Secular bar formation in galaxies with a significant amount of dark matter

By Octavio Valenzuela, Anatoly Klypin. 2002

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Using high resolution N-body simulations of stellar disks embedded in cosmologically motivated dark matter halos, we study the evolution of bars and the transfer of angular momentum between halos and bars. We find that dynamical friction results in some transfer of angular momentum to the halo, but the effect is much smaller than previously found in low resolution simulations and is incompatible with early analytical estimates. After 5 Gyrs of evolution the stellar component loses only 5% – 7% of its initial angular momentum. Mass and force resolutions are crucial for the modeling of bar dynamics. In low resolution (300 – 500 pc) simulations we find that the bar slows down and angular momentum is lost relatively fast. In simulations with millions of particles reaching a resolution of 20-40 pc, the pattern speed may not change over billions of years. Our high resolution models produce bars which are fast rotators, where the ratio of the corotation radius to the bar major semi-axis lies in the range R = 1.2 1.7, marginally compatible with observational results. In contrast to many previous simulations, we find that bars are relatively short. As in many observed cases, the bar major semi-axis is close to the exponential length of the disk. The transfer of angular momentum between inner and outer parts of the disk plays a very important role in the secular evolution of the disk and the bar. The bar formation increases the exponential length of the disk by a factor of 1.2 -1.5. The transfer substantially increases the stellar mass in the center of the galaxy and decreases the dark matter-to-baryons ratio. As the result, the central 2 kpc region is always strongly dominated by the baryonic component. At intermediate (3 – 10 kpc) scales the disk is sub-dominant. These models demonstrate that the efficiency of angular momentum transfer to the dark matter has been greatly overestimated. More realistic models produce bar structure in striking agreement with observational results.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/5b7f110889969d997451f656ff14ffd4bae1f3a1

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Citations in the corpus

Radial migration in disc galaxies — I. Transient spiral structure and dynamics (2011, methodology): “…most resolutions udies have addressed the resonant couplings between dark matter hlos and bars, but again most often only collisionless simulations were used (e.g. Debattista & Sellwood 2000; Valenzuela & Klypin 2003; Holley-Bockelmann et al. 2005; Weinberg & Katz 2007; Dubinski et al. 2009).”
The Formation of a Realistic Disk Galaxy in Λ-dominated Cosmologies (2002, background): “Once a disk of baryonic material is formed, disk instabilities might redistribute the original angular momentum of the disk both internally and to the dark matter halo (Weinberg & Katz, Valenzuela & Klypin 2003).”
Generating Equilibrium Dark Matter Halos: Inadequacies of the Local Maxwellian Approximation (2003, background): “…& Goodman 1986; Velázquez & White 1999; Taylor & Babul 2001; Font et al. 2001), the susceptibility of disks to bar instabilities (Mihos, McGaugh, & de Blok 1997), and the effects of these bars on halo central density cusps (Debattista & Sellwood 2000; Athanassoula 2002; Valenzuela & Klypin 2003).”
Dynamical Blueprints for Galaxies (2008, methodology): “An alternative approach is to use cosmological models of halo and galaxy formation to guide ones choice of the halo parameters (see, e.g., Valenzuela & Klypin 2003), but given uncertainties in the exact nature of adiabatic compression, variations among halo profiles found in different simulations,…”
A Revised Model for the Formation of Disk Galaxies: Low Spin and Dark Halo Expansion (2006, background): “Furthermore, the fraction of angular momentum that is lost to the halo is expected to be fairly small (e.g., Weinberg 1985; Debattista & Sellwood 2000; Valenzuela & Klypin 2003; O'Neill & Dubinski 2003), so that f t is expected to be close to unity.”
How Large Are the Bars in Barred Galaxies (2005, methodology): “There is similar variation in how bars are measured even when the galaxy is readily accessible; i.e., in n-body simulations – compare, for example, Debattista & Sellwood (2000), Athanassoula & Misiriotis (2002), and Valenzuela & Klypin (2003).”
Forming disc galaxies in ΛCDM simulations (2006, background): “Secular processes, E-mail: fabio@astro.washington.edu such as external gas accretion or gas displacement due to bars, may play a more important role in galaxy evolution at later epochs (Valenzuela & Klypin 2003; Debattista et al. 2004; Kormendy & Kennicutt 2004).”
Equilibrium Disk-Bulge-Halo Models for the Milky Way and Andromeda Galaxies (2005, methodology): “This approach has already been applied to the MilkyWay by Sellwood (1985, 1993), Fux (1997), and Valenzuela & Klypin (2003).”
Ejection of Supermassive Black Holes from Galaxy Cores (2007, background): “A number of other authors have reported low effective values of the dynamical friction force as it acs on massive objects that inspiral into constant-density cores (Bontekoe 1988; Bertin et al. 2003; Read et al. 2006) or on rotating bars (Weinberg & Katz 2002; Valenzuela & Klypin 2003).”
Galaxy Masses: A Review (2013, background): “However, some of these claims have been challenged on account of numerical artifacts yielding e.g. over-efficient bar slow down (Valenzuela & Klypin 2003).”
THE OUTER DISKS OF EARLY-TYPE GALAXIES. I. SURFACE-BRIGHTNESS PROFILES OF BARRED GALAXIES (2007, methodology): “These appear similar to profiles seen in N -body simulations of bar formation (e.g., Athanassoula & Misiriotis 2002; Valenzuela & Klypin 2003), and thus we suspect they are stellar-dynamical side effects of the barformation process.”
Bar Diagnostics in Edge-On Spiral Galaxies. III. N-Body Simulations of Disks (2004, background): “Only few experiments with a cosmologically motivated (but still idealized) halo (Navarro et al. 1996) have been reported so far (e.g., Valenzuela & Klypin 2003; Mayer &Wadsley 2004).”
Bar formation and evolution in disc galaxies with gas and a triaxial halo: morphology, bar strength and halo properties (2012, background): “…(e.g. Debattista & Sellwood 2000; Athanassoula 2002; Athanassoula & Misiriotis 2002; Athanassoula 2003, hereafter A03; O’Neill & Dubinski 2003; Valenzuela & Klypin 2003; Holley-Bockelmann, Weinberg & Katz 2005; Martinez-Valpuesta, Shlosman & Heller 2006; Dubinski, Berentzen & Shlosman 2009).”