Elemental Abundances in M31: A Comparative Analysis of Iron and Alpha Element Abundances in the Outer Disk, Giant Stellar Stream, and Inner Halo of M31

Abstract

We measured [Fe/H] and [$\alpha$/Fe] using spectral synthesis of low-resolution stellar spectroscopy for 70 individual red giant branch stars across four fields spanning the outer disk, Giant Stellar Stream (GSS), and inner halo of M31. Fields at M31-centric projected distances of 23 kpc in the halo, 12 kpc in the halo, 22 kpc in the GSS, and 26 kpc in the outer disk are $\alpha$-enhanced, with $⟨$[$\alpha$/Fe]$⟩$ = 0.43, 0.50, 0.41, and 0.58, respectively. The 23 kpc and 12 kpc halo fields are relatively metal-poor, with $⟨$[Fe/H]$⟩$ = $-$1.54 and $-$1.30, whereas the 22 kpc GSS and 26 kpc outer disk fields are relatively metal-rich with $⟨$[Fe/H]$⟩$ = $-$0.84 and $-$0.92, respectively. For fields with substructure, we separated the stellar populations into kinematically hot stellar halo components and kinematically cold components. We did not find any evidence of an [$\alpha$/Fe] gradient along the high surface brightness core of the GSS between $\sim$17$-$22 kpc. However, we found tentative suggestions of a negative [$\alpha$/Fe] gradient in the stellar halo, which may indicate that different progenitor(s) or formation mechanisms contributed to the build up of the inner versus outer halo. Additionally, the [$\alpha$/Fe] distribution of the metal-rich ([Fe/H] $>$ $-$1.5), smooth inner stellar halo (r${}_{\mathrm{proj}}$ $\lesssim$ 26 kpc) is inconsistent with having formed from the disruption of progenitor(s) similar to present-day M31 satellite galaxies. The 26 kpc outer disk is most likely associated with the extended disk of M31, where its high $\alpha$-enhancement provides support for an episode of rapid star formation in M31's disk, possibly induced by a major merger.

arXiv comment32 pages, 19 figures, 6 tables, ApJ in press

References in corpus (157)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Gaia mission
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• The observed properties of dwarf galaxies in and around the Local Group
• The Dartmouth Stellar Evolution Database
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• Radial Mixing in Galactic Discs
• Tracing Galaxy Formation with Stellar Halos I: Methods
• A new generation of PARSEC-COLIBRI stellar isochrones including the TP-AGB phase
• The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem
• Elemental Abundance Survey of The Galactic Thick Disk
• The Universal Stellar Mass-Stellar Metallicity Relation for Dwarf Galaxies
• Stellar Chemical Signatures And Hierarchical Galaxy Formation
• The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts
• Chemical evolution with radial mixing
• LCDM-based models for the Milky Way and M31 I: Dynamical Models
• Abundance Gradients and the Formation of the Milky Way
• Two Stellar Components in the Halo of the Milky Way
• alpha-, r-, and s-process element trends in the Galactic thin and thick disks
• Chemical Cartography with APOGEE: Metallicity Distribution Functions and the Chemical Structure of the Milky Way Disk
• The remnants of galaxy formation from a panoramic survey of the region around M31
• Simulations of Galaxy Formation in a Lambda CDM Universe II: The Fine Structure of Simulated Galactic Disks
• A giant stream of metal-rich stars in the halo of the galaxy M31
• Galactic stellar haloes in the CDM model
• Two distinct halo populations in the solar neighborhood. Evidence from stellar abundance ratios and kinematics
• The age structure of stellar populations in the solar vicinity. Clues of a two-phase formation history of the Milky Way disk
• VLT/UVES Abundances in Four Nearby Dwarf Spheroidal Galaxies: I. Nucleosynthesis and Abundance Ratios
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• The Star Formation Histories of Local Group Dwarf Galaxies I. Hubble Space Telescope / Wide Field Planetary Camera 2 Observations
• Structure and Kinematics of the Stellar Halos and Thick Disks of the Milky Way Based on Calibration Stars from SDSS DR7
• The spatial structure of mono-abundance sub-populations of the Milky Way disk
• The Haunted Halos of Andromeda and Triangulum: A panorama of galaxy formation in action
• Tracing Galaxy Formation with Stellar Halos II: Relating Substructure in Phase- and Abundance-Space to Accretion Histories
• The Panchromatic Hubble Andromeda Treasury
• In disguise or out of reach: first clues about in-situ and accreted stars in the stellar halo of the Milky Way from Gaia DR2
• The Dual Origin of Stellar Halos
• Cosmological simulations of the formation of the stellar haloes around disc galaxies
• The origin of accreted stellar halo populations in the Milky Way using APOGEE, $\text{Gaia}$, and the EAGLE simulations
• The large-scale structure of the halo of the Andromeda Galaxy Part I: global stellar density, morphology and metallicity properties
• The Milky Way: An Exceptionally Quiet Galaxy; Implications for the formation of spiral galaxies
• The birth of the Milky Way as uncovered by accurate stellar ages with Gaia
• Chemodynamical evolution of the Milky Way disk II: Variations with Galactic radius and height above the disk plane
• On the accretion origin of a vast extended stellar disk around the Andromeda galaxy
• Lambda-Cold Dark Matter, Stellar Feedback, and the Galactic Halo Abundance Pattern
• Rings and Radial Waves in the Disk of the Milky Way
• The NIR Ca II triplet at low metallicity - Searching for extremely low-metallicity stars in classical dwarf galaxies
• Mapping the stellar structure of the Milky Way thick disk and halo using SEGUE photometry
• A First Constraint on the Thick Disk Scale Length: Differential Radial Abundances in K Giants at Galactocentric Radii 4, 8, and 12 kpc
• Dynamical heating across the Milky Way disc using APOGEE and $Gaia$
• Formation and Evolution of the Disk System of the Milky Way: [alpha/Fe] Ratios and Kinematics of the SEGUE G-Dwarf Sample
• Thin disc, Thick Disc and Halo in a Simulated Galaxy
• MegaPipe: the MegaCam image stacking pipeline at the Canadian Astronomical Data Centre
• Using chemical tagging to redefine the interface of the Galactic disk and halo
• Chemodynamics of the Milky Way. I. The first year of APOGEE data
• Analysis and calibration of CaII triplet spectroscopy of Red Giant Branch stars from VLT/FLAMES observations
• Tracing chemical evolution over the extent of the Milky Way's Disk with APOGEE Red Clump Stars
• Multi-Element Abundance Measurements from Medium-Resolution Spectra. II. Catalog of Stars in Milky Way Dwarf Satellite Galaxies
• Young [$\alpha$/Fe]-enhanced stars discovered by CoRoT and APOGEE: What is their origin?
• The DEEP3 Galaxy Redshift Survey: The Impact of Environment on the Size Evolution of Massive Early-type Galaxies at Intermediate Redshift
• The Merging History of the Milky Way
• The Auriga Stellar Haloes: Connecting stellar population properties with accretion and merging history
• The Metal-Poor Halo of the Andromeda Spiral Galaxy (M31)
• Exploring Halo Substructure with Giant Stars: A diffuse star cloud or tidal debris around the Milky Way in Triangulum-Andromeda
• Chemical Cartography with APOGEE: Large-scale Mean Metallicity Maps of the Milky Way
• The large-scale structure of the halo of the Andromeda galaxy II. Hierarchical structure in the Pan-Andromeda Archaeological Survey
• Chemical abundances of the Milky Way thick disk and stellar halo II.: sodium, iron-peak and neutron-capture elements
• The Detailed Star Formation History in the Spheroid, Outer Disk, and Tidal Stream of the Andromeda Galaxy
• Chemical signatures of formation processes in the stellar populations of simulated galaxies
• Kinematics and chemical properties of the Galactic stellar populations. The HARPS FGK dwarfs sample
• Multi-Element Abundance Measurements from Medium-Resolution Spectra. I. The Sculptor Dwarf Spheroidal Galaxy
• Abundances and Kinematics of Field Stars II: Kinematics and Abundance Relationships
• Metallicity Gradients in the Milky Way Disk as Observed by the SEGUE Survey
• Global structure and kinematics of stellar haloes in cosmological hydrodynamic simulations
• Disentangling the Galactic Halo with APOGEE: I. Chemical and Kinematical Investigation of Distinct Metal-Poor Populations
• A kinematically selected, metal-poor stellar halo in the outskirts of M31
• Investigating the Andromeda Stream: III. A Young Shell System in M31
• Metallicity and Alpha-Element Abundance Measurement in Red Giant Stars from Medium Resolution Spectra
• Apocenter Pile-Up: Origin of the Stellar Halo Density Break
• A 2-3 billion year old major merger paradigm for the Andromeda galaxy and its outskirts
• Abundances for metal-poor stars with accurate parallaxes II. alpha-elements in the halo
• Stellar haloes of simulated Milky Way-like galaxies: Chemical and kinematic properties
• A Short Scale Length for the α-Enhanced Thick Disk of the Milky Way: Evidence from Low-Latitude SEGUE Data
• The Andromeda galaxy's most important merger about 2 billion years ago as M32's likely progenitor
• Phase-Space Distributions of Chemical Abundances in Milky Way-type Galaxy Halos
• The Gaia-ESO Survey: the chemical structure of the Galactic discs from the first internal data release
• The Stellar Metallicity Distribution Function of the Galactic Halo from SDSS Photometry
• Resolving the Metallicity Distribution of the Stellar Halo with the H3 Survey
• Stellar haloes in Milky-Way mass galaxies: From the inner to the outer haloes
• Radial Migration in Galactic Thick Discs
• Chemical Abundances of the Milky Way Thick Disk and Stellar Halo I.: Implications of [alpha/Fe] for Star Formation Histories in Their Progenitors
• Global Properties of M31's Stellar Halo from the SPLASH Survey. I. Surface Brightness Profile
• The Eating Habits of Milky Way Mass Halos: Destroyed Dwarf Satellites and the Metallicity Distribution of Accreted Stars
• Investigating the Andromeda Stream: II. Orbital Fits and Properties of the Progenitor
• The Dual Origin of Stellar Halos II: Chemical Abundances as Tracers of Formation History
• A New Method for Isolating M31 Red Giant Stars: The Discovery of Stars out to a Radial Distance of 165 Kiloparsecs
• Detection of the Main Sequence Turn-off of a Newly Discovered Milky Way Halo Structure in the Triangulum-Andromeda Region
• A re-interpretation of the Triangulum-Andromeda stellar clouds: a population of halo stars kicked out of the Galactic disk
• The ISLAndS project II: The Lifetime Star Formation Histories of Six Andromeda dSphs
• Stellar Population Models and Individual Element Abundances I: Sensitivity of Stellar Evolution Models
• The masses and metallicities of stellar haloes reflect galactic merger histories
• The Stellar Populations of M31 Halo Substructure
• The Nature and Origin of Substructure in the Outskirts of M31. I. Surveying the Stellar Content with HST/ACS
• On the formation of extended galactic disks by tidally disrupted dwarf galaxies
• Global Properties of M31's Stellar Halo from the SPLASH Survey: II. Metallicity Profile
• The SPLASH Survey: A Spectroscopic Portrait of Andromeda's Giant Southern Stream
• Element Ratios and the Formation of the Stellar Halo
• Kinematics and Metallicity of M31 Red Giants: The Giant Southern Stream and Discovery of a Second Cold Component at R = 20 kpc
• Was the Andromeda Stream Produced by a Disk Galaxy?
• The Stellar Content of Galaxy Halos: A Comparison between LambdaCDM Models and Observations of M31
• A clear age-velocity dispersion correlation in Andromeda's stellar disk
• The Nature and Origin of Substructure in the Outskirts of M31 -- II. Detailed Star Formation Histories
• Two chemically similar stellar overdensities on opposite sides of the plane of the Galaxy
• Lithium-Rich Giants in Globular Clusters
• The Near Infrared NaI Doublet Feature in M Stars
• Stellar Kinematics in the Complicated Inner Spheroid of M31: Discovery of Substructure Along the Southeastern Minor Axis and its Relationship to the Giant Southern Stream
• Chemical gradients in the Milky Way from the RAVE data. II. Giant stars
• Heated Disc Stars in the Stellar Halo
• The Distribution of Alpha Elements in Andromeda Dwarf Galaxies
• On the stellar populations in NGC 185 and NGC 205, and the nuclear star cluster in NGC 205 from Hubble Space Telescope observations
• The Extended Star Formation History of the Andromeda Spheroid at Twenty One Kiloparsecs on the Minor Axis
• Chemical Inhomogeneities in the Milky Way Stellar Halo
• Elemental Abundances in M31: The Kinematics and Chemical Evolution of Dwarf Spheroidal Satellite Galaxies
• The Once and Future Andromeda Stream
• A New Approach to Detailed Structural Decomposition from the SPLASH and PHAT Surveys: Kicked-up Disk Stars in the Andromeda Galaxy?
• Metallicity Evolution of the Six Most Luminous M31 Dwarf Satellites
• The internal dynamics of the Local Group dwarf elliptical galaxies NGC147, NGC185, and NGC205
• Abundances of PNe in the Outer Disk of M31
• The kinematic identification of a thick stellar disc in M31
• Evidence for the Third Stellar Population in the Milky Way's Disk
• The Spatially-Resolved Star Formation History of the M31 Outer Disc
• The SPLASH Survey: Kinematics of Andromeda's Inner Spheroid
• An HST/ACS View of the Inhomogeneous Outer Halo of M31
• Chemical Abundances of the Outer Halo Stars in the Milky Way
• Deep SDSS optical spectroscopy of distant halo stars II. Iron, calcium, and magnesium abundances
• Panchromatic Hubble Andromeda Treasury XII. Mapping Stellar Metallicity Distributions in M31
• A Global Star Forming Episode in M31 2-4 Gyr Ago
• Exploring Halo Substructure with Giant Stars. XV. Discovery of a Connection between the Monoceros Ring and the Triangulum-Andromeda Overdensity?
• The Ca II triplet in red giant spectra: [Fe/H] determinations and the role of [Ca/Fe]
• Elemental Abundances in M31: First Alpha and Iron Abundance Measurements in M31's Giant Stellar Stream
• Global Properties of M31's Stellar Halo from the SPLASH Survey: III. Measuring the Stellar Velocity Dispersion Profile
• Chemical trends in the Galactic Halo with APOGEE data
• Formation of the Andromeda Giant Stream: Asymmetric Structure and Disc Progenitor
• Spectroscopic versus Photometric Metallicities: Milky Way Dwarf Spheroidal Companions as a Test Case
• Elemental Abundances in M31: Alpha and Iron Element Abundances from Low-Resolution Resolved Stellar Spectroscopy in the Stellar Halo
• Isotropic at the Break? 3D Kinematics of Milky Way Halo Stars in the Foreground of M31
• Deep Optical Photometry of Six Fields in the Andromeda Galaxy
• Disk-Like Chemistry of the Triangulum-Andromeda Overdensity as Seen by APOGEE
• The SPLASH Survey: A Spectroscopic Analysis of the Metal-Poor, Low-Luminosity M31 dSph Satellite Andromeda X
• [$\alpha$/Fe] Abundances of Four Outer M 31 Halo Stars
• Asymmetric Drift in the Andromeda Galaxy (M31) as a Function of Stellar Age
• Collision tomography: Physical properties of possible progenitors of the Andromeda stellar stream
• Andromeda Optical and Infrared Disk Survey I. New Insights in Wide-Field Near-IR Surface Photometry
• Hide and seek between Andromeda's halo, disk, and giant stream

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• The chemical composition of globular clusters in the Local Group
• Stars made in outflows may populate the stellar halo of the Milky Way
• A bottom-heavy initial mass function for the likely-accreted blue-halo stars of the Milky Way
• Elemental Abundances in M31: Gradients in the Giant Stellar Stream
• Reading the CARDs: the Imprint of Accretion History in the Chemical Abundances of the Milky Way's Stellar Halo
• The survey of planetary nebulae in Andromeda (M31). IV. Radial oxygen and argon abundance gradients of the thin and thicker disc
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• Prospects for Detecting Gaps in Globular Cluster Stellar Streams in External Galaxies with the Nancy Grace Roman Space Telescope
• Resolved SPLASH Chemodynamics in Andromeda's PHAT Stellar Halo and Disk: On the Nature of the Inner Halo Along the Major Axis
• Asymmetric Drift of Andromeda Analogs in the IllustrisTNG Simulation
• The survey of planetary nebulae in Andromeda (M31) VII. Predictions of a major merger simulation model compared with chemodynamical data of the disc and inner halo substructures
• The origin of the metallicity distributions of the NE and W stellar shelves in the Andromeda Galaxy
• The Milky Way in context: The formation of galactic discs and chemical sequences from a cosmological perspective
• On the Use of Field RR Lyrae as Galactic Probes -- VIII. Early Formation of the Galactic Spheroid
• The survey of Planetary Nebulae in Andromeda (M31): I. Imaging the disk and halo with MegaCam@CFHT