Ground-state OH observations towards NGC 6334

Abstract

We have made observations of the four hyperfine transitions of the 2Pi(3/2), J=3/2 ground state of OH at 1612, 1665, 1667 and 1720 MHz 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 1667 MHz was detected towards almost all the continuum distribution. All transitions showed non-LTE behaviour. The 1667-/1665-MHz intensity ratios ranged 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 showed conjugate behaviour whereby one line was in absorption and the other in emission. In addition, the profiles commonly showed a flip from absorption to emission and vice versa, which has been 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.

12 pages, 12 figures, accepted for publication in MNRAS

References in corpus (1)

• OH Satellite Line Masers in the Nucleus of NGC253

Cited by in corpus (25)

• New OH Zeeman measurements of magnetic field strengths in molecular clouds
• Herschel/HIFI discovery of interstellar chloronium (H${}_2$Cl${}^{+}$)
• Detection of interstellar oxidaniumyl: abundant H2O+ towards the star-forming regions DR21, Sgr B2, and NGC6334
• Molecular line survey of the high-mass star-forming region NGC 6334I with Herschel/HIFI and the SMA
• Hot ammonia in NGC6334I & I(N)
• SiO and CH3CCH abundances and dust emission in high-mass star-forming cores
• SPLASH: The Southern Parkes Large-Area Survey in Hydroxyl - First Science from the Pilot Region
• The Abundance, Ortho/Para Ratio, and Deuteration of Water in the High-Mass Star Forming Region NGC 6334 I
• High-spatial-resolution observations of NH3 and CH3OH towards the massive twin cores NGC6334 I & I(N)
• Extended emission associated with young HII regions
• Magnetized converging flows towards the hot core in the intermediate/high-mass star-forming region NGC 6334 V
• ATCA 3mm observations of NGC6334I and I(N): dense cores, outflows and an UCHII region
• Discovery of Pulsed OH Maser Emission Stimulated by a Pulsar
• OH absorption in the first quadrant of the Milky Way as seen by THOR
• OH Survey along Sightlines of Galactic Observations of Terahertz C+
• Ionization toward the high-mass star-forming region NGC 6334 I
• Herschel/HIFI observations of spectrally resolved methylidyne signatures toward the high-mass star-forming core NGC6334I
• The interaction of young massive stars with their environment: A millimeter and submillimeter line study of NGC6334 FIR II
• The hydroxyl satellite-line `flip' as a tracer of expanding HII regions
• A Catalog of CH_3OH 7_0-6_1 A^+ Maser Sources in Massive Star-Forming Regions. II. Masers in NGC 6334F, G8.67-0.36, and M17
• The first high-resolution observations of 37.7-, 38.3- and 38.5-GHz methanol masers
• Wide-Field Infrared Imaging Polarimetry of the NGC 6334 Region: A Nest of Infrared Reflection Nebulae
• Three-dimensional distribution of hydrogen fluoride gas toward NGC6334 I and I(N)
• The richness of compact radio sources in NGC 6334D to F
• Massive Stars in Molecular Clouds Rich in High-energy Sources: The Bridge of G332.809-0.132 and CS 78 in NGC 6334