First submission of "Tracing Baryons in the Warm-Hot Intergalactic Medium with Broad Ly-alpha Absorption" PI Savage Assigned ID: 98 ----- Submission 1 (Thu Jan 20 21:14:23 GMT 2005) ----- Actually, APT tells me that there are not errors. There is a warning flag because one of the Co-Is is at an institution not in the list, but the warning message say that it is OK to submit this way. Cosmological hydrodynamical simulations predict that at the present day 30% to 50% of the baryons reside in the warm-hot intergalactic medium (WHIM). Directly detecting this gas is difficult but extremely important for tracing the evolution of baryons in the evolving universe. The best evidence so far for the WHIM comes from OVI absorbers seen toward background quasars. However, estimating the total baryon content depends on assuming a metallicity. We have recently discovered that the WHIM may also be detectable in the form of thermally broadened Ly-alpha absorption, for which the estimate of baryonic content is not dependent on an assumed metallicity. We have found many broad Ly-alpha lines toward three quasars with dN/dz(BLya)~50 for EW>30mA. In a few cases we also see accompanying OVI absorption with b(HI)/b(OVI)~4, the ratio expected if the broadening is thermal. We propose to analyze all broad Ly-alpha absorbers toward the other eleven quasars for which high S/N STIS-E140M and FUSE data exist. We will determine whether the broad to narrow absorbers are thermally broadened or composed of narrower multiple components. Finding associated metal lines will aid the analysis and will provide estimates of the metallicity of the WHIM. We will study the relation between the HI column density and line width. We will compare the properties of the low and high-redshift Ly-alpha absorption in order to search for the expected increase in the relative number of broad to narrow absorbers with decreasing redshift. We will use our results to estimate the baryonic content of the gas in the WHIM between 10^5 and 10^6 K and to obtain a revised estimate of the baryonic content of the cooler photoionized IGM at low redshift.

QUASAR ABSORPTION LINES AND IGM 12 85000 false 0.0 false false false false false SUPPORTED