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Nowak, Nina (2009): Exploring the relations between bulges and central black holes in unusual galaxies. Dissertation, LMU München: Fakultät für Physik



This thesis reports on the measurement of the masses of supermassive black holes in the centres of four galaxies using stellar dynamics. It is based on observations in the near-infrared (1.9-2.5\mum) with the integral-field spectrograph SINFONI at the Very Large Telescope (VLT). These data were used to determine the motions of stars in the very centre of the galaxies, which then were modelled to derive the mass of the central black hole using the Schwarzschild method. Such measurements were until now restricted to massive and dust-free galaxies, observed with the Hubble Space Telescope in the optical wavelength range. With SINFONI and the technique of adaptive optics it is now possible to measure the mass of supermassive black holes also in dusty, low-mass and faint galaxies. This is essential in order to understand the correlations between the evolution of galaxies and the growth of central black holes. The faint elliptical galaxy NGC4486a contains a nuclear disc of dust and stars. With a velocity dispersion of 110km/s it belongs to the class of low-mass galaxies. The mass of the central black hole is M_BH=1.26x10^7 M_sun. Fornax A, a radio galaxy located in the outskirts of the Fornax galaxy cluster, experienced a recent major merger. A mass of M_BH=1.5x10^8 M_sun was derived for the central supermassive black hole. NGC3368 and NGC3489 are both galaxies which host a composite pseudobulge, i.e. a central disclike component grown via secular evolution and an additional small classical bulge. The derived masses of the central black holes are M_BH=7.5x10^6 M_sun for NGC3368 and M_BH=6.00x10^6 M_sun for NGC3489. The tight correlation between M_BH and the velocity dispersion of the galaxy bulge, which is mainly based on elliptical galaxies, seems to be also a good indicator of the black hole mass for other galaxy types. All black hole masses derived here are in agreement with this relation. The correlation between M_BH and bulge mass, however, only seems to be valid for old classical bulges. It predicts several times larger black hole masses for the merger remnant Fornax A and for the two pseudobulge galaxies. The masses of the small classical bulge components in NGC3368 and NGC3489 seem to be a much better indicator of M_BH.