ALMA and VLA observations of the Extended Green Object G19.01-0.03



We present a study of the physical and chemical properties of the Extended Green Object (EGO) G19.01−0.03 using sub-arcsecond angular resolution Atacama Large Millimeter/submillimeter Array (ALMA) 1.05mm and Karl G. Jansky Very Large Array (VLA) 1.21cm data. G19.01−0.03 MM1, the millimetre source associated with the central massive young stellar object (MYSO), appeared isolated and potentially chemically young in previous Submillimeter Array observations. In our ∼0.4′′-resolution ALMA data, MM1 has four low-mass millimetre companions within 0.12pc, all lacking maser or outflow emission, indicating they may be prestellar cores. With a rich ALMA spectrum full of complex organic molecules, MM1 does not appear chemically young, but has molecular abundances typical of high-mass hot cores in the literature. At the 1.05mm continuum peak of MM1, N(CH3OH)=(2.22±0.01)×1018cm−2 and Tex=162.7+0.3−0.5K based on pixel-by-pixel Bayesian analysis of LTE synthetic methanol spectra across MM1. Intriguingly, the peak CH3OH Tex=165.5±0.6 K is offset from MM1's millimetre continuum peak by 0.22′′∼880au, and a region of elevated CH3OH Tex coincides with free-free VLA 5.01cm continuum, adding to the tentative evidence for a possible unresolved high-mass binary in MM1. In our VLA 1.21cm data, we report the first NH3(3,3) maser detections towards G19.01−0.03, along with candidate 25GHz CH3OH 5(2,3)−5(1,4) maser emission; both are spatially and kinematically coincident with 44GHz Class I CH3OH masers in the MM1 outflow. We also report the ALMA detection of candidate 278.3GHz Class I CH3OH maser emission towards this outflow, strengthening the connection of these three maser types to MYSO outflows.
Date made available11 Sept 2023

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