Anatomy of the Bar Instability in Cuspy Dark Matter Halos

Dubinski, John; Berentzen, I.; Shlosman, Isaac

doi:10.1088/0004-637x/697/1/293

Cited by 132 publications

(174 citation statements)

References 55 publications

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“…Hernquist & Weinberg 1992;Zhang 1999;Weinberg & Katz 2002;Athanassoula 2002Athanassoula , 2003Sellwood & Debattista 2006;Dubinski et al 2009;Saha et al 2010Saha et al , 2012, the important role played by a bar and spiral arms in galaxies has now been understood. Both a bar and spiral arms help in evolving an initially axisymmetric disc galaxy by redistributing energy and angular momentum so that the disc reaches a state of minimum energy configuration.…”

Section: Discussionmentioning

confidence: 99%

Angular momentum transport and evolution of lopsided galaxies

Saha¹,

Jog²

2014

Monthly Notices of the Royal Astronomical Society

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The surface brightness distribution in the majority of stellar galactic discs falls off exponentially. Often what lies beyond such a stellar disc is the neutral hydrogen gas whose distribution also follows a nearly exponential profile at least for a number of nearby disc galaxies. Both the stars and gas are commonly known to host lopsided asymmetry especially in the outer parts of a galaxy. The role of such asymmetry in the dynamical evolution of a galaxy has not been explored so far.Following Lindblad's original idea of kinematic density waves, we show that the outer part of an exponential disc is ideally suitable for hosting lopsided asymmetry. Further, we compute the transport of angular momentum in the combined stars and gas disc embedded in a dark matter halo. We show that in a pure star and gas disc, there is a transition point where the free precession frequency of a lopsided mode, Ω − κ, changes from retrograde to prograde and this in turn reverses the direction of angular momentum flow in the disc leading to an unphysical behaviour. We show that this problem is overcome in the presence of a dark matter halo, which sets the angular momentum flow outwards as required for disc evolution, provided the lopsidedness is leading in nature. This, plus the well-known angular momentum transport in the inner parts due to spiral arms, can facilitate an inflow of gas from outside perhaps through the cosmic filaments.

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Section: Discussionmentioning

confidence: 99%

Angular momentum transport and evolution of lopsided galaxies

Saha¹,

Jog²

2014

Monthly Notices of the Royal Astronomical Society

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“…The growth rate of a bar in a disk galaxy depends on various parameters of the disk and its gravitational interaction with the surrounding dark matter halo and preexisting ClB (if present). Numerous studies of N-body simulations show that a bar forms and grows rapidly in a cold rotating stellar disk with Toomre Q close to 1 (Hohl 1971;Sellwood & Wilkinson 1993;Athanassoula 2002;Dubinski et al 2009, and references therein). Swing amplification (Toomre 1981) and cooperation of orbital streams (Earn & Lynden-Bell 1996) are thought to play a key role in the bar growth.…”

Section: Growth Of a Bar And Its Size Evolutionmentioning

confidence: 99%

“…It is not clear to us whether this is due to the lower particle resolution in the current models (2.2 million particles). Since a low-resolution noisy simulation could artificially enhance the star-star encounters and knock stars off their resonant orbits, Holley-Bockelmann et al (2005) and Dubinski et al (2009) suggested -based on their explicit study on the model resolution and resonant behaviourthat models with a few million particles generally show convergent behaviour.…”

Section: Angular Momentum Transfer and Orbital Analysismentioning

confidence: 99%

Spin-up of massive classical bulges during secular evolution

Saha

Gerhard

Martínez-Valpuesta

2016

A&A

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Context. Classical bulges in spiral galaxies are known to rotate, but the origin of this observed rotational motion is not well understood. It has been shown recently that a low-mass classical bulge (ClB) in a barred galaxy can acquire rotation by absorbing a significant fraction of the angular momentum emitted by the bar. Aims. Our aim here is to investigate whether bars can also spin up more massive ClBs during the secular evolution of the bar, and to study the kinematics and dynamics of these ClBs. Methods. We use a set of self-consistent N-body simulations to study the interaction of ClBs with a bar that forms self-consistently in the disk. We use orbital spectral analysis to investigate the angular momentum gain by the classical bulge stars. Results. We show that the ClBs gain on average 2−6% of the disk's initial angular momentum within the bar region. Most of this angular momentum gain occurs via low-order resonances, particularly 5:2 resonant orbits. A density wake forms in the ClB which corotates and aligns with the bar at the end of the evolution. The spin-up process creates a characteristic linear rotation profile and mild tangential anisotropy in the ClB. The induced rotation is small in the centre, but is significant beyond ∼2 bulge half mass radii, where it leads to mass-weighted V/σ ∼ 0.2, and reaches a local V max /σ in ∼ 0.5 at around the scale of the bar. The resulting V/σ is tightly correlated with the ratio of the bulge size to the bar size. In all models, a box/peanut bulge forms suggesting that composite bulges may be common. Conclusions. Bar-bulge resonant interaction in barred galaxies can provide some spin-up of massive ClBs, but the process appears to be less efficient than for low-mass ClBs. Further angular momentum transfer due to nuclear bars or gas inflow would be required to explain the observed rotation if it is not primordial.

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“…The oscillations between trailing and leading ends of the bar could be related to the oscillations seen in the bar growth in N-body simulations (e.g. [24]) and may be due to non-linear coupling modes between the bar and spiral arms [25]. The leading ends of the bar are important for modelling the long bar observations.…”

Section: A Model For the Milky Way's Bar And Bulge Formed Through Secmentioning

confidence: 95%

Unifying the planar bar and the boxy bulge of the Milky Way

Martínez-Valpuesta

Gerhard

2012

EPJ Web of Conferences

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Abstract. For some time the Milky Way has been understood as a barred disk galaxy. Star count observations have provided evidence for two bars at apparently different orientations, the boxy bulge and a long planar bar. We report recent work in which we argued for a scenario where these observations can be reproduced with a single boxy bulge/bar: an evolved bar from the stellar disk and the corresponding boxy bulge generated from it through secular evolution and buckling instability. We calculated the star count distributions along different lines-of-sight for a simulated barred galaxy and an observer at the Sun position, and compared them with observations of red clump magnitude distributions. We found a good agreement between the model and the observations, even though the simulation has a single boxy bulge/bar. In this model, the different apparent orientations of the boxy bulge and planar bar are partially due to the volume effect and partially to the leading ends of the bar.

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Anatomy of the Bar Instability in Cuspy Dark Matter Halos

Cited by 132 publications

References 55 publications

Angular momentum transport and evolution of lopsided galaxies

Angular momentum transport and evolution of lopsided galaxies

Spin-up of massive classical bulges during secular evolution

Unifying the planar bar and the boxy bulge of the Milky Way

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