2 Collection of the maps

The body of HI data on a galaxy can be thought of as an array of intensities in a three dimensional system: two angular coordinates in the sky plane and radial velocity. This array is frequently referred to as a "data cube". The array values intend to show the distribution and kinematics of the gas and are displayed by means of two-dimensional maps, graphics and tables, which will be referred to from now on simply as maps. We have catalogued the maps that are representative of the overall distribution of gas. Those maps referred to particular structures in a galaxy (HI holes, bubbles, shells, tails, etc.) are only mentioned in the notes. The type of maps included in the catalogue are:

a)

The distribution of the total HI emission integrated over all radial velocities.

b)

Channel maps, or maps of intensities at a given velocity.

c)

Position-velocity diagrams, or maps of the intensity as a function of velocity and one of the coordinates, the other being kept fixed.

d)

HI velocity field, or maps of some kind of velocity derived from the spectra (peak, median, etc.) as a function of position.

e)

Rotation curves derived from the HI data.

f)

Variation of some parameters along one coordinate. This type of map may be drift scans (variation of temperature with the position at a given velocity) or distribution of the HI emission (as line integral, surface density, HI fluxes, etc.) along one coordinate on the galaxy.

g)

HI profiles at different positions inside or near the optical galaxy.

h)

Global HI profile obtained by adding the large-scale observations.

i)

Tables of data of the large-scale observations.

Other types of maps are put in the footnotes, such as dispersion velocity maps, peak brightness distribution, etc.

For this catalogue, we have applied the following selection criteria to reach a somewhat complete sample: We have taken into account only references in main journals, and we have included even galaxies with few observed positions (two or three) which can give a crude distribution of the gas. Sometimes, we found the same HI maps published in an IAU Symposium as well as in a major journal, as in the case of NGC 4038/39 (van der Hulst 1978 and 1979), or M 33 (Davies 1972 and de Jager & Davies 1971). In these cases, we took the reference that contains the main work. Other times, we found two or more references related to the same observational data. In these cases, we took the observational paper, unless new maps (with different resolution or sensitivity) were presented with the same data, e.g. NGC 6946: Carignan et al. (1990) and Boulanger & Viallefond (1992). Furthermore, preliminary reports on the observations, published in an IAU Symposium or a short letter, are only mentioned in the footnotes of the catalogue.