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Damped Lyman-α Absorbers in Cosmological SPH Simulations: the “Metallicity Problem”

Published online by Cambridge University Press:  23 September 2016

Kentaro Nagamine ,
Volker Springel  and
Lars Hernquist
Kentaro Nagamine
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, U.S.A.
Volker Springel
Affiliation:
Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85740 Garching bei München, Germany
Lars Hernquist
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, U.S.A.

Abstract

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We study the distribution of star formation rate (SFR) and metallicity of damped Lyman-α absorbers (DLAs) using cosmological smoothed particle hydrodynamics (SPH) simulations of the Λ cold dark matter (CDM) model. Our simulations include a phenomenological model for feedback by galactic winds which allows us to examine the effect of galactic outflows on the distribution of SFR and metallicity of DLAs. For models with strong galactic winds, we obtain good agreement with recent observations with respect to total neutral hydrogen mass density, NHI column-density distribution, abundance of DLAs, and for the distribution of SFR in DLAs. However, we also find that the median metallicity of simulated DLAs is higher than the values typically observed by nearly an order of magnitude. This discrepancy with observations could be due to shortcomings in the treatment of the supernova feedback or the multiphase structure of the gas in our current simulations. Recent observations by Wolfe et al. (2003a,b) seem to point to the same problem; i.e. the observed DLA metallicities are much lower than those expected from the (either observed or simulated) DLA star formation rates, a puzzle that has been known as the “missing metals”-problem for the globally averaged quantities.

Type
Session V: Intergalactic Medium
Information
Symposium - International Astronomical Union , Volume 216: Maps of the Cosmos , 2005 , pp. 266 - 273
Copyright
Copyright © Astronomical Society of the Pacific 2005 

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