Negative dynamical friction on compact objects moving through dense gas. Issue 2 (16th January 2020)

• Record Type: Journal Article
• Authors: Gruzinov, Andrei; Levin, Yuri; Matzner, Christopher D
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 492:Issue 2(2020)
• Page Start: 2755
• Page End: 2761
• Publication Date: 2020-01-16
• Subjects: accretion, accretion discs -- black hole physics; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa013
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: An overdense wake is created by a gravitating object moving through a gaseous medium, and this wake pulls back on the object and slows it down. This is conventional dynamical friction in a gaseous medium. We argue that if the object drives a sufficiently powerful outflow, the wake is destroyed and instead an extended underdense region is created behind the object. In this case the overall gravitational force is applied in the direction of the object's motion, producing a negative dynamical friction (NDF). Black holes in dense gas drive powerful outflows and may experience the NDF, although extensive numerical work is probably needed to demonstrate or refute this conclusively. NDF may be important for stellar-mass black holes and neutron stars inside 'common envelopes' in binary systems, for stellar mass black holes inside active galactic nucleus discs, or for massive black holes growing through super-Eddington accretion in early Universe.