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On the Age Estimation of LBDS 53W091

Yi, Sukyoung and Brown, Thomas M. and Heap, Sara and Hubeny, Ivan and Landsman, Wayne and Lanz, Thierry and Sweigart, Allen (2000) On the Age Estimation of LBDS 53W091. Astrophysical Journal, 533 (2). pp. 670-681. ISSN 0004-637X. doi:10.1086/308681.

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The recent spectral analysis of LBDS 53W091 by Spinrad and his collaborators has suggested that this red galaxy at z = 1.552 is at least 3.5 Gyr old. This imposes an important constraint on cosmology, suggesting that this galaxy formed at z ≳ 6.5, assuming recent estimates of cosmological parameters. While their analysis was heavily focused on the use of some UV spectral breaks as age indicators, we have performed χ2 tests to the continuum of this galaxy using its UV spectrum and photometric data (R, J, H, and K: 2000-9000 Å in rest frame). We have used the updated Yi models that are based on the Yale tracks. We find it extremely difficult to reproduce such large age estimates, under the assumption of the most probable input parameters. Using the same configuration as in Spinrad et al. (conventional solar abundance models), our analysis suggests an age of approximately 1.4-1.8 Gyr. We have improved our models over conventional ones by taking into account convective core overshoot in the stellar model calculations and realistic metallicity distributions in the galaxy population synthesis. Overshoot affects the visible continuum normalized to the UV and raises the photometry-based age estimates by 25%. The use of metallicity mixtures affects the whole spectrum and raises all continuum-based age estimates by up to a factor of 2. If the mean metallicity of the stars in this galaxy is assumed to be twice solar, the models including these two effects match the UV spectrum and photometric data of LBDS 53W091 near the age of 1.5-2.0 Gyr. Our results cannot be easily reconciled with that of Spinrad et al. The discrepancy between Spinrad et al.'s age estimate (based on the Jimenez models) and ours originates from the large difference in the model integrated spectrum: the Jimenez models are much bluer than the Yi models and the Bruzual & Charlot models. We propose to apply some viable tests to them for verification and search for the origin of the difference through a more thorough investigation. Considering the significance of the age estimates of distant galaxies as probes of cosmology, it would be an urgent task.

Item Type:Article
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URLURL TypeDescription Paper
Brown, Thomas M.0000-0002-1793-9968
Additional Information:© 2000. The American Astronomical Society. Received 1999 March 23; accepted 1999 September 29. This work was encouraged by the open-minded response of Hyron Spinrad to our initial interest in the work on LBDS 53W091 done by him and his collaborators. We thank his group, in particular Daniel Stern, for providing the spectrum of LBDS 53W091. We are grateful to Taddy Kodama for providing his metallicity distribution models and to Gustavo Bruzual for providing the spectrum of M32. The constructive criticisms and comments of Raul Jimenez, Hyron Spinrad, Gustavo Bruzual, Sydney Barnes, and Pierre Demarque improved the manuscript significantly. We owe special thanks to Raul Jimenez and Gustavo Bruzual for making their models available to us. This work was supported by the Creative Research Initiative Program of the Korean Ministry of Science and Technology grant. Part of this work was performed while S. Y. held a National Research Council–(NASA Goddard Space Flight Center) Research Associateship.
Funding AgencyGrant Number
Ministry of Science and Technology (Korea)UNSPECIFIED
National Research CouncilUNSPECIFIED
Subject Keywords:galaxies: elliptical and lenticular, cD; galaxies: evolution; galaxies: formation; galaxies: individual (53W091) ; galaxies: photometry; galaxies: stellar content
Issue or Number:2
Record Number:CaltechAUTHORS:20170408-135746484
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Official Citation:Sukyoung Yi et al 2000 ApJ 533 670
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75894
Deposited By: 1Science Import
Deposited On:14 Apr 2017 19:28
Last Modified:15 Nov 2021 16:55

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