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Submillimeter galaxies at z ~ 2: evidence for major mergers and constraints on lifetimes, IMP and CO-H_2 conversion factor

Tacconi, L. J. and Genzel, R. and Smail, I. and Neri, R. and Chapman, S. C. and Ivison, R. J. and Blain, A. and Cox, P. and Omont, A. and Bertoldi, F. and Greve, T. and Förster Schreiber, N. M. and Genel, S. and Lutz, D. and Swinbank, A. M. and Shapley, A. E. and Erb, D. K. and Cimatti, A. and Daddi, E. and Baker, J. (2008) Submillimeter galaxies at z ~ 2: evidence for major mergers and constraints on lifetimes, IMP and CO-H_2 conversion factor. Astrophysical Journal, 680 (1). pp. 246-262. ISSN 0004-637X.

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We report subarcsecond resolution IRAM PdBI millimeter CO interferometry of four z ~ 2 submillimeter galaxies (SMGs), and sensitive CO(3-2) flux limits toward three z ~ 2 UV/optically selected star-forming galaxies. The new data reveal for the first time spatially resolved CO gas kinematics in the observed SMGs. Two of the SMGs show double or multiple morphologies, with complex, disturbed gas motions. The other two SMGs exhibit CO velocity gradients of ~500 km s^−1 across ≤0.2" (1.6 kpc) diameter regions, suggesting that the star-forming gas is in compact, rotating disks. Our data provide compelling evidence that these SMGs represent extreme, short-lived "maximum" star-forming events in highly dissipative mergers of gas-rich galaxies. The resulting high-mass surface and volume densities of SMGs are similar to those of compact quiescent galaxies in the same redshift range and much higher than those in local spheroids. From the ratio of the comoving volume densities of SMGs and quiescent galaxies in the same mass and redshift ranges, and from the comparison of gas exhaustion timescales and stellar ages, we estimate that the SMG phase duration is about 100 Myr. Our analysis of SMGs and optically/UV selected high-redshift star-forming galaxies supports a "universal" Chabrier IMF as being valid over the star-forming history of these galaxies. We find that the ^(12)CO luminosity to total gas mass conversion factors at z ~ 2-3 are probably similar to those assumed at z ~ 0. The implied gas fractions in our sample galaxies range from 20% to 50%.

Item Type:Article
Related URLs:
URLURL TypeDescription
Tacconi, L. J.0000-0002-1485-9401
Genzel, R.0000-0002-2767-9653
Smail, I.0000-0003-3037-257X
Neri, R.0000-0002-7176-4046
Ivison, R. J.0000-0001-5118-1313
Blain, A.0000-0001-7489-5167
Cox, P.0000-0003-2027-8221
Omont, A.0000-0002-4721-3922
Bertoldi, F.0000-0002-1707-1775
Genel, S.0000-0002-3185-1540
Lutz, D.0000-0003-0291-9582
Shapley, A. E.0000-0003-3509-4855
Erb, D. K.0000-0001-9714-2758
Daddi, E.0000-0002-3331-9590
Additional Information:© 2008 The American Astronomical Society. Received 2007 November 13, accepted for publication 2008 January 23. We thank the staff of the IRAM Observatory for their support of this program. We are grateful to Thorsten Naab, Andi Burkert, and Amiel Sternberg for valuable discussions. We also thank the referee for constructive comments that have helped to clarify and improve the paper. I. R. S. acknowledges support from the Royal Society, and A. M. S. acknowledges support from STFC.
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords:cosmology: observations; galaxies: evolution; galaxies: formation; galaxies: high-redshift; galaxies: kinematics and dynamics; stars: luminosity function; stars: mass function
Issue or Number:1
Record Number:CaltechAUTHORS:20090514-185548161
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14227
Deposited By: Joy Painter
Deposited On:03 Jun 2009 21:25
Last Modified:04 Dec 2019 23:36

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