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Full-Text Articles in Physical Sciences and Mathematics
Noise-Driven Evolution In Stellar Systems - Ii. A Universal Halo Profile, Md Weinberg
Noise-Driven Evolution In Stellar Systems - Ii. A Universal Halo Profile, Md Weinberg
Astronomy Department Faculty Publication Series
Disc instabilities such as arm and bar formation, minor mergers and tidal encounters drive a galaxy from equilibrium. Using the theory that describes the evolution of a galaxy halo as a result of stochastic fluctuations developed in the companion paper to this one, we show that this sort of noise evolves a halo toward a standard profile, independent of its initial profile and concentration. This process can substantially redistribute the mass in dark-matter haloes in the 10 Gyr since formation. Three different noise processes are studied: (i) a bombardment by blobs of mass that are small compared to the halo …
Cooling Radiation And The Ly Alpha Luminosity Of Forming Galaxies, Ma Fardal, N Katz, Jp Gardner, L Hernquist, Dh Weinberg, R Dave
Cooling Radiation And The Ly Alpha Luminosity Of Forming Galaxies, Ma Fardal, N Katz, Jp Gardner, L Hernquist, Dh Weinberg, R Dave
Astronomy Department Faculty Publication Series
We examine the cooling radiation from forming galaxies in hydrodynamic simulations of the LCDM model (cold dark matter with a cosmological constant), focusing on the Lyα line luminosities of high-redshift systems. Primordial composition gas condenses within dark matter potential wells, forming objects with masses and sizes comparable to the luminous regions of observed galaxies. As expected, the energy radiated in this process is comparable to the gravitational binding energy of the baryons, and the total cooling luminosity of the galaxy population peaks at z 2. However, in contrast to the classical picture of gas cooling from the ~106 K …
Metal Enrichment Of The Intergalactic Medium In Cosmological Simulations, A Aguirre, L Hernquist, J Schaye, N Katz, Dh Weinberg, J Gardner
Metal Enrichment Of The Intergalactic Medium In Cosmological Simulations, A Aguirre, L Hernquist, J Schaye, N Katz, Dh Weinberg, J Gardner
Astronomy Department Faculty Publication Series
Observations have established that the diffuse intergalactic medium (IGM) at z ~ 3 is enriched to ~10-2.5 solar metallicity and that the hot gas in large clusters of galaxies (ICM) is enriched to - Z at z = 0. Metals in the IGM may have been removed from galaxies (in which they presumably form) during dynamical encounters between galaxies, by ram-pressure stripping, by supernova-driven winds, or as radiation-pressure-driven dust efflux. This study develops a method of investigating the chemical enrichment of the IGM and of galaxies, using already completed cosmological simulations. To these simulations we add dust and (gaseous) …
Hydrodynamic Simulation Of The Cosmological X-Ray Background, Rac Croft, T Di Matteo, L Hernquist, N Katz, Ma Fardal, Dh Weinberg
Hydrodynamic Simulation Of The Cosmological X-Ray Background, Rac Croft, T Di Matteo, L Hernquist, N Katz, Ma Fardal, Dh Weinberg
Astronomy Department Faculty Publication Series
We use a hydrodynamic simulation of an inflationary cold dark matter model with a cosmological constant to predict properties of the extragalactic X-ray background (XRB). We focus on emission from the intergalactic medium (IGM), with particular attention to diffuse emission from warm-hot gas that lies in relatively smooth filamentary structures between galaxies and galaxy clusters. We also include X-rays from point sources associated with galaxies in the simulation, and we make maps of the angular distribution of the emission. Although much of the X-ray luminous gas has a filamentary structure, the filaments are not evident in the simulated maps because …
Noise-Driven Evolution In Stellar Systems - I. Theory, Md Weinberg
Noise-Driven Evolution In Stellar Systems - I. Theory, Md Weinberg
Astronomy Department Faculty Publication Series
We present a theory for describing the evolution of a galaxy caused by stochastic events such as weak mergers, transient spiral structure, orbiting blobs, etc. This noise excites large-scale patterns that drive the evolution of the galactic density profile. In a dark matter halo, the repeated stochastic perturbations preferentially ring the lowest-order modes with only a very weak dependence on the details of their source. The subsequent redistribution of halo mass is determined only by the mechanics of these modes. The halo profile then evolves toward a universal asymptotic form for a wide variety of noise sources. Such a convergence …
Constraints On Cosmological Parameters From The Ly Alpha Forest Power Spectrum And Cobe Dmr, J Phillips, Dh Weinberg, Rac Croft, L Hernquist, N Katz, M Pettini
Constraints On Cosmological Parameters From The Ly Alpha Forest Power Spectrum And Cobe Dmr, J Phillips, Dh Weinberg, Rac Croft, L Hernquist, N Katz, M Pettini
Astronomy Department Faculty Publication Series
We combine COBE DMR measurements of cosmic microwave background (CMB) anisotropy with a recent measurement of the mass power spectrum at redshift z = 2.5 from Lyα forest data to derive constraints on cosmological parameters and test the inflationary cold dark matter (CDM) scenario of structure formation. By treating the inflationary spectral index n as a free parameter, we are able to find successful fits to the COBE and Lyα forest constraints in Ωm = 1 models with and without massive neutrinos and in low-Ωm models with and without a cosmological constant. Within each class of model, the …
Enrichment Of The Intergalactic Medium By Radiation Pressure-Driven Dust Efflux, A Aguirre, L Hernquist, N Katz, J Gardner, D Weinberg
Enrichment Of The Intergalactic Medium By Radiation Pressure-Driven Dust Efflux, A Aguirre, L Hernquist, N Katz, J Gardner, D Weinberg
Astronomy Department Faculty Publication Series
The presence of metals in hot cluster gas and in Lyα absorbers, as well as the mass-metallicity relation of observed galaxies, suggest that galaxies lose a significant fraction of their metals to the intergalactic medium (IGM). Theoretical studies of this process have concentrated on metal removal by dynamical processes or supernova-driven winds. Here we investigate the enrichment of the IGM by the expulsion of dust grains from galaxies by radiation pressure. We use already completed cosmological simulations to which we add dust, assuming that most dust can reach the equilibrium point between radiation pressure and gravitational forces. We find that …