TRAO Survey of the Nearby Filamentary Molecular Clouds, the Universal Nursery of Stars (TRAO-FUNS). IV. Filaments and Dense Cores in the W40 and Serpens South Regions of Aquila

TL;DR

The paper addresses how filamentary networks regulate dense-core formation in molecular clouds, focusing on W40 and Serpens South in Aquila. The authors combine Gaussian decomposition of C$^{18}$O (1--0) to separate velocity components with a Friends-of-Friends algorithm to identify velocity-coherent filaments, and apply FellWalker on N$_{2}$H$^{+}$ (1--0) maps to locate dense cores embedded within them. Virial analysis shows identified filaments are thermally supercritical and gravitationally bound; velocity gradients along filaments near embedded cores indicate longitudinal flows feeding core growth. These results indicate a median mass flow rate of about $35$ M_sun Myr^-1, with Serpens South about 40% higher than W40; dense cores show subsonic to transonic non-thermal motions while their host filaments are predominantly supersonic, implying turbulence dissipation at core scales aiding core formation.

Abstract

We present the results of molecular line observations toward the W40 and Serpens South regions of the Aquila molecular cloud complex, conducted as part of the TRAO-FUNS project to investigate the role of filamentary structures in the formation of dense cores and stars in molecular clouds. We performed a Gaussian decomposition of the C$^{18}$O spectra to disentangle multiple velocity components along the line-of-sight and a `Friends-of-Friends' algorithm on these decomposed components to identify 24 velocity-coherent filaments in the observed region. The `FellWalker' algorithm is applied on the N$_{2}$H$^{+}$ integrated intensity map to identify the dense cores embedded within the filaments. Many of the filaments previously identified from the Herschel survey are found to contain multiple velocity-coherent filaments. Virial analysis indicated that all of our identified filaments are thermally supercritical and gravitationally bound. Velocity gradients are observed along the filaments in the vicinity of embedded dense cores, indicating the presence of longitudinal flows that contribute to core formation. The median mass flow rate across the observed region is estimated to be $\sim$35 M$_{\odot}$ Myr$^{-1}$, with Serpens South showing a rate $\sim$40\% higher than W40. The analysis of non-thermal motions revealed that the dense cores mainly show subsonic to transonic motions, while their host filaments are mostly supersonic, suggesting that the turbulent motions in filaments may dissipate on smaller scales, allowing core formation. These findings highlight the essential role of the filaments' criticality, mass flow, and turbulent dissipation in the formation of dense cores within the filaments.