Water maser emission in IC 342

Free access article

Issue		A&A Volume 385, Number 3, April III 2002


Page(s)		1049 - 1055
Section		Diffuse matter in space
DOI		http://dx.doi.org/10.1051/0004-6361:20020199

A&A 385, 1049-1055 (2002)
DOI: 10.1051/0004-6361:20020199

Water maser emission in IC 342

A. Tarchi, C. Henkel, A. B. Peck and K. M. Menten

Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

(Received 19 September 2001 / Accepted 4 February 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 $S_{\rm 100\,\mu m} > 50$ Jy to 16%. The maser, associated with a star forming region ~10-15´´ west of the nucleus, consists of a single 0.5 km s ^-1 wide feature and reaches an isotropic luminosity of 10 ^-2 $L_{\odot}$ ( D=1.8 Mpc). If the time variability is intrinsic, the maser size is $\la$ $1.5\times10^{16}$ cm ( $\la$ 0.5 mas) which corresponds to a brightness temperature of $\ga$ 10 ⁹ 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 5 $\sigma$ upper limit of 25 mJy for a channel spacing of 1.05 km s ^-1.

Key words: galaxies: individual: IC 342, Maffei 2 -- galaxies: starburst -- ISM: molecules -- masers -- radio lines: ISM

Offprint request: A. Tarchi, atarchi@mpifr-bonn.mpg.de

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