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Full-Text Articles in Physical Sciences and Mathematics
Fluctuations In Finite-N Equilibrium Stellar Systems, Md Weinberg
Fluctuations In Finite-N Equilibrium Stellar Systems, Md Weinberg
Astronomy Department Faculty Publication Series
Gravitational amplification of Poisson noise in stellar systems is important on large scales. For example, it increases the dipole noise power by roughly a factor of 6 and the quadrupole noise by 50 per cent for a King model profile. The dipole noise is amplified by a factor of 15 for the core-free Hernquist model. The predictions are computed by summing over the wakes caused by each star in the system — the dressed-particle formalism of Rostoker & Rosenbluth — and are demonstrated by N-body simulation. This result implies that a collisionless N-body simulation is impossible; the fluctuation noise which …
Constraining The Metallicity Of The Low-Density Ly Alpha Forest Using O Vi Absorption, R Dave, U Hellsten, L Hernquist, N Katz, Dh Weinberg
Constraining The Metallicity Of The Low-Density Ly Alpha Forest Using O Vi Absorption, R Dave, U Hellsten, L Hernquist, N Katz, Dh Weinberg
Astronomy Department Faculty Publication Series
We present a systematic search for O VI (1032, 1037 Å) absorption in a Keck High-Resolution Echelle Spectrometer spectrum of the z = 3.62 quasar Q1422+231, with the goal of constraining the metallicity and ionization state of the low-density intergalactic medium (IGM). Comparison of C IV absorption measurements to models of the Lyα forest based on cosmological simulations shows that absorbers with NH I 1014.5 cm-2 have a mean carbon abundance [C/H] -2.5, assuming a metagalactic photoionizing background with the spectral shape predicted by Haardt and Madau in 1996. In these models, lower column density absorption arises …
Cosmological Simulations With Scale-Free Initial Conditions. I. Adiabatic Hydrodynamics, Jm Owen, Dh Weinberg, Ae Evrard, L Hernquist, N Katz
Cosmological Simulations With Scale-Free Initial Conditions. I. Adiabatic Hydrodynamics, Jm Owen, Dh Weinberg, Ae Evrard, L Hernquist, N Katz
Astronomy Department Faculty Publication Series
We analyze hierarchical structure formation based on scale-free initial conditions in an Einstein-de Sitter universe, including a baryonic component with Ωbary = 0.05. We present three independent, smoothed particle hydrodynamics (SPH) simulations, performed at two resolutions (323 and 643 dark matter and baryonic particles) and with two different SPH codes (TreeSPH and P3MSPH). Each simulation is based on identical initial conditions, which consist of Gaussian-distributed initial density fluctuations that have a power spectrum P(k) k-1. The baryonic material is modeled as an ideal gas subject only to shock heating and adiabatic heating …