http://arxiv.org/abs/1712.04452
We present Bayesian Analysis of Galaxies for Physical Inference and Parameter EStimation, or BAGPIPES, a new Python tool which can be used to rapidly generate complex model galaxy spectra and to fit these to arbitrary combinations of spectroscopic and photometric data using the MultiNest algorithm. We extensively test our ability to recover realistic star-formation histories (SFHs) with BAGPIPES by fitting mock observations of quiescent galaxies from the MUFASA simulation. We show that a double-power-law model produces better agreement with realistic SFHs than an exponentially-declining model. We then perform a detailed analysis of the SFHs of a sample of 9312 quiescent galaxies from UltraVISTA with stellar masses, $M_* > 10^{10}\ \mathrm{M_\odot}$ and redshifts $0.25 < z_\mathrm{obs} < 3.75$. The majority of our quiescent sample exhibit SFHs which rise gradually then quench relatively rapidly, over $\sim 1{-}2$ Gyr. This behaviour is consistent with recent cosmological hydrodynamic simulations, where AGN-driven feedback in the low-accretion (jet) mode is the dominant quenching mechanism. In addition, we identify two further subsets of objects with distinct SFH shapes. At $z_\mathrm{obs} \gtrsim 1$ we find a class of objects with SFHs which rise and fall very rapidly, with quenching timescales of $\lesssim 1$ Gyr. These objects are consistent with (potentially merger-triggered) quasar-mode AGN feedback. Also, at $z_\mathrm{obs} \lesssim 1$ we find a population with SFHs which quench more slowly than they rise, over $\gtrsim3$ Gyr, which we speculate to be the result of a ‘natural’ quenching process, where galaxy SFHs die down gradually due to the diminishing overall cosmic gas supply. Purely passive evolution of the quiescent population at $z_\mathrm{obs} \gtrsim 0.5$ is disfavoured by our results.
A. Carnall, R. McLure, J. Dunlop, et. al.
Thu, 14 Dec 17
9/74
Comments: 24 pages, 16 figures, submitted to MNRAS
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