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Published September 20, 2015 | Published + Submitted
Journal Article Open

Illuminating a Dark Lens: A Type Ia Supernova Magnified by the Frontier Fields Galaxy Cluster Abell 2744


SN HFF14Tom is a Type Ia SN discovered at z=1.3457 ± 0.0001 behind the galaxy cluster Abell 2744 (z = 0.308). In a cosmology-independent analysis, we find that HFF14Tom is 0.77 ± 0.15 mag brighter than unlensed Type Ia SNe at similar redshift, implying a lensing magnification of µ_(obs)=2.03 ± 0.29. This observed magnification provides a rare opportunity for a direct empirical test of galaxy cluster lens models. Here we test 17 lens models, 13 of which were generated before the SN magnification was known, qualifying as pure "blind tests." The models are collectively fairly accurate: 8 of the models deliver median magnifications that are consistent with the measured μ to within 1σ. However, there is a subtle systematic bias: the significant disagreements all involve models overpredicting the magnification. We evaluate possible causes for this mild bias, and find no single physical or methodological explanation to account for it. We do find that model accuracy can be improved to some extent with stringent quality cuts on multiply imaged systems, such as requiring that a large fraction have spectroscopic redshifts. In addition to testing model accuracies as we have done here, Type Ia SN magnifications could also be used as inputs for future lens models of Abell 2744 and other clusters, providing valuable constraints in regions where traditional strong- and weak-lensing information is unavailable.

Additional Information

© 2015 American Astronomical Society. Received 2015 May 22; accepted 2015 August 14; published 2015 September 22. This work is dedicated to our colleague and friend Tomas Dahlen, for whom this supernova has been named in memoriam. He is dearly missed. We thank the Hubble Frontier Fields team at STScI for their substantial efforts to make the HFF program successful. In particular, thanks are due to Matt Mountain for the allocation of discretionary orbits for the HFF program; to Jennifer Lotz, Norman Grogin, and Patricia Royle for accommodations in strategy and implementation to make the FrontierSN program possible; to Anton Koekemoer for HFF data processing support. We also thank the CLASH team, led by Marc Postman, for observations, catalogs, and high level science products that were of significant value for this analysis. Thanks to Jonatan Selsing for helpful comments on the manuscript. This work utilizes gravitational lensing models produced by modeling teams that were funded as part of the HST Frontier Fields program conducted by STScI. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. The lens models were obtained from the Mikulski Archive for Space Telescopes (MAST). Financial support for this work was provided to S.A.R. by NASA through grants HST-HF-51312 and HST-GO-13386 from STScI, which is operated by Associated Universities for Research in Astronomy, Inc. (AURA), under NASA contract NAS 5-26555. A.M. acknowledge the financial support of the Brazilian funding agency FAPESP (Post-doc fellowship— process number 2014/11806-9). Support for this research at Rutgers University was provided in part by NSF CAREER award AST-0847157 to SWJ. The Dark Cosmology Centre is supported by the Danish National Research Foundation. J.M.D. acknowledges support of the consolider project CSD2010-00064 and AYA2012–39475-C02-01 funded by the Ministerio de Economia y Competitividad. J.M. contributed to this research from the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA and acknowledges support from NASA Grants HST-GO-13343.05-A and HSTGO- 13386.13-A. The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/20072013) under REA grant agreement number 627288. A.Z. acknowledges financial support from NASA through grant HST-HF-51334.01-A awarded by STScI and operated by AURA. T.T. acknowledges support by the Packard Foundation in the form of Packard Research Fellowship. GLASS is funded by NASA through HST grant GO-13459. L.L.R.W. acknowledges the support of the Minnesota Supercomputing Institute. Facility: HST (WFC3).

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Submitted - 1505.06211v2.pdf

Published - Rodney_2015p70.pdf


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August 22, 2023
August 22, 2023