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Can A Kinematically Hot and Thick Disk Form A Bar? : Role of Highly Spinning Dark Matter Halos

Sandeep Kumar Kataria

TL;DR

The paper investigates how bars form in kinematically hot, thick galactic disks by examining the role of dark matter halo spin. Using controlled N-body simulations of a Milky Way–like disk in both non-rotating and highly spinning halos (Λ = 0.1), it shows that a spinning halo can trigger bar formation after several Gyr, accompanied by an ~8-fold increase in angular momentum transfer from disk to halo. Classic bar-formation criteria (Ostriker-Peebles, ELN) fail to predict this spin-induced instability, and the Jang-Kim criterion also misses the spinning-halo case, indicating the need for halo-spin–aware diagnostics. The results help explain the presence of bars in high-redshift, thick disks and highlight the importance of halo spin in secular galactic evolution.

Abstract

Recent JWST observations claim the existence of a significant fraction of bars in the kinematically hotter and thicker disk at high redshift Universe. These observations challenge the current understanding of disk stability in galaxies similar to the Milky Way. The analytical work and N-body simulations suggest that the kinematically hot (dispersion-dominated) and thick disk are stable against bar formation. In this work, we perform the controlled N-body simulations of a kinematically hot and thick disk, which is residing in a non-rotating and spinning dark matter halo. We report that the disk, which is classically stable against bar instability in the live and non-rotating halo, leads to bar formation in a spinning halo environment. The spinning halo model is 8 times more efficient in transporting angular momentum from the disk to the halo compared to the non-spinning halo. We claim that Ostriker-Peebles and ELN bar formation criteria do not predict bar formation for both the non-roating and spinning halo. The recent criteria from Jang-Kim successfully predict the bar stability for the non-rotating halo model, but not for the spinning halo model. These results provide an important insight into the bar formation processes for thick and hot disks at high redshift.

Can A Kinematically Hot and Thick Disk Form A Bar? : Role of Highly Spinning Dark Matter Halos

TL;DR

The paper investigates how bars form in kinematically hot, thick galactic disks by examining the role of dark matter halo spin. Using controlled N-body simulations of a Milky Way–like disk in both non-rotating and highly spinning halos (Λ = 0.1), it shows that a spinning halo can trigger bar formation after several Gyr, accompanied by an ~8-fold increase in angular momentum transfer from disk to halo. Classic bar-formation criteria (Ostriker-Peebles, ELN) fail to predict this spin-induced instability, and the Jang-Kim criterion also misses the spinning-halo case, indicating the need for halo-spin–aware diagnostics. The results help explain the presence of bars in high-redshift, thick disks and highlight the importance of halo spin in secular galactic evolution.

Abstract

Recent JWST observations claim the existence of a significant fraction of bars in the kinematically hotter and thicker disk at high redshift Universe. These observations challenge the current understanding of disk stability in galaxies similar to the Milky Way. The analytical work and N-body simulations suggest that the kinematically hot (dispersion-dominated) and thick disk are stable against bar formation. In this work, we perform the controlled N-body simulations of a kinematically hot and thick disk, which is residing in a non-rotating and spinning dark matter halo. We report that the disk, which is classically stable against bar instability in the live and non-rotating halo, leads to bar formation in a spinning halo environment. The spinning halo model is 8 times more efficient in transporting angular momentum from the disk to the halo compared to the non-spinning halo. We claim that Ostriker-Peebles and ELN bar formation criteria do not predict bar formation for both the non-roating and spinning halo. The recent criteria from Jang-Kim successfully predict the bar stability for the non-rotating halo model, but not for the spinning halo model. These results provide an important insight into the bar formation processes for thick and hot disks at high redshift.
Paper Structure (5 sections, 5 equations, 6 figures, 1 table)

This paper contains 5 sections, 5 equations, 6 figures, 1 table.

Table of Contents

  1. Introduction
  2. Numerical Methods
  3. Results
  4. Discussion
  5. Summary

Figures (6)

  • Figure 1: The galaxy model's rotation curve and the contribution from disk and halo separately.
  • Figure 2: Radial variation of Toomre Q parameter for the initial galaxy disk for galaxy model.
  • Figure 3: Time evolution of bar strengths for models with spin=0 (S000) and spin=0.1 (S100).
  • Figure 4: Time evolution of face-on and edge-on stellar density maps of disk for the model with spin=0 (S000). The dashed line corresponds to iso-density contours in each of the maps.
  • Figure 5: Time evolution of face-on and edge-on stellar density maps of disk for a model with spin=0.1 (S100). The dashed line corresponds to iso-density contours in each of the maps.
  • ...and 1 more figures