148 research outputs found
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.Comment: Accepted at MNRAS,12 pages, 19 figure
Antecedents and Consequences of Earnings Management: A Systematic Review of the Banking Sector in Developed and Developing Countries
The accuracy and utility of financial information are critical, but the prevalent issue of earnings management (EM) casts a shade on this goal. With a growing corpus of EM literature, a comprehensive review is essential for distilling insights and guiding future research. The paper systematically reviews 182 EM studies through the distinctive lens of developing and developed country banking institutions. With an emphasis on accrual-EM, the current study thoroughly examines and synthesizes the antecedents and consequences of bank EM. Notably, certain themes (such as corporate governance, international financial reporting standards, ownership structure and liquidity) emerge as universally relevant, bridging the gap between developed and developing markets. Conversely, themes like bank efficiency, social capital, funding structure and institutional quality, among others, tend to be context-specific. Further, the study developed a conceptual framework of antecedents and consequences of bank EM by segregating them into developed, developing, and cross-country contexts. The study is unique in its developed and developing context of appraising EM literature. The results provide a better understanding of pertinent elements in diverse institutional settings that can aid regulators and policymakers in making decisions by identifying facilitators, mitigators and consequences in developed and developing economies
Modelling Dark Matter Halo Spin using Observations and Simulations: application to UGC 5288
Dark matter (DM) halo properties are extensively studied in cosmological
simulations but are very challenging to estimate from observations. The DM halo
density profile of observed galaxies is modelled using multiple probes that
trace the dark matter potential. However, the angular momentum distribution of
DM halos is still a subject of debate. In this study we investigate a method
for estimating the halo spin and halo concentration of low surface brightness
(LSB), gas-rich dwarf barred galaxy UGC 5288, by forward modelling disk
properties derived from observations - stellar and gas surface densities, disk
scale length, HI rotation curve, bar length and bar ellipticity. We combine
semi-analytical techniques, N-body/SPH and cosmological simulations to model
the DM halo of UGC 5288 with both a cuspy Hernquist profile and a flat-core
pseudo-isothermal profile. We find that the best match with observations is a
pseudo-isothermal halo model with a core radius of kpc, and halo
spin of = 0.08 at the virial radius. Although our findings are
consistent with previous core radius estimates of the halo density profile of
UGC 5288, as well as with the halo spin profiles of similar mass analogues of
UGC5288 in the high-resolution cosmological-magneto-hydrodynamical simulation
TNG50, there still remain some uncertainties as we are limited in our knowledge
of the formation history of the galaxy. Additionally, we find that the inner
halo spin ( kpc) in barred galaxies is different from the unbarred
ones, and the halo spin shows weak correlations with bar properties.Comment: 29 pages including Appendix, 28 figures, accepted in MNRAS, comments
are welcome from the communit
Testing a theoretical prediction for bar formation in galaxies with bulges
Earlier studies have shown that massive bulges impede bar formation in disk
galaxies. Recent N-body simulations have derived a bar formation criterion that
depends on the radial bulge force in a galaxy disk. We use those simulations to
show that bars can form only when the force constant FB < 0.13, where FB
depends on the ratio of the bulge force to the total force of the galaxy at
twice the disk scale length 2R d . In this article, we test this theoretical
prediction using observational data obtained from the literature. Our sample
consists of 63 barred galaxies with a wide range of Hubble classes from the S 4
G catalogue for which bulge, disk and bar decomposition has been done. We find
that 92 % of our sample galaxies satisfy the condition FB < 0.13 for bar
formation in galaxies and hence agree with the bar formation criterion given by
the simulations.Comment: 7 pages, 5 figures, accepted for publication in A&
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