The circumgalactic medium ( CGM ) around galaxies is believed to record various forms of galaxy feedback and contain a significant portion of the “ missing baryons ” of individual dark matter halos .
However , clear observational evidence for the existence of the hot CGM is still absent .
We use intervening galaxies along 12 background AGNs as tracers to search for X-ray absorption lines produced in the corresponding CGM .
Stacking Chandra grating observations with respect to galaxy groups and different luminosities of these intervening galaxies , we obtain spectra with signal-to-noise ratios of 46-72 per 20-mÅ spectral bin at the expected O VII K \alpha line .
We find no detectable absorption lines of C VI , N VII , O VII , O VIII , or Ne IX .
The high spectral quality allows us to tightly constrain upper limits to the corresponding ionic column densities ( in particular \log [ N { { } _ { OVII } ( cm ^ { -2 } ) } ] \leq 14.2–14.8 ) .
These nondetections are inconsistent with the Local Group hypothesis of the X-ray absorption lines at z \simeq 0 commonly observed in the spectra of AGNs .
These results indicate that the putative CGM in the temperature range of 10 ^ { 5.5 } -10 ^ { 6.3 } K may not be able to account for the missing baryons unless the metallicity is less than 10 % solar .