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Abstract The Hobby–Eberly Telescope (HET) Dark Energy Experiment (HETDEX) is undertaking a blind wide-field low-resolution spectroscopic survey of 540 deg2of 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 powerR≃ 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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This content will become publicly available on May 20, 2027
Golden and Silver Dark Sirens for Precise H 0 Measurement with HETDEX
Abstract Gravitational waves (GWs) from compact binary coalescences arestandard sirensthat provide a direct measure of the source’s luminosity distance, enabling an independent measurement of the Hubble constant (H0). While abright siren—a GW event with an identified electromagnetic (EM) counterpart—provided the first such constraint, most detections, currently dominated by black hole mergers, lack EM signatures. A measurement ofH0is still possible with thesedark sirensby statistically associating GW events with galaxies in existing catalogs based on the sky localization. In this work, we explore the potential of two subsets of dark sirens categorized by their localization precision: ’golden’ dark sirens, defined by a sky area localization ≤0.1deg2, and ’silver’ dark sirens, which are more common but less precisely localized (≤1deg2). Using thefifth internal data releaseof the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX), we assess the suitability of the Visible Integral-field Replicable Unit Spectrograph (VIRUS) for spectroscopic follow-up of dark sirens. VIRUS exposures of the standard HETDEX depth provide precise redshifts and exquisite completeness withinz= 0.2. After a single year of observations with the upgraded LIGO-A#network, the combined sample of golden and silver dark sirens withz≤ 0.2 atH0 = 70 km s−1Mpc−1and follow-up VIRUS observations can potentially yield a few-percent constraint onH0. Our predictions suggest that spectroscopic redshift surveys such as HETDEX can play a key role in realizing high-precision cosmology with dark sirens in the near future.
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- PAR ID:
- 10709672
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 1003
- Issue:
- 2
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 122
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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