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

Internal Extinction in Spirals (effect of inclination)

Sombrero

NGC5866

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

Tully et al 1998 (86 galaxies) a b

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

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

R-K

U-K

Slope (R-K)

R-K K C

U-K K C

C-dependence R-K U-K

K-dependence R-K U-K

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

U-R

U-R K C

U-R K C

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

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

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