Galaxy properties in different environments: Observations

Michael Balogh University of Waterloo, Canada

(Look for 3 new job postings on AAS soon)

Outline

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

Galaxy morphology

Morphology-Density Relation

Coma cluster Clusters • Morphological mix correlates best with local galaxy density E S0 Spirals • Possibly additional effects in innermost regions (Whitmore et al. 1995; Dominguez et al. 2001)

Dressler 1980 Also: Oemler 1974; Melnick & Sargent 1977

Morphology-density: evolution

Low redshift Z~0.5

Log surface density Redshift Dressler et al. 1997; Couch et al. 1994; 1998 Fasano et al. 2000 Wide field HST: Treu et al. 2003

S to S0 transformation?

Kenney et al. 2003 Vollmer et al. 2004 • 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) Non-SF spiral galaxies from SDSS (Goto et al. 2003) First noted by Poggianti et al. (1999) in z~0.5 clusters

S to S0 transformation?

• But bulges of S0 galaxies larger than those of spirals (Dressler 1980; Christlein & Zabludoff 2004) Bulge size Dressler 1980 • 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)

Arguments against ram pressure stripping: Gill et al. 2004 1. S0 galaxies found far from the cluster core – Galaxies well beyond R Gill et al. 2004) virial may have already been through cluster core (e.g. Balogh et al. 2000; Mamon et al. 2004;

Groups (Postman & Geller 1984)

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) Local galaxy density (3d)

Galaxy colours

• • • Easier to measure than morphology (lower quality data) Easier to quantify Can be directly related to stellar population models

Early type galaxies

Tight colour-magnitude relation (Faber 1973; Visvanathan & Sandage 1977; Terlevich et al. 2001) E S0 Bower, Lucey & Ellis 1992 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)

Early-type galaxies

Z form = ∞ van Dokkum & Franx 1996: M/L evolution consistent with high formation redshift 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

Colour-magnitude relation

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

Bright Faint (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)

Baldry et al. 2003

• 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)

Butcher-Oemler effect

• Concentrated clusters at high redshift have more blue galaxies than concentrated clusters at low redshift Butcher & Oemler (1984)

Butcher-Oemler Effect

Margoniner et al. 2000 • 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) Radius (Mpc) Andreon, Lobo & Iovino 2004 Redshift Margoniner et al. 2001

• Kodama & Bower (2000) model: clusters inhibit star formation, but recent infall maintains a high blue fraction at higher redshift.

• Leads to steeper colour gradients in higher redshift clusters Ellingson et al. (2001)

Tully-Fisher relation at z~1

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

Star formation and gas

HI deficiency

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

Emission lines

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

Star formation

• 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 Cluster infall regions A901/902 supercluster (Gray et al. 2004) correlation with dark matter density Emission line fraction in SDSS and 2dFGRS (Balogh et al. 2004)

Virgo spirals

H

a

distribution

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

z~0.3

Cluster galaxy evolution

Kodama et al. 2004 Field Couch et al. 2001 Balogh et al. 2002 Fujita et al. 2003 Field Tresse et al. 2002

z~0.5

Complete H a studies: Even at z=0.5, total SFR in clusters lower than in surrounding field [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)

Emission lines at z~0.5

Dressler et al. 1997 Balogh et al. 1998

Cluster galaxy evolution

Field

2dF

Clusters

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

• Complete H a estimates based SFR • 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

Cluster galaxy evolution

Finn et al. 2003 • Complete H a estimates based SFR • 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

E+A galaxies

• Aka: k+a, a+k, PSG, PSB, HDS, e(a)…

Butcher-Oemler effect

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

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).

bright, field E+A galaxies locally may have different origin.

But UKIRT imaging Balogh et al. in prep.

emission E+A

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

The future:

• Higher redshift clusters (e.g. RCS2, CFHTLS, HIROCS) • HI and H a 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

Time run out? References to your figure here

H

a

distribution

• H a distribution shows a bimodality: mean/median of whole distribution can be misleading

Balogh et al. 2004

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