Diverse Stellar Haloes in Nearby Milky Way-Mass Disc Galaxies

Abstract

We have examined the resolved stellar populations at large galactocentric distances along the minor axis (from 10 kpc up to between 40 and 75 kpc), with limited major axis coverage, of six nearby highly-inclined Milky Way-mass disc galaxies using HST data from the GHOSTS survey. We select red giant branch stars to derive stellar halo density profiles. The projected minor axis density profiles can be approximated by power laws with projected slopes of between $-2$ and $-3.7$ and a diversity of stellar halo masses of $1-6\times 10^9{M}_{\odot }$, or $2-14\%$ of the total galaxy stellar masses. The typical intrinsic scatter around a smooth power law fit is $0.05-0.1$ dex owing to substructure. By comparing the minor and major axis profiles, we infer projected axis ratios $c/a$ at $\sim 25$ kpc between $0.4-0.75$. The GHOSTS stellar haloes are diverse, lying between the extremes charted out by the (rather atypical) haloes of the Milky Way and M31. We find a strong correlation between the stellar halo metallicities and the stellar halo masses. We compare our results with cosmological models, finding good agreement between our observations and accretion-only models where the stellar haloes are formed by the disruption of dwarf satellites. In particular, the strong observed correlation between stellar halo metallicity and mass is naturally reproduced. Low-resolution hydrodynamical models have unrealistically high stellar halo masses. Current high-resolution hydrodynamical models appear to predict stellar halo masses somewhat higher than observed but with reasonable metallicities, metallicity gradients and density profiles.

26 pages, 17 figures. Accepted for publication in MNRAS

References in corpus (26)

• Introducing the Illustris Project: Simulating the coevolution of dark and visible matter in the Universe
• The Mass-Metallicity Relation at z~2
• HyperLEDA. III. The catalogue of extragalactic distances
• Improving PARSEC models for very low mass stars
• New PARSEC evolutionary tracks of massive stars at low metallicity: testing canonical stellar evolution in nearby star forming dwarf galaxies
• The accretion origin of the Milky Way's stellar halo
• The Milky Way's circular velocity curve between 4 and 14 kpc from APOGEE data
• Tracing Galaxy Formation with Stellar Halos II: Relating Substructure in Phase- and Abundance-Space to Accretion Histories
• The Dual Origin of Stellar Halos
• Building Late-Type Spiral Galaxies by In-Situ and Ex-Situ Star Formation
• Halo Mass and Assembly History Exposed in the Faint Outskirts: the Stellar and Dark Matter Haloes of Illustris Galaxies
• The Dragonfly Nearby Galaxies Survey. I. Substantial variation in the diffuse stellar halos around spiral galaxies
• Parametrizing the Stellar Haloes of Galaxies
• The Overdensity in Virgo, Sagittarius Debris, and the Asymmetric Spheroid
• Global Properties of M31's Stellar Halo from the SPLASH Survey. I. Surface Brightness Profile
• 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
• On feathers, bifurcations and shells: the dynamics of tidal streams across the mass scale
• Stellar populations across the NGC4244 truncated galactic disk
• Rotation rates, sizes, and star formation efficiencies of a representative population of simulated disc galaxies
• Tracing the outer halo in a giant elliptical to 25 Reff
• Detection of a distinct metal-poor stellar halo in the early-type galaxy NGC 3115
• Point spread function tails and the measurements of diffuse stellar halo light around edge-on disc galaxies
• Deep Imaging of M51: a New View of the Whirlpool's Extended Tidal Debris
• The Stellar Mass of M31 as inferred by the Andromeda Optical & Infrared Disk Survey
• GHOSTS | Bulges, Halos, and the Resolved Stellar Outskirts of Massive Disk Galaxies

Cited by in corpus (15)

• The total stellar halo mass of the Milky Way
• 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 missing outskirts problem? Comparisons between stellar halos in the Dragonfly Nearby Galaxies Survey and the TNG100 simulation
• 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
• Formation of the Large Nearby Galaxies
• How Unusual is the Milky Way's Assembly History?
• d1005+68: A New Faint Dwarf Galaxy in the M81 Group
• The central spheroids of Milky Way mass-sized galaxies
• The Strikingly Metal-Rich Halo of the Sombrero Galaxy
• Elemental Abundances in M31: Iron and Alpha Element Abundances in M31's Outer Halo
• The Extended Disk Galaxy Exploration Science Survey: Description and Surface Brightness Profile Properties
• Is NGC 300 a pure exponential disk galaxy?
• Tilted outer and inner structures in edge-on galaxies?
• The "Building Blocks" of Stellar Halos