Constraining dark energy with Con-X galaxy clusters

1. Constraining dark energy with Con-X galaxy clusters In Collaboration with: Steve Allen (KIPAC) Robert Schmidt (Heidelberg) Harald Ebeling (Hawaii) Andy Fabian (Cambridge) Jochen Weller (UCL) Alexey Vikhlinin (CfA) and the Con-X Facility Science Team David Rapetti, KIPAC (Stanford/SLAC) XLIst Rencontres de Moriond

2. Outline • TheX-ray gas mass fraction, fgas(z) experiment constrains dark matter and dark energy • Current constraints (Allen et al 2004, 2006 prep., Rapetti et al 2005) • Notes on systematics • Simulated Constellation-X fgas(z) data set • Projected constraints on dark energy from Con-X fgas(z) • Other Con-X dark energy studies: X-ray+SZ, growth of structure • Conclusions XLIst Rencontres de Moriond

3. The fgas(z) experiment XLIst Rencontres de Moriond

4. Measuring the X-gas mass fraction of X-ray galaxy clusters Mgas X-ray gas mass Mtot the total cluster mass We define: From White et al 93, Fukugita et al 98, Voevodkin & Vikhlinin 04 Then The matter content of rich clusters of galaxies is expected to provide an almost fair sample of the matter content of the Universe (White & Frenk 91, White et al. 93, Eke et al.98). Then b is the bias factor that accounts for the relatively small amount of gas expelled when the cluster forms. +HST+BBNS priors when clusters alone XLIst Rencontres de Moriond

5. Spanning a redshift range to constrain dark energy • Absolute distance measurements at different redshift between 0.06<z<1.07 for the current sample of 41 Clusters (to be published). Mgas dA(z)2.5 Mtot dA(z) • It is crucial to use dynamically relaxed clusters for the fgas measurement: Regular X-ray morphology Low ellipticities Minimal centroid variation Sharp central brightness peaks centred on their dominant elliptical galaxies. • Weighted mean scatter about the best-fitting 12% (8% in distance). • For the cosmological parameter estimation together with SNe Ia and CMB data we use the Montecarlo Markov chain technique implemented in COSMOMC (Lewis & Bridle 02) and CAMB (Lewis, Challinor & Lasenby 00) to calculate the cmb power spectrum. XLIst Rencontres de Moriond

6. Current constraints XLIst Rencontres de Moriond

7. Constraints on CDM model XLIst Rencontres de Moriond

8. Constant equation of state parameter w • 68.3 and 95.4 % confidence limits • assuming flat prior. • Note the small overlaping • region for the combination of the • three data sets. It comes from the • complementary nature of SN+CMB • (WMAP1st+CBI+ACBAR) and • Clusters+CMB. • Marginalized constraints (68.3%) • w0 = -1.05 ±0.11 • Wm = 0.29 ±0.03 • Note that using only Clusters • Wm = 0.24 ±0.04 (Allen et al 04) Rapetti, Allen & Weller (2005) XLIst Rencontres de Moriond

9. SN+CMB (WMAP1st+CBI+ACBAR) Clusters data breaks the degenaracy: Wbh2,t,ns Cl+CMB (WMAP1st+CBI+ACBAR) WMAP3 nicely confirms the Cl+CMB trend ns = 0.95 + 0.015 - 0.019 Ωbh2 = 0.0223 + 0.0007 - 0.0009  = 0.09 +-0.03 Plus… 8=0.74+0.05-0.06 WMAP3 8=0.72+-0.04(Voevodkin & Vikhlinin 04) 8=0.70+-0.04(Allen et al 03) 8~0.75+-0.05in preparation XLIst Rencontres de Moriond

10. New fgas(z) constraints (41 clusters) combined with two SNe Ia data sets SNLS (Astier 05)+Clusters SNLS (Riess 04)+Clusters XLIst Rencontres de Moriond

11. Notes on systematics XLIst Rencontres de Moriond

12. No evidences for systematics in current data For r=0.25rvir(Chandra obs) b=0.83+-0.03 (+10% systematics) Assuming CDM we fit for evolution in this parameter Relaxed (sim) Unrelaxed (sim) Observations Plus, we find no evidence for trend of fgas with temperature kT. XLIst Rencontres de Moriond

13. Constellation-X analysis XLIst Rencontres de Moriond

14. Constellation-X • Con-X is one of two flagship missions in NASA’s Beyond Einstein Program ranked second only to JWST. Due for launch 2018. • The most important single feature for dark energy studies is its large collecting area (two orders-of-magnitude with respect to previous) with 5’’ angular resolution. • Con-X will carry out two powerful and independent sets of tests of dark energy: • Measure the absolute distances to clusters primarly using measurements of the fgas(z) in the largest, dynamically relaxed clusters with additional constraining power provided by follow-up SZ observations. • Together with theoretical models for the mass function and X-ray and SZ cluster surveys Con-X will help to constrain the growth of structure. XLIst Rencontres de Moriond

15. Proposed sample to constrain dark energy with the Con-X fgas(z) experiment • Construct an expanded catalogue of the most X-ray luminous, X-ray brightest clusters reaching to faint flux levels with an X-ray all-sky survey. Large-area SZ surveys like the South Pole Telescope and Planck can also provide Con-X targets. • From the ~2000 most luminous clusters in the catalogue, select the most dynamically relaxed clusters with short Con-X snapshot (~1ks) observations (2Ms total). The current MACS sample indicates 1/4 of them are enough relaxed. We conservatively assume 1/8 (~500 clusters) for our study (we also checked 1/16 obtaining similar constraints assuming the same total Con-X time). • Modest 10-12Ms of Con-X observing time (~10% over 5 first years). This implies a typical exposure time of 20ks per cluster. This leads to 5% statistical error bars. • We adopt the baseline effective area and spectral resolution describe at http://constellation.gsfc.nasa.gov/ and 5” angular resolution which is enough for the removal of point source flux contamination and to identify relaxed clusters at high z. XLIst Rencontres de Moriond

16. Evrard et al (2002) Predicted Con-X fgas(z) data Allen et al. (2003) Jenkins et al (2002) XLIst Rencontres de Moriond

17. Predicted Con-X fgas(z) data set Required Flux Limit Survey ROSAT All-Sky The predicted fgas(z) values for the proposed Con-X survey of 500 clusters with individual fgas uncertainties of 5%. A systematic scatter of 4% due to cluster-cluster variations in the bias parameter b is included.The median redshift for the sample is z~1. The predicted number density of clusters with bolometric X-ray luminosities LX>2x1045h-270 erg/s for a cluster survey flux limit of 5x10-14erg/cm2/s in the 0.1-2.4 keV band (redgas(z) values for the proposed Con-X survey of 500 with a median redshift z ~ 1. Blue curve shows for the ROSAT All-Sky survey flux limit 5x10-12erg/cm2/s. XLIst Rencontres de Moriond

18. Constraints from Con-X alone • Con-X simulated data with 5% measurement errors, 4% systematic scatter in b and using 2% priors on Ωbh2, h and b. • Evolution model: w(a)=w0+wa(1-a)=w0+2w’(1-a). • Comparable accuracy and beautifully complementary to LSST, SNAP, BAO, Planck, and cluster growth. XLIst Rencontres de Moriond

19. Current Chandra vs projected Con-X constraints Clusters Chandra • 68.3 and 95.4% confidence limits. • Note the combination of different data sets will be crucial for controling the systematics of each individual experiment. SNIa Gold Clusters Con-X CMB XLIst Rencontres de Moriond

20. Constraints on dark energy evolution using Con-X+WMAP8 simulated data • Here instead of using the 2% priors on Ωbh2, h we combine Con-X clusters with a simulated cmb TT power spectra after 8 years of WMAP as described in Upadhye, Ishak & Steinhardt 2005. • We use the dark energy model w(a)=w0+wa(1-a)=w0+2w’(1-a) to compare with other future experiments of SNe Ia and BAO shown in Linder 04,05. • Our constraints are comparable and nicely complementary to those other experiments. XLIst Rencontres de Moriond

21. Other Con-X dark energy studies XLIst Rencontres de Moriond

22. Constraints from the Con-X X-ray+SZ experiment Using the same Con-X data (most luminous and hottest clusters), i.e., no extra time. We can also measure distanceindependently of z by combining X-ray+SZ observations of galaxy clusters. X-ray+SZ 2% X-ray+SZ 0.1% yobs observed by a SZ survey (we assume 2%errors) yref predicted by the X-ray data assuming a reference cosmology (5% errors). fgas Con-X Though the X-ray+SZ experiment is less powerful (yd0.5) than the fgasd1.5 but provides: i) Precise redshift independent distance measurment ii) Test for the assumption of fgas constant with z iii) X-ray+SZ independent of b and hydrostatic equilibrium. Growth of Structure G(z)will be a powerful complementary dark energy observable ~1000 clusters: constraints <0.5% on G(z) leading to +-0.06-0.08 in w0(Majumdar & Mohr 04)… XLIst Rencontres de Moriond

23. Conclusions • In terms of direct distance measurements the X-ray method provides similar accuray to SNIa and BAO studies and has several valuable features: • The physics of galaxy clusters is relatively simple and can be accurately modeled by simulations. • Clusters can be revisited with X-ray observatories to improve signal-to-noise. • The fgas technique includes an additional constraint on Ωm from the normalization of the curve. • The combination of fgas and CMB data breaks a number of important degeneracies. • The systematic scatter in the fgas(z) is small (undetected and <12% in current data). • Direct checks on the key assumptions in the fgas method are possible using the spectral/resolution capabilities of Con-X and by combining with other data (X-ray+SZ). • Additional powerful and independent constraints on dark energy will be provided by Con-X’s contribution to growth of structure studies. XLIst Rencontres de Moriond