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''The Dark Energy Survey'' (DES) is an optical/near-infrared survey that aims to probe the dynamics of the expansion of the Universe and the growth of large scale structure. The collaboration is composed of research institutions and universities from the United States,〔(DES Collaboration Page ), DES Collaborators.〕 Brazil,〔(DES-Brazil ), DES-Brazil Consortium.〕 the United Kingdom, Germany, Spain, and Switzerland. The survey uses the 4-meter Victor M. Blanco Telescope located at Cerro Tololo Inter-American Observatory (CTIO) in Chile, outfitted with the newly designed, state-of-the-art Dark Energy Camera (DECam).〔(DES Collaboration Page - Camera ), DECam.〕 This camera allows for more sensitive images in the red part of the visible spectrum and in the near infrared, in comparison to previous instruments.〔 DECam has one of the widest fields of view (2.2-degree diameter) available for ground-based optical and infrared imaging.〔 The survey will image 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 will take five years to complete, and the survey footprint will nominally be covered te times in five photometric bands (''g'', ''r, i, z'', and ''Y''). DES officially began in August 2013 and completed its second season in February 2015. ==Overview== The Dark Energy Survey investigates the dynamics and large scale structure of the Universe using four probes: Type Ia supernovae, baryon acoustic oscillations (BAO), the number of galaxy clusters, and weak gravitational lensing. Type Ia supernovae are believed to be thermonuclear explosions that occur when white dwarf stars in binary systems accrete mass from their companion stars.〔(News about Flash Code ) News about the first 3D successful simulation of a type IA supernova.〕 These events are important for the study of cosmology because they are very bright, which allows astronomers to detect them at very large distance. The expansion of the universe can be constrained based on observations of the luminosity distance and redshift of distant type IA supernova. The other three techniques (BAO, galaxy clusters, and weak lensing) used by the Dark Energy Survey allow scientists to understand simultaneously the expansion of the universe and the evolution of the dark matter density field perturbations. These perturbations were intrinsically tied to the formation of galaxies and galaxy clusters. The standard model of cosmology assumes that quantum fluctuations of the density field of the various components that were present when our universe was very young were enhanced through a very rapid expansion called inflation. Gravitational collapse enhances these initial fluctuation as baryons fall into the gravitational potential field of more dense regions of space to form galaxies. Nevertheless, the growth rate of these dark matter halos is sensitive to the dynamics of the expansion of the Universe and DES will use this connection to probe the properties of that expansion. DECam, the new camera installed at the Victor M. Blanco Telescope by the DES collaboration, brings new observational possibilities that were not available for previous surveys, such as the Sloan Digital Sky Survey. One significant difference between previous CCD at the Victor M. Blanco Telescope and DECam is the improved quantum efficiency in the red part of the visible spectra and in the near infrared.〔http://proceedings.spiedigitallibrary.org.proxy.lib.umich.edu/proceeding.aspx?articleid=1362394〕〔(DECam Presentation ), Pdf Presentation about the specific details about how a CCD device works and about the specific properties of the DECam, made by a Fermilab specialist.〕 This is a very important property for the observation of very distant sources, like Type IA supernovae or galaxy cluster, because the expansion of the universe shifts the photons emitted from a given source towards redder wavelengths. On the other hand, Silicon, which is the main element used to make CCDs, becomes transparent for infrared light, and this issue made the development of the DECam CCD a technological challenge.〔〔 The director of DES is ( Josh Frieman ) and the collaboration is composed of many research institutes and universities. The DES collaboration itself is divided into a number of science working groups. Some of the primary working groups are: the weak lensing working group, the galaxy clusters working group, the large-scale structure working group, the supernova working group, the galaxy evolution working group, and the strong lensing working group. Other science topics include simulations, calibration, photometric redshifts, quasars, and Milky Way science. A large responsibility of the DES collaboration was the mechanical, electronic and optical development of the DECam. The collaboration has a website,〔(The Project - The Dark Energy Survey Collaboration ), The DES Project Site.〕 where scientist can release new results, presentations and articles. Some of the releases in this website are open for the general public. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「The Dark Energy Survey」の詳細全文を読む スポンサード リンク
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