Astronomy and Astrophysics, volume 404, 569-578 (2003/6-3)
Mapping of large scale 158 µm [CII] line emission: Orion A.
MOOKERJEA B., GHOSH S.K., KANEDA H., NAKAGAWA T., OJHA D.K., RENGARAJAN T.N., SHIBAI H. and VERMA R.P.
Abstract (from CDS):
We present the first results of an observational programme undertaken to map the fine structure line emission of singly ionized carbon ([CII] 157.7409µm) over extended regions using a Fabry Perot spectrometer newly installed at the focal plane of a 100cm balloon-borne far-infrared telescope. This new combination of instruments has a velocity resolution of ∼200km/s and an angular resolution of 1.5'. During the first flight, an area of 30'x15' in Orion A was mapped. These observations extend over a larger area than previous observations, the map is fully sampled and the spectral scanning method used enables reliable estimation of the continuum emission at frequencies adjacent to the [CII] line. The total [CII] line luminosity, calculated by considering up to 20% of the maximum line intensity is 0.04% of the luminosity of the far-infrared continuum. We have compared the [CII] intensity distribution with the velocity-integrated intensity distributions of 3CO(1-0), CI(1-0) and CO(3-2) from the literature. Comparison of the [CII], [CI] and the radio continuum intensity distributions indicates that the largescale [CII] emission originates mainly from the neutral gas, except at the position of M 43, where no [CI] emission corresponding to the [CII] emission is seen. Substantial part of the [CII] emission from here originates from the ionized gas. The observed line intensities and ratios have been analyzed using the PDR models by Kaufman et al. (1999ApJ...527..795K
) to derive the incident UV flux and volume density at a few selected positions. The models reproduce the observations reasonably well at most positions excepting the [CII] peak (which coincides with the position of θ1
Ori C). Possible reason for the failure could be the simplifying assumption of a homogeneous plane parallel slab in place of a more complicated geometry.
infrared: ISM - ISM: lines and bands - ISM: individual (Orion A)
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