Project AMIGA: Distance and Metallicity Gradients Along Andromeda's Giant Southern Stream from the Red Clump

Abstract

The Giant Southern Stream (GSS) of M31, a keystone signature of a major accretion event, yields crucial constraints on M31 formation and evolution models. Currently, our understanding of the GSS, in terms of both its geometry and its chemistry, results from either wide-field imaging probing only a few magnitudes below the red giant branch tip, or deep imaging or spectroscopy of isolated regions. Here, we take an alternative approach, using Hubble Space Telescope (HST) imaging to characterize the horizontal branch red clump (RC) using unbinned maximum likelihood fits to luminosity functions (LFs) from observed color-magnitude diagrams (CMDs). Comparing the RC mean magnitude across three fields at projected distances of 21, 52 and 80 kpc from M31, we find a line of sight distance gradient identical to recent literature measurements in fields along the core. We also find tentative evidence that the line of sight distance dispersion increases with projected distance from M31. Meanwhile, the metallicity in the 52 kpc field westward of the GSS core is at least as high as that in the 21 kpc GSS core field, and the peak colors of the RC in these two fields imply identical metallicities to within 0.2 dex. We discuss implications for distance and metallicity gradients both along and perpendicular to the GSS in the context of recent ground-based photometric and spectroscopic results, including evidence for a dropoff in metallicity moving westward from the GSS, as well as prospects for further constraining stellar populations in the vicinity of the GSS.

arXiv comment30 pages, 14 figures. AJ accepted. Figure quality has been reduced to meet arXiv size limits

References in corpus (75)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• emcee: The MCMC Hammer
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• The Dartmouth Stellar Evolution Database
• A large stellar evolution database for population synthesis studies. I. Scaled solar models and isochrones
• WFPC2 Stellar Photometry with HSTphot
• Intrinsic iron spread and a new metallicity scale for Globular Clusters
• A large stellar evolution database for population synthesis studies. II. Stellar models and isochrones for an alpha-enhanced metal distribution
• Star counts in the Galaxy. Simulating from very deep to very shallow photometric surveys with the TRILEGAL code
• The Frontier Fields: Survey Design
• A giant stream of metal-rich stars in the halo of the galaxy M31
• Reddening and Extinction Toward the Galactic Bulge from OGLE-III: The Inner Milky Way's Rv ~ 2.5 Extinction Curve
• Numerical Methods of Star Formation History Measurement and Applications to Seven Dwarf Spheroidals
• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry
• Properties of stellar generations in Globular Clusters and relations with global parameters
• The Ages of 55 Globular Clusters as Determined Using an Improved delta V_TO^HB Method Along with Color-Magnitude Diagram Constraints, and Their Implications for Broader Issues
• 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
• Distance to M31 With the HST and Hipparcos Red Clump Stars
• Population effects on the Red Giant Clump absolute magnitude, and distance determinations to nearby galaxies
• Synthetic Stellar Photometry - I. General considerations and new transformations for broad-band systems
• The large-scale structure of the halo of the Andromeda Galaxy Part I: global stellar density, morphology and metallicity properties
• The Split Red Clump of the Galactic Bulge from OGLE-III
• The Panchromatic Hubble Andromeda Treasury X. Ultraviolet to Infrared Photometry of 117 Million Equidistant Stars
• Taking measure of the Andromeda halo: a kinematic analysis of the giant stream surrounding M31
• The Detailed Star Formation History in the Spheroid, Outer Disk, and Tidal Stream of the Andromeda Galaxy
• Evidence for a Significant Intermediate-Age Population in the M31 Halo from Main Sequence Photometry
• Inferring the Andromeda Galaxy's mass from its giant southern stream with Bayesian simulation sampling
• A Large Stellar Evolution Database for Population Synthesis Studies. III. Inclusion of the full Asymptotic Giant Branch phase and Web tools for stellar population analyses
• Investigating the Andromeda Stream: III. A Young Shell System in M31
• The three dimensional structure of the giant stellar stream in Andromeda
• Dynamics and Stellar Content of the Giant Southern Stream in M31. I. Keck Spectroscopy of Red Giant Stars
• The GHOSTS survey. II. The diversity of Halo Color and Metallicity Profiles of Massive Disk Galaxies
• The PAndAS view of the Andromeda satellite system - I. A Bayesian search for dwarf galaxies using spatial and color-magnitude information
• Global Properties of M31's Stellar Halo from the SPLASH Survey. I. Surface Brightness Profile
• A New Method for Isolating M31 Red Giant Stars: The Discovery of Stars out to a Radial Distance of 165 Kiloparsecs
• FORS2/VLT survey of Milky Way globular clusters II. Fe and Mg abundances of 51 Milky Way globular clusters on a homogeneous scale
• Isochrones for Old (> 5 Gyr) Stars and Stellar Populations. I. Models for $-2.4\le$ [Fe/H] $\le +0.6$, $0.25\le Y\le 0.33$, and $-0.4\le$ [$\alpha$\Fe] $\le +0.4$
• The Stellar Populations of M31 Halo Substructure
• 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
• The SPLASH Survey: A Spectroscopic Portrait of Andromeda's Giant Southern Stream
• Red Giant Branch Bump Brightness and Number Counts in 72 Galactic Globular Clusters Observed with the Hubble Space Telescope
• 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?
• Dynamics and Stellar Content of the Giant Southern Stream in M31. II. Interpretation
• 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
• Sodium and Oxygen Abundances in the Open Cluster NGC 6791 from APOGEE H-Band Spectroscopy
• The Extended Star Formation History of the Andromeda Spheroid at 35 Kpc on the Minor Axis
• Galactic halo stellar structures in the Triangulum-Andromeda region
• OGLE-III Detection of the Anomalous Galactic Bulge Red Giant Branch Bump: Evidence of Enhanced Helium Enrichment
• Two estimates of the distance to the Galactic centre
• A New Approach to Detailed Structural Decomposition from the SPLASH and PHAT Surveys: Kicked-up Disk Stars in the Andromeda Galaxy?
• PAndAS in the mist: The stellar and gaseous mass within the halos of M31 and M33
• Exploring Halo Substructure with Giant Stars: The Nature of the Triangulum-Andromeda Stellar Features
• Major Substructure in the M31 Outer Halo: Distances and Metallicities along the Giant Stellar Stream
• The insidious boosting of TP-AGB stars in intermediate-age Magellanic Cloud clusters
• The peculiar Na-O anticorrelation of the bulge globular cluster NGC 6440
• The Northern wraps of the Sagittarius Stream as traced by Red Clump stars: distances, intrinsic widths and stellar densities
• Global Properties of M31's Stellar Halo from the SPLASH Survey: III. Measuring the Stellar Velocity Dispersion Profile
• Deep Photometry of Andromeda Reveals Striking Similarities in the Tidal Stream and Spheroid Populations
• Stellar Stream and Halo Structure in the Andromeda Galaxy From a Subaru/Hyper Suprime-Cam Survey
• Formation of the Andromeda Giant Stream: Asymmetric Structure and Disc Progenitor
• Absolute Magnitudes of Seismic Red Clumps in the Kepler Field and SAGA: the age dependency of the distance scale
• Deep Optical Photometry of Six Fields in the Andromeda Galaxy
• Chemical Study of the Metal-rich Globular Cluster NGC 5927
• A rogues gallery of Andromeda's dwarf galaxies I. A predominance of red horizontal branches
• Deep Hubble Space Telescope Imaging of Globular Clusters Towards the Galactic Bulge: Observations, Data Reduction and Color-Magnitude Diagrams
• [$\alpha$/Fe] Abundances of Four Outer M 31 Halo Stars
• Stroemgren - near-infrared photometry of the Baade's Window. I. The bulge globular cluster NGC6528 and the surrounding field
• Stellar Populations in the Outer Disk and Halo of the Spiral Galaxy M101
• Cartography of Triangulum-Andromeda using SDSS stars
• A Detection of Gas Associated with the M 31 Stellar Stream

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• The survey of planetary nebulae in Andromeda (M31). IV. Radial oxygen and argon abundance gradients of the thin and thicker disc
• The Strikingly Metal-Rich Halo of the Sombrero Galaxy
• On the Color-Metallicity Relation of the Red Clump and the Reddening Toward the Magellanic Clouds
• Relative Ages of Nine Inner Milky Way Globular Clusters from Proper Motion Cleaned Color-Magnitude Diagrams
• Elemental Abundances in M31: Properties of the Inner Stellar Halo
• Metallicity distribution of the progenitor of the Giant Stellar Stream in the Andromeda Galaxy
• Kinematics and Metallicity of Red Giant Branch Stars in the Northeast Shelf of M31
• 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
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