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NGC7538 IRS1 is considered the best high-mass accretion disk candidate aroundan O-type young star in the northern hemisphere. We investigated the 3Dkinematics and dynamics of circumstellar gas with very high linear resolution,from tens to 1500 AU, with the ultimate goal of building a comprehensivedynamical model for this YSO. We employed four different observing epochs ofEVN data at 6.7 GHz, spanning almost eight years, which enabled us to measure,besides line-of-sight (l.o.s.) velocities and positions, also l.o.s.accelerations and proper motions of methanol masers. In addition, we imagedwith the JVLA-B array highly-excited ammonia inversion lines, from (6,6) to(13,13), which enabled us to probe the hottest molecular gas very close to theexciting source(s). We found five 6.7 GHz maser clusters which are distributedover a region extended N-S across ~1500 AU and are associated with three peaksof the radio continuum. We proposed that these maser clusters identify threeindividual high-mass YSOs, named IRS1a, IRS1b, and IRS1c. We modeled the maserclusters in IRS1a and IRS1b in terms of edge-on disks in centrifugalequilibrium. In the first case, masers may trace a quasi-Keplerian thin disk,orbiting around a high-mass YSO, IRS1a, of up to 25 solar masses. This YSOdominates the bolometric luminosity of the region. The second disk is bothmassive (<16 Msun within ~500 AU) and thick, and the mass of the central YSO,IRS1b, is constrained to be at most a few solar masses. In summary, we presentcompelling evidence that NGC7538 IRS1 is not forming just one single high-massYSO, but consists of a multiple system of high-mass YSOs, which are surroundedby accretion disks, and are probably driving individual outflows. This newmodel naturally explains all the different orientations and disk/outflowstructures proposed for the region in previous models.

A multiple system of high-mass YSOs surrounded by disks in NGC7538 IRS1