The distribution of the warm and dense molecular gas around Cepheus A HW 2 |
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| Authors: | J M Torrelles J F Gómez G Garay L F Rodríguez L F Miranda S Curiel P T P Ho |
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| Institution: | Institut d'Estudis Espacials de Catalunya (IEEC/CSIC), Edifici Nexus, C/ Gran Capità2-4, E-08034 Barcelona, Spain; Instituto de Astrofísica de Andalucúa, CSIC, Apdo. Correos 3004, E-18080 Granada, Spain Laboratorio de Astrofísica Espacial y Física Fundamental, INTA, Apdo. Correos 50727, E-28080 Madrid, Spain Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70-264, DF 04510, México Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA |
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| Abstract: | We present VLA observations of the ( J , K )=(1, 1), (2, 2), (3, 3) and (4, 4) inversion transitions of NH3 toward the HW 2 object in Cepheus A, with 1-arcsec angular resolution. Emission is detected in the main hyperfine line of the first three transitions. The NH3(2, 2) emission shows a non-uniform 'ring' structure, which is more extended (3 arcsec) and intense than the emission seen in the (1, 1) and (3, 3) lines. A rotational temperature of ～ 30–50 K and a lower limit to the mass of ～ 1 ( X NH3/10?8)?1 M⊙ are derived for the ring structure. The spatio-kinematical distribution of the NH3 emission does not seem to be consistent with a simple circumstellar disc around the HW 2 thermal biconical radio jet. We suggest that it represents the remnant of the parental core from which both the inner 300-au (0.4 arcsec) disc, traced by the water maser spots previously found in the region, and the central object have formed. The complex velocity field of this core is probably produced from bound motions (similar to those of the inner disc) and from interaction with outflowing material. |
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| Keywords: | stars: pre-main-sequence ISM: individual: Cepheus A ISM: jets and outflows ISM: molecules radio lines: ISM |
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