Hector: a new multi-object integral field spectrograph instrument for the Anglo-Australian Telescope

Abstract

Based on the success of the SAMI integral field spectrograph (IFS) instrument on the Anglo-Australian Telescope (AAT), the capacity for large IFS nearby galaxy surveys on the AAT is being substantially expanded with a new instrument, Hector. The high fill-factor imaging fibre bundles ‘hexabundles’, of the type used on SAMI, are being improved and enlarged to cover 27-arcsec diameter. The aim is to reach 2 effective radii on most galaxies, where the galaxy rotation curve flattens and half of the angular momentum is accounted for. The boosted Hector spectral resolution of 1.3 Angstrom will enable higher order stellar kinematics to be measured on a larger fraction of galaxies than with any other IFS survey instrument. Hector will have 21 hexabundles over a 2-degree field feeding both the new Hector spectrograph and existing AAOmega spectrograph. Hector consists of new blue and red-arm spectrographs, coupled to the new high- efficiency hexabundles and a unique robotic positioner. The novel robotic positioning concept will compensate for varying telecentricity over the 2-degree-field of the AAT to recoup the light loss and correct the focus across the field. The main components are in hand, and prototypes are currently being tested ahead of commissioning in the next year. Hector will take integral field spectroscopy of 15,000 galaxies with z < 0.1 in the 4MOST WAVES-North and WAVES-South regions. The WAVES data, which will come later, will give the environment metrics necessary to relate how local and global environments influence galaxy growth through gas accretion, star formation and spins measured with Hector. The WALLABY ASKAP survey will trace HI gas across the Hector fields, which in combination with Hector will give a complete view of gas accretion and star formation.