1. Speaker: Dave Wilman (MPE) Collaborators: Mike Balogh (Waterloo), George Hau, Richard Bower (Durham); John Mulchaey, Gus Oemler (Carnegie); Ray Carlberg (Toronto) The influence of the group environment since z~0.5: Morphologies and Star Formation Wilman, Balogh, Bower et al., March 2005, MNRAS, Paper I: Group Properties & Paper II: Evolution to z≈0 Groups at 0.3 ≤ z ≤ 0.55

2. Observing the Cosmic History of Star Formation... ΛCDM cosmology Dust corrected By z ≈ 0, ≥ 50% of galaxies in groups. (Eke et al., 2004)

3. Tying star formation to structure growth Groups Clusters Press-Schechter plot of dark matter mass evolution Normalised to 10 11 M o Clusters are negligible; but groups dominate and evolve strongly Thus, can environmental processes be responsible for SFR evolution?

4. Decline in Cosmic SFR Decline in fraction of S0 galaxies in clusters (Dressler et al., 1997) Development of the red and dead population: –Cosmic Downsizing –Environmental Trends preserved and even enhanced during hierarchical assembly understanding the group environment is critical. Evolution and Environment

5. The CNOC2 Sample r’ 0 z 95%ile k-correction at magnitude limit 0%ile 100%ile

6. Colours - Bimodal Fitting

7. r’ 0 (u’-r’) 0 Stdev σ mean μ Dotted line = SDSS (z~0)

8. Colours - Bimodal Fitting f red r’ 0 Local SDSS fred(r’ 0 )

9. Colours - Bimodal Fitting CNOC2 Group galaxies only r’ 0 f red

10. Downsizing SDSS Transision mass 3x10 10 M o for full range of M/L group field (3.6μm) luminosity (IRAC Band 1) (u’-r’) 0

11. Observations: f p vs z B J ≤ -19.65 CNOC1 Postmann 00, Van Dokkum 01 clusters 2dFGRS CNOC2 Cluster cores groups field f p = fraction(EW[OII]<5Ǻ)

12. Colour - Magnitude SDSS (u’-r’) 0 SDSS r’ 0

13. Intermediate Colour Galaxies Hogg et al., 2005: SDSS k+a galaxies have preferentially intermediate colours. Seeking the Transforming Population: -Colour transformation must last at least ~0.75Gyr if SFR declines rapidly (Balogh et al, 05)

14. Morphological Composition 2.7σ 3σ3σ 29 group S0s; 7 field S0s 3.5σ M BJ ≤ -20.5: 16 group S0s; 0 field S0s! Groups Field EllipticalsS0s

15. Morphology-Density at z~0.5 Dressler et al., 1997 MORPHS clusters

16. Passive Spirals 3.2σ excess wrt field for bright galaxies in smaller groups. Out of 67 group spirals and 68 field spirals: Not seen in 2 massive groups σ v > 600km/s Predominately brighter than M Bj = -20.0! (≈M * ) Also see radial dependence Normalised by rms distance of group galaxy from group centre Groups Field

17. Colour - Magnitude SDSS (u’-r’) 0 SDSS r’ 0 groups field

18. PAH emission at IRAC 8μ Peeters et al., 2004: M81 (black); NGC 4945 (grey) Z=0Z=0.3Z=0.48

19. IRAC colour (8μ-3.6μ) diagnostic EW[OII] IRAC colour SDSS (u’-r’) 0 Large points: S/N (8μ)>2 IRAC 3.6μm Luminosity

20. Conclusions Buildup of the red sequence is still in progress: Across the luminosity range More advanced in groups Downsizing of mass for a typical star forming galaxy (but possibly no environmental dependence) Groups have excesses of faint Es and bright S0s, with similar morphological composition as irregular clusters at similar z. Transforming galaxies must have intermediate optical colours. Galaxies with intermediate optical colours are: –Often Spiral Galaxies –Usually with low/no [OII] emission (passive spirals – brighter than ~M* these are particularly common in groups) –Usually with strong PAH emission (!) –Often with k+A signatures If Spirals -> S0s then the bulge luminosity must be enhanced -> dusty central starbursts? – The AGN connection? The importance of the group environment? Work to be done!

22. Scatter in f p -σ σ (km/s) fpfp

23. Morphological Properties of individual groups

24. g139 – associated to g138 Evolutionary Type vs σ σ (km/s)

25. Segregation Group 138 dec r’ 0 dv (km/s) RA

26. Segregation Group 244 dec r’ 0 dv (km/s) RA

27. Segregation Group 37 dec r’ 0 dv (km/s) RA

28. Segregation Group 38 dec r’ 0 dv (km/s) RA

29. Figs for George? - follow

30. CNOC2 Groups at 0.3≤z≤0.55 Follow-up spectroscopy: –LDSS2 on Magellan (to R C = 22) –FORS2 on the VLT (to R C = 23.2: June ‘05) -redshifts (greater depth & completeness) -Infer presence of star-formation using the [OII] emission line HST ACS imaging (recent) –Morphological classification GALEX UV imaging (current) –star formation NIR imaging: SOFI, GTO Spitzer Chandra observations scheduled Kinematically selected from the CNOC2 redshift survey. Group detection described in Carlberg et al. (2001)

31. Magellan Spectroscopy Extended spectroscopic sample to R C =22.0 Combined sample contains: –282 0.3 ≤ z ≤ 0.55 group members in 26 groups. –334 0.3 ≤ z ≤ 0.55 serendipitous field galaxies. (= everything in FOV – targetted groups) Selection function is well understood and sample is representative. (see paper I !) [OII] emission infers presence of star formation (EW≥5Ǻ). SED fitting -> rest-frame luminosities. Groups range in σ v from < 100km/s to ~800km/s (~poor cluster) [OII]

32. HST ACS data Observations of 20 groups for 1 orbit each in F775W filter. Morphological classification possible to R~23.9 (c.f. MORPHS WFPC2) Preliminary results for 16 ACS fields… Visual classification by Gus Oemler of all galaxies with spectroscopic redshifts 0.3 ≤ z ≤ 0.55 in the 16 fields 158 classified group galaxies & 124 classified field galaxies. Classified according to the MORPHS scheme.

33. HST Morphologies

34. Baryonic Matter

35. Mass Functions

36. Other figs - follow

37. Segregation Group 24 dec r’ 0 dv (km/s) RA

38. f p (lum,env) Fraction with EW[OII] ≤ 5Ǻ 3σ3σ Jackknife errors Result holds when more massive groups excluded! (no significant trend with σ v in our range) Groups Field