Bow shock nebulae of hot massive stars in a magnetized medium

Understand

A significant fraction of OB-type, main-sequence massive stars are classified as runaway and move supersonically through the interstellar medium (ISM).

• Their strong stellar winds interact with their surroundings where the typical strength of the local ISM magnetic field is about 3.5-7 micro-G, which can result in the formation of bow shock nebulae.
• We investigate the effects of such magnetic fields, aligned with the motion of the flow, on the formation and emission properties of these circumstellar structures.
• Our axisymmetric, magneto-hydrodynamical simulations with optically-thin radiative cooling, heating and anisotropic thermal conduction show that the presence of the background ISM magnetic field affects the projected optical emission our bow shocks at Ha and [OIII] lambda 5007 which become fainter by about 1-2 orders of magnitude, respectively.