FRAGMENTATION AND EVOLUTION OF MOLECULAR CLOUDS. II. THE EFFECT OF DUST HEATING

We investigate the effect of heating by luminosity sources in a simulation of clustered star formation. Our heating method involves a simplified continuum radiative transfer method that calculates the dust temperature. The gas temperature is set by the dust temperature. We present the results of four simulations; two simulations assume an isothermal equation of state and the two other simulations include dust heating. We investigate two mass regimes, i.e., 84 M☉ and 671 M☉, using these two different energetics algorithms. The mass functions for the isothermal simulations and simulations that include dust heating are drastically different. In the isothermal simulation, we do not form any objects with masses above 1 M☉. However, the simulation with dust heating, while missing some of the low-mass objects, forms high-mass objects (∼20 M☉) which have a distribution similar to the Salpeter initial mass function. The envelope density profiles around the stars formed in our simulation match observed values around isolated, low-mass star-forming cores. We find the accretion rates to be highly variable and, on average, increasing with final stellar mass. By including radiative feedback from stars in a cluster-scale simulation, we have determined that it is a very important effect which drastically affects the mass function and yields important insights into the formation of massive stars.

[1]  Daniel J. Price,et al.  Inefficient star formation: the combined effects of magnetic fields and radiative feedback , 2009, 0904.4071.

[2]  R. Klein,et al.  THE EFFECTS OF RADIATIVE TRANSFER ON LOW-MASS STAR FORMATION , 2009, 0904.2004.

[3]  R. Klein,et al.  The Formation of Massive Star Systems by Accretion , 2009, Science.

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

[5]  D. Padgett,et al.  THE SPITZER c2d LEGACY RESULTS: STAR-FORMATION RATES AND EFFICIENCIES; EVOLUTION AND LIFETIMES , 2008, 0811.1059.

[6]  Matthew Bate,et al.  Stellar, brown dwarf and multiple star properties from hydrodynamical simulations of star cluster formation , 2008, 0811.0163.

[7]  N. Evans,et al.  A PARAMETER STUDY OF THE DUST AND GAS TEMPERATURE IN A FIELD OF YOUNG STARS , 2007, 0710.3906.

[8]  L. Hartmann,et al.  Accretion Processes in Star Formation: Second Edition , 2009 .

[9]  Daniel J. Price,et al.  The effect of magnetic fields on star cluster formation , 2008, 0801.3293.

[10]  K. Menten,et al.  Forming an early O-type star through gas accretion? , 2007, 0711.4941.

[11]  R. Klessen,et al.  The First Stellar Cluster , 2007, 0706.0613.

[12]  H. Zinnecker,et al.  Toward Understanding Massive Star Formation , 2007, 0707.1279.

[13]  Leiden,et al.  Observing the gas temperature drop in the high-density nucleus of L 1544 , 2007, 0705.0471.

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

[15]  M. Krumholz,et al.  Slow Star Formation in Dense Gas: Evidence and Implications , 2006, astro-ph/0606277.

[16]  A. Whitworth,et al.  Resolution requirements for simulating gravitational fragmentation using SPH , 2006 .

[17]  C. Clarke,et al.  The Jeans mass and the origin of the knee in the IMF , 2006, astro-ph/0603444.

[18]  P. Shapiro,et al.  Fragmentation and Evolution of Molecular Clouds. I. Algorithm and First Results , 2005, astro-ph/0505008.

[19]  M. Bate.  The dependence of the initial mass function on metallicity and the opacity limit for fragmentation , 2005 .

[20]  Christopher F. McKee,et al.  A General Theory of Turbulence-regulated Star Formation, from Spirals to Ultraluminous Infrared Galaxies , 2005, astro-ph/0505177.

[21]  R. Larson.  Thermal physics, cloud geometry and the stellar initial mass function , 2005 .

[22]  I. Bonnell,et al.  The origin of the initial mass function and its dependence on the mean Jeans mass in molecular clouds , 2004, astro-ph/0411084.

[23]  R. Klessen,et al.  The Stellar Mass Spectrum from Non-Isothermal Gravoturbulent Fragmentation , 2004, astro-ph/0410351.

[24]  Russel J. White,et al.  On the Evolutionary Status of Class I Stars and Herbig-Haro Energy Sources in Taurus-Auriga , 2004, astro-ph/0408244.

[25]  E. Keto.  The Formation of Massive Stars by Accretion through Trapped Hypercompact H II Regions , 2003, astro-ph/0309131.

[26]  G. Chabrier.  Galactic Stellar and Substellar Initial Mass Function , 2003, astro-ph/0304382.

[27]  W. Tscharnuter,et al.  From clouds to stars - Protostellar collapse and the evolution to the pre-main sequence I. Equations and evolution in the Hertzsprung-Russell diagram , 2003 .

[28]  Volker Bromm,et al.  The formation of a star cluster: predicting the properties of stars and brown dwarfs , 2002, astro-ph/0212380.

[29]  Mordecai-Mark Mac Low,et al.  The Formation of Stellar Clusters in Turbulent Molecular Clouds: Effects of the Equation of State , 2002, astro-ph/0210479.

[30]  S. Kitsionas,et al.  Smoothed Particle Hydrodynamics with particle splitting, applied to self-gravitating collapse , 2002, astro-ph/0203057.

[31]  P. Kroupa.  The Initial Mass Function of Stars: Evidence for Uniformity in Variable Systems , 2002, Science.

[32]  H. Yorke,et al.  On the Formation of Massive Stars , 2002, astro-ph/0201041.

[33]  P. Coppi,et al.  The Formation of the First Stars. I. The Primordial Star-forming Cloud , 2001, astro-ph/0102503.

[34]  R. Klessen.  The Formation of Stellar Clusters: Time-Varying Protostellar Accretion Rates , 2001, astro-ph/0101277.

[35]  L. Mundy,et al.  Tracing the Mass during Low-Mass Star Formation. II. Modeling the Submillimeter Emission from Preprotostellar Cores , 2000, astro-ph/0006183.

[36]  L. Hartmann,et al.  Accretion processes in star formation , 1999 .

[37]  C. Chandler,et al.  Circumstellar kinematics and the measurement of stellar mass for the protostars TMC1 and TMC1A , 1999 .

[38]  David K. Lynch,et al.  Thermal Emission Spectroscopy and Analysis of Dust, Disks, and Regoliths , 1999, Nursing standard (Royal College of Nursing (Great Britain) : 1987).

[39]  A. Boss.  The Jeans Mass Constraint and the Fragmentation of Molecular Cloud Cores , 1998 .

[40]  R. Klessen,et al.  Fragmentation of Molecular Clouds: The Initial Phase of a Stellar Cluster , 1997, astro-ph/9805125.

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

[42]  I. Bonnell,et al.  Modelling accretion in protobinary systems , 1995, astro-ph/9510149.

[43]  S. White,et al.  Simulations of X-ray clusters , 1994, astro-ph/9408069.

[44]  Italo Mazzitelli,et al.  New pre-main-sequence tracks for M less than or equal to 2.5 solar mass as tests of opacities and convecti on model , 1994 .

[45]  F. Palla,et al.  The pre-main-sequence evolution of intermediate-mass stars , 1993 .

[46]  J. Monaghan.  Smoothed particle hydrodynamics , 2005 .

[47]  Glenn E. Miller,et al.  The Initial mass function and stellar birthrate in the solar neighborhood , 1979 .

[48]  E. Salpeter.  The Luminosity function and stellar evolution , 1955 .