Substellar and low-mass dwarf identification with near-infrared imaging space observatories

TL;DR

This study evaluates the effectiveness of near-infrared space observatories in identifying and classifying brown dwarfs, highlighting the importance of specific filter combinations for accurate subtyping.

Contribution

It provides a comparative analysis of four major space observatories' capabilities in brown dwarf classification using near-infrared colors and suggests optimal filter combinations for improved identification.

Findings

Euclid filters perform poorly in brown dwarf typing.

WFIRST marginally better than Euclid, but still limited.

Adding medium-band filters improves subtyping accuracy.

Abstract

AIMS: We aim to evaluate the near-infrared colors of brown dwarfs as observed with four major infrared imaging space observatories: the Hubble Space Telescope (HST), the James Webb Space Telescope (JWST), the Euclid mission, and the WFIRST telescope. METHODS: We used the SPLAT SPEX/ISPEX spectroscopic library to map out the colors of the M-, L-, and T-type dwarfs. We have identified which color-color combination is optimal for identifying broad type and which single color is optimal to then identify the subtype (e.g., T0-9). We evaluated each observatory separately as well as the narrow-field (HST and JWST) and wide-field (Euclid and WFIRST) combinations. RESULTS: The Euclid filters perform poorly typing brown dwarfs and WFIRST performs only marginally better, despite a wider selection of filters. WFIRST's W146 and F062 combined with Euclid's Y-band discriminates somewhat better between broad brown dwarf categories. However, subtyping with any combination of Euclid and WFIRST observations remains uncertain due to the lack of medium or narrow-band filters. We argue that a medium band added to the WFIRST filter selection would greatly improve its ability to preselect brown dwarfs its imaging surveys. CONCLUSIONS: The HST filters used in high-redshift searches are close to optimal to identify broad stellar type. However, the addition of F127M to the commonly used broad filter sets would allow for unambiguous subtyping. An improvement over HST is one of two broad and medium filter combinations on JWST: pairing F140M with either F150W or F162M discriminates very well between subtypes.