Purveyors of fine halos: Re-assessing globular cluster contributions to the Milky Way halo build-up with SDSS-IV

Abstract

There is ample evidence in the Milky Way for globular cluster (GC) disruption. Hence one may expect that also part of the Galactic halo field stars may once have formed in GCs. We quantify the fraction of halo stars donated by GCs by searching for stars that bear the unique chemical fingerprints typical for a subset of GC stars often dubbed `second-generation stars'. These are stars showing light element abundance anomalies such as a pronounced CN-band strength accompanied by weak CH-bands. Based on this indicator, past studies have placed the fraction of halo stars with a GC origin between a few to up to 50%. Using low-resolution spectra from the most recent data release of the latest extension of the Sloan Digital Sky Survey (SDSS-IV), we were able to identify 118 metal-poor ($-1.8\le$[Fe/H]$\le -1.3$) CN-strong stars in a sample of 4470 halo giant stars out to 50 kpc. This results in an observed fraction of these stars of 2.6$\pm$0.2%. Using an updated formalism to account for the fraction of stars lost early on in the GCs' evolution we estimate the fraction of the halo that stems from disrupted clusters to be 11$\pm$1%. This number represents the case that stars lost from GCs were entirely from the first generation and is thus merely an upper limit. Our conclusions are sensitive to our assumptions of the mass lost early on from the first generation formed in the GCs, the ratio of first-to-second generation stars, and other GC parameters. We carefully test the influence of varying these parameters on the final result and find that, under realistic scenarios, the above fraction depends on the main assumptions at less than 10%. We further recover a flat trend in this fraction with Galactocentric radius, with a marginal indication of a rise beyond 30 kpc that could reflect the ex-situ origin of the outer halo. (abridged)

13 pages, 11 figures, accepted for publication in Astronomy & Astrophysics

References in corpus (37)

• The Dartmouth Stellar Evolution Database
• The Milky Way's Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from Kinematics of ~2400 SDSS Blue Horizontal Branch Stars
• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• The SEGUE Stellar Parameter Pipeline. I. Description and Initial Validation Tests
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• First stars VI - Abundances of C, N, O, Li, and mixing in extremely metal-poor giants. Galactic evolution of the light elements
• Detection of a 63 Degree Cold Stellar Stream in the Sloan Digital Sky Survey
• Evidence for the Strong Effect of Gas Removal on the Internal Dynamics of Young Stellar Clusters
• N-body modeling of globular clusters: Masses, mass-to-light ratios and intermediate-mass black holes
• On the Shoulders of Giants: Properties of the Stellar Halo and the Milky Way Mass Distribution
• The Frequency of Carbon-Enhanced Metal-Poor Stars in the Galaxy from the HERES sample
• Building Late-Type Spiral Galaxies by In-Situ and Ex-Situ Star Formation
• Looking outside the Galaxy: the discovery of chemical anomalies in 3 old Large Magellanic Cloud clusters
• Age as a Major Factor in the Onset of Multiple Populations in Stellar Clusters
• Chemical Abundances and Kinematics in Globular Clusters and Local Group Dwarf Galaxies and Their Implications for Formation Theories of the Galactic Halo
• A new distant Milky Way globular cluster in the Pan-STARRS1 3π survey
• Chemical composition and constraints on mass loss for globular clusters in dwarf galaxies: WLM and IKN
• Atypical Mg-poor Milky Way field stars with globular cluster second-generation like chemical patterns
• Comparing CN and CH Line Strengths in a Homogeneous Spectroscopic Sample of 8 Galactic Globular Clusters
• The Outer Envelopes of Globular Clusters. II. NGC 1851, NGC 5824 and NGC 1261
• Serendipitous Discovery of a Thin Stellar Stream near the Galactic Bulge in the Pan-STARRS1 3Pi Survey
• Constraining globular cluster formation through studies of young massive clusters - V. ALMA observations of clusters in the Antennae
• NGC 6535: the lowest mass Milky Way globular cluster with a Na-O anti-correlation? Cluster mass and age in the multiple population context
• The Detailed Chemical Properties of M31 Star Clusters I. Fe, Alpha and Light Elements
• Evidence for multiple populations in the intermediate age cluster Lindsay 1 in the SMC
• The Gaia-ESO Survey: A globular cluster escapee in the Galactic halo
• Insights from the Outskirts: Chemical and Dynamical Properties in the outer Parts of the Fornax Dwarf Spheroidal Galaxy
• The Global Mass Functions of 35 Galactic globular clusters: II. Clues on the Initial Mass Function and Black Hole Retention Fraction
• Spectroscopic Signatures of Extra-Tidal Stars Around the Globular Clusters NGC 6656 (M22), NGC 3201 and NGC 1851 from RAVE
• The discovery of tidal tails around the globular cluster NGC 7492 with Pan-STARRS1
• Insights into the chemical composition of the metal-poor Milky Way halo globular cluster NGC 6426
• ESO452-SC11: The lowest mass globular cluster with a potential chemical inhomogeneity
• A broad perspective on multiple abundance populations in the globular cluster NGC 1851
• An Improved Bandstrength Index for the CH G Band of Globular Cluster Giants
• New halo stars of the Galactic globular clusters M3 and M13 in the LAMOST DR1 Catalog
• The globular cluster NGC7492 and the Sagittarius tidal stream: together but unmixed

Cited by in corpus (33)

• Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure
• What is a globular cluster? An observational perspective
• Evidence from APOGEE for the presence of a major building block of the halo buried in the inner Galaxy
• From dawn till disk: Milky Way's turbulent youth revealed by the APOGEE+Gaia data
• Nitrogen enrichment and clustered star formation at the dawn of the Galaxy
• Chemodynamics of newly identified giants with globular cluster like abundance patterns in the bulge, disk, and halo of the Milky Way
• The contribution of N-rich stars to the Galactic stellar halo using APOGEE red giants
• Purveyors of fine halos. II. Chemodynamical association of halo stars with Milky Way globular clusters
• The mass fraction of halo stars contributed by the disruption of globular clusters in the E-MOSAICS simulations
• VVVX-Gaia Discovery of a Low Luminosity Globular Cluster in the Milky Way Disk
• Jurassic: A Chemically Anomalous Structure in the Galactic Halo
• Formation of N-rich field stars in the high-density building blocks of the Galactic bulge
• Excess of Ca (and Sc) produced in globular cluster multiple populations: a first census in 77 Galactic globular clusters
• Elemental Abundances in M31: Properties of the Inner Stellar Halo
• Detecting Globular Cluster Tidal Extensions with Bayesian Inference: I. Analysis of $\omega$ Centauri with Gaia EDR3
• An enquiry on the origins of N-rich stars in the inner Galaxy basedon APOGEE chemical compositions
• NGC 1261: an $r$-process enhanced globular cluster from the Gaia-Enceladus event
• Multiple stellar population mass loss in massive Galactic globular clusters
• Difference in chemical composition between the bright and faint red clump stars in the Milky Way bulge
• Globular cluster metallicity distributions in the E-MOSAICS simulations
• Evidence for C and Mg variations in the GD-1 stellar stream
• $S^5$: New insights from deep spectroscopic observations of the tidal tails of the globular clusters NGC 1261 and NGC 1904
• Multiple populations in low mass globular clusters: Palomar 13
• Wide binaries from the H3 survey: the thick disk and halo have similar wide binary fractions
• An outer shade of Pal: Abundance analysis of the outer halo globular cluster Palomar 13
• A high-resolution spectroscopic study of two new Na- and Al-rich field giants -- likely globular cluster escapees in the Galactic halo
• Chemical Tagging N-rich Field Stars with High-resolution Spectroscopy
• Discrepancies between spectroscopy and HST photometry in tagging multiple stellar populations in 22 globular clusters
• Chemodynamics of metal-poor wide binaries in the Galactic halo: Association with the Sequoia event
• The formation and disruption of globular cluster populations in simulations of present-day $L^{\ast }$ galaxies with controlled assembly histories
• Implications of time-dependent molecular chemistry in metal-poor dwarf stars
• Not all nitrogen-rich field stars originate from globular clusters
• Purveyors of fine halos III. Chemical abundance analysis of a potential omega Cen associate