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.
Water maser emission in IC342
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
