1. 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

2. Irini Sakelliou The environment of galaxies – Crete 2004 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

3. 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)

4. 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

5. 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 M DH =(1, 2, 4) x 10 12 M  kT ICM ~3keV Acreman et al. (2004), Stevens et al. (1999) Temperature map

6. Irini Sakelliou The environment of galaxies – Crete 2004 Gas mass M DH = 4 x 10 12 M  M DH = 1 x 10 12 M  ∗∗ ∗ ∗ ∗∗ ∗ cluster core passage Most of the gas is stripped during the first in-fall.

7. Irini Sakelliou The environment of galaxies – Crete 2004 4C34.16 – XMM observations Radio core wake ~20ksec XMM (0.3-5.0)keV MOS1 + MOS2 + PN co-added images 4C34.16 is a wide-angle radio galaxy (WAT) Sakelliou et al. (2004) in front profile back profile

8. Irini Sakelliou The environment of galaxies – Crete 2004 XMM results ICMWake kT 3.2±0.51.1±0.7 (keV) n 1.3±0.34.5 +11.2 (x10 -3 cm -3 ) N H 1.7±0.36.9±5.0 (x10 21 cm -2 ) V gal >1200 km s -1 Supersonic motion (0.3-5.0)keV contours on the optical image Hard image (5-8)keV Hard `bar’ in front of the galaxy -1.3

9. Irini Sakelliou The environment of galaxies – Crete 2004 Comparison with simulations Supersonic motion (v gal > 1200 km s -1 ) Large wake mass, comparable to the mass of X-ray halos. A large amount of pre-existing ISM is required galactic motion ↤ 1200 km s -1 5000 km s -1 measured kT wake

10. Irini Sakelliou The environment of galaxies – Crete 2004 The dumb-bell galaxy NGC 4782/3 – seen by Chandra 50ksec raw Chandra Image The two galaxies are members of a loose group, form a bound pair, with a separation of ~12kpc, and are spinning around each other.

11. 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)

12. 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.

13. Irini Sakelliou The environment of galaxies – Crete 2004 Summary Open questions (X-rays): 1) metalicities of wakes, 2) bow shock and its temperature 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.