5 Individual objects

DDO 22: The HI axial ratio suggests that this galaxy is seen at a high inclination. A region of high HI column density is present in the southern side of the galaxy. The kinematic and HI major axes appear to be misaligned.

DDO 43: The HI axial ratio indicates a face-on orientation. Parallel velocity contours in a regular velocity field mark a rapidly rising rotation curve. The kinematic and optical major axes are roughly perpendicular.

DDO 46: The HI distribution shows a U-shaped high-column density ridge. The velocity field is reasonably symmetric with respect to the kinematic minor axis, but asymmetric with respect to the major axis. The rotation curve is almost flat at the edge of the HI distribution.

DDO 47: Spiral structure in the outer HI disk was reported by Puche & Westpfahl (1994). No optical emission appears associated with the spiral arms. Regularly shaped, elliptical outer HI isophotes suggest a disk seen at low inclination. A number of high column density regions are distributed evenly over the disk. There is a deep hole in the HI distribution at $\alpha=\rm 7^h39^m8\fs1,~\delta=\rm 16^\circ 54' 31''$. The velocity field presents one of the few clear examples of solid-body rotation, as does the major axis XV diagram.

DDO 48: This is probably a nearly edge-on disk with a regular velocity field. The rotation curve rises rapidly near the center and flattens gradually outwards.

Figure 4: For each galaxy, all maps at 27'' resolution: (left) major axis position-velocity maps with contours at $-2\sigma~ 2^{N} \sigma$, with $N=0,\ 1,\ 2,\ \ldots$ and $\sigma$ the rms noise in empty channel maps; grayscales are logarithmic; tickmarks on the upper horizontal axis mark intervals of 1 kpc. (center) velocity fields with contour intervals of $8 ~{\rm {km~s^{-1}}}$; dashed contours mark approaching velocities; the first solid contour is at the system velocity which is printed under each object's name; WSRT beamsize is indicated by the hatched ellipse. (right): velocity dispersion maps with contour levels at 5, 7.5, 10, 12.5 $\ldots ~{\rm {km~s^{-1}}}$; greyscales are linear from $5 ~{\rm {km~s^{-1}}}$ to $20 ~{\rm {km~s^{-1}}}$.

Figure 4: continued.

Figure 4: continued.

Figure 4: continued.

Figure 4: continued.

Figure 4: continued.

Figure 4: continued.

Figure 4: continued.

NGC 2537: The HI distribution consists of a U-shaped high column-density ridge. The velocity field, irregular in the north, exhibits the characteristic spider shape of a flattening rotation curve, also evident in the XV map. NGC 2537 is sometimes classified as a Blue Compact Dwarf (BCD) galaxy and is also known as the Bear Paw Galaxy (Schorn 1988). UGC 4278 is a nearby companion. NGC 2537A occurring just east of NGC 2537 on PSS plates is not visible in the HI data. The large linewidths in the center are an artifact of the unresolved velocity gradient.

UGC 4278: The rotation curve may show a turnover. NGC 2537 is $16\farcm 6$ away at PA = $328^\circ$.

DDO 52: Most of the HI is in a low-column-density disk, with a peak $N_{\rm HI}= 1.5\times 10^{21} ~{\rm cm^{-2}}$. The velocity field is regular with a hint of a flattening rotation curve. The XV diagram shows a rather high ratio of rotational to random velocity, despite its small amplitude.

DDO 63: The HI is concentrated in a ring with a high column density, with a five times lower central minimum ( $N_{\rm HI}= 2.4\times 10^{20} ~{\rm cm^{-2}}$) at $\alpha=\rm 9^h36^m 3\fs1$ $\delta=\rm 71^\circ24'44''$. The kinematic and HI major axes are misaligned by about $30^\circ$. The rotation velocity is comparable to the HI velocity dispersion. The ring dominates the XV map. DDO 63 has also been studied by Puche & Westpfahl (1994) and Tully et al. (1978). The latter find the same kinematic/HI axis misalignment, and a comparable well-ordered, small-amplitude rotation velocity.

NGC 2976: The outer HI isophotes are well represented by ellipses. The two continuum sources (Paper I) are near to but not precisely coincident with the high HI column density regions ( $N_{\rm HI} \approx 3.5 \times 10^{21} ~{\rm cm^{-2}}$) on either side of the galaxy at $\alpha=\rm 9^h43^m1\fs 2$, $\delta=\rm 68^\circ9'44''$ (NW) and $\alpha=\rm 9^h43^m19\fs 1$, $\delta=\rm 68^\circ7'49''$ (SE). The emission at upper left in the velocity field map is unrelated G alactic foreground HI. The rotation curve flattens near the edge of the HI disk. A detailed optical study of NGC 2976 was presented by Bronkalla et al. (1992).

DDO 64: A high-column-density ridge dominates the HI structure of this probably nearly edge-on galaxy. The velocity field is poorly resolved along the minor axis. The XV map shows nearly solid-body rotation with only a hint of flattening. The feature south of DDO 64 is UGC 5272B, the feature north of it is probably noise.

Figure 5: Position-velocity map through UGC 5272B in position angle 21 degrees, with contourlevels at -5.07, 5.07($2\sigma$), 10.14, 20.28 and 40.56 mJy per beam. UGC 5272B is visible at the center of the slice (0'); DDO  64 is the larger patch to the left (north) of UGC 5272B. The slice also intersects the feature which can be seen north of DDO 64 in the HI column density map. Not much is evident in the X-V map.

DDO 68: At low column density levels, DDO 68 is reasonably symmetrical. High-column-density regions are found in the north and east of the galaxy. A deep hole devoid of HI emission is located at $\alpha=\rm 9^h53^m52\fs 2$, $\delta=\rm 29^\circ 4'15''$. Low signal-to-noise regions contribute to the irregular appearance of the velocity field. The ratio of rotational to random velocity is low.

DDO 73: The HI isophotes suggest a nearly face-on orientation. However, both velocity field and XV map indicate projected rotational velocities considerably in excess of the HI velocity dispersion.

DDO 83: The HI column density is high throughout the galaxy. The velocity field is regular and spider-like. The rotation curve rises strongly near the center and flattens at the edge of the HI disk.

DDO 87: The HI is distributed over a low-column-density disk with a number of small high column density regions, unresolved at 13'' resolution. The fragmented appearance of the velocity field is the result of low signal-to-noise ratios. The XV map shows a nearly flat rotation curve in the outer regions. The low luminosity of DDO 87 is inferred from its association with the M 81 group (Huchtmeier & Skillman 1998).

Mk 178: This galaxy is poorly resolved spatially. Its HI structure, kinematics and luminosity are similar to DDO 63, DDO 125 and DDO 165.

NGC 3738: The HI column density is high everywhere, with a central peak $N_{\rm HI}=4.5 \times 10^{21} ~{\rm cm^{-2}}$. The velocity profile and the XV map indicate a steep velocity gradient, which is difficult to fit with the tilted ring method. The indicated rotation velocity was fitted by eye to the XV map. The high velocity dispersion is an artifact of the large velocity gradient in this marginally resolved galaxy.

DDO 101: HI extent is too limited to show structure.

DDO 123: The HI is distributed evenly throughout the disk of this face-on galaxy. Irregularities in the velocity field coincide with low signal-to-noise regions. The rotation curve rises out to the edge of the HI disk.

Mk 209: The peak of the high-column-density region is $N_{\rm HI}=2.9\times 10^{21} ~{\rm cm^{-2}}$. The velocity field appears regular but could not be fitted properly because of insufficient resolution. The velocity gradient was fitted manually to the XV map; it is consistent with a solid body rotation curve. HI in Mk 209 (IZw 36) has also been observed with the VLA by Viallefond et al. (1987).

DDO 125: The HI is mainly concentrated in two high-column-density regions, separated by a low-column density center, suggesting a fragmented ring. The velocity field shows a velocity gradient along the major axis. Rotation is clearly demonstrated by the XV map. HI in DDO 125 was studied in detail by Tully et al. (1978).

DDO 133: The HI isophotes are well-represented by ellipses at the level of $N_{\rm HI}=3 \times 10^{20}~{\rm cm^{-2}}$. The rotation curve flattens slightly outwards.

DDO 165: Most of the HI is located in a ring. The velocity field is highly irregular. The maximum velocity gradient is along a line from SE to NW in position angle $120^\circ$-$140^\circ$. The rotation velocity was fitted to the XV map assuming solid-body rotation. However, the emission in the XV map is mainly due to the ring.

DDO 166: A ridge of high-column-density HI extends over the eastern side of this face-on galaxy. The velocity field has a strong gradient, in spite of the small inclination suggested by the HI isophotes. The isovelocity contours are twisted into an S-shape at the eastern side of the galaxy. Thean et al. (1997) have published VLA HI maps of NGC 5033, DDO 166 and UGC 8314.

DDO 168: Two very high HI column density regions ( $N_{\rm HI} \geq 6 \times 10^{21} ~{\rm cm^{-2}}$) occur near the center of the galaxy at $\alpha=\rm 13^h12^m16\fs 8$, $\delta=\rm 46^\circ 11'0''$and $\alpha=\rm 13^h12^m15\fs 8$, $\delta=\rm 46^\circ11'30''$. The position angle of the velocity gradient changes over the disk by approximately $20^\circ$. The peculiar structure of DDO 168 is not unique. Similar very-high column density regions combined with twisted velocity fields have been observed in other "amorphous galaxies'' such as NGC 1140 (Hunter et al. 1994) and IZw 18 (Viallefond et al. 1987; Van Zee et al. 1998). A detailed study of the mass distribution in DDO 168 was performed by Broeils (1992).

DDO 185: The HI column density map suggests a disk seen at a high inclination. The isovelocity contours are regularly spaced, consistent with the rising rotation curve shown by the position-velocity map. DDO 185 (=Holmberg IV) was used as a calibrator galaxy for the Tully-Fisher relation by Kraan-Korteweg et al. (1988).

DDO 190: The highest column densities are found on the west. The velocity field is somewhat irregular, but rotation is clearly visible. The XV map shows a hint of flattening of the rotation curve on the NW side.

DDO 216: The HI is located in the southern half of the (optical) galaxy (Sandage 1986; Lo et al. 1993). There is little sign of rotation in the velocity field and XV maps. In fact, the velocity gradient suggested by the XV map may represent a single HI cloud at a discrepant velocity. For a VLA study of DDO 216, see Lo et al. (1993).

DDO 217: The HI is distributed relatively evenly over the disk. The velocity field shows differential rotation over most of the galaxy. The difference in position angle between the inner region and the outer disk is clearly visible in the velocity field map. The XV map shows a rapid rise of the rotation velocity near the center and a gradual increase in the outer disk.