Evolutionary tracks of tidally stirred disky dwarf galaxies

Abstract

Using collisionless N-body simulations, we investigate the tidal evolution of late-type, rotationally supported dwarfs inside Milky Way-sized host galaxies. Our study focuses on a wide variety of dwarf orbital configurations and initial structures. During the evolution, the disky dwarfs undergo strong mass loss, the stellar disks are transformed into spheroids, and rotation is replaced by random motions of the stars. Thus, the late-type progenitors are transformed into early-type dwarfs as envisioned by the tidal stirring model for the formation of dwarf spheroidal (dSph) galaxies in the Local Group. We determine the photometric properties of the dwarfs, including the total visual magnitude, the half-light radius and the central surface brightness as they would be measured by an observer near the galactic center. Special emphasis is also placed on studying their kinematics and shapes. We demonstrate that the measured values are biased by a number of observational effects including the increasing angle of the observation cone near the orbital pericenter, the fact that away from the pericenter the tidal tails are typically oriented along the line of sight, and the fact that for most of the evolution the stellar components of the dwarfs are triaxial ellipsoids whose major axis tumbles with respect to the line of sight. Finally, we compare the measured properties of the simulated dwarfs to those of dwarf galaxies in the Local Group. The evolutionary tracks of the dwarfs in different parameter planes and the correlations between their different properties, especially the total magnitude and the surface brightness, strongly suggest that present-day dSph galaxies may have indeed formed from late-type progenitors as proposed by the tidal stirring scenario.

18 pages, 20 figures, 2 tables, revised version with two new figures, accepted for publication in ApJ

References in corpus (21)

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• How to make an ultra-faint dwarf spheroidal galaxy: tidal stirring of disky dwarfs with shallow dark matter density profiles
• Tidal tails of dwarf galaxies on different orbits around the Milky Way
• Tidally induced bars in gas-rich dwarf galaxies orbiting the Milky Way
• The baryon cycle of Seven Dwarfs with superbubble feedback
• Formation of Andromeda II via a gas-rich major merger and an interaction with M31
• Constraining the subgrid physics in simulations of isolated dwarf galaxies
• Radial velocities of RR Lyrae stars in and around NGC 6441
• Tidal Grinding of Dwarf Galaxies in Cluster Environments