Speaker: Dave Wilman (MPE)

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

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

3. Tying star formation to structure growth Press-Schechter plot of dark matter mass evolution Normalised to 1011 Mo Clusters are negligible; but groups dominate and evolve strongly Thus, can environmental processes be responsible for SFR evolution? Groups Clusters

4. Evolution and Environment • 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.

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

6. Colours - Bimodal Fitting

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

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

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

10. Downsizing SDSS Transision mass 3x1010Mo for full range of M/L group field (u’-r’)0 (3.6μm) luminosity (IRAC Band 1)

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

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

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

14. Groups MBJ ≤ -20.5: 16 group S0s; 0 field S0s! 2.7σ Field 3.5σ 3σ Morphological Composition Ellipticals S0s 29 group S0s; 7 field S0s

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

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

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

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

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

21. The End!

22. Scatter in fp-σ fp σ (km/s)

23. Morphological Properties of individual groups

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

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

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

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

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

29. Figs for George? - follow

30. CNOC2 Groups at 0.3≤z≤0.55 • Kinematically selected from the CNOC2 redshift survey. Group detection described in Carlberg et al. (2001) • Follow-up spectroscopy: • LDSS2 on Magellan (to RC = 22) • FORS2 on the VLT (to RC = 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

31. [OII] [OII] Magellan Spectroscopy • Extended spectroscopic sample to RC=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 σv from <100km/s to ~800km/s (~poor cluster)

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 RA r’0 dv (km/s)

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