%0 Generic %1 holden2014restframe %A Holden, B. P. %A Oesch, P. A. %A Gonzalez, V. G. %A Illingworth, G. D. %A Labbe, I. %A Bouwens, R. %A Franx, M. %A van Dokkum, P. %A Spitler, L. %D 2014 %K emission galaxy highz lines metallicity sfr %T Rest-Frame Optical Emission Lines in z~3.5 Lyman Break selected Galaxies: The Ubiquity of Unusually High OIII/Hbeta Ratios at 2 Gyr %U http://arxiv.org/abs/1401.5490 %X We present K-band spectra of rest-frame optical emission lines for 24 star-forming galaxies at z~3.2-3.7 using MOSFIRE on the Keck 1 telescope. Strong rest-frame optical O III and Hbeta emission lines were detected in 18 LBGs. The median flux ratio of O III5007 to Hbeta is 5.1+/-0.5, a factor of 5-10x higher than in local galaxies with similar stellar masses. The observed Hbeta luminosities are in good agreement with expectations from the estimated star-formation rates, and none of our sources are detected in deep X-ray stacks, ruling out significant contamination by active galactic nuclei. Combining our sample with a variety of LBGs from the literature, including 49 galaxies selected in a very similar manner, we find a high median ratio of OIII/Hbeta = 4.8+0.8-1.7. This high ratio seems to be an ubiquitous feature of z~3-4 LBGs, very different from typical local star-forming galaxies at similar stellar masses. The only comparable systems at z~0 are those with similarly high specific star-formation rates, though ~5x lower stellar masses. High specific star-formation rates either result in a much higher ionization parameter or other unusual conditions for the interstellar medium, which result in a much higher OIII/Hbeta line ratio. This implies a strong relation between a global property of a galaxy, the specific star-formation rate, and the local conditions of ISM in star-forming regions.

@misc{holden2014restframe, abstract = {We present K-band spectra of rest-frame optical emission lines for 24 star-forming galaxies at z~3.2-3.7 using MOSFIRE on the Keck 1 telescope. Strong rest-frame optical [O III] and Hbeta emission lines were detected in 18 LBGs. The median flux ratio of [O III]5007 to Hbeta is 5.1+/-0.5, a factor of 5-10x higher than in local galaxies with similar stellar masses. The observed Hbeta luminosities are in good agreement with expectations from the estimated star-formation rates, and none of our sources are detected in deep X-ray stacks, ruling out significant contamination by active galactic nuclei. Combining our sample with a variety of LBGs from the literature, including 49 galaxies selected in a very similar manner, we find a high median ratio of [OIII]/Hbeta = 4.8+0.8-1.7. This high ratio seems to be an ubiquitous feature of z~3-4 LBGs, very different from typical local star-forming galaxies at similar stellar masses. The only comparable systems at z~0 are those with similarly high specific star-formation rates, though ~5x lower stellar masses. High specific star-formation rates either result in a much higher ionization parameter or other unusual conditions for the interstellar medium, which result in a much higher [OIII]/Hbeta line ratio. This implies a strong relation between a global property of a galaxy, the specific star-formation rate, and the local conditions of ISM in star-forming regions.}, added-at = {2014-01-23T10:03:15.000+0100}, author = {Holden, B. P. and Oesch, P. A. and Gonzalez, V. G. and Illingworth, G. D. and Labbe, I. and Bouwens, R. and Franx, M. and van Dokkum, P. and Spitler, L.}, biburl = {https://www.bibsonomy.org/bibtex/21c1502a32f5939149241f6f679ff1511/miki}, description = {[1401.5490] Rest-Frame Optical Emission Lines in z~3.5 Lyman Break selected Galaxies: The Ubiquity of Unusually High [OIII]/Hbeta Ratios at 2 Gyr}, interhash = {d92e73e80402f514b6d0847df140e27c}, intrahash = {1c1502a32f5939149241f6f679ff1511}, keywords = {emission galaxy highz lines metallicity sfr}, note = {cite arxiv:1401.5490Comment: 13 pages, 8 figures, 5 color, submitted to ApJ}, timestamp = {2014-01-23T10:03:15.000+0100}, title = {Rest-Frame Optical Emission Lines in z~3.5 Lyman Break selected Galaxies: The Ubiquity of Unusually High [OIII]/Hbeta Ratios at 2 Gyr}, url = {http://arxiv.org/abs/1401.5490}, year = 2014 }