2024/01/09 by Jun Lin, Rui Guo, Lin, Jun +12 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2401.04688
openalex publication_date 2024/01/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We select 1,052,469 (754,635) thin disk stars from \it Gaia eDR3 and LAMOST DR7 in the range of Galactocentric radius R (guiding center radius Rg) from 8 to 11 kpc to investigate the asymmetries between the North and South of the disk midplane. More specifically we analyze the vertical velocity dispersion profiles (σ_vz(z)) in different bins of R (Rg) and [Fe/H]. We find troughs in the profiles of σ_vz(z) located in both the North (z ∼ 0.7 kpc) and South (z ∼ -0.5 kpc) of the disk at all radial and chemical bins studied. The difference between the Northern and Southern vertical velocity dispersion profiles (Δσ_vz(|z|)) shows a shift between curves of different R and Rg. A similar shift exists in these NS asymmetry profiles further divided into different [Fe/H] ranges. The sample binned with Rg more clearly displays the features in the velocity dispersion profiles. The shift in the peaks of the Δσ_vz profiles and the variation in the phase spiral shape binned by metallicity indicate the variation of the vertical potential profiles and the radial metallicity gradient. The wave-like signal in NS asymmetry of σ_vz(z) largely originates from phase spiral; while the NS asymmetry profiles of [Fe/H] only display a weak wave-like feature near solar radius. We perform a test particle simulation to qualitatively reproduce the observed results. A quantitative explanation of the NS asymmetry in the metallicity profile needs careful consideration of the spiral shape and the perturbation model, and we leave this for future work.