DES The Dark Energy Survey

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DES - The Dark Energy Survey
The discovery that the expansion of the universe
is accelerating was the surprise that set the
initial research program of 21st century
cosmology.
The DES is the survey that drives the
construction of DECam, the new 3 sq-degree camera
on the Blanco 4m telescope at CTIO. The 5000
square degree area of DES will be surveyed twice
per year per filter over 525 nights. The galaxy
catalog will reach 24th magnitude in griz, and
have photometric redshifts with a dispersion of
sz 0.12 for all galaxies and sz 0.02 for
clusters out to z1.3. The survey overlaps the
Sunyaev-Zeldovich cluster survey of the South
Pole Telescope and the infrared survey of the
Vista Hemisphere Survey.
The DES survey area outlined on an extinction map
of the South Galactic Cap. Credit J. Annis
(Fermilab)

• DES combines 4 probes of Dark Energy
• Weak Gravitational Lensing using a 300M galaxy
  shear catalog
• Galaxy cluster counts as a function of redshift
  and mass out to to z 1.5
• Baryon Acoustic Oscillations using a 300M
  galaxy photometric redshift catalog
• Type 1a Supernova luminosity measurements of
  1000 SN at zlt1

A map of the spatial density of galaxies in a
DES photo-z slice at 0.3 lt z lt 0.4, as
predicted from the MICE simulations,
www.ice,cat/mice. Credit E. Gaztanaga (Spain DES
Collaboration ICE-IFAE-CIEMAT)
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The strength of the DES is in the ability to
combine and compare these four methods to
increase precision or to estimate systematic
errors. These four methods will let us explore
whether the Dark Energy is a cosmological
constant. They will let us use the difference
between the purely geometrical experiments (SN,
BAO) and the experiments based on the growth of
structure (WL, Clusters) to check whether we need
to modify Einsteins Field Equations by adding a
negative pressure component to the energy density
of the universe, or by modifying the theory of
gravity away from General Relativity.
In order to understand our four probes, we
believe an extensive simulation program is
needed. The extraction of our objects for study
affects the measurements in ways that if left
uncontrolled would lead to systematic errors.
The scientists of the DES use simulations to
evaluate our cosmological analyses. The DES
simulation program aims to build a suite of
simulations from a variety of sources the cover a
range of cosmologies and physical scales. Some of
these simulations are used directly to understand
the halo mass function, the non-linear power
spectrum, and the sensitivity to baryon content.
Others are sliced into time slices to create a
light cone output and have galaxies imprinted
onto them that reproduce such observables of the
real universe as spatial clustering, luminosity
and color distributions. These are analyzed
using the tools that will be used to analyze the
DES data set in order to learn about the
systematics of the experiments. From all of this
work comes the understanding our the DES data
that will underlie our confidence in our results.
A spatial slice from a simulated galaxy catalog.
Blue spheres show the location of massive dark
matter halos. Red dots show galaxies.Figure
credit M. Busha R. Wechsler (KIPAC/Stanford)
Image by image, 3 sq-degrees by 3 sq-degrees, we
will map the Southern Galactic cap and measure
the effects of Dark Energy on our Universe.
Corrected CCD data simulation. Figure credit H.
Lin (Fermilab)
Collaborating Institutions Fermilab, University
of Illinois at Urbana-Champaign, University of
Chicago, Lawrence Berkeley National Laboratory,
National Optical Astronomy Observatory, Spain DES
Collaboration, United Kingdom DES Collaboration,
University of Michigan, DES-Brazil Consortium,
University of Pennsylvania, Argonne National
Laboratory, Ohio State University, and Santa
Cruz-SLAC-Stanford DES Consortium
www.darkenergysurvey.org