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Register a new userObservational evidence of galaxy assembly bias
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Antonio D. Montero-Dorta Dr.
Publication date
2017
fields
Physics
and research's language is
English
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We analyze the spectra of 300,000 luminous red galaxies (LRGs) with stellar masses $M_* gtrsim 10^{11} M_{odot}$ from the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). By studying their star-formation histories, we find two main evolutionary paths converging into the same quiescent galaxy population at $zsim0.55$. Fast-growing LRGs assemble $80%$ of their stellar mass very early on ($zsim5$), whereas slow-growing LRGs reach the same evolutionary state at $zsim1.5$. Further investigation reveals that their clustering properties on scales of $sim$1-30 Mpc are, at a high level of significance, also different. Fast-growing LRGs are found to be more strongly clustered and reside in overall denser large-scale structure environments than slow-growing systems, for a given stellar-mass threshold. Our results imply a dependence of clustering on stellar-mass assembly history (naturally connected to the mass-formation history of the corresponding halos) for a homogeneous population of similar mass and color, which constitutes a strong observational evidence of galaxy assembly bias.
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We use the {sc Illustris TNG300} magneto-hydrodynamic simulation, the {sc SAGE} semi-analytical model, and the subhalo abundance matching technique (SHAM) to examine the diversity in predictions for galaxy assembly bias (i.e. the difference in the large scale clustering of galaxies at a fixed halo mass due to correlations with the assembly history and other properties of host haloes). We consider samples of galaxies selected according to their stellar mass or star formation rate at various redshifts. We find that all models predict an assembly bias signal of different magnitude, redshift evolution, and dependence with selection criteria and number density. To model these non-trivial dependences, we propose an extension to the standard SHAM technique so it can include arbitrary amounts of assembly bias. We do this by preferentially selecting subhaloes with the same internal property but different {it individual} large-scale bias. We find that with this model, we can successfully reproduce the galaxy assembly bias signal in either {sc SAGE} or the {sc TNG}, for all redshifts and galaxy number densities. We anticipate that this model can be used to constrain the level of assembly bias in observations and aid in the creation of more realistic mock galaxy catalogues.
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