Mapping the Stellar Halo with the H3 Spectroscopic Survey

Abstract

Modern theories of galaxy formation predict that the Galactic stellar halo was hierarchically assembled from the accretion and disruption of smaller systems. This hierarchical assembly is expected to produce a high degree of structure in the combined phase and chemistry space; this structure should provide a relatively direct probe of the accretion history of our Galaxy. Revealing this structure requires precise 3D positions (including distances), 3D velocities, and chemistry for large samples of stars. The Gaia satellite is delivering proper motions and parallaxes for >1 billion stars to G~20. However, radial velocities and metallicities will only be available to G~15, which is insufficient to probe the outer stellar halo (>10 kpc). Moreover, parallaxes will not be precise enough to deliver high-quality distances for stars beyond ~10 kpc. Identifying accreted systems throughout the stellar halo therefore requires a large ground-based spectroscopic survey to complement Gaia. Here we provide an overview of the H3 Stellar Spectroscopic Survey, which will deliver precise stellar parameters and spectrophotometric distances for 200,000 stars to r=18. Spectra are obtained with the Hectochelle instrument at the MMT, which is configured for the H3 Survey to deliver resolution R~23,000 spectra covering the wavelength range 5150A-5300A. The survey is optimized for stellar halo science and therefore focuses on high Galactic latitude fields (|b|>30 deg.), sparsely sampling 15,000 sq. degrees. Targets are selected on the basis of Gaia parallaxes, enabling very efficient selection of bone fide halo stars. The survey began in the Fall of 2017 and has collected 88,000 spectra to-date. All of the data, including the derived stellar parameters, will eventually be made publicly available via the survey website: h3survey.rc.fas.harvard.edu.

arXiv comment14 pages, 15 figures. Resubmitted to ApJ after responding to referee

References in corpus (58)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• The chemical composition of the Sun
• Gaia Data Release 2. Summary of the contents and survey properties
• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• On the variation of the Initial Mass Function
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• dynesty: A Dynamic Nested Sampling Package for Estimating Bayesian Posteriors and Evidences
• Gaia Data Release 2: The astrometric solution
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• Small-Scale Challenges to the $\Lambda$CDM Paradigm
• The DESI Experiment Part I: Science,Targeting, and Survey Design
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• SEGUE: A Spectroscopic Survey of 240,000 stars with g=14-20
• GAIA: Composition, Formation and Evolution of the Galaxy
• Tracing Galaxy Formation with Stellar Halos I: Methods
• Co-formation of the Galactic disc and the stellar halo
• The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem
• The Radial Velocity Experiment (RAVE): first data release
• An absolutely calibrated effective temperature scale from the InfraRed Flux Method
• The Pan-STARRS1 Surveys
• Galactic stellar haloes in the CDM model
• LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) The survey science plan
• Near-Field Cosmology with Metal-Poor Stars
• Building up the Stellar Halo of the Galaxy
• Hectospec, the MMT's 300 Optical Fiber-Fed Spectrograph
• Evidence for a systematic offset of -80 micro-arcseconds in the Gaia DR2 parallaxes
• Fossil Signatures of Ancient Accretion Events in the Halo
• Oxygen Abundances in Nearby FGK Stars and the Galactic Chemical Evolution of the Local Disk and Halo
• The stellar halo of the Galaxy
• The Payne: self-consistent ab initio fitting of stellar spectra
• The GALAH Survey: Observational Overview and Gaia DR1 companion
• Gaia reveals a metal-rich in-situ component of the local stellar halo
• Hunting for the Dark Matter Wake Induced by the Large Magellanic Cloud
• Broken and unbroken: the Milky Way and M31 stellar haloes
• And yet it moves: The dangers of artificially fixing the Milky Way center of mass in the presence of a massive Large Magellanic Cloud
• Simultaneous calibration of spectro-photometric distances and the Gaia DR2 parallax zero-point offset with deep learning
• Carbon-enhanced Metal-poor Stars in SDSS/SEGUE. I. Carbon Abundance Estimation and Frequency of CEMP Stars
• Distances and parallax bias in Gaia DR2
• The origin of galactic metal-rich stellar halo components with highly eccentric orbits
• Reevaluating the Mass-Radius Relation for Low-Mass, Main Sequence Stars
• Estimating the dark matter halo mass of our Milky Way using dynamical tracers
• The Milky Way Halo in Action Space
• SDSS-V: Pioneering Panoptic Spectroscopy
• On the kinematic detection of accreted streams in the Gaia era: a cautionary tale
• The SEGUE K giant survey II: A Catalog of Distance Determinations for the SEGUE K giants in the Galactic Halo
• Bayesian analysis of resolved stellar spectra: application to MMT/Hectochelle Observations of the Draco dwarf spheroidal
• Touching The Void: A Striking Drop in Stellar Halo Density Beyond 50 kpc
• Stellar distances from spectroscopic observations: a new technique
• The $>100$ kpc Distant Spur of the Sagittarius Stream and the Outer Virgo Overdensity, as Seen in PS1 RR Lyrae Stars
• Fundamental stellar parameters and metallicities from Bayesian spectroscopy. Application to low- and high-resolution spectra
• The Pisces Plume and the Magellanic Wake
• A Gaia DR2 Mock Stellar Catalog
• Prospects for Measuring Abundances of >20 Elements with Low-resolution Stellar Spectra
• Creating mock catalogues of stellar haloes from cosmological simulations
• They Might Be Giants: An Efficient Color-Based Selection of Red Giant Stars
• 4MOST Survey Strategy Plan

Cited by in corpus (94)

• Streams, substructures and the early history of the Milky Way
• Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure
• Evidence from APOGEE for the presence of a major building block of the halo buried in the inner Galaxy
• Abundance Estimates for 16 Elements in 6 Million Stars from LAMOST DR5 Low-Resolution Spectra
• Reconstructing the Last Major Merger of the Milky Way with the H3 Survey
• Gaia early DR3 systemic motions of Local Group dwarf galaxies and orbital properties with a massive Large Magellanic Cloud
• Overview of the DESI Milky Way Survey
• The chemical characterisation of halo substructure in the Milky Way based on APOGEE
• The Poor Old Heart of the Milky Way
• Resolving the Metallicity Distribution of the Stellar Halo with the H3 Survey
• Timing the Early Assembly of the Milky Way with the H3 Survey
• Weighing the stellar constituents of the Galactic halo with APOGEE red giant stars
• Selecting accreted populations: metallicity, elemental abundances, and ages of the Gaia-Sausage-Enceladus and Sequoia populations
• The Chemo-Dynamical Groups of Galactic Globular Clusters
• Reconstructing the Disrupted Dwarf Galaxy $Gaia$-Sausage/Enceladus Using its Stars and Globular Clusters
• Orbital Clustering Identifies the Origins of Galactic Stellar Streams
• The effect of the LMC on the Milky Way system
• MINESweeper: Spectrophotometric Modeling of Stars in the Gaia Era
• The Stellar Halo of the Galaxy is Tilted & Doubly Broken
• Evidence of a dwarf galaxy stream populating the inner Milky Way Halo
• The Kinematic Properties of Milky Way Stellar Halo Populations
• The Mass of the Milky Way from the H3 Survey
• A Gaia early DR3 mock stellar catalog: Galactic prior and selection function
• The value-added catalogue for LAMOST DR8 low-resolution spectra
• Substructure in the stellar halo near the Sun. I. Data-driven clustering in Integrals of Motion space
• Galactic potential constraints from clustering in action space of combined stellar stream data
• Dynamically Tagged Groups of Metal-Poor Stars from the Best \& Brightest Survey
• The origin of metal-poor stars on prograde disk orbits in FIRE simulations of Milky Way-mass galaxies
• A Comparative Analysis of the Chemical Compositions of Gaia-Enceladus/Sausage and Milky Way Satellites using APOGEE
• The impact of early massive mergers on the chemical evolution of Milky Way-like galaxies: insights from NIHAO-UHD simulations
• Discovery of the Magellanic Stellar Stream Out to 100 Kiloparsecs
• Cluster Ages to Reconstruct the Milky Way Assembly (CARMA) I. The final word on the origin of NGC6388 and NGC6441
• Exoplanets in the Galactic context: Planet occurrence rates in the thin disk, thick disk and stellar halo of Kepler stars
• Stars made in outflows may populate the stellar halo of the Milky Way
• Transferring spectroscopic stellar labels to 217 million Gaia DR3 XP stars with SHBoost
• Distant Echoes of the Milky Way's Last Major Merger
• DM halo morphological types of MW-like galaxies in the TNG50 simulation: Simple, Twisted, or Stretched
• Velocity Dispersion of the GD-1 Stellar Stream
• Stellar halos from The Dragonfly Edge-on Galaxies Survey
• Reading the CARDs: the Imprint of Accretion History in the Chemical Abundances of the Milky Way's Stellar Halo
• Metallicity distributions of halo stars: do they trace the Galactic accretion history?
• Linking the brightest stellar streams with the accretion history of Milky Way-like galaxies
• Phase-space Properties and Chemistry of the Sagittarius Stellar Stream Down to the Extremely Metal-poor ($[Fe/H]\lesssim -3$) Regime
• The Unmixed Debris of Gaia-Sausage/Enceladus in the Form of a Pair of Halo Stellar Overdensities
• Targeting Bright Metal-poor Stars in the Disk and Halo Systems of the Galaxy
• Discovery of a new nearby globular cluster with extreme kinematics located in the extension of a halo stream
• Structure, Kinematics, and Observability of the Large Magellanic Cloud's Dynamical Friction Wake in Cold vs. Fuzzy Dark Matter
• The observable properties of galaxy accretion events in Milky Way-like galaxies in the FIRE-2 cosmological simulations
• The Cetus-Palca stream: A disrupted small dwarf galaxy. A prequel to the science possible with WEAVE with precise spectro-photometric distances
• Ancient Very Metal-Poor Stars Associated With the Galactic Disk in the H3 Survey
• The Galactic Distribution of Phosphorus: A Survey of 163 Disk and Halo Stars
• The Metallicity Gradient and Complex Formation History of the Outermost Halo of the Milky Way
• Forecasting Chemical Abundance Precision for Extragalactic Stellar Archaeology
• Extending the Chemical Reach of the H3 Survey: Detailed Abundances of the Dwarf-galaxy Stellar Stream Wukong/LMS-1
• A Lower Limit on the Mass of Our Galaxy from the H3 Survey
• Magellan/M2FS and MMT/Hectochelle Spectroscopy of Dwarf Galaxies and Faint Star Clusters within the Galactic Halo
• Gaia-Sausage-Enceladus star formation history as revealed by detailed elemental abundances
• Galactic Chemical Evolution Models Favor an Extended Type Ia Supernova Delay-Time Distribution
• Constraints on the Galactic Centre environment from Gaia hypervelocity stars II: The evolved population
• All-Sky Kinematics of the Distant Halo: The Reflex Response to the LMC
• Stars in the Local Galactic Thick Disk and Halo in Gaia EDR3: A catalogue of Half a Million Local Main-sequence Stars with Photometric Metallicities
• Robust Clustering of the Local Milky Way Stellar Kinematic Substructures with Gaia eDR3
• Disk flaring with TNG50: diversity across Milky Way and M31 analogs
• LMC-driven anisotropic boosts in stream--subhalo interactions
• Unravelling the mass spectrum of destroyed dwarf galaxies with the metallicity distribution function
• Wide binaries from the H3 survey: the thick disk and halo have similar wide binary fractions
• Exploring the ex-situ components within Gaia DR3
• Chronology of our Galaxy from Gaia colour-magnitude diagram fitting (ChronoGal) -- III. Age and metallicity distribution of Gaia-Sausage-Enceladus stars near the Sun
• No Evolution in the Half-mass Radius of Milky Way-type Galaxies over the Last 10 Gyr
• HALO7D III: Chemical Abundances of Milky Way Halo Stars from Medium Resolution Spectra
• A Ghost in Boötes: The Least Luminous Disrupted Dwarf Galaxy
• Mapping the Distant and Metal-Poor Milky Way with SDSS-V
• The global structure of the Milky Way's stellar halo based on the orbits of local metal-poor stars
• Cosmological Simulations of Stellar Halos with Gaia Sausage-Enceladus Analogues: Two Sausages, One Bun?
• The Pristine survey XXVIII. Journey to the Galactic outskirts: Mapping the outer halo red giant stars down to the very metal-poor end
• Mapping the Milky Way in 5-D with 170 Million Stars
• From order to chaos: the blurred out metallicity gradient of the Gaia-Enceladus/Sausage progenitor
• AuriDESI: Mock Catalogues for the DESI Milky Way Survey
• Orbital phase-driven biases in Galactic mass constraints from stellar streams
• First resolved stellar halo kinematics of a MW-mass galaxy outside the Local Group: A flat counter-rotating halo in NGC 4945
• A New Tidal Stream Discovered in Gaia DR3
• On the Use of Field RR Lyrae as Galactic Probes -- VIII. Early Formation of the Galactic Spheroid
• The dawn is quiet here: Rise in [$\alpha$/Fe] is a signature of massive gas accretion that fueled proto-Milky Way
• Main-sequence Turnoff Stars as Probes of the Ancient Galactic Relic: Chemo-dynamical Analysis of a Pilot Sample
• Segue 2 Recently Collided with the Cetus-Palca Stream: New Opportunities to Constrain Dark Matter in an Ultra-Faint Dwarf
• Two faces of Gaia-Sausage-Enceladus: Mining the chemical abundance space with graph attention networks
• Quantifying the Milky Way, LMC and their interaction using all-sky kinematics of outer halo stars
• Identification of a dwarf galaxy stream in Gaia, and its possible association with the VPOS structure
• Probing the Milky Way Halo with RR Lyrae Stars from Gaia Data Release 3
• The Milky Way's Early Disk Was Built in Bursts. I. Evidence from Low-angular-momentum, High-$\alpha$ Stars Scattered Out of the Protodisk by Merger Events
• Dwarf stellar haloes: a powerful probe of small-scale galaxy formation and the nature of dark matter
• A Tilt in the Dark Matter Halo of the Galaxy
• Unravelling the role of merger histories in the population of In situ stars: linking IllustrisTNG cosmological simulation to H3 survey
• Searching for and characterizing halo substructures with the GALAH DR4 survey