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arXiv · astro-ph/0411117

Spitzer and Hubble Constraints on the Physical Properties of the z~7 Galaxy Strongly Lensed by Abell 2218

E. Egami·J. -P. Kneib·G. H. Rieke·R. S. Ellis·J. Richard·J. Rigby·C. Papovich·D. Stark·M. R. Santos·J. -S. Huang·H. Dole·E. Le Floc'h·P. G. Perez-Gonzalez
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Abstract

We report the detection of a z~7 galaxy strongly lensed by the massive galaxy cluster Abell 2218 (z=0.175) at 3.6 and 4.5 um using the Spitzer Observatory and at 1.1 um using the Hubble Space Telescope. The new data indicate a refined photometric redshift in the range of 6.6-6.8 depending on the presence of Ly-alpha emission. The spectral energy distribution is consistent with having a significant Balmer break, suggesting that the galaxy is in the poststarburst stage with an age of at least ~50 Myr and quite possibly a few hundred Myr. This suggests the possibility that a mature stellar population is already in place at such a high redshift. Compared with typical Lyman break galaxies at z~3-4, the stellar mass is an order of magnitude smaller (~10^{9} Msun), but the specific star formation rate (star formation rate/M_{star}) is similarly large (> 10^{-9} yr^{-1}), indicating equally vigorous star-forming activity.

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E. Egami, J. -P. Kneib, G. H. Rieke, R. S. Ellis, J. Richard, J. Rigby, C. Papovich, D. Stark, M. R. Santos, J. -S. Huang, H. Dole, E. Le Floc'h, P. G. Perez-Gonzalez. 2004-11-18. Spitzer and Hubble Constraints on the Physical Properties of the z~7 Galaxy Strongly Lensed by Abell 2218. https://doi.org/10.1086/427550

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