barry and the BAO model comparison

Abstract

We compare the performance of four state-of-the-art models for extracting isotropic measurements of the Baryon Acoustic Oscillation (BAO) scale. To do this, we created a new, public, modular code Barry, which contains datasets, model fitting tools, and model implementations incorporating different descriptions of non-linear physics and algorithms for isolating the BAO feature. These are then evaluated for bias, correlation, and fitting strength using mock power spectra and correlation functions developed for the Sloan Digital Sky Survey Data Release 12. Our main findings are as follows: 1) All of the models can recover unbiased constraints when fit to the preand post-reconstruction simulations. 2) Models that provide physical descriptions of the damping of the BAO feature (using e.g., standard perturbation or effective-field theory arguments) report smaller errors on average, although the distribution of mock χ 2 values indicates these are underestimated. 3) Allowing the BAO damping scale to vary can provide tighter constraints for some mocks, but is an artificial improvement that only arises when noise randomly sharpens the BAO peak. 4) Unlike recent claims in the literature when utilising a BAO Extractor technique, we find no improvement in the accuracy of the recovered BAO scale. 5) We implement a procedure for combining all models into a single consensus result that improves over the standard method without obviously underestimating the uncertainties. Overall, Barry provides a framework for performing the cosmological analyses for upcoming surveys, and for rapidly testing and validating new models.

The Effect of Systematic Redshift Biases in BAO Cosmology

“…When we inject a fixed, constant offset of 10 −3 to the redshifts in this high n sample, we see a larger offset in 𝛼 from our baseline sample for lower 𝑧 eff (corresponding to the increase in bias as a proportion of total measurement with lower 𝑧 eff ), in good agreement with our analytic model. B (Hinton et al 2020). B provides a modular framework for fitting the BAO features in the galaxy power spectrum and correlation function, allowing us to easily compare the effects of different redshift ranges, datasets, and BAO extraction models from the literature.…”

Ho’oleilana: An Individual Baryon Acoustic Oscillation?

“…We attribute this mainly to nonlinear clustering and galaxy bias and to account for this effect we included an additional linear term N 1 on top of the constant N 0 , slightly increasing the order of the polynomial used to marginalize over the overall shape of the mass profile. This same procedure is used in standard BAO fitting, where a cubic or quartic polynomial is typically used to marginalize over the shape of the correlation function rather than attempting to model nonlinear effects, which ensures the constraints on the BAO peak position itself are insensitive to the broadband shape of the clustering (e.g., Ross et al 2015;Hinton et al 2020;Alam et al 2021).…”

Model-agnostic interpretation of 10 billion years of cosmic evolution traced by BOSS and eBOSS data

“…Finding a universal numerical BAO extraction method is further complicated by the fact that other features in the linear power spectrum -determined by the matter-radiation equality turnover and baryon suppression scales-show a rich cosmology dependence. Any numerical method relying on a set of hyperparameters, such as the one presented in [115], must therefore be validated to deliver standardizable results against that cosmology dependence. Since such a validated method does not yet exist in the literature, in this work we use the analytic EH98 formula [6] to obtain our Shape predictions.…”