Peering through the veil: Investigating protoplanetary disk outer edges using backside visibility

¹ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
² School of Natural Sciences, Center for Astronomy, University of Galway, Galway, H91 CF50, Ireland

^★ Corresponding authors: joelgmodiyil@gmail.com; dominik@uva.nl

Received: 11 March 2025
Accepted: 30 May 2025

Abstract

Context. Protoplanetary disks observed in scattered light reveal essential insights into the disk’s 3D architecture and dust properties. These disks, which play a crucial role in planet formation, have complex structures where the visibility of the far side of the disk can vary significantly based on several parameters.

Aims. This study aims to explore the factors impacting backside visibility in protoplanetary disks, particularly under variations in inclination, dust distribution, grain characteristics, and outer disk morphology.

Methods. Using radiative transfer simulations, we investigate how these variables influence the appearance of the backside in scattered light images.

Results. Tapered disk models with exponential tapers often obscure the backside, which supports the rarity of observed backside features. In cases where backside features are visible at lower inclinations, they likely indicate cut-off disks, as backside detection is challenging in standard tapered models at these inclinations. Additionally, factors such as dust mass, grain distribution, and disk material stratification play crucial roles in backside observability, affecting its potential detection in real observations.

Conclusions. This study contributes to understanding the detectability of the backside in protoplanetary disks, with implications for refining observational strategies and interpreting backside features in scattered light images. These findings help frame backside visibility as a critical aspect of assessing disk structure and evolution.