Systematic versus statistical uncertainties in masses and magnifications of the Hubble Frontier Fields

Abstract

The Hubble Frontier Fields data, along with multiple data sets obtained by other telescopes, have provided some of the most extensive constraints on cluster lenses to date. Multiple lens modelling teams analyzed the fields and made public a number of deliverables. By comparing these results, we can then undertake a unique and vital test of the state of cluster lens modelling. Specifically, we see how well the different teams can reproduce similar magnifications and mass profiles. We find that the circularly averaged mass profiles of the fields are remarkably constrained (scatter $\lt 5{{\ \rm per\ cent}}$) at distances of 1 arcmin from the cluster core, yet magnifications can vary significantly. Averaged across the six fields, we find a bias of −6 per cent (−17 per cent) and a scatter of ∼40 per cent (∼65 per cent) at a modest magnification of 3 (10). Statistical errors reported by individual teams are often significantly smaller than the differences among all the teams, indicating the importance of continued systematics studies in cluster lensing.

Further support for a trio of mass-to-light deviations in Abell 370: free-form grale lens inversion using BUFFALO strong lensing data

“…This feature is absent in most HFF parametric reconstructions, including the more recent ones (e.g. Sharon HFF v4; Kawamata et al 2018;Raney et al 2020b), as there is no light associated with it. Also, in Strait et al (2018), which used the free-form code SWUNITED, the substructure is not seen.…”

“…A recent model comparison paper (Raney et al 2020b) analysed halfsample mode of the magnification maps of the 6 HFF clusters. Halfsample mode is the maximum likelihood value of the magnification distribution at every pixel in the lens plane.…”

“…However, since the inception of the Hubble Frontier Fields survey (HFF; PI: J. Lotz) using the Hubble Space Telescope (HST), a range of different lens inversion methods -which use different modelling assumptions and procedures -have made it possible to estimate systematic uncertainties based on different reconstructions of the same clusters of galaxies (Lotz et al 2017). Comprehensive comparison projects were carried out based on synthetic clusters (Meneghetti et al 2017), as well as observed HFF clusters (Priewe et al 2017;Remolina González, Sharon & Mahler 2018), exploring systematic uncertainties in mass reconstructions (Raney et al 2020b), probability of magnifications (Vega-Ferrero, Diego & Bernstein 2019), and recovered LF parameters of high-z galaxies (Bouwens et al 2017a;Livermore et al 2017;.…”

Molecular gas budget and characterization of intermediate-mass star-forming galaxies at z ≈ 2–3

“…We adopted an uncertainty on magnification of 20% for all images to account for the statistical error in cluster lens modeling. We note, however, that the uncertainties are possibly dominated by systematics (e.g., Raney et al 2020).…”

Efficient Mass Estimate at the Core of Strong Lensing Galaxy Clusters Using the Einstein Radius

“…Advances in strong lens (SL) modeling, including a better understanding of SL systematics (Johnson & Sharon 2016), its effects on constraining cosmological parameters (Acebron et al 2017), magnification (Priewe et al 2017;Raney et al 2020), consequences due to the number of constraints (Mahler et al 2018), and the use of spectroscopic and photometric redshifts (Cerny et al 2018), make strong lens modeling a robust technique to study galaxy clusters and the background universe they magnify. A detailed lens model requires extensive followup: (1) imaging to identify multiple images and (2) spectroscopy of the lensed images to obtain spectroscopic redshifts of the sources (e.g., Johnson et al 2014;Zitrin et al 2014;Diego et al 2016;Kawamata et al 2016;Lotz et al 2017;Strait et al 2018;Lagattuta et al 2019;Sebesta et al 2019;Sharon et al 2020).…”