Metals in the Intergalactic Medium

Bastien Aracil (1) , Patrick Petitjean (1) , Christophe Pichon (2) , Jacqueline Bergeron (1)

1 IAP - Institut d'Astrophysique de Paris
2 OAS - Observatoire astronomique de Strasbourg

We use high spectral resolution (R=45000) and high signal-to-noise ratio (S/N \\~ 35-70 per pixel) spectra of 19 high-redshift (2.11. Our observations strongly suggest that the CIV/HI ratio decreases with decreasing tau(HI) with log[tau(CIV)]=1.3xlog[tau(HI)]-3.2. We do not detect CIV absorption statistically associated with gas of tau(HI)<1. However, we observe that a small fraction of the low density gas is associated with strong metal lines as a probable consequence of the IGM enrichment being highly inhomogeneous. We detect the presence of OVI down to tau(HI)~0.2 with log[tau(OVI)/tau(HI)] -2.0. We show that OVI absorption in the lowest density gas is located within ~300 km/s from strong HI lines. This suggests that this OVI phase may be part of winds flowing away from overdense regions. This effect is more important at the largest redshifts (z>2.4). Therefore, at the limit of present surveys, the presence of metals in the underdense regions of the IGM is still to be demonstrated.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]

Bastien Aracil, Patrick Petitjean, Christophe Pichon, Jacqueline Bergeron. Metals in the Intergalactic Medium. Astronomy and Astrophysics - A&A, 2004, 419, pp.811-819. ⟨hal-00007812⟩