The main goal of the Observational Cosmology group at IFAE is to study the origin, evolution, and fate of the universe, and, in particular, to shed light on the nature of the mysterious dark energy, responsible for the current accelerated expansion of the universe.
The Observational Cosmology Group is led by R. Miquel.
The Dark Energy Survey (DES)
In 2005, IFAE joined the preparations for the Dark Energy Survey (DES), the current leading imaging galaxy survey, and designed and built most of the readout electronics of DECam, the DES camera. DES started taking data in 2012 and has now finished its observations. The group has concentrated its data analysis on weak gravitational lensing, potentially the most powerful probe of dark energy, and related measurements, achieving very high impact and leading key DES publications.
In particular, IFAE PhD students led two of the 12 so-called “essential” papers that led to the “key” paper with the cosmological constraints from the first year of DES observations (DES-Y1), published in 2018, which has already amassed over 600 citations. In DES-Y1, IFAE’s group led analyses in a number of cutting-edge topics: galaxy-galaxy lensing; photometric redshifts, including using a new technique based on angular cross-correlations; cosmic void science, including void lensing and cross-correlations with the cosmic microwave background (CMB) temperature and lensing maps; etc.
The IFAE group is (co-)leading several key projects for the cosmological results from the first three years of observations (DES-Y3), including the test and calibration of the measurements of the galaxy shapes for the weak lensing cosmological probe (probably the most crucial measurement in DES), mass mapping, cosmology from the moments of the mass distribution, and, again, photometric redshifts from cross-correlations, and cross-correlations between DES voids and CMB lensing. During these years, members of the group have (co-)led the all-important photometric redshift working group, the galaxy-galaxy lensing group (twice), the cosmic voids group, and the shear validation group, another critical group.
Along the way, the group has held multiple leadership positions within DES, including the chairmanship of both the speakers’ bureau and the builders’ committee, which proposes who has the right to sign all DES papers.
The PAU Survey (PAUS)
The group also led the construction, commissioning and operation of PAUCam, a novel narrow-band imager with quasi-spectroscopical resolution installed at the William Herschel Telescope (WHT) in La Palma in 2015. Since then, the camera has surveyed the sky for 216 nights with an operation efficiency higher than 98%. The group has led several key publications of the PAU Survey (PAUS), demonstrating that PAUCam achieves the expected photo-z resolution. PAU was an entirely Spanish project until it started operations at the WHT. Since then, 5 groups in 4 European countries have joined, providing funds for operations in exchange for data rights.
Baryon Oscillation Spectroscopic Survey (eBOSS)
With the recent arrival of Andreu Font-Ribera (AFR) to IFAE, the group has been also involved in the analysis of the recently completed extended Baryon Oscillation Spectroscopic Survey (eBOSS). AFR co-led two of its key publications, including the joint cosmological analysis from its final dataset, and will take a similar leadership role in DESI, a continuation of eBOSS.
Next generation galaxy surveys: Euclid, DESI & LSST
For the next decade, the group is well positioned with its participation in the three most powerful next generation galaxy surveys: the ESA Euclid satellite mission, where IFAE led the development, construction and characterization of the Filter-Wheel Assembly (FWA) of the Near Infrared SpectroPhotometer (NISP), IFAE’s first flight-model space hardware; the Berkeley-led Dark Energy Spectroscopic Instrument (DESI), where IFAE designed, built and commissioned the 10 Guiding, Focusing and Alignment (GFA) cameras, the only imaging instrument in DESI; and the Dark Energy Science Collaboration (DESC) of the Legacy Survey of Space and Time (LSST) at the Vera Rubin Observatory.
The IFAE cosmology group is currently formed by 4 staff scientists, 3 postdocs and 5 PhD students.
