Overview of The SDSS-V Magellanic Genesis Survey

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/N45) 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 \gaiaDR3 data, reaching G17.5. 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.

💡 Research Summary

The Sloan Digital Sky Survey‑V Magellanic Genesis Survey (MGS) is a comprehensive spectroscopic campaign designed to map the kinematic and chemical structure of the Large and Small Magellanic Clouds (LMC and SMC) across their full spatial extents. Building on the limited coverage of earlier SDSS‑IV APOGEE‑2S observations, which sampled only about one‑third of the main bodies, MGS exploits the robotic fiber positioning system of SDSS‑V to obtain contiguous, high‑quality spectra for tens of thousands of stars.

The survey has three main components. First, the APOGEE arm targets ~14,400 oxygen‑rich asymptotic giant branch (AGB‑O) stars in the inner regions of both Clouds. These bright near‑infrared sources (10 < H < 12.9) can be observed with 15‑minute exposures, delivering S/N≈45 at R≈22,500. AGB‑O stars trace intermediate‑age populations (0.1–6 Gyr) and, as demonstrated by comparison with existing APOGEE‑2S red‑giant (RGB) samples, provide reliable stellar parameters and detailed abundances (α‑elements, C, N, O, Mg, Al, etc.). When combined with the earlier APOGEE‑2S RGB dataset, the total high‑resolution sample reaches ~22,600 giants, offering a uniform chemical map of the Clouds’ main bodies.

Second, the BOSS arm supplies medium‑resolution (R≈2,000) optical spectra for ~100,000 red‑giant (RG) stars selected from Gaia DR3 proper motions and photometry (14 < G < 17.5). Approximately 13,000 of these lie in the outer peripheries (R ≳ 8° for the LMC, ≳ 4° for the SMC), a region previously only sparsely sampled. BOSS delivers radial velocities accurate to ~5 km s⁻¹ and elemental abundances (Fe, Mg, Ca, Si, Ti, Ni) with ≲0.2 dex precision. This enables the first densely sampled, chemically‑tagged kinematic map of the low‑surface‑brightness structures that surround the Clouds: extended spiral‑like arms, tidal debris, and the stellar bridge linking the LMC and SMC. Inner‑region BOSS targets also provide a crucial baseline for interpreting the outer populations.

Third, a dedicated sub‑program observes ~300 rare evolved massive stars (supergiants, luminous blue variables, Wolf‑Rayet progenitors) and a small set of symbiotic binaries using both APOGEE and BOSS. These objects probe extreme mass‑loss, wind physics, and binary interaction processes, and they serve as cross‑checks for the broader massive‑star component of SDSS‑V.

The MGS data are complemented by Gaia astrometry, deep optical photometric surveys (SMASH, VMC, MagES, etc.), and the earlier APOGEE‑2S high‑resolution sample. Early results show that AGB‑O stars reproduce the