The vertical stellar distribution in NGC 6504: Detection of a thick disk

P. G. van Dokkum, R. F. Peletier, R. de Grijs, M Balcells

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The vertical stellar distribution of the edge-on spiral NGC 6504 is examined in seven bands (U, B, R, I, J, H, K) b fitting model distributions to the light profile at seven position along the major axis. In the inner parts of the disk the profile is well approximated by an exponential distribution. At large galactocentric distances, the profile is much less steep near the equatorial plane, being fitted better by e.g. a sech distribution. We find an excess of light at large z values, in all optical bands and at all radii. We confirm the constancy of the scaleheight as a function of radius. Our best explanation for the deviations from the sech distribution at small z is dust extinction in combination with a young disk component. This young disk component has a very small scaleheight (it is unresolved) and a smaller scalelength than that of the (thin) disk. The excess at large z can be modeled by a component that looks very much like the thick disk in the Galaxy: scaleheight approximately 4 times the scaleheight of the thin disk, and central surface brightness approximately 1% of the brightness of the thin disk.

Original languageEnglish
Pages (from-to)415-425
Number of pages11
JournalAstronomy and Astrophysics
Issue number2
Publication statusPublished - Jun 1994
Externally publishedYes


  • Galactic Bulge
  • Galactic Halos
  • Hyperbolic Functions


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