The New Molecular Cloud in Orion

In a recently discovered infrared cluster about 12' north of the Kleinmann-Low (KL) infrared nebula in Orion, we have detected microwave emission from H12CN, , NH3, U89.2, and U90.7. Three outstanding characteristics of this cloud are: (1) strong millimeter-wavelength lines of HCN, U89.2, and U90.7 with intensities comparahle to, though somewhat less than, the same lines in the KL nebula, (2) very narrow line widths (< 1.7 km ), which have allowed us to obtain improved rest frequencies for U89.2 and U9O.7 and improved limits on any hyperfine structure in these lines, and (3) a north-south ridge observed in HCN that extends over a very large area ( 5' X 18' to one-third power) from the south where it joins with the well-known Orion molecular cloud to at least 25' north of KL. Analysis of line widths and velocity gradients across the source suggests that collapse, expansion, and rotational motions are not important line broadening effects, leaving turbulence to account for the observed line widths. Subject headings: molecules, interstellar - Orion Nebula - radio lines