FRAGMENTATION OF MASSIVE DENSE CORES DOWN TO ≲ 1000 AU: RELATION BETWEEN FRAGMENTATION AND DENSITY STRUCTURE

Abstract

In order to shed light on the main physical processes controlling\nfragmentation of massive dense cores, we present a uniform study of the density\nstructure of 19 massive dense cores, selected to be at similar evolutionary\nstages, for which their relative fragmentation level was assessed in a previous\nwork. We inferred the density structure of the 19 cores through a simultaneous\nfit of the radial intensity profiles at 450 and 850 micron (or 1.2 mm in two\ncases) and the Spectral Energy Distribution, assuming spherical symmetry and\nthat the density and temperature of the cores decrease with radius following\npower-laws. We find a weak (inverse) trend of fragmentation level and density\npower-law index, with steeper density profiles tending to show lower\nfragmentation, and vice versa. In addition, we find a trend of fragmentation\nincreasing with density within a given radius, which arises from a combination\nof flat density profile and high central density and is consistent with Jeans\nfragmentation. We considered the effects of rotational-to-gravitational energy\nratio, non-thermal velocity dispersion, and turbulence mode on the density\nstructure of the cores, and found that compressive turbulence seems to yield\nhigher central densities. Finally, a possible explanation for the origin of\ncores with concentrated density profiles, which are the cores showing no\nfragmentation, could be related with a strong magnetic field, consistent with\nthe outcome of radiation magnetohydrodynamic simulations.\n