6 Notes on the individual targets

In this section we describe the images, velocity fields and rotation curves of the individual targets. In Paper II, the characteristics of the observed velocity fields and RCs will be analysed and interpreted. In Table 3 we list the inclinations and position angles, derived from both photometry and kinematics. The kinematical centres have been compared with those from photometry, based on a first moment fit and the centre of outer isophotes. Unless noted otherwise, the agreement between the kinematic and photometric centres is within one pixel.

6.1 ESO 350-IG38

Our data (Figs. 1, 2) and broad band images show that the morphology of this object is complex, apparently involving three nuclei/hot-spots. The outer H$\alpha$ and continuum isophotes appear fairly round. However, deep broad band images however reveal an asymmetric morphology at all radii. The kinematical centre of this galaxy lies between the north-west and south nuclei, approximately in the centre of the outer H$\alpha$ and continuum isophotes. The isovelocity contours are very squeezed in the centre indicating a rapid increase in the rotational velocity. At larger radii (1 to 2 arcsec) a plateau is observed on each side followed by a velocity drop after which the RC stays flat at a rather low rotational velocity. Note that the steep central velocity gradient is not necessarily continuous, but could also be explained by H$\alpha$ emitting blobs with different velocity tumbling around each other. The deformations of the isovelocity contours (strongest in the north-east region) could indicate the presence of a spiral arm or a warp. The emission lines of this galaxy are broad, on the order of 200 km s^-1 (Vader et al. 1993). Thus the full line profiles are much broader than our FSR, and the problems discussed in Sect. 3 are more serious for this galaxy.

The derived RC shows a rapid rise followed by a Keplerian like decline shortly after, then levelling out at a constant velocity of 30 km s^-1 for radii larger than five arcseconds. Between approximately one and two kpc the RC falls slightly faster than the Keplerian prediction, but this is within the uncertainties. The receding and approaching sides are in reasonable agreement.

A close look a the line profiles in the centre revealed double lines which made us attempt a decomposition of the velocity field (see Fig. 2). This yielded a regular secondary component in the central part only. After decomposing the velocity field the RC looks very different (see Fig. 2). The central high velocity part in Fig. 1 is replaced by a secondary counter rotating component spinning at high velocity. To get good agreement between the receding and approaching sides of the secondary component, its systemic velocity was adjusted. Note that the RC of the secondary component is based on a total of nine pixels only. The centre of the primary component nearly coincides with that of the total non-decomposed velocity field. The primary component has a nearly constant RC with a velocity of $\approx$ 40 km s^-1. This differs from the non-decomposed value of 30 km s^-1 because it is based on fitted, i.e. smoothed, data, and slightly different (1 pixel) centre coordinates. Moreover, since fitting Gaussian profiles to the data requires higher S/N, the radial extent of this RC is somewhat smaller than for the non-decomposed velocity field. A word of caution is necessary here: the velocity difference between the primary and secondary components is close to the FSR of the used FP2, meaning that the lines almost overlap. In effect the relative velocity of the secondary component with respect to the primary, is uncertain. Therefore we cannot exclude that the counter rotating component is an artifact. However there is a clear signature of asymmetric line profiles in the centre and some sort of multicomponent gas is needed. Observations with a FP with higher FSR (e.g. FP1) should reveal if the second component represents a counter rotating disc or not. At this stage we urge the reader to view the RC of the second component in Fig. 2 as one possible interpretation. If our interpretation is correct, the mass of the secondary component is on the order of $10 ^9 \cal M_{\odot}$.

This galaxy has the greatest H$\alpha$ luminosity in the sample and the ionised gas mass may be as great as $10 ^9 \cal M_{\odot}$, comparable to the dynamical mass estimate in Table 4.

6.2 ESO 480-IG12

This galaxy also has an overall irregular morphology. It is located in front of what appears to be a background cluster of galaxies. Three of the galaxies closest to ESO 480-IG12 have measured redshifts that are much higher than that of ESO 480-IG12. Furthermore, none of these objects show any H$\alpha$ emission at the redshift of ESO 480-IG12. Surprisingly though ESO 480-IG12 has faint warp-like extensions apparently aligned with a chain of background galaxies.

The H$\alpha$ emission is concentrated to two, or perhaps three, central H II regions. In between the H II regions the isovelocity contours are squeezed. Double and very broad components are observed in the emission line profiles, especially west of the centre (see Figs. 3 and 4). Two components have been extracted with quite different intensity levels. If we do not decompose the profiles and simply compute the velocity from the total H$\alpha$ line, the first component clearly dominates in the brightest part, but in fainter regions west of the centre, unreasonable features appear like the confusing situation with three different symmetry axes. Anyway, this would not affect the RC of the primary component since the regions with double lines are close to the minor axis. For the primary component, the velocity field shows a strong gradient along the major axis; but with a plateau in the north-west region. This coincides with the western H II region and roughly with the region where the double features in the lines are most pronounced, and thus close to where the second component has its maximum intensity. The kinematical centre is well defined along the major axis and coincides roughly with the continuum peak intensity. Due to the plateau, the kinematical centre is less well determined along the minor axis, however different choices of centre along this axis gives consistent RCs. In essence the RC does not sensitively depend on the centre coordinates or the decomposition model.

The RC derived for the main component shows solid body rotation out to a radius of $\approx\!\!3$ kpc, after which it levels out, although it is here based on the receding side only. The RC has a rather large dispersion indicating that the physical situation might be more complex than the assumed disk anatomy. For the second component, we could not obtain any sensible RC. However, the duality of the velocity peaks in the western part of the galaxy are very significant, and some sort of multicomponent gas is needed to explain the data. The ionised gas mass is of the order $10^8 \cal M_{\odot}$, thus significantly smaller than the dynamical mass estimate which is of the order $10^{10} \cal M_{\odot}$.

6.3 ESO 338-IG04

This galaxy is also well known as Tololo 1924-416 or SCHG 1924-416. Its photometric properties have been quite extensively discussed by Bergvall (1985) and Östlin et al. (1998). This galaxy has been observed with two different Fabry-Perot interferometers (FP1 and FP2, see Table 1) and thus we had the opportunity to check the consistency of the analysis (cf. Figs. 5 and 7). First, we successfully checked that the flux in the field star superimposed on the western part of the galaxy and the flux in the H$\alpha$ emission line regions were consistent between both observations. Secondly, we checked that the superimposed bright field star does not seriously affect the velocity field. Thirdly, we confirm that we find the same shape for both velocity fields.

The H$\alpha$ emission is concentrated to an extended bright central starburst region. In addition there is diffuse H$\alpha$ emission extending in a tail towards the east. There are also suggestions of a small H$\alpha$ arm emanating towards the south from the western side of the starburst. The velocity field is very irregular and does not contain a single axis of symmetry. Moreover the velocity gradient is steep in the western parts and roughly east-west orientated; while in the eastern regions the gradient is much lower, not always positive and lacking a well defined position angle. The eastern extended tail has almost no velocity gradient.

East of the centre, just at the border of the starburst region, we observe what appears to be the superposition of two patterns with different orientation (see Fig. 5). We will refer to the hypothetical component east of the centre as the perpendicular component, since its PA is roughly perpendicular to the major axis of the galaxy. However, we do not observe any double component in the profiles (in either FP2 or FP1 data). Anyway, we tried to decompose the velocity field without any conclusive results. This could mean that if there are two components present, the linewidth is too large with respect to their velocity separation or/and where the components overlap, one only sees the one with the strongest H$\alpha$emission.

In Fig. 7 we show a map of the velocity dispersion as derived from the FWHM linewidth of the FP1 data. The velocity dispersion has a fairly constant level of $\approx\!\! 100$ km s^-1. Where the major axis of the perpendicular component cross the major axis for the whole galaxy the velocity dispersion is higher and peaks at 160 km s^-1. Still, the shape of the H$\alpha$ line is consistent with one single broad component.

It is not unambiguous how to derive a RC for this galaxy. The different RCs are however consistent in the way that they all are very irregular, signifying a non equilibrium system. The general feature is an approaching side with continuous steeply rising velocity, and a receding side with very small velocity gradient. This means that the assumption of a regularly rotating disc in equilibrium must be far from reality in this galaxy. In effect the kinematical centre is not well defined.

As a cure we tried to mask away certain points of the velocity field (those in the eastern arm and the approaching side of the perpendicular component) to check if we could obtain a more regular RC. The result is shown in Fig. 6a, but the RC is still far from regular. Moreover, the decline of the average RC outside 2 kpc is faster than the Keplerian case, which is not necessarily significant since the velocity field is so perturbed.

For the hypothetical perpendicular component we could extract a regular RC (Fig. 6b) only when using a narrow sector ($S < 30 \hbox{$^\circ$}$). The implied rotational velocity is very small, but the regularity and the agreement between the approaching and receding sides still makes this component well defined.

The RC obtained from the FP1 data (Fig. 7) largely agrees with that from FP2 data (Fig. 5), but the rotational velocity of the receding side is $\approx\! 10$ km s^-1 larger for the FP1 data. The differences can be attributed to three effects: Firstly, the different spectral resolution of FP1 and FP2. Secondly, the slightly different choice of centre coordinates (an independent determination was made for the FP1 data). Thirdly, the FP1 data is somewhat deeper and reach larger radii, and since the velocity field is deprojected these outer points enter also at smaller radii. In view of this, the agreement is very good.

A last note on this galaxy is that here it is questionable that the expression "rotation curve" is adequate since there appears to be no regular rotation present. Still, the presented RCs provide important information on the complexity of the system. However, the dynamical mass estimate in Table 4 should be viewed sceptically. The ionised gas mass is of the order $10^8 \cal M_{\odot}$.

6.4 ESO 338-IG04 B

This galaxy is a physical companion of ESO 338-IG04 and is located approximately six arcminutes south-west of it, corresponding to a projected distance of $\approx\!\!70$ kpc. The H$\alpha$ image contains at least four bright H II regions (Fig. 8). The galaxy has an irregular, somewhat "bent" shape in H$\alpha$ but the velocity field is still quite regular. Along the north-west side there are twists in the isovelocity contours which may indicate the presence of a spiral arm. Just north-east of the brightest H II region there is a steep velocity gradient which we interpret as the kinematical centre, and which coincides with the centre of broad band images. The RC shows good agreement between the two sides and a gradual flattening with increasing radius. The estimated dynamical mass is $5 \ 10^9 {\cal {M}}_{\odot}$ and the ionised gas mass is of the order of $10^7 {\cal {M}}_{\odot}$.

On broad band CCD images, about $40 \hbox{$^{\prime\prime}$}$ north-west of the target galaxy, there is a small low surface brightness galaxy, which is not detected in the monochromatic H$\alpha$ images.

6.5 ESO 185-IG13

This galaxy has a nearly round shape in the continuum but a more complex H$\alpha$morphology and velocity field (Fig. 9). Broad band images reveal arms and a $\ge 30 \hbox{$^{\prime\prime}$}$ long tail extending to the north-east. The H$\alpha$ emission is strong over a large area with two peaks in the surface brightness. The velocity field appears squeezed in the north-west region, between the two peaks in the H$\alpha$surface brightness. About 1.5 arcmin south-west of the galaxy there are two galaxies present, none of which is detected in H$\alpha$ at the redshift of ESO 185-IG13.

Double components with rather different intensity have been extracted from the original lines. Both components have similar position angles but the gradients are reversed, i.e. the secondary component is counter-rotating with respect to the primary (Figs. 9 and 10). The brightest component is very similar to the total non-decomposed velocity field (compare the upper left and right panels in Fig. 9). The second component is more diffuse and regular than the first one. While the centre of the secondary component coincides with the continuum peak, the kinematical centre of the primary component is slightly offset from it ($\approx 1 \hbox{$^{\prime\prime}$}$ to the north).

The RC of the primary component shows a rapid increase followed by an almost flat slowly rising part. The agreement between the approaching and receding sides is good. The secondary component also yields a regular RC, with a low rotational velocity though. The regularity of the RC of the secondary component suggests that it is caused by a dynamically well defined object, e.g. a counter rotating disc. The estimated dynamical mass of ESO 185-IG13 is $\sim 2 \ 10^9 \cal M_{\odot}$ and the ionised gas mass is of the order of $10^8 \cal M_{\odot}$. The dynamical mass of the secondary component is $\sim 3 \ 10^8 \cal M_{\odot}$

6.6 ESO 400G-43

This galaxy presents several bright H II regions. Note that the northernmost region is not a field star. The southern H II region complex has a ring-like morphology. In the southern H II region complex we observe a symmetric and regular velocity field with velocity plateau's followed by decreasing velocity on both sides, characteristic of a disc with circular differential rotation. At larger radius ($\ge 5 \hbox{$^{\prime\prime}$}$) the north-east and south-west regions start to behave differently. In the south-west we observe the continuity of the central velocity field, although the isovelocity contours are somewhat boxy. The region north-east of the centre is more intriguing because we observe a shift of the major axis position angle, rotating from approximately 45$\hbox{$^\circ$}$ towards north, which might indicate the presence of a warp. An alternative interpretation is that the twisted isovelocity contours north of the north-east velocity plateau is due to the presence of a spiral arm. The isovelocity contours in the northern part of the velocity field seems to indicate the presence of local motions, and asymmetric line profiles are present. The kinematical centre is well defined but is slightly offset ($\approx 1 \hbox{$^{\prime\prime}$}$ towards south-west) from the peak continuum emission. Due to the irregular velocity field in the north east, the inclination is quite uncertain for this galaxy.

The RC has a strange behaviour. Following the initial solid body rise to the plateau's, there is a rapid decline after which the RC levels out and stays flat out to a radius of 15 arcsec, after which the approaching side (the only one that has H$\alpha$ signal) declines further. The remarkable thing is that after the maximum rotational velocity the decline is faster than for the Keplerian case. This is unphysical for an equilibrium disc, thus indicating that the velocity field is distorted. The "super-Keplerian'' decline can be eased somewhat, but not completely, by allowing the position angle to be variable. In the south west regions at a radius greater than $5\hbox{$^{\prime\prime}$}$ double features in the H$\alpha$ lines appear at low S/N. However, this feature is present in many consecutive pixels and is in total significant, which means that a secondary component might be present here. In the centre there are no signs of double lines and our attempts to decompose the velocity field failed. Due to the super-Keplerian behaviour of the RC the estimated mass apparently decreases with increasing radius (see Table 4). Thus the mass stated in Table 4 is very uncertain. The ionised gas mass is of the order of a few times $10^8 \cal M_{\odot}$, comparable to the dynamic estimate.

6.7 ESO 400G-43 B

This quite low surface brightness galaxy (Fig. 12) is a physical companion of ESO 400G-43 and is located approximately three arcminutes east/south-east of it (Bergvall & Jörsäter 1988), corresponding to a projected distance of $\approx\!\!70$ kpc. ESO 400G-43B has one extended central emission line region, with peak intensity in the north-west. The isovelocity contours shows axisymmetric twists south-east and (to a lesser extent) north-east of the major axis, perhaps indicating the presence of spiral arms. The shape of the RC may be affected by dust extinction, due to the high inclination. However, the best fitting kinematical inclination is significantly lower than the photometric inclination derived from ellipse-fitting of the outer isophotes, the reason for which is not well understood. In the presented RC we have applied a small correction for internal extinction in the central parts, see Fig. 12. The estimated dynamical mass is $\sim 3 \ 10^9\cal M_{\odot}$ and the ionised gas mass is of the order of a few times $10^7 {\cal {M}}_{\odot}$.

6.8 Tololo 0341-407

Even if this object has a short observing time (see Table 2) it was possible to extract a high S/N velocity field. Our data indicate that this object is in fact composed of two well separated galaxies: the eastern one being more luminous in H$\alpha$ than the western one (Figs. 13 and 14). The velocity field of the eastern component displays a rather constant velocity indicating a close to face on orientation. The western component is more inclined and shows more obvious rotation. Asymmetries in the line profiles suggested a decomposition of the velocity field into two components, one which is dominated by the eastern galaxy and the other by the western one (Figs. 13 and 14). If the connection between the first component in the eastern and western galaxy is physical is not certain; and the same is true for the secondary components. Here, the notation with a primary and secondary component may be somewhat confusing, since the secondary component of the western galaxy is actually the most luminous. Hereafter, when we mention the "first'' component of the eastern or western galaxy we refer to the strongest (most luminous) component, and vice versa for the secondary components. The secondary component of the eastern galaxy has a constant velocity, which suggests that this component belongs to the same galaxy, although the velocity is more similar the western galaxy. The second component of the western galaxy has a major axis position angle roughly perpendicular to the one of the first component, which suggest that it is dynamically distinct from it. The primary component of the eastern galaxy has a solid body RC with quite high dispersion. The primary component of the western galaxy gives a well determined RC, perhaps levelling out at large radii. The kinematical centres roughly coincide with the peaks in the continuum emission, although this is hard to determine for the eastern galaxy. The secondary components do not produce regular RCs. The eastern and western galaxies both have estimated dynamical masses around $\sim 2 \ 10^8 \cal M_{\odot}$, and the ionised gas masses are of the order of a few times $10^7 {\cal {M}}_{\odot}$.