A search for spiral galaxies with extended HI disks.

Astronomy and Astrophysics – Astrophysics

Scientific paper

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Galaxies: Fundamental Parameters, Galaxies: Kinematics And Dynamics, Galaxies: Irregular, Galaxies: Spiral, Radio Lines: Galaxies

Scientific paper

We present short 21-cm line observations of about 50 spiral galaxies, made with the Westerbork Synthesis Radio Telescope. They form the first stage of a two-stage project to study the relation between the shape of extended rotation curves and galaxy properties, such as luminosity and morphological type. In this first stage, one-dimensional information has been obtained about the kinematics and spatial distribution of the neutral hydrogen (HI) along the major axis of each galaxy. The primary goal of these observations was to find galaxies with extended neutral hydrogen disks that have regular spatial and velocity distributions. In the second stage (Broeils, in preparation, see also Broeils 1992a,b), HI synthesis observations of twelve regular systems thus selected are analysed, in order to obtain full two-dimensional information on the HI distributions and velocity fields. The results of the first stage are presented in Fig. A1, as position-velocity maps of the neutral hydrogen distribution of all galaxies in our sample. Global HI profiles and HI strip integrals are formed by integrating these maps, respectively, in the position and in the velocity directions. The strip integrals are deprojected to face-on radial surface density distributions. For each galaxy a number of global HI properties, like diameters, fluxes, hydrogen masses, profile widths and systemic velocities are determined. In a future paper these properties and their relation to optical properties will be discussed, and representative rotation velocities from the position-velocity maps will be derived in order to investigate the influence of using these velocities instead of the profile widths on the scatter and slope of the Tully-Fisher relation.

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