Rest-Frame Optical Spectra of Three Strongly Lensed Galaxies at z~2 - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate

Rest-Frame Optical Spectra of Three Strongly Lensed Galaxies at z~2 - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We present Keck II NIRSPEC rest-frame optical spectra for three recentlydiscovered lensed galaxies: the Cosmic Horseshoe z = 2.38, the Clone z =2.00, and SDSS J090122.37+181432.3 z = 2.26. The boost in signal-to-noiseratio S-N from gravitational lensing provides an unusually detailed view ofthe physical conditions in these objects. A full complement of high S-Nrest-frame optical emission lines is measured, spanning from rest-frame 3600 to6800AA, including robust detections of fainter lines such as H-gamma,SII6717,6732, and in one instance NeII3869. SDSS J090122.37+181432.3 showsevidence for AGN activity, and therefore we focus our analysis on star-formingregions in the Cosmic Horseshoe and the Clone. For these two objects, weestimate a wide range of physical properties, including star-formation rateSFR, metallicity, dynamical mass, and dust extinction. In all respects, thelensed objects appear fairly typical of UV-selected star-forming galaxies atz~2. The Clone occupies a position on the emission-line diagnostic diagram ofOIII-H-beta vs. NII-H-alpha that is offset from the locations of z~0galaxies. Our new NIRSPEC measurements may provide quantitative insights intowhy high-redshift objects display such properties. From the SII line ratio,high electron densities ~1000 cm^-3 are inferred compared to localgalaxies, and OIII-OII line ratios indicate higher ionization parameterscompared to the local population. Building on previous similar results at z~2,these measurements provide further evidence at high S-N that star-formingregions are significantly different in high-redshift galaxies, compared totheir local counterparts abridged.

Author: Kevin N. Hainline, Alice E. Shapley, Katherine A. Kornei, Max Pettini, Elizabeth Buckley-Geer, Sahar S. Allam, Douglas L. Tucker


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