Synthetic observations of first hydrostatic cores in collapsing low-mass dense cores. I. Spectral energy distributions and evolutionary sequence

摘要

The low-mass star formation evolutionary sequence is relatively well-definedboth from observations and theoretical considerations. The first hydrostaticcore is the first protostellar equilibrium object that is formed during thestar formation process. Using state-of-the-art radiation-magneto-hydrodynamic3D adaptive mesh refinement calculations, we aim to provide predictions for thedust continuum emission from first hydrostatic cores. We investigate thecollapse and the fragmentation of magnetized one solar mass prestellar densecores and the formation and evolution of first hydrostatic cores using theRAMSES code. We use three different magnetization levels for the initialconditions, which cover a large variety of early evolutionary morphology, e.g.,the formation of a disk or a pseudo-disk, outflow launching, and fragmentation.We post-process the dynamical calculations using the 3D radiative transfer codeRADMC-3D. We compute spectral energy distributions and usual evolutionary stageindicators such as bolometric luminosity and temperature. We find that thefirst hydrostatic core lifetimes depend strongly on the initial magnetizationlevel of the parent dense core. We derive, for the first time, spectral energydistribution evolutionary sequences from high-resolutionradiation-magneto-hydrodynamic calculations. We show that under certainconditions, first hydrostatic cores can be identified from dust continuumemission at 24 microns and 70 microns. We also show that single spectral energydistributions cannot help to distinguish between the formation scenarios of thefirst hydrostatic core, i.e., between the magnetized and non-magnetized models.Spectral energy distributions are a first useful and direct way to target firsthydrostatic core candidates but high-resolution interferometry is definitivelyneeded to determine the evolutionary stage of the observed sources.