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Title: A HIGHER EFFICIENCY OF CONVERTING GAS TO STARS PUSHES GALAXIES AT z ∼ 1.6 WELL ABOVE THE STAR-FORMING MAIN SEQUENCE

Local starbursts have a higher efficiency of converting gas into stars, as compared to typical star-forming galaxies at a given stellar mass, possibly indicative of different modes of star formation. With the peak epoch of galaxy formation occurring at z > 1, it remains to be established whether such an efficient mode of star formation is occurring at high redshift. To address this issue, we measure the molecular gas content of seven high-redshift (z ∼ 1.6) starburst galaxies with the Atacama Large Millimeter/submillimeter Array and IRAM/Plateau de Bure Interferometer. Our targets are selected from the sample of Herschel far-infrared-detected galaxies having star formation rates (∼300–800 M{sub ⊙} yr{sup −1}) elevated (≳4×) above the star-forming main sequence (MS) and included in the FMOS-COSMOS near-infrared spectroscopic survey of star-forming galaxies at z ∼ 1.6 with Subaru. We detect CO emission in all cases at high levels of significance, indicative of high gas fractions (∼30%–50%). Even more compelling, we firmly establish with a clean and systematic selection that starbursts, identified as MS outliers, at high redshift generally have a lower ratio of CO to total infrared luminosity as compared to typical MS star-forming galaxies, although with a smaller offset than expected based onmore » past studies of local starbursts. We put forward a hypothesis that there exists a continuous increase in star formation efficiency with elevation from the MS with galaxy mergers as a possible physical driver. Along with a heightened star formation efficiency, our high-redshift sample is similar in other respects to local starbursts, such as being metal rich and having a higher ionization state of the interstellar medium.« less
Authors:
;  [1] ; ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ;  [11] ; ;  [12] ;  [13] ;  [14] ;
  1. Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583 (Japan)
  2. Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, Irfu/Service d’Astrophysique, CEA Saclay (France)
  3. Dipartimento di Fisica e Astronomia, Universita di Padova, vicolo Osservatorio, 3, I-35122 Padova (Italy)
  4. Astronomy Centre, Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH (United Kingdom)
  5. Instituto Nazionale de Astrofisica, Osservatorio Astronomico di Padova, v.co dell’Osservatorio 5, I-35122 Padova (Italy)
  6. IRAM—Institut de RadioAstronomie Millimétrique, 300 rue de la Piscine, F-38406 Saint Martin d’Hères (France)
  7. Division of Particle and Astrophysical Science, Graduate School of Science, Nagoya University, Nagoya 464-8602 (Japan)
  8. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
  9. National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States)
  10. Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577 (Japan)
  11. Subaru Telescope, 650 North A’ohoku Place, Hilo, HI-96720 (United States)
  12. Max-Planck-Institut für extraterrestrische Physik, D-84571 Garching (Germany)
  13. European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany)
  14. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, 21218 (United States)
Publication Date:
OSTI Identifier:
22518775
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 812; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON MONOXIDE; COMPARATIVE EVALUATIONS; GALAXIES; INFRARED SPECTRA; INTERSTELLAR SPACE; LUMINOSITY; MAIN SEQUENCE STARS; MASS; NEAR INFRARED RADIATION; RED SHIFT; STAR EVOLUTION; UNIVERSE