18 / Feb / 2008 Galaxy Evolution Meeting 김태선 & 이석영 Dept. of Astronomy, Yonsei University Intrinsic Axis Ratio Distribution of Early-type Galaxies Using SDSS (DR5) SDSS-KSG Kimm & Yi (2007, ApJ)

Intrinsic Shapes Apparent Flattenings Hubble (1926) Oblate : isotropic velocity dispersion Prolate : isotropic Triaxial : anisotropic velocity dispersion ETG Kinematics ← galaxy formation process e.g. (Sandage, Freeman & Stokes, 1970 ; Binney, 1978; de Zeeuw 1980; Fasano & Vio, 1991; Lambas, Maddox & Loveday, 1992; Ryden 1992; Ryden & Vincent, 2005) Introduction 1. Introduction 2. Model 3. Data 4. Results 5. Conclusion ? M87 (AAT)

Theoretical distribution Assumption Ellipticals are geometrically perfect ellipsoid Galaxies are randomly oriented Oblate, Prolate and Triaxial Classification Franx, Illingworth & de Zeeuw (1991) Apparent Axis Ratio Distribution Franx et al. (1991) Probability distribution 1. Introduction 2. Model 3. Data 4. Results 5. Conclusion

SDSS Sample Selection and Data Analysis Morphological Classifications - Define early-types with fracdev greater than Visual inspection : spiral contaminants and severely-distorted galaxies redshift Luminosity r ≤17.5 Luminosity Dependence 1. Introduction 2. Model 3. Data 4. Results 5. Conclusion APM

Intrinsic Axis Ratio Distribution for Volume-limited Sample (con.) Random distribution of intrinsic axis ratios 1. Introduction 2. Model 3. Data 4. Results 5. Conclusion poor reduced chi-square statistics (~ 50) No linear combination of OPT types with random ARD reproduces the observed ARD of our sample !

Intrinsic Axis Ratio Distribution for Volume-limited Sample (con.) Gaussian Distribution 1. Introduction 2. Model 3. Data 4. Results 5. Conclusion

Intrinsic Axis Ratio Distribution for Volume-limited Sample range (dotted line) Comparison with other studies - μ t,β =0.95, μ t,γ =0.55, σ t,β =0.35, σ t,γ =0.2 from APMBGS (Lambas et al. 1992) - γ ≥ 0.8 for triaxial ellipticals from SAURON data ( Cappellari et al. 2007) - =0.71, =0.50 for DMH (N-body, Dubinski & Carlberg, 1991) - β=0.75 ±0.15, γ=0.6 ±0.1 for DMH (N-body, Bailin & Steinmetz, 2005) - Triaxial DMH & oblate galaxies (N-body, Novak et al, 2006) With Gaussianity, observed ARD is successfully reproduced with reduced χ 2 ~1. 1. Introduction 2. Model 3. Data 4. Results 5. Conclusion

Intrinsic ARD for different Luminosities (con.) Dichotomy Bright ellipticals : slow -rotators, core profile, boxy -isophotes Faint ellipticals : fast -rotators, power-law profile, disky isophotes (Davies et al. 1983; Bender, 1988; Kormendy & Bender, 1996; Faber et al. 1997) Division at M B ~-20 (Tremblay & Merritt, 1996; Rest & van den Bosch, 2001) Data Mr~ Introduction 2. Model 3. Data 4. Results 5. Conclusion

μ (luminous) ~ μ (less luminous) Triaxial type : "luminous" sample Consistent result with Naab et al. (2006) in terms of the ratio of the anisotropic gals ( Luminous : 0.8, less luminous : 0.4) assuming S-S, S-E and E-E mergers 1. Introduction 2. Model 3. Data 4. Results 5. Conclusion Intrinsic ARD for different Luminosities (luminous) (less luminous)

ARD (high density) ~ ARD (low density) see also (Park+2007) 1. Introduction 2. Model 3. Data 4. Results 5. Conclusion ARD for different environment

Conclusions Intrinsic shapes of Early-type galaxies are not Random Gaussian ARD ( O ) Triaxial type : “luminous” sample, oblate : “less luminous” sample very similar preference of OPT between “luminous” and “less luminous” sample no clear connection between environment and galaxy shape 1. Introduction 2. Model 3. Data 4. Results 5. Conclusion

Thanks