Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 434, Issue 3, Pages 2051-2059Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stt1149
Keywords
galaxies: individual : IC 342; galaxies: ISM; galaxies: star formation; infrared: galaxies
Categories
Funding
- John Fell Oxford University Press (OUP) Research Fund
- CSA (Canada)
- NAOC (China)
- CEA (France)
- CNES (France)
- CNRS (France)
- ASI (Italy)
- MCINN (Spain)
- SNSB (Sweden)
- STFC (UK)
- UKSA (UK)
- NASA (USA)
- STFC [ST/K00106X/1, ST/F006977/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/F006977/1, ST/K00106X/1] Funding Source: researchfish
Ask authors/readers for more resources
We present observations of the nearby spiral galaxy IC 342 with the Herschel Spectral and Photometric Imaging Receiver (SPIRE) Fourier transform spectrometer. The spectral range afforded by SPIRE, 196-671 mu m, allows us to access a number of (CO)-C-12 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 (CO)-C-13, [C i] and [N ii]. 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 (CO)-C-12 components, one at 35 K and one at 400 K with CO column densities of 6.3 x 10(17) and 0.4 x 10(17) cm(-2) and CO gas masses of 1.26 x 10(7) and 0.15 x 10(7) M-circle dot for the cold and warm components, respectively. The inclusion of the high-J (CO)-C-12 line observations indicate the existence of a much warmer gas component (similar to 400 K) confirming earlier findings from H-2 rotational line analysis from Infrared Space Observatory and Spitzer. The mass of the warm gas is 10 per cent of the cold gas, but it likely dominates the CO luminosity. In addition, we detect strong emission from [N ii] 205 mu m and the P-3(1) -> P-3(0) and P-3(2) -> P-3(1) [C i] lines at 370 and 608 mu m, respectively. The measured (CO)-C-12 line ratios can be explained by photon-dominated region (PDR) models although additional heating by e.g. cosmic rays cannot be excluded. The measured [C i] line ratio together with the derived [C] column density of 2.1 x 10(17) cm(-2) and the fact that [C i] is weaker than CO emission in IC 342 suggests that [C i] likely arises in a thin layer on the outside of the CO emitting molecular clouds consistent with PDRs playing an important role.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available