Astronomical instrumentation

Abstract:

© 2016 SPIE. We present the Final Design of the WEAVE next-generation spectroscopy facility for the William Herschel Telescope (WHT), together with a status update on the details of manufacturing, integration and the overall project schedule now that all the major fabrication contracts are in place. We also present a summary of the current planning behind the 5-year initial phase of survey operations. WEAVE will provide optical ground-based follow up of ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2-degree prime focus field of view at the WHT, with a buffered pick-and-place positioner system hosting 1000 multi-object (MOS) fibres, 20 integral field units, or a single large IFU for each observation. The fibres are fed to a single (dual-beam) spectrograph, with total of 16k spectral pixels, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting observations at R∼5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with limited coverage in each arm at R∼20000. The project is now in the manufacturing and integration phase with first light expected for early of 2018.

Abstract:

We present high-angular (0.17−0.35 arcsec) resolution imaging polarimetric observations of Mrk 231 in the 3.1 µm filter using MMT-Pol on the 6.5-m MMT, and in the 8.7 µm, 10.3 µm, and 11.6 µm filters using CanariCam on the 10.4-m Gran Telescopio CANARIAS. In combination with already published observations, we compile the 1−12 µm total and polarized nuclear spectral energy distribution (SED). The total flux SED in the central 400 pc is explained as the combination of 1) a hot (731 ± 4 K) dusty structure, directly irradiated by the central engine, which is at 1.6 ± 0.1 pc away and attributed to be in the pc-scale polar region, 2) an optically-thick, smooth and disk-like dusty structure (‘torus’) with an inclination of 48 ± 23◦ surrounding the central engine, and 3) an extinguished (AV = 36 ± 5 mag) starburst component. The polarized SED decreases from 0.77 ± 0.14 per cent at 1.2 µm to 0.31 ± 0.15 per cent at 11.6 µm and follows a power-law function, λ ∼0.57. The polarization angle remains constant (∼108◦ ) in the 1−12 µm wavelength range. The dominant polarization mechanism is explained as scattering off hot dust grains in the pc-scale polar regions.