Formation of the Andromeda Giant Stream: Asymmetric Structure and Disc Progenitor

Abstract

We focus on the evidence of a past minor merger discovered in the halo of the Andromeda galaxy (M31). Previous N-body studies have enjoyed moderate success in producing the observed giant stellar stream (GSS) and stellar shells in M31's halo. The observed distribution of stars in the halo of M31 shows an asymmetric surface brightness profile across the GSS; however, the effect of the morphology of the progenitor galaxy on the internal structure of the GSS requires further investigation in theoretical studies. To investigate the physical connection between the characteristic surface brightness in the GSS and the morphology of the progenitor dwarf galaxy, we systematically vary the thickness, rotation velocity and initial inclination of the disc dwarf galaxy in N-body simulations. The formation of the observed structures appears to be dominated by the progenitor's rotation. Besides reproducing the observed GSS and two shells in detail, we predict additional structures for further observations. We predict the detectability of the progenitor's stellar core in the phase-space density distribution, azimuthal metallicity gradient of the western shell-like structure and an additional extended shell in the north-western direction that may constrain the properties of the progenitor galaxy.

19 pages, 22 figures, accepted for MNRAS

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• 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
• Elemental Abundances in M31: First Alpha and Iron Abundance Measurements in M31's Giant Stellar Stream
• Stellar Stream and Halo Structure in the Andromeda Galaxy From a Subaru/Hyper Suprime-Cam Survey
• Elemental Abundances in M31: Gradients in the Giant Stellar Stream
• The survey of planetary nebulae in Andromeda (M31) VI. Kinematics of M31 inner-halo substructures and comparison with major-merger simulation predictions
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• The nature of the progenitor of the M31 North-western stream: globular clusters as milestones of its orbit
• Metallicities of Outer Halo M31 Globular Clusters from Integrated Light Calcium-II Triplet Spectroscopy
• Variability search in M 31 using Principal Component Analysis and the Hubble Source Catalog
• 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
• Destruction of the central black hole gas reservoir through head-on galaxy collisions
• The origin of the metallicity distributions of the NE and W stellar shelves in the Andromeda Galaxy
• 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
• AT 2016dah and AT 2017fyp: the first classical novae discovered within a tidal stream
• The origin of the black hole offset in M31
• Properties of the Lower Segment of M31's North West Stream