When starbursts meet clusters of galaxies…

1. When starbursts meet clusters of galaxies… • 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) Pierre-Alain Duc (AIM - CEA-Saclay) Rencontres de Moriond, “When UV meets IR” La Thuile, March 2005

2. When starbursts meet clusters of galaxies… • 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) Pierre-Alain Duc (AIM - CEA-Saclay) Rencontres de Moriond, “When UV meets IR” La Thuile, March 2005

3. (A lack of) activity 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 Ram pressure stripping of the galaxy ISM by the ICM • 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 Courtesy of B. Moore Harassment

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

5. (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. The infrared view of the activity in clusters • IRAS (20 years ago) • ISO (10 years ago) • Spitzer (present) • 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 • Faint infrared fluxes of galaxies located in the most nearby clusters (Virgo): • no LIRGs/ULIRGs

7. Abell 1689: • at z=0.18 HST/ACS

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

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

10. ISOCAM 15 mm observations of J1888.16 CL (z=0.56) • - discovered on deep optical AAT plates; detected in the X-rays by ROSAT (Lx=1.7 1044 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. ISOCAM 15 mm observations • of J1888.16 CL (z=0.56) • 8 15 mm sources • associated with spectroscopically confirmed cluster members

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

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

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

16. 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. When X-ray meets IR… • 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

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

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

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