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X-RAY BRIGHT GALAXY GROUPS AS COSMOLOGICAL TOOLS

X-RAY BRIGHT GALAXY GROUPS AS COSMOLOGICAL TOOLS. FABIO GASTALDELLO UNIVERSITY OF CALIFORNIA IRVINE D. BUOTE P. HUMPHREY L. ZAPPACOSTA J. BULLOCK W. MATHEWS UCSC F. BRIGHENTI BOLOGNA. OUTLINE. INTRODUCTION RESULTS AND c-M PLOT FOR X-RAY GROUPS

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X-RAY BRIGHT GALAXY GROUPS AS COSMOLOGICAL TOOLS

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  1. X-RAY BRIGHT GALAXY GROUPS AS COSMOLOGICAL TOOLS FABIO GASTALDELLO UNIVERSITY OF CALIFORNIA IRVINE D. BUOTE P. HUMPHREY L. ZAPPACOSTA J. BULLOCK W. MATHEWS UCSC F. BRIGHENTI BOLOGNA

  2. OUTLINE • INTRODUCTION • RESULTS AND c-M PLOT FOR X-RAY GROUPS • COSMOLOGICAL IMPLICATIONS OF THE c-M PLOT OF THE EXTENDED SAMPLE • CONCLUSIONS

  3. THE COSMOLOGICAL MODEL Allen et al. 2004

  4. DM DENSITY PROFILE The concentration parameter c do not depend strongly on the innermost data points, r < 0.05 rvir (Bullock et al. 2001, B01; Dolag et al. 2004, D04). Navarro et al. 2004

  5. c-M RELATION • c slowly declines as M increases (slope of -0.1) • Constant scatter (σlogc ≈ 0.14) • the normalization depends sensitively on the cosmological parameters, in particular σ8 and w (D04,Kuhlen et al. 2005). Bullock et al. 2001

  6. c-M RELATION Kuhlen et al. 2005

  7. c-M RELATION • The median c-M relation for CDM halos is well described by the semi-analytic model proposed by B01, with 2 adjustable constants • the c-M relation is adequately parameterized by a power law over a large range in mass (D04, Shaw et al. 2006)

  8. Selection Effects Wechsler et al. 2002 Concentrations for relaxed halos are larger by 10% compared to the whole population (Jing 2000, Wechsler 2002, Maccio’ 2006). They show also smaller scatter (σlogc ≈ 0.10)

  9. OBSERVATIONS: METHODS • Stellar/Galaxy Dynamics: • Advantages: can apply to most Es and many clusters • Disadvantages: velocity dispersion anisotropy, limited galaxy numbers in cluster cores, equilibrium • Gravitational Lensing: • Advantages: applicable to most clusters (z~0.2-1), no assumption about equilibrium required • Disadvantages: projection effects and substructure (esp. strong lensing), limited number of background galaxies for analysis of core (weak lensing), only statistical information in outskirts of galaxies/groups • X-Rays: • Advantages: isotropic pressure tensor, gas fills 3D potential well, data quality not limited by finite number of group/cluster galaxies, results for single objects • Disadvantages: hydrostatic equilibrium …

  10. X-RAY SYSTEMATICS • HYDROSTATIC EQUILIBRIUM • MULTIPHASE GAS/PROJECTION EFFECTS IN CORES • DISCRETE SOURCES IN Es • BKG SUBTRACTION • DEPROJECTION AND FITTING PROCEDURES

  11. X-RAY MASS DETERMINATION • Spectra averaged within circular annuli • Normalization / shape of spectrum gives gas density / temperature

  12. X-RAY MASS DETERMINATION Assume spherical symmetry Fit spectra with coronal plasma models and obtain (deprojected) spectral quantities Fit parameterized functions to radial profiles of gas density and temperature Assume hydrostatic equilibrium Calculate the radial mass profile

  13. Chandra XMM-Newton A SPECIAL ERA IN X-RAY ASTRONOMY • High sensitivity due to high effective area, i.e. more photons • 1 arcsec resolution

  14. Vikhlinin et al. 2006 Pointecouteau et al. 2005 • NFW a good fit to the mass profile • c-M relation is consistent with no variation in c and with the gentle decline with increasing M expected from CDM (α = -0.040.03, P05). Clusters X-ray results

  15. Rines & Diaferio (2006) Mandelbaum et al. (2006) c-M relation obtained using different techniques, e.g., redshift-space caustics (Rines & Diaferio 2006), weak gravitational lensing (Mandelbaum et al. 2006) are all consistent with no variation in c

  16. THE PROJECT • Improve significantly the constraints on the c-M relation by analyzing a wider mass range with many more systems, in particular obtaining accurate mass constraints on relaxed systems with 1012 ≤ M ≤ 1014 Msun • First study of the mass profiles of 7 early type galaxies with Chandra (Humphrey et al. 2006)

  17. HIGHLIGHTS ON THE GALAXY SCALE … Humphrey et al. 2006

  18. The contribution of the stellar mass Huge c > 30 in some previous X-ray studies (NGC 6482, Khosroshahi et al. 2004) Baryons (stars) and DM different distributions Fitting an NFW model to DM NFW + stellar component can bias high c (Mamon & Lokas 2005)

  19. Interaction of DM and Baryons In addition adiabatic contraction (AC) could play a role i.e. DM halo responds to condensations of baryons into stars, which should cause the DM profile to contract adiabatically in the center (Blumenthal et al. 1986). Gnedin et al. 2006

  20. HIGHLIGHTS ON THE GALAXY SCALE … Humphrey et al. 2006 • NFW+stars best fit • AC leads to more discrepant stellar M/L • c-M relation in agreement with ΛCDM

  21. THE PROJECT • Improve significantly the constraints on the c-M relation by analyzing a wider mass range with many more systems, in particular obtaining accurate mass constraints on relaxed systems with 1012 ≤ M ≤ 1014 Msun • Our recent study of the mass profiles of 7 early type galaxies with Chandra indicates c-M values consistent with ΛCDM (Humphrey et al. 2006) • There are very few constraints on groups scale (1013 ≤ M ≤ 1014 Msun), where numerical predictions are more accurate because a large number of halo can be simulated.

  22. In Gastaldello et al. 2006 (astro-ph 0610134) we selected a sample of 16 objects from the XMM and Chandra archives with the best available data with no obvious disturbance, with a dominant elliptical galaxy at the center • The best we can do to ensure hydrostatic equilibrium and recover mass from X-rays. SELECTION OF THE SAMPLE

  23. DATA ANALYSYS • Accurate bkg subtraction by modeling all components • Chandra inner regions • XMM outer regions NGC 533

  24. DATA ANALYSYS • Fit gas density and temperature simultaneously assuming only parameterizations for temperature and mass. • Advantages: • better constraints on M • easy to interpret goodness of fit

  25. DATA ANALYSIS NGC 1550 • Projection of the 3D ρ and T thus obtained to the results from spectral analysis, including the radial variation of the plasma emissivity (T,ZFe). • Using an onion peeling deprojection (e.g., Fabian et al. 1981) gives consistent results with the above method • Spectroscopic like T problem (e.g., Vikhlinin et al. 2005). Folding through responses : no change in the case of NGC 5044

  26. After accounting for the mass of the hot gas, NFW + stars is the best fit model RESULTS MKW 4 NGC 533

  27. No detection of stellar mass due to poor sampling in the inner 20 kpc or localized AGN disturbance RESULTS A 2717

  28. No detection of stellar mass due to poor sampling in the inner 20 kpc or localized AGN disturbance RESULTS Buote et al. 2002 NGC 5044

  29. RESULTS • NFW + stars best fit model • Not all the objects require stellar mass, due to poor sampling in the inner 20 kpc or localized AGN disturbance. Stellar M/L in K band for the objects with best available data is 0.570.21, in reasonable agreement with SP synthesis models (≈ 1) • Adopting more complicated models, like introducing AC or N04 did not improve the fits. AC produces too low stellar mass-to-light ratios

  30. Humphrey et al. 2006 Stellar M/L 0.760.24

  31. c-M relation for groups We obtain a slope α=-0.2260.076, c decreases with M at the 3σ level

  32. THE X-RAY c-M RELATION • Buote et al. 2006 (astro-ph 0610135) c-M relation for 39 systems ranging in mass from ellipticals to the most massive galaxy clusters (0.06-20) x 1014 Msun. • A power law fit requires at high significance (6.6σ) that c decreases with increasing M • Normalization and scatter consistent with relaxed objects

  33. THE X-RAY c-M RELATION WMAP 1 yr Spergel et al. 2003

  34. THE X-RAY c-M RELATION WMAP 3yr Spergel et al. 2006

  35. The WMAP 3 yr model is rejected at > 99.99% and the reason of its poor performance is the low value of σ8 (0.74), combined with the action of the tilt of the power spectrum and the lower value of Ωm.

  36. O D 1 Q 3 Novel evidence of dark energy using only observations in local universe

  37. CAVEATS/FUTURE WORK • HE (10% from simulations, e.g. Nagai et al. 2006) • Early formation bias • Semi-analytic model prediction of c-M • Gas physics and AC (problems also with rotation curves of spirals: Kassim et al. 2006, Gnedin et al. 2006)

  38. CONCLUSIONS • Mass constraints for X-ray bright groups derived from good quality Chandra and XMM data can be of the same quality as obtained for hot, massive clusters. This crucial mass regime has provided the crucial evidence of the decrease of c with increasing M • c-M relation offers interesting and novel approach to potentially constrain cosmological parameters

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