Astron. Astrophys. Suppl. Ser.
Volume 139, Number 1, October I 1999
|Page(s)||29 - 41|
|Published online||15 October 1999|
Empirical calibration of the λ4000 Å break*
Departamento de Astrofísica, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
2 Instituto de Astronomía, U.N.A.M., Apdo. Postal 70-264, 04510 Mexico D.F., Mexico
Send offprint request to: J. Gorgas
Accepted: 11 May 1999
Empirical fitting functions, describing the behaviour of the λ4000 Åbreak, D4000, in terms of effective temperature, metallicity and surface gravity, are presented. For this purpose, the break has been measured in 392 stars from the Lick/IDS Library. We have followed a very detailed error treatment in the reduction and fitting procedures, allowing for a reliable estimation of the break uncertainties. This calibration can be easily incorporated into stellar population models to provide accurate predictions of the break amplitude for, relatively old, composite systems.
Key words: stars: fundamental parameters / galaxies: stellar content / techniques: spectroscopic / stars: atmospheres
Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) or via http://cdsweb.u-strasbg.fr/Abstract.html
© European Southern Observatory (ESO), 1999