Mathematics – Logic
Scientific paper
Mar 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006phdt.........1n&link_type=abstract
Proefschrift, Rijksuniversiteit Groningen, 2006, viii, 338 p.
Mathematics
Logic
16
Disk Galaxies
Scientific paper
I present the results of a study of the relation between dark and luminous matter in nearby early-type disk galaxies. 68 galaxies with morphological type between S0 and Sab were observed at 21cm with the WSRT. Our data allowed for the first time to derive rotation curves outside the optical disks for a substantial number (19) of these galaxies at the high mass, high surface brightness end of the disk galaxy population. Additional long-slit optical spectra were obtained to resolve the steep velocity gradients in the central regions. Almost all galaxies in our sample were found to have declining rotation curves. The strength of the decline is coupled to the luminosity of the galaxy and can be as large as 25-50% in the brightest systems. In all cases, however, the rotation curves flatten out at large radii; no galaxies were found with a fully Keplerian decline. We find strong indications that bulges are 'maximal' and dominate the gravitational potential in the inner regions. The disk contributions are only poorly constrained by our data, which weakens the constraints on the dark matter distribution. We show that if dark haloes have density profiles as predicted by CDM, the disks can not be maximal. If dark haloes are isothermal, maximum disks are allowed. I also discuss the consequences of the decline in the rotation curves for the high-mass end of the Tully-Fisher relation. If the TF relation is constructed using the maximum rotation velocity, our galaxies are systematically offset to the low-luminosity side of the relation defined by later-type galaxies, causing a 'kink' in the relation around 200 km/s. However, this kink disappears when the asymptotic velocity at large radii is used. This strengthens the idea that the TF relation fundamentally links the mass of dark haloes to the total baryonic mass.
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