Scientific Results

Hα study of a redshift-limited subsample

Hα is a good tracer of recent star formation in places where extinction is not high. The aims of our study are :
  • To obtain a template for the global Hα emission strength. This will allow us to revise reported SF enhancements in strongly interacting systems and unexpected SF inhibition in compact groups of galaxies (e.g. Kennicutt et al. 19871994Hummel et al 1990, Gavazzi et al 199119982002Young et al 1996Boselli et al 2002, Iglesias-Páramo et al 19992002a, 2002b) all of them depending upon small/unhomogeneus control samples.
  • To investigate the dependence for isolated galaxies of Hα derived SF rates with HI, H2 and/or HI+H2, whose connection is not well defined yet for other samples (Kennicutt 19881989,1998).
  • To quantify Hα morphologies following our previous studies of interacting pairs (e.g. Combes et al. 1994) that revealed at least 3-4 fundamentally different morphologies in Hα’s light (discrete emission: nuclear dominated and/or disk dominated, as well as diffuse emission).

Our Hα sample is composed of 224 galaxies with 1500 Kms-1 ≤ VR ≤ 5000 Kms-1 and morphologies S0/a or later. The 224 galaxies comprising our sample for star formation studies, have been imaged in Hα and Gunn r filters, in order to trace respectively the regions ionised by newly born stars (HII regions) and the older stellar component. The data were obtained at the Observatorio de Sierra Nevada, CAHA, EOCA, JTK and San Pedro Mártir. (Bergond et al. in prep)