X-ray view of a massive node of the cosmic web at z∼3: II. Discovery of extended X-ray emission around a hyperluminous quasar

While the warm (T similar to 10(4) K), ionized gas in the circumgalactic medium (CGM) at z > 3 is now routinely observed around bright quasars in Ly alpha emission, little is known about the CGM hot phase (T similar to 10(7) K). Here, we report the analysis of 634 ks of Chandra X-ray observations in the MQN01 Cosmic Structure, a region containing one of the brightest Ly alpha nebulae and the largest galaxy overdensity known at z > 3. We detect approximate to 66 net counts (approximate to 8 sigma) of X-ray emission in the 0.5-2 keV band extending to at least similar to 30 kpc from the brightest quasar in MQN01. The morphology and spectrum are consistent with thermal emission from hot plasma in collisional ionization equilibrium. Quasi-stellar object (QSO) photoionization is found to have a negligible impact, and alternative scenarios such as inverse Compton scattering are disfavoured. A joint spatial and spectral Markov chain Monte Carlo (MCMC) analysis provides consistency with a beta model with a steep density profile (beta similar or equal to 2.0(-0.8)(+1.4), r(core) = 36(-16)(+13) kpc) and an average gas temperature of kT similar or equal to (1.8 +/- 0.4) keV. Assuming that the QSO resides within a virialized halo, whose virial temperature is equal to the observed gas temperature, the implied halo mass and virial radius would be M-vir similar to 3 & times; 10(13) M-circle dot and similar to 190 kpc. Further assuming that the observed emission traces the brighter inner region of a distribution extending to the virial radius, the extrapolated hot gas mass would be M-hot approximate to 2.6(-0.6)(+1.7) & times; 10(12) M-circle dot, which is similar or equal to 8.3(-9.8)(+3.0)% of M-vir, or 56(-20)(+65)% of the theoretical cosmological baryon budget of the halo. The hot gas also emits an exceptionally high X-ray luminosity, with a measured L2 - 10 = 2.25(-1.38)(+0.77) & times; 10(45) erg s(-1) within the central 30 kpc. This system is a clear outlier in the L-X-T-X plane, indicating a thermodynamic state distinct from that of evolved lower-redshift hot halos. The cooling time in the inner 15-30 kpc is comparable to the local dynamical time (1 < t(cool)/t(ff) < 10), suggesting that the gas could become locally unstable in the absence of heating or feedback. Moreover, the thermal pressure associated with the detected CGM hot phase is large enough to confine the cold and dense clumps, which are required to reproduce the high Ly alpha emission associated with the inner regions of the MQN01 structure. Although limited to a single system, our results provide unique information on the multi-phase properties of the CGM (or proto-intracluster medium) and a view of the nascent thermal hot gas phase observed in local galaxy clusters.