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- ItemFeeding vs Falling. The growth and collapse of molecular clouds in a turbulent interstellar medium(2017) Ibáñez-Mejía, Juan C.; Mac Low, Mordecai-Mark; Klessen, Ralf S.; Baczynski, ChristianIn order to understand the origin of observed molecular cloud properties, it is critical to understand how clouds interact with their environments during their formation, growth and collapse. It has been suggested that accretion-driven turbulence can maintain clouds in a highly turbulent state, prevent- ing runaway collapse, and explaining the observed non-thermal velocity dispersions. We present 3D, adaptive-mesh-refinement (AMR), magnetohydrodynamics (MHD) simulations of a kiloparsec-scale, stratified, supernova-driven, self-gravitating, interstellar medium, including diffuse heating and radia- tive cooling. These simulations model the formation and evolution of a molecular cloud population in the turbulent interstellar medium. We use zoom-in techniques to focus on the dynamics of the mass accretion and its history for individual molecular clouds. We find that mass accretion onto molecular clouds proceeds as a combination of turbulent flow and near free-fall accretion of a gravitationally bound envelope. Nearby supernova explosions have a dual role, compressing the envelope, increasing mass accretion rates, but also disrupting parts of the envelope and eroding mass from the cloud’s surface. It appears that the inflow rate of kinetic energy onto clouds from supernova explosions is in- sufficient to explain the net rate of change of the cloud kinetic energy. In the absence of self-consistent star formation, conversion of gravitational potential into kinetic energy during contraction seems to be the main driver of non-thermal motions within clouds. We conclude that although clouds interact strongly with their environments, bound clouds are always in a state of gravitational contraction, close to runaway, and their properties are a natural result of this collapse.
- ItemGravity Versus Magnetic Fields in Forming Molecular Clouds(2021-08-07) Ibáñez-Mejía, Juan C.; Mac Low, Mordecai-Mark; Klessen, Ralf S.This repository contains scripts and data for Figures 2-7 in the paper by Ibanez-Mejia, Mac Low, & Klessen (2021, Astrophys. J., submitted) entitled "Gravity Versus Magnetic Fields in Forming Molecular Clouds”.
- ItemHow do velocity structure functions trace gas dynamics in simulated molecular clouds?(2018-07-27) Chira, Roxana-Adela; Ibáñez-Mejía, Juan C.; Mac Low, Mordecai-Mark; Henning, ThomasIn Chira et al. (subm.), we investigate the time evolution of gas dynamics within simulated molecular clouds, as well as how velocity structure functions trace the dominating driving sources of turbulence. The molecular clouds are formed self-consistently within kiloparsec-scale numerical simulations of the interstellar medium that include self-gravity, magnetic fields, supernovae- driven turbulence, and radiative heating and cooling. Here, we provide the underlying data for the analysis and plots presented in the paper submitted to Astronomy & Astrophysics. The simulations are run using an implementation of the Flash code. We present data for each of the, in total, 160 timesteps in HDF5 format, the final velocity structure functions as functions of lag and time. Note that due to technical problems we are currently able to offer the raw data for those simulations that resolve the local Jeans length with 4 cells only. We will upload the higher Jeans-resolved data as soon as possible.
- ItemSupplemental Data: Effect of the heating rate on the stability of the three-phase interstellar mediumHill, Alex S.; Mac Low, Mordecai-Mark; Gatto, Andrea; Ibáñez-Mejía, Juan C.In Hill et al (2018), we investigated the impact of the far ultraviolet (FUV) heating rate on the stability of the three-phase interstellar medium using three-dimensional simulations of a 1 kpc^2, vertically-extended domain. We found that even absent a variable star formation rate regulating the FUV heating rate, the gas physics keeps the pressure in the regime in which the cold and warm neutral media coexist. Here, we provide the underlying data for the figures presented in the paper in The Astrophysical Journal. The simulations were run using an implementation of the Flash code version 4.2. We present data for one timestep from each of 22 different simulations in HDF5 format.