Monitoring of the polarized H2O maser emission around the massive protostars W75N(B)-VLA 1 and W75N(B)-VLA 2

Abstract

AbstractSeveral radio sources have been detected in the high-mass star-forming region W75N(B), among them the massive young stellar objects VLA 1 and VLA 2 are of great interest. These are thought to be in different evolutionary stages. In particular, VLA 1 is at the early stage of the photoionization and it is driving a thermal radio jet, while VLA 2 is a thermal, collimated ionized wind surrounded by a dusty disk or envelope. In both sources 22 GHz H2O masers have been detected in the past. Those around VLA 1 show a persistent linear distribution along the thermal radio jet and those around VLA 2 have instead traced the evolution from a non-collimated to a collimated outflow over a period of ∼20 years. The magnetic field inferred from the H2O masers showed a rotation of its orientation according to the direction of the major-axis of the shell around VLA 2, while it is immutable around VLA 1.We further monitored the polarized emission of the 22 GHz H2O masers around both VLA 1 and VLA 2 over a period of six years with the European VLBI Network for a total of four epochs separated by two years from 2014 to 2020. We here present the results of our monitoring project by focusing on the evolution of the maser distribution and of the magnetic field around the two massive young stellar objects.