%0 Generic %1 smit2013evidence %A Smit, R. %A Bouwens, R. J. %A Labbe, I. %A Zheng, W. %A Bradley, L. %A Donahue, M. %A Lemze, D. %A Moustakas, J. %A Umetsu, K. %A Zitrin, A. %A Coe, D. %A Postman, M. %A Gonzalez, V. %A Bartelmann, M. %A Benitez, N. %A Broadhurst, T. %A Ford, H. %A Grillo, C. %A Infante, L. %A Jimenez-Teja, Y. %A Jouvel, S. %A Kelson, D. D. %A Lahav, O. %A Maoz, D. %A Medezinski, E. %A Melchior, P. %A Meneghetti, M. %A Merten, J. %A Molino, A. %A Moustakas, L. %A Nonino, M. %A Rosati, P. %A Seitz, S. %D 2013 %K emission galaxy high-z lines %T Evidence for Ubiquitous, High-EW Nebular Emission in z~7 Galaxies: Towards a Clean Measurement of the Specific Star Formation Rate using a Sample of Bright, Magnified Galaxies %U http://arxiv.org/abs/1307.5847 %X Growing observational evidence now indicates that nebular line emission has a significant impact on the rest-frame optical fluxes of z~5-7 galaxies observed with Spitzer. This line emission makes z~5-7 galaxies appear more massive, with lower specific star formation rates. However, corrections for this line emission have been very difficult to perform reliably due to huge uncertainties on the overall strength of such emission at z>~5.5. Here, we present the most direct observational evidence yet for ubiquitous high-EW OIII+Hbeta line emission in Lyman-break galaxies at z~7, while also presenting a strategy for an improved measurement of the sSFR at z~7. We accomplish this through the selection of bright galaxies in the narrow redshift window z~6.6-7.0 where the IRAC 4.5 micron flux provides a clean measurement of the stellar continuum light. Observed 4.5 micron fluxes in this window contrast with the 3.6 micron fluxes which are contaminated by the prominent OIII+Hbeta lines. To ensure a high S/N for our IRAC flux measurements, we consider only the brightest (H_160<26 mag) magnified galaxies we have identified in CLASH and other programs targeting galaxy clusters. Remarkably, the mean rest-frame optical color for our bright seven-source sample is very blue, 3.6-4.5=-0.9+/-0.3. Such blue colors cannot be explained by the stellar continuum light and require that the rest-frame EW of OIII+Hbeta be greater than 637 Angstroms for the average source. The bluest four sources from our seven-source sample require an even more extreme EW of 1582 Angstroms. Our derived lower limit for the mean OIII+Hbeta EW could underestimate the true EW by ~2x based on a simple modeling of the redshift distribution of our sources. We can also set a robust lower limit of >~4 Gyr^-1 on the specific star formation rates based on the mean SED for our seven-source sample. (abridged)

@misc{smit2013evidence, abstract = {Growing observational evidence now indicates that nebular line emission has a significant impact on the rest-frame optical fluxes of z~5-7 galaxies observed with Spitzer. This line emission makes z~5-7 galaxies appear more massive, with lower specific star formation rates. However, corrections for this line emission have been very difficult to perform reliably due to huge uncertainties on the overall strength of such emission at z>~5.5. Here, we present the most direct observational evidence yet for ubiquitous high-EW [OIII]+Hbeta line emission in Lyman-break galaxies at z~7, while also presenting a strategy for an improved measurement of the sSFR at z~7. We accomplish this through the selection of bright galaxies in the narrow redshift window z~6.6-7.0 where the IRAC 4.5 micron flux provides a clean measurement of the stellar continuum light. Observed 4.5 micron fluxes in this window contrast with the 3.6 micron fluxes which are contaminated by the prominent [OIII]+Hbeta lines. To ensure a high S/N for our IRAC flux measurements, we consider only the brightest (H_{160}<26 mag) magnified galaxies we have identified in CLASH and other programs targeting galaxy clusters. Remarkably, the mean rest-frame optical color for our bright seven-source sample is very blue, [3.6]-[4.5]=-0.9+/-0.3. Such blue colors cannot be explained by the stellar continuum light and require that the rest-frame EW of [OIII]+Hbeta be greater than 637 Angstroms for the average source. The bluest four sources from our seven-source sample require an even more extreme EW of 1582 Angstroms. Our derived lower limit for the mean [OIII]+Hbeta EW could underestimate the true EW by ~2x based on a simple modeling of the redshift distribution of our sources. We can also set a robust lower limit of >~4 Gyr^-1 on the specific star formation rates based on the mean SED for our seven-source sample. (abridged)}, added-at = {2013-07-24T18:24:26.000+0200}, author = {Smit, R. and Bouwens, R. J. and Labbe, I. and Zheng, W. and Bradley, L. and Donahue, M. and Lemze, D. and Moustakas, J. and Umetsu, K. and Zitrin, A. and Coe, D. and Postman, M. and Gonzalez, V. and Bartelmann, M. and Benitez, N. and Broadhurst, T. and Ford, H. and Grillo, C. and Infante, L. and Jimenez-Teja, Y. and Jouvel, S. and Kelson, D. D. and Lahav, O. and Maoz, D. and Medezinski, E. and Melchior, P. and Meneghetti, M. and Merten, J. and Molino, A. and Moustakas, L. and Nonino, M. and Rosati, P. and Seitz, S.}, biburl = {https://www.bibsonomy.org/bibtex/24d8d19e2ac22300ba4328a18a9a3235d/miki}, description = {[1307.5847] Evidence for Ubiquitous, High-EW Nebular Emission in z~7 Galaxies: Towards a Clean Measurement of the Specific Star Formation Rate using a Sample of Bright, Magnified Galaxies}, interhash = {3c84e667b1183b44d21f4a644904f43b}, intrahash = {4d8d19e2ac22300ba4328a18a9a3235d}, keywords = {emission galaxy high-z lines}, note = {cite arxiv:1307.5847Comment: 9 pages, 6 figures, 1 table, submitted to the Astrophysical Journal}, timestamp = {2013-07-24T18:24:26.000+0200}, title = {Evidence for Ubiquitous, High-EW Nebular Emission in z~7 Galaxies: Towards a Clean Measurement of the Specific Star Formation Rate using a Sample of Bright, Magnified Galaxies}, url = {http://arxiv.org/abs/1307.5847}, year = 2013 }