Overview of The SDSS-V Magellanic Genesis Survey

TL;DR

This paper outlines the design and scientific goals of the SDSS-V Magellanic Genesis Survey (MGS), which aims to produce a spatially contiguous, high-resolution spectroscopic map of the Magellanic Clouds by combining APOGEE near-infrared data for inner regions with BOSS optical data for the periphery, plus time-domain observations of evolved massive stars and symbiotic binaries. By targeting ~14.4k AGB-O stars with APOGEE and ~100k red giants with BOSS, along with a ≈300-star evolved massive-star program, the survey constructs a chemo-kinematic atlas that spans the Clouds’ main bodies and outskirts, cross-calibrated with Gaia DR3. Initial results demonstrate detailed periphery kinematics, a warped LMC disk, and radial abundance patterns, illustrating the Clouds’ dynamical history and chemical evolution. The dataset provides a critical reference for understanding dwarf-dwarf interactions and the influence of the Magellanic system on the Milky Way halo, and establishes a benchmark for interpreting spectroscopic surveys of nearby galaxies.

Abstract

The Sloan Digital Sky Survey-V (SDSS-V) Magellanic Genesis survey is a spectroscopic program designed to map the kinematic and chemical structure of the Magellanic Clouds using APOGEE and BOSS spectroscopy. This overview describes the survey's design, target selection, and science goals, and highlights some first results using these data. In the inner regions of the Large and Small Magellanic Clouds (LMC and SMC), the survey obtained high-resolution near-infrared APOGEE spectra (S/N~45) of ~14,000 bright, oxygen-rich asymptotic giant branch (AGB-O) stars. These data provide contiguous spatial coverage of the Clouds' main bodies, enabling detailed chemo-dynamical studies. To explore extended structures, the survey includes BOSS optical spectroscopy of fainter red giant (RG) stars selected with \gaia~DR3 data, reaching G~17.5. Many of these targets extend to the outer regions of the Clouds, which are known to span ~20 deg (LMC) and ~12 deg(SMC) and contain diffuse substructures of unclear origin. BOSS data in the inner regions also complement APOGEE by providing elements inaccessible in the near-infrared and enabling cross-calibration between instruments. The survey further includes APOGEE and BOSS observations of ~300 evolved massive stars and a small sample of symbiotic binaries previously observed by APOGEE-1 and -2, enhancing our understanding of massive stellar evolution and complementing the SDSS-V main-sequence massive star program.

Figures (17)

• Figure 1: Map of the SDSS-IV / APOGEE-2S MCs survey fields (blue) shown on top of the Belokurov2019 RGB star density map (grayscale), projected in the Magellanic Stream coordinate system Nidever2008. While the SDSS-IV data sample a large radial and azimuthal range in the MCs, they only fill 33% of the area in the LMC and SMC main bodies. Conversely, the Magellanic Genesis Survey covers the entire Magellanic system.
• Figure 2: SDSS-V's MGS mapping across the Magellanic cloud galaxies, showing the density of targets obtained with BOSS (left) and APOGEE (right) in an Magellanic cloud centered reference frame. In total, the MGS program will observe $\approx100,000$ red giant stars with BOSS and $\approx14,400$ asymptotic giant stars with APOGEE, and will cover the majority of the extent of both of these satellite galaxies.
• Figure 3: Magellanic Genesis mapping of line-of-sight radial velocity across the Magellanic system. ( Left) BOSS data; and ( Right) APOGEE data.
• Figure 4: The [$\alpha$/Fe] abundances for APOGEE-2S LMC and SMC RGB stars (black) and AGB-O stars (red), with S/N$\geq$80 and the ASPCAP STARBAD flag not set. The chemical distribution of AGB-O stars matches that of the RGB stars quite well, though the former include few stars below [Fe/H]=$-$1.4.
• Figure 5: Map of the MCs using RG stars selected with Gaia DR3. ( Left) Stars in the Magellanic periphery extend to at least $\sim$20$^{\circ}~$ around the LMC and organize into many diffuse substructures. The origin of these features is not well understood. ( Right) Distribution of 100,659 MC RG stars observed by BOSS.