The Structure of a Self-Gravitating Protoplanetary Disk and its Implications to Direct Imaging Observations

TL;DR

This paper models the vertical structure of self-gravitating protoplanetary disks with radial gaps, predicting observable features in near-infrared scattered light that can inform us about disk mass and stability.

Contribution

It introduces a detailed model of self-gravitating disks with gaps, highlighting the impact on observable scattered light features for the first time.

Findings

A bump-like structure appears at the gap edge in NIR scattered light due to self-gravity.

No such bump is observed in sub-mm dust continuum images.

Detection of the bump can reveal the physical state of the disk.

Abstract

We consider the effects of self-gravity on the hydrostatic balance in the vertical direction of a gaseous disk and discuss the possible signature of the self-gravity that may be captured by the direct imaging observations of protoplanetary disks in future. In this paper, we consider a vertically isothermal disk in order to isolate the effects of self-gravity. The specific disk model we consider in this paper is the one with a radial surface density gap, at which the Toomre's $Q$-parameter of the disk varies rapidly in the radial direction. We calculate the vertical structure of the disk including the effects of self-gravity. We then calculate the scattered light and the dust thermal emission. We find that if the disk is massive enough and the effects of self-gravity come into play, a weak bump-like structure at the gap edge appears in the near-infrared (NIR) scattered light, while no such bump-like structure is seen in the sub-mm dust continuum image. The appearance of the bump is caused by the variation of the height of the surface in the NIR wavelength. If such bump-like feature is detected in future direct imaging observations, with the combination of sub-mm observations, it will bring us useful information about the physical states of the disk.