GHASP: A 3-D SURVEY OF SPIRAL AND IRREGULAR GALAXIES AT Hα P. AMRAM, C. ADAMI, C. BALKOWSKI, S. BLAIS-OUELLETTE, A. BOSELLI, J. BOULESTEIX, C. CARIGNAN, V. CAYATTE, L. CHEMIN, J.L. GACH, O. GARRIDO, O. HERNANDEZ, M. MARCELIN, L. MICHEL-DANSAC, H. PLANA, D. RUSSEIL, B. VOLLMER and H. WOZNIAK Université de Province Observatoire, F-13248 Marseille, Cedex 4, France E-mail: Philippe.Amram@Observatoire.cnrs-mrs.fr The survey GHASP (Gassendi HAlpha survey of SPirals) will provide a 3-D sample of about 200 nearby spiral galaxies in the Hα line, using a Fabry-Perot system. The data cubes obtained for each galaxy allow to derive line maps, velocity fields and other moment analysis. This data base will allow the following four key ponts. 1. To build a Homogeneous Local Sample of Data Cube Up to now, no homogeneous sample exists of optical data cube of nearby and isol- ated spirals with a large range of morphological types and luminosities allowing statistical and individual studies. This data base will constitute an unique and ho- mogeneous 3-D sample of velocity fields and line profiles to be used as a reference sample: 1. for nearby galaxies in various environment (clusters, groups, pairs) or 2. at different stages of evolution (interactions, mergers, starbursts ...) or 3. presenting anomalous motions (counter rotating populations, non keplerian motions...) as well as 4. for higher redshift galaxies for which the 3-D data will be available soon. 2. Mass Distribution of Spirals and Irregulars N-body simulations of cosmological evolution have now reached a sufficient res- olution to predict dark halos density profiles down to the innermost parts of spiral galaxies. Their trend is to show dense cuspy halos, which are not observed in most cases. High-resolution Hα velocity fields are complementary to HI velocity fields mapping the outer galactic regions but suffering of beam smearing and of a lack of emission in the inner regions. The GHASP sample is a sub-sample of the WHISP (Westerbork Survey of HI Spiral in Galaxies), lead by Groningen and Dwingeloo, in order to map the neutral hydrogen of some 1000 galaxies. The mass distribution Astrophysics and Space Science 281: 393–396, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands.