The large-scale structure of the halo of the Andromeda Galaxy Part I: global stellar density, morphology and metallicity properties

Abstract

We present an analysis of the large-scale structure of the halo of the Andromeda galaxy, based on the Pan-Andromeda Archeological Survey (PAndAS), currently the most complete map of resolved stellar populations in any galactic halo. Despite copious substructure, the global halo populations follow closely power law profiles that become steeper with increasing metallicity. We divide the sample into stream-like populations and a smooth halo component. Fitting a three-dimensional halo model reveals that the most metal-poor populations ([Fe/H]<-1.7) are distributed approximately spherically (slightly prolate with ellipticity c/a=1.09+/-0.03), with only a relatively small fraction (42%) residing in discernible stream-like structures. The sphericity of the ancient smooth component strongly hints that the dark matter halo is also approximately spherical. More metal-rich populations contain higher fractions of stars in streams (86% for [Fe/H]>-0.6). The space density of the smooth metal-poor component has a global power-law slope of -3.08+/-0.07, and a non-parametric fit shows that the slope remains nearly constant from 30kpc to 300kpc. The total stellar mass in the halo at distances beyond 2 degrees is 1.1x10^10 Solar masses, while that of the smooth component is 3x10^9 Solar masses. Extrapolating into the inner galaxy, the total stellar mass of the smooth halo is plausibly 8x10^9 Solar masses. We detect a substantial metallicity gradient, which declines from [Fe/H]=-0.7 at R=30kpc to [Fe/H]=-1.5 at R=150kpc for the full sample, with the smooth halo being 0.2dex more metal poor than the full sample at each radius. While qualitatively in-line with expectations from cosmological simulations, these observations are of great importance as they provide a prototype template that such simulations must now be able to reproduce in quantitative detail.

21 pages, 17 figures, accepted for publication in the Astrophysical Journal

References in corpus (17)

• The Dartmouth Stellar Evolution Database
• Two Stellar Components in the Halo of the Milky Way
• The ACS Nearby Galaxy Survey Treasury
• A Vast Thin Plane of Co-rotating Dwarf Galaxies Orbiting the Andromeda Galaxy
• The accretion origin of the Milky Way's stellar halo
• 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 Metal-Poor Halo of the Andromeda Spiral Galaxy (M31)
• The ghost of a dwarf galaxy: fossils of the hierarchical formation of the nearby spiral galaxy NGC 5907
• A kinematically selected, metal-poor stellar halo in the outskirts of M31
• Investigating the Andromeda Stream: III. A Young Shell System in M31
• Global Properties of M31's Stellar Halo from the SPLASH Survey. I. Surface Brightness Profile
• Fashionably Late? Building up the Milky Way's Inner Halo
• The Stellar Content of Galaxy Halos: A Comparison between LambdaCDM Models and Observations of M31
• The Extended Star Formation History of the Andromeda Spheroid at Twenty One Kiloparsecs on the Minor Axis
• An HST/ACS investigation of the spatial and chemical structure and sub-structure of NGC 891, a Milky Way analogue
• Unearthing Foundations of a Cosmic Cathedral: Searching the Stars for M33's Halo

Cited by in corpus (188)

• The Pristine survey I: Mining the Galaxy for the most metal-poor stars
• The extended halo of Centaurus A: uncovering satellites, streams, and substructures
• Chemical tagging with APOGEE: Discovery of a large population of N-rich stars in the inner Galaxy
• The SAGES Legacy Unifying Globulars and GalaxieS Survey (SLUGGS): Sample definition, methods, and initial results
• The Auriga Stellar Haloes: Connecting stellar population properties with accretion and merging history
• The large-scale structure of the halo of the Andromeda galaxy II. Hierarchical structure in the Pan-Andromeda Archaeological Survey
• Contributions to the accreted stellar halo: an atlas of stellar deposition
• Beyond 31 mag/arcsec^2: the low surface brightness frontier with the largest optical telescopes
• Halo Mass and Assembly History Exposed in the Faint Outskirts: the Stellar and Dark Matter Haloes of Illustris Galaxies
• The PAndAS view of the Andromeda satellite system - II. Detailed properties of 23 M31 dwarf spheroidal galaxies
• A 2-3 billion year old major merger paradigm for the Andromeda galaxy and its outskirts
• The Andromeda galaxy's most important merger about 2 billion years ago as M32's likely progenitor
• Diverse Stellar Haloes in Nearby Milky Way-Mass Disc Galaxies
• Parametrizing the Stellar Haloes of Galaxies
• A Synoptic Map of Halo Substructures from the Pan-STARRS1 3π Survey
• The outer halo globular cluster system of M31 - I. The final PAndAS catalogue
• Resolving the Metallicity Distribution of the Stellar Halo with the H3 Survey
• Galactic cirri in deep optical imaging
• Velocity anti-correlation of diametrically opposed galaxy satellites in the low redshift universe
• The GHOSTS survey. II. The diversity of Halo Color and Metallicity Profiles of Massive Disk Galaxies
• The Canada-France Imaging Survey: First results from the u-band component
• The outer halo globular cluster system of M31 - II. Kinematics
• The ARTEMIS simulations: stellar haloes of Milky Way-mass galaxies
• The masses and metallicities of stellar haloes reflect galactic merger histories
• The PAndAS Field of Streams: stellar structures in the Milky Way halo toward Andromeda and Triangulum
• Global Properties of M31's Stellar Halo from the SPLASH Survey: II. Metallicity Profile
• Touching The Void: A Striking Drop in Stellar Halo Density Beyond 50 kpc
• Structure of Brightest Cluster Galaxies and Intracluster Light
• Pristine Dwarf-Galaxy Survey I: A detailed photometric and spectroscopic study of the very metal-poor Draco II satellite
• 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
• Carbon-Enhanced Metal-Poor Stars: CEMP-s and CEMP-no Sub-Classes in the Halo System of the Milky Way
• The abundance of satellites around Milky Way- and M31-like galaxies with the TNG50 simulation: a matter of diversity
• Feeling the pull, a study of natural Galactic accelerometers. I: photometry of the delicate stellar stream of the Palomar 5 globular cluster
• The Need for Speed: Escape velocity and dynamical mass measurements of the Andromeda galaxy
• Kinematics and simulations of the stellar stream in the halo of the Umbrella Galaxy
• MOND simulation suggests the origin of some peculiarities in the Local Group
• Balancing mass and momentum in the Local Group
• The Pristine survey VIII: The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime
• Galaxies grow their bulges and black holes in diverse ways
• A Hyper Suprime-Cam View of the Interacting Galaxies of the M81 Group
• Where Do Galaxies End?
• Elemental Abundances in M31: The Kinematics and Chemical Evolution of Dwarf Spheroidal Satellite Galaxies
• The Outer Envelopes of Globular Clusters. I. NGC 7089 (M2)
• Systematic search for tidal features around nearby galaxies: I. Enhanced SDSS imaging of the Local Volume
• The imprint of cosmic reionisation on the luminosity function of galaxies
• Introducing the LBT Imaging of Galactic Halos and Tidal Structures (LIGHTS) survey. A preview of the low surface brightness Universe to be unveiled by LSST
• The Pristine survey III: Spectroscopic confirmation of an efficient search for extremely metal-poor stars
• The Detailed Chemical Properties of M31 Star Clusters I. Fe, Alpha and Light Elements
• The merger and assembly histories of Milky Way- and M31-like galaxies with TNG50: disk survival through mergers
• Star Clusters in M31: VII. Global Kinematics and Metallicity Subpopulations of the Globular Clusters
• DESI Observations of the Andromeda Galaxy: Revealing the Immigration History of our Nearest Neighbor
• Stellar Halos in Illustris- Probing the Histories of Milky Way-Mass Galaxies
• Andromeda XXI -- a dwarf galaxy in a low density dark matter halo
• On the stellar halo metallicity profile of Milky Way-like galaxies in the Auriga simulations
• A missing outskirts problem? Comparisons between stellar halos in the Dragonfly Nearby Galaxies Survey and the TNG100 simulation
• A PAndAS view of M31 dwarf elliptical satellites: NGC147 and NGC185
• Convergence of Lobatto-type Runge-Kutta methods for partitioned differential-algebraic systems of index 2
• The missing light of the Hubble Ultra Deep Field
• A-type stars in the Canada-France Imaging Survey I. The stellar halo of the Milky Way traced to large radius by blue horizontal branch stars
• The outer halo globular cluster system of M31 - III. Relationship to the stellar halo
• The difference in metallicity distribution functions of halo stars and globular clusters as a function of galaxy type: A tracer of globular cluster formation and evolution
• J-PLUS: photometric calibration of large area multi-filter surveys with stellar and white dwarf loci
• Creating mock catalogues of stellar haloes from cosmological simulations
• VEGAS: A VST Early-type GAlaxy Survey. III. Mapping the galaxy structure, interactions and intragroup light in the NGC 5018 group
• The Transverse velocity of the Andromeda system, derived from the M31 satellite population
• Major Substructure in the M31 Outer Halo: Distances and Metallicities along the Giant Stellar Stream
• 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
• Panchromatic Hubble Andromeda Treasury XII. Mapping Stellar Metallicity Distributions in M31
• A panoramic VISTA of the stellar halo of NGC 253
• Integrated Light Chemical Tagging Analyses of Seven M31 Outer Halo Globular Clusters from the Pan-Andromeda Archaeological Survey
• Two major accretion epochs in M31 from two distinct populations of globular clusters
• Detection of a distinct metal-poor stellar halo in the early-type galaxy NGC 3115
• A Global Star Forming Episode in M31 2-4 Gyr Ago
• The Saga of M81: Global View of a Massive Stellar Halo in Formation
• Using the Tip of the Red Giant Branch as a Distance Indicator in the Near Infrared
• Stellar Substructures around the Hercules Dwarf Spheroidal Galaxy
• The Survey of Centaurus A's Baryonic Structures (SCABS). II. The Extended Globular Cluster System of NGC5128 and its Nearby Environment
• The infall of dwarf satellite galaxies are influenced by their host's massive accretions
• 3D hydrodynamic simulations for the formation of the Local Group satellite planes
• The chemical composition of globular clusters in the Local Group
• Elemental Abundances in M31: First Alpha and Iron Abundance Measurements in M31's Giant Stellar Stream
• Substructure and Tidal Streams in the Andromeda Galaxy and its Satellites
• The stellar halo of isolated central galaxies in the Hyper Suprime-Cam imaging survey
• The ISLANDS project I: Andromeda XVI, An Extremely Low Mass Galaxy not Quenched by Reionization
• The Fornax3D project: discovery of ancient massive merger events in the Fornax cluster galaxies NGC 1380 and NGC 1427
• Stellar Stream and Halo Structure in the Andromeda Galaxy From a Subaru/Hyper Suprime-Cam Survey
• Tracing the anemic stellar halo of M101
• The accreted stellar halo as a window on halo assembly in L* galaxies
• Deep Imaging of M51: a New View of the Whirlpool's Extended Tidal Debris
• Stellar chemo-kinematics of the Cetus dwarf spheroidal galaxy
• The Hough Stream Spotter: A New Method for Detecting Linear Structure in Resolved Stars and Application to the Stellar Halo of M31
• Systematic Problems With Using Dark Matter Simulations to Model Stellar Halos
• Stellar halos from The Dragonfly Edge-on Galaxies Survey
• Elemental Abundances in M31: Alpha and Iron Element Abundances from Low-Resolution Resolved Stellar Spectroscopy in the Stellar Halo
• Elemental Abundances in M31: Gradients in the Giant Stellar Stream
• The Stellar Density Profile of the Distant Galactic Halo
• Radial velocities and stellar population properties of 56 MATLAS dwarf galaxies observed with MUSE
• A rogues gallery of Andromeda's dwarf galaxies I. A predominance of red horizontal branches
• The LAMOST spectroscopic survey of star clusters in M31. II. Metallicities, ages and masses
• A wide field map of intracluster globular clusters in Coma
• Chemical Abundances of Planetary Nebulae in the Substructures of M31
• The chemistry of planetary nebulae in the outer regions of M31
• [$\alpha$/Fe] Abundances of Four Outer M 31 Halo Stars
• The intrinsic ellipticity of dwarf spheroidal galaxies: constraints from the Andromeda system
• Resolved stellar streams around NGC4631 from a Subaru/Hyper Suprime-Cam survey
• A machine--vision method for automatic classification of stellar halo substructure
• Accretion in action: phase space coherence of stellar debris and globular clusters in Andromeda's South-West Cloud
• The PAndAS View of the Andromeda Satellite System. IV Global properties
• The PAndAS View of the Andromeda Satellite System. III. Dwarf galaxy detection limits
• Cosmic clocks: A Tight Radius - Velocity Relationship for HI-Selected Galaxies
• KK258, a new transition dwarf galaxy neighbouring the Local Group
• The assembly history of the Galactic inner halo inferred from alpha-patterns
• Cosmic flow around local massive galaxies
• The outermost stellar halo of NGC 5128 (Centaurus A): Radial structure
• Elemental Abundances in M31: Properties of the Inner Stellar Halo
• New views of the distant stellar halo
• Stellar Populations in the Outer Disk and Halo of the Spiral Galaxy M101
• An Empirical Calibration of the Tip of the Red Giant Branch Distance Method in the Near Infrared. I. HST WFC3/IR F110W and F160W Filters
• The M31/M33 tidal interaction: A hydrodynamic simulation of the extended gas distribution
• The survey of planetary nebulae in Andromeda (M31) VI. Kinematics of M31 inner-halo substructures and comparison with major-merger simulation predictions
• Intragroup and Intracluster Light
• Chemical Abundances of Planetary Nebulae in the Substructures of M31 -- II. The Extended Sample and A Comparison Study with the Outer-disk Group
• Project AMIGA: Distance and Metallicity Gradients Along Andromeda's Giant Southern Stream from the Red Clump
• The Size and Shape of the Milky Way Disk and Halo from M-type Brown Dwarfs in the BoRG Survey
• Elemental Abundances in M31: Iron and Alpha Element Abundances in M31's Outer Halo
• GalMod: a Galactic synthesis population model
• The elusive stellar halo of the Triangulum Galaxy
• Charting Galactic Accelerations with Stellar Streams and Machine Learning
• Hyper Wide Field Imaging of the Local Group Dwarf Irregular Galaxy IC 1613: An Extended Component of Metal-poor Stars
• Metallicity distribution of the progenitor of the Giant Stellar Stream in the Andromeda Galaxy
• Elemental abundances in M31: Individual and Coadded Spectroscopic [Fe/H] and [α/Fe] throughout the M31 Halo with SPLASH
• NGC 147, NGC 185 and CassII: a genetic approach to orbital properties, star formation and tidal debris
• The Panchromatic Hubble Andromeda Treasury XX: The Disk of M31 is Thick
• Saying Hallo to M94's Stellar Halo: Investigating the Accretion History of the Largest Pseudobulge Host in the Local Universe
• The Massive M31 Cluster G1: Detailed Chemical Abundances from Integrated Light Spectroscopy
• Origins of the Evil Eye: M64's Stellar Halo Reveals the Recent Accretion of an SMC-mass Satellite
• Kinematics and Metallicity of Red Giant Branch Stars in the Northeast Shelf of M31
• Major Substructure in the M31 Outer Halo: the East Cloud
• Tracing the Metal-Poor M31 Stellar Halo with Blue Horizontal Branch Stars
• Galaxy archaeology for wet mergers: Globular cluster age distributions in the Milky Way and nearby galaxies
• Prospects for Detecting Gaps in Globular Cluster Stellar Streams in External Galaxies with the Nancy Grace Roman Space Telescope
• No sign (yet) of intergalactic globular clusters in the Local Group
• Globular Clusters in the Outer Halo of M31
• Observing the stellar halo of Andromeda in cosmological simulations: the Auriga2PAndAS pipeline
• The Andromeda Gamma-Ray Excess: Background Systematics of the Millisecond Pulsars and Dark Matter Interpretations
• The nature of the progenitor of the M31 North-western stream: globular clusters as milestones of its orbit
• Mirach's Goblin: Discovery of a dwarf spheroidal galaxy behind the Andromeda galaxy
• Variable Stars and Stellar Populations in Andromeda XXVII: IV. An off-centered, disrupted galaxy
• Leaves on trees: identifying halo stars with extreme gradient boosted trees
• The role of accreted and in situ populations in shaping the stellar halos of low-mass galaxies
• Metallicities of Outer Halo M31 Globular Clusters from Integrated Light Calcium-II Triplet Spectroscopy
• A Dwarf Disrupting -- Andromeda XXVII and the North West Stream
• Three low surface brightness dwarfs discovered around NGC 4631
• Resolved Stellar Populations as Tracers of Outskirts
• Low-metallicity stellar halo populations as tracers of dark matter haloes
• Resolved SPLASH Chemodynamics in Andromeda's PHAT Stellar Halo and Disk: On the Nature of the Inner Halo Along the Major Axis
• The Smallest Scale of Hierarchy Survey (SSH). I. Survey Description
• Asymmetric Drift of Andromeda Analogs in the IllustrisTNG Simulation
• A Detection of Gas Associated with the M 31 Stellar Stream
• M31 circum-nuclear region: a molecular survey with the IRAM-interferometer
• Mass Modeling the Andromeda Dwarf Galaxies: Andromeda VI and Andromeda XXIII
• The kinematics of globular clusters systems in the outer halos of the Aquarius simulations
• New Globular Cluster Candidates in the M81 group
• Kinematics and metallicity of the dwarf spheroidal galaxy Andromeda XVIII
• More satellites around the nearby spiral galaxy NGC 7331
• The "Building Blocks" of Stellar Halos
• First resolved stellar halo kinematics of a MW-mass galaxy outside the Local Group: A flat counter-rotating halo in NGC 4945
• One Stream or Two -- Exploring Andromeda's North West Stream
• On the Use of Field RR Lyrae as Galactic Probes -- VIII. Early Formation of the Galactic Spheroid
• The nature of the Eastern Extent in the outer halo of M31
• Architecture of the Andromeda: a quantitative analysis of clustering in the inner stellar halo
• The extended disc and halo of the Andromeda galaxy observed with Spitzer-IRAC
• Accreted stars and stellar haloes of simulated galaxies in TNG50
• Exploring the connection between stellar halo profiles and accretion histories in $L_{\ast }$ galaxies
• A Mysterious Ring in Dark Space?
• Studying stellar halos with future facilities
• Period-Luminosity Relations for Galactic Type II Cepheids in the Sloan bands
• Neutral-Gas-Phase Metal Abundances in ZnII-Selected Quasar Absorption Line Systems near Redshift $z=1.2$
• The survey of Planetary Nebulae in Andromeda (M31): I. Imaging the disk and halo with MegaCam@CFHT
• The Role of Mass and Environment on Satellite distributions around Milky Way analogs in the Romulus25 simulation
• A "Universal" Density Profile for the Outer Stellar Halos of Galaxies
• The Exploration of Local VolumE Satellites (ELVES) Survey: A Nearly Volume-Limited Sample of Nearby Dwarf Satellite Systems
• Properties of the Lower Segment of M31's North West Stream
• Integrated Spectroscopy of Extragalactic Globular Clusters
• Gravitational octree code performance evaluation on Volta GPU
• Chemical Abundances of Seven Outer Halo M31 Globular Clusters from the Pan-Andromeda Archaeological Survey
• Stellar halos of bright central galaxies II: Scaling relations, colors and metallicity evolution with redshift