SMASH: Survey of the MAgellanic Stellar History

Abstract

The Large and Small Magellanic Clouds are unique local laboratories for studying the formation and evolution of small galaxies in exquisite detail. The Survey of the MAgellanic Stellar History (SMASH) is an NOAO community Dark Energy Camera (DECam) survey of the Clouds mapping 480 deg 2 (distributed over ∼2400 square degrees at ∼20% filling factor) to ∼24thmag in ugriz. The primary goals of SMASH are to identify low surface brightness stellar populations associated with the stellar halos and tidal debris of the Clouds, and to derive spatially resolved star formation histories. Here, we present a summary of the survey, its data reduction, and a description of the first public Data Release (DR1). The SMASH DECam data have been reduced with a combination of the NOAO Community Pipeline, the PHOTRED automated point-spread-function photometry pipeline, and custom calibration software. The astrometric precision is ∼15 mas and the accuracy is ∼2 mas with respect to the Gaia reference frame. The photometric precision is ∼0.5%-0.7% in griz and ∼1% in u with a calibration accuracy of ∼1.3% in all bands. The median 5σ point source depths in ugriz are 23.9, 24.8, 24.5, 24.2, and 23.5 mag. The SMASH data have already been used to discover the Hydra II Milky Way satellite, the SMASH 1 old globular cluster likely associated with the LMC, and extended stellar populations around the LMC out to R∼18.4 kpc. SMASH DR1 contains measurements of ∼100 million objects distributed in 61 fields. A prototype version of the NOAO Data Lab provides data access and exploration tools.

The Apache Point Observatory Galactic Evolution Experiment (APOGEE) and its successor, APOGEE‐2

“…For each APOGEE-targeted star, DR12 provides (1) target selection information sufficient to reconstruct the sampling functions, (2) reduced, calibrated 1-D spectra from 1.51-1.69 μm and generally with S/N > 100 per pixel (Nyquist sampled), with errors, bad/warning pixel flags, and instrument line-spread-function vectors (Nidever et al 2015), (3) visit-by-visit radial velocities (RVs) and RV variability, with errors, at generally 100-200 m s −1 precision, (4) stellar atmospheric parameters (T eff , log g, [Fe/H], and CNO abundances), along with uncertainties, covariances, and error flags, derived by χ 2 optimized matching the full spectra against large, 6-D libraries of synthetic spectra, and (5) elemental abundances to ∼ 0.1-0.2 dex internal accuracy for 15 chemical species (C, N, O, Na, Mg, Al, Si, S, K, Ca, Ti, V, Mn, Fe, Ni) as measured in sets of element-optimized spectral windows.…”

Stellar Streams Discovered in the Dark Energy Survey

“…Due to the incomplete southern coverage of DES, we cannot determine whether this is the signature of another stream or a diffuse stellar cloud. Other DECam imaging in the regions of the Magellanic Clouds-e.g., the Survey of the Magellanic Stellar History (Nidever et al 2017) and the Magellanic Satellites Survey (Drlica-Wagner et al 2016; Pieres et al 2017, MagLiteS;)-may be able to clarify this question in the near future. However, kinematic information will be necessary to test for any physical connection between Indus/Tucana III and this putative diffuse structure.…”

Faint (and bright) variable stars in the satellites of the Milky Way

“…Improving the distance to the satellites allows a better determination of other parameters such as the physical size (half-light radius) and absolute magnitude of the systems. As part of the Survey of the Magellanic Stellar History (SMASH, [23]), we obtained time series in gri with DECam of the recently discovered Hydra II ultra-faint dwarf ( [4]). One RR Lyrae star was found in the system and allowed us to get a distance to Hydra II of 151 ± 8 kpc.…”