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Full-Text Articles in Physical Sciences and Mathematics
The Peculiar Motions Of Early-Type Galaxies In Two Distant Rregions — Ii. The Spectroscopic Data, Gary Wegner, Matthew Colless, R. P. Saglia, Robert K. Mcmahan
The Peculiar Motions Of Early-Type Galaxies In Two Distant Rregions — Ii. The Spectroscopic Data, Gary Wegner, Matthew Colless, R. P. Saglia, Robert K. Mcmahan
Dartmouth Scholarship
We present the spectroscopic data for the galaxies studied in the EFAR project, which is designed to measure the properties and peculiar motions of early-type galaxies in two distant regions. We have obtained 1319 spectra of 714 early-type galaxies over 33 observing runs on 10 different telescopes. We describe the observations and data reductions used to measure redshifts, velocity dispersions and the Mgb and Mg2 Lick linestrength indices. Detailed simulations and intercomparison of the large number of repeat observations lead to reliable error estimates for all quantities. The measurements from different observing runs are calibrated to a common …
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
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 …
The Clustering Of High-Redshift Galaxies In The Cold Dark Matter Scenario, N Katz, L Hernquist, Dh Weinberg
The Clustering Of High-Redshift Galaxies In The Cold Dark Matter Scenario, N Katz, L Hernquist, Dh Weinberg
Astronomy Department Faculty Publication Series
We investigate the clustering of high-redshift galaxies in five variants of the cold dark matter (CDM) scenario, using hydrodynamic cosmological simulations that resolve the formation of systems with circular velocities vc ≥ 100 km s-1 (Ω = 1) or vc ≥ 70 km s-1 (Ω = 0.4). Although the five models differ in their cosmological parameters and in the shapes and amplitudes of their mass power spectra, they predict remarkably similar galaxy clustering at z = 2, 3, and 4. The galaxy correlation functions show almost no evolution over this redshift range, even though the mass …
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
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 …
The Low-Redshift Ly Alpha Forest In Cold Dark Matter Cosmologies, R Dave, L Hernquist, N Katz, Dh Weinberg
The Low-Redshift Ly Alpha Forest In Cold Dark Matter Cosmologies, R Dave, L Hernquist, N Katz, Dh Weinberg
Astronomy Department Faculty Publication Series
We study the physical origin of the low-redshift Lyα forest in hydrodynamic simulations of four cosmological models, all variants of the cold dark matter scenario. Our most important conclusions are insensitive to the cosmological model, but they depend on our assumption that the UV background declines at low redshift in concert with the declining population of quasar sources. We find that the expansion of the universe drives rapid evolution of dN/dz (the number of absorbers per unit redshift above a specified equivalent width threshold) at z1.7, but that at lower redshift the fading of the UV background …