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On the cosmic evolution of Fe/Mg in QSO absorption line systems

Dey, Arjun and Torrey, Paul and Rubin, Kate H. R. and Zhu, Guangtun Ben and Suresh, Joshua (2015) On the cosmic evolution of Fe/Mg in QSO absorption line systems. Monthly Notices of the Royal Astronomical Society, 451 (2). pp. 1806-1814. ISSN 0035-8711.

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We investigate the variation of the ratio of the equivalent widths of the Fe II λ2600 line to the Mg II λλ2796, 2803 doublet as a function of redshift in a large sample of absorption lines drawn from the Johns Hopkins University - Sloan Digital Sky Survey Absorption Line Catalog. We find that despite large scatter, the observed ratio shows a trend where the equivalent width ratio R ≡ W_(Fe II)/W_(Mg II) decreases monotonically with increasing redshift z over the range 0.55 ≤ z ≤ 1.90. Selecting the subset of absorbers where the signal-to-noise ratio of the Mg II equivalent width W_(Mg II is ≥3 and modelling the equivalent width ratio distribution as a Gaussian, we find that the mean of the Gaussian distribution varies as R ∝ (−0.045±0.005)z. We discuss various possible reasons for the trend. A monotonic trend in the Fe/Mg abundance ratio is predicted by a simple model where the abundances of Mg and Fe in the absorbing clouds are assumed to be the result of supernova (SN) ejecta and where the cosmic evolution in the SNIa and core-collapse SN rates is related to the cosmic star formation rate. If the trend in R reflects the evolution in the abundances, then it is consistent with the predictions of the simple model.

Item Type:Article
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URLURL TypeDescription Paper
Dey, Arjun0000-0002-4928-4003
Torrey, Paul0000-0002-5653-0786
Rubin, Kate H. R.0000-0001-6248-1864
Additional Information:© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 March 18. Received 2015 February 21. In original form 2014 July 25. First published online June 9, 2015. This research made use of the JHU-SDSS Metal Absorption Line Catalog (ZM13), which is based on the SDSS DR7 (Abazajian et al. 2009), and the NIST Atomic Spectra Database (Kramida et al. 2013). We thank Dr Brice Ménard for useful advice and for putting together such a scientifically useful resource. AD thanks Joan Najita for assistance with the ASURV package and Tom Matheson for useful comments on the manuscript. We are grateful to the referee for a constructive report that resulted in improving this paper. Funding for the SDSS and SDSS-II was provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society and the Higher Education Funding Council for England. The SDSS website is GBZ acknowledges partial support provided by NASA through Hubble Fellowship grant #HST-HF2-51351 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under contract NAS 5-26555. AD's research activities are supported by the National Optical Astronomy Observatory (NOAO). AD thanks the Radcliffe Institute for Advanced Study and the Institute for Theory and Computation at Harvard University for their generous support during the period when this paper was written. NOAO is operated by the Association of Universities for Research in Astronomy (AURA) under cooperative agreement with the National Science Foundation.
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
Participating InstitutionsUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
NASANAS 5-26555
Japanese MonbukagakushoUNSPECIFIED
Max Planck SocietyUNSPECIFIED
Higher Education Funding Council for EnglandUNSPECIFIED
Hubble FellowshipHST-HF2-51351
National Optical Astronomy Observatory (NOAO)UNSPECIFIED
Radcliffe Institute for Advanced StudyUNSPECIFIED
Harvard UniversityUNSPECIFIED
Association of Universities for Research in Astronomy (AURA)UNSPECIFIED
Subject Keywords:galaxies: abundances; galaxies: evolution; galaxies: haloes; intergalactic medium; quasars: absorption lines
Issue or Number:2
Record Number:CaltechAUTHORS:20151002-121708497
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Official Citation:Arjun Dey, Paul Torrey, Kate H. R. Rubin, Guangtun Ben Zhu, and Joshua Suresh On the cosmic evolution of Fe/Mg in QSO absorption line systems MNRAS (August 01, 2015) Vol. 451 1806-1814 doi:10.1093/mnras/stv604 First published online June 9, 2015
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:60707
Deposited By: George Porter
Deposited On:02 Oct 2015 19:38
Last Modified:16 Nov 2019 06:03

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