Previous results in the literature have found the young inner-disk open cluster NGC 6705 to be mildly $\alpha$-enhanced. We examined this possibility via an independent chemical abundance analysis for 11 red-giant members of NGC 6705. The analysis is based on near-infrared APOGEE spectra and relies on LTE calculations using spherical model atmospheres and radiative transfer. We find a mean cluster metallicity of $\rm [Fe/H] = +0.13 \pm 0.04$, indicating that NGC 6705 is metal-rich, as may be expected for a young inner-disk cluster. The mean $\alpha$-element abundance relative to iron is $\rm \langle [\alpha/Fe]\rangle =-0.03 \pm 0.05$, which is not at odds with expectations from general Galactic abundance trends. NGC 6705 also provides important probes for studying stellar mixing, given its turn-off mass of M$\sim$3.3 M$_\odot$. Its red giants have low $^{12}$C abundances ([$^{12}$C/Fe]=$-$0.16) and enhanced $^{14}$N abundances ([$^{14}$N/Fe]=+0.51), which are key signatures of the first dredge-up on the red giant branch. An additional signature of dredge-up was found in the Na abundances, which are enhanced by [Na/Fe]=+0.29, with a very small non-LTE correction. The $^{16}$O and Al abundances are found to be near-solar. All of the derived mixing-sensitive abundances are in agreement with stellar models of approximately 3.3 M$_{\odot}$ evolving along the red giant branch and onto the red clump. As found in young open clusters with similar metallicities, NGC 6705 exhibits a mild excess in the s-process element cerium, with $\rm [Ce/Fe] = +0.13\pm0.07$.

Red giant

Red-giant branch

10.48550/arxiv.2309.10778

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CHEMICAL CARTOGRAPHY WITH APOGEE: METALLICITY DISTRIBUTION FUNCTIONS AND THE CHEMICAL STRUCTURE OF THE MILKY WAY DISK

The Astrophysical Journal (2015)

Michael R. Hayden Jo Bovy Jon A. Holtzman David L. Nidever Jonathan C. Bird

Using a sample of 69,919 red giants from the SDSS-III/APOGEE Data Release 12, we measure the distribution of stars in the [α/Fe] versus [Fe/H] plane and the metallicity distribution functions (MDFs) across an unprecedented volume of the Milky Way disk, with radius 3 < R < 15 kpc and height kpc. Stars in the inner disk (R < 5 kpc) lie along a single track in [α/Fe] versus [Fe/H], starting with α-enhanced, metal-poor stars and ending at [α/Fe] ∼ 0 and [Fe/H] ∼ +0.4. At larger radii we find two distinct sequences in [α/Fe] versus [Fe/H] space, with a roughly solar-α sequence that spans a decade in metallicity and a high-α sequence that merges with the low-α sequence at super-solar [Fe/H]. The location of the high-α sequence is nearly constant across the disk; however, there are very few high-α stars at R > 11 kpc. The peak of the midplane MDF shifts to lower metallicity at larger R, reflecting the Galactic metallicity gradient. Most strikingly, the shape of the midplane MDF changes systematically with radius, from a negatively skewed distribution at 3 < R < 7 kpc, to a roughly Gaussian distribution at the solar annulus, to a positively skewed shape in the outer Galaxy. For stars with kpc or [α/Fe] > 0.18, the MDF shows little dependence on R. The positive skewness of the outer-disk MDF may be a signature of radial migration; we show that blurring of stellar populations by orbital eccentricities is not enough to explain the reversal of MDF shape, but a simple model of radial migration can do so.

Thick disk

Star count

10.1088/0004-637x/808/2/132

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Citations (544)

Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code – II. The Southern clusters and overview

Monthly Notices of the Royal Astronomical Society (2019)

Szabolcs Mészáros T. Masseron D. A. García–Hernández Carlos Allende Prieto Timothy C. Beers

ABSTRACT We investigate the Fe, C, N, O, Mg, Al, Si, K, Ca, Ce, and Nd abundances of 2283 red giant stars in 31 globular clusters from high-resolution spectra observed in both the Northern and Southern hemisphere by the SDSS-IV APOGEE-2 survey. This unprecedented homogeneous data set, largest to date, allows us to discuss the intrinsic Fe spread, the shape, and statistics of Al-Mg and N-C anti-correlations as a function of cluster mass, luminosity, age, and metallicity for all 31 clusters. We find that the Fe spread does not depend on these parameters within our uncertainties including cluster metallicity, contradicting earlier observations. We do not confirm the metallicity variations previously observed in M22 and NGC 1851. Some clusters show a bimodal Al distribution, while others exhibit a continuous distribution as has been previously reported in the literature. We confirm more than two populations in ω Cen and NGC 6752, and find new ones in M79. We discuss the scatter of Al by implementing a correction to the standard chemical evolution of Al in the Milky Way. After correction, its dependence on cluster mass is increased suggesting that the extent of Al enrichment as a function of mass was suppressed before the correction. We observe a turnover in the Mg-Al anticorrelation at very low Mg in ω Cen, similar to the pattern previously reported in M15 and M92. ω Cen may also have a weak K-Mg anticorrelation, and if confirmed, it would be only the third cluster known to show such a pattern.

10.1093/mnras/stz3496

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Chemodynamics of the Milky Way. I. The first year of APOGEE data

HAL (Le Centre pour la Communication Scientifique Directe) (2014)

F. Anders C. Chiappini B. X. Santiago H. J. Rocha–Pinto L. Girardi

We investigate the chemo-kinematic properties of the Milky Way disc by exploring the first year of data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE), and compare our results to smaller optical high-resolution samples in the literature, as well as results from lower resolution surveys such as GCS, SEGUE and RAVE. We start by selecting a high-quality sample in terms of chemistry ($\sim$ 20.000 stars) and, after computing distances and orbital parameters for this sample, we employ a number of useful subsets to formulate constraints on Galactic chemical and chemodynamical evolution processes in the Solar neighbourhood and beyond (e.g., metallicity distributions -- MDFs, [$\alpha$/Fe] vs. [Fe/H] diagrams, and abundance gradients). Our red giant sample spans distances as large as 10 kpc from the Sun. We find remarkable agreement between the recently published local (d $<$ 100 pc) high-resolution high-S/N HARPS sample and our local HQ sample (d $<$ 1 kpc). The local MDF peaks slightly below solar metallicity, and exhibits an extended tail towards [Fe/H] $= -$1, whereas a sharper cut-off is seen at larger metallicities. The APOGEE data also confirm the existence of a gap in the [$\alpha$/Fe] vs. [Fe/H] abundance diagram. When expanding our sample to cover three different Galactocentric distance bins, we find the high-[$\alpha$/Fe] stars to be rare towards the outer zones, as previously suggested in the literature. For the gradients in [Fe/H] and [$\alpha$/Fe], measured over a range of 6 $ < $ R $ <$ 11 kpc in Galactocentric distance, we find a good agreement with the gradients traced by the GCS and RAVE dwarf samples. For stars with 1.5 $<$ z $<$ 3 kpc, we find a positive metallicity gradient and a negative gradient in [$\alpha$/Fe].

Red clump

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First Data Release of the All-sky NOAO Source Catalog

The Astronomical Journal (2018)

David L. Nidever Arjun Dey Knut Olsen Stephen T. Ridgway Robert Nikutta

Most of the sky has been imaged with NOAO's telescopes from both hemispheres. While the large majority of these data were obtained for PI-led projects and almost all of the images are publicly available, only a small fraction have been released to the community via well-calibrated and easily accessible catalogs. We are remedying this by creating a catalog of sources from most of the public data taken on the CTIO-4m+DECam and the KPNO-4m+Mosaic3. This catalog, called the NOAO Source Catalog (NSC), contains over 2.9 billion unique objects, 34 billion individual source measurements, covers ~30,000 square degrees of the sky, has depths of ~23rd magnitude in most broadband filters with ~1-2% photometric precision, and astrometric accuracy of ~7 mas. In addition, ~2 billion objects and ~21,000 square degrees of sky have photometry in three or more bands. The NSC will be useful for exploring stellar streams, dwarf satellite galaxies, QSOs, high-proper motion stars, variable stars and other transients. The NSC catalog is publicly available via the NOAO Data Lab service.

QSOS

10.3847/1538-3881/aad68f

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The Origin of the Magellanic Stream and Its Leading Arm

The Astrophysical Journal (2008)

David L. Nidever Steven R. Majewski W. B. Burton

We explore the Magellanic Stream (MS) using a Gaussian decomposition of the H I velocity profiles in the Leiden-Argentine-Bonn (LAB) all-sky H I survey. This decomposition reveals the MS to be composed of two filaments distinct both spatially (as first pointed out by Putman et al.) and in velocity. Using the velocity coherence of the filaments, one can be traced back to its origin in what we identify as the southeast H I overdensity (SEHO) of the Large Magellanic Cloud (LMC), which includes 30 Doradus. Parts of the Leading Arm (LA) can also be traced back to the SEHO in velocity and position. Therefore, at least one-half of the trailing Stream and most of the LA originates in the LMC, contrary to previous assertions that both the MS and the LA originate in the Small Magellanic Cloud (SMC) and/or in the Magellanic Bridge. The two MS filaments show strong periodic, undulating spatial and velocity patterns that we speculate are an imprint of the LMC rotation curve. If true, then the drift rate of the Stream gas away from the Magellanic Clouds is ~49 km s−1 and the age of the MS is ~1.74 Gyr. The Staveley-Smith et al. high-resolution H I data of the LMC show gas outflows from supergiant shells in the SEHO that seem to be creating the LA and LMC filament of the MS. Blowout of LMC gas is an effect not previously accounted for but one that probably plays an important role in creating the MS and LA.

Large Magellanic Cloud

Small Magellanic Cloud

10.1086/587042

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Citations (232)

Highlights of Spanish Astrophysics VIII, Proceedings of the XI Scientific Meeting of the Spanish Astronomical Society held on September 8-12, 2014, in Teruel, Spain, ISBN 978-84-606-8760-3. A. J. Cenarro, F. Figueras, C. Hernández-Monteagudo, J. Trujillo Bueno, and L. Valdivielso (eds.), p. 375-375

L. Monteagudo Narvion M. Monelli C. Galart David L. Nidever K. Olse

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LSST Science Collaborations Observing Strategy White Paper: "Science-driven Optimization of the LSST Observing Strategy"

Philip J. Marshall W. I. Clarkson Ohad Shemmer Rahul Biswas M. de Val-Borro

White paper

Citizen Science

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Exploring Biases and Sample Selection Effects for Chemical Cartography with SDSS-III/APOGEE

American Astronomical Society Meeting Abstracts #223 (2014)

Michael R. Hayden Jon A. Holtzman Gail Zasowski L. Girardi M. Schultheis

Sample (material)

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Discovery of two neighbouring satellites in the Carina constellation with MagLiteS

Monthly Notices of the Royal Astronomical Society (2018)

G. Torrealba Vasily Belokurov S. E. Koposov K. Bechtol A. Drlica-Wagner

We report the discovery of two ultra-faint satellites in the vicinity of the Large Magellanic Cloud (LMC) in data from the Magellanic Satellites Survey (MagLiteS). Situated 18$^{\circ}$ ($\sim 20$ kpc) from the LMC and separated from each other by only $18^\prime$, Carina~II and III form an intriguing pair. By simultaneously modeling the spatial and the color-magnitude stellar distributions, we find that both Carina~II and Carina~III are likely dwarf galaxies, although this is less clear for Carina~III. There are in fact several obvious differences between the two satellites. While both are well described by an old and metal poor population, Carina~II is located at $\sim 36$ kpc from the Sun, with $M_V\sim-4.5$ and $r_h\sim 90$ pc, and it is further confirmed by the discovery of 3 RR Lyrae at the right distance. In contrast, Carina~III is much more elongated, measured to be fainter ($M_V\sim-2.4$), significantly more compact ($r_h\sim30$ pc), and closer to the Sun, at $\sim 28$ kpc, placing it only 8 kpc away from Car~II. Together with several other systems detected by the Dark Energy Camera, Carina~II and III form a strongly anisotropic cloud of satellites in the vicinity of the Magellanic Clouds.

Large Magellanic Cloud

Local Group

RR Lyrae variable

10.1093/mnras/sty170

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Citations (118)