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Abstract: We measure the angular auto-correlation functions w of SDSS galaxiesselected to have photometric redshifts 0.1 < z < 0.4 and absolute r-bandmagnitudes Mr < -21.2. We split these galaxies into five overlapping redshiftshells of width 0.1 and measure w in each subsample in order to investigate theevolution of SDSS galaxies. We find that the bias increases substantially withredshift - much more so than one would expect for a passively evolving sample.We use halo-model analysis to determine the best-fithalo-occupation-distribution HOD for each subsample, and the best-fit modelsallow us to interpret the change in bias physically. In order to properlyinterpret our best-fit HODs, we convert each halo mass to its z = 0 passivelyevolved bias bo, enabling a direct comparison of the best-fit HODs atdifferent redshifts. We find that the minimum halo bo required to host a galaxydecreases as the redshift decreases, suggesting that galaxies with Mr < -21.2are forming in halos at the low-mass end of the HODs over our redshift range.We use the best-fit HODs to determine the change in occupation number dividedby the change in mass of halos with constant bo and we find a sharp peak at bo~ 0.9 - corresponding to an average halo mass of ~ 10^12Msol-h. We thus presentthe following scenario: the bias of galaxies with Mr < -21.2 decreases as theUniverse evolves because these galaxies form in halos of mass ~ 10^12Msol-hindependent of redshift, and the bias of these halos naturally decreases asthe Universe evolves.



Autor: Ashley J. Ross, Will J. Percival, Robert J. Brunner

Fuente: https://arxiv.org/



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