1. Internal Extinction in SDSS Galaxies
Jungyeon Cho
Collaborators: C. Park & Y. Choi

2. Internal Extinction in Spirals (effect of inclination)

3. Sombrero

4. NGC5866

5. Internal Extinction (effect of inclination)
K magnitude: > ~no change
U or R mag. : > get dimmer
U-K
b/a a b 1
0.1

6. Tully et al 1998
(86 galaxies) a b

7. Data used for current study: SDSS D1
Number of SDSS spiral galaxies in the data: ~ 14K
Among them, ~8K have JHK mag.
Choi, Park, & Vogeley 07

8. -23 K
-20 3 2
C (=r90/r50)

9. R-K

10. U-K

11. Slope (R-K)

12. R-K K C

13. U-K K C

14. C-dependence
R-K
U-K

15. K-dependence
R-K
U-K

16. Origin of C-dependence
C (=r90/r50) is related to galaxy’s morphology
Origin of K dependence
If K=bright => star formation rate is high (?) => lots of dust

17. U-R

18. U-R K C

19. U-R K C

20. Conclusion
Internal extinction depends on both c and K
Internal extinction is maximum at c~0.25
Internal extinction is maximum at K ~ -23
It is uncertain for K < -23

21. What causes the scatter?
Tully et al 1998
K: ~2.2mm
R: ~700nm
I: ~ 900nm
Mag. after Galactic & k-corrections
What causes the scatter?
* Note: Insignificant absorption at K-band

22. Tully et al 1998
Mag. after Galactic, k-, & inclination correction