Constraining Dark Energy with Redshift Surveys Matthias Steinmetz (AIP)

June The Dark Side of the Universe Overview  Astronomical measurements of the cosmic equation of state  Baryonic oscillations  Dark energy survey design using large numerical simulations of the cosmic web  Some projects to measure w(z)  SDSS/BOSS  HETDEX  eRosita

Astronomical Measurements of the Cosmic Equation of State

June The Dark Side of the Universe w(z) enters only into H(z), the local Hubble parameter (assuming k=0): Measuring w(z) evolution Thus, the most direct way to get w(z) is to measure H(z). Dark Energy equation of state:

June The Dark Side of the Universe Measuring w(z) evolution Hubble Parameter Comoving Distance Luminosity Distance Angular Diameter Comoving Volume Age of Universe Baryonic Oscillations Weak Lensing SNIa Baryonic Oscillations Galaxy Clusters Age of oldest objects

June The Dark Side of the Universe Measuring w(z) with BAO © Tegmark

June The Dark Side of the Universe Baryonic oscillations © Tegmark

June The Dark Side of the Universe Eisenstein et al (2005) see baryonic oscillation in SDSS WMAP3 measures 148 ± 3 Mpc

Dark Energy Survey Simulations Using Large Numerical Simulations of the Cosmic Web

June The Dark Side of the Universe The challenge  Sampling volume required V=10 Gpc 3  Current capability of large supercomputers N= ⇒ m p = 3.6×10 10 M ⊙  Dark halo mass of a typical tracer M halo = M ⊙ ≈ 30m p

June The Dark Side of the Universe

June The Dark Side of the Universe

June The Dark Side of the Universe

June The Dark Side of the Universe © Gottlöber (AIP)

June The Dark Side of the Universe ● dark matter ■ DM halos (via friends of friends) Wagner et al 2007

June The Dark Side of the Universe ● dark matter ■ DM halos (via friends of friends)

June The Dark Side of the Universe ● dark matter ■ DM halos (via friends of friends)

June The Dark Side of the Universe

June The Dark Side of the Universe From Power Spectrum to Constraints  Scale of the sound horizon: WMAP3 measures 148 ± 3 Mpc  Measure the wavelength in both transverse and radial direction  Get r s from WMAP, and δ θ and δ z from data, which then determines both the angular diameter distance and local Hubble constant.

June The Dark Side of the Universe Effects disturbing the oscillations Physical  Non-linear evolution  Galaxy bias Statistical Cosmic Variance Cosmic Variance Shot noise Shot noise Observational Redshift distortion Redshift distortion Wrong cosmology Wrong cosmology Light-cone effect Light-cone effect Wagner et al. 2007

June The Dark Side of the Universe From the simulation to the equation of state parameter w X 1.Generating the initial power spectrum P 0 and running a toy simulation in a 1.5 Gpc/h box with w X = -1 2.Calculating the “observed” redshifts from a past light-cone around redshift z=3 and z=1 3.Determining from these redshifts the positions assuming a reference cosmology with w≠-1 3.Calculation of the power spectrum and fitting it with the initial power spectrum P 0 + parameters (bias, shot noise and especially w X )

June The Dark Side of the Universe Dependence on reference cosmology w ref =-1.2 w ref =-1 w ref =-0.8

June The Dark Side of the Universe Redshift distortion redshift space real space

June The Dark Side of the Universe Sensitivity for 1 million tracers in a 7.5Gpc 3 volume at z=3, b=3.5

June The Dark Side of the Universe Results  Light-cone effects are negligible  Scaling factors approximation for wrong reference cosmology works fine  Peculiar velocities disturb the oscillations slightly but reduce the error if shot noise is not negligible  With currently planned redshift surveys, constraints of d A (z) and H(z) at the 1% level are possible, resulting in constraints on w at the few per cent level.

Some projects to measure Dark Energy

June The Dark Side of the Universe PROJECTCOLLABOR ATORS DATECOSTDark Energy Evolution JDEMDoE, NASA20181 billionNo LSSTNSF, 8 Universities billionNo BOSSSDSS collaboration millionYes WFMOSGemini, 7 Countries millionYes HETDEXTexas, HET, AIP millionYes DESNSF, DoE, 6 Universities millionNo PanStaars eRosita Hawaii, Munich, USAF Russia, DLR, PPARC million 25 million No Major Advance to Dark Energy Minor Advance

June The Dark Side of the Universe Baryon Oscillation Spectroscopic Survey (BOSS)  New program for the SDSS telescope for 2008– ,000 deg 2 of new spectroscopy from SDSS imaging.  Other aspects of the program include stellar spectroscopic surveys for Galactic structure and a multi-fiber radial-velocity planet search.  Collaboration now forming.

June The Dark Side of the Universe Baryon Oscillation Spectroscopic Survey (BOSS)  New program for the SDSS telescope for 2008– ,000 deg 2 of new spectroscopy from SDSS imaging.  1.5 million luminous red galaxies to z = 0.8, including 4x more density at z < 0.5.  7-fold improvement on large-scale structure data from entire SDSS survey, measure the distance scale to better than 1% at z = 0.35 and z = 0.6.  Ly  forest acoustic oscillations from grid of over 100,000 z > 2.2 quasars.  Mild upgrades to the spectrographs to reach 1000 fibers per shot and more UV coverage.

June The Dark Side of the Universe HETDEX with VIRUS

June The Dark Side of the Universe Operational principle of IFU

June The Dark Side of the Universe Layout of 145 IFUs  >35000 fibers  >14 million resolution elements per exposure  Layout with 1/9 fill factor is optimized for HETDEX  IFUs are separate, so can be reconfigured into denser pattern 20’ dia field New HET wide field corrector FoV0.22 sq. arcmin per raster of 3 exposures 1 IFU with 246 fibers 145 IFUs with fibers

June The Dark Side of the Universe HETDEX will survey two huge areas on the sky to create the largest map yet of the distribution of galaxies HETDEX will measure the expansion history of the Universe with 1% precision, allowing us to measure the properties of Dark Energy for the first time The largest volume ever surveyed The total area is equivalent to 1000 times the area of the moon

June The Dark Side of the Universe We need to understand the required number of IFUs and field size. Each line is a 100-night survey, with field size of 16, 18, and 20 arcminute diameter. 1.0% accuracy is our goal and will set HETDEX apart from all other dark energy missions. The uncertainty scales by the sqrt(# of nights). Field Size and Design Study

June The Dark Side of the Universe From data to w(z)

June eROSITA Schematic view –7 mirror systems (  35 cm each) –energy range keV –PSF  20  (FOV averaged) and  15  on axis –energy resolution 130 eV at 6 keV –effective area 2500 cm 2 –a grasp of  700 cm 2 deg 2 at 1 keV eROSITA (MPE, Germany) Reference to “eROSITA: an extended X-ray survey telescope” – P.Predehl, et. al. (SPIE )

June –First all sky survey ( keV) with record sensitivity, energy and angular resolution  Registration of hot interstellar medium in ~ 100 thousand galaxy clusters and groups (Large scale structure of the Universe, DE, N(z), P(k), baryonic wiggles)  Systematic registration of all obscured accreting Black Holes in nearby galaxies and many (~million) new distant AGN (study coeval evolution of Black Holes and galaxies)  X-ray and optical follow-up of selected sources –Launch in time frame on Soyus-2 Scientific goals eROSITA

June

June The Dark Side of the Universe Dark Energy Summary  Baryonic Oscillations are a key tool to constrain properties of dark energy  Current redshift survey have the potential to constrain w(z) at the few per cent level  Planck+HETDEX+BOSS et al  Gauge diameter distance scale from z=0 to z=1100, complement to relative distance scale via supernovae  Overlapping regions in redshift for different surveys