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m 3 observing 4 results toggle results subsection 4 1 cosmology 4 2 weak lensing 4 3 gravitational waves 4 4 dwarf galaxies 4 5 baryon acoustic oscillations 4 6 type ia supernova observations 4 7 minor planets 5 gallery 6 see also 7 references 8 external links toggle the table of contents dark energy survey 13 languages العربية deutsch español فارسی français galego italiano 日本語 한국어 português русский українська 中文 edit links article talk english read edit view history tools tools move to sidebar hide actions read edit view history general what links here related changes upload file permanent link page information cite this page get shortened url switch to legacy parser print export download as pdf printable version in other projects wikimedia commons wikidata item appearance move to sidebar hide from wikipedia the free encyclopedia project to measure the expansion of the universe the dark energy survey decam mounted on victor m blanco observatory as part of dark energy survey alternative names des website www darkenergysurvey org related media on commons edit on wikidata part of a series on physical cosmology big bang universe age of the universe chronology of the universe early universe inflation baryogenesis nucleosynthesis backgrounds gravitational wave gwb microwave cmb neutrino cnb expansion and future hubble s law redshift expansion of the universe flrw metric friedmann equations lambda cdm model future of an expanding universe ultimate fate of the universe components and structure components dark energy dark matter photons baryons structure shape of the universe galaxy filament galaxy formation large quasar group large scale structure reionization structure formation experiments black hole initiative bhi boomerang cosmic background explorer cobe dark energy survey planck space observatory sloan digital sky survey sdss 2df galaxy redshift survey 2df wilkinson microwave anisotropy probe wmap scientists aaronson alfvén alpher copernicus de sitter dicke ehlers einstein ellis friedmann galileo gamow guth hawking hubble huygens kepler lemaître mather newton penrose penzias rubin schmidt smoot suntzeff sunyaev tolman wilson zeldovich list of cosmologists subject history discovery of cosmic microwave background radiation history of the big bang theory timeline of cosmological theories category astronomy portal v t e the dark energy survey des is an astronomical survey designed to constrain the properties of dark energy it uses images taken in the near ultraviolet visible and near infrared to measure the expansion of the universe using type ia supernovae baryon acoustic oscillations the number of galaxy clusters and weak gravitational lensing 1 the collaboration is composed of research institutions and universities from the united states 2 australia brazil 3 the united kingdom germany spain and switzerland the collaboration is divided into several scientific working groups the director of des is josh frieman 4 the des began by developing and building dark energy camera decam an instrument designed specifically for the survey 5 this camera has a wide field of view and high sensitivity particularly in the red part of the visible spectrum and in the near infrared 6 observations were performed with decam mounted on the 4 meter víctor m blanco telescope located at the cerro tololo inter american observatory ctio in chile 6 observing sessions ran from 2013 to 2019 as of 2021 update the des collaboration has published results from the first three years of the survey 7 decam edit a sky full of galaxies 8 decam short for the dark energy camera is a large camera built to replace the previous prime focus camera on the victor m blanco telescope the camera consists of three major components mechanics optics and ccds mechanics edit dark energy camera imager and ccds at sidet the mechanics of the camera consists of a filter changer with an 8 filter capacity and shutter there is also an optical barrel that supports 5 corrector lenses the largest of which is 98 cm in diameter these components are attached to the ccd focal plane which is cooled to 173 k 148 f 100 c with liquid nitrogen in order to reduce thermal noise in the ccds the focal plane is also kept in an extremely low vacuum of 0 00013 pascals 1 3 10 9 atm to prevent the formation of condensation on the sensors the entire camera with lenses filters and ccds weighs approximately 4 tons when mounted at the prime focus it was supported with a hexapod system allowing for real time focal adjustment 9 optics edit the camera is outfitted with u g r i z and y filters spanning roughly from 340 1070 nm 10 similar to those used in the sloan digital sky survey sdss this allows des to obtain photometric redshift measurements to z 1 decam also contains five lenses acting as corrector optics to extend the telescope s field of view to a diameter of 2 2 one of the widest fields of view available for ground based optical and infrared imaging 6 one significant difference between previous charge coupled devices ccd at the victor m blanco telescope and decam is the improved quantum efficiency in the red and near infrared wavelengths 11 9 ccds edit the dark energy camera s 1 millionth exposure the 1 millionth exposure has been combined with 127 earlier exposures to make this view of the field the scientific sensor array on decam is an array of 62 2048 4096 pixel back illuminated ccds totaling 520 megapixels an additional 12 2048 2048 pixel ccds 50 mpx are used for guiding the telescope monitoring focus and alignment the full decam focal plane contains 570 megapixels the ccds for decam use high resistivity silicon manufactured by dalsa and lbnl with 15 15 micron pixels by comparison the omnivision technologies back illuminated ccd that was used in the iphone 4 has a 1 75 1 75 micron pixel with 5 megapixels the larger pixels allow decam to collect more light per pixel improving low light sensitivity which is desirable for an astronomical instrument decam s ccds also have a 250 micron crystal depth this is significantly larger than most consumer ccds the additional crystal depth increases the path length travelled by entering photons this in turn increases the probability of interaction and allows the ccds to have an increased sensitivity to lower energy photons extending the wavelength range to 1050 nm scientifically this is important because it allows one to look for objects at a higher redshift increasing statistical power in the studies mentioned above when placed in the telescope s focal plane each pixel has a width of 0 27 on the sky resulting in a total field of view of 3 square degrees 12 survey edit des imaged 5 000 square degrees of the southern sky in a footprint that overlaps with the south pole telescope and stripe 82 in large part avoiding the milky way the survey took 758 observing nights spread over six annual sessions between august and february to complete covering the survey footprint ten times in five photometric bands g r i z and y 13 the survey reached a depth of 24th magnitude in the i band over the entire survey area longer exposure times and faster observing cadence were made in five smaller patches totaling 30 square degrees to search for supernovae 14 first light was achieved on 12 september 2012 15 after a verification and testing period scientific survey observations started in august 2013 16 the last observing session was completed on 9 january 2019 13 other surveys using decam edit after completion of the dark energy survey the dark energy camera was used for other sky surveys dark energy camera legacy survey decals covers the sky below 32 declination not including the milky way this survey covers over 9000 square degrees 17 18 the desi legacy imaging surveys legacy surveys as of data release 10 includes decals bass and mzls it also incorporating additional decam data which means that it covers almost the entire extragalactic southern sky including parts of the magellanic clouds the purpose of the legacy surveys is to find targets for the dark energy spectroscopic instrument 18 19 dark energy camera plane survey decaps covers the milky way in the southern sky 20 simulated image of the decam ccd array at focal plane each large rectangle is a single ccd the green rectangle circled in red in the upper left corner shows the size of the iphone 4 camera ccd at the same scale observing edit the footprint of the wide area survey on the sky colored region in celestial coordinates the dashed curve shows the approximate location of the milky way disk in these coordinates each year from august through february observers will stay in dormitories on the mountain during a weeklong period of work observers sleep during the day and use the telescope and camera at night there will be some des members working at the telescope console to monitor operations while others are monitoring camera operations and data process for the wide area footprint observations des takes roughly two minutes for each new image the exposures are typically 90 seconds long with another 30 seconds for readout of the camera data and slewing to point the telescope at its next target despite the restrictions on each exposure the team also need to consider different sky conditions for the observations such as moonlight and cloud cover in order to get better images des team use a computer algorithm called the observing tactician obstac to help with sequencing observations it optimizes among different factors such as the date and time weather conditions and the position of the moon obstac automatically points the telescope in the best direction and selects the exposure using the best light filter it also decides whether to take a wide area or time domain survey image depending on whether or not the exposure will also be used for supernova searches 21 results edit cosmology edit constraints on a measure of the clumpiness of the matter distribution s8 and the fractional density of the universe in matter ωm from the combined 3 des y1 measurements blue planck cmb measurements green and their combination red dark energy group published several papers presenting their results for cosmology most of these cosmology results coming from its first year data and the third year data their results for cosmology were concluded with a multi probe methodology which mainly combine the data from galaxy galaxy lensing different shape of weak lensing cosmic shear galaxy clustering and photometric data set for the first year data collected by des dark energy survey group showed the cosmological constraints results from galaxy clustering and weak lensing results and cosmic shear measurement with galaxy clustering and weak lensing results s 8 σ 8 ω m 0 3 0 5 0 773 0 020 0 026 displaystyle s_ 8 sigma _ 8 omega _ m 0 3 0 5 0 773_ 0 020 0 026 and ω m 0 267 0 017 0 030 displaystyle omega _ m 0 267_ 0 017 0 030 for λcdm s 8 0 782 0 024 0 036 displaystyle s_ 8 0 782_ 0 024 0 036 ω m 0 284 0 030 0 033 displaystyle omega _ m 0 284_ 0 030 0 033 and ω 0 82 0 20 0 21 displaystyle omega 0 82_ 0 20 0 21 at 68 confidence limits for ωcmd 22 combine the most significant measurements of cosmic shear in a galaxy survey dark energy survey group showed that σ 8 ω m 0 3 0 5 0 782 0 027 0 027 displaystyle sigma _ 8 omega _ m 0 3 0 5 0 782_ 0 027 0 027 at 68 confidence limits and σ 8 ω m 0 3 0 5 0 777 0 038 0 036 displaystyle sigma _ 8 omega _ m 0 3 0 5 0 777_ 0 038 0 036 for λcdm with ω 0 95 0 36 0 33 displaystyle omega 0 95_ 0 36 0 33 23 other cosmological analyses from first year data showed a derivation and validation of redshift distribution estimates and their uncertainties for the galaxies used as weak lensing sources 24 the des team also published a paper summarize all the photometric data set for cosmology for their first year data 25 for the third year data collected by des they updated the cosmological constraints to σ 8 ω m 0 3 0 5 0 759 0 025 0 023 displaystyle sigma _ 8 omega _ m 0 3 0 5 0 759_ 0 025 0 023 for the λcdm model with the new cosmic shear measurements 26 from third year data of galaxy clustering and weak lensing results des updated the cosmological constraints to s 8 σ 8 ω m 0 3 0 5 0 776 0 017 0 017 displaystyle s_ 8 sigma _ 8 omega _ m 0 3 0 5 0 776_ 0 017 0 017 and ω m 0 339 0 031 0 032 displaystyle omega _ m 0 339_ 0 031 0 032 in λcdm at 68 confidence limits s 8 σ 8 ω m 0 3 0 5 0 775 0 024 0 026 displaystyle s_ 8 sigma _ 8 omega _ m 0 3 0 5 0 775_ 0 024 0 026 ω m 0 352 0 041 0 035 displaystyle omega _ m 0 352_ 0 041 0 035 and ω 0 98 0 20 0 32 displaystyle omega 0 98_ 0 20 0 32 in ωcdm at 68 confidence limits 27 similarly the des team published their third year observations for photometric data set for cosmology comprising nearly 5000 deg2 of grizy imaging in the south galactic cap including nearly 390 million objects with depth reaching s n 10 for extended objects up to i a b displaystyle i_ ab 23 0 and top of the atmosphere photometric uniformity 3mmag 28 weak lensing edit des s 2021 dark matter map 29 30 using weak gravitational lensing data set projected in the foreground of observed galaxies weak lensing was measured statistically by measuring the shear shear correlation function a two point function or its fourier transform the shear power spectrum 31 in april 2015 the dark energy survey released mass maps using cosmic shear measurements of about 2 million galaxies from the science verification data between august 2012 and february 2013 32 in 2021 weak lensing was used to map the dark matter in a region of the southern hemisphere sky 29 30 in 2022 together with galaxy clustering data to give new cosmological constrains 33 34 and in 2023 with data from the planck telescope and south pole telescope to give once new improved constraints 35 36 37 38 another big part of weak lensing result is to calibrate the redshift of the source galaxies in december 2020 and june 2021 des team published two papers showing their results about using weak lensing to calibrate the redshift of the source galaxies in order to mapping the matter density field with gravitational lensing 39 40 gravitational waves edit after ligo detected the first gravitational wave signal from gw170817 41 des made follow up observations of gw170817 using decam with decam independent discovery of the optical source des team establish its association with gw170817 by showing that none of the 1500 other sources found within the event localization region could plausibly be associated with the event des team monitored the source for over two weeks and provide the light curve data as a machine readable file from the observation data set des concluded that the optical counterpart they have identified near ngc 4993 is associated with gw170817 this discovery ushers in the era of multi messenger astronomy with gravitational waves and demonstrates the power of decam to identify the optical counterparts of gravitational wave sources 42 dwarf galaxies edit spiral galaxy ngc 895 image...
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