1. Galaxy properties in different environments: Observations Michael Balogh University of Waterloo, Canada (Look for 3 new job postings on AAS soon)

2. Outline Morphology –Evolution of early and late types Colours Star formation rates, HI E+A galaxies

3. Galaxy morphology

4. E Clusters Field S0 Spirals Morphology-Density Relation Dressler 1980 Also: Oemler 1974; Melnick & Sargent 1977 Coma cluster Morphological mix correlates best with local galaxy density Possibly additional effects in innermost regions (Whitmore et al. 1995; Dominguez et al. 2001)

5. Morphology-density: evolution Dressler et al. 1997; Couch et al. 1994; 1998 Fasano et al. 2000 Wide field HST: Treu et al. 2003 Log surface density Number of galaxies Redshift N S0 /N E Low redshift Z~0.5

6. Ram pressure stripping of the disk could transform a spiral into a S0 (Gunn & Gott 1972; Solanes & Salvador-Solé 2001) Another possibility: gradual decline in SFR due to loss of gas halo (Larson, Tinsley & Caldwell 1980; Balogh et al. 2000) May lead to anemic or passive spiral galaxies (Shiyoa et al. 2002) S to S0 transformation? Kenney et al. 2003 Vollmer et al. 2004 Non-SF spiral galaxies from SDSS (Goto et al. 2003) First noted by Poggianti et al. (1999) in z~0.5 clusters

7. S to S0 transformation? But bulges of S0 galaxies larger than those of spirals (Dressler 1980; Christlein & Zabludoff 2004) Requires S0 formation preferentially from spirals with large bulges (Larson, Tinsley & Caldwell 1980) perhaps due to extended merger history in dense regions (Balogh et al. 2002) Dressler 1980 Bulge size

8. 1.S0 galaxies found far from the cluster core –Galaxies well beyond R virial may have already been through cluster core (e.g. Balogh et al. 2000; Mamon et al. 2004; Gill et al. 2004) 2. Morphology-density relation holds equally well for irregular clusters, centrally-concentrated clusters, and groups - but may be able to induce bursts strong enough to consume the gas (see Mayer et al. poster) Gill et al. 2004 Groups (Postman & Geller 1984) Local galaxy density (3d) Spiral fraction Arguments against ram pressure stripping:

9. Galaxy colours Easier to measure than morphology (lower quality data) Easier to quantify Can be directly related to stellar population models

10. Early type galaxies Bower, Lucey & Ellis 1992 Tight colour-magnitude relation (Faber 1973; Visvanathan & Sandage 1977; Terlevich et al. 2001) E S0 Kuntschner & Davies 1998 (also Poggianti et al. 2001) see also Bernardi et al. 2003 for results based on SDSS data Field early-types ~2-3 Gyr younger than clusters (Kuntschner et al. 2002)

11. Early-type galaxies van Dokkum & Franx 1996: M/L evolution consistent with high formation redshift Z form = ∞ Z form =1 De Lucia et al. 2004 Kodama et al. 2004 (also Bell et al. 2003) Disappearance of faint red galaxies by z~1

12. Colour-magnitude relation CMR for spiral galaxies also observed (e.g. Chester & Roberts 1964; Visvanathan 1981; Tully, Mould & Aaronson 1982) SDSS allows full distribution to be quantified with high precision ( Baldry et al. 2003; Hogg et al. 2003; Blanton et al. 2003) Sloan DSS data

13. Baldry et al. 2003 (u-r) Analysis of colours in SDSS data: Colour distribution in 0.5 mag bins can be fit with two Gaussians Mean and dispersion of each distribution depends strongly on luminosity Dispersion includes variation in dust, metallicity, SF history, and photometric errors Bimodality exists out to z~1 (Bell et al. 2004) Bright Faint

15. Fraction of red galaxies depends strongly on density. This is the primary influence of environment on the colour distribution. Mean colours depend weakly on environment: transitions between two populations must be rapid (or rare at the present day)

16. Butcher-Oemler effect Concentrated clusters at high redshift have more blue galaxies than concentrated clusters at low redshift Butcher & Oemler (1984)

17. Butcher-Oemler Effect Andreon, Lobo & Iovino 2004 Blue fraction depends strongly on luminosity and radius Great care needs to be taken to evaluate blue fraction at same luminosity limit, and within same (appropriate) radius. Increase in blue fraction is not just restricted to clusters (e.g. Lilly et al. 1996) Margoniner et al. 2000 Margoniner et al. 2001 Redshift Blue fraction Radius (Mpc) Blue fraction

18. Kodama & Bower (2000) model: clusters inhibit star formation, but recent infall maintains a high blue fraction at higher redshift. Ellingson et al. (2001) Leads to steeper colour gradients in higher redshift clusters

19. Tully-Fisher relation at z~1 Spiral galaxies at z~1 (both cluster and field) are brighter in B than at low redshift Z~1 cluster spirals brighter at fixed  than field spirals (?) See poster by Milvang-Jensen et al. Milvang-Jensen et al. 2004

20. Star formation and gas

21. HI deficiency Bravo-Alfaro et al. 2000 Davies & Lewis 1973 VLA imaging of Coma spirals Mark I and II imaging of Virgo galaxies 18 nearby clusters: Solanes et al. 2001

22. Emission lines Dressler, Thompson & Shectman 1985; Also Gisler 1978 Cluster galaxies of given morphological type show less nebular emission than field galaxies suggests star formation is suppressed in cluster galaxies Emission line fraction

23. Emission line fraction in SDSS and 2dFGRS (Balogh et al. 2004) A901/902 supercluster (Gray et al. 2004) correlation with dark matter density Fraction of emission-line galaxies depends strongly on environment, on all scales Trend holds in groups, field, cluster outskirts (Lewis et al. 2002; Gomez et al. 2003) Fraction never reaches 100%, even at lowest densities Star formation Cluster infall regions

24. H  distribution Koopmann & Kenney 2004 also: Vogt et al. 2004 Cluster galaxies often show peculiar distribution of H  emission: usually truncated, or globally suppressed In some cases, star formation is centrally enhanced (Moss & Whittle 1993; 2000) Virgo spirals H  for Virgo galaxy H  for normal galaxy

25. Cluster galaxy evolution Kodama et al. 2004 Couch et al. 2001 Balogh et al. 2002 Fujita et al. 2003 Tresse et al. 2002 Complete H  studies: Even at z=0.5, total SFR in clusters lower than in surrounding field Field z~0.3 z~0.5 [OII] luminosity functions: Lotz et al. 2003 Martin et al. 2000 SDSS/2dFGRS: Emission-line galaxies only: Ha distribution does not depend strongly on environment (Balogh et al. 2004)

26. Emission lines at z~0.5 Dressler et al. 1997Balogh et al. 1998

27. Clusters Field 2dF Nakata et al., in prep Postman, Lubin & Oke 2001 van Dokkum et al. 2000 Fisher et al. 1998 Czoske et al. 2001 Cluster galaxy evolution

28. Complete H  based SFR estimates Evolution in total SFR per cluster not well constrained considerable scatter of unknown origin systematic uncertainties in mass estimates make scaling uncertain Kodama et al. 2004 Finn et al. 2003

29. Cluster galaxy evolution Complete H  based SFR estimates Evolution in total SFR per cluster not well constrained considerable scatter of unknown origin systematic uncertainties in mass estimates make scaling uncertain Kodama et al. 2004 Finn et al. in prep Finn et al. 2003

30. E+A galaxies Aka: k+a, a+k, PSG, PSB, HDS, e(a)…

31. Butcher-Oemler effect Many of blue galaxies turned out to have post- starburst spectra (Dressler & Gunn 1992; Couch & Sharples 1987) Also evidence for dust- obscured star formation from infrared (Fadda et al. 2000; Duc et al. 2002; Coia et al. 2004) SDSS: Goto et al. (2003) Couch & Sharples 1987Balogh et al. in prep. SDSS E+A galaxies

32. Poggianti et al. 2004 E+A galaxies in Coma may be correlated with X-ray emission Strong luminosity evolution in E+A population (Tran et al. 2003) Also found in the field (e.g. Zabludoff et al. 1996; Balogh et al. 1999). But bright, field E+A galaxies locally may have different origin. Balogh et al. in prep. E+A emission UKIRT imaging

33. Consistent interpretation? Dense environments predominantly quench star formation, probably via a variety of mechanisms Butcher-Oemler effect: –Strength of trend in clusters still debatable –May arise from higher rate of infall of initially bluer galaxies Galaxy interactions and mergers: –Build larger bulges in dense environments –Consume available gas in rapid starburst –Present in all environments, but more so at higher densities –Establish red sequence in clusters at early times

34. The future: Higher redshift clusters (e.g. RCS2, CFHTLS, HIROCS) HI and H  distributions at higher redshift Galaxy groups, filaments etc. Direct comparison with simulations. Initial look shows current models get broad correlations correct, but details more difficult to understand

35. Time run out? References to your figure here

36. H  distribution H  distribution shows a bimodality: mean/median of whole distribution can be misleading Balogh et al. 2004

37. Infared luminosity functions Balogh et al. (2001) evidence that MF does not vary strongly with environment. Also De Propris et al. (1998): find Coma LF consistent with the field