Galaxy IC 1613

Observational Cosmology Group

  • Observational Cosmology Group

    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.

    Dark Energy Camera (DECam) on Blanco Telescope, Cerro Tololo Observatory, Chile Credit: Reidar Hahn, Fermilab

    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.

    Blanco Telescope, Cerro Tololo Observatory, Chile Credit: DES Collaboration

    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.

    The PAU camera installed on the William Herschel telescope at the Roque de los Muchachos Observatory in La Palma, Canary Islands. Credit: IFAE

    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.

    Artist's impression of the Euclid spacecraft.
    Artist's impression of the Euclid spacecraft. Credit: ESA/ATG medialab (spacecraft); NASA, ESA, CXC, C. Ma, H. Ebeling and E. Barrett (University of Hawaii/IfA), et al. and STScI (background)
  • Group Members

    Observational Cosmology Group

    Staff Researcher

    • Enrique Fernández

      Enrique Fernández

    • Andreu Font-Ribera

      Andreu Font-Ribera

    • Ramon Miquel

      Ramon Miquel

    • Cristobal Padilla

      Cristobal Padilla

    Postdoc Researcher

    • Martin B. Eriksen

      Martin B. Eriksen

    • Malgorzata Siudek

      Malgorzata Siudek

    PhD Student

    • Laura Cabayol

      Laura Cabayol

    • Umut Demirbozan

      Umut Demirbozan

    • Giulia Giannini

      Giulia Giannini

    • Calum Gordon

      Calum Gordon

    • César Ramírez

      César Ramírez

  • International Collaborations

    Observational Cosmology Group


    The Dark Energy Survey

    The Dark Energy Survey (DES) is a visible and near-infrared survey that aims to probe the dynamics of the expansion of the Universe and the growth of large-scale structure.

      Victor Blanco Telescope in Coquimbo, Chile


    Physics of the Accelerating Universe

    The PAU (Physics of the Accelerating Universe) Survey goal is to obtain photometric redshifts (photo-z) and Spectral Energy Distribution (SED) of astronomical objects with a resolution roughly one order of magnitude better than current broad band photometric surveys.

      WHT Telescope, ORM, La Palma


    The Dark Energy Spectroscopic Instrument

    The Dark Energy Spectroscopic Instrument is a scientific research instrument for conducting a spectrographic astronomical surveys of distant galaxies. Its main components are a focal plane containing 5,000 fiber-positioning robots, and a bank of spectrographs which are fed by the fibers.

      Kitt Peak, Arizona, USA
    Artist's impression of the Euclid spacecraft.



    Euclid is a visible to near-infrared space telescope currently under development by the European Space Agency and the Euclid Consortium. The objective of the Euclid mission is to better understand dark energy and dark matter by accurately measuring the acceleration of the universe.



    Legacy Survey of Space and Time

    The Vera C. Rubin Observatory, previously referred to as the Large Synoptic Survey Telescope, is an astronomical observatory currently under construction in Chile. Its main task will be an astronomical survey, the Legacy Survey of Space and Time (LSST).

      Cerro Pachon, Chile
  • Research Projects

    Observational Cosmology Group



    ASTronomy EuROpean Infrared Detection

    ASTEROID is an EU funded H2020-COMPET project whose main objective is to provide Europe with the capability to manufacture high performance infrared 2k2 Focal Plane Arrays of 15 µm pitch pixels that can be used in scientific and astronomical space and ground telescope missions.



    Enabling Weak lensing Cosmology

    Enabling Weak lensing Cosmology (EWC) is a team of cosmologists working across Europe to prepare for the next generation of astronomical data that will come from the European Space Agency Euclid mission.

  • Selected Publications

    Observational Cosmology Group

    • L Sevilla-Noarbe et al.,
      The PAU survey: star-galaxy classification with multi narrow-band data,
      Monthly Notices Of The Royal Astronomical Society 483 (2019) [DOI]
    • Alarcon, A et al.,
      The PAU Survey: early demonstration of photometric redshift performance in the COSMOS field,
      Monthly Notices Of The Royal Astronomical Society 484 (2019) [DOI]
    • Sanchez, C et al.,
      More out of less: an excess integrated Sachs-Wolfe signal from supervoids mapped out by the Dark Energy Survey,
      Monthly Notices Of The Royal Astronomical Society 484 (2019) [DOI]
    • Castander F et al.,
      The Physics of the Accelerating Universe Camera,
      Astronomical Journal 157 (2019) [DOI]
    • Baxter E et al.,
      Cosmological lensing ratios with des Y1, SPT, and Planck,
      Monthly Notices Of The Royal Astronomical Society 487 (2019) [DOI]
    • Vielzeuf, P et al.,
      Dark Energy Survey Year 1 results: cross-correlation redshifts - methods and systematics characterization,
      Monthly Notices Of The Royal Astronomical Society 477 (2018) [DOI]
    • Sánchez C et al.,
      Dark Energy Survey year 1 results: Galaxy-galaxy lensing,
      Physical Review d 98 (2018) [DOI]
    • Sánchez C et al.,
      Galaxy bias from galaxy-galaxy lensing in the DES science verification data,
      Monthly Notices Of The Royal Astronomical Society 473 (2018) [DOI]
    • Clampitt J et al.,
      Cosmic voids and void lensing in the Dark Energy Survey Science Verification data,
      Monthly Notices Of The Royal Astronomical Society 465 (2017) [DOI]
    • Sánchez C et al.,
      Imprint of DES superstructures on the cosmic microwave background,
      Monthly Notices Of The Royal Astronomical Society 465 (2017) [DOI]
    • Troxel MA et al.,
      Redshift distributions of galaxies in the Dark Energy Survey Science Verification shear catalogue and implications for weak lensing,
      Physical Review d 94 (2016) [DOI]
  • Group News


    New Cosmology Group Publication

    April 14, 2021

    “The PAU survey: Estimating galaxy photometry with deep learning” by L. Cabayol et al. has been submitted to MNRAS.

    IFAE in the media

    Latest eBoss results published in Investigación y Ciencia

    January 13, 2021

    The outreach article “El mayor mapa tridimensional del universo” by Andreu Font-Ribera and collaborators at eBoss has been published in the latest issue of Investigación y Ciencia.


    New Comology group Publicaton

    November 11, 2020

    Dark Energy Survey Year 3 Results: Weak Lensing Shape Catalogue”, led by Marco Gatti, has been uploaded to arXiv as part of the upcoming DES year 3 cosmology analysis of galaxy clustering and gravitational lensing.


    ESA's Euclid milestone achieved

    September 9, 2020

    The Near-Infrared Spectrometer and Photometer (NISP) has been installed in the Pay Load Module of Euclid’s Flight Model. This is an important milestone for the instrument.

    Collaboration meeting

    LSST Dark Energy Science Collaboration (DESC) meeting

    July 22, 2020

    The LSST Dark Energy Science Collaboration (DESC) takes place online July 20-24, 2020.

    New IFAE Member

    Andreu Font-Ribera joins IFAE

    May 6, 2020

    Andreu Font-Ribera has joined the Cosmology group at IFAE as tenure-track Ramon y Cajal Researcher.