Architecture of the Andromeda: a quantitative analysis of clustering in the inner stellar halo

Abstract

We present a quantitative measurement of the amount of clustering present in the inner $\sim 30$ kpc of the stellar halo of the Andromeda galaxy (M31). For this we analyse the angular positions and radial velocities of the carefully selected Planetary Nebulae (PNe) in the M31 stellar halo. We study the cumulative distribution of pair-wise distances in angular position and line of sight velocity space, and find that the M31 stellar halo contains substantially more stars in the form of close pairs as compared to that of a featureless smooth halo. In comparison to a smoothed/scrambled distribution we estimate that the clustering excess in the M31 inner halo is roughly $40\%$ at maximum and on average $\sim 20\%$. Importantly, comparing against the 11 stellar halo models of \cite{2005ApJ...635..931B}, which were simulated within the context of the $\Lambda \mathrm{CDM}$ cosmological paradigm, we find that the amount of substructures in the M31 stellar halo closely resembles that of a typical $\Lambda \mathrm{CDM}$ halo.

9 pages, to appear in MNRAS

References in corpus (16)

• galpy: A Python Library for Galactic Dynamics
• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• 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 Dual Origin of Stellar Halos
• On the Shoulders of Giants: Properties of the Stellar Halo and the Milky Way Mass Distribution
• The spatial distribution of the Milky Way and Andromeda satellite galaxies
• A deep kinematic survey of planetary nebulae in the Andromeda Galaxy using the Planetary Nebula Spectrograph
• M31 Transverse Velocity and Local Group Mass from Satellite Kinematics
• The outer halo globular cluster system of M31 - I. The final PAndAS catalogue
• Global Properties of M31's Stellar Halo from the SPLASH Survey. I. Surface Brightness Profile
• Stellar Kinematics in the Complicated Inner Spheroid of M31: Discovery of Substructure Along the Southeastern Minor Axis and its Relationship to the Giant Southern Stream
• Wide-Field Survey of Globular Clusters in M31. II. Kinematics of the Globular Cluster System
• Planetary Nebula Velocities in the Disk and Bulge of M31
• Spatial and Velocity clumping in an SDSS blue horizontal branch star catalogue

Cited by in corpus (3)

• The Need for Speed: Escape velocity and dynamical mass measurements of the Andromeda galaxy
• Global Properties of M31's Stellar Halo from the SPLASH Survey: III. Measuring the Stellar Velocity Dispersion Profile
• Modeling the Cosmic Dispersion Measure in the D < 120 Mpc Local Universe