Accelerated Cosmic Expansion and the Dark Energy Survey
Martin Crocce! Institute for Space Science (ICE CSIC, IEEC)!
26th International Conference on SUSY 2018 Barcelona 07/2018 Current cosmological model
• It is a “concordance” model although with some “tensions”! credit : NASA Measuring Dark Energy
1.5 Ω =0.2, w=-1.0 ➡ M Geometry: distance vs. redshift ! Ω =0.3, w=-1.0 M
ΩM=0.2, w=-1.5 1.0 (expansion history = SNIa, BAO)! ΩM=0.2, w=-0.5 r(z)
! 0 H ✦ redshift tells degree of expansion! 0.5 r(z) = ∫ dz'/H(z') ✦ light-travel distance = time! 0.0 0.0 0.5 1.0 1.5 2.0 ! € redshift z
➡ Dynamics: structure growth! Friemann, Turner and Huterer 1 (growth history = Weak Lensing, Clusters, RSD)! ! w=−1/3 ✦
growth rate depends on matter density! (today) δ
✦ (z)/ 0.1 ⟷ δ evolution in matter density ! w=−1 evolution in dark energy density
10.0 1.0 0.1 z we need both to disentangle GR vs DE ! distance Galaxy redshift surveys (measuring & correlating galaxy positions) have been very successful over the past decade or so
2dFGRS, SDSS, BOSS, VIPERS growth Galaxy redshift surveys (measuring & correlating galaxy positions) have been very successful over the past decade or so
2dFGRS, SDSS, BOSS, VIPERS Galaxy redshift surveys (measuring & correlating galaxy positions) have been very successful over the past decade or so
Limitation —> galaxies are not perfect tracers of the matter field : galaxy bias <—> degenerate with 8 or D(z) Weak Lensing source galaxies at • Matter distorts back- z ~ 1 ground galaxy shapes • Measure shapes to obtain “shear” catalog • Shear-shear correlations is an unbiased tracer of matter distribution
Observer : shapes have been “sheared” coherently by the large-scale structure
• Problems - Intrinsic Alignments, Baryon Physics, Shapes biases Weak Lensing technology has enabled accurate shape measurements • Matter distorts back- ground galaxy shapes • Measure shapes to obtain “shear” catalog • Shear-shear correlations is an unbiased tracer of matter distribution
!The “cosmic-shear” era! !2003-2008: Canada-France-Hawaii Legacy Survey: 154 deg2 ! ! 2014-2019: Hyper-Suprime Cam Survey, 1400 deg2 ! !2013-2018: Dark Energy Survey, 5000 deg2! ! 2011-2018: Kilo-Degree Survey, 1350 deg2 !4(&,#)<-'>&%6' )5!&,<&6'59'AB0-3'.)' Marisa Cristina(,)64*&'-'C!&-,*+' March, on behalf of the Dark Energy Survey Collaboration [email protected] "3-$&D'
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THE DARK ENERGY SURVEY SURVEY OPERATIONS LIGHT CURVES The median cadence for supernovae observa- • tions is 5 days. The vast majority of SN host galaxies will be • followed up spectroscopically with instruments on other telescopes to provide a host galaxy Figure 3: exposure times in each band for shal- redshift. low and deep fields For a more detailed overview of the survey • strategy, please see [2]
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3-*+"#&'%&-,#"#$' !"#$%&'&()*+' !&-,*+'"3-$&' =+).)3&.,"*' 0)!3)%)$"*-%' -#6'+43-#' (-,-3&.&,' (,)*&!!"#$'-.' !45.,-*.&6'7,)3' (+).)3&.,9' *%-!!">*-8)#')7' %"$+.*4,<&'>@#$' (-,-3&.&,!H'I455%&' !*-##"#$'.)'"6ͯ' "#7&,&#*&' /012' .&3(%-.&'"3-$&' 1/&?-' 6"-$,-3' 1/'*-#6"6-.&!''
6-.-':4-%".9' Figure 6: Two examples of light curves taken during the first part of the first observing season, *+&*;!'-#6' "#!&,8)#')7'7-;&' 1/'&<&#.!'.)' showing typical cadence. 3)#".),'("(&%"#&'' DATA QUALITY MONITORING Figure 4: A simplified overview of supernovae observations and data processing operations. The ulti- mate aim of taking SNe observations is to obtain constraints on the dark energy parameters w0,wa and ⌦⇤ Figure 1: Dark Energy Camera mounted on the Blanco 4m telescope. The Universe is getting bigger faster. Why? The Dark Energy Camera (DECam) is a specially The astonishing result of the late 1990s, show- commissioned new instrument mounted on the ing that the Universe is accelerating [6, 5], led to Blanco 4m telescope at the Cerro Tololo Inter- TOWARDS A HUBBLE PLOT aparadigmshiftincosmologyfromearlierCold American Observatory, Chile. DECam is a 570 Dark Matter (CDM) models of the Universe to megapixel camera which over the course of 525 the inclusion of dark energy, ‘Lambda’, giving us nights spread over five years will image 5000 -+*./*$01' the current ⇤CDM model of the Universe. Is Uni- square degrees of the southern sky. The Dark En- versal acceleration really caused by dark energy, ergy Survey is designed to find answers to ques- !"#$%&'()'$)"!*'+%,)' or is it due to modified gravity? Or some other tions about the nature of dark energy. explanation? The primary aim of the Dark Energy The Dark Energy Survey (DES) [8] will com- Survey is to put constraints on the dark energy bine data from observations of supernovae type Ia density ⌦⇤ and the dark energy equation of state (SNeIa), weak lensing, large scale structure and Dark Energyw (zSurvey).Thenatureofdarkenergyandthecause galaxy clustering to put robust constraints on the overview of the acceleration of our Universe is one of ‘the dark energy parameters of interest. most fundamental questions in astrophysics’ [1]. • Wide Optical and near IR survey (grizY bands)! • 525 nights over 5 seasons in 5 imaging bands! Figure 7: Fake supernovae are inserted into the di↵erence imaging pipeline to monitor the e ciency • 5000 deg2 of which 2500 overlap with South Pole Telescope ! of the pipeline. LH plot: number of fake SN recovered as a function of magnitude; RH plot: signal FIELD LOCATIONS to noise ratio of the fixed magnitude fake SN. (Shallow fields, single night) • i-band magnitud limit ~24 at S/N=10, largest survey at this sensitivity ! • 30 deg2 in time domain, SN fields visited at least once per week Figure 2: Locations of DES SN shallow (C1,C2,E1,E1,X1,X2) and deep (C3,X3) fields. OUTLOOK Ten di↵erent fields are visited in the DES SN DES observing began in September 2013, we are spectroscopic redshifts for the bulk of those SN. Observations will finish! • survey: eight shallow fields and two deep fields, by end of this year now nearly 2/3 of the way through the first sea- Science verification data is currently available to with which to calibrate the eight shallow fields. Figure 5: A glimpse of a preliminary Hubble plot. For the purposes of blinding, no numbers are son, data quality looks good. Over the next five the public and raw data from season 1 will be Cosmology from Y1! Each field is 3 square degrees. years DES will yield a photometric survey with made available one year from the date on which • ⇠ shown on the vertical axis. (hash regions) published Each field lies within the area of the wider DES around 3500 well sampled SN light curves, and it was taken. For more information please visit • survey and each has been chosen for it’s over- The plot shows a subset of 70 photomet- cosmological analysis. additionally we anticipate having the host galaxy http://www.darkenergysurvey.org • rically classified [7] SNe Ia which⇠ have host lap with other surveys which can provide useful [5] S. Perlmutter et al. Measurements of Omega and Lambda from 42 high redshift supernovae. Astrophys.J., ancillary data. galaxy spectroscopic redshifts. Light curves were fitted using SNANA [3] and References 517:565–586, 1999. The Supernova Cosmology Project. • [1] Andreas Albrecht et al. Report of the Dark Energy Task Force. astro-ph/0609591, 2006. [6] A. G. Riess et al. Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Basic ‘forced photometry’ is used here, not the distance moduli are estimated using salt2mu Constant. Astronomical Journal, 116:1009–1038, September 1998. [2] J. P. Bernstein et al.. Supernova Simulations and Strategies for the Dark Energy Survey. Astrophys. J. , • 753:152, July 2012. full ‘final photometry’ that will be used in the [4] [7] M. Sako, et al. Photometric Type Ia Supernova Candidates from the Three-year SDSS-II SN Survey Data. [3] Richard Kessler et al. Snana: A public software package for supernova analysis. arXiv:0908.4280, Aug 2009. Astrophys. J. , 738:162, September 2011. [4] John Marriner et al. A MORE GENERAL MODEL FOR THE INTRINSIC SCATTER IN TYPE Ia SUPERNOVA DISTANCE MODULI. October, 72(1), 2011. [8] The Dark Energy Survey Collaboration. The Dark Energy Survey. ArXiv Astrophysics e-prints, October 2005. Dark Energy Survey
Weak lensing (distance, structure growth)! shapes of 200 millions galaxies robust combination of probes
Baryonic acoustic oscillations (distance)! 300 millions galaxies to z=1 and beyond → shared photometry/footprint → shared analysis of systematics Galaxy clusters (distance, structure growth)! hundred of thousands of clusters up to z~1! → shared galaxy redshift estimates synergies with SPT, VHS
Type Ia supernovae (distance)! 30 sq. deg. SN fields! 3000 SNIa to z~1
Cross-correlations! Strong Lensing (distance)! Galaxies and WL x CMB lensing 30 QSO lens time delays! Arcs with multiple source redshifts Chang et al (arxiv 1708.01535) DES Year 1 Projected Dark-Matter
from 23 million galaxy shapes measured over 1300 deg2 Chang et al (arxiv 1708.01535) DES Year 1 Projected Dark-Matter
Light traces mass !!
+ Clusters over-imposed
from 23 million galaxy shapes measured over 1300 deg2 dark matter field galaxy clustering cosmic shear 2 2 2 wgal gal b D (z) 3x2pt wshear shear D (z)
gal-gal lensing
2 wgal shear b D (z) DES Y1 cosmology over 1321 deg2
sources
lenses
Lens sample •600,000 red sequence galaxies Accurate photo-z, optimal for clustering Source Sample •Metacalibration 26 Millon shapes! Two independent shape measurements ! •Im3shape 18 M. shapes pipelines (different systematics & assumptions) DES Y1 gal-gal clustering • 5 lens bins (660,000 red galaxies with ~ 1%~2% redshift error),
5:00h 4:00h 3:00h 2:00h 1:00h 0:00h 23:00h 2.00 –25
–30
1.75 –35 ] –2 –40 1.50 [arcmin
–45 gal n
1.25 Elvin-Poole, Crocce, Ross et al 2017 ! –50 (arxiv 1708.01536) 1.00 DES Y1 shear-shear correlations
Shapes of galaxies are Spin-2 quantities. Sum and difference of the product of the tangential and cross components of the shear (ellipticity) w.r.t line connecting pairs of galaxies.
amplitude and growth! rate of structure
Geometry (distances or expansion) DES Y1 shear-shear correlations • 10 two-point correlations (26 million sources)
Total S/N = 26.8
Troxel et al 2017 (arxiv 1708.01538) • Another 10 for xi_minus DES Y1 gal-gal lensing • 20 correlations Prat, Shanchez et al 2017 (arxiv 1708.01537)
+ similar with im3shape 3x2 Y1 DES Cosmological Analysis
45 different 2-pt correlations, 457 data-points
[1] Marginalizing over! ! •6 (+w) cosmological parameters! • including neutrino mass ! •7 astrophysical parameters (bias, IA)! •13 systematic parameters (shear and photo-z! calibration)
[2] Data and analysis validation! extended over two years (blinded)! ! [3] Almost every step is doubled implemented! (two shear pipelines, two analysis pipelines, ! two photo-z calibrations, two simulations ! sets, two likelihood samplers)! DES Collaboration (arxiv 1708.01530) [1] Internal consistency : 3x2pt
• Remarkable agreement of lensing and galaxy clustering! ! S8 •Most precise cosmology from LSS alone to date! ! •Combination of clustering and weak lensing (3x2pt) improves constrains from them alone ( ~ factor 2) ! • First constrain on Intrinsic Alignments Amplitude from optical data, and galaxy bias ~10 % even fully marginalised DES Collaboration (arxiv 1708.01530) [2] wCDM • DES alone does not favor wCDM
+0.20 w = 0.80 0.22 (68% CL) P (D wCDM) Rw = P (D| CDM) =0.36 | [3] From high-z to low-z the Universe at its two extremes
Consistent and comparable constrains between LSS and CMB! ! • LCDM works
6 billion yrs. ! apart ! [3] From high-z to low-z the Universe at its two extremes
Combining DESY1 + Planck (w/lensing) + BAO + JLA —> most stringent constrains so far of large-scale structure related parameters
wCDM :
Introducing w is not formally favoured DES Collaboration (arxiv 1711.00403) [4] H0 tension DES+BAO+BBN
• DES constrains on Om combined with BAO and BBN can constrain H0 ! •5 totally independent measurements of H0! •As such the distribution ! is consistent at 2.1 sigma BAO in DES-Y1
•Measuring galaxy clustering on the largest scales, optimised sample (1380 sq deg) ! •4% measurement of angular diameter distance to z ~ 0.8! •Expect a 2% in Y3 (early next year) DES Collaboration (arxiv 1712.06209) Cluster cosmology in DES-Y1 results coming soon
Cluster abundance sensitive to dark energy. Challenge is mass / obs relation! Summary results coming soon
•Weak lensing surveys are here to stay, robust and consistent results together with galaxy clustering! •DES have stress tested Planck’s LCDM, two extreme moments of the universe!
•Some tensions remaining (H0), stay tuned of DES Y3 results next year