Utilizing a Database of Simulated Geometric Albedo Spectra for Photometric Characterization of Rocky Exoplanet Atmospheres

TL;DR

This paper presents a comprehensive database of simulated rocky exoplanet spectra to aid in photometric characterization, identifying optimal filter combinations for distinguishing atmospheric compositions with future space telescopes.

Contribution

The authors developed a large spectral database using PSG and analyzed color-color plots to identify effective photometric filters for atmospheric discrimination.

Findings

Filters at 0.4, 0.58, and 0.8 micrometers can distinguish certain atmospheric constituents.

Detection of moderate abundances akin to Solar System bodies is challenging.

Multi-band photometry is recommended for initial planetary characterization.

Abstract

In anticipation of future flagship missions focused on the goal of achieving direct imaging of rocky exoplanets, we have developed a database of models to help the community examine the potential spectral characteristics of a broad range of rocky planet atmospheres. Using the publicly available Planetary Spectrum Generator (PSG), we have computed a grid of 141,600 rocky exoplanet geometric albedo spectra across a 7-dimensional parameter space. Using this grid, we have performed a color-color analysis seeking to identify the most useful near-ultraviolet and red or near-infrared photometric followup channels to combine with a green-optical (discovery) spectral channel. We found that a combination of filters at 0.4 um, 0.58 um, and (approx) 0.8um were able to distinguish between atmospheres with moderate-to-high concentrations of four different dominant absorbing constituents, given at least 10 hours of observation on a star at 10 parsec with a 15-meter-class space telescope; however, more moderate abundances similar to those of Solar System rocky bodies would be more challenging to detect. We recommend that future missions seeking to characterize directly imaged rocky exoplanets by colors alone further consider multi-band photometry as a first discriminator for planetary characteristics.