Spiral- and bar-driven peculiar velocities in Milky Way-sized galaxy simulations

Abstract

We investigate the kinematic signatures induced by spiral and bar structure in a set of simulations of Milky Way-sized spiral disc galaxies. The set includes test particle simulations that follow a quasi-stationary density wave-like scenario with rigidly rotating spiral arms, and N -body simulations that host a bar and transient, co-rotating spiral arms. From a location similar to that of the Sun, we calculate the radial, tangential and line-of-sight peculiar velocity fields of a patch of the disc and quantify the fluctuations by computing the power spectrum from a two-dimensional Fourier transform. We find that the peculiar velocity power spectrum of the simulation with a bar and transient, co-rotating spiral arms fits very well to that of APOGEE red clump star data, while the quasi-stationary density wave spiral model without a bar does not. We determine that the power spectrum is sensitive to the number of spiral arms, spiral arm pitch angle and position with respect to the spiral arm. However, it is necessary to go beyond the line of sight velocity field in order to distinguish fully between the various spiral models with this method. We compute the power spectrum for different regions of the spiral discs, and discuss the application of this analysis technique to external galaxies.

Mapping the Galactic disc with the LAMOST and Gaia red clump sample: II. 3D asymmetrical kinematics of mono-age populations in the disc between 6–14 kpc

“…We speculate that in-plane asymmetries might also be contributed by spiral arms in the solar neighborhood. For the outer disk, radial velocity asymmetries might be produced by the spiral structures that are always spatially correlated with spiral arms (Siebert et al 2012;Faure, Siebert & Famaey 2014;Grand et al 2015).…”

Young stars as tracers of a barred-spiral Milky Way

“…All non-axisymmetric components are assumed to rotate as rigid features. While there is increasing evidence that a more dynamic and transient spiral structure exists in disc galaxies from both simulations (Pettitt et al 2015;Grand et al 2015) and observations (Meidt et al 2009;Foyle et al 2011;Choi et al 2015), we use fixed potentials for their simplicity and more canonical acceptance in the literature. We note that the nature of spiral arms is still a topic of uncertainty (see Dobbs & Baba 2014 for a review), and different theories have repercussions for disc kinematics (Grand et al 2015;Sellwood et al 2019), radial migration (Sellwood & Binney 2002) and giant molecular cloud properties (Dobbs et al 2012;Baba et al 2017).…”

“…A number of recent studies have investigated the various influences on the velocity distribution in Gaia-sized fields with numerical simulations. Grand et al (2015) performed a numerical study of numerous different spiral arm models with live N -body discs. They find that velocity fields can be highly sensitive to the nature of spiral arms, be they bar driven, density wave-like, or seeded by disc instabilities.…”

Stars with fast Galactic rotation observed in Gaia TGAS: a signature driven by the Perseus arm?

“…We examine a snapshot at an earlier time from this model with a strong spiral arm as shown in Kawata et al (2014) (K14a) and a snapshot at a later time from this model with a weak spiral arm as shown in Grand et al (2015) (K14b). A comparison of this galaxy to the Milky Way including measurement of its age/velocity dispersion, bar strength and the pitch angle of the spiral arms are given for K14a in Hunt et al (2015) and for K14b in Grand et al (2015). We assume a solar radius of R0 = 8 kpc for both K14a and K14b.…”