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X-ray Properties of a Mass-Selected Group Catalog

X-ray Properties of a Mass-Selected Group Catalog. P. Mazzotta University of Roma “Tor Vergata”, Roma, Italy And Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA. Collaborators. M. Balogh R. Bower A. Edge V. Eke T. Ponman T. Theuns. H. Bohringer C. Collins

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X-ray Properties of a Mass-Selected Group Catalog

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  1. X-ray Properties of a Mass-Selected Group Catalog P. Mazzotta University of Roma “Tor Vergata”, Roma, Italy And Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  2. Collaborators • M. Balogh • R. Bower • A. Edge • V. Eke • T. Ponman • T. Theuns • H. Bohringer • C. Collins • M. Colless • S. Maddox • J. Peacock “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  3. Overview of our project • The observed X-ray luminosities of groups are inconsistent with a simple model of shock-heated ICM during the group collapse: the observed luminosities are much lower than the predicted ones • It is has been suggested that a combination of pre-heating, gas cooling and energy injection removes low entropy gas, reducing the system's X-ray luminosity. • The extent of this process is uncertain because all galaxy group catalogues have been X-ray selected. • A proper analysis would require instead a mass-selected group catalogue • Using the 2PIGG we built a mass-selected sub-sample and we proposed for observation with both Chandra and XMM-Newton. “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  4. What I am going to talk about • Today I will describe our sub-sample • I will show some preliminary results of the X-ray properties of the sub-sample • I will provide some clues that may allow you to figure out if 2PIGG groups are well defined “objects” or not “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  5. The 2 PIGG catalog Eke et al. 2004, MNRAS, 355, 769 Has been derived from the 2dFGRS Among the other, it provides: Number of galaxy members Group dispersion velocity () Estimate of the Group Mass (M=5.5 2 r/G ) From this we may estimate the Expected ICM X-ray temperature “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  6. The Mass Selected Sample Selection Criteria For this study, we selected all 2PIGG groups such as: • z<0.1 • 3·1014 <M/MO <6·1014(1.5 keV <T< 3.5 keV) • Number of galaxies Ng>10 • We get 18 groups “Groups of Galaxies in the nearby Universe” ESO 2005 workshop Important All the groups selected show a single peak in the dispersion velocity distribution (i.e. no strong contamination by substructures for the mass estimate).

  7. The Sample 1.6 keV <T<3.5 keV 5 Chandra observations 11 XMM observations 3.1·1014Mo<M<5.6·1014Mo No Observations approved for two “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  8. T=2.7±1keV T=4±0.7keV T=1.7±0.2keV  = 700 km/s  = 590 km/s  = 580 km/s C5799 C5797 C5798 Groups in the Reflex Catalog “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  9. T=2.9±0.5keV T=3.7±0.7 keV T=??±?keV  = 540 km/s  =580 km/s  =680 km/s xmm1 xmm2 xmm11 Groups in the Reflex Catalog “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  10. T=5.64±0.2keV T=???? T=3.5±0.5 keV  = 600 km/s  = 550 km/s  = 620 km/s No MOS PN only xmm8 xmm7 xmm6 Groups in the Reflex Catalog “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  11. New Groups fainter than the Reflex Catalog but detected in the RASS T=2.8±0.5 keV T= ??? keV T=1.3±0.1keV  = 530 km/s  = 560 km/s  = 720 km/s C4990 C4991 xmm9 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  12.  = 640 km/s  = 570 km/s  = 700 km/s xmm4 xmm3 xmm5 New Groups fainter than the Reflex Catalog but detected in the RASS “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  13. Guess who game!!!! Two galaxy groups at approx the same redshift and with approx the same Dispersion velocity. They both have a brighter central galaxy. Which one is the X-ray emitting group? “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  14. New Groups fainter than both the Reflex Catalog the RASS  = 730 km/s  = 480 km/s  = 710 km/s xmm10 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  15. Sample X-ray temperatures Affected by strong flares Cluster “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  16. Some “post-it like” statistics 9 groups where already known from the Reflex survey. We find 4 more X-ray emitting groups (44% more) Out of 18 groups in the sample 13 show X-ray emission (72%) 5 don’t (28%) 12 Groups provide enough X-ray photons to measure at least a single temperature. 8 out of this 12 allows to estimate a T profile in at least 4 radial bins. For 5 groups we can also derive a T map “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  17. Conclusions • Using the 2PIGG we build a mass-selected catalog of groups that we proposed for observation with both Chandra and XMM-Newton • 72% of the groups in our sample shows X-ray emission • The non X-ray emitting clusters tend to be the ones with less galaxy members • Because of low N_g, we think that the mass of these systems may have been overestimated • The X-ray temperature of all groups (but one) is consistent with our selection criteria “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  18. The future Stay tuned to see (hopefully soon) Temperature, Entropy, and Mass profiles of this (so far unique of his kind) mass selected group sample “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  19. “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

  20. “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

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