1. Galaxy Classification in the WISE Color-Luminosity Diagram
우주탐사회 ~ 12.
Galaxy Classification in the WISE Color-Luminosity Diagram
이광호 (서울대학교)
SDSS DR10
WISE

2. Optical Color-Magnitude Diagram
Red quiescent galaxies, mainly ETGs
Green Valley
Blue star-forming galaxies, mainly LTGs
Masters+11

3. Galaxy Migration in CMD
In terms of - SF quenching - Mass buildup
A Key Question Did quenching occur early in the process of mass buildup, midway, or late?
Faber+07
The transition timescale must be short (~ 1 Gyr)!!
Since the color bimodality will never be seen if the transition timescale is over a Hubble time (Pan+10).

4. To understand galaxy evolution,

6. Galaxy classification based on MIR colors Star-forming galaxies
AKARI (N3-S11) color
Transition Objects
Quiescent galaxies
Shim+2011

7. Spectral Energy Distribution
(Model) SED of Starburst galaxies
Observed SED
da Cunha+08
Unattenuated stellar spectrum
Emission by dust in the ambient ISM
Emission by dust in stellar birth cloud

8. Multi-wavelength data
SDSS DR10 + WISE combined galaxy catalog
Wide-field Infrared Survey Explorer (WISE)
All sky survey
four MIR bands (3.4, 4.6, 12, 22μm)
79,579 galaxies at 0.01< z < S/N12μm > Excluding AGNs
GALEX NUV data
WISE 설명 하나로.

9. MIR CLD CLD WISE [3.4] – [12] ≈ AKARI N3 – S11 ∝𝑺𝑭𝑹/ 𝑴 𝒔𝒕𝒂𝒓
MIR star-forming sequence (Hwang +13) : SFR ~ Mass relation
MIR emission from AGB dust (Piovan+03) : SSP with different ages (1~10 Gyr)

10. Early-type galaxies
The second population spans [3.4] – [12] corresponding the colors of ETGs with MIR-excess cover.
Piovan+03
Mean age
young
old

11. Late-type galaxies
∆MIRC: deviation of [3.4] – [12] from the SFSG (red line)
A left long tail: ∆MIRC < -1 mainly LTGs w/o SF nuclei

12. MIR Galaxy Classification MIR star-forming sequence
MIR green valley
MIR blue clump

13. vs. Optical CMD MIR green valley ≠ Optical green valley
Transition timescale from MIR GV to MIR BC: ~ # Gyrs
MIR GV → MIR BC: optically red galaxies w/ RSF → DEAD galaxies

14. NUV – r vs. [3.4] – [12]
Two-component SSP model : small amount of young (0.5, 1, 2 Gyr) populations make galaxies have MIR-excess emission (MIR GV).
NUV-excess galaxies (NUV – r > 5.4) → MIR-excess galaxies → Quiescent galaxies (Ko+13)
NUV is sensitive to very recent (<1 Gyr) SF, MIR is sensitive to SF over longer timescale.
NUV – r colors of MIR GV and MIV BC are overlapped.

15. ATLAS3D
Cappellari+13
Multi color imaging + 2D kinematics for 260 ETGs (d < 42 Mpc)
Slow / Fast Rotators
Emsellem+13

16. Conclusion
We present a new galaxy classification scheme in the WISE [3.4] – [12] color vs. 12μm luminosity diagram.
We classify galaxies into three types: MIR star-forming galaxies, MIR green valley galaxies, MIR blue clump galaxies.
To obtain a better understanding of galaxy evolution, we need to focus on RGB of galaxies.
WISE 설명 하나로.