4 Discussion

A great majority (78%) of our galaxies are of type Im (1) and Ir (61), about 2% are of type Sph (2), while the other 16% is a collection of different types from spiral to Sm. The detection rate of our sample galaxies also depends on the morphological type. 77% of the spirals (type SB to Sm) were detected; the detection rate for types Im and Ir is close to 36%, whereas the galaxies of type Sph were not detected. The detection rate depends on the optical surface brightness (S.B.) class, too. From high S.B. to low, and very low S.B. the detection rate decreases from 100% to 43%, and 25%, respectively. This trend reflects the type dependence and the fact that we deal with fainter galaxies as we descend from high S.B. to very low S.B., the median absolute magnitudes for the detected galaxies change from -15.43 (H) to -13.92 (VL) for our brightness classes. There are a few cases of high $M_{{\rm H\,{\sc I}}}/L_{B}$ values in Table 2. The galaxy with $M_{{\rm H\,{\sc I}}}/L_{B} \ge 6$ is actually found to be confused by emission from a nearby galaxy (kkr69, kkr68, see Table 2). Both profiles are nearly identical in shape, radial velocity and linewidths, but not in flux. Most of the H I flux originates from kkr68; it is not possible to separate the contribution of each galaxy to the observed H I profiles. All detected galaxies have been checked in the NED for confusion within a circle of 15' radius around the optical position. All objects found this way could be classified (on the POSS) as background objects except the discussed confusion of kkr68/69.

Galaxies in Paper I were searched from the environment of known nearby groups. The present sample essentially presents the northern sky in the RA range [14h, 23h30] including the Local Void. Hence one would expect the present sample to be more distant than the sample of Paper I which is the case with a median value of the distance of 12.5 Mpc and 21 Mpc for sampleI and sampleII, respectively. The relevant values for the linear diameters are 3.6 and 5.6 kpc, a consequence of limited sensitivity: at greater distances the detection limit is higher and we do not detect the very small objects we detect nearby. However, for the subsample of galaxies within 10 Mpc in Paper I and the present sample there are no significant differences: distance = 5.3 and 5.1 Mpc and the linear optical diameter A₀=1.4 and 1.1 kpc, respectively.

The present sample of galaxies as presented in Tables 1 and 2 is a collection of dwarf galaxies with the exception of kkr58, a brighter edge-on galaxy ( M_B=-19.95) with a "broad'' H I line. They have narrow lines (Fig. 1 and Table 2). There are 22 sample galaxies within the Local Void circle (they are indicated in Table 2: in italics for upper limits and as bold face for detections), 8 of these galaxies were detected in H I. Only one of these (kkr49) lies within the Void volume ( V₀=1076 kms^-1) very close to its projected edge. The velocity distribution of the 14 undetected galaxies is unknown. There is no reason to assume they may be fainter and smaller or have less H I mass than other galaxies in this sample on the average. If all galaxies would be in the background ( $V_{0} \ge 1500$ kms^-1) the void would be empty. If they all would be hidden by Local H I emission they would be a local phenomenon (Local Group or nearby group). So they would not populate the LV except perhaps the rim of the LV. The most unfavorable situation for an empty void would be a velocity distribution similar to that of the surrounding area outside the Local Void circle. In that case we would expect a total of two or three dwarf galaxies within the Void volume. The situation is complicated by the fact that the centre of the Void circle is situated close to the galactic equator; hence a large part of the Void area is affected by considerable galactic extinction, and within the velocity intervall of Galactic H I the weak emission of dwarf galaxies will be completely confused.

In Fig. 2 we present a histogram of corrected radial velocities from LEDA (Lyon Extragalactic Database) and the present data (shaded areas) for the field RA [14h, 23h30m], Dec. [0^-20, 60⁰] (Fig. 2 upper panel) outside the Local Void and for the Local Void itself, i.e. within a radius of 30⁰ around [18h38m, +18⁰] (Fig. 2 lower panel).

Figure 2: Histogram of the velocity distribution of galaxies in the direction of the Local Void (lower panel) and around the Local Void (upper panel). Galaxies are binned in velocity intervals of 200 kms-1 (corrected radial velocities). Our present data are given by filled symbols. The comparison sample is from the LEDA catalog. The vertical broken line indicates the velocity limit of the Local Void

Global parameters of the detected galaxies in Table 2, e.g. absolute magnitude, H I mass, and line width, point altogether toward the dwarfish character of these objects. The present sample of galaxies is relatively rich in H I (Col. 9 in Table 2). The median $M_{{\rm H\,{\sc I}}}/L_{B}$ ratio is about 2 $M_{\odot}/L_{\odot}$, the minimum value is 0.36 $M_{\odot}/L_{\odot}$. These values are rather high, another indication for the dwarfish character of these galaxies.