Up around the bend: a multi-wavelength view of the quasar 3C 345

The flat-spectrum radio quasar 3C 345 has been showing gamma-ray activity since the mid-2000s along with activity across the electromagnetic spectrum. A gamma-ray burst in 2009 was successfully linked to relativistic outflow in 43 GHz VLBI observations and has since been analyzed also using single dish measurements. A multi-wavelength follow- up VLBI observation to the 2009 flare in conjunction with 43 GHz catalogue data from the VLBA-BU-BLAZAR and BEAM-ME programs are analyzed in this study in the context of the long-term evolution of the source. We aim to probe the innermost few milli-arcseconds of the ultracompact 3C 345 jet. In the process, we analyze the long-term kinematics of the inner jet and discuss the magnetic field morphology at different scales, as well as the origin of the gamma-ray emission. New observations at 23, 43, and 86 GHz took place on ten epochs between 2017 and 2019. We calibrate the 30 data sets using the rPicard pipeline, image them in Difmap and carry out polarization calibration using the GPCAL pipeline. We complement our VLBI data with ancillay VLBI maps at multiple frequencies, as well as 43 GHz observations carried out in the framework of the BEAM-ME and VLBA-BU-BLAZAR monitoring programs. We find multiple distinct component paths in the inner jet, forming a helical geometry. The helix is anchored at a stationary feature some 0.16 mas from the 43 GHz VLBI core and has a timescale of about 8 years. The characteristic bends in the jet morphology are caused by variations in the component ejection angle. We confirm the result of previous studies that the gamma-ray emission is produced (or caused) by relativistic outflow and violent interactions within the jet.