Conference Introduction

Duncan Forbes

Swinburne University

Conference Introduction

Thanks to Meghan, Frazer and Mike

Preview the upcoming conference (ie I’ll give the least accurate talk)

Personal and biased view (ie I’ll forget to mention your seminal paper on environment)

Lets have a clean and open discussion (no plutos)…

This conference aims to…disentangle the complex interplay between nature and nurture.

Malaysia, March 2009

SOC chair:

Lourdes Verdes Montenegro

Defining Environment

Field, Group and Cluster

• Projected local number density of nearby galaxies (volume density better)

• Cluster-centric distance (which centric?)

Defining Environment

Halo, subhalo, satellite

• Halo mass• 3D dark matter density

Morphology-Density Relation

Dressler 1980

Clusters

Field

With time, spirals are replaced by S0s - Dressler et al. 1997

Morphology-SF-Density Relation

for Dwarf galaxies

Forbes et al. 2003

dI ->

dE ->

dSph

Einasto et al. 1974

Mayer et al. 2006

What supresses star formation?

Hopkins et al. 2004

Environmental Madau plot

Crain et al. 2009

Gray et al. 2004

• 2dFGRS (Lewis et al. 2002) and SDSS (Gomez et al. 2003) => pre-processing in Groups ?

• The low density Field includes some quiescent galaxies (Gray et al. 2004)

Supression at (group-like) densities

What supresses star formation?

Haines et al. 2007

Observation

Lower density, less SF

suppressed

100% star forming

What supresses star formation?

Croton et al. 2006

Model

Haines et al. 2007

Observation

Environmental Processes

• Steady gas accretion• Ram pressure stripping (gas

removal)• Strangulation (turnoff gas supply) • Interactions & Harassment (high )• Mergers (low )

Review by Boselli & Gavazzi 2006

Kacprzak et al. 2009

High redshift gas accretion

Stream-fed galaxies

Dekel et al. 2009

Rasmussen et al. 2006

Stripping in a Group

=> Formation of dark-matter free Tidal Dwarf Galaxies ?

Interactions and Mergers

Globular Cluster tidal stripping/accretion

Bekki etal. 2003

Environmental Processes

• Ram pressure stripping (gas removal)• Strangulation (turnoff gas supply) • Steady gas accretion• Interactions & Harassment (high )• Mergers (low )

Are their timescales and any feedback processes consistent with the observed

Red sequence, green valley and blue cloud ?

“The Dearth of Environment Dependence”

Van den Bosch et al. 2008

Van den Bosch etal. 2008

Formation vs Assembly

De Lucia 2007

~13 Gyrs old

dissipative

rapid burst

NGC1400

MB = -20

E/S0

Spolaor et al. 2008

50%

See poster by Foster et al.

NGC 4649 Globular Clusters

Pierce et al. 2006

Cluster-centric predictions

Caution: global vs central values

Caution: physical vs projected radii

Caution: splashback

De Lucia 2007

Isolated Elliptical GalaxiesA `control’ sample unaffected by the

group/cluster environment

• Reda, Forbes et al. (2004)• Early-type galaxy, V < 9,000 km/s, B < 14No neighbours within:• 700 km/s• 0.67 Mpc in plane of the sky• 2 B mags (factor of 6 in mass)

=> 36 ellipticals

Fundamental Plane

Deviant galaxies have young stellar populations and/or disturbed morphology

Reda, Forbes & Hau 2005

NGC 821 - the nearest isolated elliptical galaxy ?

Radial Ages - NGC 821

Proctor,Forbes etal. 2005

Galaxy Bimodality

MV ~ -20, M~3x1010 Mo, Mhalo~6x1011Mo

Luminosity function, Colour-magnitude, Star formation rates, bulge/disk ratio, X-ray emission, stellar age, AGN emission, M/L ratio

Globular Cluster Specific Frequency

Transition from hot accretion flows to cold accretion plus AGN/SN feedback (see Dekel, Keres, Croton etc)

Relative GC numbers versus host galaxy stellar

massGC TN-parameter

M* = galaxy stellar mass computed from 2MASS K-band mag

Problem: Star formation histories varyTransition at M*~few x 1010 Msun

(Forbes 2005)

Gal

axy

Hal

o M

ass

Globular Cluster System MassSpitler & Forbes 2009No clear environment trend

Globular Clusters in Galaxy Clusters

Where are the GCs in the Virgo galaxy cluster?

25% in M87 46% satellites 29% intracluster100%

The GC mass of a cluster-sizedhalo should include these 3components.

(Bekki et al. 2006)

Gal

axy

Hal

o M

ass

Globular Cluster System Mass

globular clusters are ~0.007% of a halo’s mass

Potential method for determining Halo Masses…

GC formation appears to be directly proportional to the host halo mass0.007% of Halo Mass = (Globular Cluster System Mass)

Conclusions

• Massive isolated galaxies can be quiescent• Environment influences greater for dwarfs• Galaxy (and GC) properties are bimodal• Consider formation vs assembly times• Galaxies have (strong) mass trends• Some isolated galaxies show signs of a

merger• Globular clusters provide an alternative

probe of galaxy formation and assembly• And finally…

…Not Nature vs Nurture but Nature AND Nurture

Have a great conference…