1. Starbursts in clusters of galaxies When starbursts meet clusters of galaxies… La Thuile, March 2005Rencontres de Moriond, “When UV meets IR” Pierre-Alain Duc (AIM - CEA-Saclay) ISOCAM team Dario Fadda David Elbaz Alberto Franceschini Andrea Biviano Catherine Cesarsky Alan Moorwood Bianca Poggianti et al… XMM-LSS team Marguerite Pierre (PI) Spitzer/SWIRE Team Carol Lonsdale (PI)

2. Starbursts in clusters of galaxies When starbursts meet clusters of galaxies… La Thuile, March 2005Rencontres de Moriond, “When UV meets IR” Pierre-Alain Duc (AIM - CEA-Saclay) ISOCAM team Dario Fadda David Elbaz Alberto Franceschini Andrea Biviano Catherine Cesarsky Alan Moorwood Bianca Poggianti et al… XMM-LSS team Marguerite Pierre (PI) Spitzer/SWIRE Team Carol Lonsdale (PI)

3. Starbursts in clusters of galaxies Clusters of galaxies: an a priori hostile environment for the galaxy activity (star- formation, AGN) Infalling galaxies suffer: Ram pressure => ISM lost Strangulation => External Gas reservoir lost) Harassment => Disk destroyed; stars lost (A lack of) activity in clusters of galaxies Courtesy of B. Moore Ram pressure stripping of the galaxy ISM by the ICM Harassment Indeed, locally, the star formation activity is reduced in denser environments such as clusters -> HI deficiency -> SDSS results: a decline of the mean SFR as a function of local surface density

4. Starbursts in clusters of galaxies (Some) activity in (nearby) clusters of galaxies Outskirts of clusters Merging clusters Ferrari et al., 2005 Virgo cluster of galaxies: HI contours on X-ray map Location of the emission-line galaxies in the merging cluster Abell 3921

5. Starbursts in clusters of galaxies (Much more) activity in (distant) clusters of galaxies The “Butcher-Oemler” effect As a function of redshift: Increase in the fraction of blue galaxies (Photometric BO) Increase in the fraction of spirals (Morphological BO) Increase in the fraction of star-forming galaxies and post starbursts (Spectroscopic BO) An environmental effect (role of the cluster; dynamics, ICM) or … … a field effect (general evolution of galaxies falling in the cluster) ? (A high level of) activity ? How obscured? Clustering of distant mid-IR sources?

6. Starbursts in clusters of galaxies IRAS (20 years ago) ISO (10 years ago) The infrared view of the activity in clusters Spitzer (present) Faint infrared fluxes of galaxies located in the most nearby clusters (Virgo): no LIRGs/ULIRGs The first infrared maps of a few intermediate-z clusters: evidence for a significant dust enshrouded activity; LIRGs in clusters See review by Metcalfe et al. (2005), Space Science Review ISO special issue Wide surveys: statistics on the amount of star formation in clusters of galaxies and their surrounding

7. Starbursts in clusters of galaxies Abell 1689: Abell 1689: at z=0.18 at z=0.18 HST/ACS

8. Starbursts in clusters of galaxies Chary & Elbaz, 2002 Duc et al. 2000 Star-forming activity in Abell 1689 Affected by obscuration, Metallicity, aperture effects

9. Starbursts in clusters of galaxies A population of dust enshrouded SF galaxies? Duc et al. 2000 Star-forming activity in Abell 1689

10. Starbursts in clusters of galaxies ISOCAM 15  m observations of J1888.16 CL (z=0.56) - discovered on deep optical AAT plates; detected in the X-rays by ROSAT (Lx=1.7 10 44 erg/s); shows an excess of blue galaxies (BO effect) A strip of 3 x 15 arcmin (1.3 x 5.9 Mpc) in the LW3 band covering the outskirts of the cluster - Ground-based follow-up: at ESO (WFI, SOFI, VLT) 44 MIR sources detected (redshift measured for 27 of them) Duc et al., 2004

11. Starbursts in clusters of galaxies ISOCAM 15  m observations of J1888.16 CL (z=0.56) 8 15  m sources associated with spectroscopically confirmed cluster members

12. Starbursts in clusters of galaxies A population of Luminous Infrared Galaxies in J1888.16CL Cluster members Background/foreground Star Formation Rate (Mo/yr) Infrared Luminosity (Lo) Ellipticals at z=0.6 Scd,irr at z=0.6

13. Starbursts in clusters of galaxies Histogram of optical spectral type Optical signature of dust enshrouded starburst, typical of luminous infrared starbursts (Poggianti et al., 2001) Spectroscopic properties of the LIRGs in J1888.16CL

14. Starbursts in clusters of galaxies Where, when and how the cluster IR activity was triggered ? In the surrounding field ?: are the MIR sources recently accreted field LIRGS? 8 in 100 Myr (typical duration of LIR phase) -> too many given the percentage of field LIRGs Within the cluster itself ? Velocity dispersion of MIR sources: 700 +520 -260 km/s Possible mechanism: an initial shock-induced burst before the gas is stripped by ram pressure ? Within sub-groups, accreted along filaments ? Possible mechanisms: Tidal interactions: if the velocity dispersion is low enough Effect of the global tidal field on infalling groups (Bekki, 1999) or during cluster-cluster merger (Miller, 2003)

15. Starbursts in clusters of galaxies ISOCAM 15micron map of CL0024+1654 (z=0.39) Coia et al., 2004 (Much more) activity in (distant) clusters of galaxies

16. Starbursts in clusters of galaxies Conclusions (ISO based) From mid-infrared ISOCAM data: Evidence for a dust enshrouded activity in nearby cluster of galaxies (Abell 1689, z=0.18) Discovery of even more active Luminous Infrared Galaxies in intermediate redshift clusters (i.e. J1888.16CL, z=0.56) Optical signature of dust enshrouded starbursts Most active regions in the cluster outerskirts The triggering mechanism is still unclear: tidal collisions in falling sub- structures, cluster mergers ? An IR BO effect needs to be quantified: the role of Spitzer

17. Starbursts in clusters of galaxies XMM -LSS: 10ks X-ray map with XMM-Newton of a large contiguous area (5 sq deg sofar)  A sample of X-ray selected groups and clusters SWIRE: IRAC and MIPS maps of 9 sq degree. Observed Aug 2004 ……. CFHTLS: optical ugriz Megacam images at CFHT VVDS: optical VLT/VIMOS spectra TISWAZ: optical 2dF spectra When X-ray meets IR…

18. Starbursts in clusters of galaxies XMM-Newton true color map of D1 field Nearby group of galaxies Valtchanov et al., 2005

19. Starbursts in clusters of galaxies XMM-Newton true color map of D1 field Cluster merger at intermediate z

20. Starbursts in clusters of galaxies Distant X-ray clusters XMM-Newton true color map of D1 field