Disentangling Luminosity, Morphology, Stellar Age, Star Formation, and Environment in Galaxy Evolution Daniel Christlein Andes Fellow Yale University & Universidad de Chile & Ann Zabludoff (U Arizona) ?=?= Kant: Systems of Fixed Stars, Arrangements of Worlds, Worlds of Worlds, Milky Ways of Worlds Island Universes

We know some basic statistics about galaxies: - Luminosity Function - Morphology-Environment Relation - Star Formation-Environment Relation but understanding incomplete: -environmental dependence of LF? -origin of morphological sequence? -Nature or Nurture? < Binggeli, Sandage & Tamman 1988

The Data - 6 nearby (z<0.07), rich clusters - R-band photometry - spectroscopy for ~3000 galaxies: star formation indices, stellar age indices - 2MASS J-, K-photometry -> stellar mass - quantitative morphology with GIM2D (Simard 2002) - new ML algorithm Abell 1060

Christlein & Zabludoff (2003) I s Luminosity Function Dependent on Environment? ● field and cluster overall GLFs same ● no difference for star-forming galaxies ● GLFs for quiescent galaxies steeper in clusters X

● steepening of quiescent LF ● difference between field and groups, not groups and clusters Which Environments Shape the GLF?

GLFs are pretty uniform in clusters (>60%, >40% for NEL) all galaxiesquiescent galaxies - the high-mass end

● quiescent GLF ● dwarf/giant ratio ● uniformity of GLF in clusters ● 2dF & SDSS: break in SFR ●  cD < 400 km s -1 ● gE in subclumps ● early type fraction ● HI deficiency in groups many saturation points: => Groups are where it's at! Gomez et al. Lewis et al. Are Groups the Most Important Environments? x

● quantify morphology by bulge fraction (B/T; GIM2D) ● dense environments => higher bulge fraction ● two types of transformation mechanisms: ● disk fading (e.g., ram-pressure stripping, strangulation) ● increasing bulge luminosity (e.g., tidal interactions, mergers) Christlein & Zabludoff 2004 How to Make an Early-Type Galaxy

The Discrete Maximum Likelihood Method - ansatz for parent distribution: - pipe it through maximum likelihood optimizer - natural treatment of multivariate distributions - correct relative normalization - easy to code - retains advantage of ML method Christlein, McIntosh & Zabludoff, 2004 X

How to Make an Early-Type Galaxy  B/T  late-type spirals

How to Make an Early-Type Galaxy  B/T  early-type spirals

How to Make an Early-Type Galaxy  B/T  early-type spirals & S0s

How to Make an Early-Type Galaxy  B/T  S0

How to Make an Early-Type Galaxy  B/T  S0s & Es

How to Make an Early-Type Galaxy  B/T  E

How to Make an Early-Type Galaxy  B/T  E disk-dominated bulges are brighter, but disks not fainter, in bulge-dominated systems => bulge-dominated systems (e.g., "S0s") cannot be produced by disk-fading alone

The Star Formation Gradient Gomez et al. Lewis et al. Christlein & Zabludoff 2004b MorDen

Star Formation Morphology Stellar Mass Stellar Age Star formation gradient and morphology-environment relation the same? Star formation gradient due to initial conditions?

Partial Correlation Coefficients r Star Formation,Environment. Morphology,Stellar Mass, Mean Stellar Age Star Formation EW([OII]) EnvironmentR  Morphology B/T Stellar Massfrom 2MASS J, K & D4000 Mean Stellar AgeD4000 hold constant residual correlation

Removing Morphology, Stellar Mass, Stellar Age... total SF gradient residual SF gradient r = (Z=10.9  )r = (Z=8.0  ) => SF gradient not explained by Morphology, Stellar Mass, Stellar Age gradients

Conclusions LF vs. environment - little change in LF from field -> cluster or cluster -> cluster - significant steepening of quiescent LF field -> groups - little variation of quiescent LF groups -> clusters or cluster -> cluster => strong impact of environment on SF properties, little on luminosity => lower-density envs. decisive

Bulge/Disk LFs vs. Morph. & Env. -Early Types are Early Types because Bulges are brighter, not because Disks are fainter => Bulge-enhancing processes (e.g., tidal interactions, mergers) necessary -> low-density envs Conclusions(2)

Residual SF gradient remains after accounting for Morphology, Stellar Mass, Stellar Age - smoking gun for late-epoch environmental transformations - net effect of evolutionary/formation mechanisms on star formation & morph. dependent on environment Conclusions (3)

The End

Morphology-Environment Relation SF gradient The End

- Which Environment? Radius or Local Density? Morph. Evolution (bulge enhancement) probably driven by LD but residual SF impact could have different dependence - define environmental indices sensitive to mechanisms?

uncorrected corrected Corrected vs. uncorrected Spearman Coefficients The End

Corrected vs. uncorrected Spearman Coefficients =0 uncorrected r corrected r The End