Giovanni Covone University Federico II, Naples, Italy November 19, 2014 NAOC Observatory Colloquium

Transcription

1 Stacked weak gravitational lensing: constraining galaxy clusters structure and cosmological parameters Giovanni Covone University Federico II, Naples, Italy! November 19, 2014 NAOC Observatory Colloquium

2 Summary! Why weak gravitational lensing? Stacked weak lensing by galaxy clusters in CFHTLenS: 1.the halo bias term 2. new constraints on the cosmological parameters 3. the c(m) at z~1 and z~0.3 Next step: weak lensing with the VLT Survey Telescope (VST)

3 What is Weak Gravitational Lensing

4 a short introduction to lensing (1) deflection angle source plane angular-diameter distance lens plane - measure total mass (baryonic + DM);! - well known physics (weak field limit General Relativity)! - no need to assume dynamical equilibrium!

5 a short introduction to lensing (2) first order effects: deflection of light and multiple images Galaxy Cluster SDSS J

6 a short introduction to lensing (2) first order effects: deflection of light and multiple images second order effect: differential deflection of an extended source, distortion.

7 a short introduction to lensing (2) first order effects: deflection of light and multiple images second order effect: differential deflection of an extended source, distortion. The deflection angle is a gradient of the (projected) Newtonian potential

8 Gravitational lensing effect, locally Convergence: isotropic magnification Shear: anisotropic stretching they are second derivatives of the lensing potential Much smaller of typical galaxy ellipticities!! You need a statistical approach

9 weak lensing by galaxy clusters

10 Why gravitational lensing?

11 Why gravitational lensing? What are the essential questions in fundamental cosmology? Which one can be tackled with astronomical techniques? Which methods? time scale: ~15 years

12 Why gravitational lensing? (1) What generated the baryon asymmetry? (2) What is the dark matter? (3) What is the dark energy? (4) Did inflation happen? (5) Is standard cosmology based on the correct physical principles? Euclid space mission

13 Characterising the LSS: Measurement of the halo bias Covone et al. (2014)

14 the large-scale distribution of matter Cosmological N-body simulations: DM large scale distributions Telescopes: distribution of baryons (galaxies, clusters of galaxies)

15 what is the halo bias Matter is not uniformly distributed Galaxy clusters halos are biased tracers of the underlying matter distribution. Simplified fluctua/on field with short + long wavelength (Peacock 2003)

16 what is the halo bias The halo bias is a measure of the correlated distribution of matter around galaxy clusters (White et al. 1987)

17 two terms in stacked shear profile by clusters Stacked lensing or shear-cluster cross-correlation on small scales, shear close to cluster center is dominated by the mass of the average cluster (e.g, first halo term) at large scales, the correlation between mass and clusters distribution is measured; this can be used to measure the bias factor (as function of scale; e.g. the second halo term).

18 The second-halo term 2-halo term in the mass density profiles, at scales lager than 10 Mpc. rms fluctuation in the mass distribution on scales of 8/h Mpc

19 shear contribution by the second-halo term Oguri & Takata (2011)

20 shear contribution by the second-halo term mass density at z, cluster halo parameters second order Bessel function dependence on linear power spectrum no contribution from uncorrelated matter distribution along the line of sight

21 How to measure it? The signal from the 2-halo term too low to be measured around individual clusters Method: statistically superposition of the shear signal around many (similar) clusters, to get the mean tangential shear Galaxy clusters are binned according to some observable quantity (richness, luminosity,, but not WL mass!) We also obtain the mean density profile of clusters

22 Previous results: Johnston et al. (2009) SDSS data, ~10^5 clusters local sample, below z~0.1

23 the data: CFHTLenS public CFHTLenS catalog state-of-art shear measurements from the group (lensfit, Miller et al. 2013) ugriz observations over 154 sq. deg. (4 fields) zphot measurements; accuracy 0.04 (1 + z); catastrophic outlier rate of about 4%.

24 the cluster catalog Wen et al. (2012) catalog, based on zphot from SDSS-III 132,684 clusters in the redshift range of 0.05<z<0.8 BCG defines the cluster center

25 the selected cluster sample! redshift range: 0.1 < z < 0.6 at least one radial shear measurement in the inner => 1176 galaxy clusters, median z= , 89, 457, and 287 in the 4 CFHTLS fields No further closer selection was applied

26 selection of background galaxies color selection mainly following Medezinski et al. (2010); Oguri et al. (2012) contamination fraction of foreground galaxies density of background galaxies: ~ 6 / arcmin^2 tests on COSMOS zphot catalog! (A. Phriksee master thesis, 2014)

27 profiles of individual clusters shear profiles for individual clusters from 0.1 to 20 from shear measurements to excess surface mass density

28 binning in order to sum clusters shear signal, you must choose a well-measured observable r-band optical richness scales with mass (e.g., Wen et al. 2012) stacking of clusters in six bins of optical richness (goal: ~ same SN in each bin)

29 stacked profiles: extreme bins R L *<16 DS tot M ü êpc 2 D tot DS 1 h DS 2 h 476 clusters, Mass ~ R L *<100 DS tot M ü êpc 2 D tot DS 1 h DS 2 h 10 clusters, Mass ~

30 check for systematic effects in shear measurements: tangential vs cross component shear decomposed along to directions gravitational lensing must not have a curl component (torsion) because it derives from a scalar potential in analogy to electrodynamics: E (scalar) and B (verctorial) modes B modes quantify systematic (i.e., non-gravitational) effects in shear measurements

31 check for systematic effects in shear measurements: tangential vs cross component R L *<16 DS tot M ü êpc 2 D tot DS 1 h DS 2 h 476 clusters, Mass ~ M ü êpc 2 D

32 check for systematic effects in shear measurements: tangential vs cross component M ü êpc 2 D R L *<100 DS tot M ü êpc 2 D tot DS 1 h DS 2 h 10 clusters, Mass ~

33 the fitting model (1) first halo modelled with a modified NFW (Baltz et al. 2009)!! (2) second halo term (3) offset mass component

34 the Navarro, Frenk & White profile CDM simulation: dark matter halos follows a universal profile the concentration c CDM prediction: concentration is strongly correlated with mass (and redshift)

35 BMO model (Baltz, Marshall & Oguri 2009) NFW has divergent total mass real CDM haloes expected to be truncated due to tidal effects power-law cut-off: n controls the sharpness of the truncation Note: be careful when using NFW for M(c)! Oguri & Hamana (2011): on large-scale fitting with NFW,!! mass underestimate ~10%!! c overestimated ~20%

36 halo centering offset real BCG close enough to DM halo center possible BCG misidentification => underestimate ΔΣ(R) at small scales and bias low the c measurements. additional component with azimuthally symmetric Gaussian distribution mass fraction and scale length of the Gaussian distribution are free parameters

37 the fitting model (1) first halo modelled with a modified NFW (Baltz et al. 2009)!! (2) second halo term (3) offset mass component 5 free parameters: mass, c, halo term, offset mass component + related scale length

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39 removing systematic effects: random fields random catalog of 5000 clusters with the same redshift distribution (over 4 fields) random signal must be subtracted from measured stacked profiles M ü êpc 2 D M ü êpc 2 D

40 removing systematic effects: random fields random catalog of 5000 clusters with the same redshift distribution (over 4 fields) random signal must be subtracted from measured stacked profiles M ü êpc 2 D M ü êpc 2 D spurious signal ~1-σ level, see also Miyatake et al. (2013); likely residual systematics in the shear measurements at the edges of detector.

41 results! Results of the Fit of Profiles of the Six Stacked Bins in Optical Richness

42 scaling relations (1) virial cluster mass versus optical richness in agreement with Wen et al. (2012)

43 scaling relations (1) virial cluster mass versus optical richness Warning!! we assumed no evolution from z=0 to z=0.6! (work in progress) in agreement with Wen et al. (2012)

44 the 2-halo term vs halo mass first detection beyond z~0.1 Note:" degeneracy with rms of mass distribution!

45 next step: removing the degeneracy Sereno et al. (2014, submitted)

46 joint analysis of clustering and stacked gravitational lensing of galaxy clusters matter auto-correlation function: halo density field auto-correlation function cross-correlation function stacked lensing clustering

47 the method we track clusters of galaxies rather than galaxies; we consider the same clusters catalog for both lensing and clustering; we determine bias and σ8 based exclusively on the large-scale signal. No need for a scaling relation (between mass and some baryonic properties) No need to determine the cluster selection function

48 the data set optically selected clusters of galaxies identified from the Sloan Digital Sky Survey III (SDSS-III, data release 8, Wen et al. 2012) for the 2-point correlation function: subsample of galaxy clusters, from a contiguous area of 9000 deg2 binning in 4 richness bins

49 only clustering The redshift-space 2-point correlation function

50 only stacked lensing of galaxy clusters two-point correlation function of a photometric sample of clusters selected from the SDSS at 0.1 < z < 0.6 one richness bin

51 removing degeneracy: joint analysis of clustering and stacked gravitational lensing of galaxy clusters Sereno, Veropalumbo, Marulli et al. (2014) pro: σ8 measurement does not rely on any mass-observable scaling relation pro: minimal modelling and well controlled systematics

52 direct measurement of bias red line: prediction by Tinker et al. (2010) for σ8 = 0.8 at z = 0.37.

53 Prospects The lensing signal is proportional to the matter density stacked lensing and clustering can then constrain the product stacking the signal for lenses in small redshifts bins. Requires very large survey (Euclid).

54 On the mass-concentration relation

55 c(m) relation from stacked shear at z~0.36 flatter, but slope consistent with Duffy et al. (2008), normalization differs at the 1σ level. closer to results by Bhattacharya et al. (2013), Prada et al. (2012)

56 Conclusions WL stacked analysis of 1176 clusters in CFHTLenS, 0.1<z<0.6, mass Halo bias amplitude and correlation with cluster mass as predicted in LCDM numerical simulations Scaling relation with optical richness flat M(c) and higher than Duffy et al. predictions; new determination of cosmological parameters through clustering and WL stacked lensing

57 now: VST surveys the future: Euclid

58 Weak VST, the VLT Survey Telescope P.I.: prof. Massimo Capaccioli INAF-OAC & University of Naples Federico II

59 ESO Paranal Observatory 4 UTs + 4 ATs (ESO) VISTA (UK) IR surveys VST (It) visible surveys! VST: in operation since October 2011 Atlas workshop, Durham: April 14-16, 2014

60 VST: a wide-field telescope. How wide? 1 degree 1 degree Given the scale of 0.2/px, it implies 256 Mpx

61 VST: active optics for M1 (2.6 m) correct the wavefront and compensate gravity M2 M2 M1 axial component M1 radial component gravity camera

62 VST active optics: M1 axial actuators & fixed points Axial fixed points M2 M1

63 VST active optics: M1 axial & radial actuators + safety devices M2 Radial fixed points M1

64 VST: the active M1 cell

65 OmegaCam A mosaic of x4000 px CCDs The VST camera OmegaCam, built by an international consortium (The Netherlands, Germany, Italy, ESO)

66 VST Image FWHM Distribution Cumulative distribution FWHM of the seeing image VST achieves sub-arcsec resolution ~80% of the time

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68 Share of VST observing time & scientific policy for the first 10 years ESO Public Surveys: 1. KiDS 2. ATLAS 3. VPHAS ESO public surveys INAF GTO ESO à INAF INAF ΩCam + 3 VST nights/yr Chile Percentage Year Observations: - service mode recent very - designated visitor mode positive experience

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75 The Hercules galaxy cluster (Abell 2151, z=0.036)

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80 VST ESO Public Surveys KIDS The Kilo-Degree Survey PI Konrad Kuijken (Leiden) 1500 deg 2 in 4 bands (+ NIR VISTA/VIKING survey), 2.5 magnitudes deeper than SDSS.! weak gravitational lensing: studying DM halos and DE with weak lensing; investigating galaxy and cluster evolution, large-scale angular power spectrum, and the equation of state of DE; high redshift quasars. Sky coverage The shear

81 VST ESO Public Surveys KiDS + Viking DES + VHS

82 VOICE Science Rationale VST Op'cal Imaging of the CDFS and ES1! P.I.: Giovanni Covone co- PI: Ma>a Vaccari (Cape Town, South Africa)! Goals:! Galaxy Forma'on & Evolu'on from z=2 to now Mul/- Band Deeper Ancillary Data (Moving from 24 to 26 in AB) are key to detect the bulk of the Spitzer popula/on (and search for high- z dropouts)! Gravita'onal Lensing Weak lensing map of cosmic structures: collabora/on with prof. Fan (PKU), dr L. Fu (SHNU) (Search for strong gravita/onal lenses) 82

83 Extended CDFS Field Exis'ng Data! MUYSC 32- band imaging to 25/26 (AB) over 0.25 deg 2 SWIRE ugri imaging to 24 (AB) over 4 deg 2 Background Image : SERVS Coverage 2012/ /2012 Observing Plan! Piggy Back on SUDARE for 2011/2012 & 2012/2013! VOICE Ramping Up from 2013/2014 onwards 2013/ /2014 (TBC) 83

84 Extended ES1 Field Background Image : SERVS Coverage Exis'ng Data ESIS BVRI imaging to 24.5 (AB) over 4 deg 2 WFI 2.2 m (La Silla, Chile) Observing Plan! TBC A_er Reviewing CDFS Status at the end of 2013/

85 VOICE: stragegy! gri bands data collected to search for SN (SUDARE, PI: E. Cappellaro) best seeing images to build deep mosaics to AB~26 u band deep observations (4 hours per field)

86 VOICE: status! ~50% data acquisition complete 2 papers submitted (AGN search) First public photometric catalog + zphot public in spring 2015

87 ! VEGAS on INAF-GTO VST Survey of Elliptical Galaxies in the Southern Hemisphere PI Massimo Capaccioli VST over 5 years. Multiband (u) g, r, i optical survey of ~110 galaxies with V rad < 4000 km/s in all environments (field to clusters).! Expected SB limits: 27.5 g, 27.0 r and 26.2 i mag/arcsec -2 (S/N>10 per arcsec -2 ).! Total exposure time per pointing in the three filters ~3h (~4h included overheads) for 70 gals. For the targets observed with KiDS (~40) ~1.8h are needed (g = 900s; r = 1800s; i= 1200s already available).

88 VEGAS: science aims SB out to 8-10 R e : physical correlations among standard structural parameters (total luminosity, Sersic index, effective radius, ellipticity, boxiness/diskiness);! (g r), (g i) color gradients and the connection with galaxy formation theories;! GC density and color distribution; GC luminosity function; comparison of integrated colors of GCs to the theoretical models (multiple episodes of GC formation);! SBF fluctuations for distance and chemical characterization of the stellar population out to 2-3 R e;! Stellar M/L, stellar masses, M/L gradients;! Study of the long-lived external structure and the diffuse component of the galaxies and their connection with the environment.

89 VEGAS: goals and limits Expected SB limits: 27.5 g, 27.0 r, and 26.2 i [mag arcsec -2 ] S/ N > 10. Surface brightness [g-mag/arcsec 2 ] r 1/4 [arcsec] Isophote where µ g = 27.5 mag/arcsec 2

90 VEGAS: first results on NGC 4472 UGC 7836: interacting galaxy ongoing merging

91 UGC 7836 interacting with NGC 4472 Flip the image twice about the center of NGC 4472 and subtract from the original NGC4472 center with clear asymmetry UGC 7836 The long plume twisting about the center of NGC 4472

92 Fornax Cluster Deep Survey All sources Fornax galaxies GC/UCDs candidates

93 Building a clean catalog of strong lenses in KiDS Giovanni Università Federico II, Naples Nicola INAF-Capodimonte, Naples! Team: C. Tortora, M. Capaccioli, F. La Barbera, M. Sereno, C. Shuo, M. Paolillo F. Getman, N. Roy (PhD student), A. Colonna (master thesis student)!

94 Goal & tools Build a small, but clean sample of high-confidence strong lenses form KiDS data to be used to test or train automatic tools (see thesis project by Andrea in Naples) Use visual inspection (8 trained human inspectors ) on well-selected samples of galaxies (i.e., galaxies with a high probability to be lenses) use 2Dphot (La Barbera et al. 2010) + color cutouts images

95 selecting samples! Pilot sample: bright galaxies from SDSS fields (selected for morphological study: KIWI project ) 50 ~ 600 with S/N > 100, r < 20, 0.2 < z < 0.3 N MAG_AUTO _r Selection #1: massive galaxies (stellar mass from GAMA spectroscopic catalog) ~5000 galaxies at 0.2<z<0.3

96 friendly web interface

97 results on pilot sample! putting together all individual inspections (no weight at the moment) (grade A,B,C) List of 10 candidates from 92 KiDS tiles (3 bona fide gravitational lenses) No overlap with known lenses (galaxies not in our sample), all candidates are new lenses.

98 criteria for individual inspection following Keeton & Kochanek (1996) A: I am very confident that this is a lens B: 50% probability C: very unlikely, but I cannot exclude this is a lens!

99 candidates from SDSS/KiDS fields (average grade: A)

100 Galaxy cluster Abell 2667, Covone et al. (2006) Thanks

101 COSMOS seeing<0.8 r band 5.5 hr

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103 Gravitational Lensing with VST! KiDS VOICE deep fields (Covone, Liping, Radovich) Search for strong gravitational lenses in KiDS (Covone et al.)

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105 selection of background galaxies tests on COSMOS field: (A. Phriksee master thesis, 2014)

106 should we use photometric redshifts?

107 VST-OmegaCAM competitors Telescope/Instrument D/f-ratio FoV /DIQ D DIQ Availability VST - OmegaCam 2.6m / / operating CFHT - MegaCam 3.6m / 4 1 / operating SkyMapper 1.3m/ / 0.7? 20? operating PanSTARRS 1 1.8m / / operating WIYN - ODI 3.5m / / operating CTIO - DEC 4.0m / / operating DCT Prime Focus (?) 4.2m / / >0.73 <66 operating PanSTARRS m / / ACTUEL-JPCam 2.5m / 3.6 3/ ? PanSTARRS m / / ? Subaru - Hyper Suprime 8.2m / / (planned) LSST 6.7m / / >2020 DIQ= delivered image quality ~ FWHM in arcsec of a point source

108 and real data (a) Projected distribution of dark matter in the COSMOS field from the analysis of Massey et al.! (b) Map for the baryonic matter (optical HST + X-ray XMM)

109 additional tables