Publication Date:
2002
abstract:
The detection of 22 GHz water vapor emission from IC 342 is reported,
raising the detection rate among northern galaxies with IRAS point source
fluxes S100 ?m > 50 Jy to 16%. The maser, associated with a star forming
region ~ 10-15 arcsec west of the nucleus, consists of a single 0.5 km s-1
wide feature and reaches an isotropic luminosity of 10-2 Lsun (D=1.8 Mpc).
If the time variability is intrinsic, the maser size is la 1.5*E16 cm (la
0.5 mas) which corresponds to a brightness temperature of ga 109 K. The
linewidth, luminosity, and rapid variability are reminiscent of the 8 km
s-1 super maser in Orion-KL. A velocity shift of 1 km s-1 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 5sigma upper limit of 25 mJy for a channel spacing of
1.05 km s-1.
Iris type:
01.01 Articolo in rivista