The Effects of Boxy/Peanut Bulges on Galaxy Models

Abstract

We examine the effects that the modelling of a Boxy/Peanut (B/P) bulge will have on the estimates of the stellar gravitational potential, forces, orbital structure and bar strength of barred galaxies. We present a method for obtaining the potential of disc galaxies from surface density images, assuming a vertical density distribution (height function), which is let to vary with position, thus enabling it to represent the geometry of a B/P. We construct a B/P height function after the results from a high-resolution, N-body+SPH simulation of an isolated galaxy and compare the resulting dynamical model to those obtained with the commonly used, position-independent "flat" height functions. We show that methods that do not allow for a B/P can induce errors in the forces in the bar region of up to 40% and demonstrate that this has a significant impact on the orbital structure of the model, which in turn determines its kinematics and morphology. Furthermore, we show that the bar strength is reduced in the presence of a B/P. We conclude that neglecting the vertical extent of a B/P can introduce considerable errors in the dynamical modelling. We also examine the errors introduced in the model due to uncertainties in the parameters of the B/P and show that even for generous but realistic values of the uncertainties, the error will be noticeably less than that of not modelling a B/P bulge at all.

Accepted for publication in MNRAS

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Cited by in corpus (13)

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• 2D kinematic signatures of boxy/peanut bulges
• Structural and photometric properties of barred galaxies from the Auriga cosmological simulations
• Identifying resonances of the Galactic bar in Gaia DR2: II. Clues from angle space
• Applying Schwarzschild's orbit superposition method to barred or non-barred disc galaxies
• Bars & boxy/peanut bulges in thin & thick discs: I. Morphology and line-of-sight velocities of a fiducial model
• Survival of molecular gas in a stellar feedback-driven outflow witnessed with the MUSE TIMER project and ALMA
• Constraining the dark matter content of NGC 1291 using hydrodynamic gas response simulations
• Bars and boxy/peanut bulges in thin and thick discs III. Boxy/peanut bulge formation and evolution in presence of thick discs
• Double X/Peanut Structures in Barred Galaxies -- Insights from an $N$--body Simulation
• Early Growing Supermassive Black Holes Strengthen Bars and Boxy/Peanut Bulges
• Deprojection of external barred galaxies from photometry