Absorption signatures of warm-hot gas at low redshift: Ne viii

作者：Tepper Garcia Thor^*; Richter Philipp; Schaye Joop

来源：Monthly Notices of the Royal Astronomical Society, 2013, 436(3): 2063-2081.

DOI：10.1093/mnras/stt1712

• methods: analytical
• methods: numerical
• galaxies: formation
• intergalactic medium
• quasars: absorption lines
• cosmology: theory

At z %26lt; 1 a large fraction of the baryons is thought to reside in diffuse gas that has been shock-heated to high temperatures (10 (5)-10 (6) K). Absorption by the 770.41, 780.32 A doublet of Ne viii in quasar spectra represents a unique tool to study this elusive warm-hot phase. We have developed an analytic model for the properties of Ne viii absorbers that allows for an inhomogeneous metal distribution. Our model agrees with the predictions of a simulation from the OverWhelmingly Large Simulations project indicating that the average line-of-sight metal-filling fraction within the absorbing gas is low (c(L) similar to 0.1). Most of the Ne viii in our model is produced in low-density, collisionally ionized gas (n(H) = 10(-6)-10(-4) cm(-3), T = 10 (5)-10 (6) K). Strong Ne viii absorbers (log(10)(N-NeVIII/cm(-2))14), like those recently detected by Hubble Space Telescope/Cosmic Origins Spectrograph, are found to arise in higher density gas (n(H) greater than or similar to 10(-4) cm(-3), T approximate to 5 x 10 (5) K). Ne viii cloudlets harbour only 1 per cent of the cosmic baryon budget. The baryon content of the surrounding gas (which has similar densities and temperatures as the Ne viii cloudlets) is a factor c(-1)L higher. We conclude that Ne viii absorbers are robust probes of shock-heated diffuse gas, but that spectra with signal-to-noise ratios S/N %26gt; 100 would be required to detect the bulk of the baryons in warm-hot gas.

• 出版日期2013-12