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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 {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.

  5. [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.

  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. 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.

  19. 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.

  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. 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.

  8. 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.

  9. 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.

  10. 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.

  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. 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.

  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. 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.

  20. 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.

  1. 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.

  2. 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.

  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. 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.

  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. 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.

  10. 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.

  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. 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.

  18. 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.

  19. 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.

  20. 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.

  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 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

  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 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

  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 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

  12. 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

  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. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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).

  5. 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.

  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. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  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. 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.

  18. 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.

  19. 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.

  20. 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.

  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. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  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. 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).

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  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. 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.

  20. 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.

  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 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.-

  7. 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.

  8. 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.

  9. 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.

  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. 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.

  18. 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.

  19. 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%.

  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. 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.

  2. 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.

  3. 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.

  4. 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.

  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. 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.

  9. 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.

  10. 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.

  11. 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.

  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. 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.

  15. 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.

  16. 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).

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  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. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  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. 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.

  1. 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.

  2. 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.

  3. 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

  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. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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

  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. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  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. 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

  17. 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

  18. 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

  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. 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.

  5. 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

  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