ALMA multiband polarimetry of 3C273

We used multiband Atacama Large Millimeter Array (ALMA) data to study the polarization structure of both the nucleus and the kiloparsec-scale jet of the archetypal quasar 3C 273. We modeled the wavelength-dependent polarization of the nucleus using multiband observations (2, 1.3, and 0.85mm) and applied QU-fitting to constrain Faraday rotation models with one or more polarized components.

We also produced total intensity and polarization maps of the kiloparsec-scale jet to study the evolution of the magnetic field structure along and across the jet. The data of the nucleus were best fit by two Faraday components: a high rotation measure (RM) component with RM=+(2.6_/-0.1)*10^5^rad/m^2^ and comparable RM dispersion, and a second component with RM=+(1.5+/-0.2)*10^4^rad/m^2^ and lower dispersion. The high RM is comparable to previous ALMA observations at 1.3mm, although we found clear evidence of variability when compared to previous single-band ALMA studies, highlighting the importance of broad wavelength coverage.