Science from overlapping lensing / spec-z surveys. Chris Blake (Swinburne)

Transcription

1 Science from overlapping lensing / spec-z surveys Chris Blake (Swinburne)

2 Probes of the cosmological model How fast is the Universe expanding with time? How fast are structures growing within it?

3 Redshift-space distortions RSD allow spectroscopic galaxy surveys to measure the growth rate of structure infalling galaxies virialized motions coherent flows observer

4 Why combination of lensing and RSD? Sensitive to theories of gravity in complementary ways General perturbations to FRW metric: are metric gravitational potentials, identical in General Relativity but can differ in general theories Relativistic particles (e.g. light rays for lensing) collect equal contributions and are sensitive to Non-relativistic particles (e.g. galaxies infalling into clusters) experience the Newtonian potential

5 Applications arxiv: CFHTLenS: Testing the Laws of Gravity with Tomographic Weak Lensing and Redshift Space Distortions 12 Fergus Simpson 1, Catherine Heymans 1, David Parkinson 2, Chris Blake 3, Martin Kilbinger 4,5,6, Jonathan Benjamin 7, Thomas Erben 8, Hendrik Hildebrandt 7,8, Henk Hoekstra 9,10, Thomas D. Kitching 1, Yannick Mellier 11, Lance Miller 12, arxiv: Confirmation of general relativity on large scales from weak lensing and galaxy velocities 1 Reinabelle Reyes 1, Rachel Mandelbaum 1, Uros Seljak 2-4, Tobias Baldauf 2, James E. Gunn 1, Lucas Lombriser 2, Robert E. Smith 2

6 Overlaps of lensing and spec-z surveys Improvement of cosmological measurements through addition of galaxy-galaxy lensing [e.g. determines bias of lens sample which improves RSD measurements of lenses, especially when using multiple-tracer techniques, e.g. Cai & Bernstein (2012)] Spec-z survey allows definition of lens samples (e.g. groups, galaxy types) enabling a range of studies Understanding, calibration and risk mitigation of systematic errors (photo-z errors including outliers, intrinsic alignments, cosmic shear)

7 Overlaps of lensing and spec-z surveys Mis-match between imaging and spectroscopic surveys!

8 Overlaps of lensing and spec-z surveys w a Many recent 31 July papers 2013 considering impact for cosmology of same-sky vs. different-sky lensing/spec-z surveys !1!2!3!4!5!2!1.5!1!0.5 0 w 0 ee FoM = 1.6 nn FoM = 0.9 ee + nn FoM = 7.2 ee + ne + nn FoM = ee MGFoM 1 INTRODUCTION = 0.3 nn MGFoM = 0.6 For me a key issue is systematic error control ee + The nn MGFoM era of precision = 50.1 cosmology is now a reality. Different arxiv: v1 [astro-ph.co] 30 Jul 2013 Donnacha Kirk 1, Ofer Lahav 1, Sarah Bridle 2, Stephanie Jouvel 3, Filipe B. Abdalla 1, Joshua A. Frieman 4 1 Department of Physics & Astronomy, University College London, Gower Street, London, WC1E 6BT, UK 2 Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK 3 Institut de Ciències de l Espai (ICE, IEEC/CSIC), E Bellaterra (Barcelona), Spain 4 Fermilab Center for Particle Astrophysics, Batavia, IL Kavli Institute for Cosmological Physics, The University of Chicago, Chicago, IL arxiv: v1 [astro-ph.co] 30 Jul 2013 ABSTRACT The combination of multiple cosmological probes can produce measurements of cosmological parameters much more stringent than those possible with any individual probe. Mon. Not. R. Astron. Soc. 000, 1 21 (2009) Printed 31 July 2013 (MN LATEX style file v2.2) Weon examine deviations the combination from GRof and two highly the arxiv: final correlated jointprobes constraint of late-time withstructure growth: (i) weak gravitational lensing from a survey with photometric redshifts and (ii) cross-correlations galaxy clustering andis redshift over space an order distortions of magnitude from a survey smaller with spectroscopic in redshifts. Optimising termswe of MG choose Spectroscopic FoM generic than survey when designs and RSDs Photometric soare thatincluded. our results Galaxy are applicable to a range Surveys: of In current the Same-sky following and future Benefits photometric sub-sections for redshift we Dark perturb (e.g. Energy KiDS, in turn DES, and ahsc, range Modified Euclid) and spectroscopic redshift (e.g. DESI, 4MOST, Sumire) surveys. 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9 Photometric redshift calibration Photometric redshift errors are one of the leading systematics for weak lensing tomography Mean and width of redshift distributions in each photo-z bin must be known to accuracy ~ 10-3 Method (1) : spectroscopic training set [issues : sample variance, incompleteness of training set, outliers] Method (2) : photo-z/spec-z cross-correlations [issues : degeneracies with galaxy bias, cosmic magnification] Can OzDES currently help with either method?

10 Photometric redshift calibration Training set method : suppressing sample variance systematic for DES weak lensing requires 100 AAOmega pointings or 5 VIPERS surveys! Phot-z/spec-z cross-correlation method : need ~50,000 spec-z s per unit redshift -- can use 2dFGRS, SDSS, BOSS at z < 0.6 and VIPERS at z > 0.6? OzDES is not currently transformational for this science, but photo-zs are still useful for other largescale structure topics with less stringent requirements

11 Future AAT proposals? OzDES-wide proposed in March 2013 (150 nights, 3000 deg 2 coverage) - not approved Issue (1) : time now allocated to other projects (SAMI, OzDES-deep) - only nights/semester remain? Issue (2) : can only observe DES fields in B semesters Issue (3) : need to map > 1000 deg 2 to be competitive (e.g. existing RCS2, future HSC projects) Current status : musing on competitiveness of 2014B proposal targetting KiDS, later widening to DES?