Keck/OSIRIS IFU Detection of a z ∼ 3 Damped Lyα Host Galaxy^∗

Abstract

We present Keck/OSIRIS infrared IFU observations of the z = 3.153 sub-DLA DLA2233+131, previously detected in absorption to a background quasar and studied with single slit spectroscopy and PMAS integral field spectroscopy (IFU). We used the Laser Guide Star Adaptive Optics (LGSAO) and OSIRIS IFU to reduce the point-spread function of the background quasar to FWHM∼0.15 and marginally resolve extended, foreground DLA emission. We detect [O III]λ5007 emission with a flux F [O III]λ5007 = (2.4 ± 0.5) × 10 −17 ergs s −1 cm −2 , as well as unresolved [O III]λ4959 and Hβλ4861 emission. Using a composite spectrum over the emission region, we measure dynamical mass ∼ 3.1×10 9 M . We make several estimates of star formation rate using [O III]λ5007 and Hβλ4861 emission, and measure a star formation rate of ∼ 7.1 − 13.6 M yr −1 . We map [O III]λ5007 and Hβλ4861 emission and the corresponding velocity fields to search for signs of kinematic structure. These maps allow for a more detailed kinematic analysis than previously possible for this galaxy. While some regions show slightly red and blue-shifted emission indicative of potential edge-on disk rotation, the data are insufficient to support this interpretation.