Coronagraphic observations of Fomalhaut at solar system scales

TL;DR

This study used advanced coronagraphic imaging to search for low-mass companions near Fomalhaut, setting upper mass limits and constraining models of its planetary system formation.

Contribution

It provides new observational constraints on potential companions within 10 AU of Fomalhaut, especially ruling out certain dynamical scattering scenarios for Fomalhaut b.

Findings

Upper mass limit of 12-20 Jupiter masses from 4 to 10 AU.

Rules out models where Fomalhaut b's orbit is due to scattering from inner giant planets.

Complements previous imaging by covering intermediate semi-major axes.

Abstract

We report on a search for low mass companions within 10 AU of the star Fomalhaut, using narrow band observations at 4.05 microns obtained with the Apodizing Phase Plate (APP) coronagraph on the VLT/NaCo. Our observations place a model dependent upper mass limit of 12-20 Jupiter masses from 4 to 10 AU, covering the semi-major axis search space between interferometric imaging measurements and other direct imaging non-detections. These observations rule out models where the large semi-major axis for the putative candidate companion Fomalhaut b is explained by dynamical scattering from a more massive companion in the inner stellar system, where such giant planets are thought to form.