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Szalay, Edina

doi:10.1023/a:1011917625457

Cited by 9 publications

(5 citation statements)

References 10 publications

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“…The model is COBE normalized, so that the fluctuation normalization at z = 0 in a sphere of radius 8 h −1 Mpc is σ 8 h −1 = 0.970, and the fluctuation normalization at z = 3 spherically filtered on the scale of the Jeans length for T = 2 × 10 4 K gas is σ J (z = 3) = 1.59. The model is consistent with current constraints from the cosmic microwave background (CMB) (Stompor et al 2001;Netterfield et al 2002;Pryke et al 2002), big bang nucleosynthesis (O'Meara et al 2001), and large-scale structure (Percival et al 2001;Szalay et al 2001), as well as the constraint on the size of mass fluctuations on the scale of the Jeans length at 2 < z < 4 imposed by the measured flux per pixel distribution of the Lyα forest ). We use 512 3 particles on a 1024 3 mesh in a box of comoving side L box = 25 h −1 Mpc.…”

Section: Cosmological Modelsupporting

confidence: 85%

Constraints on the ultraviolet metagalactic emissivity using the Ly forest

Meiksin

White

2003

Monthly Notices of the Royal Astronomical Society

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Numerical hydrodynamical simulations have proven a successful means of reproducing many of the statistical properties of the Lyα forest as measured in high redshift quasar spectra. The source of ionization of the intergalactic medium (IGM), however, remains unknown. We investigate how the Lyα forest may be used to probe the nature of the sources. We show that the attenuation of Lyman continuum photons by the IGM depends sensitively on the emissivity of the sources, permitting a strong constraint to be set on the required emissivity to match the measured values of the mean IGM Lyα optical depth. We find that, within the observational errors, quasi‐stellar object (QSO) sources alone are able to account for the required ultraviolet (UV) background at z≳ 4. By contrast, the emissivity of Lyman‐break galaxies (LBGs) must decline sharply with redshift, compared with the estimated emissivity at z≈ 3, so as not to overproduce the UV background and drive the mean Lyα optical depth to values that are too low. We also investigate the effect of fluctuations in the UV background, as would arise if QSOs dominated. To this end, we derive the distribution function of the background radiation field produced by discrete sources in an infinite universe, including the effects of attenuation by an intervening absorbing medium. We show that, for z≳ 5, the fluctuations significantly boost the mean Lyα optical depth, and so increase the estimate for the mean ionization rate required to match the measured mean Lyα optical depths. The fluctuations will also result in large spatial correlations in the ionization level of the IGM. We show that the large mean Lyα optical depth measured at z≈ 6 suggests such large correlations will be present if QSOs dominate the UV background. A secondary, smaller effect of the UV background fluctuations is a distortion of the pixel flux distribution. While the effect on the distribution may be too small to detect with existing telescopes, it may be measurable with the extremely large telescopes planned for the future. We also show that if QSOs dominate the UV background at z≈ 6, then they will be sufficient in number to rejuvenate the ionization of a previously ionized IGM if it has not yet fully recombined.

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Section: Cosmological Modelsupporting

confidence: 85%

Constraints on the ultraviolet metagalactic emissivity using the Ly forest

Meiksin

White

2003

Monthly Notices of the Royal Astronomical Society

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“…Dodelson et al (2002) inverted the angular clustering in an early data release of the SDSS and found = 0.14 +0.11 −0.06 , in agreement with our constraint. Szalay et al (2001) used a KL estimate of the power spectrum from the SDSS to derive a similar range of values: = 0.188 ± 0.04 and σ g 8 = 0.915 ± 0.06 for a flat universe with cosmological constant. A consensus seems to be emerging on the shape and amplitude of the galaxy power spectrum for bright, optically selected galaxies, as remarked upon by Hoyle et al (1999).…”

Section: O N C L U S I O N Smentioning

confidence: 99%

The power spectrum of galaxy clustering in the APM Survey

Padilla

Baugh

2003

Monthly Notices of the Royal Astronomical Society

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We measure the power spectrum of galaxy clustering in real space from the APM Galaxy Survey. We present an improved technique for the numerical inversion of Limber's equation that relates the angular clustering of galaxies to an integral over the power spectrum in three dimensions. Our approach is underpinned by a large ensemble of mock galaxy catalogues constructed from the Hubble volume N‐body simulations. Mock catalogues are used to test for systematic effects in the inversion algorithm and to estimate the errors on our measurement. We find that we can recover the power spectrum to an accuracy of better than 15 per cent over three decades in wavenumber. A key advantage of the use of mock catalogues to infer errors is that we can apply our technique on scales for which the density fluctuations are not Gaussian, thus probing the regime that offers the best constraints on models of galaxy formation. On large scales, our measurement of the power spectrum is consistent with the shape of the mass power spectrum in the popular ‘concordance’ cold dark matter model. The galaxy power spectrum on small scales is strongly affected by non‐linear evolution of density fluctuations, and, to a lesser degree, by galaxy bias. The rms variance in the galaxy distribution, when smoothed in spheres of radius 8 h−1 Mpc, is σg8= 0.96+0.17−0.20 and the shape of the power spectrum on large scales is described by a simple fitting formula with parameter Γ= 0.19+0.13−0.04 (these errors are the 1σ ranges for a two‐parameter fit). We use our measurement of the power spectrum to estimate the galaxy two‐point correlation function; the results are well described by a power law with correlation length r0= 5.9 ± 0.7 h−1 Mpc and slope γ= 1.61 ± 0.06 for pair separations in the range 0.1 < r/(h−1 Mpc) < 20.

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“…In addition, the speed of our code makes feasible to construct a large number of mock galaxy catalogues in a reasonable CPU time from which a reliable estimation of errors and covariance matrices can be derived. Applications along these lines to imaging data in the SDSS survey will be considered elsewhere (Connolly et al 2001;Dodelson et al 2001;Scranton et al 2001;Szalay et al 2001;Tegmark et al 2001).…”

Section: Introductionmentioning

confidence: 99%

PTHALOS: a fast method for generating mock galaxy distributions

Sheth¹

2002

Monthly Notices of the Royal Astronomical Society

186

212

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Current models of galaxy formation applied to understanding the large‐scale structure of the Universe have two parts. The first is an accurate solution of the equations of motion for the dark matter caused by gravitational clustering. The second consists of making physically reasonable approximations to the behaviour of baryons inside dark matter haloes. The first uses large, computationally intensive, N‐body simulations. We argue that because the second step is, at least at present, uncertain, it is possible to obtain similar galaxy distributions without solving the first step exactly. We describe an algorithm that is several orders of magnitude faster than N‐body simulations, but that is, nevertheless, rather accurate. The algorithm combines perturbation theory with virialized halo models of the non‐linear density and velocity fields. For two‐ and three‐point statistics the resulting fields are exact on large scales, and rather accurate well into the non‐linear regime, particularly for two‐point statistics in real and redshift space. We then show how one can use this algorithm to generate mock galaxy distributions from halo occupation numbers. As a first application, we show that it provides a good description of the clustering of galaxies in the PSCz survey. We also discuss applications to the estimation of non‐Gaussian contributions to the error bars and the covariance matrix of the power spectrum, in real and redshift space, for galaxies and dark matter. The results for the latter show good agreement with simulations, supporting the use of our method for constraining cosmological parameters from forthcoming galaxy surveys.

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Untitled

Cited by 9 publications

References 10 publications

Constraints on the ultraviolet metagalactic emissivity using the Ly forest

Constraints on the ultraviolet metagalactic emissivity using the Ly forest

The power spectrum of galaxy clustering in the APM Survey

PTHALOS: a fast method for generating mock galaxy distributions

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