Quantitative signatures of galactic superwinds on Lyα clouds and metal-line systems

We investigate possible signatures of feedback from galactic superwinds (GSWs) on the metallicity of the Ly alpha forest, using a set of high-resolution hydrodynamic simulations of a Lambda CDM model. Simulations produce metals self-consistently, based on one single parameter, the metal yield, which in turn is constrained by metallicity in the intracluster gas. We follow metals as a separate density species. The metallicity of Ly alpha clouds having column density of N-H I similar to 10(14.5)-10(15.5) cm(-2) at z = 2-4 is correctly predicted by simulations, both with and without GSWs, implying an in situ origin for these metals. However, a unique signature and sensitive test of GSWs are provided by lower column density clouds of 10(12)-10(14) cm(-2). We find that the number density of Ly alpha lines with metallicity Z >= 10(-3) Z circle dot and neutral hydrogen column density N-H I < 10(13.5) cm(-2) provides a first quantitative measure of the strength of GSWs, because metals in these systems are a contaminant. We predict that the number of such lines per unit redshift at z similar to 3 should be about 0.1 in the absence of GSWs. With the observed GSW strength, we expect to see 20-50 such lines per unit redshift. This is an observational challenge. Furthermore, we find that the difference between simulations with and without GSWs becomes much larger with regard to a subset of such clouds with high Doppler widths, since the contaminated systems are considerably hotter than the normal IGM. We also present preliminary results on C IV and O vi lines as a function of GSW strength. The filling factor of metal-rich regions is a strong function of GSWs. With and without GSWs the volume filling factor is 6.0%, 4.2%, and 1.9% and 1.0%, 0.28%, and 0.08%, respectively, for regions with metallicity greater than 10(-3), 10(-2), and 10(-1) Z circle dot. Finally, in clouds of N-H I similar to 10(14.5) cm(-2), we predict that the ratio of secondary ( e. g., N) to primary metals ( e. g., O, C) is expected to be smaller by a factor of 10 than in large galaxies, which better retain metals; this factor increases to >= 50 for N-H I <= 10(13.5) cm(-2).