The Magnetic Field Strength in the Wall of the Local Bubble toward l, b ~ 300°, 0°

Abstract

We present polarization measurements in the region around l, b = 300°, 0°, toward stars with well-determined distances, primarily in the range 40-200 pc. We argue that these observations trace polarization caused by dust in the wall of the Local Bubble (LB). Using a Chandrasekhar-Fermi analysis, we derive a plane-of-the-sky magnetic field strength, in the wall of the LB in this direction, of ⊥>=8⁺⁵_-3 μG, equivalent to a magnetic pressure of P_B/k~1.8×10⁴ K cm^-3. This pressure equals, to within the uncertainties, that in the bubble interior, as derived from EUVE observations, assuming collisional ionization equilibrium. Such a magnetic field could help us explain the observed low O VI column density associated with the LB wall.