VIRUS: status and performance of the massively replicated fiber integral field spectrograph for the upgraded Hobby-Eberly Telescope

Hill, Gary J.; Kelz, Andreas; Lee, Hanshin; MacQueen, Phillip J.; Peterson, Trent; Ramsey, Jason; Vattiat, Brian L.; DePoy, D. L.; Drory, Niv; Gebhardt, Karl; Good, John M.; Jähn, Thomas; Kriel, Herman; Marshall, J. L.; Tuttle, Sarah; Zeimann, Greg; Balderrama, Edmundo; Bryant, Randy; Buetow, Brent; Chonis, Taylor S.; Damm, George; Fabricius, Maximilian; Farrow, Daniel J.; Fowler, James R.; Froning, Cynthia S.; Haynes, Dionne; Indahl, Briana L.; Martin, Jerry; Montesano, Francesco; Mrozinski, Emily; Nicklas, H.; Noyola, Eva; Odewahn, S. C.; Peterson, Andrew; Prochaska, Travis; Rostopchin, S.; Shetrone, Matthew; Smith, Greg; Snigula, J.; Spencer, Renny; Westfall, Amy; Armandroff, T. E.; Bender, Ralf; Dalton, Gavin; Steinmetz, Matthias

doi:10.1117/12.2314280

Ground-Based and Airborne Instrumentation for Astronomy VII 2018

DOI: 10.1117/12.2314280

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VIRUS: status and performance of the massively replicated fiber integral field spectrograph for the upgraded Hobby-Eberly Telescope

Gary J. Hill

Andreas Kelz

Hanshin Lee

et al.

Abstract: The Visible Integral-field Replicable Unit Spectrograph (VIRUS) consists of 156 identical spectrographs (arrayed as 78 pairs, each with a pair of spectrographs) fed by 35,000 fibers, each 1.5 arcsec diameter, at the focus of the upgraded 10 m Hobby-Eberly Telescope (HET). VIRUS has a fixed bandpass of 350-550 nm and resolving power R~750. The fibers are grouped into 78 integral field units, each with 448 fibers and 20 m average length. VIRUS is the first example of large-scale replication applied to optical as… Show more

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Cited by 12 publications

References 33 publications

(75 reference statements)

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Revisiting the local star-forming galaxies observed in the HETDEX Pilot Survey

Shinn

2020

Monthly Notices of the Royal Astronomical Society

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I have reanalyzed the data obtained for local (z < 0.15) star-forming galaxies during the pilot survey for the Hobby Eberly Telescope Dark Energy Experiment (HETDEX)—called the HETDEX Pilot Survey (HPS)—which uses an integral-field-unit spectrograph and covers ∼3500 − 5800 Å at ∼5 Å resolution. I have newly determined the gas metallicities, 12 + log (O/H), following the Bayesian analysis scheme of the previous study, but dealing carefully with the uncertainty of strong-line calibration, performing reproducibility tests with mock data, and monitoring the convergence of the Markov-Chain Monte Carlo (MCMC) sampling. From the mock-data tests, I found that the nebular emission-line color excess E(B − V) can be overestimated by as much as 2-σ or more, although the metallicity can recover the input value to within 1-σ. The new metallicity estimates on the HPS data are from well-converged MCMC samples (effective sample sizes > 2000), and they are higher than the previous estimates by ∼2-σ. Using the HPS data, I also showed that the MCMC sampling can have the statistical accuracy as poor as the one near the iteration start if done without convergence monitoring. The overestimation of E(B − V) indicates the overestimation of the star-formation rates (SFRs) in the previous study, which can be as much as a factor of five. This finding undermines the previous suggestion of a hitherto-unknown galaxy population based on the locations of galaxies in the mass-SFR plane. I found that the independent determination of E(B − V) using either Hβ-Hγ or Hα-Hβ line pair is ideal for the analysis of forthcoming HETDEX data, but it requires additional cost.

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Revisiting the local star-forming galaxies observed in the HETDEX Pilot Survey

Shinn

2020

Monthly Notices of the Royal Astronomical Society

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The HETDEX Instrumentation: Hobby–Eberly Telescope Wide-field Upgrade and VIRUS

Hill¹,

Lee²,

MacQueen³

et al. 2021

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The Hobby–Eberly Telescope (HET) Dark Energy Experiment (HETDEX) is undertaking a blind wide-field low-resolution spectroscopic survey of 540 deg2 of sky to identify and derive redshifts for a million Lyα-emitting galaxies in the redshift range 1.9 < z < 3.5. The ultimate goal is to measure the expansion rate of the universe at this epoch, to sharply constrain cosmological parameters and thus the nature of dark energy. A major multiyear Wide-Field Upgrade (WFU) of the HET was completed in 2016 that substantially increased the field of view to 22′ diameter and the pupil to 10 m, by replacing the optical corrector, tracker, and Prime Focus Instrument Package and by developing a new telescope control system. The new, wide-field HET now feeds the Visible Integral-field Replicable Unit Spectrograph (VIRUS), a new low-resolution integral-field spectrograph (LRS2), and the Habitable Zone Planet Finder, a precision near-infrared radial velocity spectrograph. VIRUS consists of 156 identical spectrographs fed by almost 35,000 fibers in 78 integral-field units arrayed at the focus of the upgraded HET. VIRUS operates in a bandpass of 3500−5500 Å with resolving power R ≃ 800. VIRUS is the first example of large-scale replication applied to instrumentation in optical astronomy to achieve spectroscopic surveys of very large areas of sky. This paper presents technical details of the HET WFU and VIRUS, as flowed down from the HETDEX science requirements, along with experience from commissioning this major telescope upgrade and the innovative instrumentation suite for HETDEX.

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HETDEX Pilot Survey. VI. $[{\rm{O}}\,{\rm{III}}]$ Emitters and Expectations for a Local Sample of Star-forming Galaxies in HETDEX

Indahl

Zeimann

Hill

et al. 2019

ApJ

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We assemble an unbiased sample of 29 galaxies with [O II] λ3727 and/or [O III] λ5007 detections at z < 0.15 from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) Pilot Survey (HPS). HPS finds galaxies without pre-selection based on their detected emission lines via integral field spectroscopy. Sixteen of these objects were followed up with the second-generation, low resolution spectrograph (LRS2) on the upgraded Hobby-Eberly Telescope. Oxygen abundances were then derived via strong emission lines using a Bayesian approach. We find most of the galaxies fall along the massmetallicity relation derived from photometrically selected star forming galaxies in the Sloan Digital Sky Survey (SDSS). However, two of these galaxies have low metallicity (similar to the very rare green pea galaxies in mass-metallicity space). The star formation rates of this sample fall in an intermediate space between the SDSS star forming main sequence and the extreme green pea galaxies. We conclude that spectroscopic selection fills part of the mass-metallicity-SFR phase space that is missed in photometric surveys with pre-selection like SDSS, i.e., we find galaxies that are actively forming stars but are faint in

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VIRUS: status and performance of the massively replicated fiber integral field spectrograph for the upgraded Hobby-Eberly Telescope

Cited by 12 publications

References 33 publications

Revisiting the local star-forming galaxies observed in the HETDEX Pilot Survey

Revisiting the local star-forming galaxies observed in the HETDEX Pilot Survey

The HETDEX Instrumentation: Hobby–Eberly Telescope Wide-field Upgrade and VIRUS

HETDEX Pilot Survey. VI. $[{\rm{O}}\,{\rm{III}}]$ Emitters and Expectations for a Local Sample of Star-forming Galaxies in HETDEX

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