Dust entrainment in photoevaporative winds: Densities and imaging

Abstract

X-ray- and EUV- (XEUV-) driven photoevaporative winds acting on protoplanetary disks around young T-Tauri stars may crucially impact disk evolution, affecting both gas and dust distributions. We constrain the dust densities in a typical XEUV-driven outflow, and determine whether these winds can be observed at $\hat{I}¼\mathrm{m}$-wavelengths in scattered and polarised light. For an XEUV-driven outflow around a $M_{\ast }=0.7{\mathrm{M}}_{\odot }$ T-Tauri star with $L_X=2\cdot 10^{30}erg/s$, we find a dust mass-loss rate ${\dot{M}}_{\mathrm{dust}}\lesssim 4.1\cdot 10^{-11}{\mathrm{M}}_{\odot }/yr$ for an optimistic estimate of dust densities in the wind (compared to ${\dot{M}}_{\mathrm{gas}}\approx 3.7\cdot 10^{-8}{\mathrm{M}}_{\odot }/yr$). The synthesised scattered-light images suggest a distinct chimney structure emerging at intensities $I/I_{\max }<10^{-4.5}$ ($10^{-3.5}$) at $\hat{I}{»}_{\mathrm{obs}}=1.6$ ($0.4$) $\hat{I}¼\mathrm{m}$, while the features in the polarised-light images are even fainter. Observations synthesised from our model do not exhibit clear features for SPHERE IRDIS, but show a faint wind signature for JWST NIRCam under optimal conditions. In conclusion, unambiguous detections of photoevaporative XEUV winds launched from primordial disks are at least challenging with current instrumentation; this provides a possible explanation as to why disk winds are not routinely detected in scattered or polarised light.

Accepted for publication in A&A. 15 pages, 11 figures. (Affiliations updated, one reference corrected.)