Context : This paper is the second in a series of ammonia ( NH _ { 3 } ) multilevel imaging studies in high-mass star forming regions .

Aims : We want to identify the location of the maser emission from highly-excited levels of ammonia within the W51 IRS2 high-mass star forming complex , that was previously discovered in a single-dish monitoring program .

Methods : We have used the Karl G. Jansky Very Large Array ( JVLA ) at the 1 cm band to map five highly-excited metastable inversion transitions of NH _ { 3 } , ( J , K ) = ( 6,6 ) , ( 7,7 ) , ( 9,9 ) , ( 10,10 ) , and ( 13,13 ) , in W51 IRS2 with \sim 0 \hbox to 0.0 pt { . } ^ { \prime \prime } 2 angular resolution .

Results : We present detections of both thermal ( extended ) ammonia emission in the five inversion lines , with rotational states ranging in energy from about 400 to 1700 K , and point-like ammonia maser emission in the ( 6,6 ) , ( 7,7 ) , and ( 9,9 ) lines .
For the point-like emission , we estimate lower limits to the peak brightness temperatures of 1.7 \times 10 ^ { 5 } K , 6 \times 10 ^ { 3 } K , and 1 \times 10 ^ { 4 } K for the ( 6,6 ) , ( 7,7 ) , and ( 9,9 ) transitions , respectively , confirming their maser nature .
The thermal ammonia emits around a Local Standard of rest velocity of V _ { LSR } = 60 km s ^ { -1 } , near the cloud ’ s systemic velocity , appears elongated in the East-West direction across 4″ and is confined by the HII regions W51d ( to the North ) , W51d1 ( to the East ) , and W51d2 to the West .
The NH _ { 3 } masers are observed in the eastern tip of the dense clump traced by thermal NH _ { 3 } , offset by 0. ” 65 to the East from its emission peak , and have a peak velocity at \sim 47.5 km s ^ { -1 } .
No maser components are detected near the systemic velocity .
The NH _ { 3 } masers arise close to but separated ( 0 \hbox to 0.0 pt { . } ^ { \prime \prime } 65 or 3500 AU ) from the ( rare ) vibrationally-excited SiO masers , which are excited in a powerful bipolar outflow driven by the deeply-embedded high-mass young stellar object ( YSO ) W51-North .
This excludes that the two maser species are excited by the same object .
Interestingly , the NH _ { 3 } masers originate at the same sky position as a peak in a submm line of SO _ { 2 } imaged with the SMA , tracing a face-on circumstellar disk/ring around W51-North .
In addition , the thermal emission from the most highly excited NH _ { 3 } lines , ( 10,10 ) and ( 13,13 ) , shows two main condensations , the dominant one towards W51-North with the SiO/H _ { 2 } O masers , and a weaker peak at the NH _ { 3 } maser position .

Conclusions : We propose a scenario where the ring seen in SO _ { 2 } emission is a circumbinary disk surrounding ( at least ) two high-mass YSOs , W51-North ( exciting the SiO masers ) and a nearby companion ( exciting the NH _ { 3 } masers ) , separated by 3500 AU .
This finding indicates a physical connection ( in a binary ) between the two rare SiO and NH _ { 3 } maser species .