Exposed Long-lifetime First-core: A New Model of First Cores Based on Radiation Hydrodynamics

TL;DR

This paper introduces a new model of first cores called Exposed Long-lifetime First core (ELF), which are low-mass, long-lived objects in star formation, predicted to be observable despite their faintness.

Contribution

The study presents a novel radiation hydrodynamic model of first cores, showing that low-mass cores can have extended lifetimes and distinct observational signatures.

Findings

ELFs can live longer than 10,000 years due to low accretion rates.

ELFs have similar spectral energy distributions to ordinary first cores in radio wavelengths.

A significant number of ELFs may form in star-forming regions due to the abundance of low-mass cores.

Abstract

A first adiabatic core is a transient object formed in the early phase of star formation. The observation of a first core is believed to be difficult because of its short lifetime and low luminosity. On the basis of radiation hydrodynamic simulations, we propose a novel theoretical model of first cores, Exposed Long-lifetime First core (ELF). In the very low-mass molecular core, the first core evolves slowly and lives longer than 10,000 years because the accretion rate is considerably low. The evolution of ELFs is different from that of ordinary first cores because radiation cooling has a significant effect there. We also carry out radiation transfer calculation of dust-continuum emission from ELFs to predict their observational properties. ELFs have slightly fainter but similar SEDs to ordinary first cores in radio wavelengths, therefore they can be observed. Although the probabilities that such low mass cores become gravitationally unstable and start to collapse are low, we still can expect that a considerable number of ELFs can be formed because there are many low-mass molecular cloud cores in star-forming regions that can be progenitors of ELFs.