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Astron. Astrophys. 327, 966-982 (1997)

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5. Summary and conclusions

In this paper we have studied the sharpness of the peaks of the vertical luminosity and density distribution in a statistically complete sample of edge-on disk galaxies. The results obtained in this paper are based on near-infrared [FORMULA] -band observations. The main results obtained in this study are the following:

  • In the majority of our sample of edge-on disk galaxies, we find that the sharpness of the peak of the vertical profiles, characterized by the exponent 2/n of the generalized family of fitting functions ( 6) (van der Kruit 1988), varies little with position along the major axis. This result is independent of galaxy type.
  • The mean levels for the sharpness of the [FORMULA] -band luminosity peaks indicate that the vertical luminosity distributions are more peaked than expected for the intermediate sech(z) distribution, but rounder than exponential. Since projection of a galaxy causes the profile to be flattened near the galaxy plane, our result is consistent with the hypothesis that all spiral galaxies have exponential vertical profiles. The fact that we observe this in all our sample galaxies indicates that the process at work here is a process intrinsic to the disks themselves.
  • For those galaxies with the faintest absolute magnitudes, we find a lack of "rounder" profiles compared with those galaxies with brighter absolute magnitudes. This may indicate that we are hindered by an underlying dust component, which is concentrated towards the galaxy planes, and more extended in the larger galaxies than in the smaller ones, at least to an outside observer. It may be that in the smaller galaxies this dust component affects relatively fewer data points than in the larger ones, thus causing a bias towards more sharply peaked vertical profiles.
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© European Southern Observatory (ESO) 1997

Online publication: April 6, 1998