The Low-Redshift LyForest toward 3C 273 ?

We present an analysis of the Lyforest toward 3C 273 from the Space Telescope Imaging Spectrograph at � 7 km s 1 resolution, along with re-processed data from the Far Ultraviolet Spectroscopic Explorer. The high UV flux of 3C 273 allows us to probe the weak, low z absorbers. The main sample consists of 21 H I absorbers that we could discriminate to a sensitivity of logNHI � 12.5. The redshift density for absorbers with 13.1 < logNHI < 14.0 is � 1.5� below the mean for other lines of sight; for logNHI � 12.5, it is consistent with numerical model predictions. The Doppler parameter distribution is consistent with other low z samples. We find no evidence for a break in the column density power-law distribution to logNHI = 12.3. A broad Lyabsorber (BLA) is withinv � 50 km s 1 and 1.3 local frame Mpc of two � 0.5Lgalaxies, with an O VI absorber � 700 km s 1 away, similarly close to three galaxies and indicating overdense environments. We detect clustering on the �v < 1000 km s 1 scale at 3.4� significance for logNHI � 12.6, consistent with the level predicted from hydrodynamical simulations, and indication for a Lyforest void at 0.09 < z < 0.12. We find at least two components for the z = 0.0053 Virgo absorber, but the total NHI column is not significantly changed.