Identifying the Radio Bubble Nature of the Microwave Haze

TL;DR

This paper confirms the physical connection between the microwave haze and gamma-ray bubbles, revealing a sharp edge and estimating the magnetic field within these Galactic structures using multi-wavelength data.

Contribution

It provides the first direct evidence linking microwave and gamma-ray Galactic bubbles and measures their magnetic field strength using combined microwave and gamma-ray observations.

Findings

The microwave haze and gamma-ray bubbles are spatially coincident and are the same structure.

The magnetic field within the Galactic bubbles is approximately 5 microGauss.

The edge of the microwave haze is a real physical boundary, not an artifact.

Abstract

Using 7-year data from the Wilkinson Microwave Anisotropy Probe I identify a sharp "edge" in the microwave haze at high Galactic latitude (35 deg < |b| < 55 deg) that is spatially coincident with the edge of the "Fermi Haze/Bubbles". This finding proves conclusively that the edge in the gamma-rays is real (and not a processing artifact), demonstrates explicitly that the microwave haze and the gamma-ray bubbles are indeed the same structure observed at multiple wavelengths, and strongly supports the interpretation of the microwave haze as a separate component of Galactic synchrotron (likely generated by a transient event) as opposed to a simple variation of the spectral index of disk synchrotron. In addition, combining these data sets allows for the first determination of the magnetic field within a radio bubble using microwaves and gamma-rays by taking advantage of the fact that the inverse Compton gamma-rays are primarily generated by scattering of CMB photons at these latitudes, thus minimizing uncertainty in the target radiation field. Assuming uniform volume emissivity, I find that the magnetic field within our Galactic microwave/gamma-ray bubbles is ~5 muG above 6 kpc off of the Galactic plane.