Herschel-PACS observations of [OI]63um towards submillimetre galaxies at z 1
Date
2012-08-23
Authors
Coppin, Kristen
Danielson, Alice
Geach, James E.
Hodge, Jacqueline
Swinbank, Mark
Wardlow, Julie
Bertoldi, Frank
Biggs, Andy
Brandt, Niel
Caselli, Paola
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Abstract
We present Herschel-PACS spectroscopy of the [OI]63um far-infrared cooling line from a sample of six unlensed and spectroscopically-confirmed 870um-selected submillimetre (submm) galaxies (SMGs) at 1.13, tentatively detect [OI]63um in one SMG, and constrain the line flux for the non-detections. We also exploit the combination of submm continuum photometry from 250-870um and our new PACS continuum measurements to constrain the far-infrared (FIR) luminosity, L_FIR, in these SMGs to < 30%. We find that SMGs do not show a deficit in their [OI]63um-to-far-infrared continuum luminosity ratios (with ratios ranging from ~0.5-1.5%), similar to what was seen previously for the [CII]158um-to-FIR ratios in SMGs. These observed ratios are about an order of magnitude higher than what is seen typically for local ultra luminous infrared galaxies (ULIRGs), which adds to the growing body of evidence that SMGs are not simply `scaled up' versions of local ULIRGs. Rather, the PDR line-to-L_FIR ratios suggest that the star formation modes of SMGs are likely more akin to that of local normal (lower-luminosity) star-forming galaxies, with the bulk of the star formation occurring in extended regions, galaxy-scale (~kpc) in size. These observations represent the first step towards a census of the major PDR cooling lines in typical SMGs that will be attainable with ALMA, enabling detailed modelling to probe the global properties of the star formation and the evolutionary status of SMGs.
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Citation
Coppin, Kristen, Alice Danielson, James E. Geach, Jacqueline Hodge, et al. 2012. "Herschel-PACS observations of [OI]63um towards submillimetre galaxies at z 1." Monthly Notices of the Royal Astronomical Society 427:520.