Can photoionization squelching resolve the substructure crisis?

TY - JOUR

T1 - Can photoionization squelching resolve the substructure crisis?

AU - Somerville, Rachel S.

N1 - Funding Information: We thank B. Moore, A. Klypin, and A. Kravtsov for making the results of their simulations available to us electronically and for useful discussions. We also thank T. Abel, R. Barkana, J. Bullock, and A. Kravtsov for useful discussions and helpful comments on the manuscript. R. S. S. is supported by a rolling grant from PPARC.

PY - 2002/6/10

Y1 - 2002/6/10

N2 - Cold dark matter theory predicts that the Local Group should contain many more dwarf-sized objects than the observed number of dwarf galaxies - the so-called substructure problem. We investigate whether the suppression of star formation in these small objects due to the presence of a photoionizing background can resolve the problem. We make use of results from recent hydrodynamic simulations to build a recipe for the suppression of gas infall into semianalytic galaxy formation models and use these to predict the luminosity function of dwarf galaxies in the Local Group. In the models without photoionization "squelching," we predict a large excess of faint dwarf galaxies compared with the observed number in the Local Group - thus, the usual recipe for supernova feedback used in semianalytic models does not solve the substructure problem on its own. When we include photoionization squelching, we find good agreement with the observations. We have neglected tidal destruction, which probably further reduces the number of dwarf galaxies. We conclude that photoionizing squelching easily solves the substructure problem. In fact, it is likely that once this effect is taken into account, models with reduced small-scale power (e.g., warm dark matter) would underproduce dwarf galaxies.

AB - Cold dark matter theory predicts that the Local Group should contain many more dwarf-sized objects than the observed number of dwarf galaxies - the so-called substructure problem. We investigate whether the suppression of star formation in these small objects due to the presence of a photoionizing background can resolve the problem. We make use of results from recent hydrodynamic simulations to build a recipe for the suppression of gas infall into semianalytic galaxy formation models and use these to predict the luminosity function of dwarf galaxies in the Local Group. In the models without photoionization "squelching," we predict a large excess of faint dwarf galaxies compared with the observed number in the Local Group - thus, the usual recipe for supernova feedback used in semianalytic models does not solve the substructure problem on its own. When we include photoionization squelching, we find good agreement with the observations. We have neglected tidal destruction, which probably further reduces the number of dwarf galaxies. We conclude that photoionizing squelching easily solves the substructure problem. In fact, it is likely that once this effect is taken into account, models with reduced small-scale power (e.g., warm dark matter) would underproduce dwarf galaxies.

KW - Dark matter

KW - Galaxies: dwarf

KW - Galaxies: formation

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U2 - 10.1086/341444

DO - 10.1086/341444

M3 - Article

SN - 0004-637X

VL - 572

SP - L23-L26

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1 II

ER -