2025/09/16 by K. Aditya, Aditya, K., Arunima Banerjee +1
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2509.12966
openalex publication_date 2025/09/16 · openalex created_date 2025/10/18 · openalex updated_date 2026/07/28
We investigate how stellar disks sustain their ultrathin structure throughout their evolution. We follow the evolution of ultrathin stellar disks with varying dark matter (DM) halo concentration (c) using collisionless N-body simulations with AREPO. We test models embedded in steep (c = 12), shallow (c = 2), and intermediate (c = 6) DM concentrations. Our models match the observed structural properties of the stellar disk in the low surface brightness (LSB) ultrathin galaxy FGC~2366, specifically its surface brightness, disk scalelength, and vertical thinness (hz/RD = 0.1), while excluding gas, allowing us to isolate the effects of DM. The internal disk heating mechanism driven by bars is suppressed in the LSB ultrathin stellar disks regardless of the DM concentration. The ratio of disk thickness (hz) to scalelength (RD) remains constant at ≤ 0.1 throughout their evolution. To clearly establish that the LSB nature of stellar disks is the key to preventing disk thickening, we construct the initial conditions by increasing the stellar mass fraction from fs ∼ 0.01 to 0.02 and 0.04, respectively, while keeping the total mass equal to 1011 M_\odot and hz/RD ≤ 0.1 unchanged. We find that models with a higher stellar mass fraction embedded in a shallow DM potential (c = 2) form bars and undergo significant disk thickening (hz/RD ≫ 0.1) concurrent with the bar growth. We conclude that if the LSB disks are thin to begin with, they remain so throughout their evolution in isolation, regardless of the concentration of the DM halo.