASA Astrophysics Data System (ADS)

    Pettini, Max; Zych, Berkeley J.; Steidel, Charles C.; Chaffee, Fred H.

    2008-04-01

    This study focuses on some of the most metal-poor damped Lyα (DLA) absorbers known in the spectra of high-redshift QSOs, using new and archival observations obtained with ultraviolet-sensitive echelle spectrographs on the Keck and VLT telescopes. The weakness and simple velocity structure of the absorption lines in these systems allow us to measure the abundances of several elements, and in particular those of C, N and O, a group that is difficult to study in DLAs of more typical metallicities. We find that when the oxygen abundance is less than ~1/100 of solar, the C/O ratio in high-redshift DLAs and sub-DLAs matches that of halo stars of similar metallicity and shows higher values than expected from galactic chemical evolution models based on conventional stellar yields. Furthermore, there are indications that at these low metallicities the N/O ratio may also be above simple expectations and may exhibit a minimum value, as proposed by Centurión and her collaborators in 2003. Both results can be interpreted as evidence for enhanced production of C and N by massive stars in the first few episodes of star formation, in our Galaxy and in the distant protogalaxies seen as QSO absorbers. The higher stellar yields implied may have an origin in stellar rotation which promotes mixing in the stars' interiors, as considered in some recent model calculations. We briefly discuss the relevance of these results to current ideas on the origin of metals in the intergalactic medium and the universality of the stellar initial mass function. Based in part on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation. Based in part on UVES observations made with the European Southern Observatory VLT/Kueyen Telescope at Paranal, Chile, obtained in programme 078.A-0185(A) and from the public data archive. E-mail: pettini@ast.cam.ac.uk

  8. The Size and Nature of Lyman- alpha Forest Clouds Probed by QSO Pairs and Groups

    NASA Astrophysics Data System (ADS)

    Fang, Yihu; Duncan, Robert C.; Crotts, Arlin P. S.; Bechtold, Jill

    1996-05-01

    Closely separated QSO pairs and groups make it possible to probe the size, geometry, and spatial clustering of Lyα forest clouds. Recent spectroscopic observations of Q1343 + 2640A/B give evidence that the transverse sizes of Lyα clouds are very large at redshifts ~2 (as reported by Bechtold et al. in 1994). In this paper, we describe a robust Bayesian statistical method for determining cloud sizes in spherical and in thin disk geometries, apply this method to the available data, and discuss implications of our results for models of Lyα clouds. Under the assumption of a population of uniform-sized and unclustered Lyα clouds, the data from Q1343 + 2640A/B give a 99% confidence lower and upper bounds 61 < R < 533 h^-1^ kpc on the radius of spherical clouds at z ~ 1.8, with a median value of 149 h^-1^ kpc [({OMEGA}_0_, {LAMBDA}_0_) = (1,0), and h = H_0_/100 km s^-1^ Mpc^-1^]. The baryonic mass of such large clouds, if they are roughly homogeneous and quasi-spherical, is comparable to the baryonic mass of dwarf irregular galaxies. Their cosmic overdensity is close to the turnaround density but generally below the virialization density, which suggests a population of gravitationally bound but unvirialized protogalactic objects at z ~ 2. The comoving volume density of these clouds is similar to that of the faint blue galaxies (FBGs) at the limiting magnitude B~26-27, if these FBGs are distributed approximately over the range of redshift from 0.8 to 2. The timescale for dynamical collapse of overdensities like these clouds is also comparable to the cosmic time difference between z ~ 2 and z ~ 1. Both populations of objects show similar weak clustering in space. All this evidence suggests a possible identification of Lyα clouds as the collapsing progenitors of the FBGs at z~1. We also investigate the other closely separated QSO pairs with published high-quality spectra: Q0307- 1931/0307-1932, Q0107-0232/0107- 0235, and the triplet of Q1623 +268. Imposing a uniform W_0_ >= 0.4 A counting threshold on all the line lists, we find a trend of larger inferred cloud radius with larger proper separation of QSO pairs, significant at the 3.4 σ level. This indicates that the idealization of unclustered, uniform-sized spherical clouds does not accurately describe the Lyα cloud population. Present data are insufficient to resolve with confidence whether this effect is due to clustering, filamentary shape, or nonuniform cloud size. There is a suggestion, however, that at low redshifts a residual population of larger clouds remaIns.

  9. Implications of Lyman-alpha equivalent widths in active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Shields, Joseph C.; Ferland, Gary J.

    1993-01-01

    Results of photoionization calculations that examine the sensitivity of Ly-alpha emission to parameters describing the broadline clouds and incident radiation field are reported. The case of the Seyfert I galaxy NGC 5548 is considered, and good consistency is found with observed properties of the Ly-alpha zone for a cloud density of about 10 exp 11/cu cm and ratio of ionizing photon to hydrogen density near 0.2. Estimation of the cloud covering factor depends on the extrapolation of the EUV continuum. EUV cutoffs at 20 and 60 eV correspond to a range of covering factors between 0.8 and 0.5, which is larger than typically assumed in the past for luminous Seyferts. Equivalent width observations of Fairall 9 show that its continuum cannot be as soft as suggested by previous line ratio analyses and imply that its EUV continuum persists to 20 eV or more before cutting off. A method by which variability measurements can be combined with the present calculations to measure the distances to AGN, and hence the Hubble constant, is outlined.

  10. Monte Carlo treatment of Lyman-alpha. II - Radiation in a spherical atmosphere

    NASA Technical Reports Server (NTRS)

    Modali, S. B.; Brandt, J. C.; Kastner, S. O.

    1975-01-01

    Intensity and state of polarization of solar L-alpha photons as they diffuse through an inhomogeneous, spherically symmetric, isothermal geocorona are theoretically determined. The fine structure of L-alpha and Doppler redistribution of frequencies are taken into account. The calculation use the Monte Carlo technique involving Stokes vectors. Comparison of the results with OGO-4 and OSO-4 observed intensities at an altitude of 650 km shows good agreement. Calculations of the polarization versus solar zenith angle show a residual polarization at large zenith angles which is mainly due to multiply scattered photons.

  11. LRO Lyman Alpha Mapping Project (LAMP) Far-UV Maps: A New View of the Moon

    NASA Astrophysics Data System (ADS)

    Retherford, K. D.; Greathouse, T. K.; Gladstone, G. R.; Hendrix, A. R.; Mandt, K. E.; Egan, A. F.; Kaufmann, D. E.; Hayne, P. O.; Stern, S. A.; Parker, J. Wm.; Davis, M. W.; Grava, C.; Hurley, D. M.; Cahill, J. T. S.; Stickle, A. M.; Liu, Y.; Bullock, M. A.; Pryor, W. R.; Feldman, P. D.; Mukherjee, J.; Mokashi, P.; Seifert, C. J.; Versteeg, M. H.

    2016-05-01

    The LRO-LAMP investigation has provided a unique view at far-UV wavelengths, and uses an innovative way to measure surface reflectance within permanently shaded regions in order to constrain the water frost abundance at the surface.

  12. Studying low-redshift universe through observation of Damped Lyman-alpha quasar absorbers

    NASA Astrophysics Data System (ADS)

    Gharanfoli, Soheila

    2009-06-01

    In recent years, an extremely successful method to study galaxy formation and evolution, has been provided by observation of quasar absorbers. Quasar absorbers are systems intercepting our line-of-sight to a given quasar and thus produce a feature in the quasar spectrum, the so-called absorption lines. The Damped Lyman-a (DLA) and sub-Damped Lyman-a (sub-DLA) absorption features in quasar spectra are believed to be produced by intervening galaxies. However, the connection of quasar absorbers to galaxies is not well-understood, since attempts to image the absorbing galaxies have often failed. DLAs and sub-DLAs were originally thought to be the precursors of present day disk galaxies, but there is evidence that they may be dominated by gas-rich, proto-dwarf galaxies representing the basic building blocks of hierarchical growth of structure. While most DLAs appear to be metal-poor, a population of metal-rich absorbers, mostly sub-DLAs, has been discovered in recent spectroscopic studies. It is of great interest to image these metal-rich absorbers, especially with high spatial resolution, to understand the connection between the stellar and interstellar content of the underlying galaxies. This dissertation consists of several projects designed to further our understanding of galaxies and galactic structures associated with intervening quasar absorption lines. Two projects were completed that involved the imaging of 13 DLA/sub-DLA galaxies at z < 1. High angular resolution near-infrared images were obtained, using the Hokupa'a Adaptive Optics system with the QUIRC near-infrared camera on the 8-m Gemini-North telescope, and the Laser Guide Star Adaptive Optics system on the 10-m Keck telescope. Detailed properties of the identified absorber galaxies are described. They are shown to be drawn from a variety of morphological types with a range of luminosities, sizes, and impact parameters. In the other set of projects, follow-up spectroscopy was performed to confirm the spectroscopic redshifts of the candidate absorbers. In addition, optical and near-infrared spectroscopy provide necessary information to understand the luminosities, dust extinction, and star formation rates and thus the nature of these galaxies. Spectroscopy of 5 DLA/sub-DLA galaxies was performed using the 10-m Keck telescope with LRIS spectrograph, and 8-m Gemini- North telescope with the GMOS spectrograph. Several emission lines (e.g., Ha, Hb, [N II], [O II], [O III]) were detected and analyzed, which revealed the redshift, metallicity, dust extinction, and star formation rate of the candidate galaxies.

  13. The two-point correlation function of randomly distributed Lyman alpha clouds

    NASA Technical Reports Server (NTRS)

    Fardal, Mark A.; Shull, J. Michael

    1993-01-01

    It is often assumed that Ly-alpha forest clouds are randomly distributed, intergalactic objects that are highly ionized by the UV background produced by quasars. If these assumptions are true, fluctuations in the UV background should produce a nonzero two point correlation function in the Ly-alpha forest. This effect, which is really just a generalization of the proximity effect, is more significant at high redshift (z is approximately 3-4) because the mean free path for UV photons is smaller there, and the fluctuations correspondingly larger. This effect was studied using both the semi-analytic techniques of Zuo's recent papers and Monte Carlo simulations. The correlation function is expected to have a small yet potentially measurable amplitude that is consistent with current upper limits. Furthermore, the signature of this effect is distinctive because the nonzero correlation function extends over the photon mean free path, which is larger than the expected scale of large-scale structure. Observations or upper limits on this effect could provide information about the source of the ionizing background at high redshifts and the nature of the Ly-alpha forest clouds.

  14. Zn and Cr abundances in damped Lyman alpha systems from the CORALS survey

    NASA Astrophysics Data System (ADS)

    Akerman, C. J.; Ellison, S. L.; Pettini, M.; Steidel, C. C.

    2005-09-01

    We present metal abundances in 15 damped Lyα systems (DLAs) from the Complete Optical and Radio Absorption Line System (CORALS) survey, designed to be free from any biasing effects due to extinction of QSOs by dust in intervening absorbers. It has long been suggested that such biasing may explain differences in metallicity between damped Lyα systems and coeval luminous galaxies, and between model predictions and observations. We use our measured zinc and chromium abundances (combined with those for five more CORALS DLAs from the literature, giving us a very nearly complete sample) to test whether the metallicity and degree of dust depletion in CORALS DLAs are significantly different from those of existing, larger, samples of DLAs drawn from magnitude limited, optical surveys. We find that the column density weighted metallicity of CORALS DLAs, [ <(Zn/H)DLA> ] = -0.88 ± 0.21 in the redshift interval 1.86 < zabs < 3.45, is only marginally higher than that of a control sample from the by Kulkarni et al., [ <(Zn/H)DLA> ] = -1.09 ± 0.10. With the present limited statistics this difference is not highly significant. Furthermore, we find no evidence for increased dust depletions in CORALS DLAs - their [Cr/Zn] ratios conform to the known trend of increasing depletion (decreasing [Cr/Zn]) with increasing metallicity, and we have encountered no cases where Cr is as depleted as in local cold interstellar clouds. These results, when combined with the earlier findings of the CORALS survey reported by Ellison et al. in 2001, make it difficult to invoke a dust-induced bias to explain the generally low level of chemical evolution exhibited by most DLAs. Rather, they indicate that large scale optical QSO surveys give a fair census of the population of high redshift absorbers.

  15. A survey of local interstellar hydrogen from OAO-2 observations of Lyman alpha absorption

    NASA Technical Reports Server (NTRS)

    Savage, B. D.; Jenkins, E. B.

    1972-01-01

    The Wisconsin far ultraviolet spectrometer aboard OAO-2 observed the wavelength region near 1216 A for 69 stars of spectral type B2 or earlier. From the strength of the observed interstellar L sub alpha absorption, atomic hydrogen column densities were derived over distances averaging 300 pc away from the sun. The OAO data were compared to synthetic ultraviolet spectra, originally derived from earlier higher resolution rocket observations, which were computer processed to simulate the effects of absorption by different amounts of hydrogen followed by the instrumental blending.

  16. Effects of the parallel electron dynamics and finite ion temperature on the plasma blob propagation in the scrape-off layer

    SciTech Connect

    Jovanovic, D.; Shukla, P. K.; Pegoraro, F.

    2008-11-15

    A new three-dimensional model for the warm-ion turbulence at the tokamak edge plasma and in the scrape-off layer is proposed, and used to study the dynamics of plasma blobs in the scrape-off layer. The model is based on the nonlinear interchange mode, coupled with the nonlinear resistive drift mode, in the presence of the magnetic curvature drive, the density inhomogeneity, the electron dynamics along the open magnetic field lines, and the electron-ion and electron-neutral collisions. Within the present model, the effect of the sheath resistivity decreases with the distance from the wall, resulting in the bending and the break up of the plasma blob structure. Numerical solutions exhibit the coupling of interchange modes with nonlinear drift modes, causing the collapse of the blob in the lateral direction, followed by a clockwise rotation and radial propagation. The symmetry breaking, caused both by the parallel resistivity and the finite ion temperature, introduces a poloidal component in the plasma blob propagation, while the overall stability properties and the speed are not affected qualitatively.

  17. Astrophysical laser operating in the OI 8446-Åline in the Weigelt blobs of η Carinae

    NASA Astrophysics Data System (ADS)

    Johansson, S.; Letokhov, V. S.

    2005-12-01

    Within the framework of a simple model of photophysical processes in the Weigelt blobs in the vicinity of the luminous blue variable (LBV) star η Carinae, we explain the presence of the fluorescent 8446-Åand forbidden [OI] 6300-Ålines as well as the absence of the allowed OI 7774-Åline in spectra recorded with the Hubble Space Telescope (HST)/STIS instrument (Gull et al.). From atomic data and estimated stellar parameters we demonstrate that there is a population inversion and stimulated emission in the 3p3P-3s3S transition λ8446 due to photoexcitation by accidental resonance (PAR) by H Lyβ radiation.

  18. First systematic search for oxygen-line blobs at high redshift: Uncovering AGN feedback and star formation quenching

    SciTech Connect

    Yuma, Suraphong; Ouchi, Masami; Ono, Yoshiaki; Momose, Rieko; Drake, Alyssa B.; Simpson, Chris; Shimasaku, Kazuhiro; Nakajima, Kimihiko; Akiyama, Masayuki; Mori, Masao; Umemura, Masayuki

    2013-12-10

    We present the first systematic search for extended metal-line [O II] λλ3726, 3729 nebulae, or [O II] blobs (O IIBs), at z = 1.2 using deep narrowband imaging with a survey volume of 1.9 × 10{sup 5} Mpc{sup 3} on the 0.62 deg{sup 2} sky of Subaru-XMM Deep Survey (SXDS) field. We discover a giant O IIB, called 'O IIB 1', with a spatial extent over ∼75 kpc at a spectroscopic redshift of z = 1.18, and also identify a total of 12 O IIBs with a size of >30 kpc. Our optical spectrum of O IIB 1 presents [Ne V] λ3426 line at the 6σ level, indicating that this object harbors an obscured type-2 active galactic nucleus (AGN). The presence of gas outflows in this object is suggested by two marginal detections of Fe II λ2587 absorption and Fe II* λ2613 emission lines both of which are blueshifted at as large as 500-600 km s{sup –1}, indicating that the heating source of O IIB 1 is AGN or associated shock excitation rather than supernovae produced by starbursts. The number density of O IIB 1-type giant blobs is estimated to be ∼5 × 10{sup –6} Mpc{sup –3} at z ∼ 1.2, which is comparable with that of AGNs driving outflow at a similar redshift, suggesting that giant O IIBs are produced only by AGN activity. On the other hand, the number density of small O IIBs, 6 × 10{sup –5} Mpc{sup –3}, compared to that of z ∼ 1 galaxies in the blue cloud in the same M{sub B} range, may imply that 3% of star-forming galaxies at z ∼ 1 are quenching star formation through outflows involving extended [O II] emission.

  19. Three-dimensional MHD simulation of two coronal mass ejections' propagation and interaction using a successive magnetized plasma blobs model

    NASA Astrophysics Data System (ADS)

    Shen, F.; Feng, X. S.; Wang, Yuming; Wu, S. T.; Song, W. B.; Guo, J. P.; Zhou, Y. F.

    2011-09-01

    A three-dimensional (3-D), time-dependent, numerical magnetohydrodynamic (MHD) model is used to investigate the evolution and interaction of two coronal mass ejections (CMEs) in the nonhomogeneous ambient solar wind. The background solar wind is constructed on the basis of the self-consistent source surface with observed line of sight of magnetic field and density from the source surface of 2.5 Rs to Earth's orbit (215 Rs) and beyond. The two successive CMEs occurring on 28 March 2001 and forming a multiple magnetic cloud in interplanetary space are chosen as a test case, in which they are simulated by means of a two high-density, high-velocity, and high-temperature magnetized plasma blobs model, and are successively ejected into the nonhomogeneous background solar wind medium along different initial launch directions. The dynamical propagation and interaction of the two CMEs between 2.5 and 220 Rs are investigated. Our simulation results show that, although the two CMEs are separated by 10 h, the second CME is able to overtake the first one and cause compound interactions and an obvious acceleration of the shock. At the L1 point near Earth the two resultant magnetic clouds in our simulation are consistent with the observations by ACE. In this validation study we find that this 3-D MHD model, with the self-consistent source surface as the initial boundary condition and the magnetized plasma blob as the CME model, is able to reproduce and explain some of the general characters of the multiple magnetic clouds observed by satellite.

  20. Fast variations in the ultraviolet resonance lines of Alpha Camelopardalis (O9.5 Ia) - Evidence for blobs in the wind

    NASA Technical Reports Server (NTRS)

    Lamers, Henry J. G. L. M.; Snow, Theodore P.; De Jager, Cornelis; Langerwerf, A.

    1988-01-01

    The 72 IUE spectra of Alpha Cam and 19 IUE spectra of Kappa Cas, obtained during 72 hours of continuous IUE time in September 1978 were searched for variations in the profiles of the resonance lines of Si IV, C IV, and N V, and the results are discussed. The UV resonance lines in the spectra of Alpha Cam showed variations at the 2 percent level near -1800, -700, and +700 km/s. The first two variations can be explained by absorption components of outward-accelerated blobs or shells with an average acceleration of 1.5 cm/sq s. The characteristics of the blobs and shells are discussed, including the column densities and masses. No variations were found in the spectra of Kappa Cas.

  1. Mean flows and blob velocities in scrape-off layer (SOLT) simulations of an L-mode discharge on Alcator C-Mod

    DOE PAGESBeta

    Russell, D. A.; Myra, J. R.; D'Ippolito, D. A.; LaBombard, B.; Hughes, J. W.; Terry, J. L.; Zweben, S. J.

    2016-06-10

    Two-dimensional scrape-off layer turbulence (SOLT) code simulations are compared with an L-mode discharge on the Alcator C-Mod tokamak [M. Greenwald, et al., Phys. Plasmas 21, 110501 (2014)]. Density and temperature profiles for the simulations were obtained by smoothly fitting Thomson scattering and mirror Langmuir probe (MLP) data from the shot. Simulations differing in turbulence intensity were obtained by varying a dissipation parameter. Mean flow profiles and density fluctuation amplitudes are consistent with those measured by MLP in the experiment and with a Fourier space diagnostic designed to measure poloidal phase velocity. Blob velocities in the simulations were determined from themore » correlation function for density fluctuations, as in the analysis of gas-puff-imaging (GPI) blobs in the experiment. In the simulations, it was found that larger blobs moved poloidally with the ExB flow velocity, vE , in the near-SOL, while smaller fluctuations moved with the group velocity of the dominant linear (interchange) mode, vE + 1/2 vdi, where vdi is the ion diamagnetic drift velocity. Comparisons are made with the measured GPI correlation velocity for the discharge. The saturation mechanisms operative in the simulation of the discharge are also discussed. In conclusion, it is found that neither sheared flow nor pressure gradient modification can be excluded as saturation mechanisms.« less

  2. Mean Flows and Blob Velocities in Scrape-Off Layer (SOLT) Simulations of an L-mode discharge on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Russell, D. A.; Myra, J. R.; D'Ippolito, D. A.; Labombard, B.; Terry, J. L.; Zweben, S. J.

    2015-11-01

    Two-dimensional scrape-off layer turbulence (SOLT) code simulations are compared with an L-mode discharge on Alcator C-Mod. Density and temperature profiles for the simulations were obtained by smoothly fitting Thomson scatter and mirror Langmuir probe (MLP) data from the shot. Simulations differing in turbulence intensity were obtained by varying a dissipation parameter. Mean flow profiles and density fluctuation amplitudes are consistent with those measured by MLP in the experiment. Blob velocities in the simulations were determined from the correlation function for density fluctuations, as in the analysis of gas-puff-imaging (GPI) blobs in the experiment. In the simulations, it was found that larger blobs moved poloidally with the ExB flow velocity, vE , in the near-SOL, while smaller fluctuations moved with the group velocity of the dominant linear (interchange) mode, vE + 1/2 vdi, where vdi is the ion diamagnetic drift velocity. Comparisons are made with the measured GPI correlation velocity. The saturation mechanisms operative in the simulation of the discharge are explored. Work supported by the U.S. Department of Energy Office of Science, Office of Fusion Energy Sciences, under Agreement DE-FC02-99ER54512, Contract DE-AC02-09CH11466, and Princeton Plasma Physics Laboratory Subcontract S013429-U.

  3. Mean flows and blob velocities in scrape-off layer (SOLT) simulations of an L-mode discharge on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Russell, D. A.; Myra, J. R.; D'Ippolito, D. A.; LaBombard, B.; Hughes, J. W.; Terry, J. L.; Zweben, S. J.

    2016-06-01

    Two-dimensional scrape-off layer turbulence (SOLT) code simulations are compared with an L-mode discharge on the Alcator C-Mod tokamak [Greenwald et al., Phys. Plasmas 21, 110501 (2014)]. Density and temperature profiles for the simulations were obtained by smoothly fitting Thomson scattering and mirror Langmuir probe (MLP) data from the shot. Simulations differing in turbulence intensity were obtained by varying a dissipation parameter. Mean flow profiles and density fluctuation amplitudes are consistent with those measured by MLP in the experiment and with a Fourier space diagnostic designed to measure poloidal phase velocity. Blob velocities in the simulations were determined from the correlation function for density fluctuations, as in the analysis of gas-puff-imaging (GPI) blobs in the experiment. In the simulations, it was found that larger blobs moved poloidally with the E × B flow velocity, vE, in the near-SOL, while smaller fluctuations moved with the group velocity of the dominant linear (interchange) mode, vE + 1/2 vdi, where vdi is the ion diamagnetic drift velocity. Comparisons are made with the measured GPI correlation velocity for the discharge. The saturation mechanisms operative in the simulation of the discharge are also discussed. It is found that neither sheared flow nor pressure gradient modification can be excluded as saturation mechanisms.

  4. Lyα blobs like company: the discovery of a candidate 100kpc Lyα blob near to a radio galaxy with a giant Lyα halo B3J2330+3927 at z = 3.1

    NASA Astrophysics Data System (ADS)

    Matsuda, Y.; Nakamura, Y.; Morimoto, N.; Smail, Ian; De Breuck, C.; Ohta, K.; Kodama, T.; Inoue, A. K.; Hayashino, T.; Kousai, K.; Nakamura, E.; Horie, M.; Yamada, T.; Kitamura, M.; Saito, T.; Taniguchi, Y.; Tanaka, I.; Hibon, P.

    2009-11-01

    We present the discovery of a candidate of giant radio-quiet Lyα blob (RQLAB) in a large-scale structure around a high-redshift radio galaxy (HzRG) lying in a giant Lyα halo B3J2330+3927 at redshift z = 3.087. We obtained narrow- and broad-band imaging around B3J2330+3927 with Subaru/Suprime-Cam to search for Lyα emitters (LAEs) and absorbers (LAAs) at redshift z = 3.09 +/- 0.03. We detected candidate 127 LAEs and 26 LAAs in the field of view of 31 × 24arcmin2 (58 × 44 comoving Mpc). We found that B3J2330+3927 is surrounded by a 130kpc Lyα halo and a large-scale (~60 × 20 comoving Mpc) filamentary structure. The large-scale structure contains one prominent local density peak with an overdensity of greater than 5, which is 8arcmin (15 comoving Mpc) away from B3J2330+3927. In this peak, we discovered a candidate 100kpc RQLAB. The existence of both types of Lyα nebulae in the same large-scale structure suggests that giant Lyα nebulae need special large-scale environments to form. On smaller scales, however, the location of B3J2330+3927 is not a significant local density peak in this structure, in contrast to the RQLAB. There are two possible interpretations of the difference of the local environments of these two Lyα nebulae. First, RQLAB may need a prominent (δ ~ 5) density peak of galaxies to form through intense starbursts due to frequent galaxy interactions/mergers and/or continuous gas accretion in an overdense environment. On the other hand, Lyα halo around HzRG may not always need a prominent density peak to form if the surrounding Lyα halo is mainly powered by its radio and active galactic nucleus activities. Alternatively, both RQLAB and Lyα halo around HzRG may need prominent density peaks to form but we could not completely trace the density of galaxies because we missed evolved and dusty galaxies in this survey. Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. E-mail: yuichi.matsuda@durham.ac.uk

  5. Measuring Waves and Erosion in Underwater Oil Blobs and Monitoring Other Arbitrary Surfaces with a Kinect v2 Time-of-Flight Camera

    NASA Astrophysics Data System (ADS)

    Butkiewicz, T.

    2014-12-01

    We developed free software that enables researchers to utilize Microsoft's new Kinect for Windows v2 sensor for a range of coastal and ocean mapping applications, as well as monitoring and measuring experimental scenes. While the original Kinect device used structured light and had very poor resolution, many geophysical researchers found uses for it in their experiments. The new next generation of this sensor uses time-of-flight technology, and can produce higher resolution depth measurements with an order of magnitude more accuracy. It also is capable of measurement through and under water. An analysis tool in our application lets users quickly select any arbitrary surface in the sensor's view. The tools automatically scans the surface, then calibrates and aligns a measurement volume to it. Depth readings from the sensor are converted into 3D point clouds, and points falling within this volume are projected into surface coordinates. Raster images can be output which consist of height fields aligned to the surface, generated from these projected measurements and interpolations between them. Images have a simple 1 pixel = 1 mm resolution and intensity values representing mm in height from the base-plane, which enables easy measurement and calculations to be conducted on the images in other analysis packages. Single snapshots can be taken manually on demand, or the software can monitor the surface automatically, capturing frames at preset intervals. This produces time lapse animations of dynamically changing surfaces. We apply this analysis tool to an experiment studying the behavior of underwater oil in response to flowing water of different speeds and temperatures. Blobs of viscous oils are placed in a flume apparatus, which circulates water past them. Over the course of a couple hours, the oil blobs spread out, waves slowly ripple across their surfaces, and erosions occur as smaller blobs break off from the main blob. All of this can be captured in 3D, with mm

  6. A Deep Narrowband Imaging Search for C IV and He II Emission from Lyα Blobs

    NASA Astrophysics Data System (ADS)

    Arrigoni Battaia, Fabrizio; Yang, Yujin; Hennawi, Joseph F.; Prochaska, J. Xavier; Matsuda, Yuichi; Yamada, Toru; Hayashino, Tomoki

    2015-05-01

    We conduct a deep narrowband imaging survey of 13 Lyα blobs (LABs) located in the SSA22 proto-cluster at z ˜ 3.1 in the C iv and He ii emission lines in an effort to constrain the physical process powering the Lyα emission in LABs. Our observations probe down to unprecedented surface brightness (SB) limits of (2.1-3.4) × 10-18 erg s-1 cm-2 arcsec-2 per 1 arcsec2 aperture (5σ) for the He ii λ1640 and C iv λ1549 lines, respectively. We do not detect extended He ii and C iv emission in any of the LABs, placing strong upper limits on the He ii/Lyα and C iv/Lyα line ratios, of 0.11 and 0.16, for the brightest two LABs in the field. We conduct detailed photoionization modeling of the expected line ratios and find that, although our data constitute the deepest ever observations of these lines, they are still not deep enough to rule out a scenario where the Lyα emission is powered by the ionizing radiation from an obscured active galactic nucleus. Our models can accommodate He ii/Lyα and C iv/Lyα ratios as low as ≃0.05 and ≃0.07, respectively, implying that one needs to reach SB as low as (1-1.5) × 10-18 erg s-1 cm-2 arcsec-2 (at 5σ) in order to rule out a photoionization scenario. These depths will be achievable with the new generation of image-slicing integral field units such as the Multi Unit Spectroscopic Explorer (MUSE) on VLT and the Keck Cosmic Web Imager (KCWI). We also model the expected He ii/Lyα and C iv/Lyα in a different scenario, where Lyα emission is powered by shocks generated in a large-scale superwind, but find that our observational constraints can only be met for shock velocities vs ≳ 250 km s-1, which appear to be in conflict with recent observations of quiescent kinematics in LABs. .

  7. 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

  8. Investigations of the radial propagation of blob-like structure in a non-confined electron cyclotron resonance heated plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak

    SciTech Connect

    Ogata, R.; Liu, H. Q.; Ishiguro, M.; Ikeda, T.; Hanada, K.; Zushi, H.; Nakamura, K.; Fujisawa, A.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Nishino, N.; Collaboration: QUEST Group

    2011-09-15

    A study of radial propagation and electric fields induced by charge separation in blob-like structures has been performed in a non-confined cylindrical electron cyclotron resonance heating plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak using a fast-speed camera and a Langmuir probe. The radial propagation of the blob-like structures is found to be driven by E x B drift. Moreover, these blob-like structures were found to have been accelerated, and the property of the measured radial velocities agrees with the previously proposed model [C. Theiler et al., Phys. Rev. Lett. 103, 065001 (2009)]. Although the dependence of the radial velocity on the connection length of the magnetic field appeared to be different, a plausible explanation based on enhanced short-circuiting of the current path can be proposed.

  9. Hemispheric asymmetry in transition from equatorial plasma bubble to blob as deduced from 630.0 nm airglow observations at low latitudes

    NASA Astrophysics Data System (ADS)

    Park, Jaeheung; Martinis, Carlos R.; Lühr, Hermann; Pfaff, Robert F.; Kwak, Young-Sil

    2016-01-01

    Transitions from depletions to enhancements of 630.0 nm nighttime airglow have been observed at Arecibo. Numerical simulations by Krall et al. (2009) predicted that they should occur only in one hemisphere, which has not yet been confirmed observationally. In this study we investigate the hemispheric conjugacy of the depletion-to-enhancement transition using multiple instruments. We focus on one event observed in the American longitude sector on 22 December 2014: 630.0 nm airglow depletions evolved into enhancements in the Northern Hemisphere while the evolution did not occur in the conjugate location in the Southern Hemisphere. Concurrent plasma density measured by low Earth orbit (LEO) satellites and 777.4 nm airglow images support that the depletions and enhancements of 630.0 nm nighttime airglow reflect plasma density decreases and increases (blobs), respectively. Characteristics of the airglow depletions, in the context of the LEO satellite data, further suggest that the plasma density depletion deduced from the airglow data represents equatorial plasma bubbles (EPBs) rather than medium-scale traveling ionospheric disturbances from midlatitudes. Hence, the event in this study can be interpreted as EPB-to-blob transition.

  10. A Lyα blob and zabs ≈ zem damped Lyα absorber in the dark matter halo of the binary quasar Q 0151+048

    NASA Astrophysics Data System (ADS)

    Zafar, T.; Møller, P.; Ledoux, C.; Fynbo, J. P. U.; Nilsson, K. K.; Christensen, L.; D'Odorico, S.; Milvang-Jensen, B.; Michałowski, M. J.; Ferreira, D. D. M.

    2011-08-01

    Context. Q 0151+048 is a physical quasar (QSO) pair at z ~ 1.929 with a separation of 3.3 arcsec on the sky. In the spectrum of the brighter member of this pair, Q 0151+048A, a damped Lyα absorber (DLA) is observed at a higher redshift. We have previously detected the host galaxies of both QSOs, as well as a Lyα blob whose emission surrounding Q 0151+048A extends over 5 × 3.3 arcsec. Aims: We seek to constrain the geometry of the system and understand the possible relations between the DLA, the Lyα blob, and the two QSOs. We also aim at characterizing the former two objects in more detail. Methods: To study the nature of the Lyα blob, we performed low-resolution, long-slit spectroscopy with the slit aligned with the extended emission. We also observed the whole system using the medium-resolution VLT/X-shooter spectrograph and the slit aligned with the two QSOs. The systemic redshift of both QSOs was determined from rest-frame optical emission lines redshifted into the NIR. We employed line-profile fitting technique, to measure metallicities and the velocity width of low-ionization metal absorption lines associated to the DLA and photo-ionization modeling to characterize the DLA further. Results: We measure systemic redshifts of zem(A) = 1.92924 ± 0.00036 and zem(B) = 1.92863 ± 0.00042 from the H β and H α emission lines, respectively. In other words, the two QSOs have identical redshifts within 2σ. From the width of Balmer emission lines and the strength of the rest-frame optical continuum, we estimate the masses of the black holes of the two QSOs to be 109.33 M⊙ and 108.38 M⊙ for Q 0151+048A and Q 0151+048B, respectively. We then use the correlation between black hole mass and dark matter halo mass to infer the mass of the dark matter halos hosting the two QSOs: 1013.74 M⊙ and 1013.13 M⊙ for Q 0151+048A and Q 0151+048B, respectively. We observe a velocity gradient along the major axis of the Lyα blob consistent with the rotation curve of a large

  11. Emplacement mechanisms and trapping potential of gravity-driven allochthons

    SciTech Connect

    Pinney, R.B.

    1985-02-01

    Gravity-slide blocks of Paleozoic carbonate detached from the Snake River Range show evidence of episodic emplacement into the Salt Lake group (Mio-Pliocene) in the Palisades reservoir area near Alpine, Wyoming. The allochthons lie in a large graben system created by the Grand Valley listric normal fault, a reactivated thrust that soles into a ramp in the underlying Absaroka thrust. In the Alpine 7 1/2-min quadrangle, one of the detached blocks is 2 1/2 mi (4 km) by 1 mi (1.6 km) in map view and contains the Ferry Peak thrust as well as other Laramide structures. Structures and formations of the Alpine allochthon may be matched to those in the range to restore approximate predetachment position. Very low-angle westward translation at or near the surface moved the blocks across the Grand Valley fault into the graben. The current location and attitude of these allochthons are due to subsequent movement and rotation on the Grand Valley fault. The allochthons occur at different stratigraphic levels in the Salt Lake group, each level corresponding to the time of a specific emplacement event. Catastrophic emplacement of a fractured allochthon, a potential reservoir, into a lacustrine or other source rock depocenter creates a unique and potentially predictable type of petroleum occurrence. Paleogeographic reconstruction may explain anomalous occurrence of discrete allochthons in structurally low areas where it can be shown that a gravitational potential existed for detachment and sliding. The resulting trap would consist of allochthons encased in autochthonous source rock.

  12. Kinetics of gravity-driven water channels under steady rainfall

    NASA Astrophysics Data System (ADS)

    Cejas, Cesare M.; Wei, Yuli; Barrois, Remi; Frétigny, Christian; Durian, Douglas J.; Dreyfus, Rémi

    2014-10-01

    We investigate the formation of fingered flow in dry granular media under simulated rainfall using a quasi-two-dimensional experimental setup composed of a random close packing of monodisperse glass beads. Using controlled experiments, we analyze the finger instabilities that develop from the wetting front as a function of fundamental granular (particle size) and fluid properties (rainfall, viscosity). These finger instabilities act as precursors for water channels, which serve as outlets for water drainage. We look into the characteristics of the homogeneous wetting front and channel size as well as estimate relevant time scales involved in the instability formation and the velocity of the channel fingertip. We compare our experimental results with that of the well-known prediction developed by Parlange and Hill [D. E. Hill and J. Y. Parlange, Soil Sci. Soc. Am. Proc. 36, 697 (1972), 10.2136/sssaj1972.03615995003600050010x]. This model is based on linear stability analysis of the growth of perturbations arising at the interface between two immiscible fluids. Results show that, in terms of morphology, experiments agree with the proposed model. However, in terms of kinetics we nevertheless account for another term that describes the homogenization of the wetting front. This result shows that the manner we introduce the fluid to a porous medium can also influence the formation of finger instabilities. The results also help us to calculate the ideal flow rate needed for homogeneous distribution of water in the soil and minimization of runoff, given the grain size, fluid density, and fluid viscosity. This could have applications in optimizing use of irrigation water.

  13. Kinetics of gravity-driven water channels under steady rainfall.

    PubMed

    Cejas, Cesare M; Wei, Yuli; Barrois, Remi; Frétigny, Christian; Durian, Douglas J; Dreyfus, Rémi

    2014-10-01

    We investigate the formation of fingered flow in dry granular media under simulated rainfall using a quasi-two-dimensional experimental setup composed of a random close packing of monodisperse glass beads. Using controlled experiments, we analyze the finger instabilities that develop from the wetting front as a function of fundamental granular (particle size) and fluid properties (rainfall, viscosity). These finger instabilities act as precursors for water channels, which serve as outlets for water drainage. We look into the characteristics of the homogeneous wetting front and channel size as well as estimate relevant time scales involved in the instability formation and the velocity of the channel fingertip. We compare our experimental results with that of the well-known prediction developed by Parlange and Hill [D. E. Hill and J. Y. Parlange, Soil Sci. Soc. Am. Proc. 36, 697 (1972)]. This model is based on linear stability analysis of the growth of perturbations arising at the interface between two immiscible fluids. Results show that, in terms of morphology, experiments agree with the proposed model. However, in terms of kinetics we nevertheless account for another term that describes the homogenization of the wetting front. This result shows that the manner we introduce the fluid to a porous medium can also influence the formation of finger instabilities. The results also help us to calculate the ideal flow rate needed for homogeneous distribution of water in the soil and minimization of runoff, given the grain size, fluid density, and fluid viscosity. This could have applications in optimizing use of irrigation water. PMID:25375487

  14. Gravity driven current during sessile drop coalescence on a surface

    NASA Astrophysics Data System (ADS)

    Zhang, Ying; Oberdick, Samuel; Garoff, Stephen; Anna, Shelley

    2013-11-01

    We study the mixing behavior of two sessile drops following coalescence on a flat surface. The surface is composed of silicone elastomer on which the drops exhibit contact angles of about 90 degree. The two drops are of equal volume at coalescence, but different densities and viscosities. Using laser induced fluorescence, we obtain both a top view of the contact line motion and a side view of the cross-sectional flow. During the coalescence stage, the initial healing of the meniscus bridge and damping of capillary waves occur on time scales comparable to the inertio-capillary time. However, the interface between the dyed and undyed components remains sharp, with diffusive mixing occurring at much longer timescales. At intermediate time scales the motion is controlled by a gravity current, which leads to the eventual stratification into two separate horizontal layers within the composite drop. Using lubrication analysis, we characterize the gravity current as a function of the drop sizes, and the density and viscosity differences between the two merging fluids. The numerical solution of the lubrication analysis captures the observed scaling of the time dependent interface movement as a function of fluid and geometric parameters.

  15. Gravity-driven liquid flow over a flexible beam

    NASA Astrophysics Data System (ADS)

    Kim, Hyoungsoo; Howell, Peter; Popova, Marinela; Stone, Howard

    2015-11-01

    We study theoretically and experimentally the time dependence of a liquid spreading along a flexible beam. The flow is modeled using lubrication theory and the substrate is modeled as an (Euler-Bernoulli) elastic beam. We classify the model problem into two cases depending on the maximum beam deflection angle ϕmax from the horizontal, i.e. a small deflection (ϕmax < 30°) and large deflection (30° < ϕmax < 90°). For a small deflection case, we obtain asymptotic solutions for the liquid propagation speed for the early time and terminal time periods, which for the front position σ(t) show power-law behaviors σ(t) ~ t 4 / 5 and σ(t) ~ t4, respectively. The theoretical model also predicts the deflection angle of the beam at the propagating liquid front. We validate the results with experiments, which show good agreement with theory. Furthermore, for large beam deflections, we obtain experimental results demonstrating power-law behaviors, σ(t) ~ t and ϕ(t) ~ t2 for the early time period.

  16. Gravity driven current during the coalescence of two sessile drops

    NASA Astrophysics Data System (ADS)

    Zhang, Ying; Oberdick, Samuel D.; Swanson, Ellen R.; Anna, Shelley L.; Garoff, Stephen

    2015-02-01

    Coalescence of liquid drops is critical in many phenomena such as emulsion stability, inkjet printing, and coating applications. For sessile drops on a solid surface, the coalescence process is more complicated than the coalescence of drops suspended in a fluid medium as a result of the coupling of the contact line motions to the fluid flow. In this paper, we use video microscopy to track the evolution of the interfaces and contact lines as well as the internal fluid motion within a merged sessile droplet. In this study, the fluids in the coalescing drops are miscible and have similar surface tensions and drop volumes but different viscosities and densities. Coalescence occurs in three stages. During the first stage, rapid healing of the bridge between the drops occurs just after they touch. In the second stage, slower rearrangement of the liquids occurs. We show that these intermediate rearrangements are driven by gravity even for density differences of the two fluids as small as 1%. For the systems examined, little to no mixing occurs during these first two stages. Finally, in the third stage, diffusion leads to mixing of the fluids. Dimensional analysis reveals the scaling of the intermediate flow behavior as a function of density difference and geometric dimensions of the merged drop; however, the scaling with viscosity is more complicated, motivating development of a lubrication analysis of the coalescence problem. Numerical calculations based on the lubrication analysis capture aspects of the experimental observations and reveal the governing forces and time scales of the coalescence process. The results reveal that internal fluid motions persist over much longer time scales than imaging of the external interface alone would reveal. Furthermore, nearly imperceptible motions of the external composite drop interface can lead to important deviations from the predominant gravity current scaling, where viscous resistance of the lighter fluid layer plays a significant role in the internal fluid motion.

  17. On exponential stability of gravity driven viscoelastic flows

    NASA Astrophysics Data System (ADS)

    Jiang, Fei; Wu, Guochun; Zhong, Xin

    2016-05-01

    We investigate stability of an equilibrium state to a nonhomogeneous incompressible viscoelastic fluid driven by gravity in a bounded domain Ω ⊂R3 of class C3. First, we establish a critical number κC, which depends on the equilibrium density and the gravitational constant, and is a threshold of the elasticity coefficient κ for instability and stability of the linearized perturbation problem around the equilibrium state. Then we prove that the equilibrium state is exponential stability provided that κ >κC and the initial disturbance quantities around the equilibrium state satisfy some relations. In particular, if the equilibrium density ρ bar is a Rayleigh-Taylor (RT) type and ρbar‧ is a constant, our result strictly shows that the sufficiently large elasticity coefficient can prevent the RT instability from occurrence.

  18. Gravity-driven soap film dynamics in subcritical regimes

    NASA Astrophysics Data System (ADS)

    Auliel, M. I.; Castro, F.; Sosa, R.; Artana, G.

    2015-10-01

    We undertake the analysis of soap-film dynamics with the classical approach of asymptotic expansions. We focus our analysis in vertical soap film tunnels operating in subcritical regimes with elastic Mach numbers Me=O(10-1) . Considering the associated set of nondimensional numbers that characterize this flow, we show that the flow behaves as a two-dimensional (2D) divergence free flow with variable mass density. When the soap film dynamics agrees with that of a 2D and almost constant mass density flow, the regions where the second invariant of the velocity gradient is non-null correspond to regions where the rate of change of film thickness is non-negligible.

  19. Flucutations in power dissipation in a gravity driven system

    NASA Astrophysics Data System (ADS)

    Greguric, Zrinka; Cervoni, Miguel; Cressman, John

    2010-03-01

    We have studied the three dimensional motion of a disk falling through a column of water. The disk's position and orientation are measured with a high speed video camera enabling an analysis of the fluid forces acting on the disk. On average the fluid exerts a dissipative drag on the falling body. However, these forces are dynamic and lead to fluctuations in the kinetic energy of the disk. The resulting power fluctuations are of the same magnitude as the mean power dissipated by the fluid and can be large enough to cause the disk to move upward against the force of gravity. We have analyzed these fluctuations and compared their statistics to those predicted by non-equilibrium statistical theory.

  20. Direct Determination of the Magnetic Quadrupole Contribution to the Lyman-{alpha}{sub 1} Transition in a Hydrogenlike Ion

    SciTech Connect

    Weber, G.; Stoehlker, Th.; Braeuning, H.; Hess, S.; Kozhuharov, C.; Spillmann, U.; Surzhykov, A.; Maertin, R.; Winters, D. F. A.; Brandau, C.; Fritzsche, S.; Geyer, S.; Hagmann, S.; Petridis, N.; Reuschl, R.; Trotsenko, S.

    2010-12-10

    We report the observation of an interference between the electric dipole (E1) and the magnetic quadrupole (M2) amplitudes for the linear polarization of the Ly-{alpha}{sub 1} (2p{sub 3/2}{yields}1s{sub 1/2}) radiation of hydrogenlike uranium. This multipole mixing arises from the coupling of the ion to different multipole components of the radiation field. Our observation indicates a significant depolarization of the Ly-{alpha}{sub 1} radiation due to the E1-M2 amplitude mixing. It proves that a combined measurement of the linear polarization and of the angular distribution enables a very precise determination of the ratio of the E1 and the M2 transition amplitudes and the corresponding transition rates without any assumptions concerning the population mechanism for the 2p{sub 3/2} state.

  1. Evidence for a temperature rise in the outer layers of alpha Lyrae, from Copernicus observations of Lyman-alpha

    NASA Technical Reports Server (NTRS)

    Praderie, F.; Simonneau, E.; Snow, T. P., Jr.

    1975-01-01

    Copernicus satellite observations of the Ly-alpha profiles in alpha Lyrae (Vega) are used to determine whether classical radiative-equilibrium LTE model atmospheres can fit the thermal structure in the outer layers of that star. Two plane-parallel LTE model photospheres of alpha Lyrae are considered: a line-blanketed radiative-equilibrium model with an effective temperature of 9650 K and log g of 4.05, and the same model with a temperature of 9500 K and log g of 4.0. The profiles of the Ly-alpha wings are computed, and it is found that classical LTE models are unable to predict either the observed violet wing or the red wing longwards of 1239 A, regardless of the line source function. It is concluded that the electron temperature must increase outwards over the surface value reached in radiative equilibrium.

  2. 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.

  3. On the detectability of key-MeV solar protons through their nonthermal Lyman-alpha emission

    NASA Technical Reports Server (NTRS)

    Canfield, R. C.; Chang, C. R.

    1985-01-01

    The intensity and timescale of nonthermal Doppler-shifted hydrogen L alpha photon emission as diagnostics of 10 keV to 10 MeV protons bombarding the solar chromosphere during flares are investigated. The steady-state excitation and ionization balance of the proton beam are determined, taking into account all important atomic interactions with the ambient chromosphere. For a proton energy flux comparable to the electron energy flux commonly inferred for large flares, L alpha wing intensities orders of magnitude larger than observed nonflaring values were found. Investigation of timescales for ionization and charge exchange leads researchers to conclude that over a wide range of values of mean proton energy and beam parameters, Doppler-shifted nonthermal L alpha emission is a useful observational diagnostic of the presence of 10 keV to 10 MeV superthermal proton beams in the solar flare chromosphere.

  4. HST study of Lyman-alpha emission in star-forming galaxies: the effect of neutral gas flows

    NASA Astrophysics Data System (ADS)

    Kunth, Daniel; Mas-Hesse, J. M.; Terlevich, E.; Terlevich, R.; Lequeux, J.; Fall, S. Michael

    1998-06-01

    We present high dispersion HST GHRS UV spectroscopic observations of 8 H II galaxies covering a wide range of metallicities and physical properties. We have found Lyalpha \\ emission in 4 galaxies with blueshifted absorption features, leading to P Cygni like profiles in 3 of them. In all these objects the O I and Si II absorption lines are also blueshifted with respect to the ionized gas, indicating that the neutral gas is outflowing in these galaxies with velocities up to 200 km s(-1) or more. The rest of the sample shows broad damped Lyalpha \\ absorption profiles centered at the wavelength corresponding to the redshift of the H II emitting gas. We therefore find that the velocity structure of the neutral gas in these galaxies is the driving factor that determines the detectability of Lyalpha \\ in emission. Relatively small column densities of neutral gas with even very small dust content would destroy the Lyalpha \\ emission if this gas is static with respect to the ionized region where Lyalpha \\ photons originate. The situation changes dramatically when most of the neutral gas is velocity-shifted with respect to the ionized regions because resonant scattering by neutral hydrogen will be most efficient at wavelengths shorter than the Lyalpha \\ emission, allowing the Lyalpha \\ photons to escape (at least partially). This mechanism complements the effect of porosity in the neutral interstellar medium discussed by other authors, which allows to explain the escape of Lyalpha \\ photons in regions surrounded by static neutral gas, but with only partial covering factors. The anisotropy of these gas flows and their dependence on the intrinsic properties of the violent star-forming episodes taking place in these objects (age, strength, gas geometry,...) might explain (in part) the apparent lack of correlation between other properties (like metallicity) and the frequency of occurence and strength of Lyalpha \\ emission in star-forming galaxies. Attempts to derive the comoving star-formation rate at high redshifts from Lyalpha \\ emission searches are highly questionable. Based on observations with the NASA/ESA {\\it Hubble Space Telescope

  5. Observed perturbations of the velocity distribution of interstellar hydrogen atoms in the solar system with Prognoz Lyman-alpha measurements

    NASA Astrophysics Data System (ADS)

    Lallement, R.; Bertaux, J. L.; Kurt, V. G.; Mironova, E. N.

    1984-11-01

    Observations of the interplanetary Lyman α emission made at five different places in the solar system with high apogee satellites Prognoz 5 and Prognoz 6 are reported. This Lyα emission is the result of resonance scattering of solar photons by H atoms of the local interstellar medium (LISM) flowing in the solar system at the velocity - Vw and the spectral profile is an image of the velocity distribution of the atoms. A hydrogen absorption cell was used to analyze the spectral profile, the variation of Doppler shift with looking direction providing its spectral scanning. A first estimate of the LISM temperature is derived, T ≅ 8000K, and also an approximate location of Vw in fair agreement with previous measurements. The observed variation of the heating effect is of 3000K, and is independent of the existence of a potential galactic background in the vicinity of the Lyα wavelength. An upper limit of this background is found to be 15 Rayleigh.

  6. A comparison of lyman alpha and He lambda 10830 line structures and variations in early-type star atmospheres

    NASA Technical Reports Server (NTRS)

    Meisel, D. D.

    1974-01-01

    Line profiles were first obtained at maximum velocity separation of the spectroscopic binary Spica (alpha Vir), and then high resolution spectrophotometric images of selected features in the 1.1 micron spectrum of Comet Kohoutek were obtained in order to gain insight into the structures and variations in early-type star atmospheres.

  7. Constraining the Metallicity and Escape Fraction of Two z≈3.1 Lyman-Alpha Emitting Galaxies

    NASA Astrophysics Data System (ADS)

    Richardson, Mark L. A.; McLinden, E. M.; Malhotra, S.; Rhoads, J. E.; Levesque, E. M.

    2012-05-01

    We observed two z≈3.1 Lyman-α emitting galaxies (LAE) using the Near-infrared Integral Field Spectrometer (NIFS) at Gemini North, specifically looking for [OIII] 4960 & 5008Å, [OII] 3727Å, and H-β 4863Å. We detected the [OIII] doublet in both objects, determined upper limits for [OII] for both objects, and determined upper limits for H-β for one object. With the detections and upper limits we use the [OIII]/[OII] and R23 line diagnostic to attempt to constrain the metallicity and escape fraction of Ly-α. These metallicity constraints are needed to explore the behaviour of the Mass-Metallicty relation in the low-mass regime and also give insight into the star formation histories of LAE which are known to host young stellar populations. The escape fraction, when combined with an extinction correction, gives insight into the presence of neutral gas. This neutral gas is responsible for resonantly scattering any escaped Ly-α photons, increasing its optical depth to dust. For one object we constrain the metallicity to be Z≤ 0.4Z⊙ and constrain the escape fraction of Ly-α to be Fesc ≤ 30%. For the second object we are only able to constrain its escape fraction, finding 6% ≤ Fesc ≤ 40%. We would like to thank the Natural Sciences and Engineering Research Council of Canada for their financial support through a post-graduate fellowship.

  8. Analysis of coronal H I Lyman-alpha measurements in a polar region of the sun observed in 1979

    NASA Technical Reports Server (NTRS)

    Withbroe, G. L.; Kohl, J. L.; Weiser, H.

    1986-01-01

    Measurements of the intensities and spectral line profiles of resonantly scattered hydrogen Ly-alpha radiation have been used to determine hydrogen kinetic temperatures and electron densities between r = 1.5 and 2.2 solar radii in a polar region of the corona observed in 1979 near solar maximum. The mean temperature, 1.8 x 10 to the 6th K, in this region is significantly higher, by about 60 percent, than that obtained in a similar region observed in a 1980 rocket flight. The densities in these two polar regions are similar and are a factor of about 4 larger than in polar coronal holes observed at solar minimum. The flow velocities in both regions are most likely subsonic for r less than about 4 solar radii. The results reported here support the hypothesis that polar coronal holes observed at different times during the solar cycle can have different temperatures, densities, and possibly flow velocities.

  9. Diagnosing the reionization of the universe - The absorption spectrum of the intergalactic medium and Lyman alpha clouds

    NASA Technical Reports Server (NTRS)

    Giroux, Mark L.; Shapiro, Paul R.

    1991-01-01

    The thermal and ionization evolution of a uniform intergalactic medium composed of H and He and undergoing reionization is studied. The diagnosis of the metagalactic ionizing radiation background at z of about three using metal line ratios for Lyman limit quasar absorption line systems is addressed. The use of the He II Gunn-Peterson effect to diagnose the reionization source and/or nature of the Hy-alpha forest clouds is considered.

  10. The solar O III spectrum. II - Longer wavelengths, line widths, and the He II Lyman alpha radiation field

    NASA Technical Reports Server (NTRS)

    Kastner, S. O.; Behring, W. E.; Bhatia, A. K.

    1983-01-01

    The solar O III spectrum above 900 A is analyzed, including several visible and infrared lines which are important in nebular studies. The dependence of the line intensities on the rate of photoexcitation by He Ly-alpha is determined, and the observability of these lines in the solar spectrum is studied. The impact approximation is employed to calculate the expected line widths of the stronger solar O III lines. The photoexciting field at 304 A calculated from the observed intensities of the O III lines below 900 A (Bhatia et al., 1982) is compared with the field predicted by a recent model (Avrett et al., 1976). It is shown that additional radiation trapping must be present beyond that given by this model.

  11. The Lyman Alpha Reference Sample. V. The Impact of Neutral ISM Kinematics and Geometry on Lyα Escape

    NASA Astrophysics Data System (ADS)

    Rivera-Thorsen, Thøger E.; Hayes, Matthew; Östlin, Göran; Duval, Florent; Orlitová, Ivana; Verhamme, Anne; Mas-Hesse, J. Miguel; Schaerer, Daniel; Cannon, John M.; Otí-Floranes, Héctor; Sandberg, Andreas; Guaita, Lucia; Adamo, Angela; Atek, Hakim; Herenz, E. Christian; Kunth, Daniel; Laursen, Peter; Melinder, Jens

    2015-05-01

    We present high-resolution far-UV spectroscopy of the 14 galaxies of the Lyα Reference Sample; a sample of strongly star-forming galaxies at low redshifts (0.028 < z < 0.18). We compare the derived properties to global properties derived from multi-band imaging and 21 cm H i interferometry and single-dish observations, as well as archival optical SDSS spectra. Besides the Lyα line, the spectra contain a number of metal absorption features allowing us to probe the kinematics of the neutral ISM and evaluate the optical depth and and covering fraction of the neutral medium as a function of line of sight velocity. Furthermore, we show how this, in combination with the precise determination of systemic velocity and good Lyα spectra, can be used to distinguish a model in which separate clumps together fully cover the background source, from the “picket fence” model named by Heckman et al. We find that no one single effect dominates in governing Lyα radiative transfer and escape. Lyα escape in our sample coincides with a maximum velocity-binned covering fraction of ≲0.9 and bulk outflow velocities of ≳50 km s-1, although a number of galaxies show these characteristics and yet little or no Lyα escape. We find that Lyα peak velocities, where available, are not consistent with a strong backscattered component, but rather with a simpler model of an intrinsic emission line overlaid by a blueshifted absorption profile from the outflowing wind. Finally, we find a strong anticorrelation between Hα equivalent width and maximum velocity-binned covering factor, and propose a heuristic explanatory model. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO 11522, GO 11727, GO 12027, and GO 12583.

  12. Chemical abundances and ionization in sub-Damped Lyman-alpha absorbers at z < 1.5

    NASA Astrophysics Data System (ADS)

    Meiring, Joseph D.

    2008-06-01

    The chemical composition of galaxies provide important clues into galaxy formation and evolution. Quasar (QSO) absorption line systems offer a unique window into the high redshift Universe and the properties of normal galaxies at high redshift. QSO absorbers have long been used to study distant galaxies and the intergalactic medium (IGM). The Damped Lyman-a systems (DLAs), with neutral Hydrogen column densities of log N H I > 20.3, and sub-Damped Lyman-a systems (sub-DLAs) with 19.0 < log N H I < 20.3 contain the majority of the neutral gas in the Universe at high redshift, probe metallicities over ~90% of the cosmic history, and are believed to be the progenitors of modern day galaxies. Models of the chemical evolution of galaxies predict that the mean metallicity of galaxies should reach a solar value by z ~ 0 due to the ongoing cycles of star formation which enrich the galaxy with heavy elements. The DLA systems which have been the preferred class of absorbers for these investigations however appear to be metal poor at all redshifts, and show little evolution in their metallicity, contradicting the models of chemical evolution, the "missing metals problem". We have amassed a sample of 32 sub-DLAs and 3 DLAS at z abs < 1.5 using the 6.5m Magellan II telescope with the MIKE spectrograph, and the 8.2m VLT-Kueyen telescope with the UVES spectrograph to study the properties of these systems and determine their metal content. We have measured the absorption lines of multiple lines in these systems and determined column densities and abundances. We have also created grids of photoionization models using CLOUDY to determine the effects of ionization in these systems. Although the gas is largely ionized, the abundances appear not to require significant ionization corrections. We find that the sub-DLAs, especially at low z are more metal rich than the DLA systems, with [Zn/H] subDLA = -0.30 ± 0.15 and [Zn/H] DLA = -0.94 ± 0.11. These systems appear to contain ~ 40 - 75% of the comoving mass density of metals that is seen in DLAs, [Special characters omitted.] ~ (4 - 11) × 10^-7 , dependent on the ionization. Kinematically, the sub-DLAs from this sample have larger velocity widths than the DLAs, perhaps implying that they arise in more massive galaxies with deeper potential wells. We also investigate the relative abundances of [Cr/Zn], [Fe/Zn], [Mn/Fe], and [Si/Fe] in these systems to study dust depletion and nucleosynthetic effects.

  13. 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.

  14. Three-dimensional MHD simulation of the evolution of the April 2000 CME event and its induced shocks using a magnetized plasma blob model

    NASA Astrophysics Data System (ADS)

    Shen, F.; Feng, X. S.; Wu, S. T.; Xiang, C. Q.; Song, W. B.

    2011-04-01

    A three-dimensional (3-D) time-dependent, numerical magnetohydrodynamic (MHD) model with asynchronous and parallel time-marching method is used to investigate the propagation of coronal mass ejections (CMEs) in the nonhomogenous background solar wind flow. The background solar wind is constructed based on the self-consistent source surface with observed line-of-sight of magnetic field and density from the source surface of 2.5 Rs to the Earth's orbit (215 Rs) and beyond. The CMEs are simulated by means of a very simple flux rope model: a high-density, high-velocity, and high-temperature magnetized plasma blob is superimposed on a steady state background solar wind with an initial launch direction. The dynamical interaction of a CME with the background solar wind flow between 2.5 and 220 Rs is investigated. The evolution of the physical parameters at the cobpoint, which is located at the shock front region magnetically connected to ACE spacecraft, is also investigated. We have chosen the well-defined halo-CME event of 4-6 April 2000 as a test case. In this validation study we find that this 3-D MHD model, with the asynchronous and parallel time-marching method, the self-consistent source surface as initial boundary conditions, and the simple flux rope as CME model, provide a relatively satisfactory comparison with the ACE spacecraft observations at the L1 point.

  15. 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.

  16. Intergalactic Medium Emission Observations with the Cosmic Web Imager. II. Discovery of Extended, Kinematically Linked Emission around SSA22 Lyα Blob 2

    NASA Astrophysics Data System (ADS)

    Martin, D. Christopher; Chang, Daphne; Matuszewski, Matt; Morrissey, Patrick; Rahman, Shahin; Moore, Anna; Steidel, Charles C.; Matsuda, Yuichi

    2014-05-01

    The intergalactic medium (IGM) is the dominant reservoir of baryons, delineates the large-scale structure of the universe at low to moderate overdensities, and provides gas from which galaxies form and evolve. Simulations of a cold-dark-matter- (CDM-) dominated universe predict that the IGM is distributed in a cosmic web of filaments and that galaxies should form along and at the intersections of these filaments. While observations of QSO absorption lines and the large-scale distribution of galaxies have confirmed the CDM paradigm, the cosmic web of IGM has never been confirmed by direct imaging. Here we report our observation of the Lyα blob 2 (LAB2) in SSA22 with the Cosmic Web Imager (CWI). This is an integral field spectrograph optimized for low surface brightness, extended emission. With 22 hr of total on- and off-source exposure, CWI has revealed that LAB2 has extended Lyα emission that is organized into azimuthal zones consistent with filaments. We perform numerous tests with simulations and the data to secure the robustness of this result, which relies on data with modest signal-to-noise ratios. We have developed a smoothing algorithm that permits visualization of data cube slices along image or spectral image planes. With both raw and smoothed data cubes we demonstrate that the filaments are kinematically associated with LAB2 and display double-peaked profiles characteristic of optically thick Lyα emission. The flux is 10-20 times brighter than expected for the average emission from the IGM but is consistent with boosted fluorescence from a buried QSO or gravitation cooling radiation. Using simple emission models, we infer a baryon mass in the filaments of at least 1-4 × 1011 M ⊙, and the dark halo mass is at least 2 × 1012 M ⊙. The spatial-kinematic morphology is more consistent with inflow from the cosmic web than outflow from LAB2, although an outflow feature maybe present at one azimuth. LAB2 and the surrounding gas have significant and

  17. Intergalactic medium emission observations with the cosmic web imager. II. Discovery of extended, kinematically linked emission around SSA22 Lyα BLOB 2

    SciTech Connect

    Christopher Martin, D.; Chang, Daphne; Matuszewski, Matt; Morrissey, Patrick; Rahman, Shahin; Moore, Anna; Steidel, Charles C.; Matsuda, Yuichi

    2014-05-10

    The intergalactic medium (IGM) is the dominant reservoir of baryons, delineates the large-scale structure of the universe at low to moderate overdensities, and provides gas from which galaxies form and evolve. Simulations of a cold-dark-matter- (CDM-) dominated universe predict that the IGM is distributed in a cosmic web of filaments and that galaxies should form along and at the intersections of these filaments. While observations of QSO absorption lines and the large-scale distribution of galaxies have confirmed the CDM paradigm, the cosmic web of IGM has never been confirmed by direct imaging. Here we report our observation of the Lyα blob 2 (LAB2) in SSA22 with the Cosmic Web Imager (CWI). This is an integral field spectrograph optimized for low surface brightness, extended emission. With 22 hr of total on- and off-source exposure, CWI has revealed that LAB2 has extended Lyα emission that is organized into azimuthal zones consistent with filaments. We perform numerous tests with simulations and the data to secure the robustness of this result, which relies on data with modest signal-to-noise ratios. We have developed a smoothing algorithm that permits visualization of data cube slices along image or spectral image planes. With both raw and smoothed data cubes we demonstrate that the filaments are kinematically associated with LAB2 and display double-peaked profiles characteristic of optically thick Lyα emission. The flux is 10-20 times brighter than expected for the average emission from the IGM but is consistent with boosted fluorescence from a buried QSO or gravitation cooling radiation. Using simple emission models, we infer a baryon mass in the filaments of at least 1-4 × 10{sup 11} M {sub ☉}, and the dark halo mass is at least 2 × 10{sup 12} M {sub ☉}. The spatial-kinematic morphology is more consistent with inflow from the cosmic web than outflow from LAB2, although an outflow feature maybe present at one azimuth. LAB2 and the surrounding gas

  18. The Blob That Ate Physics

    ERIC Educational Resources Information Center

    Thomsen, Dietrick E.

    1975-01-01

    Summarizes some thoughts of Stephen W. Hawking who proposes that certain kinds of communications across the event horizon are possible, that they lead to the evaporation or explosion of the black hole, and, therefore, that classical or quantum mechanical causality has no meaning. (GS)

  19. Keck and VLT Observations of Super-Damped Lyman-Alpha Absorbers at z 2- 2.5: Constraints on Chemical Compositions and Physical Conditions

    NASA Astrophysics Data System (ADS)

    Kulkarni, Varsha P.; Som, Debopam; Morrison, Sean; Péroux, Celine; Quiret, Samuel; York, Donald G.

    2015-12-01

    We report Keck/Echellette Spectrograph and Imager and Very Large Telescope/Ultraviolet-Visual Echelle Spectrograph observations of three super-damped Lyα quasar absorbers with H i column densities log NH i ≥ 21.7 at redshifts 2 ≲ z ≲ 2.5. All three absorbers show similar metallicities (˜-1.3 to -1.5 dex), and dust depletion of Fe, Ni, and Mn. Two of the absorbers show supersolar [S/Zn] and [Si/Zn]. We combine our results with those for other damped Lyα a absorbers (DLAs) to examine trends between NH i, metallicity, and dust depletion. A larger fraction of the super-DLAs lie close to or above the line [X/H] = 20.59 - log NH i in the metallicity versus NH i plot, compared to the less gas-rich DLAs, suggesting that super-DLAs are more likely to be rich in molecules. Unfortunately, our data for Q0230-0334 and Q0743+1421 do not cover H2 absorption lines. For Q1418+0718, some H2 lines are covered, but not detected. CO is not detected in any of our absorbers. For DLAs with log NH i < 21.7, we confirm strong correlation between metallicity and Fe depletion, and find a correlation between metallicity and Si depletion. For super-DLAs, these correlations are weaker or absent. The absorbers toward Q0230-0334 and Q1418+0718 show potential detections of weak Lyα emission, implying star formation rates of ˜1.6 and ˜0.7 M⊙ yr-1, respectively (ignoring dust extinction). Upper limits on the electron densities from C ii*/C ii or Si ii*/Si ii are low, but are higher than the median values in less gas-rich DLAs. Finally, systems with log NH i > 21.7 may have somewhat narrower velocity dispersions Δv90 than the less gas-rich DLAs, and may arise in cooler and/or less turbulent gas. Includes observations collected during program ESO 93.A-0422 at the European Southern Observatory (ESO) Very Large Telescope (VLT) with the Ultraviolet-Visual Echelle Spectrograph (UVES) on the 8.2 m telescopes operated at the Paranal Observatory, Chile. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

  20. Detection of Lyman-alpha Emission from a Triply Imaged z = 6.85 Galaxy behind MACS J2129.4‑0741

    NASA Astrophysics Data System (ADS)

    Huang, Kuang-Han; Lemaux, Brian C.; Schmidt, Kasper B.; Hoag, Austin; Bradač, Maruša; Treu, Tommaso; Dijkstra, Mark; Fontana, Adriano; Henry, Alaina; Malkan, Matthew; Mason, Charlotte; Morishita, Takahiro; Pentericci, Laura; Ryan, Russell E., Jr.; Trenti, Michele; Wang, Xin

    2016-05-01

    We report the detection of Lyα emission at ∼9538 Å in the Keck/DEIMOS and Hubble Space Telescope WFC3 G102 grism data from a triply imaged galaxy at z=6.846+/- 0.001 behind galaxy cluster MACS J2129.4‑0741. Combining the emission line wavelength with broadband photometry, line ratio upper limits, and lens modeling, we rule out the scenario that this emission line is [O ii] at z = 1.57. After accounting for magnification, we calculate the weighted average of the intrinsic Lyα luminosity to be ∼ 1.3× {10}42 {erg} {{{s}}}-1 and Lyα equivalent width to be 74 ± 15 Å. Its intrinsic UV absolute magnitude at 1600 Å is ‑18.6 ± 0.2 mag and stellar mass (1.5+/- 0.3)× {10}7\\quad {M}ȯ , making it one of the faintest (intrinsic {L}{UV}∼ 0.14 {L}{UV}\\ast ) galaxies with Lyα detection at z∼ 7 to date. Its stellar mass is in the typical range for the galaxies thought to dominate the reionization photon budget at z≳ 7; the inferred Lyα escape fraction is high (≳ 10%), which could be common for sub-L* z≳ 7 galaxies with Lyα emission. This galaxy offers a glimpse of the galaxy population that is thought to drive reionization, and it shows that gravitational lensing is an important avenue for probing the sub-L* galaxy population.

  1. Lick optical spectra of quasar HS 1946+7658 at 10 kilometers per second resolution Lyman-alpha forest and metal absorption systems

    NASA Technical Reports Server (NTRS)

    Fan, Xiao-Ming; Tytler, David

    1994-01-01

    We present optical spectra of the most luminous known quasi stellar object (QSO) HS 1946+7658 (z(sub em) = 3.051). Our spectra have both full wavelength coverage, 3240-10570 A, and in selected regions, either high signal-to-noise ratio, SNR approximately equals 40-100, or unusually high approximately 10 km/sec resolution, and in parts of the Ly alpha forest and to the red of Ly alpha emission they are among the best published. We find 113 Ly alpha systems and six metal-line systems, three of which are new. The metal systems at z(sub abs) = 2.844 and 3.050 have complex velocity structure with four and three prominent components, respectively. We find that the system at z(sub abs) = 2.844 is a damped Ly alpha absorption (DLA) system, with a neutral hydrogen column density of log N(H I) = 20.2 +/- 0.4, and it is the cause of the Lyman limit break at lambda approximately equals 3520 A. We believe that most of the H I column density in this system is in z(sub abs) = 2.8443 component which shows the strongest low-ionization absorption lines. The metal abundance in the gas phase of the system is (M/H) approximately equals -2.6 +/- 0.3, with a best estimate of (M/H) = -2.8, with ionizaion parameter log gamma = -2.75, from a photoionization model. The ratios of the logarithmic abundances of C, O, Al, and Si are all within a factor of 2 of solar, which is important for two reasons. First, we believe that the gas abundances which we measure are close to the total abundances, because the ratio of aluminum to other elements is near cosmic, and Al is a refractory element which depletes very readily like chromium, in the interstellar medium. Second, we do not see the enhancement of O with respect to C of (O/C) approximately equals 0.5-0.9 reported in three partial Lyman limit systems by Reimers et al. (1992) and Vogel & Reimers (1993); we measure (O/C) = -0.06 for observed ions and (O/C) approximately equals 0.2 after ionization corrections, which is consistent with solar abundances. We see C II*(lambda 1335) offset by 15 km/sec with respect to C II(lambda 1334), presumably because the gas density varies from 2 to 8 cm(exp -3) with changing velocity in the DLA system. These densities imply that the damped component is 6-25 pc thick, which is reasonable for a single cloud in a cold spiral disk. They also imply that the cloud is relatively highly ionized with more C III than C II, more O III than O I, and log N(H I) = 20.72, which is 3 times the H I column. The system at z(abs) = 1.7382 is also believed to be damped with N(H I) approximately equals 10(exp 21) cm(exp -2), because we see Cr II, but its Ly alpha line will never be seen because it is below the Lyman limit of the other DLA system. We see a 2.6 sigma lack of Ly alpha forest lines well away from the QSO redshift, which may be a chance fluctuation. We also see a correlation between column density N(H I) and Doppler parameter b for 96 unsaturated Ly Alpha forest absorption lines, and although this correlation persists in the 36 Ly alpha lines which lie in regions where the SNR approximately equals 8-16, we agree with Rauch et al. (1993) that it is probably a bogus effect of low supernova remnant (SNR). The same applies to lines with very low b values: in regions where SNR less than or equal to 8 we see many Ly alpha lines which appear to have 10 less than or equal to b less than or equal to 20, but when 8 less than or equal to SNR less than or equal to 16 we see only one line with b less than or equal to 15 km/sec, and two others which we believe have b less than or equal to 20, with values of 20 and 16 km/sec. Traditional Ly alpha line samples which include all lines which have W/sigma(W) greater than or equal to 4 are not adequate to explore the distribution of the properties of individual clouds, because we need much higher (W/sigma(W)) and SNR to avoid the strong biases.

  2. A comparison of lyman alpha and HeI lambda 10830 line structure and variations in early-type star atmospheres

    NASA Technical Reports Server (NTRS)

    Meisel, D. D.

    1977-01-01

    Fabry-Perot interferometric profiles for fifty of the early-type stars including supergiants, eclipsing binaries, Bp and Ap stars, Be and shell stars, and variable stars have been obtained. Results for beta Persei (Algol) just before primary and secondary eclipses show strong emission profiles lasting about 0.1 phase. An absorption line was seen during secondary eclipse. Bright supergiant stars (O9-A2) show time-variable, complicated absorption/emission profiles similar to those obtained for the Be/shell stars.

  3. The gaseous extent of galaxies and the origin of Lyman-alpha absorption systems: A survey of galaxies in the fields of Hubble Space Telescope spectroscopic target QSOs

    NASA Technical Reports Server (NTRS)

    Lanzetta, Kenneth M.; Bowen, David B.; Tytler, David; Webb, John K.

    1995-01-01

    We present initial results of an imaging and spectroscopic survey of faint galaxies in fields of Hubble Space Telescope (HST) spectroscopic target QSOs. The primary objectives of the survey are (1) to determine the incidence, extent, and covering factor of extended gaseous envelopes of luminous galaxies and (2) to determine the fraction of Ly(alpha) absorption systems that arise in luminous galaxies. The goal of the survey is to identify in each field under construction all objects with apparent r-band magnitudes satisfying r less than 21.5 within angular distances to the QSOs satisfying 0 less thyan 1.3'. The current observations cover six fields and are 37% complete to the goal ofthe survey. These observations identify 46 galaxies at redshifts spanning z = 0.0700-0.5526 and at impact parameters to the QSOs spanning rho = 16.6-346.9/h kpc. Of these galaxies, 11 are coincident in redshift with absorption systems and 21 do not give rise to absorption to within sensitive upper limits. Nine galaxies are coincident in redshift with 'Ly(alpha)-forest' absorption systems that show Ly(alpha) absorption but no corresponding metal-line absorption, and two galaxies are coincident in redshift with C IV absorption systems that show both Ly(alpha) and C IV absorption. Various lines of evidence demonstrate that the coincident galaxies are responsible for the corresponding absorption systems and are not present as the result of chance coincidence or merely spatial correlated with the absorption systems. The most important evidence is that there exists a statistical anti-correlation between Ly(aplha) rest-frame equivalent width and the impact parameter. Each of five galaxies with rho = 70-160/h kpc give rise to Ly(alpha) absorption, and just one of nine galaxies with rho greater than 70-160/h kpc gives rise to Ly(alpha) absorption. At least eight of 23 Ly(alpha) absorption systyems arise in galaxies. On the basis of these results we reach the following conclusions: (1) At z less than or approximately = 1 most luminosu galaxies are surrounded by extended gaseous envelopes of approximately = 160/h kpc radius and of roughly unit covering factor. This conclusion confirms previous speculation that normal luminosu galaxies possess extended gaseous halos or extended gaseous disks. (2) At z less than or approximately = 1 the fraction of Ly(aplha) absorption systems-including Ly(alpha)-forest absorption systems-that arise in luminous galaxies is at least 0.32 +/- 0.10 and may be as high as 0.60 +/- 0.19. This conclusion runs contrary to the longstanding belief that Ly(alpha)-forest absorption systems arise in intergalactic clouds.

  4. Probing the Sizes of Absorbers: Correlations in the z 3.5 Lyman-alpha Forest Between Parallel Lines of Sight

    NASA Astrophysics Data System (ADS)

    Becker, G.; Sargent, W. L. W.; Rauch, M.

    2003-12-01

    Studies of the intergalactic medium along parallel lines of sight towards quasar pairs offer valuable information on the sizes of intervening absorbers as well as provide the basis for a test of the cosmological constant. We present a study of two high-redshift pairs with moderate separation observed with Keck ESI, Q1422+2309A/Q1424+2255 (z = 3.63, θ = 39'') and Q1439-0034A/B (z = 4.25, θ = 33''). The crosscorrelation of transmitted flux in the Lyα forest shows a strong peak at zero velocity lag in both pairs, suggesting that the Lyα absorbers are coherent over scales > 230-300 proper kpc. Two strong C IV systems at z = 3.4, closely separated along the line of sight, appear in Q1439B but not in Q1439A, consistent with the picture of outflowing material from an intervening galaxy. In contrast, a Mg II system at z = 1.68 does appear in both Q1439A and B. This suggests either a single absorber of size > 280 kpc or two separate, clustered absorbers. We additionally examine the impact of spectral characteristics on applying the Alcock-Paczynski test to quasar pairs, finding a strong dependence on resolution.

  5. Polarization of Lyman-Alpha Radiation from Atomic Hydrogen Excited by Electron Impact form Near Threshold to 1800 eV

    NASA Technical Reports Server (NTRS)

    James, G. K.; Slevin, J. A.; Dziczek, D.; McConkey, J. W.; Bray, Igor

    1998-01-01

    The polarization of Lyman-a radiation, produced by electron-impact excitation of atomic hydrogen, has been measured over the extended energy range from near threshold to 1800 eV. Measurements were obtained in a crossed-beam experiment using a silica-reflection linear polarization analyzer in tandem with a vacuum-ultraviolet monochromator to isolate the emitted line radiation. Comparison with various theoretical calculations shows that the present experimental results are in good agreement with theory over the entire range of electron-impact energies and, in particular, are in excellent agreement with theoretical convergent-close-coupling (CCC) calculations performed in the present work. Our polarization data are significantly different from the previous experimental measurements of Ott, Kauppila, and Fite.

  6. Optically thin H Lyman alpha production on outer planets - Low-energy proton acceleration in parallel electric fields and neutral H atom precipitation from ring current

    NASA Astrophysics Data System (ADS)

    Bhardwaj, A.; Singhal, R. P.

    1993-06-01

    A Monte Carlo model has been constructed to describe the energization and energy degradation of low-energy protons in an H2 atmosphere in the presence of parallel electric field. Numerical experiments have been performed to study the effect of initial proton energy, electric field, neutral number density, initial pitch angle, and cutoff limit on H Ly-alpha volume-emission rate. Energization of solar EUV-generated low-energy protons by parallel electric fields is incapable of producing optically thin Ly-alpha emissions on Uranus through direct collision with H2. However, nonthermal H atoms, produced through acceleration of protons in parallel electric fields, play an important role in enhancing the Ly-alpha intensity through resonant scattering of solar Ly-alpha flux; the resulting emissions are consistent with the broadening of the Ly-alpha line observed on Jupiter by IUE. The Monte Carlo model is also applied to the problem of Doppler-shifted H Ly-alpha emissions from the auroral atmosphere of Jupiter.

  7. New observations with the HST Goddard High Resolution Spectrograph of the low-redshift Lyman-Alpha clouds in the 3C 273 line of sight

    NASA Technical Reports Server (NTRS)

    Weymann, Ray; Rauch, Michael; Williams, Robert; Morris, Simon; Heap, Sally

    1995-01-01

    We presenty spectra of 3C 273 between 1216 and 1250 A obtained in the (pre-COSTAR (Corrective Optics Space Telescope Axial Replacement instrument)) configuration of the Goddard High Resolution Spectrograph (GHRS) taken with the G160M grating with a resolution approximately = 20 km/s. The two strong Ly alpha lines at velocities of approximately 1000 and approximately 1600 km/s are well fitted with Voigt profiles and yield column densities, Doppler parameters and redshifts of log N(H I)=14.19 +/- 0.04 V(sub Dop)=40.7 +/- 3.0 km/s, V = 1012.4 +/- 2.0 km/s, and log N(H I)=14.22 +/- 0.07, V(sub Dop)=34.2 +/- 3.3 km/s and V = 1582.0 +/- 2.0 km/s, respectively. Motivated by the initial announcement by Williams and Schommer of detectable H alpha emission associated with the approximately 1600 km/s cloud, we discuss the difficulty of finding models which can account for emission of that magnitude given the observed neutral hydrogen column density, though a recent reobservation by these authors has shown the initial detection to be spurious. The C/H abundance ratio is probably less than about one-fourth of the solar abundance in these clouds, although this result is very uncertain and model dependent.

  8. Ultraviolet observations of cool stars. IV - Intensities of Lyman-alpha and Mg II in epsilon Pegasi and epsilon Eridani, and line width-luminosity correlations

    NASA Technical Reports Server (NTRS)

    Mcclintock, W.; Linsky, J. L.; Henry, R. C.; Moos, H. W.

    1975-01-01

    A spectrometer on the Copernicus satellite has been used to confirm the existence of a line width-luminosity relation for the Ly-alpha and Mg II 2800-A chromospheric emission lines in K-type stars by observation of a K2 dwarf (epsilon Eri) and a K2 supergiant (epsilon Peg). Combined with previously reported observations of lines in three K giants (alpha Boo, alpha Tau, and beta Gem), the data are consistent with an identical dependence of line width on absolute visual magnitude for the Ca II K, Ly-alpha, and Mg II 2795-A lines. Surface fluxes of Ly-alpha, Mg II 2800-A, and O V 1218-A (upper limit) for epsilon Eri, and of Mg II 2800-A for epsilon Peg are also compared with values reported previously for the three giant stars.

  9. Cross-correlations of the Lyman-alpha forest with weak lensing convergence I: Analytical Estimates of S/N and Implications for Neutrino Mass and Dark Energy

    SciTech Connect

    Vallinotto, Alberto; Viel, Matteo; Das, Sudeep; Spergel, David N.

    2009-10-01

    We expect a detectable correlation between two seemingly unrelated quantities: the four point function of the cosmic microwave background (CMB) and the amplitude of flux decrements in quasar (QSO) spectra. The amplitude of CMB convergence in a given direction measures the projected surface density of matter. Measurements of QSO flux decrements trace the small-scale distribution of gas along a given line-of-sight. While the cross-correlation between these two measurements is small for a single line-of-sight, upcoming large surveys should enable its detection. This paper presents analytical estimates for the signal to noise (S/N) for measurements of the cross-correlation between the flux decrement and the convergence, {delta}F{kappa}, and for measurements of the cross-correlation between the variance in flux decrement and the convergence, <({delta}F){sup 2}{kappa}>. For the ongoing BOSS (SDSS III) and Planck surveys, we estimate an S/N of 30 and 9.6 for these two correlations. For the proposed BigBOSS and ACTPOL surveys, we estimate an S/N of 130 and 50 respectively. Since <({delta}F){sup 2}{kappa}> {proportional_to} {delta}{sub s}{sup 4}, the amplitude of these cross-correlations can potentially be used to measure the amplitude of {delta}{sub 8} at z {approx} 2 to 2.5% with BOSS and Planck and even better with future data sets. These measurements have the potential to test alternative theories for dark energy and to constrain the mass of the neutrino. The large potential signal estimated in our analytical calculations motivate tests with non-linear hydrodynamical simulations and analyses of upcoming data sets.

  10. The ultraviolet absorption spectrum of the quasar PKS 0405-12 and the local density of Lyman-alpha absorption systems

    NASA Technical Reports Server (NTRS)

    Bahcall, John N.; Jannuzi, Buell T.; Schneider, Donald P.; Hartig, George F.

    1993-01-01

    A sample of 32 absorption lines has been identified in the ultraviolet spectrum of the z = 0.57 quasar PKS 0405-12. Data cover the wavelength range 1190-3260 A. There are 10 extragalactic Ly-alpha absorption lines in the complete sample, all with observed equivalent widths greater than or equal to 0.40 A; three of the Ly-alpha lines have Ly-beta counterparts. The number of Ly-alpha lines observed in the spectrum of PKS 0405-12 is within 1 sigma of the number predicted on the basis of previous HST observations of 3C 273 and of H1821 + 643. Combining the HST observations of 3C 273, H1821 + 643, and PKS 0405-12, we estimate the local number density of Ly-alpha systems with rest equivalent widths larger than 0.32 A to be about 15 +/- 4 Ly-alpha lines per unit redshift. Ground-based images reveal a rich field of galaxies in the direction of PKS 0405-12, including many galaxies with the brightnesses and sizes expected if they belong to a cluster associated with the quasar. The quasar spectrum does not show any evidence for absorption at the redshift of the emission lines, indicating a covering factor of less than unity for the halos of galaxies in the cluster around PKS 0405 - 12.

  11. An 80 Mpc Filament of Galaxies at Redshift z=2.38

    NASA Technical Reports Server (NTRS)

    Woodgate, B.; Palunas, P.; Francis, P.; Williger, G.; Teplitz, H.

    2004-01-01

    We present the detection of 34 Lyman-alpha emission-line galaxy candidates in a 80 x 80 x 60 co-moving Mpc region surrounding the known z=2.38 galaxy cluster J2143-4423. We have confirmed 15 of these candidates in followup spectroscopy with 2dF at the AAT. The peak space density is a factor of 4 greater than that found by field samples at similar redshifts. The distribution of these galaxy candidates contains several 5-10 Mpc scale voids. We compare our observations with mock catalogs derived from the VIRGO consortium Lambda-CDM N-body simulations. Fewer than 1\\% of the mock catalogues contains voids as large as we observe. Our observations thus tentatively suggest that the galaxy distribution at redshift 2.38 contains larger voids than predicted by current models. The distribution of galaxies suggests a filament or cross-section of a great wall at least 80 x 10 Mpc in transverse extent. Three of the candidate galaxies and one previously discovered galaxy have the large luminosities and extended morphologies of "Lyman-alpha blobs". X-ray properties and physical characteristics of those blobs will be discussed in an accompanying poster by Williger et al.

  12. Computationally and experimentally assessed gravity-driven, mono- and bidisperse, particle-laden flows

    NASA Astrophysics Data System (ADS)

    Kumar, Shreyas; Huang, Kaiwen; Hin, Matt; Urdaneta, Gilberto; Mavromoustaki, Aliki; Wong, Jeffrey; Lee, Sungyon; Bertozzi, Andrea

    2013-11-01

    We present an experimental study which investigates the motion of granular materials in mono- and bi-disperse suspensions consisting of silicone oil, glass and ceramic beads. The beads are of distinct densities both denser than the oil but of approximately the same size. A finite volume of slurry is allowed to flow down an inclined plane and the subsequent flow development is recorded. The system parameters are the angle of inclination, the total particle concentration and the relative amount of heavy (ceramic) to light (glass) beads. Similarly to the results observed in previous studies of mono-disperse slurry flows, in bidisperse suspensions, there exist two stable flow regimes: the first one involves settling of particles to the substrate while, in the second one, the particles aggregate at the front of the flow. We carry out a series of experiments to investigate the effect of system parameters on the resulting flow regime patterns and compare our results with a theoretical model which incorporates the effects of shear-induced migration and sedimentation in bidisperse suspensions of negatively buoyant particles. Further, we use fluorescent particle beads to compare the particle spatio-temporal evolution observed in experiments against numerical simulations.

  13. Influence of gravity driven convection on the directional solidification of Bi/MnBi eutectic composites

    NASA Technical Reports Server (NTRS)

    Pirich, R. G.; Larson, D. J.

    1982-01-01

    The role of gravity on Bridgman-Stockharger directional solidification of eutectic Bi/MnBi has been studied in reduced gravity aboard NASA sounding rocket SPAR flight experiments and contrasted with normal gravity investigations. The directional solidification of eutectic Bi/MnBi results in a low volume fraction, faceted/nonfaceted aligned rod eutectic whose MnBi rod size, interrod spacing, thermal and magnetic properties are sensitive functions of solidification processing conditions. The morphology of the low-gravity samples showed striking differences compared with identically processed, normal gravity samples grown in the same apparatus. The MnBi rod diameter and interrod spacing distributions were significantly smaller, approximately 50 percent, for the low gravity samples compared with identically processed one gravity samples. Accompanying the smaller MnBi rod diameters observed in the flight samples, was an increase in permanent magnet properties which reached greater than 97 percent of the theoretical maximum. Gravitationally induced thermal instabilities in one-gravity which result in irregular interface movement and associated difficulty of the faceted MnBi phase to branch are suggested to explain the morphological differences between one and low gravity solidification.

  14. Gravity-driven deformation of Tenerife measured by InSAR time series analysis

    NASA Astrophysics Data System (ADS)

    Fernández, J.; Tizzani, P.; Manzo, M.; Borgia, A.; González, P. J.; Martí, J.; Pepe, A.; Camacho, A. G.; Casu, F.; Berardino, P.; Prieto, J. F.; Lanari, R.

    2009-02-01

    We study the state of deformation of Tenerife (Canary Islands) using Differential Synthetic Aperture Radar Interferometry (DInSAR). We apply the Small BAseline Subset (SBAS) DInSAR algorithm to radar images acquired from 1992 to 2005 by the ERS sensors to determine the deformation rate distribution and the time series for the coherent pixels identified in the island. Our analysis reveals that the summit area of the volcanic edifice is characterized by a rather continuous subsidence extending well beyond Las Cañadas caldera rim and corresponding to the dense core of the island. These results, coupled with GPS ones, structural and geological information and deformation modeling, suggest an interpretation based on the gravitational sinking of the dense core of the island into a weak lithosphere and that the volcanic edifice is in a state of compression. We also detect more localized deformation patterns correlated with water table changes and variations in the deformation time series associated with the seismic crisis in 2004.

  15. Gravity driven deterministic lateral displacement for suspended particles in a 3D obstacle array

    PubMed Central

    Du, Siqi; Drazer, German

    2016-01-01

    We present a simple modification to enhance the separation ability of deterministic lateral displacement (DLD) systems by expanding the two-dimensional nature of these devices and driving the particles into size-dependent, fully three-dimensional trajectories. Specifically, we drive the particles through an array of long cylindrical posts, such that they not only move parallel to the basal plane of the posts as in traditional two-dimensional DLD systems (in-plane motion), but also along the axial direction of the solid posts (out-of-plane motion). We show that the (projected) in-plane motion of the particles is completely analogous to that observed in 2D-DLD systems. In fact, a theoretical model originally developed for force-driven, two-dimensional DLD systems accurately describes the experimental results. More importantly, we analyze the particles out-of-plane motion and observe, for certain orientations of the driving force, significant differences in the out-of-plane displacement depending on particle size. Therefore, taking advantage of both the in-plane and out-of-plane motion of the particles, it is possible to achieve the simultaneous fractionation of a polydisperse suspension into multiple streams. PMID:27526935

  16. Rarefaction-singular shock dynamics for conserved volume gravity driven particle-laden thin film

    NASA Astrophysics Data System (ADS)

    Wang, L.; Mavromoustaki, A.; Bertozzi, A. L.; Urdaneta, G.; Huang, K.

    2015-03-01

    We employ a recently proposed model [Murisic et al., "Dynamics of particle settling and resuspension in viscous liquids," J. Fluid. Mech. 717, 203-231 (2013)] to study a finite-volume, particle-laden thin film flowing under gravity on an incline. For negatively buoyant particles with concentration above a critical value and buoyant particles, the particles accumulate at the front of the flow forming a particle-rich ridge, whose similarity solution is of the rarefaction-singular shock type. We investigate the structure in detail and find that the particle/fluid front advances linearly to the leading order with time to the one-third power as predicted by the Huppert solution [H. E. Huppert, "Flow and instability of a viscous current down a slope," Nature 300, 427-419 (1982)] for clear fluid (i.e., in the absence of particles). We also explore a deviation from this law when the particle concentration is high. Several experiments are carried out with both buoyant and negatively buoyant particles whose results qualitatively agree with the theoretics.

  17. Gravity driven deterministic lateral displacement for suspended particles in a 3D obstacle array.

    PubMed

    Du, Siqi; Drazer, German

    2016-01-01

    We present a simple modification to enhance the separation ability of deterministic lateral displacement (DLD) systems by expanding the two-dimensional nature of these devices and driving the particles into size-dependent, fully three-dimensional trajectories. Specifically, we drive the particles through an array of long cylindrical posts, such that they not only move parallel to the basal plane of the posts as in traditional two-dimensional DLD systems (in-plane motion), but also along the axial direction of the solid posts (out-of-plane motion). We show that the (projected) in-plane motion of the particles is completely analogous to that observed in 2D-DLD systems. In fact, a theoretical model originally developed for force-driven, two-dimensional DLD systems accurately describes the experimental results. More importantly, we analyze the particles out-of-plane motion and observe, for certain orientations of the driving force, significant differences in the out-of-plane displacement depending on particle size. Therefore, taking advantage of both the in-plane and out-of-plane motion of the particles, it is possible to achieve the simultaneous fractionation of a polydisperse suspension into multiple streams. PMID:27526935

  18. Simulation of gravity driven free-surface flow in fractured geological media

    SciTech Connect

    Kordilla, Jannes; Geyer, Tobias; Tartakovsky, Alexandre M.

    2011-08-25

    Abstract—Simulation of unsaturated free-surface flow in fractured geological media represents a challenge due to the highly heterogeneous flow field induced by extensive faults, joints and fissures. Free-surface flow in unsaturated media leads to highly intermittent flow regimes and flow velocities well above those assumed for the bulk volume. However, common modeling approaches relying on volume-averaged effective equations fail to capture this flow feature. In this work we present micro-scale flow simulations using a three-dimensional multiphase SPH code. Pairwise fluid-fluid and solid-fluid interaction forces are used to simulate a wide range of wetting conditions encountered on rock surfaces. It is shown that static contact angles for sessiles droplets are independent of the model discretization, i.e. the total amount of particles. Thus, computation times can be reduced without sacrificing qualitative or quantitative information. Furthermore we show that our model is in accordance with general scaling laws for droplet flow.

  19. Density, topography, and regional, tensile stresses: Gravity-driven extension of the northern Basin and range

    SciTech Connect

    Unruh, J.R. )

    1993-04-01

    It has long been recognized that regional topographic gradients may give rise to tectonic (non-lithostatic) stresses in the lithosphere (Artyushkov, 1973). The elevation of a buoyantly-uplifted region represents a balance between these stresses and the strength of the lithosphere. This study uses existing data on crustal and lithospheric structure in the western United States to test the hypothesis that the topographically high (1.5--2.2 km) northern Basin and Range is spreading under it own weight. Following England and Jackson (1989), the total deviatoric tensile force (Fl) in the northern Basin and Range (NBR) due to the regional high topography is the difference between the vertically-integrated lithostatic stress in the NBR and in western California. Using available velocity models for the crust and upper mantle, and empirically-derived velocity-density relationships, calculated values of Fl range between 1--3 [times] 10[sup 12] N/m. Assuming a visco-elastic rheology for the lithosphere, an average heat flow of 90 m W/m[sup 2], and a crustal thickness of 35 km, values of Fl ranging from 1--3 [times] 10[sup 12] N/m may result in horizontal extension rates of approximately 10[sup [minus]15]/s to 10[sup [minus]15]/s to 10[sup [minus]16]/s. This is comparable to the rate of seismically-released strain in the NBR, and to extension rates of 8--9 mm/yr across the region determined from geologic and geodetic data. These results imply that shear tractions on the base of the lithosphere from mantle convection are not necessary to explain NBR extension. In addition to driving active extension, the weight of the topographically high NBR may exert a compressive force on surrounding lowlands. If so, this may account for some of the active shortening in western California, and the state of horizontal compressive stress in the western Great Plains.

  20. Dense, gravity-driven granular-liquid flows down steep channels

    NASA Astrophysics Data System (ADS)

    Armanini, A.; Larcher, M.; Nucci, E.

    2011-12-01

    Debris flows are complex natural phenomena, characterized by a mixture of poorly sorted sediments and water driven by gravity. Depending on the size distribution, on the volume concentration of sediments and on the geometry and topography of the channel, flow conditions may be very different, ranging from very fast flows, dominated by granular collisions and by the turbulence on the liquid phase, to very slow and dense flows, dominated by the frictional contacts among the grains. To investigate the basic physics of debris flows, it is very useful to analyze the flow of a mixture of identical spherical particles saturated by water and driven by gravity down a steep channel in steady flow condition (Armanini et al. 2005). The flow presents three regions: an external one, near to the free surface, dominated by nearly instantaneous contacts among the particles (collisional regime), an internal region dominated by prolonged contacts among the particles (frictional regime) and a static bed in which the particles are immobile. The detailed vertical structure of this kind of flows was obtained by means of experiments carried out by Armanini et al. (2005) and Larcher et al. (2007). Armanini et al. (2009) analysed the stratification of rheological mechanisms inside the flow, focusing on the coexistence of frictional and collisional regimes, on the stress transmission inside the flow and on particles kinematics. In particular, it was observed that debris flows may show locally a typical intermittence of the flow regime, switching alternatively from frictional to collisional. While the rheology of the collisional layers is well described by the dense gas analogy (kinetic theory), a persuasive theoretical description of the frictional regime does not yet exist. A Coulombian scheme is often assumed, but this hypothesis is rather limitative because it requires a constant concentration or a distribution of particles concentration known a priori. An interesting scheme of this kind was recently proposed by GDR-Midi (2004), but this model does not contain a suitable formulation for the granular pressure (equation of state of the mixture). Following Armanini (2010), we propose a reinterpretation of the model, as weighted average of a pure Coulombian stress (dependent on the static friction angle at the static bed level) and of a dynamic stress, represented by a dynamic friction angle. Besides, a state relation is introduced for the granular pressure and the dynamic friction angle is derived from the kinetic theory. The proposed relations are finally successfully compared with the experimental data introduced above. REFERENCES A. Armanini, H. Capart, L. Fraccarollo, M. Larcher, 2005, J.F.M., 532, 269-319. A. Armanini, M. Larcher, L. Fraccarollo, Ph. Rev. E, 2009, 79, 051306. A. Armanini, 2010, Palermo, Proc. XXXII Conv. Naz. di Idr. e C.I. (in Italian) GDR MiDi, 2004. Eur. Phys. J. E, 14, 341-365 M. Larcher, L. Fraccarollo, A. Armanini, H. Capart, 2007, Journal Hydr. Res., 45, 59-71.