The Physical Origins of the Identified and Still Missing Components of the Warm–Hot Intergalactic Medium: Insights from Deep Surveys in the Field of Blazar 1ES1553+113

The relationship between galaxies and the state/chemical enrichment of the warm–hot intergalactic medium (WHIM) expected to dominate the baryon budget at low-z provides sensitive constraints on structure formation and galaxy evolution models. We present a deep redshift survey in the field of 1ES1553+113, a blazar with a unique combination of ultraviolet (UV)+X-ray spectra for surveys of the circumgalactic/intergalactic medium (CGM/IGM). Nicastro et al. reported the detection of two O vii WHIM absorbers at z = 0.4339 and 0.3551 in its spectrum, suggesting that the WHIM is metal rich and sufficient to close the missing baryons problem. Our survey indicates that the blazar is a member of a z = 0.433 group and that the higher-z O vii candidate arises from its intragroup medium. The resulting bias precludes its use in baryon censuses. The z = 0.3551 candidate occurs in an isolated environment 630 kpc from the nearest galaxy (with stellar mass $\mathrm{log}{M}_{* }/{M}_{\odot }\approx 9.7$), which we show is unexpected for the WHIM. Finally, we characterize the galactic environments of broad H i Lyα absorbers (Doppler widths of b = 40–80 km s−1; T ≲ 4 × 105 K) that provide metallicity-independent WHIM probes. On average, broad Lyα absorbers are ≈2× closer to the nearest luminous (L > 0.25L*) galaxy (700 kpc) than narrow (b < 30 km s−1; T ≲ 4 × 105 K) ones (1300 kpc) but ≈2× further than O vi absorbers (350 kpc). These observations suggest that gravitational collapse heats portions of the IGM to form the WHIM, but with feedback that does not enrich the IGM far beyond galaxy/group halos to levels currently observable in UV/X-ray metal lines.