1. Santiago Chile (5-9 Dec 2005) 1 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop 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

2. Santiago Chile (5-9 Dec 2005) 2 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop Collaborators M. Balogh M. Balogh R. Bower R. Bower A. Edge A. Edge V. Eke V. Eke T. Ponman T. Ponman T. Theuns T. Theuns H. Bohringer H. Bohringer C. Collins C. Collins M. Colless M. Colless S. Maddox S. Maddox J. Peacock J. Peacock

3. Santiago Chile (5-9 Dec 2005) 3 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop 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 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 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. 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. 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 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. Using the 2PIGG we built a mass-selected sub-sample and we proposed for observation with both Chandra and XMM-Newton.

4. Santiago Chile (5-9 Dec 2005) 4 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop What I am going to talk about Today I will describe our sub- sample Today I will describe our sub- sample I will show some preliminary results of the X-ray properties of the 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 I will provide some clues that may allow you to figure out if 2PIGG groups are well defined “objects” or not

5. Santiago Chile (5-9 Dec 2005) 5 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop 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

6. Santiago Chile (5-9 Dec 2005) 6 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop The Mass Selected Sample Selection Criteria For this study, we selected all 2PIGG groups such as: z<0.1 3·10 14 <M/M O <6·10 14 (1.5 keV <T< 3.5 keV) Number of galaxies N g >10 We get 18 groups 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. Santiago Chile (5-9 Dec 2005) 7 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop The Sample 5 Chandra observations 11 XMM observations No Observations approved for two 3.1·10 14 M o <M<5.6·10 14 M o 1.6 keV <T<3.5 keV

8. Santiago Chile (5-9 Dec 2005) 8 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop Groups in the Reflex Catalog C5799  = 700 km/s T=2.7±1keV C5797  = 590 km/s T=4±0.7keV C5798  = 580 km/s T=1.7±0.2keV

9. Santiago Chile (5-9 Dec 2005) 9 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop Groups in the Reflex Catalog xmm2 T=??±?keV  =680 km/s xmm1 T=3.7±0.7 keV  =580 km/s xmm11 T=2.9±0.5keV  = 540 km/s

10. Santiago Chile (5-9 Dec 2005) 10 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop Groups in the Reflex Catalog xmm6 T=5.64±0.2keV  = 600 km/s xmm8 No MOS PN only T=????  = 550 km/s xmm7 T=3.5±0.5 keV  = 620 km/s

11. Santiago Chile (5-9 Dec 2005) 11 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop New Groups fainter than the Reflex Catalog but detected in the RASS C4990 T=2.8±0.5 keV  = 530 km/s xmm9 T=1.3±0.1keV  = 720 km/s C4991 T= ??? keV  = 560 km/s

12. Santiago Chile (5-9 Dec 2005) 12 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop New Groups fainter than the Reflex Catalog but detected in the RASS xmm5  = 570 km/s xmm4  = 700 km/s xmm3  = 640 km/s

13. Santiago Chile (5-9 Dec 2005) 13 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop 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?

14. Santiago Chile (5-9 Dec 2005) 14 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop New Groups fainter than both the Reflex Catalog the RASS xmm10  = 730 km/s  = 480 km/s  = 710 km/s

15. Santiago Chile (5-9 Dec 2005) 15 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop Sample X-ray temperatures Affected by strong flares Cluster

16. Santiago Chile (5-9 Dec 2005) 16 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop Some “post-it like” statistics Out of 18 groups in the sample 13 show X-ray emission (72%) 5 don’t (28%) 9 groups where already known from the Reflex survey. We find 4 more X-ray emitting groups (44% more) 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

17. Santiago Chile (5-9 Dec 2005) 17 “Groups of Galaxies in the nearby Universe” ESO 2005 workshopConclusions Using the 2PIGG we build a mass-selected catalog of groups that we proposed for observation with both Chandra and XMM-Newton 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 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 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 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 The X-ray temperature of all groups (but one) is consistent with our selection criteria

18. Santiago Chile (5-9 Dec 2005) 18 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop 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

19. Santiago Chile (5-9 Dec 2005) 19 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop

20. Santiago Chile (5-9 Dec 2005) 20 “Groups of Galaxies in the nearby Universe” ESO 2005 workshop