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Published May 20, 2011 | Published
Journal Article Open

Dynamical Structure of the Molecular Interstellar Medium in an Extremely Bright, Multiply Lensed z ≃ 3 Submillimeter Galaxy Discovered with Herschel


We report the detection of CO(J = 5 → 4), CO(J = 3 → 2), and CO(J = 1 → 0) emission in the strongly lensed, Herschel/SPIRE-selected submillimeter galaxy (SMG) HERMES J105751.1+573027 at z = 2.9574 ± 0.0001, using the Plateau de Bure Interferometer, the Combined Array for Research in Millimeter-wave Astronomy, and the Green Bank Telescope. The observations spatially resolve the molecular gas into four lensed images with a maximum separation of ~9" and reveal the internal gas dynamics in this system. We derive lensing-corrected CO line luminosities of L'_(CO(1-0)) = (4.17 ± 0.41), L'_(CO(3-2)) = (3.96 ± 0.20), and L'_(CO(5-4)) = (3.45 ± 0.20) × 10^(10) (μL/10.9)^(–1) K km s^(–1) pc^2, corresponding to luminosity ratios of r_(31) = 0.95 ± 0.10, r_(53) = 0.87 ± 0.06, and r_(51) = 0.83 ± 0.09. This suggests a total molecular gas mass of M_(gas) = 3.3×10^(10) (α_(CO)/0.8) (μ_L/10.9)^(–1) M_☉. The gas mass, gas mass fraction, gas depletion timescale, star formation efficiency, and specific star formation rate are typical for an SMG. The velocity structure of the gas reservoir suggests that the brightest two lensed images are dynamically resolved projections of the same dust-obscured region in the galaxy that are kinematically offset from the unresolved fainter images. The resolved kinematics appear consistent with the complex velocity structure observed in major, "wet" (i.e., gas-rich) mergers. Major mergers are commonly observed in SMGs and are likely to be responsible for fueling their intense starbursts at high gas consumption rates. This study demonstrates the level of detail to which galaxies in the early universe can be studied by utilizing the increase in effective spatial resolution and sensitivity provided by gravitational lensing.

Additional Information

© 2011 The American Astronomical Society. Received 2011 February 18; accepted 2011 April 14; published 2011 May 3. We thank the referee for a detailed and helpful report. D.R. acknowledges support from NASA through Hubble Fellowship grant HST-HF-51235.01 awarded by STScI, operated by AURA for NASA, under contract NAS 5-26555. A.J.B. acknowledges support from NSF grant AST-0708653 to Rutgers University. IRAMis supported by INSU/CNRS(France),MPG (Germany), and IGN (Spain). Support for CARMA construction was derived from the Moore and Norris Foundations, the Associates of Caltech, the states of California, Illinois, and Maryland, and the NSF. Ongoing CARMA development and operations are supported by the NSF under a cooperative agreement, and by the CARMA partner universities. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

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