ON THE REDSHIFT EVOLUTION OF Mg II ABSOPRTION SYSTEMS
- Berkeley Center for Cosmological Physics, University of California, Berkeley, CA (United States)
- Department of Astronomy and Astrophysics and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637 (United States)
We use a halo occupation approach to connect Mg II absorbers to dark matter halos as a function of redshift. Using the model constructed in Tinker and Chen, we parameterize the conditional probability of an absorber of equivalent width W{sub r} being produced by a halo of mass M{sub h} at a given redshift, P(W{sub r} |M{sub h} , z). We constrain the free parameters of the model by matching the observed statistics of Mg II absorbers: the frequency function f(W{sub r} ), the redshift evolution n(z), and the clustering bias b{sub W} . The redshift evolution of W{sub r} >= 1 A absorbers increases from z = 0.4 to z = 2, while the total halo cross section decreases monotonically with redshift. This discrepancy can only be explained if the gaseous halos evolve with respect to their host halos. We make predictions for the clustering bias of absorbers as a function of redshift under different evolutionary scenarios, e.g., the gas cross section per halo evolves or the halo mass scale of absorbers changes. We demonstrate that the relative contribution of these scenarios may be constrained by measurements of absorber clustering at z approx> 1 and z approx 0.1. If we further assume a redshift-independent mass scale for efficient shock heating of halo gas of M{sub crit} = 10{sup 11.5} h {sup -1} M{sub sun}, absorber evolution is predominantly caused by a changing halo mass scale of absorbers. Our model predicts that strong absorbers always arise in approxM{sub crit} halos, independent of redshift, but the mass scale of weak absorbers decreases by 2 dex from 0 < z < 2. Thus, the measured anti-correlation of clustering bias and W{sub r} should flatten by z approx 1.5.
- OSTI ID:
- 21392364
- Journal Information:
- Astrophysical Journal, Vol. 709, Issue 1; Other Information: DOI: 10.1088/0004-637X/709/1/1; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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