Phase spirals in cosmological simulations of Milky Way-sized galaxies

García-Conde, Begoña; Roca-Fàbrega, S.; Antoja, T.; Ramos, P.; Valenzuela, O.

doi:10.1093/mnras/stab3417

Cited by 16 publications

(11 citation statements)

References 39 publications

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“…Bennett et al 2022), and models of a Sgr-like merger which do qualitatively reproduce the observed degree of disequilibrium in the Galactic disc require a larger mass for Sgr than is inferred from observations of its remnant (Vasiliev & Belokurov 2020). However, note that García-Conde et al (2022) find similar levels of disequilibria in a cosmological simulation with several lighter satellites, showing that a more complex dynamical history or the presence of gas dynamics may help. Alternatively, Khoperskov et al (2019) suggest that such spirals could also be caused by the buckling of the Galactic bar.…”

Section: Introductionmentioning

confidence: 67%

Multiple phase-spirals suggest multiple origins in Gaia DR3

Hunt,

Price-Whelan,

Johnston

et al. 2022

Preprint

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Gaia Data Release 2 (DR2) revealed that the Milky Way contains significant indications of departures from equilibrium in the form of asymmetric features in the phase space density of stars in the Solar neighborhood. One such feature is the zv z phase spiral discovered by Antoja et al. (2018), interpreted as the response of the disk to the influence of a perturbation perpendicular to the disk plane, which could be external (e.g., a satellite) or internal (e.g., the bar or spiral arms). In this work we use Gaia DR3 to dissect the phase spiral by dividing the local data set into groups with similar azimuthal actions, J φ , and angles, θ φ , which selects stars on similar orbits and at similar orbital phases, thus having experienced similar perturbations in the past. These divisions allow us to explore areas of the Galactic disk larger than the surveyed region. The separation improves the clarity of the z-v z phase spiral and exposes changes to its morphology across the different action-angle groups. In particular, we discover an abrupt transition to two armed 'breathing spirals' in the inner Milky Way. We conclude that the local data contains signatures of not one, but multiple perturbations with potential to use their distinct properties to infer the properties of the distinct interactions that caused them.

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Section: Introductionmentioning

confidence: 67%

Multiple phase-spirals suggest multiple origins in Gaia DR3

Hunt,

Price-Whelan,

Johnston

et al. 2022

Preprint

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“…Moreover, self-gravity can also influence the evolution of perturbations as was shown in the case of the phase spirals by Darling & Widrow (2019). Numerical simulations combined with techniques such as the Stäckel fudge will provide an invaluable tool for understanding the complicated dynamics of the Solar Neighborhood (Laporte et al 2018(Laporte et al , 2019Li 2021;Bennett et al 2022;García-Conde et al 2022;Hunt et al 2022). There is also the question of the interplay between disk perturbations and our attempts to determine the local gravitational potential and dark matter density (Banik et al 2017;Widmark et al 2021b,c,a;Sivertsson et al 2022).…”

Section: Discussionmentioning

confidence: 99%

Residuals of an Equilibrium Model for the Galaxy Reveal a State of Disequilibrium in the Solar Neighborhood

Li¹,

Widrow²

2022

Preprint

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We simultaneously model the gravitational potential and phase space distribution function (DF) of giant stars near the Sun using the Gaia DR2 radial velocity catalog. We assume that the Galaxy is in equilibrium and is symmetric about both the spin axis of the disk and the Galactic midplane. The potential is taken as a sum of terms that nominally represent contributions from the gas disk, stellar disk, bulge, and dark matter halo. Our DF model for the giants comprise two components to account for a mix of thin and thick disk stars. The DF for each component is described by an analytic function of the energy, the spin angular momentum, and the vertical energy, in accord with Jeans theorem. We present model predictions for the radial and vertical forces within ∼ 2 kpc of the Sun, highlighting the rotation curve and vertical force profile in the Solar Neighbourhood. Finally, we show residuals for star counts in the R − z and z − v z planes as well as maps of the mean radial and azimuthal velocities in the z − v z plane. Using our model for the potential, we also examine the star count residuals in action-frequency-angle coordinates. The Gaia phase spirals, velocity arches, some of the known moving groups and bending modes appear as well-defined features in these maps.

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“…This could respond simply to the lack of exploration of different setups for Sgr's halo and disc structure in the current models. It could also be connected to the existent discussion around the mass of Sagittarius at each pericentre and whether these impacts are enough to create the phase spiral (see discussion in García-Conde et al 2022). This should also be addressed in future investigations.…”

Section: The Case Of the Milky Waymentioning

confidence: 96%

Tidally induced spiral arm wraps encoded in phase space

Antoja¹,

Ramos²,

López-Guitart³

et al. 2022

Preprint

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Context. The impact of Sagittarius and other satellite galaxies such as the Large Magellanic Cloud on our Galaxy and in particular its disc is gradually being disclosed. Simulations tailored to the interaction of the Milky Way and Sagittarius show rings and spiral arms appearing in the Galaxy disc. However, spiral arms can also be induced by the bar or by disc instabilities. Aims. We aim to study the dynamics of tidally induced spiral arms in the context of the different encounters with Sagittarius and their kinematic signatures in the shape of ridges and waves in angular momentum, similar to those detected with Gaia DR2. Methods. We build toy models of the interaction between a host and a satellite galaxy using orbital integrations after a tidal distant encounter. We derive analytically the shape of the structures seen in phase space as a function of time for simple power-law potential models. We compare these models to a more realistic N-body simulation of the Milky-Way Sagittarius-like interaction and also to real data. Results. As previously found, an impulsive distant tidal approach of a galactic satellite generates a kick in velocities that leads to a 2-armed spiral structure. The arms are made of orbits in between their apocentres and pericentres, thus, correspond to regions with average negative galactocentric radial velocity. The 2-arm pattern rotates at an angular speed of Ω − 1/2κ which depends on Galactocentric radius, thus causing a wind-up with time. This winding produces ridges in the R-V φ projection with alternating signs of V R and oscillations of V R in the L Z -φ space, similar to those observed in the Gaia data. The frequency of these kinematic features increases with time, offering a powerful means to infer the potential and the perturbation's onset time and azimuthal phase. Simple Fourier analysis allows to date the impact times of simple models and even to date perturbations induced from subsequent pericentric passages that appear as simultaneous waves. For the MW, the Fourier analysis indicates a superposition of two different frequencies, confirming previous studies. Assuming that both are due to impulsive and distant pericentre passages, we find perturbation times <0.4 Gyr and in the range of 0.7-1.8 Gyr. The latter is compatible with a previous pericentre of Sagittarius and would be associated to about 4 wraps of the spiral arms in the observed radial range. Conclusions. Further work on the self-gravitating response of galactic discs and possible degeneracies with secular processes induced by the bar is necessary. An exploration of the Milky Way's kinematics over a larger radial and azimuthal range can help to better discern and date the various perturbations. Our study is a first step towards shedding some more light into the elusive structure and dynamics of the spiral arms of the Galaxy.

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Phase spirals in cosmological simulations of Milky Way-sized galaxies

Cited by 16 publications

References 39 publications

Multiple phase-spirals suggest multiple origins in Gaia DR3

Multiple phase-spirals suggest multiple origins in Gaia DR3

Residuals of an Equilibrium Model for the Galaxy Reveal a State of Disequilibrium in the Solar Neighborhood

Tidally induced spiral arm wraps encoded in phase space

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