%0 Generic %1 strom2016nebular %A Strom, Allison L. %A Steidel, Charles C. %A Rudie, Gwen C. %A Trainor, Ryan F. %A Pettini, Max %A Reddy, Naveen A. %D 2016 %K emission galaxies high-z ionisation lines metallicity %T Nebular Emission Line Ratios in z~2-3 Star-Forming Galaxies with KBSS-MOSFIRE: Exploring the Impact of Ionization, Excitation, and Nitrogen-to-Oxygen Ratio %U http://arxiv.org/abs/1608.02587 %X We present a detailed study of the rest-optical (3600-7000 Angstrom) nebular spectra of ~380 star-forming galaxies at z~2-3 obtained with Keck/MOSFIRE as part of the Keck Baryonic Structure Survey (KBSS). The KBSS-MOSFIRE sample is representative of star-forming galaxies at these redshifts, with stellar masses M*=10^9-10^11.5 M_sun and star formation rates SFR=3-1000 M_sun/yr. We focus on robust measurements of many strong diagnostic emission lines for individual galaxies: O II3727,3729, Ne III3869, H-beta, O III4960,5008, N II6549,6585, H-alpha, and S II6718,6732. Comparisons with observations of typical local galaxies from the Sloan Digital Sky Survey (SDSS) and between subsamples of KBSS-MOSFIRE show that high-redshift galaxies exhibit a number of significant differences in addition to the well-known offset in log(O III/H-beta) and log(N II/H-alpha). We argue that the primary difference between H II regions in z~2.3 galaxies and those at z~0 is an enhancement in the degree of nebular excitation, as measured by O III/H-beta and R23=log(O III+O II)/H-beta. At the same time, KBSS-MOSFIRE galaxies are ~10 times more massive than z~0 galaxies with similar ionizing spectra and have higher N/O (likely accompanied by higher O/H) at fixed excitation. These results indicate the presence of harder ionizing radiation fields at fixed N/O and O/H relative to typical z~0 galaxies, consistent with Fe-poor stellar population models that include massive binaries, and highlight a population of massive, high-specific star formation rate galaxies at high-redshift with systematically different star formation histories than galaxies of similar stellar mass today.

@misc{strom2016nebular, abstract = {We present a detailed study of the rest-optical (3600-7000 Angstrom) nebular spectra of ~380 star-forming galaxies at z~2-3 obtained with Keck/MOSFIRE as part of the Keck Baryonic Structure Survey (KBSS). The KBSS-MOSFIRE sample is representative of star-forming galaxies at these redshifts, with stellar masses M*=10^9-10^11.5 M_sun and star formation rates SFR=3-1000 M_sun/yr. We focus on robust measurements of many strong diagnostic emission lines for individual galaxies: [O II]3727,3729, [Ne III]3869, H-beta, [O III]4960,5008, [N II]6549,6585, H-alpha, and [S II]6718,6732. Comparisons with observations of typical local galaxies from the Sloan Digital Sky Survey (SDSS) and between subsamples of KBSS-MOSFIRE show that high-redshift galaxies exhibit a number of significant differences in addition to the well-known offset in log([O III]/H-beta) and log([N II]/H-alpha). We argue that the primary difference between H II regions in z~2.3 galaxies and those at z~0 is an enhancement in the degree of nebular excitation, as measured by [O III]/H-beta and R23=log[([O III]+[O II])/H-beta]. At the same time, KBSS-MOSFIRE galaxies are ~10 times more massive than z~0 galaxies with similar ionizing spectra and have higher N/O (likely accompanied by higher O/H) at fixed excitation. These results indicate the presence of harder ionizing radiation fields at fixed N/O and O/H relative to typical z~0 galaxies, consistent with Fe-poor stellar population models that include massive binaries, and highlight a population of massive, high-specific star formation rate galaxies at high-redshift with systematically different star formation histories than galaxies of similar stellar mass today.}, added-at = {2016-08-10T10:34:09.000+0200}, author = {Strom, Allison L. and Steidel, Charles C. and Rudie, Gwen C. and Trainor, Ryan F. and Pettini, Max and Reddy, Naveen A.}, biburl = {https://www.bibsonomy.org/bibtex/2b97a4ee0473054b57757d009d25bc4fc/miki}, description = {[1608.02587] Nebular Emission Line Ratios in z~2-3 Star-Forming Galaxies with KBSS-MOSFIRE: Exploring the Impact of Ionization, Excitation, and Nitrogen-to-Oxygen Ratio}, interhash = {a8915123b1973443e5e840548b39c9a8}, intrahash = {b97a4ee0473054b57757d009d25bc4fc}, keywords = {emission galaxies high-z ionisation lines metallicity}, note = {cite arxiv:1608.02587Comment: 28 pages, 26 figures. Submitted to the Astrophysical Journal}, timestamp = {2016-08-10T10:34:09.000+0200}, title = {Nebular Emission Line Ratios in z~2-3 Star-Forming Galaxies with KBSS-MOSFIRE: Exploring the Impact of Ionization, Excitation, and Nitrogen-to-Oxygen Ratio}, url = {http://arxiv.org/abs/1608.02587}, year = 2016 }