We have used the Very Large Array to search for compact milliarcsecond-size radio sources near methanol masers in high-mass star-forming regions. Such sources are required for Very Long Baseline Interferometry phase-referencing observations. We conducted p

parisonofCalibratorPositionErrorsDerivedfromVLAandVLBIData

SourceName

VLA-CPositionα(2000)δ(2000)

(Y/C VLBI)

(arcsec)

VLA-APositionα(2000)δ(2000)

(Y/A VLBI)

(arcsec)

VLBI

α(2000)δ(2000)

Error

(mas)

Note.—-Listedare,lefttoright,sourcename,positionderivedfromVLAC-arrayobservations,di erencebetweenthelatterandtheVLBIposition(easto setandnortho set),positionderivedfromVLAA-arrayobservations,di erencebetweenthelatterandtheVLBIposition,andtheVLBIpositionanditsuncertainties.Ofthecoordinatesforthelattertwopositionsonlysecondsoftimeandarcsecondsaregiven.

a

FromourVLBAobservations(Xuetal.2006).

bFromVCS3(Petrovetal.2005).