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J. C. Pinkney (Ohio Northern University), Nuker Team
In the quest to pin down the high-mass end of the Mbh- sigma correlation for galaxies, NGC 4061 may attract attention. It has the largest velocity dispersion (459 km s-1) in the Hypercat catalogue and, one would extrapolate, the most massive supermassive blackhole in the nearby universe. Here we present analysis of new spectroscopy and imaging from HST and the ground for NGC 4061. HST imaging reveals an organized dust disk with a radius of 2.5 arcseconds. Our ground-based spectroscopy reveal central H alpha emission from gas in rapid rotation. The velocity change is 270 km s-1 in 0.55 arcseconds (250 pc). This suggests a BH mass of about 2.x109 Mbh. We also obtain stellar kinematics from the absorption lines of the calcium triplet (near IR) from the ground (MDM 2.4-m) and from STIS aboard HST. We fit losvd's and Gauss-Hermite moments using a new, direct-template-fitting code. We find the rotation to be strong in the stars as well. The central velocity dispersion is only about 290 km s-1, so the black hole's sphere of influence is, in fact, not resolved. Our measurements suggest that the large (459 km s-1) dispersion was erroneous. Nevertheless, this galaxy is interesting in that it allows a comparison between the gas and stellar dynamical methods for determining BH mass. NGC 4061 is a promising target for future high-spatial-resolution spectrographs. We acknowledge support for HST proposal 9106 from NASA through a grant from the STScI, which is operated by the AURA under NASA contract NAS 5-26555, and to an LTSA grant NAG5-8238 to D. Richstone.
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.