Dark Energy Spectroscopic Instrument (DESI)

announcements

Siena Galaxy Atlas 2020 publicly released by DESI Legacy Imaging Surveys team

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The DESI Legacy Imaging Surveys team is pleased to announce the public release of the Siena Galaxy Atlas 2020 (SGA-2020), a value-added supplemental catalog to imaging Data Release 9 (DR9).

The SGA-2020 is a multiwavelength atlas of 383,620 nearby galaxies selected over the 20,000 square-degree imaging footprint based on their (large) apparent angular diameter. It has been used in Survey Validation and the Main Survey to improve the selection of BGS targets, for improved masking of faint, dark-time (ELG, LRG, QSO) targets, in secondary target programs (e.g., to facilitate studies of the peculiar velocity field in the local volume via the Tully-Fisher and Faber-Jackson relations), and more. Read more about the SGA-2020 on the AAS poster.

For each galaxy in the SGA, we carry out the following measurements:

  • We generate custom grz and W1W2 image stacks using all the available imaging (upper-left panel);
  • We use The Tractor, in the context of the legacypipe photometric pipeline to build a model of all the sources in the field (middle-left panel);
  • We subtract all the sources in the field except the object of interest from the data and measure the surface-brightness profile using nested, fixed-geometry elliptical isophotes (bottom-left panel).

This procedure yields the non-parametric grz surface-brightness profiles, g-r and r-z color-radius profiles, and grz curves of growth shown in the right-hand panels of the figure above, and more.

Documentation of the SGA-2020 can be found here. A queryable web-application is also available here.

DESI starts its 5-year survey

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After completing its Commissioning and Survey Validation phase, on May 17 the Dark Energy Spectroscopic Instrument (DESI) officially entered into “a five-year quest to map the universe and unravel the mysteries of ‘dark energy’“.

The video below shows about 30 thousand of the first galaxies measured by DESI, only a small fraction of the tens of millions of galaxies and other distant objects in the universe that will allow the DESI collaboration to construct a detailed 3D map of the universe. See the Press Release and related blog posts.

credit: David Kirkby/DESI collaboration

Operations resume on Kitt Peak

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The Kitt Peak National Observatory, where the Mayall telescope houses the Dark Energy Spectroscopic Instrument, was closed in March, 2020 due to the global coronavirus pandemic. The observatory cautiously and carefully reopened for maintenance in September, 2020 and since then has been slowly ramping up activities. Critical telescope maintenance and instrument improvements are being made in anticipation of a re-commissioning phase of DESI in November. Following this re-commissioning period, during which we will confirm that the instrument provides the same performance as it did pre-shutdown, we will start our Survey Validation phase. The team is excited and eager to once again start collecting data!

Matt Evatt and Patrick Dunlop practicing social distancing while preparing the Mayall telescope for on-sky DESI operations.

 

 

 

DESI Officially Completes Construction Phase

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On May 8, 2020, the DOE Energy Systems Acquisition Advisory Board (ESAAB) approved the CD-4 completion of construction for the DESI Project. It’s the culmination of 10 years of hard work by an incredibly dedicated and talented team and a major accomplishment for all involved. DESI is now the premier multi-object spectrograph and the first stage-IV dark energy experiment to go on-sky.

DESI Successfully Completes Commissioning Phase

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DESI commissioning has raced forward this winter, and we have now
demonstrated the key performance parameters of the instrument!
Since installation of the instrument, refinement of the performance of the 8 square
degree corrector, high-precision (10 micron) positioning of the
fibers under active feedback, accurate calibration of the spectrographs,
and on-sky commissioning of the whole user interface have been demonstrated.

All of this progress culminated in successful demonstration in March
of spectroscopy with the full DESI system of many tens of thousands
of survey targets. The image below is of a luminous red galaxy targets, easily revealing the distinctive Balmer-line signature of a post-starburst galaxy at redshift 1.286! See our blog for more details!

Remote Collaboration Meeting Successful!

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Due to growing travel restrictions and concerns regarding the COVID-19 outbreak, the DESI2020 Collaboration Meeting, originally scheduled for March 9-12 in Tucson, AZ, was held completely remotely. The online format of the meeting was very successful and many important discussions centered on early data from commissioning and preparing for the upcoming Survey Validation.

The picture shows a small group of collaboration members that were “stranded” in Tucson before travel restrictions were put in place. They practiced social distancing in the Sonoran Desert!

Congratulations to the laureates of the Nobel Prize in Physics 2019

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We learned this morning that James Peebles, Michel Mayor and Didier Queloz are sharing this year’s Nobel Prize in Physics!

The first half of the prize was awarded to James Peebles “for theoretical discoveries in physical cosmology”.

Peebles is very well known in our community for his work on the CMB, large-scale structure, dark matter, and galaxy formation, which has been foundational to much of modern cosmology. And most centrally to DESI, he was one of the people who dreamed up and predicted the baryon acoustic oscillations, decades before their discovery!

The other half of the prize is shared between Michel Mayor and Didier Queloz “for the discovery of an exoplanet orbiting an solar-type star”.

Mayor and Queloz are awarded for their first discovery of a planet orbiting a star outside our solar system. Another huge theme in modern astrophysics.

Congratulations to all three!

https://www.nobelprize.org/uploads/2019/10/press-physics2019.pdf

Finished Corrector

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The completed 6-lens corrector, weighing in at 8,900 pounds, will deliver a huge 8-square degree field-of-view. That’s a sixteen times larger field-of-view than the previous optics. The six hexapods bolted to the skirt will actively position the corrector to microns accuracy.