Large-scale structure in the Lyman-  forest--II. Analysis of a group of 10 QSOs

Liske, J.; Webb, John R.; Williger, G. M.; Fernández-Soto, A.; Carswell, R. F.

doi:10.1046/j.1365-8711.2000.02966.x

Cited by 20 publications

(24 citation statements)

References 84 publications

(110 reference statements)

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“…Møller & Kjærgaard (1992) have previously employed a somewhat more rudimentary version of our method to investigate the foreground proximity effect. Flux statistics have also been used in other contexts by Jenkins & Ostriker (1991), Webb et al (1992), Press & Rybicki (1993), Press, Rybicki & Schneider (1993), Zuo & Lu (1993), Zuo & Bond (1994), Croft et al (1999), Hui (1999), Nusser & Haehnelt (2000) and Liske et al (2000).…”

Section: Discussionmentioning

confidence: 99%

The proximity effect in a close group of QSOs

Liske

Williger

2001

Monthly Notices of the Royal Astronomical Society

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We present an analysis of the proximity effect in a sample of ten 2 A resolution QSO spectra of the Ly alpha forest at = 2.9. Rather than investigating variations in the number density of individual absorption lines we employ a novel technique that is based on the statistics of the transmitted flux itself. We confirm the existence of the proximity effect at the > 99 per cent confidence level. We derive a value for the mean intensity of the extragalactic background radiation at the Lyman limit of J = 3.5^{+3.5}_{-1.3} x 10^{-22} ergs/s/cm^2/Hz/sr. This value assumes that QSO redshifts measured from high ionization lines differ from the true systemic redshifts by ~800 km/s. We find evidence at a level of 2.6 sigma that the significance of the proximity effect is correlated with QSO Lyman limit luminosity. Allowing for known QSO variability the significance of the correlation reduces to 2.1 sigma. The QSOs form a close group on the sky and the sample is thus well suited for an investigation of the foreground proximity effect, where the Ly alpha forest of a background QSO is influenced by the UV radiation from a nearby foreground QSO. From the complete sample we find no evidence for the existence of this effect, implying either that J > 20 x 10^{-22} ergs/s/cm^2/Hz/sr or that QSOs emit at least a factor of 1.4 less ionizing radiation in the plane of the sky than along the line of sight to Earth. We do however find one counter-example. Our sample includes the fortunate constellation of a foreground QSO surrounded by four nearby background QSOs. These four spectra all show underdense absorption within +/-3000 km/s of the redshift of the foreground QSO.Comment: 17 pages, LaTeX, 11 Postscript figures, accepted for publication in MNRA

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Section: Discussionmentioning

confidence: 99%

The proximity effect in a close group of QSOs

Liske

Williger

2001

Monthly Notices of the Royal Astronomical Society

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“…In general, it is agreed that a weak clustering at scales of few hundred km s À1 is present in high-redshift Ly forest (Rauch 1998 and references therein; more recently Liske et al 2000;Penton et al 2000). At low redshifts, Ulmer (1996) analyzed the line clustering in the spectra of 12 objects from the HST/FOS Key Project (100 lines) and reported a significant excess of line pairs at velocity separations of 250-500 km s À1 .…”

Section: Clustering In the Hst/fos Samplementioning

confidence: 97%

A Uniform Analysis of the Lyα Forest atz= 0–5. IV. The Clustering and Evolution of Clouds atz≤ 1.7

Dobrzycki

Bechtold

Scott

et al. 2002

ApJ

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We present results on the evolution and clustering of Ly lines at low redshift as part of our series '' A Uniform Analysis of the Ly Forest at z ¼ 0 5.'' The sample analyzed in this paper contains 1298 Ly absorption lines from 165 quasar spectra mined from the archives of the Faint Object Spectrograph on the Hubble Space Telescope (HST). Our sample extends to z % 1:7, slightly higher than the sample analyzed by the HST Quasar Absorption Line Key Project. We confirm the result from the Key Project that the number density evolution of Ly lines at low redshifts can be described by a power law that is significantly flatter than that found at high z. We find that the evolution is somewhat steeper than obtained previously. Specifically, we find ¼ 0:54 AE 0:21 for lines with equivalent widths greater than 0.24 Å and ¼ 0:60 AE 0:14 using a variable equivalent width threshold. We find that the difference between our and Key Project results is likely attributable to different redshift coverage of the two samples. The results concerning the number density evolution are not significantly affected if one includes Ly lines which are members of metal systems. Object-to-object fluctuations in the number of lines detected are small, indicating a high degree of uniformity in the intergalactic medium on large scales. We find marginal evidence that weak and strong lines undergo different evolution. We find weak clustering for Ly lines at velocity separations DV 500 km s À1 , weaker than the level predicted from an earlier analysis by Ulmer of a small subsample of the Key Project data. We see no correlations for metal system-Ly forest or extensive metal system-Ly forest combinations.

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“…The theory has been tested by comparing predictions with observed statistics of fitted absorption lines and the transmitted flux itself (e.g., Rauch et al 1997;Davé et al 1997;Gnedin 1998;Theuns et al 1999;McDonald et al 2000;Zaldarriaga, Seljak, & Hui 2001b). Correlation between absorption in pairs of spectra has been observed (e.g., Bechtold et al 1994;Dinshaw et al 1994;Crotts & Fang 1998;D'Odorico et al 1998;Williger et al 2000;Liske et al 2000) and investigated theoretically by Charlton et al (1997), Pichon et al (2001), and Viel et al (2002).…”

Section: Introductionmentioning

confidence: 99%

Toward a Measurement of the Cosmological Geometry atz∼ 2: Predicting Lyα Forest Correlation in Three Dimensions and the Potential of Future Data Sets

McDonald

2003

ApJ

223

357

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The correlation between Ly absorption in the spectra of quasar pairs can be used to measure the transverse distance scale at z $ 2, which is sensitive to the cosmological constant ( Ã ) or other forms of vacuum energy. Using hydro-PM simulations, I compute the three-dimensional power spectrum of the Ly forest flux, P F ðkÞ, from which the redshift-space anisotropy of the correlation can be obtained. I compute directly the linear theory bias parameters of the Ly forest, potentially allowing simulation results to be extended to arbitrarily large scales. I investigate the dependence of P F ðkÞ on the primordial power spectrum, the temperature-density relation of the gas, and the mean flux decrement, finding that the redshift-space anisotropy is relatively insensitive to these parameters. A table of results is provided for different parameter variations. I investigate the constraint that can be obtained on Ã using quasars from a large survey. Assuming 13 =1 0 ð Þ 2 pairs at a separation of less than h and including separations less than 10 0 , a measurement to d5% can be made if simulations can predict the redshift-space anisotropy with d5% accuracy or to d10% if the anisotropy must be measured from the data. The Sloan Digital Sky Survey (SDSS) will obtain spectra for a factor of $5 fewer pairs than this, so follow-up observations of fainter pair candidates will be necessary. I discuss the requirements on the spectral resolution and signal-to-noise ratio (SDSS quality spectra are sufficient). I find that a box size of $40 h À1 Mpc and a resolution of $40 h À1 kpc are necessary for convergence of the calculations to d5% on all relevant scales, although somewhat poorer resolution can be used for large scales. Subject headings: cosmology: theory -intergalactic medium -large-scale structure of universemethods: N-body simulations -quasars: absorption lines On-line material: color figures

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Large-scale structure in the Lyman- forest--II. Analysis of a group of 10 QSOs

Abstract: The spatial distribution of Lyα forest absorption systems towards 10 QSOs is analysed to search for large‐scale structure over the redshift range 2.2 Show more

Cited by 20 publications

References 84 publications

The proximity effect in a close group of QSOs

The proximity effect in a close group of QSOs

A Uniform Analysis of the Lyα Forest atz= 0–5. IV. The Clustering and Evolution of Clouds atz≤ 1.7

Toward a Measurement of the Cosmological Geometry atz∼ 2: Predicting Lyα Forest Correlation in Three Dimensions and the Potential of Future Data Sets

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