Left panel: CH₃OH maser structures detected with MERLIN around NGC 7538-IRS1. Contours are 16, 32, 64, 128, 256, 512, 1024  ×  0.15 Jy beam^-1. The synthesized beam is 47 mas  ×  34 mas. Right panel: a close-up view of the CH₃OH maser features detected with the EVN around NGC 7538-IRS1. The synthesized beam is 6.3 mas  ×  4.9 mas. The triangle symbols are the identified maser features in the present work scaled logarithmically according to their peak flux density. The maser LSR radial velocity is indicated by color. A 5 Jy beam^-1 symbol is plotted for illustration in the right panels. The absolute reference position is and δ₂₀₀₀ =  + 61°28′10′′.506 as determined from the MERLIN observations. The linear polarization vectors, scaled logarithmically according to the polarization fraction P₁ (Tables 2 and 3), are overplotted.