5 Notes on individual galaxies

The notes about the morphology of each object are taken from the results in MM93, completed from the study of the present high resolution frames. Use has also been made of the analysis in terms of bulge and disk components published by Michard (1998) (M 98) for most objects of the present sample. This same analysis has been performed for the others using the techniques in M 98. The notes about the colour distributions are from the present study.

1. NGC 2549. This object contains a roundish boxy bulge, and an extended disk, the dominant component at $a=20\hbox{$^{\prime\prime}$ }$ and farther. Envelope class: thD. From observables and analysis in M 98, the disk present a ring structure with humps near 6.5 and $33\hbox{$^{\prime\prime}$ }$. Associated small fluctuations of the PA and f₄ parameters may suggest some trace of spiral structure (?). The q ratio of the disk component according to M 98 leads to an inclination larger than 80$^\circ$.

   The radial colour distributions in Fig. A1 are "regular", with rather flat V-I and sharply decreasing U-V. The azimuthal colour profiles are flat, showing the isochromes and isophotes to be nearly coincident. The colour map of Fig. A1 shows a low contrast central pattern, with a thin arclet (dust?) in coincidence with an isophotal contour. An interesting property of this galaxy lies in the subtle changes of colour associated with the ring structure, which is demonstrated in Fig. 6;

NGC 3098. It presents a boxy bulge and a disk mixed in a spheroidal envelope. The disk is dominant at $a=6\hbox{$^{\prime\prime}$ }$ and farther. Envelope class: thD. There is an inner disk, giving a fist $\epsilon$ maximum at $a=1.2\hbox{$^{\prime\prime}$ }$, and a low contrast ring with the hump near $a=9\hbox{$^{\prime\prime}$ }$. The q ratio of the disk component according to M 98 leads to an inclination larger than 84$^\circ$;

The radial colour distributions in Fig. 1 are "regular", while the colours are slightly bluer than average. No evidence for dust is seen. The CFHT frames show the majA to be bluer than surroundings for $a <10\hbox{$^{\prime\prime}$ }$ (see Fig. 4), that is in the ring region. Farther out the reverse situation occurs (see Table 10), possibly due to an outwards blueing of the spheroidal component, compared to a disk with small colour gradient;

2. NGC 3115. The large bulge dominates the SuBr, except where the low contrast ring shows up, around $a=18\hbox{$^{\prime\prime}$ }$. Nieto et al. (1991) noted the inner "decoupled" disk inside $a=5\hbox{$^{\prime\prime}$ }$. The main disk exhibits a cut-off near $a=90\hbox{$^{\prime\prime}$ }$, so that the envelope is in class spH. The q ratio of the disk component according to M 98 leads to an inclination larger than 82$^\circ$.

   The radial colour distributions are surprisingly flat. We note that the object is difficult, too large for the field of the available OHP observations. Silva et al. (1989), found the majA slightly bluer than surroundings. From an analysis in terms of a bulge and disk components, they conclude that the disk population is bluer by 0.5 in B-I than the bulge one, a conclusion very dependent upon their model. Our CFHT frames show the inner disk to be redder (see Fig. A3), while farther out the majA becomes bluer than surroundings, (see Fig. 4) in qualitative agreement with Silva et al. observations. A bulge+disk analysis according to the techniques in M 98, suggests that the B-R differences between the two component remain small. The disk is found redder near $a=3\hbox{$^{\prime\prime}$ }$ (inner disk) and bluer for $a > 15\hbox{$^{\prime\prime}$ }$ (main disk). The only evidence for dust in NGC 3115 is in the red inner disk, but this might be a population effect.

   This nearby galaxy has been much studied spectroscopically: see the survey by Fischer (1996), and the discussion of a central black hole by Kormendy et al. (1996);

3. NGC 3245. This galaxy has a modest bulge and a strongly dominating disk. There is a double ring structure with maxima near $a=5\hbox{$^{\prime\prime}$ }$ and $a=15\hbox{$^{\prime\prime}$ }$. Envelope class: exD. The q ratio of the disk component according to M 98 leads to an inclination of 62$^\circ$.

   The radial colour distributions in Fig. A4 are "regular". The relatively strong reddening towrds the center is due to a high contrast dust pattern within $3-4\hbox{$^{\prime\prime}$ }$ from center (see map in A4). This in turn contains a blue feature, $1\hbox{$^{\prime\prime}$ }$ SE from center. Is it a "hole" in the dust, or a region of relatively recent star formation?

4. NGC 4026. This object has a strongly dominant disk extending out of a boxy bulge. There is again a minute inner disk giving a first peak of the $\epsilon$ profile at $a=4.5\hbox{$^{\prime\prime}$ }$. The ring produces a hump in SuBr around $a=19\hbox{$^{\prime\prime}$ }$. Envelope class: thD. An unpublished bulge+disk analysis with the techniques of M 98 leads to an inclination larger than 80$^\circ$.

   The radial colours (see Fig. A5) are "regular". A slightly redder hump in all colour curves appears at $r=12\hbox{$^{\prime\prime}$ }$, or a majA of $a=19\hbox{$^{\prime\prime}$ }$, which put it in coincidence with the ring. According to the high resolution map of Fig. A5, the "inner disk" is redder than surroundings: this reddening is found to be less in V-I than B-V, which may rule out an explanation in terms of a dust concentration. NGC 4026 is not symmetric, the eastern side of the bulge being less bright and redder than the western (Figs. 1 and 5), due to rather thin dust throughout the disk, and/or a system of dust features. Finally, this galaxy presents a remarkable contrast between the majA and minA colours far from center (Figs. 1, 2 and Table 10), a phenomenon we have ascribed to an outwards blueing of the spheroidal component as compared to the disk;

5. NGC 4036. Again this object has a dominant disk. The morphology in the inner radius range is affected by a major dust pattern mostly along the majA. A low contrast ring may be present with maximum near $a=28\hbox{$^{\prime\prime}$ }$. An unpublished bulge+disk analysis with the techniques of M 98 leads to an inclination of 73$^\circ$. Envelope: exD class.

   An outstanding dust pattern is present (Fig. A6): three lanes of irregular structure can be recognized, with a geometry suggesting that the dust lies in the disk plane. The colour excess locally reaches E(B-V)=0.18 against background. Besides this, the object shows the minA asymmetry, with the S side redder and less bright, farther out than the lanes. The phenomenon described as "blueing of the outer bulge" is also present (Table 10);

6. NGC 4111. In the central region is seen the long ago described "peanut bulge" (Tsikoudi 1980). There is also an inner disk, giving a first $\epsilon$ maximum near $a=5\hbox{$^{\prime\prime}$ }$, and a ring showing up near $a=22\hbox{$^{\prime\prime}$ }$. Envelope class: thD.

   There is a small but high contrast central dust pattern, elongated along both galaxian axes. The map of Fig. A7 suggests that the peanut bulge may result from extinction by the overlying dust. Indeed it has been verified from the original frames, that a dust lane crosses the bulge along the minA, slightly S from center, and shows much less contrast in R than in B (no I frame is available). It is our guess that the peanut bulge would not be seen in the K band. The object is very blue compared to others in the sample, specially in the disk, away from the central dusty bulge, and in the U-V colour (Table 8): its stellar population is probably younger than average. The outer isophotes show, to a rather small extent, the blueing of the minA relative to majA noted for several other objects;

7. NGC 4350. This S0 is typical of galaxies with an spH type envelope, as the outer axis ratio increases to about 0.8. According to the analysis in M 98, the disk suffers an outer cut-off starting near $a=50\hbox{$^{\prime\prime}$ }$, while the spheroidal component increases well above an r^1/4 extrapolation of the inner bulge. The inclination may be 77$^\circ$ or larger.

   The radial colour distributions (Fig. A8) show a red central peak and a gradient above average in all colours. There is evidence in our data for a reddening of the majA compared to surroundings (see B-R map), and for minA asymmetry, the E side being brighter and bluer. A concentration of dust in the disk is proposed;

8. NGC 5308. As in several other S0's, there is an inner disk with peak SuBr near $a=7\hbox{$^{\prime\prime}$ }$. The bulge is rather boxy, and the envelope of the thD class. The analysis in M 98 points to a disk inclination of 83$^\circ$, if infinitely thin, but it should be larger and close to 90$^\circ$.

   The radial colours are standard, except for a prominent red peak inwards of $r=2.5\hbox{$^{\prime\prime}$ }$. This may be associated with the reddening of the inner disk against surroundings (Fig. A9, Table 10). Besides the object displays a strong reddening of the outer majA, again ascribed to the outwards blueing of the spheroidal component;

9. NGC 5422. This galaxy has a strong bulge, clearly brighter on the W side than on the E one. Again there is an inner disk, with first $\epsilon$ maximum near $a=6\hbox{$^{\prime\prime}$ }$, and a ring with maximum contrast near $a=23\hbox{$^{\prime\prime}$ }$. Envelope: thD class. From the M 98 analysis, the inclination is 81$^\circ$, or larger.

   The object displays high contrast dust markings nearly along the majA, but slightly displaced westwards. On the other hand there is a general reddening of the eastern side due to dust in the disk. This also produces a well defined minA asymmetry (Table 11);

10. NGC 7332. This object presents a boxy bulge, an inner disk with the first $\epsilon$ maximum near $a=4\hbox{$^{\prime\prime}$ }$, and a ring with maximum contrast near $a=28\hbox{$^{\prime\prime}$ }$. Envelope class: thD. A spectroscopic study of this object is due to Fisher et al. (1994). Our radial B-R profile for NGC 7332 are rather uncertain. The object displays a large dust pattern of moderate contrast (Fig. A11). As for NGC 4111, the disk is rather blue;
11. NGC 7457. This galaxy is less inclined than other sample objects, with a minimum axis ratio of 0.52. Because the Carter's e₄, e₆ coefficients fluctuate around zero, it is believed that one of the two components, most probably the disk, dominates the other. Envelope class: uncertain. HST observations were published by Lauer et al. (1991).

    The colours of this objects are quite flat, except for a very small central red peak (Fig. A12). They are also bluer than for most other S0's.