The Dark Energy Survey (DES) Project

Since 2005, a group at IFAE, alongside a group at ICE (Institut de Ciències de l’Espai) and another at CIEMAT (Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas) in Madrid, collaborates in the Dark Energy Survey (DES) international project, led by Fermilab (USA). The main goal of the project is to survey 5000 deg2 of the southern galactic sky, measuring positions on the sky, shapes and redshifts of about 300 million galaxies and 15000 galaxy clusters. Furthermore, another 10 deg2 of the sky will be repeatedly monitored with the goal of measuring magnitudes and redshifts of over 1000 distant type-Ia SNe. These measurements will allow detailed studies of the properties of the so-called “dark energy” that drives the current accelerated expansion of the universe.

To perform the survey, the DES Collaboration is building a large wide-field CCD camera (DECam) that will give images covering 3 deg2 on the sky. The camera, shown in Figure 1, will be mounted at the prime focus of the 4-meter Blanco Telescope, located in Cerro Tololo in Chile. In return, DES is granted 30% of all the observation time for 5 years (2011-2015).


Camera Diagram

Figure 1. A view of DECam, the camera being built by DES.


The three Spanish groups, financed by the Program of Astronomy and Astrophysics, which is part of the National Plan of I+D+I, will build the whole set of read-out electronics boards of DECam, and have designed three out of the four main boards: the Clock and Bias Board (CBB) at CIEMAT, and the Master Control Board (MCB) and the Transition Board (TB) at IFAE.


During 2008, IFAE finished the design of the first version of the TB, whose final design will be done at CIEMAT. IFAE then concentrated on the MCB, producing versions v1 and v1.1. After solving some synchronization issues, a first functional version of the MCB was delivered to FNAL in late 2008. It is shown in Fig. 2. The production and test of the whole complement of boards for DECam will take place during 2009.


Master Board Control

Figure 2. A view of one of the Master Control Boards (MCB) produced at IFAE.

In preparation for the analysis of DES supernova data, some members of IFAE, IEEC and CIEMAT joined in 2007 the program of spectroscopic monitoring of the SNe found in the Sloan Digital Sky Survey-II project, in a redshift range between 0.1 and 0.4. The group was awarded four full nights of observations in Fall 2007, which resulted in spectra of about 25 objects, including an extremely peculiar supernova, SN2007qd.

After reducing the data, producing flux-calibrated spectra that were sent to the central SDSS-II/SNe spectrum repository for their use in the common SDSS-II/SNe analyses, work started on the analysis and understanding of the properties of SN2007qd. The longer-term goal is to participate on the cosmological parameter analysis using the complete three-year data sample.


DES Graphic

Figure 3 shows the SN2007qd spectrum taken by IFAE members three days past maximum light, together with a synthetic spectrum that reproduces the most salient features of the data. Work is continuing analyzing this and three other SN2007qd spectra available.


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