Hydrodynamic Shielding and the Survival of Cold Streams
Abstract
Cold clouds in hot media are quickly crushed, shredded, and then accelerated as a result of their interaction with the background gas. The persistence of cold clouds moving at substantial velocities in harsh environments is a common yet puzzling feature of many astrophysical systems, from quasar absorption lines probing galactic halos to clouds of dust passing near Sgr A *. Here we run a set of idealized numerical experiments, subjecting a line of cold clouds at a series of mutual separations to a hot background wind. We find that this stream of clouds is able to shield itself from hydrodynamic destruction by accelerating the hot background material, creating a protective layer of co-moving gas. We write down a simple diffusion equation that reproduces the behavior of the simulations, and we discuss the implications for cosmological gas accretion and the putative galactic center dust cloud G2.
- Publication:
-
The Astronomical Journal
- Pub Date:
- September 2019
- DOI:
- 10.3847/1538-3881/ab3230
- arXiv:
- arXiv:1810.12925
- Bibcode:
- 2019AJ....158..124F
- Keywords:
-
- galaxies: halos;
- galaxy: nuclei;
- hydrodynamics;
- intergalactic medium;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Submitted to AAS Journals, comments welcome