The Gravitational Drag Force on an Extended Object Moving in a Gas

Bernal, C. G.; Sánchez-Salcedo, F. J.

doi:10.1088/0004-637x/775/1/72

Cited by 10 publications

(14 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Within this linear approximation, the collisional drag force is significantly higher for perturbers moving with Mach numbers 0.7 < M < 2. A similar trend is also seen, in numerical simulations, for low mass, extended, perturbers (Sánchez-Salcedo & Brandenburg 1999;Kim & Kim 2009;Bernal & Sánchez-Salcedo 2013). Importantly, however, these works show the force from the wake is only accurately predicted under certain conditions.…”

Section: Introductionsupporting

confidence: 73%

“…Any scenario can be completely described by two parameters: this 𝐴 parameter, and the Mach number M of the perturber moving through the gaseous background medium. The predicted force, give by Equations (3), (4) and ( 5), has been used to test numerical results, and they were found to match for suitably chosen 𝐴 and 𝑟 min (Sánchez-Salcedo & Brandenburg 1999;Kim & Kim 2009;Bernal & Sánchez-Salcedo 2013). As discussed in Section 1, these works find the forces match for when 𝑟 min has certain values.…”

Section: Linear Wakementioning

confidence: 92%

“…As the scenario becomes increasingly non-linear, the gaseous DF drag force decreases (Kim & Kim 2009) (referred to as KK09 when mentioned directly). The complex structure of the gravitationally induced wake has been studied previously using both analytic (Just & Kegel 1990;Ostriker 1999;Namouni 2010) and numerical techniques (Sánchez-Salcedo & Brandenburg 1999Kim & Kim 2007;Kim & Kim 2009;Bernal & Sánchez-Salcedo 2013). Bernal & Sánchez-Salcedo (2013) will be referred to as BS13 when directly mentioned in the text.…”

Section: Introductionmentioning

confidence: 99%

“…This element of the analysis is discussed in greater detail in Section 2.2. The analytic prescription can be extended numerically for more extreme mass perturbers, where large regions of the wake are no longer described by the linear wake (Kim & Kim 2009;Bernal & Sánchez-Salcedo 2013). The simulation work, in this regime, does not produce a clear picture of what the prediction for the non-linear wake should be.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Gaseous Dynamical Friction: A Challenge to Modern Hydrodynamical Schemes

Morton,

Khochfar,

Oñorbe

2021

Preprint

View full text Add to dashboard Cite

The process of momentum and energy transfer from a massive body moving through a background medium, known as dynamical friction (DF), is key to our understanding of many astrophysical systems. We present a series of high-resolution simulations of gaseous DF using Lagrangian hydrodynamics solvers, in the state-of-the-art multi-physics code, GIZMO. The numerical setup is chosen to allow direct comparison to analytic predictions for DF in the range of Mach 0.2 ≤ M ≤ 3. We investigate, in detail, the DF drag force, the radial structure of the wake, and their time evolution. The subsonic forces are shown to be well resolved, except at Mach numbers close to M = 1. The supersonic cases, close to M = 1, significantly undershoot the predicted force. We find that for scenarios with 0.7 < M < 2, between 10% − 50% of the expected DF force is missing. The origin of this deficit is mostly related to the wake structure close to the perturber, where the density profile of the Mach cone face shows significant smoothing, which does not improve with time. The spherical expanding perturbation of the medium is captured well by the hydro-scheme, but it is the sharp density structure, at the transition from Mach cone to average density, that introduces the mismatch. However, we find a general improvement of the force deficit with time, though significant differences remain, in agreement with other studies. This is due to (1) the structure of the far field wake (𝑟 ≥ 4𝑟 𝑠 , with 𝑟 𝑠 as the gravitational smoothing scale) being reproduced well, and (2) the fraction of total drag from the far field wake increasing with time. Dark matter sub-haloes, in typical cosmological simulations, occupy parameters similar to those tested here, suggesting that the DF which these sub-haloes experience is significantly underestimated, and hence their merger rate. Dynamical friction is a relevant benchmark and should be included as one of the standard hydro test for astrophysical simulations, since it is critical to our understanding of many systems.

show abstract

Section: Introductionsupporting

confidence: 73%

Section: Linear Wakementioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Gaseous Dynamical Friction: A Challenge to Modern Hydrodynamical Schemes

Morton,

Khochfar,

Oñorbe

2021

Preprint

View full text Add to dashboard Cite

show abstract

“…where r max 2.1 √ 2H and r min is the minimum impact parameter for the interaction. In the case of a Plummer perturber with R soft > R acc , Bernal & Sánchez-Salcedo (2013) found that r min = 2.25R soft (see also Sánchez-Salcedo & Brandenburg 1999). Putting together, the predicted torque on a softened body having R acc < R soft H, on a retrograde circular orbit, is…”

Section: Analytical Predictionsmentioning

confidence: 91%

Torques on Low-mass Bodies in Retrograde Orbit in Gaseous Disks

Sánchez-Salcedo

Chametla

Santillán

2018

ApJ

Self Cite

View full text Add to dashboard Cite

We evaluate the torque acting on a gravitational perturber on a retrograde circular orbit in the midplane of a gaseous disk. We assume that the mass of this satellite is so low it weakly disturbs the disk (type I migration). The perturber may represent the companion of a binary system with a small mass ratio. We compare the results of hydrodynamical simulations with analytic predictions. Our two-dimensional (2D) simulations indicate that the torque acting on a perturber with softening radius R soft can be accounted for by a scattering approach if R soft < 0.3H, where H is defined as the ratio between the sound speed and the angular velocity at the orbital radius of the perturber. For R soft > 0.3H, the torque may present large and persistent oscillations, but the resultant time-averaged torque decreases rapidly with increasing R soft /H, in agreement with previous analytical studies. We then focus on the torque acting on small-size perturbers embedded in full three-dimensional (3D) disks and argue that the density waves propagating at distances H from the perturber contribute significantly to the torque because they transport angular momentum. We find a good agreement between the torque found in 3D simulations and analytical estimates based on ballistic orbits. We compare the radial migration timescales of prograde versus retrograde perturbers. For a certain range of the perturber's mass and aspect ratio of the disk, the radial migration timescale in the retrograde case may be appreciably shorter than in the prograde case. We also provide the smoothing length required in 2D simulations in order to account for 3D effects.

show abstract

Binaries Traveling Through a Gaseous Medium: Dynamical Drag Forces and Internal Torques

Sánchez-Salcedo¹,

Chametla²

2014

ApJ

Self Cite

View full text Add to dashboard Cite

Using time-dependent linear theory, we investigate the morphology of the gravitational wake induced by a binary, whose center of mass moves at velocity V cm against a uniform background of gas. For simplicity, we assume that the binary's components are on circular orbits about their common center of mass. The consequences of dynamical friction is twofold. First, gas dynamical friction may drag the binary's center of mass and cause the binary to migrate. Second, drag forces also induce a braking torque, which causes the orbits of the binary components to shrink. We compute the drag forces acting on one component of the binary due to the gravitational interaction with its own wake. We show that the dynamical friction force responsible to decelerate the binary's center of mass is smaller than it is in the point-mass case because of the loss of gravitational focusing. We show that the braking internal torque depends on the Mach numbers of each binary component about their center of mass, and also on the Mach number of the center of mass of the binary. In general, the internal torque decreases with increasing the velocity of the binary relative to the ambient gas cloud. However, this is not always the case. We also mention the relevance of our results on the period distribution of binaries. Subject headings: binaries: general -black hole physics -hydrodynamics -ISM: general -waves 1 The evolution of binaries in stellar clusters due to the dynamical interactions with other stars has received considerable attention (e.g.,

show abstract

The Gravitational Drag Force on an Extended Object Moving in a Gas

Cited by 10 publications

References 23 publications

Gaseous Dynamical Friction: A Challenge to Modern Hydrodynamical Schemes

Gaseous Dynamical Friction: A Challenge to Modern Hydrodynamical Schemes

Torques on Low-mass Bodies in Retrograde Orbit in Gaseous Disks

Binaries Traveling Through a Gaseous Medium: Dynamical Drag Forces and Internal Torques

Contact Info

Product

Resources

About