Lopsided Galaxies in a cosmological context: a new galaxy-halo connection

Abstract

Disc galaxies commonly show asymmetric features in their morphology, such as warps and lopsidedness. These features can provide key information regarding the recent evolution of a given disc galaxy. In the nearby Universe, up to $\sim 30$ percent of late-type galaxies display a global non-axisymmetric lopsided mass distribution. However, the origin of this perturbation is not well understood. In this work, we study the origin of lopsided perturbations in simulated disc galaxies extracted from the TNG50 simulation of the IllustrisTNG project. We statistically explore different excitation mechanisms for this perturbation, such as direct satellite tidal interactions and distortions of the underlying dark matter distributions. We also characterize the main physical conditions that lead to lopsided perturbations. 50 percent of our sample galaxy have lopsided modes $m=1$ greater than $\sim 0.12$. We find a strong correlation between internal galaxy properties, such as central stellar surface density and disc radial extension with the strength of lopsided modes. The majority of lopsided galaxies have lower central surface densities and more extended discs than symmetric galaxies. As a result, such lopsided galaxies are less self-gravitationally cohesive, and their outer disc region is more susceptible to different types of external perturbations. However, we do not find strong evidence that tidal interactions with satellite galaxies are the main driving agent of lopsided modes. Lopsided galaxies tend to live in asymmetric dark matter halos with high spin, indicating strong galaxy-halo connections in late-type lopsided galaxies.

16 pages, 16 figures, accepted for publication in MNRAS

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• IllustrisTNG in the HSC-SSP: image data release and the major role of mini mergers as drivers of asymmetry and star formation
• JWST/CEERS sheds light on dusty star-forming galaxies: forming bulges, lopsidedness and outside-in quenching at cosmic noon
• The evolutionary pathways of disk galaxies with different sizes
• A statistical study of lopsided galaxies using random forest
• Tracing the origins of galaxy lopsidedness across cosmic time
• Distinguishing Ram Pressure from Tidal Interactions: the Size-Shape Difference (SSD) measure
• Morphological evolution of disk galaxies and their concentration, asymmetry and clumpiness (CAS) properties in simulations across Toomre's $Q$ parameter
• Identifying lopsidedness in spiral galaxies using a Deep Convolutional Neural Network
• Aligned and misaligned metallicity gradients in young stars and star-forming regions in the EAGLE discs