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

Abstract

We use the Point Process MAPping (PPMAP) algorithm to reanalyse the Herschel and SCUBA-2 observations of the L1688 and L1689 subregions of the Ophiuchus molecular cloud. PPMAP delivers maps with high resolution (here 14 arcsec, corresponding to ∼0.01pc at ∼140pc), 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 pre-stellar cores almost all lie in regions with N_(H₂) ≳ 7×10²¹ cm⁻² (corresponding to A_V ≳ 7). The dust temperature, T, tends to be correlated with the dust opacity index, β, with low T and low β 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 β are relatively high, and there is compelling evidence that feedback from these two stars has heated and compressed the filament. Filament FWHMS are typically in the range 0.10 to 0.15pc. Most filaments have line-densities in the range 25 to 65M⊙pc⁻¹⁠. If their only support is thermal gas pressure, and the gas is at the canonical temperature of 10K⁠, 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 pre-stellar).