5 Description of individual active galaxies

5.1 UGC 1395

The K' image in Fig. 1a shows an extended bulge from which two spiral arms originate. A small elongation is seen in the center, that could be due to the presence of a small bar (see below). Although this galaxy is classified as S(rs)b in the RC3, McLeod & Rieke (1995) already reported the presence of a bar with a 16 arcsec radius, PA = 145$^\circ$  and $\epsilon$ = 0.5 from their K image. It doesn't show up in our sharp-divided image in Fig. 1b, but is clearly detected in the plot of $\epsilon$ and PA with radius (Fig. 1e) which is in agreement with Peletier et al. (1999). The parameters we deduce for the bar from that plot are very similar to those reported by McLeod & Rieke (1995).

The sharp-divided image reveals the presence of a small bar, extending along PA = 139$^\circ$, up to 7 arcsec from the center. It is not detected in the PA and $\epsilon$ plot as it is too weak to be apparent. Other evidence for this nuclear bar is the curved dust pattern that surrounds the very central region in the broad band HST image (filter F606W) by Malkan et al. (1998).

The difference image in Fig. 1c shows that the overall fit is good except in the region where the arm contribution is important. The surface brightness profile (in agreement with that of McLeod & Rieke) is well fit by a bulge+disk model, except in the zone where the arm contribution is important (Figs. 1f and 1g).

5.2 IC 184

This galaxy shows rotation of the PA and twisting of the isophotes in the central region. Evidence for the existence of a bar inside the primary bar is presented in Figs. 2b and 2e, where $\epsilon$ shows two maxima for a rather constant PA. The inner bar is also evident in the broad band HST image by Malkan et al. (1998). The region connecting the two bars is visible in Fig. 2b as a thin curved elongation starting at the end of the inner (thicker) bar.

The difference image in Fig. 2c shows the two nested bars as well as the region where the spiral arms begin; the spiral arm to the north is much brighter than its southern counterpart. Due to the bars and arms, the residuals are high except in the very outer zones (Fig. 2g), and the bulge + disk fit is not very good (Fig. 2f).

5.3 IC 1816

A big bar (Fig. 3e) and three spiral arms are detected, among which the north west arm is the brightest and most detached (Fig. 3a). At large scales, the image has a somewhat triangular shape. A small galaxy is seen 35 arcsec to the south along PA = 168$^\circ$, but no redshift is available for it.

The sharp-divided image (Fig. 3b) clearly reveals the bar, the ring, and the spiral arms. Note that the very central zone appears somewhat elongated.

The bar and arms are also clearly seen in the difference image (Fig. 3c), and except for the bar region the residuals are quite small (Fig. 3g). The bulge + disk model fits the data very well except for the bar region (Fig. 3f).

The J/K' image (Fig. 3d) has a rather smooth aspect except at the very center where a small, elongated structure is seen, just in the direction traced by the offset dust lane in the broad band HST image by Malkan et al. (1998). It could be the signature of a nuclear bar within a 1 arcsec radius (see also Fig. 3e).

5.4 UGC 3223

This is a classical barred SBa galaxy, with a very large bar (Figs. 4a and 4e). The sharp-divided image (Fig. 4b) clearly reveals the bar as well as the beginning of two spiral arms originating at both extremities of the bar.

The bulge + disk model fits well the observed profile except in the bar region (Fig. 4f), and except for this (large) region the residuals are very small (Fig. 4g). The spiral arms appear most clearly in the difference image (Fig. 4c).

We find evidence for the presence of an inner bar in Fig. 4e (see Table 5). In fact, an inner bar feature is evident in the HST broad band image by Malkan et al. (1998), with a curved dust lane structure associated with it.

5.5 NGC 2639 (UGC 4544)

This galaxy appears to be very regular at first sight (Fig. 5a). However, the sharp-divided image (Fig. 5b) reveals the presence of a fat primary bar, at variance with its RSa(r) classification. We note that Fig. 5e shows a roughly constant PA value for the whole galaxy, precluding a definitive quantification of the primary bar extension. In any case, NGC 2639 has to be classified as barred (or lensed) on the basis of the IR images.

The difference image reveals the existence of two spiral arms, one to the north west and the other to the south east, which splits into two arms (Fig. 5c). The surface brightness profile (in agreement with that by Moriondo et al. 1998) decomposition, specially in the K' band (Fig. 5f), implies very small residuals except in the lense and the spiral arm region (Fig. 5g).

A red arc-like feature going from the SE spiral arm northwards to the NW arm is visible in Fig. 5d, corresponding to the presence of dust lanes which clearly appear in the broad band HST image by Malkan et al. (1998). This would indicate the presence of a small central bar. An elongated ring-like structure from 9 to 18 arcsec in radius is seen in the Pa$\alpha$ HST image by Böker et al. (1999), i.e., a ring just exterior to the bar. This small bar is further confirmed by the sharp-dividing method and the ellipse fitting applied to the HST H image (see Figs. 5e and 29).

5.6 IC 2510

The K' band image shows a bar, spiral arms and a pseudo-ring (Fig. 6a). The spiral arm to the south is clearly visible on the sharp-divided image (Fig.6b), as well as a secondary bar.

The difference image (Fig. 6c) shows very distinctly the spiral. This is the only case for which we detect a secondary bar only from one method. Moreover, primary and secondary bars have almost the same PA. We therefore quote the secondary bar as doubtful in Table 5.

The bulge + disk decomposition gives good results except in the bar region, specially in K' (Figs. 6f and 6g). The J/K'image remains quite constant (Figs. 6d and 6h).

5.7 NGC 3281

The K' image (Fig. 7a) shows an elongated boxy bulge with possible spiral arms coming out of it. This galaxy is classified as non-barred in the RC3. However, the sharp-divided image (Fig. 7b) clearly shows the existence of a weak bar. The possible existence of a bar was already suggested by Xanthopoulos (1996), on the basis of an I band image. We also detect weak spiral arms in the sharp-divided image. Since these structures are weak, the PA is roughly constant throughout the galaxy (Fig. 7e); however, they do induce a small bump in the surface brightness profiles (Fig. 7f).

The J/K' image (Fig. 7d) shows that the (J-K') color index is fainter in the nucleus, in the small spiral structure around the nucleus, and in the region of the bar.

5.8 NGC 3660 (Mrk 1291)

A strong bar is seen in the K' image of this galaxy (Fig. 8a) but the ring is barely visible. On the other hand, both the bar and ring appear clearly on the sharp-divided image (Fig. 8b).

The edges of the bar can also be seen in the difference image (Fig.8c); the bar parameters are determined from Fig. 8e. From an R image, Chapelon et al. (1999) give PA = 116$^\circ$  out to 16 arcsec for the bar. This agrees with Friedli et al. (1996) who show that bars are generally longer in K than in R.

The J/K' color image (Fig. 8d) shows a smooth structure, increasingly red towards the center, and a steep central gradient (Fig. 8h). The bar region also appears redder than the surroundings. The color map also shows clear hints of the existence of a small, red circumnuclear region.

Due to the large size of this galaxy, the bulge+disk decomposition is not reliable (Fig. 8f), as confirmed by the high residuals (Fig. 8g).

5.9 NGC 4253 (UGC 7344, Mrk 766)

This galaxy has a thick bar and a weak external ring (Fig. 9a). Its nucleus is displaced relatively to the centroid of the outer isophotes. The bar parameters from Fig. 9e are in agreement with previous results in J (Alonso-Herrero et al. 1998) and K (McLeod & Rieke 1995; Peletier et al. 1999). Note that this direction is also that of the stellar bar seen at optical wavelengths (Mulchaey & Wilson 1996; Mulchaey et al. 1996).

The sharp-divided image (Fig. 9b) reveals the presence of a small structure, possibly a secondary bar, roughly perpendicular to the main bar. This feature appears even more clearly on the difference image (Fig. 9c).

The J/K' image shows a double nuclear structure with a (J-K') color index redder than the rest of the galaxy (Fig. 9d); this structure can explain the observed decentering. Notice that in the very central zone (r < 3 arcsec) $\epsilon$ is not the same in J and K(Fig. 9e). This feature seems to correspond to that delineated by the dust pattern that surrounds the innermost 2 arcsec in the HST optical image (Malkan et al. 1998). Unfortunately, the nucleus is saturated in the infrared HST image, so we cannot analyse the presence of faint nuclear elongations. Nevertheless, a curved dust pattern feature with a radius of $\approx$4 arcsec can be seen along the NE-SW direction (Fig. 30), favouring the presence of a nuclear bar.

The profile is in good agreement with that given by McLeod & Rieke (1995). The bulge+disk fit is quite satisfactory (Figs. 9f and 9g).

5.10 NGC 4507

The K' image agrees with that of Mulchaey et al. (1997), and indeed shows no clear presence of a bar (Fig. 10a). A noticeable curved dust lane to the SE reaching the innermost 2 arcsec is visible in the HST image by Malkan et al. (1998).

The sharp-divided image (Fig. 10b) clearly shows a bar that is also apparent on the difference image (Fig. 10c). This bar had been already reported by Mulchaey et al. (1997) (r = 10.5 arcsec, PA = 53$^\circ$, $\epsilon$ = 0.34).

$\epsilon$ and PA show strong variations at 18-20arcsec from the nucleus, where the spiral arms begin (Fig. 10e) and produce a small bump over the bulge+disk fit (Fig. 10f). The bar is also apparent as a small enhancement over this fit. However, due to the relative weakness of the bar and arms, the residuals remain small (Fig. 10g). The J/K' image is quite smooth except in the very nucleus, which has much redder colors (Fig. 10d) than the outer galaxy.

5.11 NGC 4785

This galaxy has a bright thick bar (Fig. 11a) and a complex spiral structure with several arms, including a thin arm to the south with several blobs. Note that the major axis orientation varies with radius in the central 14 arcsec (Fig. 11e).

The sharp-divided image reveals the presence of a ring and shows well the spiral arms (Fig. 11b). These features are also clearly visible in the difference image (Fig. 11c), where a small central bar seems to be present. The existence of such a small bar is confirmed by the J/Kimage (Fig. 11d) and by the variations of $\epsilon$ and PA with radius (Fig. 11e) both in ground based and HST images. The sharp-dividing method applied to the NICMOS HST image shows an inner elongation of $\approx$ 1.5 arcsec along PA = 109$^\circ$  (Fig. 31).

The colour image is quite constant except at the location of the arms and inner ring which appear redder in the J/K' color image (Figs. 11d and 11h).

5.12 NGC 5347

The K' image of this galaxy only shows a large bar, the rest of the structure being very smooth with hardly any hint for the presence of spiral arms (Fig. 12a), in agreement with Mulchaey et al. (1997). Even the sharp-divided image shows no structure (Fig. 12b) except for the bright nucleus.

However, the extremities of the bar appear well in the difference image (Fig. 12c), and the existence of a bar is confirmed by the PA and $\epsilon$ variations both from ground based and HST images (Fig. 12e) (in agreement with Mulchaey et al. 1997) and by the excess over the bulge+disk fit (Figs. 12f and 12g).

Surprisingly, the J/K' image reveals a double structure separated by $\approx$ 3 arcsec, resembling a double nucleus (Fig. 12h). The close inspection of the color optical to near-infrared image by Regan & Mulchaey (1999), shows that this may result from the dust lane crossing the nucleus.

5.13 NGC 5728

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

The K' image clearly shows the presence of a small bar within the large bar (Fig. 13a), both already reported by Wozniak et al. (1995) in their BVRI images. The small bar appears even more strongly in the sharp-divided image (Fig. 13b), where a small inner ring is also visible ($r \approx$ 4 arcsec, corresponding to the ring reported by Buta & Crocker 1993). The small bar and ring as well as the extremities of the large bar are also visible in the difference image (Fig. 13c), while the nucleus and ring show weaker J relative to K'than the rest of the galaxy (Fig. 13d).

Two maxima of $\epsilon$ coupled with a constant PA (Fig. 13e) allow us to determine both primary and secondary bar parameters (see also Shaw et al. 1993; Wozniak et al. 1995).

Since we obviously do not reach the galaxy disk, the bulge+ disk fit cannot be fully correct (Figs. 13f and 13g).

5.14 ESO 139-12

This galaxy shows a very regular structure in the K' band (Fig. 14a), with a luminous bulge and no bar. No structure appears either in the sharp-divided or difference images (Figs. 14b and 14c), and the J/K'image appears to be very smooth (Figs. 14d and h). A faint and quite curved dust lane is visible in the published HST image (Malkan et al. 1998) within the central 2 arcsec only.

While $\epsilon$ does not vary much with radius, the PA does vary strongly as the isophotes are seen to rotate (Fig. 14e), probably due to the effect of the flocculent spiral structure.

The bulge+disk fit is acceptable, with residuals smaller than 20% throughout (Figs. 14f and 14g). The J/K' image shows a red nuclear region, also visible in the color gradient plot (Fig. 14h).

5.15 NGC 6814

This galaxy shows a beautiful spiral structure on the K' image, with spiral arms emerging from a thick bar (Fig. 15a). Our image appears to be quite similar to that of Mulchaey et al. (1997).

The spiral structure is seen in the sharp-divided image, where the bar is traced as a faint elongation (Fig. 15b). The spiral structure is clearly observed in the difference image (Fig. 15c).

Except for the very nucleus, the J/K' image remains constant throughout the galaxy, excepting the innermost 2 arcsec, which are redder (Figs. 15d and 15h).

The bar parameters from (Fig. 15e) are in agreement with Mulchaey et al. (1997). Note the strong and sudden change of PA at the radius where the spiral arms begin. However the bulge+disk fit is very good (Figs. 15f and 15g). The NICMOS HST image is saturated in the nucleus, so it cannot be used to gather information on the presence of inner structures. The bar is seen as a thick elongated 10 arcsec structure along the NS direction in Fig. 32.

5.16 NGC 6860

This galaxy has an asymmetrical bar along PA $\sim 10\hbox{$^\circ$ }$, more extended to the north than to the south (Fig. 16a). The ring is not apparent in the K' image, where we barely detect the beginning of a spiral arm north of the bar.

The bar in the sharp-divided image appears clearly bent (Fig. 16b), possibly due to the dynamical effects of a small inner bar (Figs. 16b, 16c, 16d). The difference image (Fig. 16c) also evidences a faint spiral arm detaching from the southern end of the outer bar to the north east, and a brighter, tighter arm starting at the west end of the inner bar to the South. The variations of $\epsilon$ and PA with radius (Fig. 16e) hints on the presence of a secondary bar.

The J/K' image confirms the existence of a small redder inner bar (Fig. 16d), that is also evidenced by the dust lane structure in the HST image by Malkan et al. (1998). The main bar and the beginning of the spiral arms appear as bumps in the bulge+disk fit (Figs. 16f and 16g). The color gradient is very steep in the central regions (Fig. 16h).

5.17 NGC 6890

Despite its classification as a non-barred galaxy, the K' image of NGC 6890 reveals a strong bar (Figs. 17a and e), together with the beginning of two spiral arms at the extremities of the bar, the northern arm being brighter than the southern one (Fig. 17b). These features are also apparent in the K' image by Mulchaey et al. (1997), but these authors give PA = 179$^\circ$  corresponding to a radius $r \approx$ 14 arcsec, where the PA strongly decreases. However, their plots of the PA and $\epsilon$ show that the bar actually extends up to about 6 arcsec with PA $\approx$ 15$^\circ$, in agreement with our values. We also note that, even considering the differences in the photometry (see Table 4) the isophotal levels differ by more than 6 magnitudes, those by Mulchaey et al. being extremely bright and most probably incorrect.

The difference image reveals a beautiful spiral structure as well as a possible inner ring (10-15 arcsec) (Fig. 17c). This inner ring seems confirmed by the J/K' image (Fig. 17d), where J appears to be somewhat larger around the nucleus than in the very central region. Notice a smooth decrease of J relative to K' with increasing radius from 2 arcsec outwards (Fig. 17h). The NICMOS HST image shows spiraling structure reaching the central arsecond, with some hints of dust at 0.5 arcsec (Fig. 33).

The bulge+disk fit is quite good except in the arm regions (Figs. 17f and 17g).

5.18 NGC 6951 (UGC 11604)

This is the first galaxy of our sample for which all the necessary data has been acquired (imaging and spectroscopy); it has been studied in detail by Pérez et al. (1999) and will not be presented here. We just note that no secondary bar is detected even in NIR HST images.