Stellar Orbital Studies in Normal Spiral Galaxies I: Restrictions to the Pitch Angle

Abstract

We built a family of non-axisymmetric potential models for normal non-barred or weakly-barred spiral galaxies as defined in the simplest classification of galaxies: the Hubble sequence. For this purpose a three-dimensional self-gravitating model for spiral arms PERLAS is superimposed to the galactic axisymmetric potentials. We analyze the stellar dynamics varying only the pitch angle of the spiral arms, from 4$°$ to 40$°$, for an Sa galaxy, from 8$°$ to 45$°$, for an Sb galaxy, and from 10$°$ to 60$°$, for an Sc galaxy. Self-consistency is indirectly tested through periodic orbital analysis, and through density response studies for each morphological type. Based on ordered behavior, periodic orbits studies show that for pitch angles up to approximately $15°$, $18°$, and $20°$ for Sa, Sb and Sc galaxies, respectively, the density response supports the spiral arms potential, a requisite for the existence of a long-lasting large-scale spiral structure. Beyond those limits, the density response tends to "avoid" the potential imposed by mantaining lower pitch angles in the density response; in that case the spiral arms may be explained as transient features rather than long-lasting large-scale structures. In a second limit, from a phase space orbital study based on chaotic behavior, we found that for pitch angles larger than $\sim 30°$, $\sim 40°$ and $\sim 50°$ for Sa, Sb, and Sc galaxies, respectively, chaotic orbits dominate all phase space prograde region that surrounds the periodic orbits sculpting the spiral arms and even destroying them. This result seems to be in good agreement with observations of pitch angles in typical isolated normal spiral galaxies.

34 pages (preprint), 14 figures, 1 Table, accepted in ApJ

References in corpus (10)

• Measurement of Galactic Logarithmic Spiral Arm Pitch Angle Using Two-Dimensional Fast Fourier Transform Decomposition
• Stellar Kinematic Constraints on Galactic Structure Models Revisited: Bar and Spiral Arm Resonances
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• Pattern speed of main spiral arms in NGC 2997: Estimate based on very young stellar complexes
• Destruction of star clusters due to the radial migration in spiral galaxies
• Pitch Angle Restrictions in Late Type Spiral Galaxies Based on Chaotic and Ordered Orbital Behavior
• Pitch angles of distant spiral galaxies
• Spiral stellar density waves and the flattening of abundance gradients in the warm gas component of spiral galaxies
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Cited by in corpus (5)

• Updating the (Supermassive Black Hole Mass) - (Spiral Arm Pitch Angle) Relation: A Strong Correlation for Galaxies with Pseudobulges
• The Contribution of Spiral Arms to the Thick Disk along the Hubble Sequence
• The imprint of arms and bars on rotation curves: in-plane and off-plane
• Dynamics of thick, open spirals in Perlas potentials
• Stellar Orbital Studies in Normal Spiral Galaxies II: Restrictions to Structural and Dynamical parameters on Spiral Arms