Panel (a): Observed gas-phase t-HCOOH emission integrated over the line profile after applying a Keplerian mask and smoothed at resolution equivalent to the TW Hya disk size. The contours and level step are at 3σ (where 1σ = 2 mJy beam−1 km s−1, in the smoothed and masked data). Panel (b): the same as in panel A but model. The synthesized beam is shown in the bottom-left corner of panels (A) and (B).