すばるが見た遠方銀河団 distant clusters of galaxies: take a closer look Masayuki Tanaka (University of Tokyo) Tadayuki Kodama (NAOJ) + PISCES team picture credits: Sloan Digital Sky Survey, Robert Lupton (Princeton)

Outline 1 – Introduction 1-1 Environmental Dependence of Galaxy Properties 2 – Large-Scale Structures at z< Observational Data 2-2 Large-Scale Structures 3 – The Build-up of the Color-Magnitude Relation 3-1 Definitions of Environments 3-2 Color-Magnitude Diagrams 4 – Summary

1-1 Environmental Dependence of Galaxy Properties cluster galaxies field galaxies environment galaxy density

Galaxies in low-density environments NGC5668

Galaxies in high-density environments Coma cluster

The environmental dependence of galay morphology was first quantified by Dressler 1980 (ApJ, 236, 351) Morphology-Density Relation galaxy densityhigh low population fraction S0 E Sp + Irr

SFR-Density + Morph.-Density Rels Revisited Tanaka et al AJ, 128, 2677 Based on a large sample of SDSS galaxies, we revisited the SFR-density and morphology-density relations. Galaxies with different luminosity have different dependence on environment. Mr < Mr* + 1 Mr* + 1 < Mr < Mr* + 2

PISCES Project - is a systematic survey of galaxy clusters at 0.4<z<1.2 Kodama et al. 2005, PASJ, 57, 309

Outline 1 – Introduction 1-1 Environmental Dependence of Galaxy Properties 2 – Large-Scale Structures at z< Observational Data 2-2 Large-Scale Structures 3 – The Build-up of the Color-Magnitude Relation 3-1 Definitions of Environments 3-2 Color-Magnitude Diagrams 4 – Summary

2-1 Observational Data Mauna Kea Observatories

redshift z=0 z=1.24 (8.6Gyr) z=0.55 (5.4Gyr) z=0.83 (7.0Gyr) Source Photometry Spectroscopy Sloan Digital Sky Survey u g r i z ~260,000 objects (DR2) Suprime-Cam (Subaru) B V R i z FOCAS (Subaru) ~200 objects Suprime-Cam (Subaru) V R i z FOCAS (Subaru) ~300 objects Suprime-Cam (Subaru) V R i z WFCAM (UKIRT) K CL RXJ0152 RDCS1252

Photometric Redshifts z=0.83 idea: galaxies at different redshifts have different observed colors.

How accurate is it?

2-2 Large-Scale Structures Mauna Kea Observatories

CL0016 at z=0.55 ACS/ HST Color composition by Ichi Tanaka

Large-Scale Structures CL0016 at z=0.55

Large-Scale Structures CL0016 at z=0.55 real structures! Hoshi et al. in prep.

RXJ0153 at z=0.83 Color composition by Ichi Tanaka

Large-Scale Structures RXJ0152 at z=0.83

Large-Scale Structures RXJ0152 at z=0.83

Large-Scale Structures RXJ0152 at z=0.83 z=0.844 z=0.842 z=0.745 z=0.782 z=0.835 z=0.837 z=0.839 z=0.844

RDCS1252 at z=1.24

Large-Scale Structures RDCS1252 at z=1.24

Outline 1 – Introduction 1-1 Environmental Dependence of Galaxy Properties 2 – Large-Scale Structures at z< Observational Data 2-2 Large-Scale Structures 3 – The Build-up of the Color-Magnitude Relation 3-1 Definitions of Environments 3-2 Color-Magnitude Diagrams 4 – Summary

3-1 Definition of Environments RDCS1252 (z=1.24) is not used from now on.

Local / Global Density local density + global density (nearest-neighbor density) (density within r=2Mpc aperture) Field :  local <  break Group :  local >  break +  global <  break Cluster ：  local >  break +  global >  break

Cluster / Group / Field Environments redshift z=0 z=0.55 z=0.83

Fast Facts galaxy-galaxy mergers <1Gyr strong field/group harassment ? strong cluster ram-pressure stripping <1Gyr weak cluster strangulation ~1Gyr weak group/cluster mechanisms star formation morphology effective env.

2-4 Colour-Magnitude Diagrams Mass Time Galaxy Colours Environment

Colour-Magnitude Diagrams red blue z=0 z=0.55 z=0.83 redshift massive less massive

Colour Dispersion around CMR z=0.83 z=0.55 z=0

Giant-to-Dwarf ratio z=0.8 z=0.5 z=0

Colour-Magnitude Diagrams red blue z=0 z=0.55 z=0.83 redshift massive less massive 2) 'Down-sizing' is delayed in low-density environments. 1) Galaxies follow the 'down-sizing' evolution.

3.3 – Spectral Diagnostics

Composite Spectra of Red Galaxies

D4000 and Hd D4000 Hd

D4000 and Hd D4000 Hd D4000 monotonically changes with time. Hd shows a peak after 0.1 – 1 Gyr of the last episode of star formation.

Model Star Formation Histories time star formation rate SSP model tau model burst model Bruzual & Charlot 2003 Model : Chabrier IMF between Msolar Solar Metallicity, No dust extinction

Spectral Diagnostics – SSP model grids: Bruzual & Charlot 2003 contours : galaxies at z=0

Spectral Diagnostics – tau model model grids: Bruzual & Charlot 2003 contours : galaxies at z=0

Spectral Diagnostics – burst model model grids: Bruzual & Charlot 2003 contours : galaxies at z=0

Outline 1 – Introduction 1-1 Environmental Dependence of Galaxy Properties 2 – Large-Scale Structures at z< Observational Data 2-2 Large-Scale Structures 3 – The Build-up of the Color-Magnitude Relation 3-1 Definitions of Environments 3-2 Color-Magnitude Diagrams 4 – Summary

Schematic View of Galaxy Evolution Environment Mass Time

Environment Mass Time Schematic View of Galaxy Evolution

Environment Mass Time Schematic View of Galaxy Evolution

Environment Mass Time Schematic View of Galaxy Evolution

Environment Mass Time Schematic View of Galaxy Evolution

Environment Mass Time Schematic View of Galaxy Evolution

Photometric Redshifts from VRiz photometry Redshifts of very blue galaxies deviate....

Fast Facts galaxy-galaxy mergers <1Gyr strong field/group harassment ? strong cluster ram-pressure stripping <1Gyr weak cluster strangulation ~1Gyr weak group/cluster mechanisms star formation morphology effective env.

redshift massive less massive red blue z=0 z=0.55 z= – We observed the build-up of the CMR. We suggest that galaxies follow the 'down-sizing' evolution, and the 'down-sizing' is delayed in low density environments. 2 – We spectroscopically confirmed the large-scale structures at z=0.83. Our current data seem to favour a scenario that star formation is quenced in a short time scale (<1Gyr). The physical process behind the build-up of the CMR would be galaxy-galaxy mergers.