Impact of the shape of the prestellar density fluctuations on the core mass function

Abstract

It is well known that departure from sphericity in the geometry of primordial dark matter halos modifies their mass function. The ellipsoidal collapse model yields a better agreement with simulations of hierarchical clustering than the original, spherical model. In the present paper, we examine the same issue in the context of star formation by studying the impact of non-sphericity of density perturbations in a gravoturbulent medium on the prestellar core mass function (CMF). An important question, notably, is to find out how ellipsoidal, instead of spherical, initial density fluctuations modify both the high-mass and low-mass tails of the CMF. Our study shows that triaxial density fluctuations indeed depart from a purely spherical form but the deformation (prolateness and ellipticity) remains modest, suggesting that the usual hypothesis of spherical collapse in existing theories of the IMF is reasonable. We find that, as in the cosmological case, the departure from sphericity increases the collapse barrier, stabilizing the prestellar cores. The striking difference between the stellar case and the cosmological one for the ellipsoidal collapse model is that, although in both cases the less dense structures are the most deformed, they correspond to small scales, thus low mass halos in cosmology but to large scales, thus large mass cores in star formation. As a result, the high mass range of the CMF is the most affected by the ellipsoidal collapse, resulting in a slightly less steep slope than the one predicted with the spherical hypothesis and a peak slightly shifted toward lower masses.

14 pages, 6 figures. Typo corrected in Eq. 27, 29 and 30: replacing $\mathcal{N}$ by $\mathcal{P}$

References in corpus (20)

• The Statistics of Supersonic Isothermal Turbulence
• Analytical theory for the initial mass function: CO clumps and prestellar cores
• On the Star Formation Efficiency of Turbulent Magnetized Clouds
• Numerical simulations of compressively driven interstellar turbulence: I. Isothermal gas
• The Fractal Density Structure in Supersonic Isothermal Turbulence: Solenoidal versus Compressive Energy Injection
• The sonic scale revealed by the world's largest supersonic turbulence simulation
• The density structure and star formation rate of non-isothermal polytropic turbulence
• Probing interstellar turbulence in cirrus with deep optical imaging: no sign of energy dissipation at 0.01 pc scale
• Initial Conditions for Star Formation: A Physical Description of the Filamentary ISM
• Evolution of the density PDF in star forming clouds: the role of gravity
• The density structure of supersonic self-gravitating turbulence
• A multi-shock model for the density variance of anisotropic, highly-magnetised, supersonic turbulence
• Rotating filament in Orion B: Do cores inherit their angular momentum from their parent filament?
• The relation between the true and observed fractal dimensions of turbulent clouds
• The turbulent gas structure in the centers of NGC253 and the Milky Way
• Unravelling the structure of magnetised molecular clouds with SILCC-Zoom: sheets, filaments and fragmentation
• Density and Velocity Correlations in Isothermal Supersonic Turbulence
• HCN $J$=4-3, HNC $J$=1-0, ${\mathrm{H}}^{13}\mathrm{CN}$ $J$=1-0, and $\mathrm{H}{\mathrm{C}}_3\mathrm{N}$ $J$=10-9 Maps of Galactic Center Region II.: Physical Properties of Dense Gas Clumps and Probability of Star Formation
• Statistical properties and correlation length in star-forming molecular clouds: I. Formalism and application to observations
• Probing the Physics of Star-Formation (ProPStar) III. No evidence for dissipation of turbulence down to 20 mpc (4 000 au) scale