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Abstract The goal of this paper is to describe the science verification of Milky Way Mapper (MWM) APOGEE Stellar Parameter and Chemical Abundances Pipeline (ASPCAP) data products published in Data Release 19 (DR19) of the fifth phase of the Sloan Digital Sky Survey (SDSS-V). We compare MWM ASPCAP atmospheric parametersT_eff, logg, 24 abundances of 21 elements (carbon, nitrogen, and oxygen have multiple sources for deriving their abundance values) and their uncertainties determined from Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectrograph spectra with those of the literature and evaluate their accuracy and precision. We also test the zero-point calibration of thev_radderived by the APOGEE Data Reduction Pipeline. This data release contains ASPCAP parameters for 964,989 stars, including all APOGEE-2 targets expanded with new observations of 336,511 stars from the Apache Point Observatory observed until 2023 July 4. Overall, the newT_effvalues show excellent agreement with the IRFM scale, while the surface gravities exhibit slight systematic offsets compared to asteroseisimic gravities. The estimated precision ofT_effis between 50 and 70 K for giants and 70–100 K for dwarfs, while surface gravities are measured with a precision of 0.07–0.09 dex for giants. We achieve an estimated precision of 0.02–0.04 dex for multiple elements, including metallicity,α, Mg, and Si, while the precision of at least 10 elements is better than 0.1 dex. 

Abstract M15 is a globular cluster with a known spread in neutron-capture elements. This paper presents abundances of neutron-capture elements for 62 stars in M15. Spectra were obtained with the Michigan/Magellan Fiber System spectrograph, covering a wavelength range from ∼4430 to 4630 Å. Spectral lines from Fei, Feii, Sri, Zrii, Baii, Laii, Ceii, Ndii, Smii, Euii, and Dyii were measured, enabling classifications and neutron-capture abundance patterns for the stars. Of the 62 targets, 44 are found to be highly Eu-enhancedr-II stars, another 17 are moderately Eu-enhancedr-I stars, and one star is found to have ans-process signature. The neutron-capture patterns indicate that the majority of the stars are consistent with enrichment by ther-process. The 62 target stars are found to show significant star-to-star spreads in Sr, Zr, Ba, La, Ce, Nd, Sm, Eu, and Dy, but no significant spread in Fe. The neutron-capture abundances are further found to have slight correlations with sodium abundances from the literature, unlike what has been previously found; follow-up studies are needed to verify this result. The findings in this paper suggest that the Eu-enhanced stars in M15 were enhanced by the same process, that the nucleosynthetic source of this Eu pollution was ther-process, and that ther-process source occurred as the first generation of cluster stars was forming. 

Abstract In this paper, we present a chemical and kinematic analysis of two ultrafaint dwarf galaxies (UFDs), Aquarius II (Aqu II) and Boötes II (Boo II), using Magellan/IMACS spectroscopy. We present the largest sample of member stars for Boo II (12), and the largest sample of red giant branch members with metallicity measurements for Aqu II (eight). In both UFDs, over 80% of targets selected based on Gaia proper motions turned out to be spectroscopic members. In order to maximize the accuracy of stellar kinematic measurements, we remove the identified binary stars and RR Lyrae variables. For Aqu II, we measure a systemic velocity of −65.3 ± 1.8 km s⁻¹and a metallicity of [Fe/H] = $-{2.57}_{-0.17}^{+0.17}$. When compared with previous measurements, these values display a ∼6 km s⁻¹difference in radial velocity and a decrease of 0.27 dex in metallicity. Similarly for Boo II, we measure a systemic velocity of $-{130.4}_{-1.1}^{+1.4}$km s⁻¹, more than 10 km s⁻¹different from the literature, a metallicity almost 1 dex smaller at [Fe/H] = $-{2.71}_{-0.10}^{+0.11}$, and a velocity dispersion 3 times smaller at ${\sigma }_{v_{\mathrm{hel}}}={2.9}_{-1.2}^{+1.6}$km s⁻¹. Additionally, we derive systemic proper-motion parameters and model the orbits of both UFDs. Finally, we highlight the extremely dark-matter-dominated nature of Aqu II and compute the J-factor for both galaxies to aid searches of dark matter annihilation. Despite the small size and close proximity of Boo II, it is an intermediate target for the indirect detection of dark matter annihilation due to its low-velocity dispersion and corresponding low dark matter density. 

ABSTRACT We present spectroscopy of individual stars in 26 Magellanic Cloud (MC) star clusters with the aim of estimating dynamical masses and V-band mass-to-light (M/LV) ratios over a wide range in age and metallicity. We obtained 3137 high-resolution stellar spectra with M2FS on the Magellan/Clay Telescope. Combined with 239 published spectroscopic results of comparable quality, we produced a final sample of 2787 stars with good quality spectra for kinematic analysis in the target clusters. Line-of-sight velocities measured from these spectra and stellar positions within each cluster were used in a customized expectation-maximization (EM) technique to estimate cluster membership probabilities. Using appropriate cluster structural parameters and corresponding single-mass dynamical models, this technique ultimately provides self-consistent total mass and M/LV estimates for each cluster. Mean metallicities for the clusters were also obtained and tied to a scale based on calcium IR triplet metallicities. We present trends of the cluster M/LV values with cluster age, mass, and metallicity, and find that our results run about 40 per cent on average lower than the predictions of a set of simple stellar population (SSP) models. Modified SSP models that account for internal and external dynamical effects greatly improve agreement with our results, as can models that adopt a strongly bottom-light IMF. To the extent that dynamical evolution must occur, a modified IMF is not required to match data and models. In contrast, a bottom-heavy IMF is ruled out for our cluster sample as this would lead to higher predicted M/LV values, significantly increasing the discrepancy with our observations. 

Abstract The eighteenth data release (DR18) of the Sloan Digital Sky Survey (SDSS) is the first one for SDSS-V, the fifth generation of the survey. SDSS-V comprises three primary scientific programs or “Mappers”: the Milky Way Mapper (MWM), the Black Hole Mapper (BHM), and the Local Volume Mapper. This data release contains extensive targeting information for the two multiobject spectroscopy programs (MWM and BHM), including input catalogs and selection functions for their numerous scientific objectives. We describe the production of the targeting databases and their calibration and scientifically focused components. DR18 also includes ∼25,000 new SDSS spectra and supplemental information for X-ray sources identified by eROSITA in its eFEDS field. We present updates to some of the SDSS software pipelines and preview changes anticipated for DR19. We also describe three value-added catalogs (VACs) based on SDSS-IV data that have been published since DR17, and one VAC based on the SDSS-V data in the eFEDS field. 

ABSTRACT As an introduction of a kinematic survey of Magellanic Cloud (MC) star clusters, we report on the dynamical masses and mass-to-light ratios (M/L) of NGC 419 (Small Magellanic Cloud) and NGC 1846 (Large Magellanic Cloud). We have obtained more than one hundred high-resolution stellar spectra in and around each cluster using the multi-object spectrograph M2FS on the Magellan/Clay Telescope. Line-of-sight velocities and positions of the stars observed in each cluster were used as input to an expectation-maximization algorithm used to estimate cluster membership probabilities, resulting in samples of 46 and 52 likely members (PM ≥ 50 per cent) in NGC 419 and NGC 1846, respectively. This process employed single-mass King models constrained by the structural parameters of the clusters and provided self-consistent dynamical mass estimates for both clusters. Our best-fitting results show that NGC 419 has a projected central velocity dispersion of $$2.44^{+0.37}_{-0.21}$$ km s−1, corresponding to a total mass of $$7.6^{+2.5}_{-1.3}\times 10^4\ {\rm M}_{\odot }$$ and V-band M/L ratio of $$0.22^{+0.08}_{-0.05}$$ in solar units. For NGC 1846, the corresponding results are $$2.04^{+0.28}_{-0.24}$$ km s−1, $$5.4^{+1.5}_{-1.4}\times 10^4\ {\rm M}_{\odot }$$, and $$0.32^{+0.11}_{-0.11}$$. The mean metallicities of NGC 419 and NGC 1846 are found to be $$\rm [Fe/H]=-0.84\pm 0.19$$ and −0.70 ± 0.08, respectively, based on the spectra of likely cluster members. We find marginal statistical evidence of rotation in both clusters, though in neither cluster does rotation alter our mass estimates significantly. We critically compare our findings with those of previous kinematic studies of these two clusters in order to evaluate the consistency of our observational results and analytic tools.