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Astrophysics and Astronomy

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Astronomy Department Faculty Publication Series

1999

Cosmology : observations

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Full-Text Articles in Physical Sciences and Mathematics

Closing In On Omega(M): The Amplitude Of Mass Fluctuations From Galaxy Clusters And The Ly Alpha Forest, Dh Weinberg, Rac Croft, L Hernquist, N Katz, M Pettini Jan 1999

Closing In On Omega(M): The Amplitude Of Mass Fluctuations From Galaxy Clusters And The Ly Alpha Forest, Dh Weinberg, Rac Croft, L Hernquist, N Katz, M Pettini

Astronomy Department Faculty Publication Series

We estimate the present-day value of the matter density parameter ΩM by combining constraints from the galaxy cluster mass function with Croft et al.'s recent measurement of the mass power spectrum, P(k), from Lyα forest data. The key assumption of the method is that cosmic structure formed by gravitational instability from Gaussian primordial fluctuations. For a specified value of ΩM, matching the observed cluster mass function then fixes the value of σ8, the rms amplitude of mass fluctuations in 8 h-1 Mpc spheres, and it thus determines the normalization of P …

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The Power Spectrum Of Mass Fluctuations Measured From The Ly Alpha Forest At Redshift Z=2.5, Rac Croft, Dh Weinberg, M Pettini, L Hernquist, N Katz Jan 1999

The Power Spectrum Of Mass Fluctuations Measured From The Ly Alpha Forest At Redshift Z=2.5, Rac Croft, Dh Weinberg, M Pettini, L Hernquist, N Katz

Astronomy Department Faculty Publication Series

We measure the linear power spectrum of mass-density fluctuations at redshift z = 2.5 from the Lyα forest absorption in a sample of 19 QSO spectra, using the method introduced by Croft et al. The P(k) measurement covers the range 2π/k ~ 450-2350 km s-1 (2-12 comoving h-1 Mpc for Ω = 1), limited on the upper end by uncertainty in fitting the unabsorbed QSO continuum and on the lower end by finite spectral resolution (0.8-2.3 Å FWHM) and by nonlinear dynamical effects. We examine a number of possible sources of systematic error and …

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