High-velocity neon line emission from the ULIRG IRAS F00183-7111: revealing the optically obscured base of a nuclear outflow

Spoon, H. W. W.; Armus, L.; Marshall, J. A.; Bernard-Salas, J.; Farrah, D.; Charmandaris, V. and Kent, B. R. (2009). High-velocity neon line emission from the ULIRG IRAS F00183-7111: revealing the optically obscured base of a nuclear outflow. Astrophysical Journal, 693(2) pp. 1223–1235.

DOI: https://doi.org/10.1088/0004-637X/693/2/1223


We report the first mid-infrared detection of highly disturbed ionized gas in the ultraluminous infrared galaxy (ULIRG) IRAS F00183–7111. The gas, traced by the 12.81 μm [Ne II] and 15.56 μm [Ne III] lines, spans a velocity range of –3500 to +3000 km s−1 with respect to systemic velocity. Optical and near-infrared spectroscopic studies show no evidence for similarly high velocity gas components in forbidden lines at shorter wavelengths. We interpret this as the result of strong extinction (AV = 10–50) on the high-velocity gas, which identifies the base of the outflow traced in 5007 Å [O III] as a plausible origin. Unusual excitation conditions are implied by a comparison of the mid-infrared low-excitation neon line emission and the polycyclic aromatic hydrocarbon (PAH) emission for a sample of 56 ULIRGs. For IRAS F00183–7111, the neon/PAH ratio is 8 times higher than the average ratio. Similar mid-infrared kinematic and excitation characteristics are found for only two other ULIRGs in our sample: IRAS 12127–1412NE and IRAS 13451+1232. Both sources have an elevated neon/PAH ratio and exhibit pronounced blue wings in their 15.56 μm [Ne III] line profiles. IRAS 13451+1232 even shows a strongly blueshifted and broad 14.32 μm [Ne V] line. While for IRAS 13451+1232 the observed [Ne III]/[Ne II] and [Ne V]/[Ne II] line ratios indicate exposure of the blueshifted gas to direct radiation from the AGN, for IRAS F00183–7111 and IRAS 12127–1412NE the neon line ratios are consistent with an origin in fast shocks in a high-density environment, and with an evolutionary scenario in which strongly blueshifted [Ne II] and [Ne III] emission trace the (partial) disruption of the obscuring medium around a buried AGN. The detection of strongly blueshifted [Ne V] emission in IRAS 13451+1232 would then indicate this process to be much further advanced in this ULIRG than in IRAS F00183–7111 and IRAS 12127–1412NE, where this line is undetected.

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