High-angular resolution observations of methanol in the infrared dark cloud core G11.11-0.12P1

Abstract

Recent studies suggest that infrared dark clouds (IRDCs) have the potential of harboring the earliest stages of massive star formation and indeed evidence for this is found toward distinct regions within them. We present a study with the Plateau de Bure Interferometer of a core in the archetypal filamentary IRDC G11.11-0.12 of a few arcsecond resolution to determine its physical and chemical structures. The data consist of continuum and line observations covering the C^(34)S 2 → 1 line and the methanol 2_k → 1_k v_t = 0 lines at 3 mm and the methanol 5_k → 4_k v_t = 0 lines at 1 mm. Our observations show extended emission in the continuum at 1 and 3 mm. The methanol 2_k → 1_k v_t = 0 emission has three maxima extending over a 1 pc scale (when merged with single-dish short-spacing observations); one of the maxima is spatially coincident with the continuum emission. The fitting results show an enhanced methanol fractional abundance (~3 × 10^(-8)) at the central peak with respect to the other two peaks, where it decreases by about an order of magnitude (~4−6 × 10^(-9)). Evidence of extended 4.5 μm emission, "wings" in the CH_3OH 2_k → 1_k spectra, and CH_3OH abundance enhancements point to the presence of an outflow in the east-west direction. In addition, we find a gradient of ~4 km s^(-1) in the same direction, which we interpret as being produced by an outflow(s)-cloud interaction.

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