The evolution of (the number density of)

morphologically-selected early-type galaxies

C. Scarlata

- Motivation- Non-parametric morphological analysis- Sample selection - Number density evolution of M.S.E.T. galaxies- Conclusions & Future

For each galaxy we measured:

• Gini coefficient• M20 • Concentration• Asymmetry

How to combine this information?

INITIAL SAMPLE: ~ 60,000 galaxies with IAB< 24, detected on the ACS images

PCi are linear combinations of the C,A,G, (and M20)

Parameter space is reduced to

2 dimensions

PC1 = 0.91 C - 0.28 A + 0.84 G

PC

2 =

0.0

5 C

- 0

.94 A

+ 0

.34 G

Principal components analysis

Meaning of the Principal Components(BRIGHT CONTROL SAMPLE, 14000 GALAXIES with IAB < 22.5)

Morphological EARLY-TYPE(Sersic n>2.5, Mark’s analysis )

-2 2 PC1 0 4

-2

P

C2

4

A>0.3

THIS TALK: PC2<1.2, PC1>1.5“SYMMETRIC”, “EARLY-TYPE” GALAXIES

Morphological EARLY-TYPE(Sersic n>2.5, Mark’s analysis )

-2 2 PC1 0 4

-2

P

C2

4

1.5

1.2

8038 PC1,PC2-selected GALAXIES with IAB<24

PC1-PC2 selected sample

>0.7

FURTHER CUT TO SAMPLE, WHICH LEAVES:7835 PC1,PC2-SELECTED GALAXIES WITH <0.7

Galaxies in shaded areacannot

“passively” evolve onto the

z=0 Kormendy relation of massive galaxies

FURTHER CUT TO SAMPLE

Kormendy relation Solid line: (Joergensen et al. 1995)

FINAL SAMPLE:6751 MORPHOLOGICALLY-SELECTED,

EARLY-TYPE galaxies down to IAB of 24.

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

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

NUMBER DENSITYOF MORPHOLOGICALLY-& KORMENDY-SELECTED EARLY-TYPE GALAXIES:

- CONSTANT OUT TO z~0.9- SHARP DROP (~x3) BEYOND!

Luminosity function (1/Vmax)

Conclusions

1. Non parametric morphological analysis robust down to I<24

2. PCA reduces the parameter space

3. PC-selected sample of early-type galaxies down to IAB=244. Decrease of factor ~3 of the number density of “early-

type” galaxies between z~0.9 and z~1.2

In progress

1. USE PCA ANALYSIS TO IDENTIFY GALAXY POPULATIONS2. STUDY EVOLUTION OF STRUCTURE, CLUSTERING

PROPERTIES, HALO-OCCUPATION-STATISTIC OF DIFFERENT POPULATIONS (see Porciani’s talk)

3. EVOLUTION = f(ENVIRONMENT)