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We present UV and optical observations from the Cosmic Origins Spectrographon the Hubble Space Telescope and Keck of a z= 0.27395 Lyman limit system (LLS)seen in absorption against the QSO PG1630+377. We detect H I absorption withlog N(HI)=17.06\pm0.05 as well as Mg II, C III, Si III, and O VI in thissystem. The column densities are readily explained if this is a multi-phasesystem, with the intermediate and low ions arising in a very low metallicity([Mg/ H] =-1.71 \pm 0.06) photoionized gas. We identify via Keck spectroscopyand Large Binocular Telescope imaging a 0.3 L_* star-forming galaxy projected37 kpc from the QSO at nearly identical redshift (z=0.27406, \Delta v = -26\kms) with near solar metallicity ([O/ H]=-0.20 \pm 0.15). The presence of verylow metallicity gas in the proximity of a near-solar metallicity, sub-L_*galaxy strongly suggests that the LLS probes gas infalling onto the galaxy. Asearch of the literature reveals that such low metallicity LLSs are notuncommon. We found that 50% (4/8) of the well-studied z < 1 LLSs havemetallicities similar to the present system and show sub-L_* galaxies with rho< 100 kpc in those fields where redshifts have been surveyed. We argue that theproperties of these primitive LLSs and their host galaxies are consistent withthose of cold mode accretion streams seen in galaxy simulations.

Evidence for Cold Accretion: Primitive Gas Flowing onto a Galaxy at z~0.274