Gone with the Molecular Wind: Photoevaporation in the Compact Dust Disk around CX Tau

Abstract We present Keck NIRSPEC+AO high-resolution ( R ∼ 25,000), mid-infrared ( M -band: 4.6–5.2 μ m) spectra of the protoplanetary disk CX Tau. CX Tau provides an ideal laboratory to study inner disk chemistry in a disk where the signs of radial drift of pebbles are present in the form of a compact mm dust disk and extended gas disk. Our data covers many 12 CO v = 1–0 ro-vibrational transitions, in addition to 13 CO and 12 CO v = 2–1. We find no evidence for CO emission in the inner disk of CX Tau at the level of 8 × 10 16 cm −2 , but do detect narrow, blueshifted absorption at ∼−6 km s −1 . A rotation diagram analysis shows that the gas temperature ranges from about 10 to 350 K, with column densities ∼9 × 10 15 and 3 × 10 17 cm −2 , respectively. In addition to our Keck-NIRSPEC spectra, we create line maps from archival JWST-MIRI IFU data using custom JDISCS reduction techniques. These maps show spatially extended (∼500 au) H 2 and [ Ne ii ]. The blueshifted CO absorption and extended H 2 and [Ne ii ] are evidence of a photoevaporative disk wind. We estimate a wind mass-loss rate from the H 2 S(1) line of ∼10 −9 M ⊙ yr −1 , which is approximately equal to the stellar accretion rate and suggests that CX Tau is in the early stages of disk dispersal.