arXiv subjects

Sandeep Kumar Kataria

Publications and source records attributed to Sandeep Kumar Kataria.

20 records · Page 2Linked to original sources

arXiv2019

The Effect of Bulge Mass on Bar Pattern Speed in Disk Galaxies

We present a study of the effect of bulge mass on the evolution of bar pattern speed in isolated disk galaxies using N-body simulations. Earlier studies have shown that disk stars at the inner resonances can transfer a significant amount of angular momentum to the dark matter halo and this results in the slow down of the bar pattern speed. In this paper we investigate how the mass of the other spheroidal component, the bulge, affects bar pattern speeds. In our galaxy models the initial bars are all rotating fast as the R parameter, which is the ratio of the corotation radius to bar radius is less than 1.4, which is typical of fast bars. However, as the galaxies evolve with time, the bar pattern speed ($Ω_p$ ) slows down leading to R $>$1.4 for all the models except for the model with the most massive bulge, in which the bar formed late and did not have time to evolve. The rapid slowdown of $Ω_p$ is due to the larger angular momentum transfer from the disk to the bulge, and is due to interactions between stars at the inner resonances and those in the bar. Hence we conclude that the decrease in $Ω_p$ clearly depends on bulge mass in barred galaxies and decreases faster for galaxies with more massive bulges. We discuss the implications of our results for observations of bar pattern speeds in galaxies.

astro-ph.GA↗

arXiv2017

A Study of the Effect of Bulges on Bar Formation in Disk galaxies

We use N-body simulations of bar formation in isolated galaxies to study the effect of bulge mass and bulge concentration on bar formation. Bars are global disk instabilities that evolve by transferring angular momentum from the inner to outer disks and to the dark matter halo. It is well known that a massive spherical component such as halo in a disk galaxy can make it bar stable. In this study we explore the effect of another spherical component, the bulge, on bar formation in disk galaxies. In our models we vary both the bulge mass and concentration. We have used two sets of models, one that has a dense bulge and high surface density disk. The second model has a less concentrated bulge and a lighter disk. In both models we vary the bulge to disk mass fraction from 0 to 0.7. Simulations of both the models show that there is an upper cutoff in bulge to disk mass ratio M b /M d above which bars cannot form; the cutoff is smaller for denser bulges( M b /M d = 0.2) compared to less denser ones (M b /M d = 0.5). We define a new criteria for bar formation in terms of bulge to disk radial force ratio (F b /F d ) at the disk scale lengths above which bars cannot form. We find that if F b /F d > 0.35, a disk is stable and a bar cannot form. Our results indicate that early type disk galaxies can still form strong bars in spite of having massive bulges.

astro-ph.GA↗