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2001MNRAS.320..465B - Mon. Not. R. Astron. Soc., 320, 465-476 (2001/February-1)

Ground-state OH observations towards NGC 6334.

BROOKS K.J. and WHITEOAK J.B.

Abstract (from CDS):

We have made observations of the four hyperfine transitions of the 2Π3/2, J=3/2 ground state of OH at 1612, 1665, 1667 and 1720MHz and the related 1.6-GHz continuum emission towards NGC 6334 using the Australia Telescope Compact Array. The observations covered all the major radio continuum concentrations aligned along the axis of NGC 6334 (V, A to F). We have detected seven OH masers plus a possible faint eighth maser; two of these masers are located towards NGC 6334-A. Absorption at 1665 and 1667MHz was detected towards almost all the continuum distribution. All transitions show non-LTE behaviour. The 1667-/1665-MHz intensity ratios range from 1.0 to 1.2, significantly less than their LTE value of 1.8. The results of the OH `Sum Rule' suggest that this discrepancy cannot be explained solely by high optical depths. The 1612- and 1720-MHz line profiles show conjugate behaviour whereby one line is in absorption and the other in emission. In addition, the profiles commonly showed a flip from absorption to emission and vice versa, which is interpreted as a density gradient. The OH line-to-continuum distribution, optical depth and velocity trends are consistent with a bar-like shape for the molecular gas which wraps around the continuum emission.

Abstract Copyright: 2001, Royal Astronomical Society

Journal keyword(s): line: profiles - masers - stars: formation - ISM: clouds - Hii regions - ISM: kinematics and dynamics

Nomenclature: Fig.1, Table 1: RCM A(W) (No. D(S)) added.

Simbad objects: 12

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