Download I. Sakelliou "Galaxy Wakes"

Galaxy Wakes –
Theory & Observations
Irini Sakelliou
University of Birmingham
D.M. Acreman, T.J. Ponman, I.R. Stevens
University of Birmingham
M.R. Merrifield
University of Nottingham
J. Pinkney
University of Michigan
physical processes that take place as a
galaxy moves through the ICM:
• Bondi-Hoyle accretion =
the accretion of ICM onto and behind the galaxy
Ignition of an AGN? Creation of a wake?
• Ram pressure stripping =
the removal of ISM from the galaxy
Enrichment of the ICM with metals? Reduction of the star formation
rate in the galaxy? Creation of a metal rich wake?
• Compression of the ISM & ICM in front of the
galaxy.
Inducing star formation?
ICM-galaxy interactions modify the properties of both:
the galaxy & the cluster
Irini Sakelliou
The environment of galaxies – Crete 2004
A moving galaxy in Abell 2125
Chandra press realease (06/01/2004)
Each panel is 34 arcsec per side
X-ray (purple), Optical
(yellow), Radio (red),
Optical [OII] (green)
Irini Sakelliou
The environment of galaxies – Crete 2004
Talk plan
• Results of simulations
• X-ray data of wake systems
• Using wakes as probes for cluster
dynamics
Irini Sakelliou
The environment of galaxies – Crete 2004
Simulations of a moving
galaxy in a cluster
• A galaxy falling towards the
cluster centre
• The galaxy has a pre-existing
halo
• MDH=(1, 2, 4) x 1012 M
• kTICM~3keV
Temperature map
Acreman et al. (2004), Stevens et al. (1999)
Irini Sakelliou
The environment of galaxies – Crete 2004
∗
∗
∗
Gas mass
MDH= 4 x 1012 M
∗
∗
∗
MDH= 1 x 1012 M
Most of the gas is stripped
during the first in-fall.
∗cluster core passage
Irini Sakelliou
The environment of galaxies – Crete 2004
4C34.16 – XMM observations
Radio core
back profile
~20ksecinXMM
front profile
(0.3-5.0)keV
MOS1 + MOS2 + PN
co-added images
Sakelliou et al. (2004)
wake
4C34.16 is a wide-angle
radio galaxy (WAT)
Irini Sakelliou
The environment of galaxies – Crete 2004
XMM results
kT
ICM
3.2±0.5
Wake
1.1±0.7
n
1.3±0.3
4.5+11.2
-1.3
NH
1.7±0.3
6.9±5.0
(keV)
(x10-3 cm-3)
(x1021 cm-2)
(0.3-5.0)keV contours on the
optical image
Vgal>1200 km s-1
Supersonic motion
Hard `bar’ in
front of the
galaxy
Irini Sakelliou
The environment of galaxies – Crete 2004
Hard image
(5-8)keV
Comparison with
simulations
galactic motion
↤
•Supersonic motion
(vgal > 1200 km s-1)
•Large wake mass,
comparable to the
mass of X-ray
halos.
•A large amount of
pre-existing ISM is
required
measured
1200 km s-1
5000 km s-1
kTwake
Irini Sakelliou
The environment of galaxies – Crete 2004
The dumb-bell galaxy
NGC 4782/3 – seen by Chandra
The two galaxies are members of a loose group, form a bound pair, with a
separation of ~12kpc, and are spinning around each other.
50ksec raw Chandra Image
Irini Sakelliou
The environment of galaxies – Crete 2004
Abell 160 –
~60ksec
Chandra
observations
A160 is a poor cluster
(kT~3keV)
z=0.045
Acreman et al. (2004)
Irini Sakelliou
The environment of galaxies – Crete 2004
A160 – wakes associated with
the cluster galaxies
• 3 statistical measures are
used to determine the direction
of the wakes
• Wakes behind ~26 galaxies
are found
• There is a significant
preference for radial orbits
Raw (0.5-2.0)keV image of a cluster
galaxy. The circle has R=30kpc.
Irini Sakelliou
The environment of galaxies – Crete 2004
Summary
•Simulations: Most of the ISM is stripped
during the first in-fall
•XMM data of 4C34.16: the properties of the
wake are consistent with the simulations;
there is a hot region in front of the galaxy
•Chandra data of Abell 160: wakes were found
associated with a number of cluster galaxies;
there is a preference for radial orbits.
Open questions (X-rays):
1) metalicities of wakes, 2) bow shock and its temperature
Irini Sakelliou
The environment of galaxies – Crete 2004