Multi-wavelength Properties and Environments of the SDSS Galaxies divided into Fine Classes

1. September 16, 2009 Joon Hyeop Lee Korea Astronomy and Space Science Institute Co-workers: Myung Gyoon Lee (SNU), Changbom Park (KIAS), Yun-Young Choi (ARCSEC) KASI Colloquium Multi-wavelength Properties and Environmentsof the SDSS Galaxies divided into Fine Classes

2. Many kinds of galaxies with various properties shape size / luminosity /mass color mass-to-light ratio surface brightness spectrum star formation AGN activity

3. How have the various galaxies formed and evolved? Classifying galaxies and comparing between different types of galaxies. Which quantity should we use to classify galaxies?

4. In many previous studies, galaxies have been investigated, using various classifications. - The three most-frequently-used quantities for galaxy classification aremorphology,color and spectral features: • morphology (early-type vs. late-type; e.g. Choi et al. 2007) • color (red vs. blue; e.g. Martin et al. 2007) • spectral features (passive vs. star-forming vs. AGN; e.g. Mateus et al. 2006) Among those several major criteria, only one criterion used to be adopted for galaxy classification in most previous studies. Early-type = Red = Passive ? Late-type = Blue = Star-forming ? NOT ALWAYS !

5. Blue early-type galaxies: elliptical morphology, but blue color • - Abraham et al. 1999; Ferreras et al. 2005; Lee et al. 2006 • Passive spiral galaxies: spiral morphology, but no signal of current star formation • - Couch et al. 1998; Goto 2003; Yamauchi & Goto 2004

6. Red AGN Seyfert Early-type Blue HII LINER Late-type Kauffmann et al. (2003) Kewley et al. (2006) Park & Choi (2005) Lee et al. (2006) → Passive, HII, Seyfert, LINER → Early-type galaxies Late-type galaxies → Red galaxies Blue galaxies Mutilateral Classification (1) Morphology (2) Color (3) Spectral Features

7. blue red early-type late-type passive HII Seyfert LINER color spectral features morphology

8. Sample Selection K-correction:Blanton et al. (2003) Evolutionary correction:Tegmark et al. (2004) Completeness limit: 14.5<rpet<17.77

9. Most physical properties of galaxies are known to be dependent on their velocity dispersion. In each quantities, sampling errors were estimated by calculating the standard deviation of the median values in 200-times repetitive samplings. “The nature of the SDSS galaxies in various classes based on morphology, colour and spectral features - I. Optical properties”, Lee et al. (2008) MNRAS, 389, 1791

10. “The nature of the SDSS galaxies in various classes based on morphology, colour and spectral features - I. Optical properties”, Lee et al. (2008) MNRAS, 389, 1791

11. pREG pBEG Compared topREG: less concentrated bluer outskirt less spheroidal Compared topBEG: bluer center more concentrated Compared topREG: totally bluer similarly concentrated hREG hBEG

12. Different origins of star formation Star formation in REGs is dominant in their outskirt, while star formation in BEGs is dominant in their center? hREG : early-type galaxies with small disk components? (gas infall?)‏ hBEG: objects in the final phase of early-type formation? (galaxy merger?)‏

13. RLGs have smaller axis ratio than that of BLGs on average. BLG RLG Late-type galaxies with large inclination may be often classified as RLGs due to dust extinction.

14. At axis ratio > 0.6 (small inclination), RLGs are more concentrated than BLGs. BLG RLG One major origin of the red color of RLGs may be their large bulge fraction.

15. pRLGs are similar to REGs in many aspects (color, axis ratio, Dn(4000), and so on), although they are less concentrated than typical REGs. These may be intermediate between early-type and late-type.

16. “The nature of the SDSS galaxies in various classes based on morphology, colour and spectral features - II. Multi-wavelength properties”, Lee et al. (2009) MNRAS, submitted REGs show narrowly-ranged median colors, which are consistent with the 6 – 8 Gyr old SSP model. pREGs have slightly bluer color than the other REGs: metallicity effect? (comp. metallicity estimation of Gallazzi et al. 2006) (2) pBEGs, lBEGs vs. hBEGs, sBEGs: SSP + EXP model?

17. “The nature of the SDSS galaxies in various classes based on morphology, colour and spectral features - II. Multi-wavelength properties”, Lee et al. (2009) MNRAS, submitted (3) The colors of pRLGs are similar to those of REGs, but RLGs (rectangles) are located on a sequence from REG colors to decreasing (u – r ) color. → redbulge + SF disk (4) pBLGs seem to have very young mean stellar ages, although they are spectroscopically passive. → passive only in the center, or recent SF quenching?

18. IRAS detection fraction BLGs are better detected than RLGs, which shows that the dominant factor to make RLGs red may be the bulge-to-disk ratio rather than dust contents.

19. Best et al. (2005) and Croft et al. (2007) showed that the fraction of radio-loud AGN host galaxies is a strong function of stellar mass. Early-type radio source: radio-loud AGNs. Late-type radio source: star formation regions. FIRST detection fraction

20. Discussion • Bulge formation vs. Disk formation • Bulge: hBLGs → (merging) → hBEGs → sBEGs(lBEGs) → pBEGs → pREGs? • Disk: pREGs → hREGs →sREGs, lREGs (→ pREGs)? • pREGs → hRLGs →sRLGs, lRLGs (→ pRLGs)?

21. Discussion • 2. The role of Environments • High local number density: accelerates the evolution of galaxies by means of frequent merging and interaction. • e.g.) pREGs ------- hBEGs ------- hBLGs • Close neighbor: directly affects star formation by either preventing it or stimulating it (according to the property of the close pair). • Sometimes affects the AGN type? • e.g.) sBLGs vs. lBLGs • Galaxy cluster: hinders the AGN activity in most red galaxies. • e.g.) sREGs, lREGs, lRLGs • Open question: Why galaxy cluster environments do not seem to prevent the star formation of red galaxies, while they prevent the AGN activity of red galaxies?

22. Future Works • To study more detailed properties of several fine classes that show some remarkable features. • e.g.) Red HII galaxies in cluster environments • Blue early-type galaxies (AKARI spectroscopy) • Radio-loud passive galaxies • and so on… • - Internal structure analysis • 2. To expand this study to intermediate and high redshifts. • e.g.) GOODS, UDF, DEEP2, SPITZER, AKARI, • or some future observations. • - Redshift evolution of the fine classes