Herschel-PACS observations of [O I]63 μm towards submillimetre galaxies at z~1
Journal article, 2012
We present Herschel-PACS spectroscopy of the [O I]63 μm far-infrared cooling line from a sample of six unlensed and spectroscopically confirmed 870 μm selected submillimetre (submm) galaxies (SMGs) at 1.1 < z < 1.6 from the LABOCA Extended Chandra Deep Field South (ECDFS) Submm Survey (LESS). This is the first survey of [O I]63 μm, one of the main photodissociation region (PDR) cooling lines, in SMGs. New high-resolution Atacama Large Millimetre Array (ALMA) interferometric 870 μm continuum imaging confirms that these six Herschel-targeted SMG counterparts are bona fide sources of submm emission. We detect [O I]63 μm in two SMGs with an SNR ≳ 3, tentatively detect [O I]63 μm in one SMG and constrain the line flux for the non-detections. We also exploit the combination of submm continuum photometry from 250 to 870 μm and our new PACS continuum measurements to constrain the far-infrared luminosity, LFIR, in these SMGs to ≲30 per cent. We find that SMGs do not show a deficit in their [O I]63 μm-to-far-infrared (FIR) continuum luminosity ratios (with ratios ranging from ≃0.5 to 1.5 per cent), similar to what was seen previously for the [C II]158 μm-to-FIR ratios in SMGs. These observed ratios are about an order of magnitude higher than what is seen typically for local ultraluminous 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-LFIR 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 galaxy-scale (˜kpc) regions. 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. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
galaxies: ISM
galaxies: star formation
infrared: ISM
galaxies: high-redshift
galaxies: starburst
submillimetre: galaxies
Author
K. E. K. Coppin
McGill University
A. L. R. Danielson
Durham University
J.E. Geach
McGill University
J. Hodge
Max Planck Society
A.M. Swinbank
Durham University
J. L. Wardlow
University of California at Irvine (UCI)
F. Bertoldi
Max Planck Society
A. D. Biggs
European Southern Observatory (ESO)
W. N. Brandt
Pennsylvania State University
P. Caselli
University of Leeds
S.C. Chapman
University of Cambridge
H. Dannerbauer
University of Vienna
J.S. Dunlop
University of Edinburgh
T. R. Greve
University College London (UCL)
F. Hamann
University of Florida
R.J. Ivison
Royal Observatory
University of Edinburgh
A. Karim
Durham University
Kirsten Kraiberg Knudsen
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
K.M. Menten
Max Planck Society
E. Schinnerer
Max Planck Society
I. Smail
Durham University
M. Spaans
University of Groningen
F. Walter
Max Planck Society
T.M.A. Webb
McGill University
P.P. van der Werf
Leiden University
Monthly Notices of the Royal Astronomical Society
0035-8711 (ISSN) 1365-2966 (eISSN)
Vol. 427 1 520-532Subject Categories
Astronomy, Astrophysics and Cosmology
Roots
Basic sciences
DOI
10.1111/j.1365-2966.2012.21977.x