A near field guide to Roman's wide-area surveys

TL;DR

The paper discusses the Roman Space Telescope's wide-area surveys, highlighting their potential for studying nearby galaxies, stellar streams, and globular clusters, and evaluates the astrometric capabilities and limitations of these surveys.

Contribution

It provides a detailed summary and visualization of known nearby universe populations within Roman's planned surveys and analyzes the expected astrometric performance and observational strategies.

Findings

Roman surveys will detect numerous nearby galaxies and stellar populations.

Longer time-baselines significantly improve proper motion measurements.

6-month revisit times limit proper motion accuracy.

Abstract

The Nancy Grace Roman Space Telescope currently plans to survey nearly 6000 square degrees of the sky, mainly in the High-Latitude Wide-Area Survey (HLWAS) and Galactic Plane Survey (GPS). Although these surveys are optimized for other science, they are also a treasure trove for studying the nearby universe. The foreground of the HLWAS includes 59 known stellar streams, 14 known satellite galaxies, and 9 globular clusters in the Milky Way, and an additional 63 galaxies within 10 Mpc spanning several orders of magnitude in stellar mass. The GPS includes an additional 38 globular clusters in its footprint. We summarize and visualize these populations and discuss some of the relevant characteristics of the planned Roman observations. We also examine the expected astrometric performance of the core surveys based on the anticipated time-baselines between observations, and point out the substantial improvement provided by longer time intervals between repeat observations. In particular, the plan for a 6-month revisit timescale in the HLWAS is a missed opportunity from the perspective of proper motions. These data will nonetheless be a powerful new resource for studying the Milky Way and its neighborhood.