ALMA observations of the η Corvi debris disc: inward scattering of CO-rich exocomets by a chain of 3–30 M_⊕planets?

Abstract

While most of the known debris discs present cold dust at tens of AU, a few young systems exhibit hot dust analogous to the Zodiacal dust. η Corvi is particularly interesting as it is old and it has both, with its hot dust significantly exceeding the maximum luminosity of an in-situ collisional cascade. Previous work suggested that this system could be undergoing an event similar to the Late Heavy Bombardment (LHB) soon after or during a dynamical instability. Here we present ALMA observations of η Corvi with a resolution of 1. 2 (∼22au) to study its outer belt. The continuum emission is consistent with an axisymmetric belt, with a mean radius of 152au and radial FWHM of 46au, which is too narrow compared to models of inward scattering of an LHB-like scenario. Instead, the hot dust could be explained as material passed inwards in a rather stable planetary configuration. We also report a 4σ detection of CO at ∼ 20au. CO could be released in situ from icy planetesimals being passed in when crossing the H 2 O or CO 2 ice lines. Finally, we place constraints on hidden planets in the disc. If a planet is sculpting the disc's inner edge, this should be orbiting at 75-100au, with a mass of 3-30 M ⊕ and an eccentricity < 0.08. Such a planet would be able to clear its chaotic zone on a timescale shorter than the age of the system and scatter material inwards from the outer belt to the inner regions, thus feeding the hot dust.

Population synthesis of exocometary gas around A stars

“…Therefore, any conclusion on the evolution of gas in discs within 20 au must be taken with caution since gas released might not be controlled by collisional processes (e.g. Marino et al 2017).…”

Resolving the FU Orionis System with ALMA: Interacting Twin Disks?

“…A 1.3 mm image is produced via ray-tracing, using RADMC3D's second-order integration of the radiative transfer equation. The model visibilities are interpolated to the same uv points as the observations via a Fast Fourier Transform (we use the same algorithm used and described in Cieza et al 2018;Marino et al 2017). These model visibilities are compared against the observed visibilities of each component in FU Ori.…”

ALMA Discovery of Dust Belts around Proxima Centauri

“…When azimuthally averaging the intensity in annuli, the S/N of the intensity profile at a given radius improves by a factor equal to the square root of the ratio between the length of the annulus and the beam diameter. This approach has been successfully used to infer the presence of rings and gaps in protoplanetary disks around young stars (Osorio et al 2014;Macias et al 2017), as well as in debris disks around old stars (Marino et al 2017). …”