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[166.03] Submillimeter water masers and a circumstellar disk in Cepheus-A

N. A. Patel, T. R. Hunter, T. K. Sridharan (CfA), S. Curiel (UNAM), J. M. Torrelles (IEEC), Q. Zhang, L. J. Greenhill, H. G. Beuther, P. T. P. Ho, J. M. Moran (CfA), J. F. Gomez (LAEFF-INTA), G. Anglada (CSIC)

We have observed the high-mass star-forming region Cepheus-A, using the Submillimeter Array at 321.2 GHz and 217.1 GHz, with an angular resolution of ~1'' and ~2.''5 at these frequencies, respectively. We have detected, for the first time in this source, the submillimeter water maser transition 10₂₉-9₃₆ (321.2 GHz). The maser emission is found to be associated with two of the protostars in the region: HW2 and HW3c, separated on the sky by about 3''. These are the very first interferometric observations of water maser emission at submillimeter wavelengths. To find out if the same gas is masing also at the well-known transition 6₁₆-5₂₃ at 22 GHz, we carried out a VLA A array snapshot of the Cepheus-A region. We will present a comparison between the submillimeter and centimeter wavelength water maser emission. The line-ratios of these transitions allow us to constrain the physical conditions of the masing gas near the protostars.

Several other lines were observed from the following molecules: ¹³CO, CN, SiO, SiS, SO₂, DCN, HC₃N, NH₂D, H₂CO, CH₃OH, CH₃CH₂CN, CH₃CH₂D, CN, HCOOCH₃, C₂H₅OH, C₂H₅CN. We will present 1''~ 2'' resolution images in some of these lines. The continuum emission from the circumstellar dust around the HW2 source (which is powering a well-known massive outflow) is detected in both 217 and 321 GHz bands. The elongated shape of this emission is perpendicular to the direction of the thermal jet previously observed with the VLA at 1.3 cm. This suggests that the submillimeter continuum emission could be arising from a circumstellar disk in Cepheus-A HW2.

The author(s) of this abstract have provided an email address for comments about the abstract: npatel@cfa.harvard.edu

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.