3D velocity fields from methanol and water masers in an intermediate-mass protostar

Abstract

We report multi-epoch VLBI observations of molecular masers towards the high-mass star forming region AFGL 5142, leading to the determination of the 3D velocity field of circumstellar molecular gas at radii <0.''23 (or 400 AU) from the protostar MM-1. Our observations of CH<SUB>3</SUB>OH maser emission enabled, for the first time, a direct measurement of infall of a molecular envelope on to an intermediate-mass protostar (radius of 300 AU, velocity of 5 km s<SUP>-1</SUP>, and infall rate of 6 × 10<SUP>-4</SUP> n <SUB>8</SUB> M <SUB>⊙</SUB> yr<SUP>-1</SUP>, where n <SUB>8</SUB> is the ambient volume density in units of 10<SUP>8</SUP> cm<SUP>-3</SUP>). In addition, our measurements of H<SUB>2</SUB>O maser (and radio continuum) emission revealed a collimated bipolar molecular outflow (and ionized jet) from MM-1. The evidence of simultaneous accretion and outflow at small spatial scales, makes AFGL 5142 an extremely compelling target for high-angular resolution studies of high-mass star formation.