Dark Energy Spectroscopic Instrument Applications in Galaxy Surveys

The Dark Energy Spectroscopic Instrument (DESI) is a state-of-the-art multi-fibre spectrograph installed on the Mayall Telescope at Kitt Peak Observatory. Over a five-year programme, DESI aims to measure precise redshifts of tens of millions of galaxies and quasars across 14,000 deg². By mapping the three-dimensional distribution of matter, DESI employs baryon acoustic oscillations and redshift-space distortions to constrain the expansion history of the Universe and the growth of cosmic structure, shedding light on the nature of dark energy. The instrument’s 5,020 fibre positioners feed ten spectrographs covering 360–980 nm at spectral resolutions of 2,000–5,000, enabling efficient acquisition of diverse target classes, including luminous red galaxies, emission line galaxies and quasars. Integration with deep imaging surveys ensures robust target selection and calibration, while a dedicated data pipeline delivers wavelength- and flux-calibrated spectra within 24 hours. Early science highlights encompass measurements of the local velocity field, refined distance indicators via the Tully–Fisher and fundamental plane relations, and the identification of peculiar systems through advanced machine-learning techniques. DESI’s unprecedented multiplexing and data quality establish it as a global reference for spectroscopic cosmology and galaxy evolution studies.

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Dark Energy Spectroscopic Instrument Applications in Galaxy Surveys publication trend

The graph below shows the total number of articles in dark energy spectroscopic instrument applications in galaxy surveys across all publications each year (not limited to Nature Index journals).

Technical terms

Redshift: A measure of the wavelength shift of spectral features due to cosmic expansion, used as a proxy for distance.

Baryon Acoustic Oscillations (BAO): Periodic fluctuations in matter density from early-universe sound waves, serving as a standard ruler for cosmological distance measurements.

Redshift-space Distortions (RSD): Apparent anisotropies in galaxy clustering caused by peculiar velocities along the line of sight, informative of structure growth rates.

Fibres: Optical cables that transmit light from individual targets in the focal plane to the spectrographs.

Spectroscopic Pipeline: Automated software suite that processes raw spectrographic data into calibrated spectra and redshift estimates.

Emission Line Galaxy (ELG): A galaxy whose spectrum is dominated by bright emission lines, indicative of ongoing star formation.

Quasar: A highly luminous active galactic nucleus, used as a tracer of large-scale structure at high redshift.

References

1. Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument. The Astronomical Journal (2022).
2. Overview of the DESI Legacy Imaging Surveys. The Astronomical Journal (2019).
3. The Spectroscopic Data Processing Pipeline for the Dark Energy Spectroscopic Instrument. The Astronomical Journal (2023).
4. Outlier Detection in the DESI Bright Galaxy Survey. The Astrophysical Journal Letters (2023).
5. The Early Data Release of the Dark Energy Spectroscopic Instrument. The Astronomical Journal (2024).
6. Validation of the Scientific Program for the Dark Energy Spectroscopic Instrument. The Astronomical Journal (2024).