2 Observations

Observations were carried out from March 28 to April 10 1995 using the Medicina 32-m radio telescope. We used a dual-polarization uncooled receiver with HEMT amplifiers, tuned to the 5₁-6₀A⁺ line rest frequency, 6668.518 MHz. The system noise temperature was about 130 K for the right circular polarization and about 140 K for the left circular polarization. The antenna gain was estimated to be about 9 Jy/K from observations of DR 21 and 3C 123 as calibrators assuming a flux density of 21 Jy and 12 Jy, respectively. Elevation gain curves were estimated to correct for small elevation gain changes, using DR21 and 3C 123 as primary calibrators and 3C 273 (42 Jy) and 3C 274 (60 Jy) as secondary calibrators.

The beamwidth at 6.7 GHz was 5.6 arcmin. The observations were made in the position-switching mode with $1^{\circ}$ separation between on and off positions. The backend was a 512-channel autocorrelator with 3.1 MHz bandwidth which provided 0.27 km s^-1 velocity resolution and 141 km s^-1 velocity coverage. Some of the detected sources were additionally observed with 0.07 km s^-1 resolution (0.78 MHz bandwidth).