Water maser emission in IC 342

The detection of 22GHz water vapor emission from IC 342 is reported, raising the detection rate among northern galaxies with IRAS point source fluxes S100μm > 50 Jy to 16%. The maser, associated with a star forming region ∼10–15 west of the nucleus, consists of a single 0.5 kms wide feature and reaches an isotropic luminosity of 10 L⊙ (D=1.8Mpc). If the time variability is intrinsic, the maser size is ∼ 1.5×10 16 cm (∼0.5mas) which corresponds to a brightness temperature of ∼10 9 K. The linewidth, luminosity, and rapid variability are reminiscent of the 8 km s super maser in Orion-KL. A velocity shift of 1 km s within two weeks and subsequent rapid fading is explained in terms of a chance alignment of two dense molecular clouds. Observations at 22 GHz toward Maffei 2 are also reported, yielding a 5σ upper limit of 25mJy for a channel spacing of 1.05 kms.