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The Physical Nature of Lyman Alpha Emitting Galaxies at z=3.1

Eric Gawiser·Pieter G. van Dokkum·Caryl Gronwall·Robin Ciardullo·Guillermo A. Blanc·Francisco J. Castander·John Feldmeier·Harold Francke·Marijn Franx·Lutz Haberzettl·David Herrera·Thomas Hickey·Leopoldo Infante·Paulina Lira·Jose Maza·Ryan Quadri·Alexander Richardson·Kevin Schawinski·Mischa Schirmer·Edward N. Taylor·Ezequiel Treister·C. Megan Urry·Shanil N. Virani
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Abstract

We selected 40 candidate Lyman Alpha Emitting galaxies (LAEs) at z ~=3.1 with observed frame equivalent widths >150A and inferred emission line fluxes >2.5x10^-17 ergs/cm^2/s from deep narrow-band and broad-band MUSYC images of the Extended Chandra Deep Field South. Covering 992 sq. arcmin, this is the largest ``blank field'' surveyed for LAEs at z ~3, allowing an improved estimate of the space density of this population of 3+-1x10^-4 h_70^3/Mpc^3. Spectroscopic follow-up of 23 candidates yielded 18 redshifts, all at z ~=3.1. Over 80% of the LAEs are dimmer in continuum magnitude than the typical Lyman break galaxy spectroscopic limit of R= 25.5 (AB), with a median continuum magnitude R ~=27 and very blue continuum colors, (V-z) ~=0. Over 80% of the LAEs have the right UVR colors to be selected as Lyman break galaxies, but only 10% also have R<=25.5. Stacking the UBVRIzJK fluxes reveals that LAEs have stellar masses ~=5x10^8 h_70^-2 M_sun and minimal dust extinction, A_V < ~ 0.1. Inferred star formation rates are ~=6 h_70^-2 M_sun/yr, yielding a cosmic star formation rate density of 2x10^-3 h_70 M_sun/yr/Mpc^3. None of our LAE candidates show evidence for rest-frame emission line equivalent widths EW_rest>240A which might imply a non-standard IMF. One candidate is detected by Chandra, implying an AGN fraction of 2+-2% for LAE candidate samples. In summary, LAEs at z ~ 3 have rapid star formation, low stellar mass, little dust obscuration and no evidence for a substantial AGN component.

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Eric Gawiser, Pieter G. van Dokkum, Caryl Gronwall, Robin Ciardullo, Guillermo A. Blanc, Francisco J. Castander, John Feldmeier, Harold Francke, Marijn Franx, Lutz Haberzettl, David Herrera, Thomas Hickey, Leopoldo Infante, Paulina Lira, Jose Maza, Ryan Quadri, Alexander Richardson, Kevin Schawinski, Mischa Schirmer, Edward N. Taylor, Ezequiel Treister, C. Megan Urry, Shanil N. Virani. 2006-03-23. The Physical Nature of Lyman Alpha Emitting Galaxies at z=3.1. https://doi.org/10.1086/504467

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