scholarly journals Achieving Extreme Resolution in Numerical Cosmology Using Adaptive Mesh Refinement: Resolving Primordial Star Formation

2002 ◽  
Vol 10 (4) ◽  
pp. 291-302
Author(s):  
Greg L. Bryan ◽  
Tom Abel ◽  
Michael L. Norman
Keyword(s):  
Star Formation ◽  
Adaptive Mesh Refinement ◽  
Dynamic Range ◽  
Parallel Implementation ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Local Refinement ◽  
First Stars ◽  
Standard Cosmological Model ◽  
The Universe

As an entry for the 2001 Gordon Bell Award in the "special" category, we describe our 3-d, hybrid, adaptive mesh refinement (AMR) codeEnzodesigned for high-resolution, multiphysics, cosmological structure formation simulations. Our parallel implementation places no limit on the depth or complexity of the adaptive grid hierarchy, allowing us to achieve unprecedented spatial and temporal dynamic range. We report on a simulation of primordial star formation which develops over 8000 subgrids at 34 levels of refinement to achieve a local refinement of a factor of 1012in space and time. This allows us to resolve the properties of the first stars which form in the universe assuming standard physics and a standard cosmological model. Achievingextreme resolutionrequires the use of 128-bit extended precision arithmetic (EPA) to accurately specify the subgrid positions. We describe our EPA AMR implementation on the IBM SP2 Blue Horizon system at the San Diego Supercomputer Center.

scholarly journals Cosmological simulations of low-mass galaxies: some potential issues

2010 ◽  
Vol 6 (S270) ◽  
pp. 503-506
Author(s):  
Pedro Colín ◽  
Vladimir Avila-Reese ◽  
Octavio Valenzuela
Keyword(s):  
Star Formation ◽  
Adaptive Mesh Refinement ◽  
Mass Fraction ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Stellar Mass ◽  
The Galaxy ◽  
Low Mass

AbstractCosmological Adaptive Mesh Refinement simulations are used to study the specific star formation rate (sSFR=SSF/Ms) history and the stellar mass fraction, fs=Ms/MT, of small galaxies, total masses MT between few × 1010 M⊙ to few ×1011 M⊙. Our results are compared with recent observational inferences that show the so-called “downsizing in sSFR” phenomenon: the less massive the galaxy, the higher on average is its sSFR, a trend seen at least since z ~ 1. The simulations are not able to reproduce this phenomenon, in particular the high inferred values of sSFR, as well as the low values of fs constrained from observations. The effects of resolution and sub-grid physics on the SFR and fs of galaxies are discussed.

Numerical Methods for Radiative Feedback from the First Stars: Ionization in Adaptive Mesh Refinement Simulations

2010 ◽  
Author(s):  
Jeffrey S. Oishi ◽  
Chris McKee ◽  
Richard Klein ◽  
Daniel J. Whalen ◽  
Volker Bromm ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Adaptive Mesh Refinement ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
First Stars ◽  
Radiative Feedback

scholarly journals Cradles of the first stars: self-shielding, halo masses, and multiplicity

2020 ◽  
Vol 492 (3) ◽  
pp. 4386-4397 ◽  
Author(s):  
Danielle Skinner ◽  
John H Wise
Keyword(s):  
Star Formation ◽  
Adaptive Mesh Refinement ◽  
Adaptive Mesh ◽  
Median Number ◽  
Background Intensity ◽  
Radiation Background ◽  
First Stars ◽  
Multiple Systems ◽  
Halo Masses ◽  
Radiation Feedback

ABSTRACT The formation of Population III (Pop III) stars is a critical step in the evolution of the early Universe. To understand how these stars affected their metal-enriched descendants, the details of how, why and where Pop III formation takes place needs to be determined. One of the processes that is assumed to greatly affect the formation of Pop III stars is the presence of a Lyman–Werner (LW) radiation background, that destroys H2, a necessary coolant in the creation of Pop III stars. Self-shielding can alleviate the effect the LW background has on the H2 within haloes. In this work, we perform a cosmological simulation to study the birthplaces of Pop III stars, using the adaptive mesh refinement code enzo. We investigate the distribution of host halo masses and its relationship to the LW background intensity. Compared to previous work, haloes form Pop III stars at much lower masses, up to a factor of a few, due to the inclusion of H2 self-shielding. We see no relationship between the LW intensity and host halo mass. Most haloes form multiple Pop III stars, with a median number of four, up to a maximum of 16, at the instance of Pop III formation. Our results suggest that Pop III star formation may be less affected by LW radiation feedback than previously thought and that Pop III multiple systems are common.

scholarly journals A common origin for the circumnuclear disc and the nearby molecular clouds in the Galactic Centre

2019 ◽  
Vol 488 (4) ◽  
pp. 5802-5810 ◽  
Author(s):  
Alessandro Ballone ◽  
Michela Mapelli ◽  
Alessandro Alberto Trani
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Adaptive Mesh Refinement ◽  
Molecular Clouds ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Common Origin ◽  
Galactic Centre ◽  
Tidal Disruption ◽  
Hydrodynamic Simulation

ABSTRACT The origin of the molecular clouds orbiting SgrA* is one of the most debated questions about our Galactic Centre. Here, we present the hydrodynamic simulation of a molecular cloud infalling towards SgrA*, performed with the adaptive-mesh-refinement code ramses. Through such simulation, we propose that the circumnuclear disc and the +20 km s−1 cloud originated from the same tidal disruption episode, occurred less than 1 Myr ago. We also show that recent star formation is to be expected in the +20 km s−1 cloud, as also suggested by recent observations.

scholarly journals Numerical simulation of star formation in filamentary dark molecular clouds

2015 ◽  
Vol 11 (S315) ◽  
pp. 103-106
Author(s):  
Pak Shing Li ◽  
Richard I. Klein ◽  
Christopher F. McKee
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Numerical Simulations ◽  
Adaptive Mesh Refinement ◽  
Molecular Clouds ◽  
Dynamic Range ◽  
Adaptive Mesh ◽  
Mass Function ◽  
Dark Cloud ◽  
Scale Down

AbstractNumerical simulations of star formation faces challenges including the huge spatial dynamic range and the presence of multiply coupled highly non-linear physics, such as magnetic field, supersonic turbulence, gravitation, radiation and protostellar outflow feedback. We present in this symposium our latest high resolution adaptive mesh refinement numerical simulations of the formation of filamentary dark molecular clouds from 4.55 pc size scale down to the formation of a protostellar cluster with maximum resolution at 28 AU. The physical properties of the long braided filamentary dark cloud formed in the simulation, the magnetic field properties of the cloud clumps, and the protostellar mass function in the simulations match well with the latest observations.

Pop III Supernova Feedback on the Formation of the First Galaxies

2019 ◽  
Vol 15 (S341) ◽  
pp. 253-256 ◽  
Author(s):  
Li-Hsin Chen ◽  
Ke-Jung Chen
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Adaptive Mesh Refinement ◽  
Initial Conditions ◽  
Adaptive Mesh ◽  
Building Blocks ◽  
Dark Matter Halos ◽  
First Stars ◽  
Stellar Feedback ◽  
First Galaxies

AbstractModern cosmological simulations suggest that the hierarchical assembly of dark matter halos provided the gravitational wells that allowed the primordial gases to form stars and galaxies inside them. The first galaxies comprised of the first systems of stars gravitationally bound in dark matter halos are naturally recognized as the building blocks of early Universe. To understand the formation of the first galaxies, we use an adaptive mesh refinement (AMR) cosmological code, Enzo to simulate the formation and evolution of the first galaxies. We first model an isolated galaxy by considering much microphysics such as star formation, stellar feedback, and primordial gas cooling. To examine the effect of Pop III stellar feedback to the first galaxy formation, we adjust the initial temperature, density distribution and metallicity distributions by assuming different IMFs of the first stars. Our results suggest that star formation in the first galaxies is sensitive to the initial conditions of Pop III supernovae and their remnants. Our study can help to correlate the populations of the first stars and supernovae to star formation inside these first galaxies which may be soon observed by the (James Webb Space Telescope JWST).

scholarly journals Star Formation with Adaptive Mesh Refinement Radiation Hydrodynamics

2010 ◽  
Vol 6 (S270) ◽  
pp. 187-194
Author(s):  
Mark R. Krumholz
Keyword(s):  
Star Formation ◽  
Adaptive Mesh Refinement ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Radiation Hydrodynamics ◽  
Adaptive Grids ◽  
Advantages And Disadvantages ◽  
Approximate Equations ◽  
Numerical Approaches

AbstractI provide a pedagogic review of adaptive mesh refinement (AMR) radiation hydrodynamics (RHD) methods and codes used in simulations of star formation, at a level suitable for researchers who are not computational experts. I begin with a brief overview of the types of RHD processes that are most important to star formation, and then I formally introduce the equations of RHD and the approximations one uses to render them computationally tractable. I discuss strategies for solving these approximate equations on adaptive grids, with particular emphasis on identifying the main advantages and disadvantages of various approximations and numerical approaches. Finally, I conclude by discussing areas ripe for improvement.

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