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
2002-01-01
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.
