Simulated observations of young gravitationally unstable protoplanetary discs

Abstract

The formation and earliest stages of protoplanetary discs remain poorly constrained by observations. ALMA will soon revolutionise this field. Therefore, it is important to provide predictions which will be valuable for the interpretation of future high sensitivity and high angular resolution observations. Here we present simulated ALMA observations based on radiative transfer modelling of a relatively massive (0.39 M ⊙ ) self-gravitating disc embedded in a 10 M ⊙ dense core, with structure similar to the pre-stellar core L1544. We focus on simple species and conclude that C 17 O 3→2, HCO + 3→2, OCS 26→25 and H 2 CO 4 04 →3 03 lines can be used to probe the disc structure and kinematics at all scales.

Direct Detection of Precursors of Gas Giants Formed by Gravitational Instability With the Atacama Large Millimeter/Submillimeter Array

“…However, in the latter work, inclination was affecting the simulated ALMA maps when a high-order, tightly wound spiral pattern was present. In our case, the disk, being very massive, develops only global, large-scale, large pitch angle m = 2-4 modes (see also Dong et al 2015), whose morphology is inherently less affected by inclination, as was also found by Douglas et al (2013). Our simulations have some limitations that could have an impact on the ALMA mocks.…”

“…Since accretion is filamentary and patchy in a turbulent core (e.g., Hayfield et al 2011) inhomogeneities in density and temperature might arise in the outer disk that could render clump identification more difficult. However, using mocks for both continuum and molecular line emission/absorption, Douglas et al (2013) have shown that a strong spiral pattern should be detectable with ALMA even in embedded disks.…”

“…Recently, several works have indeed focused on detecting spiral structure in gravitationally unstable disks using ALMA (Cossins et al 2010;Douglas et al 2013;Dipierro et al 2014;Evans et al 2015). Similar studies of marginally unstable disks exhibiting strong spiral patterns have also been carried out with near-infrared observations of scattered light (Dong et al 2015).…”

“…With the exception of Douglas et al (2013), previous works studying the detectability of spiral structure in GI disks have employed simulations with simple radiative cooling prescriptions for the disk rather than solving the full set of radiationhydrodynamic equations. This also applies to previous studies of the detectability of GI clumps for ALMA, such as in 3D MHD protostellar disk collapse simulations (Seifried et al 2016) and in 2D massive embedded disks fragmenting predominantly into brown-dwarf-sized objects (Vorobyov et al 2013).…”

Rotationally-supported disks around Class I sources in Taurus: disk formation constraints

“…In both cases, the dominant motion of the compact flattened structure during the embedded phase is infall rather than rotation. There are indeed sources where higher sensitivity and spatial resolution observations such as with Atacama Large Millimeter/submillimeter Array (ALMA) can detect features associated with disk instabilities (e.g., Cossins et al 2010;Forgan et al 2012;Douglas et al 2013). …”