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. =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: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- See also: J/ApJS/116/1 : Old Stellar Populations. VI. Absorption-Line (Trager+ 1998) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 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) -------------------------------------------------------------------------------- Note (1): Offset I_lib_=a*I_Lick_+b, where I_lib_ are indices measured on the libraries (MILES, ELODIE and STELIB) for which offsets to the Lick/IDS library are presented. I_Lick_ are indices measured on the Lick/IDS library. -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Patricia Vannier [CDS] 22-Dec-2010