科研之友
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摘要
Recent observations of the Lyman-break galaxy (LBG) luminosity LF) from z approximate to 6-10 show a steep decline in abundance with increasing redshift. However, the LF is a convolution of the mass function of dark matter halos (HMF) - which also declines sharply over this redshift range - and the galaxy-formation physics that maps halo mass to galaxy luminosity. We consider the strong observed evolution in the LF from z approximate to 6-10 in this context and determine whether it can be explained solely by the behavior of the HMF. From z approximate to 6-8, we find a residual change in the physics of galaxy formation corresponding to a similar to 0.5 dex increase in the average luminosity of a halo of fixed mass. On the other hand, our analysis of recent LF measurements at z approximate to 10 shows that the paucity of detected galaxies is consistent with almost no change in the average luminosity at fixed halo mass from z approximate to 8. The LF slope also constrains the variation about this mean such that the luminosity of galaxies hosted by halos of the same mass are all within about an order-of-magnitude of each other. We show that these results are well-described by a simple model of galaxy formation in which cold-flow accretion is balanced by star formation and momentum-driven outflows. If galaxy formation proceeds in halos with masses down to 10(8) M-circle dot, then such a model predicts that LBGs at z approximate to 10 should be able to maintain an ionized intergalactic medium as long as the ratio of the clumping factor to the ionizing escape fraction is C/f(esc) less than or similar to 10.
- 出版日期2012-4
