Herschel-SPIRE-Fourier Transform Spectroscopy of the nearby spiral galaxy IC342
| Autor: | Peter Hurley, R. Hopwood, Chris Pearson, Edward Polehampton, Eric W. Pellegrini, Georgios E. Magdis, Dimitra Rigopoulou, J. S. Virdee, Bruce Swinyard, T. L. Lim, Kevin V. Croxall, J. D. Smith |
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| Jazyk: | angličtina |
| Rok vydání: | 2013 |
| Předmět: |
Physics
Luminous infrared galaxy Cosmology and Nongalactic Astrophysics (astro-ph.CO) Spiral galaxy Molecular cloud FOS: Physical sciences Astronomy Astronomy and Astrophysics Cosmic ray Astrophysics Astrophysics - Astrophysics of Galaxies Fourier transform spectroscopy Luminosity Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) Radiative transfer Line (formation) Astrophysics - Cosmology and Nongalactic Astrophysics |
| Popis: | We present observations of the nearby spiral galaxy IC342 with the Herschel Spectral and Photometric Imaging Receiver (SPIRE) Fourier Transform Spectrometer. The spectral range afforded by SPIRE, 196-671 microns, allows us to access a number of 12CO lines from J=4--3 to J=13--12 with the highest J transitions observed for the first time. In addition we present measurements of 13CO, [CI] and [NII]. We use a radiative transfer code coupled with Bayesian likelihood analysis to model and constrain the temperature, density and column density of the gas. We find two 12CO components, one at 35 K and one at 400 K with CO column densities of 6.3x10^{17} cm^{-2} and 0.4x10^{17} cm^{-2} and CO gas masses of 1.26x10^{7} Msolar and 0.15x10^{7} Msolar, for the cold and warm components, respectively. The inclusion of the high-J 12CO line observations, indicate the existence of a much warmer gas component (~400 K) confirming earlier findings from H_{2} rotational line analysis from ISO and Spitzer. The mass of the warm gas is 10% of the cold gas, but it likely dominates the CO luminosity. In addition, we detect strong emission from [NII] 205microns and the {3}P_{1}->{3}P_{0} and {3}P_{2} ->{3}P_{1} [CI] lines at 370 and 608 microns, respectively. The measured 12CO line ratios can be explained by Photon-dominated region (PDR) models although additional heating by e.g. cosmic rays cannot be excluded. The measured [CI] line ratio together with the derived [C] column density of 2.1x10^{17} cm^{-2} and the fact that [CI] is weaker than CO emission in IC342 suggests that [CI] likely arises in a thin layer on the outside of the CO emitting molecular clouds consistent with PDRs playing an important role. 9 pages, 8 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS) |
| Databáze: | OpenAIRE |
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