ELT-METIS Imaging Simulations for Disks and Envelopes Associated with FU Ori-type Objects

Abstract We investigate the detectability of extended mid-infrared (MIR) emission associated with FU-Ori type objects (FUors) using the Mid-infrared ELT Imager and Spectrograph (METIS) coronagraphs on the 39 m Extremely Large Telescope. The imaging simulations were made for three representative filters ( λ = 3.8, 4.8, and 11.3 μ m) of the METIS instrument. We demonstrate that the detectability of the extended MIR emission using these coronagraphs is highly dependent on the uncertain nature of the central FUor and its circumstellar environment in various contexts. These contexts are: (A) whether the central radiation source is either a flat self-luminous accretion disk or a star at near-infrared (NIR) wavelengths, (B) the size of the accretion disk for the bright central MIR emission at milliarcsecond scales, (C) whether the extended emission is due to either an optically thick disk or an optically thin envelope, and (D) dust grain models. Observations at λ = 3.8 μ m will allow us to detect the extended emission in many cases, while the number of cases with detection may significantly decrease toward longer wavelengths due to the fainter nature of the extended emission and high thermal background noise. In some cases, the presence of a binary companion can significantly hamper detections of the extended MIR emission. NIR and MIR imaging observations at existing 8 m class telescopes, prior to the METIS observations, will be useful for (1) reducing the many model uncertainties and (2) searching for binary companions associated with FUors, therefore determining the best observing strategy using METIS.