Download Abell 85

Clusters of galaxies seen in X-rays:
war and peace
Florence Durret
(Institut d’Astrophysique de Paris)
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Copyright: Claude Monet
War: Abell 85
z=0.0555
Recent collaborators
Gastão B. Lima Neto (IAG, São Paulo, Brazil)
William Forman (CfA, Cambridge, USA)
Eugene Churazov (IKI,Russia & MPA, Germany)
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Abell 85 in X-rays: a main cluster, a
south blob and a filament
ROSAT PSPC
Durret, Forman, Gerbal, Jones & Vikhlinin
1998, A&A 335, 41
XMM-Newton
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The filament properties (XMM data)
XMM-Newton
RAW
Length ≥4 Mpc
Temperature 2.0±0.5 keV
Model subtracted
Durret, Lima Neto, Forman &
Churazov 2003, A&A 403, L29
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Temperature and Metallicity profiles
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In the Center:
X-ray redshift
≈ optical redshift of four
galaxies in this region
≈ 0.0533 (cz=16000 km/s)
Mean cluster redshift
0.0555 (cz=16650 km/s)
Redshift of the cD
0.0558 (cz=16734 km/s)
Even in the center the
gas and galaxies
are probably not relaxed
BUT: 2σ effect only
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Various regions in Abell 85
Three white circles: Center, Ring 1
and Ring 2
Green circle: the VSSR (Very Steep
Spectrum Radio Source)
Blue circle: the South blob
Yellow ellipse: the Impact region
Small black circles: point sources
(excised)
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Temperature and metallicity maps
NE
SE
NW
Impact
region
The center is cooler and more metal-rich
The Impact region is hotter and metal poor
NW: The northwest is cooler and more metal-rich
NE: The northeast is more metal rich
SE: The south-east is hotter AND metal poor
An arc of hotter regions is observed south to northwest
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Numerical simulations of a merger
Emissivity
X-ray gas
temperature
z=0.13
z=0.09
z=0
Bourdin, Sauvageot, Slezak, Bijaoui, Teyssier 2004, A&A 429, 443
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Temperature maps
Temperature map from
numerical simulation
kT (keV)
XMM temperature map
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A scenario for Abell 85: this cluster
has undergone several mergers
A few known facts:

The gas in metal-rich regions is expected to be colder
(center, NW)

When two clusters merge, the temperature is not
affected immediately, but hotter zones appear later

Star formation is triggered only at the beginning of the
merger, then it weakens because galaxies lose their gas
due to ram pressure stripping
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What is happening here?
Groups aligned along a filament
fall from the southeast and heat
the impact region
This first merger is
probably recent (excess
of star forming galaxies
in the Impact region)
Impact
region is
hotter
Infall of groups
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An arc of hotter regions is
observed south to northwest,
suggesting a previous merger
from the NW
A third merger from the NE
has possibly occured to
account for the metal-rich
zone in the NE
Merger
Durret, Lima Neto & Forman 2005, A&A in press
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Future work on Abell 85
Multi-band imaging with Megacam at CFHT
(almost achieved)
and
Hα imaging with the WFI at the ESO 2.2m
(almost achieved)
to analyze the galaxy distribution and star formation and
correlate them with the X-ray gas properties, in
particular the metallicity
Collaboration Christophe Adami
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Even more chaos? Abell 3376
z=0.0456
Collaborators
Gastão B. Lima Neto (IAG, São Paulo, Brazil)
Joydeep Bagchi (IUCAA, Pune, India)
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Abell 3376: extended radio sources and
a completely offcentered cD galaxy
Radio map:
strong bent source and
two faint extended relics
cD galaxy: no radio emission
DSS optical image
(circles=galaxies with redshifts
in the cluster)
970 kpc
cD galaxy
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X-ray emission stronger towards strong radio source (east)
No X-ray emission from cD galaxy
ROSAT image
cD galaxy (outside XMM F.O.V.)
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•
•
•
•
Maximum of X-ray emission coincides with strong radio source
This region (green ellipse) contains at least 5 AGN (Chandra)
No relation between east radio relic and X-ray emission
No radio emission from cD galaxy
Radio map
Smoothed X-ray images
XMM-Newton
Chandra
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Zoom of radio map
DSS optical counterpart
Radio map suggests a movement towards the West or SW
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East group falls on to main cluster
Hotter zone and fewer galaxies in contact region
DSS map, galaxies in cluster z range
X-ray temperature map (XMM)
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Bright galaxies aligned along a filament?
Orientation of filament agrees with direction of merging
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Galaxy positions and movements: not very much to be said?
Redshift histogram
Positions of galaxies
with redshifts in the cluster
But…
Wedge diagram
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HST image of the cD: is it really a cD?
Why is it so offcentered?
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Tentative interpretation

A young group at the NE (containing at least 5 AGN) is
falling on to the main cluster

Bright galaxies seem aligned along a filament, in
agreement with the merging direction

No obvious relation between X-rays and radio (relics?)

The brightest galaxy is probably not a cD and is in the
outskirts of the cluster = a fossil cluster?
Bagchi J., Lima Neto G.B. & Durret F. 2005, in preparation
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Finally peace?
Abell 496: an almost relaxed cluster
Z=0.033
Collaborators
Gastão B. Lima Neto (IAG, São Paulo, Brazil)
Tatiana Ferraz Laganá (IAG, São Paulo, Brazil)
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Abell 496 seen in X-rays (archive data)
XMM
Chandra
In X-rays the cluster looks relaxed, but with a possible sharper north edge
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Abell 496 maps from XMM-Newton data
Temperature map
Metallicity map
Emission map
The temperature and metallicity maps are not completely symmetrical
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Entropy
Pressure
NH
No apparent features in the entropy and pressure maps
Gradient in NH (4%)
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Temperature profile
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Preliminary results

The intensity map is very smooth except for a flattening towards the
North

The temperature map shows a small decrease in the very center and
south; the metallicity in these zones is higher

The pressure and entropy maps are very smooth

There is a strong gradient in Galactic NH

Global agreement with Tamura et al. (2001) A&A 379, 107
Reference:
Lima Neto, Durret & Ferraz Laganá 2005, A&A in preparation
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Complementary work on Abell 496
Multi-band imaging with Megacam at CFHT
and
Spectroscopy with Flames/Giraffe at the ESO VLT
(achieved, P.I. Véronique Cayatte)
to study dwarf galaxies in Abell 496 and analyze the galaxy distribution
and luminosity function and correlate them with the X-ray gas
properties
Collaboration Véronique Cayatte , Christophe Adami and Chantal Balkowski
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CПACИБO!
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Radio map
X-ray temperature map
Optical image
Smoothed XMM map
Raw XMM image
Chandra map
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Radio map
X-ray temperature map
Optical image
Smoothed XMM image
Raw XMM image
Chandra image
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Abell 3376
kT
Entropy
Pressure
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