SIMBAD references

We have selected 67 objects for observation that are presumably massive young stellar objects. They were from the IRAS Point Source Catalogue based on their infrared flux (F_ν≥500Jy at 100µm). All objects have been surveyed in the NH₃(1,1) and (2,2) lines, and a subsample of 53 objects in the rotational line of HCO⁺(J=1-0). 25 objects (37%) were detected in the NH₃(1,1) line, 18 objects (27%) in the NH₃(2,2) line, and 38 objects (72%) in the HCO⁺ line. Two objects, IRAS 06058+2138 and IRAS 06061+2151, have been mapped in the two ammonia transitions. From the molecular line data, we have derived the kinetic temperature T_kin and the NH₃ column densities. These data were combined with data from the literature and data derived from the IRAS fluxes (dust colour temperature T_d, optical depth τ, luminosity). No clear correlations were found; the data are, however, consistent with least square fits found by Wouterloot et al. (1988a). The probability to detect H₂O maser sources is strongly correlated with the detection of NH₃ emission: Water maser emission has been seen towards 83% of those objects with clear detections of NH₃(1,1) and (2,2) lines.