Astron. Astrophys. 325, 473-478 (1997)

3. Data

From our searchlist of 54 we detected 41 galaxies. These HI profiles are shown in Fig. 1. Optical radial velocities of member galaxies (Hickson 1993) are indicated by vertical arrows and the corresponding identifying letter. The morphological types of these galaxies are given at the lower end of the arrows. In some cases HI- and optical velocities agree perfectly (e.g. HCG 4 , HCG 41). In many cases the identification between HI-profile and the corresponding galaxy is not possible due to confusion problems. Some profiles resemble the typical two-horned profiles of individual spiral galaxies while others look like strongly confused profiles because of the effect of the overlay of several profiles which are not safely separated in velocity space (e.g. HCG 40). Some of these profiles correspond to individual galaxies, indeed ; for HCG 41, HCG 78 there is only one galaxy within the velocity range searched for HI. Both these galaxies have 'normal' HI abundances (i.e. they are close to the solid line in Fig. 2). In a few cases the separation of HI-profiles allows tentative identification of individual HI-profiles with galaxies (e.g. HCG 4, HCG 14, and HCG 78).

Fig. 1. HI profiles of the 41 detected galaxy groups observed with the 100-m radio telescope at Effelsberg which has a half power beam width of 9.3 arcmin at a wavelength of 21-cm. A few marginal cases have been added. The HCG no. is given in the upper left part of the individual profiles. Optical radial velocities of member galaxies (Hickson 1993) are indicated by vertical arrows and the corresponding identifying letter. The morphological types of these member galaxies are given at the lower end of the arrows. For all groups the observed profile corresponds to the accumulated HI-flux of the member galaxies. For HCG 41 and HCG 78 the HI-profiles correspond to individual galaxies in the velocity range searched for HI. In a few cases the good agreement between optical and radio radial velocities and the separation of HI-profiles allows a tentative identification of individual HI-profiles, e.g. HCG 4, HCG 14, and HCG 48. In HCG 19 radial velocities for only two out of four galaxies are available.

Fig. 2. The relative content of neutral hydrogen of Hickson Compact Groups of galaxies is plotted versus blue luminosity . Solid symbols represent detections, open symbols upper limits. Circles indicate spiral groups, triangles (up) are mixed spiral-S0 groups, whereas triangles (down) are S0 groups. Four nearby groups are represented by filled circles close to the solid line. The solid line represents the sample of nearby galaxies (HR1). The Coma I group (solid square) contains seven highly HI-deficient galaxies. The open square represents these HI-deficient galaxies. The spirals of the Virgo cluster (solid rhombus) are another examples of an aggregate containing HI-deficient galaxies. These HI-deficient galaxies concentrate towards the cluster's center as can be seen when selecting all spirals within a radius of 1 degree of the center (open rhombus).

In Table 1 we present the observational data: the HCG number in column 1, R.A. and Dec.(1950.0) in column 2, the optical redshift in column 3, a rough morphological description giving the total number of spirals and the total number N of galaxies in the brightest three magnitudes in column 4, the integrated blue luminosity of all member galaxies later than type E within the velocity interval searched for HI (column 5). The HI data follow; the measured HI flux (column 6), the observed peak of the line and its rms error in column 7 (for non detections only the rms noise is shown), the heliocentric radial velocity derived from the midpoint of the line at 25% and 20% of the peak and its error (column 8), and the linewidths at a level of 50%, 25%, and 20% of the line peak (column 9), and finally the relative HI-content of the group in column 10.

In Table 2 (which is only available in electronic form) we present a few derived parameter for the combined sample (i.e. data from Williams and Rood 1987 and from Table 1) : the HCG number (column 1), the 1950 position (column 2), the optical redshift (column 3), the heliocentric HI velocity (column 4) is followed by the assumed distance (column 5), the blue luminosity (column 6), the total HI-mass (column 7), and the ratio in column 8.

Velocity corrections to the centroid of the local group of galaxies have been made following de Vaucouleurs et al. (1990, RC3). Distances have been derived using a Hubble constant .

The total H I mass has been calculated by

,

where D is the distance in Mpc and is the integrated HI-flux in .

© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998

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