COLD FRONTS IN GROUPS AND COLD FRONTS IN GROUPS AND CLUSTERS AND THEIR CLUSTERS AND THEIR

DYNAMICAL STATE IN THE DYNAMICAL STATE IN THE OPTICALOPTICAL

FABIO GASTALDELLOINAF-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 OUTLINE

COLD FRONTS IN CLUSTERSCOLD FRONTS IN CLUSTERS

IN MERGING CLUSTERS IN RELAXED CLUSTERS

Markevitch & Vikhlinin 07

SLOSHING CFs IN CLUSTERSSLOSHING CFs IN CLUSTERS

Ascasibar & Markevitch 06

SLOSHING CFs IN CLUSTERSSLOSHING CFs IN CLUSTERS

• SB DISCONTUINITIES, SPIRAL FEATURES IN T

• STEEP ENTROPY GRADIENT

• cD PECULIAR VELOCITY

• ABUNDANCE DISCONTUINITIES

Ascasibar & Markevitch 06

HOW ABOUT GROUPS ?HOW ABOUT GROUPS ?

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

SLOSHING CFs IN NGC 5044SLOSHING CFs IN NGC 5044

Gastaldello+09

z=0.009 kT=1.2 keV

SLOSHING CFs IN NGC 5044SLOSHING CFs IN NGC 5044MENDEL+08 STUDY OF 111 MEMBERS:

PECULIAR VELOCITY OF 150 km/s WRT THE MEAN VELOCITY

SLOSHING CFs IN NGC 5044SLOSHING 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 1860SLOSHING CFs IN IC 1860

Di Gesu, FG, et al. in prep

z=0.022 kT=1.4 keV

SLOSHING CFs IN IC 1860SLOSHING CFs IN IC 1860

Di Gesu, FG, et al. in prep

SLOSHING CFs IN IC 1860SLOSHING CFs IN IC 1860

PRELIMINARY MODELING CONSISTENT WITH DENSITY JUMP OF 1.4.

SLOSHING CFs IN IC 1860SLOSHING 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 1860SLOSHING CFs IN IC 1860

SUBSTRUCTURE PRESENT AT THE 98.2 % LEVEL

PECULIAR VELOCITIES OF BCGs PECULIAR VELOCITIES OF BCGs AND X-RAY STATEAND 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+09

452 ABELL CLUSTERS W/ MORE THAN 10 MEMBERS

VP OF BCG

CAVAGNOLO+09

241 CLUSTERS

K0 AS INDICATOR OF THERMODYNAMICAL STATE

FG, Messa, et al. in prep

PECULIAR VELOCITIES OF BCGs PECULIAR VELOCITIES OF BCGs AND X-RAY STATEAND X-RAY STATE

CC NCC

With CF

A133 176

A1644 29

A1795 238

A496 55

A2029 61

A2052 185

A2199 156

CENTAURUS 125

A4059 27

A85 43

VVPECPEC OF BCGs AND X-RAY STATE OF BCGs AND X-RAY STATE

NO CF

A478 340

A1068 127

A2107 187

A2556 85

A2626 802

A2717 107

A3112 215

A3581 31

ESO 3060170 20

MKW3S 27

A1361 204

A2667 382

CAVEAT: SUBSTRUCTURES !CAVEAT: SUBSTRUCTURES !

vcl: 17307 km/s 16533 km/s

Vp: 802 km/s 27 km/s σv: 1057 km/s 658 km/s kT=2.9 keV

ABELL 262682 MEMBERS

CLEAR DETECTION OF SUBSTRUCTURES ALREADY IN MOHR+96

IT HOSTS A MINI RADIO HALO (GITTI+04)

PEAK 1

PEAK 2

VVPECPEC OF BCGs: SOME PEOPLE OF BCGs: SOME PEOPLE SAY ...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 < 1013 Msun, 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”

VVPECPEC OF BCGs: SOME PEOPLE OF BCGs: SOME PEOPLE SAY ...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 SUMMARY