Star formation history of early-type galaxies in low density environments. I. Nuclear line-strength indices
Abstract
This paper is the first of a series \cite[(Longhetti et al. 1997a,b)]{lon97} dedicated to the study of the star formation history in early-type galaxies which show fine structures and/or signatures of interaction. It presents nuclear line-strength indices for a sample composed of 21 shell galaxies, from the \cite[Malin & Carter (1983)]{mal83} southern survey, and 30 members of isolated interacting pairs, from the \cite[Reduzzi & Rampazzo (1995)]{red95} catalogue, located in low density environments. The spectral range covers 3700 Angstroms < lambda < 5700 Angstroms at 2.1 Angstroms FWHM resolution. We measure 16 red (lambda > 4200 Angstroms) indices defined by the Lick Group. Measures have been transformed into the Lick-IDS ``standard'' system. The procedure has been tested on a set of 5 elliptical galaxies selected from the \cite[Gonzalez (1993)]{gon93} sample. We derive also three blue (lambda < 4200) indices, namely Delta (4000 Angstroms) defined by \cite[Hamilton (1985)]{ham85}, H+K(CaII) and Hdelta /FeI defined by \cite[Rose (1984, 1985)]{ros84}. Blue indices are correlated to the age of the last starburst occurred in a galaxy \cite[(Leonardi & Rose 1996)]{leo96}. The determination of these indices, the estimate of the measurement errors and the correction for the galaxies velocity dispersions are discussed in detail. In the Appendix A we present the indices for a set of hot stars (T> 10000 K) which may be used for extending W92 fitting functions toward high temperatures. Based on observations obtained at ESO, La Silla, Chile. Tables 1-8 are also available in electronic form at CDS and Tables 9-15 are only available in electronic form at CDS: via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
- Publication:
-
Astronomy and Astrophysics Supplement Series
- Pub Date:
- June 1998
- DOI:
- 10.1051/aas:1998410
- Bibcode:
- 1998A&AS..130..251L
- Keywords:
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- GALAXIES: FUNDAMENTAL PARAMETERS;
- GALAXIES: ELLIPTICAL AND LENTICULAR;
- GALAXIES: INTERACTIONS;
- GALAXIES: EVOLUTION