The large-scale structure of the halo of the Andromeda galaxy II. Hierarchical structure in the Pan-Andromeda Archaeological Survey

Abstract

The Pan-Andromeda Archaeological Survey is a survey of $>400$ square degrees centered on the Andromeda (M31) and Triangulum (M33) galaxies that has provided the most extensive panorama of a $L_{\star }$ galaxy group to large projected galactocentric radii. Here, we collate and summarise the current status of our knowledge of the substructures in the stellar halo of M31, and discuss connections between these features. We estimate that the 13 most distinctive substructures were produced by at least 5 different accretion events, all in the last 3 or 4 Gyrs. We suggest that a few of the substructures furthest from M31 may be shells from a single accretion event. We calculate the luminosities of some prominent substructures for which previous estimates were not available, and we estimate the stellar mass budget of the outer halo of M31. We revisit the problem of quantifying the properties of a highly structured dataset; specifically, we use the OPTICS clustering algorithm to quantify the hierarchical structure of M31's stellar halo, and identify three new faint structures. M31's halo, in projection, appears to be dominated by two `mega-structures', that can be considered as the two most significant branches of a merger tree produced by breaking M31's stellar halo into smaller and smaller structures based on the stellar spatial clustering. We conclude that OPTICS is a powerful algorithm that could be used in any astronomical application involving the hierarchical clustering of points. The publication of this article coincides with the public release of all PAndAS data products.

arXiv commentAccepted for publication in the Astrophysical Journal. 51 pages, 24 figures, 5 tables. Some figures have degraded resolution. All PAndAS data products are available via the CADC at http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/community/pandas/query.html where you can also find a version of the paper with full resolution figures

References in corpus (147)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• The observed properties of dwarf galaxies in and around the Local Group
• The Dartmouth Stellar Evolution Database
• Introducing the Illustris Project: the evolution of galaxy populations across cosmic time
• Morphological Transformation from Galaxy Harassment
• LCDM-based models for the Milky Way and M31 I: Dynamical Models
• The remnants of galaxy formation from a panoramic survey of the region around M31
• A giant stream of metal-rich stars in the halo of the galaxy M31
• Eight New Milky Way Companions Discovered in First-Year Dark Energy Survey Data
• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• Eight Ultra-faint Galaxy Candidates Discovered in Year Two of the Dark Energy Survey
• A Vast Thin Plane of Co-rotating Dwarf Galaxies Orbiting the Andromeda Galaxy
• Evidence for Stellar Substructure in the Halo and Outer Disk of M31
• The Haunted Halos of Andromeda and Triangulum: A panorama of galaxy formation in action
• The great disk of Milky-Way satellites and cosmological sub-structures
• The Panchromatic Hubble Andromeda Treasury
• The Masses of the Milky Way and Andromeda galaxies
• The ACS Survey of Galactic Globular Clusters. II. Stellar Evolution Tracks, Isochrones, Luminosity Functions, and Synthetic Horizontal-Branch Models
• The large-scale structure of the halo of the Andromeda Galaxy Part I: global stellar density, morphology and metallicity properties
• The M31 Velocity Vector. II. Radial Orbit Towards the Milky Way and Implied Local Group Mass
• Uncovering CDM halo substructure with tidal streams
• Assessing the Milky Way Satellites Associated with the Sagittarius Dwarf Spheroidal Galaxy
• Color--Mass-to-Light Ratio Relations for Disk Galaxies
• On the accretion origin of a vast extended stellar disk around the Andromeda galaxy
• Sagittarius II, Draco II and Laevens 3: three new Milky Way satellites discovered in the Pan-STARRS 1 3pi Survey
• The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater
• Dark matter and visible baryons in M33
• A new method for unveiling Open Clusters in Gaia: new nearby Open Clusters confirmed by DR2
• A whirling plane of satellite galaxies around Centaurus A challenges cold dark matter cosmology
• A kinematic study of the Andromeda dwarf spheroidal system
• PAndAS' progeny: extending the M31 dwarf galaxy cabal
• Building up the globular cluster system of the Milky Way. The contribution of the Sagittarius galaxy
• Taking measure of the Andromeda halo: a kinematic analysis of the giant stream surrounding M31
• Structural parameters for the M31 dwarf spheroidals
• A Bayesian Approach to Locating the Red Giant Branch Tip Magnitude (Part II); Distances to the Satellites of M31
• Evidence for an accretion origin for the outer halo globular cluster system of M31
• A Magellanic Origin of the DES Dwarfs
• The Three-Dimensional Structure of the M31 Satellite System; Strong Evidence for an Inhomogeneous Distribution of Satellites
• The PAndAS view of the Andromeda satellite system - II. Detailed properties of 23 M31 dwarf spheroidal galaxies
• A trio of new Local Group galaxies with extreme properties
• Hydra II: a faint and compact Milky Way dwarf galaxy found in the Survey of the Magellanic Stellar History
• PAndAS' cubs: discovery of two new dwarf galaxies in the surroundings of the Andromeda and Triangulum galaxies
• The Geometric Distance and Proper Motion of the Triangulum Galaxy (M33)
• Inferring the Andromeda Galaxy's mass from its giant southern stream with Bayesian simulation sampling
• Horologium II: a Second Ultra-faint Milky Way Satellite in the Horologium Constellation
• Investigating the Andromeda Stream: III. A Young Shell System in M31
• A 2-3 billion year old major merger paradigm for the Andromeda galaxy and its outskirts
• A new population of extended, luminous star clusters in the halo of M31
• The Planes of Satellite Galaxies Problem, Suggested Solutions, and Open Questions
• Discovery of two neighboring satellites in the Carina constellation with MagLiteS
• The Andromeda galaxy's most important merger about 2 billion years ago as M32's likely progenitor
• An almost head-on collision as the origin of two off-centre rings in the Andromeda galaxy
• The three dimensional structure of the giant stellar stream in Andromeda
• The Disruption and Fueling of M33
• A warped disk model for M33 and the 21-cm line width in spiral galaxies
• The M31 Velocity Vector. I. Hubble Space Telescope Proper Motion Measurements
• Orbits of Massive Satellite Galaxies: I. A Close Look at the Large Magellanic Cloud and a New Orbital History for M33
• Dynamics and Stellar Content of the Giant Southern Stream in M31. I. Keck Spectroscopy of Red Giant Stars
• The SPLASH Survey: Internal Kinematics, Chemical Abundances, and Masses of the Andromeda I, II, III, VII, X, and XIV dSphs
• The vast thin plane of M31 co-rotating dwarfs: an additional fossil signature of the M31 merger and of its considerable impact in the whole Local Group
• The outer halo globular cluster system of M31 - I. The final PAndAS catalogue
• Deep imaging of Eridanus II and its lone star cluster
• A dynamical model of the local cosmic expansion
• Snake in the Clouds: A new nearby dwarf galaxy in the Magellanic bridge
• At the survey limits: discovery of the Aquarius 2 dwarf galaxy in the VST ATLAS and the SDSS data
• A Hero's Dark Horse: Discovery of an Ultra-Faint Milky Way Satellite in Pegasus
• The M31 Velocity Vector. III. Future Milky Way-M31-M33 Orbital Evolution, Merging, and Fate of the Sun
• Satellites of LMC-Mass Dwarfs: Close Friendships Ruined by Milky Way Mass Halos
• The PAndAS view of the Andromeda satellite system - I. A Bayesian search for dwarf galaxies using spatial and color-magnitude information
• Investigating the Andromeda Stream: II. Orbital Fits and Properties of the Progenitor
• A thousand shadows of Andromeda: rotating planes of satellites in the Millennium-II cosmological simulation
• A New Method for Isolating M31 Red Giant Stars: The Discovery of Stars out to a Radial Distance of 165 Kiloparsecs
• Discovery of Andromeda XIV: A Dwarf Spheroidal Dynamical Rogue in the Local Group?
• The outer halo globular cluster system of M31 - II. Kinematics
• Planes of satellite galaxies: when exceptions are the rule
• An Ultra-Faint Galaxy Candidate Discovered in Early Data from the Magellanic Satellites Survey
• Identifying true satellites of the Magellanic Clouds
• The alignment of satellite galaxies and cosmic filaments: observations and simulations
• The Stellar Populations of M31 Halo Substructure
• The PAndAS Field of Streams: stellar structures in the Milky Way halo toward Andromeda and Triangulum
• The Nature and Origin of Substructure in the Outskirts of M31. I. Surveying the Stellar Content with HST/ACS
• Discovery of a Faint Outer Halo Milky Way Star Cluster in the Southern Sky
• The SPLASH Survey: A Spectroscopic Portrait of Andromeda's Giant Southern Stream
• Was the Andromeda Stream Produced by a Disk Galaxy?
• The Nature and Origin of Substructure in the Outskirts of M31 -- II. Detailed Star Formation Histories
• Structure and Population of the Andromeda Stellar Halo from a Subaru/Suprime-Cam Survey
• Kinematics of Outer Halo Globular Clusters in M31
• Exploring the Properties of the M31 Halo Globular Cluster System
• Interpreting the Morphology of Diffuse Light Around Satellite Galaxies
• Galactic halo stellar structures in the Triangulum-Andromeda region
• The tidal trail of NGC205?
• The Star Formation History and Dust Content in the Far Outer Disc of M31
• A New Giant Stellar Structure in the Outer Halo of M31
• The photometric properties of a vast stellar substructure in the outskirts of M33
• The Star Formation History in The Far Outer Disc of M33
• Comparing the observable properties of dwarf galaxies on and off the Andromeda plane
• PAndAS in the mist: The stellar and gaseous mass within the halos of M31 and M33
• Bayesian Mass Estimates of the Milky Way II: The dark and light sides of parameter assumptions
• A PAndAS view of M31 dwarf elliptical satellites: NGC147 and NGC185
• A comparison of the distribution of satellite galaxies around Andromeda and the results of $\Lambda$CDM simulations
• The Spatially-Resolved Star Formation History of the M31 Outer Disc
• Simulated ΛCDM analogues of the thin Plane of Satellites around the Andromeda galaxy are not kinematically coherent structures
• A spectroscopic survey of Andromeda's Western Shelf
• A single-merger scenario for the formation of the giant stream and the warp of M31
• Young accreted globular clusters in the outer halo of M31
• Integrated Light Chemical Tagging Analyses of Seven M31 Outer Halo Globular Clusters from the Pan-Andromeda Archaeological Survey
• A Global Star Forming Episode in M31 2-4 Gyr Ago
• Evidence for Early Filamentary Accretion from the Andromeda Galaxy's Thin Plane of Satellites
• A census of orbital properties of the M31 satellites
• The Binary Galaxies NGC 147 And NGC 185
• Darwin Tames an Andromeda Dwarf: Unraveling the Orbit of NGC 205 Using a Genetic Algorithm
• Keck Spectroscopy of Red Giant Stars in the Vicinity of M31's Massive Globular Cluster G1
• Metal-Rich PNe in the Outer Reaches of M31
• The M33 Globular Cluster System with PAndAS Data: The Last Outer Halo Cluster?
• Substructure and Tidal Streams in the Andromeda Galaxy and its Satellites
• Variable stars and stellar populations in Andromeda XXV: III. A central cluster or the galaxy nucleus?
• Density Variations in the NW Star Stream of M31
• On the Stability of Satellite Planes I: Effects of Mass, Velocity, Halo Shape and Alignment
• $\Lambda$CDM Predictions for the Satellite Population of M33
• The Recent Stellar Archeology of M31 - The Nearest Red Disk Galaxy
• A Formation Scenario for the Disk of Satellites: Accretion of Satellites during Mergers
• Dynamics in the satellite system of Triangulum: Is AndXXII a dwarf satellite of M33?
• Local ultra faint dwarves as a product of Galactic processing during a Magellanic group infall
• Formation of the Andromeda Giant Stream: Asymmetric Structure and Disc Progenitor
• Galaxy Pairs in the Local Group
• Triaxial Cosmological Haloes and the Disc of Satellites
• Newly-Discovered Globular Clusters in NGC 147 and NGC 185 from PAndAS
• A spectroscopic survey of EC4, an Extended Cluster in Andromeda's halo
• Major Substructure in the M31 Outer Halo: the South-West Cloud
• The kinematic footprints of five stellar streams in Andromeda's halo
• The chemistry of planetary nebulae in the outer regions of M31
• DDO216-A1: a central globular cluster in a low-luminosity transition type galaxy
• Accretion in action: phase space coherence of stellar debris and globular clusters in Andromeda's South-West Cloud
• Unearthing Foundations of a Cosmic Cathedral: Searching the Stars for M33's Halo
• More Remote Globular Clusters in the Outer Halo of M31
• Collision tomography: Physical properties of possible progenitors of the Andromeda stellar stream
• The Andromeda Stream
• The faint globular cluster in the dwarf galaxy Andromeda I
• NGC 147, NGC 185 and CassII: a genetic approach to orbital properties, star formation and tidal debris
• Major Substructure in the M31 Outer Halo: the East Cloud
• A Search for Intergalactic Globular Clusters in the Local Group
• The nature of the progenitor of the M31 North-western stream: globular clusters as milestones of its orbit
• A Large Group of Asymptotic Giant Branch Stars in the Disk of M31: A Missing Piece of the Puzzle?
• Variable Stars and Stellar Populations in Andromeda XXVII: IV. An off-centered, disrupted galaxy
• The Double Cluster G185 in M31

Cited by in corpus (110)

• The Early Data Release of the Dark Energy Spectroscopic Instrument
• From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity
• Galactic cirri in deep optical imaging
• The faint end of the Centaurus A satellite luminosity function
• Wide-Field Survey of Dwarf Satellite Systems Around 10 Hosts in the Local Volume
• The M101 Satellite Luminosity Function and the Halo to Halo Scatter Among Local Volume Hosts
• The abundance of satellites around Milky Way- and M31-like galaxies with the TNG50 simulation: a matter of diversity
• The Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region (PHATTER) I. Ultraviolet to Infrared Photometry of 22 Million Stars in M33
• The Hubble Space Telescope Survey of M31 Satellite Galaxies I. RR Lyrae-based Distances and Refined 3D Geometric Structure
• The Pristine survey VIII: The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime
• Hidden depths in the local Universe: The Stellar Stream Legacy Survey
• 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
• A detailed study of Andromeda XIX, an extreme local analogue of ultra diffuse galaxies
• Luminosity Functions and Host-to-Host Scatter of Dwarf Satellite Systems in the Local Volume
• DESI Observations of the Andromeda Galaxy: Revealing the Immigration History of our Nearest Neighbor
• Can cosmological simulations capture the diverse satellite populations of observed Milky Way analogues?
• The outer halo globular cluster system of M31 - III. Relationship to the stellar halo
• Radial Distributions of Dwarf Satellite Systems in the Local Volume
• Comparing the Quenching Times of Faint M31 and Milky Way Satellite Galaxies
• The Satellite Luminosity Function of M101 into the Ultra-Faint Dwarf Galaxy Regime
• The nucleation fraction of Local Volume galaxies
• 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
• Two major accretion epochs in M31 from two distinct populations of globular clusters
• The Clustering of Orbital Poles Induced by the LMC: Hints for the Origin of Planes of Satellites
• The Saga of M81: Global View of a Massive Stellar Halo in Formation
• 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
• Hubble Space Telescope Observations of Two Faint Dwarf Satellites of Nearby LMC Analogs from MADCASH
• Solo dwarfs III: Exploring the orbital origins of isolated Local Group galaxies with Gaia Data Release 2
• Mapping Dark Matter with Extragalactic Stellar Streams: the Case of Centaurus A
• Tidal destruction in a low mass galaxy environment: the discovery of tidal tails around DDO 44
• Solo dwarfs II: The stellar structure of isolated Local Group dwarf galaxies
• The Hough Stream Spotter: A New Method for Detecting Linear Structure in Resolved Stars and Application to the Stellar Halo of M31
• The survey of planetary nebulae in Andromeda (M 31) V. Chemical enrichment of the thin and thicker discs of Andromeda. Oxygen to argon abundance ratios for planetary nebulae and H II regions
• Stellar halos from The Dragonfly Edge-on Galaxies Survey
• Elemental Abundances in M31: Gradients in the Giant Stellar Stream
• Detecting Thin Stellar Streams in External Galaxies: Resolved Stars & Integrated Light
• Radial velocities and stellar population properties of 56 MATLAS dwarf galaxies observed with MUSE
• The survey of planetary nebulae in Andromeda (M31). IV. Radial oxygen and argon abundance gradients of the thin and thicker disc
• The TREX Survey: Kinematical Complexity Throughout M33's Stellar Disk and Evidence for a Stellar Halo
• Evidence for a Massive Andromeda Galaxy Using Satellite Galaxy Proper Motions
• A rogues gallery of Andromeda's dwarf galaxies II. Precise Distances to 17 Faint Satellites
• A machine--vision method for automatic classification of stellar halo substructure
• The PAndAS View of the Andromeda Satellite System. IV Global properties
• A feather on the hat: Tracing the giant stellar stream around the Sombrero galaxy
• The PAndAS View of the Andromeda Satellite System. III. Dwarf galaxy detection limits
• The imprint of clump formation at high redshift. II. The chemistry of the bulge
• The Triangulum Extended (TREX) Survey: The Stellar Disk Dynamics of M33 as a Function of Stellar Age
• Elemental Abundances in M31: Properties of the Inner Stellar Halo
• A correlation between the number of satellites and the baryonic bulge-to-total ratio extending beyond the Local Group
• The M31/M33 tidal interaction: A hydrodynamic simulation of the extended gas distribution
• The Isaac Newton Telescope monitoring survey of Local Group dwarf galaxies -- IV. The star formation history of Andromeda VII derived from long period variable stars
• Uncovering fossils of the distant Milky Way with UNIONS: NGC 5466 and its stellar stream
• The survey of planetary nebulae in Andromeda (M31) VI. Kinematics of M31 inner-halo substructures and comparison with major-merger simulation predictions
• Elemental Abundances in M31: Iron and Alpha Element Abundances in M31's Outer Halo
• Ultrafaint Dwarf Galaxy Candidates in the M81 Group: Signatures of Group Accretion
• Local Group Dwarf Galaxy Detection Limit in the CSST survey
• Inflow of low-metallicity cool gas in the halo of the Andromeda galaxy
• Solo dwarfs IV: Comparing and contrasting satellite and isolated dwarf galaxies in the Local Group
• Hubble Space Telescope Imaging of Isolated Local Volume Dwarfs GALFA-Dw3 and Dw4
• Hunting ghosts: the iconic stellar stream(s) around NG5907 under scrutiny
• Elemental abundances in M31: Individual and Coadded Spectroscopic [Fe/H] and [α/Fe] throughout the M31 Halo with SPLASH
• A giant thin stellar stream in the Coma Galaxy Cluster
• Metallicity distribution of the progenitor of the Giant Stellar Stream in the Andromeda Galaxy
• The Isaac Newton Telescope monitoring survey of Local Group dwarf galaxies. II. The star formation history of Andromeda I derived from long period variables
• The Massive M31 Cluster G1: Detailed Chemical Abundances from Integrated Light Spectroscopy
• Kinematics and Metallicity of Red Giant Branch Stars in the Northeast Shelf of M31
• The Andromeda Gamma-Ray Excess: Background Systematics of the Millisecond Pulsars and Dark Matter Interpretations
• Globular Clusters in the Outer Halo of M31
• Prospects for Detecting Gaps in Globular Cluster Stellar Streams in External Galaxies with the Nancy Grace Roman Space Telescope
• Where are the extremely metal-poor stars in the Milky Way and Andromeda? Expectations from TNG50
• Observing the stellar halo of Andromeda in cosmological simulations: the Auriga2PAndAS pipeline
• How well can we unravel the accreted constituents of the Milky Way stellar halo? A test on cosmological hydrodynamical simulations
• A Dwarf Disrupting -- Andromeda XXVII and the North West Stream
• Metallicities of Outer Halo M31 Globular Clusters from Integrated Light Calcium-II Triplet Spectroscopy
• Performance Assessment of the KASI-Deep Rolling Imaging Fast-optics Telescope pathfinder
• The Complex Structure of the Bulge of M31
• The Smallest Scale of Hierarchy Survey (SSH). I. Survey Description
• 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
• Mass Modeling the Andromeda Dwarf Galaxies: Andromeda VI and Andromeda XXIII
• New Globular Cluster Candidates in the M81 group
• Identification of new M31 star cluster candidates from PAndAS images using convolutional neural networks
• Kinematics and metallicity of the dwarf spheroidal galaxy Andromeda XVIII
• The Hierarchical Structure of Galactic Haloes: Classification and characterisation with Halo-OPTICS
• 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
• First resolved stellar halo kinematics of a MW-mass galaxy outside the Local Group: A flat counter-rotating halo in NGC 4945
• A Rich Satellite Population of the NGC 4437 Group and Implications of a Magnitude Gap for Galaxy Group Assembly History
• Exploring the Diversity of Faint Satellites in the M81 Group
• Modeling Tidal Streams and Tidal Tails around Galaxies Using Deep Wendelstein Imaging Data
• Chemo-dynamical substructure in the M31 inner halo globular clusters: Further evidence for a recent accretion event
• The nature of the Eastern Extent in the outer halo of M31
• One Stream or Two -- Exploring Andromeda's North West Stream
• Andromeda XXXV: The Faintest Dwarf Satellite of the Andromeda Galaxy
• A Mysterious Ring in Dark Space?
• The Formation of M101-alike Galaxies in the Cold Dark Matter Model
• The Hierarchical Structure of Galactic Haloes: Generalised N-Dimensional Clustering with CluSTAR-ND
• The survey of Planetary Nebulae in Andromeda (M31): I. Imaging the disk and halo with MegaCam@CFHT
• Study of Integrated Spectra of Four Globular Clusters in M31
• The Role of Mass and Environment on Satellite distributions around Milky Way analogs in the Romulus25 simulation
• Central kiloparsec region of Andromeda. I. Dynamical modelling
• The PARADIGM project II: The lifetimes and quenching of satellites in Milky Way-mass haloes
• Timing Mass of the Local Group
• Galaxy clustering in the VVV Near-IR Galaxy Catalogue
• Integrated Spectroscopy of Extragalactic Globular Clusters
• walter: A Tool for Predicting Resolved Stellar Population Observations with Applications to the Roman Space Telescope
• Properties of the Lower Segment of M31's North West Stream
• The Exploration of Local VolumE Satellites (ELVES) Survey: A Nearly Volume-Limited Sample of Nearby Dwarf Satellite Systems