Collisional N-body Dynamics Coupled to Self-gravitating Magnetohydrodynamics Reveals Dynamical Binary Formation

We describe a star cluster formation model that includes individual star formation from self-gravitating, magnetized gas, coupled to collisional stellar dynamics. The model uses the Astrophysical Multi-purpose Software Environment (AMUSE) to integrate an adaptive-mesh magnetohydrodynamics code (FLASH) with a fourth order Hermite N-body code (ph4), a stellar evolution code (SeBa), and a method for resolving binary evolution (multiples). This combination yields unique star formation simulations that allow us to study binaries formed dynamically from interactions with both other stars and dense, magnetized gas subject to stellar feedback during the birth and early evolution of stellar clusters. We find that for massive stars, our simulations are consistent with the observed dynamical binary fractions and mass ratios. However, our binary fraction drops well below observed values for lower mass stars, presumably due to unincluded binary formation during initial star formation. Further, we observe a build up of binaries near the hard-soft boundary that may be an important mechanism driving early cluster contraction.

[1]  B. Fryxell,et al.  FLASH: An Adaptive Mesh Hydrodynamics Code for Modeling Astrophysical Thermonuclear Flashes , 2000 .

[2]  S. Tremaine,et al.  Galactic Dynamics , 2005 .

[3]  P. Woodward,et al.  The Piecewise Parabolic Method (PPM) for Gas Dynamical Simulations , 1984 .

[4]  Douglas C. Heggie,et al.  Binary evolution in stellar dynamics , 1975 .

[5]  S. Chatterjee,et al.  MONTE CARLO SIMULATIONS OF GLOBULAR CLUSTER EVOLUTION. V. BINARY STELLAR EVOLUTION , 2009, 0912.4682.

[6]  David P. Doane,et al.  Aesthetic Frequency Classifications , 1976 .

[7]  Harvard-Smithsonian CfA,et al.  Stellar Multiplicity , 2013, 1303.3028.

[8]  P. Hut,et al.  Building a better leapfrog , 1995 .

[9]  R. Weaver,et al.  Interstellar bubbles. II - Structure and evolution , 1977 .

[10]  K. Kusano,et al.  A multi-state HLL approximate Riemann solver for ideal magnetohydrodynamics , 2005 .

[11]  R. Klessen,et al.  GRAVITATIONAL CONTRACTION VERSUS SUPERNOVA DRIVING AND THE ORIGIN OF THE VELOCITY DISPERSION–SIZE RELATION IN MOLECULAR CLOUDS , 2015, 1511.05602.

[12]  T. Naab,et al.  Supernova blast waves in wind-blown bubbles, turbulent, and power-law ambient media , 2016, 1604.04395.

[13]  S. Zwart,et al.  The Origin of OB Runaway Stars , 2011, Science.

[14]  T. Abel,et al.  enzo+moray: radiation hydrodynamics adaptive mesh refinement simulations with adaptive ray tracing , 2010, 1012.2865.

[15]  F. I. Pelupessy,et al.  The evolution of embedded star clusters , 2011, 1111.0992.

[16]  A. Tokovinin,et al.  The mass ratio distribution of B-type visual binaries in the Sco OB2 association , 2002 .

[17]  J. Weingartner,et al.  Photoelectric Emission from Interstellar Dust: Grain Charging and Gas Heating , 1999, astro-ph/9907251.

[18]  Embedding Lagrangian Sink Particles in Eulerian Grids , 2003, astro-ph/0312612.

[19]  R. Klessen,et al.  The SILCC project - III. Regulation of star formation and outflows by stellar winds and supernovae , 2016, 1606.05346.

[20]  P. Kroupa.  On the variation of the initial mass function , 2000, astro-ph/0009005.

[21]  J. Hills.  Encounters between binary and single stars and their effect on the dynamical evolution of stellar systems , 1975 .

[22]  Andreas Burkert,et al.  Kinetic Energy Decay Rates of Supersonic and Super-Alfvénic Turbulence in Star-Forming Clouds , 1998 .

[23]  R. Klessen,et al.  Gravitational Collapse in Turbulent Molecular Clouds. II. Magnetohydrodynamical Turbulence , 2000, astro-ph/0009227.

[24]  Richard I. Klein,et al.  The Jeans Condition: A New Constraint on Spatial Resolution in Simulations of Isothermal Self-Gravitational Hydrodynamics , 1997 .

[25]  A. Tielens,et al.  Neutral Atomic Phases of the Interstellar Medium in the Galaxy , 2003 .

[26]  M. Giersz,et al.  mocca code for star cluster simulations – I. Blue stragglers, first results , 2012, 1207.6700.

[27]  S. Stahler,et al.  Embedded binaries and their dense cores , 2017, 1705.00049.

[28]  H. Yoshida.  Construction of higher order symplectic integrators , 1990 .

[29]  P. Ricker.  A Direct Multigrid Poisson Solver for Oct-Tree Adaptive Meshes , 2007, 0710.4397.

[30]  H. Zinnecker,et al.  The primordial binary population. I. A near-infrared adaptive optics search for close visual companions to A star members of Scorpius OB2 , 2004, astro-ph/0410106.

[31]  M. Mac Low,et al.  Turbulent Structure of a Stratified Supernova-driven Interstellar Medium , 2005, astro-ph/0601005.

[32]  R. Klessen,et al.  Fervent: chemistry-coupled, ionizing and non-ionizing radiative feedback in hydrodynamical simulations , 2015, 1503.08987.

[33]  T. Fukushige,et al.  Effects of Hardness of Primordial Binaries on the Evolution of Star Clusters , 2009, 1005.2237.

[34]  N. Drost,et al.  The Astrophysical Multipurpose Software Environment , 2013, 1307.3016.

[35]  M. Bate.  The importance of radiative feedback for the stellar initial mass function , 2008, 0811.1035.

[36]  T. Boeker,et al.  Stellar dynamics in gas: the role of gas damping , 2014, 1404.0379.

[37]  S. Zwart,et al.  The initial mass function of star clusters that form in turbulent molecular clouds , 2013, 1309.1223.

[38]  R. Klessen,et al.  Control of star formation by supersonic turbulence , 2000, astro-ph/0301093.

[39]  P. Padoan,et al.  INFALL-DRIVEN PROTOSTELLAR ACCRETION AND THE SOLUTION TO THE LUMINOSITY PROBLEM , 2014, 1407.1445.

[40]  Bruce G. Elmegreen,et al.  The Initial Stellar Mass Function from Random Sampling in a Turbulent Fractal Cloud , 1997 .

[41]  R. Klessen,et al.  LIMITING ACCRETION ONTO MASSIVE STARS BY FRAGMENTATION-INDUCED STARVATION , 2010, 1005.3271.

[42]  Junichiro Makino,et al.  BRIDGE: A Direct-Tree Hybrid N -Body Algorithm for Fully Self-Consistent Simulations of Star Clusters and Their Parent Galaxies , 2007, 0706.2059.

[43]  I. A. Bonnell,et al.  Modelling accretion in protobinary systems , 1995 .

[44]  M. Bate.  Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation , 2011, 1110.1092.

[45]  B. Ercolano,et al.  Before the first supernova: combined effects of H II regions and winds on molecular clouds , 2014, 1404.6102.

[46]  E. Solano,et al.  A Catalog of Wide Binary and Multiple Systems of Bright Stars from Gaia-DR2 and the Virtual Observatory , 2019, The Astronomical Journal.

[47]  J. Wisdom,et al.  Symplectic maps for the N-body problem. , 1991 .

[48]  R. Klein,et al.  An unstable truth: how massive stars get their mass , 2016, 1607.03117.

[49]  R. Klein,et al.  RADIATION-HYDRODYNAMIC SIMULATIONS OF THE FORMATION OF ORION-LIKE STAR CLUSTERS. II. THE INITIAL MASS FUNCTION FROM WINDS, TURBULENCE, AND RADIATION , 2012, 1203.2620.

[50]  Richard I. Klein,et al.  Radiation-Hydrodynamic Simulations of Collapse and Fragmentation in Massive Protostellar Cores , 2006, astro-ph/0609798.

[51]  R. Klessen,et al.  MODELING COLLAPSE AND ACCRETION IN TURBULENT GAS CLOUDS: IMPLEMENTATION AND COMPARISON OF SINK PARTICLES IN AMR AND SPH , 2010, 1001.4456.

[52]  G. Melnick,et al.  Thermal Balance in Dense Molecular Clouds: Radiative Cooling Rates and Emission-Line Luminosities , 1995 .

[53]  R. Klessen,et al.  THE INTERPLAY OF MAGNETIC FIELDS, FRAGMENTATION, AND IONIZATION FEEDBACK IN HIGH-MASS STAR FORMATION , 2010, 1010.5905.

[54]  G. Bryan,et al.  KINETIC ENERGY FROM SUPERNOVA FEEDBACK IN HIGH-RESOLUTION GALAXY SIMULATIONS , 2014, 1410.3822.

[55]  R. Klessen,et al.  A simple method to convert sink particles into stars , 2016, 1610.02538.

[56]  M. Norman,et al.  yt: A MULTI-CODE ANALYSIS TOOLKIT FOR ASTROPHYSICAL SIMULATION DATA , 2010, 1011.3514.

[57]  Francesco Palla,et al.  The Formation of Stars , 2005 .

[58]  Dongwook Lee,et al.  A solution accurate, efficient and stable unsplit staggered mesh scheme for three dimensional magnetohydrodynamics , 2013, J. Comput. Phys..

[59]  R. Klessen,et al.  Magnetic fields during the early stages of massive star formation – I. Accretion and disc evolution , 2011, 1106.4485.

[60]  Christoph Federrath,et al.  A NEW JEANS RESOLUTION CRITERION FOR (M)HD SIMULATIONS OF SELF-GRAVITATING GAS: APPLICATION TO MAGNETIC FIELD AMPLIFICATION BY GRAVITY-DRIVEN TURBULENCE , 2011, 1102.0266.

[61]  F. Inti Pelupessy,et al.  Multi-physics simulations using a hierarchical interchangeable software interface , 2011, Comput. Phys. Commun..

[62]  Frank Timmes,et al.  MODULES FOR EXPERIMENTS IN STELLAR ASTROPHYSICS (MESA) , 2010, 1009.1622.

[63]  Efficiencies of Low-Mass Star and Star Cluster Formation , 2000, astro-ph/0007383.

[64]  B. Draine.  Physics of the Interstellar and Intergalactic Medium , 2011 .

[65]  V. Hertzog,et al.  Physical Processes In The Interstellar Medium , 2016 .