The Potential of Exozodiacal Disks Observations with the WFIRST Coronagraph Instrument

TL;DR

The WFIRST Coronagraph Instrument will enable high-contrast imaging of exozodiacal dust around nearby stars, providing insights into dust production, transport, and implications for future exo-Earth observations.

Contribution

This paper presents the capabilities of WFIRST CGI to observe faint exozodiacal disks and analyze their structure and brightness, advancing debris disk physics and exoplanet imaging strategies.

Findings

Achieves contrast below 10^-7, detecting low-density debris disks.

Measures brightness and asymmetry of exozodiacal clouds.

Provides data to optimize future exo-Earth imaging missions.

Abstract

The Wide Field Infrared Survey Telescope (WFIRST) Coronagraph Instrument (CGI) will be the first high-performance stellar coronagraph using active wavefront control for deep starlight suppression in space, providing unprecedented levels of contrast, spatial resolution, and sensitivity for astronomical observations in the optical. One science case enabled by the CGI will be taking images and(R~50)spectra of faint interplanetary dust structures present in the habitable zone of nearby sunlike stars (~10 pc) and within the snow-line of more distant ones(~20pc), down to dust density levels commensurate with that of the solar system zodiacal cloud. Reaching contrast levels below~10-7 for the first time, CGI will cross an important threshold in debris disks physics, accessing disks with low enough optical depths that their structure is dominated by transport phenomena than collisions. Hence, CGI results will be crucial for determining how exozodiacal dust grains are produced and transported in low-density disks around mature stars. Additionally, CGI will be able to measure the brightness level and constrain the degree of asymmetry of exozodiacal clouds around individual nearby sunlike stars in the optical, at the ~10x solar zodiacal emission level. This information will be extremely valuable for optimizing the observational strategy of possible future exo-Earth direct imaging missions, especially those planning to operate at optical wavelengths, such as Habitable Exoplanet Observatory (HabEx) and the Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR).