Identifying embedded accreting protoplanets at and within the diffraction limit using photonic lantern spectro-astrometry

Innovation in high angular resolution imaging is essential to identifying planet formation on solar-system scales (∼ 5−10 AU) in active star forming regions beyond 150 pc. The photonic lantern is a novel fiber-optic device that can be used to overcome the observational challenges associated with imaging such close-in protoplanets. Photonic lanterns spatially filter out modal noise with high throughput and low power loss, making them appealing for a wide variety of applications including wavefront-sensing, nulling, and spectro-astrometry. Spectro-astrometry, a technique that identifies wavelength-dependent centroid shifts in spectrally-dispersed datasets, could enable the resolution of circumstellar structures within the diffraction limit when conducted with photonic lanterns. Here, we present simulations of spectro-astrometric observations of embedded protoplanets using photonic lanterns. We generate mock, 6-port photonic lantern observations of young stars with gapped circumstellar disks containing accreting protoplanets with emission at the Paschen β hydrogen line. The simulations assume a 10-m class telescope and realistic sources of both photon noise and residual adaptive optics errors. We demonstrate the detection of protoplanets with photonic lantern spectro-astrometry in the presence of circumstellar material by constraining planetary accretion characteristics such as planet separation, position angle, and stellar contrast, and we explore the biases introduced by the presence of the circumstellar material.