|Claude Carignan & Tom Oosterloo
| The seven-dish KAT-7 array was built as an engineering testbed for the 64-dish Karoo Array Telescope, known as MeerKAT, which is the South African precursor of the Square Kilometre Array (SKA). KAT-7 and MeerKAT are located close to the South African SKA core site in the Northern Cape's Karoo desert region. Construction of the KAT-7 array was completed in December 2010. The array is extremely compact, with baselines ranging from 26 to 185 m and the receivers have a very low system temperature of Tsys ~26 K. While its main purpose is to test technical solutions for MeerKAT and the SKA, scientific targets, such as NGC 253, were also observed during commissioning to test the HI line mode.
The short baselines and low system temperature of the telescope make it, despite the fact that it consists of only seven 12-m dishes, very sensitive to large-scale, low-surface-brightness emission. The KAT-7 observations of NGC 253 detected 33% more flux than previous Very Large Array observations. As can be seen in the figure, HI can be found at large distances perpendicular to the plane out to projected distances of ~10 kpc away from the nucleus and ~14 kpc at the edge of the disc.
The observations show that a large amount of HI is found outside the disk of NGC 253. The kinematics of this extra-planar gas suggests that it consists of gas blown out from the disk by the central starburst occurring in NGC 253 and by the galactic fountains in the outer parts. Analysis of the near-IR WISE data, shows clearly that the star formation rate is compatible with the starburst nature of NGC 253.
The results of these observations we recently published in the Monthly Notices of the Royal Astronomical Society (HI observations of the nearest starburst galaxy NGC 253 with the SKA precursor KAT-7 by Lucero, D.M., Carignan, C., Elson, E.C., Randriamampandry, T.H., Jarrett, T.H., Oosterloo, T.A. and Heald, G.H.; see http://arxiv.org/abs/1504.04082 )
|University of Cape Town