The fragmentation of 'pancakes' in a dark matter-dominated universe

Yuan, Wenbo; Centrella, Joan; Norman, Michael L.

doi:10.1086/186095

Cited by 9 publications

(12 citation statements)

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“…The first multidimensional applications of these methods to cosmology, using artificial viscosity for the treatment of shocks, were made by Ryu et al (1990), Cen et al (1990), and Yuan et al (1991). Ryu et al used the multidimensional fluxcorrected transport method (Sod 1985).…”

Section: Gas Dynamicsmentioning

confidence: 99%

Simulations of Structure Formation in the Universe

Bertschinger

1998

Annu. Rev. Astron. Astrophys.

278

276

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Cosmic structure has formed as a result of gravitational amplification of primordial density fluctuations together with the action of other physical processes (adiabatic gas dynamics, radiative cooling, photoionization and recombination, radiative transfer). These complex nonlinear processes, acting over a wide range of length scales (from kiloparsecs to tens of megaparsecs), make this a difficult problem for computation. During the last two decades, significant progress has been made in developing numerical methods and statistical tools for analyzing simulations and data. Combined with observational advances, numerical simulations have led to the demise of several formerly popular models and to an improved understanding of galaxy clusters, quasistellar object (QSO) absorption line systems, and other phenomena. This review summarizes these advances.

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Section: Gas Dynamicsmentioning

confidence: 99%

Simulations of Structure Formation in the Universe

Bertschinger

1998

Annu. Rev. Astron. Astrophys.

278

276

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“…Cooling processes occur on very short time scales at the center-most densest parts of the pancake structures where stars and galaxies can form from the fragmentation of the gas. (Bond et al 1984;Shapiro & Struck-Marcell 1985;Yuan, Centrella & Norman 1991;.…”

Section: Introductionmentioning

confidence: 99%

Cosmological hydrodynamics with multi-species chemistry and nonequilibrium ionization and cooling

et al. 1997

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We have developed a method of solving for multi-species chemical reaction flows in non-equilibrium and self-consistently with the hydrodynamic equations in an expanding FLRW universe. The method is based on a backward differencing scheme for the required stability when solving stiff sets of equations and is designed to be efficient for three-dimensional calculations without sacrificing accuracy. In all, 28 kinetic reactions are solved including both collisional and radiative processes for the following nine separate species: H, H + , He, He + , He ++ , H − , H + 2 , H 2 , and e − . The method identifies those reactions (involving H − and H + 2 ) ocurring on the shortest time scales, decoupling them from the rest of the network and imposing equilibrium concentrations to good accuracy over typical cosmological dynamical times. Several tests of our code are presented, including radiative shock waves, cosmological sheets, conservation constraints, and fully three-dimensional simulations of CDM cosmological evolutions in which we compare our method to results obtained when the packaged routine LSODAR is substituted for our algorithms.

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“…Evolution and fragmentation processes in these "" pancakes ÏÏ have been studied by many authors, both analytically (Sunyaev & Zeldovich 1972) and numerically (for cosmological pancakes, see, e.g., Bond et al 1984 ;Shapiro & Struck-Marcell 1985 ;Anninos, Norman, & Anninos 1995 ;Anninos & Norman 1996 ;Yuan, Centrella, & Norman 1991 ;Teyssier, & Alimi 1998 ; for Chieze, cloud-cloud collisions, see, e.g., Miniati et al 1997 ; for colliding Ñows, see, e.g., Hunter et al 1986 ;Stevens, Blondin, & Pollock 1992 ;Walder & Folini 1998). In the case of compressed pregalactic clouds, gravitational instability has been regarded as a main mechanism that induces the fragmentation of the shock-compressed sheet (e.g., Yamada & Nishi 1998).…”

Section: Introductionmentioning

confidence: 99%

Dynamical Effects of Global Thermal Instability in Shock‐compressed Gas Slabs

Yamada

Nishi

2001

ApJ

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We investigate global thermal overstability in the postshock gas Ñow behind radiative shock waves and its possible role in the fragmentation of shock-compressed gas, by linear perturbation analysis. In order to examine whether the thermal overstability can introduce any characteristic scale length into the fragmentation, we explore the existence of the maximum growth mode with a Ðnite wavelength. We take into account antisymmetric modes of perturbation, as well as symmetric ones, and a cold layer with Ðnite thickness, and we examine a wide range of parameters. The new results of this paper are : (1) there are two kinds of modes, overstable and quasi-oscillatory ; (2) unlike previous results, we do not Ðnd a dominance of low-order modes over high-overtone ones. We Ðnd a scaling relation in dispersion relations of overstable modes, which means that there is no maximum growth mode. We show that the Ðnite thickness of the cold layer only helps make clearer the di †erence between overstable and quasioscillatory modes compared to the zero cold layer thickness cases. We conclude that at least within the linear analysis, the global thermal overstability does not introduce speciÐc length scales to the fragmentation. We present a schematic picture of the driving mechanism of the global thermal instability behind radiative shock waves, and elucidate the di †erence between the stability properties of radiative and wellstudied isothermal shock waves.

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The fragmentation of 'pancakes' in a dark matter-dominated universe

Cited by 9 publications

References 0 publications

Simulations of Structure Formation in the Universe

Simulations of Structure Formation in the Universe

Cosmological hydrodynamics with multi-species chemistry and nonequilibrium ionization and cooling

Dynamical Effects of Global Thermal Instability in Shock‐compressed Gas Slabs

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