J/MNRAS/406/165 Comparison of Lick indexes (Johansson+, 2010)
Empirical calibrations of optical absorption-line indices based on the stellar
library MILES.
Johansson J., Thomas D., Maraston C.
<Mon. Not. R. Astron. Soc., 406, 165-180 (2010)>
=2010MNRAS.406..165J 2010MNRAS.406..165J
ADC_Keywords: Line Profiles ; Models
Keywords: line: profiles - stars: abundances - stars: fundamental parameters
Abstract:
Stellar population models of absorption-line indices are an important
tool for the analysis of stellar population spectra. They are most
accurately modelled through empirical calibrations of absorption-line
indices with the stellar parameters such as effective temperature,
metallicity and surface gravity, which are the so-called fitting
functions. Here we present new empirical fitting functions for the 25
optical Lick absorption-line indices based on the new stellar library
Medium resolution INT Library of Empirical Spectra (MILES). The major
improvements with respect to the Lick/IDS library are the better
sampling of stellar parameter space, a generally higher
signal-to-noise ratio and a careful flux calibration. In fact, we find
that errors on individual index measurements in MILES are considerably
smaller than in Lick/IDS. Instead, we find the rms of the residuals
between the final fitting functions and the data to be dominated by
errors in the stellar parameters. We provide fitting functions for
both Lick/IDS and MILES spectral resolutions and compare our results
with other fitting functions in the literature.
Description:
A fortran 90 code is available online in order to simplify the
implementation in stellar population models, available at
http://www.icg.port.ac.uk/~johanssj/
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 76 25 Typical Lick index errors and offsets to the
Lick/IDS library
appen.pdf 512 4413 PDF file of Fitting functions for Lick/IDS
and MILES resolutions
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See also:
J/ApJS/116/1 : Old Stellar Populations. VI. Absorption-Line (Trager+ 1998)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Index Index number
4- 12 A9 --- Name Index name
14- 19 F6.4 --- sigM Index error at the resolution of the MILES library
22- 27 F6.4 --- sigL Index error at the resolution of the Lick/IDS
library
30- 34 F5.3 --- sigT98 Index error presented in Trager et al. (1998,
Cat. J/ApJS/116/1) for the Lick/IDS library
36- 40 F5.3 --- aM MILES a coefficient (1)
42- 48 F7.4 --- bM MILES b coefficient (1)
50- 54 F5.3 --- aE ELODIE a coefficient (1)
56- 62 F7.4 --- bE ELODIE b coefficient (1)
64- 68 F5.3 --- aS STELIB a coefficient (1)
70- 76 F7.4 --- bS STELIB b coefficient (1)
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Note (1): Offset Ilib=a*ILick+b, where Ilib are indices measured on
the libraries (MILES, ELODIE and STELIB) for which offsets to the
Lick/IDS library are presented. ILick are indices measured on the
Lick/IDS library.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 22-Dec-2010