JWST MIRI MRS Observations of T Cha: Discovery of a Spatially Resolved Disk Wind

Abstract

Understanding when and how circumstellar disks disperse is crucial to constrain planet formation and migration. Thermal winds powered by high-energy stellar photons have long been theorized to drive disk dispersal. However, evidence for these winds is currently based only on small (∼3–6 km s−1) blueshifts in [Ne ii] 12.81 μm lines, which does not exclude MHD winds. We report JWST MIRI MRS spectro-imaging of T Cha, a disk with a large dust gap (∼30 au in radius) and blueshifted [Ne ii] emission. We detect four forbidden noble gas lines, [Ar ii], [Ar iii], [Ne ii], and [Ne iii], of which [Ar iii] is the first detection in any protoplanetary disk. We use line flux ratios to constrain the energy of the ionizing photons and find that argon is ionized by extreme ultraviolet, whereas neon is most likely ionized by X-rays. After performing continuum and point-spread function subtraction on the integral field unit cube, we discover a spatial extension in the [Ne ii] emission off the disk continuum emission. This is the first spatially resolved [Ne ii] disk wind emission. The mostly ionic spectrum of T Cha, in combination with the extended [Ne ii] emission, points to an evolved stage for any inner MHD wind and is consistent with the existence of an outer thermal wind ionized and driven by high-energy stellar photons. This work acts as a pathfinder for future observations aiming at investigating disk dispersal using JWST.

JWST MIRI MRS Images of Disk Winds, Water, and CO in an Edge-on Protoplanetary Disk

“…When spatially resolved, the launching radii of the H 2 wind and the atomic jet can provide further constraints on the outflow-launching mechanism. A compact emitting region is typically associated with an MHD wind (r < 1 au; Fang et al 2023b), while more extended distributions are characteristic of photoevaporative winds (Bajaj et al 2024) and jets (Murphy et al 2021;Whelan et al 2021). However, the pixel scale of the MIRI channel 3 detector (0 245, or 34 au at d = 140 pc) is large relative to the expected launching radii, and we do not meaningfully distinguish anything inside this minimum inner working angle.…”

“…The distribution is consistent with emission from a bipolar jet (see, e.g., Dougados et al 2000), which was discovered in the earlier HST and JWST images of Tau 042021 (Duchêne et al 2014(Duchêne et al , 2024. High-resolution spectroscopic studies of mid-IR [Ne II] emission typically detect either a high-velocity component (HVC) associated with collimated jets or a low-velocity component (LVC) tracing either MHD or photoevaporative disk winds in the 1D emission line profiles (Herczeg et al 2007;Güdel et al 2010;Pascucci et al 2011;Alexander et al 2014;Pascucci et al 2020) and 2D line images (Bajaj et al 2024). Although the MIRI MRS observations do not have the Images have been scaled using an asinh stretch to maximize the contrast between the background noise and the high-S/N emission from the source.…”

Modeling JWST MIRI-MRS Observations of T Cha: Mid-IR Noble Gas Emission Tracing a Dense Disk Wind

“…The simulation settings, such as the dither pattern, number of integrations, and groups per integration were kept the same as the observational settings (Pascucci et al 2021;Bajaj et al 2024) such that the spatial sampling and exposure are comparable to the real data.…”

“…Importantly, these lines of Ne and Ar can be observed with the Medium Resolution Spectrometer (MRS) Integral Field Units (IFUs) on board the Mid-Infrared Instrument (MIRI) of JWST. This instrument has observed the nearby (102.7 pc, Gaia Collaboration et al 2022) protoplanetary disk around T Cha (under Program GO 2260, Pascucci et al 2021), resulting in the first simultaneous detection of all four lines in a protoplanetary disk along with the determination of extended emission in the [Ne II] 12.81 μm line and [Ne III] 15.55 μm lines (Bajaj et al 2024).…”

“…We use the outer gas radius of 220 au (Huélamo et al 2015) for r out in Equation (4), in order to scale ρ G so as to produce nominal mass-loss rates To remedy the issue of the mass-loss rate diverging to a large radius in the self-similar models, we note that the line emissivity in the outer regions of the wind, which will be below the critical density, scales as n 2 and therefore diverges more slowly, if at all. Thus from now on, we will quote as the "true" mass-loss rate the "observable mass-loss rate" for which we would have evidence from the [Ne II] line (this being our most confidently detected line) with MIRI-MRS given the absolute flux error of 5% (Argyriou et al 2023), which dominates over the 1σ statistical uncertainty (Bajaj et al 2024).…”