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Paper: HETDEX and VIRUS: Panoramic Integral Field Spectroscopy with 35k Fibers
Volume: 507, Multi-Object Spectroscopy in the Next Decade: Big Questions, Large Surveys, and Wide Fields
Page: 393
Authors: Hill, G. J.; HETDEX Consortium
Abstract: The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) will utilize the Visible Integral-field Replicable Unit Spectrograph (VIRUS) to provide the first blind, wide-area, integral field spectroscopic survey. In this paper we provide an overview of the instrumentation and survey plans for HETDEX and the expected content of the survey. VIRUS consists of 156 integral field spectrographs (IFS, arrayed as 78 pairs) fed by 34,944 fibers, each 1.5 arcsec diameter, from the focus of the upgraded 10 m Hobby-Eberly Telescope (HET). VIRUS has a fixed bandpass of 350-550 nm and resolving power R ∼ 700. At the input, the fibers are arrayed in a 1/3 fill-factor in a 50×50 square arcsecond area. Three dithered exposures fill in the area. The IFUs are mounted in a precision plate and cover a field of 16 arcminutes with fill factor ∼1/4.5. VIRUS is the first example of large-scale replication applied to optical astronomy and is capable of surveying large areas of sky, spectrally. The main motivator for VIRUS is to map the evolution of dark energy for HETDEX, using ∼1M Lyman-α emitting galaxies (LAEs) with 1.9< z <3.5 as tracers. In addition, more than a million [OII] emitting galaxies with z<0.5, 50,000 stars, and 10,000 resolved nearby galaxies will be mapped. VIRUS production is about 80% complete and the HET upgrade is being commissioned. Spectrograph units are being deployed in two large enclosures mounted on either side of the telescope. VIRUS will provide a powerful new facility instrument for the upgraded HET, well suited to the survey niche of the telescope, and will open up large area panoramic surveys of the emission line universe for the first time. HETDEX observing is projected to run from 2016 to 2019. The full survey will include 300 billion spectral×spatial resolution elements, observed without pre-selection.
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