One Percent Determination of the Primordial Deuterium Abundance

Creators: Cooke, Ryan J.; Pettini, Max; Steidel, Charles C.

Abstract

We report a reanalysis of a near-pristine absorption system, located at a redshift z_(abs) = 2.52564 toward the quasar Q1243+307, based on the combination of archival and new data obtained with the HIRES echelle spectrograph on the Keck telescope. This absorption system, which has an oxygen abundance [O/H] = −2.769 ± 0.028 ( 1/600 of the solar abundance), is among the lowest metallicity systems currently known where a precise measurement of the deuterium abundance is afforded. Our detailed analysis of this system concludes, on the basis of eight D I absorption lines, that the deuterium abundance of this gas cloud is log_(10)(D/H) = -4.622 ± 0.015, which is in very good agreement with the results previously reported by Kirkman et al., but with an improvement on the precision of this single measurement by a factor of ~3.5. Combining this new estimate with our previous sample of six high precision and homogeneously analyzed D/H measurements, we deduce that the primordial deuterium abundance is log_(10)(D/H)_P = -4.5974 ± 0.0052 or, expressed as a linear quantity, 10^5(D/H)_P = 2.527 ± 0.030; this value corresponds to a one percent determination of the primordial deuterium abundance. Combining our result with a big bang nucleosynthesis (BBN) calculation that uses the latest nuclear physics input, we find that the baryon density derived from BBN agrees to within 2σ of the latest results from the Planck cosmic microwave background data.

Additional Information

© 2018 The American Astronomical Society. Received 2017 July 26; revised 2018 January 26; accepted 2018 January 27; published 2018 March 12. Based on observations collected at the W.M. Keck Observatory which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. We are grateful to the staff astronomers at Keck Observatory for their assistance with the observations, and to Jason X. Prochaska, Tom Barlow, and Michael T. Murphy for providing some of the software that was used to reduce the data. We also thank an anonymous referee who provided helpful suggestions that improved the presentation of this work, following a referee who was unable to respond in a timely manner. During this work, R.J.C. was supported by a Royal Society University Research Fellowship. R.J.C. acknowledges support from STFC (ST/L00075X/1, ST/P000541/1). C.C.S. has been supported by grant AST-1313472 from the U.S. NSF. This research was also supported by a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. Data presented herein were obtained at the W. M. Keck Observatory from telescope time partially allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We thank the Hawaiian people for the opportunity to observe from MaunaKea; without their hospitality, this work would not have been possible. This work used the DiRAC Data Centric system at Durham University, operated by the Institute for Computational Cosmology on behalf of the STFC DiRAC HPC Facility (http://www.dirac.ac.uk). This equipment was funded by BIS National E-infrastructure capital grant ST/K00042X/1, STFC capital grant ST/H008519/1, and STFC DiRAC Operations grant ST/K003267/1 and Durham University. DiRAC is part of the National E-Infrastructure. This research has made use of NASA's Astrophysics Data System. R.J.C. thanks S.O.C. for her impeccable timing and invaluable insight. Facility: Keck(HIRES) - . Software: Astropy (Astropy Collaboration et al. 2013), Matplotlib (Hunter 2007), NumPy (van der Walt et al. 2011).

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Accepted Version - 1710.11129.pdf

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