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arXiv · 1401.2300

Herschel Observations of Far-Infrared Cooling Lines in intermediate Redshift (Ultra)-luminous Infrared Galaxies

D. Rigopoulou·R. Hopwood·G. E. Magdis·N. Thatte·B. M. Swinyard·D. Farrah·J-S. Huang·A. Alonso-Herrero·J. J. Bock·D. Clements·A. Cooray·M. J. Griffin·S. Oliver·C. Pearson·D. Riechers·D. Scott·A. Smith·M. Vaccari·I. Valtchanov·L. Wang
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Abstract

We report the first results from a spectroscopic survey of the [CII] 158um line from a sample of intermediate redshift (0.2 10^11.5 Lsun), using the SPIRE-Fourier Transform Spectrometer (FTS) on board the Herschel Space Observatory. This is the first survey of [CII] emission, an important tracer of star-formation, at a redshift range where the star-formation rate density of the Universe increases rapidly. We detect strong [CII] 158um line emission from over 80% of the sample. We find that the [CII] line is luminous, in the range (0.8-4)x10^(-3) of the far-infrared continuum luminosity of our sources, and appears to arise from photodissociation regions on the surface of molecular clouds. The L[CII]/LIR ratio in our intermediate redshift (U)LIRGs is on average ~10 times larger than that of local ULIRGs. Furthermore, we find that the L[CII]/LIR and L[CII]/LCO(1-0) ratios in our sample are similar to those of local normal galaxies and high-z star-forming galaxies. ULIRGs at z~0.5 show many similarities to the properties of local normal and high-z star forming galaxies. Our findings strongly suggest that rapid evolution in the properties of the star forming regions of luminous infrared galaxies is likely to have occurred in the last 5 billion years.

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D. Rigopoulou, R. Hopwood, G. E. Magdis, N. Thatte, B. M. Swinyard, D. Farrah, J-S. Huang, A. Alonso-Herrero, J. J. Bock, D. Clements, A. Cooray, M. J. Griffin, S. Oliver, C. Pearson, D. Riechers, D. Scott, A. Smith, M. Vaccari, I. Valtchanov, L. Wang. 2014-01-10. Herschel Observations of Far-Infrared Cooling Lines in intermediate Redshift (Ultra)-luminous Infrared Galaxies. https://doi.org/10.1088/2041-8205/781/1/l15

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