||HETDEX and VIRUS: Panoramic Integral Field Spectroscopy with 35k Fibers
||507, Multi-Object Spectroscopy in the Next Decade: Big Questions, Large Surveys, and Wide Fields
||Hill, G. J.; HETDEX Consortium
||The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) will
utilize the Visible Integral-field Replicable Unit Spectrograph
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
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