We observed the Seyfert I active galaxy/broad line radio galaxy 3C 120 with the Chandra high energy transmission gratings and present an analysis of the soft X-ray spectrum .
We identify the strongest absorption feature ( detected at > 99.9 \% confidence ) with O viii Ly \alpha ( FWHM = 1010 ^ { +295 } _ { -265 } km s ^ { -1 } ) , blueshifted by -5500 \pm 140 km s ^ { -1 } from systemic velocity .
The absorption may be due to missing baryons in warm/hot intergalactic medium ( WHIGM ) along the line-of-sight to 3C 120 at z = 0.0147 \pm 0.0005 , or it could be intrinsic to the jet of 3C 120 .
Assuming metallicites of \sim 0.1 Z _ { \odot } , we estimate an ionic column density of N _ { O~ { } { \sc viii } } > 3.4 \times 10 ^ { 16 } cm ^ { -2 } for WHIGM and a filament depth of < 19 h ^ { -1 } _ { 70 } Mpc .
We find a baryon overdensity > 56 relative to the critical density of a \Lambda -dominated cold dark matter universe , which is in reasonable agreement with WHIGM simulations .
We detect , at marginal significance , absorption of O viii Ly \alpha at z \sim 0 due to a hot medium in the Local Group .
We also detect an unidentified absorption feature at \sim 0.71 keV .
Absorption features which might be expected along with O viii Ly \alpha , were not significant statistically .
Relative abundances of metals in the WHIGM and local absorbers may therefore be considerably different from solar .