Magnetic field at a jet base: extreme Faraday rotation in 3C 273 revealed by ALMA

Understand

We studied the polarization behavior of the quasar 3C 273 over the 1 mm wavelength band at ALMA with a total bandwidth of 7.5GHz across 223 to 243 GHz at 0.8 arcsec resolution, corresponding to 2.1 kpc at the distance of 3C 273.

• With these observations we were able to probe the optically thin polarized emission close to the jet base, and constrain the magnetic field structure.
• We computed the Faraday rotation measure using simple linear fitting and Faraday rotation measure synthesis.
• In addition, we modeled the broadband behavior of the fractional Stokes Q and U parameters (qu-fitting).