A catalogue of ionized gas velocity fields for a sample of 30 spiral and irregular galaxies of the Virgo cluster has been obtained by using 3D optical data. The aim of this survey is to study the influence of high-density environments on the gaseous kinematics of local cluster galaxies. Observations of the Hα line by means of Fabry-Perot interferometry have been performed at the Canada-France-Hawaii Telescope, European Southern Observatory 3.6-m telescope, Observatoire de Haute-Provence 1.93-m telescope and Observatoire du mont Mégantic telescope at angular and spectral samplings from 0.4 to 1.6 arcsec and 7 to 16 km s −1 . A recently developed, automatic and adaptive spatial binning technique is used to reach a nearly constant signal-to-noise ratio (S/N) over the whole field of view, allowing us to keep a high spatial resolution in high-S/N regions and extend the detection of signal in low-S/N regions. This paper is part of a series and presents the integrated emission-line and velocity maps of the galaxies. Both Hα morphologies and kinematics exhibit signs of perturbations in the form of, for example, external filaments, inner and nuclear spiral-and ring-like structures, inner kinematical twists, kinematical decoupling of a nuclear spiral, streaming motions along spiral arms and misalignment between kinematical and photometric orientation axes.

Abstract. GHASP (Gassendi Hα survey of SPirals) is a survey of Hα velocities in spiral and irregular galaxies. The observations began in 1998, with a scanning Fabry-Perot and a focal reducer attached at the Cassegrain focus of the 1.93 m telescope at the Observatoire de Haute-Provence. This paper presents the Hα maps, the 2D velocity fields and the rotation curves obtained for a set of 23 galaxies observed in October 1998 and April 1999. Most of them have already been observed in HI in the frame of the WHISP survey led at Westerbork, for which GHASP brings an interesting complement. The aim is to provide a reference sample of 2D velocity fields for about 200 nearby spiral galaxies at Hα wavelength.

We present Fabry–Perot observations obtained in the frame of the GHASP survey (Gassendi HAlpha survey of SPirals). We have derived the Hα map, the velocity field and the rotation curve for a new set of 44 galaxies. The data presented in this paper are combined with the data published in the three previous papers providing a total number of 85 of the 96 galaxies observed up to now. This sample of kinematical data has been divided into two groups: isolated (ISO) and softly interacting (SOFT) galaxies. In this paper, the extension of the Hα discs, the shape of the rotation curves, the kinematical asymmetry and the Tully–Fisher relation have been investigated for both ISO and SOFT galaxies. The Hα extension is roughly proportional to R25 for ISO as well as for SOFT galaxies. The smallest extensions of the ionized disc are found for ISO galaxies. The inner slope of the rotation curves is found to be correlated with the central concentration of light more clearly than with the type or the kinematical asymmetry, for ISO as well as for SOFT galaxies. The outer slope of the rotation curves increases with the type and with the kinematical asymmetry for ISO galaxies but shows no special trend for SOFT galaxies. No decreasing rotation curve is found for SOFT galaxies. The asymmetry of the rotation curves is correlated with the morphological type, the luminosity, the (B−V) colour and the maximal rotational velocity of galaxies. Our results show that the brightest, the most massive and the reddest galaxies, which are fast rotators, are the least asymmetric, meaning that they are the most efficient with which to average the mass distribution on the whole disc. Asymmetry in the rotation curves seems to be linked with local star formation, betraying disturbances of the gravitational potential. The Tully–Fisher relation has a smaller slope for ISO than for SOFT galaxies.

A third-generation image photon-counting system (IPCS) camera is presented, based on a GaAs photocathode that can achieve a quantum efficiency of up to 23%, which is comparable to a thick CCD but without readout noise. This system is 10 times more sensitive at Ha than previous photon-counting cameras. In terms of signal-to-noise ratio, the system outperforms CCDs for extremely faint fluxes, including antireflectioncoated, low-noise, thin CCDs. This system, with up to 1K # 1K pixels, is one of the largest monolithic IPCSs. A unique cooling system, based on a Ranque-Hilsh vortex tube, is used for this camera. Real-time centering is done by a scalable digital signal processor board. Astrophysical projects and preliminary results obtained with this new camera coupled with a scanning Fabry-Pe ´rot interferometer at the Cassegrain focus of the 3.6 m ESO telescope, the 1.93 m Observatoire de Haute Provence telescope, and the 1.6 m Observatoire du Mont Me ´gantic telescope are presented.

Arp 227 represents a prototypical example of an interacting mixed pair of galaxies located in a low-density environment. We investigate the gas properties of the pair in the X-ray, Hα, HI and CO bands. We also detect two additional members of the group in HI which indicates that the pair constitutes the dominant members of a loose group. The HI distribution shows a tail of gas that connects the spiral member, NGC 470, to the lenticular, NGC 474, showing that the two main members are currently undergoing interaction. The Hα emission reveals the presence of secondary components at the centre of NGC 470, superposed on the main component tracing the rotation of the galaxy. This latter maps a nearly unperturbed velocity field. The dominant, nearly unperturbed trend of the kinematics is confirmed by CO observations, although restricted to the centre of the galaxy. The X-ray luminosity of NGC 470 is comparable with that of a `normal' spiral galaxy. NGC 474 on the other hand is very gas-poor and has not been detected in Hα. Its X-ray luminosity is consistent with the low end of the expected emission from discrete sources. Arp 227 as a loose group shows several signatures of galaxy-galaxy interaction. Our observations suggest the presence of signatures of interaction in the overall kinematics of the spiral companion. The ongoing interaction is clearly visible only in the outer HI halo of NGC 470. While the large shell system of NGC 474 could be associated with an accretion event, the secondary components in the Hα profile in the centre of NGC 470 could be due to the interaction with the companion. The low X-ray luminosity of NGC 470 seems to be a characteristic of dynamically young systems. All the above evidence suggest that Arp 227 is an evolving group in the early phase of its evolution and that its drivers are the accretion of faint galaxies and the ongoing large-scale interaction between NGC 470 and 474