Observational Signatures of Planets in Protoplanetary Disks I: Gaps Opened by Single and Multiple Young Planets in Disks
Dong et al
It has been suggested that the gaps and cavities recently discovered in transitional disks are opened by planets. To explore this scenario, we combine two-dimensional two fluid (gas + particle) hydrodynamical calculations with fully three-dimensional Monte Carlo Radiative Transfer simulations and study the observational signatures of gaps opened by one or several planets, making qualitative comparisons with observations. We find that a single planet as small as 0.2 MJ can produce a deep gap at millimeter (mm) wavelengths and almost no features at near-infrared (NIR) wavelengths, while multiple planets can open up a few ?10 AU wide common gap at both wavelengths. Both the contrast ratio of the the gaps and the wavelength dependence of the gap sizes are broadly consistent with data. When viewed at a moderate inclination angle, a physically circular on-centered gap could appear to be off-centered from the star due to shadowing. This effect can be used to check the existence of an unseen inner disk. Planet-induced spiral arms are more apparent at NIR than at mm wavelengths. Overall, our results suggest that the planet-opening-gap scenario is a promising way to explain the origin of the transitional disks. Finally, inspired by the recent ALMA release of the image of the HL Tau disk, we show that multiple narrow gaps, well separated by bright rings, can be opened by 0.2MJ planets soon after their formation in a relatively massive disk.