A Lyman Break Galaxy Candidate at z ~ 9

June 2008 • 2008ApJ...680L..97H

Authors • Henry, Alaina L. • Malkan, Matthew A. • Colbert, James W. • Siana, Brian • Teplitz, Harry I. • McCarthy, Patrick

Abstract • We report the discovery of a z ~ 9 Lyman break galaxy candidate, selected from the NICMOS Parallel Imaging Survey as a J-dropout with J₁₁₀ - H₁₆₀ = 1.7. Spitzer/IRAC photometry reveals that the galaxy has a blue H₁₆₀ - 3.6 μm color and a spectral break between 3.6 and 4.5 μm. We interpret this break as the Balmer break and derive a best-fit photometric redshift of z ~ 9. We use Monte Carlo simulations to test the significance of this photometric redshift, and we show that there is a 96% probability of z >= 7. We estimate that the lower limit to the comoving number density of such galaxies at z ~ 9 is phi > 3.8 × 10^-6 Mpc^-3. If the high redshift of this galaxy is confirmed, this will indicate that the luminous end of the rest-frame UV luminosity function has not evolved substantially from z ~ 9 to z ~ 3. Still, some small degeneracy remains between this z ~ 9 model and models at z ~ 2-3 deep optical imaging (reaching I_AB ~ 29) can rule out the lower z models.

This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory (JPL), California Institute of Technology, under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. This work is also based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with proposals 9484, 9865, 10226, and 10899.

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IPAC Authors
(alphabetical)

James Colbert

Associate Scientist

Harry Teplitz

Senior Scientist