6 Description of individual non active galaxies

 

6.1 NGC 151

This galaxy is larger than the size of our infrared images, so we only present here the properties of the inner regions.

The K' image shows a strong and broad bar, a disky structure, a large ring, and a nuclear region roughly perpendicular to the bar (Fig. 18a). Besides confirming the presence of a weak ring, the sharp-divided image reveals the existence of a small bar roughly perpendicular to the large bar (Fig. 18b). These features appear very clearly in the difference image (Fig. 18c) and are quantified by looking at the variations of $\epsilon$ and PA with radius (Fig. 18e). The Pa$\alpha$ image by Böker et al. (1999) shows that there is star formation ocurring at the ends of the bar and along the ring. The sharp-masking method applied to the HST F160W image confirms the presence of the inner bar which can be traced closer to the nucleus ($r \approx$ 2.5 arcsec, PA = 68$^\circ$, Fig. 34).

The J/K' image shows a roughly circular redder region of 7 arcsec radius (Fig. 18d); the inner bar is seen as a slightly redder elongation along PA $\approx$ 90$^\circ$.

The bulge+disk fits are merely indicative since the image is too small to reach the disk (Fig. 18f). They show the existence of the two bars.

6.2 IC 454 (UGC 3570)

This galaxy has a particularly large bar, with the west arm more visible than the east one (Fig. 19a). The bright feature at the north west end of the bar is most probably a superimposed star. The central region of the bar and the west arm are clearly seen in the sharp-divided image (Fig. 19b), while the extremities of the bar appear more strongly on the difference image (Fig. 19c). This illustrates the fact that the sharp-dividing method is very well suited to detect elongated features which do not always appear as clearly in the difference images (in the cases where they can be nicely fit by ellipses). The PA and $\epsilon$ plots evidence the presence of a secondary bar (see also Fig. 19c).

The J/K' image and (J-K') color gradient appear quite constant except in the bulge region and central bar where (J-K') is redder (Figs. 19d and 19h). The bulge+disk fit is quite good except at the extremities of the bar (Figs. 19f and 19g).

6.3 NGC 2712 (UGC 4708)

This galaxy also has a very large bar, and well developed arms, the eastern being brighter than the western one (Fig. 20a). The sharp-divided image (Fig. 20b) reveals the presence of a small bar within the large bar. This is confirmed by the difference image (Fig. 20c), where the spiral arms are also apparent. The $\epsilon$and PA variations allow to quantify the parameters for both bars (Figs. 20e and 20h).

The J/K' image shows that the small bar is bluer, at variance with the other nuclear regions which all appear redder in (J-K') (Fig. 20e), including the surrounding emission. The joint analysis with the optical data will allow a full interpretation of this result. This structure is also visible in the color gradient, which remains constant further out (Fig. 20h).

The bulge+disk fit is obviously not good because of the strong bar and spiral arms (Figs. 20f and 20g).

6.4 NGC 2811

The entire galaxy almost fits in the K' image, which has a quite regular aspect, with no obvious bar or arms (Fig. 21a). This image is very similar to that by Jungwiert et al. (1997) in the H band. On the other hand, the sharp-divided and difference images clearly reveal the presence of a bar, a smaller bar and weak spiral arms (Figs. 21b and 21c). The existence of two bars is confirmed by the variations of $\epsilon$ and PA (Fig. 21e).

The J/K' image is smooth, with a reddish bar and a blue surrounding ring (Fig. 21d). The bulge+disk fits are satisfactory, with small residuals throughout (Figs. 21f and 21g).

6.5 NGC 3571

This galaxy does not fit entirely in the K' frame. The K' image shows no evidence for a bar (Fig. 22a), but the sharp-divided image does show the existence of a small thick bar (Fig. 22b). Due to its small size and relative roundness, the bar cannot be detected either in the difference image (Fig. 22c) nor in the $\epsilon$ and PA plots (Fig. 22e). However, the ellipse fitting to the HST image evidences this structure as a clear elongation of $\sim$2 arcsec along PA = 90$^\circ$(Fig. 22e). This is confirmed by the HST sharp-divided image (Fig. 35) derived from the Böker et al. (1999) data.

The J/K' image is quite smooth, with the central region somewhat redder than the outer zones (Fig. 22d).

The bulge+disk fits are quite good (Figs. 22e and 22f) even if we do not have an image of the entire galaxy (Fig. 23h).

6.6 NGC 3835 (UGC 6703)

A thick bar and two spiral arms can be seen in the K' image (Fig. 23a) and even better in the sharp-divided image (Fig. 23b), while the difference image only shows the spiral arms clearly, but not the bar (Fig. 23c).

The characteristics of the bar can be seen in the variations of $\epsilon$ and PA with radius (Fig. 23e).

The J/K' image shows a small extension (4 arcsec in radius) along the east-west direction where the (J-K') colour is bluer than for the rest of the galaxy (Fig. 23d). Better resolution images should be obtained in order to ascertain what causes the misalignment between this structure in the color image and the inner bar.

Because of the presence of the spiral arms, the bulge+disk fits are not very good (Figs. 23f and 23g).

6.7 NGC 4162 (UGC 7193)

The K' image of this galaxy is quite irregular (Fig. 24a); two arms with a flocculent appearance can be seen, but no bar. The sharp-divided image does not show any strong feature (Fig. 24b). On the other hand, the difference image reveals a beautiful spiral structure (Fig. 24c), with a circumnuclear ring, three rather closed spiral arms starting from the ring towards the north and three other more open spiral arms also starting from the ring but towards the south (Fig. 24c).

The $\epsilon$ and PA variations with radius may reveal the presence of a bar (Fig. 24e); however, this feature does not appear very clearly in these plots and we only have some hints of a small thick bar in Fig. 24b, so we cannot be completely certain of its detection.

The bar and spiral arms appear in the bulge+disk fits in J and K'as bumps at about 12, 20 and 38 arcsec (Figs. 24f and 24g). The J/K' image is quite smooth, with (J-K') somewhat redder at the center (Fig. 24d).

6.8 NGC  4290 (UGC 7402)

The K' image shows the bar, spiral arms and a large weak external ring (Fig. 25a); the central isophotes are twisted relative to the bar. The sharp-divided image seems to show a small structure in the center at PA = 90$^\circ$  (Fig. 25b); the bar and spiral arms are clearly seen. These structures appear even more strongly in the difference image (Fig. 25c). The $\epsilon$ and PA variations are also consistent with the existence of two bars (Fig. 25e); however, it is difficult to say if the small structure in the center is really a small bar within the bar because it is thick and faint.

The bulge+disk fits are good except in the bar and spiral arm regions (Figs. 25f and 25g). The J/K' image and the color gradient are very smooth, with a slightly redder nucleus (Figs. 25d and 25h).

6.9 NGC 4779 (UGC 8022)

A mosaic of images was obtained for this galaxy, so our data really encompasses the entire object.

The K' image shows a strong bar, and weak flocculent and asymmetric spiral structure (Fig. 26a), as confirmed by the sharp-divided image (Fig. 26b). The bar and beginning of the spiral arms appear more clearly on the difference image (Fig. 26c). Chapelon et al. (1999) find a bar with PA = 5$^\circ$  and $r \approx$ 16 arcsec. The bar that we measure is somewhat longer (Fig. 26e), in agreement with Friedli et al.'s (1996) result that bars are generally longer in Kthan in R (see also NGC 3660).

The J/K' colour image is fairly smooth (Fig. 26d). The bulge+disk fits clearly show the bar and spiral arm regions (Figs. 26f and 26g).

6.10 NGC 6012 (UGC 10083)

The K' image shows a bar with somewhat peculiar sharp edges; no evidence either for spiral arms or for a ring is seen, in spite of the classification of this galaxy as RSBR2* (Fig. 27a). This image is consistent with the smaller one obtained by de Jong & van der Kruit (1994). The peculiar aspect of the bar is confirmed by the sharp-divided and difference images (Figs. 27b and 27c), where the bar seems to be crossed by a dust lane. In this case, the bar would be young and star formation should be observable along it; we will therefore look for evidence for star formation in our spectra.

The difference image also shows evidence for bright spots towards the edges of the bar, specially towards the north (Fig. 27c); although this could be a star superimposed on the galaxy, the fact that there is a faint southern counterpart tends to indicate that these regions may both be in the galaxy.

The variations of $\epsilon$ and PA with radius (Fig. 27e) give bar parameters in agreement with de Jong's (1996) results.

The bulge+disk model fits the profiles very nicely except in the region of the bar and bright spots (Figs. 27f and 27g). The J/K' image and color gradient are quite smooth throughout the galaxy (Figs. 27d and 27h).

6.11 NGC 6155 (UGC 10385)

A small bar is visible on the K' image, together with a spiral arm starting northward and another one wrapped towards the south east (Fig. 28a). Note that the center is displaced relatively to the centroid of the outer isophotes.

The bar and north spiral arm appear faintly on the sharp-divided image (Fig. 28b) and much more clearly on the difference image (Fig. 28c). The variations of $\epsilon$ and PA with radius (Fig. 28e) show that the bar reaches a radius of 6 arcsec (PA = 120$^\circ$). A larger bar may be present up to 15 arcsec (PA = 160$^\circ$); however, we cannot be certain that it is a bar since the spiral arms seem to start at a smaller radial distance than the edges of this structure.

The bulge+disk model shows the strong contribution of the bar and spiral arms (Figs. 28f and 28g).

The J/K' image is fairly smooth and becomes redder at the very center (Figs. 28d and 28h).