COLD FRONTS IN GROUPS AND CLUSTERS AND THEIR DYNAMICAL STATE IN THE OPTICAL FABIO GASTALDELLO INAF-IASF MILAN & UC IRVINE M. MESSA, L. DI GESU S. GHIZZARDI, M. ROSSETTI, D. BUOTE, S. ETTORI, F. BRIGHENTI, W. MATHEWS

INTRO: SLOSHING COLD FRONTS AND OBSERVABLE EFFECTS SLOSHING COLD FRONTS IN THE RELAXED GROUPS NGC 5044 AND IC 1860 PECULIAR VELOCITY OF BCGs AND X-RAY THERMODYNAMICAL STATE / PRESENCE OF CFs OUTLINE

COLD FRONTS IN CLUSTERS IN MERGING CLUSTERSIN RELAXED CLUSTERS Markevitch & Vikhlinin 07

SLOSHING CFs IN CLUSTERS Ascasibar & Markevitch 06

SLOSHING CFs IN CLUSTERS SB DISCONTUINITIES, SPIRAL FEATURES IN T STEEP ENTROPY GRADIENT cD PECULIAR VELOCITY ABUNDANCE DISCONTUINITIES Ascasibar & Markevitch 06

COLD FRONTS IN CLUSTERS Markevitch & Vikhlinin 07

HOW ABOUT GROUPS ? EXAMPLES IN MERGING SYSTEMS, e.g. NGC 1404 IN FORNAX (Machacek+05)

SLOSHING CFs IN NGC 5044 Gastaldello+09 z=0.009 kT=1.2 keV

SLOSHING CFs IN NGC 5044 MENDEL+08 STUDY OF 111 MEMBERS: PECULIAR VELOCITY OF 150 km/s WRT THE MEAN VELOCITY

SLOSHING CFs IN NGC 5044 DETECTION OF A SUBSTRUCTURE (99.9 %) AT 1.4 Mpc MENDEL+08. OR NGC 5054 (DAVID+09).

SLOSHING CFs IN IC 1860 Di Gesu, FG, et al. in prep z=0.022 kT=1.4 keV

SLOSHING CFs IN IC 1860 Di Gesu, FG, et al. in prep

SLOSHING CFs IN IC 1860 PRELIMINARY MODELING CONSISTENT WITH DENSITY JUMP OF 1.4.

SLOSHING CFs IN IC 1860 STUDY OF 81 MEMBERS AVAILABLE IN NED: PECULIAR VELOCITY OF 100 km/s WRT THE MEAN VELOCITY

SLOSHING CFs IN IC 1860 SUBSTRUCTURE PRESENT AT THE 98.2 % LEVEL

PECULIAR VELOCITIES OF BCGs AND X-RAY STATE CROSS-MATCH OF X-RAY PEAK AND BCG POSITION. ONLY IN EXTREME MERGERS (A754, A3376) LARGE SEPARATION. RESULTING SAMPLE OF 54 OBJECTS COZIOL ABELL CLUSTERS W/ MORE THAN 10 MEMBERS V P OF BCG CAVAGNOLO CLUSTERS K 0 AS INDICATOR OF THERMODYNAMICAL STATE FG, Messa, et al. in prep

PECULIAR VELOCITIES OF BCGs AND X-RAY STATE CC NCC

With CF A A A A A A A CENTAURUS 125 A A85 43 V PEC OF BCGs AND X-RAY STATE NO CF A A A A A A A A ESO MKW3S 27 A A

CAVEAT: SUBSTRUCTURES ! v cl : km/s  km/s V p : 802 km/s  27 km/sσ v : 1057 km/s  658 km/s kT=2.9 keV ABELL MEMBERS CLEAR DETECTION OF SUBSTRUCTURES ALREADY IN MOHR+96 IT HOSTS A MINI RADIO HALO (GITTI+04) PEAK 1 PEAK 2

V PEC OF BCGs: SOME PEOPLE SAY... COZIOL+09: “A large fractions of BCGs have significant peculiar velocity. This has one immediate consequence, which is that most clusters harboring a dominant galaxy are not dynamically relaxed” VAN DEN BOSCH+05: “The brightest galaxy in a dark matter halo is expected to reside at rest at the centre of the halo. In this paper, we test this `Central Galaxy Paradigm' (CGP) using group catalogues extracted from the Two-Degree Field Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey (SDSS). We show that the CGP is only consistent with the data in haloes with M < M sun, while in more massive haloes the data indicate a non-zero offset between the brightest galaxy and the satellites. This indicates that either central galaxies reside at the minimum of the dark matter potential, but that the halo itself is not yet fully relaxed, or, that the halo is relaxed, but that the central galaxy oscillates in its potential well.

MIRALDA-ESCUDE’+95: “The fact that cD galaxies often have large peculiar velocities relative to the average of the cluster galaxies has been used as an argument against their identification as cluster centers: however, clusters are continuously merging, and their density peaks do not need to coincide with their centers of mass. Substructure will cause the density peaks to move, in response to the gravitational forces of the infalling material” V PEC OF BCGs: SOME PEOPLE SAY...

SLOSHING COLD FRONTS ARE STARTING TO BE DETECTED IN AN INCREASING NUMBER OF GROUPS: FEATURE PRESENT AT ALL SCALES (see also NGC 5098: Randall+09, NGC 5846: Machaceck poster) OFF-AXIS MERGERS INDUCING COLD FRONTS CAN EXPLAIN SPEEDING BCGs ALSO IN RELAXED CLUSTERS: NEEDS FURTHER INVESTIGATION TAKING CARE OF POSSIBLE SUBSTRUCTURES SUMMARY

V P OF BCGs AND X-RAY STATE KENDALL TEST: 93.2% KS TEST 97.7 %

V P OF BCGs AND X-RAY STATE NO CORRELATION, NO DIFFERENCE IN THE TWO SUBSAMPLES WITH KS TEST

V P OF BCGs AND X-RAY STATE

SLOSHING COLD FRONTS, MERGING COLD FRONTS AND OBSERVABLE EFFECTS SLOSHING COLD FRONTS IN THE RELAXED GROUPS NGC 5044 AND IC 1860 PECULIAR VELOCITY OF BCGs AND X-RAY THERMODYNAMICAL STATE / PRESENCE OF CF A2028: A CORONA NEAR A COLD FRONT OUTLINE

Gastaldello+10

A2028: A CORONA NEAR A COLD FRONT

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