Tidally Induced Bars in Gas-rich Dwarf Galaxies Orbiting the Milky Way

Gajda, Grzegorz; Łokas, Ewa L.; Athanassoula, E.

doi:10.3847/1538-4357/aaea61

Cited by 14 publications

(15 citation statements)

References 111 publications

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“…Our results are in broad agreement with the recent work of Gajda et al (2018) who studied the formation and evolution of bars in dwarf galaxies orbiting the Milky Way. Although their initial dwarf model is stable against bar formation in isolation, the bars are tidally induced and the gas fractions considered are much higher (0.3 and 0.7), the dependence of their properties on the gas fraction is similar.…”

Section: Discussionsupporting

confidence: 93%

The effect of warm gas on the buckling instability in galactic bars

Łokas

2020

A&A

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By using N-body and hydro simulations, we study the formation and evolution of bars in galaxies with significant gas content focusing on the phenomenon of the buckling instability. The galaxies are initially composed of a spherical dark matter halo and only stellar, or stellar and gaseous, disks with parameters that are similar to the Milky Way and are evolved for 10 Gyr. We consider different values of the gas fraction f = 0 − 0.3 and in order to isolate the effect of the gas, we kept the fraction constant during the evolution by not allowing the gas to cool and form stars. The stellar bars that form in simulations with higher gas fractions are weaker and shorter, and they do not form at all for gas fractions that are higher than 0.3. The bar with a gas fraction of 0.1 forms sooner due to initial perturbations in the gas, but despite the longer evolution, it does not become stronger than the one in the collisionless case at the end of evolution. The bars in the gas component are weaker; they reach their maximum strength around 4 Gyr and later decline to transform into spheroidal shapes. The distortion of the stellar bar during the buckling instability is weaker for higher gas fractions and weakens the bar less significantly, but it has a similar structure both in terms of radial profiles and in face-on projections. For f = 0.2, the first buckling lasts significantly longer and the bar does not undergo the secondary buckling event, while for f = 0.3, the buckling does not occur. Despite these differences, all bars develop boxy/peanut shapes in the stellar and gas component by the end of the evolution, although their thickness is smaller for higher gas fractions.

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Section: Discussionsupporting

confidence: 93%

The effect of warm gas on the buckling instability in galactic bars

Łokas

2020

A&A

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“…The bar always forms at the first pericenter passage and becomes shorter in time but the spheroidal shape usually survives until the end of evolution which may explain the non-spherical appearance of dSph galaxies. If the gas is included in the progenitor dwarf the tidally induced stellar bars are weaker but the effect is strong only in gas-dominated dwarfs (Gajda et al 2018). On the other hand, if the gas was stripped by ram pressure in the hot halo of the Milky Way then the bars would survive.…”

Section: Tidal Stirringmentioning

confidence: 99%

Dark matter distribution and dynamics of dwarf spheroidal galaxies

Łokas¹

2019

Proc. IAU

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I review the current status of dynamical modelling of dwarf spheroidal galaxies focusing on estimates of their dark matter content. Starting with the simplest methods using the velocity dispersion profiles I discuss the inherent issues of mass-anisotropy degeneracy and contamination by unbound stars. I then move on to methods of increasing complexity, aiming to break the degeneracy, up to recent applications of the Schwarzschild orbit superposition method. The dynamical modelling is placed in the context of possible scenarios for the formation of dwarf spheroidal galaxies, including the tidal stirring model and mergers of dwarf galaxies. The two scenarios are illustrated with examples from simulations: a comparison between the tidal evolution of dwarfs with cuspy and cored dark matter profiles and the formation of a dwarf spheroidal with prolate rotation.

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“…Bars may either form spontaneously as a consequence of disc instability (e.g. see Athanassoula 2013, for a review) or in response to an interaction with a galaxy companion (Gajda et al 2018;Pettitt & Wadsley 2018). They can also be boosted and renewed by cold gas accretion (Combes 2014).…”

Section: Introductionmentioning

confidence: 99%

The Smallest Scale of Hierarchy Survey (SSH). II. Extended star formation and bar-like features in the dwarf galaxy NGC 3741: recent merger or ongoing gas accretion?

Annibali,

Bacchini,

Iorio

et al. 2022

Preprint

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Using Large Binocular Telescope deep imaging data from the Smallest Scale of Hierarchy Survey (SSH) and archival Hubble Space Telescope data, we reveal the presence of two elongated stellar features contiguous to a bar-like stellar structure in the inner regions of the dwarf irregular galaxy NGC 3741. These structures are dominated by stars younger than a few hundred Myr and collectively are about twice as extended as the old stellar component. These properties are very unusual for dwarf galaxies in the nearby Universe and difficult to explain by hydro-dynamical simulations. From the analysis of archival 21-cm observations, we find that the young stellar "bar" coincides with an HI high-density region proposed by previous studies to be a purely gaseous bar; we furthermore confirm radial motions of a few km/s, compatible with an inflow/outflow, and derive a steeply-rising rotation curve and high HI surface density at the center, indicating a very concentrated mass distribution. We propose that the peculiar properties of the stellar and gaseous components of NGC 3741 may be explained by a recent merger or ongoing gas accretion from the intergalactic medium, which caused gas inflows towards the galaxy center and triggered star formation a few hundred Myr ago. This event may explain the young and extended stellar features, the bar-like structure, the very extended HI disc and the central HI spiral arms. The high central HI density and the steeply rising rotation curve suggest that NGC 3741 may be the progenitor or the descendant of a starburst dwarf.

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Tidally Induced Bars in Gas-rich Dwarf Galaxies Orbiting the Milky Way

Cited by 14 publications

References 111 publications

The effect of warm gas on the buckling instability in galactic bars

The effect of warm gas on the buckling instability in galactic bars

Dark matter distribution and dynamics of dwarf spheroidal galaxies

The Smallest Scale of Hierarchy Survey (SSH). II. Extended star formation and bar-like features in the dwarf galaxy NGC 3741: recent merger or ongoing gas accretion?

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