The tilt of the local velocity ellipsoid as seen by Gaia

Everall, Andrew; Evans, N. W.; Belokurov, Vasily; Schönrich, Ralph

doi:10.1093/mnras/stz2217

Cited by 30 publications

(36 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As a dynamical model, we use the JAM sph approach 7 (Cappellari 2020), which is based on the solution of the axisymmetric Jeans equations and assumes a spherically aligned velocity ellipsoid (Bacon et al 1983;Bacon 1985). The spherical alignment has proven to describe the Gaia data in the outer halo (Wegg et al 2019) and in the disk region (Hagen et al 2019;Everall et al 2019). This was also confirmed by the results in Paper I.…”

Section: Modelingsupporting

confidence: 79%

“…Previously, we used the Gaia Data Release 2 (DR2) kinematics to construct an axisymmetric dynamical model of the Milky Way disk (Nitschai et al 2020, hereafter Paper I). There we used the new spherically aligned Jeans anisotropic modeling (JAM sph ; Cappellari 2020) method, since the Gaia data (Everall et al 2019;Hagen et al 2019) showed that the velocity ellipsoid is closer to being spherically aligned than cylindrically (JAM cyl ;Cappellari 2008). But we also compared the results against JAM cyl and found negligible differences.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Dynamical Model of the Milky Way Using APOGEE and Gaia Data

Nitschai

Eilers

Neumayer

et al. 2021

ApJ

View full text Add to dashboard Cite

We construct a dynamical model of the Milky Way disk from a data set that combines Gaia EDR3 and APOGEE data throughout galactocentric radii in the range 5.0 kpc ≤ R ≤ 19.5 kpc. We make use of the spherically aligned Jeans anisotropic method to model the stellar velocities and their velocity dispersions. Building upon our previous work, our model is now fitted to kinematic maps that have been extended to larger galactocentric radii due to the expansion of our data set, probing the outer regions of the Galactic disk. Our best-fitting dynamical model suggests a logarithmic density slope of α DM = −1.602 ± 0.079syst for the dark matter halo and a dark matter density of ρ DM(R ⊙) = (8.92 ± 0.56syst) × 10−3 M ⊙ pc−3 (0.339 ± 0.022syst GeV cm3). We estimate a circular velocity at the solar radius of v circ = (234.7 ± 1.7syst) km s−1 with a decline toward larger radii. The total mass density is ρ tot(R ⊙) = (0.0672 ± 0.0015syst) M ⊙ pc−3 with a slope of α tot = −2.367 ± 0.047syst for 5 kpc ≤ R ≤ 19.5 kpc, and the total surface density is Σ(R ⊙, ∣z∣ ≤ 1.1 kpc) = (55.5 ± 1.7syst) M ⊙ pc−2. While the statistical errors are small, the error budget of the derived quantities is dominated by the three to seven times larger systematic uncertainties. These values are consistent with our previous determination, but the systematic uncertainties are reduced due to the extended data set covering a larger spatial extent of the Milky Way disk. Furthermore, we test the influence of nonaxisymmetric features on our resulting model and analyze how a flaring disk model would change our findings.

show abstract

Section: Modelingsupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Dynamical Model of the Milky Way Using APOGEE and Gaia Data

Nitschai

Eilers

Neumayer

et al. 2021

ApJ

View full text Add to dashboard Cite

show abstract

“…As an extreme test of the sensitivity of our model to the assumptions on the orientation of the velocity ellipsoid, we also have fit a model (JAM cyl ) which assumes a cylindrically-aligned velocity ellipsoid (Cappellari 2008). The JAM sph model gives a slightly better fit the data than JAM sph , consistently with the finding that the Milky Way velocity ellipsoid is nearly spherical aligned (Hagen et al 2019;Everall et al 2019). However, the difference between the parameters inferred by two JAM sph and JAM cyl models is minimal as the two solutions are not very different in the disc plane.…”

Section: Jam Fit To the Gaia Datasupporting

confidence: 52%

“…For the dynamical modelling we use a new solution of the axisymmetric Jeans equations under the assumption of a spherically-aligned velocity ellipsoid (Cappellari 2019), which was shown to describing very accurately the dynamics of the Gaia data both in the outer halo (Wegg et al 2019) and the disc region (Hagen et al 2019;Everall et al 2019). This JAM sph method was developed specifically with the Gaia data in mind.…”

Section: Bayesian Jam Modellingmentioning

confidence: 99%

First Gaia dynamical model of the Milky Way disc with six phase space coordinates: a test for galaxy dynamics

Nitschai

Cappellari

Neumayer

2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We construct the first comprehensive dynamical model for the high-quality subset of stellar kinematics of the Milky Way disc, with full 6D phase-space coordinates, provided by the Gaia Data Release 2. We adopt an axisymmetric approximation and use an updated Jeans Anisotropic Modelling method, which allows for a generic shape and radial orientation of the velocity ellipsoid, as indicated by the Gaia data, to fit the mean velocities and all three components of the intrinsic velocity dispersion tensor. The Milky Way is the first galaxy for which all intrinsic phase space coordinates are available, and the kinematics are superior to the best integral-field kinematics of external galaxies. This situation removes the long-standing dynamical degeneracies and makes this the first dynamical model highly over-constrained by the kinematics. For these reasons, our ability to fit the data provides a fundamental test for both galaxy dynamics and the mass distribution in the Milky Way disc. We tightly constrain the average total density logarithmic slope, in the radial range 3.6-12 kpc, to be α tot = −2.149 ± 0.055 and find that the dark halo slope must be significantly steeper than α DM = −1 (NFW). The dark halo shape is close to spherical and its density is ρ DM (R ) = 0.0115 ± 0.0020 M pc −3 (0.437 ± 0.076 GeV cm −3 ), in agreement with previous estimates. The circular velocity at the solar position v circ R = 236.5 ± 3.1 km s −1 (including systematics) and its radial trends are also consistent with recent determinations.

show abstract

“…On the other hand, the off-diagonal terms σ zr , σ zφ , and σ φr determine the inclination of the velocity ellipsoid which is crucial to determine the distribution of baryonic and dark matter in the Galaxy. In particular, the inclination of the SVE in the ZR plane, known as the tilt angle, is important to properly determine the dark matter distribution in the galactic plane (Büdenbender, van de Ven & Watkins 2015;Everall et al 2019;Hagen et al 2019). Furthermore, the inclination on the radial and azimuthal plane, so-called vertex deviation, in the inner regions of our galaxy allows to study the presence of non-axisymmetries such as triaxial bulges or bars (Zhao, Spergel & Rich 1994;Soto, Rich & Kuijken 2007;Simion et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Local variations of the Stellar Velocity Ellipsoid-I: the disc of galaxies in the Auriga simulations

Walo-Martín

Pérez

Grand

et al. 2021

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

The connection between the Stellar Velocity Ellipsoid (SVE) and the dynamical evolution of galaxies has been a matter of debate in the last years and there is no clear consensus whether different heating agents (e.g. spiral arms, giant molecular clouds, bars and mergers) leave clear detectable signatures in the present day kinematics. Most of these results are based on a single and global SVE and have not taken into account that these agents do not necessarily equally affect all regions of the stellar disc.We study the 2D spatial distribution of the SVE across the stellar discs of Auriga galaxies, a set of high resolution magneto-hydrodynamical cosmological zoom-in simulations, to unveil the connection between local and global kinematic properties in the disc region. We find very similar, global, σz/σr = 0.80 ± 0.08 values for galaxies of different Hubble types. This shows that the global properties of the SVE at z=0 are not a good indicator of the heating and cooling events experienced by galaxies. We also find that similar σz/σr radial profiles are obtained through different combinations of σz and σr trends: at a local level, the vertical and radial components can evolve differently, leading to similar σz/σr profiles at z=0. By contrast, the 2D spatial distribution of the SVE varies a lot more from galaxy to galaxy. Present day features in the SVE spatial distribution may be associated with specific interactions such as fly-by encounters or the accretion of low mass satellites even in the cases when the global SVE is not affected. The stellar populations decomposition reveals that young stellar populations present colder and less isotropic SVEs and more complex 2D distributions than their older and hotter counterparts.

show abstract

The tilt of the local velocity ellipsoid as seen by Gaia

Cited by 30 publications

References 51 publications

Dynamical Model of the Milky Way Using APOGEE and Gaia Data

Dynamical Model of the Milky Way Using APOGEE and Gaia Data

First Gaia dynamical model of the Milky Way disc with six phase space coordinates: a test for galaxy dynamics

Local variations of the Stellar Velocity Ellipsoid-I: the disc of galaxies in the Auriga simulations

Contact Info

Product

Resources

About