Kulas, Kristin R. and Shapley, Alice E. and Kollmeier, Juna A. and Zheng, Zheng and Steidel, Charles C. and Hainline, Kevin N. (2012) The Kinematics of Multiple-Peaked Lyα Emission in Star-Forming Galaxies at z ~ 2-3. Astrophysical Journal, 745 (1). Art. No. 33. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20120403-092029054
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We present new results on the Lyα emission-line kinematics of 18 z ~ 2-3 star-forming galaxies with multiple-peaked Lyα profiles. With our large spectroscopic database of UV-selected star-forming galaxies at these redshifts, we have determined that ~30% of such objects with detectable Lyα emission display multiple-peaked emission profiles. These profiles provide additional constraints on the escape of Lyα photons due to the rich velocity structure in the emergent line. Despite recent advances in modeling the escape of Lyα from star-forming galaxies at high redshifts, comparisons between models and data are often missing crucial observational information. Using Keck II NIRSPEC spectra of Hα (z ~ 2) and [O III]λ5007 (z ~ 3), we have measured accurate systemic redshifts, rest-frame optical nebular velocity dispersions, and emission-line fluxes for the objects in the sample. In addition, rest-frame UV luminosities and colors provide estimates of star formation rates and the degree of dust extinction. In concert with the profile sub-structure, these measurements provide critical constraints on the geometry and kinematics of interstellar gas in high-redshift galaxies. Accurate systemic redshifts allow us to translate the multiple-peaked Lyα profiles into velocity space, revealing that the majority (11/18) display double-peaked emission straddling the velocity-field zero point with stronger red-side emission. Interstellar absorption-line kinematics suggest the presence of large-scale outflows for the majority of objects in our sample, with an average measured interstellar absorption velocity offset of (Δv_(abs))=–230 km s^(–1). A comparison of the interstellar absorption kinematics for objects with multiple- and single-peaked Lyα profiles indicate that the multiple-peaked objects are characterized by significantly narrower absorption line widths. We compare our data with the predictions of simple models for outflowing and infalling gas distributions around high-redshift galaxies. While popular "shell" models provide a qualitative match with many of the observations of Lyα emission, we find that in detail there are important discrepancies between the models and data, as well as problems with applying the framework of an expanding thin shell of gas to explain high-redshift galaxy spectra. Our data highlight these inconsistencies, as well as illuminating critical elements for success in future models of outflow and infall in high-redshift galaxies.
|Additional Information:||© 2012 American Astronomical Society. Received 2011 July 18; accepted 2011 October 19; published 2011 December 28. Based, in part, on data 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 NASA, and was made possible by the generous financial support of the W. M. Keck Foundation. We thank Mark Dijkstra for helpful discussions that enhanced the presentation of our results. K.R.K. and A.E.S. acknowledge support from the David and Lucile Packard Foundation. C.C.S. acknowledges additional support from the John D. and Catherine T. MacArthur Foundation, the Peter and Patricia Gruber Foundation, and NSF grants AST-0606912 and AST-0908805. Z.Z. gratefully acknowledges support from Yale Center for Astronomy and Astrophysics through a YCAA fellowship. We wish to extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, most of the observations presented herein would not have been possible.|
|Subject Keywords:||galaxies: formation; galaxies: high-redshift; galaxies: ISM; line: profiles; radiative transfer|
|Official Citation:||The Kinematics of Multiple-peaked Lyα Emission in Star-forming Galaxies at z ~ 2-3 Kristin R. Kulas et al. 2012 ApJ 745 33|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||03 Apr 2012 16:38|
|Last Modified:||26 Dec 2012 15:01|
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