JWST/NIRCam Imaging of Young Stellar Objects. I. Constraints on Planets Exterior to the Spiral Disk Around MWC 758

MWC 758 is a young star hosting a spiral protoplanetary disk. The spirals are likely companion-driven, and two previously identified candidate companions have been identified-one at the end the Southern spiral arm at similar to 0.'' 6, and one interior to the gap at similar to 0.'' 1. With JWST/NIRCam, we provide new images of the disk and constraints on planets exterior to similar to 1 ''. We detect the two-armed spiral disk, a known background star, and a spatially resolved background galaxy, but no clear companions. The candidates that have been reported are at separations that are not probed by our data with sensitivity sufficient to detect them-nevertheless, these observations place new limits on companions down to similar to 2 M Jup at similar to 150 au and similar to 0.5 M Jup at greater than or similar to 600 au. Owing to the unprecedented sensitivity of JWST and youth of the target, these are among the deepest mass-detection limits yet obtained through direct imaging observations, and provide new insights into the system's dynamical nature.