# A centrally concentrated sub-solar mass starless core in the Taurus L1495 filamentary complex

## TL;DR

This study identifies a small, dense, starless core in the Taurus region that may be the initial condition for brown dwarf formation, providing insights into the early stages of very low-mass object formation.

## Contribution

First detailed observation of a sub-solar mass starless core in Taurus, suggesting it may form brown dwarfs or very low-mass stars, advancing understanding of their initial conditions.

## Key findings

- Core mass is 0.2-0.4 solar masses, smaller than typical prestellar cores.
- High deuterium fractionation (~30%) indicates chemical evolution.
- Possible substructures suggest early fragmentation stages.

## Abstract

The formation scenario of brown dwarfs is still unclear because observational studies to investigate its initial condition are quite limited. Our systematic survey of nearby low-mass star-forming regions using the Atacama Compact Array (aka Morita array) and the IRAM 30 m telescope in 1.2 mm continuum has identified a centrally concentrated starless condensation with a central H$_2$ volume density of $\sim$10$^6$ cm$^{-3}$, MC5-N, connected to a narrow (width $\sim$0.03 pc) filamentary cloud in the Taurus L1495 region. The mass of the core is $\sim$0.2-0.4 $M_{\odot}$, which is an order of magnitude smaller than typical low-mass prestellar cores. Taking into account a typical core to star formation efficiency for prestellar cores ($\sim$20%-40%) in nearby molecular clouds, brown dwarf(s) or very low-mass star(s) may be going to be formed in this core. We have found possible substructures at the high-density portion of the core, although much higher angular resolution observation is needed to clearly confirm them. The subsequent N$_2$H$^+$ and N$_2$D$^+$ observations using the Nobeyama 45 m telescope have confirmed the high-deuterium fractionation ($\sim$30%). These dynamically and chemically evolved features indicate that this core is on the verge of proto-brown dwarf or very low-mass star formation and is an ideal source to investigate the initial conditions of such low-mass objects via gravitational collapse and/or fragmentation of the filamentary cloud complex.