Bending Waves in Velocity Space: a First Look at the THINGS sample

Abstract

Detection of bending waves is a highly challenging task even in nearby disc galaxies due to their sub-kpc bending amplitudes. However, simulations show that the harmonic bending of a Milky Way like disc galaxy is associated with a harmonic fluctuation in the measured line of sight (los) velocities as well, and can be regarded as a kinematic signature of a manifested bending wave. Here, we look for similar kinematic signatures of bending waves in \HI discs, as they extend to much beyond the optical radii. We present a multipole analysis of the \HI los residual velocity fields of six nearby spiral galaxies from the THINGS sample, which uncovers the bending wave-induced velocity peaks. This allows us to identify the radial positions and amplitudes of the different bending modes present in the galaxies. We find that all of our sample discs show a combined kinematic signature of superposition of a few lower-order bending modes, suggesting that bending waves are a common phenomenon. The identified velocity peaks are found to be of modes $m=2,3$ and $4$, not more than 15 km s${}^{-1}$ in amplitude and spread across the entire \HI disc. Interestingly, they appear to be concentrated near the optical edge of their host galaxies. Also, $m=2$ appears to be more common than the other two modes.

Accepted in MNRAS, 12 pages, 11 figures

References in corpus (15)

• High-Resolution Rotation Curves and Galaxy Mass Models from THINGS
• What is Driving the HI Velocity Dispersion?
• Rings and Radial Waves in the Disk of the Milky Way
• The Vertical Structure of the Outer Milky Way HI Disk
• A Galactic-scale gas wave in the Solar Neighborhood
• Dynamical Centers and Non-Circular Motions in THINGS Galaxies: Implications for Dark Matter Halos
• Bending and Breathing Modes of the Galactic Disk
• A Magellanic Origin for the Warp of the Galaxy
• The Complex Structure of Stars in the Outer Galactic Disk as revealed by Pan-STARRS1
• The Flattened Dark Matter Halo of M31 as Deduced from the Observed HI Scale Heights
• Spontaneous generation of bending waves in isolated Milky Way-like discs
• Gaia-DR2 extended kinematical maps. Part II: Dynamics in the Galactic disk explaining radial and vertical velocities
• Probing interstellar turbulence in spiral galaxies using HI power spectrum analysis
• Wobbly discs -- corrugations seen in the dust lanes of edge-on galaxies
• Evidence of large scale energy cascade in the spiral galaxy NGC 5236