DES is an international collaboration involving 10 institutions from the US, and six international consortia from Brazil, the UK, Germany, Switzerland, Australia and a consortium from Spain (CIEMAT-IFAE and the ICE), The collaboration will carry out a very large and deep photometric survey of 5000 deg2 of the southern sky in five bands in the visible and near infrared (g, r, i, Z, Y), with the aim of producing the first precise characterization of the properties of the dark energy using four complementary techniques:
• Galaxy-cluster studies in conjunction with the cluster survey, based on the Sunyaev Zel’dovich Effect, that will be performed simultaneously by the South Pole Telescope (SPT);
• Study of angular correlations of galaxies in redshift shells (measuring BAO);
• Measurement of the weak lensing shear of galaxies as a function of redshift;
• Measurement of the type-Ia supernovae luminosity distance vs. redshift relation, a more established technique.
To perform the survey, the DES Collaboration has built a wide-field (3 deg2) CCD camera (DECam), which is mounted at the prime focus of the 4-meter Blanco Telescope, located in Cerro Tololo (Chile). In return, DES is granted 30% of all the observation time for 5 years (2011-2015). The DECam project is mostly funded by the US Department of Energy (DOE). Initial approval (CD-0) was given in December 2005, while final approval and full funding (CD-3b) was secured in October 2008. The Survey data taking officially started in Sep 2013 (first light and SV in 2012) and is planed to finish in Feb 2018.
Map of dark matter, measured through weak lensing with Science Verification Data (DES Collaboration)
Aim of our participation
DES-Spanish groups (The Institute of Space Sciences (IEEC-CSIC), IFAE and CIEMAT/UAM) were funded by Plan Nacional since 2006 to participate in DES. The Spanish groups have collaborated very effectively and, acting as a single institution, have been able to take important responsibilities in the collaboration:
• DES-Spain had the responsibility for the design on most of, and the production and testing of all, the front-end electronics of the camera. Now we keep the responsibility of its operation and maintenance. The main responsibility was for IFAE and CIEMAT. The ICE provide some of the production electronics and contribute to the test-bench and test-camera to test ccd and electronics.
• The The Institute of Space Sciences has been responsible for production and testing of the star guider software.
• The Institute of Space Sciences is responsible for the production of the N-body dark matter simulations (MICE) used in the DES Data Challenges and science analysis
The above tasks make our contribution to DES very visible within the collaboration. Consequently, DES-Spain is well represented in all committees governing and making decisions for DES: Management Committee (E. Gaztañaga and R. Miquel), Membership Committee (E. Sánchez), Publications Committee (R. Miquel), Science Committee (F. Castander, M.Crocce, E. Gaztañaga), DES Builders Committee (E. Fernández), Co-coordination of Large Scale Structure Working Group (E. Gaztañaga, M.Crocce), Co-coordination of Photo-z Working Group (F. Castander, E.Gaztanaga), etc. Six members of ICE have the status of being DES builders. The Spanish institutions were the first to join the DES Collaboration from outside the US, following a procedure that has become the model for other institutions, in particular for those of the UK, Brazil, Germany, Switzerland and Australia.
During 2017 we publish first cosmological results from 1st year of DES dada (Y1). DES found constraints on the value of the amplitude of clustering and the amount of dark matter (and therefore dark energy, for a flat universe) which are comparable to the ones found in the Cosmic Background Radiation (Planck results) but at more recent times. The combination of both measurements provide the best cosmological constraints to date on those quantities and they agree well with the model with a cosmological constant. DES also provide follow-up and detection of optical images for the first gravitational wave measurements from LIGO and VIRGO. Our group also lead the first BAO (Baryon Acoustic Oscillations) detection with DES. In 2017 we complete the data reduction and start exploitation of year 3 data (Y3). This full data was made public on Jan 2018. We also completed year 5 of DES observations in early 2018. We are now planing for another half a year of observations in 2018 and the scientific exploitation of Y3.
Galaxy bias from the Dark Energy Survey Science Verification data: combining galaxy density maps and weak lensing maps Chang, C., Pujol, A.,
Gaztanaga, E., et al. 2016, MNRAS, 459, 3203
CMB lensing tomography with the DES Science Verification galaxies Giannantonio, T., Fosalba, P., Cawthon, R., et al. 2016, MNRAS, 456, 3213
Galaxy clustering, photometric redshifts and diagnosis of systematics in the DES Science Verification data Crocce, M., Carretero, J., Bauer, A. H., et al. 2016, MNRAS, 455, 4301
Senior Institute members involved
, F. Castander, M. Crocce, P. Fosalba