The SPHEREx Target List of Ice Sources (SPLICES)

TL;DR

This paper presents the SPLICES catalog, a comprehensive list of over 8.6 million obscured sources in the Milky Way, designed to enable SPHEREx to study molecular ices and their origins in planetary system formation.

Contribution

It provides an updated, extensive target list for SPHEREx to observe ice sources, facilitating large-scale studies of molecular formation and distribution in the galaxy.

Findings

Catalog contains 8.6 million objects brighter than W2~12 mag.

Targets are distributed across the Milky Way, molecular clouds, and Magellanic Clouds.

Enables statistical analysis of ice molecules in diverse stellar environments.

Abstract

One of the primary objectives of the SPHEREx mission is to understand the origin of molecules such as H2O, CO2, and other volatile compounds at the early stages of planetary system formation. Because the vast majority of these compounds -- typically exceeding 95% -- exist in the solid phase rather than the gaseous phase in the systems of concern here, the observing strategy planned to characterize them is slightly unusual. Specifically, SPHEREx will target highly obscured sources throughout the Milky Way, and observe the species of concern in absorption against background illumination. SPHEREx spectrophotometry will yield ice column density measurements for millions of obscured Milky Way sources of all ages and types. By correlating those column densities with source ages, the SPHEREx mission will shed light on whether those molecules were formed in situ along with their nascent stellar systems, or whether instead they formed elsewhere and were introduced into those systems after their formation. To that end, this work describes version 7$.$1 of the SPHEREx Target List of Ice Sources (SPLICES) for the community. It contains about 8$.$6 million objects brighter than W2~12 Vega mag over much of the sky, principally within a broad strip running the length of the Milky Way midplane, but also within high-latitude molecular clouds and even the Magellanic Clouds.