A Detailed Study of Gas and Star Formation in a Highly Magnified Lyman Break Galaxy at z = 3.07

August 2007 • 2007ApJ...665..936C

Authors • Coppin, K. E. K. • Swinbank, A. M. • Neri, R. • Cox, P. • Smail, Ian • Ellis, R. S. • Geach, J. E. • Siana, B. • Teplitz, H. • Dye, S. • Kneib, J. -P. • Edge, A. C. • Richard, J.

Abstract • We report the detection of CO(3-2) emission from a bright, gravitationally lensed Lyman Break galaxy, LBG J213512.73-010143 (the ``Cosmic Eye''), at z=3.07, using the Plateau de Bure Interferometer. This is only the second detection of molecular gas emission from an LBG and yields an intrinsic molecular gas mass of (2.4+/-0.4)×10<sup>9</sup> M<sub>solar</sub>. The lens reconstruction of the UV morphology of the LBG indicates that it comprises two components separated by ~2 kpc. The CO emission is unresolved, θ<~3<sup>''</sup>, and appears to be centered on the intrinsically fainter (and also less highly magnified) of the two UV components. The width of the CO line indicates a dynamical mass of (8+/-2)×10<sup>9</sup>csc2i M<sub>solar</sub> within the central 2 kpc. Employing mid-infrared observations from Spitzer, we infer a stellar mass of M<sub>*</sub>~(6+/-2)×10<sup>9</sup> M<sub>solar</sub> and a star formation rate of ~60 M<sub>solar</sub> yr<sup>-1</sup>, indicating that the molecular gas will be consumed in <~40 Myr. The gas fractions, star formation efficiencies, and line widths suggests that LBG J213512 is a high-redshift, gas-rich analog of a local luminous infrared galaxy. This galaxy has a similar gas-to-dynamical mass fraction as observed in the submillimeter-selected population, although the gas surface density and star formation efficiency is a factor of 3 times less, suggesting less vigorous activity. We discuss the uncertainties in our conclusions arising from adopting a CO-to-H<sub>2</sub> conversion factor appropriate for either the Milky Way or local luminous infrared galaxies. These observations demonstrate that current facilities, when aided by fortuitous gravitational magnification, can study ``ordinary'' galaxies at high redshift and so act as pathfinders for ALMA.

Links

• PREPRINT http://arxiv.org/abs/0705.1721
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2007ApJ...665..936C
• ELECTR https://doi.org/10.1086%2F519789
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2007ApJ...665..936C
• PDF https://stacks.iop.org/0004-637X/665/936/pdf
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2007ApJ...665..936C
• DATA https://hst.esac.esa.int/ehst/#/pages/search;bibcode=2007ApJ...665..936C
• DATA https://irsa.ipac.caltech.edu/bibdata/2007/C/2007ApJ...665..936C.html
• SPIRES http://inspirehep.net/search?p=find+eprint+arXiv:0705.1721