Astronomy and Astrophysics – Astrophysics
Scientific paper
2002-12-16
AIP Conf.Proc. 666 (2003) 191-194
Astronomy and Astrophysics
Astrophysics
4 pages, 1 figure; To appear in proceedings of the 13th Annual Astrophysics Conference in College Park, Maryland, The Emergenc
Scientific paper
10.1063/1.1581790
Hydrodynamic cosmological simulations predict that the average opacity of the Ly-alpha forest should increase in the neighborhood of galaxies because galaxies form in dense environments. Recent observations (Adelberger et al. 2002) confirm this expectation at large scales, but they show a decrease of absorption at comoving separations Delta_r <~ 1 Mpc/h. We show that this discrepancy is statistically significant, especially for the innermost data point at Delta_r <= 0.5 Mpc/h, even though this data point rests on three galaxy-quasar pairs. Galaxy redshift errors of the expected magnitude are insufficient to resolve the conflict. Peculiar velocities allow gas at comoving distances >~ 1 Mpc/h to produce saturated absorption at the galaxy redshift, putting stringent requirements on any ``feedback'' solution. Local photoionization is insufficient, even if we allow for recurrent AGN activity that keeps the neutral hydrogen fraction below its equilibrium value. A simple ``wind'' model that eliminates all neutral hydrogen in spheres around the observed galaxies can marginally explain the data, but only if the winds extend to comoving radii ~1.5 Mpc/h.
Dav'e Romeel
Katz Neal
Kollmeier Juna A.
Weinberg David H.
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