SIMBAD references

We have conducted an HCN (J=1-0) survey of 37 star-forming and quiescent dense cloud cores. HCN emission was detected toward 31 of the 33 cores containing embedded point sources, with only weak or no HCN detection among four starless sources. We find that the J=1-0 transition of the HCN molecule is particularly well suited for revealing the early stages of star formation in molecular clouds. In the sample of star-forming cores, there is excellent spatial coincidence (better than 7") between the position of the peak integrated HCN emission and the location of the associated young stellar object (YSO). Furthermore, emission strength in this HCN transition is well correlated with the YSO class: Class 0 and Class I YSOs are preferentially detected. Detecting strong (>1 K km.s^–1) HCN emission from a molecular cloud core indicates the presence of an embedded YSO and thus, indirectly, of a collapsing core. In addition, detection of very strong (>3 K km.s^–1) HCN emission implies an 80% likelihood of the presence of an embedded Class 0 YSO.