Hubble space telescope imaging of Lyα emission at z ≈ 4.4

Steven L. Finkelstein*, Seth H. Cohen, Rogier A. Windhorst, Russell E. Ryan, Nimish P. Hathi, Keely D. Finkelstein, Jay Anderson, Norman A. Grogin, Anton M. Koekemoer, Sangeeta Malhotra, Max Mutchler, James E. Rhoads, Patrick J. McCarthy, Robert W. O'Connell, Bruce Balick, Howard E. Bond, Daniela Calzetti, Michael J. Disney, Michael A. Dopita, Jay A. FrogelDonald N.B. Hall, Jon A. Holtzman, Randy A. Kimble, Gerard Luppino, Francesco Paresce, Abhijit Saha, Joseph I. Silk, John T. Trauger, Alistair R. Walker, Bradley C. Whitmore, Erick T. Young

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    32 Citations (Scopus)


    We present the highest redshift detections of resolved Lyα emission, using Hubble Space Telescope (HST)/Advanced Camera for Surveys F658N narrowband-imaging data taken in parallel with the Wide Field Camera 3 Early Release Science program in the GOODS Chandra Deep Field-South. We detect Lyα emission from three spectroscopically confirmed z = 4.4 Lyα emitting galaxies (LAEs), more than doubling the sample of LAEs with resolved Lyα emission. Comparing the light distribution between the rest-frame ultraviolet continuum and narrowband images, we investigate the escape of Lyα photons at high redshift. While our data do not support a positional offset between the Lyα and rest-frame ultraviolet (UV) continuum emission, the half-light radius in one out of the three galaxies is significantly (>1σ) larger in Lyα than in the rest-frame UV continuum. Stacking the three LAEs in both the narrowband and UV continuum images, we find that the Lyα light appears larger than the rest-frame UV at 4.2σ significance. This Lyα flux detected with HST is a factor of 4-10 less than observed in similar filters from the ground. These results together imply that the Lyα emission is not strictly confined to its indigenous star-forming regions. Rather, for at least one object the Lyα emission is more extended, with the missing HST flux possibly existing in a diffuse outer halo. This suggests that the radiative transfer of Lyα photons in high-redshift LAEs is complicated, with the interstellar-medium geometry and/or outflows playing a significant role in galaxies at these redshifts.

    Original languageEnglish
    Article number5
    JournalAstrophysical Journal
    Issue number1
    Publication statusPublished - 1 Jul 2011


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