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Sample records for lyman-alpha flux power

  1. What Powers Lyman alpha Blobs?

    CERN Document Server

    Ao, Y; Beelen, A; Henkel, C; Cen, R; De Breuck, C; Francis, P; Kovacs, A; Lagache, G; Lehnert, M; Mao, M; Menten, K M; Norris, R; Omont, A; Tatemastu, K; Weiss, A; Zheng, Z

    2015-01-01

    Lyman alpha blobs (LABs) are spatially extended lyman alpha nebulae seen at high redshift. The origin of Lyman alpha emission in the LABs is still unclear and under debate. To study their heating mechanism(s), we present Australia Telescope Compact Array (ATCA) observations of the 20 cm radio emission and Herschel PACS and SPIRE measurements of the far-infrared (FIR) emission towards the four LABs in the protocluster J2143-4423 at z=2.38. Among the four LABs, B6 and B7 are detected in the radio with fluxes of 67+/-17 microJy and 77+/-16 microJy, respectively, and B5 is marginally detected at 3 sigma (51+/-16 microJy). For all detected sources, their radio positions are consistent with the central positions of the LABs. B6 and B7 are obviously also detected in the FIR. By fitting the data with different templates, we obtained redshifts of 2.20$^{+0.30}_{-0.35}$ for B6 and 2.20$^{+0.45}_{-0.30}$ for B7 which are consistent with the redshift of the lyman alpha emission within uncertainties, indicating that both ...

  2. Cosmological and astrophysical parameters from the SDSS flux power spectrum and hydrodynamical simulations of the Lyman-alpha forest

    CERN Document Server

    Viel, M; Viel, Matteo; Haehnelt, Martin G.

    2006-01-01

    (abridged) The flux power spectrum of the Lyman-alpha forest in quasar (QSO) absorption spectra is sensitive to a wide range of cosmological and astrophysical parameters and instrumental effects. Modelling the flux power spectrum in this large parameter space to an accuracy comparable to the statistical uncertainty of large samples of QSO spectra is very challenging. We use here a coarse grid of hydrodynamical simulations run with GADGET-2 to obtain a ``best guess'' model around which we calculate a finer grid of flux power spectra using a Taylor expansion of the flux power spectrum to first order. We find that the SDSS flux power spectrum alone is able to constrain a wide range of parameters including the amplitude of the matter power spectrum sigma_8, the matter density Omega_m, the spectral index of primordial density fluctuations n, the effective optical depth tau_eff and its evolution. The thermal history of the Intergalactic Medium (IGM) is, however, poorly constrained and the SDSS data favour either an...

  3. The impact of feedback from galaxy formation on the Lyman-alpha transmitted flux

    CERN Document Server

    Viel, Matteo; Booth, Craig M

    2012-01-01

    The forest of Lyman-alpha absorption lines seen in the spectra of distant quasars has become an important probe of the distribution of matter in the Universe. We use large, hydrodynamical simulations from the OWLS project to investigate the effect of feedback from galaxy formation on the probability distribution function and the power spectrum of the Lyman-alpha transmitted flux. While metal-line cooling is unimportant, both galactic outflows from massive galaxies driven by active galactic nuclei and winds from low-mass galaxies driven by supernovae have a substantial impact on the flux statistics. At redshift z=2.25, the effects on the flux statistics are of a similar magnitude as the statistical uncertainties of published data sets. The changes in the flux statistics are not due to differences in the temperature-density relation of the photo-ionised gas. Instead, they are caused by changes in the density distribution and in the fraction of hot, collisionally ionised gas. It may be possible to disentangle as...

  4. Minimally Parametric Constraints on the Primordial Power Spectrum from Lyman-alpha

    CERN Document Server

    Bird, Simeon

    2010-01-01

    Current analyses of the Lyman-alpha forest assume that the primordial power spectrum of density perturbations obeys a simple power law, a strong theoretical assumption which should be tested. Employing a large suite of numerical simulations which drop this assumption, we reconstruct the shape of the primordial power spectrum using Lyman-alpha data from the Sloan Digital Sky Survey (SDSS). Our method combines a minimally parametric framework with cross-validation, a technique used to avoid over-fitting the data. Future work will involve predictions for the upcoming Baryon Oscillation Sky Survey (BOSS), which will provide new Lyman-alpha data with vastly decreased statistical errors.

  5. Computing Intrinsic Lyman-alpha Fluxes of F5 V to M5 V Stars

    CERN Document Server

    Linsky, Jeffrey L; Ayres, Tom

    2013-01-01

    The Lyman-alpha emission line dominates the far-ultraviolet spectra of late-type stars and is a major source for photodissociation of important molecules including H2O, CH4, and CO2 in exoplanet atmospheres. The incident flux in this line illuminating an exoplanet's atmosphere cannot be measured directly as neutral hydrogen in the interstellar medium (ISM) attenuates most of the flux reaching the Earth. Reconstruction of the intrinsic Lyman-alpha line has been accomplished for a limited number of nearby stars, but is not feasible for distant or faint host stars. We identify correlations connecting the intrinsic Lyman-alpha flux with the flux in other emission lines formed in the stellar chromosphere, and find that these correlations depend only gradually on the flux in the other lines. These correlations, which are based on HST spectra, reconstructed Lyman-alpha line fluxes, and irradiance spectra of the quiet and active Sun, are required for photochemical models of exoplanet atmospheres when intrinsic Lyman-...

  6. Predicting Lyman-alpha and Mg II Fluxes from K and M Dwarfs Using GALEX Ultraviolet Photometry

    CERN Document Server

    Shkolnik, Evgenya L; Peacock, Sarah; Barman, Travis S

    2014-01-01

    A star's UV emission can greatly affect the atmospheric chemistry and physical properties of closely orbiting planets with the potential for severe mass loss. In particular, the Lyman-alpha emission line at 1216 Angstroms, which dominates the far-ultraviolet spectrum, is a major source of photodissociation of important atmospheric molecules such as water and methane. The intrinsic flux of Lyman-alpha, however, cannot be directly measured due to the absorption of neutral hydrogen in the interstellar medium and contamination by geocoronal emission. To date, reconstruction of the intrinsic Lyman-alpha line based on Hubble Space Telescope spectra has been accomplished for 46 FGKM nearby stars, 28 of which have also been observed by the Galaxy Evolution Explorer (GALEX). Our investigation provides a correlation between published intrinsic Lyman-alpha and GALEX far- and near-ultraviolet chromospheric fluxes for K and M stars. The negative correlations between the ratio of the Lyman-alpha to the GALEX fluxes reveal ...

  7. Minimally Parametric Power Spectrum Reconstruction from the Lyman-alpha Forest

    CERN Document Server

    Bird, Simeon; Viel, Matteo; Verde, Licia

    2010-01-01

    Current results from the Lyman alpha forest assume that the primordial power spectrum of density perturbations follows a simple power law form. We present the first analysis of Lyman alpha data to study the effect of relaxing this strong assumption on primordial and astrophysical constraints. We perform a large suite of numerical simulations, using them to calibrate a minimally parametric framework for describing the power spectrum. Combined with cross-validation, a statistical technique which prevents over-fitting of the data, this framework allows us to reconstruct the power spectrum shape without strong prior assumptions. We find no evidence for deviation from scale-invariance; our analysis also shows that current Lyman alpha data do not have sufficient statistical power to robustly probe the shape of the power spectrum at these scales. In contrast, the ongoing Baryon Oscillation Sky Survey (BOSS) will be able to do so with high precision. Furthermore, this near-future data will be able to break degeneraci...

  8. The Non-Linear Power Spectrum of the Lyman Alpha Forest

    CERN Document Server

    Arinyo-i-Prats, Andreu; Viel, Matteo; Cen, Renyue

    2015-01-01

    The Lyman alpha forest power spectrum has been measured on large scales by the BOSS survey in SDSS-III at $z\\sim 2.3$, 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 Lyman Alpha 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 Lyman Alpha forest and provide a better physical interpretation of ...

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

    Energy Technology Data Exchange (ETDEWEB)

    Vallinotto, Alberto; /Paris, Inst. Astrophys. /Fermilab; Das, Sudeep; /Princeton U. Observ. /Princeton U.; Spergel, David N.; /Princeton U. Observ. /APC, Paris; 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.

  10. Lyman-alpha emission in star-forming galaxies

    Science.gov (United States)

    Hartmann, Lee W.; Huchra, John P.; Geller, Margaret J.; O'Brien, Paul; Wilson, Robert

    1988-01-01

    IUE observations of five blue, low-metallicity, star-forming galaxies sufficiently redshifted to permit detection of Lyman-alpha are reported. The galaxies with metallicities 0.1 time solar or more have weak or absent Lyman-alpha emission. There is evidence for increasing Lyman-alpha emission with decreasing metallicity. The reduction of Lyman-alpha fluxes from recombination values is attributed to absorption of multiply scattered Lyman-alpha by dust.

  11. The Lyman-alpha Forest Flux Distribution at z\\sim 5.2 and the Evolution of the Ionizing Background

    CERN Document Server

    McDonald, P; Donald, Patrick Mc; Miralda-Escude, Jordi

    2000-01-01

    We use the redshift evolution of the lyman-alpha forest mean transmitted flux at z>2.5 to infer the evolution of the intensity of the ionizing background, using theoretical predictions for the density distribution of the intergalactic gas giving rise to the lyman-alpha forest. The proper background intensity declines gradually with redshift, decreasing by a factor \\sim 3 between z=3 and z=5. The gravitational structure formation theory of the lyman-alpha forest implies that, given the observed mean transmitted flux of \\bar{F}=0.1 in the highest redshift quasar (with a mean lyman-alpha forest redshift z=5.2), only about 3% of the lyman-alpha spectrum should have a flux higher than 50% of the continuum, and less than 0.5% of pixels should have flux above 75% of the continuum, assuming a uniform ionizing background intensity. We show that this is consistent with the spectrum shown in Fan et al.

  12. Lyman Alpha Control

    CERN Document Server

    Nielsen, Daniel Stefaniak

    2015-01-01

    This document gives an overview of how to operate the Lyman Alpha Control application written in LabVIEW along with things to watch out for. Overview of the LabVIEW code itself as well as the physical wiring of and connections from/to the NI PCI-6229 DAQ box is also included. The Lyman Alpha Control application is the interface between the ALPHA sequencer and the HighFinesse Wavelength Meter as well as the Lyman Alpha laser setup. The application measures the wavelength of the output light from the Lyman Alpha cavity through the Wavelength Meter. The application can use the Wavelength Meter’s PID capabilities to stabilize the Lyman Alpha laser output as well as switch between up to three frequencies.

  13. The intergalactic medium thermal history at redshift z=1.7--3.2 from the Lyman alpha forest: a comparison of measurements using wavelets and the flux distribution

    CERN Document Server

    Garzilli, A; Kim, T -S; Leach, S; Viel, M

    2012-01-01

    We investigate the thermal history of the intergalactic medium (IGM) in the redshift interval z=1.7--3.2 by studying the small-scale fluctuations in the Lyman alpha forest transmitted flux. We apply a wavelet filtering technique to eighteen high resolution quasar spectra obtained with the Ultraviolet and Visual Echelle Spectrograph (UVES), and compare these data to synthetic spectra drawn from a suite of hydrodynamical simulations in which the IGM thermal state and cosmological parameters are varied. From the wavelet analysis we obtain estimates of the IGM thermal state that are in good agreement with other recent, independent wavelet-based measurements. We also perform a reanalysis of the same data set using the Lyman alpha forest flux probability distribution function (PDF), which has previously been used to measure the IGM temperature-density relation. This provides an important consistency test for measurements of the IGM thermal state, as it enables a direct comparison of the constraints obtained using t...

  14. Broadband distortion modeling in Lyman-$\\alpha$ forest BAO fitting

    CERN Document Server

    Blomqvist, Michael; Bautista, Julian E; Ariño, Andreu; Busca, Nicolás G; Miralda-Escudé, Jordi; Slosar, Anže; Font-Ribera, Andreu; Margala, Daniel; Schneider, Donald P; Vazquez, Jose A

    2015-01-01

    In recent years, the Lyman-$\\alpha$ absorption observed in the spectra of high-redshift quasars has been used as a tracer of large-scale structure by means of the three-dimensional Lyman-$\\alpha$ forest auto-correlation function at redshift $z\\simeq 2.3$, but the need to fit the quasar continuum in every absorption spectrum introduces a broadband distortion that is difficult to correct and causes a systematic error for measuring any broadband properties. We describe a $k$-space model for this broadband distortion based on a multiplicative correction to the power spectrum of the transmitted flux fraction that suppresses power on scales corresponding to the typical length of a Lyman-$\\alpha$ forest spectrum. Implementing the distortion model in fits for the baryon acoustic oscillation (BAO) peak position in the Lyman-$\\alpha$ forest auto-correlation, we find that the fitting method recovers the input values of the linear bias parameter $b_{F}$ and the redshift-space distortion parameter $\\beta_{F}$ for mock dat...

  15. Modeling the Lyman-alpha Forest in Collisionless Simulations

    CERN Document Server

    Sorini, Daniele; Lukić, Zarija; Hennawi, Joseph F

    2016-01-01

    Cosmological hydrodynamic simulations can accurately predict the properties of the intergalactic medium (IGM), but only under the condition of retaining high spatial resolution necessary to resolve density fluctuations in the IGM. This resolution constraint prohibits simulating large volumes, such as those probed by BOSS and future surveys, like DESI and 4MOST. To overcome this limitation, we present Iteratively Matched Statistics (IMS), a novel method to accurately model the Lyman-alpha forest with collisionless N-body simulations, where the relevant density fluctuations are unresolved. We use a small-box, high-resolution hydrodynamic simulation to obtain the probability distribution function (PDF) and the power spectrum of the real-space Lyman-alpha forest flux. These two statistics are iteratively mapped onto a pseudo-flux field of an N-body simulation, which we construct from the matter density. We demonstrate that our method can perfectly reproduce line-of-sight observables, such as the PDF and power spe...

  16. Relativistic effects in Lyman-alpha forest

    CERN Document Server

    Iršič, Vid; Viel, Matteo

    2015-01-01

    We present the calculation of the Lyman-alpha (Lyman-$\\alpha$) transmitted flux fluctuations with full relativistic corrections to the first order. Even though several studies exist on relativistic effects in galaxy clustering, this is the first study to extend the formalism to a different tracer of underlying matter at unique redshift range ($z = 2 - 5$). Furthermore, we show a comprehensive application of our calculations to the Quasar- Lyman-$\\alpha$ cross-correlation function. Our results indicate that the signal of relativistic effects can be as large as 30% at Baryonic Acoustic Oscillation (BAO) scale, which is much larger than anticipated and mainly due to the large differences in density bias factors of our tracers. We construct an observable, the anti-symmetric part of the cross- correlation function, that is dominated by the relativistic signal and offers a new way to measure the relativistic terms at relatively small scales. The analysis shows that relativistic effects are important when considerin...

  17. The Lyman-alpha Forest Power Spectrum from the Sloan Digital Sky Survey

    CERN Document Server

    McDonald, P; Burles, S; Schlegel, D J; Weinberg, D H; Shih, D; Schaye, J; Schneider, D P; Brinkmann, J; Brunner, R J; Fukugita, M; Donald, Patrick Mc; Seljak, Uros; Burles, Scott; Schlegel, David J.; Weinberg, David H.; Shih, David; Schaye, Joop; Schneider, Donald P.; Brunner, Robert J.; Fukugita, Masataka

    2004-01-01

    We measure the power spectrum, P_F(k,z), of the transmitted flux in the Ly-alpha forest using 3035 high redshift quasar spectra from the Sloan Digital Sky Survey. This sample is almost two orders of magnitude larger than any previously available data set, yielding statistical errors of ~0.6% and ~0.005 on, respectively, the overall amplitude and logarithmic slope of P_F(k,z). This unprecedented statistical power requires a correspondingly careful analysis of the data and of possible systematic contaminations in it. For this purpose we reanalyze the raw spectra to make use of information not preserved by the standard pipeline. We investigate the details of the noise in the data, resolution of the spectrograph, sky subtraction, quasar continuum, and metal absorption. We find that background sources such as metals contribute significantly to the total power and have to be subtracted properly. We also find clear evidence for SiIII correlations with the Ly-alpha forest and suggest a simple model to account for thi...

  18. Constraints on neutrino masses from Lyman-alpha forest power spectrum with BOSS and XQ-100

    Science.gov (United States)

    Yèche, Christophe; Palanque-Delabrouille, Nathalie; Baur, Julien; du Mas des Bourboux, Hélion

    2017-06-01

    We present constraints on masses of active and sterile neutrinos in the context of the ΛCDMν and ΛWDM models, respectively. We use the one-dimensional Lyα-forest power spectrum from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III) measured by Palanque-Delabrouille et al. [1], and from the VLT/XSHOOTER legacy survey (XQ-100). In this paper, we present our own measurement of the publicly released XQ-100 quasar spectra, focusing in particular on an improved determination of the spectrograph resolution that allows us to push to smaller scales than the public release and reach k-modes of 0.070 s km-1. We compare the obtained 1D Lyα flux power spectrum to the one measured by Irsic et al. [2] to k-modes of 0.057 s km-1. Fitting Lyα data alone leads to cosmological parameters in excellent agreement with the values derived independently from Planck 2015 Cosmic Microwave Background (CMB) data. Combining BOSS and XQ-100 Lyα power spectra, we constrain the sum of neutrino masses to ∑ mν sources of systematic uncertainties. With the addition of CMB data, this bound is tightened to ∑ mν right-handed neutrinos. Combining the 1D Lyα-forest power spectrum measured by BOSS and XQ-100, we improve the two bounds to mX gtrsim 4.17 : keV and ms gtrsim 25.0 : keV (95% C.L.), slightly more constraining than what was achieved in Baur et al. 2015 [3] with BOSS data alone. The 3 σ bound shows a more significant improvement, increasing from mX gtrsim 2.74 : keV for BOSS alone to mX gtrsim 3.10 : keV for the combined BOSS+XQ-100 data set. Finally, we include in our analysis the first two redshift bins (z = 4.2 and z = 4.6) of the power spectrum measured by Viel et al. 2013 [4] with the high-resolution HIRES/MIKE spectrographs. The addition of HIRES/MIKE power spectrum allows us to further improve the two limits to mX gtrsim 4.65 : keV and ms gtrsim 28.8 : keV (95% C.L.).

  19. The Lyman alpha reference sample

    DEFF Research Database (Denmark)

    Hayes, M.; Östlin, G.; Schaerer, D.

    2013-01-01

    We report on new imaging observations of the Lyman alpha emission line (Lyα), 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 Lyman alpha emission line (Lyα), 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

  20. Observational estimates of the initial power spectrum at small scale from Lyman-$\\alpha$ absorbers

    CERN Document Server

    Demianski, M

    2003-01-01

    We present a new method of measuring the power spectrum of initial perturbations to an unprecedently small scale of $\\sim$ 10$h^{-1}$ kpc. We apply this method to a sample of 4500 Ly-$\\alpha$ absorbers and recover the cold dark matter (CDM) like power spectrum at scales $\\geq 300h^{-1}$kpc with a precision of $\\sim$ 10%. However at scales $\\sim 10 - 300 h^{-1}$kpc the measured and CDM--like spectra are noticeable different. This result suggests a complex inflation with generation of excess power at small scales. The magnitude and reliability of these deviations depend also upon the possible incompleteness of our sample and poorly understood process of formation of weak absorbers. Confirmation of the CDM--like shape of the initial power spectrum or detection of its distortions at small scales are equally important for widely discussed problems of physics of the early Universe, galaxy formation, and reheating of the Universe. Our method links the observed mass function of absorbers with the correlation function...

  1. arXiv Neutrino masses and cosmology with Lyman-alpha forest power spectrum

    CERN Document Server

    Palanque-Delabrouille, Nathalie; Baur, Julien; Magneville, Christophe; Rossi, Graziano; Lesgourgues, Julien; Borde, Arnaud; Burtin, Etienne; LeGoff, Jean-Marc; Rich, James; Viel, Matteo; Weinberg, David

    2015-01-01

    We present constraints on neutrino masses, the primordial fluctuation spectrum from inflation, and other parameters of the $\\Lambda$CDM model, using the one-dimensional Ly$\\alpha$-forest power spectrum measured by Palanque-Delabrouille et al. (2013) from SDSS-III/BOSS, complemented by Planck 2015 cosmic microwave background (CMB) data and other cosmological probes. This paper improves on the previous analysis by Palanque-Delabrouille et al. (2015) by using a more powerful set of calibrating hydrodynamical simulations that reduces uncertainties associated with resolution and box size, by adopting a more flexible set of nuisance parameters for describing the evolution of the intergalactic medium, by including additional freedom to account for systematic uncertainties, and by using Planck 2015 constraints in place of Planck 2013. Fitting Ly$\\alpha$ data alone leads to cosmological parameters in excellent agreement with the values derived independently from CMB data, except for a weak tension on the scalar index ...

  2. C IV and He II Line Emission of Lyman Alpha Blobs: Powered by Shock Heated Gas

    CERN Document Server

    Cabot, Samuel H C; Zheng, Zheng

    2016-01-01

    Utilizing {\\it ab initio} ultra-high resolution hydrodynamical simulations, we investigate the properties of the interstellar and circum-galactic medium of Ly$\\alpha$ Blobs (LABs) at $z=3$, focusing on three important emission lines: Ly$\\alpha$ 1216\\AA, \\heii 1640\\AA\\ and \\civ 1449\\AA. Their relative strengths provide a powerful probe of the thermodynamic properties of the gas when confronted with observations. By adjusting the dust attenuation effect using one parameter and matching the observed size-luminosity relation of LABs using another parameter, we show that our simulations can reproduce the observed \\civ/\\lya\\ and \\heii/\\lya\\ ratios adequately. This analysis provides the first successful physical model to account for simultaneously the LAB luminosity function, luminosity-size relation, and the \\civ/Ly$\\alpha$ and \\heii/Ly$\\alpha$ ratios, with only two parameters. The physical underpinning for this model is that, in addition to the stellar component for the \\lya\\ emission, the \\lya\\ and \\civ\\ emission...

  3. The Lyman-alpha forest in f(R) modified gravity

    CERN Document Server

    Arnold, Christian; Springel, Volker

    2014-01-01

    In this work, we analyze the Lyman-$\\alpha$ forest in cosmological hydrodynamical simulations of chameleon-type f(R) gravity with the goal to assess whether the impact of such models is detectable in absorption line statistics. We carry out a set of hydrodynamical simulations with the cosmological simulation code MG-GADGET, including star formation and cooling effects, and create synthetic Lyman-$\\alpha$ absorption spectra from the simulation outputs. We statistically compare simulations with f(R) and ordinary general relativity, focusing on flux probability distribution functions (PDFs) and flux power-spectra, an analysis of the column density and line width distributions, as well as the matter power spectrum. We find that the influence of f(R) gravity on the Lyman-$\\alpha$ forest is rather small. Even models with strong modifications of gravity, like $|\\bar{f}_{R0}| = 10^{-4}$, do not change the statistical Lyman-$\\alpha$ properties by more than 10%. The column density and line width distributions are hardl...

  4. Simulating the Lyman Alpha Forest

    CERN Document Server

    Machacek, M E; Anninos, P; Meiksin, A; Norman, M L; Machacek, Marie E.; Bryan, Greg L.; Anninos, Peter; Meiksin, Avery; Norman, Michael L.

    1998-01-01

    In this paper we review the importance of the Lyman alpha forest as a probe of structure formation in the universe. We first discuss the statistics used to describe the Lyman alpha forest and the numerical techniques used to produce simulated spectra of the forest from a given cosmological model. We then discuss the physical picture of the absorbing structures that emerges from these numerical simulations. Finally, we comment on how two of the statistics, the slope of the column density distribution and the b parameter distribution, may be used to constrain competing cosmologies.

  5. Lyman-alpha Forest Constraints on Decaying Dark Matter

    CERN Document Server

    Wang, Mei-Yu; Peter, Annika H G; Zentner, Andrew R; Purcell, Chris W

    2013-01-01

    We present an analysis of high-resolution N-body simulations of decaying dark matter cosmologies focusing on the statistical properties of the transmitted Lyman-alpha forest flux in the high-redshift intergalactic medium. In this type of model a dark matter particle decays into a slightly less massive stable dark matter daughter particle and a comparably light particle. The small mass splitting provides a non-relativistic kick velocity V_k to the daughter particle resulting in free-streaming and subsequent damping of small-scale density fluctuations. Current Lyman-alpha forest power spectrum measurements probe comoving scales up to ~ 2-3 h^-1 Mpc at redshifts z ~ 2-4, providing one of the most robust ways to probe cosmological density fluctuations on relatively small scales. The suppression of structure growth due to the free-streaming of dark matter daughter particles also has a significant impact on the neutral hydrogen cloud distribution, which traces the underlying dark matter distribution well at high re...

  6. Numerical Simulations of the Lyman-alpha forest - A comparison of Gadget-2 and Enzo

    CERN Document Server

    Regan, J A; Viel, M; Regan, John A.; Haehnelt, Martin G.

    2006-01-01

    We compare simulations of the Lyman-alpha forest performed with two different hydrodynamical codes, Gadget-2 and Enzo. A comparison of the dark matter power spectrum for simulations run with identical initial conditions show differences of 1-3% at the scales relevant for quantitative studies of the Lyman-alpha forest. This allows a meaningful comparison of the effect of the different implementations of the hydrodynamic part of the two codes. Using the same cooling and heating algorithm in both codes the differences in the temperature and the density probability distribution function are of the order of 10%. These differences can be mainly attributed to a slight mismatch in the resolution. The differences are smaller than or equal to the effects of boxsize and resolution on these statistics. Once resolution effects are taken into account the differences in the flux power spectrum - the statistics most widely used for estimating the matter power spectrum and cosmological parameters from Lyman-alpha forest data ...

  7. Fluctuations in the High-Redshift Lyman-Werner and Lyman-alpha Radiation Backgrounds

    CERN Document Server

    Holzbauer, Lauren N

    2011-01-01

    We use a new method to model fluctuations of the Lyman-Werner (LW) and Lyman-alpha radiation backgrounds at high redshift. At these early epochs the backgrounds are symptoms of a universe newly lit with its first stars. LW photons (11.5-13.6 eV) are of particular interest because they dissociate molecular hydrogen, the primary coolant in the first minihalos. By using a variation of the halo model, we efficiently generate power spectra for any choice of radiation background. We find that the LW power spectrum typically traces the matter power spectrum at large scales but turns over at the scale corresponding to the effective `horizon' of LW photons (~100 comoving Mpc), unless the sources are extremely rare. The series of horizons that characterize the Lyman-alpha flux profile shape the fluctuations of that background in a similar fashion, though those imprints are washed out once one considers fluctuations in the brightness temperature of the 21-cm signal. The Lyman-alpha background strongly affects the redshi...

  8. Inferring the IGM thermal history during reionisation with the Lyman-$\\alpha$ forest power spectrum at redshift $z \\simeq 5$

    CERN Document Server

    Nasir, Fahad; Becker, George D

    2016-01-01

    We use cosmological hydrodynamical simulations to assess the feasibility of constraining the thermal history of the intergalactic medium during reionisation with the Ly$\\alpha$ forest at $z \\simeq 5$. Pressure smoothing has a measurable impact on the transmitted flux power spectrum that can be isolated from Doppler broadening at this redshift. We parameterise the effect of pressure smoothing on the power spectrum using the cumulative energy per proton, $u_0$, deposited into a gas parcel at the mean background density, a quantity that is tightly linked with the integrated thermal history and the gas density power spectrum in the simulations. We construct mock observations of the line of sight Ly$\\alpha$ forest power spectrum and use a Markov Chain Monte Carlo approach to recover $u_{0}$ at redshifts $5 \\leq z \\leq 12$. A statistical uncertainty of $\\sim 20$ per cent is expected (at 68 per cent confidence) at $z\\simeq 5$ using high resolution spectra with a total redshift path length of $\\Delta z=4$ and a typic...

  9. Enhanced direct collapse due to Lyman {\\alpha} feedback

    CERN Document Server

    Johnson, Jarrett L

    2016-01-01

    We assess the impact of trapped Lyman {\\alpha} cooling radiation on the formation of direct collapse black holes (DCBHs). We apply a one-zone chemical and thermal evolution model, accounting for the photodetachment of H$^-$ ions, precursors to the key coolant H$_{\\rm 2}$, by Lyman {\\alpha} photons produced during the collapse of a cloud of primordial gas in an atomic cooling halo at high redshift. We find that photodetachment of H$^-$ by trapped Lyman {\\alpha} photons can lower the level of the H$_{\\rm 2}$-dissociating background radiation field required for DCBH formation substantially, dropping the critical flux by up to an order of magnitude. This translates into a large increase in the expected number density of DCBHs in the early Universe, and implies that DCBHs may be the seeds for the BHs residing in the centers of a significant fraction of galaxies today. We find that detachment of H$^-$ by Lyman {\\alpha} has the strongest impact on the critical flux for the relatively high background radiation temper...

  10. Hubble Space Telescope Imaging of Lyman Alpha Emission at z=4.4

    CERN Document Server

    Finkelstein, Steven L; Windhorst, Rogier A; Ryan, Russell E; Hathi, Nimish P; Finkelstein, Keely D; Anderson, Jay; Grogin, Norman A; Koekemoer, Anton M; Malhotra, Sangeeta; Mutchler, Max; Rhoads, James E; McCarthy, Patrick J; O'Connell, Robert W; Balick, Bruce; Bond, Howard E; Calzetti, Daniela; Disney, Michael J; Dopita, Michael A; Frogel, Jay A; Hall, Donald N B; Holtzman, Jon A; Kimble, Randy A; Luppino, Gerard; Paresce, Francesco; Saha, Abhijit; Silk, Joseph I; Trauger, John T; Walker, Alistair R; Whitmore, Bradley C; Young, Erick T

    2010-01-01

    We present the highest redshift detections of resolved Lyman alpha emission, using Hubble Space Telescope/ACS F658N narrowband-imaging data taken in parallel with the Wide Field Camera 3 Early Release Science program in the GOODS CDF-S. We detect Lyman alpha emission from three spectroscopically confirmed z = 4.4 Lyman alpha emitting galaxies (LAEs), more than doubling the sample of LAEs with resolved Lyman alpha emission. Comparing the light distribution between the rest-frame ultraviolet continuum and narrowband images, we investigate the escape of Lyman alpha photons at high redshift. While our data do not support a positional offset between the Lyman alpha and rest-frame ultraviolet (UV) continuum emission, the half-light radii in two out of the three galaxies are significantly larger in Lyman alpha than in the rest-frame UV continuum. This result is confirmed when comparing object sizes in a stack of all objects in both bands. Additionally, the narrowband flux detected with HST is significantly less than...

  11. Lyman alpha emission from the first galaxies : signatures of accretion and infall in the presence of line trapping

    NARCIS (Netherlands)

    Latif, M. A.; Schleicher, Dominik R. G.; Spaans, M.; Zaroubi, S.

    2011-01-01

    The formation of the first galaxies is accompanied by large accretion flows and virialization shocks, during which the gas is shock heated to temperatures of similar to 10(4) K, leading to potentially strong fluxes in the Lyman alpha line. Indeed, a number of Lyman alpha blobs have been detected at

  12. The Lyman-alpha Forest as a Cosmological Tool

    CERN Document Server

    Weinberg, D H; Katz, N; Kollmeier, J A; Weinberg, David H.; Dav'e, Romeel; Katz, Neal; Kollmeier, Juna A.

    2003-01-01

    We review recent developments in the theory of the Lyman-alpha forest and their implications for the role of the forest as a test of cosmological models. Simulations predict a relatively tight correlation between the local Lya optical depth and the local gas or dark matter density. Statistical properties of the transmitted flux can constrain the amplitude and shape of the matter power spectrum at high redshift, test the assumption of Gaussian initial conditions, and probe the evolution of dark energy by measuring the Hubble parameter H(z). Simulations predict increased Lya absorption in the vicinity of galaxies, but observations show a Lya deficit within Delta_r ~ 0.5 Mpc/h (comoving). We investigate idealized models of "winds" and find that they must eliminate neutral hydrogen out to comoving radii ~1.5 Mpc/h to marginally explain the data. Winds of this magnitude suppress the flux power spectrum by \\~0.1 dex but have little effect on the distribution function or threshold crossing frequency. In light of the...

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

    Science.gov (United States)

    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.

  14. Lyman Alpha Spicule Observatory (LASO)

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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. Geocoronal Lyman Alpha Observations with COS

    Science.gov (United States)

    Ake, Thomas B.

    2012-01-01

    The time-tagged mode of the Cosmic Origins Spectrograph (COS) provides a convenient method of studying the orbital variation of geocoronal Lyman-alpha emission at the altitude of HST. We have analyzed G130M blank sky exposures from scheduled STIS parallels and observations for which the target acquisition failed. We supplement these with observations of WD standard stars from flat field and sensitivity monitoring programs where the stellar Lyα profile can be modeled and its contribution to the geocoronal emission removed. Data were corrected for time-dependent sensitivity changes and gain sag. The measurements have been fit by an analytical model based on the orbital position of HST and the angle between the target and the Earth as seen from HST. The Lyα emission varies from less than 2 kR for a target observed at orbit midnight to 37 kR for one observed at the bright Earth limb at orbit noon. A long-term trend of increasing flux is evident, consistent with solar Lyα measurements by SOLSTICE on SORCE as the next solar maximum is approached. We expect the irradiance at solar maximum to be at least 50-55 kR. This level still should not trigger local count rate violations for the FUV detector, but will accelerate gain sag of the microchannel plates in the regions where Lyα falls.

  17. The redshift evolution of Lyman-$\\alpha$ absorbers

    CERN Document Server

    Valageas, P; Silk, J

    1999-01-01

    We present a model for the Lyman-alpha absorbers that treats all objects (from the low-density forest clouds to the dense damped systems) in a unified description. This approach is consistent with an earlier model of galaxies (luminosity function, metallicity) but also with the known description of the density field in the small-scale non-linear regime. We consider two cosmological models: a critical universe $\\Omega=1$ with a CDM power-spectrum, and an open CDM universe with $\\Omega_0=0.3$, $\\Lambda=0$. We reproduce the available data on column density distribution as a function of redshift, the value of the main new parameter, the background ionizing UV flux, being consistent with the observed limits. This allows a quantitatively trustable analytical description of the opacity, mass, size, velocity dispersion and metallicity of these absorbers, over a range of column densities spanning 10 orders of magnitude. Moreover, together with an earlier model of galaxy formation this draws a unified picture of the re...

  18. Lyman Alpha Signatures from Direct Collapse Black Holes

    CERN Document Server

    Dijkstra, Mark; Sobral, David

    2016-01-01

    `Direct collapse black holes' (DCBHs) provide possible seeds for supermassive black holes that exist at redshifts as high as z~7. We study Lyman Alpha (Lya) radiative transfer through simplified representations of the DCBH-scenario. We find that gravitational heating of the collapsing cloud gives rise to a Lya cooling luminosity of up to ~ 1e38(M_gas/1e6 Msun)^2 erg/s. The Lya production rate can be significantly larger during the final stages of collapse, but collisional deexcitation efficiently suppresses the emerging Lya flux. Photoionization by a central source boosts the Lya luminosity to L~1e43(M_BH/1e6 M_sun) erg/s during specific evolutionary stages of the cloud, where M_BH denotes the mass of the black hole powering this source. We predict that the width and velocity off-set of the Lya spectral line range from a few tens to few thousands km/s, depending sensitively on the evolutionary state of the cloud. We also compare our predictions to observations of CR7 (Sobral et al. 2015), a luminous Lya emitt...

  19. First stars in Damped Lyman Alpha systems

    NARCIS (Netherlands)

    Salvadori, Stefania; Ferrara, Andrea

    2011-01-01

    In order to characterize Damped Lyman Alpha systems (DLAs) potentially host- ing first stars, we present a novel approach to investigate DLAs in the context of Milky Way (MW) formation, along with their connection with the most metal-poor stars and local dwarf galaxies. The merger tree method previo

  20. First stars in Damped Lyman Alpha systems

    NARCIS (Netherlands)

    Salvadori, Stefania; Ferrara, Andrea

    In order to characterize Damped Lyman Alpha systems (DLAs) potentially host- ing first stars, we present a novel approach to investigate DLAs in the context of Milky Way (MW) formation, along with their connection with the most metal-poor stars and local dwarf galaxies. The merger tree method

  1. First Detection of Cosmic Microwave Background Lensing and Lyman-{\\alpha} Forest Bispectrum

    CERN Document Server

    Doux, Cyrille; Aubourg, Eric; Ganga, Ken; Lee, Khee-Gan; Spergel, David N; Tréguer, Julien

    2016-01-01

    We present the first detection of a correlation between the Lyman-$\\alpha$ forest and cosmic microwave background (CMB) lensing. For each Lyman-$\\alpha$ forest in SDSS-III/BOSS DR12, we correlate the one-dimensional power spectrum with the CMB lensing convergence on the same line of sight from Planck. This measurement constitutes a position-dependent power spectrum, or a squeezed bispectrum, and quantifies the non-linear response of the Lyman-$\\alpha$ forest power spectrum to a large-scale overdensity. The signal is measured at 5~$\\sigma$ and is consistent with the $\\Lambda$CDM expectation. We measure the linear and non-linear biases of the Lyman-$\\alpha$ forest with respect to the dark matter distribution. This new observable provides a consistency check for the Lyman-$\\alpha$ forest as a large-scale structure probe and tests our understanding of the relation between intergalactic gas and dark matter. In the future, it could be used to test hydrodynamical simulations and calibrate the relation between the Ly...

  2. The Lyman-alpha forest in a blazar-heated Universe

    CERN Document Server

    Puchwein, Ewald; Springel, Volker; Broderick, Avery E; Chang, Philip

    2011-01-01

    It has been realised only recently that TeV emission from blazars can significantly heat the intergalactic medium (IGM) by pair-producing high-energy electrons and positrons, which in turn excite vigorous plasma instabilities, leading to a local dissipation of the pairs' kinetic energy. In this work, we use cosmological hydrodynamical simulations to model the impact of this induced blazar heating on the Lyman-alpha forest at intermediate redshifts (z~2-3). We find that blazar heating produces an inverted equation-of-state in the IGM and naturally resolves many of the problems present in previous simulations of the forest that included photoionisation heating alone. In particular, our simulation results simultaneously reproduce the observed effective optical depth and temperature as a function of redshift, the observed probability distribution functions (PDFs) of the transmitted flux, and the observed flux power spectra, over the full redshift range 2

  3. Lyman alpha emission from the first galaxies: Signatures of accretion and infall in the presence of line trapping

    CERN Document Server

    Latif, M A; Spaans, M; Zaroubi, S

    2011-01-01

    The formation of the first galaxies is accompanied by large accretion flows and virialization shocks, during which the gas is shock-heated to temperatures of $\\sim10^4$ K, leading to potentially strong fluxes in the Lyman alpha line. Indeed, a number of Lyman alpha blobs has been detected at high redshift. In this letter, we explore the origin of such Lyman alpha emission using cosmological hydrodynamical simulations that include a detailed model of atomic hydrogen as a multi-level atom and the effects of line trapping with the adaptive mesh refinement code FLASH. We see that baryons fall into the center of a halo through cold streams of gas, giving rise to a Lyman alpha luminosity of at least $\\rm 10^{44} erg s^{-1}$ at $\\rm z=4.7$, similar to observed Lyman alpha blobs. We find that a Lyman alpha flux of $\\rm 5.0\\times 10^{-17} erg cm^{-2} s^{-1}$ emerges from the envelope of the halo rather than its center, where the photons are efficiently trapped. Such emission can be probed in detail with the upcoming J...

  4. Hydrodynamical Simulations of the Lyman $\\alpha$ Forest Model Comparisons

    CERN Document Server

    Machacek, M E; Meiksin, A; Anninos, P; Thayer, D; Norman, M L; Zhang, Y

    1999-01-01

    We investigate the properties of the Lyman alpha forest as predicted by numerical simulations for a range of currently viable cosmological models. This is done in order to understand the dependencies of the forest on cosmological parameters. Focusing on the redshift range from two to four, we show that: (1) most of the evolution in the distributions of optical depth, flux and column density can be understood by simple scaling relations, (2) the shape of optical depth distribution is a sensitive probe of the amplitude of density fluctuations on scales of a few hundred kpc, (3) the mean of the b distribution (a measure of the width of the absorption lines) is also very sensitive to fluctuations on these scales, and decreases as they increase. We perform a preliminary comparison to observations, where available. A number of other properties are also examined, including the evolution in the number of lines, the two-point flux distribution and the HeII opacity.

  5. Lyman alpha emission from the first galaxies: Implications of UV backgrounds and the formation of molecules

    CERN Document Server

    Latif, M A; Spaans, M; Zaroubi, S

    2011-01-01

    The Lyman alpha line is a robust tracer of high redshift galaxies. We present estimates of Lyman alpha emission from a protogalactic halo illuminated by UV background radiation fields with various intensities. For this purpose, we performed cosmological hydrodynamics simulations with the adaptive mesh refinement code FLASH, including a detailed network for primordial chemistry,comprising the formation of primordial molecules, a multi-level model for the hydrogen atom as well as the photo-ionization and photo-dissociation processes in a UV background. We find that the presence of a background radiation field J_21 excites the emission of Lyman alpha photons, increasing the Lyman alpha luminosity up to two orders of magnitude. For a halo of \\sim 10^10 M_sun, we find that a maximum flux of 5 \\times 10^-15 erg cm^-2 s^-1 is obtained for J21 \\times f_esc = 0.1, where f_esc is the escape fraction of the ionizing radiation. Depending on the environmental conditions, the flux may vary by three orders of magnitude. For...

  6. Lyman-alpha observations of astrospheres

    CERN Document Server

    Linsky, Jeffrey L

    2014-01-01

    Charge-exchange reactions between outflowing stellar wind protons and interstellar neutral hydrogen atoms entering a stellar astrosphere produce a region of piled-up-decelerated neutral hydrogen called the hydrogen wall. Absorption by this gas, which is observed in stellar Lyman-alpha emission lines, provides the only viable technique at this time for measuring the mass-loss rates of F-M dwarf stars. We describe this technique, present an alternative way for understanding the relation of mass-loss rate with X-ray emission, and identify several critical issues.

  7. Wandering in the Lyman-alpha forest: a study of dark matter-dark radiation interactions

    Science.gov (United States)

    Krall, Rebecca; Cyr-Racine, Francis-Yan; Dvorkin, Cora

    2017-09-01

    The amplitude of large-scale matter fluctuations inferred from the observed Sunyaev-Zeldovich (SZ) cluster mass function and from weak gravitational lensing studies, when taken at face value, is in tension with measurements of the cosmic microwave background (CMB) and baryon acoustic oscillation (BAO). In this work, we revisit whether this possible discrepancy can be attributed to new interactions in the dark matter sector. Focusing on a cosmological model where dark matter interacts with a dark radiation species until the epoch of matter-radiation equality, we find that measurements of the Lyman-alpha flux power spectrum from the Sloan Digital Sky Survey provide no support to the hypothesis that new dark matter interactions can resolve the possible tension between CMB and large-scale structure (LSS). Indeed, while the addition of dark matter-dark radiation interactions leads to an improvement of 2Δ&ln;Script L=12 with respect to the standard Λ cold dark matter (ΛCDM) model when only CMB, BAO, and LSS data are considered, the inclusion of Lyman-alpha data reduces the improvement of the fit to 2Δ&ln;Script L=6 relative to ΛCDM . We thus conclude that the statistical evidence for new dark matter interactions (largely driven by the Planck SZ dataset) is marginal at best, and likely caused by systematics in the data. We also perform a Fisher forecast analysis for the reach of a future dataset composed of a CMB-S4 experiment combined with the Large Synoptic Survey Telescope galaxy survey. We find that the constraint on the effective number of fluid-like dark radiation species, Δ Nfluid, will be improved by an order of magnitude compared to current bounds.

  8. Large-scale 3D mapping of the intergalactic medium using the Lyman Alpha Forest

    CERN Document Server

    Ozbek, Melih; Khandai, Nishikanta

    2016-01-01

    Maps of the large-scale structure of the Universe at redshifts 2-4 can be made with the Lyman-alpha forest which are complementary to low redshift galaxy surveys. We apply the Wiener interpolation method of Caucci et al. to construct three-dimensional maps from sets of Lyman-alpha forest spectra taken from cosmological hydrodynamic simulations. We mimic some current and future quasar redshift surveys (BOSS, eBOSS and MS-DESI) by choosing similar sightline densities. We use these appropriate subsets of the Lyman-alpha absorption sightlines to reconstruct the full three dimensional Lyman-alpha flux field and perform comparisons between the true and the reconstructed fields. We study global statistical properties of the intergalactic medium (IGM) maps with auto-correlation and cross-correlation analysis, slice plots, local peaks and point by point scatter. We find that both the density field and the statistical proper- ties of the IGM are recovered well enough that the resulting IGM maps can be meaningfully cons...

  9. GHRS Observations of the Lyman $\\alpha$ Forest

    CERN Document Server

    Morris, S L

    1996-01-01

    I review the results obtained using the GHRS on low redshift Lyman alpha absorbers. Until the advent of HST and the GHRS, the existence of such absorbers was doubted. The confirmation of their existence, in one of the first GHRS GTO team results to be published, must rank as one of the HSTs most interesting results. The GHRS resolution allows us to probe equivalent widths well below those detectable with the FOS, and has led to a number of interesting new questions. One example is the apparent disagreement between the GHRS result that there are many Lyman alpha absorbers which are not associated with luminous galaxies, and FOS studies which suggest that all such absorbers have a nearby galaxy causing them. This almost certainly shows that the equivalent width (or column density) range reachable by the GHRS includes gas from a wide range of causes, and not only the halos of luminous galaxies. With these data, we are seeing the debris left over from Galaxy formation, material flung out from galaxy interactions ...

  10. Characterizing Lyman Alpha Scattering in Nearby Galaxies

    Science.gov (United States)

    Bridge, Joanna; Hayes, Matthew; Melinder, Jens; Östlin, Göran; Gronwall, Caryl

    2017-01-01

    The hydrogen emission line of Lyman alpha (Lyα) has long been recognized as key to studying high redshift star-forming galaxies. However, due to the resonance of the emission line, the path that a Lyα photon takes from emission to eventual escape from the galaxy is essentially a mystery. This scattering poses a problem for using Lyα as a key emission feature of galaxies because it results in Lyα not being observed in all star-forming galaxies, and, in galaxies where it is observed, the place where the photon is originally emitted and where it is observed are two very different things. We discuss here how the Lyman-Alpha Reference Sample (LARS) provides a unique sample of 14 nearby (0.02 Space Telescope imaging. We compare the Lyα/Hα ratios with those expected from pure dust attenuation models, finding that in some cases significant positive departures are found on small scales, consistent with geometrical effects being important on sizes comparable to the HII regions. We then develop a simple scattering model in which we are able to estimate the average path length a Lyα photon travels with respect to non-resonant radiation, and quantifiy the excess dust optical depth to which Lyα radiation may be susceptible.

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

    Science.gov (United States)

    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.

  12. The visibility of Lyman Alpha Emitters during reionization

    CERN Document Server

    Dayal, Pratika; Ferrara, Andrea

    2010-01-01

    We present the first Lyman Alpha Emitter (LAE) study that combines: (i) cosmological SPH simulations run using GADGET-2, (ii) radiative transfer simulations (CRASH), and (iii) a previously developed LAE model. This complete LAE model accounts for the intrinsic LAE Lyman Alpha/continuum luminosity, dust enrichment and Lyman Alpha transmission through the intergalactic medium (IGM), to quantify the effects of reionization, dust and velocity fields on the Lyman Alpha and UV Luminosity Functions (LF). We find that a model neglecting dust sorely fails to reproduce either the slope or the magnitude of the observed Lyman Alpha and UV LFs. Clumped dust is required to simultaneously fit the observed UV and Lyman Alpha LFs, such that the intrinsic Lyman Alpha-to-continuum luminosity is enhanced by a factor f_alpha/f_c ~ 1.5 (3.7) excluding (including) peculiar velocities. The higher value including velocity fields arises since LAEs reside in large potential wells and inflows decrease their Lyman Alpha transmission. For...

  13. Baryon Acoustic Oscillations in the Lyman Alpha Forest

    CERN Document Server

    Norman, Michael L; Harkness, Robert

    2009-01-01

    We use hydrodynamic cosmological simulations in a (600 Mpc)^3 volume to study the observability of baryon acoustic oscillations (BAO) in the intergalactic medium as probed by Lyman alpha forest (LAF) absorption. The large scale separation between the wavelength of the BAO mode (~150 Mpc) and the size of LAF absorbers (~100 kpc) makes this a numerically challenging problem. We report on several 2048^3 simulations of the LAF using the ENZO code. We adopt WMAP5 concordance cosmological parameters and power spectrum including BAO perturbations. 5000 synthetic HI absorption line spectra are generated randomly piercing the box face. We calculate the cross-correlation function between widely separated pairs. We detect the BAO signal at z=3 where theory predicts to moderate statistical significance.

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

    Science.gov (United States)

    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.

  15. Search for a direction in the forest of Lyman-$\\alpha$

    CERN Document Server

    Hazra, Dhiraj Kumar

    2015-01-01

    We report the first test of isotropy of the Universe in the matter dominated epoch using the Lyman-$\\alpha$ forest data from the high redshift quasars ($z>2$) from SDSS-III BOSS-DR9 datasets. Using some specified data cuts, we obtain the probability distribution function (PDF) of the Lyman-$\\alpha$ forest transmitted flux and use the statistical moments of the PDF to address the isotropy of the Universe. In an isotropic Universe one would expect the transmitted flux to have consistent statistical characteristics in different parts of the sky. We trisect the total survey area of 3275 ${\\rm deg}^2$ along the galactic latitude and using quadrant convention. We also make three subdivisions in the data for three different signal-to-noise-ratios (SNR). Finally we obtain and compare the statistical moments in the mean redshifts of 2.3, 2.6 and 2.9. We find, that the moments from all patches agree at all redshifts and at all SNRs, within 3$\\sigma$ uncertainties. Since Lyman-$\\alpha$ transmitted flux directly maps the...

  16. The Lyman-$\\alpha$ emission in local Star-Forming Galaxies Scenario and Connection with Primeval Galaxies

    CERN Document Server

    Kunth, D; Terlevich, R J; Tenorio-Tagle, G

    1998-01-01

    We review the Lyan alpha emission in local star-forming galaxies. In most cases as already shown by the IUE, the emission is absent or much weaker than expected. This occurs because Lyman alpha photons can be resonantly scattered by the neutral gas and destroyed by even very low amounts of dust. However new Hubble Space Telescope observations (HST) indicate that other factors such as the velocity structure of the gas play a crucial role. Gas flows are likely to occur as powered by the kinetic energy released via stellar winds and supernova. We propose a scenario based on the hydrodynamics of superbubbles powered by massive bursts of star formation that naturally accounts for the variety of Lyman alpha line detections in star-forming galaxies. We caution with the attempts to derive the co-moving star formation rate at high redshift from Lyman alpha emission searches.

  17. Bias, redshift space distortions and primordial nongaussianity of nonlinear transformations: application to Lyman alpha forest

    CERN Document Server

    Seljak, Uros

    2012-01-01

    On large scales a nonlinear transformation of matter density field can be viewed as a biased tracer of the density field itself. A nonlinear transformation also modifies the redshift space distortions in the same limit, giving rise to a velocity bias. In models with primordial nongaussianity a nonlinear transformation generates a scale dependent bias on large scales. We derive analytic expressions for these for a general nonlinear transformation. These biases can be expressed entirely in terms of the one point distribution function (PDF) of the final field and the parameters of the transformation. Our analysis allows one to devise nonlinear transformations with nearly arbitrary bias properties, which can be used to increase the signal in the large scale clustering limit. We apply the results to the ionizing equilibrium model of Lyman-alpha forest, in which Lyman-alpha flux F is related to the density perturbation delta via a nonlinear transformation. Velocity bias can be expressed as an average over the Lyman...

  18. Isolating the Lyman Alpha Forest BAO Anomaly

    CERN Document Server

    Evslin, Jarah

    2016-01-01

    A 2.5-3 sigma discrepancy has been reported between the baryonic acoustic oscillation peak (BAO) in the Lyman alpha forest at z=2.34 and the best fit Planck LCDM cosmology. To isolate the origin of the tension, we consider unanchored BAO, in which the standard BAO ruler is not calibrated, eliminating any dependence on cosmology before redshift z=2.34. We consider BOSS BAO measurements at z=0.32, 0.57 and 2.34, using the full 2-dimensional constraints on the best and worst determined combinations of the angular and line of sight BAO scale, as well as isotropic BAO measurements by 6dF and SDSS at z=0.106 and z=0.15. We find that the z>0.43 data alone is in 2.8 sigma of tension with LCDM with or without the Planck best fit values of the mass fraction and the BAO scale, indicating that the tension arises not from the LCDM parameters but from the dark energy evolution itself at 0.57

  19. Molecular hydrogen in Lyman Alpha Emitters

    CERN Document Server

    Vallini, Livia; Ferrara, Andrea

    2012-01-01

    We present a physically motivated model to estimate the molecular hydrogen (H2) content of high-redshift (z~5.7,6.6) Lyman Alpha Emitters (LAEs) extracted from a suite of cosmological simulations. We find that the H2 mass fraction, (f_H2), depends on three main LAE physical properties: (a) star formation rate, (b) dust mass, and (c) cold neutral gas mass. At z~5.7, the value of f_H2 peaks and ranges between 0.5-0.9 for intermediate mass LAEs with stellar mass M_* ~ 10^{9-10} solar mass, decreasing for both smaller and larger galaxies. However, the largest value of the H2 mass is found in the most luminous LAEs. These trends also hold at z\\sim6.6, although, due to a lower dust content, f_H2(z=6.6)\\sim0.5 f_H2(z=5.7) when averaged over all LAEs; they arise due to the interplay between the H2 formation/shielding controlled by dust and the intensity of the ultraviolet (UV) Lyman-Werner photo-dissociating radiation produced by stars. We then predict the carbon monoxide (CO) luminosities for such LAEs and check tha...

  20. About AGN ionization echoes, thermal echoes, and ionization deficits in low redshift Lyman-alpha blobs

    CERN Document Server

    Schirmer, Mischa; Levenson, Nancy A; Fu, Hai; Davies, Rebecca L; Keel, William C; Torrey, Paul; Bennert, Vardha N; Pancoast, Anna; Turner, James E H

    2016-01-01

    We report the discovery of 14 Lyman-alpha blobs (LABs) at z~0.3, existing at least 4-7 billion years later in the Universe than all other LABs known. Their optical diameters are 20-70 kpc, and GALEX data imply Ly-alpha luminosities of (0.4-6.3)x10^43 erg/s. Contrary to high-z LABs, they live in low-density areas. They are ionized by AGN, suggesting that cold accretion streams as a power source must deplete between z=2 and z=0.3. We also show that transient AGN naturally explain the ionization deficits observed in many LABs: Their Ly-alpha and X-ray fluxes decorrelate below 10^6 years because of the delayed escape of resonantly scattering Ly-alpha photons. High Ly-alpha luminosities do not require currently powerful AGN, independent of obscuration. Chandra X-ray data reveal intrinsically weak AGN, confirming the luminous optical nebulae as impressive ionization echoes. For the first time, we also report mid-infrared thermal echoes from the dusty tori. We conclude that the AGN have faded by 3-4 orders of magnit...

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

    Science.gov (United States)

    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

  2. No Evidence for Lyman-alpha Emission in Spectroscopy of z > 7 Candidate Galaxies

    CERN Document Server

    Caruana, Joseph; Wilkins, Stephen M; Stanway, Elizabeth R; Lacy, Mark; Jarvis, Matt J; Lorenzoni, Silvio; Hickey, Samantha

    2012-01-01

    We present Gemini/GNIRS spectroscopic observations of 4 z-band (z~7) dropout galaxies and VLT/XSHOOTER observations of one z-band dropout and 3 Y-band (z~8-9) dropout galaxies in the Hubble Ultra Deep Field, which were selected with Wide Field Camera 3 imaging on the Hubble Space Telescope. We find no evidence of Lyman-alpha emission with a typical 5-sigma sensitivity of 5X10^-18erg/cm^2/s, and we use the upper limits on Lyman-alpha flux and the broad-band magnitudes to constrain the rest-frame equivalent widths for this line emission. Accounting for incomplete spectral coverage, we survey 3.0 z-band dropouts and 2.9 Y-band dropouts to a Lyman-alpha rest-frame equivalent width limit > 120Ang (for an unresolved emission line); for an equivalent width limit of 50Ang the effective numbers of drop-outs surveyed fall to 1.2 z-band drop-outs and 1.5 Y-band drop-outs. A simple model where the fraction of high rest-frame equivalent width emitters follows the trend seen at z=3-6.5 is inconsistent with our non-detectio...

  3. Constraining quasar host halo masses with the strength of nearby Lyman-alpha forest absorption

    CERN Document Server

    Kim, Y R; Kim, Young-Rae; Croft, Rupert

    2006-01-01

    Using cosmological hydrodynamic simulations we measure the mean transmitted flux in the Lyman alpha forest for quasar sightlines that pass near a foreground quasar. We find that the trend of absorption with pixel-quasar separation distance can be fitted using a simple power law form including the usual correlation function parameters r_{0} and \\gamma so that ( = \\sum exp(-tau_eff*(1+(r/r_{0})^(-\\gamma)))). From the simulations we find the relation between r_{0} and quasar mass and formulate this as a way to estimate quasar host dark matter halo masses, quantifying uncertainties due to cosmological and IGM parameters, and redshift errors. With this method, we examine data for ~3000 quasars from the Sloan Digital Sky Survey (SDSS) Data Release 3, assuming that the effect of ionizing radiation from quasars (the so-called transverse proximity effect) is unimportant (no evidence for it is seen in the data.) We find that the best fit host halo mass for SDSS quasars with mean redshift z=3 and absolute G band magnitu...

  4. The cross-correlation between 21cm intensity mapping maps and the Lyman-alpha forest in the post-reionization era

    CERN Document Server

    Carucci, Isabella P; Viel, Matteo

    2016-01-01

    We investigate the cross-correlation signal between 21cm intensity mapping maps and the Lyman-alpha forest in the fully non-linear regime using state-of-the-art hydrodynamic simulations. The cross-correlation signal between these fields can provide a coherent and comprehensive picture of the neutral hydrogen (HI) content of our Universe in the post-reionization era, probing both its mass content and volume distribution. We compute the auto-power spectra of both fields together with their cross-power spectrum at z = 2.4 and find that on large scales the fields are completely anti-correlated. This anti-correlation arises because regions with high (low) 21cm emission, such as those with a large (low) concentration of damped Lyman-alpha systems, will show up as regions with low (high) transmitted flux. We find that on scales smaller than k = 0.2 h/Mpc the cross-correlation coefficient departs from -1, at a scale where non-linearities show up. We use the anisotropy of the power spectra in redshift-space to determi...

  5. Lyman-alpha Emission From Cosmic Structure I: Fluorescence

    CERN Document Server

    Kollmeier, Juna A; Davé, Romeel; Gould, Andrew; Katz, Neal; Miralda-Escudé, Jordi; Weinberg, David H

    2009-01-01

    We present predictions for the fluorescent Lyman-alpha emission signature arising from photoionized, optically thick structures in Smoothed Particle Hydrodynamic (SPH) cosmological simulations of a Lambda-CDM universe using a Monte Carlo Lyman-alpha radiative transfer code. We calculate the expected Lyman-alpha image and 2-dimensional spectra for gas exposed to a uniform ultraviolet ionizing background as well as gas exposed additionally to the photoionizing radiation from a local quasar, after correcting for the self-shielding of hydrogen. As a test of our numerical methods and for application to current observations, we examine simplified analytic structures that are uniformly or anisotropically illuminated. We compare these results with recent observations. We discuss future observing campaigns on large telescopes and realistic strategies for detecting fluorescence owing to the ambient metagalactic ionization and in regions close to bright quasars. While it will take hundreds of hours on the current genera...

  6. Low-redshift evolution of the Lyman $\\alpha$ Forest

    CERN Document Server

    Theuns, T; Efstathiou, G P

    1998-01-01

    The low-redshift evolution of the intergalactic medium is investigated using hydrodynamic cosmological simulations. The assumed cosmological model is a critical density cold dark matter universe. The imposed uniform background of ionizing radiation has the amplitude, shape and redshift evolution as computed from the observed quasar luminosity function by Haardt & Madau. We have analysed simulated Lyman-alpha spectra using Voigt-profile fitting, mimicking the procedure with which quasar spectra are analysed. Our simulations reproduce the observed evolution of the number of Lyman-alpha absorption lines over the whole observed interval of z=0.5 to z=4. In particular, our simulations show that the decrease in the rate of evolution of Lyman-alpha absorption lines at z< 2, as observed by Hubble Space Telescope, can be explained by the steep decline in the photo-ionizing background resulting from the rapid decline in quasar numbers at low redshift.

  7. A connection between extremely strong Damped Lyman-alpha Systems and Lyman-alpha Emitting Galaxies at small impact parameters

    CERN Document Server

    Noterdaeme, P; Paris, I; Cai, Z; Finley, H; Ge, J; Pieri, M M; York, D G

    2014-01-01

    We present a study of ~100 high redshift (z~2-4) extremely strong damped Lyman-alpha systems (ESDLA, with N(HI)>0.5x10^22 cm^-2) detected in quasar spectra from the Baryon Oscillation Spectroscopic Survey SDSS-III DR11. We study the neutral hydrogen, metal, and dust content of this elusive population of absorbers and confirm our previous finding that the high column density end of the N(HI) frequency distribution has a relatively shallow slope with power-law index -3.6, similar to what is seen from 21-cm maps in nearby galaxies. The stacked absorption spectrum indicates a typical metallicity ~1/20th solar, similar to the mean metallicity of the overall DLA population. The relatively small velocity extent of the low-ionisation lines suggests that ESDLAs do not arise from large-scale flows of neutral gas. The high column densities involved are in turn more similar to what is seen in DLAs associated with gamma-ray burst afterglows (GRB-DLAs), which are known to occur close to star forming regions. This indicates...

  8. Exploring 21CM - Lyman Alpha Emitter Synergies for SKA

    NARCIS (Netherlands)

    Dayal, Pratika; Hutter, Anne; Müller, Volker; Trott, C. M.

    2017-01-01

    We study the signatures of reionization and ionizing properties of the early galaxies in the cross-correlations between the 21cm emission from the spin-flip transition of neutral hydrogen (H I ) and the underlying galaxy population, in particular a sub-population of galaxies visible as Lyman Alpha E

  9. Mapping High-velocity H-alpha and Lyman-alpha Emission from Supernova 1987A

    OpenAIRE

    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 {\\it 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 cr...

  10. On the Diffuse Lyman-alpha Halo Around Lyman-alpha Emitting Galaxies

    CERN Document Server

    Lake, Ethan; Cen, Renyue; Sadoun, Raphael; Momose, Rieko; Ouchi, Masami

    2015-01-01

    Ly$\\alpha$ photons scattered by neutral hydrogen atoms in the circumgalactic media or produced in the halos of star-forming galaxies are expected to lead to extended Ly$\\alpha$ emission around galaxies. Such low surface brightness Ly$\\alpha$ halos (LAHs) have been detected by stacking Ly$\\alpha$ images of high-redshift star-forming galaxies. We study the origin of LAHs by performing radiative transfer modeling of nine $z=3.1$ Lyman-Alpha Emitters (LAEs) in a high resolution hydrodynamic galaxy formation simulation. We develop a method of computing the mean Ly$\\alpha$ surface brightness profile of each LAE by effectively integrating over many different observing directions. Without adjusting any parameters, our model yields an average Ly$\\alpha$ surface brightness profile in remarkable agreement with observations. We find that observed LAHs can not be accounted for solely by photons originating from the central LAE and scattered to large radii by hydrogen atoms in the circumgalactic gas. Instead, Ly$\\alpha$ em...

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

    Science.gov (United States)

    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. New interpretations of extraterrestrial Lyman-alpha observations.

    Science.gov (United States)

    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)

    Science.gov (United States)

    Ishikawa, Shin-nosuke; Kano, R.; Kobayashi, K.; Bando, T.; Narukage, N..; Ishikawa, R.; Kubo, M.; Katsukawa, Y.; Suematsu, Y.; Hara, H.; hide

    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. The MUSCLES Treasury Survey II: Intrinsic Lyman Alpha and Extreme Ultraviolet Spectra of K and M Dwarfs with Exoplanets

    CERN Document Server

    Youngblood, Allison; Loyd, R O Parke; Linsky, Jeffrey L; Redfield, Seth; Schneider, P Christian; Wood, Brian E; Brown, Alexander; Froning, Cynthia; Miguel, Yamila; Rugheimer, Sarah; Walkowicz, Lucianne

    2016-01-01

    The ultraviolet (UV) spectral energy distributions of low-mass (K- and M-type) stars play a critical role in the heating and chemistry of exoplanet atmospheres, but are not observationally well-constrained. Direct observations of the intrinsic flux of the Lyman alpha line (the dominant source of UV photons from low-mass stars) are challenging, as interstellar HI absorbs the entire line core for even the closest stars. To address the existing gap in empirical constraints on the UV flux of K and M dwarfs, the MUSCLES HST Treasury Survey has obtained UV observations of 11 nearby M and K dwarfs hosting exoplanets. This paper presents the Lyman alpha and extreme-UV spectral reconstructions for the MUSCLES targets. Most targets are optically inactive, but all exhibit significant UV activity. We use a Markov Chain Monte Carlo technique to correct the observed Lyman alpha profiles for interstellar absorption, and we employ empirical relations to compute the extreme-UV spectral energy distribution from the intrinsic L...

  15. The bispectrum of the Lyman-alpha forest at z~2-2.4 from a Large sample of UVES QSO Absorption Spectra (LUQAS)

    CERN Document Server

    Viel, M; Heavens, A; Hähnelt, M G; Kim, T S; Springel, V; Hernquist, L

    2004-01-01

    We present a determination of the bispectrum of the flux in the Lyman-alpha forest of QSO absorption spectra obtained from LUQAS which consists of spectra observed with the high resolution Echelle spectrograph UVES. Typical errors on the observed bispectrum as obtained from a jack-knife estimator are ~ 50%. For wavenumbers in the range 0.03 s/km 2.

  16. Exploring the nature of the Lyman-$\\alpha$ emitter CR7

    CERN Document Server

    Hartwig, Tilman; Magg, Mattis; Bromm, Volker; Klessen, Ralf S; Glover, Simon C O; Whalen, Daniel J; Pellegrini, Eric W; Volonteri, Marta

    2015-01-01

    CR7 is the brightest Lyman-$\\alpha$ emitter observed at $z>6$, which shows very strong Lyman-$\\alpha$ and HeII 1640 \\AA\\ line luminosities, but no metal line emission. Previous studies suggest that CR7 hosts either young primordial stars with a total stellar mass of $\\sim 10^7\\,\\mathrm{M}_\\odot$ or a black hole of $\\sim 10^6\\,\\mathrm{M}_\\odot$. Here, we explore different formation scenarios for CR7 with a semianalytical model, based on the random sampling of dark matter merger trees. We find that primordial stars cannot account for the observed line luminosities because of their short lifetimes and because of early metal enrichment. Black holes that are the remnants of the first stars are either not massive enough, or reside in metal-polluted haloes, ruling out this possible explanation of CR7. Our models instead suggest that direct collapse black holes, which form in metal-free haloes exposed to large Lyman-Werner fluxes, are more likely the origin of CR7. However, this result is derived under optimistic ass...

  17. Clustering and lifetime of Lyman Alpha Emitters in the Epoch of Reionization

    CERN Document Server

    Hutter, Anne; Müller, Volker

    2015-01-01

    We calculate Lyman Alpha Emitter (LAE) angular correlation functions (ACFs) at $z\\simeq6.6$ and the fraction of lifetime (for the 100 Myrs preceding $z\\simeq6.6$) galaxies spend as Lyman Break Galaxies (LBGs) with/without Lyman Alpha (Ly\\alpha) emission using a model that combines SPH cosmological simulations (GADGET-2), dust attenuation and a radiative transfer code (pCRASH). The ACFs are a powerful tool that significantly narrows the 3D parameter space allowed by LAE Ly$\\alpha$ and UV luminosity functions (LFs) alone. With this work, we simultaneously constrain the escape fraction of ionizing photons $f_{esc}=0.05-0.5$, the mean fraction of neutral hydrogen in the intergalactic medium (IGM) $\\leq 0.01$ and the dust-dependent ratio of the escape fractions of Ly$\\alpha$ and UV continuum photons $f_\\alpha/f_c=0.6-1.2$. Our results show that reionization has the largest impact on the amplitude of the ACFs, and its imprints are clearly distinguishable from those of $f_{esc}$ and $f_\\alpha/f_c$. We also show that...

  18. PAH Emission Within Lyman Alpha Blobs

    CERN Document Server

    Colbert, James W; Teplitz, Harry; Francis, Paul; Palunas, Povilas; Williger, Gerard M; Woodgate, Bruce

    2010-01-01

    We present Spitzer observations of Lya Blobs (LAB) at z=2.38-3.09. The mid-infrared ratios (4.5/8um and 8/24um) indicate that ~60% of LAB infrared counterparts are cool, consistent with their infrared output being dominated by star formation and not active galactic nuclei (AGN). The rest have a substantial hot dust component that one would expect from an AGN or an extreme starburst. Comparing the mid-infrared to submillimeter fluxes (~850um or rest frame far infrared) also indicates a large percentage (~2/3) of the LAB counterparts have total bolometric energy output dominated by star formation, although the number of sources with sub-mm detections or meaningful upper limits remains small (~10). We obtained Infrared Spectrograph (IRS) spectra of 6 infrared-bright sources associated with LABs. Four of these sources have measurable polycyclic aromatic hydrocarbon (PAH) emission features, indicative of significant star formation, while the remaining two show a featureless continuum, indicative of infrared energy...

  19. The BOSS Lyman-alpha Forest Sample from SDSS Data Release 9

    CERN Document Server

    Lee, Khee-Gan; Bartsch, Leslie E; Carithers, William; Dawson, Kyle S; Kirkby, David; Lundgren, Britt; Margala, Daniel; Palanque-Delabrouille, Nathalie; Pieri, Matthew M; Schlegel, David J; Weinberg, David H; Yeche, Christophe; Aubourg, Eric; Bautista, Julian; Bizyaev, Dmitry; Blomquist, Michael; Bolton, Adam S; Borde, Arnaud; Brewington, Howard; Busca, Nicolas G; Croft, Rupert A C; Delubac, Timothee; Ebelke, Garrett; Eisenstein, Daniel J; Font-Ribera, Andreu; Ge, Jian; Hamilton, Jean-Christophe; Hennawi, Joseph F; Ho, Shirley; Honscheid, Klaus; Goff, Jean-Marc Le; Malanushenko, Elena; Malanushenko, Viktor; Miralda-Escude, Jordi; Myers, Adam D; Noterdaeme, Pasquier; Oravetz, Daniel; Pan, Kaike; Paris, Isabelle; Petitjean, Patrick; Rich, James; Rollinde, Emmanuel; Ross, Nicholas P; Rossi, Graziano; Schneider, Donald P; Simmons, Audrey; Snedden, Stephanie; Slosar, Anze; Spergel, David N; Suzuki, Nao; Viel, Matteo; Weaver, Benjamin A

    2012-01-01

    We present the BOSS Lyman-alpha (Lya) Forest Sample from SDSS Data Release 9, comprising 54,468 quasar spectra with zqso > 2.15 suitable for Lya forest analysis. This data set probes the intergalactic medium with absorption redshifts 2.0 1216 Ang), extrapolated into the forest region and normalized by a linear function to fit the expected evolution of the Lya forest mean-flux. The estimated continuum errors are ~5% rms. We also discuss possible systematics arising from uncertain spectrophotometry and artifacts in the flux calibration; global corrections for the latter are provided. Our sample provides a convenient starting point for users to analyze clustering in BOSS Lya forest data, and it provides a fiducial data set that can be used to compare results from different analyses of baryon acoustic oscillations in the Lya forest. The full data set is available from the SDSS-III DR9 web site.

  20. Lyman-alpha Forests cool Warm Dark Matter

    CERN Document Server

    Baur, Julien; Yèche, Christophe; Magneville, Christophe; Viel, Matteo

    2015-01-01

    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 the tightest bounds to date on pure dark matter particles: $m_X \\gtrsim 4.35 \\: \\rm{keV}$ (95% CL) for early decoupled thermal relics such as a hypothetical gravitino, and its corresponding bound for a non-resonantly produced right-handed neutrino $m_s \\gtrsim 31.7 \\: \\rm{keV}$ (95% CL). Thanks to SDSS-III data featuring smaller uncertainties and covering a larger redshift range than SDSS-I data, our bounds improve upon those established by previous works and are further at odds with a purely non-resonantly produced sterile neutrino as dark matter.

  1. The Lyman-$\\alpha$ signature of the first galaxies

    CERN Document Server

    Smith, Aaron; Bromm, Volker; Milosavljević, Miloš

    2014-01-01

    We present the Cosmic Lyman-$\\alpha$ Transfer code (COLT), a new massively parallel Monte-Carlo radiative transfer code, to simulate Lyman-$\\alpha$ (Ly$\\alpha$) resonant scattering through neutral hydrogen as a probe of the first galaxies. We explore the interaction of centrally produced Ly$\\alpha$ radiation with the host galactic environment. The Ly$\\alpha$ photons emitted from the luminous starburst region escape with characteristic features in the line profile depending on the density distribution, ionization structure, and bulk velocity fields. For example, the presence of anisotropic ionization exhibits a tall peak close to line centre with a skewed tail that drops off gradually. Furthermore, moderate (~10 km/s) outflow produces an amplified peak redward of line centre. Idealized models of first galaxies explore the effect of mass, anisotropic H II regions, and radiation pressure driven winds on Ly$\\alpha$ observables. We employ mesh refinement to resolve critical structures. We also post-process an ab i...

  2. Statistical Properties of Diffuse Lyman-alpha Halos around Star-forming Galaxies at z~2

    CERN Document Server

    Momose, Rieko; Nakajima, Kimihiko; Ono, Yoshiaki; Shibuya, Takatoshi; Shimasaku, Kazuhiro; Yuma, Suraphong; Mori, Masao; Umemura, Masayuki

    2015-01-01

    We present statistical properties of diffuse Lyman-alpha halos (LAHs) around high-$z$ star-forming galaxies with large Subaru samples of Lyman-alpha emitters (LAEs) at $z=2.2$. We make subsamples defined by the physical quantities of LAEs' central Lyman-alpha luminosities, UV magnitudes, Lyman-alpha equivalent widths, and UV slopes, and investigate LAHs' radial surface brightness (SB) profiles and scale lengths $r_n$ as a function of these physical quantities. We find that there exist prominent LAHs around LAEs with faint Lyman-alpha luminosities, bright UV luminosities, and small Lyman-alpha equivalent widths in cumulative radial Lyman-alpha SB profiles. We confirm this trend with the anti-correlation between $r_n$ and Lyman-alpha luminosities (equivalent widths) based on the Spearman's rank correlation coefficient that is $\\rho=-0.9$ ($-0.7$) corresponding to the $96\\%$ ($93\\%$) confidence level, although the correlation between $r_n$ and UV magnitudes is not clearly found in the rank correlation coefficien...

  3. Lyman alpha emission from the first galaxies : Implications of UV backgrounds and the formation of molecules

    NARCIS (Netherlands)

    Latif, M. A.; Schleicher, D. R. G.; Spaans, Maarten; Zaroubi, S.

    2011-01-01

    The Lyman alpha line is a robust tracer of high redshift galaxies. We present estimates of Lyman alpha emission from a protogalactic halo illuminated by UV background radiation fields with various intensities. For this purpose, we performed cosmological hydrodynamics simulations with the adaptive me

  4. Lyman alpha emission from the first galaxies : Implications of UV backgrounds and the formation of molecules

    NARCIS (Netherlands)

    Latif, M. A.; Schleicher, D. R. G.; Spaans, Maarten; Zaroubi, S.

    The Lyman alpha line is a robust tracer of high redshift galaxies. We present estimates of Lyman alpha emission from a protogalactic halo illuminated by UV background radiation fields with various intensities. For this purpose, we performed cosmological hydrodynamics simulations with the adaptive

  5. Lyman-alpha radiation hydrodynamics of galactic winds before cosmic reionization

    Science.gov (United States)

    Smith, Aaron; Bromm, Volker; Loeb, Abraham

    2017-01-01

    Radiation from the first stars and galaxies initiated the dramatic phase transition marking an end to the cosmic dark ages. The emission and absorption signatures from the Lyman-alpha transition of neutral hydrogen have been indispensable in extending the observational frontier for high-redshift galaxies into the epoch of reionization. Lyman-alpha radiative transfer provides clues about the processes leading to Lyman-alpha escape from individual galaxies and the subsequent transmission through the intergalactic medium. Cosmological simulations incorporating Lyman-alpha radiative transfer enhance our understanding of fundamental physics by supplying the inferred spectra and feedback on the gas. We discuss the dynamical impact of Lyman-alpha radiation pressure on galaxy formation throughout cosmic reionization with the first fully coupled Lyman-alpha radiation-hydrodynamics simulations. We self-consistently follow the chemistry, cooling, self-gravity, and ionizing radiation in protogalaxies and find that Lyman-alpha radiation pressure turns out to be dynamically important in several spherically symmetric simulations. As a case in point we apply our model to the COSMOS redshift 7 (CR7) galaxy at z = 6.6, which exhibits a +160 km/s velocity offset between the Lyman-alpha and HeII line peaks. We find that a massive black hole with a nonthermal Compton-thick spectrum is able to reproduce the observed Lyman-alpha signatures as a result of higher photon trapping and longer potential lifetime. We conclude with a general discussion of Lyman-alpha radiation in the first galaxies by considering simulations that cover the expected range of halo and source properties.

  6. The Lyman Alpha Reference Sample: V. The impact of neutral ISM kinematics and geometry on Lyman Alpha escape

    CERN Document Server

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

    2015-01-01

    We present high-resolution far-UV spectroscopy of the 14 galaxies of the Lyman Alpha Reference Sample; a sample of strongly star-forming galaxies at low redshifts ($0.028 < z < 0.18$). We compare the derived properties to global properties derived from multi band imaging and 21 cm HI interferometry and single dish observations, as well as archival optical SDSS spectra. Besides the Lyman $\\alpha$ line, the spectra contain a number of metal absorption features allowing us to probe the kinematics of the neutral ISM and evaluate the optical depth and and covering fraction of the neutral medium as a function of line-of-sight velocity. Furthermore, we show how this, in combination with precise determination of systemic velocity and good Ly$\\alpha$ spectra, can be used to distinguish a model in which separate clumps together fully cover the background source, from the "picket fence" model named by Heckman et al. (2011). We find that no one single effect dominates in governing Ly$\\alpha$ radiative transfer and ...

  7. Constraints on ionising photon production from the large-scale Lyman-alpha forest

    CERN Document Server

    Pontzen, Andrew; Peiris, Hiranya; Verde, Licia

    2014-01-01

    Recent work has shown that the z~2.5 Lyman-alpha forest on large scales encodes information about the galaxy and quasar populations that keep the intergalactic medium photoionized. We present the first forecasts for constraining the populations with data from current and next-generation surveys. At a minimum the forest should tell us whether galaxies or, conversely, quasars dominate the photon production. The number density and clustering strength of the ionising sources might be estimated to sub-10% precision with a DESI-like survey if degeneracies (e.g., with the photon mean-free-path, small-scale clustering power normalization and potentially other astrophysical effects) can be broken by prior information. We demonstrate that, when inhomogeneous ionisation is correctly handled, constraints on dark energy do not degrade.

  8. Reproducing the Kinematics of Damped Lyman-alpha Systems

    CERN Document Server

    Bird, Simeon; Neeleman, Marcel; Genel, Shy; Vogelsberger, Mark; Hernquist, Lars

    2014-01-01

    We examine the kinematic structure of Damped Lyman-alpha Systems (DLAs) in a series of cosmological hydrodynamic simulations using the AREPO code. We are able to match the distribution of velocity widths of associated low ionisation metal absorbers substantially better than earlier work. Our simulations produce a population of DLAs dominated by halos with virial velocities around 70 km/s, consistent with a picture of relatively small, faint objects. In addition, we reproduce the observed correlation between velocity width and metallicity and the equivalent width distribution of SiII. Some discrepancies of moderate statistical significance remain; too many of our spectra show absorption concentrated at the edge of the profile and there are slight differences in the exact shape of the velocity width distribution. We show that the improvement over previous work is mostly due to our strong feedback from star formation and our detailed modelling of the metal ionisation state.

  9. Detecting Damped Lyman-$\\alpha$ Absorbers with Gaussian Processes

    CERN Document Server

    Garnett, Roman; Bird, Simeon; Schneider, Jeff

    2016-01-01

    We develop an automated technique for detecting damped Lyman-$\\alpha$ absorbers (DLAs) along spectroscopic sightlines to quasi-stellar objects (QSOs or quasars). The detection of DLAs in large-scale spectroscopic surveys such as SDSS-III sheds light on galaxy formation at high redshift, showing the nucleation of galaxies from diffuse gas. We use nearly 50 000 QSO spectra to learn a novel tailored Gaussian process model for quasar emission spectra, which we apply to the DLA detection problem via Bayesian model selection. We propose models for identifying an arbitrary number of DLAs along a given line of sight. We demonstrate our method's effectiveness using a large-scale validation experiment, with excellent performance. We also provide a catalog of our results applied to 162 861 spectra from SDSS-III data release 12.

  10. Sample variance and Lyman-alpha forest transmission statistics

    CERN Document Server

    Rollinde, Emmanuel; Schaye, Joop; Pâris, Isabelle; Petitjean, Patrick

    2012-01-01

    We compare the observed probability distribution function of the transmission in the \\HI\\ Lyman-alpha forest, measured from the UVES 'Large Programme' sample at redshifts z=[2,2.5,3], to results from the GIMIC cosmological simulations. Our measured values for the mean transmission and its PDF are in good agreement with published results. Errors on statistics measured from high-resolution data are typically estimated using bootstrap or jack-knife resampling techniques after splitting the spectra into chunks. We demonstrate that these methods tend to underestimate the sample variance unless the chunk size is much larger than is commonly the case. We therefore estimate the sample variance from the simulations. We conclude that observed and simulated transmission statistics are in good agreement, in particular, we do not require the temperature-density relation to be 'inverted'.

  11. An excess of damped Lyman alpha galaxies near QSOs

    CERN Document Server

    Russell, D M; Ellison, S L; Benn, Chris R.; Ellison, Sara L.; Russell, David M.

    2006-01-01

    We present a sample of 33 damped Lyman alpha systems (DLAs) discovered in the Sloan Digital Sky Survey (SDSS) whose absorption redshifts (z_abs) are within 6000 km/s of the QSO's systemic redshift (z_sys). Our sample is based on 731 2.5 = 2e20 cm^-2. The derived number density of DLAs per unit redshift, n(z), within v < 6000 km/s is higher (3.5 sigma significance) by almost a factor of 2 than that of intervening absorbers observed in the SDSS DR3, i.e. there is evidence for an overdensity of galaxies near the QSOs. This provides a physical motivation for excluding DLAs at small velocity separations in surveys of intervening 'field' DLAs. In addition, we find that the overdensity of proximate DLAs is independent of the radio-loudness of the QSO, consistent with the environments of radio-loud and radio-quiet QSOs being similar.

  12. The Dynamical Masses, Densities, and Star Formation Scaling Relations of Lyman Alpha Galaxies

    CERN Document Server

    Rhoads, James E; Finkelstein, Steven L; Fynbo, Johan P U; McLinden, Emily M; Richardson, Mark L A; Tilvi, Vithal S

    2013-01-01

    We present the first dynamical mass measurements for Lyman alpha galaxies at high redshift, based on velocity dispersion measurements from rest-frame optical emission lines and size measurements from HST imaging, for a sample of nine galaxies drawn from four surveys. These measurements enable us to study the nature of Lyman alpha galaxies in the context of galaxy scaling relations. The resulting dynamical masses range from 1e9 to 1e10 solar masses. We also fit stellar population models to our sample, and use them to plot the Lyman alpha sample on a stellar mass vs. line width relation. Overall, the Lyman alpha galaxies follow well the scaling relation established by observing star forming galaxies at lower redshift (and without regard for Lyman alpha emission), though in 1/3 of the Lyman alpha galaxies, lower-mass fits are also acceptable. In all cases, the dynamical masses agree with established stellarmass-linewidth relation. Using the dynamical masses as an upper limit on gas mass, we show that Lyman alpha...

  13. Extended Lyman-alpha emission from cold accretion streams

    CERN Document Server

    Rosdahl, J

    2011-01-01

    {Abridged} We investigate the observability of cold accretion streams at redshift 3 via Lyman-alpha radiation and the feasibility of cold accretion as the main driver behind giant Lya blobs (LABs). We run cosmological zoom simulations focusing on 3 halos spanning two orders of magnitude in mass, from 10^11 to 10^13 solar masses. We use a version of the AMR code Ramses that includes radiative transfer of UV photons, and we employ a refinement strategy that allows us to resolve accretion streams in their natural environment to an unprecedented level. For the first time, we self-consistently model self-shielding in the cold streams from the cosmological UV background, which enables us to accurately predict their temperatures, ionization states and Lya luminosities. We find the efficiency of gravitational heating in cold streams in a ~10^11 solar mass halo is around 10-20% throughout most of the halo but reaching much higher values close to the center. As a result most of the Lya luminosity comes from the circumg...

  14. Chemical evolution and nature of Damped Lyman-Alpha systems

    CERN Document Server

    Calura, F; Vladilo, G

    2003-01-01

    We study the nature of Damped Lyman -Alpha systems (DLAs) by means of a comparison between observed abundances and models of chemical evolution of galaxies of different morphological type. In particular, we compare for the first time the abundance ratios as functions of metallicity and redshift with dust-corrected data. We have developed detailed models following the evolution of several chemical elements (H, D, He, C, N, O, Ne, Mg, Si, S, Fe, Ni and Zn) for elliptical, spiral and irregular galaxies. Each of the models is calibrated to reproduce the main features of a massive elliptical, the Milky Way and the LMC, respectively. In addition, we run some models also for dwarf irregular starburst galaxies. All the models share the same uptodate nucleosynthesis prescriptions but differ in their star formation histories. The role of SNe of different type (II, Ia) is studied in each galaxy model together with detailed and up to date nucleosynthesis prescriptions. Our main conclusions are: 1) when dust depletion is ...

  15. NICMOS Snapshot Survey of Damped Lyman Alpha Quasars

    CERN Document Server

    Colbert, J W; Colbert, James W.; Malkan, Matthew A.

    2001-01-01

    We image 19 quasars with 22 damped Lyman alpha (DLA) systems using the F160W filter and the Near-Infrared Camera and Multiobject Spectrograph aboard the Hubble Space Telescope, in both direct and coronagraphic modes. We reach 5 sigma detection limits of ~H=22 in the majority of our images. We compare our observations to the observed Lyman-break population of high-redshift galaxies, as well as Bruzual & Charlot evolutionary models of present-day galaxies redshifted to the distances of the absorption systems. We predict H magnitudes for our DLAs, assuming they are producing stars like an L* Lyman-break galaxy (LBG) at their redshift. Comparing these predictions to our sensitivity, we find that we should be able to detect a galaxy around 0.5-1.0 L* (LBG) for most of our observations. We find only one new possible candidate, that near LBQS0010-0012. This scarcity of candidates leads us to the conclusion that most DLA systems are not drawn from a normal LBG luminosity function nor a local galaxy luminosity fun...

  16. Damped Lyman Alpha Systems in Galaxy Formation Simulations

    CERN Document Server

    Pontzen, Andrew; Pettini, Max; Booth, C M; Stinson, Greg; Wadsley, James; Brooks, Alyson; Quinn, Thomas; Haehnelt, Martin

    2008-01-01

    We investigate the population of z=3 damped Lyman alpha absorbers (DLAs) in a recent series of high resolution galaxy formation simulations. The simulations are of interest because they form at z=0 some of the most realistic disk galaxies to date. No free parameters are available in the simulations: these have been fixed by physical and z=0 observational constraints, and thus our study provides a genuine consistency test. The precise role of DLAs in galaxy formation remains in debate, but they provide a number of strong constraints on the nature of our simulated bound systems at z=3 because of their coupled information on neutral H I densities, kinematics, metallicity and estimates of star formation activity. Our results, without any parameter-tuning, closely match the observed incidence rate and column density distributions of DLAs. Our simulations are the first to reproduce the distribution of metallicities (with a median of Z_{DLA} = Z_{solar}/20) without invoking observationally unsupported mechanisms suc...

  17. Interplanetary Lyman $\\alpha$ line profiles: variations with solar activity cycle

    CERN Document Server

    Quemerais, E; Bertaux, J L; Koutroumpa, D; Clarke, J; Kyrola, E; Schmidt, W; Qu\\'emerais, Eric; Lallement, Rosine; Bertaux, Jean-Loup; Koutroumpa, Dimitra; Clarke, John; Kyrola, Erkki; Schmidt, Walter

    2006-01-01

    Interplanetary Lyman alpha line profiles are derived from the SWAN H cell data measurements. The measurements cover a 6-year period from solar minimum (1996) to after the solar maximum of 2001. This allows us to study the variations of the line profiles with solar activity. These line profiles were used to derive line shifts and line widths in the interplanetary medium for various angles of the LOS with the interstellar flow direction. The SWAN data results were then compared to an interplanetary background upwind spectrum obtained by STIS/HST in March 2001. We find that the LOS upwind velocity associated with the mean line shift of the IP \\lya line varies from 25.7 km/s to 21.4 km/s from solar minimum to solar maximum. Most of this change is linked with variations in the radiation pressure. LOS kinetic temperatures derived from IP line widths do not vary monotonically with the upwind angle of the LOS. This is not compatible with calculations of IP line profiles based on hot model distributions of interplanet...

  18. Lyman Alpha Emitters in the Hierarchically Clustering Galaxy Formation

    CERN Document Server

    Kobayashi, Masakazu A R; Nagashima, Masahiro

    2007-01-01

    We present a new theoretical model for the luminosity functions (LFs) of Lyman alpha (Lya) emitting galaxies in the framework of hierarchical galaxy formation. We extend a semi-analytic model of galaxy formation that reproduces a number of observations for local galaxies, without changing the original model parameters but introducing a physically-motivated modelling to describe the escape fraction of Lya photons from host galaxies (f_esc). Though a previous study using a hierarchical clustering model simply assumed a constant and universal value of f_esc, we incorporate two new effects on f_esc: extinction by interstellar dust and galaxy-scale outflow induced as a star formation feedback. It is found that the new model nicely reproduces all the observed Lya LFs of the Lya emitters (LAEs) at different redshifts in z ~ 3--6. Our model predicts that galaxies with strong outflows and f_esc ~ 1 are dominant in the observed LFs, which is consistent with available observations while the simple universal f_esc model ...

  19. The Metallicity evolution of Damped Lyman-$\\alpha$ systems

    CERN Document Server

    Savaglio, S; Stiavelli, M

    1999-01-01

    We have collected absorption line measurements of 70 Damped Lyman-alpha (DLA) systems, mostly coming from high resolution data, to investigate the chemical evolution of galaxies in the redshift interval 0.0 < z < 4.4. In doing that, we have adopted the most general approach used so far, i.e. the dust depletion corrections are obtained by comparing the element abundances with four depletion patterns observed in the Milky Way. The best solution, obtained through chi^2 minimization, gives as output parameters the global DLA metallicity and the dust-to-metals ratio. Clear evolution of the metallicity vs. redshift is found, with average values going from ~1/30 solar at z~4.1 to dispersion around the average regression is significantly larger than the errors (i.e. ~0.45 dex average dispersion relative to ~0.14 dex error), indicating that the class of DLAs include objects with a range of evolutionary histories and/or initial conditions, such as total mass, formation time, matter spatial distribution, etc. We a...

  20. Giant Lyman-Alpha Nebulae in the Illustris Simulation

    CERN Document Server

    Gronke, Max

    2016-01-01

    Several `giant' Lyman-$\\alpha$ (Ly$\\alpha$) nebulae with extent $\\gtrsim 300\\,$kpc and observed Ly$\\alpha$ luminosity of $\\gtrsim 10^{44}\\,{\\rm erg}\\,{\\rm s}^{-1}\\,{\\rm cm}^{-2}\\,{\\rm arcsec}^{-2}$ have recently been detected, and it has been speculated that their presence hints at a substantial cold gas reservoir in small cool clumps not resolved in modern hydro-dynamical simulations. We use the Illustris simulation to predict the Ly$\\alpha$ emission emerging from large halos ($M > 10^{11.5}M_{\\odot}$) at $z\\sim 2$ and thus test this model. We consider both AGN and star driven ionization, and compared the simulated surface brightness maps, profiles and Ly$\\alpha$ spectra to a model where most gas is clumped below the simulation resolution scale. We find that while the cold clumps boost the Ly$\\alpha$ luminosity especially in the outer regions of the halo -- as expected by previous work -- with Illustris no additional clumping is necessary to explain the extents and luminosities of the `giant Ly$\\alpha$ nebul...

  1. Lyman-$\\alpha$ Transit Spectroscopy and the Neutral Hydrogen Tail of the Hot Neptune GJ436b

    CERN Document Server

    Kulow, Jennifer R; Linsky, Jeffery; Loyd, R O Parke

    2014-01-01

    To date, more than 750 planets have been discovered orbiting stars other than the Sun. Two sub-classes of these exoplanets, "hot Jupiters" and their less massive counterparts "hot Neptunes," provide a unique opportunity to study the extended atmospheres of planets outside of our solar system. We describe here the first far-ultraviolet transit study of a hot Neptune, specifically GJ436b, for which we use HST/STIS Lyman-$\\alpha$ spectra to measure stellar flux as a function of time, observing variations due to absorption from the planetary atmosphere during transit. This analysis permits us to derive information about atmospheric extent, mass-loss rate from the planet, and interactions between the star and planet. We observe an evolution of the Lyman-$\\alpha$ lightcurve with a transit depth of GJ436b from $8.8\\pm4.5\\%$ near mid-transit, to $22.9\\pm3.9\\%$ $\\sim2$ hours after the nominal geometric egress of the planet. Using data from the time-tag mode and considering astrophysical noise from stellar variability,...

  2. Probing the Rest-Frame Optical Continuum of z=4.5 Lyman Alpha Emitters with Spitzer

    Science.gov (United States)

    Finkelstein, Keely D.; Malhotra, S.; Rhoads, J. E.; Finkelstein, S. L.; Tilvi, V.; Grogin, N. A.; Pirzkal, N.; Dey, A.; Jannuzi, B. T.; Mobasher, B.; Pakzad, S.; Wang, J.

    2012-01-01

    We present the results from a deep Spitzer Space Telescope survey of more than 100 Lyman alpha emitters (LAEs) at z 4.5, first discovered in the Bootes field of the Large Area Lyman Alpha (LALA) survey. These Spitzer/IRAC observations probe the rest-frame optical continuum emission of these galaxies. We also have in hand NICMOS and WFC3 near-infrared (NIR) data from the Hubble Space Telescope (HST) of a sub-sample of these same galaxies. Of the more than 100 sources targeted with Spitzer, 15 sources are detected in at least two out of the four NICMOS/WFC3 and IRAC bands (1.1, 1.6, 3.6 and 4.5 microns), while another 40 sources are detected in one band. We will present the results from a SED-fitting analysis, using the suite of data in the observed NIR/mid-IR, coupled with deep ground based optical data. LAEs form the faint end of the galaxy luminosity function, thus most studies rely on stacking to constrain the rest-frame optical light, which can wash out variations in the physical properties in individual LAEs. This is the largest sample to date of high-redshift LAEs with measured NIR/IR fluxes, allowing us to place the most robust constraints yet on the spread of physical properties in the LAE population.

  3. On Detecting the X-ray Silhouette of a Damped Lyman alpha System

    CERN Document Server

    Dijkstra, M; Schärf, C; Dijkstra, Mark; Haiman, Zoltan; Scharf, Caleb

    2004-01-01

    We explore the possibility of resolving an image of a damped Lyman alpha (DLA) system in absorption against an extended, diffuse background X-ray source. Typical columns of neutral hydrogen in DLAs are high enough to block out up to ~30% of the soft X-ray flux at an observed photon energy of 0.5 keV, and we find that ~ 1% of the area of extended X-ray sources at z > 1 have their 0.5 keV flux reduced by at least 20%. We discuss the observability of such absorption and find that 300 photons per angular resolution element are required in the 0.3-8 keV band for its detection, and in order to distinguish it from intrinsic surface brightness fluctuations. For the surface brightness of the currently known high-redshift extended X-ray sources, this requires an integration time of a few Msec on Chandra. The detection will be within the reach of a routine observation with a next generation X-ray telescope such as XEUS or Generation X.

  4. The Lyman alpha Reference Sample VI: Lyman alpha escape from the edge-on disk galaxy Mrk1486

    CERN Document Server

    Duval, Florent; 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; Mansson, Tore

    2015-01-01

    While numerical simulations suggest that the strength of the Lyman alpha (Lya) line of star-forming disk galaxies strongly depends on the inclination at which they are observed (i.e. from edge-on to face-on, we expect to see a change from an attenuated Lya line to a strong Lya emission line), recent observations with the Hubble space telescope (HST) have highlighted few low-redshift highly inclined (edge-on) disk galaxies that breaks this trend. We aim to understand how a strong Lya emission line is able to escape from one of those inclined disk galaxies, named Mrk1486 (z=0.0338). For that purpose we used a large set of HST imaging and spectroscopic data to investigate both the ISM structure and the dominant source of Lya radiation inside Mrk1486. Moreover, we used a 3D Monte Carlo Lya radiation transfer code to study the radiative transfer of Lya and UV continuum photons inside a 3D geometry of neutral hydrogen (HI) and dust that models the ISM structure at the galaxy center. The analysis of IFU Halpha spect...

  5. Constraining the End of Reionization with Deep Lyman-alpha Spectroscopy

    Science.gov (United States)

    Jung, Intae; Finkelstein, Steven L.; Livermore, Rachael C.; Wold, Isak; Larson, Rebecca L.

    2017-06-01

    An immediately accessible method for studying the intergalactic medium in the reionization era is to measure the equivalent width distribution of Lyman-alpha emission from continuum-selected galaxies with follow-up spectroscopy. To search for Lyman-alpha emission from galaxies at z = 5.5-8.2, we are performing ultra-deep spectroscopic observations of candidate galaxies from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. We utilize data from the DEIMOS (optical) and MOSFIRE (near-infrared) spectrographs on the Keck 10-meter telescopes, ensuring the comprehensive wavelength coverage of Lyman-alpha emission at z ~ 6-8. We have a total of 1169 hours of spectroscopic integration of galaxies at z > 6: 738 hours for 123 galaxies with DEIMOS and 432 hours for 69 galaxies with MOSFIRE with the additional optical spectroscopic data of our sample galaxies in the GOODS-S field from VLT VANDELS survey. The Lyman-alpha fraction, the ratio of galaxies with detected Lyman-alpha emission to the number of all candidate galaxies observed, is directly measured with the completeness test of our data set by constructing detailed simulations of mock emission lines, which consider observational conditions (e.g., observational depth, wavelength coverage, and sky emission) and the probability distribution function of galaxy photometric redshifts. We present the early result on the Lyman-alpha emission equivalent width distribution of galaxies at z ~ 6 from our analysis of the DEIMOS spectroscopic dataset, determining robust upper limits on the Lyman-alpha emission.

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

    Science.gov (United States)

    Chonis, Taylor Steven

    In the upcoming era of extremely large ground-based astronomical telescopes, the design of wide-field spectroscopic survey instrumentation has become increasingly complex due to the linear growth of instrument pupil size with telescope diameter for a constant spectral resolving power. The upcoming Visible Integral field Replicable Unit Spectrograph (VIRUS), a baseline array of 150 copies of a simple integral field spectrograph that will be fed by 3:36 x 104 optical fibers on the upgraded Hobby-Eberly Telescope (HET) at McDonald Observatory, represents one of the first uses of large-scale replication to break the relationship between instrument pupil size and telescope diameter. By dividing the telescope's field of view between a large number of smaller and more manageable instruments, the total information grasp of a traditional monolithic survey spectrograph can be achieved at a fraction of the cost and engineering complexity. To highlight the power of this method, VIRUS will execute the HET Dark Energy Experiment (HETDEX) and survey & 420 degrees2 of sky to an emission line flux limit of ˜ 10-17 erg s-1 cm -2 to detect ˜ 106 Lyman-alpha emitting galaxies (LAEs) as probes of large-scale structure at redshifts of 1:9 ProQuest.).

  7. Spectroscopy of z ~ 7 candidate galaxies: Using Lyman-alpha to constrain the neutral fraction of hydrogen in the high-redshift universe

    CERN Document Server

    Caruana, Joseph; Wilkins, Stephen M; Stanway, Elizabeth R; Lorenzoni, Silvio; Jarvis, Matt J; Elbert, Holly

    2013-01-01

    Following our previous spectroscopic observations of $z>7$ galaxies with Gemini/GNIRS and VLT/XSHOOTER, which targeted a total of 8 objects, we present here our results from a deeper and larger VLT/FORS2 spectroscopic sample of Wide Field Camera 3 selected $z>7$ candidate galaxies. With our FORS2 setup we cover the 737-1070nm wavelength range, enabling a search for Lyman-$\\alpha$ in the redshift range spanning 5.06 - 7.80. We target 22 $z$-band dropouts and find no evidence of Lyman-$\\alpha$ emission. The upper limits on Lyman-$\\alpha$ flux and the broad-band magnitudes are used to constrain the rest-frame Equivalent Widths for this line emission. We analyse our FORS2 observations in combination with our previous GNIRS and XSHOOTER observations, and suggest that a simple model where the fraction of high rest-frame Equivalent Width emitters follows the trend seen at $z=3-6.5$ is inconsistent with our non-detections at $z\\sim7.8$ at the 96\\% confidence level. This may indicate that a significant neutral HI frac...

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

    Science.gov (United States)

    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. 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://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/587/A78

  9. Models of the Cosmological 21 cm Signal from the Epoch of Reionization Calibrated with Lyman-alpha and CMB Data

    CERN Document Server

    Kulkarni, Girish; Puchwein, Ewald; Haehnelt, Martin G

    2016-01-01

    We present here 21 cm predictions from high dynamic range simulations for a range of reionization histories that have been tested against available Lyman-alpha and CMB data. We assess the observability of the predicted spatial 21 cm fluctuations by ongoing and upcoming experiments in the late stages of reionization in the limit in which the hydrogen spin temperature is significantly larger than the CMB temperature. Models consistent with the available Lyman-alpha data and CMB measurement of the Thomson optical depth predict typical values of 10--20 mK^2 for the variance of the 21 cm brightness temperature at redshifts z=7--10 at scales accessible to ongoing and upcoming experiments (k < 1 h/cMpc). This is only a factor of a few below the sensitivity claimed to have been already reached by ongoing experiments. Our different models for the reionization history make markedly different predictions for the redshift evolution and thus frequency dependence of the 21 cm power spectrum and should be easily discerni...

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

    Science.gov (United States)

    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

  11. HST/ACS Lyman alpha imaging of the nearby starburst ESO338-IG04

    CERN Document Server

    Hayes, M; Mas-Hesse, J M; Kunth, D; Leitherer, C; Petrosian, A

    2005-01-01

    ESO338-IG04 is a well known, local, luminous Blue Compact Galaxy. It has a complex morphology and contains a central young starburst with compact young star clusters. The galaxy was imaged using HST/ACS in the Lyman alpha line and continuum. Using the Starburst99 synthetic spectra and other imaging data from HST/WFPC2 we developed a technique that allows us to make the first photometrically valid continuum subtraction for the LYa line. Our results are in qualitative agreement with the models of LYa escape being regulated by kinematical properties of the interstellar medium. The line-only image shows LYa in both emission and absorption. Notably, emission is seen from central bright young clusters and is in spatial agreement with the features present in a longslit spectrum taken with HST/STIS. Diffuse LYa emission regions are seen surrounding the central starburst where photons escape after one or more resonant scatterings in HI. These regions dominate the total LYa output. Photometry reveals a total LYa flux o...

  12. The Luminosity Function of Lyman Alpha Emitting Galaxies and Cosmic Reionisation of Hydrogen

    CERN Document Server

    Dijkstra, M; Haiman, Z; Dijkstra, Mark; Wyithe, Stuart; Haiman, Zoltan

    2006-01-01

    Recent observations imply that the observed number counts of Lyman Alpha (Lya) emitters evolved significantly between z=5.7 and z=6.5. It has been suggested that this evolution was due to a rapid evolution in the ionisation state, and hence transmission of the IGM which caused Lya flux from z=6.5 galaxies to be more strongly suppressed. In this paper we show that the observed evolution can be attributed entirely to the evolution in the mass function of dark matter halos housing the Lya emitters. We place constraints on the evolution of transmission in the IGM between z=6.5 and z=5.7, finding a ratio of ~1.2, which may be accounted for by the evolution of the mean IGM density through cosmic expansion. Using a model for IGM transmission, we demonstrate that Lya emitting galaxies at z=6.5 must be embedded in HII bubbles greater than 35x_HI comoving Mpc in size, where x_HI is the neutral fraction of hydrogen outside the ionised bubbles. The model of Furlanetto et al (2006) may be used to translate this into a low...

  13. ALMA observations of Lyman-alpha Blob 1: halo sub-structure illuminated from within

    CERN Document Server

    Geach, J E; Matsuda, Y; Hayes, M; Mas-Ribas, Ll; Dijkstra, M; Steidel, C C; Chapman, S C; Feldmann, R; Avison, A; Agertz, O; Ao, Y; Birkinshaw, M; Bremer, M N; Clements, D L; Dannerbauer, H; Farrah, D; Harrison, C M; Hine, N K; Kubo, M; Michalowski, M J; Scott, Douglas; Smith, D J B; Spaans, M; Simpson, J M; Swinbank, A M; Taniguchi, Y; van Kampen, E; van der Werf, P; Verma, A; Yamada, T

    2016-01-01

    We present new Atacama Large Millimeter/Submillimeter Array (ALMA) 850um continuum observations of the original Lyman-alpha Blob (LAB) in the SSA22 field at z=3.1 (SSA22-LAB01). The ALMA map resolves the previously identified submillimeter source into three components with total flux density S_850 = 1.68+/-0.06 mJy, corresponding to a star formation rate of ~150 M_sun/yr. The submillimeter sources are associated with several faint (m~27 mag) rest-frame ultraviolet sources identified in Hubble Space Telescope Imaging Spectrograph (STIS) clear filter imaging (~5850A). One of these companions is spectroscopically confirmed with Keck MOSFIRE to lie within 20 projected kpc and 250 km/s of one of the ALMA components. We postulate that some of these STIS sources represent a population of low-mass star-forming satellites surrounding the central submillimeter sources, potentially contributing to their growth and activity through accretion. Using a high resolution cosmological zoom simulation of a 10^13 M_sun halo at z...

  14. Optimizing BAO measurements with non-linear transformations of Lyman-alpha forest

    CERN Document Server

    Wang, Xinkang; Seljak, Uros

    2014-01-01

    We explore the effect of applying a non-linear transformation to the Lyman-$\\alpha$ forest transmitted flux $F=e^{-\\tau}$ and the ability of analytic models to predict the resulting clustering amplitude. Both the large-scale bias of the transformed field (signal) and the amplitude of small scale fluctuations (noise) can be arbitrarily modified, but we were unable to find a transformation that increases significantly the signal-to-noise ratio on large scales using Taylor expansion up to third order. We achieve a 33% improvement in signal to noise for Gaussianized field in transverse direction. On the other hand, we explore analytic model for the large-scale biasing of the Ly$\\alpha$ forest, and present an extension of this model to describe the biasing of the transformed fields. Using hydrodynamic simulations we show that the model works best to describe the biasing with respect to velocity gradients, but is less successful in predicting the biasing with respect to large-scale density fluctuations, especially ...

  15. The Luminosity Function of Lyman alpha Emitters at Redshift z=7.7

    CERN Document Server

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

    2010-01-01

    Lyman alpha (Lya) emission lines should be attenuated in a neutral intergalactic medium (IGM). Therefore the visibility of Lya emitters at high redshifts can serve as a valuable probe of reionization at about the 50% level. We present an imaging search for z=7.7 Lya emitting galaxies using an ultra-narrowband filter (filter width= 9A) on the NEWFIRM imager at the Kitt Peak National Observatory. We found four candidate Lya emitters in a survey volume of 1.4 x 10^4 Mpc^3, with a line flux brighter than 6x10^-18 erg/cm^2/s (5 sigma in 2" aperture). We also performed a detailed Monte-Carlo simulation incorporating the instrumental effects to estimate the expected number of Lya emitters in our survey, and found that we should expect to detect one Lya emitter, assuming a non-evolving Lya luminosity function (LF) between z=6.5 and z=7.7. Even if one of the present candidates is spectroscopically confirmed as a z~8 Lya emitter, it would indicate that there is no significant evolution of the Lya LF from z=3.1 to z~8. ...

  16. High redshift galaxies and the Lyman-alpha forest in a CDM universe

    CERN Document Server

    Croft, R A C; Springel, V; Westover, M; White, M; Croft, Rupert A.C.; Hernquist, Lars; Springel, Volker; Westover, Michael; White, Martin

    2002-01-01

    We use a cosmological hydrodynamic simulation of a cold dark matter universe to investigate theoretically the relationship between high redshift galaxies and the Lyman=alpha forest at redshift z=3. Galaxies in the simulation are surrounded by halos of hot gas, which nevertheless contain enough neutral hydrogen to cause a Ly-alpha flux decrement, its strength increasing with galaxy mass. A comparison with recent observational data by Adelberger et. al on the Ly-alpha forest around galaxies reveals that actual galaxies may have systematically less Ly-alpha absorption within 1 Mpc of them than our simulated galaxies. In order to investigate this possibility, we add several simple prescriptions for galaxy feedback on the IGM to the evolved simulation. These include the effect of photoionizing background radiation coming from galactic sources, galactic winds whose only effect is to deposit thermal energy into the IGM, and another, kinetic model for winds, which are assumed to evacuate cavities in the IGM around ga...

  17. Two-phase equilibrium and molecular hydrogen formation in damped Lyman-alpha systems

    CERN Document Server

    Liszt, H S

    2002-01-01

    Molecular hydrogen is quite underabundant in damped Lyman-alpha systems at high redshift, when compared to the interstellar medium near the Sun. This has been interpreted as implying that the gas in damped Lyman-alpha systems is warm. like the nearby neutral intercloud medium, rather than cool, as in the clouds which give rise to most H I absorption in the Milky Way. Other lines of evidence suggest that the gas in damped Lyman-alpha systems -- in whole or part -- is actually cool; spectroscopy of neutral and ionized carbon, discussed here, shows that the damped Lyman-alpha systems observed at lower redshift z $$ 2.8 are warm (though not devoid of H2). To interpret the observations of carbon and hydrogen we constructed detailed numerical models of H2 formation under the conditions of two-phase thermal equilibrium, like those which account for conditions near the Sun, but with varying metallicity, dust-gas ratio, $etc$. We find that the low metallicity of damped Lyman-alpha systems is enough to suppress H2 form...

  18. HeII emission in Lyman-alpha nebulae: AGN or cooling radiation?

    CERN Document Server

    Scarlata, C; Teplitz, H I; Bridge, C; Francis, P; Palunas, P; Siana, B; Williger, G M; Woodgate, B

    2009-01-01

    We present a study of an extended Lyman-alpha (Lya) nebula located in a known overdensity at z~2.38. The data include multiwavelength photometry covering the rest-frame spectral range from 0.1 to 250um, and deep optical spectra of the sources associated with the extended emission. Two galaxies are associated with the Lya nebula. One of them is a dust enshrouded AGN, while the other is a powerful starburst, forming stars at >~600 Msol/yr. We detect the HeII emission line at 1640A in the spectrum of the obscured AGN, but detect no emission from other highly ionized metals (CIV or NV) as is expected from an AGN. One scenario that simultaneously reproduces the width of the detected emission lines, the lack of CIV emission, and the geometry of the emitting gas, is that the HeII and the Lya emission are the result of cooling gas that is being accreted on the dark matter halo of the two galaxies, Ly1 and Ly2. Given the complexity of the environment associated with our Lya nebula it is possible that various mechanism...

  19. An 80-kpc Lyman-alpha halo around a high redshift type-2 QSO

    CERN Document Server

    Smith, Daniel J B; Simpson, Chris; Martinez-Sansigre, Alejo

    2008-01-01

    We announce the discovery of an extended emission line region associated with a high redshift type-2 QSO. The halo, which was discovered in our new wide-field narrow-band survey, resides at z = 2.85 in the Spitzer First Look Survey region and is extended over ~80 kpc. Deep VLBI observations imply that approximately 50 per cent of the radio emission is extended on scales > 200pc. The inferred AGN luminosity is sufficient to ionize the extended halo, and the optical emission is consistent with being triggered coevally with the radio source. The Lyman-alpha halo is as luminous as those found around high redshift radio galaxies, however the active nucleus is several orders of magnitude less luminous at radio wavelengths than those FRIIs more commonly associated with extended emission line regions. AMS05 appears to be a high-redshift analogue to the radio-quiet quasar E1821+643 which is core dominated but which also exhibits extended FRI-like structure and contains an optically powerful AGN. We also find evidence ...

  20. The Evolution of Damped Lyman-alpha Absorbers: Metallicities and Star Formation Rates

    CERN Document Server

    Kulkarni, V P; Lauroesch, J T; Fall, S M; Khare, P; Woodgate, B E; Palunas, P; Meiring, J; Thatte, D G; Welty, D E; Truran, J W; Kulkarni, Varsha P.; York, Donald G.; Lauroesch, James T.; Khare, Pushpa; Woodgate, Bruce E.; Palunas, Povilas; Meiring, Joseph; Thatte, Deepashri G.; Welty, Daniel E.; Truran, James W.

    2005-01-01

    The damped Lyman-alpha (DLA) and sub-DLA quasar absorption lines provide powerful probes of the evolution of metals, gas, and stars in galaxies. One major obstacle in trying to understand the evolution of DLAs and sub-DLAs has been the small number of metallicity measurements at z < 1.5, an epoch spanning \\~70 % of the cosmic history. In recent surveys with the Hubble Space Telescope and Multiple Mirror Telescope, we have doubled the DLA Zn sample at z < 1.5. Combining our results with those at higher redshifts from the literature, we find that the global mean metallicity of DLAs does not rise to the solar value at low redshifts. These surprising results appear to contradict the near-solar mean metallicity observed for nearby (z ~ 0) galaxies and the predictions of cosmic chemical evolution models based on the global star formation history. Finally, we discuss direct constraints on the star formation rates (SFRs) in the absorber galaxies from our deep Fabry-Perot Ly-alpha imaging study and other emissio...

  1. Lyman-alpha and CIII] Emission in z=7-9 Galaxies: Accelerated Reionization Around Luminous Star Forming Systems?

    CERN Document Server

    Stark, Daniel P; Charlot, Stephane; Chevallard, Jacopo; Tang, Mengtao; Belli, Sirio; Zitrin, Adi; Mainali, Ramesh; Gutkin, Julia; Vidal-Garcia, Alba; Bouwens, Rychard; Oesch, Pascal

    2016-01-01

    We discuss new Keck/MOSFIRE spectroscopic observations of four luminous galaxies at z~7-9 selected to have intense optical line emission by Roberts-Borsani et al. (2016). Previous follow-up has revealed Lyman-alpha in two of the four galaxies. Our new MOSFIRE observations confirm that Lyman-alpha is present in the entire sample. We detect Lyman-alpha emission in COS-zs7-1, confirming its redshift as z=7.154, and we detect Lyman-alpha in EGS-zs8-2 at z=7.477, verifying a tentative detection presented in an earlier study. The ubiquity of Lyman-alpha in this sample is puzzling given that the IGM is likely significantly neutral over 77 is expected to be strongly luminosity-dependent, with the most effective transmission occurring in systems with intense star formation.

  2. The most metal-rich damped Lyman alpha systems at z>1.5 I: The Data

    CERN Document Server

    Berg, Trystyn A M; Prochaska, J Xavier; Ellison, Sara L; Wolfe, Arthur M

    2014-01-01

    We present HIRES observations for 30 damped Lyman alpha systems, selected on the basis of their large metal column densities from previous, lower resolution data. The measured metal column densities for Fe, Zn, S, Si, Cr, Mn, and Ni are provided for these 30 systems. Combined with previously observed large metal column density damped Lyman alpha systems, we present a sample of 44 damped Lyman alpha systems observed with high resolution spectrographs (R~30000). These damped Lyman alpha systems probe the most chemically evolved systems at redshifts greater than 1.5. We discuss the context of our sample with the general damped Lyman alpha population, demonstrating that we are probing the top 10% of metal column densities with our sample. In a companion paper, we will present an analysis of the sample's elemental abundances in the context of galactic chemical enrichment.

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

    Energy Technology Data Exchange (ETDEWEB)

    Hayes, Matthew; Östlin, Göran; Duval, Florent; Sandberg, Andreas; Guaita, Lucia; Melinder, Jens; Rivera-Thorsen, Thøger [Department of Astronomy, Oskar Klein Centre, Stockholm University, AlbaNova University Centre, SE-106 91 Stockholm (Sweden); Adamo, Angela [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Schaerer, Daniel [Université de Toulouse, UPS-OMP, IRAP, F-31000 Toulouse (France); Verhamme, Anne; Orlitová, Ivana [Geneva Observatory, University of Geneva, 51 Chemin des Maillettes, CH-1290 Versoix (Switzerland); Mas-Hesse, J. Miguel; Otí-Floranes, Héctor [Centro de Astrobiología (CSIC-INTA), Departamento de Astrofísica, P.O. Box 78, E-28691 Villanueva de la Cañada (Spain); Cannon, John M.; Pardy, Stephen [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States); Atek, Hakim [Laboratoire dAstrophysique, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire, CH-1290 Sauverny (Switzerland); Kunth, Daniel [Institut d' Astrophysique de Paris, UMR 7095, CNRS and UPMC, 98 bis Bd Arago, F-75014 Paris (France); Laursen, Peter [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Herenz, E. Christian, E-mail: matthew@astro.su.se [Leibniz-Institut für Astrophysik (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)

    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.

  4. Diagnosing galactic feedback with the line broadening in the low redshift Lyman-alpha forest

    CERN Document Server

    Viel, M; Bolton, J S; Kim, T -S; Puchwein, E; Nasir, F; Wakker, B P

    2016-01-01

    We compare the low redshift (z ~ 0.1) Lyman-alpha forest from hydrodynamical simulations with data from the Cosmic Origin Spectrograph (COS). We find tension between the observed number of lines with b-parameters in the range 25-45 km/s and the predictions from simulations that incorporate either vigorous feedback from active galactic nuclei or that exclude feedback altogether. The gas in these simulations is, respectively, either too hot to contribute to the Lyman-alpha absorption or too cold to produce the required line widths. Matching the observed b-parameter distribution therefore requires feedback processes that thermally or turbulently broaden the absorption features without collisionally (over-)ionising hydrogen. This suggests the Lyman-alpha forest b-parameter distribution is a valulable diagnostic of galactic feedback in the low redshift Universe. We furthermore confirm the low redshift Lyman-alpha forest column density distribution is better reproduced by an ultraviolet background with an HI photo-...

  5. A deep search for 21-cm absorption in high redshift damped Lyman-alpha systems

    NARCIS (Netherlands)

    Kanekar, N; Chengalur, JN

    2003-01-01

    We present deep GMRT 21-cm absorption spectra of 10 damped Lyman-alpha systems (DLAs), of which 8 are at redshifts zgreater than or similar to1.3. HI absorption was detected in only one DLA, the z=0.5318 absorber toward PKS 1629+12. This absorber has been identified with a luminous spiral galaxy; th

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

    Science.gov (United States)

    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.

  7. An Ultraluminous Lyman Alpha Emitter with a Blue Wing at z=6.6

    CERN Document Server

    Hu, E M; Songaila, A; Barger, A J; Rosenwasser, B; Wold, I

    2016-01-01

    We report the detection of the most luminous high-redshift Lyman Alpha Emitting galaxy (LAE) yet seen, with log L(Ly alpha) = 43.9 ergs/s. The galaxy -- COSMOS Lyman alpha 1, or COLA1 -- was detected in a search for ultra-luminous LAEs with Hyper Suprime-Cam on the Subaru telescope. It was confirmed to lie at z = 6.593 based on a Lyman alpha line detection obtained from followup spectroscopy with the DEIMOS spectrograph on Keck2. COLA1 is the first very high-redshift LAE to show a multi-component Lyman alpha line profile with a blue wing, which suggests that it could lie in a highly ionized region of the intergalactic medium and could have significant infall. If this interpretation is correct, then ultra-luminous LAEs like COLA1 offer a unique opportunity to determine the properties of the HII regions around these galaxies which will help in understanding the ionization of the z ~ 7 intergalactic medium.

  8. Lyman alpha emission in starbursts: implications for galaxies at high redshift

    CERN Document Server

    Mas-Hesse, J M; Tenorio-Tagle, G; Leitherer, C; Terlevich, R J; Terlevich, E

    2003-01-01

    We present the results of a high resolution UV 2-D spectroscopic survey of star forming galaxies observed with HST-STIS. Our main aim was to map the Lyman alpha profiles to learn about the gas kinematics and its relation with the escape of Lyman alpha photons and to detect extended Lyman alpha emission due to scattering in gaseous halos. We have combined our data with previously obtained UV spectroscopy on other three star-forming galaxies. We find that the P-Cygni profile is spatially extended, smooth and spans several kiloparsecs covering a region much larger than the starburst itself. We propose a scenario whereby an expanding super-shell is generated by the interaction of the combined stellar winds and supernova ejecta from the young starbursts, with an extended low density halo. The variety of observed Lyman alpha profiles both in our sample and in high redshift starbursts is explained as phases in the time evolution of the super-shell expanding into the disk and halo of the host galaxy. The observed sha...

  9. Lyman alpha line formation in starbursting galaxies I. Moderately thick, dustless, and static HI media

    CERN Document Server

    Ahn, S H; Lee, H M; Ahn, Sang-Hyeon; Lee, Hee-Won; Lee, Hyung Mok

    2000-01-01

    We investigate the Lyman alpha line transfer in nearby and high redshift starbursting galaxies, where the effect of high optical depths and the role of dust in the scattering medium are expected to be conspicuous and should be treated in a very careful manner. We present our first results in dustless, static, and uniform HI media with moderate optical depths \\tau_0=10^{3-7}, where \\tau_0 is the line center optical depth of Lyman alpha and temperatures T=10^{1-4}K using a Monte Carlo code. We investigate the basic physics of the line transfer and confirm the criterion of a\\tau_0>10^3 for the validity of diffusion approximation suggested by Neufeld in 1990, where $a$ is the Voigt parameter. Adopting the model suggested by Tenorio-Tagle et al. in 1999, we performed a detailed calculation on the Lyman alpha line formation for each evolutionary stage of an expanding supershell. The emergent Lyman alpha profiles are characterized by the double peaks and the absorption trough at the line center. It is found that the...

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

    Science.gov (United States)

    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.

  11. Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) Maps of the Permanently Shaded Regions (PSR) at the Lunar Poles

    Science.gov (United States)

    Rojas, Paul; Retherford, Kurt; Gladstone, Randall; Stern, Alan; Egan, Anthony; Miles, Paul; Parker, Joel; Kaufmann, David; Horvath, David; Greathouse, Thomas; Versteeg, Maartem; Steffl, Andrew; Mukherjee, Joey; Davis, Michael; Slater, David; Bayless, Amanda; Feldmann, Paul; Hurley, Dana; Pryor, Wayne; Hendrix, Amanda

    2013-04-01

    The Lyman Alpha Mapping Project (LAMP) instrument on-board LRO is a UV spectrograph covering the spectral range of 57-196 nm. We present Lyman-alpha and far-UV albedo maps of the north and south poles. These maps indicate that the coldest, permanently shadowed regions (PSR) in deep polar craters have significantly lower Lyman-alpha albedo than the surrounding regions, which is best explained by a high surface porosity there - possibly related to the accumulation of volatile frosts.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  14. A study of the Lyman-$\\alpha$ line profile in DBA white dwarfs

    CERN Document Server

    Genest-Beaulieu, C

    2016-01-01

    The hydrogen abundances in DBA white dwarfs determined from optical or UV spectra have been reported to differ significantly in some studies. We revisit this problem using our own model atmospheres and synthetic spectra, and present a theoretical investigation of the Lyman-$\\alpha$ line profile as a function of effective temperature and hydrogen abundance. We identify one possible solution to this discrepancy and show considerable improvement from a detailed analysis of optical and UV spectra of DBA stars.

  15. The Impact of Lyman alpha Trapping on the Formation of Primordial Objects

    CERN Document Server

    Latif, M A; Spaans, M

    2010-01-01

    Numerous cosmological simulations have been performed to study the formation of the first objects. We present the results of high resolution 3-D cosmological simulations of primordial objects formation using the adaptive mesh refinement code FLASH by including in an approximate manner the radiative transfer effects of Lyman alpha photons. We compare the results of a Lyman alpha trapping case inside gas clouds with atomic and molecular hydrogen cooling cases.The principal objective of this research is to follow the collapse of a zero metallicity halo with an effective equation of state (that accounts for the trapping) and to explore the fate of a halo in each of the three cases, specifically, the impact of thermodynamics on fragmentation of halos.Our results show that in the case of Lyman alpha trapping, fragmentation is halted and a massive object is formed at the center of a halo. The temperature of the gas remains well above $10^{4}$ K and the halo is not able to fragment to stellar masses. In the atomic co...

  16. Chemistry of a protoplanetary disk with grain settling and Lyman alpha radiation

    CERN Document Server

    Fogel, Jeffrey K J; Bergin, Edwin A; Calvet, Nuria; Semenov, Dmitry

    2010-01-01

    We present results from a model of the chemical evolution of protoplanetary disks. In our models we directly calculate the changing propagation and penetration of a high energy radiation field with Lyman alpha radiation included. We also explore the effect on our models of including dust grain settling. We find that, in agreement with earlier studies, the evolution of dust grains plays a large role in determining how deep the UV radiation penetrates into the disk. Significant grain settling at the midplane leads to much smaller freeze-out regions and a correspondingly larger molecular layer, which leads to an increase in column density for molecular species such as CO, CN and SO. The inclusion of Lyman alpha radiation impacts the disk chemistry through specific species that have large photodissociation cross sections at 1216 A. These include HCN, NH3 and CH4, for which the column densities are decreased by an order of magnitude or more due to the presence of Lyman alpha radiation in the UV spectrum. A few spe...

  17. Spatial correlation between submillimetre and Lyman-alpha galaxies in the SSA 22 protocluster

    CERN Document Server

    Tamura, Yoichi; Nakanishi, Kouichiro; Hatsukade, Bunyo; Iono, Daisuke; Wilson, Grant W; Yun, Min S; Takata, Tadafumi; Matsuda, Yuichi; Tosaki, Tomoka; Ezawa, Hajime; Perera, Thushara A; Scott, Kimberly S; Austermann, Jason E; Hughes, David H; Aretxaga, Itziar; Chung, Aeree; Oshima, Tai; Yamaguchi, Nobuyuki; Tanaka, Kunihiko; Kawabe, Ryohei; 10.1038/nature07947

    2009-01-01

    Lyman-alpha emitters are thought to be young, low-mass galaxies with ages of ~10^8 yr. An overdensity of them in one region of the sky (the SSA 22 field) traces out a filamentary structure in the early Universe at a redshift of z = 3.1 (equivalent to 15 per cent of the age of the Universe) and is believed to mark a forming protocluster. Galaxies that are bright at (sub)millimetre wavelengths are undergoing violent episodes of star formation, and there is evidence that they are preferentially associated with high-redshift radio galaxies, so the question of whether they are also associated with the most significant large-scale structure growing at high redshift (as outlined by Lyman-alpha emitters) naturally arises. Here we report an imaging survey of 1,100-um emission in the SSA 22 region. We find an enhancement of submillimetre galaxies near the core of the protocluster, and a large-scale correlation between the submillimetre galaxies and the low-mass Lyman-alpha emitters, suggesting synchronous formation of ...

  18. Spatial correlation between submillimetre and Lyman-alpha galaxies in the SSA 22 protocluster.

    Science.gov (United States)

    Tamura, Yoichi; Kohno, Kotaro; Nakanishi, Kouichiro; Hatsukade, Bunyo; Iono, Daisuke; Wilson, Grant W; Yun, Min S; Takata, Tadafumi; Matsuda, Yuichi; Tosaki, Tomoka; Ezawa, Hajime; Perera, Thushara A; Scott, Kimberly S; Austermann, Jason E; Hughes, David H; Aretxaga, Itziar; Chung, Aeree; Oshima, Tai; Yamaguchi, Nobuyuki; Tanaka, Kunihiko; Kawabe, Ryohei

    2009-05-07

    Lyman-alpha emitters are thought to be young, low-mass galaxies with ages of approximately 10(8) yr (refs 1, 2). An overdensity of them in one region of the sky (the SSA 22 field) traces out a filamentary structure in the early Universe at a redshift of z approximately 3.1 (equivalent to 15 per cent of the age of the Universe) and is believed to mark a forming protocluster. Galaxies that are bright at (sub)millimetre wavelengths are undergoing violent episodes of star formation, and there is evidence that they are preferentially associated with high-redshift radio galaxies, so the question of whether they are also associated with the most significant large-scale structure growing at high redshift (as outlined by Lyman-alpha emitters) naturally arises. Here we report an imaging survey of 1,100-microm emission in the SSA 22 region. We find an enhancement of submillimetre galaxies near the core of the protocluster, and a large-scale correlation between the submillimetre galaxies and the low-mass Lyman-alpha emitters, suggesting synchronous formation of the two very different types of star-forming galaxy within the same structure at high redshift. These results are in general agreement with our understanding of the formation of cosmic structure.

  19. Revealing the z~2.5 Cosmic Web With 3D Lyman-Alpha Forest Tomography: A Deformation Tensor Approach

    CERN Document Server

    Lee, Khee-Gan

    2016-01-01

    Studies of cosmological objects should take into account their positions within the cosmic web of large-scale structure. Unfortunately, the cosmic web has only been extensively mapped at low-redshifts ($z1$, the required galaxy densities are inaccessible for the foreseeable future, but 3D reconstructions of Lyman-$\\alpha$ forest absorption in closely-separated background QSOs and star-forming galaxies already offer a detailed window into $z\\sim2-3$ large-scale structure. We quantify the utility of such maps for studying the cosmic web by using realistic $z=2.5$ Ly$\\alpha$ forest simulations matched to observational properties of upcoming surveys. A deformation tensor-based analysis is used to classify voids, sheets, filaments and nodes in the flux, which is compared to those determined from the underlying dark matter field. We find an extremely good correspondence, with $70\\%$ of the volume in the flux maps correctly classified relative to the dark matter web, and $99\\%$ classified to within 1 eigenvalue. Thi...

  20. Probing the Circumgalactic Medium at High-Redshift Using Composite BOSS Spectra of Strong Lyman-alpha Forest Absorbers

    CERN Document Server

    Pieri, Matthew M; Frank, Stephan; Crighton, Neil; Weinberg, David H; Lee, Khee-Gan; Noterdaeme, Pasquier; Bailey, Stephen J; Busca, Nicolas; Ge, Jian; Kirkby, David; Lundgren, Britt; Mathur, Smita; Paris, Isabelle; Palanque-Delabrouille, Nathalie; Petitjean, Patrick; Rich, James; Ross, Nicholas P; Schneider, Donald P; York, Donald G

    2013-01-01

    We present composite spectra constructed from a sample of 242,150 Lyman-alpha (Lya) forest absorbers at redshifts 2.4flux in bins 138 km/s wide (approximately the size of the BOSS resolution element). We split these absorbers into five samples spanning the range of flux -0.05 < F<0.45. Tests on a smaller sample of high-resolution spectra show that our three strongest absorption bins would probe circumgalactic regions (projected separation < 300 proper kpc and |Delta v| < 300km/s) in about 60% of cases for very high signal-to-noise ratio. Within this subset, weakening Lya absorption is associated with decreasing purity of circumgalactic selection once BOSS noise is included. Our weaker two Lya absorption samples are dominated by the intergalactic medium. We present composite spectra of these samples and a...

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

    Science.gov (United States)

    Dawson, Steven Arthur

    An early result of galaxy formation theory was the prediction that the copious ionizing radiation produced in nascent galaxies undergoing their first starbursts should in turn produce a strong Lya emission line. We report on our efforts to detect and characterize primeval galaxies by searching for this expected Lya signature with two observational techniques: serendipitous slit spectroscopy, and narrowband imaging selection. In Part I, we describe our serendipitous slit spectroscopy survey of the Hubble Deep Field and its environs, which resulted in a catalog of 74 spectroscopic redshifts spanning 0.10 5. Follow-up observations at higher resolution resulted in the additional serendipitous detection of a strong Lya-emitting galaxy at z = 5.190 (ES1). At the time of its discovery, ES1 was one of only nine known galaxies at z > 5, and was the sixth most distant known galaxy. The unprecedented spectral purity of the observation offers evidence for a galaxy-scale outflow with a. velocity of v > 300 km s -1 , consistent with wind speeds observed in powerful local starbursts (typically 10 2 to 10 3 km s -1 ), and with simulations of the late- stage evolution of Lya emission in star-forming systems. Our final serendipitous detection is the remarkable source CXOHDFN J123635.6+621424, which is both the highest redshift known spiral galaxy, and a rare example of a high redshift, hard X-ray-emitting Type II AGN. Significantly, all of these results were acquired with no direct allocation of telescope time. In Part II, we report on our implementation of narrowband imaging selection, with which we traded redshift coverage for survey volume, focusing on the systematic study of galaxies at a particular epoch in favor of chasing that rare, most-distant object. This effort resulted in a catalog of 76 z [approximate] 4.5 Lya-emitting galaxies spectroscopically-confirmed in campaigns of Keck/LRIS and Keck/DEIMOS follow-up observations to candidates selected in the Large Area Lyman

  2. The effect of Lyman $\\alpha$ radiation on mini-Neptune atmospheres around M stars: application to GJ 436b

    CERN Document Server

    Miguel, Yamila; Linsky, Jeffrey L; Rugheimer, Sarah

    2014-01-01

    Mini-Neptunes orbiting M stars are a growing population of known exoplanets. Some of them are located very close to their host star, receiving large amounts of UV radiation. Many M stars emit strong chromospheric emission in the H I Lyman $\\alpha$ line (Ly$\\alpha$) at 1215.67 \\AA, the brightest far-UV emission line. We show that the effect of incoming Ly$\\alpha$ flux can significantly change the photochemistry of mini-Neptunes' atmospheres. We use GJ 436b as an example, considering different metallicities for its atmospheric composition. For solar composition, H$_2$O-mixing ratios show the largest change because of Ly$\\alpha$ radiation. H$_2$O absorbs most of this radiation, thereby shielding CH$_4$, whose dissociation is driven mainly by radiation at other far-UV wavelengths ($\\sim1300$ \\AA). H$_2$O photolysis also affects other species in the atmosphere, including H, H$_2$, CO$_2$, CO, OH and O. For an atmosphere with high metallicity, H$_2$O- and CO$_2$-mixing ratios show the biggest change, thereby shield...

  3. Lyman-alpha forest-CMB cross-correlation and the search for the ionized baryons at high redshift

    CERN Document Server

    Croft, R A C; Hernquist, L; Croft, Rupert A.C.; Hernquist, Lars

    2005-01-01

    The intergalactic neutral hydrogen which is responsible for the Lyman alpha forest of quasar absorption is a tracer of much larger amounts of ionised hydrogen. The ionised component has yet to be detected directly, but is expected to scatter CMB photons via the Sunyaev-Zel'dovich (SZ) effect. We use hydrodynamic simulations of a LambdaCDM universe to create mock quasar spectra and CMB sky maps. We find that the high-z Lya forest gas causes temperature fluctuations of the order of 1 muK rms in the CMB on arcmin scales. The kinetic and thermal SZ effects have a similar magnitude at z=3, with the thermal effect becoming relatively weaker as expected at higher z. The CMB signal associated with lines of sight having HI column densities > 10^18 cm^-2 is only marginally stronger than that for lower column densities. The strong dependence of rms temperature fluctuation on mean Lya absorbed flux, however, suggests that the CMB signal effectively arises in lower density material. We investigate the use of the cross-cor...

  4. Lyman-alpha Emission from a Luminous z=8.68 Galaxy: Implications for Galaxies as Tracers of Cosmic Reionization

    CERN Document Server

    Zitrin, Adi; Belli, Sirio; Bouwens, Rychard; Ellis, Richard S; Roberts-Borsani, Guido; Stark, Daniel P; Oesch, Pascal A; Smit, Renske

    2015-01-01

    We report the discovery of Lyman-alpha emission (Ly$\\alpha$) in the bright galaxy EGSY-2008532660 (hereafter EGSY8p7) using the MOSFIRE spectrograph at the Keck Observatory. First reported by Roberts-Borsani et al. (2015), it was selected for spectroscopic observations because of its photometric redshift ($z_{phot}=8.57^{+0.22}_{-0.43}$), apparent brightness (H$_{160}=25.26\\pm0.09$) and red Spitzer/IRAC [3.6]-[4.5] color indicative of contamination by strong oxygen emission in the [4.5] band. With a total integration of $\\sim4.3$ hours, our data reveal an emission line at $\\simeq11776$ {\\AA} which we argue is likely Ly$\\alpha$ at a redshift $z_{spec}=8.68$, in good agreement with the photometric estimate. The line was detected independently on two nights using different slit orientations and its detection significance is $\\sim7.5\\sigma$. An overlapping sky line contributes significantly to the uncertainty on the total line flux but not the overall significance. By direct addition and a Gaussian fit, we estima...

  5. How Lyman Alpha Emission Depends On Galaxy Stellar Mass

    CERN Document Server

    Oyarzún, Grecco A; González, Valentino; Mateo, Mario; Bailey, John I; Finkelstein, Steven L; Lira, Paulina; Crane, Jeffrey D; Olszewski, Edward W

    2016-01-01

    In this work, we show how the stellar mass (M) of galaxies affects the 3fluxes and use 3D-HST/CANDELS ancillary data. In order to study the Ly-alpha EW distribution dependence on M, we split the whole sample in three stellar mass bins. We find that, in all bins, the distribution is best represented by an exponential profile of the form dN(M)/dEW= A(M)exp(-EW/W0(M))/W0(M). Through a Bayesian analysis, we confirm that lower M galaxies have higher Ly-alpha EWs. We also find that the fraction A of galaxies featuring emission and the e-folding scale W0 of the distribution anti- correlate with M, recovering expressions of the forms A(M)= -0.26(.13) logM/Msun+3.01(1.2) and W0(M)= -15.6(3.5) logM/Msun +166(34). Th...

  6. Spectroscopy of 7 Radio-Loud QSOs at 2Lyman-alpha Nebulae Accreting onto Host Galaxies

    CERN Document Server

    Roche, Nathan; Binette, Luc

    2014-01-01

    We performed long-slit optical spectroscopy (GTC-OSIRIS) of 6 radio-loud QSOs at redshifts $2Lyman-$\\alpha$ emitting nebulae, and detect extended Lyman-$\\alpha$ emission for 4, with surface brightness $\\sim10^{-16}$ ergs $\\rm cm^{-2}s^{-1}arcsec^{-2}$ and line width FWHM 400-1100 (mean 863) km $\\rm s^{-1}$. We also observed the $z\\simeq 5.9$ radio-loud QSO, SDSS J2228+0110, and find evidence of a $\\geq 10$ kpc extended Lyman-$\\alpha$ emission nebula, a new discovery for this high-redshift object. Spatially-resolved kinematics of the 5 nebulae are examined by fitting the Lyman-$\\alpha$ wavelength at a series of positions along the slit. We found the line-of-sight velocity $\\Delta(v)$ profiles to be relatively flat. However, 3 of the nebulae appear systematically redshifted by 250-460 km $\\rm s^{-1}$ relative to the Lyman-$\\alpha$ line of the QSO (with no offset for the other two), which we argue is evidence for infall. One of these (Q0805+046) had a small ($...

  7. A New Population of High Redshift, Dusty Lyman-Alpha Emitters and Blobs Discovered by WISE

    CERN Document Server

    Bridge, Carrie R; Borys, Colin J K; Petty, Sara; Benford, Dominic; Eisenhardt, Peter; Farrah, Duncan; Griffith, Roger L; Jarrett, Tom; Stanford, S Adam; Stern, Daniel; Tsai, Chao-Wei; Wright, Edward L; Wu, Jingwen

    2012-01-01

    We report a new technique to select 1.610^{13-14}L_sun) and warm colors, typically larger than submillimeter-selected galaxies (SMGs) and dust-obscured galaxies (DOGs). These traits are commonly associated with the dust being energized by intense AGN activity. We hypothesize that the combination of spatially extended Lyman-alpha, large amounts of warm IR-luminous dust, and rarity (implying a short-lived phase) can be explained if the galaxies are undergoing strong `feedback' transforming them from an extreme dusty starburst to a QSO.

  8. Abundances in Damped Lyman-$\\alpha$ Systems and Chemical Evolution of High Redshift Galaxies

    CERN Document Server

    Lü, L; Barlow, T A; Lu, Limin; Sargent, Wallace L.W.; Barlow, Thomas A.

    1997-01-01

    Recent abundance measurements in damped Lyman-alpha galaxies, supplemented with unpublished Keck observations, are discussed. The metallicity distribution with cosmic time is examined for clues about the degree of enrichment, the onset of initial star formation, and the nature of the galxies. The relative abundances of the elements are compared with the abundnce pattern in Galactic halo stars and in the Sun, taking into account of the effects of dust depletion, in order to gain insight into the stellar processes and the time scales by which the enrichment occurred.

  9. Lyman-alpha Cooling Emission from Galaxy Formation

    CERN Document Server

    Faucher-Giguere, C -A; Dijkstra, M; Hernquist, L; Zaldarriaga, M

    2010-01-01

    Recent studies have shown that galaxies accrete most of their baryons via the cold mode, from streams with temperatures T~10^4-10^5 K. At these temperatures, the streams should radiate primarily in Lya and have therefore been proposed as a model to power the Lya blobs and other high-redshift Lya sources. We introduce a new Lya radiative transfer code, aRT, and apply it to cosmological hydrodynamical simulations. We address physical and numerical issues that are critical to making accurate predictions for the cooling luminosity, but that have been mostly neglected or treated simplistically so far. We highlight the importance of self-shielding and of properly treating sub-resolution models in simulations. Most existing simulations do not self-consistently incorporate these effects, which can lead to order-of-magnitude errors in the predicted cooling luminosity. Using a combination of post-processing ionizing radiative transfer and re-simulation techniques, we develop an approximation to the consistent evolution...

  10. Coupling the emission of ionizing radiation and Lyman alpha

    Science.gov (United States)

    Hayes, Matthew

    2013-10-01

    The class of objects that reionized intergalactic hydrogen remains an observational and theoretical problem that is in contention for being the most prominent puzzle piece in contemporary astrophysics. The current consensus - determined almost entirely by ruling out bright active galaxies - is that the process was possibly begun and almost certainly finished by faint, lower-mass galaxies forming their early generations of stars. Recent observations of z 3 galaxies may even have identified the analog populations.However understanding how the emitted ionizing power of galaxies is causally related to their {robustly determined} physical properties is not a study that can be performed at high-z: neither the spatial information nor the standard multi-wavelength diagnostics are available. Moreover, on a case-by-case basis, the intervening IGM absorption is impossible to determine. These considerations have spawned a number of detailed studies with UV space telescopes, the synthesis of which however is that a characteristic population of Lyman continuum {LyC} emitting objects has not yet been identified. We show in this proposal that we have identified a characteristic trait in galaxy spectra that is highly indicative of LyC emission, by combining {a} high-z phenomenological studies, {b} new high-resolution UV spectra of local galaxies, and {c} sophisticated models of radiation transport. Believing that we have determined the signature, we propose to test the new hypothesis with deep spectroscopic observations with HST/COS under the Cycle 21 UV initiative.

  11. Lyman-alpha Blobs Like Company : The Discovery of A Candidate 100 kpc Lyman-alpha Blob Near to A Radio Galaxy with A Giant Lyman-alpha halo, B3 J2330+3927 at z=3.1

    CERN Document Server

    Matsuda, Y; Morimoto, N; Smail, Ian; De Breuck, C; Ohta, K; Kodama, T; Inoue, A K; Hayashino, T; Kousai, K; Nakamura, E; Horie, M; Yamada, T; Kitamura, M; Saitô, T; Taniguchi, Y; Tanaka, I; Hibon, P

    2009-01-01

    We present the discovery of a candidate of giant radio-quiet Lyman-alpha (Lya) blob (RQLAB) in a large-scale structure around a high-redshift radio galaxy (HzRG) lying in a giant Lya halo, B3 J2330+3927 at redshift z=3.087. We obtained Lya imaging around B3 J2330+3927 with Subaru/Suprime-Cam to search for Lya emitters (LAEs) and absorbers (LAAs) at redshift z=3.09+-0.03. We detected candidate 127 LAEs and 26 LAAs in the field of view of 31' x 24'. We found that B3 J2330+3927 is surrounded by a 130 kpc Lya halo and a large-scale (60 x 20 comoving Mpc) filamentary structure. The large-scale structure contains one prominent local density peak with an overdensity of greater than 5, which is 8' (15 comoving Mpc) away from B3 J2330+3927. In this peak, we discovered a candidate 100 kpc RQLAB. The existence of both types of Lya nebulae in the same large-scale structure suggests that giant Lya nebulae need special large-scale environments to form. On smaller scales, however, the location of B3 J2330+3927 is not a sign...

  12. The Contribution of HI-rich Galaxies to the Damped Lyman-alpha Absorber Population at z=0

    CERN Document Server

    Schneider, S E; Schneider, Jessica L. Rosenberg & Stephen E.

    2003-01-01

    We present a study of the expected properties of the low redshift damped Lyman-alpha absorber population determined from a sample of HI-selected galaxies in the local universe. We use measurements of the number density and HI cross-section of galaxies to show that the total HI cross-section at column densities sufficient to produce damped Lyman-alpha absorption is consistent with no evolution of the absorber population. We also find that the dN/dz distribution is dominated by galaxies with HI masses near 10^9 M_solar. However, because of the large dispersion in the correlation between HI mass and stellar luminosity, we find that the distribution of dN/dz as a function of L_J is nearly flat. Additionally, we demonstrate that the linewidths of the HI-selected galaxies are roughly consistent with the kinematics of damped Lyman-alpha absorbers.

  13. A Direct Precision Measurement of the Intergalactic Lyman-alpha Opacity at 2

    CERN Document Server

    Faucher-Giguere, C -A; Lidz, A; Hernquist, L; Zaldarriaga, M

    2007-01-01

    We directly measure the evolution of the intergalactic Lyman-alpha effective optical depth, tau_eff, over the redshift range 2 is <1% at z=2, 4% at z=3, and 12% at z=4. Previous measurements of tau_eff at 3power-law redshift evolution (tau_eff=0.0018(1+z)^3.92, when metals are left in), particularly near z=3.2. The observed downward departure is statistically consistent with a similar feature detected in a precision statistical measurement using Sl...

  14. The Reionization and Galaxy Evolution Probed by z=7 Lyman Alpha Emitters

    CERN Document Server

    Ota, Kazuaki; Kashikawa, Nobunari; Shimasaku, Kazuhiro; Kobayashi, Masakazu A R; Totani, Tomonori; Nagashima, Masahiro; Morokuma, Tomoki; Furusawa, Hisanori; Hattori, Takashi; Matsuda, Yuichi; Hashimoto, Tetsuya; Ouchi, Masami

    2007-01-01

    We made a narrowband NB973 (bandwidth of 200A at 9755A) imaging of the Subaru Deep Field (SDF) and found two z=7 Lyman alpha emitter (LAE) candidates down to NB973=24.9. Carrying out deep follow-up spectroscopy, we identified one of them as a real z=6.96 LAE. This has shown that galaxy formation was in progress just 750 Myr after the Big Bang. Meanwhile, the Lyman alpha line luminosity function of LAE is known to decline from z=5.7 to 6.6 in the SDF. L* at z=6.6 is 40-60% of that at z=5.7. We also confirm that the number density of z=7 LAE is only 17% of the density at z=6.6 comparing the latest SDF LAE samples. This series of significant decreases in LAE density with increasing redshift can be the result of galaxy evolution during these epochs. However, using the UV continuum luminosity functions of LAEs, those of Lyman break galaxies, and a LAE evolution model based on the hierarchical clustering, we find that galaxy evolution alone cannot explain all the decrease in density. This extra density deficit can ...

  15. Probing the Physical Properties of z=4.5 Lyman Alpha Emitters with Spitzer

    CERN Document Server

    Finkelstein, Keely D; Tilvi, Vithal; Malhotra, Sangeeta; Rhoads, James E; Grogin, Norman A; Pirzkal, Norbert; Dey, Arjun; Jannuzi, Buell T; Mobasher, Bahram; Pakzad, Sabrina; Salmon, Brett; Wang, Junzian

    2015-01-01

    We present the results from a stellar population modeling analysis of a sample of 162 z=4.5, and 14 z=5.7 Lyman alpha emitting galaxies (LAEs) in the Bootes field, using deep Spitzer/IRAC data at 3.6 and 4.5 um from the Spitzer Lyman Alpha Survey, along with Hubble Space Telescope NICMOS and WFC3 imaging at 1.1 and 1.6 um for a subset of the LAEs. This represents one of the largest samples of high-redshift LAEs imaged with Spitzer IRAC. We find that 30/162 (19%) of the z=4.5 LAEs and 9/14 (64%) of the z=5.7 LAEs are detected at >3-sigma in at least one IRAC band. Individual z=4.5 IRAC-detected LAEs have a large range of stellar mass, from 5x10^8 to 10^11 Msol. One-third of the IRAC-detected LAEs have older stellar population ages of 100 Myr - 1 Gyr, while the remainder have ages < 100 Myr. A stacking analysis of IRAC-undetected LAEs shows this population to be primarily low mass (8 -- 20 x 10^8 Msol) and young (64 - 570 Myr). We find a correlation between stellar mass and the dust-corrected ultraviolet-bas...

  16. Absorption signatures of warm-hot gas at low redshift: Broad Lyman-Alpha Absorbers

    CERN Document Server

    Tepper-García, Thorsten; Schaye, Joop; Booth, Craig M; Vecchia, Claudio Dalla; Theuns, Tom

    2012-01-01

    We investigate the physical state of HI absorbing gas at low redshift (z=0.25) using a subset of cosmological, hydrodynamic simulations from the OWLS project, focusing in particular on broad (b_HI > 40 km/s) Lyman-Alpha absorbers (BLAs), which are believed to originate in shock-heated gas in the Warm-Hot Intergalactic Medium (WHIM). Our fiducial model, which includes radiative cooling by heavy elements and feedback by supernovae and active galactic nuclei, predicts that by z=0.25 nearly 60 per cent of the gas mass ends up at densities and temperatures characteristic of the WHIM and we find that half of this fraction is due to outflows. The standard HI observables (distribution of HI column densities N_HI, distribution of Doppler parameters b_HI, b_HI - N_HI correlation) and the BLA line number density predicted by our simulations are in remarkably good agreement with observations. BLAs arise in gas that is hotter, more highly ionised and more enriched than the gas giving rise to typical Lyman-Alpha forest abs...

  17. The visibility of Lyman Alpha Emitters: constraining reionization, ionizing photons and dust

    CERN Document Server

    Hutter, A; Partl, A M; Müller, V

    2014-01-01

    We couple state of the art cosmological simulations (GADGET-2) with a dust model and a radiative transfer code (pCRASH) to build a complete model for high-redshift Lyman Alpha emitters (LAEs). Due to poor constraints available on the escape fraction of HI ionizing photons (f_esc) from galaxies, we use five different values f_esc=0.05,0.25,0.5,0.75,0.95 to post-process the cosmological simulation with pCRASH. Starting from a completely neutral Universe, we run pCRASH until reionization is complete, i.e. the average neutral hydrogen (HI) fraction drops to ~ 10^-4. For a given f_esc and combination, the only free-parameter left to match model results to observations is the relative escape of Lyman Alpha (Lya) and continuum photons from the galactic environment (f_\\alpha/f_c). Starting from a scenario wherein dust is homogeneously distributed (f_\\alpha/f_c ~ 0.68), we find that the observed LAE UV and Lya luminosity functions (LFs) jointly constrain f_esc ~ 0.05 and and f_\\alpha/f_c such that a decrease in th...

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

    Science.gov (United States)

    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.

  19. The Lyman-alpha Reference Sample: I. Survey outline and first results for Markarian 259

    CERN Document Server

    Östlin, Göran; Duval, Florent; Sandberg, Andreas; Rivera-Thorsen, Thoger; Marquart, Thomas; Orlitova, Ivana; Adamo, Angela; Melinder, Jens; Guaita, Lucia; Atek, Hakim; Cannon, John M; Gruyters, Pieter; Herenz, Edmund Christian; Kunth, Daniel; Laursen, Peter; Mas-Hesse, J Miguel; Micheva, Genoveva; Pardy, Hector Oti-Floranes Stephen A; Roth, Martin M; Schaerer, Daniel; Verhamme, Anne

    2014-01-01

    The Lyman-alpha reference sample (LARS) is a program with the Hubble Space Telescope (HST) that provides a sample of local universe laboratory galaxies in which to study the astrophysics of the visibility and strength of the Lyman-alpha (Lya) line of hydrogen. This article presents an overview of the survey, its selection function and HST imaging observations. The sample was selected from the GALEX+SDSS catalogue at z=0.028-0.19, in order to allow Lya to be captured with combinations of long pass filters in the Solar Blind Channel (SBC) of HST/ACS. In addition, LARS utilises Halpha and Hbeta narrow, and U, B, i broad-band imaging with ACS and WFC3. In order to study galaxies in which large numbers of Lya photons are produced we demanded an Halpha equivalent width > 100{\\AA}. The sample of 14 galaxies covers far UV (FUV) luminosities that overlaps with those of high-z Lya emitters and Lyman Break Galaxies (LBGs). We present the reduction steps used to obtain the Lya images, including our LARS eXtraction softwa...

  20. Lyman-alpha spectral properties of five newly discovered Lyman continuum emitters

    CERN Document Server

    Verhamme, A; Schaerer, D; Izotov, Y; Worseck, G; Thuan, T X; Guseva, N

    2016-01-01

    We have recently reported the discovery of five low redshift Lyman continuum (LyC) emitters (LCEs, hereafter) with absolute escape fractions fesc(LyC) ranging from 6 to 13%, higher than previously found, and which more than doubles the number of low redshift LCEs.We use these observations to test theoretical predictions about a link between the characteristics of the Lyman-alpha (Lya) line from galaxies and the escape of ionising photons. We analyse the Lya spectra of eight LCEs of the local Universe observed with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope (our five leakers and three galaxies from the litterature), and compare their strengths and shapes to the theoretical criteria and comparison samples of local galaxies: the Lyman Alpha Reference Survey, Lyman Break Analogs, Green Peas, and the high-redshift strong LyC leaker Ion2. Our LCEs are found to be strong Lya emitters, with high equivalent widths, EW(Lya)> 70 {\\AA}, and large Lya escape fractions, fesc(Lya) > 20%. The Lya prof...

  1. Lyman-alpha constraints on warm and on warm-plus-cold dark matter models

    CERN Document Server

    Boyarsky, Alexey; Ruchayskiy, Oleg; Viel, Matteo

    2009-01-01

    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_NRP > 8 keV (frequentist 99.7% confidence limit) or m_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_WDM. Within the mass range studied here (5 keV < m_NRP < infinity), we find that any mass value is allowed when F_WDM < 0.6 (freque...

  2. Lyman-alpha observations of comets West 1976 VI and P d'Arrest 1976 XI with Copernicus

    Science.gov (United States)

    Festou, M. C.; Keller, H. U.; Bertaux, J. L.; Barker, E. S.

    1983-02-01

    Lyman-alpha observations by the Copernicus satellite have been used to determine the production rates of hydrogen atoms of comets West 1976 VI and P/d'Arrest 1976 XI at a time when they were dynamically active (splitting or outburst of the nucleus). The observed Lyman-alpha line widths are in agreement with those observed in comet Kobayashi-Berger-Milon 1975 IX and, consequently, do not contradict the assumption that the H atoms are produced by the photodissociation of water vapor, even in CO(plus) rich comets..

  3. Lyman alpha emission from the first galaxies: implications of UV backgrounds and the formation of molecules : implications of UV backgrounds and the formation of molecules

    NARCIS (Netherlands)

    Latif, M. A.; Schleicher, D. R. G.; Spaans, M.; Zaroubi, S.

    The Lyman alpha line is a robust tracer of high redshift galaxies. We present estimates of Lyman alpha emission from a protogalactic halo illuminated by UV background radiation fields with various intensities. For this purpose, we performed cosmological hydrodynamics simulations with the adaptive

  4. Three Lyman-alpha Emitters at z approx 6: Early GMOS/Gemini Data from the GLARE Project

    CERN Document Server

    Stanway, E R; Bunker, A J; Abraham, R G; Hook, I; Rhoads, J; McCarthy, P J; Boyle, B; Colless, M; Crampton, D; Couch, W; Jorgensen, I; Malhotra, S; Murowinski, R; Roth, K; Savaglio, S; Tsvetanov, Z I; Stanway, Elizabeth R.; Glazebrook, Karl; Bunker, Andrew J.; Abraham, Roberto G.; Hook, Isobel; Rhoads, James; Carthy, Patrick J. Mc; Boyle, Brian; Colless, Matthew; Crampton, David; Couch, Warrick; J{\\o}rgensen, Inger; Malhotra, Sangeeta; Murowinski, Rick; Roth, Kathy; Savaglio, Sandra; Tsvetanov., Zlatan

    2004-01-01

    We report spectroscopic detection of three z \\sim 6 Lyman-alpha emitting galaxies, in the vicinity of the Hubble Ultra Deep Field, from the early data of the Gemini Lyman-alpha at Reionisation Era (GLARE) project. Two objects, GLARE#3001 (z =5.79) and GLARE#3011 (z =5.94), are new detections and are fainter in z' (z'_AB = 26.37 and 27.15) than any continuum-selected objects previously detected in Lyman-alpha. A third object, GLARE#1042 (z =5.83) has previously been detected in line emission from the ground; we report here a new spectroscopic continuum detection. Gemini/GMOS-S spectra of these objects, obtained using nod & shuffle, are presented together with a discussion of their photometric properties. All three objects were selected for spectroscopy via the i-drop Lyman Break technique, the two new detections from the GOODS v1.0 imaging data. The red i'-z' colors and high equivalent widths of these objects suggest a high-confidence z>5 Lyman-alpha identification of the emission lines. This brings the to...

  5. LRO-Lyman Alpha Mapping Project (LAMP) Observations of the GRAIL Impact Plumes

    Science.gov (United States)

    Retherford, Kurt D.; Greathouse, T. K.; Hurley, D. M.; Gladstone, G. R.; Hayne, P. O.; Paige, D. A.; Greenhagen, B. T.; Sefton-Nash, E.; Zuber, M. T.; Smith, D. E.; Colaprete, A.; Kaufmann, D. E.; Miles, P. F.; Grava, C.; Throop, H.; Feldman, P. D.; Hendrix, A. R.; Pryor, W. R.; Stubbs, T. J.; Glenar, D. A.; Parker, J. W.; Stern, S. A.

    2013-10-01

    The Lyman Alpha Mapping Project (LAMP) UV spectrograph on the Lunar Reconnaissance Orbiter (LRO) was positioned to directly view the expanding gas plumes from the two GRAIL spacecraft impacts on 17 December 2012. LAMP detected resonantly scattered emissions from Hg and H atoms in the sunlit regions of these plumes. The spectral, spatial, and light-curve analyses used in these gas detections are consistent with previous LAMP observations of the LCROSS impact into the permanently shadowed region of Cabeus crater. LAMP's detection of atomic H by Lyman-α emission at the Moon (a first) was facilitated by pointing at the nightside surface to eliminate sky background noise. Volatile transport of Hg and H species is known to concentrate them near the poles, and in the context of LRO-Diviner temperature measurements of these high-latitude (75.6° N) impact sites the LAMP detections address this process.

  6. Investigating the Metallicity Evolution of Sub-damped Lyman alpha Systems

    Science.gov (United States)

    Konchady, Tarini; Jorgenson, Regina

    2017-01-01

    A clear understanding of the production and build up of metals across cosmic time is a key ingredient to any theory of galaxy formation and evolution. We present chemical abundance measurements for a sample of ~20 sub-damped Lyman alpha systems (subDLAs) detected in the absorption spectra of high redshift quasars taken by the Echellette Spectrograph and Imager (ESI) on the Keck II telescope. The sample contains absorbers with neutral hydrogen column densities of 1019.0 Metal line column densities were measured using the apparent optical depth method while neutral hydrogen column densities were measured via Voigt profile fitting. We compare our measurements to those of DLAs and subDLAs from the literature to investigate the potential differences in metallicity evolution between these types of galaxies.

  7. Lyman-alpha radiation hydrodynamics of galactic winds before cosmic reionization

    CERN Document Server

    Smith, Aaron; Loeb, Abraham

    2016-01-01

    The dynamical impact of Lyman-alpha (Ly{\\alpha}) radiation pressure on galaxy formation depends on the rate and duration of momentum transfer between Ly{\\alpha} photons and neutral hydrogen gas. Although photon trapping has the potential to multiply the effective force, ionizing radiation from stellar sources may relieve the Ly{\\alpha} pressure before appreciably affecting the kinematics of the host galaxy or efficiently coupling Ly{\\alpha} photons to the outflow. We present self-consistent Ly{\\alpha} radiation-hydrodynamics simulations of high-$z$ galaxy environments by coupling the Cosmic Ly{\\alpha} Transfer code (COLT) with spherically symmetric Lagrangian frame hydrodynamics. The accurate but computationally expensive Monte-Carlo radiative transfer calculations are feasible under the one-dimensional approximation. In certain cases Ly{\\alpha} feedback significantly enhances the velocity of the shell of gas expanding around a central source. Radiative feedback alone is capable of ejecting baryons into the i...

  8. Diagnostics of MCF plasmas using Lyman-{alpha} fluorescence excited by one or two photons

    Energy Technology Data Exchange (ETDEWEB)

    Voslamber, D

    1998-11-01

    Laser-induced Lyman-{alpha} fluorescence of the hydrogen isotopes is investigated with regard to diagnostic applications in magnetically confined fusion plasmas. A formal analysis is presented for two excitation schemes: one-photon and Doppler-free two-photon excitation. The analysis includes estimates of the expected experimental errors arising from the photon noise and from the sensitivity of the observed fluorescence signals to variations of the plasma and laser parameters. Both excitation schemes are suitable primarily for application in the plasma edge, but even in the plasma bulk of large machines they can still be applied in combination with a diagnostic neutral beam. The two-photon excitation scheme is particularly attractive because it involves absorption spectra that are resolved within the Doppler width. This implies a large diagnostic potential and in particular offers a way to measure the deuterium-tritium fuel mix in fusion reactors. (author) 37 refs.

  9. Statistical properties of damped Lyman-alpha systems from Sloan Digital Sky Survey DR12

    CERN Document Server

    Bird, Simeon; Ho, Shirley

    2016-01-01

    We present new estimates for the statistical properties of damped Lyman-$\\alpha$ absorbers (DLAs). We compute the column density distribution function at $z>2$, the line density, $\\mathrm{d}N/\\mathrm{d}X$, and the neutral hydrogen density, $\\Omega_\\mathrm{DLA}$. Our estimates are derived from the DLA catalogue of \\cite{Garnett:2016}, which uses the SDSS--III DR12 quasar spectroscopic survey. This catalogue provides a probability that a given spectrum contains a DLA, allowing us to use even the noisiest data without biasing our results and thus substantially increase our sample size. We measure a non-zero column density distribution function at $95\\%$ confidence for all column densities $N_\\mathrm{HI} 4$. We show that our results are insensitive to the signal-to-noise ratio of the spectra, but that there is a residual dependence on quasar redshift for $z<2.5$, which may be due to remaining systematics in our analysis.

  10. A metallicity-spin temperature relation in damped Lyman-$\\alpha$ systems

    CERN Document Server

    Kanekar, Nissim; Briggs, Frank H; Chengalur, Jayaram N

    2009-01-01

    We report evidence for an anti-correlation between spin temperature $T_s$ and metallicity [Z/H], detected at $3.6 \\sigma$ significance in a sample of 26 damped Lyman-$\\alpha$ absorbers (DLAs) at redshifts $0.09 1.7$ have low metallicities, [Z/H] $< -1$, implying that the HI in high-$z$ DLAs is predominantly warm. The anti-correlation between $T_s$ and [Z/H] is consistent with the presence of a mass-metallicity relation in DLAs, suggested by the tight correlation between DLA metallicity and the kinematic widths of metal lines. Most high-$z$ DLAs are likely to arise in galaxies with low masses ($M_{\\rm vir} < 10^{10.5} M_\\odot$), low metallicities ([Z/H]$< -1$, and low cold gas fractions.

  11. The spin temperature of high-redshift damped Lyman-$\\alpha$ systems

    CERN Document Server

    Kanekar, N; Smette, A; Ellison, S L; Ryan-Weber, E V; Momjian, E; Briggs, F H; Lane, W M; Chengalur, J N; Delafosse, T; Grave, J; Jacobsen, D; de Bruyn, A G

    2013-01-01

    We report results from a programme aimed at investigating the temperature of neutral gas in high-redshift damped Lyman-$\\alpha$ absorbers (DLAs). This involved (1) HI 21cm absorption studies of a large DLA sample, (2) VLBI studies to measure the low-frequency quasar core fractions, and (3) optical/ultraviolet spectroscopy to determine DLA metallicities and velocity widths. Including literature data, our sample consists of 37 DLAs with estimates of the spin temperature $T_s$ and the covering factor. We find a strong $4\\sigma$) difference between the $T_s$ distributions in high-z (z>2.4) and low-z (z1 sub-sample. Since z>1 DLAs have angular diameter distances comparable to or larger than those of the background quasars, they have similar efficiency in covering the quasars. Low covering factors in high-z DLAs thus cannot account for the observed redshift evolution in spin temperatures. (Abstract abridged.)

  12. Cosmochemistry, cosmology and fundamental constants: High-resolution spectroscopy of damped Lyman-alpha systems

    CERN Document Server

    Quast, R; Smette, A; Garcet, O; Ledoux, C; López, S; Wisotzki, L

    2004-01-01

    Spectroscopy of QSO absorption lines provides essential observational input for the study of nucleosynthesis and chemical evolution of galaxies at high redshift. But new observations may indicate that present chemical abundance data are biased due to deficient spectral resolution and unknown selection effects: Recent high-resolution spectra reveal the hitherto unperceived chemical nonuniformity of molecular hydrogen-bearing damped Lyman-alpha (DLA) systems, and the novel H/ESO DLA survey produces compelling evidence for faint QSOs being attenuated by dust. We present a revised analysis of the molecular hydrogen-bearing DLA complex toward HE 0515-4414 showing nonuniform differential depletion of chemical elements onto dust grains, and introduce to the H/ESO DLA survey and its implications. Conclusively, we aim at starting an unbiased chemical abundance database established on high-resolution spectroscopic observations. New data to probe the temperature-redshift relation predicted by standard cosmology and to t...

  13. A systematic study of Lyman-Alpha transfer through outflowing shells: Model parameter estimation

    CERN Document Server

    Gronke, Max; Dijkstra, Mark

    2015-01-01

    Outflows promote the escape of Lyman-$\\alpha$ (Ly$\\alpha$) photons from dusty interstellar media. The process of radiative transfer through interstellar outflows is often modelled by a spherically symmetric, geometrically thin shell of gas that scatters photons emitted by a central Ly$\\alpha$ source. Despite its simplified geometry, this `shell model' has been surprisingly successful at reproducing observed Ly$\\alpha$ line shapes. In this paper we perform automated line fitting on a set of noisy simulated shell model spectra, in order to determine whether degeneracies exist between the different shell model parameters. While there are some significant degeneracies, we find that most parameters are accurately recovered, especially the HI column density ($N_{\\rm HI}$) and outflow velocity ($v_{\\rm exp}$). This work represents an important first step in determining how the shell model parameters relate to the actual physical properties of Ly$\\alpha$ sources. To aid further exploration of the parameter space, we ...

  14. Studying Lyman-alpha escape and reionization in Green Pea galaxies

    Science.gov (United States)

    Yang, Huan; Malhotra, Sangeeta; Rhoads, James E.; Gronke, Max; Leitherer, Claus; Wofford, Aida; Dijkstra, Mark

    2017-01-01

    Green Pea galaxies are low-redshift galaxies with extreme [OIII]5007 emission line. We built the first statistical sample of Green Peas observed by HST/COS and used them as analogs of high-z Lyman-alpha emitters to study Ly-alpha escape and Ly-alpha sizes. Using the HST/COS 2D spectra, we found that Ly-alpha sizes of Green Peas are larger than the UV continuum sizes. We found many correlations between Ly-alpha escape fraction and galactic properties -- dust extinction, Ly-alpha kinematic features, [OIII]/[OII] ratio, and gas outflow velocities. We fit an empirical relation to predict Ly-alpha escape fraction from dust extinction and Ly-alpha red-peak velocity. In the JWST era, we can use this relation to derive the IGM HI column density along the line of sight of each high-z Ly-alpha emitter and probe the reionization process.

  15. Spatially Resolved Emission of a z~3 Damped Lyman Alpha Galaxy with Keck/OSIRIS IFU

    Science.gov (United States)

    Christenson, Holly; Jorgenson, Regina

    2017-01-01

    The damped Lyman alpha (DLA) class of galaxies contains most of the neutral hydrogen gas over cosmic time. Few DLAs have been detected directly, which limits our knowledge of fundamental properties like size and mass. We present Keck/OSIRIS infrared integral field spectroscopy (IFU) observations of a DLA that was first detected in absorption toward a background quasar. Our observations use the Keck Laser Guide Star Adaptive Optics system to reduce the point-spread function of the quasar, making it possible to spatially resolve the DLA emission. We map this emission in O[III] 5007 Å. At redshift z~3, this DLA represents one of the highest redshift DLAs mapped with IFU spectroscopy. We present measurements of the star formation rate, metallicity, and gas mass of the galaxy.This project was supported in part by the NSF REU grant AST-1358980 and by the Nantucket Maria Mitchell Association.

  16. Large Area Lyman Alpha Survey: Finding Young Galaxies at z=4.5

    Science.gov (United States)

    Malhotra, S.; Rhoads, J.; Dey, A.; Stern, D.; Spinrad, H.

    Strong Lyα emission is a signpost of young stars and the absence of dust and thus indicates young galaxies. To find such a population of young galaxies at z=4.5 we started the Large Area Lyman Alpha survey (LALA). This survey achieves an unprecedented combination of volume and sensitivity by using narrow-band filters on a large format (36' × 36') camera on the 4 meter telescope at KPNO. The volume density and star-formation contribution of the Lyα emitters at z=4.5 is comparable to that of Lyman break galaxies. With many candidates and a few spectroscopic confirmations in hand we discuss what the properties of Lyα emitters imply for galaxy and star formation in the early universe.

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

    Science.gov (United States)

    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.

  18. First results from Faint Infrared Grism Survey (FIGS): first simultaneous detection of Lyman-{\\alpha} emission and Lyman break from a galaxy at z=7.51

    CERN Document Server

    Tilvi, V; Malhotra, S; Finkelstein, S L; Rhoads, J E; Windhorst, R; Grogin, N A; Koekemoer, A; Zakamska, N; Ryan, R; Christensen, L; Hathi, N; Pharo, J; Joshi, B; Yang, H; Gronwall, C; Cimatti, A; Walsh, J; OConnell, R; Straughn, A; Ostlin, G; Rothberg, B; Livermore, R C; Hibon, P; Gardner, Jonathan P

    2016-01-01

    Galaxies at high redshifts provide a valuable tool to study cosmic dawn, and therefore it is crucial to reliably identify these galaxies. Here, we present an unambiguous and first simultaneous detection of both the Lyman-\\alpha emission and the Lyman break from a z = 7.512+/- 0.004 galaxy, observed in the Faint Infrared Grism Survey (FIGS). These spectra, taken with G102 grism on Hubble Space Telescope (HST), show a significant emission line detection (6{\\sigma}) in multiple observational position angles (PA), with total integrated Ly{\\alpha} line flux of 1.06+/- 0.12 e10-17erg s-1cm-2. The line flux is nearly a factor of four higher than the previous MOSFIRE spectroscopic observations of faint Ly{\\alpha} emission at {\\lambda} = 1.0347{\\mu}m, yielding z = 7.5078+/- 0.0004. This is consistent with other recent observations implying that ground-based near-infrared spectroscopy underestimates total emission line fluxes, and if confirmed, can have strong implications for reionization studies that are based on gro...

  19. On the inversion of the scattering polarization and the Hanle effect signals in the hydrogen Lyman-$\\alpha$ line

    CERN Document Server

    Ishikawa, R; Belluzzi, L; Sainz, R Manso; Stepan, J; Bueno, J Trujillo; Goto, M; Tsuneta, S

    2014-01-01

    Magnetic field measurements in the upper chromosphere and above, where the gas-to-magnetic pressure ratio $\\beta$ is lower than unity, are essential for understanding the thermal structure and dynamical activity of the solar atmosphere. Recent developments in the theory and numerical modeling of polarization in spectral lines have suggested that information on the magnetic field of the chromosphere-corona transition region could be obtained by measuring the linear polarization of the solar disk radiation at the core of the hydrogen Lyman-$\\alpha$ line at 121.6~nm, which is produced by scattering processes and the Hanle effect. The Chromospheric Lyman-$\\alpha$ Spectropolarimeter (CLASP) sounding rocket experiment aims to measure the intensity (Stokes $I$) and the linear polarization profiles ($Q/I$ and $U/I$) of the hydrogen Lyman-$\\alpha$ line. In this paper we clarify the information that the Hanle effect can provide by applying a Stokes inversion technique based on a database search. The database contains a...

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

    Energy Technology Data Exchange (ETDEWEB)

    Fayock, B.; Zank, G. P.; Heerikhuisen, J., E-mail: brian.fayock@gmail.com, E-mail: garyp.zank@gmail.com, E-mail: jacob.heerikhuisen@uah.edu [Department of Physics and Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)

    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.

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

    CERN Document Server

    Sandberg, A; Östlin, G; Hayes, M; Kiaeerad, F

    2015-01-01

    Context. Lyman alpha 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, but the exact circumstances under which Lyman alpha escapes a galaxy are still not fully understood. Aims. The Trident project is designed to simultaneously examine Lyman alpha, H-alpha and Lyman Continuum emission from galaxies at redshift z~2, thus linking together these three aspects of ionising 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 and two custom made filters at the Nordic Optical Telescope with MOSCA. We use complementary broad band archival data in the field to make a careful candidate selection and perform optical to near-IR SED fitting. We also estimate far-infrared luminosities by matching our candidates to detections in...

  2. Ionized Gas in Damped Lyman Alpha Protogalaxies II. Comparison Between Models and the Kinematic Data

    CERN Document Server

    Wolfe, A M; Wolfe, Arthur M.

    2000-01-01

    We test semi-analytic models for galaxy formation with accurate kinematic data of damped Lyman alpha protogalaxies (DLAs) presented in the companion paper I. The models envisage centrifugally supported exponential disks at the centers of dark matter halos which are filled with ionized gas undergoing radial infall to the disks. The halo masses are drawn from cross-section weighted mass distributions predicted by CDM cosmogonies, or by the null hypothesis (TF model) that the dark matter mass distribution has not evolved since z ~ 3. In our models, C IV absorption lines detected in DLAs arise in infalling ionized clouds while the low-ion absorption lines arise from neutral gas in the disks. Using Monte Carlo methods we find: (a) The CDM models are incompatible with the low-ion statistics at more than 99% confidence whereas some TF models cannot be excluded at more than 88% confidence. (b) Both CDM and TF models agree with the observed distribution of C IV velocity widths. (c) The CDM models generate differences ...

  3. Hydrogen Lyman-alpha and Lyman-beta radiances and profiles in polar coronal holes

    CERN Document Server

    Tian, Hui; Curdt, Werner; Vial, Jean-Claude

    2009-01-01

    The hydrogen Lyman-alpha plays a dominant role in the radiative energy transport in the lower transition region, and is important for the stud- ies of transition-region structure as well as solar wind origin. We investigate the Ly-alpha profiles obtained by SUMER in coronal holes and quiet Sun. In a subset of these observations, also the Hi Lyman-beta, Si iii, and O vi lines were (quasi-) simultaneously recorded. We find that the distances between the two peaks of Ly-alpha profiles are larger in coronal holes than in the quiet Sun, indicating a larger opacity in coronal holes. This difference might result from the different magnetic structures or the different radiation fields in the two regions. Most of the Ly-beta profiles in the coronal hole have a stronger blue peak, in contrast to those in quiet-Sun regions. Whilst in both regions the Ly-alpha profiles are stronger in the blue peak. Although the asymmetries are likely to be produced by differential flows in the solar atmosphere, their detailed formation ...

  4. Elemental Abundances in Two High Column Density Damped Lyman Alpha Systems at z < 1.5

    CERN Document Server

    Rao, S M; Howk, J C; Wolfe, A M; Rao, Sandhya M.; Prochaska, Jason X.; Wolfe, Arthur M.

    2004-01-01

    We present Keck/HIRES abundance measurements and metal-line kinematic profiles of the damped Lyman alpha systems (DLAs) towards the quasars Q0933+733 (z_abs=1.479) and Q0948+433 (z_abs=1.233). These two DLAs have among the five highest HI column densities at any redshift: N(HI)=4.2E21 cm^{-2}. The metal-line data, presented here for the first time, reveal that these DLAs are noteworthy for several other reasons as well. 1) The Q0933+733 DLA exhibits simple kinematic structure with unusually narrow velocity widths as measured from its unsaturated metal lines (delta v=16 km/s). At 2.6% solar, it has the second lowest metallicity at z -1) and a significant alpha-enhancement. The strong metal lines of this DLA have made possible the detection of TiII1910, CoII2012, and MgI2026. 3) We find that the relative gas-phase abundances of both DLAs follow the general trend seen at high redshift, e.g., enhanced Zn/Fe and Si/Fe, and sub-solar Mn/Fe, indicating that there is little evolution in the nucleosynthetic patterns o...

  5. Adaptive Optics Imaging of Low-redshift Damped Lyman-alpha Quasar Absorbers

    CERN Document Server

    Chun, M R; Kulkarni, V P; Takamiya, M; Chun, Mark R.; Gharanfoli, Soheila; Kulkarni, Varsha P.; Takamiya, Marianne

    2005-01-01

    We have carried out a high angular resolution near-infrared imaging study of the fields of 6 quasars with 7 strong absorption line systems at z < 0.5, using the Hokupa'a adaptive optics system and the QUIRC near-infrared camera on the Gemini-North telescope. These absorption systems include 4 classical damped Lyman-alpha absorbers (DLAs), 2 sub-DLAs, and one Lyman-limit system. Images were obtained in the H or K' filters with FWHM between 0.2"-0.5" with the goal of detecting the absorbing galaxies and identifying their morphologies. Features are seen at projected separations of 0.5"-16.0" from the quasars and all of the fields show features at less than 2" separation. We find candidate absorbers in all of the seven systems. With the assumption that some of these are associated with the absorbers, the absorbers are low luminosity < 0.1 L*_H or L*_K; we do not find any large bright candidate absorbers in any of our fields. Some fields show compact features that are too faint for quantitative morphology, b...

  6. C, N, O Abundances in the Most Metal-Poor Damped Lyman alpha Systems

    CERN Document Server

    Pettini, Max; Steidel, Charles C; Chaffee, Fred H

    2007-01-01

    This study focuses on some of the most metal-poor damped Lyman alpha absorbers known in the spectra of high redshift QSOs, using new and archival observations obtained with UV-sensitive echelle spectrographs on the Keck and VLT telescopes. The weakness and simple velocity structure of the absorption lines in these systems allows us to measure the abundances of several elements, and in particular those of C, N, and O, a group that is difficult to study in DLAs of more typical metallicities. We find that when the oxygen abundance is less than about 1/100 of solar, the C/O ratio in high redshift DLAs and sub-DLAs matches that of halo stars of similar metallicity and shows higher values than expected from galactic chemical evolution models based on conventional stellar yields. Furthermore, there are indications that at these low metallicities the N/O ratio may also be above simple expectations and may exhibit a minimum value, as proposed by Centurion and her collaborators in 2003. Both results can be interpreted ...

  7. The primordial deuterium abundance of the most metal-poor damped Lyman-alpha system

    CERN Document Server

    Cooke, Ryan; Nollett, Kenneth M; Jorgenson, Regina

    2016-01-01

    We report the discovery and analysis of the most metal-poor damped Lyman-alpha (DLA) system currently known, which also displays the Lyman series absorption lines of neutral deuterium. The average [O/H] abundance of this system is [O/H] = -2.804 +/- 0.015, which includes an absorption component with [O/H] = -3.07 +/- 0.03. Despite the unfortunate blending of many weak D I absorption lines, we report a precise measurement of the deuterium abundance of this system. Using the six highest quality and self-consistently analyzed measures of D/H in DLAs, we report tentative evidence for a subtle decrease of D/H with increasing metallicity. This trend must be confirmed with future high precision D/H measurements spanning a range of metallicity. A weighted mean of these six independent measures provides our best estimate of the primordial abundance of deuterium, 10^5 (D/H)_P = 2.547 +/- 0.033 (log_10 (D/H)_P = -4.5940 +/- 0.0056). We perform a series of detailed Monte Carlo calculations of Big Bang nucleosynthesis (BB...

  8. The effect of dust geometry on the Lyman-alpha output of galaxies

    CERN Document Server

    Scarlata, C; Teplitz, H I; Panagia, N; Hayes, M; Siana, B; Rau, A; Francis, P; Caon, A; Pizzella, A; Bridge, C

    2009-01-01

    We present the optical spectroscopic follow-up of 31 z=0.3 Lyman-alpha (Lya) emitters, previously identified by Deharveng et al. (2008). We find that 17% of the Lya emitters have line ratios that require the hard ionizing continuum produced by an AGN. The uniform dust screen geometry traditionally used in studies similar to ours is not able to simultaneously reproduce the observed high Lya/Halpha and Halpha/Hbeta line ratios. We consider different possibilities for the geometry of the dust around the emitting sources. We find that also a uniform mixture of sources and dust does not reproduce the observed line ratios. Instead, these are well reproduced by a clumpy dust screen. This more realistic treatment of the geometry results in extinction corrected (Lya/Halpha)_C values consistent with Case B recombination theory, whereas a uniform dust screen model would imply values (Lya/Halpha)_C higher than 8.7. Our analysis shows that there is no need to invoke "ad-hoc" multi phase media in which the Lya photons only...

  9. The Lyman Alpha Reference Sample: III. Properties of the Neutral ISM from GBT and VLA Observations

    CERN Document Server

    Pardy, Stephen A; Östlin, Göran; Hayes, Matthew; Rivera-Thorsen, Thøger; Sandberg, Andreas; Adamo, Angela; Freeland, Emily; Heren, E Christian; Guaita, Lucia; Kunth, Daniel; Laursen, Peter; Mas-Hesse, J M; Melinder, Jens; Orlitová, Ivana; Otí-Floranes, Héctor; Puschnig, Johannes; Schaerer, Daniel; Verhamme, Anne

    2014-01-01

    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 Ly$\\alpha$ photons. New H I spectroscopy, obtained with the 100m 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 5 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 ext...

  10. The Column Density Distribution of the Low-Redshift Lyman-Alpha Forest in Illustris

    CERN Document Server

    Gurvich, Alex; Bird, Simeon

    2016-01-01

    We investigate the low-redshift Lyman-alpha forest column density distribution in the Illustris simulation. We show that Illustris reproduces observations extremely well in the column density range 10^12.5-10^14.5 cm^-2, relevant for the "photon underproduction crisis." We attribute this to the inclusion of AGN feedback, which changes the gas distribution so as to mimic the effect of extra photons, as well as the use of the Faucher-Giguere (2009) ultra-violet background, which is more ionizing at z=0.1 than the Haardt & Madau (2012) background previously considered. We show that the difference between simulations run with smoothed particle hydrodynamics and simulations using a moving mesh is small in this column density range. We further consider the effect of supernova feedback, Voigt profile fitting and finite resolution, all of which we show to be small. Finally, we identify a discrepancy between our simulations and observations at column densities 10^14-10^16 cm^-2, where Illustris produces too few ab...

  11. From Exoplanets to Quasars: Detection of Potential Damped Lyman Alpha Absorbing Galaxies Using Angular Differential Imaging

    CERN Document Server

    Johnson-Groh, Mara; Ellison, Sara L

    2016-01-01

    The advantages of angular differential imaging (ADI) has been previously untested in imaging the host galaxies of damped Lyman alpha (DLA) systems. In this pilot study, we present the first application of ADI to directly imaging the host galaxy of the DLA seen towards the quasar J1431+3952. K-band imaging of the field surrounding J1431+3952 was obtained on the Gemini North telescope with the adaptive optics system and a laser guide star. We computed a sensitivity curve that demonstrates the sensitivity of our observations as a function of K-band magnitude, impact parameter and DLA angular size. For an impact parameter of 0.5" (3.4 kpc at the redshift of the absorber) our mass sensitivity is log (M_star/M_sun) ~ 9.2 and drops to ~ 9.0 at separations beyond ~ 6 kpc for the smallest size model galaxy. Three candidate galaxies are identified within 5". Stellar masses were computed from the K-band photometry yielding values of log (M_star/M_sun) ~ 9.9, 9.7 and 11.1 respectively. The likely identification of the ab...

  12. The Mean Metal-line Absorption Spectrum of Damped Lyman Alpha Systems in BOSS

    CERN Document Server

    Mas-Ribas, Lluís; Pérez-Ràfols, Ignasi; Arinyo-i-Prats, Andreu; Noterdaeme, Pasquier; Petitjean, Patrick; Schneider, Donald P; York, Donald G; Ge, Jian

    2016-01-01

    We study the average absorption spectrum of the Damped Lyman Alpha system (DLA) population at $z ~ 2.5$ by stacking normalized, rest-frame shifted spectra of $\\sim 27\\,000$ DLAs from the Data Release 12 of the BOSS survey of SDSS-III. We list measurements of the mean equivalent width of 50 individual metal absorption lines in 5 intervals of DLA hydrogen column density $N_{\\rm HI}$, and overall mean equivalent widths for an additional 13 absorption features from groups of strongly blended lines. We show that the mean equivalent width of low-ionization lines increases with $N_{\\rm HI}$ as expected, but this increase is much weaker or non-existent for high-ionization lines. We develop a theoretical model to infer mean column densities from the equivalent widths of partially saturated lines, based on the presence of multiple absorption components observed in high-resolution spectra. We use this model to infer mean column densities in DLAs of 14 low-ionization species, as well as for AlIII, SIII, SiIII, CIV, SiIV,...

  13. Cross-correlation of the cosmic 21-cm signal and Lyman Alpha Emitters during reionization

    CERN Document Server

    Sobacchi, Emanuele; Greig, Bradley

    2016-01-01

    Interferometry of the cosmic 21-cm signal is set to revolutionize our understanding of the Epoch of Reionization (EoR), eventually providing 3D maps of the early Universe. Initial detections however will be low signal-to-noise, limited by systematics. To confirm a putative 21-cm detection, and check the accuracy of 21-cm data analysis pipelines, it would be very useful to cross-correlate against a genuine cosmological signal. The most promising cosmological signals are wide-field maps of Lyman alpha emitting galaxies (LAEs), expected from the Subaru Hyper-Suprime Cam (HSC) Ultra-Deep field. Here we present estimates of the correlation between LAE maps at z~7 and the 21-cm signal observed by both the Low Frequency Array (LOFAR) and the planned Square Kilometer Array Phase 1 (SKA1). We adopt a systematic approach, varying both: (i) the prescription of assigning LAEs to host halos; and (ii) the large-scale structure of neutral and ionized regions (i.e. EoR morphology). We find that the LAE-21cm cross-correlation...

  14. The Chemical Evolution of Very Metal-Poor Damped Lyman-$\\alpha$ Systems

    CERN Document Server

    Webster, David; Sutherland, Ralph S

    2015-01-01

    In earlier work we showed that a dark matter halo with a virial mass of $10^7$ M$_\\odot$ can survive feedback from its own massive stars and form stars for $\\gtrsim100$ Myr. We also found that our modelled systems were consistent with observations of ultrafaint dwarfs (UFDs), the least massive known galaxies. Very metal-poor damped Lyman-$\\alpha$ systems (DLAs) recently identified at $z\\sim2$ may represent the gas that formed at least some of the observed stars in UFDs. We compare projected sightlines from our simulations to the observed metal-poor DLAs and find that our models can reach the densities of the observed sightlines; however the metallicities are inconsistent with the single supernova simulations, suggesting enrichment by multiple supernovae. We model two scenarios for the history of these systems. The first explains the gas abundances in DLAs by a single burst of star formation. This model can produce the observed DLA abundances, but does not provide an explanation as to why the DLAs show suppres...

  15. From Mirrors to Windows: Lyman-Alpha Radiative Transfer in a Very Clumpy Medium

    CERN Document Server

    Gronke, Max; McCourt, Michael; Oh, S Peng

    2016-01-01

    Lyman-Alpha (Ly$\\alpha$) is the strongest emission line in the Universe and is frequently used to detect and study the most distant galaxies. Because Lya is a resonant line, photons typically scatter prior to escaping; this scattering process complicates the interpretation of Ly$\\alpha$ spectra, but also encodes a wealth of information about the structure and kinematics of neutral gas in the galaxy. Modeling the Ly$\\alpha$ line therefore allows us to study tiny-scale features of the gas, even in the most distant galaxies. Curiously, observed Ly$\\alpha$ spectra can be modeled successfully with very simple, homogeneous geometries (such as an expanding, spherical shell), whereas more realistic, multiphase geometries often fail to reproduce the observed spectra. This seems paradoxical since the gas in galaxies is known to be multiphase. In this Letter, we show that spectra emerging from extremely clumpy geometries with many clouds along the line of sight converge to the predictions from simplified, homogeneous mo...

  16. Damped Lyman-alpha absorbers as a probe of stellar feedback

    CERN Document Server

    Bird, Simeon; Haehnelt, Martin; Sijacki, Debora; Genel, Shy; Torrey, Paul; Springel, Volker; Hernquist, Lars

    2014-01-01

    We examine the abundance, clustering and metallicity of Damped Lyman-$\\alpha$ Absorbers (DLAs) in hydrodynamic cosmological simulations using the moving mesh code AREPO. We incorporate models of supernova and AGN feedback, and molecular hydrogen formation. We compare our simulations to the column density distribution function at $z=3$, the total DLA abundance at $z=2-4$, the measured DLA bias at $z=2$ and DLA metallicities at $z=2-4$. Our preferred models produce populations of DLAs in good agreement with most of these observations, except the DLA abundance at $z < 3$, which we show requires stronger feedback in $10^{11-12} h^{-1} M_\\odot$ mass halos. While the DLA population probes a range of halo masses, we find the cross-section is dominated by halos of mass $10^{10.5} h^{-1} M_\\odot$ at $z=3$ and $10^{11} h^{-1} M_\\odot$ at $z=2$. Simulations without feedback are in strong tension with all these observables, indicating a need for strong stellar feedback at $z=2-4$ independently of the star formation th...

  17. A Multiply-Imaged z $\\sim$ 6.3 Lyman Alpha Emitter candidate behind Abell 2261

    CERN Document Server

    Rydberg, Claes-Erik; Zackrisson, Erik; Melinder, Jens; Whalen, Daniel J; Klessen, Ralf S; Gonzalez, Juan; Östlin, Göran; Carollo, Daniela

    2016-01-01

    While the Lyman-$\\alpha$ ($\\mathrm{Ly}\\alpha$) emission line serves as an important tool in the study of galaxies at $z\\lesssim 6$, finding Ly$\\alpha$ emitters (LAE) at significantly higher redshifts has been more challenging, probably because of the increasing neutrality of the intergalactic medium above $z\\sim6$. Galaxies with extremely high rest-frame Ly$\\alpha$ equivalent widths, EW(Ly$\\alpha$) $\\gtrsim 150$ \\AA{}, at $z>6$ are good candidates for Ly$\\alpha$ follow-up observations, and can stand out in multiband imaging surveys because of their unusual colors. We have conducted a photometric search for such objects in the Cluster Lensing And Supernova survey with Hubble (CLASH), and report here the identification of three likely gravitationally-lensed images of a single LAE candidate at $z\\sim6.3$, behind the galaxy cluster Abell 2261($z = 0.225$). In the process, we also measured with Keck/MOSFIRE the first spectroscopic redshift of a multiply-imaged galaxy behind Abell 2261, at $z = 3.337$. This allows ...

  18. The Curious Case of Lyman Alpha Emitters: Growing Younger from z ~ 3 to z ~ 2?

    CERN Document Server

    Acquaviva, Viviana; Gawiser, Eric; Guaita, Lucia

    2011-01-01

    Lyman Alpha Emitting (LAE) galaxies are thought to be progenitors of present-day L* galaxies. Clustering analyses have suggested that LAEs at z ~ 3 might evolve into LAEs at z ~ 2, but it is unclear whether the physical nature of these galaxies is compatible with this hypothesis. Several groups have investigated the properties of LAEs using spectral energy distribution (SED) fitting, but direct comparison of their results is complicated by inconsistencies in the treatment of the data and in the assumptions made in modeling the stellar populations, which are degenerate with the effects of galaxy evolution. By using the same data analysis pipeline and SED fitting software on two stacked samples of LAEs at z = 3.1 and z = 2.1, and by eliminating several systematic uncertainties that might cause a discrepancy, we determine that the physical properties of these two samples of galaxies are dramatically different. LAEs at z = 3.1 are found to be old (age ~ 1 Gyr) and metal-poor (Z Z_Sun). The difference in the obse...

  19. No overdensity of Lyman Alpha Emitting Galaxies around a quasar at z~5.7

    CERN Document Server

    Mazzucchelli, C; Decarli, R; Farina, E P; Venemans, B P; Walter, F; Overzier, R

    2016-01-01

    Bright quasars, observed when the Universe was less than one billion years old (z>5.5), are known to host massive black holes (~10$^{9}$ M$_{\\odot}$), and are thought to reside in the center of massive dark matter overdensities. In this picture, overdensities of galaxies are expected around high redshift quasars. However, observations based on the detection of Lyman Break Galaxies (LBGs) around these quasars do not offer a clear picture: this may be due to the uncertain redshift constraints of LBGs, which are selected through broad-band filters only. To circumvent such uncertainties, we here perform a search for Lyman Alpha Emitting galaxies (LAEs) in the field of the quasar PSO J215.1512-16.0417 at z~5.73, through narrow band, deep imaging with FORS2 at the VLT. We study an area of 37 arcmin$^{2}$, i.e. ~206 comoving Mpc$^{2}$ at the redshift of the quasar. We find no evidence for an overdensity of LAEs in the quasar field with respect to blank field studies. Possible explanations for these findings include ...

  20. Discovery of Ubiquitous Fast Propagating Intensity Disturbances by the Chromospheric Lyman Alpha Spectropolarimeter (CLASP)

    Science.gov (United States)

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

    2016-01-01

    High cadence observations by the slit-jaw (SJ) optics system of the sounding rocket experiment known as the Chromospheric Lyman Alpha SpectroPolarimeter (CLASP) reveal ubiquitous intensity disturbances that recurrently propagate in one or both of the chromosphere or transition region at a speed much higher than the sound speed. The CLASP/SJ instrument provides a time series of 2D images taken with broadband filters centered on the Ly(alpha) line at a 0.6 s cadence. The fast propagating intensity disturbances are detected in the quiet Sun and in an active region, and at least 20 events are clearly detected in the field of view of 527'' x 527'' during the 5-minute observing time. The apparent speeds of the intensity disturbances range from 150 to 350 km/s, and they are comparable to the local Alfven speed in the transition region. The intensity disturbances tend to propagate along bright elongated structures away from areas with strong photospheric magnetic fields. This suggests that the observed propagating intensity disturbances are related to the magnetic canopy structures. The maximum distance traveled by the intensity disturbances is of about 10'', and the widths are a few arcseconds, which is almost determined by the pixel size of 1.''03. The timescale of each intensity pulse is shorter than 30 s. One possible explanation of the fast propagating intensity disturbances observed by CLASP is magneto-hydrodynamic fast mode waves.

  1. The Temporal Behaviour of Lyman-alpha Emission During Solar Flares From SDO/EVE

    CERN Document Server

    Milligan, Ryan O

    2015-01-01

    Despite being the most prominent emission line in the solar spectrum, there has been a notable lack of studies devoted to variations in Lyman-alpha (Ly$\\alpha$) emission during solar flares in recent years. The few examples that do exist, however, have shown Ly$\\alpha$ emission to be a substantial radiator of the total energy budget of solar flares (on the order of 10%). It is also a known driver of fluctuations in earth's ionosphere. The EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory now provides broadband, photometric Ly$\\alpha$ data at 10 s cadence, and has observed scores of solar flares in the 5 years since it was launched. However, the time profiles appear to display a rise time of tens of minutes around the time of the flare onset. This is in stark contrast to the rapid, impulsive increase observed in other intrinsically chromospheric features (H$\\alpha$, Ly$\\beta$, LyC, C III, etc.). Furthermore, the Ly$\\alpha$ emission peaks around the time of the peak of thermal soft X-ray e...

  2. The evolution of neutral gas in damped Lyman $\\alpha$ systems from the XQ-100 survey

    CERN Document Server

    Sánchez-Ramírez, R; Prochaska, J X; Berg, T A M; López, S; D'Odorico, V; Becker, G D; Christensen, L; Cupani, G; Denney, K D; Pâris, I; Worseck, G; Gorosabel, J

    2015-01-01

    We present a sample of 38 intervening Damped Lyman $\\alpha$ (DLA) systems identified towards 100 $z>3.5$ quasars, observed during the XQ-100 survey. The XQ-100 DLA sample is combined with major DLA surveys in the literature. The final combined sample consists of 742 DLAs over a redshift range approximately $1.6 < z_{\\rm abs} < 5.0$. We develop a novel technique for computing $\\Omega_{\\rm HI}^{\\rm DLA}$ as a continuous function of redshift, and we thoroughly assess and quantify the sources of error therein, including fitting errors and incomplete sampling of the high column density end of the column density distribution function. There is a statistically significant redshift evolution in $\\Omega_{\\rm HI}^{\\rm DLA}$ ($\\geq 3 \\sigma$) from $z \\sim 2$ to $z \\sim$ 5. In order to make a complete assessment of the redshift evolution of $\\Omega_{\\rm HI}$, we combine our high redshift DLA sample with absorption surveys at intermediate redshift and 21cm emission line surveys of the local universe. Although $\\Omeg...

  3. Chemical abundances of damped Lyman alpha systems in the XQ-100 survey

    CERN Document Server

    Berg, T A M; Sanchez-Ramirez, R; Prochaska, J X; Lopez, S; D'Odorico, V; Becker, G; Christensen, L; Cupani, G; Denney, K; Worsek, G

    2016-01-01

    The XQ-100 survey has provided high signal-noise spectra of 100 redshift 3-4.5 quasars with the X-Shooter spectrograph. The metal abundances for 13 elements in the 41 damped Lyman alpha systems (DLAs) identified in the XQ-100 sample are presented, and an investigation into abundances of a variety of DLA classes is conducted. The XQ-100 DLA sample contains five DLAs within 5000 km/s of their host quasar (proximate DLAs; PDLAs) as well as three sightlines which contain two DLAs within 10,000 km/s of each other along the same line-of-sight (multiple DLAs; MDLAs). Combined with previous observations in the literature, we demonstrate that PDLAs with logN(HI)21.0. These abundance discrepancies are independent of their line-of-sight velocity separation from the host quasar, and the velocity width of the metal lines (v90). Contrary to previous studies, MDLAs show no difference in [alpha/Fe] relative to single DLAs matched in metallicity and redshift. In addition, we present follow-up UVES data of J0034+1639, a sightl...

  4. Constraints on the gas masses of low-z damped Lyman-$\\alpha$ systems

    CERN Document Server

    Mazumdar, Parichay; Prochaska, J Xavier

    2014-01-01

    We report a deep search for redshifted HI 21 cm emission from three damped and sub-damped Lyman-$\\alpha$ absorbers (DLAs) at $z \\approx 0.1$ with the Green Bank Telescope (GBT). No evidence for a redshifted HI 21 cm emission signal was obtained in the GBT spectra of two absorbers, with the data on the third rendered unusable by terrestrial interference. The non-detections of HI 21 cm emission yield strong constraints on the HI masses of the associated galaxies, M$_{\\rm HI} < 2.3 \\times 10^9 \\times (\\Delta V/100)^{1/2}$ M$_\\odot$ for the sub-DLA at $z = 0.0830$ towards J1553+3548, and M$_{\\rm HI} < 2.7 \\times 10^9 \\times (\\Delta V/100)^{1/2}$ M$_\\odot$ for the DLA at $z = 0.0963$ towards J1619+3342, where $\\Delta V$ is the HI 21 cm line width, in km s$^{-1}$. This continues the trend of low HI masses found in all low-$z$ DLAs and sub-DLAs that have been searched for redshifted HI 21 cm emission. Low-redshift absorbers with relatively low HI column densities, $\\lesssim few \\times 10^{20}$ cm$^{-2}$, thus ...

  5. The First Observations of Low Redshift Damped Lyman-alpha Systems with the Cosmic Origins Spectrograph

    CERN Document Server

    Meiring, Joseph D; Prochaska, Jason X; Tumlinson, Jason; Werk, Jessica; Jenkins, Edward B; Thom, Chris; O'Meara, John M; Sembach, Kenneth R

    2011-01-01

    We report on the first Cosmic Origins Spectrograph (COS) observations of damped and sub-damped Lyman-alpha (DLA) systems discovered in a new survey of the gaseous halos of low-redshift galaxies. From observations of 37 sightlines, we have discovered three DLAs and four sub-DLAs. We measure the neutral gas density Omega(HI), and redshift density dN/dz, of DLA and sub-DLA systems at z<0.35. We find dN/dz=0.25 and Omega(HI)=1.4x10^-3 for DLAs, and dN/dz=0.08 with Omega(HI)=4.2x10^-5 for sub-DLAs over a redshift path delta z=11.9. To demonstrate the scientific potential of such systems, we present a detailed analysis of the DLA at z=0.1140 in the spectrum of SDSS J1009+0713. Profile fits to the absorption lines determine log N(H I)=20.68pm0.10 with a metallicity determined from the undepleted element Sulfur of [S/H]=-0.62pm0.18. The abundance pattern of this DLA is similar to that of higher z DLAs, showing mild depletion of the refractory elements Fe and Ti with [S/Fe]=+0.24pm0.22 and [S/Ti]=+0.28pm0.15. Nitro...

  6. The Low Redshift Lyman $\\alpha$ Forest in Cold Dark Matter Cosmologies

    CERN Document Server

    Davé, R; Katz, N; Weinberg, D H; Davé, Romeel; Hernquist, Lars; Katz, Neal; Weinberg, David

    1999-01-01

    We study the physical origin of the low-redshift Lyman alpha forest in hydrodynamic simulations of four CDM cosmologies. Our main conclusions are insensitive to the cosmological model but depend on our assumption that the UV background declines at low redshift. We find that the expansion of the universe drives rapid evolution of dN/dz (the number of absorbers per unit z) at z > 1.7, but that at lower redshift the fading of the UV background counters the influence of expansion, leading to slow evolution. At every redshift, weaker lines come primarily from moderate fluctuations of the diffuse, unshocked IGM, and stronger lines originate in shocked or radiatively cooled gas of higher overdensity. However, the neutral hydrogen column density associated with structures of fixed overdensity drops as the universe expands, so an absorber at z = 0 is dynamically analogous to an absorber with neutral hydrogen column density 10 to 50 times higher at z = 2-3. We find no clear distinction between lines arising in "galaxy ...

  7. Quasar-Lyman $\\alpha$ Forest Cross-Correlation from BOSS DR11 : Baryon Acoustic Oscillations

    CERN Document Server

    Font-Ribera, Andreu; Busca, Nicolas; Miralda-Escudé, Jordi; Ross, Nicholas P; Slosar, Anže; Aubourg, Éric; Bailey, Stephen; Bhardwaj, Vaishali; Bautista, Julian; Beutler, Florian; Bizyaev, Dmitry; Blomqvist, Michael; Brewington, Howard; Brinkmann, Jon; Brownstein, Joel R; Carithers, Bill; Dawson, Kyle S; Delubac, Timothée; Ebelke, Garrett; Eisenstein, Daniel J; Ge, Jian; Kinemuchi, Karen; Lee, Khee-Gan; Malanushenko, Viktor; Malanushenko, Elena; Marchante, Moses; Margala, Daniel; Muna, Demitri; Myers, Adam D; Noterdaeme, Pasquier; Oravetz, Daniel; Palanque-Delabrouille, Nathalie; Pâris, Isabelle; Petitjean, Patrick; Pieri, Matthew M; Rossi, Graziano; Schneider, Donald P; Simmons, Audrey; Viel, Matteo; Yeche, Christophe; York, Donald G

    2013-01-01

    We measure the large-scale cross-correlation of quasars with the Lyman alpha forest absorption, using over 164,000 quasars from Data Release 11 of the SDSS-III Baryon Oscillation Spectroscopic Survey. We extend the previous study of roughly 60,000 quasars from Data Release 9 to larger separations, allowing a measurement of the Baryonic Acoustic Oscillation (BAO) scale along the line of sight $c/(H(z=2.36) ~ r_s) = 9.0 \\pm 0.3$ and across the line of sight $D_A(z=2.36)~ / ~ r_s = 10.8 \\pm 0.4$, consistent with CMB and other BAO data. Using the best fit value of the sound horizon from Planck data ($r_s=147.49 Mpc$), we can translate these results to a measurement of the Hubble parameter of $H(z=2.36) = 226 \\pm 8 km/s$ and of the angular diameter distance of $D_A(z=2.36) = 1590 \\pm 60 Mpc$. The measured cross-correlation function and an update of the code to fit the BAO scale (baofit) are made publicly available.

  8. Detection of HI in Emission in the Lyman Alpha Emitting Galaxy Haro 11

    CERN Document Server

    Pardy, Stephen A; Östlin, Göran; Hayes, Matthew; Bergvall, Nils

    2016-01-01

    We present the first robust detection of HI 21 cm emission in the blue compact galaxy Haro 11 using the 100m Robert C. Byrd Green Bank Telescope (GBT). Haro 11 is a luminous blue compact galaxy with emission in both Lyman Alpha and the Lyman continuum. We detect (5.1 $\\pm$ 0.7 $\\times$10$^8$) M$_{\\odot}$ of HI gas at an assumed distance of 88 Mpc, making this galaxy HI deficient compared to other local galaxies with similar optical properties. Given this small HI mass, Haro 11 has an elevated M$_{H2}$/M$_{HI}$ ratio and a very low gas fraction compared to most local galaxies, and contains twice as much mass in ionized hydrogen as in neutral hydrogen. The HI emission has a linewidth of 71 kms$^{-1}$ and is offset 60 kms$^{-1}$ redward of the optical line center. It is undergoing a starburst after a recent merger which has elevated the star formation rate, and will deplete the gas supply in $<$ 0.2 Gyr. Although this starburst has elevated the SFR compared to galaxies with similar HI masses and linewidths, H...

  9. Nonparametric 3D map of the IGM using the Lyman-alpha forest

    CERN Document Server

    Cisewski, Jessi; Freeman, Peter E; Genovese, Christopher R; Khandai, Nishikanta; Ozbek, Melih; Wasserman, Larry

    2014-01-01

    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 HI 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 nonparametric methodology. The performance of the method is analyzed 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 feat...

  10. Transiting the Sun II: The impact of stellar activity on Lyman-$\\alpha$ transits

    CERN Document Server

    Llama, J

    2015-01-01

    High-energy observations of the Sun provide an opportunity to test the limits of our ability to accurately measure properties of transiting exoplanets in the presence of stellar activity. Here we insert transits of a hot Jupiter into continuous disk integrated data of the Sun in Lyman-alpha (Ly$\\alpha$) from NASA's SDO/EVE instrument to assess the impact of stellar activity on the measured planet-to-star radius ratio $(\\textrm{R}_\\textrm{p}/\\textrm{R}_\\star)$. In 75% of our simulated light curves we measure the correct radius ratio; however, incorrect values can be measured if there is significant short term variability in the light curve. The maximum measured value of $(\\textrm{R}_\\textrm{p}/\\textrm{R}_\\star)$ is $50\\%$ larger than the input value, which is much smaller than the large Ly$\\alpha$ transit depths that have been reported in the literature, suggesting that for stars with activity levels comparable to the Sun, stellar activity alone cannot account for these deep transits. We ran simulations withou...

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

    Science.gov (United States)

    Pryor, W.; Gangopadhyay, P.; Sandel, B.; Forrester, T.; Quemerais, E.; Moebius, E.; Esposito, L.; Stewart, I.; McClintock, W.; Jouchoux, A.; hide

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  13. HI 21cm emission from the sub-damped Lyman-alpha absorber at z=0.0063 towards PG1216+069

    CERN Document Server

    Chengalur, Jayaram N; Salter, C J; Kanekar, N; Momjian, E; Keeney, B A; Stocke, J T

    2015-01-01

    We present HI 21cm emission observations of the z ~ 0.00632 sub-damped Lyman-alpha absorber (sub-DLA) towards PG1216+069 made using the Arecibo Telescope and the Very Large Array (VLA). The Arecibo 21cm spectrum corresponds to an HI mass of ~ 3.2x10^7 solar masses, two orders of magnitude smaller than that of a typical spiral galaxy. This is surprising since in the local Universe the cross-section for absorption at high HI column densities is expected to be dominated by spirals. The 21cm emission detected in the VLA spectral cube has a low signal-to-noise ratio, and represents only half the total flux seen at Arecibo. Emission from three other sources is detected in the VLA observations, with only one of these sources having an optical counterpart. This group of HI sources appears to be part of complex "W", believed to lie in the background of the Virgo cluster. While several HI cloud complexes have been found in and around the Virgo cluster, it is unclear whether the ram pressure and galaxy harassment proces...

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

    Science.gov (United States)

    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.

  15. The VIMOS Ultra Deep Survey: Lyman Alpha Emission and Stellar Populations of Star-Forming Galaxies at 2

    CERN Document Server

    Hathi, Nimish P

    2016-01-01

    The extensive ground-based spectroscopy campaign from the VIMOS Ultra-Deep Survey (VUDS), and the deep multi-wavelength photometry in three very well observed extragalactic fields (ECDFS, COSMOS, VVDS), allow us to investigate physical properties of a large sample (~4000 galaxies) of spectroscopically confirmed faint (i_{AB}20A) increases from ~10% at z~2 to ~40% at z~5-6, which is consistent with previous studies that employ higher Lyman alpha EW cut. This increase in the LAE fraction could be, in part, due to a decrease in the dust content of galaxies as redshift increases. When we compare best-fit SED estimated stellar parameters for LAEs and non-LAEs, we find that E(B-V) is smaller for LAEs at all redshifts and the difference in the median E(B-V) between LAEs and non-LAEs increases as redshift increases, from 0.05 at z~2 to 0.1 at z~3.5 to 0.2 at z~5-6. For the luminosities probed here (~L*), we find that star formation rates (SFRs) and stellar masses of galaxies, with and without Lyman alpha in emission,...

  16. Hot Gas, Cold Gas and Sub-Halos in a Lyman-alpha Blob at Redshift 2.38

    CERN Document Server

    Francis, Paul J; Colbert, James W; Palunas, Povilas; Scarlata, Claudia; Teplitz, Harry; Williger, Gerard M; Woodgate, Bruce E

    2012-01-01

    We present integral field spectroscopy of a Lyman-alpha blob at redshift 2.38, with a spectral resolution three times better than previous published work. As with previous observations, the blob has a chaotic velocity structure, much of which breaks up into multiple components. Our spectroscopy shows, however, that some of these multiple components are extremely narrow: they have velocity widths of less than 100 km/s. Combining these new data with previous observations, we argue that this Lyman-alpha blob resides in a dark-matter halo of around 10^13 solar masses. At the centre of this halo are two compact red massive galaxies. They are surrounded by hot gas, probably a super-wind from merger-induced nuclear starbursts. This hot gas has shut down star formation in the non-nuclear region of these galaxies, leading to their red-and-dead colours. A filament or lump of infalling cold gas is colliding with the hot gas phase and being shocked to high temperatures, while still around 30kpc from the red galaxies. The...

  17. A cosmic web filament revealed in Lyman-alpha emission around a luminous high-redshift quasar

    CERN Document Server

    Cantalupo, Sebastiano; Prochaska, J Xavier; Hennawi, Joseph F; Madau, Piero

    2014-01-01

    Simulations of structure formation in the Universe predict that galaxies are embedded in a "cosmic web", where the majority of baryons reside as rarefied and highly ionized gas. This material has been studied for decades in absorption against background sources, but the sparseness of these inherently one-dimensional probes preclude direct constraints on the three-dimensional morphology of the underlying web. Here we report observations of a cosmic web filament in Lyman-alpha emission, discovered during a survey for cosmic gas fluorescently "illuminated" by bright quasars at z=2.3. With a projected size of approximately 460 physical kpc, the Lyman-alpha emission surrounding the radio-quiet quasar UM287 extends well beyond the virial radius of any plausible associated dark matter halo. The estimated cold gas mass of the nebula from the observed emission is at least ten times larger than what is typically found by cosmological simulations, suggesting that a population of intergalactic gas clumps with sub-kpc siz...

  18. Deep optical spectroscopy of extended Lyman alpha emission around three radio-quiet z=4.5 quasars

    CERN Document Server

    Courbin, F; Eigenbrod, A; Chelouche, D

    2008-01-01

    We report the first results of a spectroscopic search for Lyman alpha, envelopes around three z=4.5 radio-quiet quasars. Our observational strategy uses the FORS2 spectrograph attached to the UT1 of the Very Large Telescope (VLT) in the multi-slit mode. This allows us to observe simultaneously the quasars and several PSF stars. The spectra of the latter are used to remove the point-like quasar from the data, and to unveil the faint underlying Lyman alpha, envelopes associated with the quasars with unprecedented depth. We clearly detect an envelope around two of the three quasars. These envelopes measure respectively 10" and 13" in extent (i.e. 67 kpc and 87 kpc). This is 5 to 10 times larger than predicted by the models of Haiman & Rees (2001) and up to 100 times fainter. Our observations better agree with models involing a clumpy envelope as in Alam & Miralda-Escude (2002) or Chelouche et al. (2008). We find that the brighter quasars also have the brighter envelopes but that the extend of the envelop...

  19. Influence of the 6^1S_0-6^3P_1 Resonance on Continuous Lyman-alpha Generation in Mercury

    CERN Document Server

    Kolbe, Daniel; Walz, Jochen

    2012-01-01

    Continuous coherent radiation in the vacuum-ultraviolet at 122 nm (Lyman-alpha) can be generated using sum-frequency mixing of three fundamental laser beams in mercury vapour. One of the fundamental beams is at 254 nm wavelength, which is close to the 6^1S_0-6^3P_1 resonance in mercury. Experiments have been performed to investigate the effect of this one-photon resonance on phasematching, absorption and the nonlinear yield. The efficiency of continuous Lyman-alpha generation has been improved by a factor of 4.5.

  20. Verifying the mass-metallicity relation in damped Lyman-alpha selected galaxies at 0.1

    DEFF Research Database (Denmark)

    Christensen, Lise Bech; Møller, P.; Fynbo, J. P. U.

    2014-01-01

    A scaling relation has recently been suggested to combine the galaxy mass-metallicity (MZ) relation with metallicities of damped Lyman-alpha systems (DLAs) in quasar spectra. Based on this relation the stellar masses of the absorbing galaxies can be predicted. We test this prediction by measuring...

  1. Cosmological parameters from combining the Lyman-alpha forest with CMB, galaxy clustering and SN constraints

    CERN Document Server

    Seljak, U; McDonald, P; Seljak, Uros; Slosar, Anze; Donald, Patrick Mc

    2006-01-01

    We combine the Ly-alpha forest power spectrum (LYA) from the Sloan Digital Sky Survey (SDSS) and high resolution spectra with the cosmic microwave background (CMB) including 3-year WMAP, supernovae (SN) and galaxy clustering constraints to derive new constraints on cosmological parameters. The existing LYA power spectrum analysis is supplemented by constraints on the mean flux decrement derived using a principal component analysis for quasar continua, which improves the LYA constraints on the linear power. The joint analysis reduces the errors on all parameters and prefers the simplest 6 parameter cosmological model. We find some tension between the WMAP3 and LYA power spectrum amplitudes, at the ~2 sigma level, which is partially alleviated by the inclusion of other observations: we find sigma_8=0.85+-0.02 compared to sigma_8=0.80+-0.03 without LYA. For the slope we find n_s=0.965+-0.012. We find no evidence for running of the spectral index, dn/dln k=-0.020+-0.012, in agreement with inflation. The limits on...

  2. The Sherwood simulation suite: overview and data comparisons with the Lyman-alpha forest at redshifts 2 < z < 5

    CERN Document Server

    Bolton, James S; Sijacki, Debora; Haehnelt, Martin G; Kim, Tae-Sun; Meiksin, Avery; Regan, John A; Viel, Matteo

    2016-01-01

    We introduce a new set of large scale, high resolution hydrodynamical simulations of the intergalactic medium: the Sherwood simulation suite. These are performed in volumes 10^3-160^3 h^-3 comoving Mpc^{3}, span almost four orders of magnitude in mass resolution with up to 17.2 billion particles, and employ a variety of physics variations including warm dark matter and galactic outflows. We undertake a detailed comparison of the simulations to high resolution, high signal-to-noise observations of the Lyman-alpha forest over the redshift range 2 10^14.5 cm^-2 at 2 4. Finally, the temperature of intergalactic gas in the simulations may be slightly too low at z=2.7 and a flatter temperature-density relation is required at z=2.4, consistent with the expected effects of non-equilibrium ionisation during He-II reionisation.

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

    Science.gov (United States)

    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 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 time variations had more in the footpoint regions. On the other hand, the time variations had no dependency on the temperature of the loop.

  4. The average submillimetre properties of Lyman-alpha Blobs at z=3

    CERN Document Server

    Hine, N K; Matsuda, Y; Lehmer, B D; Michalowski, M J; Farrah, D; Spaans, M; Oliver, S J; Smith, D J B; Chapman, S C; Jenness, T; Alexander, D M; Robson, I; van der Werf, P

    2016-01-01

    Ly-alpha blobs (LABs) offer insight into the complex interface between galaxies and their circumgalactic medium. Whilst some LABs have been found to contain luminous star-forming galaxies and active galactic nuclei that could potentially power the Ly-alpha emission, others appear not to be associated with obvious luminous galaxy counterparts. It has been speculated that LABs may be powered by cold gas streaming on to a central galaxy, providing an opportunity to directly observe the `cold accretion' mode of galaxy growth. Star-forming galaxies in LABs could be dust obscured and therefore detectable only at longer wavelengths. We stack deep SCUBA-2 observations of the SSA22 field to determine the average 850um flux density of 34 LABs. We measure S_850 = 0.6 +/- 0.2mJy for all LABs, but stacking the LABs by size indicates that only the largest third (area > 1794 kpc^2) have a mean detection, at 4.5 sigma, with S_850 = 1.4 +/- 0.3mJy. Only two LABs (1 and 18) have individual SCUBA-2 > 3.5 sigma detections at a d...

  5. Lyman-Alpha Emitter Galaxies at z ~ 2.8 in the Extended Chandra Deep Field-South: I. Tracing the Large-Scale Structure via Lyman-Alpha Imaging

    CERN Document Server

    Zheng, Zhen-Ya; Rhoads, James E; Finkelstein, Steven L; Wang, Jun-Xian; Jiang, Chun-Yan; Cai, Zheng

    2016-01-01

    We present a narrowband survey with three adjacent filters for z=2.8--2.9 Lyman Alpha Emitter (LAE) galaxies in the Extended Chandra Deep Field South (ECDFS), along with spectroscopic followup. With a complete sample of 96 LAEs in the narrowband NB466, we confirm a large-scale structure at z~ 2.8. Compared to the blank field in NB470 and NB475, the LAE density excess in the NB466 field is ~6.0+/-0.8 times the standard deviation expected at z~2.8, assuming a linear bias of 2. The overdense large scale structure in NB466 can be decomposed into 4 protoclusters, whose overdensities are 4.6 - 6.6. These 4 protoclusters are expected to evolve into a Coma-like cluster at z~ 0. In the meanwhile, we investigate the average star-formation rates derived from Ly{\\alpha}, rest-frame UV and X-ray, the Ly{\\alpha} luminosity functions, the Ly{\\alpha} photon densities and their dependence on the environment. We find that the Ly{\\alpha} photon density in the overdense field (NB466) is ~50\\% higher than that in the blank field ...

  6. A coronagraphic absorbing cloud reveals the narrow-line region and extended Lyman-$\\alpha$ emission of QSO J0823+0529

    CERN Document Server

    Fathivavsari, Hassan; Noterdaeme, Pasquier; Pâris, Isabelle; Finley, Hayley; López, Sebastian; Srianand, Raghunathan; Sánchez, Paula

    2015-01-01

    We report long-slit spectroscopic observations of the quasar SDSS J082303.22+052907.6 ($z_{\\rm CIV}$$\\sim$3.1875), whose Broad Line Region (BLR) is partly eclipsed by a strong damped Lyman-$\\alpha$ (DLA; log$N$(HI)=21.7) cloud. This allows us to study the Narrow Line Region (NLR) of the quasar and the Lyman-$\\alpha$ emission from the host galaxy. Using CLOUDY models that explain the presence of strong NV and PV absorption together with the detection of SiII$^*$ and OI$^{**}$ absorption in the DLA, we show that the density and the distance of the cloud to the quasar are in the ranges 180 $$ $r_0$ $>$230 pc, respectively. Sizes of the neutral($\\sim$2-9pc) and highly ionized phases ($\\sim$3-80pc) are consistent with the partial coverage of the CIV broad line region by the CIV absorption from the DLA (covering factor of $\\sim$0.85). We show that the residuals are consistent with emission from the NLR with CIV/Lyman-$\\alpha$ ratios varying from 0 to 0.29 through the profile. Remarkably, we detect extended Lyman-$\\...

  7. HST/ACS Morphology of Lyman Alpha Emitters at Redshift 5.7 in the COSMOS Field

    CERN Document Server

    Taniguchi, Y; Scoville, N Z; Sasaki, S S; Nagao, T; Shioya, Y; Saitô, T; Ideue, Y; Nakajima, A; Matsuoka, K; Sanders, D B; Mobasher, B; Aussel, H; Capak, P; Salvato, M; Koekemoer, A; Carilli, C; Cimatti, A; Ellis, Richard S; Garilli, B; Giavalisco, M; Ilbert, O; Impey, C D; Kitzbichler, M G; Le Fèvre, O; McCracken, H J; Scarlata, C; Schinnerer, E; Smolcic, V; Tribiano, S; Trump, J R

    2009-01-01

    We present detailed morphological properties of Lyman alpha emitters (LAEs) at z~ 5.7 in the COSMOS field, based on {\\it Hubble Space Telescope} Advanced Camera for Surveys (ACS) data. The ACS imaging in the F814W filter covered 85 LAEs of the 119 LAEs identified in the full two square degree field, and 47 LAEs of them are detected in the ACS images. Nearly half of them are spatially extended with a size larger than 0.15 arcsec (~0.88 kpc at z=5.7) up to 0.4 arcsec (~2.5 kpc at z=5.7). The others are nearly unresolved compact objects. Two LAEs show double-component structures, indicating interaction or merging of building components to form more massive galaxies. By stacking the ACS images of all the detected sources, we obtain a Sersic parameter of n~0.7 with a half-light radius of 0.13 arcsec (0.76 kpc), suggesting that the majority of ACS detected LAEs have not spheroidal-like but disk-like or irregular light profiles. Comparing ACS F814W magnitudes (I_814) with Subaru/Suprime-Cam magnitudes in the NB816, ...

  8. The transverse proximity effect in the z ~ 2 Lyman-alpha forest suggests QSO episodic lifetimes of ~1 Myr

    CERN Document Server

    Kirkman, David

    2008-01-01

    We look for signs of the H~I transverse proximity effect in the spectra of 130 QSO pairs, most with transverse separations in the plane of the sky of 0.1 -- 3 Mpc at z ~ 2.2. We expected to see a decrease in Lyman-alpha forest HI absorption in the spectrum of background QSOs near the position of foreground QSOs. Instead we see no change in the absorption in front of the foreground QSOs, and we see evidence for a 50% increase in the absorption out to 6 Mpc behind the foreground QSOs. Further, we see no change in the H I absorption along the line-of-sight to the foreground QSOs, the normal line-of-sight proximity effect. We may account for the lack of change in the H I absorption if the effect of extra UV photons is canceled by higher gas density around QSOs. If so, the increase in absorption behind the QSOs then suggests that the higher gas density there is not canceled by the UV radiation from the QSOs. We can explain our observations if QSOs have had their current UV luminosities for less than approximately ...

  9. The HETDEX Pilot Survey V: The Physical Origin of Lyman-alpha Emitters Probed by Near-infrared Spectroscopy

    CERN Document Server

    Song, Mimi; Gebhardt, Karl; Hill, Gary J; Drory, Niv; Ashby, Matthew L N; Blanc, Guillermo A; Bridge, Joanna; Chonis, Taylor; Ciardullo, Robin; Fabricius, Maximilian; Fazio, Giovanni G; Gawiser, Eric; Gronwall, Caryl; Hagen, Alex; Huang, Jia-Sheng; Jogee, Shardha; Livermore, Rachael; Salmon, Brett; Schneider, Donald P; Willner, S P; Zeimann, Gregory R

    2014-01-01

    We present the results from a VLT/SINFONI and Keck/NIRSPEC near-infrared spectroscopic survey of 16 Lyman-alpha emitters (LAEs) at $z$ = 2.1 - 2.5 in the COSMOS and GOODS-N fields discovered from the HETDEX Pilot Survey. We detect rest-frame optical nebular lines (H$\\alpha$ and/or [OIII]$\\lambda$5007) for 10 of the LAEs and measure physical properties, including the star formation rate (SFR), gas-phase metallicity, gas-mass fraction, and Ly$\\alpha$ velocity offset. We find that LAEs may lie below the mass-metallicity relation for continuum-selected star-forming galaxies at the same redshift. The LAEs all show velocity shifts of Ly$\\alpha$ relative to the systemic redshift ranging between +85 and +296 km s$^{-1}$ with a mean of +180 km s$^{-1}$. This value is smaller than measured for continuum-selected star-forming galaxies at similar redshifts. The Ly$\\alpha$ velocity offsets show a moderate correlation with the measured star formation rate (2.5$\\sigma$), but no significant correlations are seen with the SFR...

  10. The Impact of Different Physical Processes on the Statistics of Lyman-limit and Damped Lyman-alpha Absorbers

    CERN Document Server

    Altay, Gabriel; Schaye, Joop; Booth, C M; Vecchia, Claudio Dalla

    2013-01-01

    We compute the z = 3 neutral hydrogen column density distribution function f(NHI) for 19 simulations drawn from the OWLS project using a post-processing correction for self-shielding calculated with full radiative transfer of the ionising background radiation. We investigate how different physical processes and parameters affect the abundance of Lyman-limit systems (LLSs) and damped Lyman-alpha absorbers (DLAs) including: i) metal-line cooling; ii) the efficiency of feedback from SNe and AGN; iii) the effective equation of state for the ISM; iv) cosmological parameters; v) the assumed star formation law and; vi) the timing of hydrogen reionization . We find that the normalisation and slope, D = d log10 f /d log10 NHI, of f(NHI) in the LLS regime are robust to changes in these physical processes. Among physically plausible models, f(NHI) varies by less than 0.2 dex and D varies by less than 0.18 for LLSs. This is primarily due to the fact that these uncertain physical processes mostly affect star-forming gas w...

  11. High-ion absorption in the proximate damped Lyman-alpha system toward Q0841+129

    CERN Document Server

    Fox, Andrew J; Petitjean, Patrick; Srianand, Raghunathan; Guimarães, Rodney

    2011-01-01

    We present VLT/UVES spectroscopy of the quasar Q0841+129, whose spectrum shows a proximate damped Lyman-alpha (PDLA) absorber at z=2.47621 and a proximate sub-DLA at z=2.50620, both lying close in redshift to the QSO itself at z_em=2.49510+/-0.00003. This fortuitous arrangement, with the sub-DLA acting as a filter that hardens the QSO's ionizing radiation field, allows us to model the ionization level in the foreground PDLA, and provides an interesting case-study on the origin of the high-ion absorption lines Si IV, C IV, and O VI in DLAs. The high ions in the PDLA show at least five components spanning a total velocity extent of ~160 km/s, whereas the low ions exist predominantly in a single component spanning just 30 km/s. We examine various models for the origin of the high ions. Both photoionization and turbulent mixing layer models are fairly successful at reproducing the observed ionic ratios after correcting for the non-solar relative abundance pattern, though neither model can explain all five compone...

  12. Detection of Diffuse Interstellar Bands in the z=0.5 Damped Lyman alpha system towards AO 0235+164

    CERN Document Server

    York, B A; Lawton, B; Churchill, C W; Snow, T P; Johnson, R A; Ryan, S G; York, Brian A.; Ellison, Sara L.; Lawton, Brandon; Churchill, Christopher W.; Snow, Theodore P.; Johnson, Rachel A.; Ryan, Sean G.

    2006-01-01

    We report the first detection of the 5705 and 5780 A Diffuse Interstellar Bands (DIBs) in a moderate redshift Damped Lyman alpha (DLA) system. We measure a rest frame equivalent width of 63.2 +- 8.7 mA for the 5705 and 216+-9 mA for the 5780 A feature in the z_abs 0.524 DLA towards AO 0235+164 and derive limits for the equivalent widths of the bands at 5797, 6284, and 6613 A. The equivalent width of the 5780 band is lower than would be expected based on the Galactic correlation of DIB strength with N(HI), but is in good agreement with the correlation with E(B-V). The relative strengths of the 5780 and 6284 A DIBs are inconsistent with all Galactic and extragalactic sightlines, except one Small Magellanic Cloud wing sightline towards Sk 143. However, the relative strengths of the 5705 and 5780 A DIBs are consistent with the Galactic relation, indicating that the relative strengths of these bands may be less sensitive to environment or that they may be associated with a similar carrier. The detection of DIBs at...

  13. Continuum subtracting Lyman-alpha images: Low redshift studies using the Solar Blind Channel of HST/ACS

    CERN Document Server

    Hayes, Matthew; Mas-Hesse, J Miguel; Kunth, Daniel

    2008-01-01

    (Abridged) We are undertaking an imaging study of local star-forming galaxies in the Lyman-alpha (Lya) emission line using the Solar Blind Channel (SBC) of the ACS onboard HST. Observations have been obtained in Lya and H-alpha and six line-free continuum filters between ~1500 AA and the I-band. In a previous article Hayes et al. (2005) we demonstrated that the production of Lya line-only images (i.e. continuum subtraction) in the SBC-only data-set is non-trivial and that supporting data is a requirement. We here develop various methods of continuum subtraction and assess their relative performance for given input spectral energy distributions (SED). We show that simple assumptions about the behavior of the UV continuum consistently lead to results that are significantly in error, and determine that a spectral fitting approach is essential. Furthermore, fitting of a single component stellar or stellar+nebular spectrum is not always sufficient for realistic template SEDs and, in order to successfully recover t...

  14. On the selection of damped Lyman alpha systems using MgII absorption at 2

    CERN Document Server

    Berg, T A M; Prochaska, J X; Sanchez-Ramirez, R; Lopez, S; D'Odorico, V; Becker, G; Christensen, L; Cupani, G; Denney, K; Worseck, G

    2016-01-01

    The XQ-100 survey provides optical and near infrared coverage of 36 blindly selected, intervening damped Lyman alpha systems (DLAs) at 2 < z < 4, simultaneously covering the MgII doublet at 2796A, 2803A, and the Ly-alpha transition. Using the XQ-100 DLA sample, we investigate the completeness of selecting DLA absorbers based on their MgII rest-frame equivalent width (W2796) at these redshifts. Of the 29 DLAs with clean MgII profiles, we find that six (20% of DLAs) have W2796 < 0.6A. The DLA incidence rate of W2796 < 0.6A absorbers is a factor of ~5 higher than what is seen in z~1 samples, indicating a potential evolution in the MgII properties of DLAs with redshift. All of the W2796 < 0.6A DLAs have low metallicities (-2.5 < [M/H] < -1.7), small velocity widths (v90 < 50 km/s), and tend to have relatively low N(HI). We demonstrate that the exclusion of these low W2796 DLAs results in a higher mean N(HI) which in turn leads to a ~7% increase in the cosmological gas density of HI of DLAs...

  15. Optical alignment of the Chromospheric Lyman-Alpha Spectro-Polarimeter using sophisticated methods to minimize activities under vacuum

    Science.gov (United States)

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

    2016-07-01

    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 instrument main scientific goal is to achieve polarization measurement of the Lyman-α line at 121.56 nm emitted from the solar upper-chromosphere and transition region with an unprecedented 0.1% accuracy. 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-α profiles. A precise alignment of the optics is required to ensure the resolutions, but experiments under vacuum conditions are needed since Ly-α 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 explain these methods and present the results for the optical alignment of the CLASP telescope and spectrograph. We 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.

  16. Determination of Coronal Mass Ejection physical parameters from combination of polarized visible light and UV Lyman-$\\alpha$ observations

    CERN Document Server

    Susino, R

    2016-01-01

    Visible-light observations of Coronal Mass Ejections (CMEs) performed with coronagraphs and heliospheric imagers (in primis on board the SOHO and STEREO missions) have offered so far the best way to study the kinematics and geometrical structure of these fundamental events. Nevertheless, it has been widely demonstrated that only combination of multi-wavelength data (including X-ray spectra, EUV images, EUV-UV spectra, and radio dynamic spectra) can provide complete information on the plasma temperature and density distributions, non-thermal motions, magnetic fields, and other physical parameters, for both CMEs and CME-related phenomena. In this work, we analyze three CMEs by combining simultaneous data acquired in the polarized visible light by the LASCO-C2 coronagraph and in the UV H I Lyman-$\\alpha$ line (1216 \\AA) by the UVCS spectrometer, in order to estimate the CME plasma electron density (using the polarization-ratio technique to infer the 3D structure of the CME) and temperature (from the comparison b...

  17. HST Emission Line Galaxies at z ~ 2: Comparing Physical Properties of Lyman Alpha and Optical Emission Line Selected Galaxies

    CERN Document Server

    Hagen, Alex; Behrens, Christoph; Ciardullo, Robin; Gebhardt, Henry S Grasshorn; Gronwall, Caryl; Bridge, Joanna S; Fox, Derek B; Schneider, Donald P; Trump, Jonathan R; Blanc, Guillermo A; Chiang, Yi-Kuan; Chonis, Taylor S; Finkelstein, Steven L; Hill, Gary J; Jogee, Shardha; Gawiser, Eric

    2015-01-01

    We compare the physical and morphological properties of z ~ 2 Lyman-alpha emitting galaxies (LAEs) identified in the HETDEX Pilot Survey and narrow band studies with those of z ~ 2 optical emission line galaxies (oELGs) identified via HST WFC3 infrared grism spectroscopy. Both sets of galaxies extend over the same range in stellar mass (7.5 < logM < 10.5), size (0.5 < R < 3.0 kpc), and star-formation rate (~1 < SFR < 100). Remarkably, a comparison of the most commonly used physical and morphological parameters -- stellar mass, half-light radius, UV slope, star formation rate, ellipticity, nearest neighbor distance, star formation surface density, specific star formation rate, [O III] luminosity, and [O III] equivalent width -- reveals no statistically significant differences between the populations. This suggests that the processes and conditions which regulate the escape of Ly-alpha from a z ~ 2 star-forming galaxy do not depend on these quantities. In particular, the lack of dependence on ...

  18. The most metal-poor damped Lyman alpha systems: An insight into dwarf galaxies at high redshift

    CERN Document Server

    Cooke, Ryan; Jorgenson, Regina A

    2014-01-01

    In this paper, we analyze the kinematics, chemistry, and physical properties of a sample of the most metal-poor damped Lyman alpha systems (DLAs), to uncover their links to modern-day galaxies. We present evidence that the DLA population as a whole exhibits a `knee' in the relative abundances of the alpha-capture and Fe-peak elements when the metallicity is [Fe/H] ~ -2.0. In this respect, the chemical evolution of DLAs is clearly different from that experienced by Milky Way halo stars, but resembles that of dwarf spheroidal galaxies in the Local Group. We also find a close correspondence between the kinematics of Local Group dwarf galaxies and of high redshift metal-poor DLAs, which further strengthens this connection. On the basis of such similarities, we propose that the most metal-poor DLAs provide us with a unique opportunity to directly study the dwarf galaxy population more than ten billion years in the past, at a time when many dwarf galaxies were forming the bulk of their stars. To this end, we have m...

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

    Science.gov (United States)

    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).

  20. 9.7 micrometer Silicate Absorption in a Damped Lyman-alpha Absorber at z=0.52

    CERN Document Server

    Kulkarni, Varsha P; Vladilo, Giovanni; Welty, Daniel E

    2007-01-01

    We report a detection of the 9.7 micrometer silicate absorption feature in a damped Lyman-alpha (DLA) system at z_{abs} = 0.524 toward AO0235+164, using the Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope. The feature shows a broad shallow profile over about 8-12 micrometers in the absorber rest frame and appears to be > 15 sigma significant in equivalent width. The feature is fit reasonably well by the silicate absorption profiles for laboratory amorphous olivine or diffuse Galactic interstellar clouds. To our knowledge, this is the first indication of 9.7 micrometer silicate absorption in a DLA. We discuss potential implications of this finding for the nature of the dust in quasar absorbers. Although the feature is relatively shallow (tau_{9.7} = 0.08-0.09), it is about 2 times deeper than expected from extrapolation of the tau_{9.7} vs. E(B-V) relation known for diffuse Galactic interstellar clouds. Further studies of the 9.7 micrometer silicate feature in quasar absorbers will open a new w...

  1. Characterizing the \\lyaf\\ flux probability distribution function using Legendre polynomials

    CERN Document Server

    Cieplak, Agnieszka M

    2016-01-01

    The Lyman-$\\alpha$ forest is a highly non-linear field with a lot of information available in the data beyond the power spectrum. The flux probability distribution function (PDF) has been used as a successful probe of small-scale physics. In this paper we argue that measuring coefficients of the Legendre polyonomial expansion of the PDF offers several advantages over measuring the binned values as is commonly done. In particular, $n$-th coefficient can be expressed as a linear combination of the first $n$ moments, allowing these coefficients to be measured in the presence of noise and allowing a clear route for marginalisation over mean flux. Moreover, in the presence of noise, our numerical work shows that a finite number of coefficients are well measured with very sharp transition into noise dominance. This compresses the available information into a small number of well-measured quantities.

  2. Modeling Lyman-\\alpha\\ Forest Cross-Correlations with LyMAS

    CERN Document Server

    Lochhaas, Cassandra; Peirani, Sébastien; Dubois, Yohan; Colombi, Stéphane; Blaizot, Jérémy; Font-Ribera, Andreu; Pichon, Christophe; Devriendt, Julien

    2015-01-01

    We use the Ly-$\\alpha$ Mass Association Scheme (LyMAS; Peirani et al. 2014) to predict cross-correlations at z = 2.5 between dark matter halos and transmitted flux in the Ly-$\\alpha$ forest, and we compare these predictions to cross-correlations measured for quasars and damped Ly-$\\alpha$ systems (DLAs) from the Baryon Oscillation Spectroscopic Survey (BOSS) by Font-Ribera et al. (2012, 2013). We calibrate and test LyMAS using Horizon-AGN hydrodynamical cosmological simulations of a $(100\\ h^{-1}\\ \\rm{Mpc})^3$ comoving volume with and without AGN feedback. We apply this calibration to a $(1\\ h^{-1}\\ \\rm{Gpc})^3$ simulation realized with $2048^3$ dark matter particles for our primary predictions. In the $100\\ h^{-1}\\ \\rm{Mpc}$ box, LyMAS reproduces the halo-flux correlations computed from the full hydrodynamic gas distribution essentially perfectly. In the $1\\ h^{-1}\\ \\rm{Gpc}$ box, the amplitude of the cross-correlation tracks the halo bias as expected, and the correlation for a halo sample with a distributio...

  3. The Signatures of Large-scale Temperature Fluctuations in the Lyman-alpha Forest

    CERN Document Server

    McQuinn, Matthew; Lidz, Adam; Zaldarriaga, Matias

    2010-01-01

    It appears inevitable that reionization processes would have produced large-scale temperature fluctuations in the intergalactic medium. Using toy temperature models and detailed heating histories in cosmological simulations of HeII reionization, we study the consequences of inhomogeneous heating for the Ly-alpha forest. The impact of temperature fluctuations in physically well-motivated models can be surprisingly subtle. In fact, we show that temperature fluctuations at the level predicted by our reionization simulations do not give rise to detectable signatures in the types of statistics that have been employed previously. However, because of the aliasing of small-scale density power to larger scale modes in the line-of-sight Ly-alpha forest power spectrum, earlier analyses were not sensitive to 3D modes with >~ 30 comoving Mpc wavelengths -- scales where temperature fluctuations are likely to be relatively largest. The ongoing Baryon Oscillation Spectroscopic Survey (BOSS) aims to measure the 3D power spect...

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

    Science.gov (United States)

    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.

  5. Damped and sub-damped Lyman-alpha absorbers in z > 4 QSOs

    CERN Document Server

    Guimaraes, Rodney; De Carvalho, Reinaldo Ramos; Djorgovski, George; Noterdaeme, Pasquier; Castro, Sandra; Poppe, Paulo Da Rocha; Aghaee, Ali

    2009-01-01

    We present the results of a survey for damped (DLA, log N(H I) > 20.3) and sub-damped Lyman-? systems (19.5 2.55 along the lines-of-sight to 77 quasars with emission redshifts in the range 4 19.5 are detected of which 40 systems are damped Lyman-? systems for an absorption length of ?X = 378. About half of the lines of sight of this homogeneous survey have never been investigated for DLAs. We study the evolution with redshift of the cosmological density of the neutral gas and ?nd, consis- tently with previous studies at similar resolution, that ?DLA,H I decreases at z > 3.5. The overall cosmological evolution of ?HI shows a peak around this redshift. The H I column density distribution for log N(H I) ? 20.3 is ?tted, consistently with previous surveys, with a single power-law of index ? ? -1.8$\\pm$0.25. This power-law overpredicts data at the high-end and a second, much steeper, power-law (or a gamma function) is needed. There is a ?attening of the function at lower H I column densities with an index of ? ?...

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

    Science.gov (United States)

    Maloney, Philip

    1993-01-01

    Recent observations using the Hubble Space Telescope of the z = 0.156 QSO 3C 273 have discovered a surprisingly large number of Ly-alpha absorption lines. In particular, Morris et al. found 9 certain and 7 possible Ly-alpha lines with equivalent widths above 25 mA. This is much larger (by a factor of 5-10) than the number expected from extrapolation of the high-redshift behavior of the Ly-alpha forest. Within the context of pressure-confined models for the Ly-alpha clouds, this behavior can be understood if the ionizing background declines sharply between z is approximately 2 and z is approximately 0. However, this requires that the ionizing photon flux drop as rapidly as the QSO volume emissivity; moreover, the absorbers must have a space density n(sub O) is approximately 2.6(N/10)h/((D/100 kpc)(sup 2)) Mpc(sup -3) where D is the present-day diameter of the absorbers. It is somewhat surprising that such necessarily fragile objects could have survived in such numbers to the present day. It is shown that it is plausible that the atomic hydrogen extents of spiral and irregular galaxies are large enough to produce the observed number of Ly-alpha absorption lines toward 3C 273, and that the neutral column densities and doppler b-values expected under these conditions fall in the range found by Morris et al. (1991).

  7. The nature of z ~ 2.3 Lyman-alpha emitters

    CERN Document Server

    Nilsson, Kim K; Møller, Palle; Möller-Nilsson, Ole; Tapken, Christian; Freudling, Wolfram; Fynbo, Johan P U

    2010-01-01

    We study the multi-wavelength properties of a set of 171 Ly-alpha emitting candidates at redshift z = 2.25 found in the COSMOS field. The candidates are shown to have different properties from those of Ly-alpha emitters found at higher redshift, by fitting the spectral energy distributions (SEDs) using a Monte-Carlo Markov-Chain technique and including nebular emission in the spectra. The dust contents and stellar masses are both higher, with A_V = 0.0 - 2.0 mag and stellar masses in the range log M_* = 9.0 - 11.0 M_sun. Young population ages are well constrained, but older population ages are typically unconstrained. In 40 % of the galaxies only a single, young population of stars is observed. We show that the ages and Ly-alpha fluxes of the best fit galaxies are correlated with their dust properties, with higher dust extinction in younger galaxies. We conclude that the stellar properties of Ly-alpha emitters at z = 2.25 are different from those at higher redshift and that they are very diverse. Ly-alpha sel...

  8. Properties of High-Redshift Lyman Alpha Clouds II. Statistical Properties of the Clouds

    CERN Document Server

    Press, W H; Press, William H.; Rybicki, George B.

    1993-01-01

    Curve of growth analysis, applied to the Lyman series absorption ratios deduced in our previous paper, yields a measurement of the logarithmic slope of distribution of \\Lya\\ clouds in column density $N$. The observed exponential distribution of the clouds' equivalent widths $W$ is then shown to require a broad distribution of velocity parameters $b$, extending up to 80 km s$^{-1}$. We show how the exponential itself emerges in a natural way. An absolute normalization for the differential distribution of cloud numbers in $z$, $N$, and $b$ is obtained. By detailed analysis of absorption fluctuations along the line of sight we are able to put upper limits on the cloud-cloud correlation function $\\xi$ on several megaparsec length scales. We show that observed $b$ values, if thermal, are incompatible, in several different ways, with the hypothesis of equilibrium heating and ionization by a background UV flux. Either a significant component of $b$ is due to bulk motion (which we argue against on several grounds), o...

  9. The Composite Spectrum of BOSS Quasars Selected for Studies of the Lyman-alpha Forest

    CERN Document Server

    Harris, David W; Suzuki, Nao; Bautista, Julian E; Dawson, Kyle S; Vivek, M; Brownstein, Joel R; Ge, Jian; Hamann, Fred; Herbst, H; Jiang, Linhua; Moran, Sarah E; Myers, Adam D; Olmstead, Matthew D; Schneider, Donald P

    2016-01-01

    The Baryon Oscillation Spectroscopic Survey (BOSS) has collected more than 150,000 $2.1 \\leq z \\leq 3.5$ quasar spectra since 2009. Using this unprecedented sample, we create a composite spectrum in the rest-frame of 102,150 quasar spectra from 800 \\AA\\ to 3300 \\AA\\ at a signal-to-noise ratio close to 1000 per pixel ($\\Delta v$ of 69 km~s$^{-1}$). Included in this analysis is a correction to account for flux calibration residuals in the BOSS spectrophotometry. We determine the spectral index as a function of redshift of the full sample, warp the composite spectrum to match the median spectral index, and compare the resulting spectrum to SDSS photometry used in target selection. The quasar composite matches the color of the quasar population to within 0.02 magnitudes in $g-r$, 0.03 magnitudes in $r-i$, and 0.01 magnitudes in $i-z$ over the redshift range $2.2

  10. Ionizing radiation fluctuations and large-scale structure in the Lyman-alpha forest

    CERN Document Server

    Croft, R A C

    2003-01-01

    We investigate the large-scale inhomogeneities of the hydrogen ionizing radiation field in the Universe at redshift z=3. Using a raytracing algorithm, we simulate a model in which quasars are the dominant sources of radiation. We make use of large scale N-body simulations of a LambdaCDM universe, and include such effects as finite quasar lifetimes and output on the lightcone, which affects the shape of quasar light echoes. We create Lya forest spectra that would be generated in the presence of such a fluctuating radiation field, finding that the power spectrum of the Lya forest can be suppressed by as much as 15 % for modes with k=0.05-1 Mpc/h. This relatively small effect may have consequences for high precision measurements of the Lya power spectrum on larger scales than have yet been published. We also investigate another radiation field probe, the cross-correlation of quasar positions and the Lya forest. For both quasar lifetimes which we simulate (10^7 yr and 10^8 yr), we expect to see a strong decrease ...

  11. Calibrating cosmological radiative transfer simulations with Lyman alpha forest data: Evidence for large spatial UV background fluctuations at z ~ 5.6 - 5.8 due to rare bright sources

    CERN Document Server

    Chardin, Jonathan; Aubert, Dominique; Puchwein, Ewald

    2015-01-01

    We calibrate here cosmological radiative transfer simulation with ATON/RAMSES with a range of measurements of the Lyman alpha opacity from QSO absorption spectra. We find the Lyman alpha opacity to be very sensitive to the exact timing of hydrogen reionisation. Models reproducing the measured evolution of the mean photoionisation rate and average mean free path reach overlap at z ~ 7 and predict an accelerated evolution of the Lyman alpha opacity at z > 6 consistent with the rapidly evolving luminosity function of Lyman alpha emitters in this redshift range. Similar to "optically thin" simulations our full radiative transfer simulations fail, however, to reproduce the high-opacity tail of the Lyman alpha opacity PDF at z > 5. We argue that this is due to spatial UV fluctuations in the post-overlap phase of reionisation on substantially larger scales than predicted by our source model, where the ionising emissivity is dominated by large numbers of sub-L* galaxies. We further argue that this suggests a signific...

  12. Evolution in the properties of Lyman-alpha emitters from redshifts z ~ 3 to z ~ 2

    CERN Document Server

    Nilsson, Kim K; Moeller, Palle; Freudling, Wolfram; Fynbo, Johan P U; Meisenheimer, Klaus; Laursen, Peter; Oestlin, Goeran

    2008-01-01

    Context: Narrow-band surveys for Ly-alpha emitters (LAEs) is a powerful tool in detecting high, and very high, redshift galaxies. Even though samples are growing at redshifts z = 3 - 6, the nature of these galaxies is still poorly known. Aims: To study the properties of z = 2.25 LAEs and compare those with the properties of z > 3 LAEs. Methods: We present narrow-band imaging made with the MPG/ESO 2.2m telescope with the WFI detector. We have made a selection for emission-line objects and find 170 candidate typical LAEs and 17 candidates which we regard as high UV-transmission LAEs. We have derived the magnitudes of these objects in 8 bands from u* to Ks, and studied if they have X-ray and/or radio counterparts. Results: We show that there has been significant evolution in the properties of LAEs between redshift z ~ 3 and z = 2.25. The spread in spectral energy distributions (SEDs) at the lower redshift is larger and we detect a significant AGN contribution in the sample. The distribution of the equivalent wid...

  13. The clustering of Lyman alpha emitters at z=7: implications for reionization and host halo masses

    CERN Document Server

    Sobacchi, Emanuele

    2015-01-01

    The Ly$\\alpha$ line of high-redshift galaxies has emerged as a powerful probe of both early galaxy evolution and the epoch of reionization (EoR). Motivated by the upcoming wide-field survey with the Subaru Hyper Supreme-Cam (HSC), we study the angular correlation function (ACF) of narrow-band selected, $z\\approx7$ LAEs. The clustering of LAEs is determined by both: (i) their typical host halo masses, $\\bar{M}_{\\rm h}$; (ii) the absorption due to a patchy EoR, characterized by an average neutral fraction of the IGM, $\\bar{x}_{\\rm HI}$. We bracket the allowed LAE ACF by exploring extreme scenarios for both the intrinsic Ly$\\alpha$ emission and the morphology of cosmic ionized patches in physical EoR models. Current LAE ACF measurements imply that the Universe is mostly ionized at $z\\approx7$, with $\\bar{x}_{\\rm HI}\\lesssim0.5$ (1-$\\sigma$) even for an extremely conservative model of intrinsic emission. The upcoming Ultra Deep campaign with the HSC could improve on these constraints by tens of percent, or $\\bar{...

  14. Lyman Alpha and MgII as Probes of Galaxies and their Environments

    CERN Document Server

    Barnes, Luke A; Kacprzak, Glenn G

    2014-01-01

    Ly{\\alpha} emission, Ly{\\alpha} absorption and MgII absorption are powerful tracers of neutral hydrogen. Hydrogen is the most abundant element in the universe and plays a central role in galaxy formation via gas accretion and outflows, as well as being the precursor to molecular clouds, the sites of star formation. Since 21cm emission from neutral hydrogen can only be directly observed in the local universe, we rely on Ly{\\alpha} emission, and Ly{\\alpha} and MgII absorption to probe the physics that drives galaxy evolution at higher redshifts. Furthermore, these tracers are sensitive to a range of hydrogen densities that cover the interstellar medium, the circumgalactic medium and the intergalactic medium, providing an invaluable means of studying gas physics in regimes where it is poorly understood. At high redshift, Ly{\\alpha} emission line searches have discovered thousands of star-forming galaxies out to z = 7. The large Ly{\\alpha} scattering cross-section makes observations of this line sensitive to even...

  15. Lyman-{\\alpha} Forest and Cosmic Weak Lensing in a Warm Dark Matter Universe

    CERN Document Server

    Markovič, Katarina

    2013-01-01

    We review the current state of the theory of large scale structure in a warm dark matter (WDM) cosmological model. In particular, we focus on the non-linear modelling of the matter power spectrum and on the mass function of dark matter haloes. We describe the results of N-body simulations with WDM and mention the effects that could be induced by baryonic physics. We also examine the halo model of large scale structure and its recently suggested modifications for a WDM cosmology, which account for the small scale smoothness of the initial matter density field and better fit the results of N-body simulations. Having described the theoretical models, we discuss the current lower limits on the WDM particle mass, m_w, which correspond to upper limits on the WDM temperature under the assumption that the particles are thermal relics. The best such constraints come from the Ly{\\alpha} forest and exclude all masses below 3.3 keV at the 2{\\sigma} confidence level. We finally review the forecasts for future lensing surv...

  16. Optical to mid-IR observations of Lyman-alpha galaxies at redshift 5 in the HUDF: a young and low mass population

    CERN Document Server

    Pirzkal, N; Rhoads, J E; Xu, C; Pirzkal, Norbert; Malhotra, Sangeeta; Rhoads, James E.; Xu, Chun

    2006-01-01

    High redshift galaxies selected on the basis of their strong Lyman-alpha emission tend to be young in age and small in mass and size. We show this by analyzing spectral Energy distribution of nine Lyman-alpha emitting (LAE) galaxies at redshifts from 4.1 to 5.7 in the Hubble Ultra Deep Field (HUDF). Restframe UV to optical (700 to 7500 Angstrom) luminosities (or upper limits) are used to constrain old stellar populations. We derive best fit, as well as maximally massive and maximally old, properties of all nine objects. We show that these objects are all very young, being most likely only a few millions years old, and not massive, the mass in stars being 1e6 to 1e8 solar masses. Deep Spitzer Infrared Array Camera (IRAC) observations of these objects, even in cases where objects were not detected, were crucial in constraining the masses of these objects. The space density of these objects, about 1.25e-4 per comoving cubic Mpc, is comparable to previously reported space density of LAEs at moderate to high redsh...

  17. Large scale opacity fluctuations in the Lyman alpha forest: evidence for QSOs dominating the ionising UV background at z ~ 5.5-6 ?

    CERN Document Server

    Chardin, Jonathan; Haehnelt, Martin G

    2016-01-01

    Lyman-alpha forest data probing the post-reionization Universe shows surprisingly large opacity fluctuations over rather large ($\\ge$50 comoving Mpc/h) spatial scales. We model these fluctuations using a hybrid approach utilizing the large volume Millennium simulation to predict the spatial distribution of QSOs combined with smaller scale full hydrodynamical simulation performed with RAMSES and post-processed with the radiative transfer code ATON. We produce realictic mock absorption spectra that account for the contribution of galaxies and QSOs to the ionising UV background. This improved models confirm our earlier findings that a significant ($\\ge$50%) contribution of ionising photons from QSOs can explain the large reported opacity fluctuations on large scales. The inferred QSO luminosity function is thereby consistent with recent estimates of the space density of QSOs at this redshift. Our simulations still somewhat struggle, however, to reproduce the very long (110 comoving Mpc/h) high opacity absorption...

  18. The lack of intense Lyman~alpha in ultradeep spectra of z=7 candidates in GOODS-S: imprint of reionization?

    CERN Document Server

    Fontana, A; Pentericci, L; Castellano, M; Giavalisco, M; Grazian, A; Boutsia, K; Cristiani, S; Dickinson, M; Giallongo, E; Maiolino, M; Moorwood, A; Santini, P

    2010-01-01

    We present ultradeep optical spectroscopy obtained with FORS2 on VLT of seven Lyman-break galaxy (LBG) candidates at z>6.5 selected in the GOODS-S field from Hawk-I/VLT and WFC3/HST imaging. For one galaxy we detect a low significance emission line (S/N10 is ~ 2%, and that of observing only one galaxy out of seven with S/N=5 is ~4%, but these can be as small as ~1E-3, depending on the details of the EW distribution. We conclude that either a significant fraction of the candidates is not at high redshift or that some physical mechanism quenches the Lyman alpha emission emerging from the galaxies at z>6.5, abruptly reversing the trend of the increasing fraction of strong emitters with increasing redshift observed up to z~ 6.5. We discuss the possibility that an increasingly neutral intergalactic medium is responsible for such quenching.

  19. 47 CFR 25.208 - Power flux density limits.

    Science.gov (United States)

    2010-10-01

    ... Region 2, the single-entry equivalent power-flux density, in the space-to-Earth direction, (EPFDdown), at... in Region 1 and 12.2-12.7 GHz in Region 2, the aggregate equivalent power-flux density, in the space... power flux density levels defined below. (1) In the region of the contiguous United States,...

  20. The ESO UVES Advanced Data Products Quasar Sample - VI. Sub-Damped Lyman-$\\alpha$ Metallicity Measurements and the Circum-Galactic Medium

    CERN Document Server

    Quiret, S; Zafar, T; Kulkarni, V P; Jenkins, E D; Milliard, B; Rahmani, H; Popping, A; Sandhya, R M; Turnshek, D A; Monier, E M

    2016-01-01

    The Circum-Galactic Medium (CGM) can be probed through the analysis of absorbing systems in the line-of-sight to bright background quasars. We present measurements of the metallicity of a new sample of 15 sub-damped Lyman-$\\alpha$ absorbers (sub-DLAs, defined as absorbers with 19.0 < log N(H I) < 20.3) with redshift 0.584 < $\\rm z_{abs}$ < 3.104 from the ESO Ultra-Violet Echelle Spectrograph (UVES) Advanced Data Products Quasar Sample (EUADP). We combine these results with other measurements from the literature to produce a compilation of metallicity measurements for 92 sub-DLAs as well as a sample of 362 DLAs. We apply a multi-element analysis to quantify the amount of dust in these two classes of systems. We find that either the element depletion patterns in these systems differ from the Galactic depletion patterns or they have a different nucleosynthetic history than our own Galaxy. We propose a new method to derive the velocity width of absorption profiles, using the modeled Voigt profile feat...

  1. Hubble Space Telescope Observations of Sub-Damped Lyman-alpha Absorbers at z < 0.5, and Implications for Galaxy Chemical Evolution

    CERN Document Server

    Som, Debopam; Meiring, Joseph; York, Donald G; Péroux, Celine; Lauroesch, James T; Aller, Monique C; Khare, Pushpa

    2015-01-01

    We report observations of four sub-damped Lyman-alpha (sub-DLA) quasar absorbers at z<0.5 obtained with the Hubble Space Telescope Cosmic Origins Spectrograph. We measure the available neutrals or ions of C, N, O, Si, P, S, Ar, Mn, Fe, and/or Ni. Our data have doubled the sub-DLA metallicity samples at z<0.5 and improved constraints on sub-DLA chemical evolution. All four of our sub-DLAs are consistent with near-solar or super-solar metallicities and relatively modest ionization corrections; observations of more lines and detailed modeling will help to verify this. Combining our data with measurements from the literature, we confirm previous suggestions that the N(HI)-weighted mean metallicity of sub-DLAs exceeds that of DLAs at all redshifts studied, even after making ionization corrections for sub-DLAs. The absorber toward PHL 1598 shows significant dust depletion. The absorbers toward PHL 1226 and PKS 0439-433 show the S/P ratio consistent with solar, i.e., they lack a profound odd-even effect. The a...

  2. Dust-depletion sequences in damped Lyman-{\\alpha} absorbers: a unified picture from low-metallicity systems to the Galaxy

    CERN Document Server

    De Cia, Annalisa; Mattsson, Lars; Petitjean, Patrick; Srianand, Raghunathan; Gavignaud, Isabelle; Jenkins, Edward B

    2016-01-01

    We study metal depletion due to dust in the interstellar medium (ISM) to infer the properties of dust grains and characterize the metal and dust content of galaxies, down to low metallicity and intermediate redshift z. We provide metal column densities and abundances of a sample of 70 damped Lyman-{\\alpha} absorbers (DLAs) towards quasars, observed at high spectral resolution with the Very Large Telescope (VLT) Ultraviolet and Visual Echelle Spectrograph (UVES). This is the largest sample of phosphorus abundances measured in DLAs so far. We use literature measurements for Galactic clouds to cover the high-metallicity end. We discover tight (scatter <= 0.2 dex) correlations between [Zn/Fe] and the observed relative abundances, which are due to dust depletion. This implies that grain-growth in the ISM is an important process of dust production. These sequences are continuous in [Zn/Fe] from dust-free to dusty DLAs, and to Galactic clouds, suggesting that the availability of refractory metals in the ISM is cr...

  3. Metallicities, dust and molecular content of a QSO-Damped Lyman-{\\alpha} system reaching log N (H i) = 22: An analog to GRB-DLAs

    CERN Document Server

    Guimarães, R; Petitjean, P; Ledoux, C; Srianand, R; Lopez, S; Rahmani, H

    2012-01-01

    We present the elemental abundance and H2 content measurements of a Damped Lyman-{\\alpha} (DLA) system with an extremely large H i column density, log N(H i) (cm-2) = 22.0+/-0.10, at zabs = 3.287 towards the QSO SDSS J 081634+144612. We measure column densities of H2, C i, C i^*, Zn ii, Fe ii, Cr ii, Ni ii and Si ii from a high signal-to-noise and high spectral resolution VLT-UVES spectrum. The overall metallicity of the system is [Zn/H] = -1.10 +/- 0.10 relative to solar. Two molecular hydrogen absorption components are seen at z = 3.28667 and 3.28742 (a velocity separation of \\approx 52 km s-1) in rotational levels up to J = 3. We derive a total H2 column density of log N(H2) (cm-2) = 18.66 and a mean molecular fraction of f = 2N(H2)/[2N(H2) + N(H i)] = 10-3.04+/-0.37, typical of known H2-bearing DLA systems. From the observed abundance ratios we conclude that dust is present in the Interstellar Medium (ISM) of this galaxy, with a enhanced abundance in the H2-bearing clouds. However, the total amount of dus...

  4. Low-Redshift Damped Lyman Alpha Galaxies Towards the Quasars B2 0827+243, PKS 0952+179, PKS 1127-145, and PKS 1629+120

    CERN Document Server

    Rao, S M; Turnshek, D A; Lane, W M; Monier, E M; Bergeron, J; Rao, Sandhya M.; Nestor, Daniel B.; Turnshek, David A.; Lane, Wendy M.; Monier, Eric M.; Bergeron, Jacqueline

    2003-01-01

    We present optical and near-infrared ground-based imaging results on four low-redshift damped Lyman alpha (DLA) galaxies. The corresponding DLA systems were discovered in our Hubble Space Telescope spectroscopic surveys for DLAs in known strong MgII absorption-line systems towards the quasars B2 0827+243 (z{DLA}=0.525), PKS 0952+179 (z{DLA}=0.239), PKS 1127-145 (z_{DLA}=0.313), and PKS 1629+120 (z{DLA}=0.532). The DLA galaxies span a mixture of morphological types from patchy, irregular, and low-surface-brightness to spiral galaxies. The luminosities range from 0.02L_K^* to 1.2L_K^*. We also discovered several extremely red objects (EROs) in two of these fields and discuss the possibility that they are associated with the DLA galaxies. These observations add to the small but growing list of DLA galaxies at low redshift. At the present time, 14 DLA galaxies in the redshift range $0.05 \\lesssim z \\lesssim 1$ have been studied. The distributions of DLA galaxy properties for these 14 cases are discussed and some ...

  5. The First Systematic Survey for Lyman Alpha Emitters at z=7.3 with Red-sensitive Subaru/Suprime-Cam

    CERN Document Server

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

    2011-01-01

    We have performed deep imaging surveys for Lyman Alpha emitters (LAEs) at redshift ~ 7.3 in two blank fields, the Subaru Deep Field (SDF) and the Subaru/XMM-Newton Deep Field (SXDF), using the Subaru/Suprime-Cam equipped with new red-sensitive CCDs and a new narrow-band filter, NB1006 (lambda_c=10,052A, FWHM=214A). By comparing the NB1006 magnitudes of detected objects with those at other shorter wavelength bands, we identified four objects as LAE candidates that exhibit luminosity excess in NB1006. By carrying out deep follow-up spectroscopy for three of them using Subaru/FOCAS and Keck/DEIMOS, a definitively asymmetric emission line is detected for one of them, SXDF-NB1006-2. Assuming this line is LyA, this object is a LAE at z=7.215 which has luminosity of 1.2^{+1.5}_{-0.6} x 10^{43} erg s-1, star formation rate (SFR) of 11 Mo yr-1 estimated from the LyA emission line, and a weighted skewness S_w = 4.90+-0.86. Another object, SDF-NB1006-2, shows variable photometry and is thus probably a quasar (QSO) or an...

  6. Photolytic behaviour of methane @ lyman alpha and 248 nm : studies in the frame of a simulation program of Titan's atmosphere (S.E.T. U.P.)

    Science.gov (United States)

    Gazeau, M. C.; Romanzin, C.; Benilan, Y.; Jolly, A.

    An experimental simulation program called S E T U P Theoretical and Experimental Simulations Useful for Planetology is currently developped in our laboratory One of our aim is to investigate the mechanisms implied in the atmospheric chemistry of Titan in order to improve their description in theoretical models Experimental simulations are planned using a dedicated device The latter consists of a reactor where the initial gas mixture will be submitted for the first time to both major energy sources that are responsible for the chemical evolution of Titan s atmosphere electrons and photons Cold plasma and a UV irradiation will be used to dissociate N 2 and CH 4 respectively Time resolved analysis of the resulting gas sample will be done using spectroscopic methods In Titan s atmosphere photolysis of methane mainly involves Lyman- alpha photons 121 6 nm Such mechanism can not be easily reproduced in the laboratory for several reasons - difficulty to work in the VUV range traditional photochemical lamps unsuitable for high speed kinetic studies ldots Therefore in our simulation experiments a pulsed laser KrF excimer delivering photons at 248 nm is used to dissociate methane Indeed a two photons 248 nm process is energetically equivalent to the single photon 121 6 nm one Hovewer branching ratios for the CH 3 CH 2 and CH radicals production and consequently the following photochemistry could be different Thus as a first step of this photochemical experiment photolysis of methane at 121 6 and 248 nm

  7. VLT/XSHOOTER & Subaru/MOIRCS Spectroscopy of HUDF-YD3: No Evidence for Lyman-alpha Emission at z=8.55

    CERN Document Server

    Bunker, Andrew J; Wilkins, Stephen M; Stanway, Elizabeth R; Lorenzoni, Silvio; Lacy, Mark; Jarvis, Matt J; Hickey, Samantha

    2013-01-01

    We present spectroscopic observations with VLT/XSHOOTER and Subaru/MOIRCS of a relatively bright Y-band drop-out galaxy in the Hubble Ultra Deep Field, first selected by Bunker et al. (2010), McLure et al. (2010) and Bouwens et al. (2010) to be a likely z~8-9 galaxy on the basis of its colours in the HST ACS and WFC3 images. This galaxy, HUDF.YD3 (also known as UDFy-38135539) has been targetted for VLT/SINFONI integral field spectroscopy by Lehnert et al. (2010), who published a candidate Lyman-alpha emission line at z=8.55 from this source. In our independent spectroscopy using two different infrared spectrographs (5 hours with VLT/XSHOOTER and 11 hours with Subaru/MOIRCS) we are unable to reproduce this line. We do not detect any emission line at the spectral and spatial location reported in Lehnert et al. (2010), despite the expected signal in our combined MOIRCS & XSHOOTER data being 5-sigma. The line emission also seems to be ruled out by the faintness of this object in recently extremely deep F105W ...

  8. Observed Faraday Effects in Damped Lyman-Alpha Absorbers and Lyman Limit Systems: The Magnetised Environment of Galactic Building Blocks at Redshift=2

    CERN Document Server

    Farnes, J S; Gaensler, B M; Haverkorn, M; O'Sullivan, S P; Curran, S J

    2016-01-01

    Protogalactic environments are typically identified using quasar absorption lines, and these galactic building blocks can manifest as Damped Lyman-Alpha Absorbers (DLAs) and Lyman Limit Systems (LLSs). We use radio observations of Faraday effects to test whether DLAs and LLSs host a magnetised medium, by combining DLA and LLS detections throughout the literature with 1.4 GHz polarization data from the NRAO VLA Sky Survey (NVSS). We obtain a control, a DLA, and a LLS sample consisting of 114, 19, and 27 lines-of-sight respectively - all of which are polarized at $\\ge8\\sigma$ to ensure Rician bias is negligible. Using a Bayesian framework, we are unable to detect either coherent or random magnetic fields in DLAs: the regular coherent magnetic fields within the DLAs must be $\\le2.8$ $\\mu$G, and the lack of depolarization is consistent with the weakly magnetised gas in DLAs being non-turbulent and quiescent. However, we find mild suggestive evidence that LLSs have coherent magnetic fields: after controlling for t...

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

    Energy Technology Data Exchange (ETDEWEB)

    Louchev, Oleg A.; Saito, Norihito; Wada, Satoshi [Advanced Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198 (Japan); Bakule, Pavel [STFC, ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX (United Kingdom); Yokoyama, Koji [Advanced Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198 (Japan); Advanced Meson Science Laboratory, RIKEN Nishina Center, RIKEN, Wako, Saitama 351-0198 (Japan); Ishida, Katsuhiko; Iwasaki, Masahiko [Advanced Meson Science Laboratory, RIKEN Nishina Center, RIKEN, Wako, Saitama 351-0198 (Japan)

    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.

  10. A quasar reddened by a sub-parsec sized, metal-rich and dusty cloud in a damped Lyman-alpha absorber at z=2.13

    CERN Document Server

    Krogager, J -K; Noterdaeme, P; Zafar, T; Møller, P; Ledoux, C; Krühler, T; Stockton, A

    2015-01-01

    We present a detailed analysis of a red quasar at z=2.32 with an intervening damped Lyman-alpha absorber (DLA) at z=2.13. Using high quality data from the X-shooter spectrograph at ESO Very Large Telescope we find that the absorber has a metallicity consistent with Solar. We observe strong C I and H$_2$ absorption indicating a cold, dense absorbing medium. Partial coverage effects are observed in the C I lines, from which we infer a covering fraction of $27 \\pm 6$ % and a physical diameter of the cloud of 0.1 pc. From the covering fraction and size, we estimate the size of the background quasar's broad line region. We search for emission from the DLA counterpart in optical and near-infrared imaging. No emission is observed in the optical data. However, we see tentative evidence for a counterpart in the H and K' band images. The DLA shows high depletion (as probed by [Fe/Zn]=-1.22) indicating that significant amounts of dust must be present in the DLA. By fitting the spectrum with various dust reddened quasar ...

  11. Keck and VLT Observations of Super-damped Lyman-alpha Absorbers at z=2=2.5: Constraints on Chemical Compositions and Physical Conditions

    CERN Document Server

    Kulkarni, Varsha P; Morrison, Sean; Peroux, Celine; Quiret, Samuel; York, Donald G

    2015-01-01

    We report Keck/ESI and VLT/UVES observations of three super-damped Lyman-alpha quasar absorbers with H I column densities log N(HI) >= 21.7 at redshifts z=2-2.5. All three absorbers show similar metallicities (-1.3 to -1.5 dex), and dust depletion of Fe, Ni, and Mn. Two of the absorbers show supersolar [S/Zn] and [Si/Zn]. We combine our results with those for other DLAs to examine trends between N(HI), metallicity, dust depletion. A larger fraction of the super-DLAs lie close to or above the line [X/H]=20.59-log N(HI) in the metallicity vs. N(HI) plot, compared to the less gas-rich DLAs, suggesting that super-DLAs are more likely to be rich in molecules. Unfortunately, our data for Q0230-0334 and Q0743+1421 do not cover H2 absorption lines. For Q1418+0718, some H2 lines are covered, but not detected. CO is not detected in any of our absorbers. For DLAs with log N(HI) 21.7 may have somewhat narrower velocity dispersions delta v_90 than the less gas-rich DLAs, and may arise in cooler and/or less turbulent gas.

  12. Kiloparsec Mass/Light Offsets in the Galaxy Pair-Lyman-alpha Emitter Lens System SDSS\\,J1011$+$0143

    CERN Document Server

    Shu, Yiping; Moustakas, Leonidas A; Stern, Daniel; Dey, Arjun; Brownstein, Joel R; Burles, Scott; Spinrad, Hyron

    2016-01-01

    We report the discovery of significant mass/light offsets in the strong gravitational lensing system SDSS\\,J1011$+$0143. We use the high-resolution \\textsl{Hubble Space Telescope} (\\textsl{HST}) F555W- and F814W-band imaging and SDSS spectroscopy of this system, which consists of a close galaxy pair with a projected separation of $\\approx 4.2$ kpc at $z_{\\rm lens} \\sim 0.331$ lensing a Lyman-alpha emitter (LAE) at $z_{\\rm source} = 2.701$. Comparisons between the mass peaks inferred from lens models and light peaks from \\textsl{HST} imaging data reveal significant spatial mass/light offsets as large as $(1.72 \\pm 0.24 \\pm 0.34)$ kpc in both filter bands. Such large mass/light offsets, not seen in isolated field lens galaxies and relaxed galaxy groups, may be related to the interactions between the two lens galaxies. The detected mass/light offsets can potentially serve as an important test for the self-interacting dark matter model. However, other mechanisms such as dynamical friction on spatially differently...

  13. The chemistry of the most metal-rich damped Lyman $\\alpha$ systems at z$\\sim2$ II. Context with the Local Group

    CERN Document Server

    Berg, Trystyn A M; Prochaska, J Xavier; Venn, Kim A; Dessauges-Zavadsky, Miroslava

    2015-01-01

    Using our sample of the most metal-rich damped Lyman $\\alpha$ systems (DLAs) at z$\\sim2$, and two literature compilations of chemical abundances in 341 DLAs and 2818 stars, we present an analysis of the chemical composition of DLAs in the context of the Local Group. The metal-rich sample of DLAs at z$\\sim2$ probes metallicities as high as the Galactic disc and the most metal-rich dwarf spheroidals (dSphs), permitting an analysis of many elements typically observed in DLAs (Fe, Zn, Cr, Mn, Si, and S) in comparison to stellar abundances observed in the Galaxy and its satellites (in particular dSphs). Our main conclusions are: (1) non-solar [Zn/Fe] abundances in metal-poor Galactic stars and in dSphs over the full metallicity range probed by DLAs, suggest that Zn is not a simple proxy for Fe in DLAs and therefore not a suitable indicator of dust depletion. After correcting for dust depletion, the majority of DLAs have subsolar [Zn/Fe] similar to dSphs; (2) at [Fe/H]$\\sim-0.5$, a constant [Mn/Fe]$\\sim-0.5$ and ne...

  14. Lyman-alpha Forest Tomography from Background Galaxies: The First Megaparsec-Resolution Large-Scale Structure Map at z>2

    CERN Document Server

    Lee, Khee-Gan; Stark, Casey; Prochaska, J Xavier; White, Martin; Schlegel, David J; Eilers, Anna-Christina; Arinyo-i-Prats, Andreu; Suzuki, Nao; Croft, Rupert A C; Caputi, Karina I; Cassata, Paolo; Ilbert, Olivier; Garilli, Bianca; Koekemoer, Anton M; Brun, Vincent Le; Fèvre, Olivier Le; Maccagni, Dario; Nugent, Peter; Taniguchi, Yoshiaki; Tasca, Lidia A M; Tresse, Laurence; Zamorani, Gianni; Zucca, Elena

    2014-01-01

    We present the first observations of foreground Lyman-$\\alpha$ forest absorption from high-redshift galaxies, targeting 24 star-forming galaxies (SFGs) with $z\\sim 2.3-2.8$ within a $5' \\times 15'$ region of the COSMOS field. The transverse sightline separation is $\\sim 2\\,h^{-1}\\mathrm{Mpc}$ comoving, allowing us to create a tomographic reconstruction of the 3D Ly$\\alpha$ forest absorption field over the redshift range $2.20\\leq z\\leq 2.45$. The resulting map covers $6\\,h^{-1}\\mathrm{Mpc} \\times 14\\,h^{-1}\\mathrm{Mpc}$ in the transverse plane and $230\\,h^{-1}\\mathrm{Mpc}$ along the line-of-sight with a spatial resolution of $\\approx 3.5\\,h^{-1}\\mathrm{Mpc}$, and is the first high-fidelity map of large-scale structure on $\\sim\\mathrm{Mpc}$ scales at $z>2$. Our map reveals significant structures with $\\gtrsim 10\\,h^{-1}\\mathrm{Mpc}$ extent, including several spanning the entire transverse breadth, providing qualitative evidence for the filamentary structures predicted to exist in the high-redshift cosmic web. ...

  15. No evidence for Population III stars or a Direct Collapse Black Hole in the z = 6.6 Lyman-$\\alpha$ emitter 'CR7'

    CERN Document Server

    Bowler, R A A; Dunlop, J S; McLeod, D J; Stanway, E R; Eldridge, J J; Jarvis, M J

    2016-01-01

    The z = 6.6 Lyman-$\\alpha$ emitter 'CR7' has been claimed to have a Population III-like stellar population, or alternatively, be a candidate Direct Collapse Black Hole (DCBH). In this paper we investigate the evidence for these exotic scenarios using recently available, deeper, optical, near-infrared and mid-infrared imaging. We find strong Spitzer/IRAC detections for the main component of CR7 at 3.6 and 4.5 microns, and show that it has a blue colour ([3.6] - [4.5] $= -1.2\\pm 0.3$). This colour cannot be reproduced by current Pop. III or pristine DCBH models. Instead, the results suggest that the [3.6] band is contaminated by the [OIII]4959,5007 emission line with an implied rest-frame equivalent width of EW_0 (H$\\beta$ + [OIII]) $\\gtrsim 2000$\\AA. Furthermore, we find that new near-infrared data from the UltraVISTA survey supports a weaker He II 1640 emission line than previously measured, with EW_0 $= 40 \\pm 30$\\AA. For the fainter components of CR7 visible in Hubble Space Telescope imaging, we find no evi...

  16. The Lyman-alpha forest of a Lyman Break Galaxy VLT Spectra of MS1512-cB58 at z=2.724

    CERN Document Server

    Savaglio, S; Padovani, P

    2001-01-01

    The high redshift galaxy MS1512-cB58 (z=2.724, m_V=20.64) has been observed with the very efficient high resolution echelle spectrograph VLT/UVES. Although this is a very challenging observational program for a Southern hemisphere telescope (the galaxy is located at +36 deg declination), high resolution spectra (FWHM ~ 26 km/s) have revealed, with unprecedented detail along a galaxy sight line, the Lyman-alpha forest due to intervening clouds in the intergalactic medium (IGM). The mean depression D_A due to IGM absorption blueward of the galaxy Ly-alpha wavelength and the number density dn/dz of Ly-alpha clouds have been compared with equivalent results obtained for QSO sight lines at similar redshifts. Our results indicate a possible excess of absorption close to the galaxy. The mean depression at ~ 150 h_65^-1 Mpc comoving (Omega_m=0.3, Omega_Lambda=0.7) from the galaxy is D_A=0.36+/-0.03, to be compared with 0.22+/-0.04, expected from a best fit to QSO sight lines. In the same region (z=2.610), the number ...

  17. Relationships between the HI 21-cm line strength, MgII equivalent width and metallicity in damped Lyman-alpha absorption systems

    CERN Document Server

    Curran, S J; Pihlström, Y M; Webb, J K

    2007-01-01

    We present the results of a survey for 21-cm absorption in four never previously searched damped Lyman-alpha absorption systems (DLAs) with the Westerbork Synthesis Radio Telescope. We add our results to other recent studies in order to address the important issues regarding the detection of cold gas, through 21-cm absorption, in DLAs: Although, due to the DLAs identified with spiral galaxies, there is a mix of spin temperature/covering factor ratios at low redshift, two recent high redshift end points confirm that this ratio does not generally rise over the whole redshift range searched (up to z = 3.39). That is, if the covering factors of many of these galaxies were a factor of >2 smaller than for the spirals, then no significant difference in the spin temperatures between these two classes would be required. Furthermore, although it is difficult to separate the relative contributions of the spin temperature and covering factor, the new results confirm that 21-cm detections tend to occur at low angular diam...

  18. The explosion energy of early stellar populations: The Fe-peak element ratios in low metallicity damped Lyman-alpha systems

    CERN Document Server

    Cooke, Ryan; Jorgenson, Regina A; Murphy, Michael T; Rudie, Gwen C; Steidel, Charles C

    2012-01-01

    The relative abundances of the Fe-peak elements (Ti-Zn) at the lowest metallicities are intimately linked to the physics of core-collapse supernova explosions. With a sample of 25 very metal-poor damped Lyman-alpha systems, we investigate the trends of the Fe-peak element ratios with metallicity. For nine of the 25 DLAs, a direct measurement (or useful upper limit) of one or more of the Ti,Cr,Co,Ni,Zn/Fe abundance ratios could be determined from detected absorption lines. For the remaining systems (without detections), we devised a new form of spectral stacking to estimate the typical Fe-peak element ratios of the DLA population in this metallicity regime. We compare these data to analogous measurements in metal-poor stars of the Galactic halo and to detailed calculations of explosive nucleosynthesis in metal-free stars. We conclude that most of the DLAs in our sample were enriched by stars that released an energy of < 3.0x10^51 erg when they exploded as core-collapse supernovae. We find one DLA that appea...

  19. C IV absorption in damped and sub-damped Lyman-alpha systems: correlations with metallicity and implications for galactic winds at z~2-3

    CERN Document Server

    Fox, Andrew J; Petitjean, Patrick; Srianand, Raghunathan

    2007-01-01

    We present a study of C IV absorption in a sample of 63 damped Lyman-alpha (DLA) systems and 11 sub-DLAs in the redshift range 1.75

  20. The First Observations of Low-Redshift Damped Lyman-{\\alpha} Systems with the Cosmic Origins Spectrograph: Chemical Abundances and Affiliated Galaxies

    CERN Document Server

    Battisti, A J; Tripp, T M; Prochaska, J X; Werk, J K; Jenkins, E B; Lehner, N; Tumlinson, J; Thom, C

    2011-01-01

    We present Cosmic Origins Spectrograph (COS) measurements of metal abundances in eight 0.083 < zabs < 0.321 damped Lyman-{\\alpha} (DLA) and sub-damped Ly{\\alpha} absorption systems serendipitously discovered in the COS-Halos survey. We find that these systems show a large range in metallicities, with -1.10 < [Z/H] < 0.31, similar to the spread found at higher redshifts. These low-redshift systems on average have subsolar metallicities, but do show a rise in metallicity over cosmic time when compared to higher-redshift systems. Utilizing our sources and those in the literature, we find the average sub-DLA metallicity is higher than the average DLA metallicity at all redshifts. Nitrogen is underabundant with respect to {\\alpha}-group elements in all but perhaps one of the absorbers. In some cases, [N/{\\alpha}] is significantly below the lowest nitrogen measurements in nearby galaxies; the nitrogen abundances are more similar to those observed in high-redshift DLAs. Systems for which depletion patter...

  1. The Lyman-alpha luminosity function at z=5.7-6.6 and the steep drop of the faint end: implications for reionization

    CERN Document Server

    Santos, Sérgio; Matthee, Jorryt

    2016-01-01

    We present new results from the widest narrow band survey search for Lyman-alpha (Lya) emitters at z=5.7, just after reionization. We survey a total of 7 deg$^2$ spread over the COSMOS, UDS and SA22 fields. We find over 11,000 line emitters, out of which 514 are robust Lya candidates at z=5.7 within a volume of 6.3x10$^6$ Mpc$^3$. Our Lya emitters span a wide range in Lya luminosities, from faint to bright (L$_{\\rm Ly\\alpha}\\sim10^{42.5-44}$ erg s$^{-1}$) and rest-frame equivalent widths (EW$_0$~25-1000 \\AA) in a single, homogeneous data-set. By combining all our fields we find that the faint end slope of the z=5.7 Lya luminosity function is very steep, with $\\alpha=-2.3^{+0.4}_{-0.3}$. We also present an updated z=6.6 Lya luminosity function, based on comparable volumes and obtained with the same methods, which we directly compare with that at z=5.7. We find a significant decline of the number density of faint Lya emitters from z=5.7 to z=6.6 (by $0.5\\pm0.1$ dex), but no evolution at the bright end/no evolut...

  2. Lyman-Alpha Emitting Galaxies as a Probe of Reionization: Large-Scale Bubble Morphology and Small-Scale Absorbers

    CERN Document Server

    Kakiichi, Koki; Ciardi, Benedetta; Graziani, Luca

    2015-01-01

    The visibility of LyA emitting galaxies during the Epoch of Reionization is controlled by both diffuse HI patches in large-scale bubble morphology and small-scale absorbers. To investigate the impact on LyA photons, we apply a novel combination of analytic and numerical calculations to three scenarios: (i) the `bubble' model, where only diffuse HI outside ionized bubbles is present; (ii) the `web' model, where HI exists only in overdense self-shielded gas; and (iii) the more realistic 'web-bubble' model, which contains both. Our analysis confirms that there is a degeneracy between the ionization structure of the intergalactic medium (IGM) and the HI fraction inferred from LyA surveys, as the three models suppress LyA flux equally with very different HI fractions. We argue that a joint analysis of the LyA luminosity function and the rest-frame equivalent width distribution/LyA fraction can break this degeneracy and provide constraints on the reionization history and its topology. We further show that constrain...

  3. The Stacked Lyman-Alpha Emission Profile from the Circum-Galactic Medium of z~2 Quasars

    CERN Document Server

    Battaia, Fabrizio Arrigoni; Cantalupo, Sebastiano; Prochaska, J Xavier

    2016-01-01

    In the context of the FLASHLIGHT survey, we obtained deep narrow band images of 15 $z\\sim2$ quasars with GMOS on Gemini-South in an effort to measure Ly$\\alpha$ emission from circum- and inter-galactic gas on scales of hundreds of kpc from the central quasar. We do not detect bright giant Ly$\\alpha$ nebulae (SB~10$^{-17}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$ at distances >50 kpc) around any of our sources, although we routinely ($\\simeq47$%) detect smaller scale <50 kpc Ly$\\alpha$ emission at this SB level emerging from either the extended narrow emission line regions powered by the quasars or by star-formation in their host galaxies. We stack our 15 deep images to study the average extended Ly$\\alpha$ surface brightness profile around $z\\sim2$ quasars, carefully PSF-subtracting the unresolved emission component and paying close attention to sources of systematic error. Our analysis, which achieves an unprecedented depth, reveals a surface brightness of SB$_{\\rm Ly\\alpha}\\sim10^{-19}$ erg s$^{-1}$ cm$^{-2}...

  4. Warm Dark Matter as a solution to the small scale crisis: new constraints from high redshift Lyman-alpha forest data

    CERN Document Server

    Viel, M; Bolton, J S; Haehnelt, M G

    2013-01-01

    We present updated constraints on the free-streaming of warm dark matter (WDM) particles derived from an analysis of the Lya flux power spectrum measured from high-resolution spectra of 25 z > 4 quasars obtained with the Keck High Resolution Echelle Spectrometer (HIRES) and the Magellan Inamori Kyocera Echelle (MIKE) spectrograph. We utilize a new suite of high-resolution hydrodynamical simulations that explore WDM masses of 1, 2 and 4 keV (assuming the WDM consists of thermal relics), along with different physically motivated thermal histories. We carefully address different sources of systematic error that may affect our final results and perform an analysis of the Lya flux power with conservative error estimates. By using a method that samples the multi-dimensional astrophysical and cosmological parameter space, we obtain a lower limit mwdm > 3.3 keV (2sigma) for warm dark matter particles in the form of early decoupled thermal relics. Adding the Sloan Digital Sky Survey (SDSS) Lya flux power spectrum does...

  5. Application of a Heat Flux Sensor in Wind Power Electronics

    Directory of Open Access Journals (Sweden)

    Elvira Baygildina

    2016-06-01

    Full Text Available This paper proposes and investigates the application of the gradient heat flux sensor (GHFS for measuring the local heat flux in power electronics. Thanks to its thinness, the sensor can be placed between the semiconductor module and the heat sink. The GHFS has high sensitivity and yields direct measurements without an interruption to the normal power device operation, which makes it attractive for power electronics applications. The development of systems for monitoring thermal loading and methods for online detection of degradation and failure of power electronic devices is a topical and crucial task. However, online condition monitoring (CM methods, which include heat flux sensors, have received little research attention so far. In the current research, an insulated-gate bipolar transistor (IGBT module-based test setup with the GHFS implemented on the base plate of one of the IGBTs is introduced. The heat flux experiments and the IGBT power losses obtained by simulations show similar results. The findings give clear evidence that the GHFS can provide an attractive condition monitoring method for the thermal loading of power devices.

  6. Cochlear power flux as an indicator of mechanical activity.

    Science.gov (United States)

    Diependaal, R J; de Boer, E; Viergever, M A

    1987-09-01

    The question of whether one can conclude just from basilar membrane (BM) vibration data that the cochlea is an active mechanical system is addressed. To this end, a method is developed which computes the power flux through a channel cross section of a short-wave cochlear model from a given BM vibration pattern. The power flux is an important indicator of mechanical activity because a rise in this function corresponds to creation of mechanical energy. The power flux method is applied to BM velocity patterns as measured by Johnstone and Yates [J. Acoust. Soc. Am. 55, 584-587 (1974)] and by Sellick et al. [Hear. Res. 10, 101-108 (1983)] in the guinea pig and by Robles et al. [Peripheral Auditory Mechanisms, edited by J.B. Allen, J.L. Hall, A.E. Hubbard, S.T. Neely, and A. Tubis (Springer, New York, 1986a), pp. 121-128, and J. Acoust. Soc. Am. 80, 1364-1374 (1986b)] in the chinchilla. Before the calculations are performed, the BM data are interpolated and smoothed in order to avoid numerical errors as a result of too few and noisy data points. The choice of the smoothing method influences the computed power flux function considerably. Nevertheless, the calculations appear to make a clear distinction between the "old" data, showing broad BM tuning (Johnstone and Yates, 1974), and the "new" data, in which the response is much more peaked (Sellick et al., 1983; Robles et al., 1986a, b). The former do not give rise to a significant increase of the power flux; the latter do, although less convincingly for the Sellick et al. (1983) data than for the Robles et al. (1986a,b) data. It is thus concluded that the recently obtained, sharply tuned BM responses reflect the presence of mechanical activity in the cochlea.

  7. Cosmological flux noise and measured noise power spectra in SQUIDs

    Science.gov (United States)

    Beck, Christian

    2016-06-01

    The understanding of the origin of 1/f magnetic flux noise commonly observed in superconducting devices such as SQUIDs and qubits is still a major unsolved puzzle. Here we discuss the possibility that a significant part of the observed low-frequency flux noise measured in these devices is ultimately seeded by cosmological fluctuations. We consider a theory where a primordial flux noise field left over in unchanged form from an early inflationary or quantum gravity epoch of the universe intrinsically influences the phase difference in SQUIDs and qubits. The perturbation seeds generated by this field can explain in a quantitatively correct way the form and amplitude of measured low-frequency flux noise spectra in SQUID devices if one takes as a source of fluctuations the primordial power spectrum of curvature fluctuations as measured by the Planck collaboration. Our theoretical predictions are in excellent agreement with recent low-frequency flux noise measurements of various experimental groups. Magnetic flux noise, so far mainly considered as a nuisance for electronic devices, may thus contain valuable information about fluctuation spectra in the very early universe.

  8. Antineutrino Flux from the Laguna Verde Nuclear Power Plant

    Directory of Open Access Journals (Sweden)

    Marisol Chavez-Estrada

    2015-01-01

    Full Text Available We present a calculation of the antineutrino flux produced by the reactors at the Laguna Verde Nuclear Power Plant in México, based on the antineutrino spectra produced in the decay chains of the fission fragments of the main isotopes in the reactor core, and their fission rates, which have been calculated using the DRAGON simulation code. We also present an estimate of the number of expected events in a detector made of plastic scintillator with a mass of 1 ton, at 100 m from the reactor cores.

  9. Antineutrino flux from the Laguna Verde Nuclear Power Plant

    CERN Document Server

    Chavez-Estrada, Marisol

    2015-01-01

    We present a a calculation of the antineutrino flux produced by the reactors at the Laguna Verde Nuclear Power Plant in M\\'exico, based on the antineutrino spectra produced in the decay chains of the fission fragments of the main isotopes in the reactor core, and their fission rates, that have been calculated using the DRAGON simulation code. We also present an estimate of the number of expected events in a detector made of plastic scintillator with a mass of 1 ton, at 100 m from the reactor cores.

  10. SO2 flux and the thermal power of volcanic eruptions

    Science.gov (United States)

    Henley, Richard W.; Hughes, Graham O.

    2016-09-01

    A description of the dynamics, chemistry and energetics governing a volcanic system can be greatly simplified if the expansion of magmatic gas can be assumed to be adiabatic as it rises towards the surface. The conditions under which this assumption is valid are clarified by analysis of the transfer of thermal energy into the low conductivity wallrocks traversed by fractures and vents from a gas phase expanding over a range of mass flux rates. Adiabatic behavior is predicted to be approached typically within a month after perturbations in the release of source gas have stabilized, this timescale being dependent upon only the characteristic length scale on which the host rock is fractured and the thermal diffusivity of the rock. This analysis then enables the thermal energy transport due to gas release from volcanoes to be evaluated using observations of SO2 flux with reference values for the H2O:SO2 ratio of volcanic gas mixtures discharging through high temperature fumaroles in arc and mantle-related volcanic systems. Thermal power estimates for gas discharge are 101.8 to 104.1 MWH during quiescent, continuous degassing of arc volcanoes and 103.7 to 107.3 MWH for their eruptive stages, the higher value being the Plinean Pinatubo eruption in 1991. Fewer data are available for quiescent stage mantle-related volcanoes (Kilauea 102.1 MWH) but for eruptive events power estimates range from 102.8 MWH to 105.5 MWH. These estimates of thermal power and mass of gas discharges are commensurate with power estimates based on the total mass of gas ejected during eruptions. The sustained discharge of volcanic gas during quiescent and short-lived eruptive stages can be related to the hydrodynamic structure of volcanic systems with large scale gaseous mass transfer from deep in the crust coupled with episodes of high level intrusive activity and gas release.

  11. Neutron flux and power in RTP core-15

    Science.gov (United States)

    Rabir, Mohamad Hairie; Zin, Muhammad Rawi Md; Usang, Mark Dennis; Bayar, Abi Muttaqin Jalal; Hamzah, Na'im Syauqi Bin

    2016-01-01

    PUSPATI TRIGA Reactor achieved initial criticality on June 28, 1982. The reactor is designed to effectively implement the various fields of basic nuclear research, manpower training, and production of radioisotopes. This paper describes the reactor parameters calculation for the PUSPATI TRIGA REACTOR (RTP); focusing on the application of the developed reactor 3D model for criticality calculation, analysis of power and neutron flux distribution of TRIGA core. The 3D continuous energy Monte Carlo code MCNP was used to develop a versatile and accurate full model of the TRIGA reactor. The model represents in detailed all important components of the core with literally no physical approximation. The consistency and accuracy of the developed RTP MCNP model was established by comparing calculations to the available experimental results and TRIGLAV code calculation.

  12. Explosive Ferroelectric Power Supply of Flux Compression Generator

    Institute of Scientific and Technical Information of China (English)

    WANG De-wu; HE Yuan-ji; TAN Hui-min

    2007-01-01

    Useful electrical pulses of a few hundred kilowatts lasting for several microseconds can be obtained by the depolarization process of PZT95/5 ferroelectric ceramics. In this paper, taking account of the dielectric relaxation, and finite resistance, a new mathematical model of PZT95/5 ferroelectric ceramics subjected to normal-mode shock wave is suggested. Explosive shock wave techniques have also been used to investigate the response of PZT95/5 ferroelectric ceramics with inductive loads in experiments. The predictions from the model have a good agreement with observed results. In addition, an explosive ferroelectric generator composed of explosive shock wave generators, electric units, and additional capacitors is design to power small-size helical flux compression generators. The test results with the maximal output energy of up to 80J are given and experimental results are also considered.

  13. Neutron flux and power in RTP core-15

    Energy Technology Data Exchange (ETDEWEB)

    Rabir, Mohamad Hairie, E-mail: m-hairie@nuclearmalaysia.gov.my; Zin, Muhammad Rawi Md; Usang, Mark Dennis; Bayar, Abi Muttaqin Jalal; Hamzah, Na’im Syauqi Bin [Nuclear and reactor Physics Section, Nuclear Technology Center, Technical Support Division, Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor (Malaysia)

    2016-01-22

    PUSPATI TRIGA Reactor achieved initial criticality on June 28, 1982. The reactor is designed to effectively implement the various fields of basic nuclear research, manpower training, and production of radioisotopes. This paper describes the reactor parameters calculation for the PUSPATI TRIGA REACTOR (RTP); focusing on the application of the developed reactor 3D model for criticality calculation, analysis of power and neutron flux distribution of TRIGA core. The 3D continuous energy Monte Carlo code MCNP was used to develop a versatile and accurate full model of the TRIGA reactor. The model represents in detailed all important components of the core with literally no physical approximation. The consistency and accuracy of the developed RTP MCNP model was established by comparing calculations to the available experimental results and TRIGLAV code calculation.

  14. MgII Absorption Lines in z=2.974 Damped Lyman-alpha System toward Gravitationally Lensed QSO APM 08279+5255 Detection of Small-scale Structure in MgII Absorbing Clouds

    CERN Document Server

    Kobayashi, N; Goto, M; Tokunaga, A; Kobayashi, Naoto; Terada, Hiroshi; Goto, Miwa; Tokunaga, Alan

    2002-01-01

    1.02-1.16 micron spectra (R ~ 7,000) of the gravitationally lensed QSO APM 08279+5255 at z_em=3.911 were obtained during the commissioning run of IRCS, the 1-5 micron near-infrared camera and spectrograph for the Subaru 8.2 m Telescope. Strong MgII doublet at 2976,2800 angstrom and FeII (2600 angstrom), FeII (2587 angstrom) absorption lines at z_abs=2.974 were clearly detected in the rest-frame UV spectra, confirming the presence of a damped Lyman-alpha system at the redshift as suggested by Petitjean et al. Also MgI (2853 angstrom) absorption line is probably detected. An analysis of the absorption lines including velocity decomposition was performed. This is a first detailed study of MgII absorption system at high redshift (z > 2.5) where the MgII doublet shifts into the near-infrared in the observer's frame. The spectra of the lensed QSO pair A and B with 0.38 arcsec separation were resolved in some exposure frames under excellent seeing condition. We extracted the MgII doublet spectra of A and B separatel...

  15. High Precision Analyses of Lyman alpha Damping Wing of Gamma-Ray Bursts in the Reionization Era: On the Controversial Results from GRB 130606A at z = 5.91

    CERN Document Server

    Totani, Tomonori; Hattori, Takashi; Kawai, Nobuyuki

    2015-01-01

    The unprecedentedly bright afterglow of GRB 130606A at z = 5.91 gave us a unique opportunity to probe the reionization era by high precision analyses of the redward damping wing of Lyman alpha absorption, but the reported constraints on the neutral hydrogen fraction (f_{HI}) in intergalactic medium (IGM) derived from spectra taken by different telescopes are in contradiction. Here we examine the origin of this discrepancy by analyzing the spectrum taken by VLT with our own analysis code previously used to fit the Subaru spectrum. Though the VLT team reported no evidence for IGM HI using the VLT spectrum, we confirmed our previous result of 3-4 sigma preference for non-zero IGM HI (f_{HI} ~ 0.06, when IGM HI extends to the GRB redshift). The fit residuals of the VLT spectrum by the model without IGM HI show the same systematic trend as the Subaru spectrum. We consider that the likely origin of the discrepancy between the two teams is the difference of the wavelength ranges adopted in the fittings; our waveleng...

  16. Cross-correlations of the Lyman-alpha forest with weak lensing convergence I: Analytical Estimates of S/N and Implications for Neutrino Mass and Dark Energy

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-10-01

    We expect a detectable correlation between two seemingly unrelated quantities: the four point function of the cosmic microwave background (CMB) and the amplitude of flux decrements in quasar (QSO) spectra. The amplitude of CMB convergence in a given direction measures the projected surface density of matter. Measurements of QSO flux decrements trace the small-scale distribution of gas along a given line-of-sight. While the cross-correlation between these two measurements is small for a single line-of-sight, upcoming large surveys should enable its detection. This paper presents analytical estimates for the signal to noise (S/N) for measurements of the cross-correlation between the flux decrement and the convergence, {delta}F{kappa}, and for measurements of the cross-correlation between the variance in flux decrement and the convergence, <({delta}F){sup 2}{kappa}>. For the ongoing BOSS (SDSS III) and Planck surveys, we estimate an S/N of 30 and 9.6 for these two correlations. For the proposed BigBOSS and ACTPOL surveys, we estimate an S/N of 130 and 50 respectively. Since <({delta}F){sup 2}{kappa}> {proportional_to} {delta}{sub s}{sup 4}, the amplitude of these cross-correlations can potentially be used to measure the amplitude of {delta}{sub 8} at z {approx} 2 to 2.5% with BOSS and Planck and even better with future data sets. These measurements have the potential to test alternative theories for dark energy and to constrain the mass of the neutrino. The large potential signal estimated in our analytical calculations motivate tests with non-linear hydrodynamical simulations and analyses of upcoming data sets.

  17. Lyman-Alpha-Emitting Galaxies at z = 2.1 in ECDF-S: Building Blocks of Typical Present-day Galaxies?

    CERN Document Server

    Guaita, L; Padilla, N; Francke, H; Bond, N A; Gronwall, C; Ciardullo, R; Feldmeier, J J; Sinawa, S; Blanc, G A; Virani, S

    2009-01-01

    We discovered a sample of 261 Ly-Alpha emitting (LAE) galaxies at z=2.1 in an ultra-deep 3727 A narrow-band MUSYC image of the Extended Chandra Deep Field-South. LAEs were selected to have rest-frame equivalent widths (EW) >20 A and emission line fluxes F>2.0 x 10^(-17)erg /cm^2/s, after carefully subtracting the continuum contributions from narrow band photometry. The median flux of our sample is F = 4.1 x 10^(-17)erg/cm^2/s, corresponding to a median Lya luminosity = 1.3 x 10^(42) erg/s at z=2.1. At emission line fluxes F= 3.8 x 10^(-17) erg/cm^2/s our sample is 90% complete. 3% of the original candidates were detected in X-rays by Chandra, and 7% were detected in the rest-frame far-UV by GALEX. The remainder of our sample has median rest-frame EW of 39 A, with only a few galaxies having rest frame EW bigger than 200 A. We find a number density of 3.2+/-0.9 x 10^(-3) Mpc^(-3), a factor of 2.1+/-0.7 increase versus LAEs at z ~ 3. We used the rest frame UV luminosity to estimate a median star formation rate o...

  18. Electromagnetic potentials basis for energy density and power flux

    Science.gov (United States)

    Puthoff, H. E.

    2016-09-01

    In rounding out the education of students in advanced courses in applied electromagnetics it is incumbent on us as mentors to raise issues that encourage appreciation of certain subtle aspects that are often overlooked during first exposure to the field. One of these has to do with the interplay between fields and potentials, with the latter often seen as just a convenient mathematical artifice useful in solving Maxwell’s equations. Nonetheless, to those practiced in application it is well understood that various alternatives in the use of fields and potentials are available within electromagnetic (EM) theory for the definitions of energy density, momentum transfer, EM stress-energy tensor, and so forth. Although the various options are all compatible with the basic equations of electrodynamics (e.g., Maxwell’s equations, Lorentz force law, gauge invariance), nonetheless certain alternative formulations lend themselves to being seen as preferable to others with regard to the transparency of their application to physical problems of interest. Here we argue for the transparency of an energy density/power flux option based on the EM potentials alone.

  19. Spectroscopic Confirmation of Three z-Dropout Galaxies at z = 6.844 - 7.213: Lyman Alpha Demography of z ~ 7 Galaxies

    CERN Document Server

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

    2011-01-01

    We present the results of our ultra-deep Keck/DEIMOS spectroscopy of z-dropout galaxies in the SDF and GOODS-N. For 3 out of 11 objects, we detect an emission line at ~ 1um with a signal-to-noise ratio of ~ 10. The lines show asymmetric profiles with high weighted skewness values, consistent with being Lya, yielding redshifts of z=7.213, 6.965, and 6.844. Specifically, we confirm the z=7.213 object in two independent DEIMOS runs with different spectroscopic configurations. The z=6.965 object is a known Lya emitter, IOK-1, for which our improved spectrum at a higher resolution yields a robust skewness measurement. The three z-dropouts have Lya fluxes of 3 x 10^-17 erg s^-1 cm^-2 and rest-frame equivalent widths EW_0^Lya = 33-43A. Based on the largest spectroscopy sample of 43 z-dropouts that is the combination of our and previous data, we find that the fraction of Lya-emitting galaxies (EW_0^Lya > 25A) is low at z ~ 7; 17 +- 10% and 24 +- 12% for bright (Muv ~= -21) and faint (Muv ~= -19.5) galaxies, respectiv...

  20. ALMA observations of a z~3.1 Protocluster: Star Formation from Active Galactic Nuclei and Lyman-Alpha Blobs in an Overdense Environment

    CERN Document Server

    Alexander, D 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

    2016-01-01

    We exploit ALMA 870um 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 Ly-alpha haloes (often termed Ly-alpha blobs: LABs). Three of the AGNs are detected by ALMA and have implied SFRs of ~220-410~M_sun/yr; the non detection of the other five AGNs places SFR upper limits of 100 kpc) do not host more luminous star formation than the smaller LABs, despite being an order of magnitude brighter in Ly-alpha emission. We use these results to discuss star formation as the power source of LABs.

  1. A SINFONI Integral Field Spectroscopy Survey for Galaxy Counterparts to Damped Lyman-alpha Systems - VI. Metallicity and Geometry as Gas Flow Probes

    CERN Document Server

    Peroux, Celine; Rahmani, Hadi; Kulkarni, Varsha P; Epinat, Benoit; Milliard, Bruno; Straka, Lorrie; York, Donald G; Rahmati, Alireza; Contini, Thierry

    2016-01-01

    The use of background quasars provides a powerful tool to probe the cool gas in the circum-galactic medium of foreground galaxies. Here, we present new observations with SINFONI and X-Shooter of absorbing-galaxy candidates at z=0.7-1. We report the detection with both instruments of the H-alpha emission line of one sub-DLA at z_abs=0.94187 with log N(HI)=19.38^+0.10_-0.15 towards SDSS J002133.27+004300.9. We estimate the star formation rate: SFR=3.6+/-2.2 solar masses per year in that system. A detailed kinematic study indicates a dynamical mass M_dyn=10^9.9+/-0.4 solar masses and a halo mass M_halo=10^11.9+/-0.5 solar masses. In addition, we report the OII detection with X-Shooter of another DLA at z_abs=0.7402 with log N(HI)=20.4+/-0.1 toward Q0052+0041 and an estimated SFR of 5.3+/-0.7 solar masses per year. Three other objects are detected in the continuum with X-Shooter but the nature and redshift of two of these objects are unconstrained due to the absence of emission lines, while the third object might...

  2. Deep HeII and CIV Spectroscopy of a Giant Lyman alpha Nebula: Dense Compact Gas Clumps in the Circumgalactic Medium of a z~2 Quasar

    CERN Document Server

    Battaia, Fabrizio Arrigoni; Prochaska, J Xavier; Cantalupo, Sebastiano

    2015-01-01

    The recent discovery by Cantalupo et al. (2014) of the largest (~500 kpc) and luminous Ly-alpha nebula associated with the quasar UM287 (z=2.279) poses a great challenge to our current understanding of the astrophysics of the halos hosting massive z~2 galaxies. Either an enormous reservoir of cool gas is required $M\\simeq10^{12}$ $M_{\\odot}$, exceeding the expected baryonic mass available, or one must invoke extreme gas clumping factors not present in high-resolution cosmological simulations. However, observations of Ly-alpha emission alone cannot distinguish between these two scenarios. We have obtained the deepest ever spectroscopic integrations in the HeII and CIV lines with the goal of detecting extended line emission, but detect neither line to a 3$\\sigma$ limiting SB $\\simeq10^{-18}$ erg/s/cm$^2$/arcsec$^2$. We construct models of the expected emission spectrum in the highly probable scenario that the nebula is powered by photoionization from the central hyper-luminous quasar. The non-detection of HeII ...

  3. Lyman alpha coronagraph research sounding rocket program

    Science.gov (United States)

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

    1985-01-01

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

  4. Lyman alpha emission in starburst galaxies

    Science.gov (United States)

    Kunth, Daniel

    1999-07-01

    We propose to perform a deep study of Ly-alpha emission and destruction in 3 star-forming galaxies. These objects have been already observed with the GHRS and exhibit a variety of situations, with Ly-alpha showing P Cyg profiles, secondary emissions or even a deep damped absorption line with no emission. They also span a range of intrinsic properties: IZW18 is a gas-rich, metal deficient dust free dwarf galaxy, Haro 2 has a simple morphology while IRAS 08339+6517 is a luminous IRAS starburst galaxy with more dust and complex Ly- alpha profile. The use of STIS will allow for the first time to study the geometrical/kinematical configuration of the ionized and neutral gas across the galaxies nuclear regions and pin point the effects of porosity and the kinematical structure of the ISM, that may play the key roles {in addition to dust} in the detectability of the line. This study will have important impact for cosmology since Ly-alpha emitters are nowaday found at high-re dshift. We strongly emphasize that since Ly-alpha is primarely a diagnostic of the ISM, a full understanding of how the ISM and Ly-alpha are related is a necessary step before we can hope to correlate Ly-alpha to the cosmic star-formation rate. Our results will be interpreted against the model of superbubble evolution developed with G. Tenorio Tagle.

  5. Lyman-alpha Absorption from Heliosheath Neutrals

    CERN Document Server

    Wood, B E; Linsky, J L; Malama, Y G; Wood, Brian E.; Izmodenov, Vladislav V.; Linsky, Jeffrey L.; Malama, Yury G.

    2006-01-01

    We assess what information HST observations of stellar Ly-alpha lines can provide on the heliosheath, the region of the heliosphere between the termination shock and heliopause. To search for evidence of heliosheath absorption, we conduct a systematic inspection of stellar Ly-alpha lines reconstructed after correcting for ISM absorption (and heliospheric/astrospheric absorption, if present). Most of the stellar lines are well centered on the stellar radial velocity, as expected, but the three lines of sight with the most downwind orientations relative to the ISM flow (Chi1 Ori, HD 28205, and HD 28568) have significantly blueshifted Ly-alpha lines. Since it is in downwind directions where heliosheath absorption should be strongest, the blueshifts are almost certainly caused by previously undetected heliosheath absorption. We make an initial comparison between the heliosheath absorption and the predictions of a pair of heliospheric models. A model with a complex multi-component treatment of plasma within the he...

  6. First Stars in Damped Lyman Alpha systems

    NARCIS (Netherlands)

    Salvadori, Stefania; Ferrara, Andrea

    In order to characterize Damped Lyα Absorption systems (DLAs) potentially hosting first stars, we present a novel approach to investigate DLAs in the context of Milky Way (MW) formation, along with their connection with the most metal-poor stars and local dwarf galaxies. The model explains the

  7. CATARACT: Computer code for improving power calculations at NREL's high-flux solar furnace

    Science.gov (United States)

    Scholl, K.; Bingham, C.; Lewandowski, A.

    1994-01-01

    The High-Flux Solar Furnace (HFSF), operated by the National Renewable Energy Laboratory, uses a camera-based, flux-mapping system to analyze the distribution and to determine total power at the focal point. The flux-mapping system consists of a diffusively reflecting plate with seven circular foil calorimeters, a charge-coupled device (CCD) camera, an IBM-compatible personal computer with a frame-grabber board, and commercial image analysis software. The calorimeters provide flux readings that are used to scale the image captured from the plate by the camera. The image analysis software can estimate total power incident on the plate by integrating under the 3-dimensional image. Because of the physical layout of the HFSF, the camera is positioned at a 20 angle to the flux mapping plate normal. The foreshortening of the captured images that results represents a systematic error in the power calculations because the software incorrectly assumes the image is parallel to the camera's array. We have written a FORTRAN computer program called CATARACT (camera/target angle correction) that we use to transform the original flux-mapper image to a plane that is normal to the camera's optical axis. A description of the code and the results of experiments performed to verify it are presented. Also presented are comparisons of the total power available from the HFSF as determined from the flux mapping system and theoretical considerations.

  8. Remote Measurement of Heat Flux from Power Plant Cooling Lakes

    Energy Technology Data Exchange (ETDEWEB)

    Garrett, Alfred J.; Kurzeja, Robert J.; Villa-Aleman, Eliel; Bollinger, James S.; Pendergast, Malcolm M.

    2013-06-01

    Laboratory experiments have demonstrated a correlation between the rate of heat loss q" from an experimental fluid to the air above and the standard deviation σ of the thermal variability in images of the fluid surface. These experimental results imply that q" can be derived directly from thermal imagery by computing σ. This paper analyses thermal imagery collected over two power plant cooling lakes to determine if the same relationship exists. Turbulent boundary layer theory predicts a linear relationship between q" and σ when both forced (wind driven) and free (buoyancy driven) convection are present. Datasets derived from ground- and helicopter-based imagery collections had correlation coefficients between σ and q" of 0.45 and 0.76, respectively. Values of q" computed from a function of σ and friction velocity u* derived from turbulent boundary layer theory had higher correlations with measured values of q" (0.84 and 0.89). Finally, this research may be applicable to the problem of calculating losses of heat from the ocean to the atmosphere during high-latitude cold-air outbreaks because it does not require the information typically needed to compute sensible, evaporative, and thermal radiation energy losses to the atmosphere.

  9. Winding Schemes for Wide Constant Power Range of Double Stator Transverse Flux Machine

    Energy Technology Data Exchange (ETDEWEB)

    Husain, Tausif; Hassan, Iftekhar; Sozer, Yilmaz; Husain, Iqbal; Muljadi, Eduard

    2015-05-01

    Different ring winding schemes for double sided transverse flux machines are investigated in this paper for wide speed operation. The windings under investigation are based on two inverters used in parallel. At higher power applications this arrangement improves the drive efficiency. The new winding structure through manipulation of the end connection splits individual sets into two and connects the partitioned turns from individual stator sets in series. This configuration offers the flexibility of torque profiling and a greater flux weakening region. At low speeds and low torque only one winding set is capable of providing the required torque thus providing greater fault tolerance. At higher speeds one set is dedicated to torque production and the other for flux control. The proposed method improves the machine efficiency and allows better flux weakening which is desirable for traction applications.

  10. Magnetic Flux Compression Using Detonation Plasma Armatures and Superconductor Stators: Integrated Propulsion and Power Applications

    Science.gov (United States)

    Litchford, Ron; Robertson, Tony; Hawk, Clark; Turner, Matt; Koelfgen, Syri

    1999-01-01

    This presentation discusses the use of magnetic flux compression for space flight applications as a propulsion and other power applications. The qualities of this technology that make it suitable for spaceflight propulsion and power, are that it has high power density, it can give multimegawatt energy bursts, and terawatt power bursts, it can produce the pulse power for low impedance dense plasma devices (e.g., pulse fusion drivers), and it can produce direct thrust. The issues of a metal vs plasma armature are discussed, and the requirements for high energy output, and fast pulse rise time requires a high speed armature. The plasma armature enables repetitive firing capabilities. The issues concerning the high temperature superconductor stator are also discussed. The concept of the radial mode pulse power generator is described. The proposed research strategy combines the use of computational modeling (i.e., magnetohydrodynamic computations, and finite element modeling) and laboratory experiments to create a demonstration device.

  11. Analytical Investigation on the Power Factor of a Flux-Modulated Permanent-Magnet Synchronous Machine

    DEFF Research Database (Denmark)

    Zhang, Xiaoxu; Liu, Xiao; Liu, Jinglin;

    2015-01-01

    Flux-modulated permanent-magnet synchronous machine (FM-PMSM) is characterized as a high-torque direct-drive electrical machine, but may suffer from the low power factor. This paper aims to investigate the issue of the low power factor in theory and explore the possibilities for improvement....... An analytical model for the FM-PMSM is developed to obtain the magnetic field distribution, and its accuracy is verified by the finite-element method. On the basis of the developed analytical model, a fast approach is developed to predict the power factor of the FM-PMSM. The analytical results indicate...

  12. Maximum Power Point Tracking Sensorless Control of an Axial-Flux Permanent Magnet Vernier Wind Power Generator

    Directory of Open Access Journals (Sweden)

    Xiang Luo

    2016-07-01

    Full Text Available Recently, Vernier permanent magnet (VPM machines, one special case of magnetic flux-modulated (MFM machines, benefiting from their compact, simple construction and low-speed/ high-torque characteristics, have been receiving increasing interest. In this paper, the Vernier structure is integrated with an axial-flux PM machine to obtain the magnetic gear effect and produce an improved torque density for direct-drive wind power generation application. Another advantage of the proposed machine is that the stator flux rotating speed can be relatively high when the shaft speed is low. With this benefit, sensorless control strategy can be easily implemented in a wide speed range. In this paper, an improved sliding mode observer (SMO is proposed to estimate the rotor position and the speed of the proposed machine. With the estimated shaft speeds, the maximum power point tracking (MPPT control strategy is applied to maximize the wind power extraction. The machine design and the sensorless MPPT control strategy are verified by finite element analysis and experimental verification.

  13. Energy Flux in the Cochlea: Evidence Against Power Amplification of the Traveling Wave.

    Science.gov (United States)

    van der Heijden, Marcel; Versteegh, Corstiaen P C

    2015-10-01

    Traveling waves in the inner ear exhibit an amplitude peak that shifts with frequency. The peaking is commonly believed to rely on motile processes that amplify the wave by inserting energy. We recorded the vibrations at adjacent positions on the basilar membrane in sensitive gerbil cochleae and tested the putative power amplification in two ways. First, we determined the energy flux of the traveling wave at its peak and compared it to the acoustic power entering the ear, thereby obtaining the net cochlear power gain. For soft sounds, the energy flux at the peak was 1 ± 0.6 dB less than the middle ear input power. For more intense sounds, increasingly smaller fractions of the acoustic power actually reached the peak region. Thus, we found no net power amplification of soft sounds and a strong net attenuation of intense sounds. Second, we analyzed local wave propagation on the basilar membrane. We found that the waves slowed down abruptly when approaching their peak, causing an energy densification that quantitatively matched the amplitude peaking, similar to the growth of sea waves approaching the beach. Thus, we found no local power amplification of soft sounds and strong local attenuation of intense sounds. The most parsimonious interpretation of these findings is that cochlear sensitivity is not realized by amplifying acoustic energy, but by spatially focusing it, and that dynamic compression is realized by adjusting the amount of dissipation to sound intensity.

  14. Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux

    Science.gov (United States)

    Bowman, Charles D.

    1992-01-01

    Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux. High thermal neutron fluxes generated from the action of a high power proton accelerator on a spallation target allows the efficient burn-up of higher actinide nuclear waste by a two-step process. Additionally, rapid burn-up of fission product waste for nuclides having small thermal neutron cross sections, and the practicality of small material inventories while achieving significant throughput derive from employment of such high fluxes. Several nuclear technology problems are addressed including 1. nuclear energy production without a waste stream requiring storage on a geological timescale, 2. the burn-up of defense and commercial nuclear waste, and 3. the production of defense nuclear material. The apparatus includes an accelerator, a target for neutron production surrounded by a blanket region for transmutation, a turbine for electric power production, and a chemical processing facility. In all applications, the accelerator power may be generated internally from fission and the waste produced thereby is transmuted internally so that waste management might not be required beyond the human lifespan.

  15. Development of an Axial Flux MEMS BLDC Micromotor with Increased Efficiency and Power Density

    Directory of Open Access Journals (Sweden)

    Xiaofeng Ding

    2015-06-01

    Full Text Available This paper presents a rigorous design and optimization of an axial flux microelectromechanical systems (MEMS brushless dc (BLDC micromotor with dual rotor improving both efficiency and power density with an external diameter of only around 10 mm. The stator is made of two layers of windings by MEMS technology. The rotor is developed by film permanent magnets assembled over the rotor yoke. The characteristics of the MEMS micromotor are analyzed and modeled through a 3-D magnetic equivalent circuit (MEC taking the leakage flux and fringing effect into account. Such a model yields a relatively accurate prediction of the flux in the air gap, back electromotive force (EMF and electromagnetic torque, whilst being computationally efficient. Based on 3-D MEC model the multi-objective firefly algorithm (MOFA is developed for the optimal design of this special machine. Both 3-D finite element (FE simulation and experiments are employed to validate the MEC model and MOFA optimization design.

  16. Multi-harmonic approach to determine load dependent local flux variations in power transformer cores

    Directory of Open Access Journals (Sweden)

    Riemer Björn

    2015-03-01

    Full Text Available This paper presents a methodology for the calculation of the flux distribution in power transformer cores considering nonlinear material, with reduced computational effort. The calculation is based on a weak coupled multi-harmonic approach. The methodology can be applied to 2D and 3D Finite Element models. The decrease of the computational effort for the proposed approach is >90% compared to a time-stepping method at comparable accuracy. Furthermore, the approach offers a possibility for parallelisation to reduce the overall simulation time. The speed up of the parallelised simulations is nearly linear. The methodology is applied to a single-phase and a three-phase power transformer. Exemplary, the flux distribution for a capacitive load case is determined and the differences in the flux distribution obtained by a 2D and 3D FE model are pointed out. Deviations are significant, due to the fact, that the 2D FE model underestimates the stray fluxes. It is shown, that a 3D FE model of the transformer is required, if the nonlinearity of the core material has to be taken into account.

  17. The Influence of Non-Uniform High Heat Flux on Thermal Stress of Thermoelectric Power Generator

    Directory of Open Access Journals (Sweden)

    Tingzhen Ming

    2015-11-01

    Full Text Available A thermoelectric generator (TEG device which uses solar energy as heat source would achieve higher efficiency if there is a higher temperature difference between the hot-cold ends. However, higher temperature or higher heat flux being imposed upon the hot end will cause strong thermal stress, which will have a negative influence on the life cycle of the thermoelectric module. Meanwhile, in order to get high heat flux, a Fresnel lens is required to concentrate solar energy, which will cause non-uniformity of heat flux on the hot end of the TEG and further influence the thermal stress of the device. This phenomenon is very common in solar TEG devices but seldom research work has been reported. In this paper, numerical analysis on the heat transfer and thermal stress performance of a TEG module has been performed considering the variation on the power of the heat flux being imposed upon the hot-end; the influence of non-uniform high heat flux on thermal stress has also been analyzed. It is found that non-uniformity of high heat flux being imposed upon the hot end has a significant effect on the thermal stress of TEG and life expectation of the device. Taking the uniformity of 100% as standard, when the heating uniformity is 70%, 50%, 30%, and 10%, respectively, the maximum thermal stress of TEG module increased by 3%, 6%, 12%, and 22% respectively. If we increase the heat flux on the hot end, the influence of non-uniformity on the thermal stress will be more remarkable.

  18. Understanding narrow SOL power flux component in COMPASS limiter plasmas by use of Langmuir probes

    Energy Technology Data Exchange (ETDEWEB)

    Dejarnac, R., E-mail: dejarnac@ipp.cas.cz [Institute of Plasma Physics, ASCR, Za Slovankou 3, 182 00 Prague (Czech Republic); Stangeby, P.C. [University of Toronto, Institute for Aerospace Studies, 4925 Dufferin St., Toronto M3H 5T6 (Canada); Goldston, R.J. [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States); Gauthier, E. [CEA, IRFM, F-13108 St Paul-lez-Durance (France); Horacek, J.; Hron, M. [Institute of Plasma Physics, ASCR, Za Slovankou 3, 182 00 Prague (Czech Republic); Kocan, M. [ITER Organisation, Route de Vinon-sur-Verdon, CS 90 046, F-13067 St Paul-lez-Durance cedex (France); Komm, M.; Panek, R. [Institute of Plasma Physics, ASCR, Za Slovankou 3, 182 00 Prague (Czech Republic); Pitts, R.A. [ITER Organisation, Route de Vinon-sur-Verdon, CS 90 046, F-13067 St Paul-lez-Durance cedex (France); Vondracek, P. [Institute of Plasma Physics, ASCR, Za Slovankou 3, 182 00 Prague (Czech Republic)

    2015-08-15

    The narrow scrape-off layer power component observed in COMPASS inner wall limiter circular discharges by means of IR thermography is investigated by Langmuir probes embedded in the limiter. The power flux profiles are in good agreement with IR observations and can be described by a double-exponential decay with a short decay length (<5 mm) just outside the separatrix and a longer one (∼50 mm) for the rest of the profile in the main scrape-off layer. Non-ambipolar currents measured at the limiter apex play a relatively modest role in the formation of the narrow component. The fraction of the deposited power due to non-ambipolarity varies between 2% and 45%. On the other hand, the measured power widths are roughly consistent in magnitude with a model that takes into account drift effects, suggesting these effects may be dominant.

  19. LOW-POWER SOLUTION FOR EDDY COVARIANCE MEASUREMENTS OF METHANE FLUX

    Science.gov (United States)

    Anderson, T.; Burba, G. G.; Komissarov, A.; McDermitt, D. K.; Xu, L.; Zona, D.; Oechel, W. C.; Schedlbauer, J. L.; Oberbauer, S. F.; Riensche, B.; Allyn, D.

    2009-12-01

    Open-path analyzers offer a number of advantages for measuring methane fluxes, including undisturbed in-situ flux measurements, spatial integration using the Eddy Covariance approach, zero frequency response errors due to tube attenuation, confident water and thermal density terms from co-located fast measurements of water and sonic temperature, and possibility of remote and mobile solar-powered or small-generator-powered deployments due to lower power demands in the absence of a pump. The LI-7700 open-path methane analyzer is a VCSEL (vertical-cavity surface-emitting laser)-based instrument. It employs an open Herriott cell and measures levels of methane with RMS noise below 5 ppb at 10 Hz sampling in controlled laboratory conditions. The power consumption of the stand-alone LI-7700 in steady-state is about 8W, so it can be deployed in any methane-generating location of interest on a portable or mobile solar-powered tower, and it does not have to have grid power or permanent industrial generator. Eddy Covariance measurements of methane flux using the LI-7700 open-path methane analyzer were conducted in 2006-2009 in five ecosystems with contrasting weather and moisture conditions: (1) sawgrass wetland in the Florida Everglades; (2) coastal wetlands in an Arctic tundra; and (3) pacific mangroves in Mexico; (4) maize field and (5) ryegrass field in Nebraska. Methane co-spectra behaved in a manner similar to that of the co-spectra of carbon dioxide, water vapor, and air temperature, demonstrating that the LI-7700 adequately measured fluctuations in methane concentration across the whole spectrum of frequencies contributing to vertical atmospheric turbulent transport at the experimental sites. All co-spectra also closely followed the Kaimal model, and demonstrated good agreement with another methane co-spectrum obtained with a TDLS (Tunable Diode Laser Spectroscope; Unisearch Associates, Inc.) over a peatland. Overall, hourly methane fluxes ranged from near-zero at

  20. The Influence of Filaments in the Private Flux Region on Divertor Particle and Power Deposition

    CERN Document Server

    Harrison, J R; Thornton, A J; Walkden, N R

    2015-01-01

    The transport of particles via intermittent filamentary structures in the private flux region of plasmas in the MAST tokamak has been investigated using a fast framing camera recording visible light emission from the volume of the lower divertor, as well as Langmuir probes and IR thermography monitoring particle and power fluxes to plasma-facing surfaces in the divertor. The visible camera data suggests that, in the divertor volume, fluctuations in light emission above the X-point are strongest in the scrape-off layer (SOL). Conversely, in the region below the X-point, it is found that these fluctuations are strongest in the private flux region (PFR) of the inner divertor leg. Detailed analysis of the appearance of these filaments in the camera data suggests that they are approximately circular, around 1-2cm in diameter. The most probable toroidal mode number is between 2 and 3. These filaments eject plasma deeper into the private flux region, sometimes by the production of secondary filaments, moving at a sp...

  1. More power and less loads in wind farms. 'Heat and flux'

    Energy Technology Data Exchange (ETDEWEB)

    Corten, G.P.; Schaak, P. [ECN Wind Energy, Petten (Netherlands)

    2004-11-01

    We consider a farm as a single energy extracting body instead of a superposition of individual energy extractors, i.e. wind turbines. As a result we found two new hypotheses called Heat and Flux. Both hypotheses reveal that the classical operation of turbines in a wind farm at the Lanchester-Betz optimum does not lead to maximum farm output. However, when the turbines at the windward side of the farm are operated below their optimum, then the power of the turbines under the lee increases in such a way that the net farm production increases slightly. Next to this production advantage of Heat and Flux operation there is also a loading advantage. The average axial loading of the upwind turbines of a farm is reduced in a 'Heat and Flux'-farm. As a result those turbines generate less turbines so that the fatigue loads of the downwind turbines reduce too. The results were confirmed by in a boundary layer tunnel by means of differential measurements between a 'Heat and Flux'-farm and a classical farm.

  2. A Vertical Flux-Switching Permanent Magnet Based Oscillating Wave Power Generator with Energy Storage

    Directory of Open Access Journals (Sweden)

    Yu Zou

    2017-06-01

    Full Text Available In this paper, an effective low-speed oscillating wave power generator and its energy storage system have been proposed. A vertical flux-switching permanent magnet (PM machine is designed as the generator while supercapacitors and batteries are used to store the energy. First, the overall power generation system is established and principles of the machine are introduced. Second, three modes are proposed for the energy storage system and sliding mode control (SMC is employed to regulate the voltage of the direct current (DC bus, observe the mechanical input, and feedback the status of the storage system. Finally, experiments with load and sinusoidal mechanical inputs are carried out to validate the effectiveness and stability of power generation for wave energy. The results show that the proposed power generation system can be employed in low-speed environment around 1 m/s to absorb random wave power, achieving over 60% power efficiency. The power generation approach can be used to capture wave energy in the future.

  3. The button effect of CANFLEX bundle on the critical heat flux and critical channel power

    Energy Technology Data Exchange (ETDEWEB)

    Park, Joo Hwan; Jun, Jisu; Suk, Ho Chun [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of); Dimmick, G. R.; Bullock, D. E.; Inch, W. [Atomic Energy of Canada Limited, Ontario (Canada)

    1997-12-31

    A CANFLEX (CANdu FLEXible fuelling) 43-element bundle has developed for a CANDU-6 reactor as an alternative of 37-element fuel bundle. The design has two diameter elements (11.5 and 13.5 mm) to reduce maximum element power rating and buttons to enhance the critical heat flux (CHF), compared with the standard 37-element bundle. The freon CHF experiments have performed for two series of CANFLEX bundles with and without buttons with a modelling fluid as refrigerant R-134a and axial uniform heat flux condition. Evaluating the effects of buttons of CANFLEX bundle on CHF and Critical Channel Power (CCP) with the experimental results, it is shown that the buttons enhance CCP as well as CHF. All the CHF`s for both the CANFLEX bundles are occurred at the end of fuel channel with the high dryout quality conditions. The CHF enhancement ratio are increased with increase of dryout quality for all flow conditions and also with increase of mass flux only for high pressure conditions. It indicates that the button is a useful design for CANDU operating condition because most CHF flow conditions for CANDU fuel bundle are ranged to high dryout quality conditions. 5 refs., 11 figs. (Author)

  4. New method of the polymeric material properties experimental investigation under powerful energy flux impact

    Science.gov (United States)

    Demidov, B. A.; Efremov, V. P.; Kalinin, Yu G.; Kazakov, E. D.; Metelkin, S. Yu; Petrov, V. A.; Potapenko, A. I.

    2015-11-01

    Investigation of the polymeric material properties under powerfull energy flux impact is relevant as for basic research (mathematical modeling of polymeric materials behavior in extreme conditions, testing the state equations), as for practical applications (for testing of protective coatings for space research and laboratory facilities). This paper presents the results of experimental studies of the interaction of polymeric materials with a relativistic electron beam produced by a high-current electron accelerator Calamary. Calamary facility provides a wide range of electron beam parameters: diameter 10-15 mm, the voltage on the diode up to 300 kV, the current through the diode up to 30 kA. New method of beam-target interaction area measurement was developed. The original method for the mechanical kick impulse measuring based on piezoelectric vibration sensor was presented. The dependence of the kick impulse from the power flux was obtained.

  5. High-flux solar absorber concept for central receiver power plants

    Science.gov (United States)

    Pomeroy, B. D.; Roberts, J. M.; Narayanan, T. V.

    1981-02-01

    For cylindrical receivers with a capacity of about 400 MW/t, an aim-at-the belt focusing strategy can produce average fluxes the order of 0.5 MW/sq m with peaks as high as 2 MW/sq m. An absorber concept is described which uses liquid sodium coolant and a three-header configuration to efficiently capture this solar power. The mechanical design of this absorber is discussed and thermal performance estimates are presented showing the solar-capture efficiency over a range of solar intensities. The sodium-flow characteristics and some potential flow-control problems are also described. A thermal-stress analysis is presented which shows that a limiting factor on the flux capability may be tube-wall creep/fatigue failure and not the heat-transfer capability of sodium.

  6. Ground heat flux and power sources of low-enthalpy geothermal systems

    Science.gov (United States)

    Bayer, Peter; Blum, Philipp; Rivera, Jaime A.

    2015-04-01

    Geothermal heat pumps commonly extract energy from the shallow ground at depths as low as approximately 400 m. Vertical borehole heat exchangers are often applied, which are seasonally operated for decades. During this lifetime, thermal anomalies are induced in the ground and surface-near aquifers, which often grow over the years and which alleviate the overall performance of the geothermal system. As basis for prediction and control of the evolving energy imbalance in the ground, focus is typically set on the ground temperatures. This is reflected in regulative temperature thresholds, and in temperature trends, which serve as indicators for renewability and sustainability. In our work, we examine the fundamental heat flux and power sources, as well as their temporal and spatial variability during geothermal heat pump operation. The underlying rationale is that for control of ground temperature evolution, knowledge of the primary heat sources is fundamental. This insight is also important to judge the validity of simplified modelling frameworks. For instance, we reveal that vertical heat flux from the surface dominates the basal heat flux towards a borehole. Both fluxes need to be accounted for as proper vertical boundary conditions in the model. Additionally, the role of horizontal groundwater advection is inspected. Moreover, by adopting the ground energy deficit and long-term replenishment as criteria for system sustainability, an uncommon perspective is adopted that is based on the primary parameter rather than induced local temperatures. In our synthetic study and dimensionless analysis, we demonstrate that time of ground energy recovery after system shutdown may be longer than what is expected from local temperature trends. In contrast, unrealistically long recovery periods and extreme thermal anomalies are predicted without account for vertical ground heat fluxes and only when the energy content of the geothermal reservoir is considered.

  7. EXPERIMENTAL DETERMINATION OF LONGITUDINAL COMPONENT OF MAGNETIC FLUX IN FERROMAGNETIC WIRE OF SINGLE-CORE POWER CABLE ARMOUR

    Directory of Open Access Journals (Sweden)

    I.A. Kostiukov

    2014-12-01

    Full Text Available A problem of determination of effective longitudinal magnetic permeability of single core power cable armour is defined. A technique for experimental determination of longitudinal component of magnetic flux in armour spiral ferromagnetic wire is proposed.

  8. On the power-law distributions of X-ray fluxes from solar flares observed with GOES

    Science.gov (United States)

    Li, You-Ping; Feng, Li; Zhang, Ping; Liu, Si-Ming; Gan, Wei-Qun

    2016-10-01

    The power-law frequency distributions of the peak flux of solar flare X-ray emission have been studied extensively and attributed to a system having self-organized criticality (SOC). In this paper, we first show that, so long as the shape of the normalized light curve is not correlated with the peak flux, the flux histogram of solar flares also follows a power-law distribution with the same spectral index as the power-law frequency distribution of the peak flux, which may partially explain why power-law distributions are ubiquitous in the Universe. We then show that the spectral indexes of the histograms of soft X-ray fluxes observed by GOES satellites in two different energy channels are different: the higher energy channel has a harder distribution than the lower energy channel, which challenges the universal power-law distribution predicted by SOC models and implies a very soft distribution of thermal energy content of plasmas probed by the GOES satellites. The temperature (T) distribution, on the other hand, approaches a power-law distribution with an index of 2 for high values of T. Hence the application of SOC models to the statistical properties of solar flares needs to be revisited.

  9. On the Power-Law Distributions of X-ray Fluxes from Solar Flares Observed with GOES

    CERN Document Server

    Li, You-ping; Zhang, Ping; Liu, Siming; Gan, Weiqun

    2016-01-01

    Power-law frequency distributions of the peak flux of solar flare X-ray emission have been studied extensively and attributed to a system of self-organized criticality (SOC). In this paper, we first show that, so long as the shape of the normalized light curve is not correlated with the peak flux, the flux histogram of solar flares also follows a power-law distribution with the same spectral index as the power-law frequency distribution of the peak flux, which may partially explain why power-law distributions are ubiquitous in the Universe. We then show that the spectral indexes of the histograms of soft X-ray fluxes observed by GOES satellites in two different energy channels are different: the higher energy channel has a harder distribution than the lower energy channel, which challenges the universal power-law distribution predicted by SOC models and implies a very soft distribution of thermal energy content of plasmas probed by the GOES. The temperature ($T$) distribution, on the other hand, approaches a ...

  10. Implementing and diagnosing magnetic flux compression on the Z pulsed power accelerator

    Energy Technology Data Exchange (ETDEWEB)

    McBride, Ryan D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bliss, David E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Gomez, Matthew R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hansen, Stephanie B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Martin, Matthew R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jennings, Christopher Ashley [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Slutz, Stephen A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Rovang, Dean C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Knapp, Patrick F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Schmit, Paul F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Awe, Thomas James [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hess, M. H. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lemke, Raymond W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Dolan, D. H. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lamppa, Derek C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jobe, Marc Ronald Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Fang, Lu [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hahn, Kelly D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Chandler, Gordon A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Cooper, Gary Wayne [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ruiz, Carlos L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Maurer, A. J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Robertson, Grafton Kincannon [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Cuneo, Michael E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sinars, Daniel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Tomlinson, Kurt [General Atomics, San Diego, CA (United States); Smith, Gary [General Atomics, San Diego, CA (United States); Paguio, Reny [General Atomics, San Diego, CA (United States); Intrator, Tom [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Weber, Thomas [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Greenly, John [Cornell Univ., Ithaca, NY (United States)

    2015-11-01

    We report on the progress made to date for a Laboratory Directed Research and Development (LDRD) project aimed at diagnosing magnetic flux compression on the Z pulsed-power accelerator (0-20 MA in 100 ns). Each experiment consisted of an initially solid Be or Al liner (cylindrical tube), which was imploded using the Z accelerator's drive current (0-20 MA in 100 ns). The imploding liner compresses a 10-T axial seed field, B z ( 0 ) , supplied by an independently driven Helmholtz coil pair. Assuming perfect flux conservation, the axial field amplification should be well described by B z ( t ) = B z ( 0 ) x [ R ( 0 ) / R ( t )] 2 , where R is the liner's inner surface radius. With perfect flux conservation, B z ( t ) and dB z / dt values exceeding 10 4 T and 10 12 T/s, respectively, are expected. These large values, the diminishing liner volume, and the harsh environment on Z, make it particularly challenging to measure these fields. We report on our latest efforts to do so using three primary techniques: (1) micro B-dot probes to measure the fringe fields associated with flux compression, (2) streaked visible Zeeman absorption spectroscopy, and (3) fiber-based Faraday rotation. We also mention two new techniques that make use of the neutron diagnostics suite on Z. These techniques were not developed under this LDRD, but they could influence how we prioritize our efforts to diagnose magnetic flux compression on Z in the future. The first technique is based on the yield ratio of secondary DT to primary DD reactions. The second technique makes use of the secondary DT neutron time-of-flight energy spectra. Both of these techniques have been used successfully to infer the degree of magnetization at stagnation in fully integrated Magnetized Liner Inertial Fusion (MagLIF) experiments on Z [P. F. Schmit et al. , Phys. Rev. Lett. 113 , 155004 (2014); P. F. Knapp et al. , Phys. Plasmas, 22 , 056312 (2015)]. Finally, we present some recent developments for designing

  11. Experimental research of the interference and phase structure of the power flux from a local source in shallow water

    Science.gov (United States)

    Belova, N. I.; Kuznetsov, G. N.; Stepanov, A. N.

    2016-05-01

    The paper studies the interference structure of low-frequency tonal and wideband signals in shallow water, received by four-component vector-scalar modules. The spatial amplitudes and phase characteristics of the scalar field are analyzed, as well as three components of the vibration velocity vector and the power flux vector. A relationship is established between the zone of interference maxima and minima and the phase gradient in the horizontal and vertical plane, the change in direction of the vertical and horizontal components of the vibration velocity vector, and the change in the depression angle of the power flux vector in the horizontal plane.

  12. Eddy Covariance Measurements of Methane Flux at Remote Sites with New Low-Power Lightweight Fast Gas Analyzer

    Science.gov (United States)

    Xu, Liukang; Burba, George; Schedlbauer, Jessica; Zona, Donatella; McDermitt, Dayle K.; Anderson, Tyler; Oberbauer, Steven; Oechel, Walter; Komissarov, Anatoly; Riensche, Brad

    2010-05-01

    Majority of natural methane production happens at remote unpopulated areas in ecosystems with little or no infrastructure or easily available grid power, such as arctic and boreal wetlands, tropical mangroves, etc. Present approaches for direct measurements of CH4 fluxes rely on fast closed-path analyzers, which have to work under significantly reduced pressures, and require powerful pumps and grid power. Power and labor demands may be reasons why CH4 flux is often measured at locations with good infrastructure and grid power, and not with high CH4 production. An instrument was developed to allow Eddy Covariance measurements of CH4 flux with power consumption 30-150 times below presently available technologies. This instrument, LI-7700, uses mangroves near La Paz (Mexico) using portable generator, and in bare agricultural field near Mead (Nebraska, USA) during 2005 through 2010. Latest data on CH4 concentration, co-spectra and fluxes, and latest details of instrumental design are examined in this presentation. Overall, hourly methane fluxes ranged from near-zero at night to about 4 mg m-2 h-1 in midday in arctic tundra. Observed fluxes were within the ranges reported in the literature for a number of wetlands in North America, including the Everglades wetlands. Diurnal patterns were similar to those measured by closed-path sensors. The LI-7700 open-path analyzer is a valuable tool for measuring long-term eddy fluxes of methane due to the good frequency response and undisturbed in-situ sampling. It enables long-term deployment of permanent, portable or mobile CH4 flux stations at remote locations with high CH4 production, because it can be powered by a solar panels or a small generator. Authors appreciate help and support provided by the LI-COR Engineering Team, Barrow Arctic Science Consortium (BASC), and numerous colleagues involved in measurements, logistics, and maintenance of the experimental field sites. This project was supported by the Small Business

  13. Linear magnetic motor/generator. [to generate electric energy using magnetic flux for spacecraft power supply

    Science.gov (United States)

    Studer, P. A. (Inventor)

    1982-01-01

    A linear magnetic motor/generator is disclosed which uses magnetic flux to provide mechanical motion or electrical energy. The linear magnetic motor/generator includes an axially movable actuator mechanism. A permament magnet mechanism defines a first magnetic flux path which passes through a first end portion of the actuator mechanism. Another permament magnet mechanism defines a second magnetic flux path which passes through a second end portion of the actuator mechanism. A drive coil defines a third magnetic flux path passing through a third central portion of the actuator mechanism. A drive coil selectively adds magnetic flux to and subtracts magnetic flux from magnetic flux flowing in the first and second magnetic flux path.

  14. Elementary Flux Mode Analysis Revealed Cyclization Pathway as a Powerful Way for NADPH Regeneration of Central Carbon Metabolism.

    Directory of Open Access Journals (Sweden)

    Bin Rui

    Full Text Available NADPH regeneration capacity is attracting growing research attention due to its important role in resisting oxidative stress. Besides, NADPH availability has been regarded as a limiting factor in production of industrially valuable compounds. The central carbon metabolism carries the carbon skeleton flux supporting the operation of NADPH-regenerating enzyme and offers flexibility in coping with NADPH demand for varied intracellular environment. To acquire an insightful understanding of its NADPH regeneration capacity, the elementary mode method was employed to compute all elementary flux modes (EFMs of a network representative of central carbon metabolism. Based on the metabolic flux distributions of these modes, a cluster analysis of EFMs with high NADPH regeneration rate was conducted using the self-organizing map clustering algorithm. The clustering results were used to study the relationship between the flux of total NADPH regeneration and the flux in each NADPH producing enzyme. The results identified several reaction combinations supporting high NADPH regeneration, which are proven to be feasible in cells via thermodynamic analysis and coincident with a great deal of previous experimental report. Meanwhile, the reaction combinations showed some common characteristics: there were one or two decarboxylation oxidation reactions in the combinations that produced NADPH and the combination constitution included certain gluconeogenesis pathways. These findings suggested cyclization pathways as a powerful way for NADPH regeneration capacity of bacterial central carbon metabolism.

  15. Exploring 21cm-Lyman Alpha Emitter Synergies for SKA

    Science.gov (United States)

    Hutter, Anne; Dayal, Pratika; Müller, Volker; Trott, Cathryn M.

    2017-02-01

    We study the signatures of reionization and ionizing properties of early galaxies in the cross-correlations between the 21 cm emission from the spin-flip transition of neutral hydrogen (H i) and the underlying galaxy population. In particular, we focus on a sub-population of galaxies visible as Lyα Emitters (LAEs). With both observables simultaneously derived from a z≃ 6.6 hydrodynamical simulation (GADGET-2) snapshot post-processed with a radiative transfer code (pCRASH) and a dust model, we perform a parameter study and aim to constrain both the average intergalactic medium (IGM) ionization state (1- ) and the reionization topology (outside-in versus inside-out). We find that, in our model, LAEs occupy the densest and most-ionized regions resulting in a very strong anti-correlation between the LAEs and the 21 cm emission. A 1000 hr Square Kilometer Array (SKA)-LOW1—Subaru Hyper Suprime-Cam experiment can provide constraints on , allowing us to distinguish between IGM ionization levels of 50%, 25%, 10%, and fully ionized at scales r≲ 10 comoving Mpc (assuming foreground avoidance for SKA). Our results support the inside-out reionization scenario where the densest knots (under-dense voids) are ionized first (last) for ≳ 0.1. Further, 1000 hr SKA-LOW1 observations should be able to confirm the inside-out scenario by detecting a lower 21 cm brightness temperature (by about 2–10 mK) in the densest regions (≳2 arcmin scales) hosting LAEs, compared to lower-density regions devoid of them.

  16. Jovian Equatorial H Lyman-alpha and the Ionosphere

    Science.gov (United States)

    Ballester, Gilda E.

    An excess of H Ly alpha emission has been a persistent feature in Jupiter's equatorial upper atmosphere since its discovery in 1978. This Ly alpha 'bulge' was found by high-resolution IUE observations to be due to broadening of the Jovian line increasing the resonant scattering of the solar Ly alpha, rather than from a local enhancement in the H density. The line broadening implies that the H column at the bulge is disturbed by a localized, non-thermal process, and two mechanisms have been proposed to explain this: one by the generation of turbulence from strong thermospheric winds or jets meeting at the bulge region and originating in the active Jovian auroral zones, the other involving a superthermal population of H atoms produced by a process analogous to the equatorial anomaly and tropical arcs on the Earth. Some line broadening was also observed in the off-bulge region while modelling of the usual bulge profile does not predict this behavior, but these observations may have been performed at a time of an unusually large extension of the bulge. We propose to make a series of high-dispersion observations (of improved S/N) for a detailed longitudinal study of the line profile which would be of benefit independently of the particular bulge conditions (to be determined with low-dispersion exposures). In addition, new insight will be gained with simultaneous ground-based observations of the newly discovered global ionospheric H3+ emissions. These emissions are diagnostic of the ionospheric temperature and ion density, and have already shown very particular characteristics in the H Ly alpha bulge region. Coordinated observations of the whole longitudinal range should therefore set new constraints on the mechanisms operating in the Jovian equatorial upper atmosphere.

  17. Lyman-alpha Damping Wing Constraints on Inhomogeneous Reionization

    CERN Document Server

    Mesinger, Andrei

    2007-01-01

    One well-known way to constrain the hydrogen neutral fraction, x_H, of the high-redshift intergalactic medium (IGM) is through the shape of the red damping wing of the Lya absorption line. We examine this method's effectiveness in light of recent models showing that the IGM neutral fraction is highly inhomogeneous on large scales during reionization. Using both analytic models and "semi-numeric" simulations, we show that the "picket-fence" absorption typical in reionization models introduces both scatter and a systematic bias to the measurement of x_H. In particular, we show that simple fits to the damping wing tend to overestimate the true neutral fraction in a partially ionized universe, with a fractional error of ~ 30% near the middle of reionization. This bias is generic to any inhomogeneous model. However, the bias is reduced and can even underestimate x_H if the observational sample only probes a subset of the entire halo population, such as quasars with large HII regions. We also find that the damping ...

  18. The Gunn-Peterson effect and the Lyman $\\alpha$ forest

    CERN Document Server

    Levshakov, S A

    1997-01-01

    We show that spatial correlations in a stochastic large scale velocity field in an otherwise smooth intergalactic medium (homogeneous comoving density) superposed on the general Hubble flow, may cause a `line-like' structure in QSO spectra similar to the population of unsaturated Ly-alpha forest lines which usually are attributed to individual clouds with 10^{11} <= N(HI) <= 5*10^{13} cm^{-2}. Therefore there is no clear observational distinction between a diffuse intergalactic medium and discrete intergalactic clouds. It follows that the HI-density in the diffuse intergalactic medium might be substantially underestimated if it is determined from the observed intensity distribution near the apparent continuum in high resolution spectra of QSOs. Our tentative estimate implies a diffuse neutral hydrogen opacity tau_{GP} = 0.3 at z = 3 and a current baryon density Omega_{IGM} = 0.08$, assuming a Hubble constant H = 70 km s^{-1} Mpc^{-1}.

  19. Oxygen sensitivity of krypton and Lyman-alpha hygrometers

    NARCIS (Netherlands)

    Dijk, van A.; Kohsiek, W.; Bruin, de H.A.R.

    2003-01-01

    The oxygen sensitivity of krypton and Lyman-¿ hygrometers is studied. Using a dewpoint generator and a controlled nitrogen/oxygen flow the extinction coefficients of five hygrometers associated with the third-order Taylor expansion of the Lambert¿Beer law around reference conditions for oxygen and f

  20. Application of Backstepping to the Virtual Flux Direct Power Control of Five-Level Three-Phase Shunt Active Power Filter

    Directory of Open Access Journals (Sweden)

    Bouzidi Mansour

    2014-03-01

    Full Text Available This paper proposes a virtual flux direct power control-space vector modulation combined with backstepping control for three-phase five-level neutral point clamped shunt active power filter. The main goal of the proposed active filtering system is to eliminate the unwanted harmonics and compensate fundamental reactive power drawn from the nonlinear loads. In this study, the voltage-balancing control of four split dc capacitors of the five-level active filter is achieved using five-level space vector modulation with balancing strategy based on the effective use of the redundant switching states of the inverter voltage vectors. The obtained results showed that, the proposed multilevel shunt active power filter with backstepping control can produce a sinusoidal supply current with low harmonic distortion and in phase with the line voltage.

  1. Assessment of gravity wave momentum flux measurement capabilities by meteor radars having different transmitter power and antenna configurations

    Science.gov (United States)

    Fritts, D. C.; Janches, D.; Hocking, W. K.; Mitchell, N. J.; Taylor, M. J.

    2012-05-01

    Measurement capabilities of five meteor radars are assessed and compared to determine how well radars having different transmitted power and antenna configurations perform in defining mean winds, tidal amplitudes, and gravity wave (GW) momentum fluxes. The five radars include two new-generation meteor radars on Tierra del Fuego, Argentina (53.8°S) and on King George Island in the Antarctic (62.1°S) and conventional meteor radars at Socorro, New Mexico (34.1°N, 106.9°W), Bear Lake Observatory, Utah (˜41.9°N, 111.4°W), and Yellowknife, Canada (62.5°N, 114.3°W). Our assessment employs observed meteor distributions for June of 2009, 2010, or 2011 for each radar and a set of seven test motion fields including various superpositions of mean winds, constant diurnal tides, constant and variable semidiurnal tides, and superposed GWs having various amplitudes, scales, periods, directions of propagation, momentum fluxes, and intermittencies. Radars having higher power and/or antenna patterns yielding higher meteor counts at small zenith angles perform well in defining monthly and daily mean winds, tidal amplitudes, and GW momentum fluxes, though with expected larger uncertainties in the daily estimates. Conventional radars having lower power and a single transmitting antenna are able to describe monthly mean winds and tidal amplitudes reasonably well, especially at altitudes having the highest meteor counts. They also provide reasonable estimates of GW momentum fluxes at the altitudes having the highest meteor counts; however, these estimates are subject to uncertainties of ˜20 to 50% and uncertainties rapidly become excessive at higher and lower altitudes. Estimates of all quantities degrade somewhat for more complex motion fields.

  2. High photon flux XUV and soft x-ray sources enabled by high harmonic generation of high power fiber lasers

    Science.gov (United States)

    Rothhardt, Jan; Hädrich, Steffen; Krebs, Manuel; Limpert, Jens; Tünnermann, Andreas

    2015-07-01

    This contribution reports on the recent advances in high harmonic generation (HHG) with high power femtosecond fiber lasers at high repetition rates. The capabilities of high power fiber lasers, the challenges of phase matching in the tight-focusing regime and recent experimental results will be discussed. In particular, post compressed pules as short as 30 fs, with ~150 μJ pulse energy at 0.6 MHz repetition rate have been used for efficient HHG into the XUV. Despite the tight focusing phase matching is ensured by providing the target gas with adequately high density. A conversion efficiency in excess of 10-6 at ~30 eV has been achieved in xenon gas. This resulted in more than 100μW of average power (>1013 photons per second), which represents the highest photon flux achieved by any HHG source in this spectral region so far. In addition, further pulse compression yielded few-cycle pulses at high average power that have enabled efficient soft Xray generation in neon and helium. HHG in neon provided more than 3·109 photons/s within a 1% bandwidth at 120 eV and helium allowed for HHG up to the water window spectral region beyond 283 eV. These compact sources provide highest photon flux on a table-top and will enable exciting applications such as nanometer-resolution imaging or coincidence spectroscopy in the near future.

  3. Direct measurement of magnetic flux compression on the Z pulsed-power accelerator

    Science.gov (United States)

    McBride, R. D.; Bliss, D. E.; Martin, M. R.; Jennings, C. A.; Lamppa, D. C.; Dolan, D. H.; Lemke, R. W.; Rovang, D. C.; Rochau, G. A.; Cuneo, M. E.; Sinars, D. B.; Intrator, T. P.; Weber, T. E.

    2016-10-01

    We report on the progress made to date for directly measuring magnetic flux compression on Z. Each experiment consisted of an initially solid aluminum liner (a cylindrical tube), which was imploded using Z's drive current (0-20 MA in 100 ns). The imploding liner compresses a 10-20-T axial seed field, Bz(0), supplied by an independently driven Helmholtz coil pair. Assuming perfect flux conservation, the axial field amplification should be well described by Bz(t) =Bz (0)×[R(0)/R(t)]2, where R is the liner's inner surface radius. With perfect flux conservation, Bz and dBz/dt values exceeding 104 T and 1012 T/s, respectively, are expected. These large values, the diminishing liner volume, and the harsh environment on Z, make it particularly challenging to measure these fields directly. We report on our latest efforts to do so using a fiber-optic-based Faraday rotation diagnostic, where the magneto-active portion of the sensor is made from terbium-doped optical fiber. We have now used this diagnostic to measure a flux-compressed magnetic field to over 600 T prior to the imploding liner hitting the on-axis fiber housing. This project was funded in part by Sandia's LDRD program and US DOE-NNSA contract DE-AC04-94AL85000.

  4. Strong Lensing Probabilities in a Cosmological Model with a Running Primordial Power Spectrum

    CERN Document Server

    Zhang, T J; Yang, Z L; He, X T; Zhang, Tong-Jie; Chen, Da-Ming; Yang, Zhi-Liang; He, Xiang-Tao

    2004-01-01

    The combination of the first-year Wilkinson Microwave Anisotropy Probe (WMAP) data with other finer scale cosmic microwave background (CMB) experiments (CBI and ACBAR) and two structure formation measurements (2dFGRS and Lyman $\\alpha$ forest) suggest a $\\Lambda$CDM cosmological model with a running spectral power index of primordial density fluctuations. Motivated by this new result on the index of primordial power spectrum, we present the first study on the predicted lensing probabilities of image separation in a spatially flat $\\Lambda$CDM model with a running spectral index (RSI-$\\Lambda$CDM model). It is shown that the RSI-$\\Lambda$CDM model suppress the predicted lensing probabilities on small splitting angles of less than about 4$^{''}$ compared with that of standard power-law $\\Lambda$CDM (PL-$\\Lambda$CDM) model.

  5. High Flux Central Receivers of Molten Salts for the New Generation of Commercial Stand-Alone Solar Power Plants

    Energy Technology Data Exchange (ETDEWEB)

    Lata, J. M.; Rodriguez, M.; Alvarez de Lara, M.

    2006-07-01

    Molten salt technology represents nowadays the most cost-effective technology for electricity generation for stand-alone Solar Power Plants. Although this technology can be applied to both concentrating technologies, Parabolic TROUGH and Central Receiver Systems (CRS), CRS technology can take advantages from its high concentration, allowing to work at high temperatures and therefore with a reduction in the size and cost of the storage system. The Receiver System is the door for which the energy passes from the field collector to the thermal-electric cycle; it represents, therefore, the core of the CRS System. SENER and CIEMAT are joining forces to face up the challenge of sizing and designing a molten salt Receiver of high thermal efficiency, able to operate at high fluxes without compromising its durability (at least 25 years). The advances in design and studies of different materials, to operate at high fluxes using molten salts as heat transfer fluid, will be presented hereafter. (Author)

  6. A Portable, Low-Power Analyzer and Automated Soil Flux Chamber System for Measuring Wetland GHG Emissions

    Science.gov (United States)

    Nickerson, Nick; Kim-Hak, David; McArthur, Gordon

    2017-04-01

    Preservation and restoration of wetlands has the potential to help sequester large amounts of carbon due to the naturally high primary productivity and slow turnover of stored soil carbon. However, the anoxic environmental conditions present in wetland soils are also the largest natural contributor to global methane emissions. While it is well known that wetlands are net carbon sinks over long time scales, given the high global warming potential of methane, the short-term balances between C uptake and storage and loss as CO2 and CH4 need to be carefully considered when evaluating the climate effects of land-use change. It is relatively difficult to measure methane emissions from wetlands with currently available techniques given the temporally and spatially sporadic nature of the processes involved (methanogenesis, methane oxidation, ebullition, etc.). For example, using manual soil flux chambers can often only capture a portion of either the spatial or temporal variability, and often have other disadvantages associated with soil atmosphere disturbance during deployment in these relatively compressible wetland soils. Automated chamber systems offer the advantage of collecting high-resolution time series of gaseous fluxes while reducing some human and method induced biases. Additionally, new laser-based analyzers that can be used in situ alongside automated chambers offer a greater minimum detectable flux than can be achieved using alternative methods such as Gas Chromatography. Until recently these types of automated measurements were limited to areas that had good power coverage, as laser based systems were power intensive and could not easily be supplemented with power from field-available sources such as solar. Recent advances in laser technology has reduced the power needed and made these systems less power intensive and more field portable in the process. Here we present data using an automated chamber system coupled to a portable laser based greenhouse gas

  7. Magnetic flux compression experiments on the Z pulsed-power accelerator

    Science.gov (United States)

    McBride, R. D.; Gomez, M. R.; Hansen, S. B.; Jennings, C. A.; Bliss, D. E.; Knapp, P. F.; Schmit, P. F.; Awe, T. J.; Martin, M. R.; Sinars, D. B.; Greenly, J. B.; Intrator, T. P.; Weber, T. E.

    2014-10-01

    We report on the progress made to date for diagnosing magnetic flux compression on Z. Each experiment consisted of an initially solid Be or Al liner (cylindrical tube), which was imploded using Z's drive current (0-20 MA in 100 ns). The imploding liner compresses a 10-T axial seed field, Bz(0), supplied by an independently driven Helmholtz coil pair. Assuming perfect flux conservation, the axial field amplification should be well described by Bz (t) =Bz (0) × [ R (0) / R (t) ]2 , where R is the liner's inner surface radius. With perfect flux conservation, Bz and dBz/dt values exceeding 104 T and 1012 T/s, respectively, are expected. These large values, the diminishing liner volume, and the harsh environment on Z, make it particularly challenging to measure these fields. We report our latest efforts to do so using three primary techniques: (1) micro B-dot probes, (2) streaked visible Zeeman spectroscopy, and (3) fiber-based Faraday rotation. We will also briefly highlight some recent developments using neutron diagnostics (ratio of secondary DT to primary DD neutrons and secondary DT neutron energy spectra) to assess the degree of magnetization in fully integrated magnetized liner inertial fusion (MagLIF) experiments on Z. This project was funded in part by Sandia's LDRD program and US DOE-NNSA Contract DE-AC04-94AL85000.

  8. Optimizing Power Density and Efficiency of a Double-Halbach Array Permanent-Magnet Ironless Axial-Flux Motor

    Science.gov (United States)

    Duffy, Kirsten P.

    2016-01-01

    NASA Glenn Research Center is investigating hybrid electric and turboelectric propulsion concepts for future aircraft to reduce fuel burn, emissions, and noise. Systems studies show that the weight and efficiency of the electric system components need to be improved for this concept to be feasible. This effort aims to identify design parameters that affect power density and efficiency for a double-Halbach array permanent-magnet ironless axial flux motor configuration. These parameters include both geometrical and higher-order parameters, including pole count, rotor speed, current density, and geometries of the magnets, windings, and air gap.

  9. Heat loss analysis-based design of a 12 MW wind power generator module having an HTS flux pump exciter

    Science.gov (United States)

    Sung, Hae-Jin; Go, Byeong-Soo; Jiang, Zhenan; Park, Minwon; Yu, In-Keun

    2016-11-01

    The development of an effective high-temperature superconducting (HTS) generator is currently a research focus; however, the reduction of heat loss of a large-scale HTS generator is a challenge. This study deals with a heat loss analysis-based design of a 12 MW wind power generator module having an HTS flux pump exciter. The generator module consists of an HTS rotor of the generator and an HTS flux pump exciter. The specifications of the module were described, and the detailed configuration of the module was illustrated. For the heat loss analysis of the module, the excitation loss of the flux pump exciter, eddy current loss of all of the structures in the module, radiation loss, and conduction loss of an HTS coil supporter were assessed using a 3D finite elements method program. In the case of the conduction loss, different types of the supporters were compared to find out the supporter of the lowest conduction loss in the module. The heat loss analysis results of the module were reflected in the design of the generator module and discussed in detail. The results will be applied to the design of large-scale superconducting generators for wind turbines including a cooling system.

  10. Influence of the drawbar pull over the power flux within the automotive transmissions

    Science.gov (United States)

    Truţă, M.; Marinescu, M.; Vînturiş, V.

    2016-08-01

    This paper performs an analysis of the drawbar pull influence over the power flow within the automotive transmissions. First part of the work presents a serial of theoretical approaches with respect to the analyzed elements. Second part of the paper reveals the vehicle's instrumentation to achieve the experimental data and some of the research results as well. The final part of the paper draws a series of conclusions with respect to mode the power loop's magnitude is influenced by the general drawbar pull. Last, but not least, technical solutions are introduced to decrease the power loops and contribute to the fuel savings.

  11. Fast estimation of defect profiles from the magnetic flux leakage signal based on a multi-power affine projection algorithm.

    Science.gov (United States)

    Han, Wenhua; Shen, Xiaohui; Xu, Jun; Wang, Ping; Tian, Guiyun; Wu, Zhengyang

    2014-09-04

    Magnetic flux leakage (MFL) inspection is one of the most important and sensitive nondestructive testing approaches. For online MFL inspection of a long-range railway track or oil pipeline, a fast and effective defect profile estimating method based on a multi-power affine projection algorithm (MAPA) is proposed, where the depth of a sampling point is related with not only the MFL signals before it, but also the ones after it, and all of the sampling points related to one point appear as serials or multi-power. Defect profile estimation has two steps: regulating a weight vector in an MAPA filter and estimating a defect profile with the MAPA filter. Both simulation and experimental data are used to test the performance of the proposed method. The results demonstrate that the proposed method exhibits high speed while maintaining the estimated profiles clearly close to the desired ones in a noisy environment, thereby meeting the demand of accurate online inspection.

  12. Research on the filtering characteristic of single phase series hybrid active power filter based on fundamental magnetic flux compensation

    Science.gov (United States)

    Tian, Jun; Chen, Qiaofu; Zhang, Yuqi

    2012-12-01

    In this article, the PWM inverter works as a controlled fundamental current source in the single phase series hybrid active power filter (APF) based on fundamental magnetic flux compensation (FMFC). The series transformer can exhibit the self-impedance of primary winding to harmonic current, which forces harmonic current to flow into passive power filter. With the influence of harmonic current, the voltage of primary winding of transformer is a harmonic voltage, which makes the inverter output currents have a certain harmonic component, and it degrades the filtering characteristics. On the basis of PWM inverter, the mathematical model of series hybrid APF is established, and the filtering characteristics of single phase APF are analysed in detail. Three methods are gained to improve filtering characteristics: reasonably designing the inverter output filter inductance, increasing series transformer ratio and adopting voltage feed-forward control. Experimental results show that the proposed APF has greater validity.

  13. Laminated Magnetic Materials Losses Analysis under Non-Sinusoidal Flux Waveforms in Power Electronics Systems

    CERN Document Server

    Aguglia, D

    2014-01-01

    Losses analyses of laminated magnetic materials subject to non-sinusoidal magnetic flux are presented. Comparative analyses on typical Fe-Si oriented and non-oriented grains and nanocrystalline materials are carried out considering the influence of harmonic phase shift and associated B-H minor loops. Experimental measurements are performed to illustrate the B-H characteristics behaviours. A special experimental effort is given on nanocrystalline material, where Steinmetz coefficients are experimentally identified to analyse the performances of the improved Generalized Steinmetz Equation (iGSE) when phase displaced minor loops occur. It is proven that the iGSE is efficient in predicting nanocrystalline losses versus variable phase displaced harmonics.

  14. Poynting flux in the neighborhood of a point charge in arbitrary motion and the raditive power loss

    CERN Document Server

    Singal, Ashok K

    2015-01-01

    From the electromagnetic field in the neighborhood of a "point charge" in arbitrary motion, we determine the Poynting flux across a spherical surface of vanishingly small radius surrounding the charge. We show that the radiative power loss turns out to be proportional to the scalar product of the instantaneous velocity and the first time derivative of the acceleration of the charge. It is thus shown that the Poynting flux is always nil in the neighbourhood of the charge in its instantaneous rest-frame, implying no radiation from an instantly stationary point charge. While this may seem to be in discordance with the familiar Larmor's formula where the instantaneous power radiated from a charge is proportional to the square of the acceleration, nevertheless, it is in complete conformity with the law of energy conservation. Aftr all in the instantaneous rest-frame of the accelerated charge, the charge has no kinetic energy of motion that could be lost into radiation. It is shown that the root cause of the discre...

  15. Development of self-powered neutron detectors for neutron flux monitoring in HCLL and HCPB ITER-TBM

    Energy Technology Data Exchange (ETDEWEB)

    Angelone, M., E-mail: maurizio.angelone@enea.it [Associazione ENEA-EURATOM sulla FusioneENEA C.R. Frascati, Via E. Fermi 45, 00044 Frascati (Italy); Klix, A. [Association KIT-EURATOM, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Pillon, M.; Batistoni, P. [Associazione ENEA-EURATOM sulla FusioneENEA C.R. Frascati, Via E. Fermi 45, 00044 Frascati (Italy); Fischer, U. [Association KIT-EURATOM, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Santagata, A. [ENEA C.R. Casaccia, via Anguillarese Km. 1,300, 00100 Roma (Italy)

    2014-10-15

    Highlights: •Self powered neutron detector (SPND) is attractive neutron monitor for TBM in ITER. •In hard neutron spectra (e.g. TBM) there is the need to optimize their response. •Three state-of-the-art SPNDs were tested using fast and 14 MeV neutrons. •The response of SPNDs is much lower than in thermal neutron flux. •FISPACT calculations performed to find out candidate materials in hard spectra. -- Abstract: Self powered neutron detectors (SPND) have a number of interesting properties (e.g. small dimensions, capability to operate in harsh environments, absence of external bias), so they are attractive neutron monitors for TBM in ITER. However, commercially available SPNDs are optimized for operation in a thermal nuclear reactor where the neutron spectrum is much softer than that expected in a TBM. This fact can limit the use of SPND in a TBM since the effective cross sections for the production of beta emitters are much lower in a fast neutron spectrum. This work represents the first attempt to study SPNDs as neutron flux monitors for TBM. Three state-of-the-art SPND available on the market were bought and tested using fast neutrons at TAPIRO fast neutron source of ENEA Casaccia and with 14 MeV neutrons at the Frascati neutron generator (FNG). The results clearly indicate that in fast neutron spectra, the response of SPNDs is much lower than in thermal neutron flux. Activation calculations were performed using the FISPACT code to find out possible material candidates for SPND suitable for operation in TBM neutron spectra.

  16. Preliminary benefit-cost analysis of the Fast Flux Test Facility (FFTF) power addition

    Energy Technology Data Exchange (ETDEWEB)

    Callaway, J.M.; Lezberg, A.J.; Scott, M.J.; Tawil, J.J.

    1984-07-01

    The primary objective of this report is to conduct a preliminary benefit-cost study for the proposed power addition to FFTF to determine whether the project is cost-effective. If the project is authorized, construction will begin in 1986 and end in 1991. Full power operation is scheduled to begin in 1991 and a project life of 20 years is assumed. The undiscounted cost during the construction period of the FFTF power addition is estimated to be approximately $117 million over the construction period (1984 dollars). An additional $3 million is estimated as the opportunity cost - or value of these resources in their most favorable alternative use - of surplus FFTF equipment and unused CRBR equipment, including materials for steam generator fabrication. The annual operating and maintenance cost of the project is estimated to be about $2.1 million in 1984 dollars. 20 references.

  17. A flow cytometric comparison of Indo-1 to fluo-3 and Fura Red excited with low power lasers for detecting Ca(2+) flux.

    Science.gov (United States)

    Bailey, Sheree; Macardle, Peter J

    2006-04-20

    Indo-1 and high-power water-cooled lasers have been the standard for flow cytometric based Ca(2+) flux measurements. With advances in technology and the availability of low-power air-cooled lasers, there is interest in alternative protocols. Here, we have compared Indo-1 with the combination of fluo-3 and Fura Red calcium indicator dyes using low-power air-cooled lasers as the excitation source. The reagents were examined in parallel to detect Ca(2+) flux in peripheral blood T lymphocytes and in a T lymphoblastoid cell line. Ca(2+) flux was detected with a FACSVantage SE equipped with an Omnichrome Series 74 Helium-Cadmium, or a Spectra Physics 177-G1202 Argon ion air-cooled laser. Following determination of optimal loading conditions, Ca(2+) flux was examined in response to membrane receptor stimulation or intracellular Ca(2+) mobilization. Dose dependent Ca(2+) flux to anti-CD3 and thapsigargin was detected with either Indo-1 or with fluo-3 and Fura Red. The profile of the Ca(2+) flux detected by Indo-1 or with fluo-3 and Fura Red appeared similar, with the combination of fluo-3 and Fura Red more sensitive under the particular test conditions. The results clearly demonstrated that Indo-1 could be usefully excited with a low-power air-cooled laser. The alternative use of fluo-3 and Fura Red does not require the availability of a UV capable laser and produced equivalent data.

  18. The effect of neutrinos on the matter distribution as probed by the Intergalactic Medium

    CERN Document Server

    Viel, Matteo; Springel, Volker

    2010-01-01

    We present a suite of full hydrodynamical cosmological simulations that quantitatively address the impact of neutrinos on the (mildly non-linear) spatial distribution of matter and in particular on the neutral hydrogen distribution in the Intergalactic Medium (IGM), which is responsible for the intervening Lyman-alpha absorption in quasar spectra. The free-streaming of neutrinos results in a (non-linear) scale-dependent suppression of power spectrum of the total matter distribution at scales probed by Lyman-alpha forest data which is larger than the linear theory prediction by about 25% and strongly redshift dependent. By extracting a set of realistic mock quasar spectra, we quantify the effect of neutrinos on the flux probability distribution function and flux power spectrum. The differences in the matter power spectra translate into a ~2.5% (5%) difference in the flux power spectrum for neutrino masses with Sigma m_{\

  19. Future projection of radiocesium flux to the ocean from the largest river impacted by Fukushima Daiichi Nuclear Power Plant

    Science.gov (United States)

    Adhiraga Pratama, Mochamad; Yoneda, Minoru; Shimada, Yoko; Matsui, Yasuto; Yamashiki, Yosuke

    2015-02-01

    Following the initial fall out from Fukushima Dai-ichi Nuclear Power Plant (FDNPP), a significant amount of radiocesium has been discharged from Abukuma River into the Pacific Ocean. This study attempted to numerically simulate the flux of radiocesium into Abukuma River by developing the multiple compartment model which incorporate the transport process of the radionuclide from the ground surface of the catchment area into the river, a process called wash off. The results from the model show that the sub-basins with a high percentage of forest area release the radionuclides at lower rate compared to the other sub-basins. In addition the results show that the model could predict the seasonal pattern of the observed data. Despite the overestimation observed between the modeled data and the observed data, the values of R2 obtained from 137Cs and 134Cs of 0.98 and 0.97 respectively demonstrate the accuracy of the model. Prediction of the discharge from the basin area for 100 years after the accident shows that, the flux of radiocesium into the Pacific Ocean is still relatively high with an order of magnitude of 109 bq.month-1 while the total accumulation of the discharge is 111 TBq for 137Cs and 44 TBq for 134Cs.

  20. Optical singularities and power flux in the near-field region of planar evanescent-field superlenses.

    Science.gov (United States)

    Perez-Molina, Manuel; Carretero, L; Acebal, P; Blaya, S

    2008-11-01

    We rigorously analyze the optical singularities and power flux in the near-field region of the novel superlenses reported in [Science317, 927 (2007)] For this purpose, we derive near-field expressions and a general criterion to classify the optical singularities in the vacuum, which are valid when the (s- or p-polarized) electromagnetic fields are generated by any planar field distribution with Cartesian or azimuthal symmetry. Such general results are particularized to the superlenses [Science317, 927 (2007)], for which we identify a sequence of optical vortices and saddles that arise from evanescent-field interference. While the saddles are always located around the focal region, the vortex locations depend on the source field. The features of the topological connection between vortices and saddles are also discussed.

  1. Active Power and Flux Control of a Self-Excited Induction Generator for a Variable-Speed Wind Turbine Generation

    Energy Technology Data Exchange (ETDEWEB)

    Na, Woonki; Muljadi, Eduard; Leighty, Bill; Kim, Jonghoon

    2017-05-11

    A Self-Excited Induction Generation (SEIG) for a variable speed wind turbine generation(VS-WG) is normally considered to be a good candidate for implementation in stand-alone applications such as battery charging, hydrogenation, water pumping, water purification, water desalination, and etc. In this study, we have examined a study on active power and flux control strategies for a SEIG for a variable speed wind turbine generation. The control analysis for the proposed system is carried out by using PSCAD software. In the process, we can optimize the control design of the system, thereby enhancing and expediting the control design procedure for this application. With this study, this control design for a SEIG for VS-WG can become the industry standard for analysis and development in terms of SEIG.

  2. Heat flux estimates of power balance on Proto-MPEX with IR imaging

    Science.gov (United States)

    Showers, M.; Biewer, T. M.; Caughman, J. B. O.; Donovan, D. C.; Goulding, R. H.; Rapp, J.

    2016-11-01

    The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) at Oak Ridge National Laboratory (ORNL) is a precursor linear plasma device to the Material Plasma Exposure eXperiment (MPEX), which will study plasma material interactions (PMIs) for future fusion reactors. This paper will discuss the initial steps performed towards completing a power balance on Proto-MPEX to quantify where energy is lost from the plasma, including the relevant diagnostic package implemented. Machine operating parameters that will improve Proto-MPEX's performance may be identified, increasing its PMI research capabilities.

  3. Heat flux estimates of power balance on Proto-MPEX with IR imaging

    Energy Technology Data Exchange (ETDEWEB)

    Showers, M., E-mail: mshower1@vols.utk.edu [Bredesen Center, University of Tennessee, Knoxville, Tennessee 37996 (United States); Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Biewer, T. M.; Caughman, J. B. O.; Goulding, R. H.; Rapp, J. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Donovan, D. C. [Bredesen Center, University of Tennessee, Knoxville, Tennessee 37996 (United States)

    2016-11-15

    The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) at Oak Ridge National Laboratory (ORNL) is a precursor linear plasma device to the Material Plasma Exposure eXperiment (MPEX), which will study plasma material interactions (PMIs) for future fusion reactors. This paper will discuss the initial steps performed towards completing a power balance on Proto-MPEX to quantify where energy is lost from the plasma, including the relevant diagnostic package implemented. Machine operating parameters that will improve Proto-MPEX’s performance may be identified, increasing its PMI research capabilities.

  4. Large-scale management of electric grids - Power flux control in an electric network; Gestion des reseaux electriques a grande echelle. Controle des flux de puissance d'un reseau electrique

    Energy Technology Data Exchange (ETDEWEB)

    Lalou, M. J. [EIA-FR, Fribourg (Switzerland); Affolter, J.-F. [HEIG-VD, Yverdon-les-Bains (Switzerland)

    2010-07-01

    Security of supply in electricity networks is a major industrial challenge for the future. It involves power generation, transmission and distribution altogether. Networks gradually approach saturation. This article presents an optimal real-time management method of power flux in an electricity network equipped with FACTS and phase measuring devices. FACTS have to be gradually introduced, however not earlier than in 10 years time, as the reliability of data transmission for their control is currently not high enough, considering the order of magnitude of the involved electric power.

  5. The Control of Fluxes of Electric Power in Networks by Means of Phase-switching Booster Transformers

    Directory of Open Access Journals (Sweden)

    Govorov F.P.

    2016-12-01

    Full Text Available roblems of increasing the efficiency of the operation of electrical networks based on the utilization of booster transformers (BT with electronic control, applied on the base of active elements in smart electric grids of power systems and giving the function of automatic correction of the parameters of the network, assuring the conditions of optimal common operation are studied in the paper. The mathematic model of the processes in the electric networks with booster transformer has been developed; the opportunity of control by means of the phase-switching BT for power fluxes in the networks has been established. It has been shown that for the groups of switching the windings 1-5 of BT occurs additional consumption of power from the supply network, but for the groups 7-11 its recuperation to the load network. Respectively, switching the windings of BT to the group 1-5 assures the shift of load current to the direction of lag, but in the case of switching to the group 7-11 – towards the outrunning. Wherein, for the groups of switching 10-11 and 1-2 one can observe the increasing of the voltage at the output of BT, but for the groups 7-8 and 4-5 it is decreasing. Based on the analysis of the results of research the diagram and constructive models of the transformer have been proposed. The quasi-stationary and transient regimes were investigated and the conditions of reliable operation at these the regimes have been determined. The ways for increasing the efficient common operation for the transformer and network in the case of switching the thyristors into the circuit of the primary winding of the transformer have been proposed.

  6. Fluxes of radiocaesium associated with suspended sediment in rivers impacted by the Fukushima Daiichi Nuclear Power Plant

    Science.gov (United States)

    Smith, Hugh; Blake, Will; Onda, Yuichi; Yoshimura, Kazuya; Taniguchi, Keisuke; Yamashiki, Yosuke; Matsuura, Yuki; Taylor, Alex

    2014-05-01

    The Fukushima Daiichi Nuclear Power Plant accident which followed the earthquake and tsunami on 11 March 2011 resulted in the release of Cs-134 and Cs-137 into the surrounding environment, where highly elevated levels are reported. There is considerable concern about the redistribution of these radioactive contaminants from the atmosphere to vegetation, soil and aquatic systems. Fluvial redistribution of radiocaesium may contaminate downstream areas that were subject to low fallout and deliver significant quantities of highly contaminated fine sediment to the coastal zone. This study reports on the magnitude of fluvial transfer of Cs-134 and Cs-137 through river networks located across the fallout region. Initially six nested river monitoring stations were established within the Abukuma River basin from June 2011. Subsequently, an additional 23 stations were established between October 2012 and January 2013, which included stations within the Abukuma basin as well as smaller coastal catchments north and south of the power plant. Combined, these 29 sites represent a globally-unique river monitoring network designed to quantify sediment-associated transfer of radiocaesium from headwaters to the Pacific Coast of Japan. The catchments range in area from 8 to 5,172 km2 and span a large range in spatially-averaged radiocaesium inventories. Flow and turbidity (converted to suspended sediment concentration) were measured at each station while bulk suspended sediment samples were collected at regular intervals using time-integrated samplers to allow measurement of Cs-134 and Cs-137 activity concentrations by gamma spectrometry. Preliminary monitoring data showed highly elevated but also highly variable fluxes of radiocaesium in rivers across the fallout region. High magnitude flows in response to typhoon events exported large quantities of radiocaesium. Rivers are an important and continuing source of radiocaesium input to the coastal environment and the Pacific Ocean in

  7. The final power calibration of the IPEN/MB-01 nuclear reactor for various configurations obtained from the measurements of the absolute average neutron flux

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Alexandre Fonseca Povoa da, E-mail: alexandre.povoa@mar.mil.br [Centro Tecnologico da Marinha em Sao Paulo (CTMSP), Sao Paulo, SP (Brazil); Bitelli, Ulysses d' Utra; Mura, Luiz Ernesto Credidio; Lima, Ana Cecilia de Souza; Betti, Flavio; Santos, Diogo Feliciano dos, E-mail: ubitelli@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    The use of neutron activation foils is a widely spread technique applied to obtain nuclear parameters then comparing the results with those calculated using specific methodologies and available nuclear data. By irradiation of activation foils and subsequent measurement of its induced activity, it is possible to determine the neutron flux at the position of irradiation. The power level during operation of the reactor is a parameter which is directly proportional to the average neutron flux throughout the core. The objective of this work is to gather data from irradiation of gold foils symmetrically placed along a cylindrically configured core which presents only a small excess reactivity in order to derive the power generated throughout the spatial thermal and epithermal neutron flux distribution over the core of the IPEN/MB-01 Nuclear Reactor, eventually lending to a proper calibration of its nuclear channels. The foils are fixed in a Lucite plate then irradiated with and without cadmium sheaths so as to obtain the absolute thermal and epithermal neutron flux. The correlation between the average power neutron flux resulting from the gold foils irradiation, and the average power digitally indicated by the nuclear channel number 6, allows for the calibration of the nuclear channels of the reactor. The reactor power level obtained by thermal neutron flux mapping was (74.65 ± 2.45) watts to a mean counting per seconds of 37881 cps to nuclear channel number 10 a pulse detector, and 0.719.10{sup -5} ampere to nuclear linear channel number 6 (a non-compensated ionization chamber). (author)

  8. Energy flux to substrate in high-power impulse magnetron sputtering measured by using optical low-coherence interferometry

    Science.gov (United States)

    Hattori, Katsuhiro; Ohta, Takayuki; Oda, Akinori; Kousaka, Hiroyuki; Ito, Masafumi

    2016-09-01

    The substrate during the plasma irradiation is heated by charged species, neutral species, and the heat radiation and the substrate temperature is determined by energy flux to the substrate. High-power impulse magnetron sputtering (HiPIMS) using short-pulse high-voltage promotes the ionization of sputtered atoms and realizes high density plasma. In this study, we measured the silicon substrate temperature with non-contact type substrate temperature measurement method using optical low-coherence interferometry(LCI) and elucidated the heating mechanisms of the substrate temperature in HiPIMS. The target material was Ti and the distance between the substrate and the target was 60mm. Ar is used as the sputtering gas. The pulse width was from 50 to 300 µsec, the pulse frequency was from 100 to 500Hz. Applied voltages were changed to be from -400V to -900V. Measurement accuracy of contact-type thermocouples and that of noncontact-type LCI were within 2 degree C and 0.7 degree C, respectively. The heat influx to the substrate was calculated from the temporal variation of substrate temperature base on the energy balance equation and increased with increasing applied voltage. The emission intensity of Ti ion increased with increasing applied voltage even though that of Ti atom was constant. These results suggested that main contribution of substrate heating is Ti ion bombardment.

  9. Gas-Rich Local Dwarf Star-Forming Galaxies and their connection with the Distant Universe

    CERN Document Server

    Kunth, D

    1998-01-01

    I discuss the properties of gas-rich forming galaxies. I particularly emphasize the latest results on Lyman alpha emission that are relevant to the search of distant young galaxies. The interdependance of the Lyman alpha escape with the properties of the ISM in starburst galaxies is outlined. A new model from G. Tenorio-Tagle and his collaborators explaining Lyman alpha profiles in starburst galaxies from the hydrodynamics of superbubbles powered by massive stars is presented. I stress again that since Lyman alpha is primarely a diagnostic of the ISM, it is mandatory to understand how the ISM and Lyman alpha are related to firmly relate Lyman alpha to the cosmic star-formation rate.

  10. Evaluation of radioactive cesium impact from atmospheric deposition and direct release fluxes into the North Pacific from the Fukushima Daiichi nuclear power plant

    Science.gov (United States)

    Tsubono, Takaki; Misumi, Kazuhiro; Tsumune, Daisuke; Bryan, Frank O.; Hirose, Katsumi; Aoyama, Michio

    2016-09-01

    The North Pacific distribution of 134Cs released from the Fukushima Daiichi nuclear power plant (F1NPP) has been investigated using an eddy-resolving model. We conducted simulations based on two scenarios: (1) an input flux that was a combination of atmospheric deposition and direct release from the F1NPP (combination-flux scenario) and (2) an input flux that took account only of the direct release of 134Cs (single-flux scenario). The combination-flux scenario simulation successfully reproduced the distribution of 134Cs activity observed in the surface layer from April 2011 to January 2014. The results indicate that 134Cs deposited via atmospheric deposition into the Kuroshio-Oyashio Interfrontal Zone and 134Cs directly released from F1NPP were both transported to south of the Subarctic Front around 42°N in June of 2012. The combination-flux scenario suggests that the 134Cs activities observed in the area north of 42°N in 2012 originated from atmospheric deposition and that the 134Cs activity was subducted in Central Mode Water during the winters of 2011 and 2012. We directly compared simulated and observed 134Cs activities in the surface layer at 179 points across a wide area to the east of 155°E from 2011 to 2013 to evaluate the accuracy of the two scenarios. The root-mean-square error and correlation coefficient, R, were 7.3 Bq m-3 and 0.86, respectively, for the combination-flux scenario and 13.8 Bq m-3 and 0.46, respectively, for the single-flux scenario, confirming that reproduction of the 134Cs activity in the North Pacific after the F1NPP accident requires taking both fluxes into consideration. Based on a linear least-squares regression between simulated and observed 134Cs activity, the total 134Cs flux into the North Pacific was estimated at 16.1±1.4 PBq.

  11. Massive Neutrinos and the Non-linear Matter Power Spectrum

    CERN Document Server

    Bird, Simeon; Haehnelt, Martin G

    2011-01-01

    We perform an extensive suite of N-body simulations of the matter power spectrum, incorporating massive neutrinos in the range M = 0.15-0.6 eV, probing the non-linear regime at scales k < 10 hMpc-1 at z < 3. We extend the widely used HALOFIT approximation (Smith et al. 2003) to account for the effect of massive neutrinos on the power spectrum. In the strongly non-linear regime HALOFIT systematically over-predicts the suppression due to the free-streaming of the neutrinos. The maximal discrepancy occurs at k \\sim 1hMpc-1, and is at the level of 10% of the total suppression. Most published constraints on neutrino masses based on HALOFIT are not affected, as they rely on data probing the matter power spectrum in the linear or mildly non-linear regime. However, predictions for future galaxy, Lyman-alpha forest and weak lensing surveys extending to more non-linear scales will benefit from the improved approximation to the non-linear matter power spectrum we provide. Our approximation reproduces the induced n...

  12. Lyman α emission from the first galaxies: signatures of accretion and infall in the presence of line trapping

    NARCIS (Netherlands)

    Latif, M. A.; Schleicher, Dominik R. G.; Spaans, M.; Zaroubi, S.

    2011-01-01

    The formation of the first galaxies is accompanied by large accretion flows and virialization shocks, during which the gas is shock heated to temperatures of similar to 10(4) K, leading to potentially strong fluxes in the Lyman alpha line. Indeed, a number of Lyman alpha blobs have been detected at

  13. Lyman α emission from the first galaxies: signatures of accretion and infall in the presence of line trapping

    NARCIS (Netherlands)

    Latif, M. A.; Schleicher, Dominik R. G.; Spaans, M.; Zaroubi, S.

    The formation of the first galaxies is accompanied by large accretion flows and virialization shocks, during which the gas is shock heated to temperatures of similar to 10(4) K, leading to potentially strong fluxes in the Lyman alpha line. Indeed, a number of Lyman alpha blobs have been detected at

  14. A class of flux observers for doubly-fed induction generators used in small power wind generation systems

    DEFF Research Database (Denmark)

    Lascu, C.; Boldea, I.; Blaabjerg, Frede;

    2013-01-01

    This paper investigates a family of stator and rotor flux observers for sensorless operation of doubly-fed induction generators (DFIG). Four stator flux observer topologies are described and compared. All proposed schemes use the voltage and current models connected in parallel or in series...... reference adaptive system and a PLL observer. The reference quantity is the measured rotor current, the adaptive model is a current estimator, and the adaptive quantity is the rotor position. Comparative experimental results with all observers on a 7.5 kW DFIG system are presented and discussed in the paper....... It is concluded that the observers are able to produce accurate results and are suitable for practical applications....

  15. A Modern Automatic Chamber Technique as a Powerful Tool for CH4 and CO2 Flux Monitoring

    Science.gov (United States)

    Mastepanov, M.; Christensen, T. R.; Lund, M.; Pirk, N.

    2014-12-01

    A number of similar systems were used for monitoring of CH4 and CO2 exchange by the automatic chamber method in a range of different ecosystems. The measurements were carried out in northern Sweden (mountain birch forest near Abisko, 68°N, 2004-2010), southern Sweden (forest bog near Hässleholm, 56°N, 2007-2014), northeastern Greenland (arctic fen in Zackenberg valley, 74°N, 2005-2014), southwestern Greenland (fen near Nuuk, 64°N, 2007-2014), central Svalbard (arctic fen near Longyearbyen, 78°N, 2011-2014). Those in total 37 seasons of measurements delivered not only a large amount of valuable flux data, including a few novel findings (Mastepanov et al., Nature, 2008; Mastepanov et al., Biogeosciences, 2013), but also valuable experience with implementation of the automatic chamber technique using modern analytical instruments and computer technologies. A range of high resolution CH4 analysers (DLT-100, FMA, FGGA - Los Gatos Research), CO2 analyzers (EGM-4, SBA-4 - PP Systems; Li-820 - Li-Cor Biosciences), as well as Methane Carbon Isotope Analyzer (Los Gatos Research) has shown to be suitable for precise measurements of fluxes, from as low as 0.1 mg CH4 m-1 d-1 (wintertime measurements at Zackenberg, unpublished) to as high as 2.4 g CH4 m-1 d-1 (autumn burst 2007 at Zackenberg, Mastepanov et al., Nature, 2008). Some of these instruments had to be customized to accommodate 24/7 operation in harsh arctic conditions. In this presentation we will explain some of these customizations. High frequency of concentration measurements (1 Hz in most cases) provides a unique opportunity for quality control of flux calculations; on the other hand, this enormous amount of data can be analyzed only using highly automated algorithms. A specialized software package was developed and improved through the years of measurements and data processing. This software automates the data flow from raw concentration data of different instruments and sensors and various status records

  16. Compact, Low-Profile Power Converters: Highly-Laminated, High-Saturation-Flux-Density, Magnetic Cores for On-Chip Inductors in Power Converter Applications

    Energy Technology Data Exchange (ETDEWEB)

    None

    2010-09-01

    ADEPT Project: Georgia Tech is creating compact, low-profile power adapters and power bricks using materials and tools adapted from other industries and from grid-scale power applications. Adapters and bricks convert electrical energy into useable power for many types of electronic devices, including laptop computers and mobile phones. These converters are often called wall warts because they are big, bulky, and sometimes cover up an adjacent wall socket that could be used to power another electronic device. The magnetic components traditionally used to make adapters and bricks have reached their limits; they can't be made any smaller without sacrificing performance. Georgia Tech is taking a cue from grid-scale power converters that use iron alloys as magnetic cores. These low-cost alloys can handle more power than other materials, but the iron must be stacked in insulated plates to maximize energy efficiency. In order to create compact, low-profile power adapters and bricks, these stacked iron plates must be extremely thin-only hundreds of nanometers in thickness, in fact. To make plates this thin, Georgia Tech is using manufacturing tools used in microelectromechanics and other small-scale industries.

  17. MHD Effects on Non-Newtonian Power-Law Fluid Past a Continuously Moving Porous Flat Plate with Heat Flux and Viscous Dissipation

    Science.gov (United States)

    Kishan, N.; Shashidar Reddy, B.

    2013-06-01

    The problem of a magneto-hydro dynamic flow and heat transfer to a non-Newtonian power-law fluid flow past a continuously moving flat porous plate in the presence of sucion/injection with heat flux by taking into consideration the viscous dissipation is analysed. The non-linear partial differential equations governing the flow and heat transfer are transformed into non-linear ordinary differential equations using appropriate transformations and then solved numerically by an implicit finite difference scheme. The solution is found to be dependent on various governing parameters including the magnetic field parameter M, power-law index n, suction/injection parameter ƒw, Prandtl number Pr and Eckert number Ec. A systematical study is carried out to illustrate the effects of these major parameters on the velocity profiles, temperature profile, skin friction coefficient and rate of heat transfer and the local Nusslet number.

  18. Power distribution of a co-axial dual-mechanical-port flux-switching permanent magnet machine for fuel-based extended range electric vehicles

    Science.gov (United States)

    Zhou, Lingkang; Hua, Wei; Zhang, Gan

    2017-05-01

    In this paper, power distribution between the inner and outer machines of a co-axial dual-mechanical-port flux-switching permanent magnet (CADMP-FSPM) machine is investigated for fuel-based extended range electric vehicle (ER-EV). Firstly, the topology and operation principle of the CADMP-FSPM machine are introduced, which consist of an inner FSPM machine used for high-speed, an outer FSPM machine for low-speed, and a magnetic isolation ring between them. Then, the magnetic field coupling of the inner and outer FSPM machines is analyzed with more attention paid to the optimization of the isolation ring thickness. Thirdly, the power-dimension (PD) equations of the inner and outer FSPM machines are derived, respectively, and thereafter, the PD equation of the whole CADMP-FSPM machine can be given. Finally, the PD equations are validated by finite element analysis, which supplies the guidance on the design of this type of machines.

  19. Long-term modelling of fly ash and radionuclide emissions as well as deposition fluxes due to the operation of large oil shale-fired power plants.

    Science.gov (United States)

    Vaasma, Taavi; Kaasik, Marko; Loosaar, Jüri; Kiisk, Madis; Tkaczyk, Alan H

    2017-09-11

    Two of the world's largest oil shale-fired power plants (PPs) in Estonia have been operational over 40 years, emitting various pollutants, such as fly ash, SOx, NOx, heavy metals, volatile organic compounds as well as radionuclides to the environment. The emissions from these PPs have varied significantly during this period, with the maximum during the 1970s and 1980s. The oil shale burned in the PPs contains naturally occurring radionuclides from the (238)U and (232)Th decay series as well as (40)K. These radionuclides become enriched in fly ash fractions (up to 10 times), especially in the fine fly ash escaping the purification system. Using a validated Gaussian-plume model, atmospheric dispersion modelling was carried out to determine the quantity and a real magnitude of fly ash and radionuclide deposition fluxes during different decades. The maximum deposition fluxes of volatile radionuclides ((210)Pb and (210)Po) were around 70 mBq m(-2) d(-1) nearby the PPs during 1970s and 1980s. Due to the reduction of burned oil shale and significant renovations done on the PPs, the deposition fluxes were reduced to 10 mBq m(-2) d(-1) in the 2000s and down to 1.5 mBq m(-2) d(-1) in 2015. The maximum deposition occurs within couple of kilometers of the PPs, but the impacted area extends to over 50 km from the sources. For many radionuclides, including (210)Po, the PPs have been larger contributors of radionuclides to the environment via atmospheric pathway than natural sources. This is the first time that the emissions and deposition fluxes of radionuclides from the PPs have been quantified, providing the information about their radionuclide deposition load on the surrounding environment during various time periods. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Procedure of calculation of the spatial distribution of temperatures and heat fluxes in the steam generator of a nuclear power installation with an RBEC fast-neutron reactor

    Science.gov (United States)

    Frolov, A. A.; Sedov, A. A.

    2016-08-01

    A method for combined 3D/1D-modeling of thermohydraulics of a once-through steam generator (SG) based on the joint analysis of three-dimensional thermo- and hydrodynamics of a single-phase heating coolant in the intertube space and one-dimensional thermohydraulics of steam-generating channels (tubes) with the use of well-known friction and heat-transfer correlations under various boiling conditions is discussed. This method allows one to determine the spatial distribution of temperatures and heat fluxes of heat-exchange surfaces of SGs with a single-phase heating coolant in the intertube space and with steam generation within tubes. The method was applied in the analytical investigation of typical operation of a once-through SG of a nuclear power installation with an RBEC fast-neutron heavy-metal reactor that is being designed by Kurchatov Institute in collaboration with OKB GIDROPRESS and Leipunsky Institute of Physics and Power Engineering. Flow pattern and temperature fields were obtained for the heavy-metal heating coolant in the intertube space. Nonuniformities of heating of the steam-water coolant in different heat-exchange tubes and nonuniformities in the distribution of heat fluxes at SG heat-exchange surfaces were revealed.

  1. High-Energy X-Ray Detection of G359.89-0.08 (SGR A-E): Magnetic Flux Tube Emission Powered by Cosmic Rays?

    Science.gov (United States)

    Zhang, Shuo; Hailey, Charles J.; Baganoff, Frederick K.; Bauer, Franz E.; Boggs, Steven E.; Craig, William W.; Christensen, Finn E.; Gotthelf, Eric V.; Harrison, Fiona A.; Mori, Kaya; Nynka, Melania; Stern, Daniel; Tomsick, John A; Zhang, Will

    2014-01-01

    We report the first detection of high-energy X-ray (E (is) greater than 10 keV) emission from the Galactic center non-thermal filament G359.89-0.08 (Sgr A-E) using data acquired with the Nuclear Spectroscopic Telescope Array (NuSTAR). The bright filament was detected up to approximately 50 keV during a NuSTAR Galactic center monitoring campaign. The featureless power-law spectrum with a photon index gamma approximately equals 2.3 confirms a non-thermal emission mechanism. The observed flux in the 3-79 keV band is F(sub X) = (2.0 +/- 0.1) × 10(exp -12)erg cm(-2) s(-1) , corresponding to an unabsorbed X-ray luminosity L(sub X) = (2.6+/-0.8)×10(exp 34) erg s(-1) assuming a distance of 8.0 kpc. Based on theoretical predictions and observations, we conclude that Sgr A-E is unlikely to be a pulsar wind nebula (PWN) or supernova remnant-molecular cloud (SNR-MC) interaction, as previously hypothesized. Instead, the emission could be due to a magnetic flux tube which traps TeV electrons. We propose two possible TeV electron sources: old PWNe (up to (is) approximately 100 kyr) with low surface brightness and radii up to (is) approximately 30 pc or MCs illuminated by cosmic rays (CRs) from CR accelerators such as SNRs or Sgr A*.

  2. A simplified method for power-law modelling of metabolic pathways from time-course data and steady-state flux profiles

    Directory of Open Access Journals (Sweden)

    Sugimoto Masahiro

    2006-07-01

    Full Text Available Abstract Background In order to improve understanding of metabolic systems there have been attempts to construct S-system models from time courses. Conventionally, non-linear curve-fitting algorithms have been used for modelling, because of the non-linear properties of parameter estimation from time series. However, the huge iterative calculations required have hindered the development of large-scale metabolic pathway models. To solve this problem we propose a novel method involving power-law modelling of metabolic pathways from the Jacobian of the targeted system and the steady-state flux profiles by linearization of S-systems. Results The results of two case studies modelling a straight and a branched pathway, respectively, showed that our method reduced the number of unknown parameters needing to be estimated. The time-courses simulated by conventional kinetic models and those described by our method behaved similarly under a wide range of perturbations of metabolite concentrations. Conclusion The proposed method reduces calculation complexity and facilitates the construction of large-scale S-system models of metabolic pathways, realizing a practical application of reverse engineering of dynamic simulation models from the Jacobian of the targeted system and steady-state flux profiles.

  3. Influence of ionisation zone motion in high power impulse magnetron sputtering on angular ion flux and NbO$_x$ film growth

    CERN Document Server

    Franz, Robert; Kolbeck, Jonathan; Anders, André

    2016-01-01

    The ion energies and fluxes in the high power impulse magnetron sputtering plasma from a Nb target were analysed angularly resolved along the tangential direction of the racetrack. A reactive oxygen-containing atmosphere was used as such discharge conditions are typically employed for the synthesis of thin films. Asymmetries in the flux distribution of the recorded ions as well as their energies and charge states were noticed when varying the angle between mass-energy analyser and target surface. More positively charged ions with higher count rates in the medium energy range of their distributions were detected in $+\\mathbf{E}\\times \\mathbf{B}$ than in $-\\mathbf{E}\\times \\mathbf{B}$ direction, thus confirming the notion that ionisation zones are associated with moving potential humps. The motion of the recorded negatively charged high-energy oxygen ions was unaffected. NbO$_x$ thin films at different angles and positions were synthesised and analysed as to their structure and properties in order to correlate ...

  4. Joule heating effects on MHD mixed convection of a Jeffrey fluid over a stretching sheet with power law heat flux: A numerical study

    Science.gov (United States)

    Babu, D. Harish; Narayana, P. V. Satya

    2016-08-01

    An analysis has been carried out to study the Joule heating effect on MHD heat transfer of an incompressible Jeffrey fluid due to a stretching porous sheet with power law heat flux and heat source. A constant magnetic field is applied normal to the stretching surface. The basic governing equations are reduced into the coupled nonlinear ordinary differential equations by using similarity transformations. The resulting equations are then solved numerically by shooting method with fourth order Runge-Kutta scheme. The effects of various physical parameters entering into the problem on dimensionless velocity and temperature distribution are discussed through graphs and tables. The results reveal that the momentum and thermal boundary layer thickness are significantly influenced by Deborah number (β), ratio of relaxation and retardation times parameter (λ), heat generation parameter (β*), Eckert number (Ec) and magnetic field parameter (M). A comparison with the previously published works shows excellent agreement.

  5. Power distribution of a co-axial dual-mechanical-port flux-switching permanent magnet machine for fuel-based extended range electric vehicles

    Directory of Open Access Journals (Sweden)

    Lingkang Zhou

    2017-05-01

    Full Text Available In this paper, power distribution between the inner and outer machines of a co-axial dual-mechanical-port flux-switching permanent magnet (CADMP-FSPM machine is investigated for fuel-based extended range electric vehicle (ER-EV. Firstly, the topology and operation principle of the CADMP-FSPM machine are introduced, which consist of an inner FSPM machine used for high-speed, an outer FSPM machine for low-speed, and a magnetic isolation ring between them. Then, the magnetic field coupling of the inner and outer FSPM machines is analyzed with more attention paid to the optimization of the isolation ring thickness. Thirdly, the power-dimension (PD equations of the inner and outer FSPM machines are derived, respectively, and thereafter, the PD equation of the whole CADMP-FSPM machine can be given. Finally, the PD equations are validated by finite element analysis, which supplies the guidance on the design of this type of machines.

  6. Comparison between the localized power loss and flux distribution in a three phase distribution transformer 100 kVA assembled from various type of T-joint geometry with staggered yoke

    Energy Technology Data Exchange (ETDEWEB)

    Daut, I.; Ahmad, D.M.M.; Taib, S. [Univ. of Malaysia at Perlis (Malaysia). School of Electrical System Engineering

    2008-07-01

    The efficient operation of power transformer cores depends to a large degree on the design of the joints between their limbs and yokes. This study compared the performances of cores with different T-joint geometries. The cores were all built from identical grades of electrical steel, notably M5. In particular, the study investigated the variation of localized power loss and flux distribution in 3-phase transformer cores of 100 kVA. All the mesh graphs of the localized power loss from the transformer cores were measured using an iron loss tester at all four types of T-joints. The flux distribution was calculated using a computational method. The localized power loss was lower at the outer edge of the T-joint, and higher at the inner edge of the T- joint. Study results revealed that the localized power loss at transformer cores assembled with a 60 degree T-joint was less than with other types. As such, the core assembled with a 60 degree T-joint is more efficient than other T-joints. The flux lines showed that the flux penetration into the centre limb of transformer core is an important factor affecting the performance of the transformer core. 5 refs., 2 figs.

  7. High-energy X-ray detection of G359.89–0.08 (SGR A–E): Magnetic flux tube emission powered by cosmic rays?

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shuo; Hailey, Charles J.; Gotthelf, Eric V.; Mori, Kaya; Nynka, Melania [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Baganoff, Frederick K. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Bauer, Franz E. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile 306, Santiago 22 (Chile); Boggs, Steven E.; Craig, William W.; Tomsick, John A. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Christensen, Finn E. [DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Harrison, Fiona A. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Zhang, William W., E-mail: shuo@astro.columbia.edu [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2014-03-20

    We report the first detection of high-energy X-ray (E > 10 keV) emission from the Galactic center non-thermal filament G359.89–0.08 (Sgr A–E) using data acquired with the Nuclear Spectroscopic Telescope Array (NuSTAR). The bright filament was detected up to ∼50 keV during a NuSTAR Galactic center monitoring campaign. The featureless power-law spectrum with a photon index Γ ≈ 2.3 confirms a non-thermal emission mechanism. The observed flux in the 3-79 keV band is F{sub X} = (2.0 ± 0.1) × 10{sup –12} erg cm{sup –2} s{sup –1}, corresponding to an unabsorbed X-ray luminosity L{sub X} = (2.6 ± 0.8) × 10{sup 34} erg s{sup –1} assuming a distance of 8.0 kpc. Based on theoretical predictions and observations, we conclude that Sgr A–E is unlikely to be a pulsar wind nebula (PWN) or supernova remnant-molecular cloud (SNR-MC) interaction, as previously hypothesized. Instead, the emission could be due to a magnetic flux tube which traps TeV electrons. We propose two possible TeV electron sources: old PWNe (up to ∼100 kyr) with low surface brightness and radii up to ∼30 pc or MCs illuminated by cosmic rays (CRs) from CR accelerators such as SNRs or Sgr A*.

  8. Development of Correlations for Windage Power Losses Modeling in an Axial Flux Permanent Magnet Synchronous Machine with Geometrical Features of the Magnets

    Directory of Open Access Journals (Sweden)

    Alireza Rasekh

    2016-11-01

    Full Text Available In this paper, a set of correlations for the windage power losses in a 4 kW axial flux permanent magnet synchronous machine (AFPMSM is presented. In order to have an efficient machine, it is necessary to optimize the total electromagnetic and mechanical losses. Therefore, fast equations are needed to estimate the windage power losses of the machine. The geometry consists of an open rotor–stator with sixteen magnets at the periphery of the rotor with an annular opening in the entire disk. Air can flow in a channel being formed between the magnets and in a small gap region between the magnets and the stator surface. To construct the correlations, computational fluid dynamics (CFD simulations through the frozen rotor (FR method are performed at the practical ranges of the geometrical parameters, namely the gap size distance, the rotational speed of the rotor, the magnet thickness and the magnet angle. Thereafter, two categories of formulations are defined to make the windage losses dimensionless based on whether the losses are mainly due to the viscous forces or the pressure forces. At the end, the correlations can be achieved via curve fittings from the numerical data. The results reveal that the pressure forces are responsible for the windage losses for the side surfaces in the air-channel, whereas for the surfaces facing the stator surface in the gap, the viscous forces mainly contribute to the windage losses. Additionally, the results of the parametric study demonstrate that the overall windage losses in the machine escalate with an increase in either the rotational Reynolds number or the magnet thickness ratio. By contrast, the windage losses decrease once the magnet angle ratio enlarges. Moreover, it can be concluded that the proposed correlations are very useful tools in the design and optimizations of this type of electrical machine.

  9. Natural Radium Detection and Inventory Flux of Isotopes in Particulate and Dissolved Phases of Seawater at Kapar Coastal Area Caused by Coal-Fired Power Plant

    Science.gov (United States)

    Mohamed, N.; Ariffin, N. A. N.; Mohamed, C. A. R.

    2016-07-01

    Distribution of 226Ra and 228Ra radioactive in marine have been studied at Kapar coastal area that closed to Sultan Salahudin Abdul Aziz Shah (SJSSAS) power station. The concentration level of 226Ra and 228Ra were measured in seawater include total suspended solids (TSSrw) and dissolved phases from September 2006 to February 2008. The measurement technique used for 226Ra and 228Ra was using cation exchange column and counted using Liquid Scintillator Ciunter (LSC). The radioactivities of 226Rasw and 228Rasw in the dissolved phase of seawater ranged from 1.29 ± 0.52 mBq/L - 3.69 ± 1.29 mBq/L and 2.12 ± 0.71 mbq/L - 17.07 ± 6.03 mBq/L respectively. The measurement of radioactivities of radium isotopes in the particulate phase of seawater ranged from 15.62 ± 1.99 Bq/kg - 241.76 ± 100.23 Bq/kg (226Ratsw) and 7.19 ± 3.21 Bq/kg - 879.66 ± 365.74 Bq/kg (228Ratsw). Radium isotopes inventory in this study showed that suspended solid have higher inventory value than seawater and sediment. Study also found that suspended solid play an important role for flux contribution at seawater. Based on the finding, the radioactivity concentration of 226Ra and 228Ra is higher in particulate phase than in dissolved phase.

  10. Power

    DEFF Research Database (Denmark)

    Elmholdt, Claus Westergård; Fogsgaard, Morten

    2016-01-01

    In this chapter, we will explore the dynamics of power in processes of creativity, and show its paradoxical nature as both a bridge and a barrier to creativity in organisations. Recent social psychological experimental research (Slighte, de Dreu & Nijstad, 2011) on the relation between power...... and creativity suggests that when managers give people the opportunity to gain power and explicate that there is reason to be more creative, people will show a boost in creative behaviour. Moreover, this process works best in unstable power hierarchies, which implies that power is treated as a negotiable...... and floating source for empowering people in the organisation. We will explore and discuss here the potentials, challenges and pitfalls of power in relation to creativity in the life of organisations today. The aim is to demonstrate that power struggles may be utilised as constructive sources of creativity...

  11. Magellan LDSS3 emission confirmation of galaxies hosting metal-rich Lyman-alpha absorption systems

    CERN Document Server

    Straka, Lorrie A; York, Donald G; Bowen, David V; Florian, Michael; Kulkarni, Varsha P; Lundgren, Britt; Peroux, Celine

    2015-01-01

    Using the Low Dispersion Survey Spectrograph 3 at the Magellan II Clay Telescope in Chile, we target candidate absorption host galaxies detected in deep optical imaging (reaching limiting apparent magnitudes of 23.0-26.5 in g; r; i; and z filters) in the fields of three QSOs, each of which shows the presence of high metallicity, strong NHI absorption systems in their spectra (Q0826-2230: zabs=0.9110, Q1323-0021: zabs = 0.7160, Q1436-0051: zabs = 0.7377; 0.9281). We confirm host galaxies at redshifts 0.7387, 0.7401, and 0.9286 for two out of four of the Ly-alpha absorption systems. For these systems, we are able to determine the SFRs; impact parameters (known from previous imaging detections); the velocity shift between the absorption and emission redshifts; and, for one system, also the emission metallicity. Based on previous photometry, we find these galaxies have L>L*. The SFRs for these galaxies, based on [O II] emission, are in the range 11-25 M_sol/yr (uncorrected for dust), while the impact parameters l...

  12. The VLT LBG Redshift Survey - V. Characterising the z = 3.1 Lyman Alpha Emitter Population

    CERN Document Server

    Bielby, R M; Shanks, T; Francke, H; Crighton, N H M; Bañados, E; González-López, Jorge; Infante, L; Orsi, A

    2016-01-01

    We present a survey of Ly$\\alpha$ emitting galaxies in the fields of the VLT LBG Redshift Survey, incorporating the analysis of narrow band number counts, the rest frame UV luminosity function and the two-point correlation function of Ly$\\alpha$ emitters at $z\\approx3.1$. Our photometric sample consists of 750 LAE candidates, over an area of 1.07 deg$^2$, with estimated equivalent widths of $\\gtrsim65$ \\AA, from 5 fields based on deep Subaru Suprime-Cam imaging data. Added to this we have obtained spectroscopic follow-up observations, which successfully detected Ly$\\alpha$ emission in 35 galaxies. Based on the spectroscopic results, we refined our photometric selection constraints, with the resulting sample having a success rate of $78\\pm18\\%$. We calculate the narrow band number counts for our photometric sample and find these to be consistent with previous studies of LAEs at this redshift. We find the $R$-band continuum luminosity function to be $\\sim10\\times$ lower than the equivalent luminosity function o...

  13. Damped Lyman Alpha Gas Metallicities at Redshifts z=0.9-2.0 from SDSS Spectra

    CERN Document Server

    Nestor, D B; Turnshek, D A; Vanden Berk, Daniel E; Nestor, Daniel B.; Rao, Sandhya M.; Turnshek, David A.; Berk, Daniel Vanden

    2003-01-01

    Using Sloan Digital Sky Survey (SDSS) early data release spectra, we have identified 370 MgII absorption systems with MgII 2796 rest equivalent widths >= 1A and redshifts z=0.9-2.2. From our previous and ongoing HST UV spectroscopic studies, we estimate that the mean neutral hydrogen column density of a system selected in this manner is N(HI) = 3.6 +/- 1.3 x10^(20) atoms cm^(-2), which corresponds to the damped Ly-alpha (DLA) regime. We have formed high signal-to-noise ratio composite spectra using 223 of these systems with z=0.9-2.0 in order to study the strength of the ZnII and CrII absorption lines corresponding to this mean neutral hydrogen column density. After making a correction for missed DLAs, overall we find that [Zn/H] = -1.13 +/- 0.19. We find [Cr/Zn] = -0.45 +/- 0.13, which indicates that approx 65% of the Cr is depleted on to grains, but this does not correct for the missed DLAs. We have also derived Zn and Cr abundances in two kinematic regimes, and within each regime we consider two redshift i...

  14. LRO Lyman Alpha Mapping Project (LAMP) Far-UV Maps: A New View of the Moon

    Science.gov (United States)

    Retherford, K. D.; Greathouse, T. K.; Gladstone, G. R.; Hendrix, A. R.; Mandt, K. E.; Egan, A. F.; Kaufmann, D. E.; Hayne, P. O.; Stern, S. A.; Parker, J. Wm.; Davis, M. W.; Grava, C.; Hurley, D. M.; Cahill, J. T. S.; Stickle, A. M.; Liu, Y.; Bullock, M. A.; Pryor, W. R.; Feldman, P. D.; Mukherjee, J.; Mokashi, P.; Seifert, C. J.; Versteeg, M. H.

    2016-05-01

    The LRO-LAMP investigation has provided a unique view at far-UV wavelengths, and uses an innovative way to measure surface reflectance within permanently shaded regions in order to constrain the water frost abundance at the surface.

  15. Lyman Alpha Emitters at Redshift 5.7 in the COSMOS Field

    CERN Document Server

    Murayama, T; Scoville, N Z; Ajiki, M; Sanders, D B; Mobasher, B; Aussel, H; Capak, P; Koekemoer, A; Shioya, Y; Nagao, T; Carilli, C; Ellis, Richard S; Garilli, B; Giavalisco, M; Kitzbichler, M G; LeFevre, O; MacCagni, D; Schinnerer, E; Smolcic, V; Tribiano, S; Cimatti, A; Komiyama, Yu; Miyazaki, S; Sasaki, S S; Koda, J; Karoji, H

    2007-01-01

    We present results from a narrow-band optical survey of a contiguous area of 1.95 deg^2, covered by the Cosmic Evolution Survey (COSMOS). Both optical narrow-band (lambda_c = 8150 AA and Delta_lambda = 120 AA) and broad-band (B, V, g', r', i', and z') imaging observations were performed with the Subaru prime-focus camera, Suprime-Cam on the Subaru Telescope. We provide the largest contiguous narrow-band survey, targetting Ly alpha emitters (LAEs) at z~5.7. We find a total of 119 LAE candidates at z~5.7. Over the wide-area covered by this survey, we find no strong evidence for large scale clustering of LAEs. We estimate a star formation rate (SFR) density of ~7*10^-4 M_sun yr^-1 Mpc^-3 for LAEs at z~5.7, and compare it with previous measurements.

  16. Chemical enrichment of Damped Lyman Alpha systems as a direct constraint on Population III star formation

    CERN Document Server

    Kulkarni, Girish; Hennawi, Joseph F; Vangioni, Elisabeth

    2013-01-01

    Damped Ly-alpha absorbers (DLAs) can be used to measure gas-phase metallicities at large cosmological lookback times with high precision. Relative abundances can still be measured accurately deep into the reionization epoch (z > 6) using transitions redward of Ly-alpha. Here we study chemical evolution of DLAs using a constrained model for evolution of galaxies and IGM to determine the degree to which DLA abundance measurements can probe Population III enrichment. We find that if the critical metallicity of Population III to II transition is 5. Thus, a sample of DLA abundance measurements at high redshift holds the promise to constrain Population III IMF. A sample of just 10 DLAs with relative abundances measured to an accuracy of 0.1 dex is sufficient to constrain the Population III IMF at 4-sigma. These constraints may prove stronger than other probes such as metal-poor stars and individual DLAs. Our results provide a global picture of the cosmic thermal, ionization, and chemical evolution, and can rule ou...

  17. Galactic winds and stellar populations in Lyman $\\alpha$ emitting galaxies at z ~ 3.1

    CERN Document Server

    McLinden, Emily M; Malhotra, Sangeeta; Finkelstein, Steven L; Richardson, Mark L A; Smith, Brent; Tilvi, Vithal S

    2014-01-01

    We present a sample of 33 spectroscopically confirmed z ~ 3.1 Ly$\\alpha$-emitting galaxies (LAEs) in the Cosmological Evolution Survey (COSMOS) field. This paper details the narrow-band survey we conducted to detect the LAE sample, the optical spectroscopy we performed to confirm the nature of these LAEs, and a new near-infrared spectroscopic detection of the [O III] 5007 \\AA\\ line in one of these LAEs. This detection is in addition to two [O III] detections in two z ~ 3.1 LAEs we have reported on previously (McLinden et al 2011). The bulk of the paper then presents detailed constraints on the physical characteristics of the entire LAE sample from spectral energy distribution (SED) fitting. These characteristics include mass, age, star-formation history, dust content, and metallicity. We also detail an approach to account for nebular emission lines in the SED fitting process - wherein our models predict the strength of the [O III] line in an LAE spectrum. We are able to study the success of this prediction be...

  18. Minihalo Model for the Low-Redshift Lyman alpha Absorbers Revisited

    Directory of Open Access Journals (Sweden)

    Lalović, A.

    2008-06-01

    Full Text Available We reconsider the basic properties of the classical minihalo model of Rees and Milgrom in light of the new work, both observational (on "dark galaxies" and masses of baryonic haloes and theoretical (on the cosmological mass function and the history of star formation. In particular, we show that more detailed models of ionized gas in haloes of dark matter following isothermal and Navarro-Frenk-White density profile can effectively reproduce particular aspects of the observed column density distribution function in a heterogeneous sample of low-and intermediate-redshift Ly$alpha$ forest absorption lines.

  19. Lyman-alpha observations in the vicinity of Saturn with Copernicus

    Science.gov (United States)

    Barker, E.; Cazes, S.; Emerich, C.; Vidal-Madjar, A.; Owen, T.

    1980-01-01

    For the first time, high-resolution Ly-alpha observations of the Saturn vicinity were completed with the Princeton spectrometer on board the Copernicus satellite. They showed that near a minimum solar activity the emissions related to several sources are 250 + or - 50 rayleighs for the interplanetary medium in a near-downwind direction, less than 100 rayleighs for the rings, 200 + or - 100 rayleighs for a torus linked to the Titan orbit, and 1400 + or - 450 rayleighs for the disk of Saturn. These results induce some constraints through the corresponding theoretical evaluations: the B ring as the primary source of the atoms for the ring emissions; an efficient production mechanism for hydrogen atoms in the Titan torus; and a slightly larger eddy diffusion coefficient in the Saturn atmosphere than in the Jupiter atmosphere near solar minimum.

  20. Strong Field-to-Field Variation of Lyman alpha Nebulae Populations at z~2.3

    CERN Document Server

    Yang, Yujin; Eisenstein, Daniel; Davé, Romeel

    2010-01-01

    Understanding the nature of distant Ly-alpha nebulae ("blobs") and connecting them to their present-day descendants requires constraining their number density, clustering, and large-scale environment. To measure these basic quantities, we conduct a deep narrowband imaging survey in four different fields, Chandra Deep Field South (CDFS), Chandra Deep Field North, and two COSMOS subfields, for a total survey area of 1.2deg^2. We discover 25 blobs at z=2.3 with Ly-alpha luminosities of 0.7-8x10^43 erg/s and isophotal areas of Aiso = 10-60 arcsec^2. The transition from compact Ly-alpha emitters (Aiso ~ a few arcsec^2) to extended blobs (Aiso > 10 arcsec^2) is continuous, suggesting a single family perhaps governed by similar emission mechanisms. Surprisingly, most blobs (16/25) are in one survey field, the CDFS. The six brightest, largest blobs with L > 1.5x10^43 erg/s and Aiso > 16 arcsec^2 lie only in the CDFS. These large, bright blobs have a field-to-field variance of sigma_v >~ 1.5 (150%) about their number ...

  1. Diffuse Interstellar Bands in Seven Intermediate Redshift Damped Lyman-Alpha Absorbers

    CERN Document Server

    Lawton, Brandon; York, Brian A; Ellison, Sara L; Snow, Theodore P; Johnson, Rachel A; Ryan, Sean G; Benn, Chris R

    2008-01-01

    We present equivalent width measurements and limits of six diffuse interstellar bands (DIBs) in seven damped Ly-alpha absorbers (DLAs) over the redshift range 0.091

  2. Statistical properties of damped Lyman-alpha systems from Sloan Digital Sky Survey DR12

    Science.gov (United States)

    Bird, Simeon; Garnett, Roman; Ho, Shirley

    2017-04-01

    We present new estimates for the statistical properties of damped Lyman-α absorbers (DLAs). We compute the column density distribution function at z > 2, the line density, dN/dX, and the neutral hydrogen density, ΩDLA. Our estimates are derived from the DLA catalogue of Garnett et al. (2016), which uses the Sloan Digital Sky Survey III Data Release 12 (SDSS-III DR12) quasar spectroscopic survey. This catalogue provides a probability that a given spectrum contains a DLA. It allows us to use even the noisiest data without biasing our results and thus substantially increases our sample size. We measure a non-zero column density distribution function at 95 per cent confidence for all column densities N_H I 4. We show that our results are insensitive to the signal-to-noise ratio of the spectra, but that there is a residual dependence on quasar redshift for z < 2.5, which may be due to remaining systematics in our analysis.

  3. The Properties of Lyman Alpha Nebulae: Gas Kinematics from Non-resonant Lines

    CERN Document Server

    Yang, Yujin; Jahnke, Knud; Davé, Romeel

    2014-01-01

    [Abridged] With VLT/X-shooter, we obtain optical and NIR spectra of six Ly-alpha blobs at z~2.3. Using three measures --- the velocity offset between the Lya line and the non-resonant [OIII] or H-alpha line (Dv_Lya), the offset of stacked interstellar metal absorption lines, and the spectrally-resolved [OIII] line profile --- we study the kinematics of gas along the line of sight to galaxies within each blob center. These three indicators generally agree in velocity and direction, and are consistent with a simple picture in which the gas is stationary or slowly outflowing at a few hundred km/s from the embedded galaxies. The absence of stronger outflows is not a projection effect: the covering fraction for our sample is limited to <1/8 (13%). The outflow velocities exclude models in which star formation or AGN produce "super" or "hyper" winds of up to ~1000km/s. The Dv_Lya offsets here are smaller than typical of LBGs, but similar to those of compact LAEs. The latter suggests that outflow speed cannot be a...

  4. Were progenitors of local L* galaxies Lyman-alpha emitters at high redshift?

    CERN Document Server

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

    2011-01-01

    The Lya emission has been observed from galaxies over a redshift span z ~ 0 - 8.6. However, the link between high-redshift Lya emitters (LAEs) and local galaxies is largely unknown. Here, we investigate the Lya properties of progenitors of a local L^{*} galaxy by combining cosmological hydrodynamic simulations with three-dimensional radiative transfer calculations using the new ART^2 code. We find that the modeled galaxies are Lya bright in redshift z= 0 - 10. In particular, the Lya luminosities of some massive progenitors at z ~ 2 - 6 are close to the observed characteristic L_{Lya}^{*} of LAEs in that redshift range. Both Lya photon escape fraction and line equivalent width increase with redshift. The Lya escape fraction correlates with a number of physical properties of the galaxy, such as mass, SFR and metallicity. We find a "viewing-angle scatter" in which the photon escape depends strongly on the galaxy morphology and orientation. Moreover, we find that high-redshift LAEs show blue-shifted Lya line prof...

  5. Clustering of galaxies near damped Lyman-alpha systems with (z) = 2.6

    Science.gov (United States)

    Wolfe, A. M

    1993-01-01

    The galaxy two-point correlation function, xi, at (z) = 2.6 is determined by comparing the number of Ly-alpha-emitting galaxies in narrowband CCD fields selected for the presence of damped L-alpha absorption to their number in randomly selected control fields. Comparisons between the presented determination of (xi), a density-weighted volume average of xi, and model predictions for (xi) at large redshifts show that models in which the clustering pattern is fixed in proper coordinates are highly unlikely, while better agreement is obtained if the clustering pattern is fixed in comoving coordinates. Therefore, clustering of Ly-alpha-emitting galaxies around damped Ly-alpha systems at large redshifts is strong. It is concluded that the faint blue galaxies are drawn from a parent population different from normal galaxies, the presumed offspring of damped Ly-alpha systems.

  6. LOOKING FOR LYMAN ALPHA EMITTING GALAXIES AT Z - 2.1

    OpenAIRE

    Guaita, Lucia

    2010-01-01

    Este proyecto de tesis de doctorado tuvo su inicio en Diciembre de 2007. En esta fecha se tomaron imágenes de la región del cielo llamada Extended Chandra Deep Field-South (ECDF-S) a través del filtro de banda angosta NB3727 y con el instrumento MO-SAIC II del telescopio de 4 metros de Cerro Tololo. El filtro está caracterizado por una longitud de onda central que corresponde a la línea Lγα con un desplazamiento hacia el rojo (redshift). z - 2.1. En este campo hemos descubierto una muestra de...

  7. Large-scale clustering of Lyman-alpha emission intensity from SDSS/BOSS

    CERN Document Server

    Croft, Rupert A C; Zheng, Zheng; Bolton, Adam; Dawson, Kyle S; Peterson, Jeffrey B; York, Donald G; Eisenstein, Daniel; Brinkmann, Jon; Brownstein, Joel; Delubac, Timothée; Font-Ribera, Andreu; Hamilton, Jean-Christophe; Lee, Khee-Gan; Myers, Adam; Palanque-Delabrouille, Nathalie; Pâris, Isabelle; Petitjean, Patrick; Pieri, Matthew M; Ross, Nicholas P; Rossi, Graziano; Schlegel, David J; Schneider, Donald P; Slosar, Anže; Vazquez, José; Viel, Matteo; Weinberg, David H; Yèche, Christophe

    2015-01-01

    (Abridged) We detect the large-scale structure of Lya emission in the Universe at redshifts z=2-3.5 by measuring the cross-correlation of Lya surface brightness with quasars in SDSS/BOSS. We use a million spectra targeting Luminous Red Galaxies at z, the amplitude of mass fluctuations, and the quasar and Lya emission bias factors. Using known values, we infer (b_alpha/3) = (3.9 +/- 0.9) x 10^-21 erg/s cm^-2 A^-1 arcsec^-2, where b_alpha is the Lya emission bias factor. If the dominant sources of Lya emission are star forming galaxies, we infer rho_SFR = (0.28 +/- 0.07) (3/b_alpha) /yr/Mpc^3 at z=2-3.5. For b_alpha=3, this value is a factor of 21-35 above previous estimates from individually detected Lya emitters, although consistent with the total rho_SFR derived from dust-corrected, continuum UV surveys. 97% of the Lya emission in the Universe at these redshifts is therefore undetected in previous surveys of Lya emitters. Our measurement is much greater than seen from stacking analyses of faint halos surroun...

  8. The evolution of superbubbles and the detection of Lyman $\\alpha$ in star-forming galaxies

    CERN Document Server

    Tenorio-Tagle, G; Kunth, D; Terlevich, E; Terlevich, R J; Tenorio-Tagle, Guillermo; Silich, Sergey A.; Kunth, Daniel; Terlevich, Elena; Terlevich, Roberto

    1999-01-01

    The detection of Ly alpha emission in star-forming galaxies in different shapes and intensities (always smaller than predicted for case B recombination) has puzzled the astronomical community for more than a decade. Here we use two dimensional calculations to follow the evolution of superbubbles and of the H II regions generated by the output of UV photons from massive stars. We show the impact caused by massive star formation in the ISM of different galaxies and we look at the conditions required to detect Ly alpha emission from a nuclear H II region, and the variety of profiles that may be expected as a function of time.

  9. Impact of Cosmic Variance on the Galaxy-Halo Connection for Lyman-$\\alpha$ Emitters

    CERN Document Server

    Mejia-Restrepo, Julian E

    2016-01-01

    In this paper we study the impact of cosmic variance and observational uncertainties in constraining the mass and occupation fraction, $f_{\\rm occ}$, of dark matter halos hosting Ly-$\\alpha$ Emitting Galaxies (LAEs) at high redshift. To this end, we construct mock catalogs from an N-body simulation to match the typical size of observed fields at $z=3.1$ ($\\sim 1 {\\rm deg^2}$). In our model a dark matter halo with mass in the range $M_{\\rm min}

  10. The Heavy Element Enrichment of Lyman alpha Clouds in the Virgo Supercluster

    CERN Document Server

    Tripp, T M; Williger, G M; Heap, S R; Bowers, C W; Danks, A C; Davé, R; Green, R F; Gull, T R; Joseph, C L; Kaiser, M E; Lindler, D; Weymann, R J; Woodgate, B E

    2002-01-01

    Using high S/N STIS echelle spectra (FWHM=7 km/s) of 3C 273, we constrain the metallicities of two Lya clouds in the vicinity of the Virgo cluster. We detect C II, Si II, and Si III absorption lines in the Lya absorber at z = 0.00530. Previous observations with FUSE have revealed Ly beta - Ly theta lines at this redshift, thereby accurately constraining N(H I). We model the ionization of the gas and derive [C/H] = -1.2^{+0.3}_{-0.2}, [Si/C] = 0.2+/-0.1, and log n_{H} = -2.8+/-0.3. The model implies a small absorber thickness, ~70 pc, and thermal pressure p/k ~ 40 cm^{-3} K. It is most likely that the absorber is pressure confined by an external medium because gravitational confinement would require a very high ratio of dark matter to baryonic matter. Based on Milky Way sight lines in which carbon and silicon abundances have been reliably measured in the same interstellar cloud (including new measurements presented herein), we argue that the overabundance of Si relative to C is not due to dust depletion. Inste...

  11. H-alpha features with hot onsets III. Fibrils in Lyman-alpha and with ALMA

    CERN Document Server

    Rutten, Robert J

    2016-01-01

    In H-alpha most of the solar surface is covered by a dense canopy of long opaque fibrils, but predictions for quiet-Sun observations with ALMA have ignored this fact. Comparison with Ly-alpha suggests that the large opacity of H-alpha fibrils is caused by hot precursor events. Application of a recipe that assumes momentary Saha-Boltzmann extinction during their hot onset to millimeter wavelengths suggests that ALMA will observe the H-alpha fibril canopy, not acoustic shocks underneath, and will yield data more interesting than if this canopy were transparent.

  12. The Local Lyman-$\\alpha$ Forest; 1, Distribution of HI Absorbers, Doppler Widths, and Baryon Content

    CERN Document Server

    Penton, S V; Stocke, J T; Penton, Steven V.; Stocke, John T.

    1999-01-01

    In Paper I of this series (astro-ph/9911117) we described observations of 15 extragalactic targets taken with the Hubble Space Telescope GHRS/G160M grating for studies of the low-z Lya forest. We reported the detection of 110 Lya absorbers at significance level >3 sigma in the redshift range z=0.002-0.069, over a total pathlength of 116,000 km/s. In this second paper, we evaluate the physical properties of these Lya absorbers and compare them to their high-z counterparts. The distribution of Doppler parameters is similar to that at high redshift, with mean b = 35.0 +- 16.6 km/s. The true Doppler parameter may be somewhat lower, owing to component blends and non-thermal velocities. The distribution of equivalent widths exhibits a significant break at W~133mA, with an increasing number of weak absorbers (10mA-100mA). Adopting a curve of growth with b = 25 +- 5km/s and applying a sensitivity correction as a function of equivalent width and wavelength, we derive the distribution in column density, Nh^{-1.80+-0.05...

  13. Metallicities and dust content of proximate damped Lyman alpha systems in the Sloan Digital Sky Survey

    CERN Document Server

    Ellison, Sara L; Mendel, J Trevor

    2010-01-01

    Composite spectra of 85 proximate absorbers (log N(HI)>20 and velocity difference between the absorption and emission redshift, dv6000 km/s, with further sub-samples to investigate the metal line dependence on N(HI) and QSO luminosity. Low (e.g. SiII and FeII) and high ionization (e.g. SiIV and CIV) species alike have equivalent widths (EWs) that are larger by factors of 1.5 -- 3 in the dv6000 km/s spectrum. The EWs show an even stronger dependence on dv if only the highest neutral hydrogen column density (log N(HI)>20.7) absorbers are considered. We conclude that PDLAs generally have higher metallicities than intervening absorbers, with the enhancement being a function of both dv and N(HI). It is also found that absorbers near QSOs with lower rest-frame UV luminosities have significantly stronger metal lines. We speculate that absorbers near to high luminosity QSOs may have had their star formation prematurely quenched. Finally, we search for the signature of dust reddening by the PDLAs, based on an analysis...

  14. A Reverse Monte Carlo study of H+D Lyman alpha absorption from QSO spectra

    CERN Document Server

    Levshakov, S A; Takahara, F

    1997-01-01

    A new method based on a Reverse Monte Carlo [RMC] technique and aimed at the inverse problem in the analysis of interstellar (intergalactic) absorption lines is presented. The line formation process in chaotic media with a finite correlation length $(l > 0)$ of the stochastic velocity field (mesoturbulence) is considered. This generalizes the standard assumption of completely uncorrelated bulk motions $(l \\equiv 0)$ in the microturbulent approximation which is used for the data analysis up-to-now. It is shown that the RMC method allows to estimate from an observed spectrum the proper physical parameters of the absorbing gas and simultaneously an appropriate structure of the velocity field parallel to the line-of-sight. The application to the analysis of the H+D Ly$\\alpha$ profile is demonstrated using Burles & Tytler [B&T] data for QSO 1009+2956 where the DI Ly$\\alpha$ line is seen at $z_a = 2.504$. The results obtained favor a low D/H ratio in this absorption system, although our upper limit for the ...

  15. Extended Lyman alpha haloes around individual high-redshift galaxies revealed by MUSE

    CERN Document Server

    Wisotzki, L; Blaizot, J; Brinchmann, J; Herenz, E C; Schaye, J; Bouché, N; Cantalupo, S; Contini, T; Carollo, C M; Caruana, J; Courbot, J -B; Emsellem, E; Kamann, S; Kerutt, J; Leclercq, F; Lilly, S J; Patrício, V; Sandin, C; Steinmetz, M; Straka, L A; Urrutia, T; Verhamme, A; Weilbacher, P M; Wendt, M

    2015-01-01

    We report the detection of extended Ly alpha emission around individual star-forming galaxies at redshifts z = 3-6 in an ultradeep exposure of the Hubble Deep Field South obtained with MUSE on the ESO-VLT. The data reach a limiting surface brightness (1sigma) of ~1 x 10^-19 erg s^-1 cm^-2 arcsec^-2 in azimuthally averaged radial profiles, an order of magnitude improvement over previous narrowband imaging. Our sample consists of 26 spectroscopically confirmed Ly alpha-emitting, but mostly continuum-faint (m_AB >~ 27) galaxies. In most objects the Ly alpha emission is considerably more extended than the UV continuum light. While 5 of the faintest galaxies in the sample show no significantly detected Ly alpha haloes, the derived upper limits suggest that this is just due to insufficient S/N. Ly alpha haloes therefore appear to be (nearly) ubiquitous even for low-mass (~10^8-10^9 M_sun) star-forming galaxies at z>3. We decompose the Ly alpha emission of each object into a compact `continuum-like' and an extended ...

  16. Lyman {\\alpha} radiative transfer in the high-redshift, dusty Universe

    CERN Document Server

    Laursen, Peter

    2010-01-01

    The significance of the Ly{\\alpha} emission line as a probe of the high-redshift Universe has long been established. Originating mainly in the vicinity of young, massive stars and in association with accretion of large bulks of matter, it is ideal for detecting young galaxies, the fundamental building blocks of our Universe. Since many different processes shape the spectrum and the spatial distribution of the Ly{\\alpha} photons in various ways, a multitude of physical properties of galaxies can be unveiled. However, this also makes the interpretation of Ly{\\alpha} observations notoriously difficult. Because Ly{\\alpha} is a resonant line, it scatters on neutral hydrogen, having its path length from the source to our telescopes vastly increased, and taking it through regions of unknown physical conditions. In this work, a numerical code capable of calculating realistically the radiative transfer of Ly{\\alpha} is presented. The code is capable of performing the radiative transfer in an arbitrary and adaptively r...

  17. Evidence for a direct collapse black hole in the Lyman-alpha source CR7

    CERN Document Server

    Smith, Aaron; Loeb, Abraham

    2016-01-01

    Throughout the epoch of reionization the most luminous Ly{\\alpha} emitters are capable of ionizing their own local bubbles. The CR7 galaxy at $z \\approx 6.6$ stands out for its combination of exceptionally bright Ly{\\alpha} and HeII 1640 Angstrom line emission but absence of metal lines. As a result CR7 may be the first viable candidate host of a young primordial starburst or direct collapse black hole. High-resolution spectroscopy reveals a +160 km s$^{-1}$ velocity offset between the Ly{\\alpha} and HeII line peaks while the spatial extent of the Ly{\\alpha} emitting region is $\\sim 16$ kpc. The observables are indicative of an outflow signature produced by a strong central source. We present one-dimensional radiation-hydrodynamics simulations incorporating accurate Ly{\\alpha} feedback and ionizing radiation to investigate the nature of the CR7 source. We find that a Population III star cluster with $10^5$ K blackbody emission ionizes its environment too efficiently to generate a significant velocity offset. ...

  18. Lyman alpha emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy

    CERN Document Server

    Deharveng, Jean-Michel; Barlow, Tom A; Peroux, Celine; Milliard, Bruno; Friedman, Peter G; Martin, D Christopher; Morrissey, Patrick; Schiminovich, David; Forster, Karl; Seibert, Mark; Wyder, Ted K; Bianchi, Luciana; Donas, Jose; Heckman, Timothy M; Lee, Young-Wook; Madore, Barry F; Neff, Susan G; Rich, R Michael; Szalay, A S; Welsh, Barry Y; Yi, Sukyoung K

    2008-01-01

    The GALEX (Galaxy Evolution Explorer) spectroscopic survey mode, with a resolution of about 8 A in the FUV (1350 - 1750 A) and about 20 A in the NUV (1950 - 2750 A) is used for a systematic search of Ly-a emitting galaxies at low redshift. This aims at filling a gap between high-redshift surveys and a small set of objects studied in detail in the nearby universe. A blind search of 7018 spectra extracted in 5 deep exposures (5.65 sq.deg) has resulted in 96 Ly-a emitting galaxy candidates in the FUV domain, after accounting for broad-line AGNs. The Ly-a EWs (equivalent width) are consistent with stellar population model predictions and show no trends as a function of UV color or UV luminosity, except a possible decrease in the most luminous that may be due to small-number statistics. Their distribution in EW is similar to that at z about 3 but their fraction among star-forming galaxies is smaller. Avoiding uncertain candidates, a sub-sample of 66 objects in the range 0.2 < z < 0.35 has been used to build ...

  19. Polarimetry of the HI Lyman-alpha for coronal magnetic field diagnostics

    Science.gov (United States)

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

    1993-01-01

    We discuss and analyze the possible sources of observational and instrumental uncertainty that can be encountered in measuring magnetic fields of the solar corona through polarimetric observations of the Hanle effect of the coronal Ly-alpha line. The Hanle effect is the modification of the linear polarization of a resonantly scattered line, due to the presence of a magnetic field. Simulated observations are used to examine how polarimetric measurements of this effect are affected by the line-of-sight integration, the electron collisions, and the Ly-alpha geocorona. We plan to implement the coronal magnetic field diagnostics via the Ly-alpha Hanle effect using an all-reflecting Ly-alpha coronagraph/polarimeter (Ly-alphaCoPo) which employs reflecting multilayer mirrors, polarizers, and filters. We discuss here the requirements for such an instrument, and analyze the sources of instrumental uncertainty for polarimetric observations of the coronal Ly-alpha Hanle effect. We conclude that the anticipated polarization signal from the corona and the expected performance of the Ly-alphaCoPo instrument are such that the Ly-alpha Hanle effect method for coronal field diagnostics is feasible.

  20. The effects of the small-scale DM power on the cosmological neutral hydrogen (\\HI) distribution at high redshifts

    CERN Document Server

    Sarkar, Abir; Das, Subinoy; Sethi, Shiv K; Bharadwaj, Somnath; Marsh, David J E

    2015-01-01

    The particle nature of dark matter remains a mystery. In this paper, we consider two dark matter models---Late Forming Dark Matter (LFDM) and Ultra-Light Axion (ULA) models---where the matter power spectra show novel effects on small scales. The high redshift universe offers a powerful probe of their parameters. In particular, we study two cosmological observables: the neutral hydrogen (HI) redshifted 21-cm signal from the epoch of reionization, and the evolution of the collapsed fraction of HI in the redshift range $2 4 \\times 10^5$ (for LFDM) and the axion mass $m_a > 2.6 \\times 10^{-23} \\, \\rm eV$ (for ULA). The comparison of the collapsed mass fraction inferred from damped Lyman-$\\alpha$ observations to the theoretical predictions of our models lead to the weaker bounds: $z_f > 2 \\times 10^5$ and $m_a > 10^{-23} \\, \\rm eV$. These bounds are consistent with other constraints in the literature using different observables and, in the case of ULAs, are also consistent with a solution to the cusp-core problem...

  1. Feedback Control System Design of the Power LED Luminous Flux%功率型LED光通量的反馈控制系统设计

    Institute of Scientific and Technical Information of China (English)

    谢一菁

    2016-01-01

    为实现 LED光通量的反馈控制系统,采用以 STM32F103C8T6单片机为核心的最小系统、电源模块、LED驱动控制电路模块、光强度检测模块组成系统.该系统是以 PT4115作为驱动模块,输出电流恒定来驱动功率型 LED.并采用两个相同的驱动模块,同时用频率相同占空比不同可独立调节的 PWM来控制白光LED与黄光LED发光.采用BH1750FVI光强度测试模块检测LED发光量及在LCD12864液晶屏上显示,并反馈到单片机系统,从而控制并调整PWM占空比以实现人机交互.%To achieve LED luminous flux feedback control system,this proj ect adopts the STM32F103C8T6 single-chip microcomputer as the core of minimum system module,power module, LED the drive control circuit,light intensity detection module.As PT4115 drive module of the sys-tem,the output current constant power type LED to drive.Using two identical driver module,at the same time,different compared with the same frequency can be adj usted independently of PWM to con-trol the white LED with yellow LED.Using BH1750FVI light intensity test module testing LED quantity and in LCD12864 LCD screen display,and feedback to the single-chip microcomputer system, so as to control and adj ust the PWM duty cycle to achieve human-computer interaction.

  2. Methane Flux

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Methane (CH4) flux is the net rate of methane exchange between an ecosystem and the atmosphere. Data of this variable were generated by the USGS LandCarbon project...

  3. Specification of ROP flux shape

    Energy Technology Data Exchange (ETDEWEB)

    Min, Byung Joo [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of); Gray, A. [Atomic Energy of Canada Ltd., Chalk River, ON (Canada)

    1997-06-01

    The CANDU 9 480/SEU core uses 0.9% SEU (Slightly Enriched Uranium) fuel. The use f SEU fuel enables the reactor to increase the radial power form factor from 0.865, which is typical in current natural uranium CANDU reactors, to 0.97 in the nominal CANDU 9 480/SEU core. The difference is a 12% increase in reactor power. An additional 5% increase can be achieved due to a reduced refuelling ripple. The channel power limits were also increased by 3% for a total reactor power increase of 20%. This report describes the calculation of neutron flux distributions in the CANDU 9 480/SEU core under conditions specified by the C and I engineers. The RFSP code was used to calculate of neutron flux shapes for ROP analysis. Detailed flux values at numerous potential detector sites were calculated for each flux shape. (author). 6 tabs., 70 figs., 4 refs.

  4. A new approach to scaling of the scrape-off layer and divertor plasma in JET

    Energy Technology Data Exchange (ETDEWEB)

    Harbour, P.J.; Loarte, A.; Clement, S.; De Kock, L.; Jaeckel, H.J.; Lesourd, M.; O' Brien, D.P.; Summers, D.D.R.; Tagle, J.A. (JET Joint Undertaking, Abingdon (United Kingdom))

    1992-12-01

    An analytical model of the SOL/divertor magnetic geometry is applied to JET. Exponential decay lengths, [lambda], are related to differences in magnetic fluxes and are expressed in terms of [lambda] at midplane. Consistent values of [lambda] are usually obtained from Langmuir probes in the SOL or in the divertor, and with Lyman-[alpha] and Balmer-[alpha] profiles in the divertor. Scaling of [lambda] is presented: It is only slightly affected by , by X-point to target distance and by input power (other than the usual changes [Omega][yields]L[yields]H); it increases strongly with B[sub [phi

  5. Developing structural, high-heat flux and plasma facing materials for a near-term DEMO fusion power plant: The EU assessment

    Energy Technology Data Exchange (ETDEWEB)

    Stork, D., E-mail: derek.stork@btinternet.com [Euratom – CCFE Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Agostini, P. [ENEA, Brasimone Research Centre, 40032 Cumugnano, Bologna (Italy); Boutard, J.L. [CEA, cab HC, Saclay, F-91191 Gif-sur-Yvette (France); Buckthorpe, D. [AMEC, Booths Park, Chelford Road, Knutsford, Cheshire WA16 8QZ (United Kingdom); Diegele, E. [Karlsruhe Institute for Technology, IMF-I, D-7602 Karlsruhe (Germany); Dudarev, S.L. [Euratom – CCFE Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); English, C. [National Nuclear Laboratory, Chadwick House, Warrington Road, Birchwood Park WA3 6AE (United Kingdom); Federici, G. [EFDA Power Plant Physics and Technology, Boltzmannstr. 2, Garching 85748 (Germany); Gilbert, M.R. [Euratom – CCFE Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Gonzalez, S. [EFDA Power Plant Physics and Technology, Boltzmannstr. 2, Garching 85748 (Germany); Ibarra, A. [CIEMAT, Avda. Complutense 40, Madrid (Spain); Linsmeier, Ch. [Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, EURATOM Association, 52425 Jülich (Germany); Li Puma, A. [CEA, DEN, Saclay, DM2S, SERMA, F-91191 Gif-sur-Yvette (France); Marbach, G. [CEA, cab HC, Saclay, F-91191 Gif-sur-Yvette (France); Morris, P.F. [Formerly of TATA Steel Europe, Swinden Technology Centre, Moorgate, Rotherham S60 3AR (United Kingdom); Packer, L.W. [Euratom – CCFE Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Raj, B. [Indian National Academy of Engineering, Shaheed Jeet Singh Marg, New Delhi 110016 (India); Rieth, M. [Karlsruhe Institute for Technology, IMF-I, D-7602 Karlsruhe (Germany); and others

    2014-12-15

    The findings of the EU ‘Materials Assessment Group’ (MAG), within the 2012 EU Fusion Roadmap exercise, are discussed. MAG analysed the technological readiness of structural, plasma facing and high heat flux materials for a DEMO concept to be constructed in the early 2030s, proposing a coherent strategy for R and D up to a DEMO construction decision. A DEMO phase I with a ‘Starter Blanket’ and ‘Starter Divertor’ is foreseen: the blanket being capable of withstanding ⩾2 MW yr m{sup −2} fusion neutron fluence (∼20 dpa in the front-wall steel). A second phase ensues for DEMO with ⩾5 MW yr m{sup −2} first wall neutron fluence. Technical consequences for the materials required and the development, testing and modelling programmes, are analysed using: a systems engineering approach, considering reactor operational cycles, efficient maintenance and inspection requirements, and interaction with functional materials/coolants; and a project-based risk analysis, with R and D to mitigate risks from material shortcomings including development of specific risk mitigation materials. The DEMO balance of plant constrains the blanket and divertor coolants to remain unchanged between the two phases. The blanket coolant choices (He gas or pressurised water) put technical constraints on the blanket steels, either to have high strength at higher temperatures than current baseline variants (above 650 °C for high thermodynamic efficiency from He-gas coolant), or superior radiation-embrittlement properties at lower temperatures (∼290–320 °C), for construction of water-cooled blankets. Risk mitigation proposed would develop these options in parallel, and computational and modelling techniques to shorten the cycle-time of new steel development will be important to achieve tight R and D timescales. The superior power handling of a water-cooled divertor target suggests a substructure temperature operating window (∼200–350 °C) that could be realised, as a

  6. Developing structural, high-heat flux and plasma facing materials for a near-term DEMO fusion power plant: The EU assessment

    Science.gov (United States)

    Stork, D.; Agostini, P.; Boutard, J. L.; Buckthorpe, D.; Diegele, E.; Dudarev, S. L.; English, C.; Federici, G.; Gilbert, M. R.; Gonzalez, S.; Ibarra, A.; Linsmeier, Ch.; Li Puma, A.; Marbach, G.; Morris, P. F.; Packer, L. W.; Raj, B.; Rieth, M.; Tran, M. Q.; Ward, D. J.; Zinkle, S. J.

    2014-12-01

    The findings of the EU 'Materials Assessment Group' (MAG), within the 2012 EU Fusion Roadmap exercise, are discussed. MAG analysed the technological readiness of structural, plasma facing and high heat flux materials for a DEMO concept to be constructed in the early 2030s, proposing a coherent strategy for R&D up to a DEMO construction decision. A DEMO phase I with a 'Starter Blanket' and 'Starter Divertor' is foreseen: the blanket being capable of withstanding ⩾2 MW yr m-2 fusion neutron fluence (∼20 dpa in the front-wall steel). A second phase ensues for DEMO with ⩾5 MW yr m-2 first wall neutron fluence. Technical consequences for the materials required and the development, testing and modelling programmes, are analysed using: a systems engineering approach, considering reactor operational cycles, efficient maintenance and inspection requirements, and interaction with functional materials/coolants; and a project-based risk analysis, with R&D to mitigate risks from material shortcomings including development of specific risk mitigation materials. The DEMO balance of plant constrains the blanket and divertor coolants to remain unchanged between the two phases. The blanket coolant choices (He gas or pressurised water) put technical constraints on the blanket steels, either to have high strength at higher temperatures than current baseline variants (above 650 °C for high thermodynamic efficiency from He-gas coolant), or superior radiation-embrittlement properties at lower temperatures (∼290-320 °C), for construction of water-cooled blankets. Risk mitigation proposed would develop these options in parallel, and computational and modelling techniques to shorten the cycle-time of new steel development will be important to achieve tight R&D timescales. The superior power handling of a water-cooled divertor target suggests a substructure temperature operating window (∼200-350 °C) that could be realised, as a baseline-concept, using tungsten on a copper

  7. Constraining Neutrino mass using the large scale HI distribution in the Post-reionization epoch

    CERN Document Server

    Pal, Ashis Kumar

    2016-01-01

    The neutral intergalactic medium in the post reionization epoch allows us to study cosmological structure formation through the observation of the redshifted 21 cm signal and the Lyman-alpha forest. We investigate the possibility of measuring the total neutrino mass through the suppression of power in the matter power spectrum. We investigate the possibility of measuring the neutrino mass through its imprint on the cross-correlation power spectrum of the 21-cm signal and the Lyman-alpha forest. We consider a radio-interferometric measurement of the 21 cm signal with a SKA1-mid like radio telescope and a BOSS like Lyman-alpha forest survey. A Fisher matrix analysis shows that at the fiducial redshift z = 2.5, a 10,000 hrs 21-cm observation distributed equally over 25 radio pointings and a Lyman-alpha forest survey with 30 quasars lines of sights in $1 {\\rm deg}^2$, allows us to measure $\\Omega_{\

  8. Neutrino mass limits: Robust information from the power spectrum of galaxy surveys

    Science.gov (United States)

    Cuesta, Antonio J.; Niro, Viviana; Verde, Licia

    2016-09-01

    We present cosmological upper limits on the sum of active neutrino masses using large-scale power spectrum data from the WiggleZ Dark Energy Survey and from the Sloan Digital Sky Survey - Data Release 7 (SDSS-DR7) sample of Luminous Red Galaxies (LRG). Combining measurements on the Cosmic Microwave Background temperature and polarisation anisotropies by the Planck satellite together with WiggleZ power spectrum results in a neutrino mass bound of 0.37 eV at 95% C.L., while replacing WiggleZ by the SDSS-DR7 LRG power spectrum, the 95% C.L. bound on the sum of neutrino masses is 0.38 eV. Adding Baryon Acoustic Oscillation (BAO) distance scale measurements, the neutrino mass upper limits greatly improve, since BAO data break degeneracies in parameter space. Within a ΛCDM model, we find an upper limit of 0.13 eV (0.14 eV) at 95% C.L., when using SDSS-DR7 LRG (WiggleZ) together with BAO and Planck. The addition of BAO data makes the neutrino mass upper limit robust, showing only a weak dependence on the power spectrum used. We also quantify the dependence of neutrino mass limit reported here on the CMB lensing information. The tighter upper limit (0.13 eV) obtained with SDSS-DR7 LRG is very close to that recently obtained using Lyman-alpha clustering data, yet uses a completely different probe and redshift range, further supporting the robustness of the constraint. This constraint puts under some pressure the inverted mass hierarchy and favours the normal hierarchy.

  9. Critical flux determination by flux-stepping

    DEFF Research Database (Denmark)

    Beier, Søren; Jonsson, Gunnar Eigil

    2010-01-01

    In membrane filtration related scientific literature, often step-by-step determined critical fluxes are reported. Using a dynamic microfiltration device, it is shown that critical fluxes determined from two different flux-stepping methods are dependent upon operational parameters such as step......, such values are more or less useless in itself as critical flux predictors, and constant flux verification experiments have to be conducted to check if the determined critical fluxes call predict sustainable flux regimes. However, it is shown that using the step-by-step predicted critical fluxes as start...

  10. From elementary flux modes to elementary flux vectors: Metabolic pathway analysis with arbitrary linear flux constraints.

    Science.gov (United States)

    Klamt, Steffen; Regensburger, Georg; Gerstl, Matthias P; Jungreuthmayer, Christian; Schuster, Stefan; Mahadevan, Radhakrishnan; Zanghellini, Jürgen; Müller, Stefan

    2017-04-01

    Elementary flux modes (EFMs) emerged as a formal concept to describe metabolic pathways and have become an established tool for constraint-based modeling and metabolic network analysis. EFMs are characteristic (support-minimal) vectors of the flux cone that contains all feasible steady-state flux vectors of a given metabolic network. EFMs account for (homogeneous) linear constraints arising from reaction irreversibilities and the assumption of steady state; however, other (inhomogeneous) linear constraints, such as minimal and maximal reaction rates frequently used by other constraint-based techniques (such as flux balance analysis [FBA]), cannot be directly integrated. These additional constraints further restrict the space of feasible flux vectors and turn the flux cone into a general flux polyhedron in which the concept of EFMs is not directly applicable anymore. For this reason, there has been a conceptual gap between EFM-based (pathway) analysis methods and linear optimization (FBA) techniques, as they operate on different geometric objects. One approach to overcome these limitations was proposed ten years ago and is based on the concept of elementary flux vectors (EFVs). Only recently has the community started to recognize the potential of EFVs for metabolic network analysis. In fact, EFVs exactly represent the conceptual development required to generalize the idea of EFMs from flux cones to flux polyhedra. This work aims to present a concise theoretical and practical introduction to EFVs that is accessible to a broad audience. We highlight the close relationship between EFMs and EFVs and demonstrate that almost all applications of EFMs (in flux cones) are possible for EFVs (in flux polyhedra) as well. In fact, certain properties can only be studied with EFVs. Thus, we conclude that EFVs provide a powerful and unifying framework for constraint-based modeling of metabolic networks.

  11. Developing Structural, High-heat flux and Plasma Facing Materials for a near-term DEMO Fusion Power Plant: the EU Assessment

    CERN Document Server

    Stork, D; Boutard, J-L; Buckthorpe, D; Diegele, E; Dudarev, S L; English, C; Federici, G; Gilbert, M R; Gonzalez, S; Ibarra, A; Linsmeier, Ch; Puma, A Li; Marbach, G; Morris, P F; Packer, L W; Raj, B; Rieth, M; Tran, M Q; Ward, D J; Zinkle, S J

    2014-01-01

    The findings of the EU 'Materials Assessment Group' (MAG), within the 2012 EU Fusion Roadmap exercise, are discussed. MAG analysed the technological readiness of structural, plasma facing and high heat flux materials for a DEMO concept to be constructed in the early 2030s, proposing a coherent strategy for R&D up to a DEMO construction decision. Technical consequences for the materials required and the development, testing and modelling programmes, are analysed using: a systems engineering approach, considering reactor operational cycles, efficient maintenance and inspection requirements, and interaction with functional materials/coolants; and a project-based risk analysis, with R&D to mitigate risks from material shortcomings including development of specific risk mitigation materials.

  12. Flux-P: Automating Metabolic Flux Analysis

    OpenAIRE

    Ebert, Birgitta E.; Anna-Lena Lamprecht; Bernhard Steffen; Blank, Lars M.

    2012-01-01

    Quantitative knowledge of intracellular fluxes in metabolic networks is invaluable for inferring metabolic system behavior and the design principles of biological systems. However, intracellular reaction rates can not often be calculated directly but have to be estimated; for instance, via 13C-based metabolic flux analysis, a model-based interpretation of stable carbon isotope patterns in intermediates of metabolism. Existing software such as FiatFlux, OpenFLUX or 13CFLUX supports experts in ...

  13. Flux Modulation in the Electrodynamic Loudspeaker

    DEFF Research Database (Denmark)

    Halvorsen, Morten; Tinggaard, Carsten; Agerkvist, Finn T.

    2015-01-01

    . Measurements of the generated AC flux modulation shows, that eddy currents are the main source to magnetic losses in form of phase lag and amplitude changes. Use of a copper cap shows a decrease in flux modulation amplitude at the expense of increased power losses. Finally, simulations show...

  14. Power Split Strategy for Fuel Cell Hybrid Electric System Stratégie de séparation des flux de puissance pour un système électrique hybride à pile à combustible

    Directory of Open Access Journals (Sweden)

    Di Domenico D.

    2009-11-01

    Full Text Available The power management of a hybrid system composed of a fuel cell, a battery and a DC/DC power converter is developed. A decoupled control strategy is proposed, aimed at balancing the power flow between the stack and the battery and avoiding electrochemical damage due to low oxygen concentration in the fuel cell cathode. The controller is composed of two components. The first controller regulates the compressor, and as a consequence the oxygen supplied to the cathode, via a classic Proportional-Integral controller. The second controller optimally manages the current demanded by the fuel cell and battery via a linear-quadratic control strategy acting on the converter. An Extended Kalman Filter is also designed in order to estimate the battery State of Charge. The closed-loop performance was tested in simulation using a 310th-order system model. Ce papier illustre une stratégie de gestion de puissance pour un système hybride composé d’une pile à combustible, d’une batterie et d’un convertisseur DC/DC. Dans le but d’équilibrer les flux de puissance entre la pile à combustible et la batterie et d’éviter les dégâts causés par une dépression d’oxygène dans le cathode de la pile, un contrôleur découplé est proposé. Ce contrôleur se compose de deux parties. La première, un régulateur proportionnel-intégral, commande le compresseur et, par conséquent, le flux d’oxygène fourni au cathode. La deuxième, un régulateur linéaire-quadratique, gère le courant demandé par la pile à combustible et la batterie. Pour estimer l’état de charge de la batterie, un filtre de Kalman étendu a aussi été conçu. Les performances de la stratégie ont été analysées en simulation avec un modèle de batterie du 310e ordre.

  15. Development of a high-heat flux cooling element with potential application in a near-term fusion power plant divertor

    Energy Technology Data Exchange (ETDEWEB)

    Nicholas, Jack Robert, E-mail: jack.nicholas@eng.ox.ac.uk [Osney Thermo-Fluids Laboratory, University of Oxford, Oxford (United Kingdom); Ireland, Peter [Osney Thermo-Fluids Laboratory, University of Oxford, Oxford (United Kingdom); Hancock, David [CCFE, Culham, Oxfordshire (United Kingdom); Robertson, Dan [Rolls-Royce Plc., Derby, Derbyshire (United Kingdom)

    2015-10-15

    Highlights: • Laminate jet impingement system introduced for high pressure operation (17 MPa+). • Numerical thermo-fluid analysis on baseline geometry. • Cascade impingement shown to reduce divertor mass flow rate requirements and increase fluid temperature change. • Numerical thermo-fluid analysis validated using scaled experiments with air. - Abstract: A low temperature jet impingement based heat sink module has been developed for potential application in a near-term fusion power plant divertor. The design is composed of a number of hexagonal CuCrZr sheets bonded together in a stack to form a laminate structure. This method allows the production of complex flow paths using relatively simple manufacturing techniques. The thermo-fluid performance of a baseline design employing cascade jet impingement has been assessed and compared to a non-cascade case. Experimental validation of the numerical work was carried out on a scaled model using air as the working fluid. Local heat transfer coefficients were obtained on the surface using surface temperature data from thermochromic liquid crystals.

  16. Metal Abundances in a Damped Lyman-alpha System Along Two Lines of Sight at z=0.93

    CERN Document Server

    López, S; Gregg, M D; Wisotzki, L; Wucknitz, O; Guzman, A

    2005-01-01

    We study metal abundances in the z=0.9313 damped Lya system observed in the two lines-of-sight, A and B, toward the gravitationally-lensed double QSO HE0512-3329. Spatially resolved STIS spectra constrain the neutral-gas column density to be LogN(HI)=20.5 in both Aand B. UVES spectra (spectral resolution FWHM=9.8 km/s) show, in contrast, significant line-of-sight differences in the column densities of MnII and FeII; these are not due to observational systematics. We find that [Mn/H]=-1.44 and [Fe/H]=-1.52 in damped Lya system A, while [Mn/H]=-0.98 and [Fe/H]>-1.32, and possibly as high as [Fe/H] approx. -1 in damped Lya system B. A careful assessment of possible systematic errors leads us to conclude that these transverse differences are significant at a 5 sigma level or greater. Although nucleosynthesis effects may also be at play, we favor differential dust-depletion as the main mechanism producing the observed abundance gradient. The transverse separation is 5 kpc at the redshift of the absorber, which is ...

  17. Lyman-\\alpha{} Emitters in the context of hierarchical galaxy formation: predictions for VLT/MUSE surveys

    CERN Document Server

    Garel, Thibault; Blaizot, Jérémy

    2015-01-01

    The VLT Multi Unit Spectroscopic Explorer (MUSE) integral-field spectrograph can detect Ly\\alpha{} emitters (LAE) in the redshift range $2.8 \\lesssim z \\lesssim 6.7$ in a homogeneous way. Ongoing MUSE surveys will notably probe faint Ly\\alpha{} sources that are usually missed by current narrow-band surveys. We provide quantitative predictions for a typical wedding-cake observing strategy with MUSE based on mock catalogs generated with a semi-analytic model of galaxy formation coupled to numerical Ly\\alpha{} radiation transfer models in gas outflows. We expect $\\approx$ 1500 bright LAEs ($F_{Ly\\alpha}$ $\\gtrsim$ $10^{-17}$ erg s$^{-1}$ cm$^{-2}$) in a typical Shallow Field (SF) survey carried over $\\approx$ 100 arcmin$^2$, and $\\approx$ 2,000 sources as faint as $10^{-18}$ erg s$^{-1}$ cm$^{-2}$ in a Medium-Deep Field (MDF) survey over 10 arcmin$^2$. In a typical Deep Field (DF) survey of 1 arcmin$^2$, we predict that $\\approx$ 500 extremely faint LAEs ($F_{Ly\\alpha}$ $\\gtrsim$ $4 \\times 10^{-19}$ erg s$^{-1}$...

  18. Ubiquitous giant Lyman $\\alpha$ nebulae around the brightest quasars at $z\\sim3.5$ revealed with MUSE

    CERN Document Server

    Borisova, Elena; Lilly, Simon J; Marino, Raffaella A; Gallego, Sofia G; Bacon, Roland; Blaizot, Jeremy; Bouché, Nicolas; Brinchmann, Jarle; Carollo, C Marcella; Caruana, Joseph; Finley, Hayley; Herenz, Edmund C; Richard, Johan; Schaye, Joop; Straka, Lorrie A; Turner, Monica L; Urrutia, Tanya; Verhamme, Anne; Wisotzki, Lutz

    2016-01-01

    Direct Lyman a imaging of fluorescent emission from intergalactic gas at z~2 has recently revealed giant cosmological structures around luminous quasars with unexpected physical properties, e.g. the Slug Nebula (Cantalupo et al. 2014). Despite their high luminosity, the detection rate of such systems in narrow-band and spectroscopic surveys is very low, i.e. less than 10%. If intrinsic and not due to observational limitations, such a low detection frequency would encode crucial information on the distribution and properties of cold gas around quasars, their emission opening angle and duty cycle. In this study, we exploit the unique capabilities of the MUSE ESO/VLT to perform a blind survey for giant Ly $\\alpha$ nebulae around 17 of the brightest radio-quiet quasars at 3

  19. Electron impact excitation of H2 - Rydberg band systems and the benchmark dissociative cross section for H Lyman-alpha

    Science.gov (United States)

    Shemansky, D. E.; Hall, D. T.; Ajello, J. M.

    1985-01-01

    The cross sections sigma R 1 (2p) for excitation of H Ly-alpha emission produced by electron impact on H2 is reexamined. A more accurate estimate for sigma R 1 (2p) is obtained based on Born approximation estimates of the H2 Rydberg system cross sections using measured relative excitation functions. The obtained value is (8.18 + or -1.2) x 10 to the -18th sq cm at 100 eV, a factor of 0.69 below the value universally applied to cross section measurements over the past decade. Cross sections for the H2 Rydberg systems fixed in magnitude by the Born approximation have also been obtained using experimentally determined excitation functions. Accurate analytic expressions for these cross sections allow the direct calculation of rate coefficients.

  20. Diagnosing the reionization of the universe - The absorption spectrum of the intergalactic medium and Lyman alpha clouds

    Science.gov (United States)

    Giroux, Mark L.; Shapiro, Paul R.

    1991-01-01

    The thermal and ionization evolution of a uniform intergalactic medium composed of H and He and undergoing reionization is studied. The diagnosis of the metagalactic ionizing radiation background at z of about three using metal line ratios for Lyman limit quasar absorption line systems is addressed. The use of the He II Gunn-Peterson effect to diagnose the reionization source and/or nature of the Hy-alpha forest clouds is considered.

  1. Search for cold gas in z>2 damped Lyman-alpha systems: 21-cm and H_2 absorption

    CERN Document Server

    Srianand, R; Petitjean, P; Noterdaeme, P; Ledoux, C; Salter, C J; Saikia, D J

    2011-01-01

    (Abridged) We present the results of a systematic GBT and GMRT survey for 21-cm absorption in a sample of 10 DLAs at 2 2 is predominantly constituted by WNM. The detection rate of 21-cm absorption seems to be higher for systems with higher N(HI) or metallicity. However, no clear correlation is found between the integrated 21-cm optical depth (or spin temperature) and either N(HI), metallicity or velocity spread of the low ionization species. There are 13 DLAs in our sample for which high resolution optical spectra covering the expected wavelength range of H_2 absorption are available. We report the detection of H_2 molecules in the z_abs = 3.3871 21-cm absorber towards J0203+1134 (PKS 0201+113). In 8 cases, neither H_2 nor 21-cm absorption are detected. The lack of 21-cm and H_2 absorption in these systems can be explained if most of the HI in these DLAs originate from low density high temperature gas. In one case we have a DLA with 21-cm absorption not showing H_2 absorption. In two cases, both species are d...

  2. The Gravitational Lensing in the QSO 1208+10 from the Proximity Effect in its $Lyman \\alpha$ Forest

    CERN Document Server

    Giallongo, E; Cristiani, S; D'Odorico, S

    1999-01-01

    The quasar Q1208+1011 (z_{em}=3.8) is the second highest redshift double quasar ever detected. Several indications point toward it being a gravitational lensed system, although a definitive proof is still lacking. We present new evidence of its lensed nature based on the weakness of the ``proximity effect'' measured in the high resolution Lyman absorption spectrum of the QSO. A luminosity amplification as large as 22 has been derived from this analysis. Indications on the redshift of the lensing galaxy can be obtained from the analysis of the intervening heavy element absorption systems discovered in the QSO high resolution spectrum. On statistical and dynamical grounds a MgII system present at z=1.13 appears as the most likely candidate for the lensing galaxy. We compare the observed parameters with a simple isothermal model for the lens to derive the properties of the lensing galaxy. The resulting magnification factor is smaller, although marginally consistent with that derived by the analysis of the proxim...

  3. Galaxy Group at z=0.3 Associated with the Damped Lyman Alpha System Towards Quasar Q1127-145

    CERN Document Server

    Kacprzak, G G; Churchill, C W

    2010-01-01

    We performed a spectroscopic galaxy survey, complete to $m_{F814W}\\leq20.3$ ($L_B>0.15L_B^{\\star}$ at z=0.3), within 100x100'' of the quasar Q1127-145 ($z_{em}=1.18$). The VLT/UVES quasar spectrum contains three $z_{abs}<0.33$ MgII absorption systems. We obtained eight new galaxy redshifts, adding to the four previously known, and galaxy star formation rates (SFRs) and metallicities were computed where possible. A strong MgII system [$W_r(2796)=1.8$A], which is a known damped Ly$\\alpha$ absorber (DLA), had three previously identified galaxies; we found two additional galaxies associated with this system. These five galaxies form a group with diverse properties, such as a luminosity range of $0.04\\leq L_B\\leq0.63 L_B^{\\star}$, an impact parameter range of $17\\leq D \\leq 241$ kpc and velocity dispersion of $\\sigma$=115 km/s. The DLA group galaxy redshifts span beyond the 350 km/s velocity spread of the metallic absorption lines of the DLA itself. The two brightest group galaxies have SFRs of $\\sim$few $M_{\\o...

  4. First Detection of NaI D lines in High-Redshift Damped Lyman-alpha Systems

    CERN Document Server

    Kondo, S; Gässler, W; Hayano, Y; Iye, M; Kamata, Y; Kanzawa, T; Kobayashi, N; Minowa, Y; Nedachi, K; Oya, S; Pyo, T S; Saint-Jacques, D; Takami, H; Takato, N; Terada, H; Tokunaga, A; Tsujimoto, T; Churchill, Christopher W.; Gaessler, Wolfgang; Hayano, Yutaka; Iye, Masanori; Kamata, Yukiko; Kanzawa, Tomio; Kobayashi, Naoto; Kondo, Sohei; Minowa, Yosuke; Nedachi, Ko; Oya, Shin; Pyo, Tae-Soo; Takami, Hideki; Takato, Naruhisa; Terada, Hiroshi; Tokunaga, Alan; Tsujimoto, Takuji

    2006-01-01

    A Near-infrared (1.18-1.35 micron) high-resolution spectrum of the gravitationally-lensed QSO APM 08279+5255 was obtained with the IRCS mounted on the Subaru Telescope using the AO system. We detected strong NaI D 5891,5897 doublet absorption in high-redshift DLAs at z=1.062 and 1.181, confirming the presence of NaI, which was first reported for the rest-frame UV NaI 3303.3,3303.9 doublet by Petitjean et al. This is the first detection of NaI D absorption in a high-redshift (z>1) DLA. In addition, we detected a new NaI component in the z=1.062 DLA and four new components in the z=1.181 DLA. Using an empirical relationship between NaI and HI column density, we found that all "components" have large HI column density, so that each component is classified as DLA absorption. We also detected strong NaI D absorption associated with a MgII system at z=1.173. Because no other metal absorption lines were detected in this system at the velocity of the NaI absorption in previously reported optical spectra (observed 3.6...

  5. Deep SAURON Spectral-Imaging of the diffuse Lyman-alpha halo LAB1 in SSA22

    CERN Document Server

    Bower, R; Bacon, R; Wilman, R J; Sullivan, M; Chapman, S C; Davies, R L; De Zeeuw, P T; Emsellem, E; Bower, Richard

    2004-01-01

    We have used the SAURON panoramic integral field spectrograph to study the structure of the Ly-alpha emission-line halo, LAB1, surrounding the sub-millimeter galaxy SMM J221726+0013. This emission-line halo was discovered during a narrow-band imaging survey of the z=3.1 large-scale structure in the SSA22 region. Our observations trace the emission halo out to almost 100 kpc from the sub-millimeter source and identify two distinct Ly-alpha `mini-haloes' around the nearby Lyman-break galaxies. The main emission region has a broad line profile, with variations in the line profile seeming chaotic and lacking evidence for a coherent velocity structure. The data also suggests that Ly-alpha emission is suppressed around the sub-mm source. Interpretation of the line structure needs care because Ly-alpha may be resonantly scattered, leading to complex radiative transfer effects, and we suggest that the suppression in this region arises because of such effects. We compare the structure of the central emission-line halo...

  6. Discovery of Massive, Mostly Star-formation Quenched Galaxies with Extremely Large Lyman-alpha Equivalent Widths at z ~ 3

    CERN Document Server

    Taniguchi, Yoshiaki; Kobayashi, Masakazu A R; Nagao, Tohru; Shioya, Yasuhiro; Scoville, Nick Z; Sanders, David B; Capak, Peter L; Koekemoer, Anton M; Toft, Sune; McCracken, Henry J; Fevre, Olivier Le; Tasca, Lidia; Sheth, Kartik; Renzini, Alvio; Lilly, Simon; Carollo, Marcella; Kovac, Katarina; Ilbert, Olivier; Schinnerer, Eva; Fu, Hai; Tresse, Laurence; Griffiths, Richard E; Civano, Francesca

    2015-01-01

    We report a discovery of 6 massive galaxies with both extremely large Lya equivalent width and evolved stellar population at z ~ 3. These MAssive Extremely STrong Lya emitting Objects (MAESTLOs) have been discovered in our large-volume systematic survey for strong Lya emitters (LAEs) with twelve optical intermediate-band data taken with Subaru/Suprime-Cam in the COSMOS field. Based on the SED fitting analysis for these LAEs, it is found that these MAESTLOs have (1) large rest-frame equivalent width of EW_0(Lya) ~ 100--300 A, (2) M_star ~ 10^10.5--10^11.1 M_sun, and (3) relatively low specific star formation rates of SFR/M_star ~ 0.03--1 Gyr^-1. Three of the 6 MAESTLOs have extended Ly$\\alpha$ emission with a radius of several kpc although they show very compact morphology in the HST/ACS images, which correspond to the rest-frame UV continuum. Since the MAESTLOs do not show any evidence for AGNs, the observed extended Lya emission is likely to be caused by star formation process including the superwind activit...

  7. PACS-Herschel FIR detections of Lyman-alpha emitters at 2.0

    CERN Document Server

    Oteo, I; García, A M Pérez; Cepa, J; Ederoclite, A; Sánchez-Portal, M; Pintos-Castro, I; Pérez-Martínez, R; Altieri, B; Andreani, P; Aussel, H; Berta, S; Cimatti, A; Daddi, E; Elbaz, D; Schreiber, N Förster; Genzel, R; Lutz, D; Magnelli, B; Maiolino, R; Poglitsch, A; Popesso, P; Pozzi, F; Sturm, E; Tacconi, L; Valtchanov, I

    2012-01-01

    In this work we analyze the physical properties of a sample of 56 spectroscopically selected star-forming (SF) Ly$\\alpha$ emitting galaxies at 2.0$\\lesssim$z$\\lesssim$3.5 using both a spectral energy distribution (SED) fitting procedure from rest-frame UV to mid-IR and direct 160$\\mu$m observations taken with the Photodetector Array Camera & Spectrometer (PACS) instrument onboard \\emph{Herschel Space Observatory}. We define LAEs as those Ly$\\alpha$ emitting galaxies whose rest-frame Ly$\\alpha$ equivalent widths (Ly$\\alpha$ EW$_{rest-frame}$) are above 20\\AA, the typical threshold in narrow-band searches. Ly$\\alpha$ emitting galaxies with Ly$\\alpha$ EW$_{rest-frame}$ are called non-LAEs. As a result of an individual SED fitting for each object, we find that the studied sample of LAEs contains galaxies with ages mostly below 100Myr and a wide variety of dust attenuations, SFRs, and stellar masses. The heterogeneity in the physical properties is also seen in the morphology, ranging from bulge-like galaxies t...

  8. Molecular Hydrogen in the Damped Lyman-alpha System towards GRB 120815A at z=2.36

    CERN Document Server

    Krühler, T; Fynbo, J P U; Vreeswijk, P M; Schmidl, S; Malesani, D; Christensen, L; De Cia, A; Hjorth, J; Jakobsson, P; Kann, D A; Kaper, L; Vergani, S D; Afonso, P M J; Covino, S; Postigo, A de Ugarte; D'Elia, V; Filgas, R; Goldoni, P; Greiner, J; Hartoog, O E; Milvang-Jensen, B; Nardini, M; Piranomonte, S; Rossi, A; Sánchez-Ramírez, R; Schady, P; Schulze, S; Sudilovsky, V; Tanvir, N R; Tagliaferri, G; Watson, D J; Wiersema, K; Wijers, R A M J; Xu, D

    2013-01-01

    [Abridged] Molecular hydrogen H_2 is a key requirement for star-formation, frequently observed along sightlines in the Galaxy and to the Magellanic Clouds, but notoriously hard to detect directly beyond z ~ 0. In the DLAs associated with long gamma-ray bursts (GRBs), which are tightly linked to vigorous star-formation, H_2 has remained largely elusive, and has been unequivocally detected only towards GRB 080607 and possibly towards GRB 060206. Here, we present the discovery of H_2-rich gas, including the presence of vibrationally-excited H_2^* in the optical spectrum of the afterglow of GRB 120815A at z=2.36 obtained with X-shooter at the VLT. The galactic environment of GRB 120815A is characterized by a strong DLA with log(N(H)/cm^-2) = 21.95 +/- 0.10, prominent H_2 absorption in the Lyman-Werner bands (log(N(H_2)/cm^-2) = 20.53 +/- 0.04) and thus a molecular gas fraction log f(H_2)=-1.14 +/- 0.10. The distance d between the absorbing neutral gas and GRB 120815A is constrained via photo-excitation modeling o...

  9. Far ultraviolet imaging from the IMAGE spacecraft. 3. Spectral imaging of Lyman-alpha and OI 135.6 nm

    OpenAIRE

    Mende, S. B.; Heetderks, H.; H. U. Frey; Stock, J. M.; Lampton, M.; Geller, S. P.; Abiad, R.; Siegmund, O. H. W.; Habraken, Serge; Renotte, Etienne; Jamar, Claude; Rochus, Pierre; Gérard, Jean-Claude; Sigler, R.; Lauche, H.

    2000-01-01

    Two FUV Spectral imaging instruments, the Spectrographic Imager (SI) and the Geocorona Photometer (GEO) provide IMAGE with simultaneous global maps of the hydrogen (121.8 nm) and oxygen 135.6 nm components of the terrestrial aurora and with observations of the three dimensional distribution of neutral hydrogen in the magnetosphere (121.6 nm). The SI is a novel instrument type, in which spectral separation and imaging functions are independent of each other. In this instrument, two-dimensional...

  10. A SINFONI Integral Field Spectroscopy Survey for Galaxy Counterparts to Damped Lyman-alpha Systems - IV. Masses and Gas Flows

    CERN Document Server

    Peroux, Celine; Kulkarni, Varsha P; York, Donald G

    2013-01-01

    The circumgalactic medium (CGM) of typical galaxies is crucial to our understanding of the cycling of gas into, through and out of galaxies. One way to probe the CGM is to study gas around galaxies detected via the absorption lines they produce in the spectra of background quasars. Here, we present medium resolution and new ~0.4-arcsec resolution (~3 kpc at z~1) 3D observations with VLT/SINFONI of galaxies responsible for high-N(HI) quasar absorbers. These data allow to determine in details the kinematics of the objects: the four z~1 objects are found to be rotation-supported as expected from inclined discs, while the fifth z~2 system is dispersion-dominated. Two of the systems show sign of interactions and merging. In addition, we use several indicators (star formation per unit area, a comparison of emission and absorption kinematics, arguments based on the inclination and the orientation of the absorber to the quasar line-of-sight and the distribution of metals) to determine the direction of the gas flows i...

  11. Solar H-alpha features with hot onsets. III. Long fibrils in Lyman-alpha and with ALMA

    Science.gov (United States)

    Rutten, R. J.

    2017-02-01

    In H-alpha most of the solar surface is covered by dense canopies of long opaque fibrils, but predictions for quiet-Sun observations with ALMA have ignored this fact. Comparison with Ly-alpha suggests that the extraordinary opacity of H-alpha fibrils is caused by hot precursor events. Application of a recipe that assumes momentary Saha-Boltzmann extinction during their hot onset to millimeter wavelengths suggests that ALMA will observe H-alpha-like fibril canopies, not acoustic shocks underneath, and will yield data more interesting than if these canopies were transparent. An additional file is available at the end of the PDF file of this article.This study is offered as compliment to M.W.M. de Graauw. Our ways, objects, instruments and spectral domains parted after the 1970 eclipse but converge here.

  12. Mock Quasar-Lyman-{\\alpha} Forest Data-sets for the SDSS-III Baryon Oscillation Spectroscopic Survey

    CERN Document Server

    Bautista, Julian E; Font-Ribera, Andreu; Pieri, Matthew M; Busca, Nicolás G; Miralda-Escudé, Jordi; Palanque-Delabrouille, Nathalie; Rich, James; Dawson, Kyle; Feng, Yu; Ge, Jian; Gontcho, Satya Gontcho A; Ho, Shirley; Goff, Jean Marc Le; Noterdaeme, Pasquier; Pâris, Isabelle; Rossi, Graziano; Schlegel, David

    2014-01-01

    We describe mock data-sets generated to simulate the high-redshift quasar sample in Data Release 11 (DR11) of the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). The mock spectra contain Ly{\\alpha} forest correlations useful for studying the 3D correlation function including Baryon Acoustic Oscillations (BAO). They also include astrophysical effects such as quasar continuum diversity and high-density absorbers, instrumental effects such as noise and spectral resolution, as well as imperfections introduced by the SDSS pipeline treatment of the raw data. The Ly{\\alpha} forest BAO analysis of the BOSS collaboration, described in Delubac et al. 2014, has used these mock data-sets to develop and cross-check analysis procedures prior to performing the BAO analysis on real data, and for continued systematic cross checks. Tests presented here show that the simulations reproduce sufficiently well important characteristics of real spectra. These mock data-sets will be made available together with the data at t...

  13. The ALFALFA HI Absorption Pilot Survey: A Wide-Area Blind Damped Lyman Alpha System Survey of the Local Universe

    CERN Document Server

    Darling, Jeremy; Haynes, Martha P; Giovanelli, Riccardo

    2011-01-01

    We present the results of a pilot survey for neutral hydrogen (HI) 21 cm absorption in the Arecibo Legacy Fast Arecibo L-Band Feed Array (ALFALFA) Survey. This project is a wide-area "blind" search for HI absorption in the local universe, spanning -650 km/s = 2x10^20 cm^-2) is Delta z = 7.0 (129 objects, assuming T_s = 100 K and covering fraction unity); for super-DLAs (N_HI >= 2x10^21 cm^-2) it is Delta z= 128.2 (2353 objects). We re-detect the intrinsic HI absorption line in UGC 6081 but detect no intervening absorption line systems. We compute a 95% confidence upper limit on the column density frequency distribution function f(N_HI,X) spanning four orders of magnitude in column density, 10^19 (T_s/100 K)(1/f) cm^-2 < N_HI < 10^23 (T_s/100 K)(1/f) cm^-2, that is consistent with previous redshifted optical damped Ly alpha surveys and the aggregate HI 21 cm emission in the local universe. The detection rate is in agreement with extant observations. This pilot survey suggests that an absorption line sear...

  14. THE LYMAN ALPHA REFERENCE SAMPLE. V. THE IMPACT OF NEUTRAL ISM KINEMATICS AND GEOMETRY ON Lyα ESCAPE

    Energy Technology Data Exchange (ETDEWEB)

    Rivera-Thorsen, Thøger E.; Hayes, Matthew; Östlin, Göran; Duval, Florent; Sandberg, Andreas; Guaita, Lucia; Adamo, Angela [Department of Astronomy, Oskar Klein Centre, Stockholm University, AlbaNova University Centre, SE-106 91 Stockholm (Sweden); Orlitová, Ivana [Astronomical Institute, Academy of Sciences of the Czech Republic, Boční II, CZ-14131 Prague (Czech Republic); Verhamme, Anne; Schaerer, Daniel [Geneva Observatory, University of Geneva, 51 Chemin des Maillettes, CH-1290 Versoix (Switzerland); Mas-Hesse, J. Miguel [Centro de Astrobiología (CSIC–INTA), Departamento de Astrofísica, P.O. Box 78, E-28691 Villanueva de la Cañada (Spain); Cannon, John M. [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States); Otí-Floranes, Héctor [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 106, B. C. 22800 Ensenada (Mexico); Atek, Hakim [Laboratoire d’Astrophysique, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire, CH-1290 Sauverny (Switzerland); Herenz, E. Christian [Leibniz-Institut für Astrophysik (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Kunth, Daniel, E-mail: trive@astro.su.se [Institut d’Astrophysique de Paris, UMR 7095 CNRS and UPMC, 98 bis Bd Arago, F-75014 Paris (France); and others

    2015-05-20

    We present high-resolution far-UV spectroscopy of the 14 galaxies of the Lyα Reference Sample; a sample of strongly star-forming galaxies at low redshifts (0.028 < z < 0.18). We compare the derived properties to global properties derived from multi-band imaging and 21 cm H i interferometry and single-dish observations, as well as archival optical SDSS spectra. Besides the Lyα line, the spectra contain a number of metal absorption features allowing us to probe the kinematics of the neutral ISM and evaluate the optical depth and and covering fraction of the neutral medium as a function of line of sight velocity. Furthermore, we show how this, in combination with the precise determination of systemic velocity and good Lyα spectra, can be used to distinguish a model in which separate clumps together fully cover the background source, from the “picket fence” model named by Heckman et al. We find that no one single effect dominates in governing Lyα radiative transfer and escape. Lyα escape in our sample coincides with a maximum velocity-binned covering fraction of ≲0.9 and bulk outflow velocities of ≳50 km s{sup −1}, although a number of galaxies show these characteristics and yet little or no Lyα escape. We find that Lyα peak velocities, where available, are not consistent with a strong backscattered component, but rather with a simpler model of an intrinsic emission line overlaid by a blueshifted absorption profile from the outflowing wind. Finally, we find a strong anticorrelation between Hα equivalent width and maximum velocity-binned covering factor, and propose a heuristic explanatory model.

  15. Design of Double Stator Axial Flux Permanent Magnet Synchronous Wind Power Generator%双定子轴向磁场永磁同步风力发电机的设计

    Institute of Scientific and Technical Information of China (English)

    邓秋玲; 黄守道; 刘婷

    2012-01-01

    Axial flux machines can compete with traditional radial flux machines in terms of torque and power density if the number of pole-pairs is sufficiently high and the ratio of axial length to outer diameter is low. However, it is difficult to manufacture the armature core of the axial flux machine. So this paper proposed a new method. The stator of the machine was realized by using soft magnet compound (SMC) to form a teeth, which was combined with a strip punched laminated core and concentrated winding. Then the electromagnetic design of the machine was performed, and the magnetic field was simulated in the Ansoft Infinite Element Analysis method. Design results and simulation results have indicated that the suitable choice of the main dimensions of the machine and the ratio of the number of pole to slot can achieve sinusoidal emf waveform and small cogging torque.%研究表明:如果电机的极数足够多,轴向长度与外径的比率足够小的话,轴向磁场电机比传统径向磁场电机的转矩和功率密度大.轴向磁场电机的缺点是电枢铁心制造比较困难.为此本文提出一种新的结构方案,用软磁复合材料形成定子的齿部,再与带冲叠片形成的铁心轭部结合起来形成定子铁心,并且使用集中绕组.然后对这种新型轴向磁场电机进行了电磁设计,并用Ansoft有限元法对电机的磁场进行了仿真.结果表明:通过合理地选择主要尺寸和极数/槽数比,可以获得正弦波的电动势波形和较小的齿槽转矩.

  16. 塔式太阳能电站集热管非均匀受热特性研究%Heat transfer performance of water-vapor receiver with uneven heat flux in solar power tower plant

    Institute of Scientific and Technical Information of China (English)

    曹传钊; 韩临武; 徐海卫; 刘明义; 裴杰

    2015-01-01

    塔式太阳能电站吸热器中的集热管是光热转换的核心组件。集热管面向镜场的半圆周受热,且热流密度沿圆周和轴向不断变化,背向镜场的半圆周绝热,同时集热管内水-蒸汽工质的沸腾流动换热尤为复杂,研究其受热特性有助于深入了解塔式电站吸热器集热管的整体性能。为此,建立了轴向和周向不均匀热流边界条件下水-蒸汽集热管内的数值模型。基于 Fluent平台,计算三维、非稳态的汽液两相流动,通过模拟分析呈现了管内的汽液两相流动特性,同时揭示了在这种极不均匀热流条件下,集热管的温度分布规律及其传热特性。%Heat collector pipe in receiver of solar thermal power tower plants is a kernel unit to convert solar energy into thermal energy.Only the semi-circumference facing the heliostat field receives heat flux,while the other semi-circumference depart from the heliostat field is adiabatic.What's more,the heat transfer of boiling flow in the pipe with the water-vapor as the working fluid is especially complex.So the understand-ing of the heat transfer characteristics in it is significant and important.Through Fluent software,numeri-cal model of the water-vapor tube under uneven heat flux boundary with semi-circumference heated and the other semi-circumference adiabatic was established.The three-dimensional and unsteady water-vapor two-phase flow was numerically simulated.So,flow characteristics of the two-phase flow were obtained,and temperature distribution and heat transfer characteristics of the tube under uneven heat flux were revealed.

  17. A Reconnecting Flux Rope Dynamo

    CERN Document Server

    Baggaley, Andrew W; Shukurov, Anvar; Subramanian, Kandaswamy

    2009-01-01

    We develop a new model of the fluctuation dynamo in which the magnetic field is confined in thin flux ropes advected by a multi-scale flow modeling turbulence. Magnetic dissipation occurs only via reconnection of the flux ropes. We investigate the kinetic energy release into heat, mediated by the dynamo action, both in our model and by solving the induction equation with the same flow. We find that a flux rope dynamo is an order of magnitude more efficient at converting mechanical energy into heat. The probability density of the magnetic energy release in reconnections has a power-law form with the slope -3, consistent with the Solar corona heating by nanoflares.

  18. Reconnecting flux-rope dynamo

    Science.gov (United States)

    Baggaley, Andrew W.; Barenghi, Carlo F.; Shukurov, Anvar; Subramanian, Kandaswamy

    2009-11-01

    We develop a model of the fluctuation dynamo in which the magnetic field is confined to thin flux ropes advected by a multiscale model of turbulence. Magnetic dissipation occurs only via reconnection of the flux ropes. This model can be viewed as an implementation of the asymptotic limit Rm→∞ for a continuous magnetic field, where magnetic dissipation is strongly localized to small regions of strong-field gradients. We investigate the kinetic-energy release into heat mediated by the dynamo action, both in our model and by solving the induction equation with the same flow. We find that a flux-rope dynamo is an order of magnitude more efficient at converting mechanical energy into heat. The probability density of the magnetic energy release in reconnections has a power-law form with the slope -3 , consistent with the solar corona heating by nanoflares.

  19. Reconnecting flux-rope dynamo.

    Science.gov (United States)

    Baggaley, Andrew W; Barenghi, Carlo F; Shukurov, Anvar; Subramanian, Kandaswamy

    2009-11-01

    We develop a model of the fluctuation dynamo in which the magnetic field is confined to thin flux ropes advected by a multiscale model of turbulence. Magnetic dissipation occurs only via reconnection of the flux ropes. This model can be viewed as an implementation of the asymptotic limit R_{m}-->infinity for a continuous magnetic field, where magnetic dissipation is strongly localized to small regions of strong-field gradients. We investigate the kinetic-energy release into heat mediated by the dynamo action, both in our model and by solving the induction equation with the same flow. We find that a flux-rope dynamo is an order of magnitude more efficient at converting mechanical energy into heat. The probability density of the magnetic energy release in reconnections has a power-law form with the slope -3 , consistent with the solar corona heating by nanoflares.

  20. The extent of the influence and flux estimation of volatile mercury from the aeration pool in a typical coal-fired power plant equipped with a seawater flue gas desulfurization system.

    Science.gov (United States)

    Sun, Lumin; Feng, Lifeng; Yuan, Dongxing; Lin, Shanshan; Huang, Shuyuan; Gao, Liangming; Zhu, Yong

    2013-02-01

    Before being discharged, the waste seawater from the flue gas desulfurization system of coal-fired power plants contains a large amount of mercury, and is treated in aeration pools. During this aeration process, part of the mercury enters the atmosphere, but only very limited impact studies concerning this have been carried out. Taking a typical Xiamen power plant as an example, the present study targeted the elemental mercury emitted from the aeration pool. Concentrations of dissolved gaseous mercury as high as 1.14 ± 0.17 ng·L(-1) were observed in the surface waste seawater in the aeration pool, and gaseous elemental mercury (GEM) as high as 10.94 ± 1.89 ng·m(-3) was found in the air above the pool. To investigate the area affected by this GEM through air transfer, the total mercury in the dust and topsoil samples around the aeration pool were analyzed. Much higher values were found compared to those at a reference site. Environmental factors other than solar radiation had limited influence on the concentrations of the mercury species in the pool. A simulation device was built in our laboratory to study the flux of mercury from the aeration pool into the air. The results showed that more than 0.59 kg of mercury was released from the aeration pool every year, occupying 0.3% of the total mercury in the waste seawater. The transfer of mercury from water to air during the aeration pool and its environmental influence should not be ignored.

  1. Constraints on mixed dark matter from anomalous strong lens systems

    CERN Document Server

    Kamada, Ayuki; Takahashi, Tomo

    2016-01-01

    Recently it has been claimed that the warm dark matter (WDM) model cannot at the same time reproduce the observed Lyman-{\\alpha} forests in distant quasar spectra and solve the small-scale issues in the cold dark matter (CDM) model. As an alternative candidate, it was shown that the mixed dark matter (MDM) model that consists of WDM and CDM can satisfy the constraint from Lyman-{\\alpha} forests and account for the "missing satellite problem" as well as the reported 3.5 keV anomalous X-ray line. We investigate observational constraints on the MDM model using strong gravitational lenses. We first develop a fitting formula for the nonlinear power spectra in the MDM model by performing N-body simulations and estimate the expected perturbations caused by line-of-sight structures in four quadruply lensed quasars that show anomaly in the flux ratios. Our analysis indicates that the MDM model is compatible with the observed anomaly if the mass fraction of the warm component is smaller than 0.47 at the 95% confidence ...

  2. Flux-P: Automating Metabolic Flux Analysis

    Directory of Open Access Journals (Sweden)

    Birgitta E. Ebert

    2012-11-01

    Full Text Available Quantitative knowledge of intracellular fluxes in metabolic networks is invaluable for inferring metabolic system behavior and the design principles of biological systems. However, intracellular reaction rates can not often be calculated directly but have to be estimated; for instance, via 13C-based metabolic flux analysis, a model-based interpretation of stable carbon isotope patterns in intermediates of metabolism. Existing software such as FiatFlux, OpenFLUX or 13CFLUX supports experts in this complex analysis, but requires several steps that have to be carried out manually, hence restricting the use of this software for data interpretation to a rather small number of experiments. In this paper, we present Flux-P as an approach to automate and standardize 13C-based metabolic flux analysis, using the Bio-jETI workflow framework. Exemplarily based on the FiatFlux software, it demonstrates how services can be created that carry out the different analysis steps autonomously and how these can subsequently be assembled into software workflows that perform automated, high-throughput intracellular flux analysis of high quality and reproducibility. Besides significant acceleration and standardization of the data analysis, the agile workflow-based realization supports flexible changes of the analysis workflows on the user level, making it easy to perform custom analyses.

  3. Clustering of Emerging Flux

    Science.gov (United States)

    Ruzmaikin, A.

    1997-01-01

    Observations show that newly emerging flux tends to appear on the Solar surface at sites where there is flux already. This results in clustering of solar activity. Standard dynamo theories do not predict this effect.

  4. The ultraviolet spectra of intermediate-redshift quasars

    Science.gov (United States)

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

    1985-01-01

    In the present sample of 21 intermediate redshift quasars, for which IUE Lyman-alpha line flux and UV continuum observations have been conducted, an extrapolation of the continuum to the X-ray region is noted to fall at least 2-sigma above the measured X-ray flux, at 2 keV, for two-thirds of the sample. The strength of Lyman-alpha is well correlated with the luminosity at 1450 A, and an estimate of the covering factor on the basis of the ratio of the number of Lyman-alpha to ionizing protons yields a value for the sample which, at about 0.17, is consistent with the number of observed Lyman discontinuities.

  5. Size-Flux Relation in Solar Active Regions

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    We present a study of the relationship between integral area and corre-sponding total magnetic flux for solar active regions. It is shown that some of theserelationships are satisfied to simple power laws. Fractal examination showed thatsome of these power laws can not be justified inside the simple models of stationarymagnetic flux tube aggregation. All magnetic fluxes and corresponding areas werecalculated using the data measured with the Solar Magnetic Field Telescope of theHuairou Solar Observing Station in Beijing.

  6. FLUXES FOR MECHANIZED ELECTRIC WELDING,

    Science.gov (United States)

    WELDING FLUXES, WELDING ), (* WELDING , WELDING FLUXES), ARC WELDING , WELDS, STABILITY, POROSITY, WELDING RODS, STEEL, CERAMIC MATERIALS, FLUXES(FUSION), TITANIUM ALLOYS, ALUMINUM ALLOYS, COPPER ALLOYS, ELECTRODEPOSITION

  7. A time-varying magnetic flux concentrator

    Science.gov (United States)

    Kibret, B.; Premaratne, M.; Lewis, P. M.; Thomson, R.; Fitzgerald, P. B.

    2016-08-01

    It is known that diverse technological applications require the use of focused magnetic fields. This has driven the quest for controlling the magnetic field. Recently, the principles in transformation optics and metamaterials have allowed the realization of practical static magnetic flux concentrators. Extending such progress, here, we propose a time-varying magnetic flux concentrator cylindrical shell that uses electric conductors and ferromagnetic materials to guide magnetic flux to its center. Its performance is discussed based on finite-element simulation results. Our proposed design has potential applications in magnetic sensors, medical devices, wireless power transfer, and near-field wireless communications.

  8. Patterns of Flux Emergence

    Science.gov (United States)

    Title, A.; Cheung, M.

    2008-05-01

    The high spatial resolution and high cadence of the Solar Optical Telescope on the JAXA Hinode spacecraft have allowed capturing many examples of magnetic flux emergence from the scale of granulation to active regions. The observed patterns of emergence are quite similar. Flux emerges as a array of small bipoles on scales from 1 to 5 arc seconds throughout the region that the flux eventually condenses. Because the fields emerging from the underlying flux rope my appear many in small segments and the total flux (absolute sum) is not a conserved quantity the amount of total flux on the surface may vary significantly during the emergence process. Numerical simulations of flux emergence exhibit patterns similar to observations. Movies of both observations and numerical simulations will be presented.

  9. Magnetic Flux Controllers for Induction Heating Applications

    Institute of Scientific and Technical Information of China (English)

    Valentin Nemkov; Robert Goldstein; Robert Ruffini

    2004-01-01

    Application of magnetic flux controllers/concentrators to induction heating coils can drastically improve the process efficiency and heat pattern control. Presentation includes: benefits provided by flux controllers, materials available for controllers, application techniques, computer assisted design of induction coils with concentrators, examples of applications. Depending on induction system design, magnetic flux controllers can concentrate heating in a specified area,change heat source distribution and shield a particular part zone or external area preventing unintended eddy current heating.Besides of the coil efficiency improvement and optimal power distribution, magnetic flux controllers reduce the coil current demand from a supplying circuitry thus strongly reducing losses in busswork, cables, transformers and inverter components.Improvement that can be achieved due to magnetic flux controllers is case dependable. 2D and 3D computer simulation allows the designer to predict accurately effect of controllers on the coil parameters and temperature distribution and optimize the whole electromagnetic system. Special attention in presentation is paid to new magnetodielectric materials optimized for induction heating conditions. These materials have high magnetic permeability and saturation flux density,excellent machinability, good chemical and temperature resistance. Concentrators from these materials can work in a wide range of frequencies and specific powers. Examples of magnetic flux controller application include surface hardening of shafts and gears, induction surface hardfacing and brazing.

  10. Mathematical modeling of isotope labeling experiments for metabolic flux analysis.

    Science.gov (United States)

    Nargund, Shilpa; Sriram, Ganesh

    2014-01-01

    Isotope labeling experiments (ILEs) offer a powerful methodology to perform metabolic flux analysis. However, the task of interpreting data from these experiments to evaluate flux values requires significant mathematical modeling skills. Toward this, this chapter provides background information and examples to enable the reader to (1) model metabolic networks, (2) simulate ILEs, and (3) understand the optimization and statistical methods commonly used for flux evaluation. A compartmentalized model of plant glycolysis and pentose phosphate pathway illustrates the reconstruction of a typical metabolic network, whereas a simpler example network illustrates the underlying metabolite and isotopomer balancing techniques. We also discuss the salient features of commonly used flux estimation software 13CFLUX2, Metran, NMR2Flux+, FiatFlux, and OpenFLUX. Furthermore, we briefly discuss methods to improve flux estimates. A graphical checklist at the end of the chapter provides a reader a quick reference to the mathematical modeling concepts and resources.

  11. Prompt atmospheric neutrino flux

    CERN Document Server

    Jeong, Yu Seon; Enberg, Rikard; Kim, C S; Reno, Mary Hall; Sarcevic, Ina; Stasto, Anna

    2016-01-01

    We evaluate the prompt atmospheric neutrino flux including nuclear correction and $B$ hadron contribution in the different frameworks: NLO perturbative QCD and dipole models. The nuclear effect is larger in the prompt neutrino flux than in the total charm production cross section, and it reduces the fluxes by $10\\% - 30\\%$ depending on the model. We also investigate the uncertainty using the QCD scales allowed by the charm cross section data from RHIC and LHC experiments.

  12. $Ly \\alpha$ Fluorescent Excitation of FeII in Active Galactic Nuclei

    CERN Document Server

    Sigut, T A A; Pradhan, Anil K.

    1998-01-01

    We have calculated FeII emission line strengths for Active Galactic Nuclei Broad-Line Regions using precise radiative transfer and Iron Project atomic data. We improve the treatment of all previously considered excitation mechanisms for the FeII emission, continuum fluorescence, collisional excitation, fluorescence by self-overlap among the iron lines, and fluorescent excitation by Lyman-alpha. We demonstrate that Lyman-alpha fluorescence is of fundamental importance in determining the strength of the FeII emission. In addition to enhancing the ultraviolet and optical FeII flux, Lyman-alpha fluorescence also results in significant near-infrared FeII emission in the 8500-9500 Angstrom wavelength range. New observations are suggested to probe this effect in strong FeII emitting quasars.

  13. Video Meteor Fluxes

    Science.gov (United States)

    Campbell-Brown, M. D.; Braid, D.

    2011-01-01

    The flux of meteoroids, or number of meteoroids per unit area per unit time, is critical for calibrating models of meteoroid stream formation and for estimating the hazard to spacecraft from shower and sporadic meteors. Although observations of meteors in the millimetre to centimetre size range are common, flux measurements (particularly for sporadic meteors, which make up the majority of meteoroid flux) are less so. It is necessary to know the collecting area and collection time for a given set of observations, and to correct for observing biases and the sensitivity of the system. Previous measurements of sporadic fluxes are summarized in Figure 1; the values are given as a total number of meteoroids striking the earth in one year to a given limiting mass. The Gr n et al. (1985) flux model is included in the figure for reference. Fluxes for sporadic meteoroids impacting the Earth have been calculated for objects in the centimeter size range using Super-Schmidt observations (Hawkins & Upton, 1958); this study used about 300 meteors, and used only the physical area of overlap of the cameras at 90 km to calculate the flux, corrected for angular speed of meteors, since a large angular speed reduces the maximum brightness of the meteor on the film, and radiant elevation, which takes into account the geometric reduction in flux when the meteors are not perpendicular to the horizontal. They bring up corrections for both partial trails (which tends to increase the collecting area) and incomplete overlap at heights other than 90 km (which tends to decrease it) as effects that will affect the flux, but estimated that the two effects cancelled one another. Halliday et al. (1984) calculated the flux of meteorite-dropping fireballs with fragment masses greater than 50 g, over the physical area of sky accessible to the MORP fireball cameras, counting only observations in clear weather. In the micron size range, LDEF measurements of small craters on spacecraft have been used to

  14. Suprathermal Charged Particle Acceleration by Small-scale Flux Ropes.

    Science.gov (United States)

    Zank, G. P.; le Roux, J. A.; Webb, G. M.

    2015-12-01

    We consider different limits of our recently developed kinetic transport theory to investigate the potential of super-Alvenic solar wind regions containing several small-scale flux ropes to explain the acceleration of suprathermal ions to power-law spectra as observations show. Particle acceleration is modeled in response to flux-rope activity involving contraction, merging (reconnection), and collisions in the limit where the particle gyoradius is smaller than the characteristic flux-rope scale length. The emphasis is mainly on the statistical variance in the electric fields induced by flux-rope dynamics rather than on the mean electric field induced by multiple flux ropes whose acceleration effects are discussed elsewhere. Our steady-state analytical solutions suggest that particle drift acceleration by flux ropes, irrespective of whether displaying incompressible or compressible behavior, can yield power laws asymptotically at higher energies whereas an exponential spectral rollover results asymptotically when field-aligned guiding center motion acceleration occur by reconnection electric fields from merging flux ropes. This implies that at sufficiently high particle energies, drift acceleration might dominate. We also expect compressive flux ropes to yield harder power-law spectra than incompressible flux ropes. Preliminary results will be discussed to illustrate how particle acceleration might be affected when both diffusive shock and small-scale flux acceleration occur simultaneously at interplanetary shocks.

  15. Electron heat flux instability

    Science.gov (United States)

    Saeed, Sundas; Sarfraz, M.; Yoon, P. H.; Lazar, M.; Qureshi, M. N. S.

    2017-02-01

    The heat flux instability is an electromagnetic mode excited by a relative drift between the protons and two-component core-halo electrons. The most prominent application may be in association with the solar wind where drifting electron velocity distributions are observed. The heat flux instability is somewhat analogous to the electrostatic Buneman or ion-acoustic instability driven by the net drift between the protons and bulk electrons, except that the heat flux instability operates in magnetized plasmas and possesses transverse electromagnetic polarization. The heat flux instability is also distinct from the electrostatic counterpart in that it requires two electron species with relative drifts with each other. In the literature, the heat flux instability is often called the 'whistler' heat flux instability, but it is actually polarized in the opposite sense to the whistler wave. This paper elucidates all of these fundamental plasma physical properties associated with the heat flux instability starting from a simple model, and gradually building up more complexity towards a solar wind-like distribution functions. It is found that the essential properties of the instability are already present in the cold counter-streaming electron model, and that the instability is absent if the protons are ignored. These instability characteristics are highly reminiscent of the electron firehose instability driven by excessive parallel temperature anisotropy, propagating in parallel direction with respect to the ambient magnetic field, except that the free energy source for the heat flux instability resides in the effective parallel pressure provided by the counter-streaming electrons.

  16. On the Taxonomy of Flux Vacua

    Energy Technology Data Exchange (ETDEWEB)

    Giryavets, Alexander

    2004-04-25

    We investigate several predictions about the properties of IIB flux vacua on Calabi-Yau orientifolds, by constructing and characterizing a very large set of vacua in a specific example, an orientifold of the Calabi-Yau hypersurface in WP{sub 1,1,1,1,4}{sup 4}. We find support for the prediction of Ashok and Douglas that the density of vacua on moduli space is governed by det(-R-{omega}) where R and {omega} are curvature and Kaehler forms on the moduli space. The conifold point {psi} = 1 on moduli space therefore serves as an attractor, with a significant fraction of the flux vacua contained in a small neighborhood surrounding {psi} = 1. We also study the functional dependence of the number of flux vacua on the D3 charge in the fluxes, finding simple power law growth.

  17. Characterization of ion fluxes and heat fluxes for PMI relevant conditions on Proto-MPEX

    Science.gov (United States)

    Beers, Clyde; Shaw, Guinevere; Biewer, Theodore; Rapp, Juergen

    2016-10-01

    Plasma characterization, in particular, particle flux and electron and ion temperature distributions nearest to an exposed target, are critical to quantifying Plasma Surface Interaction (PSI). In the Proto-Material Plasma Exposure eXperiment (Proto-MPEX), the ion fluxes and heat fluxes are derived from double Langmuir Probes (DLP) and Thomson Scattering in front of the target assuming Bohm conditions at the sheath entrance. Power fluxes derived from ne and Te measurements are compared to heat fluxes measured with IR thermography. The comparison will allow conclusions on the sheath heat transmission coefficient to be made experimentally. Different experimental conditions (low and high density plasmas (0.5 - 6 x 1019 m-3) with different magnetic configuration are compared. This work was supported by the U.S. D.O.E. contract DE-AC05-00OR22725.

  18. AP1000功率量程中子注量率正变化率高紧急停堆定值和时间常数研究%Study on Setpoint and Time Constant for AP1000 Power Range High Positive Neutron Flux Rate Reactor Trip

    Institute of Scientific and Technical Information of China (English)

    王银丽; 罗炜; 张英; 朱宏亮; 杨戴博; 袁彬

    2015-01-01

    Nuclear instrumentation system is an important part of safety instrument and control system in nuclear power plant. This paper introduces the principle of AP1000 power range high positive neutron flux rate reactor trip, and analyses the relationship of the trigger of this reactor trip with setpoint, time constant and power rate. The design of setpoint and time constant for power range high positive neutron flux rate reactor trip is verified on MATLAB software platform based on the transient process data of rod ejection and normal operation transient also.%核仪表系统(RPN)是核电厂仪控系统的重要组成部分。本文介绍了AP1000功率量程中子注量率正变化率高紧急停堆的基本原理,对该紧急停堆信号触发与停堆定值、时间常数、功率变化率的关系进行了分析,并以MATLAB软件为平台,基于弹棒事故和正常运行瞬态两种典型工况的瞬态过程数据,对AP1000功率量程中子注量率正变化率高紧急停堆定值和时间常数的设计进行了仿真验证。

  19. Fine fuel heating by radiant flux

    Science.gov (United States)

    David Frankman; Brent W. Webb; Bret W. Butler; Don J. Latham

    2010-01-01

    Experiments were conducted wherein wood shavings and Ponderosa pine needles in quiescent air were subjected to a steady radiation heat flux from a planar ceramic burner. The internal temperature of these particles was measured using fine diameter (0.076mm diameter) type K thermocouples. A narrow angle radiometer was used to determine the emissive power generated by the...

  20. Structural control of metabolic flux.

    Directory of Open Access Journals (Sweden)

    Max Sajitz-Hermstein

    Full Text Available Organisms have to continuously adapt to changing environmental conditions or undergo developmental transitions. To meet the accompanying change in metabolic demands, the molecular mechanisms of adaptation involve concerted interactions which ultimately induce a modification of the metabolic state, which is characterized by reaction fluxes and metabolite concentrations. These state transitions are the effect of simultaneously manipulating fluxes through several reactions. While metabolic control analysis has provided a powerful framework for elucidating the principles governing this orchestrated action to understand metabolic control, its applications are restricted by the limited availability of kinetic information. Here, we introduce structural metabolic control as a framework to examine individual reactions' potential to control metabolic functions, such as biomass production, based on structural modeling. The capability to carry out a metabolic function is determined using flux balance analysis (FBA. We examine structural metabolic control on the example of the central carbon metabolism of Escherichia coli by the recently introduced framework of functional centrality (FC. This framework is based on the Shapley value from cooperative game theory and FBA, and we demonstrate its superior ability to assign "share of control" to individual reactions with respect to metabolic functions and environmental conditions. A comparative analysis of various scenarios illustrates the usefulness of FC and its relations to other structural approaches pertaining to metabolic control. We propose a Monte Carlo algorithm to estimate FCs for large networks, based on the enumeration of elementary flux modes. We further give detailed biological interpretation of FCs for production of lactate and ATP under various respiratory conditions.

  1. EL-2 reactor: Thermal neutron flux distribution; EL-2: Repartition du flux de neutrons thermiques

    Energy Technology Data Exchange (ETDEWEB)

    Rousseau, A.; Genthon, J.P. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-07-01

    The flux distribution of thermal neutrons in EL-2 reactor is studied. The reactor core and lattices are described as well as the experimental reactor facilities, in particular, the experimental channels and special facilities. The measurement shows that the thermal neutron flux increases in the central channel when enriched uranium is used in place of natural uranium. However the thermal neutron flux is not perturbed in the other reactor channels by the fuel modification. The macroscopic flux distribution is measured according the radial positioning of fuel rods. The longitudinal neutron flux distribution in a fuel rod is also measured and shows no difference between enriched and natural uranium fuel rods. In addition, measurements of the flux distribution have been effectuated for rods containing other material as steel or aluminium. The neutron flux distribution is also studied in all the experimental channels as well as in the thermal column. The determination of the distribution of the thermal neutron flux in all experimental facilities, the thermal column and the fuel channels has been made with a heavy water level of 1825 mm and is given for an operating power of 1000 kW. (M.P.)

  2. AXUV bolometer and Lyman-α camera systems on the TCV tokamak

    Science.gov (United States)

    Degeling, A. W.; Weisen, H.; Zabolotsky, A.; Duval, B. P.; Pitts, R. A.; Wischmeier, M.; Lavanchy, P.; Marmillod, Ph.; Pochon, G.

    2004-10-01

    A set of seven twin slit cameras, each containing two 20-element linear absolute extreme ultraviolet photodiode arrays, has been installed on the Tokamak à Configuration Variable. One array in each camera will operate as a bolometer and the second as a Lyman-alpha (Lα) emission monitor for estimating the recycled neutral flux. The camera configuration was optimized by simulations of tomographic reconstructions of the expected Lα emission. The diagnostic will provide spatial and temporal resolution (10 μs) of the radiated power and the Lα emission that is considerably higher than previously achieved. This optimism is justified by extensive experience with prototype systems, which include first measurements of Lα light from the divertor.

  3. Atmosphere–Surface Fluxes of CO2 using Spectral Techniques

    DEFF Research Database (Denmark)

    Sørensen, Lise Lotte; Larsen, Søren Ejling

    2010-01-01

    Different flux estimation techniques are compared here in order to evaluate air–sea exchange measurement methods used on moving platforms. Techniques using power spectra and cospectra to estimate fluxes are presented and applied to measurements of wind speed and sensible heat, latent heat and CO2...

  4. Net Ecosystem Carbon Flux

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Net Ecosystem Carbon Flux is defined as the year-over-year change in Total Ecosystem Carbon Stock, or the net rate of carbon exchange between an ecosystem and the...

  5. Aeronet Solar Flux

    Data.gov (United States)

    National Aeronautics and Space Administration — SolRad-Net (Solar Radiation Network) is an established network of ground-based sensors providing high-frequency solar flux measurements in quasi-realtime to the...

  6. Flux in Tallinn

    Index Scriptorium Estoniae

    2004-01-01

    Rahvusvahelise elektroonilise kunsti sümpoosioni ISEA2004 klubiõhtu "Flux in Tallinn" klubis Bon Bon. Eestit esindasid Ropotator, Ars Intel Inc., Urmas Puhkan, Joel Tammik, Taavi Tulev (pseud. Wochtzchee). Klubiõhtu koordinaator Andres Lõo

  7. Flux in Tallinn

    Index Scriptorium Estoniae

    2004-01-01

    Rahvusvahelise elektroonilise kunsti sümpoosioni ISEA2004 klubiõhtu "Flux in Tallinn" klubis Bon Bon. Eestit esindasid Ropotator, Ars Intel Inc., Urmas Puhkan, Joel Tammik, Taavi Tulev (pseud. Wochtzchee). Klubiõhtu koordinaator Andres Lõo

  8. Nitrous Oxide Flux

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Nitrous Oxide (N20) flux is the net rate of nitrous oxide exchange between an ecosystem and the atmosphere. Data of this variable were generated by the USGS...

  9. Radiative transfer effects in primordial hydrogen recombination

    CERN Document Server

    Ali-Haïmoud, Yacine; Hirata, Christopher M

    2010-01-01

    The calculation of a highly accurate cosmological recombination history has been the object of particular attention recently, as it constitutes the major theoretical uncertainty when predicting the angular power spectrum of Cosmic Microwave Background anisotropies. Lyman transitions, in particular the Lyman-alpha line, have long been recognized as one of the bottlenecks of recombination, due to their very low escape probabilities. The Sobolev approximation does not describe radiative transfer in the vicinity of Lyman lines to a sufficient degree of accuracy, and several corrections have already been computed in other works. In this paper, the impact of some previously ignored radiative transfer effects is calculated. First, the effect of Thomson scattering in the vicinity of the Lyman-alpha line is evaluated, using a full redistribution kernel incorporated into a radiative transfer code. The effect of feedback of distortions generated by the optically thick deuterium Lyman-alpha line blueward of the hydrogen ...

  10. Carbon Dioxide Flux Measurement Systems

    Data.gov (United States)

    Oak Ridge National Laboratory — The Southern Great Plains (SGP) carbon dioxide flux (CO2 flux) measurement systems provide half-hour average fluxes of CO2, H2O (latent heat), and sensible heat. The...

  11. Flux Emergence (Theory)

    Science.gov (United States)

    Cheung, Mark C. M.; Isobe, Hiroaki

    2014-12-01

    Magnetic flux emergence from the solar convection zone into the overlying atmosphere is the driver of a diverse range of phenomena associated with solar activity. In this article, we introduce theoretical concepts central to the study of flux emergence and discuss how the inclusion of different physical effects (e.g., magnetic buoyancy, magnetoconvection, reconnection, magnetic twist, interaction with ambient field) in models impact the evolution of the emerging field and plasma.

  12. Theoretical magnetic flux emergence

    OpenAIRE

    MacTaggart, David

    2011-01-01

    Magnetic flux emergence is the subject of how magnetic fields from the solar interior can rise and expand into the atmosphere to produce active regions. It is the link that joins dynamics in the convection zone with dynamics in the atmosphere. In this thesis, we study many aspects of magnetic flux emergence through mathematical modelling and computer simulations. Our primary aim is to understand the key physical processes that lie behind emergence. The first chapter intro...

  13. Flux Emergence (Theory

    Directory of Open Access Journals (Sweden)

    Mark C. M. Cheung

    2014-07-01

    Full Text Available Magnetic flux emergence from the solar convection zone into the overlying atmosphere is the driver of a diverse range of phenomena associated with solar activity. In this article, we introduce theoretical concepts central to the study of flux emergence and discuss how the inclusion of different physical effects (e.g., magnetic buoyancy, magnetoconvection, reconnection, magnetic twist, interaction with ambient field in models impact the evolution of the emerging field and plasma.

  14. Mobile Greenhouse Gas Flux Analyzer for Unmanned Aerial Vehicles Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In this SBIR Phase I effort, Los Gatos Research (LGR) proposes to develop a highly-accurate, lightweight, low-power gas analyzer for eddy flux covariance...

  15. 47 CFR 27.55 - Power strength limits.

    Science.gov (United States)

    2010-10-01

    ..., provided that such operations complied with paragraph (a)(4)(i) of this section. (b) Power flux density...-746 MHz band in accordance with the provisions of § 27.50(c)(6), the power flux density that would be... antenna mounting structure. (c) Power flux density limit for stations operating in the 746-757 MHz,...

  16. Turbulent fluxes by "Conditional Eddy Sampling"

    Science.gov (United States)

    Siebicke, Lukas

    2015-04-01

    Turbulent flux measurements are key to understanding ecosystem scale energy and matter exchange, including atmospheric trace gases. While the eddy covariance approach has evolved as an invaluable tool to quantify fluxes of e.g. CO2 and H2O continuously, it is limited to very few atmospheric constituents for which sufficiently fast analyzers exist. High instrument cost, lack of field-readiness or high power consumption (e.g. many recent laser-based systems requiring strong vacuum) further impair application to other tracers. Alternative micrometeorological approaches such as conditional sampling might overcome major limitations. Although the idea of eddy accumulation has already been proposed by Desjardin in 1972 (Desjardin, 1977), at the time it could not be realized for trace gases. Major simplifications by Businger and Oncley (1990) lead to it's widespread application as 'Relaxed Eddy Accumulation' (REA). However, those simplifications (flux gradient similarity with constant flow rate sampling irrespective of vertical wind velocity and introduction of a deadband around zero vertical wind velocity) have degraded eddy accumulation to an indirect method, introducing issues of scalar similarity and often lack of suitable scalar flux proxies. Here we present a real implementation of a true eddy accumulation system according to the original concept. Key to our approach, which we call 'Conditional Eddy Sampling' (CES), is the mathematical formulation of conditional sampling in it's true form of a direct eddy flux measurement paired with a performant real implementation. Dedicated hardware controlled by near-real-time software allows full signal recovery at 10 or 20 Hz, very fast valve switching, instant vertical wind velocity proportional flow rate control, virtually no deadband and adaptive power management. Demonstrated system performance often exceeds requirements for flux measurements by orders of magnitude. The system's exceptionally low power consumption is ideal

  17. Decision no. 2011-DC-0216 of the French nuclear safety authority from May 5, 2011, ordering the Laue Langevin Institute to proceed to a complementary safety evaluation of its basic nuclear facility (high flux reactor - INB no. 67) in the eyes of the Fukushima Daiichi nuclear power plant accident; Decision no. 2011-DC-0216 de l'Autorite de surete nucleaire du 5 mai 2011 prescrivant a l'Institut Laue Langevin (ILL) de proceder a une evaluation complementaire de la surete de son installation nucleaire de base (Reacteur a Haut Flux - INB n.67) au regard de l'accident survenu a la centrale nucleaire de Fukushima Daiichi

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-07-01

    As a consequence of the accident of the Fukushima Daiichi nuclear power plant (Japan), the French Prime Minister entrusted the French nuclear safety authority (ASN) with the mission to carry out a safety analysis re-evaluation of the French nuclear facilities, and in particular the nuclear power plants. A decision has been addressed by the ASN to each nuclear operator with the specifications of this safety re-evaluation analysis and the list of facilities in concern. This document is the decision addressed to the Laue Langevin Institute, operator of the high flux research reactor (RHF) of Grenoble (France). (J.S.)

  18. The Flux-Flux Correlation Function for Anharmonic Barriers

    CERN Document Server

    Goussev, Arseni; Waalkens, Holger; Wiggins, Stephen

    2010-01-01

    The flux-flux correlation function formalism is a standard and widely used approach for the computation of reaction rates. In this paper we introduce a method to compute the classical and quantum flux-flux correlation functions for anharmonic barriers essentially analytically through the use of the classical and quantum normal forms. In the quantum case we show that the quantum normal form reduces the computation of the flux-flux correlation function to that of an effective one dimensional anharmonic barrier. The example of the computation of the quantum flux-flux correlation function for a fourth order anharmonic barrier is worked out in detail, and we present an analytical expression for the quantum mechanical microcanonical flux-flux correlation function. We then give a discussion of the short-time and harmonic limits.

  19. Flux pinning in superconductors

    CERN Document Server

    Matsushita, Teruo

    2014-01-01

    The book covers the flux pinning mechanisms and properties and the electromagnetic phenomena caused by the flux pinning common for metallic, high-Tc and MgB2 superconductors. The condensation energy interaction known for normal precipitates or grain boundaries and the kinetic energy interaction proposed for artificial Nb pins in Nb-Ti, etc., are introduced for the pinning mechanism. Summation theories to derive the critical current density are discussed in detail. Irreversible magnetization and AC loss caused by the flux pinning are also discussed. The loss originally stems from the ohmic dissipation of normal electrons in the normal core driven by the electric field induced by the flux motion. The readers will learn why the resultant loss is of hysteresis type in spite of such mechanism. The influence of the flux pinning on the vortex phase diagram in high Tc superconductors is discussed, and the dependencies of the irreversibility field are also described on other quantities such as anisotropy of supercondu...

  20. Flux Pinning in Superconductors

    CERN Document Server

    Matsushita, Teruo

    2007-01-01

    The book covers the flux pinning mechanisms and properties and the electromagnetic phenomena caused by the flux pinning common for metallic, high-Tc and MgB2 superconductors. The condensation energy interaction known for normal precipitates or grain boundaries and the kinetic energy interaction proposed for artificial Nb pins in Nb-Ti, etc., are introduced for the pinning mechanism. Summation theories to derive the critical current density are discussed in detail. Irreversible magnetization and AC loss caused by the flux pinning are also discussed. The loss originally stems from the ohmic dissipation of normal electrons in the normal core driven by the electric field induced by the flux motion. The readers will learn why the resultant loss is of hysteresis type in spite of such mechanism. The influence of the flux pinning on the vortex phase diagram in high Tc superconductors is discussed, and the dependencies of the irreversibility field are also described on other quantities such as anisotropy of supercondu...