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Title: THE GRAVITATIONAL DRAG FORCE ON AN EXTENDED OBJECT MOVING IN A GAS

Using axisymmetrical numerical simulations, we revisit the gravitational drag felt by a gravitational Plummer sphere with mass M and core radius R{sub s} moving at constant velocity V{sub 0} through a background homogeneous medium of adiabatic gas. Since the potential is non-diverging, there is no gas removal due to accretion. When R{sub s} is larger than the Bondi radius R{sub B} , the perturbation is linear at every point and the drag force is well fitted by the time-dependent Ostriker's formula with r{sub min} = 2.25R{sub s} , where r{sub min} is the minimum impact parameter in the Coulomb logarithm. In the deep nonlinear supersonic regime (R{sub s} << R{sub B} ), the minimum radius is no longer related to R{sub s} but to R{sub B} . We find r{sub min}=3.3M{sup -2.5}R{sub B} for Mach numbers of the perturber between 1.5 and 4, although r{sub min}= 2M{sup -2}R{sub B}=2GM/V{sup 2}{sub 0} also provides a good fit at M>2. As a consequence, the drag force does not depend sensitively on the nonlinearity parameter A, defined as R{sub B} /R{sub s} , for A values larger than a certain critical value A{sub cr}. We show that our generalized Ostriker's formula for themore » drag force is more accurate than the formula suggested by Kim and Kim.« less
Authors:
;  [1]
  1. Instituto de Astronomía, Universidad Nacional Autónoma de México, P.O. Box 70-264, Ciudad Universitaria, 04510 Mexico City (Mexico)
Publication Date:
OSTI Identifier:
22270959
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 775; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; COMPUTERIZED SIMULATION; DRAG; GRAVITATIONAL INTERACTIONS; HYDRODYNAMICS; IMPACT PARAMETER; NONLINEAR PROBLEMS; STAR ACCRETION; TIME DEPENDENCE; VELOCITY