The Galactic Center with Roman

TL;DR

Adding a Galactic center field to the Roman Space Telescope's survey would enable high-cadence observations of millions of stars, unlocking new insights into stellar populations, black hole growth, and gravitational wave sources.

Contribution

Proposes including a Galactic center field in the GBTDS to significantly enhance the scientific capabilities and data richness of Roman's Galactic studies.

Findings

Enables detection of star-compact object binaries potentially merging as gravitational wave sources.

Provides high-precision proper motions and parallaxes for stellar dynamics studies.

Facilitates diverse science cases including exoplanet detection, stellar variability, and black hole accretion.

Abstract

We advocate for a Galactic center (GC) field to be added to the Galactic Bulge Time Domain Survey (GBTDS). The new field would yield high-cadence photometric and astrometric measurements of an unprecedented ${\sim}$3.3 million stars toward the GC. This would enable a wide range of science cases, such as finding star-compact object binaries that may ultimately merge as LISA-detectable gravitational wave sources, constraining the mass function of stars and compact objects in different environments, detecting populations of microlensing and transiting exoplanets, studying stellar flares and variability in young and old stars, and monitoring accretion onto the central supermassive black hole. In addition, high-precision proper motions and parallaxes would open a new window into the large-scale dynamics of stellar populations at the GC, yielding insights into the formation and evolution of galactic nuclei and their co-evolution with the growth of the supermassive black hole. We discuss the possible trade-offs between the notional GBTDS and the addition of a GC field with either an optimal or minimal cadence. Ultimately, the addition of a GC field to the GBTDS would dramatically increase the science return of Roman and provide a legacy dataset to study the mid-plane and innermost regions of our Galaxy.