5 Discussion

Here we present a case-by-case analysis of the behavior of the objets of our sample, giving special attention to the objects that show more evidence of peculiarity.

The galaxy that presents the highest effective radius in $JHK_{\rm s}$ - IC 5105 - has one of the highest deviations between effective radii in infrared and B bands. This galaxy is the most luminous object in our sample. It presents slightly boxy isophotes, and shows small color gradients. These features seem to indicate that its population distribution is homogeneous throughout the radius; the infrared integrated colors are dominated by stellar populations type IV-VI, most influenced by the contribution of AGB carbon stars.

Galaxy NGC 7562 shows a similar behavior. Like IC 5105, it presents very similar effective radii in $JHK_{\rm s}$ and B, and it has the second highest infrared effective radius. In the flux rate diagram, it is located in a bluer-than-average J/H region. So, a contribution of a less metal-rich population is more likely to be present in its infrared colors. This galaxy has a physical companion, NGC 7562A, 2.3 arcmin away.

NGC 1400 shows the smallest effective radius of the sample, and is also the less luminous. This galaxy is a member of a physical association of galaxies (NGC 1407 being the most important) where it is the second most luminous. Its order 3 coefficients present an almost monotonic growth, which can indicate regions of high extinction. It is classified as lenticular, despite the fact that a de Vaucouleurs law fits very well its brightness profile. In relation to the Fundamental Plane, it is the object farthest from the average behavior of the sample.

The galaxy NGC 1600, whose brightness profiles were very well fitted by Sérsic's law, presents the highest effective radius in B compared to the $JHK_{\rm s}$ ones, indicating that its infrared-dominating stellar population is concentrated in the central region of the galaxy. This galaxy presents boxy isophotes, being the brightest galaxy of a physical association. NGC 720 has also a profile fitted by Sérsic's law (albeit not as well as the former). The central region of the profiles of this galaxy is responsible for the major deviation of the applied laws, being very planar; taking this region (which extends up to 10 $^{\prime\prime}$) off the profile, the de Vaucouleurs law fits very well. But we see that its isophotes are disky in this very region, becoming boxy in the external region; this is a strong evidence of the presence of a stellar disk in the central region. Goudfrooij et al. (1994), using BVI photometry, also arrived at this conclusion. Note that in the two cases where it was necessary to apply Sérsic's law, the value of the n parameter was lower than 4 (1.5 and 1.8 for NGC 1600 and NGC 720, respectively), indicating that these two objects have a brightness profile more compact than the profiles of the rest of the sample galaxies, well fitted by the de Vaucouleurs law.

Abrupt variations of position angle (more than 40$^\circ$) ocurred in the galaxies NGC 596, NGC 636 and NGC 7626. The first presents very low ellipticity, which means that, at least in part, the variation of the position angle can be spurious. NGC 636 shows slightly disky isophotes. In both objects, we can see strong and nonconstant variations in the Fourier coefficients; Michard & Marchal (1994), through V photometry, proposed for both objects a disk structure in the internal region. For NGC 596, Goudfooij et al. (1994) found the same result. Ferrari et al. (1999) found, for NGC 636, a conical axisymmetrical distribution of dust. Ionized gas in the form of a small internal disk, perpendicular to the orientation of the dust cone, was also found for this galaxy (Macchetto et al. 1996).

The galaxies NGC 7192, NGC 7562 and NGC 7619 are the most displaced with respect to the average in the flux ratios diagram. Its infrared colors are likely to be compatible with the average Galactic clusters population. NGC 7619 is a member of Pegasus I cluster, being the brightest component, followed by NGC 7626. Both present disky isophotes and abrupt variations of A3 and B3 coefficients, possibly indicating high extinction regions. Forbes & Thomson (1992) found evidence of tidal interactions between these two galaxies; since these interactions can induce star formation bursts, this could explain, at least in part, the fact that its infrared colors are among the bluest of our sample.