Access to Astronomical Catalogues

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
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 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.


History:
    From electronic version of the journal
(End)                                      Patricia Vannier [CDS]    22-Dec-2010