The statistical properties of stars and their dependence on metallicity: the effects of opacity

Abstract

We report the statistical properties of stars and brown dwarfs obtained from four radiation hydrodynamical simulations of star cluster formation that resolve masses down to the opacity limit for fragmentation. The calculations are identical except for their dust and gas opacities. Assuming dust opacity is proportional to metallicity, the calculations span a range of metallicities from 1/100 to 3 times solar, although we emphasise that changing the metallicity has other thermodynamic effects that the calculations do not capture (e.g. on the thermal coupling between gas and dust). All four calculations produce stellar populations whose statistical properties are difficult to distinguish from observed stellar systems, and we find no significant dependence of stellar properties on opacity. The mass functions and properties of multiple stellar systems are consistent with each other. However, we find protostellar mergers are more common with lower opacities. Combining the results from the three calculations with the highest opacities, we obtain a stellar population consisting of more than 500 stars and brown dwarfs. Many of the statistical properties of this population are in good agreement with those observed in our Galaxy, implying that gravity, hydrodynamics, and radiative feedback may be the primary ingredients for determining the statistical properties of low-mass stars. However, we do find indications that the calculations may be slightly too dissipative. Although further calculations will be required to understand all of the effects of metallicity on stellar properties, we conclude that stellar properties are surprisingly resilient to variations of the dust and gas opacities.

Accepted for publication in MNRAS, 30 pages, 23 figures. Electronic versions of Tables 3 and 4, and animations can be found at http://www.astro.ex.ac.uk/people/mbate/. arXiv admin note: substantial text overlap with arXiv:1110.1092

References in corpus (31)

• Binary interaction dominates the evolution of massive stars
• The High Angular Resolution Multiplicity of Massive Stars
• Inviscid SPH
• The Effects of Radiative Transfer on Low-Mass Star Formation
• The Importance of Radiative Feedback for the Stellar Initial Mass Function
• The impact of magnetic fields on single and binary star formation
• Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition
• The Disk Population of the Chamaeleon I Star-Forming Region
• Star formation at very low metallicity. I: Chemistry and cooling at low densities
• Comparative statistics and origin of triple and quadruple stars
• A search for binary systems among the nearest L dwarfs
• The Wide Brown Dwarf Binary Oph 1622-2405 and Discovery of A Wide, Low Mass Binary in Ophiuchus (Oph 1623-2402): A New Class of Young Evaporating Wide Binaries?
• The primordial binary population II: Recovering the binary population for intermediate mass stars in Sco OB2
• Visual Binaries in the Orion Nebula Cluster
• Near-infrared cross-dispersed spectroscopy of brown dwarf candidates in the Upper Sco association
• A Survey for Spectroscopic Binaries Among Very Low-Mass Stars
• The Jeans mass and the origin of the knee in the IMF
• Why haven't loose globular clusters collapsed yet?
• Driven and Decaying Turbulence Simulations of Low-Mass Star Formation: From Clumps to Cores to Protostars
• Evidence for a Turnover in the IMF of Low Mass Stars and Sub-stellar Objects: Analysis from an Ensemble of Young Clusters
• The Stellar Mass Distribution in the Giant Star Forming Region NGC 346
• Infrared Spectroscopy and Analysis of Brown Dwarf and Planetary Mass Objects in the Orion Nebula Cluster
• Dust-cooling--induced Fragmentation of Low-metallicity Clouds
• Binary Formation in Star-Forming Clouds with Various Metallicities
• Metallicity and the Universality of the IMF
• A New Brown Dwarf Desert? A Scarcity of Wide Ultracool Binaries
• Cool Subdwarf Investigations II: Multiplicity
• The Metallicity of Stars with Close Companions
• The scale-free character of the cluster mass function and the universality of the stellar IMF
• Growth of dust grains in a low-metallicity gas and its effect on the cloud fragmentation
• Speckle Interferometry of Metal-Poor Stars in the Solar Neighborhood. I

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