Radial alignment of elliptical galaxies by the tidal force of a cluster of galaxies

Abstract

Unlike the random radial orientation distribution of field elliptical galaxies, galaxies in a cluster are expected to point preferentially towards the center of the cluster, as a result of the cluster's tidal force on its member galaxies. In this work an analytic model is formulated to simulate this effect. The deformation time scale of a galaxy in a cluster is usually much shorter than the time scale of change of the tidal force; the dynamical process of the tidal interaction within the galaxy can thus be ignored. An equilibrium shape of a galaxy is then assumed to be the surface of equipotential, which is the sum of the self-gravitational potential of the galaxy and the tidal potential of the cluster at this location. We use a Monte-Carlo method to calculate the radial orientation distribution of these galaxies, by assuming the NFW mass profile of the cluster and the initial ellipticity of field galaxies. The radial angles show a single peak distribution centered at zero. The Monte-Carlo simulations also show that a shift of the reference center from the real cluster center weakens the anisotropy of the radial angle distribution. Therefore, the expected radial alignment cannot be revealed if the distribution of spatial position angle is used instead of that of radial angle. The observed radial orientations of elliptical galaxies in cluster Abell~2744 are consistent with the simulated distribution.

8 pages, 6 figures, 2 tables. MNRAS in press

References in corpus (5)

• CIRS: Cluster Infall Regions in the Sloan Digital Sky Survey I. Infall Patterns and Mass Profiles
• Combining Lens Distortion and Depletion to Map the Mass Distribution of A1689
• Three Different Types of Galaxy Alignment within Dark Matter Halos
• X-ray properties in massive galaxy clusters: XMM-Newton observations of the REFLEX-DXL sample
• Radial Alignment in Simulated Clusters

Cited by in corpus (10)

• Tidal alignment of galaxies
• Time evolution of intrinsic alignments of galaxies
• Unveiling the Intrinsic Alignment of Galaxies with Self-Calibration and DECaLS DR3 data
• Intrinsic Morphology of Ultra-diffuse Galaxies
• KiDS-1000: cross-correlation with Planck cosmic microwave background lensing and intrinsic alignment removal with self-calibration
• Exploring the origin of ultra-diffuse galaxies in clusters from their primordial alignment
• The Next Generation Fornax Survey (NGFS): VI. The Alignment of Dwarf Galaxies in The Fornax Cluster
• Primordial alignment of elliptical galaxies in intermediate redshift clusters
• Living with Neighbors. III. The Origin of the Spin$-$Orbit Alignment of Galaxy Pairs: A Neighbor versus the Large-scale Structure
• Mock Observations: Three Different Types of Galaxy Alignment in TNG100 Simulations