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Astron. Astrophys. 346, 415-427 (1999)

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Near-infrared observations of galaxies in Pisces-Perseus

III. Global scaling relations of disks and bulges

G. Moriondo 1, R. Giovanelli 2 and M.P. Haynes 2

1 Dipartimento di Astronomia e Scienza dello spazio, Universita' di Firenze, L.E. Fermi 5, I-50125 Firenze, Italy
2 Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853, USA

Received 26 November 1998 / Accepted 29 March 1999


We determine the parameters of scaling relations analogous to the Fundamental Plane of elliptical galaxies for the bulges and disks of a sample of 40 spiral galaxies. To this end we derive structural parameters (scalelengths and surface brightnesses) from near infrared H band images, and kinematical parameters (rotational velocities) from optical rotation curves. In the case of the disks, we test the accuracy of the derived relation as a distance indicator by comparing its scatter to that of the H band Tully-Fisher relation for the same sample, and find that the accuracy attained by the latter is slightly higher (the dispersion is 19% versus 23% for this sample). It is speculated that the difference is due to the more robust character of global parameters, rather than those associated with the inner parts of disks. It also apperas that (a) either the stellar mass-to-light ratios of bulge and disk increase with the size of the components, or (b) the bulge and disk relative contributions to the overall rotation of the galaxy (and, as a consequence, to its total mass) become steadily smaller with increasing size.

Key words: galaxies: structure – galaxies: fundamental parameters – galaxies: distances and redshifts – infrared: galaxies

Send offprint requests to: gmorio@arcetri.astro.it

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© European Southern Observatory (ESO) 1999

Online publication: May 21, 1999