STELLAR POPULATIONS OF Ly{alpha} EMITTERS AT z {approx} 6-7: CONSTRAINTS ON THE ESCAPE FRACTION OF IONIZING PHOTONS FROM GALAXY BUILDING BLOCKS
- Department of Astronomy, Graduate School of Science, University of Tokyo, Tokyo 113-0033 (Japan)
- Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
- Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver V6T 1Z1 (Canada)
- Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States)
- SUPA Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom)
We investigate the stellar populations of Ly{alpha} emitters (LAEs) at z = 5.7 and 6.6 in a 0.65 deg{sup 2} sky of the Subaru/XMM-Newton Deep Survey (SXDS) Field, using deep images taken with the Subaru/Suprime-Cam, United Kingdom Infrared Telescope/Wide Field Infrared Camera, and Spitzer/Infrared Array Camera (IRAC). We produce stacked multiband images at each redshift from 165 (z = 5.7) and 91 (z = 6.6) IRAC-undetected objects to derive typical spectral energy distributions (SEDs) of z {approx} 6-7 LAEs for the first time. The stacked LAEs have as blue UV continua as the Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) z-dropout galaxies of similar M{sub UV}, with a spectral slope {beta} {approx} -3, but at the same time they have red UV-to-optical colors with detection in the 3.6 {mu}m band. Using SED fitting we find that the stacked LAEs have low stellar masses of {approx}(3-10) x 10{sup 7} M{sub sun}, very young ages of {approx}1-3 Myr, negligible dust extinction, and strong nebular emission from the ionized interstellar medium, although the z = 6.6 object is fitted similarly well with high-mass models without nebular emission; inclusion of nebular emission reproduces the red UV-to-optical colors while keeping the UV colors sufficiently blue. We infer that typical LAEs at z {approx} 6-7 are building blocks of galaxies seen at lower redshifts. We find a tentative decrease in the Ly{alpha} escape fraction from z = 5.7 to 6.6, which may imply an increase in the intergalactic medium neutral fraction. From the minimum contribution of nebular emission required to fit the observed SEDs, we place an upper limit on the escape fraction of ionizing photons of f {sup ion}{sub esc} {approx} 0.6 at z = 5.7 and {approx}0.9 at z = 6.6. We also compare the stellar populations of our LAEs with those of stacked HST/WFC3 z-dropout galaxies.
- OSTI ID:
- 21474476
- Journal Information:
- Astrophysical Journal, Vol. 724, Issue 2; Other Information: DOI: 10.1088/0004-637X/724/2/1524; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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