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The evolution of (the number density of) morphologically-selected early-type galaxies

C. Scarlata. The evolution of (the number density of) morphologically-selected early-type galaxies. - Motivation Non-parametric morphological analysis Sample selection Number density evolution of M.S.E.T. galaxies Conclusions & Future. For each galaxy we measured:

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The evolution of (the number density of) morphologically-selected early-type galaxies

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  1. C. Scarlata The evolution of (the number density of) morphologically-selected early-type galaxies • - Motivation • Non-parametric morphological analysis • Sample selection • Number density evolution of M.S.E.T. galaxies • Conclusions & Future

  2. For each galaxy we measured: • Gini coefficient • M20 • Concentration • Asymmetry INITIAL SAMPLE: ~ 60,000 galaxies with IAB< 24, detected on the ACS images How to combine this information?

  3. PC2 = 0.05C - 0.94 A + 0.34G PC1 = 0.91 C- 0.28A+ 0.84 G Principal components analysis PCi are linear combinations of the C,A,G, (and M20) Parameter space is reduced to 2 dimensions

  4. Morphological EARLY-TYPE (Sersic n>2.5, Mark’s analysis ) Meaning of the Principal Components (BRIGHT CONTROL SAMPLE, 14000 GALAXIES with IAB < 22.5) A>0.3 -2 PC2 4 -2 2 PC1 0 4

  5. Morphological EARLY-TYPE (Sersic n>2.5, Mark’s analysis ) THIS TALK: PC2<1.2, PC1>1.5 “SYMMETRIC”, “EARLY-TYPE” GALAXIES -2 PC2 4 1.2 -2 2 PC1 0 4 1.5 8038 PC1,PC2-selected GALAXIES with IAB<24

  6. PC1-PC2 selected sample >0.7 FURTHER CUT TO SAMPLE, WHICH LEAVES: 7835 PC1,PC2-SELECTED GALAXIES WITH<0.7

  7. Kormendy relation Solid line: (Joergensen et al. 1995) Galaxies in shaded area cannot “passively” evolve onto the z=0 Kormendy relation of massive galaxies FURTHER CUT TO SAMPLE

  8. FINAL SAMPLE: 6751 MORPHOLOGICALLY-SELECTED, EARLY-TYPE galaxies down to IAB of 24.

  9. Evolution of the number density of morphologically- & Kormendy-selected early-type galaxies

  10. Evolution of the number density of morphologically- & Kormendy-selected early-type galaxies • NUMBER DENSITY • OF MORPHOLOGICALLY- • & KORMENDY-SELECTED • EARLY-TYPE GALAXIES: • CONSTANT OUT TO z~0.9 • SHARP DROP (~x3) BEYOND!

  11. Luminosity function (1/Vmax)

  12. Conclusions • Non parametric morphological analysis robust down to I<24 • PCA reduces the parameter space • PC-selected sample of early-type galaxies down to IAB=24 • Decrease of factor ~3 of the number density of “early-type” galaxies between z~0.9 and z~1.2 In progress • USE PCA ANALYSIS TO IDENTIFY GALAXY POPULATIONS • STUDY EVOLUTION OF STRUCTURE, CLUSTERING PROPERTIES, HALO-OCCUPATION-STATISTIC OF DIFFERENT POPULATIONS (see Porciani’s talk) • EVOLUTION = f(ENVIRONMENT)

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