A PPMAP analysis of the filamentary structures in Ophiuchus L1688 and L1689

TL;DR

This study employs the PPMAP algorithm to analyze Herschel and SCUBA-2 data, revealing detailed filamentary structures and physical conditions in the Ophiuchus L1688 and L1689 regions, with implications for star formation processes.

Contribution

First application of PPMAP to Herschel and SCUBA-2 data for high-resolution mapping of filaments in Ophiuchus, providing new insights into their physical properties and star formation activity.

Findings

Filaments are typically 0.10-0.15 pc wide.

Most filaments are highly supercritical if supported only by thermal pressure.

Starless cores are likely to disperse rather than form stars.

Abstract

We use the PPMAP (Point Process MAPping) algorithm to re-analyse the \textit{Herschel} and SCUBA-2 observations of the L1688 and L1689 sub-regions of the Ophiuchus molecular cloud. PPMAP delivers maps with high resolution (here $14''$, corresponding to $\sim 0.01\,{\rm pc}$ at $\sim 140\,{\rm pc}$), by using the observations at their native resolutions. PPMAP also delivers more accurate dust optical depths, by distinguishing dust of different types and at different temperatures. The filaments and prestellar cores almost all lie in regions with $N_{\rm H_2}\gtrsim 7\times 10^{21}\,{\rm cm}^{-2}$ (corresponding to $A_{_{\rm V}}\gtrsim 7$). The dust temperature, $T$, tends to be correlated with the dust opacity index, $\beta$, with low $T$ and low $\beta$ tend concentrated in the interiors of filaments. The one exception to this tendency is a section of filament in L1688 that falls -- in projection -- between the two B stars, S1 and HD147889; here $T$ and $\beta$ are relatively high, and there is compelling evidence that feedback from these two stars has heated and compressed the filament. Filament {\sc fwhm}s are typically in the range $0.10\,{\rm pc}$ to $0.15\,{\rm pc}$. Most filaments have line densities in the range $25\,{\rm M_{_\odot}\,pc^{-1}}$ to $65\,{\rm M_{_\odot}\,pc^{-1}}$. If their only support is thermal gas pressure, and the gas is at the canonical temperature of $10\,{\rm K}$, the filaments are highly supercritical. However, there is some evidence from ammonia observations that the gas is significantly warmer than this, and we cannot rule out the possibility of additional support from turbulence and/or magnetic fields. On the basis of their spatial distribution, we argue that most of the starless cores are likely to disperse (rather than evolving to become prestellar).