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Published January 20, 2014 | Published + Submitted
Journal Article Open

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


We report the first results from a spectroscopic survey of the [C II] 158 μm line from a sample of intermediate redshift (0.2 10^(11.5) L_☉), using the Spectral and Photometric Imaging REceiver-Fourier Transform Spectrometer on board the Herschel Space Observatory. This is the first survey of [C II] 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 [C II] 158 μm line emission from over 80% of the sample. We find that the [C II] line is luminous, in the range (0.8-4) × 10^(–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 [C_(II)]/L_(IR) ratio in our intermediate redshift (U)LIRGs is on average ~10 times larger than that of local ULIRGs. Furthermore, we find that the L [C_(II)]/L_(IR) and L [C_(II)]/L_(CO(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 (U)LIRGs is likely to have occurred in the last 5 billion years.

Additional Information

© 2014 American Astronomical Society. Received 2013 October 11; accepted 2013 December 6; published 2014 January 6. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. We thank the anonymous referee for his/her insightful comments. D.R. and G.E.M. acknowledge support from grant ST/K00106X/1 and the John Fell Oxford University Press (OUP) Research Fund (G.E.M.). This Letter is based on data from Herschel's SPIRE-FTS. SPIRE has been developed by a consortium of institutes led by Cardiff University (UK) and including: University of Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, University of Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, University of Sussex (UK); and Caltech, JPL, NHSC, University of Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC, UKSA (UK); and NASA (USA). Facilities: Herschel, IRAM:30m, APEX

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Published - 2041-8205_781_1_L15.pdf

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