MeerKAT calibration and imaging challenges (when luxury problems attack)

Main Colloquium
Prof. Oleg Smirnov
SCHEDULED
Rhodes University, Grahamstown, South Africa

I will present some early images obtained with the MeerKAT radio telescope, and discuss the calibration and imaging challenges posed by the instrument. The combination of exceptional L-band sensitivity and abundance of short spacings has already made for some spectacular radio maps, revealing faint extended structure in exquisite detail. At the same time, such an embarrassment of morphological detail pushes at the limitations of conventional CLEAN-based deconvolution techniques. I will present observations that highlight these limitations, and discuss emerging deconvolution techniques that could potentially alleviate such problems. I will also discuss the sheer data size challenge of MeerKAT, and look at computing approaches and techniques for dealing with them.

The first Large Survey Project observations with MeerKAT

Special Colloquium
Dr. Ian Heywood
CANCELED
University of Oxford, UK

MeerKAT is a 64-element radio interferometer, and is the South African precursor to the mid-frequency component of the Square Kilometre Array. Officially inaugurated in July of last year, observations have already begunfor two of its Large Survey Projects. These are ThunderKAT, which aims tostudy explosive and accretion-powered transient phenomena, and MIGHTEE which will use deep radio continuum, polarisation and spectral-line measurements to study galaxy evolution across the history of the Universe. In this talk I will provide an overview of MeerKAT, some of the first results from MIGHTEE and ThunderKAT, and describe some of the data processing challenges.

The nuclear star cluster at the Galactic centre

Main Colloquium
Dr. Rainer Schödel
SCHEDULED
Instituto de Astrofísica de Andalucía - CSIC, Granada, Spain

Sagittarius A\*, the Milky Way's central four million solar mass black hole, is surrounded by a star cluster of roughly 25 million solar masses. This cluster appears to be similar to the nuclear clusters that are observed in the majority of galaxies. In this talk I will review our current knowledge about the nuclear cluster of the Milky Way and present some yet unpublished results. Our analysis of the star formation history excludes a quasi-continuous star formation and shows that the cluster is mostly very old (~10 Gyr) and metal rich (about twice solar), which gives us some clues as to its formation. A few percent of its mass formed in the last ~300 Myr. There appears to exist the predicted stellar density cusp around Sagittarius A*, which is of great relevance for the potential future detection of extreme mass ratio inspiral events from similar systems by space-based gravitational wave observatories.