Hintze Centre for Astrophysical Surveys

Abstract:

We show that high quality laser guide star (LGS) adaptive optics (AO) observations of nearby early-type galaxies are possible when the tip-tilt correction is done by guiding on nuclei while the focus compensation due to the changing distance to the sodium layer is made 'open loop'. We achieve corrections such that 40% of flux comes from R<0.2 arcsec. To measure a black hole mass (M•) one needs integral field observations of both high spatial resolution and large field of view. With these data it is possible to determine the lower limit to M• even if the spatial resolution of the observations are up to a few times larger than the sphere of influence of the black hole. © 2010 American Institute of Physics.

Abstract:

We investigate the accuracy of mass determinations MBH of supermassive black holes in galaxies using dynamical models of the stellar kinematics. We compare 10 of our MBH measurements, using integral-field OASIS kinematics, to published values. For a sample of 25 galaxies we confront our new MBH derived using two modeling methods on the same OASIS data. © 2010 American Institute of Physics.

Abstract:

We report the discovery of multi-scale X-ray jets from the accreting neutron star X-ray binary, Circinus X-1. The bipolar outflows show wide opening angles and are spatially coincident with the radio jets seen in new highresolution radio images of the region. The morphology of the emission regions suggests that the jets from Circinus X-1 are running into a terminal shock with the interstellar medium, as is seen in powerful radio galaxies. This and other observations indicate that the jets have a wide opening angle, suggesting that the jets are either not very well collimated or precessing. We interpret the spectra from the shocks as cooled synchrotron emission and derive a cooling age of ∼1600 yr. This allows us to constrain the jet power to be 3×10³⁵ erg s^-1 ≲ Pjet ≲ 2×10³⁷ erg s^-1, making this one of a few microquasars with a direct measurement of its jet power and the only known microquasar that exhibits stationary large-scale X-ray emission. © 2010. The American Astronomical Society. All rights reserved.

Abstract:

We present an analysis of observations of the doubly-lensed double hotspot in the giant radio galaxy J0816+5003 from MERLIN, MDM, WIYN, WHT, UKIRT and the VLA. The images of the two hotspot components span a factor of two in radius on one side of the lensing galaxy at impact parameters of less than 500pc. Hence we measure the slope of the lensing potential over a large range in radius, made possible by significant improvement in the accuracy of registration of the radio and optical frame and higher resolution imaging data than previously available. We also infer the lens and source redshifts to be 0.332 and > 1 respectively. Purely on the basis of lens modelling, and independently of stellar velocity dispersion measurements, we find the potential to be very close to isothermal.