A ‘Rosetta Stone’ for Protoplanetary Disks: The Synergy of Multi-Wavelength Observations

Abstract

The recent progress in instrumentation and telescope development has brought us different ways to observe protoplanetary disks, including interferometers, space missions, adaptive optics, polarimetry, and time-and spectrally-resolved data. While the new facilities have changed the way we can tackle the existing open problems in disk structure and evolution, there is a substantial lack of interconnection between different observing techniques and their user communities. Here, we explore the complementarity of some of the stateof-the-art observing techniques, and how they can be brought together in a collective effort to understand how disks evolve and disperse at the time of planet formation.This paper was born at the "Protoplanetary Discussions" meeting in Edinburgh, 2016. Its goal is to clarify where multi-wavelength observations of disks converge in unveiling disk structure and evolution, and where they diverge and challenge our current understanding. We discuss caveats that should be considered when linking results from different observations, or when drawing conclusions based on limited datasets (in terms of wavelength or sample). We focus on disk properties that are currently being revolutionized by multi-wavelength observations. Specifically: the inner disk radius, holes and gaps and their link to large-scale disk structures, the disk mass, and the accretion rate. We discuss how the links between them, as well as the apparent contradictions, can help us to disentangle the disk physics and to learn about disk evolution.

On the Mass Accretion Rates of Herbig Ae/Be Stars. Magnetospheric Accretion or Boundary Layer?

“…Although there is not yet a consensus about the physical validity of MA in HAeBe stars, this scenario is the one that has been more frequently used to derive accretion rates in these sources (but see Section 5). In this section, the MA-based approaches from which accretion rates can (or cannot) be derived for HAeBes and the corresponding accuracies are discussed (see also Section 5 in the review of [92] for a discussion on the lower limits).…”

The first multidimensional view of mass loss from externally FUV irradiated protoplanetary discs

“…There is now overwhelming evidence that planets form from discs of material around young stars (for reviews see e.g. Williams & Cieza 2011;Andrews 2015;Owen 2016;Sicilia-Aguilar et al 2016;Haworth et al 2016a;Ercolano & Pascucci 2017). The vast majority of studies of disc evolution and planet formation consider the young star-disc in isolation and such approaches are proving very effective at understanding the myriad physical processes that take place in planet-forming discs.…”

An Exo–Kuiper Belt with an Extended Halo around HD 191089 in Scattered Light

“…Multiwavelength studies can provide complementary insights into understanding circumstellar disks, since different wavelengths probe distinct regions and parameter space for a disk (Ertel et al 2012;Sicilia-Aguilar et al 2016). In this paper, we focus on using scattered-light observations to understand one of these systems.…”