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Resolved spectroscopy of gravitationally lensed galaxies: recovering coherent velocity fields in subluminous z ~ 2–3 galaxies

Jones, T. A. and Swinbank, A. M. and Ellis, R. S. and Richard, J. and Stark, D. P. (2010) Resolved spectroscopy of gravitationally lensed galaxies: recovering coherent velocity fields in subluminous z ~ 2–3 galaxies. Monthly Notices of the Royal Astronomical Society, 404 (3). pp. 1247-1262. ISSN 0035-8711.

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We present spatially resolved dynamics for six strongly lensed star-forming galaxies at z= 1.7–3.1 , each enlarged by a linear magnification factor of ~ ×8 . Using the Keck laser guide star AO system and the OH-Suppressing Infra-Red Imaging Spectrograph integral field unit spectrograph, we resolve kinematic and morphological detail in our sample with an unprecedented fidelity, in some cases achieving spatial resolutions of ≃100 pc. With one exception our sources have diameters ranging from 1 to 7 kpc, integrated star formation rates of 2–40 M_⊙ yr^(−1) (uncorrected for extinction) and dynamical masses of 10^(9.7−10.3) M_⊙ . With this exquisite resolution, we find that four of the six galaxies display coherent velocity fields consistent with a simple rotating disc model. Our model fits imply ratios for the systemic to random motion, V_c sin i/σ , ranging from 0.5 to 1.3 and Toomre disc parameters Q < 1 . The large fraction of well-ordered velocity fields in our sample is consistent with data analysed for larger, more luminous sources at this redshift. We demonstrate that the apparent contradiction with earlier dynamical results published for unlensed compact sources arises from the considerably improved spatial resolution and sampling uniquely provided by the combination of adaptive optics and strong gravitational lensing. Our high-resolution data further reveal that all six galaxies contain multiple giant star-forming H ii regions whose resolved diameters are in the range 300 pc to 1.0 kpc, consistent with the Jeans length expected in the case of dispersion support. From the kinematic data, we calculate that these regions have dynamical masses of 10^(8.8−9.5) M_⊙, also in agreement with local data. However, the density of star formation in these regions is ~100× higher than observed in local spirals; such high values are only seen in the most luminous local starbursts. The global dynamics and demographics of star formation in these H ii regions suggest that vigorous star formation is primarily governed by gravitational instability in primitive rotating discs. The physical insight provided by the combination of adaptive optics and gravitational lensing suggests it will be highly valuable to locate many more strongly lensed distant galaxies with high star formation rates before the era of the next-generation ground-based telescopes when such observations will become routine.

Item Type:Article
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Jones, T. A.0000-0001-5860-3419
Ellis, R. S.0000-0001-7782-7071
Richard, J.0000-0001-5492-1049
Additional Information:© 2010 The Authors. Journal compilation © 2010 RAS. Accepted 2010 January 18. Received 2010 January 13; in original form 2009 October 23. We thank Randy Campbell, Mark Kassis, Jim Lyke and Hien Tran for their dedication and assistance in obtaining these observations. We thank the anonymous referee for suggestions which improved the content and clarity of this paper. AMS gratefully acknowledges a Royal Astronomical Society Sir Norman Lockyer Research Fellowships and a Royal Society travel grant. RSE acknowledges financial support from the Royal Society. JR acknowledges support from an EU Marie Curie fellowship. DPS acknowledges support from an STFC Postdoctoral Research Fellowship. These observations were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.
Funding AgencyGrant Number
Royal Astronomical Society Sir Norman Lockyer Research FellowshipsUNSPECIFIED
EU Marie Curie fellowshipUNSPECIFIED
Science and Technology Facilities Council (STFC) Postdoctoral Research FellowshipUNSPECIFIED
Subject Keywords:galaxies: evolution, galaxies: formation, galaxies: high-redshift
Issue or Number:3
Record Number:CaltechAUTHORS:20100607-075122486
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Official Citation:Resolved spectroscopy of gravitationally lensed galaxies: recovering coherent velocity fields in subluminous z 2–3 galaxies (p 1247-1262) T. A. Jones, A. M. Swinbank, R. S. Ellis, J. Richard, D. P. Stark Published Online: Mar 11 2010 11:08AM DOI: 10.1111/j.1365-2966.2010.16378.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:18573
Deposited By: Ruth Sustaita
Deposited On:07 Jun 2010 15:44
Last Modified:03 Oct 2019 01:44

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