The enigmatic globular cluster UKS~1 obscured by the bulge: \textit{H}-band discovery of nitrogen-enhanced stars

Abstract

The presence of nitrogen-enriched stars in globular clusters provides key evidence for multiple stellar populations (MPs), as has been demonstrated with globular cluster spectroscopic data towards the bulge, disk, and halo. In this work, we employ the VVV Infrared Astrometric Catalogue (VIRAC) and the DR16 SDSS-IV release of the APOGEE survey to provide the first detailed spectroscopic study of the bulge globular cluster UKS~1. Based on these data, a sample of six selected cluster members was studied. We find the mean metallicity of UKS~1 to be [Fe/H]$=-0.98\pm 0.11$, considerably more metal-poor than previously reported, and a negligible metallicity scatter, typical of that observed by APOGEE in other Galactic globular clusters. In addition, we find a mean radial velocity of $66.1\pm 12.9$ km s${}^{-1}$, which is in good agreement with literature values, within 1$\sigma$. By selecting stars in the VIRAC catalogue towards UKS~1, we also measure a mean proper motion of (${\mu }_{\alpha }\cos (\delta )$, ${\mu }_{\delta }$) $=$ ($-2.77\pm 0.23$,$-2.43\pm 0.16$) mas yr${}^{-1}$. We find strong evidence for the presence of MPs in UKS~1, since four out of the six giants analysed in this work have strong enrichment in nitrogen ([N/Fe]$\gtrsim +0.95$) accompanied by lower carbon abundances ([C/Fe]$\lesssim -0.2$). Overall, the light- (C, N), $\alpha$- (O, Mg, Si, Ca, Ti), Fe-peak (Fe, Ni), Odd-Z (Al, K), and the \textit{s}-process (Ce, Nd, Yb) elemental abundances of our member candidates are consistent with those observed in globular clusters at similar metallicity. Furthermore, the overall star-to-star abundance scatter of elements exhibiting the multiple-population phenomenon in UKS~1 is typical of that found in other global clusters (GCs), and larger than the typical errors of some [X/Fe] abundances. Results from statistical isochrone fits in the VVV colour-magnitude diagrams indicate an age ...

arXiv comment16 pages, 9 figures, 3 tables, A&A (in press)

References in corpus (69)

• Gaia Data Release 2. Summary of the contents and survey properties
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• The Dartmouth Stellar Evolution Database
• Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
• The Sixteenth Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra
• Co-formation of the Galactic disc and the stellar halo
• VISTA Variables in the Via Lactea (VVV): The public ESO near-IR variability survey of the Milky Way
• ASPCAP: The Apogee Stellar Parameter and Chemical Abundances Pipeline
• Multiple Stellar Populations in Globular Clusters
• Na-O Anticorrelation and HB. VIII. Proton-capture elements and metallicities in 17 globular clusters from UVES spectra
• A catalogue of masses, structural parameters and velocity dispersion profiles of 112 Milky Way globular clusters
• Mean proper motions, space orbits and velocity dispersion profiles of Galactic globular clusters derived from Gaia DR2 data
• The Data Reduction Pipeline for the Apache Point Observatory Galactic Evolution Experiment
• Origin of the system of globular clusters in the Milky Way
• Massive binaries as the source of abundance anomalies in globular clusters
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE) Spectrographs
• Target Selection for the SDSS-IV APOGEE-2 Survey
• Yields of AGB and SAGB models with chemistry of low- and high-metallicity Globular Clusters
• APOGEE Data Releases 13 and 14: Data and Analysis
• Stellar populations in the Milky Way bulge region : Towards solving the Galactic bulge and bar shapes using 2MASS data
• Origin of the abundance patterns in Galactic globular clusters: constraints on dynamical and chemical properties of globular clusters
• Life in the fast lane: a direct view of the dynamics, formation, and evolution of the Milky Way's bar
• Chemodynamical history of the Galactic Bulge
• The elemental composition of the Sun III. The heavy elements Cu to Th
• Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. VI. Age and abundance structure of the stellar populations in the central sub-kpc of the Milky Way
• Constraining the thick disc formation scenario of the Milky Way
• Homogeneous Analysis of Globular Clusters from the APOGEE Survey with the BACCHUS Code. II. The Southern Clusters and Overview
• VIRAC: The VVV Infrared Astrometric Catalogue
• Exploring Anticorrelations and Light Element Variations in Northern Globular Clusters Observed by the APOGEE Survey
• The Gaia-ESO Survey. Mg-Al anti-correlation in iDR4 globular clusters
• Chemical Abundances in Field Red Giants from High-Resolution H-Band Spectra using the APOGEE Spectral Linelist
• Light, Alpha, and Fe-Peak Element Abundances in the Galactic Bulge
• An accurate and self-consistent chemical abundance catalogue for the APOGEE/Kepler sample
• An Abundance Analysis for Five Red Horizontal Branch Stars in the Extremely Metal Rich Globular Cluster NGC 6553
• APOGEE Chemical Abundances of Globular Cluster Giants in the Inner Galaxy
• A homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code. I. The Northern clusters
• Extinction ratios in the inner Galaxy as revealed by the VVV survey
• Atypical Mg-poor Milky Way field stars with globular cluster second-generation like chemical patterns
• How Many Components? Quantifying the Complexity of the Metallicity Distribution in the Milky Way Bulge with APOGEE
• Discovery of VVV CL001. A Low-Mass Globular Cluster Next to UKS~1 in the Direction of the Galactic Bulge
• Milky Way demographics with the VVV survey. IV. PSF photometry from almost one billion stars in the Galactic bulge and adjacent southern disk
• Distances of the bulge globular clusters Terzan 5, Liller 1, UKS 1 and Terzan 4 based on HST NICMOS photometry
• Kinematics of the local disk from the RAVE survey and the Gaia first data release
• New galactic star clusters discovered in the VVV survey. Candidates projected on the inner disk and bulge
• Discovery of a Metal-Poor Field Giant with a Globular Cluster Second-Generation Abundance Pattern
• Chemodynamics of newly identified giants with globular cluster like abundance patterns in the bulge, disk, and halo of the Milky Way
• The Relationship Between Globular Cluster Mass, Metallicity, and Light Element Abundance Variations
• Two Groups of Red Giants with Distinct Chemical Abundances in the Bulge Globular Cluster NGC 6553 Through the Eyes of APOGEE
• HST NICMOS Photometry of the reddened bulge globular clusters NGC 6528, Terzan 5, Liller 1, UKS 1 and Terzan 4
• Evidence of AGB pollution in Galactic globular clusters from the Mg-Al anticorrelations observed by the APOGEE survey
• Near-Infrared photometry and spectroscopy of NGC 6539 and UKS 1: two intermediate metallicity Bulge Globular Clusters
• Discovery of a new stellar sub-population residing in the (inner) stellar halo of the Milky Way
• H-band discovery of additional Second-Generation stars in the Galactic Bulge Globular Cluster NGC 6522 as observed by APOGEE and Gaia
• Resonant Trapping in the Galactic Disc and Halo and its Relation with Moving Groups
• Self-consistent analysis of stellar clusters: An application to HST data of the halo globular cluster NGC 6752
• Dynamical Orbital classification of selected N-rich stars with \textit{Gaia} DR2 astrometry
• Purveyors of fine halos. II. Chemodynamical association of halo stars with Milky Way globular clusters
• Mergers, tidal interactions, and mass exchange in a population of disc globular clusters
• Detailed chemical composition and orbit of the new globular cluster FSR1758: Implications for the accretion of the Sequoia dwarf galaxy onto the Milky Way
• Discovery of a nitrogen-enhanced mildly metal-poor binary system: Possible evidence for pollution from an extinct AGB Star
• Proton capture elements in the globular cluster NGC 2808 I. First detection of large variations in Sodium abundances along the Red Giant Branch
• Stellar mass-loss, rotation and the chemical enrichment of early type galaxies
• Deep Hubble Space Telescope Imaging of Globular Clusters Towards the Galactic Bulge: Observations, Data Reduction and Color-Magnitude Diagrams
• Galactic globular clusters: a new catalog of masses, structural parameters, velocity dispersion profiles, proper motions and space orbits
• Chemical abundances in the metal-intermediate GC NGC 6723
• Discovery of Tidal RR LYRAE stars in the Bulge Globular Cluster M 62
• The Orbit of the new Milky Way Globular Cluster FSR1716 = VVV-GC05

Cited by in corpus (26)

• The Chemo-Dynamical Groups of Galactic Globular Clusters
• Aluminum Enhanced Metal-Poor Stars buried in the Inner Galaxy
• Dynamically Tagged Groups of Metal-Poor Stars from the Best \& Brightest Survey
• VVV CL001: Likely the Most Metal-Poor Surviving Globular Cluster in the Inner Galaxy
• Galactic ArchaeoLogIcaL ExcavatiOns (GALILEO) I. An updated census of APOGEE N-rich giants across the Milky Way
• APOGEE discovery of a chemically atypical star disrupted from NGC 6723 and captured by the Milky Way bulge
• APOGEE spectroscopic evidence for chemical anomalies in dwarf galaxies: The case of M~54 and Sagittarius
• A census of new globular clusters in the Galactic bulge
• Jurassic: A Chemically Anomalous Structure in the Galactic Halo
• Discovery of a new nearby globular cluster with extreme kinematics located in the extension of a halo stream
• CAPOS: the bulge Cluster APOgee Survey II. The Intriguing "Sequoia" Globular Cluster FSR 1758
• Abundance analysis of APOGEE spectra for 58 metal-poor stars from the bulge spheroid
• Unveiling the nature of 12 new low-luminosity Galactic Globular Cluster Candidates
• CAPOS: The bulge Cluster APOgee Survey III. Spectroscopic Tomography of Tonantzintla 2
• APOGEE-2S Discovery of Light- and Heavy-Element Abundance Correlations in the Bulge Globular Cluster NGC 6380
• Inspection of 19 globular cluster candidates in the Galactic bulge with the VVV survey
• APOGEE-2S view of the globular cluster Patchick 125 (Gran 3). New metallicity and elemental abundances from high-resolution spectroscopy
• Galactic ArchaeoLogIcaL ExcavatiOns (GALILEO) II. t-SNE Portrait of Local Fossil Relics and Structures
• Chrono-chemodynamical analysis of the globular cluster NGC 6355: Looking for the fundamental bricks of the Bulge
• CAPOS: The bulge Cluster APOgee Survey V. Elemental abundances of the bulge globular cluster HP 1
• Spectroscopic Observations of Obscured Populations in the Inner Galaxy: 2MASS-GC02, Terzan 4, and the 200 km/s stellar peak
• Investigating Phosphorus Abundances in a Sample of APOGEE-2 Bulge Globular Clusters
• Variable stars in the VVV globular clusters. II. NGC6441, NGC6569, NGC6626 (M28), NGC6656 (M22), 2MASS-GC02, and Terzan10
• A possible GeV-TeV connection in the direction of the Globular Cluster UKS 1
• Photo-chemo-dynamical analysis and the origin of the bulge globular cluster Palomar 6
• UVES analysis of red giants in the bulge globular cluster NGC 6522