The properties of Planck Galactic cold clumps in the L1495 dark cloud

TL;DR

This study investigates 16 Planck Galactic Cold Clumps in the L1495 dark cloud, revealing their physical, chemical, and dynamical properties, and highlighting their early evolutionary stages and turbulence-dominated nature.

Contribution

It provides detailed observational analysis of PGCCs in L1495, including core properties, virial analysis, and chemical depletion, advancing understanding of early star formation stages.

Findings

Dense cores have low temperatures (11-14 K) and high column densities.

Most dense cores are turbulence-dominated with virial parameters indicating some are unbound.

CO depletion is prevalent, especially in prestellar core candidates.

Abstract

Planck Galactic Cold Clumps (PGCCs) possibly represent the early stages of star formation. To understand better the properties of PGCCs, we studied 16 PGCCs in the L1495 cloud with molecular lines and continuum data from Herschel, JCMT/SCUBA-2 and the PMO 13.7 m telescope. Thirty dense cores were identified in 16 PGCCs from 2-D Gaussian fitting. The dense cores have dust temperatures of $T_{\rm d}$ = 11-14 K, and H$_{2}$ column densities of $N_{\rm H_{2}}$ = 0.36-2.5$\times10^{22}$ cm$^{-2}$. We found that not all PGCCs contain prestellar objects. In general, the dense cores in PGCCs are usually at their earliest evolutionary stages. All the dense cores have non-thermal velocity dispersions larger than the thermal velocity dispersions from molecular line data, suggesting that the dense cores may be turbulence-dominated. We have calculated the virial parameter $\alpha$ and found that 14 of the dense cores have $\alpha$ $<$ 2, while 16 of the dense cores have $\alpha$ $>$ 2. This suggests that some of the dense cores are not bound in the absence of external pressure and magnetic fields. The column density profiles of dense cores were fitted. The sizes of the flat regions and core radii decrease with the evolution of dense cores. CO depletion was found to occur in all the dense cores, but is more significant in prestellar core candidates than in protostellar or starless cores. The protostellar cores inside the PGCCs are still at a very early evolutionary stage, sharing similar physical and chemical properties with the prestellar core candidates.