The dynamics of stellar discs in live dark-matter haloes

Fujii, Michiko S.; Bédorf, Jeroen; Baba, Junichi; Zwart, Simon Portegies

doi:10.1093/mnras/sty711

Cited by 45 publications

(81 citation statements)

References 63 publications

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“…We also find that the final state of the galactic disc is sensitive to the fraction of disc mass to the total mass of the galaxy (f d ) in the initial conditions. This parameter controls the bar instability in the sense that a larger value of f d causes the bar to form earlier (Fujii et al 2018). This parameter correlates with the radial velocity dispersion of the disc at R = 8 kpc but anti-correlates with the total surface density (Kz/sπG) at R = 8 kpc.…”

Section: Discussionmentioning

confidence: 99%

“…A developing galactic bar transfers a part of its angular momentum into the halo (Athanassoula 2002;Dubinski et al 2009). As a consequence, if the halo has an initial spin, the final bar becomes shorter (Long et al 2014;Fujii et al 2018). Widrow et al (2008) showed that galaxy models, similar to the MW, tend to develop bars that are too long when compared to observations.…”

Section: Dark-matter Halomentioning

confidence: 99%

“…In these Tables, we also summarize the disk-to-total mass fraction (f d ), which is measured for the mass within 2.2R d . In Fujii et al (2018), we showed that f d is a critical parameter to control the bar formation epoch. We therefore add f d to the model parameters.…”

Section: Galactic Discmentioning

confidence: 99%

“…In general, bars grow longer by transferring their angular momentum to the halo, and the pattern speed slows down (Athanassoula 2002). If the halo initially has a spin then the pattern speed of the bar increases and the bar length becomes shorter as the halo spin increases (Long et al 2014;Fujii et al 2018). For model MWc, we adopt a range of different halo spin parameters where we keep the other parameters fixed.…”

Section: Halo Spinmentioning

confidence: 99%

“…11. A larger f d results in earlier bar formation (Fujii et al 2018), which causes the velocity dispersion to increase as f d increases. The results of Fig.…”

Section: Comparison With Disc Observationsmentioning

confidence: 99%

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Modelling the Milky Way as a dry Galaxy

Fujii

Bédorf

Baba

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We construct a model for the Milky Way Galaxy composed of a stellar disc and bulge embedded in a dark-matter halo. All components are modelled as N -body systems with up to 8 billion equal-mass particles and integrated up to an age of 10 Gyr. We find that net angular-momentum of the dark-matter halo with a spin parameter of λ = 0.06 is required to form a relatively short bar (∼ 4 kpc) with a high pattern speed (40-50 km s −1 ). By comparing our model with observations of the Milky Way Galaxy, we conclude that a disc mass of ∼ 3.7 × 10 10 M and an initial bulge scale length and velocity of ∼ 1 kpc and ∼ 300 km s −1 , respectively, fit best to the observations. The disc-to-total mass fraction (f d ) appears to be an important parameter for the evolution of the Galaxy and models with f d ∼ 0.45 are most similar to the Milky Way Galaxy. In addition, we compare the velocity distribution in the solar neighbourhood in our simulations with observations in the Milky Way Galaxy. In our simulations the observed gap in the velocity distribution, which is expected to be caused by the outer Lindblad resonance (the so-called Hercules stream), appears to be a time-dependent structure. The velocity distribution changes on a time scale of 20-30 Myr and therefore it is difficult to estimate the pattern speed of the bar from the shape of the local velocity distribution alone.

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Section: Discussionmentioning

confidence: 99%

Section: Dark-matter Halomentioning

confidence: 99%

Section: Galactic Discmentioning

confidence: 99%

Section: Halo Spinmentioning

confidence: 99%

“…11. A larger f d results in earlier bar formation (Fujii et al 2018), which causes the velocity dispersion to increase as f d increases. The results of Fig.…”

Section: Comparison With Disc Observationsmentioning

confidence: 99%

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Modelling the Milky Way as a dry Galaxy

Fujii

Bédorf

Baba

et al. 2018

Monthly Notices of the Royal Astronomical Society

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The shapes of spiral arms in the S⁴G survey and their connection with stellar bars

Díaz-García¹,

Salo²,

Knapen³

et al. 2019

A&A

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Context. Spiral galaxies are very common in the local Universe, but their formation, evolution, and interplay with bars remain poorly understood after more than a century of astronomical research on the topic. Aims. We use a sample of 391 nearby galaxies from the S 4 G survey to characterise the winding angle and amplitude of spiral arms as a function of disc properties, such as bar strength, in all kinds of spirals (grand-design, multi-armed, and flocculent). Methods. We derived global pitch angles in 3.6 µm de-projected images from i) average measurements of individual logarithmic spiral segments, and ii) for a subsample of 32 galaxies, from 2-D Fourier analyses. The strength of spirals was quantified from the tangential-to-radial force ratio and from the normalised m = 2 Fourier density amplitudes. Results. In galaxies with more than one measured logarithmic segment, the spiral pitch angle varies on average by ∼ 10 • between segments, but by up to 15 − 20 • . The distribution of the global pitch angle versus Hubble type (T ) is very similar for barred and non-barred galaxies when 1 T 5. Most spiral galaxies (> 90%) are barred for T > 5. The pitch angle is not correlated with bar strength, and only weakly with spiral strength. The amplitude of spirals is correlated with bar strength (and less tightly, with bar length) for all types of spirals. The mean pitch angle is hardly correlated with the mass of the supermassive black hole (estimated from central stellar velocity dispersion), with central stellar mass concentration, or with shear, questioning previous results in the literature using smaller samples. Conclusions. We do not find observational evidence that spiral arms are driven by stellar bars or by invariant manifolds. Most likely, discs that are prone to the development of strong bars are also reactive to the formation of prominent spirals, explaining the observed coupling between bar and spiral amplitudes.

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Bulge formation through disc instability

Devergne

Cattaneo

Bournaud

et al. 2020

A&A

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We use simulations to study the growth of a pseudobulge in an isolated thin exponential stellar disc embedded in a static spherical halo. We observe a transition from later to earlier morphological types and an increase in bar prominence for higher disc-to-halo mass ratios, for lower disc-to-halo size ratios, and for lower halo concentrations. We compute bulge-to-total stellar mass ratios B/T by fitting a two-component Sérsic-exponential surface-density distribution. The final B/T is strongly related to the disc’s fractional contribution fd to the total gravitational acceleration at the optical radius. The formula B/T = 0.5 fd1.8 fits the simulations to an accuracy of 30%, is consistent with observational measurements of B/T and fd as a function of luminosity, and reproduces the observed relation between B/T and stellar mass when incorporated into the GALICS 2.0 semi-analytic model of galaxy formation.

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The dynamics of stellar discs in live dark-matter haloes

Cited by 45 publications

References 63 publications

Modelling the Milky Way as a dry Galaxy

Modelling the Milky Way as a dry Galaxy

The shapes of spiral arms in the S⁴G survey and their connection with stellar bars

Bulge formation through disc instability

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The dynamics of stellar discs in live dark-matter haloes

Cited by 45 publications

References 63 publications

Modelling the Milky Way as a dry Galaxy

Modelling the Milky Way as a dry Galaxy

The shapes of spiral arms in the S4G survey and their connection with stellar bars

Bulge formation through disc instability

Contact Info

Product

Resources

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The shapes of spiral arms in the S⁴G survey and their connection with stellar bars