GALATEA: The 15-m Galactic Archaeology Spectroscopic Surveyor

TL;DR

GALATEA proposes a dedicated $15$ m, wide-field, high-multiplex spectroscopic facility to tackle northern Local Group chemodynamics. By combining a $\sim 1~\mathrm{deg}^2$ field of view, $10{,}000$ fibres, and resolutions up to $R \simeq 25{,}000$, it enables deep, high-resolution spectroscopy of faint stars across the Milky Way’s outer disc, halo, and the M31/M33 system, in synergy with Gaia and GaiaNIR. This would yield comprehensive $6$-D phase-space and detailed chemical maps, testing $\Lambda$CDM substructure, tracing warps and tidal features, and constraining binary evolution and compact remnants, with broad implications for galaxy formation, Local Group dynamics, exoplanet birth environments, and fundamental physics. The envisioned northern-hemisphere facility would complement southern surveys and ELTs, enabling all-sky, multi-epoch stellar spectroscopy and serving as a crucial feeder for next-generation follow-up observations.

Abstract

\textsc{GALATEA} (the \emph{Galactic Archaeology and Local-group Astrophysics Telescope for Extended Areas}) is a concept for a dedicated 15-m, wide-field, 10,000-fibre spectroscopic survey facility in the northern hemisphere, optimized for degree-scale, multi-object spectroscopy. With a $\sim 1~\mathrm{deg}^2$ corrected field-of-view and both medium- ($R \simeq 5{,}000$--$10{,}000$) and high-resolution ($R \simeq 20{,}000$--$25{,}000$) modes, \textsc{GALATEA} would open a new regime in Galactic and Local Group astronomy: deep, chemically detailed spectroscopy of vast samples of individual stars in the outer disc, warp, flare, halo substructures, M31, M33 and their dwarf satellites, far beyond the reach of current surveys. By delivering precise radial velocities and detailed chemical abundances for stars with exquisite astrometry and photometry from \emph{Gaia} and its proposed near-infrared successor \emph{GaiaNIR}, \textsc{GALATEA} will complete and fully exploit the 6D phase-space and chemodynamical information for these populations. Compared to existing northern multi-object spectroscopic facilities (BOSS, APOGEE, DESI, LAMOST, WEAVE, PFS), \textsc{GALATEA} delivers an order-of-magnitude jump in survey power ($\propto D^{2} \times N_{\mathrm{fibres}}$) by combining a 15-m aperture, $\sim 1~\mathrm{deg}^2$ field, and 10{,}000 fibres in a single dedicated facility. It is also strongly complementary to 30--40\,m ELTs: GALATEA provides the wide-field, high-multiplex discovery and chemodynamical mapping, while ELTs deliver deep, high-resolution follow-up of the faintest or most complex targets.

Figures (1)

• Figure 1: Comparison of the minimum airmass at transit for a WST-like southern site (top, $\varphi \simeq -25^\circ$) and GALATEA (bottom, $\varphi \simeq +30^\circ$), shown in Galactic coordinates (Aitoff projection, $\ell$ centred on the anticentre). Only the sky visible from each site is coloured; the colour scale indicates the minimum airmass in the range $1.0 \le X_{\min} \le 1.3$. Red stars mark the positions of M31, M33 and the known Milky Way dwarf spheroidal satellites, highlighting the complementary low-airmass access to Local Group targets from the two hemispheres.